An extended class of stabilizable uncertain systems

Abstract

The system of equations $\frac{{dx}}{{dt}} = A\left( \cdot \right)x + B\left( \cdot \right)u$, where A(·) ∈ ℝ^{n × n}, B(·) ∈ ℝ^{n × m}, S(·) ∈ R^{n × m}, is considered. The elements of the matrices A(·), B(·), S(·) are uniformly bounded and are functionals of an arbitrary nature. It is assumed that there exist k elements ${\alpha _{{i_i}{j_l}}}\left( \cdot \right)\left( {l \in \overline {1,k} } \right)$ of fixed sign above the main diagonal of the matrix A(·), and each of them is the only significant element in its row and column. The other elements above the main diagonal are sufficiently small. It is assumed that m = n −k, and the elements β _ij (·) of the matrix B(·) possess the property $\left| {{\beta _{{i_s}s}}\left( \cdot \right)} \right| = {\beta _0} > 0\;at\;{i_s}\; \in \;\overline {1,n} \backslash \left\{ {{i_1}, \ldots ,{i_k}} \right\}$. The other elements of the matrix B(·) are zero. The positive definite matrix H = {h _ij } of the following form is constructed. The main diagonal is occupied by the positive numbers h _ii = h _i , ${h_{{i_l}}}_{{j_l}}\, = \,{h_{{j_l}{i_l}}}\, = \, - 0.5\sqrt {{h_{{i_l}}}_{{j_l}}} \,\operatorname{sgn} \,{\alpha _{{i_l}}}_{{j_l}}\left( \cdot \right)$. The other elements of the matrix H are zero. The analysis of the derivative of the Lyapunov function V(x) = x*H ^–1 x yields h _i $\left( {i \in \overline {1,n} } \right)$ and λ _i ≤ 0 $\left( {i \in \overline {1,n} } \right)$ such that for S(·) = H ^‒1ΛB(·), Λ = diag(λ₁, ..., λ _n ), the system of the considered equations becomes globally exponentially stable. The control is robust with respect to the elements of the matrix A(·).