The engine idling start-stop technology can realize energy conservation and emission reduction, thus it has a very promising application. However, the start-stop technology does not match well with conventional automatic transmissions because of the vehicle starting delay, starting shock and safety problems. In order to overcome these problems, in this paper, we conducted a research on system level, based on a start-stop vehicle platform and the interfaces between engine, automatic transmission and other parts were analyzed. Based on comprehensive analyzing of the start-stop principle, the technical scheme of TCU (transmission control unit) control system was designed and a coordinated control strategy between TCU, EMS (engine management system) and the electrical oil pump was built. The coordinated control module contained three parts corresponding the engine auto-stop process, engine auto-start process, and the electrical oil pump control strategy. The control strategy for engine auto-stop and auto-stop process was to guarantee the starter operating only when the driveline was open to avoid starting failure and damage to the engine starter device, and the boundary conditions and CAN communication signals were expressed in these parts. An intelligent control strategy of the electrical oil pump was developed to satisfy the automatic transmission pressure requirement during engine restart and auto-stop, as well as decreasing the energy consumption. The rotating speed of the electrical oil pump was controlled based on the engine starting process and engine speed. This coordinated control strategy can avoid engine starting failure and guarantee the system normal operation and driving safety. In order to satisfy the special starting requirements of start-stop function, a mathematical model of starting process and clutch control system was built. The model contained the engine, torque converter, AT starting clutch, and vehicle body, the current to pressure characteristic, and friction characteristic of clutch. Based on model simulation, abnormal shifting operations caused by driver such as shift selector changing during start-stop process were considered in the starting control strategy. In different conditions, the control pressure for five clutches was different. By this control logic design, vehicle launching delay can be eliminated, and the shifting shock caused by abnormal operations can be avoided. The starting control strategy improved vehicle launching responsiveness and comfort significantly. The TCU application software was developed based on 'V process' from control module to target code, then the code was integrated with the target controller. A test environment on a prototype vehicle was established to verify the feasibility of the proposed control strategies. The test results indicated that the transmission functioned favorably, the speed of output shaft changed smoothly instead of changing sharply, and a quick and smooth starting performance of intuitive feeling was achieved when the engine was restarted. The findings in this study are valuable for forward designs of an AT for matching with start-stop system and also have great engineering application value.%为解决传统自动变速器与发动机怠速启停系统匹配时产生的起步迟滞和发动机启动失败等问题,该文设计了变速器控制器TCU(transmission control unit)、发动机管理系统EMS(engine management system)和电动泵的协同控制策略,通过所设计的协同控制极大地提高了启动成功率,并通过电动泵智能调速控制方法为自动变速器离合器提前建立油压,避免起步迟滞.该文设计的电动泵的智能调速方法可以减小油泵泵油损失,提高液压系统效率.为了实现平稳舒适的起步换挡,推导了液力机械式自动变速器AT(automatic transmission)车辆起步动力学模型和离合器控制系统模型,基于模型设计了起步离合器油压控制方法,提出了离合器卸油至接触点的控制方法,当车辆再次起步时可以提早响应约400 ms.在自动启停过程中还考虑了换挡杆切换的特殊工况,保证了系统的大覆盖率.通过整车搭载试验验证了所设计的控制策略具备可行性,起步过程中变速器输出轴转速变化平顺,起步冲击度大大降低.电动泵的智能调速控制方法可降低油耗约1.5%.该文的研究方法首次实现了自主品牌AT变速器与启停系统的良好匹配及应用,具有一定的参考意义.
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