Research On AFS/DYC Integrated Control Of Three-axle Electric Truck

With the development of logistics industry and the requirement of environment protection,the number of electric commercial vehicles is more and more,so it is urgent to improve the lateral stability and safety of commercial vehicles.Active Front Steer(AFS)and Direct Yaw-Moment Control(DYC)are the principal methods of vehicle lateral stability control.The integrated control of AFS and DYC can complement each other,which will greatly improve the vehicle steering characteristics and handling stability.At the same time,the integrated control of AFS and DYC is also of great significance to improve the active safety of vehicles,and thus become the research hotspot.However,because of its large mass,high center of gravity,long body and other characteristics,the lateral stability and steering characteristics of commercial vehicles are inadequate,which are prone to accidents in emergency and complex working conditions.In order to address the problem,the driver model and motor model are built.Based on Truck Sim,the real vehicle parameters are set up.Two upper controllers based on model predictive control(MPC)and Adaptive MPC are designed respectively.The control effects of the two controllers under the conditions of constant speed and constant speed are compared.The design of the lower controller includes the steering characteristics and torque distribution.The fuzzy control is used to fuse the two variable angle transmission ratios based on the constant yaw rate and lateral acceleration gain to complete the design of the steering characteristics.The optimization objective of the torque distribution strategy is to minimize tyre utilization and to compare it with the torque distribution strategy for one-sided braking.Through the co simulation of Truck Sim-MATLAB,the vehicle state response under different working conditions is analyzed.Finally,the hardware in the loop experiment platform of AFS / DYC integrated control for three-axis electric truck is built by Truck Sim and Lab VIEW,and the designed integrated control strategy is compiled and embedded into the hardware in the loop platform for multi working condition test.Research shows that:(1)Two variable angular transmission ratios with constant gain are fused based on fuzzy control.The ideal angular transmission ratio can keep the steering characteristics of the vehicle and improve driving comfort and lateral stability of the vehicle.(2)The optimal torque distribution strategy based on quadratic programming is superior to the tire force distribution strategy,resulting in a 11.5% reduction in the total tire utilization.This strategy can make the distribution of wheel torque more reasonable,improve the stability margin of tyres and the vehicle mobility under complex conditions.(3)Under the condition of constant speed,the vehicle control effect based on adaptive MPC algorithm is better than that based on MPC algorithm,and the control effect of the two control algorithms on high-attached road surface and the medium-high speed is better than that of the low-attached road surface and the low speed.Both integrated control strategies can improve the vehicle handling stability.(4)Under variable speed conditions,the vehicle based on Adaptive MPC algorithm can follow the change of vehicle speed,update the information of vehicle status in time and transfer it to the controller for rolling optimization solution.Compared with the vehicle based on MPC algorithm,the robustness of the adaptive predictive controller is demonstrated and the vehicle state response is decreased by about 20%.It guarantees the AFS/DYC integrated control system to adjust to the change of vehicle speed and improves the handling stability of the vehicle to complex conditions.