Is the stepper motor the same as the servo motor?
The control accuracy of the AC servo motor is guaranteed by the rotary encoder at the back of the motor shaft. Taking Panasonic digital AC servo motor as an example, for a motor with a standard 2500 line encoder, the pulse equivalent is 360 degrees /10000=0.036 degrees due to the adoption of the four octave technique in the drive. For a motor with a 17 bit encoder, the drive turns 217=131072 pulses per receiver, i.e., its pulse equivalent is 360 DEG /131072=9.89 sec. It is the pulse equivalent 1/655 of stepping motor with step angle of 1.8 degrees.
Stepper motor and servo motor is different. The difference between the two is as follows:First, the control accuracy is differentThe step angle of two phase hybrid stepping motor is usually 3.6 degree and 1.8 degree, and the step angle of five phase hybrid stepping motor is usually 0.72 degree and 0.36 degree. There are also some high-performance stepping motors with smaller stepping angle. As a Stone Company for the production of the WEDM machine of the stepper motor, the step angle is 0.09 degrees; Germany bergerlahr company (BERGER LAHR) three-phase hybrid step motor production by the step angle dial switch is set to 1.8 degrees, 0.9 degrees, 0.72 degrees, 0.36 degrees, 0.18 degrees, 0.09 DEG and 0.072 DEG, 0.036 DEG, compatible with the step angle two-phase and five phase hybrid stepping motor.
Three, the torque frequency characteristics are differentThe output torque of the stepping motor decreases with the increase of the speed, and it drops sharply at higher speed, so the maximum working speed is usually 300 to 600RPM. AC servo motor for constant torque output, that is, at its rated speed (generally 2000RPM or 3000RPM) within the rated torque can be output at rated speed above the constant power output.
Two, low frequency characteristicsLow frequency vibration is easy to occur in stepping motors at low speeds. Vibration frequency is related to load and drive performance. Vibration frequency is generally considered as half of the no-load take-off frequency of motor. The low frequency vibration, which is determined by the working principle of the stepper motor, is very harmful to the normal operation of the machine. When stepping motor works at low speed, damping technology should be adopted to overcome low frequency vibration, such as adding damper on motor or subdividing technology on drive.AC servo motors operate very smoothly and do not vibrate even at low speeds. AC servo system has resonance suppression function, it can cover mechanical rigidity shortage, and the system has frequency analysis function (FFT), it can detect the resonance point of the machine, so that it is easy to adjust the system.
