Topic 3

INTRODUCTION: Systematic errors of up to 20mm and more have been reported in determining the center of pressure (COP) with force plates [1]. Experimentally these errors are determined by applying a point load to the force plate at a defined point and comparing the true coordinates of this point with the coordinates calculated from the signals of the force plate. The correction formulas given in the literature use polynomial approximations based on these measurements [4]. From analytical models it is known that the errors are due to the statically overdetermined configuration [3]. In this paper it will be shown that only with certain restrictions can these correction formulas be applied to distributed loads. The general construction of a force plate consists of a stiff plate resting on four posts (Fig. 1). In each of the four posts (i=1...4) there are tri-axial force transducers measuring compressive and tensile forces Fi z , in the z direction, as well as shearing forces Fi x , and Fi y , in the x and y directions respectively. From these