Simscape multibody in R2022b

I having some problems when I try to open a Multidody model in R2022b. They are models that work fien in R2021b ond previous but not in R2022b. I get an error when I try to open a stp file. I can open it in R2021b but not in R2022b.

Find attached a simple example. It runs ok in R2021b but when I try to run it in R2022b I get this warning:

['untitled_R2021b/Solid2'] : Frame F1 [Frame1]: The geometric feature the origin is based on, "planar surface 26", does not exist. The geometry may have changed. Resolve this issue in order to remove the warning.

I can't open the FileSolid Cuerpo3.stp. I get this error.

The parameter File Name is an invalid file. Error reading file C:\Users\Vicente\Desktop\Stanford\Cuerpo3.stp.

Any ideas about why this happens?

Best regards

[Shree Charan]

HI @Vicente Casanova, MATLAB File Solid block supports STEP files of release types AP 203 E1/E2, AP 214, and AP 242. Further CAD drawing and assembly files, which do not contain the necessary data for a solid element, cannot be imported to the block.

You may read about the same at Solid element with properties derived from external file - MATLAB - MathWorks India.

I tried to open the same in MATLAB R2021b and got the same error. 'Cuerpo3.stp' seems to be of an invalid type.

[Vicente Casanova]

Hi Shree

Tanks for your answer but I don't understand why the same file works un R2021 and not in R2022, What happened to the forward compatibility.

Anyways, can you, please, tell me how can I make an assembly (I use Siemens NX but can do in SolidWorks), export and load into a file solid block?.

I really don't know whay "which do not contain the necessary data for a solid element" means.

Best regards and thanks again

[Vicente Casanova]

Hi Nathan

Thank you very much for your help.

My problem is that I have some (a lot of them) examples that I use in my classes and they are done as assemblies. I use Siemens NX for the CAD work. What I usually do is open a file with the full mechanism (usually downloaded from GrabCad or other repositories), and export it as as a few step files to be imported in Simscape. I put in the same file all the parts rigidldlly connected and connectct the solids with the appropriated joint in Simscape. It worked so far. But in this version when I export an assembly it is not recognized in Simscape. I have done a couple of examples combining the parts into one solid but I can't use the constraints available in the assembly.

Let me give you an example. This wheel (can't attach the file but you can download from

https://www.vexrobotics.com/cadmodels/upload/download/upload_id/622b363c-ed5e-4f73-bb79-5d6c414e6eea/key/69c3fb58309c4f1d582c9563cd6b08b8472b89967025d4323c01ca4a0e5d3a2c)

has to be exported in two files: Roller.stp and Body.stp. I have to connect the rollers with the body using revolute joints for a proper simulation.

I open the file in NX and it is an assembly of 4 solids. Two of them for the roller and the other two for the body. No problem with the roller, I can join the two parts into a single solid. But the body:

has to join the body itself an the 14 little axis (I need them for the revolute joint in Simscape). How can I join the assembly without redoing it?.

Is any way to export a previouslly done assembly to be recognized in Simscape as I did in the previous versions?. Is it better if i use SW instead of NX?

Any suggestion is very welcome. I have a lot of work (assemblies) done and it'd be a tragedy if I have to do it again.

Best regards

[Nathan Hardenberg]

Hi Vicente.

Firstly, please comment on the/my according answer next time, if you need clarification. This makes it easier, to later connect the discussion.

Regarding your reply:

• Did my suggestion work for you in this example?
• Do you have a lot of examples of CAD-Assemblies, or lots of already done Simscape models?

Toward your questions in the end. There is a "Simscape Multibody Link" plugin for Inventor, Creo and Solidworks, which creates a Simscape Model from your CAD assembly. With this the joints are already connected the same as in the assembly. I recommend doing this if you have moving parts. If you do not have moving parts I would just connect all bodies and export as one object

Answer 1

[Nathan Hardenberg]

I do not know, why this worked for you in R2021b. I did not test it in that version, but it did not seem to work for @Shree Charan in R2021b.

But what is the problem here: The Cuerpo3.stp file does contain two solids. This is most likely not supported.

To fix this open the Cuerpo3.stp file in you CAD software of choice and only export the body that you want to really have. Or combine both/all as one body an export that.

I did that for you and exported the bodies seperatly and one combined (see attachement). Use the appropriate one and the problem should be solved.

EDIT: You also seem to have a geometric Frame (Frame F1) based on a geometric feature. Maybe you have to create this frame again, after changing the file. Not necessarily, but just something to keep in mind.

Answer 2

[Vicente Casanova]

Hi Nathan

Thanks again.

Did my suggestion work for you in this example?. Yes, it worked. But I would rather not have to do it as it is a lot of work. The examples are from the work of several students through, maybe, 5 years or more. Some of the examples have a lot of parts and is difficult to join them togheter without using assemblies.

Do you have a lot of examples of CAD-Assemblies, or lots of already done Simscape models?. Both. Usually we use the assembly to split it into a few step files to be joined in Simscape. The problem is that many of the step files include several parts that can be simulated as a single file solid because there is no motion between the parts.

I've used the plugin for SW but it creates a model whith a lot of files solids and is a bit difficult to 'read'. For example, if I have a chassis with 10 screws, you get 11 file solid blocks and i'd like to have only one single block. Of course, I can remove the screws but the animation is less realistic and sometime i need the small details to put the frames to connect with joints.

Can I convert a step file that works in R2021 and previous into a step file (of any other format) that works in R2022?.

I'd like not to lose the work of this years just for a versión change.

Best regards