#robotics Logs

Nov 26 2013

00:08 armyofevilrobots aliexpress has some narrower ones. One sec.
00:09 armyofevilrobots Damn, didn't save, but it's in there.
00:09 armyofevilrobots 2 meters by 18"-ish iirdc.
00:09 MrCurious k, searching there
00:10 Jak_o_Shadows right. Proportional control. Hmmm.
00:10 MrCurious only 808 results...
00:15 armyofevilrobots http://www.aliexpress.com/item/9pcs-15x60mm-L-390mm-Flat-Aluminium-profile-Extrusion-for-DIY-CNC-Router-Base-CNC-Working-Table/1328981839.html
00:15 armyofevilrobots for example.
00:16 armyofevilrobots Those are shorties though.
00:16 armyofevilrobots expensive for extrusion shipping though.
00:17 MrCurious huh $14 ea, shipping $40
00:17 MrCurious yeah
00:17 armyofevilrobots better: http://www.aliexpress.com/store/product/1pcs-15x60mm-flat-Aluminum-Extrusion-1560-L1000mm-Industrial-Aluminum-Profile-accessories-for-DIY-CNC-Base-windon/134277_1328935041.html
00:18 MrCurious nice. $100 worth of those would meet my need
00:18 MrCurious but the shipping would be too insane
00:18 armyofevilrobots at that price, just ordering 80/20 is going to make more sense.
00:19 armyofevilrobots Sorry for getting your hopes up. I didn't notice the shipping before.
00:19 MrCurious no worries
00:19 MrCurious worked out why printer wasnt printing
00:19 MrCurious seems turning the power on is reqquired
00:20 Jak_o_Shadows Similarly, apparently auto-rotate needs to be enabled on android to have rotation data
00:21 MrCurious yep
00:21 MrCurious my auto rotate gets confused in gmail. and locks to the wrong orientation
00:21 GuShH extrusions? buy locally you dumbwits
00:22 GuShH if you even think about buying aluminum extrusions from china I will personally beat you with a stick
00:22 MrCurious they dont have the extrusions that i want
00:22 Jak_o_Shadows I'm writing an app, it'll eventually do PID control to go in a straight line. I'm looking at P atm, so I want better numbers
00:22 GuShH find another place
00:22 MrCurious suppose i can heck another shop
00:23 MrCurious yeah, 8020 may be the answer
00:24 MrCurious but thats painful expensive if you bury the quill into it....
00:25 armyofevilrobots Yeah, it's really nice working on the router where there is a cheap mdf spoilboard. I am really lazy about depth of cut.
00:26 MrCurious i think that will be the plan...
00:27 MrCurious 3/4 mdf on top of 1/3 aluminum sheet
00:27 armyofevilrobots Too deep, meh, just level the table with a flycutter after.
00:27 armyofevilrobots :)
00:27 GuShH lol
00:27 MrCurious suppose i could imbed some t-slots on te aluminum sheet, and put mdf near it
00:28 GuShH o.O
00:28 armyofevilrobots It's not really a flycutter, just a big ass dado bit, but it works.
00:28 armyofevilrobots can't run coolant on mdf though, so that's a bit of a pita. Just air cooling.
00:28 GuShH use high density plastic instead
00:28 MrCurious that looks tempting http://www.ebay.com/itm/33-Bosch-Rexroth-45-Series-T-Slot-Aluminum-Extrusions-20-Pcs-20-3-4-45mmx90mm-/161158247396?pt=LH_DefaultDomain_0&hash=item2585c7b3e4
00:28 GuShH not as cheap but it doesn't care about fluids
00:29 armyofevilrobots I tried uhmw but it was too slippery.
00:29 MrCurious no plans for it. but i think that much 8020 would solve itself
00:29 GuShH you have to index it somehow
00:29 GuShH with pegs or similar
00:29 GuShH or metal edges
00:29 armyofevilrobots Yeah. Maybe integrated dogholes.
00:29 MrCurious the cnc can index it, then i can tap the holes
00:29 MrCurious only issue is when its replace the mdf time
00:29 GuShH I mean index both parts and fasten them one way or another to prevent the low friction from doing it's thang
00:29 MrCurious lining up the holes again
00:30 MrCurious unless i use mdf 1 to make replacement
00:30 GuShH hmm
00:30 MrCurious and always keep a hot replacement
00:30 MrCurious as a template
00:30 ShH wants a tum
00:30 GuShH should put something together ...
00:41 MrCurious and a moment of inspiration....
00:41 MrCurious i made a t-track running sled for my table saw out of wood.
00:42 MrCurious its off ever so slightly
00:42 MrCurious just realized making it from aluminum, and using screws to fine adjust....
00:42 MrCurious would give me the precision i want
00:43 MrCurious !q2w3df5g6h790-=\-0976rw321qwer7u9-\
00:45 GuShH stroke
00:46 GuShH or cat invasion
00:48 MrCurious cleaning keyboard in prep for interview tomorrow
00:48 MrCurious notepad, laptop and resumes ready
00:50 MrCurious pre-interview panic woo hoo
15:17 MrCurious which is worse... the interview, or waiting after it for results?
16:01 MrCurious interviews are like multitasking.... only with one T
18:02 KongfuPanda GuShH, http://www.youtube.com/watch?v=UgDg26msXyM
18:16 robotustra hmmm
18:16 robotustra cartoon bbw
18:18 GuShH KongfuPanda: heh
21:17 MrCurious does the day bring any interesting stories?
21:18 GargantuaSauce i have sprung a huge boner for canfield joints
21:18 GargantuaSauce gonna get my printer working again and build one sometime soon
21:19 GargantuaSauce https://www.youtube.com/watch?v=xVdwIiGUTMc
21:20 MrCurious nice delta
21:20 GargantuaSauce http://www.cae.tntech.edu/~scanfield/ME3610/Canfield_Joint/CAD%20dwgs/carpal_kin.h the dude writes fucking ENGINEER-code though
21:26 MrCurious :)
21:28 GargantuaSauce anyway it has a full hemisphere of motion and is incapable of twisting/tangling a wire attached to the gimbal
21:29 GargantuaSauce so it'd make a pretty sweet platform for, say, a camera and directional antenna
21:33 MrCurious could be nice robot wrists....
21:33 GargantuaSauce maybe, though they're only 2dof
21:33 GargantuaSauce no twisting
21:33 MrCurious add a twist motor :)
21:37 GargantuaSauce learning how to control it is going to be interesting
21:38 GargantuaSauce i have no idea how to handle overconstrained systems
21:39 ace4016 delta robots are fun
21:39 ace4016 you can do the math yourself
21:45 GargantuaSauce the math needs to come after the conceptual backing ;)
21:46 GargantuaSauce like a kinematic chain makes perfect sense to me but once you add cycles to the graph i don't even
21:55 dthem is currently programming a AOI robot from home over vn
21:56 Jak_o_Shadows Any clues on the dynamics of a skid-skeer tricycle?
21:57 GargantuaSauce probably more skid than steer
21:57 GargantuaSauce or is the third wheel a caster?
22:02 Jak_o_Shadows caster, yeah.
22:05 GargantuaSauce oh, then it's just the usual differential drive deal
22:06 GargantuaSauce i had a good link for this but i cant find it
22:08 Jak_o_Shadows ha.
22:12 GargantuaSauce yeah crap, it was a good one too! very intiuitive rather than just throwing a bunch of math at you
22:12 GargantuaSauce but here's one that just throws a bunch of math at you http://www.cs.columbia.edu/~allen/F13/NOTES/icckinematics.pdf
22:12 Jak_o_Shadows wooo, maths
22:12 Jak_o_Shadows ty
22:13 GargantuaSauce but aside from that the obvious is true....forward motion is proportional to the sum of the wheels' rotational speeds
22:13 GargantuaSauce turning is proportional to their difference
22:14 Jak_o_Shadows Yeah. I have the angle setup so I can read in a desired compass direction. I was doing bang-bang control, but it was failing when there was a large amount of misalignment
22:14 Jak_o_Shadows Plus, I couldn't analyse it
22:20 Jak_o_Shadows I should buy a tachometer
22:21 GargantuaSauce it is pretty simple to make a crude encoder
22:42 eadthem if your looking for knematics as in for a delta type robot
22:43 eadthem i have atmel code that calculates the magnitudes for a given x y z and back
22:43 eadthem not fast code
22:43 eadthem even when optimised
22:45 GargantuaSauce nah once i understand what's going on, writing the code is the easy/fun part
22:48 eadthem well if you want a refrence http://final.servegame.com/public/inverseKinematics/
22:48 eadthem theres some PDF's i collected
22:48 eadthem clavdelt.pdf is where i got most of my how it works stuff from
22:48 GargantuaSauce cool
22:49 eadthem sidecenterpoint.png is how my code thinks of the robot top down
22:51 eadthem aparently ace4016 helped when i was working on it
22:51 eadthem as did rue_house
22:57 GargantuaSauce i suspect dealing with the canfield joint is going to be significantly more complicated
22:57 GargantuaSauce cause the kinematic chains to the end effectuator have twice as many degrees of freedom and they are not all coplanar
22:58 GargantuaSauce though supposedly it does have a closed-form solution which i find surprising!
22:58 eadthem mmm
22:58 eadthem http://selenianboondocks.com/wp-content/uploads/2010/06/basicCanfieldJoint.gif
22:59 eadthem like that ?
22:59 GargantuaSauce yeah
22:59 eadthem looks like a nomal delta
22:59 MrCurious GargantuaSauce: ty forruining ramstein for me....
22:59 MrCurious du du hast du hast mich!
22:59 GargantuaSauce see those cylindrical sections by the 'knee'?
23:00 eadthem just the motor plate is the same size as the end effector
23:00 MrCurious you hate you hate me
23:00 GargantuaSauce those are joints
23:00 eadthem shuldnt matter
23:00 GargantuaSauce https://www.youtube.com/watch?v=xVdwIiGUTMc
23:00 eadthem ya and
23:00 eadthem o
23:00 eadthem ya check the code
23:00 eadthem it might handle it alredy
23:00 eadthem but that is not what i was thinking
23:01 GargantuaSauce well i found the inventor's code http://www.cae.tntech.edu/~scanfield/ME3610/Canfield_Joint/CAD%20dwgs/carpal_kin.h
23:01 GargantuaSauce but it's....what it is
23:32 GuShH GargantuaSauce: a lump of .... ?
23:32 GargantuaSauce sauce
23:33 GuShH there's some pasta too
23:33 GargantuaSauce from the code-in-a-header to the cargo cult stdin input, it's ENGINEER CODE
23:35 GargantuaSauce http://www.cae.tntech.edu/~scanfield/ME3610/Canfield_Joint/model%20controlled%20with%20mouse/ this is kinda cool, wish the sauce was there
23:44 rue_house there a youtube vid of it, I run linux
23:48 GargantuaSauce so do i, it works in wine
23:52 GargantuaSauce http://www.cae.tntech.edu/~scanfield/ME3610/Canfield_Joint/dynamics/CHAP4.PDF explains it pretty well
23:53 GargantuaSauce i suspect the math would be notably simpler if it were properly vectorized
23:54 GargantuaSauce maybe i'll try and play whiteboard hero or maybe i'll just go ahead and implement it straight from the paper
23:56 Jak_o_Shadows Damn I wish i had a good sized whiteboard
23:57 GargantuaSauce mine is only like 60x40cm
23:58 Jak_o_Shadows I should get some whiteboard paint.
23:58 GargantuaSauce a full whiteboard wall would be pretty sweet