An efficient robust adaptive control scheme is presented for nonlinear robotic arm systems with bounded time-varying parameters. Unlike other controllers for time-varying robotic models, the presented control scheme does not require the calculation of the regressor matrix and does not impose any restrictions on the rate of changes of unknown robol parameters. The controller is simple, computationally fast and provides stable trajectory tracking in the presence of a class of state-dependent disturbances. Stability analysis indicates that the tracking error will eventually converge into a closed region, which can be made arbitrarily small by adjusting the control parameters.