Error-Based Feedforward Control for a Charge-Coupled Device Tracking System

Abstract

High control bandwidth is usually restricted in a finite sampling rate of a charge-coupled device (CCD)-based tracking loop, which hinders a good closed-loop performance. Conventionally, a rate feedforward controller is usually used to improve the control performance; however, it is restricted by the line-of-sight (LOS) rate, which is required to be estimated due to only the LOS error available in the CCD-based tracking control system. Besides that, it is also affected by the inverse of the control model. A new error-based feedforward (EBF) control mode is proposed to overcome these difficulties. Due to being plugged into an existing feedback control loop, the closed-loop performance of the CCD-based control system can be minimized by optimizing a Q-filter. The closed-loop stability and robustness with this EBF control system are investigated on the condition of the gain margin and the phase margin of the open-loop transfer function. Furthermore, this paper proposes a new criterion to enhance the robustness of the EBF control system and reveals the sensitivity function property. Because of not being restricted by an accurate model, this new feedforward controller cannot lead to a compromise between error attenuation and noise propagation in the control loop. Simulations and experiments are both used to testify the effectiveness of the improved control mode.