Ac servo motor can be divided into synchronous ac servo motor and induction ac servo motor
The drip ac servo motor can be divided into synchronous ac servo motor and asynchronous ac servo motor Asynchronous ac servo motor is what you call induction ac servo motor
Synchronous ac servo motor is more complicated than induction motor, but it is simpler than dc motor. Its stator and induction motor have a symmetrical three-phase winding on the stator. The rotor is different, and the different rotor structure is divided into two types: electromagnetic and non-electromagnetic. The non-electromagnetic type is divided into hysteresis, permanent magnet and reactive type. The magnetic hysteresis and reactive synchronous motor are inefficient, low power factor and small manufacturing capacity. The permanent magnet synchronous motor is used in nc machine tool. Compared with the electromagnetic type, the permanent magnet is simple, reliable and efficient. The disadvantages are large volume and poor launch features. But the permanent magnet synchronous motor with high remanence, high coercive force of rare earth magnets, than about 1/2, small dc electric dimension quality reduce 60 ﹪, rotor inertia reduced to 1/5 of the dc motor. Compared with asynchronous motors, the efficiency is high because of the use of permanent magnet excitation, which eliminates excitation loss and related stray loss
Asynchronous ac servo motor refers to ac induction motor. It has three phases and a single phase, and also has a squirrel-cage and wire-wound type, which is usually used in the three-phase induction motor. Its structure is simple, compared with the direct current motor of the same capacity, the quality is one half, and the price is only one third of the direct current motive. The drawback is that it is not economical to achieve a wide range of smooth speed adjustment and must absorb backward excitation current from the grid. This makes the power grid power factor worse. The asynchronous type ac servo motor for the squirrel cage rotor is called the asynchronous ac servo motor, which is represented by IM.
On the control strategy, based on the motor voltage and frequency control method and the mathematic model of steady state open loop flux trajectory control method can achieve good servo characteristic, the current widely used is based on the mathematical model of permanent magnet motor dynamic decoupling vector control method, which is the core of modern servo system control method. Although people in order to further improve the control characteristics and stability, and puts forward the feedback linearization control and sliding mode variable structure control, adaptive control theory, and does not rely on mathematical model of fuzzy control and neural network control method, but mostly on the basis of vector control additional application of these control methods. High-performance servo Control and must rely on high precision of rotor position feedback, people always wanted to cancel the link, the development without position sensor technology (Sensorless Control). Up to now, in the commercialization of the products, the sensorless technology can only achieve about 1:100 of speed ratio, can be used in some low for position and speed servo control situations of accuracy is not high, such as pure pursuit of quick start stop sewing machine servo control and braking, high performance processing for this technology is still a long way to go.
