function[angles,helicang]=cardan(s1neut,s2neut,s1mov,s2mov,sequence)
Description: This program calculates the intersegmental motion expressed
in terms of Cardan angles (joint coordinate system) and helical
angles (Woltring, 1994) between two segments.
Input: s1neut: markers of segment 1 in anatomical position
s2neut: markers of segment 2 in anatomical position
s1mov: markers of segment 1 during the movement
s2mov: markers of segment 2 during the movement
sequence: string e.g. 'xyz' would mean:
- first rotation about x-axis of segment 1
- y is floating axis
- last rotation about z-axis of segment 2
Note that segment 1 and 2 may contain a redundant number of
markers (>3).
Output: angles: amount of rotation about x,y,z axes (alpha,beta,gamma)
helicangles: helical angles (Woltring, 1994)
Author: Christoph Reinschmidt, HPL, The University of Calgary
Date: November, 1995
Last Changes: November 28, 1996
Version: 1.0
References:
(1) Grood, E.W., and Suntay, W.J. (1983) A joint coordinate
system for the clinical description of three-dimensional
motions: applications to the knee.
J. biomech. Engng 105, 136-144.
(2) Woltring, H.J. (1994) 3-D attitude representation of
human joints: A standardization proposal.
J. Biomechanics 27, 1399-1414.