中文摘要：

针对液压机的电液系统控制难题,提出非线性级联控制器,对液压机在慢速加压阶段的位移、压力进行复合控制.为了克服系统参数不确定性对压力控制带来的显著影响,该非线性级联控制器的压力控制环采用扰动观测器对油液体积弹性模量、伺服比例阀流量增益、液压缸泄漏系数等参数的不确定性所产生的集中扰动进行在线估计及补偿,利用无源性定理证明了压力控制环的稳定性;考虑到系统参数不确定性及各种外干扰对滑块位移控制带来的不利影响,该非线性级联控制器的位移控制环基于滑模控制而设计;位移控制和压力控制的切换取决于当前位移.实验结果表明,该非线性级联控制器能够使得液压机在慢速加压阶段实现高精度、平稳的位移控制及压力控制,可以实现这两者之间的平稳切换.

英文摘要：

A nonlinear cascade controller was proposed to control the position and pressure during the slow compression stage in view of the control problems faced in the electrohydraulic systems of hydraulic press.The pressure control loop of the nonlinear cascade controller adopted a disturbance observer to estimate and compensate for the lumped disturbance on-line in order to overcome the significant influence of the system parametric uncertainties on the pressure control performance.The lumped disturbance on-line was caused by the parametric uncertainties associated with the bulk modulus of the oil,flow gain of the servoproportional valve,leakage coefficient of the hydraulic cylinder,and so on.The stability of the pressure control loop was proved using the passivity theorem.The position control loop of the nonlinear cascade controller was designed based on the sliding mode control considering the negative influence of the system parametric uncertainties and various external disturbances on the position control performance.The switch between the position control and the pressure control was depended on current position.The experimental results demonstrate that the proposed nonlinear cascade controller can make the hydraulic press achieve high-precision and smooth position control and pressure control during the slow compression stage,and make the switch between the position control and pressure control smooth.