GRAFCET and Petri Nets Outline Introduction GRAFCET - EPFL

Divider by 2
Examples of logical graphs
(1)
(2)
(3)
(4)
1
2
3
4
a
a'
a
a'
S
S
a
S
↑a
1
(1) ↑a
2 S
(2) ↑a
a
Controlling
system
S
a
m
G
(A)
(1)
(2)
(3)
1
2
3
↑m
D
b
G
a
D
(1) m pressed
b
2 Go to right
(2) Arrived on right
(B)
3 Go to left
1
(3) Arrived on left
(1) ↑m
2 V
1
(2) b
(1) ↑m.a
3
2 V
(3) a
(2) b
1
Real-Time Programming GRAFCET and Petri nets 17
© J.-D. Decotignie, 2007
Real-Time Programming GRAFCET and Petri nets 18
© J.-D. Decotignie, 2007
Example
Increment a counter
reservoir
m
Initial conditions
Tanks empty, valves closed
Sensors and actuators
V i , W i = 1 if open
V 1
h i , b i = 1 if level above sensor tank 1
b 1
operations:
W 1
Fill each tank until above h i ,
close valve V i and open W i until
level below b i . Procees cannot
be repeated before both tanks
are empty
h 1
h 2
b 2
W 2
tank 2
(1)
(2)
(3)
1
2
3
(C←0)*
=1
↑a
(C←C+1)*
V 2
GRAFCET and Petri nets 20
↑a
a
Stable
situation
(C←0)*
(C←C+1)*
{2} {3} {2} {3}
Real-Time Programming GRAFCET and Petri nets 19
© J.-D. Decotignie, 2007
Real-Time Programming © J.-D. Decotignie, 2007