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Abstract
In view of the singular nature of the letter by Johnson (1970), the following comments are made on the various sections of Johnson's letter seriatim, starting with Johnson's summary:
(a)The procedure described by Porter (1969) is not a procedure “for synthesizing a linear feedback control law which will realize a certain pre selected closed-loop eigenvalue pattern for a linear dynamical system”. It is concerned (Porter 1969) “with the application of the direct method of Liapunov” to the problem of assigning the closed-loop eigenvalues “in such a way that asymptotic stability or a sufficient margin of absolute stability is achieved”.
(b)In view of comment 0 (a), it is difficult to divine the intended meaning of the statement: “In addition, another method is proposed” (Johnson 1970).