Decoupling With Stability of Linear Systems by Static-State Feedback

A solution is presented to a long-standing open problem of control theory, the decoupling of linear systems using static-state feedback while assuring stability. Both diagonal and block decoupling is considered. The earliest known investigation of system decoupling dates back to 1934 and all past stable solutions were obtained under restrictive assumptions on system, block structure, or on a particular form of the control law. Most often, the results were limited to regular state feedback. The present formulation avoids restrictive hypotheses. The system is stabilized first and then decoupled while preserving stability. The existence of decoupling feedback is conditioned by system invariants with respect to the group of stability-preserving decoupling transformations. Since nonregular state feedback is authorized, some well-known results of regular decoupling are not retained. In particular, the presence of interconnection zeros does not prevent a stable decoupling to be achievable.