A new concept of a dynamical system representation is proposed. The idea of the representation is simple: combination of nonlinear coordinate transformation and time scale transformation. Introducing a projected refer...
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A new concept of a dynamical system representation is proposed. The idea of the representation is simple: combination of nonlinear coordinate transformation and time scale transformation. Introducing a projected referential trajectory and a moving frame on it, the coordinate transformation separates a system state into sub-states tangent to the trajectory and orthogonal one. Then time scale transformation using the arc length of the trajectory yields a state equation in which the state evolves spatially around the trajectory. As one of the advantages of the proposed method, time scale transformation enables us to ignore dynamics of the tangent sub-state at the same time. Therefore, the proposed representation realizes one-degree model reduction for smooth control systems. Since all transformation used in this article is invertible, this reduction is recoverable. Copyright (C) 2021 The Authors.
Exploring unknown environments is one of the main applications of mobile robotic systems. Since explorative trajectories can be used to gather information on the environment as well as on the internal dynamics of the ...
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Exploring unknown environments is one of the main applications of mobile robotic systems. Since explorative trajectories can be used to gather information on the environment as well as on the internal dynamics of the robotic system, we propose a combined parameter estimation and mapping approach consisting of three steps: first, the parameter estimation problem is addressed by nonlinear optimization. Then, clustering is used to classify the estimated parameters. Finally, Support Vector Machines (SVMs) are used to expand the optimal parameter values of the recorded data onto the entire map. The proposed approach is applied to a wheeled mobile rover system in a scenario with sharply changing surface properties. Further, it is assumed that the model structure is known and the slip parameter is estimated during the exploration as it depends on system-surface interaction. From the simulations, it was demonstrated that the proposed approach can estimate the position-dependent slip parameter and identify more than 90 % of the surface map. Copyright (C) 2021 The Authors.
There are various different attitude representations that describe the orientation of a rigid body in space and allow the transformation between different coordinate systems. Among others, they differ in number of var...
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There are various different attitude representations that describe the orientation of a rigid body in space and allow the transformation between different coordinate systems. Among others, they differ in number of variables, uniqueness of the representation and their continuity. However, in spite of some of them being based on angles, none of them constitutes a simple representation of an angle between two arbitrary vectors. We tackle this issue by proposing a novel attitude representation that directly incorporates the desired angle. The usefulness of this representation is demonstrated in the attitude reconstruction from temperature data, which then leads to an order reduction of a non-linear system. Copyright (C) 2021 The Authors.
The Hepatitis C Virus is the main cause of chronic liver diseases. The acute stage of infection is usually asymptomatic, and persistence in most of the infected individuals leads to chronic hepatitis, hepatic cirrhosi...
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The Hepatitis C Virus is the main cause of chronic liver diseases. The acute stage of infection is usually asymptomatic, and persistence in most of the infected individuals leads to chronic hepatitis, hepatic cirrhosis, and, finally, hepatocellular carcinoma. In order to avoid the chronic or advanced stages of this disease, when HCV is detected, cells activate the immune response mediated by interferon. Interferon is released by the infected hepatocytes and surrounding sentinel cells. Interferon activates the JAK-STAT signaling pathway and stimulates several ISG genes. Recently, it has been reported that only seven of them show a significant anti-HCV response. The aim of this study was to investigate, from a mathematical-modeling point of view, whether ISG over-expression leads the system to an irreversible clearance state. A mathematical model for the molecular machinery involved in cells infected with hepatitis C and the immune response was used to reproduce viral dynamics. The model considers seven ISG proteins. Our results suggest that the ISG proteins play an essential role in the hepatitis dynamics, and there is a possibility of produce the clearance state. Their robustness is evaluated. Copyright (C) 2020 The Authors.
The heart is an organ with a continuous activity whose heart rate and strength contractions are modulated by several physiological subsystems. These subsystems can be seen as weakly coupled oscillators. The electrical...
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The heart is an organ with a continuous activity whose heart rate and strength contractions are modulated by several physiological subsystems. These subsystems can be seen as weakly coupled oscillators. The electrical and mechanical oscillators are considered in this manuscript. 1:1 synchronization mode is a typical response of the healthy heart. However, although the heart rhythm as a system of weakly coupled oscillators was studied recently, little attention has been paid to the synchronization modes of the electrical stimulation-contractile response coupling in isolated mouse heart. This study aimed to describe with a minimalistic mathematical model the synchronization modes on the electrical stimulation-contractile response coupling in the whole heart. In this paper, we propose a minimal linear coupled oscillator model to study the synchronization modes. It contains four variables, and it is validated with experimental results. The local stability is studied. We predict through in-silico experiments the presence of several synchronization modes, and these could be associated with arrhythmias. (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
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