Modeling and Analysis of Picking
Warehouses Using Simio
Jeff Smith
Industrial and Systems Engineering
Auburn University
jsmith@auburn.edu
Simio Learning Resources
• Videos (http://www.simio.com/videos)
• Publications
– Introduction to Simio (Included PDF and downloadable seven-part video
series)
– Joines, J.A. and Roberts, S.D., Simulation Modeling with SIMIO: A
Workbook
– Kelton, W.D., J.S. Smith, and D.T. Sturrock Simio & Simulation: Modeling,
Analysis, Applications
Key Simio Object Concepts
Object: Defines data, logic, behavior, view, events, and
interaction with other objects.
Model: An object that is executable.
Project: A collection of models/objects.
A project can be loaded as a library.
Properties: Static inputs to an object.
States: Changeable values associated with an object
Events: Supports communication between objects.
Fired when key things happen.
Resource: Constrains the system. Any object (even an entity)
may be a resource.
Entity: A dynamic object that may move through system
Transporter: An entity that can “work on” or carry other entities.
Vehicles and Workers are entities (and resources).
Simio User Interface
•
•
•
•
•
•
Files Menu
Ribbons
Project Tabs
Libraries
Project
Current
Model
• Properties
• Facility View
Standard Library
Source: Generate entities of a specified type and arrival pattern.
Sink: Destroy entities.
Server: Capacitated process, such as a machine.
Workstation: Capacitated process, includes setup, process, tear-down.
Combiner: Batches entities with a parent entity (e.g., pallet).
Separator: Splits batches or copies entities.
Resource: Seized/Released by objects.
Vehicle: Fixed route or on-demand pickups/drop-offs.
Worker: Moveable resource, for stationary and non-stationary tasks.
BasicNode: Simple intersection, fixed object input.
TransferNode: Change destination/get rides, fixed object output.
Connector: Zero travel time.
Path: Entities independently move at their own speeds.
TimePath: Entities complete travel in a specified time.
Conveyor: Accumulating/non-accumulating conveyor devices.
Simple Flow Line
Arrive
Server 1
Server 2
Depart
Object Hierarchy - The Family of “Objects”
Object Instance
Object
Definition
Object Runspace
(Realization)
Simple Flow Line - Details
Arrive
Server 2
Server 1
Tandem Queueing Model
Arrival Rate
Mean IAT
Mean IAT
Service Rate
Mean ST
Mean ST
r
L
W
25.00 entities/hr
0.04 hr
2.40 min
Server 1
30.00
0.03
2.00
0.83
5.00
0.20
Server 2
35.00 entities/hr
0.03 hr
1.71 min
0.71
2.50
7.50 entities
0.10
0.30 hrs
Depart
Editing Object Properties
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Displayed in Properties Window
Defined by object builder
Integers, Booleans, rules, expressions, …
Expression editor (down arrow at right):
“Top 10” Expressions
• X (a number – integer or real)
• Random.Exponential(mean)
• Random.Triangular(min, mode, max)
• Random.Uniform(min, max)
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ServerName.Capacity.ScheduledUtilization
ServerName.InputBuffer.Contents
DefaultEntity.Population.TimeInSystem.Average
DefaultEntity.Population.NumberInSystem.Average
SinkName.InputBuffer.NumberEntered
SinkName.TimeInSystem.Average
Simple Flow Line – Expressions
• Source1
– Interarrival Time: Random.Exponential(2.4)
• Server1
– Processing Time: Random.Exponential(2)
• Server2
– Processing Time: Random.Exponential(1.7)
Simple Flow Line - Experiment
Arrive
Server 1
Server 2
Depart
Simple Flow Line – Responses
Arrive
Server 1
Server 2
Depart
Simple Flow Line – SMORE Plots
Arrive
Server 1
Server 2
Depart
Simple Flow Line – Throughput Response
Arrive
Server 1
Server 2
Depart
Buffers and Referenced Properties
Arrive
Server 1
Server 2
Depart
Buffers and Referenced Properties
Arrive
Server 1
Server 2
Depart
Buffers and Referenced Properties
Arrive
Server 1
Server 2
Depart
Simple Picking Warehouse
• Pickers
– Walk speed: 1 meter/sec
– Pick time: Uniform(10, 20) sec
– Pack time: Triangular(.5, 2, 3.5) min
• Fork Lift
– Travel speed: 1.5 meters/sec
– Load time: Uniform(5, 10) sec
– Unload time: Uniform(20, 30) sec
Racks
45 m
30 pick positions in each
rack (approximate using
15 evenly spaced
locations)
Decisions:
• Number of pickers
• Number of pack stations
• Number of forklifts