Offset-free motor position control of an elastic drive system through reference position correction

For elastic drive systems the motor shaft position does not correspond to the load position. Therefore, load side position feedback is usually used in the control to achieve correct positioning of the system. This paper proposes an alternative approach, that allows for a correct positioning using the motor position feedback for control. This is achieved through the online correction of the reference position using a robust Extended Kalman Filter. Using the load feedback it estimates an idealised, offset-free motor position. The correction factor calculated from the difference between the measured and the estimated motor position is then used for reference position correction (RPC). The proposed RPC method is implemented on a belt-driven test bed and evaluated for different movements, load oscillations and significant parameter errors to show its functionality and its suitability for industrial application.