The slide of our paper presented at The International Conference on Advanced Technology & SciencesAt 2016, ICAT’16. The paper can be found here, https://www.researchgate.net/publication/309620060_Elevator_System_A_Case_Study_of_Coloured_Petri_Nets

1. Elevator System. A Case Study of Coloured Petri Nets
E. Assiri2 M. Assiri1 R. Janicki1
1Department of Computing and Software
McMaster University
2Mohawk College
ICAT, 2016
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 1 / 14

2. Outline
1 Introduction
2 The Elevator System
3 Coloured Petri Nets
4 CPN-based Modeling of Elevator System
5 Analysis
6 Conclusion
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 2 / 14

3. Introduction
Coloured Petri Nets (CPN) are an extension of Petri Nets, and are
often used to model behaviours of large variety of complex systems.
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 3 / 14

4. Introduction
Coloured Petri Nets (CPN) are an extension of Petri Nets, and are
often used to model behaviours of large variety of complex systems.
The elevator system is one of the software engineering benchmarks
that are frequently used to test the expressive power, readability and
convenience of various formal specification techniques.
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 3 / 14

5. Introduction
Coloured Petri Nets (CPN) are an extension of Petri Nets, and are
often used to model behaviours of large variety of complex systems.
The elevator system is one of the software engineering benchmarks
that are frequently used to test the expressive power, readability and
convenience of various formal specification techniques.
The model presented in this paper is independent on the number of
floors and elevators, it covers in substantial detail different stages of
the elevator system. We believe our model is flexible enough to be
adapted to different algorithms and rules, and may eventually evolve
in a standard formal model of the elevator system.
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 3 / 14

6. The Elevator System
The elevator system is usually defined as follows: An elevator system is to
be installed in a building with m floors and n cars. The elevator and the
control mechanisms are supplied by the manufacturer. The internal
mechanism of an elevator system is assumed (given). The problem
concerns the logistics of moving cars between floors according to the
following constraints:
Each elevator’s car has a set of buttons - one for each floor. These
buttons illuminate when pressed and signal the elevator to move to
the corresponding floor. The illumination is cancelled when the
corresponding floor is visited by the car.
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 4 / 14

7. The Elevator System (Cont.)
On the wall outside the elevator each floor has two buttons (with the
exception of the ground and the top floors). One button is pressed to
request an upward moving elevator and another button is pressed to
request a downward moving elevator. If both buttons are pressed,
then each direction is assigned to a different car. These buttons
illuminate when pressed. The illumination is cancelled when the
assigned car visits the floor.
When an elevator has not received any requests for service, it should
be held at its parking floor with its doors closed until it receives
further requests.
All requests for elevators from floors (i.e. hall calls) must be serviced
eventually. The applied algorithm controls the priority of floors.
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 5 / 14

8. The Elevator System (Cont.)
All requests for floors within elevators (i.e. car calls) must be serviced
eventually, with floors usually serviced sequentially in the direction of
travel.
Each elevator’s car has an emergency button which when pressed
causes a warning signal that is sent to the site manager. The car is
then deemed ”out of service”. Each car has a mechanism to cancel
its ”out of service” status.
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 6 / 14

9. Coloured Petri Nets
A semi-formal definition
N = (P, T, A, Σ, C, N, E, G, I)
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 7 / 14

10. CPN-based Modeling of Elevator System
Our model of the elevator system consists of four major interconnected
but independent sub-models, namely:
A. Timing Car-structure
Represents the elevators cars
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 8 / 14

11. CPN-based Modeling of Elevator System
Our model of the elevator system consists of four major interconnected
but independent sub-models, namely:
A. Timing Car-structure
Represents the elevators cars
B. Timing Hall-call
Assigns hall-calls to the appropriate car
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 8 / 14

12. CPN-based Modeling of Elevator System
Our model of the elevator system consists of four major interconnected
but independent sub-models, namely:
A. Timing Car-structure
Represents the elevators cars
B. Timing Hall-call
Assigns hall-calls to the appropriate car
C. Timing Car-call
Coordinates placed car-calls with its car
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 8 / 14

13. CPN-based Modeling of Elevator System
Our model of the elevator system consists of four major interconnected
but independent sub-models, namely:
A. Timing Car-structure
Represents the elevators cars
B. Timing Hall-call
Assigns hall-calls to the appropriate car
C. Timing Car-call
Coordinates placed car-calls with its car
D. Timing System-cycle
Operates cars to service requested calls
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 8 / 14

14. A. Timing Car-Structure
CarsTiming Cars
Timing_Cars
initialize_tcars()
DatabaseTiming Database
Timing_Database
initialize_tdatabase()
Timing DatabaseTiming Cars
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 9 / 14

15. A. Timing Hall-call
Prk Sys
Hall_Call
Prk Sys
CarsTiming Cars
Timing_Cars
initialize_tcars()
Coordinator
Coordinator
initialize_coordination()
Hall's_Buttons
Hall's_Buttons
initialize_halls'_buttons()
Hall's_Buttons
Requested
Hall Call
Requested_Hall_Call
DatabaseTiming Database
Timing_Database
initialize_tdatabase()
Release Hall Call
[releas_guard(HB,C)]
Assign Hall Call
[asn_guard(rhc,car,DB)]
Cupd_coord(HB,C)
illuminate_hall_btn(HB,C)
carasn_hcall(car,rhc)
(#hall_call rhc)
rhc
hall_call(HB,C,DB)
released(C) C
HB
DB
upd_asn
(car,rhc,DB)
DB
DB
Timing Cars
Timing Database
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 10 / 14

16. C. Timing Car-call
CarsTiming Cars
Timing_Cars
initialize_tcars()
Calls_Counters
Calls_Counters
initialize_coord ()
DatabaseTiming Database
Timing_Database
initialize_tdatabase()
Car's_ButtonsCar's_Buttons
Car's_Buttons
initialize_car's_buttons ()
Car's_Buttons
Place Car Call
[plc_gaurd(CB,CC,car) ]
CCupd_ccoord(CB,CC)
DBcarsnd_ccall(CB,CC,car) upd_db_(CB,CC,DB,car)
CB illuminate_btn(CB,CC,car)
Timing DatabaseTiming Cars
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 11 / 14

17. D. Timing System-cycle
CarsTiming Cars
Timing_Cars
initialize_tcars()
Timing Cars
out of service
Timing_Cars
DatabaseTiming Database
Timing_Database
initialize_tdatabase()
Doors
Doors
initialize_counters ()
Database_Timing Database
Timing_Database
initialize_tdatabase()
Car's_ButtonsCar's_Buttons
Car's_Buttons
initialize_car's_buttons ()
Car's_Buttons
Hall's_ButtonsHall's_Buttons
Hall's_Buttons
initialize_halls'_buttons()
Hall's_Buttons
warning
to manager
Hall Call
LOG
Hall_Call_LOG
Car Call
LOG
Car_Call_LOG
initialize_car_call_log ()
Maintain
[mnt_guard(car,c)]
0
Restart
[rst_guard(car)]
Transfer
[trn_guard(car)]
Arrive
[arr_guard(CB,car,cnt)]
suspend(car)
car
car
restart(car)
car
transfer(car)
upd_trn(car,DB) DB
cararrive(car,cnt)
upd_cnt(car,cnt) cnt
upd_arr(car,DB)
DB
upd_susp(car,DB)DB
DB
upd_rst
(car,DB)
unilluminate_hall_btn
(HB,car)
HBCB unilluminate_btn
(CB,car)
reset_car's_btns(CB)CB
return_hall_call
(HB,car)
HB
log_hall(car) log_car(CB,CL,car)CL
Timing Database
Timing Database
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 12 / 14

18. Analysis
we used the simulation-based performance analysis, with various
parameters including numbers of cars and floors, types of decision
algorithms, specified floors, etc. The results of our simulation-based
performance analysis has proved validity and applicability of our model in
various situations.
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 13 / 14

19. Conclusion
Conclusion.
Questions ?
Ryszard Janicki
janicki@mcmaster.ca
E. Assiri, M. Assiri, R. Janicki Elevator System. A Case Study of Coloured Petri Nets ICAT, 2016 14 / 14