Research On The Absolute Posture Sensing Principles Of A Class Of Quasi-Zero-Stiffness-based Vibration Systems

Automotive intelligent technology can provide people with more comfortable,safe,convenient and intelligent services,which is an important development direction of modern automobiles.As a key component of automotive electronic control systems,vibration sensors play an important role in the intelligent development of automobiles.Many automotive low-frequency active vibration control systems such as active vibration suspension,active seats,and vibration isolation of precision instruments for special vehicles usually require accurate,real-time absolute vibration posture feedback for better performance.However,traditional linear absolute vibration displacement and angular displacement sensing techniques often have defects in installation,accuracy,and cost.It is difficult to balance accuracy,real-time performance,and cost when directly calculating or indirectly estimating the vibration posture through inertial measurement technology such as accelerometer or gyroscope.Therefore,it is imperative to study a class of high-performance low-frequency absolute vibration posture sensing theory.In this paper,a class of convenient,cheap and high-precision absolute vibration sensing systems is constructed taking the great potential advantage of geometric nonlinear structures in low-frequency vibration systems.Based on the study of the dynamics of a quasi zero stiffness system with excellent low frequency characteristics,some theories and methods that can be used to effectively measure the absolute vibration displacement and angular displacement of the vehicle have been put forward.The main contents and achievements of this paper can be summarized as follows:(1)A single degree of freedom quasi zero stiffness vibration sensing system with geometric nonlinear damping is developed to measure the absolute vertical displacement and torsion angular displacement using a spring-roller negative stiffness mechanism.The amplitude accuracy and phase difference expressions of the sensing system are deduced.The effect of pre-compression of compression spring,linear damping coefficient and amplitude of measured signal on the measurement performance are studied,and the dynamic measurement performance under different input are given.The problem of multiple solutions that may exist in the sensor system is also studied.A test platform is built to verify the effectiveness of the vertical quasi-zero-stiffness sensing system,and a preliminary test of the measurement performance is conducted.The test results show that the resonant frequency of the corresponding linear system can be reduced from 2Hz to 1.188 Hz by introducing a spring roller negative stiffness mechanism.For vibration excitation above 1.5 Hz,the amplitude error of the sensor system is less than 10%,and the phase error is less than 25°.The research indicated that by the geometric nonlinear damping,the frequency range of the multi solution phenomenon can be effectively controlled without loss of measurement precision,thus the range of frequency measurement and the range of amplitude measurement can be expanded.(2)A 3-axis torsion quasi-zero-stiffness angular vibration displacement sensing system is proposed.The system includes geometric nonlinear parts of spherical shell,spherical core and spring,and a photoelectric relative angular displacement measurement part.The stiffness characteristics of the sensing system under small torsional vibration and small horizontal vibration are studied.Based on the harmonic balance method,the amplitude accuracy and phase accuracy of the sensor system under different excitation are analyzed accordingly.The numerical simulations of the measurement performance of the sensing system under torsional harmonic excitation,periodic excitation and random excitation are given.(3)A six degree of freedom quasi-zero-stiffness vibration posture sensing system is proposed based on the Stewart configuration and the single degree of freedom quasi-zero-stiffness system as its leg.The kinematics characteristics of Stewart platform is analyzed,and the coupling stiffness characteristics of six degree of freedom system is studied.The dynamic simulation of the six degree of freedom sensing system is carried out,and the expression of the measurement accuracy of the sensing system is given.The influence of different measurement amplitudes and coupling stiffness on the measurement performance is analyzed,and the measurement performance of the sensing system under different excitation is numerically simulated.