What is servo mechanism and where is it used

What is servo mechanism

A servomechanism is a force amplifier mechanism in which the output accurately follows the input but with great power. It is an automatic device that can do error sensing and negative feedback will be given to correct the performance of a mechanism. Servomechanism can be electrical, mechanical, hydraulic, or optical. A servomechanism is different from other control systems because it controls a parameter by commanding the time-based derivative of that parameter. A servomechanism controlling position is capable of changing the velocity of a system because the time-based derivative of position is velocity.

In servomechanism, a controlled output of a mechanism is compared with the controlled input, and their difference it may be the positions is called the error signal and it can change the output to its desired value. An error signal will be sent to compare with the input and it is called feedback, the total process with the input, output feedback, and the error signal is known as a closed-loop.

What is the purpose of a servomechanism

  • Accurate control of motion can be done without the need for human attention or it can also be called as automatic control
  • Accuracy can be maintained with mechanical load variations, changes in the environment, power supply fluctuations, and aging and deterioration of components.
  • Output can be controlled from a remotely located input, without the use of mechanical linkage
  • High powered devices can be controlled by the signals from a low powered devices

Where is servomechanism used

  • Servomechanism is used in military, fire control, and marine navigation equipment
  • It is used in automatic machine tools, satellite tracking antennas, remote control airplanes anti-aircraft gun control system, automatic navigation systems in boats and planes
  • Radio controlled models
  • Autofocus camera to accurately position the lens
  • Modern hard dive use magnetic servo systems with sub-micrometer positioning accuracy
  • It is used in width and thickness control equipment in the industry and in opening and closing valves in furnaces.

What is meant by servo

A servo is a small device that has an output shaft and this shaft can be positioned to the specific angular position by sending the servo a coded signal, as long as the coded signal exists in the input the servo will maintain its angular position of the shaft. When the coded signal changes then the angular position of the servo shaft changes. It can be called as a closed-loop self-correcting control system, it usually contains some mechanism such as motor, like when motor runs it controls some other mechanism. If the device moves in the wrong direction or in the wrong angle an error voltage or an error angular is produced then the error signal are matched and compared with the reference signal and are supplied to activate the servo

Classification of servo mechanism

Servomechanisms can be classified into two they are the open and closed-loop systems.

Open and closed-loop system

Input transducer will convert the angular movement into a demand voltage which is then amplified and the amplified voltage drives the motor which turns the output shaft connected to a load. Major problems of this configuration is that there is no way to ensure that the output is following changes of the input and the output voltage will vary as the gain of the amplifier alters with time and temperature and because of these problems open-loop control is not good enough for close tolerance control and more control is achieved by closed-loop system. The closed-loop system feeds output positional information to an error detector which compares it with the demand, the input transducer converts the angular movement into a demand voltage. If the input shaft and output shaft are lined up then there will be no difference between the demand and feedback voltage so no error voltage is produced, feedback transducer produces a feedback voltage proportional to the angular movement of the output shaft.