In this paper the tracking problem for rigid robot manipulators with uncertain parameters and unmodelled torque actuators (DC motors) is addressed and solved by combined first/second-order sliding mode control methodology. The robot is electrically-driven through a pulse-width modulated actuator supply voltage. The proposed controller does not require the availability of the joint velocity, is insensitive to smooth load disturbances and guarantees a global domain of attraction. Computer simulations confirm the feasibility of the proposed approach.