functionality microcontrollers for different I/O or code space. Keywords: Petri Nets, Time-out Nets, Security System, Alarm, Interval Specifying. 1. INTRODUCTION.
A Car Security System Model based Timed Petri Nets Georgi Popov.- Technical University-Sofia Plamen Angelov – Burgas Free University s
Abstract. This report presents a Time(-d) Petri Net based model of a hypothetical car security system with RF remote control unit. Our suggestion possess most important features found on such type of systems realized with set of buttons - arm, disarm and silent. The Petri Net-oriented techniques with interval timing are used for our design purposes to reach a control recoverability modeling time-outs. The proposed solution can be charged to modify or add features as required. The code can also be moved to a various type of functionality microcontrollers for different I/O or code space. Keywords: Petri Nets, Time-out Nets, Security System, Alarm, Interval Specifying. 1. INTRODUCTION The time ordering to the design process and its decomposition allow to detect the existing errors, which value is in an exponential dependence of phase model levels. The aim of this paper is to propose an appropriate security system design tool with own formal syntax, simulation rules and transformations, conserving initial semantics. Petri Nets based techniques [1,2] are advantageous for these purposes. The formalisms with interval specifying are suitable to describe a their real-time behavior including a set of parallel processes, protocols, timeouts, conditions etc. The general classes of Petri Nets type extended with temporal restrictions allow to model various timed parameters and correct net and system implementation respectively. 2. A CAR SECURITY SYSTEM MODEL In the present work, we suggest an automobile security system block diagram with RF remote control unit shown in fig.1. Our solution implements the following basic functions: code hopping alarm system; Arm/Disarming; Silent mode; Trunk release; locking/unlocking of doors; door and sensor trigger inputs.
RF receiver Inputs: *Ignition *Doors *Trigger *Shock
Car Security System
Otputs: * LED *Parking Lights *Lock *Unlock *Trunk *Immob
fig.1. Car security system functions
A system model using Interval Timed Petri Nets - oriented techniques [4] is presented in fig.2. The structural elements (places and transitions) of our suggestion are specified at table 1 (transitions) and table 2 (places).
t21 Silent
Arm (audible)
Ignition
t1
t20 Disarm
p7
Silent t2
t3
Arm
t5
p1 p2
t6
t4
Disarmed
Disarm t19
t7 Disarm
p3
t8 Ignition
t18 t17
Door
Audible Alarm
Armed Shock
Shock t9
t10
t16
p4 t11 t12 [40,40]
Silent
p5
Arm t15 Arm
t13 Silent t14 [40,40]
Door t22
Silent Alarm p6
fig.2. A TPN model of car security system
table 1 - transitions t1,t2,t3,t4: Trigger Type Events; t14: Re-Arm Time-Out 2 (40s); t5: Silent Arm; t15: Cancel Alarm With Audible Arm Button; t6: Audible Arm; t16: Cancel Alarm With Silent Arm Button; t7: Disarm; t17: Alarm After Opened Door; t8: Autoarming Time-Out 1 (20s); t18: Alarm After Turn Ignition; t9: Audible Alarm After Shock Activation; t19: Disarm After Audible Alarm; t10: Silent Alarm After Shock Activation; t20: Disarm After Silent Alarm; t11: Re-Arm Time-Out 2 (40s); t21: Auto Arm Off (Ignition On); t12: Cancel Alarm With Audible Arm Button t22: Audible Alarm (Opened Door). t13: Cancel Alarm With Silent Arm Button
table 2 - places
I. BASIC STATES: p4-"Armed": State with action upon entry: *the parking lights flash one time (50ms); *the siren chirp one time for 50rns (if the system is audible armed); *lock door for 500ms; *disable engine; *led flash; p5-"Audible Alarm": State with action upon entry: * the parking lights flash; * the siren on; * pager send; * LED flash; p6-"Silent Alarm": State with action upon entry: * the parking lights flash; * pager send; * LED flash; p7-"Disarmed": State with action upon entry: * the parking lights flash two times for 40ms; * the siren chirp two times for 40rns(if the system is audible armed); * the siren chirp two times (if an alarm has been occurred); * unlock door for 500rns; * enable engine; * led off; II. SUBSIDIARY STATES: p1 - A System Audible Mode; p2 - A System Silent Mode; p3 - An Internal Auto arm Flag.
The system can be armed in two modes: silent (p2 is marked) or audible (p1 is marked). In the silent mode, the shock sensors cause a silent alarm - the bell is off, only the pager and parking lights are active. The arming in this mode is required for noisy places - towns, streets etc. The opening the door (t22, t17) in the arm mode, always cause the audible alarm. The alarm duration is 40s (t11,t14). If no remote control signal generated, the system will rearm automatically. After remote control disarm command, the system establishes to the disarmed state for 20s and rearms. During this time-out, the user must turn on the engine key to disable rearming (t21). The presented solution is optimized using our program product "PetSym". The following model properties are proved: safeness, boundness, liveness etc. On the base of these results would be realized a prototype of a system.
4. CONCLUSIONS
Functional example of Car alarm system (fig.3) is taken from [3], where the system is represented by graph model. The main advantage of the model by graph lies in its readability, because graph notation is more popular than the timed Petri nets.
Fig.3 Graph model of car system This model has the following disadvantages: During a 30s time-out (state Alarm), if the button is pressed ARM, the system goes into state Armed. Also on condition Drive, if the button is pressed ARM (box of Remote), must be completed in two states and Immob Armed; Due to limited capacity of the columns compared to timed Petri nets do not fully describe the conflict situations in time; Model is not suitable for simulation. The suggested system kernel with proven correct behavior during the verification procedure can be developed and extended adding new feature: and functions - code learning, antirobe, only immobilize, alarm memory etc. Proposed model based on Time(-d) Petri Nets is an advantageous as compare as other similar solution [5] specified with FSA state diagrams and change tables. The introduced temporal restrictions allow to reach a structural recoverability and demonstrate a realtime behavior of the complex security systems. REFERENCES 1. Pertova P. Popov G., A model of Car Security System using TPNets, 12-th International Conference: Systems for Automation of Engineering and Research” and DECUS NUG Seminar’98, St. Konstantin Resort, Sept.,20-21th,1998. 2. Petrova P., Popov G., A Model of a Code Interface Control Panel For Security Systems with Time-out Nets, SAER'97, St. Konstantin resort, Sept. 20-21,1997,pp. 64-67. 3. Microchip.”Secure Data Products Handbook", 1997/1998.
