ergoCub 1.2 S/N:002 – Hands issues

[giotherobot]

Robot Name 🤖

ergoCub 1.2 S/N:002

Request/Failure description

There are 2 main issues in the hands:

1. In the left hand the ring/pinky fingers are not movin at all;
2. In the right hand the index and middle fingers are unable to fully close;

In addition in both hands the thumb is loose or falling off.

Detailed context

Left hand status

Robot

GUI

Right hand status

Robot

Thumb detail:

GUI

Additional context

Possible related issues:

#1839
#1849

How does it affect you?

Very difficult to perform manipulation experiments and data collection.

[S-Dafarra]

Now also the right pinky refuses to close, even after a full reboot.

[S-Dafarra]

Despite the intervention of @AntonioConsilvio, after about 30 minutes of usage, the right pinky stopped working again

[AntonioConsilvio]

Hi @giotherobot @S-Dafarra!

Left Hand

The problem was related to this issue:

• ergoCub 1.2 S/N:002 – The fingers may refuse to close completely until a full reboot #1839

I replaced the tendon and now it is working. (more info check the comment).

Right Hand

Regarding the index and middle fingers, I was able to adjust the tendons so that they are a little tighter and improve the closure, but they still don't reach full closure.

For the time being (more for the index finger which is the worst), the only solution is to try to replace the tendon.

Pinky problem

The problem on the right pinky, was very much the same as on the left. So I think they might have the same cause.

In fact, investigating further I tried to find out what was happening on the right pinky. Moving the joint with the jogger I noticed that after a while of use this was happening (more and more often):

VID_20240805_163401.mp4

The tendon creates a loop and prevents the finger from working properly and the tendon from breaking. I am not sure what this behaviour is due to, because I have checked the sheath and insertion and found no problems.

I have replaced the tendon and it seems to be working properly.

We will wait for a longer test to see if the problem recurs

Thumb

To solve the problem of the thumbs coming off, the finger is being redesigned, as soon as we have the new parts they will be mounted.

[S-Dafarra]

The tendon creates a loop and prevents the finger from working properly

Wow, nice catch! This maybe is also happening on the 001 (see #1863).
I believe this behavior should be prevented somehow. Maybe adding a lid of some sort?

cc @fiorisi

[AntonioConsilvio]

Hi @S-Dafarra @giotherobot, We performed numerous tests and made some mechanical upgrades. Now the finger clasp should reach (or come much closer to) the hardware limit, and the tendons should no longer break so easily.

We also fixed the thumb, so it shouldn't come off anymore.

I will proceed with closing this issue, so that if there are future issues, we know they are after these modifications.