The servo system using permanent magnet AC servo motor is divided into two modes: rectangular wave current drive and sine wave current drive according to the current drive in the current loop. Then the structure of the current loop and speed loop of the servo system is quite different. In analog control or digital-analog control systems, the speed loop of the rectangular wave drive system mostly uses a brushless DC tachogenerator as the speed feedback element, while the sine wave drive system mostly uses a resolver as an absolute position sensor and current commutation control. And speed feedback components. The resolver output sine and cosine signals are converted in the rdc (resolver-digital converter) application specific integrated circuit to provide the necessary signals for the position loop, speed loop and current loop control of the servo system. The speed feedback signal is proportional to The voltage signal of the speed. Of course, there are still some systems that use incremental V converters. The shaft speed is first quantified as digital information, and then the analog speed voltage signal is obtained by D/A conversion through a special circuit. Therefore, when the base speed is low, it is not The continuity will be revealed.

　　This article is taken from ------"Permanent Magnet Brushless DC Motor Technology"