JP3521072B2 - Vehicle speed and vehicle length measurement method for moving objects - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method for measuring a vehicle speed, a length, and the like of a moving object from a signal waveform obtained by detecting the moving object with a sensor or the like. The present invention relates to a method of monitoring vehicle traffic on a road network and measuring a vehicle speed and a vehicle length used for control. [0002] At present, as sensors for measuring traffic volume, there are an ultrasonic sensor, a light wave sensor, an image sensor, a magnetic sensor and the like. [0003] Generally, the main measurement target in performing road traffic control and the like is the vehicle speed (or traffic volume). Specific amounts for grasping the traffic volume include so-called point traffic volume and space occupancy. The former is the number of vehicles passing a certain point on the road within a certain period of time, and the latter is the spatial ratio of a certain length of lane on the road occupied by the vehicle. The point traffic volume can use various sensors according to the situation of the installation place, and is effective when measuring the traffic volume relatively easily. Since the size of the traffic varies greatly, it is not possible to accurately grasp the traffic volume only from the point traffic volume, and it is necessary to measure the space occupancy according to the purpose. In order to obtain such a space occupancy, it is necessary to identify the type of the vehicle running on the road or directly measure the size of the vehicle such as the vehicle length. In order to measure the vehicle length in addition to measuring the vehicle speed (or traffic volume), a new sensor must be added or the accuracy of the sensor must be increased, and the device itself becomes large-scale. Costs will also increase. Therefore, as shown in FIG. 4, the present applicant has proposed a device for detecting the number, speed, and length of a moving body using a vehicle speed detecting sensor such as a magnetic sensor. In FIG. 4, R is a road surface, and the road surface R has two sensors (for example, magnetic sensors) 111a and 111b that output signals according to the movement of the moving body C, and outputs of the sensors 111a and 111b. 112a and 112b for amplifying the signal with a predetermined gain are embedded. The analyzer 120 measures the speed, the number of vehicles, and the vehicle length of the moving object C based on the outputs from the amplifiers 112a and 112b. [0007] As shown in FIG.
In order to measure the vehicle speed and the vehicle length with respect to the signal waveforms ea and eb output from the two sensors 111 (a and b), for example, a threshold voltage (threshold voltage) of a predetermined level is used.
+ Vl and -Vl are set, and the threshold voltage + V
From the time when l, -Vl and the signal waveforms ea, eb cross,
Various kinds of information measured from a moving body traveling on a road are obtained. That is, in FIG. 5, the times when the signal waveform ea of the sensor 111a crosses the threshold voltages + V and -V are represented by t11, t13 and t1.
5, and the time when the signal waveform eb of the sensor 111b crosses the threshold voltages + V and −V is represented by t12, t14,
Assuming that the vehicle speed of the moving object C is t16, the vehicle speed can be calculated from any of the time differences X1, X2, and X3 for speed detection, and if the values of X1, X2, and X3 are averaged and calculated,
A more accurate vehicle speed can be obtained. However, if the time L = t15-t11 corresponding to the vehicle length of the vehicle running on the road, there is a problem that a time considerably longer than the time corresponding to the actual vehicle length is detected. This is the sensor 111
It is considered that (a, b) is to output a detection signal in response before the vehicle comes directly above it. Therefore, although it is difficult to accurately measure the vehicle length using a sensor or the like, a measuring device that can be easily obtained to measure the space occupancy according to the required accuracy at the measuring point is required. Had been. SUMMARY OF THE INVENTION The present invention uses a sensor for measuring point traffic volume as it is, and accurately measures not only vehicle speed (traffic volume) but also vehicle length of passing vehicles. The purpose is to provide a simple method . [0012] The invention according to claim 1 is a system in which a moving body moving on the road surface at a predetermined interval on the road surface has a time difference.
The first and second magnetic sensors are arranged so as to be able to detect when the moving body passes on the road surface.
A first detection signal output from the first magnetic sensor;
And second detection output from the second magnetic sensor
The signal moves away from the zero level of the signal for vehicle length calculation.
Positive and negative first threshold voltage levels set to
First, second, fifth, and sixth times at which the first and last crosses are made, respectively . Next, a value which is smaller than the first threshold voltage level value and which is close to the 0 level of the signal
The second threshold voltage level for calculating the vehicle speed set in
A bell and the first detection signal and the second detection signal
Serial first time, and a third time to cross each after the second time, and detects the fourth time, the time of the third
The vehicle speed calculation value detected from the time difference and the fourth time difference,
A first time difference and a fifth time difference, or the vehicle speed calculation value;
The movement based on the second time and the sixth time difference
Calculate the vehicle length of the body . The magnetic sensor detects that a moving object has passed on a road surface.
Output a signal with almost the same waveform as shown in the figure below.
Are arranged at predetermined intervals so that FIG. 1 shows a vehicle length measuring method according to the present invention.
Which is a circuit diagram of the vehicle speed and the vehicle length measuring apparatus of a vehicle for carrying. In FIG. 1, reference numerals 11a and 11b denote first and second sensors which output detection signals in accordance with the movement of a moving body, and for example, a magnetic sensor, a capacitance sensor, or the like can be used. 12a and 12b are the first and second
Is an amplifier that amplifies the output of the sensors 11a and 11b with a predetermined gain. The amplifier is configured to be able to amplify a signal including a DC component in cooperation with a magnetic sensor, and has a characteristic of removing a noise component. Is preferred. The first and second detection signals output from the first and second sensors 11a and 11b are supplied to an amplifier 12a,
12b, and is output to the analysis device 20 and the measured value output K
Is output as The analyzer 20 includes a phase detector 13,
Time difference detection unit 14, storage unit 15, control unit 18, calculation unit 1
6, a dividing circuit 17. The phase detectors 13a, 13b, 13c, 13
d is for finding a feature point indicated by two detection signals output from the first and second sensors 11a and 11b,
In this embodiment, the vehicle speed is measured from the signals detected by the phase detectors 13a and 13c, and the vehicle length is measured from the signals detected by the phase detectors 13b and 13d. The time difference detector 14 is provided with the phase detector 13
a, 13b, 13c, and 13d convert the input time difference from the output as a series of pulse signals into data, perform an operation of sequentially obtaining the input time difference, and perform the above-described operation according to a program controlled by a microcomputer or the like from the control unit 18. The output intervals of the phase detectors 13a, 13b, 13c and 13d are counted, and the time difference information within a certain range is output to the next storage unit 15 with an identification code added thereto. Storage unit 15
The time difference information within the predetermined time stored in the
At 6, the vehicle speed and the vehicle length are measured based on the command from the control unit 18. The vehicle speed value and the vehicle length value are obtained in plurals,
By dividing by the number of information sampled in the next dividing circuit 17, it can be obtained as an average measured value. In carrying out the measuring method of the present invention,
The acquired detection value will be described with reference to FIG. First, the first and second sensors 11 (a,
For the first and second detection signals of b), a second threshold voltage for calculating the vehicle speed + Vv, (−Vv) is set, and + V is set as the first threshold voltage for calculating the vehicle.
1 and (-Vl) are set. The first detection signal detected by the first sensor 11a has a first signal waveform indicated by Ea. The time at which it crosses the vehicle length calculation threshold voltage + Vl is t1, the vehicle speed calculation threshold is Voltage V
The time to cross v is t3, and the time to cross the vehicle length calculation threshold voltage -Vl is t5. The second detection signal detected by the second sensor 11b is Eb
, And the time when it crosses the vehicle length calculation threshold voltage -Vl is represented by t2,
The time at which the vehicle speed calculation threshold voltage Vv crosses is t4, and the time at which the vehicle length calculation threshold voltage -Vl crosses is t6. The vehicle speed calculation threshold voltage Vv
Is set near 0 V because the detection accuracy is improved by using the waveform of the portion of the waveform indicated by the sensor signal E where the rate of change is large. However, since the vicinity of 0 V is easily affected by noise, It is preferable to set a slightly higher level. The vehicle length calculation threshold voltage Vl is
Setting the voltage value to a certain distance from 0 V enables measurement of a time interval closer to the actual vehicle length. In the actual setting, the sensitivity varies depending on the installation conditions (especially the direction) of the sensor. Therefore, it is important to finely adjust the vehicle length calculation threshold voltage Vl after installing the sensor 11. A first sensor 11a and a second sensor 11b
Assuming that the separation distance from X is X (see FIG. 4), the vehicle speed V of the moving object C is measured as follows. V = X / (t4−t3) Although the time difference for speed measurement is measured only at one place in FIG. 2, it is obtained at many timings as shown in FIG. If the average is measured, a more accurate vehicle speed V can be obtained. The vehicle length L of the moving body C is determined by the first sensor 11
Assuming that the vehicle length measured from the first detection signal Ea of a is L1, the measurement is performed as follows. L1 = (t5−t1) × V = (t5−t1) × X / (t
4-t3) Similarly, assuming that the vehicle length measured from the second detection signal Eb of the second sensor 11b is L2, the measurement is performed as follows. L2 = (t6-t2) × V = (t6-t2) × X / (t
4-t3) The vehicle length L may be either L1 or L2, but the average value of these two measured values, Lave, is
It may be a measured value, which is a value with higher accuracy. Lave = (L1 + L2) / 2 The vehicle length detection threshold voltage V
Since 1 has an appropriate value that differs depending on the sensitivity of the sensor 11, the environment of the installation location, and the like, it is desirable to set the value after performing several pass tests of the moving body after installation. For the sake of explanation, the contents of the signal time difference circuit are shown by individual block diagrams, but the time difference detection circuit 14, the storage unit 15, the operation unit 16, the division circuit 17, etc.
Similar signal processing can be performed by the CPUs. Further, such a time difference detection circuit may be configured by an analog circuit. Further, the above embodiment has described the signal processing for obtaining the time difference information of the detection signal and estimating the vehicle speed.
The characteristic points of the detection signal waveforms of the first and second sensors 11a and 11b are extracted by a signal processing program by a computer, the type of the vehicle, the number of passing vehicles, and the like are obtained, and these are displayed or printed out. It is also possible. According to the present invention, a conventional system for measuring the vehicle speed of a moving object using a plurality of sensors is provided only by increasing the number of samples to be measured by setting a threshold voltage for detecting a vehicle length. In addition, the vehicle length can be accurately measured in addition to the vehicle speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of an apparatus for implementing a method of the present invention. FIG. 2 is a waveform diagram showing a relationship between a waveform of a signal detected by a sensor of the present invention and a threshold value. FIG. 3 is a flow chart of the method of the present invention. FIG. 4 shows a conventional example of a vehicle speed detecting device. FIG. 5 is a waveform diagram of a signal detected by the detection device of FIG. 4; [Description of Signs] 11: sensor, 12: amplifier, 13: phase detector, 2
0: analyzer, Ea: first detection signal of first sensor 11a, Eb: second detection signal of second sensor 11b, V
l: threshold voltage for vehicle length calculation, Vv: threshold voltage for vehicle speed calculation, t1 to t6: time when the detection signal E of the sensor 11 crossed each threshold voltage.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01B 7/04 G01P 3/66

Claims (1)

(57) Claims 1. A first moving body which moves on the road surface at a predetermined interval on the road surface so as to be detected with a time difference.
And a second magnetic sensor, a first detection signal output from the first magnetic sensor obtained when the moving body passes on the road surface, and a first detection signal output from the second magnetic sensor. The second detection signal first and second crosses first and last respectively with the positive and negative first threshold voltage levels set to values apart from the zero level of the signal for vehicle length calculation.
And a fifth threshold voltage level for detecting a vehicle speed which is set to a value smaller than the first threshold voltage level value and to a value near the zero level of the signal while detecting the fifth and sixth times. And the first
And the third detection signal and the second detection signal detect a third time and a fourth time, respectively, at which the third detection signal and the second detection signal cross after the first time and the second time, respectively. Detecting a vehicle speed based on the time difference ; and calculating the vehicle speed based on the vehicle speed calculated value, the first time and the fifth time difference, or the vehicle speed calculated value and the second time and the sixth time difference. A method for measuring a vehicle speed and a vehicle length of a moving object, comprising calculating a vehicle length of the moving object.