Time-Delay Systems and Their Applications in Engineering 2014

It is well known that, together with the increasing expectations of system dynamic performances, the delay information in practical systems or processes should not be neglected in the modelling procedure. Time delay is a very common phenomenon in the engineering world. In fact, many industrial processes include after effect phenomena in their inner dynamics. And actuators, sensors, and field networks that are involved in feedback loops usually introduce unavoidable delays. The theoretical research about delay related systems should be very important, and it is surely a rewarding topic for researchers. In the past few decades, there has been an increasing interest in time-delayed systems from control scientists and engineers. On one hand, time delays are inherent in various engineering systems and often deteriorate the main system performances.Those delays can cause instabilities of original systems and make it harder for the system analysis, controller design or state estimation. To tackle these disadvantages, special attention must be paid and necessary compensation should be applied in the design process. On the other hand, the nice properties of time delays may also bring a new vision for our practical design. For example, if dealt with properly, the delay elements can really be treated as the oscillation generator or chatting compensator. In this special issue, most papers are concerned with the stability analysis and control problems of time-delay systems. Among them, five papers investigate the simplified or improved stability criteria of time-delayed systems; seven papers consider the extended stability analysis problems of the complex systems with time delay. Based on the existing control theory, three papers discuss the output-feedback control strategies for the stochastic high-order nonlinear systems and complex interconnected time-delay systems; one paper concerns the asymptotic tracking control for a class of nonlinear systems with unknown failures of hysteretic actuators; two papers cover the optimal control problem of the nonlinear systems with time delay and the calculus variations with time delays; four papers focus on the robustH ∞