Use of adaptive fuzzy systems in parameter tuning of sliding-mode controllers

The paper proposes to combine adaptive fuzzy systems with sliding-mode control (SMC) to solve the chattering problem of SMC for robotic applications. In the design of the controller, special attention is paid to chattering elimination without a degradation of the tracking performance. Furthermore, the a priori knowledge required of the system dynamics for design is kept to a minimum. The paper first considers the basic principles of sliding-mode and fuzzy controllers. Implementation difficulties and most popular solutions are then overviewed. Next, the design of a SMC reported in the literature is outlined and guidelines for the selection of controller parameters for the best tracking performance without chattering are presented. A novel approach based on the introduction of a "chattering variable" is developed. This variable, as a measure of chattering, is used as an input to an adaptive fuzzy system responsible for the minimization. Online tuning of parameters by fuzzy rules is carried out for the SMC. The experimental results obtained are given, and conclusions are presented.