G. Monsees

Adaptive switching gain for a discrete-time sliding mode controller

Sliding mode control is a well-known technique capable of making the closed loop system robust with respect to certain kinds of parameter variations and unmodelled dynamics. The sliding mode control law consists of a continuous component which is based on the model knowledge and discontinuous component which is based on the model uncertainty. This paper extends two known adaption laws for the switching gain for continuous-time sliding mode controllers to the multiple input case. Because these adaption laws have some fundamental problems in discrete-time, we introduce a new adaption law specifically designed for discrete-time sliding mode controllers.

Nonminimum phase output tracking using sliding modes

This paper introduces a stable feedforward controller which gives approximate tracking for discrete time nonminimum phase linear systems by only using a bounded preview of the desired output signal. The methods presented in this paper are based on the method of Dichotomies, which is adapted to the bounded preview time. Special attention is given to marginally stable zeros, which were not permitted in previous publications. It is shown that the error due to the bounded preview time is bounded, and decreasing while increasing the preview time. The performance of the feedforward controller is then further increased by adding a sliding mode controller within the feedforward controller. A simulation example demonstrates the applicability of the proposed controllers.