Rettig, Oliver

09-14-2006, 07:29 PM

Dear all,

we implement an algorithm for gait event detection.

For smoothing and derivating the data we want to use the WOLTRING

filter. We have found Tony Reina's Matlab MEX interface for the GCVSPL

and SPLDER packages based on Dwight Meglan's C Code on the web address

http://www.isbweb.org/software/sigproc.html.

We have the problem to find the correct VAL value for the WOLTRING

GCVSPL package.

We found three approaches:

1. From dan@indy1.motorlab.nsi.eduSun

VAL = sampling_freq/(2*PI*cut_off_freq)**(2*order)

2. from Ton van den Bogert

w0factor = (sqrt(2.0)-1)**(0.5/m)

val = 1.0/dt*(2*pi*f0/w0factor)**(-2*m)

3. Tony Reina

VAL = (EMG-sampling_freqency/1000.0) /

pow(2*PI*EMG_CUTOFF_FREQUENCY/1000.0/pow( (sqrt(2.0)-1),0.5/M),2.0*M)

(including in EMG example)

Our questions are:

Do anybody know what is the correct equation for calculating the mode

value VAL from given cut-off-frequeny?

And why the factor 1000 appears in the equation from Tony Reina?

Many thanks

Kai Kraft

Oliver Rettig

we implement an algorithm for gait event detection.

For smoothing and derivating the data we want to use the WOLTRING

filter. We have found Tony Reina's Matlab MEX interface for the GCVSPL

and SPLDER packages based on Dwight Meglan's C Code on the web address

http://www.isbweb.org/software/sigproc.html.

We have the problem to find the correct VAL value for the WOLTRING

GCVSPL package.

We found three approaches:

1. From dan@indy1.motorlab.nsi.eduSun

VAL = sampling_freq/(2*PI*cut_off_freq)**(2*order)

2. from Ton van den Bogert

w0factor = (sqrt(2.0)-1)**(0.5/m)

val = 1.0/dt*(2*pi*f0/w0factor)**(-2*m)

3. Tony Reina

VAL = (EMG-sampling_freqency/1000.0) /

pow(2*PI*EMG_CUTOFF_FREQUENCY/1000.0/pow( (sqrt(2.0)-1),0.5/M),2.0*M)

(including in EMG example)

Our questions are:

Do anybody know what is the correct equation for calculating the mode

value VAL from given cut-off-frequeny?

And why the factor 1000 appears in the equation from Tony Reina?

Many thanks

Kai Kraft

Oliver Rettig