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Ribosomes play a pivotal role in cell growth, since they are deputed to build amino acids for proteins assembly. Ribosomes consist of a small and a large sub-unit, whose binding occurs on mRNA strands. Both small and large sub-units origin from a common precursor of rRNA. In this note we propose a novel model of cell growth explicitly dealing with small and large ribosomal sub-units, as well as with their common precursor. Proteins are also included, since it is known they exert a control feedback on ribosome biogenesis: the modeling assumption is that the precursor synthesis is switched off when the ribosome-over-protein ratio exceeds a given threshold. The qualitative analysis of the proposed model is carried out with the aim of showing that there exist conditions on the model parameters according to which the exponential growth is ensured, that means all the state variables have an exponential time law, all sharing the same (positive) exponential growth rate. The model parameters have been assessed in order to provide meaningful time evolution of all the molecular players involved, and to result consistent with an existing, less complex model of cellular growth accounting for only ribosomes and proteins, recently exploited as a growth module inside a scaffold whole-cell model connecting metabolism, growth and cycle for the budding yeast Saccharomyces cerevisiae, the experimental model usually exploited for eukaryotic cells.

This study investigates a parameterization of all output-rectifying retrofit controllers for distributed design of a structured controller. It has been discovered that all retrofit controllers can be characterized as a constrained Youla parameterization, which is difficult to solve analytically. For synthesis, a tractable and insightful class of retrofit controllers, referred to as output-rectifying retrofit controllers, has been introduced. An unconstrained parameterization of all output-rectifying retrofit controllers can be derived under a technical assumption on measurability of the interaction signal. The aim of this note is to reveal the structure of all output-rectifying retrofit controllers in the general output-feedback case without interaction measurement. It is found out that the existing developments can be generalized based on system inversion. The result leads to the conclusion that output-rectifying retrofit controllers can readily be designed even in the general case., QC 20220315

This study addresses incident handling during an adverse event for dynamical networked control systems. Incident handling can be divided into five steps: detection, analysis, containment, eradication, and recovery. For networked control systems, the containment step can be conducted through physical disconnection of an attacked subsystem. In accordance with the disconnection, the equipped attack detection unit should be reconfigured to maintain its detection capability. In particular, separating the detection subunit associated with the disconnected subsystem is considered as a specific reconfiguration scheme in this study. This article poses the problem of disconnection-aware attack detection and isolation with the separation-based detector reconfiguration. The objective is to design an attack detection unit that preserves its detection and isolation capability even under any possible disconnection and separation. The difficulty arises from network topology variation caused by disconnection that can possibly lead to stability loss of the distributed observer inside the attack detection unit. A solution is proposed based on an existing controller design technique referred to as retrofit control. Furthermore, an application to low-voltage power distribution networks with distributed generation is exhibited. Numerical examples evidence the practical use of the proposed method through a benchmark distribution network., QC 20220525

Since modern network systems are managed by multiple operators, practical distributed controller design is required to be independently performed in a distributed manner. The independent design of distributed controllers, referred to as distributed design, enables the synthesis process to be scalable. Nevertheless, distributed design methods have not yet been fully developed because of its difficulty. As a novel scheme for control of network systems, this paper presents a distributed design method of glocal (global/local) controllers. In the glocal structure, a global controller is introduced into the controller to be designed in addition to local decentralized controllers. The key idea to realize distributed design is to represent the original network system as a hierarchical cascaded system composed of reduced-order models each of which stands for the dynamics of global and local behaviors, here referred to as hierarchical model decomposition. Distributed design is achieved by designing controllers for the reduced-order models owing to the cascade structure. A numerical example demonstrates the effectiveness of the proposed glocal control., QC 20200702

In this paper, we propose a method to establish a networked control system that maintains its stability in the presence of certain undesirable incidents on local controllers. We call such networked control systems weakly resilient. We first derive a necessary and sufficient condition for the weak resilience of networked systems. Networked systems do not generally satisfy this condition. Therefore, we provide a method for designing a compensator which ensures the weak resilience of the compensated system. Finally, we illustrate the efficiency of the proposed method by a power system example based on the IEEE 14-bus test system., QC 20170607

This paper proposes a singular perturbation approximation for semistable linear systems. In particular, we derive a novel expression of error systems in the Laplace domain. As a result, we obtain an h2-error bound in terms of the sum of eigenvalues of an index matrix, which coincides with a controllability gramian of the state-derivative. Furthermore, we show that the singular perturbation model appropriately preserves the semistability of the original system and also guarantees the stability of the error system. The efficiency of the proposed method is shown through a numerical example of a Markov chain model approximation., QC 20140317

This paper proposes a singular perturbation approximation that preserves system passivity and an interconnection topology among subsystems. In the first half of this paper, we develop a singular perturbation approximation valid for stable linear systems. Using the relation between the singular perturbation and the reciprocal transformation, we derive a tractable expression of the error system in the Laplace domain, which provides a novel insight to regulate the approximating quality of reduced models. Then in the second half, we develop a structured singular perturbation approximation that focuses on a class of interconnected systems. This structured approximation provides a reduced model that not only possesses fine approximating quality, but also preserves the original interconnection topology and system passivity., QC 20131105

In this paper, we develop a dissipativity-preserving model reduction method based on a generalized singular perturbation approximation. This model reduction framework can deal with not only standard singular perturbation approximation but also projection-based model reduction as a special case. To develop such a model reduction method, we investigate a condition under which system dissipativity is appropriately preserved through the approximation. Moreover, deriving a novel factorization of the error system in the Laplace domain, we derive an a priori error bound in terms of the H2-norm. The efficiency of the model reduction is shown through an example of interconnected second-order systems., QC 20140911