Dual motor input in friction drive systems

Abstract

A drive system, a robot incorporating the drive system, and a method for operating the drive system are disclosed herein. A drive system can include a friction drive set, a first motor, and a second motor. The friction drive set can have a sun member centered on a longitudinal axis, a plurality of planet members, a first ring member surrounding and engaged with each of the plurality of planet members, and a second ring member surrounding and engaged with each of the plurality of planet members and adjacent to the first ring member along the longitudinal axis. The first and second motors can have respective stators and rotors. The first rotor can be engaged for substantially concurrent rotation with the first ring member. The second rotor can be engaged for substantially concurrent rotation with the sun member.

Description

DUAL MOTOR INPUT IN FRICTION DRIVE SYSTEMSBACKGROUND1. Field

[0001] The present disclosure relates to drive systems, especially systems in which an input is directed into a friction drive set and produces an output from the friction drive set.2. Description of Related Prior Art

[0002] U.S. Pub. No. 2012 / 0035014 discloses TRANSMISSION SYSTEMS. The transmission systems includes an input (22), an output (34) and an epicyclic geartrain comprising first and second gearsets. The first gearset comprises a first sun gear (2) in mesh with a set of first planet gears (4), which are rotatably carried by a first planet carrier (6) and are in mesh with a first annulus gear (8). The second gearset comprises a second sun gear (10), which is connected to rotate with the first sun gear (2) and is in mesh with a set of second planet gears (12), which are rotatably carried by a second planet carrier (14) and are in mesh with a second annulus gear (18). One of the planet carriers (6) of one of the gearsets is connected to rotate with the annulus gear ( 18) of the other gearset. The two connected sun gears (2), (10) and the input (22) are connected to the rotors (24, 20) of respective electric motor generators (E2, El), the electrical stator connections of which are connected together via a controller (30) arranged to control the flow of electrical power between them. The input (22) is selectably connectable to the other (14) of the planet carriers and to the other (8) of the annulus gears by first (C2) and second (Cl) selectably operable clutches, respectively, whereby the transmission system has two regimes. FIG. 2 of the ‘014 publication discloses an embodiment in which two motor / generators are nested within one another and the rotor 20 of El is situated outside the stator 26 and not inside it.

[0003] U.S. Pat. No. 11002345 discloses a Compound Planetary Friction Drive comprising a first sun wheel (2) and planetary wheels (3), wherein said first sun wheel (2) engages said planetary wheels (3), which planetary wheels (3) are arranged with two outer parts (3b) having a first radius (rl) and a central part (3a) having a second radius (r2), wherein the second radius (r2) differs from the first radius (rl) and transition regions (3c) are provided between the outer parts (3b) and the central part (3a), and wherein an outer ring annulus (1) and a central ring annulus (5) are provided that are in driving engagement with the planetary wheels (3), wherein the outer ring annulus (1) has two parts between which, along the length of the planetary wheels (3), the central ring annulus (5) is disposed, wherein the first sun wheel (2) is in frictional engagement with the outer parts (3b) of the planetaryAtty Ref: 112540-0010. WO1 - 1 -wheels (3), said outer parts (3b) of the planetary wheels (3) are in frictional engagement with the parts of the outer ring annulus (1) and the central ring annulus (5) is in frictional engagement with the central part (3a) of the planetary wheels (3), wherein the planetary wheels (3) are both hollow and compressible uninterruptedly along their entire length spanning the outer parts (3b), the transition regions (3c) and the central part (3a).

[0004] The background description provided herein is for the purpose of generally presenting background context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.SUMMARY

[0005] This section provides a simplified summary in order to provide a basic understanding of some aspects described herein. This summary is not an extensive overview and is not intended to identify “key” or “critical” elements of the present disclosure or to delineate the scope of the various aspects described herein. The purpose of this portion of the document is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0006] A drive system can include a friction drive set, a first motor, and a second motor. The friction drive set can have a sun member having an annular outer periphery centered on a longitudinal axis. The friction drive set can also have a plurality of planet members each engaged with the annular outer periphery and spaced from one another about the longitudinal axis. The friction drive set can also have a first ring member surrounding and engaged with each of the plurality of planet members. The friction drive set can also have a second ring member surrounding and engaged with each of the plurality of planet members and adjacent to the first ring member along the longitudinal axis. The first motor can have a first stator and a first rotor and can be centered on the longitudinal axis. The second motor can have a second stator and a second rotor and can be centered on the longitudinal axis. The first rotor can be engaged with the first ring member for substantially concurrent rotation with the first ring member. The second rotor can be engaged with the sun member for substantially concurrent rotation with the sun member.

[0007] According to other features, the second ring member can extend along the longitudinal axis between a first side and a second side. The first side of the second ring member can be directed toward the first stator along the longitudinal axis. The first side can be closer to the first stator than the second side along the longitudinal axis. A mechanical interconnection between the first rotor andAtty Ref: 112540-0010. WO1 - 2 -the first ring member may not extend past the second side of the second ring member. The first rotor can be connected to a radially-outer surface of the first ring member. The second ring member and the first rotor can be spaced from one another along the longitudinal axis.

[0008] In other features, the first ring member can include a first portion and a second portion. The second ring member can extend along the longitudinal axis between a first side and a second side. The second side of the second ring member can be directed away from the first stator along the longitudinal axis. The first side can be closer to the first stator than the second side along the longitudinal axis. The second ring member can be positioned between the first portion of the first ring member and the second portion of the first ring member along the longitudinal axis. A mechanical interconnection between the first rotor and the first ring member may not extend past or overlap the second ring member along the longitudinal axis. The drive system can also include an output member engaged with the second ring member for concurrent rotation, wherein the output member can be positioned only on the second side of the second ring member along the longitudinal axis.

[0009] According to additional features, the drive system can also include a heat transfer member positioned radially between the first stator and the second stator. The first stator and the second stator can share a plurality of stator laminations. Each of the plurality of stator laminations can have a first set of stator teeth facing radially outwards and supporting a first winding for driving the first rotor. Each of the plurality of stator laminations can also have a second set of stator teeth facing radially inwards and supporting a second winding for driving the second rotor.

[0010] According to other features, the drive system can also include at least one brake selectively engageable with one of the first rotor and the second rotor to selectively inhibit rotation of the one of the first rotor and the second rotor. The first motor and the second motor can be positioned between the first friction drive set and the at least one brake. The at least one brake can be further defined as a first brake that can be selectively engageable with the first rotor to selectively inhibit rotation of the first rotor and a second brake that can be selectively engageable with the second rotor to selectively inhibit rotation of the second rotor.

[0011] In other features, the second motor can be further defined as nested within the first motor.

[0012] According to additional features, neither the first ring member and the second member may be grounded.

[0013] A robot can include a base, a first drive system, and a first link. The first drive system can be positioned on the base. The first drive system can have a friction drive set having a sun memberAtty Ref: 112540-0010. WO1 - 3 -having an annular outer periphery centered on a first longitudinal axis. The friction drive set can also have a plurality of planet members each engaged with the annular outer periphery and spaced from one another about the first longitudinal axis. The friction drive set can also have a first ring member surrounding and engaged with each of the plurality of planet members. The friction drive set can also have a second ring member surrounding and engaged with each of the plurality of planet members and adjacent to the first ring member along the first longitudinal axis. The first motor can have a first stator and a first rotor and can be centered on the first longitudinal axis. The second motor can have a second stator and a second rotor and can be centered on the first longitudinal axis. The first rotor can be engaged with the first ring member for substantially concurrent rotation with the first ring member. The second rotor can be engaged with the sun member for substantially concurrent rotation with the sun member. The first link can be rotatably mounted on the base and can be engaged with the second ring member whereby the first drive system is configured to rotate the first link about the first longitudinal axis.

[0014] According to other features, the robot can also include a second drive system and a second link. The second drive system can be positioned on the first link and can have a friction drive set. The friction drive set can have a sun member having an annular outer periphery centered on a second longitudinal axis. The friction drive set can also have a plurality of planet members each engaged with the annular outer periphery of the sun member of the second drive system and spaced from one another about the second longitudinal axis. The friction drive set can also have a first ring member surrounding and engaged with each of the plurality of planet members of the second drive system. The friction drive set can also have a second ring member surrounding and engaged with each of the plurality of planet members of the second drive system and adjacent to the first ring member of the second drive system along the second longitudinal axis. The first motor can have a first stator and a first rotor and can be centered on the second longitudinal axis. The second motor can have a second stator and a second rotor and can be centered on the second longitudinal axis. The first rotor of the second drive system can be engaged with the first ring member of the second drive system for substantially concurrent rotation with the first ring member of the second drive system. The second rotor of the second drive system can be engaged with the sun member of the second drive system for substantially concurrent rotation with the sun member of the second drive system. The second link can be rotatably mounted on the base and can be engaged with the second ring member of the second drive system whereby the second drive system is configured to rotate the second link about the second longitudinal axis. The second longitudinal axis can be transverse to the first longitudinal axis.Atty Ref: 112540-0010. WO1 - 4 -

[0015] A method of operating a robot can include driving a first link of the robot which is rotatably mounted on a base of the robot. The driving can include controlling, with a controller, a first motor, positioned on the base and centered on a first longitudinal axis, to rotate a first rotor of the first motor in a first direction at a first speed of rotation. The driving can also include controlling, with the controller, a second motor, positioned on the base and centered on the first longitudinal axis, to rotate a second rotor of the second motor in a second direction at a second speed of rotation. The first rotor can be mechanically coupled to the first link through a first ring member of a friction drive set positioned on the base. The second rotor can be mechanically coupled to the first link through a sun member of the friction drive set.

[0016] In other features, the driving can be further defined as driving the first link at a third speed by the controlling the first motor and the controlling the second motor being further defined such that the first direction and the second direction are the same.

[0017] According to additional features, the driving can be further defined as driving the first link at a fourth speed less than the third speed by the controlling of the first motor further defined such that the first speed is zero revolutions per minute and the controlling of the second motor further defined such that the second speed is greater than zero revolutions per minute.

[0018] According to other features, the driving can be further defined as driving the first link at a fifth speed less than the fourth speed by one of the controlling of the first motor further defined such that the first speed is greater than zero revolutions per minute and the controlling the second motor is further defined such that the second speed is zero revolutions per minute or the controlling of the first motor and the controlling the second motor further defined such that the first direction and the second direction are opposite to one another.

[0019] In other features, the method can further include driving a second link that is mounted upon the link. The driving of the second link can include controlling, with the controller, a third motor, positioned on the link and centered on a second longitudinal axis, to rotate a third rotor of the third motor in a third direction at a third speed of rotation. The driving of the second link can also include controlling, with the controller, a fourth motor, positioned on the link and centered on the second longitudinal axis, to rotate a fourth rotor of the fourth motor in a fourth direction at a fourth speed of rotation. The third rotor can be mechanically coupled to the second link through a first ring member of a second friction drive set positioned on the link. The fourth rotor can be mechanically coupled to the second link through a second sun member of the second friction drive set. The second longitudinal axis can be transverse to the first longitudinal axis.Atty Ref: 112540-0010. WO1 - 5 -BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The detailed description set forth below references the following drawings:

[0021] Figure 1 is a schematic cross-section of a drive system according to an exemplary embodiment of the present disclosure; and

[0022] Figure 2 is a schematic view of a robot incorporating drive systems as disclosed in Figure 1.DETAILED DESCRIPTION

[0023] A plurality of different embodiments of the present disclosure is shown in the Figures of the application. Similar features are shown in the various embodiments of the present disclosure. Similar features across different embodiments have been numbered with a common reference numeral and have been differentiated by an alphabetic suffix. Also, to enhance consistency, the structures in any particular drawing share the same alphabetic suffix even if a particular feature is shown in less than all embodiments. Similar features are structured similarly, operate similarly, and / or have the same function unless otherwise indicated by the drawings or this specification. Furthermore, particular features of one embodiment can replace corresponding features in another embodiment or can supplement other embodiments unless otherwise indicated by the drawings or this specification.

[0024] The present disclosure, as demonstrated by the exemplary embodiments, described below, can provide a drive system, a robot incorporating the drive system, and methods for operating the drive system. The drive system can provide a continuously variable motion transmission ratio. The exemplary embodiments include a friction drive set.

[0025] The exemplary drive system applies a co-axial motor approach wherein a first motor can be an outer rotor BLDC (brushless direct current) motor coupled to a first ring member of a friction drive set and a second motor can be an inner rotor BLDC motor coupled to the sun member of the friction drive set. The first and second motors can be in a co-axial and nested relationship with one another wherein the stator of the sun motor occupies an inside diameter of the stator of the ring motor. In various embodiments, such as those exemplary embodiments disclosed herein, a second ring member of the friction drive set can be the output.

[0026] Referring now to Figure 1, an exemplary drive system 10 can include an exemplary friction drive set 12. The exemplary friction drive set 12 includes an exemplary sun member 14 having an annular outer periphery 106 centered on a longitudinal axis 30. The exemplary friction drive set 12 includes an exemplary idling hollow second sun wheel 15. The exemplary friction driveAtty Ref: 112540-0010. WO1 - 6 -set 12 also includes an exemplary first ring member (or first ring roller or outer ring annulus) 16. The exemplary first ring member 16 includes a first portion 108 and a second portion 110.

[0027] The exemplary friction drive set 12 also includes a plurality of planet members (or rollers or planetary wheel), such as planet members 18, 20. The exemplary plurality of planet members each engaged with the annular outer periphery 106 and spaced from one another about the longitudinal axis 30. The exemplary planet members 18, 20 are positioned operably between the exemplary sun member 14 and the exemplary first ring member 16. The exemplary first ring member 16 surrounds and is engaged with each of said plurality of planet members.

[0028] The exemplary friction drive set 12 also includes an exemplary second ring member (or second ring roller or central ring annulus) 22 engaged with each of the first plurality of exemplary planet members 18, 20. The exemplary second ring member 22 surrounds and is engaged with each of the plurality of planet members. The exemplary second ring member 22 is adjacent to the first ring member 16 along the longitudinal axis and between the exemplary first and second portions 108, 110.

[0029] It is noted that the sun member, planet members, and first and second ring members can engage one or more other of the members through traction grease and / or friction between respective mating surfaces to transmit rotation, as disclosed in US11002345, which is hereby incorporated by reference in its entirety. US10041581 is also hereby incorporated by reference in its entirety as an alternative friction drive system.

[0030] The exemplary drive system 10 also includes an exemplary first motor 24. The exemplary first motor 24 has an exemplary first stator 26. The exemplary first motor 24 also has an exemplary first rotor 28. The exemplary second ring member 22 and the exemplary first rotor 28 are spaced from one another along the longitudinal axis 30. The exemplary first motor 24 is centered on an exemplary first longitudinal axis 30.

[0031] The exemplary drive system 10 also includes an exemplary second motor 32. The exemplary second motor 32 has an exemplary second stator 34. The exemplary second motor 32 also has an exemplary second rotor 36. The exemplary second motor 32 is centered on the exemplary first longitudinal axis 30. The exemplary second motor 32 is nested within the exemplary first motor 24.

[0032] The exemplary first rotor 28 is engaged with the exemplary first ring member 16 for substantially concurrent rotation with the exemplary first ring member 16. The exemplary second rotor 36 is engaged with the exemplary sun member 14 for substantially concurrent rotation with the exemplary sun member 14.

[0033] As is known, slip is possible in friction drives in contrast to “engagement” or “positive” drives, such as drives that include gears. It is therefore noted that substantially concurrentAtty Ref: 112540-0010. WO1 - 7 -rotation is rotation as the frictional characteristics of the members used in an exemplary embodiment of the present disclosure permit. While, in the exemplary embodiment, slip is not a consideration between the members 14 and 16, it is a consideration in the engagement between member 14 and members 18 and 20, between members 18 and 20 and members 16 and 110, and between members 18 and 20 and member 22.

[0034] Figure 1 also shows the exemplary friction drive set 12, the exemplary first motor 24, and the exemplary second motor 32 are contained in an interior of an exemplary housing 38. The interior of the exemplary housing 38 can be closed at one end by an exemplary cover 40. The exemplary drive system 10 also includes various bearings, which are illustrated in Figure 1 as blocks, such as referenced at 44 and 46. Figure 1 also shows an exemplary output member 48 fixed for concurrent rotation with the exemplary second ring member 22. Figure 1 also shows an exemplary shaft 50 fixed for concurrent rotation with the exemplary second rotor 36. Figure 1 also discloses a seal 42 to close off the inside of the housing 38. The seal 42 is optional and may only be necessary in some applications while other applications may benefit from eliminating the drag that a seal can add into the system dynamics.

[0035] As is also shown in Figure 1, the exemplary second ring member 22 extends along the exemplary first longitudinal axis 30 between an exemplary first side 52 and an exemplary second side 54. The exemplary first side 52 of the exemplary second ring member 22 is directed toward the exemplary first stator 26 along the exemplary first longitudinal axis 30. The exemplary first side 52 is closer to the exemplary first stator 26 than the exemplary second side 54 along the exemplary first longitudinal axis 30.

[0036] As is also shown in Figure 1, a mechanical interconnection between the exemplary first rotor 28 and the exemplary first ring member 16 does not extend past the exemplary second side 54 of the exemplary second ring member 22 or overlap the second ring member 22. A mechanical interconnection can include a direct connection in various embodiments of the present disclosure. A mechanical interconnection of the present disclosure can also include an indirect connection. In the exemplary embodiment shown in Figure 1, the mechanical interconnection is an indirect connection between the exemplary first rotor 28 and a radially-outer side 56 of the exemplary first ring member 16, through an exemplary ring 112. In other embodiments, a direct mechanical interconnection can be defined by the exemplary first rotor 28 and the exemplary first ring member 16. Arranging the mechanical interconnection between the exemplary first rotor 28 and the exemplary first ring member 16 such that it does not extend past the exemplary second side 54 of the exemplary second ringAtty Ref: 112540-0010. WO1 - 8 -member 22 or overlap the second ring member 22 along the longitudinal axis 30 makes embodiments of the present disclosure more compact, which in turn increases the torque density of the system.

[0037] In the exemplary embodiment, the exemplary first ring member 16 and the exemplary second ring member 22 can be permitted to idle. In the exemplary embodiment, only the exemplary stators 26, 34 are grounded.

[0038] The exemplary output member 48 is engaged with the exemplary second ring member 22 for concurrent rotation. In other words, the two components rotate together. The exemplary output member 48 is positioned only on the exemplary second side 54 of the exemplary second ring member 22 along the exemplary first longitudinal axis 30. The exemplary output member 48 and the exemplary second ring member 22 are engaged to one another by being separately-formed and subsequently joined together. In other embodiments, the exemplary output member 48 and the exemplary second ring member 22 can be engaged to one another by being integrally-formed.

[0039] The exemplary drive system 10 also includes an exemplary heat transfer member 60. The exemplary heat transfer member 60 is positioned radially between the exemplary first stator 26 and the exemplary second stator 34. The exemplary heat transfer member 60 is tube-shaped, having a radially-inner side 62 and a radially-outer side 64 and extending along the exemplary first longitudinal axis 30 between a first end 66 and a second end 68. The exemplary heat transfer member 60 is configured to redirect heat flow from a radial direction from the laminations of the exemplary first stator 26 and the exemplary second stator 34 into an axial direction along the exemplary first longitudinal axis 30, to direct heat axially to an exemplary heat sink 70.

[0040] A heat transfer member included in one or more embodiments of the present disclosure could be solid or fully or partially hollow, with one or more input ports and one or more output ports, to allow for the passage of a flowable liquid or gas heat exchange medium. The exemplary heat transfer member 60 is solid. A heat transfer member included in one or more embodiments of the present disclosure could be formed from one or more various materials, including copper, aluminum, or a thermally conductive epoxy. A heat transfer member included in one or more embodiments of the present disclosure could be some combination of materials, such as by way of example and not limitation, a copper ring with some flowable thermally conductive material on both the outer diameter and inner diameter of the copper ring to ensure optimal heat transfer from the lamination into the copper and subsequently into the heat sink.

[0041] In one or more embodiments of the present disclosure, the first stator and second stator could share a plurality of stator laminations. Each of such stator laminations would have a first set of stator teeth facing radially outwards and supporting a first winding for driving the exemplary firstAtty Ref: 112540-0010. WO1 - 9 -rotor 28. Each of such stator laminations would also have a second set of stator teeth facing radially inwards and supporting a second winding for driving the exemplary second rotor 36. In such embodiments, a heat transfer member could include a plurality of discrete tubes positioned equidistantly about the longitudinal axis 30 and extending through apertures defined in the shared stator laminations.

[0042] The exemplary drive system 10 also includes at least one brake selectively engageable with one of the exemplary first rotor 28 and the exemplary second rotor 36 to selectively inhibit rotation of the one of the exemplary first rotor 28 and the exemplary second rotor 36. In the exemplary embodiment, the exemplary drive system 10 includes a first brake 72 selectively engageable with the exemplary first rotor 28 to selectively inhibit rotation of the exemplary first rotor 28. In the exemplary embodiment, the exemplary drive system 10 also includes a second brake 74 selectively engageable with the exemplary second rotor 36 to selectively inhibit rotation of the exemplary second rotor 36. The exemplary first motor 24 and the exemplary second motor 32 are positioned between the exemplary friction drive set 12 set and the brake 74. Either or both of the exemplary brakes 72, 74 can be an inductive brake, a pin-style brake wherein a linear motion enabled by a solenoid, or similar, brings a pin coupled to the chassis into engagement with the moving members, or an electrostatic brake as detailed in US 10355624 and US2024 / 0213892, which are hereby incorporated by reference.

[0043] An output brake, or brake engageable with the output 48, is not disclosed due to one of the primary features derived from the friction drive itself, a slip torque condition. This is a design parameter in a friction drive that permits a slipping action to occur between the input and output members wherein the friction drive is not transmitting torque but is permitted to slip. When a brake is applied to the output it could be detrimental to the ability to realize the slip torque feature. However, it is valuable in some cases to add an output brake wherein the slip torque feature could be selectively disabled during some part of the operation of the larger system or in the case that some applications of the final system benefit from the slip torque feature and some do not. In these cases, the output brake is included and only used when desired. Likewise, the ring and sun brakes are only necessary to enable ring and sun modes and to prevent back-drivability. If, in a particular embodiment, the mode of operation will only involve both motors rotating in the same direction or if the motors themselves will be used as the brake, then extraneous brakes could be eliminated.

[0044] As is also shown in Figure 1, exemplary drive system 10 also includes a support structure 78 that supports the exemplary brake 72. The exemplary support structure 78 also supports an exemplary encoder 80 of the exemplary drive system 10. The exemplary encoder 80 is configured to sense the rotational position and velocity of the exemplary first rotor 28. The exemplary driveAtty Ref: 112540-0010. WO1 - 10 -system 10 also includes an exemplary encoder 82 configured to sense the rotational position and velocity of the exemplary second rotor 36. One or both of the encoders 80, 82 can be one of many commonly available technologies used in the art. One example is a capacitive encoder that is disclosed in US6492911 which is hereby incorporated by reference. In addition, optical, magnetic, and inductive encoders are possible options as well.

[0045] The exemplary drive system 10 also includes an exemplary controller 86. The exemplary controller 86 is configured to receive signals from the exemplary encoders 80, 82. The exemplary controller is also configured to control the operation of the first motor 24, the second motor 32, and the brakes 72, 74. An exemplary controller that can be utilized in the exemplary embodiments disclosed herein can be Texas Instruments F2800137PT, but other commercially available microcontrollers could be selected. The operation of the exemplary drive system 10 will be described in greater detail below.

[0046] Figure 2 discloses an exemplary robot 88 having an exemplary base 90, an exemplary first link 92, and the first exemplary drive system 10. The first exemplary drive system 10 is positioned in the exemplary base 90. The exemplary first link 92 is engaged with the exemplary second ring member 22 and for concurrent rotation and is rotatable relative to the exemplary base 90 about an axis 114. The exemplary output member 48 may define a portion of the first link 92. The exemplary robot 88 includes an exemplary second link 94 rotatably engaged with the exemplary first link 92 about an exemplary axis 116, an exemplary third link 96 rotatably engaged with the exemplary second link 94 about an exemplary axis 118, and an exemplary fourth link 98 rotatably engaged with the exemplary third link 96 about an exemplary axis 120. Figure 2 also discloses that the exemplary robot 88 has exemplary drive systems 110, 210, and 310 respectively positioned drive the links 94, 96, 98 in rotation. The exemplary drive systems 10, 110, 210, 310 are identical. However, it is noted that in one or more other embodiments of the present disclosure the drive systems 10, 110, 210, 310 would not necessarily be identical and can be smaller or larger relative to one another based on the requirement of the joint. In an industrial robot, the lower the joint is in the kinematic structure, the larger and more powerful it is, typically. Therefore, drive system 310 can be smaller than drive system 10. In addition, not all joints my include a drive system with a brake. The exemplary robot 88 is an arm but the present disclosure is not limited to robotic arms and can be applied to robots that do take forms other than an arm.

[0047] Figure 2 also discloses an exemplary controller 100 of the exemplary robot 88. The exemplary controller 100 can be configured to execute control over the exemplary drive systems 10, 110, 210, 310 and the respective controller of each of the exemplary drive systems 10, 110, 210, 310.Atty Ref: 112540-0010.W01 - 11 -The Texas Instruments F2800137PT or another commercially available microcontroller could be utilized as the exemplary controller 100. The exemplary controller 100 can be separate from exemplary controllers 86, wherein each exemplary drive system 10, 110, 210, 310 can have a controller 86 that communicates to controller 100 or controller 100 can include the elements of controller 86 within it wherein controller 100 has direct access to each motor, brake, and controller for two or more drives.

[0048] A method of operating the exemplary robot 88 can include driving the exemplary first link 92. It is noted that the following description for driving the exemplary first link 92 is applicable for driving any of the other links 94, 96, 98 as well. The step / operation of the driving can include controlling, with the controller 86 or the controller 100, the exemplary first motor 24 to rotate the exemplary first rotor 28 in a first direction at a first speed of rotation. The step / operation of the driving can include controlling, with the controller 86 or the controller 100, the exemplary second motor 32 to rotate the exemplary second rotor 36 in a second direction at a second speed of rotation.

[0049] The exemplary first motor 24 can be designed to run optimally within a first speed range and the exemplary second motor 32 can be designed to run optimally within a second speed range. The first and second speed ranges can be independent of one another.

[0050] The exemplary link 92 can be driven at a relatively high speed by controlling the exemplary first motor 24 and controlling the exemplary second motor 32 such that the first direction and the second direction are the same. In other words, the exemplary sun member 14 and exemplary ring member 16 are rotated in the same direction. The exemplary sun member 14 and exemplary ring member 16 are additive with respect to one another and working together. This permits a high-speed range by permitting both motors 24, 32 to supply torque to the output at a smaller gear ratio resulting in higher speeds (herein referenced as support mode).

[0051] The exemplary link 92 can be driven at a relatively medium speed (less than high speed) by controlling the exemplary first motor 24 such that the first speed is zero revolutions per minute controlling the exemplary second motor 32 such that the second speed is greater than zero revolutions per minute. Thus, the first rotor 28 can be held stationary while the second rotor 36 can be rotated. For medium speed, the first rotor 28 can be stopped with the brake 72. The second rotor 36 would thus carry the load and supply all of the torque to the output member 48. This “medium” speed range can end when the second motor 32 reaches its top efficient speed.

[0052] The exemplary link 92 can be driven at a relatively low speed (less than medium speed) by alternative approaches. In one approach, the first motor 24 can be controlled such that the first speed is greater than zero revolutions per minute and the second motor 32 can be controlled such thatAtty Ref: 112540-0010.W01 - 12 -the second speed is zero revolutions per minute. Thus, the first rotor 28 can be rotated while the second rotor 36 can be held stationary (herein referenced as ring mode). The second rotor 36 can be held stationary by engaging the brake 74.

[0053] In a second approach for “low” speed, the first motor 24 and the second motor 32 can be controlled such that the rotors 28 and 36 are rotated in opposite directions (herein referenced as ring subtract mode). This effectively increases the gear ratio and permits both motors to run in their more efficient speed range.

[0054] The present disclosure also contemplates that any of the motors can operate as a generator in response to various conditions in an operating environment. By way of example and not limitation, in the ring subtract mode or a sun subtract mode, one motor is operating in a direction that is opposite to the direction of the other motor and one of the motors is thus removing energy from the rotating system. This energy can flow through the controller and back into a power source to achieve good efficiency. To practice this mode of operation, both motors be configured to be capable of operating as a generator and, in addition, the controller can be configured to be capable of passing energy from the motors to the power source. In addition, there are modes of operation contemplated by the present disclosure wherein both motors can be operated as a generator to actively apply braking force to the robot. In such a case, both motors are generators and supply energy through the controller to the power source.

[0055] In various embodiments of the present disclosure, the two motors can operate in all modes, dynamically switching from one to another based on many factors in the system including torque, speed, remaining battery life, predicted possible failures in one of the two motors or their associated drives, supply voltage level, and thermal state of the motors and drives, to name a few.

[0056] Embodiments of the present disclosure can be applied as single or dual input and a single output, with the remaining elements permitted to idle. In the context of a multi-stage friction drive, the output can be coupled to the last stage ring roller, the two inputs can be coupled to the first stage sun roller and ring roller, and the remaining drive components permitted to idle. In addition, while the traditional gearboxes in the industry are often defined by a gear ratio (speed and torque ratio of the input to the output), a friction drive has no gears but still has a ratio better defined as a drive ratio which is the input member speed to the output member speed regardless of the number of stages within the friction drive.

[0057] As used herein, “sun mode” refers to the exemplary second rotor 36 (connected to the sun) carrying the load and supplying all torque to the output. As used herein, “support mode” refers to the exemplary first rotor 28 and the exemplary second rotor 36 rotating in the same direction andAtty Ref: 112540-0010.W01 - 13 -both supplying torque to the output at a smaller drive ratio, resulting in higher speeds. The speed range when operating in sun mode can extend to an upper limit wherein the sun motor reaches its top efficient speed.

[0058] As used herein, “ring mode” refers to the exemplary second rotor 36 being locked (such as by the exemplary brake 74) and the first rotor carrying the load and supplying all torque to the output. As used herein, “sun subtract mode” or “ring subtract mode” refers to the exemplary first rotor 28 and the exemplary second rotor 36 rotating in opposite directions. The designator “sun” or “ring” differentiates between which rotor is providing the direction of rotation. For example, in sun subtract mode the exemplary first rotor 28 is providing the output direction of rotation and the exemplary second rotor 36 (connected to the sun) is rotating in an opposite direction and is thus subtracting from the overall transmission of rotation. When operating in subtract mode, the motor associated with subtracting can function as a generator and transfer energy back to the power supply.

[0059] In the disclosed, exemplary embodiments, the modes of operation can tend towards the sun mode and the support mode and can tend away from ring mode, sun subtract mode, and ring subtract mode. This can be accomplished by selecting a drive ratio that is higher than what would typically be used in the operating environment. For example, if an exemplary robotic joint is typically using a 100: 1 gear ratio with a prior art gear system or a 100: 1 drive ratio in a prior art friction drive system, an embodiment of the present disclosure could select a multi-stage friction drive ratio of 150: 1 or 200: 1 such that the typical operating range of the system is in the most efficient space for both motors. Furthermore, this drive ratio selection can take into account the specific torque requirements at specific speeds. In the context of a humanoid exemplary robot, the hip joint must be rated for a specific torque at low speeds to accomplish carrying a heavy payload. An embodiment of the present disclosure can be designed then to achieve that requirement with a drive ratio that would be much higher than expected because both motors would contribute to the output torque in order to achieve the highest torque density in the system. However, while being capable of efficiently achieving the rated torque for carrying the heavy payload, the embodiment of the present disclosure could also achieve an even higher torque at lower speeds for some type of exemplary robot overload mode. In addition, while not capable in presently-known robots, the system of the present disclosure would permit a much higher speed to be achieved when the payload is not present. In the context of a humanoid exemplary robot, when not loaded up, an exemplary robot according to the present disclosure could achieve relatively faster running speeds by utilizing the disclosed system in one or more joints. Another example would include very fast motions in the arm of a humanoid when performing dexterous operations with a tool or similar effector. An exemplary robot arm designed toAtty Ref: 112540-0010.W01 - 14 -handle heavy payloads is typically slow and operating a tool such as a screwdriver is slow in practice. An exemplary robot arm joint or joints could be produced by the present disclosure to permit the same heavy payload handling capability while also permitting very fast dexterous operation.

[0060] The present disclosure contemplates engaging either motor to the planetary members 18, 20. Such engagement can involve coupling of one of the motors to the rotating combination of these members. In a planetary drive, a structure that couples to the rotating combination of planet members is referred to as a carrier, but the exemplary system 10 does not include a carrier. The inventor contemplates a carrier-like structure that would couple the members 18, 20 to one of the motors, instead of that motor being coupled to the sun member or to the first ring member.

[0061] What has been described above includes examples of the subject innovation. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the disclosed subject matter, but many further combinations and permutations of the subject innovation are possible. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein is intended merely to be illustrative and does not pose a limitation on the scope of any innovation disclosed herein unless otherwise claimed. The word “exemplary” is used to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word “exemplary” is intended to present concepts in a concrete fashion. Further, any statements set forth within the Detailed Description of this document and addressing a prior art device(s) are the observations of the inventor and such statements themselves are not prior art or admissions as to what is prior art.

[0062] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Unless indicated otherwise by context, the term “or” is to be understood as an inclusive “or.” Terms such as “first”, “second”, “third”, etc. when used to describe multiple devices or elements, are so used only to convey the relative actions, positioning and / or functions of the separate devices, and do not necessitate either a specific order for such devices or elements, or any specific quantity or ranking of such devices or elements. Use of the terms “about” or “approximately” are intended to cover values that are above and / or below a stated value or range, or within manufacturing tolerances, as would be understood by one having ordinary skill in the art in the respective context. In some instances, this may encompass values in a range of approx. + / -10%; in other instances there may be encompassed values in a range of approx. + / -5%; in yet other instances values in a range of approx. + / -2% may be encompassed; and in yet further instances, this may encompass values in a range of approx. + / -!%.Atty Ref: 112540-0010.W01 - 15 -

[0063] It will be understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof, unless indicated herein or otherwise clearly contradicted by context. Recitations of a value range herein, unless indicated otherwise, serves as a shorthand for referring individually to each separate value falling within the stated range, including the endpoints of the range, each separate value within the range, and all intermediate ranges subsumed by the overall range, with each incorporated into the specification as if individually recited herein. Unless indicated otherwise, or clearly contradicted by context, methods described herein can be performed with the individual steps executed in any suitable order, including: the precise order disclosed, without any intermediate steps or with one or more further steps interposed between the disclosed steps; with the disclosed steps performed in an order other than the exact order disclosed; with one or more steps performed simultaneously; and with one or more disclosed steps omitted, unless expressly contradicted by the text herein or context.

[0064] While the present disclosure has been described with reference to one or more exemplary embodiments, it is to be understood that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to a particular embodiment disclosed herein as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will be viewed as covering any embodiment falling within the scope of the appended claims. Various aspects or features described herein may be implemented as a method, apparatus, or article of manufacture using standard programming and / or engineering techniques.

[0065] Also, the right to claim for patent coverage a particular sub-feature, a sub-component, or a sub-element of any disclosed embodiment, singularly or in one or more sub-combinations with any other sub-feature(s), sub-component(s), or sub-element(s), is hereby unconditionally reserved by the Applicant. Also, particular sub-feature(s), sub-component(s), and sub-element(s) of one embodiment that is disclosed herein can replace particular sub-features, sub-components, and subelements of another embodiment disclosed herein or can supplement and be added to another embodiment unless expressly indicated otherwise by the drawings or this specification. The inventor also asserts that any of the claims set forth after this detailed description can be combined with any other claim or claims regardless of whether or not there is a direct line of dependency, unless there isAtty Ref: 112540-0010.W01 - 16 -an express indication in this text or the drawings unambiguously indicating that such a combination is not possible. The order of the claims and the lines of dependency are irrelevant to the various ways that the features, elements, sub-elements, components, sub-components, etc. of the present disclosure can be combined and thus claimed. Further, the doctrine of claim differentiation is to be applied in construing the appended claims. Further, the use of the word “can” in this document is not an assertion that the subject preceding the word “can” is unimportant or unnecessary or “not critical” relative to anything else in this document. The word “can” is used herein in a positive and affirming sense and no other motive should be presumed. More than one patentable “invention” may be disclosed in the present disclosure and it is noted that an “invention” is defined by the content of a patent claim and not by the content of descriptive text or drawings.Atty Ref: 112540-0010.W01 - 17 -

Claims

CLAIMSWhat is claimed is:

1. A drive system comprising: a friction drive set having a sun member having an annular outer periphery centered on a longitudinal axis, a plurality of planet members each engaged with said annular outer periphery and spaced from one another about said longitudinal axis, a first ring member surrounding and engaged with each of said plurality of planet members, and a second ring member surrounding and engaged with each of said plurality of planet members and adjacent to said first ring member along said longitudinal axis; a first motor having a first stator and a first rotor and centered on said longitudinal axis; and a second motor having a second stator and a second rotor and centered on said longitudinal axis, wherein said first rotor is engaged with said first ring member for substantially concurrent rotation with said first ring member and wherein said second rotor is engaged with said sun member for substantially concurrent rotation with said sun member.

2. The drive system of claim 1 wherein said second ring member extends along said longitudinal axis between a first side and a second side, wherein said first side of said second ring member is directed toward said first stator along said longitudinal axis, wherein said first side is closer to said first stator than said second side along said longitudinal axis, and wherein a mechanical interconnection between said first rotor and said first ring member does not extend past said second side of said second ring member.

3. The drive system of claim 2 wherein said first rotor is connected to a radially-outer surface of said first ring member.Atty Ref: 112540-0010.W01 - 18 -4. The drive system of claim 1 wherein: said first ring member includes a first portion and a second portion; said second ring member extends along said longitudinal axis between a first side and a second side; said second side of said second ring member is directed away from said first stator along said longitudinal axis; said first side is closer to said first stator than said second side along said longitudinal axis; said second ring member is positioned between said first portion of said first ring member and said second portion of said first ring member along said longitudinal axis; and a mechanical interconnection between said first rotor and said first ring member does not extend past or overlap said second ring member along said longitudinal axis.

5. The drive system of claim 4 further comprising: an output member engaged with said second ring member for concurrent rotation, wherein said output member is positioned only on said second side of said second ring member along said longitudinal axis.

6. The drive system of claim 1 wherein said second ring member and said first rotor are spaced from one another along said longitudinal axis.

7. The drive system of claim 1 further comprising: a heat transfer member positioned radially between said first stator and said second stator.

8. The drive system of claim 1 wherein said first stator and said second stator share a plurality of stator laminations, each of said plurality of stator laminations having a first set of stator teeth facing radially outwards and supporting a first winding for driving said first rotor and also having a second set of stator teeth facing radially inwards and supporting a second winding for driving said second rotor.Atty Ref: 112540-0010.W01 - 19 -9. The drive system of claim 1 further comprising: at least one brake selectively engageable with one of said first rotor and said second rotor to selectively inhibit rotation of said one of said first rotor and said second rotor.

10. The drive system of claim 9 wherein said first motor and said second motor are positioned between said first friction drive set and said at least one brake.

11. The drive system of claim 9 wherein said at least one brake is further defined as: a first brake selectively engageable with said first rotor to selectively inhibit rotation of said first rotor; and a second brake selectively engageable with said second rotor to selectively inhibit rotation of said second rotor.

12. The drive system of claim 1 wherein said second motor further defined as nested within said first motor.

13. The drive system of claim 1 wherein neither of said first ring member and said second member are grounded.

14. A robot comprising: a base; a first drive system having: a friction drive set having a sun member having an annular outer periphery centered on a first longitudinal axis, a plurality of planet members each engaged with said annular outer periphery and spaced from one another about said first longitudinal axis, a first ring member surrounding and engaged with each of said plurality of planet members, and a second ring member surrounding and engaged with each of said plurality of planet members and adjacent to said first ring member along said first longitudinal axis, a first motor having a first stator and a first rotor and centered on said first longitudinal axis, andAtty Ref: 112540-0010.W01 - 20 -a second motor having a second stator and a second rotor and centered on said first longitudinal axis, wherein said first rotor is engaged with said first ring member for substantially concurrent rotation with said first ring member and wherein said second rotor is engaged with said sun member for substantially concurrent rotation with said sun member; and a first link rotatably mounted on said base and engaged with said second ring member whereby said first drive system is configured to rotate said first link about said first longitudinal axis.

15. The robot of claim 14 further comprising: a second drive system having: a friction drive set having a sun member having an annular outer periphery centered on a second longitudinal axis, a plurality of planet members each engaged with said annular outer periphery of said sun member of said second drive system and spaced from one another about said second longitudinal axis, a first ring member surrounding and engaged with each of said plurality of planet members of said second drive system, and a second ring member surrounding and engaged with each of said plurality of planet members of said second drive system and adjacent to said first ring member of said second drive system along said second longitudinal axis, a first motor having a first stator and a first rotor and centered on said second longitudinal axis, and a second motor having a second stator and a second rotor and centered on said second longitudinal axis, wherein said first rotor of said second drive system is engaged with said first ring member of said second drive system for substantially concurrent rotation with said first ring member of said second drive system and wherein said second rotor of said second drive system is engaged with said sun member of said second drive system for substantially concurrent rotation with said sun member of said second drive system; and a second link rotatably mounted on said base and engaged with said second ring member of said second drive system whereby said second drive system is configured to rotate said second link about said second longitudinal axis, wherein said second longitudinal axis is transverse to said first longitudinal axis.Atty Ref: 112540-0010.W01 - 21 -16. A method of operating a robot comprising: driving a first link of the robot which is rotatably mounted on a base of the robot, said driving including: controlling, with a controller, a first motor, positioned on the base and centered on a first longitudinal axis, to rotate a first rotor of the first motor in a first direction at a first speed of rotation, and controlling, with the controller, a second motor, positioned on the base and centered on the first longitudinal axis, to rotate a second rotor of the second motor in a second direction at a second speed of rotation, wherein the first rotor is mechanically coupled to the first link through a first ring member of a friction drive set positioned on the base and the second rotor is mechanically coupled to the first link through a sun member of the friction drive set.

17. The method of claim 16 wherein said driving is further defined as driving the first link at a third speed by said controlling the first motor and said controlling the second motor being further defined such that the first direction and the second direction are the same.

18. The method of claim 17 wherein said driving is further defined as driving the first link at a fourth speed less than the third speed by: said controlling the first motor is further defined such that the first speed is zero revolutions per minute; and said controlling the second motor is further defined such that the second speed is greater than zero revolutions per minute.

19. The method of claim 16 wherein said driving is further defined as driving the first link at a fifth speed less than the fourth speed by one of: said controlling the first motor is further defined such that the first speed is greater than zero revolutions per minute and said controlling the second motor is further defined such that the second speed is zero revolutions per minute; or said controlling the first motor and said controlling the second motor are further defined such that the first direction and the second direction are opposite to one another.Atty Ref: 112540-0010.W01 - 22 -20. The method of claim 16 further comprising: driving a second link that is mounted upon the link, said driving the second link including: controlling, with the controller, a third motor, positioned on the link and centered on a second longitudinal axis, to rotate a third rotor of the third motor in a third direction at a third speed of rotation, and controlling, with the controller, a fourth motor, positioned on the link and centered on the second longitudinal axis, to rotate a fourth rotor of the fourth motor in a fourth direction at a fourth speed of rotation, wherein the third rotor is mechanically coupled to the second link through a first ring member of a second friction drive set positioned on the link and the fourth rotor is mechanically coupled to the second link through a second sun member of the second friction drive set, wherein said second longitudinal axis is transverse to said first longitudinal axis.Atty Ref: 112540-0010.W01 - 23 -

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