Robust flow control in data‐communication networks with multiple time‐delays

Abstract

SUMMARYRobust controller design for a flow control problem where uncertain multiple time-varying time-delays exist is considered. Although primarily data-communication networks are considered, the presented approach can also be applied to other flow control problems and can even be extended to other control problems where uncertain multiple time-varying time-delays exist. Besides robustness, tracking and fairness requirements are also considered. To solve this problem, an H ∞ optimization problem is set up and solved. Unlike previous approaches, where only a suboptimal solution could be found, the present approach allows to design an optimal controller. Simulation studies are carried out in order to illustrate the time-domain performance of the designed controllers. The obtained results are also compared to the results of a suboptimal controller obtained by an earlier approach.

Decentralized controller design by continuous pole placement for neutral time-delay systems

“…In such a case, it may be easier to implement a time-delay controller that is composed of some delay elements and finite-impulse-response filters, but much fewer integrators (e.g. see Ünal et al, 2010). Therefore, extending the present design approach to allow the design of time-delay controllers is a plausible line for further research.…”

Stable ℋ∞ flow controller design using approximation of FIR filters

“…The slowest response, on the other hand, is produced by the controller designed by Algorithm 3 using the -approximation method, which reaches the steady state in about 70 tu. The low-frequency oscillations at the steady state are due to the oscillations in the forward time delays and are unavoidable unless exact time delays are known in advance by the controllers (Quet et al, 2002;Ü nal et al, 2010). Apart from these oscillations, all of the stable H 1 flow controllers designed here satisfy both the tracking and the weighted fairness requirements, as shown in Figure 6(b)-(e).…”

“…As in Quet et al (2002) andÜ nal et al (2010), we consider a network with n sources feeding a single bottleneck node. The dynamics of the queue length at the bottleneck node are given as…”