I. Introduction
Feedback control, as one of the core control strategies in industrial automation, plays a vital role in modern industrial production. Its basic principle lies in comparing the output signal of the controlled object with the desired value, obtaining the error signal, and adjusting the output of the controller based on this error signal, so as to realize the precise control of the controlled object. This paper will elaborate on the basic principles of feedback control, including its definition, characteristics, working process, types and applications in industrial automation.
II. Definition and characteristics of feedback control
Definition
Feedback control refers to the comparison of the actual results after the completion of a certain action and task, so as to have an impact on the conduct of the next action and play a role in control. Its basic principle is the process of returning the output information of the system to the input, comparing it with the input information, and utilizing the deviation between the two for control. Feedback control is actually using the past to guide the future, so that the implementation of planning decisions and the original plan itself in the dynamic to achieve coordination.
Characteristics
(1) Timeliness: feedback control can plan decisions in the implementation of each step of the process caused by the objective effect, timely response, and accordingly adjust, modify the next step in the implementation of the program.
(2) Dynamic: feedback control makes the implementation of program decisions and the original plan itself in the dynamic to achieve coordination, in order to adapt to the changing external environment and internal conditions.
(3) after-effects: feedback control is mainly on the consequences of the feedback, and cast the fact that it is difficult to change, and replace the old plan with a new plan, a new decision to replace the original decision-making takes a certain amount of time.
III. Feedback control process
The working process of feedback control mainly includes the following steps:
Setting the desired value: first of all, the desired output value of the controlled object needs to be set as the target of control.
Measure the actual output: through sensors and other measuring devices, real-time measurement of the actual output value of the controlled object.
Compare the error: Compare the actual output value with the desired value to get the error signal.
Adjust the controller output: according to the size and direction of the error signal, the controller calculates the corresponding control signal to adjust the input of the controlled object.
Feedback loop: the adjusted input acts on the controlled object, generating a new output, again compared with the desired value, forming a feedback loop.
IV. Types of feedback control
According to the role of the feedback signal, feedback control can be divided into two types of positive feedback and negative feedback:
Positive feedback: Positive feedback enhances the net input, i.e., if a change increases the output of the system, then positive feedback strengthens the tendency of this increase. Positive feedback is often used in applications where the response of the system needs to be increased or the signal amplified.
Negative feedback: Negative feedback reduces the net input, i.e., if a change increases the output of the system, then negative feedback stabilizes the output of the system by adjusting the input to reduce this increase. Negative feedback is the most commonly used feedback method in the control system, because it can improve the stability of the system and control accuracy.
V. Application of feedback control in industrial automation
Feedback control is widely used in industrial automation, including but not limited to the following aspects:
Temperature control: In chemical and metallurgical industries, the temperature of equipment such as reactors and heating furnaces needs to be precisely controlled. The actual temperature is measured by temperature sensors and compared with the set temperature, and the controller adjusts the power of the heating or cooling equipment according to the error signal, thus realizing the precise control of temperature.
Pressure control: In the oil and gas industry, it is necessary to control the pressure of pipelines, storage tanks and other equipment in a stable manner. Through the pressure sensor to measure the actual pressure, and compared with the set pressure, the controller according to the error signal to adjust the valve opening or pump output flow, so as to realize the stable control of pressure.
Flow control: In the water treatment, pharmaceutical and other industries, it is necessary to accurately control the flow of liquid or gas. Through the flow sensor to measure the actual flow, and compared with the set flow, the controller according to the error signal to adjust the output of the pump or valve, so as to realize the precise control of the flow.
Position control: In machinery manufacturing, automated assembly and other industries, the position of equipment such as robotic arms and conveyor belts needs to be precisely controlled. Through the position sensor to measure the actual position, and compared with the set position, the controller according to the error signal to adjust the output torque or speed of the drive motor, so as to realize the precise control of the position.
VI. Summary
Feedback control as one of the core control strategies in industrial automation, its basic principle is to compare the output signal of the controlled object with the desired value, get the error signal, and adjust the output of the controller based on this error signal, so as to realize the precise control of the controlled object. Feedback control is characterized by timeliness, dynamics and after-effects, and has been widely used in industrial automation. Through a deep understanding of the basic principles and application scenarios of feedback control, its key role in industrial automation can be better grasped and provide strong support for the realization of more efficient and stable automated production.