PARAMETER-ESTIMATION FOR A PROSTHETIC ANKLE

The mechanical parameters of a model of an energy storage and return a nkle prosthesis are estimated for normal level walking by means of an optimization procedure. The walking cycle is divided into six fields, such that the power does not change sign within each field; the transi tion between successive fields occurs at zero power. The optimal sprin g stiffness as a function of time, is found by optimizing a quadratic cost function to minimize the difference between the estimated ankle m oments and the moments in normal walking. The optimization is subjecte d to four continuous constraints within each field and to two continui ty constraints for the transitions between successive fields. The time -varying spring stiffness and the implications of additional external energy are discussed and are presented as recommendations for the desi gner.