2020-07-31 16:29:48 Editor:凯福
When we choose the positioning mechanism, we do not understand the difference between the stepper motor and the servo motor, do not understand the difference between the stepper motor and the servo motor, or do not understand the characteristics of the servo motor and the stepper motor, with these problems, we carried out a detailed comparison for easy access:
| Stepper motor | Servo motor | |
| Phase number | 2 , 3, 5 phase, microstep system | DC servo and AC servo |
| constitute | By single mechanism | motor, encoder and driver |
| Drive control | To drive the stepper motor must have a controller, just input pulse to the driver can be simple in the open loop mode for high-precision positioning control | The input pulse is compared with the position and speed information of the encoder and then the drive current is controlled |
| Positioning | High-precision positioning can be accomplished with the open loop mode, and there will be no cumulative Angle error when stopping | Closed-loop control for accurate positioning |
| respond | Superior start and stop responsiveness | The positioning end signal can be obtained, and a warning signal will be output when the load is abnormal |
| Moment of force | In the low-speed field, the output torque can be large, but in the high-speed field, the torque will gradually decrease | High and stable torques are achieved even at high speeds At the same time as the input pulse, it operates in step mode |
| maintenance | Simple construction, so easy maintenance | Many components, high damage probability |
| precision | Depends on step Angle and drive subdivision | Depends on the accuracy of its encoder |
| Price | Low | High |
The above is the difference between stepper motor and servo motor comparison table, then what is the difference between stepper motor and servo motor, let's take a look:
| Stepper motor | Servo motor | |
| Different control accuracy | The step Angle of the two-phase hybrid stepping motor is generally 3.6 degrees and 1.8 degrees, and the step Angle of the five-phase hybrid stepping motor is generally 0.72 degrees and 0.36 degrees. There are also some high-performance stepper motors with smaller step angles: 0.18, 0.09, 0.072, 0.036 | The control accuracy of the AC servo motor is guaranteed by the rotary encoder at the rear end of the motor shaft. Taking Panasonic's all-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 frequency quadrupling technology used inside the driver. For a motor with a 17-bit encoder, the driver receives 217=131072 pulse motor for one revolution, that is, its pulse equivalent is 360 degrees /131072=9.89 seconds. It is 1/655 of the pulse equivalent of a stepper motor with a step Angle of 1.8 degrees |
| Different low frequency characteristics | Low-frequency vibration is easy to occur at low speed. The vibration frequency is related to the load and the performance of the driver, and it is generally believed that the vibration frequency is half of the no-load take-off frequency of the motor. This low-frequency vibration phenomenon determined by the working principle of the stepper motor is very unfavorable to the normal operation of the machine. When the stepper motor works at a low speed, damping technology should generally be used to overcome low-frequency vibration, such as adding a damper to the motor, or using subdivision technology on the driver | Ac servo motor runs very smoothly, even at low speeds there is no vibration phenomenon. The AC servo system has resonance suppression function, which can cover the lack of rigidity of the machine, and the frequency resolution function (fft) in the system can detect the resonance point of the machine, which is easy to adjust the system |
| The moment frequency characteristic is different | The output torque decreases with the increase of speed, and will drop sharply at higher speed, so its maximum working speed is generally 300 ~ 600rpm | It is a constant torque output, that is, within its rated speed (generally 2000rpm or 3000rpm), it can output rated torque, and above the rated speed is a constant power output |
| Different overload capacity | Generally does not have overload capability | Has a strong overload capacity |
| Take Panasonic AC servo system as an example, it has speed overload and torque overload capability. Its maximum torque is three times the rated torque and can be used to overcome the inertial torque of the inertial load at the moment of start. Because the stepper motor does not have this overload capacity, in order to overcome this inertia moment in the selection, it is often necessary to choose a motor with a larger torque, and the machine does not need so much torque during normal operation, and the phenomenon of torque waste appears. | ||
| Different operating performance | The control is open-loop control, and the starting frequency is too high or the load is too large, and the stopping speed is too high, and the overshoot phenomenon is easy. So in order to ensure the control accuracy, the problem of raising and lowering speed should be handled well | Closed-loop control, the driver can directly sample the motor encoder feedback signal, the internal position ring and speed ring, generally does not appear stepper motor lost step or overshot phenomenon, control performance is more reliable |
| The speed response performance is different | It takes 200 to 400 milliseconds to accelerate from rest to working speed (generally several hundred revolutions per minute) | The acceleration performance is good, taking Panasonic msma400w AC servo motor as an example, from static acceleration to its rated speed of 3000rpm only a few milliseconds, can be used for control occasions requiring fast start and stop |
The above is the difference between stepper motor and servo motor. Ac servo system is superior to stepper motor in many performance aspects. However, in some situations where the requirements are not high, stepper motors are often used as execution motors. Therefore, in the design process of the control system, it is necessary to comprehensively consider the control requirements, costs and other factors, and choose the appropriate control motor. In the stepper motor and servo motor difference table also made a rough comparison, welcome to communicate!
English 
Login
