Seat reaction force

Hello everyone,

I am still working on a model that should perform sitting down and standing up based on the SeatedHuman application. I drive left and right leg symmetrically, and only have motion in the sagittal plane. However, when the model sits down on the seat, it happens sometimes, that seat reaction force will not be symmetric between left and right hand side. I am using the conditional contacts defined in the SeatedHuman application, but I do not have leg, arm and back rests included.

Do you have any idea, where this asymmetry in support forces in a symmetric task might come from?

Thank you very much and best regards

Hi Ramona,

Sorry for the slow answer

Please try to check these things:
[li] run the kinematics of the model
[/li][li] check things like knee joint position is indeed symmetric, so dump the Kneejoint.r value for both knees after having solved kinematics.
[/li][li] do several of such checks to make sure kinematics are not the root of the behaviour you see.
[/li][li] Check the accelerations of the pelvis or trunk make sure there are no accelerations sideways to the model which from you description should be zero. So check …thorax.rDDot
[/li][li] if all above shows no sign of non symmetry move to next item otherwise double check your drivers.
[/li][li] ensure that the support forces which are defined in the model have a symmetric setup… so same amount of elements on both sides… exaxctly same settings for left and right support muscles…

Hope some of it helps you to identify the issue.

Best regards

Dear Søren,

thank you very much for your inputs. We will try this out and see, if it helps.

Best regards