Comparison of Nonlinear Controllers for Speed Control of DC Motor

DC motor is a device which is extensively used in industries, robotics and domestic appliance due to its ease in controllability and high reliability. DC motor has nonlinearities like friction, backlash, dead zone that degrade the performance at low speed. Due to mechanical wear and environmental changes parameter value of DC motor get changed. Also varying loading creates change in rotor speed. This paper focused speed on control of such nonlinear model of DC motor. A nonlinear and robust sliding mode control (SMC) and linear active disturbance rejection control (LADRC) controllers are formulated and implemented to control speed of nonlinear DC motor. Performance of both controllers is evaluated under parameter variation and external disturbances that is varying load torque. Both controllers drive the system output to desired reference and robust against external disturbances and nonlinearities of system. But linear active disturbance rejection control is not robust against parameter variation. While sliding mode control is robust against external disturbance, model uncertainties and parameter variation and gives satisfactory results.