System for targeted braking of vehicles

A system for identifying momentary location and the momentary velocity of, in particular, a rail-bound vehicle, has a transmission/evaluation unit having an antenna for emitting a high-frequency pulse and for receiving a reflected pulse reply signal. Surface wave identification marks having individual coding are arranged at intervals from one another in an area of and along a prescribed travel path of the vehicle. The mutual phase shift of at least two pulse reply signals can be measured as a Doppler shift and the travel velocity can be calculated therefrom via the relative velocity with pulse interrogations of an identification mark following one another at least twice at a predetermined location before/after traversing a specific identification mark. The point in time change in operational sign of the Doppler shift is acquired for this identification mark, and is the point in time of traversal of the location of the specific identification mark.

BACKGROUND OF THE INVENTION 
The present invention is directed to a system for targeted braking of 
vehicles, such as railroad trains. 
It is desirable or even necessary, particularly for the automatic operation 
of vehicles such as railroad trains, that the vehicles come to a stop at a 
precise point at loading stations and the like in railroad stations. This 
exact stopping should be achieved from full speed insofar as possible, 
that is, it need not be obtainable by slowly creeping to the stopping 
point. Such an exactly targeted stopping in railroad stations is desirable 
for example, for commuter passenger traffic and can even be absolutely 
necessary when the individual cars can only be entered or exited when the 
train stops at an absolutely specific point in the station (such as, for 
example, in St. Petersburg). This type of station has no actual platform 
but, rather, a track tunnel of the train is connected to a tunnel for 
waiting passengers only by individual small cross-connecting tunnels in 
front of whose end a respective car door of the stopped train is located 
in the track tunnel. 
It is required given such a targeted braking that the automatic operational 
unit of the incoming train is informed at sufficiently close distances or 
time intervals about the locations at which the train is situated at the 
moment. For example, light barriers can be employed for this purpose, the 
automatic operational unit of the train receiving a signal when they are 
traversed. It is not only necessary in rugged rail operation, but also in 
the operation of trolleys and the like that the signal means have 
extraordinary ruggedness, durability and insensitivity to contamination. 
This is because the operating reliability and safety is critically 
dependent on the effectiveness of such route markings and their failure 
could lead to dangerous situations or even to serious accidents. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide reliable and simply 
evaluatable route marking for use in a system for determining momentary 
location and velocity of rail-type vehicles. 
In general terms the present invention is a system for identifying a 
momentary location and momentary velocity of a rail-bound vehicle. The 
vehicle has a transmission/evaluation means having an antenna for emitting 
a high-frequency pulse and for receiving a reflected pulse reply signal. 
Surface wave identification marks having individual coding are arranged at 
intervals from one another in an area of and along a prescribed travel 
path. A mutual phase shift of at least two pulse reply signals is measured 
as a Doppler shift and the travel velocity can be calculated therefrom via 
the relative velocity with pulse interrogations of an identification mark 
following one another at least twice at a location before/after traversing 
a specific identification mark. The point in time of the change in 
operational sign of the Doppler shift is acquired for this identification 
mark, this being the point in time of traversal of the prescribed location 
of the identification mark. 
In a further development of the present invention, the exact path velocity 
is calculated for the known height of the motion path of the antenna of 
the transmission/evaluation means, from the relative velocity measured at 
a location X.sub.1, and from the chronological duration of the traversal 
of the distance .vertline.X.sub.1 -X.sub.0 .vertline. between the 
locations X.sub.1 and X.sub.0, wherein X.sub.0 is the location of the 
identification mark. The system is also useable for calculating location 
and velocity values for targeted braking of the vehicle. 
The present invention is based on identification marks, what are referred 
to as ID tags. These identification marks for toll ticketing at toll 
stations of a motor highway system already employed in a system of Siemens 
AG in Oslo are suitable for being exactly identified in non-contacting 
fashion over a distance of meters. The ID tags are specific surface wave 
components.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 2 depicts an identification mark 1, which is a photolithographically 
applied stripe structure on the surface of a substrate member 2. The 
substrate member 2 is composed of highly piezoelectric coupling material 
such as lithium nitrate, lithium tantalate and the like. A part 3 of this 
stripe structure is an interdigital transducer to whose electrical 
terminals dipoles of the antenna 4 are connected. The stripe structure of 
the reflector 5 has locations that are isolated in omitted reflector 
strips, the distribution thereof in the reflector structure 5, to be more 
precise, forming the prescribable coding. In practice, such a reflector 
structure 5 has several hundred reflector strips arranged in a periodic 
sequence, resulting in a great number of coding possibilities. FIG. 3 
shows the pulse sequence 10 (envelope) contained in the pulse reply of the 
identification mark 1 and is the reply of the coding of the reflector 
structure 5 to a received burst 11. 
According to a feature of the present invention, such identification marks 
are installed at appropriate distances from one another preceding a stop 
location for the train in the track region or at the tunnel wall. Each and 
every identification mark of such a braking distance section has its own 
unique coding, that cannot be mistaken for the other identification marks 
of this section. For example, a train entering a station moves over this 
sequence of identification marks or moves along this sequence of 
identification marks. When moving past each of the identification marks, 
the automatic control system of the train knows exactly where the train is 
located at the moment or the exact localized point that has been reached 
at the moment. 
A program for decelerating to a greater or lesser degree from one to 
another identification mark when, for example, entering the station can be 
calculated or, respectively, identified in advance from the operational 
data of the train. The program is selected such that the incoming train is 
continuously decelerated from full speed with a greatest possible rate of 
deceleration without the wheels of the railroad vehicle sliding on the 
rail. Sliding of the wheels on the rails would not only wear the surfaces 
of the wheels but, due to the indefiniteness of the sliding friction, the 
train would come to a standstill at a location completely different from 
the prescribed location. 
It must be taken into consideration, however, that the respectively 
maximally obtainable rolling friction of the railroad wheel on the track 
can have different values, so that it cannot be assumed that an optimally 
short braking distance will be achieved in every instance. This 
indefiniteness is to be taken into consideration in the program for the 
braking in such a way that an anticipated, longer braking distance is 
assumed and an approximate maximum value of the coefficient of rolling 
friction at the moment and an anticipated value for the remainder of the 
braking distance is identified, for example, together with the braking in 
a first section of the entire retardation path. The braking, for example, 
can then ensue automatically with a correspondingly modified program. It 
is even more beneficial to make the predictive estimates according to the 
rules of fuzzy logic from values already measured at the moment and to 
achieve, if not the optimum program, nonetheless an approximate optimum of 
the braking. 
Each and every individual identification mark can be unambiguously 
recognized proceeding from the moving train with the assistance of the 
aforementioned identification marks in the track or, respectively, tunnel 
region close to the moving train and on the basis of the coding of these 
identification marks. As a result, the momentary position of the moving 
train is known. Over and above this, however, the speed of the train can 
also be exactly identified above ground with high precision with the 
assistance of the identification marks, namely free of any and all 
imprecisions that caused by slippage and that are unavoidable when 
measuring the travel speed from the circumferential velocity of the 
rolling wheel. On the contrary, an immediate determination as to whether 
slippage of the rolling wheel is presently occurring can be made from the 
speed which has been exactly identified using the identification marks. 
The speed calculated with the rolling wheel merely has to be compared to 
the exactly measured value and the difference derives as slippage. 
The present invention, however, can be utilized not only in railroad 
operations but can also be employed in other comparable transportation 
means. To this extent, the specification for the implementation of the 
present invention set forth below can also be transferred without further 
ado to such comparable cases. 
The inventively applied evaluation method provides that burst pulses 11 
having an appropriately high carrier frequency are output by a pulse 
transmitter. This burst pulse is picked up by the surface wave structure 
3, 5 of the identification mark 1 via the antenna 4 of the identification 
mark 1 and is converted by the latter into a characteristic pulse reply 
signal 10. The characteristic of the pulse reply signal 10 is dependent 
upon the selected structure of the reflector 5 of the identification mark. 
The pulse reply signal 10 that is transmitted back to the evaluation means 
by the identification mark contains further information in addition to 
containing the coding of the reflector. Since the pulse transmission and 
pulse reply evaluation means attached to the moving train approaches the 
identification mark with the velocity of the train, a Doppler frequency 
shift of the carrier frequency of the pulse reply signal occurs (from 
which the relative speed between the train and the respective 
identification mark can be calculated). The absolute speed of the train 
can be immediately calculated from the measured relative speed, namely 
without any slippage error, with the known, structurally conditioned 
attitudinal positions of the identification mark in the track region or at 
the tunnel wall on the one hand and of the place of application of the 
transmission/evaluation means at the train, on the other hand. 
The exact moment at which the train travels past the respective 
identification mark as route mark can be identified from the curve of the 
measured Doppler frequency shift. The zero-axis crossing of the Doppler 
frequency shift is the location of the route mark. 
The Doppler shift can be identified and evaluated as a frequency shift or 
(given correspondingly small values) as a phase shift relative to a 
reference phase. 
The present invention is thus directed to those measures for determining 
the curve of the relative speed between the identification/route mark and 
the transmission/reception antenna of the transmission/evaluation means 
from the Doppler frequency/phase shift of the carrier frequency of the 
pulse reply signal or of a part thereof and of thus identifying both the 
true speed as well as the exact position of the train (or of some other 
vehicle). The coincidence of the position of the train with the position 
identified by the identification mark is acquired using the zero-axis 
crossing of the Doppler frequency/phase shift of the carrier frequency of 
the reply signal (or of a part thereof). The distance between the 
transmission/reception antenna for the pulse reply signal mechanically 
coupled to the train and the identification mark when traveling past the 
latter can likewise be calculated from the Doppler frequency/phase shift 
(if this value is not already known). When this distance value is known, 
the reliability and precision of the inventive system can be checked at 
any time from the coincidence of the measured value and the known value on 
the basis of a measurement thereof as set forth above. The exact lay of 
the position of the identification mark as a route mark relative to the 
train is calculated from the relationship between the speed of the train 
and its relative speed. The direction of the respective connecting line 
between the identification mark and the transmission/reception antenna of 
the evaluation means derives at any location of the motion path from these 
two speeds. The location of the route mark derives as a intersection of 
this connecting line proceeding from various positions of the train, i.e. 
positions of the transmission/reception antenna. In particular, this 
location also derives from the intersection of one of these connecting 
lines with the above-described perpendicular or with the straight line 
proceeding parallel to the travel path that the aforementioned 
perpendicular distance between antenna and mark has when traveling 
therepast. Conversely, the distance between the identification mark can be 
calculated as the intersection of the above connecting lines. 
The sectional view of FIG. 1 is attached for illustrating these geometrical 
conditions. This figure shows the identification mark 1 that is 
interrogated as a route mark in the track region. FIG. 1 also depicts the 
rail 29 and a car wheel 30. Further identification marks are route marks 
1', 1". There can be no mistaken identities because each of the 
identification marks outputs its own coded, that is unmistakable, pulse 
reply signal upon interrogation. 
Corresponding to the travel path of the car 31 having the wheels 3, the 
transmission/reception antenna 9 of the evaluation means 8 moves on the 
travel path 20 parallel to the rail 29. The perpendicular distance, i.e. 
the distance between antenna 9 and identification mark 1 when traveling 
therepast is referenced "a". When, at the moment of the illustrated 
position of the antenna 9 relative to the identification mark 1, an 
interrogation pulse is transmitted, then a relative velocity V.sub.rel 
corresponding to the connecting ray r.sub.1 derives as Doppler shift 
velocity. This velocity value is measured as frequency or phase shift 
between at least two interrogated and received pulse reply signals that 
follow one another in a short time. The angle .alpha. is the directional 
angle of the connecting line r.sub.1. When this, which occurred at 
location x.sub.1 repeats at location x.sub.2, the relative velocity 
V.sub.rel2 for the connecting line r.sub.2 is obtained. The 
correspondingly diminished relative velocity thereby derives and the 
relative velocity is zero at points x.sub.0. This effect is utilized for 
identifying the location x.sub.0 and the point in time at which the 
identification mark 1 is traversed. 
The coding of the identification mark employed as route marks contains the 
respectively allocated position number in the sequence of a plurality of 
route marks arranged at intervals from one another. Such a sequence of 
route marks is preferably provided in the braking area preceding a 
station. Such route marks, however, can also be provided elsewhere on the 
path, for example, in order to merely measure the speed of the train 
without slippage. As mentioned, the identification marks with surface wave 
structures employed as route mark are passive components that require no 
power supply whatsoever. Their range of operation is relatively limited, 
but this is an advantage in the present case, because it substantially 
precludes disturbing influences from the environment. 
The invention is not limited to the particular details of the apparatus 
depicted and other modifications and applications are contemplated. 
Certain other changes may be made in the above described apparatus without 
departing from the true spirit and scope of the invention herein involved. 
It is intended, therefore, that the subject matter in the above depiction 
shall be interpreted as illustrative and not in a limiting sense.