A nonlinear energy sink enhanced by active varying stiffness for spacecraft structure: theory, simulation, and experiment

A conventional nonlinear energy sink (NES) proposed for spacecraft structure can achieve vibration reduction without changing the resonant frequencies. However, large additional mass limits its engineering applications, and the robustness needs to be improved. A novel nonlinear energy sink with active varying stiffness (NES-AVS) device is proposed for reducing the mass of the conventional NES and enhancing the vibration reduction effects. A two degrees-of-freedom equivalent model of the scaled spacecraft structure is proposed. A harmonic balance method is applied to analyze the effect of the vibration reduction of the equivalent model, and the results are verified numerical simulations. The results show that the NES-AVS can achieve better vibration reduction effects, especially in small damping and mass. A finite element model of the scaled spacecraft structure with the NES-AVS is developed. The NES-AVS device is experimentally embedded in the scaled spacecraft structure. The variable stiffness device is realized by a steel plate with the compression force adjusted by a piezoelectric actuator. An active controller is used to control the actuator by the dSPACE module. The experimental results demonstrate that the NES-AVS has a better effect of the vibration reduction of the spacecraft structure than that of the conventional NES in multiple modes and different excitations. Compared with the conventional NES, the mass of the NES-AVS is reduced by 90%. The experiment and the theory have the same trends that the vibration reduction performance of the NES-AVS can be improved by adjusting the active control parameters. This work devotes to providing a new design scheme of the NES.