Hi Brent,

SÃ¸ren 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

>