#robotics Logs

Jan 16 2019

12:00 AM rue_shop1: https://www.youtube.com/watch?v=2laujomh0JY
12:04 AM rue_shop1: there arne't enough non-commercial robots dancing
12:13 AM rue_mohr: https://www.youtube.com/watch?v=gB9n2gHsHN4
12:39 AM eturner303: Enjoying your build log photos rueshop1
12:46 AM eturner303: here's a few of the arm I'm working on, unfortunately not quite finished with the gripper--still working on pneumatics
12:46 AM eturner303: https://www.anninrobotics.com/forum/robot-builds/my-aluminum-ar2-build-log
12:49 AM rue_mohr: arms 9, 8, 7, and 6 are mods of the same design
12:51 AM rue_mohr: looking pretty good
12:52 AM rue_mohr: its an interesting design
12:53 AM rue_mohr: eturner303, have any other projects?
12:57 AM rue_mohr: oooh, I thinks my web browser is crashing now
01:01 AM eturner303: yeah currently working on a modified Dextra hand. still waiting on some micro stepper motors to arrive but the fingers are mostly done: https://twitter.com/eturner303/status/1083180490545217536?s=19
01:06 AM rue_mohr: what kinda motors
01:13 AM eturner303: micro steppers with 1000-1 gear reduction to provide enough torque to operate the fingers
01:15 AM eturner303: RB-Pol-319 Pololu 1000:1 motors
01:16 AM rue_mohr: high speed?
01:16 AM rue_mohr: you dont want to go DC servo?
01:23 AM eturner303: https://www.pololu.com/product/1596
01:23 AM eturner303: with gear reduction it runs about 16 RPM. needed something small enough to put in the base of each finger, this motor has a cross section of 10 mm by 12 mm
01:25 AM rue_mohr: 16 rpm is a bit high then isn't it?
01:27 AM eturner303: using a tendon approach so the murderer is just turning a spool to reel in the tendon wire, versus directly bending a joint
01:28 AM eturner303: here's a video: Check out @eturner303’s Tweet: https://twitter.com/eturner303/status/1083565218909679616?s=09
01:31 AM eturner303: sorry autocorrect fail. murderer=motor
01:32 AM rue_mohr: its ok, I have an autocorrect too
01:32 AM rue_mohr: you can damn near just mash the keyboard and I'll understand ya
01:33 AM rue_mohr: how do you think the passive return will work out
01:35 AM rue_mohr: http://ruemohr.org/~ircjunk/robots/sparrow1/p1080426.jpg
01:36 AM rue_mohr: http://ruemohr.org/~ircjunk/robots/sparrow1/p1030901.jpg
01:36 AM rue_mohr: http://ruemohr.org/~ircjunk/robots/sparrow1/p1070327.jpg
01:37 AM rue_mohr: http://ruemohr.org/~ircjunk/robots/sparrow1/p1070365.jpg
01:37 AM rue_mohr: need a palm design refinement
01:40 AM rue_mohr: hmm I was supposed to work out the motion control on the small rings ebfore building the big ones
01:40 AM rue_mohr: http://ruemohr.org/~ircjunk/robots/sparrow1/slide.htm
01:54 AM eturner303: I honestly don't love the passive return mechanism oh, I think these orthodontics rubber bands I'm using the finger joints will wear out, and doesn't provide enough Force for spring motion to do things like flicking motions
01:55 AM rue_mohr: does it take lots of force to curl the finger?
01:56 AM rue_mohr: I know sometimes that design surprises people that way
01:56 AM eturner303: in the next rev I might try to do two separate wires per finger to avoid the rubber bands, but I would need to move all them motors into the wrist because they won't fit the way I'm doing it now
01:56 AM eturner303: it actually took surprisingly more Force than I expected in my test rig to fully contract the finger, I was surprised
01:57 AM rue_mohr: hmm ok
01:57 AM eturner303: but that's it for contraction, when finger is fully extended there's not much return force from the rubber bands at that point
01:57 AM eturner303: full contraction rather
01:57 AM rue_mohr: did you design that hand?
01:58 AM rue_mohr: eturner303,
01:59 AM eturner303: I've been modifying the original Dextra freecad designs for this revision, mainly fixing some issues I had in my test prints related to tendon paths and the rubber band mounts. I started a new clean room design for a REV 2 in fusion 360
02:00 AM rue_mohr: hmm I tweeted you soemthing
02:00 AM rue_mohr: dunno how to drop a link tho
02:01 AM rue_mohr: https://twitter.com/RueNahcMohr
02:01 AM rue_mohr: there...?
02:01 AM rue_mohr: hmm because it was at you, it doesn't show on mine..... hmmmm
02:01 AM eturner303: I see it, very nice!
02:02 AM rue_mohr: k
02:02 AM rue_mohr: its a mod of a track design I did
02:02 AM rue_mohr: one of my buddies was making a suit for haloween
02:03 AM rue_mohr: it was a surprise on that one too regarding contraction force
02:03 AM eturner303: did you use fishing line for the tendons or something else
02:03 AM rue_mohr: he used woven dog collar material
02:04 AM rue_mohr: and , iirc elastics for retract
02:04 AM rue_mohr: shaped pvc pipe for the wrist, dont have a pic of that
02:04 AM eturner303: you're working with air muscles too? I see it on your feed
02:05 AM rue_mohr: yea
02:05 AM rue_mohr: for the 12' mecha
02:05 AM eturner303: very cool
02:05 AM rue_mohr: you can find a video on youtube of the servo control for single acting
02:06 AM rue_mohr: but I didn't document the clockspeed I was using for the avr, so I'm not sure of the pulse times
02:06 AM rue_mohr: I'm gonna redo it using stm32 with doubleacting
02:06 AM rue_mohr: and pressure control
02:07 AM rue_mohr: the pressure control gives me force control, and with position reporting gives me force feedback
02:07 AM rue_mohr: which I have working over a serial link
02:07 AM eturner303: force feedback very cool. are you doing compliance in the joints?
02:08 AM rue_mohr: yes, thats part of the reason for the pneumatic
02:08 AM rue_mohr: a 12' robot is just always gonna be broken if its not compliant
02:08 AM eturner303: :)
02:08 AM rue_mohr: 3.66m what country you in? :)
02:09 AM eturner303: USA
02:09 AM rue_mohr: ah!
02:10 AM rue_mohr: 8-| I didn't take a pic of the force feedback with the symmetric controllers over the serial link...
02:11 AM eturner303: currently trying to get a MHF2-8D1 pneumatic gripper installed on my arm, using an airtac pressure valve
02:14 AM rue_mohr: digital or proportional valve?
02:14 AM eturner303: I have no experience with pneumatics so it's new to me.
02:14 AM eturner303: http://www.airskys.com/4v210-08-solenoid-valve/
02:14 AM eturner303: this is the valve I'm using
02:14 AM rue_mohr: digital
02:14 AM eturner303: connected to one of the relay outs
02:14 AM rue_mohr: is it a double acting cylinder?
02:14 AM eturner303: yes
02:15 AM rue_mohr: hmm, yea, you can either be powered-open or powered-closed
02:15 AM rue_mohr: haha I really need to get sleep
02:15 AM rue_mohr: would help if I were tired
02:15 AM eturner303: me too. I have work in the AM
02:15 AM rue_mohr: what do you need to know about the pneumatics?
02:16 AM eturner303: thanks for the tips, I enjoyed your Twitter feed!
02:16 AM eturner303: going to bed
02:16 AM rue_mohr: gngiht
09:50 AM SoCo_cpp__ is now known as SoCo_cpp_
12:20 PM flowbee is now known as eturner303
12:40 PM wildlander is now known as wildlander_
12:40 PM wildlander_ is now known as wildlander