Added cart-pole example

[kanekosh]

Summary

This PR adds a cart-pole example to the docs. I also added two corresponding tests:

1. Test that checks the cart-pole ODE model and its partials.
2. Test that checks the cart-pole optimization result.

Related Issues

None

Backwards incompatibilities

None

New Dependencies

None

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[robfalck]

Looks like you need an __init__.py in the dymos/examples/cart_pole directory so it gets installed as a part of the package.

[kanekosh]

I forgot to commit __init__... Now it should be able to pass all the tests and docs build check.

[coveralls]

Coverage decreased (-0.3%) to 95.215% when pulling 6f80eeb on kanekosh:cartpole_docs into 425becc on OpenMDAO:master.

[bernardopacini]

Sorry for messing up the history here -- I went through and signed all of the commits to conform to the OpenMDAO standard.

[kanekosh]

The docs build failed last time because we were using SNOPT in the embedded code. Now we use IPOPT instead so that it can pass the docs build check.

[robfalck]

There's a few stale file changes in here. Everything is good except the history is a bit messed up.

Please run this from your cartpole_docs branch to see if we can resolve the unrelated changes:

git remote add upstream https://github.com/OpenMDAO/dymos  # If you don't already have upstream as a remote
git pull upstream master
git push origin cartpole_docs

[bernardopacini]

I am not sure I got that to work as intended. I'll keep debugging this to clean it up.

[robfalck]

Seems to have worked. There were some other files updated recently (load_case.py and the workflow yml files) that are no longer showing up as changed. Should be good now.

[bernardopacini]

Seems to have worked. There were some other files updated recently (load_case.py and the workflow yml files) that are no longer showing up as changed. Should be good now.

I cleaned it up a bit further by dropping some commits that are already on master that would be duplicate. It should be set now, though let me know if you see any issues.