Patent Publication Number: US-2021170607-A1

Title: Flexible mechanical joint

Description:
FIELD 
     This disclosure generally relates mechanical joints, for example mechanical joints for use in robotics, and in particular a flexible mechanical joint which may be employed as a neck joint in a robot. 
     BACKGROUND 
     Description of the Related Art 
     Mechanical joints are used to couple parts to one another. Mechanical joints often allow movement of one part with respect to another part, for example providing one or more degrees of freedom for pivoting, rotation or articulation about one or more axes. Mechanical joints come in a large variety of forms, for example a knuckle joint, pin joint, hinge joint, ball and socket joint, or prismatic joint. A suitable mechanical joint is often selected based on a particular application, desired type of movement and/or stress to which the joint will be subjected. 
     Robots may include one or more joints between parts thereof. For example, robots with moveable robotic appendages may include one or more joints between various links of the moveable robotic appendage which provides one or more degrees of freedom for the moveable robotic appendage. 
     BRIEF SUMMARY 
     A flexible mechanical joint may provide multiple degrees of freedom, for example allowing one part to curl about a set of axes that lie in a common plane and that are radially spaced with respect to one another about a common intersection point. The flexible mechanical joint may take the form of a flexible mechanical neck joint which may be used in a robot to mimic a human neck, allowing a robotic head to tilt with respect to a robotic thorax in a fashion similar to a human head. The flexible mechanical joint is composed of a series of links, which may be shaped like disks, the links coupled by a series of flexures that allow the series of disks to curl. The flexures are distributed around a longitudinal axis of the flexible mechanical joint, for instance at 45 degree increments, which allows the flexible mechanical joint to curl in any direction. The flexible mechanical joint is actuated through one or more cables, for instance a set of four cables. The cables may, for example, be distributed at four opposing corners of the links. The cables may be fixed to a last one of the links and pass through a number of throughholes in each of the links. Actuation (e.g., tensioning, relaxing) of the cables controls both a configuration (i.e., amount of curl about one or more axes) and a stiffness of the flexible mechanical joint. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings. 
         FIG. 1  is a top, left side, rear isometric view of a flexible mechanical joint in the form of a flexible mechanical neck joint according to at least one illustrated implementation, including a set of links and flexures coupling links of respective pairs of the links together, the flexible mechanical joint illustrated in an unarticulated configuration. 
         FIG. 2  is a left side elevational view of the flexible mechanical joint of  FIG. 1 , also illustrated in the unarticulated configuration. 
         FIG. 3  is a cross-sectional view of the flexible mechanical joint of  FIGS. 1 and 2  taken along a section line that passes through a longitudinal axis of the flexible mechanical joint, the flexible mechanical joint illustrated in the unarticulated configuration. 
         FIG. 4  is a cutaway view of the flexible mechanical joint of  FIGS. 1 and 2  taken along the section line that passes through the longitudinal axis of the flexible mechanical joint, the flexible mechanical joint illustrated in the unarticulated configuration. 
         FIG. 5  is a top, right side, front isometric view of a lower portion of the flexible mechanical joint of  FIGS. 1 and 2  with several links of an upper portion removed to better illustrate an intermediary one of the links and flexures thereof. 
         FIG. 6A  is an isometric view of one of the links of the flexible mechanical joint of  FIGS. 1 and 2 , according to at least one illustrated implementation. 
         FIG. 6B  is a top plan view of the one of the links of  FIG. 6A . 
         FIG. 7  is a side elevational view of the one of the flexures, according to at least one illustrated implementation. 
         FIG. 8  is cross-sectional view of the flexible mechanical joint of  FIGS. 1 and 2  illustrated in an unarticulated configuration, and showing a routing of a cable according to at least one illustrated implementation. 
         FIG. 9  is a front elevational view of the flexible mechanical joint of  FIGS. 1 and 2  illustrated in a first fully articulated configuration. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed implementations and embodiments. However, one skilled in the relevant art will recognize that the implementations and embodiments may be practiced without one or more of these specific details, or with other methods, components, structures, materials, etc. In other instances, well-known structures associated with mechanical joints, and actuators (e.g., solenoids, electric motors, electromagnets, pneumatic or hydraulic piston and associated pressure reservoirs and valves) operable to cause articulation of mechanical joints, have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments. 
     Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.” 
     Reference throughout this specification to “in one implementation” or “in an implementation” or “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the implementation or embodiment is included in at least one implementation or at least one embodiment. Thus, the appearances of the phrases “in one implementation” or “in an implementation” or “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same implementation or embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     The headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments. 
       FIG. 1  shows a flexible mechanical joint  100  according to at least one illustrated implementation, the flexible mechanical joint  100  illustrated in  FIG. 1  in an unarticulated configuration. The flexible mechanical joint  100  may be used to moveably or articulatably couple a robot head to a robot thorax or other portion of a robot, and thus be interchangeably denominated as a flexible mechanical neck joint  100 . 
     The flexible mechanical joint  100  comprises a base or proximate-most link  102 , an end or distal-most link  104 , and a set of plate or intermediary links  106   a - 106   n  (fourteen shown, collectively  106 ) located between the base or proximate-most link  102  and the end or distal-most link  104 . The plate or intermediary links  106   a - 106   n  of the set of plate or intermediary links  106  are arrayed with respect to one another, for example in a stack. The plate or intermediary links  106   a - 106   n  of the set of plate links  106  may taper in size or dimension, going from relatively larger to relatively smaller as the set is traversed from a proximate end to a distal end of the stack, where the proximate end is an end of the stack (e.g., plate or intermediary link  106   a ) that is closest to the base or proximate-most link  102  and the distal end is the end of the stack (e.g., plate or intermediary link  106   n ) that is closest to the end or distal-most link  104 . The size or dimension in which the taper occurs may depend on the overall geometry of the plate or intermediary links  106   a - 106   n.  For example, the size or dimension may correspond to a measure of a length of a perimeter or boundary of a major face of the plate or intermediary links  106   a - 106   n,  a length or width of the plate or intermediary links  106   a - 106   n  or of a major face, or an area of a major face of the plate or intermediary links  106   a - 106   n.    
     The end or distal-most link  104  has a set of cable connection points or cavities  108   a - 108   d  (four shown, collectively  108 ) and a set of end-effector connection features, anchors, or points  110  (four shown). The cable connection points or cavities  108   a - 108   d  may be arrayed about a center or longitudinal axis of the end or distal-most link  104 ; the cable connection points or cavities  108   a - 108   d  angularly spaced from one another. The end-effector connection features, anchors, or points  110  may be arrayed about a center or longitudinal axis of the end or distal-most link  104 ; the end-effector connection features, anchors, or points  110  angularly spaced from one another. 
     As best illustrated in  FIGS. 5, 6A and 6B , each of the plate or intermediary links  106   a - 106   n  has a respective set of cable pass-through-holes  112   a - 112   d  (only a subset is visible in  FIG. 1 , collectively  112 ). The pass-through-holes  112   a - 112   d  may be arrayed about a center or longitudinal axis of the respective one of the plate or intermediary links  106   a - 106   n;  the pass-through-holes  112   a - 112   d  angularly spaced from one another. Notably, the plate or intermediary links  106   a - 106   n  may be rotationally oriented with respect to one another to generally radially align each of the pass-through-holes  112   a - 112   d  with corresponding pass-through-holes  112   a - 112   d  on each of the plate or intermediary links  106   a - 106   n.  For example, a first pass-through-hole  112   a  on each of the plate or intermediary links  106   a - 106   n  may be aligned with one another about a longitudinal axis when the flexible mechanical joint  100  is in an unarticulated configuration. Additionally, the end link  104  may be rotationally oriented with respect to the plate or intermediary links  106   a - 106   n  to generally radially align respective ones of the cable connection cavities  108   a - 108   d  with corresponding ones of the pass-through-holes  112   a - 112   d  on each of the plate or intermediary links  106   a - 106   n . For example, a first one of the cable connection cavities  108   a  may be aligned about a longitudinal axis with a first one of pass-through-holes  112   a  on each of the plate or intermediary links  106   a - 106   n  when the flexible mechanical joint  100  is in an unarticulated configuration. 
       FIG. 2  shows the flexible mechanical joint  100  of  FIG. 1 , in particular illustrating a plurality of flexures  202   a - 202   o  (collectively  202 ). While fifteen flexures  202  are illustrated the flexible mechanical joint  100  may include a larger or smaller number of flexures  202 . A proximate-most flexure  202   a  couples base link  102  with a first or proximate-most plate link  106   a,  and a distal-most flexure  202   o  couples a distal-most plate link  106   n  with end link  104 . Each of a number of intermediate flexures  202   b - 202   n  couple together respective plate links  106   a - 106   n  of successive pairs plate links  106   a - 106   n . Each of the flexures  202  comprise a thin hinge that allows for rotation of a structure attached to one side relative to the other around an axis of rotation of the flexure  202 , the axis of rotation of the flexure being along the link running along a length of the thin hinge of the flexure. The flexures  202  may take the form of living hinges. For example, flexure  202   a  allows for plate link  106   a  to rotate with respect to base link  102  around an axis extending along the length of the flexure  202   a,  which is parallel to the Z-axis. The flexures  202  in this implementation, when in a relaxed or unactuated state, all flexures  202  have a respective axis of rotation that is perpendicular to a Y-axis of the flexible mechanical joint  100 , with the flexure  202   a  having an axis of rotation parallel to the Z-axis and each following flexure having a respective axis of rotation offset from the previous by 45 degrees around the Y-axis. For example, the flexure  202   b  has an axis of rotation 45 degrees away from the axis of rotation of  202   a,  the axis of rotation of  202   b  being pointing the axis pointing half way between the positive X-axis and the positive Z-axis. Due to the incremental rotation of the flexure axes, every fourth flexure (e.g.,  202   a,    202   e,    202   l , and  202   m,  and  202   b,    202   f,    202   j,  and  202   n ) in the illustrated implementation forms a set of flexures having parallel axes of rotation. Each of the plate links  106 , base link  102 , and end link  104  have sloped or beveled faces that allow for clearance for the rotation around the flexures. 
     Planes  204  and  206  are indicated in  FIG. 2  by the broken lines passing through the flexible mechanical joint  100 . The planes  204  and  206  are parallel to the X-Y plane of the flexible mechanical joint  100  and are used to create the cross-sectional views in  FIGS. 3, 4, and 8 . 
       FIG. 3  shows the flexible mechanical joint  100  in cross-section, the cross-sectional view taken along plane  204  through the center of the flexible mechanical joint  100 . An inner channel  302  extends along a center or longitudinal axis of the flexible mechanical joint  100 . The inner channel  302  provides a conduit or passage for electrical wires, fluid carrying tubing, mechanical cables, or other flexible structures to pass through the inside of the flexible mechanical joint  100 . The inner channel  302  extends through every plate link  106  as well as base link  102  and end link  104 . Broken lines indicate the axis of rotation of the flexures  202   c,    202   g,    202   k,  and  202   o  that have axis of rotation on plane  204 . The plate links  106  on either side of the flexures  202  are connected by a thin hinge section and so the entire flexible mechanical joint  100  is one continuous body. Some implementations may have a spring or similar structure within or around the inner channel  302 , which may prevent the mechanism from buckling and may contribute a restoring force to the mechanism. 
       FIG. 4  shows the flexible mechanical joint  100  in cross-section, the cross-sectional view taken along plane  204  ( FIG. 2 ).  FIG. 4  shows all plate links  106  and flexures  202 . Planes  404  and  406  are indicated by the broken lines extending through the flexible mechanical joint  100 . The planes  404  and  406  are parallel to the X-Z plane of the flexible mechanical joint  100 . 
       FIG. 5  shows a lower portion of the flexible mechanical joint  100  of  FIG. 1 , better illustrating one of the plate links  106   j.    FIG. 5  clearly shows a number of cable pass-through holes  112   a - 112   d  and the inner channel  302  in plate link  106   j,  as well as flexure  202   k  which connects plate link  106   j  with plate link  106   k.    
       FIG. 6A  clearly shows a single plate link  106   i  of the flexible mechanical joint  100  ( FIG. 1 ) as an example of a plate link. 
       FIG. 6 b    depicts a top orthogonal cross-section view of the flexure joint  100  with a cross-section between plane  404  and plane  406 .  FIG. 6 b    clearly shows a single plate link  106   i  of the flexible mechanical joint  100  ( FIG. 1 ) as an example of a plate link. 
       FIG. 7  shows a flexure  700  that may be used as a joint in an implementation of the flexible mechanical joint  100  ( FIG. 1 ). Flexure  700  links together a first link  701  and a second link  702  by a thin hinge  704 . The hinge  704 , made of a material (e.g., metal), that allows for repeated rotation of the second link  702  relative to the first link  701  about an axis that extends through a middle of the hinge  704 . The hinge  704  may take the form of a living hinge. The flexure  700  may include a pair of opposed circular channels  706  that delineate the hinge  704 . The circular or arcuate profile of the channels  706  may advantageously reduce stress on the material of the flexure  700 , and provide sufficient room to accommodate rotation of the first link  701  with respect to the second link  702 . The flexure  700  may include a pair of opposed slots that delineate the first link  701  from second link  702 , the first and the second links  701 ,  702  having opposed faces that slope away from one another as the slots are traversed from an interior to an exterior thereof, the slope defined by a combined angle theta  708 . This may advantageously provide sufficient room to accommodate the rotation of the first link  701  with respect to the second link  702 , while also providing a hard stop to limit the rotation once an angle theta  708  is achieved by the flexure in either direction. The hard stop advantageously protects against the fracturing of the hinge  704 . 
       FIG. 8  shows the flexible mechanical joint  100  ( FIG. 1 ), illustrating a cable  802   d  that extends through cable pass-through-holes  112   d,  according to at least one illustrated implementation. Cable pass-through-holes  112   a  and  112   d  are shown extending through the length of the flexible mechanical joint  100 , to cable connection cavities  108   a  and  108   d  respectively. The cable  802   d  runs through cable pass-through-holes  112   d  in each of the plate links  106  to cable connection cavity  108   d  where the cable  802   d  is coupled to the end link  104 , for example at a cable tie-point or anchor  804   d.  Other cables similarly pass through sets of cable pass-through-holes  112   a ,  112   b,  and  112   c  in each of the plate links  106 , and attached to cable connection cavities  108   a,    108   b,  and  108   c,  but are not depicted in  FIG. 8  to avoid unnecessary cluttering of the drawings. 
       FIG. 9  shows the flexible mechanical joint  100  ( FIG. 1 ) in an articulated configuration, according to at least one illustrated implementation. The base link  102  has a longitudinal axis  901  and the end link  104  has a longitudinal axis  902 . 
     Due to the actuation (e.g., tensioning, movement) of the cables (e.g., cable  802   d ) extending through the flexible mechanical joint  100 , the end link longitudinal axis  902  is pitched away from the base link longitudinal axis  901  by a bend angle  903 . The actuation is caused by tensioning and retracting cables (e.g., four cables), thereby creating a shorter pathway  904  on one side of the flexible mechanical joint  100  and relaxing and thereby extending the cables thereby creating a longer pathway  906  on the other side of the flexible mechanical joint  100 . This tensioning and relaxing of cables causes flexures having an axis of rotation parallel (or close to parallel) to the intended bend axis to rotate in the bend direction. In this actuation, the flexures having an axis extending parallel to the Z-axis of the flexible mechanical joint  100  (namely  202   a,    202   e ,  202   i,  and  202   m ) are the flexures mainly contributing to the bend. 
     The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure. 
     To the extent that they are not inconsistent with the specific teachings and definitions herein, all of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including but not limited to U.S. Provisional Application Ser. No. 62/943,949, filed Dec. 5, 2019 are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary, to employ systems, circuits and concepts of the various patents, applications and publications to provide yet further embodiments.