Elevator Example

Elevator Example 1

To show the basic concepts of discrete event systems, we have included here a simple elevator example: This elevator systems demonstrates events, CPU-time/virtual-time and the future event set. Twenty employees are generated to arrive at random times varying between 3 and 20 seconds. The employees will then (if needed) stand in line in front of the elevator, waiting for the elevator to bring them to their destinationfloor. The elevator itself can carry a maximum of 5 employees and will depart when it's full or when no employee arrives within 10 seconds after the last one. The time it takes for the elevator to bring the employees to their floors, depends in this case only on the number of employees inside and can vary between 26 and 40 seconds.

The events that will take place during the simulation are the following:

An employee arrives in the queue
An employee enters the elevator
The elevator departs
The elevator arrives

Furthermore, two of the previous events can be predicted beforehand and that gives us the following future events:

An employee will arrive in the elevator system (at a given time)
The elevator will arrive (at a given time)

In the example at the bottom of this page we use a list to show the (future) events. In this list a blue bar shows the last event that took place, beneath the blue bar the future events are listed and above the blue bar the events are listed.

The simulation will stop when 20 employees have entered the elevator and the the already discussed CPU- and virtual-time will be shown in the textfields. To interrupt the simulation at any time simply push the 'Stop' button (and push 'Resume' to continue).

If you want to simulate faster without graphics, you can activate the 'Fast simulation' checkbox.

Back to Lesson 1 Next Elevator Simulation