Abstract
An interactor matrix plays several important roles in the control system theory. Recently, we presented a simple method to derive a special interactor matrix using Moore-Penrose pseudoinverse. But, the structure of the proposed interactor was not specified. A triangular structure of interactor is useful for multivariable adaptive control. In this note, it will be shown a derivation of interactor with lower triangular structure. For this, a property of the interactor which we reported will play an important role.