数字阀的分级控制及非线性

作为数字阀电—机械转换器的步进电动机，在连续跟踪控制下由于驱动其转子旋转的电流为正弦波电流，因此阀的输入—输出特性表现出某种重复特征，该重复特征称为数字阀的分级控制特性。由于步进电动机的磁路存在磁饱和与磁滞，因此在数字阀输入—输出关系上表现为波动和滞环等非线性。为了分析数字阀的非线性，采用正弦波曲线模拟磁路的饱和与磁滞非线性；建立数字阀输入—输出特性的支配方程构建数字阀输入—输出理论模型；设计试验装置实际测量数字阀分级控制的非线性指标，并验证理论结果的正确性。理论及试验结果表明数字阀的非线性度、滞环及分辨率等指标与分级控制的级数成反比。据此，增大数字阀的分级数是减小其非线性、提高控制精度的有效途径。

STAGE CONTROL AND NONLINEARITES OF DIGITAL VALVES

In a digital valve which uses a stepper motor under continuous control as the electrical-to-mechanical interface, because of the sinusoidal wave driving currents the input-output characteristics demonstrate repetitive features, which is defined as stage control of the digital valve. Due to the existence of saturation and hysteresis in electromagnetic circuit of the stepper motor, the correspondent nonlinearities are also involve in the input-output characteristics of the digital valve. Sinusoidal curve is used to simulate the electromagnetic nonlinearities and dominant equations are established to describe the input-output characteristics of the digital valve. A special experiment is designed to obtained the nonlinear parameters, such as nonlinear error rate, hysteresis and resolution of the digital valve under stage control. It is concluded from theoretical and experimental results that the nonlinear error rate of the digital valve is approximately proportional to the stage number used in the digital valve and by increasing the number of stage control, the nonlinear error rate can be effectively reduced and thus the accuracy improved in the digital valve. In fact, the digital valve with multi-stage control is applied in the electrohydraulic force servo control in material test system (MTS).