Published in

What is a Servo Motor and How it Works?


By Unblocked Hub

August 3, 2022

Servo motors are part of a closed loop system and consist of several parts, one of which is a control circuit. Servo motor, shaft, amplifier and an encoder or resolver. A servo motor is a self-contained electrical device that rotates the parts of a machine with high efficiency and great precision. The output shaft of this motor can be moved at a certain angle in a position and speed that an ordinary motor does not have. The servo motor uses a normal motor. And it's paired with a sensor for positional feedback. The controller is the most important part of the servo motor. It was designed specifically for this purpose.

The servo motor is a closed-loop mechanism that includes position feedback. The motor is controlled by an analog or digital electrical signal that determines the amount of movement. Represents the last command position for the shaft. A type of encoder acts as a sensor, providing speed and position feedback. This circuit is placed in the body of the motor. It is usually equipped with a gear system.

Servo motor types are classified into different types according to their applications. Such as AC servo motor, DC servo motor. There are three main considerations for evaluating servo motors. Firstly, depending on their type, AC or DC, secondly, depending on the type of change used, whether the motor uses brushes or not, and the third issue is whether the motor has a rotation area, whether the rotation is synchronous or asynchronous.

AC or DC is the most basic classification of the motor according to the type of current it will use. From a performance perspective, the primary difference between AC and DC motors is in controlling speed. The speed of a DC motor is directly proportional to its voltage. In an AC motor, speed is determined by the frequency of the applied voltage and the number of magnetic poles. While both AC and DC motors are used in servo systems, AC motors will withstand higher current. And in applications with high repetitions such as Robots, AC motors are more commonly used in servo applications.

A DC servo motor is switched mechanically with brushes or electronically without brushes using a commutator. Brush motors are generally cheaper and easier to use. Brushless designs are more reliable, have higher efficiency and are less noisy. The commutator is a rotary electrical switch that periodically reverses the current direction between the rotor and the drive circuit. It consists of a cylinder with multiple metal contact parts on the rotor. Two or more electrical contacts, called brushes, are made of a soft conductive material, such as carbon press, against the commutator. As it rotates, it makes sliding contact with the segments of the commutator. Although AC brushless design is mostly used in servo systems, DC brushed motor is sometimes used due to its simplicity and low cost. The most commonly used type is the permanent magnet type. Brushless DC motors typically replace the brush in a brushed DC motor by using a hall effect sensor or encoder. AC motors are generally brushless.

DC motors are generally divided into brushed and brushless. AC motors are distinguished by the speed of their rotating synchronous or asynchronous fields. In an AC motor, the speed depends on the frequency of the supply voltage. This speed is called synchronous speed. Therefore, in a synchronous motor, the rotor speed is equal to the stator speed. However, in an asynchronous motor, the rotor rotates at a slower speed than the rotating magnetic field of the stator. The speed of the asynchronous motor can be changed by various control methods. For example, changing the number of poles or changing the welding frequency.

 Servo motor applications are applied in many industrial and commercial systems. And it is also used in products such as robotics. A servo motor is used to realize precise angle of movement at each joint of a robot. Camera autofocus uses a servo motor built into the camera that precisely corrects the position of the lens. Antenna positioning systems and servo motors are used for both azimuth and positioning.