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| Introduction | |
| Build a New Model | |
| The Clock | |
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Process and Arrival Times |
| Resources | |
| Assembling Work | |
| Results | |
| Graphics | |
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Glossary |
This Glossary is a simple introduction to some of the commonly used terms in SIMUL8. Use SIMUL8's Help to find more detail.
The SIMUL8 Clock is a vital element of every simulation. There are 2 main reasons for this:
- The clock allows the SIMUL8 user to "see" what the model is doing during each simulated time period by displaying a clock face.
- The clock schedules when events will happen to work items, like when jobs start, when they stop, and when a new item will enter the simulation. It creates a list of when these will take place, and this forms the core of the simulation
An Event, in simulation terms is when something happens. For example, starting work on a new job is an event, stopping work is an event, but actually doing the job is not. The Event is the start or stop element only, not what comes in between. It could be said that an event occurs when there is a change of state in one of the elements that make up the model.
Graphics let a viewer see what's going on in a simulation, vital of course for presentation purposes, but equally important so that as a model is being built it can be built accurately, and any errors found easily.
For presentation purposes SIMUL8 simulations can easily be animated, so that movement of work items can be shown, and also so that stores and machinery (or other places where jobs take place) can be achieved by simple mouse clicks
Found in Work Entry Points, the Inter Arrival Time is simply the average time between new work items being pushed into the system
When a new work item is generated into a Simulation, it is exactly the same as every other item. Labels let you tell items apart by attaching a Label, or property, to the item, and then giving the Label a numeric or Text value.
An example of a Label would be Age. Everyone has an age, but ages differ form person to person. Part Number is another example of a Label. Each part has a part number that may be different.
An Object is a generic term used to mean something that has been placed on the simulation window. Any number of Objects can exist in SIMUL8, in virtually any combination.
Random Numbers allow a simulation to behave in a random way, within the limits you set. This means they can exhibit real life forms of behavior, based around a Probability Distribution
Random Numbers can be best described by example. Take, for example a simple dice. There is a 1 in 6 chance of each side of the dice coming up following a throw - some people would call this an equal probability of being sampled. Anyone who has played a board game knows that it doesn't seem like an equal chance of any side coming up, but of you throw a dice often enough you'll see that in the long term there is a 1 out of 6 chance of any side coming up.
SIMUL8 random numbers are organized into 30,000 individual sets. This means that you have a "virtually" unlimited set to draw from. Each Object in a simulation can use a different Distribution (like Normal or Exponential) meaning that you can get as close as possible to real life conditions. The default in SIMUL8 is to use the same set of random numbers over and over again, with new streams available by clicking the Dice button
The Reset button returns the simulation to its starting conditions, clearing out statistics and setting all randomness back to a repeatable baseline.
A Resource is a SIMUL8 object that allows jobs to take place. You don't need to include resources in a simulation, but if you do then they act as a constraint or switch when attached to work centers.
Resources can have shift patterns, so that staff availability can be simulated, and can represent staff or other key pieces of equipment that have limited availability.
The purpose of a simulation is to produce data. Each Object in SIMUL8 collects results about itself. Results can be added to a Summary page by Right Clicking over the desired item.
The Results Collection Period is the amount of time the simulation will run for while collecting results. This is expressed in the time units the model is working in, so if the model works in minutes, the SIMUL8 default, then 1 day equals 1440 minutes and this is the figure to be entered in the Results Collection Period dialog.
Routing Arrows are the arrows that connect objects in SIMUL8. They are 1 way arrows only, so if a 2 way arrow is required then redraw the arrow in the opposite direction. Routing Arrows act like railway lines - if an arrow isn't there then the route doesn't exist. Draw or amend arrows by using Route Drawing Mode.
When SIMUL8 is in Route Drawing mode you can add or delete Routing Arrows between objects. To add a Routing Arrow select Route Drawing Mode form the toolbar, and click on the object the arrow is to start from. The cursor will change image. Now move the cursor to the destination object and click again. When the cursor is over a valid destination it will again change image, indicating that an arrow can be inserted.
Run is the term used to describe a simulation as it is performing calculations and producing results. SIMUL8 simulations are run simply by pressing the Run button on the toolbar.
The Simulation Window is the SIMUL8 workspace. It's the area that you can drop objects like work centers and stores onto.
A Storage Area is a SIMUL8 objects that receives work items, and will hold them until another object, usually a work center, pulls them out. Storage Areas are inert objects, they don't push or pull items, and can be limited to a maximum size.
SIMUL8 templates are pre built simulations. They are normally configured through a simple interface, like a spreadsheet with buttons and other controls, so that the user doesn't need to know anything at all about simulation.
Each time a model is run it will use the same random numbers, and produce the same results - unless some change has taken place in the structure of the simulation. A Trial runs the simulation multiple times, automatically changing Random Numbers after each run and producing a slightly different result. SIMUL8 will then produce results in the form of Average, Upper and Lower ranges so that the effect of the randomness operating within the simulation can be appreciated.
The result of running a Trial is that the statement "on 95% (or 90%) of occasions a result between the upper and lower ranges is expected" can be made.
Visual Logic is SIMUL8's internal logic building language. It can be driven by events (whenever something happens in the simulation, like work starting on a job or work finishing) or by things like the Reset button being pressed, or a certain time being reached.
Visual Logic allows Conditional logic to be used, for example "if storage area A has more than 10 parts in it then increase the number of operators to 2, otherwise set the number of operators to 1" relies on conditions. This can be captured by Visual Logic.
Other significant things like reading from a table or importing data from a spreadsheet can also be accomplished with Visual Logic.
Work Centers are the driving force in a SIMUL8 simulation. They have a Pull and Push element, meaning they will attempt to pull work in from any source, and after processing it they will push it to the next valid destination.
Work Centers have a Processing Time, derived form a distribution, and may have rules used to control where work items are pulled form or pushed to
Work Items are pushed into a SIMUL8 simulation through Work Entry Points. The rate that they are pushed in at is based on the Inter arrival Rate set. This rate can be turned off, and parts supplied whenever demanded by a Work Center if necessary, by ticking the Unlimited Arrivals option.
The last point in a Work Items route through a simulation is normally a Work Exit Point. These points normally represent the end of the area of interest in the simulation, and simply collect statistics about Time in System and numbers of items that reached the work Entry Point.
A Work Item is the object that flows through a simulation. Work Items are all the same when they are first generated, but can be identified and made unique, through the use of Graphic images or Labels.
This Glossary is a simple introduction to some of the commonly used terms in SIMUL8. Use SIMUL8's Help to find more detail.