Abstract: Powershift technology has been widely used in heavy tractors in recent years due to its advantages of uninterrupted power during shifting. As one of the core parts of the power shift transmission, the electrohydraulic control system is responsible for cooling and lubrication as well as shifting operations, and its control process has a direct impact on vehicle performance and shift quality. It is of great significance to put forward a reasonable control strategy of wet clutch oil pressure for improving and optimizing the shifting quality of power shift gearbox. In this paper, the sliding friction, shift time and jerk are selected as the evaluation indicators of shift quality. The relationship between the three indicators and the electrohydraulic control system of the PST was established through formula deduction. According to the output characteristics of the wet clutch during the shifting process, the power shifting process was divided into four stages: the original gear phase, the torque phase, the inertia phase, and the new gear phase. Combined with the shift evaluation indicators, a wet clutch hydraulic control strategy was proposed. The process of shifting 1st gear to 2nd gear was taken as an example. The corresponding Statechart control model was established in the AMESim simulation platform. The genetic algorithm was used to optimize the key parameters in the control model, and then run the simulation which the parameter optimization results were applied. Compared with the simple control strategy, the application of this control strategy could reduce the maximum jerk during the shift from 22.14 m/s3 to 9.78 m/s3. At the same time, the sliding friction per unit area of the wet clutch friction plate was 0.163 J/mm2 which was less than the allowable value. The effectiveness and rationality of the optimized control strategy for improving the shift quality were verified.

Key words: powershift, shift quality, wet clutch, hydraulic pressure segment control, genetic algorithm

摘要： 动力换挡技术因具备换挡过程中动力不中断的优点，近年来逐渐被广泛应用于重型拖拉机中。而电液控制系统作为动力换挡变速箱的核心部分之一，其控制过程对车辆性能及换挡品质有直接影响。提出合理的湿式离合器油压控制策略，对改善和优化动力换挡变速箱的换挡品质具有重要意义。选定滑摩功、换挡时间和冲击率作为换挡品质评价指标，通过理论推导建立了三者与动力换挡变速箱电液控制系统之间的联系，根据湿式离合器在换挡过程中输出特性的变化，将动力换挡过程划分为原挡位、扭矩相、惯性相和新挡位4个阶段，结合换挡品质评价指标提出了湿式离合器油压分段控制策略，并以前进1挡换前进2挡为例，在AMESim仿真平台建立相应的Statechart控制模型，针对控制模型中的关键参数运用遗传算法进行优化，将参数优化结果应用于控制系统中并运行仿真。与简单控制策略相比，应用本文所提出的控制策略后，可使换挡过程中产生的最大冲击率由22.14 m/s3降为9.78 m/s3，同时湿式离合器摩擦片单位面积上的滑摩功为0.163 J/mm2，远小于许用值。验证了该控制策略经优化后对改善换挡品质的有效性及合理性。

关键词: 动力换挡, 换挡品质, 湿式离合器, 油压分段控制, 遗传算法