Researches On Robust Fault Detection And Fault Tolerant Control Of Time-delay Systems

In practical engineering applications, due to the continuous expending scale of control system, increasing complexity and the huge investment, the system reliabil-ity and security should be improved urgently. However, in the event of faults on actuators, sensors, or other system components, the desired performance of closed-loop control system can not be ensured, and even instable. The technology of fault diagnosis and fault tolerant control is an effective method to solve this problem. In order to improve the performance of fault detection filters and fault tolerant controllers, in this thesis, by utilizing the parameter-dependent Lyapunov function and LMI technique, we systematically and further study the problems of robust H? performance analysis, state-feedback controller and filter synthesis design, and fault tolerant control for time-delay systems (networked control systems). A system-atically new fault detection and fault tolerant control methodologies is presented. Parts of our developed theories are applied to the fault detection niters and fault tolerant controllers designs of computer-simulated truck-trailer system and unsta-ble batch reactor model by simulations. The results obtained in this thesis have less conservatism and computational complexity, because the delay decomposition approach, reciprocally convex technique and input-output method were applied in the treatment process of the delay. The main research can be briefly described as follows:1. The fault detection problem for discrete-time fuzzy networked systems with time-varying delay and multiple packet losses is investigated.The communica-tion links between the plant and the FFDF are assumed to be imperfect, and the missing probability is governed by an individual random variable satisfying a certain probabilistic distribution over the interval [01]. The discrete-time fuzzy networked system is first transformed into the form of interconnection of two subsystems by applying an input-output method and a two-term approx-imation approach, which is employed to approximate the time-varying delay. Our attention is focused on the design of FFDF such that, for all data miss-ing conditions, the overall fault detection dynamics are input-output stable in mean square and a guaranteed performance is ensured. Sufficient condi-tions are first established via H? performance analysis for the existence of the desired FFDF, meanwhile, the corresponding solvability conditions for the desired FFDF gains are characterized in terms of the feasibility of a convex optimization problem.2. The fault detection problem for NCSs with discrete and infinite distributed delays subject to random packet losses and nonlinear perturbation is studied. Different from existing results for FD, the proposed ones are toward closed-loop design problem, that is, the controller gain, and the FDF gains are designed simultaneously. Both sensor-to-controller and controller-to-actuator packet losses are modeled as two different mutually independent Bernoulli distributed white sequences with known conditional probability distributions. By utilizing an observer-based FDF as a residual generator, the FD for networked nonlinear systems with mixed delays and packet losses is formulated as an H? model-matching problem. Attention is focused on designing the FDF in the closed-loop system setup such that the estimation error between the residuals and filtered faults is made as small as possible, and at the same time, the closed-loop networked nonlinear system is exponentially stable in the mean-square sense.3. The fault tolerant, fuzzy control for a class of NNCSs with state delay and ac-tuator failures is studied. By utilizing the input delay approach, an equivalent continuous-time generalized T-S fuzzy model with both interval time-varying network-induced delay and data packet dropout is obtained. By employing the delay decomposition approach, the information of the delayed plant states can be taken into full consideration. The sufficient condition is formulated in the form of a nonconvex matrix inequality, of which a feasible solution can be obtained by solving a minimization problem in terms of LMI with cone complementarity linearization algorithm. The key features of the approach include the use of a tighter bounding technique (reciprocally convex combi-nation lemma) and the introduction of uncorrelated augmented matrix items into the Lyapunov functional, by which the less conservative condition is get.4. The robust fault tolerant controller design approach is provided for NCSs with state delay and stochastic actuator failures. By utilizing the input delay ap-proach, an equivalent, continuous-time generalized time delay system with both state and input is obtained. New delay-dependent sufficient conditions that ensure the asymptotic mean-square stability of NCSs with stochastic actua- tor failures are derived in terms of LMIs. It is realized by employing a new Lyapunov-Krasovskii function in the decomposed integral intervals and the in-versely weighted convex combination of quadratic terms of integral quantities is handled directly by reciprocally convex combination technique. Moreover, the proposed approach involves neither slack variable nor any model transfor-mation. 5. The reliable H? control is investigated for discrete-time Takagi-Sugeno (T-S) fuzzy systems with time-varying delay and actuator faults based on input-output approach when the state is available and unavailable respectively. A discrete-time homogeneous Markov chain is used to represent the stochastic behavior of actuator faults. The discrete-time T-S fuzzy system is transformed into the form of interconnection of two subsystems by employing a new model transformation for the delayed state variables. Input-output approach (Scaled Small Gain (SSG) Theorem) is developed to analyze the stochastic stability. By using a parameter dependent Lyapunov function, sufficient conditions for the input-output mean square stability and existence of the H? performance are established. Meanwhile, the reliable H? fuzzy controller design method is also presented.Finally, concluding remarks are given. Some unsolved problems and develop-ment direction for the robust fault detection and fault tolerant control of time-delay systems (NCSs) are proposed. Furthermore, the prospects of the further study are given.