https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Tue, 19 May 2026 13:32:26 GMT 2026-05-19T13:32:26Z http://hdl.handle.net/10985/9952 Phénomènes dynamiques en usinage : Prédiction de l’état géométrique des surfaces usinées COFFIGNAL, Gérard; DUCHEMIN, Jérôme; ILLOUL, Lounès; GENGEMBRE, Christophe; LORONG, Philippe; GUSKOV, Mikhail Présentation concernant la modélisation des phénomènes dynamiques en usinage. Cette modélisation a pour particularité de permettre la prédiction de la géométrie des surfaces usinées (défauts de forme, d'ondulation) que la pièce soit considérée comme rigide ou flexible. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/9952 2013-01-01T00:00:00Z COFFIGNAL, Gérard DUCHEMIN, Jérôme ILLOUL, Lounès GENGEMBRE, Christophe LORONG, Philippe GUSKOV, Mikhail Présentation concernant la modélisation des phénomènes dynamiques en usinage. Cette modélisation a pour particularité de permettre la prédiction de la géométrie des surfaces usinées (défauts de forme, d'ondulation) que la pièce soit considérée comme rigide ou flexible. http://hdl.handle.net/10985/11599 A reconfigurable damage-tolerant controller based on a modal double-loop framework GENARI, Helói F.G; COFFIGNAL, Gérard; NOBREGA, Euripedes; MECHBAL, Nazih Active vibration control of flexible structures has received considerable attention in the latest decades. However, several related control problems remain open to new investigations such as robust performance, spillover instability, and structural changes due to damage. Specifically in the case of damage, it may significantly aggravate closed-loop performance. Damage-tolerant active control is a recent research area that includes structural damage effect reduction in the controller design requirements. This paper presents a novel control method based on a modal double-loop controller design, aiming for vibration reduction of noncollocated flexible structures subject to damage and encompassing online reconfigurability. The first controller is designed for the healthy system in order to comply with predefined performance and robustness requirements, based on modal H∞H∞ norm. The second controller complements the closed-loop performance if the structure is damaged. A reconfigurable modal technique is adopted to design the second controller, using online modal structural parameter change information to update the controller. To assess the proposed method, finite element models are developed for a case study structure, including health and damage conditions. Results show the effectiveness of the methodology along with performance improvement compared to single-loop controllers based on regular H∞H∞ and modal H∞H∞ approaches. Sun, 01 Jan 2017 00:00:00 GMT http://hdl.handle.net/10985/11599 2017-01-01T00:00:00Z GENARI, Helói F.G COFFIGNAL, Gérard NOBREGA, Euripedes MECHBAL, Nazih Active vibration control of flexible structures has received considerable attention in the latest decades. However, several related control problems remain open to new investigations such as robust performance, spillover instability, and structural changes due to damage. Specifically in the case of damage, it may significantly aggravate closed-loop performance. Damage-tolerant active control is a recent research area that includes structural damage effect reduction in the controller design requirements. This paper presents a novel control method based on a modal double-loop controller design, aiming for vibration reduction of noncollocated flexible structures subject to damage and encompassing online reconfigurability. The first controller is designed for the healthy system in order to comply with predefined performance and robustness requirements, based on modal H∞H∞ norm. The second controller complements the closed-loop performance if the structure is damaged. A reconfigurable modal technique is adopted to design the second controller, using online modal structural parameter change information to update the controller. To assess the proposed method, finite element models are developed for a case study structure, including health and damage conditions. Results show the effectiveness of the methodology along with performance improvement compared to single-loop controllers based on regular H∞H∞ and modal H∞H∞ approaches. http://hdl.handle.net/10985/11655 A modal H∞-norm-based performance requirement for damage-tolerant active controller design GENARI, Helói F.G; COFFIGNAL, Gérard; NOBREGA, Euripedes; MECHBAL, Nazih Damage-tolerant active control (DTAC) is a recent research area that encompasses control design methodologies resulting from the application of fault-tolerant control methods to vibration control of structures subject to damage. The possibility of damage occurrence is not usually considered in the active vibration control design requirements. Damage changes the structure dynamics, which may produce unexpected modal behavior of the closed-loop system, usually not anticipated by the controller design approaches. A modal H∞H∞ norm and a respective robust controller design framework were recently introduced, and this method is here extended to face a new DTAC strategy implementation. Considering that damage affects each vibration mode differently, this paper adopts the modal H∞H∞ norm to include damage as a design requirement. The basic idea is to create an appropriate energy distribution over the frequency range of interest and respective vibration modes, guaranteeing robustness, damage tolerance, and adequate overall performance, taking into account that it is common to have previous knowledge of the structure regions where damage may occur during its operational life. For this purpose, a structural health monitoring technique is applied to evaluate modal modifications caused by damage. This information is used to create modal weighing matrices, conducting to the modal H∞H∞ controller design. Finite element models are adopted for a case study structure, including different damage severities, in order to validate the proposed control strategy. Results show the effectiveness of the proposed methodology with respect to damage tolerance. Sun, 01 Jan 2017 00:00:00 GMT http://hdl.handle.net/10985/11655 2017-01-01T00:00:00Z GENARI, Helói F.G COFFIGNAL, Gérard NOBREGA, Euripedes MECHBAL, Nazih Damage-tolerant active control (DTAC) is a recent research area that encompasses control design methodologies resulting from the application of fault-tolerant control methods to vibration control of structures subject to damage. The possibility of damage occurrence is not usually considered in the active vibration control design requirements. Damage changes the structure dynamics, which may produce unexpected modal behavior of the closed-loop system, usually not anticipated by the controller design approaches. A modal H∞H∞ norm and a respective robust controller design framework were recently introduced, and this method is here extended to face a new DTAC strategy implementation. Considering that damage affects each vibration mode differently, this paper adopts the modal H∞H∞ norm to include damage as a design requirement. The basic idea is to create an appropriate energy distribution over the frequency range of interest and respective vibration modes, guaranteeing robustness, damage tolerance, and adequate overall performance, taking into account that it is common to have previous knowledge of the structure regions where damage may occur during its operational life. For this purpose, a structural health monitoring technique is applied to evaluate modal modifications caused by damage. This information is used to create modal weighing matrices, conducting to the modal H∞H∞ controller design. Finite element models are adopted for a case study structure, including different damage severities, in order to validate the proposed control strategy. Results show the effectiveness of the proposed methodology with respect to damage tolerance. http://hdl.handle.net/10985/20075 A general method to accurately simulate material removal in virtual machining of flexible workpieces COFFIGNAL, Gérard; ILLOUL, Lounes; LORONG, Philippe Multi-axis milling and other computer numerical control machining processes allow us to create very complex geometries and thin parts. In this context, virtual machining is a powerful tool, but the simultaneous vibrations of the tool and workpiece are not easy to define and take into account. This paper presents a general method with which to simulate material removal when both the workpiece and tool are assumed to be non-rigid. We consider that they both vibrate when we define the Boolean chip. This is not usually considered with the aim of predicting the machined surface vibrations and the resulting geometric defects including roughness. By extending the material frame associated with the non-rigid workpiece, our method precisely defines the material removal for any tool or workpiece. It then allows us to establish a method of deriving efficient numerical approximations with which to simulate a succession of machining operations from roughening to finishing. Two kinds of finite element approximations are linked. One is a classical elastic finite element model including damping. The second, which is kinematically linked to the first, accurately describes the relative motion of each part of the tool with respect to the workpiece, and ensures the description of material removal and related forces. Two industrial examples show the potential of the method. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/20075 2015-01-01T00:00:00Z COFFIGNAL, Gérard ILLOUL, Lounes LORONG, Philippe Multi-axis milling and other computer numerical control machining processes allow us to create very complex geometries and thin parts. In this context, virtual machining is a powerful tool, but the simultaneous vibrations of the tool and workpiece are not easy to define and take into account. This paper presents a general method with which to simulate material removal when both the workpiece and tool are assumed to be non-rigid. We consider that they both vibrate when we define the Boolean chip. This is not usually considered with the aim of predicting the machined surface vibrations and the resulting geometric defects including roughness. By extending the material frame associated with the non-rigid workpiece, our method precisely defines the material removal for any tool or workpiece. It then allows us to establish a method of deriving efficient numerical approximations with which to simulate a succession of machining operations from roughening to finishing. Two kinds of finite element approximations are linked. One is a classical elastic finite element model including damping. The second, which is kinematically linked to the first, accurately describes the relative motion of each part of the tool with respect to the workpiece, and ensures the description of material removal and related forces. Two industrial examples show the potential of the method. http://hdl.handle.net/10985/8234 Optimal Sensors Placement to Enhance Damage Detection in Composite Plates FENDZI, Claude; MOREL, Julien; COFFIGNAL, Gérard; MECHBAL, Nazih; GUSKOV, Mikhail; RÉBILLAT, Marc This paper examines an important challenge in ultrasonic structural health monitoring (SHM), which is the problem of the optimal placement of sensors in order to accurately detect and localize damages. The goal of this study is to enhance damage detection through an optimal sensor placement (OSP) algorithm. The problem is formulated as a global optimization problem, where the objective function to be maximized is evaluated by a ray tracing approach, which approximately models Lamb waves propagation. A genetic algorithm (GA) is then used to solve this optimization problem. Simulations and experiments were conducted to validate the proposed method on a carbon epoxy composite plate. Results show the effectiveness and the advantages of the proposed method as a tool for OSP with reasonable computation time. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8234 2014-01-01T00:00:00Z FENDZI, Claude MOREL, Julien COFFIGNAL, Gérard MECHBAL, Nazih GUSKOV, Mikhail RÉBILLAT, Marc This paper examines an important challenge in ultrasonic structural health monitoring (SHM), which is the problem of the optimal placement of sensors in order to accurately detect and localize damages. The goal of this study is to enhance damage detection through an optimal sensor placement (OSP) algorithm. The problem is formulated as a global optimization problem, where the objective function to be maximized is evaluated by a ray tracing approach, which approximately models Lamb waves propagation. A genetic algorithm (GA) is then used to solve this optimization problem. Simulations and experiments were conducted to validate the proposed method on a carbon epoxy composite plate. Results show the effectiveness and the advantages of the proposed method as a tool for OSP with reasonable computation time. http://hdl.handle.net/10985/9221 Application of a Combined Active Control and Fault Detection Scheme to an Active Composite Flexible Structure. VERGÉ, Michel; COFFIGNAL, Gérard; GANAPATHI, Manickam; MECHBAL, Nazih In this paper, the problem of increasing reliability of active control procedure is considered. Indeed, a design method of rejection perturbation in presence of potentially faults, on a flexible structure with integrated piezo-ceramics, is presented. The piezo-ceramics are used as actuators and sensors. A single unit based solution, which handles both control action and fault diagnosis is proposed. The algorithm uses H∞ optimization techniques. A full order model of the structure is first obtained via both finite-element (FE) approach and identification procedure. This model is then reduced in order to be used in our robust approach. By a suitable choice of weightings functions, the provided method is able to reject disturbance robustly and to estimate occurred faults. The case of sensors and actuators faults is discussed. The choice of weightings for diagnosis and control systems is also tackled. Finally, the effectiveness of this integrated method is confirmed by both simulation and experimental results. Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/10985/9221 2006-01-01T00:00:00Z VERGÉ, Michel COFFIGNAL, Gérard GANAPATHI, Manickam MECHBAL, Nazih In this paper, the problem of increasing reliability of active control procedure is considered. Indeed, a design method of rejection perturbation in presence of potentially faults, on a flexible structure with integrated piezo-ceramics, is presented. The piezo-ceramics are used as actuators and sensors. A single unit based solution, which handles both control action and fault diagnosis is proposed. The algorithm uses H∞ optimization techniques. A full order model of the structure is first obtained via both finite-element (FE) approach and identification procedure. This model is then reduced in order to be used in our robust approach. By a suitable choice of weightings functions, the provided method is able to reject disturbance robustly and to estimate occurred faults. The case of sensors and actuators faults is discussed. The choice of weightings for diagnosis and control systems is also tackled. Finally, the effectiveness of this integrated method is confirmed by both simulation and experimental results. http://hdl.handle.net/10985/11654 Damage-tolerant active control using a modal H∞H∞-norm-based methodology GENARI, Helói F.G; COFFIGNAL, Gérard; NOBREGA, Euripedes; MECHBAL, Nazih A new approach for vibration reduction of flexible structures subject to damage is here proposed, based on modal H∞H∞-norm control. Considering that structural damage provokes different effects on each vibration mode, the proposed method concentrates the control action on modes that are indeed suffering the worst damage consequences. For this purpose, a new modal H∞H∞ norm is introduced, weighing each mode according to control design convenience. Based on this norm, a regular H∞H∞ controller design is applied, using the linear matrix inequality approach. Simulated and experimental results show significant advantages of the proposed methodology over the regular H∞H∞ approach, including damage tolerance. Sun, 01 Jan 2017 00:00:00 GMT http://hdl.handle.net/10985/11654 2017-01-01T00:00:00Z GENARI, Helói F.G COFFIGNAL, Gérard NOBREGA, Euripedes MECHBAL, Nazih A new approach for vibration reduction of flexible structures subject to damage is here proposed, based on modal H∞H∞-norm control. Considering that structural damage provokes different effects on each vibration mode, the proposed method concentrates the control action on modes that are indeed suffering the worst damage consequences. For this purpose, a new modal H∞H∞ norm is introduced, weighing each mode according to control design convenience. Based on this norm, a regular H∞H∞ controller design is applied, using the linear matrix inequality approach. Simulated and experimental results show significant advantages of the proposed methodology over the regular H∞H∞ approach, including damage tolerance. http://hdl.handle.net/10985/8898 Simulation of a finishing operation : milling of a turbine blade and influence of damping COFFIGNAL, Gérard; BALMES, Etienne; TEXIER, Anthony; LORONG, Philippe; GUSKOV, Mikhail Milling is used to create very complex geometries and thin parts, such as turbine blades. Irreversible geometric defects may appear during finishing operations when a high surface quality is expected. Relative vibrations between the tool and the workpiece must be as small as possible, while tool/workpiece interactions can be highly non-linear. A general virtual machining approach is presented and illustrated. It takes into account the relative motion and vibrations of the tool and the workpiece. Both deformations of the tool and the workpiece are taken into account. This allows predictive simulations in the time domain. As an example the effect of damping on the behavior during machining of one of the 56 blades of a turbine disk is analysed in order to illustrate the approach potential. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/10985/8898 2012-01-01T00:00:00Z COFFIGNAL, Gérard BALMES, Etienne TEXIER, Anthony LORONG, Philippe GUSKOV, Mikhail Milling is used to create very complex geometries and thin parts, such as turbine blades. Irreversible geometric defects may appear during finishing operations when a high surface quality is expected. Relative vibrations between the tool and the workpiece must be as small as possible, while tool/workpiece interactions can be highly non-linear. A general virtual machining approach is presented and illustrated. It takes into account the relative motion and vibrations of the tool and the workpiece. Both deformations of the tool and the workpiece are taken into account. This allows predictive simulations in the time domain. As an example the effect of damping on the behavior during machining of one of the 56 blades of a turbine disk is analysed in order to illustrate the approach potential. http://hdl.handle.net/10985/11239 A data-driven temperature compensation approach for Structural Health Monitoring using Lamb waves FENDZI, Claude; COFFIGNAL, Gérard; MECHBAL, Nazih; GUSKOV, Mikhail; RÉBILLAT, Marc This paper presents a temperature compensation method for Lamb wave structural health monitoring. The proposed approach considers a representation of the piezo-sensor signal through its Hilbert transform that allows one to extract the amplitude factor and the phase shift in signals caused by temperature changes. An ordinary least square (OLS) algorithm is used to estimate these unknown parameters. After estimating these parameters at each temperature in the operating range, linear functional relationships between the temperature and the estimated parameters are derived using the least squares method. A temperature compensation model is developed based on this linear relationship that allows one to reconstruct sensor signals at any arbitrary temperature. The proposed approach is validated numerically and experimentally for an anisotropic composite plate at different temperatures ranging from Formula to Formula . A close match is found between the measured signals and the reconstructed ones. This approach is interesting as it needs only a limited set of piezo-sensor signals at different temperatures for model training and temperature compensation at any arbitrary temperature. Damage localization results after temperature compensation demonstrate its robustness and effectiveness. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11239 2016-01-01T00:00:00Z FENDZI, Claude COFFIGNAL, Gérard MECHBAL, Nazih GUSKOV, Mikhail RÉBILLAT, Marc This paper presents a temperature compensation method for Lamb wave structural health monitoring. The proposed approach considers a representation of the piezo-sensor signal through its Hilbert transform that allows one to extract the amplitude factor and the phase shift in signals caused by temperature changes. An ordinary least square (OLS) algorithm is used to estimate these unknown parameters. After estimating these parameters at each temperature in the operating range, linear functional relationships between the temperature and the estimated parameters are derived using the least squares method. A temperature compensation model is developed based on this linear relationship that allows one to reconstruct sensor signals at any arbitrary temperature. The proposed approach is validated numerically and experimentally for an anisotropic composite plate at different temperatures ranging from Formula to Formula . A close match is found between the measured signals and the reconstructed ones. This approach is interesting as it needs only a limited set of piezo-sensor signals at different temperatures for model training and temperature compensation at any arbitrary temperature. Damage localization results after temperature compensation demonstrate its robustness and effectiveness.