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Testing End Levels

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  • Testing End Levels

    We do alot of mechanical testing on specimens with a wide range of
    stiffness. We're using a MTS sevohydraulic system with old analog
    controllers which are very dependable but are old technology. With the
    older technology, it is very difficult to hit and maintain end levels due to
    specimen stiffness. We know can preset the servo gain by performing
    preliminary tests but this is not always possible because of the
    availibility and variability of each specimen. We can crank up the servo
    gain at the beginning of the each test but that creates a problem because
    the stiffness of the specimen could be changing too and the servo loop
    control could cause the testing system to become unstable ("ringing").
    Does anyone have a solution for this problem using our existing equipment???
    Also, does anyone have any experience for solving this problem using the
    digital controllers with "calculated variable control"???
    Many thanks for any input.


    Jerry W.Alexander
    Research Associate
    Institute of Orthopedic Research & Education
    6565 Fannin
    Mail Station F115
    Houston, Texas 77030
    Pager (713)764-1879
    Fax (713)797-6658

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