#robotics Logs

Oct 08 2015

01:28 mrdata anonnumberanon, ltspice is a circuit simulator maintained by Linear corp
01:28 anonnumberanon mrdata, it's not in my Debian packages
01:28 mrdata they make it free, and make all their models available
01:28 mrdata it runs on wine
01:28 mrdata so, it's a windows product that has wine support
01:29 anonnumberanon So if you're telling me this it is because it beats every other free software and open source software that exist?
01:30 mrdata they maintain it; so you dont have to.. and it has a large user community
01:30 mrdata other circuit sim products are either totally closed and expensive, or totally open but have no user base
01:30 anonnumberanon mrdata, so what's the catch?
01:30 mrdata no particular catch. i use it quite a bit
01:31 mrdata in fact i am running a sim with it now
01:31 mrdata for a magnetics project
01:31 anonnumberanon Yes but how do they make money if they don't charge you for it?
01:33 mrdata they ship it with models for all their chips
01:33 mrdata so it is easy to sim with theirs
01:34 anonnumberanon :) that's what I thought
01:34 mrdata spice models for other chips are available sometimes, from the user community
01:35 mrdata and i think texas instruments publishes those for their stuff
01:35 mrdata and those run on ltspice
01:35 anonnumberanon can it simulate a load?
01:36 mrdata yes
01:36 anonnumberanon can it simulate battery discharging?
01:36 mrdata what do you wanrt to do?
01:36 anonnumberanon lol that would be sick
01:37 mrdata for that, you would make a voltage source that is a file on your computer maybe
01:37 anonnumberanon I'm building a humanoid robot.
01:38 anonnumberanon Would love chec king the effects of diodes and capacitors onto a servo power board.
01:43 mrdata i'll show you a screen shot of my sim right now..
01:44 mrdata http://imgur.com/unChpPa
01:48 data sleep
01:52 anonnumberanon mrdata, ah nice, have fun with making the Death Star
06:58 deshipu guys guys guys
06:58 deshipu the underactuated robotics course is starting again
06:58 deshipu https://www.edx.org/course/underactuated-robotics-mitx-6-832x-0
06:58 deshipu highly recommended for anyone building anything walking
09:12 veverak deshipu: awesp,e
09:12 veverak :)
09:12 veverak *awesome
10:16 mrdata underactuated?
10:18 deshipu mrdata: yes, basically with more degree of freedom than actuators
10:19 mrdata hmm... https://en.wikipedia.org/wiki/Underactuation
10:20 deshipu yes, the first two lectures are dedicated to defining the term formally :)
10:22 eedEvil wiggles it, just a little
10:23 SpeedEvil https://www.youtube.com/watch?v=pgaEE27nsQw is awesome
10:23 SpeedEvil Flexible Muscle-Based Locomotion for Bipedal Creatures
10:24 eedEvil wishes he had the energy for that cou
10:30 SpeedEvil The muscle-based thing is broadly similar
12:38 rue_school yes, need to get with my 12' mecha
12:38 rue_school but I need to clean out my room here too
13:03 SpeedEvil I like my mechs oldschool.
13:03 SpeedEvil https://whisperingdark.files.wordpress.com/2013/06/baba.jpg
13:35 Kamondelious hehe, I made something like that a while back. https://www.youtube.com/watch?v=06G4Ua1ULuQ
13:36 rue_school you did your own servo drivers?
13:36 rue_school or is that $1200 in digital servos?
13:39 Kamondelious Those are Dynamixel AX-12s , so about $600 in servos and an Arbotix controller http://www.vanadiumlabs.com/arbotix.html
13:47 deshipu that is a lot of servos
13:59 Kamondelious I had changed that design to add another DOF for heel-toe walking. https://www.youtube.com/watch?v=R3TLOWMTLZQ
14:00 Kamondelious The heel was a poorly designed so if balance ever shifted onto it, the robot would fall over.
14:03 Kamondelious I corrected it in a later design, but scrapped it for being a little too heavy.
14:13 deshipu you use it in mech warfare?
14:16 Kamondelious That was the goal, but I didn't finish in time to compete.
14:17 deshipu I don't understand why people keep on putting batteries on the legs
14:17 Kamondelious lower centre of gravity, it really helped
14:18 Kamondelious I went a little overkill there though
14:18 Kamondelious the run time was good
14:18 deshipu but the legs then have horrible inertia, and your center of gravity moves with every leg movement
14:19 deshipu doesn't that make it very hard to plan the movement?
14:19 Kamondelious yeah that's where adding the hell toe helped too
14:19 Kamondelious It does
14:19 deshipu it make the equations for the leg motions into third degree differential equations...
14:22 deshipu how do you even solve that? iterating?
14:22 Kamondelious With poses
14:22 deshipu poses don't account for acceleration and inertia
14:23 Kamondelious nope
14:23 Kamondelious if the pose engine is dynamic you can have it adjust the pose to account for it though
14:27 deshipu the pose engine?
14:28 deshipu so you used ready software?
14:28 deshipu but it would need to know the weights of all the parts of the robot, not to mention the configuration?
16:13 Kamondelious Perhaps sequencer is a better description.
16:15 Kamondelious Poses simplifies things a bit as I was setting the pose with a actual robot, which included gravity.
16:16 Kamondelious It's not nearly as scientific and the math that is done is easier for an 8 bit micro controller to do on the fly without having to crunch out trig tables.
16:17 Kamondelious Use an IMU to get an idea for how much to compensate for
16:18 deshipu the problem is, your zero movement point is going to be a different place when you set a static pose, than it is when the robot is moving into that pose from a different pose
16:18 deshipu the ineratia adds to the center of gravity
16:19 deshipu inertia*
16:19 deshipu and with heavy batteries on the legs, it's going to add a lot
16:19 Kamondelious Yes it was very bothersome and why I abandoned that design
16:20 Kamondelious Those videos are from 4 years ago. ;)
16:20 deshipu do you have a newer approach now?
16:21 deshipu I'm kinda fascinated by the mech warfare
16:21 deshipu but at the same time disappointed
16:23 Kamondelious I do and has evolved a fair bit as I optimize it.
16:23 Kamondelious Yeah I know what you mean
16:29 Kamondelious Here's pictures of the evolution up to it's current state which hasn't been touched in about a year. http://forums.trossenrobotics.com/gallery/browseimages.php?do=browseimages&c=17&page=2
16:29 deshipu I mean, it's just standing there and shooting
16:29 deshipu I wish the mobility was actually more important
16:29 deshipu something like capture the flag
16:29 deshipu also, more difficult terrain, where you could have shorter path if you have better gaits
16:30 Kamondelious This is what it currently looks like : http://forums.trossenrobotics.com/gallery/showimage.php?i=5437&c=17
16:30 deshipu is that a rpi?
16:30 Kamondelious Yes
16:30 deshipu in that black box
16:31 deshipu looks battletechy
16:31 Kamondelious Using the Pi camera module simplified things
16:31 Kamondelious hehe, yeah
16:32 deshipu I wish I had the budget for dynamixels
16:32 deshipu instead I use $1.5 servos
16:33 deshipu https://hackaday.io/project/7168-logicoma-kun <-- this is my best looking robot so far
16:33 deshipu wouldn't qualify for mech warfare, because it both walks and rolls
16:55 Kamondelious Yeah, but it looks a lot better than most Mech Warfare entries. ;)
16:57 deshipu well, it's made for looks, not for functionality
16:58 deshipu the ones made for functionality are just servos glued together
16:58 deshipu I wonder if doing the mech warfare in a smaller scale would make it more interesting
16:59 deshipu mkae the robot 5cm high, not 25cm
16:59 deshipu then it can move around more
16:59 deshipu use a laser, not a bb gun, then you only need optical sensors
16:59 deshipu etc.
17:13 SpeedEvil http://www.modelrockets.co.uk/shop/klima-model-rocket-motors/d3-six-pack-18mm-rocket-glider-motor-p-3311.html?osCsid=011abd6cf08154e223f8c8d3610aca04
17:17 deshipu SpeedEvil: hmm?
17:17 deshipu SpeedEvil: that still has the problem of detecting the hit
17:18 deshipu I suppose when you have a camera, you could just make a snapshot, and after the match count how many of them were hits
17:20 SpeedEvil I was more imagining 'bits of robot spread everywhere'
17:55 verak loves spending night with python
17:56 veverak <3
17:56 veverak and robotics math <3
18:06 veverak what was the better version of "three euler angles" to define rotation in space?
18:11 veverak quaternions!
18:29 theBear i wish I had a camera :-( then i could just make a snapshot, on a whim, like, whenever my fickle ass desired it
18:29 theBear oh wait, i do now, a cheap old reflex canon EARLY digicam.... it's got vga res ! that's like, a WHOLE computer screen, adn they're way bigger than standard size photo prints !
18:30 theBear it came with a 1/8" -> db9 cable <grin> that kinda old
18:43 rue_school wow bear
18:43 rue_school want a 2.3MP camera?
18:43 rue_school maybe a 3M?
18:43 rue_school wait, the blackberries I got are 5M
18:43 rue_school ?
18:44 rue_school prolly only cost me $20 to send to ya
18:50 veverak ok
18:50 verak did quaternion math, not sure if right
18:55 ace4016 quats are fun
18:55 ace4016 dual quats are even more fun
18:57 theBear heh i was just waxing lyrical, at the moment while i'm in a between-phones transition period again (just when i got used to my sexy new (pretty old by normal standards) hitech s2 recently, i effing lost it just an hour after the battery ran out, it may well be in this flat, if not it was very close by, but i ain't finding it, and i gotta mourn before i setup the replacement one i hocked together... anyway) due to this i often carry at least one
18:57 theBear not-phone-today phone resurrected outta the repairs/spares/dead pile that has more megapixels than i'll ever know what to do with :-) just ya know, phones don't feel like cameras, so much less dignified
19:20 veverak ace4016: I don't get it
19:20 veverak thought copying functions from internetz and using them the way I wanted was not exactly the right hing
19:51 theBear heh, not exactly, plus when yer can't find one the way you want, you'll be EFFED (in the aye....) not to mention that just learning the standard rules and paradigms, basic-classic sort/whatever algos etc, is not only very educating in general (physics is everything, programming i guess is mathing, and well, math is a lotta things..) but you'll probly find you can bang out a loop or a bubble sort straight off the cuff faster than the increasingly
19:51 theBear trying to make your life hard google machine can find an example
19:52 ace4016 veverak, didn't look at how they actually work?
19:52 veverak ace4016: did, it was fine
19:53 verak just made wrong way about how to work wit
19:53 veverak tried to make quaternion from head, failed
19:53 ace4016 ah, hehe
19:53 veverak using "axisangle_to_q(vector, theta)"
19:53 veverak to get idea how quaternions are mad was much better choice :)
19:54 ace4016 i've sadly not gotten to use dual quaternions for anything useful yet though. quats though...useful
19:56 veverak first time quaternons :)
20:00 veverak well
20:00 veverak work done
20:00 veverak now I need to do a lot of ... tests
20:06 veverak ace4016: http://git.veverak.org/robotz.git/blob/master/tote/algo/leg.py
20:06 veverak I am using quaternions logic to reverse effect of rotation
20:07 ace4016 nice
20:07 verak would like to use it as only way to define "rotation" in entire pro
20:07 veverak but I still struggle with figuring out what that 4 numbers exactly means, so will see
20:08 ace4016 you could write it out on paper looking at it symbolically
20:08 veverak maybe making it Object, that can give you either "q vector" or "vector and theta"
20:08 veverak would make work with it inside the program much easier
20:09 veverak I understand the formula on wiki that represents it
20:09 veverak https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation
20:09 veverak q = cos...
20:10 veverak interpretation from the functiosn I've got seems like coeficients from that formula
20:14 veverak nah, I suppose making Quaternions simple objects that can be accesed/modified via multiple forms would work best for me
20:50 veverak ace4016: http://git.veverak.org/robotz.git/blob/master/brainz/algo/quaternions.py
20:50 veverak this object could do the work for now I suppose
20:50 veverak :)
20:56 SpeedEvil http://imgur.com/gallery/YRfPMxZ
21:20 orlock heya zhanx-
21:21 orlock http://en.crypt.net.au/TStar/20151006_061630.jpg - parts are all together now, no pics though
22:23 zhanx- Nice