| Distributed-drive electric vehicles have their drive systems arranged independently within each wheel,resulting in a significantly streamlined chassis configuration,further improving transmission efficiency and facilitating a rational layout of the vehicle space.However,there is also a serious fail-safe problem,as each wheel drive system is completely independent,and if one side of the system fails during feed-back braking,the whole vehicle will be instantly destabilised by the additional transverse moment generated by the unilateral braking force.A braking force compensation and stability control strategy based on the feed-back braking system and the Electronic Park Brake(EPB)is proposed to address the vehicle safety problems caused by single-side failure under feed-back braking conditions.The main research of this paper includes:First,Based on the structural characteristics of the distributed drive vehicle,a sevendegree-of-freedom dynamics model of the front-wheel drive vehicle,a hub motor model,a model of the electric power-assisted hydraulic braking system and a battery model are constructed,and the accuracy of the constructed models is verified;the single-side feedback braking failure mechanism is analysed through the constructed models,and the destabilisation characteristics of the vehicle after failure and the inadequacy of the "torque cut-off + hydraulic compensation" control are verified through simulation.Secondly,Based on the working principle of the electronic parking brake system,the mathematical model of the electronic parking brake system is derived and a complete simulation model is built using AMESim;for the characteristics of the electronic parking brake system,a self-anti-disturbance controller is designed and the effectiveness and accuracy of the control strategy is verified through simulation.Then,a braking force distribution strategy to maximize energy recovery is developed;for the vehicle instability problem caused by the single-side failure of the feedback brake,an overall vehicle stability control strategy based on model predictive control is proposed,and the effectiveness of the built control strategy is verified through joint simulation;To address the issue of smooth electro-hydraulic switching at the end of feed-back braking,a dynamic coordinated control strategy is developed and its effectiveness verified.Finally,hardware-in-the-loop control tests were designed using hardware equipment such as NI-PXI and EPB systems,including electronic parking brake system clamping force control tests and feedback brake single-side failure brake compensation stability control hardware-in-the-loop tests.The test results show effectiveness of the control strategy in this paper.Based on theoretical,simulation and experimental analysis,the analysis of the singleside failure mechanism of feed-back braking and the development of control strategies are carried out,which provide theoretical reference and engineering application value for the in-depth study of braking failure control of distributed drive vehicles. |
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