中文摘要：

针对电液位置控制系统在负载弹性刚度含有负值时系统出现不稳定现象,以及外负载力方向切换时干扰大而导致系统定位刚度差等问题,对负载弹性刚度为负值的电液位置控制系统构成及其数学模型的分析.采用二阶微分正反馈补偿的方法可以消除负载弹性刚为负值时对系统造成不利的影响.液压弹簧刚度处于最小值时,系统稳定性差、响应慢,在此情况下对系统进行建模仿真,得到的系统特性曲线表明：采用二阶微分正反馈补偿后系统稳定且拥有足够的稳定裕量,系统能够达到3 Hz以上的频宽.

英文摘要：

In light of an electro-hydraulic control system with the variable hydraulic stiffness under the spring load with a negative value,the system will be unstable,in addition,the external load changing the direction of the external load will cause a huge interference and result in poor position stiffness.Analysis the composition and mathematical model of the electro-hydraulic control system under the spring load with a negative value,a method for eliminating bad effects of system under the spring load with a negative value by introducing positive feedback compensation.When the hydraulic spring stiffness reach minimum situation,system is in poor stability and low-response stage,modeling and simulation of the system in this situation,system characteristics crrves obtained show that system will be stable and with sufficient stability margin after positive feedback compensation,system can achieve more than 3 Hz bandwidth.