Levitation Of Objects Research Articles

Acoustic levitation of an object larger than the acoustic wavelength

Levitation and manipulation of objects by sound waves have a wide range of applications in chemistry, biology, material sciences, and engineering. However, the current acoustic levitation techniques are mainly restricted to particles that are much smaller than the acoustic wavelength. In this work, it is shown that acoustic standing waves can be employed to stably levitate an object much larger than the acoustic wavelength in air. The levitation of a large slightly curved object weighting 2.3 g is demonstrated by using a device formed by two 25 kHz ultrasonic Langevin transducers connected to an aluminum plate. The sound wave emitted by the device provides a vertical acoustic radiation force to counteract gravity and a lateral restoring force that ensure horizontal stability to the levitated object. In order to understand the levitation stability, a numerical model based on the finite element method is used to determine the acoustic radiation force that acts on the object.

Anti-windup Fractional Order $$\textit{PI}^\lambda -\textit{PD}^\mu $$ PI λ - PD μ Controller Design for Unstable Process: A Magnetic Levitation Study Case Under Actuator Saturation

Many studies have been conducted by researchers globally in the recent past on the control scheme to stabilize the levitated object of magnetic levitation system (MLS) at the unstable equilibrium point though very small amount of work has been reported regarding the design and tuning of fractional order controller for unstable process, especially in the presence of actuator saturation. In this paper, a novel methodology of fractional order \(PI^\lambda -PD^\mu \) controller for MLS is proposed for both stabilizing the system and removing the actuator saturation. Fractional order control facilitates an extra degree of freedom to change the order of integrator, arise a new concept to diminish the error windup during actuator saturation. The tuning of gain parameter of PID controller is done using the conventional pole placement technique, while a simple tuning method is proposed here to tune fractional parameter using stability margin and sensitivity function. Stability of the proposed controller scheme employed to MLS is analyzed on the basis of Riemann sheets concept in w-plane. To compensate for saturation due to integral term, back-calculation anti-windup scheme is used here. Experimental demonstration of proposed scheme on magnetic levitation confirms the ability of the controller to reject the external random perturbations as well as its robustness against the variation of system parameters.

Development of Magnetic Levitation System for Science and Technology Education: Magnetic Levitation Control by Using a Hall Element Displacement Sensor with Neural Network

SUMMARYIn this study, we developed a magnetic levitation system using a Hall element displacement sensor with neural network for science and technology education. The sensor configured with three Hall elements was devised in order to measure displacement from an electromagnet to a levitated object with a permanent magnet. Use of the Hall element displacement sensor achieves a lower cost magnetic levitation system. Furthermore, three‐layered feedforward neural network was utilized in order to improve the precision of the Hall element displacement sensor. Finally, operation verification of the developed magnetic levitation system was conducted by designing state feedback regulator with observer.

The effect of acoustically levitated objects on the dynamics of ultrasonic actuators

This paper presents a comprehensive model, coupling a piezoelectric actuator operating at ultrasonic frequencies to a near-field acoustically levitated object through a compressible thin layer of gas such that the combined dynamic response of the system can be predicted. The latter is derived by introducing a simplified model of the nonlinear squeezed layer of gas and a variational model of the solid structure and the piezoelectric elements. Since the harmonic forces applied by the entrapped fluid depend on the levitated object's height and vertical motion, the latter affects the impedance of the driving surface, affecting the natural frequencies, damping ratios, and amplification of the actuator. Thus, the developed model is helpful when devising a resonance tracking algorithm aimed to excite a near-field acoustic levitation based apparatus optimally. Validation of the suggested model was carried out using a focused experimental setup geared to eliminate the effects that were already verified in the past. In agreement with the model, the experimental results showed that the natural frequency and damping ratio of a designated mode decrease monotonically with the levitated object's average height, whereas the amplification of the mode increases with the levitation height.

A rotational traveling wave based levitation device – Modelling, design, and control

Described is a device acting on an acoustically levitated object by manipulating the pressure and flow of a thin layer of air such that its rotation can be precisely controlled without mechanical contact. Virtual work analysis assists in simplifying the multi-actuator control problem into one governed by a single controllable parameter. Actuation is accomplished by a vibrating annulus capable of producing ultrasonic standing and traveling waves. Thus creating the acoustic excitation that affects the pressure in a thin, intermediate layer of gas. A distinctive vibration pattern is required to generate the temporal and spatial pressure field of the squeezed air layer that gives rise to both acoustic levitation force and rotational torque. Described are the physical and design development stages leading to an optimized structure, all followed by verifying and dynamics-calibration experiments. Moreover, by precisely controlling the ratio of standing and traveling waves in the annulus, in a closed-loop, one can control the shear forces applied by the squeezed air layer, thus creating a non-contacting levitated object manipulation mechanism. Through an algebraic transformation, the over-actuated setup is converted to a simplified single control-parameter problem. The transformation links the standing waves ratio, and hence the rotational torque, to the amplitudes and phases of the actuators. This arrangement leads to an effective closed loop methodology that was implemented experimentally, showing good performance and exhibiting rapid angular positioning.

Modeling and closed loop control of near-field acoustically levitated objects

The present paper introduces a novel approach for modeling the governing, slow dynamics of near-field acoustically levitated objects. This model is sufficiently simple and concise to enable designing a closed-loop controller, capable of accurate vertical positioning of a carried object. The near-field acoustic levitation phenomenon exploits the compressibility, the nonlinearity and the viscosity of the gas trapped between a rapidly oscillating surface and a freely suspended planar object, to elevate its time averaged pressure above the ambient pressure. By these means, the vertical position of loads weighing up to several kilograms can be varied between dozens and hundreds of micrometers. The simplified model developed in this paper is a second order ordinary differential equation where the height-dependent stiffness and damping terms of the gas layer are derived explicitly. This simplified model replaces a traditional model consisting of the equation of motion of the levitated object, coupled to a nonlinear partial differential equation, accounting for the behavior of the entrapped gas. Due to the relatively simple form of the model developed here, it constitutes a convenient foundation for model based control algorithms, governing the slow dynamics of near-field acoustically levitated objects. Indeed, based on the former, a height dependent, gain scheduled PID controller is developed and verified numerically and experimentally, both providing satisfying results.

System and Method for Obtaining Simultaneous Levitation and Rotation of a Ferromagnetic Object

In this work a practical demonstration for simultaneous levitation and rotation for a ferromagnetic cylindrical object is presented. A hollow steel cylinder has been arranged to remain suspended stably under I-core electromagnet utilizing dc attraction type levitation principle and then arranged to rotate the levitated object around 1000 rpm speed based on eddy current based energy meter principle. Since the object is to be rotating during levitated condition the device will be frictionless, energy-efficient and robust. This technology may be applied to frictionless energy meter, wind turbine, machine tool applications, precision instruments and many other devices where easy energy-efficient stable rotation will be required. The cascade lead compensation control scheme has been applied for stabilization of unstable levitation system. The proposed device is successfully tested in the laboratory and experimental results have been produced.

Holographic acoustic elements for manipulation of levitated objects.

Sound can levitate objects of different sizes and materials through air, water and tissue. This allows us to manipulate cells, liquids, compounds or living things without touching or contaminating them. However, acoustic levitation has required the targets to be enclosed with acoustic elements or had limited manoeuvrability. Here we optimize the phases used to drive an ultrasonic phased array and show that acoustic levitation can be employed to translate, rotate and manipulate particles using even a single-sided emitter. Furthermore, we introduce the holographic acoustic elements framework that permits the rapid generation of traps and provides a bridge between optical and acoustical trapping. Acoustic structures shaped as tweezers, twisters or bottles emerge as the optimum mechanisms for tractor beams or containerless transportation. Single-beam levitation could manipulate particles inside our body for applications in targeted drug delivery or acoustically controlled micro-machines that do not interfere with magnetic resonance imaging.

On the slow dynamics of near-field acoustically levitated objects under High excitation frequencies

This paper introduces a simplified analytical model describing the governing dynamics of near-field acoustically levitated objects. The simplification converts the equation of motion coupled with the partial differential equation of a compressible fluid, into a compact, second order ordinary differential equation, where the local stiffness and damping are transparent. The simplified model allows one to more easily analyse and design near-field acoustic levitation based systems, and it also helps to devise closed-loop controller algorithms for such systems. Near-field acoustic levitation employs fast ultrasonic vibrations of a driving surface and exploits the viscosity and the compressibility of a gaseous medium to achieve average, load carrying pressure. It is demonstrated that the slow dynamics dominates the transient behaviour, while the time-scale associated with the fast, ultrasonic excitation has a small presence in the oscillations of the levitated object. Indeed, the present paper formulates the slow dynamics under an ultrasonic excitation without the need to explicitly consider the latter. The simplified model is compared with a numerical scheme based on Reynolds equation and with experiments, both showing reasonably good results.

Noncontact orientation of objects in three-dimensional space using magnetic levitation.

This paper describes several noncontact methods of orienting objects in 3D space using Magnetic Levitation (MagLev). The methods use two permanent magnets arranged coaxially with like poles facing and a container containing a paramagnetic liquid in which the objects are suspended. Absent external forcing, objects levitating in the device adopt predictable static orientations; the orientation depends on the shape and distribution of mass within the objects. The orientation of objects of uniform density in the MagLev device shows a sharp geometry-dependent transition: an analytical theory rationalizes this transition and predicts the orientation of objects in the MagLev device. Manipulation of the orientation of the levitating objects in space is achieved in two ways: (i) by rotating and/or translating the MagLev device while the objects are suspended in the paramagnetic solution between the magnets; (ii) by moving a small external magnet close to the levitating objects while keeping the device stationary. Unlike mechanical agitation or robotic selection, orienting using MagLev is possible for objects having a range of different physical characteristics (e.g., different shapes, sizes, and mechanical properties from hard polymers to gels and fluids). MagLev thus has the potential to be useful for sorting and positioning components in 3D space, orienting objects for assembly, constructing noncontact devices, and assembling objects composed of soft materials such as hydrogels, elastomers, and jammed granular media.

Pixie dust

We propose a novel graphics system based on the expansion of 3D acoustic-manipulation technology. In conventional research on acoustic levitation, small objects are trapped in the acoustic beams of standing waves. We expand this method by changing the distribution of the acoustic-potential field (APF). Using this technique, we can generate the graphics using levitated small objects. Our approach makes available many expressions, such as the expression by materials and non-digital appearance. These kinds of expressions are used in many applications, and we aim to combine them with digital controllability. In the current system, multiple particles are levitated together at 4.25-mm intervals. The spatial resolution of the position is 0.5 mm. Particles move at up to 72 cm/s. The allowable density of the material can be up to 7 g/cm 3 . For this study, we use three options of APF: 2D grid, high-speed movement, and combination with motion capture. These are used to realize floating screen or mid-air raster graphics, mid-air vector graphics, and interaction with levitated objects. This paper reports the details of the acoustic-potential field generator on the design, control, performance evaluation, and exploration of the application space. To discuss the various noncontact manipulation technologies in a unified manner, we introduce a concept called "computational potential field" (CPF).

Design and Implementation of a Magnetic Levitation System Controller using Global Sliding Mode Control

This paper presents global sliding mode control and conventional sliding mode control for stabilization position of a levitation object. Sliding mode control will be robusting when in sliding mode condition. However, it is not necessarily robust at attaining phase. In the global sliding mode control, the attaining motion phase was eliminated, so that the robustness of the controller can be improved. However, the value of the parameter uncertainties needs to be limited. Besides that, the common problem in sliding mode control is high chattering phenomenon. If the chattering is too large, it can make the system unstable due the limited ability of electronics component. The strategy to overcome the chattering phenomenon is needed. Based on simulation and experimental results, the global sliding mode control has better performance than conventional sliding mode control.

Three-dimensional mid-air acoustic manipulation by ultrasonic phased arrays.

The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method.

Electric Levitation Usingϵ-Near-Zero Metamaterials

The ability to manufacture metamaterials with exotic electromagnetic properties has potential for surprising new applications. Here we report how a specific type of metamaterial--one whose permittivity is near zero--exerts a repulsive force on an electric dipole source, resulting in levitation of the dipole. The phenomenon relies on the expulsion of the time-varying electric field from the metamaterial interior, resembling the perfect diamagnetic expulsion of magnetostatic fields. Leveraging this concept, we study some realistic requirements for the levitation or repulsion of a polarized particle radiating at any frequency, from microwave to optics.

1D24 Basic Study on Magnetic Levitation System by Using Superconducting Coil(The 12th International Conference on Motion and Vibration Control)

Superconducting technique is applied to the levitation system. Persistent current in superconducting coil and control current in copper coil are used for levitating object and controlling object, respectively. The system is composed of a superconducting coil, a copper coil, a levitated object, a photo sensor, a PID controller, and power amplifiers. In this paper, basic study on superconducting coil and solenoid coil, and the dynamic characteristics of levitated object are performed. As a result, it is found that the levitated object continues to levitate at a distance 9.0 mm for ≈ 15 s. This may be the first trial that superconducting coil is used for magnetic levitation.

202 近距離場音波浮揚による非接触加振の研究(セッション5 音響・超音波利用)

This study concerns non-contact excitation of planer objects by using near-field acoustic levitation, in which a planer object having relatively large size and weight is levitated on a ultrasonic vibration plate with 10-100 μm air gap. This phenomenon has been studied as a non-contact transportation technology for a fragile thin plate such as flat panel display glass substrate. In this study, we investigate the possibility of this phenomenon as a technology for non-contact excitation of planer objects. In this paper, we propose a non-contact excitation method to vibrate the levitated object at arbitrary low frequency by modulating the ultrasonic amplitude of the vibration plate. An experimental study of non-contact excitation of plate specimens near the natural frequencies suggests that the system consisting of the vibration plate, the air gap, and the levitated plate can be modeled as a two-degree-of-freedom dynamical system.

Study on Transient Properties of Levitated Object in Near-Field Acoustic Levitation

A new approach to the study on the transient properties of the levitated object in near-field acoustic levitation (NFAL) is presented. In this article, the transient response characteristics, including the levitated height of an object with radius of 24 mm and thickness of 5 mm, the radial velocity and pressure difference of gas at the boundary of clearance between the levitated object and radiating surface (squeeze film), is calculated according to several velocity amplitudes of radiating surface. First, the basic equations in fluid areas on Arbitrary Lagrange—Euler (ALE) form are numerically solved by using streamline upwind petrov galerkin (SUPG) finite elements method. Second, the formed algebraic equations and solid control equations are solved by using synchronous alternating method to gain the transient messages of the levitated object and gas in the squeeze film. Through theoretical and numerical analyses, it is found that there is a oscillation time in the transient process and that the response time does not simply increase with the increasing of velocity amplitudes of radiating surface. More investigations in this paper are helpful for the understanding of the transient properties of levitated object in NFAL, which are in favor of enhancing stabilities and responsiveness of levitated object.

Acoustic levitator for contactless transport and mixing of droplets in air

Acoustic levitation is a simple and cost-effective method for investigation of small amounts of any kind of material. Standard levitators focus the standing acoustic wave only along its traveling direction. Therefore, levitated objects (entrapped in the potential minima) are separated by potential maxima which cannot be overcome. Thorough design of the emitter plate and consequently its vibration pattern allows a more complex acoustic field between the emitter and reflector, establishing multiple potential minima perpendicular to the wave propagation direction in the H1-mode. The number of minima is regulated by changing the emitter-reflector distance H. Thus, multiple solid or liquid samples can be simultaneously levitated and rapidly transported over several centimeters by controlling H. A piezoelectrically driven droplet generator was used to eject pL droplets into the acoustic field and coalesce them to a 1–2 μL sized droplet in the preferred potential minimum. Two suspended droplets were transported and mixed when two potential minima were merged into one by increasing H. During pattern transition, high pressure fluctuation might increase droplet Bond number beyond its critical value and cause droplet atomization. This was prevented by continuous adjustment of acoustic power.

자기부상시스템의 자기력 모델링 시스템 개발

This paper proposes an equipment and an algorithm for modeling the magnetic force of electromagnets in magnetic levitation systems. We assume that the magnetic force model is represented in terms of a 2D lookup table. The 2D lookup table is constructed by applying noncausal filtering and interpolation to data measured by the proposed modeling equipment. The proposed modeling equipment is designed such that it can measure the magnetic force exerted on the levitation object while it changes the voltage applied to the electromagnet and position of the levitation object. The algorithm of making a 2D lookup table has two stages. The data measured by the proposed modeling equipment is smoothed by a noncausal filter and then the 2D lookup table is obtained by interpolating filtered data. The proposed modeling method has advantages of time-saving, model consistency, and chance of automation for mass production. We show the validity of proposed method through control experiments.

G134 空気旋回流のアレイ構造を用いた高性能非接触吸引デバイスに関する研究(一般講演(5))

We present a novel application of the MEMS technology to a non-contact gripper using arrayed spiral air flows, in order to mitigate flow-induced vibration during the levitation of objects. For handling fragile objects such as silicon wafers and solar panels, we employ a gripping technology with continuous air-blowing, which would enable damage-free handling without contamination. MEMS-based grippers in a size of 5 inch square are demonstrated in this study. It is shown that the attraction force is successfully obtained by the negative pressure of a spiral flow in each chamber, and that open holes play an important role in eliminating the interaction between the neighboring chambers and narrowing the holding gap so as to increase the force density over the entire object.