Enhanced Disturbance Observer Based on Acceleration Measurement for Fast Steering Mirror Systems

In this paper, a modified disturbance observer (DOB) for fast steering mirror (FSM) optical system based on a charge-coupled device (CCD) and inertial sensors is proposed. Combining a DOB with the classical cascaded multiloop feedback control, including position loop, velocity loop, and acceleration loop, that the disturbance suppression performance of line-of-sight in an FSM system can be significant improved. However, due to the quadratic differential in the FSM acceleration open-loop response, in fact, it is very difficult to realize an integral algorithm to compensate a quadratic differential in practical application. Thus, the conventional DOB controller has to be simplified further to make a concession, which eventuates in still insufficient disturbance compensation, particularly at low frequency. To solve this problem, an enhanced DOB control structure, which changes the compensation plant to be the acceleration open-loop and avoids the saturation of double integration skillfully, is proposed. The recommended method optimizes the controller design, which is conducive to controller fulfillment in practical systems. A series of comparative experimental results demonstrate that the disturbance suppression performance of the FSM control system can be effectively improved by the proposed approach.