# FDK solver

Why if I give the follow kind of driver and without put force in the system, I obtain a knee rotation of 25 degrees?

``````
[SIZE=3]AnyKinEqSimpleDriver[/SIZE] KneeForceDep = {
DriverPos = {0.0,0.0,0.0,0.0};
DriverVel = {0.000,0.000,0.0,0.000};
[SIZE=3]
[/SIZE][SIZE=3]AnyKinMeasureOrg[/SIZE][SIZE=3] [/SIZE]OrgLin[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]{
[SIZE=3][/SIZE][SIZE=3]AnyKinLinear[/SIZE][SIZE=3] [/SIZE]lin[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]{
[SIZE=3][/SIZE]Ref=-1;[SIZE=3]
[/SIZE][SIZE=3]AnyRefNode[/SIZE][SIZE=3] [/SIZE]&ShankNode[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]Main.HumanModel.BodyModel.Right.Leg.Seg.Shank.KneeJoint;[SIZE=3]
[/SIZE][SIZE=3]AnyRefNode[/SIZE][SIZE=3] [/SIZE]&ThighNode[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]Main.HumanModel.BodyModel.Right.Leg.Seg.Thigh.KneeJoint;
[SIZE=3][/SIZE]};
[SIZE=3][/SIZE]MeasureOrganizer={0,2};[SIZE=3] // TRASLATION X;Y;Z
[/SIZE]};[SIZE=3]//
[/SIZE][SIZE=3]AnyKinMeasureOrg[/SIZE][SIZE=3] [/SIZE]RotOrg[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]{
[SIZE=3][/SIZE][SIZE=3]AnyKinRotational[/SIZE][SIZE=3] [/SIZE]rot[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]{
[SIZE=3][/SIZE]Type[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]RotAxesAngles;
[SIZE=3][/SIZE][SIZE=3]AnyRefNode[/SIZE][SIZE=3] [/SIZE]&ShankNode[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]Main.HumanModel.BodyModel.Right.Leg.Seg.Shank.KneeJoint.RotNode;
[SIZE=3][/SIZE][SIZE=3]AnyRefNode[/SIZE][SIZE=3] [/SIZE]&ThighNode[SIZE=3] [/SIZE]=[SIZE=3] [/SIZE]Main.HumanModel.BodyModel.Right.Leg.Seg.Thigh.KneeJoint.RotNode;
[SIZE=3]

[/SIZE]};
[SIZE=3][/SIZE]MeasureOrganizer={1,2};[SIZE=3] // ROTATION Y;Z
[/SIZE]};[SIZE=3]
[/SIZE]CType = {Hard,Hard,ForceDep,Hard};
Reaction.Type = {On,On,Off,On};
};

``````

Pleas help me!!!
Thanks,
Giovanni

Giovanni,

it’s tough to say what’s happening without seeing the full model.

will it also rotate if you switch ForceDep to hard?

Can it be gravity?