An experimental method to estimate upper limbs inertial parameters during handcycling

This study proposes an experimental method to estimate personalized inertia parameters of upper limbs during handcycling by using a planar dynamic model. The handle forces are expressed as a product of a matrix describing the kinematics terms and a vector of inertial parameters of arm and forearm. The parameters are estimated by measuring the handle forces during a suitable “passive test” and inverting the mentioned matrix. The data was acquired while an operator actuated the handle, and the subject’s muscles were relaxed. To validate the estimation procedure, it was applied to a custom-made artificial arm mechanism and the results were compared to its known parameters. The method was then used to estimate the inertia parameters of six human subjects. The estimated parameters were used to compute the exchanged forces and compared with the measured ones obtaining an average error of 14 % both for Fx, and Fy. These errors are significantly smaller than those obtained using dynamic parameters extracted from the literature to compute the forces, which were 50 % for Fx and 19 % for Fy. An individual evaluation of inertia parameters better describes interaction forces during handcycling, especially for subjects whose body structures are different from average population.