Abstract: This paper,based on an electrically driven robot manipulator,has formulated a dimensionlessmathematical model of its control system.Next it analyzes the controllability of both the linearized sys-tem and the real nonlinear system due to many nonlinear factors of the system itself and due to the limita-tion of the source voltage.All results show that when the system is considered as linear,it is completelycontrollable.But under certain conditions we connot by using ordinary state feedback control realizc itscomplete controllability which however may be attained by utilizing intelliegent controllcr,i.e.,acomputer-based nonlinear controller with appropriate control strategy.