Types of Servo Motors and Manufacturing Process

Servo motors are categorized into DC and AC types, each with unique characteristics. DC servo motors include brushed and brushless variants, with the former being cost-effective but requiring maintenance, and the latter offering high efficiency and low maintenance. AC servo motors consist of asynchronous and synchronous types, with the latter providing better performance but a more complex structure. The structure of servo motors includes the motor body, sensors, controller, and driver. The manufacturing process involves design, machining, winding, assembly, and testing to ensure high performance and reliability.

Types of Servo Motors

Servo motors are mainly divided into two categories: DC servo motors and AC servo motors.

DC Servo Motors

• Brushed DC Servo Motor: It has a low cost and simple structure, with a large starting torque and wide speed control range. However, it requires regular maintenance (such as replacing carbon brushes), generates electromagnetic interference, and has higher environmental requirements.
• Brushless DC Servo Motor: It is small in size, light in weight, high in output power, fast in response, high in speed, low in inertia, smooth in rotation, and stable in torque. The control is complex, but it can easily achieve intelligence. It has electronic commutation, requires no maintenance, has high efficiency, low operating temperature, low noise, low electromagnetic radiation, and a long service life.

AC Servo Motors

• Asynchronous AC Servo Motor: It has a simple structure and is lightweight and inexpensive. However, it cannot economically achieve a very wide range of smooth speed control. It must absorb lagging excitation current from the power grid, resulting in a poor power factor.
• Synchronous AC Servo Motor: It has a more complex structure than induction motors but simpler than DC motors. Depending on the rotor structure, it can be divided into electromagnetic and non-electromagnetic types. Non-electromagnetic types include hysteresis, permanent magnet, and reluctance types. Permanent magnet synchronous motors have the advantages of simple structure, reliable operation, and high efficiency, but they are larger in size and have poor starting characteristics.

Structure of Servo Motors

The structure of a servo motor mainly consists of the following parts:

Motor Body

• Stator: The stator core is usually made of laminated silicon steel sheets. The slots on its surface are embedded with two-phase windings. One phase is the excitation winding, and the other is the control winding. The two windings are spatially positioned 90° apart in electrical angle.
• Rotor: The structure of the rotor varies depending on the type of motor. For example, the rotor of a permanent magnet synchronous motor consists of permanent magnets and bearings, which generate torque through magnetic field action.

Sensors

Sensors are used to detect the position, speed, acceleration, and other parameters of the motor and feedback this information to the controller and driver. Common sensors include encoders, Hall elements, potentiometers, etc.

Controller

The controller is the core component of a servo motor, mainly responsible for controlling the motor’s speed, position, and other parameters. Controllers typically use digital signal processors (DSP) or microcontroller (MCU) chips.

Driver

The driver is the power source of the servo motor, mainly responsible for converting the motor’s control signal into a drive signal. Drivers usually use power semiconductor devices such as MOSFETs and IGBTs.

Manufacturing Process of Servo Motors

The manufacturing process of servo motors is relatively complex and mainly includes the following steps:

Design and Planning

Based on application scenarios and customer requirements, computer-aided design (CAD) software is used to create a three-dimensional model of the motor and perform analysis to determine parameters such as the motor’s speed, torque, and power.

Machining

The machining process includes milling, turning, drilling, cutting, etc. High-precision machines and tools are required to ensure that the size and shape of the motor meet the design requirements.

Winding Production

The production of windings needs to be determined based on the motor’s speed, voltage, current, and other parameters to determine the number of turns and cross-sectional area of the coil. Common winding processes include layered winding, single-layer winding, and cross-winding.

Assembly

Assemble the processed housing, wound coils, rotors, and other components. The assembly process must be carried out strictly according to the design requirements, including bearing installation, coil fixation, rotor alignment, etc.

Testing and Debugging

After manufacturing, rigorous testing and debugging are required to verify the performance and reliability of the motor, including tests of parameters such as speed, torque, and position.