Over the last decade a lot of research effort has been put into design of sophisticated control strategies for robots with system partial state feedback. However, the poor quality of velocity measurements may significantly deteriorate the control performance of these methods. In the area of observer design for nonlinear systems there is not one standard design like there is for linear systems. In this thesis we propose two solutions for observer and observer based controller design. The first solution is applicable for serial robots but the second solution is extended the previous results to a vast cite="mailto:Reza" The inclusion of actuators into the dynamic equations complicates the controller structure and its stability analysis since the systems are described by third-order differential equations . The designed controller consists of two parts: observer based 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 asymptotic stability of the tracking error. A key point in this design strategy is a fine tuning of the controller and observer structure to each other, which provides solutions to the output-feedback robot control problem. To show the validity of the proposed schemes the algorithm is implemented on a two link serial manipulator and a slider crank as an example of constrained systems, also the simulations are repeated for two case studies considering that they are actuated by BDC (Brushed DC) motors. The proposed methods are in fact model based but the simulations verify practically the robustness of the system against system uncertainties and input disturbance. The proof of the theorems has being done by the Lyapunov theorem, where a positive function is shown to have a negative differentiation with respect to time. Key Words: Velocity observer, Observer based controller, Lyapunov theorem, Asymptotic stability, Lipschitz systems, Robotic systems, Back stepping controller, Actuator dynamic.
