PATENT DOCUMENT

Publication Number: US-11108282-B2
Application Number: US-201816200960-A
Country: US
Kind Code: B2

Title: Powered joint with wireless transfer

Abstract:
A powered joint having a first joint component and second joint component in which the first joint component has multiple degrees of rotational freedom with respect to the second joint component, the powered joint including one or more power transmission coils associated with the first component; a plurality of power receiving coils associated with the second component; a sensor which determines the orientation of the second component with respect to the first component; and a control circuit for selectively connecting one of the plurality of power receiving coils to a power receiving circuit based on information received from the sensor.

Claims:
The invention claimed is: 
     
       1. A powered articulated mechanical joint comprising:
 a first articulated mechanical joint component mechanically coupled to a second articulated mechanical joint component, in which the first articulated mechanical joint component has multiple degrees of rotational freedom with respect to the second articulated mechanical joint component; 
 one or more power transmission coils associated with the first articulated mechanical joint component; 
 a plurality of power receiving coils associated with the second articulated mechanical joint component; 
 a sensor which determines the orientation of the second articulated mechanical joint component with respect to the first articulated mechanical joint component; and 
 a control circuit for selectively connecting one of the plurality of power receiving coils to a power receiving circuit based on information received from the sensor. 
 
     
     
       2. A powered articulated mechanical joint as claimed in  claim 1  wherein the sensor is one of: a gyroscope; an accelerometer; a magnetic field sensor; an IMU; a compass; and a gravity switch. 
     
     
       3. A powered articulated mechanical joint as claimed in  claim 2  including a single transmission coil. 
     
     
       4. A powered articulated mechanical joint as claimed in  claim 3  including two orthogonal power receiving coils or three orthogonal power receiving coils. 
     
     
       5. A powered articulated mechanical joint as claimed in  claim 4  wherein the articulated mechanical joint is a ball and socket joint. 
     
     
       6. A powered articulated mechanical joint comprising:
 a first articulated mechanical joint component mechanically coupled to a second articulated mechanical joint component in which the first articulated mechanical joint component has multiple degrees of rotational freedom with respect to the second articulated mechanical joint component; 
 a plurality of power transmission coils associated with the first articulated mechanical component; 
 one or more power receiving coils associated with the second articulated mechanical component; 
 a sensor that determines the orientation of the second articulated mechanical component with respect to the first articulated mechanical component; and 
 a control circuit for selectively activating one of the plurality of power transmission coils based on information received from the sensor. 
 
     
     
       7. A powered articulated mechanical joint as claimed in  claim 6  wherein the sensor is one of: a gyroscope; an accelerometer; a magnetic field sensor; an IMU; a compass; and a gravity switch. 
     
     
       8. A powered articulated mechanical joint as claimed in  claim 7  including a single power receiving coil. 
     
     
       9. A powered articulated mechanical joint as claimed in  claim 8  including two orthogonal power transmission coils or three orthogonal power transmission coils. 
     
     
       10. A powered articulated mechanical joint as claimed in  claim 9  wherein the articulated mechanical joint is a ball and socket joint. 
     
     
       11. An arrangement for powering a device having free spatial movement in two or more dimensions, the arrangement comprising:
 a powered support connected to two or more relatively moveable elements by a powered articulated mechanical joint, the powered articulated mechanical joint having a first articulated mechanical joint component mechanically coupled to a second articulated mechanical joint component, the first articulated mechanical joint component having multiple degrees of rotational freedom with respect to the second articulated mechanical joint component, the powered articulated mechanical joint further comprising:
 a plurality of power transmission coils associated with the first articulated mechanical joint component; and 
 a plurality of power receiving coils associated with the second articulated mechanical joint component; 
 wherein the transmission and receiving coils are spaced apart and are rotatably movable relative to each other. 
 
 
     
     
       12. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint includes at least two orthogonally arranged power transmission coils and at least two orthogonally arranged power receiving coils. 
     
     
       13. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint includes three orthogonally arranged power transmission coils and three orthogonally arranged power receiving coils. 
     
     
       14. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint has transmission coils arranged on a curved surface. 
     
     
       15. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint has receiving coils arranged on a curved surface. 
     
     
       16. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint includes permanent magnets located within each coil having polarities that maintain respective transmission and receiving coil pairs in alignment. 
     
     
       17. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint includes a pair of transmission coils driven with opposite polarity. 
     
     
       18. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint includes an orientation sensor to power appropriate transmission coils based on the relative orientation of the transmission and receiving coils. 
     
     
       19. An arrangement as claimed in  claim 11  including three relatively movable elements. 
     
     
       20. A powered articulated mechanical joint as claimed in  claim 4  wherein the articulated mechanical joint is a universal joint. 
     
     
       21. A powered articulated mechanical joint as claimed in  claim 9  wherein the articulated mechanical joint is a universal joint. 
     
     
       22. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint is a universal joint. 
     
     
       23. An arrangement as claimed in  claim 11  wherein the powered articulated mechanical joint is a ball and socket joint.

Description:
FIELD 
     The present invention relates to a powered joint having an inductive power transfer (IPT) system. More particularly, although not exclusively, the invention relates to coil and core topologies for use in the transmitters and receivers of such systems. 
     BACKGROUND 
     IPT systems are a well-known area of established technology (for example, wireless charging of electric toothbrushes) and developing technology (for example, wireless charging of handheld devices on a ‘charging mat’). Typically, a primary side generates a time-varying magnetic field from a transmitting coil or coils. This magnetic field induces an alternating current in a suitable receiving coil that can then be used to charge a battery, or power a device or other load. In some instances, it is possible for the transmitter or the receiver coils to be connected with capacitors to create a resonant circuit, which can increase power throughput and efficiency at the corresponding resonant frequency. 
     A basic problem that must be overcome in any IPT system design is ensuring efficient power transfer. One approach to improve performance has been to require precise alignment of the transmitter and receiver coils, such as in the case of wireless charging of electric toothbrushes that use a dedicated charging mount. However, powered joints often require a large range of relative movement between joint components and so such tightly coupled solutions are unsuitable. 
     Powered joints may be employed in applications such as robotics where power transfer is required between the parts of complex articulated joints, including ball joints and universal joints. The use of a wired connection may constrain the range of motion, suffer from failure due to material fatigue, or result in vulnerable and unsightly exterior wiring. Typical IPT systems may not be useful, due to their inability to efficiently supply power over a wide range of movement. 
     US20030214255 discloses that providing a plurality of orthogonal transmitter coils improves the likelihood of a receiver coil intersecting the flux lines of the magnetic field. However, no detail is given as to a suitable receiver coil for this arrangement or how it may be implemented in a powered joint. 
     US20010000960 discloses an array of in-phase spiral current loops disposed adjacent to one another, defining a non-planar surface such as a sphere. However, again no detail is given on a suitable receiver coil arrangement or how it may be implemented in a powered joint. 
     WO2013/141717 discloses a range of transmitter and receiver coil topologies utilizing orthogonal sets of coils but there is no disclosure as to how these may be implemented within a joint. 
     It is an object of the invention to provide a powered joint providing effective power transfer over a wide range of movement, or to at least provide the public with a useful choice. 
     SUMMARY 
     According to one example embodiment there is provided a powered joint having a first joint component and second joint component in which the first joint component has multiple degrees of rotational freedom with respect to the second joint component, the powered joint including:
         one or more power transmission coils associated with the first component;   a plurality of power receiving coils associated with the second component;   a sensor which determines the orientation of the second component with respect to the first component; and   a control circuit for selectively connecting one of the plurality of power receiving coils to a power receiving circuit based on information received from the sensor.       

     According to another example embodiment there is provided a powered joint having a first joint component and second joint component in which the first joint component has multiple degrees of rotational freedom with respect to the second joint component, the powered joint including:
         a plurality of power transmission coils associated with the first component;   one or more power receiving coils associated with the second component;   a sensor which determines the orientation of the second component with respect to the first component; and   a control circuit for selectively connecting one of the plurality of power transmitting coils to a coil drive circuit based on information received from the sensor.       

     According to a further example embodiment there is provided a powered joint having a first joint component and second joint component in which the first joint component has multiple degrees of rotational freedom with respect to the second joint component, the powered joint including:
         one or more power transmission coil associated with the first component; and   one or more power receiving coil associated with the second component,   wherein the receiving coil is spaced away from the transmitting coil and remains generally aligned with a radial line from the center of the transmitting coil throughout the range of movement of the joint.       

     According to another example embodiment there is provided a core formed of a magnetically permeable material comprising an outer partial hemisphere having a central post projecting from the hemisphere towards the center of the hemisphere. 
     According to a still further example embodiment there is provided a powered joint having a first joint component and second joint component in which the first joint component has multiple degrees of rotational freedom with respect to the second joint component, the powered joint including:
         one or more power transmission coils associated with the first component; and   one or more power receiving coil associated with the second component;   wherein each coil has an associated magnet so that proximate transmitter and receiver coil pairs are maintained in alignment due to magnetic attraction between the magnets.       

     According to a yet further example embodiment there is provided a powered joint having a first joint component and second joint component in which the first joint component has multiple degrees of rotational freedom with respect to the second joint component, the powered joint including:
         a plurality of power transmission coils associated with the first component; and   a plurality of power receiving coils associated with the second component;   wherein the transmission and receiving coils are spaced apart and are rotatably movable relative to each other.       

     According to another example embodiment there is provided a powered joint having a first joint component and second joint component in which the first joint component has one or more degrees of rotational freedom with respect to the second joint component, the powered joint including:
         a power transmission coil associated with the first component; and   a power receiving coil associated with the second component   wherein the power receiving coil is moveable with respect to the second component so that it can be maintained in a desired alignment with the power transmission coil.       

     According to a still further example embodiment there is provided an arrangement for powering a device having free spatial movement in two or more dimensions including a powered support connected to two or more relatively moveable elements by a powered joint having a first joint component and a second joint component, the first joint component having multiple degrees of rotational freedom with respect to the second joint component, the powered joint including:
         a plurality of power transmission coils associated with the first component; and   a plurality of power receiving coils associated with the second component;   wherein the transmission and receiving coils are spaced apart and are rotatably movable relative to each other.       

     According to a yet further example embodiment there is provided a powered ball and socket joint having a ball having multiple degrees of rotational freedom with respect to socket, the powered joint including:
         a helically wound power transmission coil provided in the ball; and   a helically wound power receiving coil provided in the socket.       

     It is acknowledged that the terms “comprise”, “comprises” and “comprising” may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, these terms are intended to have an inclusive meaning—i.e., they will be taken to mean an inclusion of the listed components which the use directly references, and possibly also of other non-specified components or elements. 
     Reference to any document in this specification does not constitute an admission that it is prior art, validly combinable with other documents or that it forms part of the common general knowledge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings which are incorporated in and constitute part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of embodiments given below, serve to explain the principles of the invention, in which: 
         FIG. 1A  shows a single transmitter coil and a single receiver coil rotatable with multiple degrees of rotational freedom; 
         FIG. 1B  shows the arrangement of  FIG. 1A  when one coil is rotated with respect to the other; 
         FIG. 2A  shows a coil arrangement consisting of 3 orthogonal receiver coils having multiple degrees of rotational freedom with respect to a spaced apart transmitter coil; 
         FIG. 2B  shows a coil arrangement consisting of 3 orthogonal receiver coils having multiple degrees of rotational freedom with respect to a surrounding transmitter coil; 
         FIG. 2C  shows a coil arrangement consisting of 3 orthogonal receiver coils having multiple degrees of rotational freedom with respect to 3 orthogonal transmitter coils; 
         FIG. 3A  shows a coil arrangement in which several spiral coils are located on the surface of a sphere which moves relative to a single coil; 
         FIG. 3B  shows a coil arrangement in which several spiral coils are located on the surface of a first sphere which moves relative to a second sphere having spiral coils on its surface; 
         FIG. 4A  shows a coil arrangement in which one or more receiver coils are arranged radially around a transmitting coil; 
         FIG. 4B  shows the coil arrangement of the type shown in  FIG. 4A  wherein the transmitting coil has a central transmitter core; 
         FIG. 4C  shows the coil arrangement of the type shown in  FIG. 4A  wherein the transmitting coil has a central transmitter core and the receiving coil includes an arcuate core; 
         FIGS. 5A-5B  show a pot core type arrangement allowing rotation with multiple degrees of rotational freedom; 
         FIGS. 6A-6F  show coil arrangements in which magnets are used to align the transmitter and receiver coils; 
         FIGS. 7A-7C  show powered joints in which helical transmitting and receiving coils are located near the surface of a ball and socket; and 
         FIG. 8  is a diagram of an IPT system in which power is transmitted to a platform using tethers. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  illustrates a coil arrangement  100  including a transmitter coil  101  that receives power from a source (not shown) to generate an alternating magnetic field. A receiving coil  102  is rotatable relative to transmitting coil  101  about its axis  103  and may be tilted as shown in  FIG. 1B . Optimum power transfer occurs when the coils have the highest coupling coefficient in the position shown in  FIG. 1A . However, coupling decreases as the receiving coil  102  is tilted with respect to the transmitting coil  101 , as shown in  FIG. 1B . If the coils  101  and  102  are oriented such that the coupling coefficient is low, then the supplied power will be significantly reduced. While capable of transferring power, this arrangement is not particularly suitable for efficiently supplying constant power to moving components requiring a relatively large degree of rotational freedom. 
     The receiver coil arrangement  202  of  FIG. 2A  has three orthogonal coils. This arrangement allows three degrees of rotational freedom with one receiving coil having good coupling in any position. The arrangement shown in  FIG. 2B  is suitable for use in a ball and socket joint with the transmitter coil housed in the socket and the receiving coil assembly  202  housed within the ball. The arrangement could also be employed in a universal joint. This arrangement ensures that at least one of the receiving coils is sufficiently coupled with the transmitter coil to effectively transfer power in all relative positions. However, to select the best coupled receiving coil may require measurement of the coupling between coils, which may take too long for real world applications. To enable rapid coil switching a sensor  203  may be provided to determine the orientation of the receiver coil arrangement  202  with respect to the transmitter coil  101 . The orientation sensor may be any one of a gyroscope, accelerometer, magnetic field sensor, IMU, compass, gravity switch, or any other appropriate means of determining orientation. Based on the positional information from sensor  203  a controller  204  may selectively connect one of the receiver coils to a power flow controller supplying power to a load on the receiver side of the joint. The controller  204  may store in memory which coil to select based orientation information from the sensor. To improve transfer efficiency additional transmitter and/or receiver coils may also be provided at other angles. 
     A coil arrangement  205  including a three orthogonal transmitter coils  206  and 3 orthogonal receiver coils  207  is shown in  FIG. 2C . As in the previous topology, a suitable orientation sensor  208  may be used to selectively connect one transmitter coil with the best coupled receiver coil. 
     Another way to achieve improved coupling in a device having multiple degrees of rotational freedom is to position a series of spiral transmitter or receiver coils  305  on the surface of a spherical transmitter which is rotatable relative to a transmitter or receiver coil  303  as shown in  FIG. 3A . This type of arrangement may be suitable for a ball and socket joint. A transmitter and receiver pair may be selected or multiple transmitter coils may be driven with opposite polarity to enhance power transfer to a single receiver coil.  FIG. 3B  shows an arrangement where both the transmitter  301  and receiver  302  have an arrangement of helical coils  305  and  304  on their spherical surfaces to enable both rotation and orbiting about each other. 
       FIG. 4A  shows an arrangement that may be particularly suitable for a ball and socket joint where one or more receiver coils  402  are provided in the socket part of a joint and a central transmitter coil  401  is provided in the ball part of the joint. The one or more receiver coils  402  may be arranged in a ring around a central transmitter coil  401  or vice versa. This topology utilizes the fact that transmitter coil  401  produces a generally toroidal magnetic flux (one flux line is indicated at  403 ) and each receiver coil moves generally along these flux lines. In the case of rotation about the axis of the joint the flux is substantially uniform. When the ball is tilted relative to the socket each receiver coil generally follows the flux lines and so remains well coupled to the transmitter coil. This topology thus provides good coupling over a wide range of relative joint movements without requiring coil switching. 
     To further improve coupling a core having high magnetic permeability, such as a ferrite core  403  shown in  FIG. 4B , may be used to shape the magnetic field. The ferrite core  403  extends above and below the coil, and if used in a ball joint, may extend to the periphery of the ball, as shown in  FIG. 4C . Additionally, a ferrite core  404  may extend through coil  402  and around the socket of the ball joint, as shown in  FIG. 4C , such as to maintain only a small air gap between transmitter and receiver ferrites  403  and  404  throughout the range of movement of the joint. The other receiver coils may also have similar ferrites which connect at the top. The placement of the ferrites may be arranged to preferentially power different coils at different joint positions. 
     Another arrangement utilizing ferrites to improve the magnetic coupling is shown in  5 A and  5 B. In this embodiment a pot core type ferrite structure  500  is used including an upper ferrite consisting of a hemispherical part  501  and a central post  502  and a lower ferrite consisting of a hemispherical part  503  and a central post  504 . A transmitter coil  506  is wound about post  504  and a receiver coil  505  is wound about post  502 . In this arrangement the two ferrite sections are free to rotate and tilt with respect to each other, as shown in the tilted view in  FIG. 5B . This arrangement ensures that there is always only a small air gap between posts  502  and  504  and hemispheres  501  and  503  at all times ensuring a high magnetic permeability path in all orientations and thus efficient power transfer in all orientations without the need for any coil switching. 
     An alternative means of maintaining alignment of transmitter and receiver coils may be provided by magnets of opposite polarity associated with transmitting and receiving coils as shown in  FIG. 6A . In this embodiment coil  601  is wound about permanent magnet  603  and coil  602  is wound about permanent magnet  604 . The opposing faces of the permanent magnets have opposite magnetic polarity so that they attract to each other to align the coils. The permanent magnets also provide a high magnetic permeability path for the magnetic flux to improve power transfer. Whilst centralized coil alignment is shown any suitable alignment that assists with power transfer may be employed. 
     This general method of coil alignment is shown in a ball and socket joint in  FIGS. 6B and 6C . In this embodiment coil  602  is mounted in fixed relation to socket  611  near to ball  612 . Coil  601  is provided within a cavity in ball  612  and is free to move relative to ball  612 . The cavity may be empty or filled with a fluid or some other medium. Alternatively coil  601  may be supported by resilient elements which return coil  601  to a centralized position when no external magnetic force is present but allow movement within the cavity. Flexible conductive wires  613  convey power to or from coil  601  whilst allowing relatively free movement of coil  601  within the cavity. Due to magnetic attraction between magnets  603  and  604  coils  601  and  602  are held close and in alignment when ball  612  moves with respect to socket  611 , as illustrated in  FIG. 6C  where coil  601  has moved within the cavity relative to its original position shown in  FIG. 6B . 
       FIGS. 6D and 6E  show an alternate embodiment in which the moveable coil is located in the socket. In this case the arrangement is generally the same as for that shown in  FIGS. 6B and 6C  except that coil  601  is located in a cavity within the socket  611  instead of being within a cavity in the ball.  FIG. 6F  shows a variant of the design shown in  FIGS. 6D and 6E  including resilient elements  614  that act to centralize coil  601  but which stretch to allow coil  601  to follow coil  602  due to the magnetic attraction between magnets. 
       FIGS. 7A to 7C  show a further coil arrangement for a ball and socket joint utilizing helical coils  701  and  702  wound close to the surface of each of the ball  712  and socket  711 . A cutaway view of the socket with the ball inserted is shown in  FIGS. 7A and 7B  (i.e. a similar helically hound winding is provided in the socket but only the cross-sections of the windings are visible). A top view of a helical coil  701  is shown in  FIG. 7C . Due to the distribution of the helical windings over the ball and socket effective power transfer may be achieved over a relatively large range of movement as shown in  FIG. 7B . 
       FIG. 8  shows a system to provide power wirelessly through tethers  815  to a hanging device or platform  816 , allowing the device or platform  816  to rotate with respect to the tethers  815 . A pair of IPT ball connectors  801  and  802 , such as those shown in  FIG. 2C , are held in place by a joint (not shown) that maintains a fixed separation while allowing the ball connectors  801  and  802  to rotate with multiple degrees of rotational freedom. One example of a suitable application for this arrangement is a delta robot, commonly used in  3 D printers, where a heated nozzle is positioned typically using three tethers moving up and down on belts attached to fixed support poles. The heated nozzle requires power to heat it, and the use of such an inductive power transfer system  800  may reduce wear on electronic components. 
     The described coil arrangements provide good inductive coupling in mechanical joints. While embodiments have been described with reference to a particular joint configuration, they could also be applied to other systems having multiple degrees of rotational freedom that would benefit from the simplicity of wireless power transfer. These applications include, but are not limited to robotics, prosthetics, industrial automation, household and industrial appliances and toys. 
     While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the Applicant&#39;s general inventive concept.

Metadata:
Filing Date: 20181127
Publication Date: 20210831
Grant Date: 20210831
Priority Date: 20160601
Inventors: MISHRIKI, FADY
DELA CRUZ, Lawrence Bernardo
ROBERTSON, DANIEL JAMES
TERRY, John Kinnear
REN, SAINING
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J50/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "B25J17/0275", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/0081", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/0037", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "B25J17/0275", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J50/90", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B5/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/79", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B5/79", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 60478838