Servo motor positioning realization - Solutions - Huaqiang Electronic Network

Servos are primarily controlled by pulse signals. In simple terms, when a servo motor receives a pulse, it rotates by an angle corresponding to that pulse, allowing for precise movement. Since the servo motor itself can generate pulses, it emits a specific number of pulses each time it moves through a certain angle. This creates a feedback loop, enabling the system to know exactly how many pulses were sent and how many were received. As a result, the motor’s rotation can be controlled with high accuracy—up to 0.001 mm. DC servos come in two main types: brushed and brushless. Brushed motors are cost-effective, have a straightforward design, and offer good starting torque and speed control. However, they require regular maintenance due to carbon brushes, produce electromagnetic interference, and are more sensitive to environmental conditions. They are commonly used in applications where cost is a key factor.

Brushless motors, on the other hand, are smaller, lighter, and more powerful. They respond quickly, operate at higher speeds, and have lower inertia, leading to smoother and more stable performance. While their control systems are more complex, they are easier to integrate with smart systems. They use electronic commutation, which can be either square wave or sine wave, offering greater flexibility. These motors are maintenance-free, efficient, and generate less heat and electromagnetic radiation, making them ideal for a wide range of environments.

AC servo motors are also brushless and can be either synchronous or asynchronous. In motion control applications, synchronous motors are most commonly used. They have a broad power range and can deliver high power output. However, they tend to have higher inertia, and their maximum speed decreases significantly as power increases. Therefore, they are best suited for low-speed, smooth operation scenarios.

Inside a servo motor, the rotor is made of a permanent magnet. The three-phase U/V/W motor, controlled by the servo driver, generates an electromagnetic field. The rotor turns under this magnetic force, and the encoder attached to the motor sends back feedback signals to the driver. Based on this feedback, the driver adjusts the rotor's position to match the target value, ensuring accurate control. The precision of the servo motor largely depends on the resolution (number of lines) of the encoder.

When comparing AC and brushless DC servos, AC servos typically offer better performance because they use sine wave control, resulting in lower torque ripple. DC servos, while simpler and more affordable, use trapezoidal wave control. Each type has its own advantages depending on the application requirements, such as cost, complexity, and performance needs.