Adaptive disturbance compensation and load torque estimation for speed control of a servomechanism

In this paper, an adaptive disturbance compensation (ADC) scheme for the speed control of a servomechanism is proposed. The idea of the proposed ADC is to adaptively adjust the compensator gains so that the output of the actual plant after compensation will faithfully follow the output of the nominal model. The major benefits of the ADC are twofold - disturbance/uncertainties attenuation and load torque estimation. The stability of the proposed ADC is verified by Lyapunov stability analysis. In addition, an integrated motion control structure consisting of the proposed ADC, a feedback controller and a friction compensator is developed to deal with the contour following problem. In this paper, the friction compensator designed based on the LuGre friction model is used to effectively reduce the large contouring error that often occurs when there is a reverse motion. Two experiments have been conducted to verify the effectiveness of the proposed approach. The test bench of the load torque estimation experiment consists of a servo motor and a hysteresis dynamometer, while the contour following experiment is conducted on an X-Y table. Experimental results show that the proposed approach exhibits satisfactory performance.