Chapter 7 Entity Transfer Dr. Jason Merrick. Simulation with Arena — Entity Transfer and Steady-State Statistical Analysis C7/2 What We’ll Do... Types

Chapter 7Entity Transfer

Dr. Jason Merrick

Simulation with Arena — Entity Transfer and Steady-State Statistical Analysis C7/2

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)


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


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


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


Transporter Concepts

• Carts, fork lifts, trucks, wheelchairs, people, …

• When entity is ready to go somewhere, it needs to be “picked up” and moved

• Use Transporters — “moveable” resources

• 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.


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)– Velocity (50 feet/min.)– Initial Position (accept Arbitrary default)– Options ... When Freed ... (Remain Where Freed)– Can have Schedules, Failures, Statistics– Picture for animation, including Ride Point

Consistency of time anddistance units across model


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.)


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


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


Distances for Transporters

• Define contents of the Distance Set Cart_Dst

• Distances (in feet) moved by parts:

– Blank cells: part movements that don’t occur

• Place 11 Distance modules (Transfer panel)– Beginning, Ending Stations– Member of what Distance Set?– Numerical Distance– Direction is implied — need not be symmetric

Units!!

Units!!


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


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)


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):


System Improvement (?): Replace Transporters with Conveyor

• Replace Transporters with a conveyor• Loop conveyor to follow main path, clockwise• Six entrance/exit points

– Load, Unload takes 0.25 minute– Each part is 4 feet per side, but want 6 feet of conveyor

space for clearance on corners

• Speed = 20 feet/minute• Distances:

OrderRelease

Cell 1

Cell 4

Cell 2

Cell 3

Exit System

24

21

39

39

21

24

Units!!


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


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)


Change Transporters to Non-Accum. 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)


Change Transporters to Non-Accum. 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


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


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

Documents

Chapter 7 Entity Transfer Dr. Jason Merrick. Simulation with Arena — Entity Transfer and Steady-State Statistical Analysis C7/2 What We’ll Do... Types