A variable positive-negative stiffness joint with low frequency vibration isolation performance

Abstract

A new vibration isolation joint with combined positive and negative stiffness is proposed, which also supports multi-directional stiffness adjustment. Two sets of opposed buckling Euler beams are used as the variable stiffness structure. The effective length of the beam is changed by moving the slider, which in turn changes the structural stiffness. In the horizontal direction the structure provides adjustable positive stiffness. In the vertical direction it can provide adjustable negative or positive stiffness. A disk spring with nonlinear stiffness characteristics is used as the load-bearing spring and is connected in parallel with the variable stiffness structure. The static and dynamic characteristics show that the structure has good passive low-frequency vibration isolation performance. By actively moving the slider to change the structural stiffness, the equilibrium position of the system can be changed, active actuation can be performed, and active control of ultra-low frequency vibration isolation can be achieved.