Re: [CAD_CAM_EDM_DRO] Re: missile guidance vs. CNC

Missiles, Missiles, missiles! I used to work on Missiles WAY back when I
was in the Air Force. Don't want to talk about the guidance systems...even
if I could. Was pretty interesting at the time tho'.

Smoke
-----Original Message-----
From: Jon Elson <jmelson@...>
To: CAD_CAM_EDM_DRO@egroups.com <CAD_CAM_EDM_DRO@egroups.com>
Date: Wednesday, November 29, 2000 10:16 PM
Subject: [CAD_CAM_EDM_DRO] Re: missile guidance vs. CNC

>
>
>Alan Marconett KM6VV wrote:
>
>> Jeff,
>>
>> I'm not EVEN trying to "straighten you out"! ;>) But I will comment on
>> the missile guidance system. I think what you're saying is that
>> acceleration in down range and cross range directions is counted, the
>> missile is "steered" with the cross range error, and when the missile
>> gets to it's "terminal point" (a spot in space from where it can
>> "ballistic free fall" on the target), it separates the payload, which
>> then "falls" the rest of the way. Does this work for mills? Not sure
>> there! I'm already over my head!
>
>No, missile guidance is pretty different from machining. The big

difference

>is a missile only has to hit the target, it doesn't matter what path it

takes

>to get there, or how smooth the path is. (It is true that there is not a
>great choice of paths due to fuel constraints, etc.) Anyway, the need
>to have complete control over the entire contour during the entire
>cutting motion of the system is kind of different. (Of course, the
>missile really needs tight control of an essentially unstable vehicle
>all the time during the boost phase, and that is done by planning a
>trajectory, checking error and making fine corrections to get back on
>course, so that part is actually not so different.)
>
>Maybe the real difference is that the missile only looks at the target,
>not the trajectory. If the missile finds itself off course, it doesn't
>try to get back to the old trajectory (that may be impossible) it
>plans a new trajectory from where it is now to the target. (At
>least, it makes the most sense to do it this way, but maybe the
>missiles really have a fixed trajectory, and have to stay on it.)
>The CNC should never plan a new trajectory, it has to stay
>on the one defined by the toolpath program.
>
>Jon
>
>
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