A H(subscript∞) Tracking-Based Adaptive Sliding-Mode Controller for Nonlinear Pneumatic Path Tracking Systems via a Functional Approximation Approach

Abstract

It's difficult for pneumatic actuator systems to fit into an accurate dynamic model for model-based sliding-mode control design because of the nonlinear and time-varying characteristics. The objective of this research is to develop a new H(subscript ∞) tracking-based adaptive sliding-mode controller for nonlinear pneumatic actuator systems. The controller initially uses a Fourier series-based functional approximation to reach an unknown function so as to circumvent the prerequisites of the models. The H(subscript ∞) tracking technique can then be incorporated into an adaptive sliding-mode control method to protect the derived controller from approximated errors, un-modeled dynamics and disturbances. Thus, system dynamic models are not necessary for achieving the proposed controller design with H(subscript ∞) tracking performance and trial-and-error is not required to select an approximation function. System stability is ensured through the new laws for the coefficients of the Fourier-series functions which are derived from a Lyapunov function. In addition, the serious chattering problem can be reduced through the projected H(subscript∞)tracking-based adaptive sliding-mode controller control method by means of the H(subscript∞) tracking controller in comparison with the Fourier series-based adaptive sliding-mode controller. Consequently, the practical experiments on a rodless pneumatic servo system are successfully implemented with different path tracking profiles, which validates the proposed method.