Acoustic Pressure Fields Generated With a High Frequency Acoustic Levitator

2017 ◽  
Author(s):  
Michael W. Sracic ◽  
Jordan D. Petrie ◽  
Henry A. Moroder ◽  
Ryan T. Koniecko ◽  
Andrew R. Abramczyk ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Acoustic Field ◽  
Vibration Amplitude ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Mechanical Vibration ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Pressure Magnitude ◽  
Acoustic Levitator

Acoustic levitation is an advantageous particle positioning mechanism currently employed for applications of x-ray spectroscopy and micro-material manufacturing[1], [2]. By levitating a particle using only acoustic pressure waves, one eliminates the need for a container or other physical structure which may contaminate the specimen. Unfortunately, the pressure field generated by a standing acoustic wave is susceptible to periodic instabilities, and a particle that is levitated in this field tends to vibrate. The amplitude of the vibration is largest in the directions that are orthogonal to the axis in which the acoustic wave is generated. Therefore, by generating additional acoustic waves in each orthogonal axis, the vibration amplitude of the levitated particle is significantly reduced. The authors have shown this phenomenon to be true in a previous study[3]. In this paper, the authors explore the details of the pressure field that is generated with the device. A single degree-of-freedom relationship is developed between the acoustic field pressure, the location of the levitated particle, and the mechanical vibration needed to produce levitation. In order to levitate a 100 micrometer diameter water droplet at 55 kilohertz, the calculations suggest that the transducer must achieve an average surface vibration amplitude of at least 6.43 micrometers. This mechanical vibration must produce a root means-squared pressure amplitude of 933 Pascal. Under these conditions, the particle will levitate approximately 0.4 millimeters below a zero pressure node. To validate the use of the single degree of freedom relationships and to explore the acoustic field for one, two, and three-axis levitation, the authors designed and prototyped an acoustic levitator capable of generating standing waves in three orthogonal directions. Using a simple electrical control circuit, the acoustic wave transducers of each axis can be turned on individually or simultaneously. An experiment was developed to measure the pressure of the acoustic field using a microphone. Preliminary pressure magnitude results were measured for one-axis levitation along the center of the vertical axis of the levitator. The measurements suggest that the theoretical development provides a valid first approximation for the pressure magnitude and required mechanical vibration amplitude.

scholarly journals Automated Insertion of Objects Into an Acoustic Robotic Gripper

Proceedings ◽  
2020 ◽  
Vol 64 (1) ◽  
pp. 40
Author(s):  
Marc Röthlisberger ◽  
Marcel Schuck ◽  
Laurenz Kulmer ◽  
Johann W. Kolar
Keyword(s):  
Acoustic Field ◽  
Acoustic Waves ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Acoustic Power ◽  
Industrial Applications ◽  
High Density ◽  
Analytical Models ◽  
Acoustic Levitation ◽  
Mechanical Contact

Acoustic levitation forces can be used to manipulate small objects and liquid without mechanical contact or contamination. To use acoustic levitation for contactless robotic grippers, automated insertion of objects into the acoustic pressure field is necessary. This work presents analytical models based on which concepts for the controlled insertion of objects are developed. Two prototypes of acoustic grippers are implemented and used to experimentally verify the lifting of objects into the acoustic field. Using standing acoustic waves and by dynamically adjusting the acoustic power, the lifting of high-density objects (>7 g/cm3) from acoustically transparent surfaces is demonstrated. Moreover, a combination of different acoustic traps is used to lift lower-density objects from acoustically reflective surfaces. The provided results open up new possibilities for the implementation of acoustic levitation in robotic grippers, which have the potential to be used in a variety of industrial applications.

Predicting Bubble Migration due to Bjerknes Force in a Complex 3D Geometry: Numerical and Experimental Results

2012 ◽  
Author(s):  
Francisco I. Valentin ◽  
Silvina Cancelos
Keyword(s):  
Acoustic Field ◽  
High Speed ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Piezoelectric Materials ◽  
Bubble Diameter ◽  
Absolute Pressure ◽  
Flowing Fluid ◽  
3D Geometry ◽  
Bjerknes Force

While the Bjerknes force is not the only force experienced by a bubble subjected to an acoustic field; studies of bubble translation in non-flowing fluid have identified Bjerknes force as being the most influential. Therefore, Bjerknes force can be used to trap bubbles in predefined locations of maximum and minimum absolute pressure. Specifically challenging is to determine these locations in complex geometries because direct measurement of the acoustic pressure for the whole system is generally not possible. The objective of this research is to numerically predict Bjerknes force effect on bubble migration and accumulation in a complex 3D geometry that includes piezoelectric materials, elastic materials and a fluid media. A numerical solution of the acoustic pressure field was obtained for this geometry, valid in the range of small pressure oscillations. Additionally, using the linearized Rayleigh-Plesset equation, which gives the volumetric oscillations of a bubble subjected to an acoustic field, the Bjerknes force was numerically computed. By knowing the Bjerknes force, a bubble migration pattern upon entering the system was predicted. A CMOS high speed camera was used to experimentally monitor bubble multimode excitation and bubble response to a stationary pressure field validating our numerical results. Results are presented for experiments conducted for a 1mm bubble diameter with acoustic fields ranging from 7 to 10 kHz which correspond to values of the structure and/or the bubble’s resonant frequency.

Mechanical Vibration Filters With Nonlinear Characteristics

1960 ◽  
Vol 82 (4) ◽  
pp. 369-375
Author(s):  
Will J. Worley
Keyword(s):  
Steady State ◽  
Mechanical Vibration ◽  
Nonlinear Characteristics ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Nonlinear Springs ◽  
Sinusoidal Oscillations ◽  
Single Mass ◽  
Linear And Nonlinear ◽  
Differential Analyzer

The behavior of a single degree of freedom system consisting of a single mass mounted on a spring and damper attached to an oscillating base is investigated. Steady-state and transient sinusoidal oscillations are applied to the base to which the suspension is attached. The response of the mass is recorded for various combinations of linear and nonlinear springs and dampers. Solutions are obtained with a differential analyzer.

The Estimation of Viscous and Coulomb Damping in Harmonically Excited Oscillators

1999 ◽  
Author(s):  
J.-W. Liang ◽  
B. F. Feeny
Keyword(s):  
Free Vibration ◽  
Numerical Simulations ◽  
Dry Friction ◽  
Mechanical Vibration ◽  
Degree Of Freedom ◽  
Identification Algorithm ◽  
Single Degree Of Freedom ◽  
Coulomb Damping ◽  
Single Degree

Abstract This paper proposes a simple identification algorithm for estimating both viscous and dry friction in harmonically forced single-degree-of-freedom mechanical vibration systems. The method is especially suitable for the identification of systems for which the traditional free-vibration scheme is difficult to implement. Numerical simulations are included to show the effectiveness of the proposed algorithm. A numerical perturbation study is also included for insight on the robustness of the algorithm.

Enhancement of Reconstruction Accuracy of the HELS Method

2002 ◽  
Author(s):  
Tatiana Semenova ◽  
Sean F. Wu
Keyword(s):  
Acoustic Field ◽  
Matrix Equation ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Back Propagation ◽  
Three Dimensional ◽  
Constrained Minimization ◽  
Reconstruction Accuracy ◽  
New Strategy ◽  
Reconstruction Point

The validity of the HELS method (Wu, 2000) for reconstructing the acoustic pressure field inside the minimum circle that encloses an arbitrary object is examined. Results show that the HELS solutions are approximate and the corresponding matrix equation is ill conditioned in general for back propagation of the acoustic field. Accordingly, the further the reconstruction point moves inside the minimum circle, the worse the reconstruction accuracy becomes. To overcome this difficulty new strategy for sensor placement is proposed. This strategy together with a constrained minimization are shown to yield satisfactory reconstruction inside the minimum circle. The same procedures can be extended to three-dimensional problems.

Parameters optimization of series–parallel inerter system with negative stiffness in controlling a single–degree–of–freedom system under base excitation

2021 ◽  
pp. 107754632098533
Author(s):  
Marcial Baduidana ◽  
Xiaoran Wang ◽  
Aurelien Kenfack-Jiotsa
Keyword(s):  
Primary Structure ◽  
Vibration Amplitude ◽  
Tuned Mass Damper ◽  
Harmonic Excitation ◽  
Negative Stiffness ◽  
Base Excitation ◽  
Single Degree Of Freedom ◽  
White Noise Excitation ◽  
Single Degree ◽  
Mass Damper

This study proposes a series–parallel inerter system with negative stiffness for the passive vibration control of an undamped single–degree–of–freedom system under base excitation. The necessary and sufficient conditions for stability of series-parallel inerter system with negative stiffness are established by Routh–Hurwitz criterion, and the stability boundary is obtained. The tuning parameters of the series-parallel inerter system with negative stiffness are determined through fixed point theory, and a comparison between the vibration mitigation performance of series-parallel inerter system with negative stiffness, series–parallel inerter system (without negative stiffness), and tuned mass damper is presented considering both harmonic excitation, transient excitation, and random (white noise) excitation. The results of this study demonstrate that under base harmonic excitation, series-parallel inerter system with negative stiffness outperforms the series–parallel inerter system and tuned mass damper in terms of suppression bandwidth and reducing the peak vibration amplitude of the primary mass. In the case of base acceleration–excited primary structure, more than 49.84% and 67.53% improvement can be obtained from series-parallel inerter system with negative stiffness as compared with tuned mass damper in terms of suppression bandwidth and reducing the peak vibration amplitude, respectively. Whereas in the case of base displacement–excited primary structure, more than 78% and 80% improvement can be obtained from series-parallel inerter system with negative stiffness, respectively, following the same criteria. A slightly lower improvement has been obtained from series-parallel inerter system with negative stiffness as compared with series–parallel inerter system, which justified the superiority of series–parallel inerter system compared to tuned mass damper. The transient response investigation showed that series-parallel inerter system with negative stiffness outperforms the series–parallel inerter system and tuned mass damper in terms of much shorter stabilization times and lower peak amplitude of the primary mass. Finally, the further comparison among these devices (series-parallel inerter system with negative stiffness, series–parallel inerter system, and tuned mass damper) under white noise excitation also shows that series-parallel inerter system with negative stiffness is superior to series–parallel inerter system and tuned mass damper for a small inertance mass ratio. This result could provide a theoretical basis for the design of inerter-based isolators with negative stiffness.

scholarly journals Mathematical modeling of monochromatic acoustic wave diffraction on a system of bodies and on flat screens

2021 ◽  
Vol 2142 (1) ◽  
pp. 012002
Author(s):  
S G Daeva ◽  
A L Beskin ◽  
N N Trokhachenkova
Keyword(s):  
Integral Equation ◽  
Acoustic Wave ◽  
Acoustic Pressure ◽  
Pressure Field ◽  
Sound Propagation ◽  
Hypersingular Integral Equation ◽  
Piecewise Constant ◽  
Solid Objects ◽  
Partial Filling ◽  
Complex Shapes

Abstract Some problems of diffraction of a monochromatic acoustic wave on surfaces of complex shapes are considered. To solve such problems, an approach is applied, in which the problem is reduced to a boundary hypersingular integral equation, where the integral is understood in the sense of a finite value according to Hadamard. Such approach allows solving diffraction problems both on solid objects and on thin screens. To solve the integral equation, the method of piecewise constant approximations and collocations, developed in the previous works of the author, is used. In the present study, examples of modeling the diffraction of an acoustic wave by bodies with partial filling are given. It is shown how the filling of bodies influences the acoustic pressure field, and the field direction patterns are given. An example of applying this approach to solving the problem of sound propagation in an urban area is also given: the diffraction of an acoustic wave from a point source on a system of buildings is considered. The presented results demonstrate that this method allows constructing reflected fields and analyze their characteristics on surfaces of complex shapes.

scholarly journals A cross-species neural integration of gravity for motor optimization

2021 ◽  
Vol 7 (15) ◽  
pp. eabf7800
Author(s):  
Jeremie Gaveau ◽  
Sidney Grospretre ◽  
Bastien Berret ◽  
Dora E. Angelaki ◽  
Charalambos Papaxanthis
Keyword(s):  
Optimization Strategy ◽  
Motor Patterns ◽  
Activation Patterns ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Neural Integration ◽  
Gravity Effects ◽  
Neural Signature ◽  
Experimental Findings ◽  
Muscular Activation

Recent kinematic results, combined with model simulations, have provided support for the hypothesis that the human brain shapes motor patterns that use gravity effects to minimize muscle effort. Because many different muscular activation patterns can give rise to the same trajectory, here, we specifically investigate gravity-related movement properties by analyzing muscular activation patterns during single-degree-of-freedom arm movements in various directions. Using a well-known decomposition method of tonic and phasic electromyographic activities, we demonstrate that phasic electromyograms (EMGs) present systematic negative phases. This negativity reveals the optimal motor plan’s neural signature, where the motor system harvests the mechanical effects of gravity to accelerate downward and decelerate upward movements, thereby saving muscle effort. We compare experimental findings in humans to monkeys, generalizing the Effort-optimization strategy across species.

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