Composition principle and application characterist

2022-10-18
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The composition, principle and application characteristics of open-loop and closed-loop systems

open loop control (open loop, so the refueling speed will be very slow at the same time) refers to the control equipment whose length, width and height are 400mm respectively × 300mm × 400mm. Through operation, only control the output, regardless of the consequences of control. It is also called non feedback control system. In CNC machine tools, it is composed of stepping motor and stepping motor drive circuit. The second case of numerical control device: first, check whether the force measuring piston is installed correctly. According to the input command, a pulse command is sent to the stepping motor drive line through calculation, so as to drive the workbench to move a certain distance. This kind of servo system is relatively simple, stable and easy to master and use, but the improvement of accuracy and speed is limited. Therefore, it is generally only used for some economical CNC machine tools that do not consider external influences, or have small inertia or low accuracy requirements

closed loop control system is an automatic control system with a closed loop composed of signal positive path and feedback path, also known as feedback control system. The CNC machine tool is composed of servo motor, comparison circuit, servo amplification circuit, speed detector and position detector installed on the workbench. This system automatically detects the actual displacement of the workbench, compares it with the command value, and controls it with the difference value. This system has high positioning accuracy, but it is complex, difficult to debug and maintain, and expensive. It is mainly used for high-precision and large-scale CNC machine tools

The working principle of the semi closed loop servo system is similar to that of the closed loop servo system, except that the position detector is not installed on the workbench, but on the shaft of the servo motor. The accuracy, speed and dynamic characteristics of this servo system are better than open-loop servo system, and its complexity and cost are lower than closed-loop servo system. It is mainly used in most small and medium-sized CNC machine tools

for example, in the fully automatic washing machine (closed-loop), when adding water to the washing machine, there is an infrared sensor inside, which scans the water level. When the water level is appropriate, the washing machine automatically stops adding water

if it is an open-loop washing machine, the water level needs to be seen by people. People will turn off the tap when they think the water level is appropriate. In short, if the feedback is judged by human, the system is open-loop. If the feedback is judged by the machine itself, the system is closed-loop (end)

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