### Author Topic: polar information  (Read 1875 times)

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#### benji

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• Posts: 832
##### polar information
« on: January 02, 2008, 07:43:42 AM »
hey folks, i have my hexapod that i want it to send to my computer through serial port information about how much CMs did it walk plus the angle (orientation) each time it walks a straight line.
since its a hexapod i can have a close measurerment of how much did it walk by software
but i still need somthing(a sensor?anyways i have a sharp ir) to get a precise measurement.
well second, what about the orientation? whats better for my hexa? a compass or a gyro?
i know about a compass, but whats a gyro? would it make a better choice here?

thanks for any ideas.
good ol' BeNNy

• Full Member
• Posts: 102
##### Re: polar information
« Reply #1 on: January 02, 2008, 01:50:37 PM »
A gyro tells you the angular rate (velocity), so you have to integrate (sum up) the velocity measurements to get a rough estimate of the angle which will drift over time.  The compass is probably a better choice although it could be susceptible to electric fields.

#### benji

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##### Re: polar information
« Reply #2 on: January 07, 2008, 04:14:00 PM »
is there some algorithm (using a sharp ir) to aquire the distance the robot has moved precisly?
good ol' BeNNy

#### dunk

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##### Re: polar information
« Reply #3 on: January 07, 2008, 04:54:31 PM »
Quote
is there some algorithm (using a sharp ir) to aquire the distance the robot has moved precisly?

sorry to sound pessimistic but no. not precisely.

if your robot was one dimensional (for example ran along a railway track) then it would be possible if it was in range of a wall at the end of the track.
as soon as you add another dimension to the mix it becomes a very processor intensive problem and the solution is only ever an estimate.

to further research the problem you want to read up on SLAM. (Simultaneous Localization And Mapping)
http://www.societyofrobots.com/robotforum/index.php?topic=1674.0

dunk.

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##### Re: polar information
« Reply #4 on: January 07, 2008, 04:58:19 PM »
Define 'precisely'

Then check sensor datasheets to see if they fit within that error. And this doesn't even account for sensor drift.

SLAM is to handle sensor drift based on mapping. Hard stuff, really . . .

#### benji

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##### Re: polar information
« Reply #5 on: January 08, 2008, 07:07:30 AM »
well my acceptable error is 1 cm , and about slam i read about it but still not sure what approach to go for,,
good ol' BeNNy

#### airman00

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• narobo.com
##### Re: polar information
« Reply #6 on: January 17, 2008, 11:29:27 AM »
may i see a picture or video of the hexapod?

( yes i plan on building one)
Check out the Roboduino, Arduino-compatible board!

www.Narobo.com

#### benji

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