Key State Parameter Estimation And Method For Distributed Electric Vehicles

This paper is supported by the project of National Natural Science Foundation of China,which named "Integrated Development and Application of Dynamic Simulation Software for Distributed Drive Electric Vehicles".In this study,The distributed electric vehicle driven by wheel motor is used as the research object.Based on the dynamics of vehicle system and its control principle,a distributed drive vehicle model of seven degrees of freedom is constructed.In addition,this study designs a vehicle state observer based on the trackless Kalman filter theory,and builds a joint simulation platform for Simulink and CarSim.Finally,a vehicle state quantity test system and a wheel motor-driven test vehicle are designed for verification.The main contents of this article are as follows:(1)The establishment of a co-simulation platform Based on Simulink and Carsim software,a distributed driving electric vehicle co-simulation platform including Simulink motor model and Carsim vehicle model is built in this paper.By disconnecting the power source of the CarSim traditional diesel vehicle model,the Simulink motor model is connected to the model,and the co-simulation platform is built.Then the model is verified by the co-simulation experiment.The co-simulation of double shift line experiment and serpentine winding pile experiment shows that both the Carsim vehicle model and the Simulink motor model have good response characteristics.The establishment of this co-simulation platform provides the basis for subsequent vehicle state estimation.(2)The establishment of a 7-DOF vehicle model and the design of vehicle state observer Based on the co-simulation platform,a 7-DOF nonlinear vehicle dynamics model including vertical,horizontal,yaw and four-wheel rotation was constructed by simulink software,which is compared and verified by CarSim vehicle model.When designing the trackless Kalman filter state observer,the key parameters such as the longitudinal speed,lateral speed,yaw rate,longitudinal acceleration and the lateral acceleration are estimated,which takes the steering wheel angle,wheel motor torque and wheel speed as inputs.Finally,the simulation experiments are performed on the observer with double shift conditions with high adhesion coefficient and double shift conditions with low adhesion coefficient.Simulation results:The absolute error of the state estimation is within 0.15%for high adhesion coefficient road surface,and within 0.2%for low adhesion coefficient road surface,which shows that the established vehicle dynamics model is accurate and effective,and can reflect the state of the vehicle in real time.(3)The construction of vehicle state quantity test system The variables that need to be measured in this paper include the wheel motor torque,the steering wheel angle,the wheel speeds of the four wheels,and the key state quantities to be estimated include longitudinal speed,lateral speed,yaw rate,longitudinal acceleration,and lateral acceleration.Since the torque of the wheel motor is not easily measured,it is converted into the current and voltage of the in-wheel motor,which are measured by the self-designed current and voltage signal acquisition devices;The steering wheel angle signal is measured by the force steering wheel installed on the original steering wheel of the car.The wheel speed signal is obtained by the relative motion between the ring gear installed in the rotating part of the axle and the wheel speed sensor installed in the non-rotating part;The key state quantity to be estimated is measured by the attitude and orientation integrated navigation system(product model:XW-ADU5630),which mainly includes the high-precision MEMS gyro,the accelerometer and the attitude measurement algorithm(4)The experimental verification of key state parameter observation methods The production of test vehicle is based on a domestic electric vehicle.First of all,the original pre-precursor mode is changed to four-wheel independent mode.Then the steering knuckles,lower control arms,shock absorbers and brakes of the front and rear suspensions are modified to facilitate the installation of the drive motors.The reasonable assembly of the wheel motor system and suspension system solves the problem of increased wheelbase and unsprung mass In this way,the safety and good sports characteristics of the test vehicle during the actual vehicle test are guaranteed.