Passivity-based versus disturbance observer based robot control: Equivalence and stability

Disturbance observer based robot control algorithms provide good control pe rformance while giving a straightforward method of gain selection. Unfortun ately, the stability of these algorithms has not been shown rigorously for nonlinear systems such as robots. This paper demonstrates that a disturbanc e observer based algorithm can be made equivalent to the well-known passivi ty-based approaches of Sadegh and Horowitz and Slotine and Li. This is acco mplished by choosing a specific design of the Q(s) filter (described in the paper) of the disturbance observer. By doing so, the stability of the dist urbance observer based approach can be proven rigorously. An additional ben efit of the equivalence of the two approaches is the ability To coinbine an adaptive controller to the disturbance observer based approach.