Servo motors, widely used actuators in automatic control systems, play a crucial role in daily operations due to their excellent control speed and positional accuracy. They precisely convert voltage signals into torque and speed, effectively driving and controlling various objects. The rotor speed of a servo motor is completely governed by the input signal and responds extremely quickly. Furthermore, this motor possesses excellent characteristics such as a small electromechanical time constant, high linearity, and low starting voltage, efficiently converting received electrical signals into precise angular displacement or angular velocity output on the motor shaft. Servo motors are mainly divided into two categories: DC and AC. A common characteristic is that they do not rotate when the signal voltage is zero, and their speed decreases smoothly as the torque increases.
While stepper motors typically have a step angle of 1.8° (two-phase) or 0.72° (five-phase), the accuracy of AC servo motors depends on the accuracy of the motor encoder. Taking a servo motor as an example, its encoder is 16-bit. The driver receives 2^16 = 65,536 pulses per revolution. The pulse equivalent for one motor revolution is 360'/65,536 = 0.0055. This achieves closed-loop position control, fundamentally overcoming the stepper motor's step loss problem.
Torque-Frequency Characteristics: The output torque of a stepper motor decreases with increasing speed, and drops sharply at higher speeds. Its operating speed is generally tens to hundreds of revolutions per minute. In contrast, an AC servo motor provides constant torque output up to its rated speed (generally 2000 or 3000 r/min), and constant power output at its rated speed (E).
Overload Capacity: Taking a Panasonic AC servo motor as an example.
Acceleration Performance: When a stepper motor is unloaded, it takes 200-400ms to accelerate from a standstill to several hundred revolutions per minute; the AC servo motor has better acceleration performance.