Answer: A. Open-loop control system, closed-loop control system, semi-closed-loop control system.
Answer analysis:
Depending on the different control motion modes, machine tool CNC systems can indeed be divided into different categories. For the given options, we can analyze them one by one:
A. Open-loop control system, closed-loop control system, semi-closed-loop control system:
Open-loop control system: This system does not have a detection device or a feedback circuit, and usually uses a stepper motor as a driving element. The command feed pulse output by the CNC device is amplified by the drive circuit and converted into a current pulse signal that controls the power on/off of each stator winding of the stepper motor, drives the stepper motor to rotate, and then drives the workbench to move through the machine tool transmission mechanism.
Its characteristics are simple control, fast response speed, wide application range (especially for occasions where processing accuracy requirements are not very high) and low cost.
Closed-loop control system: This system achieves precise control of each axis of the machine tool through feedback control of parameters such as position, speed, force, etc. during the processing process.
Closed-loop control systems can accurately control errors in the machining process in real time, achieve high-precision machining, and have strong stability, wide application, and high reliability.
Semi-closed-loop control system: This system is between open loop and closed loop, usually the servo encoder is fed back to the CNC system, and the accuracy is high.
These three categories are divided based on the different control motion methods, so option A is accurate.
B. Point control system and continuous control system:
* This classification does not directly correspond to the control motion method of the machine tool CNC system. Point control system may refer to a point-to-point control system, that is, the machine tool moves from one point to another at a set predefined speed, but this is only one aspect of motion control and does not fully reflect the control motion method of the CNC system.
C. Multifunctional CNC system and economical CNC system:
* This classification is based on the function and economy of the CNC system and has no direct connection with the control motion method.
D. NC system and CNC system:
* NC (Numerical Control) system is a CNC system, which is a relatively broad term and does not directly reflect the difference in control motion methods.
In summary, according to the different ways of controlling motion, the CNC system of machine tools can be divided into open-loop control system, closed-loop control system and semi-closed-loop control system. Therefore, the correct answer is A.