The development direction of controllers in the past 30 years and the next 10 years

In the 1970s, controllers began to derive two kinds of products, DCS and PLC, from two different application fields corresponding to traditional instruments and relay groups. There are quite a few differences between these two kinds of products at the initial stage. DCS pays more attention to loop control, while PLC pays more attention to discrete logic control. At that time, DCS used general CPU to process programs by soft interpretation, while PLC relied on bit block processor similar to AMD2910 to process logic. Relatively speaking, DCS was more inclined to software in system structure, while PLC was more like traditional hardware relay group.

After decades of development, the concepts of DCS and PLC are suddenly ambiguous, because PLC has also added a general CPU to the system, especially soft logic PLC is no different from DCS in instruction processing principle, but the user instructions of upper computer software are different. However, DCS is not static. DCS has made great progress in network, multi-DPU cooperative work and redundancy, and most of them have adopted X86 architecture, making full use of the technological achievements of PC.

So now the difference between DCS and PLC is quite small. In terms of specific technology, DCS has a distributed real-time database based on token network, which can ensure that the image data in each DPU is up-to-date through full communication, while PLC pays more attention to stand-alone work in this area. Even if it is networked, it is assumed that only a small amount of data exchange is needed between two PLCs, so the master-slave structure is adopted for communication.