With the development of electronic computer technology and other high technology, the level of automatic control technology is getting higher and higher, more and more widely used, more and more important role. Especially in the automation of the production process, factory automation, robotics, integrated management engineering, aerospace engineering, military technology and other fields, automatic control technology plays a key role.
Principle analysis
From the point of view of the way of control, the automatic control system has two kinds of closed loop and open loop.
Closed-loop control
Closed-loop control, which is also known as (negative) feedback control, is similar in principle to the purposeful behavior of human beings and animals, and the system composition consists of sensors (equivalent to the senses), controls (equivalent to the brain and nerves), and actuators (equivalent to the arms and legs and muscles). The sensor detects the state information (output) of the controlled object and transmits it into physical (electrical) signals to the control device. The control device compares the deviation of the current state (output) of the controlled object to the desired state (given amount), generates a control signal, and drives the controlled object through the actuator so that its state of motion is close to the desired state. In practice, the closed-loop (feedback) control methods are varied, used in different fields and various aspects of the current widely used and rapid development of: optimal control, adaptive control, expert control (i.e., expert knowledge base based on the establishment of control rules and procedures), fuzzy control, fault-tolerant control, intelligent control.
Open-loop control
Open-loop control is also called program control, which is in accordance with a pre-determined program, in order to send out signals to control the object. According to the conditions of signal generation, open-loop control has time limit control, sequence control, conditional control. since the 1980s, with microelectronics technology to produce programmable controllers in industrial control (elevators, multi-step machine tools, water plants) in a wide range of applications. Of course, some complex systems or processes often use a combination of multiple control types and multiple types of control programs.