Necessary and sufficient conditions for almost strict positive realness and their application to direct implicit adaptive control systems

It is shown that almost strict positive realness (ASPR) of a linear system is equivalent to its hyper minimum phaseness. The reformulation and extension of stability conditions for some classes of direct adaptive control systems are given based on the hyper minimum phaseness of the plant. The new conditions are easy to check and helpful for establishing interrelations between implicit adaptive control and adaptive control with an implicit reference model.