Research On Composite Braking And Fault Tolerance Control Of Multi-axle Independent Electric Drive Vehicles

Multi-axle heavy load vehicle is widely used in military field and engineering because of its excellent transport capacity.In recent years,due to the continuous development of electric vehicle technology,Multi-axle electric drive vehicles have emerged at the historic moment,with the huge advantages of low pollution,low vibration and noise,high energy efficiency and fast control response.However,the military multi-axle vehicle has a long body and the number of axles is generally more than four,resulting in a large dead weight and load.At the same time,due to the relatively complex road conditions,the military multi-axle vehicle has higher requirements for its own mobility,which makes the military multi-axle vehicle has higher energy consumption and higher requirements for vehicle operating stability.Therefore,in order to reduce the energy consumption of the multi-axle electric drive vehicle and improve its endurance,it is of far-reaching significance to study the energy-saving control strategy under the current conditions.Based on the national key research and development project "Multi-system Efficient integrated hub motor action module and vehicle torque vector distribution technology"(project No.2021YFB2500703),this paper takes a 16×10 hub motor driven vehicle as the research object,and conducts indepth research on its composite braking and fault-tolerant control.The main research contents are as follows.In this paper,the braking system of the 16×10 wheel motor driven vehicle is analyzed,and the Amesim model of the electro-hydraulic composite braking system is built based on the relevant parameters of the braking system,and the response characteristics of the system are analyzed by simulation.The results show that the response characteristics are in line with the requirements of engineering practice.In order to verify the reasonableness of the hydraulic brake system model,the bench test of the hydraulic circuit brake system was carried out.Based on the single wheel hydraulic circuit system,its response characteristics under step input and emergency braking conditions were tested.The test results show that the response time of the hydraulic braking system is between 0.1-0.2s,which conforms to the requirements of relevant laws and regulations,and also shows that the hydraulic braking system model has a strong rationality.In addition,the 39-degree-of-freedom vehicle dynamics model was built using Matlab/Simulink software,which laid the foundation for the subsequent control strategy co-simulation verification.This paper builds a compound braking and fault-tolerant control strategy model for the 16×10 hub motor driven vehicle studied.The overall structure can be divided into three layers,from top to bottom are the perception layer,the control layer and the executive layer.Among them,the control layer is divided into three modules according to different problems: The first module is an electro-hydraulic composite braking force distribution strategy based on axle load.By comparing various inter-axle braking force distribution methods and combining with the structural characteristics of the vehicle studied,an equivalent four-axis model based on axle load is established to distribute inter-axle braking force.First,it determines whether the electric mechanism force can participate in braking according to the driver’s expected braking intensity,speed and battery state.The motor braking torque is evenly distributed,and then the hydraulic braking torque of each shaft is distributed according to the intershaft braking force distribution strategy.The second module is the coordinated control strategy of electro-hydraulic composite braking force.Firstly,the braking intensity correction strategy is established for the pressure building stage,and then the coordinated control strategy based on feedforward feedback control algorithm is developed for the braking mode switching stage.The third module is faulttolerant control strategy.According to different forms of motor failure during braking,two control strategy modules of active and passive fault tolerance are developed respectively.Combined with Amesim and Matlab/Simulink software,the combined braking and fault-tolerant control strategy model is verified by co-simulation.The simulation results show that the proposed electro-hydraulic composite braking force distribution strategy based on axle load distribution can provide sufficient braking torque during vehicle braking.The braking torque distribution of each axle is reasonable and consistent with the calculation results of axle load.Meanwhile,the energy recovery rate is also at a high level.With the participation of braking force coordination control strategy,the braking impact decreases by 45.82% and 81.17% during the pressure building stage and the braking mode switching moment,respectively,and the braking ride comfort is significantly improved.The proposed fault-tolerant control strategy can reduce the maximum yaw velocity and lateral displacement of the vehicle by more than 95% and 98% respectively under various motor failure conditions during braking,which effectively improves the braking stability of the vehicle.