Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: benji on January 02, 2008, 07:43:42 AM

Title: polar information
Post by: benji 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.

Title: Re: polar information
Post by: bulkhead 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.

Title: Re: polar information
Post by: benji 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?

Title: Re: polar information
Post by: dunk 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 (http://www.societyofrobots.com/robotforum/index.php?topic=1674.0)


dunk.

Title: Re: polar information
Post by: Admin on January 07, 2008, 04:58:19 PM

Define 'precisely' :P

(what is your acceptable error?)

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 . . .

Title: Re: polar information
Post by: benji 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,,

Title: Re: polar information
Post by: airman00 on January 17, 2008, 11:29:27 AM

may i see a picture or video of the hexapod????


( yes i plan on building one)

Title: Re: polar information
Post by: benji on January 17, 2008, 04:32:36 PM

actually the bot isnt made yet, its a final year project so we are in the phase of studies ,,im still not sure what mapping algo should i use, im tryin to find about SLAM but im still searching and reading,once the bot is done i would surely upload the photos

.. actually its made of alminum 3 legs each side (its not a spider shaped one)