Hmi implementation using radar chart for dual-loop system

This article presents a method to implement the Human Machine Inter-face (HMI) for providing high visibility of dual-loop system to encourage good operations and maintenance practices. The proposed method is based on the employment of radar chart to display key performance metrics of simultaneous and independent control of two identical loops for extensive event monitoring. Two level control loops utilizing two Proportional-Integral-Derivative (PID) function blocks of a single Programmable Logic Controller (PLC) are used as the case study to show the workability of the proposed HMI implementation. Each loop consists of a transmitter for measuring the controlled level an inverter for inverting the PLC output to adjust a pump speed, and a power meter form easuring the pump power consumption. The transmitter outputs from both control loops are applied to the PLC analog input module, and then separately scaled to be available to each PID block. The PLC analog output module is used to pass the PID block outputs for manipulating inlet flow rates. The performance metrics including the set point, process variable, manipulated variable, and pump power consumption of both control loops are detected and collected by the HMI/Supervisory Control and Data Acquisition (SCADA)station. All detected data of four performance metrics are represented on the axes of radar chart in real time by using the Wonder ware In Touch software. The script functions to save and load the specified data to the SQL server database are also created on the HMI/SCADA station. Experimental results confirm that the proposed HMI implementation can function correctly.