PROGRAMMABLE LOGIC CONTROLLER SYSTEM FOR PERFORMING A PROPORTIONAL-INTEGRAL-DIFFERENTIAL AUTO-CONTROL PROCESS IN ORDER TO MAINTAIN A TARGET WATER QUALITY VALUE BY INSERTING WATER TREATMENT CHEMICAL FOR COMPENSATING FLOW RATE VARIATIONS

摘要

PURPOSE: A programmable logic controller system for performing a proportional-integral-differential(PID) auto-control process in order to maintain a target water quality value by inserting water treatment chemical is provided to stably and accurately perform the PID auto-control process without using a PID controller.;CONSTITUTION: A computer(300) of a main control room comprises a PID(Proportional-Integral-Differential) control software. The computer creates a PID control command. The computer transfers the PID control command to a local control programmable logic controller(304) of a chemical room. The local control PLC(Programmable Logic Controller) of the chemical room receives the PID control command. The local control PLC of the chemical room performs calculation and control operations. A chemical injector(306) of the chemical room receives a control signal of the local control PLC. The chemical injector of the chemical room injects a directed amount of chemicals.;COPYRIGHT KIPO 2012