CMC tool with slow target does not work properly
Posted: Wed Jan 12, 2022 9:12 am
Hello List,
I created a number of models and created trajectories for it. There are no muscles involved, but a few constraints.
I use the CMC-tool in the slow target mode. For simple models it works fine, you just have to set the weights correctly.
But a more complete model (26 bodies, 29 coordinates/actuators, 3 weldconstraints, 1 contact force with ground) the simulation goes wild.
Here a picture of the model I tried to set the weights for CMC as good as possibe, now all weights are at 1000. Also played with the PD parameters, but that didn't help too much.
Tried both 50Hz en 100Hz sample rate in the trajectory.trc file. Making the motion slower helped a bit but not much.
The model and all data can we found in github: https://github.com/SietseAchterop/Rowin ... r/BootBaan.
To test the system use Bootbaan.osim (generated from bootbaan.py) and trajectory.mot (generated from trajectory.py and the IK tool).
On github you can find both a video of the result of the IK-tool and the result of the CMC-tool that shows the error: bootbaan_IK_video.webm and bootbaan_CMC_video.webm.
This plot shows how the controller fails.
se_inout and se_updown (red and blue) give the intended behavior of the left elbow, and the other two what happens to the elbow when CMC is at work.
In this example the tracking is correct for about 2 seconds and then suddenly deviates violently.
I really don't know what I can do to make the system stable. Is this system too complicated for CMC when using slow target mode?
Note that I don't use muscles (yet) and maybe there are implicit assumptions that there should be some?
I sometimes get this idea when reading the documentation.
Help would be most welcome!
Sietse
I created a number of models and created trajectories for it. There are no muscles involved, but a few constraints.
I use the CMC-tool in the slow target mode. For simple models it works fine, you just have to set the weights correctly.
But a more complete model (26 bodies, 29 coordinates/actuators, 3 weldconstraints, 1 contact force with ground) the simulation goes wild.
Here a picture of the model I tried to set the weights for CMC as good as possibe, now all weights are at 1000. Also played with the PD parameters, but that didn't help too much.
Tried both 50Hz en 100Hz sample rate in the trajectory.trc file. Making the motion slower helped a bit but not much.
The model and all data can we found in github: https://github.com/SietseAchterop/Rowin ... r/BootBaan.
To test the system use Bootbaan.osim (generated from bootbaan.py) and trajectory.mot (generated from trajectory.py and the IK tool).
On github you can find both a video of the result of the IK-tool and the result of the CMC-tool that shows the error: bootbaan_IK_video.webm and bootbaan_CMC_video.webm.
This plot shows how the controller fails.
se_inout and se_updown (red and blue) give the intended behavior of the left elbow, and the other two what happens to the elbow when CMC is at work.
In this example the tracking is correct for about 2 seconds and then suddenly deviates violently.
I really don't know what I can do to make the system stable. Is this system too complicated for CMC when using slow target mode?
Note that I don't use muscles (yet) and maybe there are implicit assumptions that there should be some?
I sometimes get this idea when reading the documentation.
Help would be most welcome!
Sietse