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Understanding Simio Modeling and Experiments
Aug 19, 2024
Simio Module Introduction - Video 2 Notes
Overview
Continuation from the first video where an initial Simio model of a two-station flow line was built.
Objectives for this video:
Specify object properties for the model.
Introduce Simio experiment concepts.
Model Components
Source Object
: Creates entities.
Servers
: Process entities.
Sync Object
: Tabulates results and destroys entities.
Arrival and Service Rates
Customer arrival rate:
25 per hour
.
Service times:
Server 1
: 2 minutes on average.
Server 2
: 1.71 minutes on average.
Reality Check
:
Service rates:
Server 1: 30 per hour (60 min / 2 min).
Server 2: 35 per hour (60 min / 1.71 min).
Arrival rate (25) is less than service rates (30 and 35), indicating the system is nominally stable.
Distribution of Times
Arrival and service times are assumed to follow an
exponential distribution
:
Arrival time mean:
2.4 minutes
.
Service time mean for Server 1:
2 minutes
.
Service time mean for Server 2:
1.71 minutes
.
Use of
Simio Expressions
in modeling:
Random Exponential
: Expression
random.exponential(mean)
is utilized.
Setting Object Properties
Source Object (Source One)
:
Set arrival time property to mean of 2.4 minutes.
Server Object
:
Set processing time property for Server 1 and Server 2 using the Expression Builder.
Server 1:
random.exponential(2)
.
Server 2:
random.exponential(1.71)
.
Running the Model
Updated parameters were applied to the model.
Results are similar to previous runs, maintaining system stability.
A verification method checks if around
600 entities
flow through the system over
24 hours
.
Expected: Arrival rate (25) * Time (24) = 600.
Simio Expressions Overview
Common distributions available in Simio:
Uniform, Triangular, Exponential, Normal, Log Normal.
Expression Builder
: Assists in building expressions by providing tooltips and sublists for ease of use.
Simio Experiments
Transition from interactive modeling to simulation experiments:
Set the ending time to a
run length
of
240 hours
.
Observations should be around
6000
for this duration.
Explanation of
Predictable Randomness
:
The model yields consistent results due to the random number generator starting at the same point each run unless altered.
Running Experiments
Created a new experiment in Simio with default settings (10 replications).
Results show statistical summaries:
Minimum, Maximum, Average of observations across replications.
Conclusion
Next video will focus on using experiments for interpreting results.
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Full transcript