A Quasi-zero-stiffness Vibration Isolation System And Its Application On The On-board Precision Vibration Isolation

The vibration control is an important issue of the device security. As the development of the technology, the vibration isolation of the precision instruments is becoming increasingly important. The requirements of vibration control are increasingly high because of the using of many high-tech equipments. Effectively reducing the vibration and the resulting harm are important issues of the vibration control. Mainly the passive vibration isolation included the springs or the rubbers can not solve the problem of the low-frequency vibration isolation. It is very important to effetely reduce the natural frequency of the vibration isolators .The new type of negative stiffness vibration isolators, achieving a lower natural frequency because of positive and negative stiffness parallel principle, isolate low frequency vibration, but the theory is not ye mature.First, countered a new type of negative stiffness mechanism and a vibration isolation system of the mechanism merged with a positive stiffness spring, the load and the static characteristics of the mechanism and the system, the damping, vibration transmissibility, power magnification and the mean square response dynamic characteristics of quasi-zero-stiffness vibration isolation system are analyzed. The results show that the negative stiffness mechanism merged with a positive stiffness can be a quasi-zero-stiffness vibration isolation system when the quasi-zero-stiffness condition is satisfied. Its relative damping ratio is higher then that of the conventional vibration isolation system, so it benefits reducing resonance peak. Its vibration transmissibility and the peak of vibration transmissibility are obviously lower than that of the conventional vibration isolation system, its isolation effective area is obviously narrower than that of the conventional vibration isolation system. Maximum dynamic stress of elastic element of the quasi-zero stiffness of active vibration isolation system is less than that of the quasi-zero stiffness of the passive vibration isolation system, but the latter is better than the former at random vibration isolation.Second, the stiffness properties of a mechanism and vibration isolation system of the mechanism after being merged into the linear main spring are analyzed. The main harmonic, sub-harmonic and super harmonic resonance amplitude-frequency response expressions of passive isolation system with quasi zero stiffness are mainly deduced. The results show that negative stiffness definitely emerges from the mechanism and the negative stiffness region broadens as the ratio of the initial deformation of the spring to the length of the bar increases. The quasi zero stiffness emerges from the vibration isolation system and the quasi zero stiffness region broadens as the ratio of the stiffness of the main spring to the total stiffness of the spring in the mechanism and the ratio of the initial deformation of the spring to the length of the bar in the mechanism increase. Compared to the amplitude-frequency characteristics of Duffing equation, the response amplitude-frequency characteristics of the same kind of harmonic resonance of the two equations exist great deviation. To the motion differential equations of this kind of passive isolation system, it's incorrect to use the product of the amplitude exciting from the displacement and the square of exciting frequency instead of the exciting force amplitude of unit quality as the solution of Duffing equation, theoretically corrects the long wrong practices.Finally, the article analyzes, based on the pseudo-excitation method, the response of the precision instruments in the vehicle under the non-stationary excitations of the road, and optimizes the 1/2 car-quasi-zero-stiffness system through the NCD module of the MATLAB, and finally gets the optimal design parameters of the damping system. The simulation proved that the optimization design of the quasi-zero-stiffness vibration isolation system is correct and feasible.In this paper, there are two innovative points:(1) To the motion differential equations of this kind of passive isolation system, it's incorrect to use the product of the amplitude exciting from the displacement and the square of exciting frequency instead of the exciting force amplitude of unit quality as the solution of Duffing equation, theoretically corrects the long wrong practices.(2)The car-precision instruments model was established. And the dynamic equation of the model was established and analyzed in the non-stationary. The response was obtained and the stiffness was optimized.