Circular Halbach negative stiffness isolating from torsional vibration: Design, modeling and experiments

Excessive torsional vibration is detrimental to the operation performance of key mechanical equipment. To attenuate low-frequency torsional vibration in high payload occasions, the negative stiffness isolator has been widely employed. However, due to the space constraints of compact rotating machinery, it is difficult to promote negative stiffness for counteracting high positive stiffness. Therefore, a circular Halbach torsion negative stiffness isolator is proposed to provide high torsional magnetic negative stiffness for low-frequency isolation. The semi-analytical expressions of tangential-tangential coupling and tangential-radial coupling for tile magnets are derived to calculate the magnetic torque and the torsional stiffness of circular magnetic arrays, and then the influences of structural parameters on magnetic negative stiffness are investigated. The simulation results show that the circular Halbach array has the much higher magnetic stiffness than the circular traditional array. The dynamic responses of the proposed torsional isolator are analyzed based on harmonic balance method. Moreover, experimental results show that the onset isolation frequencies of circular Halbach isolator and circular traditional isolator can be decreased by 32.57% and 17.90% respectively compared with the linear isolator. Therefore, it is demonstrated that the proposed circular Halbach isolator has a preferable performance for low frequency torsional isolation.