Kinematics error with human model

Main Forum
1

Hello

I would like to apply linkage mechanism to human model. I made a linkage mechanism using rigid body in Anybody and can run kinematic analysis without error.

When I apply linkage to human model, Some tolerance errors were occured.
But any Joint between human and linkage was not set.

If I made just one link, one joint, one motion, kinematic analysis could be run.
If the number of link were more than two, error would be occured.

I wish to apply the linkage(orthosis_thigh_4bar.main_rev04.any) to human model.

Please check my file.

Thanks.

2

Hi

I have taken a look at the model and found two issues:

The mechanism adds two segments = 12 rigid body dof to the model
It has two revolute joints, one spherical, and a drivers = 14 constraints…

This is part of the reason why it does not run.

[ul]
[li]You need to remove the driver it is not needed for this configuration…[/li][li] When the driver has been removed you need to also adjust the lengths of the bars or move the points because the bars are too long to be able to reach the point specified… [/li] [/ul]

You can also consider to replace the spherical joint with a linear constraint only constraining 2 dof (x,y))… the z direction is also constrained though the rev. joints.

Best regards
Søren

3

Thanks for your help.

but my linkage model(orthosis_thigh_4bar.main_rev04) which is in zip file has any errors when I analyze linkage only.

Total d.o.f is 36, total constraints is 36

When I apply the linkage to human model, the error was occured.

And this linkage is gait for human, so we need a motion.

I attached full linkage file (orthosis_thigh_4bar.main_rev04) and human model file which is applied the linkage.

Please check again all of two files.

Thanks.

4

Hi

I can see that the model which is included in the human model now is different from before and includes the segs and joints as the standalone model.

Please do the following to make it run.

[ol]
Improve the initial conditions for the segments in the model.
To do this simply run the standalone model
Solve the first timestep
Find the “r” and “axes” values for the four segs in the ModelTreee
Then right click and select dump, then instant value will be copied to the message window.
Do this for “r” and “axes” of all four segs
Then copy these lines into each seg so r becomes r0 and Axes becomes Axes0, r0 and Axes0 are the loading positions and by doing this you provide a good guess. Taken from the separate model.

[/ol]

[LIST=2]
Set the tStart value to 0.1 or similar, the motion driver Data values starts at 0 which is also the tStart value you have now, this causes a problem. So either expand the motion driver T values or start the analysis a little later.

[/LIST]

Best regards
Søren

5

I modified r0, Axes0 values from seperated model.

I made tStart = 0.1, but the second problem which is in AnyKinEqInterPolDriver was occured.

When the kenematic analysis is started, there is error message(Time, ‘t’, has an invalid value for this interpolation).

I have no idea how I can validate Time ‘t’ in Environment.

I attached modified file as you said.

Please check the file one more.

Your comments was really big help.

Thank you.

6

Thanks for your help.

Your advise was really big help for me.

So, I could fix my model which was modifed by changing position and angle.

I have 1 more question.

I want gait to be attached to HipJoint and shank.

I made a spherical joint between gait and hip joint

but I couldn’t make connection between shank and gait.

Maybe I think, the trajectories of shank and gait are different.

So spring element was made to make interval but didn’t work.

Do you have any tips or solution?

I attached my file and please check again.

I want the shank to follow the kneelink in file.

Thanks.

7

Hi,

Attached please find a modified version of your model.

Best regards,
Moonki Jung

8

I can’t run kinematic to continue at time step 171.
I don’t know how can I fix it.

Please tell me how can I do ? And I attach file too.
Thank you.

9

Hi

If the model runs until step 171 and then fails kinematically it can be related a marker dropping out (then the it goes back to 0,0,0) this may make the model fail.

Please inspect the trajectory data to ensure you have no drop out markers in the data.

If you do not have marker drop out please inspect the motion you do get until step 171 and try move markers closer to the positions they were place on the subject, while doing the experiment.

Best regards
Søren