Re: Deadband violation ?

From: j.allport@utoronto.ca
Date: Tue Jul 13 2004 - 13:13:47 EDT

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    I would have thought it meant a satellite drifting outside its control
    deadband... that is a box (in the simple case) in 'phase space' wherein no
    control input is required.
    
    Consider a 1D simplification of a phase plane control system...
    
    For example, a satellite in the exact desired position, but with a high velocity
    relative to that position, may require control input because it's outside the
    control system deadband in the velocity axis. It hasn't violated its physical
    position boundary, but its velocity relative to that position has been violated.
    
    Alternatively, for a satellite that may be out of position, but with a velocity
    toward the desired position, no control input would be necessary because it is
    already returning. It is still within its deadband. Assuming a constant velocity
    relative to desired point, it will at some point (likely -before- attaining its
    desired position) require another control input because it has violated the
    velocity axis for that position.
    
    I hope I've explained the concept well enough. I wouldn't want to say more
    without drawing a phase-plane plot. Pictures say so much more. :) As for whether
    that's the correct interpretation of this case, I don't know.
    
    Cheers,
    JCA
    
    Quoting John Locker <john@satcom.freeserve.co.uk>:
    
    > Hi all,
    > 
    > Can anyone explain what is meant by "deadband violation" when  refering to
    > geo comsats ?
    > I was under the impression it related to a bird drifting outside its
    > control
    > box , however I read something today that makes me think that theory is
    > wrong......anyone help ?
    > 
    > 
    > Many thanks,
    > 
    > John.
    > 
    > 
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