GaitLowerExtremity inverse dynamics won't run from optimised kinematics


I’m using AnyBody 4. 1. 1. 1273 and AMMRV1.1.

I have modified this GaitLowerExtremity model for modelling a cyclist. The model was set up using one c3d file and runs fine (most of the time - occasionally a singular KKT matrix causes an issue but this is usually resolved by rerunning the motionandparameteroptimization). When I switch the c3d file for another one (of the same cyclist) the motion and parameter optimisation stage runs fine but once the inverse dynamics is started it fails the kinematic analysis in time step 0. The model should be using its own generated output which it ran fine but I’m currently at a loss to explain why it won’t run for any of the other c3d files I have. All the files have the same markers and marker positioning shouldn’t be a problem as they were all captured during the same session from one cyclist.

I’ve attached the model with 2 c3d files. Mod.c3d is the one that won’t run and Mod2.c3d will run.

Any assistance would be much appreciated,

Hi Alex,

It is just a matter of initial conditions. As there is a joint bettween the foot and pedal the initial conditions have to be good enough for this constraint to solve.
With the file Mod.c3d the left foot is just too far from the pedal. Change that in the Mannequin file and it will work nicely.

Best regards, Sylvain.

Thanks for that Sylvain.

Regards, Alex