FBM242 FOXBORO
Motors found it difficult to modify relay and contactor control systems,with large volume,high noise,inconvenient maintenance,and poor reliability when adjusting factory production lines.Therefore,the famous”General Ten”bidding index was proposed.
In 1969,the American Digital Equipment Company developed the first programmable controller(PDP-14),which was tested on General Motors’production line and showed significant results;In 1971,Japan developed the first programmable controller(DCS-8);In 1973,Germany developed the first
programmable controller;In 1974,China began developing programmable controllers.In 1977,China promoted PLC in industrial applications.[3]
The initial purpose was to replace mechanical switching devices(relay modules).However,since 1968,the functions of PLCs have gradually replaced relay control boards,and modern PLCs have more functions.Its purpose extends from single process control to the control and monitoring of the entire manufacturing system
development
In the early 1970s,microprocessors emerged.People quickly introduced it into programmable logic controllers,which added functions such as computation,data transmission,and processing,completing industrial control devices that truly have computer characteristics.The programmable logic controller at this time is a product of the combination of microcomputer technology and conventional relay control concepts.After the development of personal computers,in order to facilitate and reflect the functional characteristics of programmable controllers,programmable logic controllers were named Programmable Logic Controller(PLC).
In the late 1970s,programmable logic controllers entered the stage of practical development,and computer technology had been fully introduced into programmable controllers,resulting in a leap in their functionality.Its higher computing speed,ultra small size,more reliable industrial anti-interference design,analog operation,PID function,and extremely high cost-effectiveness have established its position in modern industry.
In the early 1980s,programmable logic controllers were widely used in advanced industrial countries.The number of countries producing programmable controllers in the world is increasing,and the production is increasing day by day.This marks the maturity stage of programmable controllers.
The 1980s to mid-1990s were the fastest growing period for programmable logic controllers,with an annual growth rate of 30-40%.During this period,the processing capacity of PLC for analog signals,digital operations,human-machine interface,and network capabilities were significantly improved.Programmable logic controllers gradually entered the field of process control,replacing the dominant DCS system in some applications.
