Add a shoulder bag in Plug-in-gait_simple

#1

Hi,

Inspired by the example of shoulder bag model and the Mocap Plug-in-gait_simple model, I wonder if I can add a backpack in the gait model. And make the analysis about the backpack influence during walking.

I’ve finished adding the bag segment, creating the left and right strap, just follow the one-strap shoulder bag example, it seems great before executing the inverse-dynamics study.

However, errors occur while executing the inverse-dynamic study.

So I wonder if there are anywhere else I should pay attention to, or make some modification to.

Thanks a lot!
Best regards!

#2

Hi @kalhuang. That is a good question. There could be several things wrong here. For example, did you add the kinematic and kinetic constraints for the backpack to the inverse dynamic study? Since I don’t know what error you get it is hard for me to speculate.

I would say that there may be a basic problem in your setup. You making some assumption which may not hold completely.

  1. You assume the kinematics don’t change when you add a backpack.
  2. You assume the force from the ground doesn’t change when you add the backpack.

The first assumption may be OK in simple cases. The second assumption is problem since the forces from the plates will no longer match your person. In this cases GRF prediction models maybe better. Alternatively, you need to actually record data from persons walking with different backpacks.

Best wishes,