Page 66 - DCAP601_SIMULATION_AND_MODELING

Simulation and Modelling

Notes Visualisation

Visual Interactive Simulation (VIS) has been available since the late 1970’s. Before this simulation
models were simply ‘black boxes’ - data going in and results coming out. In such a scenario
establishing credibility and confidence in the simulation model would not have been easy.

Using on-screen animations in a simulation model enables the status of the model to be viewed
as it progresses e.g. a machine that breaks down may change its color to red. This enables visual
cues to be passed back to the operator of the simulation model, so action could be taken.
Additionally, visualisation is useful in convincing management of the model’s credibility. For
example, in manufacturing if the Directors can see a visualisation of the production line with
widgets travelling down a conveyor belt, it would do more to sell the concept of the model than
a ‘black box’, churning out data.
With VIS the prime motivation is not only portrayal of the running simulation model but also
the interaction with it. For example, in using the above scenario, if the User wanted to see how
the production line would run with an extra machine then he could simply ‘plug in’ a machine,
at the appropriate position, and monitor the effect that this would have on the model.

Visual Interactive (VIM) takes this concept one stage further by allowing the model to be
created interactively. This allows a model to be constructed by dragging (with a mouse) ‘Entities’
(machines, parts etc.) from a library onto a frame. The entities could then be connected in the
desired order. Many of the advanced VIM simulation tools allow program code to be attached to
the entities and events, therefore making the model potentially more sophisticated and flexible.
Visualisation and simulation are extensively used in the training of operational staff, especially
where the training cannot be carried out in real life

Example: Shutting down the reactor of a nuclear power station after an
earthquake.

Object Oriented Simulation

Object Oriented techniques have been developed since the early 1960’s as a result of simulation
development (SIMULA). Until recently, the two were not coupled despite their original tandem
development. There are currently only a handful of Object Oriented simulation applications
available on a commercial basis; one of the most prominent of these is iBright Ltd’s ‘baseSim’.
The main difference between traditional program development and Object Oriented techniques
is the way in which the data and the program code are stored and manipulated. In traditional
software, the data and the program code are intermingled throughout the program, making
data security and integrity difficult to achieve (it is sometimes possible for one procedure to
cause knock-on effects as global data is changed). However, in Object Oriented simulation
software all data and procedures relating to a single entity (object) are encapsulated within an
object, with the object controlling its own interaction and data integrity permissions with other
objects. Clearly, the methods inside the object could cause similar knock-on effects, if poorly
implemented.

Object Oriented simulation tools, in particular iBright Ltd’s ‘baseSim’, are very powerful as they
make use of Object Oriented techniques such as modularity, class structure, inheritance, hierarchy
and polymorphism.

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