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New technique for CoM calculation
In biomechanics, the motion of the centre of mass (CoM) is often topic of research and the accuracy of its estimation is crucial to the results. Typically, there are two ways to calculate the trajectory, namely integration of the ground reaction forces or using kinematic estimates from motion capturing. Both methods have their individual shortcomings.
Moritz Maus , Andre Seyfarth and Sten Grimmer have proposed a new method to combine data, that leads to physically consistent results, i.e. the outcome of the method are forces and a CoM motion, and the 2nd derivative of the motion times the mass is exactly the force. It combines those parts of the kinematic and dynamic measurements that are considered to be the most reliable. The algorithm is using different parts of the Fourier spectrum to overcome the inaccuracies of each measurement system.
Results of different CoM methods for a 55 sec trial with standing, walking and running.
In experiments and simulations, the authors show that the calculated motion and force very closely resemble the measured data. This closeness, together with the physical consistency, renders these data very reliable CoM estimates that can be used for further investigations with greater confidence.
Literature: Maus, H.-M., Seyfarth, A., and Grimmer, S. (2011). Combining forces and kinematics for calculating consistent centre of mass trajectories. J Exp Biol 214, 3511–3517.
DOI:10.1242/jeb.057422
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