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Body position can be monitored in 3D using miniature accelerometers and earth-magnetic field sensors
B Kemp1, A J Janssen, B van der Kamp
1Department of Neurology and Clinical Neurophysiology, University Hospital Leiden, The Netherlands. kemp@rullf2.leidenuniv.nl
Objectives:
The study and diagnosis of movement disorders can be improved by monitoring body position simultaneously with the EMG.
Methods:
We developed a monitor of the 3-dimensional (3D) orientation of body parts that can be applied in long-term ambulatory recordings in the daily life of a patient. The 3D sensor combines miniature sensors for earth's gravity and magnetism. It measures 60 x 50 x 10 mm and draws less than 1 mA of current from +/-5 V battery power. The non-horizontal direction of earth magnetism, as well as torque (pronation) of the body part, is corrected mathematically.
Results:
This results in a measurement of the 3D orientation of a body part in terms of vertical inclination and horizontal azimuth.
Conclusions:
Calibration measurements indicate that this method is fairly accurate and practically applicable.