Multicriteria Gain Tuning for Rotorcraft Flight Controls (also entitled The Development of the Conduit Advanced Control System Design and Evaluation Interface with a Case Study Application Fly by Wire Helicopter Design)

Handling qualities analysis and control law design would seem to be naturally complimenting components of aircraft flight control system design, however these two closely coupled disciplines are often not well integrated in practice. Handling qualities engineers and control system engineers may work in separate groups within an aircraft company. Flight control system engineers and handling quality specialists may come from different backgrounds and schooling and are often not aware of the other group's research. Thus while the handling qualities specifications represent desired aircraft response characteristics, these are rarely incorporated directly in the control system design process. Instead modem control system design techniques are based on servo-loop robustness specifications, and simple representations of the desired control response. Comprehensive handling qualities analysis is often left until the end of the design cycle and performed as a check of the completed design for satisfactory performance. This can lead to costly redesign or less than satisfactory aircraft handling qualities when the flight testing phase is reached. The desire to integrate the fields of handling qualities and flight,control systems led to the development of the CONDUIT system. This tool facilitates control system designs that achieve desired handling quality requirements and servo-loop specifications in a single design process. With CONDUIT, the control system engineer is now able to directly design and control systems to meet the complete handling specifications. CONDUIT allows the designer to retain a preferred control law structure, but then tunes the system parameters to meet the handling quality requirements

Integration of MATLAB Simulink(Registered Trademark) Models with the Vertical Motion Simulator

This paper describes the integration of MATLAB Simulink(Registered TradeMark) models into the Vertical Motion Simulator (VMS) at NASA Ames Research Center. The VMS is a high-fidelity, large motion flight simulator that is capable of simulating a variety of aerospace vehicles. Integrating MATLAB Simulink models into the VMS needed to retain the development flexibility of the MATLAB environment and allow rapid deployment of model changes. The process developed at the VMS was used successfully in a number of recent simulation experiments. This accomplishment demonstrated that the model integrity was preserved, while working within the hard real-time run environment of the VMS architecture, and maintaining the unique flexibility of the VMS to meet diverse research requirements

Design of fault tolerant control system for individual blade control helicopters

This dissertation presents the development of a fault tolerant control scheme for helicopters fitted with individually controlled blades. This novel approach attempts to improve fault tolerant capabilities of helicopter control system by increasing control redundancy using additional actuators for individual blade input and software re-mixing to obtain nominal or close to nominal conditions under failure. An advanced interactive simulation environment has been developed including modeling of sensor failure, swashplate actuator failure, individual blade actuator failure, and blade delamination to support the design, testing, and evaluation of the control laws. This simulation environment is based on the blade element theory for the calculation of forces and moments generated by the main rotor. This discretized model allows for individual blade analysis, which in turn allows measuring the consequences of a stuck blade, or loss of the surface area of the blade itself, with respect to the dynamics of the whole helicopter. The control laws are based on non-linear dynamic inversion and artificial neural network augmentation, which is a mix of linear and nonlinear methods that compensates for model inaccuracies due to linearization or failure. A stability analysis based on the Lyapunov function approach has shown that bounded tracking error is guaranteed, and under specific circumstances, global stability is guaranteed as well. An analysis over the degrees of freedom of the mechanical system and its impact over the helicopter handling qualities is also performed to measure the degree of redundancy achieved with the addition of individual blade actuators as compared to a classic swashplate helicopter configuration. Mathematical analysis and numerical simulation, using reconfiguration of the individual blade control under failure have shown that this control architecture can potentially improve the survivability of the aircraft and reduce pilot workload under failure conditions

V/STOL AND digital avionics system for UH-1H

A hardware and software system for the Bell UH-1H helicopter was developed that provides sophisticated navigation, guidance, control, display, and data acquisition capabilities for performing terminal area navigation, guidance and control research. Two Sperry 1819B general purpose digital computers were used. One contains the development software that performs all the specified system flight computations. The second computer is available to NASA for experimental programs that run simultaneously with the other computer programs and which may, at the push of a button, replace selected computer computations. Other features that provide research flexibility include keyboard selectable gains and parameters and software generated alphanumeric and CRT displays

A spiral guidance approach concept for commercial VTOL operations

The results of an investigation of the guidance and navigation requirements for VTOL spiral descents in the presence of winds are reported. Models were developed to describe the spiral maneuver and candidate guidance laws were formulated and analyzed. An important element of the guidance scheme is a unique wind estimator which uses the perturbations in bank angle and heading to improve the knowledge of the winds. Finally, recommendations for additional research, including a flight program, were outlined to evaluate the spiral guidance concept

Helicopter Handling Qualities

Helicopters are used by the military and civilian communities for a variety of tasks and must be capable of operating in poor weather conditions and at night. Accompanying extended helicopter operations is a significant increase in pilot workload and a need for better handling qualities. An overview of the status and problems in the development and specification of helicopter handling-qualities criteria is presented. Topics for future research efforts by government and industry are highlighted

Spécification de lois de commande pour hélicoptères orientée Qualités de Vol

However, following this previous study, initializing efficiently the procedure appears to be fundamentally important for the speed of the tuning process. Then, a methodology to initialize the gains is developed, through the creation and the efficient usage of new Flying Qualities-based charts for equivalent simplified models. Thanks to these charts, we can quickly get a set of tunings in accordance with Flying Qualities requirements.These charts offer a wide variety of sets in the space of proper tunings, but these tunings are not necessarily satisfactory, at least from energetic and uncoupling points of view. In order to improve the efficiency of the initial tuning, two additional constraints are taken into account. Thus, an uncoupling criterion and an energetic criterion are developed. Then, the methodology to generate and use the charts is improved by including these two new constraints.Thanks to a fast evaluation, we can see that the usage of the chart is not enough to obtain a final satisfying tuning. Thus, a complete full procedure of tuning is proposed. It is a direct procedure with three main steps : initialization, linear adjustment and non linear adjustment. Each step is evaluated and validated. The full procedure is evaluated and validated as well. A full study is led and highlights the value of using such a methodology. As a demonstration, the final gains obtained are implemented on a simulator.This thesis has permitted the development of the first full and direct procedure of tuning of helicopters control laws taking into account Flying Qualities, energetic and uncoupling criteria. Besides the remar- kable time gained for the tuning process, significant improvements in Handling Qualities can be noticed during piloted simulations with the gains integrating requirements from ADS-33. Among the possible perspectives, it should be interesting to : keep developing EagHEL, extend the charts to others control laws, and lead evaluations with test pilots on a simulator.Ces travaux s'inscrivent dans le domaine de l'étude des lois de commandes de vol pour hélicoptères, telles qu'elles sont implémentées sur les engins actuels. Les automaticiens doivent régler les gains de ces lois de manière à respecter au mieux les exigences de Qualités de Pilotage extraites des normes ADS-33 (Aeronautical Design Standards). La norme traduit ces exigences en termes de critères de Qualités de Vol, utilisés dans ce cadre. Ces critères permettent d'évaluer la qualité de la stabilité de la machine, la qualité de l'agilité de la machine, et la qualité du suivi des consignes du pilote par la machine. Ces trois critères traduisent la pilotabilité de l’hélicoptère pour un pilote moyen de référence. Mise à part une technique d’optimisation interactive développée à la NASA depuis 40 ans, il n'existe pas de méthode appropriée à ce problème. Les réglages sont donc effectués de manière empirique et itérative. L'ONERA aborde cette question via une approche méthodologique structurée. L'objectif de la thèse consiste à développer cette méthodologie de manière à gérer deux contraintes supplémentaires par rapport aux capacités des méthodes de synthèse classiques en automatique. La première est la capacité à prendre en compte la structure contrainte des lois de commande. La seconde concerne les exigences spécifiques en terme de Qualités de Vol selon la norme ADS-33. La première méthode développée consiste en une technique d'amélioration des Qualités de Vol par analyse de sensibilités entre les gains et les critères. Pour cela, un outil d'aide au réglage des lois de commande pour hélicoptères prenant en compte des critères de Qualités de Vol est développé : EagHEL (Environment for designing and AdjustinG HelicoptEr flight control Laws). Grâce à lui, l'étude de sensibilités est facilitée. Le bilan qui s'ensuit permet d'établir des guides de réglage. Ces guides sont ensuite utilisés pour améliorer les Qualités de Vol. Cette première technique apporte une aide remarquable à l'amélioration locale des Qualités de Vol lors des réglages menés. Suite à cette étude, il apparait cependant que l'initialisation du réglage revêt une importance fondamentale quant à la rapidité du réglage. Ainsi, une méthodologie d'initialisation des gains est proposée, via la création et l'utilisation efficace de nouveaux abaques de Qualités de Vol pour modèles équivalents simplifiés. Ces abaques permettent d'obtenir rapidement un ensemble de réglages respectant un ensemble de contraintes de Qualités de Vol. Cependant, l'abaque offre un choix large dans le champ de réglages adéquats, sans pour autant obtenir systématiquement des résultats satisfaisants par la suite, d'un point de vue énergétique et découplage notamment. Afin d'améliorer l'efficacité de ce réglage initial, deux contraintes supplémentaires sont prises en compte. Un critère de découplage et un critère énergétique sont ainsi développés. Puis la méthodologie de génération et d'utilisation des abaques est améliorée en intégrant ces deux nouvelles contraintes. Une rapide évaluation permet de constater que l'utilisation de l'abaque seule ne permet pas d'obtenir un réglage final satisfaisant. Un processus complet de réglage est donc proposé. C'est un processus direct possédant trois étapes principales : initialisation, ajustement linéaire et ajustement non linéaire. Chaque étape est évaluée puis validée. Le processus complet est également évalué et validé. Une étude complète est menée et met en évidence l'intérêt de recourir à une telle méthodologie. A titre de démonstration les réglages obtenus sont implémentés sur simulateur. Cette thèse a permis le développement du premier processus complet et direct de réglage des gains de lois de commande de vol pour hélicoptères intégrant des critères de types Qualités de Vol, énergétique et découplage. Outre le gain remarquable en temps de réglage, une amélioration notable des qualités de vol est remarquée en simulation pilotée avec les gains intégrant des contraintes issues des normes ADS33. Parmi les perspectives envisageables, on peut citer : continuer le développement de EagHEL, étendre les abaques à d’autres lois de pilotage, évaluer l'intérêt des réglages par des pilotes d'essais sur simulateur

Navigation and guidance requirements for commercial VTOL operations

The NASA Langley Research Center (LaRC) has undertaken a research program to develop the navigation, guidance, control, and flight management technology base needed by Government and industry in establishing systems design concepts and operating procedures for VTOL short-haul transportation systems in the 1980s time period. The VALT (VTOL Automatic Landing Technology) Program encompasses the investigation of operating systems and piloting techniques associated with VTOL operations under all-weather conditions from downtown vertiports; the definition of terminal air traffic and airspace requirements; and the development of avionics including navigation, guidance, controls, and displays for automated takeoff, cruise, and landing operations. The program includes requirements analyses, design studies, systems development, ground simulation, and flight validation efforts

Aeronautical Engineering, a continuing bibliography with indexes, supplement 173

This bibliography lists 704 reports, articles and other documents introduced into the NASA scientific and technical information system in March 1984

Aeronautical engineering: A continuing bibliography with indexes (supplement 286)

This bibliography lists 845 reports, articles, and other documents introduced into the NASA scientific and technical information system in Dec. 1992. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics