| The distributed drive electric vehicle with the in-wheel motor as the drive unit eliminates the complex power transmission device,and has a torque control mode with fast response and precise execution.The simple chassis structure also endows the vehicle more ability for improvement in handling stability.It is considered to be one of the most promising electric vehicle architectures by international automotive scholars.However,the distributed electric drive chassis has significant redundancy characteristics.Under the condition of electromechanical coupling of a multi-execution system,the mechanical mechanism,and the internal connection between the energy source and power source are very complicated.There exists the coupling between the in-wheel motors,wheel,suspension and steering mechanism as for the dynamics and kinematics modeling.When different control units intervene,due to the overlapping interference of control functions and the conflict of power allocation for different objectives in the energy management system,this may lead to the inconsistent execution or even partial failure of the control.Vehicle active safety technology is the core driving force to promote the innovation of the automobile industry.In view of the above problems,this paper takes the distributed drive electric vehicle as the research object.This paper focuses on the efficient coordination of the distributed electric drive chassis control subsystems to improve the lateral stability of the vehicle,and the use of in-wheel motor torque distribution method to realize the coordinated optimization of vehicle safety and energy saving.It aims to provide theoretical basis and technical support for the development of distributed electric drive vehicles.The main research work and contributions of this paper are summarized as follows.1)In view of the explosive growth of electronic control units,the low degree of integration for control subsystems,and the coupling conflict problem of multi-objective optimization for the distributed drive electric vehicle chassis,a multi-agent system-based integrated architecture is proposed.It introduces a novel distributed control method to integrate the active front steering system(AFS)and the direct yaw moment control system(DYC).The cooperative control strategies between AFS and DYC are obtained through Pareto-optimality theory to ensure optimal control performance of AFS and DYC.Then,on the basis of dynamic interaction between agents,terminal constraints,including terminal cost function and terminal input with local static feedback,are designed to guarantee the asymptotic stability of the closedloop system.The hardware-in-the-loop test platform based on the steering control unit is built.The test results show that the proposed control architecture can effectively improve the vehicle lateral stability.It also provides a paradigm for the large-scale integrated control of the vehicle chassis subsystem.2)To avoid the rollover and instability state of the distributed drive pure electric SUV under the emergency steering condition,a multi-agent system integrated control architecture for the integration of active front steering system(AFS)and active suspension system(ASS)is proposed.Considering the constraints of actuator saturation and vehicle stability,decoupling the vehicle lateral and vertical motion and analyzing the effective control region of subsystems.Then a multi-constrained distributed model predictive control(MDMPC)approach is designed.Through minimizing linear convex combination of objective functions,the cooperative control strategy is ultimately solved by the Pareto-optimality theory.Moreover,vehicle lateral and roll motion stability region described by the phase plane is employed to bound the controllable limits and achieve the dynamic cooperation between AFS and ASS.The feasibility of the proposed control strategy is verified by simulation and hardware-in-the-loop(HIL)experiments.The test results under the large-curvature steering maneuver show that the vehicle roll stability can be enhanced.3)To realize a trade-off between the energy efficiency optimization for in-wheel motors and the vehicle yaw motion stability control,a dual-model predictive control(MPC)-based hierarchical framework is presented to realize the energy saving while improving the handling stability for DDEVs.Considering the time-varying state variables,a linear-time-varying modelpredictive-control(LTV-MPC)method is adopted to update the model parameters in real-time and guarantee the modeling accuracy.The soft constraint constructed by the phase plane is introduced in the LTV-MPC to ensure the vehicle stability,based on which,a relaxation factor is designed to reduce the energy consumption due to the excessive direct-yaw-moment control inputs.The simulation and field test results show that the proposed torque-vector control method can achieve the energy-saving based on ensuring the vehicle stability.4)Considering the control priority of vehicle handling performance and stability control with different stability margins,a Takagi-Sugeno(T-S)fuzzy-based robust H∞ control method is proposed to ensure the vehicle performance.Thanks to the T-S fuzzy modeling technology,the tire nonlinear characteristics are described by fuzzy rules,based on which the vehicle lateral dynamics model is established.Next,the safety region represented by the tire slip angles phase plane αf-αr is presented to evaluate the vehicle stability performance,based on which,a multi-objective optimization function is transformed into a standard robust performance optimization problem with dynamic weight coefficients.A T-S fuzzy-based robust H∞ state feedback controller is then designed to ensure the system stability and H∞ performance.The hardware-in-the-loop experiment proves that the proposed controller can effectively guarantee the vehicle handling stability performance. |
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