Placement variations and their diagnosis

This paper investigates the impact of placement and orientation variations on the quality of sensed data. Different types of human movements are considered, namely, balancing, skipping, leaping; climbing up and down a staircase, and running. For data collection, tri-axis accelerometer sensors are used. As target placements, arms, thighs, knees, ankle, and waist are considered. Likewise, four different orientation angles were considered during deployment, namely, 0, 30, 45, and 85 degrees. The features employed to investigate placement and orientation variations were zero\mean-value crossing rate, correlation coefficients, cross-correlation, and auto-correlation. A particular focus was given to steady slow movements (climbing up and down a staircase) and steady fast movements (running). Remarkably, the fast movements are less affected by placement variations in comparison to the slow movements. Moreover, it will be shown that the effect of orientation variations for all types of movements are insignificant when absolute acceleration instead of the accelerations of individual axes are independently considered.