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A brief introduction to automatic control systems
Release Date:
Oct 17,2019
In an open-loop control system, the system output is controlled only by the input, resulting in relatively poor control accuracy and disturbance suppression characteristics. In open-loop control systems, those based on sequential logic control are called sequential control systems; they consist of sequential control devices, detection elements, actuators, and the controlled industrial object. They are mainly used in the control of processes such as machinery, chemical industry, material loading and transportation, as well as in manipulators and automated production lines.
First: An automatic control system mainly consists of four components: controller, controlled object, actuator, and transmitter.
Then: According to different control principles, automatic control systems are divided into open-loop control systems and closed-loop control systems.
Open-loop control system
In an open-loop control system, the system output is controlled only by the input, resulting in relatively poor control accuracy and disturbance suppression characteristics. In open-loop control systems, those based on sequential logic control are called sequential control systems; they consist of sequential control devices, detection elements, actuators, and controlled industrial objects. They are mainly applied in the control of processes such as machinery, chemical industry, material loading and transportation, as well as in manipulators and automated production lines.
Closed-loop control system
A closed-loop control system is based on the feedback principle, using the deviation between the output and the desired value to control the system, achieving better control performance. Closed-loop control systems are also called feedback control systems.
According to the given signal classification, automatic control systems can be divided into constant value control systems, servo control systems, and program control systems.
Constant value control system
The given value remains unchanged, and the system output is required to approach the given desired value with a certain accuracy. Automatic control systems for temperature, pressure, flow, liquid level height, motor speed, etc., in production processes belong to constant value systems.
Servo control system
The given value changes according to an unknown time function, and the output is required to follow the changes of the given value. For example, radar antenna systems tracking satellites.
Program control system
The given value changes according to a certain time function. For example, program-controlled machine tools.
Therefore: Automatic control systems have been widely applied in various fields of human society.
In industry, various physical quantities encountered in production processes such as metallurgy, chemical industry, and machinery manufacturing—including temperature, flow, pressure, thickness, tension, speed, position, frequency, phase, etc.—all have corresponding control systems. On this basis, digital control systems with better control performance and higher automation levels have been established by using digital computers, as well as process control systems with dual functions of control and management. Applications in agriculture include automatic water level control systems and automatic operation systems for agricultural machinery.
In military technology, examples of automatic control applications include various types of servo systems, fire control systems, guidance and control systems, etc. In aerospace, aviation, and navigation, besides various forms of control systems, applications also include navigation systems, remote control systems, and various simulators.
Additionally, in office automation, library management, traffic management, and even daily household chores, automatic control technology has practical applications. With the development of control theory and control technology, the application fields of automatic control systems continue to expand, covering almost all areas including biology, medicine, ecology, economics, and society.
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