Most robust control schemes for rigid robots assume velocities measurements to be available. Although it is possible to measure velocities by using tachometers, this increases costs, and the signals delivered may be contaminated with noise. Since the use of encoders allows reading joint position pretty accurately, sometimes it is desirable to estimate joint velocities through an observer. This paper presents a robust control scheme designed in conjunction with a linear observer. Uniform ultimate boundedness for the tracking and observation errors are guaranteed. Experiments are included to support the theoretical results and to show that the performance of the new control-observer law is better, in comparison with well-known algorithms reported in the literature.