(searched for: doi:10.1109/tia.2014.2328780)
Meccanica pp 1-20; https://doi.org/10.1007/s11012-021-01461-w
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Journal of Vibration Engineering & Technologies, Volume 8, pp 751-760; https://doi.org/10.1007/s42417-019-00188-z
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AIP Advances, Volume 8; https://doi.org/10.1063/1.5005964
Magnetic levitation positioning system (MLPS) is considered to be the state of the art in inspection and manufacturing systems in vacuum. In this paper, a magnetic gravity compensator with annular magnet array (AMA-MGC) for MLPS is proposed. Benefiting from the double-layer annular Halbach magnet array on the stator, the proposed AMA-MGC possesses the advantages of symmetrical force, high force density and small force fluctuation. Firstly, the basic structure and operation principle of the AMA-MGC are introduced. Secondly, the basic characteristics of the AMA-MGC such as magnetic field distribution, levitation force, parasitic force and parasitic torque are analyzed by the three-dimensional finite element analysis (3-D FEA). Thirdly, the influence of structural parameters on force density and force fluctuation is investigated, which is conductive to the design and optimization of the AMA-MGC. Finally, a prototype of the AMA-MGC is constructed, and the experiment shows good agreement with the 3-D FEA results.
MATEC Web of Conferences, Volume 119; https://doi.org/10.1051/matecconf/201711901013
Magnetic levitation vibration isolators have attracted more and more attention in the field of high-precision measuring and machining equipment. In this paper, we describe a tubular horizontal-gap passive magnetic levitation vibration isolator. Four typical topologies of the tubular horizontal-gap passive magnetic levitation vibration isolator are proposed. The analytical expression of magnetic force is derived. The relationship between levitation force, force density, force ripple and major structural parameters are analysed by finite element method, which is conductive to the design and optimization of the tubular horizontal-gap passive magnetic levitation vibration isolator. The force characteristics of different topologies of the tubular horizontal-gap passive magnetic levitation vibration isolator are compared and evaluated from the aspect of force density, force ripple and manufacturability. In comparison with conventional passive magnetic levitation vibration isolators, the proposed tubular horizontal-gap passive magnetic levitation vibration isolator shows advantage in higher force density.
Mechanical Systems and Signal Processing, Volume 84, pp 673-698; https://doi.org/10.1016/j.ymssp.2016.07.050
Shock and Vibration, Volume 2016, pp 1-12; https://doi.org/10.1155/2016/5327207
In this paper, we describe a flat-type vertical-gap passive magnetic levitation vibration isolator (FVPMLVI) for active vibration isolation system (AVIS). A dual-stator scheme and a special stator magnet array are adopted in the proposed FVPMLVI, which has the effect of decreasing its natural frequency, and this enhances the vibration isolation capability of the FVPMLVI. The structure, operating principle, analytical model, and electromagnetic and mechanical characteristics of the FVPMLVI are investigated. The relationship between the force characteristics (levitation force, horizontal force, force ripple, and force density) and major structural parameters (width and thickness of stator and mover magnets) is analyzed by finite element method. The experiment result is in good agreement with the theoretical analysis.1. IntroductionActive vibration isolation system (AVIS), which integrates actuators with passive gravity compensation devices, can effectively improve the accuracy of measuring and machining equipment. Therefore, active vibration isolation systems have been widely used in many advanced industrial applications such as microscopy and lithography. As an important component of active vibration isolation system, the passive gravity compensation device plays the role of supporting and vibration isolation, and such characteristics like high force density and low natural frequency are required. More importantly, lower natural frequency leads to wider vibration isolation bandwidth and lower vibration transmissibility. Owing to the advantage of low natural frequency, air springs are widely adopted as passive gravity compensation devices in many active vibration isolation systems. However, some ultraprecision equipment must operate in a moderate vacuum, for example, extreme ultraviolet lithography . It is difficult for air springs to be applied in vacuum environment, because air springs need compressed gas . To solve the problem, passive magnetic levitation vibration isolator is used as a substitute for air spring.Passive magnetic levitation vibration isolators generate levitation force by interaction between magnets and have drew increased interest in recent years due to their feature of vacuum compatibility. Puppin and Fratello proposed a vibration isolation apparatus composed of four passive magnetic levitation vibration isolators in 2002; its natural frequency is 6.1 Hz at a load of 4 kg and 5.8 Hz at a load of 15 kg . Zhu et al. proposed a passive magnetic levitation vibration isolator composed of ring-shaped permanent magnets; they studied its axial force and stiffness characteristics, and its natural frequency is about 6 Hz . Robertson et al. proposed a multipole array passive magnetic levitation vibration isolator  and studied the design method of passive magnetic levitation vibration isolators [5, 6]. Lomonova et al. also studied the design method of passive magnetic levitation vibration isolators [7–9]. Zhu et al. proposed a vibration isolator composed of permanent magnets and rubber ligaments, they reduced the natural frequency of the vibration isolator by about 50%, and its lowest natural frequency is 2.75 Hz . Xu et al. designed a vibration isolation system composed of permanent magnets and a coil spring . Wu et al. designed a vibration isolator composed of three cuboidal magnets and a coil spring; its natural frequency is reduced from 10.45 Hz to 4.96 Hz at a load of 2.29 kg . Shin analyzed the maximum vibration transmissibility of a vibration isolator composed of four magnets and two coil springs . Zheng et al. designed a vibration isolator composed of ring-shaped magnets and a coil spring; its natural frequency is reduced from 9.0 Hz to 5.8 Hz . As mentioned above, most published works about this kind of device show higher natural frequency than air springs, which is adverse for vibration isolation.Herein, we propose a flat-type vertical-gap passive magnetic levitation vibration isolator (FVPMLVI) that features vacuum compatibility, low natural frequency, and no mechanical contact. A dual-stator scheme is adopted in the proposed FVPMLVI to decrease its natural frequency. This paper focuses on the operation principle and characteristics analysis of the FVPMLVI and provides useful advices for its application. This paper is organized as follows. In Section 2, the structure and operation principle of the FVPMLVI are introduced. In Section 3, the analytical model of the FVPMLVI is established. In Section 4, the electromagnetic and mechanical characteristics of the FVPMLVI are studied in detail by finite element method, and the force characteristics experiment is carried out. A summary is included in Section 5.2. Structure and Operating PrincipleThe proposed flat-type vertical-gap passive magnetic levitation vibration isolator consists of three components, that is, upper stator, mover, and lower stator, as shown in Figure 1. The mover consists of an aluminum plate and two vertically magnetized magnets. Both the upper and the lower stators consist of an aluminum plate, three vertically magnetized magnets, and two horizontally magnetized magnets. The magnetization direction of the magnets is shown as arrows in Figures 1 and 2. The major structural parameters of flat-type vertical-gap passive magnetic levitation vibration isolator are shown in Figure 2.Figure 1: The structure of flat-type vertical-gap passive magnetic levitation vibration isolator.Figure 2: The major structural parameters of flat-type vertical-gap passive magnetic levitation vibration isolator and the magnetization direction of magnets.The flat-type vertical-gap passive magnetic levitation vibration isolator generates levitation force by the attraction and repulsion between stator and mover magnets. The mover is suspended above the stator by the magnetic force between stator and mover magnets. When the mover moves relative to the stators along the vertical direction, the upper stator and mover generate attractive force with negative stiffness and the lower stator and mover generate repulsive force with positive stiffness; thus the total levitation force is near-constant. When the mover moves relative to the stators along the horizontal direction, the total levitation force generated by magnets on the left side and the right side is also near-constant. Through adopting the dual-stator structure and inserting horizontally magnetized magnets, the flat-type vertical-gap passive magnetic levitation vibration isolator can generate near-constant levitation force and near-zero stiffness in six-degree of freedom stroke, which is useful for improving the vibration isolation performance of active vibration isolation system.The proposed flat-type vertical-gap passive magnetic levitation vibration isolator has two advantages: () using parallel magnetized cubic magnets; the vertically and horizontally magnetized magnets used in FVPMLVI are parallel magnetized cubic magnets; compared with radially magnetized magnets used in many vibration isolators, the parallel magnetized cubic magnets have advantages of simple structure, good manufacturability, and low cost; and () low natural frequency. The natural frequency of FVPMLVI can be decreased effectively by adopting dual-stator scheme and special stator magnet array.3. Analytical ModelThe force generated by flat-type vertical-gap passive magnetic levitation vibration isolator can be calculated by superposition of magnetic force between each two magnets (one of the two magnets is on the stator and another is on the mover). The magnetic force between magnets can be calculated by the equivalent charge model. The equivalent charge model of flat-type vertical-gap passive magnetic levitation vibration isolator is shown in Figure 3. The cuboidal magnets are equivalent to a series of charged rectangular surface.Figure 3: The equivalent charge model of flat-type vertical-gap passive magnetic levitation vibration isolator.According to the work of Allag et al. , the magnetic force between two magnets with parallel and perpendicular magnetization can be expressed as and , separately. Since there are 6 vertically magnetized magnets on the stators and 2 vertically magnetized magnets on the mover, thus there are pairs of magnets with parallel magnetization. Similarly, there are 4 horizontally magnetized magnets on the stators; thus there are pairs of magnets with perpendicular magnetization. Then, the force of the flat-type vertical-gap passive magnetic levitation vibration isolator is given bywhere is the magnetic force between two magnets with parallel magnetization and is the magnetic force between two magnets with perpendicular magnetization.Thus the stiffness and natural frequency of the flat-type vertical-gap passive magnetic levitation vibration isolator can be expressed as (2) and (3).where is the stiffness, is the variation of force, and is the displacement.where is the natural frequency, is the total mass of mover, and load is the gravitational acceleration.As shown in (3), compared to stiffness , the force ripple within unit displacement is a better indicator which can reflect the vibration isolator’s vibration isolation performance, because the natural frequency is directly related to vibration isolation ability. Therefore, force ripple is analyzed instead of stiffness in the next section.4. Electromagnetic and Mechanical Characteristics AnalysisIn order to provide useful advice for application, the electromagnetic and mechanical characteristics of FVPMLVI such as levitation force, horizontal force, force ripple, and force density are analyzed in this section. Firstly, the force characteristics of FVPMLVI which varied with mover position are studied, and the principle of reducing force ripple is analyzed. Then, the influence of major structural parameters on the device performance like levitation force, force density, and force ripple is studied. At last, the force char
Published: 1 November 2015
2015 International Conference on Sustainable Mobility Applications, Renewables and Technology (SMART) pp 1-5; https://doi.org/10.1109/smart.2015.7399245
Conference: 2015 International Conference on Sustainable Mobility Applications, Renewables and Technology (SMART), 2015-11-23 - 2015-11-25
Many modern advanced electromagnetic devices, e.g. motors and actuators, use permanent magnets as a source of magnetic fields. The strong and reliable magnetic fields of today's rare-earth permanent magnets increase their force density. Most of them are based on the interaction between the magnetic field of permanent magnets and current-carrying coils. However, magnetic couplings or electromagnetic vibration isolation systems rely on the strong and position-dependent passive force between permanent magnets instead of an active force resulting from a current. An accurate, noise-free computational description of these interactions is therefore essential for future developments of these high-performance devices. The considered configurations are free-space unbounded problems and do not exhibit structural periodicity. As a three-dimensional magnetic field solution is required, the analytical surface charge method is the model of choice. The expressions for the interaction force between PMs with an (anti-)parallel, perpendicular, and rotated magnetization are derived considering a configuration with two PMs. These could be extended to include various other electromagnetic device structures. Further, the developments in the analytical surface charge expressions of the interaction forces between cuboidal permanent magnets are addressed. Finally, extensions to the surface charge method are proposed, aiming to create a fully 6-DoF permanent magnet interaction model, which can serve as a fast, analytical replacement to the finite element method.