The word "servo" comes from the Greek word "slave". "Servo motor" can be understood as a motor that absolutely obeys the command of the control signal: before the control signal is sent out, the rotor stands still; when the control signal is sent out, the rotor rotates immediately; When the control signal disappears, the rotor can stop immediately.
The servo motor is a micro motor used as an actuator in an automatic control device. Its function is to convert an electrical signal into an angular displacement or angular velocity of a rotating shaft.
working principle
1. The servo system (servo mechanism) is an automatic control system that enables the output controlled quantities such as the position, orientation, and state of an object to follow any change in the input target (or given value). The servo mainly relies on pulses for positioning. Basically, it can be understood that when the servo motor receives one pulse, it will rotate the angle corresponding to one pulse to achieve displacement.
Because the servo motor itself has the function of sending pulses, so every time the servo motor rotates an angle, it will send out a corresponding number of pulses, so that it echoes with the pulses received by the servo motor, or it is called a closed loop. In this way, the system will know How many pulses are sent to the servo motor, and how many pulses are received back at the same time, so that the rotation of the motor can be precisely controlled to achieve precise positioning, which can reach 0.001mm.
DC and AC Servo Motors
1. DC servo motors are divided into brushed and brushless motors.
Brushed motors are low in cost, simple in structure, large in starting torque, wide in speed regulation range, easy to control, and require maintenance, but inconvenient maintenance (replacement of carbon brushes), electromagnetic interference, and 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 in inertia, smooth in rotation and stable in torque. The control is complicated, and it is easy to realize intelligence. Its electronic commutation method is flexible, and it can be square wave commutation or sine wave commutation. The motor is maintenance-free, has high efficiency, 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. Its power range is large and it can achieve a large power. Large inertia, low maximum rotational speed, and decreases rapidly as power increases. Therefore, it is suitable for applications that run smoothly at low speeds.
3. The rotor inside the servo motor is a permanent magnet. 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 feedback signal of the motor is sent to the driver. Compared with the target value, adjust the angle of rotation of the rotor. The accuracy of the servo motor depends on the accuracy (number of lines) of the encoder.
The functional difference between AC servo motor and brushless DC servo motor:
AC servo is better because it is controlled by sine wave and the torque ripple is small. A DC servo is a trapezoidal wave. But DC servo is relatively simple and cheap.
Permanent Magnet AC Servo Motor
The main advantages of permanent magnet AC servo motors compared with DC servo motors are:
⑴No brush and commutator, so it works reliably and has low requirements for maintenance and maintenance.
(2) Stator winding heat dissipation is more convenient.
⑶ Small inertia, easy to improve the rapidity of the system.
⑷Suitable for high-speed and high-torque working conditions.
⑸ Small volume and weight under the same power.
