The Research On Vehicle-ultra Platform With Low Frequency And Ultra-low Frequency

With the continuous improvement of Chinese scientific and technological strength,The size and weight of precision equipment are increasing,and the structure tends to be precise and complex,more and more high requirements are put forward for the smoothness of the road transportation process of precision equipment.The tudies have shown that the vibration of vehicles transported by road is mainly low-frequency ultra-low-frequency vibrationd which tributed between 0hz-25 hz.However,the traditional isolation system has the characteristics of high starting vibration isolation frequency and resonance problem,and can't solve the problem of low frequency vibration isolation of less than 10 hz frequency.From the need for the smooth transportation of precision equipment,at present,it is urgent to design a hyperstable platform with the characteristics of low-frequency and ultra-low-frequency vibration isolation in all three directions to improve the technical level and the maturity in the field of ultra-low frequency vibration isolation and promote the improvement of transportation quality of precision equipment in China.This paper is based on a theory of SD oscillators with geometrically nonlinear characteristics presented in 2006 by Q.J.Cao of Harbin Institute of Technology.A new model of low frequency and ultra-low frequency vibration isolation with quasi-zero stiffness with three degrees of freedom is proposed and demonstrated combining the theoretical derivation with simple harmonic excitation and numerical calculation and virtual prototype simulation technology.According to the results of the demonstration and the actual situation of the project,Design the 3 DOF low frequency and ultra-low frequency Isolator with quasi-zero stiffness,and conducted experimental verification.The main contents of this paper are as follows:Firstly,the theoretical model with the characteristics of low-frequency and ultralow-frequency in 3 DOF is established based on the theory of SD oscillator.Analyzing the motion differential equation and stiffness equation of the model to obtain the parameter ratio of its quasi-zero stiffness.The amplitude frequency characteristic and acceleration transfer rate and absolute displacement transfer rate under the simple harmonic acceleration excitation are obtainned by means of the averaging method.The influence of different parameters on amplitude frequency characteristics and acceleration transfer rate and absolute displacement transfer rate are discussed.Secondly,Determine the relevant physical parameters of the low frequency and ultra-low frequency Isolator model based on the theoretical derivation and the vibration of vehicles and the corresponding bearing capacity of vibration isolators during road transport.A virtual prototype simulation based on multi-rigid dynamics software Adams is presented for this model.Enterring random spectrum of vehicle vibration in threedirections to get the response indexes in three directions and verify the good vibration isolation performance of low frequency and ultra-low frequency vibration isolation theory.Finally,Design the low frequency and ultra-low frequency Isolator with three degrees of freedom according to the results of theoretical model analysis and simulation analysis and the knowledge of mechanical design.Carring out vibration experiments and impact experiment and thrust experiment separately to evaluation of the design accuracy of the vibration Isolator.We can get the conclusion that the vibration Isolator of low-frequency and ultra-low-frequency has the lower initial isolation frequency and the larger decays comparing with the traditional linear Isolator under the same excitation input conditions,and it can isolate the vibration of the vehicle more effectively to ensure the safe transportation of precision instruments.