Structural modification to achieve antiresonance in helicopters

Wang, B. P.; Kitis, L.; Pilkey, Walter D.; Palazzolo, Alan

doi:10.2514/3.44769

Cited by 10 publications

(4 citation statements)

References 6 publications

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“…DSM methods compute the optimal structural modifications (mass, damping and stiffness system parameter modifications) that enable to achieve the desired specifications. Traditionally, structural modification has been widely adopted over the decades to assign natural frequencies [18][19][20], mode shapes [21,22] and antiresonance frequencies [23][24][25]. Recently, DSM has been adopted also to increase the robustness against the system uncertainties in motion planning [26] and to improve the subspace of the allowable motion in linear vibratory feeders excited through harmonic excitation [27].…”

Section: Motivations and State Of The Artmentioning

confidence: 99%

Integrated Inverse Dynamics and Optimized Mechanical Design in Underactuated Linear Vibratory Feeders Under Periodic Excitation

Bettega

Richiedei

Tamellin

et al. 2023

J. Vib. Eng. Technol.

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Purpose This paper proposes an integrated method for optimizing the response of underactuated linear vibratory feeders operating in open-loop control, under generic periodic excitations. The goal is ensuring a uniform motion of the tray, despite the presence of less actuators than degrees of freedom and of several specifications of the desired motion. Method To cope with the underactuated nature of these systems and with their non-minimum phase behavior, dynamic structural modification and the inverse dynamics approach are properly integrated by exploiting a common definition of the system internal dynamics. In the inverse dynamics problem, the inverse dynamics is stabilized through output redefinition and the resulting ordinary differential equations are integrated to compute causal actuation forces, ensuring almost-exact tracking for as many coordinates as the number of actuators. The tracking of the remaining coordinates of interest is improved through a proper design of the mechanical parameters, based on the modification of the internal dynamics. Results The effectiveness of the proposed method is assessed through numerical simulations performed on the challenging case of a 14-degrees of freedom underactuated non-minimum phase linear vibratory feeder adopted in manufacturing plants to convey products. Conclusion The results evidence the benefits obtained by integrating structural modification together with inverse dynamics. Inverse dynamics is effective, since the tracking error on the imposed coordinates is negligible. On the other hand, the benefits introduced by dynamic structural modification are proved as well, by the reduction of the tracking error also for the non-imposed coordinates.

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Section: Motivations and State Of The Artmentioning

confidence: 99%

Integrated Inverse Dynamics and Optimized Mechanical Design in Underactuated Linear Vibratory Feeders Under Periodic Excitation

Bettega

Richiedei

Tamellin

et al. 2023

J. Vib. Eng. Technol.

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“…In [88] the application of the antiresonance theory for engineering applications in helicopters is discussed placing either passive, semi-active or active TMDs at collocated or noncollocated locations. In [89] the AA in helicopters is studied in order to absorb the rotor induced vibrations. Two methods are provided: the first one performs AA by modifying only the existing stiffness of two fuselage elements by solving a polynomial.…”

Section: Antiresonance Assignment In Helicoptersmentioning

confidence: 99%

Beyond the Tuned Mass Damper: a Comparative Study of Passive Approaches to Vibration Absorption Through Antiresonance Assignment

Richiedei

Tamellin

Trevisani

2021

Arch Computat Methods Eng

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Vibration absorption is a core research area in the design and control of structures and machines, and exploiting antiresonances is an effective approach for systems under harmonic excitation. This paper proposes a comparative study and a review of the main passive techniques to antiresonance assignment proposed in the recent literature, by discussing them through some numerical examples too. The techniques discussed include the well-known Tuned Mass Damper, which has been widely developed in the literature. However, as the title reveals, great attention is paid to the methods inherited from the field of dynamic structural modification that assign antiresonances without modifying the number of degrees of freedom, by exploiting a proper modification of the system inertial and stiffness parameters. Due to higher mathematical complexity, these approaches have been less investigated in the literature although they are an effective and less invasive approach to antiresonance assignment, especially for machines. To puzzle out the complicated subject matter of antiresonances, their background and their key features are also discussed by reviewing the main theoretical results and their relationship with the assignment techniques. The paper is also enriched with several numerical examples to compare different methods and investigate the features of antiresonances. The concluding remarks of the paper bring together some open issues in this field of research and outlines some possible research directions.

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“…Inverse structural modification, on the other hand, is used to identify the changes required to obtain desired dynamic properties, usually expressed in terms of desirable natural frequencies and mode shapes. Several researchers, including Park and Park [2,3], Wang et al [4], Mottershead et al [5], and Kyprianou et al [1,6], have concentrated on the inverse structural modification approach. There are very few studies devoted to the topic of direct structural modification.…”

Section: Introductionmentioning

confidence: 99%

An investigation on structural dynamic modification of a machine casing

Hanouf

Abdelrahman²,

Ahmad³

2022

IOP Conf. Ser.: Mater. Sci. Eng.

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Investigation on structural dynamic characteristic is a crucial step in the noise, vibration and harshness (NVH) analysis in order to enhance the structural vibration, which subsequently contribute to improving the acoustical environment. The excitation of the structure can produce high vibration which could be transferred to the other parts of the body, then lead to high noise radiating components. Structural dynamic modification is one of the important techniques in the design of mechanical structures. It is an application of experimental modal analysis technique to investigate the effect of the physical and geometrical parameters on the dynamic properties of the structures such as frequencies and mode shapes. This paper investigates the dynamic properties of a machine casing structure which is extensively used in industrial applications. This investigation had successfully produced natural frequencies and their associated mode shapes of such open box for the original structure and modified structure. The study establishes the step-by-step procedures to carry out experimental modal analysis on the structures, using single input excitation and single output responses (SISO) technique. To ensure the validity of the results obtained an inverse method was done by fixing the response and moving the excitation. The results found were absolutely the same. Finally, comparison between results obtained from analysis showed significant differences on both frequencies and mode shapes.

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Structural modification to achieve antiresonance in helicopters

Cited by 10 publications

References 6 publications

Integrated Inverse Dynamics and Optimized Mechanical Design in Underactuated Linear Vibratory Feeders Under Periodic Excitation

Integrated Inverse Dynamics and Optimized Mechanical Design in Underactuated Linear Vibratory Feeders Under Periodic Excitation

Beyond the Tuned Mass Damper: a Comparative Study of Passive Approaches to Vibration Absorption Through Antiresonance Assignment

An investigation on structural dynamic modification of a machine casing

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