N. A. Bodunov
Saint-Petersburg Electrotechnical University "LETI",
Department of mathematics № 1,
5 Prof. Popova, Saint-Petersburg,
197376, Russia,
Linear periodic control system of special type is considered. It is assumed that transfer functions of a system have zero poles. Frequency conditions for asymptotic stability and instability of this system are obtained using Liapunov’s second method and the Yakubovitch-Kalman frequency lemma.