Electromagnetic actuator and positioning device

Abstract

To provide an electromagnetic actuator capable of moving along a translational axis at high acceleration.SOLUTION: With respect to an electromagnetic actuator with two units 2, 3, these units are configured to cause guided motions with respect to each other in a translational direction T and a rotational direction R upon electromagnetic interaction and have a bearing gap between them. To this end, the electromagnetic actuator is configured to supply compressed gas into the bearing gap to form a film of gas between units 2, 3, comprising a frictionless floating bearing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electromagnetic actuator provided with a frictionless floating bearing, and a positioning device provided with such an electromagnetic actuator, particularly a parallel kinematic positioning device.

Background Art

[0002] Known parallel kinematic positioning systems, particularly hexapod platforms, are used for load movement, precise positioning, alignment and displacement in all six degrees of freedom, i.e., three linear axes and three rotational axes. The hexapod comprises six actuators acting together on a single moving platform.

[0003] In prior art hexapods, screw-driven actuators are used to enable precise positioning. However, these systems are often plagued by wear and damage when used for very repetitive motion applications. Furthermore, they do not provide the high accelerations and speeds often required, for example, in motion simulation applications.

[0004] U.S. Patent No. 0,500,676 and U.S. Patent No. 1,090,761 disclose electromagnetic actuators having a frictionless air bearing motion guidance for the translational motion of a front optical element in a laser beam focusing subsystem of a laser scanning system. However, these electromagnetic actuators only enable translational motion and not rotational motion.

[0005] It is desirable to provide an electromagnetic actuator that is suitable for use in parallel kinematic positioning systems, particularly hexapods, and is capable of moving along the translational axis with high acceleration.

Summary of the Invention

[0006] According to a first embodiment, an electromagnetic actuator is provided. The electromagnetic actuator comprises two units, which are configured to produce or allow guiding motion toward each other in the translational direction and in the rotational direction by electromagnetic interaction. The two units have a bearing gap in between. The electromagnetic actuator is configured to supply pressurized gas to the bearing gap to create a film of gas that constitutes a frictionless floating bearing between the units. The guiding motion toward each other in the rotational direction may also be around the translational direction.

[0007] Passive rotational degrees of freedom can overcome limitations in motion by simplifying the actuation technique and eliminating potential over-constraints. Active rotational degrees of freedom can increase the versatility of electromagnetic actuators in terms of additional drive options.

[0008] One part of the unit may be a first unit and the other part may be a second unit. The first unit may have a projection that protrudes into the second unit in the translational direction to guide the movement of the second unit relative to the first unit in the translational and rotational directions. The second unit may constitute a bush surrounding the projection of the first unit and define an intermediate bearing gap, and / or be arranged concentrically with respect to the projection of the first unit. The second unit may have a closed end cap to construct a piston having a piston chamber when combined with the first unit, and the piston chamber is intended to be supplied with pressurized gas, preferably via a piston chamber gas duct provided or formed in the projection.

[0009] The electromagnetic actuator may further include a gas supply device having a gas supply terminal and a gas supply passage configured to supply pressurized gas, particularly air, from a gas source, particularly a compressor, to the gas supply terminal, and from the gas supply terminal, via at least one nozzle gas duct, to at least one nozzle provided in one of the units. Preferably, the bush includes at least one nozzle for supplying pressurized gas to the bearing gap. The gas supply terminal may form part of one of the units, preferably a second unit. At least one nozzle or at least one nozzle gas duct may be provided on or formed in the projection. It is advantageous if the projection includes an exhaust groove connected to an exhaust gas duct of the projection for discharging pressurized gas from the bearing gap or piston chamber.

[0010] One of the units, preferably a first unit, may comprise at least one magnet, and the other unit, preferably a second unit, may comprise at least one coil, preferably a voice coil, which interacts with at least one magnet by electromagnetic interaction in response to the activation of at least one coil. At least one magnet may be located within the housing of the first unit. The housing may be arranged concentrically with respect to a projection of the first unit on the outside of the second unit.

[0011] The second unit includes or may be constructed as a bobbin housing at least one coil, the coil may be concentrically arranged outside a projection of the first unit, or project into a recess of a housing having hollow cylindrical symmetry, the housing housing at least one magnet. The second unit may also include a sleeve concentrically arranged outside the bobbin to cover at least a portion of the outer surface of the bobbin to provide an intermediate sleeve gap. The electromagnetic actuator may be configured to supply compressed gas to the sleeve gap, in particular to cool the bobbin or at least one coil housed by the bobbin. The bobbin may house a gas supply terminal.

[0012] The sleeve may be rotatably attached to the bobbin, preferably by at least two O-rings, particularly elastic O-rings that generate a clamping force between the bobbin and the sleeve. The O-rings may be spaced apart from each other in the translational direction so that the sleeve gap can be sealed in the translational direction by the O-rings.

[0013] Alternatively or additionally, the sleeve may be rotatably attached to the inner sleeve by adhesive or welding.

[0014] The electromagnetic actuator may include a power supply device having a power supply terminal and a power line configured to supply power from an energy source to the power supply terminal. The power supply terminal may be connected to at least one coil for power supply.

[0015] The units may be configured to limit their translational and / or rotational motion relative to each other. The predetermined angular range Φ of the rotational motion of the units relative to each other may be between 10 and 350 degrees, preferably between 40 and 320 degrees, and most preferably between 140 and 220 degrees. Each unit may be provided with a stopper, which may be configured to contact with each other to limit the predetermined translational and / or rotational motion of two units relative to each other to predetermined translational and angular ranges Φ, respectively.

[0016] The electromagnetic actuator may include an encoder, preferably an optical encoder, for encoding the relative positions of the two units in at least one of the translational and rotational directions. The encoder may be linear, incremental, or absolute.

[0017] The encoder may include at least one optical sensor provided on one of the units, preferably the first unit. The encoder may further include at least one encoder scale provided on the other unit, preferably the second unit. The encoder scale may be a grid having detectable lines extending along at least one of the translational and rotational directions. The optical sensor may be configured to read at least one encoder scale for encoding the relative positions of the two units. The encoder may include a first sensor configured to interact with a first encoder scale, which is embodied as a grid having lines extending in the rotational direction, in order to detect the relative translational position of the units. The encoder may optionally or additionally include a second sensor configured to interact with a second encoder scale, which is embodied as a grid having lines extending in the translational direction, in order to detect the relative rotational position of the units.

[0018] The first and second grids may be integrally realized to form a two-dimensional grid on a cylindrical surface, preferably the outer surface of the sleeve of the second unit or the outer surface of the bobbin. The second sensor may be positioned at an angle offset by about 90 degrees in the rotational direction from the first sensor.

[0019] Alternatively, the encoder may have one of the following: a linear variable differential transformer (LVDT) sensor, a magnetic sensor, an interferometer sensor, or a capacitive sensor.

[0020] The electromagnetic actuator may include a controllable valve configured to control the gas pressure in the piston chamber. This valve may be controlled based on an external load acting on one of the units, preferably a second unit, during the operation of the electromagnetic actuator to generate a counterbalancing force on each unit, such as conveying a static or passive load. The controllable valve may be an electronically proportional valve.

[0021] The electromagnetic actuator may further include a locking unit for locking the units together against movement in at least one of the translational and rotational directions. This locking unit may include an expandable collet provided on one of the units, preferably the second unit, and a corresponding opening on the other unit, preferably the first unit, for receiving the expandable distal end of the expandable collet to lock the second unit against at least the translational motion of the first unit.

[0022] The locking unit is adjustable via a controllable valve by reducing the pressure in the expandable collet during actuator operation, and as a result, an internal brake is provided for locking the position of the second unit relative to the first unit by a force that may be supplied by a spring pushing the expandable collet back together to the locked position.

[0023] One of the units, preferably a first unit, may form a stator, and the other unit, preferably a second unit, may form a runner or a rotor.

[0024] According to a second aspect, a motion or positioning device is provided comprising a base, a positioning platform, and at least one of the electromagnetic actuators described above. One of the units is directly or indirectly connected to the base, and the other unit is directly or indirectly connected to the positioning platform. The motion or positioning device may be a parallel motion device, preferably a hexapod.

[0025] (Terms and Definitions) The term "translational direction T" includes the opposite direction along the translation axis, and preferably any parallel direction.

[0026] The term "direction of rotation R" includes the opposite direction around the translation axis, particularly the direction along a circular line centered on / concentric with respect to the translation axis, and preferably any parallel direction.

[0027] The term "translational movement" includes movement in the front - rear direction along the translation axis.

[0028] The term "rotational movement" includes movement in both directions along a circular line concentric with the translation axis.

[0029] As used herein, the term "or" should generally be understood as an inclusive "or" unless otherwise specified. For example, the expression "feature A or feature B" shall include only feature A, or only feature B, or a combination of features A and B.

Brief Description of the Drawings

[0030] [Figure 1] A computer - generated exploded perspective view of an electromagnetic actuator representing the first embodiment of the present invention is shown. [Figure 2] Computer - generated perspective views of the electromagnetic actuator according to FIG. 1 from different viewing angles and different states are shown. Viewpoint (a) shows the electromagnetic actuator in an extended state, and viewpoint (b) shows the electromagnetic actuator in a stored or locked and rotated state. The independence between rotational movement and translational movement, that is, the ability to perform both movements independently, is emphasized. [Figure 3] Top views of the electromagnetic actuator of FIGS. 1 and 2 are shown. [Figure 4] A longitudinal cross - sectional view of the electromagnetic actuator along line A - A defined in FIG. 3 is shown. [Figure 5] A cross - sectional view of an electromagnetic actuator according to the second embodiment of the present invention is shown. [Figure 6] Two different cross - sectional views of an electromagnetic actuator according to the third embodiment of the present invention are shown. [Figure 7] A front view of a hexapod having six electromagnetic actuators according to the present invention is shown. FIG. 7b shows a perspective view thereof.

Modes for Carrying Out the Invention

[0031] Electromagnetic actuators are described in relation to the translational and rotational motion of a motion axis in a parallel kinematic movement or positioning device, preferably in a hexapod. Electromagnetic actuators may be used not only in motion axis devices that require repeated high-speed translational motion of each of the objects or elements being moved or positioned, but also in place of or in addition to other motion or positioning systems.

[0032] Referring to Figures 1 to 4, a two-degree-of-freedom (2DOF) electromagnetic actuator according to the present invention is shown, which provides closed-loop translational positioning and passive rotational motion guided by an air bearing.

[0033] The electromagnetic actuator 1 comprises a rotor (first unit) 2 and a stator (second unit) 3. The rotor 2 surrounds the stator 3 so as to be movable relative to both the translational direction T and the rotational direction R along the translational direction T.

[0034] A bearing gap is provided between the rotor 2 and the stator 3. During operation of the electromagnetic actuator according to the present invention, pressurized gas, particularly pressurized air, is supplied to the bearing gap, and a gas film constituting a frictionless floating bearing is formed between the rotor 2 and the stator 3.

[0035] The rotor 2 comprises a housing 4, a projection 5, and an encoder 6. The projection 5 functions specifically as a magnetic central pole and is located at the distal end of the housing 4. The projection 5 includes an end cap in the form of a joint 7 intended to connect to a movable or positioning element, such as the platform of a hexapod. In the assembled state, the end cap attaches the projection 5 to the distal end of the housing 4, for example, by screw connections or snap-fit ​​connections. The projection is preferably made of magnetic steel.

[0036] The projection 5 has a cylindrical projection 8 and protrudes into the stator 3 in the translational direction T to guide the movement of the stator 3 relative to the rotor 2.

[0037] The stator 3 constitutes a bobbin-shaped air bearing bush comprising two coils 21 mounted on the outer surface of a bobbin 9, spaced apart from each other in the translational direction T. The bobbin 9 is arranged concentrically outside the protrusions 8 of the projection 5.

[0038] The outer cylindrical sleeve 10 of the stator 3 is arranged concentrically on the outside of the bobbin 9 and forms an intermediate sleeve gap by covering at least a portion of the outer surface of the bobbin 9 and the coil 21 attached to the bobbin. The bobbin is configured to receive pressurized gas via a nozzle gas duct (not shown) provided on the bobbin and includes a gas supply terminal 22 and a plurality of nozzles 9' electrically connected to the sleeve gap and the bearing gap. The bobbin 9 may be made of aluminum, preferably hard anodized aluminum, brass, or any combination thereof. In particular, both the sleeve gap and the bearing gap are filled with pressurized gas, especially pressurized air, supplied from the same source to form a gas film that constitutes a frictionless floating bearing within the bearing gap, while providing gas circulation between the sleeve gap and the bearing gap, primarily to cool the coil 21, which are respectively located on the outer surface of the bobbin.

[0039] The sleeve 10 is preferably rotatably attached to the outer surface of the bobbin 9 by at least two elastic O-rings 9'' that generate a clamping force between the bobbin 9 and the sleeve 10. The O-rings 9'' are positioned apart from each other in the translational direction T so that the sleeve gap is sealed in the translational direction T by the O-rings 9''. Alternatively or additionally, the sleeve 10 is rotatably attached to the outer surface of the bobbin 9 by adhesive or welding. This can prevent loosening of the connection due to deterioration of the O-rings 9'' over time. The distal end of the stator 3, away from the rotor 2, is provided with a closed end cap in the form of a joint 11 intended to connect to a fixed base element, such as the base plate of a hexapod, in order to construct a piston having a piston chamber 12 in combination with the rotor 2.

[0040] The rotor 2 and stator 3 are each equipped with stoppers 13 and 14. The stoppers 13 and 14 are configured to contact the rotor 2 and stator 3 in such a way that they restrict their relative translational and / or rotational motion to a predetermined translational and angular range Φ, respectively.

[0041] With regard to limiting the rotational motion R, the housing 4 of the rotor 2 includes a stopper 13 realized by an unclosed peripheral wall extending from the distal end of the housing 4. The opening in the unclosed peripheral wall preferably receives a stopper 14 realized by a contact portion provided on the bobbin 9 to limit the rotational motion of the rotor 2 to a predetermined angular range Φ, at least in the translationally stored state of the bobbin 9 (see Figures 2 and 4). The stoppers 13, 14 are designed to allow the rotational motion R to be within an angular range Φ of 10 to 350 degrees, preferably 40 to 320 degrees, and most preferably 140 to 220 degrees.

[0042] Furthermore, the electromagnetic actuator 1 is provided with a locking unit for locking the rotor 2 and the stator 3 relative to movement in the translational direction T. In this embodiment, the locking unit is a non-permanent cantilever snap-fit ​​connection. Specifically, the locking unit comprises an expandable collet 15 attached to the joint 11 of the stator 3, and a corresponding opening realized by drilled holes 16, 17 having at least two different diameters along the translational direction T, particularly in the center of the projection 8 of the projection 5. In the retracted / locked position, the expandable distal end 18 of the expandable collet 15 is received in the opening and snaps out as it transitions from the smaller diameter first drilled hole 16 to the larger diameter second drilled hole 17 in order to lock the translational motion of the rotor 2 relative to the stator 3.

[0043] The locking unit is adjustable via a controllable valve (not shown) during the operation of the electromagnetic actuator 1 to provide an internal brake for locking the translational position of the rotor 2 relative to the stator 3. To move the rotor 2 to the locked position, the pressure in the expandable collet 15 and piston chamber 12 is reduced, and as a result, the force provided by the spring 19 pushes the expandable collet 15 back to the locked / retracted position.

[0044] The controllable valve may be an electronically proportional valve configured to control the gas pressure in the piston chamber 12. In this embodiment, the controllable valve is located outside the electromagnetic actuator 1. In other embodiments, the controllable valve forms part of the electromagnetic actuator 1. For example, the controllable valve may be located on the bobbin 9.

[0045] Referring to Figures 1 and 4, a plurality of permanent magnets 20 are provided circumferentially on the inner surface of the housing 4 of the rotor 2. Two coils 21 are provided on the outer surface of the bobbin 9. The coils 21 interact with the magnets 20 in response to the activation of the coils 21 in order to generate relative translational and / or rotational motion between the stator and the rotor.

[0046] The bobbin 9 includes a gas supply terminal 22 that interacts with a gas supply device 23, and a gas supply line / passage 24 configured to supply pressurized gas from a gas source to the gas supply terminal 22. In this embodiment, the gas supply terminal 22 is supplied not only with pressurized gas, particularly pressurized air, for the bearing gap and / or sleeve gap, but also with electrical energy for coils to power them in order to interact with the magnets 20. The gas supply device 23 includes at least one nozzle 25 that supplies pressurized gas to the bearing gap between the stator 3 and the rotor 2, and / or to the sleeve gap for cooling, via at least one nozzle gas duct provided in the bobbin 9, and the pressurized gas is discharged through the nozzle 9'. The pressurized gas is supplied from a compressor. The electrical energy is supplied from a power grid, for example, the public power grid.

[0047] Returning to Figure 1, the housing 4 of the rotor 2 has an opening for receiving an optical encoder 6 for encoding the relative position of the stator 3 and the rotor 2 in at least one of the translational direction T and the rotational direction R. The optical encoder 6 comprises at least one optical sensor 26 that interacts with at least one encoder scale 27 provided on the outer surface of the sleeve 10. Preferably, the encoder scale 27 is a grid having detectable lines extending along at least one of the translational direction T and the rotational direction R. The optical sensor 26 is configured to read at least one encoder scale 27 for encoding the relative position of the stator 3 with respect to the rotor 2. The encoder 6 is a linear encoder, preferably one of an incremental encoder or an absolute encoder. The encoder scale may be made of aluminum, stainless steel and / or biaxially oriented polyethylene terephthalate.

[0048] Preferably, a first optical sensor 26 is provided, configured to interact with a first encoder scale 27, which is embodied as a grid having parallel lines / rings extending in the rotational direction, in order to detect the relative translational position between the stator 3 and the rotor 2; and a second sensor 26 is provided, configured to interact with a second encoder scale 27, which is embodied as a grid having parallel lines extending in the translational direction, in order to detect the relative rotational position between the stator 3 and the rotor 2.

[0049] In other embodiments, the first and second grids are integrated to form a two-dimensional grid. The second sensor 26 is positioned at an angle offset by approximately 90 degrees in the rotational direction from the first sensor 26.

[0050] Figure 5 shows a cross-sectional view of a second embodiment of the electromagnetic actuator 1 according to the present invention. Here, some details of the electromagnetic actuator shown in Figures 1 to 4 are the same as or at least similar to those actually included in the electromagnetic actuator of the second embodiment, but are omitted for clarity or simplification. The differences between the second embodiment of the electromagnetic actuator shown in Figure 5 and the first embodiment shown in Figures 1 to 4 will be explained below.

[0051] The projection 5 of the first unit 2 of the electromagnetic actuator 1 is enclosed or surrounded by the inner wall of the second unit 3 which defines an internal hollow cylindrical portion or bushing. This inner wall acts as the magnetic central pole and air bearing surface and is made of magnetic steel. The projection 5 or its protrusion 8 is made of aluminum and acts as an air bearing shaft, and has a nozzle (not shown) for the outlet of compressed gas that is guided to the nozzle via a nozzle gas duct (not shown) within the protrusion 8, forming a film of compressed gas in the corresponding air bearing gap between the projection 5 and the air bearing surface.

[0052] The first unit 2 is provided with a bobbin 9 made of aluminum. The bobbin 9 houses a coil 21. The bobbin 9 protrudes into a further (external) hollow cylindrical portion of the second unit 3, which is positioned between the inner wall portion defining the hollow cylindrical portion of the second unit 3 and the outer wall portion of the second unit 3. The outer wall portion of the second unit 3 houses a plurality of permanent magnets 20 arranged circumferentially and is made of magnetic steel that constitutes the housing 4 or at least the housing portion of the second unit 3. The permanent magnets 20 are intended to interact with the coil 21 by electrical excitation, with a magnetic gap between them.

[0053] Pressurized gas is supplied to the piston chamber 12 for counterbalancing purposes via a separate piston chamber gas duct (not shown), preferably provided on the projection 8 of the projection 5, which has an outlet or nozzle at the end of the projection 8 adjacent to the piston chamber 12.

[0054] Exhaust grooves (not shown) are provided circumferentially near the end of the protrusion 8 at intervals to exhaust pressurized gas from the air bearing gap and piston chamber 12, and these exhaust grooves are electrically connected to an exhaust gas duct (not shown).

[0055] Figure 6 shows a third embodiment of the electromagnetic actuator 1 according to the present invention in two different cross-sectional views. Similarly, some details of the electromagnetic actuator shown in Figures 1 to 4 are identical or at least similar to those actually included in the electromagnetic actuator of the third embodiment, but are omitted for clarity or simplification. Regarding the third embodiment of the electromagnetic actuator shown in Figure 6, only the differences from the first embodiment shown in Figures 1 to 4 will be described below.

[0056] The projection 5 or protrusion 8 of the first unit 2 of the electromagnetic actuator 1 is enclosed or surrounded by a portion of the second unit 3, which is formed as a substantially hollow cylindrical or cylindrical bush made of aluminum. This hollow cylindrical portion of the second unit 3 houses the coil 21 circumferentially to form a bobbin 9. The second unit 3 also houses a cylindrical sleeve 10, which is coaxially positioned outside it such that the surface of the sleeve 10 is flush with the surface of the second unit 3 adjacent to the sleeve. The sleeve 10 houses an encoder scale 27 that interacts with a corresponding optical sensor 26.

[0057] Each projection 5 or its protrusion 8 functions as a magnetic central pole and also functions as an air bearing shaft having a nozzle 9' for the outlet of compressed gas, which is guided to the nozzle via a nozzle gas duct (not shown) within the protrusion 8. The hollow cylindrical portion surrounding the second unit 3 or its protrusion 8 functions as an air bearing bush, complementary to the air bearing shaft realized by the protrusion 8, and the compressed gas or air discharged from the nozzle 9' is guided between the air bearing bush and the air bearing gap to the air bearing gap, forming a film of compressed gas between them.

[0058] The second unit 3 contains a housing section or housing 4 made of magnetic steel, which houses multiple permanent magnets 20 arranged circumferentially within the housing 4, surrounding or enclosing the coil 21 of the bobbin 9. Furthermore, the housing 4 surrounds or encloses most of the sleeve 10 and houses an optical sensor 26 that interacts with an encoder scale 27 attached to or integrally formed with the sleeve 10. The housing 4 or housing section can also be manufactured integrally with the second unit 3.

[0059] The end of the bobbin 9 of the second unit 3, together with the end of the projection 8 of the projection 5, forms a piston chamber 12. Pressurized gas for counterbalancing is supplied to this piston chamber 12 via a separate piston chamber gas duct 28 provided on the projection 8, which has an outlet or nozzle at the end of the projection 8 adjacent to the piston chamber 12. Exhaust grooves 30 are provided circumferentially near the end of the projection 8 to exhaust the pressurized gas from the air bearing gap and also from the piston chamber 12, and these exhaust grooves are electrically connected to an exhaust gas duct 32.

[0060] Each end of the first unit 2 and the second unit 3 is provided with a corresponding joint 7 or 11 for connecting to further elements, such as movable or positionable elements or fixed base elements.

[0061] Figure 7 shows the parallel kinematic positioning device 34, which is in the form of a hexapod including six electromagnetic actuators 1 as described above, from two different viewpoints. [Explanation of Symbols]

[0062] 1. Electromagnetic actuator 2. First Unit 3. Second Unit 4. Housing (of the first unit 2 or the second unit 3) 5 protrusions 6 encoders 7,11 Joint 8 (Protrusion of projection 5) 9 bobbins 9' (Bobbin 9) Nozzle 9' O-ring (attached to bobbin 9) 10 sleeves 12 Piston chamber 13,14 Stopper 15 Expandable Collets 16, 17 Drill holes 18. Expandable distal end (of expandable collet 15) 19 Spring 20 magnets 21 coils 22 Gas supply terminals 23 Gas supply equipment 24 Gas supply lines 25 nozzles 26 Optical Sensors 27 Encoder scale 28 Piston chamber gas duct 30 Exhaust groove 32 Exhaust gas duct 34 Parallel kinematic positioning device

Claims

1. An electromagnetic actuator (1) comprising two units (2, 3), The two units (2, 3) are configured such that electromagnetic interaction causes or allows for guiding movement toward each other in the translational direction (T) and rotational direction (R), and that there is a bearing gap between the two units (2, 3). The electromagnetic actuator (1) is configured to supply pressurized gas to the bearing gap to form a gas film that constitutes a frictionless floating bearing between the units (2, 3), An electromagnetic actuator (1) wherein the predetermined angular range of rotational motion of the units (2, 3) relative to each other is between 10 degrees and 350 degrees.

2. One of the units (2) is the first unit (2), and the other of the units (2, 3) is the second unit (3), The electromagnetic actuator (1) according to claim 1, wherein the first unit (2) has a projection (5) that protrudes into the second unit (3) in the translational direction to guide the movement of the second unit (3) relative to the first unit (2) in the translational direction (T) and the rotational direction (R).

3. The electromagnetic actuator (1) according to claim 2, further comprising a gas supply device (23) having a gas supply terminal (22) and a gas supply passage (24), wherein the gas supply device (23) is configured to supply pressurized gas from a gas source to the gas supply terminal (22), and from the gas supply terminal (22) through at least one nozzle gas duct to at least one nozzle (9') provided in one of the units (2, 3), and the at least one nozzle (9') is configured to supply the pressurized gas to the bearing gap.

4. The electromagnetic actuator (1) according to claim 3, wherein the at least one nozzle (9') or the at least one nozzle gas duct is provided within the projection (5).

5. The electromagnetic actuator (1) according to claim 3 or 4, wherein the projection (5) is provided with an exhaust groove (30) connected to an exhaust gas duct (32) of the projection (5) which is configured to exhaust pressurized gas from the bearing gap and piston chamber (12).

6. One of the units (2, 3) comprises at least one magnet (20), and the other of the units (2, 3) comprises at least one coil (21), wherein the at least one coil (21) interacts with the at least one magnet (20) by electromagnetic interaction in response to the activation of the at least one coil (21), The electromagnetic actuator (1) according to any one of claims 2 to 5, wherein the at least one magnet (20) is disposed within one housing (4) of the unit (2, 3) and is arranged concentrically with respect to the projection (5) of the first unit (2).

7. The electromagnetic actuator (1) according to claim 6, wherein the second unit (3) comprises or is designed as a bobbin (9) arranged concentrically with respect to the projection (5), the bobbin housing the at least one coil (21).

8. The electromagnetic actuator (1) according to claim 7, wherein the bobbin protrudes into a recess of the housing (4) having hollow cylindrical symmetry, and the housing (4) houses the at least one magnet (20).

9. A sleeve (10) is arranged concentrically on the outside of the bobbin (9) such that it covers at least a portion of the outer surface of the bobbin (9) and provides an intermediate sleeve gap. The electromagnetic actuator (1) according to claim 7 or 8, wherein the at least one coil (21) is disposed between the bobbin (9) and the sleeve (10).

10. The electromagnetic actuator (1) according to claim 9, wherein the electromagnetic actuator (1) is configured to supply compressed gas to the sleeve gap.

11. The electromagnetic actuator (1) according to claim 9 or 10, wherein the sleeve (10) is rotatably attached to the bobbin (9).

12. The electromagnetic actuator (1) according to any one of claims 1 to 11, wherein the units (2, 3) are configured to restrict each other's translational motion.

13. The electromagnetic actuator (1) according to any one of claims 1 to 12, wherein the actuator (1) comprises an encoder (6).

14. The encoder (6) comprises at least one optical sensor (26) provided on one of the units (2, 3), and at least one encoder scale (27) provided on the other of the units (2, 3). The encoder scale (27) is a grid having detectable lines extending along at least one of the translational direction (T) and the rotational direction (R), The optical sensor (26) is configured to read the at least one encoder scale (27) in order to encode the relative positions of the two units (2, 3). The electromagnetic actuator (1) according to claim 13, comprising: a first sensor configured to interact with a first encoder scale embodied as a grid having lines extending in the rotational direction for detecting the relative translational positions of the units (2, 3); and a second sensor configured to interact with a second encoder scale embodied as a grid having lines extending in the translational direction for detecting the relative rotational positions of the units (2, 3).

15. The electromagnetic actuator (1) according to claim 14, wherein the first grid and the second grid are integrated to form a two-dimensional grid on a cylindrical surface.

16. The electromagnetic actuator (1) according to any one of claims 3 to 15, further comprising a locking unit (15) for locking the units (2, 3) relative to each other with respect to motion in at least one of the translational direction (T) and the rotational direction (R).

17. The electromagnetic actuator (1) according to claim 16, wherein the locking unit (15) is adjustable via a controllable valve by reducing the pressure of an expandable collet during operation of the actuator (1), thereby providing an internal brake for locking one position of the unit (2, 3) relative to the other of the unit (2, 3) by a force provided by a spring pushing the expandable collets together back to the locked position.

18. The electromagnetic actuator (1) according to claim 3, wherein the second unit (3) has a closed end cap so as to be combined with the first unit (2) to construct a piston having a piston chamber (12), and the piston chamber (12) is configured to be supplied with pressurized gas from the gas supply device (23).

19. The electromagnetic actuator (1) according to any one of claims 1 to 18, wherein one of the units (2, 3) forms a runner and a rotor, and the other of the units (2, 3) forms a stator.

20. The device comprises a base, a positioning platform, and at least one electromagnetic actuator (1) according to any one of claims 1 to 19. A positioning device in which one of units (2, 3) is connected to the base and the other of units (2, 3) is connected to the positioning platform.

21. The positioning device according to claim 20, wherein the positioning device corresponds to a parallel kinematics manipulator (34).

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