The main differences between an open loop (often called an open-loop system) and a closed-loop system are reflected in the working principle, structural composition, stability, and control effect. The following is a detailed explanation of the difference between the two:
1. Working principle
Open-loop system: There is only a forward action but no reverse connection between the control device and the controlled object. That is, the output of the system has no effect on the control action, and there is no feedback mechanism between the output and the input.
The control action is directly derived from the input, and there is a clear correspondence between the input and the output.
Closed-loop system: The output is directly or indirectly fed back to the input to form a closed loop and participate in the control. The input of the system affects the output and is directly or indirectly affected by the output. By introducing a feedback mechanism, the system can adjust the control action according to the change of the output to achieve the predetermined control target.
2. Structural composition
Open-loop system: The structure is relatively simple, mainly composed of a control device and a controlled object, and there is no detection equipment to detect the change of the output.
Closed-loop system: The structure is relatively complex, and in addition to the control device and the controlled object, it also includes feedback and comparison links. The feedback link is used to detect changes in the output and convert it into a feedback signal; the comparison link is used to compare the feedback signal with the input signal to generate a deviation signal as a control basis.
3. Stability
Open-loop system: Stability is relatively easy to solve because the system has no feedback mechanism, so the introduction of the feedback loop will not increase the complexity of the system. However, the open-loop system is very sensitive to changes in system parameters, and the control accuracy and interference suppression performance are relatively poor.
Closed-loop system: It has the ability to suppress interference, is insensitive to changes in component characteristics, and can improve the response characteristics of the system. However, the introduction of the feedback loop also increases the complexity of the system and may cause system stability problems.
Therefore, when designing a closed-loop system, appropriate control strategies and algorithms need to be adopted to ensure the stability of the system.
4. Control effect
Open-loop system: The control accuracy mainly depends on the components used in the system and the accuracy of the calibration.
Since it is impossible to detect and correct errors, the control effect is relatively poor.
It is generally only used in some occasions where external influences can be ignored, inertia is small, or accuracy requirements are not high.
Closed-loop system: By introducing a feedback mechanism, errors can be detected and corrected in real time, making the correction action more accurate and powerful.
Therefore, the closed-loop system has higher control accuracy and better anti-interference performance. It is widely used in situations with high requirements for the external environment and high precision.
In summary, there are significant differences between the open loop (open-loop system) and the closed-loop system in terms of working principle, structural composition, stability, and control effect.
When selecting a control system, it is necessary to select the appropriate system type according to the specific application scenario and control requirements.