January 31st, 2023
The Differences Between Open-loop Control System and Closed-loop Control System
Automatic control systems are classified by the structural characteristics of the system and can be divided into open-loop control systems and closed-loop control systems. What is the difference between these two, this article will introduce them to you.
I. Open-loop control system
Between the control device and the controlled object, there is only a cis-action and no reverse link, the system neither needs to measure the output quantity, nor needs to feed it back to the input to compare with the given input quantity, so the input quantity of the system is the given value of the system.
The open-loop control system, on the other hand, is characterized by the fact that there is no link in the system and the action signal is transmitted from input to output in a single direction.
Characteristics of open-loop control system.
*There is no feedback link in the system, no feedback measuring element is needed, so the structure is simpler and lower cost.
*The system works in open loop and has good stability.
*The system can not achieve the role of automatic adjustment, the error caused by interference can not be self-corrected, so the control accuracy is not high enough.
Therefore, the open-loop control system is suitable for applications where the relationship between the input and output quantities is fixed and the internal and external disturbances are small. In order to ensure a certain control accuracy, the open-loop control system must use high-precision components.
2. Closed-loop control system
It sends the output quantity of the controlled object back to the input and compares it with the given input quantity to form a deviation signal, which acts on the controller to make the output quantity of the system converge to its desired value.
Closed-loop control system is characterized by the presence of feedback links in the system, the role of the signal according to the closed-loop transfer, the system's output has a direct impact on the role of control.
Closed-loop control systems have the following characteristics compared to open-loop control systems.
*the system has a negative feedback link, can automatically adjust the output amount of compensation, the perturbation caused by changes in the parameters in the system and the system outside the perturbation, have a certain anti-interference ability.
*The system uses negative feedback, in addition to reducing system errors and improving control accuracy, it can also accelerate the transition process of the system, but the control quality of the system is related to the accuracy of the feedback element.
*The system works in closed loop, which may produce instability, so there is a stability problem.
Closed-loop control system since the interference, the use of negative feedback auto-adjustment role, can effectively suppress everything is wrapped in the negative feedback loop on the forward channel of the perturbation effect on the controlled quantity, and can closely follow the given role, so that the broken control quantity in accordance with the changes in the given signal and change, so as to achieve complex and accurate control. Therefore, this, closed-loop control system is also often called automatic regulation system, the controller in the system is also often called regulator.
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