Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

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Varnu01
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Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by Varnu01 »

Good Day to all FreeCAD Users, Creators and Contributors

It is with great pleasure to announce the release of the Nikra-DAP FreeCAD WorkBench (revision 1)

The FreeCAD Nikra-DAP WorkBench is a planar multibody dynamics workbench that is based on Prof. Nikravesh's DAP solver. (DAP: Dynamics Analysis Program) Any multibody planar mechanism can be modelled in FreeCAD and solved in Nikra-DAP. You can create an animation of your mechanism as well as comprehensive output plots of positions, velocities and energies.

Here is an example of a Planar Dynamic Mechanism you can model and solve in Nikra-DAP (Tutorial)

Image


Acknowledgements:
Information on the Nikra-DAP team can be found here

Prof. Nikravesh's (University of Arizona) work on computational dynamics has led to the creation of the Nikra-DAP workbench. Formulations were adapted from Planar Multibody Dynamics (Parviz E. Nikravesh) 2nd Ed

A big thank you to our funders:
  • This project is funded through Engineering X, an international collaboration founded by the Royal Academy of Engineering and Lloyd's Register Foundation.
  • This project is also part of the Engineering X: Engineering Skills Where They are Most Needed Mission, which seeks to support the delivery of skills and education programmes that will lead to development of much needed engineering skills capacity, enhanced safety standards, and infrastructure that will remain safe and fit for purpose.
Image


Installation:
All files can be found here: https://github.com/ljplessis/Nikra-DAP

This workbench can be installed locally by copying the Nikra-DAP file into the Mod folder in your FreeCAD directory.

In order for this workbench to work correctly, FreeCAD Plot as well as Assembly 4 should also be installed on your computer through the addon manager.

Usage:
A Basic Overview as well as Tutorials can be found in the ReadMe file.

If you have any queries, issues or recommendations, please feel free to reach out to either @Varnu01 or @karolis.

Kind regards
The Nikra-DAP team
Last edited by Varnu01 on Wed Feb 23, 2022 12:47 pm, edited 1 time in total.
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Kunda1
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by Kunda1 »

Wow, where did you folks come from?! :lol:
First I've heard of this. Looks amazing!
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by bambuko »

Varnu01 wrote: Why Assembly 4?
...
Nikra-DAP was designed with Assembly 4 in mind and makes use of the LCS, Master Sketch and Sub-Assemblies when creating a DAP mechanism.
However, Nikra-DAP does still work well with Assembly 2 files. It is recommended however that a mechnanism created in Assembly 4 is used....
Of course you are perfectly free to choose and recommend whichever assembly workbench you prefer ;)
but if it will work with Assembly 2, will it work with Assembly 3 as well?
I am using Link branch and Assembly3
you can also download ... and try it here
excellent Assembly3 tutorials here
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NewJoker
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by NewJoker »

Great news :D

I've never heard about this MBD solver but it seems really cool.

Some time ago the development of Dynamics workbench (using MBDyn as a solver) has been started and is still continued:
https://forum.freecadweb.org/viewtopic. ... &start=390
https://gitlab.com/josegegas/freecad-mb ... -workbench
https://www.youtube.com/user/josegegas/videos

The Dynamics workbench looks very promising and capable of large motion studies (as you can see on the linked YouTube channel) but the other workbench introduced in the current thread is also interesting. At first glance, it appears to be more user-friendly. It's great that graphs can be easily created and all the currently presented functionality is contained within the GUI, without the need to write some code pieces or edit files. I hope that all the most important quantities (such as displacements, velocities, accelerations and forces) can be plotted.

In terms of open-source software, there is a severe lack of solutions for analyzing simple mechanisms, preferably literally drawn as sketches. There are some commercial programs (mainly SAM but also Working Model 2D and additional modules in CAD software such as SolidWorks or Inventor) but no free/open-source ones. The only way is to use full 3D MBD solvers like MBDyn. Often it's an overkill and a lot of effort to simulate a basic linkage. Hopefully, the workbench shown here might make the whole process easier even though it's still necessary to create a 3D model.

In fact, there's a similar problem with FEA of beam, frame and truss structures. There are almost no free solutions worth attention that can be used to analyze just these types of members. One has to use a whole FEM solver with all its features and build the model from 1D elements. Fortunately, FreeCAD already has beam elements implemented in FEM module. They come from CalculiX and can be problematic (also, not all section types are available in FreeCAD) but it's still likely the best open-source solution at the moment.
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iplayfast
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by iplayfast »

Looks interesting.
Looks like it has a dependency on scipy What is that?
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NewJoker
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by NewJoker »

iplayfast wrote: Sat Feb 26, 2022 7:16 am Looks like it has a dependency on scipy What is that?
SciPy is a Python library used for complex scientific calculations. It features modules for numerical integration, Fast Fourier Transform, optimization and differential equation solving, among others.
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Varnu01
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by Varnu01 »

Kunda1 wrote: Wed Feb 23, 2022 12:39 pm Wow, where did you folks come from?! :lol:
First I've heard of this. Looks amazing!
We are a dedicated team from South Africa. The Dap Solver has not been available until now (only the formulations are present in Nikravesh's book)
However we are still working on missing features before we can even think of incorporating this into the Addon Manager.
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Varnu01
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by Varnu01 »

bambuko wrote: Wed Feb 23, 2022 12:45 pm Of course you are perfectly free to choose and recommend whichever assembly workbench you prefer ;)
but if it will work with Assembly 2, will it work with Assembly 3 as well?
Thank you for this question.

Assembly 3 files are not compatible with Nikra-Dap. As mentioned in the documentation, the parameter inputs were designed to select LCS's when defining certain points in the assembly. As far as we know these are only present in Assembly 2 & 4.

We also wanted to avoid parts of the topological naming issue so Assembly 4 also made sense in that regard.
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Karolis
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by Karolis »

NewJoker wrote: Thu Feb 24, 2022 9:36 am Great news :D

I've never heard about this MBD solver but it seems really cool.

In terms of open-source software, there is a severe lack of solutions for analyzing simple mechanisms, preferably literally drawn as sketches. There are some commercial programs (mainly SAM but also Working Model 2D and additional modules in CAD software such as SolidWorks or Inventor) but no free/open-source ones. The only way is to use full 3D MBD solvers like MBDyn. Often it's an overkill and a lot of effort to simulate a basic linkage. Hopefully, the workbench shown here might make the whole process easier even though it's still necessary to create a 3D model.


Hi NewJoker,

Thank you very much for your encouraging words. I fully agree with your observations about making a solution available for analyzing simple mechanisms. Credit needs to go to Prof Nikravesh for the excellent work he's done over many years to develop Planar Multibody Dynamic techniques, and of course the team who worked with me to develop the Nikra-DAP workbench.

For our revision 1 workbench, we unfortunately cannot plot accelerations and forces at the moment, but they are scheduled to be added in Revision 2 that will be released early 2023. We can however plot velocities, positions (in 2D & 3D coordinate systems) as well energies (kinetic, potential and total) in Revision 1.

Kind regards,
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Re: Nikra-DAP FreeCAD Workbench (MultiBody Dynamics Analysis)

Post by bambuko »

Varnu01 wrote: Thu Mar 03, 2022 12:57 pm ...We also wanted to avoid parts of the topological naming issue so Assembly 4 also made sense in that regard.
Thank you for your reply.
May I point out that you are "misguided" in your assertion that using Assembly 4 is the (only) way to avoid TPN ;)

Anyway, since Assembly3 files are not compatible... nothing for me here ;)
I am using Link branch and Assembly3
you can also download ... and try it here
excellent Assembly3 tutorials here
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