The Experts below are selected from a list of 8754 Experts worldwide ranked by ideXlab platform
Charles Perrin - One of the best experts on this subject based on the ideXlab platform.
-
continuous State Space Representation of a bucket type rainfall runoff model a case study with the gr4 model using State Space gr4 version 1 0
Geoscientific Model Development, 2018Co-Authors: Léonard Santos, Guillaume Thirel, Charles PerrinAbstract:Abstract. In many conceptual rainfall–runoff models, the water balance differential equations are not explicitly formulated. These differential equations are solved sequentially by splitting the equations into terms that can be solved analytically with a technique called “operator splitting”. As a result, only the solutions of the split equations are used to present the different models. This article provides a methodology to make the governing water balance equations of a bucket-type rainfall–runoff model explicit and to solve them continuously. This is done by setting up a comprehensive State-Space Representation of the model. By representing it in this way, the operator splitting, which makes the structural analysis of the model more complex, could be removed. In this State-Space Representation, the lag functions (unit hydrographs), which are frequent in rainfall–runoff models and make the resolution of the Representation difficult, are first replaced by a so-called “Nash cascade” and then solved with a robust numerical integration technique. To illustrate this methodology, the GR4J model is taken as an example. The substitution of the unit hydrographs with a Nash cascade, even if it modifies the model behaviour when solved using operator splitting, does not modify it when the State-Space Representation is solved using an implicit integration technique. Indeed, the flow time series simulated by the new Representation of the model are very similar to those simulated by the classic model. The use of a robust numerical technique that approximates a continuous-time model also improves the lag parameter consistency across time steps and provides a more time-consistent model with time-independent parameters.
-
State-Space Representation of a bucket-type rainfall-runoff model: a case study with State-Space GR4 (version 1.0)
Geoscientific Model Development Discussions, 2017Co-Authors: Léonard Santos, Guillaume Thirel, Charles PerrinAbstract:In many conceptual rainfall-runoff models, the water balance differential equations are not explicitly formulated. These differential equations are solved sequentially by splitting the equations into terms that can be solved analytically with a technique called "operator splitting". As a result, only the resolutions of the split equations are used to present the different models. This article provides a methodology to make the governing water balance equations of a bucket-type rainfall-runoff model explicit. This is done by setting up a comprehensive State-Space Representation of the model. By representing it in this way, the operator splitting, which complexifies the structural analysis of the model, is removed. In this State-Space Representation, the lag functions (unit hydrographs), which are frequent in this type of model and make the resolution of the Representation difficult, are replaced by a so-called "Nash cascade". This substitution also improves the lag parameter consistency across time steps. To illustrate this methodology, the GR4J model is taken as an example. The flow time series simulated by the new Representation of the model are very similar to those simulated by the classic model. The State-Space Representation provides a more time-consistent model with time-independent parameters.
Léonard Santos - One of the best experts on this subject based on the ideXlab platform.
-
continuous State Space Representation of a bucket type rainfall runoff model a case study with the gr4 model using State Space gr4 version 1 0
Geoscientific Model Development, 2018Co-Authors: Léonard Santos, Guillaume Thirel, Charles PerrinAbstract:Abstract. In many conceptual rainfall–runoff models, the water balance differential equations are not explicitly formulated. These differential equations are solved sequentially by splitting the equations into terms that can be solved analytically with a technique called “operator splitting”. As a result, only the solutions of the split equations are used to present the different models. This article provides a methodology to make the governing water balance equations of a bucket-type rainfall–runoff model explicit and to solve them continuously. This is done by setting up a comprehensive State-Space Representation of the model. By representing it in this way, the operator splitting, which makes the structural analysis of the model more complex, could be removed. In this State-Space Representation, the lag functions (unit hydrographs), which are frequent in rainfall–runoff models and make the resolution of the Representation difficult, are first replaced by a so-called “Nash cascade” and then solved with a robust numerical integration technique. To illustrate this methodology, the GR4J model is taken as an example. The substitution of the unit hydrographs with a Nash cascade, even if it modifies the model behaviour when solved using operator splitting, does not modify it when the State-Space Representation is solved using an implicit integration technique. Indeed, the flow time series simulated by the new Representation of the model are very similar to those simulated by the classic model. The use of a robust numerical technique that approximates a continuous-time model also improves the lag parameter consistency across time steps and provides a more time-consistent model with time-independent parameters.
-
State-Space Representation of a bucket-type rainfall-runoff model: a case study with State-Space GR4 (version 1.0)
Geoscientific Model Development Discussions, 2017Co-Authors: Léonard Santos, Guillaume Thirel, Charles PerrinAbstract:In many conceptual rainfall-runoff models, the water balance differential equations are not explicitly formulated. These differential equations are solved sequentially by splitting the equations into terms that can be solved analytically with a technique called "operator splitting". As a result, only the resolutions of the split equations are used to present the different models. This article provides a methodology to make the governing water balance equations of a bucket-type rainfall-runoff model explicit. This is done by setting up a comprehensive State-Space Representation of the model. By representing it in this way, the operator splitting, which complexifies the structural analysis of the model, is removed. In this State-Space Representation, the lag functions (unit hydrographs), which are frequent in this type of model and make the resolution of the Representation difficult, are replaced by a so-called "Nash cascade". This substitution also improves the lag parameter consistency across time steps. To illustrate this methodology, the GR4J model is taken as an example. The flow time series simulated by the new Representation of the model are very similar to those simulated by the classic model. The State-Space Representation provides a more time-consistent model with time-independent parameters.
Guillaume Thirel - One of the best experts on this subject based on the ideXlab platform.
-
continuous State Space Representation of a bucket type rainfall runoff model a case study with the gr4 model using State Space gr4 version 1 0
Geoscientific Model Development, 2018Co-Authors: Léonard Santos, Guillaume Thirel, Charles PerrinAbstract:Abstract. In many conceptual rainfall–runoff models, the water balance differential equations are not explicitly formulated. These differential equations are solved sequentially by splitting the equations into terms that can be solved analytically with a technique called “operator splitting”. As a result, only the solutions of the split equations are used to present the different models. This article provides a methodology to make the governing water balance equations of a bucket-type rainfall–runoff model explicit and to solve them continuously. This is done by setting up a comprehensive State-Space Representation of the model. By representing it in this way, the operator splitting, which makes the structural analysis of the model more complex, could be removed. In this State-Space Representation, the lag functions (unit hydrographs), which are frequent in rainfall–runoff models and make the resolution of the Representation difficult, are first replaced by a so-called “Nash cascade” and then solved with a robust numerical integration technique. To illustrate this methodology, the GR4J model is taken as an example. The substitution of the unit hydrographs with a Nash cascade, even if it modifies the model behaviour when solved using operator splitting, does not modify it when the State-Space Representation is solved using an implicit integration technique. Indeed, the flow time series simulated by the new Representation of the model are very similar to those simulated by the classic model. The use of a robust numerical technique that approximates a continuous-time model also improves the lag parameter consistency across time steps and provides a more time-consistent model with time-independent parameters.
-
State-Space Representation of a bucket-type rainfall-runoff model: a case study with State-Space GR4 (version 1.0)
Geoscientific Model Development Discussions, 2017Co-Authors: Léonard Santos, Guillaume Thirel, Charles PerrinAbstract:In many conceptual rainfall-runoff models, the water balance differential equations are not explicitly formulated. These differential equations are solved sequentially by splitting the equations into terms that can be solved analytically with a technique called "operator splitting". As a result, only the resolutions of the split equations are used to present the different models. This article provides a methodology to make the governing water balance equations of a bucket-type rainfall-runoff model explicit. This is done by setting up a comprehensive State-Space Representation of the model. By representing it in this way, the operator splitting, which complexifies the structural analysis of the model, is removed. In this State-Space Representation, the lag functions (unit hydrographs), which are frequent in this type of model and make the resolution of the Representation difficult, are replaced by a so-called "Nash cascade". This substitution also improves the lag parameter consistency across time steps. To illustrate this methodology, the GR4J model is taken as an example. The flow time series simulated by the new Representation of the model are very similar to those simulated by the classic model. The State-Space Representation provides a more time-consistent model with time-independent parameters.
Bruno Dehez - One of the best experts on this subject based on the ideXlab platform.
-
Five degrees of freedom linear State-Space Representation of electrodynamic thrust bearings
Journal of Sound and Vibration, 2017Co-Authors: J. Van Verdeghem, Virginie Kluyskens, Bruno DehezAbstract:Electrodynamic bearings can provide stable and contactless levitation of rotors while operating at room temperatures. Depending solely on passive phenomena, specific models have to be developed to study the forces they exert and the resulting rotordynamics. In recent years, models allowing us to describe the axial dynamics of a large range of electrodynamic thrust bearings have been derived. However, these bearings being devised to be integrated into fully magnetic suspensions, the existing models still suffer from restrictions. Indeed, assuming the spin speed as varying slowly, a rigid rotor is characterised by five independent degrees of freedom whereas early models only considered the axial degree. This paper presents a model free of the previous limitations. It consists in a linear State-Space Representation describing the rotor's complete dynamics by considering the impact of the rotor axial, radial and angular displacements as well as the gyroscopic effects. This set of ten equations depends on twenty parameters whose identification can be easily performed through static finite element simulations or quasi-static experimental measurements. The model stresses the intrinsic decoupling between the axial dynamics and the other degrees of freedom as well as the existence of electrodynamic angular torques restoring the rotor to its nominal position. Finally, a stability analysis performed on the model highlights the presence of two conical whirling modes related to the angular dynamics, namely the nutation and precession motions. The former, whose intrinsic stability depends on the ratio between polar and transverse moments of inertia, can be easily stabilised through external damping whereas the latter, which is stable up to an instability threshold linked to the angular electrodynamic cross-coupling stiffness, is less impacted by that damping.
-
Linear State-Space Representation of Heteropolar Electrodynamic Bearings With Radial Magnetic Field
IEEE Transactions on Magnetics, 2016Co-Authors: Corentin Dumont, Virginie Kluyskens, Bruno DehezAbstract:Electrodynamic bearings can operate without active control means. In that case, the dynamic behavior of the bearing relies solely on passive electromagnetic phenomena which can be studied using specific models. In recent years, linear State-Space Representations linking the forces and the relative motion between the stationary and moving parts of such a bearing were obtained without making any assumption on the kinematics of the rotor axis. However, significant limitations remain regarding the topology of the bearing. As regards heteropolar bearings with radial magnetic field, the latter refers to: 1) the number of winding phases; 2) the number of pole pairs of the permanent magnets (PMs) and winding; 3) the presence of PMs at the rotor or at the stator; and 4) the presence of a ferromagnetic yoke attached to the winding. This paper presents a model free of these limitations. Compared with existing models, few additional complexities are introduced in the State-Space Representation. As a result, the dynamics of a wider range of heteropolar electrodynamic bearings can now be studied with a linear model.
-
Linear State-Space Representation of the Axial Dynamics of Electrodynamic Thrust Bearings
IEEE Transactions on Magnetics, 2016Co-Authors: J. Van Verdeghem, Virginie Kluyskens, Corentin Dumont, Bruno DehezAbstract:Electrodynamic bearings can guide rotating objects without contact and active control means. Consequently, their performance relies on passive phenomena that require specific models to be predicted. In the case of electrodynamic thrust bearings, early models involved assumptions on the rotor axial kinematics. This precludes their use for predicting the bearing behavior in dynamic conditions, which is critical when studying stability aspects. Other models require numerically solving of Faraday's current law and the rotor equation of motion to obtain the dynamics of the bearing, thereby excluding a fast identification of its stability properties. Recently, a parametric model without these kinematic assumptions was derived. It consists in a linear State-Space Representation that allows studying the dynamic performance of electrodynamic thrust bearings using conventional system analysis tools. However, this model links up the rotor displacement to the currents in a winding with only two phases. This paper introduces a model free of this limitation, allowing to consider bearings with a higher number of phases, an improved copper usage, and potentially increased performance. Furthermore, the proposed model directly links up the rotor displacement to the force and torque exerted by the thrust bearing without requiring to solve for the currents. This also minimizes the number of State-Space equations and model parameters. Finally, in addition to the modeling aspects, a set of bearing topologies that have not been explored yet and can be studied using the proposed model is introduced.
L. Wanhammar - One of the best experts on this subject based on the ideXlab platform.
-
ISCAS (3) - Implementation of maximally fast ladder wave digital filters using a numerically equivalent State-Space Representation
ISCAS'99. Proceedings of the 1999 IEEE International Symposium on Circuits and Systems VLSI (Cat. No.99CH36349), 1999Co-Authors: O. Gustafsson, L. WanhammarAbstract:Ladder wave digital filters is a class of IIR digital filters derived from double resistively terminated ladder networks, which gives them good stability and low sensitivity to variations in the element values. An approach to design maximally fast bit-serial ladder wave digital filters is presented based on the numerically equivalent State-Space Representation of the signal-flow graph. An algorithm for finding the minimal sample period from the numerically equivalent State-Space Representation is also given. Maximally fast filters is an efficient way to achieve low power consumption on the algorithmic level. Further, we show an approach to map the operations to an optimal hardware structure, that can be implemented using bit-parallel, digit-serial, or bit-serial arithmetic.
-
Implementation of maximally fast ladder wave digital filters using a numerically equivalent State-Space Representation
1999 IEEE International Symposium on Circuits and Systems (ISCAS), 1999Co-Authors: O. Gustafsson, L. WanhammarAbstract:Ladder wave digital filters is a class of IIR digital filters derived from double resistively terminated ladder networks, which gives them good stability and low sensitivity to variations in the element values. An approach to design maximally fast bit-serial ladder wave digital filters is presented based on the numerically equivalent State-Space Representation of the signal-flow graph. An algorithm for finding the minimal sample period from the numerically equivalent State-Space Representation is also given. Maximally fast filters is an efficient way to achieve low power consumption on the algorithmic level. Further, we show an approach to map the operations to an optimal hardware structure, that can be implemented using bit-parallel, digit-serial, or bit-serial arithmetic.