含负值弹性刚度负载电液位置伺服系统研究

Research on the Stability of Electro Hydraulic Position Servo System with Negative Spring Stiffness Load

针对电液位置伺服系统在负值弹性刚度负载作用下,系统失稳且特性尚未详细探讨等问题,分析其数学模型;根据负值弹性刚度绝对值与执行件液压刚度的比值大小分段讨论了系统特性,其特性表现为,系统在含有负值弹性刚度时为本质不稳定,且负值弹性刚度绝对值越大特性越差。然后,对系统进行校正探讨:在负值弹性刚度绝对值较小的情形,选用常规校正;负值弹性刚度绝对值较大的情形下,为了大幅度削弱负载对系统的影响,需采用微分反馈校正装置;而负值弹性刚度绝对值与液压刚度值相当时,除了采用微分反馈校正装置外,还需加入动压反馈装置来增加系统阻尼,以降低外干扰对系统的影响。最后对系统进行数值仿真,结果表明:加入校正和结构补偿后,系统保持稳定,其稳态误差小于1%,上升时间小于0.2s。

Mathematical model of electro-hydraulic position control system is established,system characteristics are analyzed according to the ratio between the absolute value of the negative elastic stiffness and the hydraulic stiffness of the actuator.The system under the loads with negative spring stiffness will be unstable,and the greater the absolute value of the negative stiffness is,the worse the performance of the system is.The compensation commonly used was chosen when absolute value of negative stiffness is small.The differential positive feedback compensation was employed when system has a large absolute value of negative stiffness,and a dynamic pressure feedback is also required when the absolute value of negative stiffness approximates to the hydraulic stiffness,the adverse effect of negative stiffness on the system was eliminated after these compensations.These compensations are verified by digital simulations of electro-hydraulic position servo system with negative spring stiffness,the results show that the system is stable after structural compensation,and the rise time is less than 0.2s,the steady state error is less than 1%.