What Is a Small Servo Motor?
A small servo motor is a motor capable of high-precision positioning and speed control.
The motor has built-in speed and torque controllers, which provide feedback to the command value to achieve high-precision control. The word “servo” in servo motor is derived from the Greek word servus (slave), which includes the meaning of moving precisely in response to commands.
DC servo motors, powered by direct current, were once the primary choice, but AC servo motors, driven by alternating current, have now become the mainstream due to their superior durability and ease of maintenance. Although the term “small” is used in this article, there is no clear definition of the term.
The classification is made according to the line-up of each motor manufacturer, such as large, small, and precision.
Uses of Small Servo Motors
Small servo motors are used in production lines, measuring equipment, medical equipment, and other applications that require precise motion. Specific examples include machine tools, industrial robots, precision instruments and electronic components, liquid crystal displays, semiconductor manufacturing equipment, inspection equipment, and biological equipment.
For example, an industrial robot used in an automobile manufacturing plant can perform tasks such as picking, welding, and painting on parts repeatedly and accurately, and this is achieved through precise control by servo motors. In our daily lives, servo motors are also used in various office automation equipment and automobiles.
Principle of Small Servo Motors
Servo motors can operate accurately when combined with multiple devices. A servo motor system consists of a controller as the control tower, a driver or servo amplifier as the control unit, and a motor as the drive unit. In addition, an encoder serves as a detector to determine the actual driving status of the motor.
When a servo motor operates, the controller transmits operating conditions such as position, revolutions, torque, and speed to the driver. Based on the conditions transmitted by the driver and the motor’s rotation status transmitted by the encoder, the driver applies the optimum power to the motor for rotation, and the motor is controlled based on feedback from the encoder to achieve the target rotation conditions communicated by the controller.
In general, either a speed control system or a position control system is used when the servo controller gives commands to the driver.
Other Information on Small Servo Motors
Differences Between AC Servo Motors and DC Servo Motors
In addition to servo motors, there are various other types of motors, including DC motors, AC motors, and pulse motors. Among these, there are two types of servo motors: DC servo motors, which are DC motors, and AC servo motors, which are AC motors. AC servo motors are currently the most widely used.
AC servo motors use a permanent magnet on a rotating shaft called the rotor which is surrounded by an iron core and coils, forming a stator around the rotating shaft. The stator generates a magnetic field by passing an electric current through the stator’s coil in accordance with the timing of the frequency of the alternating current. This generates an attractive or repulsive force between the stator and the permanent magnet on the rotating shaft, causing the rotating shaft to rotate.
The rotating shaft is operated without contact with the coil, so the only frictional sliding part is the bearing. Since current flows through the stator side, it is the stator on the outside of the motor that generates heat. From the standpoint of heat dissipation, AC motors are easier to dissipate heat because the stator, which is on the outside of the motor, generates heat.
On the other hand, DC servo motors provide high torque even though they are relatively small. Another feature of DC servomotors is their controllability and low cost. However, DC motors cause brush wear because the brushes and commutator are in direct contact and conduct electricity. Maintenance is required to deal with the wear, and another disadvantage is the possibility of sparks caused by brush wear powder in some environments.