Servo motor positioning realization - Solutions - Huaqiang Electronic Network

Single chip microcomputer STM32L151CCU6

Mobile phone crystal 3.2*2.5mm 3225 26M (26.000MHZ) 7.5PF 10PPM 20PPM 30PPM

SMD aluminum electrolytic capacitor

Photocoupler

Servo motors are primarily controlled using pulse signals. When a servo motor receives one pulse, it rotates by an angle corresponding to that pulse, allowing for precise movement. Since the motor itself can emit pulses, it creates a feedback loop — meaning the system knows exactly how many pulses were sent and how many were returned. This closed-loop system enables highly accurate control, achieving positioning precision up to 0.001 mm. DC servo motors come in two main types: brushed and brushless. Brushed motors are cost-effective, have a simple design, offer high starting torque, and are easy to control and maintain. However, they require periodic maintenance due to carbon brush wear and may produce electromagnetic interference, making them more suitable for general industrial or residential applications where cost is a concern.

Brushless motors, on the other hand, are compact, lightweight, and provide high output with fast response times. They operate smoothly, have stable torque, and are easier to integrate with smart systems. Their electronic commutation allows for flexible control, such as square wave or sine wave commutation. These motors are maintenance-free, energy-efficient, and generate less heat and electromagnetic noise, making them ideal for various environments and demanding applications.

AC servo motors are also brushless but differ in their operation. They are typically divided into synchronous and asynchronous types, with synchronous motors being more common in motion control systems. These motors can handle a wide range of power outputs and are known for their high torque. However, they tend to have higher inertia and lower maximum speeds, especially when power increases. This makes them more suitable for low-speed, smooth-motion applications.

Inside a servo motor, the rotor is made of a permanent magnet. The three-phase windings (U, V, W) controlled by the servo driver create an electromagnetic field, causing the rotor to rotate. An encoder attached to the motor provides feedback to the driver, which compares the actual position with the target value to adjust the rotation angle. The accuracy of the motor depends largely on the resolution (number of lines) of the encoder.

When comparing AC and DC servo motors, AC servo motors generally offer smoother performance due to sine wave control, resulting in lower torque ripple. In contrast, DC servo motors use trapezoidal wave control, which is simpler and more cost-effective. While AC systems are more complex, they are often preferred in high-precision applications, while DC systems remain popular for budget-conscious projects.