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Research On Lateral Stability Control System Of Distributed Drive Electric Vehicles(DDEV)

Posted on:2020-09-23Degree:MasterType:Thesis
Country:ChinaCandidate:Q Y ChenFull Text:PDF
GTID:2392330620951076Subject:Control Science and Engineering
Abstract/Summary:PDF Full Text Request
Under the social background of increasing environmental pollution and increasing concern about limited energy,the emergence of electric vehicles has become an effective way to solve the above environmental and energy problems.Distributed Drive Electric Vehicles(DDEV)uses four hub motors embedded in the wheels in its structure,which makes the wheels of the vehicle individually controllable and its control methods more flexible.At the same time,it becomes more difficult for DDEV to run stead ily because of increasing the complexity of dynamic coupling and the degree of freedom of control.In this paper,some uncertain stabilit y problems such as understeer and lateral instability of DDEV in sharp turn are studied.The main contents of this paper are divided into the following parts:Firstly,according to the structure characteristics and working characteristics o f distributed drive electric vehicle,the dynamic model of DDEV is built,including its two-degree-of-freedom vehicle dynamics model,seven-degree-of-freedom vehicle dynamics model and tire model.According to the established model,the characteristic parameters of DDEV's steep turning stability problem are further analyzed and obtained.Secondly,according to the characteristics of DDEV's steep turning,such as the great sideslip angle of its center of mass,the dangerous situation of vehicle rollover easily,and the big influence of the yaw rate of electric vehicle on the vehicle's heading angle,a lateral stability control system based on fuzzy control is proposed,which includes the direct yaw moment controller of the upper layer and the moment distribution controller of the lower layer.Based on the fuzzy control algorithm,the upper controller obtains the total yaw moment according to the deviation of sideslip angle and yaw rate.The lower controller distributes the yaw moment from the upper controller to four hub motors to drive the whole vehicle.The above control system is simulated and analyzed.The simulation experiments of low sp eed,medium speed,high speed,low adhesion coefficient and high adhesion coefficient are carried out respectively.The control effect of the system is tested.Finally,in order to solve the problem of poor adaptive ability and unsatisfactory control accuracy of the lateral stability control system based on fuzzy control,a lateral stability control system based on fuzzy neural network(FNN)is proposed.The system controller includes the upper direct yaw moment controller and the lower torque distribution controller.The upper controller obtains the total required direct yaw moment according to the deviation of sideslip angle and yaw rate.The structure of the controller is based on FNN algorithm,and the parameters of FNN network are determined by the error of sideslip angle and yaw rate based on the BP back-learning algorithm.In order to minimize the tire utilization rate,the lower controller distributes the yaw moment from the upper controller to four hub motors to drive the whole vehicle.Similarly,the control system is simulated and analyzed to test the control improvement effect of the system.The simulation results show that the proposed control system significantly improves the lateral stability of DDEV,avoids understeering,rollover and sideslip,and solves the uncertain stability problem of the lateral stability control system based on fuzzy control.The control system has strong adaptive ability and higher control accuracy.
Keywords/Search Tags:Distributed drive electric vehicle, fuzzy neural network, lateral stability, adaptive
PDF Full Text Request
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