Abstract-In this paper, we propose a device for the Position and Orientation (P&O) reconstruction of human segmental locomotion tasks. It is based on three mono-axial accelerometers and three angular velocity sensors, geometrically arranged to form two orthogonal terns. The device was bench tested using step-by-step motorbased equipment. The characteristics of the six channels under bench test conditions were: crosstalk absent, non linearity 0,

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.

A simple wearable device for sit-to-stand timing detection was designed and constructed with rate gyroscopes and accelerometers and a dedicated adaptive algorithm. The method was validated by comparison with optoelectronic equipment. Results from the comparison showed a maximal error always lower than 2.5 x 10(-2) s for start and stop detection.

A simple inertial measurement unit (IMU) incorporating rate gyroscopes and accelerometers has been tested to investigate the trunk kinematics during the sit-to-stand. It was affixed at trunk L5 level and used for sit-to-stand position and orientation reconstruction. The method was validated with standard optoelectronic equipment and results were also compared to the ones obtained by means of a Fast Video Camera. Comparative results showed for the IMU better performance than the system based on the Fast Video Camera. During the rising the mean pitch error was always lower than 5.2 x 10(-1) degrees and the mean Euclidean error lower than 5.9 x 10(-3) m in the sagittal plane.

No abstract