Patent Publication Number: US-11654034-B2

Title: Hand assembly for an arm prosthetic device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/809,624, filed Jul. 27, 2015, now U.S. Pat. No. 10,299,941 issued May 28, 2019, which is a continuation of U.S. patent application Ser. No. 12/027,141 filed Feb. 6, 2008, now U.S. Pat. No. 9,114,028 issued Aug. 25, 2015, which claims priority to U.S. Provisional Patent Application Ser. No. 60/899,833, filed Feb. 6, 2007 and U.S. Application Ser. No. 60/963,639, filed Aug. 6, 2007, each of which is hereby incorporated by reference in its entirety. 
    
    
     STATEMENT OF GOVERNMENT INTEREST 
     This invention was made with Government support under Contract Number W911NF-06-C-001 awarded by the U.S. Army RDECOM ACQ CTR. The Government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     The present development relates to mechanical and medical devices and, more particularly, to prosthetics. More particularly, the development utilizes mechanical structure and user or motor stimuli to operate the prosthesis similarly to a human limb. 
     BACKGROUND INFORMATION 
     Existing prosthetic arms having limited movement for the user. Further, there are limited options for those patients who have lost their entire arm, shoulder to hand. Also, hand portions of existing prosthetic arms give the user, in many instances, one degree of movement. These prosthetics give limited capability with respect to, amongst other things, finer tasks. 
     Accordingly, there is a need for a prosthetic that replaces an arm from shoulder to hand and that has increased degrees of freedom. There is also a need for a prosthetic hand that moves in a realistic manner. 
     SUMMARY 
     It is one aspect of the present device to provide a prosthetic that will allow the user improved range of motion, improved tactile capabilities, increased comfort for the user, and decreased reliance on manual positioning of the prosthesis. 
     In accordance with one aspect of the invention, the present device employs a compliant structure that incorporates a shoulder flexion joint, a shoulder abduction joint, a humeral rotator, an elbow flexion joint, a wrist rotation joint, and a wrist flexion joint. The present device also discloses a hand assembly. 
     In accordance with one embodiment of the device, the shoulder flexion joint assembly includes a motor, a belt, a pulley, a gear train, a harmonic drive, a potentiometer, a non-backdriving clutch, and a compliance sensor. The electrically driven motor rotor drives the belt that is defined by two pulleys. The first pulley is magnetically driven by the motor rotor. The second pulley is driven by the belt and engages the harmonic drive. The harmonic drive has an interior wave generator that corresponds with the flexible spline. The spline in turn engages the exterior circular spline, resulting in drastic reduction rates and driving the shoulder output flange, allowing the shoulder joint flexion movement. 
     In accordance with another aspect of the shoulder flexion joint, the joint assembly also discloses a clutch. The clutch has an input cage, an output hex, and a clutch race, or ground. When the shoulder flexion joint is acted upon by an output force, the output hex is engaged in a friction lock with the clutch race and bearings lining the exterior of the output hex, preventing backward transfer of power through the clutch. 
     In accordance with another aspect of the shoulder flexion joint, the joint assembly also discloses a shoulder compliance sensor. The sensor provides the shoulder flexion joint with measured compliance. The sensor utilizes the interior rim of the circular spline of the harmonic drive. The exterior rim of the circular spline additionally accommodates stationary reactor elements and series elastic elements. The circular spline, series elastic elements and reactor elements are circumferentially disposed around the interior of a clamp. Together, the clamp and a compliance reactor substantially enclose the circular spline, series elastic elements, and reactor elements. The clamp and compliance reactor remain stationary while the circular spline, series elastic elements, and reactor elements are rotatably disposed around the exterior rim of the spline. Additionally, a magnet is disposed on the exterior rim of the circular spline. Upon application of force, the position of the circular spline alters causing the series elastic elements to compress against the reactor elements. The movement of the reactor elements transmits the rotational displacement of the circular spline via the reactor movement in relation to the stationary magnet. In this manner, the compliance is built into the shoulder flexion joint and works to absorb energy when the joint is subjected to a load or an unexpected shock. 
     In accordance with the shoulder abduction joint, the joint features a shoulder flexion mount. The shoulder flexion joint fastens to the shoulder flexion mount. The abductor also discloses a harness mount. 
     The humeral rotator features a harmonic drive, a motor, a motor armature, a potentiometer and a humeral mount. The support structure of the humeral rotator has a humeral mount site at the output of the rotator. The motor drives the motor armature, which in turn drives the wave generator of the harmonic drive. The wave generator drives the interior flexible spline, which in turn interacts with the outer circular spline. The circular spline then drives the rotational movement of the humeral rotator. 
     In further accordance with an aspect of the humeral rotation site, the potentiometer features a position pot and a potentiometer shaft. 
     In accordance with another embodiment of the device, the elbow flexion joint is further comprised of a motor armature, a motor rotor, a motor rotor magnet integrated into the motor rotor, a sun gear also integrated into the motor rotor, four planet gears, a ring gear, a harmonic drive, and a potentiometer. 
     In accordance with another aspect of the elbow flexion joint, the motor armature applies electrical force to the motor rotor magnet integrated onto the surface of the motor rotor. The motor rotor in turn rotationally drives the sun gear also integrated on the motor rotor. The sun gear rotationally drives the four planet gears. The planet gears in turn react against 
     the stationary ring gear to effect rotation of the carrier plate, providing the first stage of reduction. 
     In accordance with a further aspect of the elbow flexion joint, the carrier plate drives the harmonic drive wave generator. The harmonic drive has an interior wave generator that corresponds with the flexible spline. The spline in turn engages the exterior circular spline, resulting in drastic reduction rates and driving the elbow output, allowing the elbow flexion joint movement. 
     In accordance with a further aspect of the elbow flexion joint, the elbow flexion joint also discloses a compliance sensor. The sensor provides the elbow flexion joint with measured compliance. The sensor utilizes the interior rim of the circular spline of the harmonic drive. The exterior rim of the circular spline additionally accommodates stationary reactor elements and series elastic elements. The circular spline, series elastic elements and reactor elements are circumferentially disposed around the interior of a clamp. Together, the clamp and a compliance reactor substantially enclose the circular spline, series elastic elements, and reactor elements. The clamp and compliance reactor remain stationary while the circular spline, series elastic elements, and reactor elements are rotatably disposed around the exterior rim of the spline. Additionally, a magnet is disposed on the exterior rim of the circular spline. Upon application of force, the position of the circular spline alters causing the series elastic elements to compress against the reactor elements. The movement of the reactor elements transmits the rotational displacement of the circular spline via the reactor movement in relation to the stationary magnet. In this manner, the compliance is built into the elbow flexion joint and works to absorb energy when the joint is subjected to a load or an unexpected shock. 
     The wrist rotation site features a harmonic drive, a motor, a motor armature, and a potentiometer. The motor drives the motor armature, which in turn drives the wave generator of the harmonic drive. The wave generator drives the interior flexible spline, which in turn interacts with the outer circular spline. The circular spline then drives the rotational movement of the wrist rotator. 
     In further accordance with an aspect of the wrist rotation site, the potentiometer features a position pot and a potentiometer shaft. 
     The wrist flexion joint is further comprised of a motor, an output arm, a gear train, and a series of elastic elements. The wrist flexion joint is driven by a motor that in turn drives the gear train. A final stage-driven gear transfers power to the output arm. The output arm connects to the main wrist flexion joint by a pivot axle. 
     In further accordance with an aspect of the wrist flexion joint, the output arm contains series elastic elements, a compliance sensor magnet, and a drive arm. The exterior casing of the output arm encloses the drive arm, which features at one end of the arm an opening defined to accept the pivot axle. The opposing end of the arm includes a compliance magnetic sensor. Disposed laterally at either side of the drive arm is a series elastic element. 
     In accordance with another aspect of the present device, the hand assembly is comprised of structures replicating a thumb, an index finger, and the grouping of the middle, ring, and pinky fingers. The thumb structure is driven by two parallel actuators that provide the structure with two inputs and two outputs. The two parallel actuators give the thumb structure opposition movement with the index finger and lateral movement. The two actuators are connected in parallel and fixed to the interior structure of the hand assembly. The thumb structure also features a flexural element separating the base of the thumb structure from the load-bearing portion of the structure. The base portion of the structure houses a sensor measuring the displacement of the loaded portion of the thumb relative to the thumb structure rest position. The load-bearing portion of the thumb structure contains the magnet whose displacement the sensor measures. In one embodiment of the thumb structure, the flexural structure is provided by linear flexural elements. Another embodiment of the thumb structure provides for spiral flexural elements. The sensor measuring displacement allows a calculation of the compliance to the thumb in both directions. The measured compliance allows continuous measurement of the force applied to the thumb structure in both directions. 
     In accordance with another aspect of the present device, the index finger structure of the hand assembly contains a rotating element at the base of the index finger that drives the motion of the finger. The index finger structure is comprised of a base joint that is connected to the rotating element. The base joint supports the lower phalanx structure. The lower phalanx structure terminates at the middle joint. The middle joint then supports the middle phalanx structure. The middle phalanx structure terminates at the farthest joint. The farthest joint then supports the upper phalanx structure. 
     In further accordance with the present device, the index finger structure and its integrated phalanx structures are kinematically determinate based on the rotation of the base element. When driven by the rotating element, the index finger structure is constrained to follow a set trajectory, enabling precise dexterity of index finger movement. In this way, the user can rely on the fixed trajectory of the index finger to perform fine tasks, such as pinching or retrieving small objects. In another embodiment of the index finger, the middle phalanx structure is fixedly joined to the upper phalanx structure. 
     In accordance with another aspect of the present device, the middle, ring, and pinky finger structures (MRP structures) are integrated into the hand assembly. Each of the three structures originates with a base joint supporting a lower phalanx structure. Each lower phalanx structure terminates at a middle joint. Each middle joint then supports a middle phalanx structure. Each middle phalanx joint terminates at a farthest joint. Each farthest joint then supports an upper phalanx structure. 
     Each individual MRP structure features an indeterminate linkage between the base joint and middle joint, and a deterministic linkage between the middle joint and farthest joint. As a result, the base and middle joints of the individual finger structures will continue to operate until the joint motion is impeded. During a grasping action, the middle phalanx structure will continue to operate even if the base phalanx structure is impeded by the object being grasped. This indeterminate linkage assists in creating a conforming grasp for the hand structure and is enabled by the double differential of the MRP transmissions. 
     Additionally, the MRP structures have indeterminate gear sets allowing the three structures to move separately in order to grasp or conform around an obstacle. Two differential gear sets incorporated into the hand assembly structure drive the MRP structures. The first differential gear is driven by the actuator and has outputs at the rotating element of one finger structure and at the input of the second differential gear. The second differential gear has outputs at the rotating elements of the remaining fingers. As one actuator drives all three MRP structures separately, the MRP structures are linked and under-actuated. As a result of the differential gear assembly, if one MRP structure encounters an obstacle, it will stop, but the other MRP structures will still move freely until they encounter an obstacle. 
     In accordance with another aspect of the present device, a non-backdriveable clutch controls the reaction of the thumb structure, the index finger structure and the linked MRP structures to the application of an output load. This embodiment of the clutch provides that any output torque on the hand assembly will result in a friction lock of the clutch. In this embodiment, the output hex of the clutch locks against the input spline and the bearings disposed between the output and input. Further, this embodiment of the clutch provides that upon sufficient input torque, the clutch unlocks and allows additional input movement without the user having to manually reset the hand assembly. 
     In accordance with another aspect of the present device, a planetary gear stage transfers torque from the actuator to the output stage. The actuator drives the planetary stage&#39;s ring gear which, through interaction with the planet gears, drives the planet&#39;s carrier, which then drives the output stage. The sun gear is attached through a spring to ground. Any torque applied to the planetary stage will cause a displacement of the sun gear until the torque is balanced by the displacement of the spring. Thus, the spring stores elastic energy and increases the compliance of the index structure. The use of the spring attached to the sun gear allows measurement of load on the structures without the addition of a load cell. 
     In accordance with another embodiment of the present device, a stage driver and timing belt transfer torque to the index finger structure and the MPR structures. The stage driver transfers the torque to the timing belt, loosening one side of the timing belt and tightening the opposite side. In further accordance with the current device, a tensioner positioned between the stage driver and its corresponding pulley displaces as the tension of the timing belt changes. The tensioner displacement stores energy. Inference of the load applied to the structure can be based upon that displacement. The use of this tensioner allows measurement of load on the structures without the addition of a load cell. The tensioner additionally stores elastic energy and increases the compliance of the structures. 
     These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the appended claims and accompanying drawings. 
     The same compliance method is applied to the MRP drive, allowing it to store elastic energy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein: 
         FIG.  1    is a perspective view of one embodiment of a prosthetic arm apparatus according to the present invention; 
         FIG.  2    is an exploded view of the prosthetic arm apparatus of  FIG.  1   ; 
         FIG.  3    is a rear view of a shoulder abductor of the prosthetic arm apparatus of  FIG.  1    according to the present invention; 
         FIG.  4    is a front view of the shoulder abductor of  FIG.  3   ; 
         FIG.  5    is a side view of the shoulder abductor of  FIG.  3   ; 
         FIG.  6    is a perspective view of the shoulder abductor of  FIG.  3   ; 
         FIG.  7    is an exploded perspective view of the shoulder abductor of  FIG.  6   ; 
         FIG.  8    is a perspective view of a shoulder flexion assembly of the prosthetic arm apparatus of  FIG.  1    according to the present invention; 
         FIG.  9    is a reverse perspective view of the shoulder flexion assembly of  FIG.  8   ; 
         FIG.  10    is an exploded perspective view of the shoulder flexion assembly of  FIG.  8   ; 
         FIG.  11    is a cross-sectional perspective view of the shoulder flexion assembly of  FIG.  8   ; 
         FIG.  12    is a top view of a non-backdriving clutch according to the present invention; 
         FIG.  13    is a perspective view of a fully assembled compliance subassembly of the shoulder flexion assembly of  FIG.  8   ; 
         FIG.  14    is a perspective view of the bottom portion of the compliance subassembly of  FIG.  13   ; 
         FIG.  15    is a perspective view of the top portion of the compliance subassembly of  FIG.  13   ; 
         FIG.  16    is a perspective view of a humeral rotator of the prosthetic arm apparatus of  FIG.  1    according to the present invention; 
         FIG.  17    is a cross-sectional perspective view of the humeral rotator of  FIG.  16   ; 
         FIG.  18    is a perspective view of an elbow flexion assembly of the prosthetic arm apparatus of  FIG.  1    according to the present invention; 
         FIG.  19    is a cross-sectional perspective view of one embodiment of the elbow flexion assembly shown without the radial mount; 
         FIG.  20    is a cross-sectional perspective view of the elbow flexion assembly shown with the radial mount; 
         FIG.  21    is a perspective view showing the compliance subassembly of the elbow flexion assembly of  FIG.  19   ; 
         FIG.  22    is an exploded perspective view of the elbow flexion assembly of  FIG.  18   ; 
         FIG.  23    is a perspective view of a wrist rotator of the prosthetic arm apparatus of  FIG.  1    according to the present invention; 
         FIG.  24    is a cross-sectional perspective view of the wrist rotator of  FIG.  23   ; 
         FIG.  25    is a perspective view of a wrist flexion assembly and a hand control module of the prosthetic arm apparatus of  FIG.  1    according to the present invention; 
         FIG.  26    is a rear perspective view of the wrist flexion assembly and hand control module of  FIG.  25   ; 
         FIG.  27    is a cross-sectional perspective view of the wrist flexion assembly and hand control module of  FIG.  25   ; 
         FIG.  28    is a perspective view of a wrist assembly output arm of  FIG.  25   ; 
         FIG.  29    is a side view of a hand assembly of the prosthetic arm apparatus of  FIG.  1    according to one embodiment; 
         FIG.  30    is a front view of one embodiment of the hand assembly of  FIG.  29   ; 
         FIG.  31    is a perspective view of one embodiment of the hand assembly of  FIG.  29    showing an index finger tensioner assembly; 
         FIG.  32    is a cross-sectional view of one embodiment of the hand assembly of  FIG.  29    showing an MRP tensioner assembly; 
         FIG.  33    is a front cross-sectional view of one embodiment of the MRP differential drive of  FIG.  30   ; 
         FIG.  34    is a front cross-sectional view of one embodiment of thumb differential drives and an index finger differential drive of  FIG.  30   ; 
         FIG.  35    is a side view of one embodiment of the hand assembly of  FIG.  30    showing a tactile feedback sensor according to the present invention; 
         FIG.  36    is a perspective view of one embodiment of the tactile feedback sensor and a feedback actuator of the prosthetic arm apparatus of  FIG.  1   ; 
         FIG.  37    is a perspective view of another embodiment of the tactile feedback sensor and feedback actuator of the prosthetic arm apparatus of  FIG.  1    according to the present invention; 
         FIG.  38    is an exploded view of a portion of the hand showing another embodiment of the index and MRP fingers drives; 
         FIG.  39    is an exploded view of another embodiment of the hand; 
         FIG.  40    is a perspective view of another embodiment of the hand; and 
         FIG.  41    is a perspective cutaway view of the hand. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS.  1  and  2   , a prosthetic arm apparatus  10  for attachment to a shoulder of a shoulder disarticulated amputee includes a plurality of segments, including a shoulder abductor  12 , a shoulder flexion assembly  14 , a humeral rotator  16 , an elbow flexion assembly  18 , a wrist rotator  20 , a wrist flexion assembly  22 , and a hand assembly  24 . The prosthetic arm apparatus  10 , in the exemplary embodiment, has the dimensions and weight of a female arm of a fiftieth percentile, so that many different users may comfortably use the prosthetic arm apparatus  10 . As should be understood by those skilled in the art, the prosthetic arm apparatus  10  may be constructed to larger or smaller dimensions if desired. 
     Referring to  FIG.  3   , one embodiment of the shoulder abductor  12  is shown. The shoulder abductor  12  includes a harness mount  26 . The harness mount  26  has harness interface holes  28  that may be used to attach the abductor  12  to a prosthetic harness (not shown) or other system for supporting the prosthetic arm apparatus  10 . In the exemplary embodiment, the harness may be one disclosed in co-pending U.S. patent application Ser. No. 12/026,971, by Altobelli, et al., entitled Dynamic Support Apparatus filed on Feb. 6, 2008, which is hereby incorporated by reference. 
     Referring to  FIG.  4   , the shoulder abductor  12  also has a shoulder flexion assembly mount  30 , shown according to one embodiment. The shoulder flexion assembly mount  30  interfaces with the shoulder flexion assembly  14  to mount the shoulder flexion assembly  14  onto the shoulder abductor  12 . In one embodiment, the flexion assembly mount  30  has interface holes  32  to facilitate connection of the shoulder flexion assembly  14  by attachment means such as bolts. 
     Referring to  FIG.  5   , the shoulder abductor  12  further includes an abductor joint  34 , shown according to one embodiment. The abductor joint  34  is used to pivot the shoulder flexion assembly mount  30  away from the harness mount  26  and back toward the harness mount  26 . 
     Referring to  FIGS.  6  and  7   , the shoulder abductor  12  includes an abductor motor  36  to control the pivotal movement of the abductor joint  34 , both the shoulder abductor  12  and abductor motor  36  shown according to one embodiment. In this embodiment, the abductor motor  36  is a brushed DC motor controlling the pivotal movement through an abductor belt  38  connected to a worm drive  41  driving a worm wheel  39  connected to an abductor harmonic drive  40 . 
     Referring to  FIGS.  8  and  9   , the shoulder flexion assembly  14 , in one embodiment, has a main shoulder housing  42 , with an abductor interface  44  for connecting the shoulder flexion assembly  14  to the shoulder abductor  12 . The shoulder flexion assembly  14  also has a humeral interface  46  for connecting the humeral rotator  16  to the shoulder flexion assembly  14 . 
     Referring to  FIGS.  10  and  11   , in one embodiment, shoulder flexion motor magnets  52  are disposed around an exterior  58  of a shoulder flexion motor rotor  54 . In this embodiment, a shoulder flexion motor armature  55  drives the shoulder flexion motor rotor  52 , which in turn drives a shoulder flexion motor pulley  56  around a motor shaft  58 . The shoulder flexion motor pulley  56  supports a shoulder flexion belt  60 , which is linked between the shoulder flexion motor pulley  56  and a shoulder flexion belt-driven pulley  62 . The shoulder flexion belt-driven pulley  62  drives a shoulder flexion harmonic drive wave generator  64 . A shoulder flexion harmonic drive flexspline  66  rotates against the shoulder flexion harmonic drive wave generator  64  and a shoulder flexion harmonic drive circular spline  68 , resulting in reduced speed for the joint movement. The shoulder flexion harmonic drive flexspline  66  is connected to the abductor interface  44 , and is thus able to rotate the shoulder flexion assembly  14  in reference to the abductor interface. 
     Referring to  FIG.  11   , in one embodiment, a non-backdriving clutch  70  is disposed inside the main shoulder housing  42 . The non-backdriving clutch  70  allows the prosthetic arm  10  to hold position by locking when the prosthetic arm  10  is not moving. 
     Referring to  FIG.  12   , in one embodiment, roller bearings  72  line the interface between an input cage  74  and an output hex  76 . When a force is applied to the shoulder abductor interface  44 , the output hex  76  locks against the bearing race  78  and the roller bearings  72 . This prevents the shoulder flexion assembly  14  from moving due to force applied to its output, shoulder abductor interface  44 . Upon the exertion of a necessary amount of input force through the clutch input cage  74 , the output hex  76  disengages and allows the shoulder flexion assembly  14  to move. The clutch input cage  74  and the output hex  76  are both constrained by a clutch race  78 . It should be understood by those skilled in the art, that other mechanisms could be used to prevent backdriving of the prosthetic arm  10 , such as a clutch that locks in one direction or a solenoid with brakes that engage when the solenoid is powered. 
     Referring to  FIG.  13   , in one embodiment, a compliance subassembly  50  includes a compliance reactor  80  positioned on top of the shoulder flexion harmonic drive circular spline  68  and held in place by the clamp  82 . The compliance reactor  80  measures the amount of displacement in the compliance subassembly  50  in relation to the position of a compliance sensor magnet  84 . 
     Referring to  FIG.  14   , in one embodiment, the interior of compliance subassembly  50  includes series elastic elements  86 . The shoulder flexion harmonic drive circular spline  68  defines the interior of the compliance subassembly  50  and is formed to accommodate the placement of the series elastic elements  86  around an outer diameter  87  of the shoulder flexion harmonic drive circular spline  68 . The series elastic elements  86  are confined by the shoulder flexion harmonic drive circular spline  68  and the clamp  82 . 
     Referring to  FIG.  15   , the placement of the compliance reactor  80  in relation to the series elastic elements  86  and reactor elements  88  is shown. In this embodiment, three reactor elements  88  are positioned around the compliance reactor  80 , equidistant to each other. One series elastic element  86  is placed on either side of each reactor element  88 . When the shoulder flexion assembly  14  is subjected to unexpected force, such as a sudden jolt or impact, the compliance reactor  80  and reactor elements  88  displace from their rest positions and compress against the series elastic elements  86 . In that way, the compliance subassembly  50  attenuates the shock being transferred to the rest of the shoulder flexion assembly  14 . The compliance reactor  80  may also measure the amount of displacement and compliance by measuring the movement of the compliance reactor  80  in relation to the stationary position of the compliance sensor magnet  84 . 
     Referring to  FIG.  16   , one embodiment of the humeral rotator  16  is shown. The humeral rotator  16  includes an outer bearing carrier  90  and an arm control module  51  ( FIG.  2   ). The first control housing  92  is used to connect the humeral rotator  16  to the shoulder flexion assembly  14 . The inner rotational elements of the humeral rotator are held in place by a clamp  94 , which is fastened to the outer bearing carrier  90 . A humeral mount  96  passes through the clamp  94  and includes an elbow interface  98  for attaching the elbow flexion assembly  18  to the humeral rotator  16 . 
       FIG.  17    shows a cross-sectional view of the humeral rotator  16 . A humeral motor armature  100  drives a humeral motor rotor  102  having humeral magnets  104  disposed on its surface. The lower portion of the motor rotor  102  engages a humeral harmonic drive wave generator  106 . A humeral harmonic drive flexspline  108  rotates with the humeral harmonic drive wave generator  106  against the humeral harmonic drive circular spline  110 , resulting in a speed of rotation reduction as the humeral harmonic drive flexspline  108  causes the humeral mount  96  to move. Bearings  111  and  113  support the humeral motor rotor  102 . Bearings  106  support the harmonic drive components  106 ,  108 ,  110 . A bearing support  114  caps the outer bearing carrier  90  between the outer bearing carrier  90  and the first control housing  92 . 
     Still referring to  FIG.  17   , the one embodiment, a humeral potentiometer  116  of the humeral rotator  16 , measures the rotational displacement of a humeral potentiometer shaft  118  that rotates proportionately to the humeral mount  96 . 
     Referring to  FIG.  18   , the elbow flexion assembly  18  includes an elbow joint  120  and a radial mount  122 . The elbow joint  120  includes a slot  124  into which the elbow interface  98  of the humeral rotator is inserted to facilitate connection of the elbow flexion assembly  18  to the humeral rotator  16 . The radial mount  122  provides a second electronics housing  126 , in which an ACM stack  128  is located. The radial mount  122  includes a wrist interface  130 , for attachment of the wrist rotator  20 . 
     Referring to  FIG.  19   , the elbow joint  120  includes an elbow motor armature  132  that drives an elbow motor rotor  134 . Elbow magnets  136  are disposed at one end of the motor rotor  134 , and the opposing end of the motor rotor  134  has a sun gear  138 . As the motor armature  132  drives the sun gear  138 , the sun gear  138  in turn drives four planetary gears  140  positioned equidistant from each other around the sun gear  138 . The four planetary gears  140  in turn react against a ring gear  142 , giving the elbow flexion assembly  18  a first stage of speed reduction through an elbow harmonic drive wave generator  148  which also acts as the planet carrier. The elbow harmonic drive wave generator  148  powers the elbow harmonic drive flexspline  146 , which drives against the elbow harmonic drive circular spline  144 , giving the elbow flexion assembly  18  a second stage of reduction. The elbow harmonic drive flexspline  146  then drives the motion of the elbow flexion assembly  18 . Bearings  150  and crossed roller bearings  152  support the outer perimeter of the elbow flexion assembly  18 . Although described with both a planetary gear system and an elbow harmonic drive, the elbow flexion assembly  18  could be controlled solely by a harmonic drive by changing the gear reduction ratio. 
     Referring to  FIG.  20   , in the embodiment shown, the radial mount  122  is structurally fixed to the elbow joint  120 , such that when the elbow joint is actuated, the radial mount  122  moves. Referring to  FIG.  21   , an elbow compliance subassembly  154  is incorporated into the elbow flexion assembly  18 . A plurality of arms  156  extends from the center portion of the elbow compliance subassembly  154 . Each arm  156  has an elbow series elastic element  158  disposed on either side of the arm  156 . Similar to the shoulder flexion assembly  14 , if the elbow flexion assembly  18  is subject to a torque, the elbow compliance subassembly  154 , with its series elastic elements  158 , is capable of absorbing the shock attenuating the torque magnitude through the rest of the elbow flexion assembly  18 . 
     Referring to  FIG.  22   , the ACM stack  128 , includes circuit boards  160  connected to one another by structural standoffs  162 . The structural standoffs  162  are constructed of a conductive material, so that electrical power may be passed through the circuit boards  160 . The structural standoffs allow power to be supplied to each circuit board  160  without conventional power connections. 
     Referring to  FIG.  23   , the wrist rotator  20  includes a wrist outer bearing carrier  164 , a wrist clamp  166 , a wrist potentiometer  168 , an elbow interface  170 , and a wrist flexion assembly interface  172 . 
     Referring to  FIG.  24   , movement of the wrist rotator  20  is controlled by a harmonic drive similar to that described for the humeral rotator. A wrist rotator motor armature  174  drives a wrist rotator motor rotor  176  having wrist rotator magnets  178  disposed to its surface. The lower portion of the wrist rotator motor rotor  176  integrates a wrist rotator harmonic drive wave generator  180 . A wrist rotator harmonic drive flexspline  182  rotates with the wrist rotator harmonic drive wave generator  180  against a wrist rotator harmonic drive circular spline  184 , resulting in reduction in the speed of rotation as the wrist rotator harmonic drive flexspline  182  causes the wrist flexion assembly interface  172  to move with respect to the rest of the wrist rotator  20 . Bearings  185  support the wrist rotator motor rotor  176 . Bearings  186  support the harmonic drive components  180 ,  182 , and  184 . 
     Still referring to  FIG.  24   , the wrist potentiometer  168  of the wrist rotator  20  is disposed at one end of a wrist shaft  188  and measures the rotational displacement thereof. The wrist shaft  188  may be tubular, having an electronics channel  190  for passing electronic power and controls through the wrist rotator  20 . 
     Referring to  FIG.  25   , the wrist flexion assembly  22  includes hand control module circuit boards  192 , an input support structure  194 , an output arm  196 , and a hand interface  198 . The input support structure  194  connects the wrist rotator  20  with the wrist flexion assembly  22 . The output arm  196  has positive and negative flexion, such that the output arm  196  is able to move in two opposite directions in reference to the support structure  194 . The hand interface  198  allows the hand assembly  24  to be connected to the wrist flexion assembly  22 . Referring to  FIG.  26   , the wrist flexion assembly  22 , has wrist electrical connections  200  for supplying power to a wrist flexion motor  202 . 
     Referring to  FIG.  27   , in the embodiment shown, the wrist flexion motor  202  drives a wrist flexion output gear  204 , which in turn drives a wrist flexion final stage-driven gear  206 . A wrist flexion pivot axle  208  of the output arm  196  is axially disposed inside an opening defined by the interior of the wrist flexion final stage-driven gear  206 . Wrist flexion series elastic elements  210  are disposed in the interior of the output arm  196 . Movement of the wrist flexion final stage-driven gear  206  facilitates the positive and negative motion of the output arm  196 . A non-backdriving clutch  212  is disposed at one end of the wrist flexion output gear  204 . 
     Referring to  FIG.  28   , the output arm  196  has a wrist flexion drive arm  214 , which is driven by the wrist flexion final stage-driven gear  206 . The end of the wrist flexion drive arm  214  accommodates a wrist flexion compliance sensor magnet  216 . The wrist flexion series elastic elements  210  are disposed on either side of the wrist flexion drive arm  214 , and the wrist flexion series elastic elements  210  and the drive arm  214  are substantially enclosed within the output arm  196 . Similar to the elbow flexion assembly  18  and the shoulder flexion assembly  14 , if the wrist flexion assembly  22  is subjected to a force, the wrist flexion drive arm  214  compresses the wrist flexion series elastic elements  210  and attenuates the force through the rest of the wrist flexion assembly  22 . 
     The following is a description of one embodiment of the hand assembly. Other embodiments of the hand assembly are described and shown elsewhere in this specification. Referring to  FIGS.  29  and  30    the hand assembly  24  includes a hand support  218  for providing an interface for connecting the hand assembly  24  to the wrist flexion output arm  196 . The hand assembly  24  also includes a thumb structure  220 , an index finger structure  222 , and an MRP structure  224  replicating a middle finger  226 , a ring finger  228 , and a pinky finger  230 . The thumb structure  220  is driven by two thumb drives  232  that feed into a single differential, giving the thumb structure  220  two degrees of freedom of movement. The index finger structure  222  is driven by a single index drive  234  and the MRP structure  224  is driven by a single MRP drive  236  that feeds a double differential. 
     Referring to  FIG.  31   , the index finger structure  222  (not shown) is driven by the index drive  234  through an index drive pulley  238 , an index tensioner  240 , an index tension belt  242 , and an index finger pulley  244 . The index drive pulley  238  is stage driven and transfers the torque to the index tension belt  242 , which in turn rotates the index finger pulley  244 , causing the index finger structure  222  to move. As the index tension belt  242  transfers the torque, one side of the index tension belt  242  tightens and the other side loosens, depending on which direction the index drive pulley  238  is rotated. The index tensioner  240  is located between the index drive pulley  238  and the index finger pulley  244  and the index tensioner  240  displaces in relation to the change in load to maintain the tension of the index tension belt  242 . The index tensioner  240  has one side grounded and the other side capable of displacement upon the application of a load. The index tensioner  240  may instead ground the moveable side of the index tensioner  240  with a spring. 
     Referring to  FIG.  38   , in another embodiment, the index finger structure  222  is driven through an index sun shaft  350 , a set of index planets  352 , an index planet carrier  354 , an index ring gear  356 , and an index drive gear  358 . The index drive  360  drives the index ring gear  356 , turning the index planets  352 , the turning of which causes the index planet carrier  354  to rotate. The index drive gear  358  is driven by the external teeth of the index planet carrier  354 , causing the index structure  222  to move. Any torque transmitted by the index planet carrier  354  will react against the index sun shaft  350  causing it to rotationally displace the index spring  362  through the index spring mount  364 . This rotational displacement, sensed by an index potentiometer  366  can be used to infer the load on the index finger structure  222 . This rotational displacement can be used to store elastic energy. 
     Referring to  FIG.  31   , the thumb structure  220  is mounted on a thumb support  246 , which is driven by the two thumb differential drives  232 . The thumb structure  220  has flexural cuts  248  at its base allowing the compliant thumb structure  220  to move when a load is applied to it. 
     Referring to  FIG.  32   , the hand assembly  24  includes an MRP drive pulley  250  driven by the MRP drive  236  (not shown). The MRP drive pulley  250  is connected through an MRP tension belt  252  to the MRP pulley  254 , enabling movement of the MRP structure  224 . The MRP drive pulley  250  is stage driven and transfers the load to the MRP tension belt  252 , which in turn rotates the linked MRP structure  224  via the MRP pulley  254 . As the MRP tension belt  252  transfers the torque, one side of the MRP tension belt  252  tightens as the other side loosens. An MRP tensioner  256  located at one side of the MRP tension belt  252  displaces in relation to the change in load to maintain the tension of the MRP tension belt  252 . 
     Referring to  FIG.  38   , in another embodiment, the MRP finger structures  224  are driven through an MRP sun shaft  370 , a set of MRP planets  372 , an MRP planet carrier  374 , an MRP ring gear  376 , and an MRP drive gear  378 . The MRP drive  380  drives the MRP ring gear  376 , turning the MRP planets  372 , the turning of which causes the MRP planet carrier  374  to rotate. The MRP drive gear  378  is driven by the external teeth of the MRP planet carrier  374 , causing the MRP structures  224  to move. Any torque transmitted by the MRP planet carrier  374  will react against the MRP sun shaft  370  causing it to rotationally displace the MRP spring  382  through the MRP spring mount  384 . This rotational displacement can be used to store elastic energy. 
     Referring to  FIG.  33    the MRP differential drive  236  includes a main MRP drive gear  258 . The MRP drive gear  258  drives a first MRP input axle  260 . The first MRP input axle  260  drives a first differential idler gear  259  which optionally drives a middle spur gear  262  or a differential interface gear  261 . The middle spur gear  262  drives a middle pivot axle  264 . The middle finger  226  is mounted on the middle pivot axle  264  and is thus actuated by the MRP differential drive  236 . The differential interface gear  261  drives a second MRP input axle  266 . The second MRP input axle  266  drives a second differential idler gear  263  which optionally drives a ring spur gear  268  or a pinky spur gear  272 . The ring spur gear  268  drives a ring pivot axle  270 . The ring finger  228  is mounted on the ring pivot axle  270  and is thus actuated by the MRP differential drive  236 . The pinky spur gear  272  drives a pinky pivot axle  274 . The pinky finger  230  is mounted on the pinky pivot axle  274  and is thus actuated by the MRP drive  236 . While the MRP drive  236  drives the middle finger  226 , the ring finger  228  and the pinky finger  230 , the gear configuration of the first input axle  260  and the second input axle  266  allows independent movement for the under-actuated finger gear system of the MRP structures  224 . 
     Referring to  FIGS.  39 - 41   , in another embodiment of the hand, the MRP differential drive includes an MRP drive gear  378  which drives a double differential allowing the MRP fingers to conformably wrap around an object. The MRP drive gear  378  drives a first MRP input axle  400 . The first input axle  400  drives a first differential idler gear  402  which optionally drives a middle spur gear  404  or a differential interface gear  406 . The middle spur gear  404  drives a middle pivot axle  264 . The middle finger  226  is mounted on the middle pivot axle  264  and is thus actuated by the MRP drive  236 . The differential interface gear  406  drives a second MRP input axle  408 . The second MRP input axle  408  drives a second differential idler gear  410  which optionally drives a ring spur gear  412  or a pinky spur gear  414 . The ring spur gear  412  drives a ring pivot axle  270 . The ring finger  228  is mounted on the ring pivot axle  270  and is thus actuated by the MRP drive  236 . The pinky spur gear  414  drives a pinky pivot axle  274 . The pinky finger  230  is mounted on the pinky pivot axle  274  and is thus actuated by the MRP drive  236 . While the MRP drive  236  drives the middle finger  226 , the ring finger  228  and the pinky finger  230 , the gear configuration of the first input axle  400  and the second input axle  408  allows independent movement for the under-actuated finger gear system of the MRP structures  224 . 
     Referring to  FIG.  34    the thumb differential drives  232  control the movement of the thumb structure  220  and are driven by thumb actuators  276 . The thumb actuators  276  have non-backdriving thumb clutches  278  to prevent output loads from reaching and backdriving the thumb actuators. One thumb actuator  276  drives a first thumb output drive  280  and a first thumb output gear  282 . The first thumb output gear  282  in turn drives a first thumb transfer gear  284 , which drives a fixed differential shaft  286 . The fixed differential shaft  286  drives one thumb differential bevel gear  287 . The second thumb actuator  276  drives a second thumb output drive  288  and a second thumb output gear  290 . The second thumb output gear  290  drives a second thumb transfer gear  292 , which drives a thumb differential bevel gear  294 . The two thumb differential bevel gears  287  and  294  operate the thumb structure  220  in its two degrees of motion. 
     The thumb structure  220 , the index finger structure  222 , and MRP structure  224  in one embodiment are covered in silicone, which provides additional friction and aids in gripping objects. In some embodiments, the entire hand assembly  24  may also be covered in silicone to provide additional grip for holding objects. In other embodiments, the silicone material may be replaced by other compliant materials. 
     The various parts of the prosthetic arm apparatus  10  are preferably constructed from plastic or magnesium. However, where more strength is desired, the parts may be made of aluminum, titanium or steel. In other embodiments, the various parts of the prosthetic arm may be constructed of other metals or plastics, depending on the desired characteristics, including strength and weight, of the various part. 
     Referring to  FIG.  35   , a tactile feedback sensor  296  may be positioned on the inner side of the thumb structure  220 . The tactile feedback sensor  296  may be a pressure sensor, force sensor, a displacement sensor, or other similar sensor capable of providing the user with feedback. Referring to  FIG.  36   , the tactile feedback sensor  296  is operatively connected to a feedback actuator  298 . The tactile feedback sensor  296  may be connected to the feedback actuator  298  by either wires or wirelessly. In operation, as the user grips an object with the hand assembly  24 , feedback sensor  296  reads the displacement of or the force exerted on the thumb structure  220 . That reading is then sent to the feedback actuator  298 , which gives the user tactile feedback that indicates the strength of the grip. Feedback actuator  298  may be placed on the chest of the user, or in any other location capable of receiving tactile feedback, such as on a user&#39;s residuum  300 . Referring to  FIG.  37   , the feedback actuator  298  may be located on a foot controller  302  that is used to control hand assembly  24 . 
     Feedback actuator  298  may be a vibration motor, such as any vibration motor known in the art, placed against the skin of the user. As the user grips an object, feedback actuator  298  begins vibrating, notifying the user how strong the object is being gripped. As the force on or displacement of the tactile feedback sensor  296  changes, frequency and/or amplitude of vibration may also change, notifying the amputee of a changing grip. For example, if a vibrating actuator  298  is placed at the chest of the user as in  FIG.  36   , the user will feel the vibration at his chest. 
     The feedback actuator  298  may also be placed wherever the controller for the hand assembly  24  is located. For example, if a foot controller  302  controls the hand assembly  24 , the feedback actuator  298  may be incorporated into the foot controller  302 . The user will then receive tactile feedback of the strength of the prosthetic grip at the same location where the controller is located. 
     The actuator  298  may also be a pressure actuator that applies pressure against the user&#39;s skin. For example, the actuator  298  may have a rod that increases pressure against the amputee&#39;s skin as the hand assembly  24  increases its grip on an object. 
     Although described with a single tactile feedback sensor  296 , additional tactile feedback sensors may be placed at other locations on the hand assembly  24 . For example, additional tactile feedback sensors  296  may be placed on the index finger structure  222 , the MRP structures  224 , on the palm of the hand assembly  24 , or on any combination of these positions or any other location. Each tactile feedback sensor  296  would then be operatively connected to an associated feedback actuator  298 . Multiple tactile feedback sensors  296  and actuators  298  would provide more sophisticated tactile feedback of the strength of the grip, improving the control of the hand assembly  24 . 
     In operation, the prosthetic arm apparatus is able to move substantially similar to a human arm. Referring to  FIGS.  29  and  30   , starting with the hand assembly  24 , the thumb structure  220 , index finger structure  222 , and MRP structure  224  are each driven independent of the others, and therefore, each may be actuated without actuating the other two structures. The thumb actuator  276  driving the thumb miter gear  294  controls the thumb structure&#39;s movement in a direction toward or away from the center of the palm of the hand assembly  24 , as shown in  FIG.  34   . The thumb actuator  276  driving the lateral rotation shaft  286  controls the thumb structure&#39;s movement in a direction toward or away from the side of the palm of the hand assembly  24 , as shown in  FIG.  34   . The thumb actuators  276  ( FIG.  34   ) provide the thumb structure  220  with four degrees of freedom in the thumb structure&#39;s movement. The index finger structure  222 , driven by a single index differential drive  234 , may be actuated with two degrees of freedom. Specifically, the index finger structure  222  may be actuated toward or away from the palm of the hand assembly  24 , wherein the movement path is similar to that of a human index finger while making or releasing a fist. The middle finger  226 , ring finger  228 , and pinky finger  230  of the MRP structure  224  are actuated by the MRP differential drive  236 . Additionally, the middle finger  226 , ring finger  228 , and pinky finger  230  are actuated toward or away from the palm of the hand assembly  24 , similar to the index finger structure  222 . However, the middle finger  226 , ring finger  228 , and pinky finger  230  are each geared separately, such that the rate of movement of each is different, simulating human finger movement. 
     Referring to  FIG.  1   , the hand assembly  24  is mounted on the wrist flexion assembly  22  via the hand interface  198 , as shown in  FIG.  25   . Referring to  FIG.  25   , as the output arm  196  of the wrist flexion assembly  22  is actuated, the hand assembly  24  is also caused to move. The output arm  196  of the wrist flexion assembly  22  may be actuated pivotally about wrist flexion pivot axle  208 , as shown in  FIG.  27   , moving the hand interface  198  to the left or right, and thus pivoting the hand assembly  24  in relation to the input support structure  192 . 
     Referring back to  FIG.  1   , the wrist flexion assembly  22  is attached to the wrist rotator  20  via wrist flexion assembly interface  172 , shown in  FIG.  23   . Referring to  FIGS.  23  and  24   , when actuated, the wrist flexion assembly interface  172  is rotated about wrist shaft  188  in relation to the wrist outer bearing carrier  164 . Therefore, the wrist flexion assembly  22 , and attached hand assembly  24  are also caused to rotate in reference to the wrist outer bearing carrier  164  by actuation of the wrist rotator  20 . Therefore, the wrist rotator  20  allows the prosthetic arm apparatus  10  to move in a way similar to a human arm opening a door. 
     Referring back to  FIG.  1   , the wrist rotator  20  is attached to the elbow flexion assembly  18  via the wrist interface  130 , shown in  FIG.  18   . Referring to  FIG.  20   , when the elbow flexion assembly  18  is actuated, the radial mount  122  is rotated about the axis of motor rotor  134 . The wrist rotator  20 , wrist flexion assembly  22 , and hand assembly  24  are thus also caused to rotate about the axis of motor rotor  134  because they are attached at the wrist interface to the radial mount  122 . Therefore, the elbow flexion joint  18  allows the prosthetic arm apparatus  10  to perform hammering motion. 
     Referring back to  FIG.  1   , the elbow flexion assembly  18  is attached to the humeral rotator  16  via the humeral mount  96 , shown in  FIG.  27   . Referring to  FIG.  16   , actuation of the humeral rotator  16  causes the humeral mount  96  to rotate in relation to the outer bearing carrier  90  of the humeral rotator  16 . Since the elbow flexion assembly  18 , wrist rotator  20 , wrist flexion assembly  22 , and hand assembly  24  are attached to the humeral mount  96 , they are also caused to rotate in relation to the outer bearing carrier  90 . This allows the prosthetic arm apparatus  10  to rotate to perform an arm wrestling motion. 
     Referring back to  FIG.  1   , the humeral rotator  16  is attached to the shoulder flexion assembly  14  though the humeral interface  46 , shown in  FIG.  9   . Referring to  FIG.  9   , actuation of the shoulder flexion assembly  14  causes the main shoulder housing  42  to pivot about the center of the abductor interface  44 . Since the humeral rotator  16 , elbow flexion assembly  18 , wrist rotator  20 , wrist flexion assembly  22 , and hand assembly  24  are attached to the main housing  42 , they are also caused to rotate in relation to the abductor interface  44 . Therefore, the shoulder flexion assembly  14  allows the prosthetic arm apparatus  10  to move along the torso simulating running motion. 
     Referring to  FIG.  1   , the shoulder flexion joint  14  is attached to the shoulder abductor  12  through the shoulder flexion assembly mount  30 , shown in  FIG.  5   . Referring to  FIG.  5   , the shoulder abductor  12  is attached to a harness that is worn by the user via harness mount  26 . When the shoulder abductor  12  is actuated in a positive direction, the shoulder flexion assembly mount  30  pivots away from the harness mount  26 , and the user. Similarly, by actuating the shoulder abductor in a negative direction, the shoulder flexion assembly mount  30  is pivoted toward the harness mount  26  and the user. Since the shoulder flexion assembly  14 , humeral rotator  16 , elbow flexion assembly  18 , wrist rotator  20 , wrist flexion assembly  22 , and hand assembly  24  are attached to shoulder abductor  12  at the flexion assembly mount  30 , they are also caused to pivot with the shoulder flexion assembly mount  30 . 
     One characteristic of the prosthetic arm apparatus described herein is that it provides the user with substantially the same movement capabilities and degrees of freedom of a human arm, including full shoulder functionality. Additionally, since each segment of the plurality of segments operates independently of each other segment of the plurality of segments, fewer segments may be used for less severe amputees. For example, a transhumeral amputee may have full shoulder functionality in the residuum, in which case the shoulder abductor  12  and shoulder flexion assembly  14  segments would be omitted from the prosthetic arm apparatus  10 . The resulting prosthetic arm apparatus  10  would include the humeral rotator  16 , the elbow flexion assembly  18 , the wrist rotator  20 , the wrist flexion assembly  22 , and the hand assembly  24 , wherein the humeral rotator  16  would be attached to the prosthetic harness. A further advantage of the present invention is the use of non-backdriving clutches to preclude movement of the segments due to forces exerted on the prosthetic arm apparatus  10  when not in motion. This saves power because power to the prosthetic arm apparatus  10  is turned off whenever the arm is not in motion. 
     An additional characteristic of the apparatus is that the hand assembly includes independently moving fingers and is capable of completing fine tasks such as pinching, grasping non-uniform objects, and lifting small objects off flat surfaces. Also, the tactile feedback sensor provides the user with feedback, during use of the prosthetic arm apparatus, such as the force of a grip. The apparatus also includes silicon covering on the finger structures, providing, amongst other things, grip for grasping objects. The rigid fingernail  304  provides a backstop for the silicon finger cover to enhance gripping capability. The rigid fingernail  304  also allows the user to lift small objects from a surface with the prosthetic arm apparatus  10 . 
     Although the invention has been described in the context of a prosthetic arm, an apparatus according to the elements of this invention could be used in other robotic tools, such as those used in manufacturing. 
     While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention.