Modbus通讯绝对值编码器应用于PLC位置测控系统的实时性分析

Analysis of the Real Time Property about Applying Modbus Communication Absolute Value Encoder to PLC System

绝对值编码器广泛应用于位置控制系统,其Modbus通讯方式为大多数PLC读取绝对值编码器位置数据提供了便利。但是由于Modbus通讯传输速率及PLC扫描周期的影响,PLC读取的编码器位置数据存在滞后性。本文基于Modbus通讯规范和PLC通讯原理,以三菱FX3U PLC和通用型绝对编码器为例,分析了滞后产生的原因及其滞后时间,并在此基础上给出了具体的应用建议。

Absolute value encoder is widely used in position control system.Its Modbus communication mode provides convenience for most PLC to read position data of absolute value encoder.However,due to the influence of Modbus communication transmission rate and PLC scanning cycle,the encoder position data read by PLC has hysteresis.Based on Modbus communication standard and PLC communication principle,taking Mitsubishi FX3U PLC and general absolute encoder as examples,this paper analyzes the cause of delay and its delay time,and on this basis,gives some application suggestions.