Simulation different from hardware

[zuzuba]

Simulation different from hardware

[polzounov]

Hi!
It seems that we used the wrong equations to derive the simulator so it currently can not be relied on, I actually removed it on the dev branch but have not updated the master branch yet.

Due to problems with getting the simulator to work, we set it aside temporarily, but we can work on it a bit more if it's needed/valuable for users.

Also we are happy to take pull requests if you think you would be able/willing 😃

Cheers

[zuzuba]

Hi!
Thanks for your quick reply.
I am doing experiments on learning controllers and, in that context, the simulator is a much faster tool to test new ideas before moving to time-consuming experiments on hardware. Therefore, for my work, it would be valuable to have a trustworthy simulator.

I am happy to contribute by helping to fix the current one. Down the road, it would be nice to have also simulations with process and measurement noise that can be turned off and on with a flag but, as a start, I think that a simple deterministic simulator would do the job.

May I ask you how you derived the equations for the dynamics in the simulator? Have you tested them against those provided in the Quanser manual? Do you have an idea of where they may be failing (dynamics of theta_dot_dot, alpha_dot_dot or system parameters)?

Thanks a lot for your help.

Cheers

[polzounov]

I originally used the Quanser Qube Servo2-USB workbook to derive the state space equations and another member of my team use the Quanser Rotary pendulum workbook.
It turns out that the two workbooks had different equations, so either one or both of them are wrong.

Then we found this paper

There is also some code trying to derive the equations in this repo, but it seems I likely made a mistake somewhere in the derivations.

I also tried to get a mujoco simulator working for myself in this repo; the dynamics here seem realistic, but they don't match the Qube

Let me know if there's any material you would like for me to send you (workbooks, papers, or code).

Cheers

[polzounov]

Hi @zuzuba,

We have a working simulator now.
Just pass use_simulator=True when creating the environment.

You can look at this notebook to see how the dynamics of the simulator match up to the hardware

Please let us know if this is helpful!

Cheers