AbstractThe return difference matrix F(s) of a multivariable control system with respect to its gain elements is obtainable directly from the inverse transfer matrix T−1(s), which is in turn derived (by elimination of undriven node groups) from the coefficient matrix of the set of independent differential equations describing the system. Thus, no knowledge of the system's topology is required in order to obtain F(s). Furthermore, the inverse of one of the submatrices of T−1(s) yields the idealized response, if all gain elements are assumed to exhibit infinite gain.