Study on a low frequency vibration isolator based on combined positive and negative stiffness

To suppress the adverse effects caused by micro-vibration on orbiting spacecraft, a novel low frequency vibration isolator which combines a spiral flexure spring (SFS) with a magnetic spring in parallel is developed; SFS is employed as a positive stiffness element to support the payload, and then the finite element model of SFS is adopted to analyze its axial stiffness. Moreover, the magnetic spring is fabricated by three coaxial magnetic rings that are arranged in attraction to provide negative stiffness for lowering the natural frequency of the isolator. The characteristic of magnetic stiffness is investigated based on the equivalent current model, and the linearization of magnetic stiffness near the equilibrium position is further obtained. The vibration isolation performance of the designed isolator and its corresponding linear system is compared through analysis of their displacement transmissibility. The results demonstrate that the designed low frequency vibration isolator can effectively isolate micro-vibration, lower the natural frequency of the isolator, and expand the bandwidth for vibration isolation. Additionally, the damping characteristic is improved near the resonance region, and the resonance peak is attenuated greatly.