1: Open-loop control: simply refers to the movement part (such as a stepper motor) after receiving the control system instructions, there is a deviation, and feedback correction cannot be made , commonly known as open-loop

2 : Semi-closed-loop control: Simply refers to the movement part (such as a servo motor) after receiving the control system instructions, deviation occurs, after using input fixed data in advance, and perform pitch compensation correction, commonly known as pitch compensation or semi-closed loop

3 : Full-closed-loop control: simply refers to the movement part (such as linear motor) receiving the control system instructions, and deviation occurs, which is detected by the high-precision grating ruler, and feedback correction is performed in real time

To sum up: full-closed loop is the most ideal control method, because it must be used in conjunction with imported high-precision grating scales, but the price is extremely expensive, and the cost of most machine tools on the market cannot afford it, and most manufacturers declare " Closed-loop control", in fact, it is "semi-closed-loop control" at most, and an absolute servo motor with an encoder must be used to feed back the signal and perform pitch compensation (Ruijun uses the Renishaw laser interferometer from Renishaw in the United Kingdom for detection, and the price of the whole set of instruments is as high as Millions, the general manufacturers do not have it at all, it will only appear in the brochures) In order to save costs or do not understand the technical structure at all, most manufacturers use ordinary relative servo motors that cannot be compensated by feedback signals at all. It's a gimmick, fooling around