In automatic control system, the system whose output can change with the input with a certain precision is called servo system, also called servo system. The servo system of NC machine tool refers to an automatic control system with the position and speed of the moving parts of the machine tool as the control quantity, also known as servo system. Servo system consists of servo drive device and drive element (or actuator servo motor). The high-performance servo system also has a detection device to feed back the actual output state.
The function of CNC machine tool servo system is to receive the command signal of CNC device and drive the moving parts of the machine tool to follow the command pulse to ensure fast and accurate action, which requires high-quality speed and position servo. The above mainly refers to the feed servo control, in addition to the main motion servo control, but the control requirements are not as high as the former. The accuracy and speed of CNC machine tools often depend mainly on the servo system.
Application trend
Automatic control system not only develops rapidly in theory, but also changes rapidly in application devices. Modular, digital, high-precision and long-life equipment will be updated every 3 ~ 5 years. The traditional AC servo motor has soft characteristics and its output characteristics are not single-valued. Stepper motors generally adopt open-loop control, which can't locate accurately. The motor itself also has a speed resonance region. The position tracking performance of pwm speed control system is poor, and the frequency conversion speed control is simple, but sometimes the accuracy is not enough. DC motor servo system is widely used in position servo system because of its excellent performance, but it also has some shortcomings, such as complex structure, prominent contradiction of ultra-low speed dead zone, noise caused by reversing brush and maintenance problems. The new permanent magnet AC servo motor has developed rapidly, especially after the development from square wave control to sine wave control, the system performance is better, the speed range is wide, especially the low speed performance is superior.