Modeling And Stability Study Of Multi-Axle EV Based On ADAMS And SIMULINK

Traditional mechanical transmission system is not necessary to EV with in-wheel-motors,which have a lot of advantages that it simplifies the vehicle structure and lower the mass center.As a result, it has become the research focus in the automotive industry. Vehicle test platformhas been developed for multi-axis EV with in-wheel motors at abroad. The paper focuses on themulti-axle electric vehicle steering stability and establishes simulation test platform formulti-body dynamics model based on the ADAMS. Stability controller is designed, whichadopts the torque allocation algorithm, to reduce the tire load. The simulation results show thatthe designed controller can improve vehicle steering stability. The main research contents are asfollows.Firstly, given vehicle actual demand and research target, multi-axle vehicle model isestablished with model car data by use of ADAMS software. The vehicle dynamic model isdivided into steering system, suspension system, motor model, body and cab model, high andlow adhesion road model and drive control file, etc. The simulation test on the high frictioncoefficient road and low friction coefficient road validated the high accuracy of the establishedmodel.Secondly, vehicle hierarchical control strategy is developed based on the structurecharacteristics of the electric vehicle. In the upper controller, PID method is adopted to controlthe deviation between desired velocity and actual velocity to control velocity in real time.Because motor torque could be controlled independently, DYC method based on fuzzyalgorithm is designed. The paper establishes the2DOF reference model to obtain target yawrate and side slip angle. The aim of DYC can achieve the function that make the error betweentarget value and actual value close to zero. Due to the motor number is more than the number ofcontrol variables in the bottom controller, the paper designs torque optimized allocationalgorithm based on the vehicle stability in order to solve the drive torque redundancy controlallocation problem. Meanwhile, the paper considers the impact to vehicle steering stability because of axle loads transfer, the weight coefficient is added to optimized function. The torqueis allocated according to load when the function can’t meet the driving torque optimizationallocation.Finally, the paper implements the offline simulation, which includes the step angle input ofsteering wheel and the sine angle input of steering wheel on high friction coefficient road,middle friction coefficient road and low friction coefficient road. The simulation results showthe yaw rate and side slip angle is controlled the small range based on fuzzy DYC. Due to moredriving torque on the tire of larger vertical force to make the friction force increase, vehicle canretain good body attitude by use of optimized torque allocation algorithm compared to averagetorque allocation. In conclusion, the designed stability control strategy can improve the steeringperformance of vehicle efficiently.