Servo motors are widely used as the mainstream motor drive machines in the electronics industry. Since their invention, they have been considered a potential replacement for stepper motors. However, this development process inevitably brings many related problems. Therefore, this article will collect questions from the platform and provide answers, hoping to be helpful to everyone.
1. What is a servo motor? What types are there? What are its working characteristics?
Servo motors, also known as actuator motors, are used as actuators in automatic control systems to convert received electrical signals into angular displacement or angular velocity output on the motor shaft. They are broadly classified into DC and AC servo motors. Their main characteristic is that they do not rotate when the signal voltage is zero, and their speed decreases uniformly as the torque increases.
2. What is the purpose of the rotor in a servo motor?
The rotor inside a servo motor is a permanent magnet. The three-phase electricity (UNN) controlled by the driver creates an electromagnetic field, causing the rotor to rotate under the influence of this magnetic field. Simultaneously, the motor's built-in encoder feeds back signals to the driver. The driver compares the feedback value with the target value and adjusts the rotor's rotation angle accordingly. The accuracy of a servo motor depends on the accuracy (line count) of the encoder.
3. Differences between AC servo motors and brushless DC servo motors
AC servo motors are generally considered superior because they use a sine wave to control the ball screw, resulting in less torque ripple. DC servo motors use a trapezoidal wave. However, DC servo motors are simpler and cheaper. Since the 1980s, with the development of integrated circuits, power electronics, and AC variable speed drive technology, permanent magnet AC servo drive technology has seen significant advancements. Leading electrical manufacturers worldwide have successively launched their own series of AC servo motors and servo drives, continuously improving and updating them. AC servo systems have become the main development direction for contemporary high-performance servo systems, putting the older DC servo motors at risk of obsolescence. Since the 1990s, commercially available AC servo systems worldwide have adopted fully digitally controlled sine wave motor servo drives. The development of AC servo drive devices in the transmission field is progressing rapidly.
4. Comparison of permanent magnet AC servo motors and DC servo motors
The main advantages of permanent magnet AC servo motors are as follows:
① It has no brushes or steering gear, therefore it is reliable in operation and requires little maintenance;
② The stator windings are relatively easy to cool;
③ Low inertia, which easily improves the system's speed of operation (bellows coupling);
④ Suitable for high-speed, high-torque operation;
⑤ It has a smaller volume and weight for the same power.
