Enhanced disturbance observer based on acceleration measurement for fast steering mirror systems

Abstract

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 DOB with the classical cascaded multi-loop feedback control (MFC), including position loop, velocity loop, acceleration loop, the disturbance suppression performance of line-of-sight (LOS) in 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 disturbance observer (EDOB) 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 the disturbance suppression performance of the FSM control system can be effectively improved by the proposed approach.