Relay Sliding Mode Control Based on the Input-Output Model

Abstract

Uncertainties, parameter changes, and disturbances lie among the most frequently encountered problems in practical control applications. Sliding mode control (SMC) is one of the robust control methods developed to provide a certain control performance under such circumstances. SMC can also be achieved in relay control systems. The aim is to obtain an overall system that is robust to disturbances, noise, and parameter changes by forcing the relay element to operate in sliding mode. While SMC methods have been traditionally developed in state -space, in relay control systems, it is possible to define SMC based on the input-output model of a system. This way, sliding motion can be achieved by only utilizing the output signal, without the need to know or measure the system states. In this study, the relay sliding mode control method based on the input-output model proposed in previous studies is revisited. Sliding conditions under ideal operating conditions are reformulated to fortify the theoretical background. Some additional issues, namely the effects of disturbances and measurement noise on the sliding mode conditions, are addressed and analyzed in detail. Finally, the theoretical results are put to the test by detailed simulation examples.