When apply external loads from a force plate in an inverse dynamics analysis, how should the external moment data be defined? Should it be the moment with respect to the model origin, or the moment with respect to the center of pressure, or the moment with respect to the force plate origin?
Thanks,
Dan Dorman
External Moment Origin Coordinates
- Daniel Dorman
- Posts: 3
- Joined: Mon Jan 26, 2009 12:29 pm
RE: External Moment Origin Coordinates
I compared my gait inverse dynamic simulation results to the results from tutorial 3, and noticed that the knee moments for my results were much higher than the tutorial. I'm wondering if this could be due to incorrectly applied ground reaction moments? I need to know how the ground reaction moments need to be applied for the inverse dynamics analysis, and what origin the moments should be defined with respect to.
Thanks,
Dan
Thanks,
Dan
- Maria Isabel Orselli
- Posts: 39
- Joined: Wed Mar 17, 2010 5:30 pm
RE: External Moment Origin Coordinates
Hi Daniel,
I have the same doubt. Did you discover anything about how to report the ground reaction moment ?
thanks
Maria Isabel
I have the same doubt. Did you discover anything about how to report the ground reaction moment ?
thanks
Maria Isabel
RE: External Moment Origin Coordinates
I believe you need to report the GRM with respect to the center of pressure. For all level gait, the GRM in the X and Z direction will be zero, and the GRM (vertical free moment) in the Y direction will be non-zero (but not very big ~ usually less than 10Nm in magnitude for normal gait, so this shouldnt effect your results too much I would imagine).
-Tim
-Tim
- Maria Isabel Orselli
- Posts: 39
- Joined: Wed Mar 17, 2010 5:30 pm
RE: External Moment Origin Coordinates
Hi Tim
You are right. I took a careful look inside the data in an grf archieve in the exemple directory and all make sence.
Thank you
Maria Isabel
You are right. I took a careful look inside the data in an grf archieve in the exemple directory and all make sence.
Thank you
Maria Isabel