Abstract: The tractor pulls  different agricultural implements  to complete different operations, and its operation requirements change with the different traction machinery. Aiming at the problem that highpower tractors have different operating requirements under different working conditions, a multiworking condition shifting adaptive control method is proposed. Firstly, the requirements of different conditions on the power and economy of the tractor are analyzed. Slip rate, the throttle opening and vehicle speed are chosen as the control parameters, according to the requirements of the workings conditions, calculating the theoretical shift schedule that takes into account the power and the economy, and adopt neural network offline training shift schedule to realize intelligent control of shift control. Secondly, in view of the problem of cyclic shifting caused by random load fluctuations under heavy loads, the acceleration and the throttle opening changes are introduced as parameters. Fuzzy logic is used to judge the tractor load and the drivers operation intention to obtain the speed correction coefficient, and the shifting speed is corrected to expand the range of shift. A longitudinal dynamic simulation model of a highpower tractor is built by Simulink to verify the effectiveness of the shifting strategy. The simulation results show that in terms of fuel economy, the fuel economy of road transportation and light load operating conditions decreases by 5.78% and 3.28%, respectively. In terms of power performance, while ensuring the overcoming of traction resistance, the acceleration time under light load and heavy load conditions is faster, the speed fluctuation is reduced, and the problem of cyclic shifting under heavy load conditions is effectively avoided.

Key words: tractor, shift schedule, neural network, speed correction, adaptive control

摘要： 拖拉机牵引不同农机具完成不同作业，其作业要求随着牵引机具的不同而变化。针对大功率拖拉机在不同工况下作业要求不同的问题，提出一种多工况换挡自适应控制方法。分析不同工况对拖拉机动力性经济性的要求，以滑转率、油门开度和速度为参数,根据工况要求计算兼顾动力性和经济性的理论换挡规律，采用神经网络离线训练换挡规律实现挡位智能控制；针对重载荷下随机载荷波动导致循环换挡问题，引入加速度和油门开度变化量作为参数，利用模糊逻辑判断拖拉机负载和驾驶员操作意图得到速度修正系数，对换挡速度进行修正，扩大挡位使用范围；通过对拖拉机纵向动力学分析，利用Simulink搭建大功率拖拉机数学仿真模型，并建立变速箱换挡控制系统硬件在环仿真平台验证换挡策略的有效性。仿真结果表明，在燃油经济性方面，道路运输和轻载荷作业工况燃油经济性分别下降5.78%、3.28%。在动力性方面，保证克服牵引阻力的同时，轻载荷和重载荷工况加速时间较快，速度波动减小且有效避免重载荷工况下循环换挡问题。

关键词: 拖拉机, 换挡规律, 神经网络, 速度修正, 自适应换挡