Error-based Feedforward Control for Photoelectric Tracking System

In this paper, an approach to enhance the tracking performance of charge-coupled device (CCD)-based photoelectric tracking system (PTS) is proposed. The CCD sensor is usually utilized to provide the line of sight (LOS) errors directly, by which the PTS is widely used for visual fine tracking control. Generally speaking, the higher the closed-loop bandwidth of the system, the better the closed-loop performance of the system. However, the tracking performance of PTS is greatly limited by a low CCD sampling rate, which causes insufficient error attenuation performance when tracking maneuvering targets or suffering platform disturbances. In order to extend the tracking error attenuation bandwidth, especially at middle frequency, an error-based feedforward control (EBFC) method is recommended. Combining the LOS error from CCD and the controller output, the relative position of target can be estimated, which is helpful for producing a high-gain controller to suppress LOS errors. The feedforward node is designed before the inner loop to construct a pure and novel forward route, which makes the feedforward controller acting as a lead-lag controller to ensure the stability of system, actually. Simultaneously, the control bandwidth and controller design analysis of this method is presented. A few comparative experimental results show that the improved control method can effectively enhance the error attenuation performance of the LOS for the CCD-based PTS.