Research On ABS/ESP And Coordinated Control Based On Hub Motor Vehicle

Due to the increasingly prominent energy and environmental problems,in the field of automotive research,researchers around the world have shifted their focus from traditional fuel vehicles to new energy vehicles.With the increasingly complex driving environment,the application and development of active safety control technology in electric vehicles has become particularly important,especially Anti-lock braking system(ABS)and Electronic Stability Program(ESP).ABS and ESP,as the core electronic systems of vehicle stability control,have always been a research hotspot.Both can independently control the wheel braking force.Without cooperative control,actuators interfere with each other and the controller cannot achieve global optimization.In this thesis,the experimental prototype vehicle of in-wheel motor drive developed by our research group is taken as the research object.Firstly,the vehicle dynamics modeling and road adhesion coefficient estimation in ABS and ESP control systems are studied.Then,the ABS and ESP control algorithms are studied respectively.Finally,the coordination and hierarchical coordination control strategies of ABS/ESP are studied,and the simulation and experimental verification are carried out.Specific studies are as follows:(1)Study on estimation of road adhesion coefficient.Road adhesion coefficient is an important parameter for ABS and ESP control strategy.Considering the tire state response and slip characteristics,two methods of road adhesion coefficient estimation based on tire slip characteristics and vehicle dynamic parameter analysis are proposed.The method of tire slip characteristics is mainly to analyze the relationship between slip rate and adhesion coefficient by Burckhardt tire model.The recursive least squares method and Fuzzy logic algorithm are used to estimate the road adhesion coefficient,and the estimation model is verified on the experimental platform.The method based on vehicle dynamics parameter analysis is to estimate the adhesion coefficient by extended Kalman,unscented Kalman and particle filter according to the improved Dugoff tire model,and the accuracy of algorithm is verified by real vehicle experiments.(2)Study on ABS Control.According to the relationship between slip rate and road adhesion coefficient,ABS controller based on road recognition is designed.According to different road adhesion conditions,the optimal slip rate of the current road is calculated.Taking the optimal slip rate as the control object,the ABS controller based on PID,sliding mode variable structure and robust control algorithm is designed.According to the established vehicle eight-degree-of-freedom model,the optimal slip rate calculation module and ABS controller are established,and the simulation experiment is carried out.According to the comparison of the simulation results,the sliding mode controller is selected as the ABS controller in the coordinated control.(3)Study on ESP Control.By analyzing the causes of vehicle instability,the unilateral wheel braking torque distribution strategy suitable for in-wheel motor drive vehicle is determined.According to the selected control parameters(sideslip angle and yaw rate),the ESP controller based on PID,fuzzy logic,optimal control and fuzzy sliding mode algorithm is designed,and the simulation experiments are carried out under different road conditions and different vehicle speeds.According to the comparison of the simulation results,the fuzzy sliding mode controller is selected as the ESP controller in the coordinated control.(4)Study on ABS/ESP coordinated control.By studying the working state of ABS and ESP,the timing of ABS and ESP intervention is analyzed,and the corresponding ABS/ESP coordinated control strategy and hierarchical coordinated control strategy are formulated,and simulation experiments are carried out on different road surfaces and different vehicle speeds.The simulation results show that hierarchical coordinated control can improve the braking stability and driving safety of the vehicle under different conditions.