adjusting the gravity compensation to compensate for more than the arm itself

[Benjamin Cohen]

Hey 

I'm interested in having the PR2 manipulate a 3-4lb object for long periods of time. I know that technically that amount of weight is within the allowed payload for each arm but I was wondering if it would be possible to tweak the counterbalance in one of the arms to account for it. Meaning, I'll go through the "Counter Balance Adjustment" process with the object in the gripper's hand. Can the magic "system of springs and linkages" compensate for an additional 3-4 pounds? Has anyone tried this before?

thanks,

-- ben

[Ilia Baranov]

Hello!

Two comments:

1) The springs are already almost at their limits, with ~ +/- 4 lbs of force on either end for adjustment. Theoretically this should be in the limit.

Practically, if the joints of your specific PR2 are a little sticky/ vary a little (as normal) you might only have ~1lbs of extra room to play with.

2)

You would have to ensure that the object remains fixed in the exact same position and orientation at all times. If it shifts, the counterbalance is totally thrown off.

Other than that, I would suggest attaching some small weights and trying it out!