Adaptive torque ripple compensation technique based on the variable structure control and its applications to gear driven motion systems

In this paper, a robust adaptive control scheme is proposed to reduce the effect of harmonic disturbances in gear driven feed drive systems. Harmonic forces are one of the most common disturbances in feed drives utilized in wide variety of applications such as in robotic systems or in various machine tools. They are generated, for instance, due to the external disturbances or internally by the servo structure itself such as torque ripples of the motor and gear mechanism. An adaptive torque ripple compensation technique is developed in this research, which can track the amplitude and phase of the sinusoidal disturbance forces. A suppression signal is then generated to reject the specific frequency of the disturbances. In conjunction with the ripple compensator, a robust feedback controller is designed employing the sliding mode variable structure control framework. Both, controller stability and the adaptation convergence are proven using the Lyapunov theory. The controller is then transformed into a PID-like structure and implemented in various gear driven servo systems where its performance is verified experimentally.