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- Performance comparison of servo motor and stepping motor
- time：06-12-2014source：hangfa news
- Stepper motor
- Servo motor
- As an open-loop control system for stepping motor, and modern digital control technology has a substantial connection. At present, digital control systems, stepper motors are widely used. With the advent of fully digital servo system, have been increasingly used in digital control servo motor system. In order to adapt to the development trend of digital control, most of the motion control system using stepper motors or as a force motor digital servo motor. Although they are similar in control mode (pulses and direction signal), but in terms of performance and applications there is a big difference. Now compare the performance of both.
- 1, control accuracy of different
- Two-phase hybrid stepping motor step angle of 1.8 °, 0.9 degrees, five-phase hybrid stepping motor stride angle is 0.72, 0.36 °. Some high performance stepper motor through the subdivision will pave the pitch angle is smaller. Sanyo (SANYO DENKI) production of two phase hybrid stepping motor and its stepping angle can be set through dip switches for 1.8, 0.9 degrees, 0.72 °, 0.36, 0.09, 0.18 degrees degrees, 0.072, 0.036 degrees, compatible with a five-phase and two-phase hybrid stepping motor stride angle.
- Servo motor control accuracy guaranteed by the back-end of the motor shaft rotary encoder. For example, for standard 2000-line encoder motor, because the drive is often adopted by four times times the frequency, pulse equivalent for 360 °/8000=0.045 °. With 17 bit encoder motor, drive each round receive 131,072 pulse motor, its pulse equivalent for 360 °/131072=0.0027466 °, is the step angle 1.8 ° stepper motor pulse equivalent of one-six hundred and fifty fifth.
- 2,Low frequency characteristics of different
- Stepper motor in low speed prone to low frequency vibration phenomena. Vibration frequency and load and drive performance-related, generally considered vibration frequency for motor take off half the frequency. The stepper motor works of low frequency vibration phenomenon determined by the normal operation of the machine is very negative. When the stepper motor at low speed, should generally be used to overcome the phenomenon of low frequency vibration damping technology, such as adding dampers in the motor or the drive using subdivision techniques and so on.
- Servo motor running very smoothly and vibration does not occur even at low speeds.
- Servo system with resonant suppression, may cover insufficient rigidity of the machine and system with frequency analysis function (FFT), mechanical resonance can be detected, and easy to adjust.
- 3,Torque-frequency characteristics of different
- Stepper motor output torque as the speed decreased and at higher speeds, drop precipitously, so the maximum operating speed is generally 300~600RPM.
- Servo motor for constant torque output, which at its rated speed or less, can output the rated torque, constant power output at rated speed above.
- 4,Overload capacity
- Stepper motors generally do not have overload. Servo motors with high overload capacity. Servo systems, for example, it has the speed-load and torque overload capacity. Its maximum torque rated torque, two to three times that can be used to overcome inertia load moment of inertia moment it starts. Stepper motor because no such overload capacity, at the time of selection in order to overcome this moment of inertia, often need to select a larger torque from the electric motor, which during normal operation of the machine does not need that much torque, there is a moment wasted.
- 5,Performance of different
- Step motor control for open-loop control, start frequency is too high or excessive load easily lost or locked-rotor phenomenon, stop high speed prone to overshoot phenomenon, so as to ensure that it is accurate, litre, speed problems should be handled well. Servo drive system for closed-loop control, drives directly to the motor encoder feedback signal is sampled, internal structure and position loop speed, there was no stepper motors lose steps or overshoot phenomena, control performance, more reliable.
- 6,Response properties
- Stepping motor to accelerate from standstill to the working speed (typically hundreds of revolutions per minute) need to 200~400 milliseconds. Servo system accelerate performance, typically accelerate from zero to the speed 3000RPM only takes a few milliseconds, rapid start-stop control for on-demand applications.
- To sum up, servo system performance is better than in many stepper motors. But in some requirements of the occasion also frequently force motor with stepping motor.
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