Joint resistance

Archive AnyScript Yahoo archive
1

Dear AnyBody supports:

I am building a finger model to fit the experimental data. In some
cases, the model does not converge. One of the possibilities is that
the passive joint resistance is considered in the model. The joint
resistance is like a torional spring, its magnitude is proportinal to
the angular displacement away from the neutral position. My question
is how to build the joint resistance in a joint?

For example, the joint (CMC) is defined as following. Can you show me
hot to add a passive joint moment with a magnitude proportinal to the
joint angular displacement?

Thanks, John Wu

+++++++++++++++++++++++++++++++++++++++++++
AnyFolder Jnts = {
AnyUniversalJoint CMC =
{ Axis1 = y;
Axis2 = z;
AnyRefNode &GroundNode = …GlobalRef.Metacarpal_thumb;
AnyRefNode &ProximalNode = …Segs.Proximal_Phalanx.CMC_JT_Node;
};
};

AnyFolder Drivers = {
AnyKinEqInterPolDriver CMCMotion = {
AnyUniversalJoint &Jnts = Main.ThumbModel.Jnts.CMC;
FileName = “FPL_cmc.txt”;
Type = Bspline;
BsplineOrder = 4;
Reaction.Type = {Off,Off};
};
};

AnyFolder Measurements = {
AnyForceMomentMeasure CMC_M =
{
AnyForceBase &CMC_M = Main.Drivers.CMCMotion.Reaction;
AnyRefNode &CMC_ref = Main.ThumbModel.GlobalRef.Metacarpal_thumb;
};
};

2

Hi John

This can be done using a the AnyForce object

If you have the jnt

AnyFolder Jnts = {

   AnyUniversalJoint CMC =

   {

     Axis1 = y;

     Axis2 = z;

     AnyRefNode &GroundNode = ..GlobalRef;

     AnyRefNode &ProximalNode = ..mass;

   };

 };

The AnyForce object can be used for creating the moment reaction depending
of the kinematics of the joint

 AnyForce JointResistance ={

   AnyVar Stiffness1=0.01;

   AnyVar Stiffness2=0.02;



   AnyUniversalJoint &ref=.Jnts.CMC;

   F={ref.Pos[0]*Stiffness1, ref.Pos[0]*Stiffness2}; //here you can have

any expression depending on pos, vel or acc

 };

 }; // MyModel

I hope it is this kind of solution you are looking after, otherwise please
write again.

Best regards

Søren

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of johnzengwu
Sent: 26 September 2008 23:51
To: anyscript@yahoogroups.com
Subject: [AnyScript] Joint resistance

Dear AnyBody supports:

I am building a finger model to fit the experimental data. In some
cases, the model does not converge. One of the possibilities is that
the passive joint resistance is considered in the model. The joint
resistance is like a torional spring, its magnitude is proportinal to
the angular displacement away from the neutral position. My question
is how to build the joint resistance in a joint?

For example, the joint (CMC) is defined as following. Can you show me
hot to add a passive joint moment with a magnitude proportinal to the
joint angular displacement?

Thanks, John Wu

+++++++++++++++++++++++++++++++++++++++++++
AnyFolder Jnts = {
AnyUniversalJoint CMC =
{ Axis1 = y;
Axis2 = z;
AnyRefNode &GroundNode = …GlobalRef.Metacarpal_thumb;
AnyRefNode &ProximalNode = …Segs.Proximal_Phalanx.CMC_JT_Node;
};
};

AnyFolder Drivers = {
AnyKinEqInterPolDriver CMCMotion = {
AnyUniversalJoint &Jnts = Main.ThumbModel.Jnts.CMC;
FileName = “FPL_cmc.txt”;
Type = Bspline;
BsplineOrder = 4;
Reaction.Type = {Off,Off};
};
};

AnyFolder Measurements = {
AnyForceMomentMeasure CMC_M =
{
AnyForceBase &CMC_M = Main.Drivers.CMCMotion.Reaction;
AnyRefNode &CMC_ref = Main.ThumbModel.GlobalRef.Metacarpal_thumb;
};
};

[Non-text portions of this message have been removed]

3

Søren:

Thanks. I did as you suggested and it works.

John

— In anyscript@yahoogroups.com, AnyScript Support <anyscriptsup@…>
wrote:
>
> Hi John
>
>
>
> This can be done using a the AnyForce object
>
>
>
> If you have the jnt
>
>
>
> AnyFolder Jnts = {
>
> AnyUniversalJoint CMC =
>
> {
>
> Axis1 = y;
>
> Axis2 = z;
>
> AnyRefNode &GroundNode = …GlobalRef;
>
> AnyRefNode &ProximalNode = …mass;
>
> };
>
> };
>
>
>
> The AnyForce object can be used for creating the moment reaction
depending
> of the kinematics of the joint
>
>
>
> AnyForce JointResistance ={
>
> AnyVar Stiffness1=0.01;
>
> AnyVar Stiffness2=0.02;
>
>
>
> AnyUniversalJoint &ref=.Jnts.CMC;
>
> F={ref.Pos[0]*Stiffness1, ref.Pos[0]*Stiffness2}; //here you
can have
> any expression depending on pos, vel or acc
>
>
>
> };
>
> }; // MyModel
>
>
>
>
>
> I hope it is this kind of solution you are looking after, otherwise
please
> write again.
>
>
>
> Best regards
>
> Søren
>
>
>
> _____
>
> From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com]
On Behalf
> Of johnzengwu
> Sent: 26 September 2008 23:51
> To: anyscript@yahoogroups.com
> Subject: [AnyScript] Joint resistance
>
>
>
> Dear AnyBody supports:
>
> I am building a finger model to fit the experimental data. In some
> cases, the model does not converge. One of the possibilities is that
> the passive joint resistance is considered in the model. The joint
> resistance is like a torional spring, its magnitude is proportinal to
> the angular displacement away from the neutral position. My question
> is how to build the joint resistance in a joint?
>
> For example, the joint (CMC) is defined as following. Can you show me
> hot to add a passive joint moment with a magnitude proportinal to the
> joint angular displacement?
>
> Thanks, John Wu
>
> +++++++++++++++++++++++++++++++++++++++++++
> AnyFolder Jnts = {
> AnyUniversalJoint CMC =
> { Axis1 = y;
> Axis2 = z;
> AnyRefNode &GroundNode = …GlobalRef.Metacarpal_thumb;
> AnyRefNode &ProximalNode = …Segs.Proximal_Phalanx.CMC_JT_Node;
> };
> };
>
> AnyFolder Drivers = {
> AnyKinEqInterPolDriver CMCMotion = {
> AnyUniversalJoint &Jnts = Main.ThumbModel.Jnts.CMC;
> FileName = “FPL_cmc.txt”;
> Type = Bspline;
> BsplineOrder = 4;
> Reaction.Type = {Off,Off};
> };
> };
>
> AnyFolder Measurements = {
> AnyForceMomentMeasure CMC_M =
> {
> AnyForceBase &CMC_M = Main.Drivers.CMCMotion.Reaction;
> AnyRefNode &CMC_ref = Main.ThumbModel.GlobalRef.Metacarpal_thumb;
> };
> };
>
>
>
>
>
> [Non-text portions of this message have been removed]
>