Bicoprime Factor Stability Criteria and Uncertainty Characterisation∗

Bicoprime factorisations can be considered a generalisation of the well known coprime factorisations. This paper deals with the possible applications of such factorisations in control theory. The concept of minimal dimension bicoprime factorisations is introduced and shown to be especially beneficial in the case of normal rank deficient and redundant control systems. Some methods of obtaining a bicoprime factorisation for a plant are given based on state-space data, right or left coprime factorisations and left or right standard factorisations. Finally, bicoprime factor uncertainty is characterised and shown to have an interesting structure closely resembling the standard four-block uncertainty.