ESI 6529 Digital Simulation Techniques

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ESI 6529 Digital Simulation Techniques

• Lecture 6

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STATION SUBMODELS

• A large simulation model can be decomposed into
  separate submodels whose size and complexity are
  more manageable.
• A submodel may represent a station (a collection
  of blocks describing an area where entities are
  processed). A single generic station submodel can
  be used to represent many workstations which have
  the same composition. Each station submodel has a
  unique station name or station number.

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Station Visitation Sequence

• Many simulation models involve multiple entity
  types and multiple stations. Each entity type may
  visit the stations in a different order. SIMAN
  allows a separate station visitation sequence for
  each entity type. The following special purpose
  attributes are defined in SIMAN to assists
  automatic flow routing.
• Station Attribute M It stores the current
  station number for each entity. Initially, M 0
  for each new entity. The value of M is
  automatically updated to the number of the
  destination station when an entity is transferred
  using a ROUTE Block.
• Sequence Set Number NS It specifies a
  particular sequence for each entity type.
  Initially, NS 0 for each new entity.
• Stage Index IS It indicates how many stages the
  entity has advanced into a given sequence.
  Initially, IS 0 for each new entity.

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EXAMPLE 5 A JOBSHOP PROBLEM

• A four-machine jobshop processes three job
  types. Each job type has its own station
  visitation sequence, as shown in the table below.
  
• The time between job arrivals is exponentially
  distributed with a mean of 8 minutes. 40 are
  type 1 jobs, 35 are type 2 jobs, and 25 are
  type 3 jobs. The processing times are
  triangularly distributed. The individual job
  routings and processing time parameters (in
  minutes) are given on the next page.
• Collect statistics on the machine utilization,
  number of jobs waiting in each queue, the overall
  flowtime, and the flowtime for each individual
  job type. Run the simulation for one 8-hour
  shift then clear the statistics and run for 10
  consecutive 8-hour shifts.

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