Abstract:
Methods and apparatus for manufacturing and controlling an elongate robotic instrument, or robotic endoscope, are provided which may include any number of features. One feature is a robotic link that can be easily manufactured and can withstand the forces related to use within a robotic instrument. Another feature is a joint on the link that increases compressive strength and minimizes stress between links. Yet another feature is an elongate robotic instrument that is constructed from a single type of link.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/615,897, (filed Nov. 10, 2009; titled “ROBOTIC LINKAGE,” now abandoned), which claims the benefit under 35 U.S.C. 119 of U.S. Provisional Patent Application No. 61/113,453 (filed Nov. 11, 2008; titled “ROBOTIC LINKAGE”), each of which is incorporated herein by reference. 
    
    
     INCORPORATION BY REFERENCE 
     All publications, including patents and patent applications, mentioned in this specification are herein incorporated by reference in their entirety to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. 
     FIELD OF INVENTION 
     The present invention relates generally to elongate robotic instruments and elongate surgical robots, such as robotic endoscopes. More particularly, it relates to methods and apparatuses for manufacturing and forming elongate robotic instruments. 
     BACKGROUND 
     The forms of elongate robotic instruments vary widely, but many elongate robotic instruments share the features of a mechanical, movable structure under some form of control. The mechanical structure or kinematic chain (analogous to the human skeleton) of an elongate robotic instrument can be formed from several links (analogous to human bones), actuators (analogous to human muscle), and joints between the links, permitting one or more degrees of freedom of motion of the links. A continuum or multi-segment elongate robotic instrument can be a continuously curving device, like an elephant trunk for example. An example of a continuum or multi-segment elongate robotic instrument is a snake-like endoscopic device. 
     Snake-like endoscopic devices can transfer forces from an actuator to particular sections of links in the snake-like device to effect articulation of that section or link. During articulation, these links are subjected to large stresses that can result in breakage or failure of the link and thus, failure of the endoscopic device. These failures typically occur at the weak point between links, such as at the joints. 
     A typical robotic link is made from a metal or alloy, such as aluminum or stainless steel. The links can be manufactured by laser cutting tubes, by laser sintering, by metal injection molding, or other processes as known in the art. Furthermore, a snake-like endoscopic device can often include several types of links, such as distal and proximal links for attachment to actuators, and intermediate links therebetween. However, manufacturing elongate robotic devices with these materials, as well as needing several different types of links for each device, can be expensive and add to the cost of an elongate robotic instrument. 
     An elongate robotic instrument, and more particularly a link that is used to make up the elongate robotic instrument, is therefore needed that can be manufactured efficiently and inexpensively while still being able to withstand the stresses imposed upon it during normal use. 
     SUMMARY 
     In one embodiment, a robotic link is provided comprising a link having an outer wall surface and an inner wall surface, a pair of outer hinge portions on a first end of the link, each outer hinge portion having an inner bearing surface positioned between the inner wall surface and an outer ear, and a pair of inner hinge portions on a second end of the link, each inner hinge portion having an outer bearing surface positioned between the outer wall surface and an inner ear. 
     In some embodiments, the robotic link comprises a polymer. The robotic link can comprise PEEK, for example. 
     In one embodiment, each of the pair of outer hinge portions are diametrically opposed across the link. In another embodiment, each of the pair of inner hinge portions are diametrically opposed across the link. In some embodiments, an axis of rotation of the outer hinge portions are substantially perpendicular to an axis of rotation of the inner hinge portions. 
     The robotic link can further comprise a guide block positioned along each inner and outer hinge portion. In some embodiments, a tendon guide is positioned integrally within the link along each inner and outer hinge portion. The robotic link can also comprise an integrated pulley and tendon guide positioned integrally within the link along each outer hinge portion. In some embodiments, the robotic link comprises an integrated pulley and tendon guide positioned integrally within the link along each inner and outer hinge portion. 
     In one embodiment, the robotic link has an outer diameter of less than or equal to 19.05 millimeters (0.75 inches). 
     A flexible robotic instrument is provided, comprising a first link and a second link each having an outer wall surface and an inner wall surface, a pair of outer hinge portions disposed on a first end of each link, each outer hinge portion having an inner bearing surface positioned between the inner wall surface and an outer ear of each link, and a pair of inner hinge portions on a second end of each link, each inner hinge portion having an outer bearing surface positioned between the outer wall surface and an inner ear of each link, wherein the outer bearing surface of the first link is configured to slidably support the outer ear of the second link, and wherein the inner bearing surface of the second link is configured to slidably support the inner ear of the first link. 
     In some embodiments, the first and second links comprise a polymer. The first and second links can comprise PEEK, for example. 
     In one embodiment, an interior volume of the instrument is sized to accommodate at least two working channels. 
     In some embodiments, each of the pair of outer hinge portions are diametrically opposed across the first and second links. Similarly, each of the pair of inner hinge portions can be diametrically opposed across first and second links. In one embodiment, the outer hinge portions are substantially perpendicular to the inner hinge portions. 
     The flexible robotic instrument can further comprise a guide block positioned along each inner and outer hinge portion. In some embodiments, a tendon guide is positioned integrally within the first and second links along each inner and outer hinge portion. In other embodiments, the flexible robotic instrument can comprise an integrated pulley and tendon guide positioned integrally within the first and second links along each inner and/or outer hinge portion. 
     In one embodiment, the flexible robotic instrument has an outer diameter of less than or equal to 19.05 millimeters (0.75 inches. 
     The flexible robotic instrument can further comprise a plurality of actuation tendons. 
     In one embodiment, the first and second link of the flexible robotic instrument can articulate up to approximately +/−30 degrees individually. 
     A method of manufacturing a robotic link is provided, comprising introducing a polymer into a mold, and recovering from the mold a link having an outer wall surface and an inner wall surface, a pair of outer hinge portions on a first end of the link, each outer hinge portion having an inner bearing surface positioned between the inner wall surface and an outer ear, the link also having a pair of inner hinge portions on a second end of the link, each inner hinge portion having an outer bearing surface positioned between the outer wall surface and an inner ear. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 a -1 b    are illustrations of an elongate robotic instrument. 
         FIG. 2  is an exploded view of the elongate robotic instrument of  FIGS. 1 a   - 1   b.    
         FIGS. 3 a -3 b    illustrate a double-knee-joint of a robotic link. 
         FIGS. 4 a -4 b    are illustrations some embodiments of attachment points of actuation tendons and coil tubes in a robotic link. 
         FIGS. 5 a -5 c    are illustrations of various embodiments of robotic links. 
         FIG. 6  is an illustration of another embodiment of a robotic link for use in an elongate robotic instrument. 
         FIGS. 7 a -7 b    are illustrations of a universal robotic link for use in an elongate robotic instrument. 
         FIG. 8  illustrates an elongate robotic instrument comprising a plurality of universal links. 
         FIG. 9  shows a factor of safety for aluminum vs. victrex link designs. 
         FIG. 10  is a bar graph illustrating predicted link strength vs. testing. 
         FIGS. 11 a -11 d    are schematic illustrations showing the effect of guide blocks within a link and vertebra diameter on dead space. 
         FIG. 12  is a cross sectional view of links with guide blocks. 
         FIG. 13  is a cross sectional view of links without guide blocks. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1 a    is a side view of an elongate robotic instrument  100  comprising at least one individually articulatable segment  102 . The elongate robotic instrument can comprise any number of articulatable segments, depending on the desired length of the instrument. One embodiment includes four such articulatable segments. As shown in  FIG. 1 a   , the instrument includes a distal (farther from the base) boundary portion  104 , an intermediate portion  106 , and a proximal boundary portion  116 . As shown in  FIG. 1 a   , the boundary portions includes front links  108  and  118 , middle links  110  and  120 , and back links  112  and  122 , and the intermediate portion includes multiple intermediate links  114 . In  FIG. 1 a   , the segment  102  extends from the middle of boundary portion  104  (i.e., the middle of link  110 ) to the middle of boundary portion  116  (i.e., the middle of link  120 ). The embodiment of  FIG. 1 a    includes a total of seven intermediate links per segment, but in other embodiments various numbers of intermediate links can be used. 
     As will be described in more detail below, the front link  108  and middle link  110  are manufactured to provide features for coil tube and actuation tendon terminations, and the middle link  110  and back link  112  are manufactured to provide pulley features for the coil tubes and actuation tendons. 
       FIG. 1 b    is a cross sectional view of instrument  100  of  FIG. 1 a   . It can be seen that instrument  100  provides room for at least two working channels or lumens  124  and  126 . These working lumens can house various components, such as air and water channels, vacuum channels, fiber optic illumination light bundles, an imaging system (e.g., a fiber optic imaging system), surgical tools, and/or position and orientation sensors (e.g., electromagnetic sensors (such as those made by the Ascension company), accelerometers, etc). In some embodiments, position and orientation sensors can be placed in other portions of the instrument, such as along the inner or outer wall of the instrument. The working lumens generally extend through the length of the instrument  100 . Generally, a user views live or delayed video feed from the imaging system via a video cable (e.g., wire or optical fiber, not shown) or through wireless transmission of the video signal. These channels and other amenities are shown generically, because such channels and amenities are well known in the art. The instrument  100  further includes actuation tendons  128  for changing the shape of the robotic instrument. The actuation tendons can be housed in coil tubes to provide additional strength and protection for the tendons, for example. In one embodiment the tendons are made from ultra high molecular weight polyethylene (UHMWP). In some embodiments, the actuation tendons can run straight through the robotic instrument. In other embodiments, the actuation tendons can be helixed through the robotic instrument. In one embodiment, the steerable portion of each segment in the robotic instrument utilizes four actuation tendons for movement. Thus, an instrument having four steerable segments would require sixteen actuation tendons to achieve the full range of motion. 
       FIG. 2  is an exploded view of robotic links that can make up a robotic instrument, similar to the robotic instrument  100  of  FIGS. 1 a -1 b   . As shown in  FIG. 2 , distal boundary portion  204  includes front link  208 , middle link  210 , and back link  212 . Intermediate portion  206  comprises a plurality of intermediate links  214 . Not shown in  FIG. 2  is the proximal boundary portion (similar to proximal boundary portion  116  in  FIG. 1 ). The instrument  100  of  FIG. 1 a    included seven intermediate links per segment plus 1.5 links from each boundary portion for a total of ten links, whereas the instrument shown in  FIG. 2  includes only five intermediate links per segment plus 1.5 links from each boundary portion, for a total of eight links. If each pair of links is capable of articulating approximately +/−30 degrees individually, for example, then each segment of  FIG. 1 a    can articulate 150 degrees, and each segment of  FIG. 2  can articulate 120 degrees. Front link  208  may provide a termination point for a first pair of actuation tendons  228  and/or coil tubes. Middle link  210  may provide a termination point for a second pair of actuation tendons  229  and/or coil tubes. In another embodiment described below, the tendons may alternatively engage the front and middle links at pulley wheels  242 , which are sized to fit within pulley slots  243  in the middle and back links. As will also be described in more detail below, pulling on one of the first pair of actuation tendons can cause a segment of the robotic instrument to move in a first plane (e.g., the X-plane), and pulling on one of the second pair of actuation tendons can cause the segment to move in a second plane (e.g., the Y-plane). 
     In order to reduce manufacturing costs, various implementations of the robotic links described herein can be made of a plastic or polymer. In one embodiment, the robotic links are polyaryletheretherketone (PEEK). The robotic links can be formed or manufactured by injection molding a polymer into a mold and then recovering a link from the mold, or by other methods as known in the art. The mold can be preformed to provide a link having any or all of the features described herein. 
     It can be seen in  FIG. 2  that each link, including front link  208 , middle link  210 , back link  212 , and intermediate links  214 , comprises a pair of outer hinge portions  230  and a pair of inner hinge portions  232 . The pair of outer hinge portions can be positioned substantially perpendicular to the pair of inner hinge portions (e.g., a line running through the pair of outer hinge portions is substantially perpendicular to a line running through the pair of inner hinge portions). Staggering the pairs of hinges in substantially perpendicular planes allows each link to move at the hinges with one degree of freedom relative to an adjacent link. Three connected links results in a serial kinematic chain having two degrees of freedom. Thus, the joint between the first and second links in a segment can move within a first plane, while the joint between the second and third links in a segment can move within a second plane that is substantially perpendicular to the first plane. In one embodiment, the joint between two adjacent links can articulate approximately 30 degrees (e.g., +−0.30 degrees in either direction with respect to one another. Furthermore, in one embodiment, a pair of adjacent links can have a length of approximately 27.94 millimeters (1.1 inches). 
       FIGS. 3 a -3 b    illustrate zoomed-in perspective views of the outer and inner hinge portions of each robotic link (hinge pin holes are omitted from the drawings). As can be seen in  FIG. 3 a   , outer hinge portion  330  includes an inner bearing surface  334  and an outer ear  336 . Similarly, in  FIG. 3 b   , inner hinge portion  332  includes an outer bearing surface  338  and an inner ear  340 . As shown in  FIGS. 3 a -3 b   , each outer hinge portion  330  has an inner bearing surface  334  positioned between an inner wall surface  335  of the link and the outer ear  336 . Similarly, each inner hinge portion  332  has an outer bearing surface  338  positioned between an outer wall surface  339  and the inner ear  340 . It should be understood that the outer hinge portions  330  can be on a distal end of each link, and the inner hinge portions  332  can be on a proximal end of each link, as shown in  FIG. 2 . Alternatively, the outer hinge portions  330  can be on a proximal end of each link, and the inner hinge portions  332  can be on a distal end of each link (not shown). 
     When the inner hinge portion of one robotic link is joined to the outer hinge portion of another robotic link, the outer ear  336  rests in and is supported by the outer bearing surface  338 , and the inner ear  340  rests in and is supported by the inner bearing surface  334 . In some embodiments, the inner and outer bearing surfaces  334  and  338  are cup shaped or curved bearing surfaces, and the outer and inner ears  336  and  340  are sized to fit flush within and against their respective mating bearing surfaces, thus minimizing friction between each ear and bearing surface while maximizing the strength of the joint. Furthermore, the outside surface  341   b  of the inner ear of one link can be in slidable contact with the inside surface  341   a  of the outer ear of a mated link, which provides additional support to strengthen the joint formed when two links are coupled. 
     This inner/outer hinge portion configuration allows the distal pair of hinges of a first link to engage with the proximal pair of hinges of a second link. Each adjacent link can then be coupled to the next at the hinges to form a pivot joint, such as by inserting a pin, rivet, etc, through a hole in the hinges, for example. It should be understood that when the inner hinge portion of a one link is coupled to the outer hinge portion of another link, a rivet or other fixation device (not shown) can additionally secure the hinge portions together. When two links are mated in this way, the inner and outer ears slide on their associated bearing surfaces, which provides an effective load distribution when the links are axially compressed (e.g., such an axial load is not solely borne by hinge pins that hold the two links together). In addition, the sliding mated inner and outer hinge portions provide effective lateral load capacity. 
     When the inner and outer hinge portions pictured in  FIGS. 3 a -3 b    are joined together, the joint can be referred to as a “double-knee-joint.” The double-knee-joint minimizes stress on the hinges when adjacent robotic links are coupled together and subjected to the forces consistent with actuation and movement of a robotic instrument. By strengthening the formerly weak point of actuation between adjacent links with this double-knee-joint design, the robotic links of the present invention can thus be manufactured from a polymer, such as PEEK, to reduce cost and improve ease of manufacturing. 
       FIGS. 4 a -4 b    illustrate two embodiments of terminating pairs of actuation tendons at their respective robotic links. Referring back to  FIG. 2 , it should be understood that actuation tendons are typically terminated at only the front link  208  and middle link  210  of the proximal boundary links of each segment (e.g., to provide x- and y-axis steering for the segment). In the embodiment shown in  FIG. 4 a   , each actuation tendon  428  housed in a coil tube can terminate at or connect to a single point in the link, such as by crimping, glue, soldering, etc. However, in the embodiment shown in  FIG. 4 b   , each actuation tendon  428  can wrap around pulley wheel  442  and be directed back towards the proximal end of the instrument (as shown by the arrows in actuation tendon  428 ). Pulley wheels  442  can be discrete mechanical pulleys sized to fit within pulley slots  443  in the sidewalls of each link. Using pulleys as a termination point for the actuation tendons causes a modification of the amount of force (mechanical advantage) applied to each segment when the tendons are actuated (e.g., pulled). The pulley provides a decrease in the distal force required to actuate a segment, at the cost of increased distal displacement. Eliminating the pulley requires a greater distal force for actuation but decreases the cable displacement required. 
     In operation, pulling each of the respective actuation tendons will increase the tension in the pulled tendon and cause the segment to articulate in the direction of the pulled tendon as the links articulate at their respective hinges. Additionally, when one tendon is tensioned, the opposite tendon in the segment can be slacked to accommodate movement of the segment, especially the tendon positioned 180 degrees or opposite from the tensioned tendon. 
       FIG. 4 b    also illustrates a robotic link having guide blocks  444  positioned along each inner hinge portion (guide blocks can be positioned along both the outer and inner hinge portions, not shown in  FIG. 4 b   ). The guide blocks can include a pair of lumens, as shown, for receiving actuation tendons. The guide blocks act as tendon guides and function to position the actuation tendons along each hinge. This causes the distance between the hinge and the off-axis cables to be reduced, and minimizes out-of-plane motion when a pair of cables is actuated. 
     In the illustrative link embodiments shown and described above, the same interchangeable link design can be used for both the boundary and intermediate portions of a segment. Thus, manufacturing costs are further reduced by eliminating the need for different link designs, and so using a single design that can be inexpensively manufactured by, e.g., injection molding, for all links in the kinematic chain. Various other link designs may also be used. 
       FIG. 5 a    illustrates another embodiment of intermediate links  514 , and  FIG. 5 b    illustrates another embodiment of front link  508 , middle link  510 , and back link  512  for use in an elongate robotic instrument. The links shown in  FIGS. 5 a -5 b    can include many of the features described above in  FIGS. 1-4 . For example, outer hinge portions  530  and inner hinge portions  532  can correspond, respectively, to outer hinge portions  230  and inner hinge portions  232  of  FIG. 2 . In addition, the guide blocks  444  described in  FIGS. 4 a -4 b    have now been incorporated into the body of the robotic link itself as an integrated tendon guides  544 . As can be seen in  FIG. 5 a   , actuation tendon guides  544  comprise a plurality of lumens integrally formed into the wall of each robotic link. The actuation tendons (not shown) can be routed through tendon guides  544  to provide the same function as the guide blocks described above (i.e., to keep the actuation tendons positioned along the hinges in each link). 
     This design has the additional advantages of saving costs by reducing the number of parts, simplifying assembly, increasing available lumen/working channel volume within the robotic instrument, allowing helixed actuation tendons (if helixed) to propagate during assembly more easily, and avoiding restriction of local slack of the helixed tendons during articulation.  FIG. 5 c    illustrates another view of actuation tendon guides  544  incorporated into the walls of the robotic links. It can be seen from  FIG. 5 c    that the actuation tendon guides include at least two lumens per hinge portion per link. So in the link illustrated in  FIG. 5 c    having four hinges, the tendon guides include eight lumens. 
       FIG. 6  is another embodiment of a robotic link having actuation tendon guides  644  incorporated into the wall of the link. The embodiment of  FIG. 6  is similar to that described above with respect to  FIG. 5 a   , however the lumens of tendon guides  644  are incorporated at an angle with respect to the hinge instead of running parallel with the robotic instrument. The angled tendon guides allow the maximum articulation radius (lever arm) while still avoiding the hinge, at the cost of added friction in the instrument. 
       FIGS. 7 a -7 b    illustrate one embodiment of a universal robotic link  702 . In  FIGS. 7 a -7 b   , outer hinge portions  730 , inner bearing surface  734 , inner wall surface  735 , outer ear  736 , inner hinge portions  732 , outer bearing surface  738 , outer wall surface  739 , and inner ear  740  can correspond, respectively, to outer hinge portions  330 , inner bearing surface  334 , inner wall surface  335 , outer ear  336 , inner hinge portions  332 , outer bearing surface  338 , outer wall surface  339 , and inner ear  340  of  FIG. 3 . 
     Universal link  702  further includes integrated pulley and tendon guide  704 , which has a pulley portion  706  and a tendon guide portion  708 . The pulley portion can have a flat surface to reduce friction (the flat surface minimized contact area with a tendon passing over it), or alternatively the pulley portion can include a groove. The integrated pulley and tendon guide  704  combines the features of both the pulleys (e.g., pulley wheels  242  and pulley slots  243  in  FIG. 2 ) and guide blocks or actuation tendon guides (e.g., guide blocks  444  in  FIG. 4  or tendon guides  544  in  FIG. 5 ) into a single component. Thus, each universal can provide for an actuation tendon wrapping around pulley portion  706  (e.g., similar in function to the front, middle, and back links described above in  FIG. 2 ), or, alternatively, can be used as a intermediate link in which the actuation tendons pass through the lumens of the tendon guide portion  708  of each link. 
     In the embodiment of  FIGS. 7 a -7 b   , the integrated pulley and tendon guides  704  are positioned on the universal link in alignment with the outer hinge portions  732 . Actuation tendon guides  746  can be positioned on the universal link in alignment with the inner hinge portions to provide lumens for which to route actuation tendons along the inner hinge portions as well. In other embodiments, the integrated pulley and tendon guides  704  can be positioned in alignment with the inner hinge portions and the tendon guides  746  can be positioned in alignment with the outer hinge portions, or alternatively, the integrated pulley and tendon guides  704  can be positioned in alignment with both the inner and outer hinge portions (e.g., four integrated pulley and tendon guides  704  per universal link). 
     The universal links described herein integrate all the features that are necessary for intermediate links and all the features that are needed in boundary links into a single link. Advantages of this design include: lower tooling costs (only one link is needed therefore only one tool needs to be made); the pulley has been integrated, and there is no bonding necessary of a separate pulley to the link; the pulley has a flat surface instead of a groove, which substantially reduces friction; the pulley has been implemented in such a way that derailing of the cable is very difficult due to the fact that the cable takes the shortest distance between lumens; even under compression/slack of the actuation tendons, the cables do not derail since they are guided and aligned by the lumens; and, all of the features have been implemented in such a way that the link can be manufactured by injection molding, which reduces the manufacturing cost substantially while maintaining the strength necessary for a robotic instrument. 
       FIG. 8  is a side view of an elongate robotic instrument  800  comprising at least one universal link  802 . The universal link  802  can correspond to the universal links  702  described above. The elongate robotic instrument can comprise any number of articulatable segments, depending on the desired length of the instrument, but a preferred embodiment includes four segments. Each segment can comprise a distal boundary portion  804 , an intermediate portion  806 , and a proximal boundary portion  816 . As shown in  FIG. 8 , the boundary portions can include three universal links. The intermediate portion  806  can include any number of universal links, depending on the desired segment length and maximum desired angle of articulation. To utilize universal links in the distal boundary portion  804  of instrument  800 , actuation tendons (not shown) can be attached to or routed around pulley portions integrated into the sidewall of the universal links. To utilize universal links in the intermediate portion  806 , the actuation tendons can pass through the tendon guides integrated into the sidewall of the universal links, as described above with reference to  FIG. 7 . 
       FIG. 9  compares various embodiments of robotic link designs. Each robotic link illustrated has been subjected to forces to determine a factor of safety (FOS). A factor of safety is used here as an indicator of the relative strengths of different link designs. Referring to  FIG. 9 , link  2  is a robotic link made out of machined aluminum with a force applied to its inner hinge portions  3 . Link  2  has a FOS of 4.0. Similarly, link  4  is a robotic link made out of injection molded plastic with a force applied to its inner hinge portions  5 . Link  4  has a FOS of 2.7. Link  6  is a robotic link made out of machined aluminum with a force applied to its outer hinge portions  7 . Link  6  has a FOS of 4.1. Similarly, link  8  is a robotic link made out of injection molded plastic with a force applied to its outer hinge portions  9 . Link  8  has a FOS of 2.9. 
       FIG. 10  is a chart comparing empirical data showing the strengths of various link designs and materials with theoretical data. 
       FIGS. 11 a -11 d    illustrates various pie charts illustrating the effect of link diameter and the use of guide blocks on the internal volume available in a robotic instrument.  FIG. 11 a    illustrates internal volume usage of a robotic instrument comprising robotic links with a 0.75-inch outer diameter and utilizing guide blocks.  FIG. 11 b    illustrates the internal volume usage of a robotic instrument comprising robotic links with a 0.7-inch outer diameter and utilizing guide blocks.  FIG. 11 c    illustrates internal volume usage of a robotic instrument comprising robotic links with a 0.75 inch outer diameter and no guide blocks (e.g., integrated tendon guides).  FIG. 11 d    illustrates the internal volume usage of a robotic instrument comprising robotic links with a 0.7-inch outer diameter and no guide blocks (e.g., integrated tendon guides). 
       FIG. 12  is a cross sectional view of a robotic instrument  1200 , showing the internal volume of a link when the link utilizes guide blocks  1244 .  FIG. 12  further illustrates working channels  1224  and  1226  and actuation tendons  1228 .  FIG. 13  is a cross sectional view of a robotic instrument  1300 , showing the internal volume of a link when the link does not utilize external guide blocks. Rather, the instrument of  FIG. 13  can use integrated tendon guides, as described above. It can be easily seen that the embodiment shown in  FIG. 13  reserves a larger volume of the interior cavity of the robotic instrument for working channels  1324  and  1326  and actuation tendons  1328 . 
     Aspects of various embodiments include: dimensioning and design of the part to make it mass-manufacturable by injection molding while still withstanding the high compressive loading that occurs inside robotic endoscopes; double knee-joint to resolve compressive loading during articulation, integrated static pulley; flat pulley surface to reduce friction; and, integrated design of cable routing features that allows the same part to be used as a segment boundary and passive link. 
     As for additional details pertinent to the present invention, materials and manufacturing techniques may be employed as within the level of those with skill in the relevant art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts commonly or logically employed. Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. Likewise, reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “and,” “said,” and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The breadth of the present invention is not to be limited by the subject specification, but rather only by the plain meaning of the claim terms employed.