Linear electromagnetic machine system with bearing housings having pressurized gas

A linear electromagnetic machine includes a stator, a translator, and a bearing system. The bearing system maintains alignment against lateral displacement of the translator relative to the stator, as the translator reciprocates axially. More particularly, the bearing system maintains a motor air gap between the stator and a magnetic section of the translator. The stator includes a plurality of stator teeth and windings, which form a plurality of phases. The stator teeth and windings are arranged using a hoop stack with spines to form a stator bore and define the motor air gap. The bearing system can include bearing housings that are configured to form a bearing interface with a surface of the translator. The bearing interface can include a contact bearing or a non-contact bearing, such as a gas bearing. Current is controlled in the phases to convert between electrical energy and kinetic energy of the translator.

BACKGROUND

Linear motors convert between electrical energy and kinetic energy of a moving element. The design of linear motors must ensure efficient operation, cost effective construction, and reliability. In order to match the efficiency of rotary generators, it's necessary for a linear generator to be compatible with an inexpensive and lightweight oscillator design, employ high-efficiency materials, allow geometry optimization, and provide high copper slot fill. The present disclosure addresses all four requirements.

SUMMARY

In some embodiments, the present disclosure is directed to a linear electromagnetic machine (LEM). The LEM includes a stator, a translator, and two bearing housings. The stator includes a plurality of windings and a stator bore. The translator is configured to electromagnetically interact with the stator and is arranged to move axially within the stator bore substantially along the axis. The translator includes a translator bearing surface. A first of the two bearing housings is coupled to the stator at a first longitudinal location, and a second of the two bearing housings is coupled to the stator at a second longitudinal location. The first bearing housing and the translator bearing surface are capable of forming a first bearing gap and the second bearing housing and the translator bearing surface are capable of forming a second bearing gap. For example, the first and second bearing gaps may be configured to contain a pressurized gas, and function as a gas bearing. In a further example, in some embodiments, the LEM is configured for oil-less operation.

In some embodiments, the translator includes a magnet section. For example, the magnet section and the stator bore are capable of forming a motor air gap. In some embodiments, the magnet section includes a plurality of magnets arranged in longitudinally stacked rows. In some embodiments, an interior row of the longitudinally stacked rows includes magnets having a first axial length. In some such embodiments, a terminal row of the longitudinally stacked rows includes magnets having a second axial length less than the first axial length. In some embodiments, the translator includes at least one structural feature that engages at least one magnet of the magnet section to constrain axial motion of the at least one magnet. In some embodiments, the plurality of magnets are bonded to a surface of the translator. In some embodiments, the translator includes a wrap positioned radially over the magnet section. For example, the wrap constrains lateral displacement of the magnets.

In some embodiments, the magnet section includes a first longitudinal length and the plurality of windings includes a second longitudinal length. The second longitudinal length may be greater than, equal to, or less than the first longitudinal length. In some embodiments, the magnet section includes a magnetic pole length and the stator includes a plurality of slots and teeth having a slot pitch. In some such embodiments, the magnetic pole length and the slot pitch are not substantially equal.

In some embodiments, the plurality of windings are grouped into a plurality of phases and each phase of the plurality of phases includes one or more windings of the plurality of windings. For example, in some embodiments, the plurality of phases is equal to or greater than three phases. In a further example, each winding of the plurality of windings corresponds to a phase.

In some embodiments, the magnet section includes a plurality of magnets and the stator includes a plurality of stator teeth arranged azimuthally around the stator bore. The plurality of stator teeth include a pair of consecutive stator teeth having a first azimuthal gap. The magnet section includes a second azimuthal gap between azimuthally consecutive magnets of the magnet section. The first azimuthal gap and the second azimuthal gap are configured to substantially maintain azimuthal alignment. In some embodiments, the first azimuthal gap is larger than the second azimuthal gap in the azimuthal direction. In some embodiments, the translator includes a feature configured to constrain azimuthal rotation.

In some embodiments, the first bearing housing is coupled to the stator by a first flexure assembly that is configured to provide mechanical stiffness at least to lateral displacement and the second bearing housing is affixed to the stator by a second flexure assembly that is configured to provide mechanical stiffness at least to lateral displacement.

In some embodiments, the present disclosure is directed to a linear machine. The linear machine includes a stator having a stator bore, a translator, at least one bearing housing that includes a surface, and an assembly configured to affix the at least one bearing housing to the stator. The translator is configured to move linearly relative to the stator. In some embodiments, the translator includes a magnet section and a bearing surface. The stator bore and the magnet section form a motor air gap. The bearing surface and the surface form a bearing interface that is capable of aligning the translator to the at least one bearing housing. The assembly provides relatively more stiffness to lateral displacement than to pitch and yaw of the bearing housing to maintain the motor air gap. In some embodiments, the bearing housings are axially located so as to allow the magnetic section of the translator to travel beyond an end of a stator, beyond an axial length of a hoop stack of a stator, or both.

In some embodiments, the translator includes a translator tube, the magnet section is affixed to the translator tube, and the bearing surface includes an outer surface of the translator tube.

In some embodiments, the assembly includes at least one mount rigidly affixed to the stator and at least one flexure affixed to the at least one mount and to the at least one bearing housing. The at least one flexure provides the relatively more stiffness to lateral displacement than to pitch and yaw of the bearing housing. In some embodiments, fixtures such as, for example, spherical joints may be used in lieu of, or in addition to flexures.

In some embodiments, the bearing housing extends at least partially azimuthally around the bearing surface and the at least one flexure extends at least partially azimuthally around the bearing housing.

In some embodiments, the bearing interface is a gas bearing interface, and the linear machine is configured for oil-less operation, or otherwise operation without liquid lubricant. In some embodiments, the bearing interface is a liquid or solid interface, and the linear machine is configured for oil-less operation. For example, pressurized gas is provided to the gas bearing to provide stiffness against lateral displacement.

DETAILED DESCRIPTION

The present disclosure is directed to linear electric machines, components thereof, and methods of controlling linear electric machines. A linear electric machine includes a stationary component, the stator, and a movable portion, the translator. The stator and the translator are configured to interact with each other electromagnetically. For example, the stator may include one or more phases and the translator may include a magnet section that includes one or more magnets. Motion of the translator may be affected by electrical current in windings of the phases. To illustrate, currents in the phases may be controlled to move the translator by applying a force in the direction of motion of the translator (e.g., act as a motor), or currents in the phases may be controlled to decelerate (i.e., brake) the translator by applying a force opposite the direction of motion of the translator (e.g., act as a generator). Alternatively, in a linear electrical system such as a generator, current induced in the windings may be extracted as electrical energy. A bearing system maintains alignment of the translator relative to the stator, and possible other components to achieve a desired or predictable trajectory. For example, a bearing system may constrain motion of the translator in directions away from the intended trajectory.

FIGS. 1-3show illustrative linear electromagnetic machines (LEM), in accordance with some embodiments of the present disclosure.

FIG. 1shows a cross-sectional view of illustrative LEM100, in accordance with some embodiments of the present disclosure. LEM100includes translator160, stator150, bearing housings102and104, bearing mounts103and105, flexures113and115, features123-126, and bearing interfaces112and114. Translator160includes tube162and section163configured to interact electromagnetically with stator150. For example, section163(also referred to as an “electromagnet section” or “magnet section”) may include a magnet section having permanent magnets, electromagnets, an induction section, or a combination thereof. Although referred to as a tube, tube162may have any suitable cross-sectional shape, and accordingly bearing interfaces112and114may have a corresponding shape. For example, in some embodiments, tube162may have a rectangular cross section, and accordingly bearing interfaces112and114may be flat rather than annular. In a further example, in some embodiments, tube162may have at least one circular cross section for a first longitudinal distance (i.e., axial distance) and at least one rectangular cross section for a second longitudinal distance, where the first and second longitudinal distances may be equal or different.

Stator150and section163interact electromagnetically to cause motion of translator160, affect motion of translator160, convert kinetic energy of translator160(e.g., based on the mass on velocity of translator160) to electrical energy (e.g., in windings of phases of stator150and, if desired, power electronics coupled thereto), convert electrical energy (e.g., in windings of phases of stator150and, if desired, power electronics coupled thereto) into kinetic energy of translator160, or a combination thereof. Motor gap151(as referred to as “motor air gap”) between stator150(e.g., laminated ferrous teeth thereof) and section163(e.g., permanent magnets thereof) affects reluctance of the electromagnet magnetic interaction between stator150and translator160. For example, the smaller motor gap151, the larger the motor force constant (e.g., larger magnetic flux) that can be achieved between stator150and translator160. However, if motor gaps151nears zero (e.g., at one or more locations), translator160may contact stator150causing friction, impact, deformation, electrical shorts, reduced performance, failure, or any combination thereof. Accordingly, bearings are used to maintain the lateral alignment of stator150and translator160(e.g., to maintain motor gap151in an operable range).

In some embodiments, as illustrated, bearing housings102and104are affixed to stator150by bearing mounts103and105, and flexures113and115. For example, rigidly affixing bearing housings102and104to stator150may help in counteracting lateral (e.g., radial) loads on translator160. In some embodiments, one or both of bearing housings102and104may be coupled to stator150by flexures113and115, having prescribed a stiffness or compliance in one or more directions. In some embodiments, flexures113and115may be affixed to stator150, and bearing mounts103and105need not be included. In some embodiments, flexures113and115need not be included, and bearing mounts103and105may be affixed to bearing housings102and104, respectively. In some embodiments, one or both bearing housings102and104need not be affixed to stator150and may be affixed to any other suitable stationary component (e.g., an external frame). In some embodiments, only one bearing housing (e.g., bearing housing102or bearing housing104) is needed. To illustrate, the cantilever mounting of the bearing housing to support the translator may provide minimal constraints on the translator which provides more tolerance to misalignments.

In some embodiments, one or both bearing interfaces112and114are configured as contact bearings. In some embodiments, one or both bearing interfaces112and114are configured as non-contact bearings. In some embodiments, one or both bearing interfaces112and114are configured as gas bearings (e.g., a type of non-contact bearing). In some such embodiments, one or both bearing housings102and104are configured to receive bearing gas from features123-126, which may include respective ports for receiving respective bearing gas supplies. For example, referencing a tubular geometry, each of bearing housings102and104may include a bearing surface arranged at a radially inward surface, configured to interface to respective annular gas bearings in bearing interfaces112and114. Tube162may include a cylindrical bearing surface configured to interface to annular bearing interfaces112and114. During operation, bearing interfaces112and114allow translator160to move along axis190with low or near-zero friction, and prevent substantial lateral (e.g., radial) motion off from axis190. For example, bearing interfaces112and114may be configured to maintain motor air gap151between stator150(e.g., iron stator teeth and copper windings thereof) and section163during operation. It will be understood that bearing interfaces112and114, and motor air gap151may respectively have any suitable thickness. For example, in general the thicknesses are preferred to be as thin as possible while ensuring reliable operation. In some embodiments, bearing interfaces112and114are configured to be 20-150 microns thick and motor air gap151is configured to be 20-40 mm thick.

In an illustrative example, in which bearing interfaces112and114are configured as gas bearings, bearing gas is configured to exit bearing housings102and104(e.g., to form respective gas bearings in bearing interfaces112and114) in a substantially radially inward direction (i.e., streamlines directed towards axis190). Bearing gas may flow through porous sections of bearing housings102and104, ducts and orifices within bearing housings102and104, or a combination thereof, to reach respective bearing interfaces112and114.

In some embodiments, bearing housings102and104may include a coating, a consumable layer, a dry film lubricant, an abradable coating, or a combination thereof, at corresponding bearing surfaces to accommodate, for example, contact with translator160while limiting or avoiding damage to the translator, bearing housing, or both. In some embodiments, translator160may include a coating, a consumable layer, a dry film lubricant, an abradable coating, or a combination thereof, to accommodate, for example, contact with bearing housings102and104while limiting or avoiding damage to the translator, bearing housing, or both. In some embodiments, a bearing housing extends fully and continuously (e.g., 360° azimuthally) around a translator. In some embodiments, a bearing housing includes one or more bearing segments that extend for an azimuthal range around a translator that is less than 360°. For example, a bearing housing may include four bearing segments each extending about ninety degrees around the translator, with azimuthal gaps in between the bearing segments. A bearing housing may include any suitable number of bearing segments having any suitable number of gaps, and arranged in any suitable configuration, around a translator.

In some embodiments, translator160may include one or more pistons or end caps affixed to axial ends of tube162. For example, tube162may act as a rigid body coupling the pistons and other components to form a rigid translator. In a further example, LEM100may be included as part of a linear generator (e.g., as illustrated inFIG. 36), in which one piston is configured to contact a reaction section and the other piston is configured to contact a gas spring. Although section163is illustrated inFIG. 1as being axially shorter than stator150, section163may be axially shorter, longer, or the same length as stator150, in accordance with some embodiments of the present disclosure. In some embodiments, whether section163is longer, shorter, or the same length as stator150, section163or portions thereof may be capable of being positioned axially outside of stator150(e.g., axially beyond ends of stator150).

FIG. 2shows a perspective view of illustrative LEM200with cooling, in accordance with some embodiments of the present disclosure. LEM200includes stator250, translator260, bearing assemblies202and204, and cooling system270. Translator260is configured to move along axis290, as constrained by bearing assemblies202and204. Stator250, which may include a plurality of phases, is configured to interact electromagnetically with a section of translator260that may include permanent magnets, an electromagnet, an induction section, or a combination thereof. Bearing assemblies202and204may each include one more bearing housings, one or more mounts, one or more flexures, any other suitable components, or any suitable combination thereof to form a bearing interface with translator160(e.g., with surface262thereof that may act as a bearing surface). In some embodiments, LEM200may be configured for air cooling, liquid cooling, or both. Cooling system270may include plenums, jackets, shrouds, shields, vanes, any other suitable hardware, or any combination thereof to guide a cooling fluid around components of stator250. For example, LEM200may be configured for air-cooling, and cooling system270may include a cooling jacket, shroud, or both configured to receive and guide cooling air throughout stator250. In a further example, LEM200may be configured for liquid cooling, and cooling system270may include a cooling jacket configured to receive and guide cooling fluid through stator250. In some embodiments, as illustrated, stator250includes spines208, and end plates210, which are described further in the context ofFIGS. 4-13, for example. As illustrated, bearing assembly202includes, bearing housing225, flexure221, mount222, and feature220(e.g., which may include a feature for adjusting bearing stiffness, or a port for bearing gas). In some embodiments, tie-rods251are included to provide axial compression to components of stator250. For example, tie-rods251may include sections (e.g., threaded sections) at each end that extend axially through end plates210, and washers, nuts, crimp connectors, or other terminations are affixed to the sections to engage endplates210and maintain compression.

FIG. 3shows a perspective view of illustrative linear electromagnetic machine300including hoop stack351and spines352, in accordance with some embodiments of the present disclosure. Hoop stack351includes a plurality of hoops (e.g., including hoop353shown for reference) arranged along axis390to form a stator bore (e.g., formed by stator teeth affixed to hoops of hoop stack351). Hoop stack351, as illustrated, includes end plates354, which are arranged on respective axial ends of the plurality of hoops for structural support. Spines353are coupled to end plates354and the hoops of hoop stack351to maintain alignment of the hoops. In some embodiments, one or more optional tie-rods359may be included to provide axial compression to hoop stack351(e.g., tie-rods359may engage with end plates354). Bearing assemblies302and304maintain alignment (e.g., lateral alignment of a motor gap) between stator350and translator360. Further description of hoops, coils, stator teeth, and assemblies thereof are described in the context ofFIGS. 4-13, for example. A plurality of phase leads370corresponding to coils of hoop stack351.

A stator is a LEM component configured to accommodate current in one or more phases, electromotive force in the one or more phases, or both, to provide an electromagnetic interaction with a translator. The electromagnetic interaction includes a magnetic flux interaction (e.g., with a motor air gap affecting the reluctance), a force interaction (e.g., with a force constant affecting the current-force relationship), or both.

FIG. 4shows a perspective view of illustrative stator400, in accordance with some embodiments of the present disclosure. Stator400includes a plurality of stator teeth402(e.g., ferrous elements, lamination stacks, or both), arranged to form a stator bore, as illustrated. Although shown as circular, stator teeth may define any suitable compound surface that may define a motor air gap (e.g., flat, curved, segmented, piecewise, circular, non-circular, or otherwise). In some embodiments, spines452, end plates454, and tie-rods452, or any combination thereof, provide structural support to maintain alignment of stator400. Leads413from the plurality of windings of stator400may be directed to power electronics, coupled among subsets of themselves (e.g., to form a star neutral, to couple two or more windings directly in series), or a combination thereof. Although not shown inFIG. 4, one or more bearing housings may be affixed to stator400for constraining lateral displacement of a translator configured to interact electromagnetically with stator400(e.g., forming a motor air gap with stator400). In some embodiments, tie-rods451are included to provide axial compression to components (e.g., hoop-coils, stator teeth402, or both) of stator400.

A stator (e.g., stator400) may include a plurality of ferrous elements for directing magnetic flux. These ferrous elements, or “stator teeth,” may include some number of lamination stacks (e.g., shown inFIG. 6) arranged in a circular pattern (e.g., arranged by a hoop as illustrated inFIGS. 5 and 7). The lamination stacks are each a linear stack that together, when arranged in a circle, may approximate a circular stator bore. The inclusion of more stator teeth may provide a more uniform air gap (e.g., between the teeth and a translator having a magnet section), allow tighter air gaps, potentially allow for better motor performance, or a combination thereof. The inclusion of fewer stator teeth may reduce part count and assembly cost. In some embodiments, in order to achieve high reliability, a cooling system provides stator and winding cooling, the stator is configured for easy-to-route phase leads, the stator is configured to allow space for insulating material (e.g., dielectric insulation, thermal insulation, or both), or a combination thereof.

FIG. 5shows a perspective view of illustrative hoop500, in accordance with some embodiments of the present disclosure. Hoop500is configured to accommodate a set of stator teeth arranged at least partially azimuthally around axis590of hoop500(e.g., the azimuthal direction is around axis592). For reference with regard to a stator, as illustrated inFIG. 5, axis592represents the axial direction (i.e., longitudinal), axis591represents the radial direction (i.e., lateral), and axis590represents the azimuthal direction. Hoop500includes body501(e.g., the main structural portion or a “stiffening ring”), optional recesses504configured to accommodate or otherwise engage with one or more spines, optional anti-racking tabs502, and optional docks503. For example, four recesses504are illustrated inFIG. 5, although any suitable number of recesses may be included to accommodate corresponding spines. In some embodiments, the hoop includes no recesses and the spines connects to the hoop500with or without any additional features. Anti-racking tabs502extend axially from body501and are configured to prevent azimuthal or lateral deformation of laminations of stator teeth. Anti-racking tabs502may, in some embodiments, include one or more holes or other features configured to allow cooling air flow to permeate the stator (e.g., to flow through anti-racking tabs502to windings and stator teeth). Docks503are configured to accommodate or otherwise engage features of stator teeth to maintain position of stator teeth, react forces on stator, or both. Hoop500may be constructed of metal, sheet metal, plastic, or any other sheet material, including any suitable processing (e.g., bending, breaking, pressing/stamping, cutting, brazing, welding, adhering, or otherwise) to form shapes, form features, attach features, or any combination thereof (e.g., anti-racking tabs502, recessing504, docks503).

FIG. 6shows an axial view and a perspective view of illustrative stator tooth600, which includes a plurality of laminations, in accordance with some embodiments of the present disclosure. Lamination601is shown to illustrate a thin sheet of material, of which a stator tooth is formed. A plurality of laminations similar to601, although they need not be identical, are stacked to form stator tooth600. For example, a plurality of steel laminations may be cut from sheet metal (e.g., by punching, laser cutting, plasma cutting, wire EDM, water jet cutting, or any other cutting technique), and affixed (e.g., bonded, interlocked, welded, cleated, or any other suitable means) to one another to form a lamination stack (i.e., stator tooth600). For reference with regard to a stator, as illustrated inFIG. 6, axis692represents the axial direction, axis691represents the radial direction, and axis690represents the azimuthal direction (e.g., azimuthal around axis692). As illustrated, stator tooth600includes features650and651for axial engagement of stator teeth. Features650an651may include bosses, recesses, grooves, slots, steps, raised portions, any other suitable geometric feature for engaging an axially adjacent stator tooth (e.g., affixed to an adjacent hoop), or any combination thereof. In some embodiments, features650and651provide indexing features for assembly of a hoop stack (e.g., hoop stack351inFIG. 3), aid in alignment of a hoop stack, or both.

Region605represents a recess configured to accommodate one or more windings. For example, regions similar to region605of stator teeth at a particular axial location align to form a void volume in which electronically conductive windings (e.g., of coils) can be wound or otherwise inserted. In some embodiments, stator tooth600or region605thereof is wrapped or otherwise covered with an electrically insulating material (e.g., such as Nomex sheeting) to prevent windings from electrically shorting to stator tooth600. In alternative embodiments, the electrically conductive windings is wrapped or otherwise covered with an electrically insulating material (e.g., such as Nomex tape) to prevent the windings from electrically shorting to stator tooth600. Feature603, which includes a notch as illustrated, is configured to allow stator tooth600to engage with a hoop (e.g., as illustrated inFIG. 7). For example, feature603may engage with dock503of hoop500ofFIG. 5. Stator tooth tip604(also referred to as a stator tooth tip) is used to define, along with like features of a plurality of stator teeth, a stator bore. In some embodiments, the shape of the stator tooth tip604may be flat in an azimuthal direction (e.g., in the direction of690). In alternative embodiments, the shape of the stator tooth tip604may have a convex, concave or any other appropriate shape required to provide a desirable stator bore surface. As illustrated by the dotted contour in the face view, tooth tip604may be curved or otherwise contoured to more closely approximate a circle (e.g., a circular stator bore).

In an illustrative example, lamination601may include thin, low-loss, high-permeability lamination steel. In a further illustrative example, lamination601may cause a stator tooth shape optimized to form a motor air gap and provide high copper slot fill (e.g., more windings, or turns of windings). As illustrated inFIG. 6, the laminations (e.g., lamination601) of stator tooth600have sufficiently uniform thickness such that stator tooth600has a rectangular profile when viewed in the axial direction. In some embodiments, the thickness of lamination601need not be uniform. For example, lamination601may have a smaller thickness at the tooth tip604than at the outer radial end (e.g., where feature603is located) such that when stator tooth600is formed the stator tooth600forms a V-like profile when viewed in the axial direction (e.g., the inner surface of the stator tooth is smaller than the outer surface area of the stator tooth). This V-like profile may reduce or eliminate the azimuthal gap between adjacent stator teeth at the outer diameter of a set of stator teeth (e.g., as shown by ring of stator teeth inFIG. 7), thereby increasing the amount of steel material in the stator, which could reduce the flux density and increase efficiency.

FIG. 7shows a perspective view of illustrative hoop701with set of stator teeth702arranged (“hoop-teeth assembly”), in accordance with some embodiments of the present disclosure. Set of stator teeth702locally define stator bore703at a particular axial position or position range. Each tooth of set of stator teeth702engages with a dock of hoop701(e.g., of which dock753is one). In some embodiments, each dock753includes feature754(e.g., a slot as illustrated) that engages with a stator tooth (e.g., of stator teeth702) and feature755(e.g., a flexure, as illustrated) for maintaining engagement. In some embodiments, set of stator teeth702may be welded, brazed, glued, crimped, or otherwise affixed to hoop701, and feature755may be but need not be included. Feature756(e.g., one or more holds as illustrated) is configured to provide a path for cooling air to flow, to help cool the coils (or windings thereof), stator teeth, hoops, spines, tie-rods, or a combination thereof. In some embodiments, feature756may be selectively covered to divide sections of a stator into two or more cooling zones.

In some embodiments, as illustrated, set of stator teeth702include azimuthal gap704which is configured to provide an anti-rotation force on a translator, configured to allow a feature of a translator to move thin (e.g., a rail), allow coil leads to be routed away from the windings, or any combination thereof. In some embodiments, lead cover705may be included to guide coil leads away from the windings, provide for alignment of stator teeth, or both. For example, lead cover705may be comprised of internal passages to route or guide coil leads away from the windings. Additionally, lead cover705may be comprised of a dielectric material (e.g., a plastic) to electrically insulate the coil leads from the set of stator teeth702and stiffening ring701. In some embodiments, one or more azimuthal gaps at stator bore703may be included among the set of stator teeth. In some embodiments, no substantially distinct azimuthal gaps at stator bore703are included among the set of stator teeth. In some embodiments, one or more azimuthal gaps at stator bore703are included and configured to provide anti-rotation forces. Feature711(e.g., one or more holes as illustrated) may be included to accommodate a tie-rod, provide an axial cooling path for cooling air, or both.

In an illustrative example, a hoop may be a stamped part, used to control the circularity of a single tooth-array. The hoop together with any suitable number of or type of spines and any suitable number of or type of end plates control straightness of the stator bore when many tooth arrays are stacked in series axially. A hoop may include any suitable features to affix, engage, preload, or any combination thereof, the lamination stack onto their alignment positions to reliably define the stator bore, allow snap-together assembly, or both. The stacked assembly allows the use of stator tooth tips (e.g., as shown inFIG. 6) to improve motor efficiency and reduce magnet losses, while still allowing for easy coil insertion, good slot fill, and simple stator assembly. In some embodiments, stator teeth include alignment bosses and pockets, stamped in the lamination to provide positive alignment when axially stacking multiple tooth arrays together.

In some embodiments, a stack of hoop-teeth assemblies is put into compression to improve the stiffness of the stator assembly. In some embodiments, a hoop-teeth assembly may be assembled under compression and fixed in position by tie rods, welds, glue, or a combination thereof. In some such embodiments, it may be necessary to include features (e.g., tabs) to prevent the individual lamination stacks or stator teeth from buckling or racking when loaded in compression (e.g., through the use of anti-racking tabs). These features could be separate pieces, or they could be integrated into the hoop design.

In some embodiments, a set of stator teeth may include azimuthal gaps at the radially outer region of the ring of stator teeth (e.g., based on the tooth design). These gaps may be filled or otherwise avoided by including stator tooth laminations with a greater thickness at the radially outer ends (e.g., so the stator tooth tapers in azimuthally at lesser radii). For example, when viewed axially, a stator tooth may have a V-shape in the radial direction instead of uniform thickness. The use of a V-shape may improve electromagnetic performance, but may increase resistance to the flow of cooling fluid through the stator.

FIG. 8shows an axial view and a perspective view of illustrative coil800, in accordance with some embodiments of the present disclosure. Coil800includes winding802and leads804. In some embodiments, as illustrated, coil800includes a length of an electronically conductive material wrapped in a suitable shape (e.g., circular as illustrated) to form the winding (i.e., winding802). The remaining portion of the electronically conductive material forms the leads (i.e., leads804). For example, leads804may be coupled to other leads (e.g., of other coils), power electronics, electrical terminals, a neutral wye connection, any other suitable connection, or any combination thereof. In an illustrative example, when coil800is included in a phase controlled by a full bridge, both leads804may be coupled to suitable nodes of an H-bridge circuit for current control. In a further illustrative example, when coil800is included in a phase controlled by a half bridge, one of leads804may be coupled to a suitable node of the half-bridge circuit for current control, and the other lead of leads804may be connected to a neutral wye. In a further illustrative example, when coil800is included in a phase, leads804may be coupled to leads of other coils (e.g., the phase includes more than one coil).

In some embodiments, coil800may be formed from copper wire, aluminum wire, any other suitable metal wire, or any combination thereof. For example, copper wire having N laminated strands (e.g., where N is an integer) may be wound (e.g., around a mandrel or other tool to define coil bore830) to form windings802, and the unwound ends form leads804(e.g., of any suitable length). In some embodiments, as illustrated, winding802, leads804, or both may be wrapped with an electronically insulating material to prevent shorting (e.g., such as Nomex, Kapton, or other suitable material or materials). In some embodiments, leads804include electrical terminations (e.g., crimped connectors, soldered ends, or other suitable components or treatments) at the ends. In some embodiments, coil bore830is the same as or larger than a stator bore. For example, coil bore830may be larger than a stator bore to prevent windings802from incidental contact with a translator. In a further example, coil bore830may be larger than a stator bore, with radially inner portions of stator teeth being arranged radially inward of coil bore830. A plurality of coils, each similar to coil800, may be included in a stator (e.g., stator400ofFIG. 4), making up phases of the stator. For example, each phase may include one or more coils, electrically coupled in series. In a further example, each phase may include one coil. In some embodiments, a coil, or a winding thereof, may be formed using bondable wire, wire with bondable insulation, or both. For example, the coil is formed and then the coil, or winding portion thereof, is heated (e.g., baked in an oven) to set. A coil may include wire having any suitable cross section such as, for example, round, square, or any other suitable shape. A coil may include wire of any suitable material such as, for example, copper, aluminum, or any other suitable wire.

FIG. 9shows a perspective view of illustrative spine900, in accordance with some embodiments of the present disclosure. Spine900is configured to locate, arrange, maintain, align, or otherwise affect an axial stack of hoops of a stator. Spine900includes a length901that is configured to axially span one or more hoops of a stator. Spine900may be configured to provide axial stiffness, azimuthal stiffness, lateral stiffness (e.g., radial), or a combination thereof to a stack of hoops. A stator may include any suitable number of spines, having any suitable shape. For example, although illustrated as rectangular, a spine may be curved (e.g., to follow an azimuthal arc), segmented, bent, defined by a regular or irregular shape in a plane, or any other suitable shape. In some embodiments, as illustrated, spine900includes features902for affixing or otherwise coupling to hoops of a stator. Features902may include, for example, holes, slots, recesses, bosses, teeth, pins, threaded fasteners (e.g., threaded studs), any other suitable features, or any combination thereof to locate and maintain arrangement of hoops. One or more spines, each similar to spine900, may be included in a stator (e.g., stator400ofFIG. 4), to provide structural support, alignment, or both for the stator and components thereof. In some embodiments, spine900spans the length of a single hoop and is attached to other spines in an axial direction such that, when axially stacked, collective span the length of the stator. In some embodiments, spine900spans the length of multiple hoops and is attached to other similar spines in an axial direction such that, when stacked axially, collectively span the length of the stator. In some embodiments, spines help define the stator bore by aligning the stator teeth that are included in the hoop-teeth assemblies. Further, spines provide stiffness against twisting or other displacement of stator teeth, and thus potentially the stator bore, during operation.

FIG. 10shows a perspective view of illustrative end plate1000, in accordance with some embodiments of the present disclosure. End plate1000is configured to define the axial extent of the hoop stack. For example, end plate1000may be similar to hoop500, but without a corresponding coil or stator teeth. In a further example, end plate1000may be similar to hoop500including a corresponding coil or stator teeth. In a further example, end plate1000need not be similar to hoop500, and may, but need not, include corresponding coil(s) or stator teeth. In some embodiments, end plate1000is identical to a hoop (e.g., the terminal hoop at either axial end of the stator serves as the end plate, without a separate component needed). In some embodiments, end plate1000may be affixed to, or otherwise coupled to, one or more spines (e.g., similar to spine900ofFIG. 9). For example, features901may include holes, slots, recesses, bosses, teeth, pins, threaded fasteners (e.g., threaded studs), any other suitable features, or any combination thereof to interface to one or more spines. In some embodiments, end plate1000is structurally stiffer than each hoop of the stack, to provide structural rigidity to the assembled stator. End plate1000includes end plate bore1030, which is larger than the stator bore. End plate bore1030allows a translator to move axially without impeding the translator's motion. In some embodiments, one or two end plates, each similar to end plate1000, may be included in a stator (e.g., stator400ofFIG. 4), arranged at longitudinal ends of the stator. For example, an end plate may be included at each longitudinal end of the stator (e.g., two end plates are included). In some embodiments, in addition to capping the ends of the stator, end plates1000may be used in intermediate locations within the stator to provide additional structural support to the stator stack. In some embodiments, end plates1000may be used to directly attach the bearings to the stator. In some embodiments, one or more end plates may be arranged within a hoop stack (e.g., between two hoop-teeth assemblies). An end plate can be of any suitable design configured to help hold the hoops together. A spine can be of any suitable design configured to help hold the hoops together. In some embodiments, a stator need not include a spine, an end plate, or both. In some embodiments, end plate1000includes features1001for interfacing with and engaging spines. In some embodiments, end plate1000includes features1002for interfacing with and engaging tie-rods.

FIG. 11shows a perspective view of illustrative assembly1100including end plate1101, one hoop-teeth assembly and one coil (collectively hoop-coil assembly1102, or “hoop-coil”), and spines1103and1104, in accordance with some embodiments of the present disclosure. Spines1103and1104are coupled to end plate1101, which defines a first axial side of a stator. Hoop-coil assembly1102includes a hoop, set of stator teeth1105, and one or more coils1106, and is arranged axially in-line with end plate1101(e.g., along an axis of the stator). In some embodiments, assembly1100is a first building block for a completed stator.FIG. 12shows a perspective view of illustrative assembly1200including end plate1101, several hoop-coil assemblies1202(e.g., including hoop-coil assembly1102), and spines1103and1104, in accordance with some embodiments of the present disclosure. Assembly1200is a partially assembled stator. Hoop-coil assemblies1202are stacked along the axis of the stator. In some embodiments, leads1213of hoop-coil assemblies1202are directed in the same orientation, although they need not be. In some embodiments, assembly1200is a prerequisite for a completed stator (e.g., stator1300ofFIG. 13).FIG. 13shows a perspective view of illustrative assembled stator1300, including end plates1101and1301, hoop-coils1302(e.g., including hoop-coil assemblies1202), and spines1103and1104, in accordance with some embodiments of the present disclosure. Hoop-coil assemblies1302are stacked along the axis of stator1300, thus defining a stator bore (e.g., stator teeth1305define the stator bore). For example, the stator bore along with a magnet section of a translator define the motor air gap. In some embodiments, leads1313of hoop-coil assemblies1302are directed in the same orientation, although they need not be. In some embodiments, leads1313are coupled to power electronics (e.g., as illustrated inFIGS. 33, 34, and 36) configured to control current in one or more of leads1313(e.g., that may correspond to phases). In some embodiments, some of leads1313are coupled to power electronics and some of leads1313are coupled to other leads (e.g., to arrange coils in series or parallel, or to form a neutral wye or star node). In some embodiments, one or more of hoop-coil assemblies1302is affixed to spines1103and1104(e.g., by fastening, crimping, interlocking, pressing, tooth-groove interfaces, pinned, or otherwise located and constrained). In some embodiments, spines1103and1104provide lateral alignment (e.g., to ensure a substantially straight stator bore) for hoop-coil assemblies1302. Stator1300includes four spines as illustrated (e.g., spine1103,1104,1304and1306), but a stator may include any suitable of spines. In some embodiments, the axial length, number of phases, or both may be selected by forming longer stacks (e.g., using longer or shorter spines, using offset spines, and more or less hoop-coils in the stack). In some embodiments, optional tie-rods1351may be included to provide axial compression. In some embodiments, the hoop-coil assemblies are stacked such that adjacent hoop-coil assemblies interface or engage at their respective stator teeth interfaces such that the stator teeth bear any compressive loads in the axial direction, while, optionally, the hoops and spines maintain alignment.

In an illustrative example, end plates1101and1301may be configured to interface with bearing mounts, flexures, or bearing housings configured to constrain lateral (e.g., radial) displacement of a translator that is configured to interact electromagnetically with stator1300. In some embodiments, the hoop-coil assemblies adjacent to end plates need not have a coil at the axially outer end (e.g., between the hoop-coil assembly and the end plate). For example, each hoop-coil assembly of a stack may include two coils, one on each axial end of the stator teeth, except for the first and last hoop-coil which only include coils on the axially inside end (e.g., away from the end plate). In some embodiments, each hoop-coil assembly of a stack may include two coils, one on each axial end of the stator teeth, including the first and last hoop-coil assembly (e.g., the hoop-coil assemblies adjacent the end plates).

FIG. 14shows a side view of illustrative axial lamination1400and a perspective view of illustrate set of axial lamination stacks1450, in accordance with some embodiments of the present disclosure. Axial lamination1400includes a plurality of teeth (e.g., including tooth1401), separated by a plurality of slots (e.g., slot1402). Lamination stacks1450(e.g., including lamination stack1460), as illustrated, include a set of lamination stacks (each stack include a plurality of laminations similar to lamination1400) arranged to form stator bore1453. The set of stator teeth of lamination stacks1450define stator bore1453. Slots1454extend at least partially azimuthally around stator bore1453, arranged in between axially consecutive rows of stator teeth. In some embodiments, wire may be wound in slots1454to form windings. In some embodiments, coils may be installed in slots1454, with phase leads routed in any suitable way. In some embodiments, the lamination stacks of the set of lamination stacks have an axial length equal to or shorter than the length of the stator. In some embodiments, lamination stacks1450are arranged using structural and alignment fixtures, features, components, or any combination therein. For example, lamination stacks1450could be structurally supported and aligned at least one hoop (e.g., similar to hoop353inFIG. 3), spine (e.g., spine352inFIG. 3), end plate (e.g., end plate354inFIG. 3), tie rods (e.g., tie rods359inFIG. 3), or any combination thereof.

FIG. 15shows a face view of illustrative hoop-coil1500, with lead management cover (e.g., using cover1503), azimuthal gap1504, and spines1510-1513, in accordance with some embodiments of the present disclosure. Hoop-coil assembly1500includes hoop1502, set of stator teeth1501, a coil (e.g., including winding1520and leads1521and1522), and cover1503. In some embodiments, as illustrated, azimuthal gap1504is included among set of stator teeth1501to affect an anti-clocking force on a translator configured to interact electromagnetically with a stator that includes hoop-coil assembly1500. Hoop1502is coupled to, or otherwise constrained from lateral motion (e.g., radial, azimuthal, or otherwise) by, spines1510,1511,1512, and1513. Cover1503, which may but need not extend axially and radially across hoop-coil1502, is configured to protect and guide leads1521and1522away from winding1520to power electronics, leads of other windings, a neutral wye/star node, or any other suitable electrical terminal. In some embodiments, the presence of cover1503causes a second azimuthal gap among set of stator teeth1501In some embodiments, azimuthal gaps (e.g., azimuthal gap1504and azimuthal gap for cover1503) may be located at any suitable azimuthal location (e.g., substantially 180 degrees apart), may have any suitable size (e.g., substantially the same size), or both. In some embodiments, one or more azimuthal gap between stator teeth of a hoop-coil assembly may be configured to affect an anti-clocking force on a translator configured to interact electromagnetically with a stator that includes the hoop-coil assembly.FIG. 7, as illustrated, shows uniform azimuthal gaps between stator teeth for the teeth between the azimuthal gap1504and the azimuthal gap for cover1503, however, this need not be the case. Stator teeth can be arranged in a hoop-coil assembly with any suitable number of azimuthal gaps with any suitable sizes. In some embodiments, a hoop-coil assembly may include two coils per hoop (e.g., on opposite axial sides of set of stator teeth), although any suitable number of coils may be included in a hoop-coil (e.g., one or more coils). In some embodiments, the stator laminate tooth pitch (also referred to as the stator slot pitch) may vary from one hoop-coil assembly to another hoop-coil assembly based on their axial location within a stator stack. In some embodiments, if the velocity profile of a translator is the highest at the midpoint of a stroke (e.g., the center of a stator), a longer stator slot pitch in the middle of the stator may be desired because it could lower the phase frequency and the concomitant core losses. Similarly, if the velocity profile of a translator is the lowest near the end of a stroke (e.g., the ends of a stator), a shorter stator slot pitch at the ends of the stator may be desired because they would increase the phase frequency, or EMF-per-turn, thereby allowing a greater contribution of work (i.e., force over a distance) from the end windings. In some embodiments, the hoop-coil assemblies located at the end sections of the stator may include a shorter stator slot pitch as compared to the stator slot pitch of hoop-coil assemblies in the center section of the stator.

As illustrated inFIGS. 11-13, a plurality of hoops with corresponding coils and stator teeth (e.g., a plurality of hoop-coil assemblies1500ofFIG. 15) may be stacked axially to form a stator. For example, the plurality of hoops with corresponding coils may be stacked along one or more spines (e.g., spines1510-1513) for alignment, securement, or both. In some embodiments, the number of turns of winding comprising the coil is the same for each hoop-coil assembly. In some embodiments, the number of turns of winding comprising the coil may vary between hoop-coil assemblies. For example, in some embodiments, a hoop-coil assembly located towards an end of a stator may include a coil with fewer winding turns, a hoop-coil assembly located towards the center of a stator may include a coil with more winding turns, or both, or vise-versa.

In some embodiments, a stator need not include separate spines. For example, in some embodiments, a plurality of hoop-coils may be stacked axially, optionally aligned around a central mandrel (e.g., as a proxy for a magnet section plus motor air gap), and then welded or bonded to each other. In a further example, the hoop-coils may be placed into compression by axially preloading (e.g., with tie-rods to put the stack in compression) and then wielding, axially preloading then clamping, or both. In some embodiments, a plurality of hoop-coils may be stacked axially, and placed in compression axially using one or more tie rods that extend through the stack of hoops. For example, in some embodiments, tie-rods may be used in addition to, or instead of, spines and end plates. In some embodiments, each of the axially stacked hoops interface with the spines, and tie-rods are used to place the axial stack of hoop-coil assemblies in axial compression.

In some embodiments, the components of the present disclosure are configured (e.g., in order to keep manufacturing costs low) to leverage existing motor manufacturing infrastructure (e.g. presses, dies, coil machines, insulation systems), make efficient use of lamination sheet material, provide compatibility with automated assembly and validation methods, allow streamlined hand-assembly, and provide sufficient cooling options in order to achieve high power density and low material and assembly cost.

In an illustrative example, exposed stator teeth (e.g., metal) and windings (e.g., copper wire or aluminum wire) around the radial outside of the stacked assembly (i.e., the stator) provide access for either passive or active motor cooling, in order to control temperatures and improve motor life (e.g., under large current loads), motor efficiency, motor power, or any combination thereof. In some embodiments, a shroud (e.g., shown inFIG. 4) may be installed in order to more effectively direct cooling air into the magnet air gap between windings, between stator teeth, or a combination thereof.

The translating assembly or “translator” electromagnetically interacts with a stator to convert between electric energy and kinetic energy. Accordingly, the translator is capable of moving under electromagnetic forces, moving under any forces applied to the translator, generating an electromotive force (emf) in phases of the stator (e.g., and conversely react to an emf generated by the stator), achieving a nominally linear path of movement, and withstanding thermal and mechanical loadings experienced during operation (e.g., cycles).

FIG. 16shows a side view of illustrative translator1600, in accordance with some embodiments of the present disclosure.FIG. 17shows an axial end view of translator1600, in accordance with some embodiments of the present disclosure. The axial end view ofFIG. 16is taken from direction1601. Translator1600includes tube1612. Translator1600includes section1613, which may include features (e.g., magnets) for enabling a desired electromagnetic interaction with a stator. Translator1600also optionally includes rail1616configured to provide a position index, an anti-clocking bearing surface, or both. In some embodiments, translator1600does not include rails, and sufficient anti-clocking stiffness in the azimuthal direction is provided through the electromagnetic interaction between the translator and stator (e.g., a stator having azimuthal gaps between stator teeth). In some embodiments, translator1600, or components thereof, may be symmetrical about axis1690(e.g., including circular shapes centered at axis1690, fastener patterns, arrangement of rails, and other aspects having rotational symmetry). In some embodiments, translator1600, or components thereof, need not be symmetrical about axis1690. In some embodiments, section1613may have substantially the same diameter as tube1612. In some embodiments, section1613may have a diameter smaller or larger than tube1612. In some embodiments, the outer dimensions of section1613, tube1612, or both, may be uniform, nonuniform, or both in the axial direction. For example, tube1612may include a taper, step, or both. In a further example, section1613may have a larger diameter at or near its axial center. In some embodiments, the translator1600may comprise of several sections made of different materials. In some embodiments, material composition of section of the translator1600may be optimized for desired properties such as weight, mechanical strength and electrical or thermal properties.

Rail1616includes, for example, surface1640, which may include a feature for position indication or indexing; surface1641, which may include an anti-clocking bearing surface; and surface1642, which may include an anti-clocking bearing surface. In some embodiments, a translator may include zero, one, two, or more than two rails, having any suitable azimuthal or axial positioning on a translator, in accordance with the present disclosure. For example, in some embodiments, a translator may include more than one rail to provide multiple position indications (e.g., for redundancy, accuracy, symmetry, or a combination thereof). In some embodiments, translator1600need not include any anti-clocking rails. In some embodiments, magnetic interactions between the translator and the stator may provide adequate anti-clocking stiffness in the azimuthal direction. In some embodiments, without anti-clocking rail1616, for example, position indexing features may be attached directly to translator1600, integrated directly in translator1600, or both (e.g., attached directly to tub1612, integrated directly in tube1612, or both). In some embodiments, surfaces1641and1642are configured to interface with corresponding anti-clocking bearings (e.g., which may include anti-clocking gas bearings). Anti-clocking bearings provide stiffness in the azimuthal direction, thus preventing or reducing azimuthal motion of the translator. In some embodiments, surface1640may include machined features for position indication or indexing, magnetic tape for position indication or indexing, any other suitable feature for position indication or indexing, or any combination thereof. In some embodiments, sensing the position of the translator relative to the stator may be determined by sensing the position of one or more rows of magnetic features section1613of the translator in conjunction with or without the use of external position indexing features. For example, a back electromotive force (emf) may be measured in one or more phase windings to determine a relative position of the stator and translator. In a further example, a control signal (e.g., a pulse-width modulation signal for applying current), a measured current, or both may be used to determine a relative position of the stator and translator.

FIG. 18shows a side cross-sectional view of an end of illustrative translator tube1810, and rail1812, in accordance with some embodiments of the present disclosure. For example, rails may be configured to constrain rotational motion of the translator and/or to mount an encoder tape for position measurement. In some embodiments, the rail is affixed (e.g., bolted, welded, glued, taped, or any combination thereof) to the translator. Rail1812can be affixed to translator tube1810through any suitable means such as bolted, welded, glued, taped, or any combination thereof. In some embodiments, rail1812can be affixed to translator tube1810at any suitable location of the translator tube and at any suitable location of the rail. For example, and rail1812need not be affixed to the translator tube1810over the entire axial length of the rail (e.g., there can be portions of the rail that are not affixed to the translator tube).

FIG. 19shows a side view of a portion of illustrative translator1900having magnet section1913, in accordance with some embodiments of the present disclosure. Translator1900includes tube1912and magnet section1913(e.g., which may be similar to section1613ofFIG. 16). A magnet section may include any suitable features that may interact electromagnetically with phases of a stator. For example, as illustrated, a magnet sections may include an array of (N)orth and (S)outh arranged magnets (e.g., with N or S poles facing outward as illustrated), a Halbach array, any other suitable magnetic array, or any combination thereof. In some embodiments, the axial lengths of N and S magnet rows may be substantially the same or substantially different. For example, magnet rows towards the axial ends of section1913may contribute less to the generation of magnetic field and may be shorter in axial length then magnet rows towards the axial center of section1913(e.g., as illustrated inFIG. 22). Magnet section1913includes optional end features1920and1921, which serve to delineate magnet section1913and may function to help transfer force (e.g., axial force) exerted on translator1900. Magnet section1913also includes optional locating features1922, which are configured to locate rows of like-polarity arranged magnets. Locating features1922may be configured to locate magnets as rows, columns, a grid, or any other suitable arrangement having any suitable pole pitch. In some embodiments, a corresponding stator may include a suitable number of phases, having a suitable axial phase length in view of the pole pitch. Center axis1990is shown for reference. For example, magnet section1913may be symmetric, near symmetric, or otherwise have a symmetry about center axis1990.

FIG. 20shows a perspective view of a portion of illustrative translator2000having features2004for arranging magnets (not shown inFIG. 20), in accordance with some embodiments of the present disclosure. Features2004are configured to aid in arranging magnets of section2002. In some embodiments, as illustrated, features2004include raised ridges, configured to act as indexes for positioning magnets during assembly, operation, or both. Additionally, features2004(e.g., ridges) may provide resistance against axial acceleration and help keep the magnets in place. Additionally, in some embodiments, suitable adhesive may be used to bond the magnets to the translator. Features2004may be, but need not be evenly spaced. For example, features2004may be spaced axially to accommodate magnets of varying axial lengths (e.g., shorter magnets at the axial ends).

FIG. 21shows a perspective view of a portion of illustrative translator section2100having magnets2104arranged, in accordance with some embodiments of the present disclosure. Translator section2100is shown with magnets2102and2103removed for clarity (e.g., an operable translator includes the magnets affixed to body2110). Magnets2104are arranged into rows2152arranged at a particular axial position or position range and extending at least partially azimuthally around body2110, and stacks2151arranged at a particular azimuthal position or position range and extending axially. For example, a row of rows2152may extend azimuthally around body2110, while a stack of stacks2151may extend the full or near-full axial length of body2110. In another example, a row of rows2152may partially extend azimuthally around body2110, while a stack of stacks2151may extend the full or near-full axial length of body2110. Magnets2104may be arranged in rows2152of alternating polar orientation (e.g., N and S). In some embodiments, all magnets in a row having the same polar orientation, while magnets along a stack have alternating polar orientation. In some embodiments, as illustrated, bondings2101are arranged radially underneath magnets2104to aid in affixing magnets2104to body2110. Body2110may be constructed of any suitable material and may be configured to interface with one or more translator tubes (e.g., having bearing surfaces) to form a translator. For example, body2110may be comprised of a metal composite, which could reduce eddy losses in the translator. In some embodiments, a translator tubes are comprised of non-ferrous materials and body2110is comprised of a ferrous material in order to complete the magnetic circuit (e.g., in a Hallbach arrangement). In some embodiments, body2110may include bearing surfaces (e.g., body2110and magnets2204may form a translator without additional structural components). In some embodiments, magnets are press fit into the translator or section thereof (e.g., radially or axially pressed). For example, magnets may be arranged inside of a translator or section thereof (e.g., if press fit axially or 3-D printed) such that a layer of material (e.g., metal) exists between magnets and stator teeth.

FIG. 22shows a cross-sectional view of a portion of illustrative magnet section2200, in accordance with some embodiments of the present disclosure. In some embodiments, a translator assembly includes one or more end features2202to constrain the position/motion of magnets2210(e.g., resist acceleration of magnets). In some embodiments, a translator assembly includes one or more locating features2204to constrain the position/motion of magnets2211and2210(e.g., resist acceleration of magnets). In an illustrative example, features2004ofFIG. 20may include end features2202, locating features2204, or both. In some embodiments, magnets are bonded to a translator tube (e.g., using adhesive). In some embodiments, a magnet assembly is wrapped using a material (e.g., a material compliant with thermal expansion) to protect the magnets, as illustrated inFIG. 23. In some embodiments, features2004and end features2202are machine into or affixed to a body (e.g., similar to body2110inFIG. 21) that is affixed to one or more translator tubes (e.g., similar to the translator tube1612inFIG. 16).

FIG. 23shows a perspective view of illustrative translator2300having wrap2301, in accordance with some embodiments of the present disclosure. In some embodiments, section2302includes magnets arranged in an array (e.g., partially or fully extending around or axially along the translator tube). Optional wrap2301is included to apply a compressive force on the magnets (e.g., in the inward radial direction), protect the magnets from rubbing/collisions, prevent ejection of any of the magnets (e.g., in the event of a bonding failure), or a combination thereof. In some embodiments, optional wrap2301may be compliant with thermal expansion. In some embodiments, wrap2301may include, for example, a Kevlar-based material. For example, in some embodiments, wrap2301is applied by wrapping a sheet of Kevlar material around section2302in one or more layers (e.g., similar to a spool). A wrap may be applied to any suitable section such as, for example, section1613ofFIG. 16, with any suitable axial length along a suitable section and with any suitable thickness.

While stator and magnet section design affect motor efficiency, bearing designs can affect the mechanical efficiency of the LEM, (e.g., the amount of power lost to bearing friction and windage during operation). For example, provided a streamlined cylindrical oscillator and modest peak surface speeds, windage losses can be minimized, and thus mechanical loss tends to be dominated by friction heating in the bearings, which support the oscillator shaft and magnet array (e.g., the translator). Some illustrative examples of linear contact bearing types include plane dry-film bearings, linear ball bearings, and oil-lubricated plane bearings. These solutions typically impose one or more constraints on a system such as, for example, a continuous lubrication requirements and/or short maintenance interval, an inability to handle high acceleration or velocity (e.g., without excessive wear or component damage), short replacement intervals and part life, high friction losses, or a combination thereof. The machines and systems of the present disclosure may include contact bearings, non-contact bearings, or both.

In some embodiments, the present disclosure describes self-aligning aerostatic bearings (e.g., referred to herein as air bearings or gas bearings). Gas bearings may be useful for applications that require high velocities (e.g., >2, >5, >10, >15 m/s), high mechanical efficiency (e.g., low friction losses), long maintenance intervals, and high durability. Gas bearings operate by flooding a small gap (e.g., a gap at a bearing interface) with pressurized air or other gas via orifices, porous media, any other suitable flow restriction, or a combination thereof. As the surface of the translator moves laterally (e.g., radially) closer to the fixed bearing surface (i.e., the air gap lessens), the bearing gas flow restriction tightens, and the pressure in the bearing gap increases. The pressure provides a restoring force to prevent, or limit instances and severity of, the translator surface contacting the bearing surface of the bearing housing. In some embodiments, the gas bearings of the present disclosure consume a modest amount of pressurized gas, and as long as, for example, the feed air is filtered, and the load capacity of the bearing is not exceeded, the gas bearings may have a long operating life, even at very high reversing accelerations, while minimizing or eliminating friction losses relative to contact bearings or hydrodynamic bearings.

FIG. 24shows a perspective view of illustrative bearing housing2400, in accordance with some embodiments of the present disclosure. As illustrated, bearing housing2400is configured to extend azimuthally around a translator having a circular bearing surface. In some embodiments, bearing housing2400may include one or more azimuthal, radial, or axial pieces that may be assembled to form a complete bearing housing. As illustrated, bearing housing2400is configured to accommodate a gas bearing, and includes passages2410and flow restrictions2420. Passages2410direct and distribute flow of bearing gas within bearing housing2400to flow restrictions2420. Passages2410may include, for example, plenums, channels, manifolds, filters, drilled holes, machines recesses, flow control features, ports for sensor (e.g., to sense bearing gas pressure, flow or temperature), ports for receiving a supply of bearing gas, ports for removing condensate (e.g., condensed water, oil, or other condensed fluids), any other suitable features, or any combination thereof. Flow restrictions2420are configured to provide the bearing gas to the bearing interface (e.g., a bearing gap) at bearing bore2430. Flow restrictions2420provide bearing gas at a desired pressure and flow rate to the gas bearing, which provides lateral stiffness to off-axis motion of the translator. Flow restriction2420may include, for example, orifices, porous sections, or both, or any other suitable flow-restricting features. For example, in some embodiments, flow restrictions2420include an array of orifices along bearing bore2430. In some embodiments, flow restrictions2420includes a thickness of porous material along bearing bore2430. In some embodiments, bearing housing2400may include a coating, a consumable layer, a dry film lubricant, an abradable coating, or a combination thereof, at bearing bore2430to accommodate, for example, contact with a translator.

Although bearing housing2400is shown inFIG. 24as having a cylindrical bearing bore2430, a bearing housing may include any suitable surface for creating a bearing interface. For example, a bearing housing may include a semi-circular surface, a flat surface, a non-circular curved surface, a piecewise flat or curved surface, any other suitable continuous, piecewise, or segmented surface, or any combination thereof. For example, a bearing housing may include more than one cylindrical surfaces, separated axially, for forming respective bearing interfaces. In a further example, a LEM may include, at a particular axial region, a set of three, four, or more bearing housings having flat surfaces and forming respective bearing interfaces with corresponding flat surfaces of a translator (e.g., a translator having a triangular, rectangular, or other polygonal cross-section). In some embodiments, a bearing housing need not include passages2410or flow restrictions2420. For example, a bearing housing may be configured as a contact slide bearing, with a low-friction coating applied at bearing bore2430.

FIG. 25shows side view and axial view of a portion of an illustrative assembly including bearing housing2502, bearing mounts2503and2505, flexure2513, and flexure mounts2504and2506, in accordance with some embodiments of the present disclosure. Flexure2513is affixed to bearing mounts2503and2505, and also affixed to flexure mounts2504and2506. Flexure mounts2504and2506are affixed to bearing housing2502. Bearing mounts2503and2505may be affixed to a stator, a frame system (e.g., a frame member or bulkhead), a cylinder, any other suitable component that is substantially stationary relative to the translator, or any combination thereof. As illustrated, flexure2513is relatively stiff against lateral displacement of bearing housing2502(e.g., to maintain lateral alignment), and is relatively less stiff to pitch and yaw of bearing housing2502(e.g., to accommodate perturbations during operation, minor misalignments, or asymmetries of the translator tube). For example, the assembly ofFIG. 25may allow a translator to continue low-friction operation in the event of (e.g., thermal distortion, force-based distortion) that may cause bending of the translator or other components.

The aligning feature may include a self-aligning flexure (e.g., a ring flexure, a spherical flexure), joint (e.g., a spherical joint, a Heim joint), or both, which allows the bearing housings to self-align to the translator tube (e.g., by pitch, yaw, or other non-azimuthal rotation), thus reducing the precision of tolerances required of the components at the bearing interface. In some embodiments, the self-aligning feature is integrated into or is a part of the bearing (e.g., a spherical bearing). A flexure is particularly helpful with cylindrical gas bearings, because of their tight clearances and relative inability to apply moments. It will be understood that the present disclosure does not require that the bearing housings be mounted via self-aligning mounts, and any suitable mount may be used to couple a bearing housing to a stationary component (e.g., a stator). In some embodiments, flexure2513allows self-aligning of bearing housing2502to the translator (e.g., to counteract translator asymmetries or deformation) while keeping the electromagnetic section substantially centered in the stator (e.g., a more uniform motor air gap).

In some embodiments, bearing housings (e.g., bearing housing2502) and may be arranged such that at least a portion of a magnet section (e.g., section1613ofFIG. 16) may axially travel beyond the axial length of a stator (e.g., stator350ofFIG. 3), beyond the axial length of a hoop stack of a stator (e.g., hoop stack351ofFIG. 3), or both. For example, bearing housings may be affixed to a stator (e.g., via bearing mounts2503and2505) at a sufficient distance from the stator to allow a magnet section to axially travel beyond the stator (or hoop stack therein) such that at least a portion of the magnet section (and magnets thereof) is not electromagnetically interacting with the stator (or hoop stack therein). This type of configuration and LEM operation may be advantageous for efficiency, power, costs, manufacturing, or maintenance purposes, or any other suitable purpose, or any combination thereof. In some embodiments, the bearing housings may be arranged such that at least a portion of a magnet section (e.g., section1613ofFIG. 6) may not axially travel beyond the axial length of a stator (e.g., stator350ofFIG. 3), beyond the axial length of a hoop stack of a stator (e.g., hoop stack351ofFIG. 3), or both.

FIG. 26shows a cut-away cross-sectional view of translator2600and stator2650, in accordance with some embodiments of the present disclosure. In some embodiments, stator2650may include relief2604to accommodate rail2616during axial motion of translator2600(e.g., when rail2616is axially coincident with bearing housing2650). In some embodiments, an air gap between translator2600and stator2650need not be maintained in relief2604. In some embodiments, a stator includes one or more reliefs to accommodate corresponding features of a translator during axial motion of the translator. For example, while a portion of a stator is configured to form an air gap with a translator (e.g., having a predetermined magnetic reluctance and dimensional tolerance with magnet section2601), other portions of stator need not for an air gap with the translator.

FIG. 27shows cross-sectional view of translator2700and bearing housing2750, in accordance with some embodiments of the present disclosure. In some embodiments, bearing housing2750may include one or more reliefs2704to accommodate rail2716during axial motion of translator2700(e.g., when rail2716is axially coincident or otherwise overlapping with bearing housing2750). As shown inFIG. 27, a gas bearing arranged radially between bearing housing2750and translator2700does not extend into one or more reliefs2704. In some embodiments, a gas bearing arranged radially between bearing housing2750and translator2700does extend into one or more reliefs2704. In some embodiments, bearing housing2750are of clamshell-type construction, as illustrated, wherein two components mate together to form the complete bearing housing2750, as shown inFIG. 27. In some embodiments, a bearing housing may be constructed of a single azimuthally continuous housing (e.g., as illustrated inFIG. 24). It should be noted that for clarity and ease of illustration the drawings of the present patent application are not necessarily drawn to scale and do not reflect the actual or relative size of each feature. A bearing housing may be any suitable shape such as, for example, round, rectangular, polygonal, curved, or any other shape including a single segment or more than one segment. Although shown as cylindrical in the present disclosure, a translator “tube” may include any suitable cross-sectional shape or cross-sectional shape profile along its axial length. For example, a translator tube may include an outer surface that is a bearing surface, and the bearing surface may be flat, round, curved, segmented, or any other suitable profile at which a bearing gap may be formed to contain a gas bearing.

FIG. 28shows an end view of translator2800and additional components, in accordance with some embodiments of the present disclosure. Translator2800includes rail2816, which is at least partially rigidly affixed to a translator tube of translator2800. Bearing gaps2845and2846are arranged between rail2816and bearing housings2841and2842, respectively. Bearing gaps2845and2846are configured to be filled with a bearing gas having a pressure suitable for functioning as a gas bearing to maintain or otherwise constrain an azimuthal position of translator2800(e.g., during operation or other processes).

Bearing housings2841and2842are configured to interface to corresponding gas bearings, which in turn interface with corresponding surfaces of rail2816. In some embodiments, bearing housings2841and2842are stationary relative to translator2800. For example, bearing housings2841and2842may be rigidly or flexibly mounted to (e.g., fastened to), flexibly mounted to (e.g., mounted via a flexure to), or integrated into (e.g., be a single piece as) a stator, a bearing housing for constraining lateral motion of translator, a frame system, any other suitable stationary component, or any combination thereof. In some embodiments, bearing housings2841and2842are configured to generate corresponding gas bearings providing azimuthal stiffness to the orientation of translator2800(e.g., against azimuthal rotation of translator2800, thus providing azimuthal anti-clocking). As illustrated, feed lines2871and2872are configured to provide bearing gas to respective bearing housings2841and2842(e.g., pressurized bearing gas supplied from a compressor or gas spring at greater than 1 atm). In some embodiments, contact bearings may be included instead of, or in addition to, gas bearings. For example, any or all of bearing housings2841and2842may alternatively include a bearing surface configured to contact rail2816, or otherwise limit azimuthal rotation of rail2816, while allowing rail2816to slide in the axial direction.

Position sensor2840is configured to sense a relative or absolute position of respective rails2815and2816(e.g., and accordingly the position of other features of translator2800). In some embodiments, translator2800is a rigid assembly (e.g., with each component moving with substantially the same velocity other than vibrations, pressure-induced strain, or other small perturbations). In some embodiments, for example, position sensor2840may include an encoder read head (e.g., a magnetic or optical encoder read head), and rail2816include corresponding encoder tape2817(e.g., magnetic or optical tape). In some embodiments, position sensor2840may include an encoder read head (e.g., a magnetic or optical encoder read head), and rail2816includes one or more indexing features to indicate position. In some embodiments, position sensor2840is stationary relative to translator2800, and is thus able to sense the relative motion of the translator with respect to a stator, a cylinder, a bearing housing, any other suitable component, or any combination thereof. For example, position sensor2840may be rigidly mounted to (e.g., fastened to), flexibly mounted to (e.g., mounted via a flexure to), or integrated into (e.g., be a single piece as) a stator, a bearing housing, a structural frame system, any other suitable stationary component, or any combination thereof. Position sensor2840may include an absolute sensor, a relative sensor, an incremental sensor, any other suitable sensor type for measuring a position of translator2800, or any combination thereof.

FIG. 29shows a cross-sectional view of illustrative translator2900and stator2970, in accordance with some embodiments of the present disclosure. The cross-sectional view ofFIG. 29is taken at an axial location, showing translator tube2902, magnet assembly2903, and stator2970. Magnet assembly2903is coupled to translator tube2902(e.g., using a press fit, fastening, bonding, or any other technique to form a rigid assembly). Stator2970may include, for example, phase windings and stator teeth (e.g., iron or steel, laminated sheets). Stator2970forms motor air gap2972with magnet assembly2903of translator2900(e.g., motor air gap2972affects electromagnetic interactions of stator2970and translator2900by changing the magnetic reluctance). In some embodiments, stator2970may include an azimuthal gap2971that continues the axial length of stator2970or a portion thereof, and magnet assembly2903of translator2900may include a corresponding azimuthal gap2901that continues the axial length of magnet assembly2903or a portion thereof. The gaps in the stator (e.g., gap2971) and the magnet assembly (e.g., gap2901) may be azimuthally aligned, and during operation, act to maintain an azimuthal relative position of magnetic assembly2903and stator2970(e.g., and thus the relative position of translator2900and stator2970). Stator2970and translator2900may include any suitable number of corresponding gaps (e.g., a translator may include one or more gaps, and a stator may include one or more gaps), configured to provide anti-clocking of the translator. When corresponding gaps of the stator and translator are misaligned azimuthally, an electromagnetic force is generated causing the gaps to align. For example, in the event of azimuthal misalignment, a restoring force is generated. In some embodiments, the one or more gaps in the stator may allow for phase windings to be passed through for routing (e.g., by providing an open path for wires to be routed away from the phase windings). Although shown inFIG. 29as being approximately equal, gap2971and gap2901need not be equal in azimuthal length. For example, in some embodiments, gap2971and gap2901may have different azimuthal lengths and their corresponding centerline azimuthal positions may align. In some embodiments, anti-clocking forces between the stator and translator may be the result of larger salience due to intentional gaps in the repetition of stator laminate pole teeth and the magnet segments of the translator. The intentional gaps can be utilized to optimize for force/power density and anti-rotation force by varying the width of the gap between stator laminate pole tooth, the width of the gap between translator poles (magnets), and the thickness of the magnets. In some embodiments, stator laminate pole teeth do not include any intentional anti-clocking gaps. In some embodiments, anti-clocking forces between the stator and translator may be the result of a smaller salience in the magnetic field and reluctance profile due to the segmentation of stator laminate pole teeth and magnet array. In some embodiments, the anti-clocking stiffness may be provided by the sum or accumulation effect of all the small anti-clocking forces, each spanning the small physical gap between adjacent stator tooth.

FIG. 30shows a cross-sectional view of illustrative translator3000and stator3070, in accordance with some embodiments of the present disclosure. The cross-sectional view ofFIG. 30is taken at an axial location, showing translator tube3002, magnets3003and3013, and stator3070. Magnets3003and3013are coupled to translator tube3002(e.g., using a press fit, fastening, bonding, or any other technique to form a rigid assembly). Stator3070may include, for example, phase windings (not shown) and stator teeth3075and3076. Stator3070forms motor air gap3072with magnets3003and3013of translator3000(e.g., motor air gap3072affects electromagnetic interactions of stator3070and translator3000by changing the magnetic reluctance). In some embodiments, stator3070may include an azimuthal gap3071that continues the axial length of stator3070or a portion thereof, and translator3000may include a corresponding azimuthal gap3001between magnets3003and3013that continues the axial length of a magnet array or a portion thereof. In some embodiments, azimuthal gap3071is larger than, or equal to, azimuthal gap3001. For example, as illustrated, azimuthal gap3071is larger than azimuthal gap3001. It should be noted that for clarity and ease of illustration these drawings are not necessarily drawn to scale.

FIG. 31shows a block diagram of a LEM, which includes illustrative motor air gap3150, in accordance with some embodiments of the present disclosure. Stator3101includes stator teeth3103, windings3102, and any other suitable components (not shown), in accordance with the present disclosure. Translator3120includes an array of magnets (e.g., shown as having polarity orientation N or SinFIG. 31). Stator teeth3103and translator3120form motor air gap3150. When current is applied to windings3102(e.g., as illustrated by “X” representing current into the page, and “0” representing current out of the page), a magnetic flux is generated (e.g., as illustrated by magnetic flux3105). Motor air gap3150affects magnetic flux3105(e.g., by affecting the reluctance of the magnetic circuit). Windings3102may be wound in any suitable orientation, and optionally coupled to in any suitable configuration (e.g., in series in either winding orientation).

FIG. 32shows a block diagram of illustrative motor air gap3250, having a pole-pitch configuration, in accordance with some embodiments of the present disclosure. Stator3201includes slot pitch3210, and translator section3203includes pole pitch3220. In some embodiments, slot pitch3210and pole-pitch3220may be selected to affect electromagnetic interactions between stator3201and translator section3203. For example, in some embodiments, slot pitch3210and pole-pitch3220may be selected as unequal to reduce cogging forces. In an illustrative example, a ration of pole pitch3220to slot pitch3210may be approximately 14/15. It will be understood that a LEM may include any suitable slot pitch and pole pitch, in accordance with the present disclosure. In some embodiments, the slot pitch3201may change between hoops based on the location of the hoop within the stator stack. In some embodiments, since the velocity profile of the translator may be highest at the midpoint of the stroke, a longer slot pitch in the middle of the stator would lower the phase frequency and the concomitant core losses, which increases proportionally to the square of the frequency. Similarly, a shorter stator slot pitch at an end of the stator would increase the phase frequency, or EMF-per-turn, where the translator is moving at a slower speed, allowing a greater contribution of force/work from the end windings. Therefore, in some embodiments, the hoops located at the end sections of the stator may include a shorter stator slot pitch as compared to the stator slot pitch for hoops in the center section of the stator.

FIG. 33shows a block diagram of illustrative LEM system3300, in accordance with some embodiments of the present disclosure. LEM system3300, as illustrated, includes control system3310, power electronics3320, cooling system3321, sensors3311, stator3350, translator3360, bearing housings3330and3331, bearing gas management system3380, and bearing gas supply3390. Components of LEM system3300are coupled, as illustrated, by a gap interface, signal interface, flow interface, mechanical interface, phase lead interface, or a combination thereof. For example, translator3360is coupled to stator3350by a gap interface (e.g., a motor air gap), bearing housing3330by a gap interface (e.g., a bearing interface such as a gas bearing), and bearing housing3331by a gap interface (e.g., a bearing interface such as a gas bearing).

Control system3310is configured to interface with (e.g., provide control signals to, receive feedback from) power electronics3320to control currents in phases of stator3350(e.g., as described in the context ofFIG. 34). Power electronics3320is coupled to stator3350by a plurality of phase leads, which may include lengths of electrically conductive material, electrical terminals and terminations, connectors, sensors (e.g., current sensors), any other suitable components, or any combination thereof. Control system3310is configured to interface with (e.g., provide control signals to, receive feedback from) cooling system3321to control cooling of stator3350(e.g., to remove heat from windings, stator teeth, hoops, or a combination thereof). For example, cooling system3321may include one or more cooling jackets, plenums, manifolds, pumps, compressors, filters, sensors, any other suitable components, or any combination thereof. In a further example, cooling system3321may exchange heat and fluid with a reservoir (e.g., the environment provides cooling air and accepts heated air). In a further example, control system3310may be communicatively coupled to cooling system3321and is configured to provide a control signal to cooling system3321to cause heat removal from a plurality of windings of stator3350. Control system3310is configured to interface with (e.g., provide control signals to, receive sensor signals from) sensors3311, which may include, for example,

Bearing housings3330and3331may include any suitable number and type of bearing housing, in accordance with the present disclosure. As illustrated, bearing housings3330and3331are configured for gas bearings (e.g., using bearing gas management system3380and bearing gas supply3390), although a LEM system may include any suitable type of bearing (e.g., contact or non-contact). In some embodiments, one or more sensors is coupled to each bearing housings3330and3331, configured to sense, for example, bearing gas pressure, bearing gas temperature, bearing gas flow rate, bearing housing acceleration (e.g., an accelerometer may be affixed to a bearing housing to measure vibration), bearing housing temperature, any other suitable property or behavior, or any combination thereof.

Bearing gas management system3380is configured to control at least one aspect of respective bearing gas provided to bearing housings3330and3331. For example, bearing gas management system3380may include one or more filters, compressors, pumps, pressure regulators, valves, sensors, any other suitable components, or any combination thereof for providing bearing gas to bearing housings3330and3331. For example, control system3310is configured to interface with (e.g., provide control signals to, receive feedback from) bearing gas management system3380for controlling at least one property of the bearing gas. In a further example, control system3310is configured to interface with (e.g., provide control signals to, receive feedback from) bearing gas management system3380for controlling a stiffness of the bearing interface (e.g., to lateral displacement of translator3360) between translator3360and bearing housings3330and3331. Bearing gas supply3390may include one or more filters, compressors, pumps, pressure regulators, valves, sensors, any other suitable components, or any combination thereof for providing bearing gas to bearing gas management system3380. In some embodiments, bearing gas management system3380and bearing gas supply3390may be combined as a single system. In some embodiments, bearing gas supply3390need not be included (e.g., bearing gas management system3380may intake atmospheric air).

In some embodiments, stator3350includes a plurality of coils and an axis, translator3360is arranged to move axially along the axis, and bearing housing3330, bearing housing3331, or both are coupled to stator3350to constrain lateral motion of translator3360. For example, the coils include windings that interface with a plurality of stator teeth that define an axis (e.g., an axis of a stator bore). In some such embodiments, control system3310is configured to control axial displacement of the translator, and control lateral displacement of the translator. For example, bearing housing3330, bearing housing3331, or both, and translator3360form a bearing interface, and control system3310is configured to control a stiffness of the bearing interface against the lateral displacement of translator3360. In an illustrative example, the bearing interface may include a gas bearing interface configured for oil-less operation (e.g., without the use of liquid lubricant).

In some embodiments, bearing gas management system3380is configured to provide a pressurized gas to the bearing interface. In some such embodiments, control system3310is communicatively coupled to bearing gas management system3380and is configured to provide a control signal to bearing gas management system3380to cause the pressurized gas to be provided to the bearing interface. For example, control system3310may cause bearing gas management system3380to control a property of the pressurized gas to control the lateral stiffness to lateral displacement of the translator. To illustrate, bearing gas management system3380may provide a pressurized gas to the bearing gap by opening a valve. To further illustrate, bearing gas management system3380may provide pressurized gas by controlling a valve, a pressure regulator, or both.

In some embodiments, power electronics3320are coupled to a plurality of windings of stator3350. Control system3310is communicatively coupled to power electronics3320and is configured to provide a control signal to power electronics3320to cause electrical current to flow in at least one winding of the plurality of windings to control the axial displacement of translator3360.

In some embodiments, one or more sensors of LEM system3300include a position sensor that senses an axial position of translator3360relative to stator3350. In some such embodiments, control system3310is communicatively coupled to the sensor (e.g., of sensors3311) and is configured to cause electrical current to flow in the plurality of windings of stator3350based on the axial position of translator3360. In some embodiments, control system3310is configured to estimate an axial position of translator3360relative to stator3350and cause electrical current to flow in the plurality of windings of stator3350based on the axial position of translator3360.

In some embodiments, translator3360includes at least one rail having a rail surface (e.g., as illustrated inFIGS. 16-18andFIG. 28). System3300may optionally include at least one anti-clocking bearing housing (e.g., bearing housing3332) coupled to stator3350and configured to constrain azimuthal motion of translator3360, wherein anti-clocking bearing housing3332and the rail surface form a rail interface. For example, control system3310is configured to cause the rail interface to achieve a stiffness against azimuthal motion of the translator.

In some embodiments, bearing housing3330is arranged on a first longitudinal side of stator3350to constrain the lateral motion of translator3360at the first longitudinal side of stator3350, and bearing housing3331is arranged on a second longitudinal side of stator3350to constrain the lateral motion of translator3360at the second longitudinal side of stator3350.

In some embodiments, control system3310is configured to control a LEM by causing electric current to flow in at least one winding of a plurality of windings of a stator to apply a force on a translator along a longitudinal axis of the stator, and controlling lateral stiffness to lateral displacement of the translator arranged to move along a longitudinal axis of the stator. For example, the translator and the stator may form a motor air gap, and the lateral stiffness provided by the bearings is capable of maintaining the motor air gap in an operable range. For example, causing electric current to flow at least one winding may include providing a control signal to power electronics3320that are electrically coupled to the plurality of windings. In a further example,

In some embodiments, control system3310is configured to monitor a property of the bearing gas, bearing housing, or both, for a fault condition and, in response to an identification of the fault condition, brake the translator. For example, control system3310may brake the translator by causing power electronics3320to apply currents to phases of stator3350that cause a force on translator3360that oppose motion of translator3360(e.g., thus reducing a velocity of, or even stopping translator3360). To illustrate, control system3310may monitor a mass flowrate of bearing gas, a pressure of bearing gas, a temperature of bearing gas, a temperature of a bearing housing, a vibration of a bearing housing, a force load on a bearing housing, a translator position trajectory, or a combination thereof.

FIG. 34shows a diagram of illustrative system3400, in accordance with some embodiments of the present disclosure. System3400includes LEM3440, power electronics system3430, control system3450, and auxiliary system3470. System3400may be referred to as a LEM system. It will be understood that while shown separately inFIG. 34, LEM3440and power electronics system3430may be integrated, or otherwise combined to any suitable extent. For example, in some embodiments, LEM3440and power electronics system3430may be affixed (e.g., directly or indirectly) to one another and coupled by phase leads3435. In a further example, in some embodiments, power electronics system3430may be integrated as part of LEM3440. In a further example, LEM3440may include a stator having a plurality of phases and a translator (e.g., and other suitable components such as cylinders, bearings, plumbing, etc.), with phase leads3435that are coupled to DC bus3425by power electronics system3430.

In some embodiments, LEM3440may include one or more translators which may undergo reciprocating motion relative to corresponding one or more stators under the combined effects of gas pressures and electromagnetic forces. The translators may, but need not, include permanent magnets, which may generate a back electromotive force (emf) in phases of the respective stator. It will be understood that, as used herein and as widely understood, back emf refers to a voltage. Power electronics system3430are configured to control current in the phases of the stator of a LEM. For example, power electronics system3430may expose phase leads of phases of a stator to one or more buses of a DC bus, a neutral, a ground, or a combination thereof.

Power electronics system3430may include, for example, switches (e.g., insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistor (MOSFET)), diodes, current sensors, voltage sensors, circuitry for managing PWM signals, any other suitable components, or any suitable combination thereof. For example, power electronics system3430may include one or more H-bridges, or other motor control topology of switches for applying current to one or more phases. In some embodiments, power electronics system3430may interface with LEM3440via phase leads3435which couple to windings of the stators, and power electronics system3430may interface with a grid-tie inverter (not shown) via DC bus3425(e.g., a pair of buses, one bus at a higher voltage relative to the other bus). Bus3422and bus3424together form DC bus3425in system3400. For example, bus3422may be at nominally 800V relative to 0V of bus3424(e.g., bus322is the “high” and bus324is the “low”). Bus3422and bus3424may be at any suitable, nominal voltage (e.g., >100 VDC, >200 VDC, >400 VDC, >600 VDC, over 800 VDC), which may fluctuate in time about a mean value, in accordance with the present disclosure. Accordingly, the term “DC bus” as used herein shall refer to a pair of buses having a roughly fixed mean voltage difference, although the instantaneous voltage may fluctuate, vary, exhibit noise, or otherwise be non-constant.

FIG. 35shows a block diagram of illustrative phase control system3500, in accordance with some embodiments of the present disclosure. Phase control system3500, as shown illustratively inFIG. 35, includes phase controller3502, power electronics3504, and power supply3514. In some embodiments, each phase control system (e.g., similar to phase control system3500) controls an application of current to a single phase of a multiphase stator. Further, each phase control system may include elements of the overall electrical system distributed to each phase control system (e.g., elements of control system3450, power electronics system3430, and auxiliary systems3470ofFIG. 34). In an illustrative example, phase control system3500may be included along with other phase controllers (e.g., other similar controllers) to control phase of a plurality of phases of a stator.

In some embodiments, phase controller3502is configured to control current in one or more phases of a stator. In some embodiments, a desired or commanded current to be applied to the corresponding phase is calculated locally by phase controller3502. In some embodiments, a desired or commanded current to be applied to the one or more phases is communicated from a central controller, which determines currents to be applied on each of the phases (e.g., of the stator, and optionally other phases of other stators). For example, the desired or commanded current to be applied to the one or more phases may be determined to achieve a measured magnet or translator position, to achieve a total LEM force (e.g., summed from the electromagnetic force applied by each phase), to a achieve a translator velocity or acceleration, to achieve a desired translator position (e.g., an apex position), or any combination thereof.

In some embodiments, phase controller3502is configured to sense magnetic flux in the corresponding phase. For example, phase controller3502may sense the phase's magnetic flux and use the sensed flux as a control feedback. In some such embodiments, phase controller3502need not include a current sensor or be configured to receive input from a current sensor. Further, in some such embodiments, phase controller3502includes a current sensor with relatively reduced performance, requirements, cost, or a combination thereof.

In some embodiments, the current applied to or voltage applied across each phase is controlled locally (i.e., by an instance of phase control system3500) to any suitable degree. In some embodiments, phase controller3502may execute a local control loop on phase current. For example, a current command may be communicated over a communication link from a central controller to phase controller3502. Any suitable part of the control mechanism may also be distributed in accordance with the present disclosure. For example, a position measurement may be distributed to every phase and each phase controller3502may determine desired position and force to determine a current command, which may be applied by power electronics3504.

In some embodiments, phase controller3502is configured to provide a control signal to power electronics3504. Power electronics3504is configured to electrically couple to the phase leads of the phase, and provide the current to the phase. Accordingly, power electronics3504includes components configured for amperages and voltages relevant to the DC bus and phase leads. For example, power electronics3504may include any suitable components of power electronics system3430ofFIG. 34. Phase controller3502need not be configured to electrically manage or interact with such large currents or voltages as required by the phase leads and power electronics3504. In some embodiments, phase controller3502and power electronics3504may be combined or integrated into a single module configured to control and apply current to the phase. In some embodiments, power electronics3504may be shared among more than one phase. For example, power electronics3504may include multiple power circuits, be configured to receive multiple control signals, and be configured to apply current to more than one phase.

In some embodiments, each phase control system may estimate position of the translator relative to the stator, rather than a central algorithm estimating or measuring position. Accordingly, the central algorithm may be distributed among several phase control systems. In some embodiments, each position estimator for multiple phase control systems may be part of a distributed position estimator. The distributed position estimator may estimate position based on, for example, the sensing of phase voltage in each corresponding phase. In some such embodiments, a dedicated position sensor need not be included, thus saving the cost and reliability concerns of the position sensor.

Power supply3514is configured to power components of phase control system3500, aside from applying current to the corresponding phase. For example, power supply3514may provide power for processing functions of phase controller3502, diagnostics (e.g., for power electronics3504), any other suitable process requiring power, or any suitable combination thereof. In some embodiments, each phase control system may include a power supply (e.g., similar to power supply3514).

In some embodiments, suitable components of phase control system3500may be coupled to grid via coupling3550. For example, power electronics3504, may be coupled to coupling3550. In some embodiments, coupling3550may include cables or buses transmitting AC power (e.g., three-phase 480 VAC). In some embodiments, coupling3550may include cables or buses transmitting DC power (e.g., a DC bus), which may be coupled to a grid via a grid-tie inverter separate from phase control system3500, for example.

In some embodiments, suitable components of phase control system3500may be coupled to one or more phases of a LEM via phase leads3554. For example, power electronics3504may be coupled to phase leads3554. In some embodiments, phase leads3554may include two phase leads per phase corresponding to phase control system3500(e.g., six phase leads of three phases correspond to phase control system3500, or a full bridge topology). In some embodiments, phase leads3554may include one phase lead per phase corresponding to phase control system3500(e.g., six phase leads of six wye-connected phases correspond to phase control system800, or a half-bridge topology). In some embodiments, phase leads may be wired in a star configuration. For example, for a wye-type configuration, one phase lead from each phase may be coupled together to form a neutral (e.g., having net zero current input or output, so phase currents must sum to zero), while each phase control system applies a controlled phase voltage, and thus current, to the other lead of the corresponding phase. In some such embodiments, only some of the DC bus voltage (e.g., the difference between a bus and the neutral voltage) may be available to apply across each phase. In some embodiments, phase leads for each phase may be wired in an independent configuration. For example, a phase control system may include a full H-bridge per phase, and may be able to apply the full DC bus voltage across the phase in either direction (e.g., to cause a desired current to flow in either direction). This configuration provides a larger voltage range available to each phase as well as control independence from the other phases. For example, without a common neutral wye connection, the phase currents need not sum to zero.

In some embodiments, suitable components of phase control system3500may be coupled to communications (COMM) link3556. For example, phase controller3502, power electronics3504, power supply3514, or a combination thereof may be coupled to COMM link3556. In some embodiments, COMM link3556may include a wired communications link such as, for example, an ethernet cable, a serial cable, any other suitable wired link, or any combination thereof. In some embodiments, COMM link3556may include a wireless communications link such as, for example, a WiFi transmitter/receiver, a Bluetooth transmitter/receiver, any other suitable wireless link, or any combination thereof. COMM link3556may include any suitable communication link enabling transmission of data, messages, signals, information, or a combination thereof. In some embodiments, phase control system3500is coupled to a central control system via communications link3556. For example, in some embodiments, phase controller3502communicates with a central controller via COMM link3556.

In some embodiments, phase control system3500may be configured to extract power from the corresponding phase of the LEM. For example, in the event of a detected system failure or loss of communication, phase controller3502may attempt to extract energy from the kinetic energy of a translator by commanding current in the opposite direction of a back emf in the corresponding phase.

In some embodiments, which include a long stator and short magnet section (e.g., the phases extend spatially beyond a magnet section), some phases are unused for at least some of the magnet travel. For example, when a portion of a magnet section is not under a phase (e.g., not axially overlapping with at least some of the phase), the phase will not interact electromagnetically with the magnet section in a significant way. Unused phases may be used as inductors and phase control system3500may be configured to store energy in capacitors or perform power conversion to help regulate the DC bus voltage, bus current, bus power, or a combination thereof. Accordingly, phase control system3500, or phase controller3502thereof, may be used for other purposes besides exciting an electromagnetic force in the LEM.

In some embodiments, a LEM, or components thereof, may be tested, operated, characterized, measured, or otherwise interrogated. For example, a stator may be coupled by phase leads to power electronics, and current may be applied to phases to measure ohmic resistance, measure winding inductance, test for shorts among windings, test thermal response of the stator, test power electronics, test a control system, or a combination thereof. In a further example, a LEM may be coupled to power electronics by phase leads, coupled to a cooling system, and coupled to a bearing gas management system. The control system may cause the power electronics to apply current to the phase leads (e.g., to cause the translator to move axially and achieve a desired trajectory), cause the cooling system to provide a coolant (e.g., cooling air) to the stator, cause bearing gas to be provided to one or more bearing housings, and cause bearing gas to be provided to one or more anti-clocking bearing housings.

In an illustrative example, a LEM may be included as part of a linear generator (e.g., as illustrated inFIG. 36). The ability to test the LEM, and components thereof, without first installing, for example, in a linear generator or other system may allow easier maintenance, trouble-shooting, and characterization of the LEM, without the complexity of the additional components of the linear generator. For example, a linear generator may include two LEMs, and it is advantageous to be able to test either LEM as a stand-alone unit. In some embodiments, an external energy source provides the force to cause translator movement (e.g., including a compressor, electromagnetic source, or other suitable source). In some embodiments, a LEM may be operated as a stand-alone unit as part of a generator, pump, compressor, or actuator.

FIG. 36shows a cross-sectional view of illustrative generator assembly3600, in accordance with some embodiments of the present disclosure. Generator assembly3600is configured as an opposed, free-piston generator. Generator assembly3600includes translators3610and3620, which are configured to move along axis3606(e.g., translate linearly along axis3606). Translators3610and3620are configured to move within cylinders3602,3604and3605, thus forming expansion and compression volumes3697,3698, and3699for performing boundary work (e.g., determined using the integral ∫PdV over a suitable range such as a stroke or cycle). For clarity, the spatial arrangement of the systems and assemblies described herein will generally be referred to in the context of cylindrical coordinates, having axial, radial, and azimuthal directions. It will be understood that any suitable coordinate system may be used (e.g., cylindrical coordinates may be mapped to any suitable coordinate system), in accordance with the present disclosure. Note that axis3606is directed in the axial direction, and the radial direction is defined as being perpendicular to axis3606(e.g., directed away from axis3606). The azimuthal direction is defined as the angular direction around axis3606(e.g., orthogonal to both axis3606and the radial direction, and directed around axis3606).

In some embodiments, the stationary components of generator assembly3600include cylinder3602, cylinder3604, cylinder3605, stator3618, stator3628, bearing housing3616, bearing housing3617, bearing housing3626, and bearing housing3627. In some embodiments, bearing housings3616and3617are coupled to stator3618(e.g., either directly connected, or coupled by an intermediate component such as a flexure, mount, or both). For example, bearing housings3616and3617may be aligned to (e.g., laterally or axially aligned), and affixed to, stator3618to maintain a radial air gap between magnet assembly3613and stator3618. Similarly, in some embodiments, bearing housings3626and3627are rigidly coupled to stator3628. In a further example, in some embodiments, bearing housing3626and3627are aligned to stator3618, but affixed to another portion of a generator assembly or components thereof.

Translator3610includes tube3612, piston3611, piston3614, and magnet assembly3613, all substantially rigidly coupled to move as a substantially rigid body along axis3606, relative to the stationary components. Translator3620includes tube3622, piston3621, piston3624, and magnet assembly3623, all substantially rigidly coupled to move as a substantially rigid body along axis3606. In some embodiments, magnet assemblies3613and3623may be a region of tubes3612and3622, respectively. In some embodiments, magnet assemblies3613and3623may include separate components affixed to tubes3612and3622, respectively. Reaction section3697is bounded by pistons3611and3621, as well as bore3603of cylinder3602. Gas springs3698and3699are bounded by respective pistons3614and3624, as well as respective cylinders3604and3605. Accordingly, as translators3610and3620move along axis3606, the volumes of reaction section3697, gas spring3698, and gas spring3699expand and contract. Further, for example, pressures within those volumes decrease or increase as the volume increases or decreases, respectively. Each of bearing housings3616,3617,3626, and3627is configured to provide a gas bearing between itself and the corresponding translator (e.g., tube3612and3622). For example, each of bearing housings3616,3617,3626, and3627may be configured to direct pressurized gas to the gas bearing (e.g., via a flow system). In an illustrative example, each of bearing housings3616,3617,3626, and3627may be configured to direct pressurized gas having an absolute pressure greater than ambient pressure (e.g., 1 atm at sea level) to the gas bearing such that bearing gas has sufficient pressure to flow through the gas bearing and into the environment (e.g., directly or via other ducting). In some embodiments, bearing gas may be pressurized relative to the environment (e.g., about 1 atm), a pressure in a breathing system (e.g., a boost pressure, or a gas pressure in an exhaust system that may be greater than or less than 1 atm), or any other suitable pressure reference. In some embodiments, generator assembly3600is configured for oil-less operation (e.g., without the use of lubricating liquids or without the use of solid-to-solid contact bearings), with bearing housings3616,3617,3626, and3627forming gas bearings against translators3610and3620. Cylinder3602includes bore3603, which houses compression section3697. Cylinder3602also includes illustrative ports3619and ports3629, which couple bore3603to the outside of cylinder3602to allow fluid exchange.

Stator3618, magnet assembly3613, tube3612, and bearing housings3616and3617form linear electromagnetic machine (LEM)3656. Similarly, stator3628, magnet assembly3623, tube3622, and bearing housings3626and3628form LEM3652. Further, a LEM may optionally include one or more pistons affixed to the translator. For example, a LEM may be defined to include stator3618, translator3610, and bearing housings3616and3617. In a further example, a LEM may be defined to include stator3628, translator3620, and bearing housings3626and3627. A LEM includes a stationary assembly (e.g., a stator and bearing housings) and a translating assembly (e.g., a translator) that is constrained to move along an axis, wherein the stator is capable of applying an electromagnetic force on the translator to cause and/or effect motion along the axis. The bearing housings of a LEM may be, but need not be, affixed to the stator. For example, the bearings housings may be coupled to the stator, a structural frame, a cylinder, either directly or by one or more intervening components, or any combination thereof. Stators3618and3628may include a plurality of phase windings, which form a plurality of phases. The current in each of the phases may be controlled by a control system (e.g., which may include corresponding power electronics and processing equipment) to affect the position of translators3610and3620, motion of translators3610and3620, work interactions with translators3610and3620, or any combination thereof. In some embodiments, magnet assemblies3613and3623include permanent magnets arranged in an array (e.g., of alternating North and South poles). Because translators3610and3620move as substantially rigid assemblies, electromagnetic forces applied to respective magnet assemblies3613and3623accelerate and decelerate translators3610and3620. In some embodiments, stators3618and3628may be air-cooled (e.g., by an air cooling system), liquid-cooled (e.g., by a liquid cooling system), or both. In some embodiments, stators3618and3628are arranged around respective translators3610and3620, or respective magnet assemblies3613and3623thereof (e.g., the motor air gap is arcuate with a thickness profile). For example, stators3618and3628may extend fully around (e.g., 360 degrees azimuthally around) or partially around (e.g., having azimuthally arranged segments and azimuthally arranged gaps between windings of a phase) respective translators3610and3620. In some embodiments, stators3618and3628are arranged axially along respective translators3610and3620, or respective magnet assemblies3613and3623thereof. For example, magnet assemblies3613and3623may include flat magnet sections and stators3618and3628may include flat surfaces that correspond to the magnet sections (e.g., the motor air gap is planar with a thickness profile). In some embodiments, stators3618and3628extend axially along respective translators3610and3620, or respective magnet assemblies3613and3623thereof.

It will be understood that the present disclosure is not limited to the embodiments described herein and can be implemented in the context of any suitable system. In some suitable embodiments, the present disclosure is applicable to reciprocating engines and compressors. In some embodiments, the present disclosure is applicable to free-piston engines and compressors. In some embodiments, the present disclosure is applicable to combustion and reaction devices such as a reciprocating engine and a free-piston engine. In some embodiments, the present disclosure is applicable to non-combustion and non-reaction devices such as reciprocating compressors and free-piston compressors. In some embodiments, the present disclosure is applicable to linear reciprocating devices with driver section (e.g., gas springs). In some embodiments, the present disclosure is applicable to oil-free reciprocating and free-piston engines and compressors. In some embodiments, the present disclosure is applicable to oil-free free-piston engines with internal or external combustion or reactions. In some embodiments, the present disclosure is applicable to oil-free free-piston engines that operate with compression ignition (e.g., homogeneous charge compression ignition (HCCI), stratified charge compression ignition (SCCI), or other compression ignition), spark ignition, or both. In some embodiments, the present disclosure is applicable to oil-free free-piston engines that operate with gaseous fuels, liquid fuels, or both. In some embodiments, the present disclosure is applicable to linear free-piston engines. In some embodiments, the present disclosure is applicable to engines that can be combustion engines with internal combustion/reaction or any type of heat engine with external heat addition (e.g., from a heat source or external reaction such as combustion).