ergoCub 1.1 S/N:001 – Fingers cannot reach lower limit

[PasMarra]

Robot Name 🤖

ergoCub 1.1 S/N:001

Request/Failure description

While commanding fingers closure, using the motorgui, I've noticed that some fingers got stuck before reaching the set point.

Detailed context

right_thumb

right_thumb_oc get stuck at 52 deg.

right_fingers

As you can see, we are missing something on the other fingers.

left_thumb

left_thumb_oc works fine.

left_fingers

As you can see, we are missing something on the other fingers.

Additional context

No response

How does it affect you?

Cannot perform any grasp

[simeonedussoni]

today i gave a look at this problem.

It turned out to be due to the loose tensioning of the related tendons.

most of the issue could be solved acting on the tensioner but for the right middle finger this was not sufficient. Actually the tensioner arrived at the end and exited from the threaded receptacle.

I prepared a small spacer to be installed to temporarily fix this.

meanwhile I also finely-tuned all the fingers in order to reach endstops in closure while preserving the opening range of motion.

It turned out that the endstop need to be finely calibrated also in software since the FAP encoder read in some cases a few degrees less tha 90 with the finger fully pushed to the endstop (but this is not a problem from the point of view of the grasping at least at the present development stage)

cc @sgiraz @AntonioConsilvio @Fabrizio69 @fbiggi

[AntonioConsilvio]

Hi @PasMarra, me and @fbiggi intervened on the middle finger of the right hand.

The finger was getting stuck in the middle of its range of motion, and we disassembled the finger and replaced the spring that had stretched. On opening the finger, we found that the fingertip connector had detached and stuck in the finger leverage, compromising the finger closure.

I also replaced the FAP cable as it was damaged @fgarini.

Now the robot can be use, so please give us a feedback about the functioning of fingers! Thank you!

cc @simeonedussoni