Line-of-Sight Stabilization Enhancement With Hybrid Sensing in a Piezoelectric Mirror-Based Cubic Stewart Platform

Space observation missions demand stringent pointing requirements. This article thus investigated a dual-stage vibration isolation and precision pointing system consisting of a cubic Stewart platform and a piezoelectric mirror. Due to the unloading control among these stages and the limited control bandwidth of piezoelectric mirror caused by the low sampling rate of the charge-coupled device (CCD), the closed-loop performance is inevitably restricted. Therefore, a high-bandwidth disturbance feedforward method based on hybrid measurement of the inertial gyro and the CCD is proposed to compensate residual vibrations, which breaks the limitation of closed-loop bandwidth and thereby enhances the disturbance resistance performance. To avoid the dependence on the accurate inverse model of the control plant at high frequency, the proposed feedforward controller is designed based on the partial compensation principle, further optimizing the feedforward controller by utilizing a constructed low-pass filter instead of the typical integrator. Besides, a frequency splitting strategy is presented to eliminate motion coupling existing in gyro signals, so as to realize unloading control under disturbance loading. Simulations and experiments demonstrate the effectiveness of the proposed method.