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What is the working principle of a servo motor?

Time : 2021-08-04 Hits : 1333

Servo mechanism is an automatic control system that enables the output controlled quantity of the object's position, orientation, state, etc. to follow the arbitrary change of the input target (or given value). Servo mainly relies on pulses for positioning. Basically, it can be understood that when the servo motor receives 1 pulse, it will rotate the angle corresponding to 1 pulse to achieve displacement. Because the servo motor itself has the function of sending pulses, so every time the servo motor has the function of sending out pulses, Rotating an angle, it will send out a corresponding number of pulses, so that it echoes the pulses received by the servo motor, or is called a closed loop. In this way, the system will know how many pulses have been sent to the servo motor, and how many pulses have been received at the same time. In this way, the rotation of the motor can be controlled very accurately, so as to achieve precise positioning, which can reach 0.001mm. 

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1.DC servo motors are divided into brush and brushless motors. The brush motor has low cost, a simple structure, large starting torque, a wide speed range, easy control, and maintenance is required, but the maintenance is inconvenient (changing carbon brushes), causing electromagnetic interference and requiring environmental requirements. Therefore, it can be used in common industrial and civil occasions that are sensitive to cost.

The brushless motor is small in size, light in weight, large in output, fast in response, high in speed, small inertia, smooth in rotation, and stable in torque. The control is complex, easy to realize intelligence, and its electronic commutation method is flexible, and it can be square wave commutation or sine wave commutation. The motor is maintenance-free, highly efficient, low operating temperature, low electromagnetic radiation, long life, and can be used in various environments.

2. AC servo motors are also brushless motors, which are divided into synchronous and asynchronous motors. At present, synchronous motors are generally used in motion control. They have a large power range and can achieve great power. Large inertia, low maximum rotation speed, and rapid decrease as the power increases. Therefore, it is suitable for low-speed and smooth running applications.

3. The rotor inside the servo motor is a permanent magnet, and the U/V/W three-phase electricity controlled by the driver forms an electromagnetic field. The rotor rotates under the action of this magnetic field. At the same time, the encoder of the motor feedback signal to the driver, and the driver according to the feedback value Compare with the target value and adjust the angle of rotation of the rotor. The accuracy of the servo motor is determined by the accuracy of the encoder (number of lines).

The functional difference between AC servo motor and brushless DC servo motor: AC servo is better because it is controlled by a sine wave, the torque ripple is small. The DC servo is a trapezoidal wave. But DC servo is simpler and cheaper.

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