Publications of Ghislain Raze
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See detailPassive control of multiple structural resonances with piezoelectric vibration absorbers
Raze, Ghislain ULiege; Dietrich, Jennifer ULiege; Kerschen, Gaëtan ULiege

in Journal of Sound and Vibration (2021), 515

A novel sequential tuning procedure for passive piezoelectric shunts targeting multiple structural modes is proposed in this work. The control authority on each targeted mode can be quantitatively chosen ... [more ▼]

A novel sequential tuning procedure for passive piezoelectric shunts targeting multiple structural modes is proposed in this work. The control authority on each targeted mode can be quantitatively chosen ab initio and is shown to be limited by passivity requirements, which highlights the fundamental limitations of multimodal piezoelectric shunts. Based on effective characteristics of the piezoelectric system around resonance, electrical damping ratios and resonance frequencies are derived using well-established single-mode formulae from the literature, thereby fully specifying the characteristics of the shunt impedance. The proposed approach is numerically verified and experimentally validated on piezoelectric beams by emulating the shunt with a digital vibration absorber. [less ▲]

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See detailExperimental study on active tuned inerter-dampers: application to active damping using force feedback
Zhao, Guoying; Paknejad, Ahmad; Raze, Ghislain ULiege et al

in Journal of Sound and Vibration (2021), 514

In this paper, a modified active tuned inerter damper concept which is more suitable for practical applications is proposed. The proposed device is composed of a pair of collocated reactive actuator and ... [more ▼]

In this paper, a modified active tuned inerter damper concept which is more suitable for practical applications is proposed. The proposed device is composed of a pair of collocated reactive actuator and force sensor. A second-order low-pass filter and a proportional term are combined to form the controller. The equivalent mechanical model of the controller's components is derived in order to better interpret the coupled system. The second-order low-pass filter is mechanically equivalent to a pure mechanical network which comprises an inerter, a spring and a damper connected in parallel. The proportional term mechanically represents a spring which is connected in series with the inherent actuator spring. Simple regressions are derived based on the ℋ∞ optimisation criterion wherein the optimal feedback gains are calculated to minimise the maximal response of the driving-point receptance of the system. The numerical study is also experimentally validated. The obtained results are found to correspond well with the theoretical developments. [less ▲]

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See detailH∞ optimization of multiple tuned mass dampers for multimodal vibration control
Raze, Ghislain ULiege; Kerschen, Gaëtan ULiege

in Computers and Structures (2021), 248

In this paper, a new computational method for the purpose of multimodal vibration mitigation using multiple tuned mass dampers is proposed. Classically, the minimization of the maximum amplitude is ... [more ▼]

In this paper, a new computational method for the purpose of multimodal vibration mitigation using multiple tuned mass dampers is proposed. Classically, the minimization of the maximum amplitude is carried out using direct H∞ optimization. However, as shall be shown in the paper, this approach is prone to being trapped in local minima, in view of the nonsmooth character of the problem at hand. This is why this paper presents an original alternative to this approach through norm-homotopy optimization. This approach, combined with an efficient technique to compute the structural response, is shown to outperform direct H∞ optimization in terms of speed and performance. Essentially, the outcome of the algorithm leads to the concept of all-equal-peak design for which all the controlled peaks are equal in amplitude. This unique design is new with respect to the existing body of knowledge. [less ▲]

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See detailPiezoelectric Digital Vibration Absorbers for Multimodal Vibration Mitigation of Complex Mechanical Structures
Raze, Ghislain ULiege

Doctoral thesis (2021)

Engineering structures are becoming lighter and more complex to accommodate the ever-increasing demand for performance and to comply with stringent environmental regulations. This trend comes with several ... [more ▼]

Engineering structures are becoming lighter and more complex to accommodate the ever-increasing demand for performance and to comply with stringent environmental regulations. This trend comes with several challenges, one of which is the increased susceptibility to high-amplitude vibrations. These vibrations can be detrimental to structural performance and lifetime, and may sometimes even threaten safety. Passive and active vibration reduction techniques can provide a solution to this issue. Among the possibilities, piezoelectric damping is an attractive option, due to its compact and lightweight character, its reduced cost and its tunability. This technique uses the ability of a piezoelectric transducer to transform part of its mechanical energy into electrical energy. The converted energy can then be dissipated by connecting a shunt circuit to the transducer. However, the difficulty of realizing such circuits limits the broad applicability of piezoelectric shunting. This doctoral thesis investigates the potential of replacing the electrical circuit comprising classical components such as resistors and inductors by a digital unit and a current source, thereby creating a digital vibration absorber (DVA). Virtually any circuit can be emulated with a digital controller, providing this approach with an extreme versatility for vibration mitigation of complex mechanical structures. In this regard, the DVA is first analyzed in terms of power consumption and stability of the controlled system. Then, effective and easy-to-use tuning approaches for the control of multiple structural modes either with passive electrical circuits or a DVA are proposed, namely a passivity-based tuning of shunt circuits, a modal-based synthesis of electrical networks interconnecting multiple piezoelectric transducers, and a numerical norm-homotopy optimization resulting in an all-equal-peak design. These techniques are eventually applied and adapted to real-life structures with potentially complex dynamics. Specifically, effective vibration mitigation is demonstrated on structures exhibiting nonlinear behaviors and high modal density. [less ▲]

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See detailActive nonlinear energy sink using force feedback under transient regime
Zhao, Guoying; Raze, Ghislain ULiege; Paknejad, Ahmad et al

in Nonlinear Dynamics (2020), 102(3), 1319-1336

In this paper, an active nonlinear energy sink (ANES) based on force feedback is investigated. The proposed device is composed of a pair of collocated actuator and force sensor. The control law is ... [more ▼]

In this paper, an active nonlinear energy sink (ANES) based on force feedback is investigated. The proposed device is composed of a pair of collocated actuator and force sensor. The control law is implemented by feeding back the output of the force sensor, through one single and one double integrator of its cube. Its working principle can be understood by an equivalent mechanical network which consists of a dashpot, an inerter and a cube root inerter. Although the nonlinear assignment between the spring and mass or inerter quantities is different from that of traditional nonlinear energy sinks (NESs), it is found that ANES and NES behave similarly in terms of their slow- scale dynamics and the vibration mitigation effectiveness. The damping mechanism of ANES through targeted energy transfer and resonance capture cascade is demonstrated. Closed-form expressions for properly tuning the feedback gains are derived. Numerical simulations are performed to validate the analytical analysis. [less ▲]

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See detailActive vibration damping of bladed structures
Paknejad, Ahmad; Raze, Ghislain ULiege; Zhao, Guoying et al

in Desmet, Wim; Pluymers, Bert; Moens, David (Eds.) et al Proceedings of ISMA 2020 - International Conference on Noise and Vibration Engineering and USD 2020 - International Conference on Uncertainty in Structural Dynamics (2020, October)

This paper investigates the potential of using an active control system to mitigate broadband vibrations of bladed structures. Piezoelectric patches are used for both sensing the motion and actuating the ... [more ▼]

This paper investigates the potential of using an active control system to mitigate broadband vibrations of bladed structures. Piezoelectric patches are used for both sensing the motion and actuating the control force. To maximize control authority, the size and location of piezoelectric patches are optimized based on maximizing the strain energy. Two new designs of active control law, which are inspired by force-feedback configuration, are developed for the plant having alternating pole-zero pairs in the frequency response function (FRF). Numerical simulations are performed to assess the performance of the designed control system in terms of the closed-loop damping of the system with high modal density. The parameters of the control law are tuned based on maximizing the minimum damping of the first family of modes. Experimental tests are performed to validate the numerical design. [less ▲]

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See detailPassive control of a periodic structure using a network of periodically-coupled piezoelectric shunt circuits
Raze, Ghislain ULiege; Dietrich, Jennifer ULiege; Paknejad, Ahmad et al

in Desmet, Wim; Pluymers, Bert; Moens, David (Eds.) et al Proceedings of ISMA 2020 - International Conference on Noise and Vibration Engineering and USD 2020 - International Conference on Uncertainty in Structural Dynamics (2020, October)

This work proposes a method to synthesize an electrical network which, when coupled to a complex periodic or nearly-periodic structure through an array of piezoelectric transducers, provides multimodal ... [more ▼]

This work proposes a method to synthesize an electrical network which, when coupled to a complex periodic or nearly-periodic structure through an array of piezoelectric transducers, provides multimodal vibration mitigation. The structure is decomposed into multiple substructures and a reduced-order model is built for each of them. From these models, it is possible to synthesize a network with simple algebraic transformations. The link between these transformations and electromechanical modal coupling is derived, and conditions are given in order to guarantee the passivity of the electrical network. The proposed approach is illustrated on a bladed rail, for which damping of one or multiple families of blade modes is demonstrated. [less ▲]

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See detailA Digital Absorber for Nonlinear Vibration Mitigation
Raze, Ghislain ULiege; Guichaux, Sylvain; Jadoul, Andy et al

in Kerschen, Gaëtan; Brake, Matthew; Renson, Ludovic (Eds.) Nonlinear Structures & Systems, Volume 1 (2020, September 13)

In this study, a digital impedance is used to realize both a linear and a nonlinear piezoelectric tuned vibration absorber in order to mitigate the vibrations of a nonlinear structure. The digital ... [more ▼]

In this study, a digital impedance is used to realize both a linear and a nonlinear piezoelectric tuned vibration absorber in order to mitigate the vibrations of a nonlinear structure. The digital processing unit enables the synthesis of impedances with arbitrary functional forms, thereby easing the implementation of nonlinear absorbers. The superior performance of the nonlinear absorber over its linear counterpart is demonstrated experimentally. Various nonlinear functional forms are also tested in the absorber and illustrate the relevance of the principle of similarity (i.e. the same nonlinear functional form as that in the host structure should be used in the absorber). [less ▲]

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See detailMultimodal vibration damping using a simplified current blocking shunt circuit
Raze, Ghislain ULiege; Paknejad, Ahmad; Zhao, Guoying et al

in Journal of Intelligent Material Systems and Structures (2020), 31(14), 1731-1747

The tuning of a simplified current blocking shunt circuit able to mitigate the vibration amplitude of multiple structural resonances is addressed in this paper. The proposed strategy exploits the two-port ... [more ▼]

The tuning of a simplified current blocking shunt circuit able to mitigate the vibration amplitude of multiple structural resonances is addressed in this paper. The proposed strategy exploits the two-port network formalism in combination with physically-motivated approximations to tune sequentially the electrical elements of the different branches of the shunt circuit. The resulting tuning method does not resort to optimization algorithms and requires only the knowledge of quantities that are easy to measure experimentally. It is demonstrated both numerically and experimentally using a piezoelectric beam. [less ▲]

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See detailActive nonlinear inerter damper for vibration mitigation of Duffing oscillators
Zhao, Guoying; Raze, Ghislain ULiege; Paknejad, Ahmad et al

in Journal of Sound and Vibration (2020), 473

In this paper, a nonlinear active damping strategy based on force feedback is proposed. The proposed device is composed of a pair of collocated actuator and force sensor. The control law is formed by ... [more ▼]

In this paper, a nonlinear active damping strategy based on force feedback is proposed. The proposed device is composed of a pair of collocated actuator and force sensor. The control law is formed by feeding back the output of the force sensor, through one single, one double integrator and another double integrator of its cube. An equivalent mechanical network which consists of a dashpot, an inerter and a cube root inerter is developed to enable a straightforward interpretation of the physics behind. Closed-form expressions for the optimal feedback gains are derived. Numerical validations are performed to demonstrate the proposed control strategy. [less ▲]

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See detailMultimodal vibration damping of nonlinear structures using multiple nonlinear absorbers
Raze, Ghislain ULiege; Kerschen, Gaëtan ULiege

in International Journal of Non-Linear Mechanics (2020), 119

This paper presents a tuning methodology for multiple nonlinear vibration absorbers that mitigate several nonlinear resonances simultaneously. Specifically, the objective is to maintain equal peaks in the ... [more ▼]

This paper presents a tuning methodology for multiple nonlinear vibration absorbers that mitigate several nonlinear resonances simultaneously. Specifically, the objective is to maintain equal peaks in the frequency response for all controlled resonances in an as large as possible range of forcing amplitudes. Relying on an all-equal-peak design for linear regimes of motion and adopting a principle of similarity for nonlinear regimes, a semi-analytical expression of the absorber coefficients is derived using first-order harmonic balance and a series expansion of the harmonic coefficients. The proposed methodology is demonstrated numerically using two spring-mass systems. [less ▲]

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See detailActive Nonlinear Energy Sink Using Integral Force Feedback
Zhao, Guoying; Raze, Ghislain ULiege; Paknejad, Ahmad et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXVIII (2020, February)

Excessive vibrations in mechanical structures can cause many problems such as reducing structural integrity and compromising the commissioning of precise instruments. Tuned mass dampers (TMDs) are often ... [more ▼]

Excessive vibrations in mechanical structures can cause many problems such as reducing structural integrity and compromising the commissioning of precise instruments. Tuned mass dampers (TMDs) are often employed to suppress undesirable vibrations. However, they are known to be effective only in a frequency band limited around one vibration mode and to be sensitive to the variation of primary structures. Alternatively, nonlinear energy sinks (NESs) can be used as they do not have a preferential resonance frequency making them more robust and capable of damping multiple resonances. In this paper, the performance of an active nonlinear energy sink (ANES) is investigated, which is realized using a novel integral force feedback controller. Unlike the traditional NES, which is realized by a cubic spring, a dashpot and an inertial mass, the proposed ANES is equivalent to a mechanical system which consists of a cubic root inerter, a dashpot and a linear spring. Because of the full analogy with a mechanical network, the stability of the proposed active system is guaranteed. Although the form of the proposed ANES is different from that of traditional NESs, it is found that the targeted energy transfer phenomenon also occurs with the ANES and the control effectiveness is similar to traditional NESs. [less ▲]

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See detailA digital nonlinear piezoelectric tuned vibration absorber
Raze, Ghislain ULiege; Jadoul, Andy; Guichaux, Sylvain et al

in Smart Materials and Structures (2020), 29(1), 015007

This study presents the practical realization of a digital vibration absorber that, owing to the flexibility provided by the digital unit, synthesizes linear and nonlinear shunt circuits. The absorber ... [more ▼]

This study presents the practical realization of a digital vibration absorber that, owing to the flexibility provided by the digital unit, synthesizes linear and nonlinear shunt circuits. The absorber, composed of a microprocessor and a current source, is connected to the host structure with piezoelectric patches. The performance of both circuits is compared experimentally for a nonlinear host structure. The superiority of a properly-tuned nonlinear absorber over its linear counterpart is validated, but the limits of the nonlinear absorber are also explored. Moreover, the accuracy of the tuning procedure and formulas is assessed through experimental parametric studies. [less ▲]

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See detailNonlinear positive position feedback control for mitigation of nonlinear vibrations
Zhao, Guoying ULiege; Paknejad, Ahmad; Raze, Ghislain ULiege et al

in Mechanical Systems and Signal Processing (2019), 132

This paper investigates the potential of using a nonlinear positive position feedback controller for vibration mitigation of a Duffing oscillator. The proposed controller is designed based on the ... [more ▼]

This paper investigates the potential of using a nonlinear positive position feedback controller for vibration mitigation of a Duffing oscillator. The proposed controller is designed based on the principle of similarity which states that anti-vibration devices should be governed by the same equations as those of the host structure. Closed-form expressions for the H∞ optimal control parameters that minimise the maximal response of the structure are firstly derived for the linear positive position feedback controller and then extended to the nonlinear counterpart. The harmonic balance method is employed to approximate the analytical solutions. Both numerical simulations and experimental validations are performed to demonstrate the proposed control strategy. [less ▲]

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See detailA Multimodal Nonlinear Tuned Vibration Absorber
Raze, Ghislain ULiege; Kerschen, Gaëtan ULiege

in Kovacic, Ivana; Lenci, Stefano (Eds.) IUTAM Symposium on Exploiting Nonlinear Dynamics for Engineering Systems (2019, July 25)

This paper presents a tuning methodology to design a vibration absorber able to mitigate the vibratory amplitude of multiple resonances of a nonlinear structure. The linear characteristics of the absorber ... [more ▼]

This paper presents a tuning methodology to design a vibration absorber able to mitigate the vibratory amplitude of multiple resonances of a nonlinear structure. The linear characteristics of the absorber are first tuned to obtain the equal-peak design on every mode to be controlled when the structure is behaving linearly. Nonlinearities are then introduced intentionally in the absorber to counteract the effect of the nonlinearities inside the host structure. Their functional formis chosen according to a principle of similarity, and their coefficients are determined to enforce equal peaks in the nonlinear regime. [less ▲]

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See detailMitigation of nonlinear vibrations with a digital piezoelectric tuned vibration absorber
Raze, Ghislain ULiege; Guichaux, Sylvain; Jadoul, Andy et al

Poster (2019, July 02)

This work presents an experimental realization of a digital piezoelectric vibration absorber. A piezoelectric transducer coupled to a structure may convert a part of its mechanical energy into electrical ... [more ▼]

This work presents an experimental realization of a digital piezoelectric vibration absorber. A piezoelectric transducer coupled to a structure may convert a part of its mechanical energy into electrical energy. This energy can then be dissipated through an impedance, often called shunt circuit. Depending on the complexity of the circuit and on the required parameters for its physical constituents, its practical realization may be uneasy. A solution to circumvent these issues altogether is to use a digital impedance. Owing to the flexibility offered by the digital processing unit, almost any impedance can be synthesized, including nonlinear ones with arbitrary functional forms. In this work, the digital impedance is used to realize a linear or nonlinear piezoelectric tuned vibration absorber to mitigate the resonance of a nonlinear structure. The superior performance of the nonlinear absorber over its linear counterpart is demonstrated. Various nonlinear functional forms are also tested in the absorber and illustrate the relevance of a principle of similarity (i.e. the same functional form should be used in the absorber as that in the host structure) for performance. [less ▲]

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See detailSuppression of Delay-induced Instabilities of Digital Piezoelectric Vibration Absorbers
Raze, Ghislain ULiege; Paknejad, Ahmad; Zhao, Guoying et al

in Benjeddou, Ayech; Mechbal, Nazih; Deü, Jean-François (Eds.) Proceedings of the 9th ECCOMAS Thematic Conference on Smart Structures and Materials - SMART 2019 (2019, July)

Digital piezoelectric vibration absorbers synthesizing passive shunt circuits may be subject to instabilities. This work investigates the cause for these instabilities, and highlights the role of sampling ... [more ▼]

Digital piezoelectric vibration absorbers synthesizing passive shunt circuits may be subject to instabilities. This work investigates the cause for these instabilities, and highlights the role of sampling delays in their onset. If for practical reasons the sampling frequency cannot be increased, a stabilization procedure which anticipates the sampling delays is proposed. The theoretical developments in this work are experimentally validated on a piezoelectric beam. [less ▲]

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See detailHybridization of Active Control and Pasive Resonant Shunt
Paknejad, Ahmad; Raze, Ghislain ULiege; Zhao, Guoying et al

in Benjeddou, Ayesh; Mechbal, Nazih; Deü, Jean-François (Eds.) Proceedings of the 9th ECCOMAS Thematic Conference on Smart Structures and Materials (2019, July)

Resonant shunt circuit applied on a transducer like piezoelectric or voice coil is widely used as a passive control technique to damp a specific vibration mode. While very simple and robust, the damping ... [more ▼]

Resonant shunt circuit applied on a transducer like piezoelectric or voice coil is widely used as a passive control technique to damp a specific vibration mode. While very simple and robust, the damping capability is proportional to the electromechanical coupling of the transducer. On the other hand, one of the major difficulties that arises in practical implementation of purely active vibration control is the power consumption required for conditioners and control units. The idea of using hybrid control system is proposed in this study to combine the passive shunt device with an active control in order to improve the performance with low power consumption. Both active voltage source and active current source are proposed and compared. The method of maximum damping, i.e. maximizing the exponential time-decay rate of the response subjected to the external impulse forcing function, is used to optimize the parameters of the passive and hybrid control systems. The advantage of using hybrid control configuration in comparison with purely active control system is also investigated in terms of power consumption. [less ▲]

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See detailA Simplified Current Blocking Piezoelectric Shunt Circuit for Multimodal Vibration Mitigation
Raze, Ghislain ULiege; Jadoul, Andy; Broun, Valery et al

in Dervilis, Nikolaos (Ed.) Special Topics in Structural Dynamics & Experimental Techniques, Volume 5 (2019, June 13)

This paper presents a novel arrangement of a current blocking shunt circuit for the mitigation of multiple structural resonances. The number of required electrical components is reduced compared to the ... [more ▼]

This paper presents a novel arrangement of a current blocking shunt circuit for the mitigation of multiple structural resonances. The number of required electrical components is reduced compared to the previous versions of this circuit proposed in the literature. This paper also proposes a tuning methodology for the electrical parameters of this circuit based on the evaluation of the electromechanical coupling between the electrical circuit and the structure. Effective mitigation performance can be expected with little knowledge of the host structure. A comparison with the solutions in the literature demonstrates the efficiency of the proposed approach. [less ▲]

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See detailActive tuned inerter-damper for smart structures and its ℋ ∞ optimisation
Zhao, Guoying; Raze, Ghislain ULiege; Paknejad, Ahmad et al

in Mechanical Systems and Signal Processing (2019), 129

In this paper, an active tuned inerter damper (ATID) is proposed and theoretically analysed. The proposed device is composed of a pair of collocated reactive actuator and force sensor. It is functioned by ... [more ▼]

In this paper, an active tuned inerter damper (ATID) is proposed and theoretically analysed. The proposed device is composed of a pair of collocated reactive actuator and force sensor. It is functioned by feeding back the output of the force sensor, through both single and double integrators to drive the actuator in order to destructively interfere with the host structure vibrations. The equivalent mechanical components for the single integrator and the double integrator are identified to correspond to a dashpot and an inerter, respectively. The ℋ ∞ optimisation criterion is used for tuning the ATID, and closed-form expressions for the feedback gains are derived. © 2019 Elsevier Ltd [less ▲]

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