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Residual Signals (residual + signal)

Distribution by Scientific Domains
Engineering85%

Selected Abstracts

The role of hexose transport and phosphorylation in cAMP signalling in the yeast Saccharomyces cerevisiae

FEMS YEAST RESEARCH, Issue 1 2001
Filip Rolland
Abstract Glucose-induced cAMP signalling in Saccharomyces cerevisiae requires extracellular glucose detection via the Gpr1-Gpa2 G-protein coupled receptor system and intracellular glucose-sensing that depends on glucose uptake and phosphorylation. The glucose uptake requirement can be fulfilled by any glucose carrier including the Gal2 permease or by intracellular hydrolysis of maltose. Hence, the glucose carriers do not seem to play a regulatory role in cAMP signalling. Also the glucose carrier homologues, Snf3 and Rgt2, are not required for glucose-induced cAMP synthesis. Although no further metabolism beyond glucose phosphorylation is required, neither Glu6P nor ATP appears to act as metabolic trigger for cAMP signalling. This indicates that a regulatory function may be associated with the hexose kinases. Consistently, intracellular acidification, another known trigger of cAMP synthesis, can bypass the glucose uptake requirement but not the absence of a functional hexose kinase. This may indicate that intracellular acidification can boost a downstream effect that amplifies the residual signal transmitted via the hexose kinases when glucose uptake is too low. [source]

Adaptive unknown input observer approach for aircraft actuator fault detection and isolation

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2007
Dan Wang
Abstract In this paper, an adaptive unknown input observer (UIO) approach is developed to detect and isolate aircraft actuator faults. In a multiple-model scheme, a bank of parallel observers are constructed, each of which is based on a model that describes the system in the presence of a particular actuator fault. The observers are constructed based on a modified form of the standard UIO to generate fault-dependant residual signals, such that when a model matches the system, the residual signal will be zero. Otherwise, the residual will be definitely non-zero and governed uniquely by the faulty signal. For locked actuators and loss of actuator effectiveness, in which the locked position and the reduced effectiveness are additional unknowns, we develop an adaptive scheme to estimate these unknown parameters. To the best of our knowledge, this is the first adaptive UIO presented. We prove that the proposed adaptive algorithms guarantee that both the residual signals and the estimation errors of the unknown parameters converge exponentially when a model matches the plant. By further designing a model-matching index, the fault can be isolated accurately. A condition for the approach is that for an nth order system, there must be n independent measurements available. This requirement limits the applicability of our proposed approach. The condition is certainly satisfied by all state-feedback control systems. However, for some other systems, extra efforts may be needed to increase the number of measurements. The method is applied to a linear model of the F-16 aircraft with controller. The results show that the approach is effective. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Robust fault detection and isolation for parameter-dependent LFT systems

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2010
Xuejing Cai
Abstract In this paper, we consider robust fault detection and isolation (FDI) problems for faulty linear systems with linear fractional transformation (LFT) parameter dependency and propose an observer-based solution by using multiobjective optimization techniques. To simplify the design process, a general faulty LFT system will be constructed from the standard LFT description by converting actuator/system component faults into sensor faults first. Then a bank of parameter-dependent FDI filters will be designed to identify each fault. Each FDI filter will generate a residual signal to track an individual fault with minimum error and to suppress the effects of disturbances, time-varying parameters and other fault signals. The design of LFT parameter-dependent FDI filters, as a multiobjective optimization problem, will be formulated in terms of linear matrix inequalities (LMIs) and can be solved efficiently. A numerical example is used to demonstrate the proposed fault detection and isolation approach for LFT systems with different parametric structures. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Fault detection of networked control systems with packet based periodic communication

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2009
Yongqiang Wang
Abstract Fault detection of networked control systems (NCS) with communication constraints is discussed in this paper. A so-called packet-based periodic communication strategy is proposed and two kinds of optimal observer-based residual generators are designed. One residual generator is designed based on the lifted model of NCS, which generates residual signals every communication period. The other works at a faster rate, i.e. it generates residual signals every sampling period and is more suitable for prompt fault detection. Comparison with traditional periodic-communication-sequence-based scheduling strategy reveals superiority of this new communication strategy. Simulation results are also provided to illustrate effectiveness of the proposed method. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Adaptive unknown input observer approach for aircraft actuator fault detection and isolation

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2007
Dan Wang
Abstract In this paper, an adaptive unknown input observer (UIO) approach is developed to detect and isolate aircraft actuator faults. In a multiple-model scheme, a bank of parallel observers are constructed, each of which is based on a model that describes the system in the presence of a particular actuator fault. The observers are constructed based on a modified form of the standard UIO to generate fault-dependant residual signals, such that when a model matches the system, the residual signal will be zero. Otherwise, the residual will be definitely non-zero and governed uniquely by the faulty signal. For locked actuators and loss of actuator effectiveness, in which the locked position and the reduced effectiveness are additional unknowns, we develop an adaptive scheme to estimate these unknown parameters. To the best of our knowledge, this is the first adaptive UIO presented. We prove that the proposed adaptive algorithms guarantee that both the residual signals and the estimation errors of the unknown parameters converge exponentially when a model matches the plant. By further designing a model-matching index, the fault can be isolated accurately. A condition for the approach is that for an nth order system, there must be n independent measurements available. This requirement limits the applicability of our proposed approach. The condition is certainly satisfied by all state-feedback control systems. However, for some other systems, extra efforts may be needed to increase the number of measurements. The method is applied to a linear model of the F-16 aircraft with controller. The results show that the approach is effective. Copyright © 2006 John Wiley & Sons, Ltd. [source]

FAULT DETECTION, ISOLATION AND RECONSTRUCTION FOR DESCRIPTOR SYSTEMS

ASIAN JOURNAL OF CONTROL, Issue 4 2005
Tae-Kyeong Yeu
ABSTRACT In this paper, we consider fault detection, isolation and reconstruction problem for descriptor systems with actuator faults and sensor faults, respectively. When actuator faults exist in the system, the fault detection and isolation (FDI) problem is solved through an unknown input observer regarding remaining faults excluded a specified fault as unknown inputs. Whereas, in existing sensor faults, the fault detection is only achieved by the unknown input observer and residual signals. Since the derivative signal of sensor fault is generated in the error dynamics between the actual system and the derived observer. The main objective of this work attempts the reconstruction of the faults. The reconstruction can be achieved by sliding mode observer including feedforward injection map and compensation signal. Finally, the isolation problem of sensor faults is solved by reconstructing all of the faults. [source]