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From: smith@sndpit.dec.com (Willie Smith)
Newsgroups: comp.robotics
Subject: Re: 6 DOF Joysticks
Message-ID: <669@sousa.enet.dec.com>
Date: 7 Dec 90 21:02:46 GMT
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Organization: Digital Equipment Corporation
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In article [...], minsky@media-lab.MEDIA.MIT.EDU (Marvin Minsky) writes...
>In article [...] gerry@frc2.frc.ri.cmu.edu (Gerry Roston) writes:
>>In article [...] smith@sctc.com (Rick Smith) writes:
>>   Ideally, you want the kinematics of the joystick (well, hand controller) to
>>   match that of the robot. 
> 
>> ... tests done at JPL and elsewhere
>>have shown that to perform meaningful tasks, force reflection is
>>required and that time delay from your sensors (cameras, force
>>sensors, etc) will seriously degrade performance.
> 
>Terms like "seriously degraded" seriously degrade our appreciation of
>some problems.  I mention this because I'm convninced that earth-based
>remote control of, for example, a space station, would yiled a huge
>advantage in performance/cost payoff.  So the question is, what did
>"tests done at JPL and elsewhere" really demonstrate?  
> 
>Consider that the internal sensor-brain-muscle roudtrip time of a
>human is of the order of 1/5 second [...]

Another consideration is that humans can learn to predict and anticipate
control inputs to systems with long delays.  After about 1/2 hour driving
my (simulated) lunar teleoperated vehicle I've found I can do significantly
better than when I started, and the 'training time' gets shorter with 
repeated 'missions'.

While I don't doubt that force-feedback and other tightly-coupled systems
can get unstable when the delay approximates the human reaction time, more
loosely-coupled systems (joysticks and video feedback with Heads-Up-Display 
to show the operator where he's pointing his controls) allow the operator to
compensate for the delays.  Yes, precision tasks take longer, but nothing is
quite as bad as the expected "move, wait to see what happened, move again..."
case, even when running with a full 3-second lunar teleoperations delay.

In case anyone is interested, the vehicle in question is a modified RC 
truck with TV camera and transmitter, controlled by a Z80-based S-100 
machine, with the received TV signal routed through an Amiga with genlock 
for HUD.  You can indeed do lunar teleoperations research in your basement!
The phase II vehicle is based on lawn-tractor wheels and cordless drill 
motors, with a couple of onboard computers.  Lots more documentation 
available on request.

Willie Smith
smith@sndpit.enet.dec.com
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