Newsgroups: comp.robotics
Path: brunix!sgiblab!swrinde!elroy.jpl.nasa.gov!decwrl!concert!inxs.concert.net!taco!eos.ncsu.edu!rmlegran
From: rmlegran@eos.ncsu.edu (RICHARD MARK LEGRAND)
Subject: Polariod sonar blanking dilemma 
Message-ID: <1993Oct18.214610.20660@ncsu.edu>
Sender: news@ncsu.edu (USENET News System)
Organization: North Carolina State University
Date: Mon, 18 Oct 1993 21:46:10 GMT
Lines: 23

I am using the infamous Polaroid sonar modules on an autonomous vehicle,
and I am having problems with sensing obstacles less than a foot or
so away from the transducer.

I'm pretty sure this is because of the internal blanking that the module
performs to prevent detecting the transducer ring.  The real problem
seems to be that closer objects (closer than 1.3 feet) lie within this
blanking period and instead of the first echo being received, the second or
third echo is received giving the illusion that there is as much as two
or three times the actual distance to the nearest object.

Is there a way to improve the module's performance by having it indicate that
objects less than 1.3 feet away are simply 1.3 feet away instead of 2 or 3
feet away (for example)?  Has anyone dealt with this problem and had any
success?

Any suggestions are welcome.

Thanks,

Richard LeGrand
North Carolina State University
Center for Robotics and Intelligent Machines
