digit finger_tip/finger_base contact for accurate sensor info

[shivanimall]

Hello,

Wondering about this:

I see that the finger_tip and finger_base are both loaded with different digit.stl meshes
https://github.com/facebookresearch/tacto/blob/master/experiments/grasp_stability/setup/robots/sawyer_wsg50.urdf#L742
https://github.com/facebookresearch/tacto/blob/master/experiments/grasp_stability/setup/robots/sawyer_wsg50.urdf#L778

I am curious from the back-end sensor perspective, is the sensor loaded exactly on face of the finger_tip of the digit mesh.

1/ my main concern is that if say finger_base or some part other than finger_tip touches the object, is that still ok to generate accurate readings for tactile/depth maps? From my pictures/readings I generated, some of these do not have the impressions even though a contact happened.

2/ so, do you recommend switching sensor to an omnitact sensor? would I face the same problem if omnitact finger_base touches instead of the finger_tip?

3/ also, I have to touch the points on the object from the normal vector direction to the surface, so would you say (flat-facing) digit sensor may not be the best fit?

Please let me know if my question is unclear.
and, thank you for your continued support on Tacto!

[wx405557858]

Hi @shivanimall,

1. yes, the tactile sensing is for finger_tip. The finger_base is only for mounting the DIGIT sensor onto different grippers/hands and doesn't have tactile sensing.

2. if you are more interested in detecting contact from different directions, omnitact sounds suitable for it. The camera has its FOV and sensing area, and doesn't cover finger_base yet.

3. yeah, the limitation of the flat sensors is that they have to be pressed in almost the surface normal direction. DIGIT sensor has a curved gel, that could give some tolerance. Some visual guidance might be helpful to get the surface normal estimation.

[shivanimall]

thank you @wx405557858 for the detailed responses and help.

I am interested in touching the surface from normal direction, and for every desired touch point I have access to the surface normal. And yes, I am using visualisation aid for this as well.

But it seems like when I touch the desired point from the surface normal vector direction(which goes outwards, so I touch inwards), digit sensor's "finger edge tip" of the finger and not the "curved finger part" ( I can illustrate with a picture if it isn't clear) touches many times. However, the "curved finger part" has the sensor not the tip.
So for many such touch points, omnitact is a better fit, while in some other cases Digit seems better. What are your thoughts?

Also, didn't quite understand your comment on omnitact in (2) for this doesn't cover finger_base yet.

[wx405557858]

Hi @shivanimall ,

Is the "edge tip" of the sensor the finger base? or it is the case of the DIGIT sensor? An image would be helpful!

Oh, for (2), I was trying to say the camera cannot see the bottom plate of the omnitact. The bottom plate is not covered with silicone gels and is only for mounting purposes.