AC Motors Components & Measurements control DC Motor Devices EE-Tools Instruments Motors News Servo Motor Types of Motors

Servo Motor – Types, Construction, Working, Controlling & Applications

What is Servo Motor

Forms of Servo Motors – Development, Controlling and Purposes

To decide on a motor is the toughest activity, based mostly on design criteria corresponding to value, torque, acceleration, positional accuracy, power and far more. There are numerous kinds of motors like DC, Servo, and Stepper obtainable for several types of software. But, Servo motors include fast functioning, high torque, and correct rotation. Yes, Stepper Motors are a high-performance various of the servo. However to setup a Stepper is more difficult than a Servo Motor.

To know more about Servo motors working, development, mechanism, varieties, and software, proceed reading…

What’s Servo Motor?

Servo is an electromagnetic system uses a destructive feedback mechanism to converts an electric signal into controlled motion. Principally, servos behave like as actuators which give exact control over velocity, acceleration, and linear or angular position. It consists of four things: DC motor, place sensor, gear practice, and a management circuit. The gear mechanism related with the motor supplies the suggestions to the place sensor.

If the motor of the servo is operated by DC then it’s referred to as a DC servo motor and whether it is operated by AC then it is referred to as as AC servo motor. The gear of the servo motor is usually made up of plastic but in high power servos, it is made up of metallic.

Servo motors being manufactured by many corporations some of them are FUTABA, HITECH, AIRTRONICS, and JR RADIOS. They are the same in manufacturing however totally different in connector sort, wire colours, and so forth. There are numbers of forms of servos are available out there, AC, DC, continuous, positional and linear servo motor.

Varieties of Servo Motors

On the Basis of Rotation

  1. Positional Rotation Servos: Positional servos can rotate the shaft in about half of the circle. Also, it has the function to protect the rotational sensor from over-rotating. Positional servos are mainly used in limbs, robotic arms, and in many other locations.
  2. Steady Rotation Servos: Continous servos are comparable in development to the positional servo. But, it may move in each clockwise and anticlockwise instructions. These kinds of servos are utilized in radar methods and robots.
  3. Linear Servos: Once more linear servos are also like a positional servo, however with further gears to the regulate the output from round to back-and-forth. These sort of servos are used in high mannequin airplanes and are uncommon to seek out on the shops.

On the Basis of Operating Signal

There are also two kinds of servo motors used which differ in processing info and signal.

  1. Analog Servomotors

Analog servos are operated over PWM (Pulse Width Modulation) alerts. And, the range of the signal is four.8V to 6V. In such a servo, the PWM is off when the servo is at rest. The torque produced at rest time makes the starting time inactive. Also, an analog servo can have the ability to send 50 pulses per seconds only.

  1. Digital Servomotors

Using small microprocessors Digital Servo receives sign and acts at high-frequency voltage pulses. A digital servo can be capable of send 300 pulses per seconds, which could be very excessive compared to an analog servo. Digital servo provides a clean response and consistent torque, resulting from quicker pulse. Digital servos eat more power than an analog servo.


On the Foundation of Working Power

  1. DC Servo Motor

DC Servos are used for offering quick torque response and are also called a everlasting magnet DC motor or individually excited DC motor. The rationale behind providing quick torque response is because of the torque and flus are decoupled. Thus, a small variation within the armature voltage or present can produce a notable shift within the place or velocity of the shaft. DC servos are most used servo motors amongst all the kinds.

  1. AC Servo Motor

There are two kinds of AC servo motors one is 2 part and the second is 3 part. Primarily two-phase squirrel cage servo motor is used for low power purposes. And, three-phase squirrel cage servo is used for top energy methods.

Development of Servo Motor

The Servo motor is DC motor which has 5 following elements:-

  1. Stator Winding: This kind of winding wound on the stationary part of the motor. It’s also often known as area winding of the motor.
  2. Rotor Winding: Such a winding wound on the rotating part of the motor. Additionally it is often known as an armature winding of the motor.
  3. Bearing: These are of two varieties,i.e, font bearing and back bearing that are used for the movement of the shaft.
  4. Shaft: The armature winding is coupled on the iron rod is called the shaft of the motor.
  5. Encoder: It has the approximate sensor which determines the rotational velocity of motor and revolution per minute of the motor.Construction of Servo Motor

Mechanism of Servo Motor

It consists of three primary varieties:

  1. Controlling Gadget
  2. Output Sensor
  3. Suggestions system

The servo motor works on the phenomenon of the automatic closed-loop system. The controller is required for this closed-loop system. This controller consists of a comparator and a feedback path. It has one output and two inputs. In this, for producing an output signal, the comparator is used to match the required reference signal and this output signal is sensed by the sensor. The enter signal for the motor is termed as a suggestions signal. On the idea of the feedback sign, the motor starts working. Comparator sign known as a logic signal of the motor. The motor can be ON for the desired time when the logical distinction is larger and the motor can be OFF for the desired time when the logical difference is lower. Principally, a comparator is used to determine that motor can be ON or OFF. Proper functioning of the motor might be carried out with the assistance of a superb controller.Internal parts of Servo Motor

Controlling of Servo Motor:

The servo motors could be managed by the tactic PWM i.e., Pulse Width Modulation. These ship electrical alerts of inconsistent width to the motor. The width pulse is diversified within the vary of 1 millisecond to 2 milliseconds and transfer this to the servo motors with repeating 50 occasions in a second. The width of the heart beat controls the angular position of the rotating shaft. On this, three phrases are used which exhibits the controlling of the servomotor i.e., a maximum pulse, minimum pulse and repetition fee.

For example, The servo moves with the heart beat of 1 millisecond to show motor in the direction of 0˚ whereas a pulse of two milliseconds to show motor in the direction of 180˚ Between the angular positions, the heart beat width interchange by itself. Subsequently, the servo turns to the 90˚ with the heart beat of width 1.5 milliseconds.


There are three wires or leads in each servo motors. The 2 wires used from constructive supply and floor provide whereas the third wire is used to regulate the signal.


Working of Servo Motors

The servo has a place sensor, a DC motor, a gear system, a control circuit. The DC motor run at high velocity and low torque when getting energy from a battery. This velocity is lower and torque might be larger than gear and shaft meeting related to DC motors. The place of shaft senses by place sensor from its particular place and provide info to the control circuit. The signal is decoded by the control circuit from the place sensor and handles the path of rotation to get the right place. It wants a DC provide of 4.eight V to 6 V.

The discount gearbox is related to a shaft which decreases the RPM of the motor. The output shaft of the reduction gearbox is identical as of motor which is related with encoder or potentiometer. The output of the encoder is then related to the management circuit. The wires of the servomotor are additionally related to the management circuit. The motor control via microcontroller by sending alerts within the type of PWM which decodes the control circuit to rotate the motor in required angle the management circuit moves the motor in a clockwise or anticlockwise course, with this the shaft also rotates in the desired path. the encoder sends the suggestions signal to the control circuit. When the motor reaches to required angle, the control circuit stops motor accordingly with the acquired alerts from an encoder.

For example., if the motor is at 30˚and microcontroller provides angle 60˚ to the motor then control circuit rotates the motor in a clockwise path. When the motor reaches 60˚, the encoder sends a sign to the management circuit to stop the motor.

Purposes of Servo Motors

Listed here are some purposes used to regulate velocity when the servo is overheaded or over rotating:

  • They’re used to regulate the positioning and movement of elevators in radio controlled airplanes
  • They play an necessary position in robotics info of robotic due to their clean switching on or off and accurate positioning.
  • They’re utilized in hydraulic techniques to take care of hydraulic fluid within the aerospace business.
  • In radio controlled toys these are also used.
  • They’re used to extend or replay the disc trays in electronic units comparable to DVDs or Blue-ray Disc gamers.
  • They are used to take care of the velocity of automobiles within the vehicle industries.

Benefits & Disadvantages of Servo Motors


  • The driving force will improve the current to the motor coil once we place a heavy load on the motor as it makes an attempt to rotate the motor.
  • In servo motor, the Excessive-speed operation might be attainable.


  • The price will probably be larger.
  • The servo motor shouldn’t be appropriate for precision control of rotation as a result of the servo motor is making an attempt to rotate in line with the command pulses, however lags behind.

Related Electrical Drives Articles