In this note we propose a robust tracking controller for robots that requires only position measurements. The controller consists of two parts : a linear observer part that generates an estimated error state from the error on the joint position and a linear feedback part that utilizes this estimated state. It is shown that this computationally efficient controller yields semi-global uniform ultimate boundedness of the tracking error. An interesting feature of the controller is that it straightforwardly extends recent results on robust control of robots by linear state feedback to linear estimated-state feedback.