Optimal Control Of The Gear Shift Of Two-speed Transmission In Electric Vehicle

At present, the development of the pure electric vehicles has entered into a relativelymature time, pure electric vehicles on the market already emerge in endlessly. As moreand more pure electric vehicles have been produced, the demand of people for pure electricvehicles no longer stay on the original expectations, but hope that pure electric vehiclesnot only have good driving comfort, economy, but also have great dynamic performancecompared to traditional internal combustion engine vehicles.Due to the change range of motor speed is larger, pure electric vehicle usually e-quipped with a single-speed transmission. If it wants to meet the demand of powerperformance, the performance of the drive motor and power requirements are quite high,virtually the cost is increased. In order to reduce drive train size, minimize the cost andalso improve the transmission efciency, we have proposed a innovative2-speed trans-mission to improve the grade ability at low-speed and efciency at high-speed, therebyreducing the design requirements of motor. It includes a permanent magnet synchronousmotor, a2-speed AMT (Automated Manual Transmission), an inverted dry clutch, mainreducer and diferential and so on. It is simple in structure, convenient in layout, andas adopting dry clutch the efciency is high. Manipulation of the clutch can realize nopower interruption shift, so as to improve the comprehensive performance of pure electricvehicles.In this paper, by constructing a new type of simulation platform of two-speed trans-mission drive system in pure electric vehicles, after the validation of model accuracy, nopower interruption of transmission shift control is operated. The shifting controller isbased on optimal control method, and compared to the traditional PID control method.The main research contents of this article are as follows:1、 The drive system structures of pure electric vehicle are introduced in details, theperformance of pure electric vehicles are analyzed, and the principle of choosing gearnumbers of the pure electric vehicles is introduced, and the research status of pureelectric vehicle drive system.2、 The two-speed transmission drive system structure of pure electric vehicle are intro-duced in details, and its working mode. The main is focused on the shifting process. By analyzing diferent shift control methods, determine the shift control methodadopted by the article, it is based on the optimal control.3、 The equivalent AMESim simulation model of the vehicle is established, and thedynamic performances of the vehicle simulation model are validated.4、 The shift process of two-speed transmission were analyzed, and the shifting controlleris designed. Take the up shift process for example, in the torque phase, a feed-forward controller is adopted for the precise control of traction motor output torqueand clutch friction torque, as it is easy to implement relatively. In the inertial phase,take the minimizing friction work of clutch, minimizing the vehicle longitudinal jerkand ensuring the transmission output torque change smoothly as the control goals,a linear quadratic optimal controller is designed. Then, through of-line simulationof the optimal controller get the optimal trajectory curves of drive motor torque andclutch slipping speed.5、 Based on the of-line simulation results of the optimal controller, ftting out thenormalized curves of the traction motor torque and clutch speed diference for onlinesimulation experiment. The ftted clutch slipping speed is used as the referencetrajectory and the ftted motor torque is used as the feed-forward control of the on-line controller. In order to compensate the disturbances and modeling errors, a PIDcontroller is added to ensure the closed-loop control performance.6、 Finally, in diferent driving conditions, the feed-forward and feedback controller isconfrmed through a large amount of tests on a complete power train simulationmodel, and compared with the traditional PID controller. The calibration of theproposed controller is much easier than that of pure PID controller, because thefeed-forward part of the proposed controller considered the simple but dominantsystem dynamics. The designed controller works very well even with large variationof vehicle mass and road grade and optimizes the clutch friction work and the vehiclejerk.