Java Reference
In-Depth Information
Table 9.2
Constant and random delay
Constant delay
Random delay
Piece
Time
Piece
Time
Screw
1 200
Screw
1 398
Nut
2 000
Nut
2 860
Screw
2 400
Screw
3 026
Screw
3 600
Screw
4 585
Nut
4 000
Nut
4 936
Screw
4 800
Screw
6 137
Nut
6 000
Nut
7 614
Screw
6 000
Screw
7 839
Screw
7 200
Screw
9 090
Nut
8 000
Nut
10 477
Screw
8 400
Screw
10 807
The event lifetime is random and is evaluated according to the expression
coded in class
PieceSource
. The delay between two nut pieces is between
2000 and 3000 milliseconds, while the delay between two screw pieces is
between 1200 and 1800 milliseconds (see Table 9.2 right side).
■
9.5
■
Prototype 2: Work cell simulator
The second prototype implements the finite state automata that describe the
behaviour of all the work cell subsystems. We will not implement the full set
of requirements specified in Section 9.1. In fact, we will leave a few syn-
chronization aspects out of this prototype in order to give the reader the
opportunity to complete them as exercises. This prototype visualizes the
evolution of the simulation in a graphical user interface.
9.5.1
Analysis
As described in Section 9.2, the work cell is composed of the inventory
system, the drill, the cutter, the transport and the assembler. We model the
inventory system with three distinct processes: two sources of pieces that
supply nuts and screws to the machines' input buffers and a sink that con-
sumes bolts from the assembler's output buffer. Every work cell subsystem
behaves as a finite state machine. The AGV has deterministic transport and
load times, while the other subsystems have stochastic processing times that
can range in a given interval (e.g. between the maximum value and half of it).
The work cell subsystems synchronize their activities by exchanging
events. Table 9.3 lists the event types that the work cell subsystems can
raise and listen to.
