#robotics Logs

Apr 19 2015

02:09 Jak_o_Shadows GA. Genetic algo?
02:09 Vetaxili Yes.
02:13 Jak_o_Shadows yup, you'd be ahead of me
02:17 ace4016 i don't know of any papers in particular, but NASA has done alot of published work into GAs iirc
02:18 ace4016 i did do optimization in grad school...sounds like you have ot make the obstacles a very negative objective and the goal a very positive goal
02:19 Jak_o_Shadows I've done a bit of optmisation too, but nothing that really focuses on when you have incomplete data
02:24 Vetaxili I did GA last year at uni. The concept of it I understand, but I don't seem to be able to connect it with the concept of braitenberg vehicles.
02:27 ace4016 Vetaxili, GA is just a goal oriented thing; braitenberg vehicles can be affected by goals
02:29 Vetaxili I have no problem implementing a single braitenberg vehicle, e.g. a lover or a coward. I think my problem is trying to use both at the same time since in the simulation thr agent has to avoid obstacles but go towards a goal
02:30 ace4016 make a weighted value between the two choices and put it in the performance function; let the scenarios pick which one is best :P
02:33 Vetaxili It is what I'm trying to do. The set of weights that results in the agent being closest to the goal location but the most central to all the obstacles seen is supposed to be picked as the best one. But that's what is supposed to happen in theory :P I think my problem starts when computing local intesity
02:34 Vetaxili Meh, I don't know actually... lol
04:05 rue_shop4 I'm working on a power adatper load tester
04:05 rue_shop4 so I can get the feaking load curve out of these unregulated **** adapters
04:19 jzk http://www.faa.gov/uas/legislative_programs/section_333/333_authorizations/media/Amazon_com_11290.pdf
11:22 claudiop Hi. What's the simplest steering mechanism to do on a homemade four wheel vehicle?
11:23 claudiop Rack and pinion seems simple, but how can the wheels rotate relative to themselves if there's no shaft between both wheels?
11:23 claudiop *i hope to be asking in the right place*
12:29 ace4016 claudiop, have you looked at the various steering techniques used in wheeled vehicles? robots aren't so unique to not use them
12:31 claudiop ace4016, Yes, even studied about the wheel control mechanisms car do have. But i can't have a clue on how to apply them only with DIY stuff.
12:31 rue_bed claudiop, what kinda robot you have?
12:32 rue_bed you making one from an rc car?
12:33 claudiop rue_bed, none right now. I just want to try to get my raspberry with a few motors to make a car, and keep upgrading it whenever i have time, like going solar, cameras n' stuff.
12:33 claudiop I don't want something like a three wheel car
12:33 claudiop It would look weird, and i want it to be able to be bi-directional
12:33 rue_bed heh
12:33 rue_bed tracks?
12:34 claudiop tracks waste a lot of mechanical energy, don't them?
12:36 rue_bed but they look cool, so does it matter?
12:36 ace4016 they also do well against not even terrain :P
12:37 claudiop It does if it is supposed to go solar someday if i decide to spend some money on it
12:37 ace4016 claudiop, this should be simple enough: http://en.wikipedia.org/wiki/Ackermann_steering_geometry
12:37 rue_bed controling motion with ackermann platforms is really really messy and has lots of awkward limitations, (ever had to do a 40 point turn?)
12:38 ace4016 hehe
12:39 rue_bed robots use that 'stupid' 3 wheel thing because it allows for 0 radius turns
12:39 claudiop Ok, lets go first with the simple part. How should i make the front wheels? Rear wheels can have a shaft connecting both, but in front wheels the shaft has to end in few centimeters.
12:39 claudiop Any known scheme on how to deal with such shaft?
12:39 rue_bed ackermann steering?
12:40 rue_bed your gonna insisst?
12:40 claudiop Not really, but front wheels can't have a solid shaft, no matter the steering
12:40 ace4016 rack and pinion steering could work too
12:40 rue_bed if you have two, and they turn, its ackermann
12:41 rue_bed did you look up ackermann steering yet?
12:41 rue_bed its REALLY hard to get the linkages right
12:41 rue_bed if you dont get them right, it drags one of the wheels sideways when it turns
12:41 rue_bed they cant just turn the same amount
12:42 rue_bed its a nasty set of calculations based on things like how wide the cars wheels are and what the distance between the front and back wheels is
12:42 claudiop I did, both of those. But how do the wheels hold themselves? How to deal with friction if i limit myself to get a ring at the end of the shaft?
12:43 claudiop Im trying to begin with the basic idea. The scheme can come later
12:43 rue_bed claudiop, do yo have a building supplies store near you?
12:43 rue_bed claudiop, do you have a heat gun?
12:44 claudiop If by building you mean construction, house things, and such things, yea. And yea to the heat gun too
12:44 ace4016 actually...do you have to make the steering wheels powered?
12:44 claudiop Not really. I was thinking about rear wheel drive
12:44 ace4016 simplifies things a bit
12:45 rue_bed actually, your better off buying an old rc car
12:46 rue_bed but you need this link
12:46 claudiop With the idea i do have, i don't thing an old rc car chassis would work, unless it was only meant to take the steering and absolutely not a thing more (which would make it expensive)
12:46 rue_bed .. please stand by
12:47 claudiop My vehicle has to be symmetrical, both side to side and front to back. Thats why an rc chassis would be bad
12:47 rue_bed how big is your robot?
12:47 claudiop There is no robot yet, but i want to make it like 50 cm by 20/30 or so
12:48 claudiop 20 inches by 8-12 if you do not understand metrical
12:49 rue_bed I'm canadian, all my projects use both imperial AND metric measurements
12:50 rue_bed your lucky if any two screws on any of my projects use the same head!
12:51 rue_bed I'v even been known to make a dimention thats 3inches +5mm!
12:51 rue_bed BECAUSE IT JUST LOOKED BETTER WITH THE 5MM!
12:52 claudiop And let me guess... all your robots are used to clean snow? If you don't mind can you tell what have you already build so i can have some fresh ideas?
12:52 rue_bed my drafting teacher hateed me for using the dimention "as required"
12:53 rue_bed http://ruemohr.org/~ircjunk/robots/robots2.html
12:53 rue_bed aha! found it!
12:53 rue_bed claudiop, ..
12:53 rue_bed http://ruemohr.org/~ircjunk/tutorials/mech/p1010110.jpg
12:53 rue_bed flattened pvc pipe is a GREAT source for plastic to make things from
12:53 claudiop Seriously? ;)
12:53 rue_bed get 3" or 4"
12:54 claudiop And how can i for example make an hinge?
12:54 claudiop PVC isn't the way, is it?
12:55 rue_bed no just buy a hinge
12:55 claudiop There are such things for sell? I mean, like the ones on steering mechanisms?
12:55 rue_bed if you need a perpendicular hinge you can make it from pvc plate and a coathanger bar
12:56 rue_bed claudiop, do you remmeber I said that the linkages are EXTREMELY dependent on the width and length of your car?
12:57 rue_bed going for shower, bbl
12:57 claudiop Not sure, it is possible it was left behind, but since you're asking for it I'll assume you did
12:57 claudiop Oh ok, thanks anyway ;)
14:03 lebenserfahrung Thinking of snake-inspired micro-robots. Any ideas fellas?
17:19 rue_house lots of servos, making big bots?