Robust internal model-based control of sampled-data systems: An adaptive sliding-mode approach

An adaptive discrete-time, internal model–based sliding mode control scheme is proposed for continuous-time linear time-invariant systems subject to disturbances assumed to be captured by an uncertain exosystem. Building upon a robust internal model-based control framework, an adaptive mechanism inspired by active disturbance rejection is introduced to estimate online the disturbance, eliminating the need for a priori knowledge of disturbance bounds. The proposed approach explicitly accounts for discretization effects inherent to digital implementations and ensures bounded tracking error under an output-feedback configuration. To this end, an observer is designed to reconstruct the required states and disturbance-related dynamics. Experimental results on a quarter-car suspension setup demonstrate improved disturbance rejection and robustness compared to internal model–based and adaptive sliding mode controllers.