Servomechanism
![Industrial servomotor
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.](/Images/godic/202502/15/Servomotor5517.jpg")
![Small R/C servo mechanism1. 1. electric motor
2. position feedback potentiometer
3. reduction gear
4. actuator arm](/Images/godic/202502/15/Servo5517.jpg")
A servomechanism, sometimes shortened to servo, is an automatic device that uses error-sensing negative feedback to correct the performance of a mechanism and is defined by its function. It usually includes a built-in encoder. A servomechanism is sometimes called a heterostat since it controls a system's behavior by means of heterostasis.