Research On Fault Tolerant Control Of Complex Systems With Application To Near Space Vehicle

At present, with the rapid development and progress of the society, the scale of the complexcontrol system becomes biger and biger, the demands for the satety, reliability and maintainability ofthese complex control systems are increasing. In order to reduce the number of catastrophic accidents,reduce the environment pollution, reduce the losses of social economic assets and protect the lives ofthe people, the technology about fault diagnosis and fault tolerant control of comolex control systemsprovides an alternative road for solving the problems described above. In the past few decades, thetechnology about fault diagnosis and fault-tolerant control of the complex control system has madeconsiderable progress. Especially in the past ten years, along with the quickly development of thecomputer network, pattern recognition, machine learning and all kinds of advanced control algorithms,many new methods and technologies are introduced into the fields of fault diagnosis and fault tolerantcontrol, which greatly enrich the research contents of fault diagnosis and fault-tolerant controltechnology.Near Space Vehicle (NSV) is a class of hypersonic aircraft, which can acrosses "air""space" twodifferent regions for maneuver flying, it has attracted the research interesting of all developedcountries. The flight speed of this kind of complex aircraft is more than Mach5or higher. The flightregion of this aircraft is the20-100km from the sea level, according to the mission requirement, thiscomplex aircraft take vertical rocket-propelled launch or air level launch by the large transport aircraft,which mkes use of hydrocarbon or hydrogen as fuel and ultilizes air-breathing scramjet engine as thepropulsion for hypersonic flight, the complex aircraft can reach evrywhere of the world within2hours.For such kind of complex aircraft, the technology about fault diagnosis and fault tolerant control mustbe considered in the designing of the flight control systems in order to enhance the safety, reliabilityand maintainability of this kind of aircraft.Currently United States, Russia, France, United Kingdom, Japan and other aerospace powercountries have put a lot of manpower and material resources for developing the flight technology ofnear space hypersonic vehicle, they have achieved lots of research results, even some keytechnologies have entered the engineering verification phase, while, the research on near spacehypersonic vehicle in our country is in the initial stage. The related universities and institutes aredoing some key basic researches (such as materials, power, control, etc.), and they have achievedsome important results. Based on the existing research results, this study is further investigating the technology about fault tolerant control of near space vehicle control (including active fault tolerancecontrol and passive fault tolerance control). This research is divided into the following five sections:First: The longitudinal flight dynamical systems of near space hypersonic vehicle aretransformed into a linearized model at the equilibrium point by using the small perturbationlinearization technique. Meanwhile, this study takes into account the effects of the attack angleuncertainty and unknown disturbance input on the controlled systems, and makes use of the robustcontrol technique designing a robust passive fault tolerant cotroller for the the longitudinal flightdynamics of near space hypersonic vehicle in the presence of the partial loss fault of controleffectiveness. Then, the stability of the closed-loop control system is analysed using Lyapunovstability theory. Finally, simulation results are given to show the good fault tolerance ability of theproposed control approach.Second: For the complex nonlinear attitude control systems of near space vehicle, we selectangle of attack and angular velocity as the antecedent variables of fuzzy rules. Then the attitudecontrol system of near space vehicle is transformed into a Takagi–Sugeno (T-S) fuzzy model. For theestablished T-S fuzzy model, we consider the effects of unknown parameter perturbation, and design apassive fault tolerant fuzzy controller for the T-S fuzzy model of near space vehicle under someactuator failures case by using robust control technique. In the sense of Lyapunov stability, theclosed-loop control systems is proved to be robust asymptotic reliable. Finally, simulation results aregiven to verify the good dynamic characteristics of the proposed passive fault tolerant approach bydoing simulation comparison.Third: For the T-S fuzzy model of near space vehicle attitude control system, this study takes intoaccount the impact of external disturbance factors to the controlled system, and based on thegeneralized extended system approach, a novel fault estimation and compensation strategies isdeveloped for the attitude control systems of near space vehicle with sensor time varying fault. Finally,Matlab simulation results are given to illustrate the feasibility of the proposed sensor fault estimationand compensation technology.Fourth: For the T-S fuzzy model of near space vehicle attitude control system in some actuatorstuck faults case, this study design an iterative learning observer, which can be used for observeringthe dynamic change of the controlled system real-time. Once an actuator stuck fault occurs, the faultcompensation control input is produced on line by using the observer error signal, which can reducethe effect of the actuator stuct fault to the controlled system. Thus, the purpose of faultaccommodation is achieved. Finally, Matlab simulation results are given to illustrate the effectivenessand potential of the proposed control strategy. Fifth: For the nonlinear attitude control system of near space vehicle in re-entry flight phase, thisstudy assumes that the rotation movement of Earth and the translational motion of aircraft hardly affectthe rotational motion of aircraft. When an abrupt fault occurred in the dynamic equations of nearspace vehicle, this study design a nonlinear fault detection observer for monitoring the dynamic changeof the controlled systems. Then, an active fault tolerant control scheme is presented on the basis of thedouble-loop sliding mode control strategy for the faulty system. Finally, Matlab simulation resultsdomenstrate that the proposed active fault tolerant control approach has a satisfactory controlperformance in spite of actuator fault.