Magnetic suspension system, carrier for magnetic suspension system and method of operating magnetic suspension system

Abstract

There is provided a magnetic levitation system comprising: a base structure; a carrier movable relative to the base structure in a transport direction; and at least one active magnetic bearing configured to generate a magnetic retention force acting in a retention direction for retaining the carrier at the base structure. The carrier and / or the base structure includes a plurality of damping units, a first damping unit of the plurality of damping units being tuned to a first frequency or a first frequency range, and a second damping unit of the plurality of damping units being tuned to a second frequency or a second frequency range.

Description

[0001] This application is a divisional application of the invention patent application with the application date of March 1, 2019, application number 201980093452.X, and invention name "Magnetic levitation system, carrier for magnetic levitation system and method for operating magnetic levitation system". Technical Field

[0002] Various embodiments of the present disclosure relate to a magnetic levitation system configured to hold and transport a carrier, particularly to hold and transport a carrier in a vacuum chamber. More specifically, a magnetic levitation system configured to hold, position and / or move a carrier in a vacuum chamber without contact is described. Various embodiments further relate to a carrier for a magnetic levitation system, the carrier being configured to carry an object, such as a substrate or a mask, in a vacuum chamber. In addition, a method of operating a magnetic levitation system is described. Background Art

[0003] Magnetic levitation systems can be used for non-contact or substantially non-contact transport of a carrier relative to a base structure, for example at sub-atmospheric pressure in a vacuum chamber. An object carried by the carrier, such as a substrate or a mask, can be transported from a first position in the vacuum system, i.e., a loading position, to a second position in the vacuum system, such as a deposition position. Magnetic levitation systems allow substantially non-contact transport of the carrier and can reduce the generation of small particles in the vacuum processing system because friction between the carrier and the transport system is reduced or completely avoided.

[0004] Magnetic levitation systems typically include one or more actively controlled magnetic bearings configured to hold a carrier at a predetermined distance from a base structure via magnetic forces. Accurate active control of the carrier's position may be difficult because the carrier, which is held substantially contactlessly via magnetic forces, tends to vibrate. Such vibrations may be caused by the active magnetic bearings of the magnetic levitation system or other sources.

[0005] Complex control algorithms of active magnetic bearings can be used to reduce carrier vibrations. However, reducing or avoiding oscillations of a carrier of a magnetic levitation system can be challenging, particularly because the oscillatory behavior of the carrier is typically complex and depends on the size, shape, and material of the carrier and the size, shape, and material of the object carried by the carrier. Oscillations of the carrier can adversely affect the transport stability and positioning accuracy of the carrier.

[0006] Therefore, it would be beneficial to improve the transport and positioning accuracy of a carrier of a magnetic levitation system.In addition, it would be beneficial to provide a carrier for a magnetic levitation system that is suitable for accurate and precise transport and retention at a base structure of the magnetic levitation system. Summary of the invention

[0007] In view of the above, a magnetic levitation system, a carrier for the magnetic levitation system and a method for operating the magnetic levitation system are provided.

[0008] According to one aspect of the present disclosure, a magnetic levitation system is provided. The magnetic levitation system includes: a base structure; a carrier, the carrier is movable relative to the base structure in a transport direction; and at least one active magnetic bearing, the at least one active magnetic bearing is configured to generate a magnetic holding force acting in a holding direction for holding the carrier at the base structure. The carrier includes a plurality of damping units, a first damping unit of the plurality of damping units is tuned to a first frequency or a first frequency range, and a second damping unit of the plurality of damping units is tuned to a second frequency or a second frequency range.

[0009] According to another aspect of the present disclosure, a magnetic levitation system is provided. The magnetic levitation system includes: a base structure; a carrier, the carrier is movable relative to the base structure in a transport direction; and at least one active magnetic bearing, the at least one active magnetic bearing is configured to generate a magnetic holding force acting in a holding direction for holding the carrier at the base structure. The base structure includes a plurality of damping units, a first damping unit of the plurality of damping units is tuned to a first frequency or a first frequency range, and a second damping unit of the plurality of damping units is tuned to a second frequency or a second frequency range.

[0010] The first frequency is different from the second frequency. In some embodiments, the first frequency may substantially correspond to a first normal frequency of the carrier, and the second frequency may substantially correspond to a second normal frequency of the carrier. Thus, different normal modes of the carrier can be damped using the plurality of damping units.

[0011] According to another aspect of the present disclosure, there is provided a carrier for a magnetic levitation system, the carrier being configured to interact with a base structure of the magnetic levitation system so that the carrier can be held at the base structure and movable relative to the base structure. The carrier comprises a plurality of damping units, a first damping unit of the plurality of damping units being tuned to a first frequency or a first frequency range, and a second damping unit of the plurality of damping units being tuned to a second frequency or a second frequency range.

[0012] According to another aspect of the present disclosure, a base structure of a magnetic levitation system is provided, the base structure being configured to interact with a carrier of the magnetic levitation system so that the carrier can be held at the base structure and movable relative to the base structure. At least one active magnetic bearing is disposed at the carrier or the base structure to generate a magnetic holding force acting in a holding direction for holding the carrier at the base structure. The base structure includes a plurality of damping units, a first damping unit of the plurality of damping units being tuned to a first frequency or a first frequency range, and a second damping unit of the plurality of damping units being tuned to a second frequency or a second frequency range.

[0013] According to another aspect described herein, a method for operating a magnetic levitation system is provided, the magnetic levitation system comprising a base structure and a carrier movable relative to the base structure in a transport direction. The method comprises actively controlling at least one active magnetic bearing to generate a magnetic holding force to hold the carrier at the base structure. In addition, the method comprises damping vibrations of the carrier with a plurality of damping units fixed to the carrier, a first damping unit of the plurality of damping units being tuned to a first frequency or a first frequency range, and a second damping unit of the plurality of damping units being tuned to a second frequency or a second frequency range.

[0014] According to another aspect described herein, a method for operating a magnetic levitation system is provided, the magnetic levitation system comprising a base structure and a carrier movable relative to the base structure in a transport direction. The method comprises actively controlling at least one active magnetic bearing to generate a magnetic holding force that holds the carrier at the base structure. In addition, the method comprises damping vibrations of the base structure with a plurality of damping units fixed to the base structure, a first damping unit of the plurality of damping units being tuned to a first frequency or a first frequency range, and a second damping unit of the plurality of damping units being tuned to a second frequency or a second frequency range.

[0015] Further aspects, advantages and features of the disclosure are apparent from the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to understand in detail the manner in which the above-mentioned features of the present disclosure are achieved, a more particular description of the present disclosure briefly outlined above may be obtained with reference to a number of embodiments. The accompanying drawings relate to a number of embodiments of the present disclosure and are described as follows. Typical embodiments are depicted in the drawings and detailed in the following description.

[0017] Figure 1 is a schematic side view of a magnetic levitation system according to various embodiments described herein.

[0018] Figure 2 is a schematic side view of a magnetic levitation system according to various embodiments described herein.

[0019] Figure 3A is a schematic side view of a carrier according to various embodiments described herein.

[0020] Figure 3B It is shown Figure 3A Graph of the oscillatory behavior of a carrier, the carrier vibrating in different normal modes.

[0021] Figure 4A is a schematic diagram illustrating the operating principle of a damping unit configured as a tuned mass damper as used in various embodiments described herein.

[0022] Figure 4B is a schematic diagram showing the damping unit being mounted to a carrier.

[0023] Figure 4C is a schematic cross-sectional view showing two damping units in a common housing as used in various embodiments described herein.

[0024] Figure 5 is a graph showing the location of the natural frequency of a typical undamped carrier.

[0025] Figure 6 is a flow chart illustrating a method of operating a magnetic levitation system according to various embodiments described herein. DETAILED DESCRIPTION

[0026] Reference will now be made in detail to various embodiments, one or more examples of which are shown in the figures. Each example is provided by way of explanation and is not intended to be limiting. For example, features shown or described as part of one embodiment may be used on other embodiments or in conjunction with other embodiments to produce yet another embodiment. The present disclosure is intended to include such modifications and variations.

[0027] In the following description of the drawings, the same reference numerals refer to the same or similar parts. Generally speaking, only the differences with respect to a single plurality of embodiments are described. Unless otherwise specified, the description of a part or aspect in one embodiment also applies to the corresponding part or aspect in another embodiment.

[0028] Figure 1is a schematic cross-sectional view of a magnetic levitation system 100 according to various embodiments described herein. The magnetic levitation system 100 includes a base structure 110 and a carrier 120, which can be held at the base structure 110 in a non-contact or substantially non-contact manner and is movable relative to the base structure 110 in a transport direction T. The base structure 110 may include one or more tracks. At least one active magnetic bearing 112 may be disposed at the track of the base structure 110. In some embodiments, a plurality of active magnetic bearings are disposed at the base structure 110 and are arranged such that the carrier can move along the base structure 110 while the carrier is held at the base structure in a non-contact or substantially non-contact manner by the plurality of active magnetic bearings. In another embodiment, one or more active magnetic bearings may be disposed at the carrier and configured to interact magnetically with the base structure.

[0029] At least one active magnetic bearing 112 may be arranged above the carrier 120 during transport of the carrier, and the magnetic holding force generated by the at least one active magnetic bearing 112 may act on the carrier in a holding direction V, which is typically a substantially vertical direction. In other words, the at least one active magnetic bearing 112 may provide a controlled magnetic force that pulls the carrier in an upward direction toward the at least one active magnetic bearing 112 and holds the carrier at a predetermined distance from the at least one active magnetic bearing.

[0030] exist Figure 1 In the depicted embodiment, the base structure 110 includes a top rail arranged above the carrier 120, and the carrier 120 is held below the top rail. Alternatively or additionally, the base structure 110 may include a bottom rail arranged below the carrier, wherein the carrier is held above the bottom rail. At least one active magnetic bearing 112 may be configured to generate a magnetic force acting between the base structure 110 and the carrier 120 in a holding direction V, so that the carrier is held at a predetermined distance from the base structure. In some embodiments, the at least one active magnetic bearing 112 is configured to generate a magnetic force acting in a substantially vertical direction.

[0031] In some embodiments, at least one active magnetic bearing 112 comprises an actuator arranged at the base structure 110, in particular at the top rail of the base structure 110. The actuator may comprise a controllable magnet, such as an electromagnet. The actuator may be actively controllable for maintaining a predetermined distance between the base structure 110 and the carrier 120. A magnetic counterpart 118 may be arranged at the carrier 120, in particular at the head portion of the carrier. The magnetic counterpart 118 of the carrier may interact magnetically with the actuator of the at least one active magnetic bearing 112.

[0032] More specifically, output parameters such as the current applied to the actuator may be controlled based on input parameters such as the distance between the carrier and the base structure. Specifically, the distance between the base structure 110 and the carrier 120 may be measured by a distance sensor, and the magnetic field strength of the actuator may be set based on the measured distance. In particular, in the case where the distance is above a predetermined threshold, the magnetic field strength may be increased, and in the case where the distance is below the threshold, the magnetic field strength may be reduced. The actuator may be controlled by closed loop or feedback control.

[0033] There is a risk that the control of the at least one active magnetic bearing 112 causes carrier vibrations. A specific control algorithm for controlling the at least one active magnetic bearing may be provided to reduce carrier vibrations at least in a low frequency range (e.g. below 30 Hz). However, it is typically difficult to reduce or avoid carrier vibrations in a higher frequency range (e.g. above 30 Hz or above 50 Hz) with the control of the active magnetic bearing. The reduction of vibrations in the so-called "critical damping range" between 50 Hz and 250 Hz is particularly difficult. High frequency ranges, e.g. above 300 Hz, are typically less problematic, since the control of the active magnetic bearing 112 typically does not provide enough power in said range to cause carrier vibrations.

[0034] Depending on the size, shape and material of the carrier 120, so-called "eigenmodes" or natural vibrations of the carrier may hinder a stable and robust control of the carrier position by the active magnetic bearings. For example, an already small excitation amplitude caused by the control of the at least one active magnetic bearing 112 may lead to a large resonance of the carrier at the natural frequency of the carrier. Complex control algorithms of the active magnetic bearings may be used to reduce the vibrations of the carrier during magnetic levitation, at least in the low frequency range. Alternatively or additionally, a damping unit may be used to reduce the vibrations of the carrier. For example, an active or passive damping unit may be provided for damping the carrier vibrations during magnetic levitation.

[0035] However, the above measures may not be sufficient to allow accurate positioning and stable transportation of a carrier using magnetic force. A number of embodiments described herein are intended to further improve the transportation stability and positioning accuracy of a carrier of a magnetic levitation system.

[0036] According to various embodiments described herein, the carrier 120 includes a plurality of damping units 130, wherein a first damping unit 131 of the plurality of damping units is tuned to a first frequency or a first frequency range, and a second damping unit 132 of the plurality of damping units is tuned to a second frequency or a second frequency range. The first frequency (first frequency range) is different from the second frequency (second frequency range). Alternatively or additionally, the base structure includes a plurality of damping units or a second plurality of damping units.

[0037] In other words, the carrier 120 and / or the base structure include a plurality of damping units, each of which is specifically tuned to specifically damp vibrations of a predetermined frequency. As used herein, a damping unit that is "tuned to" a specific frequency substantially provides a maximum damping effect at the frequency to which the damping unit is tuned (hereinafter referred to as the "damping frequency" of the damping unit). The damping effect provided by the tuned damping unit typically decreases from the damping frequency toward higher and lower frequencies. In other words, the damping curve of the damping unit has a minimum at the damping frequency and rises toward both sides of the damping frequency, thereby efficiently damping the carrier vibrations at the damping frequency. In the case of a broadband damper tuned to an extended frequency range, this rise is slow, while in the case of a small-bandwidth damper tuned to a specific frequency (e.g., a specific natural frequency of the carrier), this rise is steep. Specifically, the damping unit is configured so that vibrations at the frequency to which the damping unit is tuned can be effectively damped. As used herein, a damping unit "tuned to" a specific natural frequency of a carrier may be understood as a damping unit having a damping frequency within 10 Hz of the natural frequency to which the damping unit is tuned.

[0038] The damping ratio is a dimensionless constant of a damping unit, which characterizes the damping strength of the damping unit. In the mathematical description of oscillations, the damping ratio characterizes the factor before the first derivative of a local function. A damping ratio of 1 (critical damping) characterizes a damping unit that damps oscillations within one cycle (i.e., without exceeding the specification). A damping ratio of zero characterizes an undamped system. Values ​​of the damping ratio between 0 and 1 characterize a low damping system. A damping unit tuned to a damping frequency as used herein typically provides a damping ratio of 0.1 or greater at the damping frequency.

[0039] There are various ways to tune the damping unit to a specific damping frequency. For example, the damping unit may be a passive damper, such as a vibration absorber or a tuned mass damper having a damping mass movably fixed to the body to be damped via a spring element. The damping frequency depends on the spring constant of the damping mass and the spring element. Thus, the damping frequency can be set by providing, for example, a specific combination of the length and material of the damping mass, the spring element.

[0040] The carrier is characterized by a plurality of natural modes in which the carrier can vibrate. Each oscillation state of the carrier can be described by the superposition of a plurality of natural modes of the carrier. Each natural mode is characterized by a natural frequency. The basic natural mode of the carrier is the natural mode with the lowest natural frequency, i.e. the basic natural frequency. The basic natural frequency of the carrier (which can be understood as the vibration frequency of the vibration mode of the entire vibration of the carrier, i.e. the vibration frequency of the rigid body mode) is typically in the frequency range between 5 Hz and 30 Hz. Higher-order natural modes are characterized by higher natural frequencies in which the carrier can vibrate.

[0041] The natural modes of the carrier can be rigid body modes (where the carrier vibrates as a whole) and elastic modes (where different parts of the carrier vibrate relative to each other, such as torsion modes or bending modes). Typically, the oscillation state of the carrier is a superposition of rigid body modes and elastic modes at multiple natural frequencies. Depending on the properties of the carrier, the first elastic natural frequency may occur in the range between 50 Hz and 80 Hz.

[0042] Corresponding considerations apply to the oscillatory behavior of the base structure induced by the at least one active magnetic bearing.

[0043] In a magnetic levitation system, most of the carrier vibrations are typically caused by the magnetic holding force of at least one active magnetic bearing, which acts in a holding direction V, typically in a vertical direction. Therefore, the vibration amplitude of the carrier is highest in the holding direction V. Therefore, according to various embodiments described herein, at least some of the plurality of damping units 130 are oriented such that carrier vibrations in the holding direction V are damped.

[0044] However, carrier vibrations with amplitudes in other directions, for example in a lateral direction, are also possible. A lateral direction as used herein is a direction transverse to the holding direction V, in particular a horizontal direction perpendicular to the holding direction V. For example, lateral carrier vibrations may be caused by horizontally acting components of magnetic forces, which are generated by at least one active magnetic bearing. It may be reasonable in some embodiments to provide at least one damping unit (hereinafter referred to as lateral vibration damping unit) which is oriented such that carrier vibrations in a lateral direction are damped.

[0045] As described above, carrier vibrations in the low frequency range below 30 Hz can be efficiently damped by active control of at least one active magnetic bearing. However, higher order natural modes of the carrier characterized by higher natural frequencies cannot typically be adequately suppressed by control of the magnetic levitation forces. At least some of the damping units may be tuned to such higher natural frequencies of the carrier or to a frequency range that includes at least one or more higher natural frequencies.

[0046] According to some embodiments described herein, the first damping unit 131 is tuned to a first frequency in the frequency range from 50 Hz to 250 Hz, in particular to a first natural frequency of the carrier in the range, and the second damping unit 132 is tuned to a second frequency in the frequency range from 50 Hz to 250 Hz, in particular to a second natural frequency of the carrier in the range that is different from the first frequency. For example, the first damping unit 131 is tuned to a natural frequency of a second-order natural mode of the carrier, and the second damping unit 132 is tuned to a natural frequency of a third-order natural mode of the carrier. Typically, the natural frequencies of at least the second to fifth-order natural modes of the carrier are in the frequency range from 50 Hz to 250 Hz.

[0047] Figure 5 is a graph showing the natural frequency of a typical undamped carrier. The x-axis shows the frequency in Hertz and the y-axis shows the relative amplitude of the carrier oscillation at the corresponding frequency expressed in a logarithmic scale (in dB). Only the oscillatory behavior of the carrier in the holding direction V is shown. Figure 5 As is clearly shown, the fundamental natural mode of the carrier has a fundamental natural frequency E0 in the frequency range between 5 Hz and 30 Hz. Figure 5 As shown by the high peak value, in the absence of damping, the carrier can be excited to high amplitude vibration at the basic natural frequency E0.

[0048] A plurality of natural modes of the carrier have natural frequencies E2, E3, E4, E5 within the critical damping range X between 50 Hz and 250 Hz. Other higher order natural modes may exist in the critical damping range X depending on the carrier characteristics. Figure 5 As shown by the peaks in the critical frequency range X, without damping the carrier can be excited to vibrations with considerable amplitudes at these frequencies. A damped carrier with multiple damping units tuned to frequencies in the critical frequency range X has less pronounced peaks in the critical frequency range X.

[0049] During transport of the carrier, the carrier can be vibrated at a basic natural frequency E0 and / or one or more higher natural frequencies E1, E2, E3, E4, E5, E6. The vibration excitation can occur in a forced manner by a magnetic holding force generated by at least one active magnetic bearing 112. The basic natural mode can be damped at least to a certain extent by a controller of at least one active magnetic bearing. A plurality of damping units 130 can be tuned to at least some natural frequencies, such as the natural frequencies E1, E2, E3, E4 and / or E5 of the first to fifth natural modes of the carrier. In some embodiments, a plurality of damping units are tuned to different frequencies within a critical damping range from 50 Hz to 250 Hz, which frequencies do not necessarily correspond exactly to the natural frequencies. If several damping units are tuned to different frequencies distributed within the critical frequency range, the natural modes of the carrier within the range will also be significantly damped.

[0050] return Figure 1 , the first damping unit 131 and the second damping unit 132 can be tuned to different frequencies, in particular different natural frequencies of the carrier, more particularly different frequencies in the critical frequency range between 50 Hz and 250 Hz. In some embodiments, the first damping unit 131 and the second damping unit 132 are tuned to different high-order natural frequencies in the critical frequency range between 50 Hz and 250 Hz. Therefore, the vibration of the carrier in the critical damping range between 50 Hz and 250 Hz can be reliably damped, and smooth and reliable carrier transportation can be provided.

[0051] In some embodiments, the first damping unit 131 and the second damping unit 132 are oriented to damp the carrier vibration in the holding direction V or the vibration of the base structure in the holding direction V. In particular, the plurality of damping units 130 may be configured as passive dampers, wherein the damping mass is configured to be movable in the holding direction V. The damping mass movably fixed to the carrier (or to the base structure) to vibrate in the holding direction V can counteract the carrier vibration (or the vibration of the base structure) in the holding direction V. Therefore, the carrier vibration in the holding direction caused by the at least one active magnetic bearing 112 can be reliably reduced.

[0052] In some embodiments, the plurality of damping units 130 includes three or more damping units, five or more damping units, eight or more damping units, or even fifteen or more damping units, which are respectively oriented to damp vibrations in the retention direction V.

[0053] like Figure 1As depicted, the carrier may include a head portion that interacts magnetically with the base structure 110 and a bottom portion that is configured to carry an object, in particular a substrate 10. The first damping unit 131 and / or the second damping unit 132 may be disposed at the head portion of the carrier. In particular, five or more damping units of the plurality of damping units may be disposed at the head portion of the carrier 120. The elastic mode of the carrier caused by at least one active magnetic bearing is typically stronger at the head portion of the carrier than at the bottom portion of the carrier, because the head portion is closer to the base structure during transport of the carrier. Therefore, vibrations of the carrier can be damped more efficiently.

[0054] In some embodiments, which may be combined with other embodiments described herein, the plurality of damping units 130 comprises at least one central damping unit arranged in a central portion of the carrier in the transport direction T and / or at least one edge damping unit arranged in a front portion or a rear portion of the carrier in the transport direction T. The central damping unit 133 may be substantially tuned to the natural frequency of the natural mode having the maximum amplitude in the central portion of the carrier. Alternatively or additionally, the edge damping unit 134 may be substantially tuned to the natural frequency of the natural mode having the maximum amplitude in the corresponding edge portion of the carrier in which the edge damping unit 134 is arranged. Thus, different natural modes of the carrier can be efficiently damped with associated damping units, the damping units also being adapted to damp the corresponding natural modes by corresponding positioning. In some embodiments, two or more edge damping units are provided, at least one edge damping unit being arranged in the front portion of the carrier and at least one edge damping unit being arranged in the rear portion of the carrier in the transport direction T.

[0055] In some embodiments, two or more central damping units are arranged in a central part of the carrier. The central damping units may be tuned to the same frequency or to different frequencies, in particular to different natural frequencies of a natural mode of the carrier having a maximum vibration amplitude in the central part of the carrier, respectively. In some embodiments, two or more edge damping units are arranged in an edge part of the carrier in the transport direction T. The edge damping units may be tuned to the same frequency or to different frequencies, in particular to different natural frequencies of a natural mode of the carrier having a maximum vibration amplitude in an edge part of the carrier, respectively.

[0056] In some embodiments, the edge damping unit 134 is tuned to a higher frequency than the central damping unit 133. This is because the high-order natural modes of the carrier in the critical damping range typically have the maximum vibration amplitude in the edge region of the carrier. For example, the central damping unit 133 is tuned to a frequency in the range between 50 Hz and 120 Hz, and the edge damping unit 134 is tuned to a frequency in the range between 150 Hz and 250 Hz.

[0057] Figure 2 is a schematic side view of a magnetic levitation system 200 according to various embodiments described herein. Figure 2 Most of the details of the magnetic levitation system 200 correspond to Figure 1 The details of the magnetic levitation system 100 can be referred to the above description and will not be repeated herein.

[0058] The magnetic levitation system 200 includes a base structure 110, which may include a top rail and a bottom rail. At least one active magnetic bearing 112 may be arranged at the base structure 110, in particular at the top rail. At least one active magnetic bearing 112 is configured to generate a magnetic holding force acting in a holding direction V for holding the carrier in a floating state at the base structure. In some embodiments, at least one drive unit 114 for moving the carrier in a transport direction T may be arranged at the base structure 110, for example, at the bottom rail of the base structure. At least one drive unit 114 may be a linear motor configured to transport the carrier along the base structure in the transport direction T. The carrier may include a counterpart at the bottom portion, which is configured to interact magnetically with at least one drive unit 114.

[0059] The carrier 120 comprises a plurality of damping units 130, a first damping unit being tuned to a first frequency f1, a second damping unit being tuned to a second frequency f2, and a third damping unit being tuned to a third frequency f3, wherein the first frequency, the second frequency and the third frequency are different. Other damping units that are tunable to other frequencies or at least partially tuned to the same frequency may be provided. Figure 2 In the depicted example, five damping units are arranged at the head portion 121 of the carrier, in particular in a linear array. Two edge damping units are tuned to the same frequency f1 (e.g., a frequency between 120 Hz and 200 Hz, such as about 160 Hz) and are arranged symmetrically with respect to a vertical axis intersecting the center of the carrier. One central damping unit is arranged in the middle of the carrier in the transport direction T and is tuned to a frequency f3 (e.g., a frequency between 80 Hz and 120 Hz, such as about 105 Hz). Two additional central damping units are arranged in the central part of the carrier and are tuned to the same frequency f2 (e.g., a frequency between 60 Hz and 90 Hz, such as about 85 Hz).

[0060] like Figure 2 As depicted, in some embodiments, the arrangement of the damping units may be symmetrical about an axis intersecting the center of the carrier. In some embodiments, five or more damping units may be provided, each tuned to a different frequency or a different frequency range.

[0061] In some embodiments that may be combined with other embodiments described herein, the plurality of damping units include 3 or more damping units, particularly 5 or more damping units, more particularly 8 or more damping units, which are tuned to 3 or more different frequencies, particularly frequencies within a critical damping range between 50 Hz and 250 Hz.

[0062] If a number of damping units are provided that are tuned to different frequencies distributed within a critical frequency range from 50 Hz to 250 Hz, it may not be necessary to tune the damping units exactly to the natural frequencies of the carrier. This is because a number of damping units (e.g., five or more damping units) having damping frequencies within the critical damping range will also significantly damp the natural frequencies within said range, even if the damping frequencies of the damping units do not exactly correspond to the natural frequencies of the carrier. This approach, which aims to damp the dynamic carrier eigenmodes within a certain frequency range with a plurality of differently tuned damping units, is referred to herein as the "multi damper concept". It may not be necessary to tune the damping units exactly to the natural modes or eigenmodes of the carrier.

[0063] Three or more damping units, in particular five or more damping units, may be arranged in a linear array, in particular at a head portion 121 of the carrier configured to interact with at least one active magnetic bearing 112. The arrangement of a plurality of damping units 130 in a linear array, wherein the linear array extends in the transport direction T, may be beneficial for reliable damping in an extended frequency range without inducing additional vibration modes. In particular, as Figure 2 Depicted schematically, the array of damping units may be symmetrical or substantially symmetrical about an axis intersecting vertically with the centre of the carrier.

[0064] The outermost damping units may be tuned to higher frequencies, whereas the centrally arranged damping units may be tuned to lower frequencies.

[0065] The carrier has a dimension of 1 m or more, in particular 2 m or more, more particularly 3 m or more or even 4 m or more in the transport direction T and / or the holding direction V. Large carriers have considerable weight, which generally reduces the values ​​of the normal frequencies of the corresponding eigenmodes. Lower frequencies can generally be damped more easily than higher frequencies.

[0066] In some embodiments that may be combined with other embodiments described herein, the carrier comprises a plurality of compartments or slots (also referred to herein as "tilger boxes"), each compartment or slot housing a damping unit. In one embodiment, at least one or more compartments house a damping unit. For example, in Figure 2In the depicted embodiment, each compartment houses one damping unit. In another embodiment, at least one or more compartments house two damping units. For example, in the embodiment depicted in FIG3 , each compartment houses two damping units tuned to different frequencies.

[0067] The damping unit can be inserted into a compartment or slot to be fixed to the carrier. Specifically, the carrier may include a plurality of compartments or slots having the same size, and a plurality of damping units tuned to different frequencies may have the same size, so that each damping unit can be inserted into any compartment of a plurality of compartments of the same shape. Replacement of the damping unit and rearrangement of the damping unit (for example, in order to optimize the damping effect provided by the plurality of damping units) can be easily performed. In particular, the carrier may include a plurality of compartments or slots of corresponding shapes in a head portion of the carrier, the compartments being arranged in a linear array. This allows the damping unit to be quickly and easily mounted at the carrier, and allows the overall damping effect provided by the plurality of damping units to be quickly and easily replaced and optimized.

[0068] According to a separate aspect described herein, at least one damping unit may be tuned to a fundamental natural frequency of the carrier and / or to a damping frequency in a range between 5 Hz and 30 Hz. Thus, vibrations of the carrier below the fundamental natural frequency can be damped more reliably. The fundamental natural frequency of the carrier is typically in a range between 5 Hz and 30 Hz. The fundamental natural frequency of the carrier typically refers to a rigid body mode in which the carrier vibrates as a whole. Thus, control loop-based damping in the frequency range between 5 Hz and 30 Hz can be supplemented with structural damping via one or more damping units. Since in this case the control loop of the active magnetic bearing has to perform less vibration damping in the low frequency range, the excitation of the carrier vibrations by the active magnetic bearing in the higher frequency range can be reduced. Thus, a better overall damping result can be achieved.

[0069] In some embodiments, which can be combined with other embodiments described herein, at least one damping unit may be provided for damping a rigid body mode of the carrier and / or at least one damping unit may be provided for damping an elastic mode of the carrier.

[0070] In some embodiments, the plurality of damping units comprises at least one lateral vibration damping unit 136 oriented to damp carrier vibrations in a second direction different from the holding direction V, in particular substantially perpendicular to the holding direction V. The at least one lateral vibration damping unit 136 may be tuned to damp horizontal carrier vibrations f hThe at least one lateral vibration damping unit 136 may have a similar structure to other damping units oriented to damp vibrations in the holding direction V, however, the lateral vibration damping unit is mounted at the carrier in a rotated manner (e.g. rotated 90°) so that horizontal vibrations can be damped. For example, the carrier may include at least one compartment or slot oriented such that a damping unit inserted in the at least one compartment or slot damps horizontal carrier vibrations.

[0071] In some embodiments, the carrier may include at least one first compartment having a shape that is rotated, in particular rotated by 90°, relative to the shape of the at least one second compartment. Thus, the damping unit inserted in the at least one first compartment may damp vertical carrier vibrations, and the damping unit inserted in the at least one second compartment may damp horizontal carrier vibrations.

[0072] In some embodiments, the carrier includes at least one lateral vibration damping unit 136 tuned to the carrier's fundamental natural frequency. Carrier vibrations at the carrier's fundamental natural frequency typically have high amplitudes without damping (see Figure 5 0 in E0), so that even the horizontal component of such carrier vibrations may not be negligible. Therefore, it may be reasonable to damp the horizontal vibration component vibrating at the basic natural frequency of the carrier with at least one lateral vibration damping unit 136.

[0073] In some embodiments, which may be combined with other embodiments described herein, at least one damping unit of the plurality of damping units may be arranged at the bottom portion 122 of the carrier, in particular below a substrate holding portion of the carrier configured to hold the substrate 10. In particular, at least one lateral vibration damping unit 136 may be arranged at the bottom portion 122 of the carrier, and at least one damping unit configured to damp vibrations in the holding direction V may be arranged at the head portion 121 of the carrier.

[0074] In some embodiments that may be combined with other embodiments described herein, the plurality of damping units include at least one broadband damper, in particular a broadband damper tuned to a frequency range between 30 Hz and 60 Hz. The broadband damper may be configured to provide a damping ratio of at least 0.1 in an extended frequency range of, for example, 10 Hz or higher and / or 30 Hz or lower. For example, the broadband damper may be configured to provide a damping ratio of at least 0.1 in at least a frequency range extending from 40 Hz to 50 Hz. The broadband damper can not only damp frequencies within a specific damping range of the broadband damper, but can also affect natural frequencies of the carrier outside the damping range of the broadband damper. For example, a broadband damper tuned to a frequency range between 30 Hz and 60 Hz can even attenuate vibration peaks at higher order natural frequencies to a certain extent, such as Figure 5E2 and E3 are depicted. The damping effect of a small bandwidth damper may be stronger than that of a broadband damper, but is locally limited to a frequency region close to the damping frequency of the small bandwidth damper. In some embodiments, the broadband damper is a Lanchester damper.

[0075] Figure 3A is a schematic diagram of a carrier 320 of a magnetic levitation system according to various embodiments described herein. Figure 3A Most of the details of vector 320 correspond to Figure 1 and Figure 2 The details of the carrier 120 can be referred to the above description, and will not be repeated herein. In particular, Figure 3A The carrier 320 is configured so that the carrier can be Figure 1 and Figure 2 Transport in a magnetic levitation system as depicted. Specifically, as described in further detail above, the carrier 320 is configured to interact with a base structure of the magnetic levitation system such that the carrier can be retained at the base structure and is movable relative to the base structure.

[0076] The carrier comprises a plurality of damping units 130, in particular three or more damping units tuned to different frequencies. In particular, the carrier 320 comprises eight or more damping units or sixteen or more damping units. The damping units may be tuned to eight or more different frequencies or even sixteen or more different frequencies. In some embodiments, each of the damping units is tuned to a frequency different from the other damping units. In other embodiments, some of the damping units are tuned to the same or substantially the same frequency. Figure 3A In an exemplary embodiment of the carrier 320, the carrier 320 includes sixteen damping units tuned to sixteen different frequencies. For example, the carrier may have eight compartments accommodating the sixteen damping units. In other embodiments, more or fewer damping units may be provided that may be partially tuned to the same frequency. Each damping unit may be arranged in a separate compartment of the carrier, or alternatively, as Figure 3A Schematically depicted, two or more damping units may each be received in one compartment of the carrier.

[0077] exist Figure 3A In an embodiment, sixteen damping units are tuned to different frequencies within a critical frequency range from 50 Hz to 250 Hz. In other embodiments, at least some of the damping units may be tuned to frequencies outside the critical frequency range.

[0078] In some embodiments that may be combined with other embodiments described herein, the plurality of damping units comprises eight or more damping units tuned to eight or more different frequencies in the frequency range from 65 Hz to 200 Hz, in particular wherein the frequencies are distributed in the frequency range from 65 Hz to 200 Hz, e.g., substantially uniformly. For example, there may be at least one damping unit associated with each frequency sector having a width of 20 Hz in the frequency range from 65 Hz to 200 Hz. In the frequency range from 65 Hz to 250 Hz, the distance between two adjacent damping frequencies damped by the respective damping units may be no greater than 20 Hz.

[0079] exist Figure 3A In the exemplary embodiment depicted, sixteen damping units are provided that are tunable to the following damping frequencies: f a =200Hz, f b =186Hz, f c =172Hz, f d =160Hz, f e =148Hz, f f =138Hz, f g =128Hz, f h =118Hz, f i =110Hz, f j =88Hz, f k =102Hz, f l =95Hz, f m =81Hz, f n =76Hz, f o =70Hz, f p =65 Hz. This frequency distribution dispersed in the critical damping range is to be understood as an example. Clearly, a different number of damping units tuned to different frequencies may be provided. However, it is beneficial to provide a plurality of damping units with damping frequencies distributed in the critical frequency range. This "multi-damper concept" allows reliable damping of carrier vibrations, including carrier vibrations at natural frequencies in the critical frequency range, without the need for the dampers to be tuned exclusively to the natural frequencies of the carrier in said range. Rather, by providing a plurality of dampers tuned to damping frequencies dispersed in the frequency range to be damped, natural modes in said frequency range can also be reliably damped.

[0080] like Figure 3A As depicted, the outermost damping unit is tuned to a higher frequency (here: f a+b+c+d ) edge damping units. The centrally arranged damping units are tuned to the lower frequency (here: f e+f+g+h+i+j+k+i+m+n+o+p )’s central damping unit.

[0081] Figure 3B It is shown Figure 3A Graph of the oscillatory behavior of a carrier of FIG. 1 , which vibrates in different normal modes. The x-axis shows the dimension of the carrier in the transport direction T, and the y-axis shows the vibration amplitudes of different normal modes of the carrier in the holding direction V at different positions of the carrier. For example, there may be a normal mode of the carrier with a normal frequency of about f=85 Hz, the respective normal mode having a maximum vibration amplitude in the center of the carrier. This normal mode can be represented by a damping frequency f j (88Hz) and f m (81 Hz) is particularly effective in damping. For example, there may be a normal mode of the carrier with a normal frequency of about f = 200 Hz, the corresponding normal mode having a maximum vibration amplitude at the edge of the carrier. This normal mode can be damped by a central damping unit with a damping frequency f a (200Hz) and f b The edge damping unit at (186 Hz) is particularly efficient in damping.

[0082] In some embodiments, two, four or more edge damping units may be arranged in the front and rear parts of the carrier in the transport direction T, and two, four or more central damping units may be arranged in the central part of the carrier in the transport direction. In a number of implementations, the edge damping units may be tuned to a higher frequency than the central damping units. This is because higher-order natural modes with higher natural frequencies typically have maximum vibration amplitudes at the edges of the carrier, at least when a frequency range from 50 Hz to 300 Hz is envisaged.

[0083] The carrier 320 may have a head portion 121 configured to interact with an active magnetic bearing of a base structure and a bottom portion 122 configured to hold an object, in particular a substrate 10. The head portion 121 and the bottom portion 122 may be connected to each other via a flexible connection 127. In some embodiments, the flexible connection comprises a flexible material, in particular an elastic material that allows relative movement of the head portion 121 relative to the bottom portion 122. A carrier 320 having several movably connected carrier portions has a lower natural frequency than a rigid, integral carrier with a corresponding weight. In some embodiments, a plurality of damping units 130 are arranged at the head portion of the carrier 120, for example in one or more linear arrays.

[0084] like Figure 3A As depicted, the carrier 320 may include a plurality of compartments 125, each compartment 125 accommodating two damping units of the plurality of damping units tuned to different frequencies. For example, the plurality of compartments 125 may be provided in a linear array, each compartment being shaped to accommodate two damping units. A space-saving damping unit arrangement can be provided. Figure 4CTwo damping units configured to be received in one compartment 125 are schematically depicted.

[0085] The plurality of damping units used in the various embodiments described herein may be passive damping units, active damping units and / or semi-active damping units. In particular, the plurality of damping units may be passive damping units, in particular mechanical passive damping units. Passive damping units, in particular passive vibration absorbers or tuned mass dampers may also be referred to as "tilgers".

[0086] As used herein, a "passive damping unit" may be understood as a damping unit that does not include an active control. For example, a damping block may be mounted on a carrier so that the movement caused by the damping block relative to the carrier naturally damps the vibration of the carrier. In another embodiment, the damping block may be mounted at a base structure via a spring element so as to be movable relative to the base structure. In other words, the passive damping unit does not include an actuator and / or a sensor. For example, the passive damping unit may include a damping block, which is movably connected to the carrier, for example, via a spring element and / or an elastic material. The properties of the damping block and the spring element may be set so that the damping effect of the damping unit has a maximum value at a specific damping frequency. For example, the weight of the damping block and / or the spring constant of the spring element may be suitable for tuning the damping unit to a predetermined damping frequency.

[0087] Figure 4A is a schematic diagram illustrating the operating principle of a passive damping unit, in particular a tuned mass damper 135, which can be used in various embodiments described herein. At least some or all of the plurality of damping units 130 may be configured as a tuned mass damper 135, respectively. Figure 4A Only one damping unit among the plurality of damping units 130 is shown. The other damping units may have similar arrangements.

[0088] In some embodiments described herein, the plurality of damping units 130 are passive damping units, in particular vibration absorbers, more particularly tuned mass dampers 135 .

[0089] In some embodiments, the tuned mass damper 135 includes a damping mass 145 and at least one spring element 141, which movably connects the damping mass 145 to a carrier so that the damping mass 145 can oscillate relative to the carrier. The at least one spring element 141 may include one or more leaf springs. Optionally, the tuned mass damper may also include a damping mechanism 142 for damping vibrations of the damping mass 145. The damping mechanism 142 may include a flexible material, such as an elastic material such as a foam or a viscous material, wherein the damping mass 145 is at least partially embedded in the flexible material to damp the movement of the damping mass 145. Alternatively or additionally, the damping mechanism 142 may include a magnet element configured to induce a current in a conductor element when the damping mass oscillates relative to the carrier. The induced current can be released as heat, thereby quickly reducing the vibration energy of the oscillating damping mass.

[0090] In some embodiments, Figure 4B Schematically depicted, the tuned mass damper 135 may be provided with a vacuum sealed housing 146 that can be inserted into a compartment 125 provided at the carrier. Both the first damping unit 131 and the second damping unit 132 may be tuned mass dampers 135, the first damping unit 131 and the second damping unit 132 being received in respective compartments of the carrier. The damping units may be quickly and easily replaced and rearranged at the carrier.

[0091] Figure 4C is a schematic cross-sectional view showing two damping units in a common housing as used in various embodiments described herein. The damping unit is arranged in a vacuum sealed housing 146 which can be easily inserted into one compartment 125 of a carrier so that a compact damping unit arrangement can be provided at the carrier.

[0092] Figure 4C The depicted damping unit is a tuned mass damper 135 , which respectively comprises a damping mass 145 , at least one spring element 141 movably connecting the damping mass 145 to a carrier via a vacuum-tight housing 146 , and a damping mechanism 142 for damping vibrations of the damping mass 145 .

[0093] The damping mechanism 142 includes a magnetic element that can be disposed at the damping block 145, so that when the damping block 145 vibrates, the magnetic element moves relative to the vacuum sealed housing 146. The moving magnetic element induces a current in a conductor element disposed at the vacuum sealed housing 146, so that the vibration energy of the damping block 145 can be dissipated as heat. Therefore, the vibration of the damping block 145 can be damped more quickly.

[0094] like Figure 4CSchematically depicted, two damping units may be arranged in a common housing, wherein the two damping units may be tuned to different frequencies. In particular, the characteristics of at least one spring element 141 of the first damping unit may be different from the characteristics of at least one spring element 141' of the second damping unit (depicted thicker to illustrate a larger spring constant). Alternatively, the damping masses and / or damping mechanisms of the two damping units may be different in order to adjust the damping frequency, bandwidth and / or damping ratio of the damping units.

[0095] According to another aspect described herein, a method of operating a magnetic levitation system comprising a base structure 110 and a carrier 120 movable in a transport direction T relative to the base structure is described.

[0096] Figure 6 6 is a flow chart showing a method of operating a magnetic levitation system according to multiple embodiments described herein. In box 610, the method includes actively controlling at least one active magnetic bearing 112 to generate a magnetic holding force in a holding direction V for holding a carrier at a base structure, and during active control, damping the vibration of the carrier with a plurality of damping units 130 fixed to the carrier. In particular, a plurality of normal modes of the carrier caused by active control of at least one active magnetic bearing can be damped by a plurality of damping units. The plurality of damping units include a first damping unit 131 tuned to a first frequency or a first frequency range and a second damping unit 132 tuned to a second frequency or a second frequency range. Additional damping units may be provided. For example, the plurality of damping units may include three or more damping units, eight or more damping units, or even sixteen or more damping units fixed to the carrier.

[0097] Alternatively or additionally, vibrations of the base structure may be damped with a (second) plurality of damping units fixed to the base structure. In particular, a plurality of normal modes of the base structure caused by active control of at least one active magnetic bearing may be damped by the (second) plurality of damping units. The (second) plurality of damping units may comprise three or more damping units, eight or more damping units or even sixteen or more damping units fixed to the base structure, which are particularly tuned to different frequencies or frequency ranges.

[0098] In optional block 620, the carrier is transported along the base structure in a vacuum system using a drive unit while suspending the carrier using at least one active magnetic bearing until the carrier reaches a processing location.

[0099] In optional block 630, the substrate 10 carried by the carrier is processed at the processing location. The carrier is not necessarily suspended by the magnetic levitation system during processing. For example, material is deposited on the substrate 10, which is at the processing location. In some embodiments, the substrate 10 can be a semiconductor wafer processed at the processing location, or the substrate can be a large area substrate for display manufacturing, and deposition materials, such as organic materials or metals, can be deposited on the large area substrate, which is at the processing location. The large area substrate can have a diameter greater than 1 m. 2 Size, for example 10m 2 or larger, and / or the large area substrate may be a glass substrate.

[0100] In some embodiments, which may be combined with other embodiments described herein, damping vibrations of the carrier includes damping multiple normal modes of the carrier with multiple damping units tuned to three or more different frequencies, in particular eight or more different frequencies, in particular in a frequency range between 50 Hz and 250 Hz.

[0101] In some embodiments that may be combined with other embodiments described herein, damping vibrations of the carrier further includes damping at least one normal mode of the carrier, in particular a rigid body mode of the carrier, in a frequency range between 5 Hz and 30 Hz via a controller actively controlling at least one active magnetic bearing.

[0102] According to a separate aspect described herein, damping vibrations of the carrier comprises damping a fundamental normal mode of the carrier, in particular a rigid body mode, with at least one damping unit tuned to a frequency in a range between 5 Hz and 30 Hz. In particular, the at least one damping unit may be tuned to a frequency in a range between 5 Hz and 30 Hz and may be configured to supplement the damping provided by the controller of the at least one active magnetic bearing in said frequency range.

[0103] In some embodiments that may be combined with other embodiments described herein, damping vibrations of the carrier comprises damping at least one carrier vibration with a lateral vibration damping unit oriented to damp vibrations of the carrier in a lateral direction perpendicular to the holding direction V, in particular wherein the lateral vibration damping unit is tuned to a frequency in the range between 5 Hz and 100 Hz.

[0104] In some embodiments, which may be combined with other embodiments described herein, damping vibrations of the carrier includes damping at least one normal mode of the carrier in a frequency range between 20 Hz and 60 Hz with a broadband damper, in particular with a damping unit tuned to a frequency range from 40 Hz to 50 Hz.

[0105] In some embodiments, which may be combined with other embodiments described herein, vibrations of the carrier are damped with a plurality of tuned mass dampers tuned to eight or more different frequencies in a frequency range between 50 Hz and 250 Hz. The tuned mass dampers may be oriented to damp vertical carrier vibrations.

[0106] Embodiments described herein are particularly directed to magnetic levitation systems that are configured to transport carriers in a substantially vertical orientation. "Substantially vertical" as used herein may be understood as a carrier orientation that is completely vertical or has a deviation of 10° or less from the vertical direction. Therefore, a carrier may be transported by a magnetic levitation system when carrying a substrate that is substantially vertically oriented. In other embodiments, the magnetic levitation system may be configured to transport differently oriented carriers, such as carriers that are substantially horizontally oriented during transportation.

[0107] The above specification describes in detail the damping of carrier vibrations by a plurality of damping units disposed at the carrier. However, it should be noted that at least one magnetic bearing may cause not only vibrations of the carrier but also vibrations of the base structure. The base structure may be a fixed track or frame along which the carrier can move using a magnetic levitation system. Therefore, in some embodiments, a plurality of damping units may be arranged at the base structure so that the vibrations of the base structure can be damped using the plurality of damping units. In another embodiment, a first plurality of damping units may be disposed at the carrier for damping the carrier vibrations, and a second plurality of damping units may be disposed at the base structure for damping the vibrations of the base structure.

[0108] The plurality of damping units disposed at the base structure and configured to damp vibrations of the base structure may be similar or identical to the plurality of damping units disposed at the carrier as described in detail herein. Specifically, the critical damping range of the base structure may substantially correspond to the critical damping range of the carrier, and the plurality of damping units may be disposed at the base structure, the plurality of damping units being tuned to different frequencies within the critical damping range. It is to be understood that any details of the plurality of damping units disposed at the carrier as described herein may be applicable to the plurality of damping units disposed at the base structure.

[0109] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be envisaged without departing from the basic scope thereof, and the scope of the disclosure is to be determined by the scope of the appended claims.

Claims

1. A magnetic levitation system, comprising: Base structure; a carrier movable relative to the base structure in a transport direction; and at least one active magnetic bearing, the at least one active magnetic bearing being configured to generate a magnetic holding force acting in a holding direction for holding the carrier at the base structure, Wherein the carrier comprises at least one damping unit for damping vibrations of the carrier in a frequency range from 65 Hz to 200 Hz. 2 . The magnetic levitation system of claim 1 , wherein the at least one damping unit is at least one passive damping unit.

3. The magnetic levitation system of claim 1, wherein the at least one damping unit comprises at least one broadband damper.

4. The magnetic levitation system of claim 3, wherein the at least one broadband damper provides a damping ratio of at least 0.1 in a frequency range from 40 Hz to 50 Hz.

5. The magnetic levitation system of claim 1, wherein the at least one damping unit is oriented to damp vibrations in the holding direction.

6. The magnetic levitation system of claim 1, wherein the carrier comprises a head portion configured to interact with the at least one active magnetic bearing, wherein the at least one damping unit is arranged at the head portion. 7 . The magnetic levitation system of claim 1 , wherein the at least one damping unit comprises eight or more damping units tuned to eight or more different frequencies within a frequency range from 65 Hz to 200 Hz.

8. The magnetic levitation system of claim 1, wherein the at least one damping unit comprises at least one lateral vibration damping unit (136), the at least one lateral vibration damping unit being oriented to damp carrier vibrations in a second direction different from the retaining direction (V).

9. The magnetic levitation system of claim 8, wherein the at least one lateral vibration damping unit (136) is arranged at a bottom portion (122) of the carrier.

10. A carrier (120) for a magnetic levitation system, the carrier being configured to interact with a base structure (110) of the magnetic levitation system such that the carrier is held at the base structure and is movable relative to the base structure, the carrier comprising: At least one damping unit (130) is used to damp the carrier vibration in a frequency range from 65 Hz to 200 Hz. The carrier according to claim 10 , wherein the at least one damping unit is at least one passive damping unit.

12. The carrier of claim 10, wherein the at least one damping unit comprises at least one broadband damper.

13. The carrier of claim 12, wherein the at least one broadband damper provides a damping ratio of at least 0.1 in a frequency range from 40 Hz to 50 Hz.

14. The carrier of claim 10, wherein the at least one damping unit is oriented to damp vibrations in a holding direction.

15. A method of operating a magnetic levitation system (100), the magnetic levitation system comprising a base structure (110) and a carrier (120) movable relative to the base structure in a transport direction (T), the method comprising: actively controlling at least one active magnetic bearing (112) to generate a magnetic holding force to hold the carrier at the base structure; and At least one damping unit (130) is used to damp vibrations of the carrier in a frequency range from 65 Hz to 200 Hz. The method of claim 15 , wherein the at least one damping unit is at least one passive damping unit.

17. The method of claim 15, wherein the at least one damping unit comprises at least one broadband damper.

18. The method of claim 17, wherein the at least one broadband damper provides a damping ratio of at least 0.1 in a frequency range from 40 Hz to 50 Hz.

19. The method of claim 15, wherein the at least one damping unit is oriented to damp vibrations in a holding direction.

20. The method of claim 15, wherein the carrier comprises a head portion interacting with the at least one active magnetic bearing, wherein the at least one damping unit is arranged at the head portion.

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