This paper investigates the sufficient conditions for self-identification of adaptive structure systems with the control input using variable structural parameters in the systems. The principle of the self-identification is explained by the effect of the control input on the eigen-values and eigenvectors of linear systems. Based on the principle and sensitivity analyses of modal properties , the sufficient conditions for self-identification are derived, where the controllability and

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... y of modal properties with respect to the control input are introduced. In numerical examples , two spring-mass systems with variable stiffness or variable mass parameters are examined . The results indicate that the self-identifiabilty of each system can be evaluated with the derived conditions.