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Browse Prior Art Database

Locating Cartridges in Dual-Ported Bins of Automated Storage Libraries

IP.com Disclosure Number: IPCOM000112817D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 114K

Publishing Venue

IBM

Related People

Dang, CH: AUTHOR [+2]

Abstract

Disclosed is a method for locating cartridges in dual-ported bins of a robotic library having two dual-gripper pickers which can act concurrently.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

Locating Cartridges in Dual-Ported Bins of Automated Storage Libraries

       Fig. 1  Bi-directional Cartridge Secured by Two Detents

      Disclosed is a method for locating cartridges in dual-ported
bins of a robotic library having two dual-gripper pickers which can
act concurrently.  Having two (m=2) concurrent pickers capable of
accessing any cartridge reduces the average response time of the
library to mount a cartridge, eqn.  (1), by squaring the picker
utilization U.  Since the utilization of any unsaturated resource is
less than one, squaring the picker utilization reduces its magnitude,
hence lessening the average response time in eqn.  (1).

           m
 Rt(m pickers) = St / (1 - U)                           (1)
 Where:  Rt  = average picker response time in seconds,
         St  = picker service (cycle) time in seconds,
         m   = number of pickers (1 or 2) acting concurrently
               in one library box,
         U   = picker utilization, 0 < U < 1.

      In eqn.  (1), the picker utilization U is the ratio of the
library workload and the maximum workload capable by the m pickers.
This utilization is defined in eqn.  (2).  In eqn.  (2), we define
the maximum workload of the m pickers in a library box, Wmax, to be
the number of pickers m times 3600/St.  The 3600 term comes from
there being 3600 seconds per hour.

U = W/Wmax                                             (2)

Where:  W    = customer workload in fetches per hour

        Wmax = m*(3600/St) = maximum fetches per hour

      In order that the two independent pickers operate complete
concurrently, we advocate that one picker operate on each side of a
wall of cartridges.  The cartridges are bi-directional, meaning that
either end can be grasped by the grippers of a picker and inserted
into a optical drive.  So that each of the two pickers has access to
all of the bi-directional cartridges, the cartridges must be stored
in bins which are open at each end, or dual-ported.  These
dual-ported bins are different from today's bins which are open at
only one end, or single-ported.  Our bi-directional cartridge is
secured in the dual-ported bins via spring-loaded detents, Figs. 1
and 2.

      In both Figs. 1 and 2, top views are shown of the
bi-directional cartridge 10 enclosing one optical disk 20.  This
cartridge has two pairs of opposing slots 11 to allow gripping of the
cartridge at either end by the grippers of a robotic picker.  The
cartridge door 12 extends across the entire length of the cartridge.
Door 12 slides laterally to expose the hub 21 of the optical disk to
the spindle motor of the I/O device and to expose the optical
recording surface 22 to the write/read laser(s).  There are also two
pairs of slots 13 and holes 14 for seating the cartridge in I/O
devices.  The symmetry of cartrid...