Disturbance Feedforward Control of Tip-Tilt Mirror With Gyro Measuring for Large-Amplitude Vibration Rejection

A traditional tip-tilt mirror control system with an image loop is used to effectively reject structural vibrations in optical telescopes. However, its bandwidth is restricted by low sampling rate and large time delay of imaging sensors, which is insufficient to suppress disturbances outside the bandwidth, even the large-amplitude disturbances within the bandwidth. This paper proposed a disturbance feedforward method base on fusion of inertial gyro and imaging sensor to solve this problem. Accurate measurement of disturbance is the premise of disturbance feedforward. Thus we utilize gyro integral to obtain high-precision and high-bandwidth disturbance signals. The traditional model-based inverse control suffers from model accuracy, which reduces the control bandwidth and response to low-frequency disturbances. Therefore, an optimized feedforward controller is proposed to reduce the dependence on the model accuracy and break the limitation of bandwidth, which realizes the elimination of large-amplitude disturbances. Simulations and experiments demonstrate that the proposed method can not only accurately measure high-bandwidth disturbance signals, but also significantly suppress large-amplitude and narrow-band disturbances. The results suggest that gyro measurement provides great convenience for the optimized feedforward method applied to other servo control system.