Adding Payload in Mocap Model

HI, I am carrying out a study of analysis of carrying a backpack load in Mocap Model. Before this study, first I attached the payload on standing human, which I could do it successfully. But when it comes to attaching the payload in Mocap Model, I am facing issues as the code runs without any error but when I carry out analysis study, I cant see human model attached with payload. Can some one guide me where I am mistaking in my code. I am attaching files for reference.

Hi sakshiagarwal

It looks like you have two sets of constraints working on the backpack model.
You have soft constraints between backpack and human which looks apparently ok, but you seem also to have 6 hard constraints between backpack and the ground.

These are defined in bottom of your backpack assembly, generated by SolidWorks, these constraints prevent the backpack from moving with the pelvis, they need to be removed.

Best regards

Thanks Søren

As you rightly pointed out the mistake which i was making, I commented Anyfolder Mates in Backpack assembly file and now I could see the model walking with the payload…

Thanks for your support.


When I tried running the simulation of payload with mocap model, I could not see the weight of payload added to the mocap model (Fz component in Force plate 1, 2 ,3).

Can you tell where I need to make changes in the code to involve weight of payload in inverse dynamic study

Hi sakshiagarwal,

In a normal mocap model the ground reaction are measured and applied. If you have experimental data with payload included you can reuse this concept and the only thing you will need to do is to add the backpack into the model with the right weight.

If on the other hand you do not have experimental data with the payload you will have to do GRF predictions, please see for details on this. To predict the GRF it requires you to have fullbody kinematics measured.

Best regards