Grasp assist system with triple Brummel soft anchor

A grasp assist system includes a glove, finger saddles attached to a respective glove finger, one or more tendon actuators, and artificial tendons. The saddles have a rectangular body partially circumscribing a respective glove finger. Each saddle includes end lobes at opposite distal ends of the body. A first end of each tendon is secured to one of the tendon actuators. A second end forms a triple Brummel loop defining a main loop and two anchor loops. The anchor loops are disposed around the lobes. The saddles may form a rounded, double-headed arrow shape that is at least double the thickness of the body. The finger saddles are anisotropic, with different bending strengths depending on the axis, and may be constructed of thermoplastic polyurethane-coated nylon. Flexion and/or contact sensors and a controller, may be used. A method of connecting the tendon actuator to the finger is also disclosed.

TECHNICAL FIELD

The present disclosure relates generally to a glove-based grasp assist system, and more particularly to a triple Brummel soft anchor for use in the system.

SUMMARY

A glove-based grasp assist system is disclosed herein. The system connects tendon actuators, e.g., motorized rotary ball screw assemblies, pulley systems, or other actuators, to glove fingers of a user-worn glove via flexible artificial tendons and flexible finger saddles. The finger saddles are sewn or otherwise secured to material of the glove. Each tendon is secured to end lobes of the finger saddles via a triple Brummel loop soft anchor connection. The present approach is intended to improve upon the performance of existing arcuate finger saddles or cylindrical phalange rings of the type engaged by a single, circumferentially-extending tendon loop, for instance as disclosed in U.S. Pat. No. 8,255,079 titled “Human Grasp Assist Device and Method of Use” and U.S. Pat. No. 9,067,325 titled “Human Grasp Assist Device of Goods”, both of which are hereby incorporated reference in their entireties.

The finger saddles according to the present disclosure are specially configured to evenly distribute a tensile load from a respective flexible tendon acting on a particular phalange/finger segment, for instance the medial or distal phalanges of the users fingers. The triple Brummel configuration, when looped over and around the end lobes of the finger saddles, forms the soft anchor with two tendon anchor points. Such construction minimizes cinching or pinching in operation, which in turn helps avoid damage to the glove material and user discomfort. Additionally, use of the soft anchor facilitates in-place maintenance of the tendons, i.e., repair or replacement of the tendons without requiring the user to first remove the glove, with this capability improving overall operating efficiency.

The grasp assist system having the disclosed soft anchor may be used to selectively assist the natural grasping forces or other hand motions of a user. Power assist capabilities provided by one or more tendon actuators are selectively activated when the user executes a grasp maneuver, with the term “grasp maneuver” meaning a user-initiated, muscle-based motion of the user's hands involving the manual flexing of the user's fingers and/or thumb, regardless of whether the user grasps or otherwise makes contact with an external object during execution of the grasp maneuver. In other words, the user first decides when and bow far to move his or her fingers. The system then automatically assists in moving the user's fingers in response to such user-initiated motion. Exemplary hand maneuvers may include the grasping of a work tool or the mere flexing the user's empty hand against the natural resistance of the glove. The system configured as set forth herein may improve efficiency of work based or recreational applications, as well as rehabilitation of user's having limited finger movement strength, and dexterity.

A grasp assist system according to an example embodiment includes a glove, finger saddles, tendon actuators, and artificial tendons. The glove, which has multiple glove fingers, is configured to be worn on a hand of a human user. Each finger saddle is attached to a posterior surface of respective one of the glove fingers and includes a rectangular body partially circumscribing a respective one of the glove fingers. Additionally, each finger saddle includes a pair of end lobes disposed at opposite distal ends of the rectangular body. The tendons have a respective first end secured or otherwise connected to one of the tendon actuators and a second end defining a triple Brummel loop. The triple Brummel loop includes a pair of Brummel loops disposed around a respective one of the end lobes to form a soft anchor, with the soft anchor providing two tendon anchor points for a respective one of the tendons when the tendons are placed under tension by operation of the tendon actuators.

A shape of an outer perimeter of each of the finger saddles is a rounded, double-headed arrow in some configurations. A thickness of the end lobes may be at least double a thickness of the rectangular body.

The finger saddles are anisotropic, such that a bending strength of the end lobes exceeds a bending strength of the rectangular body in a first axial direction, and a bending strength of the rectangular body exceeds a bending strength of the end lobes in a second axial direction that is orthogonal to the first axial direction.

The finger saddles may be constructed of thermoplastic polyurethane-coated nylon.

The grasp assist system may also include a sensor and a controller in communication with the actuators and sensor. The controller may be configured, in response to feedback signals from the sensor, to selectively command application of the tension to one or more of the flexible tendons.

The sensor may include a flexion sensor configured to measure, as part of the feedback signals, a level of flexion of each of the glove fingers. The sensor may also include a set of contact sensors connected to the glove and configured to detect contact between the glove and an object as an additional part of the feedback signals.

The end lobes may define through holes, with the finger saddles sewn to the posterior surface of the glove fingers via the through holes.

A triple Brummel soft anchor is also disclosed for use in a grasp assist system having a tendon actuator and a glove configured to be worn on a hand of a user. The soft anchor may include a finger saddle configured to attach to a posterior surface of a glove finger of the glove, and having a rectangular body with a length sufficient for partially circumscribing the glove finger when the finger saddle is attached to the glove finger. The finger saddle in this embodiment defines a pair of end lobes at opposite distal ends of the rectangular body. A flexible artificial tendon has a first end forming a single loop of a size sufficient for connecting to the tendon actuator, and a second end defining a triple Brummel loop that includes a pair of Brummel loops disposed around a respective one of the end lobes and forming a soft anchor providing two anchor points on the finger saddle

Additionally, a method is disclosed for connecting a flexible tendon to a glove finger in a grasp assist system having a tendon actuator and a glove configured to be worn on a hand of a human user. The method may include attaching a finger saddle to a posterior surface of a finger of the glove, the finger saddle having a rectangular body partially circumscribing the glove finger and defining a pair of end lobes at opposite distal ends of the rectangular body. The method also includes forming a triple Brummel loop at a first end of a length of artificial tendon, such that the triple Brummel loop defines a main Brummel loop and a pair of anchor Brummel loops. A second end of the artificial tendon is attached to the tendon actuator, with the method further including inserting the end lobes of the finger saddle into a respective one of the anchor Brummel loops such that the finger saddle forms a soft anchor with two tendon anchor points. Tension is then applied as part of the method to the flexible tendon, via a controller and the tendon actuator, at a level sufficient for tightening the pair of anchor Brummel loops or around the finger saddle.

The above summary is not intended to represent every embodiment or aspect of the present disclosure. Rather, the foregoing summary exemplifies certain novel aspects and features as set thrill herein. The above noted and other features and advantages of the present disclosure will be more easily understood from the following detailed description of representative embodiments and modes for carrying out the present disclosure when taken in connection with the accompanying drawings and the appended claims.

The present disclosure is susceptible to modifications and alternative forms, with representative embodiments shown by way of example in the drawings and described in detail below. However, inventive aspects of this disclosure are not limited to the particular forms disclosed. Rather, the present disclosure is intended to cover modifications, equivalents, combinations, and alternatives falling within the scope of the disclosure as defined by the appended claims.

DETAILED DESCRIPTION

With reference to the drawings, wherein like reference numbers refer to the same or similar components throughout the several views, an embodiment of a grasp assist system10as described herein is shown schematically inFIG. 1. The system10, which is configured to be worn on either hand11of a human user although the illustration shows by non-limiting example the left hand), selectively assists the user in executing a grasp maneuver in which the user initiates movement of the user's fingers11F and/or a thumb11T. The system10described herein utilizes a Triple Brummel tendon configuration as part of a soft anchor transmitting tension to one or more fingers11F and/or a thumb11T of the hand11, as will be described in further detail below with particular reference toFIGS. 7-8C.

The grasp assist system10shown inFIG. 1may be connectable to and configured for use as part of a pressurized space suit (not shown) of the type used in aerospace operations. Non-aerospace applications may also be realized, such as manufacturing, construction, or medical rehabilitation, or recreational applications such as scuba diving, and therefore the space glove application described herein is merely illustrative of the general concepts of the various embodiments.

In the non-limiting example embodiment ofFIG. 1, the grasp assist system10is a multi-layered glove having an optional inner bladder layer12worn on/immediately adjacent to the user's hand11, an intermediate restraint layer1containing the drive improvements disclosed below, a hardware layer16containing one or more drivetrains20and a controller50(both depicted inFIGS. 2 and 3), and an optional protective outer layer18. The outer layer18has a glove portion18G and a forearm portion18F, with the protective outer layer18configured for wear over the hardware layer16. For the term “glove” will be used at times to refer generally to the combination of layers comprising the optional bladder layer12, when used, the restraint layer14, the hardware layer16, and the glove portion18G (when used).

With respect to the optional bladder layer12, this flexible structure may be constructed of a suitable polymer or rubber material. In some embodiments, the bladder layer12may be connected to a pressure supply IS to pressurize the bladder payer12. In the example of a space glove embodiment, for instance, the pressure supply15may be part of a pressurized space suit. In no-aerospace applications, the pressure supply15may be a pneumatic accumulator, i.e., a canister of compressed air or other suitable inert gas, or a scuba tank in an exemplary scuba application. Use of the pressure supply15may facilitate a built-in restorative force for gently returning the user's hand11to a relaxed “open” pose as a default position, as opposed to a “closed” or “grasping” position such as when the system10is assisting in the grasping of an object in the user's hand.

The restraint layer14functions by retaining shape of the bladder layer12to the fingers11F, thumb11T, and a palm11P of the user's hand11, as well as by protecting and insulating the user's hand11. The restraint layer14may be equipped with portions of one or more drivetrain(s)20(seeFIGS. 2 and 3) and other components that operatively connect to the user's fingers11F and, possibly, the user's thumb11T. The term “drivetrain”, as used herein, comprises components shown inFIG. 2, starting from the actuator22to the finger saddle28, i.e., actuator22, conduit24, tendon25, palm bar26, and saddle28for a given drivetrain20. The restraint layer14may be optionally constructed of a suitable low-density, high-performance material. For instance, the restraint layer may be constructed of a polytrophic liquid crystal polymer, e.g., VECTRAN™.

The hardware layer16ofFIG. 1, which may be worn on the user's wrist and forearm (not shown), contains the controller50and one or more tendon actuators22shown inFIGS. 2 and 3. For instance, the hardware layer16may be mounted on the posterior side of the user's forearm between the restraint layer14and the outer layer18. The hardware layer16may in some embodiments be attached to the underside of the optional outer layer18, such as via a hook-and-loop connection, magnetically, or using zippers, snap closures, or other application-suitable fasteners.

In some embodiments, the optional outer layer18wraps around, covers, and protects the restraint layer14and the hardware layer16from dust, debris, and other hazards. The glove portion180covers and protects the restraint layer14, while the forearm portion18F forms a protective wrap around the hardware layer16. Suitable materials of construction of the outer layer18, particularly the glove portion18G, may include puncture-resistant/fiber-reinforced silicon rubber finger caps, e.g., KEVLAR™, a suitable flame-retardant fabric material, etc. The forearm portion18F forms a gauntlet and may be constructed, e.g., or a reinforced biaxially-oriented polyethylene terephthalate (BoPET) material and polytetrafluoroethylene (PTFE) fabric. When the grasp assist system10is used in the embodiment of a space application noted above, the outer layer18may be embodied as a Thermal Micrometeoroid Garment (TMG) constructed of a blend of waterproof, impact resistant, and fire resistant fabrics, with similar or different materials used in other embodiments depending on the application.

FIG. 2depicts one example of the drivetrain20noted above in a configuration that is suitable for use with the example grasp assist system10ofFIG. 1. The controller50receives input signals (arrow CC1) from a set of glove sensors23, including one or more flexion sensors (SF)23A and a set of optional contact sensors (SC)23B. The contact sensors23B may be embedded in the outer layer18, e.g., on one or more phalanges of the glove portion18G. Such locations provide strong grasp assistance when the contact sensors23B detect external contact. The contact sensors23B may be optionally embodied as load sensors or Force Sensitive Resistors (FSR), i.e., commercially-available flexible circuits made of conductive ink laminated between layers of plastic. The contact sensors23B may be used to measure or detect contact with the fingers11F or another portion of the glove when the user interacts with external objects or tools. The contact sensors23B then report the detected contact to the controller50, which may adjust tension on the tendons25in response to the reported contact.

In response to receipt of the input signals (arrow CC1), the controller50calculates required tensile forces and then, via a set of control signals (arrow CCO), drives a plurality of the tendon actuators22, with the tendon actuators22also labeled Actuators1,2, and3for clarity inFIG. 2. The driven tendon actuators22apply the calculated tensile forces to a set of conduits24, e.g., a Bowden cable, system in which a hollow outer conduit (made of stainless steel or other suitable material) is lined with PTFE or other suitable wear-resistant coating and contains a flexible tendon25located therein. Thus, the calculated tensile forces are automatically applied to some or all of the conduits24and tendons25in response to the input signals (arrow CC1) from the love sensors23.

The drivetrain20may be configured to drive a conventional full grasp, or to drive fewer fingers11F of the hand11shown inFIG. 1, with or without driving the thumb11T. Connected to the restraint layer14, e.g., sewn into place, may be a plurality of finger saddles28. Each finger saddle28partially circumscribes a phalange of a finger11E of the operator's hand11(seeFIG. 1) when the restraint layer14is worn on the hand by the user. Tensile forces are imparted to the drive tendons25, which are operatively integrated within the accompanying conduits24and joined to the restraint layer14by a palm bar26as shown, thus indirectly acting on the user's fingers11F/thumb11T through the intervening finger saddles28when the restraint layer is worn. For added clarity, the finger saddles28are also labeled inFIG. 2as “little”, “ring”, “middle”, and “index” corresponding to the particular finger11F of the operator's hand11depicted inFIG. 1.

The finger saddles28, described in greater detail below with reference toFIGS. 7-8C, are configured to smoothly distribute tensile/pulling forces generated by the tendon actuators22. Such forces are transmitted along the tendons25, e.g., across the posterior of the medial phalanges of the user's fingers11F. In some embodiments, the finger saddles28may be constructed of thermoplastic polyurethane (TPU)-coated nylon straps that are laser cut to form a band having flared or lobed ends forming anchors that ultimately interface with the tendons25. The individual finger saddles28are sufficiently flexible to enable the finger saddles28to gently contour around the user's fingers11F whenever a mating tendon25is under tension. The tendons25themselves may be configured as a braid of multiple high-strength, wear-resistance fluorocarbon or other suitable materials, e.g., braided TEFLON™ and VECTRAN™ or other suitable fibers.

Three tendon actuators22are used with the tendons25in the illustrated example embodiment ofFIG. 2. Each tendon25is secured to one of the tendon actuators22at one end of the tendon25, e.g., via securing a single tendon loop to a tendon fastener or hook122or other retaining feature of the tendon actuator22. At another end, the tendon25is secured to the finger saddles28via a triple Brummel loop connection to form a “soft anchor”, i.e., components ultimately engaging and pulling on the user's fingers11F ofFIG. 1are flexible or comfortably compliant under tension. The thumb11T, the primary fingers (i.e., the index and middle fingers), and the secondary fingers (ring and little)11F of the user's hand11(FIG. 1) may each have a dedicated tendon actuator22, similar to the tendon actuator assembly as disclosed in U.S. Pat. No. 8,255,079 and noted above as being incorporated by reference in its entirety.FIG. 2shows the index and middle fingers (11F) each having its own dedicated tendon actuator22. Alternatively, the secondary fingers11F, commonly referred to as the ring and little fingers, may be coupled to a single shared tendon actuator22as shown inFIG. 3. An example embodiment of a shared tendon actuator assembly is described in U.S. Pat. No. 9,149,933, which is likewise incorporated by reference in its entirety. Other actuators such as pulley systems or other types of solenoid drive systems may be used in lieu of the incorporated tendon actuators22, without limitation, and therefore the tendon actuators22are not limited to rotary hall screw embodiments.

Referring now to the example single-actuator embodiment ofFIG. 3, movement of a give finger11F occurs when the tendon actuator22exerts a pulling force on the flexible tendon25, which moves freely through a hollow outer conduit24and mounted palm bar26, similar to operation of a bicycle brake using a Bowden cable system. This pulling force on the tendon25in turn transfers a mechanical pulling force on the operatively connected finger saddle28. The outer conduit24may be constructed of a stainless steel conduit lined with an abrasion-free material such as PTFE. The conduit24of the Bowden cable system in such an embodiment possesses high strength in the axial direction while remaining flexible in all other directions, such that the conduit does not impede the user's wrist movements. Providing such a conduit also provides structural support between the tendon actuators22and the palm bar26, thereby maintaining relative positioning of the palm bar26and the tendon actuators22as static under dynamic loading conditions.

In operation when the glove is worn, the tendon actuators22pull on and thus tension the tendons25, with the tendons25routed through the hardware layer16ofFIG. 1to the restraint layer14through the conduits24anchored at the palm bar26and looping around the finger saddles28located on the medial joints of the user's fingers11F when the glove is worn. As the tendon actuator22pulls the tendon(s)25, the user's finger11F is guided into a flexed position as shown inFIG. 3. The user may provide an extension three to open his or her hand in one embodiment.

In another embodiment, the extension force or “restorative” force is automatically implemented when the controller50determines that the user's grasp is being released. One possible approach for providing the restorative force is use of the pressurized bladder layer12and the external pressure supply15shown schematically inFIG. 1, or using mechanical springs embedded in the glove portion18G or other parts of the glove. The restraint layer14becomes a semi-rigid body when the bladder layer12is pressurized. When the users grip releases and transitions to a relaxed state, interposition of the pressurized bladder layer12between the hand11and the restraint layer14passively returns the pulling tendons25into a relaxed/non-grasping pose.

FIG. 4is a more detailed perspective view illustration of the respective palm-side140of the restraint layer14shown inFIG. 1, with glove fingers111F and a glove thumb111T shown for example left-handed glove.FIG. 5is a more detailed perspective view illustration of the grasp assist system10from the posterior or back side of the user's right hand in accordance with a right-banded glove system described herein. Depicted in these views are the finger saddles28, the conduits24, and the palm bar26noted above with reference toFIG. 2. Wherever motion of the tendon actuators22or other components of the grasp assist system10could potentially rub on or abrade contact areas of the restraint layer14due to relative motion, such contact areas may be shielded with reinforced patches of PTFE fabric or other suitable wear-resistant materials. The tendons25connect to the ends of the finger saddles28using the triple Brummel loop connection depicted inFIGS. 7-8C.

Referring now toFIG. 5, this view depicts possible placement of sensor cable restraints30, sensor conduits32, and the flexion sensor(s)23A on the restraint layer14. The flexion sensors23A may be optionally embodied as string potentiometers29as shown, or as motion capture devices, bend sensors, joint angle sensors, or other suitable sensors, and used to track, finger flexion and a resultant change in relative position and attitude (e.g., pitch, yaw, roll) in free space of each phalange of the user's fingers11F. The sensor cable restraints30may be segmented and spaced apart as shown, with a plurality of sensor cable restraints30used per finger of the restraint layer14. The flexion sensor23A, which may be optionally embodied string potentiometers29as shown, are used to track the position and/or attitude (e.g., pitch, yaw, and roll) in free space of each phalange of the user's fingers11F (seeFIGS. 1 and 3), and to thereby allow the controller50to determine motion and relative position of each of the fingers11F and, when used, the thumb11T. To avoid adversely affecting durability of the bladder layer12, the flexion sensors23A may be integrated outside of the restraint layer14as shown, such as by using a fabric-tape addition on the outside of the restraint layer14. Depending on the selected operating mode, as the user's fingers flex, the tendon actuators22ofFIGS. 2 and 3may respond with synchronized grasp assistance, thereby offering intuitive operation of the grasp assist system10.

In general, the flexion sensors23A may be used to determine flexion of the phalanges for the user's index, middle, and ring fingers11F. Such sensors23A may be placed on the posterior of the user's hand11as shown inFIG. 5and mounted on the restraint layer14. The flexion sensors23A may be mounted on a custom plate attached to a stainless steel wrist cuff35, e.g., in the above-noted space glove embodiment. When string potentiometers are used for the flexion sensors23A, sensor strings29(FIG. 5) route along the posterior side141of the restraint layer14, around a ratchet mechanism34used to selectively adjust the fit of the restraint layer14, through a PTFE-lined conduit32, up the fingers11F through the segmented sensor cable restraints30, and link to a fabric seam located at the tip of the distal phalanges as shown.

The palm bar26, shown in part inFIG. 4, serves as a sturdy anchor for the conduits24, which are routed into the palm bar26via a conduit manifold33. In this manner, the palm bar26ensures that structural components of the retaining layer14are securely fitted to the user's hand11. The palm bar26may be configured with application-suitable fit and curvature, e.g., for a Phase VI space suit glove as manufactured by ILC DOVER, LP, of Frederica, Del., modified to include passageways for the tendons25and conduits24.

The flexible conduit manifold33may be constructed of fabric or other suitable textile and is used to concentrate and attach the conduits24to the palm-side140, adjacent to the palm bar26, of the restraint layer14. As noted above, each tendon25is contained within a respective conduit24to form the operative cable tension system, e.g., a Bowden cable system, with the conduits24received within the manifold33. The tendons25emerge from the palm bar26and extend along and/or about the fingers of the restraint layer14with operable connection to each respective saddle28as will be described with further detail below. In some embodiments, the palm bar26may be constructed of 316 SS (Stainless Steel), for instance, using a direct metal laser sintering process, and integrated with the ratchet mechanism34located on the posterior141as shown inFIG. 5, so that the palm bar26is adjustable during use. The palm bar26thus acts an anchor or ground for the conduits24, and thus is configured to withstand force loads in excess of loads experienced by a typical space suit palm bar.

Referring briefly toFIGS. 6A and 6B, a single loop in the form of a Brummel eye splice may be used to connect an artificial tendon to a cylindrical structure serving the function of a fastener. One such approach is disclosed in the above-noted incorporated reference U.S. Pat. No. 9,067,325. A braided tendon25may be configured as shown inFIG. 6Aso as to define three loop regions L1, L2, and L3. Eye slots80and81may then be formed in the braided tendon25. The tendon25is then fed through the eye slots80and81as shown to create and then remove a twist in the braided tendon. The resulting Brummel loop to (or “splice”) L1, when the tendon25is placed under tension, ultimately cinches down upon itself in a manner similar, to a Chinese finger trap. Friction from this connection cancels out the longitudinal force of tension on the tendon25, and the resultant braid B1of the tendon25in the area of loop regions L2and L3ofFIG. 6Bdistributes a load across an area to avoid stress concentrations.

While such a single loop configuration is usable in embodiments employing a rectangular or cylindrical finger saddle, i.e., by wrapping the Brummel loop L1circumferentially around and onto such a saddle or phalange ring, and thus around the phalange of a user's finger11F (FIG. 1) so that the tendon25pulls directly on the posterior of the user's finer11F, the approach ofFIGS. 6A and 6Bmay be sub-optimal for certain applications and purposes, including long-term durability and user comfort.

With reference toFIG. 7, the finger saddle28may be sewn into place in the material of the restraint layer14ofFIGS. 1, 4, and 5, e.g., via a plurality of through-holes84. Each saddle28has an elongated rectangular body91that flares or widens into end lobes E1and E2. That is, the finer saddle28has an outer perimeter (in plan view) in the shape of a rounded, double-headed arrow as shown, or other shape suitable for anchoring the tendons25at two opposing anchor points of the finger saddles28. The end lobes E1and E2may define the through-holes84as shown, and/or other points may be used to connect the finger saddle28to a posterior of the glove fingers as shown inFIG. 5.

More specifically, rather than looping the tendon25circumferentially around the user's finger11F (FIG. 1), the end lobes E1and E2form an anchor with two different and opposite tendon anchor points for securing the tendon25. This construction, when coupled with the triple Brummel configuration set forth below with reference toFIGS. 8A-C, enables smooth distribution of pulling forces along the lateral sides of the user's finger11F (FIG. 1), as opposed to pulling equally around the circumference of the users finger11F.

The end lobes E1and E2, which define side walls85extending generally parallel to an axis of the user's finger11F, have a thickness that exceeds a thickness of the rectangular body91, by a factor of two or more, i.e., at least double-thickness. A small shoulder94may be formed in the end lobes E1and E1. Using the triple Brummel soft anchor for the construction of the tendon25, the tendon25may be looped over and around the end lobes E1and E2as shown, such that the tendon25is positioned adjacent to the side walls85. Tension applied by the tendon actuators22ofFIGS. 2 and 3in the direction of arrow T ultimately tightens braids B1A, B1B, and B2, which in turn are formed via splicing of the tendon25as shown.

The finger saddle28used as part of the grasp assist system10is anisotropic, a property represented by orthogonal bending strength grain lines90and92indicating different bending strengths in the width (X) and length (Y) axes of the finger saddle28. That is, a bending strength of the end lobes E1and E2exceeds a bending strength of the rectangular body91in a first axial direction, and a bending strength of the rectangular body91exceeds a bending strength of the end lobes E1and E3in a second axial direction that is orthogonal to the first axial direction, e.g., the N and Y axes. Grain lines92represent that the end lobes E1and E2are configured to withstand tensile forces from the tendon25, and grain lines90indicate that the axial portion91freely and evenly flexes when the tendon25is tensioned by the tendon actuators22.

FIGS. 8A8B, and8C collectively describe an embodiment of a method for forming a triple Brummel soft anchor connection usable as part of the grasp assist system10ofFIG. 1or another system employing the finger saddles28described above. A length of tendon25may be arranged lengthwise on a surface, with an end95of the tendon25shown to the right from the perspective ofFIG. 8A. Node pairs N1, N2, and N3represent points along a length of the tendon25that form holes or eye slots, e.g., formed by splitting through the tendon25. The node pairs N1, N2, N3, which are configured such that the the braided tendon25passes therethrough, ultimately match up with each other through the processes of forming the triple Brummel loop disclosed herein.

Example inter-nodal distances, from left-to-right, are 0.625″ (inches) between the first node of node pair N1and the first node of node pair N2, 1″ between the two nodes forming the node pair N2, 1.25″ between the second node of node pair N2and the first node of node pair N3, 1″ between the nodes forming the node pair N3, and 0.625″ between the second node of node pair N3and the second node of node pair N1. Different distances may be used in other embodiments, with the depicted example distances being illustrative of node spacing resulting in a loop size usable with the finger saddle28ofFIG. 7.

InFIG. 8B, the end95of the tendon25ofFIG. 8Ais arranged in a first tendon loop L1with nodes of the node pairs N2and N3disposed on opposite sides of the first tendon loop L1. The portion of tendon25located proximate the nodes of node pair N1, in this stage of forming the triple Brummel loop configuration, are spliced, woven, or otherwise braided together using a Brummel splice or loop technique to form the braid B2.

FIG. 8Cshows completion of the process by forming two additional “Brummel” loops L2A and L2B. Nodes of the node pair N2ofFIG. 8Bare spliced, woven, or otherwise looped together to form the braid B1A. Similarly, inter-nodal lengths of the tendon25defining nodes of node pair N3inFIG. 8Bare spliced, woven, or otherwise looped together to form braid B1B. Formation of smaller anchor Brummel loops L2A and L2B out of the larger loop L1shown inFIG. 8Beffectively forms a third/main Brummel loop L3A. Thus, in accordance with the method described herein, the three loops of the disclosed triple Brummel loop configuration are the Brummel loops L2A, L2B, and L3A.

An alternative embodiment for forming the above-described triple Brummel soft anchor connection entails creating the braids B1A and B1B prior to forming the braid B2. That is, braid1A ofFIGS. 8B and 8Cmay be formed by sowing end95of the tendon25at the node pair N2to thereby form loop L2A. End95is then sown at node pair N3to form braid B1B, with this process resulting in formation of loop L2B. Braid B2is then formed to provide loop L3A. Other approaches or sequences may be envisioned within the scope of the disclosure, and therefore the embodiments described with reference toFIGS. 8A, 8B, and 8Care exemplary of the present teachings and non limiting.

Referring again toFIG. 7, the Brummel loops L2A and L2B when formed according to the process depicted inFIGS. 8A-8Care wrapped loosely around the lobed ends E1and E2of the finger saddle28. The distal end of the tendon25connects to a translatable portion of the tendon actuators22as shown inFIGS. 2 and 3, e.g., to the tendon fastener122. Tension (arrow T) applied to the tendon25by the tendon actuators22tightens the braids B1A and B1B so that the Brummel loops L2A and L2B close and tighten around the rectangular body91immediately adjacent to the lobed ends E1and E2. The Brummel loop L3A ofFIG. 8Ccloses in response to the applied tension (arrow T). Releasing the tension (arrow T) loosens the Brummel loops L2A, L2B, and L3A ofFIG. 8C. Thus, unlike designs in which a single looped end of the tendon25circumscribe the user's finger, extend all the way around a lengthwise axis of the finger saddle28, the configuration ofFIG. 7enables the tendon25to be replaced or repaired as needed without having to remove die glove from the user's hand11(seeFIG. 1).

As noted above with reference toFIGS. 6A and 6B, placing the tendon25under tension ultimately cinches the various braids B2, B1A, and B1B of the tendon25in a manner similar to a Chinese finger trap. The tendon25in proximity to the end25experiences high friction under such tension. The cinching action distributes stress concentration to allow forces acting on the braids B2, B1, and B1B to cancel out. Thus, tension toward the tendon actuators22tightens the braids B2, B1, and B2while tension applied to end95has the opposite effect. Symmetry of construction of the braids B1A and B1B may be relied on to help cancel lateral tension forces between braids B1A and B1B.

As will be understood from the forgoing disclosure, a method of connecting the flexible tendon25to a glove finger in the grasp assist system10ofFIG. 1includes attaching the finger saddle28ofFIG. 7to a posterior surface of a finger of the glove, as shown inFIG. 5, e.g., via sewing. The method may include forming a triple Brummel loop at or near a first end95of a given one of the tendons25, i.e., the end95ofFIG. 8A, such that the triple Brummel loop is funned defining a main Brummel loop (loop L3A) and a pair of anchor Brummel loops L2A and L2B, all of which are shown inFIG. 8C.

A second end of the artificial tendon25is connected to the tendon actuator22shown inFIG. 2 or 3. The end lobes E1and E2of the finger saddle28shown inFIG. 7are then inserted into a respective one of the anchor Brummel loops L2A and L2B such that the finger saddle28forms a soft anchor with two tendon anchor points as noted above. The method thereafter includes applying tension to the tendon25, via use of the controller50and the tendon actuator22ofFIGS. 2 and 3, at a level sufficient for tightening the pair of anchor Brummel loops L2A and L2B on or around the finger saddle28.

While some of the best modes and other embodiments have been described in detail, various alternative designs and embodiments exist for practicing the present teachings defined in the appended claims. Those skilled in the art, now having benefit of this disclosure, will recognize that modifications may be made to the disclosed embodiments without departing from the scope of the present disclosure. Moreover, the present concepts expressly include combinations and sub-combinations of the described elements and features. The detailed description and the drawings are supportive and descriptive of the present teachings, with the scope of the present teachings defined by the claims appended hereto.