We obtain new necessary and sufficient conditions for the consistency of discretetime time-independent linear control systems with incomplete feedback and bilinear systems. We find a relationship between the consistency of time-independent systems and the eigenvalue assignment problem. We show that consistency is sufficient and, in certain cases, necessary condition for the arbitrary assignability of the eigenvalues for discrete-time systems with coefficients of special form.The present paper is the second part of [1], and here we continue the numbering of formulas, assertions, lemmas, theorems, corollaries, and remarks. The notation, definitions, results, and formulas in [1] required in forthcoming considerations are used without additional comments. By J we denote the first unit superdiagonal matrix; i.e.,
NECESSARY CONDITIONS AND SUFFICIENT CONDITIONS FOR THE CONSISTENCY OF A TIME-INDEPENDENT SYSTEMLet i 1 (λ), . . . , i s (λ) be nontrivial invariant polynomials [2, p. 134] of the matrix A of degrees n 1 ≥ · · · ≥ n s > 0, respectively (n 1 + · · · + n s = n), and let n 0 := n 1 + 3n 2 + · · · + (2s − 1)n s . Assertion 2. If the system Σ (respectively, Ω) is consistent, then mk ≥ n 0 (respectively, r ≥ n 0 ).Proof. If the system Σ (respectively, Ω) is ϑ-consistent for ϑ = 1, then m = k = n (respectively, r = n 2 ); consequently, mk = n 2 . Obviously, n 0 ≤ n 2 . Consider the case in which ϑ > 1. In this case, det A = 0 by virtue of Assertion 1. It is well known [2, p. 192] that the set of matrices commuting with the matrix A forms a linear subspace M ⊂ M n of dimension n 0 . Take a basis P 1 , . . . , P n0 in M. Set H := α 1 P 1 + · · · + α n0 P n0 , where the α i ∈ K are found from the conditionRelation (33) is a system of mk equations with n 0 unknown coefficients α i . If mk < n 0 , then system (33) always has a nontrivial solution α = (α 1 , . . . , α n0 ). In this case, we have H = 0 and C * HB = 0. Since H commutes with A, we have C * A i HA −i B = C * HB = 0 for all i = 1, . . . , n 2 −1.Consequently, relations (31) hold for the matrix H = 0. By Theorem 4, the system Σ is not consistent.510