This paper is mainly concerned with the design of a hybrid robust output tracker for a class of systems with a direct feed-through term and bounded matched nonlinear disturbances. First, we present a continuous-time linear quadratic analog tracker (LQAT) based on sliding mode control (SMC), and the existence of sliding manifold is guaranteed with the proposed controller in the continuous-time domain. After designing the continuous-time SMC-based tracker, a digital redesign approach using Euler's approximation method is newly proposed to directly obtain a discrete-time SMC-based tracker from the continuous-time SMC-based tracker, and the hitting condition is also satisfied such that the existence of sliding manifold is guaranteed in the hybrid controlled systems. Therefore, the output tracking performance with the proposed discrete-time SMC-based tracker can be also satisfied as the continuous-time SMC-based tracker. Illustrative examples are given to demonstrate the success of the proposed digital-redesign-based SMC algorithm.
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