Tomar, Mahendra Singh; Zamani, Majid
(2020):
Compositional Quantification of Invariance Feedback Entropy for Networks of Uncertain Control Systems.
In: IEEE Control Systems Letters, Vol. 4, No. 4: pp. 827832

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Abstract
In the context of uncertain control systems, the notion of invariance feedback entropy (IFE) quantifies the state information required by any controller to render a subset Q of the state space invariant. IFE equivalently also quantifies the smallest bit rate, from the coder to the controller in the feedback loop, above which Q can be made invariant over a digital noiseless channel. In this letter, we consider discretetime uncertain control systems described by difference inclusions and establish three results for IFE. First, we show that the IFE of a discretetime uncertain control system Sigma and a nonempty set Qis upper bounded by the largest possible IFE of Sigma and any member of any finite partition of Q . Second, we consider two uncertain control systems, Sigma(1) and Sigma(2), which are identical except for the transition function, such that the behavior of Sigma(1) is included within that of Sigma(2). For a given nonempty subset of the state space, we show that the IFE of Sigma(2) is larger or equal to the IFE of Sigma(1). Third, we establish an upper bound for the IFE of a network of uncertain control subsystems in terms of the IFEs of smaller subsystems. Further, via an example, we show that the upper bound is tight for some systems. Finally, to illustrate the effectiveness of the results, we compute an upper bound and a lower bound of the IFE of a network of uncertain, linear, discretetime subsystems describing the evolution of temperature of 100 rooms in a circular building.