Permanent Magnet Assemblies for Passive Accessories

Abstract

The present disclosure relates to a permanent magnet assembly for a user-worn device, the permanent magnet assembly including at least two sub-magnets. Each of the at least two sub-magnets has a magnet body defining a respective longitudinal axis. Each sub-magnet generates a magnetic field and has a respective magnetic moment vector associated therewith. At least one magnetic moment vector is tilted with respect to the respective longitudinal axis. Two adjacent sub-magnets of the at least two sub-magnets are attached together to form a body of the permanent magnet assembly. The at least two sub-magnets are coaxially disposed with respect to each other and rotationally oriented with respect to each other such that the assembly magnetic moment vector is tilted with respect to the body longitudinal axis by less than or equal to a weighted average tilt of the magnetic moment vectors of the at least two sub-magnets.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED ART) This application claims the benefit of European Patent Application No. 22307018.6, filed December 22, 2022, the contents of which are incorporated herein by reference.

[0002] FIELD OF THE INVENTION The present disclosure relates to the technical field of determining and / or tracking the location of passive accessories, and more particularly to a permanent magnet assembly for a user-worn device and a system for determining the operation of the user-worn device by a user. More particularly, the present disclosure relates to a method for manufacturing a permanent magnet assembly for a user-worn device. [Background technology]

[0003] In the technical field of location determination and / or tracking of devices held or worn by a user (i.e., user-worn devices), providing multiple magnetometers enables measuring magnetic fields associated with magnetic objects disposed within or coupled to the user-worn device. User-worn devices using this technology may be electronically and / or electrically passive. More specifically, electrically passive means that the user-worn device may not include a power source (e.g., a battery) and / or a means for receiving power (e.g., wireless power transmission via an induction coil) to power the electronic functions of the user-worn device. Electronically passive means that no calculations or processing are performed (or occur) on the user-worn device. Magnetometer measurements enable determining and / or tracking the location of magnetic objects within a sensing volume generated by the multiple magnetometers. Location may include the position and / or orientation of the magnetic object. In some applications, the magnetic object may be disposed within a writing device (e.g., a stylus) that can be manipulated by a user on a writing substrate during user operation. The location of the writing device on the writing substrate can be determined based on magnetic field measurements associated with the magnetic object.

[0004] In current applications, a magnetic object disposed within or coupled to a user-worn device can be approximated by a dipole, enabling the location and / or tracking of the magnetic object within a sensing volume generated by multiple magnetometers. Specifically, the magnetic object can be a permanent magnet. A magnetic object approximated as a dipole can generate a magnetic field that is rotationally symmetric about at least one axis. Such a magnetic object can be manipulated by a user within the sensing volume, enabling tracking of the magnetic object's movement and / or location determination in five degrees of freedom. The five degrees of freedom can include translation of the magnetic object (and the user-worn device to which the magnetic object is coupled) along three axes, a first rotation about a first axis, and a second rotation about a second axis. Rotation of the magnetic object around at least one axis about which the magnetic field is rotationally symmetric may not be detectable. In each application, a magnetic object is used that has a shape, such as a ring or a cylinder, with a body axis about which the magnetic object is rotationally symmetric. When a magnetic object having a rotationally symmetric magnetic field is desired, in the ideal case, the magnetization direction coincides with the body axis, making the magnetic object a rotating cylinder. However, current methods for providing near-perfect alignment of the magnetization direction (e.g., an angular deviation of less than 0.5°) with the body axis are very complicated and expensive. One exemplary method for providing near-perfect alignment of the magnetization direction can be achieved by sorting magnetic objects that do not have perfect alignment of the magnetization direction. The sorted magnetic objects may be recycled. This approach remains very time-consuming, energy-consuming, and costly, resulting in an overall complex process for providing magnetic objects with near-perfect alignment of the magnetization direction. On the other hand, the more the magnetization direction deviates from the body axis, the less accurate the location and / or tracking of the magnetic object and the user-worn device to which the magnetic object is attached.

[0005] An object of the present disclosure is to cost-effectively improve the accuracy of location determination and / or tracking of magnetic objects and user-worn devices to which the magnetic objects are attached. Summary of the Invention

[0006] The present disclosure relates to a permanent magnet assembly as defined in claim 1, a user-worn device as defined in claim 10, and a system for determining operation of a user-worn device by a user as defined in claim 11. According to claim 13, a method for manufacturing a permanent magnet assembly is provided. The dependent claims present embodiments of the present disclosure.

[0007] According to a first aspect of the present disclosure, a permanent magnet assembly for a user-worn device is provided. The permanent magnet assembly includes at least two sub-magnets. Each of the at least two sub-magnets has a magnet body defining a respective longitudinal axis. Each sub-magnet generates a magnetic field and has a respective magnetic moment vector associated with it. At least one magnetic moment vector is tilted with respect to the respective longitudinal axis. Two adjacent sub-magnets of the at least two sub-magnets are attached together to form a body of the permanent magnet assembly. The body has a body longitudinal axis and defines an assembly magnetic moment vector. The at least two sub-magnets are coaxially disposed with each other and rotationally oriented with respect to each other such that the assembly magnetic moment vector is tilted with respect to the body longitudinal axis less than or equal to a weighted average tilt of the magnetic moment vectors of the at least two sub-magnets. The weighted average tilt may be defined by the sum of the single tilts of the sub-magnet magnetic moment vectors with respect to their respective longitudinal axes, each weighted by the length of the magnetic moment vector of each sub-magnet. Specifically, the assembly magnetic moment vector may be equally tilted with respect to the weighted average tilt of the magnetic moment vectors of at least two sub-magnets only if not all magnetic moment vectors of the sub-magnets of the permanent magnet assembly are tilted with respect to their respective longitudinal axes. More specifically, the assembly magnetic moment vector may be equally tilted with respect to the weighted average tilt of the magnetic moment vectors of at least two sub-magnets only if only one magnetic moment vector of the sub-magnets of the permanent magnet assembly is tilted with respect to its respective longitudinal axis. Specifically, the assembly magnetic moment vector may be less tilted than the weighted average tilt of the magnetic moment vectors of at least two sub-magnets only if at least two magnetic moment vectors of the sub-magnets of the permanent magnet assembly are tilted with respect to their respective longitudinal axes. The permanent magnet assembly can provide improved location accuracy.In particular, compared to magnetic objects that do not include at least two sub-magnets, the disclosed permanent magnet assemblies may be more cost-effective and / or result in an assembly magnetic moment vector that is more aligned with the body longitudinal axis.

[0008] According to a second aspect of the present disclosure, there is provided a user-worn device operable within a sensing volume created by a plurality of magnetometers, the user-worn device comprising at least one permanent magnet assembly according to the first aspect, and the user-worn device further comprising a housing in which the permanent magnet assembly is disposed at a predetermined location.

[0009] According to a third aspect of the present disclosure, there is provided a system for determining a user's manipulation of a user-worn device. The system includes the user-worn device according to the second aspect and a plurality of magnetometers configured to generate a sensing volume and to measure a magnetic field associated with at least one permanent magnet assembly. The system is further configured to track movement and / or location of the at least one permanent magnet assembly in at least five degrees of freedom.

[0010] According to a fourth aspect of the present disclosure, there is provided a method for manufacturing a permanent magnet assembly having a desired predetermined magnetic strength. The method includes providing a first submagnet and at least a second submagnet. The first submagnet and the second submagnet each have a magnet body defining a respective longitudinal axis. The method further includes coaxially assembling the first submagnet and the second submagnet to form a body of the permanent magnet assembly. The first submagnet and the second submagnet are assembled together such that their respective longitudinal axes coincide and define a body longitudinal axis. The method further includes evaluating, by a processing unit, an assembly magnetic moment vector resulting from a magnetic field jointly generated by the first submagnet and the second submagnet. Additionally, the method includes rotationally orienting the first submagnet relative to the second submagnet about their respective longitudinal axes to minimize a tilt of the assembly magnetic moment vector relative to the body longitudinal axis. Specifically, the method may include using multiple magnetometers to measure the magnetic fields generated by the sub-magnets and / or the permanent magnet assembly. The method may provide a permanent magnet assembly that is more cost-effective and / or has a magnetic moment vector that is more aligned with the body longitudinal axis than a magnetic object that does not include at least two sub-magnets. This results in a permanent magnet assembly whose location can be determined and / or tracked with improved accuracy. Specifically, the orientation of the permanent magnet assembly is substantially coaxial with the body longitudinal axis. For example, if the permanent magnet assembly is attached to a pointer or stylus, pointing and / or writing accuracy may be related to the orientation accuracy and thus improved. [Brief explanation of the drawings]

[0011] Other features will be apparent from the accompanying drawings, which form a part of this disclosure. The drawings are intended to further explain the disclosure and enable those skilled in the art to practice it. However, these drawings are intended as non-limiting examples. Common reference symbols in different figures indicate similar or similar features. [Figure 1] FIG. 10 is a schematic diagram of a system for determining a user-worn device mode of operation according to a third aspect of the present disclosure, including a user-worn device according to a second aspect of the present disclosure. [Figure 2A] 1 is a schematic diagram of a prior art magnetic object; [Figure 2B] 1 is a schematic diagram of a prior art magnetic object; [Figure 3A] FIG. 2 is a schematic diagram of a first sub-magnet of a permanent magnet assembly of a first exemplary configuration according to a first embodiment. [Figure 3B] FIG. 2 is a schematic diagram of a first sub-magnet of a permanent magnet assembly of a first exemplary configuration according to a first embodiment. [Figure 4A] FIG. 2 is a schematic diagram of a second sub-magnet of a permanent magnet assembly of a first exemplary configuration according to a first embodiment. [Figure 4B] FIG. 2 is a schematic diagram of a second sub-magnet of a permanent magnet assembly of a first exemplary configuration according to a first embodiment. [Figure 5A] 4a and 4b are schematic diagrams of a first configuration of a permanent magnet assembly comprising the first sub-magnet of FIGS. 3a and 3b and the second sub-magnet of FIGS. 4a and 4b; [Figure 5B] 4a and 4b are schematic diagrams of a first configuration of a permanent magnet assembly comprising the first sub-magnet of FIGS. 3a and 3b and the second sub-magnet of FIGS. 4a and 4b; [Figure 5C] 4a and 4b are schematic diagrams of a first configuration of a permanent magnet assembly comprising the first sub-magnet of FIGS. 3a and 3b and the second sub-magnet of FIGS. 4a and 4b; [Figure 5D] 4a and 4b are schematic diagrams of a first configuration of a permanent magnet assembly comprising the first sub-magnet of FIGS. 3a and 3b and the second sub-magnet of FIGS. 4a and 4b; [Figure 6A]FIG. 10 is a schematic diagram of a first sub-magnet of a permanent magnet assembly of a second exemplary configuration according to a first embodiment. [Figure 6B] FIG. 10 is a schematic diagram of a first sub-magnet of a permanent magnet assembly of a second exemplary configuration according to a first embodiment. [Figure 7A] FIG. 10 is a schematic diagram of a second sub-magnet of a permanent magnet assembly of a second exemplary configuration according to the first embodiment. [Figure 7B] FIG. 10 is a schematic diagram of a second sub-magnet of a permanent magnet assembly of a second exemplary configuration according to the first embodiment. [Figure 8A] FIG. 10 is a schematic diagram of a third sub-magnet of a permanent magnet assembly of a second exemplary configuration according to a first embodiment. [Figure 8B] FIG. 10 is a schematic diagram of a third sub-magnet of a permanent magnet assembly of a second exemplary configuration according to a first embodiment. [Figure 9A] 8a and 8b, a schematic diagram of a second configuration of a permanent magnet assembly comprising the first sub-magnet of FIGS. 6a and 6b, the second sub-magnet of FIGS. 7a and 7b, and the third sub-magnet of FIGS. 8a and 8b. [Figure 9B] 8a and 8b, a schematic diagram of a second configuration of a permanent magnet assembly comprising the first sub-magnet of FIGS. 6a and 6b, the second sub-magnet of FIGS. 7a and 7b, and the third sub-magnet of FIGS. 8a and 8b. [Figure 9C] 8a and 8b, a schematic diagram of a second configuration of a permanent magnet assembly comprising the first sub-magnet of FIGS. 6a and 6b, the second sub-magnet of FIGS. 7a and 7b, and the third sub-magnet of FIGS. 8a and 8b. [Figure 10A] FIG. 10 is a schematic diagram of a third exemplary configuration of a permanent magnet assembly comprising first, second, and third sub-magnets, wherein the transverse vector component of the third sub-magnet is greater than the sum of the transverse vector components of the first and second sub-magnets. [Figure 10B] FIG. 10 is a schematic diagram of a third exemplary configuration of a permanent magnet assembly comprising first, second, and third sub-magnets, wherein the transverse vector component of the third sub-magnet is greater than the sum of the transverse vector components of the first and second sub-magnets. [Figure 10C]FIG. 10 is a schematic diagram of a third exemplary configuration of a permanent magnet assembly comprising first, second, and third sub-magnets, wherein the transverse vector component of the third sub-magnet is greater than the sum of the transverse vector components of the first and second sub-magnets. [Figure 11] FIG. 10 schematically illustrates a process flow diagram of a method for manufacturing a permanent magnet assembly according to a fourth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] A permanent magnet assembly, a user-worn device, a system for determining user manipulation of a user-worn device, and a method for manufacturing a permanent magnet assembly according to the present disclosure are described below with reference to the drawings.

[0013] FIG. 1 schematically illustrates a user-worn device 100 and a system 10 for determining manipulation of the user-worn device 100 by a user U, according to an embodiment of the present disclosure. The user-worn device 100 comprises a housing 101 and a permanent magnet assembly 110. The permanent magnet assembly 110 is disposed at a predetermined location within the housing 101 of the user-worn device 100. The location of the user-worn device 100 may thereby be determined and / or tracked based on the determined and / or tracked location of the permanent magnet assembly 110. The permanent magnet assembly 110 is aligned with a body longitudinal axis 116 and an assembly magnetic moment vector

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[0016] The system 10 includes a user-worn device 100 according to any of the embodiments and / or features described herein. The system 10 further includes a plurality of magnetometers 300. The plurality of magnetometers 300 may be configured to create a sensing volume M. The plurality of magnetometers 300 may be associated with a magnetometer plane 310 (see FIG. 1 ). More specifically, the magnetometer plane 310 may be defined by a plane that may extend across a majority of the plurality of magnetometers 300. As shown in FIG. 1 , the system 10 may have a reference coordinate system XYZ. The plurality of magnetometers 300 may be associated with the reference coordinate system XYZ. The system 10 is configured to define the reference coordinate system XYZ for the plurality of magnetometers 300. The reference coordinate system XYZ may include a first reference axis X, a second reference axis Y, and a vertical reference axis Z. The first reference axis X and the second reference axis Y may be orthogonal to each other. The vertical reference axis Z may be orthogonal to the first reference axis X and the second reference axis Y. The vertical reference axis Z may extend through the center of the multiple magnetometers 300. In an embodiment, the first reference axis X and the second reference axis Y may be defined on the magnetometer plane 310. In this case, the vertical reference axis Z may be orthogonal to the magnetometer plane 310. In an embodiment, the multiple magnetometers 300 may be integrated into a wall, furniture, a notebook, an electronic device, a screen or display, a keyboard, a manufacturing stage, a manufacturing bench, a calibration stage, and / or a mouse pad.

[0017] In an embodiment, the user-worn device 100 may be operable within a sensing volume M. Specifically, the user-worn device 100 may be operable on or above an interaction surface 210. More specifically, the interaction surface 210 may be defined within the sensing volume M. The interaction surface 210 may be understood as a physical constraint associated with the plurality of magnetometers 300. For example, the interaction surface 210 may be defined by a first set of geometric parameters relative to the plurality of magnetometers 300 and / or a reference coordinate system XYZ. More specifically, the first set of geometric parameters may indicate the geometric shape of the interaction surface 210. The first set of geometric parameters may include a point and a normal vector on the interaction surface 210 (thereby defining an infinite surface), at least three coplanar points defining a finite surface, a center point, a radius and a normal vector in the case of a disk-shaped surface, and / or two axes defined on the surface (e.g., two dimensions may define a rectangular surface). The above-described interaction surface configuration may be based on a first set of geometric parameters. The interaction surface 210 may include a set of partial surfaces having different orientations and / or positions relative to one another. This allows for determining the location of the user-worn device on any surface, even complex surfaces (e.g., due to the polygonal shape of the surface, curved surfaces). The first set of geometric parameters may include predetermined geometric parameters associated with the interaction surface 210.

[0018] The multiple magnetometers 300 may be configured to measure magnetic fields associated with the permanent magnet assemblies 110. Each magnetometer of the multiple magnetometers 300 may be configured to measure a magnetic field associated with at least one permanent magnet assembly 110 along a first reference axis X, a second reference axis Y, and / or a perpendicular reference axis Z. In other words, each magnetometer of the multiple magnetometers 300 may be configured to perform magnetic field measurements along one axis (i.e., one dimension), two axes (i.e., two dimensions), or three axes (i.e., three dimensions). The number of magnetometers provided may depend on the size of the interaction surface 210 on which the user-worn device 100 operates or the desired size of the sensing volume in which the user-worn device 100 operates. The multiple magnetometers 300 may be configured to collect magnetic field measurements associated with at least one permanent magnet assembly 110 within the sensing volume up to a maximum measurement distance. In an embodiment, the maximum measurement distance may be 18 cm, more specifically 15 cm. In other embodiments, the maximum measurement distance may be greater than 18 cm, for example, approximately 30 cm, depending on the magnetic strength of the permanent magnet assembly 110 being measured or tracked. In an embodiment, the maximum measurement distance may be defined between the farthest point on the interaction surface 210 or within the sensing volume and the nearest magnetometer of the plurality of magnetometers 300.

[0019] In an embodiment, the system 10 may include an interaction support 200 having an interaction support surface (see FIG. 1 ). The interaction surface 210 may be at least a partial surface of the interaction support surface. The interaction support 200 may not include ferromagnetic properties, e.g., ferromagnetic particles. In an embodiment, the interaction support 200 may be a piece of furniture (e.g., a table), a notebook, an electronic device, a screen or display, a plate, a wall, a keyboard, or a mouse pad. The interaction surface 210 may be defined based on a first set of geometric parameters associated with the interaction support 200. More specifically, the type of the interaction support 200 may be a known one, e.g., a notebook or a mouse pad. Such an interaction support 200 may be defined by a set of predetermined geometric parameters. A partial surface of the interaction support surface may be used as the interaction surface 210. Thus, the set of predetermined parameters may include data associated with the interaction surface configuration of the interaction surface 210, more specifically, geometric data. As an example, these parameters may indicate the position and / or orientation of the interaction surface 210 relative to a reference coordinate system XYZ. In an embodiment, the first set of geometric parameters may be determined by interactive surface recognition, as described below.

[0020] The interaction surface 210 may be defined within the sensing volume M. The interaction surface 210 is aligned along a first surface axis x s , the second surface axis y s , and the vertical surface axis z s and more specifically, the axes may be orthogonal to each other (see, for example, FIG. 1). s and the second surface axis y s may be defined on the interaction surface 210. In an embodiment, a plurality of magnetometers 300 may be disposed within or attached to the interaction support 200.

[0021] 1, the user-worn device 100 is a dial. In other embodiments, the user-worn device 100 may be a computer mouse, a keyboard, a toy, a stylus, or a brush. In embodiments, the user-worn device 100 may be an accessory tool, for example, a ruler. The user-worn device 100 is configured in a device coordinate system x d , y d , z d The housing 101 of the user-worn device 100 may have a first device axis x d , the first device axis x d A second device axis, y, perpendicular to d , and the vertical device axis z d The vertical device axis z d is the first device axis x d and the second device axis y d In an embodiment, the vertical device axis z d may be perpendicular to the device contact surface or point and / or perpendicular to the first device axis x d and the second device axis y d The device contact surface or point may be a portion of the user-worn device 100 that may contact the interaction surface 210 (i.e., in some embodiments, a surface on which the user-worn device 100 may be operated) during user operation. In the dial 100 of FIG. 1, the body longitudinal axis 116 is perpendicular to the vertical device axis z d In other embodiments of the dial or other user-worn device 100, the body longitudinal axis 116 is aligned perpendicular to the vertical device axis z. d In some embodiments, the device coordinate system may be defined within the geometric center of the user-worn device 100.

[0022] The user wearable device 100 may be electrically and / or electronically passive. More specifically, electrically passive means that the user wearable device 100 may not include a power source (e.g., a battery) and / or a means for receiving power (e.g., wireless power transmission via an induction coil) to power the functions (e.g., electronic functions) of the user wearable device 100. Electronically passive means that no computation or processing is performed (or occurs) on the user wearable device 100. This allows the user wearable device 100 to be easily recycled and reduces its impact on the environment.

[0023] The system 10, and more particularly the plurality of magnetometers 300, is configured to measure a magnetic field associated with at least one permanent magnet assembly 110. The system 10 may be configured to determine a permanent magnet assembly location of the at least one permanent magnet assembly 110 based on collected magnetic field measurements within a sensing volume M relative to a reference coordinate system XYZ. The permanent magnet assembly location may include a permanent magnet assembly position and / or a permanent magnet assembly orientation relative to a reference coordinate system XYZ associated with the at least one permanent magnet assembly 110. The system 10 may also determine a magnetic moment vector

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[0026] The user wearable device 100 and / or the at least one permanent magnet assembly 110 may be mobile, i.e., freely movable within the reference coordinate system XYZ. In other words, during user operation (i.e., operation in which the user wearable device 100 and / or the at least one permanent magnet assembly 110 is manipulated by the user), the user wearable device 100 within the sensing volume M and / or relative to the interaction surface 210 may be manipulated by a user U within the sensing volume M. The manipulation of the user wearable device 100 may include manipulation of the location of the user wearable device 100 and / or manipulation of one or more manipulation features of the user wearable device 100. In other words, the user wearable device 100 may include one or more manipulation features, for example, a feature movable relative to the housing 101 of the user wearable device 100 to trigger at least one specific event (i.e., a trigger event) associated with additional functionality. At least one trigger event, such as a click event, a scroll event, or a selection event, may cause an action and / or may be used to control an action in a digital environment (i.e., an environment controlled by a computer or a network of computers), more specifically, a virtual environment, based on user input. Manipulating the location of the user-worn device 100 may include manipulating the orientation of the user-worn device 100 and / or manipulating the position of the user-worn device 100. In some embodiments, the system 10 may be configured to determine a first type of trigger event when the tracked movement includes a rotation of the at least one permanent magnet assembly 110 about a first trigger axis that is not the body longitudinal axis 116. In embodiments, the system 10 may further be configured to determine a second type of trigger event when the tracked movement includes a rotation of the at least one permanent magnet assembly 110 about a second trigger axis that is not the body longitudinal axis 116 and that is also different from the first trigger axis. Specifically, the first trigger axis may be orthogonal to the body longitudinal axis 116. In particular, the second trigger axis may be orthogonal to the first trigger axis and / or may be orthogonal to the body longitudinal axis 116 .

[0027] The system 10 may further comprise a processing unit 400. In an embodiment, the system 10 may be connectable to the processing unit 400. The processing unit 400 may be configured to determine a location and / or track the movement of the at least one permanent magnet assembly 110 in at least five degrees of freedom. The location may include the position and / or orientation of the at least one permanent magnet assembly 110. The processing unit 400 may further be configured to determine a trigger event. In an embodiment, the system 10 may comprise an electronic device. In an embodiment, the processing unit 400 may be integrated into the electronic device. In an embodiment, the electronic device may be a tablet, a mobile phone, a laptop, a computer, a virtual reality (VR) set, or a television.

[0028] In an embodiment, system 10, and more specifically, processing unit 400, may be configured to track user-worn device 100 and / or at least one permanent magnet assembly 110 over a period of time comprising multiple time samples. During user operation, system 10 may be configured to track movement and / or manipulation of user-worn device 100 within the sensing volume and / or relative to interaction surface 210 over a period of time. More specifically, system 10 may be configured to determine a position and / or orientation of at least one permanent magnet assembly 110 at each time sample and may store the determined location (or interaction) for each time sample.

[0029] The system 10 may further include at least one output interface 500 (see FIG. 1 ). The at least one output interface 500 may be configured to represent the user-worn device 100. More specifically, the at least one output interface 500 may be configured to visually reproduce the user-worn device 100 as a virtual object. The system 10 may be configured to reproduce manipulation of the user-worn device 100 as manipulation of the virtual object on the at least one output interface 500. The system 10 may be configured to visually reproduce a trigger event on the at least one output interface 500. In an embodiment, the output interface 500 may be a display or screen or a VR headset. A translation of the user-worn device 100 on the interaction surface 210 in a certain direction may be represented as a translation of the user-worn device 100 represented on the at least one output device 500.

[0030] 3-10, the permanent magnet assembly 110 includes at least two sub-magnets 110a, 110b, and 110c. Each of the at least two sub-magnets 110a, 110b, and 110c has a magnet body 114a, 114b, and 114c that defines a respective longitudinal axis 116a, 116b, and 116c. Each sub-magnet 110a, 110b, and 110c generates a magnetic field and a respective magnetic moment vector associated with the respective sub-magnet 110a, 110b, and 110c.

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[0035] The weighted average tilt is the sub-magnet magnetic moment vectors 116a, 116b, 116c relative to their respective longitudinal axes 116a, 116b, 116c.

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[0038] The weighted average slope can be described by the following equation:

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[0040] Here, (n) is the total number of sub-magnets 110a, 110b, 110c included in the permanent magnet assembly 110, for example, two, three, four or more sub-magnets 110a, 110b, 110c. (φ i ) is a single tilt of the sub-magnets 110a, 110b, 110c. For example, φ1 is a single tilt of the first sub-magnet 110a, more specifically, the magnetic moment vector of the first sub-magnet 110a relative to the longitudinal axis 116a of the first sub-magnet 110a.

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[0044] In an embodiment, the assembly magnetic moment vector

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[0051] In an embodiment, the assembly magnetic moment vector

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[0055] The permanent magnet assembly 110 according to the present disclosure can provide improved accuracy in determining location, in other words, can improve the accuracy in determining and / or tracking the location of the permanent magnet assembly 110 by the multiple magnetometers 300. In particular, compared to a magnetic object that does not include at least two sub-magnets 110a, 110b, 110c, the disclosed permanent magnet assembly 110 can be more cost-effective and / or have an assembly magnetic moment vector that is more aligned with the body longitudinal axis 116.

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[0057] To better illustrate these technical effects, Figures 2a and 2b show, in comparison, a highly schematic representation of a standard magnetic object 110'. This standard magnetic object 110' may be a permanent magnet and may have a cylindrical body 114' defining a longitudinal body axis 116'. While the prior art magnetic object 110' is magnetized along the longitudinal body axis 116', the resulting magnetic field is not ideal and deviates from the mechanical body axis 116'. Therefore, the associated magnetic moment vector

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[0060] The present disclosure provides a cost-effective and simple solution for improving accuracy by providing an improved magnetic object, i.e., permanent magnet assembly. The solution is to provide a permanent magnet assembly 110 comprising at least two sub-magnets 110a, 110b, and 110c, as outlined above with general reference to Figures 3-10. Even though the sub-magnets 110a, 110b, and 110c may suppress large angular deviations, such as those of standard magnetic objects described above, the resulting angular deviation of the permanent magnet assembly 110 can approach zero, e.g., 0.5° or less, or can at least be reduced. The figures show three exemplary configurations of the permanent magnet assembly 110 according to the present disclosure.

[0061] Figures 3a, 3b, 4a, 4b, and 5a-5d highly schematically show a first exemplary arrangement of a permanent magnet assembly 110 comprising two sub-magnets 110a, 110b, including a first sub-magnet 110a and a second sub-magnet 110b.

[0062] 3a and 3b, the first sub-magnet 110a has a magnet body 114a (which may also be referred to as the first magnet body 114a). The first magnet body 114a defines a longitudinal axis 116a (which may also be referred to as the first longitudinal axis 116a) of the first sub-magnet 110a. The first sub-magnet 110a generates a magnetic field and a magnetic moment vector associated with the first sub-magnet 110a.

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[0065] 4a and 4b, the second sub-magnet 110b has a magnet body 114b (which may also be referred to as the second magnet body 114b). The second magnet body 114b defines a longitudinal axis 116b (which may also be referred to as the second longitudinal axis 116b) of the second sub-magnet 110b. The second sub-magnet 110b generates a magnetic field and a magnetic moment vector associated with the second sub-magnet 110b.

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[0068] In the first exemplary configuration shown, the first and second magnetic moment vectors

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[0075] With further reference to FIGS. 3a and 4a, each magnetic moment vector

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[0081] In general, the vertical vector component

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[0088] Thereby, each horizontal vector component

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[0099] In other embodiments, each horizontal vector component

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[0105] In the embodiment, the first sub-magnet 110a and the second sub-magnet 110b have a longitudinal vector component

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[0108] In some embodiments, the two sub-magnets 110a, 110b may be glued together. Specifically, the contact surfaces may be glued together. In embodiments, the sub-magnets 110a, 110b may be coated and / or overmolded. Specifically, the permanent magnet assembly 110 may be coated and / or overmolded to provide additional holding strength to the sub-magnets 110a, 110b. Other adhesive and / or cohesive bonding connections may also be possible. In some embodiments, the sub-magnets 110a, 110b may be attached together by an external holding structure. In examples, the external holding structure may comprise a resin molded over the permanent magnet assembly 110, and / or a cage-like holder, and / or a structure within the user-worn device 100 into which the permanent magnet assembly 110 is placed and / or secured.

[0109] In general, the term “sub-magnet” may refer to a magnetic object that may include components made of a magnetic material, i.e., a magnetic material having magnetic properties measurable by the magnetometers 300. The sub-magnets 110a, 110b, and 110c of the permanent magnet assembly 110 may be permanent magnets, such as magnets containing ferrite and / or neodymium. In embodiments, the sub-magnets 110a, 110b, and 110c may be configured to generate a non-zero magnetic field. In embodiments, the sub-magnets 110a, 110b, and 110c may comprise a paramagnetic or diamagnetic material. The term sub-magnet indicates that a sub-magnet itself may not have the magnetic strength desired or required for an application, but forms part of a functionally separate permanent magnet assembly 110 and provides a portion of the desired or required magnetic strength. Specifically, the combined magnetic strength of all of the sub-magnets 110a, 110b, and 110c included in the permanent magnet assembly 110 collectively forms the desired or required magnetic strength. For example, compared to the single standard magnetic object 110' of Figures 2a and 2b having a desired or required magnetic strength, the single standard magnetic object 110' may be split into two sub-magnets 110a, 110b that may be used to form a permanent magnet assembly 110 as shown in Figures 3a, 3b, 4a, 4b, and 5a-5d. The two sub-magnets 110a, 110b may each be half the size of the single standard magnetic object 110' and each have half the desired or required magnetic strength.

[0110] In embodiments, the sub-magnets 110a, 110b, 110c may have the same size and / or the same magnetic strength. However, in embodiments, at least two or all of the sub-magnets 110a, 110b, 110c may have different sizes and / or different magnetic strengths. Specifically, all or at least some of the sub-magnets 110a, 110b, 110c may have the same length along the longitudinal axes 116a, 116b, 116c. In some embodiments, at least one sub-magnet 110a, 110b, 110c may have a length along the longitudinal axes 116a, 116b, 116c that is different from the other sub-magnets 110a, 110b, 110c. In some embodiments, each of the at least two sub-magnets 110a, 110b, 110c may have a different length along the longitudinal axes 116a, 116b, 116c.

[0111] In embodiments, the sub-magnets 110a, 110b, and 110c may comprise a ferromagnetic or ferrimagnetic material. As described above, the sub-magnets 110a, 110b, and 110c may comprise magnet bodies 114a, 114b, and 114c extending along longitudinal axes 116a, 116b, and 116c. More specifically, the sub-magnets 110a, 110b, and 110c may have lengths measured along the longitudinal axes 116a, 116b, and 116c (e.g., along the z-axis), widths (e.g., along the y-axis) and thicknesses (e.g., along the x-axis) measured orthogonally to the longitudinal axes 116a, 116b, and 116c.

[0112] In some embodiments, the length of the sub-magnets 110a, 110b, 110c may be greater than their width and / or thickness, however, in other embodiments, the length of the sub-magnets 110a, 110b, 110c may be less than their width and / or thickness.

[0113] In embodiments, the magnet bodies 114a, 114b, 114c may have a cylindrical shape, whereby the longitudinal axes 116a, 116b, 116c are defined as the axis, e.g., height, of the cylinder (see FIGS. 3-10). In embodiments, the magnet bodies 114a, 114b, 114c of the sub-magnets 110a, 110b, 110c may not be elongated. For example, the length measurement along the longitudinal axes 116a, 116b, 116c may be shorter than the width and / or thickness. In such cases, the magnet bodies 114a, 114b, 114c may still have a cylindrical shape, whereby the longitudinal axes 116a, 116b, 116c may define the axis, e.g., height, of the cylinder. In embodiments, one or more of the sub-magnets 110a, 110b, 110c may have a non-cylindrical magnet body 114a, 114b, 114c. In some embodiments, at least one or some or all of the magnet bodies 114a, 114b, 114c may have an annular shape, for example, a ring shape.

[0114] The above discussion regarding the size and shape of the sub-magnets 110a, 110b, 110c is equally applicable to the permanent magnet assembly 110, specifically its body 114, which may have a length, width, and thickness. In an embodiment, the body 114 of the permanent magnet assembly 110 may have a cylindrical or annular shape.

[0115] Depending on the magnetization direction, the sub-magnets 110a, 110b, and 110c can generate an associated magnetic field, which is schematically indicated by a south pole "S" and a north pole "N." Specifically, the sub-magnets 110a, 110b, and 110c can be configured to generate a symmetric magnetic field. More specifically, the sub-magnets 110a, 110b, and 110c can be configured to generate a rotationally symmetric magnetic field. As mentioned above, the magnetizations do not have to be perfectly aligned with the respective longitudinal axes 116a, 116b, and 116c. However, in embodiments, the permanent magnet assembly 110 can include one or more sub-magnets whose magnetizations coincide with the respective longitudinal axes 116a, 116b, and 116c.

[0116] magnetic moment vector

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[0119] Figures 6a, 6b, 7a, 7b, 8a, 8b, and 9a-9c highly schematically show a second exemplary arrangement of a permanent magnet assembly 110 comprising three sub-magnets 110a, 110b, including a first sub-magnet 110a, a second sub-magnet 110b, and a third sub-magnet.

[0120] 6a and 6b, the first sub-magnet 110a has a magnet body 114a (which may also be referred to as the first magnet body 114a). The first magnet body 114a defines a longitudinal axis 116a (which may also be referred to as the first longitudinal axis 116a) of the first sub-magnet 110a. The first sub-magnet 110a generates a magnetic field and a magnetic moment vector associated with the first sub-magnet 110a.

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[0123] 7a and 7b, the second sub-magnet 110b has a magnet body 114b (which may also be referred to as the second magnet body 114b). The second magnet body 114b defines a longitudinal axis 116b (which may also be referred to as the second longitudinal axis 116b) of the second sub-magnet 110b. The second sub-magnet 110b generates a magnetic field and a magnetic moment vector associated with the second sub-magnet 110b.

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[0126] 8a and 8b, the third sub-magnet 110c has a magnet body 114c (which may also be referred to as the third magnet body 114c). The third magnet body 114c defines a longitudinal axis 116c (which may also be referred to as the third longitudinal axis 116c) of the third sub-magnet 110c. The third sub-magnet 110c generates a magnetic field and a magnetic moment vector associated with the third sub-magnet 110c.

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[0129] The bodies 114a, 114b, 114c of the three sub-magnets 110a, 110b, 110c may have a cylindrical shape, or may have an annular shape, for example a ring shape, as further described above with respect to the second exemplary configuration.

[0130] In the second exemplary configuration shown, the first and second magnetic moment vectors

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[0138] As with the first exemplary configuration, each magnetic moment vector

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[0148] As best shown in Figures 6b, 7b, 8b, 9b, and 9c, the respective transverse vector components

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[0166] Thereby, each horizontal vector component

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[0176] The three or more sub-magnets 110a, 110b, 110c of the second exemplary configuration may be attached together in a manner similar to that described with respect to the first exemplary configuration. For example, the three (or more) sub-magnets 110a, 110b, 110c may have a longitudinal vector component

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[0179] 10a-10c highly schematically illustrate a third exemplary arrangement of a permanent magnet assembly 110 comprising three sub-magnets 110a, 110b, including a first sub-magnet 110a, a second sub-magnet 110b, and a third sub-magnet. One or more features of the third exemplary configuration may be similar to the second exemplary configuration. The difference between this third exemplary configuration and the second exemplary configuration is the transverse vector component

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[0182] In this example, the third transverse vector component of the third sub-magnet 110c is

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[0197] Specifically, the three sub-magnets 110a, 110b, and 110c are arranged coaxially with each other, and the assembly magnetic moment vector

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[0200] More specifically, with reference to FIGS. 10a, 10b, and 10c, the first sub-magnet 110a and the second sub-magnet 110b are attached together. The second sub-magnet 110b and the third sub-magnet 110c are attached together. That is, the first sub-magnet 110a, the second sub-magnet 110b, and the third sub-magnet 110c are disposed adjacent to each other and in contact. In this example, the second sub-magnet 110b is disposed between the first sub-magnet 110a and the third sub-magnet 110c. In other embodiments, the first sub-magnet 110a or the third sub-magnet 110c may be disposed adjacent to each other. Thereby, the three sub-magnets 110a, 110b, and 110c have a body longitudinal axis 116 and an assembly magnetic moment vector

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[0208] It should be understood that one, some, or all of the above features described with respect to a particular arrangement may be combined with any other arrangement of permanent magnet assemblies 110. It should further be understood that a user worn device 100 according to the second aspect of the present disclosure may include two or more permanent magnet assemblies 110, which may be similarly or differently configured. In an embodiment, the user worn device 100 may include at least one permanent magnet assembly 110, as well as at least one single magnetic object 110' that is not part of the permanent magnet assembly 110.

[0209] 11 , a method 600 for manufacturing a permanent magnet assembly 110 having a desired predetermined magnetic strength is provided according to a fourth aspect of the present disclosure. The method 600 may be specially configured for manufacturing a permanent magnet assembly 110 as described hereinabove. The method 600 includes providing (610) a first sub-magnet 110a and at least second sub-magnets 110b, 110c. The first sub-magnet 110a and the second sub-magnets 110b, 110c each have a magnet body 114a, 114b, 114c defining a respective longitudinal axis 116a, 116b, 116c. The method further includes coaxially combining (630) the first sub-magnet 110a and the second sub-magnets 110b, 110c together to form the body 114 of the permanent magnet assembly 110. The first sub-magnet 110a and the second sub-magnets 110b, 110c are assembled together such that their respective longitudinal axes 116a, 116b, 116c coincide and define a body longitudinal axis 116. The method includes, by the processing unit 400, calculating an assembly magnetic moment vector resulting from the magnetic fields jointly generated by the first sub-magnet 110a and the second sub-magnets 110b, 110c.

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[0213] In an embodiment, the method further comprises:

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[0217] In an embodiment, a first sub-magnet 110a and at least second sub-magnets 110b, 110c may be provided, which in combination provide a desired predetermined magnetic strength of the permanent magnet assembly 110. Specifically, a first sub-magnet 110a and at least second sub-magnets 110b, 110c may be provided, which in combination provide a desired predetermined magnetic strength. More specifically, the respective longitudinal vector components of the first sub-magnet 110a and at least second sub-magnets 110b, 110c

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[0219] In an embodiment, the assembly magnetic moment vector

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[0223] In an embodiment, the assembly magnetic moment vector

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[0227] In an embodiment, the assembly magnetic moment vector

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[0233] In an embodiment, combining the sub-magnets 110a, 110b, 110c together (630) may further include fixedly positioning one of the first sub-magnet 110a and the second sub-magnet 110b, 110c at a known location. The known location may include a known position and / or orientation in a reference coordinate system, for example, the XYZ reference coordinate system of the system 10 according to the third aspect. Specifically, one of the first sub-magnet 110a and the second sub-magnet 110b, 110c may be fixedly positioned with the longitudinal axis of the sub-magnet at a known orientation. In an example, each fixedly positioned sub-magnet 110a, 110b, 110c may be at a fixed location within a holder configured to fixedly hold one of the sub-magnets 110a, 110b, 110c. In other words, the known location may be a location (i.e., position and / or orientation) known to the processing unit 400. In an embodiment, the first sub-magnet 110a and the other of the second sub-magnets 110b, 110c have an assembly magnetic moment vector

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[0235] In an embodiment, the assembly magnetic moment vector

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[0244] In an embodiment, a first sub-magnet 110a, a second sub-magnet 110b, and a third sub-magnet 110c may be provided that, in combination, provide a desired predetermined magnetic strength of the permanent magnet assembly 110. Specifically, the first sub-magnet 110a, the second sub-magnet 110b, and the third sub-magnet 110c can collectively provide a desired predetermined magnetic strength of the permanent magnet assembly 110. More specifically, the respective longitudinal vector components of the first sub-magnet 110a, the second sub-magnet 110b, and the third sub-magnet 110c

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[0246] In some embodiments having at least three sub-magnets 110a, 110b, 110c, the transverse vector component

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[0251] In some embodiments having at least three sub-magnets 110a, 110b, 110c, the transverse vector component

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[0257] In an embodiment, four or more sub-magnets 110a, 110b, 110c may be used in the same manner as any one of the previous method steps, or may be used in the same manner as any one of the previous method steps.

[0258] While the present disclosure has been described above and is defined in the appended claims, it should be understood that the present disclosure can also be defined according to the following embodiments. 1. A permanent magnet assembly (110) for a user-worn device (100), comprising: at least two sub-magnets (110a, 110b, 110c) each having a magnet body (114a, 114b, 114c) defining a respective longitudinal axis (116a, 116b, 116c); Each sub-magnet (110a, 110b, 110c) generates a magnetic field and a respective magnetic moment vector associated with each sub-magnet (110a, 110b, 110c).

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Claims

1. A permanent magnet assembly (110) for a user-worn device (100), comprising: - at least two sub-magnets (110a, 110b, 110c) each having a magnet body (114a, 114b, 114c) defining a respective longitudinal axis (116a, 116b, 116c); Each sub-magnet (110a, 110b, 110c) generates a magnetic field and a respective magnetic moment vector associated with said respective sub-magnet (110a, 110b, 110c). [Equation 1] and at least one magnetic moment vector [Equation 2] are inclined with respect to the respective longitudinal axes (116a, 116b, 116c), two adjacent sub-magnets (110a, 110b, 110c) of said at least two sub-magnets (110a, 110b, 110c) have a body longitudinal axis (116) and an assembly magnetic moment vector [Equation 3] are attached together to form a body (114) of the permanent magnet assembly (110) defining - the at least two sub-magnets (110a, 110b, 110c) are arranged coaxially with respect to each other and the assembly magnetic moment vector [Equation 4] the magnetic moment vectors of the at least two sub-magnets (110a, 110b, 110c) relative to the body longitudinal axis (116) [Equation 5] and a weighted average tilt of the magnet assemblies (110) that are rotationally oriented relative to one another such that the tilt is less than or equal to the weighted average tilt of the magnet assemblies (110).

2. Each magnetic moment vector [Equation 6] is a longitudinal vector component extending along each of the longitudinal axes (116a, 116b, 116c), [Equation 7] and a transverse vector component extending perpendicular to said respective longitudinal axes (116a, 116b, 116c). [Equation 8] and the vertical vector component is defined by [Equation 9] The combination of the assembly magnetic moment vector [Equation 10] The resulting vertical vector component of [0011] and the horizontal vector component [0012] The combination of the assembly magnetic moment vector [0013] The resulting transverse vector component of [0014] The permanent magnet assembly (110) of claim 1, defining:

3. The at least two sub-magnets (110a, 110b, 110c) are arranged such that the respective transverse vector components [Equation 15] The resulting transverse vector component [0016] 3. The permanent magnet assembly (110) of claim 2, wherein the permanent magnet assembly (110) is rotationally oriented relative to one another to provide minimization of

4. The permanent magnet assembly (110) according to any one of claims 1 to 3, wherein the at least two sub-magnets (110a, 110b, 110c) comprise a first sub-magnet (110a) and a second sub-magnet (110b) attached together.

5. At least when dependent on claim 2, the first sub-magnet (110a) and the second sub-magnet (110b) have the respective transverse vector components [Equation 17] 5. The permanent magnet assembly (110) of claim 4, wherein the magnets are rotationally oriented relative to one another such that the magnets are oriented in opposite directions.

6. When dependent on at least claims 2 and 4, the first sub-magnet (110a) and the second sub-magnet (110b) are arranged such that the longitudinal vector component [Equation 18] The permanent magnet assembly (110) according to any one of claims 1 to 5, wherein the magnets are arranged coaxially with each other such that they are oriented in the same direction.

7. The permanent magnet assembly (110) according to any one of claims 4 to 6, wherein the at least two sub-magnets (110a, 110b, 110c) further comprise a third sub-magnet (110c) attached to one of the first or second sub-magnets (110a, 110b).

8. When dependent on at least claim 2, the horizontal vector component [Equation 19] One of the horizontal vector components is [Equation 20] If the sum of the lengths of the other horizontal vector components is greater than [Equation 21] is the horizontal vector component [Equation 22] The permanent magnet assembly (110) of claim 7, wherein the magnets are arranged in a direction opposite to the component of the sum of

9. When dependent on at least claim 2, the horizontal vector component [Equation 23] Any of the horizontal vector components [0000] If the length of the horizontal vector component [Equation 25] is the assembly magnetic moment vector [Equation 26] the resulting transverse vector component of [0000] The permanent magnet assembly (110) of claim 7, arranged to minimize

10. A user-worn device (100) operable within a sensing volume (M) created by a plurality of magnetometers (300), comprising: At least one permanent magnet assembly (110) according to any one of claims 1 to 9; and a housing (101) in which the permanent magnet assembly (110) is disposed at a predetermined location, wherein the user-worn device (100) is electrically and / or electronically passive.

11. A system (10) for determining operation of a user-worn device (100) by a user (U), comprising: A user-worn device (100) according to claim 10; a plurality of magnetometers (300) configured to generate a sensing volume and configured to measure a magnetic field associated with the at least one permanent magnet assembly (110); The system (10) is configured to track the movement and / or location of the at least one permanent magnet assembly (110) in at least five degrees of freedom.

12. The system (10) of claim 11, comprising a processing unit (400) configured to control a representation of the user-worn device (100) on an output device (500).

13. A method (600) for manufacturing a permanent magnet assembly (110) having a desired predetermined magnetic strength, comprising: - providing (610) a first sub-magnet (110a) and at least a second sub-magnet (110b, 110c) each having a magnet body (114a, 114b, 114c) defining a respective longitudinal axis (116a, 116b, 116c); - Coaxially assembling (630) the first sub-magnet (110a) and the second sub-magnet (110b, 110c) together to form a body (114) of the permanent magnet assembly (110), whereby the respective longitudinal axes (116a, 116b, 116c) coincide and define a body longitudinal axis (116); - by the processing unit 400, an assembly magnetic moment vector resulting from the magnetic field jointly generated by said first sub-magnet (110a) and said second sub-magnets (110b, 110c), [0000] evaluating (640) - the assembly magnetic moment vector relative to the body longitudinal axis (116) [0000] and rotating (650) the first sub-magnet (110a) relative to the second sub-magnets (110b, 110c) about the respective longitudinal axes (116a, 116b, 116c) so that tilt of the first sub-magnet (110a) relative to the second sub-magnets (110b, 110c) is minimized.

14. the assembly magnetic moment vector [Equation 30] is evaluated (640) by the processing unit (400) to determine the assembly magnetic moment vector relative to the body longitudinal axis (116). [Equation 31] 14. The method (600) of claim 13, further comprising evaluating the angular deviation (φ) of

15. The combining (630) of the sub-magnets (110a, 110b, 110c) together includes fixedly placing one of the first sub-magnet (110a) and the second sub-magnet (110b, 110c) at a known location, and more specifically, the other of the first sub-magnet (110a) and the second sub-magnet (110b, 110c) at a known location such that the assembly magnetic moment vector relative to the body longitudinal axis (116) is aligned with the magnet. [Equation 32] 15. The method (600) of claim 13 or 14, wherein the first and second electrodes are rotated (650) about their respective longitudinal axes (116a, 116b, 116c) to minimize tilt of the first and second electrodes.

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