液压伺服系统一般将供油压力视作恒定值，但大流量工况及长管道的管道效应会引发供油压力波动，供油压力的动态变化导致伺服控制系统动态特性改变，使伺服控制精度降低． 针对该问题，文中基于 BackStepping 控制法，将变化的供油压力作为伺服系统未知参量进行估计，利用含有估计项的李雅普诺夫函数导数必须负定的原则，提出一种供油压力估计方法，使伺服系统能够适应供油压力的不确定性变化，保持良好的位移跟随特性． 实验结果表明，在变化的供油压力下，采用所提出的极值压力估计控制方法比采用供油压力确定值的 BackStepping 方法的位移跟随精度更高．

The hydraulic servo system generally regards the oil pressure as a constant，but the large flow condition and the pipeline effect in the long pipe will cause the oil supply pressure to fluctuate． These supply pressure chan-ges the result in servo system dynamic characteristic variation and thus degrade the control performance． To solve this problem，the changing oil supply pressure is estimated as an unknown parameter of the servo system based on the BackStepping control method． When Lyapunov functional derivative containing the estimation term isused，the principle must be negative and estimation method of the oil supply pressure is thus obtained． The servo system can adapt to the uncertain changes in supply pressure and keep precise position tracking performance． Experimental results show that the proposed estimation controller has higher position tracking accuracy when compared with the controller with good knowledge of supply pressure value．