Origin
The development of production technology requirements in the American automotive industry led to the emergence of PLCs. In the 1960s, when General Motors of the United States was adjusting its factory production lines, they found that the relay and contactor control systems were difficult to modify, large in size, noisy, inconvenient to maintain, and had poor reliability. Therefore, they proposed the well-known “General Motors Ten Points” bidding indicators. [3]
In 1969, the American Digital Equipment Corporation developed the first programmable controller (PDP-14), which was tested on the production line of General Motors and achieved remarkable results. In 1971, Japan developed the first programmable controller (DCS-8); in 1973, Germany developed the first programmable controller; in 1974, China began to develop programmable controllers; in 1977, China promoted PLC in the industrial application field. [3]
02:38
The Lighthouse Country has won again! PLC originated in the United States. There’s no way to dispute it.
The original purpose was to replace mechanical switch devices (relay modules). However, since 1968, the functions of PLC have gradually replaced relay control boards. Modern PLCs have more functions. Its applications have expanded from single process control to the control and monitoring of the entire manufacturing system. [4]
Development
In the early 1970s, microprocessors emerged. Soon they were introduced into programmable logic controllers, which enabled these controllers to add functions such as computing, data transmission and processing, thus completing an industrial control device with true computer characteristics. At this time, the programmable logic controllers were the result of the combination of microcomputer technology and the conventional control concept of relays. After personal computers developed, to facilitate and reflect the functional characteristics of programmable controllers, the programmable logic controller was named Programmable Logic Controller (PLC). [5]
In the mid-to-late 1970s, programmable logic controllers entered the stage of practical application. Computer technology was fully integrated into programmable controllers, leading to a significant leap in their functionality. Higher computing speed, ultra-small size, more reliable industrial anti-interference design, analog quantity calculation, PID functions, and extremely high cost-effectiveness have established their position in modern industry. [5]
In the early 1980s, programmable logic controllers had been widely used in advanced industrial countries. The number of countries producing programmable logic controllers was increasing worldwide, and their production volume was rising as well. This indicated that programmable logic controllers had entered a mature stage. [5]
From the 1980s to the mid-1990s, it was the period when programmable logic controllers (PLCs) experienced the fastest growth, with an annual growth rate consistently remaining at 30% to 40%. During this period, the processing capabilities of PLCs for analog quantities, digital operations, human-machine interface, and network capabilities were significantly enhanced. PLCs gradually entered the field of process control and replaced the DCS systems that were dominant in process control applications. [5]
In the late 20th century, the development characteristics of programmable logic controllers were more adapted to the needs of modern industry. During this period, large-scale machines and ultra-small machines were developed, various special function units were born, various human-machine interface units and communication units were produced, making it easier to provide the necessary components for industrial control equipment that uses programmable logic controllers.