中文摘要：

动力换挡变速器具有换挡进程中动力输出不中断的优点，在拖拉机和工程机械上得到广泛应用。分析了拖拉机动力换挡自动变速器工作原理，对其在国内外的应用进行了综述。并根据当前变速器换挡控制技术的发展趋势，研究了动力换挡自动变速器传动系统、电液技术、换挡规律以及所采用的换挡控制策略。本文的研究可为动力换挡变速器在农业机械上的应用提供理论参考。

英文摘要：

Due to the output power is uninterrupted in the process of gear shift, powershift transmission was widely used on tractor and construction machinery. Firstly, the operating principle of automatic powershift transmission on tractor is present. Then, the technique development of powershift transmission and its application on tractor at home and abroad is summarized. At the same time, the drive system, electrohydraulic technique, gear shift rules and gear shift control strategy of powershift transmission are studied according to the current development trend of gear shift control technique. Research results of this paper can provide a theoretical reference for the application of powershift transmission on agricultural machinery.