JPS5816149B2 - Idoutai no Ichi Kenchi Houshiki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the position of a moving object by using a leaky coaxial cable in a frequency range without radiation.

Most of the methods that have been developed so far to detect the position of a moving object using a leaky coaxial cable are those that transmit transmission waves in the frequency range where the radiation mode exists from the leaky coaxial cable to the leaky coaxial cable. It is.

However, when a leaky coaxial cable is laid along the route of a moving object and used for position detection, it is common to also communicate between the moving object and a fixed base.

For this purpose, it is necessary to use two different frequencies for communication and position sensing, or to perform communication and position sensing by distributing the same frequency at appropriate locations in the transmission system.

In the former case, depending on the location where the leaky coaxial cable is installed, surrounding conditions, etc., radio waves must be allocated for two frequency bands based on the Radio Law.

In the latter case, since a signal that has undergone some modulation for communication is also used for position detection, measures are required to prevent position detection errors due to modulation.

Furthermore, for communication, the strength of the signal received by a mobile unit or fixed base must be stable, so a position detection method that utilizes the fact that the strength of electromagnetic waves radiated from a leaky coaxial cable decreases in the longitudinal direction is used. is difficult to apply.

In the method of generating a position detection signal by longitudinal fluctuation of the induced electromagnetic field at a frequency in a region where the radiation mode of the leaky coaxial cable does not exist, the position detection signal is generated by the noise emitted by the current collector of the moving object, the spark plug, etc. There is a concern that this may lead to errors.

The purpose of the present invention is to use a low frequency in which the radiation mode of leaky coaxial cables does not exist, so that communication between mobile objects and fixed bases is not hindered (and frequency allocation for position detection based on the Radio Law). The object of the present invention is to provide a position detection method that does not require the above and is robust against noise emitted by moving objects.

In the present invention, in order to eliminate the need for frequency allocation and licenses based on the Radio Law, the electromagnetic field induced around the leaky coaxial cable at a low frequency where the radiation mode of the leaky coaxial cable does not exist is stipulated in the Radio Law. A transmission wave with a strength that is within the range of a weak electric field is transmitted to a leaky coaxial cable.

Given this frequency range and the strength of the induced electromagnetic field, there is a concern that errors may occur in the conventionally proposed position detection method that uses periodic changes in the electromagnetic field strength in the longitudinal direction due to the noise emitted by the moving object. Therefore, in the present invention, the phase difference between the axial component and the circumferential component of the induced magnetic field is reversed as the so-called "zigzag slot-shaped" leakage coaxial cable moves in the length direction. Perform detection operation.

As mentioned above, in order for the phase difference between the axial component and the circumferential component of the induced magnetic field to reverse as it moves in the longitudinal direction, the radiating slot array of the leaky coaxial cable must change the excitation phase of the circumferential component within the radiating slot. It must have a structure in which the longitudinal direction is reversed at a certain period.

A case will be described in which the present invention is applied to automatic operation of a mobile object (bus) on a dedicated travel path of a transportation system for the purpose of transporting passengers.

In FIG. 1, a mobile body 1 is equipped with two loop antennas 2 and 3 for position detection, a position detection pulse generator 4, a signal processing device 5, and a communication antenna 13.

A leaky coaxial cable 7 is laid along the dedicated running path 6 of the moving body 1 at a position directly below the moving body 1 and close to the outer surface of the running path 6.

Two loop antennas 2 and 3 are fixed to the lower part of the moving body 1 so as to be close to the leaky coaxial cable 7.

The detection signals from both antennas are input to the pulse generator 4, and pulses are generated as the phase difference between the two signals is inverted.

The signal processing device 5 that receives the pulse calculates the current position of the mobile object 1 based on the pulse and the command sent from the fixed base on the ground, stores it, and transmits the position information to the fixed base via the antenna 13 as necessary. and send.

The antenna 13 also transmits and receives other signals between the fixed base and the mobile unit 1.

The principle of the present invention will be explained with reference to FIG.

An example is the so-called single zigzag slot type.

A leaky coaxial cable 7 is used.

At frequencies below the radiation cutoff frequency fc, the magnetic field 14 is induced only in the vicinity of the radiation slot 8 in the direction of the arrow.

In the zigzag slot type leaky coaxial cable, the direction of the axial component of the magnetic field 14 is reversed in adjacent slots, whereas the direction of the circumferential component is not reversed.

Therefore, if the loop antenna 2 detects the axial component of the magnetic field 14, and the loop antenna 3 detects the circumferential component, the phase difference between the detected voltages of the loop antennas 2 and 3 will be as shown in FIG. The angle changes by 180° each time the angle moves by a distance P.

Here, P is the arrangement interval of the slots 8.

FIG. 4 shows a device that generates pulses by inverting the phase difference.

9 and 9' amplify the detection voltage of the loop antennas 2 and 3 and transform it into a pulse having a constant shape.

10 is an AND circuit whose gate opens only when the outputs of 9 and 9' are in phase.

The rectifier circuit 11 converts the signal into a DC signal, and this DC signal is compared with a reference voltage built into a pulse generation circuit 12. When the signal exceeds the threshold of the reference voltage, the pulse generation circuit 12 generates a pulse.

In the present invention, the change in the phase difference between the two components of the magnetic field induced in the vicinity of the leaky coaxial cable is used for position detection, so it is less susceptible to fluctuations in longitudinal magnetic field strength and surrounding conditions.

Furthermore, since this method uses frequencies below the radiation cutoff frequency, electromagnetic waves in the radiation region of the leaky coaxial cable can be effectively utilized, and there is no need to receive special radio wave allocation for position detection.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing one embodiment of the present invention, Fig. 2 is a detailed diagram of the positional relationship between the leaky coaxial cable and the loop antenna, Fig. 3 is an explanatory diagram of the operation, and Fig. 4 is an in-vehicle installation for position detection. A schematic diagram showing an example of a device. 1: Mobile object, 2: Loop antenna for detecting axial component of magnetic field, 3: Loop antenna for detecting circumferential component of magnetic field, 4: Position detection pulse generator, 5: Position signal processing device, 6: Travel path for mobile object , 7: Leaky coaxial cable, 8: Radiation standant, 9, 9': Waveform amplification/shaping circuit, 10: Logic gate (AND circuit, etc.), 11: Rectifier circuit, 12: Pulse generation circuit, 13: Communication use Antenna, 14: Induced magnetic field.

Claims (1)

[Claims] 1. A leaky coaxial cable having a row of radiation slots on the outer conductor and having a structure in which the excitation phase of the circumferential component of the electric field in the radiation slots is reversed at a certain period is laid along the travel path of the moving body, and A transmission wave with a frequency lower than the radiation cutoff frequency fc determined by the structure of the leaky coaxial cable is transmitted to the leaky coaxial cable, and is coupled to the circumferential component and the axial component of the magnetic field induced in the vicinity of the leaky coaxial cable, respectively. Two antennas are fixed to a moving body in close proximity to the leaky coaxial cable, and a phenomenon is utilized in which the phase difference between the voltage or current detected by the two antennas is reversed as the moving body moves in the longitudinal direction. A method for detecting the position of a moving object.