Analysis and Design of a Speed Controller for Electric Load Simulators

Electric load simulator (ELS) is a resonant system and has a large coefficient caused by the stiffness of shaft. Its dynamic performance is always limited and stability is hard to be guaranteed. Besides, its external disturbance is the active motion of an actuator, and output is the load torque, which are both different from conventional servo systems. Therefore, the speed controller of ELS needs to be specially designed. In this paper, a speed controller for ELS is proposed to improve the dynamic performance and stability of ELS. The proposed controller consists of three control terms: a proportional (P) control term, a speed reference feedforward term, and a load torque compensation term. The tracking performance and surplus torque suppression performance of ELS with the proposed controller are analyzed in this paper. Stability analysis in discrete domain is carried out to guarantee the stability for digital applications. Robustness is also analyzed and an extended state observer is designed to compensate uncertainties and estimate speed. Furthermore, the proposed speed controller is compared with other three control methods. Experimental results on ELS are provided and validate the effectiveness of the proposed method.