Near-field Acoustic Levitation Research Articles

Numerical solution and sensitivity analysis of time–space fractional near-field acoustic levitation model using Caputo and Grünwald–Letnikov derivatives

Numerical solution and sensitivity analysis of time–space fractional near-field acoustic levitation model using Caputo and Grünwald–Letnikov derivatives

Stability analysis of near-field acoustic levitation considering misalignment and inclination

The near-field acoustic levitation (NFAL) technique is attracting increasing attention because of its compact design and environmental friendliness. An intriguing aspect of NFAL is the restoring performance when the levitated object is misaligned with the radiator. While numerous studies have proposed models to predict this performance, they typically consider only the misalignment of the levitated object and disregard its inclination. Consequently, this paper presents a numerical model that accounts for both misalignment and inclination to investigate the stability of NFAL systems. First, the Reynolds equation, which describes the variation in pressure distribution, is introduced. Due to the misalignment, a hypothetical reflector with a groove is applied to conveniently express the film thickness. The Reynolds equation is then solved using the eight-point discrete method in conjunction with the boundary equations, and spline interpolation is used to determine the inclination angle. This approach yields the relationship between the restoring force and the eccentricity, which is validated experimentally. Furthermore, parametric studies reveal that increasing the radiator vibration amplitude or the reflector weight enhances the stability. It is also observed that air provides higher stability compared to hydrogen, and a flexible radiator exhibits higher stability compared to a rigid radiator. With decreasing film thickness (e.g., by reducing the vibration amplitude or increasing the weight of the reflector), the stability in the inclination direction is improved at the cost of increased probability of levitation failure.

A novel two-dimensional non-contact platform based on near-field acoustic levitation

Near-field Acoustic Levitation (NFAL) is an advanced non-contact handling method with promising applications in the field of manufacturing semiconductors and Micro-Electro-Mechanical Systems. This study presents a novel two-dimensional non-contact platform based on NFAL, constructed by two independent bumped and holed rails. The bumped rail is cross-placed under the holed rail, and the bumps are passed through the holes to ensure two rails being nested and combined. The effective region of the platform is consisted of bumped and non-holed regions simultaneously. So, the distribution of the bumps and holes can be designed to optimize the performance of two-dimensional transportation. Two rails can be vibrated independently to realize one-dimensional transportation and simultaneously to realize two-dimensional transportation. The governing equation of squeeze film, considering the amplitude distribution of the rails, is established to analyze the performances. An experimental test-bed is constructed to test the levitation and transportation performance to verify the numerical study. Both numerical and experimental results prove that the platform based on NFAL is a feasible and easy method to realize non-contact two-dimensional transportation.

Design and performance evaluation of a noncontact rotation actuator driven by near-field ultrasonic energy

The innovation of novel drive methods based on smart materials is an important way to promote the development of machines and equipment to the direction of high speed, high efficiency, clean and intelligence. Based on the piezoelectric drive principle and near-field acoustic levitation (NFAL) technology, a noncontact rotation actuator is proposed driven by ultrasonic energy. Under the action of ultrasonic energy generated by the ultrasonic emitter, the object can be stably levitated and driven to rotate at a certain speed. The electroacoustic conversion structure of the actuator is designed and its performance parameters are predicted. To verify the levitation and driving performance, a testing system for the actuator is developed. The structural and dynamic parameters’ influence on the rotor motion are investigated by experimental means, and the optimal parameter combination is acquired. The experiment results show that the maximum driving speed of the optimized rotor can reach 3145 rpm and the maximum noncontact driving torque is about 1.24 mNm under the excitation frequency of 20.21 kHz and the excitation voltage of 225 Vp-p. The proposed levitating drive method based on ultrasonic energy is expected to show great potential in the field of noncontact operation or actuation.

A novel non-contact carrying and transportation method based on near-field acoustic levitation and negative pressure adsorption

A novel non-contact carrying and transportation method based on near-field acoustic levitation and negative pressure adsorption

On the coupled dynamics of near-field acoustic levitation bearing

Near field acoustic levitation (NFAL) bearings, as an alternative non-contact bearing solution, has been proposed and advanced in variable aspects in recent years. To further investigate the property of NFAL and fulfill its theoretical frame, a model based on the stiffness model to analysis the coupled dynamics of the NFAL bearing system, which takes the impact of dynamic stiffness on the levitated object into consideration is proposed. In this model, due to the impact of the driving surface vibration and the dynamic stiffness on the levitated object, a real-time movement of the levitated object is superimposed on the time-averaged movement. By inducing the real-time vibration of the levitated object into the model, it is found that the levitation force and the driving frequency will no longer follow an approximate hyperbolic tangent relationship. The model indicates that, when approaching a certain frequency, the stiffness-mass system of the bearing resonates, and then the phase of the two surfaces begins to increase rapidly, thereby increasing the amplitude of the actual air gap. It is verified with experiments that the object can only be levitated above the resonant frequency.

Theoretical investigation of the levitation force generated by underwater squeeze action

Previous research has experimentally demonstrated the feasibility of near-field acoustic levitation (NFAL) in water. This paper proposes an analytical model of underwater NFAL to study its levitation performance. At first, the fluid’s compressibility must be determined because it is significant to the model’s accuracy. Therefore, the Reynolds equations describing the film pressure distribution are deduced based on fluid film lubrication theory for incompressible and compressible fluids. The calculated squeeze film forces for each case are compared with experimental observations from the literature to confirm the fluid’s compressibility. The comparison results show that the theoretical numerical results under the compressible condition are closer than the incompressible condition to the experimental data. Further numerical results show that increasing the water temperature decreases the mean squeeze film force when the water temperature is higher than 20 °C. In addition, the mean squeeze film force is increased by increasing the vibration amplitude.

The levitation and driving performance of a contact-free manipulation device actuated by ultrasonic energy

To avoid the problems of wear, scratching, and contact pollution caused by traditional physical contact operations on high-precision materials or parts, a non-contact manipulation concept based on the near-field acoustic levitation effect and piezoelectric drive theory is proposed. The contact-free handling device can stably suspend the disc-shaped object and drive the object to rotate at a certain speed under the action of ultrasonic energy. The stable levitation capacity of the contact-free handling device relies on the vertical suspending force and horizontal restoring force derived from the W-type acoustic wave generated by the acoustic emission units. If the upper surface of the suspended disk has a specific configuration, a component driving force is generated when acoustic radiation is applied to it. To explore effective methods to improve the levitation effect, acoustic emission units were designed and fabricated, mathematical models of the suspending force and restoring force were built based on nonlinear acoustics and aerodynamics theories, and the influencing factors of these forces were investigated. In addition, a testing system for a contact-free manipulating device was fabricated to verify the levitation and driving performance using experimental methods.

Measurement of Holding Force and Transportation Force Acting on Tabular Object in Near-Field Acoustic Levitation.

The holding force acting on a levitated object during near-field acoustic levitation has not been statically and directly measured so far. In this study, it was considered to realize such a measurement when a levitated object has a large displacement from the vibration source. In previous studies, under restricted conditions, the holding force has been calculated indirectly by image processing or measured from the balance with gravity by tilting the apparatus. In this article, the force was measured based on the magnetic force (MF) compensation principle. This is the first attempt to measure the force directly and statically under arbitrary conditions. One side of a rectangular rotor, which was placed above the acoustic radiation surface, received the holding force. The other side of the rotor received the MF generated by a solenoid. The holding force was estimated from the electric current flowing in the solenoid when the holding force and the MF were balanced. The holding force acting on the rotor surfaces was affected by the deviation between the rotor and the radiation surface. The holding force increased with increasing vibration amplitude or decreasing air gap between the rotor and the radiation surface. When the vibration sources were opposed, the holding force was affected by their vibration phase difference. The holding force was maximum at the opposite vibration phase and decreased with decreasing vibration phase difference. When the vibration sources were arranged in the transportation direction, the transportation force occurred and increased with increasing vibration amplitude of the destination vibration source. These measurement results agree well with the analysis results.

Study on near-field acoustic levitation characteristics in a pressurized environment

The influence of the ambient pressure on the load capacity of near-field acoustic levitation is studied. Theoretical models based on the acoustic radiation pressure and hydrodynamic lubrication theory are built, taking into account the changes of the ambient pressure. Both simulation and measured results show that the levitation force is positively proportional to the ambient pressure. The levitation force increased by 4–5 times at an ambient pressure of 0.5 MPa. A maximum load capacity of 0.309 MPa is obtained.

A Novel Non-Contact Carrying and Transportation Method Based on Near-Field Acoustic Levitation and Negative Pressure Adsorption

A Novel Non-Contact Carrying and Transportation Method Based on Near-Field Acoustic Levitation and Negative Pressure Adsorption

A Non-Contact Manipulation for Robotic Applications: A Review on Acoustic Levitation

Robots play an important role all over the world in the industrial field in terms of dealing with various materials, performing duties quickly and high accuracy as well as in the pharmaceutical/chemical field since robots can handle some issues better than human. Robotic manipulation is the term used to describe how robots deal with many objects. This article reviews the contact and non-contact manipulation with their most common robotic applications and focusing on the non-contact manipulation since it can do specific tasks which contact manipulation cannot do. Reviewing of the robotic non-contact manipulation which include the metal-based robotic manipulation such as magnetic and electrostatic levitation and the non-metal-based robotic manipulation method such as aerodynamic and acoustic levitation have been made in this article. The main core of this article is acoustic levitation which considered one of the most important levitation and manipulation method due to the recent advancements that made it proper to deal with any kind of materials. Here, we review the renowned three methods of acoustic levitation that already using in robotic non-contact manipulation which are standing wave, near-field and single-beam acoustic levitation. Then, we present a performance characteristic of the reviewed methods and the summary of controlling strategies, followed by conclusion and future recommendations for acoustic levitation methods as a non-contact manipulation.

Rapid rise of planar object by near-field acoustic levitation on recessed acoustic radiation surface

Near-field acoustic levitation (NFAL) can be observed for a planar object placed on the vibrating surface of a longitudinal vibrator. However, for a vibrating surface with a recess, not only NFAL was observed, but also jumping behavior with a snapping sound. This phenomenon was examined analytically and experimentally with bolt-clamped Langevin transducers and a duralumin vibratory horn. Jumping occurred when the minimum value of the acoustic radiation force was larger than the weight of the object. The snapping sound during jumping was generated by the sound pressure that was focused at the center of the bottom surface of the object when the acoustic radiation force peaked due to acoustic resonance in the recessed space.

Design of Ultrasonic Levitation Control System Based on FPGA

As a method to achieve containerless processing, the object levitation technique has a broad application prospect in vital research fields. However, the levitation distance of Electromagnetic levitation, near-field acoustic levitation is not far enough to complete cantainerless processing, and the stability of ultrasonic levitation that use single emitter or single transductor array is still needed to be improved. Therefore, this paper proposes a new embedding electronic system based on FPGA controller to drive a construction of transducer arrays that perpendicularly formed by uniaxial concave sphere and uniaxial biplane. A phase delay algorithm is used on this system to change the position of the stand wave points to move the object smoothly. Furthermore, through experimental validation, this system has a stable signal output to reach the goal of levitation and control.

Theoretical analysis of a contactless transportation system for cylindrical objects based on ultrasonic levitation.

Contactless transportation systems based on near-field acoustic levitation have the benefit of compact design and easy control which are able to meet the cleanliness and precision demands required in precision manufacturing. However, the problems involved in contactless positioning and transporting cylindrical objects have not yet been addressed. This paper introduces a contactless transportation system for cylindrical objects based on grooved radiators. A groove on the concave surface of the radiator produces an asymmetrical pressure distribution which results in a thrusting force to drive the levitator horizontal movement. The pressure distribution between the levitator and the radiator is acquired by solving the Reynolds equation. The levitation and the thrusting forces are obtained by integrating the pressure and the pressure gradient over the concave surface, respectively. The predicted results of the levitation force agree well with experimental observations from the literature. Parameter studies show that the thrusting force increases and converges to a stable value as the groove depth increases. An optimal value for the groove arc length is found to maximize the thrusting force, and the thrusting force increases as the groove width, the radiator vibration amplitude, and the levitator weight increase.

Dynamic Invariance in Near-Field Acoustic Levitation

Abstract It is possible to levitate a mass by vibrating a flat disk located under the mass. This near-field acoustic levitation is particularly useful for eliminating friction between moving objects. This paper presents an experimental and theoretical study of the dynamic behavior of a levitating mass for different magnitudes of oscillation of the flat disk. The magnitude of the vibration of the mass appears to be independent of the amplitude of the vibration of the disk over a range of two orders of magnitude. This unusual behavior is due to the simultaneous changes of the stiffness of the air film and the natural frequency of the system as the plate vibration is changed. As the plate oscillation is reduced, the distance to resonance decreases, allowing an increase of the ratio of the output to input signals in such a way that the output remains constant. This result can be useful for improving the energy efficiency of the levitation.

Development of multi-degree-of-freedom noncontact transportation using holding force in near-filed acoustic levitation and consideration of factors of unstable operation

A non-contact transport method using near-field acoustic levitation has been studied. In this research, the levitated object is transported by multiple stators in steps. This transport method requires a large number of stators, but it has the advantage of precisef positioning because the levitated object is stopped and held on each stator. In addition, by arranging stators in two dimensions, transportation in two-dimensional direction is realized, but stable operation is not obtained, such as unintended rotation in transportation. Through experiments and analysis, we clarified under what conditions the transported object rotates.

Mechanical Analysis and Experimental Research on Ultrasonic Levitated Conical Rotor Piezoelectric Actuator

This work presents a novel conical rotor non-contact piezoelectric actuator based on the principle of near-field acoustic levitation. The conical rotor is levitated and driven by a single stator, while generating two orthogonal standing waves and superimposing a travelling wave vibration on the stator. A frequency sensitivity analysis is conducted for the stator structural parameters, based on a dynamics calculation. An acoustic field simulation is conducted and the sound pressure distribution is obtained. The acoustic radiation force is calculated at different voltages and frequencies. A prototype is fabricated, and the vibration characteristics are experimentally obtained. A test system is built for the actuator, and the conical rotor successfully achieves levitation and rotation. The levitation height and rotation speed of the 3.37[Formula: see text]g rotor are 0.4[Formula: see text]mm and 2300[Formula: see text]r/min, respectively. The acoustic simulations are validated experimentally and show reasonable agreement.

Levitating Force and Stability Analysis of Near-field Acoustic Levitation using Flexural Vibrations of the Plate

Levitating Force and Stability Analysis of Near-field Acoustic Levitation using Flexural Vibrations of the Plate

1Pa4-4 Effect of eigenmode in cavity on acoustic radiation force in near-field acoustic levitation

1Pa4-4 Effect of eigenmode in cavity on acoustic radiation force in near-field acoustic levitation