Patent Publication Number: US-2022217899-A1

Title: Transplanter systems for automated controlled growth environments

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to U.S. provisional application Ser. No. 62/847,259 filed May 13, 2019, the disclosure of which is incorporated herein by reference for all purposes. 
    
    
     BACKGROUND 
     Field of the Disclosure 
     The disclosure relates generally to transplanter systems and subsystems and, more particularly, to transplanters for use in automated crop production, such as indoor controlled growth environments or outdoor agriculture. 
     Description of Related Art 
     The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology. 
     During the twentieth century, agriculture slowly began to evolve from a conservative industry to a fast-moving high-tech industry. Global food shortages, climate change and societal changes drove a move away from manually-implemented agriculture techniques toward computer-implemented technologies. In the past, and in many cases still today, farmers only had one growing season to produce the crops that would determine their revenue and food production for the entire year. However, this is changing. With indoor growing as an option and with better access to data processing technologies, the science of agriculture has become more agile. It is adapting and learning as new data is collected and insights are generated. 
     Advancements in technology are making it feasible to control the effects of nature with the advent of “controlled environment agriculture.” Improved efficiencies in space utilization, lighting, and a better understanding of hydroponics, aeroponics, crop cycles, and advancements in environmental control systems have allowed humans to better recreate environments conducive for agriculture crop growth with the goals of greater yield per square foot, better nutrition and lower cost. 
     US Patent Publication Nos. 2018/0014485 and 2018/0014486, both assigned to the assignee of the present disclosure and incorporated by reference in their entirety herein, describe environmentally controlled vertical farming systems. The vertical farming structure (e.g., a vertical column) may be moved about an automated conveyance system in an open or closed-loop fashion, exposed to precision-controlled lighting, airflow and humidity, with ideal nutritional support. US Patent Pub. No. US 2017/0055460 (“Brusatore”) describes a system for continuous automated growing of plants. A vertical array of plant supporting arms extends radially from a central axis. Each arm includes pot receptacles which receive the plant seedling, and liquid nutrients and water. The potting arms are rotated beneath grow lamps and pollinating arms. 
     Various systems and machines for transplanting a plant or root-bound plug from a first container to a second container are known. For example, U.S. Publication No. 2004/0020110A1 discloses a transplanter assembly that includes grippers and various actuators for grasping a plant held in a first container and placing it in a second container. Generally, most known transplanting systems operate in a vertical orientation. In particular, the grippers are moved vertically up and down when performing transplanting operations. Furthermore, most known transplanting systems operate to transfer a plug or plant from a first container to a second, larger container that includes ample space for the plant root ball or plug. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure is directed to automated transplanter systems and subsystems. For example, the disclosure sets forth a plug gripper and assembly adapted to transplant plugs into tight-fitting plug holders. The disclosure also conveys a transplanter assembly useful in transplant operations where a plug holder is oriented at a non-perpendicular angle to the surface of a grow tower or other structure that contains the plug holder. The disclosure also provides a transplanter system useful in transplanting plugs into grow towers where the plug holders are oriented horizontally. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional block diagram illustrating an example controlled environment agriculture system. 
         FIG. 2  is a perspective view of an example controlled environment agriculture system. 
         FIGS. 3A and 3B  are perspective views of an example grow tower. 
         FIG. 4A  is a top view of an example grow tower;  FIG. 4B  is a perspective, top view of an example grow tower;  FIG. 4C  is an elevation view of a section of an example grow tower; and  FIG. 4D  is a sectional, elevation view of a portion of an example grow tower. 
         FIG. 5A  is a perspective view of a portion of an example grow line. 
         FIG. 5B  is a perspective view of an example tower hook. 
         FIG. 6  is an exploded, perspective view of a portion of an example grow line and reciprocating cam mechanism. 
         FIG. 7A  is a sequence diagram illustrating operation of an example reciprocating cam mechanism. 
         FIG. 7B  illustrates an alternative cam channel including an expansion joint. 
         FIG. 8  is a profile view of an example grow line and irrigation supply line. 
         FIG. 9  is a side view of an example tower hook and integrated funnel structure. 
         FIG. 10  is a profile view of an example grow line. 
         FIG. 11A  is perspective view of an example tower hook and integrated funnel structure; 
         FIG. 11B  is a section view of an example tower hook and integrated funnel structure; and 
         FIG. 11C  is a top view of an example tower hook and integrated funnel structure. 
         FIG. 12  is an elevation view of an example carriage assembly. 
         FIG. 13A  is an elevation view of the example carriage assembly from an alternative angle to  FIG. 12 ; and  FIG. 13B  is a perspective view of the example carriage assembly. 
         FIG. 14  is a partial perspective view of an example automated laydown station. 
         FIG. 15A  is a partial perspective view of an example automated pickup station; and, 
         FIG. 15B  is an alternative partial perspective view of the example automated pickup station. 
         FIG. 16  is a perspective view of an example end effector for use in an automated pickup or laydown station. 
         FIGS. 17A and 17B  are partial, perspective views of an example gripper assembly mounted to an end effector for releasably grasping grow towers. 
         FIG. 18  is a partial perspective view of the example automated pickup station. 
         FIG. 19  is partial perspective view of the example automated pickup station that illustrates an example constraining mechanism that facilitates location of grow towers. 
         FIG. 20  is a side view of an example inbound harvester conveyor. 
         FIG. 21  is a functional block diagram of the stations and conveyance mechanisms of an example central processing system. 
         FIG. 22  is a partial perspective view of an example pickup conveyor. 
         FIG. 23A  is a perspective view of an example harvester station. 
         FIG. 23B  is a top view of an example harvester machine. 
         FIG. 23C  is a perspective view of an example harvester machine. 
         FIG. 24A  is an elevation view of an example end effector for use in a transplanter station and illustrates how plug grippers may be moved from a first angular orientation to a second angular orientation. 
         FIG. 24B  is a perspective view of an example transplanter station. 
         FIG. 24C  is a schematic view of an example transplanter station. 
         FIG. 24D  is a side view illustrating a grow tower with open side faces. 
         FIG. 25  illustrates an example of a computer system that may be used to execute instructions stored in a non-transitory computer readable medium (e.g., memory) in accordance with embodiments of the disclosure. 
         FIG. 26A  is a perspective view of a plug gripper in a retracted position. 
         FIG. 26B  is a perspective view of a plug gripper in an extended position. 
         FIG. 26C  is a bottom plan view of a plug gripper illustrating a stripper plate. 
         FIG. 26D  is a side view of a plug gripper. 
         FIG. 27A  is a perspective view of an example plug tray; and  FIG. 27B  is a perspective view of an example plug. 
         FIG. 28  is a cut-away, perspective view of an infeed mechanism for use in a transplanter station. 
         FIG. 29  is a cut-away, perspective view of an outfeed mechanism for use in a transplanter station. 
         FIG. 30A  is a perspective view of a grow tower disposed on a track;  FIG. 30B  is a side, elevation view of a grow tower disposed on a track;  FIG. 30C  is a perspective view of a track section; and  FIG. 30D  is a side elevation view illustrating how an actuator may register and align a grow tower against a track. 
         FIG. 31A  is a perspective view of an example engagement actuator;  FIG. 31B  is a side elevation view of an example engagement actuator; and  FIG. 31C  is a side view illustrating an engagement actuator, a grow tower and a track. 
         FIG. 32A  is a perspective view of an alternative plug gripper;  FIG. 32B  is a perspective view of an arm assembly of the alternative plug gripper;  FIG. 32C  is a side elevation view of the alternative plug gripper;  FIG. 32D  is a front elevation view of the alternative plug gripper;  FIG. 32E  is a front elevation view of the plug gripper in a retracted position; and  FIG. 32F  is a bottom view of the alternative plug gripper. 
         FIG. 33A  is a perspective view of another alternative plug gripper;  FIG. 33B  is a front elevation view of the plug griper; and  FIG. 33C  is a side elevation view of the alternative plug gripper. 
     
    
    
     DETAILED DESCRIPTION 
     The present description is made with reference to the accompanying drawings, in which various example embodiments are shown. However, many different example embodiments may be used, and thus the description should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete. Various modifications to the exemplary embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the disclosure. Thus, this disclosure is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
     The present disclosure describes transplanter systems and subsystems. In one implementation, these systems and subsystems may be configured for use in automated crop production systems for controlled environment agriculture. Embodiments of the disclosure can be implemented in a vertical farm production system that includes grow towers as described herein. The present invention, however, is not limited to any particular crop production environment, which may be an automated controlled grow environment, an outdoor environment or any other suitable crop production environment. Furthermore, implementations of the invention may be used in systems that use other growth structures, instead of grow towers, such as grow walls, modular grow structures and the like. 
     For didactic purposes, the following describes a vertical farm production system configured for high density growth and crop yield.  FIGS. 1 and 2  illustrate a controlled environment agriculture system  10  according to one possible embodiment of the invention. At a high level, the system  10  may include an environmentally-controlled growing chamber  20 , a vertical tower conveyance system  200  disposed within the growing chamber  20  and configured to convey grow towers  50  with crops disposed therein, and a central processing facility  30 . The crops or plants species that may be grown may be gravitropic/geotropic and/or phototropic, or some combination thereof. The crops or plant species may vary considerably and include various leaf vegetables, fruiting vegetables, flowering crops, fruits and the like. The controlled environment agriculture system  10  may be configured to grow a single crop type at a time or to grow multiple crop types concurrently. 
     The system  10  may also include conveyance systems for moving the grow towers in a circuit throughout the crop&#39;s growth cycle, the circuit comprising a staging area configured for loading the grow towers into and out of the vertical tower conveyance mechanism  200 . The central processing system  30  may include one or more conveyance mechanisms for directing grow towers to stations in the central processing system  30 —e.g., stations for loading plants into, and harvesting crops from, the grow towers. The vertical tower conveyance system  200 , within the growing chamber  20 , is configured to support and translate one or more grow towers  50  along grow lines  202 . Each grow tower  50  is configured for containing plant growth media that supports a root structure of at least one crop plant growing therein. Each grow tower  50  is also configured to releasably attach to a grow line  202  in a vertical orientation and move along the grow line  202  during a growth phase. Together, the vertical tower conveyance mechanism  200  and the central processing system  30  (including associated conveyance mechanisms) can be arranged in a production circuit under control of one or more computing systems. 
     The growth environment  20  may include light emitting sources positioned at various locations between and along the grow lines  202  of the vertical tower conveyance system  200 . The light emitting sources can be positioned laterally relative to the grow towers  50  in the grow line  202  and configured to emit light toward the lateral faces of the grow towers  50  that include openings from which crops grow. The light emitting sources may be incorporated into a water-cooled, LED lighting system as described in U.S. Publ. No. 2017/0146226A1, the disclosure of which is incorporated by reference herein. In such an embodiment, the LED lights may be arranged in a bar-like structure. The bar-like structure may be placed in a vertical orientation to emit light laterally to substantially the entire length of adjacent grow towers  50 . Multiple light bar structures may be arranged in the growth environment  20  along and between the grow lines  202 . Other lighting systems and configurations may be employed. For example, the light bars may be arranged horizontally between grow lines  202 . 
     The growth environment  20  may also include a nutrient supply system configured to supply an aqueous crop nutrient solution to the crops as they translate through the growth chamber  20 . As discussed in more detail below, the nutrient supply system may apply aqueous crop nutrient solution to the top of the grow towers  50 . Gravity may cause the solution travel down the vertically-oriented grow tower  50  and through the length thereof to supply solution to the crops disposed along the length of the grow tower  50 . The growth environment  20  may also include an airflow source configured to, when a tower is mounted to a grow line  202 , direct airflow in the lateral growth direction of growth and through an under-canopy of the growing plant, so as to disturb the boundary layer of the under-canopy of the growing plant. In other implementations, airflow may come from the top of the canopy or orthogonal to the direction of plant growth. The growth environment  20  may also include a control system, and associated sensors, for regulating at least one growing condition, such as air temperature, airflow speed, relative air humidity, and ambient carbon dioxide gas content. The control system may for example include such sub-systems as HVAC units, chillers, fans and associated ducting and air handling equipment. Grow towers  50  may have identifying attributes (such as bar codes or RFID tags). The controlled environment agriculture system  10  may include corresponding sensors and programming logic for tracking the grow towers  50  during various stages of the farm production cycle and/or for controlling one or more conditions of the growth environment. The operation of control system and the length of time towers remain in growth environment can vary considerably depending on a variety of factors, such as crop type and other factors. 
     As discussed above, grow towers  50  with newly transplanted crops or seedlings are transferred from the central processing system  30  into the vertical tower conveyance system  200 . Vertical tower conveyance system  200  moves the grow towers  50  along respective grow lines  202  in growth environment  20  in a controlled fashion, as discussed in more detail below. Crops disposed in grow towers  50  are exposed to the controlled conditions of growth environment (e.g., light, temperature, humidity, air flow, aqueous nutrient supply, etc.). The control system is capable of automated adjustments to optimize growing conditions within the growth chamber  20  to make continuous improvements to various attributes, such as crop yields, visual appeal and nutrient content. In addition, US Patent Publication Nos. 2018/0014485 and 2018/0014486 describe application of machine learning and other operations to optimize grow conditions in a vertical farming system. In some implementations, environmental condition sensors may be disposed on grow towers  50  or at various locations in growth environment  20 . When crops are ready for harvesting, grow towers  50  with crops to be harvested are transferred from the vertical tower conveyance system  200  to the central processing system  30  for harvesting and other processing operations. 
     Central processing system  30 , as discussed in more detail below, may include processing stations directed to injecting seedlings into towers  50 , harvesting crops from towers  50 , and cleaning towers  50  that have been harvested. Central processing system  30  may also include conveyance mechanisms that move towers  50  between such processing stations. For example, as  FIG. 1  illustrates, central processing system  30  may include harvester station  32 , washing station  34 , and transplanter station  36 . Harvester station  32  may deposit harvested crops into food-safe containers and may include a conveyance mechanism for conveying the containers to post-harvesting facilities (e.g., preparation, washing, packaging and storage) that are beyond the scope of this disclosure. 
     Controlled environment agriculture system  10  may also include one or more conveyance mechanisms for transferring grow towers  50  between growth environment  20  and central processing system  30 . In the implementation shown, the stations of central processing system  30  operate on grow towers  50  in a horizontal orientation. In one implementation, an automated pickup station  43 , and associated control logic, may be operative to releasably grasp a horizontal tower from a loading location, rotate the tower to a vertical orientation and attach the tower to a transfer station for insertion into a selected grow line  202  of the growth environment  20 . On the other end of growth environment  20 , automated laydown station  41 , and associated control logic, may be operative to releasably grasp and move a vertically-oriented grow tower  50  from a buffer location, rotate the grow tower  50  to a horizontal orientation and place it on a conveyance system for loading into harvester station  32 . In some implementations, if a grow tower  50  is rejected due to quality control concerns, the conveyance system may bypass the harvester station  32  and carry the grow tower to washing station  34  (or some other station). The automated laydown and pickup stations  41  and  43  may each comprise a six-degrees of freedom robotic arm, such as a FANUC robot. The stations  41  and  43  may also include end effectors for releasably grasping grow towers  50  at opposing ends. 
     Growth environment  20  may also include automated loading and unloading mechanisms for inserting grow towers  50  into selected grow lines  202  and unloading grow towers  50  from the grow lines  202 . In one implementation, the load transfer conveyance mechanism  47  may include a powered and free conveyor system that conveys carriages each loaded with a grow tower  50  from the automated pickup station  43  to a selected grow line  202 . Vertical grow tower conveyance system  200  may include sensors (such as RFID or bar code sensors) to identify a given grow tower  50  and, under control logic, select a grow line  202  for the grow tower  50 . Particular algorithms for grow line selection can vary considerably depending on a number of factors and is beyond the scope of this disclosure. The load transfer conveyance mechanism  47  may also include one or more linear actuators that pushes the grow tower  50  onto a grow line  202 . Similarly, the unload transfer conveyance mechanism  45  may include one or more linear actuators that push or pull grow towers from a grow line  202  onto a carriage of another powered and free conveyor mechanism, which conveys the carriages  1202  from the grow line  202  to the automated laydown station  41 .  FIG. 12  illustrates a carriage  1202  that may be used in a powered and free conveyor mechanism. In the implementation shown, carriage  1202  includes hook  1204  that engages hook  52  attached to a grow tower  50 . A latch assembly  1206  may secure the grow tower  50  while it is being conveyed to and from various locations in the system. In one implementation, one or both of load transfer conveyance mechanism  47  and unload transfer conveyance mechanism  45  may be configured with a sufficient track distance to establish a zone where grow towers  50  may be buffered. For example, unload transfer conveyance mechanism  45  may be controlled such that it unloads a set of towers  50  to be harvested unto carriages  1202  that are moved to a buffer region of the track. On the other end, automated pickup station  43  may load a set of towers to be inserted into growth environment  20  onto carriages  1202  disposed in a buffer region of the track associated with load transfer conveyance mechanism  47 . 
     Grow Towers 
     Grow towers  50  provide the sites for individual crops to grow in the system. As  FIGS. 3A and 3B  illustrate, a hook  52  attaches to the top of grow tower  50 . Hook  52  allows grow tower  50  to be supported by a grow line  202  when it is inserted into the vertical tower conveyance system  200 . In one implementation, a grow tower  50  measures 5.172 meters long, where the extruded length of the tower is 5.0 meters, and the hook is 0.172 meters long. The extruded rectangular profile of the grow tower  50 , in one implementation, measures 57 mm×93 mm (2.25″×3.67″). The hook  52  can be designed such that its exterior overall dimensions are not greater than the extruded profile of the grow tower  50 . The foregoing dimensions are for didactic purposes. The dimensions of grow tower  50  can be varied depending on a number of factors, such as desired throughput, overall size of the system, and the like. For example, the grow tower  50  may be up to 10 meters long or greater, for example. 
     Grow towers  50  may include a set of grow sites  53  arrayed along at least one face of the grow tower  50 . In the implementation shown in  FIG. 4A , grow towers  50  include grow sites  53  on opposing faces such that plants protrude from opposing sides of the grow tower  50 . Transplanter station  36  may transplant seedlings into empty grow sites  53  of grow towers  50 , where they remain in place until they are fully mature and ready to be harvested. In one implementation, the orientation of the grow sites  53  are perpendicular to the direction of travel of the grow towers  50  along grow line  202 . In other words, when a grow tower  50  is inserted into a grow line  202 , plants extend from opposing faces of the grow tower  50 , where the opposing faces are parallel to the direction of travel. Although a dual-sided configuration is preferred, the invention may also be utilized in a single-sided configuration where plants grow along a single face of a grow tower  50 . 
     U.S. application Ser. No. 15/968,425 filed on May 1, 2018, which is incorporated by reference herein for all purposes, discloses an example tower structure configuration that can be used in connection with various embodiments of the invention. In the implementation shown, grow towers  50  may each consist of three extrusions which snap together to form one structure. As shown, the grow tower  50  may be a dual-sided hydroponic tower, where the tower body  103  includes a central wall  56  that defines a first tower cavity  54   a  and a second tower cavity  54   b .  FIG. 4B  provides a perspective view of an exemplary dual-sided, multi-piece hydroponic grow tower  50  in which each front face plate  101  is hingeably coupled to the tower body  103 . In  FIG. 4B , each front face plate  101  is in the closed position. The cross-section of the tower cavities  54   a ,  54   b  may be in the range of 1.5 inches by 1.5 inches to 3 inches by 3 inches, where the term “tower cavity” refers to the region within the body of the tower and behind the tower face plate. The wall thickness of the grow towers  50  may be within the range of 0.065 to 0.075 inches. A dual-sided hydroponic tower, such as that shown in  FIGS. 4A and 4B , has two back-to-back cavities  54   a  and  54   b , each preferably within the noted size range. In the configuration shown, the grow tower  50  may include (i) a first V-shaped groove  58   a  running along the length of a first side of the tower body  103 , where the first V-shaped groove is centered between the first tower cavity and the second tower cavity; and (ii) a second V-shaped groove  58   b  running along the length of a second side of the tower body  103 , where the second V-shaped groove is centered between the first tower cavity and the second tower cavity. The V-shaped grooves  58   a ,  58   b  may facilitate registration, alignment and/or feeding of the towers  50  by one or more of the stations in central processing system  30 . U.S. application Ser. No. 15/968,425 discloses additional details regarding the construction and use of towers that may be used in embodiments of the invention. Another attribute of V-shaped grooves  58   a ,  58   b  is that they effectively narrow the central wall  56  to promote the flow of aqueous nutrient solution centrally where the plant&#39;s roots are located. Other implementations are possible. For example, a grow tower  50  may be formed as a unitary, single extrusion, where the material at the side walls flex to provide a hinge and allow the cavities to be opened for cleaning. U.S. application Ser. No. 16/577,322 filed on Sep. 20, 2019, which is incorporated by reference herein for all purposes, discloses an example grow tower  50  formed by a single extrusion. 
     As  FIGS. 4C and 4D  illustrate, grow towers  50  may each include a plurality of cut-outs  105  for use with a compatible plug holder  158 , such as the plug holder disclosed in any one of co-assigned and co-pending U.S. patent application Ser. Nos. 15/910,308, 15/910,445 and 15/910,796, each filed on 2 Mar. 2018, the disclosures of which is incorporated herein for any and all purposes. As shown, the plug holders  158  may be oriented at a 45-degree angle relative to the front face plate  101  and the vertical axis of the grow tower  50 . It should be understood, however, that tower design disclosed in the present application is not limited to use with this particular plug holder or orientation, rather, the towers disclosed herein may be used with any suitably sized and/or oriented plug holder. As such, cut-outs  105  are only meant to illustrate, not limit, the present tower design and it should be understood that the present invention is equally applicable to towers with other cut-out designs. Plug Holder  158  may be ultrasonically welded, bonded, or otherwise attached to tower face  101 . 
     The use of a hinged front face plate simplifies manufacturing of grow towers, as well as tower maintenance in general and tower cleaning in particular. For example, to clean a grow tower  50  the face plates  101  are opened from the body  103  to allow easy access to the body cavity  54   a  or  54   b . After cleaning, the face plates  101  are closed. Since the face plates remain attached to the tower body  103  throughout the cleaning process, it is easier to maintain part alignment and to insure that each face plate is properly associated with the appropriate tower body and, assuming a double-sided tower body, that each face plate  101  is properly associated with the appropriate side of a specific tower body  103 . Additionally, if the planting and/or harvesting operations are performed with the face plate  101  in the open position, for the dual-sided configuration both face plates can be opened and simultaneously planted and/or harvested, thus eliminating the step of planting and/or harvesting one side and then rotating the tower and planting and/or harvesting the other side. In other embodiments, planting and/or harvesting operations are performed with the face plate  101  in the closed position. 
     Other implementations are possible. For example, grow tower  50  can comprise any tower body that includes a volume of medium or wicking medium extending into the tower interior from the face of the tower (either a portion or individual portions of the tower or the entirety of the tower length. For example, U.S. Pat. No. 8,327,582, which is incorporated by reference herein, discloses a grow tube having a slot extending from a face of the tube and a grow medium contained in the tube. The tube illustrated therein may be modified to include a hook  52  at the top thereof and to have slots on opposing faces, or one slot on a single face. 
     Vertical Tower Conveyance System 
       FIG. 5A  illustrates a portion of a grow line  202  in vertical tower conveyance system  200 . In one implementation, the vertical tower conveyance system  200  includes a plurality of grow lines  202  arranged in parallel. As discussed above, automated loading and unloading mechanisms  45 ,  47  may selectively load and unload grow towers  50  from a grow line  202  under automated control systems. As  FIG. 5A  shows, each grow line  202  supports a plurality of grow towers  50 . In one implementation, a grow line  202  may be mounted to the ceiling (or other support) of the grow structure by a bracket for support purposes. Hook  52  hooks into, and attaches, a grow tower  50  to a grow line  202 , thereby supporting the tower in a vertical orientation as it is translated through the vertical tower conveyance system  200 . A conveyance mechanism moves towers  50  attached to respective grow lines  202 . 
       FIG. 10  illustrates the cross section or extrusion profile of a grow line  202 , according to one possible implementation of the invention. The grow line  202  may be an aluminum extrusion. The bottom section of the extrusion profile of the grow line  202  includes an upward facing groove  1002 . As  FIG. 9  shows, hook  52  of a grow tower  50  includes a main body  53  and corresponding member  58  that engages groove  1002  as shown in  FIGS. 5A and 8 . These hooks allow the grow towers  50  to hook into the groove  1002  and slide along the grow line  202  as discussed below. Conversely, grow towers  50  can be manually unhooked from a grow line  202  and removed from production. This ability may be necessary if a crop in a grow tower  50  becomes diseased so that it does not infect other towers. In one possible implementation, the width of groove  1002  (for example, 13 mm) is an optimization between two different factors. First, the narrower the groove the more favorable the binding rate and the less likely grow tower hooks  52  are to bind. Conversely, the wider the groove the slower the grow tower hooks wear due to having a greater contact patch. Similarly, the depth of the groove, for example 10 mm, may be an optimization between space savings and accidental fallout of tower hooks. 
     Hooks  52  may be injection-molded plastic parts. In one implementation, the plastic may be polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), or an Acetyl Homopolymer (e.g., Delrin® sold by DuPont Company). The hook  52  may be solvent bonded to the top of the grow tower  50  and/or attached using rivets or other mechanical fasteners. The groove-engaging member  58  which rides in the rectangular groove  1002  of the grow line  202  may be a separate part or integrally formed with hook  52 . If separate, this part can be made from a different material with lower friction and better wear properties than the rest of the hook, such as ultra-high-molecular weight polyethylene or acetal. To keep assembly costs low, this separate part may snap onto the main body of the hook  52 . Alternatively, the separate part also be over-molded onto the main body of hook  52 . 
     As  FIGS. 6 and 10  illustrate, the top section of the extrusion profile of grow line  202  contains a downward facing t-slot  1004 . Linear guide carriages  610  (described below) ride within the t-slot  1004 . The center portion of the t-slot  1004  may be recessed to provide clearance from screws or over-molded inserts which may protrude from the carriages  610 . Each grow line  202  can be assembled from a number of separately fabricated sections. In one implementation, sections of grow line  202  are currently modeled in 6-meter lengths. Longer sections reduce the number of junctions but are more susceptible to thermal expansion issues and may significantly increase shipping costs. Additional features not captured by the Figures include intermittent mounting holes to attach the grow line  202  to the ceiling structure and to attach irrigation lines. Interruptions to the t-slot  1004  may also be machined into the conveyor body. These interruptions allow the linear guide carriages  610  to be removed without having to slide them all the way out the end of a grow line  202 . 
     At the junction between two sections of a grow line  202 , a block  612  may be located in the t-slots  1004  of both conveyor bodies. This block serves to align the two grow line sections so that grow towers  50  may slide smoothly between them. Alternative methods for aligning sections of a grow line  202  include the use of dowel pins that fit into dowel holes in the extrusion profile of the section. The block  612  may be clamped to one of the grow line sections via a set screw, so that the grow line sections can still come together and move apart as the result of thermal expansion. Based on the relatively tight tolerances and small amount of material required, these blocks may be machined. Bronze may be used as the material for such blocks due to its strength, corrosion resistance, and wear properties. 
     In one implementation, the vertical tower conveyance system  200  utilizes a reciprocating linear ratchet and pawl structure (hereinafter referred to as a “reciprocating cam structure or mechanism”) to move grow towers  50  along a path section  202   a ,  202   b  of a grow line  202 . In one implementation, each path section  202   a ,  202   b  includes a separate reciprocating cam structure and associated actuators.  FIGS. 5A, 6 and 7  illustrate one possible reciprocating cam mechanism that can be used to move grow towers  50  across grow lines  202 . Pawls or “cams”  602  physically push grow towers  50  along grow line  202 . Cams  602  are attached to cam channel  604  (see below) and rotate about one axis. On the forward stroke, the rotation is limited by the top of the cam channel  604 , causing the cams  602  to push grow towers  50  forward. On the reserve or back stroke, the rotation is unconstrained, thereby allowing the cams to ratchet over the top of the grow towers  50 . In this way, the cam mechanism can stroke a relatively short distance back and forth, yet grow towers  50  always progress forward along the entire length of a grow line  202 . A control system, in one implementation, controls the operation of the reciprocating cam mechanism of each grow line  202  to move the grow towers  50  according to a programmed growing sequence. In between movement cycles, the actuator and reciprocating cam mechanism remain idle. 
     The pivot point of the cams  602  and the means of attachment to the cam channel  604  consists of a binding post  606  and a hex head bolt  608 ; alternatively, detent clevis pins may be used. The hex head bolt  608  is positioned on the inner side of the cam channel  604  where there is no tool access in the axial direction. Being a hex head, it can be accessed radially with a wrench for removal. Given the large number of cams needed for a full-scale farm, a high-volume manufacturing process such as injection molding is suitable. ABS is suitable material given its stiffness and relatively low cost. All the cams  602  for a corresponding grow line  202  are attached to the cam channel  604 . When connected to an actuator, this common beam structure allows all cams  602  to stroke back and forth in unison. The structure of the cam channel  604 , in one implementation, is a downward facing u-channel constructed from sheet metal. Holes in the downward facing walls of cam channel  604  provide mounting points for cams  602  using binding posts  606 . 
     Holes of the cam channel  604 , in one implementation, are spaced at 12.7 mm intervals. Therefore, cams  602  can be spaced relative to one another at any integer multiple of 12.7 mm, allowing for variable grow tower spacing with only one cam channel. The base of the cam channel  604  limits rotation of the cams during the forward stroke. All degrees of freedom of the cam channel  604 , except for translation in the axial direction, are constrained by linear guide carriages  610  (described below) which mount to the base of the cam channel  604  and ride in the t-slot  1004  of the grow line  202 . Cam channel  604  may be assembled from separately formed sections, such as sections in 6-meter lengths. Longer sections reduce the number of junctions but may significantly increase shipping costs. Thermal expansion is generally not a concern because the cam channel is only fixed at the end connected to the actuator. Given the simple profile, thin wall thickness, and long length needed, sheet metal rolling is a suitable manufacturing process for the cam channel. Galvanized steel is a suitable material for this application. 
     Linear guide carriages  610  are bolted to the base of the cam channels  604  and ride within the t-slots  1004  of the grow lines  202 . In some implementations, one carriage  610  is used per 6-meter section of cam channel. Carriages  610  may be injection molded plastic for low friction and wear resistance. Bolts attach the carriages  610  to the cam channel  604  by threading into over molded threaded inserts. If select cams  602  are removed, these bolts are accessible so that a section of cam channel  604  can be detached from the carriage and removed. 
     Sections of cam channel  604  are joined together with pairs of connectors  616  at each joint; alternatively, detent clevis pins may be used. Connectors  616  may be galvanized steel bars with machined holes at 20 mm spacing (the same hole spacing as the cam channel  604 ). Shoulder bolts  618  pass through holes in the outer connector, through the cam channel  604 , and thread into holes in the inner connector. If the shoulder bolts fall in the same position as a cam  602 , they can be used in place of a binding post. The heads of the shoulder bolts  618  are accessible so that connectors and sections of cam channel can be removed. 
     In one implementation, cam channel  604  attaches to a linear actuator, which operates in a forward and a back stroke. A suitable linear actuator may be the T13-B4010MS053-62 actuator offered by Thomson, Inc. of Redford, Va.; however, the reciprocating cam mechanism described herein can be operated with a variety of different actuators. The linear actuator may be attached to cam channel  604  at the off-loading end of a grow line  202 , rather than the on-boarding end. In such a configuration, cam channel  604  is under tension when loaded by the towers  50  during a forward stroke of the actuator (which pulls the cam channel  604 ) which reduces risks of buckling.  FIG. 7A  illustrates operation of the reciprocating cam mechanism according to one implementation of the invention. In step A, the linear actuator has completed a full back stroke; as  FIG. 7A  illustrates, one or more cams  602  may ratchet over the hooks  52  of a grow tower  50 . Step B of  FIG. 7A  illustrates the position of cam channel  604  and cams  602  at the end of a forward stroke. During the forward stroke, cams  602  engage corresponding grow towers  50  and move them in the forward direction along grow line  202  as shown. Step C of  FIG. 7A  illustrates how a new grow tower  50  (Tower 0) may be inserted onto a grow line  202  and how the last tower (Tower 9) may be removed. Step D illustrates how cams  602  ratchet over the grow towers  50  during a back stroke, in the same manner as Step A. The basic principle of this reciprocating cam mechanism is that reciprocating motion from a relatively short stroke of the actuator transports towers  50  in one direction along the entire length of the grow line  202 . More specifically, on the forward stroke, all grow towers  50  on a grow line  202  are pushed forward one position. On the back stroke, the cams  602  ratchet over an adjacent tower one position back; the grow towers remain in the same location. As shown, when a grow line  202  is full, a new grow tower may be loaded and a last tower unloaded after each forward stroke of the linear actuator. In some implementations, the top portion of the hook  52  (the portion on which the cams push), is slightly narrower than the width of a grow tower  50 . As a result, cams  602  can still engage with the hooks  52  when grow towers  50  are spaced immediately adjacent to each other.  FIG. 7A  shows 9 grow towers for didactic purposes. A grow line  202  can be configured to be quite long (for example, 40 meters) allowing for a much greater number of towers  50  on a grow line  202  (such as 400-450). Other implementations are possible. For example, the minimum tower spacing can be set equal to or slightly greater than two times the side-to-side distance of a grow tower  50  to allow more than one grow tower  50  to be loaded onto a grow line  202  in each cycle. 
     Still further, as shown in  FIG. 7A , the spacing of cams  602  along the cam channel  604  can be arranged to effect one-dimensional plant indexing along the grow line  202 . In other words, the cams  602  of the reciprocating cam mechanism can be configured such that spacing between towers  50  increases as they travel along a grow line  202 . For example, spacing between cams  602  may gradually increase from a minimum spacing at the beginning of a grow line to a maximum spacing at the end of the grow line  202 . This may be useful for spacing plants apart as they grow to increase light interception and provide spacing, and, through variable spacing or indexing, increasing efficient usage of the growth chamber  20  and associated components, such as lighting. In one implementation, the forward and back stroke distance of the linear actuator is equal to (or slightly greater than) the maximum tower spacing. During the back stroke of the linear actuator, cams  602  at the beginning of a grow line  202  may ratchet and overshoot a grow tower  50 . On the forward stroke, such cams  602  may travel respective distances before engaging a tower, whereas cams located further along the grow line  202  may travel shorter distances before engaging a tower or engage substantially immediately. In such an arrangement, the maximum tower spacing cannot be two times greater than the minimum tower spacing; otherwise, a cam  602  may ratchet over and engaging two or more grow towers  50 . If greater maximum tower spacing is desired, an expansion joint may be used, as illustrated in  FIG. 7B . An expansion joint allows the leading section of the cam channel  604  to begin traveling before the trailing end of the cam channel  604 , thereby achieving a long stroke. In particular, as  FIG. 7B  shows, expansion joint  710  may attach to sections  604   a  and  604   b  of cam channel  604 . In the initial position ( 702 ), the expansion joint  710  is collapsed. At the beginning of a forward stroke ( 704 ), the leading section  604   a  of cam channel  604  moves forward (as the actuator pulls on cam channel  604 ), while the trailing section  604   b  remains stationary. Once the bolt bottoms out on the expansion joint  710  ( 706 ), the trailing section  604  of cam channel  604  begins to move forward as well. On the back stroke ( 708 ), the expansion joint  710  collapses to its initial position. 
     Other implementations for moving vertical grow towers  50  may be employed. For example, a lead screw mechanism may be employed. In such an implementation, the threads of the lead screw engage hooks  52  disposed on grow line  202  and move grow towers  50  as the shaft rotates. The pitch of the thread may be varied to achieve one-dimensional plant indexing. In another implementation, a belt conveyor include paddles along the belt may be employed to move grow towers  50  along a grow line  202 . In such an implementation, a series of belt conveyors arranged along a grow line  202 , where each belt conveyor includes a different spacing distance among the paddles to achieve one-dimensional plant indexing. In yet other implementations, a power-and-free conveyor may be employed to move grow towers  50  along a grow line  202 . Still further, although the grow line  202  illustrated in the various figures is horizontal to the ground, the grow line  202  may be sloped at a slight angle, either downwardly or upwardly relative to the direction of tower travel. Still further, while the grow line  202  described above operates to convey grow towers in a single direction, the grow line  202  may be configured to include multiple sections, where each section is oriented in a different direction. For example, two sections may be perpendicular to each other. In other implementations, two sections may run parallel to each other, but have opposite directions of travel. 
     Irrigation &amp; Aqueous Nutrient Supply 
       FIG. 8  illustrates how an irrigation line  802  may be attached to grow line  202  to supply an aqueous nutrient solution to crops disposed in grow towers  50  as they translate through the vertical tower conveyance system  200 . Irrigation line  802 , in one implementation, is a pressurized line with spaced-apart holes disposed at the expected locations of the towers  50  as they advance along grow line  202  with each movement cycle. For example, the irrigation line  802  may be a PVC pipe having an inner diameter of 1.5 inches and holes having diameters of 0.125 inches. The irrigation line  802  may be approximately 40 meters in length spanning the entire length of a grow line  202 . To ensure adequate pressure across the entire line, irrigation line  802  may be broken into shorter sections, each connected to a manifold, so that pressure drop is reduced. 
     As  FIG. 8  shows, a funnel structure  902  collects aqueous nutrient solution from irrigation line  802  and distributes the aqueous nutrient solution to the cavity(ies)  54   a ,  54   b  of the grow tower  50  as discussed in more detail below.  FIGS. 9 and 11A  illustrate that the funnel structure  902  may be integrated into hook  52 . For example, the funnel structure  902  may include a collector  910 , first and second passageways  912  and first and second slots  920 . As  FIG. 9  illustrates, the groove-engaging member  58  of the hook may disposed at a centerline of the overall hook structure. The funnel structure  902  may include flange sections  906  extending downwardly opposite the collector  910  and on opposing sides of the centerline. The outlets of the first and second passageways are oriented substantially adjacent to and at opposing sides of the flange sections  906 , as shown. Flange sections  906  register with central wall  56  of grow tower  50  to center the hook  52  and provides additional sites to adhere or otherwise attach hook  52  to grow tower  50 . In other words, when hook  52  is inserted into the top of grow tower  50 , central wall  56  is disposed between flange sections  906 . In the implementation shown, collector  910  extends laterally from the main body  53  of hook  52 . 
     As  FIG. 11B  shows, funnel structure  902  includes a collector  910  that collects nutrient fluid and distributes the fluid evenly to the inner cavities  54   a  and  54   b  of tower through passageways  912 . Passageways  912  are configured to distribute aqueous nutrient solution near the central wall  56  and to the center back of each cavity  54   a ,  54   b  over the ends of the plug holders  158  and where the roots of a planted crop are expected. As  FIG. 11C  illustrates, in one implementation, the funnel structure  902  includes slots  920  that promote the even distribution of nutrient fluid to both passageways  912 . For nutrient fluid to reach passageways  912 , it must flow through one of the slots  920 . Each slot  920  may have a V-like configuration where the width of the slot opening increases as it extends from the substantially flat bottom surface  922  of collector  910 . For example, each slot  920  may have a width of 1 millimeter at the bottom surface  922 . The width of slot  920  may increase to 5 millimeters over a height of 25 millimeters. The configuration of the slots  920  causes nutrient fluid supplied at a sufficient flow rate by irrigation line  802  to accumulate in collector  910 , as opposed to flowing directly to a particular passageway  912 , and flow through slots  920  to promote even distribution of nutrient fluid to both passageways  912 . 
     In operation, irrigation line  802  provides aqueous nutrient solution to funnel structure  902  that even distributes the water to respective cavities  54   a ,  54   b  of grow tower  50 . The aqueous nutrient solution supplied from the funnel structure  902  irrigates crops contained in respective plug containers  158  as it trickles down. In one implementation, a gutter disposed under each grow line  202  collects excess water from the grow towers  50  for recycling. 
     Other implementations are possible. For example, the funnel structure may be configured with two separate collectors that operate separately to distribute aqueous nutrient solution to a corresponding cavity  54   a ,  54   b  of a grow tower  50 . In such a configuration, the irrigation supply line can be configured with one hole for each collector. In other implementations, the towers may only include a single cavity and include plug containers only on a single face  101  of the towers. Such a configuration still calls for a use of a funnel structure that directs aqueous nutrient solution to a desired portion of the tower cavity but obviates the need for separate collectors or other structures facilitating even distribution. 
     Automated Pickup &amp; Laydown Stations 
     As discussed above, the stations of central processing system  30  operate on grow towers  50  in a horizontal orientation, while the vertical tower conveyance system  200  conveys grow towers in the growth environment  20  in a vertical orientation. In one implementation, an automated pickup station  43 , and associated control logic, may be operative to releasably grasp a horizontal grow tower from a loading location, rotate the tower to a vertical orientation and attach the tower to a transfer station for insertion into a selected grow line  202  of the growth environment  20 . On the other end of growth environment  20 , automated laydown station  41 , and associated control logic, may be operative to releasably grasp and move a vertically-oriented grow tower  50  from a buffer location, rotate the grow tower  50  to a horizontal orientation and place it on a conveyance system for processing by one or more stations of central processing system  30 . For example, automated laydown station  41  may place grow towers  50  on a conveyance system for loading into harvester station  32 . The automated laydown station  41  and pickup station  43  may each comprise a six-degrees of freedom (six axes) robotic arm, such as a FANUC robot. The stations  41  and  43  may also include end effectors for releasably grasping grow towers  50  at opposing ends. 
       FIG. 14  illustrates an automated laydown station  41  according to one implementation of the invention. As shown, automated laydown station  41  includes robot  1402  and end effector  1450 . Unload transfer conveyance mechanism  45 , which may be a power and free conveyor, delivers grow towers  50  from growth environment  20 . In one implementation, the buffer track section  1406  of unload transfer conveyance mechanism  45  extends through a vertical slot  1408  in growth environment  20 , allowing mechanism  45  to convey grow towers  50  attached to carriages  1202  outside of growth environment  20  and towards pick location  1404 . Unload transfer conveyance mechanism  45  may use a controlled stop blade to stop the carriage  1202  at the pick location  1404 . The unload transfer conveyance mechanism  45  may include an anti-roll back mechanism, bounding the carriage  1202  between the stop blade and the anti-roll back mechanism. 
     As  FIG. 12  illustrates, receiver  1204  may be attached to a swivel mechanism  1210  allowing rotation of grow towers  50  when attached to carriages  1202  for closer buffering in unload transfer conveyance mechanism  45  and/or to facilitate the correct orientation for loading or unloading grow towers  50 . In some implementations, for the laydown location and pick location  1404 , grow towers  50  may be oriented such that hook  52  faces away from the automated laydown and pickup stations  41 ,  43  for ease of transferring towers on/off the swiveled carriage receiver  1204 . Hook  52  may rest in a groove in the receiver  1204  of carriage  1202 . Receiver  1204  may also have a latch  1206  which closes down on either side of the grow tower  50  to prevent a grow tower  50  from sliding off during acceleration or deceleration associated with transfer conveyance. 
       FIG. 16  illustrates an end effector  1450 , according to one implementation of the invention, that provides a pneumatic gripping solution for releasably grasping a grow tower  50  at opposing ends. End effector  1450  may include a beam  1602  and a mounting plate  1610  for attachment to a robot, such as robotic arm  1402 . A top gripper assembly  1604  and a bottom gripper assembly  1606  are attached to opposite ends of beam  1602 . End effector  1450  may also include support arms  1608  to support a grow tower  50  when held in a horizontal orientation. For example, support arms  1608  extending from a central section of beam  1602  mitigate tower deflection. Support arms  1608  may be spaced ˜1.6 meters from either gripper assembly  1604 ,  1606 , and may be nominally 30 mm offset from a tower face, allowing 30 mm of tower deflection before the support arms  1608  catch the tower. 
     Bottom gripper assembly  1606 , as shown in  FIGS. 17A and 17B , may include plates  1702  extending perpendicularly from an end of beam  1602  and each having a cut-out section  1704  defining arms  1708   a  and  1708   b . A pneumatic cylinder mechanism  1706 , such as a guided pneumatic cylinder sold by SMC Pneumatics under the designation MGPM40-40Z, attaches to arms  1708   a  of plates  1702 . Arms  1708   b  may include projections  1712  that engage groove  58   b  of grow tower  50  when grasped therein to locate the grow tower  50  in the gripper assembly  1606  and/or to prevent slippage. The gripper assembly  1606 , in the implementation shown, operates like a lobster claw—i.e., one side of the gripper (the pneumatic cylinder mechanism  1706 ) moves, while the other side (arms  1708   b ) remain static. On the static side of the gripper assembly  1606 , the pneumatic cylinder mechanism  1706  drives the grow tower  50  into the arms  1708 , registering the tower  50  with projections  1712 . Friction between a grow tower  50  and arms  1708   b  and pneumatic cylinder mechanism  1706  holds the tower  50  in place during operation of an automated laydown or pick up station  41 ,  43 . To grasp a grow tower  50 , the pneumatic cylinder mechanism  1706  may extend. In such an implementation, pneumatic cylinder mechanism  1706  is retracted to a release position during a transfer operation involving the grow towers  50 . In one implementation, the solenoid of pneumatic cylinder mechanism  1706  is center-closed in that, whether extended or retracted, the valve locks even if air pressure is lost. In such an implementation, loss of air pressure will not cause a grow tower  50  to fall out of end effector  1450  while the pneumatic cylinder mechanism  1706  is extended. 
     Top gripper assembly  1604 , in one implementation, is essentially a mirror image of bottom gripper assembly  1606 , as it includes the same components and operates in the same manner described above. Catch plate  1718 , in one implementation, may attach only to bottom gripper assembly  1606 . Catch plate  1718  may act as a safety catch in case the gripper assemblies fail or the grow tower  50  slips. Other implementations are possible. For example, the gripper assemblies may be parallel gripper assemblies where both opposing arms of each gripper move when actuated to grasp a grow tower  50 . 
     Robot  1402  may be a 6-axis robotic arm including a base, a lower arm attached to the base, an upper arm attached to the lower arm, and a wrist mechanism disposed between the end of the upper arm and an end effector  1450 . For example, robot  1402  may 1) rotate about its base; 2) rotate a lower arm to extend forward and backward; 3) rotate an upper arm, relative to the lower arm, upward and downward; 4) rotate the upper arm and attached wrist mechanism in a circular motion; 5) tilt a wrist mechanism attached to the end of the upper arm up and down; and/or 6) rotate the wrist mechanism clockwise or counter-clockwise. However, modifications to end effector  1450  (and/or other elements, such as conveyance mechanisms and the like) may permit different types of robots and mechanisms, as well as use of robots with fewer axes of movement. As  FIG. 18  illustrates, robot  1402  may be floor mounted and installed on a pedestal. Inputs to the robot  1402  may include power, a data connection to a control system, and an air line connecting the pneumatic cylinder mechanism  1706  to a pressurized air supply. On pneumatic cylinder mechanism  1706 , sensors may be used to detect when the cylinder is in its open state or its closed state. The control system may execute one or more programs or sub-routines to control operation of the robot  1402  to effect conveyance of grow towers  50  from growth environment  20  to central processing system  20 . 
     When a grow tower  50  accelerates/decelerates in unload transfer conveyance mechanism  45 , the grow tower  50  may swing slightly.  FIGS. 18 and 19  illustrate a tower constraining mechanism  1902  to stop possible swinging, and to accurately locate, a grow tower  50  during a laydown operation of automated laydown station  41 . In the implementation shown, mechanism  1902  is a floor-mounted unit that includes a guided pneumatic cylinder  1904  and a bracket assembly including a guide plate  1906  that guides a tower  50  and a bracket arm  1908  that catches the bottom of the grow tower  50 , holding it at a slight angle to better enable registration of the grow tower  50  to the bottom gripper assembly  1606 . A control system may control operation of mechanism  1902  to engage the bottom of a grow tower  50 , thereby holding it in place for gripper assembly  1606 . 
     The end state of the laydown operation is to have a grow tower  50  laying on the projections  2004  of the harvester infeed conveyor  1420 , as centered as possible. In one implementation, a grow tower  50  is oriented such that hook  52  points towards harvester station  32  and, in implementations having hinged side walls, and hinge side down. The following summarizes the decisional steps that a controller for robot  1402  may execute during a laydown operation, according to one possible implementation of the invention. 
     Laydown Procedure Description 
     The Main program for the robot controller may work as follows:
         A control system associated with central processing system  30  may activate the robot controller&#39;s Main program.   Within the Main program, the robot controller may check if robot  1402  is in its home position.   If robot  1402  is not in its home position, it enters its Home program to move to the home position.   The Main program then calls the reset I/O program to reset all the I/O parameters on robot  1402  to default values.   Next, the Main program runs the handshake program with the central processing controller to make sure a grow tower  50  is present at the pickup location  1404  and ready to be picked up.   The Main program may run an enter zone program to indicate it is about to enter the transfer conveyance zone.   The Main program may run a Pick Tower program to grasp a grow tower  50  and lift it off of carriage  1202 .   The Main program may then call the exit zone program to indicate it has left the transfer conveyance zone.   Next the Main program runs the handshake program with the central processing controller to check whether the harvester infeed conveyor  1420  is clear and in position to receive a grow tower  50 .   The Main program may then run the enter zone program to indicate it is about to enter the harvester infeed conveyor zone.   The Main program runs a Place Tower program to move and place the picked tower onto the infeed conveyor  1420 .   The Main program then calls an exit zone program to indicate it has left the harvester infeed conveyor zone.   The Home program may then run to return robot  1402  to its home position.   Lastly, the Main program may run the handshake program with the central processing controller to indicate robot  1402  has returned to its home position and is ready to pick the next grow tower  50 .       

     The Pick Tower program may work as follows:
         Robot  1402  checks to make sure the grippers  1604 ,  1606  are in the open position. If the grippers are not open, robot  1402  will throw an alarm.   Robot  1402  may then begin to move straight ahead which will push the end effector  1450  into the tower face so that the grow tower is fully seated against the back wall of the grippers  1604 ,  1606 .   Robot  1402  may then move sideways to push the rigid fingers  1712  against the tower walls to engage groove  58   b.      Robot  1402  may activate robot outputs to close the grippers  1604 ,  1606 .   Robot  1402  may wait until sensors indicate that the grippers  1604 ,  1606  are closed. If robot  1402  waits too long, robot  1402  may throw an alarm.   Once grip is confirmed, robot  1402  may then move vertically to lift grow tower  50  off of the receiver  1204 .   Next, robot  1402  may then pull back away from pick location  1404 .       

     The Place Tower program may work as follows:
         Robot  1402  may move through two waypoints that act as intermediary points to properly align grow tower  50  during the motion.   Robot  1402  continues on to position end effector  1450  and grow tower  50  just above the center of the harvester in-feed conveyor  1450 , such that the tower is in the correct orientation (e.g., hinge down on the rigid fingers, hook  52  towards harvester station  32 ).   Once the conveyor position is confirmed, robot  1402  may then activate the outputs to open grippers  1604 ,  1606  so that grow tower  50  is just resting on the rigid fingers  1712  and support arms  1608 .   Robot  1402  may wait until the sensors indicate that grippers  1604 ,  1606  have opened. If robot  1402  waits too long, robot  1402  may throw an alarm.   After grippers  1604 ,  1606  are released, robot  1402  may then move vertically down. On the way down the projections  2004  of harvester infeed conveyor  1420  take the weight of grow tower  50  and the rigid fingers  1712  and support arms  1608  of end effector  1450  end up under grow tower and not in contact.   Lastly, robot  1402  may then pull end effector  1450  towards robot  1402 , away from harvester infeed conveyor  1420 , and slides rigid fingers  1712  of end effector  1450  out from under grow tower  50 .       

       FIGS. 15A and 15B  illustrate an automated pickup station  43  according to one implementation of the invention. As shown, automated pickup station  43  includes robot  1502  and pickup conveyor  1504 . Similar to automated laydown station  41 , robot  1502  includes end effector  1550  for releasably grasping grow towers  50 . In one implementation, end effector  1550  is substantially the same as end effector  1450  attached to robot  1402  of automated laydown station  41 . In one implementation, end effector  1550  may omit support arms  1608 . As described herein, robot  1502 , using end effector  1550 , may grasp a grow tower  50  resting on pickup conveyor  1504 , rotate the grow tower  50  to a vertical orientation and attach the grow tower  50  to a carriage  1202  of loading transfer conveyance mechanism  47 . As discussed above, loading transfer conveyance mechanism  47 , which may include be a power and free conveyor, delivers grow towers  50  to growth environment  20 . In one implementation, the buffer track section  1522  of loading transfer conveyance mechanism  47  extends through a vertical slot in growth environment  20 , allowing mechanism  47  to convey grow towers  50  attached to carriages  1202  into growth environment  20  from stop location  1520 . Loading transfer conveyance mechanism  47  may use a controlled stop blade to stop the carriage  1202  at the stop location  1520 . The loading transfer conveyance mechanism  47  may include an anti-roll back mechanism, bounding the carriage  1202  between the stop blade and the anti-roll back mechanism. 
     The following summarizes the decisional steps that a controller for robot  1502  may execute during a pickup operation, according to one possible implementation of the invention. 
     Pickup Procedure Description 
     The Main program for the robot controller may work as follows for robot  1502 :
         The central processing controller may activate the Main program.   Within the Main program, robot  1502  controller will check if robot  1502  is in its home position.   If robot  1502  is not in its home position, robot  1502  will enter its home program to move to the home position of the robot  1502 .   The Main program may then call the reset  10  program to reset I/O values on robot  1502  to their default values.   Next, the Main program may run the handshake program with the central processing controller to request a decision code indicating which station (pickup conveyor  1504  or the transplanter transfer conveyor  2111 ) has a grow tower  50  ready for pickup.   The Main program may run the enter zone program to indicate it is about to enter the pickup location based on the decision code from above.   The Main program may then run the Pick Tower program to grab a tower and lift it from the specified conveyor based on the decision code from above.   The Main program may then call the exit zone program to indicate it has left the pickup location based on the decision code from above.   Next the Main program may run the handshake program with the central processing controller to check whether loading transfer conveyance mechanism  47  has a carriage  1202  in place and is ready to receive a grow tower  50 .   The Main program may then run the enter zone program to indicate it is about to enter the transfer conveyance zone.   The Main program may run the Place Tower program to move and place the picked grow tower onto receiver  1204  of carriage  1202 .   The Main program may then call the exit zone program to indicate it has left the transfer conveyance zone.   Robot  1502  then run the go to Home program to return robot  1502  to its home position.   Lastly, the Main program may run the handshake program with the central processing controller to indicate robot  1502  has returned to its home position and is ready to pick up the next grow tower  50 .       

     The Pick Tower program may work as follows:
         Robot  1502  may check to make sure the grippers are in the open position. If they are not open, robot  1502  will throw an alarm.   If the decision location resolves to the transplanter transfer conveyor  2111 , robot  1502  will move vertically to align with the grow tower  50  on the transplanter transfer conveyor  2111 .   Robot  1502  may then begin to move straight ahead to push end effector  1550  into the tower face so that the grow tower  50  is fully seated against the back wall of the grippers.   Robot  1502  moves upwards to lift grow tower  50  to rest the tower on the rigid fingers of the grippers.   Robot  1502  may then activate robot  1502  outputs to close the grippers.   Robot  1502  may wait until the sensors indicate that the grippers are closed. If robot  1502  waits too long, robot  1502  will throw an alarm.   Once grip is confirmed, robot  1502  moves vertically and pulls back away from the pickup conveyor  1504  or the transplanter transfer conveyor  2111 .       

     The Place Tower program may work as follows:
         Robot  1502  may move through two waypoints that act as intermediary points to properly align grow tower  50  during the motion.   Robot  1502  continues on to position end effector  1550  and grow tower  50  in line with receiver  1204  of carriage  1202 .   Robot  1502  may then move forward to point  1520  which will position the tower hook  52  above the channel in receiver  1204 .   Robot  1502  may then move down which will position the tower hook  52  to be slightly above (e.g., ˜10 millimeters) above the channel of receiver  1204 .   Robot  1502  may activate the outputs to open the grippers so that the hook  52  of tower  50  falls into the channel of receiver  1204 .   Robot  1502  may wait until the sensors indicate that the grippers have opened. If robot  1502  waits too long, robot  1502  will throw an alarm.   Once the grippers are released, robot  1502  may move straight back away from the tower.       

     Central Processing System 
     As discussed above, central processing system  30  may include harvester station  32 , washing station  34  and transplanter station  36 . Central processing system  30  may also include one or more conveyors to transfer grow towers  50  to or from a given station. For example, central processing system  30  may include harvester outfeed conveyor  2102 , washer infeed conveyor  2104 , washer outfeed conveyor  2106 , transplanter infeed conveyor  2108 , and transplanter outfeed conveyor  2110 . These conveyors can be belt or roller conveyors adapted to convey grow towers  50  laying horizontally thereon. As described herein, central processing system  30  may also include one or more sensors for identifying grow towers  50  and one or more controllers for coordinating and controlling the operation of various stations and conveyors. 
       FIG. 21  illustrates an example processing pathway for central processing system  30 . As discussed above, a robotic picking station  41  may lower a grow tower  50  with mature crops onto a harvester infeed conveyor  1420 , which conveys the grow tower  50  to harvester station  32 .  FIG. 20  illustrates a harvester infeed conveyor  1420  according to one implementation of the invention. Harvester infeed conveyor  1420  may be a belt conveyor having a belt  2002  including projections  2004  extending outwardly from belt  2002 . Projections  2004  provide for a gap between belt  2002  and crops extending from grow tower  50 , helping to avoid or reduce damage to the crops. In one implementation, the size the projections  2004  can be varied cyclically at lengths of grow tower  50 . For example, projection  2004   a  may be configured to engage the end of grow tower  50 ; top projection  2004   d  may engage the opposite end of grow tower  50 ; and middle projections  2004   b, c  may be positioned to contact grow tower  50  at a lateral face where the length of projections  2004   b, c  are lower and engage grow tower  50  when the tower deflects beyond a threshold amount. The length of belt  2002 , as shown in  FIG. 20  can be configured to provide for two movement cycles for a grow tower  50  for each full travel cycle of the belt  2002 . In other implementations, however, all projections  2004  are uniform in length. 
     As  FIG. 21  shows, harvester outfeed conveyor  2102  conveys grow towers  50  that are processed from harvester station  32 . In the implementation shown, central processing system  30  is configured to handle two types of grow towers: “cut-again” and “final cut.” As used herein, a “cut-again” tower refers to a grow tower  50  that has been processed by harvester station  32  (i.e., the crops have been harvested from the plants growing in the grow tower  50 , but the root structure of the plant(s) remain in place) and is to be re-inserted in growth environment  20  for crops to grow again. As used herein, a “final cut” tower refers to a grow tower  50  where the crops are harvested and where the grow tower  50  is to be cleared of root structure and growth medium and re-planted. Cut-again and final cut grow towers  50  may take different processing paths through central processing system  30 . To facilitate routing of grow towers  50 , central processing system  30  includes sensors (e.g., RFID, barcode, or infrared) at various locations to track grow towers  50 . Control logic implemented by a controller of central processing system  30  tracks whether a given grow tower  50  is a cut-again or final cut grow tower and causes the various conveyors to route such grow towers accordingly. For example, sensors may be located at pick position  1404  and/or harvester infeed conveyor  1420 , as well as at other locations. The various conveyors described herein can be controlled to route identified grow towers  50  along different processing paths of central processing system  30 . As shown in  FIG. 21 , a cut-again conveyor  2112  transports a cut-again grow tower  50  toward the work envelope of automated pickup station  43  for insertion into grow environment  20 . Cut-again conveyor  2112  may consist of either a single accumulating conveyor or a series of conveyors. Cut-again conveyor  2112  may convey a grow tower  50  to pickup conveyor  1504 . In one implementation, pickup conveyor  1504  is configured to accommodate end effector  1450  of automated pickup station  43  that reaches under grow tower  50 . Methods of accommodating the end effector  1450  include either using a conveyor section that is shorter than grow tower  50  or using a conveyor angled at both ends as shown in  FIG. 22 . 
     Final cut grow towers  50 , on the other hand, travel through harvester station  32 , washing station  34  and transplanter  36  before reentering growth environment  20 . With reference to  FIG. 21 , a harvested grow tower  50  may be transferred from harvester outfeed conveyor  2102  to a washer transfer conveyor  2103 . The washer transfer conveyor  2103  moves the grow tower onto washer infeed conveyor  2104 , which feeds grow tower  50  to washing station  34 . In one implementation, pneumatic slides may push a grow tower  50  from harvester outfeed conveyor  2102  to washer transfer conveyor  2103 . Washer transfer conveyor  2103  may be a three-strand conveyor that transfers the tow to washer infeed conveyor  2104 . Additional pusher cylinders may push the grow tower  50  off washer transfer conveyor  2103  and onto washer infeed conveyor  2104 . A grow tower  50  exits washing station  34  on washer outfeed conveyor  2106  and, by way of a push mechanism, is transferred to transplanter infeed conveyor  2108 . The cleaned grow tower  50  is then processed in transplanter station  46 , which inserts seedlings into grow sites  53  of the grow tower. Transplanter outfeed conveyor  2110  transfers the grow tower  50  to final transfer conveyor  2111 , which conveys the grow tower  50  to the work envelope of automated pickup station  43 . 
     In the implementation shown in  FIG. 23A , harvester station  34  comprises crop harvester machine  2302  and bin conveyor  2304 . Harvester machine  2302  may include a rigid frame to which various components, such as cutters and feed assemblies, are mounted. Harvester machine  2302 , in one implementation, includes its own feeder mechanism that engages a grow tower  50  and feeds it through the machine. In one implementation, harvester machine  2302  engages a grow tower  50  on the faces that do not include grow sites  53  and may employ a mechanism that registers with grooves  58   a ,  58   b  to accurately locate the grow tower and grow sites  53  relative to harvesting blades or other actuators. In one implementation, harvester machine  2302  includes a first set of rotating blades that are oriented near a first face  101  of a grow tower  50  and a second set of rotating blades on an opposing face  101  of the grow tower  50 . As the grow tower  50  is fed through the harvester machine  2302 , crop extending from the grow sites  53  is cut or otherwise removed, where it falls into a bin placed under harvester machine  2302  by bin conveyor  2304 . Harvester machine  2302  may include a grouping mechanism, such as a physical or air grouper, to group the crops at a grow site  53  away from the face plates  101  of the grow towers  50  in order to facilitate the harvesting process. 
     Bin conveyor  2304  may be a u-shaped conveyor that transports empty bins the harvester station  34  and filled bins from harvester station  32 . In one implementation, a bin can be sized to carry at least one load of crop harvested from a single grow tower  50 . In such an implementation, a new bin is moved in place for each grow tower that is harvested. In one implementation, grow towers  50  enter the harvester machine  2302  full of mature plants and leave the harvester machine  2302  with remaining stalks and soil plugs to be sent to the next processing station. 
       FIG. 23B  is a top view of an example harvester machine  2302 . Circular blades  2306  extending from a rotary drive system  2308  harvest plants on opposing faces  101   a  of grow towers  50 . In one implementation, rotary drive system  2308  is mounted to a linear drive system  2310  to move the circular blades  2306  closer to and farther away from the opposing faces  101   a  of the grow towers  50  to optimize cut height for different types of plants. In one implementation, each rotary drive system  2308  has an upper circular blade and a lower circular blade (and associated motors) that intersect at the central axis of the grow sites of the grow towers  50 . Harvester machine  2302  may also include an alignment track  2320  that includes a set of rollers that engage groove  58  of the grow tower  50  as it is fed through the machine. Harvester machine  2302  may also include a tower drive system that feeds grow towers through the machine at a constant rate. In one implementation, the tower drive system includes two drive wheel and motor assemblies located at opposite ends of harvester machine  2302 . Each drive wheel and motor assembly may include a friction drive roller on the bottom and a pneumatically actuated alignment wheel on the top. As  FIG. 23C  illustrates, harvester machine  2302  may also include a gathering chute  2330  that collects harvested crops cut by blades  2306  as it falls and guides it into bins located under the machine  2302 . In another implementation, the harvester station  34  may include a track including an alignment feature and one or more engagement actuators, as discussed above, to align the grow tower  50  relative to harvesting blades that are moved across a stationary grow tower  50 . In another implementation, the harvesting blades may be replaced by another harvest mechanism, such as a picker assembly adapted to harvest different types of crops. 
     Washing station  34  may employ a variety of mechanisms to clean crop debris (such as roots and base or stem structures) from grow towers  50 . To clean a grow tower  50 , washing station  34  may employ pressurized water systems, pressurized air systems, mechanical means (such as scrubbers, scrub wheels, scrapers, etc.), or any combination of the foregoing systems. In implementations that use hinged grow towers (such as those discussed above), the washing station  34  may include a plurality of substations including a substation to open the front faces  101  of grow towers  50  prior to one or more cleaning operations, and a second substation to close the front faces  101  of grow towers after one or more cleaning operations. 
     Transplanter Station 
     Transplanter station  36 , in one implementation, includes an automated mechanism to inject root-bound plugs into grow sites  53  of grow towers  50 . In one implementation, the transplanter station  36  receives plug trays containing root-bound plugs including seedlings to be transplanted into the plug holders  158  of the grow towers  50 . In one implementation, transplanter station  36  includes a robotic arm and an end effector that includes one or more plug grippers that grasps root-bound plugs from a plug tray and inserts them into plug holders  158  of grow tower  50 . For implementations where grow sites  53  extend along a single face of a grow tower, the grow tower may be oriented such that the single face faces upwardly or laterally. For implementations where grow sites  53  extend along opposing faces of a grow tower  50 , the grow tower  50  may be oriented such that the opposing faces having the grow sites  53  face laterally (horizontally). In other implementations, as  FIG. 24D  shows, the front face plates  101  of grow towers  50  may be decoupled and rotated such that the grow sites  53  face generally upwardly for transplant operations. 
       FIGS. 24A, 24B and 24C  illustrate an example transplanter station  36  according to one possible implementation. Transplanter station  36  may include a plug tray conveyor  2430  that positions plug trays  2432  within the working envelope of a robotic arm  2410  and associated end effector. Transplanter station  36  may also include a feed mechanism that loads a grow tower  50  into place for transplanting. Transplanter station  36  may include one or more robotic arms  2410  (such as a six-axis robotic arm), each having an end effector  2402  and one or more plug grippers  2406  each adapted to grasp a root-bound plug from a plug tray and inject the root bound plug into a grow site  53  of a grow tower  50 . 
       FIG. 24A  illustrates an example end effector  2402  that includes a carriage  2404  and multiple plug grippers  2406  extending from the carriage  2404 . The plug grippers  2406  are attached to carriage  2404  and are each pivotable from a first angular orientation to a second angular orientation. In a first angular orientation (top illustration of  FIG. 24A ), plug grippers  2406  extend perpendicularly relative to the carriage  2404 . In one implementation, plug grippers  2406  are positioned in this first angular orientation when picking plugs from a plug tray  2470 . In the second angular orientation shown in  FIG. 24A , each plug gripper  2406  extends at a 45-degree (or other desired) angle relative to the carriage  2404 . The 45-degree angle may be useful for injecting plugs into the plug containers  158  of grow towers  50  that, as discussed above, extend at a 45-degree angle relative to the injection plane or front face  101  of a grow tower  50 . Other implementations are possible. For example, the second angular orientation will generally conform to the angular orientation of plug containers  158 . For example, the plug containers  158  illustrated in the various drawings are oriented ˜45 degrees relative to the front face  101  (injection plane) of a given grow tower  50 . Therefore, the second angular orientation is also ˜45 degrees, matching the angular orientation of the plug containers  158 . Accordingly, the second angular orientation will generally vary with the targeted or designed angular orientation of the plug container and may vary depending on design goals and engineering constraints. Furthermore, the spacing of plug grippers  2406  generally conforms to the spacing of the plug containers  158 . 
     A pneumatic actuator system may control the pivoting of the plug grippers  2406  between the first angular orientation and the second angular orientation. For example, a common bar or other member  2452  may attach to each of the plug grippers  2406  as shown in  FIG. 24A . The common bar  2452  may also be attached to or otherwise guided by features of carriage  2404  and slidable there along. As shown in  FIG. 24A , one or more actuators  2450  attached to the common bar  2452  may move from a retracted position to an extended position, moving common bar  2452  and causing each of plug grippers  2406  to rotate about their respective attachment points to carriage  2404 . In operation, the plug grippers  2406  may be in the first position when picking up root-bound plugs from a plug tray, and then may be moved to the second position prior to insertion of the plugs into plug containers  158 . In such an insertion operation, the robotic arm  2410  can be programmed to insert the plug grippers in a direction of motion parallel with the orientation of the plug container  158 , generally along a path having the second angular orientation relative to the insertion plane. 
     Using the end effector  2402  illustrated in  FIG. 24A , multiple plug containers  158  may be filled in a single operation. In addition, the robotic arm  2410  may be configured to perform the same operation at other regions on one or both sides of a grow tower  50 . As  FIG. 24B  shows, in one implementation, several robotic arms  2410 , each having an end effector  2402 , may be used to lower processing time for a given grow tower  50 . After grow sites  53  are filled, the grow tower  50  is ultimately conveyed to automated pickup station  43 , as described herein, and ultimately inserted into the controlled growth environment  20 . In the implementation shown, an infeed mechanism (see below) moves a grow tower  50  in a single operation into transplanter station where multiple robotic arms  2410  (and associated end effectors  2402 ) operate to fill all grow sites  53  of a grow tower before an outfeed mechanism moves the tower  50  from the station  36 . Other implementations are possible. For example, transplanter station  36  may be configured to move a robotic arm  2410  along a grow tower  50  to reduce the number of robotic arms  2410  required. Alternatively, the transplanter station  36  may be configured to convey sections of a grow tower  50  to a robotic arm  2410  in successive transplant operations. In other implementations, a single end effector  2402  may correspond to a section and side of a grow tower  50 . In such an implementation, the robotic or other actuation systems for moving the end effector  2402  may be simplified. 
       FIG. 26A  illustrates an example plug gripper  2406  in a retracted position.  FIG. 26B  illustrates an example plug gripper  2406  in an extended position. In the implementation shown, plug gripper  2406  includes a base  2602 , a stripper plate assembly  2604 , an actuator  2606 , and opposing gripper arms  2608   a ,  2608   b . Base  2602  rotatably attaches to carriage  2404  of end effector  2402  as shown in  FIG. 24A . As  FIG. 26C  shows, stripper plate assembly  2604  comprises extension member  2610  extending from base  2602  and stripper plate  2612  extending from extension member  2610 . Extension member  2610  holds stripper plate  2612  at a desired distance from base  2602 . Actuator  2606  is operative to move gripper arms  2608   a,b  from a retracted position ( FIG. 26A ) to an extended position ( FIG. 26B ). Gripper arms  2608   a ,  2608   b  extend through slots  2614  of stripper plate  2612  when the plug gripper is moved from the retracted to the extended position. In the implementation shown, stripper plate  2612  has an overall U-shape and extends substantially over the entire area (or at least over the entire width in one dimension) defined by the top of the plug container  2704  of a plug tray  2702  (see  FIG. 27A ). In other implementations, the stripper plate  2612  may have a substantially rectangular overall configuration. As  FIGS. 26A and 26B  show, each gripper arm  2608   a ,  2608   b  may include two prongs; however, each gripper arm  2608   a ,  2608   b  may include fewer or more prongs. In the implementation shown, when actuator  2606  is in the retracted position, the ends of gripper arms  2608   a ,  2608   b  are substantially at the same level as stripper plate  2612  with ends engaged in respective slots  2614 . When actuator  2606  is in the extended position, gripper arms  2608   a ,  2608   b  extend past stripper plate  2612  through slots  2614 . Additionally, when the gripper arms  2608   a ,  2608   b  are extended, they may be configured to extend at an angle toward one another to hold a plug securely. This slight interference forces gripper arms  2608   a  and  2608   b  to pinch together slightly as they extend, creating a secure hold on the seedling plug. In one implementation, the gripper arm material is a tempered stainless steel to provide adequate spring force while maintaining corrosion resistance and cleanability. In one implementation, the width of gripper arms  2608   a ,  2608   b  are narrowed at the top region  2609  under the screws  2607  to act as a flexure and concentrate the majority of the bending at that location. Other implementations are possible. The dimensions and overall configuration of the gripper arms will depend on the application, as well as the shape and configuration of the plugs and plug trays. In addition, stripper plate  2612  may not include slots. In such an implementation, gripper arms  2608   a ,  2608   b  extend along opposing outside edges of the plate. In one implementation, the stripper plate  2612  may include features near the ends of what would otherwise be complete slots  2614  to help guide the  2608   a ,  2608   b.    
       FIG. 32A  is a perspective view of an alternative plug gripper  3200 . As  FIG. 32  illustrates, plug gripper  3200  comprises actuator  3202 , guide bracket  3204 , and arm assembly  3206 . Actuator  3202 , in one implementation, is a pneumatic linear actuator that attaches to guide bracket  3204  and arm assembly  3206 . Arm assembly  3206  includes two laterally opposing palm sections  3212  extending from base section  3210 . Arms  3208  extend from the palm sections  3212 , as shown in  FIG. 32B . Expansion and retraction of actuator  3202  causes arm assembly  3206  to move relative to guide bracket  3204 , as shown in  FIGS. 32C, 32D and 32E . Guide bracket  3204  includes first and second guide members  3216  that extend upwardly from a stripper plate  3214 . As  FIGS. 32A and 32F  show, similar to gripper  2406 , arms  3208  extend through slots  3216  of stripper plate  3214  as the actuator  3202  moves between the retracted and extended positions. In the implementation shown, stripper plate  3214  has an overall U-shape and extends substantially over the entire area (or at least over the entire width in one dimension) defined by the top of the plug container  2704  of a plug tray  2702  (see  FIG. 27A ). In other implementations, the stripper plate  3214  may have a substantially rectangular overall configuration. 
     In the implementation shown, guide members  3216  and stripper plate  3214  are configured to include a substantially U-shaped configuration. In one implementation, the inner surfaces of guide members  3216  are configured to contact and guide arms  3208  as the extend and retract. In one implementation, the inner surfaces of guide members  3216  can be coated to mitigate mechanical wear due to frictional contact with arm assembly  3206 . The location of slots  3218  are configured to cause arms  3208  to bend inwardly to facilitate gripping of a plug as they extend beyond stripper plate  3214 . In one implementation, arms  3208  may be reinforced relative to palm sections  3212  to promote arm assembly  3206  to bend at palm sections  3212  leaving the arms  3208  substantially straight. In one implementation, arms  3208  may be reinforced by configuring them to have a slight arc as shown in  FIG. 32B  to resist bending. 
     Guide members  3216  also have the advantage of deflecting away from the arms  3208  leaves or other parts of a plant extending from the plug being gripped. In addition, the outer surfaces of guide members  3216  may also be configured to facilitate insertion of the gripper  3200  into a plug site  53  of a grow tower  50 . For example, the contour of the outer surface of guide members  3216  can be configured to guide the gripper  3200  into plug containers  158  as they are inserted. 
       FIG. 33A  is a perspective view of yet another alternative plug gripper. Plug gripper  3300  comprises actuator  3302 , bracket  3304 , arm assembly  3306  and stripper plate  3312 . Plug gripper  3300  differs from grippers  2450  and  3200  in that the actuator  3302  attaches directly to and moves the stripper plate  3312 , instead of arm assembly  3306 . Arm assembly  3302  attaches to bracket  3304 ; otherwise, arm assembly  3308  is substantially the similar to the arm assembly  3206  discussed above. As actuator  3302  retracts, it causes stripper plate  3312  to move arms  3308  inwardly, as discussed above, to grip a plug. As actuator extends, arms  3308  move outwardly. 
     The configuration of plug gripper  3300  requires the robotics associated with transplanter  36  to operate somewhat differently. In particular, because arms  3308  do not move relative to stripper plate  3312 , the robotic arm connected to the plug gripper  3300  must move during plug pickup and insertion operations. For example, during an insertion operation, the robotics inject the gripper  3300  holding a plug into a plug site  53 . When stripper plate  3312  is moved to a programmed distance relative to the plug site  53 , the robotics must move gripper away from the plug site  53  at the same speed and angular orientation as the actuator extends. In this manner, stripper plate  3312  remains in the same place relative to the plug site  53  and pushes the plug away into plug site  53 , as the robotic arm extracts arms  3308  from the plug site  53 . Conversely, during a plug pickup operation, the robotic arm must move the arms  3308  toward the plug to be grasped at the same speed that the actuator retracts. Otherwise, plug gripper  3300  is substantially interchangeable with plug gripper  2406  or  3200 . 
       FIG. 27A  shows an example plug tray  2702  that is configured to hold a plurality of root-bound plugs to be inserted into respective grow sites  53  of a grow tower  50 . Plug tray  2702  contains a two-dimensional array of plug containers  2704 .  FIG. 27B  illustrates an example shape of a root-bound plug  2706  that a plug container  2704  may hold. In one implementation, the number of plug containers  2704  in a given row can match the number of plug grippers  2406  attached to end effector  2602 . In other implementations, the number of plug containers  2704  in a given row can be a multiple of the number of plug grippers  2406  attached to end effector  2602 . In one implementation, gripper arms  2608   a ,  2608   b  are configured to spear into the plug medium and pinch the plug  2706  to grasp a plug  2706  substantially near its outer surface. Similarly, the inner dimensions of plug holder  158  of a grow tower  50  are also configured to substantially match the dimension of plug container  2704  and the corresponding plug  2706 . Accordingly, when a plug gripper  2406  holds a plug, gripper arms  2608   a ,  2608   b  hold it in place relatively firmly from the outer surface of the plug  2706 . In addition, the gripper arms  2608   a ,  2608   b  and plug  2706  are dimensioned, in one implementation, to essentially achieve a press fit with respect to the plug holder  158 . As discussed below, stripper plate  2612 , spanning the entire width of a plug  2706  in at least one dimension, prevents a plug  2706  from sliding back out of the plug holder  158  when gripper arms  2608   a ,  2608   b  are retracted. 
       FIG. 28  illustrates an infeed mechanism  2802  that facilitates insertion of a grow tower  50  into transplanter station  36 . In one implementation, transplanter station  36  includes a track (discussed below) that guides and aligns grow tower  50  for transplanting operations. In the implementation shown, infeed mechanism  2802  may include a drive wheel and motor assembly to feed a grow tower  50  into transplanter station  36 . In one implementation, the drive wheel and motor assembly may include a friction drive roller  2804  that engages the grow tower  50  from the bottom and a pneumatically-actuated alignment wheel  2806  that engages top groove  58  of grow tower  50 , pressing it against friction drive roller  2804 . Infeed mechanism  2802  may further include a lead-in feature  2808  to guide the grow tower  50  into infeed mechanism  2802  to correct for gross misalignment of the grow tower  50 . In one implementation, a control system drives infeed mechanism  2802  to operate until an entire grow tower  50  is inserted into transplanter station  36 . As discussed, infeed mechanism  2802  drives a grow tower  50  causing it to slide along a track  2420  of transplanter station  36  (see  FIG. 24C ). Other implementations for feeding towers  50  into transplanter station  36  are possible. For example, in other implementations, the groove region  58  of a grow tower  50  may include a row of teeth extending along the length of the tower. In such an implementation, a friction drive wheel can be replaced by a toothed wheel that positively engages the teeth in grove region  58 . Such an implementation would allow the infeed mechanism to track the position of the grow tower as it moves through the transplanter  36 . 
     After transplanter station  36  completes one or more transplanting operations for a given grow tower  50 , a control system drives outfeed mechanism  2902  to translate the grow tower  50  out of transplanter station  36  where it can be eventually injected into growth environment  20 .  FIG. 29  illustrates an outfeed mechanism  2902  according to one implementation of the invention. Similar to infeed mechanism  2802 , outfeed mechanism  2902  includes a drive wheel and motor assembly. In the implementation shown, friction drive roller  2904  engages the bottom of grow tower  50 , while a pneumatically-actuated alignment wheel  2906  engages groove  50  from the top of grow tower  50  driving the grow tower  50  against friction drive roller  2904 . In one implementation, outfeed mechanism  2902  may include an actuated stop to accurately locate grow tower  50  relative to the station  36 . 
       FIGS. 30A, 30B and 30C  illustrate a track  2420  that may be used to guide a grow tower  50  within and along a transplanter station  36 . As  FIG. 24C  illustrates, as infeed mechanism  2802  translates a grow tower  50 , track  2420  acts as a guide.  FIG. 30B  illustrates an example profile for track  2420 . The track profile may include a base section  3002 , side ridges  3004  and guide projection  3006 . Ridges  3004  and guide projection  3006  run substantially the length of track  2420 .  FIG. 30C  illustrates a track section  3020 , a plurality of which may be aligned and attached to transplanter station  36  to form track  2420 . For example, track section  3020  may be one meter in length. In such an implementation, five track sections may be used to form a 5-meter track  2420 . Track section  3020  may be made of plastic (such as high-density polyethylene (HDPE), ultra-high molecular weight (UHMW) polyethylene, Delrin® offered by DuPont®, etc.) or some other low-friction, wear-resistant material. The profile of guide projection  3006  substantially matches, and is the inverse form, of at least a section of groove  58  of grow tower  50 . As shown in  FIG. 30B , grow tower  50  contacts and slides along ridges  3004  as it moves in and out of transplanter station  36 , guided by projection  3006 . In the implementation shown, the modeled distance between groove  58  and projection  3006  is approximately 1-2 millimeters. 
     A variety of configurations involving groove  58  and projection  3006  are possible.  FIG. 30B  illustrates that the cross-section profile of grow tower  50  includes a substantially V-shaped section define a groove  58  along the length of grow tower  50  and that the cross-section profile of track  2420  includes a matching, substantially V-shaped section defining projection  3006 . In other implementations, the profile sections defining these features can be semi-circular, triangular or any other suitable shape. Furthermore, the profile sections associated with groove  58  and projection  3006  need not be perfectly complimentary. In general, projection  3006  can be any suitable shape that guides a grow tower  50  along groove  58  during transfer operations, and that centers grow tower  50  along the alignment feature provided by projection  3006  when one or more engagement actuators (see below) exert a force to press the grow tower  50  against the track  2420 . 
     Grow tower  50 , as discussed above, may be a relatively long structure (e.g., ˜5-10 meters) composed of an extruded plastic. Accordingly, the relative locations of grow sites  53  may vary over the length of a grow tower  50 . For example, a slight curvature or other variation of a grow tower  50  may cause the grow sites  53  to vary in one or two dimensions in addition to the longitudinal axis along which the grow sites  53  are spaced. This variation may prevent challenges to the transplant operations described herein. For example, the attachment of plug grippers  2406  to a common carriage  2404  requires that the front face plate  101  is substantially uniform across the length of the carriage  2404 . Accordingly, to facilitate the transplant operations described herein, it may be advantageous to reduce spatial variation across grow sites  53 . As  FIG. 24C  illustrates, in one implementation, transplanter station  36  includes tower registration actuators  2422  disposed above track  2420 . After a grow tower  50  is inserted into transplanter station  36 , actuators  2422  are controlled to press down on grow tower  50  at defined points along and above track  2420 . The force exerted by actuators  2422  deflects grow tower  50 , causing groove  58  to register against projection  3006  and centering the grow tower along track  2420 . Registering the surface of groove  58  against projection  3006  reduces variation of grow sites  53  along grow tower  50  in two dimensions. In particular and with reference to a grow tower  50  disposed on track  2420 , if the length of a grow tower  50  is considered the x-axis, the width or face of a grow tower  50  the y-axis and the height the z-axis, then registration of the grow tower  50  against profile section  3006  and track  2420  generally reduces variation of the grow sites  53  relative to each other in the y- and z-axes. Accordingly, transplanter station  36  may include cameras or other sensors to locate grow sites  53  in the remaining x-axis dimension to facilitate insertion of plugs at plug holders  158 . Still further, such an implementation allows relaxation of manufacturing tolerances for grow towers  50  and/or reduces the number of sensors required to locate the plug holders  158  for transplant operations. 
       FIG. 30D  illustrates an example tower registration actuator  2422  according to one possible implementation of the invention. In the implementation shown, tower registration actuator  2422  includes a linear actuator  3024  (e.g., a pneumatic actuator), a ball and swivel joint  3022 , and an engagement member  3026  mounted to the end of the actuator. As  FIG. 30D  illustrates, the profile of engagement member  3026  may substantially match the outer, upper surface of grow tower  50 . The profile of engagement member  3026  can be an extruded, molded or machined part and may vary in length depending on a variety of engineering and other design considerations. For example, engagement member  3026  may be 3-6 centimeters in length. In other implementations, engagement member may be 0.5 meters in length. As  FIG. 24C  illustrates, multiple actuators  2422  may be disposed along track  2420  to facilitate registration of various sections of grow tower  50  relative to an operator, such as robotic arm  2410 . Other implementations are possible. For example, as  FIGS. 31A-C  demonstrate, engagement member  3026  may be have a disc shape with a flat profile configured to engage the upper surfaces of grow tower  50 , as opposed to groove  58 . In both configurations, ball and swivel joint  3022  allows for misalignment when pressing the grow tower  50  against projection  3006  of track  2420 . 
     The following description sets forth an example process flow and operation for transplanter station  36  according to one possible implementation of the invention. Infeed mechanism  2802  feeds a grow tower  50  into transplanter station along track  2420  until it hits a defined stop location. As  FIG. 24C  illustrates, transplanter station  36  contains the entire grow tower  50 . The grow tower  50  is oriented such that the opposing tower faces  101  with plug holders  158  face horizontally. Actuators  2422  press grow tower  50  onto track  2420  reducing variation in two dimensions of the location of plug holders  158  along grow tower  50 , as discussed above. A control system operates robotic arms  2410  and respective end effectors  2402  to pick up rows of plugs from a plug tray  2432  and insert them into plug holders  158 , as discussed below. In the implementation shown in  FIG. 24C , a given robotic arm  2410  may be cycled through four insertion operations to inject plugs at two regions and on each side of grow tower  50 . After transplanter station  36  fills all plug holders  158  of grow tower  50 , actuators  2422  release the tower  50 , allowing outfeed mechanism  2902  to feed the grow tower  50  from transplanter station  36 . 
     During a transplant operation, plug grippers  2406  are positioned over respective plug containers  2704  of a plug tray  2432 . In some implementations, robotic arm  2410  positions plug grippers  2406  such that stripper plate  2612  is positioned substantially adjacent to the top surface of a root-bound plug contained in plug container  2704  and/or at the top surface of plug container  2704 . Actuators  2606  are then controlled to drive gripper arms  2608   a ,  2608   b  into the lateral sides of plug container  2704  to engage a plug. Robotic arm  2410  then moves end effector  2402  vertically upward to lift the plugs out of their respective plug containers  2704 . Robotic arm  2410  then moves the end effector  2402  such that the plugs are in a horizontal orientation near the insertion plane of the grow tower  50  and facing the horizontally-arranged plug holders  158  of grow tower  50 . Pneumatic controls cause plug grippers  2406  to rotate to the desired insertion angle (in one embodiment, 45 degrees). Robotic arm  2410  then moves the end effector  2402  at the desired insertion angle causing plug grippers  2406  to insert the plugs into respective plug holders  158 . Actuators  2606  are then controlled to retract grippers  2608   a ,  2608   b  along the insertion angle. Stripper plate  2612  may cause a plug to remain in plug holder  158 . Robotic arm  2410  then moves end effector  2402  away from grow tower  50  and back to plug tray  2702  to begin another transplant cycle. 
     A variety of implementations are possible. A single robotic arm can be used in connection with an assembly that moves robotic arm along the grow tower  50 . Alternatively, the grow tower  50  could be incrementally moved relative to the robotic arm. Plug trays may be oriented vertically instead of horizontally. In such a configuration, a robotic arm may need not operate in six degrees of freedom to effect the plug insertion operations described herein. Still further, grow towers  50  may be opened prior to transplanting operations, as discussed above. In such an implementation, the faces  101  of grow tower  50  may be oriented horizontally, eliminating the need for robotic arm to orient the plug grippers  2406  horizontally. Still further, other actuators, such as a cartesian gantry system, may be used in lieu of robotic arms. 
     One or more of the controllers discussed above, such as the one or more controllers for central processing system  30  (or one or more stations therein), may be implemented as follows.  FIG. 25  illustrates an example of a computer system  800  that may be used to execute program code stored in a non-transitory computer readable medium (e.g., memory) in accordance with embodiments of the disclosure. The computer system includes an input/output subsystem  802 , which may be used to interface with human users or other computer systems depending upon the application. The I/O subsystem  802  may include, e.g., a keyboard, mouse, graphical user interface, touchscreen, or other interfaces for input, and, e.g., a LED or other flat screen display, or other interfaces for output, including application program interfaces (APIs). Other elements of embodiments of the disclosure, such as the controller, may be implemented with a computer system like that of computer system  800 . 
     Program code may be stored in non-transitory media such as persistent storage in secondary memory  810  or main memory  808  or both. Main memory  808  may include volatile memory such as random-access memory (RAM) or non-volatile memory such as read only memory (ROM), as well as different levels of cache memory for faster access to instructions and data. Secondary memory may include persistent storage such as solid-state drives, hard disk drives or optical disks. One or more processors  804  reads program code from one or more non-transitory media and executes the code to enable the computer system to accomplish the methods performed by the embodiments herein. Those skilled in the art will understand that the processor(s) may ingest source code, and interpret or compile the source code into machine code that is understandable at the hardware gate level of the processor(s)  804 . The processor(s)  804  may include graphics processing units (GPUs) for handling computationally intensive tasks. 
     The processor(s)  804  may communicate with external networks via one or more communications interfaces  807 , such as a network interface card, WiFi transceiver, etc. A bus  805  communicatively couples the I/O subsystem  802 , the processor(s)  804 , peripheral devices  806 , communications interfaces  807 , memory  808 , and persistent storage  810 . Embodiments of the disclosure are not limited to this representative architecture. Alternative embodiments may employ different arrangements and types of components, e.g., separate buses for input-output components and memory subsystems. 
     Those skilled in the art will understand that some or all of the elements of embodiments of the disclosure, and their accompanying operations, may be implemented wholly or partially by one or more computer systems including one or more processors and one or more memory systems like those of computer system  800 . In particular, the elements of automated systems or devices described herein may be computer-implemented. Some elements and functionality may be implemented locally, and others may be implemented in a distributed fashion over a network through different servers, e.g., in client-server fashion, for example. 
     Although the disclosure may not expressly disclose that some embodiments or features described herein may be combined with other embodiments or features described herein, this disclosure should be read to describe any such combinations that would be practicable by one of ordinary skill in the art. Unless otherwise indicated herein, the term “include” shall mean “include, without limitation,” and the term “or” shall mean non-exclusive “or” in the manner of “and/or.” 
     Those skilled in the art will recognize that, in some embodiments, some of the operations described herein may be performed by human implementation, or through a combination of automated and manual means. When an operation is not fully automated, appropriate components of embodiments of the disclosure may, for example, receive the results of human performance of the operations rather than generate results through its own operational capabilities. 
     All references, articles, publications, patents, patent publications, and patent applications cited herein are incorporated by reference in their entireties for all purposes to the extent they are not inconsistent with embodiments of the disclosure expressly described herein. However, mention of any reference, article, publication, patent, patent publication, and patent application cited herein is not, and should not be taken as an acknowledgment or any form of suggestion that they constitute valid prior art or form part of the common general knowledge in any country in the world, or that they are disclose essential matter. 
     Several features and aspects of the present invention have been illustrated and described in detail with reference to particular embodiments by way of example only, and not by way of limitation. Those of skill in the art will appreciate that alternative implementations and various modifications to the disclosed embodiments are within the scope and contemplation of the present disclosure. Therefore, it is intended that the invention be considered as limited only by the scope of the appended claims.