# Two Questions.

Hello,

I have a Question:

For the WheelTurn example from the repository 5, I perform a
parametric sweep for x location and wheel angle (I created, this angle

I do a parametric sweep of x position from 0.15 to 025 (with increment
of 0.01), and a wheel angle sweep of 0-60 deg (with increment of 3
deg, the wheel angle is measured from the positive global y-axis).
While performing this sweep, I realized that at certain points, the
AnyBody gives me error saying that constraint is not satisfied–This
is okay, but the strange thing is that all neighbouring points are
fine. For example:

at x=0.21, deg = 3 --simulation fail.
But at:
x=0.21, deg =0;
x=0.21, deg =5;
x=0.22, deg =3;
x=0.20, deg =3;
[all are suurounding points of x=0.21, deg=3]

at all these points, the simulation works fine…I cannot figure out
what is the problem. And it happens at some other points too.

It seem for me that the simulation does not act like a “continuous
functions”–it failed at some point although points at surrounding
works fine.

Can anyone explain this?

Thanks,
Leng-Feng

Hello Leng-Feng,

The message you are geting usually means that the model has
insufficient boundary conditions. I am wondering whether this could
be connected to the variation of the angle about the z axis. Could
you describe how this angle variation implemented?

Thanks,
John

— In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@…>
wrote:
>
> Hello,
>
> I have a Question:
>
> For the WheelTurn example from the repository 5, I perform a
> parametric sweep for x location and wheel angle (I created, this
angle
>
> I do a parametric sweep of x position from 0.15 to 025 (with
increment
> of 0.01), and a wheel angle sweep of 0-60 deg (with increment of 3
> deg, the wheel angle is measured from the positive global y-axis).
> While performing this sweep, I realized that at certain points, the
> AnyBody gives me error saying that constraint is not satisfied–
This
> is okay, but the strange thing is that all neighbouring points are
> fine. For example:
>
> at x=0.21, deg = 3 --simulation fail.
> But at:
> x=0.21, deg =0;
> x=0.21, deg =5;
> x=0.22, deg =3;
> x=0.20, deg =3;
> [all are suurounding points of x=0.21, deg=3]
>
> at all these points, the simulation works fine…I cannot figure
out
> what is the problem. And it happens at some other points too.
>
> It seem for me that the simulation does not act like a “continuous
> functions”–it failed at some point although points at surrounding
> works fine.
>
> Can anyone explain this?
>
> Thanks,
> Leng-Feng
>

Hello Dr John,

The implementation of the axis is done by defining a AnyFixedFrame and
rotate it by a propriate angle (as shown in the
“RevoluteJointDefinition.any” file in the file section).

This is very strange that there are some “dead Point”–like
singularity points in which only at that point the simulation gives an
error but the point surronding it is fine (as described).

By the way, can you explain more about the Boundary Constraint idea a
little more detail? Why is it happen and why it causes the problem.

Thanks,
Leng-Feng

— In anyscript@yahoogroups.com, “AnyBody Support” <support@…> wrote:
>
> Hello Leng-Feng,
>
> The message you are geting usually means that the model has
> insufficient boundary conditions. I am wondering whether this could
> be connected to the variation of the angle about the z axis. Could
> you describe how this angle variation implemented?
>
> Thanks,
> John
>
> — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> wrote:
> >
> > Hello,
> >
> > I have a Question:
> >
> > For the WheelTurn example from the repository 5, I perform a
> > parametric sweep for x location and wheel angle (I created, this
> angle
> > rotate about the z-axis).
> >
> > I do a parametric sweep of x position from 0.15 to 025 (with
> increment
> > of 0.01), and a wheel angle sweep of 0-60 deg (with increment of 3
> > deg, the wheel angle is measured from the positive global y-axis).
> > While performing this sweep, I realized that at certain points, the
> > AnyBody gives me error saying that constraint is not satisfied–
> This
> > is okay, but the strange thing is that all neighbouring points are
> > fine. For example:
> >
> > at x=0.21, deg = 3 --simulation fail.
> > But at:
> > x=0.21, deg =0;
> > x=0.21, deg =5;
> > x=0.22, deg =3;
> > x=0.20, deg =3;
> > [all are suurounding points of x=0.21, deg=3]
> >
> > at all these points, the simulation works fine…I cannot figure
> out
> > what is the problem. And it happens at some other points too.
> >
> > It seem for me that the simulation does not act like a “continuous
> > functions”–it failed at some point although points at surrounding
> > works fine.
> >
> > Can anyone explain this?
> >
> > Thanks,
> > Leng-Feng
> >
>

Hi Leng-Feng,

It sounds like your method should be ok. What I was concerned about
was whether you had implemented a joint with insufficient support.

In general an AnyBody model needs connections to the surrroundings
that can provide enough reaction forces to balance the overall
model. Also the internal parts of the model must be balanced, which
normally is done by the muscles. If any support anywhere in the
model is insufficient, then the equilibrium equations will be
singular, and the problem has not solution.

You are welcome to zip your model and upload it to the group. The we
shall take a look at it.

Best regards,
John

## — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@…> wrote: > > Hello Dr John, > > The implementation of the axis is done by defining a AnyFixedFrame and > rotate it by a propriate angle (as shown in the > “RevoluteJointDefinition.any” file in the file section). > > This is very strange that there are some “dead Point”–like > singularity points in which only at that point the simulation gives an > error but the point surronding it is fine (as described). > > By the way, can you explain more about the Boundary Constraint idea a > little more detail? Why is it happen and why it causes the problem. > > Thanks, > Leng-Feng > > > — In anyscript@yahoogroups.com, “AnyBody Support” <support@> wrote: > > > > Hello Leng-Feng, > > > > The message you are geting usually means that the model has > > insufficient boundary conditions. I am wondering whether this could > > be connected to the variation of the angle about the z axis. Could > > you describe how this angle variation implemented? > > > > Thanks, > > John > > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@> > > wrote: > > > > > > Hello, > > > > > > I have a Question: > > > > > > For the WheelTurn example from the repository 5, I perform a > > > parametric sweep for x location and wheel angle (I created, this > > angle > > > rotate about the z-axis). > > > > > > I do a parametric sweep of x position from 0.15 to 025 (with > > increment > > > of 0.01), and a wheel angle sweep of 0-60 deg (with increment of 3 > > > deg, the wheel angle is measured from the positive global y- axis). > > > While performing this sweep, I realized that at certain points, the > > > AnyBody gives me error saying that constraint is not satisfied-

> > This
> > > is okay, but the strange thing is that all neighbouring points
are
> > > fine. For example:
> > >
> > > at x=0.21, deg = 3 --simulation fail.
> > > But at:
> > > x=0.21, deg =0;
> > > x=0.21, deg =5;
> > > x=0.22, deg =3;
> > > x=0.20, deg =3;
> > > [all are suurounding points of x=0.21, deg=3]
> > >
> > > at all these points, the simulation works fine…I cannot
figure
> > out
> > > what is the problem. And it happens at some other points too.
> > >
> > > It seem for me that the simulation does not act like
a “continuous
> > > functions”–it failed at some point although points at
surrounding
> > > works fine.
> > >
> > > Can anyone explain this?
> > >
> > > Thanks,
> > > Leng-Feng
> > >
> >
>

Hello Dr John,

Thanks. I uploaded my file in the file section–called
"WheelTurn_Lee.rar ".

The location where I change the x position and the tile angle, I made
a comment. The file where these two parameters located are:

x position - in WheelTurn.Main.any
tile angle - in Environment.any

Thanks for your time and assistance.

Thanks,
Leng-Feng

— In anyscript@yahoogroups.com, “AnyBody Support” <support@…> wrote:
>
> Hi Leng-Feng,
>
> It sounds like your method should be ok. What I was concerned about
> was whether you had implemented a joint with insufficient support.
>
> In general an AnyBody model needs connections to the surrroundings
> that can provide enough reaction forces to balance the overall
> model. Also the internal parts of the model must be balanced, which
> normally is done by the muscles. If any support anywhere in the
> model is insufficient, then the equilibrium equations will be
> singular, and the problem has not solution.
>
> You are welcome to zip your model and upload it to the group. The we
> shall take a look at it.
>
> Best regards,
> John
>
> — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> wrote:
> >
> > Hello Dr John,
> >
> > The implementation of the axis is done by defining a AnyFixedFrame
> and
> > rotate it by a propriate angle (as shown in the
> > “RevoluteJointDefinition.any” file in the file section).
> >
> > This is very strange that there are some “dead Point”–like
> > singularity points in which only at that point the simulation
> gives an
> > error but the point surronding it is fine (as described).
> >
> > By the way, can you explain more about the Boundary Constraint
> idea a
> > little more detail? Why is it happen and why it causes the problem.
> >
> > Thanks,
> > Leng-Feng
> >
> >
> > — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
> wrote:
> > >
> > > Hello Leng-Feng,
> > >
> > > The message you are geting usually means that the model has
> > > insufficient boundary conditions. I am wondering whether this
> could
> > > be connected to the variation of the angle about the z axis.
> Could
> > > you describe how this angle variation implemented?
> > >
> > > Thanks,
> > > John
> > >
> > > — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> > > wrote:
> > > >
> > > > Hello,
> > > >
> > > > I have a Question:
> > > >
> > > > For the WheelTurn example from the repository 5, I perform a
> > > > parametric sweep for x location and wheel angle (I created,
> this
> > > angle
> > > > rotate about the z-axis).
> > > >
> > > > I do a parametric sweep of x position from 0.15 to 025 (with
> > > increment
> > > > of 0.01), and a wheel angle sweep of 0-60 deg (with increment
> of 3
> > > > deg, the wheel angle is measured from the positive global y-
> axis).
> > > > While performing this sweep, I realized that at certain
> points, the
> > > > AnyBody gives me error saying that constraint is not satisfied-
> -
> > > This
> > > > is okay, but the strange thing is that all neighbouring points
> are
> > > > fine. For example:
> > > >
> > > > at x=0.21, deg = 3 --simulation fail.
> > > > But at:
> > > > x=0.21, deg =0;
> > > > x=0.21, deg =5;
> > > > x=0.22, deg =3;
> > > > x=0.20, deg =3;
> > > > [all are suurounding points of x=0.21, deg=3]
> > > >
> > > > at all these points, the simulation works fine…I cannot
> figure
> > > out
> > > > what is the problem. And it happens at some other points too.
> > > >
> > > > It seem for me that the simulation does not act like
> a “continuous
> > > > functions”–it failed at some point although points at
> surrounding
> > > > works fine.
> > > >
> > > > Can anyone explain this?
> > > >
> > > > Thanks,
> > > > Leng-Feng
> > > >
> > >
> >
>

Hi Leng-Feng

I have tried your model and have some suggestions.

When i first loaded the model WheelTurn_Lee\WheelTurn_Main.any

The wheel hub where set to this location

AnyVec3 Hub = {2.2, -0.05, 0.30};

since the Throax is attached at {0,0,0} it will not assemble
kinemtatically there is no way it will be able to reach.

x=0.21, deg =0;
x=0.21, deg =5;
x=0.22, deg =3;
x=0.20, deg =3;

I am in doubt what is the x value so i assume it is the x component
of the Wheelhub.sRel. I tried to run the inverse analysis and you
are right if fails to balance the system, for x=0.21 and tilt =3 deg.

My theory is the following: the model is supported at the thorax
which is connected rigidly to the ground. This means that the
muscles in the spine do not have to carry almost any load. This
should not be a problem, but if you have large muscles groups in
this case the spine with very low activation it can make the problem
difficult to solve numerically, because it makes the problem ill-
conditioned.

To avoid this i have made some changes in the JointAndDrivers.any
file. These changes removes the support of the thorax and adds them
to the pelvis instead. These changes resolves the problems for
x=0.21 and tilt =3 deg, i have not tested it for other
configurations.

I have uploaded the file WheelTurn_Lee_JointAndDrivers.any

I hope this solves the problems, otherwise please write again.

Best regards
SÃ¸ren, AnyBody Support

— In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@…>
wrote:
>
> Hello Dr John,
>
> Thanks. I uploaded my file in the file section–called
> "WheelTurn_Lee.rar ".
>
> The location where I change the x position and the tile angle, I
> a comment. The file where these two parameters located are:
>
> x position - in WheelTurn.Main.any
> tile angle - in Environment.any
>
> Thanks for your time and assistance.
>
> Thanks,
> Leng-Feng
>
> — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
wrote:
> >
> > Hi Leng-Feng,
> >
> > It sounds like your method should be ok. What I was concerned
> > was whether you had implemented a joint with insufficient
support.
> >
> > In general an AnyBody model needs connections to the
surrroundings
> > that can provide enough reaction forces to balance the overall
> > model. Also the internal parts of the model must be balanced,
which
> > normally is done by the muscles. If any support anywhere in the
> > model is insufficient, then the equilibrium equations will be
> > singular, and the problem has not solution.
> >
> > You are welcome to zip your model and upload it to the group.
The we
> > shall take a look at it.
> >
> > Best regards,
> > John
> >
> > — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> > wrote:
> > >
> > > Hello Dr John,
> > >
> > > The implementation of the axis is done by defining a
AnyFixedFrame
> > and
> > > rotate it by a propriate angle (as shown in the
> > > “RevoluteJointDefinition.any” file in the file section).
> > >
> > > This is very strange that there are some “dead Point”–like
> > > singularity points in which only at that point the simulation
> > gives an
> > > error but the point surronding it is fine (as described).
> > >
> > > By the way, can you explain more about the Boundary Constraint
> > idea a
> > > little more detail? Why is it happen and why it causes the
problem.
> > >
> > > Thanks,
> > > Leng-Feng
> > >
> > >
> > > — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
> > wrote:
> > > >
> > > > Hello Leng-Feng,
> > > >
> > > > The message you are geting usually means that the model has
> > > > insufficient boundary conditions. I am wondering whether
this
> > could
> > > > be connected to the variation of the angle about the z axis.
> > Could
> > > > you describe how this angle variation implemented?
> > > >
> > > > Thanks,
> > > > John
> > > >
> > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee”
<lengfenglee@>
> > > > wrote:
> > > > >
> > > > > Hello,
> > > > >
> > > > > I have a Question:
> > > > >
> > > > > For the WheelTurn example from the repository 5, I perform
a
> > > > > parametric sweep for x location and wheel angle (I
created,
> > this
> > > > angle
> > > > > rotate about the z-axis).
> > > > >
> > > > > I do a parametric sweep of x position from 0.15 to 025
(with
> > > > increment
> > > > > of 0.01), and a wheel angle sweep of 0-60 deg (with
increment
> > of 3
> > > > > deg, the wheel angle is measured from the positive global
y-
> > axis).
> > > > > While performing this sweep, I realized that at certain
> > points, the
> > > > > AnyBody gives me error saying that constraint is not
satisfied-
> > -
> > > > This
> > > > > is okay, but the strange thing is that all neighbouring
points
> > are
> > > > > fine. For example:
> > > > >
> > > > > at x=0.21, deg = 3 --simulation fail.
> > > > > But at:
> > > > > x=0.21, deg =0;
> > > > > x=0.21, deg =5;
> > > > > x=0.22, deg =3;
> > > > > x=0.20, deg =3;
> > > > > [all are suurounding points of x=0.21, deg=3]
> > > > >
> > > > > at all these points, the simulation works fine…I cannot
> > figure
> > > > out
> > > > > what is the problem. And it happens at some other points
too.
> > > > >
> > > > > It seem for me that the simulation does not act like
> > a “continuous
> > > > > functions”–it failed at some point although points at
> > surrounding
> > > > > works fine.
> > > > >
> > > > > Can anyone explain this?
> > > > >
> > > > > Thanks,
> > > > > Leng-Feng
> > > > >
> > > >
> > >
> >
>

Hello SÃ¸ren,

You are right, the x position is the hub’s x position.

Thanks, currently I am trying the modified code for all other points,
and will let you know how it work out.

The thing I don’t quite understand is that, for example, if we have
place the wheel in a space infront of the human (let say, a square in
the x-z plane, and in this square, the wheel is within the ‘reachable’
region of the hand), isn’t that the simulation ‘should’ works in ALL
points in that region?

The strange thing is it work on the ‘side’(limits) of the square but
some points inside that region the simulation failed… speaking in
another way: the simulation works when x=0.1 and x=0.3, thus it
‘should’ works in all other points between 0.1 and 0.3.

This is the part that I still don’t get it why. It act if there are
some ‘singularity point’.

Can you point out to me where I missed? Also, do you have the
documentation on the WheelTurn example (for repository 5)–or any
report (I see in the presentation file that this model is used for
shoulder verification)?

Thanks for your (and other people in this support group) timely response.

Thanks,
Leng-Feng

— In anyscript@yahoogroups.com, “AnyBody Support” <support@…> wrote:
>
> Hi Leng-Feng
>
> I have tried your model and have some suggestions.
>
> When i first loaded the model WheelTurn_Lee\WheelTurn_Main.any
>
> The wheel hub where set to this location
>
> AnyVec3 Hub = {2.2, -0.05, 0.30};
>
> since the Throax is attached at {0,0,0} it will not assemble
> kinemtatically there is no way it will be able to reach.
>
> You write about the parameters
> x=0.21, deg =0;
> x=0.21, deg =5;
> x=0.22, deg =3;
> x=0.20, deg =3;
>
> I am in doubt what is the x value so i assume it is the x component
> of the Wheelhub.sRel. I tried to run the inverse analysis and you
> are right if fails to balance the system, for x=0.21 and tilt =3 deg.
>
> My theory is the following: the model is supported at the thorax
> which is connected rigidly to the ground. This means that the
> muscles in the spine do not have to carry almost any load. This
> should not be a problem, but if you have large muscles groups in
> this case the spine with very low activation it can make the problem
> difficult to solve numerically, because it makes the problem ill-
> conditioned.
>
> To avoid this i have made some changes in the JointAndDrivers.any
> file. These changes removes the support of the thorax and adds them
> to the pelvis instead. These changes resolves the problems for
> x=0.21 and tilt =3 deg, i have not tested it for other
> configurations.
>
> I have uploaded the file WheelTurn_Lee_JointAndDrivers.any
>
> I hope this solves the problems, otherwise please write again.
>
> Best regards
> SÃ¸ren, AnyBody Support
>
>
>
> — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> wrote:
> >
> > Hello Dr John,
> >
> > Thanks. I uploaded my file in the file section–called
> > "WheelTurn_Lee.rar ".
> >
> > The location where I change the x position and the tile angle, I
> > a comment. The file where these two parameters located are:
> >
> > x position - in WheelTurn.Main.any
> > tile angle - in Environment.any
> >
> > Thanks for your time and assistance.
> >
> > Thanks,
> > Leng-Feng
> >
> > — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
> wrote:
> > >
> > > Hi Leng-Feng,
> > >
> > > It sounds like your method should be ok. What I was concerned
> > > was whether you had implemented a joint with insufficient
> support.
> > >
> > > In general an AnyBody model needs connections to the
> surrroundings
> > > that can provide enough reaction forces to balance the overall
> > > model. Also the internal parts of the model must be balanced,
> which
> > > normally is done by the muscles. If any support anywhere in the
> > > model is insufficient, then the equilibrium equations will be
> > > singular, and the problem has not solution.
> > >
> > > You are welcome to zip your model and upload it to the group.
> The we
> > > shall take a look at it.
> > >
> > > Best regards,
> > > John
> > >
> > > — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> > > wrote:
> > > >
> > > > Hello Dr John,
> > > >
> > > > The implementation of the axis is done by defining a
> AnyFixedFrame
> > > and
> > > > rotate it by a propriate angle (as shown in the
> > > > “RevoluteJointDefinition.any” file in the file section).
> > > >
> > > > This is very strange that there are some “dead Point”–like
> > > > singularity points in which only at that point the simulation
> > > gives an
> > > > error but the point surronding it is fine (as described).
> > > >
> > > > By the way, can you explain more about the Boundary Constraint
> > > idea a
> > > > little more detail? Why is it happen and why it causes the
> problem.
> > > >
> > > > Thanks,
> > > > Leng-Feng
> > > >
> > > >
> > > > — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
> > > wrote:
> > > > >
> > > > > Hello Leng-Feng,
> > > > >
> > > > > The message you are geting usually means that the model has
> > > > > insufficient boundary conditions. I am wondering whether
> this
> > > could
> > > > > be connected to the variation of the angle about the z axis.
> > > Could
> > > > > you describe how this angle variation implemented?
> > > > >
> > > > > Thanks,
> > > > > John
> > > > >
> > > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee”
> <lengfenglee@>
> > > > > wrote:
> > > > > >
> > > > > > Hello,
> > > > > >
> > > > > > I have a Question:
> > > > > >
> > > > > > For the WheelTurn example from the repository 5, I perform
> a
> > > > > > parametric sweep for x location and wheel angle (I
> created,
> > > this
> > > > > angle
> > > > > > rotate about the z-axis).
> > > > > >
> > > > > > I do a parametric sweep of x position from 0.15 to 025
> (with
> > > > > increment
> > > > > > of 0.01), and a wheel angle sweep of 0-60 deg (with
> increment
> > > of 3
> > > > > > deg, the wheel angle is measured from the positive global
> y-
> > > axis).
> > > > > > While performing this sweep, I realized that at certain
> > > points, the
> > > > > > AnyBody gives me error saying that constraint is not
> satisfied-
> > > -
> > > > > This
> > > > > > is okay, but the strange thing is that all neighbouring
> points
> > > are
> > > > > > fine. For example:
> > > > > >
> > > > > > at x=0.21, deg = 3 --simulation fail.
> > > > > > But at:
> > > > > > x=0.21, deg =0;
> > > > > > x=0.21, deg =5;
> > > > > > x=0.22, deg =3;
> > > > > > x=0.20, deg =3;
> > > > > > [all are suurounding points of x=0.21, deg=3]
> > > > > >
> > > > > > at all these points, the simulation works fine…I cannot
> > > figure
> > > > > out
> > > > > > what is the problem. And it happens at some other points
> too.
> > > > > >
> > > > > > It seem for me that the simulation does not act like
> > > a “continuous
> > > > > > functions”–it failed at some point although points at
> > > surrounding
> > > > > > works fine.
> > > > > >
> > > > > > Can anyone explain this?
> > > > > >
> > > > > > Thanks,
> > > > > > Leng-Feng
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hello SÃ¸ren,

> > My theory is the following: the model is supported at the thorax
> > which is connected rigidly to the ground. This means that the
> > muscles in the spine do not have to carry almost any load. This
> > should not be a problem, but if you have large muscles groups in
> > this case the spine with very low activation it can make the problem
> > difficult to solve numerically, because it makes the problem ill-
> > conditioned.

The changes you made to the model… I wonder, will this causes the
inacuracy in the modeling of the human repository? I guess the answer
is probably not, but why not?

Thanks,
Leng-Feng

— In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@…> wrote:
>
> Hello SÃ¸ren,
>
> You are right, the x position is the hub’s x position.
>
> Thanks, currently I am trying the modified code for all other points,
> and will let you know how it work out.
>
> The thing I don’t quite understand is that, for example, if we have
> place the wheel in a space infront of the human (let say, a square in
> the x-z plane, and in this square, the wheel is within the ‘reachable’
> region of the hand), isn’t that the simulation ‘should’ works in ALL
> points in that region?
>
> The strange thing is it work on the ‘side’(limits) of the square but
> some points inside that region the simulation failed… speaking in
> another way: the simulation works when x=0.1 and x=0.3, thus it
> ‘should’ works in all other points between 0.1 and 0.3.
>
> This is the part that I still don’t get it why. It act if there are
> some ‘singularity point’.
>
> Can you point out to me where I missed? Also, do you have the
> documentation on the WheelTurn example (for repository 5)–or any
> report (I see in the presentation file that this model is used for
> shoulder verification)?
>
> Thanks for your (and other people in this support group) timely
response.
>
> Thanks,
> Leng-Feng
>
>
>
> — In anyscript@yahoogroups.com, “AnyBody Support” <support@> wrote:
> >
> > Hi Leng-Feng
> >
> > I have tried your model and have some suggestions.
> >
> > When i first loaded the model WheelTurn_Lee\WheelTurn_Main.any
> >
> > The wheel hub where set to this location
> >
> > AnyVec3 Hub = {2.2, -0.05, 0.30};
> >
> > since the Throax is attached at {0,0,0} it will not assemble
> > kinemtatically there is no way it will be able to reach.
> >
> > You write about the parameters
> > x=0.21, deg =0;
> > x=0.21, deg =5;
> > x=0.22, deg =3;
> > x=0.20, deg =3;
> >
> > I am in doubt what is the x value so i assume it is the x component
> > of the Wheelhub.sRel. I tried to run the inverse analysis and you
> > are right if fails to balance the system, for x=0.21 and tilt =3 deg.
> >
> > My theory is the following: the model is supported at the thorax
> > which is connected rigidly to the ground. This means that the
> > muscles in the spine do not have to carry almost any load. This
> > should not be a problem, but if you have large muscles groups in
> > this case the spine with very low activation it can make the problem
> > difficult to solve numerically, because it makes the problem ill-
> > conditioned.
> >
> > To avoid this i have made some changes in the JointAndDrivers.any
> > file. These changes removes the support of the thorax and adds them
> > to the pelvis instead. These changes resolves the problems for
> > x=0.21 and tilt =3 deg, i have not tested it for other
> > configurations.
> >
> > I have uploaded the file WheelTurn_Lee_JointAndDrivers.any
> >
> > I hope this solves the problems, otherwise please write again.
> >
> > Best regards
> > SÃ¸ren, AnyBody Support
> >
> >
> >
> > — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> > wrote:
> > >
> > > Hello Dr John,
> > >
> > > Thanks. I uploaded my file in the file section–called
> > > "WheelTurn_Lee.rar ".
> > >
> > > The location where I change the x position and the tile angle, I
> > > a comment. The file where these two parameters located are:
> > >
> > > x position - in WheelTurn.Main.any
> > > tile angle - in Environment.any
> > >
> > > Thanks for your time and assistance.
> > >
> > > Thanks,
> > > Leng-Feng
> > >
> > > — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
> > wrote:
> > > >
> > > > Hi Leng-Feng,
> > > >
> > > > It sounds like your method should be ok. What I was concerned
> > > > was whether you had implemented a joint with insufficient
> > support.
> > > >
> > > > In general an AnyBody model needs connections to the
> > surrroundings
> > > > that can provide enough reaction forces to balance the overall
> > > > model. Also the internal parts of the model must be balanced,
> > which
> > > > normally is done by the muscles. If any support anywhere in the
> > > > model is insufficient, then the equilibrium equations will be
> > > > singular, and the problem has not solution.
> > > >
> > > > You are welcome to zip your model and upload it to the group.
> > The we
> > > > shall take a look at it.
> > > >
> > > > Best regards,
> > > > John
> > > >
> > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> > > > wrote:
> > > > >
> > > > > Hello Dr John,
> > > > >
> > > > > The implementation of the axis is done by defining a
> > AnyFixedFrame
> > > > and
> > > > > rotate it by a propriate angle (as shown in the
> > > > > “RevoluteJointDefinition.any” file in the file section).
> > > > >
> > > > > This is very strange that there are some “dead Point”–like
> > > > > singularity points in which only at that point the simulation
> > > > gives an
> > > > > error but the point surronding it is fine (as described).
> > > > >
> > > > > By the way, can you explain more about the Boundary Constraint
> > > > idea a
> > > > > little more detail? Why is it happen and why it causes the
> > problem.
> > > > >
> > > > > Thanks,
> > > > > Leng-Feng
> > > > >
> > > > >
> > > > > — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
> > > > wrote:
> > > > > >
> > > > > > Hello Leng-Feng,
> > > > > >
> > > > > > The message you are geting usually means that the model has
> > > > > > insufficient boundary conditions. I am wondering whether
> > this
> > > > could
> > > > > > be connected to the variation of the angle about the z axis.
> > > > Could
> > > > > > you describe how this angle variation implemented?
> > > > > >
> > > > > > Thanks,
> > > > > > John
> > > > > >
> > > > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee”
> > <lengfenglee@>
> > > > > > wrote:
> > > > > > >
> > > > > > > Hello,
> > > > > > >
> > > > > > > I have a Question:
> > > > > > >
> > > > > > > For the WheelTurn example from the repository 5, I perform
> > a
> > > > > > > parametric sweep for x location and wheel angle (I
> > created,
> > > > this
> > > > > > angle
> > > > > > > rotate about the z-axis).
> > > > > > >
> > > > > > > I do a parametric sweep of x position from 0.15 to 025
> > (with
> > > > > > increment
> > > > > > > of 0.01), and a wheel angle sweep of 0-60 deg (with
> > increment
> > > > of 3
> > > > > > > deg, the wheel angle is measured from the positive global
> > y-
> > > > axis).
> > > > > > > While performing this sweep, I realized that at certain
> > > > points, the
> > > > > > > AnyBody gives me error saying that constraint is not
> > satisfied-
> > > > -
> > > > > > This
> > > > > > > is okay, but the strange thing is that all neighbouring
> > points
> > > > are
> > > > > > > fine. For example:
> > > > > > >
> > > > > > > at x=0.21, deg = 3 --simulation fail.
> > > > > > > But at:
> > > > > > > x=0.21, deg =0;
> > > > > > > x=0.21, deg =5;
> > > > > > > x=0.22, deg =3;
> > > > > > > x=0.20, deg =3;
> > > > > > > [all are suurounding points of x=0.21, deg=3]
> > > > > > >
> > > > > > > at all these points, the simulation works fine…I cannot
> > > > figure
> > > > > > out
> > > > > > > what is the problem. And it happens at some other points
> > too.
> > > > > > >
> > > > > > > It seem for me that the simulation does not act like
> > > > a “continuous
> > > > > > > functions”–it failed at some point although points at
> > > > surrounding
> > > > > > > works fine.
> > > > > > >
> > > > > > > Can anyone explain this?
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Leng-Feng
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hello SÃ¸ren,

The simulation now failed at x=0.19 & angle=6 deg. How to resolve this?

Thanks,
Leng-Feng

— In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@…> wrote:
>
> Hello SÃ¸ren,
>
> you actually explained here…my bad.
>
> > > My theory is the following: the model is supported at the thorax
> > > which is connected rigidly to the ground. This means that the
> > > muscles in the spine do not have to carry almost any load. This
> > > should not be a problem, but if you have large muscles groups in
> > > this case the spine with very low activation it can make the
problem
> > > difficult to solve numerically, because it makes the problem ill-
> > > conditioned.
>
> The changes you made to the model… I wonder, will this causes the
> inacuracy in the modeling of the human repository? I guess the answer
> is probably not, but why not?
>
>
> Thanks,
> Leng-Feng
>
>
>
>
> — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@> wrote:
> >
> > Hello SÃ¸ren,
> >
> > You are right, the x position is the hub’s x position.
> >
> > Thanks, currently I am trying the modified code for all other points,
> > and will let you know how it work out.
> >
> > The thing I don’t quite understand is that, for example, if we have
> > place the wheel in a space infront of the human (let say, a square in
> > the x-z plane, and in this square, the wheel is within the ‘reachable’
> > region of the hand), isn’t that the simulation ‘should’ works in ALL
> > points in that region?
> >
> > The strange thing is it work on the ‘side’(limits) of the square but
> > some points inside that region the simulation failed… speaking in
> > another way: the simulation works when x=0.1 and x=0.3, thus it
> > ‘should’ works in all other points between 0.1 and 0.3.
> >
> > This is the part that I still don’t get it why. It act if there are
> > some ‘singularity point’.
> >
> > Can you point out to me where I missed? Also, do you have the
> > documentation on the WheelTurn example (for repository 5)–or any
> > report (I see in the presentation file that this model is used for
> > shoulder verification)?
> >
> > Thanks for your (and other people in this support group) timely
> response.
> >
> > Thanks,
> > Leng-Feng
> >
> >
> >
> > — In anyscript@yahoogroups.com, “AnyBody Support” <support@> wrote:
> > >
> > > Hi Leng-Feng
> > >
> > > I have tried your model and have some suggestions.
> > >
> > > When i first loaded the model WheelTurn_Lee\WheelTurn_Main.any
> > >
> > > The wheel hub where set to this location
> > >
> > > AnyVec3 Hub = {2.2, -0.05, 0.30};
> > >
> > > since the Throax is attached at {0,0,0} it will not assemble
> > > kinemtatically there is no way it will be able to reach.
> > >
> > > You write about the parameters
> > > x=0.21, deg =0;
> > > x=0.21, deg =5;
> > > x=0.22, deg =3;
> > > x=0.20, deg =3;
> > >
> > > I am in doubt what is the x value so i assume it is the x component
> > > of the Wheelhub.sRel. I tried to run the inverse analysis and you
> > > are right if fails to balance the system, for x=0.21 and tilt =3
deg.
> > >
> > > My theory is the following: the model is supported at the thorax
> > > which is connected rigidly to the ground. This means that the
> > > muscles in the spine do not have to carry almost any load. This
> > > should not be a problem, but if you have large muscles groups in
> > > this case the spine with very low activation it can make the
problem
> > > difficult to solve numerically, because it makes the problem ill-
> > > conditioned.
> > >
> > > To avoid this i have made some changes in the JointAndDrivers.any
> > > file. These changes removes the support of the thorax and adds them
> > > to the pelvis instead. These changes resolves the problems for
> > > x=0.21 and tilt =3 deg, i have not tested it for other
> > > configurations.
> > >
> > > I have uploaded the file WheelTurn_Lee_JointAndDrivers.any
> > >
> > > I hope this solves the problems, otherwise please write again.
> > >
> > > Best regards
> > > SÃ¸ren, AnyBody Support
> > >
> > >
> > >
> > > — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
> > > wrote:
> > > >
> > > > Hello Dr John,
> > > >
> > > > Thanks. I uploaded my file in the file section–called
> > > > "WheelTurn_Lee.rar ".
> > > >
> > > > The location where I change the x position and the tile angle, I
> > > > a comment. The file where these two parameters located are:
> > > >
> > > > x position - in WheelTurn.Main.any
> > > > tile angle - in Environment.any
> > > >
> > > > Thanks for your time and assistance.
> > > >
> > > > Thanks,
> > > > Leng-Feng
> > > >
> > > > — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
> > > wrote:
> > > > >
> > > > > Hi Leng-Feng,
> > > > >
> > > > > It sounds like your method should be ok. What I was concerned
> > > > > was whether you had implemented a joint with insufficient
> > > support.
> > > > >
> > > > > In general an AnyBody model needs connections to the
> > > surrroundings
> > > > > that can provide enough reaction forces to balance the overall
> > > > > model. Also the internal parts of the model must be balanced,
> > > which
> > > > > normally is done by the muscles. If any support anywhere in the
> > > > > model is insufficient, then the equilibrium equations will be
> > > > > singular, and the problem has not solution.
> > > > >
> > > > > You are welcome to zip your model and upload it to the group.
> > > The we
> > > > > shall take a look at it.
> > > > >
> > > > > Best regards,
> > > > > John
> > > > >
> > > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee”
<lengfenglee@>
> > > > > wrote:
> > > > > >
> > > > > > Hello Dr John,
> > > > > >
> > > > > > The implementation of the axis is done by defining a
> > > AnyFixedFrame
> > > > > and
> > > > > > rotate it by a propriate angle (as shown in the
> > > > > > “RevoluteJointDefinition.any” file in the file section).
> > > > > >
> > > > > > This is very strange that there are some “dead Point”–like
> > > > > > singularity points in which only at that point the simulation
> > > > > gives an
> > > > > > error but the point surronding it is fine (as described).
> > > > > >
> > > > > > By the way, can you explain more about the Boundary
Constraint
> > > > > idea a
> > > > > > little more detail? Why is it happen and why it causes the
> > > problem.
> > > > > >
> > > > > > Thanks,
> > > > > > Leng-Feng
> > > > > >
> > > > > >
> > > > > > — In anyscript@yahoogroups.com, “AnyBody Support”
<support@>
> > > > > wrote:
> > > > > > >
> > > > > > > Hello Leng-Feng,
> > > > > > >
> > > > > > > The message you are geting usually means that the model has
> > > > > > > insufficient boundary conditions. I am wondering whether
> > > this
> > > > > could
> > > > > > > be connected to the variation of the angle about the z
axis.
> > > > > Could
> > > > > > > you describe how this angle variation implemented?
> > > > > > >
> > > > > > > Thanks,
> > > > > > > John
> > > > > > >
> > > > > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee”
> > > <lengfenglee@>
> > > > > > > wrote:
> > > > > > > >
> > > > > > > > Hello,
> > > > > > > >
> > > > > > > > I have a Question:
> > > > > > > >
> > > > > > > > For the WheelTurn example from the repository 5, I
perform
> > > a
> > > > > > > > parametric sweep for x location and wheel angle (I
> > > created,
> > > > > this
> > > > > > > angle
> > > > > > > > rotate about the z-axis).
> > > > > > > >
> > > > > > > > I do a parametric sweep of x position from 0.15 to 025
> > > (with
> > > > > > > increment
> > > > > > > > of 0.01), and a wheel angle sweep of 0-60 deg (with
> > > increment
> > > > > of 3
> > > > > > > > deg, the wheel angle is measured from the positive global
> > > y-
> > > > > axis).
> > > > > > > > While performing this sweep, I realized that at certain
> > > > > points, the
> > > > > > > > AnyBody gives me error saying that constraint is not
> > > satisfied-
> > > > > -
> > > > > > > This
> > > > > > > > is okay, but the strange thing is that all neighbouring
> > > points
> > > > > are
> > > > > > > > fine. For example:
> > > > > > > >
> > > > > > > > at x=0.21, deg = 3 --simulation fail.
> > > > > > > > But at:
> > > > > > > > x=0.21, deg =0;
> > > > > > > > x=0.21, deg =5;
> > > > > > > > x=0.22, deg =3;
> > > > > > > > x=0.20, deg =3;
> > > > > > > > [all are suurounding points of x=0.21, deg=3]
> > > > > > > >
> > > > > > > > at all these points, the simulation works fine…I
cannot
> > > > > figure
> > > > > > > out
> > > > > > > > what is the problem. And it happens at some other points
> > > too.
> > > > > > > >
> > > > > > > > It seem for me that the simulation does not act like
> > > > > a “continuous
> > > > > > > > functions”–it failed at some point although points at
> > > > > surrounding
> > > > > > > > works fine.
> > > > > > > >
> > > > > > > > Can anyone explain this?
> > > > > > > >
> > > > > > > > Thanks,
> > > > > > > > Leng-Feng
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

Hi Leng-Feng

We have investigated the matter a bit further and it seems you have
helped us discover a bug in the system, which will lead to
recruitment errors in rare cases. Thanks!

It seems there is a bug in the RotVector rotational measure which
can be triggered at 0,90,180,270 and 360 if at the same time there
is applied a moment to the measure like in this case, where it fails
at zero deg. In the environment.any file you use a revolute joint
for the hub and there is a moment applied to the hub. In the system
the revolute joint is made using a RotVector as the rotational
measure.

A temporary fix of your model is to replace the Revolute joint with
a joint made from an AnyKinLinear and an AnyKinRotational measure
which are using a RotAxesAngle measure as the type:

file

// Join the wheels to the chair (ground, actually)

AnyRevoluteJoint Hub = {

`````` AnyRefNode &Ground = .WheelRef.Hub;

AnySeg &Wheel = .Wheel;

Axis = y;
``````

};

AnyKinRotational Rot={

``````   AnyRefNode &Ground = .WheelRef.Hub;

AnySeg &Wheel = .Wheel;

Type=RotAxesAngles;

Axis1=y;

Axis2=z;

Axis3=x;

};
``````

// Drive the wheels. This in turn determines the hand movement

AnyKinEqSimpleDriver WheelDr = {

`````` AnyRevoluteJoint &Joint = .Hub;

DriverPos = {0};

DriverVel = {Main.WheelParameters.Omega*pi/180};

Reaction.Type = {0}; // Let applied moment through
``````

};

// Moment affecting the wheels and caried by the muscles

AnyForce Moment = {

`````` AnyRevoluteJoint &Joint = .Hub;

F = {Main.WheelParameters.M};
``````

};

With these ones:

AnyKinEqSimpleDriver ReplicaRevolute={

`````` AnyKinLinear Lin={

AnyRefNode &Ground = ..WheelRef.Hub;

AnySeg &Wheel = ..Wheel;

};

AnyKinRotational Rot={

AnyRefNode &Ground = ..WheelRef.Hub;

AnySeg &Wheel = ..Wheel;

Type=RotAxesAngles;

Axis1=y;

Axis2=z;

Axis3=x;

};

DriverPos={0,0,0,0,0,0};

DriverVel={0,0,0,Main.WheelParameters.Omega*pi/180,0,0};

Reaction.Type={1,1,1,0,1,1};
``````

};

AnyKinMeasureOrg ReplicaRevoluteFree={

`````` AnyKinEqSimpleDriver &ref=.ReplicaRevolute;

MeasureOrganizer={3};
``````

};

AnyForce Moment = {

`````` AnyKinMeasureOrg &Hub = .ReplicaRevoluteFree;
``````

F = {Main.WheelParameters.M};

};

The model should behave in the exact same way, but will be much more
stable at the specified angles mentioned above, i hope.

We are sorry for the inconvenience this have caused you and would
like to thank you again for your help in solving this issue.

Our R&D department are working on resolving the matter 100% and on
removing the bug from the system permanently. Hopefully this will be
done soon, and hopefully this temporary fix will solve your current
problems.

Best regards

SÃ¸ren, AnyBody Support

— In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@…>
wrote:
>
> Hello SÃ¸ren,
>
> The simulation now failed at x=0.19 & angle=6 deg. How to resolve
this?
>
>
>
> Thanks,
> Leng-Feng
>
>
> — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
wrote:
> >
> > Hello SÃ¸ren,
> >
> > you actually explained here…my bad.
> >
> > > > My theory is the following: the model is supported at the
thorax
> > > > which is connected rigidly to the ground. This means that
the
> > > > muscles in the spine do not have to carry almost any load.
This
> > > > should not be a problem, but if you have large muscles
groups in
> > > > this case the spine with very low activation it can make the
> problem
> > > > difficult to solve numerically, because it makes the problem
ill-
> > > > conditioned.
> >
> > The changes you made to the model… I wonder, will this causes
the
> > inacuracy in the modeling of the human repository? I guess the
> > is probably not, but why not?
> >
> > Thanks for your time.
> >
> > Thanks,
> > Leng-Feng
> >
> >
> >
> >
> > — In anyscript@yahoogroups.com, “Leng-Feng Lee” <lengfenglee@>
wrote:
> > >
> > > Hello SÃ¸ren,
> > >
> > > You are right, the x position is the hub’s x position.
> > >
> > > Thanks, currently I am trying the modified code for all other
points,
> > > and will let you know how it work out.
> > >
> > > The thing I don’t quite understand is that, for example, if we
have
> > > place the wheel in a space infront of the human (let say, a
square in
> > > the x-z plane, and in this square, the wheel is within
the ‘reachable’
> > > region of the hand), isn’t that the simulation ‘should’ works
in ALL
> > > points in that region?
> > >
> > > The strange thing is it work on the ‘side’(limits) of the
square but
> > > some points inside that region the simulation failed…
speaking in
> > > another way: the simulation works when x=0.1 and x=0.3, thus it
> > > ‘should’ works in all other points between 0.1 and 0.3.
> > >
> > > This is the part that I still don’t get it why. It act if
there are
> > > some ‘singularity point’.
> > >
> > > Can you point out to me where I missed? Also, do you have the
> > > documentation on the WheelTurn example (for repository 5)–or
any
> > > report (I see in the presentation file that this model is used
for
> > > shoulder verification)?
> > >
> > > Thanks for your (and other people in this support group) timely
> > response.
> > >
> > > Thanks,
> > > Leng-Feng
> > >
> > >
> > >
> > > — In anyscript@yahoogroups.com, “AnyBody Support” <support@>
wrote:
> > > >
> > > > Hi Leng-Feng
> > > >
> > > > I have tried your model and have some suggestions.
> > > >
> > > > When i first loaded the model
WheelTurn_Lee\WheelTurn_Main.any
> > > >
> > > > The wheel hub where set to this location
> > > >
> > > > AnyVec3 Hub = {2.2, -0.05, 0.30};
> > > >
> > > > since the Throax is attached at {0,0,0} it will not assemble
> > > > kinemtatically there is no way it will be able to reach.
> > > >
> > > > You write about the parameters
> > > > x=0.21, deg =0;
> > > > x=0.21, deg =5;
> > > > x=0.22, deg =3;
> > > > x=0.20, deg =3;
> > > >
> > > > I am in doubt what is the x value so i assume it is the x
component
> > > > of the Wheelhub.sRel. I tried to run the inverse analysis
and you
> > > > are right if fails to balance the system, for x=0.21 and
tilt =3
> deg.
> > > >
> > > > My theory is the following: the model is supported at the
thorax
> > > > which is connected rigidly to the ground. This means that
the
> > > > muscles in the spine do not have to carry almost any load.
This
> > > > should not be a problem, but if you have large muscles
groups in
> > > > this case the spine with very low activation it can make the
> problem
> > > > difficult to solve numerically, because it makes the problem
ill-
> > > > conditioned.
> > > >
> > > > To avoid this i have made some changes in the
JointAndDrivers.any
> > > > file. These changes removes the support of the thorax and
> > > > to the pelvis instead. These changes resolves the problems
for
> > > > x=0.21 and tilt =3 deg, i have not tested it for other
> > > > configurations.
> > > >
> > > > I have uploaded the file WheelTurn_Lee_JointAndDrivers.any
> > > >
> > > > I hope this solves the problems, otherwise please write
again.
> > > >
> > > > Best regards
> > > > SÃ¸ren, AnyBody Support
> > > >
> > > >
> > > >
> > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee”
<lengfenglee@>
> > > > wrote:
> > > > >
> > > > > Hello Dr John,
> > > > >
> > > > > Thanks. I uploaded my file in the file section–called
> > > > > "WheelTurn_Lee.rar ".
> > > > >
> > > > > The location where I change the x position and the tile
angle, I
> > > > > a comment. The file where these two parameters located are:
> > > > >
> > > > > x position - in WheelTurn.Main.any
> > > > > tile angle - in Environment.any
> > > > >
> > > > > Thanks for your time and assistance.
> > > > >
> > > > > Thanks,
> > > > > Leng-Feng
> > > > >
> > > > > — In anyscript@yahoogroups.com, “AnyBody Support”
<support@>
> > > > wrote:
> > > > > >
> > > > > > Hi Leng-Feng,
> > > > > >
> > > > > > It sounds like your method should be ok. What I was
concerned
> > > > > > was whether you had implemented a joint with
insufficient
> > > > support.
> > > > > >
> > > > > > In general an AnyBody model needs connections to the
> > > > surrroundings
> > > > > > that can provide enough reaction forces to balance the
overall
> > > > > > model. Also the internal parts of the model must be
balanced,
> > > > which
> > > > > > normally is done by the muscles. If any support anywhere
in the
> > > > > > model is insufficient, then the equilibrium equations
will be
> > > > > > singular, and the problem has not solution.
> > > > > >
> > > > > > You are welcome to zip your model and upload it to the
group.
> > > > The we
> > > > > > shall take a look at it.
> > > > > >
> > > > > > Best regards,
> > > > > > John
> > > > > >
> > > > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee”
> <lengfenglee@>
> > > > > > wrote:
> > > > > > >
> > > > > > > Hello Dr John,
> > > > > > >
> > > > > > > The implementation of the axis is done by defining a
> > > > AnyFixedFrame
> > > > > > and
> > > > > > > rotate it by a propriate angle (as shown in the
> > > > > > > “RevoluteJointDefinition.any” file in the file
section).
> > > > > > >
> > > > > > > This is very strange that there are some “dead Point”–
like
> > > > > > > singularity points in which only at that point the
simulation
> > > > > > gives an
> > > > > > > error but the point surronding it is fine (as
described).
> > > > > > >
> > > > > > > By the way, can you explain more about the Boundary
> Constraint
> > > > > > idea a
> > > > > > > little more detail? Why is it happen and why it causes
the
> > > > problem.
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Leng-Feng
> > > > > > >
> > > > > > >
> > > > > > > — In anyscript@yahoogroups.com, “AnyBody Support”
> <support@>
> > > > > > wrote:
> > > > > > > >
> > > > > > > > Hello Leng-Feng,
> > > > > > > >
> > > > > > > > The message you are geting usually means that the
model has
> > > > > > > > insufficient boundary conditions. I am wondering
whether
> > > > this
> > > > > > could
> > > > > > > > be connected to the variation of the angle about the
z
> axis.
> > > > > > Could
> > > > > > > > you describe how this angle variation implemented?
> > > > > > > >
> > > > > > > > Thanks,
> > > > > > > > John
> > > > > > > >
> > > > > > > > — In anyscript@yahoogroups.com, “Leng-Feng Lee”
> > > > <lengfenglee@>
> > > > > > > > wrote:
> > > > > > > > >
> > > > > > > > > Hello,
> > > > > > > > >
> > > > > > > > > I have a Question:
> > > > > > > > >
> > > > > > > > > For the WheelTurn example from the repository 5, I
> perform
> > > > a
> > > > > > > > > parametric sweep for x location and wheel angle (I
> > > > created,
> > > > > > this
> > > > > > > > angle
> > > > > > > > > rotate about the z-axis).
> > > > > > > > >
> > > > > > > > > I do a parametric sweep of x position from 0.15 to
025
> > > > (with
> > > > > > > > increment
> > > > > > > > > of 0.01), and a wheel angle sweep of 0-60 deg
(with
> > > > increment
> > > > > > of 3
> > > > > > > > > deg, the wheel angle is measured from the positive
global
> > > > y-
> > > > > > axis).
> > > > > > > > > While performing this sweep, I realized that at
certain
> > > > > > points, the
> > > > > > > > > AnyBody gives me error saying that constraint is
not
> > > > satisfied-
> > > > > > -
> > > > > > > > This
> > > > > > > > > is okay, but the strange thing is that all
neighbouring
> > > > points
> > > > > > are
> > > > > > > > > fine. For example:
> > > > > > > > >
> > > > > > > > > at x=0.21, deg = 3 --simulation fail.
> > > > > > > > > But at:
> > > > > > > > > x=0.21, deg =0;
> > > > > > > > > x=0.21, deg =5;
> > > > > > > > > x=0.22, deg =3;
> > > > > > > > > x=0.20, deg =3;
> > > > > > > > > [all are suurounding points of x=0.21, deg=3]
> > > > > > > > >
> > > > > > > > > at all these points, the simulation works fine…I
> cannot
> > > > > > figure
> > > > > > > > out
> > > > > > > > > what is the problem. And it happens at some other
points
> > > > too.
> > > > > > > > >
> > > > > > > > > It seem for me that the simulation does not act
like
> > > > > > a “continuous
> > > > > > > > > functions”–it failed at some point although
points at
> > > > > > surrounding
> > > > > > > > > works fine.
> > > > > > > > >
> > > > > > > > > Can anyone explain this?
> > > > > > > > >
> > > > > > > > > Thanks,
> > > > > > > > > Leng-Feng
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>