Abstract
This paper describes the design of a non-overshooting proportional-integral-derivative (PID) controller with both pre-assigned initial integral state and a perturbation compensation scheme for motor positioning systems. According to the requirement of non-overshooting output response and the specified settling time in tracking a step reference signal, the PID gains and the initial integral state are determined systematically. The proposed PID control provides a continuous control signal when the nominal system is subject to sudden set-point changes, implying smooth system performance. To compensate for the system perturbation resulting from parameter variations and unknown load disturbances, an integral sliding perturbation observer is proposed and integrated into the PID-controlled system, which requires neither access to the time derivative of the state vector nor accurate knowledge of system parameters. A sliding mode is ensured throughout the entire response, and system perturbation is estimated by feeding a switching signal through an integrator. Due to the low-pass filtering characteristic of the integral action and the reduction of the required switching gain, the proposed scheme not only precisely compensates for system perturbation within the interested frequency range, but also effectively alleviates the chattering problem in control signals. The usefulness of the proposed design is demonstrated through an experimental study of a motor drive under load variations and disturbances.
