Near-field Acoustic Levitation Research Articles

3P-38 Positioning of an object in near-field acoustic levitation and its application(Poster Session)

3P-38 Positioning of an object in near-field acoustic levitation and its application(Poster Session)

Modeling and experimental study on near-field acoustic levitation by flexural mode

Near-field acoustic levitation (NFAL) has been used in noncontact handling and transportation of small objects to avoid contamination. We have performed a theoretical analysis based on nonuniform vibrating surface to quantify the levitation force produced by the air film and also conducted experimental tests to verify our model. Modal analysis was performed using ANSYS on the flexural plate radiator to obtain its natural frequency of desired mode, which is used to design the measurement system. Then, the levitation force was calculated as a function of levitation distance based on squeeze gas film theory using measured amplitude and phase distributions on the vibrator surface. Compared with previous fluid-structural analyses using a uniform piston motion, our model based on the nonuniform radiating surface of the vibrator is more realistic and fits better with experimentally measured levitation force.

近距離場音波浮揚を用いた搬送技術(強力超音波,<小特集>音響関連新技術 音響技術でできること)

近距離場音波浮揚を用いた搬送技術(強力超音波,<小特集>音響関連新技術 音響技術でできること)

On the horizontal wobbling of an object levitated by near-field acoustic levitation

A circular planar object can be levitated with several hundreds of microns by ultrasonic near-field acoustic levitation (NFAL). However, when both the sound source and the levitated object are circularly shaped and the center of the levitated object does not coincide with the source center, instability problem often occurs. When this happens, it becomes difficult to pick up or transport the object for the next process. In this study, when the center of the levitated object was offset from the source center, the moving direction of the levitated object was predicted by using the time averaged potential around the levitated object. The wobbling frequency of the levitated object was calculated by analyzing the nonlinear wobbling motion of the object. It was shown that the predicted wobbling frequencies agreed with measured ones well. Finally, a safe zone was suggested to avoid the unstable movement of an object.

A non-contact linear bearing and actuator via ultrasonic levitation

In this study, the design and testing of a linear bearing using near-field acoustic levitation (NFAL) phenomenon was performed. A pair of Langevin transducers placed at either end of a beam with either a right-angle V-shaped or Λ-shaped cross-section was used to excite and absorb ultrasonic flexural vibrations transmitted along the length of the beam from one transducer to the other. The beam was used as a guide rail, supporting a slider formed from a short length of beam with the same cross-section. This arrangement provides a small and inexpensive non-contact bearing with magnetic field immunity and without generating a magnetic field, both useful characteristics for clean room and precision actuators. The slider was levitated by the vibration of the beam up to 100μm, and was moved successfully in either direction by traveling waves transmitted along the guide rail. In a 300-mm long prototype, objects up to 160g (60.5kg/m2) were levitated and transported. A transportation speed of 138mm/s was obtained for a slider of 90g. The stiffness of the levitation was found to be 1.1N/μm/m2 for this prototype.

Use of Near-Field Acoustic Levitation in Experimental Sliding Contact

The paper presents an investigation into producing the self-levitation effect using piezo-electric actuators (PZTs). Self-levitation has been demonstrated and results are presented and discussed. A relationship between the levitation distance and weight of the levitating sample has been found. In addition, the orientation and position of the PZTs has been found to affect the levitation distance. Modal shapes of the vibration plates used have been produced through modeling and found to accurately correlate with the experimental results found. Additional evidence suggests that the type of vibration plate material affects the separation distance, possibly due to the material’s properties of acoustic reflection.

A Low-Profile Design for the Noncontact Ultrasonically Levitated Stage

In this paper, we propose a new low-profile design for a linear bearing based on Near-Field Acoustic Levitation (NFAL). Two flat beams at a 45° angle are used as a guide rail, and a slider is levitated by ultrasonic bending vibrations excited along the beams. The beams are excited by a pair of Langevin transducers with “+”-shaped vibration direction converters (L-L converters) to install the transducers in the same plane of the beam and to lower the total height of the setup. First, the design of the vibration converter is described. Then, a two-phase driving system to excite a traveling wave is investigated theoretically and experimentally. The levitation characteristics and the sliding performance of the prototype stage are measured and discussed.

Non-contact transportation system using Near-Field Acoustic Levitation

Non-contact transportation system using Near-Field Acoustic Levitation

An investigation of the effect of sound field distribution on the stability of the levitated object in the near-field acoustic levitation

Near-field acoustic levitation (NFAL) is a method that levitates an object or group of particles using the ultrasonic force. It is observed that, when a circular piston type of source is employed, stability problems can occur which makes the object position unpredictable. For example, a thin, circular planar object wobbles to lateral direction like a pendulum when its center is not precisely coincident with the center of source. In this study, the motive force, which makes the levitated object swivel through the center of source, is investigated by varying the sizes of the object and the source. To this end, a visualization of the sound field in the micro gap between the levitated object and source is made by using a photo view of the motion of fine powder scattered inside. The result is compared with the calculation result by BEM. A further investigation is experimentally made on any relation between the temperature distribution on the surface of the levitated object and the acoustic force. The experimental visualizations and numerical modeling results suggest that one may have a model describing the instability of the levitated object in NFAL, if a proper simplified mathematical model is set up in the further study.

A novel ultrasonic clutch using near-field acoustic levitation

This paper investigates design, fabrication and drive of an ultrasonic clutch with two transducers. For the two transducers, one serving as a driving element of the clutch is connected to a driving shaft via a coupling, and the other serving as a slave element of the clutch is connected to a slave shaft via another coupling. The principle of ultrasonic levitation is first expressed. Then, a series-resonant inverter is used to generate AC voltages at input terminals of each transducer, and a speed measuring system with optic sensors is used to find the relationship between rotational speed of the slave shaft and applied voltage of each transducer. Moreover, contact surfaces of the two transducers are coupled by the frictional force when both the two transducers are not energized, and separated using the ultrasonic levitation when at least one of the two transducers is energized at high voltages at resonance.

Theoretical and experimental examination of near-field acoustic levitation.

A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense.

Effect of acoustic energy leakage on the near-field acoustic levitation

Effect of acoustic energy leakage on the near-field acoustic levitation

A Multi-Transducer Near Field Acoustic Levitation System for Noncontact Transportation of Large-Sized Planar Objects

A new noncontact transportation system, which consists of multiple ultrasonic transducers and operates based on near-field acoustic levitation, is proposed to transport a large-sized planar object such as a glass substrate for liquid crystal devices. Using the proposed systems consisting of two and three transducers, the suspension characteristics of the levitated objects are studied as functions of both size difference and angles between the vibration systems and the levitated object. As a result, the holding force is proved to increase as the angle increases and is maximum when the horizontal dimensions of the system and the object coincide.

Non-contact transportation using near-field acoustic levitation

Near-field acoustic levitation, where planar objects 10 kg in weight can levitate stably near the vibrating plate, is successfully applied both to non-contact transportation of objects and to a non-contact ultrasonic motor. Transporting apparatuses and an ultrasonic motor have been fabricated and their characteristics measured. The theory of near-field acoustic levitation both for a piston-like sound source and a flexural vibration source is also briefly described.

Holding characteristics of planar objects suspended by near-field acoustic levitation

The authors have found the acoustic levitation phenomenon where planar objects of 10 kg weight can be levitated near a vibration surface. This phenomenon has been studied for non-contact transportation. A circular planar object can be suspended without contacting a circular vibration plate. We have studied the holding force which acts horizontally on the levitated objects. The horizontal position of the object is stabilized by this force. In this paper, we discuss the effect of the radius of a levitated object, levitation distance, displacement amplitude of the vibration plate and the vibration mode on the suspending force.

Transporting objects without contact using flexural traveling waves

Near-field acoustic levitation is successfully applied to transport objects without contact. Planar objects having a weight greater than 10 kgf can be stably levitated near a vibrating plate. An experimental apparatus has been fabricated to measure the transportation speed and transient characteristics.

Non-contact substance transportation using nearfield acoustic levitation

Non-contact substance transportation using nearfield acoustic levitation