Research On Vibration Technology Of Vehicle Seat Based On Parallel Mechanism

The vibration isolation performance of vehicle seat suspension plays a key role in improving occupant comfort and health.Especially for the construction machinery and vehicles under the condition of non-pavement pavement,there are many low-frequency road excitations.Among all kinds of road excitation,low-frequency vibration is the most harmful to human health and even causes different degrees of human injury.At present,the traditional linear seat suspension which is widely used in order to ensure higher load-carrying capacity and smaller static displacement is more suitable for general linear spring with higher natural frequency,so the isolation performance under low frequency excitation is poor.But the nonlinear seat suspension of parallel mechanism with high static stiffness and low dynamic stiffness can solve this problem.The nonlinear seat suspension of parallel mechanism has the advantage of small static displacement and low natural frequency,so it is suitable for isolating low-frequency and ultra-low-frequency vibration.However,due to the restriction of the size design and the seat regulations,the parallel mechanism and seat have high static stiffness and low dynamic stiffness,which makes the parallel mechanism have the characteristics of high dynamic stiffness and low dynamic stiffness.Therefore,the research on the optimization design and vibration isolation performance of the seat suspension of the parallel of the mechanism is of great theoretical and engineering significance to improve the ride comfort of automobile.The work completed is as follows:(1)Modeling and statics analysis of seat suspension of parallel mechanism analysis.Based on the principle of parallel positive and negative stiffness,a new type of seat suspension of parallel mechanism is designed.It is established that the stiffness regulating mechanism of high-static stiffness based on connecting rod spring is in parallel with the elastic element of low-dynamic stiffness arranged vertically.Firstly,the static analysis of the low stiffness regulating mechanism in the parallel mechanism is carried out,and the influence of main parameters on the recovery force and stiffness of the stiffness regulating mechanism is analyzed by using the derived formulas of recovery force,stiffness and displacement.Then,the static analysis and stiffness variation analysis of the vibration isolation system of the seat suspension after parallel connection are carried out,and the influence characteristics of different parameters on the recovery force and stiffness of the parallel mechanism are found out.It is of great significance to optimize the design of seat suspension of parallel mechanism to exert high static stiffness and low dynamic stiffness.(2)The optimum design of suspension seat parameters of parallel mechanism,the effect of different parameters of parallel mechanism and stiffness of parallel mechanism.The optimization algorithm of parameters coordinated processing is selected.The accelerated particle swarm optimization algorithm based on the evolution of the constrained extremum optimization problem is a trade-off the parameters of the seat suspension.An efficient design method for compromise to achieve ideal working conditions.Through the optimization of the seat suspension parameters of the parallel mechanism,the final parameters meet the requirements of automobile seat design regulations and size design,and the minimum dynamic stiffness of the seat suspension vibration isolation system of the parallel mechanism tends to zero,that is to say,it tends to quasi-zero stiffness.(3)Dynamic modeling and analysis of seat suspension of parallel mechanism.The nonlinear dynamic equation under simple harmonic excitation is established,and the amplitude-frequency response of the suspension system is compared with the numerical solution based on Runge kutta method based on the calculation of harmonic balance method,and the accuracy of the steady-state response of the dynamic equation is verified.Secondly,the necessary stability analysis of the dynamic system is carried out to determine the stability boundary condition and the condition of restraining jumping phenomenon.Finally,the effects of different structural parameters on the response amplitude,displacement transfer rate and initial vibration isolation frequency are analyzed.It is verified that the parallel mechanism seat suspension has better low-frequency vibration isolation performance and wider vibration isolation frequency band than the traditional linear seat suspension,and even achieves the effect of full frequency vibration isolation.(4)Seat simulation analysis of parallel mechanism.Considering the application of parallel mechanism seat is applied in different working conditions,a seven degrees-of-freedom(DOF)of the human-seat-car coupled model is established.The vibration coupling parameter model is composed of a quarter vehicle model,seat suspension and four DOF human body lumped parameter model.The responses of human body under harmonic base excitation,road impulse load excitation,multi-frequency combination excitation and random excitation based on white noise method are obtained by MATLAB/Simulink simulation.The evaluation index of vibration comfort is introduced,and the vibration isolation performance of the parallel mechanism seat is quantitatively analyzed.(5)Innovative design and experimental analysis of parallel mechanism seat suspension.The innovative design of the parallel mechanism seat suspension is carried out,and the double spring design is adopted on the basis of the original single spring of low-dynamic stiffness regulating structure.Based on the optimized parameters,the physical prototype of the seat suspension was machined,and the experiments were carried out at fixed frequency and sweep frequency.The experimental results show that the vibration isolation performance of the parallel mechanism seat suspension is better than that of the equivalent linear seat suspension without low-dynamic stiffness adjustment and has better low-frequency vibration isolation performance.