Page 64 - DCAP601_SIMULATION_AND_MODELING

Simulation and Modelling

Notes
Figure 4.2: Approaches to Discrete Event Simulation

There are also three approaches to describing the discrete simulation, see the Diagram above
[Pidd, 1992].
1. Event: This approach describes an instantaneous change, usually from a stop event to a
start event. This is the most common one used, easy to understand and efficient and is
acceptable to implement.
2. Activities: Represents duration. Essentially groups a number of events in order to describe
an activity carried out by an entity e.g. a machine loading. This approach is easy to
understand and to implement but is not efficient.
3. Process: These approach groups activities to describe the life cycle of an entity e.g. a
machine. This is less common and more difficult to plan and implement, but is generally
thought to be the most efficient.

Tasks Define the most common and easy to understand approach used in
describing the discrete simulation.

More Common uses of DES

Diagnosing Process Issues

Simulation approaches are particularly well equipped to help users diagnose issues in complex
environments. The Goal (Theory of Constraints) illustrates the importance of understanding
bottlenecks in a system. Only process ‘improvements’ at the bottlenecks will actually improve
the overall system. In many organizations bottlenecks become hidden by excess inventory,
overproduction, variability in processes and variability in routing or sequencing. By accurately
documenting the system inside a simulation model it is possible to gain a bird’s eye view of the
entire system.

A working model of a system allows management to understand performance drivers. A
simulation can be built to include any number of performance KPIs such as: worker utilization,
on-time delivery rate, scrap rate, cash cycles, and so on.

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