14 CFR 25.351 - Yaw maneuver conditions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... angle of paragraph (c) of this section, it is assumed that the cockpit rudder control is suddenly...) With the airplane in unaccelerated flight at zero yaw, it is assumed that the cockpit rudder control is suddenly displaced to achieve the resulting rudder deflection, as limited by: (1) The control system on...

Wind tunnel investigations of forebody strakes for yaw control on F/A-18 model at subsonic and transonic speeds

NASA Technical Reports Server (NTRS)

Erickson, Gary E.; Murri, Daniel G.

1993-01-01

Wind tunnel investigations have been conducted of forebody strakes for yaw control on 0.06-scale models of the F/A-18 aircraft at free-stream Mach numbers of 0.20 to 0.90. The testing was conducted in the 7- by 10-Foot Transonic Tunnel at the David Taylor Research Center and the Langley 7- by 10-Foot High-Speed Tunnel. The principal objectives of the testing were to determine the effects of the Mach number and the strake plan form on the strake yaw control effectiveness and the corresponding strake vortex induced flow field. The wind tunnel model configurations simulated an actuated conformal strake deployed for maximum yaw control at high angles of attack. The test data included six-component forces and moments on the complete model, surface static pressure distributions on the forebody and wing leading-edge extensions, and on-surface and off-surface flow visualizations. The results from these studies show that the strake produces large yaw control increments at high angles of attack that exceed the effect of conventional rudders at low angles of attack. The strake yaw control increments diminish with increasing Mach number but continue to exceed the effect of rudder deflection at angles of attack greater than 30 degrees. The character of the strake vortex induced flow field is similar at subsonic and transonic speeds. Cropping the strake planform to account for geometric and structural constraints on the F-18 aircraft has a small effect on the yaw control increments at subsonic speeds and no effect at transonic speeds.

Integration of vehicle yaw stabilisation and rollover prevention through nonlinear hierarchical control allocation

NASA Astrophysics Data System (ADS)

Alberding, Matthäus B.; Tjønnås, Johannes; Johansen, Tor A.

2014-12-01

This work presents an approach to rollover prevention that takes advantage of the modular structure and optimisation properties of the control allocation paradigm. It eliminates the need for a stabilising roll controller by introducing rollover prevention as a constraint on the control allocation problem. The major advantage of this approach is the control authority margin that remains with a high-level controller even during interventions for rollover prevention. In this work, the high-level control is assigned to a yaw stabilising controller. It could be replaced by any other controller. The constraint for rollover prevention could be replaced by or extended to different control objectives. This work uses differential braking for actuation. The use of additional or different actuators is possible. The developed control algorithm is computationally efficient and suitable for low-cost automotive electronic control units. The predictive design of the rollover prevention constraint does not require any sensor equipment in addition to the yaw controller. The method is validated using an industrial multi-body vehicle simulation environment.

Vehicle yaw stability control via H∞ gain scheduling

NASA Astrophysics Data System (ADS)

Zhang, Jinhua; Sun, Weichao; Feng, Zhiguang

2018-06-01

Yaw stability control (YSC) is rather significant in a vehicle lateral motion, since it can considerably reduce casualties caused by vehicle instability. Nevertheless with the vehicle running, the parameters, such as vehicle mass and moment of inertial, can be perturbed because of variation of capacity, loadage and consumption of fuel, hence some of nominal controllers cannot always work satisfactorily. To overcome the aforementioned deficiency, a gain scheduled H∞ YSC controller is developed in this paper, taking the vehicle mass and moment of inertial as the scheduled variables, now that the gain scheduled H∞ controller can guarantee both the robustness against parameter perturbation and the adjustability of tracking accuracy. Then the constructed controller is verified via numerical simulation and MATLAB-CarSim coalition simulation. The simulation results indicate that the designed controller can indeed improve the vehicle handing performance under circumstance of lateral stability.

Chassis integrated control for active suspension, active front steering and direct yaw moment systems using hierarchical strategy

NASA Astrophysics Data System (ADS)

Zhao, Jing; Wong, Pak Kin; Ma, Xinbo; Xie, Zhengchao

2017-01-01

This paper proposes a novel integrated controller with three-layer hierarchical structure to coordinate the interactions among active suspension system (ASS), active front steering (AFS) and direct yaw moment control (DYC). First of all, a 14-degree-of-freedom nonlinear vehicle dynamic model is constructed. Then, an upper layer is designed to calculate the total corrected moment for ASS and intermediate layer based on linear moment distribution. By considering the working regions of the AFS and DYC, the intermediate layer is functionalised to determine the trigger signal for the lower layer with corresponding weights. The lower layer is utilised to separately trace the desired value of each local controller and achieve the local control objectives of each subsystem. Simulation results show that the proposed three-layer hierarchical structure is effective in handling the working region of the AFS and DYC, while the quasi-experimental result shows that the proposed integrated controller is able to improve the lateral and vertical dynamics of the vehicle effectively as compared with a conventional electronic stability controller.

Adaptive integral feedback controller for pitch and yaw channels of an AUV with actuator saturations.

PubMed

Sarhadi, Pouria; Noei, Abolfazl Ranjbar; Khosravi, Alireza

2016-11-01

Input saturations and uncertain dynamics are among the practical challenges in control of autonomous vehicles. Adaptive control is known as a proper method to deal with the uncertain dynamics of these systems. Therefore, incorporating the ability to confront with input saturation in adaptive controllers can be valuable. In this paper, an adaptive autopilot is presented for the pitch and yaw channels of an autonomous underwater vehicle (AUV) in the presence of input saturations. This will be performed by combination of a model reference adaptive control (MRAC) with integral state feedback with a modern anti-windup (AW) compensator. MRAC with integral state feedback is commonly used in autonomous vehicles. However, some proper modifications need to be taken into account in order to cope with the saturation problem. To this end, a Riccati-based anti-windup (AW) compensator is employed. The presented technique is applied to the non-linear six degrees of freedom (DOF) model of an AUV and the obtained results are compared with that of its baseline method. Several simulation scenarios are executed in the pitch and yaw channels to evaluate the controller performance. Moreover, effectiveness of proposed adaptive controller is comprehensively investigated by implementing Monte Carlo simulations. The obtained results verify the performance of proposed method. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Efficient direct yaw moment control: tyre slip power loss minimisation for four-independent wheel drive vehicle

NASA Astrophysics Data System (ADS)

Kobayashi, Takao; Katsuyama, Etsuo; Sugiura, Hideki; Ono, Eiichi; Yamamoto, Masaki

2018-05-01

This paper proposes an efficient direct yaw moment control (DYC) capable of minimising tyre slip power loss on contact patches for a four-independent wheel drive vehicle. Simulations identified a significant power loss reduction with a direct yaw moment due to a change in steer characteristics during acceleration or deceleration while turning. Simultaneously, the vehicle motion can be stabilised. As a result, the proposed control method can ensure compatibility between vehicle dynamics performance and energy efficiency. This paper also describes the results of a full-vehicle simulation that was conducted to examine the effectiveness of the proposed DYC.

Knowledge, attitudes and practices towards yaws and yaws-like skin disease in Ghana.

PubMed

Marks, Michael; Kwakye-Maclean, Cynthia; Doherty, Rachel; Adwere, Paul; Aziz Abdulai, Abdul; Duah, Fredrick; Ohene, Sally-Ann; Mitja, Oriol; Oguti, Blanche; Solomon, Anthony W; Mabey, David C W; Adu-Sarkodie, Yaw; Asiedu, Kingsley; Ackumey, Mercy M

2017-07-01

Yaws is endemic in Ghana. The World Health Organization (WHO) has launched a new global eradication campaign based on total community mass treatment with azithromycin. Achieving high coverage of mass treatment will be fundamental to the success of this new strategy; coverage is dependent, in part, on appropriate community mobilisation. An understanding of community knowledge, attitudes and practices related to yaws in Ghana and other endemic countries will be vital in designing effective community engagement strategies. A verbally administered questionnaire was administered to residents in 3 districts in the Eastern region of Ghana where a randomised trial on the treatment of yaws was being conducted. The questionnaire combined both quantitative and qualitative questions covering perceptions of the cause and mechanisms of transmission of yaws-like lesions, the providers from which individuals would seek healthcare for yaws-like lesions, and what factors were important in reaching decisions on where to seek care. Chi-square tests and logistic regression were used to assess relationships between reported knowledge, attitudes and practices, and demographic variables. Thematic analysis of qualitative data was used to identify common themes. A total of 1,162 individuals participated. The majority of individuals (n = 895, 77%) reported that "germs" were the cause of yaws lesions. Overall 13% (n = 161) of respondents believed that the disease was caused by supernatural forces. Participants frequently mentioned lack of personal hygiene, irregular and inefficient bathing, and washing with dirty water as fundamental to both the cause and the prevention of yaws. A majority of individuals reported that they would want to take an antibiotic to prevent the development of yaws if they were asymptomatic (n = 689, 61.2%), but a substantial minority reported they would not want to do so. A majority of individuals (n = 839, 72.7%) reported that if they had a yaws-like skin lesion

Integrated Chassis Control of Active Front Steering and Yaw Stability Control Based on Improved Inverse Nyquist Array Method

PubMed Central

2014-01-01

An integrated chassis control (ICC) system with active front steering (AFS) and yaw stability control (YSC) is introduced in this paper. The proposed ICC algorithm uses the improved Inverse Nyquist Array (INA) method based on a 2-degree-of-freedom (DOF) planar vehicle reference model to decouple the plant dynamics under different frequency bands, and the change of velocity and cornering stiffness were considered to calculate the analytical solution in the precompensator design so that the INA based algorithm runs well and fast on the nonlinear vehicle system. The stability of the system is guaranteed by dynamic compensator together with a proposed PI feedback controller. After the response analysis of the system on frequency domain and time domain, simulations under step steering maneuver were carried out using a 2-DOF vehicle model and a 14-DOF vehicle model by Matlab/Simulink. The results show that the system is decoupled and the vehicle handling and stability performance are significantly improved by the proposed method. PMID:24782676

Integrated chassis control of active front steering and yaw stability control based on improved inverse nyquist array method.

PubMed

Zhu, Bing; Chen, Yizhou; Zhao, Jian

2014-01-01

An integrated chassis control (ICC) system with active front steering (AFS) and yaw stability control (YSC) is introduced in this paper. The proposed ICC algorithm uses the improved Inverse Nyquist Array (INA) method based on a 2-degree-of-freedom (DOF) planar vehicle reference model to decouple the plant dynamics under different frequency bands, and the change of velocity and cornering stiffness were considered to calculate the analytical solution in the precompensator design so that the INA based algorithm runs well and fast on the nonlinear vehicle system. The stability of the system is guaranteed by dynamic compensator together with a proposed PI feedback controller. After the response analysis of the system on frequency domain and time domain, simulations under step steering maneuver were carried out using a 2-DOF vehicle model and a 14-DOF vehicle model by Matlab/Simulink. The results show that the system is decoupled and the vehicle handling and stability performance are significantly improved by the proposed method.

Yawing characteristics during slippage of the nacelle of a multi MW wind turbine

NASA Astrophysics Data System (ADS)

Kim, M.-G.; Dalhoff, P. H.; Gust, P.

2016-09-01

High aerodynamic yaw loads coupled with electrical failures in the wind turbine can result to a slippage of the nacelle, due to limited braking capabilities of the yaw system. A slippage on the other hand can lead to a mechanical malfunction of the yaw system. To analyse the yawing characteristics of a wind turbine during nacelle slippage situations, a detailed multibody system model of the yaw system has been developed and incorporated in a multibody system model of a wind turbine based on a 3.3 MW turbine. Extreme load cases which lead to a nacelle slippage have been simulated. The dynamics and loads on different wind turbine components are presented and discussed. First results show minimal load increases of the rotor torque and the bending moments of the blade root sections during slippage but unfavourable rotational speeds of the yaw drives.

Unconventional Rotor Power Response to Yaw Error Variations

DOE PAGES

Schreck, S. J.; Schepers, J. G.

2014-12-16

Continued inquiry into rotor and blade aerodynamics remains crucial for achieving accurate, reliable prediction of wind turbine power performance under yawed conditions. To exploit key advantages conferred by controlled inflow conditions, we used EU-JOULE DATA Project and UAE Phase VI experimental data to characterize rotor power production under yawed conditions. Anomalies in rotor power variation with yaw error were observed, and the underlying fluid dynamic interactions were isolated. Unlike currently recognized influences caused by angled inflow and skewed wake, which may be considered potential flow interactions, these anomalies were linked to pronounced viscous and unsteady effects.

Direct yaw moment control and power consumption of in-wheel motor vehicle in steady-state turning

NASA Astrophysics Data System (ADS)

Kobayashi, Takao; Katsuyama, Etsuo; Sugiura, Hideki; Ono, Eiichi; Yamamoto, Masaki

2017-01-01

Driving force distribution control is one of the characteristic performance aspects of in-wheel motor vehicles and various methods have been developed to control direct yaw moment while turning. However, while these controls significantly enhance vehicle dynamic performance, the additional power required to control vehicle motion still remains to be clarified. This paper constructed new formulae of the mechanism by which direct yaw moment alters the cornering resistance and mechanical power of all wheels based on a simple bicycle model, including the electric loss of the motors and the inverters. These formulation results were validated by an actual test vehicle equipped with in-wheel motors in steady-state turning. The validated theory was also applied to a comparison of several different driving force distribution mechanisms from the standpoint of innate mechanical power.

Exploratory Investigation of Forebody Strakes for Yaw Control of a Generic Fighter with a Symmetric 60 deg Half-Angle Chine Forebody

NASA Technical Reports Server (NTRS)

Ross, Holly M.; ORourke, Matthew J.

1997-01-01

Forebody strakes were tested in a low-speed wind tunnel to determine their effectiveness producing yaw control on a generic fighter model with a symmetric 60 deg half-angle chine forebody. Previous studies conducted using smooth, conventionally shaped forebodies show that forebody strakes provide increased levels of yaw control at angles of attack where conventional rudders are ineffective. The chine forebody shape was chosen for this study because chine forebodies can be designed with lower radar cross section (RCS) values than smooth forebody shapes. Because the chine edges of the forebody would fix the point of flow separation, it was unknown if any effectiveness achieved could be modulated as was successfully done on the smooth forebody shapes. The results show that use of forebody strakes on a chine forebody produce high levels of yaw control, and when combined with the rudder effectiveness, significant yaw control is available for a large range of angles of attack. The strake effectiveness was very dependent on radial location. Very small strakes placed at the tip of the forebody were nearly as effective as very long strakes. An axial translation scheme provided almost linear increments of control effectiveness.

Detailed field test of yaw-based wake steering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleming, Paul; Churchfield, Matt; Scholbrock, Andrew

This study describes a detailed field-test campaign to investigate yaw-based wake steering. In yaw-based wake steering, an upstream turbine intentionally misaligns its yaw with respect to the inflow to deflect its wake away from a downstream turbine, with the goal of increasing total power production. In the first phase, a nacelle-mounted scanning lidar was used to verify wake deflection of a misaligned turbine and calibrate wake deflection models. In the second phase, these models were used within a yaw controller to achieve a desired wake deflection. This paper details the experimental design and setup. Lastly, all data collected as partmore » of this field experiment will be archived and made available to the public via the U.S. Department of Energy's Atmosphere to Electrons Data Archive and Portal.« less

Detailed field test of yaw-based wake steering

DOE PAGES

Fleming, Paul; Churchfield, Matt; Scholbrock, Andrew; ...

2016-10-03

This study describes a detailed field-test campaign to investigate yaw-based wake steering. In yaw-based wake steering, an upstream turbine intentionally misaligns its yaw with respect to the inflow to deflect its wake away from a downstream turbine, with the goal of increasing total power production. In the first phase, a nacelle-mounted scanning lidar was used to verify wake deflection of a misaligned turbine and calibrate wake deflection models. In the second phase, these models were used within a yaw controller to achieve a desired wake deflection. This paper details the experimental design and setup. Lastly, all data collected as partmore » of this field experiment will be archived and made available to the public via the U.S. Department of Energy's Atmosphere to Electrons Data Archive and Portal.« less

Yaws in the Western Pacific Region: A Review of the Literature

PubMed Central

Capuano, Corinne; Ozaki, Masayo

2011-01-01

Until the middle of the 20th century, yaws was highly endemic and considered a serious public health problem in the Western Pacific Region (WPR), leading to intensive control efforts in the 1950s–1960s. Since then, little attention has been paid to its reemergence. Its current burden is unknown. This paper presents the results of an extensive literature review, focusing on yaws in the South Pacific. Available records suggest that the region remains largely free of yaws except for Papua New Guinea, Solomon Islands, and Vanuatu. Many clinical cases reported recently were described as “attenuated”; advanced stages are rare. A single intramuscular injection of benzathine penicillin is still effective in curing yaws. In the Pacific, yaws may be amenable to elimination if adequate resources are provided and political commitment revived. A mapping of yaws prevalence in PNG, Solomon, and Vanuatu is needed before comprehensive country-tailored strategies towards yaws elimination can be developed. PMID:22235208

Epidemiology of yaws: an update

PubMed Central

Kazadi, Walter M; Asiedu, Kingsley B; Agana, Nsiire; Mitjà, Oriol

2014-01-01

Yaws, a neglected tropical disease, is targeted for eradication by 2020 through large-scale mass-treatment programs of endemic communities. A key determinant for the success of the eradication campaign is good understanding of the disease epidemiology. We did a review of historical trends and new information from endemic countries, with the aim of assessing the state of knowledge on yaws disease burden. Transmission of yaws is now present in Africa, Asia, and the South Pacific. At least 12 countries are known to harbor yaws cases and 21 to 42 million people live in endemic areas. Between 2008 and 2012 more than 300,000 new cases were reported to the World Health Organization. Yaws presented high geographical variation within a country or region, high seasonality for incidence of active disease, and evidence that low standards of hygiene predispose to suffering of the disease. Key data issues include low levels of reporting, potential misdiagnosis, and scarce documentation on prevalence of asymptomatic infections. Currently available data most likely underestimates the magnitude of the disease burden. More effort is needed in order to refine accuracy of data currently being reported. A better characterization of the epidemiology of yaws globally is likely to positively impact on planning and implementation of yaws eradication. PMID:24729728

Experimental determination of the Yawing Moment due to Yawing Contributed by the Wing, Fuselage, and Vertical Tail of a Midwing Airplane Model

DTIC Science & Technology

1943-06-01

derivative Cnr, the rate of change of yawing-momer.t coefficient with yawing angular velocity, contributed ’by the wing, the fuselage, and the...derivative Cn , the rate of change of yawing--moraent coefficient with yawing angular velocity. Al- though theoretical methods for obtaining the...yaw. T CD -3 SYMBOLS ’n rate of change of yawing-moment coefficient with yawing angular velocity per unit of rh/2V ÖCn/d (^-’ \\ 27 J P

Mapping the Epidemiology of Yaws in the Solomon Islands: A Cluster Randomized Survey

PubMed Central

Marks, Michael; Vahi, Ventis; Sokana, Oliver; Puiahi, Elliot; Pavluck, Alex; Zhang, Zaixing; Dalipanda, Tenneth; Bottomley, Christian; Mabey, David C.; Solomon, Anthony W.

2015-01-01

Yaws, a non-venereal treponemal disease, is targeted for eradication by 2020 but accurate epidemiological data to guide control programs remain sparse. The Solomon Islands reports the second highest number of cases of yaws worldwide. We conducted a cluster randomized survey of yaws in two provinces of the Solomon Islands. One thousand four hundred and ninety-seven (1,497) children 5–14 years of age were examined. Clinical signs of active yaws were found in 79 children (5.5%), whereas 140 children (9.4%) had evidence of healed yaws lesions. Four hundred and seventy (470) (31.4%) children had a positive Treponema pallidum particle agglutination assay (TPPA). Two hundred and eighty-five (285) children (19%) had a positive TPPA and rapid plasma regain assay. Risk of yaws increased with age and was more common in males. The prevalence of yaws at village level was the major risk factor for infection. Our findings suggest the village, not the household, should be the unit of treatment in the World Health Organization (WHO) yaws eradication strategy. PMID:25422395

Mapping the epidemiology of yaws in the Solomon Islands: a cluster randomized survey.

PubMed

Marks, Michael; Vahi, Ventis; Sokana, Oliver; Puiahi, Elliot; Pavluck, Alex; Zhang, Zaixing; Dalipanda, Tenneth; Bottomley, Christian; Mabey, David C; Solomon, Anthony W

2015-01-01

Yaws, a non-venereal treponemal disease, is targeted for eradication by 2020 but accurate epidemiological data to guide control programs remain sparse. The Solomon Islands reports the second highest number of cases of yaws worldwide. We conducted a cluster randomized survey of yaws in two provinces of the Solomon Islands. One thousand four hundred and ninety-seven (1,497) children 5-14 years of age were examined. Clinical signs of active yaws were found in 79 children (5.5%), whereas 140 children (9.4%) had evidence of healed yaws lesions. Four hundred and seventy (470) (31.4%) children had a positive Treponema pallidum particle agglutination assay (TPPA). Two hundred and eighty-five (285) children (19%) had a positive TPPA and rapid plasma regain assay. Risk of yaws increased with age and was more common in males. The prevalence of yaws at village level was the major risk factor for infection. Our findings suggest the village, not the household, should be the unit of treatment in the World Health Organization (WHO) yaws eradication strategy. © The American Society of Tropical Medicine and Hygiene.

Integrated Mapping of Yaws and Trachoma in the Five Northern-Most Provinces of Vanuatu

PubMed Central

Taleo, Fasihah; Marks, Michael; Sokana, Oliver; Last, Anna; Willis, Rebecca; Garae, Mackline; Bong, Annie; Chu, Brian K; Courtright, Paul; Kool, Jacob; Taleo, George; Rory, Jean Jacque; Solomon, Anthony W

2017-01-01

Yaws and trachoma are targeted for eradication and elimination as public health problems. In trachoma-endemic populations mass administration of azithromycin can simultaneously treat yaws. We conducted a population-based prevalence survey in the five northernmost provinces of Vanuatu, where trachoma and yaws are suspected to be co-endemic. Clinical signs of trachoma were evaluated using the WHO simplified grading system, and skin examination with a serological rapid diagnostic test used to identify yaws. We enrolled 1004 households in 59 villages over 16 islands, and examined 3650 individuals of all ages for trachoma. The overall adjusted prevalence of trachomatous inflammation-follicular (TF) in 1–9 year-olds was 12.0% (95% Confidence Interval: 8.1–16.7%), and the overall adjusted prevalence of TT in those aged 15 years and greater was 0.04% (95% CI 0–0.14%). In multivariate analysis, the odds of children having TF was 2.6 (95% CI = 1.5–4.4) times higher in households with unimproved latrines, and independently associated with the number of children in the household (OR 1.3, 95% CI = 1.0–1.6 for each additional child). We examined the skin of 821 children aged 5–14 years. Two children had yaws, giving an estimated prevalence of active yaws in those aged 5–14 years of 0.2% (95% CI = 0.03–0.9%). Mass treatment with azithromycin is recommended in these provinces. Given the apparent low burden of yaws, integration of yaws and trachoma control programmes is likely to be useful and cost-effective to national programmes. PMID:28118354

High transonic speed transport aircraft study. [aerodynamic characteristics of single-fuselage, yawed-wing configuration

NASA Technical Reports Server (NTRS)

Kulfan, R. M.; Neumann, F. D.; Nisbet, J. W.; Mulally, A. R.; Murakami, J. K.; Noble, E. C.; Mcbarron, J. P.; Stalter, J. L.; Gimmestad, D. W.; Sussman, M. B.

1973-01-01

An initial design study of high-transonic-speed transport aircraft has been completed. Five different design concepts were developed. These included fixed swept wing, variable-sweep wing, delta wing, double-fuselage yawed-wing, and single-fuselage yawed-wing aircraft. The boomless supersonic design objectives of range=5560 Km (3000 nmi), payload-18 143 kg (40 000lb), Mach=1.2, and FAR Part 36 aircraft noise levels were achieved by the single-fuselage yawed-wing configuration with a gross weight of 211 828 Kg (467 000 lb). A noise level of 15 EPNdB below FAR Part 36 requirements was obtained with a gross weight increase to 226 796 Kg (500 000 lb). Although wing aeroelastic divergence was a primary design consideration for the yawed-wing concepts, the graphite-epoxy wings of this study were designed by critical gust and maneuver loads rather than by divergence requirements. The transonic nacelle drag is shown to be very sensitive to the nacelle installation. A six-degree-of-freedom dynamic stability analysis indicated that the control coordination and stability augmentation system would require more development than for a symmetrical airplane but is entirely feasible. A three-phase development plan is recommended to establish the full potential of the yawed-wing concept.

An analysis of a nonlinear instability in the implementation of a VTOL control system

NASA Technical Reports Server (NTRS)

Weber, J. M.

1982-01-01

The contributions to nonlinear behavior and unstable response of the model following yaw control system of a VTOL aircraft during hover were determined. The system was designed as a state rate feedback implicit model follower that provided yaw rate command/heading hold capability and used combined full authority parallel and limited authority series servo actuators to generate an input to the yaw reaction control system of the aircraft. Both linear and nonlinear system models, as well as describing function linearization techniques were used to determine the influence on the control system instability of input magnitude and bandwidth, series servo authority, and system bandwidth. Results of the analysis describe stability boundaries as a function of these system design characteristics.

Eradication of Yaws: Historical Efforts and Achieving WHO's 2020 Target

PubMed Central

Asiedu, Kingsley; Fitzpatrick, Christopher; Jannin, Jean

2014-01-01

Background Yaws, one of the 17 neglected tropical diseases (NTDs), is targeted for eradication by 2020 in resolution WHA66.12 of the World Health Assembly (2013) and the WHO roadmap on NTDs (2012). The disease frequently affects children who live in poor socioeconomic conditions. Between 1952 and 1964, WHO and the United Nations Children's Fund (UNICEF) led a global eradication campaign using injectable benzathine penicillin. Recent developments using a single dose of oral azithromycin have renewed optimism that eradication can be achieved through a comprehensive large-scale treatment strategy. We review historical efforts to eradicate yaws and argue that this goal is now technically feasible using new tools and with the favorable environment for control of NTDs. We also summarize the work of WHO's Department of Control of Neglected Tropical Diseases in leading the renewed eradication initiative and call on the international community to support efforts to achieve the 2020 eradication goal. The critical factor remains access to azithromycin. Excluding medicines, the financial cost of yaws eradication could be as little as US$ 100 million. Conclusions The development of new tools has renewed interest in eradication of yaws; with modest support, the WHO eradication target of 2020 can be achieved. PMID:25254372

Failure of PCR to Detect Treponema pallidum ssp. pertenue DNA in Blood in Latent Yaws.

PubMed

Marks, Michael; Katz, Samantha; Chi, Kai-Hua; Vahi, Ventis; Sun, Yongcheng; Mabey, David C; Solomon, Anthony W; Chen, Cheng Y; Pillay, Allan

2015-01-01

Yaws, caused by Treponema pallidum ssp. pertenue, is a neglected tropical disease closely related to venereal syphilis and is targeted for eradication by 2020. Latent yaws represents a diagnostic challenge, and current tools cannot adequately distinguish between individuals with true latent infection and individuals who are serofast following successful treatment. PCR on blood has previously been shown to detect T. pallidum DNA in patients with syphilis, suggesting that this approach may be of value in yaws. We performed real-time PCR for Treponema pallidum ssp. pertenue on blood samples from 140 children with positive T. pallidum Particle Agglutination (TPPA) and Rapid Plasma Reagin (RPR) tests and 7 controls (negative serology), all collected as part of a prospective study of yaws in the Solomon Islands. All samples were also tested by a nested PCR for T. pallidum. 12 patients had clinical evidence of active yaws whilst 128 were considered to have latent yaws. 43 children had high titre rapid plasma reagins (RPRs) of ≥1:32. PCR testing with both assays gave negative results in all cases. It is possible that the failure to detect T. pallidum ssp. pertenue in blood reflects lower loads of organism in latent yaws compared to those in latent infection with T. pallidum ssp. pertenue, and/or a lower propensity for haematogenous dissemination in yaws than in syphilis. As the goal of the yaws control programme is eradication, a tool that can differentiate true latent infection from individuals who are serofast would be of value; however, PCR of blood is not that tool.

Failure of PCR to Detect Treponema pallidum ssp. pertenue DNA in Blood in Latent Yaws

PubMed Central

Chi, Kai-Hua; Vahi, Ventis; Sun, Yongcheng; Mabey, David C.; Solomon, Anthony W.; Chen, Cheng Y.; Pillay, Allan

2015-01-01

Yaws, caused by Treponema pallidum ssp. pertenue, is a neglected tropical disease closely related to venereal syphilis and is targeted for eradication by 2020. Latent yaws represents a diagnostic challenge, and current tools cannot adequately distinguish between individuals with true latent infection and individuals who are serofast following successful treatment. PCR on blood has previously been shown to detect T. pallidum DNA in patients with syphilis, suggesting that this approach may be of value in yaws. We performed real-time PCR for Treponema pallidum ssp. pertenue on blood samples from 140 children with positive T. pallidum Particle Agglutination (TPPA) and Rapid Plasma Reagin (RPR) tests and 7 controls (negative serology), all collected as part of a prospective study of yaws in the Solomon Islands. All samples were also tested by a nested PCR for T. pallidum. 12 patients had clinical evidence of active yaws whilst 128 were considered to have latent yaws. 43 children had high titre rapid plasma reagins (RPRs) of ≥1:32. PCR testing with both assays gave negative results in all cases. It is possible that the failure to detect T. pallidum ssp. pertenue in blood reflects lower loads of organism in latent yaws compared to those in latent infection with T. pallidum ssp. pertenue, and/or a lower propensity for haematogenous dissemination in yaws than in syphilis. As the goal of the yaws control programme is eradication, a tool that can differentiate true latent infection from individuals who are serofast would be of value; however, PCR of blood is not that tool. PMID:26125585

Prevalence Study of Yaws in the Democratic Republic of Congo Using the Lot Quality Assurance Sampling Method

PubMed Central

Gerstl, Sibylle; Kiwila, Gédeon; Dhorda, Mehul; Lonlas, Sylvaine; Myatt, Mark; Ilunga, Benoît Kebela; Lemasson, Denis; Szumilin, Elisabeth; Guerin, Philippe J.; Ferradini, Laurent

2009-01-01

Background Until the 1970s the prevalence of non-venereal trepanomatosis, including yaws, was greatly reduced after worldwide mass treatment. In 2005, cases were again reported in the Democratic Republic of the Congo. We carried out a survey to estimate the village-level prevalence of yaws in the region of Equator in the north of the country in order to define appropriate strategies to effectively treat the affected population. Methodology/Principal Findings We designed a community-based survey using the Lot Quality Assurance Sampling method to classify the prevalence of active yaws in 14 groups of villages (lots). The classification into high, moderate, or low yaws prevalence corresponded to World Health Organization prevalence thresholds for identifying appropriate operational treatment strategies. Active yaws cases were defined by suggestive clinical signs and positive rapid plasma reagin and Treponema pallidum hemagglutination serological tests. The overall prevalence in the study area was 4.7% (95% confidence interval: 3.4–6.0). Two of 14 lots had high prevalence (>10%), three moderate prevalence (5–10%) and nine low prevalence (<5%.). Conclusions/Significance Although yaws is no longer a World Health Organization priority disease, the presence of yaws in a region where it was supposed to be eradicated demonstrates the importance of continued surveillance and control efforts. Yaws should remain a public health priority in countries where previously it was known to be endemic. The integration of sensitive surveillance systems together with free access to effective treatment is recommended. As a consequence of our study results, more than 16,000 people received free treatment against yaws. PMID:19623266

14 CFR 29.351 - Yawing conditions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... paragraph (a) of this section, in unaccelerated flight with zero yaw, at forward speeds from zero up to 0.6... produce the load required in paragraph (a) of the section, in unaccelerated flight with zero yaw, at...

Pilot-in-the-Loop Evaluation of a Yaw Rate to Throttle Feedback Control with Enhanced Engine Response

NASA Technical Reports Server (NTRS)

Litt, Jonathan S.; Guo, Ten-Huei; Sowers, T. Shane; Chicatelli, Amy K.; Fulton, Christopher E.; May, Ryan D.; Owen, A. Karl

2012-01-01

This paper describes the implementation and evaluation of a yaw rate to throttle feedback system designed to replace a damaged rudder. It can act as a Dutch roll damper and as a means to facilitate pilot input for crosswind landings. Enhanced propulsion control modes were implemented to increase responsiveness and thrust level of the engine, which impact flight dynamics and performance. Piloted evaluations were performed to determine the capability of the engines to substitute for the rudder function under emergency conditions. The results showed that this type of implementation is beneficial, but the engines' capability to replace the rudder is limited.

14 CFR 27.351 - Yawing conditions.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) of this section, in unaccelerated flight with zero yaw, at forward speeds from zero up to 0.6 VNE— (1... required in paragraph (a) of this section, in unaccelerated flight with zero yaw, at forward speeds from 0...

Some epidemiological aspects of the eradication of yaws

PubMed Central

Hackett, C. J.

1960-01-01

Much has been learnt of the epidemiology of yaws during eradication campaigns in populations in which the prevalence of active yaws was high, but not all has been published. The recognition of the importance of latent cases in the maintenance of yaws has contributed to the effectiveness of these campaigns. Yaws eradication activities are extending into populations where at present active yaws is often not high. Planning of effective and economical eradication measures, especially in such populations, needs as complete a picture of the disease as possible, from its transmission and the factors that favour this until the death of the infected person, before or after cure of the infection either after chemotherapy or spontaneously. By revealing the many gaps that still remain in our knowledge of yaws, this summary may encourage those who have gathered valuable material during field work to study and prepare it for publication. PMID:13710280

Wind Plant Power Optimization through Yaw Control using a Parametric Model for Wake Effects -- A CFD Simulation Study

DOE PAGES

Gebraad, P. M. O.; Teeuwisse, F. W.; van Wingerden, J. W.; ...

2016-01-01

This article presents a wind plant control strategy that optimizes the yaw settings of wind turbines for improved energy production of the whole wind plant by taking into account wake effects. The optimization controller is based on a novel internal parametric model for wake effects, called the FLOw Redirection and Induction in Steady-state (FLORIS) model. The FLORIS model predicts the steady-state wake locations and the effective flow velocities at each turbine, and the resulting turbine electrical energy production levels, as a function of the axial induction and the yaw angle of the different rotors. The FLORIS model has a limitedmore » number of parameters that are estimated based on turbine electrical power production data. In high-fidelity computational fluid dynamics simulations of a small wind plant, we demonstrate that the optimization control based on the FLORIS model increases the energy production of the wind plant, with a reduction of loads on the turbines as an additional effect.« less

Consideration of dynamic loads on the vertical tail by the theory of flat yawing maneuvers

NASA Technical Reports Server (NTRS)

Boshar, John; Davis, Philip

1946-01-01

Dynamic yawing effects on vertical tail loads are considered by a theory of flat yawing maneuvers. A comparison is shown between computed loads and the loads measured in flight in a fighter airplane. The dynamic effects were investigated on a large flying boat for both an abrupt rudder deflection and a sinusoidal rudder deflection. Only a moderate amount of control deflection was found to be necessary to attain the ultimate design load on the tail. In order to take into account dynamic effects in design, specifications of yawing maneuverability or control movement are needed.

Influence of yaw on propeller aerodynamic characteristics

NASA Astrophysics Data System (ADS)

Nguyen, Van Bang; Rozehnal, Dalibor; Hnidka, Jakub; Pham, Vu Uy

2018-06-01

Between the propeller axis and free stream direction, it can still be a non-zero yaw angle. This paper introduces some propeller experiments, in which the propeller aerodynamic characteristics have been determined in various yaw angle and different rotational speeds. The experimental aerodynamic characteristics are acquired dynamic values, from which the influence of yaw conditions on the frequency and the amplitude of propeller thrust and torque can be obtained.

14 CFR 27.351 - Yawing conditions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Yawing conditions. 27.351 Section 27.351 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Strength Requirements Flight Loads § 27.351 Yawing conditions. (a...

Research on Performance of Wire-controlled Hydraulic Steering System Based on Four-wheel Steering

NASA Astrophysics Data System (ADS)

Tao, P.; Jin, X. H.

2018-05-01

In this paper, the steering stability and control strategy of forklift are put forward. Drive based on yawing moment distribution of rotary torque coordination control method, through analyzing the linear two degree of freedom model of forklift truck, forklift yawing angular velocity and mass center side-slip Angle of expectations, as the control target parameters system, using fuzzy controller output driving forklift steering the yawing moment, to drive rotary torque distribution, make the forklift truck to drive horizontal pendulum angular velocity and side-slip Angle tracking reference model very well. In this paper, the lateral stability control system were designed, the joint simulation in MATLAB/Simulink, the simulation results show that under the different partial load, the control system can effectively to control side forklift lateral stability, enhanced the forklift driving safety, for the side forklift steering stability study provides a theoretical basis.

Modular multimorphic kinematic arm structure and pitch and yaw joint for same

DOEpatents

Martin, H. Lee; Williams, Daniel M.; Holt, W. Eugene

1989-01-01

A multimorphic kinematic manipulator arm is provided with seven degrees of freedom and modular kinematic redundancy through identical pitch/yaw, shoulder, elbow and wrist joints and a wrist roll device at the wrist joint, which further provides to the manipulator arm an obstacle avoidance capability. The modular pitch/yaw joints are traction drive devices which provide backlash free operation with smooth torque transmission and enhanced rigidity. A dual input drive arrangement is provided for each joint resulting in a reduction of the load required to be assumed by each drive and providing selective pitch and yaw motions by control of the relative rotational directions of the input drive.

Impact of Community Mass Treatment with Azithromycin for Trachoma Elimination on the Prevalence of Yaws

PubMed Central

Marks, Michael; Vahi, Ventis; Sokana, Oliver; Chi, Kai-Hua; Puiahi, Elliot; Kilua, Georgina; Pillay, Allan; Dalipanda, Tenneth; Bottomley, Christian; Solomon, Anthony W.; Mabey, David C.

2015-01-01

Background Community mass treatment with 30mg/kg azithromycin is central to the new WHO strategy for eradicating yaws. Both yaws and trachoma— which is earmarked for elimination by 2020 using a strategy that includes mass treatment with 20mg/kg azithromycin—are endemic in the Pacific, raising the possibility of an integrated approach to disease control. Community mass treatment with azithromycin for trachoma elimination was conducted in the Solomon Islands in 2014. Methods We conducted a study to assess the impact of mass treatment with 20mg/kg azithromycin on yaws. We examined children aged 5-14 years and took blood and lesion samples for yaws diagnosis. Results We recruited 897 children, 6 months after mass treatment. There were no cases of active yaws. Serological evidence of current infection was found in 3.6% (95% CI= 2.5-5.0%). This differed significantly between individuals who had and had not received azithromycin (2.8% vs 6.5%, p=0.015); the prevalence of positive serology in 5-14 year-olds had been 21.7% (95% CI=14.6%-30.9%) 6 months prior to mass treatment. Not receiving azithromycin was associated with an odds of 3.9 for infection (p=0.001). National figures showed a 57% reduction in reported cases of yaws following mass treatment. Discussion Following a single round of treatment we did not identify any cases of active yaws in a previously endemic population. We found a significant reduction in latent infection. Our data support expansion of the WHO eradication strategy and suggest an integrated approach to the control of yaws and trachoma in the Pacific may be viable. PMID:26241484

Rolling Moments Due to Rolling and Yaw for Four Wing Models in Rotation

NASA Technical Reports Server (NTRS)

Knight, Montgomery; Wenzinger, Carl J

1932-01-01

This report presents the results of a series of autorotation and torque tests on four different rotating wing systems at various rates of roll and at several angles of yaw. The investigation covered an angle of attack range up to 90 degrees and angles of yaw of 0 degree, 5 degrees, 10 degrees, and 20 degrees. The tests were made in a 5-foot, closed-throat atmospheric wind tunnel. The object of the tests was primarily to determine the effects of various angles of yaw on the rolling moments of the rotating wings up to large angles of attack. It was found that at angles of attack above that of maximum lift the rolling moments on the wings due to yaw (or side slip) from 5 degrees to 20 degrees were roughly of the same magnitude as those due to rolling. There was a wide variation in magnitude of the rolling moment due to yaw angle. The rates and ranges of stable autorotation for the monoplane models were considerably increased by yaw, whereas for an unstaggered biplane they were little affected. The immediate cause of the rolling moment due to yaw is apparently the building up of large loads on the forward wing tip and the reduction of loads on the rearward wing tip.

Modular multimorphic kinematic arm structure and pitch and yaw joint for same

DOEpatents

Martin, H.L.; Williams, D.M.; Holt, W.E.

1987-04-21

A multimorphic kinematic manipulator arm is provided with seven degrees of freedom and modular kinematic redundancy through identical pitch/yaw, shoulder, elbow and wrist joints and a wrist roll device at the wrist joint, which further provides to the manipulator arm an obstacle avoidance capability. The modular pitch/yaw joints are traction drive devices which provide backlash free operation with smooth torque transmission and enhanced rigidity. A dual input drive arrangement is provided for each joint resulting in a reduction of the load required to be assumed by each drive means and providing selective pitch and yaw motions by control of the relative rotational directions of the input drive means. 12 figs.

Analysis of Effectiveness of Phoenix Entry Reaction Control System

NASA Technical Reports Server (NTRS)

Dyakonov, Artem A.; Glass, Christopher E.; Desai, Prasun, N.; VanNorman, John W.

2008-01-01

Interaction between the external flowfield and the reaction control system (RCS) thruster plumes of the Phoenix capsule during entry has been investigated. The analysis covered rarefied, transitional, hypersonic and supersonic flight regimes. Performance of pitch, yaw and roll control authority channels was evaluated, with specific emphasis on the yaw channel due to its low nominal yaw control authority. Because Phoenix had already been constructed and its RCS could not be modified before flight, an assessment of RCS efficacy along the trajectory was needed to determine possible issues and to make necessary software changes. Effectiveness of the system at various regimes was evaluated using a hybrid DSMC-CFD technique, based on DSMC Analysis Code (DAC) code and General Aerodynamic Simulation Program (GASP), the LAURA (Langley Aerothermal Upwind Relaxation Algorithm) code, and the FUN3D (Fully Unstructured 3D) code. Results of the analysis at hypersonic and supersonic conditions suggest a significant aero-RCS interference which reduced the efficacy of the thrusters and could likely produce control reversal. Very little aero-RCS interference was predicted in rarefied and transitional regimes. A recommendation was made to the project to widen controller system deadbands to minimize (if not eliminate) the use of RCS thrusters through hypersonic and supersonic flight regimes, where their performance would be uncertain.

Displacement and force coupling control design for automotive active front steering system

NASA Astrophysics Data System (ADS)

Zhao, Wanzhong; Zhang, Han; Li, Yijun

2018-06-01

A displacement and force coupling control design for active front steering (AFS) system of vehicle is proposed in this paper. In order to investigate the displacement and force characteristics of the AFS system of the vehicle, the models of AFS system, vehicle, tire as well as the driver model are introduced. Then, considering the nonlinear characteristics of the tire force and external disturbance, a robust yaw rate control method is designed by applying a steering motor to generate an active steering angle to adjust the yaw stability of the vehicle. Based on mixed H2/H∞ control, the system robustness and yaw rate tracking performance are enforced by H∞ norm constraint and the control effort is captured through H2 norm. In addition, based on the AFS system, a planetary gear set and an assist motor are both added to realize the road feeling control in this paper to dismiss the influence of extra steering angle through a compensating method. Evaluation of the overall system is accomplished by simulations and experiments under various driving condition. The simulation and experiment results show the proposed control system has excellent tracking performance and road feeling performance, which can improve the cornering stability and maneuverability of vehicle.

Assessment of Wind Turbine Component Loads Under Yaw-Offset Conditions

DOE PAGES

Damiani, Rick R.; Dana, Scott; Annoni, Jennifer; ...

2018-04-13

Renewed interest in yaw control for wind turbine and power plants for wake redirection and load mitigation demands a clear understanding of the effects of running with skewed inflow. In this paper, we investigate the physics of yawed operations, building up the complexity from a simplified analytical treatment to more complex aeroelastic simulations. Results in terms of damage equivalent loads (DELs) and extreme loads under operating, misaligned conditions are compared to data collected from an instrumented, utility-scale wind turbine. The analysis shows that multiple factors are responsible for the DELs of the various components, and that airfoil aerodynamics, elastic characteristicsmore » of the rotor, and turbulence intensities are the primary drivers. Both fatigue and extreme loads are observed to have relatively complex trends with yaw offsets, which can change depending on the wind-speed regime. As a result, good agreement is found between predicted and measured trends for both fatigue and ultimate loads.« less

Assessment of Wind Turbine Component Loads Under Yaw-Offset Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Damiani, Rick R.; Dana, Scott; Annoni, Jennifer

Renewed interest in yaw control for wind turbine and power plants for wake redirection and load mitigation demands a clear understanding of the effects of running with skewed inflow. In this paper, we investigate the physics of yawed operations, building up the complexity from a simplified analytical treatment to more complex aeroelastic simulations. Results in terms of damage equivalent loads (DELs) and extreme loads under operating, misaligned conditions are compared to data collected from an instrumented, utility-scale wind turbine. The analysis shows that multiple factors are responsible for the DELs of the various components, and that airfoil aerodynamics, elastic characteristicsmore » of the rotor, and turbulence intensities are the primary drivers. Both fatigue and extreme loads are observed to have relatively complex trends with yaw offsets, which can change depending on the wind-speed regime. As a result, good agreement is found between predicted and measured trends for both fatigue and ultimate loads.« less

Community seroprevalence survey for yaws and trachoma in the Western Division of Fiji

PubMed Central

Cocks, Naomi; Rainima-Qaniuci, Merelesita; Yalen, Chelsea; Macleod, Colin; Nakolinivalu, Apisalome; Migchelsen, Stephanie; Roberts, Chrissy h.; Butcher, Robert; Kama, Mike; Mabey, David; Marks, Michael

2016-01-01

Background Both yaws and trachoma are endemic in several countries in the Pacific. In co-endemic countries there may be potential synergies between both control programmes. Methods We undertook a cluster randomised trachoma and yaws seroprevalence survey of children in the Western Division of Fiji. Children were examined for skin lesions consistent with active yaws. A dried blood spot was collected which was tested using the Treponema pallidum particle agglutination (TPPA) test and an ELISA to detect antibodies against Pgp3. Results A total of 607 children from 305 households across 23 villages were recruited into the survey. On skin examination, no child had clinical evidence of yaws, and the TPPA assay was negative in all children (0%, 95% CI 0.0–0.6). The seroprevalence of Pgp3 antibodies was 20.9% (95% CI 17.8–24.6%). Discussion In this study there was neither clinical nor serological evidence that transmission of yaws was ongoing. The Pgp3 seroprevalence pattern was consistent with either low level transmission of ocular Chlamydia trachomatis or exposure to C. trachomatis in the birth canal which is consistent with a survey conducted in the same region in 2013. These data suggest neither yaws nor ocular chlamydia infection are a significant public health problem in the Western Division of Fiji. PMID:27852877

Community seroprevalence survey for yaws and trachoma in the Western Division of Fiji.

PubMed

Cocks, Naomi; Rainima-Qaniuci, Merelesita; Yalen, Chelsea; Macleod, Colin; Nakolinivalu, Apisalome; Migchelsen, Stephanie; Roberts, Chrissy H; Butcher, Robert; Kama, Mike; Mabey, David; Marks, Michael

2016-12-01

Both yaws and trachoma are endemic in several countries in the Pacific. In co-endemic countries there may be potential synergies between both control programmes. We undertook a cluster randomised trachoma and yaws seroprevalence survey of children in the Western Division of Fiji. Children were examined for skin lesions consistent with active yaws. A dried blood spot was collected which was tested using the Treponema pallidum particle agglutination (TPPA) test and an ELISA to detect antibodies against Pgp3. A total of 607 children from 305 households across 23 villages were recruited into the survey. On skin examination, no child had clinical evidence of yaws, and the TPPA assay was negative in all children (0%, 95% CI 0.0-0.6). The seroprevalence of Pgp3 antibodies was 20.9% (95% CI 17.8-24.6%). In this study there was neither clinical nor serological evidence that transmission of yaws was ongoing. The Pgp3 seroprevalence pattern was consistent with either low level transmission of ocular Chlamydia trachomatis or exposure to C. trachomatis in the birth canal which is consistent with a survey conducted in the same region in 2013. These data suggest neither yaws nor ocular chlamydia infection are a significant public health problem in the Western Division of Fiji. © The Author 2016. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene.

14 CFR 25.351 - Yaw maneuver conditions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Yaw maneuver conditions. 25.351 Section 25.351 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... airplane inertia forces. In computing the tail loads the yawing velocity may be assumed to be zero. (a...

14 CFR 25.351 - Yaw maneuver conditions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Yaw maneuver conditions. 25.351 Section 25.351 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... airplane inertia forces. In computing the tail loads the yawing velocity may be assumed to be zero. (a...

Yaws: 110 years after Castellani's discovery of Treponema pallidum subspecies pertenue.

PubMed

Stamm, Lola V

2015-07-01

Yaws is a neglected infectious disease that affects mostly children and adolescents living in poor, rural communities in humid, tropical areas of Africa, southeast Asia, and the Pacific Islands. The etiological agent of yaws, Treponema pallidum subspecies pertenue (T. pertenue), was discovered by Aldo Castellani in 1905 shortly after Schaudinn and Hoffmann discovered the etiological agent of syphilis, T. pallidum subspecies pallidum. The discovery of T. pertenue enabled the development of animal models and the identification of an effective antibiotic treatment (i.e., penicillin) for yaws. A World Health Organization (WHO) mass treatment campaign from 1952 to 1964 reduced the global burden of yaws by 95%, but failed to eradicate this disease. Today, 110 years after Castellani's discovery of T. pertenue, yaws is again targeted for eradication. Recent advances in the treatment and diagnosis of yaws improve the likelihood of success this time. However, several challenges must be overcome to make the goal of yaws eradication attainable. © The American Society of Tropical Medicine and Hygiene.

Evaluation of a Rapid Diagnostic Test for Yaws Infection in a Community Surveillance Setting

PubMed Central

Marks, Michael; Goncalves, Adriana; Vahi, Ventis; Sokana, Oliver; Puiahi, Elliot; Zhang, Zaixing; Dalipanda, Tenneth; Bottomley, Christian; Mabey, David; Solomon, Anthony W.

2014-01-01

Yaws is a non-venereal treponemal infection caused by Treponema pallidum ssp. pertenue. The WHO has launched a worldwide control programme, which aims to eradicate yaws by 2020. The development of a rapid diagnostic test (RDT) for serological diagnosis in the isolated communities affected by yaws is a key requirement for the successful implementation of the WHO strategy. We conducted a study to evaluate the utility of the DPP test in screening for yaws, utilizing samples collected as part of a community prevalence survey conducted in the Solomon Islands. 415 serum samples were tested using both traditional syphilis serology (TPPA and quantitative RPR) and the Chembio DPP Syphilis Screen and Confirm RDT. We calculated the sensitivity and specificity of the RDT as compared to gold standard serology. The sensitivity of the RDT against TPPA was 58.5% and the specificity was 97.6%. The sensitivity of the RDT against RPR was 41.7% and the specificity was 95.2%. The sensitivity of the DPP was strongly related to the RPR titre with a sensitivity of 92.0% for an RPR titre of >1/16. Wider access to DPP testing would improve our understanding of worldwide yaws case reporting and the test may play a key role in assessing patients presenting with yaws like lesions in a post-mass drug administration (MDA) setting. PMID:25211018

Evaluation of a rapid diagnostic test for yaws infection in a community surveillance setting.

PubMed

Marks, Michael; Goncalves, Adriana; Vahi, Ventis; Sokana, Oliver; Puiahi, Elliot; Zhang, Zaixing; Dalipanda, Tenneth; Bottomley, Christian; Mabey, David; Solomon, Anthony W

2014-09-01

Yaws is a non-venereal treponemal infection caused by Treponema pallidum ssp. pertenue. The WHO has launched a worldwide control programme, which aims to eradicate yaws by 2020. The development of a rapid diagnostic test (RDT) for serological diagnosis in the isolated communities affected by yaws is a key requirement for the successful implementation of the WHO strategy. We conducted a study to evaluate the utility of the DPP test in screening for yaws, utilizing samples collected as part of a community prevalence survey conducted in the Solomon Islands. 415 serum samples were tested using both traditional syphilis serology (TPPA and quantitative RPR) and the Chembio DPP Syphilis Screen and Confirm RDT. We calculated the sensitivity and specificity of the RDT as compared to gold standard serology. The sensitivity of the RDT against TPPA was 58.5% and the specificity was 97.6%. The sensitivity of the RDT against RPR was 41.7% and the specificity was 95.2%. The sensitivity of the DPP was strongly related to the RPR titre with a sensitivity of 92.0% for an RPR titre of >1/16. Wider access to DPP testing would improve our understanding of worldwide yaws case reporting and the test may play a key role in assessing patients presenting with yaws like lesions in a post-mass drug administration (MDA) setting.

Vehicle handling and stability control by the cooperative control of 4WS and DYC

NASA Astrophysics Data System (ADS)

Shen, Huan; Tan, Yun-Sheng

2017-07-01

This paper proposes an integrated control system that cooperates with the four-wheel steering (4WS) and direct yaw moment control (DYC) to improve the vehicle handling and stability. The design works of the four-wheel steering and DYC control are based on sliding mode control. The integration control system produces the suitable 4WS angle and corrective yaw moment so that the vehicle tracks the desired yaw rate and sideslip angle. Considering the change of the vehicle longitudinal velocity that means the comfort of driving conditions, both the driving torque and braking torque are used to generate the corrective yaw moment. Simulation results show the effectiveness of the proposed control algorithm.

Expressions for the Total Yaw Angle

DTIC Science & Technology

2016-09-01

1. Introduction 1 2. Mathematical Notation 1 3. Total Yaw Expression Derivations 2 3.1 First Derivation 2 3.2 Second Derivation 4 3.3 Other...4 iv Approved for public release; distribution is unlimited. 1. Introduction The total yaw angle, γt , of a ballistic projectile is... elevation angles from spherical coordinates.∗ We again place point A at the end point of V. Now imagine a plane parallel to the y-z plane that includes

Effects of internal yaw-vectoring devices on the static performance of a pitch-vectoring nonaxisymmetric convergent-divergent nozzle

NASA Technical Reports Server (NTRS)

Asbury, Scott C.

1993-01-01

An investigation was conducted in the static test facility of the Langley 16-Foot Transonic Tunnel to evaluate the internal performance of a nonaxisymmetric convergent divergent nozzle designed to have simultaneous pitch and yaw thrust vectoring capability. This concept utilized divergent flap deflection for thrust vectoring in the pitch plane and flow-turning deflectors installed within the divergent flaps for yaw thrust vectoring. Modifications consisting of reducing the sidewall length and deflecting the sidewall outboard were investigated as means to increase yaw-vectoring performance. This investigation studied the effects of multiaxis (pitch and yaw) thrust vectoring on nozzle internal performance characteristics. All tests were conducted with no external flow, and nozzle pressure ratio was varied from 2.0 to approximately 13.0. The results indicate that this nozzle concept can successfully generate multiaxis thrust vectoring. Deflection of the divergent flaps produced resultant pitch vector angles that, although dependent on nozzle pressure ratio, were nearly equal to the geometric pitch vector angle. Losses in resultant thrust due to pitch vectoring were small or negligible. The yaw deflectors produced resultant yaw vector angles up to 21 degrees that were controllable by varying yaw deflector rotation. However, yaw deflector rotation resulted in significant losses in thrust ratios and, in some cases, nozzle discharge coefficient. Either of the sidewall modifications generally reduced these losses and increased maximum resultant yaw vector angle. During multiaxis (simultaneous pitch and yaw) thrust vectoring, little or no cross coupling between the thrust vectoring processes was observed.

Diagrams of Spacecraft Reaction Control System (RCS) Function

NASA Image and Video Library

1964-01-13

S64-03506 (1964) --- Diagrams shows Gemini spacecraft functions of the thrusters in the Gemini spacecraft's re-entry control system. Thrusters may be fired in various combinations to cause yaw, roll and pitch.

The effect of large aspect ratio wing yaw on active separation control

NASA Astrophysics Data System (ADS)

Tewes, Philipp; Taubert, Lutz; Wygnanski, Israel

2014-11-01

The applicability of the boundary layer independence principle to turbulent boundary layers developing on infinitely yawed wings, suggested that active separation control might be carried out differently to the two presumably independent developing boundary layers. At low incidence or flap deflection the control of the spanwise component of the flow is effective provided the aggregate number of actuators is small. In this case the actuator jets provide jet-curtains that virtually eliminate the spanwise flow component of the flow in their vicinity. At higher incidence or flap deflection, the focus of the active separation control has to shift to the chordwise component that has to overcome a high adverse pressure gradient. The idea was proven experimentally on a flapped wing based on a NACA 0012 airfoil that could be swept back and forward while being suspended from a ceiling of a wind tunnel connected to a six-component balance. The experiments were carried out at Reynolds numbers varying between 300,000 and 500,000. The project was supported in part by a grant from AFOSR.

Mathematical Modeling of Programmatic Requirements for Yaws Eradication

PubMed Central

Mitjà, Oriol; Fitzpatrick, Christopher; Asiedu, Kingsley; Solomon, Anthony W.; Mabey, David C.W.; Funk, Sebastian

2017-01-01

Yaws is targeted for eradication by 2020. The mainstay of the eradication strategy is mass treatment followed by case finding. Modeling has been used to inform programmatic requirements for other neglected tropical diseases and could provide insights into yaws eradication. We developed a model of yaws transmission varying the coverage and number of rounds of treatment. The estimated number of cases arising from an index case (basic reproduction number [R0]) ranged from 1.08 to 3.32. To have 80% probability of achieving eradication, 8 rounds of treatment with 80% coverage were required at low estimates of R0 (1.45). This requirement increased to 95% at high estimates of R0 (2.47). Extending the treatment interval to 12 months increased requirements at all estimates of R0. At high estimates of R0 with 12 monthly rounds of treatment, no combination of variables achieved eradication. Models should be used to guide the scale-up of yaws eradication. PMID:27983500

A wind-tunnel investigation of wind-turbine wakes in different yawed and loading conditions

NASA Astrophysics Data System (ADS)

Bastankhah, Majid; Porté-Agel, Fernando

2015-04-01

Wind-turbine wakes have negative effects on wind-farm performance. They are associated with: (a) the velocity deficit, which reduces the generated power of downwind turbines; and (b) the turbulence level, which increases the fatigue loads on downwind turbines. Controlling the yaw angle of turbines can potentially improve the performance of wind farms by deflecting the wake away from downwind turbines. However, except for few studies, wakes of yawed turbines still suffer from the lack of systematic research. To fill this research gap, we performed wind-tunnel experiments in the recirculating boundary-layer wind tunnel at the WIRE Laboratory of EPFL to better understand the wakes of yawed turbines. High-resolution stereoscopic particle image-velocimetry (S-PIV) was used to measure three velocity components in a horizontal plane located downwind of a horizontal-axis, three-blade model turbine. A servo-controller was connected to the DC generator of the turbine, which allowed us to apply different loadings. The power and thrust coefficients of the turbine were also measured for each case. These power and thrust measurements together with the highly-resolved flow measurements enabled us to study different wake characteristics such as the energy entrainment from the outer flow into the wake, the wake deflection and the helicoidal tip vortices for yawed turbines.

Correction of contaminated yaw rate signal and estimation of sensor bias for an electric vehicle under normal driving conditions

NASA Astrophysics Data System (ADS)

Zhang, Guoguang; Yu, Zitian; Wang, Junmin

2017-03-01

Yaw rate is a crucial signal for the motion control systems of ground vehicles. Yet it may be contaminated by sensor bias. In order to correct the contaminated yaw rate signal and estimate the sensor bias, a robust gain-scheduling observer is proposed in this paper. First of all, a two-degree-of-freedom (2DOF) vehicle lateral and yaw dynamic model is presented, and then a Luenberger-like observer is proposed. To make the observer more applicable to real vehicle driving operations, a 2DOF vehicle model with uncertainties on the coefficients of tire cornering stiffness is employed. Further, a gain-scheduling approach and a robustness enhancement are introduced, leading to a robust gain-scheduling observer. Sensor bias detection mechanism is also designed. Case studies are conducted using an electric ground vehicle to assess the performance of signal correction and sensor bias estimation under difference scenarios.

Occurrence of congenital, cardiovascular, visceral, neurologic, and neuro-ophthalmologic complications in late yaws: a theme for future research.

PubMed

Román, G C; Román, L N

1986-01-01

Late lesions of yaws are thought to be limited to skin, bones and joints, without congenital, visceral, or central nervous system (CNS) involvement. However, the treponemes isolated from patients with yaws, endemic syphilis, and venereal syphilis are genetically identical subspecies of Treponema pallidum. The controversy surrounding distinctions between syphilis and yaws is presented in its historical context, and reports of congenital, visceral, and CNS complications of yaws are reviewed. Isolation of treponemes from aqueous humor, as well as CSF abnormalities in 24.9% of 902 patients with yaws, indicate the existence of CNS involvement. The high prevalence of tropical myeloneuropathies of unknown origin discovered in areas of previous treponemal endemicity, particularly in Jamaica and Colombia, may represent late complications of yaws. Careful analysis of the collected evidence indicates that potential sequelae of yaws include congenital, visceral, and tertiary CNS lesions identical to those of venereal syphilis. The current worldwide resurgence of endemic treponematoses provides an unparalleled opportunity to settle conclusively questions still unanswered regarding the natural history of these infections.

Preliminary Study Using Forward Reaction Control System Jets During Space Shuttle Entry

NASA Technical Reports Server (NTRS)

Restrepo, Carolina; Valasek, John

2006-01-01

Failure or degradation of the flight control system, or hull damage, can lead to loss of vehicle control during entry. Possible failure scenarios are debris impact and wing damage that could result in a large aerodynamic asymmetry which cannot be trimmed out without additional yaw control. Currently the space shuttle uses aerodynamic control surfaces and Reaction Control System jets to control attitude. The forward jets are used for orbital maneuvering only, while the aft jets are used for yaw control during entry. This paper develops a controller for using the forward reaction control system jets as an additional control during entry, and assesses its value and feasibility during failure situations. Forward-aft jet blending logic is created, and implemented on a simplified model of the space shuttle entry flight control system. The model is validated and verified on the nonlinear, six degree-of-freedom Shuttle Engineering Simulator. A rudimentary human factors study was undertaken using the forward cockpit simulator at Johnson Space Center, to assess flying qualities of the new system and pilot workload. Results presented in the paper show that the combination of forward and aft jets provides useful additional yaw control, in addition to potential fuel savings and the ability to balance the use of the fuel in the forward and aft tanks to meet availability constraints of both forward and aft fuel tanks. Piloted simulation studies indicated that using both sets of jets while flying a damaged space shuttle reduces pilot workload, and makes the vehicle more responsive.

A piloted simulation investigation of yaw dynamics requirements for turreted gun use in low-level helicopter air combat

NASA Technical Reports Server (NTRS)

Decker, William A.; Morris, Patrick M.; Williams, Jeffrey N.

1988-01-01

A piloted, fixed-base simulation study was conducted to investigate the handling qualities requirements for helicopter air-to-air combat using turreted guns in the near-terrain environment. The study used a version of the helicopter air combat system developed at NASA Ames Research Center for one-on-one air combat. The study focused on the potential trade-off between gun angular movement capability and required yaw axis response. Experimental variables included yaw axis response frequency and damping and the size of the gun-movement envelope. A helmet position and sighting system was used for pilot control of gun aim. Approximately 340 simulated air combat engagements were evaluated by pilots from the Army and industry. Results from the experiment indicate that a highly-damped, high frequency yaw response was desired for Level I handling qualities. Pilot preference for those characteristics became more pronounced as gun turret movement was restricted; however, a stable, slow-reacting platform could be used with a large turret envelope. Most pilots preferred to engage with the opponent near the own-ship centerline. Turret elevation restriction affected the engagement more than azimuth restrictions.

Static investigation of several yaw vectoring concepts on nonaxisymmetric nozzles

NASA Technical Reports Server (NTRS)

Mason, M. L.; Berrier, B. L.

1985-01-01

A test has been conducted in the static test facility of the Langley 16-Foot Transonic Tunnel to determine the flow-turning capability and the effects on nozzle internal performance of several yaw vectoring concepts. Nonaxisymmetric convergent-divergent nozzles with throat areas simulating dry and afterburning power settings and single expansion ramp nozzles with a throat area simulating a dry power setting were modified for yaw thrust vectoring. Forward-thrust and pitch-vectored nozzle configurations were tested with each yaw vectoring concept. Four basic yaw vectoring concepts were investigated on the nonaxisymmetric convergent-divergent nozzles: (1) translating sidewall; (2) downstream (of throat) flaps; (3) upstream (of throat) port/flap; and (4) powered rudder. Selected combinations of the rudder with downstream flaps or upstream port/flap were also tested. A single yaw vectoring concept, post-exit flaps, was investigated on the single expansion ramp nozzles. All testing was conducted at static (no external flow) conditions and nozzle pressure ratios varied from 2.0 up to 10.0.

Heat generation in Aircraft tires under yawed rolling conditions

NASA Technical Reports Server (NTRS)

Dodge, Richard N.; Clark, Samuel K.

1987-01-01

An analytical model was developed for approximating the internal temperature distribution in an aircraft tire operating under conditions of yawed rolling. The model employs an assembly of elements to represent the tire cross section and treats the heat generated within the tire as a function of the change in strain energy associated with predicted tire flexure. Special contact scrubbing terms are superimposed on the symmetrical free rolling model to account for the slip during yawed rolling. An extensive experimental program was conducted to verify temperatures predicted from the analytical model. Data from this program were compared with calculation over a range of operating conditions, namely, vertical deflection, inflation pressure, yaw angle, and direction of yaw. Generally the analytical model predicted overall trends well and correlated reasonably well with individual measurements at locations throughout the cross section.

Development of mining guidance and control systems

NASA Technical Reports Server (NTRS)

1979-01-01

New fundamental interface sensor concepts were identified and investigated including tabulation of the physical and performance characteristics of two new interface detector concepts: - natural background radiation and magnetic spin resonance. Studies of guidance and control techniques for the longwall miner identified three basic systems for use in automated/remote controlled longwall mining. The following projects were initiated: system study which will more completely define the longwall guidance and control system design concepts; integration of the various control functions (vertical, yaw, and roll); and hardware technical requirements.

The evolutionary origin of jaw yaw in mammals

PubMed Central

Grossnickle, David M.

2017-01-01

Theria comprises all but three living mammalian genera and is one of the most ecologically pervasive clades on Earth. Yet, the origin and early history of therians and their close relatives (i.e., cladotherians) remains surprisingly enigmatic. A critical biological function that can be compared among early mammal groups is mastication. Morphometrics and modeling analyses of the jaws of Mesozoic mammals indicate that cladotherians evolved musculoskeletal anatomies that increase mechanical advantage during jaw rotation around a dorsoventrally-oriented axis (i.e., yaw) while decreasing the mechanical advantage of jaw rotation around a mediolaterally-oriented axis (i.e., pitch). These changes parallel molar transformations in early cladotherians that indicate their chewing cycles included significant transverse movement, likely produced via yaw rotation. Thus, I hypothesize that cladotherian molar morphologies and musculoskeletal jaw anatomies evolved concurrently with increased yaw rotation of the jaw during chewing cycles. The increased transverse movement resulting from yaw rotation may have been a crucial evolutionary prerequisite for the functionally versatile tribosphenic molar morphology, which underlies the molars of all therians and is retained by many extant clades. PMID:28322334

Challenges and key research questions for yaws eradication.

PubMed

Marks, Michael; Mitjà, Oriol; Vestergaard, Lasse S; Pillay, Allan; Knauf, Sascha; Chen, Cheng-Yen; Bassat, Quique; Martin, Diana L; Fegan, David; Taleo, Fasihah; Kool, Jacob; Lukehart, Sheila; Emerson, Paul M; Solomon, Anthony W; Ye, Tun; Ballard, Ronald C; Mabey, David C W; Asiedu, Kingsley B

2015-10-01

Yaws is endemic in west Africa, southeast Asia, and the Pacific region. To eradicate yaws by 2020, WHO has launched a campaign of mass treatment with azithromycin. Progress has been made towards achievement of this ambitious goal, including the validation of point-of-care and molecular diagnostic tests and piloting of the strategy in several countries, including Ghana, Vanuatu, and Papua New Guinea. Gaps in knowledge need to be addressed to allow refinement of the eradication strategy. Studies exploring determinants of the spatial distribution of yaws are needed to help with the completion of baseline mapping. The finding that Haemophilus ducreyi causes lesions similar to yaws is particularly important and further work is needed to assess the effect of azithromycin on these lesions. The integration of diagnostic tests into different stages of the eradication campaign needs investigation. Finally, studies must be done to inform the optimum mass-treatment strategy for sustainable interruption of transmission. Copyright © 2015 World Health Organization. Published by Elsevier Ltd/Inc/BV. All rights reserved. Published by Elsevier Ltd.. All rights reserved.

Parametric study of a simultaneous pitch/yaw thrust vectoring single expansion ramp nozzle

NASA Technical Reports Server (NTRS)

Schirmer, Alberto W.; Capone, Francis J.

1989-01-01

In the course of the last eleven years, the concept of thrust vectoring has emerged as a promising method of enhancing aircraft control capabilities in post-stall flight incursions during combat. In order to study the application of simultaneous pitch and yaw vectoring to single expansion ramp nozzles, a static test was conducted in the NASA-Langley 16 foot transonic tunnel. This investigation was based on internal performance data provided by force, mass flow and internal pressure measurements at nozzle pressure ratios up to 8. The internal performance characteristics of the nozzle were studied for several combinations of six different parameters: yaw vectoring angle, pitch vectoring angle, upper ramp cutout, sidewall hinge location, hinge inclination angle and sidewall containment. Results indicated a 2-to- 3-percent decrease in resultant thrust ratio with vectoring in either pitch or yaw. Losses were mostly associated with the turning of supersonic flow. Resultant thrust ratios were also decreased by sideways expansion of the jet. The effects of cutback corners in the upper ramp and lower flap on performance were small. Maximum resultant yaw vector angles, about half of the flap angle, were achieved for the configuration with the most forward hinge location.

A new formulation of the understeer coefficient to relate yaw torque and vehicle handling

NASA Astrophysics Data System (ADS)

Bucchi, F.; Frendo, F.

2016-06-01

The handling behaviour of vehicles is an important property for its relation to performance and safety. In 1970s, Pacejka did the groundwork for an objective analysis introducing the handling diagram and the understeer coefficient. In more recent years, the understeer concept is still mentioned but the handling is actively managed by direct yaw control (DYC). In this paper an accurate analysis of the vehicle handling is carried out, considering also the effect of drive forces. This analysis brings to a new formulation of the understeer coefficient, which is almost equivalent to the classical one, but it can be obtained by quasi-steady-state manoeuvres. In addition, it relates the vehicle yaw torque to the understeer coefficient, filling up the gap between the classical handling approach and DYC. A multibody model of a Formula SAE car is then used to perform quasi-steady-state simulations in order to verify the effectiveness of the new formulation. Some vehicle set-ups and wheel drive arrangements are simulated and the results are discussed. In particular, the handling behaviours of the rear wheel drive (RWD) and the front wheel drive (FWD) architectures are compared, finding an apparently surprising result: for the analysed vehicle the FWD is less understeering than for RWD. The relation between the yaw torque and the understeer coefficient allows to understand this behaviour and opens-up the possibility for different yaw control strategies.

A static investigation of yaw vectoring concepts on two-dimensional convergent-divergent nozzles

NASA Technical Reports Server (NTRS)

Berrier, B. L.; Mason, M. L.

1983-01-01

The flow-turning capability and nozzle internal performance of yaw-vectoring nozzle geometries were tested in the NASA Langley 16-ft Transonic wind tunnel. The concept was investigated as a means of enhancing fighter jet performance. Five two-dimensional convergent-divergent nozzles were equipped for yaw-vectoring and examined. The configurations included a translating left sidewall, left and right sidewall flaps downstream of the nozzle throat, left sidewall flaps or port located upstream of the nozzle throat, and a powered rudder. Trials were also run with 20 deg of pitch thrust vectoring added. The feasibility of providing yaw-thrust vectoring was demonstrated, with the largest yaw vector angles being obtained with sidewall flaps downstream of the nozzle primary throat. It was concluded that yaw vector designs that scoop or capture internal nozzle flow provide the largest yaw-vector capability, but decrease the thrust the most.

Targeted presurgical decompensation in patients with yaw-dependent facial asymmetry

PubMed Central

Kim, Kyung-A; Lee, Ji-Won; Park, Jeong-Ho; Kim, Byoung-Ho; Ahn, Hyo-Won

2017-01-01

Facial asymmetry can be classified into the rolling-dominant type (R-type), translation-dominant type (T-type), yawing-dominant type (Y-type), and atypical type (A-type) based on the distorted skeletal components that cause canting, translation, and yawing of the maxilla and/or mandible. Each facial asymmetry type represents dentoalveolar compensations in three dimensions that correspond to the main skeletal discrepancies. To obtain sufficient surgical correction, it is necessary to analyze the main skeletal discrepancies contributing to the facial asymmetry and then the skeletal-dental relationships in the maxilla and mandible separately. Particularly in cases of facial asymmetry accompanied by mandibular yawing, it is not simple to establish pre-surgical goals of tooth movement since chin deviation and posterior gonial prominence can be either aggravated or compromised according to the direction of mandibular yawing. Thus, strategic dentoalveolar decompensations targeting the real basal skeletal discrepancies should be performed during presurgical orthodontic treatment to allow for sufficient skeletal correction with stability. In this report, we document targeted decompensation of two asymmetry patients focusing on more complicated yaw-dependent types than others: Y-type and A-type. This may suggest a clinical guideline on the targeted decompensation in patient with different types of facial asymmetries. PMID:28523246

Targeted presurgical decompensation in patients with yaw-dependent facial asymmetry.

PubMed

Kim, Kyung-A; Lee, Ji-Won; Park, Jeong-Ho; Kim, Byoung-Ho; Ahn, Hyo-Won; Kim, Su-Jung

2017-05-01

Facial asymmetry can be classified into the rolling-dominant type (R-type), translation-dominant type (T-type), yawing-dominant type (Y-type), and atypical type (A-type) based on the distorted skeletal components that cause canting, translation, and yawing of the maxilla and/or mandible. Each facial asymmetry type represents dentoalveolar compensations in three dimensions that correspond to the main skeletal discrepancies. To obtain sufficient surgical correction, it is necessary to analyze the main skeletal discrepancies contributing to the facial asymmetry and then the skeletal-dental relationships in the maxilla and mandible separately. Particularly in cases of facial asymmetry accompanied by mandibular yawing, it is not simple to establish pre-surgical goals of tooth movement since chin deviation and posterior gonial prominence can be either aggravated or compromised according to the direction of mandibular yawing. Thus, strategic dentoalveolar decompensations targeting the real basal skeletal discrepancies should be performed during presurgical orthodontic treatment to allow for sufficient skeletal correction with stability. In this report, we document targeted decompensation of two asymmetry patients focusing on more complicated yaw-dependent types than others: Y-type and A-type. This may suggest a clinical guideline on the targeted decompensation in patient with different types of facial asymmetries.

Field Test Results of Using a Nacelle-Mounted Lidar for Improving Wind Energy Capture by Reducing Yaw Misalignment (Presentation)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleming, P.; Scholbrock, A.; Wright, A.

2014-11-01

Presented at the Nordic Wind Power Conference on November 5, 2014. This presentation describes field-test campaigns performed at the National Wind Technology Center in which lidar technology was used to improve the yaw alignment of the Controls Advanced Research Turbine (CART) 2 and CART3 wind turbines. The campaigns demonstrated that whether by learning a correction function to the nacelle vane, or by controlling yaw directly with the lidar signal, a significant improvement in power capture was demonstrated.

Cross-axis adaptation of torsional components in the yaw-axis vestibulo-ocular reflex

NASA Technical Reports Server (NTRS)

Trillenberg, P.; Shelhamer, M.; Roberts, D. C.; Zee, D. S.

2003-01-01

The three pairs of semicircular canals within the labyrinth are not perfectly aligned with the pulling directions of the six extraocular muscles. Therefore, for a given head movement, the vestibulo-ocular reflex (VOR) depends upon central neural mechanisms that couple the canals to the muscles with the appropriate functional gains in order to generate a response that rotates the eye the correct amount and around the correct axis. A consequence of these neural connections is a cross-axis adaptive capability, which can be stimulated experimentally when head rotation is around one axis and visual motion about another. From this visual-vestibular conflict the brain infers that the slow-phase eye movement is rotating around the wrong axis. We explored the capability of human cross-axis adaptation, using a short-term training paradigm, to determine if torsional eye movements could be elicited by yaw (horizontal) head rotation (where torsion is normally inappropriate). We applied yaw sinusoidal head rotation (+/-10 degrees, 0.33 Hz) and measured eye movement responses in the dark, and before and after adaptation. The adaptation paradigm lasted 45-60 min, and consisted of the identical head motion, coupled with a moving visual scene that required one of several types of eye movements: (1) torsion alone (-Roll); (2) horizontal/torsional, head right/CW torsion (Yaw-Roll); (3) horizontal/torsional, head right/CCW torsion (Yaw+Roll); (4) horizontal, vertical, torsional combined (Yaw+Pitch-Roll); and (5) horizontal and vertical together (Yaw+Pitch). The largest and most significant changes in torsional amplitude occurred in the Yaw-Roll and Yaw+Roll conditions. We conclude that short-term, cross-axis adaptation of torsion is possible but constrained by the complexity of the adaptation task: smaller torsional components are produced if more than one cross-coupling component is required. In contrast, vertical cross-axis components can be easily trained to occur with yaw head

Design fabrication and installation of a yaw measuring device

NASA Technical Reports Server (NTRS)

1979-01-01

The results of work performed in the development and testing of a yaw measuring device are summarized. A review of the yaw measurement method; and the techniques and hardware needed for its implementation are presented. A description and summary of the tests performed at the U.S. Bureau of Mines Bruceton facility are included. Conclusions are summarized and recommendations for a unit capable of operation in a mine environment are presented.

F-15B ACTIVE - First supersonic yaw vectoring flight

NASA Technical Reports Server (NTRS)

1996-01-01

On Wednesday, April 24, 1996, the F-15 Advanced Control Technology for Integrated Vehicles (ACTIVE) aircraft achieved its first supersonic yaw vectoring flight at Dryden Flight Research Center, Edwards, California. ACTIVE is a joint NASA, U.S. Air Force, McDonnell Douglas Aerospace (MDA) and Pratt & Whitney (P&W) program. The team will assess performance and technology benefits during flight test operations. Current plans call for approximately 60 flights totaling 100 hours. 'Reaching this milestone is very rewarding. We hope to set some more records before we're through,' stated Roger W. Bursey, P&W's pitch-yaw balance beam nozzle (PYBBN) program manager. A pair of P&W PYBBNs vectored (horizontally side-to-side, pitch is up and down) the thrust for the MDA manufactured F-15 research aircraft. Power to reach supersonic speeds was provided by two high-performance F100-PW-229 engines that were modified with the multi-directional thrust vectoring nozzles. The new concept should lead to significant increases in performance of both civil and military aircraft flying at subsonic and supersonic speeds.

F-18 HARV yaw rate expansion flight #125 with Inverted Recovery

NASA Technical Reports Server (NTRS)

1991-01-01

NASA's Dryden Flight Research Center, Edwards, CA, used an F-18 Hornet fighter aircraft as its High Angle-of-Attack (Alpha) Research Vehicle (HARV) in a three-phased flight research program lasting from April 1987 until September 1996. The aircraft completed 385 research flights and demonstrated stabilized flight at angles of attack between 65 and 70 degrees using thrust vectoring vanes, a research flight control system, and (eventually) forebody strakes (hinged structures on the forward side of the fuselage to provide control by interacting with vortices, generated at high angles of attack, to create side forces). This combination of technologies provided carefree handling of a fighter aircraft in a part of the flight regime that was otherwise very dangerous. Flight research with the HARV increased our understanding of flight at high angles of attack (angle of the wings with respect to the direction in which the aircraft was heading), enabling designers of U.S. fighter aircraft to design airplanes that will fly safely in portions of the flight envelope that pilots previously had to avoid. Flight 125 with the HARV involved yaw rate expansion up to 50 degrees per second (moving the nose to the left or right at that rate). NASA research pilot Ed Schneider was the pilot, and the purpose of the flight was to look at the spin characteristics of the HARV. The sequence in this particular video clip includes the first and second maneuvers in the flight. On the first maneuver, the pilot attempted to achieve a yaw rate of 40 degrees per second and actually went to 47 degrees. The spin was oscillatory in pitch (up and down) and roll (rotating around the longitudinal axis). Recovery was normal. On the second maneuver of the flight in which Schneider tried to achieve a yaw rate of 40 degrees per second, the aircraft overshot to 54 degrees per second during an oscillatory spin. In the course of the recovery, the aircraft rolled after a large sideslip buildup. Moderate aft stick

Indirect adaptive output feedback control of a biorobotic AUV using pectoral-like mechanical fins.

PubMed

Naik, Mugdha S; Singh, Sahjendra N; Mittal, Rajat

2009-06-01

This paper treats the question of servoregulation of autonomous underwater vehicles (AUVs) in the yaw plane using pectoral-like mechanical fins. The fins attached to the vehicle have oscillatory swaying and yawing motion. The bias angle of the angular motion of the fin is used for the purpose of control. Of course, the design approach considered here is applicable to AUVs for other choices of oscillation patterns of the fins, which produce periodic forces and moments. It is assumed that the vehicle parameters, hydrodynamic coefficients, as well the fin forces and moments are unknown. For the trajectory control of the yaw angle, a sampled-data indirect adaptive control system using output (yaw angle) feedback is derived. The control system has a modular structure, which includes a parameter identifier and a stabilizer. For the control law derivation, an internal model of the exosignals (reference signal (constant or ramp) and constant disturbance) is included. Unlike the direct adaptive control scheme, the derived control law is applicable to minimum as well as nonminimum phase biorobotic AUVs (BAUVs). This is important, because for most of the fin locations on the vehicle, the model is a nonminimum phase. In the closed-loop system, the yaw angle trajectory tracking error converges to zero and the remaining state variables remain bounded. Simulation results are presented which show that the derived modular control system accomplishes precise set point yaw angle control and turning maneuvers in spite of the uncertainties in the system parameters using only yaw angle feedback.

Microprocessor control system for 200-kilowatt Mod-OA wind turbines

NASA Technical Reports Server (NTRS)

Nyland, T. W.; Birchenough, A. G.

1982-01-01

The microprocessor system and program used to control the operation of the 200-kW Mod-OA wind turbines is described. The system is programmed to begin startup and shutdown sequences automatically and to control yaw motion. Rotor speed and power output are controlled with integral and proportional control of the blade pitch angle. Included in the report are a description of the hardware and a discussion of the software programming technique. A listing of the PL/M software program is given.

Lockheed L-1101 avionic flight control redundant systems

NASA Technical Reports Server (NTRS)

Throndsen, E. O.

1976-01-01

The Lockheed L-1011 automatic flight control systems - yaw stability augmentation and automatic landing - are described in terms of their redundancies. The reliability objectives for these systems are discussed and related to in-service experience. In general, the availability of the stability augmentation system is higher than the original design requirement, but is commensurate with early estimates. The in-service experience with automatic landing is not sufficient to provide verification of Category 3 automatic landing system estimated availability.

Design of integrated pitch axis for autopilot/autothrottle and integrated lateral axis for autopilot/yaw damper for NASA TSRV airplane using integral LQG methodology

NASA Technical Reports Server (NTRS)

Kaminer, Isaac; Benson, Russell A.; Coleman, Edward E.; Ebrahimi, Yaghoob S.

1990-01-01

Two designs are presented for control systems for the NASA Transport System Research Vehicle (TSRV) using integral Linear Quadratic Gaussian (LQG) methodology. The first is an integrated longitudinal autopilot/autothrottle design and the second design is an integrated lateral autopilot/yaw damper/sideslip controller design. It is shown that a systematic top-down approach to a complex design problem combined with proper application of modern control synthesis techniques yields a satisfactory solution in a reasonable period of time.

Quantification of wing and body kinematics in connection to torque generation during damselfly yaw turn

NASA Astrophysics Data System (ADS)

Zeyghami, Samane; Bode-Oke, Ayodeji T.; Dong, HaiBo

2017-01-01

This study provides accurate measurements of the wing and body kinematics of three different species of damselflies in free yaw turn flights. The yaw turn is characterized by a short acceleration phase which is immediately followed by an elongated deceleration phase. Most of the heading change takes place during the latter stage of the flight. Our observations showed that yaw turns are executed via drastic rather than subtle changes in the kinematics of all four wings. The motion of the inner and outer wings were found to be strongly linked through their orientation as well as their velocities with the inner wings moving faster than the outer wings. By controlling the pitch angle and wing velocity, a damselfly adjusts the angle of attack. The wing angle of attack exerted the strongest influence on the yaw torque, followed by the flapping and deviation velocities of the wings. Moreover, no evidence of active generation of counter torque was found in the flight data implying that deceleration and stopping of the maneuver is dominated by passive damping. The systematic analysis carried out on the free flight data advances our understanding of the mechanisms by which these insects achieve their observed maneuverability. In addition, the inspiration drawn from this study can be employed in the design of low frequency flapping wing micro air vehicles (MAV's).

Differential Canard deflection for generation of yawing moment on the X-31 with and without the vertical tail. M.S. Thesis - George Washington Univ.

NASA Technical Reports Server (NTRS)

Whiting, Matthew Robert

1996-01-01

The feasibility of augmenting the available yaw control power on the X-31 through differential deflection of the canard surfaces was studied as well as the possibility of using differential canard control to stabilize the X-31 with its vertical tail removed. Wind-tunnel tests and the results of departure criteria and linear analysis showed the destabilizing effect of the reduction of the vertical tail on the X-31. Wind-tunnel testing also showed that differential canard deflection was capable of generating yawing moments of roughly the same magnitude as the thrust vectoring vanes currently in place on the X-31 in the post-stall regime. Analysis showed that the X-31 has sufficient aileron roll control power that with the addition of differential canard as a yaw controller, the wind-axis roll accelerations will remain limited by yaw control authority. It was demonstrated, however, that pitch authority may actually limit the maximum roll rate which can be sustained. A drop model flight test demonstrated that coordinated, wind axis rolls could be performed with roll rates as high as 50 deg/sec (full scale equivalent) at 50 deg angle of attack. Another drop model test was conducted to assess the effect of vertical tail reduction, and an analysis of using differential canard deflection to stabilize the tailless X-31 was performed. The results of six-degree-of-freedom, non-linear simulation tests were correlated with the drop model flights. Simulation studies then showed that the tailless X-31 could be controlled at angles of attack at or above 20 deg using differential canard as the only yaw controller.

Vehicle dynamics control by using a three-dimensional stabilizer pendulum system

NASA Astrophysics Data System (ADS)

Goodarzi, A.; Naghibian, M.; Choodan, D.; Khajepour, A.

2016-12-01

Active safety systems of a vehicle normally work well on tyre-road interactions, however, these systems deteriorate in performance on low-friction road conditions. To combat this effect, an innovative idea for the yaw moment and roll dynamic control is presented in this paper. This idea was inspired by the chase and run dynamics animals like cheetahs in the nature; cheetahs have the ability to swerve while running at very high speeds. A cheetah controls its dynamics by rotating its long tail. A three-dimensional stabilizer pendulum system (3D-SPS) resembles the rotational motion of the tail of a cheetah to improve the stability and safety of a vehicle. The idea has been developed in a stand-alone 3D stabilizer pendulum system as well as in an integrated control system, which consists of an ordinary differential braking direct yaw control (DYC) and active steering control that is assisted by the 3D-SPS. The performance of the proposed 3D-SPS has been evaluated over a wide range of handling manoeuvres by using a comprehensive numerical simulation. The results show the advantage of 3D-SPS over conventional control approaches, which are ineffective on low-friction road conditions and high lateral acceleration manoeuvres. It should however be noted that the best vehicle dynamics performance is obtained when an integrated 3D-SPS and DYC and AFS is utilised.

Wind tunnel measurements of wake structure and wind farm power for actuator disk model wind turbines in yaw

NASA Astrophysics Data System (ADS)

Howland, Michael; Bossuyt, Juliaan; Kang, Justin; Meyers, Johan; Meneveau, Charles

2016-11-01

Reducing wake losses in wind farms by deflecting the wakes through turbine yawing has been shown to be a feasible wind farm control approach. In this work, the deflection and morphology of wakes behind a wind turbine operating in yawed conditions are studied using wind tunnel experiments of a wind turbine modeled as a porous disk in a uniform inflow. First, by measuring velocity distributions at various downstream positions and comparing with prior studies, we confirm that the nonrotating wind turbine model in yaw generates realistic wake deflections. Second, we characterize the wake shape and make observations of what is termed a "curled wake," displaying significant spanwise asymmetry. Through the use of a 100 porous disk micro-wind farm, total wind farm power output is studied for a variety of yaw configurations. Strain gages on the tower of the porous disk models are used to measure the thrust force as a substitute for turbine power. The frequency response of these measurements goes up to the natural frequency of the model and allows studying the spatiotemporal characteristics of the power output under the effects of yawing. This work has been funded by the National Science Foundation (Grants CBET-113380 and IIA-1243482, the WINDINSPIRE project). JB and JM are supported by ERC (ActiveWindFarms, Grant No. 306471).

Prevalence of Active and Latent Yaws in the Solomon Islands 18 Months after Azithromycin Mass Drug Administration for Trachoma

PubMed Central

Sokana, Oliver; Nachamkin, Eli; Puiahi, Elliot; Kilua, Georgina; Pillay, Allan; Bottomley, Christian; Solomon, Anthony W.; Mabey, David C.

2016-01-01

Introduction Both yaws and trachoma are endemic in the Pacific. Mass treatment with azithromycin is the mainstay of the WHO strategy for both the eradication of yaws and the elimination of trachoma as a public health problem, but the dose recommended for trachoma is lower than that for yaws. In countries where both diseases are endemic, there is a potential for synergy between yaws and trachoma control programs if mass treatment with the lower dose of azithromycin was shown to be effective for the treatment of yaws. In an earlier study, we demonstrated a profound reduction in the clinical and serological prevalence of yaws following a single round of mass treatment with azithromycin 20 mg/kg undertaken for the purposes of trachoma elimination. Methods This survey was conducted 18 months following a single round of azithromycin mass treatment in the same communities in which we had conducted our previous six-month follow-up survey. We examined children aged 1–14 years and took blood and lesion samples for yaws diagnosis using the Treponema pallidum particle agglutination assay (TPPA) and the non-treponemal Rapid Plasma Reagin (RPR) test. Results A total of 1,284 children were enrolled in the study. Amongst children aged 5–14 years, 223 had a positive TPPA (27.5%, 95% CI 13.6–47.7%). The TPPA seroprevalence amongst this age group did not differ significantly from either our pre-mass treatment survey or our initial follow-up survey. Thirty-five children had positive TPPA and positive RPR (4.3%, 95% CI 2.1–8.7%), and this did not differ significantly from our initial post-mass drug administration (MDA) follow-up survey (4.3% versus 3.5%, p = 0.43) but remained significantly lower than our initial pre-MDA survey (4.3% vs 21.7%, p <0.0001). Village-level MDA coverage was strongly associated with dual-seropositivity (p = 0.005). Amongst children aged 1–4 years, 16 had a positive TPPA (3.5%, 95% CI 1.6–7.1%). This did not differ significantly from the

Prevalence of Active and Latent Yaws in the Solomon Islands 18 Months after Azithromycin Mass Drug Administration for Trachoma.

PubMed

Marks, Michael; Sokana, Oliver; Nachamkin, Eli; Puiahi, Elliot; Kilua, Georgina; Pillay, Allan; Bottomley, Christian; Solomon, Anthony W; Mabey, David C

2016-08-01

Both yaws and trachoma are endemic in the Pacific. Mass treatment with azithromycin is the mainstay of the WHO strategy for both the eradication of yaws and the elimination of trachoma as a public health problem, but the dose recommended for trachoma is lower than that for yaws. In countries where both diseases are endemic, there is a potential for synergy between yaws and trachoma control programs if mass treatment with the lower dose of azithromycin was shown to be effective for the treatment of yaws. In an earlier study, we demonstrated a profound reduction in the clinical and serological prevalence of yaws following a single round of mass treatment with azithromycin 20 mg/kg undertaken for the purposes of trachoma elimination. This survey was conducted 18 months following a single round of azithromycin mass treatment in the same communities in which we had conducted our previous six-month follow-up survey. We examined children aged 1-14 years and took blood and lesion samples for yaws diagnosis using the Treponema pallidum particle agglutination assay (TPPA) and the non-treponemal Rapid Plasma Reagin (RPR) test. A total of 1,284 children were enrolled in the study. Amongst children aged 5-14 years, 223 had a positive TPPA (27.5%, 95% CI 13.6-47.7%). The TPPA seroprevalence amongst this age group did not differ significantly from either our pre-mass treatment survey or our initial follow-up survey. Thirty-five children had positive TPPA and positive RPR (4.3%, 95% CI 2.1-8.7%), and this did not differ significantly from our initial post-mass drug administration (MDA) follow-up survey (4.3% versus 3.5%, p = 0.43) but remained significantly lower than our initial pre-MDA survey (4.3% vs 21.7%, p <0.0001). Village-level MDA coverage was strongly associated with dual-seropositivity (p = 0.005). Amongst children aged 1-4 years, 16 had a positive TPPA (3.5%, 95% CI 1.6-7.1%). This did not differ significantly from the seroprevalence in this age group that had been

14 CFR 29.351 - Yawing conditions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Yawing conditions. 29.351 Section 29.351 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... furnishing the reacting inertia forces; and (2) Maximum main rotor speed. (b) To produce the load required in...

14 CFR 27.351 - Yawing conditions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Yawing conditions. 27.351 Section 27.351 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... reacting inertia forces; and (2) Maximum main rotor speed. (b) To produce the load required in paragraph (a...

14 CFR 27.351 - Yawing conditions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Yawing conditions. 27.351 Section 27.351 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... reacting inertia forces; and (2) Maximum main rotor speed. (b) To produce the load required in paragraph (a...

14 CFR 29.351 - Yawing conditions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Yawing conditions. 29.351 Section 29.351 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... furnishing the reacting inertia forces; and (2) Maximum main rotor speed. (b) To produce the load required in...

Behavior of aircraft antiskid breaking systems on dry and wet runway surfaces: A slip-ratio-controlled system with ground speed reference from unbraked nose wheel

NASA Technical Reports Server (NTRS)

Tanner, J. A.; Stubbs, S. M.

1977-01-01

An experimental investigation was conducted at the Langley aircraft landing loads and traction facility to study the braking and cornering response of a slip ratio controlled aircraft antiskid braking system with ground speed reference derived from an unbraked nose wheel. The investigation, conducted on dry and wet runway surfaces, utilized one main gear wheel, brake, and tire assembly of a DC-9 series 10 airplane. During maximum braking, the average ratio of the drag force friction coefficient developed by the antiskid system to the maximum drag force friction coefficient available was higher on the dry surface than on damp and flooded surfaces, and was reduced with lighter vertical loads, higher yaw angles, and when new tire treads were replaced by worn treads. Similarly, the average ratio of side force friction coefficient developed by the tire under antiskid control to the maximum side force friction coefficient available to a freely rolling yawed tire decreased with increasing yaw angle, generally increased with ground speed, and decreased when tires with new treads were replaced by those with worn treads.

Wind Tunnel Investigation of Fuselage Stability in Yaw with Various Arrangements of Fins

NASA Technical Reports Server (NTRS)

Hoggard, H Page, Jr

1940-01-01

An investigation was made in the 7-by-10 foot wind tunnel to determine the effects of dorsal-type fins and various arrangements of fins on the aerodynamic characteristics of a streamline circular fuselage. Comparative plots of the aerodynamic characteristics of the fuselage alone and the fuselage with various fin arrangements are given to show their effects on coefficients of yawing moment, drag, and lateral force. Results are also given for one case in which a rear fin on a circular fuselage was faired with modeling clay to obtain a fuselage shape with the same side elevation as the fuselage with the unfaired fin but with an elliptical cross section over the rearward portion of the fuselage. The results indicated that fin area to the rear of the center of gravity of the fuselage was beneficial in reducing the magnitude of the unstable yawing moments at large angles of yaw; whereas, fin area forward of the center of gravity was harmful. The dorsal-type fin was more effective for increasing the yawing stability of the fuselage than was a smoothly faired rearward portion with the same side elevation as the fuselage with the unfaired dorsal type fin. The minimum drag coefficient and the slope of the curve of yawing-moment coefficient of the fuselage at zero yaw were unaffected by the addition of the fins, within the experimental accuracy of the tests.

Estimation of longitudinal force, lateral vehicle speed and yaw rate for four-wheel independent driven electric vehicles

NASA Astrophysics Data System (ADS)

Chen, Te; Xu, Xing; Chen, Long; Jiang, Haobing; Cai, Yingfeng; Li, Yong

2018-02-01

Accurate estimation of longitudinal force, lateral vehicle speed and yaw rate is of great significance to torque allocation and stability control for four-wheel independent driven electric vehicle (4WID-EVs). A fusion method is proposed to estimate the longitudinal force, lateral vehicle speed and yaw rate for 4WID-EVs. The electric driving wheel model (EDWM) is introduced into the longitudinal force estimation, the longitudinal force observer (LFO) is designed firstly based on the adaptive high-order sliding mode observer (HSMO), and the convergence of LFO is analyzed and proved. Based on the estimated longitudinal force, an estimation strategy is then presented in which the strong tracking filter (STF) is used to estimate lateral vehicle speed and yaw rate simultaneously. Finally, co-simulation via Carsim and Matlab/Simulink is carried out to demonstrate the effectiveness of the proposed method. The performance of LFO in practice is verified by the experiment on chassis dynamometer bench.

Wind tunnel tests of a free yawing downwind wind turbine

NASA Astrophysics Data System (ADS)

Verelst, D. R. S.; Larsen, T. J.; van Wingerden, J. W.

2014-12-01

This research paper presents preliminary results on a behavioural study of a free yawing downwind wind turbine. A series of wind tunnel tests was performed at the TU Delft Open Jet Facility with a three bladed downwind wind turbine and a rotor radius of 0.8 meters. The setup includes an off the shelf three bladed hub, nacelle and generator on which relatively flexible blades are mounted. The tower support structure has free yawing capabilities provided at the base. A short overview on the technical details of the experiment is given as well as a brief summary of the design process. The discussed test cases show that the turbine is stable while operating in free yawing conditions. Further, the effect of the tower shadow passage on the blade flapwise strain measurement is evaluated. Finally, data from the experiment is compared with preliminary simulations using DTU Wind Energy's aeroelastic simulation program HAWC2.

PAB3D Simulations of a Nozzle with Fluidic Injection for Yaw Thrust-Vector Control

NASA Technical Reports Server (NTRS)

Deere, Karen A.

1998-01-01

An experimental and computational study was conducted on an exhaust nozzle with fluidic injection for yaw thrust-vector control. The nozzle concept was tested experimentally in the NASA Langley Jet Exit Test Facility (JETF) at nozzle pressure ratios up to 4 and secondary fluidic injection flow rates up to 15 percent of the primary flow rate. Although many injection-port geometries and two nozzle planforms (symmetric and asymmetric) were tested experimentally, this paper focuses on the computational results of the more successful asymmetric planform with a slot injection port. This nozzle concept was simulated with the Navier-Stokes flow solver, PAB3D, invoking the Shih, Zhu, and Lumley algebraic Reynolds stress turbulence model (ASM) at nozzle pressure ratios (NPRs) of 2,3, and 4 with secondary to primary injection flow rates (w(sub s)/w(sub p)) of 0, 2, 7 and 10 percent.

Where the Road Ends, Yaws Begins? The Cost-effectiveness of Eradication versus More Roads

PubMed Central

Fitzpatrick, Christopher; Asiedu, Kingsley; Jannin, Jean

2014-01-01

Introduction A disabling and disfiguring disease that “begins where the road ends”, yaws is targeted by WHO for eradication by the year 2020. The global campaign is not yet financed. To evaluate yaws eradication within the context of the post-2015 development agenda, we perform a somewhat allegorical cost-effectiveness analysis of eradication, comparing it to a counterfactual in which we simply wait for more roads (the end of poverty). Methods We use evidence from four yaws eradication pilot sites and other mass treatment campaigns to set benchmarks for the cost of eradication in 12 known endemic countries. We construct a compartmental model of long-term health effects to 2050. Conservatively, we attribute zero cost to the counterfactual and allow for gradual exit of the susceptible (at risk) population by road (poverty reduction). We report mean, 5th and 95th centile estimates to reflect uncertainty about costs and effects. Results Our benchmark for the economic cost of yaws eradication is uncertain but not high –US$ 362 (75–1073) million in 12 countries. Eradication would cost US$ 26 (4.2–78) for each year of life lived without disability or disfigurement due to yaws, or US$ 324 (47–936) per disability-adjusted life year (DALY). Excluding drugs, existing staff and assets, the financial cost benchmark is US$ 213 (74–522) million. The real cost of waiting for more roads (poverty reduction) would be 13 (7.3–20) million years of life affected by early-stage yaws and 2.3 (1.1–4.2) million years of life affected by late-stage yaws. Discussion Endemic countries need financing to begin implementing and adapting global strategy to local conditions. Donations of drugs and diagnostics could reduce cost to the public sector and catalyze financing. Resources may be harnessed from the extractive industries. Yaws eradication should be seen as complementary to universal health coverage and shared prosperity on the post-2015 development agenda. PMID:25255131

Development of a Multilocus Sequence Typing (MLST) scheme for Treponema pallidum subsp. pertenue: Application to yaws in Lihir Island, Papua New Guinea

PubMed Central

Godornes, Charmie; Giacani, Lorenzo; Barry, Alyssa E.; Mitja, Oriol

2017-01-01

Background Yaws is a neglected tropical disease, caused by Treponema pallidum subsp. pertenue. The disease causes chronic lesions, primarily in young children living in remote villages in tropical climates. As part of a global yaws eradication campaign initiated by the World Health Organization, we sought to develop and evaluate a molecular typing method to distinguish different strains of T. pallidum subsp. pertenue for disease control and epidemiological purposes. Methods and principal findings Published genome sequences of strains of T. pallidum subsp. pertenue and pallidum were compared to identify polymorphic genetic loci among the strains. DNA from a number of existing historical Treponema isolates, as well as a subset of samples from yaws patients collected in Lihir Island, Papua New Guinea, were analyzed using these targets. From these data, three genes (tp0548, tp0136 and tp0326) were ultimately selected to give a high discriminating capability among the T. pallidum subsp. pertenue samples tested. Intragenic regions of these three target genes were then selected to enhance the discriminating capability of the typing scheme using short readily amplifiable loci. This 3-gene multilocus sequence typing (MLST) method was applied to existing historical human yaws strains, the Fribourg-Blanc simian isolate, and DNA from 194 lesion swabs from yaws patients on Lihir Island, Papua New Guinea. Among all samples tested, fourteen molecular types were identified, seven of which were found in patient samples and seven among historical isolates or DNA. Three types (JG8, TD6, and SE7) were predominant on Lihir Island. Conclusions This MLST approach allows molecular typing and differentiation of yaws strains. This method could be a useful tool to complement epidemiological studies in regions where T. pallidum subsp. pertenue is prevalent with the overall goals of improving our understanding of yaws transmission dynamics and helping the yaws eradication campaign to succeed

Maximization of the annual energy production of wind power plants by optimization of layout and yaw-based wake control: Maximization of wind plant AEP by optimization of layout and wake control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gebraad, Pieter; Thomas, Jared J.; Ning, Andrew

This paper presents a wind plant modeling and optimization tool that enables the maximization of wind plant annual energy production (AEP) using yaw-based wake steering control and layout changes. The tool is an extension of a wake engineering model describing the steady-state effects of yaw on wake velocity profiles and power productions of wind turbines in a wind plant. To make predictions of a wind plant's AEP, necessary extensions of the original wake model include coupling it with a detailed rotor model and a control policy for turbine blade pitch and rotor speed. This enables the prediction of power productionmore » with wake effects throughout a range of wind speeds. We use the tool to perform an example optimization study on a wind plant based on the Princess Amalia Wind Park. In this case study, combined optimization of layout and wake steering control increases AEP by 5%. The power gains from wake steering control are highest for region 1.5 inflow wind speeds, and they continue to be present to some extent for the above-rated inflow wind speeds. The results show that layout optimization and wake steering are complementary because significant AEP improvements can be achieved with wake steering in a wind plant layout that is already optimized to reduce wake losses.« less

Combined pitching and yawing motion of airplanes

NASA Technical Reports Server (NTRS)

Baranoff, A V; Hopf, L

1931-01-01

This report treats the following problems: The beginning of the investigated motions is always a setting of the lateral controls, i.e., the rudder or the ailerons. Now, the first interesting question is how the motion would proceed if these settings were kept unchanged for some time; and particularly, what upward motion would set in, how soon, and for how long, since therein lie the dangers of yawing. Two different motions ensue with a high rate of turn and a steep down slope of flight path in both but a marked difference in angle of attack and consequently different character in the resultant aerodynamic forces: one, the "corkscrew" dive at normal angle, and the other, the "spin" at high angle.

Low-speed wind-tunnel investigation of a porous forebody and nose strakes for yaw control of a multirole fighter aircraft

NASA Technical Reports Server (NTRS)

Fears, Scott P.

1995-01-01

Low-speed wind-tunnel tests were conducted in the Langley 12-Foot Low-Speed Tunnel on a model of the Boeing Multirole Fighter (BMRF) aircraft. This single-seat, single-engine configuration was intended to be an F-16 replacement that would incorporate many of the design goals and advanced technologies of the F-22. Its mission requirements included supersonic cruise without afterburner, reduced observability, and the ability to attack both air-to-air and air-to-ground targets. So that it would be effective in all phases of air combat, the ability to maneuver at angles of attack up to and beyond maximum lift was also desired. Traditional aerodynamic yaw controls, such as rudders, are typically ineffective at these higher angles of attack because they are usually located in the wake from the wings and fuselage. For this reason, this study focused on investigating forebody-mounted controls that produces yawing moments by modifying the strong vortex flowfield being shed from the forebody at high angles of attack. Two forebody strakes were tested that varied in planform and chordwise location. Various patterns of porosity in the forebody skin were also tested that differed in their radial coverage and chordwise location. The tests were performed at a dynamic pressure of 4 lb/ft(exp 2) over an angle-of-attack range of -4 deg to 72 deg and a sideslip range of -10 deg to 10 deg. Static force data, static pressures on the surface of the forebody, and videotapes of flow-visualization using laser-illuminated smoke were obtained.

Postural responses to yaw rotation of support surface.

PubMed

Chen, Chiung-Ling; Lou, Shu-Zon; Wu, Hong-Wen; Wu, Shyi-Kuen; Yeung, Kwok-Tak; Su, Fong-Chin

2013-02-01

The purposes of this study were to investigate EMG and kinematic responses to yaw rotation of a support surface. Twenty people participated in four conditions, i.e., two velocities (240°/s, 120°/s) and two amplitudes (30°, 15°). Longer latency and smaller muscle responses were induced for yaw rotation, and distal ankle and knee muscles were activated earlier than trunk and neck muscles. Joint kinematics demonstrated larger angular displacements in axial rotation. Velocity and amplitude did not affect onset latency or magnitude of muscle activation but had significant effects on joint movements and COM displacements. Preliminary information about normative data of healthy subjects was obtained, and questions were generated about optimal velocity and amplitude test protocols that require further investigation. Copyright © 2012 Elsevier B.V. All rights reserved.

Roll and Yaw of Paramecium swimming in a viscous fluid

NASA Astrophysics Data System (ADS)

Jung, Sunghwan; Jana, Saikat; Giarra, Matt; Vlachos, Pavlos

2012-11-01

Many free-swimming microorganisms like ciliates, flagellates, and invertebrates exhibit helical trajectories. In particular, the Paramecium spirally swims along its anterior direction by the beating of cilia. Due to the oblique beating stroke of cilia, the Paramecium rotates along its long axis as it swims forward. Simultaneously, this long axis turns toward the oral groove side. Combined roll and yaw motions of Paramecium result in swimming along a spiral course. Using Particle Image Velocimetry, we measure and quantify the flow field and fluid stress around Paramecium. We will discuss how the non-uniform stress distribution around the body induces this yaw motion.

[The prevalence of yaws among the Aka in the Congo].

PubMed

Coldiron, M; Obvala, D; Mouniaman-Nara, I; Pena, J; Blondel, C; Porten, K

2013-05-01

This study, conducted in 2012 in two districts of the Congo (Bétou and Enyellé), screened for yaws (endemic treponemiasis) that could be treated by a single dose of azithromycin. The screening involved a clinical history, followed by a clinical examination of the children reporting dermatological problems. A rapid diagnostic test for treponema was performed on the children with suspicious lesions. Of 6215 children screened, 485 (7.8%) had such lesions; 480 (99.0%) of them had a rapid diagnostic test, and it was positive for 183 (38.1%). This so-called Morges strategy is aimed at eradicating yaws in endemic areas.

Propellers in yaw

NASA Technical Reports Server (NTRS)

Ribner, Herbert S

1945-01-01

It was realized as early as 1909 that a propeller in yaw develops a side force like that of a fin. In 1917, R. G. Harris expressed this force in terms of the torque coefficient for the unyawed propeller. Of several attempts to express the side force directly in terms of the shape of the blades, however, none has been completely satisfactory. An analysis that incorporates induction effects not adequately covered in previous work and that gives good agreement with experiment over a wide range of operating conditions is presented. The present analysis shows that the fin analogy may be extended to the form of the side-force expression and that the effective fin area may be taken as the projected side area of the propeller.

Wind-tunnel investigation at supersonic speeds of a remote-controlled canard missile with a free-rolling-tail brake torque system

NASA Technical Reports Server (NTRS)

Blair, A. B., Jr.

1985-01-01

Wind tunnel tests were conducted at Mach numbers 1.70, 2.16, and 2.86 to determine the static aerodynamic characteristics of a cruciform canard-controlled missile with fixed or free rolling tailfin afterbodies. Mechanical coupling effects of the free-rolling-tail afterbody were investigated by using an electronic electromagnetic brake system providing arbitrary tail-fin brake torques with continuous measurements of tail-to-mainframe torque and tail roll rate. Remote-controlled canards were deflected to provide pitch, yaw, and roll control. Results indicate that the induced rolling moment coefficients due to canard yaw control are reduced and linearized for the free-rolling-tail (free-tail) configuration. The canards of the latter provide conventional roll control for the entire angle-of-attack test range. For the free-tail configuration, the induced rolling moment coefficient due to canard yaw control increased and the canard roll control decreased with increases in brake torque, which simulated bearing friction torque. It appears that a compromise in regard to bearing friction, for example, low-cost bearings with some friction, may allow satisfactory free-tail aerodynamic characteristics that include reductions in adverse rolling-moment coefficients and lower tail roll rates.

Diagnostics for Yaws Eradication: Insights From Direct Next-Generation Sequencing of Cutaneous Strains of Treponema pallidum

PubMed Central

Marks, Michael; Fookes, Maria; Wagner, Josef; Butcher, Robert; Ghinai, Rosanna; Sokana, Oliver; Sarkodie, Yaw-Adu; Lukehart, Sheila A; Solomon, Anthony W; Mabey, David C W; Thomson, Nicholas

2018-01-01

Abstract Background Yaws-like chronic ulcers can be caused by Treponema pallidum subspecies pertenue, Haemophilus ducreyi, or other, still-undefined bacteria. To permit accurate evaluation of yaws elimination efforts, programmatic use of molecular diagnostics is required. The accuracy and sensitivity of current tools remain unclear because our understanding of T. pallidum diversity is limited by the low number of sequenced genomes. Methods We tested samples from patients with suspected yaws collected in the Solomon Islands and Ghana. All samples were from patients whose lesions had previously tested negative using the Centers for Disease Control and Prevention (CDC) diagnostic assay in widespread use. However, some of these patients had positive serological assays for yaws on blood. We used direct whole-genome sequencing to identify T. pallidum subsp pertenue strains missed by the current assay. Results From 45 Solomon Islands and 27 Ghanaian samples, 11 were positive for T. pallidum DNA using the species-wide quantitative polymerase chain reaction (PCR) assay, from which we obtained 6 previously undetected T. pallidum subsp pertenue whole-genome sequences. These show that Solomon Islands sequences represent distinct T. pallidum subsp pertenue clades. These isolates were invisible to the CDC diagnostic PCR assay, due to sequence variation in the primer binding site. Conclusions Our data double the number of published T. pallidum subsp pertenue genomes. We show that Solomon Islands strains are undetectable by the PCR used in many studies and by health ministries. This assay is therefore not adequate for the eradication program. Next-generation genome sequence data are essential for these efforts. PMID:29045605

Yawed-Landing Investigation of a Model of the Convair Y2-2 Airplane, TED No. NACA DE 363

NASA Technical Reports Server (NTRS)

Hoffman, Edward L.; Fisher, Lloyd J.

1950-01-01

A model of the Convair Y2-2 airplane was tested in Langley tank no. 2 to determine whether satisfactory stability in yawed landings was possible with a certain ventral fin. Free-body landings were made in smooth and rough water at two speeds and two rates of descent with the model yawed 15deg. The behavior of the model was determined by visual observations and from motion-picture re.cords. It was concluded that satisfactory stability was possible with the ventral fin as tested but that the characteristics of the model shock absorbers and the settings of the elevon control surfaces had an appreciable influence on behavior.

Effects of Mach Numbers on Side Force, Yawing Moment and Surface Pressure

NASA Astrophysics Data System (ADS)

Sohail, Muhammad Amjad; Muhammad, Zaka; Husain, Mukkarum; Younis, Muhammad Yamin

2011-09-01

In this research, CFD simulations are performed for air vehicle configuration to compute the side force effect and yawing moment coefficients variations at high angle of attack and Mach numbers. As the angle of attack is increased then lift and drag are increased for cylinder body configurations. But when roll angle is given to body then side force component is also appeared on the body which causes lateral forces on the body and yawing moment is also produced. Now due to advancement of CFD methods we are able to calculate these forces and moment even at supersonic and hypersonic speed. In this study modern CFD techniques are used to simulate the hypersonic flow to calculate the side force effects and yawing moment coefficient. Static pressure variations along the circumferential and along the length of the body are also calculated. The pressure coefficient and center of pressure may be accurately predicted and calculated. When roll angle and yaw angle is given to body then these forces becomes very high and cause the instability of the missile body with fin configurations. So it is very demanding and serious problem to accurately predict and simulate these forces for the stability of supersonic vehicles.

Progress in multirate digital control system design

NASA Technical Reports Server (NTRS)

Berg, Martin C.; Mason, Gregory S.

1991-01-01

A new methodology for multirate sampled-data control design based on a new generalized control law structure, two new parameter-optimization-based control law synthesis methods, and a new singular-value-based robustness analysis method are described. The control law structure can represent multirate sampled-data control laws of arbitrary structure and dynamic order, with arbitrarily prescribed sampling rates for all sensors and update rates for all processor states and actuators. The two control law synthesis methods employ numerical optimization to determine values for the control law parameters. The robustness analysis method is based on the multivariable Nyquist criterion applied to the loop transfer function for the sampling period equal to the period of repetition of the system's complete sampling/update schedule. The complete methodology is demonstrated by application to the design of a combination yaw damper and modal suppression system for a commercial aircraft.

Reusable Reentry Satellite (RRS) system design study. Phase B, appendix E: Attitude control system study

NASA Technical Reports Server (NTRS)

1991-01-01

A study which consisted of a series of design analyses for an Attitude Control System (ACS) to be incorporated into the Re-usable Re-entry Satellite (RRS) was performed. The main thrust of the study was associated with defining the control laws and estimating the mass and power requirements of the ACS needed to meet the specified performance goals. The analyses concentrated on the different on-orbit control modes which start immediately after the separation of the RRS from the launch vehicle. The three distinct on-orbit modes considered for these analyses are as follows: (1) Mode 1 - A Gravity Gradient (GG) three-axis stabilized spacecraft with active magnetic control; (2) Mode 2 - A GG stabilized mode with a controlled yaw rotation rate ('rotisserie') using three-axis magnetic control and also incorporating a 10 N-m-s momentum wheel along the (Z) yaw axis; and (3) Mode 3 - A spin stabilized mode of operation with the spin about the pitch (Y) axis, incorporating a 20 N-m-s momentum wheel along the pitch (Y) axis and attitude control via thrusters. To investigate the capabilities of the different controllers in these various operational modes, a series of computer simulations and trade-off analyses have been made to evaluate the achievable performance levels, and the necessary mass and power requirements.

Reusable Reentry Satellite (RRS) system design study. Phase B, appendix E: Attitude control system study

NASA Astrophysics Data System (ADS)

1991-02-01

A study which consisted of a series of design analyses for an Attitude Control System (ACS) to be incorporated into the Re-usable Re-entry Satellite (RRS) was performed. The main thrust of the study was associated with defining the control laws and estimating the mass and power requirements of the ACS needed to meet the specified performance goals. The analyses concentrated on the different on-orbit control modes which start immediately after the separation of the RRS from the launch vehicle. The three distinct on-orbit modes considered for these analyses are as follows: (1) Mode 1 - A Gravity Gradient (GG) three-axis stabilized spacecraft with active magnetic control; (2) Mode 2 - A GG stabilized mode with a controlled yaw rotation rate ('rotisserie') using three-axis magnetic control and also incorporating a 10 N-m-s momentum wheel along the (Z) yaw axis; and (3) Mode 3 - A spin stabilized mode of operation with the spin about the pitch (Y) axis, incorporating a 20 N-m-s momentum wheel along the pitch (Y) axis and attitude control via thrusters. To investigate the capabilities of the different controllers in these various operational modes, a series of computer simulations and trade-off analyses have been made to evaluate the achievable performance levels, and the necessary mass and power requirements.

A Synopsis of Yaw-Induction Techniques Used During Projectile Free-Flight Aerodynamics Experiments

DTIC Science & Technology

2013-03-01

the projectile exits the launch tube is often needed. Over the years, numerous yaw-induction techniques have been developed to deliberately...launch phase, and provide insight pertaining to their implementation and success based upon some quantitative results. 2. WORN TUBES AS YAW...disturbances are predominantly introduced while the projectile is still in bore or in transition (i.e., mechanically disengaged from the gun tube but not

Flight Behavior of an Asymmetric Body through Spark Range Experiments Using Roll-Yaw Resonance for Yaw Enhancement

DTIC Science & Technology

2015-07-01

free-flight experimental techniques were employed16,17 throughout the design cycle for these airframes to define the outer mold line and formulate...balloting and sabot discard. Tip-off due to balloting is likely small in this study due to the large contact surface of the plastic sabot against the...cycles or projectile without internal symmetry and yaw induction near muzzle) for better assessment. Set values of = −200 and

Diagnostics for Yaws Eradication: Insights From Direct Next-Generation Sequencing of Cutaneous Strains of Treponema pallidum.

PubMed

Marks, Michael; Fookes, Maria; Wagner, Josef; Butcher, Robert; Ghinai, Rosanna; Sokana, Oliver; Sarkodie, Yaw-Adu; Lukehart, Sheila A; Solomon, Anthony W; Mabey, David C W; Thomson, Nicholas

2018-03-05

Yaws-like chronic ulcers can be caused by Treponema pallidum subspecies pertenue, Haemophilus ducreyi, or other, still-undefined bacteria. To permit accurate evaluation of yaws elimination efforts, programmatic use of molecular diagnostics is required. The accuracy and sensitivity of current tools remain unclear because our understanding of T. pallidum diversity is limited by the low number of sequenced genomes. We tested samples from patients with suspected yaws collected in the Solomon Islands and Ghana. All samples were from patients whose lesions had previously tested negative using the Centers for Disease Control and Prevention (CDC) diagnostic assay in widespread use. However, some of these patients had positive serological assays for yaws on blood. We used direct whole-genome sequencing to identify T. pallidum subsp pertenue strains missed by the current assay. From 45 Solomon Islands and 27 Ghanaian samples, 11 were positive for T. pallidum DNA using the species-wide quantitative polymerase chain reaction (PCR) assay, from which we obtained 6 previously undetected T. pallidum subsp pertenue whole-genome sequences. These show that Solomon Islands sequences represent distinct T. pallidum subsp pertenue clades. These isolates were invisible to the CDC diagnostic PCR assay, due to sequence variation in the primer binding site. Our data double the number of published T. pallidum subsp pertenue genomes. We show that Solomon Islands strains are undetectable by the PCR used in many studies and by health ministries. This assay is therefore not adequate for the eradication program. Next-generation genome sequence data are essential for these efforts. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America.

Type-2 fuzzy logic control of a 2-DOF helicopter (TRMS system)

NASA Astrophysics Data System (ADS)

Zeghlache, Samir; Kara, Kamel; Saigaa, Djamel

2014-09-01

The helicopter dynamic includes nonlinearities, parametric uncertainties and is subject to unknown external disturbances. Such complicated dynamics involve designing sophisticated control algorithms that can deal with these difficulties. In this paper, a type 2 fuzzy logic PID controller is proposed for TRMS (twin rotor mimo system) control problem. Using triangular membership functions and based on a human operator experience, two controllers are designed to control the position of the yaw and the pitch angles of the TRMS. Simulation results are given to illustrate the effectiveness of the proposed control scheme.

A Study on Aircraft Engine Control Systems for Integrated Flight and Propulsion Control

NASA Astrophysics Data System (ADS)

Yamane, Hideaki; Matsunaga, Yasushi; Kusakawa, Takeshi; Yasui, Hisako

The Integrated Flight and Propulsion Control (IFPC) for a highly maneuverable aircraft and a fighter-class engine with pitch/yaw thrust vectoring is described. Of the two IFPC functions the aircraft maneuver control utilizes the thrust vectoring based on aerodynamic control surfaces/thrust vectoring control allocation specified by the Integrated Control Unit (ICU) of a FADEC (Full Authority Digital Electronic Control) system. On the other hand in the Performance Seeking Control (PSC) the ICU identifies engine's various characteristic changes, optimizes manipulated variables and finally adjusts engine control parameters in cooperation with the Engine Control Unit (ECU). It is shown by hardware-in-the-loop simulation that the thrust vectoring can enhance aircraft maneuverability/agility and that the PSC can improve engine performance parameters such as SFC (specific fuel consumption), thrust and gas temperature.

A Flight Control System Architecture for the NASA AirSTAR Flight Test Infrastructure

NASA Technical Reports Server (NTRS)

Murch, Austin M.

2008-01-01

A flight control system architecture for the NASA AirSTAR infrastructure has been designed to address the challenges associated with safe and efficient flight testing of research control laws in adverse flight conditions. The AirSTAR flight control system provides a flexible framework that enables NASA Aviation Safety Program research objectives, and includes the ability to rapidly integrate and test research control laws, emulate component or sensor failures, inject automated control surface perturbations, and provide a baseline control law for comparison to research control laws and to increase operational efficiency. The current baseline control law uses an angle of attack command augmentation system for the pitch axis and simple stability augmentation for the roll and yaw axes.

Comparative study on the wake deflection behind yawed wind turbine models

NASA Astrophysics Data System (ADS)

Schottler, Jannik; Mühle, Franz; Bartl, Jan; Peinke, Joachim; Adaramola, Muyiwa S.; Sætran, Lars; Hölling, Michael

2017-05-01

In this wind tunnel campaign, detailed wake measurements behind two different model wind turbines in yawed conditions were performed. The wake deflections were quantified by estimating the rotor-averaged available power within the wake. By using two different model wind turbines, the influence of the rotor design and turbine geometry on the wake deflection caused by a yaw misalignment of 30° could be judged. It was found that the wake deflections three rotor diameters downstream were equal while at six rotor diameters downstream insignificant differences were observed. The results compare well with previous experimental and numerical studies.

An Analytical Solution for Yaw Maneuver Optimization on the International Space Station and Other Orbiting Space Vehicles

NASA Technical Reports Server (NTRS)

Dobrinskaya, Tatiana

2015-01-01

This paper suggests a new method for optimizing yaw maneuvers on the International Space Station (ISS). Yaw rotations are the most common large maneuvers on the ISS often used for docking and undocking operations, as well as for other activities. When maneuver optimization is used, large maneuvers, which were performed on thrusters, could be performed either using control moment gyroscopes (CMG), or with significantly reduced thruster firings. Maneuver optimization helps to save expensive propellant and reduce structural loads - an important factor for the ISS service life. In addition, optimized maneuvers reduce contamination of the critical elements of the vehicle structure, such as solar arrays. This paper presents an analytical solution for optimizing yaw attitude maneuvers. Equations describing pitch and roll motion needed to counteract the major torques during a yaw maneuver are obtained. A yaw rate profile is proposed. Also the paper describes the physical basis of the suggested optimization approach. In the obtained optimized case, the torques are significantly reduced. This torque reduction was compared to the existing optimization method which utilizes the computational solution. It was shown that the attitude profiles and the torque reduction have a good match for these two methods of optimization. The simulations using the ISS flight software showed similar propellant consumption for both methods. The analytical solution proposed in this paper has major benefits with respect to computational approach. In contrast to the current computational solution, which only can be calculated on the ground, the analytical solution does not require extensive computational resources, and can be implemented in the onboard software, thus, making the maneuver execution automatic. The automatic maneuver significantly simplifies the operations and, if necessary, allows to perform a maneuver without communication with the ground. It also reduces the probability of command

A driver-adaptive stability control strategy for sport utility vehicles

NASA Astrophysics Data System (ADS)

Zhu, Shenjin; He, Yuping

2017-08-01

Conventional vehicle stability control (VSC) systems are designed for average drivers. For a driver with a good driving skill, the VSC systems may be redundant; for a driver with a poor driving skill, the VSC intervention may be inadequate. To increase safety of sport utility vehicles (SUVs), this paper proposes a novel driver-adaptive VSC (DAVSC) strategy based on scaling the target yaw rate commanded by the driver. The DAVSC system is adaptive to drivers' driving skills. More control effort would be exerted for drivers with poor driving skills, and vice versa. A sliding mode control (SMC)-based differential braking (DB) controller is designed using a three degrees of freedom (DOF) yaw-plane model. An eight DOF nonlinear yaw-roll model is used to simulate the SUV dynamics. Two driver models, namely longitudinal and lateral, are used to 'drive' the virtual SUV. By integrating the virtual SUV, the DB controller, and the driver models, the performance of the DAVSC system is investigated. The simulations demonstrate the effectiveness of the DAVSC strategy.

Attitude analysis of the Earth Radiation Budget Satellite (ERBS) yaw turn anomaly

NASA Technical Reports Server (NTRS)

Kronenwetter, J.; Phenneger, M.; Weaver, William L.

1988-01-01

The July 2 Earth Radiation Budget Satellite (ERBS) hydrazine thruster-controlled yaw inversion maneuver resulted in a 2.1 deg/sec attitude spin. This mode continued for 150 minutes until the spacecraft was inertially despun using the hydrazine thrusters. The spacecraft remained in a low-rate Y-axis spin of .06 deg/sec for 3 hours until the B-DOT control mode was activated. After 5 hours in this mode, the spacecraft Y-axis was aligned to the orbit normal, and the spacecraft was commanded to the mission mode of attitude control. This work presents the experience of real-time attitude determination support following analysis using the playback telemetry tape recorded for 7 hours from the start of the attitude control anomaly.

A wind-tunnel investigation of wind-turbine wakes in yawed conditions

NASA Astrophysics Data System (ADS)

Bastankhah, Majid; Porté-Agel, Fernando

2015-06-01

Wind-tunnel experiments were performed to study the performance of a model wind turbine and its wake characteristics in a boundary layer under different operating conditions, including different yaw angles and tip speed ratios. High-resolution particle image- velocimetry (PIV) was used to measure the three velocity components in a horizontal plane at hub height covering a broad streamwise range from upstream of the turbine to the far- wake region. Additionally, thrust and power coefficients of the turbine were measured under different conditions. These power and thrust measurements, together with the highly-resolved flow measurements, enabled us to systematically study different wake properties. The near-wake region is found to have a highly complex structure influenced by different factors such as tip speed ratio and wake rotation. In particular, for higher tip speed ratios, a noticeable speed-up region is observed in the central part of near wake, which greatly affects the flow distribution in this region. In this regard, the behavior of the near wake for turbines with similar thrust coefficients but different tip speed ratios can vary widely. In contrast, it is shown that the mean streamwise velocity in the far wake of the turbine with zero yaw angle has a self-similar Gaussian distribution, and the strength of wake in this region is consistent with the magnitude of the thrust coefficient. With increasing yaw angle, as expected, the power and thrust coefficients decrease, and the wake deflection increases. The measurements also reveal that, in addition to turbulent momentum flux, lateral mean momentum flux boosts the flow entrainment in only one side of the wake, which results in a faster wake recovery in that side. It is also found that the induced velocity upstream of a yawed turbine has a non-symmetric distribution, and its distribution is in agreement with the available model in the literature. Moreover, the results suggest that in order to accurately

Design development of the Apollo command and service module thrust vector attitude control systems

NASA Technical Reports Server (NTRS)

Peters, W. H.

1978-01-01

Development of the Apollo thrust vector control digital autopilot (TVC DAP) was summarized. This is the control system that provided pitch and yaw attitude control during velocity change maneuvers using the main rocket engine on the Apollo service module. A list of ten primary functional requirements for this control system are presented, each being subordinate to a more general requirement appearing earlier on the list. Development process functions were then identified and the essential information flow paths were explored. This provided some visibility into the particular NASA/contractor interface, as well as relationships between the many individual activities.

Development of a sensitivity analysis technique for multiloop flight control systems

NASA Technical Reports Server (NTRS)

Vaillard, A. H.; Paduano, J.; Downing, D. R.

1985-01-01

This report presents the development and application of a sensitivity analysis technique for multiloop flight control systems. This analysis yields very useful information on the sensitivity of the relative-stability criteria of the control system, with variations or uncertainties in the system and controller elements. The sensitivity analysis technique developed is based on the computation of the singular values and singular-value gradients of a feedback-control system. The method is applicable to single-input/single-output as well as multiloop continuous-control systems. Application to sampled-data systems is also explored. The sensitivity analysis technique was applied to a continuous yaw/roll damper stability augmentation system of a typical business jet, and the results show that the analysis is very useful in determining the system elements which have the largest effect on the relative stability of the closed-loop system. As a secondary product of the research reported here, the relative stability criteria based on the concept of singular values were explored.

Research developing closed loop roll control for magnetic balance systems

NASA Technical Reports Server (NTRS)

Covert, E. E.; Haldeman, C. W.

1981-01-01

Computer inputs were interfaced to the magnetic balance outputs to provide computer position control and data acquisition. The use of parameter identification of a means of determining dynamic characteristics was investigated. The thyraton and motor generator power supplies for the pitch and yaw degrees of freedom were repaired. Topics covered include: choice of a method for handling dynamic system data; applications to the magnetic balance; the computer interface; and wind tunnel tests, results, and error analysis.

Wind-tunnel investigation to determine the low speed yawing stability derivatives of a twin jet fighter model at high angles of attack

NASA Technical Reports Server (NTRS)

Coe, P. L., Jr.; Newsom, W. A., Jr.

1974-01-01

An investigation was conducted to determine the low-speed yawing stability derivatives of a twin-jet fighter airplane model at high angles of attack. Tests were performed in a low-speed tunnel utilizing variable-curvature walls to simulate pure yawing motion. The results of the study showed that at angles of attack below the stall the yawing derivatives were essentially independent of the yawing velocity and sideslip angle. However, at angles of attack above the stall some nonlinear variations were present and the derivatives were strongly dependent upon sideslip angle. The results also showed that the rolling moment due to yawing was primarily due to the wing-fuselage combination, and that at angles of attack below the stall both the vertical and horizontal tails produced significant contributions to the damping in yaw. Additionally, the tests showed that the use of the forced-oscillation data to represent the yawing stability derivatives is questionable, at high angles of attack, due to large effects arising from the acceleration in sideslip derivatives.

Inflight redesign of the IUE attitude control system

NASA Technical Reports Server (NTRS)

Femiano, M. D.

1986-01-01

The one- and two-gyro system designs of the International Ultraviolet Explorer (IUE) attitude control system (ACS) are examined. The inertial reference assembly that provides the primary attitude reference for IUE consists of six rate sensors which are single-axis rate integrating gyros. The gyros operate in a pulse rebalanced mode that produces an output pulse for 0.01 arcsec of motion about the input axis. The functions of the fine error sensor, fine sun sensor (FSS), the IUE reaction wheels, the onboard computer, and the hold/slew algorithm are described. The use of the hold/slew algorithm to compute the control voltage for the ACS based on the Kalman filter is studied. A two-gyro system was incorporated into IUE following gyro failure. The procedures for establishing attitude control with the two-gyro design based on the FSS is analyzed. The performance of the two-gyro system is evaluated; it is observed that the pitch and yaw gyro control is 0.24 arcsec and the control is sufficient to permit extended periods of observation.

Sensitivity analysis of automatic flight control systems using singular value concepts

NASA Technical Reports Server (NTRS)

Herrera-Vaillard, A.; Paduano, J.; Downing, D.

1985-01-01

A sensitivity analysis is presented that can be used to judge the impact of vehicle dynamic model variations on the relative stability of multivariable continuous closed-loop control systems. The sensitivity analysis uses and extends the singular-value concept by developing expressions for the gradients of the singular value with respect to variations in the vehicle dynamic model and the controller design. Combined with a priori estimates of the accuracy of the model, the gradients are used to identify the elements in the vehicle dynamic model and controller that could severely impact the system's relative stability. The technique is demonstrated for a yaw/roll damper stability augmentation designed for a business jet.

Behavior of aircraft antiskid braking systems on dry and wet runway surfaces. A slip-velocity-controlled, pressure-bias-modulated system

NASA Technical Reports Server (NTRS)

Stubbs, S. M.; Tanner, J. A.; Smith, E. G.

1979-01-01

The braking and cornering response of a slip velocity controlled, pressure bias modulated aircraft antiskid braking system is investigated. The investigation, conducted on dry and wet runway surfaces, utilized one main gear wheel, brake, and tire assembly of a McDonnell Douglas DC 9 series 10 airplane. The landing gear strut was replaced by a dynamometer. The parameters, which were varied, included the carriage speed, tire loading, yaw angle, tire tread condition, brake system operating pressure, and runway wetness conditions. The effects of each of these parameters on the behavior of the skid control system is presented. Comparisons between data obtained with the skid control system and data obtained from single cycle braking tests without antiskid protection are examined.

Comparative efficacy of low-dose versus standard-dose azithromycin for patients with yaws: a randomised non-inferiority trial in Ghana and Papua New Guinea.

PubMed

Marks, Michael; Mitjà, Oriol; Bottomley, Christian; Kwakye, Cynthia; Houinei, Wendy; Bauri, Mathias; Adwere, Paul; Abdulai, Abdul A; Dua, Fredrick; Boateng, Laud; Wangi, James; Ohene, Sally-Ann; Wangnapi, Regina; Simpson, Shirley V; Miag, Helen; Addo, Kennedy K; Basing, Laud A; Danavall, Damien; Chi, Kai H; Pillay, Allan; Ballard, Ronald; Solomon, Anthony W; Chen, Cheng Y; Bieb, Sibauk V; Adu-Sarkodie, Yaw; Mabey, David C W; Asiedu, Kingsley

2018-04-01

A dose of 30 mg/kg of azithromycin is recommended for treatment of yaws, a disease targeted for global eradication. Treatment with 20 mg/kg of azithromycin is recommended for the elimination of trachoma as a public health problem. In some settings, these diseases are co-endemic. We aimed to determine the efficacy of 20 mg/kg of azithromycin compared with 30 mg/kg azithromycin for the treatment of active and latent yaws. We did a non-inferiority, open-label, randomised controlled trial in children aged 6-15 years who were recruited from schools in Ghana and schools and the community in Papua New Guinea. Participants were enrolled based on the presence of a clinical lesion that was consistent with infectious primary or secondary yaws and a positive rapid diagnostic test for treponemal and non-treponemal antibodies. Participants were randomly assigned (1:1) to receive either standard-dose (30 mg/kg) or low-dose (20 mg/kg) azithromycin by a computer-generated random number sequence. Health-care workers assessing clinical outcomes in the field were not blinded to the patient's treatment, but investigators involved in statistical or laboratory analyses and the participants were blinded to treatment group. We followed up participants at 4 weeks and 6 months. The primary outcome was cure at 6 months, defined as lesion healing at 4 weeks in patients with active yaws and at least a four-fold decrease in rapid plasma reagin titre from baseline to 6 months in patients with active and latent yaws. Active yaws was defined as a skin lesion that was positive for Treponema pallidum ssp pertenue in PCR testing. We used a non-inferiority margin of 10%. This trial was registered with ClinicalTrials.gov, number NCT02344628. Between June 12, 2015, and July 2, 2016, 583 (65·1%) of 895 children screened were enrolled; 292 patients were assigned a low dose of azithromycin and 291 patients were assigned a standard dose of azithromycin. 191 participants had active yaws and 392 had presumed

14 CFR 25.499 - Nose-wheel yaw and steering.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Nose-wheel yaw and steering. 25.499 Section 25.499 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... inertia forces. (d) For other than the nose gear, its attaching structure, and the forward fuselage...

Community-based mass treatment with azithromycin for the elimination of yaws in Ghana-Results of a pilot study.

PubMed

Abdulai, Abdul Aziz; Agana-Nsiire, Patrick; Biney, Frank; Kwakye-Maclean, Cynthia; Kyei-Faried, Sardick; Amponsa-Achiano, Kwame; Simpson, Shirley Victoria; Bonsu, George; Ohene, Sally-Ann; Ampofo, William Kwabena; Adu-Sarkodie, Yaw; Addo, Kennedy Kwasi; Chi, Kai-Hua; Danavall, Damien; Chen, Cheng Y; Pillay, Allan; Sanz, Sergi; Tun, Ye; Mitjà, Oriol; Asiedu, Kingsley Bampoe; Ballard, Ronald C

2018-03-01

The WHO yaws eradication strategy consists of one round of total community treatment (TCT) of single-dose azithromycin with coverage of > 90%.The efficacy of the strategy to reduce the levels on infection has been demonstrated previously in isolated island communities in the Pacific region. We aimed to determine the efficacy of a single round of TCT with azithromycin to achieve a decrease in yaws prevalence in communities that are endemic for yaws and surrounded by other yaws-endemic areas. Surveys for yaws seroprevalence and prevalence of skin lesions were conducted among schoolchildren aged 5-15 years before and one year after the TCT intervention in the Abamkrom sub-district of Ghana. We used a cluster design with the schools as the primary sampling unit. Among 20 eligible primary schools in the sub district, 10 were assigned to the baseline survey and 10 to the post-TCT survey. The field teams conducted a physical examination for skin lesions and a dual point-of-care immunoassay for non-treponemal and treponemal antibodies of all children present at the time of the visit. We also undertook surveys with non-probabilistic sampling to collect lesion swabs for etiology and macrolide resistance assessment. At baseline 14,548 (89%) of 16,287 population in the sub-district received treatment during TCT. Following one round of TCT, the prevalence of dual seropositivity among all children decreased from 10.9% (103/943) pre-TCT to 2.2% (27/1211) post-TCT (OR 0.19; 95%CI 0.09-0.37). The prevalence of serologically confirmed skin lesions consistent with active yaws was reduced from 5.7% (54/943) pre-TCT to 0.6% (7/1211) post-TCT (OR 0.10; 95% CI 0.25-0.35). No evidence of resistance to macrolides against Treponema pallidum subsp. pertenue was seen. A single round of high coverage TCT with azithromycin in a yaws affected sub-district adjoining other endemic areas is effective in reducing the prevalence of seropositive children and the prevalence of early skin lesions

Community-based mass treatment with azithromycin for the elimination of yaws in Ghana—Results of a pilot study

PubMed Central

Abdulai, Abdul Aziz; Agana-Nsiire, Patrick; Biney, Frank; Kwakye-Maclean, Cynthia; Kyei-Faried, Sardick; Amponsa-Achiano, Kwame; Simpson, Shirley Victoria; Bonsu, George; Ohene, Sally-Ann; Ampofo, William Kwabena; Adu-Sarkodie, Yaw; Addo, Kennedy Kwasi; Chi, Kai-Hua; Danavall, Damien; Chen, Cheng Y.; Pillay, Allan; Sanz, Sergi; Tun, Ye; Mitjà, Oriol; Ballard, Ronald C.

2018-01-01

Introduction The WHO yaws eradication strategy consists of one round of total community treatment (TCT) of single-dose azithromycin with coverage of > 90%.The efficacy of the strategy to reduce the levels on infection has been demonstrated previously in isolated island communities in the Pacific region. We aimed to determine the efficacy of a single round of TCT with azithromycin to achieve a decrease in yaws prevalence in communities that are endemic for yaws and surrounded by other yaws-endemic areas. Methods Surveys for yaws seroprevalence and prevalence of skin lesions were conducted among schoolchildren aged 5–15 years before and one year after the TCT intervention in the Abamkrom sub-district of Ghana. We used a cluster design with the schools as the primary sampling unit. Among 20 eligible primary schools in the sub district, 10 were assigned to the baseline survey and 10 to the post-TCT survey. The field teams conducted a physical examination for skin lesions and a dual point-of-care immunoassay for non-treponemal and treponemal antibodies of all children present at the time of the visit. We also undertook surveys with non-probabilistic sampling to collect lesion swabs for etiology and macrolide resistance assessment. Results At baseline 14,548 (89%) of 16,287 population in the sub-district received treatment during TCT. Following one round of TCT, the prevalence of dual seropositivity among all children decreased from 10.9% (103/943) pre-TCT to 2.2% (27/1211) post-TCT (OR 0.19; 95%CI 0.09–0.37). The prevalence of serologically confirmed skin lesions consistent with active yaws was reduced from 5.7% (54/943) pre-TCT to 0.6% (7/1211) post-TCT (OR 0.10; 95% CI 0.25–0.35). No evidence of resistance to macrolides against Treponema pallidum subsp. pertenue was seen. Discussion A single round of high coverage TCT with azithromycin in a yaws affected sub-district adjoining other endemic areas is effective in reducing the prevalence of seropositive children

Parametric system identification of catamaran for improving controller design

NASA Astrophysics Data System (ADS)

Timpitak, Surasak; Prempraneerach, Pradya; Pengwang, Eakkachai

2018-01-01

This paper presents an estimation of simplified dynamic model for only surge- and yaw- motions of catamaran by using system identification (SI) techniques to determine associated unknown parameters. These methods will enhance the performance of designing processes for the motion control system of Unmanned Surface Vehicle (USV). The simulation results demonstrate an effective way to solve for damping forces and to determine added masses by applying least-square and AutoRegressive Exogenous (ARX) methods. Both methods are then evaluated according to estimated parametric errors from the vehicle’s dynamic model. The ARX method, which yields better estimated accuracy, can then be applied to identify unknown parameters as well as to help improving a controller design of a real unmanned catamaran.

Leading edge flap system for aircraft control augmentation

NASA Technical Reports Server (NTRS)

Rao, D. M. (Inventor)

1984-01-01

Traditional roll control systems such as ailerons, elevons or spoilers are least effective at high angles of attack due to boundary layer separation over the wing. This invention uses independently deployed leading edge flaps on the upper surfaces of vortex stabilized wings to shift the center of lift outboard. A rolling moment is created that is used to control roll in flight at high angles of attack. The effectiveness of the rolling moment increases linearly with angle of attack. No adverse yaw effects are induced. In an alternate mode of operation, both leading edge flaps are deployed together at cruise speeds to create a very effective airbrake without appreciable modification in pitching moment. Little trim change is required.

Enhanced Engine Control for Emergency Operation

NASA Technical Reports Server (NTRS)

Litt, Jonathan S.

2012-01-01

C-MAPSS40k engine simulation has been developed and is available to the public. The authenticity of the engine performance and controller enabled the development of realistic enhanced control modes through controller modification alone. Use of enhanced control modes improved stability and control of an impaired aircraft. - Fast Response is useful for manual manipulation of the throttles - Use of Fast Response improved stability as part of a yaw rate feedback system. - Use of Overthrust shortened takeoff distance, but was generally useful in flight, too. Initial lack of pilot familiarity resulted in discomfort, especially with yaw rate feedback, but that was the only drawback, overall the pilot found the enhanced modes very helpful.

Experimental investigation on the dissipative and elastic characteristics of a yaw colloidal damper destined to carbody suspension of a bullet train

NASA Astrophysics Data System (ADS)

Suciu, B.; Tomioka, T.

2016-09-01

Yaw damper represents a major source of excitation for flexural vibration of the railway carbody. In order to reduce transmissibility of such undesired excitation, yaw damper should allow for large force transmission at low working frequencies, but should behave as vibration isolator at high working frequencies. Unfortunately, the yaw oil damper (OD), which is nowadays in service, has poor intrinsic elastic capabilities and provides damping forces varying as a power function versus the piston speed. Since colloidal damper (CD) has intrinsic elastic capabilities and larger damping forces at lower excitation frequencies, it occurs as an attractive alternative solution to traditional yaw dampers. In this work, a yaw CD destined to carbody suspension of a bullet train was designed and manufactured; then, its dynamic characteristics, produced by both the frictional and colloidal effects, were evaluated from the experimental results, obtained during horizontal vibration tests, performed on a ball-screw shaker. Compared to the corresponding classical yaw OD, the trial yaw CD allowed for: weight reduction of 31.6%; large damping force, dissipated energy and spring constant at long piston stroke under low excitation frequency; low damping force, dissipated energy and spring constant at short piston stroke under high excitation frequency. Elastic properties were justified by introducing a model for the spring constant that included the effect of pore size distribution.

The spacecraft control laboratory experiment optical attitude measurement system

NASA Technical Reports Server (NTRS)

Welch, Sharon S.; Montgomery, Raymond C.; Barsky, Michael F.

1991-01-01

A stereo camera tracking system was developed to provide a near real-time measure of the position and attitude of the Spacecraft COntrol Laboratory Experiment (SCOLE). The SCOLE is a mockup of the shuttle-like vehicle with an attached flexible mast and (simulated) antenna, and was designed to provide a laboratory environment for the verification and testing of control laws for large flexible spacecraft. Actuators and sensors located on the shuttle and antenna sense the states of the spacecraft and allow the position and attitude to be controlled. The stereo camera tracking system which was developed consists of two position sensitive detector cameras which sense the locations of small infrared LEDs attached to the surface of the shuttle. Information on shuttle position and attitude is provided in six degrees-of-freedom. The design of this optical system, calibration, and tracking algorithm are described. The performance of the system is evaluated for yaw only.

Effect of yaw angle on steering forces for the lunar roving vehicle wheel

NASA Technical Reports Server (NTRS)

Green, A. J.

1974-01-01

A series of tests was conducted with a Lunar Roving Vehicle (LRV) wheel operating at yaw angles ranging from -5 to +90 deg. The load was varied from 42 to 82 lb (187 to 365 N), and the speed was varied from 3.5 to 10.0 ft/sec (1.07 to 3.05 m/sec). It was noted that speed had an effect on side thrust and rut depth. Side thrust, rut depth, and skid generally increased as the yaw angle increased. For the range of loads used, the effect of load on performance was not significant.

Computer program for post-flight evaluation of the control surface response for an attitude controlled missile

NASA Technical Reports Server (NTRS)

Knauber, R. N.

1982-01-01

A FORTRAN IV coded computer program is presented for post-flight analysis of a missile's control surface response. It includes preprocessing of digitized telemetry data for time lags, biases, non-linear calibration changes and filtering. Measurements include autopilot attitude rate and displacement gyro output and four control surface deflections. Simple first order lags are assumed for the pitch, yaw and roll axes of control. Each actuator is also assumed to be represented by a first order lag. Mixing of pitch, yaw and roll commands to four control surfaces is assumed. A pseudo-inverse technique is used to obtain the pitch, yaw and roll components from the four measured deflections. This program has been used for over 10 years on the NASA/SCOUT launch vehicle for post-flight analysis and was helpful in detecting incipient actuator stall due to excessive hinge moments. The program is currently set up for a CDC CYBER 175 computer system. It requires 34K words of memory and contains 675 cards. A sample problem presented herein including the optional plotting requires eleven (11) seconds of central processor time.

Targeted Treatment of Yaws With Household Contact Tracing: How Much Do We Miss?

PubMed Central

Dyson, Louise; Marks, Michael; Crook, Oliver M; Sokana, Oliver; Solomon, Anthony W; Bishop, Alex; Mabey, David C W; Hollingsworth, T Déirdre

2018-01-01

Abstract Yaws is a disabling bacterial infection found primarily in warm and humid tropical areas. The World Health Organization strategy mandates an initial round of total community treatment (TCT) with single-dose azithromycin followed either by further TCT or active case-finding and treatment of cases and their contacts (the Morges strategy). We sought to investigate the effectiveness of the Morges strategy. We employed a stochastic household model to study the transmission of infection using data collected from a pre-TCT survey conducted in the Solomon Islands. We used this model to assess the proportion of asymptomatic infections that occurred in households without active cases. This analysis indicated that targeted treatment of cases and their household contacts would miss a large fraction of asymptomatic infections (65%–100%). This fraction was actually higher at lower prevalences. Even assuming that all active cases and their households were successfully treated, our analysis demonstrated that at all prevalences present in the data set, up to 90% of (active and asymptomatic) infections would not be treated under household-based contact tracing. Mapping was undertaken as part of the study “Epidemiology of Yaws in the Solomon Islands and the Impact of a Trachoma Control Programme,” in September–October 2013. PMID:29140407

Advanced piloted aircraft flight control system design methodology. Volume 2: The FCX flight control design expert system

NASA Technical Reports Server (NTRS)

Myers, Thomas T.; Mcruer, Duane T.

1988-01-01

The development of a comprehensive and electric methodology for conceptual and preliminary design of flight control systems is presented and illustrated. The methodology is focused on the design states starting with the layout of system requirements and ending when some viable competing system architectures (feedback control structures) are defined. The approach is centered on the human pilot and the aircraft as both the sources of, and the keys to the solution of, many flight control problems. The methodology relies heavily on computational procedures which are highly interactive with the design engineer. To maximize effectiveness, these techniques, as selected and modified to be used together in the methodology, form a cadre of computational tools specifically tailored for integrated flight control system preliminary design purposes. The FCX expert system as presently developed is only a limited prototype capable of supporting basic lateral-directional FCS design activities related to the design example used. FCX presently supports design of only one FCS architecture (yaw damper plus roll damper) and the rules are largely focused on Class IV (highly maneuverable) aircraft. Despite this limited scope, the major elements which appear necessary for application of knowledge-based software concepts to flight control design were assembled and thus FCX represents a prototype which can be tested, critiqued and evolved in an ongoing process of development.

Correlation of forebody pressures and aircraft yawing moments on the X-29A aircraft at high angles of attack

NASA Technical Reports Server (NTRS)

Fisher, David F.; Richwine, David M.; Landers, Stephen

1992-01-01

In-flight pressure distributions at four fuselage stations on the forebody of the X-29A aircraft have been reported at angles of attack from 15 to 66 deg and at Mach numbers from 0.22 to 0.60. At angles of attack of 20 deg and higher, vortices shed from the nose strake caused suction peaks in the pressure distributions that generally increased in magnitude with angle of attack. Above 30 deg-angle of attack, the forebody pressure distributions became asymmetrical at the most forward station, while they remained nearly symmetrical until 50 to 55 deg-angle of attack for the aft stations. Between 59 to 66 deg-angle of attack, the asymmetry of the pressure distributions changed direction. Yawing moments for the forebody alone were obtained by integrating the forebody pressure distributions. At 45 deg-angle of attack, the aircraft yaws to the right and at 50 deg and higher, the aircraft yaws to the left. The forebody yawing moments correlated well with the aircraft left yawing moment at an angle of attack of 50 deg or higher. At a 45 deg-angle of attack, the forebody yawing moments did not correlate well with the aircraft yawing moment, but it is suggested that this was due to asymmetric pressures on the cockpit region of the fuselage which was not instrumented. The forebody was also shown to provide a positive component of directional stability of the aircraft at angles of attack of 25 deg or higher. A Mach number effect was noted at angles of attack of 30 deg or higher at the station where the nose strake was present. At this station, the suction peaks in the pressure distributions at the highest Mach number were reduced and much more symmetrical as compared to the lower Mach number pressure distributions.

Stagnation-point Heat Transfer to Blunt Shapes in Hypersonic Flight, Including Effects of Yaw

NASA Technical Reports Server (NTRS)

Eggers, A J , Jr; Hansen, C Frederick; Cunningham, Bernard E

1958-01-01

An approximate theory is developed for predicting the rate of heat transfer to the stagnation region of blunt bodies in hypersonic flight. Attention is focused on the case where wall temperature is small compared to stagnation temperature. The theoretical heat-transfer rate at the stagnation point of a hemispherical body is found to agree with available experimental data. The effect of yaw on heat transfer to a cylindrical stagnation region is treated at some length, and it is predicted that large yaw should cause sizable reductions in heat-transfer rate.

Experimental investigation of yawing-rolling coupling effects on unsteady aerodynamic characteristics of an aircraft

NASA Astrophysics Data System (ADS)

Shen, Lin; Huang, Da; Wu, Genxing

2018-05-01

In this paper, an aircraft model was tested in the wind tunnel with different degrees of yaw-roll coupling at different angles of attack. The dynamic increments of yawing and rolling moments are compared to study the coupling effects on damping characteristics. The characteristic time constants are calculated to study the changes of flow field structure related to coupling ratios. The damping characteristics and time lag effects of aerodynamic loads calculated by dynamic derivative method are also compared with experimental results to estimate the applicability of linear superposition principle at large angles of attack.

Differential Pressures on a Pitot-venturi and a Pitot-static Nozzle over 360 Degrees Pitch and Yaw

NASA Technical Reports Server (NTRS)

Bear, R M

1928-01-01

Measurements of the differential pressures on two navy air-speed nozzles, consisting of a Zahm type Pitot-Venturi tube and a SQ-16 two-pronged Pitot-static tube, in a tunnel air stream of fixed speed at various angles of pitch and yaw between 0 degrees and plus or minus 180 degrees. This shows for a range over -20 degrees to +20 degrees pitch and yaw, indicated air speeds varying very slightly over 2 per cent for the Zahm type and a maximum of about 5 per cent for the SQ-16 type from the calibrated speed at 0 degree. For both types of air-speed nozzle the indicated air speed increases slightly as the tubes are pitched or yawed several degrees from their normal 0 degrees altitude, attains a maximum around plus or minus 15 degrees to 25 degrees, declines rapidly therefrom as plus or minus 40 degrees is passed, to zero in the vicinity of plus or minus 70 degrees to 100 degrees, and thence fluctuates irregular from thereabouts to plus or minus 180 degrees. The complete variation in indicated air speed for the two tubes over 360 degree pitch and yaw is graphically portrayed in figures 9 and 10. For the same air speed and 0 degree pitch and yaw the differential pressure of the Zahm type Pitot-Venturi nozzle is about seven times that of the SQ-16 type two-prolonged Pitot-static nozzle.

Alcohol and disorientation-responses. VI, Effects of alcohol on eye movements and tracking performance during laboratory angular accelerations about the yaw and pitch axes.

DOT National Transportation Integrated Search

1972-12-01

Alcohol ingestion interferes with visual control of vestibular eye movements and thereby produces significant decrements in performance at a compensatory tracking task during oscillation about the yaw axis; significant or consistent decrements in per...

Some experiments on Yaw stability of wind turbines with various coning angles

NASA Technical Reports Server (NTRS)

Bundas, D.; Dugundji, J.

1981-01-01

A horizontal axis wind turbine was constructed to study the effect of coning angle on the yawing moments produced. Coning angles of 0 deg, +10 deg and -10 deg were studied in the upwind and downwind cases. Moment and rotational frequency of the blades at each yaw angle setting were taken. It was found that as the coning angle increased from -10 deg to +10 deg in either the upwind or downwind case the stability decreased. The downwind case was slightly more stable for all coning angles than was the upwind case. It is found that all the previous cases were stable for high rotation speeds, but at lower rotation speeds, they were all unstable and could not self start unless held in the wind.

The estimation of the rate of change of yawing moment with sideslip

NASA Technical Reports Server (NTRS)

Imlay, Frederick H

1938-01-01

Wind-tunnel data are presented on the rate of change of yawing moment with sideslip for tests of 9 complete airplane models, 20 fuselage shapes, and 3 wing models with various combinations of dihedral, sweepback, and twist. The data were collected during a survey of existing information, which was made to find a reliable method of computing the yawing moment due to sideslip. Important errors common to methods of computation used at present appear to be due to large interference effects, the investigation of which will undoubtedly require an extensive program of systematic wind-tunnel tests. At present it is necessary to place considerable reliance on past design experience in proportioning an airplane so as to obtain a reasonable degree of directional stability.

The Effect of Large Angles of Yaw on the Accuracy of Wing-Tip Yawmeters

NASA Technical Reports Server (NTRS)

Golden, Jacob

1942-01-01

The present method used by the NACA for the measurement of sideslip angles in flight involves the use of a device called the yawmeter. The operation of this instrument depends on the motion of a free-swinging vane which, mounted ahead of the wing tip, alines itself with the local wind direction. Because of the flow pattern about the airplane, the local wind direction at the yaw vane may be slightly different from the direction of the relative wind and the yaw-vane readings may be in error. This error is corrected by using half the difference between the readings of two vanes, one on each wing, for unyawed flight as a calibration constant. It is possible, however, that, because of the change in location of the vane with respect to the flow pattern at large angles of yaw, the constant obtained for unyawed flight may not apply. The present report covers power-off tests made in the free-flight tunnel to check the validity of this method.

Static thrust-vectoring performance of nonaxisymmetric convergent-divergent nozzles with post-exit yaw vanes. M.S. Thesis - George Washington Univ., Aug. 1988

NASA Technical Reports Server (NTRS)

Foley, Robert J.; Pendergraft, Odis C., Jr.

1991-01-01

A static (wind-off) test was conducted in the Static Test Facility of the 16-ft transonic tunnel to determine the performance and turning effectiveness of post-exit yaw vanes installed on two-dimensional convergent-divergent nozzles. One nozzle design that was previously tested was used as a baseline, simulating dry power and afterburning power nozzles at both 0 and 20 degree pitch vectoring conditions. Vanes were installed on these four nozzle configurations to study the effects of vane deflection angle, longitudinal and lateral location, size, and camber. All vanes were hinged at the nozzle sidewall exit, and in addition, some were also hinged at the vane quarter chord (double-hinged). The vane concepts tested generally produced yaw thrust vectoring angles much less than the geometric vane angles, for (up to 8 percent) resultant thrust losses. When the nozzles were pitch vectored, yawing effectiveness decreased as the vanes were moved downstream. Thrust penalties and yawing effectiveness both decreased rapidly as the vanes were moved outboard (laterally). Vane length and height changes increased yawing effectiveness and thrust ratio losses, while using vane camber, and double-hinged vanes increased resultant yaw angles by 50 to 100 percent.

Wake flow control using a dynamically controlled wind turbine

NASA Astrophysics Data System (ADS)

Castillo, Ricardo; Wang, Yeqin; Pol, Suhas; Swift, Andy; Hussain, Fazle; Westergaard, Carsten; Texas Tech University Team

2016-11-01

A wind tunnel based "Hyper Accelerated Wind Farm Kinematic-Control Simulator" (HAWKS) is being built at Texas Tech University to emulate controlled wind turbine flow physics. The HAWKS model turbine has pitch, yaw and speed control which is operated in real model time, similar to that of an equivalent full scale turbine. Also, similar to that of a full scale wind turbine, the controls are developed in a Matlab Simulink environment. The current diagnostic system consists of power, rotor position, rotor speed measurements and PIV wake characterization with four cameras. The setup allows up to 7D downstream of the rotor to be mapped. The purpose of HAWKS is to simulate control strategies at turnaround times much faster than CFD and full scale testing. The fundamental building blocks of the simulator have been tested, and demonstrate wake steering for both static and dynamic turbine actuation. Parameters which have been studied are yaw, rotor speed and combinations hereof. The measured wake deflections for static yaw cases are in agreement with previously reported research implying general applicability of the HAWKS platform for the purpose of manipulating the wake. In this presentation the general results will be introduced followed by an analysis of the wake turbulence and coherent structures when comparing static and dynamic flow cases. The outcome of such studies could ultimately support effective wind farm wake flow control strategies. Texas Emerging Technology Fund (ETF).

Effects of the installation and operation of jet-exhaust yaw vanes on the longitudinal and lateral-directional characteristics of the F-14 airplane

NASA Technical Reports Server (NTRS)

Reubush, David E.; Berrier, Bobby L.

1987-01-01

A wind tunnel investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of the installation and use of jet exhaust yaw vanes on the longitudinal and lateral-directional characteristics of the F-14 aircraft. The model was tested at Mach numbers from 0.70 to 1.25 at angles of attack from 0 deg to 4.3 deg. Compressed air was used to simulate nozzle exhaust flow from jet off up to a nozzle pressure ratio of 8. The results of the investigation show that the yaw vanes can augment the rudders to provide directional control, but further investigation will be necessary to optimize the deflection schedule associated with the various nozzle power settings.

Yawed-Rolling Tire Mechanical Properties Testing of the Navy T-45 Aircraft Tires

NASA Technical Reports Server (NTRS)

Daugherty, Robert H.

2000-01-01

The T-45 Goshawk is a United States Navy Jet aircraft used primarily as a trainer. The aircraft design makes use of "off the shelf" hardware as much as possible and was found to have unusual directional control issues during around operations. The aircraft was involved in numerous pilot-induced-oscillation incidents as well as observed to have unusual directional control reactions to failed main gear tires, a condition that is normally handled relatively easily by conventional aircraft steering control techniques. The behavior of the aircraft's tires had previously been modeled in simulators as a result of approximations provided in 40-year-old reference publications. Since knowledge of the true tire cornering and braking behavior is essential to modeling, understanding, and fixing directional control problems, the United States Navy requested assistance from the NASA Langley Research Center's (LARC) Aircraft Landing Dynamics Facility (ALDF) to define the yawed-rolling mechanical properties of the T-45 aircraft tires. The purpose of this report is to document the results of testing the subject tires at the NASA LaRC ALDF in September 1998. Brief descriptions of the Instrumented Tire Test Vehicle (ITTV) are included to familiarize the reader with the ITTV capabilities, data acquisition system, test and measurement techniques, data accuracy, and analysis and presentation of the testing results.

Full drive-by-wire dynamic control for four-wheel-steer all-wheel-drive vehicles

NASA Astrophysics Data System (ADS)

Fahimi, Farbod

2013-03-01

Most of the controllers introduced for four-wheel-steer (4WS) vehicles are derived with the assumption that the longitudinal speed of the vehicle is constant. However, in real applications, the longitudinal speed varies, and the longitudinal, lateral, and yaw dynamics are coupled. In this paper, the longitudinal dynamics of the vehicle as well as its lateral and yaw motions are controlled simultaneously. This way, the effect of driving/braking forces of the tires on the lateral and yaw motions of the vehicle are automatically included in the control laws. To address the dynamic parameter uncertainty of the vehicle, a chatter-free variable structure controller is introduced. Elimination of chatter is achieved by introducing a dynamically adaptive boundary layer thickness. It is shown via simulations that the proposed control approach performs more robustly than the controllers developed based on dynamic models, in which longitudinal speed is assumed to be constant, and only lateral speed and yaw rate are used as system states. Furthermore, this approach supports all-wheel-drive vehicles. Front-wheel-drive or rear-wheel-drive vehicles are also supported as special cases of an all-wheel-drive vehicle.

Advanced AFCS developments on the XV-15 tilt rotor research aircraft. [Automatic Flight Control System

NASA Technical Reports Server (NTRS)

Churchill, G. B.; Gerdes, R. M.

1984-01-01

The design criteria and control and handling qualities of the Automatic Flight Control System (AFCS), developed in the framework of the XV-15 tilt-rotor research aircraft, are evaluated, differentiating between the stability and control criteria. A technically aggressive SCAS control law was implemented, demonstrating that significant benefits accrue when stability criteria are separated from design criteria; the design analyses for application of the control law are presented, and the limit bandwidth for stabilization in hovering flight is shown to be defined by rotor or control lag functions. Flight tests of the aircraft resulted in a rating of 3 on the Cooper-Harper scale; a possibility of achieving a rating of 2 is expected if the system is applied to the yaw and heave control modes.

Studying Wake Deflection of Wind Turbines in Yaw using Drag Disk Experiments and Actuator Disk Modeling in LES

NASA Astrophysics Data System (ADS)

Howland, Michael; Bossuyt, Juliaan; Meyers, Johan; Meneveau, Charles

2015-11-01

Recently, there has been a push towards the optimization in the power output of entire large wind farms through the control of individual turbines, as opposed to operating each turbine in a maximum power point tracking manner. In this vane, the wake deflection by wind turbines in yawed conditions has generated considerable interest in recent years. In order to effectively study the wake deflection according to classical actuator disk momentum theory, a 3D printed drag disk model with a coefficient of thrust of approximately 0.75 - 0.85 and a diameter of 3 cm is used, studied under uniform inflow in a wind tunnel with test section of 1 m by 1.3 m, operating with a negligible inlet turbulence level at an inflow velocity of 10 m/s. Mean velocity profile measurements are performed using Pitot probes. Different yaw angles are considered, including 10, 20, and 30 degrees. We confirm earlier results that (e.g.) a 30 degree yaw angle deflects the center of the wake around 1/2 of a rotor diameter when it impinges on a downstream turbine. Detailed comparisons between the experiments and Large Eddy Simulations using actuator disk model for the wind turbines are carried out in order to help validate the CFD model. Work supported by NSF (grants CBET-113380 and IIA-1243482, the WINDINSPIRE project) and by ERC (ActiveWindFarms, grant no. 306471).

Behavior of aircraft antiskid braking systems on dry and wet runway surfaces - A velocity-rate-controlled, pressure-bias-modulated system

NASA Technical Reports Server (NTRS)

Stubbs, S. M.; Tanner, J. A.

1976-01-01

During maximum braking the average ratio of drag-force friction coefficient developed by the antiskid system to maximum drag-force friction coefficient available at the tire/runway interface was higher on dry surfaces than on wet surfaces. The gross stopping power generated by the brake system on the dry surface was more than twice that obtained on the wet surfaces. With maximum braking applied, the average ratio of side-force friction coefficient developed by the tire under antiskid control to maximum side-force friction available at the tire/runway interface of a free-rolling yawed tire was shown to decrease with increasing yaw angle. Braking reduced the side-force friction coefficient on a dry surface by 75 percent as the wheel slip ratio was increased to 0.3; on a flooded surface the coefficient dropped to near zero for the same slip ratio. Locked wheel skids were observed when the tire encountered a runway surface transition from dry to flooded, due in part to the response time required for the system to sense abrupt changes in the runway friction; however, the antiskid system quickly responded by reducing brake pressure and cycling normally during the remainder of the run on the flooded surface.

Explicit and implicit calculations of turbulent cavity flows with and without yaw angle

NASA Astrophysics Data System (ADS)

Yen, Guan-Wei

1989-08-01

Computations were performed to simulate turbulent supersonic flows past three-dimensional deep cavities with and without yaw. Simulation of these self-sustained oscillatory flows were generated through time accurate solutions of the Reynolds averaged complete Navier-Stokes equations using two different schemes: (1) MacCormack, finite-difference; and (2) implicit, upwind, finite-volume schemes. The second scheme, which is approximately 30 percent faster, is found to produce better time accurate results. The Reynolds stresses were modeled, using the Baldwin-Lomax algebraic turbulence model with certain modifications. The computational results include instantaneous and time averaged flow properties everywhere in the computational domain. Time series analyses were performed for the instantaneous pressure values on the cavity floor. The time averaged computational results show good agreement with the experimental data along the cavity floor and walls. When the yaw angle is nonzero, there is no longer a single length scale (length-to-depth ratio) for the flow, as is the case for zero yaw angle flow. The dominant directions and inclinations of the vortices are dramatically different for this nonsymmetric flow. The vortex shedding from the cavity into the mainstream flow is captured computationally. This phenomenon, which is due to the oscillation of the shear layer, is confirmed by the solutions of both schemes.

Neural Flight Control System

NASA Technical Reports Server (NTRS)

Gundy-Burlet, Karen

2003-01-01

The Neural Flight Control System (NFCS) was developed to address the need for control systems that can be produced and tested at lower cost, easily adapted to prototype vehicles and for flight systems that can accommodate damaged control surfaces or changes to aircraft stability and control characteristics resulting from failures or accidents. NFCS utilizes on a neural network-based flight control algorithm which automatically compensates for a broad spectrum of unanticipated damage or failures of an aircraft in flight. Pilot stick and rudder pedal inputs are fed into a reference model which produces pitch, roll and yaw rate commands. The reference model frequencies and gains can be set to provide handling quality characteristics suitable for the aircraft of interest. The rate commands are used in conjunction with estimates of the aircraft s stability and control (S&C) derivatives by a simplified Dynamic Inverse controller to produce virtual elevator, aileron and rudder commands. These virtual surface deflection commands are optimally distributed across the aircraft s available control surfaces using linear programming theory. Sensor data is compared with the reference model rate commands to produce an error signal. A Proportional/Integral (PI) error controller "winds up" on the error signal and adds an augmented command to the reference model output with the effect of zeroing the error signal. In order to provide more consistent handling qualities for the pilot, neural networks learn the behavior of the error controller and add in the augmented command before the integrator winds up. In the case of damage sufficient to affect the handling qualities of the aircraft, an Adaptive Critic is utilized to reduce the reference model frequencies and gains to stay within a flyable envelope of the aircraft.

The effect of spring pads in the secondary suspension of railway vehicles on bogie yaw resistance

NASA Astrophysics Data System (ADS)

Michálek, Tomáš; Zelenka, Jaromír

2015-12-01

This paper deals with properties of bogie yaw resistance of an electric locomotive with secondary suspension consisting of flexi-coil springs supplemented with tilting spring pads. Transversal stiffness of a sample of a spring/pad assembly was measured on a dynamic test stand of the University of Pardubice (Czech Republic) and the results were applied into a multi-body model of the locomotive created in the simulation tool 'SJKV'. On the basis of the simulation results, a detailed analysis of the bogie yaw resistance was performed in order to explain the effect in dynamic behaviour of the locomotive when the moment against bogie rotation (and therefore the distribution of guiding forces on individual wheels, as well) is influenced with the vehicle speed in a certain curve. Results of this analysis show that the application of suspension elements with strongly directionally dependent transversal stiffness into the secondary suspension can just lead to a dependency of the bogie yaw resistance on cant deficiency, i.e. on the vehicle speed in curve. This fact has wide consequences on the vehicle dynamics (especially on the guiding behaviour of the vehicle in curves) and it also points out that the current method of evaluation of the bogie yaw resistance according to relevant standards, which is related with assessment of the quasistatic safety of a railway vehicle against derailment, is not objective enough.

Mod-2 wind turbine system development. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

1982-01-01

The development of the MOD-2 wind turbine through acceptance testing and initial operational evaluation is documented. Pitch control hydraulic system, yaw control system, drive train, electrical power station, control system, operations and maintenance experience, and availability are discussed.

Digital Flight Control System Redundancy Study

DTIC Science & Technology

1974-07-01

has its own separate power supr, y . d. Digital Processor The digital processor consists of the followdnq components: (1) Program Counter - This...1-3 Yaw Axis Control 108 1-4 Autothrottle (Airspeed Hold Mode) 109 1-5 Approach Power Compensation 110 1-6 Glideslope Flare 111 I-7 Glideslope Track...considsred to the extent that they imposed constraints on the candidate con- figurations. Cost, size, weight, power , maintainability, survivability and

Haemophilus ducreyi as a cause of skin ulcers in children from a yaws-endemic area of Papua New Guinea: a prospective cohort study.

PubMed

Mitjà, Oriol; Lukehart, Sheila A; Pokowas, Gideon; Moses, Penias; Kapa, August; Godornes, Charmie; Robson, Jennifer; Cherian, Sarah; Houinei, Wendy; Kazadi, Walter; Siba, Peter; de Lazzari, Elisa; Bassat, Quique

2014-04-01

Skin infections with ulceration are a major health problem in countries of the south Pacific region. Yaws, caused by Treponema pallidum subspecies pertenue and diagnosed by the presence of skin ulcers and a reactive syphilis serology, is one major cause, but this infection can be confused clinically with ulcers due to other causative agents. We investigated T pallidum pertenue and another bacterium known to cause skin infections in the Pacific islands-Haemophilus ducreyi-as causes of skin ulceration in a yaws-endemic region. Additionally, we identified specific signs and symptoms associated with these causative agents of cutaneous ulcers and compared these findings with laboratory-based diagnoses. We did a prospective cohort study of five yaws-endemic villages (total population 3117 people) during a yaws elimination campaign in Papua New Guinea in April, 2013. We enrolled all consenting patients with chronic moist or exudative skin ulcers. We undertook a detailed dermatological assessment, syphilis serology, and PCR on lesional swabs to detect the presence of T pallidum pertenue and H ducreyi. Patients with PCR-confirmed bacterial infections were included in a comparative analysis of demographics and clinical features. Full outcome data were available for 90 people with skin ulcers. Of these patients, 17 (19%) had negative results in all molecular tests and were therefore excluded from the comparative analyses. A bacterial cause was identified in 73 (81%) participants-either H ducreyi (n=42), T pallidum pertenue (yaws; n=19), or coinfection with both organisms (dual infection; n=12). The demographic characteristics of the patients infected with yaws and with H ducreyi were similar. Skin lesions in patients with yaws and in those with dual infection were larger than those in patients infected with H ducreyi (p=0·071). The lesions in patients with yaws and dual infection were more circular in shape (79% and 67%) than in those infected with H ducreyi (21%; p<0·0001

Effect of Variation of Chord and Span of Ailerons on Rolling and Yawing Moments in Level Flight

NASA Technical Reports Server (NTRS)

Heald, R H; Strother, D H

1929-01-01

This report presents the results of an investigation of the rolling and yawing moments due to ailerons of various chords and spans on two airfoils having the Clark Y and U. S. A. 27 wing sections. Some attention is devoted to a study of the effect of scale on rolling and yawing moments and to the effect of slightly rounding the wing tips. The results apply to level flight with the wing chord set at an angle of attack of +4 degrees and to conditions of zero pitch, zero yaw, and zero roll of the airplane. It is planned later to extend the investigation to other attitudes for monoplane and biplane combinations. The work was conducted in the 10 foot wind tunnel of the Bureau of Standards on models of 60-inch span and 10-inch chord. (author)

A new approach to correct yaw misalignment in the spinning ultrasonic anemometer

NASA Astrophysics Data System (ADS)

Ghaemi-Nasab, M.; Davari, Ali R.; Franchini, S.

2018-01-01

Single-axis ultrasonic anemometers are the modern instruments for accurate wind speed measurements. Despite their widespread and ever increasing applications, little attention has been paid up to now to spinning ultrasonic anemometers that can accurately measure both the wind speed and its direction in a single and robust apparatus. In this study, intensive wind-tunnel tests were conducted on a spinning single-axis ultrasonic anemometer to investigate the yaw misalignment in ultrasonic wind speed measurements during the yaw rotation. The anemometer was rotating inside the test section with various angular velocities, and the experiments were performed at several combinations of wind speed and anemometer angular velocity. The instantaneous angular position of the ultrasonic signal path with wind direction was measured using an angular position sensor. For a spinning anemometer, the circulatory wake and the associated flow distortion, along with the Doppler effect, impart a phase shift in the signals measured by the anemometer, which should be added to the position data for correcting the yaw misalignment. In this paper, the experimental data are used to construct a theoretical model, based on a response surface method, to correct the phase shift for various wind speeds and anemometer rotational velocities. This model is shown to successfully correct the velocity indicated by the spinning anemometer for the phase shift due to the rotation, and can easily be used in the calibration process for such anemometers.

Attitude control system design using a flywheel suspended by two gimbals

NASA Astrophysics Data System (ADS)

Peres, R. W.; Ricci, M. C.

2015-10-01

This work presents the attitude control system design procedures for a three axis stabilized satellite in geostationary orbit, which contains a flywheel suspended by two gimbals. The use of a flywheel with two DOFs is an interesting option because with only one device it's possible to control the torques about vehicle's three axes; through the wheel speed control and gyrotorquing phenomenon with two DOFs. If the wheel size and speed are determined properly it's possible to cancel cyclic torques using gas jets only periodically to cancel secular disturbance torques. The system, based on a flywheel, takes only one pitch/roll (earth) sensor to maintain precise attitude, unlike mass expulsion based control systems, which uses propellants continuously, beyond roll, pitch and yaw sensors. It is considered the satellite is in nominal orbit and, therefore, that the attitude's acquisition phase has already elapsed. Control laws and system parameters are determined in order to cancel the solar pressure radiation disturbance torque and the torque due to misalignment of the thrusters. Stability is analyzed and step and cyclic responses are obtained.

A general-purpose balloon-borne pointing system for solar scientific instruments

NASA Technical Reports Server (NTRS)

Polites, M. E.

1990-01-01

A general purpose balloonborne pointing system for accommodating a wide variety of solar scientific instruments is described. It is designed for precise pointing, low cost, and quick launch. It offers the option of three-axis control, pitch-yaw-roll, or two-axis control, pitch-yaw, depending on the needs of the solar instrument. Simulation results are presented that indicate good pointing capability at Sun elevation angles ranging from 10 to 80 deg.

Pitch, roll, and yaw moment generator for insect-like tailless flapping-wing MAV

NASA Astrophysics Data System (ADS)

Phan, Hoang Vu; Park, Hoon Cheol

2016-04-01

In this work, we proposed a control moment generator, which is called Trailing Edge Change (TEC) mechanism, for attitudes change in hovering insect-like tailless flapping-wing MAV. The control moment generator was installed to the flapping-wing mechanism to manipulate the wing kinematics by adjusting the wing roots location symmetrically or asymmetrically. As a result, the mean aerodynamic force center of each wing is relocated and control moments are generated. The three-dimensional wing kinematics captured by three synchronized high-speed cameras showed that the flapping-wing MAV can properly modify the wing kinematics. In addition, a series of experiments were performed using a multi-axis load cell to evaluate the forces and moments generation. The measurement demonstrated that the TEC mechanism produced reasonable amounts of pitch, roll and yaw moments by shifting position of the trailing edges at the wing roots of the flapping-wing MAV.

The Effect of Lateral-Directional Control Coupling on Pilot Control of an Airplane as Determined in Flight and in a Fixed-Base Flight Simulator

NASA Technical Reports Server (NTRS)

Vomaske, Richard F.; Sadoff, Melvin; Drinkwater, Fred J., III

1961-01-01

A flight and fixed-base simulator study was made of the effects of aileron-induced yaw on pilot opinion of aircraft lateral-directional controllability characteristics. A wide range of adverse and favorable aileron-induced yaw was investigated in flight at several levels of Dutch-roll damping. The flight results indicated that the optimum values of aileron- induced yaw differed only slightly from zero for Dutch-roll damping from satisfactory to marginally controllable levels. It was also shown that each range of values of aileron-induced yawing moment considered satisfactory, acceptable, or controllable increased with an increase in the Dutch- roll damping. The increase was most marked for marginally controllable configurations exhibiting favorable aileron-induced yaw. Comparison of fixed-base flight simulator results with flight results showed agreement, indicating that absence of kinesthetic motion cues did not markedly affect the pilots' evaluation of the type of control problem considered in this study. The results of the flight study were recast in terms of several parameters which were considered to have an important effect on pilot opinion of lateral-directional handling qualities, including the effects of control coupling. Results of brief tests with a three-axis side-arm controller indicated that for control coupling problems associated with highly favorable yaw and cross-control techniques, use of the three-axis controller resulted in a deterioration of control relative to results obtained with the conventional center stick and rudder pedals.

? observer-based decentralised fuzzy control design for nonlinear interconnected systems: an application to vehicle dynamics

NASA Astrophysics Data System (ADS)

Latrach, Chedia; Kchaou, Mourad; Guéguen, Hervé

2017-05-01

In this study, a decentralised output learning control strategy for a class of nonlinear interconnected systems is studied. Based on Takagi-Sugeno fuzzy (TS) model to approximate the considered interconnected nonlinear systems, a decentralised observer-based control scheme is designed to override the external disturbances such that the ? performance is achieved. The appealing attributes of this approach include: (1) the closed-loop system exhibits a robustness against nonlinear interconnections and external disturbance, (2) by one-step procedure, the gain matrices of observer and controller are obtained on a single step. In simulation results, the controller design is evaluated on the steering stability of a car where the nonlinear model describes the side slip, roll and yaw motions of the automotive vehicle equipped with four-wheel-steering and active suspension.

Yaws, syphilis, sexuality, and the circulation of medical knowledge in the British Caribbean and the Atlantic world.

PubMed

Paugh, Katherine

2014-01-01

This history of the disease categories "yaws" and "syphilis" explores the interplay between European and African medical cultures in the early modern Atlantic world. The assertion made by both early modern and modern medical authorities, that yaws and syphilis are the same disease, prompts a case study of the history of disease that reflects on a variety of issues in the history of medicine: the use of ideas about contagion to demarcate racial and sexual difference at sites around the British Empire; the contrast between persistently holistic ideas about disease causation in the Black Atlantic and the growth of ontological theories of disease among Europeans and Euro-Americans; and the controversy over the African practice of yaws inoculation, which may once have been an effective treatment but was stamped out by plantation owners who viewed it as a waste of their enslaved laborers' valuable time.

Eigenspace Design of Helicopter Flight Control Systems

DTIC Science & Technology

1990-11-01

Attitude Changes ......... 44 2.6 Yaw Cross Coupling Criteria . ............................................... 45 I 4. i Definition of the Rigid Body...laws. The methodology detailed in this report allows the designer to synthesize control laws which result in desirable response types such as attitude ...it is simple to relate the desired frequency response characteristics to the natural frequencies and damping factors or the time constants of the

Simulator study of the effectiveness of an automatic control system designed to improve the high-angle-of-attack characteristics of a fighter airplane

NASA Technical Reports Server (NTRS)

Gilbert, W. P.; Nguyen, L. T.; Vangunst, R. W.

1976-01-01

A piloted, fixed-base simulation was conducted to study the effectiveness of some automatic control system features designed to improve the stability and control characteristics of fighter airplanes at high angles of attack. These features include an angle-of-attack limiter, a normal-acceleration limiter, an aileron-rudder interconnect, and a stability-axis yaw damper. The study was based on a current lightweight fighter prototype. The aerodynamic data used in the simulation were measured on a 0.15-scale model at low Reynolds number and low subsonic Mach number. The simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative combat maneuvering. Results of the investigation show the fully augmented airplane to be quite stable and maneuverable throughout the operational angle-of-attack range. The angle-of-attack/normal-acceleration limiting feature of the pitch control system is found to be a necessity to avoid angle-of-attack excursions at high angles of attack. The aileron-rudder interconnect system is shown to be very effective in making the airplane departure resistant while the stability-axis yaw damper provided improved high-angle-of-attack roll performance with a minimum of sideslip excursions.

Pitched and Yawed Circular Jets in Cross-Flow

NASA Technical Reports Server (NTRS)

Milanovic, Ivana M.; Zaman, K. B. M. Q.; Reddy, D. R. (Technical Monitor)

2002-01-01

Results from an experimental investigation of flow field generated by pitched and yawed jets discharging from a flat plate into a cross-flow are presented. The circular jet was pitched at alpha = 20 degrees and 45 degrees and yawed between beta = 0 degrees and 90 degrees in increments of 15 degrees. The measurements were performed with two X-wires providing all three components of velocity and turbulence intensity. These data were obtained at downstream locations of x = 3, 5, 10 and 20, where the distance x normalized by the jet diameter, is measured from the center of the orifice. Data for all configurations were acquired at a momentum-flux ratio J = 8. Additionally, for selected angles and locations, surveys were conducted for J = 1.5, 4, and 20. As expected, the jet penetration is found to be higher at larger alpha. With increasing beta the jet spreads more. The rate of reduction of peak streamwise vorticity, with the downstream distance is significantly lessened at higher alpha but is found to be practically independent of alpha. Thus, at the farthest measurement station x = 20, omega(sub xmax) is about five times larger for beta = 0 degrees compared to the levels at beta = 0 degrees. Streamwise velocity within the jet-vortex structure is found to depend on the parameter J. At J = 1.5 and 4, 'wake-like' velocity profiles are observed. In comparison, a 'jet-like' overshoot is present at higher J.

A new continuous sliding mode control approach with actuator saturation for control of 2-DOF helicopter system.

PubMed

Sadala, S P; Patre, B M

2018-03-01

The 2-degree of freedom (DOF) helicopter system is a typical higher-order, multi-variable, nonlinear and strong coupled control system. The helicopter dynamics also includes parametric uncertainties and is subject to unknown external disturbances. Such complicated system requires designing a sophisticated control algorithm that can handle these difficulties. This paper presents a new robust control algorithm which is a combination of two continuous control techniques, composite nonlinear feedback (CNF) and super-twisting control (STC) methods. In the existing integral sliding mode (ISM) based CNF control law, the discontinuous term exhibits chattering which is not desirable for many practical applications. As the continuity of well known STC reduces chattering in the system, the proposed strategy is beneficial over the current ISM based CNF control law which has a discontinuous term. Two controllers with integral sliding surface are designed to control the position of the pitch and the yaw angles of the 2- DOF helicopter. The adequacy of this specific combination has been exhibited through general analysis, simulation and experimental results of 2-DOF helicopter setup. The acquired results demonstrate the good execution of the proposed controller regarding stabilization, following reference input without overshoot against actuator saturation and robustness concerning to the limited matched disturbances. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Intervention criterion and control research for active front steering with consideration of road adhesion

NASA Astrophysics Data System (ADS)

Wu, Xiaojian; Zhou, Bing; Wen, Guilin; Long, Lefei; Cui, Qingjia

2018-04-01

A multi-objective active front steering (AFS) control system considering the road adhesion constraint on vehicle stability is developed using the sliding mode control (SMC) method. First, an identification function combined with the relationship between the yaw rate and the steering angle is developed to determine whether the tyre state is linear or nonlinear. On this basis, an intervention criterion for the AFS system is proposed to improve vehicle handling and stability in emergent conditions. A sideslip angle stability domain enveloped by the upper, lower, left, and right boundaries, as well as the constraint of road adhesion coefficient, is constructed based on the ? phase-plane method. A dynamic weighting coefficient to coordinate the control of yaw rate and sideslip angle, and a control strategy that considers changing control objectives based on the desired yaw rate, the desired sideslip angle, and their proportional weights, are proposed for the SMC controller. Because road adhesion has a significant effect on vehicle stability and to meet the control algorithm's requirement of real-time access to vehicle states, a unscented Kalman filter-based state observer is proposed to estimate the adhesion coefficient and the required states. Finally, simulations are performed using high and low road adhesion conditions in a Matlab/Simulink environment, and the results show that the proposed AFS control system promptly intervenes according to the intervention criterion, effectively improving vehicle handling and stability.

Barn owls maximize head rotations by a combination of yawing and rolling in functionally diverse regions of the neck.

PubMed

Krings, Markus; Nyakatura, John A; Boumans, Mark L L M; Fischer, Martin S; Wagner, Hermann

2017-07-01

Owls are known for their outstanding neck mobility: these birds can rotate their heads more than 270°. The anatomical basis of this extraordinary neck rotation ability is not well understood. We used X-ray fluoroscopy of living owls as well as forced neck rotations in dead specimens and computer tomographic (CT) reconstructions to study how the individual cervical joints contribute to head rotation in barn owls (Tyto furcata pratincola). The X-ray data showed the natural posture of the neck, and the reconstructions of the CT-scans provided the shapes of the individual vertebrae. Joint mobility was analyzed in a spherical coordinate system. The rotational capability was described as rotation about the yaw and roll axes. The analyses suggest a functional division of the cervical spine into several regions. Most importantly, an upper region shows high rolling and yawing capabilities. The mobility of the lower, more horizontally oriented joints of the cervical spine is restricted mainly to the roll axis. These rolling movements lead to lateral bending, effectively resulting in a side shift of the head compared with the trunk during large rotations. The joints in the middle of the cervical spine proved to contribute less to head rotation. The analysis of joint mobility demonstrated how owls might maximize horizontal head rotation by a specific and variable combination of yawing and rolling in functionally diverse regions of the neck. © 2017 Anatomical Society.

The cost and cost-effectiveness of rapid testing strategies for yaws diagnosis and surveillance.

PubMed

Fitzpatrick, Christopher; Asiedu, Kingsley; Sands, Anita; Gonzalez Pena, Tita; Marks, Michael; Mitja, Oriol; Meheus, Filip; Van der Stuyft, Patrick

2017-10-01

Yaws is a non-venereal treponemal infection caused by Treponema pallidum subspecies pertenue. The disease is targeted by WHO for eradication by 2020. Rapid diagnostic tests (RDTs) are envisaged for confirmation of clinical cases during treatment campaigns and for certification of the interruption of transmission. Yaws testing requires both treponemal (trep) and non-treponemal (non-trep) assays for diagnosis of current infection. We evaluate a sequential testing strategy (using a treponemal RDT before a trep/non-trep RDT) in terms of cost and cost-effectiveness, relative to a single-assay combined testing strategy (using the trep/non-trep RDT alone), for two use cases: individual diagnosis and community surveillance. We use cohort decision analysis to examine the diagnostic and cost outcomes. We estimate cost and cost-effectiveness of the alternative testing strategies at different levels of prevalence of past/current infection and current infection under each use case. We take the perspective of the global yaws eradication programme. We calculate the total number of correct diagnoses for each strategy over a range of plausible prevalences. We employ probabilistic sensitivity analysis (PSA) to account for uncertainty and report 95% intervals. At current prices of the treponemal and trep/non-trep RDTs, the sequential strategy is cost-saving for individual diagnosis at prevalence of past/current infection less than 85% (81-90); it is cost-saving for surveillance at less than 100%. The threshold price of the trep/non-trep RDT (below which the sequential strategy would no longer be cost-saving) is US$ 1.08 (1.02-1.14) for individual diagnosis at high prevalence of past/current infection (51%) and US$ 0.54 (0.52-0.56) for community surveillance at low prevalence (15%). We find that the sequential strategy is cost-saving for both diagnosis and surveillance in most relevant settings. In the absence of evidence assessing relative performance (sensitivity and specificity

Multivariable Control Law Design for the AFTI/F-16 with a Failed Control Surface Using a Parameter-Adaptive Controller.

DTIC Science & Technology

1987-12-01

Appendix D: Macro Listings D-1 Appendix E: MATRIXx Simulation E-1 Bibiliography Vita iv e List of Figures Figure Page 1-1 Self -Tuning Regulator 6 2-1 AFTI...Command 59 4-25 Yaw Rate Command - Three Pulses 60 4-26 Adaptive Yaw Rate Respose - Three Pulses 61 4-27 Adaptive Pitch Angle Response - Three Pulses 62 4...several types of adaptive controllers (regulators). Three of the simplest controllers are gain scheduling, model reference, and self -tuning

A novel vehicle dynamics stability control algorithm based on the hierarchical strategy with constrain of nonlinear tyre forces

NASA Astrophysics Data System (ADS)

Li, Liang; Jia, Gang; Chen, Jie; Zhu, Hongjun; Cao, Dongpu; Song, Jian

2015-08-01

Direct yaw moment control (DYC), which differentially brakes the wheels to produce a yaw moment for the vehicle stability in a steering process, is an important part of electric stability control system. In this field, most control methods utilise the active brake pressure with a feedback controller to adjust the braked wheel. However, the method might lead to a control delay or overshoot because of the lack of a quantitative project relationship between target values from the upper stability controller to the lower pressure controller. Meanwhile, the stability controller usually ignores the implementing ability of the tyre forces, which might be restrained by the combined-slip dynamics of the tyre. Therefore, a novel control algorithm of DYC based on the hierarchical control strategy is brought forward in this paper. As for the upper controller, a correctional linear quadratic regulator, which not only contains feedback control but also contains feed forward control, is introduced to deduce the object of the stability yaw moment in order to guarantee the yaw rate and side-slip angle stability. As for the medium and lower controller, the quantitative relationship between the vehicle stability object and the target tyre forces of controlled wheels is proposed to achieve smooth control performance based on a combined-slip tyre model. The simulations with the hardware-in-the-loop platform validate that the proposed algorithm can improve the stability of the vehicle effectively.

Fuzzy Controller Design Using Evolutionary Techniques for Twin Rotor MIMO System: A Comparative Study.

PubMed

Hashim, H A; Abido, M A

2015-01-01

This paper presents a comparative study of fuzzy controller design for the twin rotor multi-input multioutput (MIMO) system (TRMS) considering most promising evolutionary techniques. These are gravitational search algorithm (GSA), particle swarm optimization (PSO), artificial bee colony (ABC), and differential evolution (DE). In this study, the gains of four fuzzy proportional derivative (PD) controllers for TRMS have been optimized using the considered techniques. The optimization techniques are developed to identify the optimal control parameters for system stability enhancement, to cancel high nonlinearities in the model, to reduce the coupling effect, and to drive TRMS pitch and yaw angles into the desired tracking trajectory efficiently and accurately. The most effective technique in terms of system response due to different disturbances has been investigated. In this work, it is observed that GSA is the most effective technique in terms of solution quality and convergence speed.

Fuzzy Controller Design Using Evolutionary Techniques for Twin Rotor MIMO System: A Comparative Study

PubMed Central

Hashim, H. A.; Abido, M. A.

2015-01-01

This paper presents a comparative study of fuzzy controller design for the twin rotor multi-input multioutput (MIMO) system (TRMS) considering most promising evolutionary techniques. These are gravitational search algorithm (GSA), particle swarm optimization (PSO), artificial bee colony (ABC), and differential evolution (DE). In this study, the gains of four fuzzy proportional derivative (PD) controllers for TRMS have been optimized using the considered techniques. The optimization techniques are developed to identify the optimal control parameters for system stability enhancement, to cancel high nonlinearities in the model, to reduce the coupling effect, and to drive TRMS pitch and yaw angles into the desired tracking trajectory efficiently and accurately. The most effective technique in terms of system response due to different disturbances has been investigated. In this work, it is observed that GSA is the most effective technique in terms of solution quality and convergence speed. PMID:25960738

Molecular Differentiation of Treponema pallidum Subspecies in Skin Ulceration Clinically Suspected as Yaws in Vanuatu Using Real-Time Multiplex PCR and Serological Methods

PubMed Central

Chi, Kai-Hua; Danavall, Damien; Taleo, Fasihah; Pillay, Allan; Ye, Tun; Nachamkin, Eli; Kool, Jacob L.; Fegan, David; Asiedu, Kingsley; Vestergaard, Lasse S.; Ballard, Ronald C.; Chen, Cheng-Yen

2015-01-01

We developed a TaqMan-based real-time quadriplex polymerase chain reaction (PCR) to simultaneously detect Treponema pallidum subspecies pallidum, T. pallidum subsp. pertenue, and T. pallidum subsp. endemicum, the causative agents of venereal syphilis, yaws, and bejel, respectively. The PCR assay was applied to samples from skin ulcerations of clinically presumptive yaws cases among children on Tanna Island, Vanuatu. Another real-time triplex PCR was used to screen for the point mutations in the 23S rRNA genes that have previously been associated with azithromycin resistance in T. pallidum subsp. pallidum strains. Seropositivity by the classical syphilis serological tests was 35.5% among children with skin ulcerations clinically suspected with yaws, whereas the presence of T. pallidum subsp. pertenue DNA was only found in lesions from 15.5% of children. No evidence of T. pallidum subsp. pertenue infection, by either PCR or serology was found in ∼59% of cases indicating alternative causes of yaws-like lesions in this endemic area. PMID:25404075

Positioning and tracking control system analysis for mobile free space optical network

NASA Astrophysics Data System (ADS)

Li, Yushan; Refai, Hazem; Sluss, , James J., Jr.; Verma, Pramode; LoPresti, Peter

2005-08-01

Free Space Optical (FSO) communication has evolved to be applied to the mobile network, because it can provide up to 2.5Gbps or higher data rate wireless communication. One of the key challenges with FSO systems is to maintain the Line of Sight (LOS) between transmitter and receiver. In this paper, the feasibility and performance of applying the FSO technology to the mobile network is explored, and the design plan of the attitude positioning and tracking control system of the FSO transceiver is investigated. First, the system architecture is introduced, the requirements for the control system are analyzed, the involved reference frames and frame transformation are presented. Second, the control system bandwidth is used to evaluate the system performance in controlling a positioning system consisting of a gimbal and a steering mirror, some definitions to describe the positioning accuracy and tracking capacity are given. The attitude control of a FSO transceiver is split into 2 similar channels: pitch and yaw. Using an equivalent linear control system model, the simulations are carried out, with and without the presence of uncertainties that includes GPS data errors and sensor measurement errors. Finally, based on the simulation results in the pitch channel, the quantitative evaluation on the performance of the control system is given, including positioning accuracy, tracking capability and uncertainty tolerance.

A novel pre-control method of vehicle dynamics stability based on critical stable velocity during transient steering maneuvering

NASA Astrophysics Data System (ADS)

Chen, Jie; Song, Jian; Li, Liang; Ran, Xu; Jia, Gang; Wu, Kaihui

2016-05-01

The current research of direct yaw moment control (DYC) system focus on the design of target yaw moment and the distribution of wheel brake force. The differential braking intervention can effectively improve the lateral stability of the vehicle, however, the effect of DYC can be improved a step further by applying the control of vehicle longitudinal velocity. In this paper, the relationship between the vehicle longitudinal velocity and lateral stability is studied, and the simulation results show that a decrease of 5 km/h of longitudinal velocity at a particular situation can bring 100° increasing of stable steering upper limit. A critical stable velocity considering the effect of steering and yaw rate measurement is defined to evaluate the risk of losing steer-ability or stability. A novel velocity pre-control method is proposed by using a hierarchical pre-control logic and is integrated with the traditional DYC system. The control algorithm is verified through a hardware in-the-loop simulation system. Double lane change (DLC) test results on both high friction coefficient (μ) and low μ roads show that by using the pre-control method, the steering effort in DLC test can be reduced by 38% and 51% and the peak value of brake pressure control can be reduced by 20% and 12% respectively on high μ and low μ roads, the lateral stability is also improved. This research proposes a novel DYC system with lighter control effort and better control effect.

Recall of symptoms and treatment of syphilis and yaws by healthy blood donors screening positive for syphilis in Kumasi, Ghana.

PubMed

Sarkodie, Francis; Owusu-Dabo, Ellis; Hassall, Oliver; Bates, Imelda; Bygbjerg, Ib C; Ullum, Henrik

2016-09-01

To describe the recalled medical history, clinical manifestations, and treatment of yaws and syphilis by syphilis seroreactive blood donors in Kumasi, Ghana. Of the blood donors at Komfo Anokye Teaching Hospital, Kumasi, Ghana tested with the syphilis rapid diagnostic test (RDT) and later by rapid plasma reagin (RPR) test, 526 were seroreactive. Four hundred and seventy-one (89.5%) of these subjects were confirmed with the Ortho-Vitros Syphilis TP test as the gold standard and were interviewed to determine past or present clinical manifestations of yaws and syphilis. Of the 471 respondent donors, 28 (5.9%) gave a history of skin lesions and sores; four (14.3%) of these subjects, who were all male and RPR-positive, recalled a diagnosis of syphilis. All four reported having had skin lesions/bumps with slow-healing sores, but only one of them had had these symptoms before the age of 15 years. A small proportion of confirmed seroreactive donors in this sample had any recall of symptoms or treatment for yaws or syphilis. These data suggest that clinical questioning adds little further information to the current screening algorithm. The relative contribution of yaws and syphilis to frequent positive tests in endemic areas remains speculative. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Adaptive Path Control of Surface Ships in Restricted Waters.

DTIC Science & Technology

1980-08-01

and Fn=0.116-- Random Walk Disturbance Model 31 6. Optimal Gains for Tokyo Mazu at H/T=- and Fn=0.116-- Random Walk Disturbance Model 39 7. RMS Cost J...yaw mass moment of inertia [kgm 2 V =21 /pL nondimensional yaw mass moment of inertia zz zz J optimal control or Weighted Least-Squares cost function...J RMS cost , eq. (70) J 5yaw added mass moment of inertia [kgm 2 iz=2Jz/pL nondimensional yaw added mass moment of inertia zz zz K Kalman-Bucy state

Explicit and implicit calculations of turbulent cavity flows with and without yaw angle. M.S. Thesis

NASA Technical Reports Server (NTRS)

Yen, Guan-Wei

1989-01-01

Computations were performed to simulate turbulent supersonic flows past three-dimensional deep cavities with and without yaw. Simulation of these self-sustained oscillatory flows were generated through time accurate solutions of the Reynolds averaged complete Navier-Stokes equations using two different schemes: (1) MacCormack, finite-difference; and (2) implicit, upwind, finite-volume schemes. The second scheme, which is approximately 30 percent faster, is found to produce better time accurate results. The Reynolds stresses were modeled, using the Baldwin-Lomax algebraic turbulence model with certain modifications. The computational results include instantaneous and time averaged flow properties everywhere in the computational domain. Time series analyses were performed for the instantaneous pressure values on the cavity floor. The time averaged computational results show good agreement with the experimental data along the cavity floor and walls. When the yaw angle is nonzero, there is no longer a single length scale (length-to-depth ratio) for the flow, as is the case for zero yaw angle flow. The dominant directions and inclinations of the vortices are dramatically different for this nonsymmetric flow. The vortex shedding from the cavity into the mainstream flow is captured computationally. This phenomenon, which is due to the oscillation of the shear layer, is confirmed by the solutions of both schemes.

Emergency Multiengine Aircraft System for Lateral Control Using Differential Thrust Control of Wing Engines

NASA Technical Reports Server (NTRS)

Burken, John J. (Inventor); Burcham, Frank W., Jr. (Inventor); Bull, John (Inventor)

2000-01-01

Development of an emergency flight control system is disclosed for lateral control using only differential engine thrust modulation of multiengine aircraft is currently underway. The multiengine has at least two engines laterally displaced to the left and right from the axis of the aircraft. In response to a heading angle command psi(sub c) is to be tracked. By continually sensing the heading angle psi of the aircraft and computing a heading error signal psi(sub e) as a function of the difference between the heading angle command psi(sub c) and the sensed heading angle psi, a track control signal is developed with compensation as a function of sensed bank angle phi. Bank angle rate phi, or roll rate p, yaw rate tau, and true velocity produce an aircraft thrust control signal ATC(sub psi(L,R)). The thrust control signal is differentially applied to the left and right engines, with equal amplitude and opposite sign, such that a negative sign is applied to the control signal on the side of the aircraft. A turn is required to reduce the error signal until the heading feedback reduces the error to zero.

X-29 vortex flow control tests

NASA Technical Reports Server (NTRS)

Hancock, Regis; Fullerton, Gordon

1992-01-01

A joint Air Force/NASA X-29 aircraft program to improve yaw control at high angle of attack using vortex flow control (VFC) is described. Directional VFC blowing proved to a be a powerful yaw moment generator and was very effective in overriding natural asymmetries, but was essentially ineffective in suppressing wing rock. Symmetric aft blowing also had little effect on suppressing wing rock.

Determination of the SNPP VIIRS SDSM Screen Relative Transmittance From Both Yaw Maneuver and Regular On-Orbit Data

NASA Technical Reports Server (NTRS)

Lei, Ning; Chen, Xuexia; Xiong, Xiaoxiong

2015-01-01

The Visible Infrared Imaging Radiometer Suiteaboard the Suomi National Polar-orbiting Partnership (SNPP) satellite performs radiometric calibration of its reflective solar bands primarily through observing a sunlit onboard solar diffuser (SD). The SD bidirectional reflectance distribution function(BRDF) degradation factor is determined by an onboard SD stability monitor (SDSM), which observes the Sun through a pinhole screen and the sunlit SD. The transmittance of the SDSM pinhole screen over a range of solar angles was determined prelaunch and used initially to determine the BRDF degradation factor.The degradation-factor-versus-time curves were found to have a number of very large unphysical undulations likely due to the inaccuracy in the prelaunch determined SDSM screen transmittance.To refine the SDSM screen transmittance, satellite yaw maneuvers were carried out. With the SDSM screen relative transmittance determined from the yaw maneuver data, the computed BRDFdegradation factor curves still have large unphysical ripples, indicating that the projected solar horizontal angular step size in the yaw maneuver data is too large to resolve the transmittance at a fine angular scale. We develop a methodology to use both the yaw maneuver and a small portion of regular on-orbit data to determine the SDSM screen relative transmittance at a fine angular scale. We determine that the error standard deviation of the calculated relative transmittance ranges from 0.00030 (672 nm) to 0.00092 (926 nm). With the newly determined SDSM screen relative transmittance, the computed BRDF degradation factor behaves much more smoothly over time.

Investigation of the current yaw engineering models for simulation of wind turbines in BEM and comparison with CFD and experiment

NASA Astrophysics Data System (ADS)

Rahimi, H.; Hartvelt, M.; Peinke, J.; Schepers, J. G.

2016-09-01

The aim of this work is to investigate the capabilities of current engineering tools based on Blade Element Momentum (BEM) and free vortex wake codes for the prediction of key aerodynamic parameters of wind turbines in yawed flow. Axial induction factor and aerodynamic loads of three wind turbines (NREL VI, AVATAR and INNWIND.EU) were investigated using wind tunnel measurements and numerical simulations for 0 and 30 degrees of yaw. Results indicated that for axial conditions there is a good agreement between all codes in terms of mean values of aerodynamic parameters, however in yawed flow significant deviations were observed. This was due to unsteady phenomena such as advancing & retreating and skewed wake effect. These deviations were more visible in aerodynamic parameters in comparison to the rotor azimuthal angle for the sections at the root and tip where the skewed wake effect plays a major role.

Controller design for a class of nonlinear MIMO coupled system using multiple models and second level adaptation.

PubMed

Pandey, Vinay Kumar; Kar, Indrani; Mahanta, Chitralekha

2017-07-01

In this paper, an adaptive control method using multiple models with second level adaptation is proposed for a class of nonlinear multi-input multi-output (MIMO) coupled systems. Multiple estimation models are used to tune the unknown parameters at the first level. The second level adaptation provides a single parameter vector for the controller. A feedback linearization technique is used to design a state feedback control. The efficacy of the designed controller is validated by conducting real time experiment on a laboratory setup of twin rotor MIMO system (TRMS). The TRMS setup is discussed in detail and the experiments were performed for regulation and tracking problem for pitch and yaw control using different reference signals. An Extended Kalman Filter (EKF) has been used to observe the unavailable states of the TRMS. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Aircraft control system

NASA Technical Reports Server (NTRS)

Kendall, Greg T. (Inventor); Lisoski, Derek L. (Inventor)

2007-01-01

A solar rechargeable, long-duration, span-loaded flying wing, having no fuselage or rudder. Having a two-hundred foot wingspan that mounts photovoltaic cells on most all of the wing's top surface, the aircraft uses only differential thrust of its eight propellers to turn, pitch and yaw. The wing is configured to deform under flight loads to position the propellers such that the control can be achieved. Each of five segments of the wing has one or more motors and photovoltaic arrays, and produces its own lift independent of the other segments, to avoid loading them. Five two-sided photovoltaic arrays, in all, are mounted on the wing, and receive photovoltaic energy both incident on top of the wing, and which is incident also from below, through a bottom, transparent surface.

Computer program for post-flight evaluation of a launch vehicle upper-stage on-off reaction control system

NASA Technical Reports Server (NTRS)

Knauber, R. N.

1982-01-01

This report describes a FORTRAN IV coded computer program for post-flight evaluation of a launch vehicle upper stage on-off reaction control system. Aerodynamic and thrust misalignment disturbances are computed as well as the total disturbing moments in pitch, yaw, and roll. Effective thrust misalignment angle time histories of the rocket booster motor are calculated. Disturbing moments are integrated and used to estimate the required control system total inpulse. Effective control system specific inpulse is computed for the boost and coast phases using measured control fuel useage. This method has been used for more than fifteen years for analyzing the NASA Scout launch vehicle second and third-stage reaction control system performance. The computer program is set up in FORTRAN IV for a CDC CYBER 175 system. With slight modification it can be used on other machines having a FORTRAN compiler. The program has optional CALCOMP plotting output. With this option the program requires 19K words of memory and has 786 cards. Running time on a CDC CYBER 175 system is less than three (3) seconds for a typical problem.

A new momentum management controller for the space station

NASA Technical Reports Server (NTRS)

Wie, B.; Byun, K. W.; Warren, V. W.

1988-01-01

A new approach to CMG (control moment gyro) momentum management and attitude control of the Space Station is developed. The control algorithm utilizes both the gravity-gradient and gyroscopic torques to seek torque equilibrium attitude in the presence of secular and cyclic disturbances. Depending upon mission requirements, either pitch attitude or pitch-axis CMG momentum can be held constant: yaw attitude and roll-axis CMG momentum can be held constant, while roll attitude and yaw-axis CMG momentum cannot be held constant. As a result, the overall attitude and CMG momentum oscillations caused by cyclic aero-dynamic disturbances are minimized. A state feedback controller with minimal computer storage requirement for gain scheduling is also developed. The overall closed-loop system is stable for + or - 30 percent inertia matrix variations and has more than + or - 10 dB and 45 deg stability margins in each loop.

Integration of Externally Carried Weapon Systems with Military Helicopters (L’Integration des Systemes d’Armes Transportes en Charge Externe sur les Helicopteres Militaires)

DTIC Science & Technology

1990-04-01

Np - Yaw to Roll Derivative (Yaw/Roll Coupling) Hr - Yaw to Yaw Rate Derivative (Yaw Damping) M - Pitch to Incidence Derivative (Incidence Stability) F...system is installed in the same configuration as used on the land based vehicle, simply by bolting-on to the limited number of available hard points...helicopters not originally designed to take external loads. The limited number of hard points on the fuselage structure leads to define supports of complex

Multirate sampled-data yaw-damper and modal suppression system design

NASA Technical Reports Server (NTRS)

Berg, Martin C.; Mason, Gregory S.

1990-01-01

A multirate control law synthesized algorithm based on an infinite-time quadratic cost function, was developed along with a method for analyzing the robustness of multirate systems. A generalized multirate sampled-data control law structure (GMCLS) was introduced. A new infinite-time-based parameter optimization multirate sampled-data control law synthesis method and solution algorithm were developed. A singular-value-based method for determining gain and phase margins for multirate systems was also developed. The finite-time-based parameter optimization multirate sampled-data control law synthesis algorithm originally intended to be applied to the aircraft problem was instead demonstrated by application to a simpler problem involving the control of the tip position of a two-link robot arm. The GMCLS, the infinite-time-based parameter optimization multirate control law synthesis method and solution algorithm, and the singular-value based method for determining gain and phase margins were all demonstrated by application to the aircraft control problem originally proposed for this project.

Controls design with crossfeeds for hovering rotorcraft using quantitative feedback theory

NASA Technical Reports Server (NTRS)

Tischler, Mark B.; Biezad, Daniel J.; Cheng, Rendy

1996-01-01

A multi-input, multi-output controls design with dynamic crossfeed pre-compensation is presented for rotorcraft in near-hovering flight using Quantitative Feedback Theory (QFT). The resulting closed-loop control system bandwidth allows the rotorcraft to be considered for use as an inflight simulator. The use of dynamic, robust crossfeeds prior to the QFT design reduces the magnitude of required feedback gain and results in performance that meets most handling qualities specifications relative to the decoupling of off-axis responses. Handling qualities are Level 1 for both low-gain tasks and high-gain tasks in the roll, pitch, and yaw axes except for the 10 deg/sec moderate-amplitude yaw command where the rotorcraft exhibits Level 2 handling qualities in the yaw axis caused by phase lag. The combined effect of the QFT feedback design following the implementation of low-order, dynamic crossfeed compensators successfully decouples ten of twelve off-axis channels. For the other two channels it was not possible to find a single, low-order crossfeed that was effective. This is an area to be investigated in future research.

Optimisation of active suspension control inputs for improved performance of active safety systems

NASA Astrophysics Data System (ADS)

Čorić, Mirko; Deur, Joško; Xu, Li; Tseng, H. Eric; Hrovat, Davor

2018-01-01

A collocation-type control variable optimisation method is used to investigate the extent to which the fully active suspension (FAS) can be applied to improve the vehicle electronic stability control (ESC) performance and reduce the braking distance. First, the optimisation approach is applied to the scenario of vehicle stabilisation during the sine-with-dwell manoeuvre. The results are used to provide insights into different FAS control mechanisms for vehicle performance improvements related to responsiveness and yaw rate error reduction indices. The FAS control performance is compared to performances of the standard ESC system, optimal active brake system and combined FAS and ESC configuration. Second, the optimisation approach is employed to the task of FAS-based braking distance reduction for straight-line vehicle motion. Here, the scenarios of uniform and longitudinally or laterally non-uniform tyre-road friction coefficient are considered. The influences of limited anti-lock braking system (ABS) actuator bandwidth and limit-cycle ABS behaviour are also analysed. The optimisation results indicate that the FAS can provide competitive stabilisation performance and improved agility when compared to the ESC system, and that it can reduce the braking distance by up to 5% for distinctively non-uniform friction conditions.

Electronic differential control of 2WD electric vehicle considering steering stability

NASA Astrophysics Data System (ADS)

Hua, Yiding; Jiang, Haobin; Geng, Guoqing

2017-03-01

Aiming at the steering wheel differential steering control technology of rear wheel independent driving electric wheel, considering the assisting effect of electronic differential control on vehicle steering, based on the high speed steering characteristic of electric wheel car, the electronic differential speed of auxiliary wheel steering is also studied. A yaw moment control strategy is applied to the vehicle at high speed. Based on the vehicle stability reference value, yaw rate is used to design the fuzzy controller to distribute the driving wheel torque. The simulation results show that the basic electronic differential speed function is realized based on the yaw moment control strategy, while the vehicle stability control is improved and the driving safety is enhanced. On the other hand, the torque control strategy can also assist steering of vehicle.

Dynamic stability characteristics in pitch, yaw, and roll of a supercritical-wing research airplane model. [langley 8-foot transonic tunnel tests

NASA Technical Reports Server (NTRS)

Boyden, R. P.

1974-01-01

The aerodynamic damping in pitch, yaw, and roll and the oscillatory stability in pitch and yaw of a supercritical-wing research airplane model were determined for Mach numbers of 0.25 to 1.20 by using the small-amplitude forced-oscillation technique. The angle-of-attack range was from -2 deg to 20 deg. The effects of the underwing leading-edge vortex generators and the contributions of the wing, vertical tail, and horizontal tail to the appropriate damping and stability were measured.

A non-Hertzian method for solving wheel-rail normal contact problem taking into account the effect of yaw

NASA Astrophysics Data System (ADS)

Liu, Binbin; Bruni, Stefano; Vollebregt, Edwin

2016-09-01

A novel approach is proposed in this paper to deal with non-Hertzian normal contact in wheel-rail interface, extending the widely used Kik-Piotrowski method. The new approach is able to consider the effect of the yaw angle of the wheelset against the rail on the shape of the contact patch and on pressure distribution. Furthermore, the method considers the variation of profile curvature across the contact patch, enhancing the correspondence to CONTACT for highly non-Hertzian contact conditions. The simulation results show that the proposed method can provide more accurate estimation than the original algorithm compared to Kalker's CONTACT, and that the influence of yaw on the contact results is significant under certain circumstances.

The Control System for the X-33 Linear Aerospike Engine

NASA Technical Reports Server (NTRS)

Jackson, Jerry E.; Espenschied, Erich; Klop, Jeffrey

1998-01-01

The linear aerospike engine is being developed for single-stage -to-orbit (SSTO) applications. The primary advantages of a linear aerospike engine over a conventional bell nozzle engine include altitude compensation, which provides enhanced performance, and lower vehicle weight resulting from the integration of the engine into the vehicle structure. A feature of this integration is the ability to provide thrust vector control (TVC) by differential throttling of the engine combustion elements, rather than the more conventional approach of gimballing the entire engine. An analysis of the X-33 flight trajectories has shown that it is necessary to provide +/- 15% roll, pitch and yaw TVC authority with an optional capability of +/- 30% pitch at select times during the mission. The TVC performance requirements for X-33 engine became a major driver in the design of the engine control system. The thrust level of the X-33 engine as well as the amount of TVC are managed by a control system which consists of electronic, instrumentation, propellant valves, electro-mechanical actuators, spark igniters, and harnesses. The engine control system is responsible for the thrust control, mixture ratio control, thrust vector control, engine health monitoring, and communication to the vehicle during all operational modes of the engine (checkout, pre-start, start, main-stage, shutdown and post shutdown). The methodology for thrust vector control, the health monitoring approach which includes failure detection, isolation, and response, and the basic control system design are the topic of this paper. As an additional point of interest a brief description of the X-33 engine system will be included in this paper.

Active Wake Redirection Control to Improve Energy Yield (Poster)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Churchfield, M. J.; Fleming, P.; DeGeorge, E.

Wake effects can dramatically reduce the efficiency of waked turbines relative to the unwaked turbines. Wakes can be deflected, or 'redirected,' by applying yaw misalignment to the turbines. Yaw misalignment causes part of the rotor thrust vector to be pointed in the cross-stream direction, deflecting the flow and the wake. Yaw misalignment reduces power production, but the global increase in wind plant power due to decreased wake effect creates a net increase in power production. It is also a fairly simple control idea to implement at existing or new wind plants. We performed high-fidelity computational fluid dynamics simulations of themore » wake flow of the proposed Fishermen's Atlantic City Windfarm (FACW) that predict that under certain waking conditions, wake redirection can increase plant efficiency by 10%. This means that by applying wake redirection control, for a given watersheet area, a wind plant can either produce more power, or the same amount of power can be produced with a smaller watersheet area. With the power increase may come increased loads, though, due to the yaw misalignment. If misalignment is applied properly, or if layered with individual blade pitch control, though, the load increase can be mitigated. In this talk we will discuss the concept of wake redirection through yaw misalignment and present our CFD results of the FACW project. We will also discuss the implications of wake redirection control on annual energy production, and finally we will discuss plans to implement wake redirection control at FACW when it is operational.« less

Correlation of side-force and yawing-moment data for TACV configurations at large angles of sideslip

DOT National Transportation Integrated Search

1974-01-01

Methods developed by Woolard and Ruetenik and Zartarian for predicting the side force and yawing moment on TACV configurations due to side winds are compared against available data from wind-tunnel tests. The predicted side force based on slender-bod...

Flight Investigation of the Stability and Control Characteristics of a 0.13-Scale Model of the Convair XFY-1 Vertically Rising Airplane During Constant-Altitude Transitions, TED No. NACA DE 368

NASA Technical Reports Server (NTRS)

Lovell, Powell M., Jr.; Kibry, Robert H.; Smith, Charles C., Jr.

1953-01-01

An investigation is being conducted to determine the dynamic stability and control characteristics of a 0.13-scale flying model of the Convair XFY-1 vertically rising airplane. This paper presents the results of flight tests to determine the stability and control characteristics of the model during constant-altitude slow transitions from hovering to normal unstalled forward flight. The tests indicated that the airplane can be flown through the transition range fairly easily although some difficulty will probably encountered in controlling the yawing motions at angles of attack between about 60 and 40. An increase in the size of the vertical tail will not materially improve the controllability of the yawing motions in this range of angle of attack but the use of a yaw damper will make the yawing motions easy to control throughout the entire transitional flight range. The tests also indicated that the airplane can probably be flown sideways satisfactorily at speeds up to approximately 33 knots (full scale) with the normal control system and up to approximately 37 knots (full scale) with both elevons and rudders rigged to move differentially for roll control. At sideways speeds above these values, the airplane will have a strong tendency to diverge uncontrollably in roll.

B-52 stability augmentation system reliability

NASA Technical Reports Server (NTRS)

Bowling, T. C.; Key, L. W.

1976-01-01

The B-52 SAS (Stability Augmentation System) was developed and retrofitted to nearly 300 aircraft. It actively controls B-52 structural bending, provides improved yaw and pitch damping through sensors and electronic control channels, and puts complete reliance on hydraulic control power for rudder and elevators. The system has experienced over 300,000 flight hours and has exhibited service reliability comparable to the results of the reliability test program. Development experience points out numerous lessons with potential application in the mechanization and development of advanced technology control systems of high reliability.

Integrated Orbit, Attitude, and Structural Control System Design for Space Solar Power Satellites

NASA Technical Reports Server (NTRS)

Woods-Vedeler, Jessica (Technical Monitor); Moore, Chris (Technical Monitor); Wie, Bong; Roithmayr, Carlos

2001-01-01

The major objective of this study is to develop an integrated orbit, attitude, and structural control system architecture for very large Space Solar Power Satellites (SSPS) in geosynchronous orbit. This study focuses on the 1.2-GW Abacus SSPS concept characterized by a 3.2 x 3.2 km solar-array platform, a 500-m diameter microwave beam transmitting antenna, and a 500 700 m earth-tracking reflector. For this baseline Abacus SSPS configuration, we derive and analyze a complete set of mathematical models, including external disturbances such as solar radiation pressure, microwave radiation, gravity-gradient torque, and other orbit perturbation effects. The proposed control system architecture utilizes a minimum of 500 1-N electric thrusters to counter, simultaneously, the cyclic pitch gravity-gradient torque, the secular roll torque caused by an o.set of the center-of-mass and center-of-pressure, the cyclic roll/yaw microwave radiation torque, and the solar radiation pressure force whose average value is about 60 N.

Integrated Orbit, Attitude, and Structural Control Systems Design for Space Solar Power Satellites

NASA Technical Reports Server (NTRS)

Wie, Bong; Roithmayr, Carlos M.

2001-01-01

The major objective of this study is to develop an integrated orbit, attitude, and structural control systems architecture for very large Space Solar Power Satellites (SSPS) in geosynchronous orbit. This study focuses on the 1.2-GW Abacus SSPS concept characterized by a 3.2 x 3.2 km solar-array platform, a 500-m diameter microwave beam transmitting antenna, and a 500 x 700 m earth-tracking reflector. For this baseline Abacus SSPS configuration, we derive and analyze a complete set of mathematical models, including external disturbances such as solar radiation pressure, microwave radiation, gravity-gradient torque, and other orbit perturbation effects. The proposed control systems architecture utilizes a minimum of 500 1-N electric thrusters to counter, simultaneously, the cyclic pitch gravity-gradient torque, the secular roll torque caused by an offset of the center-of-mass and center-of-pressure, the cyclic roll/yaw microwave radiation torque, and the solar radiation pressure force whose average value is about 60 N.

Forebody tangential blowing for control at high angles of attack

NASA Technical Reports Server (NTRS)

Kroo, I.; Rock, S.; Roberts, L.

1991-01-01

A feasibility study to determine if the use of tangential leading edge blowing over the forebody could produce effective and practical control of the F-18 HARV aircraft at high angles of attack was conducted. A simplified model of the F-18 configuration using a vortex-lattice model was developed to obtain a better understanding of basic aerodynamic coupling effects and the influence of forebody circulation on lifting surface behavior. The effect of tangential blowing was estimated using existing wind tunnel data on normal forebody blowing and analytical studies of tangential blowing over conical forebodies. Incorporation of forebody blowing into the flight control system was investigated by adding this additional yaw control and sideforce generating actuator into the existing F-18 HARV simulation model. A control law was synthesized using LQG design methods that would schedule blowing rates as a function of vehicle sideslip, angle of attack, and roll and yaw rates.

Point-of-care tests for syphilis and yaws in a low-income setting - A qualitative study of healthcare worker and patient experiences.

PubMed

Marks, Michael; Esau, Tommy; Asugeni, Rowena; Harrington, Relmah; Diau, Jason; Toloka, Hilary; Asugeni, James; Ansbro, Eimhin; Solomon, Anthony W; Maclaren, David; Redman-Maclaren, Michelle; Mabey, David C W

2018-04-01

The human treponematoses comprise venereal syphilis and the three non-venereal or endemic treponematoses yaws, bejel, and pinta. Serological assays remain the most common diagnostic method for all treponemal infections. Point-of-care tests (POCTs) for syphilis and yaws allow testing without further development of infrastructure in populations where routine laboratory facilities are not available. Alongside the test's performance characteristics assessed through diagnostic evaluation, it is important to consider broader issues when rolling out a POCT. Experience with malaria POCT roll-out in sub-Saharan Africa has demonstrated that both healthcare worker and patient beliefs may play a major role in shaping the real-world use of POCTs. We conducted a qualitative study evaluating healthcare worker and patient perceptions of using a syphilis/yaws POCT in clinics in the East Malaita region of Malaita province in the Solomon Islands. Prior to the study serology was only routinely available at the local district hospital. The POCT was deployed in the outpatient and ante-natal departments of a district hospital and four rural health clinics served by the hospital. Each site was provided with training and an SOP on the performance, interpretation and recording of results. Treatment for those testing positive was provided, in line with Solomon Islands Ministry of Health and Medical Services' guidelines for syphilis and yaws respectively. Alongside the implementation of the POCT we facilitated semi-structured interviews with both nurses and patients to explore individuals' experiences and beliefs in relation to use of the POCT. Four main themes emerged in the interviews: 1) training and ease of performing the test; 2) time taken and ability to fit the test into a clinical workflow; 3) perceived reliability and trustworthiness of the test; and 4) level of the health care system the test was most usefully deployed. Many healthcare workers related their experience with the POCT

Fuzzy chaos control for vehicle lateral dynamics based on active suspension system

NASA Astrophysics Data System (ADS)

Huang, Chen; Chen, Long; Jiang, Haobin; Yuan, Chaochun; Xia, Tian

2014-07-01

The existing research of the active suspension system (ASS) mainly focuses on the different evaluation indexes and control strategies. Among the different components, the nonlinear characteristics of practical systems and control are usually not considered for vehicle lateral dynamics. But the vehicle model has some shortages on tyre model with side-slip angle, road adhesion coefficient, vertical load and velocity. In this paper, the nonlinear dynamic model of lateral system is considered and also the adaptive neural network of tire is introduced. By nonlinear analysis methods, such as the bifurcation diagram and Lyapunov exponent, it has shown that the lateral dynamics exhibits complicated motions with the forward speed. Then, a fuzzy control method is applied to the lateral system aiming to convert chaos into periodic motion using the linear-state feedback of an available lateral force with changing tire load. Finally, the rapid control prototyping is built to conduct the real vehicle test. By comparison of time response diagram, phase portraits and Lyapunov exponents at different work conditions, the results on step input and S-shaped road indicate that the slip angle and yaw velocity of lateral dynamics enter into stable domain and the results of test are consistent to the simulation and verified the correctness of simulation. And the Lyapunov exponents of the closed-loop system are becoming from positive to negative. This research proposes a fuzzy control method which has sufficient suppress chaotic motions as an effective active suspension system.

A tyre slip-based integrated chassis control of front/rear traction distribution and four-wheel independent brake from moderate driving to limit handling

NASA Astrophysics Data System (ADS)

Joa, Eunhyek; Park, Kwanwoo; Koh, Youngil; Yi, Kyongsu; Kim, Kilsoo

2018-04-01

This paper presents a tyre slip-based integrated chassis control of front/rear traction distribution and four-wheel braking for enhanced performance from moderate driving to limit handling. The proposed algorithm adopted hierarchical structure: supervisor - desired motion tracking controller - optimisation-based control allocation. In the supervisor, by considering transient cornering characteristics, desired vehicle motion is calculated. In the desired motion tracking controller, in order to track desired vehicle motion, virtual control input is determined in the manner of sliding mode control. In the control allocation, virtual control input is allocated to minimise cost function. The cost function consists of two major parts. First part is a slip-based tyre friction utilisation quantification, which does not need a tyre force estimation. Second part is an allocation guideline, which guides optimally allocated inputs to predefined solution. The proposed algorithm has been investigated via simulation from moderate driving to limit handling scenario. Compared to Base and direct yaw moment control system, the proposed algorithm can effectively reduce tyre dissipation energy in the moderate driving situation. Moreover, the proposed algorithm enhances limit handling performance compared to Base and direct yaw moment control system. In addition to comparison with Base and direct yaw moment control, comparison the proposed algorithm with the control algorithm based on the known tyre force information has been conducted. The results show that the performance of the proposed algorithm is similar with that of the control algorithm with the known tyre force information.

Vision-based flight control in the hawkmoth Hyles lineata

PubMed Central

Windsor, Shane P.; Bomphrey, Richard J.; Taylor, Graham K.

2014-01-01

Vision is a key sensory modality for flying insects, playing an important role in guidance, navigation and control. Here, we use a virtual-reality flight simulator to measure the optomotor responses of the hawkmoth Hyles lineata, and use a published linear-time invariant model of the flight dynamics to interpret the function of the measured responses in flight stabilization and control. We recorded the forces and moments produced during oscillation of the visual field in roll, pitch and yaw, varying the temporal frequency, amplitude or spatial frequency of the stimulus. The moths’ responses were strongly dependent upon contrast frequency, as expected if the optomotor system uses correlation-type motion detectors to sense self-motion. The flight dynamics model predicts that roll angle feedback is needed to stabilize the lateral dynamics, and that a combination of pitch angle and pitch rate feedback is most effective in stabilizing the longitudinal dynamics. The moths’ responses to roll and pitch stimuli coincided qualitatively with these functional predictions. The moths produced coupled roll and yaw moments in response to yaw stimuli, which could help to reduce the energetic cost of correcting heading. Our results emphasize the close relationship between physics and physiology in the stabilization of insect flight. PMID:24335557

Vision-based flight control in the hawkmoth Hyles lineata.

PubMed

Windsor, Shane P; Bomphrey, Richard J; Taylor, Graham K

2014-02-06

Vision is a key sensory modality for flying insects, playing an important role in guidance, navigation and control. Here, we use a virtual-reality flight simulator to measure the optomotor responses of the hawkmoth Hyles lineata, and use a published linear-time invariant model of the flight dynamics to interpret the function of the measured responses in flight stabilization and control. We recorded the forces and moments produced during oscillation of the visual field in roll, pitch and yaw, varying the temporal frequency, amplitude or spatial frequency of the stimulus. The moths' responses were strongly dependent upon contrast frequency, as expected if the optomotor system uses correlation-type motion detectors to sense self-motion. The flight dynamics model predicts that roll angle feedback is needed to stabilize the lateral dynamics, and that a combination of pitch angle and pitch rate feedback is most effective in stabilizing the longitudinal dynamics. The moths' responses to roll and pitch stimuli coincided qualitatively with these functional predictions. The moths produced coupled roll and yaw moments in response to yaw stimuli, which could help to reduce the energetic cost of correcting heading. Our results emphasize the close relationship between physics and physiology in the stabilization of insect flight.

Some effects of nonlinear variation in the directional-stability and damping-in-yawing derivatives on the lateral stability of an airplane

NASA Technical Reports Server (NTRS)

Sternfield, Leonard

1951-01-01

A theoretical investigation has been made to determine the effect of nonlinear stability derivatives on the lateral stability of an airplane. Motions were calculated on the assumption that the directional-stability and the damping-in-yawing derivatives are functions of the angle of sideslip. The application of the Laplace transform to the calculation of an airplane motion when certain types of nonlinear derivatives are present is described in detail. The types of nonlinearities assumed correspond to the condition in which the values of the directional-stability and damping-in-yawing derivatives are zero for small angle of sideslip.

Analysis of Aeroheating Augmentation due to Reaction Control System Jets on Orion Crew Exploration Vehicle

NASA Technical Reports Server (NTRS)

Dyakonov, Artem A.; Buck, Gregory M.; Decaro, Anthony D.

2009-01-01

The analysis of effects of the reaction control system jet plumes on aftbody heating of Orion entry capsule is presented. The analysis covered hypersonic continuum part of the entry trajectory. Aerothermal environments at flight conditions were evaluated using Langley Aerothermal Upwind Relaxation Algorithm (LAURA) code and Data Parallel Line Relaxation (DPLR) algorithm code. Results show a marked augmentation of aftbody heating due to roll, yaw and aft pitch thrusters. No significant augmentation is expected due to forward pitch thrusters. Of the conditions surveyed the maximum heat rate on the aftshell is expected when firing a pair of roll thrusters at a maximum deceleration condition.

Comparison of X-31 Flight and Ground-Based Yawing Moment Asymmetries at High Angles of Attack

NASA Technical Reports Server (NTRS)

Cobleigh, Brent R.; Croom, Mark A.

2001-01-01

Significant yawing moment asymmetries were encountered during the high-angle-of-attack envelope expansion of the two X-31 aircraft. These asymmetries caused position saturations of the thrust-vectoring vanes and trailing-edge flaps during some stability-axis rolling maneuvers at high angles of attack. The two test aircraft had different asymmetry characteristics, and ship two has asymmetries that vary as a function of Reynolds number. Several aerodynamic modifications have been made to the X-31 forebody with the goal of minimizing the asymmetry. These modifications include adding transition strips on the forebody and noseboom, using two different length strakes, and increasing nose bluntness. Ultimately, a combination of forebody strakes, nose blunting, and noseboom transition strips reduced the yawing moment asymmetry enough to fully expand the high-angle-of-attack envelope. Analysis of the X-31 flight data is reviewed and compared to wind-tunnel and water-tunnel measurements. Several lessons learned are outlined regarding high-angle-of-attack configuration design and ground testing.

Point-of-care tests for syphilis and yaws in a low-income setting – A qualitative study of healthcare worker and patient experiences

PubMed Central

Esau, Tommy; Asugeni, Rowena; Harrington, Relmah; Diau, Jason; Toloka, Hilary; Asugeni, James; Ansbro, Eimhin; Solomon, Anthony W.; Maclaren, David; Redman-Maclaren, Michelle; Mabey, David C. W.

2018-01-01

Introduction The human treponematoses comprise venereal syphilis and the three non-venereal or endemic treponematoses yaws, bejel, and pinta. Serological assays remain the most common diagnostic method for all treponemal infections. Point-of-care tests (POCTs) for syphilis and yaws allow testing without further development of infrastructure in populations where routine laboratory facilities are not available. Alongside the test’s performance characteristics assessed through diagnostic evaluation, it is important to consider broader issues when rolling out a POCT. Experience with malaria POCT roll-out in sub-Saharan Africa has demonstrated that both healthcare worker and patient beliefs may play a major role in shaping the real-world use of POCTs. We conducted a qualitative study evaluating healthcare worker and patient perceptions of using a syphilis/yaws POCT in clinics in the East Malaita region of Malaita province in the Solomon Islands. Prior to the study serology was only routinely available at the local district hospital. Methods The POCT was deployed in the outpatient and ante-natal departments of a district hospital and four rural health clinics served by the hospital. Each site was provided with training and an SOP on the performance, interpretation and recording of results. Treatment for those testing positive was provided, in line with Solomon Islands Ministry of Health and Medical Services’ guidelines for syphilis and yaws respectively. Alongside the implementation of the POCT we facilitated semi-structured interviews with both nurses and patients to explore individuals’ experiences and beliefs in relation to use of the POCT. Results and discussion Four main themes emerged in the interviews: 1) training and ease of performing the test; 2) time taken and ability to fit the test into a clinical workflow; 3) perceived reliability and trustworthiness of the test; and 4) level of the health care system the test was most usefully deployed. Many

Using the centre of percussion to design a steering controller for an autonomous race car

NASA Astrophysics Data System (ADS)

Kritayakirana, Krisada; Gerdes, J. Christian

2012-01-01

Understanding how a race car driver controls a vehicle at its friction limits can provide insights into the development of vehicle safety systems. In this paper, a race car driver's behaviour inspires the design of an autonomous racing controller. The resulting controller uses the vehicle's centre of percussion (COP) to design feedforward and feedback steering. At the COP, the effects of rotation and translation from the rear tire force cancel each other out; consequently, the feedforward steering command is robust to the disturbances from the rear tire force. Using the COP also simplifies the equations of motion, as the vehicle's lateral motion is decoupled from the vehicle's yaw motion and highlights the challenge of controlling a vehicle when the rear tires are highly saturated. The resulting dynamics can be controlled with a linear state feedback based on a lane-keeping system with additional yaw damping. Utilising Lyapunov theory, the closed-loop system is shown to remain stable even when the rear tires are highly saturated. The experimental results demonstrate that an autonomous vehicle can operate at its limits while maintaining a minimal lateral error.

Control Laws for a Dual-Spin Stabilized Platform

NASA Technical Reports Server (NTRS)

Lim, K. B.; Moerder, D. D.

2008-01-01

This paper describes two attitude control laws suitable for atmospheric flight vehicles with a steady angular momentum bias in the vehicle yaw axis. This bias is assumed to be provided by an internal flywheel, and is introduced to enhance roll and pitch stiffness. The first control law is based on Lyapunov stability theory, and stability proofs are given. The second control law, which assumes that the angular momentum bias is large, is based on a classical PID control. It is shown that the large yaw-axis bias requires that the PI feedback component on the roll and pitch angle errors be cross-fed. Both control laws are applied to a vehicle simulation in the presence of disturbances for several values of yaw-axis angular momentum bias. It is seen that both control laws provide a significant improvement in attitude performance when the bias is sufficiently large, but the nonlinear control law is also able to provide improved performance for a small value of bias. This is important because the smaller bias corresponds to a smaller requirement for mass to be dedicated to the flywheel.

Multiaxis control power from thrust vectoring for a supersonic fighter aircraft model at Mach 0.20 to 2.47

NASA Technical Reports Server (NTRS)

Capone, Francis J.; Bare, E. Ann

1987-01-01

The aeropropulsive characteristics of an advanced twin-engine fighter aircraft designed for supersonic cruise have been studied in the Langley 16-Foot Tansonic Tunnel and the Lewis 10- by 10-Foot Supersonic Tunnel. The objective was to determine multiaxis control-power characteristics from thrust vectoring. A two-dimensional convergent-divergent nozzle was designed to provide yaw vector angles of 0, -10, and -20 deg combined with geometric pitch vector angles of 0 and 15 deg. Yaw thrust vectoring was provided by yaw flaps located in the nozzle sidewalls. Roll control was obtained from differential pitch vectoring. This investigation was conducted at Mach numbers from 0.20 to 2.47. Angle of attack was varied from 0 to about 19 deg, and nozzle pressure ratio was varied from about 1 (jet off) to 28, depending on Mach number. Increments in force or moment coefficient that result from pitch or yaw thrust vectoring remain essentially constant over the entire angle-of-attack range of all Mach numbers tested. There was no effect of pitch vectoring on the lateral aerodynamic forces and moments and only very small effects of yaw vectoring on the longitudinal aerodynamic forces and moments. This result indicates little cross-coupling of control forces and moments for combined pitch-yaw vectoring.

Comparison of RPR 'teardrop' card test, VDRL and FTA-ABS tests results on sera from persons with suspected yaws in Columbia.

PubMed

Hopkins, D R; Florez, D

1977-08-01

A small study comparing results of the rapid plasma reagin (RPR) teardrop card test performed in the field, with results of Venereal Disease Research Laboratory (VDRL) and fluorescent treponemal antibody absorption (FTA-ABS) tests performed in the laboratory on venous blood specimens from the same suspected yaws patients was undertaken in Columbia in July 1975. The results suggest that the RPR teardrop card test may be used to screen for infectious, or potentially infectious, yaws patients under field conditions, but that it will not reliably detect patients with VDRL titres of 1:2 or less, or all patients in whom sera are reactive in the FTA-ABS test.

Comparison of RPR 'teardrop' card test, VDRL and FTA-ABS tests results on sera from persons with suspected yaws in Columbia.

PubMed Central

Hopkins, D R; Florez, D

1977-01-01

A small study comparing results of the rapid plasma reagin (RPR) teardrop card test performed in the field, with results of Venereal Disease Research Laboratory (VDRL) and fluorescent treponemal antibody absorption (FTA-ABS) tests performed in the laboratory on venous blood specimens from the same suspected yaws patients was undertaken in Columbia in July 1975. The results suggest that the RPR teardrop card test may be used to screen for infectious, or potentially infectious, yaws patients under field conditions, but that it will not reliably detect patients with VDRL titres of 1:2 or less, or all patients in whom sera are reactive in the FTA-ABS test. PMID:336143

X-29A Lateral-Directional Stability and Control Derivatives Extracted From High-Angle-of-Attack Flight Data

NASA Technical Reports Server (NTRS)

Iliff, Kenneth W.; Wang, Kon-Sheng Charles Wang

1996-01-01

The lateral-directional stability and control derivatives of the X-29A number 2 are extracted from flight data over an angle-of-attack range of 4 degrees to 53 degrees using a parameter identification algorithm. The algorithm uses the linearized aircraft equations of motion and a maximum likelihood estimator in the presence of state and measurement noise. State noise is used to model the uncommanded forcing function caused by unsteady aerodynamics over the aircraft at angles of attack above 15 degrees. The results supported the flight-envelope-expansion phase of the X-29A number 2 by helping to update the aerodynamic mathematical model, to improve the real-time simulator, and to revise flight control system laws. Effects of the aircraft high gain flight control system on maneuver quality and the estimated derivatives are also discussed. The derivatives are plotted as functions of angle of attack and compared with the predicted aerodynamic database. Agreement between predicted and flight values is quite good for some derivatives such as the lateral force due to sideslip, the lateral force due to rudder deflection, and the rolling moment due to roll rate. The results also show significant differences in several important derivatives such as the rolling moment due to sideslip, the yawing moment due to sideslip, the yawing moment due to aileron deflection, and the yawing moment due to rudder deflection.

attitude control design for the solar polar orbit radio telesope

NASA Astrophysics Data System (ADS)

Gao, D.; Zheng, J.

This paper studies the attitude dynamics and control of the Solar Polar Orbit Radio Telescope SPORT The SPORT which consists of one parent satellite and eight tethered satellites runs around the Sun in a polar orbit The parent satellite locates at the mass center of the constellation and tethered satellites which are tied with the parent satellite through a non-electric rope rotate around the parent satellite It is also supposed that the parent satellite and all tethered satellites are in a plane when the constellation works begin figure htbp centerline includegraphics width 3 85in height 2 38in 75271331 6a6eb71057 doc1 eps label fig1 end figure Fig 1 the SPORT constellation Firstly this paper gives the dynamic equations of the tethered satellite and the parent satellite From the dynamic characteristic of the tethered satellite we then find that the roll axis is coupled with the yaw axis The control torque of the roll axis can control the yaw angle But the control torque of the roll axis and pitch axis provided by the tether is very small it can not meet the accuracy requirement of the yaw angle In order to improve the attitude pointing accuracy of the tethered satellite a gradient pole is set in the negative orientation of the yaw axis The gradient pole can improve not only the attitude accuracy of roll angle and pitch angle but also that of the yaw angle indirectly As to the dynamic characteristic of the parent satellite the roll axis is coupled with the pitch axis due to the spinning angular velocity At the same

A vehicle stability control strategy with adaptive neural network sliding mode theory based on system uncertainty approximation

NASA Astrophysics Data System (ADS)

Ji, Xuewu; He, Xiangkun; Lv, Chen; Liu, Yahui; Wu, Jian

2018-06-01

Modelling uncertainty, parameter variation and unknown external disturbance are the major concerns in the development of an advanced controller for vehicle stability at the limits of handling. Sliding mode control (SMC) method has proved to be robust against parameter variation and unknown external disturbance with satisfactory tracking performance. But modelling uncertainty, such as errors caused in model simplification, is inevitable in model-based controller design, resulting in lowered control quality. The adaptive radial basis function network (ARBFN) can effectively improve the control performance against large system uncertainty by learning to approximate arbitrary nonlinear functions and ensure the global asymptotic stability of the closed-loop system. In this paper, a novel vehicle dynamics stability control strategy is proposed using the adaptive radial basis function network sliding mode control (ARBFN-SMC) to learn system uncertainty and eliminate its adverse effects. This strategy adopts a hierarchical control structure which consists of reference model layer, yaw moment control layer, braking torque allocation layer and executive layer. Co-simulation using MATLAB/Simulink and AMESim is conducted on a verified 15-DOF nonlinear vehicle system model with the integrated-electro-hydraulic brake system (I-EHB) actuator in a Sine With Dwell manoeuvre. The simulation results show that ARBFN-SMC scheme exhibits superior stability and tracking performance in different running conditions compared with SMC scheme.

Accumulation of Inertial Sensory Information in the Perception of Whole Body Yaw Rotation.

PubMed

Nesti, Alessandro; de Winkel, Ksander; Bülthoff, Heinrich H

2017-01-01

While moving through the environment, our central nervous system accumulates sensory information over time to provide an estimate of our self-motion, allowing for completing crucial tasks such as maintaining balance. However, little is known on how the duration of the motion stimuli influences our performances in a self-motion discrimination task. Here we study the human ability to discriminate intensities of sinusoidal (0.5 Hz) self-rotations around the vertical axis (yaw) for four different stimulus durations (1, 2, 3 and 5 s) in darkness. In a typical trial, participants experienced two consecutive rotations of equal duration and different peak amplitude, and reported the one perceived as stronger. For each stimulus duration, we determined the smallest detectable change in stimulus intensity (differential threshold) for a reference velocity of 15 deg/s. Results indicate that differential thresholds decrease with stimulus duration and asymptotically converge to a constant, positive value. This suggests that the central nervous system accumulates sensory information on self-motion over time, resulting in improved discrimination performances. Observed trends in differential thresholds are consistent with predictions based on a drift diffusion model with leaky integration of sensory evidence.

Multi-Objective Sliding Mode Control on Vehicle Cornering Stability with Variable Gear Ratio Actuator-Based Active Front Steering Systems.

PubMed

Ma, Xinbo; Wong, Pak Kin; Zhao, Jing; Xie, Zhengchao

2016-12-28

Active front steering (AFS) is an emerging technology to improve the vehicle cornering stability by introducing an additional small steering angle to the driver's input. This paper proposes an AFS system with a variable gear ratio steering (VGRS) actuator which is controlled by using the sliding mode control (SMC) strategy to improve the cornering stability of vehicles. In the design of an AFS system, different sensors are considered to measure the vehicle state, and the mechanism of the AFS system is also modelled in detail. Moreover, in order to improve the cornering stability of vehicles, two dependent objectives, namely sideslip angle and yaw rate, are considered together in the design of SMC strategy. By evaluating the cornering performance, Sine with Dwell and accident avoidance tests are conducted, and the simulation results indicate that the proposed SMC strategy is capable of improving the cornering stability of vehicles in practice.

Multi-Objective Sliding Mode Control on Vehicle Cornering Stability with Variable Gear Ratio Actuator-Based Active Front Steering Systems

PubMed Central

Ma, Xinbo; Wong, Pak Kin; Zhao, Jing; Xie, Zhengchao

2016-01-01

Active front steering (AFS) is an emerging technology to improve the vehicle cornering stability by introducing an additional small steering angle to the driver’s input. This paper proposes an AFS system with a variable gear ratio steering (VGRS) actuator which is controlled by using the sliding mode control (SMC) strategy to improve the cornering stability of vehicles. In the design of an AFS system, different sensors are considered to measure the vehicle state, and the mechanism of the AFS system is also modelled in detail. Moreover, in order to improve the cornering stability of vehicles, two dependent objectives, namely sideslip angle and yaw rate, are considered together in the design of SMC strategy. By evaluating the cornering performance, Sine with Dwell and accident avoidance tests are conducted, and the simulation results indicate that the proposed SMC strategy is capable of improving the cornering stability of vehicles in practice. PMID:28036037

Effect of Variation of Chord and Span of Ailerons on Rolling and Yawing Moments at Several Angles of Pitch

NASA Technical Reports Server (NTRS)

Heald, R H; Strother, D H; Monish, B H

1931-01-01

This report presents the results of an extension to higher angles of attack of the investigation of the rolling and yawing moments due to ailerons of various chords and spans on two airfoils having the Clark Y and U. S. A. 27 wings. The measurements were made at various angles of pitch but at zero angle of roll and yaw, the wing chord being set at an angle of +4 degrees to the fuselage axis. In the case of the Clark Y airfoil the measurements have been extended to a pitch angle of 40 degrees, using ailerons of span equal to 67 per cent of the wing semispan and chord equal to 20 and 30 per cent of the wing chord. The work was conducted on wing models of 60-inch span and 10-inch chord.

Effect of stabilizer location upon pitching and yawing moments in spins as shown by tests with the spinning balance

NASA Technical Reports Server (NTRS)

Bamber, M J; Zimmerman, C H

1933-01-01

Tests were made with the spinning balance in a 5-foot wind tunnel to study the effect of stabilizer location upon the pitching and yawing moments given by the tail surfaces in spinning attitudes. The tests revealed that the horizontal surfaces, when in a normal location, seriously reduced the effectiveness of the fin and rudder, particularly at angles of attack of 50 degrees or more. The tests also revealed that a more forward or more rearward location gave no consistent or decided improvement; that a lower location greatly increased the shielding so that the yawing moment from the combination was in general less than that given by the bare fuselage; and that a higher location decreased the shielding and gave a favorable interference effect, particularly at the high angles of attack. Additional results regarding the stabilizer and the elevator are given.

Longwall Guidance and Control Development

NASA Technical Reports Server (NTRS)

1982-01-01

The longwall guidance and control (G&C) system was evaluated to determine which systems and subsystems lent themselves to automatic control in the mining of coal. The upper coal/shale interface was identified as the reference for a vertical G&C system, with two sensors (the natural backgound and the sensitized pick) being used to locate and track this boundary. In order to insure a relatively smooth recession surface (roof and floor of the excavated seam), a last and present cut measuring instrument (acoustic sensor) was used. Potentiometers were used to measure elevations of the shearer arms. The intergration of these components comprised the vertical control system (pitch control). Yaw and roll control were incorporated into a face alignment system which was designed to keep the coal face normal to its external boundaries. Numerous tests, in the laboratory and in the field, have confirmed the feasibility of automatic horizon control, as well as determining the face alignment.

PID self tuning control based on Mamdani fuzzy logic control for quadrotor stabilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Priyambodo, Tri Kuntoro, E-mail: mastri@ugm.ac.id; Putra, Agfianto Eko; Department of Computer Science and Electronics, Universitas Gadjah Mada, Yogyakarta

Quadrotor as one type of UAV have the ability to perform Vertical Take Off and Landing (VTOL). It allows the Quadrotor to be stationary hovering in the air. PID (Proportional Integral Derivative) control system is one of the control methods that are commonly used. It is usually used to optimize the Quadrotor stabilization at least based on the three Eulerian angles (roll, pitch, and yaw) as input parameters for the control system. The three constants of PID can be obtained in various methods. The simplest method is tuning manually. This method has several weaknesses. For example if the three constantsmore » are not exact, the resulting response will deviate from the desired result. By combining the methods of PID with fuzzy logic systems where human expertise is implemented into the machine language is expected to further optimize the control system.« less

Intelligent Robotic Systems Study (IRSS), phase 2

NASA Technical Reports Server (NTRS)

1990-01-01

Under the Intelligent Robotics System Study (IRSS) contract, a generalized robotic control architecture was developed for use with the ProtoFlight Manipulator Arm (PFMA). The controller built for the PFMA provides localized position based force control, teleoperation and advanced path recording and playback capabilities. Various hand controllers can be used with the system in conjunction with a synthetic time delay capability to provide a realistic test bed for typical satellite servicing tasks. The configuration of the IRSS system is illustrated and discussed. The PFMA has six computer controllable degrees of freedom (DOF) plus a seventh manually indexable DOF, making the manipulator a pseudo 7 DOF mechanism. Because the PFMA was not developed to operate in a gravity field, but rather in space, it is counter balanced at the shoulder, elbow and wrist and a spring counterbalance has been added near the wrist to provide additional support. Built with long slender intra-joint linkages, the PFMA has a workspace nearly 2 meters deep and possesses sufficient dexterity to perform numerous satellite servicing tasks. The manipulator is arranged in a shoulder-yaw, pitch, elbow-pitch, and wrist-pitch, yaw, roll configuration, with an indexable shoulder roll joint. Digital control of the PFMA is implemented using a variety of single board computers developed by Heurikon Corporation and other manufacturers. The IRSS controller is designed to be a multi-rate, multi-tasking system. Independent joint servos run at a 134 Hz rate and position based impedance control functions at 67 Hz. Autonomous path generation and hand controller inputs are processed at a 33 Hz.

Pilot-model measurements of pilot responses in a lateral-directional control task

NASA Technical Reports Server (NTRS)

Adams, J. J.

1976-01-01

Pilot response during an aircraft bank-angle compensatory control task was measured by using an adaptive modeling technique. In the main control loop, which is the bank angle to aileron command loop, the pilot response was the same as that measured previously in single-input, single-output systems. The pilot used a rudder to aileron control coordination that canceled up to 80 percent of the vehicle yawing moment due to aileron deflection.

Vertical eye position-dependence of the human vestibuloocular reflex during passive and active yaw head rotations.

PubMed

Thurtell, M J; Black, R A; Halmagyi, G M; Curthoys, I S; Aw, S T

1999-05-01

Vertical eye position-dependence of the human vestibuloocular reflex during passive and active yaw head rotations. The effect of vertical eye-in-head position on the compensatory eye rotation response to passive and active high acceleration yaw head rotations was examined in eight normal human subjects. The stimuli consisted of brief, low amplitude (15-25 degrees ), high acceleration (4,000-6,000 degrees /s2) yaw head rotations with respect to the trunk (peak velocity was 150-350 degrees /s). Eye and head rotations were recorded in three-dimensional space using the magnetic search coil technique. The input-output kinematics of the three-dimensional vestibuloocular reflex (VOR) were assessed by finding the difference between the inverted eye velocity vector and the head velocity vector (both referenced to a head-fixed coordinate system) as a time series. During passive head impulses, the head and eye velocity axes aligned well with each other for the first 47 ms after the onset of the stimulus, regardless of vertical eye-in-head position. After the initial 47-ms period, the degree of alignment of the eye and head velocity axes was modulated by vertical eye-in-head position. When fixation was on a target 20 degrees up, the eye and head velocity axes remained well aligned with each other. However, when fixation was on targets at 0 and 20 degrees down, the eye velocity axis tilted forward relative to the head velocity axis. During active head impulses, the axis tilt became apparent within 5 ms of the onset of the stimulus. When fixation was on a target at 0 degrees, the velocity axes remained well aligned with each other. When fixation was on a target 20 degrees up, the eye velocity axis tilted backward, when fixation was on a target 20 degrees down, the eye velocity axis tilted forward. The findings show that the VOR compensates very well for head motion in the early part of the response to unpredictable high acceleration stimuli-the eye position- dependence of the

Different strategies for spatial updating in yaw and pitch path integration

PubMed Central

Goeke, Caspar M.; König, Peter; Gramann, Klaus

2013-01-01

Research in spatial navigation revealed the existence of discrete strategies defined by the use of distinct reference frames during virtual path integration. The present study investigated the distribution of these navigation strategies as a function of gender, video gaming experience, and self-estimates of spatial navigation abilities in a population of 300 subjects. Participants watched videos of virtual passages through a star-field with one turn in either the horizontal (yaw) or the vertical (pitch) axis. At the end of a passage they selected one out of four homing arrows to indicate the initial starting location. To solve the task, participants could employ two discrete strategies, navigating within either an egocentric or an allocentric reference frame. The majority of valid subjects (232/260) consistently used the same strategy in more than 75% of all trials. With that approach 33.1% of all participants were classified as Turners (using an egocentric reference frame on both axes) and 46.5% as Non-turners (using an allocentric reference frame on both axes). 9.2% of all participants consistently used an egocentric reference frame in the yaw plane but an allocentric reference frame in the pitch plane (Switcher). Investigating the influence of gender on navigation strategies revealed that females predominantly used the Non-turner strategy while males used both the Turner and the Non-turner strategy with comparable probabilities. Other than expected, video gaming experience did not influence strategy use. Based on a strong quantitative basis with the sample size about an order of magnitude larger than in typical psychophysical studies these results demonstrate that most people reliably use one out of three possible navigation strategies (Turners, Non-turners, Switchers) for spatial updating and provides a sound estimate of how those strategies are distributed within the general population. PMID:23412683

Effects of reaction control system jet flow field interactions on the aerodynamic characteristics of a 0.010-scale space shuttle orbiter model in the Langley Research Center 31 inch CFHT (OA85)

NASA Technical Reports Server (NTRS)

Daileda, J. J.; Marroquin, J.

1974-01-01

An experimental investigation was conducted to obtain detailed effects on supersonic vehicle hypersonic aerodynamic and stability and control characteristics of reaction control system jet flow field interactions with the local vehicle flow field. A 0.010-scale model was used. Six-component force data and wing, elevon, and body flap surface pressure data were obtained through an angle-of-attack range of -10 to +35 degrees with 0 deg angle of sideslip. The test was conducted with yaw, pitch and roll jet simulation at a free-stream Mach number of 10.3 and reaction control system plume simulation of flight dynamic pressures of 5, 10 and 20 PSF.

Modulation of vergence by off-vertical yaw axis rotation in the monkey: normal characteristics and effects of space flight

NASA Technical Reports Server (NTRS)

Dai, M.; Raphan, T.; Kozlovskaya, I.; Cohen, B.

1996-01-01

Horizontal movements of both eyes were recorded simultaneously using scleral search coils in 2 rhesus monkeys before and after the COSMOS 2229 space-flight of 1992-1993. Another 9 monkeys were tested at comparable time intervals and served as controls. Ocular vergence, defined as the difference in horizontal position between the left and right eyes, was measured during off-vertical yaw axis rotation (OVAR) in darkness. Vergence was modulated sinusoidally as a function of head position with regard to gravity during OVAR. The amplitude of peak-to-peak modulation increased with increments in tilt of the angle of the rotational axis (OVAR tilt angle) that ranged from 15 degrees to 90 degrees. Of the 11 monkeys tested, 1 had no measurable modulation in vergence. In the other 10, the mean amplitude of the peak to peak modulation was 5.5 degrees +/- 1.3 degrees at 90 degrees tilt. Each of these monkeys had maximal vergence when its nose was pointed close to upward (gravity back; mean phase: -0.9 degree +/- 26 degrees). After space flight, the modulation in vergence was reduced by over 50% for the two flight monkeys, but the phase of vergence modulation was not altered. The reduction in vergence modulation was sustained for the 11-day postflight testing period. We conclude that changes in vergence are induced in monkeys by the sinusoidal component of gravity acting along the naso-occipital axis during yaw axis OVAR, and that the modulation of the vergence reflex is significantly less sensitive to linear acceleration after space flight.

A Nonlinear Fuel Optimal Reaction Jet Control Law

DTIC Science & Technology

2002-07-29

derive a nonlinear fuel optimal attitude control system (ACS) that drives the final state to the desired state according to a cost function that...αroll = 0.22 rad/s2 and αyaw = 0.20 rad/s2. [ ] ( )( )ωωτω rrr&r r&r ⋅×−⋅= ⋅Ω−= − 2 1 1 II QQ (9) where, Q r is the attitude quaternion ...from Table-1 regarding the relative performance of the nonlinear controller with a conventional PID controller ( used in this paper as a benchmark for

Product of the SNPP VIIRS SD Screen Transmittance and the SD BRDF (RSB) From Both Yaw Maneuver and Regular On-Orbit Data

NASA Technical Reports Server (NTRS)

Lei, Ning; Xiong, Xiaoxiong

2016-01-01

To assure data quality, the Earth-observing Visible Infrared Imaging Radiometer Suite (VIIRS) regularly performs on-orbit radiometric calibrations of its 22 spectral bands. The primary calibration radiance source for the reflective solar bands (RSBs) is a sunlit solar diffuser (SD). During the calibration process, sunlight goes through a perforated plate (the SD screen) and then strikes the SD. The SD scattered sunlight is used for the calibration, with the spectral radiance proportional to the product of the SD screen transmittance and the SD bidirectional reflectance distribution function (BRDF). The BRDF is decomposed to the product of its value at launch and a numerical factor quantifying its change since launch. Therefore, the RSB calibration requires accurate knowledge of the product of the SD screen transmittance and the BRDF (RSB; launch time). Previously, we calculated the product with yaw maneuver data and found that the product had improved accuracy over the prelaunch one. With both yaw maneuver and regular on orbit data, we were able to improve the accuracy of the SDSM screen transmittance and the product for the solar diffuser stability monitor SD view. In this study, we use both yaw maneuver and a small portion of regular on-orbit data to determine the product for the RSB SD view.

NASA Ares I Launch Vehicle Roll and Reaction Control Systems Lessons Learned

NASA Technical Reports Server (NTRS)

Butt, Adam; Popp, Chris G.; Jernigan, Frankie R.; Paseur, Lila F.; Pitts, Hank M.

2011-01-01

On April 15, 2010 President Barak Obama made the official announcement that the Constellation Program, which included the Ares I launch vehicle, would be canceled. NASA s Ares I launch vehicle was being designed to launch the Orion Crew Exploration Vehicle, returning humans to the moon, Mars, and beyond. It consisted of a First Stage (FS) five segment solid rocket booster and a liquid J-2X Upper Stage (US) engine. Roll control for the FS was planned to be handled by a dedicated Roll Control System (RoCS), located on the connecting interstage. Induced yaw or pitch moments experienced during FS ascent would have been handled by vectoring of the booster nozzle. After FS booster separation, the US Reaction Control System (ReCS) would have provided the US Element with three degrees of freedom control as needed. The lessons learned documented in this paper will be focused on the technical designs and producibility of both systems along with the partnership between NASA and Boeing, who was on contract to build the Ares I US Element, which included the FS RoCS and US ReCS. In regards to partnership, focus will be placed on integration along with technical work accomplished by Boeing with special emphasis on each task order. In summary, this paper attempts to capture key lessons learned that should be helpful in the development of future launch vehicle RCS designs.

Linear parameter varying representations for nonlinear control design

NASA Astrophysics Data System (ADS)

Carter, Lance Huntington

Linear parameter varying (LPV) systems are investigated as a framework for gain-scheduled control design and optimal hybrid control. An LPV system is defined as a linear system whose dynamics depend upon an a priori unknown but measurable exogenous parameter. A gain-scheduled autopilot design is presented for a bank-to-turn (BTT) missile. The method is novel in that the gain-scheduled design does not involve linearizations about operating points. Instead, the missile dynamics are brought to LPV form via a state transformation. This idea is applied to the design of a coupled longitudinal/lateral BTT missile autopilot. The pitch and yaw/roll dynamics are separately transformed to LPV form, where the cross axis states are treated as "exogenous" parameters. These are actually endogenous variables, so such a plant is called "quasi-LPV." Once in quasi-LPV form, a family of robust controllers using mu synthesis is designed for both the pitch and yaw/roll channels, using angle-of-attack and roll rate as the scheduling variables. The closed-loop time response is simulated using the original nonlinear model and also using perturbed aerodynamic coefficients. Modeling and control of engine idle speed is investigated using LPV methods. It is shown how generalized discrete nonlinear systems may be transformed into quasi-LPV form. A discrete nonlinear engine model is developed and expressed in quasi-LPV form with engine speed as the scheduling variable. An example control design is presented using linear quadratic methods. Simulations are shown comparing the LPV based controller performance to that using PID control. LPV representations are also shown to provide a setting for hybrid systems. A hybrid system is characterized by control inputs consisting of both analog signals and discrete actions. A solution is derived for the optimal control of hybrid systems with generalized cost functions. This is shown to be computationally intensive, so a suboptimal strategy is proposed that

From Wake Steering to Flow Control

DOE PAGES

Fleming, Paul A.; Annoni, Jennifer; Churchfield, Matthew J.; ...

2017-11-22

In this article, we investigate the role of flow structures generated in wind farm control through yaw misalignment. A pair of counter-rotating vortices are shown to be important in deforming the shape of the wake and in explaining the asymmetry of wake steering in oppositely signed yaw angles. We motivate the development of new physics for control-oriented engineering models of wind farm control, which include the effects of these large-scale flow structures. Such a new model would improve the predictability of control-oriented models. Results presented in this paper indicate that wind farm control strategies, based on new control-oriented models withmore » new physics, that target total flow control over wake redirection may be different, and perhaps more effective, than current approaches. We propose that wind farm control and wake steering should be thought of as the generation of large-scale flow structures, which will aid in the improved performance of wind farms.« less

Optimum Actuator Selection with a Genetic Algorithm for Aircraft Control

NASA Technical Reports Server (NTRS)

Rogers, James L.

2004-01-01

The placement of actuators on a wing determines the control effectiveness of the airplane. One approach to placement maximizes the moments about the pitch, roll, and yaw axes, while minimizing the coupling. For example, the desired actuators produce a pure roll moment without at the same time causing much pitch or yaw. For a typical wing, there is a large set of candidate locations for placing actuators, resulting in a substantially larger number of combinations to examine in order to find an optimum placement satisfying the mission requirements and mission constraints. A genetic algorithm has been developed for finding the best placement for four actuators to produce an uncoupled pitch moment. The genetic algorithm has been extended to find the minimum number of actuators required to provide uncoupled pitch, roll, and yaw control. A simplified, untapered, unswept wing is the model for each application.

The application of hydraulics in the 2,000 kW wind turbine generator

NASA Technical Reports Server (NTRS)

Onufreiczuk, S.

1978-01-01

A 2000 kW turbine generator using hydraulic power in two of its control systems is being built under the management of NASA Lewis Research Center. The hydraulic systems providing the control torques and forces for the yaw and blade pitch control systems are discussed. The yaw-drive-system hydraulic supply provides the power for positioning the nacelle so that the rotary axis is kept in line with the direction of the prevailing wind, as well as pressure to the yaw and high speed shaft brakes. The pitch-change-mechanism hydraulic system provides the actuation to the pitch change mechanism and permits feathering of the blades during an emergency situation. It operates in conjunction with the overall windmill computer system, with the feather control permitting slewing control flow to pass from the servo valve to the actuators without restriction.

Validation of the actuator disc and actuator line techniques for yawed rotor flows using the New MEXICO experimental data

NASA Astrophysics Data System (ADS)

Breton, S.-P.; Shen, W. Z.; Ivanell, S.

2017-05-01

Experimental data acquired in the New MEXICO experiment on a yawed 4.5m diameter rotor model turbine are used here to validate the actuator line (AL) and actuator disc (AD) models implemented in the Large Eddy Simulation code EllipSys3D in terms of loading and velocity field. Even without modelling the geometry of the hub and nacelle, the AL and AD models produce similar results that are generally in good agreement with the experimental data under the various configurations considered. As expected, the AL model does better at capturing the induction effects from the individual blade tip vortices, while the AD model can reproduce the averaged features of the flow. The importance of using high quality airfoil data (including 3D corrections) as well as a fine grid resolution is highlighted by the results obtained. Overall, it is found that both models can satisfactorily predict the 3D velocity field and blade loading of the New MEXICO rotor under yawed inflow.

Wind turbine with automatic pitch and yaw control

DOEpatents

Cheney, Jr., Marvin Chapin; Spierings, Petrus A. M.

1978-01-01

A wind turbine having a flexible central beam member supporting aerodynamic blades at opposite ends thereof and fabricated of uni-directional high tensile strength material bonded together into beam form so that the beam is lightweight, and has high tensile strength to carry the blade centrifugal loads, low shear modulus to permit torsional twisting thereof for turbine speed control purposes, and adequate bending stiffness to permit out-of-plane deflection thereof for turbine yard control purposes. A selectively off-set weighted pendulum member is pivotally connected to the turbine and connected to the beam or blade so as to cause torsional twisting thereof in response to centrifugal loading of the pendulum member for turbine speed control purposes.

Evaluation of SMART sensor displays for multidimensional precision control of Space Shuttle remote manipulator

NASA Technical Reports Server (NTRS)

Bejczy, A. K.; Brown, J. W.; Lewis, J. L.

1982-01-01

An enhanced proximity sensor and display system was developed at the Jet Propulsion Laboratory (JPL) and tested on the full scale Space Shuttle Remote Manipulator at the Johnson Space Center (JSC) Manipulator Development Facility (MDF). The sensor system, integrated with a four-claw end effector, measures range error up to 6 inches, and pitch and yaw alignment errors within + or 15 deg., and displays error data on both graphic and numeric displays. The errors are referenced to the end effector control axes through appropriate data processing by a dedicated microcomputer acting on the sensor data in real time. Both display boxes contain a green lamp which indicates whether the combination of range, pitch and yaw errors will assure a successful grapple. More than 200 test runs were completed in early 1980 by three operators at JSC for grasping static and capturing slowly moving targets. The tests have indicated that the use of graphic/numeric displays of proximity sensor information improves precision control of grasp/capture range by more than a factor of two for both static and dynamic grapple conditions.

A simulation investigation of scout/attack helicopter directional control requirements for hover and low-speed tasks

NASA Technical Reports Server (NTRS)

Bivens, Courtland C.; Guercio, Joseph G.

1987-01-01

A piloted simulator experiment was conducted to investigate directional axis handling qualities requirements for low speed and hover tasks performed by a Scout/Attack helicopter. Included were the directional characteristics of various candidate light helicopter family configurations. Also, the experiment focused on conventional single main/tail rotor configurations of the OH-58 series aircraft, where the first-order yaw-axis dynamic effects that contributed to the loss of tail rotor control were modeled. Five pilots flew 22 configurations under various wind conditions. Cooper-Harper handling quality ratings were used as the primary measure of merit of each configuration. The results of the experiment indicate that rotorcraft configurations with high directional gust sensitivity require greater minimum yaw damping to maintain satisfactory handling qualities during nap-of-the-Earth flying tasks. It was also determined that both yaw damping and control response are critical handling qualities parameters in performing the air-to-air target acquisition and tracking task. Finally, the lack of substantial yaw damping and larger values of gust sensitivity increased the possibility of loss of directional control at low airspeeds for the single main/tail rotor configurations.

Gain scheduled linear quadratic control for quadcopter

NASA Astrophysics Data System (ADS)

Okasha, M.; Shah, J.; Fauzi, W.; Hanouf, Z.

2017-12-01

This study exploits the dynamics and control of quadcopters using Linear Quadratic Regulator (LQR) control approach. The quadcopter’s mathematical model is derived using the Newton-Euler method. It is a highly manoeuvrable, nonlinear, coupled with six degrees of freedom (DOF) model, which includes aerodynamics and detailed gyroscopic moments that are often ignored in many literatures. The linearized model is obtained and characterized by the heading angle (i.e. yaw angle) of the quadcopter. The adopted control approach utilizes LQR method to track several reference trajectories including circle and helix curves with significant variation in the yaw angle. The controller is modified to overcome difficulties related to the continuous changes in the operating points and eliminate chattering and discontinuity that is observed in the control input signal. Numerical non-linear simulations are performed using MATLAB and Simulink to illustrate to accuracy and effectiveness of the proposed controller.

Cat vestibular neurons that exhibit different responses to active and passive yaw head rotations

NASA Technical Reports Server (NTRS)

Robinson, F. R.; Tomko, D. L.

1987-01-01

Neurons in the vestibular nuclei were recorded in alert cats during voluntary yaw rotations of the head and during the same rotations delivered with a turntable driven from a record of previous voluntary movements. During both voluntary and passive rotations, 35 percent (6/17) of neurons tested responded at higher rates or for a larger part of the movement during voluntary movements than during the same rotations delivered with the turntable. Neck sensory input was evaluated separately in many of these cells and can account qualitatively for the extra firing present during active movement.

The Drag Coefficient of Parabolic Bodies of Revolution Operating at Zero Cavitation Number and Zero Angle of Yaw

NASA Technical Reports Server (NTRS)

Johnson, Virgil E., Jr.; Rasnick, Thomas A.

1961-01-01

The form-drag coefficient of parabolic bodies of revolution with fineness ratios greater than 1 operating at zero angle of yaw and zero cavitation number is determined both theoretically and experimentally. Agreement between theory and experiment is very good, The theoretical form-drag coefficient of paraboloids is about half the form-drag coefficient of cones of comparable fineness ratio.

Free-flight investigation of forebody blowing for stability and control

NASA Technical Reports Server (NTRS)

Brandon, Jay M.; Simon, James M.; Owens, D. Bruce; Kiddy, Jason S.

1996-01-01

A free-flight wind-tunnel investigation was conducted on a generic fighter model with forebody pneumatic vortex control for high angle-of-attack directional control. This is believed to be the first flight demonstration of a forebody blowing concept integrated into a closed-loop flight control system for stability augmentation and control. The investigation showed that the static wind tunnel estimates of the yaw control available generally agreed with flight results. The control scheme for the blowing nozzles consisted of an on/off control with a deadband. Controlled flight was obtained for the model using forebody blowing for directional control to beyond 45 deg. angle of attack.

Dexterous Humanoid Robotic Wrist

NASA Technical Reports Server (NTRS)

Ihrke, Chris A. (Inventor); Bridgwater, Lyndon (Inventor); Reich, David M. (Inventor); Wampler, II, Charles W. (Inventor); Askew, Scott R. (Inventor); Diftler, Myron A. (Inventor); Nguyen, Vienny (Inventor)

2013-01-01

A humanoid robot includes a torso, a pair of arms, a neck, a head, a wrist joint assembly, and a control system. The arms and the neck movably extend from the torso. Each of the arms includes a lower arm and a hand that is rotatable relative to the lower arm. The wrist joint assembly is operatively defined between the lower arm and the hand. The wrist joint assembly includes a yaw axis and a pitch axis. The pitch axis is disposed in a spaced relationship to the yaw axis such that the axes are generally perpendicular. The pitch axis extends between the yaw axis and the lower arm. The hand is rotatable relative to the lower arm about each of the yaw axis and the pitch axis. The control system is configured for determining a yaw angle and a pitch angle of the wrist joint assembly.

Control effectiveness and tip-fin dihedral effects for the HL-20 lifting-body configuration at Mach numbers from 1.6 to 4.5

NASA Technical Reports Server (NTRS)

Cruz, Christopher I.; Ware, George M.

1995-01-01

Wind tunnel tests were made with a scale model of the HL-20 in the Langley Unitary Plan Wind Tunnel. Pitch control was investigated by deflecting the elevon surfaces on the outboard fins and body flaps on the fuselage. Yaw control tests were made with the all movable center fin deflected 5 deg. Almost full negative body flap deflection (-30 deg) was required to trim the HL-20 (moment reference center at 0.54-percent body length from nose) to positive values of life in the Mach number range from 1.6 to 2.5. Elevons were twice as effective as body flaps as a longitudinal trim device. The elevons were effective as a roll control, but because of tip-fin dihedral angle, produced about as much adverse yawing moment as rolling moment. The body flaps were less effective in producing rolling moment, but produced little adverse yawing moment. The yaw effectiveness of the all movable center fin was essentially constant over the angle-of-attack range at each Mach number. The value of yawing moment, however, was small. Center-fin deflection produced almost no rolling moments. The model was directionally unstable over most of the Mach number range with tip-fin dihedral angles less than the baseline value of 50 deg.

Design and Testing of Three-Axis Satellite Attitude Determination and Stabilization Systems That Are Based on Magnetic Sensing and Actuation

DTIC Science & Technology

2002-11-27

than a liability. It stabilizes yaw and pitch by using a badminton -birdie type configuration, one like that pictured in Fig. 2. The basic principal...of metal or Kevlar that resemble the tape in a carpenter’s retractable tape measure. Fig. 2. Badminton -birdie-type spacecraft pitch-yaw stabilization...A second design uses a new passive aerodynamic pitch-yaw stabilization system. This latter system is based on the concept of a badminton birdie and

TRMM On Orbit Attitude Control System Performance

NASA Technical Reports Server (NTRS)

Robertson, Brent; Placanica, Sam; Morgenstern, Wendy

1999-01-01

This paper presents an overview of the Tropical Rainfall Measuring Mission (TRMM) Attitude Control System (ACS) along with detailed in-flight performance results for each operational mode. The TRMM spacecraft is an Earth-pointed, zero momentum bias satellite launched on November 27, 1997 from Tanegashima Space Center, Japan. TRMM is a joint mission between NASA and the National Space Development Agency (NASDA) of Japan designed to monitor and study tropical rainfall and the associated release of energy. Launched to provide a validation for poorly known rainfall data sets generated by global climate models, TRMM has demonstrated its utility by reducing uncertainties in global rainfall measurements by a factor of two. The ACS is comprised of Attitude Control Electronics (ACE), an Earth Sensor Assembly (ESA), Digital Sun Sensors (DSS), Inertial Reference Units (IRU), Three Axis Magnetometers (TAM), Coarse Sun Sensors (CSS), Magnetic Torquer Bars (MTB), Reaction Wheel Assemblies (RWA), Engine Valve Drivers (EVD) and thrusters. While in Mission Mode, the ESA provides roll and pitch axis attitude error measurements and the DSS provide yaw updates twice per orbit. In addition, the TAM in combination with the IRU and DSS can be used to provide pointing in a contingency attitude determination mode which does not rely on the ESA. Although the ACS performance to date has been highly successful, lessons were learned during checkout and initial on-orbit operation. This paper describes the design, on-orbit checkout, performance and lessons learned for the TRMM ACS.

Attitude control system for a lightweight flapping wing MAV.

PubMed

Tijmons, Sjoerd; Karásek, Matěj; de Croon, G C H E

2018-03-14

Robust attitude control is an essential aspect of research on autonomous flight of flapping wing Micro Air Vehicles. The mechanical solutions by which the necessary control moments are realised come at the price of extra weight and possible loss of aerodynamic efficiency. Stable flight of these vehicles has been shown by several designs using a conventional tail, but also by tailless designs that use active control of the wings. In this study a control mechanism is proposed that provides active control over the wings. The mechanism improves vehicle stability and agility by generation of control moments for roll, pitch and yaw. Its effectiveness is demonstrated by static measurements around all the three axes. Flight test results confirm that the attitude of the test vehicle, including a tail, can be successfully controlled in slow forward flight conditions. Furthermore, the flight envelope is extended with robust hovering and the ability to reverse the flight direction using a small turn space. This capability is very important for autonomous flight capabilities such as obstacle avoidance. Finally, it is demonstrated that the proposed control mechanism allows for tailless hovering flight. © 2018 IOP Publishing Ltd.

The Effect of Yaw Coupling in Turning Maneuvers of Large Transport Aircraft

NASA Technical Reports Server (NTRS)

McNeill, Walter E.; Innis, Robert C.

1965-01-01

A study has been made, using a piloted moving simulator, of the effects of the yaw-coupling parameters N(sub p) and N(sub delta(sub a) on the lateral-directional handling qualities of a large transport airplane at landing-approach airspeed. It is shown that the desirable combinations of these parameters tend to be more proverse when compared with values typical of current aircraft. Results of flight tests in a large variable-stability jet transport showed trends which were similar to those of the simulator data. Areas of minor disagreement, which were traced to differences in airplane geometry, indicate that pilot consciousness of side acceleration forces can be an important factor in handling qualities of future long-nosed transport aircraft.

Genetic diversity in Treponema pallidum: implications for pathogenesis, evolution and molecular diagnostics of syphilis and yaws

PubMed Central

Šmajs, David; Norris, Steven J.; Weinstock, George M.

2013-01-01

Pathogenic uncultivable treponemes, similar to syphilis-causing Treponema pallidum subspecies pallidum, include T. pallidum ssp. pertenue, T. pallidum ssp. endemicum and Treponema carateum, which cause yaws, bejel and pinta, respectively. Genetic analyses of these pathogens revealed striking similarity among these bacteria and also a high degree of similarity to the rabbit pathogen, T. paraluiscuniculi, a treponeme not infectious to humans. Genome comparisons between pallidum and non-pallidum treponemes revealed genes with potential involvement in human infectivity, whereas comparisons between pallidum and pertenue treponemes identified genes possibly involved in the high invasivity of syphilis treponemes. Genetic variability within syphilis strains is considered as the basis of syphilis molecular epidemiology with potential to detect more virulent strains, whereas genetic variability within a single strain is related to its ability to elude the immune system of the host. Genome analyses also shed light on treponemal evolution and on chromosomal targets for molecular diagnostics of treponemal infections. PMID:22198325

The Effect of Faster Engine Response on the Lateral Directional Control of a Damaged Aircraft

NASA Technical Reports Server (NTRS)

May, Ryan D.; Lemon, Kimberly A.; Csank, Jeffrey T.; Litt, Jonathan S.; Guo, Ten-Huei

2012-01-01

The integration of flight control and propulsion control has been a much discussed topic, especially for emergencies where the engines may be able to help stabilize and safely land a damaged aircraft. Previous research has shown that for the engines to be effective as flight control actuators, the response time to throttle commands must be improved. Other work has developed control modes that accept a higher risk of engine failure in exchange for improved engine response during an emergency. In this effort, a nonlinear engine model (the Commercial Modular Aero-Propulsion System Simulation 40k) has been integrated with a nonlinear airframe model (the Generic Transport Model) in order to evaluate the use of enhanced-response engines as alternative yaw rate control effectors. Tests of disturbance rejection and command tracking were used to determine the impact of the engines on the aircraft's dynamical behavior. Three engine control enhancements that improve the response time of the engine were implemented and tested in the integrated simulation. The enhancements were shown to increase the engine s effectiveness as a yaw rate control effector when used in an automatic feedback loop. The improvement is highly dependent upon flight condition; the airframe behavior is markedly improved at low altitude, low speed conditions, and relatively unchanged at high altitude, high speed.

Variable Structure Control of a Hand-Launched Glider

NASA Technical Reports Server (NTRS)

Anderson, Mark R.; Waszak, Martin R.

2005-01-01

Variable structure control system design methods are applied to the problem of aircraft spin recovery. A variable structure control law typically has two phases of operation. The reaching mode phase uses a nonlinear relay control strategy to drive the system trajectory to a pre-defined switching surface within the motion state space. The sliding mode phase involves motion along the surface as the system moves toward an equilibrium or critical point. Analysis results presented in this paper reveal that the conventional method for spin recovery can be interpreted as a variable structure controller with a switching surface defined at zero yaw rate. Application of Lyapunov stability methods show that deflecting the ailerons in the direction of the spin helps to insure that this switching surface is stable. Flight test results, obtained using an instrumented hand-launched glider, are used to verify stability of the reaching mode dynamics.

Quantifying the In-Flight Yaw, Pitch, and Roll of a Semi-Rigidly Mounted Potassium Vapour Magnetometer Suspended Under a Heavy-Lift Multi-Rotor UAV and its Impact on Data Quality

NASA Astrophysics Data System (ADS)

Walter, C. A.; Braun, A.; Fotopoulos, G.

2017-12-01

Research is being conducted to develop an Unmanned Aerial System (UAS) that is capable of reliably and efficiently collecting high resolution, industry standard magnetic data (magnetic data with a fourth difference of +/- 0.05 nT) via an optically pumped vapour magnetometer. The benefits of developing a UAS with these capabilities include improvements in the resolution of localized airborne surveys (2.5 km by 2.5 km) and the ability to conduct 3D magnetic gradiometry surveys in the observation gap evident between traditional terrestrial and manned airborne magnetic surveys (surface elevation up to 120 m). Quantifying the extent of an optically pumped vapour magnetometer's 3D orientation variations, while in-flight and suspended under a UAS, is a significant advancement to existing knowledge as optically pumped magnetometers have an orientation-dependent (to the primary magnetic field vector) process for measuring the magnetic field. This study investigates the orientation characteristics of a GEM Systems potassium vapour magnetometer, GSMP-35U, while semi-rigidly suspended 3 m under a DJI S900, heavy-lift multi-rotor UAV (Unmanned Aerial Vehicle) during an airborne surveying campaign conducted Northeast of Thunder Bay, Ontario, Canada. A nine degrees of freedom IMU (Inertial Measurement Unit), the Adafruit GY-80, was used to quantify the 3D orientation variations (yaw, pitch and roll) of the magnetic sensor during flight. The orientation and magnetic datasets were indexed and linked with a date and time stamp (within 1 ms) via a Raspberry Pi 2, acting as an on-board computer and data storage system. Analysing the two datasets allowed for the in-flight orientation variations of the potassium vapour magnetometer to be directly compared with the gathered magnetic and signal quality data of the magnetometer. The in-flight orientation characteristics of the magnetometer were also quantified for a range of air-speeds and flight maneuvers throughout the survey. Overall

Design of a mixer for the thrust-vectoring system on the high-alpha research vehicle

NASA Technical Reports Server (NTRS)

Pahle, Joseph W.; Bundick, W. Thomas; Yeager, Jessie C.; Beissner, Fred L., Jr.

1996-01-01

One of the advanced control concepts being investigated on the High-Alpha Research Vehicle (HARV) is multi-axis thrust vectoring using an experimental thrust-vectoring (TV) system consisting of three hydraulically actuated vanes per engine. A mixer is used to translate the pitch-, roll-, and yaw-TV commands into the appropriate TV-vane commands for distribution to the vane actuators. A computer-aided optimization process was developed to perform the inversion of the thrust-vectoring effectiveness data for use by the mixer in performing this command translation. Using this process a new mixer was designed for the HARV and evaluated in simulation and flight. An important element of the Mixer is the priority logic, which determines priority among the pitch-, roll-, and yaw-TV commands.

Trajectory tracking in quadrotor platform by using PD controller and LQR control approach

NASA Astrophysics Data System (ADS)

Islam, Maidul; Okasha, Mohamed; Idres, Moumen Mohammad

2017-11-01

The purpose of the paper is to discuss a comparative evaluation of performance of two different controllers i.e. Proportional-Derivative Controller (PD) and Linear Quadratic Regulation (LQR) in Quadrotor dynamic system that is under-actuated with high nonlinearity. As only four states can be controlled at the same time in the Quadrotor, the trajectories are designed on the basis of the four states whereas three dimensional position and rotation along an axis, known as yaw movement are considered. In this work, both the PD controller and LQR control approach are used for Quadrotor nonlinear model to track the trajectories. LQR control approach for nonlinear model is designed on the basis of a linear model of the Quadrotor because the performance of linear model and nonlinear model around certain nominal point is almost similar. Simulink and MATLAB software is used to design the controllers and to evaluate the performance of both the controllers.

Simulation model of the F/A-18 high angle-of-attack research vehicle utilized for the design of advanced control laws

NASA Technical Reports Server (NTRS)

Strickland, Mark E.; Bundick, W. Thomas; Messina, Michael D.; Hoffler, Keith D.; Carzoo, Susan W.; Yeager, Jessie C.; Beissner, Fred L., Jr.

1996-01-01

The 'f18harv' six degree-of-freedom nonlinear batch simulation used to support research in advanced control laws and flight dynamics issues as part of NASA's High Alpha Technology Program is described in this report. This simulation models an F/A-18 airplane modified to incorporate a multi-axis thrust-vectoring system for augmented pitch and yaw control power and actuated forebody strakes for enhanced aerodynamic yaw control power. The modified configuration is known as the High Alpha Research Vehicle (HARV). The 'f18harv' simulation was an outgrowth of the 'f18bas' simulation which modeled the basic F/A-18 with a preliminary version of a thrust-vectoring system designed for the HARV. The preliminary version consisted of two thrust-vectoring vanes per engine nozzle compared with the three vanes per engine actually employed on the F/A-18 HARV. The modeled flight envelope is extensive in that the aerodynamic database covers an angle-of-attack range of -10 degrees to +90 degrees, sideslip range of -20 degrees to +20 degrees, a Mach Number range between 0.0 and 2.0, and an altitude range between 0 and 60,000 feet.

Flatness-Based Tracking Control and Nonlinear Observer for a Micro Aerial Quadcopter

NASA Astrophysics Data System (ADS)

Rivera, G.; Sawodny, O.

2010-09-01

This paper deals with the design of a nonlinear observer and a differential flat based path tracking controller for a mini aerial quadcopter. Taking into account that only the inertial coordinates and the yaw angle are available for measurements, it is shown, that the system is differentially flat, allowing a systematic design of a nonlinear tracking control in open and closed loop. A nonlinear observer is carried out to estimate the roll and pitch angle as well as all the linear and angular velocities. Finally the performance of the feedback controller and observer are illustrated in a computer simulation.

Application of a passivity based control methodology for flexible joint robots to a simplified Space Shuttle RMS

NASA Technical Reports Server (NTRS)

Sicard, Pierre; Wen, John T.

1992-01-01

A passivity approach for the control design of flexible joint robots is applied to the rate control of a three-link arm modeled after the shoulder yaw joint of the Space Shuttle Remote Manipulator System (RMS). The system model includes friction and elastic joint couplings modeled as nonlinear springs. The basic structure of the proposed controller is the sum of a model-based feedforward and a model-independent feedback. A regulator approach with link state feedback is employed to define the desired motor state. Passivity theory is used to design a motor state-based controller to stabilize the error system formed by the feedforward. Simulation results show that greatly improved performance was obtained by using the proposed controller over the existing RMS controller.

Solar Sail Attitude Control System for the NASA Near Earth Asteroid Scout Mission

NASA Technical Reports Server (NTRS)

Orphee, Juan; Diedrich, Ben; Stiltner, Brandon; Becker, Chris; Heaton, Andrew

2017-01-01

An Attitude Control System (ACS) has been developed for the NASA Near Earth Asteroid (NEA) Scout mission. The NEA Scout spacecraft is a 6U cubesat with an eighty-six square meter solar sail for primary propulsion that will launch as a secondary payload on the Space Launch System (SLS) Exploration Mission 1 (EM-1) and rendezvous with a target asteroid after a two year journey, and will conduct science imagery. The spacecraft ACS consists of three major actuating subsystems: a Reaction Wheel (RW) control system, a Reaction Control System (RCS), and an Active Mass Translator (AMT) system. The reaction wheels allow fine pointing and higher rates with low mass actuators to meet the science, communication, and trajectory guidance requirements. The Momentum Management System (MMS) keeps the speed of the wheels within their operating margins using a combination of solar torque and the RCS. The AMT is used to adjust the sign and magnitude of the solar torque to manage pitch and yaw momentum. The RCS is used for initial de-tumble, performing a Trajectory Correction Maneuver (TCM), and performing momentum management about the roll axis. The NEA Scout ACS is able to meet all mission requirements including attitude hold, slews, pointing for optical navigation and pointing for science with margin and including flexible body effects. Here we discuss the challenges and solutions of meeting NEA Scout mission requirements for the ACS design, and present a novel implementation of managing the spacecraft Center of Mass (CM) to trim the solar sail disturbance torque. The ACS we have developed has an applicability to a range of potential missions and does so in a much smaller volume than is traditional for deep space missions beyond Earth.

Predicting Ares I Reaction Control System Performance by Utilizing Analysis Anchored with Development Test Data

NASA Technical Reports Server (NTRS)

Stein, William B.; Holt, K.; Holton, M.; Williams, J. H.; Butt, A.; Dervan, M.; Sharp, D.

2010-01-01

The Ares I launch vehicle is an integral part of NASA s Constellation Program, providing a foundation for a new era of space access. The Ares I is designed to lift the Orion Crew Module and will enable humans to return to the Moon as well as explore Mars.1 The Ares I is comprised of two inline stages: a Space Shuttle-derived five-segment Solid Rocket Booster (SRB) First Stage (FS) and an Upper Stage (US) powered by a Saturn V-derived J-2X engine. A dedicated Roll Control System (RoCS) located on the connecting interstage provides roll control prior to FS separation. Induced yaw and pitch moments are handled by the SRB nozzle vectoring. The FS SRB operates for approximately two minutes after which the US separates from the vehicle and the US Reaction Control System (ReCS) continues to provide reaction control for the remainder of the mission. A representation of the Ares I launch vehicle in the stacked configuration and including the Orion Crew Exploration Vehicle (CEV) is shown in Figure 1. Each Reaction Control System (RCS) design incorporates a Gaseous Helium (GHe) pressurization system combined with a monopropellant Hydrazine (N2H4) propulsion system. Both systems have two diametrically opposed thruster modules. This architecture provides one failure tolerance for function and prevention of catastrophic hazards such as inadvertent thruster firing, bulk propellant leakage, and over-pressurization. The pressurization system on the RoCS includes two ambient pressure-referenced regulators on parallel strings in order to attain the required system level single Fault Tolerant (FT) design for function while the ReCS utilizes a blow-down approach. A single burst disk and relief valve assembly is also included on the RoCS to ensure single failure tolerance for must-not-occur catastrophic hazards. The Reaction Control Systems are designed to support simultaneously firing multiple thrusters as required

Lateral Stability and Control Measurements of a 0.0858-Scale Model of the Lockheed XF-104 Airplane at Transonic Speeds

NASA Technical Reports Server (NTRS)

Arabian, Donald D.; Schmeer, James W.

1955-01-01

An investigation of the lateral stability and control effectiveness of a 0.0858-scale model of the Lockheed XF-104 airplane has been conducted in the Langley 16-foot transonic tunnel. The model has a low aspect ratio, 3.4-percent-thick wing with negative dihedral. The horizontal tail is located on top of the vertical tail. The investigation was made through a Mach number range of 0.80 to 1.06 at sideslip angles of -5 deg. to 5 deg. and angles of attack from 0 deg. to 16 deg. The control effectiveness of the aileron, rudder, and yaw damper were determined through the Mach number and angle-of-attack range. The results of the investigation indicated that the directional stability derivative was stable and that positive effective dihedral existed throughout the lift-coefficient range and Mach number range tested. The total aileron effectiveness, which in general produced favorable yaw with rolling moment, remained fairly constant for lift coefficients up to about 0.8 for the Mach number range tested. Yawing-moment effectiveness of the rudder changed little through the Mach number range. However, the yaw damper effectiveness decreased about 30 percent at the intermediate test Mach numbers.

Applications of system identification methods to the prediction of helicopter stability, control and handling characteristics

NASA Technical Reports Server (NTRS)

Padfield, G. D.; Duval, R. K.

1982-01-01

A set of results on rotorcraft system identification is described. Flight measurements collected on an experimental Puma helicopter are reviewed and some notable characteristics highlighted. Following a brief review of previous work in rotorcraft system identification, the results of state estimation and model structure estimation processes applied to the Puma data are presented. The results, which were obtained using NASA developed software, are compared with theoretical predictions of roll, yaw and pitching moment derivatives for a 6 degree of freedom model structure. Anomalies are reported. The theoretical methods used are described. A framework for reduced order modelling is outlined.

STAYLAM: A FORTRAN program for the suction transition analysis of a yawed wing laminar boundary layer

NASA Technical Reports Server (NTRS)

Carter, J. E.

1977-01-01

A computer program called STAYLAM is presented for the computation of the compressible laminar boundary-layer flow over a yawed infinite wing including distributed suction. This program is restricted to the transonic speed range or less due to the approximate treatment of the compressibility effects. The prescribed suction distribution is permitted to change discontinuously along the chord measured perpendicular to the wing leading edge. Estimates of transition are made by considering leading edge contamination, cross flow instability, and instability of the Tollmien-Schlichting type. A program listing is given in addition to user instructions and a sample case.

Radiation beam collimation system and method

DOEpatents

Schmidt, Oliver A.; Ramanathan, Mohan

2015-08-18

The invention provides a method for collimating a radiation beam, the method comprising subjecting the beam to a collimator that yaws and pitches, either separately or simultaneously relative to the incident angle of the beam. Also provided is a system for collimating radiation beams, the system comprising a collimator body, and a stage for pitching and yawing the body. A feature of the invention is that a single, compact mask body defines one or a plurality of collimators having no moving surfaces relative to each other, whereby the entire mask body is moved about a point in space to provide various collimator opening dimensions to oncoming radiation beams.

Static and yawed-rolling mechanical properties of two type 7 aircraft tires

NASA Technical Reports Server (NTRS)

Tanner, J. A.; Stubbs, S. M.; Mccarty, J. L.

1981-01-01

Selected mechanical properties of 18 x 5.5 and 49 x 17 size, type 7 aircraft tires were evaluated. The tires were subjected to pure vertical loads and to combined vertical and lateral loads under both static and rolling conditions. Parameters for the static tests consisted of tire load in the vertical and lateral directions, and parameters for the rolling tests included tire vertical load, yaw angle, and ground speed. Effects of each of these parameters on the measured tire characteristics are discussed and, where possible, compared with previous work. Results indicate that dynamic tire properties under investigation were generally insensitive to speed variations and therefore tend to support the conclusion that many tire dynamic characteristics can be obtained from static and low speed rolling tests. Furthermore, many of the tire mechanical properties are in good agreement with empirical predictions based on earlier research.

Closed Loop Real-Time Evaluation of Missile Guidance and Control Components: Simulator Hardware/Software Characteristics and Use

DTIC Science & Technology

1974-08-01

Node Control Logic 2-27 2.16 Pitch Channel Frequence Response 2-36 2.17 Yaw Channel Frequency Response 2-37 K 4 2.18 Analog Computer Mechanlzation of...8217S 0 121 £l1:c IL-I. TABLE I Elements of the Slgma 5 Digital Computer System Xerox Model- Performance MIOP Channel Description Number Characteristics...transfer control signals to or from the CPU. The MIOP can handle up to 32 I/0 channels each operating simultaneously, provided the overall data

Multivariable control of a rolling spider drone

NASA Astrophysics Data System (ADS)

Lyu, Haifeng

The research and application of Unmanned Aerial Vehicles (UAVs) has been a hot topic recently. A UAV is dened as an aircraft which is designed not to carry a human pilot or operated with remote electronic input by the flight controller. In this thesis, the design of a control system for a quadcopter named Rolling Spider Drone is conducted. The thesis work presents the design of two kinds of controllers that can control the Drone to keep it balanced and track different kinds of input trajectories. The nonlinear mathematical model for the Drone is derived by the Newton-Euler method. The rotational subsystem and translational system are derived to describe the attitude and position motion of Drone. Techniques from linear control theory are employed to linearize the highly coupled and nonlinear quadcopter plant around equilibrium points and apply the linear feedback controller to stabilize the system. The controller is a digital tracking system that deploys LQR for system stability design. Fixed gain and adaptive gain scheduled controllers are developed and compared with different LQR weights. Step references and reference trajectories involving signicant variation for the yaw angle in the xy-plane and three-dimensional spaces are tracked in the simulation. The physical implementation and an output feedback controller are considered for future work.

Aerodynamic Characteristics and Control Effectiveness of the HL-20 Lifting Body Configuration at Mach 10 in Air

NASA Technical Reports Server (NTRS)

Scallion, William I.

1999-01-01

A 0.0196-scale model of the HL-20 lifting-body, one of several configurations proposed for future crewed spacecraft, was tested in the Langley 31-Inch Mach 10 Tunnel. The purpose of the tests was to determine the effectiveness of fin-mounted elevons, a lower surface flush-mounted body flap, and a flush-mounted yaw controller at hypersonic speeds. The nominal angle-of-attack range, representative of hypersonic entry, was 2 deg to 41 deg, the sideslip angles were 0 deg, 2 deg, and -2 deg, and the test Reynolds number was 1.06 x 10 E6 based on model reference length. The aerodynamic, longitudinal, and lateral control effectiveness along with surface oil flow visualizations are presented and discussed. The configuration was longitudinally and laterally stable at the nominal center of gravity. The primary longitudinal control, the fin-mounted elevons, could not trim the model to the desired entry angle of attack of 30 deg. The lower surface body flaps were effective for roll control and the associated adverse yawing moment was eliminated by skewing the body flap hinge lines. A yaw controller, flush-mounted on the lower surface, was also effective, and the associated small rolling moment was favorable.

TRMM On-Orbit Performance Re-Accessed After Control Change

NASA Technical Reports Server (NTRS)

Bilanow, Steve

2006-01-01

The Tropical Rainfall Measuring Mission (TRMM) spacecraft, a joint mission between the U.S. and Japan, launched onboard an HI1 rocket on November 27,1997 and transitioned in August, 2001 from an average operating altitude of 350 kilometers to 402.5 kilometers. Due to problems using the Earth Sensor Assembly (ESA) at the higher altitude, TRMM switched to a backup attitude control mode. Prior to the orbit boost TRMM controlled pitch and roll to the local vertical using ESA measurements while using gyro data to propagate yaw attitude between yaw updates from the Sun sensors. After the orbit boost, a Kalman filter used 3-axis gyro data with Sun sensor and magnetometers to estimate onboard attitude. While originally intended to meet a degraded attitude accuracy of 0.7 degrees, the new control mode met the original 0.2 degree attitude accuracy requirement after improving onboard ephemeris prediction and adjusting the magnetometer calibration onboard. Independent roll attitude checks using a science instrument, the Precipitation Radar (PR) which was built in Japan, provided a novel insight into the pointing performance. The PR data helped identify the pointing errors after the orbit boost, track the performance improvements, and show subtle effects from ephemeris errors and gyro bias errors. It also helped identify average bias trends throughout the mission. Roll errors tracked by the PR from sample orbits pre-boost and post-boost are shown in Figure 1. Prior to the orbit boost the largest attitude errors were due to occasional interference in the ESA. These errors were sometime larger than 0.2 degrees in pitch and roll, but usually less, as estimated from a comprehensive review of the attitude excursions using gyro data. Sudden jumps in the onboard roll show up as spikes in the reported attitude since the control responds within tens of seconds to null the pointing error. The PR estimated roll tracks well with an estimate of the roll history propagated using gyro data

Curved-flow, rolling-flow, and oscillatory pure-yawing wind-tunnel test methods for determination of dynamic stability derivatives

NASA Technical Reports Server (NTRS)

Chambers, J. R.; Grafton, S. B.; Lutze, F. H.

1981-01-01

The test capabilities of the Stability Wind Tunnel of the Virginia Polytechnic Institute and State University are described, and calibrations for curved and rolling flow techniques are given. Oscillatory snaking tests to determine pure yawing derivatives are considered. Representative aerodynamic data obtained for a current fighter configuration using the curved and rolling flow techniques are presented. The application of dynamic derivatives obtained in such tests to the analysis of airplane motions in general, and to high angle of attack flight conditions in particular, is discussed.

The effect of lateral controls in producing motion of an airplane as computed from wind-tunnel data

NASA Technical Reports Server (NTRS)

Weick, F. E.; Jones, R. T.

1976-01-01

An analytical study of the lateral controllability of an airplane has been made in which both the static rolling and yawing moments supplied by the controls and the reactions due to the inherent stability of the airplane have been taken into account. A hypothetical average airplane, embodying the essential characteristics of both the wind tunnel models and the full size test airplanes, was assumed for the study. Computations made of forced rolling and yawing motions of an F-22 airplane caused by a sudden deflection of the ailerons were found to agree well with actual measurements of these motions. The conditions following instantaneous full deflections of the lateral control have been studied, and some attention has been devoted to the controlling of complete turn maneuvers.

a New Efficient Control Method for Blended Wing Body

NASA Astrophysics Data System (ADS)

Wu, Wenhua; Chen, Dehua; Qin, Ning; Peng, Xin; Tang, Xinwu

The blended wing body (BWB) is the hottest one of the aerodynamic shapes of next generation airliner because of its' high lift-drag ratio, but there are still some flaws that cut down its aerodynamical performance. One of the most harmful flaws is the low efficiency of elevator and direction rudder, this makes the BWB hard to be controlled. In this paper, we proposed a new control method to solve this problem by morphing wing—that is, to control the BWB only by changing its wing shape but without any rudder. The pitching moments, rolling moments and yawing moments are plotted versus the parameters section and the wing shape in figures and are discussed in the paper. The result shows that the morphing wing can control the moments of BWB more precisely and in wider range. The pitching moments, rolling moments and yawing moments increases or decreases linearly or almost linearly, with the value of the selected parameters. These results show that using morphing wing is an excellent aerodynamic control way for a BWB craft.

Oscillation damping means for magnetically levitated systems

DOEpatents

Post, Richard F [Walnut Creek, CA

2009-01-20

The present invention presents a novel system and method of damping rolling, pitching, or yawing motions, or longitudinal oscillations superposed on their normal forward or backward velocity of a moving levitated system.

Computational analysis of stall and separation control in centrifugal compressors

NASA Astrophysics Data System (ADS)

Stein, Alexander

2000-10-01

A numerical technique for simulating unsteady viscous fluid flow in turbomachinery components has been developed. In this technique, the three-dimensional form of the Reynolds averaged Navier-Stokes equations is solved in a time-accurate manner. The flow solver is used to study fluid dynamic phenomena that lead to instabilities in centrifugal compressors. The results indicate that large flow incidence angles, at reduced flow rates, can cause boundary layer separation near the blade leading edge. This mechanism is identified as the primary factor in the stall inception process. High-pressure jets upstream of the compressor face are studied as a means of controlling compressor instabilities. Steady jets are found to alter the leading edge flow pattern and effectively suppress compressor instabilities. Yawed jets are more effective than parallel jets and an optimum yaw angle exists for each compression system. Numerical simulations utilizing pulsed jets have also been done. Pulsed jets are found to yield additional performance enhancements and lead to a reduction in external air requirements for operating the jets. Jets pulsed at higher frequencies perform better than low-frequency jets. These findings suggest that air injection is a viable means of alleviating compressor instabilities and could impact gas turbine technology. Results concerning the optimization of practical air injection systems and implications for future research are discussed. The flow solver developed in this work, along with the postprocessing tools developed to interpret the results, provide a rational framework for analyzing and controlling current and next generation compression systems.

Nonlinear Evolution of Azimuthally Compact Crossflow-Vortex Packet over a Yawed Cone

NASA Astrophysics Data System (ADS)

Choudhari, Meelan; Li, Fei; Paredes, Pedro; Duan, Lian; NASA Langley Research Center Team; Missouri Univ of Sci; Tech Team

2017-11-01

Hypersonic boundary-layer flows over a circular cone at moderate incidence angle can support strong crossflow instability and, therefore, a likely scenario for laminar-turbulent transition in such flows corresponds to rapid amplification of high-frequency secondary instabilities sustained by finite amplitude stationary crossflow vortices. Direct numerical simulations (DNS) are used to investigate the nonlinear evolution of azimuthally compact crossflow vortex packets over a 7-degree half-angle, yawed circular cone in a Mach 6 free stream. Simulation results indicate that the azimuthal distribution of forcing has a strong influence on the stationary crossflow amplitudes; however, the vortex trajectories are nearly the same for both periodic and localized roughness height distributions. The frequency range, mode shapes, and amplification characteristics of strongly amplified secondary instabilities in the DNS are found to overlap with the predictions of secondary instability theory. The DNS computations also provide valuable insights toward the application of planar, partial-differential-equation based eigenvalue analysis to spanwise inhomogeneous, fully three-dimensional, crossflow-dominated flow configurations.

The MOD-OA 200 kilowatt wind turbine generator design and analysis report

NASA Astrophysics Data System (ADS)

Andersen, T. S.; Bodenschatz, C. A.; Eggers, A. G.; Hughes, P. S.; Lampe, R. F.; Lipner, M. H.; Schornhorst, J. R.

1980-08-01

The project requirements, approach, system description, design requirements, design, analysis, system tests, installation safety considerations, failure modes and effects analysis, data acquisition, and initial performance for the MOD-OA 200 kw wind turbine generator are discussed. The components, the rotor, driven train, nacelle equipment, yaw drive mechanism and brake, tower, foundation, electrical system, and control systems are presented. The rotor includes the blades, hub and pitch change mechanism. The drive train includes the low speed shaft, speed increaser, high speed shaft, and rotor brake. The electrical system includes the generator, switchgear, transformer, and utility connection. The control systems are the blade pitch, yaw, and generator control, and the safety system. Manual, automatic, and remote control and Dynamic loads and fatigue are analyzed.

The MOD-OA 200 kilowatt wind turbine generator design and analysis report

NASA Technical Reports Server (NTRS)

Andersen, T. S.; Bodenschatz, C. A.; Eggers, A. G.; Hughes, P. S.; Lampe, R. F.; Lipner, M. H.; Schornhorst, J. R.

1980-01-01

The project requirements, approach, system description, design requirements, design, analysis, system tests, installation safety considerations, failure modes and effects analysis, data acquisition, and initial performance for the MOD-OA 200 kw wind turbine generator are discussed. The components, the rotor, driven train, nacelle equipment, yaw drive mechanism and brake, tower, foundation, electrical system, and control systems are presented. The rotor includes the blades, hub and pitch change mechanism. The drive train includes the low speed shaft, speed increaser, high speed shaft, and rotor brake. The electrical system includes the generator, switchgear, transformer, and utility connection. The control systems are the blade pitch, yaw, and generator control, and the safety system. Manual, automatic, and remote control and Dynamic loads and fatigue are analyzed.

A passivity based control methodology for flexible joint robots with application to a simplified shuttle RMS arm

NASA Technical Reports Server (NTRS)

Sicard, Pierre; Wen, John T.

1991-01-01

The main goal is to develop a general theory for the control of flexible robots, including flexible joint robots, flexible link robots, rigid bodies with flexible appendages, etc. As part of the validation, the theory is applied to the control law development for a test example which consists of a three-link arm modeled after the shoulder yaw joint of the space shuttle remote manipulator system (RMS). The performance of the closed loop control system is then compared with the performance of the existing RMS controller to demonstrate the effectiveness of the proposed approach. The theoretical foundation of this new approach to the control of flexible robots is presented and its efficacy is demonstrated through simulation results on the three-link test arm.

F/A-18 forebody vortex control. Volume 1: Static tests

NASA Technical Reports Server (NTRS)

Kramer, Brian R.; Suarez, Carlos J.; Malcolm, Gerald N.; Ayers, Bert F.

1994-01-01

A wind tunnel test was conducted on a six percent model of the F/A-18 at the NASA Ames 7 X 10-Foot Low Speed Wind Tunnel. The primary objective of the test was to evaluate several forebody vortex control configurations at high angles of attack in order to determine the most effective method of obtaining well behaved yawing moments, in preparation for the rotary balance test. Both mechanical and pneumatic systems were tested. Single and dual rotating nose tip strakes and a vertical nose strake were tested at different sizes and deflections. A series of jet blowing configurations were located at various fuselage stations, azimuth angles, and pointing angles ranging from straight aft to 60 deg canted inboard. Slot blowing was investigated for several slot lengths and fuselage stations. The effect of blowing rate was tested for both of these pneumatic systems. The most effective configurations were then further tested with a variation of both sideslip angle and Reynolds number over a range of angles of attack from 0 to 60 deg. It was found that a very robust system can be developed that provides yawing moments at angles of attack up to 60 deg that significantly exceeds that available from 30 deg of rudder deflection (F/A-18 maximum) at 0 deg angle of attack.

Control system of hexacopter using color histogram footprint and convolutional neural network

NASA Astrophysics Data System (ADS)

Ruliputra, R. N.; Darma, S.

2017-07-01

The development of unmanned aerial vehicles (UAV) has been growing rapidly in recent years. The use of logic thinking which is implemented into the program algorithms is needed to make a smart system. By using visual input from a camera, UAV is able to fly autonomously by detecting a target. However, some weaknesses arose as usage in the outdoor environment might change the target's color intensity. Color histogram footprint overcomes the problem because it divides color intensity into separate bins that make the detection tolerant to the slight change of color intensity. Template matching compare its detection result with a template of the reference image to determine the target position and use it to position the vehicle in the middle of the target with visual feedback control based on Proportional-Integral-Derivative (PID) controller. Color histogram footprint method localizes the target by calculating the back projection of its histogram. It has an average success rate of 77 % from a distance of 1 meter. It can position itself in the middle of the target by using visual feedback control with an average positioning time of 73 seconds. After the hexacopter is in the middle of the target, Convolutional Neural Networks (CNN) classifies a number contained in the target image to determine a task depending on the classified number, either landing, yawing, or return to launch. The recognition result shows an optimum success rate of 99.2 %.

Buffet induced structural/flight-control system interaction of the X-29A aircraft

NASA Technical Reports Server (NTRS)

Voracek, David F.; Clarke, Robert

1991-01-01

High angle-of-attack flight regime research is currently being conducted for modern fighter aircraft at the NASA Ames Research Center's Dryden Flight Research Facility. This flight regime provides enhanced maneuverability to fighter pilots in combat situations. Flight research data are being acquired to compare and validate advanced computational fluid dynamic solutions and wind-tunnel models. High angle-of-attack flight creates unique aerodynamic phenomena including wing rock and buffet on the airframe. These phenomena increase the level of excitation of the structural modes, especially on the vertical and horizontal stabilizers. With high gain digital flight-control systems, this structural response may result in an aeroservoelastic interaction. A structural interaction on the X-29A aircraft was observed during high angle-of-attack flight testing. The roll and yaw rate gyros sensed the aircraft's structural modes at 11, 13, and 16 Hz. The rate gyro output signals were then amplified through the flight-control laws and sent as commands to the flaperons and rudder. The flight data indicated that as the angle of attack increased, the amplitude of the buffet on the vertical stabilizer increased, which resulted in more excitation to the structural modes. The flight-control system sensors and command signals showed this increase in modal power at the structural frequencies up to a 30 degree angle-of-attack. Beyond a 30 degree angle-of-attack, the vertical stabilizer response, the feedback sensor amplitude, and control surface command signal amplitude remained relatively constant. Data are presented that show the increased modal power in the aircraft structural accelerometers, the feedback sensors, and the command signals as a function of angle of attack. This structural interaction is traced from the aerodynamic buffet to the flight-control surfaces.

Handling performance control for hybrid 8-wheel-drive vehicle and simulation verification

NASA Astrophysics Data System (ADS)

Ni, Jun; Hu, Jibin

2016-08-01

In order to improve handling performance of a hybrid 8-Wheel-Drive vehicle, the handling performance control strategy was proposed. For armoured vehicle, besides handling stability in high speed, the minimum steer radius in low speed is also a key tactical and technical index. Based on that, the proposed handling performance control strategy includes 'Handling Stability' and 'Radius Minimization' control modes. In 'Handling Stability' control mode, 'Neutralsteer Radio' is defined to adjust the steering characteristics to satisfy different demand in different speed range. In 'Radius Minimization' control mode, the independent motors are controlled to provide an additional yaw moment to decrease the minimum steer radius. In order to verify the strategy, a simulation platform was built including engine and continuously variable transmission systems, generator and battery systems, independent motors and controllers systems, vehicle dynamic and tyre mechanical systems. The simulation results show that the handling performance of the vehicle can be enhanced significantly, and the minimum steer radius can be decreased by 20% which is significant improvement compared to the common level of main battle armoured vehicle around the world.

Cockpit integration from a pilot's point of view

NASA Technical Reports Server (NTRS)

Green, D. L.

1982-01-01

Extensive experience in both operational and engineering test flight was used to suggest straightforward changes to helicopter cockpit and control system design that would improve pilot performance in marginal and instrument flight conditions. Needed control system improvements considered include: (1) separation of yaw from cyclic force trim; (2) pedal force proportional to displacement rate; and (3) integration of engine controls in collective stick. Display improvements needed include: (1) natural cuing of yaw rate in attitude indicator; (2) collective position indication and radar altimeter placed within primary scan; and (3) omnidirectional display of full range airspeed data.

Flight investigation of the effect of tail boom strakes on helicopter directional control

NASA Technical Reports Server (NTRS)

Kelly, Henry L.; Crowell, Cynthia A.; Yenni, Kenneth R.; Lance, Michael B.

1993-01-01

A joint U.S. Army/NASA flight investigation was conducted utilizing a single-rotor helicopter to determine the effectiveness of horizontally mounted tail boom strakes on directional controllability and tail rotor power during low-speed, crosswind operating conditions. Three configurations were investigated: (1) baseline (strakes off), (2) single strake (strake at upper shoulder on port side of boom), and (3) double strake (upper strake plus a lower strake on same side of boom). The strakes were employed as a means to separate airflow over the tail boom and change fuselage yawing moments in a direction to improve the yaw control margin and reduce tail rotor power. Crosswind data were obtained in 5-knot increments of airspeed from 0 to 35 knots and in 30 deg increments of wind azimuth from 0 deg to 330 deg. At the most critical wind azimuth and airspeed in terms of tail rotor power, the strakes improved the pedal margin by 6 percent of total travel and reduced tail rotor power required by 17 percent. The increase in yaw control and reduction in tail rotor power offered by the strakes can expand the helicopter operating envelope in terms of gross weight and altitude capability. The strakes did not affect the flying qualities of the vehicle at airspeeds between 35 and 100 knots.

Wind-Tunnel Investigation at Low Speed of the Yawing, Pitching, and Static Stability Characteristics of a 1/10-Scale Model of the Grumman F9F-9 Airplane, TED No. NACA AD 3109

NASA Technical Reports Server (NTRS)

Wolhart, Walter D.; Thomas, David F., Jr.

1955-01-01

An experimental investigation has been made in the Langley stability tunnel to determine the low-speed yawing, pitching, and static stability characteristics of a 1/10-scale model of the Grumman F9F-9 airplane. Tests were made to determine the effects of duct-entrance-fairing plugs on the static lateral and longitudinal stability characteristics of the complete model in the clean condition. The remaining tests were concerned with determining tail contributions as well as the effect of duct-entrance-fairing plugs, slats, flaps, and landing gear on the yawing and pitching stability derivatives. These data are presented without analysis in order to expedite distribution.

Solar Dynamics Observatory Guidance, Navigation, and Control System Overview

NASA Technical Reports Server (NTRS)

Morgenstern, Wendy M.; Bourkland, Kristin L.; Hsu, Oscar C.; Liu, Kuo-Chia; Mason, Paul A. C.; O'Donnell, James R., Jr.; Russo, Angela M.; Starin, Scott R.; Vess, Melissa F.

2011-01-01

-observing instruments: Helioseismic and Magnetic Imager (HMI), led by Stanford University; Atmospheric Imaging Assembly (AIA), led by Lockheed Martin Space and Astrophysics Laboratory; and Extreme Ultraviolet Variability Experiment (EVE), led by the University of Colorado. The basic mission is to observe the Sun for a very high percentage of the 5-year mission (10-year goal) with long stretches of uninterrupted observations and with constant, high-data-rate transmission to a dedicated ground station to be located in White Sands, New Mexico. These goals guided the design of the spacecraft bus that will carry and service the three-instrument payload. Overarching design goals for the bus are geosynchronous orbit, near-constant Sun observations with the ability to fly through eclipses, and constant HGA contact with the dedicated ground station. A three-axis stabilized ACS is needed both to point at the Sun accurately and to keep the roll about the Sun vector correctly positioned with respect to the solar north pole. This roll control is especially important for the magnetic field imaging of HM I. The mission requirements have several general impacts on the ACS design. Both the AIA and HMI instruments are very sensitive to the blurring caused by jitter. Each has an image stabilization system (ISS) with some ability to filter out high frequency motion, but below the bandwidth of the ISS the control system must compensate for disturbances within the ACS bandwidth or avoid exciting jitter at higher frequencies. Within the ACS bandwidth, the control requirement imposed by AIA is to place the center of the solar disk no more than 2 arc sec, 3 , from a body-defined target based on one of the GTs that accompany the instrument. This body-defined target, called the science reference boresight (SRB), was determined from the postlaunch orientation of the GTs by averaging the bounding telescope boresights for pitch to get a pitch SRB coordinate, and by averaging the bounding boresights for yaw toet the

Flight evaluation of stabilization and command augmentation system concepts and cockpit displays during approach and landing of powered-lift STOL aircraft

NASA Technical Reports Server (NTRS)

Franklin, J. A.; Innis, R. C.; Hardy, G. H.

1980-01-01

A flight research program was conducted to assess the effectiveness of manual control concepts and various cockpit displays in improving altitude (pitch, roll, and yaw) and longitudinal path control during short takeoff aircraft approaches and landings. Satisfactory flying qualities were demonstrared to minimum decision heights of 30 m (100 ft) for selected stabilization and command augmentation systems and flight director combinations. Precise landings at low touchdown sink rates were achieved with a gentle flare maneuver.

Best Practices from the Design and Development of the Ares I Launch Vehicle Roll and Reaction Control Systems

NASA Technical Reports Server (NTRS)

Butt, Adam; Paseur, Lila F.; Pitts, Hank M.

2012-01-01

On April 15, 2010 President Barak Obama made the official announcement that the Constellation Program, which included the Ares I launch vehicle, would be canceled. NASA s Ares I launch vehicle was being designed to launch the Orion Crew Exploration Vehicle, returning humans to the moon, Mars, and beyond. It consisted of a First Stage (FS) five segment solid rocket booster and a liquid J-2X Upper Stage (US) engine. Roll control for the FS was planned to be handled by a dedicated Roll Control System (RoCS), located on the connecting interstage. Induced yaw or pitch moments experienced during FS ascent would have been handled by vectoring of the booster nozzle. After FS booster separation, the US Reaction Control System (ReCS) would have provided the US Element with three degrees of freedom control as needed. The best practices documented in this paper will be focused on the technical designs and producibility of both systems along with the partnership between NASA and Boeing, who was on contract to build the Ares I US Element, which included the FS RoCS and US ReCS. In regards to partnership, focus will be placed on integration along with technical work accomplished by Boeing. This will include detailed emphasis on task orders developed between NASA and Boeing that were used to direct specific work that needed to be accomplished. In summary, this paper attempts to capture key best practices that should be helpful in the development of future launch vehicle and spacecraft RCS designs.

Dynamic Stability Instrumentation System (DSIS). Volume 3; User Manual

NASA Technical Reports Server (NTRS)

Daniels, Taumi S.; Boyden, Richmond P.; Dress, David A.; Jordan, Thomas L.

1996-01-01

The paper is an operating manual for the Dynamic Stability Instrumentation System in specific NASA Langley wind tunnels. The instrumentation system performs either a synchronous demodulation or a Fast Fourier Transform on dynamic balance strain gage signals, and ultimately computes aerodynamic coefficients. The dynamic balance converts sting motor rotation into pitch or yaw plane or roll axis oscillation, with timing information provided by a shaft encoder. Additional instruments control model attitude and balance temperature and monitor sting vibrations. Other instruments perform self-calibration and diagnostics. Procedures for conducting calibrations and wind-off and wind-on tests are listed.

Waterhammer Testing and Modeling of the Ares I Upper Stage Reaction Control System

NASA Technical Reports Server (NTRS)

Williams, J. Hunter; Holt, Kimberly A.

2010-01-01

NASA's Ares I rocket is the agency's first step in completing the goals of the Constellation Program, which plans to deliver a new generation of space explorers into low earth orbit for future missions to the International Space Station, the moon, and other destinations within the solar system. Ares I is a two-stage rocket topped by the Orion crew capsule and its service module. The launch vehicle's First Stage is a single, five-segment reusable solid rocket booster (RSRB), derived from the Space Shuttle Program's four segment RSRB. The vehicle's Upper Stage, being designed at Marshall Space Flight Center (MSFC), is propelled by a single J-2X Main Engine fueled with liquid oxygen and liquid hydrogen. During active Upper Stage flight of the Ares I launch vehicle, the Upper Stage Reaction Control System (US ReCS) will perform attitude control operations for the vehicle. The US ReCS will provide three-axis attitude control capability (roll, pitch, and yaw) for the Upper Stage while the J-2X is not firing and roll control capability while the engine is firing. Because of the requirements imposed upon the system, the design must accommodate rapid pulsing of multiple thrusters simultaneously to maintain attitude control. In support of these design activities and in preparation for Critical Design Review, analytical models of the US ReCS propellant feed system have been developed using the Thermal Hydraulic Library of MSC.EASY5 v.2008, herein referred to as EASY5. EASY5 is a commercially available fluid system modeling package with significant history of modeling space propulsion systems. In Fall 2009, a series of development tests were conducted at MSFC on a cold-flow test article for the US ReCS, herein referred to as System Development Test Article (SDTA). A subset of those tests performed were aimed at examining the effects of waterhammer on a flight-representative system and to ensure that those effects could be quantified with analytical models and incorporated into

Wind tunnel research comparing lateral control devices, particularly at high angles of attack X : various control devices on a wing with a fixed auxiliary airfoil

NASA Technical Reports Server (NTRS)

Weick, Fred E; Noyes, Richard W

1933-01-01

Results are given of a series of systemic tests comparing lateral control devices with particular reference to their effectiveness at high angles of attack. These tests were made with two sizes of ordinary ailerons and different sizes of spoilers on a Clark Y wing model having a narrow auxiliary airfoil fixed ahead and above the leading edge, the chords of the main and auxiliary airfoils being parallel. In addition, the auxiliary airfoil itself was given angular deflection. The purpose was to provide rolling moments for lateral control. The tests were made in a 7 by 10 foot wind tunnel. They included both force and rotation tests to show the effect of the devices on the lift and drag characteristics of the wing and on the lateral stability characteristics, as well as lateral control. They showed that none of the aileron arrangements tried would give rolling control of an assumed satisfactory value at all angles of attack up to the stall. However, they would give satisfactory values, but at the expense of abnormally high deflections and very heavy hinge moments. The most effective combination of ailerons and spoilers gave satisfactory values of rolling moment at angles of attack below the stall, and the values did not fall off as rapidly above the stall as with ailerons alone. With an arrangement of this type having the proper relative proportions and linkage, it should be possible to obtain reasonably satisfactory yawing moments and control forces. Deflecting one-half of the auxiliary airfoil downward for the purpose of control gave strong favorable yawing moments at all angles of attack, but gave very small rolling moments at the low angles of attack.

Sailplane Glide Performance and Control Using Fixed and Articulating Winglets. M.S. Thesis

NASA Technical Reports Server (NTRS)

Colling, James David

1995-01-01

An experimental study was conducted to investigate the effects of controllable articulating winglets on glide performance and yawing moments of high performance sailplanes. Testing was conducted in the Texas A&M University 7 x 10 foot Low Speed Wind Tunnel using a full-scale model of the outboard 5.6 feet of a 15 meter class high performance sailplane wing. Different wing tip configurations could be easily mounted to the wing model. A winglet was designed in which the cant and toe angles as well as a rudder on the winglet could be adjusted to a range of positions. Cant angles used in the investigation consisted of 5, 25, and 40 degrees measured from the vertical axis. Toe-out angles ranged from 0 to 22.5 degrees. A rudder on the winglet was used to study the effects of changing the camber of the winglet airfoil on wing performance and wing yawing moments. Rudder deflections consisted of-10, 0, and 10 degrees. Test results for a fixed geometry winglet and a standard wing tip are presented to show the general behavior of winglets on sailplane wings, and the effects of boundary-layer turbulators on the winglets are also presented. By tripping the laminar boundary-layer to turbulent before laminar separation occurs, the wing performance was increased at low Reynolds numbers. The effects on the lift and drag, yawing moment, pitching moment, and wing root bending moment of the model are presented. Oil flows were used on the wing model with the fixed geometry winglet and the standard wing tip to visualize flow directions and areas of boundary layer transition. A cant angle of 25 degrees and a toe-out angle of 2.5 degrees provided an optimal increase in wing performance for the cant and toe angles tested. Maximum performance was obtained when the winglet rudder remained in the neutral position of zero degrees. By varying the cant, toe, and rudder angles from their optimized positions, wing performance decreases. Although the winglet rudder proved to be more effective in

The impact of hybrid and electric powertrains on vehicle dynamics, control systems and energy regeneration

NASA Astrophysics Data System (ADS)

Crolla, David A.; Cao, Dongpu

2012-01-01

The background to the development of so-called green or low-carbon vehicles continues to be relentlessly reviewed throughout the literature. Research and development (R&D) on novel powertrains - often based on electric or hybrid technology - has been dominating automotive engineering around the world for the first two decades of the twenty-first century. Inevitably, most of the R&D has focused on powertrain technology and energy management challenges. However, as new powertrains have started to become commercially available, their effects on other aspects of vehicle performance have become increasingly important. This article focuses on the review of the integration of new electrified powertrains with the vehicle dynamics and control systems. The integration effects can be discussed in terms of three generic aspects of vehicle motions, namely roll-plane, pitch-plane and yaw-plane, which however are strongly coupled. The topic on regenerative suspension is further discussed. It quickly becomes clear that this integration poses some interesting future engineering challenges to maintain currently accepted levels of ride, handling and stability performance.

Heavy Class Helicopter Fuselage Model Drag Reduction by Active Flow Control Systems

NASA Astrophysics Data System (ADS)

De Gregorio, F.

2017-08-01

A comprehensive experimental investigation of helicopter blunt fuselage drag reduction using active flow control is being carried out within the European Clean Sky program. The objective is to demonstrate the capability of several active flow technologies to decrease fuselage drag by alleviating the flow separation occurring in the rear area of some helicopters. The work is performed on a simplified blunt fuselage at model-scale. Two different flow control actuators are considered for evaluation: steady blowing, unsteady blowing (or pulsed jets). Laboratory tests of each individual actuator are first performed to assess their performance and properties. The fuselage model is then equipped with these actuators distributed in 3 slots located on the ramp bottom edge. This paper addresses the promising results obtained during the wind-tunnel campaign, since significant drag reductions are achieved for a wide range of fuselage angles of attack and yaw angles without detriment of the other aerodynamic characteristics.

49 CFR 571.126 - Standard No. 126; Electronic stability control systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... counterclockwise steering, and the other series uses clockwise steering. The maximum time permitted between each... or side slip derivative with respect to time; (4) That has a means to monitor driver steering inputs... dwell steering input (time T0 + 1 in Figure 1) must not exceed 35 percent of the first peak value of yaw...

49 CFR 571.126 - Standard No. 126; Electronic stability control systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... counterclockwise steering, and the other series uses clockwise steering. The maximum time permitted between each... or side slip derivative with respect to time; (4) That has a means to monitor driver steering inputs... dwell steering input (time T0 + 1 in Figure 1) must not exceed 35 percent of the first peak value of yaw...

Actuated forebody strake controls for the F-18 high alpha research vehicle

NASA Technical Reports Server (NTRS)

Murri, Daniel G.; Shah, Gautam H.; Dicarlo, Daniel J.; Trilling, Todd W.

1993-01-01

A series of ground-based studies have been conducted to develop actuated forebody strake controls for flight test evaluations using the NASA F-18 High-Alpha Research Vehicle. The actuated forebody strake concept has been designed to provide increased levels of yaw control at high angles of attack where conventional rudders become ineffective. Results are presented from tests conducted with the flight-test strake design, including static and dynamic wind-tunnel tests, transonic wind-tunnel tests, full-scale wind-tunnel tests, pressure surveys, and flow visualization tests. Results from these studies show that a pair of conformal actuated forebody strakes applied to the F-18 HARV can provide a powerful and precise yaw control device at high angles of attack. The preparations for flight testing are described, including the fabrication of flight hardware and the development of aircraft flight control laws. The primary objectives of the flight tests are to provide flight validation of the groundbased studies and to evaluate the use of this type of control to enhance fighter aircraft maneuverability.

Design and stable flight of a 21 g insect-like tailless flapping wing micro air vehicle with angular rates feedback control.

PubMed

Phan, Hoang Vu; Kang, Taesam; Park, Hoon Cheol

2017-04-04

An insect-like tailless flapping wing micro air vehicle (FW-MAV) without feedback control eventually becomes unstable after takeoff. Flying an insect-like tailless FW-MAV is more challenging than flying a bird-like tailed FW-MAV, due to the difference in control principles. This work introduces the design and controlled flight of an insect-like tailless FW-MAV, named KUBeetle. A combination of four-bar linkage and pulley-string mechanisms was used to develop a lightweight flapping mechanism that could achieve a high flapping amplitude of approximately 190°. Clap-and-flings at dorsal and ventral stroke reversals were implemented to enhance vertical force. In the absence of a control surface at the tail, adjustment of the location of the trailing edges at the wing roots to modulate the rotational angle of the wings was used to generate control moments for the attitude control. Measurements by a 6-axis load cell showed that the control mechanism produced reasonable pitch, roll and yaw moments according to the corresponding control inputs. The control mechanism was integrated with three sub-micro servos to realize the pitch, roll and yaw controls. A simple PD feedback controller was implemented for flight stability with an onboard microcontroller and a gyroscope that sensed the pitch, roll and yaw rates. Several flight tests demonstrated that the tailless KUBeetle could successfully perform a vertical climb, then hover and loiter within a 0.3 m ground radius with small variations in pitch and roll body angles.

Flight evaluation of advanced controls and displays for transition and landing on the NASA V/STOL systems research aircraft

NASA Technical Reports Server (NTRS)

Franklin, James A.; Stortz, Michael W.; Borchers, Paul F.; Moralez, Ernesto, III

1996-01-01

Flight experiments were conducted on Ames Research Center's V/STOL Systems Research Aircraft (VSRA) to assess the influence of advanced control modes and head-up displays (HUD's) on flying qualities for precision approach and landing operations. Evaluations were made for decelerating approaches to hover followed by a vertical landing and for slow landings for four control/display mode combinations: the basic YAV-8B stability augmentation system; attitude command for pitch, roll, and yaw; flightpath/acceleration command with translational rate command in the hover; and height-rate damping with translational-rate command. Head-up displays used in conjunction with these control modes provided flightpath tracking/pursuit guidance and deceleration commands for the decelerating approach and a mixed horizontal and vertical presentation for precision hover and landing. Flying qualities were established and control usage and bandwidth were documented for candidate control modes and displays for the approach and vertical landing. Minimally satisfactory bandwidths were determined for the translational-rate command system. Test pilot and engineer teams from the Naval Air Warfare Center, the Boeing Military Airplane Group, Lockheed Martin, McDonnell Douglas Aerospace, Northrop Grumman, Rolls-Royce, and the British Defense Research Agency participated in the program along with NASA research pilots from the Ames and Lewis Research Centers. The results, in conjunction with related ground-based simulation data, indicate that the flightpath/longitudinal acceleration command response type in conjunction with pursuit tracking and deceleration guidance on the HUD would be essential for operation to instrument minimums significantly lower than the minimums for the AV-8B. It would also be a superior mode for performing slow landings where precise control to an austere landing area such as a narrow road is demanded. The translational-rate command system would reduce pilot workload for

A piloted simulator study on augmentation systems to improve helicopter flying qualities in terrain flight

NASA Technical Reports Server (NTRS)

Chen, R. T. N.; Talbot, P. D.; Gerdes, R. M.; Dugan, D. C.

1979-01-01

Four basic single-rotor helicopters, one teetering, on articulated, and two hingeless, which were found to have a variety of major deficiencies in a previous fixed-based simulator study, were selected as baseline configurations. The stability and control augmentation systems (SCAS) include simple control augmentation systems to decouple pitch and yaw responses due to collective input and to quicken the pitch and roll control responses; SCAS of rate-command type designed to optimize the sensitivity and damping and to decouple the pitch-roll due to aircraft angular tate; and attitude-command type SCAS. Pilot ratings and commentary are presented as well as performance data related to the task. SCAS control usages and their gain levels associated with specific rotor types are also discussed.

Dynamics and control of tethered antennas/reflectors in orbit

NASA Astrophysics Data System (ADS)

Liu, Liangdong; Bainum, Peter M.

The system linear equations for the motion of a tethered shallow spherical shell in orbit with its symmetry axis nominally following the local vertical are developed. The shell roll, yaw, tether out-of-plane swing motion and elastic vibrations are decoupled from the shell and tether in-plane pitch motions and elastic vibrations. The neutral gravity stability conditions for the special case of a constant length rigid tether are given for in-plane motion and out-of-plant motion. It is proved that the in-plane motion of the system could be asymptotically stable based on Rupp's tension control law, for a variable length tether. However, the system simulation results indicate that the transient responses can be improved significantly, especially for the damping of the tether and shell pitch motion, by an optimal feedback control law for the rigid variable length tether model. It is also seen that the system could be unstable when the effect of tether flexibility is included if the control gains are not chosen carefully. The transient responses for three different tension control laws are compared during typical station keeping operations.

Communication and Distributed Control in Multi-Agent Systems

DTIC Science & Technology

2011-08-01

centre of mass of the simulated aircraft and moving with them, we can identify three class of rotations allowed to the MAVs: yaw, pitch, and roll. In...a customised version of the swinglet1 (see Figure 1), a 420g light 80cm wing-span mono/fixed-wing MAV produced by senseFlyTM2, generally used for...replicate its work in a faithful way. 2.3.2 Customised (Parker’s-based) implementation of Reynolds’ algo- rithm As aforementioned there are some degrees of

Boundary layer stability on a yawed spinning body of revolution and its effect on the magnus force and moment

NASA Technical Reports Server (NTRS)

Jacobson, I. D.; Morton, J. B.

1972-01-01

The parameters are established which are important to the stability of a boundary layer flow over a yawed spinning cylinder in a uniform stream. It is shown that transition occurs asymmetrically in general and this asymmetry can be important for the prediction of aerodynamic forces and moments (e.g., the Magnus effect). Instability of the steady-state boundary layer flow is determined using small disturbance theory. Although the approach is strictly valid only for the calculation of the conditions for stability in the small, experimental data indicate that in many problems, it provides a good estimate for the transition to turbulence.

Development of helicopter attitude axes controlled hover flight without pilot assistance and vehicle crashes

NASA Astrophysics Data System (ADS)

Simon, Miguel

In this work, we show how to computerize a helicopter to fly attitude axes controlled hover flight without the assistance of a pilot and without ever crashing. We start by developing a helicopter research test bed system including all hardware, software, and means for testing and training the helicopter to fly by computer. We select a Remote Controlled helicopter with a 5 ft. diameter rotor and 2.2 hp engine. We equip the helicopter with a payload of sensors, computers, navigation and telemetry equipment, and batteries. We develop a differential GPS system with cm accuracy and a ground computerized navigation system for six degrees of freedom (6-DoF) free flight while tracking navigation commands. We design feedback control loops with yet-to-be-determined gains for the five control "knobs" available to a flying radio-controlled (RC) miniature helicopter: engine throttle, main rotor collective pitch, longitudinal cyclic pitch, lateral cyclic pitch, and tail rotor collective pitch. We develop helicopter flight equations using fundamental dynamics, helicopter momentum theory and blade element theory. The helicopter flight equations include helicopter rotor equations of motions, helicopter rotor forces and moments, helicopter trim equations, helicopter stability derivatives, and a coupled fuselage-rotor helicopter 6-DoF model. The helicopter simulation also includes helicopter engine control equations, a helicopter aerodynamic model, and finally helicopter stability and control equations. The derivation of a set of non-linear equations of motion for the main rotor is a contribution of this thesis work. We design and build two special test stands for training and testing the helicopter to fly attitude axes controlled hover flight, starting with one axis at a time and progressing to multiple axes. The first test stand is built for teaching and testing controlled flight of elevation and yaw (i.e., directional control). The second test stand is built for teaching and

Self-motion perception and vestibulo-ocular reflex during whole body yaw rotation in standing subjects: the role of head position and neck proprioception.

PubMed

Panichi, Roberto; Botti, Fabio Massimo; Ferraresi, Aldo; Faralli, Mario; Kyriakareli, Artemis; Schieppati, Marco; Pettorossi, Vito Enrico

2011-04-01

Self-motion perception and vestibulo-ocular reflex (VOR) were studied during whole body yaw rotation in the dark at different static head positions. Rotations consisted of four cycles of symmetric sinusoidal and asymmetric oscillations. Self-motion perception was evaluated by measuring the ability of subjects to manually track a static remembered target. VOR was recorded separately and the slow phase eye position (SPEP) was computed. Three different head static yaw deviations (active and passive) relative to the trunk (0°, 45° to right and 45° to left) were examined. Active head deviations had a significant effect during asymmetric oscillation: the movement perception was enhanced when the head was kept turned toward the side of body rotation and decreased in the opposite direction. Conversely, passive head deviations had no effect on movement perception. Further, vibration (100 Hz) of the neck muscles splenius capitis and sternocleidomastoideus remarkably influenced perceived rotation during asymmetric oscillation. On the other hand, SPEP of VOR was modulated by active head deviation, but was not influenced by neck muscle vibration. Through its effects on motion perception and reflex gain, head position improved gaze stability and enhanced self-motion perception in the direction of the head deviation. Copyright © 2010 Elsevier B.V. All rights reserved.

Wind-Tunnel Investigation at Low Speed of the Yawing Stability Derivatives of a 1/9-Scale Powered Model of the Convair XFY-1 Vertically Rising Airplane, TED No. NACA DE 373

NASA Technical Reports Server (NTRS)

Queijo, M. J.; Wolhart, w. D.; Fletcher, H. S.

1953-01-01

An experimental investigation has been conducted in the Langley stability tunnel at low speed to deter+nine the yawing stability derivatives of a 1/9-scale powered model of the Convair XFY-1 vertically rising airplane. Effects of thrust coefficient were investigated for the complete model and for certain components of the model. Effects of control deflections and of propeller blade angle were investigated for the complete model. Most of the tests were made through an angle-of-attack range from about -4deg to 29deg, and the thrust coefficient range was from 0 to 0.7. In order to expedite distribution of these data, no analysis of the data has been prepared for this.

Design of a robust control law for the Vega launcher ballistic phase

NASA Astrophysics Data System (ADS)

Valli, Monica; Lavagna, Michèle R.; Panozzo, Thomas

2012-02-01

This work presents the design of a robust control law, and the related control system architecture, for the Vega launcher ballistic phase, taking into account the complete six degrees of freedom dynamics. To gain robustness a non-linear control approach has been preferred: more specifically the Lyapunov's second stability theorem has been exploited, being a very powerful tool to guarantee asymptotic stability of the controlled dynamics. The dynamics of Vega's actuators has also been taken into account. The system performance has been checked and analyzed by numerical simulations run on real mission data for different operational and configuration scenarios, and the effectiveness of the synthesized control highlighted: in particular scenarios including a wide range of composite's inertial configurations performing various typologies of maneuvers have been run. The robustness of the controlled dynamics has been validated by 100 cases Monte Carlo analysis campaign: the containment of the dispersion for the controlled variables - say the composite roll, yaw and pitch angles - confirmed the wide validity and generality of the proposed control law. This paper will show the theoretical approach and discuss the obtained results.

Flight evaluation of pneumatic forebody vortex control in post-stall flight

NASA Technical Reports Server (NTRS)

Walchli, Lawrence A.

1994-01-01

The following topics are discussed: (1) X-29 description; Vortex Flow Control (VFC) technology description; (3) X-29 VFC wind tunnel results (forebody only); (4) X-29 VFC wind tunnel results (full configuration yawing moment); (5) X-29 VFC wind tunnel results (full configuration C(sub n) with sideslip); (6) X-29VFC wind tunnel results (full configuration pitching moment); (7) VFC optimized nozzle details; (8) X-29 forebody nozzle configuration; (9) X-29 VFC system stored gas schematic; (10) X-29 VFC system stored gas installation; (11) VFC effectiveness at zero sideslip; (12) VFC effectiveness at 35 AOA with sideslip; (13) 'VFC Roll' at 40 AOA; (14) Effects of VFC on wing rock; (15) Integrated controls C(sub n) prediction; (16) Proposed F-15 with lateral control laws with active VFC; (17) Simulated F-15 roll performance with active VFC; (18) Simulated F-15 spin recovery with active VFC; (19) Test team restructuring; (20) testbed selection; (21) Simulation for risk reduction; (22) Benefits of high pressure system; and (23) Advanced weapon system integration.

Optimizing the Operation of Windfarms, Energy Storage and Flexible Loads in Modern Power Systems and Deregulated Electricity Markets

NASA Astrophysics Data System (ADS)

Dar, Zamiyad

The amount of wind energy in power systems is increasing at a significant rate. With this increased penetration, there are certain problems associated with the operation of windfarms which need careful attention. In the operations side, the wake effects of upstream wind turbines on downstream wind turbines can cause a reduction in the total generated power of a windfarm. On the market side, the fluctuation of real-time prices can make the operation of windfarms less profitable. Similarly, the intermittent nature of wind power prevents the windfarms from participating in the day-ahead and forward markets. On the system side, the volatile nature of wind speeds is also an obstacle for windfarms to provide frequency regulation to the system. In this thesis, we address these issues and optimize the operation of windfarms in power systems and deregulated electricity markets. First, the total power generation in a windfarm is maximized by using yaw angle of wind turbines as a control variable. We extend the existing wake models to include the effects of yaw misalignment and wake deflection of wind turbines. A numerical study is performed to find the optimal values of induction factor and yaw misalignment angle of wind turbines in a single row of a windfarm for achieving the maximum total power with wake effects. The numerical study shows that the maximum power is achieved by keeping the induction factor close to 1/3 and only changing the yaw angle to deflect the wake. We then propose a Dynamic Programming Framework (DPF) to maximize the total power production of a windfarm using yaw angle as the control variable. We compare the windfarm efficiency achieved with our DPF with the efficiency values obtained through greedy control strategy and induction factor optimization. We also extend our expressions to a windfarm with multiple rows and columns of turbines and perform simulations on the 3x3 and 4x4 grid topologies. Our results show that the optimal induction factor for

Curved-flow, rolling-flow, and oscillatory pure-yawing wind-tunnel test methods for determination of dynamic stability derivatives

NASA Technical Reports Server (NTRS)

Chambers, J. R.; Grafton, S. B.; Lutze, F. H.

1981-01-01

Dynamic stability derivatives are evaluated on the basis of rolling-flow, curved-flow and snaking tests. Attention is given to the hardware associated with curved-flow, rolling-flow and oscillatory pure-yawing wind-tunnel tests. It is found that the snaking technique, when combined with linear- and forced-oscillation methods, yields an important method for evaluating beta derivatives for current configurations at high angles of attack. Since the rolling flow model is fixed during testing, forced oscillations may be imparted to the model, permitting the measurement of damping and cross-derivatives. These results, when coupled with basic rolling-flow or rotary-balance data, yield a highly accurate mathematical model for studies of incipient spin and spin entry.

Moving-Base Simulation Evaluation of Control/Display Integration Issues for ASTOVL Aircraft

NASA Technical Reports Server (NTRS)

Franklin, James A.

1997-01-01

A moving-base simulation has been conducted on the Vertical Motion Simulator at Ames Research Center using a model of an advanced, short takeoff and vertical landing (STOVL) lift fan fighter aircraft. This experiment expanded on investigations during previous simulations with this STOVL configuration with the objective of evaluating (1) control law modifications over the low speed flight envelope, (2) integration of the throttle inceptor with flight control laws that provide direct thrust command for conventional flight, vertical and short takeoff, and flightpath or vertical velocity command for transition, hover, and vertical landing, (3) control mode blending for pitch, roll, yaw, and flightpath control during transition from wing-borne to jet-borne flight, and (4) effects of conformal versus nonconformal presentation of flightpath and pursuit guidance symbology on the out-the-window display for low speed STOVL operations. Assessments were made for takeoff, transition, hover, and landing, including precision hover and landing aboard an LPH-type amphibious assault ship in the presence of winds and rough seas. Results yielded Level 1 pilot ratings for the flightpath and vertical velocity command modes for a range of land-based and shipboard operation and were consistent with previous experience with earlier control laws and displays for this STOVL concept. Control mode blending was performed over speed ranges in accord with the pilot's tasks and with the change of the basic aircraft's characteristics between wing-borne and hover flight. Blending of yaw control from heading command in hover to sideslip command in wing-borne flight performed over a broad speed range helped reduce yaw transients during acceleration through the low speed regime. Although the pilots appreciated conformality of flightpath and guidance symbols with the external scene during the approach, increased sensitivity of the symbols for lateral path tracking elevated the pilots' control activity

Wind Plant Power Optimization and Control under Uncertainty

NASA Astrophysics Data System (ADS)

Jha, Pankaj; Ulker, Demet; Hutchings, Kyle; Oxley, Gregory

2017-11-01

The development of optimized cooperative wind plant control involves the coordinated operation of individual turbines co-located within a wind plant to improve the overall power production. This is typically achieved by manipulating the trajectory and intensity of wake interactions between nearby turbines, thereby reducing wake losses. However, there are various types of uncertainties involved, such as turbulent inflow and microscale and turbine model input parameters. In a recent NREL-Envision collaboration, a controller that performs wake steering was designed and implemented for the Longyuan Rudong offshore wind plant in Jiangsu, China. The Rudong site contains 25 Envision EN136-4 MW turbines, of which a subset was selected for the field test campaign consisting of the front two rows for the northeasterly wind direction. In the first row, a turbine was selected as the reference turbine, providing comparison power data, while another was selected as the controlled turbine. This controlled turbine wakes three different turbines in the second row depending on the wind direction. A yaw misalignment strategy was designed using Envision's GWCFD, a multi-fidelity plant-scale CFD tool based on SOWFA with a generalized actuator disc (GAD) turbine model, which, in turn, was used to tune NREL's FLORIS model used for wake steering and yaw control optimization. The presentation will account for some associated uncertainties, such as those in atmospheric turbulence and wake profile.

Intelligent Control for the BEES Flyer

NASA Technical Reports Server (NTRS)

Krishnakumar, K.; Gundy-Burlet, Karen; Aftosmis, Mike; Nemec, Marian; Limes, Greg; Berry, Misty; Logan, Michael

2004-01-01

This paper describes the effort to provide a preliminary capability analysis and a neural network based adaptive flight control system for the JPL-led BEES aircraft project. The BEES flyer was envisioned to be a small, autonomous platform with sensing and control systems mimicking those of biological systems for the purpose of scientific exploration on the surface of Mars. The platform is physically tightly constrained by the necessity of efficient packing within rockets for the trip to Mars. Given the physical constraints, the system is not an ideal configuration for aerodynamics or stability and control. The objectives of this effort are to evaluate the aerodynamics characteristics of the existing design, to make recommendaaons as to potential improvements and to provide a control system that stabilizes the existing aircraft for nominal flight and damaged conditions. Towards this several questions are raised and analyses are presented to arrive at answers to some of the questions raised. CART3D, a high-fidelity inviscid analysis package for conceptual and preliminary aerodynamic design, was used to compute a parametric set of solutions over the expected flight domain. Stability and control derivatives were extracted from the database and integrated with the neural flight control system. The Integrated Vehicle Modeling Environment (IVME) was also used for estimating aircraft geometric, inertial, and aerodynamic characteristics. A generic neural flight control system is used to provide adaptive control without the requirement for extensive gain scheduling or explicit system identification. The neural flight control system uses reference models to specify desired handling qualities in the roll, pitch, and yaw axes, and incorporates both pre-trained and on-line learning neural networks in the inverse model portion of the controller. Results are presented for the BEES aircraft in the subsonic regime for terrestrial and Martian environments.

Global Sliding Mode Control for the Bank-to-Turn of Hypersonic Glide Vehicle

NASA Astrophysics Data System (ADS)

Zhang, J.; Yu, Y. F.; Yan, P. P.; Fan, Y. H.; Guo, X. W.

2017-03-01

The technology of Bank-to-Turn has been recognized as an attractive direction due to their significance for the control of hypersonic glide vehicle. Strong coupling existing among pitch, yaw and roll channel was a great challenge for banking to turn, and thus a novel global sliding mode controller was designed for hypersonic glider in this paper. Considering the coupling among channels as interference, we can use invariance principle of sliding mode motion to realize the decoupling control. The global sliding mode control system could eliminate the stage of reaching, which can lead to the realization of whole systematic process decoupling control. When the global sliding mode factor was designed, a minimum norm pole assignment method of the sliding mode matrix was introduced to improve the robustness of the system. The method of continuity of symbolic function was adopted to overcome the chatter, which furtherly modify the transient performance of the system. The simulation results show that this method has good performance of three channel decoupling control and guidance command tracking. And it can meet the requirements of the dynamic performance of the system.

Influence of motion coupling and nonlinear effects on parametric roll for a floating production storage and offloading platform

PubMed Central

Greco, M.; Lugni, C.; Faltinsen, O. M.

2015-01-01

Occurrence and features of parametric roll (PR) on a weather-vaning floating production storage and offloading (FPSO) platform with a turret single-point mooring-line system are examined. The main focus is on the relevance of motions coupling and nonlinear effects on this phenomenon and on more general unstable conditions as well as on the occurrence and severity of water on deck. This work was motivated by recent experiments on an FPSO model without mooring systems highlighting the occurrence of parametric resonance owing to roll–yaw coupling. A three-dimensional numerical hybrid potential-flow seakeeping solver was able to capture this behaviour. The same method, extended to include the mooring lines, is adopted here to investigate the platform behaviour for different incident wavelengths, steepnesses, headings, locations of the turret and pretensions. From the results, sway and yaw tend to destabilize the system, also bringing chaotic features. The sway–roll–yaw coupling widens the existence region of PR resonance and increases PR severity; it also results in a larger amount of shipped water, especially at smaller wavelength-to-ship length ratio and larger steepness. The chaotic features are excited when a sufficiently large yaw amplitude is reached. Consistently, a simplified stability analysis showed the relevance of nonlinear-restoring coefficients, first those connected with the sway–yaw coupling then those associated with the roll–yaw coupling, both destabilizing. From the stability analysis, the system is unstable for all longitudinal locations of the turret and pre-tensions examined, but the instability weakens as the turret is moved forward, and the pre-tension is increased. The use of a suitable dynamic-positioning system can control the horizontal motions, avoiding the instability. PMID:25512590

Resume and analysis of NACA lateral control research

NASA Technical Reports Server (NTRS)

Weick, Fred E; Jones, Robert T

1937-01-01

An analysis of the principal results of recent NACA lateral control research is made by utilizing the experience and progress gained during the course of the investigation. Two things are considered of primary importance in judging the effectiveness of different control devices: the (calculated) banking and yawing motion of a typical small airplane caused by a deflection of the control, and the stick force required to produce this deflection. The report includes a table in which a number of different lateral control devices are compared on these bases.

A study of pilot modeling in multi-controller tasks

NASA Technical Reports Server (NTRS)

Whitbeck, R. F.; Knight, J. R.

1972-01-01

A modeling approach, which utilizes a matrix of transfer functions to describe the human pilot in multiple input, multiple output control situations, is studied. The approach used was to extend a well established scalar Wiener-Hopf minimization technique to the matrix case and then study, via a series of experiments, the data requirements when only finite record lengths are available. One of these experiments was a two-controller roll tracking experiment designed to force the pilot to use rudder in order to coordinate and reduce the effects of aileron yaw. One model was computed for the case where the signals used to generate the spectral matrix are error and bank angle while another model was computed for the case where error and yaw angle are the inputs. Several anomalies were observed to be present in the experimental data. These are defined by the descriptive terms roll up, break up, and roll down. Due to these algorithm induced anomalies, the frequency band over which reliable estimates of power spectra can be achieved is considerably less than predicted by the sampling theorem.

Real time health monitoring and control system methodology for flexible space structures

NASA Astrophysics Data System (ADS)

Jayaram, Sanjay

This dissertation is concerned with the Near Real-time Autonomous Health Monitoring of Flexible Space Structures. The dynamics of multi-body flexible systems is uncertain due to factors such as high non-linearity, consideration of higher modal frequencies, high dimensionality, multiple inputs and outputs, operational constraints, as well as unexpected failures of sensors and/or actuators. Hence a systematic framework of developing a high fidelity, dynamic model of a flexible structural system needs to be understood. The fault detection mechanism that will be an integrated part of an autonomous health monitoring system comprises the detection of abnormalities in the sensors and/or actuators and correcting these detected faults (if possible). Applying the robust control law and the robust measures that are capable of detecting and recovering/replacing the actuators rectifies the actuator faults. The fault tolerant concept applied to the sensors will be in the form of an Extended Kalman Filter (EKF). The EKF is going to weigh the information coming from multiple sensors (redundant sensors used to measure the same information) and automatically identify the faulty sensors and weigh the best estimate from the remaining sensors. The mechanization is comprised of instrumenting flexible deployable panels (solar array) with multiple angular position and rate sensors connected to the data acquisition system. The sensors will give position and rate information of the solar panel in all three axes (i.e. roll, pitch and yaw). The position data corresponds to the steady state response and the rate data will give better insight on the transient response of the system. This is a critical factor for real-time autonomous health monitoring. MATLAB (and/or C++) software will be used for high fidelity modeling and fault tolerant mechanism.

MOD-0A 200 kW wind turbine generator design and analysis report

NASA Astrophysics Data System (ADS)

Anderson, T. S.; Bodenschatz, C. A.; Eggers, A. G.; Hughes, P. S.; Lampe, R. F.; Lipner, M. H.; Schornhorst, J. R.

1980-08-01

The design, analysis, and initial performance of the MOD-OA 200 kW wind turbine generator at Clayton, NM is documented. The MOD-OA was designed and built to obtain operation and performance data and experience in utility environments. The project requirements, approach, system description, design requirements, design, analysis, system tests, installation, safety considerations, failure modes and effects analysis, data acquisition, and initial performance for the wind turbine are discussed. The design and analysis of the rotor, drive train, nacelle equipment, yaw drive mechanism and brake, tower, foundation, electricl system, and control systems are presented. The rotor includes the blades, hub, and pitch change mechanism. The drive train includes the low speed shaft, speed increaser, high speed shaft, and rotor brake. The electrical system includes the generator, switchgear, transformer, and utility connection. The control systems are the blade pitch, yaw, and generator control, and the safety system. Manual, automatic, and remote control are discussed. Systems analyses on dynamic loads and fatigue are presented.

MOD-0A 200 kW wind turbine generator design and analysis report

NASA Technical Reports Server (NTRS)

Anderson, T. S.; Bodenschatz, C. A.; Eggers, A. G.; Hughes, P. S.; Lampe, R. F.; Lipner, M. H.; Schornhorst, J. R.

1980-01-01

The design, analysis, and initial performance of the MOD-OA 200 kW wind turbine generator at Clayton, NM is documented. The MOD-OA was designed and built to obtain operation and performance data and experience in utility environments. The project requirements, approach, system description, design requirements, design, analysis, system tests, installation, safety considerations, failure modes and effects analysis, data acquisition, and initial performance for the wind turbine are discussed. The design and analysis of the rotor, drive train, nacelle equipment, yaw drive mechanism and brake, tower, foundation, electricl system, and control systems are presented. The rotor includes the blades, hub, and pitch change mechanism. The drive train includes the low speed shaft, speed increaser, high speed shaft, and rotor brake. The electrical system includes the generator, switchgear, transformer, and utility connection. The control systems are the blade pitch, yaw, and generator control, and the safety system. Manual, automatic, and remote control are discussed. Systems analyses on dynamic loads and fatigue are presented.

A position and attitude vision measurement system for wind tunnel slender model

NASA Astrophysics Data System (ADS)

Cheng, Lei; Yang, Yinong; Xue, Bindang; Zhou, Fugen; Bai, Xiangzhi

2014-11-01

A position and attitude vision measurement system for drop test slender model in wind tunnel is designed and developed. The system used two high speed cameras, one is put to the side of the model and another is put to the position where the camera can look up the model. Simple symbols are set on the model. The main idea of the system is based on image matching technique between the 3D-digital model projection image and the image captured by the camera. At first, we evaluate the pitch angles, the roll angles and the position of the centroid of a model through recognizing symbols in the images captured by the side camera. And then, based on the evaluated attitude info, giving a series of yaw angles, a series of projection images of the 3D-digital model are obtained. Finally, these projection images are matched with the image which captured by the looking up camera, and the best match's projection images corresponds to the yaw angle is the very yaw angle of the model. Simulation experiments are conducted and the results show that the maximal error of attitude measurement is less than 0.05°, which can meet the demand of test in wind tunnel.

Digital avionics: A cornerstone of aviation

NASA Technical Reports Server (NTRS)

Spitzer, Cary R.

1990-01-01

Digital avionics is continually expanding its role in communication (HF and VHF, satellite, data links), navigation (ground-based systems, inertial and satellite-based systems), and flight-by-wire control. Examples of electronic flight control system architecture, pitch, roll, and yaw control are presented. Modeling of complex hardware systems, electromagnetic interference, and software are discussed.

Analysis of Control-Oriented Wake Modeling Tools Using Lidar Field Results

DOE PAGES

Annoni, Jennifer; Fleming, Paul; Scholbrock, Andrew; ...

2018-02-08

Wind turbines in a wind farm operate individually to maximize their own performance regardless of the impact of aerodynamic interactions on neighboring turbines. Wind farm controls can be used to increase power production or reduce overall structural loads by properly coordinating turbines. One wind farm control strategy that is addressed in literature is known as wake steering, wherein upstream turbines operate in yaw misaligned conditions to redirect their wakes away from downstream turbines. The National Renewable Energy Laboratory (NREL) in Golden, CO conducted a demonstration of wake steering on a single utility-scale turbine. In this study, the turbine was operatedmore » at various yaw misalignment setpoints while a lidar mounted on the nacelle scanned five downstream distances. The lidar measurements were combined with turbine data, as well as measurements of the inflow made by a highly instrumented meteorological mast upstream. The full-scale measurements are used to validate controls-oriented tools, including wind turbine wake models, used for wind farm controls and optimization. This paper presents a quantitative comparison of the lidar data and controls-oriented wake models under different atmospheric conditions and turbine operation. The results show good agreement between the lidar data and the models under these different conditions.« less

Analysis of Control-Oriented Wake Modeling Tools Using Lidar Field Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annoni, Jennifer; Fleming, Paul; Scholbrock, Andrew

Wind turbines in a wind farm operate individually to maximize their own performance regardless of the impact of aerodynamic interactions on neighboring turbines. Wind farm controls can be used to increase power production or reduce overall structural loads by properly coordinating turbines. One wind farm control strategy that is addressed in literature is known as wake steering, wherein upstream turbines operate in yaw misaligned conditions to redirect their wakes away from downstream turbines. The National Renewable Energy Laboratory (NREL) in Golden, CO conducted a demonstration of wake steering on a single utility-scale turbine. In this study, the turbine was operatedmore » at various yaw misalignment setpoints while a lidar mounted on the nacelle scanned five downstream distances. The lidar measurements were combined with turbine data, as well as measurements of the inflow made by a highly instrumented meteorological mast upstream. The full-scale measurements are used to validate controls-oriented tools, including wind turbine wake models, used for wind farm controls and optimization. This paper presents a quantitative comparison of the lidar data and controls-oriented wake models under different atmospheric conditions and turbine operation. The results show good agreement between the lidar data and the models under these different conditions.« less

Stability and Control CFD Investigations of a Generic 53 Degree Swept UCAV Configuration

NASA Technical Reports Server (NTRS)

Frink, Neal T.

2014-01-01

NATO STO Task Group AVT-201 on "Extended Assessment of Reliable Stability & Control Prediction Methods for NATO Air Vehicles" is studying various computational approaches to predict stability and control parameters for aircraft undergoing non-linear flight conditions. This paper contributes an assessment through correlations with wind tunnel data for the state of aerodynamic predictive capability of time-accurate RANS methodology on the group's focus configuration, a 53deg swept and twisted lambda wing UCAV, undergoing a variety of roll, pitch, and yaw motions. The vehicle aerodynamics is dominated by the complex non-linear physics of round leading-edge vortex flow separation. Correlations with experimental data are made for static longitudinal/lateral sweeps, and at varying frequencies of prescribed roll/pitch/yaw sinusoidal motion for the vehicle operating with and without control surfaces. The data and the derived understanding should prove useful to the AVT-201 team and other researchers who are developing techniques for augmenting flight simulation models from low-speed CFD predictions of aircraft traversing non-linear regions of a flight envelope.

Fault-tolerant control of electric vehicles with in-wheel motors using actuator-grouping sliding mode controllers

NASA Astrophysics Data System (ADS)

Li, Boyuan; Du, Haiping; Li, Weihua

2016-05-01

Although electric vehicles with in-wheel motors have been regarded as one of the promising vehicle architectures in recent years, the probability of in-wheel motor fault is still a crucial issue due to the system complexity and large number of control actuators. In this study, a modified sliding mode control (SMC) is applied to achieve fault-tolerant control of electric vehicles with four-wheel-independent-steering (4WIS) and four-wheel-independent-driving (4WID). Unlike in traditional SMC, in this approach the steering geometry is re-arranged according to the location of faulty wheels in the modified SMC. Three SMC control laws for longitudinal velocity control, lateral velocity control and yaw rate control are designed based on specific vehicle motion scenarios. In addition the actuator-grouping SMC method is proposed so that driving actuators are grouped and each group of actuators can be used to achieve the specific control target, which avoids the strong coupling effect between each control target. Simulation results prove that the proposed modified SMC can achieve good vehicle dynamics control performance in normal driving and large steering angle turning scenarios. In addition, the proposed actuator-grouping SMC can solve the coupling effect of different control targets and the control performance is improved.

Control strategies for wind farm power optimization: LES study

NASA Astrophysics Data System (ADS)

Ciri, Umberto; Rotea, Mario; Leonardi, Stefano

2017-11-01

Turbines in wind farms operate in off-design conditions as wake interactions occur for particular wind directions. Advanced wind farm control strategies aim at coordinating and adjusting turbine operations to mitigate power losses in such conditions. Coordination is achieved by controlling on upstream turbines either the wake intensity, through the blade pitch angle or the generator torque, or the wake direction, through yaw misalignment. Downstream turbines can be adapted to work in waked conditions and limit power losses, using the blade pitch angle or the generator torque. As wind conditions in wind farm operations may change significantly, it is difficult to determine and parameterize the variations of the coordinated optimal settings. An alternative is model-free control and optimization of wind farms, which does not require any parameterization and can track the optimal settings as conditions vary. In this work, we employ a model-free optimization algorithm, extremum-seeking control, to find the optimal set-points of generator torque, blade pitch and yaw angle for a three-turbine configuration. Large-Eddy Simulations are used to provide a virtual environment to evaluate the performance of the control strategies under realistic, unsteady incoming wind. This work was supported by the National Science Foundation, Grants No. 1243482 (the WINDINSPIRE project) and IIP 1362033 (I/UCRC WindSTAR). TACC is acknowledged for providing computational time.

Custom electronic subsystems for the laboratory telerobotic manipulator

NASA Technical Reports Server (NTRS)

Glassell, R. L.; Butler, P. L.; Rowe, J. C.; Zimmermann, S. D.

1990-01-01

The National Aeronautics and Space Administration (NASA) Space Station Program presents new opportunities for the application of telerobotic and robotic systems. The Laboratory Telerobotic Manipulator (LTM) is a highly advanced 7 degrees-of-freedom (DOF) telerobotic/robotic manipulator. It was developed and built for the Automation Technology Branch at NASA's Langley Research Center (LaRC) for work in research and to demonstrate ground-based telerobotic manipulator system hardware and software systems for future NASA applications in the hazardous environment of space. The LTM manipulator uses an embedded wiring design with all electronics, motor power, and control and communication cables passing through the pitch-yaw differential joints. This design requires the number of cables passing through the pitch/yaw joint to be kept to a minimum. To eliminate the cables needed to carry each pitch-yaw joint's sensor data to the VME control computers, a custom-embedded electronics package for each manipulator joint was developed. The electronics package collects and sends the joint's sensor data to the VME control computers over a fiber optic cable. The electronics package consist of five individual subsystems: the VME Link Processor, the Joint Processor and the Joint Processor power supply in the joint module, the fiber optics communications system, and the electronics and motor power cabling.

Vection is the main contributor to motion sickness induced by visual yaw rotation: Implications for conflict and eye movement theories

PubMed Central

Pretto, Paolo; Oberfeld, Daniel; Hecht, Heiko; Bülthoff, Heinrich H.

2017-01-01

This study investigated the role of vection (i.e., a visually induced sense of self-motion), optokinetic nystagmus (OKN), and inadvertent head movements in visually induced motion sickness (VIMS), evoked by yaw rotation of the visual surround. These three elements have all been proposed as contributing factors in VIMS, as they can be linked to different motion sickness theories. However, a full understanding of the role of each factor is still lacking because independent manipulation has proven difficult in the past. We adopted an integrative approach to the problem by obtaining measures of potentially relevant parameters in four experimental conditions and subsequently combining them in a linear mixed regression model. To that end, participants were exposed to visual yaw rotation in four separate sessions. Using a full factorial design, the OKN was manipulated by a fixation target (present/absent), and vection strength by introducing a conflict in the motion direction of the central and peripheral field of view (present/absent). In all conditions, head movements were minimized as much as possible. Measured parameters included vection strength, vection variability, OKN slow phase velocity, OKN frequency, the number of inadvertent head movements, and inadvertent head tilt. Results show that VIMS increases with vection strength, but that this relation varies among participants (R2 = 0.48). Regression parameters for vection variability, head and eye movement parameters were not significant. These results may seem to be in line with the Sensory Conflict theory on motion sickness, but we argue that a more detailed definition of the exact nature of the conflict is required to fully appreciate the relationship between vection and VIMS. PMID:28380077

Experimental study of tail-span effects on a generic canard-controlled missile

NASA Technical Reports Server (NTRS)

Blair, A. B., Jr.; Dillon, James L.; Watson, Carolyn B.

1992-01-01

An experimental investigation was conducted on a cruciform canard controlled missile configuration to determine the effects of tail span/canard span ratio on controllability. The investigation was conducted over the Mach number range of 1.75 to 3.50. Reductions of tail span/canard span ratio produced lower static margins and higher trim angle of attack. The results show that canard controls can provide pitch- and yaw-control as well as roll-control by proper selection of the tail span/canard span ratio.

Measurement of the Static Stability and Control and the Damping Derivatives of a 0.13-Scale Model of the Convair XFY-1 Airplane, TED No. NACA DE 368

NASA Technical Reports Server (NTRS)

Johnson, Joseph L.

1954-01-01

An investigation has been conducted to determine the static stability and control and damping in roll and yaw of a 0.13-scale model of the Convair XFY-1 airplane with propellers off from 0 deg to 90 deg angle of attack. The tests showed that a slightly unstable pitch-up tendency occurred simultaneously with a break in the normal-force curve in the angle-of-attack range from about 27 deg to 36 deg. The top vertical tail contributed positive values of static directional stability and effective dihedral up to an angle of attack of about 35 deg. The bottom tail contributed positive values of static directional stability but negative values of effective dihedral throughout the angle-of-attack range. Effectiveness of the control surfaces decreased to very low values at the high angles of attack, The model had positive damping in yaw and damping in roll about the body axes over the angle-of-attack range but the damping in yaw decreased to about zero at 90 deg angle of attack.

A Study of the Characteristics of Human-Pilot Control Response to Simulated Aircraft Lateral Motions

NASA Technical Reports Server (NTRS)

Cheatham, Donald C

1954-01-01

Report presents the results of studies made in an attempt to provide information on the control operations of the human pilot. These studies included an investigation of the ability of pilots to control simulated unstable yawing oscillations, a study of the basic characteristics of human-pilot control response, and a study to determine whether and to what extent pilot control response can be represented in an analytical form.

An Analysis of Once-per-revolution Oscillating Aerodynamic Thrust Loads on Single-Rotation Propellers on Tractor Airplanes at Zero Yaw

NASA Technical Reports Server (NTRS)

Rogallo, Vernon L; Yaggy, Paul F; Mccloud, John L , III

1956-01-01

A simplified procedure is shown for calculating the once-per-revolution oscillating aerodynamic thrust loads on propellers of tractor airplanes at zero yaw. The only flow field information required for the application of the procedure is a knowledge of the upflow angles at the horizontal center line of the propeller disk. Methods are presented whereby these angles may be computed without recourse to experimental survey of the flow field. The loads computed by the simplified procedure are compared with those computed by a more rigorous method and the procedure is applied to several airplane configurations which are believed typical of current designs. The results are generally satisfactory.

Vehicle active steering control research based on two-DOF robust internal model control

NASA Astrophysics Data System (ADS)

Wu, Jian; Liu, Yahui; Wang, Fengbo; Bao, Chunjiang; Sun, Qun; Zhao, Youqun

2016-07-01

Because of vehicle's external disturbances and model uncertainties, robust control algorithms have obtained popularity in vehicle stability control. The robust control usually gives up performance in order to guarantee the robustness of the control algorithm, therefore an improved robust internal model control(IMC) algorithm blending model tracking and internal model control is put forward for active steering system in order to reach high performance of yaw rate tracking with certain robustness. The proposed algorithm inherits the good model tracking ability of the IMC control and guarantees robustness to model uncertainties. In order to separate the design process of model tracking from the robustness design process, the improved 2 degree of freedom(DOF) robust internal model controller structure is given from the standard Youla parameterization. Simulations of double lane change maneuver and those of crosswind disturbances are conducted for evaluating the robust control algorithm, on the basis of a nonlinear vehicle simulation model with a magic tyre model. Results show that the established 2-DOF robust IMC method has better model tracking ability and a guaranteed level of robustness and robust performance, which can enhance the vehicle stability and handling, regardless of variations of the vehicle model parameters and the external crosswind interferences. Contradiction between performance and robustness of active steering control algorithm is solved and higher control performance with certain robustness to model uncertainties is obtained.

75 FR 63050 - Airworthiness Directives; Eurocopter France (Eurocopter) Model AS350B, BA, B1, B2, B3, D, AS355E...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-14

... point of the yaw channel ball-type control sheath stop, of a Model AS355N helicopter fitted with the... the non-modified cross- member may cause it to crack. A crack can reduce the yaw control travel. This... discovered in the area of the center cross-member at station X 2325, at the attachment point of the yaw...

Late Eocene Myanmar tectonics constrained by magnetostratigraphy of the Yaw Formation, Chidwin Basin, Kalewa

NASA Astrophysics Data System (ADS)

Dupont-Nivet, Guillaume; Licht, Alexis; Bernard, Annabelle; Roperch, Pierrick; Win, Zaw; Jaeger, Jean-Jacques; Aung, Day Wa; Kaythi, Myat; Hnin Swe, Hnin; Poblete, Fernando

2017-04-01

Sedimentary basins in Myanmar have recorded key events of the India-Asia collision including associated geodynamic movements and paleoclimatic records. In particular, Paleogene deposits provide invaluable insight on the accretion of the Burma terrane, its rotation associated with the alleged extrusion of Indochina and the formation of the Indo-Burman ranges. They also yield unique records of monsoonal intensity during the growth of the Tibetan Plateau and a rich paleontological assemblage including some of the earliest primates. However, understanding the potential relations between these recorded events is strongly hindered by insufficient age control on these deposits. As part of the Myanmar Geodynamic & Paleoclimate Initiative and the ERC "MAGIC" project, our initial focus is to date Paleogene deposits of Myanmar with better accuracy using magnetostratigraphy. We present preliminary results from the Chindwin Basin where we sampled a 400-meter section of the top of the Yaw formation recording a major sedimentological facies transition previously estimated roughly as Eocene to Oligocene in age. Detailed rock magnetic analyses enabled to identify and isolate primary Characteristic Remanent Magnetizations of normal and reversed polarities carried by iron sulfides, iron carbonates and/or iron oxides. A correlation to the Geomagnetic Polarity Time Scale can be proposed suggesting deposition between the base of chrons C16n2n and the base of C13r (36.3 and 34.8 Ma). This age suggests the facies transition may be more likely associated with regional tectonics such as the Indo-Burman uplift rather than sea-level drop linked to ice-sheet formation at the Eocene-Oligocene Transition at 33.9 Ma. In addition, the mean observed paleomagnetic declination (13.3+/-3.7°) is statistically indistinguishable from declinations expected by geodynamic models with limited vertical-axis rotations of the Burma terrane and therefore supports little to no rotational extrusion since 35 Ma.

Orion Entry Flight Control Stability and Performance

NASA Technical Reports Server (NTRS)

Strahan, Alan L.; Loe, Greg R.; Seiler, Pete

2007-01-01

The Orion Spacecraft will be required to perform entry and landing functions for both Low Earth Orbit (LEO) and Lunar return missions, utilizing only the Command Module (CM) with its unique systems and GN&C design. This paper presents the current CM Flight Control System (FCS) design to support entry and landing, with a focus on analyses that have supported its development to date. The CM FCS will have to provide for spacecraft stability and control while following guidance or manual commands during exo-atmospheric flight, after Service Module separation, translational powered flight required of the CM, atmospheric flight supporting both direct entry and skip trajectories down to drogue chute deploy, and during roll attitude reorientation just prior to touchdown. Various studies and analyses have been performed or are on-going supporting an overall FCS design with reasonably sized Reaction Control System (RCS) jets, that minimizes fuel usage, that provides appropriate command following but with reasonable stability and control margin. Results from these efforts to date are included, with particular attention on design issues that have emerged, such as the struggle to accommodate sub-sonic pitch and yaw control without using excessively large jets that could have a detrimental impact on vehicle weight. Apollo, with a similar shape, struggled with this issue as well. Outstanding CM FCS related design and analysis issues, planned for future effort, are also briefly be discussed.

Influence of motion coupling and nonlinear effects on parametric roll for a floating production storage and offloading platform.

PubMed

Greco, M; Lugni, C; Faltinsen, O M

2015-01-28

Occurrence and features of parametric roll (PR) on a weather-vaning floating production storage and offloading (FPSO) platform with a turret single-point mooring-line system are examined. The main focus is on the relevance of motions coupling and nonlinear effects on this phenomenon and on more general unstable conditions as well as on the occurrence and severity of water on deck. This work was motivated by recent experiments on an FPSO model without mooring systems highlighting the occurrence of parametric resonance owing to roll-yaw coupling. A three-dimensional numerical hybrid potential-flow seakeeping solver was able to capture this behaviour. The same method, extended to include the mooring lines, is adopted here to investigate the platform behaviour for different incident wavelengths, steepnesses, headings, locations of the turret and pretensions. From the results, sway and yaw tend to destabilize the system, also bringing chaotic features. The sway-roll-yaw coupling widens the existence region of PR resonance and increases PR severity; it also results in a larger amount of shipped water, especially at smaller wavelength-to-ship length ratio and larger steepness. The chaotic features are excited when a sufficiently large yaw amplitude is reached. Consistently, a simplified stability analysis showed the relevance of nonlinear-restoring coefficients, first those connected with the sway-yaw coupling then those associated with the roll-yaw coupling, both destabilizing. From the stability analysis, the system is unstable for all longitudinal locations of the turret and pre-tensions examined, but the instability weakens as the turret is moved forward, and the pre-tension is increased. The use of a suitable dynamic-positioning system can control the horizontal motions, avoiding the instability. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

ADDJUST - An automated system for steering Centaur launch vehicles in measured winds

NASA Technical Reports Server (NTRS)

Swanson, D. C.

1977-01-01

ADDJUST (Automatic Determination and Dissemination of Just-Updated Steering Terms) is an automated computer and communication system designed to provide Atlas/Centaur and Titan/Centaur launch vehicles with booster-phase steering data on launch day. Wind soundings are first obtained, from which a smoothed wind velocity vs altitude relationship is established. Design for conditions at the end of the boost phase with initial pitch and yaw maneuvers, followed by zero total angle of attack through the filtered wind establishes the required vehicle attitude as a function of altitude. Polynomial coefficients for pitch and yaw attitude vs altitude are determined and are transmitted for validation and loading into the Centaur airborne computer. The system has enabled 14 consecutive launches without a flight wind delay.

Stability and optimised H∞ control of tripped and untripped vehicle rollover

NASA Astrophysics Data System (ADS)

Jin, Zhilin; Zhang, Lei; Zhang, Jiale; Khajepour, Amir

2016-10-01

Vehicle rollover is a serious traffic accident. In order to accurately evaluate the possibility of untripped and some special tripped vehicle rollovers, and to prevent vehicle rollover under unpredictable variations of parameters and harsh driving conditions, a new rollover index and an anti-roll control strategy are proposed in this paper. Taking deflections of steering and suspension induced by the roll at the axles into consideration, a six degrees of freedom dynamic model is established, including lateral, yaw, roll, and vertical motions of sprung and unsprung masses. From the vehicle dynamics theory, a new rollover index is developed to predict vehicle rollover risk under both untripped and special tripped situations. This new rollover index is validated by Carsim simulations. In addition, an H-infinity controller with electro hydraulic brake system is optimised by genetic algorithm to improve the anti-rollover performance of the vehicle. The stability and robustness of the active rollover prevention control system are analysed by some numerical simulations. The results show that the control system can improve the critical speed of vehicle rollover obviously, and has a good robustness for variations in the number of passengers and longitude position of the centre of gravity.

Satellite-Tracking Millimeter-Wave Reflector Antenna System For Mobile Satellite-Tracking

NASA Technical Reports Server (NTRS)

Densmore, Arthur C. (Inventor); Jamnejad, Vahraz (Inventor); Woo, Kenneth E. (Inventor)

2001-01-01

A miniature dual-band two-way mobile satellite-tracking antenna system mounted on a movable vehicle includes a miniature parabolic reflector dish having an elliptical aperture with major and minor elliptical axes aligned horizontally and vertically, respectively, to maximize azimuthal directionality and minimize elevational directionality to an extent corresponding to expected pitch excursions of the movable ground vehicle. A feed-horn has a back end and an open front end facing the reflector dish and has vertical side walls opening out from the back end to the front end at a lesser horn angle and horizontal top and bottom walls opening out from the back end to the front end at a greater horn angle. An RF circuit couples two different signal bands between the feed-horn and the user. An antenna attitude controller maintains an antenna azimuth direction relative to the satellite by rotating it in azimuth in response to sensed yaw motions of the movable ground vehicle so as to compensate for the yaw motions to within a pointing error angle. The controller sinusoidally dithers the antenna through a small azimuth dither angle greater than the pointing error angle while sensing a signal from the satellite received at the reflector dish, and deduces the pointing angle error from dither-induced fluctuations in the received signal.

Controlled banked turns in coleopteran flight measured by a miniature wireless inertial measurement unit.

PubMed

Li, Yao; Cao, Feng; Thang Vo Doan, Tat; Sato, Hirotaka

2016-09-28

The mechanisms and principles of insect flight have long been investigated by researchers working on micro and nano air vehicles (MAVs/NAVs). However, studies of insect flight maneuvers require high speed filming and high spatial resolution in a small experimental space, or the tethering of the insect to a fixed place. Under such artificial conditions, the insects may deviate its flying behavior from that of regular flight. In this study, we mounted a tiny wireless system, or 'backpack', on live beetles (Mecynorrhina torquata; length 62 ± 8 mm; mass 7.4 ± 1.3 g) freely flying in a large laboratory space. The backpack contains a micro inertial measurement unit (IMU) that was especially designed and manufactured for this purpose. Owing to the small mass (∼1.30 g) and dimensions (∼2.3 cm 2 ) of the backpack and the high accuracy of the IMU, we could remotely record the beetle in free flight. The free flight data revealed a strong linear correlation between the roll angle and yaw angular velocity. The strength of the correlation was quantified by the correlation coefficients and mean values. The change in roll angle preceded the change in yaw angular velocity. Moreover, there were frequent fluctuations in the roll angular velocity, which were uncorrelated with the yaw angular velocity. Apart from the strong correlation, these findings imply that Mecynorrhina torquata actively manipulates its roll rotation without coupling to the yaw rotation.

Method for calculating the rolling and yawing moments due to rolling for unswept wings with or without flaps or ailerons by use of nonlinear section lift data

NASA Technical Reports Server (NTRS)

Martina, Albert P

1953-01-01

The methods of NACA Reports 865 and 1090 have been applied to the calculation of the rolling- and yawing-moment coefficients due to rolling for unswept wings with or without flaps or ailerons. The methods allow the use of nonlinear section lift data together with lifting-line theory. Two calculated examples are presented in simplified computing forms in order to illustrate the procedures involved.

Design and test of a simulation system for autonomous optic-navigated planetary landing

NASA Astrophysics Data System (ADS)

Cai, Sheng; Yin, Yanhe; Liu, Yanjun; He, Fengyun

2018-02-01

In this paper, a simulation system based on commercial projector is proposed to test the optical navigation algorithms for autonomous planetary landing in laboratorial scenarios. The design work of optics, mechanics and synchronization control are carried out. Furthermore, the whole simulation system is set up and tested. Through the calibration of the system, two main problems, synchronization between the projector and CCD and pixel-level shifting caused by the low repeatability of DMD used in the projector, are settled. The experimental result shows that the RMS errors of pitch, yaw and roll angles are 0.78', 0.48', and 2.95' compared with the theoretical calculation, which can fulfill the requirement of experimental simulation for planetary landing in laboratory.

Spatial orientation of the vestibular system

NASA Technical Reports Server (NTRS)

Raphan, T.; Dai, M.; Cohen, B.

1992-01-01

1. A simplified three-dimensional state space model of visual vestibular interaction was formulated. Matrix and dynamical system operators representing coupling from the semicircular canals and the visual system to the velocity storage integrator were incorporated into the model. 2. It was postulated that the system matrix for a tilted position was a composition of two linear transformations of the system matrix for the upright position. One transformation modifies the eigenvalues of the system matrix while another rotates the pitch and roll eigenvectors with the head, while maintaining the yaw axis eigenvector approximately spatially invariant. Using this representation, the response characteristics of the pitch, roll, and yaw eye velocity were obtained in terms of the eigenvalues and associated eigenvectors. 3. Using OKAN data obtained from monkeys and comparing to the model predictions, the eigenvalues and eigenvectors of the system matrix were identified as a function of tilt to the side or of tilt to the prone positions, using a modification of the Marquardt algorithm. The yaw eigenvector for right-side-down tilt and for downward pitch cross-coupling was approximately 30 degrees from the spatial vertical. For the prone position, the eigenvector was computed to be approximately 20 degrees relative to the spatial vertical. For both side-down and prone positions, oblique OKN induced along eigenvector directions generated OKAN which decayed to zero along a straight line with approximately a single time constant. This was verified by a spectral analysis of the residual sequence about the straight line fit to the decaying data. The residual sequence was associated with a narrow autocorrelation function and a wide power spectrum. 4. Parameters found using the Marquardt algorithm were incorporated into the model. Diagonal matrices in a head coordinate frame were introduced to represent the direct pathway and the coupling of the visual system to the integrator. Model

Observing Mode Attitude Controller for the Lunar Reconnaissance Orbiter

NASA Technical Reports Server (NTRS)

Calhourn, Philip C.; Garrick, Joseph C.

2007-01-01

The Lunar Reconnaissance Orbiter (LRO) mission is the first of a series of lunar robotic spacecraft scheduled for launch in Fall 2008. LRO will spend at least one year in a low altitude polar orbit around the Moon, collecting lunar environment science and mapping data to enable future human exploration. The LRO employs a 3-axis stabilized attitude control system (ACS) whose primary control mode, the "Observing mode", provides Lunar Nadir, off-Nadir, and Inertial fine pointing for the science data collection and instrument calibration. The controller combines the capability of fine pointing with that of on-demand large angle full-sky attitude reorientation into a single ACS mode, providing simplicity of spacecraft operation as well as maximum flexibility for science data collection. A conventional suite of ACS components is employed in this mode to meet the pointing and control objectives. This paper describes the design and analysis of the primary LRO fine pointing and attitude re-orientation controller function, known as the "Observing mode" of the ACS subsystem. The control design utilizes quaternion feedback, augmented with a unique algorithm that ensures accurate Nadir tracking during large angle yaw maneuvers in the presence of high system momentum and/or maneuver rates. Results of system stability analysis and Monte Carlo simulations demonstrate that the observing mode controller can meet fine pointing and maneuver performance requirements.

Implementation of internal model based control and individual pitch control to reduce fatigue loads and tower vibrations in wind turbines

NASA Astrophysics Data System (ADS)

Mohammadi, Ebrahim; Fadaeinedjad, Roohollah; Moschopoulos, Gerry

2018-05-01

Vibration control and fatigue loads reduction are important issues in large-scale wind turbines. Identifying the vibration frequencies and tuning dampers and controllers at these frequencies are major concerns in many control methods. In this paper, an internal model control (IMC) method with an adaptive algorithm is implemented to first identify the vibration frequency of the wind turbine tower and then to cancel the vibration signal. Standard individual pitch control (IPC) is also implemented to compare the performance of the controllers in term of fatigue loads reduction. Finally, the performance of the system when both controllers are implemented together is evaluated. Simulation results demonstrate that using only IMC or IPC alone has advantages and can reduce fatigue loads on specific components. IMC can identify and suppress tower vibrations in both fore-aft and side-to-side directions, whereas, IPC can reduce fatigue loads on blades, shaft and yaw bearings. When both IMC and IPC are implemented together, the advantages of both controllers can be used. The aforementioned analysis and comparisons were not studied in literature and this study fills this gap. FAST, AreoDyn and Simulink are used to simulate the mechanical, aerodynamic and electrical aspects of wind turbine.

Manual control of yaw motion with combined visual and vestibular cues

NASA Technical Reports Server (NTRS)

Zacharias, G. L.; Young, L. R.

1977-01-01

Measurements are made of manual control performance in the closed-loop task of nulling perceived self-rotation velocity about an earth-vertical axis. Self-velocity estimation was modelled as a function of the simultaneous presentation of vestibular and peripheral visual field motion cues. Based on measured low-frequency operator behavior in three visual field environments, a parallel channel linear model is proposed which has separate visual and vestibular pathways summing in a complementary manner. A correction to the frequency responses is provided by a separate measurement of manual control performance in an analogous visual pursuit nulling task. The resulting dual-input describing function for motion perception dependence on combined cue presentation supports the complementary model, in which vestibular cues dominate sensation at frequencies above 0.05 Hz. The describing function model is extended by the proposal of a non-linear cue conflict model, in which cue weighting depends on the level of agreement between visual and vestibular cues.

Exploring bird aerodynamics using radio-controlled models.

PubMed

Hoey, Robert G

2010-12-01

A series of radio-controlled glider models was constructed by duplicating the aerodynamic shape of soaring birds (raven, turkey vulture, seagull and pelican). Controlled tests were conducted to determine the level of longitudinal and lateral-directional static stability, and to identify the characteristics that allowed flight without a vertical tail. The use of tail-tilt for controlling small bank-angle changes, as observed in soaring birds, was verified. Subsequent tests, using wing-tip ailerons, inferred that birds use a three-dimensional flow pattern around the wing tip (wing tip vortices) to control adverse yaw and to create a small amount of forward thrust in gliding flight.

A satellite-tracking millimeter-wave reflector antenna system for mobile satellite-tracking

NASA Technical Reports Server (NTRS)

Densmore, Arthur C. (Inventor); Jamnejad, Vahraz (Inventor); Woo, Kenneth E. (Inventor)

1995-01-01

A miniature dual-band two-way mobile satellite tracking antenna system mounted on a movable ground vehicle includes a miniature parabolic reflector dish having an elliptical aperture with major and minor elliptical axes aligned horizontally and vertically, respectively, to maximize azimuthal directionality and minimize elevational directionality to an extent corresponding to expected pitch excursions of the movable ground vehicle. A feed-horn has a back end and an open front end facing the reflector dish and has vertical side walls opening out from the back end to the front end at a lesser horn angle and horizontal top and bottom walls opening out from the back end to the front end at a greater horn angle. An RF circuit couples two different signal bands between the feed-horn and the user. An antenna attitude controller maintains an antenna azimuth direction relative to the satellite by rotating it in azimuth in response to sensed yaw motions of the movable ground vehicle so as to compensate for the yaw motions to within a pointing error angle. The controller sinusoidally dithers the antenna through a small azimuth dither angle greater than the pointing error angle while sensing a signal from the satellite received at the reflector dish, and deduces the pointing angle error from dither-induced fluctuations in the received signal.

Investigations of Lateral Stability of a Glide Bomb Using Automatic Control Having No Time Lag

NASA Technical Reports Server (NTRS)

Sponder, E. W.

1950-01-01

The investigation of the lateral stability of an automatically controlled glide bomb led also to the attempt of clarifying the influence of a phugoid oscillation or of any general longitudinal oscillation on the lateral stability of a glide bomb. Under the assumption that its period of oscillation considerably exceeds the rolling and yawing oscillation and that c(sub a) is, at least in sections, practically constant, the result of this test is quite simple. It becomes clear that the influence of the phugoid oscillation may be replaced by suitable variation of the rolling-yawing moment on a rectilinear flight path instead of the phugoid oscillation. If the flying weight of the glide bomb of unchanged dimensions is increased, an increase of the flight velocity will be more favorable than an increase of the lift coefficient. The arrangement of the control permits lateral stability to be achieved in every case; a minimum rolling moment due to sideslip proves of great help.

Flight Characteristics of a 1/4-Scale Model of the XFV-1 Airplane (TED No. NACA DE-378)

NASA Technical Reports Server (NTRS)

Kelly, Mark W.; Smaus, Louis H.

1952-01-01

A l/4-scale dynamically similar model of the XFV-1 airplane has been flown in the Ames 40- by 80-foot wind tunnel, using the trailing flight-cable technique. This investigation was devoted to establishing the flight characteristics of the model in forward flight from hovering to wing stall, and in yawed flight (wing span alined with the relative wind) from hovering to the maximum speed at which controlled flight could be maintained. Landings, take-offs, and hovering characteristics in flights close to the ground were also investigated.. Since the remote control system for the model was rather complicated and provided artificial damping about the pitch, roll, and yaw axes, sufficient data from the control-system calibration tests are included in this report to specify the performance of the control system in relation to both the model flight tests and the design of an automatic control system for the full-scale airplane. The model in hovering flight appeared to be neutrally stable. The response of the model to the controls was very rapid, and it was always necessary to provide some amount of artificial damping to maintain control. The model could be landed with little difficulty by hovering approximately a foot above the floor and then cutting the power. Take-offs were more difficult to perform, primarily because the rate of change in power to the model motors was limited by the characteristics of the available power source. The model was,capable of controlled yawed flight at translational velocities up to and including 20 feet per second. The effectiveness of the controls decreased with increasing speed, however, and at 25 fps control in pitch, and probably roll, was lost completely. The model was flown in controlled forward flight from hovering up to 70 fps. During these flights the model appeared to be more difficult to control in yaw than it was in pitch or roll. The flights of the model were recorded by motion picture cameras. These motion pictures are

Adaptive Control Responses to Behavioral Perturbation Based Upon the Insect

DTIC Science & Technology

2006-11-01

the legs. Visual Sensors Antennal Mechanosensors Antennal Chemosensors Descending Interneurons Controlling Yaw...animals, the antenna were moved back and forth several times with servo motors to identify units that respond to antennal movement in either direction or...role of antennal postures and movements in plume tracking behavior. To date, results have shown that male moths tracking plumes in different wind

Motion of the two-control airplane in rectilinear flight after initial disturbances with introduction of controls following an exponential law

NASA Technical Reports Server (NTRS)

Klemin, Alexander

1937-01-01

An airplane in steady rectilinear flight was assumed to experience an initial disturbance in rolling or yawing velocity. The equations of motion were solved to see if it was possible to hasten recovery of a stable airplane or to secure recovery of an unstable airplane by the application of a single lateral control following an exponential law. The sample computations indicate that, for initial disturbances complex in character, it would be difficult to secure correlation with any type of exponential control. The possibility is visualized that the two-control operation may seriously impair the ability to hasten recovery or counteract instability.

A finite-step method for estimating the spanwise lift distribution of wings in symmetric, yawed, and rotary flight at low speeds

NASA Technical Reports Server (NTRS)

Krenkel, A. R.

1978-01-01

The finite-step method was programmed for computing the span loading and stability derivatives of trapezoidal shaped wings in symmetric, yawed, and rotary flight. Calculations were made for a series of different wing planforms and the results compared with several available methods for estimating these derivatives in the linear angle of attack range. The agreement shown was generally good except in a few cases. An attempt was made to estimate the nonlinear variation of lift with angle of attack in the high alpha range by introducing the measured airfoil section data into the finite-step method. The numerical procedure was found to be stable only at low angles of attack.

Course Keeping Control of an Autonomous Boat using Low Cost Sensors

NASA Astrophysics Data System (ADS)

Yu, Zhenyu; Bao, Xinping; Nonami, Kenzo

This paper discusses the course keeping control problem for a small autonomous boat using low cost sensors. Comparing with full scale ships, a small boat is more sensitive to the environmental disturbances because of its small size and low inertia. The sensors available in the boat are a low cost GPS and a rate gyro while the commonly used compass in ship control is absent. The combined effect from disturbance, poor accuracy and significant delay in GPS measurement makes it a challenging task to achieve good performance. In this paper, we propose a simple dynamic model for the boat's horizontal motion. The model is based on the Nomoto's model and can be seen as an extension to it. The model describes the dynamics between rudder deflection and the boat's velocity vector angle while Nomoto's model reveals that between rudder deflection and the boat's yaw angle. With the proposed model there is no need for a yaw sensor for control if the boat's moving direction can be measured. GPS is a convenient device for that job. Based on the derived model, we apply mixed H2/H∞ control method to design the controller. It can guarantee the robust stability, and as the same time it can optimize the performance in the sense of H2 norm. The experimental data show that the proposed approach is proved to be effective and useful.

Thermal Nondestructive Evaluation Report: Inspection of the Refurbished Manipulator Arm System in the Manipulator Development Facility at Johnson Space Center 10-12 January 2001

NASA Technical Reports Server (NTRS)

Cramer, K. Elliott

2002-01-01

On 4 December 2002, a failure of the Refurbished Manipulator Arm System (RMAS) occurred in the Manipulator Development Facility (MDF) at Johnson Space Center. When the Test Director commanded a should pitch maneuver to lift the arm from its payload bay pedestal, the yaw controls failed. This, coupled with a gravitational forces (due to the angle of the shoulder joint with respect to vertical), resulted in uncontrolled arm motion. The shoulder yaw joint moved approximately 20 degrees, causing the extended arm to strike and severely damage the port side MDF catwalk handrails. The arm motion stopped after impact with the handrails. On 10-12 January 2001, inspections were performed on the port face of the lower and upper arms of the RMAS using a infrared thermography developed at Langley Research Center. This paper presents the results of those nondestructive inspections and provides a complete description of the anomalies found and their locations.

Electric machine differential for vehicle traction control and stability control

NASA Astrophysics Data System (ADS)

Kuruppu, Sandun Shivantha

Evolving requirements in energy efficiency and tightening regulations for reliable electric drivetrains drive the advancement of the hybrid electric (HEV) and full electric vehicle (EV) technology. Different configurations of EV and HEV architectures are evaluated for their performance. The future technology is trending towards utilizing distinctive properties in electric machines to not only to improve efficiency but also to realize advanced road adhesion controls and vehicle stability controls. Electric machine differential (EMD) is such a concept under current investigation for applications in the near future. Reliability of a power train is critical. Therefore, sophisticated fault detection schemes are essential in guaranteeing reliable operation of a complex system such as an EMD. The research presented here emphasize on implementation of a 4kW electric machine differential, a novel single open phase fault diagnostic scheme, an implementation of a real time slip optimization algorithm and an electric machine differential based yaw stability improvement study. The proposed d-q current signature based SPO fault diagnostic algorithm detects the fault within one electrical cycle. The EMD based extremum seeking slip optimization algorithm reduces stopping distance by 30% compared to hydraulic braking based ABS.

Computer graphics testbed to simulate and test vision systems for space applications

NASA Technical Reports Server (NTRS)

Cheatham, John B.; Wu, Chris K.; Lin, Y. H.

1991-01-01

A system was developed for displaying computer graphics images of space objects and the use of the system was demonstrated as a testbed for evaluating vision systems for space applications. In order to evaluate vision systems, it is desirable to be able to control all factors involved in creating the images used for processing by the vision system. Considerable time and expense is involved in building accurate physical models of space objects. Also, precise location of the model relative to the viewer and accurate location of the light source require additional effort. As part of this project, graphics models of space objects such as the Solarmax satellite are created that the user can control the light direction and the relative position of the object and the viewer. The work is also aimed at providing control of hue, shading, noise and shadows for use in demonstrating and testing imaging processing techniques. The simulated camera data can provide XYZ coordinates, pitch, yaw, and roll for the models. A physical model is also being used to provide comparison of camera images with the graphics images.

Modelling and Closed-Loop System Identification of a Quadrotor-Based Aerial Manipulator

NASA Astrophysics Data System (ADS)

Dube, Chioniso; Pedro, Jimoh O.

2018-05-01

This paper presents the modelling and system identification of a quadrotor-based aerial manipulator. The aerial manipulator model is first derived analytically using the Newton-Euler formulation for the quadrotor and Recursive Newton-Euler formulation for the manipulator. The aerial manipulator is then simulated with the quadrotor under Proportional Derivative (PD) control, with the manipulator in motion. The simulation data is then used for system identification of the aerial manipulator. Auto Regressive with eXogenous inputs (ARX) models are obtained from the system identification for linear accelerations \\ddot{X} and \\ddot{Y} and yaw angular acceleration \\ddot{\\psi }. For linear acceleration \\ddot{Z}, and pitch and roll angular accelerations \\ddot{θ } and \\ddot{φ }, Auto Regressive Moving Average with eXogenous inputs (ARMAX) models are identified.

Quadcopter Path Following Control Design Using Output Feedback with Command Generator Tracker LOS Based At Square Path

NASA Astrophysics Data System (ADS)

Nugraha, A. T.; Agustinah, T.

2018-01-01

Quadcopter an unstable system, underactuated and nonlinear in quadcopter control research developments become an important focus of attention. In this study, following the path control method for position on the X and Y axis, used structure-Generator Tracker Command (CGT) is tested. Attitude control and position feedback quadcopter is compared using the optimal output. The addition of the H∞ performance optimal output feedback control is used to maintain the stability and robustness of quadcopter. Iterative numerical techniques Linear Matrix Inequality (LMI) is used to find the gain controller. The following path control problems is solved using the method of LQ regulators with output feedback. Simulations show that the control system can follow the paths that have been defined in the form of a reference signal square shape. The result of the simulation suggest that the method which used can bring the yaw angle at the expected value algorithm. Quadcopter can do automatically following path with cross track error mean X=0.5 m and Y=0.2 m.

Extension to the dynamic modeling of the large angle magnetic suspension test fixture. M.S. Thesis - Old Dominion Univ., May 1995 Progress Report, 1 Nov. 1994 - 30 Apr. 1995

NASA Technical Reports Server (NTRS)

Foster, Lucas E.; Britcher, Colin P.

1995-01-01

The Large Angle Magnetic Suspension Test Fixture (LAMSTF) is a laboratory scale proof-of-concept system. The configuration is unique in that the electromagnets are mounted in a circular planar array. A mathematical model of the system had previously been developed, but was shown to have inaccuracies. These inaccuracies showed up in the step responses. Eddy currents were found to be the major cause of the modeling errors. In the original system, eddy currents existed in the aluminum baseplate, iron cores, and the sensor support frame. An attempt to include the eddy current dynamics in the system model is presented. The dynamics of a dummy sensor ring were added to the system. Adding the eddy current dynamics to the simulation improves the way it compares to the actual experiment. Also presented is a new method of determining the yaw angle of the suspended element. From the coil currents the yaw angle can be determined and the controller can be updated to suspend at the new current. This method has been used to demonstrate a 360 degree yaw angle rotation.

National Transonic Facility model and model support vibration problems

NASA Technical Reports Server (NTRS)

Young, Clarence P., Jr.; Popernack, Thomas G., Jr.; Gloss, Blair B.

1990-01-01

Vibrations of models and model support system were encountered during testing in the National Transonic Facility. Model support system yaw plane vibrations have resulted in model strain gage balance design load limits being reached. These high levels of vibrations resulted in limited aerodynamic testing for several wind tunnel models. The yaw vibration problem was the subject of an intensive experimental and analytical investigation which identified the primary source of the yaw excitation and resulted in attenuation of the yaw oscillations to acceptable levels. This paper presents the principal results of analyses and experimental investigation of the yaw plane vibration problems. Also, an overview of plans for development and installation of a permanent model system dynamic and aeroelastic response measurement and monitoring system for the National Transonic Facility is presented.

Independently Controlled Wing Stroke Patterns in the Fruit Fly Drosophila melanogaster

PubMed Central

Chakraborty, Soma; Bartussek, Jan; Fry, Steven N.; Zapotocky, Martin

2015-01-01

Flies achieve supreme flight maneuverability through a small set of miniscule steering muscles attached to the wing base. The fast flight maneuvers arise from precisely timed activation of the steering muscles and the resulting subtle modulation of the wing stroke. In addition, slower modulation of wing kinematics arises from changes in the activity of indirect flight muscles in the thorax. We investigated if these modulations can be described as a superposition of a limited number of elementary deformations of the wing stroke that are under independent physiological control. Using a high-speed computer vision system, we recorded the wing motion of tethered flying fruit flies for up to 12 000 consecutive wing strokes at a sampling rate of 6250 Hz. We then decomposed the joint motion pattern of both wings into components that had the minimal mutual information (a measure of statistical dependence). In 100 flight segments measured from 10 individual flies, we identified 7 distinct types of frequently occurring least-dependent components, each defining a kinematic pattern (a specific deformation of the wing stroke and the sequence of its activation from cycle to cycle). Two of these stroke deformations can be associated with the control of yaw torque and total flight force, respectively. A third deformation involves a change in the downstroke-to-upstroke duration ratio, which is expected to alter the pitch torque. A fourth kinematic pattern consists in the alteration of stroke amplitude with a period of 2 wingbeat cycles, extending for dozens of cycles. Our analysis indicates that these four elementary kinematic patterns can be activated mutually independently, and occur both in isolation and in linear superposition. The results strengthen the available evidence for independent control of yaw torque, pitch torque, and total flight force. Our computational method facilitates systematic identification of novel patterns in large kinematic datasets. PMID:25710715

Independently controlled wing stroke patterns in the fruit fly Drosophila melanogaster.

PubMed

Chakraborty, Soma; Bartussek, Jan; Fry, Steven N; Zapotocky, Martin

2015-01-01

Flies achieve supreme flight maneuverability through a small set of miniscule steering muscles attached to the wing base. The fast flight maneuvers arise from precisely timed activation of the steering muscles and the resulting subtle modulation of the wing stroke. In addition, slower modulation of wing kinematics arises from changes in the activity of indirect flight muscles in the thorax. We investigated if these modulations can be described as a superposition of a limited number of elementary deformations of the wing stroke that are under independent physiological control. Using a high-speed computer vision system, we recorded the wing motion of tethered flying fruit flies for up to 12,000 consecutive wing strokes at a sampling rate of 6250 Hz. We then decomposed the joint motion pattern of both wings into components that had the minimal mutual information (a measure of statistical dependence). In 100 flight segments measured from 10 individual flies, we identified 7 distinct types of frequently occurring least-dependent components, each defining a kinematic pattern (a specific deformation of the wing stroke and the sequence of its activation from cycle to cycle). Two of these stroke deformations can be associated with the control of yaw torque and total flight force, respectively. A third deformation involves a change in the downstroke-to-upstroke duration ratio, which is expected to alter the pitch torque. A fourth kinematic pattern consists in the alteration of stroke amplitude with a period of 2 wingbeat cycles, extending for dozens of cycles. Our analysis indicates that these four elementary kinematic patterns can be activated mutually independently, and occur both in isolation and in linear superposition. The results strengthen the available evidence for independent control of yaw torque, pitch torque, and total flight force. Our computational method facilitates systematic identification of novel patterns in large kinematic datasets.

Unsteady aerodynamic analysis of space shuttle vehicles. Part 4: Effect of control deflections on orbiter unsteady aerodynamics

NASA Technical Reports Server (NTRS)

Reding, J. P.; Ericsson, L. E.

1973-01-01

The unsteady aerodynamics of the 040A orbiter have been explored experimentally. The results substantiate earlier predictions of the unsteady flow boundaries for a 60 deg swept delta wing at zero yaw and with no controls deflected. The test revealed a previously unknown region of discontinuous yaw characteristics at transonic speeds. Oilflow results indicate that this is the result of a coupling between wing and fuselage flows via the separated region forward of the deflected elevon. In fact, the large leeward elevon deflections are shown to produce a multitude of nonlinear stability effects which sometimes involve hysteresis. Predictions of the unsteady flow boundaries are made for the current orbiter. They should carry a good degree of confidence due to the present substantiation of previous predictions for the 040A. It is proposed that the present experiments be extended to the current configuration to define control-induced effects. Every effort should be made to account for Reynolds number, roughness, and possible hot-wall effects on any future experiments.

Entry Atmospheric Flight Control Authority Impacts on GN and C and Trajectory Performance for Orion Exploration Flight Test 1

NASA Technical Reports Server (NTRS)

McNamara, Luke W.

2012-01-01

One of the key design objectives of NASA's Orion Exploration Flight Test 1 (EFT-1) is to execute a guided entry trajectory demonstrating GN&C capability. The focus of this paper is the ight control authority of the vehicle throughout the atmospheric entry ight to the target landing site and its impacts on GN&C, parachute deployment, and integrated performance. The vehicle's attitude control authority is obtained from thrusting 12 Re- action Control System (RCS) engines, with four engines to control yaw, four engines to control pitch, and four engines to control roll. The static and dynamic stability derivatives of the vehicle are determined to assess the inherent aerodynamic stability. The aerodynamic moments at various locations in the entry trajectory are calculated and compared to the available torque provided by the RCS system. Interaction between the vehicle's RCS engine plumes and the aerodynamic conditions are considered to assess thruster effectiveness. This document presents an assessment of Orion's ight control authority and its effectiveness in controlling the vehicle during critical events in the atmospheric entry trajectory.

Lidar-Enhanced Wind Turbine Control: Past, Present, and Future: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scholbrock, Andrew; Fleming, Paul; Wright, Alan

2016-07-01

This paper will look at the development of lidar-enhanced controls and how they have been used for turbine load reduction with pitch actuation, as well as increased energy production with improved yaw control. Ongoing work will also be discussed to show that combining pitch and torque control using feedforward nonlinear model predictive control can lead to both reduced loads and increased energy production. Future work is also proposed on extending individual wind turbine controls to the wind plant level and determining how lidars can be used for control methods to further lower the cost of wind energy by minimizing wakemore » impacts in a wind farm.« less

Computer program for prediction of capture maneuver probability for an on-off reaction controlled upper stage

NASA Technical Reports Server (NTRS)

Knauber, R. N.

1982-01-01

A FORTRAN coded computer program which computes the capture transient of a launch vehicle upper stage at the ignition and/or separation event is presented. It is for a single degree-of-freedom on-off reaction jet attitude control system. The Monte Carlo method is used to determine the statistical value of key parameters at the outcome of the event. Aerodynamic and booster induced disturbances, vehicle and control system characteristics, and initial conditions are treated as random variables. By appropriate selection of input data pitch, yaw and roll axes can be analyzed. Transient response of a single deterministic case can be computed. The program is currently set up on a CDC CYBER 175 computer system but is compatible with ANSI FORTRAN computer language. This routine has been used over the past fifteen (15) years for the SCOUT Launch Vehicle and has been run on RECOMP III, IBM 7090, IBM 360/370, CDC6600 and CDC CYBER 175 computers with little modification.

Stability and control of the Gossamer human powered aircraft by analysis and flight test

NASA Technical Reports Server (NTRS)

Jex, H. R.; Mitchell, D. G.

1982-01-01

The slow flight speed, very light wing loading, and neutral stability of the Gossamer Condor and the Gossamer Albatross emphasized apparent-mass aerodynamic effects and unusual modes of motion response. These are analyzed, approximated, and discussed, and the resulting transfer functions and dynamic properties are summarized and compared. To verify these analytical models, flight tests were conducted with and electrically powered Gossamer Albatross II. Sensors were installed and their outputs were telemetered to records on the ground. Frequency sweeps of the various controls were made and the data were reduced to frequency domain measures. Results are given for the response of: pitch rate, airspeed and normal acceleration from canard-elevator deflection; roll rate and yaw rate from canard-rudder tilt; and roll rate and yaw rate from wing warp. The reliable data are compared with the analytical predictions.

Feedback control laws for highly maneuverable aircraft

NASA Technical Reports Server (NTRS)

Garrard, William L.; Balas, Gary J.

1995-01-01

During this year, we concentrated our efforts on the design of controllers for lateral/directional control using mu synthesis. This proved to be a more difficult task than we anticipated and we are still working on the designs. In the lateral-directional control problem, the inputs are pilot lateral stick and pedal commands and the outputs are roll rate about the velocity vector and side slip angle. The control effectors are ailerons, rudder deflection, and directional thrust vectoring vane deflection which produces a yawing moment about the body axis. Our math model does not contain any provision for thrust vectoring of rolling moment. This has resulted in limitations of performance at high angles of attack. During 1994-95, the following tasks for the lateral-directional controllers were accomplished: (1) Designed both inner and outer loop dynamic inversion controllers. These controllers are implemented using accelerometer outputs rather than an a priori model of the vehicle aerodynamics; (2) Used classical techniques to design controllers for the system linearized by dynamics inversion. These controllers acted to control roll rate and Dutch roll response; (3) Implemented the inner loop dynamic inversion and classical controllers on the six DOF simulation; (4) Developed a lateral-directional control allocation scheme based on minimizing required control effort among the ailerons, rudder, and directional thrust vectoring; and (5) Developed mu outer loop controllers combined with classical inner loop controllers.

Base pressure and heat transfer tests of the 0.0225-scale space shuttle plume simulation model (19-OTS) in yawed flight conditions in the NASA-Lewis 10x10-foot supersonic wind tunnel (test IH83)

NASA Technical Reports Server (NTRS)

Foust, J. W.

1979-01-01

Wind tunnel tests were performed to determine pressures, heat transfer rates, and gas recovery temperatures in the base region of a rocket firing model of the space shuttle integrated vehicle during simulated yawed flight conditions. First and second stage flight of the space shuttle were simulated by firing the main engines in conjunction with the SRB rocket motors or only the SSME's into the continuous tunnel airstream. For the correct rocket plume environment, the simulated altitude pressures were halved to maintain the rocket chamber/altitude pressure ratio. Tunnel freestream Mach numbers from 2.2 to 3.5 were simulated over an altitude range of 60 to 130 thousand feet with varying angle of attack, yaw angle, nozzle gimbal angle and SRB chamber pressure. Gas recovery temperature data derived from nine gas temperature probe runs are presented. The model configuration, instrumentation, test procedures, and data reduction are described.

A piloted simulator investigation of augmentation systems to improve helicopter nap-of-the-earth handling qualities

NASA Technical Reports Server (NTRS)

Chen, R. T. N.; Talbot, P. D.; Gerdes, R. M.; Dugan, D. C.

1978-01-01

A piloted simulation study assessed various levels of stability and control augmentation designed to improve the handling qualities of several helicopters in nap-of-the-earth (NOE) flight. Five basic single rotor helicopters - one teetering, two articulated, and two hingeless - which were found to have a variety of major deficiencies in a previous fixed-based simulator study were selected as baseline configurations. The stability and control augmentation systems (SCAS) include simple control augmentation systems (CAS) to decouple pitch and yaw responses due to collective input and to quicken the pitch and roll control responses; SCAS of rate command type designed to optimize the sensitivity and damping and to decouple the pitch-roll due to aircraft angular rate; and attitude command type SCAS. Pilot ratings and commentary are presented as well as performance data related to the task. SCAS control usage and their gain levels associated with specific rotor type are also discussed.

The Magsat three axis arc second precision attitude transfer system

NASA Technical Reports Server (NTRS)

Schenkel, F. W.; Heins, R. J.

1981-01-01

The Magsat Attitude Transfer System (ATS), which provides attitude alteration in pitch, yaw, and roll is described. A remote vector magnetometer extends from Magsat on a 20 ft boom, requiring vector orientation by reference to coordinate axes determined by a set of star mapping cameras. The ATS was designed to perform in a solar illuminated environment by using an optically narrow bandwidth with synchronous demodulation at 9300 A. The pitch/yaw optical design, the electrooptics, and signal and switching diagrams are provided. Simple mirrors with no moving parts are placed on the magnetometer to reflect a collimated beam from the ATS for attitude indication, which is accurate to one part in 96. Alignment was completed within 24 hr after launch.

Control Systems

NASA Technical Reports Server (NTRS)

1984-01-01

Boeing Commercial Airplane Company's Flight Control Department engineers relied on Langley developed software package known as ORACLS to develop an advanced control synthesis package for both continuous and discrete control system. Package was used by Boeing for computerized analysis of new system designs. Resulting applications include a multiple input/output control system for the terrain-following navigation equipment of the Air Forces B-1 Bomber, and another for controlling in flight changes of wing camber on an experimental airplane. ORACLS is one of 1,300 computer programs available from COSMIC.

Theoretical Calculation of the Power Spectra of the Rolling and Yawing Moments on a Wing in Random Turbulence

NASA Technical Reports Server (NTRS)

Eggleston, John M; Diederich, Franklin W

1957-01-01

The correlation functions and power spectra of the rolling and yawing moments on an airplane wing due to the three components of continuous random turbulence are calculated. The rolling moments to the longitudinal (horizontal) and normal (vertical) components depend on the spanwise distributions of instantaneous gust intensity, which are taken into account by using the inherent properties of symmetry of isotropic turbulence. The results consist of expressions for correlation functions or spectra of the rolling moment in terms of the point correlation functions of the two components of turbulence. Specific numerical calculations are made for a pair of correlation functions given by simple analytic expressions which fit available experimental data quite well. Calculations are made for four lift distributions. Comparison is made with the results of previous analyses which assumed random turbulence along the flight path and linear variations of gust velocity across the span.

NASA Ares I Launch Vehicle First Stage Roll Control System Cold Flow Development Test Program Overview

NASA Technical Reports Server (NTRS)

Butt, Adam; Popp, Christopher G.; Holt, Kimberly A.; Pitts, Hank M.

2010-01-01

The Ares I launch vehicle is the selected design, chosen to return humans to the moon, Mars, and beyond. It is configured in two inline stages: the First Stage is a Space Shuttle derived five-segment Solid Rocket Booster and the Upper Stage is powered by a Saturn V derived J-2X engine. During launch, roll control for the First Stage (FS) is handled by a dedicated Roll Control System (RoCS) located on the connecting Interstage. That system will provide the Ares I with the ability to counteract induced roll torque while any induced yaw or pitch moments are handled by vectoring of the booster nozzle. This paper provides an overview of NASA s Ares I FS RoCS cold flow development test program including detailed test objectives, types of tests run to meet those objectives, an overview of the results, and applicable lessons learned. The test article was built and tested at the NASA Marshall Space Flight Center in Huntsville, AL. The FS RoCS System Development Test Article (SDTA) is a full scale, flight representative water flow test article whose primary objective was to obtain fluid system performance data to evaluate integrated system level performance characteristics and verify analytical models. Development testing and model correlation was deemed necessary as there is little historical precedent for similar large flow, pulsing systems such as the FS RoCS. The cold flow development test program consisted of flight-similar tanks, pressure regulators, and thruster valves, as well as plumbing simulating flight geometries, combined with other facility grade components and structure. Orifices downstream of the thruster valves were used to simulate the pressure drop through the thrusters. Additional primary objectives of this test program were to: evaluate system surge pressure (waterhammer) characteristics due to thruster valve operation over a range of mission duty cycles at various feed system pressures, evaluate temperature transients and heat transfer in the

Normative data on angular vestibulo-ocular responses in the yaw axis measured using the video head impulse test.

PubMed

Matiño-Soler, Eusebi; Esteller-More, Eduard; Martin-Sanchez, Juan-Carlos; Martinez-Sanchez, Jose-M; Perez-Fernandez, Nicolas

2015-03-01

To analyze vestibulo-ocular responses using the video head impulse test in the yaw axis. Prospective. Tertiary and university hospital. Two hundred twelve healthy subjects with no history of vestibular or neurologic impairment. Video head impulse test in the lateral semicircular canal plane. Vestibulo-ocular reflex (VOR) gain and appearance of refixation saccades (RSs) considering sex, age, and head impulse velocity and direction. Mean gain was 1.06 ± 0.07, and there were no differences between sexes. For all the impulses (n = 9,654; 4,947 rightward and 4,707 leftward), VOR gain decreased as head impulse velocity increased. When gain was evaluated by age and head velocity, it was steady until age 70 years for higher-velocity impulses and until age 90 years for lower-velocity head impulses. RSs were detected in 52 subjects, occurring after impulses to both sides of the head in 22 of these subjects. The number of subjects with RSs was significantly higher after age 71 years, and velocity was correlated, not with age, but with head impulse velocity. VOR gain was stable until age 90 years and thereafter dropped. However, this decrease occurred progressively in younger subjects as head impulse velocity increased, with VOR gain for faster head impulses decreasing significantly in subjects older than 70 years. This finding, in addition to the appearance of RSs, can be explained by the effect of aging on the deterioration of the vestibular system in the semicircular canals.

Immersive cyberspace system

NASA Technical Reports Server (NTRS)

Park, Brian V. (Inventor)

1997-01-01

An immersive cyberspace system is presented which provides visual, audible, and vibrational inputs to a subject remaining in neutral immersion, and also provides for subject control input. The immersive cyberspace system includes a relaxation chair and a neutral immersion display hood. The relaxation chair supports a subject positioned thereupon, and places the subject in position which merges a neutral body position, the position a body naturally assumes in zero gravity, with a savasana yoga position. The display hood, which covers the subject's head, is configured to produce light images and sounds. An image projection subsystem provides either external or internal image projection. The display hood includes a projection screen moveably attached to an opaque shroud. A motion base supports the relaxation chair and produces vibrational inputs over a range of about 0-30 Hz. The motion base also produces limited translation and rotational movements of the relaxation chair. These limited translational and rotational movements, when properly coordinated with visual stimuli, constitute motion cues which create sensations of pitch, yaw, and roll movements. Vibration transducers produce vibrational inputs from about 20 Hz to about 150 Hz. An external computer, coupled to various components of the immersive cyberspace system, executes a software program and creates the cyberspace environment. One or more neutral hand posture controllers may be coupled to the external computer system and used to control various aspects of the cyberspace environment, or to enter data during the cyberspace experience.

Adaptive Control Using Neural Network Augmentation for a Modified F-15 Aircraft

NASA Technical Reports Server (NTRS)

Burken, John J.; Williams-Hayes, Peggy; Karneshige, J. T.; Stachowiak, Susan J.

2006-01-01

Description of the performance of a simplified dynamic inversion controller with neural network augmentation follows. Simulation studies focus on the results with and without neural network adaptation through the use of an F-15 aircraft simulator that has been modified to include canards. Simulated control law performance with a surface failure, in addition to an aerodynamic failure, is presented. The aircraft, with adaptation, attempts to minimize the inertial cross-coupling effect of the failure (a control derivative anomaly associated with a jammed control surface). The dynamic inversion controller calculates necessary surface commands to achieve desired rates. The dynamic inversion controller uses approximate short period and roll axis dynamics. The yaw axis controller is a sideslip rate command system. Methods are described to reduce the cross-coupling effect and maintain adequate tracking errors for control surface failures. The aerodynamic failure destabilizes the pitching moment due to angle of attack. The results show that control of the aircraft with the neural networks is easier (more damped) than without the neural networks. Simulation results show neural network augmentation of the controller improves performance with aerodynamic and control surface failures in terms of tracking error and cross-coupling reduction.

Reconfigurable Control with Neural Network Augmentation for a Modified F-15 Aircraft

NASA Technical Reports Server (NTRS)

Burken, John J.; Williams-Hayes, Peggy; Kaneshige, John T.; Stachowiak, Susan J.

2006-01-01

Description of the performance of a simplified dynamic inversion controller with neural network augmentation follows. Simulation studies focus on the results with and without neural network adaptation through the use of an F-15 aircraft simulator that has been modified to include canards. Simulated control law performance with a surface failure, in addition to an aerodynamic failure, is presented. The aircraft, with adaptation, attempts to minimize the inertial cross-coupling effect of the failure (a control derivative anomaly associated with a jammed control surface). The dynamic inversion controller calculates necessary surface commands to achieve desired rates. The dynamic inversion controller uses approximate short period and roll axis dynamics. The yaw axis controller is a sideslip rate command system. Methods are described to reduce the cross-coupling effect and maintain adequate tracking errors for control surface failures. The aerodynamic failure destabilizes the pitching moment due to angle of attack. The results show that control of the aircraft with the neural networks is easier (more damped) than without the neural networks. Simulation results show neural network augmentation of the controller improves performance with aerodynamic and control surface failures in terms of tracking error and cross-coupling reduction.

Continued investigations in the NAAL low speed wind tunnel into the effects of the air breathing propulsion system on orbiter subsonic stability and control characteristics (OA62A)

NASA Technical Reports Server (NTRS)

Mennell, R.

1974-01-01

Experimental aerodynamic investigations were conducted on a stingmounted 0.0405-scale representation (model 43-0) of the 140A/B Space Shuttle Orbiter in a Low Speed Wind Tunnel. The NASA designation for this test was 0A62A. The primary test objective was to continue studies, initiated on tests 0A16 and 0A71A and 0A71C, in optimizing the air breathing propulsion system (ABPS) and investigating the aerodynamic effects of various nacelle number/location configurations on the orbiter stability and control characteristics. Orbiter stability and control characteristics, both with and without ABPS, were investigated at elevon deflections of 0, + or -5, + or -19, + or -5, and -20 deg; aileron deflections of 0 and 10 deg (about 0 deg elevon); and rudder deflections of 0, -7.5, and -15 deg. Aerodynamic force and moment data was measured in the body axis system by a 2.5-inch task type internal balance. The model was sting supported through the base region with a nominal angle of attack range of -4 to 30 deg. Yaw polars were recorded over the beta range of -10 to 10 deg at fixed angles of attack of 0, 5, 10, and 15 deg.

Wind Tunnel Results of Pneumatic Forebody Vortex Control Using Rectangular Slots a Chined Forebody

NASA Technical Reports Server (NTRS)

Alexander, Michael; Meyn, Larry A.

1994-01-01

A subsonic wind tunnel investigation of pneumatic vortex flow control on a chined forebody using slots was accomplished at a dynamic pressure of 50 psf resulting in a R(n)/ft of 1.3 x 10(exp 6). Data were acquired from angles of attack ranging from -4deg to +34deg at side slips of +0.4deg and +10.4deg. The test article used in this study was the 10% scale Fighter Lift and Control (FLAC) advanced diamond winged, vee-tailed fighter configuration. Three different slot blowing concepts were evaluated; outward, downward, and tangential with ail blowing accomplished asymmetrically. The results of three different mass flows (0.067, 0.13, and 0.26 lbm/s; C(sub mu)'s of less than or equal to 0.006, 0.011. and 0.022 respectively) were analyzed and reported. Test data are presented on the effects of mass flows, slot lengths and positions and blowing concepts on yawing moment and side force generation. Results from this study indicate that the outward and downward blowing slots developed yawing moment and side force increments in the direction opposite of the blowing side while the tangential blowing slots generated yawing moment and side force increments in the direction towards the blowing side. The outward and downward blowing slots typically produced positive pitching moment increments while the tangential blowing slots typically generated negative pitching moment increments. The slot blowing nearest the forebody apex was most effective at generating the largest increments and as the slot was moved aft or increased in length, its effectiveness at generating forces and moments diminished.

Control for small-speed lateral flight in a model insect.

PubMed

Zhang, Yan Lai; Sun, Mao

2011-09-01

Controls required for small-speed lateral flight of a model insect were studied using techniques based on the linear theories of stability and control (the stability and control derivatives were computed by the method of computational fluid dynamics). The main results are as follows. (1) Two steady-state lateral motions can exist: one is a horizontal side translation with the body rolling to the same side of the translation by a small angle, and the other is a constant-rate yaw rotation (rotation about the vertical axis). (2) The side translation requires an anti-symmetrical change in the stroke amplitudes of the contralateral wings, and/or an anti-symmetrical change in the angles of attack of the contralateral wings, with the down- and upstroke angles of attack of a wing having equal change. The constant-rate yaw rotation requires an anti-symmetrical change in the angles of attack of the contralateral wings, with the down- and upstroke angles of attack of a wing having differential change. (3) For the control of the horizontal side translation, control input required for the steady-state motion has an opposite sign to that needed for initiating the motion. For example, to have a steady-state left side-translation, the insect needs to increase the stroke amplitude of the left wing and decrease that of the right wing to maintain the steady-state flight, but it needs an opposite change in stroke amplitude (decreasing the stroke amplitude of the left wing and increasing that of the right wing) to enter the flight.