3-D attitude representation of human joints: a standardization proposal

Area of Science:

• Biomechanics
• Human Movement Analysis
• Robotics

Background:

• Existing 3D joint and segment angle conventions suffer from singularities, asymmetries, and adverse properties.
• Classical Cardanic/Eulerian angles are prone to gimbal-lock and non-orthogonality issues, impacting accuracy.
• There is a need for an unambiguous and easily interpretable 3D joint angle standard.

Purpose of the Study:

• To propose a novel convention for 3D joint angles based on the attitude vector derived from Euler's theorem.
• To provide a standard that is easily explainable to clinicians and implementable in software.
• To offer a convention that overcomes the disadvantages of existing methods, such as gimbal-lock.

Main Methods:

• Development of a new 3D joint angle convention utilizing the attitude vector concept.
• Comparison of the proposed convention with classical Cardanic/Eulerian angles.
• Sensitivity analysis and physical interpretation of the attitude vector standard.
• Experimental validation of the proposed convention's advantages.

Main Results:

• The proposed attitude vector convention provides unambiguous and interpretable 3D joint angles.
• It eliminates gimbal-lock and non-orthogonality issues inherent in Cardanic/Eulerian conventions.
• The attitude vector components exhibit superior metrical properties and are less sensitive to errors and uncertainties.
• Experimental results demonstrate the practical advantages of the new standard.

Conclusions:

• The attitude vector convention offers a robust and practical solution for 3D joint angle measurement.
• This new standard enhances accuracy and reliability in biomechanical and clinical applications.
• The proposed method simplifies 3D motion analysis and interpretation for researchers and clinicians alike.