JPS629865B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a vehicle position detection method.

In vehicle operation systems that run on the tracks of trains, trains, etc., wireless communication methods using leaky coaxial cables, open coaxial cables, parallel two-wire cables, etc. using VHF and UHF bands are replacing the conventional LF band guidance methods. It has been used to avoid noise from vehicles. However, the conventional cable laying method cannot effectively detect the vehicle position. That is,
Conventionally, a single cable is usually laid along the rail, so position detection is possible by detecting changes in the electric field level, but distance detection accuracy is limited when changes in the external environment are taken into account. This is extremely unsatisfactory.

An object of the present invention is to provide a vehicle position detection method that solves these problems.

Normally, the distance accuracy is unsatisfactory with a system using one cable, so in the present invention, two cables are provided on both sides of the rail, and each cable is alternately leaky type (including open type) and sealed type. They are laid at regular intervals, and when facing each other, if one cable is a closed type, the other is a leaky type, and the cables are arranged so that radio waves are always radiated from one of the cables. Economically, a two-strand cable is a burden, but a sealed type is extremely economical compared to a leaky type, and because two cables are installed at the same time, it is recommended to install a leaky type for the entire length of the run. There is no big difference compared to . Due to the cable arrangement described above, vehicles running on the rails simply receive radio waves from one of the cables, and stable communication is maintained. On the other hand, in a vehicle, two antennas facing each cable are placed on both sides of the vehicle, and radio waves from the cables on the opposite side are received, and the electric field of each signal is detected by a receiver installed on each side. Is it a leaky section?
By easily detecting whether it is a closed section and counting the number of repetitions from a base point (such as a station), the distance, that is, the traveling position, is detected. Furthermore, in general communication, extremely high quality communication can be maintained by combining the signals of two receivers.

The above explanation assumes that two receivers are used to receive signals, but it is also possible to use one receiver to periodically switch between two antennas or to automatically receive radio waves from a leaky cable by detecting an electric field. It is also possible to switch to the other side, and this is not a constraint on the present invention.

Next, details will be explained with reference to the drawings.

Figure 1 shows two coaxial cables laid along a rail. 1 is a leaky coaxial cable, 2 is a sealed coaxial cable, and the left and right coaxes have 1 and 2 facing each other alternately. The repetition interval for each type of cable is, for example, 100 m, since the length of the cable winding storage drum is often 100 m. Signals from a base radio receiving device 6 installed at a base point, for example, a station, are distributed and connected to these two cables. 5 indicates a vehicle such as a train or a train, and two radio receivers 4, 4' are installed therein.
Communication is carried out with the base through antennas 3 and 3' provided between the cables facing each other. 7 is the rail.

Figure 2 shows the configuration of two radio receivers installed in a vehicle, with two antennas 10 and 1 on both sides of the vehicle.
The signal from 0' is sent to the receiving section (receiver high frequency amplification section,
The amplified signals connected to the intermediate frequency amplification section) 11, 11' are detected by the discriminators 13, 13' to become audio signals, and the respective outputs are synthesized by the signal synthesizer 14, amplified by the audio amplifier 15, and sent to the handset. 17 to enable general voice communication. (In addition, the explanation regarding the transmitter is omitted in this text.) As a signal combiner, there is a method of selectively switching the one with a better S/N, or a method of square-law synthesis according to the S/N of each receiver. Although there are other methods, their explanation will be omitted since they are not directly related to the present invention.

Now, the IF extracted from the middle of the intermediate frequency amplification stage
The IF signal is converted into a DC signal by electric field detectors 12, 12'. At this time, when a moving vehicle receives radio waves by radio, it is frequently affected by standing waves and the received electric field output fluctuates greatly.
Therefore, an appropriate time constant is provided to rectify the IF signal and convert it into a DC signal.

The distance determiner 16 compares the difference in electric field strength between the signals from the electric field detectors 12 and 12', counts the number of repetitions of the strength of the electric field from the base point, and calculates the distance from the base point of the vehicle, that is, the position. judge.

FIG. 3 shows an example in which the receiver explained in FIG. 2 is configured with one receiver instead of two. That is, the signals from the two antennas 10, 10' are switched by the antenna switch 18 to select one of the stronger signals. Specifically, the IF signal amplified by the receiving section (high frequency, intermediate frequency amplifying section) 11 is judged by the electric field detector 12, and if the output falls below a predetermined level, the antenna switching signal is sent to the antenna switching device 18. Switch to the appropriate antenna side, that is, the leaky coaxial cable side. A discriminator and audio amplifying section 19 transmit the audio signal to the handset 17. 16 is a distance determiner that counts and compares the DC output of the electric field detector 12 and the number of outputs of the antenna switching signal to determine the distance.In principle, it differs from the one explained in FIG. The only difference is that instead of counting changes in electric field strength, the number of antenna switching is counted, and the other functions are exactly the same.

Figures 4 and 5 show each antenna 1 in an actual vehicle.
The electric field fluctuations input through 0 and 10' are shown using the distance L from the base point as a parameter. When two receivers are used, each electric field detector output (Figure 7) is set with an appropriate time constant. The waveform that is smoothed by the circuit and removes the steady DC component after rectification of the IF signal becomes a rectangular wave as shown in Figure 8. By counting the number of pulses, it is easy to distinguish between leaky coax and sealed coax that can be repeated from the base point. The number of cable connections can be determined and the vehicle position from the base point can be detected.

Figure 6 shows how the received electric field changes in one section of the leaky coax, and ΔL is the traveling distance within the time constant;
S is the vehicle speed, and Δt is a time constant. By appropriately selecting the rectifying and smoothing time constant of the electric field detector in relation to the speed of the vehicle, it is possible to determine the distance of the received electric field from the beginning of the leaky coaxial cable section.
More accurate position determination can be performed by combining the number of repetitions of the leaky coaxial cable and the sealed coaxial cable up to that point and the determination distance within one section of the leaky coaxial cable. Specifically, the patent “Electric field strength detection method for vehicle position detection” (Japanese Patent Application Laid-Open No. 55-41144) was filed on the same day.
The details are described in the following publication.

As explained above, the present invention enables the recent
It is possible to have the communication system of a vehicle running on the rails detect the position of a train using the VHF or UHF band, and together with the voice communication system, it can make a major contribution to vehicle operation. We can expect great effects from expanding functionality.

It goes without saying that the present invention is not limited to vehicles running on specific lanes such as rails, but is also effective for detecting the position of vehicles on expressways, for example.

In addition, in order to improve detection accuracy, it is possible to consider methods such as keeping the cable installation position and the vehicle's antenna within a certain distance, but with the recent development of electronic technology, complex logical processing can be used to accurately control fluctuations in the received electric field. The signals from the cables can be easily identified, and the cable installation can be done under highly flexible conditions.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a vehicle position detection method according to the present invention, FIGS. 2 and 3 are block diagrams showing an embodiment of a wireless receiver installed in a vehicle, and FIGS. The figure shows changes in electric field received by the antenna, and FIGS. 7 and 8 are examples of output waveforms of the electric field detector. In the figure, 1... leaky coaxial cable, 2...
... Sealed coaxial cable, 3, 3', 10, 10'...
...Antenna, 4,4'...Vehicle radio (receiving section), 5
...Vehicle, 6...Base transmitting/receiving device, 7...Rail,
11, 11'... Receiving section, 12, 12'... Electric field detector, 13, 13'... Discriminator, 1
4...Signal synthesizer, 15...Audio amplifier, 16...
. . . distance determiner, 17 . . . handset, 18 . . . antenna switch, 19 . . . discriminator and audio amplifier.

Claims (1)

[Scope of Claims] 1. In a vehicle position detection method that uses radio waves to detect the position of a vehicle traveling on a certain lane, a leaky or open coaxial cable and a sealed coaxial cable are installed on both sides of the vehicle along the lane. The radiated radio waves of the signals transmitted from the base station are received from the leaky or open coaxial cable section by the two antennas installed on both sides of the vehicle, and each antenna receives the radiated radio waves of the signal transmitted from the base station from each cable. A vehicle position detection method that detects the distance or position traveled from a certain base point by detecting the number of repeated receptions and the strength of the received electric field. 2. The traveling distance from the connection point is determined by comparing the received electric field strength at a certain point of the leaky or open coaxial cable with the electric field strength at different connection points of the cable as a reference. A vehicle position detection method according to claim 1.