Velocity Measures

[zhuber07]

I am creating a biomechanical model of the human neck. I have created measures that calculate position, velocity, and acceleration of different muscles during motions, and am having a hard time with the velocity.

When the velocity function is made, I specified the to_marker and the from_marker and the reference_marker. I created 2 functions, one where the reference_marker was the to_marker and one where it was the from_marker. The final velocities are different, and I am wondering where I went wrong. I expected them to be the same, as the same 2 markers are used in both cases. Any help would be appreciated, thanks!

 

[GregLocock]

You used the same reference marker in each case? the velocity should be reversed in sign between the two functions.

post your code,

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[zhuber07]

There is a velocity jump at the beginning of each trial, and those are opposite, which I expected, but R_SCM_VEL ends with a final velocity of 53 mm/sec, while R_SCM_VEL2 ends with a final velocity of 49mm/sec. The code for the creation of the markers is below.

R_SCM_VEL
!!!!!!!!Beginning

if cond=(.gui.funcBldr.displayed)
if cond=(eval(alert("warning", "Function Builder is already displayed. Proceeding will erase existing contents. Proceed?", "Yes", "No", "",1) != 1))
return
end
end
int dia disp dia=.gui.funcBldr par="Function Measure", "", "", "", (UNIQUE_NAME("FUNCTION_MEA"))
measure cre function measure=.model_1.R_SCM_VEL function="VM(MARKER_84, MARKER_85, MARKER_85)" &
units = no_units create_measure_display = yes
! set measure plotting attributes
measure attributes measure=.model_1.R_SCM_VEL &
&
&

int dialog execute dialog=.gui.funcBldr undisp=yes

!!!!!!!End

R_SCM_VEL2

!!!!!!!!Beginning

if cond=(.gui.funcBldr.displayed)
if cond=(eval(alert("warning", "Function Builder is already displayed. Proceeding will erase existing contents. Proceed?", "Yes", "No", "",1) != 1))
return
end
end
int dia disp dia=.gui.funcBldr par="Function Measure", "", "", "", (UNIQUE_NAME("FUNCTION_MEA"))
measure cre function measure=.model_1.R_SCM_VEL2 function="VM(MARKER_84, MARKER_85, MARKER_85)" &
units = no_units create_measure_display = yes
! set measure plotting attributes
measure attributes measure=.model_1.R_SCM_VEL2 &
&
&

int dialog execute dialog=.gui.funcBldr undisp=yes

!!!!!!!End

Thanks again for your help,

Zach

 

[GregLocock]

ah sorry I don't read cmd, but ti looks to me as though those are measuring the exact same thing

the critical line

function="VM(MARKER_84, MARKER_85, MARKER_85)"

is the same in each




Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?