Drivers

Dear all,

I have some problems in driving my model. I use the gait lower extremity and set all joint positions/ velocities to zero (drivers), because I would like to drive my model in the sagittal plane and keep everything constant in the Z-axis.

Without adding any drivers, the inverse dynamics model works perfectly.
Then I add the following driver for the big toe:

AnyKinLinear RTLin = {
AnyRefFrame &LabOrigin = …EnvironmentModel.GlobalRef;
AnyRefFrame &RT = Main.Studies.HumanModel.BodyModel.Right.Leg.Seg.Foot.BigToeNode;
};

AnyKinEqInterPolDriver RTdriver =
{
MeasureOrganizer = {0,1};
Type = Bspline;
BsplineOrder = 4;

FileName = “RT.txt”; --> File containing t - x - y

AnyKinMeasure &Lin = .RTLin;
Reaction.Type = {Off, Off};
};

I drive the bigtoejoint of the model with respect to the global axis. Unfortunately, at initial position analysis, I get 2 more unknowns than constraints (or 1 when I only drive the y or x position of the bigtoejoint). I know I forget something simple, but why does the driver add unknowns instead of constraints and hence cannot solve the initial conditions anymore?

Thanks in advance,

René

(4.2.1, AMMRV 1.2)

Hi René

As i understand it you are driving the model with a full set of modified joint drivers found using markers.

Then you add two or one more constraint between the foot and the ground?

This will not work since the model is already fully kinematical constrained by the joint drivers and the driver on pelvis and you will end up having to many unknowns.

In such a case this constraints should have been added together with the mocap or you will need to have all/some the jointdrivers as soft kinematic constraints.

Best regards
Søren