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How to choose stepper motor or servo motor

2018 - 07 - 09 Times of browsing:470

PI how to choose the stepper motor or servo motor

The difference of electric motor used in electric cylinder is different, but in the aspect of dynamic load and static load, the material safety factor is different, and the type of electric cylinder is also different.


1. The step motor is an open loop control element step motor which transforms the electric pulse signal into angular displacement or line displacement. In the case of non overloading, the speed of the motor and the azimuth of the suspension depend only on the frequency of the pulse signal and the number of pulses, and is not affected by the change of the load.


When the stepping drive receives a pulse signal, the SDG electric cylinder drives a fixed view on the direction of the stepping motor's setting, called the "step angle", and its rotation is done step by step with a fixed view.


The ability to manipulate angular displacement by manipulating the number of pulses, and then to reach the precise positioning, can manipulate the speed and speed of the motor rolling through the pulse control frequency, and then reach the intention of high speed.


2, the servo motor is also called the performance motor. In the automatic control system, it is used as a fulfilling element to convert the received signal into the angular displacement or angular velocity output on the motor axis. The rotor inside the servo motor is a permanent magnet, and the three-phase U/V/W controlled by the driver constitutes an electromagnetic field.


The rotor scrolls under the effect of the magnetic field, and the encoder response signal is given to the driver, and the driver is compared with the target value to adjust the rolling view point of the rotor. The accuracy of servo motor depends on the accuracy of the encoder (line number), that is, the servo motor itself has the function of announcing the pulse.


When it rotates one point of view, it will announce the corresponding number of pulses, so that the pulse of the servo driver and the servo motor encoder form the reference, so it is closed loop control and the step motor is open loop control.




The difference between the stepping motor and the servo motor is that:


1, the control precision is different. The more the phase and the number of the stepping motor, the more precision it is. The servo motor takes the block in its own encoder. The more the encoder is, the higher the precision is.


2, the control method is different; one is the open loop control, and the other one is closed-loop control.


3, the low frequency characteristics are different. The step motor is easy to show low frequency oscillation at low speed. When it is used at low speed, it usually uses damping skill or subdivision skill to overcome the low frequency oscillation scene. The servo motor operation is very stable, even at low speed, it will not show the oscillation. The communication servo system has the function of resonance suppression, which can cover the lack of mechanical rigidity, and the system has frequency analysis function (FFT) inside the system, which can detect the mechanical resonance points to facilitate the system adjustment.


4, the torque frequency characteristics are different; the output torque of the stepper motor will decrease with the increase of the speed, and the communication servo motor is constant torque output.


5, overload can not be the same; stepper motor usually does not have overload ability, and communication motor has strong overload ability.


6, the operation function is different. The control of the stepping motor is open loop control, the starting frequency is too high or the load is too large to lose the step or the block and turn. When the speed is too high, the overspeed is easy to show the overshoot and the servo drive system is closed loop control. The driver can directly sample the reaction signal of the motor encoder, and the internal position is made up of the azimuth. The ring and speed loop usually do not show the scene of stepping or overshoot of stepping motor, and the control function is more reliable.


7, the speed echo function is different; the step motor is 100 milliseconds from the stop speed to the operation speed demand, and the communication servo system has a better speed, usually only a few milliseconds, which can be used to request the quick start and stop operation.


To sum up, the communication servo system is superior to the stepper motor in many functions, but the price ratio is different. Low speed, small load, considering more cost factors, you can choose stepper motor cylinder (stepper motor cylinder).




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