Why is a Tachometer Added to a Servomechanism?

A servomechanism is an automatic control system that uses feedback to maintain the desired position or speed of an object. A tachometer is a device that measures the rotational speed of a shaft or motor. In a servomechanism, a tachometer is added to:

1. Adjust Damping
Damping is the resistance of a system to oscillations or vibrations. In a servomechanism, damping is essential to prevent overshooting or oscillations of the controlled object. By adding a tachometer, the system can adjust damping to optimize the response time and stability of the system. The tachometer measures the rotational speed of the shaft and provides feedback to the controller to adjust the damping accordingly.

2. Reduce Steady State Error
Steady-state error is the difference between the desired position or speed and the actual position or speed of the controlled object when the system has reached a steady-state condition. In a servomechanism, steady-state error can be caused by friction, load disturbances, or other factors. By adding a tachometer, the system can measure the actual speed of the shaft and adjust the control input to reduce steady-state error.

3. Convert Velocity to DC Voltage
A tachometer can also convert the velocity of the shaft to a proportional DC voltage. This voltage can be used as a feedback signal to the controller to adjust the control input. The voltage can be amplified or attenuated depending on the requirements of the system.

Conclusion
A tachometer is added to a servomechanism to improve the response time, stability, and accuracy of the system. By measuring the rotational speed of the shaft, the system can adjust damping, reduce steady-state error, and convert velocity to a DC voltage. This helps to maintain the desired position or speed of the controlled object.