External Work Computation from Motion Capture and Accelerometer
Abstract
The external mechanical work (WEXT) depends on the energy variations of the body centre of mass (CM). Its computation is generally based on the analysis of the trajectory of the CM, obtained by direct dynamic (force plates) or by kinematic (MOCAP systems). The availability of low-cost inertial motion units (IMU) would allow getting the same result from accelerations. Comparing the WEXT computed through a reliable multi-segments kinematic model with that obtained by integration of accelerations, recorded by a tri-axial sensor placed at the lumbar vertebrae, was the objective of this project. The WEXT from acceleration data was always greater than the reference one. Further, the overestimation increased with the progression speed. The shape of the energies signals was different, questioning the reliability of the results. The integration of gyroscopic data, available with many IMU, could improve the results. In order to estimate the WEXT, we would suggest investigating other possible models using one or more IMU. Meanwhile, the traditional methods (direct or inverse dynamic) can give more reliable results.
