Improved reduced-order model for control of flexible-link robots

An improved reduced-order model is given for controls design in flexible multi-link robot arms. The model does not simply truncate the assumed-mode-shape series, but incorporates quasi-steady-state information about the neglected modes; a singular perturbation approach is used. Based on this model, the controller is composed of an inner loop based on input-output feedback linearization and an outer loop that stabilizes the internal dynamics (e.g. the flexible modes) using a second singular perturbation design. We show how to stabilize the internal dynamics by selecting a physically meaningful modified performance output for tracking; this output is the slow portion of the link-tip motions. That is, the tracking requirement is relaxed so that the zero dynamics are controllable through a boundary layer correction that stabilizes the flexible modes