An Improved Principal Coordinate Frame for use with Spatial Rigid Body Displacement Metrics

Abstract

This paper presents an improved definition of a coordinate frame, entitled the principal frame (PF), that is useful for metric calculations on spatial rigid-body displacements. For a finite set of displacements a point mass model of the moving rigid-body is employed. Next, we compute the centroid and principal axes associated with the point mass locations. The PF is then determined from the principal axes. Here, a new algorithm for determining the PF from the principal axes is proposed. The PF is invariant with respect to the choice of the fixed coordinate frame as well as the system of units used; therefore, the PF is useful for left invariant metric computations. An example including a set of 10 spatial rigid-body displacements is presented to demonstrate the application and utility of the PF.