Nonlinear Dynamics Analysis And Parameter Optimization Of Quasi-zero Stiffness Air Suspension System With Gas-gas Linkage

The gas-gas linkage quasi-zero stiffness air suspension is a strongly nonlinear system with an air spring to carry the load and air actuators in parallel to provide negative stiffness.There are also pipelines with solenoid valves between the air spring and air actuators.The low dynamic stiffness and high static stiffness is provided for better comfort and road friendliness.This paper analyses the non-linear dynamics of the gas-gas linkage system in both disconnected and connected states and optimizes its parameters to meet the comprehensive performance requirements of the vehicle under different operating conditions.Firstly,the parts of quasi zero stiffness air suspension system are selected based on the stability of the linear quasi-zero stiffness vibration isolator,and the three-dimensional model is established by CATIA.The mathematical model of the nonlinear system is set up based on the basic principles of fluid mechanics and thermodynamics.Then,the stability of the equilibrium points is analyzed using Lyapunov first method,and the qualitative analysis of the attractive region is conducted through the bifurcation diagram and phase diagram.By Taylor series expansion and cell-mapping theory,the attractive region of the system is quantitatively analyzed to obtain the parametric feasible domain under stable conditions.Finally,the performance of the quasi-zero stiffness suspension with the selected parameters under the stability constraint is verified by simulation and experiment.Secondly,genetic algorithm is used to optimize the performance of quasi-zero stiffness air suspension with gas-gas linkage.The optimization rates before and after the optimization are calculated respectively.Under the condition of interconnection,the spring mass acceleration(comfort index)is optimized by 15%,the tyre dynamic load(road friendliness index)is optimized by 12.7%,the dynamic deflection of the suspension(space occupation index)increases by 44.3%,and the adjustable air spring pressure(stability index)is degraded by 32%.Under non-interconnected condition,spring mass acceleration(comfort index)is optimized by 24.9%,the tyre dynamic load(road friendliness index)is optimized by 20.6%,the dynamic deflection of suspension(space occupation index)is degraded by 14.3%,and the adjustable air pressure(stability index)is degraded by 14.6%.Finally,the performance of gasgas linkage quasi-zero stiffness suspension system under stability constraints is verified through simulation analysis and experiments.Finally,a semi-vehicle model is found with the quarter-suspension model verified by experiments in order to further verify the improvement of the quasi-zero stiffness air suspension with gas-gas linkage on the pitch angle and acceleration of the vehicle.Lagrange energy method in multi-body dynamics is used to construct the state equation of semi-vehicle suspension.The simulation showed that the comfort of quasi-zero stiffness air suspension at connected state is better than that at the non-interconnected state,and both two states are better than that of air suspension.