智能阀门定位器的控制设计

Control design of the intelligent valve positioner

摘要:

针对工业过程控制中阀门定位器阀位控制不精确，易造成阀门阀位往复波动不稳定现象，设计了一款气动智能阀门定位控制电路板。其中硬件设计以微处理STC12C5A60S2为核心并输出双极性PWM(脉宽调制)脉冲驱动压电阀，外围电路包括电源转换电路、I/V转换电路、A/D采样电路、按键和液晶显示电路等；软件设计由于阀门控制及执行过程是非线性时变的系统，很难建立精确数学模型，所以控制系统采用模糊PID(比例积分微分)控制算法替代常规PID控制。通过软件硬件两方面改进设计，可以有效避免阀位波动不稳定现象，稳定过渡时间只需1.2 s且系统无超调量；在Matlab中，采用阀门各机构所建立数学模型的传递函数及阀位实测数据进行仿真。通过波形对比，得出所设计的阀门定位器控制电路板，能使阀门控制更加稳定、快速、准确。

Abstract:

The inaccurate control of the valve positioner in industrial process control would cause the valve position to reciprocate and fluctuate. To solve this problem, a circuit board of pneumatic intelligent valve positioning control is designed. The hardware design is based on micro-processing STC12C5A6052 and outputs bipolar PWM(Pulse Width Modulation) pulse to drive the piezoelectric valve. The peripheral circuit includes power conversion circuit, I/V conversion circuit, A/D sampling circuit, button and liquid crystal display circuit, etc. Because the valve control and execution process is nonlinear time-varying, it is difficult to establish an accurate mathematical model. Therefore, a fuzzy PID(Proportion Integration Differentiation) control algorithm is utilized instead of the conventional PlD control in the control system. By improving the designs in software and hardware, the valve position fluctuation can be effectively avoided. The stable transition time is only 1.2 s and the system has no overshoot. In Matlab, the transfer function of the mathematical model and the measured data of the valve position are simulated by various mechanisms of the valve. Through waveform comparison, the control circuit board of designed valve positioner can make the valve control more stable, fast and accurate.