Coordinated Toruqe Control For Mode-Switch Of Full Hybrid Electric Vehicle

The gradual deletion of oil resources and national regulations on vehicle emissionof increasingly high demand led vehicle manufacturers to develop hybrid electricvehicle. Because large capacity battery is too hard to gain revolutionary headway in thenear future, the development of pure electric vehicle is limited. And hybrid electricvehicle will play its advantages in a relatively long time.Energy management and control strategy of mode switching are very important indeveloping hybrid electric vehicle. However, many manufacturers and research unitsfocus on designing the energy management strategy of hybrid electric vehicle, and theresearching on dynamic process of mode switching is not enough. Hybrid electricvehicle has multiple modes of operation, and it will work in different modes in adifferent road and driver demand situation, so it will produce the mode switching. Thedynamic response characteristics of motor and engine are different, if the motor andengine torque do not be controlled, it will cause the output torque fluctuation and drivesystem impact, and influence the running smoothness of vehicle. Thus, it is important todesign torque coordinated control strategy to control the motor and engine torque inmode switching process, and it is necessary to study in this area.Because the hybrid electric vehicle with two clutches does not have the specialmotor for starting engine, the drive motor must provide torque to start the engine withdriving the vehicle. This process involves the clutch engagement process, must controlthe components work coordinative, so that the motor star engine process could becompleted rapidly and smoothly. In addition, the dynamic processes of hybrid powersystem also include other driving mode switching processes, braking mode switchingprocesses and driving and braking mode switching processes, and all of these dynamicprocesses must be controlled with torque coordinated in order to satisfy the quality ofmode switching processes.In this paper, the hybrid electric vehicle with one motor and two clutches as theresearch object, study the control strategy for dynamic processes of mode switching, thefollowing works were done:①The hybrid electric vehicle structure was analyzed first, and the systemparameters were given, and the dynamic analysis of modes was done; the enginedynamic characteristic was analyzed, and the engine dynamic torque output model was built; using the relevant test data, the battery model was built; motor dynamic torqueoutput model was built; the dynamic process for clutch engagement was analyzed, andthe clutch model was built; the AMT model was built; according to the relationshipabout the transmission system, the vehicle longitudinal dynamic model was built.②Divide the hybrid electric vehicle operation area, and determine the boundary ofoperation modes and the torque of power sources. According to analysis of thetraditional vehicle brake force distribution, combined with the regulatory requirements,identify the motor and hydraulic brake force in different braking strength.③Analyze the evaluation criteria of the mode switching processes; design thefuzzy controller about the clutch engagement process; based on energy managementdevelop the control strategy of mode switching processes.④Develop the bench test for the process of motor start engine in order to verifythat the hybrid system can smoothly realize the process. Build the vehicle and controlstrategy simulation model based on Matlab/Simulink, and develop simulation study foreach operation mode switching processes of the hybrid electric vehicle. The results ofthe moding and simulation are analyzed including non-coordinated and coordinatedtorque control strategy. The results show that with using the coordinated torque controlstrategy can effectively reduce the torque fluctuation and jerk value of mode switchingprocesses, and improves the vehicle drivability.