Newsgroups: comp.robotics
Path: brunix!uunet!haven.umd.edu!darwin.sura.net!howland.reston.ans.net!usc!elroy.jpl.nasa.gov!decwrl!netcomsv!netcom.com!nagle
From: nagle@netcom.com (John Nagle)
Subject: Re: Safety of large mobile robots
Message-ID: <nagleC9FzC1.GAn@netcom.com>
Organization: NETCOM On-line Communication Services (408 241-9760 guest)
References: <1993Jun29.215740.17141@comp.lancs.ac.uk> <1993Jun30.053804.4113@cs.ucf.edu>
Distribution: na
Date: Wed, 30 Jun 1993 16:04:49 GMT
Lines: 48

wampner@next1 (Eric Wampner) writes:

>Mr D Ingles writes
>> Can anyone give me any information on what techniques are being used  
>with 
>> regards to safety of large mobile robots.
>I think most of us in this channel deal with less than, er, say automatic
>forklifts in out work/play. I have seen such things, Fun to watch, but
>designed to work in a closed warehouse, not an uncontrolled environment.

       Caterpillar makes a nice robotic forklift designed for use in
environments with people.  This is a full-sized forklift, and load ratings
to 8000 pounds are available.  Basic guidance is laser triangulation using
bar-coded markers attached to walls.  The vehicle must have three markers
in sight at all times to navigate, so you end up putting up quite a few
of the aluminum plates used.  There are also some fine positioning sensors
in the forks.

       The safety system starts with a bumper on the front, like most AGVs.
It's a big sheet of flexible material protecting the whole
front of the vehicle, suspended about 1' in front of the vehicle body.
The vehicle has a top speed of 1MPH, so that 1' is greater than the
stopping distance.

       There are also swinging IR sensors in front, ultrasonic sensors 
in back, and beam break sensors along the sides and at some pinch points.
Emergency stop buttons are also fitted.  It also has a horn, turn signals,
and backup beeper.

       Caterpillar's video, though, shows some setups that make me a
bit nervous.  The usual configuration is an improvement on a standard
forklift; the forks not only move up and down, but lift the load up and
bring it back over the vehicle body, so the load is within the vehicle's
bounds when the vehicle is in motion.  But in one special application,
truck unloading of racks of car seats, a frame with the cross-section
of a semitrailer is handled.  The vehicle drives into the trailer
(which is equipped with bar-coded guidance plates on the inside) and
picks up or deposits a rack of car seats.  The load blocks the vehicle's
sensors in one direction, and is wider than the vehicle.  So there is
a potential for a person to be trapped behind the load.  They considered
this, and there's an interlock system to indicate and control whether
the interior of the trailer belongs to people or robots at the moment.
And for its trip through the plant, the vehicle turns around, so that
the load is behind it and it can sense obstacles in front of itself.
But there are movements in the loading dock area that don't seem to
have solid protection.

					John Nagle
