The Design Of Vehicle Control System And Research On Drive Control Strategy For Pure Electric Vehicle

The control system of electric vehicle consists of motor and its control unit, battery andits management system, vehicle control unit, etc. The task of vehicle control system is toguarantee the good performance of vehicle. In order to make sure that subsystems cancoordinate well with each other and that control functions of vehicle control system can betotally achieved, the communication mode between various subsystems should be definedclearly.It is driving control and fault diagnosis that make the core part of control technologywhich plays a significant impact on the performance of vehicle, like power, economy, safetyand comfort. Upon the project “Research on vehicle control strategy and development ofcontrol system test platform for pure electric vehicle” developed by a company and JilinUniversity, the purposes of this research are to formulate a reasonable vehicle control strategy,design software and hardware of vehicle control system, and finish debugging on targetvehicle so that the indexes requirements of vehicle performance can be met. The maincontents of this paper are as follows:1. According to the required indexes of power and economy for target vehicle,parameters of both motor and battery pack have been matched. After analyzing theperformance characteristic of power components, the new performance indexes of vehiclehave been checked right.2. According to the key signal, gear signal, accelerator pedal signal, statuses of motor andbatteries, vehicle speed, and reference to the performance characteristic of power components,control mode is divided into four parts including creep mode, reversing mode, driving mode,and limping mode. Control characteristic of motor torque for each mode is formulated toimprove economic performance while power indexes are achieved as well.3. Detecting and processing the failure of position sensor of accelerator pedal byrestricting its value and its changing rate, processing the failure of motor by limiting itsoutput power and dealing with fault of CAN communication by limiting discharge current of batteries. Through fault diagnosis and process, the reliability of the vehicle control system hasbeen improved.4. Choosing a distributed network topology structure for CAN network on the basis ofdemanding analysis function of vehicle control system and definition of hardware interface ofvehicle control unit, both of which are resulted from the needs of target vehicle, and formingCAN communication protocol for each control unit. Finally, it is finished for softwaredesign of vehicle controller, which has a modularized and layered structure, and writing forcode of control strategy.5. The driving control strategy is verified by joint simulation between vehicle modelcreated in CRUISE and strategy model created in MATLAB/Simulink. The simulation resultshows that the control strategy can meet the dynamic and economy indexes and that thereliability of vehicle control system can also be improved.6. The pedals and pressure signals are calibrated through shakedown test on targetvehicle, and driving control strategy is also verified. Test results show that the vehicle can startsmoothly and that its dynamic and economy performances can meet the required indexes.