State Feedback Fuzzy Adaptive Control for Active Shimmy Dampingg

In the context of aircraft, shimmy is an oscillatory phenomenon of the landing gear mainly due to the tire and the landing gear structural dynamics. This phenomenon which can result in severe damage to the landing gear must be damped. This paper presents a new nose landing gear model including an actuator model and a simple tire/road interface description approximating the Pacejka model to allow the active damping of the shimmy phenomenon. Two state feedback control solutions, based on indirect and direct fuzzy adaptive theories, are also presented and compared with a more classic Proportional Integral Derivative (PID) solution. Results corresponding to different test scenarios and robustness analysis show that the proposed controllers are able to efficiently damp the shimmy phenomenon, unlike the PID controller

CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999

The proceedings of a workshop sponsored by the Confederation of European Aerospace Societies (CEAS), the American Institute of Aeronautics and Astronautics (AIAA), the National Aeronautics and Space Administration (NASA), Washington, D.C., and the Institute for Computer Applications in Science and Engineering (ICASE), Hampton, Virginia, and held in Williamsburg, Virginia June 22-25, 1999 represent a collection of the latest advances in aeroelasticity and structural dynamics from the world community. Research in the areas of unsteady aerodynamics and aeroelasticity, structural modeling and optimization, active control and adaptive structures, landing dynamics, certification and qualification, and validation testing are highlighted in the collection of papers. The wide range of results will lead to advances in the prediction and control of the structural response of aircraft and spacecraft

Robust and Multi-Objective Model Predictive Control Design for Nonlinear Systems

The multi-objective trade-off paradigm has become a very valuable design tool in engineering problems that have conflicting objectives. Recently, many control designers have worked on the design methods which satisfy multiple design specifications called multi-objective control design. However,the main challenge posed for the MPC design lies in the high computation load preventing its application to the fast dynamic system control in real-time. To meet this challenge, this thesis has proposed several methods covering nonlinear system modeling, on-line MPC design and multi-objective optimization. First, the thesis has proposed a robust MPC to control the shimmy vibration of the landing gear with probabilistic uncertainty. Then, an on-line MPC method has been proposed for image-based visual servoing control of a 6 DOF Denso robot. Finally, a multi-objective MPC has been introduced to allow the designers consider multiple objectives in MPC design. In this thesis, Tensor Product (TP) model transformation as a powerful tool in the modeling of the complex nonlinear systems is used to find the linear parameter-varying (LPV) models of the nonlinear systems. Higher-order singular value decomposition (HOSVD) technique is used to obtain a minimal order of the model tensor. Furthermore, to design a robust MPC for nonlinear systems in the presence of uncertainties which degrades the system performance and can lead to instability, we consider the parameters of the nonlinear systems with probabilistic uncertainties in the modeling using TP transformation. In this thesis, a computationally efficient methods for MPC design of image-based visual servoing, i.e. a fast dynamic system has been proposed. The controller is designed considering the robotic visual servoing system's input and output constraints, such as robot physical limitations and visibility constraints. The main contributions of this thesis are: (i) design MPC for nonlinear systems with probabilistic uncertainties that guarantees robust stability and performance of the systems; (ii) develop a real-time MPC method for a fast dynamical system; (iii) to propose a new multi-objective MPC for nonlinear systems using game theory. A diverse range of systems with nonlinearities and uncertainties including landing gear system, 6 DOF Denso robot are studied in this thesis. The simulation and real-time experimental results are presented and discussed in this thesis to verify the effectiveness of the proposed methods

Robust Semi-active Control of Aircraft Landing Gear System Equipped with Magnetorheological Dampers

Landing is the most critical operational phase of an aircraft since it directly affects the passenger safety and comfort. The factors such as the undesirable wind and ground effects, runway unevenness, excessive sink speeds and approach speeds and pilot errors can deteriorate the landing performance of an aircraft several times during its entire lifetime. When an aircraft lands, large amplitude vibrations get transmitted to the fuselage from the runway thereby causing safety and comfort problems and hence need to be suppressed quickly. Landing gear is an essential assembly that prevents the aircraft fuselage from the ground loads. A shock absorber which is considered as the heart of the landing gear assembly plays an important role in this process by absorbing the vibrations during landing. The existing Oleo-pneumatic shock absorbers are the most efficient in absorbing the vibrations during each aircraft operation. However, they are unable to provide the continuously variable damping required during the landing phase which might reduce their efficiency. Moreover, to account for the uncertainties during landing, a damper capable of providing the variable damping effect can play a vital role in increasing the passenger safety. A semi-active control system of a landing gear suspension can solve the problem of excessive vibrations effectively by providing a variable damping during each operational phase. Magnetorheological (MR) dampers are one of the most efficient and attractive solutions that can provide the continuously variable damping required depending on a control command. This thesis focuses on the concept of the semi-active aircraft suspension system using the MR damper with the implementation of robust control strategy. Initially, the dynamic behavior of the MR damper is studied using the parametric modeling approach. Spencer dynamic model is adopted for simulating the dynamic behavior of the MR damper. This is followed by the analysis of the energy dissipation patterns of the MR damper for different excitation inputs. A semi-active suspension system is developed for a three degree-of-freedom (3 DOF) aircraft model considering a tri-cycle landing gear configuration. A switching technique is developed in the simulation of the landing procedure which enables the system to switch from the single degree of freedom to three degrees of freedom system in order to simulate the sequential touching of the two wheels of the main landing gears and the nose landing gear wheel with the ground. For developing the semi-active MR suspension system, two different controller approaches, namely, the Linear Quadratic Regulator (LQR) and the H∞ control are adopted. The results of the designed controllers are compared for a particular landing scenario for studying the performance of the controllers in reducing the overshoot of the bounce response as well as the bounce rate response. The simulation results confirmed the improved performance of the robust controller compared to the optimal control strategy when the aircraft is subjected to the disturbances during landing. Finally, implementing the robust control approach, the landing performance of an aircraft embedded with the semi-active suspension system is simulated and analyzed for different sink velocities considering the disturbances

Aeronautical engineering: A continuing bibliography with indexes (supplement 323)

This bibliography lists 518 reports, articles, and other documents introduced into the NASA scientific and technical information system in November 1995. 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

Estratégias de controle de trajetórias para cadeira de rodas robotizadas

Orientador: Eleri CardozoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Desde os anos 80, diversos trabalhos foram publicados com o objetivo de propor soluções alternativas para usuários de cadeira de rodas motorizadas com severa deficiência motora e que não possuam capacidade de operar um joystick mecânico. Dentre essas soluções estão interfaces assistivas que auxiliam no comando da cadeira de rodas através de diversos mecanismos como expressões faciais, interfaces cérebro-computador, e rastreamento de olho. Além disso, as cadeiras de rodas ganharam certa autonomia para realizar determinadas tarefas que vão de desviar de obstáculos, abrir portas e até planejar e executar rotas. Para que estas tarefas possam ser executadas, é necessário que as cadeiras de rodas tenham estruturas não convencionais, habilidade de sensoriamento do ambiente e estratégias de controle de locomoção. O objetivo principal é disponibilizar uma cadeira de rodas que ofereça conforto ao usuário e que possua um condução segura não importando o tipo de deficiência do usuário. Entretanto, durante a condução da cadeira de rodas, o desalinhamento das rodas castores podem oferecer certo perigo ao usuário, uma vez que, dependendo da maneira em que elas estejam orientadas, instabilidades podem ocorrer, culminando em acidentes. Da mesma forma, o desalinhamento das rodas castores é considerado um dos principais causadores de desvios de trajetória que ocorrem durante a movimentação da cadeira de rodas, juntamente com diferentes distribuições de pesos ou diferentes atritos entre as rodas e o chão. Nesta dissertação, é considerado apenas o desalinhamento das rodas castores como único causador de desvio de trajetória da cadeira de rodas e, dessa forma, são propostas soluções que possam reduzir ou até mesmo eliminar o efeito deste desalinhamento. Com a implementação das melhores soluções desenvolvidas neste trabalho, é possível fazer com que diversas interfaces assistivas que têm baixa taxa de comandos possam ser utilizadas, uma vez que o usuário não precisa, constantemente, corrigir o desvio da trajetória desejada. Ademais, é elaborado um novo projeto de cadeira de rodas "inteligente" para a implementação das técnicas desenvolvidas neste trabalhoAbstract: Since the 1980s several works were published proposing alternative solutions for users of powered wheelchairs with severe mobility impairments and that are not able to operate a mechanical joystick. Such solutions commonly focus on assistive interfaces that help commanding the wheelchair through distinct mechanisms such as facial expressions, brain-computer interfaces, and eye tracking. Besides that, the wheelchairs have achieved a certain level of autonomy to accomplish determined tasks such as obstacle avoidance, doors opening and even path planning and execution. For these tasks to be performed, it is necessary the wheelchairs to have a non conventional designs, ability to sense the environment and locomotion control strategies. The ultimate objective is to offer a comfortable and safe conduction no matter the user's mobility impairments. However, while driving the wheelchair, the caster wheels' misalignment might offer risks to the user, because, depending on the way they are initially oriented, instabilities may occur causing accidents. Similarly, the caster wheels' misalignment can be considered, among others like different weight distribution or different friction between wheel and floor, one of the main causes of path deviation from the intended trajectory while the wheelchair is moving. In this dissertation, it is considered the caster wheels' misalignment as the unique generator of wheelchair path deviation and, therefore, it is proposed different solutions in order to reduce or even eliminate the effects of the misalignment. The implementation of the best solutions developed in this work allows assistive interfaces with low rate of commands to be widespread, once the user does not need to, constantly, correct path deviation. Additionally, a new smart wheelchair project is elaborated for the implementation of the techniques developed in this workMestradoEngenharia de ComputaçãoMestre em Engenharia Elétrica88882.329382/2019-01CAPE

New dynamic modeling and pratical control design for MacPherson suspension system

The ride quality, handling, and stability are three main issues in vehicle suspension design. Different suspension systems have been designed in the past to fulfil these conflicting requirements. One of the popular suspension systems integrated in small and midsize passenger cars is MacPherson suspension system. A suspension system is either passive if a conventional damper is incorporated or is semi-active with a variable damper. A new control oriented dynamic model of the MacPherson suspension system is developed in this thesis to consider the effects of the suspension structure on the dynamic response and a new kinematic model is proposed to investigate those suspension kinematic parameters affecting both handling performance and stability of the vehicle. The performance of MacPherson suspension system under alternative hybrid semi-active controls is evaluated. It is shown that the contribution of different control strategies on the ride quality enhancement of the vehicle could be similar whereas their effectiveness on the performance of suspension kinematc parameters is completely different. Using the H {592} robust control theory, a full state feedback controller is designed to improve MacPherson suspension specifications. The gain of the controller is optimized so that the trade-off between the requirements is achieved. To be more practical and to reduce the design cost, H, output feedback control theory is employed to design a controller with the minimal cost design. To optimize the controller gain, the LMI and Genetic Algorithm optimization tools are used. It is shown that the output controller can improve the suspension performance close to that of a full state feedback controller. A magnetorheological damper with continuously variable damping is considered as the actuator to the system. In order to tune the current signal of the damper so as to track the desired force calculated from the controller unit, a mathematical dynamic model of the damper is required. For modelling the damper, the MR damper is characterized by a piece-wise polynomial model which is identified by using the data acquired from various tests in the laboratory. The dynamic behaviour of the MR damper on control performance is investigated. The Hardware-in-the-Loop Simulation is made and the effectiveness of the controllers is evaluated through experiments

Aeronautical Engineering. A continuing bibliography with indexes, supplement 142

This bibliography lists 398 reports, articles, and other documents introduced into the NASA scientific and technical information system in November 1981