Periodic compensation of a class of decentralized systems with fixed modes

This paper first finds that the high frequency ( ω ) periodic controller suggested in Lee, Meerkov, and Runolfsson (1987) for fixed mode removal, and pole and zero placement, of a class of decentralized systems ( A , B i , C i ) all the strongly interconnected channels of which satisfy C i B i = 0 , causes large, O ( ω ) , oscillations in the outputs. Next it proposes an alternative controller, a dual of the above, that achieves the compensation with oscillations of O ( 1 ) only.