Abstract:
A parallel robotic manipulator for generating 3 dimensional structures includes a set of redeployable towers adapted to transport one or more cables, and at least one drive source operable to draw or traverse the cables across a rendering area. An end-effector suspended from the cables is operable to deposit extrudate onto the rendering area, and a nozzle in the end-effector is configured to selectively deposit the extrudate at predefined locations based on the position of the cable. A control unit has control logic for directing the drive source, in which the cables are responsive to the drive source for disposing the end-effector either along the cables or drawn and extended from the towers. An extrudate reservoir and a pump in fluidic communication with the reservoir allows the pump to force the extrudate for deposition at the predefined location responsive to the control logic.

Description:
RELATED APPLICATIONS: 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/237,670, filed Oct. 6, 2015, entitled “ CABLE DRIVEN MANIPULATOR FOR ADDITIVE MANUFACTURING,” incorporated herein by reference in entirety. 
     
    
     BACKGROUND 
       [0002]    Printing technology has evolved in recent decades to support various mediums for generating traditional hardcopy output from electronic sources, typically a computer program. Modern output rendering includes high resolution graphics, full color, and machine readable codes such as bar and square codes readable by optical scanning. 3-dimensional (3D) printing is evolving to allow rendering of small objects by controlled emission or extrusion of a sufficiently solid substance. 
         [0003]    Additive manufacturing leverages 3D printing for replacing conventional manufacturing and fabrication by providing an alternative to components which would otherwise be formed by molding or machining, for example. A 3D printing apparatus directs a “printed” or formed material, in contrast to ink deposition as in  2 D printing, and aggregates formed objects due to the thickness of the material. The conventional 3D printing approach directs a print head mounted in a frame on tracks or guides corresponding to the length, width and depth of the printing volume in the frame. 
       SUMMARY 
       [0004]    A cable driven parallel manipulator for generating 3-dimensional (3D) structures includes an arrangement of towers adapted to transport one or more cables, and at least one drive source operable to draw or traverse the cables across a rendering area. An end-effector suspended from the cables is operable to deposit extrudate (extruded material) onto the rendering area, and a nozzle in the end-effector is configured to selectively deposit the extrudate at predefined locations based on the position of the cable. A control unit has control logic for directing the drive source, in which the cables are responsive to the drive source for disposing the end-effector either along the cables or drawn and extended from the towers. An extrudate reservoir and a pump in fluidic communication with the reservoir allows the pump to force the extrudate for deposition at the predefined location responsive to the control logic. 
         [0005]    At present, large scale additive manufacturing is complicated by the need to have a large and cumbersome structure to support a relatively small end effector. Configurations disclosed below utilize the advantages of a cable driven parallel manipulator to substantially overcome the problems associated with current additive manufacturing devices. The disclosed approach replaces a conventional fixed frame with 3 towers located at an outer region of a workspace or rendering area. A cable running from each tower is connected to the centrally located end effector. Motors located on the towers or the end effector operate as actuators to spool and unspool the cables to dispose the end effector throughout the workspace. 
         [0006]    3D printing or additive manufacturing designs rely on a large supporting frame, are unable to be moved, are a fixed size, and cannot print on the final location. This design is relatively portable, much lower cost, and is capable of easily adapting to the environment in which it is placed. Conventional machines rely on large, immobile, and fixed size frames, and often these must be placed inside of an even larger structure, meaning that it is impossible for these machines to manufacture directly into the environment, and they cannot be easily moved or adjusted to accommodate new operations. Omission of a large, rigid frame and the ability to function without a large, permanent foundation provide greater versatility since the shape, size, and overall geometry of the printer can be adjusted to suit any workspace. Additionally, the simple suspended construction enables the erection, disassembly, and repositioning of the printer for redeployment with far reduced effort. 
         [0007]    Configurations herein are based, in part, on the observation that controlled deposition of rendered material, common for hardcopy paper printing, has been extended to 3-dimensional (3D) printing by deposition of a structural material, rather than ink, onto a rendering area. Unfortunately, conventional approaches to 3D printing suffer from the shortcoming that printing or fabrication is limited to serial robotic manipulations inside a fixed frame. Print heads or other end-effectors for material deposition is controlled by serial manipulation along a rail or track suspended within the frame. Unfortunately, conventional approaches to 3D printing suffer from the shortcoming that each robotic element performs in a single degree-of-freedom (DOF), and a resulting print positon derived from an aggregation of the single DOF manipulations within the frame. Such an approach limits the finished fabrication product to a size dictated by the frame, and burdens print/fabrication accuracy and relative robotic mass of the apparatus from the use of serial manipulations. 
         [0008]    Robotic and mechanized structures can be broadly classified, based on their architecture, as either serial or parallel. A serial robot is made up of a succession of rigid bodies from the base to the end-effector, each of them being linked to its predecessor and its successor by one-degree-of-freedom joint, typically to provide a pivot, rotation, or linear translation. Serial robots are typically characterized by a low load capacity-to-mass ratio and limited accuracy, but enjoy ease of design and subsequent kinematic analysis due to the relative simplicity of one degree of freedom at each joint segment. In contrast, configurations herein employ a parallel robotic arrangement. Such a parallel robot is made up of an end-effector with multiple degrees of freedom from a fixed base, linked together by at least two independent kinematics chains. Actuation takes place through the multiple simple actuators, therefore contributing to an integrated or combined kinetic influence on the end effector based on the multiple actuators. Conventional approaches do not provide for attachment of an end effector to various cable-driven parallel manipulators for a 3D extrusion nozzle. 
         [0009]    In configurations herein, the set of support towers suspending the extruder over a rendering are is adapted for transition to a second rendering area for portability of the manipulator. In the example configuration, the frame includes three towers, each tower having a corresponding cable suspended therefrom, and the towers each have a drive source such as a winch for retracting and extending the cables. Alternatively, or in addition, the drive source includes at least one winch attached to the end-effector, such that each winch corresponds to a particular cable for drawing the winch and attached end-effector across the rendering area, thus the towers suspend the cable for traversal by a winch kinetically coupled to the end-effector. 
         [0010]    The extrudate is a material or substance suitable for application to the rendering area for generating a desired dimensional structure, or object for fabrication, and may be a liquid form for dispensing and rendering, and subsequently achieve a solid or semi-solid state for support of subsequently applied extrudate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The foregoing and other objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0012]      FIG. 1  is a context diagram of a fabrication environment suitable for use with configurations disclosed herein that exhibits parallel manipulations of an end effector depositing extrudate for object fabrication; 
           [0013]      FIG. 2  is a perspective view of the approach of  FIG. 1  in fabrication use; 
           [0014]      FIG. 3  shows cable actuators disposed in the extruder in the apparatus of  FIG. 2 ; 
           [0015]      FIG. 3A  shows the extruder of  FIG. 3  in greater detail; 
           [0016]      FIG. 4  shows cable actuators disposed in the towers in the apparatus of  FIG. 2 ; and 
           [0017]      FIG. 5  shows a plan view of alternate arrangement of the approach of  FIG. 2  using fixed cables traversed by the actuators. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Depicted below is example of a frameless, cable driven parallel manipulator depicted by an extruder supported by the cables over the rendering area for precise deposition of extruded material for fabricating a desired form, structure or shape. A fabrication apparatus using the disclosed parallel manipulators is adapted for large scale fabrication since it is not bounded by a fixed frame for housing conventional serial manipulators. 
         [0019]    The extruder, as employed herein, defines the end-effector of the actuator driven cables. The robotic term “end effector” generally refers to a device, manipulator or instrument at the end of a robotic member for interaction with the environment, depending on the application of the robot. It is the culmination of the movement and effects of the parallel or serial robotic translations for performing the task, measurement or operation that the robot was intended to perform. Therefore, the extruder is an end-effector of the parallel robotic manipulators defined by the towers and the actuators (winches). 
         [0020]    As a conventional example, example, U.S. Pub. No. 2013/0292039 shows a fabricator supported by at least three elongated support members. It includes onboard actuators that translate the fabricator relative to the ends of the support members. However, the approach in &#39;039 includes reservoirs or other storage devices for storing the material to be deposited (or ingredient(s) used in producing the deposited material onboard the fabricator. Thus, the &#39;039 approach the suspended actuator contains all the materials for extruding/deposition. In contrast, the disclosed approach employs extrusion materials (extradite) in a separate reservoir and a feed pipe supplying the extruder, such that the extruder can be much lighter since it need not contain all the extruded material and mixing apparatus. 
         [0021]      FIG. 1  is a context diagram of a fabrication environment suitable for use with configurations disclosed herein that exhibits parallel manipulations of an end effector depositing extrudate for additive manufacturing in fields such as construction and industrial machinery. Referring to  FIG. 1 , in a fabrication environment  100 , a rendering area  102  is flanked by towers  110 - 1  . . .  110 - 2  ( 110  generally) each supporting a cable  112 - 1  . . .  112 - 2  ( 112  generally). The cables  112  support an extruder  120 , or end-effector. Thus, the apparatus for forming additive structures includes an extruder  120  attached to at least one cable and adapted for movement over a rendering area while supported by the cable  112 . Combined movement of the cables  112 , by extending or retracting, disposes the extruder  120  into positions  120 ′ or  120 ″ by altering the respective length of the cables  112 ′- 1 ,  112 ″- 1  and  112 ′- 2 ,  112 ″- 2 , shown by dotted lines. Movement of the cables  112  therefore affects both a lateral position  122  and a height  124  of the extruder  120 . A feed vessel  130  transports extrudate  132  material from a hopper  134  to the extruder  120  for deposition onto the rendering area  102 . 
         [0022]    In particular configurations, discussed further below, a plurality of cable support towers  110  may be disposed adjacent to the rendering area  102 , such that each of the towers is adapted for supporting a respective cable. At least one cable actuator, and likely several, are in communication with a corresponding cable  112  and configured to dispose the extruder  120  over the rendering area  102 . The feed vessel  130  couples to the extruder  120  and is configured to transport the extrudate  132  to the extruder  120  for controlled deposition onto the rendering area  102 . 
         [0023]      FIG. 2  is a perspective view of the approach of  FIG. 1  in fabrication use. Referring to  FIGS. 1 and 2 , by employing  3  or more towers  110  and corresponding cables  112 , lateral movement  122  may occur in two dimensions over the region defining the rendering area  102 , and the third dimension defining the height  124 . The feed vessel  130  is either sufficiently rigid and/or suspended from the towers  110  or cables  112  to avoid interference with extrudate deposition onto the rendering area  102 . Fabrication logic  142  from a controller  140  controls actuators manipulating the cables  112  as well as the extruder  120  for depositing the extrudate (extruded material) to form a structure under fabrication  150 , or fabricated object. The extruder  120  includes an extrusion pump for precise metering of extruded material  134  which forms the structure under fabrication  150 . 
         [0024]    The use of multiple actuators and cables  112  acting on a single end-effector defined by the extruder  120  provides parallel manipulations of the end effector. The parallel manipulator is therefore defined by a plurality of actuators, such that the extruder  120  defines an end-effector of the collective cable manipulations from each of the towers  110 , in which the corresponding actuators contribute to the parallel manipulations of the extruder  120 . Each of the actuators is responsive to a common control for positioning the extruder at a location defined by fabrication logic  142  in the controller  140 . The position of the extruder  120  in the 3D space defined by the rendering area  102  is therefore controlled by adjusting a length of each cable  112  from the towers  110  to the extruder  120 , which is performed by actuators in either the towers  110  or the extruder  120 , discussed further below. 
         [0025]    Continuing to refer to  FIG. 2 , the extruder  120  further includes a nozzle  136  in communication with the feed vessel  130  for receiving extrudate  132 , and an extrusion pump  180  coupled to the nozzle  132  for dispensing precise quantities of extruded material  152  onto the rendering area  102  based on a position above the rendering area. The extrusion pump  180  may be operated by any suitable source, such as an electric motor or actuator in the extruder. 
         [0026]    In contrast to conventional approaches, utilizing a fixed frame for supporting and containing all actuators, print heads and associated supports, the towers  110  are independently positioned on moveable bases  104 - 1  . . .  104 - 2  ( FIG. 1, 104  generally), and may be readily deployed to define the rendering area  102  applicable to the structure under fabrication  150 . Accordingly, the towers  110  are disposed outside a perimeter of the rendering area  102 , such that the rendering area defines the limits of the fabricated structure  150  resulting from the extrusion operations of the extruder  120 . Each of the towers  110 , therefore, is a detached cable support and actuator  170 , adapted to be disposed to an alternate location independently of the others of the plurality of towers. The rendering area  102  may be altered or enlarged by moving one, some or all of the bases  104  and corresponding towers  110 . 
         [0027]      FIG. 3  shows cable actuators disposed in the extruder in the apparatus of  FIG. 2 . Referring to  FIGS. 2 and 3 , a plurality of cables  112  attaches to the extruder  120 , each cable having a corresponding actuator  170  in the extruder, in which the actuators  170  are configured to spool the cable  112  to alter the length of the cable  112  to a respective tower  110 . The actuators  170  provide parallel manipulations of the extruder  120  by disposing the extruder  120  over the rendering area  102  based on the unspooled length of each cable for three dimensional ( 3 F) positioning over the rendering area. Therefore, the cable actuators  170  are disposed in the extruder  120 , such that each cable has a corresponding cable actuator  170  and winds or unwinds the cable  112  from a spool driven by the actuator to modify the effective (unrolled) length of the cable to the corresponding tower. Each cable  112  further comprising an attachment  113  to a respective one of the plurality of towers  110 , such that the extruder  120  is configured to traverse above the rendering area  102  by extending or retracting the cable relative to the respective tower  110 . 
         [0028]    A supply of extrudate  132  material is stored in a hopper  134  adjacent to the rendering area  102 , and pumped to the extruder  120 , rather than burdening the extruder  120  with a cargo of extrudate. The hopper  132  contains the extrudate  132  for forming a fabricated structure  150 , and an extrudate pump  160  coupled to the hopper  134  is for transporting the extrudate through the feed vessel  130  attached to the extrudate pump  160  and suspended above the rendering area  102 . 
         [0029]      FIG. 3A  shows the extruder of  FIG. 3  in greater detail. The example of  FIG. 3  shows a side elevation of a structure having two towers for clarity, and  FIG. 3A  shows a configuration with 3 cables corresponding to 3 towers  110 , similar to the layout of  FIG. 2 . Any suitable number of towers  110  and actuators  170  may be employed, however at least 3 towers are employed when traversing a two dimensional rendering area  102  (with the third dimension begin height). In  FIG. 3A , actuators  170 - 1  . . .  170 - 3  ( 170  generally) draw or extract a respective cable  112  onto a spool  171 - 1  . . .  171 - 3  ( 171  generally) to change the effective length of the cable  112  to the corresponding tower  110 . Control signals  146  emanate from the fabrication logic  142  via a control bus  144 , leading to each actuator  170  and the extrusion pump  180 , fed by the feed vessel  130 . 
         [0030]    The extrusion pump  180  and actuators  170  are controlled by the fabrication logic  142  in the controller  140  for defining the limits of the rendering area  102  and for driving the actuators  170  and extruder  120  for additively forming the fabricated structure  150  by controlled extrusion of the extrudate  132  at predetermined locations in the rendering area  102 . The fabrication logic  142  directs the actuators  170  to draw or extend the cables  112  to change the height and location of the extruder  120  to correspond to a predetermined program, plan or file containing specific parameters about the structure under fabrication  150 . Any suitable parameters may be employed, depending on the precision of the extrusion pump  180  and granularity of control of the actuators  170 , such a through stepper motors or other rotation control of the spooled cables  112 . 
         [0031]    The material from which the structure under fabrication  150  is formed may be any suitable material, stored initially in the hopper  134  as extrudate  132 . The extrudate  132  flows through the feed vessel  130 , forced by the extrudate pump  160  to the extruder  120 , where the extrusion pump  180  deposits precisely controlled quantities of extruded material  152 . The extrudate pump  160  is a high power cycled or continuous pump for moving the extrudate up through the feed vessel  130  and maintain a ready supply of extrudate to the extruder  120 . The extrusion pump  180  performs finer control for metering specific amounts of extruded material as directed from the fabrication logic  142 . 
         [0032]    The extrudate  132  material is sufficiently fluid to flow through the feed vessel  130  and extrusion pump  180 , yet sufficiently firm to maintain a structural firmness of the structure under fabrication  150 . Typically a water or solvent based mixture would be employed to facilitate subsequent curing or drying. Concrete, plaster, gypsum, and/or polymer based materials provide some examples of extrudate. Additives such as chopped basalt fiber, frequently used as a low cost substitute for carbon fiber or rebar in concrete, may also be employed. The addition of the fiber enhances strength without sacrificing the excellent thermal and sound insulating properties of the extrudate  132 . Sodium silicate, also known as “water glass” may also be added to the mixture for additional binding strength and reduced shrinkage during the setting process. Sodium Silicate can also be used for a number of purposes including as an extremely strong and waterproof adhesive resin, and as an excellent sealant. 
         [0033]      FIG. 4  shows cable actuators disposed in the towers in the apparatus of  FIG. 2 . Referring to  FIGS. 2 and 4 , an alternate approach disposes the actuators  170  on the towers, lessening the mass of the extruder  120 . The example of  FIG. 4 , defines a cable actuator  170  at each of the towers  110 , such that the cable  112  is engaged with the actuator  170  at a proximate end and attached to the extruder  170  at a distal end, such that the cable actuators  170  are adapted to dispose the extruder  120  for traversing the rendering area  102  by retracting or extending the cables. Each tower  110  has a respective cable  112  and actuator  170 , such that each cable  112  attaches to the extruder  120  in a fixed manner for providing parallel manipulations of the extruder for three dimensional (3D) positioning over the rendering area  102 . In the example of  FIG. 4 , the actuator  170  is defined by a winch at each of the towers  110 , each winch being responsive to the fabrication logic  142 , such that each of the actuators  170  is operable to drive the winch for spooling and unspooling the cable for disposing the extruder  120  at a height and location above the rendering area  102 . 
         [0034]      FIG. 5  shows a plan view of an alternate arrangement of the approach of  FIG. 2  using fixed cables traversed by the actuators. In the example of  FIG. 5 , the cable actuators  170  are again disposed in the extruder  120 , such that the cable further includes an attachment to a respective one of the plurality of towers. The extruder  120  is configured to traverse above the rendering area  102  by drawing the actuator along the cable toward or away from the respective tower. In  FIG. 5 , the extruder  120  mounted actuator  170  does not wind and accumulate the cable  110  around a spool  171 , but rather traverses the length of the cable, drawing in on one side and expelling the cable on an opposed side such that the effective length of the cable on both sides remains constant. Positioning is performed by disposing the extruder  120  at an intersection of multiple cables  112 . 
         [0035]    In one configuration, the 3D fabrication approach disclosed herein is operable at remote sites for establishing dwelling structures. Such usage anticipates the 3D printer being used for the construction of the habitat is a cable driven parallel manipulator design. This type of design makes the printer lightweight, compact, portable, and scalable. The extruder  120  has four motorized winches, each connected with a cable to a support tower  110  positioned at the corners of the print or rendering area  102 . The support towers  110  are large tripods, roughly  30  feet tall, to optimize stability and ease of setup. This design can be easily dismantled and reassembled in a new location to print additions or entirely new structures. The extrudate  132  is prepared by combining clay, basalt fiber, and water glass in an auger stirred container located near the printer. A peristaltic pump is used to pump the mixed extrudate through a pipe or feed vessel  130  to the extruder  120 . Another auger in the extruder is used to force the material through the nozzle. 
         [0036]    This configuration supports extraterrestrial colonization efforts through the use of an inflatable shell used during the printing process to conserve water by collecting water vapors that are released during the drying process. This shell would only be pressurized with planetary atmosphere enough to hold the shell up and is not otherwise climate controlled. The collected water is recycled back into the system to print the rest of the structure. After construction is complete the shell can be repurposed. The entire fabrication operation requires only a few days to complete. In the interest of preventing any chance of compromising the habitat&#39;s strength, the print would be scheduled to take place when the weather forecast is clear of any significant storms. 
         [0037]    The controller  140 , fabrication logic  142  and control bus  144  may be any suitable microprocessor based processor and transport platform. It will be appreciated by those skilled in the art that alternate configurations of the disclosed invention include a multiprogramming or multiprocessing computerized device such as a workstation, handheld or laptop computer or dedicated computing device or the like configured with software and/or circuitry (e.g., a processor as summarized above) to process any or all of the method operations disclosed herein as embodiments of the invention. Still other embodiments of the invention include software programs such as a Java Virtual Machine and/or an operating system that can operate alone or in conjunction with each other with a multiprocessing computerized device to perform the method embodiment steps and operations summarized above and disclosed in detail below. One such embodiment comprises a computer program product that has a non-transitory computer-readable storage medium including computer program logic encoded thereon that, when performed in a multiprocessing computerized device having a coupling of a memory and a processor, programs the processor to perform the operations disclosed herein as embodiments of the invention to carry out data access requests. Such arrangements of the invention are typically provided as software, code and/or other data (e.g., data structures) arranged or encoded on a non-transitory computer readable storage medium such as an optical medium (e.g., CD-ROM), floppy or hard disk or other medium such as firmware or microcode in one or more ROM, RAM or PROM chips, field programmable gate arrays (FPGAs) or as an Application Specific Integrated Circuit (ASIC). The software or firmware or other such configurations can be installed onto the computerized device (e.g., during operating system execution or during environment installation) to cause the computerized device to perform the techniques explained herein as embodiments of the invention. 
         [0038]    While the system and methods defined herein have been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.