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Data filtering and differentiation

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  • Data filtering and differentiation

    Dear fellow networkers,

    I am developing a research project which involves the use of a rotary encoder
    to provide displacement data to a resolution of 0.5 mm in 3.0 m at a frequency
    of 500 Hz. I wish to derive velocity and acceleration data and have been using
    a Butterworth filter for smoothing and differentiation of kinematic data which
    is essentially parabolic in path. I would be most appreciative of any help
    that can be provided as to:

    1. Is the Butterworth a suitable filter or is there a better
    alternative? I believe I have implemented a 4th order Recursive Butterworth?

    2. Can anyone tell me what coefficients I should use for the terms in
    the filter to produce a given cutoff frequency or is there a reference which
    would list such information?

    3. Can anyone direct me to a good review on data filtering in
    biomechanics? In particular I need information on the actual
    smoothing/differentiation algorithms. Code examples in C, Fortran etc would be
    very helpful.

    4. I would appreciate it if anyone could email me sample source code
    of any smoothing/differentiation routines.

    Thankyou in advance for any assistance that you can provide. It is
    greatly appreciated.
    Robert Newton Internet:
    Lecturer in Biomechanics ACSnet: rnewton@loki.une.oz
    University of NewEngland,
    Northern Rivers Phone: +61 (066) 203762
    P.O. Box 157
    Lismore NSW Australia