Velocity vectors

[Misha Patel]

If I have a model and it is moving, is there any way to see the vector or velocity at a point on that model?

[jimmy d]

You can run a point kinematics analysis;
http://simtk-confluence.stanford.edu:80 ... m+Workflow

There is a point kinematics tutorial that you can run through;
http://simtk-confluence.stanford.edu:80 ... cs+Example

[Misha Patel]

Thanks for the link to the tutorial.

Is there any more explanation on how to actually do point kinematics... the download file only seems to contain models and motions but not really an explanation of what to do

[Thomas Uchida]

Is there any more explanation on how to actually do point kinematics... the download file only seems to contain models and motions but not really an explanation of what to do

It works like the other analyses. I suggest looking through the documentation on Confluence (http://simtk-confluence.stanford.edu:80 ... h+Analyses) and trying it on a simple model first.

[Misha Patel]

Thanks, the link was very useful.
When it comes to the 'input' section of the analyze tool, what does the 'control' file do?

[Thomas Uchida]

When it comes to the 'input' section of the analyze tool, what does the 'control' file do?

Please read the documentation. See, in particular, the controls section on the "Getting Started with Analyses" page (http://simtk-confluence.stanford.edu:80 ... h+Analyses).

[Misha Patel]

So is it necessary to have controls or can you do point kinematics without it?

[Thomas Uchida]

So is it necessary to have controls or can you do point kinematics without it?

From the "How to Use the Analysis Tool" page (http://simtk-confluence.stanford.edu:80 ... lysis+Tool): "If you are running an analysis on an existing simulation, you will most often specify a set of controls and states output by that simulation." For what simulation results are you running an analysis?

[Misha Patel]

I am trying to run the point kinematics on the 'leg6dof9musc.osim' model... I have loaded a motion and so I have selected loaded motion.

But I am unsure what file to load for the controls, I seem to be getting all 0's when I don't have a control file.\

When I copy this example and use all the same files I still don't get non-0 results:

http://simtk-confluence.stanford.edu:80 ... lysis+Tool

I'm using a code in MATLAB to process the data.

[Thomas Uchida]

I am trying to run the point kinematics on the 'leg6dof9musc.osim' model... I have loaded a motion and so I have selected loaded motion. But I am unsure what file to load for the controls, I seem to be getting all 0's when I don't have a control file.\

Thank you for the explanation. The zeros have nothing to do with whether you have provided a controls file. I suspect the issue is that you have not properly configured the PointKinematics analysis. Here is an example:
- open leg6dof9musc.osim
- load Swing\leg69_IK_swing.mot
- select Analyze… from the Tools menu
- in the Analyses tab, click Add and select PointKinematics
- select PointKinematics (the item that now appears at the top of the list)
- click the Edit button at the bottom of the window
- beside "body_name", double-click "ground", type "toes_r", and press <Enter>
- beside "relative_to_body_name", double-click "none", type "ground", and press <Enter>
- click OK and then Run