Analysis On The Influence Of Active Power Distribution Stability Of Four-wheel Drive Vehicles And Research On Sliding Mode Variable Structure Control

Aiming at the situation of over-steer/under-steer caused by the attachment conditions of the tires and road surface when the vehicle is turning,this paper takes four-wheel drive vehicles as the research object and adopts the methods of theoretical analysis,modeling and simulation,and hardware-in-the-loop testing.With sliding mode variable structure algorithm as the core control strategy,how the active power distribution of four-wheel drive vehicles affects the steering stability is studied,which solves the problem of oversteer/understeer when the vehicle is turning,so that the vehicle can steer according to the ideal state and improve the steering stability of the vehicle,the research results have certain theoretical significance and practical reference value.The main work of this paper is as follows:(1)The research status of four-wheel drive vehicles at home and abroad is studied,the structure of key components of four-wheel drive vehicle power distribution is analyzed and mathematical models are established,the dynamic model of four-wheel drive vehicle is developed,and Simulink models such as engine,transmission,transmission system and tire are built.Lay a theoretical foundation for the next performance simulation and test.(2)Analyzed how the active power distribution of the four-wheel drive vehicle affects the steering stability,and simulated and analyzed the influence process of the fixed ratio power distribution between the axles/wheels on the yaw rate and the side slip angle of the center of mass in Simulink,providing the following control strategies reference.(3)A power distribution control strategy based on sliding mode variable structure is established.In order not to affect the front wheel steering,and based on the previous simulation results(the power distribution between the wheels has a significantly greater impact on the steering stability than the power distribution between the axles).Simulink and Carsim co-simulation were carried out for the method of power distribution control between the rear axle wheels,which proved the effectiveness of the control strategy.(4)Based on the four-wheel drive vehicle bench built,the NI hardware-in-the-loop platform was used to carry out hardware-in-the-loop tests.Power distribution tests were carried out under single-shift/double-shift steering conditions,which proved that the control strategy proposed in this paper can be very effective.Good to improve the steering stability of the car.