Time-varying Multiple Time-delays Research Articles

Performance and robustness analysis of a fuzzy-immune flow controller in ATM networks with time-varying multiple time-delays

For the Asynchronous Transfer Mode (ATM) networks with time-varying multiple time-delays, a more realistic model for the available bit rate (ABR) traffic class with explicit rate feedback is introduced. A fuzzy-immune controller is designed, which can adjust the rates of ABR on-line, overcome the bad effect caused by the saturation nonlinearity and satisfy the weighted fairness. Also, the sufficient condition that guarantees the stability of the closed-loop system with a fuzzy-immune controller is presented in theory for the first time. The algorithm exhibits good performance, and most importantly, has a solid theoretical foundation and can be implemented in practice easily. Simulation results show that the control system is rapid, adaptive, robust, and meanwhile, the quality of service (QoS) is guaranteed.

Stable H∞ Controller Design for Systems with Multiple Time-Delays: The Case of Data-Communication Networks

Stable H∞ controller design is considered for systems which involve multiple time-delays. Flow control problem in data-communication networks is chosen to present the proposed design approach. An algorithm, which produces a robust stable controller, is developed. An example is also presented, where the optimal controller, which is unstable, fails to produce a stable response due to nonlinear effects. The proposed controller, however, can robustly stabilize the system and produce desired response despite uncertain time-varying multiple time-delays.

Control of Stochastic Systems with Time-Varying Multiple Time Delays: LMI Approach

This paper deals with the class of continuous-time linear systems with Markovian jumps and multiple time delays. The systems that we are treating are assumed to have time-varying delays in their dynamics which can be different and also have uncertainties in the system parameters. The time-varying structure of the bounded uncertainties is considered. Delay-dependent conditions for stochastic stability and stochastic stabilizability and their robustness are considered. A design algorithm for a stabilizing memoryless controller is proposed. All the results are given in the LMI formalism.

Rate-based flow controllers for communication networks in the presence of uncertain time-varying multiple time-delays

An H ∞ based robust controller is designed for a rate-feedback flow-control problem in single-bottleneck communication networks. The controller guarantees stability robustness to uncertain time-varying multiple time-delays in different channels. It also brings the queue length at the bottleneck node to the desired steady-state value asymptotically and satisfies a weighted fairness condition. Lower bounds for stability margins for uncertainty in the time-delays and for the rate of change of the time-delays are derived. A number of simulations are included to demonstrate the time-domain performance of the controller. Trade offs between robustness and time-domain performance are also discussed.