Design And Study On A Six Degrees-of-freedom Quasi-zero-stiffness Vibration Isolation Platform

Firstly,a novel quasi-zero-stiffness(QZS)strut is proposed by combining a cam-roller-flexible-beam mechanism and a coil spring,which could achieve low-frequency vibration isolation in single degree-of-freedom(DOF).The theoretical model was established to analyze its static characteristics.And the QZS characteristics were realized through the parametric design.The equation of motion of an equipment(lumped mass)supported by the QZS strut under harmonic excitation was analyzed approximately by using Harmonic Balance method.The relationship between amplitude and frequency as well as the force transmissibility of the vibration isolation system was obtained,and the analytical results were verified by the numerical solutions.Meanwhile,the force transmissibility was used to assess its performance of vibration isolation.Further,the influences of key parameters,such as the amplitude of excitation force and damping,on its response and force transmissibility were discussed.The results show that the frequency band of the QZS system is obviously extended towards low frequency,and the performance of vibration isolation is improved significantly.In addition,with the change of key parameters,the performance of vibration isolation would change distinctly.Secondly,to solve the problem of low-frequency vibration isolation in multiple directions,a six-DOF QZS vibration isolation platform mounted on eight QZS struts was constructed.And the load-displacement and the stiffness-displacement relationships were obtained by static analysis of the six-DOF QZS vibration isolation platform.By means of numerical simulations,it was proved that this vibration isolation platform possesses QZS characteristic in all six DOFs.Moreover,the effect of the incline angle between the QZS strut and the vertical direction on the performance of the six-DOF QZS vibration isolation platform was discussed,which shows that the load-carrying capacity and the performance of vibration isolation can be enhanced by parametric design of this angle.Finally,the dynamic model of the six-DOF QZS vibration isolation platform was established,and the Harmonic Balance method was used to derive the first approximation of the primary resonance.Based on these solutions,the amplitude-frequency characteristic and the force transmissibility on the six-DOF QZS vibration isolation platform were obtained,which were verified by numerical simulations obtained by the Runge-Kutta method.And its performance of vibration isolation in all six DOFs were evaluated by force transmissibility in corresponding directions.The results indicate that the performance of the six-DOF QZS vibration isolation platform is much better than that of the linear platform composed of eight linear struts.Furthermore,the influences of excitation amplitude,damping ratio,sturt parameter and incline angle on the performance of the six-DOF QZS platform were discussed.Additionally,the deterioration in the quality of vibration isolation caused by cam-roller assembly error and existence of linear struts were also analyzed.