Introduction
Accurate position control of DC motors is essential in many industrial and robotic applications where system uncertainties, external disturbances, and parameter variations significantly affect performance. Traditional control techniques often fail to provide robust performance under such conditions. This paper presents a robust DC motor position control strategy using an Extended State Observer (ESO) combined with Sliding Mode Control (SMC). The ESO is employed to estimate total disturbances, including unmodeled dynamics and external loads, in real time. The estimated disturbances are compensated within the control law, enhancing robustness. Sliding Mode Control is utilized to ensure fast response, high tracking accuracy, and strong disturbance rejection. The proposed controller is modeled and simulated in MATLAB/Simulink, and its performance is evaluated under varying load conditions and parameter uncertainties. Simulation results demonstrate superior position tracking, reduced steady-state error, and improved robustness compared to conventional PI-based controllers.
Methodology
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DC Motor Modeling
A mathematical model of the DC motor is developed using electrical and mechanical equations to represent armature voltage, current, speed, and position dynamics in MATLAB/Simulink. -
Extended State Observer (ESO) Design
An ESO is implemented to estimate unmeasured states and lumped disturbances, including load torque variations and parameter uncertainties, in real time. -
Sliding Mode Controller (SMC) Design
A sliding surface is defined based on position error and its derivative. The SMC control law is designed to ensure robust tracking performance and disturbance rejection. -
Controller Integration
The ESO outputs are integrated with the SMC to compensate for disturbances, improving system robustness and reducing steady-state error. -
Simulation and Validation
The complete ESO–SMC controlled DC motor model is simulated in MATLAB/Simulink under different reference inputs and load disturbances to evaluate tracking accuracy, robustness, and stability.