| With the progress of science and technology and the improvement of people’s quality of life,the requirements for vehicles are higher,and the ride comfort should be improved under the premise of ensuring the operation stability of vehicles.Suspension system is a connection structure composed of body,frame and wheels,and its dynamic characteristics directly affect the safety and ride comfort of the automobile.The design process requires to improve the comfort of the vehicle in operation as far as possible under the premise of ensuring the safety performance,which is of great significance to the study of the suspension system.The main contents of this paper are as follows:(1)Based on the fractional-order Bingham model of MR fluid damper,the single-degree-of-freedom(DOF)1/4 vehicle suspension system was modeled.The forced vibration of nonlinear vehicle suspension system with MR fluid damper under harmonic excitation was studied.The primary resonance response of the suspension system is studied,and the approximate analytical solution is obtained by means of the average method.The amplitude-frequency response equation of the steady-state solution of the system is solved,and the stability conditions of the system are obtained.The amplitude-frequency response curves of the numerical solution and the analytical solution were drawn by MATLAB to verify the accuracy of the approximate analytical solution.The influence of fractional order and MR fluid damping coefficient in fractional-order Bingham model on the dynamic characteristics of suspension system is analyzed in detail.By comparing the hysteretic damping forces of integer-order and fractional-order Bingham model,it is shown that the fractional-order model can better describe the hysteretic characteristics,which provides a reference for the application of fractional-order magnetorheological fluid model in vehicle suspension system.(2)A fractional-order Bingham model based on magnetorheological damper is used to study the vibration control of a 1/4 degree of freedom nonlinear vehicle suspension system under harmonic excitation.The main resonance response of the suspension system under semi-active control is analyzed,and the approximate analytical solution of the system is obtained by means of the average method.The amplitude-frequency response equation of the steady-state solution of the system is solved,and the stability conditions of the system are obtained.By drawing the amplitude-frequency response curves of the numerical solution and the analytical solution,the correctness of the approximate analytical solution is verified.The influence of semi-active control on ride comfort was studied,and a combined control strategy of passive control and semi-active control was proposed,and the influence of vibration control parameters on the control effect was analyzed.The analysis results show that the combined control can improve the ride comfort of the vehicle and effectively control the vibration amplitude of the sprung mass of the suspension.(3)Fractional-order Bingham model of magnetorheological fluid damper was used to model the two-DOF 1/4 vehicle suspension system,and dynamics analysis was carried out based on the two-DOF nonlinear vehicle suspension system.The dynamic response of the two-degree-of-freedom model under the ground harmonic excitation is studied,and the approximate analytical solution of the system is obtained by means of the average method.The amplitude-frequency response equation of the steady-state solution of the system is solved,and the stability conditions of the system are obtained.The amplitude-frequency curve is drawn by MATLAB programming,and the numerical solution is compared with the analytical solution,and the fitting effect is very good.(4)The dynamics analysis of vehicle suspension control system with two degrees of freedom was carried out by analytical method.The control effect of the semi-active control on the two-degree-of-freedom model is studied,and the approximate analytical solution of the system is obtained by means of the average method.By drawing the amplitude-frequency curve,the numerical solution fits well with the analytical solution.By comparing the amplitude-frequency curves of the semi-active control and the passive control,it is found that the semi-active control can reduce the deformation of the suspension at the first resonant frequency,but it can increase the deformation at the second resonant frequency.The RMS value of acceleration of suspension sprung mass is drawn,and it is found that although the semi-active control increases the deformation of suspension at the second resonance frequency,the RMS value of acceleration of suspension sprung mass decreases to some extent.The results show that the combination control can not only improve the ride comfort,but also reduce the deformation of the suspension. |
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