Task Space Control of Articulated Robot Near Kinematic Singularity: Forward Dynamics Approach

In this study, a forward dynamics-based control (FDC) framework is proposed for task space control of a nonredundant robot manipulator. The FDC framework utilizes forward dynamic robot simulation and an impedance controller to solve the inverse kinematics problem. For the practical use of the proposed control framework, the accuracy, robustness, and stability of robot motion are considered. Taking advantage of the stability of the implicit Euler method, a high-gain PD controller enables accurate end-effector pose tracking in the task space without losing stability even near the kinematic singularities. Also, the robustness of the controller is enhanced by borrowing the structure of the nonlinear robust internal-loop compensator. Lastly, the selective joint damping injection and spring force saturation are applied to the impedance controller so that the robot motion can always stay within the given dynamic constraints. This study suggests a new, effective solution for the kinematic singularity problem of non-redundant robot manipulators.