Control of ankle plantar flexion

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1

Hi AnyBody group,

I have recently been collecting some gait data sets and inputting
them into a modified freeposture model for analysis. I am currently
having difficulty with getting the toe node on the mannequin to follow
the marker coordinates. This is obviously giving abnormal results for
plantar and dorsiflexion, as well as eversion and inversion. Looking
at the Vaughan model, there seems to be a fair amount of restriction
on the ankle movements and i’m not sure if its data controlled or ‘man
made’. Looking at the previous post from Mike, it seems adding deltoid
and lateral collateral ligaments maybe a good way to help control the
ankles movements.

I have also played with the idea of adding extra markers to the foot
(over the cubiod) to drive the movement in the model.

Has anyone else shared my experience with inability to control the
ankle, are there any suggestions to help?

many thanks

Peter

2

Hi Peter

Adding ligaments to the ankle will not change the motion of the ankle in
anyway, this is inverse dynamics so the motion is always prescribed. Adding
the ligaments will of course help carry the load but that is another thing.

It should be possible to make the toe node follow the marker more or less,
but it can be difficult to control. One simple thing to check is if you are
using the local coordinate system on the toe marker as basis for you
kinematic measure?

So it should look like something like this

AnyKinEqSimpleDriver ToeMarker ={

AnyKinLinear lin ={

AnyRefNode &ref1=.Toemaker;

AnyFixedRefFrame &ref2=.GlobalRef;

Ref=0; //This will make this measure use the Toemarker coordinate system

for the measurements.

};

MeasureOrganizer={0}; //pick out the x direction I recall this to be
normal to the foot, please verify…

DriverPos={0};

DriverVel={0};

};

If you do not specify the Ref=0; line it will use the global coordinate
system and then the foot flexion can be difficult to control, I have seen
this on a early version of the gait model.

I do not understand what you mean by “manmade” all the dof in the Vaughan
model is driven by the marker data.

I hope this made things clearer, otherwise please write again.

Best regards

Søren, AnyBody Support

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of peter.worsley
Sent: 08 April 2008 15:37
To: anyscript@yahoogroups.com
Subject: [AnyScript] Control of ankle plantar flexion

Hi AnyBody group,

I have recently been collecting some gait data sets and inputting
them into a modified freeposture model for analysis. I am currently
having difficulty with getting the toe node on the mannequin to follow
the marker coordinates. This is obviously giving abnormal results for
plantar and dorsiflexion, as well as eversion and inversion. Looking
at the Vaughan model, there seems to be a fair amount of restriction
on the ankle movements and i’m not sure if its data controlled or ‘man
made’. Looking at the previous post from Mike, it seems adding deltoid
and lateral collateral ligaments maybe a good way to help control the
ankles movements.

I have also played with the idea of adding extra markers to the foot
(over the cubiod) to drive the movement in the model.

Has anyone else shared my experience with inability to control the
ankle, are there any suggestions to help?

many thanks

Peter

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

3

Hi Soren,

my driver for toe is as follows;

AnyKinEqSimpleDriver MetatarsalYLDrv={
AnyKinLinear lin={
AnyRefFrame &ref1=Main.Model.HumanModel.Left.Leg.Seg.Foot.LTOE;
AnyRefFrame &ref2=Main.MarkerTopology.M14.FreeMarker;
Ref=0;
};
MeasureOrganizer={2};
DriverPos={0};
Reaction.Type={Off};
DriverVel={0};
};

All other markers are driving the model well appart from the foot. (measure
organiser is in the z coordinate for ankle plantar flexion and dorsiflexion.)
The Vaughan data looks very smooth and I could not find a Pointsmarker file, has
the data been processed before it was modeled?

By adding the ligaments I was hoping to add constriant for enverison/inversion,
are you saying this is not possible?

many thanks

Peter

AnyBody Support <support@anybodytech.com> wrote: Hi Peter

Adding ligaments to the ankle will not change the motion of the ankle in
anyway, this is inverse dynamics so the motion is always prescribed. Adding
the ligaments will of course help carry the load but that is another thing.

It should be possible to make the toe node follow the marker more or less,
but it can be difficult to control. One simple thing to check is if you are
using the local coordinate system on the toe marker as basis for you
kinematic measure?

So it should look like something like this

AnyKinEqSimpleDriver ToeMarker ={

AnyKinLinear lin ={

AnyRefNode &ref1=.Toemaker;

AnyFixedRefFrame &ref2=.GlobalRef;

Ref=0; //This will make this measure use the Toemarker coordinate system

for the measurements.

};

MeasureOrganizer={0}; //pick out the x direction I recall this to be
normal to the foot, please verify…

DriverPos={0};

DriverVel={0};

};

If you do not specify the Ref=0; line it will use the global coordinate
system and then the foot flexion can be difficult to control, I have seen
this on a early version of the gait model.

I do not understand what you mean by “manmade” all the dof in the Vaughan
model is driven by the marker data.

I hope this made things clearer, otherwise please write again.

Best regards

Søren, AnyBody Support

From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com] On Behalf
Of peter.worsley
Sent: 08 April 2008 15:37
To: anyscript@yahoogroups.com
Subject: [AnyScript] Control of ankle plantar flexion

Hi AnyBody group,

I have recently been collecting some gait data sets and inputting
them into a modified freeposture model for analysis. I am currently
having difficulty with getting the toe node on the mannequin to follow
the marker coordinates. This is obviously giving abnormal results for
plantar and dorsiflexion, as well as eversion and inversion. Looking
at the Vaughan model, there seems to be a fair amount of restriction
on the ankle movements and i’m not sure if its data controlled or ‘man
made’. Looking at the previous post from Mike, it seems adding deltoid
and lateral collateral ligaments maybe a good way to help control the
ankles movements.

I have also played with the idea of adding extra markers to the foot
(over the cubiod) to drive the movement in the model.

Has anyone else shared my experience with inability to control the
ankle, are there any suggestions to help?

many thanks

Peter

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

Users of the AnyBody Modeling System help each other create biomechanical models
in the AnyScript language.Yahoo! Groups Links

Yahoo! for Good helps you make a difference

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

4

Hi Peter,

You set MeasureOrganizer={2}; so this is Z direction. But to control
ankle plantar flexion must use the X direction that is normal to the
foot. Actually the rotation for ankle plantar flexion is around Z but
you are driving a linear measure of the toe so you need to pick the
normal axis to the foot: X axis. That mean to set MeasureOrganizer=
{0};.

The data of this model comes from the book by Vaughan et al: Dynamics
of Human Gait. These data sets are available from the ISB web
homepage, directly as text file I think. So we didn’t had to process
any c3d file.

The ligaments or muscles do not add any kinematic constraint to the
model. By using inverse dynamics we first define the motion (this is
done by the way of joints and drivers only) and then come the forces
in muscles and ligaments that are calculated by the software.

Best regards,
Sylvain, AnyBody Support.

— In anyscript@yahoogroups.com, Peter Worsley <peter.worsley@…>
wrote:
>
> Hi Soren,
>
> my driver for toe is as follows;
>
> AnyKinEqSimpleDriver MetatarsalYLDrv={
> AnyKinLinear lin={
> AnyRefFrame
&ref1=Main.Model.HumanModel.Left.Leg.Seg.Foot.LTOE;
> AnyRefFrame &ref2=Main.MarkerTopology.M14.FreeMarker;
> Ref=0;
> };
> MeasureOrganizer={2};
> DriverPos={0};
> Reaction.Type={Off};
> DriverVel={0};
> };
>
> All other markers are driving the model well appart from the foot.
(measure organiser is in the z coordinate for ankle plantar flexion
and dorsiflexion.) The Vaughan data looks very smooth and I could not
find a Pointsmarker file, has the data been processed before it was
modeled?
>
> By adding the ligaments I was hoping to add constriant for
enverison/inversion, are you saying this is not possible?
>
> many thanks
>
> Peter
>
> AnyBody Support <support@…> wrote: Hi Peter
>
>
>
> Adding ligaments to the ankle will not change the motion of the
ankle in
> anyway, this is inverse dynamics so the motion is always
prescribed. Adding
> the ligaments will of course help carry the load but that is
another thing.
>
>
>
> It should be possible to make the toe node follow the marker more
or less,
> but it can be difficult to control. One simple thing to check is if
you are
> using the local coordinate system on the toe marker as basis for you
> kinematic measure?
>
>
>
> So it should look like something like this
>
>
>
>
>
> AnyKinEqSimpleDriver ToeMarker ={
>
> AnyKinLinear lin ={
>
> AnyRefNode &ref1=.Toemaker;
>
> AnyFixedRefFrame &ref2=.GlobalRef;
>
> Ref=0; //This will make this measure use the Toemarker
coordinate system
> for the measurements.
>
> };
>
> MeasureOrganizer={0}; //pick out the x direction I recall this
to be
> normal to the foot, please verify…
>
> DriverPos={0};
>
> DriverVel={0};
>
> };
>
>
>
> If you do not specify the Ref=0; line it will use the global
coordinate
> system and then the foot flexion can be difficult to control, I
have seen
> this on a early version of the gait model.
>
>
>
> I do not understand what you mean by “manmade” all the dof in the
Vaughan
> model is driven by the marker data.
>
>
>
> I hope this made things clearer, otherwise please write again.
>
>
>
> Best regards
>
> Søren, AnyBody Support
>
>
>
>
>
> _____
>
> From: anyscript@yahoogroups.com [mailto:anyscript@yahoogroups.com]
On Behalf
> Of peter.worsley
> Sent: 08 April 2008 15:37
> To: anyscript@yahoogroups.com
> Subject: [AnyScript] Control of ankle plantar flexion
>
>
>
> Hi AnyBody group,
>
> I have recently been collecting some gait data sets and inputting
> them into a modified freeposture model for analysis. I am currently
> having difficulty with getting the toe node on the mannequin to
follow
> the marker coordinates. This is obviously giving abnormal results
for
> plantar and dorsiflexion, as well as eversion and inversion. Looking
> at the Vaughan model, there seems to be a fair amount of restriction
> on the ankle movements and i’m not sure if its data controlled
or ‘man
> made’. Looking at the previous post from Mike, it seems adding
deltoid
> and lateral collateral ligaments maybe a good way to help control
the
> ankles movements.
>
> I have also played with the idea of adding extra markers to the foot
> (over the cubiod) to drive the movement in the model.
>
> Has anyone else shared my experience with inability to control the
> ankle, are there any suggestions to help?
>
> many thanks
>
> Peter
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
> ------------------------------------
>
> Users of the AnyBody Modeling System help each other create
biomechanical models in the AnyScript language.Yahoo! Groups Links
>
>
>
>
>
>
> ---------------------------------
> Yahoo! for Good helps you make a difference
>
> [Non-text portions of this message have been removed]
>

5