Constant force mechanisms and constant torque mechanisms

Abstract

Systems are provided for producing a constant force over a stroke length. In one embodiment, a system for producing a constant force includes a rotor including one or more first magnetic pole-pairs and a translator including one or more second magnetic pole-pairs. The translator and rotor are arranged concentrically and centered around a z-axis and the translator is configured to surround the rotor with the one or more second pole-pairs of the translator facing the one or more first pole-pairs of the rotor. The rotor is separated from the translator by an air gap. Also disclosed herein are magnetic constant torque mechanisms.

Description

Docket No. PSU24304PCTCONSTANT FORCE MECHANISMS AND CONSTANT TORQUE MECHANISMSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 701,278, entitled “TRANSVERSE-FLUX CONSTANT FORCE MECHANISM” and filed on September 30, 2024, and also to U.S. Provisional Application No. 63 / 701,326, entitled “HELICAL MAGNETIC SPRING AND CONSTANT TORQUE MECHANISM” and filed on September 30, 2024, the entire contents of all of which are hereby incorporated by reference for all purposes.GOVERNMENT SUPPORT

[0002] This invention was made with government support under contract No. DE-EE0009958 awarded by the Department of Energy. The U.S. government has certain rights in the invention.TECHNICAL FIELD

[0003] Embodiments of the subject matter disclosed herein relate to constant force mechanisms and constant torque mechanisms, and more particularly, to mechanisms utilizing magnets arranged to produce transverse flux.BACKGROUND

[0004] A constant force mechanism (CFM) creates a near constant force over a prescribed stroke length. A CFM is useful for applications where the required force needs to be independent of the displacement such as when gripping a fragile object, providing gravity compensation, vibration isolation, and when preforming medical procedures. In some examples, a CFM may be integrated into exercise equipment to provide a constant force for an athlete to push or pull against. Many CFMs use mechanical mechanisms such as springs counterweights and linkages. Pneumatic springs and hydraulic mechanisms are also used when very high balancing forces are required.

[0005] A constant torque mechanism (CTM) is a device that exerts a constant torque across a prescribed angular stroke length. CTMs are used in a wide range of specialized applications such as in aerospace, automotive, and medical rehabilitation. CTMs have also been studied for use in robotic joints and can be incorporated into gravity compensation mechanisms.SUMMARY

[0006] In one example, a system for a CFM includes a rotor including one or more first pole-pairs and a translator including one or more second pole-pairs. The translator and rotor are arranged concentrically and centered around a z-axis. The translator is configured to surround the rotor with the one or more second pole-pairs of the translator facing the one or more first pole-pairs of the rotor, and the rotor is separated from the translator by an air gap.Docket No. PSU24304PCT

[0007] It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 depicts a cross sectional view of a transverse-flux magnetic CFM including an outer translator, an air gap, and an inner rotor.

[0009] FIG. 2 depicts half of a cross sectional view of the transverse-flux magnetic CFM.

[0010] FIG. 3 depicts a perspective view of the transverse-flux magnetic CFM.

[0011] FIG. 4 plots the axial force produced by the transverse-flux magnetic CFM against the axial position of the translator.

[0012] FIG. 5 is a table that includes the parameters of the transverse-flux magnetic CFM used to generate the plot in FIG. 4.

[0013] FIG. 6A is 3-D Finite element analysis (FEA) surface field plot as a function of the air gap angle and axial position for inner rotor radial magnetic flux density.

[0014] FIG. 6B is a 3-D FEA surface field plot as a function of the air gap angle and axial position for translator axial flux density.

[0015] FIG. 7 is 3-D FEA computed axial force field components shown as a function of axial position when the rotor and translator are at three different positions.

[0016] FIG. 8 is a diagram showing magnetic flux density axial width definitions.

[0017] FIG. 9 is a cross sectional view of the transverse-flux magnetic CFM with a Halbach array of magnets.

[0018] FIG. 10 is a tabic that includes the specifications and performances for a plurality of transverse-flux magnetic CFM configurations.

[0019] FIG. 11 is a table that includes the specifications and performances for an experimental design of the transverse-flux magnetic CFM.

[0020] FIG. 12A is a plot of translator force as a function of translational position and electrical angle for a 4 pole-pair magnetic CFM design.

[0021] FIG. I2B is a plot of rotor torque as a function of translational position and electrical angle for a 4 pole-pair magnetic CFM design.

[0022] FIG. 13 A is a plot of translator force as a function of angular position for the 4 pole-pair magnetic CFM design.

[0023] FIG. 13B is a plot of rotor torque as a function of angular position for the 4 pole-pair magnetic CFM design.

[0024] FIG. 14 is an image of a prototype of the inner rotor.Docket No. PSU24304PCT

[0025] FIG. 15 is an image of a prototy pe of the outer translator.

[0026] FIG. 16 is an image of a prototy pe of the transverse-flux magnetic CFM including the prototype of die inner rotor and the prototy pe of the outer translator.

[0027] FIG. 17A is a perspective view for a first two pole magnetic constant torque mechanism (CTM).

[0028] FIG. 17B shows the magnet magnetization directions for the magnetic sections of the CTM of FIG. 10A.

[0029] FIG. 18 is a table of example design parameters for the first tw o pole magnetic CTM.

[0030] FIG. 19 is a series of plots that show the FEA calculated imier rotor radial flux density and outer rotor azimuthal magnetic flux density within the air gap at outer rotor angular positions in 90 degree increments. The multiplication of the two field components is also shown.

[0031] FIG. 20 is a plot of torque as a function of outer rotor angular position and inner rotor axial position.

[0032] FIG. 21 is a plot of axial force as a function of outer rotor angular position and inner rotor axial position.

[0033] FIG. 22A is a perspective view- for a second two pole magnetic CTM.

[0034] FIG. 22B shows the magnet magnetization directions for the magnetic sections of the CTM of FIG. 1 A.

[0035] FIG. 23 includes a plot of torque and a plot of translational force versus angular position for five different axial positions when using N-50 grade magnets.

[0036] FIG. 24 is a table of performance metrics for the second two pole magnetic CTM.

[0037] FIG. 25 includes a B-H curve for different grade magnets and a FEA computed force versus mechanical angle.

[0038] FIG. 26 is a diagram of a proof-of-principle transverse-flux magnetic CTM design.

[0039] FIG. 27 is a perspective view' for a segmented tw o pole magnetic CTM.DETAILED DESCRIPTION

[0040] The following description relates to various embodiments for a transverse-flux magnetic CFM. A CFM may have many applications, such as within precision engineering, robotics, biomedical engineering, and energy harvesting. A given CFM may be able to produce a constant force over a given range oppositions, called a stroke length. Depending on the mechanism of the CFM, the stroke length may be defined as an angular displacement, or a linear displacement. The possible applications of a CFM may be expanded if the CFM has a relatively lon stroke length. Additionally, the CFM may have more useful applications if the constant force can be adjusted e.g., the CFM can be set to produce a constant force within a range of force values.

[0041] Magnetic forces can be used to create a CFM. In one example, reluctance force between a magnet and ferromagnetic material can be used to create a constant force over a relatively long strokeDocket No. PSU24304PCT length. However, the force density for a reluctance based CFM is low, and most reluctance-based CFMs do not exceed 60 N. In another example, a positive and negative stiffness spring may be combined together to produce a CFM with a stroke length of 10 mm, which may be a relatively short stroke length. In some examples of a CFM, the constant force relies on the field being made uniform along the same direction as the motion of the CFM device. Generating a constant field in the same direction as the motion of components of the CFM device may result in a reduced stroke length and may also result in the need to use large and complicated magnet arrangements to create the uniform force.

[0042] Thus, embodiments are disclosed herein for a magnetic CFM configured to create a constant force based on a uniform transverse flux field flow. The uniform transverse flux field flow may be generated between two cylindrical shells, each shell including an alternating arrangement of magnets polarized radially inward and magnets polarized radially outward. This thereby circumvents the challenge of trying to create a uniform field along the same direction as the motion of the CFM device. The CFMs disclosed herein may be simple to build and can be scalable to any size.

[0043] FIGS. 1, 2, and 3 depict a first example of a transverse-flux magnetic CFM 100 from three different views, and are therefore described collectively. The transverse-flux magnetic CFM 100 may be cylindrical in shape with a circular top 134. a circular bottom 136 and a curved body 138. and may be oriented with respect to a cylindrical coordinate system. The cylindrical coordinate system may include a z-axis 112 extending axially through the center 116 of the cylinder, a radial axis 114 extending radially outward from the center 116, and an azimuthal angle 118. which represents the angle of a point relative to the radial axis 114. The transverse-flux magnetic CFM 100 may include a plurality of annularly shaped layers including a first layer 102, an outer translator 104 separated from an inner rotor 108 by an air gap 106, and a second layer 110 surrounding a central gap 120, and each layer may be concentrically -arranged (e.g., centered on the center 116). The central gap 120 may be a circular in shape and filled with air, or another material. The central gap has a radius rsi. The central gap 120 maybe surrounded by the second layer 110. The second layer 110 may be made of steel or another metallic material and be defined by an inner radius rstand an outer radius riL. The thickness of the second layer 110 may be referred to as tstand may be the difference between the outer radius rtiand the inner radius rsi. The second layer 110 may be coupled to the inner rotor 108. In some examples, the second layer 110 may be coupled to a brake (not shown) that fixes the inner rotor 108 and the second layer 110 in a set position and prevents them from rotating or translating.|0044| The inner rotor 108 may be defined by an inner radius ruand an outer radius rin, with a thickness defined as t;. The inner rotor 108 may be positioned in face sharing contact with the outer circumference of the second layer 110. The inner rotor 108 may be comprised of a first set of magnetic segments 122. In the example shown, the first set of magnetic segments 122 includes four pole-pairs of magnetic segments; however, other numbers of pole-pairs are possible. Each magnetic segment of the first set of magnetic segments 122 may be an arc segment of the inner rotor 108 equal in size to each ofDocket No. PSU24304PCT the other magnetic segments within the first set of magnetic segments 122, and with a thickness of tj. A pole-pair may be a set of two adjacent magnetic segments, such as a first magnetic segment 124 and a second magnetic segment 126, polarized in opposite radial directions. The first magnetic segment 124 is magnetically polarized radially towards the center 116, as indicated by an arrow within the first magnetic segment f24. The second magnetic segment 126 is magnetically polarized radially away from the center 116 as indicated by an arrow within the second magnetic segment 126. Each magnetic segment within the first set of magnetic segments 122 may have a length wtalong the z-axis.

[0045] The inner rotor 108 may be separated from the outer translator 104 by the air gap 106. The air gap 106 may have an inner radius rio, outer radius roi. and a thickness g. The air gap 106 may allow the outer translator 104 to translate freely across the inner rotor 108. The outer translator 104 may be defined by an inner radius roi. an outer radius roo, and a thickness to. The outer translator 104 may be comprised of a second set of magnetic segments 128. The second set of magnetic segments 128 may include two axial rows, with each row containing four pole-pairs of magnetic segments; however, other numbers of pole-pairs and other numbers of rows are possible. Each magnetic segment of the second set of magnetic segments 128 may be an arc segment of the outer translator 104 equal in size to each of the other magnetic segments within the second set of magnetic segments 128, and with a thickness of t0. Each magnetic segment of the second set of magnetic segments 128 may have the same central arc angle as each magnetic segment within the first set of magnetic segments 122. Similarly to the segments of the first set of magnetic segments 122, the second set of magnetic segments 128 may be made up of pole-pairs such that adjacent magnetic segments arc polarized in opposite radial directions. The second set of magnetic segments 128 may include a plurality' of pole-pairs of magnetic segments arranged into a first row 130 and a second row 132. The first row 130 and the second row 132 may have an identical shape and an identical number of pole-pairs (e.g., four pole-pairs in each row). The first row' 130 may be positioned above the second row 132 along the z-axis. Additionally, the second row 132 may be positioned such that each magnetic segment within the second row 132 of a first magnetic polarity is positioned directly below a magnetic segment within the first row 130 of a second, opposite magnetic polarity. Each magnetic segment within the second set of magnetic segments 128 may have a length along the z-axis w0. In some examples w0= whsuch that the outer translator 104 is twice as long as the inner rotor 108. This may be visualized in FIG. 3. and one magnetic pole-pair from the first row 130 and one magnetic pole-pair from the second row 132 is removed in FIG. 3 so the inner rotor 108 can be visualized.

[0046] The outer translator 104 may be coupled to the inner circumference of the first layer 102. The first layer 102 may be made of steel or another metallic material and be defined by an inner radius rooand have a thickness of tso. In some examples, the first layer 102 and the second layer 110 may be referred to as back steel or back iron because they may be made of steel or iron and provide a backing for the outer translator 104 and inner rotor 108, respectively. The first layer 102 may be coupled to theDocket No. PSU24304PCT outer translator 104. In some examples, the first layer 102 may include attachment mechanisms to couple the outer translator 104 to one or more moveable loads. In some examples, the outer translator 104 may be integrated into a track wherein the outer translator 104 is able to translate along the z-axis. There may be brakes included within the track that prevent the outer translator 104 from translating to a position that exceeds the stroke length of tire transverse-flux magnetic CFM 100.In some examples, the thickness of the inner rotor t, may be greater than the thickness of the outer translator 104 t0.

[0047] The outer translator 104 may be positioned at the azimuthal angle 118 from the inner rotor 108, which may be adjusted. In some examples, the second layer 110 may be coupled to a motor or gearbox. The motor and / or gearbox may be configured to rotate the second layer 110 about a rotational axis, which in some examples is the z-axis, and apply a brake once the second layer 110 is rotated to a desired angle. The second layer 110 is coupled to the inner rotor 108, so the inner rotor 108 may be rotated to the same position as the second layer 110. The inner rotor 108 may be fixed in a position along the z-axis; however, the outer translator 104 may be capable of translating axially along the z- axis. The outer translator 104 surrounds the inner rotor 108, so the outer translator 104 may translate across the inner rotor 108 as the outer translator 104 translates axially. The outer translator may be coupled to one or more external sources of force. When the outer translator 104 translates across the inner rotor 108 along the z-axis, an axial force (e.g. a force along the z-axis) is created between the inner rotor 108 and the outer translator 104 that is constant over an operating stroke length. The axial force on the outer translator 104 may be directed antiparallel to the displacement of the outer translator 104 along the z-axis. By rotating the inner rotor 108, the force magnitude can be adjusted, allowing for a variable constant force to be achieved. In an example where the transverse-flux magnetic CFM 100 is integrated into a piece of exercise equipment, the outer translator may be coupled to a handle for an athlete to apply force in opposition to the constant force generated between the outer translator and the inner rotor. The athlete may be able to apply a constant force to the piece of exercise equipment over the stroke length of the CFM. Applying a constant force to the exercise equipment may mimic exercises that move weights under the influence of gravity . By integrating a CFM into an exercise device, exercises that may be performed using free weights under Earth’s gravity may be performed under zero gravity conditions, such as within a space station.

[0048] The constant force created over a stroke length for a given version of the transverse-flux magnetic CFM 100 is shown in the plot 400 of FIG. 4. The translational position of the outer translator 104 relative to the inner rotor 108 is plotted along the x-axis 404 (referred to as the axial position zt). When zt= 0 mm the outer translator 104 is centered relative to the inner rotor 108 along the z-axis, and so zt= 0 mm may be called the central translational position. The axial force is plotted along the y-axis 406. The axial force may be the force the transverse-flux magnetic CFM 100 generates parallel to the z-axis 112. A line 402 shows axial force as a function of the axial position of the outer translator 104.Docket No. PSU24304PCTThe definition of the constant force region and operating range are also shown in FIG. 5. The stroke length of the device is defined asZs =Ze ~Zb

[0049] where zeand z,-> are the end and beginning points of the stroke length taken to be at the point that the force reaches 98% of the center peak force:F(.-f) = F(.-i,) = 0.98F / ,

[0050] The peak force is defined to be the force at the center of the stroke length at zt= 0 mm:

[0051] where the outer translator 104 is centered relative to the inner rotor 108. As shown in FIG. 4. the axial force is approximately constant between the position zj and the position ze. The parameters of the transverse-flux magnetic CFM 100 used to calculate the data displayed in plot 400 are shown in table 500 of FIG. 5.

[0052] The force creation within the air gap can be understood by studying the individual field terms and evaluating the product of the field. The axial force equation is given by:

[0053] where the surface integral is evaluated over an air gap cylinder located at rgand that has ±3u’oaxial length. The superscript terms R and T denote the inner rotor 108 and the outer translator 104 field terms. The subscript terms r and z denote the radial component and the axial component of the field. The radial flux density of the inner rotor 108 Bgprimarily travels transversely to the direction of axial motion and therefore the radial flux density is maintained uniform along the entire length of the inner rotor 108. Using the prototype values shown in table 500. the inner rotor radial flux density Bgis plotted in FIG. 6A and FIG. 6B shows the axial flux density Bj on the outer translator. Since the Bj is only non-zero at the intersection of the two rows of magnetic segments (e.g. the first row 130 and the second row 132), the motion relative to the inner rotor 108 results in a non-changing field product. The non-changing field product is shown in FIG. 7, in which a plot of the outer translator’s axial field and inner rotor’s radial field along the axial length at the peak electrical angle of 9e= 90° for three different translational positions zt= [0.9.18] mm is shown. The 3-D FEA computed axial force field components shown as a function of z when at (r. 0e) = (rg. 90 ) and the rotor and outer translator are positioned at (0e, zt) = (0°, 0 mm) for a first field plot 700, at (0e, zt) = (0°, 9 mm) for a second field plot 702, and at (0e, zt) = (0°, 18 mm) for a third field plot 704. The electrical and mechanical angular position 9mare defined as B = pe0m, where peis the number of pole-pairs within the rotor of CFM. Each row of the translator may include the same number of pole-pairs as the rotor, so pemay also represent theDocket No. PSU24304PCT number of pole-pairs within each row of the translator. The field product is also shown, and the product does not change in form as the outer translator 104 moves past the uniform imier radial field thereby yielding the constant force over the stroke range.

[0054] It should be noted that unlike CFMs that use axial field paths to generate constant force, the magnets used to generate the uniform field through tire transverse field path are thin and simple to design and assemble. The stroke length can be approximated from the axial and radial field lengths. For instance, FIG. 8 shows a plot 800 of the magnetic flux density as a function of axial position including the inner rotor radial flux density B and translator axial flux density B . The radial field constant region axial length, z,-. and the axial field pulse length. z0are marked in regions of overlap between the inner rotor radial flux density B and translator axial flux density Fj. As the constant force occurs when the two fields overlap, it can then be identified that the stroke length, zs, is approximately equal to z s « z i. —z o

[0055] when Wj > wo. This constraint limits the side lobes of the outer magnets’ axial flux density interacting with the imier magnet. The stroke length can be increased by increasing the axial length of the magnets or hying to reduce the pulse width z0of the outer magnet’s axial flux density’.

[0056] Different pole-pair numbers and magnet arrangements were examined to determine their effects on the torque performance. A Halbach array magnet arrangement and a radially magnetized magnet arrangement were examined. An example of a radially magnetized magnet arrangement is shown in FIGS. 1, 2 and 3. An example of a Halbach array magnet arrangement 900 is shown in FIG. 9. Similarly to the transverse-flux magnetic CFM 100, the Halbach array magnet arrangement 900 includes an inner rotor 906 surrounding an iimer gap 908 and separated from an outer translator 902 by an air gap 904. The outer translator 902 may include a first group of magnets 910 arranged in a cylindrical shell shape (arranged annularly around the air gap 904). The iimer rotor 906 may include a second group of magnets 912 in a cylindrical shell shape (e.g., arranged annularly around the inner gap 908). The first group of magnets 910 and the second group of magnets 912 may each have the same number of magnetic segments, and each magnetic segment may be an arc segment with the same arc angle. A cylindrical Halbach arrangement such as the example Halbach array magnet arrangement 900 includes pole-groups such as a first pole-group 914 arranged within a cylindrical structure such as an inner rotor 906. or an outer translator 902. The first pole-group 914 includes a first left tangentially polarized magnet 916, a first inward radially polarized magnet 918. a first right tangentially polarized magnet 920, and a first outward radially polarized magnet 922. The tangentially polarized magnets may be polarized perpendicularly to the radially polarized magnets. The polarization and order of polarized magnets within the first pole-group 914 may be repeated within all pole-groups in the inner rotor 906 and the outer translator 902. A cylindrical Halbach array such as the example Halbach array magnetDocket No. PSU24304PCT arrangement 900 is theoretically capable of producing a strong magnetic field on the interior of the cylinder, but produces virtually no magnetic field on the exterior of the cylinder. It was determined that back-iron, such as the first layer 102 and / or the second layer 110 of FIG. 1, had almost no effect on the torque for the Halbach design, so no steel was included in the Halbach array designs. The performance of CFMs made with a Halbach array magnet arrangement and radially magnetized magnet arrangements with various numbers of pole-pairs or pole-groups were evaluated. The specifications of the evaluated designs and the performance results for each design are summarized in table 1000 of FIG. 10.

[0057] Table 1000 gives the design parameters and summarizes the performance for each CFM. The table lists the number of pole-pairs as a design parameter for both CFMs made with and without a Halbach array. However, for CFMs made with a Halbach array, the pole-pair number represents the number of pole-groups included in the CFM. The Halbach array designs had higher mass energy density when including the back iron in the comparison. The smallest stroke length for the radial magnet design of zs= 34 mm was equal to the longest Halbach design stroke length. Based on this analysis, an experimental prototype was developed having the radial magnet design with pg= 4 pole-pairs. The 4 pole-pair radially magnetized design has higher peak force and is easier to build and assemble than the Halbach array arrangements.

[0058] An experimental proof-of-principle CFM design was mechanically designed using (pe, pao) = (4,2) pole-pairs, where po is the number of pole-pairs within a row of the translator and paois the number of rows within the outer translator. The inner rotor may have the same number of pole-pairs as the number of pole-pairs within each row of the translator. In this example, the inner rotor may have 4 pole-pairs. To facilitate tolerance inaccuracies and rapid prototyping, the air gap was increased to g = 2 mm. Table 1100 of FIG. 11 lists the performance metrics for the g = 1 mm and 2 mm designs. The finite element analy sis calculated force as a function of axial position at the different angular positions is shown in plot 1200 of FIG. 12A and torque as a function of axial position at the different angular positions is shown in plot 1202 of FIG. 12B. The angular positions shown are given in electrical angles, 0e. The peak force was computed to be Fp= 1371 N with a zs= 32 mm stroke length.

[0059] The axial force can be adjusted by rotating the inner rotor, which will change the field interaction between the rotor and translator, allowing the constant force magnitude to be changed between the positive and negative maximum force magnitudes. The torque required to adjust the force is zero at the central translational position, where zt= 0 mm. The change in force at five different translation positions as a function of electrical angular position is shown in plot 1300 of FIG. 13A and torque at five different translation positions as a function of electrical angular position is shown in plot 1302 of FIG. 13B. The translational positions zt= -31.9 mm and zt= 31.9 mm shown in FIG. 13A and FIG. 13B correspond to the zero force and peak torque translational positions. In the constant force region, between -16 mm and 16 mm translational position, the force can be seen to vary sinusoidally with angle. The angle can be used to select a desired force value and is simply a co-sinusoidal function:Docket No. PSU24304PCTThe torque requirements to adjust the rotor to the necessary angle is shown in FIG. 13B. The torque is sizable and therefore a gearbox with a brake can be used to adjust and hold the required force value.

[0060] An experimental prototy pe was mechanically designed and fabricated. FIGS. 14-16 show the experimental prototype. FIG. 14 is an image of an inner rotor 1400, FIG. 15 is an image of an outer translator 1500, and FIG. 16 is an image of the prototype including the inner rotor 1400, outer translator 1500, and a mounting apparatus 1600. The iimer rotor 1400 may be designed similarly to the inner rotor 108 of FIGS. 1, 2 and 3. The inner rotor 1400 may include a row of radially oriented pole-pairs. Each pole-pair may include a magnet polarized in a first radial direction adjacent to a magnet polarized in a second radial direction that is antiparallel to the first radial direction. In the experimental prototy pe each magnet may be comprised of four magnetic segments polarized in the same direction and arranged to form the shape of a single, larger magnet. Four magnetic segments may be used to form a larger magnet to form a prototype of sufficient size. For example, the inner rotor 1400 includes a first magnetic pole 1402 comprised of a first magnet 1404, a second magnet 1406, a third magnet 1408, and a fourth magnet 1410. The first magnet 1404, the second magnet 1406, the third magnet 1408. and the fourth magnet 1410 may all be magnetically polarized in a first radial direction, and may functionally form a first magnetic segment similar to the first magnetic segment 124. A second magnetic pole 1412 and a third magnetic pole 1414 may be positioned adjacent to the first magnetic pole 1402 and may each be made of four magnets polarized in a second radial direction antiparallel to the first radial direction (and may functionally form a second magnetic segment similar to the second magnetic segment 126 and a third magnetic segment). The inner rotor 1400 may7be coupled to a second layer 1416 similar to the second layer 110 of FIGS. 1, 2 and 3. The second layer 1416 may be steel and the magnetic poles may be coupled to the second layer 1416. The second layer 1416 may' further be coupled to a first rotor shaft 1418 and a second rotor shaft 1422. which both extend along the z-axis 112. The first rotor shaft 1418 may include a circular face 1420 configured to couple to a circular face of the inner rotor 1400, which may be similar to the annular portion of the imrer rotor 108 and the second layer 110 that form a portion of the circular top 134 shown in the perspective view of the CFM shown in FIG. 3. There may be a similar circular face to circular face 1420 coupled to the second rotor shaft 1422. In some examples, the rotor shafts may be made of steel or another metallic material.

[0061] FIG. 15 is an image of the outer translator 1500. The outer translator 1500 may include a layer of magnets 1504 coupled to a first layer 1502, similar to the first layer 102 shown in FIGS. 1, 2, and 3. The first layer 1502 may surround the layer of magnets 1504. and the layer of magnets 1504 may surround a circular central aperture 1506 sized such that the inner rotor 1400 may extend through the circular central aperture 1506 with an allowance for an air gap such as the air gap 106 described with respect to FIGS. 1. 2, and 3. The layer of magnets 1504 may include a first row of magnets 1508 similarDocket No. PSU24304PCT to the first row 130 described with respect to FIGS. 1, 2, and 3 and a second row of magnets 1510 similar to the second row 132 described with respect to FIGS. 1, 2, and 3. The first row of magnets 1508 may be positioned above the second row of magnets 1510. Each row of magnets may be comprised of the same number of pole-pairs, and similarly to the inner rotor 1400, each pole-pair may include four magnets polarized in a first radial direction and four magnets polarized antiparallel to the first direction to form a prototype of sufficient size.

[0062] The first layer 1502 may include an annular top face 1530 that includes a plurality of attachment points and a plurality of apertures, including a first attachment point 1512, a second attachment point 1514. a third attachment point 1516, and a fourth attachment point 1518. as well as a first aperture 1520, a second aperture 1522, a third aperture 1524, and a fourth aperture 1526. The attachment points may each be identical to the first attachment point 1512. The first attachment point 1512 may include a central aperture 1528 set into the annular top face 1530 of the outer translator 1500, a first raised aperture 1532, and a second raised aperture 1534. The first raised aperture 1532 and the second raised aperture 1534 may be positioned on either side of the central aperture 1528 and include a raised body with a central aperture. Each of the first aperture 1520. the second aperture 1522, the third aperture 1524, and the fourth aperture 1526 may be set into the annular top face 1530. There may be similar structures to the first attachment point 1512. the second attachment point 1514, the third attachment point 1516. the fourth attachment point 1518, the first aperture 1520, the second aperture 1522, the third aperture 1524 and the fourth aperture 1526 on a bottom circular face 1536 of the outer translator 1500.

[0063] The inner rotor 1400 may be set within the circular central aperture 1506 of the outer translator 1500 and mounted within a mounting apparatus 1600, as shown in FIG. 16. The mounting apparatus 1600 may include a first mounting block 1602 and a second mounting block 1604. The first mounting block 1602 may include one or more apertures through which rods can extend. In some examples, a first set of rods 1606 may be anchored to a square plate 1608. The first set of rods may be locked in place relative to the square plate 1608. The first set of rods may extend from the square plate 1608, through apertures in the first mounting block 1602, and may be rigidly coupled to the outer translator 1500. Each rod within the first set of rods may be coupled to the outer translator 1500 via one of the first aperture 1520, the second aperture 1522, the third aperture 1524, and the fourth aperture 1526. In this way, if the position of the square plate 1608 is adjusted, the position of the outer translator 1500 is adjusted by the same amount. In some examples, there may be a second set of rods 1610. Each rod within the second set of rods 1610 may be coupled to the first mounting block 1602 by a mounting device such as a mounting device 1612. Each rod within the second set of rods 1610 may extend through the outer translator 1500 through one of the first attachment point 1512. the second attachment point 1514. the third attachment point 1516, the fourth attachment point 1518. The second set of rods 1610 may extend out of the bottom circular face 1536 of the outer translator 1500 and be rigidly coupled to the second mounting block 1604.Docket No. PSU24304PCT

[0064] The first mounting block 1602 may include an aperture through which the first rotor shaft 1418 can extend and rotate. The second mounting block 1604 may include an aperture through which die second rotor shaft 1422 can extend and rotate. The second rotor shaft 1422 may extend out of the second mounting block 1604 and include an attachment point 1614. In some examples the attachment point 1614 may be coupled to a motor, which may produce a torque capable of changing the angle that the inner rotor 1400 is positioned at relative to the outer translator 1500.

[0065] The first mounting block 1602 and the second mounting block 1604 may couple the outer translator 1500 and the inner rotor 1400 to a test stand, which is not shown. The test stand may include a mechanism, such as a linear bar screw or linear actuator, that may be configured to change the position of the outer translator 1500 relative to the inner rotor 1400. The mounting apparatus 1600 is one example apparatus for mounting the inner rotor 1400 and outer translator 1500; however, other configurations are possible that allow for the controlled rotation of the inner rotor 1400 and allow the outer translator 1500 to translate relative to the inner rotor 1400.

[0066] Therefore, according to the embodiments within, a CFM may be constructed out of magnets that produce magnetic flux transverse to the direction of the constant force generated by the CFM. The CFM may include a cylindrical / annular inner rotor surrounded by a cylindrical / annular outer translator. The inner rotor may be separated from the outer translator by an air gap. The inner rotor may be coupled to a rotor or gearbox that may rotate the inner rotor and brake the rotor in position in response to commands from a computer or operator. The outer translator may be configured to move parallel to the length of the inner rotor (e.g. parallel to the z-axis). The inner rotor may include a number of adjacent pole-pairs arranged to face the interior of the outer translator. The outer translator may include two rows of pole-pairs arranged such that the rows are stacked along the z-axis. Each row of the outer translator may include a number of adjacent pole-pairs arranged to face the pole-pairs of the inner rotor. The polepairs may be comprised of adjacent magnetic segments with each magnetic segment having a radial magnetic polarity antiparallcl to the magnetic polarity of adjacent magnetic segments. In other examples, the inner rotor and both rows of the outer translator may include magnetic segments arranged in a Halbach pattern formed out of pole-groups of four magnets with alternating radial and transverse polarities. Each row of the outer translator may have a particular height, which in some examples may be equal to the height of the inner rotor. The pole-pairs within the rows of the outer translator may be arranged such that magnets of antiparallel polarities are arranged adjacently vertically. For example, a magnet with a radially inward magnetic polarity may be arranged above a magnet with a radially outward magnetic polarity. In some examples, there may be a steel or iron layer on the internal surface of the inner rotor, and a steel or iron layer on the external surface of the outer translator.

[0067] The above-described arrangement of magnets may produce a magnetic field where the radial flux density due to the inner rotor is primarily transverse to the direction of axial motion of the translator (e.g. the z-direction) and uniform along the length of the inner rotor. The arrangement of magnets described above may also produce a magnetic field where the axial flux density produced byDocket No. PSU24304PCT die translator is only non-zero where the outer translator is aligned with the inner rotor. The field product between the radial flux density due to the inner rotor and the axial flux density due to the translator may dierefore be non-changing as the outer translator translates across the inner rotor over a stroke length. The non-changing field product results in a constant axial force over the stroke length. The angular position of the inner rotor relative to the outer translator influences the magnitude of the axial force, and therefore the magnitude of the constant force may be adjusted by changing the angle between the inner rotor and the outer translator. In some examples, the inner rotor may be coupled to a motor or gearbox to adjust the angle between the inner rotor and outer translator and a brake may be applied to maintain the angle.

[0068] A perspective view of a first constant torque mechanism (CTM) design 1700 is shown in FIG. 17A, and a cross sectional view of the first CTM design 1700 is shown in FIG. 17B. The first CTM design 1700 may include an outer rotor 1702 and an inner rotor 1704. The outer rotor 1702 may be a cylindrical shell that surrounds the inner rotor 1704. which is also a cylindrical shell. The inner rotor 1704 may be separated from the outer rotor 1702 by an air gap 1706. The first CTM design 1700 may be described with respect to cylindrical coordinates including a z-axis over which the inner rotor 1704 and the outer rotor 1702 are centered, a radial axis that extends from the z-axis to a radial position on the first CTM design 1700 and an azimuthal angle used to define the angular position of a point in cylindrical coordinates. In one example, the azimuthal angle may be used to define an angle between the outer rotor 1702 and the inner rotor 1704. In the example shown in FIG. 17A. the angle between the outer rotor 1702 and the inner rotor 1704 is 90°. The inner shell may have an inner radius r;iand an outer radius rl0. The outer rotor 1702 may have an iimer radius roiand an outer radius r00. The air gap may have a thickness of roi— rio.

[0069] The outer rotor 1702 may be configured to translate and rotate with respect to the inner rotor 1704. The inner rotor 1704 may be unable to translate, but may be configured to rotate. The inner rotor 1704 and the outer rotor 1702 may include one or more semicircular magnetic segments. Each magnetic segment may be a magnetic segment with a first magnetic polarity and shaped like half of an annular slice of the inner rotor or outer rotor. Each semicircular magnetic segment of the iimer rotor 1704 and the outer rotor 1702 may be planar. Each magnetic segment may be in face sharing contact with another magnetic segment of an opposite magnetic polarity to fonn an annular segment of the inner rotor 1704 or outer rotor 1702. The outer rotor 1702 may include a first outer magnetic segment 1708 of a first polarity in face sharing contact with a second outer magnetic segment 1710 of a second polarity, a third outer magnetic segment 1712 of a third polarity in face sharing contact with a fourth outer magnetic segment 1714 of a fourth polarity, and a fifth outer magnetic segment 1716 of the second polarity in face sharing contact with a sixth outer magnetic segment 1718 of the first polarity. The magnetic segments of the outer rotor 1702 may be arranged into a lower layer 1732 and an upper layer 1734, each layer comprising a series of magnetic segments adjacent to each other along the z-axis and whose magnetic polarities form a Halbach pattern. The upper layer 1734 may include the first outerDocket No. PSU24304PCT magnetic segment 1708, the third outer magnetic segment 1712, and the fifth outer magnetic segment 1716. The lower layer 1732 may include the second outer magnetic segment 1710, the fourth outer magnetic segment 1714, and the sixth outer magnetic segment 1718. The imrer rotor 1704 may be constructed of magnetic segments similar to the magnetic segments that comprise the outer rotor 1702. The magnetic segments that comprise the inner rotor 1704 may be arranged in a Halbach pattern similar to the Halbach pattern of the outer rotor 1702.

[0070] In FIG. 17B, the magnetic segments that comprise the imrer rotor 1704 and the outer rotor 1702 are shown in a block diagram 1736. The block diagram 1736 is a cross sectional view of the first CTM design 1700. if the angle between the inner rotor 1704 and the outer rotor 1702 were zero degrees. The direction of the magnetic polarity of each magnetic segment is shown by arrows contained within each magnetic segment. In FIG. 17B. the first polarity is an inward radial polarity, the second polarity is an outward radial polarity, the third polarity is in the -z direction, and the fourth polarity is in the +z direction. Each magnetic segment is shown to have a width w, which is consistent between the segments that make up the inner rotor 1704 and the segments that make up the outer rotor 1702. The segments that make up the outer rotor 1702 have a thickness toand the segments that make up the inner rotor 1704 have a thickness t,. The outer rotor 1702 may be translated a distance z, along the z-axis relative to the inner rotor 1704, which as shown in the block diagram 1736 may be z,=w. The block diagram 1736 shows the segments that make up the inner rotor 1704. The inner rotor 1704 may include a first inner magnetic segment 1726 of the first polarity in face sharing contact with a second inner magnetic segment 1730 of the second polarity, a third inner magnetic segment 1724 of the fourth polarity in face sharing contact with a fourth inner magnetic segment 1728 of the third polarity, and a fifth inner magnetic segment 1722 of the second polarity in face sharing contact with a sixth inner magnetic segment 1720 of the first polarity.

[0071] When z,=0, the inner rotor 1704 and the outer rotor 1702 may be arranged in such a way that magnetic segments with radial polarities are adjacent along the radial axis, while magnetic segments with axial polarities are adjacent along the radial axis to magnetic segments with antiparallel polarities. For example, if z,=0, the first outer magnetic segment 1708 of the first polarity is radially adjacent to the first inner magnetic segment 1726 of the first polarity and the fifth outer magnetic segment 1716 of the second polarity is radially adjacent to the fifth inner magnetic segment 1722 of a second polarity, but the third outer magnetic segment 1712 of the third polarity is adjacent to the third inner magnetic segment 1724 of the fourth polarity.

[0072] The Halbach array magnets are arranged to create pa= 2 poles along the axial length. Also, the magnet vector directions only change at 180°, thereby creating pe = 2 poles along the azimuthal direction.

[0073] The torque in the air gap can be computed by evaluating the Maxwell’s stress tensor such thatDocket No. PSU24304PCT

[0075] where L = the axial stack length of the CTM. The axial length in the second integral is 3L with the assumption that at this axial distance the field is minimal (assumed zero). The magnetic fields primarily circulate axially (transversely) and therefore the rotors create a highly uniform axial flux density Bz and radial flux density Br along the majority of the azimuth length. For example, using the geometric values shown in Table 1800 of FIG. 18, a 3-D finite element analysis (FEA) computed plot of the inner rotor radial flux density Br' as well as the outer rotor azimuthal flux density B is shown in plot 1902 of FIG. 19 at the 9O= 0° angular position. The superscripts denote inner and outer rotor field components. Plot 1902 is an illustration of the FEA calculated inner rotor radial flux density' B± and outer rotor azimuthal magnetic flux density B% within the airgap when the outer rotor angular position is 90= 0°. The multiplication of the two field components is also shown. Plot 1904, plot 1906, and plot 1908 show the flux density field interactions at outer rotor mechanical angles 9O= 90°, 0O= 180° and 0O= 270° respectively. This CTM analysis used NdFeB N-50 magnet grade. The change in torque is caused by the changes in the spatial field interactions, as a function of position. FIG. 19 shows the position change of the outer rotor field relative to the fixed inner rotor field at 900increments. The multiplication of the two spatially distributed fields is also shown. As the inner rotor radial field is constant across almost 180 ° the outer rotor’s azimuthal field interaction with the imier radial field will remain unchanging, therefore creating a remarkably uniform torque - creating quasi-zero stiffness.

[0076] The resulting torque as a function of outer rotor mechanical angle 9Oand inner rotor axial position zi is illustrated in FIG. 20. The torque is uniform for a span of 130°. FIG. 21 shows that if the rotors are not axially centered the axial force can be very high, such as 14 N. However, if the CTM is located at either 9O= ±90°, the force required to adjust the torque magnitude will be zero. This is because at this position the force producing Bz axial field components spatially cancels out, as shown in FIG. 21. A mechanical brake will be needed to hold the CTM at new axial positions.

[0077] Due to the torque producing field components flowing transverse to the direction of motion, this type of magnetic CTM has been termed a transverse-flux CTM. It should also be noted that a Halbach array along the axial length was selected as it was shown to create a higher torque density than when only using radially magnetized magnets.

[0078] To increase the torque, without increasing the outer radius, the number of pole-pairs along the axial length can be increased for a second CTM design 2200 shown in FIGS. 22A and 22B. A / )„ = 3 pole design using r = 40 mm is shown in FIGS. 22A and FIG. 22B. The second CTM design 2200 isDocket No. PSU24304PCT shown in a perspective view in FIG. 22A and in a cross sectional view in FIG. 22B. The inner rotor contains 4-poles as this allows the torque to be fully reversed in magnitude via the axial positioning of the inner rotor. The specifications of the second CTM design may be organized in the table 2400 of FIG. 24.

[0079] The second CTM design 2200 may include an outer rotor 2202 and an iimer rotor 2204, similar to the outer rotor 1702 and the iimer rotor 1704 in FIGS. 17A and 17B but with additional magnetic segments. For example, the outer rotor 2202 may include 10 magnetic segments and the inner rotor 2204 may include 14 magnetic segments. The magnetic segments that make up the outer rotor 2202 and the inner rotor 2204 may be identical in shape to the magnetic segments that make up the outer rotor 1702 and the inner rotor 1704. The inner rotor 2204 may surround an inner layer 2206, which may be a cylindrical shell positioned within the inner rotor 2204. The inner layer 2206 may be equal to the inner rotor 2204 in length and may be made of a metallic material such as iron or steel.

[0080] The inner rotor 2204 may include two more magnetic segments than the outer rotor 2202. The magnetic segments of the inner rotor 2204 may be arranged in a Halbach pattern similar to the magnetic segments described with respect to FIGS. 10A and 17B. The magnetic segments of the inner rotor 2204 and the outer rotor 2202 may be arranged in a Halbach pattern. In FIGS. 22A and 22B, the polarities of the magnetic segments are indicated similarly as in FIGS. 17A and 17B, e.g., the first polarity (an inward radial polarity) in red. the second polarity (an outward radial polarity) in blue, the third polarity (in the -z direction) in light green, and the fourth polarity7(in the +z direction) in dark green. The outer rotor 2202 and the inner rotor 2204 may each be comprised of a plurality of interdigitated magnets, each magnet comprising two or more discontinuous magnetic segments of the same polarity. The outer rotor 2202 may be comprised of a first magnet of the first polarity7(e.g., the red segments in FIG. 22A), a second magnet of the second polarity (e.g., the blue segments, a third magnet of the third polarity' (e.g., the light green segments, and a fourth magnet of the fourth polarity (e.g., the dark green segments). Each of the first and second magnets may comprise three magnetic segments while each of the third and fourth magnets may comprise two magnetic segments. The end segments may be of the first and second polarity and not of the third or fourth polarity. The inner rotor 2204 may be comprised of a first magnet of the first polarity (e.g., the red segments), a second magnet of the second polarity (e.g., the blue segments, a third magnet of the third polarity (e.g., the light green segments, and a fourth magnet of the fourth polarity' (e.g., the dark green segments). Each of the first and second magnets of the inner rotor may comprise four magnetic segments while each of the third and fourth magnets of the inner rotor may comprise three magnetic segments. The end segments may be of the first and second polarity and not of the third or fourth polarity.

[0081] Plot 2300 of FIG. 23 shows the torque versus angular position for the CTM of FIGS. 22A and 22B at five axial positions and plot 2302 of FIG. 23 shows the force versus angular position for the CTM of FIGS. 22A and 22B at five axial positions. The axial field fringing causes the peak torque andDocket No. PSU24304PCT zero force to be at z, = 19.75 mm and not z, = 20mm. When using the N-50 grade Nd-Fe-B magnets is computed to be Tp= 285.6 Nm, table 1700 of FIG. 17 summarizes the performance metrics.

[0082] Plot 2302 of FIG. 23 shows that when the axial position is shifted off-center (at z, = ±10 mm) the force is no longer zero at 0o= 90°. This will make adjusting the torque more difficult. To understand tire reason for this off-center phase shift, consider the B-H curves for other selected magnet grades as shown in plot 2500 of FIG. 25. The N-50 grade magnet has the smallest linear region (and lower coercivity), this makes the N-50 grade magnet more prone to entering the non-linear operating region. To confirm this plot 2502 of FIG. 25 shows the torque versus angle plots for the selected magnet grades when at z,=10 mm. The N48M grade magnet greatly increases the symmetry, shifting the 0 N angle crossing from 84° to 89°. This magnet grade was therefore selected for prototype construction.

[0083] To construct the magnetic CTM the magnetic segments themselves may be segmented. FIG. 27 shows a 16 segment per pole-pair CTM 2700. The 16 segment per pole-pair CTM 2700 may be identical to the second CTM design 2200. but each magnetic segment is constructed out of 8 individual magnetic pieces (e.g., individual magnets). For example, the 16 segment per pole-pair CTM 2700 may include an outer rotor 2702 and an inner rotor 2706 each comprised of a plurality of magnetic segments of various polarities, as described above with respect to FIGS. 22A and 22B. Each magnetic segment, such as a first magnetic segment 2704 of the outer rotor 2702, may be comprised of a plurality (e.g., eight) of individual magnetic pieces. Each magnetic piece was parallel magnetized in the radial direction. The non-ideal magnetization affected the torque by introducing torque ripple. The peak-to- peak torque ripple for the 16 segment design was computed to be 5.9%.

[0084] There may be many methods that could be used to further reduce this torque ripple such as skewing the rotors by angular offsetting the axially positioned magnets.

[0085] A CTM prototype is illustrated in FIG. 26. FIG. 26 shows the second CTM design 2200 integrated into a rotor assembly 2600. The rotor assembly 2600 may include a cylindrical chamber 2604 that houses the second CTM design 2200. The cylindrical chamber 2604 may be integrated into the rotor assembly 2600 in such a way that the cylindrical chamber 2604 can be positioned in place and mounted in a variety of technical applications. For example, the rotor assembly 2600 may be bolted in place within a WEC. The inner rotor 2204 may surround a rotor shaft 2602. The rotor shaft 2602 may extend through tire center of the inner rotor 2204 and extend out of the cylindrical chamber 2604. The external portion of the rotor shaft 2602 may couple to external loads. In one example, the rotor shaft may be coupled to a cable in such a way that the second CTM design 2200 can provide constant torque to the cable to place the cable under pretension. The torque output to the rotor shaft 2602 is adjustable through the translation of the inner rotor 2204 relative to the outer rotor 2202. In one example, the outer rotor 2202 is axially fixed in place but free to rotate while the inner rotor is coupled to one or more actuators that control the translational and rotational position of the inner rotor. Constant torque is created through the rotation of the outer rotor 2202. In some examples, the outer rotor 2202 may rotate at 40 rpm and therefore the losses associated with the magnets creating eddy currents are minuscule.Docket No. PSU24304PCTThe amount of thermal energy generated by miniscule eddy currents may not result in impediments to die function of the rotor assembly 2600. It is to be appreciated that the 16 segment per pole-pair CTM 2000 of FIG. 20 could be incorporated into a CTM prototype similar to that of FIG. 26, such that the magnetic segments may be comprised of individual magnetic pieces, which may provide for easier manufacturing, for example.

[0086] The magnetic CTMs disclosed herein can utilize a transverse flux magnet arrangement to create a highly constant torque over a 130° stroke length. Unlike limited-angle torque motors, the magnetic CTM does not need power to provide the constant torque. And unlike mechanical based CTMs, the torque value can be fully adjustable. The force required to adjust the torque is zero at the CTM center point. When off center, the axial forces are very high. A proto-type magnetic CTM (e.g., of FIG. 19 but using segmented magnetic segments) has a calculated peak torque of 284 Nm. If this peak torque was applied on a wave energy converter’s winch drum with a 0.1m radius, this would provide 2.840N of holding force (or 289kg mass support).

[0087] The figures show various example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above / below one another, at opposite sides to one another, or to the left / right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of die component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top / bottom, uppcr / lowcr, abovc / bclow, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example.

[0088] The disclosure also provides support for a system for a constant force mechanism comprising: a rotor including one or more first pole-pairs, a translator including one or more second pole-pairs, wherein the translator and rotor are arranged concentrically and centered around a z-axis. the translator is configured to surround the rotor with the one or more second pole-pairs of the translatorDocket No. PSU24304PCT facing the one or more first pole-pairs of the rotor, and wherein the rotor is separated from the translator by an air gap. In a first example of the system, each pole-pair comprises a pair of adjacent magnets with a first magnet having a first radial magnetic polarization and a second magnet having a second radial magnetic polarization that is antiparallel to the first radial magnetic polarization. In a second example of the system, optionally including the first example, the rotor is a cylindrical shell, and wherein the one or more first pole-pairs comprise an outer circumference of the rotor and a second layer coupled to the first pole-pairs comprises an inner circumference of the rotor. In a third example of the system, optionally including one or both of the first and second examples, the cylindrical shell includes an annular top. an annular bottom, and a curved body and is configured to rotate along a rotational axis that is the same as the z-axis that extends perpendicularly through a center of the annular top and the annular bottom. In a fourth example of the system, optionally including one or more or each of the first through third examples, the second layer is made of steel or iron. In a fifth example of the system, optionally including one or more or each of the first through fourth examples, the translator is a cylindrical shell wherein one or more second pole-pairs comprise an inner circumference of the translator and a first layer coupled to the second pole-pairs comprises an outer circumference of the translator. In a sixth example of the system, optionally including one or more or each of the first through fifth examples, the cylindrical shell includes an annular top, an annular bottom, and a curved body and is configured to translate axially along the z-axis that extends perpendicularly through a center of the annular top and the annular bottom. In a seventh example of the system, optionally including one or more or each of the first through sixth examples, the first layer is made of steel or iron. In an eighth example of the system, optionally including one or more or each of the first through seventh examples, the translator includes two rows of second pole-pairs, where each row of second pole-pairs constitutes a circumference of the translator and the two rows are arranged in a stack along the z-axis. In a ninth example of the system, optionally including one or more or each of the first through eighth examples, die two rows arc arranged such that magnets within the second pole-pairs with the first radial magnetic polarization are not adjacent to magnets with radial magnetic polarization along the z-axis and that magnets with the second radial magnetic polarization are not adjacent to magnets with the second radial magnetic polarization along the z-axis. In a tenth example of the system, optionally including one or more or each of the first through ninth examples, the rotor includes an equal number of first pole-pairs to a number of second pole-pairs within each row of the translator. In an eleventh example of the system, optionally including one or more or each of the first through tenth examples, the second pole-pairs of the translator and the first pole-pairs of the rotor each have an equal height along the z-axis. In a twelfth example of the system, optionally including one or more or each of the first through eleventh examples, a constant force is produced between the rotor and translator and the constant force is independent of a position of the translator along the z-axis within a stroke length. In a thirteenth example of the system, optionally including one or more or each of the first through twelfth examples, a magnitude of the constant force is adjusted by changing an angle between the rotor and the translator. In a fourteenthDocket No. PSU24304PCT example of the system, optionally including one or more or each of the first through thirteenth examples, die rotor is coupled to a motor and / or gearbox to rotate the rotor and change an angle between the rotor and the translator.

[0089] The disclosure also provides support for a constant force mechanism (CFM), comprising: a rotor comprising a first plurality of magnetic segments aimularly arranged around an outer circumference of the rotor, the first plurality of magnetic segments positioned to form a first plurality of pole-pairs, each pole-pair comprising a pair of adjacent magnet segments with antiparallel radial magnetic polarizations, and a translator surrounding the rotor and comprising a second plurality of magnetic segments annularly arranged around an inner circumference of the translator, the second plurality of magnetic segments positioned to form two rows of a second plurality of pole-pairs, the translator configured to translate axially along a rotational axis of the rotor. In a first example of the CFM. the rotor is separated from the translator by an air gap. In a second example of the CFM, optionally including the first example, the first plurality of pole-pairs includes a same number of polepairs as the second plurality of pole-pairs. In a third example of the CFM, optionally including one or both of the first and second examples, the first plurality of magnetic segments is mounted on a first layer of backing material and the second plurality of magnetic segments is mounted on a second layer of backing material.

[0090] The disclosure also provides support for a constant torque mechanism (CTM), comprising: an inner rotor including one or more first magnetic segments, an outer rotor including one or more second magnetic segments, wherein the outer rotor is a first cylindrical shell of a first radius and the inner rotor is a second cylindrical shell of a second radius, and the outer rotor and the inner rotor are arranged concentrically and centered around a central axis and wherein each of the first magnetic segments and each of the second magnetic segments comprise a flat semicircle of a first radius and a flat semicircle of a second radius, respectively, and wherein a polarity of the outer rotor changes every 180° of the outer rotor and a polarity of the inner rotor changes every 180° of the inner rotor, and the outer rotor includes at least three pole-pairs along an axial length of the outer rotor, parallel to the central axis, and the inner rotor includes at least three pole-pairs along an axial length of the inner rotor, parallel to the central axis. In a first example of the CTM, the one or more first magnetic segments include a first set of magnetic segments with a first magnetic polarity, a second set of magnetic segments with a second magnetic polarity, a third set of magnetic segments with a third magnetic polarity, and a fourth set of magnetic segments with a fourth magnetic polarity, and wherein the first magnetic polarity is radially inward, the second magnetic polarity is radially outward, the third magnetic polarity is in a first axial direction and the fourth magnetic polarity is antiparallel to the third magnetic polarity. In a second example of the CTM, optionally including the first example, a first magnetic segment of the first set of magnetic segments is coupled in face sharing contact to a second magnetic segment of the second set of magnetic segments to form a first annular segment, a third magnetic segment of the third set of magnetic segments is coupled in face sharing contact with a fourth magnetic segment of the fourth setDocket No. PSU24304PCT of magnetic segments to form a second annular segment, and a fifth magnetic segment of the first set of magnetic segments is coupled in face sharing contact with a sixth magnetic segment of the second set of magnetic segments to form a third annular segment. In a third example of the CTM, optionally including one or both of the first and second examples, the first annular segment is adjacent to the second annular segment along the central axis and the third annular segment is adjacent to tire second annular segment along the central axis. In a fourth example of the CTM, optionally including one or more or each of the first through third examples, the one or more first magnetic segments and the one or more second magnetic segments are each arranged into a respective Halbach array. In a fifth example of the CTM, optionally including one or more or each of the first through fourth examples, a width of each of the one or more first magnetic segments is equal to a width of each of the one or more second magnetic segments. In a sixth example of the CTM, optionally including one or more or each of the first through fifth examples, the inner rotor is configured to rotate and translate relative to the outer rotor, which is also configured to rotate. In a seventh example of the CTM, optionally including one or more or each of the first through sixth examples, the constant torque mechanism is configured to deliver a constant torque over a stroke length greater than ninety degrees and wherein a magnitude of the constant torque is adjustable by translating the inner rotor relative to the outer rotor.

[0091] The description of embodiments has been presented for purposes of illustration and description. Suitable modifications and variations to the embodiments may be performed in light of the above description. The described systems are exemplary in nature, and may include additional elements and / or omit elements. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or properties disclosed.

[0092] The foregoing described aspects depict different components contained within, or connected with different other components. It is to be understood that such depicted architectures are merely exemplary , and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected," or "operably coupled," to each other to achieve the desired functionality.

[0093] As used in this application, an element or step recited in the singular and proceeded with the word "a" or "an " should be understood as not excluding plural of said elements or steps, unless such exclusion is stated. Furthermore, references to "one embodiment” or “one example” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. The terms "first,” “second,” “third,” and so on are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on theirDocket No. PSU24304PCT objects. The following claims particularly point out subject matter from the above disclosure that is regarded as novel and non-obvious.

Claims

Docket No. PSU24304PCTCLAIMS1. A system for a constant force mechanism, comprising: a rotor including one or more first pole-pairs; and a translator including one or more second pole-pairs: wherein the translator and rotor are arranged concentrically and centered around a z-axis, the translator is configured to surround the rotor with the one or more second pole-pairs of the translator facing the one or more first pole-pairs of the rotor, and wherein the rotor is separated from the translator by an air gap.

2. The system of claim 1, wherein each pole-pair comprises a pair of adjacent magnets with a first magnet having a first radial magnetic polarization and a second magnet having a second radial magnetic polarization that is antiparallel to the first radial magnetic polarization.

3. The system of claim 1. wherein the rotor is a cylindrical shell, wherein the one or more first pole-pairs comprise an outer circumference of the rotor, and wherein a second layer coupled to the one or more first pole-pairs comprises an inner circumference of the rotor.

4. The system of claim 3, wherein the cylindrical shell includes an annular top, an annular bottom, and a curved body and is configured to rotate along a rotational axis that is the same as the z-axis that extends perpendicularly through a center of the annular top and the annular bottom.

5. The system of claim 4, wherein the second layer is made of steel or iron.

6. The system of claim 2, wherein the translator is a cylindrical shell, wherein the one or more second pole-pairs comprise an inner circumference of the translator, and wherein a first layer coupled to the one or more second pole-pairs comprises an outer circumference of the translator.

7. The system of claim 6, wherein the cylindrical shell includes an annular top, an annular bottom, and a curved body and is configured to translate axially along the z-axis that extends perpendicularly through a center of the annular top and the annular bottom.

8. The system of claim 7, wherein the first layer is made of steel or iron.

9. The system of claim 7, wherein the translator includes two rows of second pole-pairs, where each row of second pole-pairs constitutes a circumference of the translator and the two rows are arranged in a stack along the z-axis.Docket No. PSU24304PCT10. The system of claim 9, wherein the two rows are arranged such that magnets within the second pole-pairs with the first radial magnetic polarization are not adjacent to magnets with radial magnetic polarization along the z-axis and that magnets with the second radial magnetic polarization are not adjacent to magnets with the second radial magnetic polarization along the z-axis.

11. The system of claim 1, wherein the rotor includes an equal number of first pole-pairs to a number of second pole-pairs within each row of the translator.

12. The system of claim 11, wherein the second pole-pairs of the translator and the first pole-pairs of the rotor each have an equal height along the z-axis.

13. The system of claim 11, wherein a constant force is produced between the rotor and translator and the constant force is independent of a position of the translator along the z-axis within a stroke length.

14. The system of claim 13 wherein a magnitude of the constant force is adjusted by changing an angle between the rotor and the translator.

15. The system of claim 4, wherein the rotor is coupled to a motor and / or gearbox to rotate the rotor and change an angle between the rotor and the translator.

16. A constant force mechanism (CFM), comprising: a rotor comprising a first plurality’ of magnetic segments annularly arranged around an outer circumference of the rotor, the first plurality' of magnetic segments positioned to form a first plurality of pole-pairs, each pole-pair comprising a pair of adjacent magnet segments with antiparallel radial magnetic polarizations; and a translator surrounding the rotor and comprising a second plurality of magnetic segments annularly arranged around an inner circumference of the translator, the second plurality of magnetic segments positioned to fonn two rows of a second plurality of pole-pairs, the translator configured to translate axially along a rotational axis of the rotor.

18. The CFM of claim 16, wherein the rotor is separated from the translator by an air gap.

19. The CFM of claim 16, wherein the first plurality of pole-pairs includes a same number of polepairs as the second plurality of pole-pairs.Docket No. PSU24304PCT20. The CFM of claim 16, wherein the first plurality of magnetic segments is mounted on a first layer of backing material and the second plurality of magnetic segments is mounted on a second layer of backing material.

21. A constant torque mechanism, comprising: an inner rotor including one or more first magnetic segments; an outer rotor including one or more second magnetic segments; wherein the outer rotor is a first cylindrical shell of a first radius and the inner rotor is a second cylindrical shell of a second radius, and die outer rotor and the inner rotor are arranged concentrically and centered around a central axis and wherein each of the first magnetic segments and each of the second magnetic segments comprise a flat semicircle of a first radius and a flat semicircle of a second radius, respectively, and wherein a polarity of the outer rotor changes every 180° of the outer rotor and a polarity of the inner rotor changes every 180° of the inner rotor, and the outer rotor includes at least three pole-pairs along an axial length of the outer rotor, parallel to the central axis, and the inner rotor includes at least three pole-pairs along an axial length of the inner rotor, parallel to the central axis.

22. The constant torque mechanism of claim 21. wherein the one or more first magnetic segments include a first set of magnetic segments with a first magnetic polarity, a second set of magnetic segments with a second magnetic polarity, a third set of magnetic segments with a third magnetic polarity, and a fourth set of magnetic segments with a fourth magnetic polarity', and wherein the first magnetic polarity is radially inward, the second magnetic polarity is radially outward, the third magnetic polarity is in a first axial direction and the fourth magnetic polarity is antiparallel to the third magnetic polarity.

23. The constant torque mechanism of claim 22, wherein a first magnetic segment of the first set of magnetic segments is coupled in face sharing contact to a second magnetic segment of the second set of magnetic segments to form a first annular segment, a third magnetic segment of the third set of magnetic segments is coupled in face sharing contact with a fourth magnetic segment of the fourth set of magnetic segments to form a second annular segment, and a fifth magnetic segment of the first set of magnetic segments is coupled in face sharing contact with a sixth magnetic segment of the second set of magnetic segments to form a third annular segment.

24. The constant torque mechanism of claim 23, wherein the first annular segment is adjacent to the second annular segment along the central axis and the third annular segment is adjacent to the second annular segment along the central axis.

25. The constant torque mechanism of claim 21, wherein the one or more first magnetic segments and the one or more second magnetic segments are each arranged into a respective Halbach array.Docket No. PSU24304PCT26. The constant torque mechanism of claim 21, wherein a width of each of the one or more first magnetic segments is equal to a width of each of the one or more second magnetic segments.

27. The constant torque mechanism of claim 21, wherein the inner rotor is configured to rotate and translate relative to the outer rotor, which is also configured to rotate.

28. The constant torque mechanism of claim 21, wherein the constant torque mechanism is configured to deliver a constant torque over a stroke length greater than ninety degrees and wherein a magnitude of the constant torque is adjustable by translating the inner rotor relative to the outer rotor.

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