Is it feasible to reconstruct body segment 3-D position and orientation using accelerometric data?

Abstract

Abstract-The analysis of the mechanics of the musculo-skeletal system during the execution of a motor task requires the determination of the instantaneous position and orientation of the body segments involved in relation to an inertial system of reference. By using adequately assembled uniaxial accelerometric sensors, an easy-to-manage measurement system can be obtained that estimates the three-dimensional position and orientation (P&O) of a body segment through an appropriate analytical model. However, the extent to which experimental errors, in particular accelerometers (ACs) assembly inaccuracies, affect such estimation has never been systematically investigated. This paper systematically analyzes the sensitivity of analytical models of body segment P&O reconstruction through a six-AC system and a nine-AC system to different sources of experimental error. We simulated and statistically assessed the performance of these models in the case of body segment motions typical of movements under muscular control.The results obtained indicated that the inaccuracy in the orientation of the individual AC's active axes and the offset error in the AC responses were the major sources of P&O estimation errors. In particular, no accurate estimation of position was possible with the analytical models analyzed. Under the motion conditions simulated in this study, no substantial advantages were found in using a nine-AC system rather than a six-AC system.Considering that the magnitudes of the simulated experimental errors were quite low ( 0.1 deg: AC's orientation; 10 4 m: uncertainty of the distance between two ACs; 10 2 ms 2 : random error; 0.5 10 2 ms 2 : offset error), the results indicate that none of the two ACs systems analyzed is suitable for body segment P&O estimation in routine biomechanical applications.Index Terms-accelerometer, accuracy, human movement analysis, simulation, 3-D rigid body position and orientation.

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“…This would allow assessment of the efficacy of other treatments in a less subjective manner than is currently available. Examples of work using such sensors for measuring body segment positions are can be found in [5] and [6]. These two publications show the progression from using solely accelerometer data to incorporating gyro measurements.…”

“…These two publications show the progression from using solely accelerometer data to incorporating gyro measurements. Although the system in [5] led to estimates that became unreliable even after a very short time, addition of gyros to the system in [6] gave a far better position and orientation reconstruction estimator over a short test.…”