Servomotor
[1][2] It constitutes part of a servomechanism, and consists of a suitable motor coupled to a sensor for position feedback and a controller (often a dedicated module designed specifically for servomotors).
The input to its control is a signal (either analog or digital) representing the desired position of the output shaft.
This type of servomotor is not widely used in industrial motion control, but it forms the basis of the simple and cheap servos used for radio-controlled models.
[5] Both of these enhancements, usually in combination with a PID control algorithm, allow the servomotor to be brought to its commanded position more quickly and more precisely, with less overshooting.
This can be observed when switching on an inkjet printer; the controller will move the ink jet carrier to the extreme left and right to establish the end positions.
A servomotor can immediately turn to whatever angle the controller instructs it to, regardless of the initial position at power up if an absolute encoder is used.
The encoder and controller of a servomotor are an additional cost, but they optimize the performance of the overall system (for all of speed, power, and accuracy) relative to the capacity of the basic motor.
Incremental systems, like stepper motors, often combine their inherent ability to measure intervals of rotation with a simple zero-position sensor to set their position at start-up.
[13] For large industrial servomotors, AC induction motors are typically used, often with variable frequency drives to allow control of their speed.
These standard modules accept a single direction and pulse count (rotation distance) as input.
The grey/green cylinder is the brush-type DC motor . The black section at the bottom contains the planetary reduction gear , and the black object on top of the motor is the optical rotary encoder for position feedback . This is the steering actuator of a large robot vehicle.
