Criteria for optimality in movements (contribution to 5th WCB, Munich)

Authors: Eriksson, 
Document Type: Article
Pubstate: Published
Journal: Journal of Biomechanics
Volume: 39, suppl 1   S54
Year: 2006


A general algorithm, based on a temporal finite element interpolation of displacements and controls, was developed for the evaluation of optimal movements between initial and final configurations. The algorithm, primarily aimed at musculoskeletal movement simulations, was found efficient and reliable, even for complicated dynamic formulations, [1]. The result from the algorithm is the configuration as function of time, but also the set of a priori unknown control forces needed to create the desired motion. With sufficient freedom in the description of the control forces, they are chosen to optimize some measure of the movement or the controls. A common criterion is to minimize the forces needed to produce the movement. Another interesting possibility is to seek the smoothest movement. Methods for minimization of either jerks or accelerations, following an idea by Flash and Hogan, [2], were introduced in the algorithm. Examples of limb movement indicate that the introduced optimization criteria strongly influence the obtained solutions. This observation is independent of whether the muscular forces are seen as a redundant set of individual forces, or are summed to resultant forces or moments at the considered joints. The presentation describes the developed algorithm, the studied optimization criteria, and the conclusions from a set of examples concerned with bio-mechanical targeted movement. [1] A. Eriksson, Analysis methodology based on temporal FEM for bio-mechanical simulations. In: M. Ursino, C. A. Brebbia, G. Pontrelli, E. Magosso (Eds.), Modelling in Medicine and Biology VI, WIT Press, Southampton, 2005. [2] T. Flash, N. Hogan, The coordination of arm movements: an experimentally confirmed mathematical model, J. Neurosci. 5, 1688-1703, 1985.