OBSERVER BASED SLIDING MODE CONTROLLER DESIGN FOR POSITION CONTROL OF A SERVO SYSTEM HAVING UNCERTAINTIES AND DISTURBANCES

Servo systems are used extensively in many industrial applications that require precise position control. However, parameter uncertainties, matched and unmatched disturbances encountered in most of these applications adversely affect the controller performance. Therefore, in industrial control applications, robustness is at least as important as precision. In this study, an Extended State Observer- based Sliding Mode Controller (GDGKKK) design is presented for precise position control of a rotary servo system having parameter uncertainties and disturbance input. The performance of the proposed controller has been tested by performing simulation studies for five different uncertainty and disturbance input scenarios and compared with the traditional Sliding Mode Control (SMC) and Proportional Derivative (PD) control to evaluate its effectiveness. The mathematical model of the Quanser SRV02 rotary servo unit was used in the simulation studies in MATLAB/Simulink software. The simulation results show that the PD control is very sensitive to load changes and disturbances and while the traditional SMC control is insensitive to load changes and matched disturbances, it is sensitive to mismatched disturbances. On the other hand, the results clearly showed that the proposed GDGKKK controller offers extremely successful disturbance rejection performance against both load changes and matched and unmatched disturbances.