Transcript Simulation with Arena - Virginia Commonwealth University

Chapter 7
Entity Transfer
Dr. Jason Merrick
What We’ll Do ...
• Types of Entity Transfers
• Resource-Constrained Transfers
• Transporters (Model 7.1)
• Conveyors
– Non-accumulating (Model 7.2)
– Accumulating (Model 7.3)
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/2
Types of Entity Transfers
• Connect
– Zero-delay
– Connection graphic vs. module Labels (no graphic)
• Route
– Non-zero-delay — constant, r.v., expression
– Stations, animated Routes
– Fixed routes vs. entity-dependent Sequences
• Connect and Route both assume:
– No limit on number in transit at a time
– Entities have their own feet
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/3
Resource-Constrained Transfers
• Limit total number of entities in transit at a time
– Telecommunications (number of packets)
– Logistics (number of vehicles)
• Entities still have their own feet
• Model via existing constructs — think creatively
– Model “space” on the “road” as a Resource
– Limit number of Units of this Resource
– Entity must Seize unit of “space” resource before beginning
trip, Release it at end of trip
• The “space” resource must be defined via a
Resources module if > 1 unit is required
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/4
Resource-Constrained Transfers
(cont’d.)
• Leave Data area of many logic modules
–
–
–
–
–
Tran Out… button
Seize a unit of the “space” resource
Priority (1 is highest, …)
If no units are free, entity must stay where it is
Option for Load Time
• Enter Data area of many logic modules
– Tran In… button
– Release the unit of the “space” resource
– Option for Unload Time
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/5
Transporter Concepts
•
•
Carts, fork lifts, trucks, wheelchairs, people, …
•
•
•
Use Transporters — “moveable” resources
When entity is ready to go somewhere, it needs to be
“picked up” and moved
Activities: Request, Transport, and Free
Two types of Transporters
– Free-Path (we’ll do)
• Travel time depends only on velocity, distance
• Ignore “traffic jams” and their resulting delays
– Guided (won’t do)
• AGVs, intersections, etc.
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/6
Creating Transporters
• Transporter data module (Transfer panel)
– Transporter name (Cart in our model)
– Number of Units (2)
– Free Path vs. Guided (accept Free Path default)
– Distance Set (accept default name Cart_Dst)
Consistency of time and
– Velocity (50 feet/min.)
distance units across model
–
–
–
–
Initial Position (accept Arbitrary default)
Options ... When Freed ... (Remain Where Freed)
Can have Schedules, Failures, Statistics
Picture for animation, including Ride Point
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/7
Requesting a Transporter
• Entity is done at a station, wants to move on
• Leave Data area, Tran Out… button
– Transfer Type: Request
– Transporter name (Cart)
– Rule (Smallest Distance)
• Applies when > 1 transporter is available
• Other options include Cyclical, Preferred Order, Random
– Priority of this request (1)
• Applies when demand for transporters exceeds supply
– Load Time (0.25 min.)
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/8
Entity Animation During the
Transporter Request Process
• Use an Arena Storage (similar to a queue)
– Place to store entity to make it show in animation
– Get at via animate subdialog in most logic modules
• Leave for Next Station area
• Select Storage radio button
• Storage name (accept default)
• Check Unstore box to decrement Storage statistics
– Produces animation object that looks like an animated
queue, except for default color (green)
• Can edit the storage animation just like a queue
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/9
Freeing a Transporter
• Entity has arrived at its next station on a
Transporter
• Enter Data area of this station, Tran In… button
– Select Free Transporter radio button
• Arena keeps track of which one, unit number
– Unload Time (0.25 min.)
• Transporter is now available, will position itself
according to Options ... When Freed … in
Transporter data module
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/10
Distances for Transporters
•
•
Define contents of the Distance Set Cart_Dst
Distances (in feet) moved by parts:
To
Cell 1
F
Order Release
r
Cell 1
o
Cell 2
m
Cell 3
Cell 4
•
37
Cell 2
Cell 3
Cell 4
Exit System
74
45
139
Units!!
92
55
147
45
92
155
118
– Blank cells: part movements that don’t occur
Place 11 Distance modules (Transfer panel)
–
–
–
–
Beginning, Ending Stations
Member of what Distance Set?
Numerical Distance Units!!
Direction is implied — need not be symmetric
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/11
Animating Transporter Movement
• Part of Distance module
• Beginning, Ending stations
– First, move module handle to appropriate physical location
(organize Distance modules — maybe many)
– Then, drag animation (stations, line) where they belong
• Dragging module handle also moves animation
• Use Shift+Drag on handle to leave animation where it is
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/12
Animating Transporter Movement
(cont’d.)
• Line characteristics — double-click on line
– # Points — then drag to correct animation position
– Maybe Rotate/Flip entity as it moves, line Colors
• Parking Areas for Transporters
– Double-click on double circle, Points…, Add, …
– Like a queue — Points vs. Line, Color, Rotate, Flip
• Drag around for realistic positioning
– There could be many animation stations for a single logical
station, but you should have only one parking area per
Station (delete others)
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/13
More Distances —
Empty Transporters
•
•
•
Above Distances incomplete — only for entities
Transporters must also move when empty
– In general, n(n - 1) distances need definition for network
with n nodes
– Some not possible — Order Release to Exit System
Additional distances to define (grayed):
To
Order
Release
Order
Release
Cell 1
Cell 2
37
74
Cell 4
92
129
55
147
F
Cell 1
155
r
Cell 2
118
139
o
Cell 3
71
92
129
m
Cell 4
34
55
92
139
100
121
158
37
Exit System
45
Cell 3
45
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
Exit
System
155
118
74
C7/14
System Improvement (?): Replace
Transporters with Conveyor
•
•
•
Replace Transporters with a conveyor
Loop conveyor to follow main path, clockwise
Six entrance/exit points
•
•
Speed = 20 feet/minute
Distances:
– Load, Unload takes 0.25 minute
– Each part is 4 feet per side, but want 6 feet of conveyor
space for clearance on corners
Cell 1
Units!!
39
Cell 2
24
21
Order
Release
Exit Sy stem
24
21
Cell 4
39
Cell 3
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/15
Conveyor Concepts
•
•
•
•
•
•
Entity to be conveyed must wait for space
Conveyor consists of cells
– Equal size, constantly moving
Entities might require multiple contiguous cells
Must define cell size; tradeoff involved:
– Small cells: accurate model but slow execution
– Large cells: less accurate but faster
Entities Access space, Convey, and Exit
Conveyor = series of linear Segments
– Each segment starts and ends with a Station
– Link to form loops, diverge points, converge points
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/16
Types of Conveyors
• Both travel in a single, irreversible direction
• Nonaccumulating: belt, bucket line, escalator
– Spacing between entities on it doesn’t change
– Entire conveyor stops for entity Access/Exit if Load/Unload
time is > 0
• Accumulating:
rollers, freeway
– Conveyor never stops moving
– If entity on it stops to Exit, other entities behind it are
blocked and bunch up (entities ahead of it keep moving)
– When blockage ends, blocked entities go on but maybe not
all at once (spacing requirements)
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/17
Change Transporters to NonAccum. Conveyors (Model 7.2)
• Modify Transporter model (Model 7.1)
• Define Variables Load Time, Unload Time
• Delete Transporter module
• Add Conveyor module (Transfer panel)
–
–
–
–
–
–
–
Name, Segment Set (define Segments later)
Velocity, Cell Size definitions
Initial status: Active
Max Cells Occupied (for “biggest” possible entity)
Type: Nonaccumulating
Entity Size: Cell Size
Conveyor statistics (check box)
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/18
Change Transporters to NonAccum. Conveyors (Model 7.2)
(cont’d.)
• Every Tran Out:
change Request to Access
– Conveyor = Loop Conveyor
– # of Cells to Access = 2
– Load Time = Load Time (Variable name)
• Every Tran In:
change Free Transporter to Exit
Conveyor
– Unload Time = Unload Time (Variable name)
• Replace Distances with Segments (need 6)
– Beginning, Ending Stations, Segment Set Name
– Define distances for simulation
• Units = actual length (in feet), not number of cells
– Place lines for animation
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/19
Digression: Manual Change of
Variable Values During Run
•
•
•
Increase Load Time and Unload Time to 2 during
run (see effect on conveyor stopping)
Pause the run:
– Suppose you do this at time TNOW = 301.885
Use Run Controller: Run/Command menu option or
301.885>ASSIGN Load Time = 2
301.885>ASSIGN Unload Time = 2
•
•
Resume the run: Close Controller window;
OK for demos; questionable for “real” runs
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/20
Change Conveyors to
Accumulating Type (Model 7.3)
• Modify Model 7.2 (with non-accumulating
conveyors)
• Conveyor module
– Change Type to Accumulating
– Specify Entity Size to 4 to allow entities to bunch up closer
than the 6 feet needed for an entity
• When a blockage is removed, entities will automatically re-space
themselves to consume 6 feet each
• Verify effect by increasing Load/Unload times
Simulation with Arena — Entity Transfer and
Steady-State Statistical Analysis
C7/21