EP0098896B1

EP0098896B1 - Systems for locating mobile objects by using inductive radio frequency lines

Info

Publication number: EP0098896B1
Application number: EP19820106432
Authority: EP
Inventors: Yoshinobu C/O Sumitomo Electr. Ind. Kobayashi; Tamio C/O Sumitomo Electr. Ind. Ltd. Ueno; Koji Kanagawa
Original assignee: Mitsui Engineering and Shipbuilding Co Ltd; Sumitomo Electric Industries Ltd
Current assignee: Mitsui Engineering and Shipbuilding Co Ltd; Sumitomo Electric Industries Ltd
Priority date: 1982-07-16
Filing date: 1982-07-16
Publication date: 1987-10-28
Also published as: EP0098896A1; DE98896T1; DE3277529D1

Description

The invention relates to a system for detecting a mobile object as defined in the precharacterizing part of claim 1. Such a system is disclosed, for example, in document FR-A-2,369,136.
The above mentioned system enables to detect and control mobile objects, such as a train, travelling crane on running tracks. In container yards of wharf, for instance, the installation of conventional multi-wire type lines for radio-frequency will not be allowed since it requires under-ground construction. In such case a relative position locating system may be used which counts the number of crossings in the twisted-pair type inductive radio-frequency lines.
As shown in Fig. 1, in a prior art system for detecting a mobile object the twisted-pair type inductive lines 1 are installed along the track of the mobile object and a radio-frequency power supply 2 is connected to the lines 1. A pair of antennas 5 and 6 are attached to the mobile object keeping a fixed interval lengthwise of the lines. In the antennas,, magnetic flux which is exemplified by dotted lines in Fig. 1, will generate induced currents flowing in the directions corresponding to those phases of the currents in the twisted-pair lines 1, the lines 1 having crossings 3, 4, ..., spaced at fixed intervals whereby the phase of current flowing in the lines 1, as shown by an arrow in the Fig. 1, alternates at an interval equal to that between the crossings.
Now, assuming that the phases of the induced currents in the antennas 5, 6 and the current in the lines 1 have a relation shown by the lines in Fig. 1, the currents in the antennas 5, and 6 are in an opposite phase to each other.
When the phase-relation between the antennas 5, 6 and the lines 1 has been varied as shown by the one-dot-and-dash lines in Fig. 1, as the mobile object travels rightwardly in the figure, the current in the antennas 5 and 6 are in the same phase.
Such phase relation between the antennas 5, 6 alters with the every passage of the antennas, i.e., the mobile object, through crossing. Hence, the number of the phase alternation is counted to thereby obtain the number of crossings through which the mobile object has passed, thus indicating the relative position thereof.
In the above case, however, the mobile object is determined merely of its relative location of the travelling route, whereby an absolute position sensing method is required in addition. A typical way of the absolute position detecting of a mobile object is to install a plurality of twisted-pair type inductive lines for radio-frequency with different intervals between crossings and with different frequencies allocated so that the combinations of the phases of the induced currents in the antennas and sensing for each lines are indicative of the absolute location of the mobile object.
In the above case, however, position of the mobile object can be determined in its relative location on the travelling route and other lines for sensing the absolute location of the object are to be installed.
A typical example of a system for detecting the absolute position of a mobile object on the predetermined travelling route is carried out by installing a plurality of a twisted-pair type inductive lines in parallel to the travelling line of the moving object and by detecting the combination of the phases of the induced currents in the antennas for each signal line installed.
A typical means for detecting the absolute position of a mobile object on a travelling route is to combine the phase relations of the induced currents in an antenna by each of the twisted-pair type inductive lines. In this case some specific signal frequency will be allocated to each of the line.
Another absolute position detecting system for the mobile object is similar to the one illustrated in Fig. 1. In this case some signal sources are located at specific positions on the travelling route of the object with abovementioned detecting lines for the relative position detection of the object. The presence of the object is simply determined when antenna(s) detects the specific signal from the source on the pre-determqned zone on the travelling route.
Such a system, however, requires signal sources to be installed along the inductive frequency lines and moreover needs frequency discriminators which will increase the installation costs and will cause difficulties for maintenance, especially when a large number of detecting zones may exist.
An object of the invention is to provide an absolute position locating system which lends itself for employment also where it is difficult to install the multi-pairs of twisted inductive radio-frequency lines and which is inexpensive to produce and simple to install.
The present invention provides a system for detecting a mobile object on a predetermined travelling route utilizing twisted-pair type inductive radio frequency lines, which are installed parallel to each other along said travelling route and comprise a plurality of crossings at intervals therebetween, said intervals having two specific different lengths p1 and p2 (p2>p1) within an area necessary for detecting the absolute position of the mobile object, said system being characterized in that the mobile object is equipped with a reference antenna, an auxiliary antenna and a comparison antenna, all provided for inducing currents therein by interaction with said radio frequency lines the space I between said reference and comparison antennas meeting the following relations:
and the currents induced in the antennas are detected by detector means and compared in a logic circuit in terms of phases and power levels, said logic circuit producing a signal of "1" or "0" level depending on the coincidence or non-coincidence of the comparison results.
The present invention enables simple and economical means for detecting an absolute position of a mobile object on its travelling lines. The combination of large and small intervals between crossings of the radio-frequency inductive lines and reference, comparison and auxiliary antennas are utilized.
The circuits for comparing the phases or levels of the currents induced in the reference antenna and in the auxiliary antenna may be modified. They operate as a proper detecting means for the position of the reference antenna in the vicinity of crossings and actuate the logic circuit which compares the phases or the levels of the currents induced.
In the following preferred embodiments of the invention are explained with reference to the Figures, in which

Fig. 1 shows the prior art detecting system as discussed above,
Figs. 2, 4, 6 and 7 show diagrams for explaining the operation principle on which the present invention is based, and
Fig. 3 and 5 show two different embodiments of the invention.

Referring to Fig. 2, the positional relation between signal sensing antennas and twisted-pair type inductive radio-frequency lines 1 is shown, in which reference numeral 7 designates a reference antenna, 8 designates an auxiliary antenna, 9 designates a comparison antenna, 2 designates a radio-frequency power supply, and 3 and 4 designate the crossings of the line 1, the reference antenna 7 and the comparison antenna 9 being attached to a mobile object (not shown in the Figure) keeping a distance I along the lines 1. The crossings in lines 1 are spaced at a predetermined interval L or 2L (2L=two times the interval L), the distance I being set in a range to meet the relation of L:-51<2L.
Fig. 3 shows a block diagram of a sensor 10 attached together with antennas 7, 8 and 9 in Fig. 2 to said mobile object. Output signals of the above three antennas 7, 8, 9 are supplied to respective input terminals 7', 8' and 9' of the sensor 10. Reference numeral 13 designates a phase comparator which compares the signal phases of input signals on input terminals 7' and 8' and outputs a digital value "1" or "0" corresponding to the comparison results, indicating whether the signals are in the opposite phase or in the same phase. A phase comparator 14 compares the signal phases of input signals on input terminals 7' and 9' and outputs a digital value "1" or "0" corresponding to the comparison results, indicating whether the signals are in the opposite phase or in the same phase. These phase comparators also serve as an analog/digital converter generating digital signals corresponding to comparison results of analog amounts. Reference numeral 15 designates an AND gate, 16 designates a shift register of five stages supplied with an output of AND gate 15 and a shift pulse S from phase comparator 13, and 17 designates an AND gate for decoding the contents of the shift register 16.
Assuming that the antennas 7, 8 and 9 are positioned as shown in Fig. 2 following the movement of the mobile object, since antennas 7 and 8 are positioned at both sides of the crossing point 3, induced currents in the antennas 7, 8 have opposite phases so that the phase comparator 13 in Fig. 3 feeds a digital signal "1" to one input terminal of AND gate 15 and a shift pulse S to the shift register 16.
The antennas 7 and 9 are similarly positioned at both side of the crossing 4 so that the induced current in each antenna is in an opposite phase whereby the phase comparator 14 in Fig. 3 outputs a digital signal "1". The AND gate 15, which is supplied with "1" signals from both antennas, outputs "1" to the shift register 16 so that one additional "1" signal is written into the shift register to be read therefrom.
On the other hand, when the interval between the crossings 3 and 4 in Fig. 2 is 2L, and when the antennas 7 and 8 are further located at both sides of the crossing point 3, the phase comparator 13 outputs a signal "1". However, as there is no crossing between the antennas 7 and 9, the currents therein are in the same phase and the phase comparator 14 outputs "0".
Fig. 4 shows an example of an arrangement of the crossings a, b, c, and d. A pattern of combinations of intervals between crossings in the twisted-pair type inductive radio-frequency lines 1 and variations in arrangement of antennas 7, 8, and 9 are also illustrated.
When the antennas 7, 8 and 9 move rightwardly along the above lines 1, positioning of them vs the crossings are shown in the lower part of this figure. The figure also indicates that relative spaces between the antennas are kept unchanged during their movement on the route. When the antennas 7 and 8 are located at both sides of crossings, i.e. when the phase of the antenna 7 is reverse to that of the antenna 8, the phase comparator 13 outputs "1" signal. Thus, one condition to output a signal to the shift register 16 is established. In such a condition, the phases of the antennas 7 and 9 are compared with each other. When the phases are equal, the phase comparator 14 outputs a "0" signal, and when the phases are opposite, it outputs "1" signal. As a result, the AND gate 15 outputs signals to the shift register 16. In this embodiment the signals from AND gate 15 are equal to the signals from the comparator 14.
When the antennas 7 and 8 pass the crossings a to e, the readings of the shift register 16 will be "1", "0", "0", "1" and "1" respectively, as shown in Fig. 4.
Thus, each time when the reference antenna 7 passes the crossing, the shift register 16 shows readings of "1" or "0" depending on whether the antenna 7 and 9 are positioned between crossings or not. In Fig. 3, the respective columns 16-1, 16-2, ..., 16-5 of the shift register 16 shows "1", "1", "0", "0" and "1" respectively.
Hence, when the antennas 7 and 8 are presently positioned across the crossing e, i.e., the antenna 7 passes the crossing e, then AND gate 17 outputs a digital signal "1" to an output terminal 18. The present location of the antennas and also that of the mobile object will be displayed on the shift register by combination of the digital codes which imply the absolute address of the object on the travelling route.
The intervals between crossings, outside the absolute position detecting area on the route of the object are set to a constant length larger than the interval I, i.e., the distance between the antennas 7 and 9, whereby the phase comparator 14 always outputs "0" signal and the readings on the shift register 16 will become always "0". On the contrary, each time when the reference antenna 7 passes a crossing, the phase comparator 13 outputs a "1" signal to the terminal 19 thereby providing a location detecting signal with the moving object.
In Fig. 3, the AND gate 15 can be eliminated so that the output terminal of the phase comparator 14 is connected directly to the shift register 16, thus enabling the output signal of the phase comparator13to be used as a drive signal forthe phase comparator 14. The phase comparison of the induced currents in the antennas 7 and 9 will result in digital signals "1" or "0", only when the reference antenna 7 passes a crossing as shown in Figs. 2 and 4.
When in Fig. 2 the alignment of the antennas 7 and 8 are altered, the comparison of the phases of the induced currents in the antennas 7 and 9 is carried out just before the reference antenna 7 has reached a crossing, instead of doing the same just after the reference antenna has passed a crossing.
In this case, the phase comparison circuit 14 is designed so as to output the digital signal "1" or "0", depending on whether ths phases of the induced currents in the antennas and 9 are in the same phase or not, i.e., depending on the presence of the crossing 4 between the antennas 7 and 9, respectively.
In this way the address information for the mobile object is stored as "11001" in the shift register in Fig. 3, thus enabling the AND gate 17 to an output signal "1" to the terminal 18.
Another example of the preferred embodiment of this invention is shown in Fig. 5. In the block diagram 17-1,17-2,17-3, ...17-5 are AND gates, the other elements being provided with numerals equivalent to those used in Fig. 3.
In Fig. 6 a diagram similar to that disclosed in Fig. 4 shows the address of an area in the twisted-pair type inductive radio-frequency lines 1 to illustrate the functions of the circuit in Fig. 5. In case that the interval between the crossings in the relative location detecting zone is designed to be larger than the interval between the aforementioned antennas 7 and 9, the shift register 16 maintains the reading of "0" in the relative location detecting area and therefore the address is kept unchanged as (00000) until the reference antenna 7 passes the crossing a in Fig. 6.
Thereafter, the first column of the shift register 16-1 shows "1" when the reference antenna 7 passes the crossing a and consequently the terminal 18-1 at the AND gate 17-1 outputs the signal "1". Similar operations take place when the antenna 7 passes the crossings b, c, and so on, and the AND gates 17-2, 17-3, 17-4, ...in Fig. 5 output "1" to the corresponding terminals 18-2, 18-3, 18-4... respectively. Hence, the address of the mobile object is determined at every crossing a, b, c, ...on the travelling route of the object.
Another preferred embodiment of the invention is shown in Fig. 7, in which reference antenna 7, as shown in Fig. 7-A, is located perpendicularly to the lines 1, and the auxiliary antenna 8 and the comparison antenna 9 being provided in a parallel position to the same.
Fig. 7-B shows for a region in the vicinity of the crossing 3 a curve a' for the power level received by the reference antenna 7 and a curve b' for the power level received by the antennas 8 and 9. The reference antenna 7 is vertically positioned and provided with the maximum power on the crossing 3, the power level diminishing, up to zero as it leaves the crossing point. The antenna 8 and 9 are provided with almost "zero power" on the crossing 3, the power level going back gradually, to a constant value as it leaves the crossing 3.
On the other hand, the phases of the induced currents in the reference antenna 7 and the comparison antenna 9 are either in the same phase or in the altered phase, depending on whether the crossing 4 is present between them or not.
The reference antenna 7, the auxiliary antenna 8 and the comparison antenna 9 are connected to the input terminals 7', 8' and 9' in Fig. 3 respectively, where the phase comparator 13 therein is to be replaced by a level comparator which is equivalent thereto in its function. The level comparator outputs "1" to one of the two input terminals of the AND gate 15, shift pulse terminal of the shift register 16, and output terminal 19. The other components in Fig. 3 function in the same manner as the above embodiments.
In Fig. 7, the antennas 7 and 9 may be set with an interval equal to the minimum interval L in the lines 1, so that the levels of the induced currents in both the antennas 7 and 9 be compared only when the antenna 7 is positioned in the vicinity of the crossing. The results of the comparison in such configuration are shown in Fig. 7-C. The levels at the antennas 7 and 9 are about equal to each other so that the comparison results are "O"s, and in Fig. 7-D, where the antenna 9 is positioned at the crossing 4, the power level is almost zero.
As described above, the spaces between the neighbouring two crossings in the inductive lines may be expressed by the two values, namely p1 and p2, where p2 is larger than p1. In the present invention, the only one requisit for p1 and p2 is to satisfy the following relations:
or
These conditions imply that p1 is larger than I/2 so that the number of crossings which are present between the two antennas 7 and 9 are kept unchanged along the lines. An implication of the above relations is that p1 is less than I in order to detect the absolute position of the mobile object. Other implications of the above relations are that p1 is less than I when the absolute address of the mobile object on the inductive lines is detected with a short distance between two neighbouring crossings. On the contrary it is required that p2 is larger than I when detection of the absolute position of the object is necessary along the inductive lines with long distance of two neighbouring crossings.

Claims

A system for detecting a mobile object on a predetermined travelling route utilizing twisted-pair type inductive radio frequency lines (1), which are installed parallel to each other along said travelling route and comprise a plurality of crossings (3, 4) at intervals therebetween, said intervals having two specific different lengths p1 and p2 (p2>p1) within an area necessary for detecting the absolute position of the mobile object,
characterized. in that:
the mobile object is equipped with a reference antenna (7), an auxiliary antenna (8) and a comparison antenna (9), all provided for inducing currents therein by interaction with said radio frequency lines (1) the space I between said reference and comparison antennas meeting the following relations:
and that the currents induced in the antennas (7, 8, 9) are detected by detector means and compared in a logic circuit (13-15) in terms of phases and power levels, said logic circuit producing a signal of "1" or "0" level depending on the coincidence or non-coincidence of the comparison results.