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In this article, we present a local observer based on infinitesimal observability along trajectories. The gain of this observer derives from a dynamical Lyapunov equation. The inputs for which the observer converges are those which render the system observable at each point of the Ω-limit of the unknown trajectory (infinitesimal observability at infinity along trajectories). The performance of the proposed observer is illustrated with an application to DC machine. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the problem of observer design for a class of implicit nonlinear systems of index one. To solve this problem, an implicit observer which is given by an implicit system is usually used. The implementation of this kind of observer requires an optimization algorithm to solve at each time the algebraic constraints. Alternatively, an explicit observer which is described by an ordinary differential equation can be used. The advantage of this approach is that no optimization algorithm is required. Moreover the observer initialization may be done outside the constraints. In this paper it is shown that, under some conditions, the existence of an implicit observer implies the existence of an explicit one. Then, an explicit observer is given for implicit state affine systems whose dynamic involves an additional nonlinear term depending on the input, the output and the implicit variable. [Copyright &y& Elsevier]

Abstract: The problem of designing an unknown input observer for linear systems and its application to fault detection is widely studied in the literature. For nonlinear systems, only subclasses of nonlinear systems and sufficient conditions have been stated. In this paper an unknown input observer design for state affine systems is considered. Based on the geometric approach, a necessary and sufficient condition is given for the existence of an unknown input observer. [Copyright &y& Elsevier]

In-line monitoring of the primary drying of the lyophilization process of a pharmaceutical product in vials is addressed in this article. A soft sensor (observer) based on the high gain concept is designed to this purpose. The proposed observer combines the physical measure of the frozen product temperature at the bottom of the vial with a simplified mathematical model of the process. This approach allows the continuous estimation of the entire temperature profile of the product and the monitoring of the state of progression of the primary drying phase. The main issues arising in the design of this observer are discussed. A detailed and experimentally validated mono-dimensional model is used as a source of measured data, in order to compare and validate by means of numerical simulations the results provided by the soft sensor. Finally, the performance of the high gain observer is compared with that of a Kalman filter-based observer previously proposed for the same process, evidencing the advantages of the high gain approach. [ABSTRACT FROM AUTHOR]

This paper is focused on the monitoring of the primary drying phase of the lyophilisation process of pharmaceuticals in vial. Monitoring is required to ensure that the maximum temperature of the product is maintained at a safe value in order to avoid denaturation, and the position of the moving front of sublimation has to be monitored since its evolution gives the state of progression of the primary drying. Furthermore, the information coming from the monitoring system, which includes the estimation of the transport coefficients, can be used in a control loop designed to minimise the drying time beside ensuring product quality. To this purpose, a soft-sensor (observer) has been developed, based on the extended Kalman filter algorithm: it requires a model of the process (a simplified model is used in order to reduce the computational load) and some physical measurements (in this case the temperature of the product at the bottom of the vial, that can be measured by a thermocouple). The main issues arising in the design of this observer have been discussed. A detailed mono-dimensional model experimentally validated has been used at first to compare the results provided by the observer by means of numerical simulations, and then the results obtained in a pilot freeze-dryer are shown. [ABSTRACT FROM AUTHOR]

Summary: The paper presents an investigation of a new electromagnetic signal for the diagnosis of the doubly fed induction generator (DFIG). The signal is acquired by using a dedicated sensor located on the bus surface of the DC link in the DFIG system. To demonstrate the feasibility and efficiency of applying this signal in condition monitoring of DFIG, a procedure of diagnosing stator asymmetrical fault is shown. Physical phenomena of the defect are first analysed to obtain the harmonic signature. Afterwards, the benchmark will be processed with the defect to extract the specific signature in the DC bus magnetic field. The experiment results show that the proposed signal can be efficiently applied in the diagnosis of wind power generators. [ABSTRACT FROM AUTHOR]

We study controlled systems which are uniformly observable and differentially observable with an order larger than the system state dimension. We establish that they may be transformed into a (partial) triangular canonical form but with possibly non locally Lipschitz functions. We characterize the points where this Lipschitzness may be lost and investigate the link with uniform infinitesimal observability. [ABSTRACT FROM AUTHOR]