Large flexible solar panels have the properties of light weight, low stiffness, and weak damping, which leads to low-frequency and large-amplitude vibrations. The existing vibration control methods of solar panels mainly adopt intelligent piezoelectric structures. However, the disadvantage is that the large stroke drive and control are limited. In the present study, a semi-active vibration control approach is proposed for flexible space solar panels based on magnetically controlled joints. The magnetic stiffness comes from the linear relationship between the joint output torque and rotation angle. The magnetic damping stems from the eddy current damping resulting from the relative motion between the permanent magnet rotor and the stator core of the joint. Firstly, the coupling dynamic modeling of a flexible plate and magnetic joints is established by adopting the Lagrange equation and the assumed mode approach. Secondly, semi-active vibration control simulations of the coupled system are performed. Meanwhile, the influence of the variable joint stiffness on the system frequency-shift effect is studied. Finally, the experimental platform is built, and simultaneously, non-contact permanent magnets and airflow are used to simulate single- and multi- frequency excitations, respectively. The experimental results indicate that, in the range of 0.06–0.343 Hz, magnetic damping is the leading factor with magnetic stiffness being the auxiliary. Additionally, it is also experimentally verified that the dual joint actuation has good synchronization. This study provides a new solution for the low-frequency vibration control of large flexible space structures.

With the evolution of space exploration, large flexible appendages have been developed in space structures. External perturbation or attitude maneuvering stimulates the vibration (low frequencies) of the aforementioned structures. In this research, a novel joint mechanism was developed in conjunction with active control to inhibit the low-frequency vibration of a large flexible appendage. A compact active joint, based on the idea of electromagnetic direct drive, was designed. The dynamic equations for the large flexible appendage system and the active joint were derived using the Lagrange function with the assumed-modes approach. Single- and multi-frequency excitations were simulated by two noncontact strategies for periodic vibration stimulation along the direction of rotation. The research results revealed that the interference signal had a primary frequency bandwidth of 0.07–0.63 Hz, and the vibration attenuation was prominent between 5.95 and 32.41 dB within the valid bandwidth. Effective inhibition of both the larger and the smaller amplitude vibrations at frequencies lower than 1 Hz could be realized using the proposed active joint without attachment of intelligent materials onto the flexible appendage surface.

Low-frequency and large-amplitude vibration of flexible appendages in space can be induced when a spacecraft performs attitude maneuvers and thermal alternations during orbit operation. In this paper, a novel joint mechanism combined with a semi-active method for variable stiffness control is proposed to suppress the low-frequency vibrations of flexible jointed appendages. The variable stiffness of the joint is derived from the linear relationship between its output torque and rotation angle when direct current (DC) power is applied to the coils. Based on the Lagrange equation and the assumed mode method, the coupling dynamic relationships of the active joint and two flexible appendages are established, and semi-active vibration control simulations are performed. A ground experimental platform is built to simulate the microgravity environment in space. The frequency shift effect of rigid body motion and elastic vibration under impact disturbance are investigated. In addition, the effect of variable stiffness control on the elastic deformation of flexible appendages is studied. The simulation and experimental results indicated that the proposed method can control both the rigid body motion of the system and the elastic vibration of the appendages. It has been found that the major frequency bandwidth of the interference signal is within 0.3–1.0 Hz with a substantial vibration attenuation of 1.82–16.62 dB for the joint and 4.86–11.48 dB for the flexible appendages.