Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
1999-01-19
2001-04-17
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C700S218000, C700S259000, C414S275000
Reexamination Certificate
active
06219313
ABSTRACT:
TECHNICAL FIELD
This invention relates to a system and method for adaptively engaging cartridges stored in an automated cartridge library.
BACKGROUND ART
Automated cartridge libraries store and manage large numbers of data cartridges, typically containing magnetic tape on which data is recorded. These libraries are comprised of arrays of storage cells, each cell typically being formed to contain a single data cartridge. The arrays each hold a plurality of data cartridges, and each data cartridge typically has some kind of identifying information, such as a label or bar code. A robot arm, having an optical system for selecting cartridges, is operable to locate a selected storage cell and use an associated reach mechanism to retrieve a data cartridge from the selected cell.
The storage cells are preferably constructed with exact dimensions that correspond to the size of the cartridges, since the cartridges must be positioned in a precise manner if the robotic arm is to grasp them correctly. However, mechanical frame and robot arm tolerances are large enough to cause significant variation in the cell depth within a given library, where cell depth is defined as the distance from the robot arm to the face of a cartridge stored in a particular cell. As a result, it is difficult for the reach mechanism to always extend a specific distance and be assured of reliably engaging a cartridge.
A few prior art systems have addressed the problem of cell depth variation. For example, U.S. Pat. No. 5,040,159 issued to Oliver et al. discloses an optical disk handling system which uses a controller to simultaneously control the position of the reach mechanism and to monitor the force exerted by the motor via shaft encoders and motor current and voltage feedback. The reach mechanism is moved toward a cartridge until a specified force exerted by the motor is encountered, indicating engagement with the cartridge.
As another example, U.S. Pat. No. 5,790,338 issued to Kanai et al. discloses a library apparatus having a photosensor mounted to the tip of the reach mechanism. A robot controller calculates the position of the selected cell and moves the reach mechanism to the calculated position in a coarse control. Then, a target element relating to the selected cell is detected based on the signal from the photosensor. A position recognition controller determines the displacement of the actual position of the selected cell from the calculated position, causing the robot controller to further position the reach mechanism in fine control.
Although the above systems do provide solutions to accommodating variable cell depth within an automated storage library, these solutions are overly complex, costly, and may be susceptible to failure.
Therefore, a need exists for a system and method of adaptive cartridge engagement that reduces the complexity of the control systems and associated software, eliminates the need for multiple sensors mounted on the moving reach mechanism which are subject to dust and flexible cabling failures, and increases the reliability of cartridge engagement by the reach mechanism.
DISCLOSURE OF INVENTION
Therefore, it is an object of the present invention to provide a system and method for cartridge engagement in an automated cartridge library that accounts for variance in cell depths within a given library.
It is another object of the present invention to provide a system and method for adaptively engaging cartridges that do not require complex control systems and software for reliable cartridge engagement.
It is a further object of the present invention to provide a system and method for adaptive cartridge engagement that do not require multiple sensors mounted on the moving reach mechanism.
It is a still further object of the present invention to provide a system and method of adaptively engaging cartridges that reduces product and assembly costs.
Accordingly, a method for adaptively engaging cartridges stored in cells within an automated cartridge library is provided. The method includes receiving a request to extend a reach mechanism of a robot arm to engage a cartridge stored in a selected cell. Next, the method includes initiating a move profile to extend the reach mechanism from a starting position toward the cartridge, where the move profile comprises a set of commanded positions and corresponding commanded velocities. The method further includes comparing a sensed position of the reach mechanism with the commanded position to determine a position error. The move profile is maintained until the position error exceeds an error threshold. The move profile is then terminated to obtain a final position of the reach mechanism, where the final position reflects a specific depth of the selected cell from the robot arm.
In a preferred embodiment, the method further includes determining if appropriate calibrated depth information is available for the selected cell. If not, a nominal move profile is initiated, where the nominal move profile is preferably selected from a plurality of profiles based on the properties of the cartridge to be engaged. If appropriate calibrated depth information is available for the selected cell, a calibrated move profile is initiated. The move profile preferably includes a constant stall velocity at which it is deemed safe to encounter the cartridge. Once the move profile is terminated, the method preferably includes determining if the final position is within a predetermined tolerance range. If so, the final position is saved in a database. If not, an error condition is preferably reported.
To carry out the method of the present invention, an automated cartridge library capable of adaptive cartridge engagement is provided. The library includes a housing having a plurality of storage cells located therein, where each cell is formed to hold a data cartridge. A robot arm is actuable within the housing, the robot arm having a reach mechanism for extending toward a selected cell. A motor is associated with the reach mechanism and is operable to extend the reach mechanism toward the selected cell. The motor has a position feedback sensor, such as a position encoder, for determining a sensed position of the reach mechanism. A library controller is operable to receive a request to extend the reach mechanism to engage a cartridge stored in the selected cell and to initiate a move profile to extend the reach mechanism from a starting position toward the cartridge, where the move profile comprises a set of commanded positions and corresponding commanded velocities. A motor controller in communication with the library controller is operable to compare the sensed position of the reach mechanism with the commanded position to determine a position error and maintain the move profile until the position error exceeds an error threshold. The motor controller is further operable to terminate the move profile to obtain a final position of the reach mechanism, wherein the final position reflects a specific depth of the selected cell from the robot arm. In a preferred embodiment, the library controller further includes a database for storing cell depth information.
The above objects and other objects, features, and advantages of the present invention are more readily understood from a review of the attached drawings and the accompanying specification and claims.
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Lane Terry L.
Ries James L.
Brooks & Kushman P.C.
Dinh Tan
Storage Technology Corporation
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