Patent Publication Number: US-2005121929-A1

Title: Humanoid robotics

Description:
BACKGROUND TO THE INVENTION  
      This invention relates to humanoid robotics and, more especially, to a robotic forearm and hand configuration.  
      Whilst the actuation means incorporated as part of the forearm may take other forms, in the hereinafter described embodiment of the forearm of the configuration air muscles are employed in the displacement of structural elements of the robotic hand being elements each of which serves the role of a skeletal bone portion of the hand and wrist-simulating joint.  
      An air muscle sometimes referred to, variously, as fluidic muscle, rubbertuator, or McKibben muscle, comprises: an expansible tubular chamber, generally of an elastomeric material, most commonly rubber, having an air inlet port and an air exhaust port, a common port being, generally, employed for both of these functions; a braided sheath which embraces said tubular chamber throughout its length; and first and second closure arrangements, at the ends, respectively, of the tubular chamber. The Specification of UK Patent GB No 2255961, dated 13 Mar. 1992, contains a disclosure of a mechanical actuator having an air muscle as above stated, the air muscle serving as actuator traction element.  
      The air inlet and exhaust porting means of the air muscle may be constituted as a single combined port commonly integral with one or the other of the closure arrangements, but it may be separate from such closure arrangement, being, advantageously, a tapping at the mid-length position of the tubular chamber.  
      Introduction of air, or other suitable fluid, under pressure, to the chamber causes it to expand rapidly, this, in turn, producing radial expansion, also, of the braided sheath. It is characteristic of the braided sheath, that radial expansion of its expansible tubular chamber is accompanied by a contraction in its length. If the ends of the sheath are respectively coupled, the one to a, possibly movable, datum, a force-reaction part of the actuation system, the other to a system part movable with respect to said reaction part, contraction of the braided sheath gives rise to a tensile force which acts on the movable system part moving it against reaction at the datum force-reaction part in accordance with the extent of contraction in the sheath.  
      Air muscles need to be pulled out when ‘empty’ (relaxed) in order to be able to deliver their full stroke when inflated. In some cases this extension of the muscle is achieved by a second air muscle coupled to the first, usually acting antagonistically, more often by a conventional mechanical spring arrangement or other similar elastic means which carries out the return movement of a part to be moved. In either circumstance a return movement is effected of the part that has been moved by the air muscle under previous inflation of its tubular chamber. It will be apparent that the muscle and its associated muscle-extension means must, whatever its character, be coupled together, the one acting to pull-out, to extend, the other, and, in turn, to be extended by the other.  
      A major virtue of the air muscle in the context of humanoid robotics, more particularly the humanoid forearm, is the ability to accommodate within the limited space available, many more actuators of air muscle form than is possible using other types of actuator, of the moving piston variety, for example.  
      Whilst air muscles have been employed in at least one prior robotic forearm for the actuation of the hand and constituent parts thereof, the degrees of movement available in the prior art arrangement has, notwithstanding the local relatively large number of muscles employed, been quite limited in number, around twelve.  
      This has arisen, apparently, as a result of the departure in the modelling of the humanoid hand. The humanoid hand to be powered by the several air muscles in the forearm exhibited marked differences from the human hand that it purported to emulate, notably in the number and local relative disposition of the digits and their phalanges. The number degrees of movement in the hand being severely limited, as stated, and each degree of hand movement being under the control of one or, sometimes two, individual air muscles, the number of air muscles present in the forearm and employed in the actuation of the hand and its several (constituent parts was correspondingly small. These muscles were, perforce, supported in the forearm at positions spaced apart around the central shaft, the radius, of the forearm, this by reason, apparently, of the need to prevent or minimise wear arising as a result of abrasive continuous space-seeking jostling contact between the several muscles. The wear referred to has been attributable, in the main, not to contact between the muscle sheaths themselves but to contact between the sheaths and protuberant portions integral with muscle closure end means of the muscles and connection elements adjacent to such closure means.  
      It has been assessed that for a robotic hand to be able to execute the range of movement achievable by the human hand, it should be able to exhibit twenty four degrees of movement.  
      The dexterity of the prior art robotic hand has, as a result of its inadequate modelling of the human hand, been incapable of performing many of the movements desirable in the hand, the best known approximation having been twelve degrees of movement.  
      According to the invention, a robotic forearm and hand configuration is as set out in the claims schedule hereof, and the content of said claims and the inter-dependencies therebetween are to be regarded, notionally, as being set out here, also.  
      Such robotic forearm and hand configurations are capable of closely mimicking the movements of the human hand, exhibiting, as such configurations do, all twenty-four degrees of movement observed in the hand. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      A robotic forearm and hand configuration in accordance with the invention is hereinafter described with reference to the accompanying drawings in which:  
       FIG. 1  is a pictorial diagram of the robotic forearm and hand configuration;  
       FIG. 2  shows, in plan, a longitudinal section through part of the hand portion, the wrist joint, and certain elements of the forearm;  
       FIG. 3  shows a part-section taken in the plane III-III of  FIG. 2 ;  
       FIG. 4  shows, in plan, the hand and the wrist-simulating joint;  
       FIG. 5  depicts a side view of a finger-simulating digit;  
       FIG. 6  depicts an edge view of the digit of  FIG. 5   a;    
       FIG. 7  depicts a side view of the thumb-simulating digit;  
       FIG. 8  is a projected plan view of the digit of  FIG. 7 ; and  
       FIG. 9  shows a detail of the digit of  FIGS. 7 and 8 . 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION  
      The robotic forearm and hand configuration comprises: a hand portion  11 , a forearm portion  13 , and means incorporated in said forearm  13  and operative to produce local relative angular movements in the several movable parts of the forearm and hand configuration, all as hereinafter described. The hand portion  11  comprises: a rigid-main palm part  15   a;  projecting from said palm part  15   a  at a transversely extensive forward boundary  17  thereof, rigid first, second, and third link elements  19   a,    19   b,    19   c,  respectively; first, second and third finger-simulating digits,  21   a,    21   b,    21   c,  respectively; first and second auxiliary palm parts  15   b,    15   c,  respectively; a rigid fourth link element  19   d;  a finger-simulating fourth digit  21   d;  and a fifth or thumb-simulating digit.  
      The link elements  19   a,    19   b,    19   c,  are respectively pivotally coupled at side by side positions to the main palm part  15  at or adjacent to said forward boundary  17  in such manner as to permit angular movement of said link elements  19   a,    19   b,    19   c,  about respective pivot axes substantially normal to the main palm part  15 .  
      The link elements  19   a,    19   b,    19   c,  have portions  23   a,    23   b,    23   c,  respectively, said portions projecting forwardly of the forward boundary  17 .  
      The digits  21   a,    21   b,    21   c,  are respectively pivotally coupled to the link elements  19   a,    19   b,    19   c,  at axes, as  25   a,  extending transversely of the main palm part  15   a,  orthogonal to the pivot axes of the link elements, as  19   a.    
      The auxiliary palm part  15   b  is supported adjacent to a first side-boundary  27  of the main palm part  15   a  at bearing means  29 , being bearing means permitting local relative pitch movement of the auxiliary palm part  15   b  about an axis X - - - X extending transversely of the main palm part  15   a.    
      The fourth link element  19   d  is pivotally coupled to the auxiliary palm part  15   b  at a position adjacent to its forward boundary  31 , the pivot axis being substantially normal to the plane of the link element  15   b,  notionally the plane of the drawing. As with the link elements, as  19   a,  the link element  19   d  has a portion  23   d  which projects forwardly of the forward auxiliary palm part boundary  31 .  
      The fourth digit  21   d  is pivotally coupled to the fourth link element  19   d  at a location  25   d,  being pivotally coupled to the link element  19   d  for angular displacement thereof about an axis transversely orthogonal to the pivot axis of the link element  19   d  and parallel to the axis X - - - X.  
      As may be gathered, the pivotal couplings between the finger-simulating digits  21   a  to  21   d  and the link elements  19   a  to  19   d,  respectively, and the pivotal couplings between the link elements  19   a  to  19   d  and the main  15   a  or auxiliary palm part  15   b,  as the case may be, collectively simulate the knuckle part of the hand.  
      The auxiliary palm part  15   c  is part, the root part, of a carrier arrangement  33 . The auxiliary palm part  15   c  is supported in bearings  35 , defining pivot axis Y - - - Y, the bearings  35  being carried by the main palm part  15   a  at a position adjacent to a side boundary  37  thereof, being a side boundary transversely remote from the side boundary  27 .  
      The auxiliary palm part  15   c  is connected to the fifth or thumb-simulating digit  39  by a coupling part  41 , the longitudinal axis L - - - L of which is forwardly inclined at an acute angle with respect to the axis Y - - - Y. The coupling part  41 , which has a circumferentially extending flange  41   f,  is supported in bearings  41   b  such as to be angularly displaceable about its inclined axis Y - - - Y.  
      The fifth, or thumb-simulating, digit  39  is angularly displaceable with respect to coupling part  41  about an axis normal to the axis L - - - L, being, in the drawing, the axis at  39 ′ normal to the plane of the drawing.  
      The forearm portion  13  comprises a shaft  43  and a multiplicity of air muscles  45 , being, in number, not less than the number of degrees of angular movement available throughout the forearm and hand configuration.  
      The shaft  43 , being the radius-simulating portion of the forearm  13 , has, at one end  43   a,  a pivotal coupling with an upper arm portion  46  at an elbow joint  47 . The shaft  43  at its other end  43   b  is received within a bore  49  formed in a wrist joint-carrying stanchion  51 . The stanchion  51  which is of square cross-section has a cylindrical transverse passage  51   a  therethrough.  
      The wrist-simulating joint  53  includes opposed parallel plates  55   a,    55   b,  respectively, the one  55   a  being integral with or constituting a portion of the main palm, part  15 , the other  55   b  being supported, at one end, by a side wall member  57  upstanding from the main palm part  15 , and, at the other, by the stanchion  51 , the plate  55   b  being fixed to the stanchion  51  with a portion of its inwardly facing surface  55   b ′ in face to face contact with a face portion of the stanchion  51 , the face of the stanchion  51  that is parallel to the stanchion face portion that is in contact with the surface  55   b ′ being, itself, in contact with the main palm part  15 . The plate portion  55   a  and the plate  55   b  have axially aligned apertures,  57   a,    57   b,  respectively.  
      A universal joint between the hand and forearm portions of the configuration is constituted as a double bearing arrangement  61  having first and second bearing portions  63   a,    63   b,  respectively.  
      The bearing portion  63   a  comprises a block  65 , of square cross-section, having first, second, third and fourth passages  67   a,    67   b,    67   c,    67   d,  respectively. The first passage  67   a,  which extends between two opposite faces of the block  65 , has a cylindrical passage portion intermediate two conical end portions. The second passage  67   b  is a threaded cylindrical passage extending from a third face of the block  65  to communicate with the passage  65   a  with the axis of the passage  65   b  orthogonal to that of the passage  65   a.  The third and fourth passages  67   c,    67   d,  are aligned with their common axis orthogonal to the axes of both the passage  65   a  and the passage  65   b.    
      The block  65  is held fixed with respect to the plates  55   a,    55   b,  screws  69   a,    69   b,  respectively, extending through and being under clamping pressure with, the inner races  71   a,    71   b,  respectively, of rolling bearings  73   a,    73   b,  respectively located each with an Interference fit between the bearing outer races and respective walls of the apertures  57   a,    57   b.    
      The other portion  63   b  of the double bearing comprises a double rolling bearing, the outer races of which have an interference fit with the wall of the transverse stanchion passage  51   a.  A screw  75  Extends through the inner races of the double bearing  63   b  into the threaded passage  67   b.    
      The universal joint configuration  61  permits relative movement between the hand  11  and forearm  13  about the two orthogonal axes, namely the transverse axis defined by the screw  75  and the axis normal to the latter axis, being the axis extending longitudinally of the passage  67   a.    
      The air muscles  45 , being the actuation members for inducing angular displacements between the several parts of which the configuration is composed are clustered lengthwise about the shaft  43 . The muscles  45  are each anchored at one end to a local reference frame portion (not shown), not necessarily being the same reference frame portion for each muscle, being a portion (not shown) incorporated in the elbow joint  47 .  
      The air muscles are equal in number to not less than the number of angular movements capable of being executed between the several parts of the configuration in performing the variety of movements of which the forearm, hand and the wrist joint are capable, around fifty muscles being present in the forearm for this purpose. Movement of the several elements of the configuration is effected either by a single muscle and a conventional spring or, where appropriate, by two muscles. Air muscles being, of course, capable of exerting tractive forces, only, either a conventional spring or a second muscle must be employed to effect return movement extending the first muscle to its full length preparatory to the execution of the next full working stroke of the muscle. For further general discussion of the matter here addressed reference should be made to the specification of Applicant&#39;s co-pending UK Patent Application GB No.  
      The objective of the design is to provide a configuration capable of performing substantially all of the functions of which the human hand, including, as examples, the ability to bring the thumb, forefinger and small finger together with their tips in contact. The hand as hereinbefore described is so capable, but as indicated, such dexterity demands the provision in the local relatively small compass of the forearm of many air muscles. Not all of these are, of course, active at any given time, but a substantial number of muscles might be so active in the performance of compound movements of the hand and wrist joint. It is important, therefore, that the muscles should present a smooth encounter with one another thereby to minimise mutual abrasion during space-seeking jostling contact therebetween. A feature of the muscle commonly the cause of such abrasion is the protuberance presented by the means employed to close the muscle at its ends.  
      Not infrequently, the closure means has comprised or included the common circlip, the screw-form pinion of a rack and pinion band tightening mechanism and the tail end of the clip, being liable to rise away from the encircling band portion of the clip, each constituting a hazard so far as abrasive contact between muscles is concerned.  
      Applicants&#39;s co-pending UK Patent Application GB No offers a favoured design for the end-closure of the muscle.  
      Protuberances of the sort mentioned are not present in the latter design. Liability of failure of such muscles, as a result of abrasive contact therebetween, is very substantially reduced least. The limitation of prior art forearm air muscle arrangements, the number of muscles that may be gathered around the radius, that is to say, is obviated. Whereas in prior arrangements around twelve muscles only could be incorporated in the forearm, muscle designs in accordance with the last mentioned co-pending patent application enables a full set of muscles, around forty-eight, to be employed, packed together in space-seeking jostling contact, this without subjecting the several muscles to any substantial increase in muscle failure rate under their rubbing contact.  
      The allusion to the muscle design of Applicant&#39;s co-pending UK Patent Application GB No is solely for the purpose of pointing to the problem encountered in at least certain prior art muscle designs, and to direct attention to a practical air-muscle configuration possessing characteristics as to the smooth muscle conformation to be sought for any air muscle suitable for employment as one of many such muscles to be incorporated in the forearm.  
      Returning to the matter of the configuration of the hand  11  and, more particularly, to the form of the several finger-and thumb-simulating digits each digit comprising a multiplicity of phalange-simulating segments  77 , three segments in the fingers, two in the thumb. Each segment  77  comprises two spaced parallel flat plates, as  77   a,    77   b,  respectively, the spaced plates of contiguous segments  77  overlapping at end, portions  79   a,    79   b,  respectively, thereof and being coupled together at parallel pivot axes, as  81 , orthogonal to the planes of the parallel plates  77   a,    77   b  and intercepting said parallel plates at a position within said overlapping end portions  79   a,    79   b.    
      In the case of the finger-simulating digits  21   a  to  21   d,  though not the thumb-simulating digit  39 , tendon guide wheels, as  83 , are pinned to the link elements  19   a  to  19   d,  respectively.  
      Tendon guide posts, as  85 , are respectively outstanding from the several digits, both finger and thumb, at appropriately distributed locations thereof.  
      The drawings are largely self-explanatory. Tendons  87  from muscles of the forearm  13  are routed by way of the passage  67   a  through the bearing block  65 , passing around appropriate guide posts  85  and/or guide wheels,  83  for the finger-simulating digits  21   a  to  21   d,    41   f  for the thumb-simulating digit  39  to optimally selected tendon fixing positions, which may be the guide post  85  positions, typically as shown, of the several relatively angularly movable parts of the hand  11 , phalanges of the finger digits  21   a  to  21   d,  the thumb-simulating digit  39 , relatively angularly movable members at the wrist-simulating joint  53 , the radius-simulating member  49  and the main palm part  15 , that is to say.  
      In each of the finger-simulating digits  21   a  to  21   d,  the endmost and next adjacent phalanges of the digit are biassed towards the unbent state, each by a leaf spring  88 , this in order to avoid employing a tendon where this is desirable.  
      In addition to these features, sensors for sensing different physical variables arising both within the configuration and in the environment with which the configuration interfaces, are to be incorporated at appropriate locations of the configuration.  
      Movement sensors, as  89 , distributed throughout the configuration at appropriate locations serve to sense relative angular movements between hand  11  with respect to the forearm  13  about the wrist joint, of the fingers  21   a  to  21   d  with respect to one another, of the thumb  35  with respect to the main palm part  15 , of the several phalanges  77  of both the fingers and the thumb-simulating digits, and of the auxiliary palm parts  15   a,    15   b,  with respect to the main palm part  15 . Spacings between parallel plates  77   a,    77   b,  of which the phalanges  77  of the several digits are constituted, serve to accommodate sensors and associated electronics.  
      The dexterity achievable as a result of the various combinations of independent pivotal movements permitted at the several finger-simulating joints, and particularly at the thumb-simulating joint, gives rise to a robotic hand closely comparable in the range of movements capable of being executed to that achievable with the human hand.