Hi Brent,
Søren has been traveling this week, so I had a brief look at your
model instead.
You really understand the AnyScript features and structure very well.
I noticed that you are adding the necessary items to existing folders
in the BNDR file, and that is very nice structuring.
But I did not fully understand the function of the massless
SpringRightSeg and its left counterpart. So let me give you a general
explanation and relate that to your model:
When you add an anyforce to a joint and want to use the joint angle
to specify the size of the force, then the force gets the same
direction as the joint angle and works between the two segments
metting at the joint.
So to work out the direction of the force, investigate the direction
of the joint angle. In the pedal example, the joint angle gets bigger
as the pedal is depressed, and this should also make the torsional
spring moment bigger, albeit working against the joint angle. So the
definition is like this:
F = -..SpringStiff*.HingeJoint.Pos;
i.e. the torque gets bigger in absolute value but works against the
increase of the joint angle and therfore has the minus sign in front.
So if I modify your hip position variable in the mannequin file like
this:
AnyVector HipFlexion = {80, 70, 60, 50, 40, 30, 20};
then the LowerJointRight.Pos will extend during the movement. If the
associated spring is going to help this extansion then the spring
force must be positive and decreasing just like the
ForceLowerRight.Fout you have defined is. This torque will be added
directly to the joint and will affect the two segments joined there
and consequently the body parts attached to the segments.
It seems to me you hve done it correctly, but as I said, I do not
really understand what the massless spring segment does.
I hope this helps.
Best regards,
John
— In anyscript@yahoogroups.com, “blulrey” <blulrey@…> wrote:
>
> I am still having trouble figuring out the directions. I have
uploaded a copy of my model in
> AnyForce_Direction.zip
>
> I started with the standing model, and included some of the drivers
from the free posture
> move model (I think you suggested this method awhile go). There is
a file named BNDR.any
> which contains the device I added to the environment, as well as
the model environment
> connection. The device has a torsional spring near each hip joint,
and segments that contact
> the chest and each thigh. There should be forces pushing up on the
chest and down on each
> thigh. I modeled the spring with AnyForces at the joints of the
device.
>
> I cannot tell which direction to apply the AnyForces. When looking
at the coordinate systems,
> I thought it should be positive for the upper segment, and negative
for the lower segments.
> A positive moment about the z axis would push up, and a negative
moment would push
> down. However, when looking at the reactions, and at the result of
> AnyForceMomentMeasures, it seems like a positive AnyForce must be
applied to the lower
> segments also. This doesn’t make sense to me.
>
> I would appreciate any help.
> Thank you,
> Brent
>