Comment on "Eigenstructure assignment for linear systems" by A.N. Andry, et al. [Aerospace control]

In the above-titled paper (see ibid., vol.AES-19, p.711-729, Sept. 1983), an achievability subspace is given and used for eigenstructure assignment of linear systems with gain output feedback. The commenter shows that the achievability subspace is not generally achievable.<
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