Automatic self-calibration of body worn triaxial-accelerometers for application in healthcare

In healthcare acceleration sensors have various applications in monitoring movements for prevention, diagnostics, therapy and rehabilitation. Unfortunately they react sensitive against changes of environmental conditions and therefore it is necessary to calibrate them from time to time. This paper introduces a technique for automatic self-calibration of body worn triaxial-accelerometers that do neither need any user interaction nor a special calibration procedure. The data are calibrated automatically during operation of the sensor. The method does not require any knowledge about the actual orientation of the sensor and uses the activity of the subject to calibrate, because the activity is the region of interest for evaluation. The error of the automatic self-calibration will be as small as the error of common techniques for calibration that need an additional procedure, whereby an important error source will be excluded. The resulting algorithm is so small and compact, that it can even be transferred onto a sensor system and executed by its microprocessor.