Analysis And Optimization Of Vehicle ISD Suspension Handling Stability

With the rapid development of automobile industry,people put forward higher requirements for vehicle handling stability and ride comfort.Suspension connecting wheels and frame is an important system to ensure safe,stable and comfortable driving of automobiles.At present,passive suspension is still the most widely used suspension,so how to improve its performance is the focus of automotive research.In this paper,ISD(Inerter-Spring-Damper,ISD)suspension is taken as the research object,focusing on the parameters design and optimization of ISD suspension,dynamic characteristics,K&C characteristics,geometric structure parameters and bushing optimization,as well as vehicle handling and stability.Aiming at 1/4,1/2 and multi-body dynamic vehicle models,the dynamic characteristics and mechanism of ISD suspension,K&C characteristics and vehicle handling stability are analyzed.Through genetic algorithm,sensitivity analysis and power flow theory,the parameters of ISD suspension components,geometric parameters and bushing at the connection with the frame are optimized,so that the overall performance of ISD suspension is optimized.The main research contents of this paper include:(1)Establishment of 1/4 Vehicle ISD Suspension,determination of ISD Suspension component parameters for Vehicles and optimization of ISD suspension parameters.The dynamic model of 1/4 vehicle ISD suspension is established.Based on dynamic vibration absorption theory,the displacement response amplitude ratio of the main vibration system with damping is deduced,and the influence of mass ratio,natural frequency ratio and damping ratio of ISD absorber on displacement response is discussed.The parameters of ISD suspension components are preliminarily determined according to classical dynamic vibration absorption theory.Based on the difference between ISD and dynamic vibration absorber,a multi-objective optimization function is established,and its component parameters are optimized by genetic algorithm.(2)Establishment of 1/2 vehicle virtual prototype model,analysis of the displacement transfer characteristics between various displacement indexes of ISD suspension and the influence of different component parameters on the driving performance of suspension.The state equation and vibration transfer function of the suspension are deduced.The transmission characteristics of the suspension are studied.The influence of the parameters of each element on the amplitude-frequency characteristics of ISD suspension is analyzed.(3)Analysis of kinematics and compliance characteristics of suspension.The topological relationship between ISD suspension structures is analyzed,and the K&C(Kinematics&Compliance)analysis model of front and rear ISD suspension is established.The K&C characteristics and handling of ISD suspension are analyzed from three aspects:wheel alignment parameters,longitudinal and lateral displacement of suspension,and pitch and roll stiffness,through parallel wheel trevel,opposite wheel trevel and brake/drive conditions.(4)Optimization of structural parameters and bushing parameters of ISD suspension based on sensitivity analysis and vibration power flow theory.Aiming at the deterioration parameters of K&C characteristics and comprehensive performance parameters,the single-objective and multi-objective optimization functions are established,and the sensitivity of different geometric parameters to different performance parameters is analyzed,and the suspension hard-point parameters are optimized according to their sensitivity values.Based on the theory of mechanical-electrical similarity and power flow,the lining is established.The mechanical network diagram of 1/4 vehicle ISD suspension is presented.Thevenin’s theorem in circuit analysis is introduced to calculate the power flow that flows through the ISD shock absorption system to the body,and to optimize the selection of ISD suspension bushing.(5)Establishment of ISD Suspension Vehicle Model,analysis of handling stability of vehicle with ISD suspension based on national standard test and actual working conditions.The multi-body dynamic model of the vehicle with ISD suspension is established.Based on the national standard evaluation criteria for handling stability and actual driving conditions,the vehicle handling stability is evaluated under the conditions of serpentine pavement test,correctness test and overtaking condition,and through depressed pavement.The vehicle body attitude,lateral acceleration and yaw rate are obtained.The stability evaluation index changes with time,compares the handling stability of ISD suspension vehicle with that of traditional passive suspension vehicle,and analyses the handling stability of ISD suspension vehicle.