Semi-active vibration control of two flexible plates using an innovative joint mechanism

Abstract

Abstract With the advancement of space technology, space flexible jointed appendages have been applied widely. The low-frequency vibration problem is inevitable because of the external disturbances or attitude maneuvering in micro-gravity environment. In this study, an innovative joint mechanism was proposed and a new methodology for semi-active technique of joint variable stiffness control was utilized to suppress the low-frequency vibration of flexible jointed appendages. The joint mechanism, based on the direct drive principle, exhibits a compact structure and integrates with an electro-permanent-magnet driving mechanism. First, the concept design of joint mechanism is introduced. Second, dynamic equations of active joint and two flexible plates are obtained using Lagrange equation and assumed mode method. Finally, two types of non-contact periodic vibration excitation methods along rotation direction are proposed. A self-made electro–magnetic vibration exciter was employed to achieve single-frequency excitation, and two fans were placed on both sides of flexible appendages to induce multi-frequency excitation. According to numerical simulations and experimental results, when the joint torsional stiffness changes, frequency-shift phenomenon occurs, and the natural frequency of the system varies subsequently. Furthermore, the experimental results demonstrated that the major frequency bandwidth of interference signal was 0.06–0.63 Hz with a significant vibration attenuation of 5.41–26.94 dB for joint-1 and 5.63–16.48 dB for joint-2 in effective bandwidth. The low frequency vibration of flexible appendages system can be attenuated robustly, which verifies the effectiveness of this semi-active methodology.