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Acoustic and Structural Impedance and Intensity
Published in Colin H. Hansen, Foundations of Vibroacoustics, 2018
The mechanical impedance is defined as the ratio of the force, F, acting on a surface or system to the velocity of the system at the point of application of the force. If the system is a vibrating surface, then the surface velocity, u, is equal to the acoustic particle velocity, u, at an adjacent point in the surrounding fluid. If the vibrating surface of area, S, is subject to a uniform acoustic pressure, p, and is vibrating with a uniform normal velocity, then the mechanical impedance is: () Zm=Fu=pSu=ZsS=ZAS2
Vibration Isolation for Noise Control
Published in Randall F. Barron, Industrial Noise Control and Acoustics, 2002
There are many cases in which the velocity of the mass is an important vibration function to be controlled, instead of the displacement. In this case, the mechanical impedance ZM may be utilized. The mechanical impedance gives a measure of how strongly the system resists applied forces (or moments). The mechanical impedance is defined as the ratio of the applied force to the resulting velocity of the system: ZM=F(t)v(t)
Whole-Body Vibration
Published in Neil J. Mansfield, Human Response to Vibration, 2004
It is possible to investigate the response of humans in a dynamic environment by their mechanical responses. The two principal approaches are to make assessments at the “driving point” (i.e., the site of the human contact with the loading force) or remote from the driving point (Figure 2.18). At the driving point, mechanical impedance methods use measures of force and acceleration (or velocity) to determine the response of the body as a whole. Measurements of acceleration remote from the driving point are usually used in combination with simultaneous measures at the driving point to calculate how vibration is transmitted through the body (transmissibility).
Modeling and structural control of a building with holonomic constraints
Published in Australian Journal of Structural Engineering, 2022
Carlos F. Rengifo, Diego A. Bravo
The mechanical impedance quantifies the force exerted by a system in opposition to changes in its velocity. Mathematically, the mechanical impedance is defined as the quotient between a change in the input force and the corresponding change in velocity (Khalil and Dombre 2004). The stiffer a system is, the higher its mechanical impedance. In linear systems, the mechanical impedance is defined as the Laplace transform of the force divided by the Laplace transform of the velocity (Richardson et al. 2005).
A fully-actuated quadcopter representation using quaternions
Published in International Journal of Control, 2022
J. Cariño, H. Abaunza, P. Castillo
Energy shaping is a technique that is closely associated with the control of kinematic chains, like robotic arms. The premise is to change the dynamics of the system in order to have a different mechanical impedance. The main objective of the proposed controller is to change the potential energy of the system in order to mitigate the effects that the couple dynamics have on the system. The fundamentals and a more thorough description of this type of control can be found in Brogliato et al. (2007).
Analytical Model of the Electro-Mechanical Impedance Response of Frame Structures with L-Shaped Beams
Published in Research in Nondestructive Evaluation, 2020
Mohsen Mohsenzadeh, Seyed Reza Hamzeloo, Mohsen Barzegar, Ali Pourkamali Anaraki
Monitoring and evaluating the health of structures, on services, reduces maintenance cost, increases productivity time and reliability. Online structural health monitoring (SHM) is an attractive subject that in recent decades in many different industries, including aerospace, mechanical and civil and is gradually replacing the traditional methods of nondestructive testing. The electro-mechanical impedance spectroscopy method has gained acceptance as an effective technique for structural health monitoring, damage detection, and failure prevention. This method uses a piezoelectric wafer active sensor (PWAS) with an impedance measurement device. By bonding it onto the structure, the electrical impedance which is coupled with local structural–mechanical impedance is measured by a self-sensing circuit at its terminals. The coupling of single patch with a continuum media (structure) in a wide range of frequencies lead to agitation/excitation of natural frequencies of the structure. When a PZT patch attached to a structure, a coupled system of a patch with almost no weight and structure with a large mass and stiffness can be actuated by PZT electrically and as a spot in structure. The general concept is the mechanical impedance of the structure emerges in electrical impedance of Piezoelectric. This phenomenon is called coupling effect and the multi-mode coupling vibrations happen due to the fact that when a wide range of actuation is occurred, the direct actuation of natural frequencies of structure in this range disclosed in electromechanical impedance spectrum. The mechanical resonance spectrum of the structure is reflected in a virtually identical spectrum of peaks and valleys in the electro-mechanical impedance spectrum. The mechanical impedance of structure depends directly on the mass and structural stiffness which are defined as the ratio of force to velocity. Boundary conditions, defects and temperature have also direct impact on the mass and stiffness of the structure and consequently influence the impedance of structures [1–8].