LQG controllers for discrete-time multivariable systems with different transport delays in signal channels [Comments and author´s reply]

For original paper see ibid., vol.145, no.5, p.449-462, (1998). Recently, Grimble presented a design of stochastic LQG optimal controller for discrete-time systems with different time delays in different channels. This note points out that the theoretical results on which the statistical approach lies were already published before. Indeed, the case of a multi input/output control system with non-equal time delays was previously considered at three levels. The original author explains why this may seem to be so, and justifies his original publication