Study On Hybrid Four-wheel Drive Vehicle Traction Control

The deterioration of the global environment, the energy crisis and other problemsspawned fuel cell vehicles, pure electric vehicles and hybrid vehicles. At present, thereare various hybrid vehicles with all kinds of powertrain solutions in vehicle market, butmost of them are in the form of front-wheel drive or rear-wheel drive. With theincreasing requirements of vehicle users, on vehicle fuel economy, power performance,stability and etc., some foreign vehicle companies with high level hybrid vehicletechnology have released hybrid four-wheel drive vehicles. Just like the conventionalfour-wheel drive vehicles, the traction control is also significant to hybrid four-wheeldrive vehicles.This paper took a hybrid four-wheel drive vehicle as the research object, thenstudied torque distribution control strategy and traction control strategy for drivingconditions of this vehicle, designed a traction controller and conducted a simulation oncontrol strategies. The primary research content consists of the following aspects:①Established vehicle model, engine model, drive motor model, electro-hydrauliclimited slip differential model, powertrain system model, PAC2002magic formula tiremodel and auxiliary calculation model.②Analyzed the work mode of this vehicle; proposed a method to distribute torqueto front and rear drive axle; formulated energy management control strategy and torquedistribution control strategy; allocated the driver requested torque and traction controlrequested torque to each drive axle and each power source.③According to the relationship between road adhesion coefficient and drivewheel slip ratio, determined the optimum slip ratio of drive wheel; formulated tractioncontrol strategy and the trigger/exit decision logic of traction control system; designed atraction controller to realize above control strategies.④Established an offline simulation model for this vehicle by using MATLAB/Simulink software, simulated and verified those control strategies in complex roadconditions.The simulation results indicated that: in complex road conditions, the torquedistribution control strategy and traction control strategy formulated in this study caneffectively suppress the excessive slip of the drive wheels, make full use of current roadadhesion conditions，improve the acceleration performance, avoid the movement interfering and power cycling of the front and rear drive axles when they driveindependently.