Skip to main content
V
VR_971331812-Amethyst
12-Amethyst
March 14, 2023
Solved

Change velocity of servo motor according to force applied.

  • March 14, 2023
  • 1 reply
  • 2501 views

Hello.

Is it possible to set the velocity of a servo motor depending on the load applied to it, inside a dynamic analysis?

For example, the linear drive (or hydraulic cylinder) below, would have a variation on velocity, depending on the angle of the arm, due to the variations on torque applied to the electrical motor (or pump).

This would go according to the motor's torque and speed curve.

And, how to give a maximum speed? It would also need a domain.

If, linear drive force F<=5000N, then Velocity (mm/s) is 20.

If, linear drive force F>5000N, then Velocity (mm/s) is 20-0,001*F

My objective is to determine predict the magnitude of the velocity of the load.

VR_9713318_1-1678818968527.png

 

I could first get the force in function of time, got to excel and calculate the velocity in function of time, thengo back to creo and add it the servo, but this would need a few iterations and extra steps, before I get the equations correctly.

 

Mr.  @SweetPeasHub, I have seen other thread that you participated, showing great knowledge of servo motors. Could you help me with this one?

Thanks!

 

 

 

Best answer by SweetPeasHub

The independent (primary) variable has to be speed of the joint, because that can be defined before you define the force motor.

So, flip the motor curve like shown and put in the details of the curve. A function cannot have two/multiple answers so it needs some slope other than vertical. This allows the motor to apply no force at speed of 20.1 and a a reverse force if it tries to go faster than 20.1. The slope may need to be tweaked, steeper is better for the actual model but the analysis may jump too fast into a negative force for an almost vertical line. You may need a domain for negative speeds to catch everything but if you understand me so far that should be easy. Finally, you may need to make a tighter mechanism tolerance like 1e-6 as shown. (File-Prepare-Model Properties-Mechanism-->change)

 

SweetPeasHub_3-1678885737716.png

 

SweetPeasHub_1-1678885137892.png

 

SweetPeasHub_2-1678885189934.png

 

SweetPeasHub_4-1678885863167.png

 

1 reply

S
SweetPeasHub17-PeridotAnswer
17-Peridot
March 15, 2023

The independent (primary) variable has to be speed of the joint, because that can be defined before you define the force motor.

So, flip the motor curve like shown and put in the details of the curve. A function cannot have two/multiple answers so it needs some slope other than vertical. This allows the motor to apply no force at speed of 20.1 and a a reverse force if it tries to go faster than 20.1. The slope may need to be tweaked, steeper is better for the actual model but the analysis may jump too fast into a negative force for an almost vertical line. You may need a domain for negative speeds to catch everything but if you understand me so far that should be easy. Finally, you may need to make a tighter mechanism tolerance like 1e-6 as shown. (File-Prepare-Model Properties-Mechanism-->change)

 

SweetPeasHub_3-1678885737716.png

 

SweetPeasHub_1-1678885137892.png

 

SweetPeasHub_2-1678885189934.png

 

SweetPeasHub_4-1678885863167.png

 

    V
    VR_971331812-AmethystAuthor
    12-Amethyst
    March 15, 2023

    Hello.

    Thank you, very much!

    It worked perfectly.

    Since I know the force variation during the whole movement, I also know the velocity domain. This allowed me to simplify, using only one equation, for now.

    VR_9713318_4-1678912179024.png

    Resulting Force behavior

    VR_9713318_3-1678912157590.png

    Since our main goal for the mechanism of the product was to keep the Force almost constant during the movement, the variations are small if the load doesn't change, but now we can simulate with several loads and see the variation of velocity.

    Behavior with max load

    VR_9713318_5-1678912307800.png

    Difference of velocity between maximum and zero load (only structure mass)

    VR_9713318_6-1678912722525.png

     

    Now, I'll refine the Force behavior (FxVel) based on the motor Torque x angular speed to get more accurate results.

    Thanks again!

     

      S
      SweetPeasHub17-Peridot
      17-Peridot
      March 16, 2023

      I am so glad to hear this worked for you!😊

      Terms & ConditionsAccessibility statement