Utilization of non-causal uncertainty blocks in the robust flow controller design problem for data-communication networks

Ünal, Hakkı Ulaş; İftar, Altuğ

doi:10.1109/cca.2008.4629584

Cited by 6 publications

(19 citation statements)

References 10 publications

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“…As opposed to our earlier work [21], here, using [25], we allowed the uncertain part of the time-delays to be negative. The improvement in the time-domain results obtained by this relaxation can be observed from the simulation results given in [25].…”

Section: Discussionmentioning

confidence: 99%

“…Recently, however,Ünal andİftar [24] showed that, under certain conditions, a small-gain theorem is valid for systems that involve non-causal blocks. Extending this result,Ünal andİftar [25] also showed that non-causal uncertainty blocks can indeed be used in the robust flow controller design for networks with multiple time-delays. Although an alternative approach (see Remark 3 at the end of Section 2) exists, in the present work, we remove the assumption of non-negativity on the uncertain parts of the time-delays, by allowing the uncertainty block to be non-causal.…”

Section: Introductionmentioning

confidence: 93%

“…We note that i,2 could be taken as √ 2 + i , as shown in [25]. Here, however, we let i,2 = 2 √ 2 + i as in [19], so that we can compare our results to those of [19].…”

Section: Remarkmentioning

confidence: 99%

“…However, using the result of [25], we can still apply the small-gain theorem as long as i (t) := h i + i (t) 0, ∀t 0, ∀i, which is naturally satisfied since round-trip time-delays cannot actually be time-advances. By Theorem 2 of [25] (which is an extension of the well-known small-gain theorem [26]), if we choose K to stabilize the system with = 0 and make the L 2 -induced norm of the system from w 1 to z 1 in Figure 3 less than 1, then the overall system is robustly stable for all uncertainties satisfying (10). Alternatively, if K stabilizes the system with = 0 and make the L 2 -induced norm of the system from w 1 to z 1 in Figure 3 …”

Section: Remarkmentioning

confidence: 99%

“…However, given the result of [25], it is more natural and more straightforward to directly use , which is non-causal, as the uncertainty block.…”

Section: Remarkmentioning

confidence: 99%

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

Ünal

Ataşlar-Ayyıldız

İftar

et al. 2010

Intl J Robust & Nonlinear

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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.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 93%

“…We note that i,2 could be taken as √ 2 + i , as shown in [25]. Here, however, we let i,2 = 2 √ 2 + i as in [19], so that we can compare our results to those of [19].…”

Section: Remarkmentioning

confidence: 99%

Section: Remarkmentioning

confidence: 99%

“…However, given the result of [25], it is more natural and more straightforward to directly use , which is non-causal, as the uncertainty block.…”

Section: Remarkmentioning

confidence: 99%

See 3 more Smart Citations

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

Ünal

Ataşlar-Ayyıldız

İftar

et al. 2010

Intl J Robust & Nonlinear

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Performance and Robustness of Flow Controllers Designed Using Non‐causal Uncertainty Blocks

Ünal

İftar

2011

Asian Journal of Control

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According to some recent results, use of non‐causal uncertainty blocks may be advantageous in the robust controller design of systems with multiple uncertain time‐delays. In this work, performance and robustness improvements obtained by utilizing such an approach are presented. The flow controller design problem for networks with multiple uncertain time‐delays is considered as a case study. It is shown that higher performance levels and larger stability margins are, in general, obtained by using non‐causal uncertainty blocks. A number of simulations, which illustrate the time‐domain performance improvement, are also presented.

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A small gain theorem for systems with non-causal subsystems

ínal

İftar

2008

Automatica

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Utilization of non-causal uncertainty blocks in the robust flow controller design problem for data-communication networks

Cited by 6 publications

References 10 publications

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

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

Performance and Robustness of Flow Controllers Designed Using Non‐causal Uncertainty Blocks

A small gain theorem for systems with non-causal subsystems

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