FreeCAD as pre-post processor for MBDyn
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Re: FreeCAD as pre-post processor for MBDyn
Hey josegegas, would you please make a tutorial on cycloidal gearbox simulation? It is helpful to understand force interactions between disks and pins.
Re: FreeCAD as pre-post processor for MBDyn
Hi. Sorry but what you see in the video is just an animation, not a MBD simulation. I basically just programmed a script to move the parts as they would in a real cycloidal gearbox.
Re: FreeCAD as pre-post processor for MBDyn
OK, understood. Do you think the latest MBDyn WB is ready for this simulation? I want to try it myself as part of learning process.
Hi. Sorry but what you see in the video is just an animation, not a MBD simulation. I basically just programmed a script to move the parts as they would in a real cycloidal gearbox.
Re: FreeCAD as pre-post processor for MBDyn
It depends on what exactly you would like to model. It is for sure ready to model all the mechanism but not the contact between parts. Contact is not a very mature part yet. To model the motion you only need the motion equations of the gearbox, which can be found easily on Internet or derived from the gearbox design, and then use the existing joints... It would be interesting to model it as in this example:JamesLiu wrote: ↑Sat Jan 08, 2022 1:18 amOK, understood. Do you think the latest MBDyn WB is ready for this simulation? I want to try it myself as part of learning process.
Hi. Sorry but what you see in the video is just an animation, not a MBD simulation. I basically just programmed a script to move the parts as they would in a real cycloidal gearbox.
https://www.sky-engin.jp/en/MBDynExampl ... /ex11.html
So you can get the input and output torque, and probably the efficiency as well, assuming some coefficients.
You may want to have a look at the "Wankel engine" example:
it is somehow similar to the cycloidal gearbox. You will find the example on GitLab.
Re: FreeCAD as pre-post processor for MBDyn
It depends on what exactly you would like to model. It is for sure ready to model all the mechanism but not the contact between parts. Contact is not a very mature part yet. To model the motion you only need the motion equations of the gearbox, which can be found easily on Internet or derived from the gearbox design, and then use the existing joints... It would be interesting to model it as in this example:
Thank you for the instruction! However, my primary interest is the contact force vector between cycloidal disk and pins.
Re: FreeCAD as pre-post processor for MBDyn
Hi There,
I am trying to model simple pendulum as per the link.
https://www.youtube.com/watch?v=6pIKi2hK-5M
Problem:
While creating structural node, I am getting, error as follows.
I tried different geometry also. There is something I am missing here. It is allowing me to go ahead and even completing the simulation until free fall. A new error starts while creating revolute joint.
Please let me know, where I am making mistake.
I am on 0.19.4. Is this the mistake?
Thanks in advance.
I am trying to model simple pendulum as per the link.
https://www.youtube.com/watch?v=6pIKi2hK-5M
Problem:
While creating structural node, I am getting, error as follows.
Code: Select all
<class 'AttributeError'>: 'Part.Solid' object has no attribute 'CenterOfGravity'
Please let me know, where I am making mistake.
I am on 0.19.4. Is this the mistake?
Thanks in advance.
Re: FreeCAD as pre-post processor for MBDyn
Thanks JamesLiu.
I just downloaded 0.2 and checked. This error vanished and new error started. I will check further.
For information, the error is:
Addition of 'Rigid bodies' works fine.
Is this something related to Windows-10? I am on windows-10.
Thanks again ..
I just downloaded 0.2 and checked. This error vanished and new error started. I will check further.
For information, the error is:
Code: Select all
Running the Python command 'MBdyn_AddStaticBody' failed:
Traceback (most recent call last):
File "C:\Program Files\FreeCAD 0.20\Mod\freecad-mbdyn-dynamics-workbench-master\MBdynGui.py", line 1856, in Activated
dyn.AddStaticBody(b[0])
File "C:\Program Files\FreeCAD 0.20\Mod\freecad-mbdyn-dynamics-workbench-master\dynamics.py", line 504, in AddStaticBody
Dummybody(a, baseBody, baseBody.Label)
File "C:\Program Files\FreeCAD 0.20\Mod\freecad-mbdyn-dynamics-workbench-master\dummybody.py", line 56, in __init__
obj.addProperty("App::PropertyDistance","absolute center of mass X","Absolute center of mass","absolute center of mass X",1).absolute_center_of_mass_X = cmx
Invalid property name 'absolute center of mass X'
Is this something related to Windows-10? I am on windows-10.
Thanks again ..
Re: FreeCAD as pre-post processor for MBDyn
bumping thread (what's the status of this WB since we're close to a FreeCAD v0.20 release?)
Alone you go faster. Together we go farther
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Please mark thread [Solved]
Want to contribute back to FC? Checkout:
'good first issues' | Open TODOs and FIXMEs | How to Help FreeCAD | How to report Bugs
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Re: FreeCAD as pre-post processor for MBDyn
Did you somehow select the node and the surface and then wrote an expression for the vertical force equal to the penetration multiplied by a stiffness, and zero when the penetration is negative, or is there a GUI button that I failed to find?josegegas wrote: ↑Wed Dec 22, 2021 4:32 pm The elastic contact example was set exactly as you described it. There is a structural force determined by the distance between the two nodes. It is basically an adaptation of this example:
https://www.sky-engin.jp/en/MBDynExampl ... /ex09.html
The "bouncing brick" is also the same, although there is one node at each corner of the brick, to which a structural force is applied. All the nodes are rigidly attached together.
I think that this feature would greatly increase the real-world usability of MbDyn, as mechanisms often have catches and locks, all of which you cannot simulate without collisions.
I just had a look into the blender world: https://www.youtube.com/watch?v=V_QByJsZeRw
I've never used Blender, do you know how accurate the physics model behind this is?