Research On Decentralized Adaptive Fuzzy Control Algorithms Of Uncertain Large-scale Nonlinear Systems And Their Applications

The last three decades have witnessed a great deal of progress in terms of control design for nonlinear systems. Owing to uncertainty as well as nonlinearity of actual systems in the natural world, more and more substance is being attached to research into nonlinear control, especially to study on adaptive intelligent control and they have resided with international hot spots recently. Moreover, partly through physical inability for subsystem information exchange sometime and partly through lack of enough computing capacities for some single central controllers, decentralized control techniques may be given priority for these complicated situations.By systematically combining Lyapunov function design, feedback linearization, decentralized control and fuzzy control techniques etc., an attempt was made in this dissertation not only to forward deep development of control science but also to provide better approaches to practical engineering problems, up to a certain point. The main contributions of the thesis are characterized by the following novel features:(1) two novel observer-based decentralized indirect adaptive fuzzy control (IAFC) schemes were proposed for SISO affine nonlinear large-scale systems such that the interconnected IAFC systems are guaranteed to be asymptotically stable, one of which is obtained predicated upon both H_∞tracking technique and a fuzzy adaptive observer and the other of which upon both robust control technique, fuzzy systems and a linear state observer;(2) two novel observer-based decentralized direct adaptive fuzzy control (DAFC) architectures were put forward for SISO nonaffine nonlinear large-scale systems such that the tracking error of the interconnected DAFC system was ensured to converge to zero or to a small neighborhood of the origin, one of which obtained grounded in a fuzzy system, H_∞tracking technique and a linear error observer and the other of which in a fuzzy system, singular perturbation technique and a high gain observer;(3) three novel decentralized hybrid adaptive fuzzy control (HAFC) approaches were propounded by adopting a weighting factor to total up the control efforts from both IAFC and DAFC for different classes of SISO large-scale nonlinear systems with a view to incorporating plant knowledge and control knowledge at the same time, where the first utilizes full state feedback such that the HAFC system takes on asymptotically stable complexion, the second takes output feedback such that the tracking error of the HAFC system can be convergent to a tunable residuary set of the origin, and the third is a cooperation-based decentralized output feedback control design such that arbitrarily strong mismatching interconnections were accommodated in particular, the tracking error of the controlled plant remaining an adjustable neighborhood of the origin;(4) both a novel decentralized indirect adaptive state feedback fuzzy controller and a novel decentralized hybrid adaptive output feedback fuzzy controller were developed for a class of MIMO large-scale nonlinear systems, and both their controller singularity problems were solved under the respective untied design frameworks of the proposed controllers using a regular reverse matrix, the closed-loop MIMO systems being shown to be asymptotically stable;(5) more successful applications of the proposed adaptive fuzzy control algorithms to several important engineering problems were intensively studied in point of decentralized feedback. The problems include, but weren't limited to: longitudinally decentralized robust output feedback control of following vehicles in automated high systems, temperature decentralized output feedback H_∞control in continuously stirred tank reactors, and decentralized output feedback control of both robotic manipulators and two- legged robots.Detailed contrasts between the proposed control algorithms and existing ones involved were made to show the decentralized adaptive fuzzy controllers to possess many advantages such as stronger practicality, better performance, more reasonable design etc. over the others. On the other hand, all of the developed controllers were proved to be valid through numerical simulations such that they are able to successfully get through with the predetermined control tasks. Besides, simulation results of the H_∞tracking-based decentralized indirect and direct adaptive fuzzy controllers still showed that the smaller the prescribed attenuation levels are, the better the tracking performance of the closed-loop systems becomes but the larger the control input are required to be, whereas those of the decentralized HAFC algorithms further showed that the HAFC systems can display better performance than the IAFC and DAFC systems, i.e. the tracking errors and control efforts can made smaller.