The computer in the DDC system participates in the closed-loop control process. It can not only completely replace the analog regulator, but also realize the multi-loop PID (proportional-integral-derivative) adjustment, and without changing the hardware, it can realize various complicated by changing the program. Controls such as cascade control, feedforward control, nonlinear control, adaptive control, worry control, fuzzy control, etc.
Since the computer in the DDC system directly undertakes the control task, the system (system) is required to have good real-time performance, high reliability, and strong adaptability. In order to make full use of the computer's utilization, a computer usually has to control several or dozens of loops, so it is necessary to design the application software reasonably, so that it can complete all functions without losing the opportunity. The DDC system is the most typical system used by computers for industrial production process control. It has been widely used in materials thermal processing, chemical, machinery, metallurgy and other departments. In a DDC system, a computer is used as a digital controller.