The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Eckehard Schöll - One of the best experts on this subject based on the ideXlab platform.
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Control of Unstable Steady States by extended time-delayed feedback.
Physical review. E Statistical nonlinear and soft matter physics, 2007Co-Authors: Thomas Dahms, Philipp Hövel, Eckehard SchöllAbstract:Time-delayed feedback methods can be used to control Unstable periodic orbits as well as Unstable Steady States. We present an application of extended time delay autosynchronization introduced by Socolar [Phys. Rev. E 50, 3245 (1994)] to an Unstable focus. This system represents a generic model of an Unstable Steady State which can be found, for instance, in Hopf bifurcation. In addition to the original controller design, we investigate effects of control loop latency and a bandpass filter on the domain of control. Furthermore, we consider coupling of the control force to the system via a rotational coupling matrix parametrized by a variable phase. We present an analysis of the domain of control and support our results by numerical calculations.
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Control of Unstable Steady States by extended time-delayed feedback.
Physical Review E, 2007Co-Authors: Thomas Dahms, Philipp Hövel, Eckehard SchöllAbstract:Time-delayed feedback methods can be used to control Unstable periodic orbits as well as Unstable Steady States. We present an application of extended time delay autosynchronization introduced by Socolar et al. to an Unstable focus. This system represents a generic model of an Unstable Steady State which can be found for instance in a Hopf bifurcation. In addition to the original controller design, we investigate effects of control loop latency and a bandpass filter on the domain of control. Furthermore, we consider coupling of the control force to the system via a rotational coupling matrix parametrized by a variable phase. We present an analysis of the domain of control and support our results by numerical calculations.Comment: 11 pages, 16 figure
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Conversion of stability in systems close to a Hopf bifurcation by time-delayed coupling.
Physical review. E Statistical nonlinear and soft matter physics, 2007Co-Authors: Chol-ung Choe, Philipp Hövel, Valentin Flunkert, Hartmut Benner, Eckehard SchöllAbstract:We propose a control method with time delayed coupling which makes it possible to convert the stability features of systems close to a Hopf bifurcation. We consider two delay-coupled normal forms for Hopf bifurcation and demonstrate the conversion of stability, i.e., an interchange between the sub- and supercritical Hopf bifurcation. The control system provides us with an unified method for stabilizing both the Unstable periodic orbit and the Unstable Steady State and reveals typical effects like amplitude death and phase locking. The main method and the results are applicable to a wide class of systems showing Hopf bifurcations, for example, the Van der Pol oscillator. The analytical theory is supported by numerical simulations of two delay-coupled Van der Pol oscillators, which show good agreement with the theory.
Thomas Dahms - One of the best experts on this subject based on the ideXlab platform.
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Control of Unstable Steady States by extended time-delayed feedback.
Physical review. E Statistical nonlinear and soft matter physics, 2007Co-Authors: Thomas Dahms, Philipp Hövel, Eckehard SchöllAbstract:Time-delayed feedback methods can be used to control Unstable periodic orbits as well as Unstable Steady States. We present an application of extended time delay autosynchronization introduced by Socolar [Phys. Rev. E 50, 3245 (1994)] to an Unstable focus. This system represents a generic model of an Unstable Steady State which can be found, for instance, in Hopf bifurcation. In addition to the original controller design, we investigate effects of control loop latency and a bandpass filter on the domain of control. Furthermore, we consider coupling of the control force to the system via a rotational coupling matrix parametrized by a variable phase. We present an analysis of the domain of control and support our results by numerical calculations.
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Control of Unstable Steady States by extended time-delayed feedback.
Physical Review E, 2007Co-Authors: Thomas Dahms, Philipp Hövel, Eckehard SchöllAbstract:Time-delayed feedback methods can be used to control Unstable periodic orbits as well as Unstable Steady States. We present an application of extended time delay autosynchronization introduced by Socolar et al. to an Unstable focus. This system represents a generic model of an Unstable Steady State which can be found for instance in a Hopf bifurcation. In addition to the original controller design, we investigate effects of control loop latency and a bandpass filter on the domain of control. Furthermore, we consider coupling of the control force to the system via a rotational coupling matrix parametrized by a variable phase. We present an analysis of the domain of control and support our results by numerical calculations.Comment: 11 pages, 16 figure
Philipp Hövel - One of the best experts on this subject based on the ideXlab platform.
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Control of Unstable Steady States by extended time-delayed feedback.
Physical review. E Statistical nonlinear and soft matter physics, 2007Co-Authors: Thomas Dahms, Philipp Hövel, Eckehard SchöllAbstract:Time-delayed feedback methods can be used to control Unstable periodic orbits as well as Unstable Steady States. We present an application of extended time delay autosynchronization introduced by Socolar [Phys. Rev. E 50, 3245 (1994)] to an Unstable focus. This system represents a generic model of an Unstable Steady State which can be found, for instance, in Hopf bifurcation. In addition to the original controller design, we investigate effects of control loop latency and a bandpass filter on the domain of control. Furthermore, we consider coupling of the control force to the system via a rotational coupling matrix parametrized by a variable phase. We present an analysis of the domain of control and support our results by numerical calculations.
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Control of Unstable Steady States by extended time-delayed feedback.
Physical Review E, 2007Co-Authors: Thomas Dahms, Philipp Hövel, Eckehard SchöllAbstract:Time-delayed feedback methods can be used to control Unstable periodic orbits as well as Unstable Steady States. We present an application of extended time delay autosynchronization introduced by Socolar et al. to an Unstable focus. This system represents a generic model of an Unstable Steady State which can be found for instance in a Hopf bifurcation. In addition to the original controller design, we investigate effects of control loop latency and a bandpass filter on the domain of control. Furthermore, we consider coupling of the control force to the system via a rotational coupling matrix parametrized by a variable phase. We present an analysis of the domain of control and support our results by numerical calculations.Comment: 11 pages, 16 figure
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Conversion of stability in systems close to a Hopf bifurcation by time-delayed coupling.
Physical review. E Statistical nonlinear and soft matter physics, 2007Co-Authors: Chol-ung Choe, Philipp Hövel, Valentin Flunkert, Hartmut Benner, Eckehard SchöllAbstract:We propose a control method with time delayed coupling which makes it possible to convert the stability features of systems close to a Hopf bifurcation. We consider two delay-coupled normal forms for Hopf bifurcation and demonstrate the conversion of stability, i.e., an interchange between the sub- and supercritical Hopf bifurcation. The control system provides us with an unified method for stabilizing both the Unstable periodic orbit and the Unstable Steady State and reveals typical effects like amplitude death and phase locking. The main method and the results are applicable to a wide class of systems showing Hopf bifurcations, for example, the Van der Pol oscillator. The analytical theory is supported by numerical simulations of two delay-coupled Van der Pol oscillators, which show good agreement with the theory.
G. V. Uma - One of the best experts on this subject based on the ideXlab platform.
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ANFIS based sensor fault detection for continuous stirred tank reactor
Applied Soft Computing, 2011Co-Authors: U.s. Banu, G. V. UmaAbstract:In this paper, an Adaptive Neuro-Fuzzy Inference System (ANFIS) based Sensor fault detection and isolation for Continuous Stirred Tank Reactor (CSTR) is proposed. CSTR is a highly nonlinear process exhibiting stable and Unstable Steady State at different operating regions. Fault detection (FD) of such a complicated CSTR process is a mind boggling problem. In this paper, an ANFIS based 'dedicated observer' scheme is dealt along with statistical methods for the detection of the fault. The result shows the feasibility of using the proposed method for the detection of sensor faults in CSTR.
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Fault Tolerant Control of CSTR with ANFIS Based Dedicated Observer and State Feedback Control using Linear Quadratic Regulator under Abrupt Sensor Failure Conditions
Instrumentation Science & Technology, 2009Co-Authors: U.s. Banu, G. V. UmaAbstract:Abstract In this paper, Fault Tolerant Control (FTC) is attempted using an Adaptive Neuro Fuzzy Inference System (ANFIS) based dedicated observer and a Linear Quadratic Regulator (LQR) based State feedback control under abrupt sensor failure, is proposed. A Continuous Stirred Tank Reactor (CSTR) is a highly nonlinear process, exhibiting stable and Unstable Steady State at different regions. Fault Detection and Isolation (FDI) of such a complicated CSTR process is a mind boggling problem. In this paper, an ANFIS based dedicated observer scheme is dealt along with a statistical method of detection of the fault. Also, LQR based State feedback control is used for the closed loop servo and regulatory control. The result shows the feasibility of using the proposed method for the fault tolerant control of CSTR under abrupt sensor failure conditions.
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Fuzzy gain scheduled pole placement based State feedback control of CSTR
IET-UK International Conference on Information and Communication Technology in Electrical Sciences (ICTES 2007), 2007Co-Authors: U.s. Banu, G. V. UmaAbstract:CSTR plays a vital role in almost all the chemical industries. Continuous stirred tank reactor (CSTR) is a highly nonlinear process exhibiting stable and Unstable Steady State at different regions. Control of CSTR in the complete range is a mind boggling problem. In this paper, a fuzzy scheduled pole placement based State feedback control of CSTR is investigated. The entire region is divided into three regions; low, middle and the high region. The low and the high region have stable Steady State and the middle region have Unstable Steady State. Initially, the gain matrix of the State feedback controller is computed for each region using pole placement technique. Then using fuzzy gain scheduler, the complete controller is formed. The result shows the feasibility of using the proposed controller for the control of CSTR. In this chapter optimal control of CSTR is investigated for the tracking and regulatory problems.
Luca Rossi - One of the best experts on this subject based on the ideXlab platform.
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Generalized Transition Fronts for One-Dimensional Almost Periodic Fisher-KPP Equations
Archive for Rational Mechanics and Analysis, 2016Co-Authors: Grégoire Nadin, Luca RossiAbstract:This paper investigates the existence of generalized transition fronts for Fisher-KPP equations in one-dimensional, almost periodic media. Assuming that the linearized elliptic operator near the Unstable Steady State admits an almost periodic eigenfunction, we show that such fronts exist if and only if their average speed is above an explicit threshold. This hypothesis is satisfied in particular when the reaction term does not depend on x or (in some cases) is small enough. Moreover, except for the threshold case, the fronts we construct and their speeds are almost periodic, in a sense. When our hypothesis is no longer satisfied, such generalized transition fronts still exist for an interval of average speeds, with explicit bounds. Our proof relies on the construction of sub and super solutions based on an accurate analysis of the properties of the generalized principal eigenvalue
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Transition fronts for the Fisher-KPP equation
Transactions of the American Mathematical Society, 2016Co-Authors: François Hamel, Luca RossiAbstract:This paper is concerned with transition fronts for reaction-diffusion equations of the Fisher-KPP type. Basic examples of transition fronts connecting the Unstable Steady State to the stable one are the standard traveling fronts, but the class of transition fronts is much larger and the dynamics of the solutions of such equations is very rich. In the paper, we describe the class of transition fronts and we study their qualitative dynamical properties. In particular, we characterize the set of their admissible asymptotic past and future speeds and their asymptotic profiles and we show that the transition fronts can only accelerate. We also classify the transition fronts in the class of measurable superpositions of standard traveling fronts.
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Wave-like solutions for nonlocal reaction-diffusion equations: a toy model
Mathematical Modelling of Natural Phenomena, 2013Co-Authors: Grégoire Nadin, Luca Rossi, Leonid Ryzhik, Benoît PerthameAbstract:Traveling waves for the nonlocal Fisher Equation can exhibit much more complex behaviour than for the usual Fisher equation. A striking numerical observation is that a traveling wave with minimal speed can connect a dynamically Unstable Steady State~$0$ to a Turing Unstable Steady State~$1$, see \cite{NPT}. This is proved in \cite{AlfaroCoville, FangZhao} in the case where the speed is far from minimal, where we expect the wave to be monotone. Here we introduce a simplified nonlocal Fisher equation for which we can build simple analytical traveling wave solutions that exhibit various behaviours. These traveling waves, with minimal speed or not, can (i) connect monotonically $0$ and $1$, (ii) connect these two States non-monotonically, and (iii) connect $0$ to a wavetrain around $1$. The latter exist in a regime where time dynamics converges to another object observed in \cite{BNPR, GVA}: a wave that connects $0$ to a pulsating wave around $1$.
