中文摘要：

针对传统拖拉机轻载荷作业形式下（如播种、除草、移栽、收获等）发动机功率利用率较低、油耗较高等问题，通过分析拖拉机最佳经济性指标及其影响因素，提出一种以拖拉机燃油消耗率最低为目标的经济性换挡规律。这不仅需要发动机工作点在最低油耗经济区，还要求拖拉机具有较高的牵引效率，为此引入驱动轮滑转率，制定了以拖拉机速度、驱动轮转速、发动机转速、油门开度以及变速器传动比为控制参数的经济性换挡规律及其控制策略。采用模糊控制对驾驶意图进行识别，将驾驶员对换挡过程的干预引入到变速器控制中，以真实反映拖拉机实际作业环境。并以装备动力换挡自动变速器的东方红LA2004拖拉机为研究对象，对其轻载工况进行了仿真分析。结果表明，采用经济性换挡规律，能够使变速器挡位和发动机油门开度随着牵引负荷变化，保证发动机工作点处于在油耗较低的经济区域内，降低了拖拉机的燃油消耗率，实现拖拉机实际速度的稳定。该研究为拖拉机自动变速器控制系统开发提供了理论依据。

英文摘要：

When working at light load operation （such as sowing, weeding, transplanting, harvesting, etc. ）, the traditional tractor has the problem of low power utilization ratio and high fuel consumption. Through analyzing the best economy index and its influence factors of tractor, a kind of economical shift rule is put forward, which based on the minimum fuel consumption rate of tractor. It requires not only the operating point of the engine located at the lowest fuel consumption zone, also need the tractor traction efficiency to be higher. For this reason, the slip rate of driving wheel is introduced to constitute economical shift rule and its control strategy, which takes the speed, drive wheel speed, engine speed, throttle opening and transmission gear ratio of tractor as control parameters. The fuzzy control is used to identify the driving intention, and the driver intervention on the shifting process is introduced to the transmission control, which can reflect the actual working environment of the tractor. Taking the YTO LA2004 wheeled tractor which equipped with automatic power shift transmission as investigative subject, the simulation analysis of light load working condition is carried out. The results show that the gear and throttle opening change with traction load, which ensure that the working point of the engine is in a low fuel consumption zone. The fuel consumption rate of tractor is reduced and the stability of the actual speed of the tractor is achieved. A theoretical basis for the development of automatic transmission control system of tractor is provided by the research.