Research on Torque Distribution Control for Four Wheel Drive Vehicle under Steering Condition
|Keywords||Four Wheel Drive Vehicle Torque Distribution Yaw moment ControlStrategy Simulation|
With the development of automotive technology, the performance of vehicle power,handling and stability, and safety is required more and more higher. Since four wheeldrive technology can take full advantage of the wheels’ adhesion force, vehicle canobtain the greatest possible driving force, so more and more limousines and sport utilityvehicles are beginning to use this technology. This paper are studied by light four wheeldriving vehicle, torque distribution control strategy under steering situation isparticularly studied in this paper. It can actively distribute driving force between left andright wheel in rear axle to improve lateral motion of vehicle body, thus inhibit the trendof oversteering and understeer and improve the performance of vehicle handlingstability and safety. The mainly research work carried on the following：①Foreign four wheel drive technology was analyzed. Four wheel drive torquedistribution structure was confirmed. The torque distribution characteristics anddifferential characteristic of inter-axle torque distribution device and wheel torquedistribution device was analyzed. Vehicle coordinate system and main structure ofdynamics model for four wheel drive vehicle were confirmed, and vehicle dynamicmathematical models were established. These models includes engine model, drivelineand wheel dynamics model, tire model, vehicle model and other auxiliary calculationmodule, which provided the foundations for building torque distribution control systemof off-line simulation platform.②The influence of inter-axle torque distribution and wheel torque distribution onvehicle driving stability were analyzed by using tire friction circle. The general structureof vehicle torque distribution control strategy was designed by using idea of hierarchicalmodular, the calculation method of desired yaw rate and desired sideslip angle based ontwo degrees of freedom linear vehicle model was confirmed. Sideslip angle estimationalgorithm based on the full-dimensional state observer is designed. Besides, vehiclespeed, road adhesion coefficient and wheel vertical load estimation algorithm weredetermined. A calculation algorithm of target yaw moment based on sliding modecontrol was developed. Torque distribution control algorithm for four wheel drivevehicle based on yaw moment distribution was proposed.③Based on four wheel drive vehicle model and yaw moment distribution controlalgorithm, torque distribution control strategy for four wheel drive vehicle off-line simulation platform are carried up by Matlab/Simulink. Off-line simulation for fourwheel drive vehicle torque distribution control strategy is conducted in typical steeringconditions. The simulation results indicate: The torque distribution control strategyduring different conditions in this paper can distribute actively driving force betweenleft and right wheel in rear axle according to vehicle state, inhibit effectively the trendof vehicle oversteer and understeer and improve the performance of vehicle steering andhandling stability.