Abstract:
A compliant tool holder is provided for use with robots, unmanned ground vehicles, and the like. The compliant tool holder is characterized in that it involves the use of means for compliance, such as springs, rubber, plastics, metals, composites, shock mounts, vibration mounts, or similar means for permitting compliant movement in three rotational and three translational degrees of freedom during end effector changes. The compliant tool holder reduces costs associated with automated tool change in the field, and allows for more rapid switching of end effectors, enabling a greater range of uses for robots and unmanned ground vehicles.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/392,662, filed Oct. 13, 2010, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    Manipulators on mobile robots require specialized end effectors in order to accomplish particular missions. Currently, deployed systems have end effectors designed, built, and installed at the factory. Factory installed tools can only be repaired or replaced in a factory. This limits the effectiveness of the robot to those missions which can be achieved with a single tool. Heretofore, when a new candidate task is identified, the typical response has been to design and build a new robot intended to perform the specific task. Sometimes existing unmanned ground vehicles (UGV) platforms are used, but just as often, a new robot is created to specifically address the task. This has resulted in a proliferation of small UGVs, each performing admirably on tasks within each of its subset of core competencies, but is generally unsuitable for tasks that vary too widely from its essential purpose. It is impractical to expect field teams to carry multiple UGVs, each suited for a specific task. In addition to the strain on the physical resources of the field team (e.g., transportation and maintenance), different robots come with different control schemes. This reduces the ability of the operator to capitalize on the experience and intuition gained from operating previous robots, because the operator cannot rely on the trained reflexes developed while controlling previous robots. In fact, these differing control schemes lead to operator errors and inefficient control. 
         [0003]    Another approach has been to design new, more capable robots, but this approach has drawbacks because even if a robot were designed and built to perform all of the tasks currently assigned to UGVs, it would quickly become outdated as new tasks and jobs are identified. Additionally, external variables, such as physical environment, make UGVs designed for one environment wholly impractical for use in another environment, meaning a number of new robot types would need to be designed, tested, and built. Systems with replaceable end effectors are also ineffective because they require a technician and possibly a number of specialty tools. Generally, these changes would require a technician to remove the current tool and to attach its replacement. This may involve physically disconnecting the tool, disconnecting electrical connections, physically attaching the new tool, and hooking up its electrical connections. The system may also require reconfiguring the control software for each specialized tool. Particularly, in time critical applications, such as military or civilian Explosives Ordinance Disposal (EOD), this process is too slow and interferes with missions. 
         [0004]    In addition, it takes a robust design to survive the normal working environment for such devices, both during deployment on the mobile robot and when the manipulator and tools are being stored or transported. Mechanical connections must be compliant to minor variations in manufacturing tolerances of mating components, or environmental tolerances which develop when a tool is dropped or bumped against another tool in the toolbox, or caused by the presence of debris, such as dirt and sand, captured from the working environment. 
         [0005]    Robotic arms often require specialized configurations to accomplish their particular mission, requiring change in the length of a link in the arm or attaching a different end effector or tool. Different manipulator systems exhibit a wide range of force capacity, rigidity, accuracy and static friction. 
         [0006]    Tools that attach to links of the robotic arm that are pivoting or rotating must be able to withstand the large bending movements and torques that result from this. 
         [0007]    Despite the need for robotic arms to pivot and rotate, to date, tool holders have been rigidly attached to robot platforms, resulting in difficulties in attaching and changing end effectors on the robotic arm. The problems encountered with a rigid tool holder mount are numerous. They include limitations of accuracy of motion, calibration error, sensor drift, system structural flexibility, debris, wear, and damage. Different manipulator systems exhibit a wide range of manipulator properties. A combination of self-aligning features combined with tool holder compliance allows reliable tool change under a wide range of real-world conditions. Current tool holders, however, lack sufficient self-aligning features. 
         [0008]    For example, in WO 2011/019742, the tool holder (item 4) is attached to a tool station that is securely and rigidly attached to a surface via the block (item 410 of FIG. 19B). Because it is rigidly attached to the surface of the robot, compliance is limited to the degree of translational movement of the arm, which can be imprecise based on the number of joints and the amount of wear in those joints. The resulting process of attaching and disengaging end effectors is time-consuming and must be done with fine precision. This time consumption is not optimal for use in, for example, EOD. 
         [0009]    The limitations of the existing art are obvious. Limited movement possibilities of the tool holder (i.e., in one plane only) combined with limited self-aligning features of the assembly, reliant on the ability of the arm to change planes and angles, make end effector interchange in the field tedious and hazardous. 
         [0010]    In addition to the associated danger, the limited range of movement of prior tool holder assemblies results in increased cost of production. Robotic arms with rigidly attached tool holder assemblies must be equipped with another means of allowing for attachment and detachment of end effectors. Typically this would be accomplished through the use of numerous cameras for alignment by the end user; however, attachment of multiple cameras increases cost, and such cameras may not be useful in certain real-world scenarios due to weather or other uncontrollable conditions. 
         [0011]    A further solution to the problem of limited tool holder compliance may be the use of multiple sensors placed on the robotic arm and the tool holder itself for feedback alignment. Again, however, this method is expensive, and the wear from subsequent use limits the effectiveness of this solution. Further, as with multiple cameras for end-user alignment, uncontrollable conditions may limit the effectiveness of this solution. 
         [0012]    Yet another solution to the issue of limited tool holder compliance may be to introduce compliance into the robotic arm itself. This solution is not desirable, as incorporating this freedom into the robotic arm results in increased weight on the arm, increasing forces on the various joints. This increased force results in a need for greater strength in the joints, further increasing the weight of the robot or UGV. Further, with robotic arms of greater length, increased weight at the distal end increases concerns related to leverage. Thus, introducing compliance into the arm itself is not optimal. 
         [0013]    Thus, it is an object of the present invention to provide a compliance system for a tool holder which overcomes these deficits in the prior art, by allowing movement of the tool holder in six degrees of freedom. The compliant tool holder system of the present invention allows for different levels of deflection of the tool holder based on the force applied by the robotic arm and end effector as attachment or detachment takes place. The compliant tool holder has stiffness tailored to the three translational degrees of freedom, tilt and yaw rotational degrees of freedom, and rotational degree of freedom about the axis of the tool of the end effector. The tool holder is mounted to a base using means for compliantly mounting tool holder components together, such as springs or the like. A base is rigidly mounted to the structure of the robot, UGV, or guided machine. However, the compliant mounts restrain the tool holder in all degrees of freedom while permitting deflection proportional to the force applied, allowing for self-alignment and greater ease of end effector exchange. 
       SUMMARY OF THE INVENTION 
       [0014]    The current invention provides a compliant tool holder for automatically engaging and separating robotic end effectors from their manipulator arms during deployment, thus allowing unhindered integration of end effectors. The compliant tool holder includes a lower tool base, and upper tool base, means for compliance, and a tool station. The means for compliance are positioned between the upper tool base and a lower tool base, so that the upper tool base and tool station may move in three translational degrees of freedom and three rotational degrees of freedom during end effector attachment and detachment. This movement allows for more rapid end effector changes. 
         [0015]    The current invention also provides for a compliant tool holder, including a lower base, means for compliance, upper base, and tool station that is formed as one integral piece. The invention further provides for a compliant tool holder wherein the tool station and upper tool base are one integral component, removably attached to the lower tool base via the means for compliance. Means for compliance may be removably attached to the upper tool base and lower tool base by a plurality of fasteners, or they may also be integral to the lower tool base and upper tool base. The compliant tool station may be attached to a robot, guided machine, or unmanned vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  illustrates an exploded view of the tool holder assembly of the present invention; 
           [0017]      FIG. 2   a  illustrates a top-perspective view of the tool holder assembly of the present invention; 
           [0018]      FIG. 2   b  illustrates a side-perspective view of the tool holder assembly of the present invention; 
           [0019]      FIG. 2   c  illustrates a front-perspective view of the tool holder assembly of the present invention; 
           [0020]      FIG. 2   d  illustrates a side-perspective view of the tool holder assembly of the present invention; 
           [0021]      FIG. 3  illustrates a top-perspective view of the tool holder assembly and a robotic end effector; 
           [0022]      FIG. 4  illustrates a side-perspective view of the tool holder assembly receiving an end effector; 
           [0023]      FIG. 5  illustrates a side-perspective view of the tool holder assembly receiving an end effector; 
           [0024]      FIG. 6  illustrates a side-perspective view illustrating an end effector for use with the tool holder assembly of the present invention; 
           [0025]      FIG. 7  illustrates a side-perspective view of the tool station of the tool holder assembly of the present invention; 
           [0026]      FIG. 8  illustrates an exploded view of the tool station for use with the tool holder assembly of the present invention; and 
           [0027]      FIG. 9  illustrates an embodiment of the tool holder assembly of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    The following description is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0029]    An object of the present invention is to provide a compliant tool holder for automatically engaging and separating robotic end effectors from their manipulator arms during deployment, thus allowing unhindered integration of end effectors. 
         [0030]    The tool holder assembly can provide a platform to engage a first and second light-weight mechanical joint member for automated coupling. The joint members provide a rigid connection, for connecting an end effector to a robotic manipulator. End effectors for attaching using an automated tool change assembly can include components such as a retrievable delivery device, gamble grip, dozer, shovel, tilting tools, plow, drills, saws, cutters, grinders, sensors, camera, disrupter, arm extenders, arm linkages, digging tools, and pan-tilt table. One skilled in the art will recognize this list is not exhaustive and the use of other types of robot components with the compliant tool holder of the present invention is possible. 
         [0031]    With reference to  FIG. 1 , a tool holder assembly  100  can have a lower tool base  102 , upper tool base  105 , means for compliance  114  positioned between the lower tool base  102  and upper tool base  105 , and a tool station  106 . The lower tool base  102  and upper tool base  105  may each be comprised of a plurality of parallel arms. The lower tool base  102  can be a hollow member forming cavity  108  about the center and providing a beveled surface  110  on an inner surface surrounding cavity  108 . The tool holder  100  may be formed out of any suitable material, including but not limited to, Aflas, Buna-N, Butyl, ECH, EPDM, EVA, gum, Ionomer, latex, neoprene, polyethylene foam, polyethylene rubber, polyimide, polyurethane, santoprene, SBR, silicone, vinyl, and Viton® Flouroelastomer. The material may also be a plastics such as ABS, acetal copolymer, acetate, cast acrylic, extruded acrylic, butyrate, Cirlex Polyimide, CTFE, Delrin® Acetal resin, FEP, HDPE Polyethylene, Hydex, Kapton® Polyimide, LDPE polyethylene, polyphenyl oxide, nylon, PEEK, PETG, PFA, polycarbonate, polyester, polypropylene, polystyrene, polysulfone, PPS, PTFE, PVC, PVDF, Radel, Rulon, Teflon® PTFE, polyamide-imide, Tucrite, UHMW polyethylene, VHMW polyethylene, polyetherimide, and Vespel® polyimide. The tool holder  100  may also be injection-molded plastic or metals such as steel, stainless steel, steel cable, stainless steel cable, titanium, aluminum, or may be composite materials containing fiberglass, carbon fiber, Kevlar, or aramid fibers. These materials provide sufficient flexibility, or give, to provide compliance to the tool holder assembly  100  during the process of a robotic arm connecting with or decoupling from an end effector. Any number of compliant tool holders  100  can be used on a robot or UGV, depending on the space available on the robot. 
         [0032]    In a preferred nonlimiting embodiment, the tool holder assembly  100  is formed as a single integrated component, comprising sections corresponding to a lower tool base  102 , upper tool base  105 , means for compliance  114 , and tool station  106 . 
         [0033]    In a preferred nonlimiting embodiment, the lower tool base  102  is substantially u-shaped, having a plurality of parallel arms  104   a - 104   b  integral with an end portion  103 . 
         [0034]    In another preferred nonlimiting embodiment, the lower tool base  102  is substantially c-shaped. The parallel arms  104   a - 104   b  and the end portion  103  have a beveled surface  110  on the surface facing the cavity  108 . The portions of the arms  104   a - 104   b  distal to the end portion  103  of the lower base  102  are angled towards each other. In a preferred nonlimiting embodiment, the beveled surface  110  is at a 45 degree angle relative to the flat top of the lower tool base  102 . 
         [0035]    With continued reference to  FIG. 1 , an upper tool base  105  is attached to the lower tool base  102 . In a preferred nonlimiting embodiment, the upper tool base  105  includes a beveled surface  112  formed about the exterior of the upper tool base  105 . The beveled surface  112  can be coincident with the beveled surface  110  of the lower tool base  102 . 
         [0036]    In yet another nonlimiting embodiment, the upper tool base  105  may be a single piece, having a plurality of parallel arms integral with an end portion. In this nonlimiting embodiment, the end portion and the arms may be beveled to be coincident to, and form a complementary angle with, the beveled surface  110  of the lower tool base  102 . 
         [0037]    In a further nonlimiting embodiment, the upper tool base  105  and the tool station  106  may be a single integrated component, wherein the means for compliance  114  are positioned between the lower tool base  102  and the integrated component. 
         [0038]    With continued reference to  FIG. 1 , means for compliance  114  are positioned between the lower tool base  102  and the upper tool base  105 . In a preferred nonlimiting embodiment, the means for compliance  114  are positioned between the beveled surface  110  of the lower tool base  102  and the beveled surface  112  of the upper tool base  105 . The means for compliance  114  can be attached using any type of fasteners  116  connected through the lower tool base  102  through the means for compliance  114 , and received by the upper tool base  105 . The fasteners  116  may be screws, pins, pegs, or the like. The fasteners  116  removably attach the lower tool base  102  to the means for compliance  114  and upper tool base  105 . The invention is not limited to one particular fastener, as one skilled in the art could use other fasteners to form a connection between the lower tool base  102 , upper tool base  105 , and means for compliance  114 . In a preferred nonlimiting embodiment, the means for compliance  114  have one or more integrated studs  127  for attachment to the upper tool base  105  and/or lower tool base  102 . In yet another preferred nonlimiting embodiment, the means for compliance  114  have an opening through the center that is threaded so that attachment of the means for compliance  114  to the lower tool base  102  and upper tool base  105  may be accomplished by a screw fastener. 
         [0039]    In a preferred nonlimiting embodiment, the means for compliance  114  are integral with the lower tool base  102  and upper tool base  105 , eliminating the need for fasteners  116 . 
         [0040]    Upper tool base  105  can be attached to the tool station  106  using fasteners  117  received in the upper tool base  105  into a receptacle in the bottom of the tool station  106 . The invention is not limited to one particular fastener, as one skilled in the art could use other fasteners to form a connection. Additionally, upper tool base  105  and tool station  106  may be a single integral piece. When assembled, the means for compliance  114 , formed of a flexible material, act to support movement of the upper tool base  105  relative to the lower tool base  102 . In a preferred nonlimiting embodiment, the number of means for compliance suitable for achieving desired movement in the translational and rotational degrees of freedom may be from 3-6, with 4 being a preferred number of mounting means. In addition, force applied to the tool station  106  during attachment and detachment of end effectors can be passed through to the means for compliance  114 . Thus, the tool station  106  and upper tool base  105  may move relative to the lower tool base  102 , which is rigidly mounted to the body of a robot. 
         [0041]    In a preferred nonlimiting embodiment, the means for compliance  114  may be shock mounts, vibration mounts, air springs, gas springs, resilient stoppers, wire rope isolator mounts, or the like. The means for compliance  114  may be formed of a compliant material, for example, rubbers such as Aflas, Buna-N, Butyl, ECH, EPDM, EVA, gum, Ionomer, latex, neoprene, polyethylene foam, polyethylene rubber, polyimide, polyurethane, santoprene, SBR, silicone, vinyl, and Viton® Flouroelastomer. The material may also be a plastics such as ABS, acetal copolymer, acetate, cast acrylic, extruded acrylic, butyrate, Cirlex Polyimide, CTFE, Delrin® Acetal resin, FEP, HDPE Polyethylene, Hydex, Kapton® Polyimide, LDPE polyethylene, polyphenyl oxide, nylon, PEEK, PETG, PFA, polycarbonate, polyester, polypropylene, polystyrene, polysulfone, PPS, PTFE, PVC, PVDF, Radel, Rulon, Teflon® PTFE, polyamide-imide, Tucrite, UHMW polyethylene, VHMW polyethylene, polyetherimide, and Vespel® polyimide. The means for compliance  114  may also be injection-molded plastic or metals, such as steel, stainless steel, steel cable, stainless steel cable, titanium, aluminum, or may be composite materials containing fiberglass, carbon fiber, Kevlar, or aramid fibers. 
         [0042]    With reference to  FIG. 2   a , an upper view of the tool holder assembly  100  shows the lower tool base  102  and the upper tool base  105  in the assembled position. Tool station  106  is attached to the upper tool base  105 . With reference to  FIG. 2   b , the assembled tool holder is shown with the means for compliance  114  positioned between the lower tool base  102  and upper tool base  105 . With reference to  FIG. 2   c , means for compliance  114  are shown positioned between the lower tool base  102  and upper tool base  105 , the upper tool base  105  being rigidly attached to the tool station  106 .  FIG. 2   d  is a side view of the tool holder assembly  100  showing the tool station  106  attached to the lower tool base  102  attached thereto via the means for compliance  114  attached to the upper tool base  105 . 
         [0043]    With reference to  FIGS. 2   a - d , means for compliance  114  are positioned between upper tool base  105  and lower tool base  102 , allowing upper tool base  105 , with tool station  106  firmly attached or integral thereto, to move freely in proportion to the force applied by the robotic arm (not shown) attaching to or detaching from an end effector (not shown) stored in the tool station. 
         [0044]    With reference to  FIG. 3 , a tool base assembly  120  of the end effector (not shown) attached to a manipulator (not shown) is seen positioned proximate to the tool holder assembly  100 . The robotic arm (not shown) moves the end effector into position for detachment utilizing the multiple joints. However the robotic arm can only move in limited degrees of freedom; it may rotate relative to the base on which it sits (not shown), and the joints allow movement through two translational degrees of freedom. As the arm maneuvers the end effector into position, the guiding mechanisms of the tool base assembly, which can be pins  130   a - b  or guide plates must engage with the optional guides  442   a - 442   b  to be guided to the track of the tool station  106 . The ramped surfaces (not shown) act as ramps with respect to pins  130   a - 130   b  of tool base assembly  120  of an end effector (not shown), guiding the tool base assembly  120  of the end effector into engagement with the tool station  106  as the robotic arm (not shown) lowers the tool base assembly  120  of the end effector into the tool station  106 . 
         [0045]    With reference to  FIG. 6 , a tool base assembly  120  of an end effector is shown with pins  130   a ,  130   c ,  130   d  (pin  130   b  is hidden behind the tool base assembly  120 ). The pins guide the end effector into the tool station  106  during detachment (described previously), and allow interaction of the end effector, and thus the robotic arm, with the tool station  106 . Force applied by the arm, through the end effector, moves the tool station  106  and upper tool base  105  in translational and rotational degrees of freedom. Any type of tool base assembly  120  may be utilized with the compliant tool holder assembly of the present invention, including assemblies that lack pins and utilize guide plates. 
         [0046]    With reference to  FIG. 7 , an exemplary tool station  106  for engaging end effectors (not shown) is shown. The tool station  106  serves the function of holding the tools when not in use by a robotic arm or manipulator. In addition, tool station  106  can provide correct positioning for tool base assembly  120  of an end effector during engagement. The tool station  106  can also compliantly interact with the tool base assembly  120  of an end effector for disengagement. 
         [0047]    With reference to  FIG. 8 , an exploded image of the exemplary tool station  106  is shown. Tool station  106  can have arms  430   a - 430   b , having holes  432   a - 432   b ,  434   a - 434   b  for connecting arms  430   a - 430   b  with block  444 . Arms  430   a - 430   b  can further have a two-stage track  436   a - 436   b . Track  436   a - 436   b  has ramped surfaces  438   a - 438   b  formed on an outer surface of ramps  440   a - 440   b . The ramped surfaces  438   a - 438   b  act as ramps with respect to pins  130   a - 130   b  of tool base assembly  120  of an end effector (not shown), guiding the tool base assembly  120  into engagement with the tool station  106  as the robotic arm (not shown) lowers the tool base assembly  120  into the tool station  106  (see  FIG. 3-6 ). Optional guides  442   a - 442   b  provide for lateral alignment of the lower pins  130   a    130   b  with the tool station  106 . Block  444  includes holes  446   a - 446   b ,  447   a - 447   b ,  448   a - 448   b  holding the arms  430   a - 430   b  together. 
         [0048]    With continuing reference to  FIG. 8 , plates  454   a - 454   b  are provided having a striker  458   a  (not shown) and  458   b  positioned on an internal surface extending outward having a ramped surface  459  on one side thereof. The plates  454   a - 454   b  can be attached by a hollow cylindrical bar  460  coupled to holes  461   a - 461   b . The plates  454   a - 454   b  can also have a manual release  469  attached with holes  462   a  and  464   a  to holes  463   a - 463   b , respectively. Holes  466   a - 466   b  and  468   a - 468   b  are provided for fastening plates  454   a - 454   b  to the arms  430   a - 430   b.    
         [0049]    To briefly describe the usual process of end effector disengagement, the wrist assembly of a robotic arm (not shown) is driven electronically (or by manual placement) onto the tool station  106 . This movement causes the slanted face  470  of the plates  454   a - 454   b  to contact the locking collar of the robotic wrist (not shown). Moving the locking collar onto slanted face of plates  454   a - 454   b  when the collar is locked, forces the collar to open, causing the pins (not shown) of the locking collar to move out of a lock ring (not shown) and lock plate (not shown). The pins  130   a    130   d  of the tool base assembly  120  slide onto the ramped surfaces  438   a - 438   b . The ramped surfaces  438   a - 438   b  guide the pins into the two-stage tracks  436   a - b . The lower pins move along the tracks  436   a - 436   b . Rotational freedom about the axis of pins  130   a - 130   b  facilitates placement of the tool on tool station  106 . Contacting the striker  458   b , pins  130   a - 130   b  cause the striker to open, allowing the pins to enter further tracks  436   a - 436   b , moving the upper pins  130   c    130   d  further onto the ramp, placing the lower pins in a position adjacent the lock ramps, and guiding them into the tracks  436   a - 436   b . When the pins  130   c - 130   d  have entered the tracks  436   a - 436   b , all degrees of freedom are restricted. With release of pins (not shown), the wrist assembly of the robotic arm (not shown) can be rotated, automatically or manually. The wrist assembly of the robotic arm (not shown) is rotated automatically using a motor inside the wrist assembly. The locking collar (not shown) is blocked by a follower ring (not shown). The striker  458   b  is closed, locking the tool base assembly  120  of the end effector into place. The wrist assembly (not shown) is disconnected. 
         [0050]    With reference to  FIG. 3 , the position of the tool base assembly  120  of the end effector is slightly off-center in relation to tool holder assembly  100 . Compliance will be needed therebetween as the tool base assembly  120  of the end effector engages with the tool holder assembly  100  via interaction with the tool station  106 . As the tool base assembly  120  of the end effector is forced into the tool holder assembly  100 , the means for compliance  114  attached to the upper tool base  105  will provide compliance to the tool station  106  which is attached to the upper tool base  105 . After the tool base assembly  120  of the end effector has disengaged from the wrist assembly (not shown), resistance from the means for compliance  114  will return the upper tool base  105  and tool station  106  to a set position. Uniform movement of the tool station  106  with relationship to the tool base assembly  120  of the end effector as the means for compliance  114  each are temporarily altered in shape, provides an additional motion. The tool holder assembly  100  provides compliance along six degrees of freedom. 
         [0051]    With continuing reference to  FIG. 3 , the tool base assembly  120  of the end effector engages the tool holder assembly  100  via the tool station  106  only if the tool station is compliant in the plane of yaw rotational movement. In the present invention, the means for compliance  114  provide freedom of rotation to the upper tool base  105  and tool station  106  to account for the slight change in alignment of the tool base assembly  120  of the end effector during engagement. 
         [0052]    With reference to  FIGS. 4 and 5 , the tool holder assembly  100  is shown with the tool base assembly  120  of the end effector in position for engagement. With continued reference to  FIGS. 4 and 5 , pins  130   a    130   c  are shown in slightly different positions between the two figures, indicating the positioning of the tool base assembly  120  of the end effector with relationship to the tool holder assembly  100 . However, the tool base assembly  120  of the end effector is not aligned with the tool station  106  in either of  FIG. 4  or  5  and compliance to engage is needed. Force from the tool base assembly  120  of the end effector attached to the manipulator (not shown) translated to the tool station  106  causes movement of the upper tool base via the means for compliance  114 . The means for compliance  114  thus provide compliance to the tool station, allowing for end effector attachment or detachment. 
         [0053]    With reference to  FIG. 9 , another embodiment of the compliant tool holder assembly is shown. In this preferred nonlimiting embodiment, lower tool base  102  is substantially u-shaped, having a plurality of parallel arms  104   a - 104   b  integral with an end section  103 , wherein the arms  104   a - 104   b  extend away from the end section  103  and define a cavity. In this embodiment, a plurality of first brackets,  901   a - 901   b  are removably attached to the lower tool base  102 . In a preferred nonlimiting embodiment, the first brackets are removably attached to the plurality of parallel arms  104   a - 104   b  by fasteners  902 , said first brackets being angled so that while one section of the bracket is flush with arm  104   a  of the lower tool base  102 , the means for compliance  114  may still be angled relative to both the lower tool base  102  and the tool station  106 . In a preferred nonlimiting embodiment, the first brackets are angled at 45 degrees relative to the flat top of the lower tool base  102  such that means for compliance  114  are at an angle of 45 degrees relative to the tool base  102  and the tool station  106 . The invention is not limited to one particular fastener, as one skilled in the art could use other fasteners to form a connection. 
         [0054]    With continuing reference to  FIG. 9 , means for compliance  114  are attached to the first brackets  901   a - 901   b  with fasteners  903 . While the figure displays fasteners with end nuts for securing the mounting means to first brackets, the invention is not limited to one particular fastener, as one skilled in the art could use other fasteners to form a connection. The fasteners  903  pass through the means for compliance  114  and connect the first brackets  901   a - 901   b , the means for compliance  114 , and second brackets  904   a - 904   b . Said second brackets  904   a - 904   b  are angled such that while they are flush with the means for compliance  114 , they may also be flush with the tool station  106 , allowing the means for compliance  114  to be at an angle relative to the top of the lower tool base  102  and the bottom of the tool station  106 . Sufficient compliance may be achieved with a plurality of means for compliance  114 . In a preferred nonlimiting embodiment there are four means for compliance  114  at a 45 degree angle relative to the top of the lower tool base  102  and the bottom of tool station  106 ; However, sufficient compliance may be achieved with any number of mounting means. Tool station  106  is removably attached to second brackets  904   a - 904   b , allowing tool station  106  to move in translational and rotational degrees of freedom relative to the lower tool base  102 , which is rigidly attached to the body of the robot. 
         [0055]    As with the lower tool base  102 , upper tool base  105 , and tool station, brackets  901   a - 901   b  and  904   a - 904   b  may be made of any suitable material, including Aflas, Buna-N, Butyl, ECH, EPDM, EVA, gum, Ionomer, latex, neoprene, polyethylene foam, polyethylene rubber, polyimide, polyurethane, santoprene, SBR, silicone, vinyl, and Viton® Flouroelastomer. The material may also be a plastics such as ABS, acetal copolymer, acetate, cast acrylic, extruded acrylic, butyrate, Cirlex Polyimide, CTFE, Delrin® Acetal resin, FEP, HDPE Polyethylene, Hydex, Kapton® Polyimide, LDPE polyethylene, polyphenyl oxide, nylon, PEEK, PETG, PFA, polycarbonate, polyester, polypropylene, polystyrene, polysulfone, PPS, PTFE, PVC, PVDF, Radel, Rulon, Teflon® PTFE, polyamide-imide, Tucrite, UHMW polyethylene, VHMW polyethylene, polyetherimide, and Vespel® polyimide. Brackets  901   a - 901   b  and  904   a - 904   b  may also be injection-molded plastic or metals, such as steel, stainless steel, steel cable, stainless steel cable, titanium, aluminum, or may be composite materials containing fiberglass, carbon fiber, Kevlar, or aramid fibers. 
         [0056]    The tool holder assembly  100  can provide different levels of compliance in the six degrees of freedom. Different levels of deflection and stiffness are possible; different degrees of freedom can be provided to account for these. The means for compliance  114  provide maximum deflection in the three translational degrees of freedom. Tilt and yaw rotational degrees of freedom are provided to a lesser extent. The rotational degree of freedom about the axis of the tool has the smallest allowable deflection. It is envisioned that one skilled in the art could provide any number of combinations of deflection orientations using the present invention. 
         [0057]    While the present invention has been described in connection with the preferred embodiments, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiments for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.