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[DPRG] Placement and interpretation of ultrasonic
Subject: [DPRG] Placement and interpretation of ultrasonic
From: Chris Jang
cjang at ix.netcom.com
Date: Wed Jun 6 06:06:48 CDT 2007
>Only problem with this method is that it can be difficult to tell the
>difference between the reflections from each pulse. Pulses return via
>multiple paths from everything in front of the sensor, not just the
>nearest object.
>
>Some of the more complex robots (and ground radar) exploit the multiple
>return pulses to build their map faster, and I've read a paper
>( http://www-personal.umich.edu/~johannb/Papers/paper32.pdf ) that
>'scatter-fires' the sonar units in a pseudo-random fashion, then applies a
>best-fit algorithm to the results in order to differentiate between
>reflections from the associated tx and other txs with an overlapping field
>of view or multiple reflection paths around the robot.
I had been envious of pulsed time of flight rangefinding systems like
LIDAR and SONAR as they appear so much easier than vision. I had thought
that clear distance maps would just come out as by magic. But in two
cases, LIDAR on Stanford's Grand Challenge robot and SONAR from this
paper, some form of stochastic inference was necessary. The raw sensor
data did not make sense. Also, in both cases, time-domain filters were
used (e.g. Kalman filter) to update a belief model.
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