Servo motors are specially designed motors to be used in control applications and robotics. They are used for precise position and speed control at high torques. It consists of a suitable motor, position sensor and a sophisticated controller. Servo motors can be characterized according the motor controlled by servomechanism, i.e. if DC motor is controlled using servomechanism, it is called as DC Servo motor. Thus major types of Servo motor may be - (i) DC Servo motor, (ii) AC Servo motor.
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Servo motors are available in power ratings from fraction of watt upto few 100 watts. They are having high torque capabilities. The rotor of servo motor is made smaller in diameter and longer in length, so that it has low inertia.
What is Servomechanism?
How does a Servo motor work?
Command input is given according to the required position of the shaft. If the feedback signal differs from the given input, an error signal is generated. This error signal is then amplified and applied as the input to the motor, which causes the motor to rotate. And when the shaft reaches to the required position, error signal becomes zero, and hence the motor stays standstill holding the position.
How is the servo motor controlled?
1ms will move the shaft anticlockwise at -90°, a pulse of 1.5ms will move the shaft at the neutral position that 0° and a pulse of 2ms will move the shaft clockwise at +90°.
When servo motor is commanded to move by applying pulses of appropriate width, the shaft moves to and holds the required position. If an external force is trying to change the position of the shaft, the motor resists to change. Pulses need to be repeated for the motor to hold the position.