JP2002279583A - Ultrasonic vehicle sensor and vehicle speed measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ultrasonic vehicle sensor allowing accurate measurement of a sonic velocity in a propagation space for ultrasonic waves and the use of the measurement result for finding a vehicle speed with high precision. SOLUTION: The ultrasonic vehicle sensor comprises speed measurement ultrasonic heads 53, 54 for transmitting ultrasonic waves at an angle to downward to permit the measurement of the speed of a traveling vehicle using Doppler effect and existence detection ultrasonic heads 55, 56 for transmitting the ultrasonic waves right downward to permit the identification of the vehicle traveling right thereunder. A sonic velocity is found from a time for receiving the road surface reflected waves of signals transmitted from the existence detection ultrasonic heads and the sonic velocity is used in calculating the vehicle speed from the reception frequency of the signals received by the speed measurement ultrasonic heads. The sonic velocity in a space where the ultrasonic waves are actually propagated is actually measured and the actual measurement value is used in computing the vehicle speed, therefore producing an increase in measurement precision of the vehicle speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vehicle sensor for detecting the traveling speed of a traveling vehicle and a method for measuring the vehicle speed, and more particularly, to accurately grasping the sound speed in a space where ultrasonic waves propagate. Thus, the vehicle speed can be calculated with high accuracy.

[0002]

2. Description of the Related Art Conventionally, several types of ultrasonic vehicle sensors are known. The vehicle detector, which detects the presence of a vehicle on the road, transmits ultrasonic waves from the ultrasonic head installed on the road toward the road surface directly below at a fixed cycle and receives the reflected wave. To determine the presence or absence of a vehicle on the road. In addition, the vehicle sensor for the purpose of detecting the speed of the traveling vehicle transmits ultrasonic waves obliquely downward from the ultrasonic head installed on the road toward the upstream direction, and the Doppler effect that appears in the reflected wave from the traveling vehicle is Use to measure the running speed of the vehicle.

As shown in FIG. 5, the ultrasonic vehicle sensor for speed detection is attached to an arm 52 extending on a road from a pole 51 on the side of a road, and a transmitter 53 and a receiver constituting an ultrasonic head. And a control unit 100 installed on the side of the road or on the pole 51. The transmitter 53 and the receiver 54 are
As a standard, it is installed at a height of 5.5 m from the road surface, obliquely looking down the upstream direction of the traveling road, and a temperature sensor 60 for measuring the temperature is attached to the side of the receiver 54 or the like. .

The control unit 100 includes a transmission circuit 140 for outputting a transmission signal, an amplifier (amplifier) 110 for amplifying a reception signal,
First A for converting a reception level of a reception signal into a digital value
/ D converter 130, a frequency measurement circuit 120 for measuring the frequency of the received signal, a threshold 160 set for identifying the received signal due to the direct reflection of the ultrasonic wave, the direction in which the transmitter 53 and the receiver 54 face, An angle setting unit 170 for setting an angle θ with the road surface, a second A / D converter 150 for converting a temperature detected by the temperature sensor 60 into a digital value, and a CPU 300 for controlling the operation of the control unit 100 are provided. ing.

[0005] The CPU 300 executes a program to control the transmission operation of the transmission circuit 140 by the transmission control unit 3.
20, a reception level measurement unit 310 that measures the reception level of the reception signal, and a threshold comparison unit that compares the reception level with the threshold 160
350 and frequency measurement unit 340 that measures the frequency of the received signal
And a temperature measuring unit 330 that measures the temperature of the temperature sensor 60
And a speed calculation unit 360 that calculates a vehicle speed using data of each unit.

The ultrasonic wave transmitted obliquely (angle θ) at the transmission frequency f0 from the ultrasonic head is transmitted at a vehicle speed V (km / h).
When the vehicle hits the vehicle, the reflected wave of the Doppler frequency fd according to (Equation 1) returns to the ultrasonic head. fd = 2c · f0 · V · cos θ / (c + w · cos θ) (c−w · cos θ−V · cos θ) (Equation 1) where c: sound speed (m / sec), w: wind speed (m / se)
c) The sound speed c depends on the temperature as shown in (Equation 2). c = 331.5 + 0.6t (Equation 2) Here, t: temperature (° C.) Accordingly, the sound speed c is obtained from the temperature t measured by the temperature sensor 60, and the wind speed w is measured by the anemometer (the wind speed is compared with the sound speed). Can be ignored because it is extremely small)
By measuring the frequency of the signal received in 54, the vehicle speed V can be obtained from (Equation 1).

In this vehicle sensor, the transmission circuit 140 outputs a transmission signal having a frequency f0 under the control of the transmission control section 320. This transmission signal is converted into an ultrasonic wave by the transmitter 53 and sent out.
Received at. The received signal is amplified by the amplifier 110, and the received level is converted into a digital value by the first A / D converter 130.
Taken in by U300. The frequency fd of the received signal is measured by the frequency measurement circuit 120, and the measurement result is taken into the CPU 300 by the frequency measurement unit 340. The temperature t measured by the temperature sensor 60 is determined by the second A / D converter 15.
After being converted to a digital value by 0, it is taken into the CPU 300 by the temperature measuring unit 330.

The threshold comparing section 350 compares the received reception level with the threshold 160, and determines whether the reception level of the reflected wave is the threshold 160.
Is exceeded, the reflected wave is regarded as a direct reflected wave of the transmission signal, and a detection signal is output to the speed calculation unit 360. In response to this, the speed calculation unit 360 obtains the sound velocity c from (Equation 2) using the temperature t input from the temperature measurement unit 330, and inputs the angle θ input from the angle setting unit 170 and the frequency θ from the frequency measurement unit 340. Using the frequency fd of the received signal, the wind speed w input from the anemometer, and the frequency f0 of the transmitted signal, the vehicle speed V is calculated from (Equation 1).

[0009]

However, the temperature sensor 60 mounted on the receiver 55 only measures the temperature around the mounting position, and cannot accurately measure the temperature in the space where the ultrasonic wave propagates. . For example, temperature sensor 60
Is exposed to direct sunlight, the measured temperature increases, and temperature information that is different from the temperature of the ultrasonic wave propagation space is sent to the control unit 100. Therefore, if the sound speed is calculated based on this temperature and the vehicle speed V is calculated using the sound speed, the vehicle speed including an error will be calculated.

The present invention solves such a conventional problem, and can accurately measure the sound velocity in the ultrasonic wave propagation space, and can obtain the vehicle speed with high accuracy using the measurement result. Provide ultrasonic vehicle detector,
It is another object of the present invention to provide a vehicle measurement method.

[0011]

SUMMARY OF THE INVENTION Accordingly, in the present invention, an ultrasonic vehicle sensor is provided which transmits ultrasonic waves obliquely downward to measure the speed of a running vehicle using the Doppler effect. A sound wave head, and a presence detecting ultrasonic head for transmitting an ultrasonic wave directly under the vehicle to identify a vehicle traveling directly below the vehicle. And a vehicle speed is calculated from the reception frequency of the reception signal received by the speed measurement ultrasonic head using the sound speed.

Further, in the vehicle speed measuring method using the ultrasonic vehicle sensor, a receiving time of a reflected wave of a signal transmitted from the presence detecting ultrasonic head is obtained, and the reflected wave is converted into a road surface reflected wave from the receiving time. Or identify the vehicle reflected wave, when the road surface reflected wave, from the reception time and the installation height of the presence detection ultrasonic head, calculate the sound speed in the ultrasonic wave propagation space, using the calculated sound speed The vehicle speed of the traveling vehicle is calculated from the measurement result of the ultrasonic head for speed measurement.

Therefore, the speed of sound in the space where the ultrasonic waves actually propagate can be measured, and the vehicle speed can be calculated using the measured value, so that the accuracy of measuring the vehicle speed can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic vehicle sensor according to an embodiment of the present invention, as shown in FIG. 1, transmits an ultrasonic wave obliquely downward to detect a vehicle speed of a traveling vehicle, and a transmitter 53 and a receiver. Container 54
And a presence ultrasonic head comprising a transmitter 55 and a receiver 56 for transmitting an ultrasonic wave immediately below to detect the presence of the vehicle.

The vehicle sensor having both the speed ultrasonic head and the presence ultrasonic head has been developed to enable the type of a passing vehicle to be determined.

According to the classification criteria for vehicle types, as shown in FIG.
Based on vehicle height and length, they are classified into four types: buses, large cargo, small cargo, and passenger cars. Conventionally, vehicle types are identified by using both an ultrasonic vehicle sensor installed on the road and a loop sensor embedded in the road. , Small cargo, and large vehicles are identified, and the height of the floor of the vehicle is identified by a loop sensor to distinguish large cargo from buses.

However, installation of the loop detector requires excavation of the road. Therefore, the ultrasonic vehicle detector has been devised as a device for determining the type of vehicle without the construction of the road surface. In this device, the speed ultrasonic head detects the vehicle speed of the traveling vehicle, and the presence ultrasonic head requires the vehicle height and the vehicle to pass immediately below the presence ultrasonic head. Time, and
The roof shape of the vehicle is detected.

To enable this detection, the transmission signal is repeatedly transmitted from the presence ultrasonic head at a fine transmission interval of 10 ms. At this time, the transmission signal is transmitted with a different frequency or pulse width so that it can be distinguished from the preceding and following transmission signals. By outputting the transmission signal densely from the presence ultrasonic head in this way, it becomes possible to grasp the vehicle shape as shown in FIG. 4 from the reflected wave.

The vehicle height can be measured from the reflection time of the reflected wave received by the existing ultrasonic head. The vehicle length can be calculated by multiplying the sensing time during which the vehicle is sensed by the vehicle speed based on the reception signal of the presence ultrasonic head.
The distinction between a bus and a large cargo can be identified as a bus if the vehicle has a flat roof, and a large cargo if the vehicle has a flat roof.

FIG. 1 shows the configuration of a control unit 10 for measuring the sound speed in the ultrasonic wave propagation space and obtaining the vehicle speed using the measurement result in the ultrasonic vehicle sensor.

The control unit 10 includes a first transmission circuit for outputting a transmission signal transmitted from the transmitter 53 of the velocity ultrasonic head.
14, a first amplifier 11 for amplifying the signal received by the receiver 54 of the velocity ultrasonic head, a first A / D converter 13 for converting the reception level of the reception signal into a digital value, First frequency measuring circuit 12 for measuring frequency
A first threshold value 16 for setting a threshold value for a reception signal of the speed ultrasonic head; an angle setting unit 17 for setting an angle θ between a direction in which the transmitter 53 and the receiver 54 face and a road surface; A second transmitting circuit 22 for outputting a transmission signal transmitted from a transmitter 55 of the ultrasonic head, and a receiver 56 of the ultrasonic head for presence
A second amplifier 20 that amplifies the signal received by the second A / D converter 21 that converts the reception level of the received signal into a digital value, a second frequency measurement circuit 15 that measures the frequency of the received signal, A second threshold value 19 for setting a threshold value for a reception signal of the presence ultrasonic head, an installation height setting unit 18 for setting an installation height H (m) of the existence ultrasonic head, and a control unit
And a CPU 30 for controlling the operation of the CPU 10.

The CPU 30 executes a program to control a transmission operation of the first transmission circuit 14, and a first reception level for measuring a reception level of a reception signal of the speed ultrasonic head. A measuring section 31, a first threshold comparing section 35 for comparing the received level with the first threshold 16, a first frequency measuring section 34 for measuring the frequency of the received signal, and a vehicle speed using data of each section. A speed calculation unit 36 to calculate,
Second transmission control unit 42 for controlling the transmission operation of second transmission circuit 22
A second reception level measuring unit 41 for measuring a reception level of a reception signal of the presence ultrasonic head;
A second threshold comparing section 40 for comparing the threshold 19, a second frequency measuring section 37 for measuring the frequency of the received signal, and a reception time of the received signal received by the receiver 56 based on the value measured by the timer 39. And a sound speed calculation unit 33 that calculates the sound speed in the ultrasonic wave propagation space.

In this apparatus, a signal is transmitted from the transmitter 55 of the existence ultrasonic head, and the time until the reflected wave on the road surface is received by the receiver 56 is measured. The sound speed c in the ultrasonic wave propagation space is calculated from the head installation height H. Then, the vehicle speed of the traveling vehicle is calculated using the sound speed c and the Doppler frequency detected by the speed ultrasonic head.

FIG. 2 is a flowchart showing the operation procedure of the apparatus in this case. Step 1: The second transmission circuit 22 transmits a transmission signal of the frequency f for 2 ms under the control of the second transmission control unit 42, and Step 2: waits until the next transmission starts. Repeat this.

Step 3: Receiver of ultrasonic head for presence
The reflected wave X received by 56 is amplified by the second amplifier 20, the received level is converted into a digital value by the third A / D converter 21, and is taken into the CPU 30 by the second received level measuring unit 41. Step 4: The second threshold comparing section 40 compares the reception level input from the second reception level measuring section 41 with the second threshold 19,
When the reception level exceeds the second threshold value 19, a detection signal is output to the sound speed calculation unit 33. Step 5: The sound speed calculation unit 33 acquires the frequency X of the received signal measured by the second frequency measurement circuit 15 through the second frequency measurement unit 37. Step 6: The frequency X matches the frequency f of the transmission signal. Identify whether or not. If they match, Step 7: The measured value of the timer 39 representing the reception time X from the start of transmission to the reception point is fetched through the reception time measuring unit 38. It is determined which of the two is a wave.
× The sound speed c is obtained from the installation height H / reception time X). The obtained sound speed c is output to the speed calculation unit 36.

On the other hand, the first transmission circuit 14 includes a first transmission control unit.
Under the control of 32, the transmission signal of the frequency f0 is repeatedly output. This transmission signal is converted into an ultrasonic wave by the transmitter 53 and transmitted. Step 9: The receiver 56 of the ultrasonic head for velocity uses the reflected wave X
Is received, the first amplifier 11 amplifies it, the first A / D converter 13 converts the received level into a digital value, and the first received level measuring unit 31 takes the value into the CPU 30. Step 10: The first threshold comparing section 35 compares the reception level input from the first reception level measuring section 31 with the first threshold 16,
When the reception level exceeds the first threshold 16, a detection signal is output to the speed calculation unit 36.

Step 11: In response to this, the speed calculator 36
Obtains the frequency fd of the reception signal measured by the first frequency measurement circuit 12 through the first frequency measurement unit 34. Step 12: Input the sound speed c, the installation angle θ, the reception frequency fd, the transmission frequency f0, and the anemometer (Expression 1) using the wind speed w (this wind speed data can be omitted)
Then, the vehicle speed V is calculated.

As described above, in the ultrasonic vehicle sensor, the speed of sound of the traveling vehicle is detected by actually measuring the sound speed in the propagation space of the ultrasonic wave, and the calculation accuracy of the vehicle speed is improved. be able to.

[0029]

As is apparent from the above description, the ultrasonic vehicle sensor and the vehicle speed measuring method of the present invention can determine the vehicle speed without requiring a temperature sensor. In this method, the sound speed in the space where the ultrasonic wave actually propagates is actually measured, and the vehicle speed is calculated using the measured value, so that the error factor due to the mounting position of the temperature sensor can be eliminated, and the vehicle speed can be reduced. Measurement accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ultrasonic vehicle sensor according to an embodiment of the present invention;

FIG. 2 is a flowchart showing an operation procedure of the ultrasonic vehicle sensor according to the embodiment;

FIG. 3 is a diagram for explaining vehicle type classification conditions;

FIG. 4 is a diagram showing a vehicle silhouette obtained from a detection result of the ultrasonic vehicle sensor according to the embodiment;

FIG. 5 is a block diagram showing a configuration of a conventional ultrasonic vehicle sensor.

[Explanation of symbols]

 10, 100 control unit 11 first amplifier 12 first frequency measurement circuit 13, 130 first A / D converter 14 first transmission circuit 15 second frequency measurement circuit 16 first threshold 17, 170 angle setting unit 18 installation height 19 second Threshold value 20 Second amplifier 21 Third A / D converter 22 Second transmission circuit 30, 300 CPU 31 First reception level measurement unit 32 First transmission control unit 33 Sound velocity calculation unit 34 First frequency measurement unit 35 First threshold comparison unit 36 Speed calculation unit 37 Second frequency measurement unit 38 Reception time measurement unit 39 Timer 40 Second threshold value comparison unit 41 Second reception level measurement unit 42 Second transmission control unit 51 Pole 52 Arm 53 Speed ultrasonic head transmitter 54 Speed Ultrasonic head receiver 55 Presence ultrasonic head transmitter 56 Presence ultrasonic head receiver 60 Temperature sensor 110 Amplifier 120 Frequency measurement circuit 140 Transmission circuit 150 2nd A / D converter 160 Threshold 310 Reception level measurement unit 320 Transmission control unit 33 0 Temperature measurement section 340 Frequency measurement section 350 Threshold comparison section 360 Speed calculation section

Claims (3)

[Claims] An ultrasonic head for transmitting ultrasonic waves obliquely downward to measure the vehicle speed of a traveling vehicle using the Doppler effect, and an ultrasonic head directly below to identify a vehicle traveling immediately below. The presence detection ultrasonic head to transmit to, to determine the sound speed from the reception time of the road surface reflected wave of the signal transmitted from the presence detection ultrasonic head, using the sound speed, the speed measurement ultrasonic head An ultrasonic vehicle detector for calculating a vehicle speed from a reception frequency of a received signal. 2. A speed measurement ultrasonic head for transmitting ultrasonic waves obliquely downward to measure the vehicle speed of a traveling vehicle using the Doppler effect, and an ultrasonic wave immediately below to identify a vehicle traveling immediately below. In the vehicle speed measurement method in the ultrasonic vehicle sensor comprising an ultrasonic head for presence detection to transmit to, the reception time of the reflected wave of the signal transmitted from the ultrasonic head for presence detection is obtained, from the reception time Identify whether the reflected wave is a road reflected wave or a vehicle reflected wave, and when the reflected wave is a road reflected wave, calculate the sound velocity in the ultrasonic wave propagation space from the reception time and the installation height of the presence detection ultrasonic head. Using the calculated sound speed to calculate the vehicle speed of the running vehicle from the measurement result of the speed measurement ultrasonic head. 3. An ultrasonic head for transmitting ultrasonic waves obliquely downward to measure the vehicle speed of a traveling vehicle using the Doppler effect, and an ultrasonic head directly below to identify a vehicle traveling immediately below. A control program for an ultrasonic vehicle sensor having an ultrasonic head for presence detection that transmits to a computer, a reception time measuring means for obtaining a reception time of a reflected wave of a signal transmitted from the ultrasonic head for presence detection. Identifying the reflected wave as a road surface reflected wave or a vehicle reflected wave from the reception time, and when the reflected wave is a road surface reflected wave, calculating a sound speed from the reception time and the installation height of the presence detection ultrasonic head. Calculation means, a transmission frequency of a signal transmitted from the speed measurement ultrasonic head, a reception frequency of a reception signal received by the speed measurement ultrasonic head, and the sound velocity calculation means calculate Program for functioning as a speed calculation means for calculating a vehicle speed of the traveling vehicle using the speed of sound, the transmission angle of the signal transmitted from the speed measuring ultrasonic head.