Stepper motor is a kind of discrete motion equipment, which has substantial connection with modern digital control technology. In the current domestic digital control system, the use of stepper motors is very extensive. With the appearance of the all-digital AC servo system, AC servo motors are increasingly used in digital control systems. In order to get used to the development trend of digital control, most of the motion control systems use stepper motors or full digital AC servo motors as performance motors. Although the two are similar in control method (pulse train and direction signal), there is a big difference in the use function and the use occasion. The use of the two is now used as a comparison. Different control accuracy 不同 The step angle of two-phase hybrid stepping motor is generally 3.6 \u0026 deg ;, 1.8 \u0026 deg ;, and the step angle of five-phase hybrid stepping motor is generally 0.72 \u0026 deg ;, 0.36 \u0026 deg ;. There are also some high-performance stepping motors with smaller step angles. For example, a stepping motor for slow-walking machine tools produced by Stone Co., Ltd. has a step angle of 0.09 \u0026 deg ;; a three-phase hybrid stepper motor produced by BERGER LAHR of Germany can have a step angle of Dip switches are set to 1.8 \u0026 deg ;, 0.9 \u0026 deg ;, 0.72 \u0026 deg ;, 0.36 \u0026 deg ;, 0.18 \u0026 deg ;, 0.09 \u0026 deg ;, 0.072 \u0026 deg ;, 0.036 \u0026 deg ;, compatible with two-phase and five-phase hybrid stepping motor Step angle. 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 fully digital AC servo motor as an example, for a motor with a standard 2500-line encoder, the pulse equivalent is 360 \u0026 deg; /10000=0.036\u0026deg; because the drive uses the quadruple frequency technology. For a motor with a 17-bit encoder, each time the driver receives 217 = 131072 pulses, the motor rotates once, that is, its pulse equivalent is 360 \u0026 deg; /131072=9.89 seconds. It is 1/655 of the pulse equivalent of a stepping motor with a step angle of 1.8 \u0026 deg ;. The torque frequency characteristics are different
The output torque of a stepping motor decreases with the increase of the speed, and it will decrease sharply at a higher speed, so its maximum operating speed is generally 300 to 600 RPM. The AC servo motor has constant torque output, that is, it can output additional torque within its additional speed (generally 2000RPM or 3000RPM), and constant power output above the additional speed. Low-frequency characteristics are different Stepping motors tend to exhibit low-frequency oscillations at low speeds. The oscillation frequency is related to the load condition and the driver’s function. Generally, the oscillation frequency is considered to be half of the no-load jump frequency of the motor. This low-frequency oscillation phenomenon, which is determined by the operating principle of a stepper motor, is very unsightly about the normal operation of the machine. When the stepper motor is operating at low speed, damping technology should be selected to overcome the low frequency oscillation phenomenon, such as adding a damper to the motor or subdividing technology on the driver. The operation of the AC servo motor is very stable, and it will not show oscillation even at low speed. The AC servo system has the function of resonance suppression, which can include the lack of mechanical rigidity, and the system has a frequency analysis function (FFT), which can detect the resonance point of the machine and facilitate system adjustment. Different overload capacity Stepper motors generally do not have overload capacity. AC servo motor has strong overload capacity.
Take Panasonic AC servo system as an example, it has speed overload and torque overload capabilities. Its maximum torque is three times the extra torque, which can be used to overcome the inertia moment of the inertia load at the moment of starting. Because stepping motors do not have such an overload capability, in order to overcome such inertia moments during selection, it is often necessary to select a motor with a larger torque, and the machine does not require such a large torque during normal operation, which presents a torque Waste. The operating functions of different stepper motors are open-loop control. If the starting frequency is too high or the load is too large, it will cause the phenomenon of lost steps or stalls. When the speed is too high, it will cause the phenomenon of overshoot. Should deal with the problem of rising and falling speed. The AC servo drive system is closed-loop control. The driver can directly sample the response signals of the motor encoder, and internally constitutes the azimuth loop and speed loop. Generally, the stepping motor does not lose steps or overshoot, and the control function is more reliable. Speed response functions are different. Stepping motors require 200 to 400 milliseconds from stopping to accelerate to the operating speed (generally several hundred revolutions per minute). The AC servo system has a better acceleration function. Taking Panasonic’s MSMA 400W AC servo motor as an example, it only takes a few milliseconds from stopping to accelerate to its additional speed of 3000 RPM, which can be used for control occasions that require quick start and stop. In summary, the AC servo system is superior to the stepper motor in many functions. However, stepper motors are often used as performance motors in some less demanding situations. Therefore, in the design process of the control system, factors such as control requirements, cost and other aspects fan motor suppliers must be summarized, and an appropriate control motor should be selected.
Tags: fan motor suppliers
ZHEJIANGQI