Research On Optimal Control Algorithm Of Gear Shifting Operations For Vehicle

With the development of automobile electronic control technology and automatictransmission technique,the gear shift process is no longer limited to functionrealization.Improving the drivability and shift quality of vehicles have been the essentialrequirements for automobile.In the process of vehicle driving, shift quality is an especiallyimportant determinant of the overall quality of the vehicle performance. It plays a crucialrole in vehicle’s power performance, passengers comfort and longevity of powertrainsystem. Therefore, it is significantly important to control the shift quality during thedevelopment of the automatic transmission system. Based on the DEUTZ BF4M1013electronic unit pump diesel engine and Allison S2000clutch-to-clutch automatictransmission, this paper proposes an optimal control research on the coordinated powertraincontrol during shift process, for improving of the comprehensive performance of shift jerkand friction loss.Firstly, the dynamic equations of gear shifting is acquired with the dynamic analysisusing the Lagrange method on the planetary transmission. By detailed analyzing the stagesof shifting process, the quantitative relationship and the ideal rules of overlapping betweenpressures of the on-coming clutch and the off-going clutch are obtained during torque stage.And the method to decrease shift jerk with coordinate powertrain control during inertiastage is also obtained. Then the results of theory analysis are validated by the experiment ofshift process, laying a foundation for designing the optimal control algorithm and makingcontrol strategy in shifting process.Secondly, taking into consideration of the performance index of shift quality, the jerkand friction loss, and combining the theory and experiment analysis, the shape of turbinespeed and output speed objective tracking trajectories are determined. Then the researchaimed to improve shift quality is transferred into the linear quadratic optimal trackingcontrol problem. By using the minimum principle, the optimal control problem is solved.Based on the shape of objective trajectories, the value of performance index is used as astandard to optimize shift time under different conditions. According to the optimal shifttime, the optimal tracking trajectories of turbine speed and output speed are decided. And the calibration process of optimal shift time is designed.Finally, the coordinated powertrain control strategy of clutch-to-clutch automatictransmission for gear shifting is proposed. Through the designed optimal control algorithm,the control trajectories of clutch friction torque and the turbine torque are obtained. Then bythe coordinated control of the engine and automatic transmission, the tracking control ofobjective torque values are realized to achieve optimal comprehensive performance of jerkand friction loss. And the coordinated powertrain control strategy for gear shifting isverified in the offline simulation model. The results show that, with the proposed controlstrategy of gear shifting, the shift jerk and friction loss are significantly reduced, and theshift quality is effectively improved. Meanwhile, the simulation researches are alsodeveloped with different transmission shaft characteristics and different shift time.