| Tire force control is the most direct and effective vehicle active safety technology at present,but the tire force is greatly affected by road surface conditions,so it is the key link in the design of vehicle dynamics stability control system to obtain the environmental information such as tire-road friction coefficient in real time and accurately.Distributed driven electric vehicles(DDEV)have outstanding advantages in energy saving and emission reduction,structural arrangement and vehicle dynamics control,and can easily and accurately obtain the electrical parameters of the driving motor,the pressure of the hydraulic braking system,Important operating parameters such as battery charge status(SOC)and rotational speed provide a reliable source of information for accurate estimation of tire-road friction coefficient.Therefore,taking DDEV as the research object,this paper studies the new method of estimating tire-road friction coefficient by using the parameters of electricity and hydraulic,the main contents are as follows:(1)The torque distribution method of electric vehicle.The fuzzy decision model of driver’s intention identification is established,and the additional yaw torque sliding mode controller based on yaw rate and sideslip angle is designed respectively,and the control strategy of driving torque distribution is designed by using the weight coefficient,combining the wheel dynamic,static load and additional transverse pendulum torque,and the front and rear axle power fixed ratio allocation method,brake strength and battery SOC design braking torque allocation control strategy.(2)The method of tire-road friction estimation which fuses the parameters of electro-hydraulic and so on.The nonlinear three-degree-of-freedom dynamic model,hub motor model and brake model of distributed drive electric vehicle are established.Based on the observation equation of the adhesion coefficient of the pavement using the electro-hydraulic parameters,this paper presents an estimation compensation method for the tire-road friction coefficient under the driving/braking condition based on the change rate of the driving/braking torque and the slope of the sliding(shifting)rate curve,and compensates for the estimation of the tire-road friction coefficient under the steering condition according.(3)The decision method of vehicle driving condition.The method of extracting the characteristic information of vehicle driving state is established,and the weight decision mechanism of tire-road friction estimation under the condition of single working condition is designed.The validity of the proposed estimation method is verified by the co-simulation of Carsim and Matlab.The simulation results show that the proposed method of tire-road friction coefficient estimation has the advantages of high estimation accuracy,strong self-adaptability and strong robustness,and provides an important solution for improving the control performance of vehicle dynamics stability. |
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