Modelling influence of Poisson's contraction on squeeze film levitation of planar objects

This study proposes a spherical rotor gyroscope based on the near-field acoustic levitation (NFAL) principle, which utilizes high-frequency vibration to levitate objects at a short distance near the driving surface. The ultrasonic suspended gyroscope consists of a piezoelectrically excited stator and a spherical rotor. The stator was excited to generate ultrasonic vibration under the action of the inverse piezoelectric effect, provide non-contact support for the spherical rotor, and drive it to rotate with the traveling wave vibration. When the spherical rotor obtained sufficient angular momentum, the driving voltages were changed to induce the standing wave vibration and thus provide a stable levitation force field for the rotor. At this stage, the rotor was only subjected to the effects of gravity and levitation force and the spherical rotor rotated at a high speed to obtain gyroscopic inertia. Herein, the finite element model of the stator was established for dynamic analysis, and an acoustic–structure coupling model was established to analyze the non-contact supporting force of the gyroscope. The prototype was manufactured, and the stator was tested for vibration, and test platforms for levitation height, rotation speed, and gyroscopic inertia of the non-contact ultrasonic levitated spherical rotor gyroscope were built. The stator vibration performance was consistent with the simulation analysis result. The levitation height could be as high as tens of microns at the operating frequency. The rotation speed could reach 5600 r/min, and the gyroscopic inertia was verified. Therefore, the feasibility of NFAL for a levitated gyroscope was verified.

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Design and experimental research on ultrasonic levitated spherical rotor gyroscope

Wang

Lei

Chen

et al. 2020

AIP Advances

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On the horizontal dynamic performance of standing wave-type near-field ultrasonic levitation

Liu,

Zhao,

Sun

et al. 2024

Physics of Fluids

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Near-field ultrasonic levitation (NFUL) technology is increasingly attracting attention for its advantages of non-contact nature, compactness, and environmental friendliness. Nevertheless, the development of NFUL is hindered by challenges such as carrying capacity and stability. To date, most studies have focused on the static stability of NFUL, primarily through analysis of the restoring force. However, there remains a significant gap in the literature regarding the motion prediction of levitated objects, which is the focus of this paper. A numerical model coupling the levitated object and the squeeze film is established, and then, the Reynolds equation considering the motion parameters of the levitator is derived. Since the misalignment and inclination of the levitator are concurrent cases, its inclination needs to be considered in the film thickness expression. Subsequently, due to the introduction of an imaginary levitator with a groove, the eight-point discrete method is applied to solve the discontinuous film thickness problem. Thereupon, the pressure profile is obtained by determining the inclination angle of the levitator using the spline interpolation. The motion trajectory and frequency of the levitator are estimated utilizing the time-marching method and corroborated through experimental measurements. Both numerical and experimental results indicate that the motion frequency initially increases sharply with rising the preset eccentricity, before gradually diminishing. Additionally, higher motion frequencies are observed at larger amplitudes of the vibrator and lower weights of the levitator. Comparatively, the motion frequency of a levitator under a flexible vibrator is also found to be higher than that under a rigid vibrator.

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Stabilizing near-field acoustic levitation: Investigation of non-linear restoring force generated by asymmetric gas squeeze film

Liu

Shi

Feng

et al. 2020

The Journal of the Acoustical Society of America

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The instability of a floating object is the main factor preventing near-field acoustic levitation (NAFL) from being widely used in the manufacture of micro-electro-mechanical systems. Therefore, investigating the restoring force due to the generation mechanisms of NAFL is necessary to ensure the stable levitation of the floating object. This study presents a theoretical analysis to evaluate the restoring force based on the gas-film-lubrication theory. The gas-film pressure between the reflector and the radiator is expressed in the form of the dimensionless Reynolds equation in a cylindrical coordinate system, which is solved by an eight-point discrete grid method due to the discontinuous gas-film distribution. An experimental rig is constructed to measure the restoring force at various eccentricities, which can be used to support the developed numerical model. The theoretical results show that the restoring force increases with an increment in eccentricity, which agrees with experimental results. Furthermore, theoretical prediction results indicate that the restoring force increases when the amplitude of the radiator and weight of the levitator increases, which indicates higher system stability. The results of the radiator vibration mode on the restoring force show that the restoring force is the largest in the first-order mode.

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Modelling influence of Poisson's contraction on squeeze film levitation of planar objects

Cited by 5 publications

References 13 publications

Design and experimental research on ultrasonic levitated spherical rotor gyroscope

Design and experimental research on ultrasonic levitated spherical rotor gyroscope

On the horizontal dynamic performance of standing wave-type near-field ultrasonic levitation

Stabilizing near-field acoustic levitation: Investigation of non-linear restoring force generated by asymmetric gas squeeze film

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