Hand grip forces

Hi Anybody,

I am using the Golf model, included in the vicon-mocap-examples. The problem is that when I run the model with my data (including 2 force plates for each leg), the hand grip HAND_GRIP_FORCES (AnyReacForce) is noisy and too high, affecting the whole result.
This first graph is my result, and for comparison, the second graph is the result from the original example included in the vicon-mocap-examples (Use GRF prediction):

The golf club weight is the same for both models (0.2 kg). Is there anything that I am doing wrong?

Best,

Chan

Hi Chan,

Welcome to the AnyScript forum!

I suspect this is happening because your model also includes residual forces at the pelvis. These residual forces at the pelvis are normally implemented using AnyReacForce in models that use Force plates. What you are seeing could simply be a consequence of having two AnyReacForce: one at the pelvis and the other at the hand. This configuration can be used by the model to unload the human muscles by overloading the AnyReacForce to the global reference frame.

I suggest you switch the pelvis residuals to use weak general muscles as is the case in models using GRF prediction. You can do so by adding the following line in the beginning of LabSpecificData.any

#define MOCAP_HUMAN_GROUND_RESIDUALS "PelvisWeak"

When the pelvis residual force is simulated by weak general muscles, the residual force is minimized as the general muscle force is minimized by the muscle recruitment criterion.

I hope this helps.

Best regards,
Dave

Hi Dave,

The PelvicWeak already includes the model when the GRF prediction is off.

I tried another way by adding this line to the InverseDynamicSettings.any
InverseDynamics.Criterion.UpperBoundOnOff = Off;

I'm unsure if this is right, but the model is more stable. However, the hands and club reaction forces are still too high and noisy.

I noticed that the club is not fixed relative to the palm node. Close to the ball contact, it moves towards the body (vertically) or to the right side (when you look from the front). I think this may cause instability in the club and hand force.

Best,
Chan

Hi Chan,

Please try look at the acceleration of the hand and club. If you seen noisy forces in the hands it is likely because of noisy. If this the case you may consider filter settings, these can be applied directly on individual markers (using marker driver class ) or on an overall level in C3DSettings folder.

Best Regards
Søren