Fault Tolerant Control System Research Using Sliding Mode Control Approach

Our main research interest is in the area of’sliding modes’. The earliest work in this field of research considered sliding modes in the context of control. The approach involves forcing the closed-loop system trajectories to evolve along a surface in the state-space by means of a nonlinear control strategy. The closed-loop system performance is specified by appropriate surface selection, and robustness is ensured via a control law which forces the states to remain on the surface. Theoretically sliding mode controllers are able to completely reject the effect of a class of uncertainties-known as matched uncertainties. This unique robustness property has stimulated research in this area for over two decades.Our main goal is to seek for method to handle the issues mentioned in the literature and add new contributions with sliding mode combined to other techniques to make any lack of efficiency avoidable, and apply to systems in connected to other component in classical way or over network.This dissertation presents, networked control system based fault tolerant control system, firstly aims to show the fault tolerant control system method over ignored possible network i.e. working with a structure without going into network’s issue, and then gives the control system in the presence of the network influenced by time delay, packed dropout, traffic disturbance. The dissertation also conducts new combination techniques dealing with fault tolerant control system starting by system identification, using RBF-ARX model combined to sliding mode control, where it’s sliding surface design, lie to Eigenvalues assignmentand shows its independence from control law. The advantage of the RBF-ARX model, is its joy of an off-line nonlinear model parameter optimization, using LMM (Levenberg-Marquardt method), and a linear parameter estimation using LSM (Least Squares method) with SVD (Singular value decomposition). The example used for the application of this approach is an electro-hydraulic system with leakage issue where the measurement could not be accurate. This system uses the interface which could implement many of the AMESim facilities while the model is running in the Simulink of Matlab. In particular, the parameters of the AMESim model could be changed within AMESim in the normal way, actually the model in AMESIM, somehow is transformed into S-function. Normally AMESim and Simulink run simultaneously. In other part of this dissertation, a new approach is given, which consists on decoupling fashion sliding mode control, dealing with subsystems instead of whole system. This approach presents a strategy based on the selection of piecewise sliding surface partition, and we apply the PwLTool which has as purpose to delimit regions where sliding mode occurs, then we may linearize the complex system into a simple linearized model in the delimited regions. An attempt to apply this strategy to the3water tank level system as example is given. The novelty of our approach is the design of sliding surface in piecewise style.The dissertation carries out also a comprehensive comparison to an input-output linearization and sliding mode control using an inverted pendulum system as an example with linear quadratic regulation, attempting to capture the general intent of SMC, where there is still a great deal to be done in SMC.A classical way to control a system is to compute a linear controller using the first order approximation of the system dynamics around the origin which gives a local linear approximation of the system.The feedback linearization approach to non-linear control design is an algebraic transformation of non-linear system dynamics into a fully or partially linear one, so that linear control techniques can be applied.The method to calculate the input-output feedback of a system uses some mathematical tools to mention here, lie-derivative, lie-bracket and involutive condition, this example shows that both the LQR and the SMC were able to control the inverted pendulum in a robust fashion. The SMC had better disturbance (or any other abrupt anomalies) rejection qualities than the LQR.A typical control system contains an industrial controller, controlled process and some kind input/output channel, usually in a communication network, where its behavior usually, can be simulated with state flow models, Petri nets, or in a custom made schemes in a MatlabSimEvents toolbox.In this dissertation, we use True-Time toolbox (for Matlab) as a simple and easy way to realize several network types and it is written in C++MEX language, to investigate how the performance of a control loop could be influenced by a delay, and implement the approximated feedback linearization sliding mode controller and how far it performance could stand in the presence of multi-issues, like presence of fault, disturbance, network induced delay, traffic interference disturbance which provoke certainly a random time delay. It showed also that the scheduling run tasks changes with the change in the additional delay or traffic disturbance.Further more we have carried out a serious comparaison with recent researches in the same field, and we find out that the sliding mode controller with approximate feedback linearization implemented seems coping positively with the issues mentioned above to certain limit but so far acceptable.