TReX's Examples

The Lift Controller

Description of the example

This example describes the interaction between the motor of a lift and one of its control panels. The two elements are modeled by extended finite-state machines and communicate through two counters (global integer variables). The following figure represents the behavior of the lift.

The global variable c stores at any time the current floor as the variable g stores the goal (the floor that the lift must reach). The motor waits for an order from the control part. This order should be up one floor (c := c+1) or down one floor (c := c-1). The order is represented by the variable a which is updated correctly according to the goal g searched by the control panel. After that, the control program compares the values of c and g until they are equal and finally chooses a new goal floor arbitrarily. The number of floors is parametrized by the parameter N.

Experimental results

We have analysed the system in two ways:

by instaciating the parameter N with 2, 3, 4, 5, 10, 100, 1000000.
by keeping parameter.

The following table gives the memory consumed and the time spent for each system version. (We used a Sun Sparc 10 with 1Go of memory.)

Version	Memory (Mo)	Time (s)	Reachable Conf.
2	6.3	0.06	lift_2.scf
3	6.3	5.98	lift_3.scf
4	6.4	5.33	lift_4.scf
5	6.4	6.72	lift_5.scf
10	6.4	6.45	lift_10.scf
100	6.4	6.64	lift_100.scf
1000000	6.4	6.51	lift_1000000.scf
N	6.5	7.91	lift_infinite.scf

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