Comparison of Model Reference Control Schemes for Motor Speed Control Under Variable Load Torque

Abstract

Accurate motion control is required in mechatronic and robotic systems and is particularly important when the inverse kinematic control of robotic manipulators is done by controlling each joint independently; for this reason, it is necessary to find methods to optimize the position control strategies used in robotics, which can be achieved by focusing on controlling the speed of actuators. Controlled DC motors should be tested under extreme conditions for such applications. Performance indices pertaining to actuator wear-out and control accuracy are used for the evaluation. This study proposes a speed control strategy for a direct current motor that uses a model reference control (MRC) scheme and combines it with an internal model control (IMC) based proportional-integral (PI) controller. Three different controllers are used in the MRC to compare the performance of the proposed strategy with an IMC-based PID (Proportional Integral Derivative) controller in numerical simulations. For the experimental tests, particular tuning parameters are presented for the PID to control a DC motor when only a first-order model is identified. The proposed MRC-IMC scheme imposes a first-order response to the actuator while compensating for disturbances caused by load torque variations. Simulation and experimental results validate a better performance of the proposed control strategy.