!!"! # ;email: Tiberiu.Letia@aut.utcluj.ro;
Adina.Astilean@aut.utcluj.ro; Radu.Miron@aut.utcluj.ro; Maria.SANTA@aut.utcluj.ro
Abstract: The railway traffic is characterized as a large and dynamic system with uncertain properties
related to resource loading, train arrivals and failures. Despite these uncertainties, the control system is
expected to guarantee that all the trains behave according to their timelines. The current approach solves
the railway traffic control problem using the resource allocation. The trains are considered tasks with
specified temporal behaviors that have to fulfill their deadlines. The solutions based on open loop, closed
loop with independent, coordinated and heterarchical controllers are defined and compared. The control
signals are implemented and verified using time Petri nets. Some algorithms for control system
implementation are given. The method evaluations are performed using the meter functions: utility,
utilization, reservation and efficiency. The results obtained through simulations show that the proposed
distributed controllers solve adequately the control problems and can be used for large scale
implementation.
$%&’ railway traffic control, resource allocation, scheduling, realtime control, distributed control,
Petri nets, train specification.
1. INTRODUCTION
The railway traffic control system is a dynamic one that
operates in an environment with uncertain properties that
include transient resource overloads, arbitrary arrivals,
arbitrary failures and decreases of traffic parameters. Unlike
classical realtime control applications that usually concern
only the response times to meet the deadlines, railway traffic
involves the reasoning about endtoend timelines and the
reaction to events such that the global traffic system fulfills
the time requirements.
Despite many uncertainties, the control system is expected to
guarantee that all the trains behave according to timelines.
The current paper solves the Railway Traffic Control (RTC)
problem using the resource allocation. The railway resources
are lines, switches and platforms. They can be allocated
synchronously (in a specified period of time) or
asynchronously (until the occurrence of an event of release).
From another point of view, the allocation can be performed
offline, before a train starts, or online, during the system
evolution when a train reaches some points. The main control
problems of train traffic are analyzed, developed and
modeled, starting with a complete but ideal set of
requirements.Then, more complex situations are progressively
introduced, offering solutions for many sets of characteristics.
Figure 1 presents a part of a railway network with the
following specified elements: traffic lights, denoted by
s1,…,s8; switch points; detectors, represented by squares;
interlockings (an aggregate of switches), denoted by I
0
, …, I
3
;
platforms, denoted by P
1
, …, P
8
; lines, denoted by L
1
and L
2
;
trains, denoted by T
1
, …, T
4
. The presence of trains on the
line is signalized by detectors. The railway network is
composed of a set of linked resources (lines, platforms etc.).
The state of a resource can be reserved or released.
Fig. 1. Example of railway structure
The term ( is introduced to define the control problem. It
consists of the moves of a train from a given platform (line) of
a railway station, to a specified platform (line) of another
railway station. An example of a synthetic description of such
a task is given in Table 1.
Train
Departure Arrival
Place Time Place Time
T
1
S_A.P
1
0 S_B.P
7
15
T
2
S_A.P
4
6 S_B.P
5
25
T
3
S_B.P
5
5 S_A.P
4
22
T
4
S_B.P
8
9 S_A.P
1
36
2nd IFAC Symposium on Telematics Applications
Politehnica University, Timisoara, Romania
October 5-8, 2010
978-3-902661-84-5/10/$20.00 © 2010 IFAC 1 10.3182/20101005-4-RO-2018.00002