Abstract:
Storage library systems and methods of operating and assembling library systems are provided. The storage library system may include a stationary support member having a first axis and a cartridge transport assembly. The cartridge transport assembly includes a cartridge retrieving mechanism configured to retrieve a removable media cartridge, said cartridge transport assembly being coupled to the support member, wherein the cartridge retrieving mechanism is positionable in four degrees of freedom. The method of operating a tape library may include transmitting instruction signals to a robotics controller disposed on a cartridge transport assembly, translating the cartridge transport assembly along a stationary support member, and positioning the cartridge retrieving mechanism in four degrees of freedom relative to the stationary support member.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to storage libraries. More specifically, the present invention relates to cartridge transfer mechanisms for tape storage libraries.  
       BACKGROUND OF THE INVENTION  
       [0002]     Magnetic tape cartridges have proven to be an efficient and effective medium for data storage in computer systems. Large computer systems may utilize numerous cartridges for data storage purposes as well as a plurality of tape drives for reading and/or writing data to and from storage cartridges in a timely manner. Typically, as the number of storage cartridges grows, it becomes more efficient to organize the cartridges in automated storage libraries. Automated storage libraries including magnetic tape cartridges may improve access speed and reliability of data storage systems having large numbers of magnetic tape cartridges.  
         [0003]     Automated cartridge libraries generally include a plurality of storage bins or slots for storing library tape cartridges, a cartridge transport mechanism including a robotic cartridge retrieval mechanism (often referred to as a “picker”), and one or more tape drives. The robotic picker may be controlled to select a specific storage tape cartridge from the library and transfer the tape cartridge between a storage slot and a tape drive within seconds. The robotic picker typically includes a “gripper” mechanism positioned on the robotic picker. A plurality of actuator mechanisms are disposed in the library for positioning the gripper at the desired location and in the desired orientation in order to retrieve the desired cartridge from a storage bin. After the robotic picker has positioned the gripper near the desired tape cartridge, the gripper may be activated to engage or grip the tape cartridge to remove the cartridge from the storage bin. The robotic arm may move the gripper and tape cartridge to a location to load the tape cartridge into a tape drive, load port (for adding or removing tapes from the library), and the like.  
         [0004]     Another configuration for a storage library features a roughly cylindrical chamber, with racks provided along the interior of the circular wall. The retrieval/loading transport mechanism is positioned in the center of the chamber and is operated in a cylindrical coordinate fashion. In this configuration, the tape cartridges are positioned around the transport mechanism at equal radial distances, resulting in a roughly cylindrical library enclosure.  
         [0005]     It may be desirable to provide a cartridge transport assembly that can reliably position a cartridge retrieval mechanism within a storage library system enclosure without an excessive amount of mechanical support and positioning components. It may be further desirable to provide a transport assembly that can be tested prior to its incorporation into the storage library system.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     In accordance with embodiments of the present invention, a storage library system is provided. The storage library system comprises: a stationary support member having a first axis and a cartridge transport assembly. The cartridge transport assembly comprises a cartridge retrieving mechanism configured to retrieve a removable media cartridge, said cartridge transport assembly being coupled to the support member, wherein the cartridge retrieving mechanism is positionable in four degrees of freedom.  
         [0007]     In accordance with other embodiments of the present invention, a storage library system is provided comprising: a stationary support member having a first axis and a cartridge transport assembly coupled to the stationary support member. The cartridge transport assembly comprises: a first carriage coupled to the vertical support member; a first actuator coupled to the first carriage and the stationary support member configured to actuate linear movement of the first carriage along the stationary support member; a second carriage movably coupled to the first carriage; a second actuator engaging the first and second carriages configured to actuate linear movement of the second carriage along a second axis non-parallel to the first axis; a third carriage movably coupled to the second carriage; a third actuator engaging the second and third carriages configured to actuate linear movement of the third carriage along a third axis non-parallel to the first axis and the second axis; and a cartridge retrieval mechanism coupled to the third carriage.  
         [0008]     In accordance with other embodiments of the present invention, a method of operating a tape library is provided. The method comprises: transmitting instruction signals to a robotics controller disposed on a cartridge transport assembly; translating the cartridge transport assembly along a stationary support member; and positioning the cartridge retrieving mechanism in four degrees of freedom relative to the stationary support member.  
         [0009]     In accordance with other embodiments of the present invention, a method of assembling a tape library, comprising: assembling a cartridge transport assembly comprising mounting the cartridge transport assembly to a stationary support member in a storage library system; and prior to mounting the cartridge transport assembly to the stationary support member, testing four degrees of freedom of movement of the cartridge retrieval mechanism.  
         [0010]     Other features and aspects of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the features in accordance with embodiments of the invention. The summary is not intended to limit the scope of the invention, which is defined solely by the claims attached hereto. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a simplified top view of a storage library system in accordance with embodiments of the present invention.  
         [0012]      FIGS. 2A-2C  are perspective views of a storage library system in accordance with embodiments of the present invention.  
         [0013]      FIG. 3  is a perspective view of a cartridge transport assembly in accordance with embodiments of the present invention.  
         [0014]      FIGS. 4A-4C  are perspective views of a z-axis assembly in accordance with embodiments of the present invention.  
         [0015]      FIG. 5  is a perspective view of an x-axis assembly in accordance with embodiments of the present invention.  
         [0016]      FIGS. 6A-6B  are perspective views of a rotary assembly in accordance with embodiments of the present invention.  
         [0017]      FIGS. 7A-7C  are perspective views of an extension assembly and cartridge retrieval mechanism in accordance with embodiments of the present invention.  
         [0018]      FIG. 8  is a circuit diagram of a robotics controller in accordance with embodiments of the present invention. 
     
    
       [0019]     In the following description, reference is made to the accompanying drawings which form a part thereof, and which illustrate several embodiments of the present invention. It is understood that other embodiments may be utilized and structural and operational changes may be made without departing from the scope of the present invention. The use of the same reference symbols in different drawings indicates similar or identical items.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0020]      FIG. 1  is a simplified block diagram of an exemplary automated storage library system  100  for the storage and retrieval of a plurality of storage cartridges  114  stored therein.  FIG. 2A  is a perspective view of the library system  100  with the top and side walls removed for clarity.  FIG. 2B  is a perspective view of the cartridge transport assembly  120  having the z-axis assembly  150  and other portions removed for clarity. The library system  100  may include an enclosure  101 , which houses one or more media drives  112 , a plurality of data storage cartridges  114  stored in bins or storage slots  116 , a primary support member  132 , a supplemental support member  130 , and a cartridge transport assembly  120  that may be equipped with a cartridge retrieval mechanism (e.g., a gripper)  122  for transporting a selected cartridge  114  between a media drive  112  and a storage slot  116 . The storage library system  100  further includes a library controller  104  that communicates with a host  102  to control the actions of the cartridge transport assembly  120  and media drives  112  to retrieve and/or store data.  
         [0021]     The library controller  104  may include a single general purpose computer, microprocessor, microcontroller, and the like. Alternatively, a separate cartridge loader controller and a library system controller may be included. A general library controller  104 , tape cartridge loader controller, or library system controller may include any programmable general purpose computer or processor and preferably will have a suitably programmed microprocessor or microcontroller. The input-output connections between the library controller and various other components of the library system  100  may include well-known industry standard cabling and communication protocols. For example, Ethernet, Inter Integrated Circuit bus (I 2 C), Small Computer System Interface (SCSI), ultra-wide SCSI, fast SCSI, fibre channel, and the like.  
         [0022]     The library controller  104  may operate to coordinate movements and actions of media drives  112 , cartridge transport assembly  120 , and the like. The controller  104  may include a suitable processor as described above and is typically interconnected with a host  102 , which sends access commands to controller  104 . The data recorded to or read from one or more of the cartridges  114  may be transmitted between one of the drives  112  to the host  102  through the library controller  104 , or a second data path connection, e.g., a fibre channel bridge or the like. The library controller  104  may also be coupled to a robotics controller  140  disposed on the cartridge transport assembly  120  via a flexible umbilical data/power cable  142 .  
         [0023]     Media drives  112  may include, for example, magnetic tape drives and/or optical disk drives, and cartridges  114  may include, for example, magnetic and/or optical storage devices. An exemplary drive includes the SDLT™ 320 magnetic tape drive, and an exemplary storage cartridge includes the Super DLTape™ Type I storage cartridge, both sold by Quantum Corporation. The examples described herein generally relate to a magnetic tape library including multiple magnetic tape cartridges. It should be understood, however, that the various embodiments are contemplated with use for other types of storage media and storage media libraries. For example, a storage library may include optical media devices alone or in combination with magnetic media storage devices and the like.  
         [0024]     An automated storage library system  100  may further include various other features such as load ports for manually adding and removing cartridges to and from the library, various access doors, control panels, power supplies, and the like as are known in the art. For clarity, however, such additional features have been omitted from the description.  
         [0025]     The cartridge transport assembly  120  selectively moves and positions the tape cartridges  114  within the internal cavity  106  of the tape library  100 . More specifically, the transport assembly  120  is adapted to retrieve any one of the tape cartridges  114  from any of the storage bins  116  and transfer the tape cartridges  114  to any one of the media drives  112 , another one of the storage bins  116 , or elsewhere in the library cavity  106 . The cartridge transport assembly  120  may be provided with a cartridge retrieval mechanism  122 . The cartridge retrieval mechanism  122  may be configured to grasp the individual cartridges  114  and allows for the transfer of the cartridges  114  within the library cavity  106 . The cartridge retrieval mechanism  122  can be designed in various ways, as would be understood by one of ordinary skill in the art.  
         [0026]      FIG. 3  is an exploded perspective view of the cartridge transport assembly  120 , in accordance with embodiments of the present invention. The cartridge transport assembly  120  includes a z-axis assembly  150 , which may be coupled to the primary support member  132  and the secondary support member  130  via a z-axis carriage  137 , as shown in  FIGS. 2A-2C . The z-axis assembly  150  supports an x-axis assembly  500 , which supports a rotary assembly  600 , which, in turn, supports an extension assembly  700 . The cartridge retrieval mechanism  122  is supported by the extension assembly  700 . These components comprise a robotic subassembly  300 .  
         [0027]      FIGS. 4A-4C  illustrate the z-axis assembly  150 , in accordance with embodiments of the present invention.  FIG. 4A  shows an exploded perspective view,  FIG. 4B  shows a top perspective view, and  FIG. 4C  shows a bottom perspective view of the z-axis assembly  150 . The z-axis assembly  150  may be provided with a y-axis actuator  152  (shown in  FIGS. 2B-2C ), which effectuates movement of the cartridge transport assembly  120  along the secondary support member  132  in the y-direction. The y-axis actuator  152  may comprise, for example, a DC brush motor coupled to pulleys  138  and belts  139  to actuate movement of the z-axis carriage  137 . The z-axis assembly  150  may also be provided with a primary support flange  134 , which mates with the primary support member  132 , to provide a more balanced support for the cartridge transport assembly  120 . The primary support flange  134  may also be coupled to a counterweight  136 , which can help to reduce the load on the y-axis actuator  152  when translating the cartridge transport assembly  120  along the y-axis.  
         [0028]     The z-axis assembly  150  may also include a recess  154  for receiving the robotics controller  140 , which is coupled to the umbilical data/power cable  142 . In accordance with embodiments of the present invention, the robotics controller  140  may be configured to receive commands and power from the library controller  104  via the umbilical cable  142 , to process those commands to generate specific positioning commands, and to control the positioning of the various actuators of the cartridge transport assembly  120  to position the cartridge retrieval mechanism  122  in the desired positions to perform the desired tasks, as will be described in greater detail below.  
         [0029]     The z-axis assembly  150  may be configured to support an x-axis assembly  500  and may be provided with a z-axis actuator configured to translate the x-axis assembly  500  in the z-direction. The z-axis actuator may comprise, for example, a z-axis motor  168 , which is coupled to a movable belt  164  to cause lateral movement of a plate  162  mounted on the belt  164 . The x-axis assembly  500  is coupled to the plate  162 , thereby enabling the z-axis actuator to actuate linear movement in the z-direction of the x-axis assembly  500  relative to the z-axis assembly  150 . To provide stability for the movement of the x-axis assembly  500 , the x-axis assembly  500  may also be coupled to a slide bearing  158  mounted on a guide rail  156  on the z-axis assembly  150 , and have roller bearings  504  (shown in  FIG. 5 ) which engage a guide flange  161 . The z-axis assembly  150  may further be provided with a z-axis home sensor  160  that may be used to determine when the x-axis assembly  500  is located at the home position by sensing when a light beam is broken by a flange  508  (shown in  FIG. 5 ) provided on the x-axis assembly  500 .  
         [0030]     The robotics controller  140  may send data, commands, and other signals to the various components of the cartridge transport assembly  120  via a ribbon cable  159 , which is coupled to a ribbon cable interface provided on the x-axis assembly  500 . The ribbon cable  159  is of sufficient length that the connection between the ribbon cable  159  and the interface can be maintained throughout the range of motion of the x-axis assembly  500  along the guide rail  156 .  
         [0031]     The x-axis assembly  500  is shown in enlarged perspective view in  FIG. 5 . The x-axis assembly  500  may include an x-axis actuator comprising an x-axis motor  518  which is coupled to a pulley  506 . A movable belt (not shown) may be provided between the pulley  506  and a second pulley  507 . A rotary assembly  600  (shown in greater detail in  FIG. 6 ) is coupled to the belt such that rotation of the pulley  506  caused by the motor  518  actuates linear movement of the rotary assembly  600  in the x-direction relative to the x-axis assembly  500 . To provide stability for the movement of the rotary assembly  600 , the x-axis assembly  500  may also be provided with a guide flange  502  and a slide bearing mounted on a guide rail  514  (shown in  FIG. 3 ) provided between apertures  510   a - 510   b . The rotary assembly may be coupled to the slide bearing and provided with rollers  602  which engage the guide flange  502 , to thereby guide the rotary assembly in its linear movement and provide support for the gripper  122 . The x-axis assembly  500  may also be provided with a pair of sensors  512 , which can detect the linear position of the rotary assembly  600 .  
         [0032]      FIG. 6A  shows a top perspective view of a rotary assembly  600  which is supported by the x-axis assembly  500  and is configured to slide laterally along the x-axis.  FIG. 6B  is a bottom perspective view of the rotary assembly  600 . In the illustrated embodiment, the rotary assembly  600  comprises a rotating portion  610  rotatably coupled to a base portion  620 . The base portion  620  is coupled to the slide bearing and the belt provided on the x-axis assembly and is configured to move linearly along the guide rail and the guide flange  502 . The rotating portion  610  includes a motor  604  coupled to a pulley  622 , which, in turn, is coupled to a belt  624 . The belt  624  engages a hub  626  which protrudes from the base portion  620 . Rotation of the motor  604  causes the belt  624  to engage the stationary hub  626 , thereby causing the rotating portion  610  to rotate about the y-axis relative to the base portion  620 .  
         [0033]     The base portion  620  may also include a ribbon cable  606  coupled to an interface provided on the x-axis assembly  500  and having a sufficient length such that the cable  606  may maintain a connection with the interface across the complete range of movement of the rotary assembly  600  in the x-direction. Another ribbon cable  608  is loosely wound about the shaft from the base portion  620  and provides data connectivity between the base portion  620  and the rotational portion  610 . This data connection can provide control signals to the motor  604  and the cartridge retrieval mechanism  122 .  
         [0034]      FIG. 7A  is a front perspective view of the cartridge retrieval mechanism  122  and an extension assembly  700 ,  FIG. 7B  is a rear perspective view, and  FIG. 7C  is an exploded perspective view. The extension assembly  700  may include a pair of flanges  720  which are coupled with a pair of flanges  612  provided on the rotational portion  610  of the rotary assembly  600  such that the extension assembly  700  rotates with the rotational portion  610 . The cartridge retrieval mechanism  122  is mounted on the extension assembly  700  and may be configured to be translated in the direction indicated by the arrow E in  FIG. 7 . This direction is defined by the rotational position of the extension assembly  700  and permits the cartridge retrieval mechanism  122  to be rotated to the desired orientation and then be extended to either grasp or release a tape cartridge retained by the gripper fingers  704  of the cartridge retrieval mechanism  122 . The cartridge retrieval mechanism  122  may include a slide block  708  which engages a flange  706  on the extension assembly  700  and may also be guided in its linear movement by a guide rails  702  and  722 . A extension motor  718  may be provided on the extension assembly  700  to rotate a pulley  724 , which, in turn, moves a belt  726  which actuates movement of the cartridge retrieval mechanism  122  along the guide rail  702 . A sensor  716  may be provided to detect the position of the cartridge retrieval mechanism  122 .  
         [0035]     The cartridge retrieval mechanism  122  may also be provided with a pair of ribbon cables  710   a - 710   b , which provide data connectivity between interfaces  614   a - 614   b  on the rotary assembly  600  and the cartridge retrieval mechanism  122 . These ribbon cables  710   a - 710   b  may carry control commands to a gripper motor  712  and to carry data to and from an optical positioning sensor  714  on the cartridge retrieval mechanism  122 .  
         [0036]     As described above, the cartridge transport assembly  120  may include a robotic controller  140 , which receives positioning instructions via an umbilical data/power cable  142  from the library controller  104 . This robotic controller  140  is incorporated into the z-axis assembly  150  and travels with the z-axis assembly  150  up and down the y-axis during operation.  
         [0037]      FIG. 8  is a schematic diagram of a robotic controller  140 , in accordance with embodiments of the present invention. The robotic controller  140  may include a robotics processor printed wiring assembly (PWA)  802 , which can perform many of the tasks normally executed by the library controller in conventional storage library systems. In these embodiments, these tasks are offloaded from the library controller and are instead handled by the robotics processor  802 . The robotics processor  802  may be configured to control the positioning of the cartridge retrieval mechanism  122  in various ways. In some embodiments, the library controller  104  may receive an I/O request from the host  102  and will determine which tape cartridge  114  will need to be retrieved and loaded into a media drive  112  in order to fulfill the I/O request. The library controller  104  may process the high level I/O request to produce a low level command to the robotic controller  104 . For example, the library controller  104  may provide specific motor encoder instructions to be transmitted to the individual actuators in the cartridge transport assembly  120 .  
         [0038]     In other embodiments, the library controller  104  may provide higher level instructions that need to be further processed by the robotics processor  802  in order to generate the motion profiles. For example, the library controller  104  may issue a command to retrieve the tape cartridge  114  from a particular slot number in the library system  100 . The robotics processor  802  receives the command and, given the current position of the cartridge retrieval mechanism  122 , determines the appropriate motion profiles to issue to each actuator in order to position the cartridge retrieval mechanism  122  to retrieve the tape cartridge  114  from the desired slot number.  
         [0039]     In yet other embodiments, the robotics controller  140  may be configured to respond to high level commands from the library controller  104 . This command may be, for example, as simple as “INVENTORY”. Upon receiving the INVENTORY command, the robotics controller  140  may be configured to sequentially position the cartridge transport assembly  120  adjacent to each of the slots  116  in the library system  100  to detect the presence and identity of each cartridge  114  loaded in the system  100 . The complete inventor can then be returned to the library controller  104 .  
         [0040]     In yet other embodiments of the present invention, the robotics controller  140  may be further configured with a power supply for receiving power of a particular voltage via the umbilical  142  and converting that power to the appropriate voltage for each of the various motors in the cartridge transport assembly  120 . For example, in one embodiment, the library controller  104  transmits 55 V DC current over the umbilical data/power cable  142  to the robotics controller  104 . The robotics controller  104  includes a power supply which converts this high voltage 55 V DC current to the logic and drive voltages utilized by the various motors and logic components on the cartridge transport assembly  120 . These voltages can be, e.g., 12 V, 5 V, 3 V, 1.8 V, etc. In other embodiments, the current transmitted over the umbilical cable  142  may be an AC current, and the robotics controller  140  may convert the AC current to the drive voltages utilized by the various actuators on the cartridge transport assembly  120 .  
         [0041]     By providing a single high voltage power supply on the robotics controller  140 , the number of conductors on the power cable connecting the power supply to the power-utilizing component (e.g., z-axis motor  168 ) can be greatly lessened than it would if all the power supply voltages were provided from the library controller  104 . In addition, the amount of EMI shielding used on the umbilical cable  142  can be reduced, due to the much lower DC motor currents induced on the cable.  
         [0042]     In accordance with embodiments of the present invention, the operation of the cartridge transport assembly  120  is as follows. The library controller  104  receives an I/O command from a host system  102  which requires that data be either written to or read from a tape cartridge  114 . Accordingly, the cartridge transport assembly  120  may be instructed to retrieve the tape cartridge  114  from one of the storage slots  116  and insert the cartridge  114  into one of the desired media drives  112 . The library controller  104  transmits one or more instructions to the robotics controller  140 . As described above, the robotics controller  140  may receive the high level commands from the library controller  104  and determine the optimal series of movements in each of the degrees of freedom of the cartridge transport assembly  120  in order to position the cartridge retrieval mechanism  122  in the desired position.  
         [0043]     For example, the robotics controller  140  may be instructed to retrieve the cartridge located in slot  116   a  and load it into the media drive  112   a  (as shown in  FIG. 2 ). In order to perform this function, the cartridge retrieval mechanism  122  must be positioned adjacent the slot  116   a . This can be done by transmitting a control signal to the encoder for the y-axis actuator  152  to position the cartridge retrieval mechanism  122  at the appropriate position along the y-axis, transmitting a control signal to the encoder for the z-axis actuator  168  to position the cartridge retrieval mechanism  122  at the appropriate position along the z-axis, transmitting a control signal to the encoder for the x-axis actuator  518  to position the cartridge retrieval mechanism  122  at the appropriate position along the x-axis, and transmitting a control signal to the encoder for the rotary motor  604  to rotate the cartridge retrieval mechanism  122  such that the gripper fingers  704  are properly oriented to grasp the cartridge  114  in slot  116   a . The robotics controller  140  may issue these signals to perform the positioning in the four degrees of freedom in parallel, in series, or various combinations thereof. The robotics controller  140  may also utilize feedback from optical signals received from the optical positioning sensor  714  in order to position the gripper fingers  704 .  
         [0044]     Once the gripper fingers  704  are positioned adjacent the cartridge  114 , the robotics controller  140  may issue control signals to the extension motor  718 , thereby causing the gripper fingers  704  to extend towards the cartridge  114 . The robotics controller  140  may then issue the control signal to actuate the stepper motor to cause the gripper fingers  704  to grasp the cartridge  114 .  
         [0045]     After the cartridge  114  is secured by the cartridge retrieval mechanism  122 , the robotics controller  140  may issue a control signal causing the extension motor  718  to withdraw the gripper fingers  704 , thereby extracting the cartridge  114  from the slot  1116   a . The robotics controller  140  then issues control signals to reposition the cartridge retrieval mechanism  122  in the x-direction, y-direction, z-direction, and rotationally, in order to position the cartridge  114  adjacent the load port for the media drive  112 . The extension motor  718  may again be activated to extend the gripper fingers  704  to insert the cartridge  114  into the media drive  112 .  
         [0046]     Embodiments incorporating the above-described cartridge transport system may achieve numerous advantages over existing designs. For example, embodiments of the present invention may facilitate the verification, testing, and repair of cartridge transport assemblies by enabling the cartridge transport assembly to be more thoroughly tested without needing to be installed in a library enclosure. In other storage libraries, the cartridge transport assembly may comprise a vertical support member mounted in the library enclosure. A gripper assembly may be mounted to the support member and configured to travel up and down the support member to provide movement in the y-direction. The vertical support member is mounted on rails along the top and bottom of the library enclosure to enable the entire support member and gripper assembly to move along the rails in the x-direction. Because the library enclosure is integral with the x-direction positioning of the cartridge transport assembly, if there is a failure in the cartridge transport assembly, the entire library must be tested and repaired. Alternatively, if the gripper assembly is decoupled from the vertical support member for testing, the x-direction movement cannot be tested. If the y-direction actuators are provided on the gripper assembly, then the y-direction movement can be partially tested without mounting the gripper assembly on the support member. However, in order to test the complete range of motion of the cartridge transport assembly, an extensive setup of the vertical support member and the x-direction guide rails must be provided.  
         [0047]     In contrast, with embodiments of the present invention, positioning of the gripper assembly in the x-direction and the z-direction in addition to rotational positioning and gripper extension may be provided on a single subassembly  300 . In addition, the y-direction actuators are also provided on the subassembly  300 , leaving the fixed support member  132  as the only external positioning component. Therefore, the subassembly  300  may be thoroughly tested in the laboratory prior to assembly in the storage library system  100 . This can enable a manufacturer to verify proper operation before proceeding with subsequent manufacturing and assembly steps. This process of testing prior to integration can help to reduce manufacturing costs by identifying and repairing failures earlier in the manufacturing process.  
         [0048]     This testing may further be facilitated by having the robotics controller  140  provided in the subassembly  300 . Because the robotics controller  140  is configured to receive high level commands, it may not be necessary to have an entire library controller  104  in the test laboratory to issue positioning commands to the cartridge transport assembly  120 . These commands may be issued to the robotics controller  140  from a personal computer or simplified control system provided in the test laboratory.  
         [0049]     The foregoing description of the preferred embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. For example, in the above-described embodiments, the data is transmitted from the library controller  104  to the robotics controller  140  via the umbilical cable  142 . In other embodiments, other methods of passing data between the two controllers may be used, such as, e.g., a wireless data connection.  
         [0050]     The various actuators described herein may be implemented in various forms to effectuate relative movements between the various components of the cartridge transport assembly, in accordance with embodiments of the present invention. In particular, various combinations of motors, gears, pulleys, and other actuators may be used. In addition, the specific types of motors and connections described herein are for exemplary purposes only and, in other embodiments, may be replaced with suitable motors and connections as would be understood by one of ordinary skill in the art.  
         [0051]     It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples, and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.