The differential equations describing the dynamic behaviour of a robotic arm lncluding drives and gears are strongly coupled and highly nonlinear especially in case of an articulated arm. In order to allow the application of the well developed theory and control synthesis procedures for linear systems, a low order, coupled, linear and autonomous model is derived by linearization and order reduction which is - at least for nowadays stiff robots equipped with powerful drives - accurate enough for controller design and - if necessary - path prediction. The suggested procedure is simple and allows to estimate the influence of coupling terms as well as an easy updating of the model and/or controller parameters according to the actual working area