Omni Wheeled Boe-Bot?
Hey, I'm trying to start a project with my boe-bot and need some help.· What I'm thinking of doing is taking the Board of Education off of my boe-bot and making either a new·trigonal or square chassi for it (most likely square) and hooking up for omni wheels to it so it can strafe.·
Here is my problem-
···· 1 - I don't now if the bs2 can handle the program for omni wheels in autonomous mode with at least four ir sensors for distance detection and anything else I try to do
···· 2 - I don't know if the regular 4 AA battery pack can handle the four servos and the board
Can someone give me some feed back on my project...
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Education is what remains after one has forgotten what one has learned in school. - Albert Einstein
Here is my problem-
···· 1 - I don't now if the bs2 can handle the program for omni wheels in autonomous mode with at least four ir sensors for distance detection and anything else I try to do
···· 2 - I don't know if the regular 4 AA battery pack can handle the four servos and the board
Can someone give me some feed back on my project...
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Education is what remains after one has forgotten what one has learned in school. - Albert Einstein
Comments
Thanks for the imput.
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Education is what remains after one has forgotten what one has learned in school. - Albert Einstein
Would a PWMPAL help in this instance - It is not a lot more than the ServoPal (cheaper if you need two).
I'm not sure this would work - just wondering.
What kind (brand or source)·of wheels are you thinking of using?
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 1/21/2008 8:32:25 PM GMT
If I only used three omni wheels in a triangular pattern would servoPALs be necessary or recommended?· I did not want to do all the vector sums, but if it can make my project feasible·I'll do the math.
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Education is what remains after one has forgotten what one has learned in school. - Albert Einstein
Post Edited (robotyro) : 1/22/2008 2:27:40 AM GMT
The expensive part of the project is the servopals, which I still want to know if they would be necessary with three servos, and the servos themselves.
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Education is what remains after one has forgotten what one has learned in school. - Albert Einstein
I really think you need a double wheel like this http://www.robotobjects.com/scripts/prodView.asp?idproduct=306·($10.77 times three = $32.31).
See this video - http://www.youtube.com/watch?v=HTPnX1vDymw
This is a WowWee bot with Omni Wheels. A picture (moving) is worth a thousand words.
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
Post Edited (Whit) : 1/24/2008 2:56:34 AM GMT
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- Stephen
Good luck with your project.
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David
There are 10 types of people in this world,...
Those that understand binary numbers, and those that don't!!!
With omni wheels you need at least three wheels and four would be easier to program -less vector sums to do.
But can anyone answer my question - if I only use three servos would servoPALs be necessary?
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Education is what remains after one has forgotten what one has learned in school. - Albert Einstein
Could you define what you mean by "mecanum wheels"? I know of many sources for wheels and tires for various sized robotic platforms. Perhaps I could help if I knew what they were.
Could you speak just a bit more about programming the omni wheels, inre your comment about "vector sums"? If you know of a tutuorial, that would be great as well.
Whether you can drive three R/C servos is more a matter of what else you're doing in the program than anything else. Each R/C servo places a software load on the Stamp, since it is a single threaded processor. If you have no other time constraints within your program, I'd guess you could drive three R/C servos without too much trouble. A co-processor would certainly offload a lot of the work, and permit you more time for other duties with the Stamp.
Regards,
Bruce Bates
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There is no pleasure in having nothing to do;
the fun is in having lots to do, and not doing it!
This site - http://www.societyofrobots.com/robot_omni_wheel.shtml - also has the info on the vector stuff that come with omni wheels. In short you need to send different pulse values to the wheels in order for them to turn and strafe. This is not too hard with four wheels, but with three you need to do send odd pulses even to get the bot to move forward.
If I add IR for distance detection would that over-load the BS2?
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Education is what remains after one has forgotten what one has learned in school. - Albert Einstein
It's not overloading the processor so much as it's having ample time to do what you need to do in your program. You will have to provide PULSOUT output pulses at regular intervals to the R/C servos for them to maintain thier positions. Ordinarily you would put pauses in there as well, but other instructions (doing other things) work as well as pauses (PAUSE statement) as far as "time wasting" is concerned, except you're not wasting time as you would with a PAUSE statement.
To answer your "load" question more directly, you need to view your R/C servo timings (on paper) and how long it takes to send out your I/R pulse, and receive an "answer" (again on paper). Then you have nearly enough data to answer your own question.
In general terms, I suspect you may be okay if you use a PBASIC Stamp that's faster than the BS-2 (BS-2sx and on up), but that's just a gut feeling based on my past programming efforts in this area. Once you have decided on which PBASIC Stamp you are at least planning to use, then you know its speed characteristics as well, and that's the last piece of input you will need for your "paper" timing chart.
If you come up short time-wise, look at the next faster PBASIC Stamp! I suppose you could jump right to a PBASIC Stamp BS-2px and skip the timing nonsense, but I don't like to use any larger processor than is necessary. Call me a purist if you wish
I hope that's not too overly complicated an explaination.
Regards,
Bruce Bates
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There is no pleasure in having nothing to do;
the fun is in having lots to do, and not doing it!
Here is a 2" Omni wheel (link below). It's not quite a mecanum wheel, but that's the best I've found so far:
http://www.imagesco.com/catalog/robot/wheels.html
Regards,
Bruce Bates
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There is no pleasure in having nothing to do;
the fun is in having lots to do, and not doing it!
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Education is what remains after one has forgotten what one has learned in school. - Albert Einstein
They may not look as nice, but...
You'll need some hard sheeting(plywood made for RC-hobbyists should be good),
Cut two pieces that are roundish, say 6 or 8-sided.
Drill holes in the corners, and in the center.
Mount the two pieces with a spacer between them(an inch should be enough), and make certain that you rotate one of the pieces in relation to the other.
When threading a thin metal rod(pianowire?) from one side to another, it should make at pretty sharp angle...
Now comes the difficult part.
You need to cut, carve or cast rollers to mount on those thin axles.
Also, consider slipping a small plastic bead on each end of the wire to buffer the roller, and possibly notch the plywood sides so that the roller has more room.
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