Design and feedforward control of large-rotation two-axis scan mirror assembly with MEMS sensor integration

As a key component of electro-optical systems, a Two-axis Scan mirror AssemblY (TSAY) is usually used for Line-of-Sight (LOS) precision pointing, tracking, scanning, and stabilizing. Therefore, it is necessary for a TSAY to have a large angular range, high dynamic characteristics, and small mirror surface distortion. Furthermore, vibration from carriers of electro-optical systems, such as spacecraft and airplanes, is inevitable, so it is critical to guarantee the control accuracy of a TSAY under vibration. In this paper, a TSAY prototype is designed and developed. To increase the control bandwidth, structural topology optimization is applied to the TSAY's elliptical mirror to reduce the moment of inertia, meanwhile keeping surface flatness. A flexible hinge is adopted to achieve a large angular range. To suppress the angular perturbation caused by the base linear vibration, an adaptive feedforward loop with base-integrated Micro-Electro-Mechanical System (MEMS) accelerators is constructed to enhance the TSAY's feedback loop. Simulation and experimental results show that the TSAY prototype's two-axis mechanical angular ranges are more than ±3.2°, the mirror surface flatness Root Mean Square (RMS) value is better than 0.04λ, and the closed-loop bandwidth is beyond 330 Hz. These are suitable for most applications. Besides, the angular perturbation caused by the base vibration can be suppressed more than 37.7% with the addition of the adaptive feedforward loop.