Ohmin Kwon

Improved Results on Stability of Time-delay Systems using Wirtinger-based Inequality

Abstract This paper concerns with the problem of delay-dependent stability analysis of time-delay systems. By help of Wirtinger based inequality which gives very close estimating bound of Jensens inequality, an extended inequality is proposed. Using the new inequality and tuning parameters, a generalized criterion for stability of time-delay systems is established. Two numerical examples are given to describe the less conservatism of the proposed methods.

Design of Delay Dependent Robust Controller for Uncertain Systems with Time Varying Delay

Abstract This paper investigates the controller synthesis problem of uncertain systems with time varying delays. A robust controller with delay compensation is proposed, based on Lyapunov function method. The stability criterion of the closed-loop system, which is dependent on the size of the time delay and the size of its derivative, is derived in the form of linear matrix inequalities (LMI). Examples show that the results using the method in this paper are less conservative than most existing results by other methods.

Output Feedback Guaranteed Cost Control for Linear Uncertain System with Input Saturation

Abstract In this paper, a method is proposed for designing an output feedback guaranteed cost controller for a linear uncertain system with input saturation. The uncertainty is norm bounded time-varying. A quadratic cost function is considered as a performance measure for the given closed-loop system. Using the saturation indicator which is the ratio of control output and saturated plant input, sufficient conditions of quadratic stability are given by a finite number of Linear Matrix Inequalities(LMIs) that can be solved efficiently. A convex optimization with LMIs constraints is formulated to design a controller which minimizes the given cost function.