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slewis
06-24-2011, 04:51 AM
Hi all
I am a fairly new Matlab user and wondering if anyone can help. I have lots of global coordinate data and I want to convert these to local coordinates and then calculate Euler angles. I've had a look on Matlab Central but can't find anything that really helps. Any advice appreciated.
Thanks
Sandra

bogert
06-24-2011, 11:51 AM
Sandra,

Take a look at our Kinemat software at http://isbweb.org/software/movanal/kinemat.

Another useful resource might be the Appendix of Christoph Reinschmidt's dissertation which is online here (http://www.sportsci.com/topics2/Tutorials/digitizing/markers_study/Christoph%20Dissertation.htm).

Ton van den Bogert

dhume
06-24-2011, 01:04 PM
Hey Sandra,

Here (http://pastebin.com/s9mbfGvd) is an old .m-file I created to calculate local rotation matrices given global shell coordinates. Once you have [R] it's just some algebra to obtain the Euler angles. You may find this (http://en.wikipedia.org/wiki/Euler_angles#Relationship_to_other_representations ) section on Wikipedia helpful.

Donald Hume

tfeix38
06-25-2011, 03:52 AM
Hi Sandra,

For coordinate transformations and to switch between various rotation representations I use the robotics toolbox by Peter Corke:
http://petercorke.com/Robotics_Toolbox.html

It all kind of functions to switch between Rotations Matrices, Homogeneous transforms, Quaternions and Euler angles.

Best, Thomas

twrigley92
06-26-2011, 05:08 AM
Matlab's Aerospace Toolbox contains routines to extract / convert between various rotational representations: rotation matrices, euler/cardan angles, quaternions (euler parameters), etc.

Tim Wrigley
University of Melbourne

tandresen
06-26-2011, 10:05 AM
You might find it helpful to look at the figure [4-6] for Euler angles in Herbert Goldstein’s “Classical Mechanics”. It’s an easy-to-remember diagram.

You should find the book in the library.

Ted

bhejrati24
06-26-2011, 02:17 PM
I have the below issue which is related to this thread, I would appreciate if anyone could help me:
We are using VICON system for Kinematic analysis in our lab. I use my own model for motion capturing and I don't use any of VICON templates for humman motion capturing and evaluating the joint angles. What I do is that I use the marker position (x,y,z) obtained from the Vicon and I use the code that I have written to obtain the angles. My question is: If I use the Vicon joint angles instead of my code, are the angles (Euler, helical....) returned by the Vicon, when I check joint kinematics option to save in a Csv file, bio-mechanically meaningful to evaluate flexion/exten, external/internal rotation and etc of human joints? or they are just meaningful when I use the standard templates of the Vicon?

jwilliams33
06-27-2011, 12:56 PM
Sandra

I am aware of a company that offers bespoke matlab code writing solutions if you are unable to resolve your difficulties. The cost is very reasonable and may be worth considering if you remain stuck. Contact Dr. Robinson on hrobinson@h-scientific.co.uk for details
Best of luck

rg123
10-15-2012, 10:41 AM
MATLAB has built-in functionality for Euler Angles (http://www.mathworks.com/discovery/euler-angles.html) that would probably be the best to utilize. These would be less error-prone as they have been put through testing for accuracy.