Subject:
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Re: A robot who knows his position
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 27 Apr 1999 22:53:34 GMT
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Original-From:
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John A. Tamplin <jat@liveonthenetNOSPAM.com>
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Viewed:
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1029 times
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On Tue, 27 Apr 1999, Mario Ferrari wrote:
> The equations to deduce the bot position from wheel movements are pretty easy
> to use and understand, but I had to face the problem that they require floating
> point computations and trigonometry. Floating-point math is out of the reach of
> any present software solution on the RCX, so I decided to use fixed-point math
> with 4 decimal digits emulated using integers.
Actually, software floating point is quite doable on the H8. In fact, at
least egcs 1.1.[1,2] includes FP emulation (config/fp-bit.c), which gets
put into libgcc2.a, which get merged into libgcc.a. You don't have to do
anything special to use them -- just use float variables as normal (the H8
port treats float and double as the same -- 32 bit floats).
> The fixed-point math routines (sin, cos, arcsin, sqrt) contained in the program
> may be useful for other projects too.
You can get the various math functions typically in libm.a from glibc. It
takes a bit of work to get them compiled, since glibc is intended for 32
bit targets running a Unix-like OS, but I have been able to get all the
str* functions and most of the math functions compiled and they work fine.
Software emulation of floating point isn't terribly fast, but it is quite
usable.
When I have the time (yeah, you've heard that before so don't hold your
breath), I plan on releasing a configuration to use the parts of glibc that
make sense on the RCX so you can just link your code to libc.a as usual to
get all of these functions.
John A. Tamplin Traveller Information Services
jat@LiveOnTheNet.COM 2104 West Ferry Way
256/705-7007 - FAX 256/705-7100 Huntsville, AL 35801
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 1 Reply:
 | | Re: A robot who knows his position
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| (...) This is great! I thought it was possible, but my knowledge of C isn't simply enough to figure out HOW TO. (...) Yes, when you have floats you can use/adapt standard math libraries. I'll try this. (...) This would be of great help (not only to (...) (25 years ago, 28-Apr-99, to lugnet.robotics)
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Message is in Reply To:
| | A robot who knows his position
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| I had some success in my first experiment with odometry. My goal was to build and program a bot that at every moment knows where he is. My creature uses a very simple and standard differential-drive: two large independent driving wheels on the left (...) (25 years ago, 27-Apr-99, to lugnet.robotics)
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