Design of a Sliding-Mode Control System Resistant to Internal Disturbances for a High-Power DC Motor

Abstract

The aim of this research is to design a sliding-mode controller to control a high-power DC motor when internal disturbances are present. Internal disturbances in motors are one of the most important problems whose impact on motor performance must be studied. Using conventional controllers to control high-power DC motors when internal disturbances occur has a weak impact on stability and reducing static error.

A sliding-mode control algorithm was utilized to improve the performance of these motors during transient internal dynamic conditions, such as changes in the resistance value of the inductor coil due to temperature rise or changes in its inductance value due to magnetic saturation, which causes motor disturbances. A mathematical model for high-power DC motors was derived based on its dynamic equations, in preparation for utilizing the sliding-mode controller equations and deducing the sliding surface. This results in a control law that transfers the studied state variable from the surface on which it operates to the sliding surface, ensuring that the system returns to the desired operating point immediately upon the occurrence of any disturbance. The system was then modeled in Matlab-Simulink. The values ​​of some basic parameters of the motor were changed at a certain time point and the time response curve of both motor current and speed was monitored. Simulation tests showed that the control processes with variable structure achieved a good response compared to the traditional (PID) controller, as the slide controller (SMC) eliminated the maximum overshoot and returned the output to the stable state within a very short time (0.01 sec), and also reduced the static error value by (0.3%).