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  • responses about jerk

    Dear Suscribers,

    I want to thank everybody who answered to my message about jerk or
    acceleration derivatives. The responses I got follow.

    Thanks,


    Stephane


    -----------------------------------------------------------------------
    Date: 17-JUN-1994 18:17:15.92
    From: SMTP%"grerfx00@ccmail.iasl.ca.boeing.com"
    Subj: Re: jerk or acceleration derivative
    To: bouilland
    CC:
    77 records, external message id MAIL$0195914800050098.MAI
    Attributes: New message

    Stephane:

    In regard to your message...
    ================================================== ===========================
    Dear subscribers,

    The "jerk" or body segments acceleration's derivative is sometimes used as
    a
    comfort criteria.I would like to know why, and what is it's physical
    meaning? I also would like to know if there are normative studies about this
    comfort criteria (i.e. : When does the jerk become uncomfortable?).
    I also wonder if differentiation technics (using quintic spline for
    example) of motion analysis systems data are sufficiently reliable to access
    the jerk which means the third numeric derivative of position data.

    Thanks in advance to those who will answer me, I will sum up the responses.

    Stephane Bouilland
    Universite de Valenciennes
    France
    E-mail :
    bouilland@univ-valenciennes.fr
    ================================================== ============================

    . I recently was wondering about the same things myself. The way I
    explain jerk is first to say it is the rate of change of acceleration. This is
    obvious, but it helps explain what it means to the person experiencing the
    jerk. It means that the person must be able to react to the change in
    acceleration. So, if the acceleration comes on too quickly, or
    unexpectedly, it could knock down a standing person!

    I found some references in train comfort literature:

    H.H. Jacobs "Factors Contributing to the Retention of Seated Passengers
    During
    Seated Stops", a US Technical report, number UMTA-MA-06-0048-79-6.

    H. Jacobs "Please Remain Seated: Seat Designs to Help Retain Passengers
    During
    Emergency Stops", from the proceedings of the 24th annual meeting of the
    Human
    Factors Society.

    Abernathy "Effects of Deceleration and Rate of Deceleration on Live Seated
    Human Subjects", from Transportation Research Record number 646.

    Pepler "Passenger Comfort in Ground Vehicles", from Human Factors in
    Transport
    Research edited by Oborne and Levis.

    Another source was the ASME standard for moving walks.

    I hope this gets you going in the right direction.

    Good luck!

    Rush Green
    Boeing Commercial Airplane Group
    Seattle, WA
    email: grerfx00@ccmail.iasl.ca.boeing.com

    ================== RFC 822 Headers ==================

    Dear Stephane,

    In response to your "jerk" query, I can add a little but not much.
    I was introduced to jerk, i.e. the derivative of acceleration, from
    mechanical engineering classes. It is simply the change in acceleration
    of a body already in or put into motion. The applications I have seen
    were primarily in the design of elevators or other lifting apparatus. A
    change in acceleration of a high enough magnitude produces what amounts
    to a jerk for the passengers. This can be felt in some high speed
    elevators at the beginning or end of motion.

    I hope this was of some help to you.

    Dan Ferris
    University of Central Florida

    --------------------------------------------------------------------------

    jerk is the time derivative of accelerations and so it measures the
    variation of the inertia actions. the bigger the jerk the bigger the
    variation in the inertia actions (forces and torques)

    From: SMTP%"LEGNANI@icil64.cilea.it"
    --------------------------------------------------------------------------

    Simply, it is the rate of exchange of acceleration. Try looking it
    up in a Mechanical Engineering text that discusses camshaft
    kinematics. Jerk is an important parameter in cam design.

    I am not familiar with any biomechanical references to jerk.

    kbb
    From: SMTP%"blairk@world.std.com"
    --------------------------------------------------------------------------

    If acceleration is measured directly with an accelerometer then only one
    differentiation must be performed to get jerk.
    From: SMTP%"gottesma@salus.med.uvm.edu"
    --------------------------------------------------------------------------
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