Structural Design And Implementation Of Active Vibration Isolation System Based On Combined Positive And Negative Stiffness

Active vibration isolation system is an important device which provides the vibrationenvironment for precision instruments.The key to achieve precise vibration isolation at low frequency is to realize extremely low structural natural frequency and good carrying capacity,as well as introducing active vibration control.In this paper,the following research work has been completed on structural techniques of active vibration isolation technology:According to the demand indicators,the methods for realizing low-frequency,active vibration control and six-degree-of-freedom vibration isolation are analyzed.The principle of combined positive and negative stiffness to achieve extremely low natural frequency and maintain high load carrying capacity is described,and the principles of negative stiffness of the combined compression spring structure and ring-shaped permanent magnet structure was studied.The overall scheme of active vibration isolation system based on combined positive and negative stiffness is put forward,which is composed of combined compression spring structure,upright pendulum mechanism and ring-shaped permanent magnet structure.The mechanical model of the system is established,force conditions are analyzed and the isolator's stiffness models of combined positive and negative stiffness mechanism in the vertical and horizontal direction are deduced respectively.The influence of structural parameters on the stiffness of combined compression spring structure,pendulum mechanism and ring-shaped permanent magnet structure are qualitatively analyzed.Structural parameters of the isolator are calculated.The methods of optimizing the parameters of combined compression spring structure and pendulum mechanism are proposed,which reduce the nonlinearity of the stiffness in vertical direction and increase the concentration of the stiffness in horizontal direction.The structure of the isolator is designed based on DFMA criterion,the contents of structural design are elaborated in detail from passive and active structures.The static characteristics of key structural components are vertified by ANSYS statics simulation.The dynamic analysis of the isolator is carried out.The influence of natural frequencies and modes of key structural components is analyzed,and the vibration transmissibility and harmonic response of the isolator under harmonic excitation is studied.It is proved that the isolator with combined positive and negative stiffness have lower natural frequency at 0.5~1Hzand better vibration isolation effect.,The integration of isolator prototype is realized according to the design.