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In lugnet.technic, Brian Davis wrote:
> In lugnet.technic, Chris Shepherd wrote:
>
> > I have built a realistic grasping end effecter that can feel
> > when something in is its grasp (without touch sensors).
>
> Nice. And I agree, nice-looking. I once Bricklinked some of those same "rubber
> skirt" pieces for this, but never did get them in an effecter that I liked (I
> was trying smaller at the time). Now I use the flexible 1x2 studless beams that
> first showed up in some of the old hockey sets:
>
> http://www.peeron.com/inv/parts/45590
>
> These seem to make ideal, compliant "fingers" to pick things up.
>
> > there are two rotation sensors, one with a
> > rigid spur gear and one with a slip clutch
> > gear.
>
> I must be missing something - why use two rotation sensors? Just monitor the one
> on the clutch gear - if it stops advancing and the program is still commanding
> the motor to turn, you know that the jaws have stalled and the fingers are on
> something. If you're careful about how you use the rotation readings, you can
> even tell the rough size of whatever the gripper is holding. I've used this on
> the NXT on several occasions (although not for a gripper), with the nice feature
> that there it requires *no* sensor ports (the rotation sensor is built into the
> motor).
>
> Here's an example of a way to "DetectStall" on the NXT:
>
> http://www.brickshelf.com/cgi-bin/gallery.cgi?i=2036021
You are not missing anything, I missed your idea, one sensor will do just fine.
I was comparing sensor reading to sensor reading and your point compares sensor
reading to motor on/off condition, which is even better.
I have never considered your idea of motor stall. That is probably because I am
notorious for high gear ratios. When I use worm gears especially, I usually
avoid stalling because of the high forces generated. But using a 1/10th second
stall, not many bad things will happen.
Great ideas, thanks.
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Message is in Reply To:
 | | Re: End effector that can "feel"
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| (...) Nice. And I agree, nice-looking. I once Bricklinked some of those same "rubber skirt" pieces for this, but never did get them in an effecter that I liked (I was trying smaller at the time). Now I use the flexible 1x2 studless beams that first (...) (19 years ago, 19-Jan-08, to lugnet.technic, lugnet.robotics)
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