ON ROBUST STABILITY OF LINEAR NEUTRAL SYSTEMS WITH TIME-VARYING DELAYS

The application of direct Lyapunov method to stability of neutral systems with time-varying delays is usually encountered with the restrictive assumption on the function in the right side of the differential equation. This function is supposed to satisfy the Lipshitz condition with respect to the delayed state derivative with a constant less than 1. In the present paper we extend input-output approach to stability of neutral type systems with uncertain time-varying delays and norm-bounded uncertainties. This allows to avoid the assumption on the Lipshitsian constant. Sufficient stability criteria are derived in the frequency domain and in the time domain, where the descriptor discretized Lyapunov Krasovskii Functional (LKF) is applied. As a by-product, new necessary conditions for neutral-delay-independent/retarded-delay-dependent stability are obtained. The method can be easily extended to L2-gain analysis and can be applied to design problems.