Robust impedance control for SEAs

The SEA-driven robots such as NASA Valkrie, DLR hand-arm system, and Rethink Robotics Baxter and Sawyer have been developed to enhance interactive ability since they are able to balance safety and performance needs. On the other hand, impedance control is an effective way to generate the wanted interactive behaviors. However, its progress is greatly hindered due to the fact that there lacks the systematic synthesis technique. In this paper, we study robust impedance control for SEAs¹. First, interaction model is given based on the law of conservation of energy and Newton's third law of motion, by which interactive stability is rigorously analyzed from the input–output viewpoint. Second, an extended passivity theorem is deduced via introducing passivity indices; Third, a robust impedance control framework is built and then the resulting multicriterion optimization problem is solved by the LMI-based approach with a full-order controller and by the nonsmooth optimization approach with a structural controller, respectively. Finally, numerical examples corroborate the effectiveness of this robust impedance control scheme.