Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore
doi:10.3850/978-981-18-6021-8_OR-07-0179
Controller Design for Piezo-driven Segmented Fast Steering Mirror
1Department of Mechanical Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8503 Japan
2FIRST, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8503 Japan
ABSTRACT
To improve the performance of laser processing and inter-satellite optical communications, fast steering mirrors (FSMs) for optical path driving are required to have high responsiveness, high accuracy, and large aperture. However, the larger the mirror aperture, the lower the frequency of uncontrollable natural modes and the more difficult it is to increase the bandwidth of the FSM. In this study, an FSM with a large aperture and high response will be realized by integrating small mirror devices (SMDs) with high natural frequencies and wide bandwidth. The SMDs are driven by piezoelectric actuators (PEAs) suitable for high response drives. When multiple mirrors are arranged on the same plane and used as a single mirror, the amplitude of the out-of-plane translational displacement of each SMD increases with the distance between the center of the SMD and the axis of the FSM rotation. Since the relationship between applied voltage and displacement of PEA is nonlinear, the reference frequency responses are affected by the nonlinearities at high frequencies, even with feedback control. Therefore, the integrated mirror surface formed by multiple SMDs will suffer from dynamic flatness degradation. This paper proposes a simple controller gain adjustment based on the similarity of PEA hysteresis to obtain a uniform feedback response of multiple SMDs. The proposed method is experimentally compared with a conventional hysteresis compensation method using the classical Bouc-Wen model. The Bouc-Wen model method requires four tuning parameters, while the proposed method tunes only one. The obtained uniformity of the SMD responses is comparable for both methods, confirming the effectiveness of the proposed method.
Keywords: Fast steering mirror, Piezoelectric, Hysteresis, Cooperative control
1Department of Mechanical Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8503 Japan
2FIRST, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8503 Japan
ABSTRACT
To improve the performance of laser processing and inter-satellite optical communications, fast steering mirrors (FSMs) for optical path driving are required to have high responsiveness, high accuracy, and large aperture. However, the larger the mirror aperture, the lower the frequency of uncontrollable natural modes and the more difficult it is to increase the bandwidth of the FSM. In this study, an FSM with a large aperture and high response will be realized by integrating small mirror devices (SMDs) with high natural frequencies and wide bandwidth. The SMDs are driven by piezoelectric actuators (PEAs) suitable for high response drives. When multiple mirrors are arranged on the same plane and used as a single mirror, the amplitude of the out-of-plane translational displacement of each SMD increases with the distance between the center of the SMD and the axis of the FSM rotation. Since the relationship between applied voltage and displacement of PEA is nonlinear, the reference frequency responses are affected by the nonlinearities at high frequencies, even with feedback control. Therefore, the integrated mirror surface formed by multiple SMDs will suffer from dynamic flatness degradation. This paper proposes a simple controller gain adjustment based on the similarity of PEA hysteresis to obtain a uniform feedback response of multiple SMDs. The proposed method is experimentally compared with a conventional hysteresis compensation method using the classical Bouc-Wen model. The Bouc-Wen model method requires four tuning parameters, while the proposed method tunes only one. The obtained uniformity of the SMD responses is comparable for both methods, confirming the effectiveness of the proposed method.
Keywords: Fast steering mirror, Piezoelectric, Hysteresis, Cooperative control
