Image measurement-based two-stage control of Stewart platform

The Stewart platform has six degrees of freedom motion characteristics and can be used as both vibration isolation and tracking platform. However, the vibration isolation function requires low system bandwidth, while the tracking function requires high system bandwidth, which makes it difficult to achieve high precision tracking using the Stewart platform with vibration isolation function. To solve this technical problem, a high-bandwidth tilt correction system is introduced to form a two-stage control structure, so as to improve the accuracy. The traditional two-stage control needs to design decoupling link and independent measurement sensors to achieve hierarchical control. In this paper, a control method based on a single sensor is proposed to improve the traditional dual-order structure to avoid decoupling and achieve a high-precision closed-loop for the Stewart-TTM. In order to further improve the tracking accuracy of the system at low frequencies, a PI-PI controller is designed. Theoretical analysis and experimental verification show that the Stewart dual-stage control structure based on image measurement can not only meet the requirements of vibration isolation, but also achieve high-precision tracking control. Compared with the traditional PI controller, the PI-PI control proposed in the tilt correction system can effectively improve the tracking accuracy.