Published online by Cambridge University Press: 27 January 2014
This paper studies the periodic feedback stabilization of the controlled lineartime-periodic ordinary differential equation:ẏ(t) = A(t)y(t) + B(t)u(t),t ≥ 0, where [A(·), B(·)] is aT-periodic pair, i.e.,A(·) ∈ L∞(ℝ+;ℝn×n) andB(·) ∈ L∞(ℝ+;ℝn×m) satisfy respectivelyA(t + T) = A(t)for a.e. t ≥ 0 andB(t + T) = B(t)for a.e. t ≥ 0. Two periodic stablization criteria for aT-period pair [A(·), B(·)] areestablished. One is an analytic criterion which is related to the transformation over timeT associated with A(·); while another is a geometriccriterion which is connected with the null-controllable subspace of[A(·), B(·)]. Two kinds of periodic feedback lawsfor a T-periodically stabilizable pair [ A(·),B(·) ] are constructed. They are accordingly connected with two Cauchy problemsof linear ordinary differential equations. Besides, with the aid of the geometriccriterion, we find a way to determine, for a given T-periodicA(·), the minimal column number m, as well as atime-invariant n×m matrix B, suchthat the pair [A(·), B] isT-periodically stabilizable.