Combined PD-H∞ approach to control of flexible link manipulators using only directly measurable variables

A control scheme for flexible link manipulators, which makes use only of directly measurable variables and thus is well suited for practical implementations, is presented, The scheme is based on a combined PD-H-infinity design that takes into account the actual coupling between the rigid and flexible dynamics of these kinds of manipulators and needs feedback only from directly available sensor readings, This contrasts with other approaches reported in the literature that require full-state feedback or even feedback of the rigid unperturbed variables, which simply cannot be measured. It is shown that the proposed design, in spite of its ease of implementation, maintains good closed-loop tracking properties,