DPRG mailing list archives: [DPRG] Tilt-Compass versus AHRS-IMU

Mon Nov 9 22:03:58 CST 2009

Our Robo-Magellan robot has used both tilt-compensated, and non-tilt
compensated compasses.  It really didn't make a huge difference, unless you
were climbing steep inclines, because it's not like you are sitting still
trying to get a bearing.  The tilt ends up working into the motion equation
like noise.  The much larger problem to overcome is how your software is
going to be smart, when you drive over a man-hole cover, or a big steel
ramp, or around that new huge cast-iron statue they just put up on the park.
Our robot always had an affinity for being attracted to those big metal
light poles in the park up at the Seattle Center.  Big, metal, and big
electric field being generated by the wiring in the pole, I am guessing.

The place where the tilt-compensated compass really makes a huge difference
is on a flying vehicle, where the compensation really needs to work even
when flying inverted.  That's where most of the off-the-shelf compensated
ones really fall down.

-Ted

From: dprglist-bounces at dprg.org [mailto:dprglist-bounces at dprg.org] On Behalf
Of Andrew Lynch
Sent: Monday, November 09, 2009 11:35 AM
To: DPRGlist at dprg.org
Subject: [DPRG] Tilt-Compass versus AHRS-IMU

I am trying to decided whether to purchase a Tilt-Compensated Compass or
AHRS/IMU for a outdoor ground based vehicle. 
Tilt comp Compass:
http://www.sparkfun.com/commerce/product_info.php?products_id=8656 (Example
and Brief Description) 

AHRS/IMU -
http://en.wikipedia.org/wiki/Attitude_and_Heading_Reference_Systems

A tilt-compensated compass will only provide heading information.  An AHRS
will provide roll, pitch and yaw of the vehicle while recording obstacle
measurements.  The ground vehicle should only roll and pitch less no more
than 30 degrees.  

Has anyone had success in outdoor navigation with only a tilt-based compass
? 

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