Upper limb joint angle measurement in occupational health

Abstract

Usual human motion capture systems are designed to work in controlled laboratory conditions. For occupational health, instruments that can measure during normal daily life are essential, as the evaluation of the workers' movements is a key factor to reduce employee injury- and illness-related costs. In this paper, we present a method for joint angle measurement, combining inertial sensors (accelerometers and gyroscopes) and magnetic sensors. This method estimates wrist flexion, wrist lateral deviation, elbow flexion, elbow pronation, shoulder flexion, shoulder abduction and shoulder internal rotation. The algorithms avoid numerical integration of the signals, which allows for long-time estimations without angle estimation drift. The system has been tested both under laboratory and field conditions. Controlled laboratory tests show mean estimation errors between 0.06° and of 1.05°, and standard deviation between 2.18° and 9.20°. Field tests seem to confirm these results when no ferromagnetic materials are close to the measurement system.

Keywords::

• inertial measurement system
• occupational health
• joint angle measurement
• wearable sensors

Acknowledgements

We are indebted to Emir Díaz Martínez for his support in the field tests.

Conflict of interest disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work has been financed in part by ‘Fremap Mutua de Accidentes de Trabajo y Enfermedades Profesionales de la Seguridad Social Número 61’.