Research On Sliding Mode Fault-Tolerant Control Algorithm For Delta-Operator Time-Delay Systems

The modern control systems are developing scaling, complicating and networking, and the integration of the system is more and more high, so the systems are more and more prone to fault, which requires reasonable fault-tolerant control method in the control system design. Besides, due to the problem of signal transmission distance or network delay, the time delay is often occurred in the modern control systems, which will lead to the corresponding performance decline and even systems unstability. On the other hand, with the rapid development of digital control technology, it is urgent to adopt a more suitable method of discrete control under high speed sampling. As a new discretization method, Delta operator can solve all kinds of problems of the traditional shift operator method in the high speed sampling. Therefore, it is of great practical signif icance to study the fault-tolerant control of Delta-operator time-delay systems. In this paper, the wireless control system of quad-rotor is used as the theory background, based on the sliding mode control technique, the fault-tolerant control problem of a class of Delta-operator time-delay system is analyzed and studied. The main works and innovations of this paper are as follows:First, the paper research background, purpose and significance is introduced, the research on time-delay systems, the development process of Delta operator and the development of related control technology, sliding mode control and fault tolerant control, are reviewed in detail. This paper introduces the structure and working principle of quad-rotor half-physical simulation platform, establishes the mathematical model of the system, and designs and develops a set of fault tolerance testing software system based on the platform.Secondly, a fault-tolerant control method based on adaptive sliding mode control is proposed for a class of Delta-operator constant time-delay system with actuator failure. Reduced order model of the system is obtained by the linear transformation method, then a linear sliding surface is designed, and the sufficient conditions of sliding surface is given by linear matrix inequalities(LMIs), combined with adaptive control theory, an adaptive sliding mode control law is established, making th e time-delay systems stable when fault occurs.Third, for the Delta-operator time-delay fault systems, the parameter uncertainty and states non-measurable problems in the systems are considered, and an output feedback sliding mode control strategy based on reaching law is presented. In the design of the sliding surface, output feedback is introduced and the system uncertainty is considered. In the control law design, a new adaptive reaching law is adopted, which can not only improve the sliding mode reaching speed and reduce the chattering, but also enhance the robustness of the algorithm.Fourth, for the Delta-operator time-delay fault systems, system parameter uncertainties, external disturbances and time-varying delays are taken into account, then a sliding mode control strategy based on nonlinear sliding surface is proposed. In the sliding surface design, the nonlinear term is added, which can change the characteristic of the sliding mode and improve the dynamic quality of the systems. A nonlinear sliding mode control law is designed by using the adaptive method to estimate the unknown actuator faults, and the system is able to maintain stability under the condition of fault and disturbance.Finally, the above methods are applied to the quad-rotor half-physical simulation platform. The simulation results are given and the control effect of the proposed methods is analyzed and illustrated.