JPS5952993B2 - Vehicle speed detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle speed detection device that detects speed based on changes in the reception level of signals transmitted between a twisted loop antenna installed along a railway track and an on-board antenna. The aim is to provide this type of device that is fail-safe.

Normally, the speed of a vehicle running on wheels is detected by detecting the number of rotations of the wheels, but for levitated vehicles such as magnetic levitation, there is no simple speed detection method. One possible method is to twist a loop antenna along the vehicle antenna and measure the time interval at which the reception level of the signal transmitted between the loop antenna and the on-board antenna changes to detect the vehicle speed. In general, in vehicle operation control, low speed detection means are used in various ways to ensure the safety of passengers, but most of them are required to have a fail-safe function. To give you the first and second examples, for example, when a wheelless vehicle such as the above-mentioned floating type is equipped with an oncoming train control (ATC) system,
When equipped with a device, a signal for speed detection is received from the on-board antenna to the above-mentioned stranded loop antenna on the ground,
Usually, a method is considered to detect the time interval at which the amplitude change of the received signal changes over time and output a detection signal, but the amplitude change due to the vehicle speed becomes no signal when the vehicle stops. Therefore, it cannot be distinguished from no signal at the time of equipment failure. Therefore, if the device malfunctions when the vehicle is running at high speed and the amplitude change amount becomes no signal, the circuit condition of the device becomes the circuit condition when the vehicle is stopped, and the device is in a dangerous state where it is possible to accelerate above the ATC speed limit. Therefore, the failsafe function is not satisfied. Further, when a door opening permission signal is given under the vehicle stop condition where the amplitude change amount is no signal, there is a danger that the door may open while the vehicle is running, as described above.

The reason why the above-mentioned dangerous situation occurs is that the loss of the receiving amplitude change when the detection signal should be output and the loss of the signal at the time of a failure are the same phenomenon.

Therefore, in order to construct a fail-safe circuit, it is important to construct a circuit under the condition that when outputting a detection signal, there is an AC input signal which is a speed detection signal, and when no detection signal is output, there is no AC input signal. This is the easiest method. The present invention provides a low speed detection device whose circuit is configured based on the above-mentioned logical conditions.

As one example of this, consider the case where a train CT with a transmitting antenna CA on the train passes over a twisted loop antenna (hereinafter simply referred to as a loop) LA on the ground, as shown in Figure 1A. Is it generated by the signal generator SG on the car?
When an AC signal with a frequency FO transmitted to the ground from the on-board antenna CA is received on the ground via the loop LA, the received waveform changes in phase at the twisting point of the loop LA, as shown in Figure 1B. is reversed 180 degrees and looks exactly like what is shown in the same figure? Modulate the carrier wave FO/ with the modulated wave of period T and carry it? FOr suppressed double-side band wave (FO-1/T), (FO+1'/T)
will be almost the same. The period T shown in the figure is inversely proportional to the vehicle speed. Therefore, the frequency components in the figure are as shown in FIG. 2. That is, (FO-1/T), (F
If O+1/T) is the frequency FO(7) width sideband, then
Vehicle speed force bark》 Frequency 1/T increases and both sides band? As the frequency interval between and the center frequency FO becomes larger and becomes farther away from the frequency of FO, and as the vehicle speed becomes lower, the side band waves approach the center frequency FO.

Therefore, if the signal of the received waveform is passed through the circuit of the bandpass filter BPF having the frequency characteristic shown by the broken line in FIG. 2, the output signal of the filter BPF can be obtained only when the vehicle is at low speed. In this way, it is possible to configure a detection circuit that obtains an output only when the vehicle is at low speed. ,In addition, above, I mentioned that the frequency component of FO is suppressed, but for reference, I will explain the reason.For example, if the amplitude is the same?
The frequencies are respectively (FOl/T) and (FO+1/T
) is the sum of the two waves.

The above wave has a peak amplitude of 2 A, and is a wave that makes the wave of frequency FO zero (reverses the phase) every period T/2. Also, the phase is every period T/2! Since the polarity is reversed,
If you look at the components of the cycle number VO over a long period of time, they cancel each other out and become zero.

As mentioned above, when the vehicle is at high speed, the two waves of frequency (FO-1/T) and (FO+1/T) are separated to the left and right of frequency FO as shown in Figure 2, and a filter with the characteristics shown in the figure is applied. Output is cut off by BPF and output only at low speeds.
However, if we consider the case where the on-board antenna CA stops exactly on the twisting point of the loop LA, there will be an inconvenience that the output signal of the above-mentioned detection circuit will disappear. As shown in the table, take measures such as providing two loops with different twisting points, or providing two on-board antennas whose spacing is different from that of the twisting points.

In the above table, when the number of on-board antennas is 2, for example, the antenna spacing is the ground loop stranding spacing x (1/2+n) (where n is an integer). When the number of above-ground loops is two, for example, the twisting positions of both loops are arranged at the center between the other twisting frames. Figures 3 to 5 show examples of ground equipment and vehicle low speed detection operations, etc., in the case of item 1 in the above table, where the number of ground loops is 2, the number of on-board antennas is 1, and one type of wave is transmitted from on-board. FIG.

In other words, in FIG. 3, signals of the number of loops JO are looped from the on-board antenna CA of a vehicle CT running on loops LA1 and LA2, which are laid so that the strand positions are at the center of the distance between the other strands. FIG. 4 is a state diagram in which radiation is transmitted toward LAl and LA2, and FIG.
The output side of a receiving circuit consisting of PFl, BPF2, front-stage amplifiers FAl, FA2, level detectors LDl, LD2, rear-stage amplifiers BAl, BA2, rectifiers RFl, RF2, etc. connected to them as shown in the figure is connected in parallel. FIG. 2 is a block diagram of a vehicle speed detection circuit configured to operate a relay Ry. FIG. 5 is a time chart showing the operating state of vehicle speed detection. For example, when a vehicle CT is running while decelerating,
This is a time chart of the detection operation showing a state in which the on-vehicle antenna CA stops just when it comes to the twisting point P of the loop LA2.

That is, Fig. 5A shows a state in which the time interval of phase inversion shown in Fig. 1B increases as the vehicle decelerates.
, b represents. Then, when the vehicle CT stops when the on-board antenna CA comes to the twisting point P of the loop LA2,
The received signal of loop LA2 disappears as shown in Figure 5b, but since the position of the on-board antenna CA with respect to loop LA is in the middle of the strand spacing, the received signal of loop LA1 disappears as shown in Figure 5a. Continuously received. Therefore, vehicle C
Due to the deceleration of T, the received wave passes through the filter BPF], BPF2
When reaching the passband frequency of , the output of the receiving circuit connected to loop LA1 increases in level as shown in FIG. 5C, and the level of the output of the receiving circuit connected to loop LA2 similarly increases as shown in FIG. , the above-mentioned on-board antenna C
The received output level decreases depending on the stationary position of A. However, since both output circuits are connected in parallel to drive relay Ry, as shown in Figure 5e, the output level of relay Ry driven by both reception outputs decreases as shown in figure 5d. However, the operation is maintained by the output of C in the figure, which serves as the output for deceleration detection. By installing the loops LA1 and LA2 shown in FIG. 3 in this way, connecting their reception output circuits in parallel, and driving the deceleration detection relay Ry, the on-board antenna CA can be connected to the loops LA1 and LA2.
The inconvenience that would occur if A2 stopped on any of the twisting points is eliminated, and failsafe is maintained.

It should be noted that the above has described an example in the case of item 1 in the above table, and descriptions regarding other items in the table are omitted.

[Brief explanation of the drawing]

Fig. 1A is a schematic diagram showing the installation state of a vehicle and a twisted loop antenna that transmit signals from the on-board antenna, Fig. 1B is a schematic diagram of the signal waveform received by the antenna, and Fig. 2 is a diagram showing the transmission frequency of the signal. A characteristic diagram showing the sideband wave as the center frequency and the required pass frequency band of the filter. Figure 3 is an explanatory diagram of the state when two twisted loop antennas are installed. Figure 4 is a diagram showing the state of the two twisted loop antennas. Signal receiving circuit block diagram, 5th
The figure is a time chart for explaining the operation of the equipment shown in FIGS. 3 and 4. CT...train, LA, LA1, LA2...
...Twisted loop antenna, CA...Vehicle antenna, BPFl, BPF2...Band pass filter, FO...Transmission frequency, (FO-1/T),
(FO+1/T)...Both side band frequency.

Claims (1)

[Claims] 1. AC signals of a predetermined frequency are transmitted and received between ground loop antennas that are strung at equal intervals along the vehicle route and the antenna installed on the vehicle, and the vehicle is traveling. A filter whose bandpass frequency is the transmission frequency and the double-side band frequency corresponding to the vehicle detection speed by utilizing the fact that the received signal waveform becomes a double-side band modulated wave state in which the transmission frequency component is suppressed. What is claimed is: 1. A vehicle speed detection device characterized in that the low speed of the vehicle is detected by detecting the level of a signal passing through the filter.