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From: smith@sctc.com (Rick Smith)
Newsgroups: comp.robotics
Subject: Re: 6 DOF Joysticks
Keywords: teleoperation
Message-ID: <1990Dec6.232210.2638@sctc.com>
Date: 6 Dec 90 23:22:10 GMT
References: <18232@hydra.gatech.EDU>
Distribution: na
Organization: Secure Computing Technology Corporation
Lines: 48

gm26@prism.gatech.EDU (MCMURRAY,GARY V) writes:

>I am interested in finding out information on the development of 6 DOF
>joysticks by various people.  In particular , I am interested in the
>manner that the motions of the joystick are converted into a motion for
>the robot.

I spent a year or so working on a project invloving this, and you connect
the components together like this:

off-the-shelf 6 DOF joystick ==> LOTS OF WORK ==> off-the-shelf robot

The LOTS OF WORK section is the implementation of your teleoperation control
scheme. We looked at several approaches, and it all depends on your joystick
and your robot's geometry. I don't think there's much out there in the way
of off-the-shelf teleoperation software that supports a range of joysticks
and robots. Usually the best you can do is buy a robot with a handheld
programming control that uses something approximating a joystick.

I assume that by "joystick" you mean anything that will map operator movements
into robot motions, and not just handles like they use on video games...

In the project I worked on, we planned to do teleoperation controlled by
DataGloves -- that's those bizarre gauntlets that measure finger flexes
and hand position/orientation. We were going to use hand displacement
(scaled by a gain signal from a foot pedal) to specify end effector
displacement. The project was axed before the robot was built, though we
had lots of fun with the DataGloves.

On the other hand (sorry!) we had another project evaluating 6 DOF hand
controllers... I got the impression that the classic technique there was
to use displacement to specify a velocity vector for the robot's end effector
motion. Let go of the controller and motion stopped; exert some effort
and motion followed the direction/orientation you pushed.

Ideally, you want the kinematics of the joystick (well, hand controller) to
match that of the robot. Thus, the DataGlove is really best with a cartesian
robot, as are the 6 DOF generalizations of 2 DOF joysticks. With articulated
robots like Pumas, however, you have to worry about singularities in your
work envelope (e.g. places you can't quite reach). If you look
around, though, there IS some company that builds an articulated hand
controller designed to match the kinematic configuration of things like Pumas.
Sorry, but I don't remember the company name. I do remember that they cost
lots, though you save something in software development by avoiding the
singularity issue.

Rick.
smith@sctc.com   Arden Hills, Minnesota