- Servomechanism Definition: A servomechanism is an automated control system designed to maintain system output at a desired level using feedback loops.
- Components: The system includes a controlled device, an output sensor, and a feedback system to monitor and adjust the device’s performance.
- Servo Motor Basics: A servo motor consists of a small DC motor equipped with a gear system and a potentiometer for precise control.
- Working Principle of Servo Motor: The servo motor adjusts its position by comparing the feedback from the potentiometer with an external command, stopping when both match.
- Application: This precise control makes servo motors ideal for applications where accurate positioning is crucial.
Servo Motor Working Principle
A servomechanism is a closed-loop controller that holds a mechanical output at a commanded position, speed or torque. The working principle of servo motor is that idea applied to a motor shaft: the drive runs until feedback matches the command.
What is Servomechanism?
A servo system primarily consists of three basic components: a controlled device, an output sensor and a feedback path.
A servomechanism is an automatic closed loop control system that regulates a device using a feedback signal. That signal is the difference between the measured output and a reference input.
When a reference or command is applied, the output sensor reading is compared with it. The feedback path forms a third signal, the error, which becomes the input to the controlled device.
That error keeps adjusting the device while the measured output differs from the command.
After the device reaches the commanded output, the reference and the measured output match. The error is then too small to drive the device further, so the output holds until the next command is applied.
Hence the primary task of a servomechanism is to hold the output at the desired value when load or other disturbances change.
Working Principle of Servo Motor
A hobby servo is usually a DC motor plus extra parts that close a position loop. A typical unit has a small DC motor, a potentiometer, a gear train and a comparator circuit. Industrial servos may instead use an AC or brushless motor and an encoder. A bare small DC motor spins fast but produces too little shaft torque for most loads.
The gear train inside the servo reduces that high motor speed and raises the shaft torque to a usable value. The output turns more slowly than the motor.
Initially the shaft sits where the potentiometer produces no position signal. That potentiometer voltage and an external command go into an error-detector amplifier. The amplifier boosts the difference and uses it to drive the motor.
This amplified error signal acts as the input power of the DC motor and the motor starts rotating in the commanded direction. As the motor shaft turns, the potentiometer wiper turns with it through the gear train.
As the potentiometer wiper turns, its signal changes with shaft angle. When that signal matches the external command at the amplifier, the error falls to zero and the motor stops.
At that point the amplifier has no error to send to the motor, so the shaft holds. That is the simple analog model of a hobby servo motor.
