#robotics Logs

Jun 24 2015

00:43 anonnumberano How to make my own strong robot servos for cheap? (torque of 14kg.cm or more)
00:44 anonnumberano like this one which is sooo expensive: http://www.trossenrobotics.com/dynamixel-ax-12-robot-actuator.aspx
00:55 rue_house wolfmanjm, you awake?
00:55 wolfmanjm yep
00:55 rue_house anonnumberano, get winshoeld wiper motors
01:02 anonnumberano kinda something people don't do
01:04 wolfmanjm rue_house: I'm awake ;)
01:04 wolfmanjm still trying to get my damned quadruped to do something predictable with its legs ;)
01:05 anonnumberano everything I've seen, they are huge, they have large metal gear housings...sigh
01:16 anonnumberano I need it the same size of the one I linked so I can make a combat robot with it to compete in Robo-One.
01:31 rue_house ok
01:31 rue_house so, I have a library,
01:31 rue_house just a sec
01:32 rue_house http://ruemohr.org/~ircjunk/programming/c/ik/
01:32 rue_house so, what I need to help you use it is a drawing of your leg with dimentions on it
01:34 wolfmanjm rue_house: that appears to be Invers kinematics
01:34 wolfmanjm I already have that working
01:35 wolfmanjm I was looking for Forward Kinematics
01:35 wolfmanjm ie given angles of the servos determine the XYZ of the leg
01:35 rue_house I can show you how to do it, the 2d.c can do the forward
01:36 rue_house so give me the drawing with some numebrs and I'll show ya!
01:36 wolfmanjm it is similar to this http://tote.readthedocs.org/en/latest/ik.html
01:36 rue_house tho 3d.c might be a better fit
01:36 wolfmanjm I also use his Inverse Kinematics
01:37 rue_house what are the dimentions?
01:37 wolfmanjm #define COXA 36.5F
01:37 wolfmanjm #define FEMUR 32.5F
01:37 wolfmanjm #define TIBIA 65.0F
01:37 rue_house Fathoms?
01:37 wolfmanjm that is joint to joint
01:38 wolfmanjm mm
01:38 rue_house ok
01:38 wolfmanjm ignore the F
01:38 wolfmanjm my leg is slightly different but the same IK works for my leg as it does for his
01:38 rue_house ok, so, you start from the leg tip
01:39 wolfmanjm I just twiddled the coordinate systems around as I like a consistent coordinate system for the legs
01:39 rue_house http://ruemohr.org/~ircjunk/programming/c/
01:39 rue_house I think 3d.c and 3d.h is better for you
01:39 wolfmanjm I have a simulation written in opengl too ;)
01:40 rue_house start from the tip, translate the point by the last segment length
01:40 rue_house then rotate it by the first joint angle,
01:40 wolfmanjm I have a 3d vector library ;) That stuff I understand very well. However the Forward kinematics is a little beyond my understanding
01:40 rue_house then translate, then rotate
01:41 rue_house so, what posture is your zero angle
01:41 wolfmanjm that works fine for graphical stuff but I want to plug in 3 angles and get three coordinates out
01:41 rue_house you gonna argue or listen
01:41 wolfmanjm but yea I see what you are saying
01:41 rue_house 3d.c will give you a result thats a 3d point for your endpoint
01:41 wolfmanjm that is one way to do it ;)
01:42 wolfmanjm yea I can use opengl to do that... great idea
01:42 rue_house thats the way to do it
01:42 rue_house dont use opengl
01:42 mrdata why not?
01:42 wolfmanjm yea deshipu pointed me at this... https://en.wikipedia.org/wiki/Denavit%E2%80%93Hartenberg_parameters
01:42 rue_house it wont tell you the result, its not portable, and its obficated process
01:43 wolfmanjm rue_house: I like opengl.... I was the manager of the opengl group for the small SGI box at SGI ;)
01:43 wolfmanjm so i Kinda have a bias there
01:43 rue_house ok, if it all fails, I have a way that will work, just ask
01:43 rue_house but now I'm freed up to go to bed
01:44 wolfmanjm I understand thanks... your library is very simple and elegant :) I just don;t need to implement yet another 3d math library ;)
01:44 wolfmanjm actually if I want this to run on my edison I'll use your stuff, thanks
01:45 wolfmanjm I like the simplicity of your solution though.. saves doing that math stuff with the Denavi Haertenberg stuff
01:46 wolfmanjm you pointed me in a direction I had not considered :)
01:46 wolfmanjm the simple solution ;)
21:31 blib anyone here? I have a battery question
21:33 ace4016 yes
21:33 blib hi ace4016
21:34 ace4016 hi
21:34 blib I'm looking for a 19v battery
21:34 blib http://www.amazon.com/Poweradd-Apollo-Pro-Multi-Voltage-Compatible/dp/B00F4KBA3M - have any suggestions for a battery better than this? (Preferably higher current/mAh, lower weight/price)
21:36 ace4016 hrm, what's the purpose of the batteries?
21:37 blib ace4016: powering various things apart from a arm embedded board that pulls 19v and is rated at around 50w
21:37 ace4016 http://www.batteryspace.com/19-2v-nimh-battery-pack-series.aspx
21:38 ace4016 you kind of linked a battery charger
21:38 ace4016 not sure how well that would hold supplying power like an actual battery
21:39 blib it does say it can supply upto 3A
21:40 ace4016 yea, but it's a charger. not sure if the logic in it won't view the board as something to supply power to
21:40 blib ace4016: the nimh's are costing 4500mAh = $90. That one is 23000mAh = $90
21:41 ace4016 they have lithium batteries on that site too then :P
21:42 ace4016 and as i mentioned, it has a charging circuit as its output
21:44 blib ace4016: don't see 19v batteries
21:44 ace4016 18.5 or higher should do
21:44 ace4016 there are also other websites
21:44 ace4016 i'd just be wary of using a battery powered battery charger as a battery itself
21:46 blib what's another good site for such batteries?
21:46 blib also how does one convert 23000mAh to Wh?
21:47 ace4016 convert mAh to Ah, then multiply it by the voltage
21:50 blib thanks
21:51 ace4016 i don't battery shop much, so not sure. if you want cheap, alibaba or dx or so probably have cheap prices
21:51 ace4016 ebay might too but it tends to not really be a deal anymore these days
21:52 blib ace4016: https://www.sparkfun.com/products/10736 - any thoughts on this sensor?
21:53 ace4016 possibly a bit pricey, but most things on sparkfun are
21:53 ace4016 not sure about performance...
21:55 blib ace4016: what would you use?
21:55 blib I need a sensor box
21:55 ace4016 i'd do more research and also have a requirement to weight on
21:56 blib ace4016: I'm looking for something that is easy to connect to my computer, and has a bunch of sensors. The more the merrier. :)
21:56 ace4016 hehe, what kind of sensors? you may have to assemble your own
21:57 blib All the sensors that come with a cell phone.
21:57 blib I don't need camera
21:57 ace4016 if you can afford that board from sparkfun, that will meet your requirement
21:58 blib ace4016: I can afford it, will get that one
22:08 rue_shop3 wolfmanjm, you got the forward kin working now?
22:52 blib ace4016: what is a good light weight camera for a robot?
23:00 rue_shop3 an auto backup camera off ebay for cars
23:00 rue_shop3 whats a good first person video link for quadcopter flying?
23:02 wolfmanjm rue_shop3: not yet, I don;t actually need it yet, seem sto all be working well with just IK
23:23 rue_shop3 <sharing links>
23:23 rue_shop3 http://ruemohr.org/~ircjunk/robots/sparrow1/p1070308.jpg
23:23 rue_shop3 http://ruemohr.org/~ircjunk/robots/sparrow1/p1070327.jpg
23:23 rue_shop3 http://ruemohr.org/~ircjunk/robots/sparrow1/p1070328.jpg
23:23 rue_shop3 http://ruemohr.org/~ircjunk/robots/sparrow1/p1070329.jpg
23:24 rue_shop3 http://ruemohr.org/~ircjunk/robots/sparrow1/p1070330.jpg
23:24 rue_shop3 http://ruemohr.org/~ircjunk/robots/sparrow1/p1070331.jpg
23:24 rue_shop3 </sharing links>
23:40 logy Hello everyone, I always liked robots and all about them, i have great ideas and etc. I just want to ask, I dont know where to start with learning about how to control a robot (example a car or crane) via wifi or bluetooth or even via wires. I know how to make for example an hidraulic robot arm, but how to set it up to do some work automatical, i dont know where to begin. So can anyone give me some advice?
23:42 Triffid_Hunter logy: start with an arduino and some R/C hobby servos
23:44 logy Triffid_Hunter: thx, any websites, articles that you can suggest?
23:44 Triffid_Hunter logy: too many, use google to find them :P