Servo motor

A servo motor is a rotary actuator or a motor that allows for precise control in terms of angular position, acceleration, and velocity. It has certain capabilities that a regular motor does not have.

Types of servo motors

Servo motors can be of different types based on their applications and they are

• AC servo motor
• DC servo motor
• Positional servo motor
• Continuous rotational servo motor
• Linear servo motor

A typical servo motor comprises of three wires i.e. power, control, and ground, and thus size and shape of the motor is depending on their application.

Principle Of working

• Servo motor works on the pulse width modulation (PWM) principle which means its angle of rotation is controlled by the duration of the pulse applied to its control PIN. This servomotor is made up of a DC motor which is controlled by a variable resistor (potentiometer) and some gears.

Mechanism

• A servo motor is a close loop servomechanism that uses position feedback to control its motion and final position and the input to its control is a signal that can be either analog or digital representing the position commanded for the output shaft.
• The servo motor has incorporated some type of encoder to provide position and speed feedback. In the simplest case, we measure only its position. Thus the measured position of the output is compared with the command position, the external input to the controller. Now if the output position differs from that of the expected output an error signal is generated which then causes the motor to rotate in either direction as per need to bring the output shaft to the appropriate position. Thus when the position approaches the error signal reduces to zero and then the motor will stop.
• This servomotor’s position can only sense by a potentiometer and by bang-bang control of their motor. Further, the motor will always rotate at full speed. Though this type of servomotor doesn’t have many uses in industrial motion control however it forms the basis of simple and cheap servo used for radio control models.
• Servomotors also find uses in optical rotary encoders to measure the speed of the output shaft and variable speed drive to control the motor speed. When this is combined with the PID control algorithm then it allows the servomotor to be in its command position more quickly and more precisely with less overshooting.

Application

• In robotics
• Conveyor belt
• Camera autofocus
• The solar tracking system, etc.