针对伺服比例阀中存在的多种非线性因素,提出包含滞环、磁饱和、时变参数、摩擦、液动力等特征在内的阀整体模型.基于非线性电路原理,建立比例电磁铁的集中参数模型.在多个不同固定气隙下进行电磁铁的阶跃电压动态测试,获取一系列磁化特性曲线,通过曲线拟合和数据插值等方法建立电感、电磁力增益和耗散电阻等电磁铁关键参数的非线性函数式.根据动力学方程建立阀体机械运动部件的模型,采用直接测量和间接估算相结合的方法确定各项参数值.通过实验获取恒定压差下稳态液动力与阀芯开度的关系曲线,并提供拟合后的数学表达式.为验证伺服比例阀综合模型的准确性,设计开环和闭环2种测试方法.开环时直接给电磁铁施加恒定电压,并采集电流与阀芯位移的阶跃响应曲线;闭环时通过阀芯位置PID控制器,分别测试空载与加载时的阀芯动态响应特性.仿真和实验结果表明,仿真模型在同样的参数和测试条件下获得与实验相吻合的响应曲线,验证模型的有效性,为后续针对伺服比例阀的控制器开发和故障诊断等工作提供有效的工具.
For multiple nonlinear factors inherent in the servo-solenoid valve, an overall model of the valve was proposed, including the features of hysteresis, magnetic saturation, time-varying parameters, friction and flow force. First, a lumped-parameter model of the proportional solenoid was built based on the principle of nonlinear circuit. Step voltage dynamic tests of the solenoid under different constant air-borne gaps were conduct, so that a series of magnetization curves were obtained. Through curve fitting and data interpolation of the experimental results, nonlinear function expressions of main parameters were built, such as the inductance, electromagnetic-force gain and dissipation resistor. Second, the model of the valve's mechanical motion part was built based on kinetic equation, and the values of parameters were gained by direct measurements and indirect calculation. Then, the steady-state flow force versus valve opening under constant pressure drop was measured by experiment. After curve-fitting, the expression of flow force was provided. Finally, to validate the combination model of the valve, two methods including open-loop and closed-loop tests were designed. During the open-loop test, constant voltages were exerted on/off the solenoid instantly and the step response of current and spool displacement were measured. In the closed-loop test, a PID controller was used to test the step response of the spools displacement with/without hydraulic load. The results show that, the response curves from the simulation model under the same parameters and test conditions shows good agreement with the experimental results. It validates the valve's model and provides an effective tool for controller design and failure diagnosis.