| Distributed drive electric vehicle(DDEV)has a variety of operating status that changes frequently.Under each operating status,three major problems of uncertain characteristics,dynamic coupling of the system and multiple fault modes make it difficult to achieve the longitudinal and lateral stability of DDEV coordinately.It is difficult to guarantee the longitudinal and lateral stability of DDEV simultaneously under traditional stability control methods.In order to guarantee the longitudinal and lateral stability of DDEV simultaneously under variable operating status,this thesis studies a multi-model control method based on intelligent control to solve the uncertain characteristics problem,dynamic coupling problem and multiple fault modes problem of DDEV under multiple operating status,this thesis mainly includes:(1)Research on the stability control method of DDEV under variable operating status based on multi model control.Most of the existing stability control strategies are designed for a single operating status of the vehicle,which cannot guarantee the longitudinal and lateral stability of DDEV simultaneously under variable operating status,and can not guarantee the stability of DDEV during switching of variable operating status.Aiming at solving the variable operating status problem of the longitudinal and lateral stability of DDEV,this thesis proposes a model predictive-based multiple model controller(MP-MMC)to guarantee the optimal longitudinal and lateral stability of DDEV under acceleration,uniform speed,deceleration,different speeds and different steering angles,using the state variables including slip rate,speed,and tire side angle.(2)Research on the robust compensation control method of DDEV based on feedforward and feedback.Due to the lack of robustness and the shortcomings,the existing stability control strategies cannot effectively solve the uncertain characteristics problem of longitudinal and lateral stability of DDEV,such as uncertain disturbance,uncertain models,and uncertain parameters.Aiming at solving the uncertain characteristic problem between the longitudinal and lateral stability,this thesis proposes a feedforward and feedback-based robust compensation controller(FF-RCC).Here,the Kalman filter-based feedforward compensation method solves the effect of uncertain external disturbances on lateral stability.Then,a neural network-based feedback method is designed to solve the uncertain model problem.The slip prediction compensation method based on the model prediction is adopted to ensure the instantaneousness robustness of longitudinal stability.In this way,the robustness of the vehicle to the uncertain characteristics of longitudinal and lateral stability can be improved efficiently.(3)Research on the dynamic decoupling control method of DDEV based on multiple layers structure.Two main types of coupling problems of the active front and rear wheels in the steering system,and the steering and driving systems,are researched in this thesis.At the same time,the driving environment of DDEV increases the dynamic characteristics of these coupling relationships,and it is necessary to study an effective decoupling method and appropriate control structure to ensure the longitudinal and lateral stability of DDEV in the case of tyre lateral saturation and excessive longitudinal slip.Aiming at solving the dynamic coupling problem of the system,this thesis proposes a multiple layers dynamic decoupling controller(MLDDC),in which a diagonal decoupling method is designed to solve the coupling problem of the front and rear wheels in the steering system.The antiskid movement and lateral anti-saturation methods solve the coupling problem between the drive system and the steering system,and ensure the optimal slippage and lateral deviation of the vehicle.In this way,the longitudinal and lateral stability of the tyre is guaranteed.(4)Research on the multiple fault modes-tolerant control method of DDEV based on multi-model control.The longitudinal and lateral stability usually has different fault status,which may cause the operating performance of DDEV to be unstable.However,traditional fault-tolerant controllers are only suitable for one single fault status,and it is difficult to accurately distinguish the current fault mode and effectively implement optimal fault-tolerant control.Aiming at solving this multiple fault modes problem,this thesis proposes a multiple model-based fault-tolerant controller(MMFTC).By distinguishing different fault types,the adaptiveness of fault-tolerant control is improved,and the model predictive control method is used to implement the observation and compensation of fault actuator,and to improve the control effect of vehicle longitudinal and lateral stability under multiple fault modes.Finally,this thesis verifies the multi-model control method based on intelligent control of the longitudinal and lateral stability of DDEV in the designed Carsim-Matlab simulation platform.The simulation results show that the above research can be used under various operating status.It provides important theoretical methods for the stability control of electric vehicles,and has high research significance and application value. |
