Robust Controller Design based on IMC Scheme for Motion Control of DC Servo Systems

In this article, a robust controller is designed based on the internal mode control (IMC) scheme for the motion control of the DC servo system. The challenging part in servo systems is the robust tracking in the presence of plant uncertainties and load variations. The proposed controller design has an interesting structure, i.e., integer filter term cascaded with PD controller. This work identified the integer IMC filter whose single optimal tuning parameter is selected using a simple iterative approach based on the minimization of integral absolute error (IAE) and total variation (TV). Control effort minimization is also equally significant because of the actuator saturation constraints which eventually cause the wear and tear and can make the system unstable at the worst case. The tuning parameter is the filter time constant, which trades off the performance, robustness, and control effort. As a result, the proposed controller handles the parametric uncertainty and load disturbances effectively not at the cost of higher control effort. This paper compares the tracking performance and control effort with different filter structures which cascaded with the PD controller, and it concludes with a novel controller structure with the introduction of 2-degree of freedom (DOF) pre-filter along with the controller which provides a good compromise between faster tracking performance and control effort minimization and it is compared with the literature regarding performance indices, i.e., IAE, TV, and Ms. This controller prevents the actuator to saturate when there is abrupt change in the reference tracking command. The simulation results show that the proposed control enhances performance (IAE), stability \((M_s)\) and minimizes the control effort (TV). Also, robustness analysis has been carried out with perturbations in process model parameter.