An Output Tracking Integrated Discrete PID-based Sliding Mode Control on SISO Systems

SMC (sliding mode control) has been widely employed to compensate for the system uncertainty and disturbance. However, the chattering problem, caused by the discontinuous characteristic of switching function used in traditional SMC, greatly deteriorates the performance of SMC and has become the main limitation for its applications. Also, implementing the SMC in digital systems could make it even worse due to the limited sampling time. Moreover, as a state tracking control scheme, traditional SMC cannot be employed in the applications where the system states are not available. To alleviate these problems, the paper presents the development of a novel control method, so called “the output tracking integrated discrete PID (proportional-integral-derivative)-based SMC” for the SISO (single-input-single-output) system, along with the controller design approaches (i.e., the traditional SMC design approach and the model reference approach). Without the need of system states, this novel method allows for eliminating chattering problem and the steady state error that may exists in such control methods as the continuous PID-based SMC. In order to demonstrate the effectiveness of the developed method, experiments were carried out on a commercially available piezoelectric actuator with varying sampling times, as compared to the continuous PID-based SMC. The results illustrate that the tracking performance with the proposed method is much better than the continuous PID-based SMC.