基于LabVIEW的最小二乘法校正在控制中的应用

在自动控制系统中传感器的非线性特性和测量的准确性直接影响设备的控制精度,尤其是针对特殊测量而设计的传感器需要有自动校准功能以提高测量的准确性。工业自动化领域对设备级的控制大量采用可编程逻辑控制器PLC进行控制,然而PLC通常不具备非线性传感器自动校准所要求的数据计算能力。采用PLC同时采集被校准传感器的输出值和标准传感器的输出值,再将2个传感器的输出值传给LabVIEW上位机。基于LabVIEW设计的非线性传感器校正仪采用回归分析技术,应用最小二乘法原理,上位机对传感器的输出值进行拟合,得到满足精度要求的最佳拟合方程及最佳拟合系数。通过LabVIEW上位机与PLC的数据通讯,LabVIEW上位机将拟合系数回传给PLC,PLC利用拟合系数实现对被校传感器的校正。

Application of least square method based on LabVIEW in industrial automation system

The non-linearity and precision of sensors and actuators in the industrial automation system have large effects on the control accuracy,it is necessary that the self-designed sensor for special measurement has the function of selfcalibration to enhance the precision of measurement.The devices and equipment are normally controlled by Programmable Logic Controller （PLC）,but the PLC does not have the capability of large scale mathematical calculation needed by nonlinear sensor calibration.In this paper,the output data of standard sensor and sensor to be calibrated are simultaneously collected by PLC,then the data are transferred to LabVIEW.A nonlinear calibrator is designed based on the LabVIEW virtual instrument by utilizing the regression technology and the least square method.The optimum fitted equation and coefficient is obtained by the LabVIEW through calculation,then the fitted coefficient is transferred from LabVIEW to PLC and the calibration of sensor is realized by PLC.