Horizontal Levitation Research Articles

Design of Zero-Power Control Strategy With Resisting Tilt of Hybrid Magnetic Levitation System

Traditional multipoint hybrid maglev systems cannot realize the zero-power horizontal levitation state under eccentric load, which means the steady-state current is zero, and the air gap of each magnet is equal. This article proposes a new maglev system with two rotary magnets to solve this problem. The two magnets can move on an annular guideway to counteract the moment caused by the eccentric load. At first, we established the linear parameter varying model of this maglev system. Then, the control strategy is designed, which consists of a zero-power horizontal levitation controller and rotation controller. The levitation control is realized by introducing feedback of integral current and deviation of air gap in the proportional-derivative control system. The rotation controller employs a centroid observer and centroid Jacobian. It outputs the rotating angle at the demand of the zero-power and horizontal levitation. Experimental results demonstrate that the proposed maglev system has a better zero power and horizontal levitation performance than without rotary magnets. The direction of the air gap variation is opposite to that of the loading direction. The variation size of air gap length depends on the load weight, whereas rotation angle is related to the load weight and loading position.

An analysis of diamagnetic levitation away from a suspending magnet’s central axis

This paper extends previous work about diamagnetic levitation to include positions not along the central axis of a single suspending magnet. Previous work assumes a single levitating magnet located at the central axis of a permanent or electromagnet. However several applications require magnets located away from that axis, but still levitating in an axis symmetric field. This paper presents a mathematical model to allow one to calculate equilibrium positions for levitating magnets rotors using multiple levitating magnets for suspension. In order to compare with experiments, this paper contains specific equations for cylindrical levitating and suspending magnets. Additionally, the mathematical model can predict levitation positions for horizontal levitation configuration using two suspending magnets. Experimental results for equilibrium positions agree well with theoretical predictions. Using this formulation, the authors designed and successfully demonstrated a working diamagnetic suspended motor and generator system. The results have been reported in an earlier publication.

Dependence of Horizontal Vibration Characteristics on Load Weight Distribution in Magnetic Levitation Type Seismic Isolation Device

We have developed a magnetic levitation type seismic isolation device. The device could remove any horizontal vibrations very effectively. Three-layer structure was adopted in the device. The bottom layer was composed of permanent magnets. The middle layer comprised HTS bulks and permanent magnets. The top layer consisted of HTS bulks. The horizontal vibration characteristics in the middle layer depended on the air gap between the bottom and middle layers; the air gap was closely related to the load weight distribution in the top and middle layers. Inhomogeneous load weight distribution caused the different air gap in each bulk. Horizontal levitation against the inhomogeneous load weight distribution, however, could be obtained by adjusting the initial offset angle of each bulk in field-cooling process. The smaller initial air gap was effective in realizing horizontal levitation; the difficulty of horizontal levitation increased with the initial air gap. Independent of the load weight distribution, almost the same characteristics of horizontal vibration were obtained in the small initial air gap.

Stability of Alternative Horizontal Levitation Electromagnetic Continuous Casting of Aluminum Sheet.

Stability of Alternative Horizontal Levitation Electromagnetic Continuous Casting of Aluminum Sheet.

Vapor Levitation Epitaxy—A New Concept in Crystal Growth

Bell Communications Research (Bellcore) scientists Herbert M. Cox, Steve G. Hummel and Vassilis G. Keramidas recently unveiled a revolutionary crystal growth process used in growing semiconductor materials of importance to many areas of fiber optic communications. The technique, called Vapor Levitation Epitaxy (VLE), is based on the concept of floating wafers while growing thin film crystalline layers on them. The method has produced exceptionally pure materials such as GaAs, InP, InGaAs, InGaAsP and GalnP. The capability of growing ultra high purity materials combined with the ability to grow ultra thin layers-a few atoms thick-makes the new technique uniquely powerful. In addition, exceptional uniformity of thickness and materials composition can be achieved across the whole area of two-inch diameter wafers. These capabilities are essential to the growth of multilayer structures needed for new applications in photonic and electronic devices and integrated circuits, and integrated opto-electronics for fiber optic communications. The VLE apparatus has two adjacent growth chambers capped with porous disks and a horizontal levitation track with a series of small gas jet holes along its center (see Figure 1). The gas jets suspend the wafer on a cushion of gas as it is moved between the wafer loading area and the growth region of the apparatus. Each growth chamber is supplied independently with vapors for the particular material to be grown. During growth, the wafer floats a few tenths of a millimeter above the chamber suspended stably by the growth vapors as

Vapor levitation epitaxy: A new concept in epitaxial crystal growth

Abstract The concept of a new epitaxial growth technique called Vapor Levitation Epitaxy (VLE) is described. With this technique the substrate is floated above the growth apparatus by the growht vapors emerging from a chamber through a porous disc. Growth occurs on the underside of the substrate. Movement of the substrate from one growth chamber to an adjacent chamber provides very abrupt doping and compositional interfaces. The substrate is moved to and from the growth chambers along a horizontal levitation track on a cushion of gas. GaAs, InP and InGaAs layers, as well as quantum-well heterostructures, have been grown with a VLE system.

Single crystal growth by the horizontal levitation zone melting method

The method used to prepare large single crystals of some rare earth metals and intermetallic compounds is described. A levitated molten zone is passed along a rod shaped sample which is contained in a cold crucible in the horizontal position. The high frequency power system used to both create and levitate the molten zone is also described. The conditions required to grow crystals larger than one cubic centimeter of both incongruwnt and congruent melting compounds are given. The quality and some pertinent property values of the crystals as determined by X-ray and metallographic methods are included.