#robotics Logs
May 07 2013
#robotics Calendar
01:01 Triffid_Hunter rue_house: max232? yes
01:02 rue_house it should work pretty good
01:02 Triffid_Hunter works ok, but they don't have the raw current drive on the output to be anywhere near as good as a proper gate driver
01:02 rue_house built in voltage mult, current limiting
01:02 Triffid_Hunter so can't switch fast
01:03 rue_house I wonder what they top out at, I should set one up with a squarewave and current tap it on the scope
01:04 Triffid_Hunter I'd guess 100mA or so
01:04 rue_house :) I'm interested to try it now
01:04 Triffid_Hunter saw a crazy gate driver the other day.. tc4427 or so from memory. rated to push 12A!
01:04 rue_house wow
01:04 rue_house run a small motor off that
01:05 rue_house (they usually have a 12 ohms or so rdson)
01:05 Triffid_Hunter rue_house: can't do it for any length of time, it'll overheat
01:05 Triffid_Hunter but for charging and discharging a 1-40nF capacitor they're golden
01:11 rue_bed I think I drove a small motor with a hip4081 once
01:13 yahweh Hey Rue, is there anything you need from Digikey in the coming months?
01:14 MrCurious finally got the networking right on these two robot arms
01:16 MrCurious odroid-u2 connects to house wireless, and serves it to the raspberry pi over ethernet crossover dhcp, which hosts its own wireless access point and serves networking to its clients
01:23 rue_bed hehe
01:23 yahweh That's not an answer Rue!
01:23 MrCurious mind numbing good fun
01:26 yahweh Hey
01:26 yahweh Hey
01:26 yahweh Get back here
01:29 MrCurious now you have gone and done it
01:30 yahweh It's okay, I know where he lives.
01:30 yahweh I'll go over to his house tomorrow and paint his mower bot pink if he doesn't answer.
01:32 MrCurious you should paint rainbows in his windows
02:38 RifRaf first parts for testing http://imagebin.org/256774
03:20 Triffid_Hunter RifRaf: nice :)
03:21 Triffid_Hunter be interesting to see how long the plexi lasts
03:22 RifRaf wekk its not stiff enough for the main frame and the heating bed holder part would melt, have no 6mm aluminium yet but wanted to start seeing it
03:23 RifRaf maybe 15mm acrylic would be suitable for the main frame but thinking 6 or 10mm ali
03:24 RifRaf and 3mm ali for the bed part should do eh?
03:30 Triffid_Hunter yep
04:11 RifRaf Triffid_Hunter, making the frame like this from 6mm aluminium welded would be better than just the big square part http://penguin.nu/Media/Default/Windows-Live-Writer/Prusa-i3-Single-Sheet-Laser-Cut-Build-Lo_12646/5D-20130127-6955.jpg
04:12 RifRaf maybe even just 4mm
04:14 Triffid_Hunter yep that'd work
09:01 rue_house hah
09:02 rue_house bah, no fiar, rif has a cnc
09:09 Tom_itx he does?
09:09 Tom_itx what do you need cnc'd?
09:10 rue_house just looking at the reprap parts he's cutting
09:11 Tom_itx i didn't see those
09:11 rue_house think with a ream and a lathe I can make a spool valve?
09:11 rue_house http://imagebin.org/256774
09:12 Tom_itx i don't know why not
09:13 Tom_itx like on a gas shutoff?
09:14 rue_house like in a hydraulic block
09:17 Triffid_Hunter rue_house: he uses a plexi cutter at his work I think, doesn't have one @home
09:17 rue_house yea
09:18 rue_house http://www.atos.com/english/images/components/solenoid_valves4.png
09:33 Tom_itx depends on the pressure i suppose
13:29 min|dvir|us Hi. I'm looking into getting an unmanned aerial vehicle like a quadcopter or an RC plane. What UAV has the characteristically longest flight time?
13:29 jigoe Gliders.
13:29 min|dvir|us How long will they fly for?
13:30 jigoe Depends where you live and what the weather is, this guy got lucky. http://vimeo.com/43074193
13:30 min|dvir|us Ahh, that's unfortunate.
13:30 jigoe 5 hour flight time.
13:31 min|dvir|us I'm looking to fly 500 miles without refueling/recharging. Is that impractical by today's standards, even with extreme wizardry?
13:31 jigoe Yes.
13:33 min|dvir|us I know helicopters and airplanes (both manned) can do this. What is stopping a UAV from it?
13:35 GargantuaSauce regulations
13:35 GargantuaSauce what country are you in?
13:35 min|dvir|us USA, but let's ignore regulations for now.
13:35 min|dvir|us I'm thinking about physical capacity.
13:36 GargantuaSauce well with that sort of range the scale of the thing needs to be not dissimilar to that of a "real" plane
13:36 GargantuaSauce electric power is probably ruled out
13:38 GargantuaSauce so we're talking something pretty damn big, with an internal combustion engine or perhaps a brayton cycle engine
13:38 GargantuaSauce wingspan of probably at least like 4 metres to be able to carry enough fuel
13:39 min|dvir|us That's shitty.
13:39 GargantuaSauce and its mass will certainly be greater than that which would allow it to be classified as an r/c model
13:39 min|dvir|us I can't believe we've not invented high density batteries.
13:39 SorcererX atleast you aren't trying to send something into space
13:40 min|dvir|us SorcererX: you didn't see the guy who strapped a camera to a balloon?
13:40 SorcererX min|dvir|us: I said space, not "space"
13:40 SorcererX eg. minimum 100 km
13:41 min|dvir|us What is the most dense battery technology today?
13:43 GargantuaSauce lithium polymer is probably the best bet but the energy density is still much lower than petroleum fuels i think
13:44 GargantuaSauce and unlike fuel, as you expend the energy the mass does not decrease
13:44 GargantuaSauce so an increase in scale brings about diminishing returns in terms of range
13:44 min|dvir|us And a huge amount of solar panels wouldn't give me nearly enough charge, right?
13:44 GargantuaSauce if you had a few million dollars of r&d that'd be approachable, a few groups are doing that but it is still extremely nascent
13:44 SorcererX Zinc-Air is much denser, not rechargeable though
13:45 GargantuaSauce lots of advances in materials sciences etc involved in that
13:45 SorcererX Li-ion is apparently also more dense than LiPo in the right configuration, costs more though
13:46 GargantuaSauce and yeah as i said, aside from the technical limitations there's a LOT of red tape to overcome in the process
13:46 min|dvir|us There are existing solar panels though.
13:46 GargantuaSauce yes and they are heavy
13:47 SorcererX GargantuaSauce: yeah, for instance here you are not allowed to fly anything remote controlled outside of eye-sight
13:47 GargantuaSauce even maintaining radio contact over that range would be hard
13:48 GargantuaSauce anyway to answer the original question, i'd say the best bet for commodity r/c hardware in terms of flight time would be one of the bigger flying wings
13:48 GargantuaSauce i've been looking at the x-8 lately
13:48 GargantuaSauce still much smaller than something you'd need to get 500 miles but it'd be a start
13:51 min|dvir|us Is it possible to domesticate owls or somesuch to do what I want?
13:51 min|dvir|us Probably the wrong place to ask.
13:51 GargantuaSauce lol
13:52 GargantuaSauce are you trying to fly drugs around or something
13:52 min|dvir|us No, but I realized a long time ago that my goals coincide with a drug dealer's particularly well.
13:53 min|dvir|us My eventual goal is to create a fully autonomous robot.
13:53 min|dvir|us So gas would be out of the question.
13:54 GargantuaSauce i doubt it's much harder to refuel something autonomously than to recharge its batteries
13:54 GargantuaSauce anyway what you're proposing is strictly illegal
13:55 min|dvir|us Then the law is behind the times.
13:55 GargantuaSauce think about how carefully air traffic has to be regulated
13:56 GargantuaSauce it is going to take a LOT of reformation to work fully autonomous air vehicles into that equation
13:57 min|dvir|us Alright, I'll bite. Even if my autonomous UAV is caught, there would be no way to trace it back to me.
13:57 GargantuaSauce what if you crash into an airliner and kill hundreds of people?
13:57 min|dvir|us Theoretically, not my problem anymore.
13:58 min|dvir|us Of course what I say now is probably completely different than what I'd say if my autonomous UAV killed a bunch of people.
13:58 GargantuaSauce i would hope so
13:59 GargantuaSauce but i would imagine that is a situation that is to be avoided
13:59 min|dvir|us Any situation where my autonomous UAV is compromised is to be avoided.
14:00 min|dvir|us I can do exactly what I need to do right now with today's technology, except for two things.
14:00 min|dvir|us Load-carrying capacity and battery density.
14:02 GargantuaSauce so you've already written the software that allows for autonomous navigation without endangering other aircraft in the airspace, and interacting with ATC?
14:02 min|dvir|us I wouldn't be flying in "airspace".
14:02 GargantuaSauce that is patently false
14:02 min|dvir|us Perhaps I don't know.
14:03 min|dvir|us Airspace is some certain altitude and above, right?
14:03 GargantuaSauce i think you need to read every letter of the FAA regulations before you even consider this further from a technical perspective
14:04 GargantuaSauce dead serious
14:05 min|dvir|us I'm succifiently convinced that what I want to do is not feasible today.
14:05 min|dvir|us But consider this: even if my UAV is compromised, there would be no way to trace it back to me.
14:06 GargantuaSauce i think that is pretty shortsighted
14:06 min|dvir|us GargantuaSauce: why do you say this?
14:06 SorcererX so doing something illegal and endangering others is fine as long as you don't get caught?
14:06 min|dvir|us SorcererX: "doing something illegal" and "endangering others" are not to be grouped together.
14:07 GargantuaSauce in this context the two very much go hand in hand
14:07 min|dvir|us I disagree, although there might be parts of a regulation that would help against endangering others.
14:08 min|dvir|us Would you have any moral complaints if my UAV was illegal but didn't hurt anyone?
14:08 SorcererX yes
14:09 GargantuaSauce pilots have very strict rules to follow
14:09 GargantuaSauce this is so that they don't run into each other
14:09 GargantuaSauce planes go fast and pilots are not omniscient
14:10 GargantuaSauce think of the rules of the road
14:10 min|dvir|us Yeah, like speed limits?
14:10 GargantuaSauce drivers have to behave a certain way in order to not constantly endanger each other
14:10 min|dvir|us Speed limits were invented in the 60s to conserve fuel amidst fears of shortages.
14:11 min|dvir|us Now they are used largely to fund city hall.
14:11 min|dvir|us Indeed, studies state that removing speed limits means that drivers will drive at speeds at which they are comfortable, *reducing* the amount of accidents.
14:12 GargantuaSauce you're really set on this arent you
14:12 min|dvir|us My point is that the law is not always better in terms of safety.
14:12 min|dvir|us Sometimes the law doesn't even know what it's doing, like you said in the case of UAVs.
14:12 GargantuaSauce i think you know exactly nothing about aviation
14:13 min|dvir|us In 100 years when UAVs are the norm, there will be different laws.
14:13 min|dvir|us Laws intended for UAVs, which will be readily available from Amazon.com or something.
14:14 GargantuaSauce yes and they will have sophisticated and standardized control systems
14:14 GargantuaSauce with very tight regulations governing their use and behaviour
14:14 min|dvir|us GargantuaSauce: think about Google's self-driving cars, which are illegal.
14:14 min|dvir|us Are you as against them as you are against an autonomous UAV?
14:14 GargantuaSauce i am not fucking against an autonomous uav
14:14 GargantuaSauce jesus christ
14:15 min|dvir|us Are you as in fear for other people's lives with them as you are with an autonomous UAV?
14:15 GargantuaSauce i am saying that until the regulations are advanced to account for their existence, they will be dangerous
14:15 min|dvir|us Bullshit.
14:16 min|dvir|us Regulations are correlated with increased safety only because it benefits public opinion.
14:17 min|dvir|us If the public wanted danger, it would be illegal not to kill people less than once a day.
14:17 min|dvir|us Or some stupid shit.
14:17 min|dvir|us Regulations are what you use when you'd rather rely on someone else's findings than make them yourself.
14:18 GargantuaSauce i sincerely hope you never fly an aircraft
14:18 GargantuaSauce of any size
14:18 GargantuaSauce i'm done with this
14:19 min|dvir|us You sound frustrated, and I'm sorry about that.
14:19 min|dvir|us If not me, then someone else.
14:19 min|dvir|us And the law *will* change.
14:20 min|dvir|us If you don't like it, don't live until the day.
14:20 GargantuaSauce i look forward to the law changing
14:21 GargantuaSauce pilots have to be able to make assumptions about the behaviour of other aircraft
14:21 GargantuaSauce that behaviour is dictated by the aviation regulations
14:21 min|dvir|us What do you think I'm doing, making some kamikaze UAV?
14:21 GargantuaSauce if it's not following those regulations, yes
14:21 min|dvir|us That's absurd, dude.
14:22 min|dvir|us If I jump, am I endangering other aircraft?
14:22 GargantuaSauce you are talking about making a commercial uav that follows your own set of rules
14:23 min|dvir|us Well, as you know, it's in my best interest to keep my UAV from being compromised.
21:01 MrCurious rue: you see the robot lawnmower kick starter?
21:02 MrCurious send... more.... robots....
21:12 MrCurious tar zxvf gprolog-1.4.4.tar.gz
21:34 MrCurious the phrase of the day... "Not only is the sky falling, but the pieces are burning!"
21:34 rue_house I dont care about a mowerbot kickstarter
21:34 rue_house my mowerbot is for me
21:42 Tom_itx besides it uses a rope not a kickstart
21:47 MrCurious lol
22:51 rue_shop2 robot arm controller
22:51 rue_shop2 stepper based
22:51 rue_shop2 3x 2803 drivers
22:51 rue_shop2 3x 74595 output chips
22:51 rue_shop2 1x mega162 controller
22:51 rue_shop2 1x max232 serial
22:51 rue_shop2 I love this, there is a chip for everything now
22:53 Tom_itx time to quit. everything i was working on is working
22:53 rue_shop2 http://www.ebay.ca/itm/Power-Supply-For-DC-DC-Step-Down-Module-12V-Switch-to-5V-3-3V-For-LCD-Car-Radio-/271202037491?pt=LH_DefaultDomain_0&hash=item3f24e6aef3
22:53 rue_shop2 rue, buy this
22:53 Tom_itx added tool number to the display with the length offset below it
22:53 Tom_itx fixed a couple other things
22:54 Tom_itx fixed the tool table to match my cad cam tool table
22:54 Tom_itx so i can preset all my tools
22:54 Tom_itx then just set the fixture offset and run the file
22:55 rue_shop2 http://www.ebay.ca/itm/DC-DC-Converter-Buck-Step-down-Module-Voltage-LED-Power-3A-12V-To-5V-3-3V-WST-/390565500901?pt=LH_DefaultDomain_0&hash=item5aef8497e5
22:55 rue_shop2 or that
22:55 rue_shop2 Tom_itx, is the packaged capability pretty primitive?
22:55 Tom_itx ?
22:55 Tom_itx what do you mean?
22:56 Tom_itx you can set it up any way you want it
22:56 rue_shop2 oh I'm an idiot, car cig lighter usb supplies are $1
22:57 Tom_itx i got something similar to those
22:57 rue_shop2 Tom_itx, out of the box, what is it set up for?
22:57 Tom_itx nothing specific
22:57 Tom_itx you have several options to get started
22:57 Tom_itx you can pick a preset setup and mod it
22:58 Tom_itx you can run a configuration program
22:58 Tom_itx you can run it from the cd before installing as as im
22:58 Tom_itx sim
22:58 Tom_itx you need a machine with low latency numbers
22:59 rue_shop2 so why are you programming it all yourself
22:59 Tom_itx i'm adding features
22:59 Tom_itx display stuff
22:59 Tom_itx like the tach spedo
22:59 rue_shop2 my question is, are the featrues it coems with really basic?
22:59 Tom_itx you can customize it any way you want
23:00 Tom_itx it will run out of the box once it's configured for your machine
23:00 rue_shop2 Im saying how it is on install
23:00 rue_shop2 I know you can make it do anything
23:00 Tom_itx if i can do it anybody can
23:00 rue_shop2 I'm asking, out of the box, on install, is it pretty basic what It can do
23:00 Tom_itx it's not bad but there isn't really a default setup
23:00 Tom_itx you can pick from several though
23:00 rue_shop2 are they pretty basic for capabilites?
23:01 Tom_itx you gotta tell it what you have first
23:01 Tom_itx i'm not sure what you're asking really
23:01 rue_shop2 I can tell
23:01 Tom_itx it's a full fledged cnc control
23:01 Tom_itx but you have to tell it what you've got
23:01 Tom_itx sorta like the reprap stuff but different
23:02 Tom_itx it's not hard to pick up though
23:02 Tom_itx i'm just adding some custom stuff to mine is all
23:02 Tom_itx it will run steppers from the parport stock
23:02 Tom_itx you can set fixture offsets and tool offsets and cutter comp etc stock
23:03 Tom_itx it will run up to 9 axis
23:03 Tom_itx load it up then ask questions
23:04 Tom_itx i can help get you going
23:04 Tom_itx all the parameters are in their docs but you gotta look for some of em
23:04 Tom_itx all their gcodes are described there as well
23:05 Tom_itx there are a handfull of free cad cam ppl are using on it
23:05 Tom_itx they're having a fest in my town next month for a week on it
23:05 Tom_itx i plan to attend a day if i can
23:05 MrCurious Lawn-Bot Repair Channel :)
23:09 rue_shop2 wow, mega162 has 2 usarts
23:09 rue_shop2 Tom_itx, anyone come up with a free cadcam program?
23:20 Tom_itx there are sheetcam, pycam and a handfull of others
23:20 Tom_itx nothing really good
23:20 Tom_itx i think pycam takes a cad file and spits out gcode
23:21 Tom_itx there are lots of subroutines you can run that people have written
23:21 Tom_itx and it comes with a bunch of them preloaded now
23:21 Tom_itx i haven't used them myself since i have cad cam already
23:28 vatula Hi guys. I'm new, but probably will stay for a while. I've found that my scarce knowledge from robotic courses are not enough to do even simple stuff like control of differential drive robot
23:29 Triffid_Hunter vatula: get an arduino and some shields and start playing
23:30 vatula I tried. I've got 3pi
23:30 vatula My problem is modeling :)
23:30 Triffid_Hunter vatula: ah, you need some computational geometry background
23:31 vatula Well, I don't think so :) Geometry is simple
23:31 Triffid_Hunter vatula: which bit is troublesome then?
23:32 vatula Hm. Stright to the business, huh? I'm trying to create a model for a PID
23:32 vatula And I'm not sure if I'm doing the right thing right now.
23:33 Triffid_Hunter ah.. it's actually harder to make a model for PID than it is to simply tune it by hand while observing a real system
23:34 Triffid_Hunter what are you applying PID to? the wheel velocities?
23:34 vatula Ah, that comment at least helps me with my self-appraisal :)
23:34 vatula PID to velocities
23:34 vatula Well, to an angular velocity actually
23:35 Triffid_Hunter you can nest PID loops you know
23:35 vatula So, the problem:
23:35 Triffid_Hunter so you can have your angular loop giving individual velocities to velocity loops, and for extra points you can have those feeding current loops
23:35 vatula 5 infrared sensors located in an arc in the front of a 3pi carcas (which is round)
23:36 vatula This is a line-follower
23:37 vatula Data from sensors in in form [0, 1000, 2000, 3000, 4000] if black is sensed exactly below sensors [0..4]
23:38 vatula thus my reference signal is 2000
23:39 Triffid_Hunter vatula: http://youtu.be/A4hzCcFikm0 <-- for inspiration :)
23:40 vatula Haha :) Well, building maze solver is my next big thing I guess :)
23:41 vatula I'm describing my dynamics as w = a*theta+b*u, where w = an angular velocity, theta is my model (right?) = angle between the center of the robot and sensor that senses black
23:42 vatula Am I on a right track?
23:42 Triffid_Hunter no idea, sounds like something from academia
23:42 Triffid_Hunter I'd personally just be plugging <distance from center> into the PID and just tuning it until it works
23:43 vatula The thing is - something similar is done in 3pi examples. But I wanted to understand the thing from the beginning %-)
23:44 vatula And tried to get my head around those academic concepts since that was something from courses
23:44 Triffid_Hunter I'm interested in less structured, more organic approaches, like the robot that uses an accelerometer to work out what all its muscles do
23:45 Triffid_Hunter it converges on a correct model of its legs surprisingly quickly
23:46 vatula Yeah. 3pi is to simple. But that's what I have :) I guess I'll hang around. Maybe someone remembers something from school/uni about all that stuff
23:47 Triffid_Hunter I think you're overcomplicating things by trying to work out angles and distances and stuff based on physical geometries of the robot
23:49 Triffid_Hunter seriously, try distance_from_center = (whichever sensor sees the most black); velocity_delta = PID(distance_from_center, values you tune by experimenting); wheel1_speed = base_speed + velocity_delta; wheel2_speed = base_speed - velocity_delta;
23:55 vatula Triffid_Hunter: try distance_from_center is a radius :) It will be the same for all sensors
23:55 vatula Since 3pi is round and sensors palced in arc
23:56 Triffid_Hunter vatula: nono I mean if the middle sensor sees black, it's 0. if the one to the left sees black, it's -1. if the 2nd to the right sees black, it's +2
23:56 vatula Ah!
23:56 Triffid_Hunter it really can be that simple, and have the PID constants provide all the emergent behaviour necessary
23:56 vatula That model is great!
23:57 Triffid_Hunter vatula: if you want some inspiration about emergent behaviour, go check out BEAM robotics
23:57 Triffid_Hunter I sincerely believe that we'll never achieve useful AI without thoroughly embracing emergent behaviours and robotic self-discovery
23:58 Triffid_Hunter like lego and linux, I think a complex robotic mind is made up of many simple building blocks connected in a fluid and dynamic fashion, rather than any sort of rigid structural understanding of anything
23:59 vatula Triffid_Hunter: I need to start somewhere in the beginning before I even start thinking about problems in the current implementation of most robotic platorms :)
23:59 Triffid_Hunter for example, if one of your robot's wheels were eccentric, you'd have a hell of a time trying to get it to work with a rigid model, but the simple PID loop would probably handle it fine
23:59 Triffid_Hunter or if you lost a tyre in the middle of a run or something like that