Are you the copyright owner or authorized to act on the copyright owner's
behalf?

Yes.

What work was allegedly infringed? If possible, please provide a URL:

(1) CAD files of mechanical design :  
https://github.com/plenprojectcompany/plen-3DModel_SolidWorks  
(2) STL files generated from the above CAD files:  
https://github.com/plenprojectcompany/PLEN2/tree/master/stl  
(3) CAD files of electronic design:  
https://github.com/plenprojectcompany/plen-ControlBoard  
(4) CAD files of electronic design:  
https://github.com/plenprojectcompany/plen-HeadBoard  
(5) CAD files of electronic design:  
https://github.com/plenprojectcompany/plen-RS485Board  

Please provide a detailed description of the original copyrighted work that
has allegedly been infringed. If possible, include a URL to where it is
posted online.

I have concept that the componets of the Robot should be as opensource. I
told this concept to the PLEN Project Company and they agreed my concept.
So I shared them my original copyrighted work, such as the mechanical and
eletronic design files, and robot control source code.
However, they put my original copyrighted work to their github account
where I don't have the access authority. And they change the state of
content without my permission.
Now that things have come to this pass, I decided to make my all
copyrighted works as to be closed. I have already requested several times
to them that they should remove my works from their github. But they have
ignored my request for months.

Now, as you pointed out, I consider not to be closed my copyrighted content
but I shall continue in public in my github account under the the Creative
Commons BY 4.0..

What files should be taken down? Please provide URLs for each file, or if
the entire repository, the repository's URL:

https://github.com/plenprojectcompany/plen-3DModel_SolidWorks  
https://github.com/plenprojectcompany/PLEN2/tree/master/stl  
https://github.com/plenprojectcompany/plen-ControlBoard  
https://github.com/plenprojectcompany/plen-HeadBoard  
https://github.com/plenprojectcompany/plen-RS485Board

Have you searched for any forks of the allegedly infringing files or
repositories? Each fork is a distinct
repository and must be identified separately if you believe it is
infringing and wish to have it taken down.

Yes. There are some forks. I noticed by your pointed, They have the right
to maintain their files and repositoris under the the Creative Commons BY
4.0
If the my copyrighted content at PlenProjectCompany would take down, I
should let them know the original repositoried URL.

Is the work licensed under an open source license? If so, which open source
license? Are the allegedly infringing files being used under the open
source license, or are they in violation of the license?

It is the Creative Commons BY 4.0. As you pointed out, I may not change
license in spite of they removed my copyrighted content from my repository
by illegal access and they insist that their repository's content is
original.
In this case, I have asked already the Creative Commons staff about this
situation.
Now the solution is that I will my copyrighted content under same license
at my github account and they must remove my copyrighted content from their
repositories.

What would be the best solution for the alleged infringement? Are there
specific changes the other person can make other than removal?

I think the best solution is that I will my copyrighted content under same
license at my github account and they must remove my copyrighted content
from their repositories.

Do you have the alleged infringer's contact information? If so, please
provide it:

PLENProject Compay [private]

Type (or copy and paste) the following statement: "I have a good faith
belief that use of the copyrighted materials described above on the
infringing web pages is not authorized by the copyright owner, or its
agent, or the law. I have taken fair use into consideration."

I have a good faith belief that use of the copyrighted materials described
above on the infringing web pages is not authorized by the copyright owner,
or its agent, or the law. I have taken fair use into consideration.

Type (or copy and paste) the following statement: "I swear, under penalty
of perjury, that the information in this notification is accurate and that
I am the copyright owner, or am authorized to act on behalf of the owner,
of an exclusive right that is allegedly infringed."

I swear, under penalty of perjury, that the information in this
notification is accurate and that I am the copyright owner, or am
authorized to act on behalf of the owner, of an exclusive right that is
allegedly infringed.

Please confirm that you have you have read our Guide to Submitting a DMCA
Takedown Notice:
https://help.github.com/articles/guide-to-submitting-a-dmca-takedown-notice/

I have read and understand GitHub's Guide to Filing a DMCA Notice.

So that we can get back to you, please provide either your telephone number
or physical address:

[private]

Please type your full legal name below to sign this request:  
[private]

