Jump Landing Inverse Dynamics: Pelvis Ty Issue During Pre-Landing

[Jin Z]

Hello,

I am running Inverse Dynamics on stop-jump landing data as a checkpoint before running RRA. At the time range before the landing where the model has no ground contact, my inverse dynamics results (run with external GRF forces) come out problematic as shown in the image below, where the blue line (my ID result) is supposed to fluctuate about zero.

Red: GRF curve. Blue: ID results (with external forces)

Stop Jump Landing with GRF.png (37.23 KiB) Viewed 282 times

I have previous archival simulation data of a different jump (vertical jump) give correct results despite there also being a time interval where the model is not making contact with the ground shown below. Here the ID results fluctuate about zero, which is the result I'm trying to achieve. However I am struggling to replicate this trend in my stop-jump data.

Vertical Jump Landing with GRF.png (20.56 KiB) Viewed 282 times

Hence I know that it is possible to achieve proper simulation results with a model in flight phase of the motion. However I'm not sure what the issue is with my inputs that causes the ID pelvis Ty curve to drift so far down. This will later create an unacceptably large mass change recommendations in RRA. Does anyone have some insight into how to fix this issue or if there is a "common mistakes" reason that causes this to happen for jumping simulations?

Thanks,

Jin

[Jin Z]

Hello all,

I am still trying to figure out my problem of what could cause Inverse Dynamics Pelvis Ty force result (run with external force) to fall so far out of range. As I have verified that all my inputs are setup correctly in the GUI and unable to find any problems with my marker or GRF data, I would greatly appreciate some suggestions from anyone who has worked a lot with Inverse Dynamics and has encountered this kind of result, particularly with flight-phase motion in a jump landing (or even running).

Thank you,

Jin