Working principle of servo motor

- Nov 06, 2018-

1, servo system (servo mechanism) is to enable the position of the object, azimuth, state and other output controlled quantity can follow the input target (or given value) of any change in the automatic control system. Servo is mainly based on pulses to locate, basically can be understood, the servo motor received 1 pulses, will rotate 1 pulses corresponding to the angle, so as to achieve displacement, because the servo motor itself has the function of emitting pulses, so the servo motor each rotation angle, will emit a corresponding number of pulses, so that, The pulse accepted by the servo motor forms an echo, or a closed loop, so that the system will know how many pulses are sent to the servo motor, and at the same time how many pulses are collected back, so that the rotation of the motor can be precisely controlled, so as to achieve accurate positioning, can reach 0.001mm. DC Servo motor is divided into brushed and brushless motor. Brushed motor cost is low, simple structure, large starting torque, wide range of speed regulation, easy to control, need maintenance, but maintenance is not convenient (change carbon brush), produce electromagnetic interference, the environment has requirements.

It can therefore be used for cost-sensitive ordinary industrial and civil occasions. Brushless motor small size, light weight, large output, fast response, high speed, small inertia, smooth rotation, torque stability. The control is complex, easy to realize intelligent, its electronic phase change method is flexible, can square wave phase change or sine wave phase change.

Motor Maintenance-free, high efficiency, low operating temperature, electromagnetic radiation is very small, long life, can be used in a variety of environments. 

2, AC servo motor is also brushless motor, divided into synchronous and asynchronous motor, the current motion control is generally used synchronous motor, its power range is large, can do a lot of power. Large inertia, the maximum rotation speed is low, and decreases rapidly with the increase of power.

Therefore suitable for low-speed smooth operation of the application. 

3, the servo motor inside the rotor is the permanent magnet, the drive control of the u/v/w three-phase electricity to form an electromagnetic field, the rotor under the action of this magnetic field, while the motor comes with the encoder feedback signal to the driver, the driver according to the feedback value and the target value comparison, adjust the rotor rotation angle.

The accuracy of the servo motor depends on the accuracy of the encoder (number of lines). AC servo motor and brushless DC servo motor in the functional difference: AC servo is better, because it is sine wave control, torque pulsation is small. DC Servo is a trapezoidal wave. But DC Servo is relatively simple and inexpensive.