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From: rstevew@armory.com (Richard Steven Walz)
Subject: Re: Inverse Kinematics
Organization: The Armory
Date: Sat, 24 Sep 1994 02:38:30 GMT
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In article <35s70j$6nf@news.iastate.edu>,
Chris Clover <clov@iastate.edu> wrote:
>In article <1994Sep21.115130.19186@jarvis.cs.toronto.edu> rbh@gambit.utias.utoronto.ca (Roger Barry Hertz) writes:
>
>>One question I have about inverse kinematic solution for a 6R 
>>mechanism is how to keep track of multiple solutions.
>>This is especially trying when solutions disappear and reappear
>>again.
>
>
>I'm not exactly sure what you mean by "disappear and reappear".  The 
>inverse solutions I have seen for higher degree of freedom manipulators
>usually involve joint angles that can flip sign due to some squart root 
>or inverse sin or cos.  Craig (Intro to Robotics, p.116) gives a pretty
>good discussion on choosing which solution to use depending on whether
>you want the "closest" solution to where you are already at or if you
>are trying to avoid an obstacle, etc.
>
>
>Chris Clover (clov@iastate.edu)
>Iowa Center for Emerging Manufacturing Technology
>Iowa State University
>Ames, Iowa 50011
-----------------------------------------------------
Well, don't solutions on a given path appear and disappear with the
constraints from obstacle avoidance and when a joint or joints reach end
of travel in that vector or when multiple paths are to be optimized into
one and the multiple vector solutions shrink to one or none for a given
vector or vector set, as in, "you can't get there from here"? Also such
can appear or disappear from reverse calculation of cantilever and obtuse
strains. All I know about it is in my one old text about this stuff for 
industrial robots and the solution forms and methods for up to 6 freedoms.
Those methods are in all the texts I've seen on the subject. Some problems
can be nasty. I'd love to see a FAQ file on that stuff with some sample
problems.
-Steve Walz   rstevew@armory.com

