title: Determination of axial rotation angles of limb segments - a new method.
abstract: This paper describes a new method of determining the axial rotation angle of a limb segment during three-dimensional movement. Instead of describing the three-dimensional rotation by a three-step rotation (Euler/Cardan angles), a one-step rotation (instantaneous screw axis), or a non-step rotation (floating axis method), the new method uses a two-step rotation to describe the three-dimensional rotation of the limb segment: the rotation of the long axis of the limb segment about a specific axis passing through the proximal joint centre and perpendicular to the long axis of the limb segment, and the axial rotation about the long axis. A short review of previous methods followed by a full description of the principle of the new method with detailed derivation of some important equations (Appendices), comparison with Euler/Cardan angles and a simple experimental demonstration are given in this paper. A method of solving the gimbal-lock problem when using this method is also proposed.
authors.affiliation: Bioengineering Unit, University of Strathclyde, Glasgow, UK. cheng@me.queensu.ca
authors.forename: P L
authors.initials: PL
authors.lastname: Cheng
authors.forename: A C
authors.initials: AC
authors.lastname: Nicol
authors.forename: J P
authors.initials: JP
authors.lastname: Paul
mesh_terms: D001696:Biomechanical Phenomena; D001698:Biomedical Engineering; D001330:Electronic Data Processing; D005121:Extremities / Q000502:physiology*; D005542:Forearm / Q000502:physiology; D006801:Humans; D008722:Methods; D008954:Models, Biological; D009068:Movement; D012399:Rotation; D014102:Torsion Abnormality; D014741:Video Recording