JPH06309587A - Mobile object detector - Google Patents

Abstract

PURPOSE:To provide a mobile object detector capable of surely detecting that a mobile object is stopped in a short period of time. CONSTITUTION:A loop coil 1 is provided along the travelling path 5 of the mobile object 4 and electromagnetically couples with the mobile object 4 and an inductance L changes. An oscillation circuit 2, of which oscillation frequency (f) changes corresponding to the change of the inductance L, outputs it as a frequency signal S1. A processing circuit 3 detects the mobile object 4 when the frequency signal S1 changes equal to or mire than a first set value K from a reference frequency f0. When the rate of the change of the frequency signal S1 is equal to or less than a second set value M after the mobile object 4 is detected, the stoppage of the mobile object 4 is detected and a mobile object stoppage signal S2 is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving body detecting device, and more specifically, it detects a moving body from a change in an oscillation frequency according to a change in inductance of a loop coil, and moves by a rate of change in the oscillation frequency after the detection. This relates to a technique for detecting body stoppage.

[0002]

2. Description of the Related Art A moving body detecting device utilizing a change in inductance of a loop coil is known in the fields of railway and road traffic. As a method of detecting a change in inductance, a method of detecting an unbalanced voltage by a bridge circuit and a method of detecting a change in oscillation frequency of an oscillation circuit are generally known.

[0003]

However, since the conventional moving body detecting device detects the absolute value of the inductance change, the moving body can be detected by the inductance change of a certain value or more, but the moving body can be detected. It was not possible to judge whether the car was moving or stopped. Also,
There is also a method of determining that the moving body is stopped when the moving body detection continues for a certain time or more, but it is difficult to separate the stop and the low speed running. When the accuracy of separation is sought, the detection time becomes long.

An object of the present invention is to solve the above-mentioned problems and to provide a moving body detecting apparatus capable of surely detecting that a moving body is stopped in a short time.

[0005]

In order to solve the above-mentioned problems, the present invention is a moving body detecting device including a loop coil, an oscillation circuit, and a processing circuit, wherein the loop coil is a traveling body of the moving body. The circuit is provided along a path, and the inductance is changed by electromagnetically coupling with the moving body.The oscillation circuit is connected to the loop coil, and the oscillation frequency changes according to the change in the inductance. The processing circuit receives the frequency signal, detects the moving body when the frequency signal changes by a first set value or more with respect to a reference frequency, and detects the moving body. After that, when the rate of change of the frequency signal is equal to or less than the second set value, the stop of the moving body is detected, and the moving body stop signal is output.

[0006]

The loop coil is provided along the traveling path of the moving body and is electromagnetically coupled to the moving body to change the inductance. The oscillation circuit is connected to the loop coil and oscillates according to the change in the inductance. Since the frequency changes and is output as a frequency signal, the oscillation frequency changes so as to be substantially symmetrical between the entering side and the advancing side of the moving body, and a frequency signal that generally changes in a mountain shape can be obtained.

Since the processing circuit receives the frequency signal and detects the moving body when the frequency signal changes by the first set value or more with respect to the reference frequency, the presence or absence of the moving body can be surely detected.

Since the processing circuit detects the stop of the moving body when the rate of change of the frequency signal is equal to or less than the second set value after detecting the moving body, the processing circuit outputs the moving body stop signal.
It is possible to confirm the presence of the moving body and surely detect that the moving body is stopped in a short time.

[0009]

1 is a block diagram showing the configuration of a first embodiment of a moving object detecting apparatus according to the present invention. The figure shows a case where an entrance of a parking lot is provided, 1 is a loop coil, 2 is an oscillation circuit, 3 is a processing circuit, 4 is a moving body, 5 is a traveling path, and 6 is a breaker. The moving body 4 is usually a vehicle such as an ordinary passenger car or an aircraft that runs on a runway, but it includes a metallic material used in an automation line and a carrier box that generates an eddy current or a magnetic material that changes a magnetic circuit. It may be a carrier box.

The loop coil 1 is provided along the traveling path 5 of the moving body 4 and is electromagnetically coupled to the moving body 4 to change the inductance L. In the embodiment, the loop coil 1 is embedded at a depth of 5 to 10 cm in the ground from the viewpoint of preventing passage obstacles.

The oscillator circuit 2 is connected to the loop coil 1, the oscillation frequency f changes in accordance with the change in the inductance L, and outputs the frequency signal S1. Capacitor 21
Are connected in parallel to the loop coil 1 and
At the same time, the oscillation frequency f is determined. The oscillation frequency f is set at room temperature and within a range of 25 kHz to 50 kHz without electromagnetically coupling with a moving body such as a passenger car.

The processing circuit 3 is composed of a microcomputer, and the frequency signal S1 is first relative to the reference frequency f0.
The moving body 4 is detected when the set value K has changed by more than K. The reference frequency f0 corresponds to the oscillation frequency f and is 25 kHz.
It is set within the range of ˜50 kHz. After detecting the moving body 4, the processing circuit 3 detects the stop of the moving body 4 when the rate of change of the frequency signal S1 is equal to or less than the second set value M, and outputs the moving body stop signal S2.

FIG. 2 is a diagram showing changes in the oscillation frequency with changes in the inductance of the loop coil. The figure shows a case where the moving body 4 passes over the loop coil 1 at a constant speed. The horizontal axis represents the moving distance of the moving body, and the vertical axis represents the frequency change with respect to the reference frequency. In the case of the loop coil 1, since the oscillating frequency f changes so that the approaching side and the advancing side of the moving body 4 are substantially symmetrical, the frequency signal S1 that generally changes in a mountain shape is obtained.

FIG. 3 is a diagram showing changes in the oscillating frequency when the moving body temporarily stops on the loop coil and passes by.
The horizontal axis represents the sampling time, and the vertical axis represents the frequency change with respect to the reference frequency. The flat part shows the state where the moving body 4 is stopped. FIG. 3 shows the structure shown in FIG.
Will be similar to.

FIG. 4 shows a first embodiment of the moving body detecting apparatus according to the present invention.
6 is a timing chart for explaining the operation of the embodiment.
In the figure, S1 is a frequency signal, S3 is a moving body detection signal, and S2 is a moving body stop signal. The frequency signal S1 is
For convenience of explanation, it is shown by being converted into a frequency change with respect to the reference frequency f0. Referring to FIG. 1, FIG. 4 will be described together with its operation.

As described above, the loop coil 1 is provided along the traveling path 5 of the moving body 4 and is electromagnetically coupled to the moving body 4 to change the inductance L. The oscillation circuit 2 includes the loop coil 1. 1, the oscillation frequency f is changed according to the change of the inductance L, and is output as the frequency signal S1.
1 is input and the moving body 4 is detected when the frequency signal S1 changes by the first set value K or more with respect to the reference frequency f0. Therefore, at time t1, the moving body detection “existence” state is set, and thereafter, the time t4. Then, the moving object is detected as "absent". Therefore, the presence or absence of the moving body 4 can be reliably detected.

The processing circuit 3 detects the stop of the moving body 4 and outputs the moving body stop signal S2 when the rate of change of the frequency signal S1 is equal to or less than the second set value M after detecting the moving body 4. Therefore, at time t2, the moving body is stopped “present” state, and then at time t3, the moving body is stopped “absent” state.
Therefore, it is not necessary to determine that the moving body detection has continued for a certain period of time or longer, and it is possible to confirm the presence of the moving body 4 and reliably detect that the moving body 4 is stopped in a short time.

Further, as shown in FIG. 2, the frequency signal S1
Has a mountainous characteristic, and if it is determined by tracking the frequency signal S1 whether the change in the oscillation frequency is on the entry side or the entry side, the stop position of the moving body 4 is determined by the absolute value of the change on the frequency signal S1. Can also be specified.

Since the present invention detects the stop of the moving body 4 by paying attention to the fact that the flat portion is obtained when the frequency change should be obtained, the arrangement shape of the loop coil 1 has a predetermined inductance. It is sufficient that the inductance is changed even after the moving object detection signal S3 is obtained by changing the value.

FIG. 5 is a flow chart showing the operation of the signal processing circuit in the first embodiment. This will be described with reference to FIG.

As a first step, the reference frequency f0 is read as an initial value.

As the second step, the current frequency f is read and the change amount Δf with respect to the reference frequency is obtained.

As a third step, the variation Δf is compared with the first set value K, and if the variation Δf is less than the first set value K, it is processed as a moving object detection “absent”, and the variation Δf is If the value is equal to or larger than the first set value K, it is processed as the presence of the moving body detection. When the moving body detection is “absent”, the process returns to the second step, and the second step and the third step are repeated until the moving body detection “present” is processed. When the processing is performed as the moving body detection “present”, the moving body detection signal S3 is obtained at time t1.

As a fourth step, when processing is performed with the presence of the moving body detected as “present”, the difference between the current change amount Δf and the change amounts Δf (1) to Δf (n) before the last time is calculated, and the difference is the If the value is equal to or less than the set value M of 2, the mobile body is processed as "present", and if it exceeds the second set value M, the mobile body is processed as "absent". The reason why the difference between the n change amounts is taken is to prevent malfunction due to noise, and when the difference between all the n change amounts is equal to or less than the second set value M, the moving body is stopped.
Process as. When the processing is performed with the moving body stopped “none”, the current change amount Δf is set as the previous change amount Δf (1),
The change amounts Δf (1) to Δf (n-1) before the previous time are sequentially shifted, and the second step to the fourth step are repeated until it is detected that the moving body has stopped. Stop moving body "Yes"
When processed as, the mobile body stop signal S2 is output at time t2. The current change amount Δf is set as the previous change amount Δf (1), and the change amounts Δf (1) to Δf before the previous time are set.
(N-1) is sequentially shifted, and the second step to the fourth step are repeated until it is processed as "absence" of the moving body stop. When the mobile body is processed as “none”, time t
At 3, the moving body stop signal S2 is stopped. When the amount of change Δf is less than the first set value K, it is processed as moving body detection “absent”, and the moving body detection signal S3 is stopped at time t4.

Further, in the first embodiment, the processing circuit 3 is
The correction unit 31 has a correction unit 31, and the correction unit 31 changes the reference frequency f0 by following the frequency signal S1. For example, the oscillation frequency f when the loop coil 1 is not electromagnetically coupled to the moving body 4
The reference frequency f0h is changed according to the equation (1) according to the ratio between d and the designed set frequency fK.

F0h = f0 * (fd / fK) (1) As a result, when the oscillation frequency f changes due to temperature drift, the reference frequency f0h also changes. Are canceled out, and the detection accuracy of the moving body detection signal S3 and the moving body stop signal S2 is improved.

Further, since the temperature drift changes slowly, the reference frequency f0h due to the correction can be time-delayed so as not to respond to noise that changes the oscillation frequency f rapidly.

FIG. 6 shows a second embodiment of the moving body detecting apparatus according to the present invention.
7 is a timing chart for explaining the operation of the second embodiment, and FIG. 7 is a flow chart showing the operation of the signal processing circuit in the second embodiment. In this embodiment, the reference frequency f0 follows the frequency signal S1 and changes with a certain delay time. 6 and 7,
The same reference numerals as those in FIGS. 4 and 5 denote the same components. f0h is the corrected reference frequency. The differences will be described below.

In the present embodiment, the change amount Δf is obtained from the difference between the corrected reference frequency f0h and the current oscillation frequency f, and the change amount Δf is moved when the change amount Δf becomes equal to or more than the first first set value K. The body detection signal S3 is obtained.

The correction of the reference frequency f0h is performed according to the equation (1) and with a certain time delay. The fixed time delay is the change amount Δf of this time and the change amounts Δf (1) to Δf before the previous time, which are provided from the viewpoint of preventing erroneous detection due to noise.
It is set to be sufficiently longer than the time for obtaining the difference from (n).
Therefore, even if the second set value M is set small, the stop "absence" cannot be detected due to the change of the reference frequency f0h.

As a result, it is possible to obtain a moving body detection device which does not erroneously detect temperature drift or the like.

The processing circuit 3 creates a moving body pattern from the change in the frequency signal S1 and normalizes the moving body pattern. For example, even if an ordinary passenger car passes over the loop coil 1 at high speed and the time axis of the frequency signal is shortened, the time axis is expanded by the normalization, and the frequency change as shown in FIG. 2 is obtained. Therefore, if the moving body pattern is normalized according to the traveling speed, the type of the moving body is identified, and the distinguishability of the stop or low speed traveling is improved, and the highly accurate moving body stop signal S2 is obtained.

INDUSTRIAL APPLICABILITY The present invention can reliably detect the stop of a moving body, and is therefore useful for gate control in a parking lot, traffic signal control for controlling a traffic signal by stop, warning for stop when "stop", and the like. It is also possible to detect a right-turn vehicle in a place where there is no right-turn lane.

[0034]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a moving body detection device that can reliably detect that a moving body is stopped in a short time. (B) It is possible to provide a moving body detection device that can detect the stop of a moving body without being affected by temperature drift or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a moving body detection device according to the present invention.

FIG. 2 is a diagram showing a change in oscillation frequency with a change in inductance of a loop coil.

FIG. 3 is a diagram showing a change in oscillation frequency when a moving body temporarily stops and passes on a loop coil.

FIG. 4 is a timing chart for explaining the operation of the first embodiment of the moving body detection device according to the present invention.

FIG. 5 is a flowchart showing the operation of the signal processing circuit in the first embodiment.

FIG. 6 is a timing chart for explaining the operation of the second embodiment of the moving body detection device according to the present invention.

FIG. 7 is a flowchart showing an operation of a signal processing circuit in the second embodiment.

[Explanation of symbols]

 1 Loop coil 2 Oscillation circuit 3 Processing circuit 31 Correction unit 4 Moving body 5 Traveling path 6 Circuit breaker L Inductance f Oscillation frequency f0 Reference frequency K First setting value M Second setting value S1 Frequency signal S2 Moving body stop signal

Claims (3)

[Claims] 1. A moving body detection device including a loop coil, an oscillation circuit, and a processing circuit, wherein the loop coil is provided along a traveling path of the moving body and is electromagnetically coupled to the moving body. The inductance changes, the oscillation circuit is connected to the loop coil, the oscillation frequency changes according to the change of the inductance, and outputs as a frequency signal, the processing circuit, the frequency signal Is input, the moving body is detected when the frequency signal changes by a first set value or more with respect to a reference frequency, and the rate of change of the frequency signal after the moving body is detected is less than or equal to a second set value. At the time of, the moving body detection device detects the stop of the moving body and outputs a moving body stop signal. 2. The moving body detection device according to claim 1, wherein the processing circuit has a correction unit, and the correction unit changes the reference frequency by following the frequency signal. 3. The moving body detection device according to claim 1, wherein the processing circuit creates a moving body pattern from a change in the frequency signal and normalizes the moving body pattern.