Passivity Based Versus Disturbance Observer Based Robot Control: Equivalence and Stability

Abstract Disturbance Observer based robot control algorithms provide good performance while giving a straightforward method of gain selection. Unfortunately, the stability of these algorithms has not been shown rigorously for nonlinear systems such as robots. This paper demonstrates that a disturbance observer based algorithm can be made equivalent to the well known passivity based approaches of Sadegh and Horowitz, and Slotine and Li. By doing so, the stability of the disturbance observer based approach can be proven rigorously. An additional benefit of the equivalence of the two approaches is the ability to combine an adaptive controller to the disturbance observer based approach. This addition yields a controller that is both easy to tune and robustly stable to parameter variations.