Comments on "The design of linear regulators optimal for time multiplied performance indices"

A procedure for the design of linear regulators optimal with respect to a time-multiplied performance index was suggested in a recent paper by Man and Smith. A counterexample, presented subsequently [2], indicated that the procedure was in error. It is shown that the optimal feedback control law must contain time-varying gains as opposed to the time-invariant gains as suggested by Man and Smith. This fact was also overlooked in [2].