Comparison Of LQR And PID Control Approaches In Enhancing Stability Of DC Motor Systems

Abstract

DC motors are widely utilized in various applications, including industrial automation, robotics, and household devices, due to their versatility and broad speed regulation range. Among the types of DC motors, the series DC motor is notable for its high starting torque, which makes it suitable for operations requiring significant initial force. However, this motor type presents several challenges, including instability, speed fluctuations under varying torque conditions, and the potential for excessive speeds under no-load conditions. To address these issues and achieve precise speed control, a reliable controller is essential. This study presents a comparative analysis of two control strategies—Proportional-Integral-Derivative (PID) and Linear Quadratic Regulator (LQR)—for stabilizing the speed of a series DC motor. Simulations were conducted using MATLAB, with the motor speed tested under five different setpoints to evaluate performance metrics such as response time, overshoot, and steady-state error. The results demonstrate that both controllers achieve minimal steady-state error; however, distinct differences are observed in other performance aspects. The PID controller exhibits a faster response time but is associated with significant overshoot, approximately 20%, and a starting current overshoot of about 460%. In contrast, the LQR controller effectively eliminates overshoot and reduces starting current overshoot to approximately 188%, offering a smoother and more stable control performance. This comparative study highlights the trade-offs between the two controllers and provides insights into their suitability for specific applications. The findings contribute to advancing the implementation of optimal control techniques in DC motor systems, ensuring stability and efficiency in engineering applications.