A Hybrid Sliding Mode Strategy for Minimum-Phase Systems with Output Constraints

A new setpoint control scheme is proposed for single-input systems, where a regulated output must be transferred between two setpoints, with the additional requirement that a set of limited outputs remain within prescribed bounds. The strategy is based on a max-min selector system frequently used in the process control and aerospace fields. The regulators used for the controlled and outputs are of the sliding mode type, where the sliding variable is defined as the difference between an output and its limit. The max and min arrangements enjoy many beneficial properties, including a separation principle allowing the independent design of the sliding regulators, with overall asymptotic stability guarantee. The paper details the stability proof for the separate min and max selector systems and describes the invariance properties leading to limit protection. Some results applicable to the max-min case are also included. Design guidelines, as well as a detailed simulation example, demonstrate practical applicability.