Lightweight robot manipulators have considerable structural flexibility. Hence, the elastic behavior of the robot arms must be considered in control system design. Owing to the complexity of a dynamic model of flexible robots, it is desirable to design a controller simple. Furthermore, since the robot must handle a wide variety of payloads, the robustness of the control system becomes very important. In this thesis, a simple and robust control system is proposed. The closed-loop system is shown to be stable in the sense of Lyapunov and robust to uncertainty in system parameters. The simulation results are presented to show the robustness of the simple controller against payload variations.