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robotology / assistive-rehab

Assistive and Rehabilitative Robotics
https://robotology.github.io/assistive-rehab/doc/mkdocs/site
BSD 3-Clause "New" or "Revised" License
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Investigate why a skeleton can get lost during a TUG #238

Closed vvasco closed 5 years ago

vvasco commented 5 years ago

We want to have a deep understanding of why a skeleton can be lost during a TUG. This occurs typically when the robot navigates to reach the finish line or during the exercise while tracking the skeleton. The second case might occur when the skeleton approaches the robot and only few keypoints remain in the FOV. If this is the reason, this might be avoided in a bigger space, increasing the distance from the skeleton that the navController tries to keep.

pattacini commented 5 years ago

@vvasco do we have an estimate of how good is the 3D reconstruction of the skeleton when the robot is moving the head and/or controlling the base during TUG?

Asking since I think the 3D points can get − hopefully only a bit − "blurred" because of gazing/navigation.

vvasco commented 5 years ago

I'll check this out during the experiments for the analysis of the loss of the skeleton. For now, what I noticed is that the step length extracted is reasonable, but the impact of the potential skeleton flickering on this specific metric might be minor (the signal is also filtered out).

vvasco commented 5 years ago

I report here three scenarios while performing a TUG.

Scenario TUG
(1) No skeleton loss normal-tug
(2) Skeleton lost during navigation:
- stiff rotation of the base		 skel-lost-beginning
(3) Skeleton lost while walking:
- few keypoints in the FOV		 skel-lost-tug-fast

(1) No skeleton loss

This is an example of the skeleton we have during a TUG, when everything goes smoothly and navigation, attention and user's walking do not affect the skeleton tracking.

(2) Skeleton lost during navigation

This is an example of skeleton loss while the robot navigates towards the finish line. The base rotates quite fast to reach the target with an angle within the angular tolerance and the gaze does not counteract for it. This causes the skeleton tracking to be lost.

(3) Skeleton lost while walking

This is an example of skeleton loss while walking, during a TUG execution. We can see that when approaching the robot, few keypoints stay within the FOV. Therefore the threshold keys-recognition-percentage is not reached and the skeletonRetriever creates a skeleton with a new id.
The distance between robot and skeleton target is set to 1.5 m due to reduced space, but in a bigger space a higher distance might help keep more keypoints in the FOV.

Regarding the drag during navigation/gazing, the skeleton is quite stable when the robot navigates towards the user, it flickers when there is a snap rotation of the base.

vvasco commented 5 years ago

We can reduce the drag by reducing the velocity-angular-saturation of navController (see c86e3b69e054939a6fa9b00498ded711acf04952).