It is known from German Offenlegungsschrift No. 41 02 812 to place a line serving as an antenna in a permanent way and to detect by means of a radio transmitter and re- ceiver when the receiver is positioned at a place where the received signal strength is 0. A train may hereby be brought to a standstill in a given position relative to the zero point.

This technique has the drawback that the antenna line in the permanent way must be very long if a train is to be brought to a standstill from a very high speed. In prac- tice, the prior art cannot be used in connection with high travelling speeds.

An object of the invention is to develop a system of the above-mentioned type further so that it may be used in a more dynamic environment. Dynamic environment here means an environment in which objects can move at even very

high speeds while maintaining an accurate positioning and control of the movements of the objects, including bring- ing the object to a standstill in an accurate position.

This object is achieved in that the control signals emit- ted from the transmitter units contain information on the pattern of movement of the movable object. If, e. g., it is a matter of determining the position of a given trans- mitter unit, this may take place either in that the transmitter unit is adapted to transfer positional infor- mation to the antenna, but it may also take place in that the transmitter unit transfers an identification signal and that a computer is arranged in the train, provided with information on the position of a transmitter unit with a given identification. The transmitter units are also called a TAG that may be compared to the art dis- closed in Danish Patent Application No. 0247/98.

The invention involves the great advantage over the pre- viously mentioned prior art that a plurality of TAGs may be arranged for decelerating a train from a high speed, said TAGs being scanned successively by the antenna for correct deceleration of the train. A TAG, e. g. of the type described in the above-mentioned Danish patent ap- plication, may be quite small and inexpensive. When the extent of the TAG is small relative to the extent of the antenna on the train, the positions of the antenna in which the received signal strength is 0, may be deter- mined very accurately. Fix points may hereby be provided along the section on which the movable object moves.

The transmitter units may hereby transfer information to the movable object, such as information on the position and speed of the movable object.

It is expedient that the control signals contain informa- tion on stopping of the movable object. The places where the received signal strength is 0 may be used as fix points, but it may also be expedient to define the fix point by a threshold value which is different from 0.

As stated in claim 6, it is expedient that stopping of the movable object is determined as a given distance from the fix point.

This primarily provides the advantage that the movable object may be stopped with a soft transition from move- ment to standstill.

Finally, it is an advantage, as stated in claim 7, that a plurality of transmitter units or TAGs are arranged at a mutual distance along a section, and that the antenna of the movable object along the section receives start, move and stop commands from the transmitter units.

This provides a flexible system which may be used for controlling movable objects in a completely arbitrary manner according to desire and need.

Precisely in connection with control of train traffic and particularly of driverless trains it is of paramount im- portance that top security is provided, which necessarily requires that all train positions for start and stop can be controlled precisely, which may be ensured by using the principles of the invention. In case of high speed trains slipping or sliding of the wheels will always oc- cur, and reliable deceleration can therefore only take place by means of a plurality of TAGs, which may be ar- ranged at a mutual distance along the permanent way ac- cording to the invention.

The invention also generally relates to a method of con- trolling train traffic, e. g. driverless trains, where the train has an antenna which is adapted to emit signals and to receive control signals emitted from a transmitter unit in the permanent way.

The method is characterized by generating control infor- mation on the basis of information which is received from two or more transmitter units in a group of transmitter units, cf. claim 8. The control information from the transmitter units may be supplemented with control infor- mation from an odometer which is connected with the wheels of the train. At low speeds, the odometer informa- tion may be used for stopping the train very accurately at a predetermined distance from a fix point. When the transmitter units may be localized and identified sepa- rately according to the invention, their mutual distance may be detected, which may be used for calibrating the odometer equipment.

Preferably, the train also has a train computer which may be provided with information on the respective train, e. g. length, braking properties and timetable, said in- formation being compared to the information from the transmitter units for stopping the train at a predeter- mined place relative to the group of transmitter units.

The invention moreover relates to a system for performing the method according to claims 8-11 and of the type de- fined in the introductory portion of claim 12. The system is characterized in that it comprises groups of transmit- ter units arranged in the permanent way, each group hav- ing at least two transmitter units positioned at a prede- termined mutual distance and adapted to transfer control signals to the antenna of the train. The control signals

comprise information for positional determination of the respective transmitter unit.

The invention will be explained more fully below with reference to an embodiment shown in the drawing, in which fig. 1 shows the basic structure of communications con- nections which are used in connection with the invention, fig. 2 shows the basic structure of the communications connection, seen from above, fig. 3 shows an example of a magnetic field characteris- tic which occurs in connection with the communications connection in figs. 1 and 2, fig. 4 shows a preferred embodiment of a receiver for use in connection with the invention, while fig. 5 basically illustrates a system for performing the method according to the invention.

Figs. 1 and 2 schematically show an antenna which is gen- erally designated 1, and which has four conductors 6,7, 8,9.

The antenna is adapted to emit and receive signals via a unit 10, e. g. as explained in Danish Patent Application No. 0247/98.

As will be seen in fig. 2, the direction of a current supplied from the unit 10 in the antenna is shown by ar- rows.

Additionally, fig. 1 schematically shows a section 5 be- low which a transmitter unit 4, which consists of a tag known per se, is arranged.

The system according to figs. 1 and 2 operates in the following manner.

When the antenna is moved along the path 5 toward the transmitter unit 4, the magnetic field that occurs be- cause of the current in the antenna 1 will affect the transmitter unit 4, which will reflect a signal back to the antenna 4 proportional to the field emitted from the antenna.

The strength of this reflected signal will depend on the distance between the antenna and the transmitter unit, as will be explained more fully in connection with fig. 3.

It is shown in fig. 3 that when the antenna unit 1 with the conductor 6 moves in the X-direction toward the transmitter unit 4, the magnetic field (B) will increase numerically as shown at 11 when the antenna 4 reaches the tag 4. A short distance before the conductor passes the transmitter unit 4, the magnetic field will reach a nu- merical maximum, as shown at 12, and then decrease sharply until the field is 0, as shown at 12A, where the conductor 6 is positioned above the transmitter unit 4, which corresponds to the mutual positions of the antenna 1 and the transmitter unit 4 shown in figs. 1 and 2. At the point 12A, a phase shift of the magnetic field takes place. When the antenna is then moved further on, the magnetic field will increase in a positive direction. As will thus be seen, the magnetic field increases as shown at 13 and reaches a maximum, where it again decreases at the central part of the antenna, shown at 14, and then reaches a minimum at 15, following which the magnetic

field again increases when the second conductor 8 ap- proaches the tag 4. This is shown at 17, which is symmet- rical with the portion 13 shown in fig. 3. As soon as the conductor 8 is positioned above the transmitter unit 4, a zero point will be obtained again, shown at 18A, follow- ing which the magnetic field will increase to reach a maximum shown at 18 and then decrease toward zero when the antenna is moved even further away.

As will be appreciated, the zero points 12A, 18A, which are positioned at a fixed mutual distance, may be used e. g. for determining the speed of the antenna relative to the transmitter unit, it being possible simply to detect the times at which the antenna conductors 6,8 pass the transmitter unit 4.

It appears from fig. 3 that the signal strength is rela- tively small outside the zero points 12A and 12B. In par- ticular if the signal strength generally decreases, the threshold value 0 is not so well-defined as the shown threshold values TA and TB, which will increase the accu- racy of the fix points.

As the threshold values are determined by purely physical conditions, they may advantageously be used as fix points, e. g. in connection with the stopping of a movable object, as an antenna is then merely to be placed on the movable object and to be connected to a transmitter unit.

If the object is to be stopped accurately at a given dis- tance from the fix point, this may be done by means of an encoder or an electronic odometer positioned on the mov- able object.

It will moreover be appreciated that if a plurality of transmitter units are arranged along e. g. the section 5 in fig. 1, they may be used for controlling the movable

object, as the transmitter units 4 may be arranged such that they give control information to the antenna, which is accurately adapted to the desired pattern of movement of the object. This will be explained more fully in con- nection with fig. 5.

Finally, it is noted that the information from the trans- mitter unit 4 may be transferred to the unit 10 via the antenna 1, as is explained in the above-mentioned Danish patent application.

Fig. 4 shows a transmitter/receiver for use in connection with the invention.

This system, which is generally designated 20, essen- tially corresponds to the disclosure of the above-men- tioned Danish patent application, and will therefore just be explained to the extent to which it is necessary for the understanding of the principles of the invention.

As will be seen in fig. 4, the system 20 is connected to the antenna 1. The antenna 1 can transmit and receive signals from an antenna circuit 22, which in turn may re- ceive a transmit signal from an oscillator 21 for the supply of current to the antenna 1. When the antenna 1 receives signals e. g. from one of the transmitter units 4 in the preceding figures, the signals, as is explained in connection with the above-mentioned patent application, will be fed to a receiver, which is arranged so as to be able to divide the output signal into a DC signal which is used as an indication of the presence of a transmitter unit, and an AC signal, here shown by ID, which may be an information signal, e. g. an identification signal emitted from the transmitter unit 4. The whole thing is con- trolled in a microcontroller 32, which is moreover ca- pable of transmitting and receiving data via a connection

33 to peripheral equipment not shown. Compared to the re- ceiver according to the above-mentioned Danish applica- tion, the receiver is additionally arranged such that it can determine the zero points/fix points which are men- tioned in connection with figs. 1-3.

Thus, the invention provides an extremely flexible system which is particularly suitable in connection with the control of driverless trains, it being possible partly to position, partly to stop and partly to control various parameters in connection with the steering/control of the driverless trains.

Fig. 5 shows a permanent way 5 having a pair of TAGs 4.

Furthermore, a train 34 is outlined and inside it the units 1 and 20 from fig. 4, an odometer 36, a control circuit 35, a train computer 37 and a radio antenna 38 are shown. The mode of operation of the system will be described in connection with the case where a train is to be decelerated from a high speed and to stop at an accu- rate place, e. g. at a train platform.

According to the invention, a plurality of TAGs, e. g. five, are provided, said TAGs being distributed over a section of some kilometres from the platform. At a dis- tance from the platform where the speed of the train is high, the TAGs are relatively far apart, while the TAGs are positioned mutually more closely close to the plat- form. When the circuit 20 detects that the antenna 1 has passed the first TAG, a message will be sent to the train computer 37 which registers that this TAG is the first one in a deceleration course. The train is decelerated in accordance with braking parameters stored in the train computer. The braking process may be monitored by means of the odometer 36 and the control circuit 35. The train computer 37 can predict when and at which speed the train

is to pass the next TAG, and if a deviation should be ob- served, it is possible to change the braking characteris- tic which is stored in the train computer. It will be ap- preciated that possible slipping or sliding of the wheels may be compensated completely in this manner. Preferably, the system will be arranged such that the train passes the last TAG before the platform at a quite low speed, so that the final stopping takes place on the basis of the odometer information. The train computer 37 contains in- formation on how long the train is, so that the train may be stopped at the accurate place on the platform. Because the TAGs 4 are small relative to the extent of the an- tenna 1, the zero crossing explained in connection with fig. 3 may be detected with a very great accuracy, of the order of less than one centimetre. It is thus possible to bring a high speed train to a standstill in an accurate position. Finally, the train computer 37 may be connected via a radio antenna 38 to a monitoring centre which can both transmit information to the train and receive infor- mation on the pattern of movement of the train.