| The four-wheel independent drive electric vehicle(4WIDEV)represents the mainstream trend of the future development for the automobile industry,and it is an effective way to alleviate the problems of oil scarcity,environmental population,and traffic safety.The handling and stability control is significant to improve the active safety performance for vehicles,meanwhile,the performance of the control systems under emergency driving conditions needs to be improved due to the advanced vehicle technology and upgrading of highway grade.The4 WIDEV breaks through the traditional mechanics of the electric vehicle,the driving and braking torque of the motor can be adjusted independently,continuously,and precisely.Therefore,the 4WIDEV has better actuation flexibility due to the increase of the controllable degree of freedom,these characteristics make it has potential advantages to realize the handling and stability control.Besides,the 4WIDEV is a complicated nonlinear dynamics system coupling with the longitudinal,lateral,and vertical motions,as well as a typical overdrive system with multiple actuators,which provides higher requirements for the development of handling and stability control systems.This paper relies on the National Key Research and Development Program of China Project(2019YFB1600800)‘National new energy vehicles safety operation collaborative prevention and control platform based on end network cloud' and the Key Research and Development Program of Shaanxi Project(2018ZDCXL-GY-05-03-01)‘Key technology research on distributed drive pure electric passenger vehicle',this paper takes the 4WIDEV as the research object and focus on the key technologies of state parameter estimation and handling stability control.The main contributions of this thesis as follows:(1)The vehicle dynamics model of 4WIDEV is established.Based on the requirements of control strategy development and simulation experiment,the correlation models are established to provide the model foundation and simulation platform for the research of state and parameter estimation method and handling stability control strategy.These models include the vehicle body model,wheel model,tire model,hydraulic braking system model,field-oriented control model of permanent magnet synchronous motor(PMSM),vehicle speed following and trajectory tracking models of the driver.Meanwhile,take the high precision vehicle model of Car Sim as a reference,the rationality and accuracy of the vehicle dynamics model are verified by the simulation experiments under the typical conditions for test the vehicle handling and stability.(2)The modified methodology for state and parameter estimation of the vehicle combined with the antlion optimization(ALO)and unscented Kalman filter(UKF)algorithms is researched.Because of the high cost and difficulty of the direct measurement of the state and parameters for 4WIDEV,this paper designed a state and parameter estimator by combined with the ALO and UKF algorithms.To analyze the feasibility of the ALO algorithm,five optimization test functions are selected and optimized by GA,PSO,and ALO respectively.And then,to solve the problem of the degraded accuracy caused by the unknown noise information,the ALO algorithm is emerged into the UKF to identify the statistical property of the system process noise and measurement noise.Finally,the MATLAB/Simulink-Car Sim co-simulation model is established,and the effectiveness and accuracy of the proposed estimator are verified.(3)The handling and stability coordinated control strategy based on the adaptive nonsingular fast terminal sliding mode control(ANFTSMC)is proposed.First,the ideal vehicle model with two degrees of freedom is utilized as a reference,while the constraints of road adhesion condition are taken into account,and the control objectives are confirmed.Meanwhile,the coupling relationship between the yaw rate and side slip angle and its characterization law on the vehicle motion state are analyzed.Second,to accurately judge the driving state of the vehicle,based on the phase plane analysis methodology,the side slip angle-side slip angle rate phase planes are plotted for different initial condition,according to the variation trend of the phase trajectories,the influence of vehicle speed and road adhesion coefficient on the range of stability region is analyzed,the stability region boundary coefficients are further extracted,and the stability region delimitation guidelines are formulated to provide a basis for the intervention of the handling and stability control strategy.And then,to solve the problem of the conventional SMC cannot converge the balance point within a limited time,based on the NFTSMC,the direct yaw moment controllers are established to tracking the desired yaw rate and side slip angle respectively.Moreover,the adaptive law is utilized to estimate the upper bound of system uncertainty and external disturbance to alleviate the system chattering,and the controller weight is adaptively adjusted based on the degree of vehicle instability to realize the coordinated control of vehicle handling and stability.At last,the simulation results indicated that,compared with the traditional SMC control strategy,the ANFTSMC controller can notably improve vehicle handling and stability.(4)The torque optimal distribution strategy based on the multiobjective optimization theory and torque redistribution strategy with actuator failure are studied.First,based on the NSGA-II algorithm,the torque optimal distribution strategy is proposed to find the optimal longitudinal forces,with minimum tire load utilization ratio,torque distribution error,and tire slip energy loss as the optimization objective,and consideration of the actuator constraints.Second,to solve the instability problem due to the insufficient output torque of the failure motor,the PMSM fault tree is built by utilizing the fault tree analysis methodology,and the output characteristic of the failure motor is investigated by the simulation of the uniform excitationloss fault,based on this,the failure factor is defined to represent the output torque capability of the motor.And then,the torque redistribution strategy under the single motor failure condition is proposed by employing the quadratic programming algorithm.Finally,the simulation results demonstrated that,compared with the average distribution strategy,the proposed torque optimal distribution strategy can improve vehicle stability and decrease the error for tracking the desired vehicle state,meanwhile,the torque redistribution strategy can guarantee the stability of the vehicle under the single motor failure condition.(5)The 4WIDEV test platform based on the A&D5435 is developed and the vehicle tests are carried out.To validate the feasibility of the proposed estimation method and control strategy for the real vehicle,the 4WIDEV is developed,and the test vehicle platform is established based on the A&D5435 rapid prototyping controller.The road tests are conducted under different driving conditions,the experimental results verify that the state and parameter estimation methodology has superior accuracy,and with the proposed handling and stability control strategy,the vehicle has strong driving stability without instability conditions such as side slipping or drifting. |
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