A Dynamic Analysis of the Upper Extremity: Planar Motions

Abstract

Free body diagrams of arm segments show what forces are involved in planar motions. To represent equilibrium D'Alembert's principle is applied in graphical vector diagrams. From these diagrams are derived equations for determining joint force and torque reactions to weight and inertia. The equations make it clear that accelerations and physical constants are needed. A graphical vector acceleration diagram shows how linear accelerations can be determined from angular accelerations, derived in turn by finite differences from displacement time data. Experimental methods of determining kinematic data and constants are described. The analysis rationale is then used to establish an algorithm for programmed computation by digital computer. The output information is presented in a sample set of curves for one of the several types of motions treated.