Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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"TiL'Ti~IG SYSTETJI !=OR RAILWAY ROLLING STOCK'°
Tilting trains offer a solution to the pPoblem of comfort when running in
a curve at high speeds. However, the increase in speed in the curve also gives
rise to an increase in the stresses on the carriage wheel which in the
majority
of circumstances prevents the exploitation of all the possibilities of
increasing
speed provided by the tilting system.
Tilting trains which have been designed to date operate by the detection
and identification of characteristics of the curves encountered in real time.
They utilise the parameters related to the dynamic response of the veh(cle,
for
example speed and acceleration which the sensors fixed in the train pick up.
When among the signals produced through track variations measured by the
on-board sensors (normal cornering speed meters and accelerometers) an
approach to a curve is identified, this operates the tilting devices giving
rise to
the inclination of the vehicle in relation to the bogie by meahs of some pre-
fixed control strategies.
This form'of operation gives rise to a number of disadvantages which we
list belooV:
- By definition, there is delay in identification of the curve. A specified
lapse
of time has to pass before the system detects that there is a curve.
-The standard of inclination of the vehidie produced by the tilting systems at
-. ,- present in service is not the best one from the poirit of view of
passenger
comfort.
- Anticipated operation of the system, if it exists, is independent of the
type of
curve which is approaching.
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In order to avoid these problems, the system which is the subject of
the invention makes use of previous knowledge of the journey and utilises
s equipment (called SDP) which detects the position of the train continuously
with accuracy of a few metres, this consisting of an intelligent control unit
programmed with a standard set of command parameters obtained by
means of the application of a conventional programme of dynamic simulation
of behaviour of the vehicle in a curve having a calculation of inverse
io dynamics, these establishing that the dynamic parameter is the lateral
acceleration of the passenger in the vehicle in accordance with a pre-fixed
profile.
According to a broad aspect of the present invention, there is provided
is a tilting system which is mounted completely on a railway vehicle. The
system comprises a memory unit containing memorized parameters of a
plurality of routes. The memorized parameters of each of the routes are
divided into sections. Each of the sections is identified at least by radius
of
curvature, length of curve, difference in curves of inner and outer rails and
2o memorized absolute position. A position detector system continually sends
actual parameters of speed and actual absolute position of the vehicle to an
intelligent control unit establishing a set of instructions on the basis of
the
values of the memorized parameters and actual parameters. Tilting actuator
units are placed between a bogie chassis and a vehicle frame and
Zs connected to the control unit to receive the instructions so as to effect
the
orientation of the vehicle frame at track curves.
Figure 1 is a block diagram of the system which is the subject of the
invention.
Figure 2 is a diagrammatic view of a practical implementation of the
invention in which the chassis of the bogie and the frame of a railway vehicle
are indicated by a quadrilateral outline.
3s Figure 3 is a sectional view in elevation of another practical
implementation of the invention.
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Figure 4 is a diagrammatic view of the tilting actuator in figure 3.
s Figure 5 is a representation with coordinates of a profile of
accelerations (a) to be used for the system.
In what follows we describe an example of a practical implementation,
which is not limitative, of the present invention. We do not discount
to absolutely other forms of implementation in which minor changes can be
introduced which do not detract from the fundamental idea; on the contrary,
this invention embraces all its variants.
216$29
3
This system of tilting consists of the following units (figure 1):
- The position detector system (1) (tailed SDI') which is responsible for
determining at any moment the speed and absolute position of the vehicle on
the (rack.
- The fitting control unit (2) (UCB), which generates the instructions for
tilting
and controls their execution in real time.
- Axle orientation system (3) which, causes the lateral carriage wheel
stresses
in the two axles of one and the same bogie to be equalised and, in addition,
Deduces its maximum value in a curve. In this way the velocity of the vehicle
in
the curve is increased.
- The tilting actuators (4) are responsible for executing in a mechanical
manner
the tilting instructions generated by the (UCB).
- Vehicle (6).
A memory unit (5) of the journey which is divided into sections identified
by their parameters such as absolute position, radius of curvature, length of
each section of curve, etc.
each curve has an entry transition curve (cte), the curve (c) as such and
an exit transition curve (cts) (figure 5).
6n this unit (5) there are identified the sections of curve in which the
operation of the tilting system is to corriinerice:
The operating method of the tilting system is as follows. The (SDP) (1)
21~282~
informs the (LICB) (2) of the absolute real position and travelling velocity
of the
vehicle. The (UCB) (2) receives this information and consults Its journey
memory (5) in order to find out the route parameters at this point. If this
positron coincides with a section of curve in which the tilting system has to
operate, an instruction signal (cur) is generated for the tilting actuators
(4) and
for the axle orientation system (3) in accordance with a standard set of
parameters related to the travelling velocity and the characteristics of the
route.
This standard set of parameters is a standardised curve (cur) with
abscissas and ordinates of the following form:
cur = func.param(vel,Lt,R,per,pos)
where:
cur = instruction standae'd
func.param = function of the parameters
vel = travelling velocity of vehicle
Lt = length of the transition curve
R = radius of curvature of the route
per = difference in curvature between inner
and.
outer Pail
pos = absolute position for which cur is evalu-
ated.
The set of parameters is drawn up using, for example, polynomial or
harmonic functions.
The set of parameters (func.param) is unique for all curves and for
each type of vehicle. in order to obtain the standard instruction (cur) in
each
case it is sufficient to input the values of vel, Lt, Fl, per and pos in the
previous
fotmula.
5
This standard set of parameters or standard behaviour of the vehicle
in the curve is de$ned for the user as the most suitable for the type of route
to
be taken by the vehicle and it is d2pendent upon the dynamic characteristics
of the vehicle, the type of actuator used, as well as its physical location
and this
can be obtained in conventional manner by means of theoretical or practical
methods of analysis.
An example of how to obtain this standard set of parameters for a
cohc~ete case is as follows. Given the type of route to be covered, the
dynamic characteristics of the vehicle, the type of actuator and its location
in
the vehicle, a dynamic simulation is produced by computer of the behaviour of
the vehicle in a curve.
These (conventional) simulation programmes have, among other
facilities, an inverse dynamic calculation package. ~IVith this faciliiy it is
possible
to find out what standard has to be followed by a commahd signal (standard
commahd) of an actuator in order for a dynamic parameter of the vehicle to
follow a pre-established standard. This is to say, knowing beforehand what is
tE'~e answer to the problem (the pre-established standard for a dynamic
parari~eter of the vehicle) one has to find out what is the question (,the
standard
for the actuator). the standard obtained is adjusteii and given parameters by
means of a con-ventional metfiod, this being by use of polynomial or harmonic
functions.
For this system of tilting the pre-established standard which has been
- .fixed as the objective is a trapezoidal outline for the lateral
acceleration (a)
experienced by the passenger (figure ~). The shape of this curve is
proportional to the profile of the curvature of the route (I/R) and the
amplitude
of maximum lateral acceleration (amax) of the passenger, which is for example,
limited to 0.55 m/sz.
_ ~ ~~62&2~ _
s
cte =-entry transition curve
c = curve proper
cts = exit transition curve
Pa = absolute position
The actuators (4) are what initiate the tilting. They are positioned
between the chassis of the bogie (8) and, directly or indirectly, the frame of
the
vehicle (7). They can be of various types, such as: hydraulic, eieciro-
mechanical, etc. In order to produce in the frame (4) the desired effect of
tilting, they may have certain mechanical elements between the bogie and the
frame which ensure a relative turn between both. They also incorporate some
turning meters (9) which supply the (UCB) (2).
We describe hereafter two examples of practical implementation,
which are hot limitative, showing the mechanical configuration of a tilting
vehicle: articulated configuratien and configur-ation with differentiated
suspension.
Configuration 1: articulated (figure 2)
This configuration is based upon the ihcorporation between the bogie
chassis (8) and the frame (7) of a rail vehicle of a tilt-ing cross-beam (10)
shown by means of a quadrilateral outline; for example by means of the shafts
(11). This tilting dross-beam (10) supports the base of the secondary vertical
suspension (12) which can be of conventional type with springs or pneumatic
cylinders. The only relative movePnent permitted between tfie bogie chassis
aiid the tilting cross-beam is one of turning in the directiori of movement
(balancing tum).
Configuration 2: secondary differentiated suspension (figures 3 and 4).
The other possible configuratioh for the tilting system consists of fixing
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in a conventional bogie two tilting actuators (4) between the bogie chassis
(81 ) and the base (b) of the secondary vertical suspension (13). The task of
s these actuators (4) is that of creating a relative displacement of the base
(b)
of the secondary vertical suspension in relation to the bogie chassis (8~).
We describe hereafter an example of the application of this
solution which consists of incorporating two hydraulic cylinders (14) of
simple
uo effect and of tipping types supported within the base of the helicoidal
springs
(15) of the secondary suspension of a conventional passenger bogie. The
body of the cylinder is contained within the interior space of the spring.
The prol'Slem created by this solution is that the cylinder (14)
~s has to bear the weighs: of the frame (7) which is above it.
Figure ~~ shows a transverse section of a conventional bogie
having spring type vertical suspension in which one can see the assembly of
the tilting cylinder bas~sd upon this configuration.
zo
It will bE~ understood that in place of the profile of lateral and
angular acceleration, one can programme the profile of the speed or
displacement (only if it is to be derived) of the vehicle/passenger, or with
uncompensated acceleration what is the uncompensated lateral acceleration
.'s through gravity or othE~r related variable.
