Periodic compensation of a class of decentralized systems with fixed modes

This paper first finds that the high frequency (ωω) 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,Bi,CiA,Bi,Ci) all the strongly interconnected channels of which satisfy CiBi=0CiBi=0, causes large, O(ω)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)O(1) only.