Justifying Simulation to Managers

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Justifying Simulation to Managers

• Jerry Banks

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Advantages
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Choose Correctly

• Test every aspect of a proposed change without
  committing resources
• Once the concrete has been poured, changes can be
  very expensive

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Time Revision

• Speed up or slow down phenomena so that they can
  be investigated
• Entire shift in minutes
• Hours to look at all events occurring during one
  minute of simulated activity

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Understand Why?

• Why did certain phenomena occur in the real
  system?
• Reconstruct the scene with simulation
• Difficult to accomplish with a real system

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Explore Possibilities

• Modify the model and observe the changes in the
  computer
• Without disruption of the real system

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Identify Constraints

• Discover bottlenecks
• Discover their cause

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Diagnose Problems

• Factory floor is so complex that it is impossible
  to consider all of the interactions

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Develop Understanding

• In many cases designs are based on thoughts about
  the way a system operates
• Simulation provides understanding about how
  systems really operate

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Visualize the Plan

• Animation shows the system in simulated operation
• Various angles
• Levels of magnification
• In 3-D

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Build Consensus

• Using simulation to present design changes
  creates an objective opinion
• Easier to accept verified and validated model
  results than a persons opinion

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Prepare for Change

• Answer what if? questions
• The possibilities are unlimited

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Wise Investment

• Cost of simulation is typically lt1 of the total
  investment
• Cost of a change or modification after
  installation is great

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Train the Team

• Models designed for training allow learning
  without the cost and disruption of on-the-job
  training

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Specify Requirements

• By simulating different capabilities for a
  machine, requirements can be determined

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Disadvantages
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Model Building Requires Special Training

• An art learned over time through experience
• Models constructed by two individuals will be
  different

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Interpreting Results Difficult

• Random outputs
• Is randomness the cause of differences?
• What statistical methods?

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Time Consuming and Expensive

• Two person weeks to two person years
• 6,000/week

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Used when Analytical Solution is Possible

• Use of queueing theory
• Use of inventory theory

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In Defense of Simulation
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Special Purpose Simulation Software

• Powerful constructs
• Conveyors
• Path Movers
• Bridge Cranes
• Kinematics
• etc.

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Output Analyzers

• Sophisticated capabilities
• Built-in
• Add-on
• Separate product

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Faster and Better

• Hardware
• Software

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About Closed Form Solutions

• Real systems are too complex

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End