Optimization Design And Coordinated Control For Active Geometry Suspension

People’s requirements for vehicle handling and stability are constantly improving.Active geometry suspension can improve vehicle handling stability by controlling vehicle camber and toe angle.At present,active geometry suspension uses actuators to control single wheel alignment parameters and achieves good results.In order to improve the efficiency of active geometry suspension and understand the performance potential of it,this paper explores the optimal design and coordinated control of active variable structure suspension which simultaneously adjusts camber and toe angle to improve vehicle dynamics performance.In this paper,the optimization design and control strategy of active geometry suspension are studied,focusing on the optimization of actuator space position,modeling of the influence of camber angle and toe angle on lateral force and actuator control strategy.The results provide an optimization method of active variable structure suspension under multiple actuators,which is helpful to reduce the coupling of camber angle and toe angle under multiple actuators and improve the efficiency of active geometry suspension.The tire lateral force model of active geometry suspension is established to understand the performance potential of active geometry suspension.Aiming at the lateral stability of vehicle when turning at high speed,the coordinated control strategy of camber and toe actuator is proposed.The main contents and conclusions are as follows:1.Active variable structure suspension modeling and optimization design;First,the sensitivity analysis of the suspension hard point is carried out,and the hard point position sensitive to the camber angle and toe angle is found as the outer mounting point of the actuator;then,the active geometry suspension model is established,and the effectiveness of the actuator is verified;finally,the multi-objective optimization method is used to determine the inner mounting point position of the actuator,effectively reducing the coupling of camber angle and toe angle,and the efficiency of active geometry suspension is improved.2.The effects of camber and toe on lateral force;First,the theoretical tire model is described,and the relationship of the camber,toe and lateral force of the tire is obtained;then,the vehicle simulation is carried out,and the range of camber and toe changes under different working conditions is studied;then,the camber and toe are adjusted,and the distribution diagram of the lateral force of the tire under different working conditions is obtained;finally,the tire side under the active geometry suspension is established.The radial force model can reflect the numerical relationship among camber,toe and tire lateral force.3.Influence of active variable structure suspension on handling stability;First,the selection of steering stability evaluation indexes is carried out to provide the basis for the subsequent simulation and analysis;then,the variation rules of each index are studied under the action of camber actuator alone,toe actuator alone and two actuators together: camber actuator has a greater impact on the centroid sideslip angle,steering wheel angle and roll angle,and has a greater impact on the longitudinal acceleration The influence of lateral acceleration and yaw rate is relatively small;the toe actuator has a greater impact on the centroid sideslip angle and steering wheel angle,and a smaller impact on the longitudinal acceleration,lateral acceleration,roll angle and yaw rate;finally,the interaction effect of the two actuators is compared with that of the single actuator.For the indexes other than the roll angle,the interaction effect from strong to weak is: camber and toe act at the same time,toe act alone and camber act alone.For the roll angle,the camber actuator has a good effect,but the toe actuator has a little effect.4.Coordinated control strategy of camber and toe actuator;First,the structure of active geometry suspension coordinated control system is introduced;second,the lateral motion state of vehicle is determined by energy phase plane method,and the trigger condition of actuator is determined;then,the two degree of freedom vehicle dynamics model is established to solve the reference lateral force;then,the camber and toe distribution strategy is designed to achieve camber and toe distribution,and the table is obtained by combining the vehicle state;finally,the simulation results show that the active geometry suspension can keep the energy phase trajectory in a safe area all the time.In the double line change case,the maximum tire lateral force is higher than the original vehicle 6.5% when the active camber and toe in start to play a role,the peak value of the side slip angle of the vehicle is lower than that of the original vehicle 45.5%,the valley value is higher than the original car 46.4%.