JP2003185734A - Ultrasonic sensor, and method of controlling ultrasonic frequency - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic type vehicle sensor for detecting the optimum ultrasonic frequency easily. <P>SOLUTION: This sensor is provided with a drive frequency regulating means 13 for regulating stepwisely a drive frequency of an ultrasonic transmitter, and a memory means 16 for recording a reception level of a received signal received by an ultrasonic receiver while updating it to a higher reception level. The drive frequency regulating means compares a reception level of a new received signal with the reception level stored in the memory means to regulate the drive frequency to a direction heighten the reception level of the received signal. The ultrasonic frequency is controlled to the optimum frequency without measuring a consumed current in the ultrasonic transmitter, so as to eliminate a current measuring circuit. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor for detecting a vehicle traveling on a road, a method for controlling the ultrasonic frequency of the transmitter, and a computer for defining the operation of the ultrasonic sensor. -Regarding the program and the storage medium in which the program is recorded, in particular, the ultrasonic frequency suitable for the transmitter can be set with a simple configuration.

[0002]

2. Description of the Related Art A conventional ultrasonic vehicle detector transmits an ultrasonic wave toward a road surface and determines the presence or absence of a vehicle based on the time until the reflected wave is received. As shown in FIG. 5, this ultrasonic vehicle detector comprises an ultrasonic head 20 installed on the road and a control unit 10 for the ultrasonic head 20. The ultrasonic head 20 transmits ultrasonic waves to the road surface. Transmitter 21 to
Receiver 22 that receives the reflected waves of ultrasonic waves and converts them into electrical signals
Further, the control unit 10 includes an amplifier 11 for amplifying a received signal, an A / D converter 12 for converting the received signal into a digital signal, a drive circuit 14 for driving the transmitter 21, and an ultrasonic wave. The presence / absence of a vehicle is determined by the time from transmission to reception of
It has a PU 13 and a current measuring circuit 15 for measuring the current consumption when the driving circuit 14 drives the transmitter 21. The transmitter 21 and the receiver 22 of the ultrasonic head 20 are configured by using the same ultrasonic element.

As shown in FIG. 3, the ultrasonic head 20 is attached to an arm 32 extending from the pole 31 standing on the side of the road to the traveling road, and normally at a height of 5.5 m from the road surface. is set up. The ultrasonic head 20 includes a control unit 10
A driving signal having a frequency of about 25 kHz and a transmission time of 2 ms is repeatedly sent from the driving circuit 14 of FIG. In the transmitter 21 of the ultrasonic head 20, the built-in piezoelectric element is excited by the drive signal received from the drive circuit 14, and the transmission wave having the ultrasonic frequency corresponding to the frequency of the drive signal is transmitted directly below.

4A and 4B show a transmission wave A transmitted from the transmitter A of the ultrasonic head A shown in FIG. 3 and a receiver to show a state where no vehicle is present on the road. The reflected wave received by A is displayed. The transmitter A is shown in FIG.
As shown in Fig. 2, it is 2 in a cycle of 100 ms according to the drive signal.
The ms transmission wave A is repeatedly transmitted. The receiver A is shown in FIG.
As shown in (b), the reflected wave reflected on the road surface (road surface reflected wave A) is received at the time when the delay time A elapses after the transmission wave A is transmitted.

Further, FIGS. 4C and 4D show a transmission wave B transmitted from the transmitter B of the ultrasonic head B of FIG. 3 and a receiver in order to show a state where a vehicle exists on the road. The reflected wave received by B is displayed. The transmitter B transmits the transmission wave B in the same cycle as the transmitter A, and the receiver B receives the reflected wave reflected by the vehicle (vehicle reflected wave B). At this time, the delay time B from the transmission of the transmission wave B to the reception of the vehicle reflected wave B is shorter than the delay time A when there is no vehicle.

The received signal of the receiver 22 is an amplifier of the control unit 10.
Amplified by 11, converted into digital data by the A / D converter 12 and input to the CPU 13, the CPU 13 calculates the delay time of the reflected wave, and when it is shorter than the delay time A of the road surface reflected wave, It is determined that the vehicle exists.

In this ultrasonic type vehicle detector, the optimum frequency of the drive signal for driving the transmitter 21 changes due to temperature changes, aging changes, etc. of the transmitter 21. Therefore, the current measuring circuit 15 measures the current consumption when the transmitter 21 is driven by the drive circuit 14, and the CPU 13 controls the frequency of the drive current so that this measured value becomes maximum. This is because the current consumption is large, the transmission output of the transmitter 21 is large, that is,
This is because it indicates that strong ultrasonic waves are being transmitted. The CPU 13 always pays attention to the current consumption measured by the current measuring circuit 15, and when the current consumption shows a decrease, finely adjusts the frequency of the drive signal to increase the current consumption, thereby optimizing the ultrasonic frequency. It keeps the frequency.

As described above, in the conventional ultrasonic type vehicle sensor, the control for driving the transmitter at the optimum driving frequency is performed without being affected by the temperature change and the secular change.

[0009]

However, since the drive signal to the transmitter of the ultrasonic type vehicle sensor is a periodic signal, it is technically difficult to accurately measure the current consumption, and this is a technical problem. If the measurement accuracy is low, there is a problem that the ultrasonic frequency cannot be maintained in an optimum state.

The present invention solves these conventional problems and provides an ultrasonic sensor capable of easily detecting the optimum ultrasonic frequency, and also provides an ultrasonic frequency control method and a computer therefor. -The purpose is to provide a program and a storage medium recording the program.

[0011]

Therefore, according to the present invention, in an ultrasonic sensor for detecting an object by ultrasonic waves, drive frequency adjusting means for stepwise adjusting the drive frequency of the ultrasonic transmitter and ultrasonic wave receiving. And a storage means for recording the reception level of the received signal by the reflected wave from the same object received by the device, the drive frequency adjusting means, the drive frequency adjustment means, for the stepwise adjustment of the drive frequency, the ultrasonic transmitter at the drive frequency. The receiving level of the received signal when driven is recorded in the storage means, and the driving frequency is increased by one step or lowered by one step, and the received level of the received signal at that time is compared with the received level recorded in the storage means. , The drive frequency is updated so that a higher reception level can be obtained.

Further, in the ultrasonic frequency control method of an ultrasonic sensor for detecting an object by ultrasonic waves, a reception level when the ultrasonic transmitter is driven at a predetermined driving frequency and a predetermined step width for the driving frequency. Compare the reception level when the ultrasonic transmitter is driven by adding the frequency adjustment amount, and if the reception level when the frequency adjustment amount is added is higher, the drive frequency with the frequency adjustment amount is added. If the reception level is lower when the frequency is adjusted, the reception level when the ultrasonic transmitter is driven at the predetermined drive frequency, and the frequency adjustment from the drive frequency. Is compared with the reception level when the ultrasonic transmitter is driven, and if the reception level when the frequency adjustment is subtracted is higher, the drive frequency obtained by subtracting the frequency adjustment The are to be set to a new drive frequency.

The computer program of the ultrasonic detector for detecting an object by the ultrasonic wave of the present invention causes the computer to drive the ultrasonic transmitter at a predetermined drive frequency,
A procedure for calculating the reflection distance of the ultrasonic wave from the reception signal received by the ultrasonic receiver at that time, confirming that it is a reflection wave from a predetermined object, and recording the reception level of the reception signal in the memory, The ultrasonic transmitter is driven by adding a frequency adjustment amount of a predetermined step width to the drive frequency, the ultrasonic wave reflection distance is calculated from the received signal received by the ultrasonic receiver at that time, and the ultrasonic wave is reflected from the object. Make sure it's a wave,
A procedure for comparing the reception level of this reception signal with the reception level recorded in the memory, and as a result of the comparison, when the reception level of the reception signal when the frequency adjustment component is added to the drive frequency is higher, The procedure of setting a new drive frequency by adding a frequency adjustment amount to the drive frequency, and as a result of the comparison, when the reception level recorded in the memory is higher, the ultrasonic transmitter is changed from the drive frequency to the frequency. Driving by subtracting the adjustment amount, calculating the reflection distance of the ultrasonic wave from the received signal received by the ultrasonic receiver at that time, confirming that it is a reflected wave from the object, and receiving this received signal A step of comparing the level with the reception level recorded in the memory, and as a result of the comparison, when the reception level of the reception signal when the frequency adjustment component is subtracted from the drive frequency is higher, To execute a step of setting the minus the frequency adjustment amount from the dynamic frequency as a new driving frequency.

Therefore, the ultrasonic frequency can be controlled to the optimum frequency without measuring the current consumption of the ultrasonic transmitter, and the current measuring circuit can be eliminated.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, an ultrasonic vehicle detector according to an embodiment of the present invention includes an ultrasonic head 20 having a transmitter 21 and a receiver 22, an amplifier 11, an A / D converter. It includes a device 12, a drive circuit 14, a control unit 10 including a CPU 13 and a memory 16. CPU13 of this ultrasonic type vehicle detector
Each time the frequency of the drive signal is finely adjusted, the magnitude of the road surface reflected wave received by the receiver 22 is stored in the memory 16, the frequency at which the magnitude is maximized is searched, and the optimum ultrasonic wave is detected. Determine the frequency.

FIG. 2 shows the CPU of this ultrasonic vehicle detector.
13 shows an operation flow of 13. As the initial value of the drive signal, the drive frequency F is set to 25 kHz and the frequency fine adjustment amount α is set to 25 Hz, and the result is stacked in the memory 16 (step 1), waits for transmission timing (step 2), and is transmitted at frequency F. The device 21 is driven (step 3), and the reception of the reflected wave is waited (step 4).

The receiver 22 receives the reflected wave and the signal is A
When it is converted into digital data by the / D converter 12 and input, the delay time from transmission to reception is calculated, and from the delay time, the received wave is a reflected wave from the road surface (road surface reflected wave),
It is determined whether the wave is a reflected wave from the vehicle (vehicle reflected wave) (step 5). When the received wave is the vehicle reflected wave, the process proceeds to step 2, and when the received wave is the road surface reflected wave, the received level is stacked in the memory 16 as LV (step 6).
Thus, the level LV of the road surface reflected wave when the transmitter 21 is driven at the drive frequency F is recorded in the memory 16.

Next, the transmission timing is waited (step 7), the transmitter 21 is driven at the finely adjusted drive frequency F + α (step 8), and the reception of the reflected wave is waited (step 9). When the receiver 22 receives the reflected wave and the signal is converted into digital data by the A / D converter 12 and input, it is determined whether the received wave is a road surface reflected wave or a vehicle reflected wave according to the delay time from transmission to reception. Yes (step 10). When the received wave is the vehicle reflected wave, the process proceeds to step 2, and when the received wave is the road surface reflected wave, the received level is compared with the LV recorded in the memory 16 (step 11).

In step 11, LV is calculated from the reception level.
Is higher (LV> reception level), drive frequency F
It is determined that the driving frequency F is closer to the optimum frequency than + α, and α in the memory 16 is changed to −α, and the process proceeds to step 2 (step 12). On the other hand, in step 11, when the reception level is equal to or higher than LV (LV ≦ reception level), it is determined that the drive frequency F + α is closer to the optimum frequency than the drive frequency F, and the drive frequency is updated to F + α (F ← F + α ), And the process proceeds to step 2 (step 13).

When the change to -α is made in step 12, the transmitter is driven at the drive frequency F and the reception level LV of the road surface reflected wave at that time is set by the procedure after returning to step 2. The data is recorded in the memory, and the transmitter is driven at the drive frequency F-α in which the drive frequency F is finely adjusted to a minus value, and the reception level of the road surface reflected wave at that time and the LV are compared. . Then, as a result of the comparison, "L
If V> reception level ", the frequency fine adjustment is set to α and the procedure from step 2 is repeated.
If ≦ reception level ”, the drive frequency is updated to F-α and the procedure from step 2 is repeated.

In step 13, the drive frequency is F +
When the value is updated to α (= F ₁ ), the transmitter is driven at the updated driving frequency F ₁ and the memory of the reception level LV of the road surface reflected wave at that time is stored by the procedure after returning to step 2. Is recorded, and the drive frequency F ₁ + α
The driving of the transmitter is performed, and the reception level of the road surface reflected wave at that time and the LV are compared. And as a result of the comparison,
If "LV> reception level", the frequency fine adjustment is -α
, The procedure from step 2 is repeated, and
If “LV ≦ reception level”, set the drive frequency to F ₁ + α
And the procedure from step 2 is repeated.

Therefore, assuming that the optimum drive frequency remains F when the vehicle is not present on the road surface, the drive frequency of the transmitter is switched in the following order. F → (F + α) → F → (F-α) → F → (F + α) → F → (F-α) → F. Further, if the optimum driving frequency changes to F + α after this, The drive frequency of the transmitter is switched in the following order. → (F + α) → (F + α) → (F + 2α) → (F + α) → F → (F + α) → (F + 2
α) → (F + α) → F → By such a procedure, the frequency F of the drive signal is adjusted to the optimum frequency.

Such a procedure is defined in a computer program, and the CPU of the control unit carries out processing according to the program. Further, this computer program can be recorded in a portable storage medium, the storage medium can be attached to another device, and the operation according to the program can be performed in another device.

[0024]

As is clear from the above description, the ultrasonic sensor of the present invention can control the driving frequency of the transmitter to the optimum frequency without measuring the current consumption of the transmitter. Therefore, the number of current measuring circuits can be reduced, and the control unit can be downsized.

Further, the ultrasonic frequency control method and computer program of the present invention can cause the ultrasonic sensor to perform an appropriate operation for controlling the drive frequency.

[Brief description of 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 flow chart showing an operation procedure of the ultrasonic vehicle sensor according to the embodiment.

FIG. 3 is a diagram showing an installation state of a conventional ultrasonic vehicle detector,

FIG. 4 is a diagram showing transmission and reception waveforms in a conventional ultrasonic vehicle detector,

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

[Explanation of symbols]

10 Control unit 11 amplifier 12 A / D converter 13 CPU 14 Drive circuit 15 Current measurement circuit 16 memory 20 ultrasonic head 21 transmitter 22 receiver 31 Paul 32 arms

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Claims (6)

[Claims] 1. In an ultrasonic sensor for detecting an object by ultrasonic waves, drive frequency adjusting means for stepwise adjusting a drive frequency of an ultrasonic transmitter, and reflected waves from the same object received by an ultrasonic receiver. Storage means for recording the reception level of the reception signal by the drive frequency adjusting means, wherein the drive frequency adjusting means receives the reception when the ultrasonic transmitter is driven at the drive frequency for stepwise adjustment of the drive frequency. The reception level of the signal is recorded in the storage means, the driving frequency is changed stepwise, the reception level of the reception signal at that time is compared with the reception level recorded in the storage means, and the reception level An ultrasonic sensor characterized by updating to a drive frequency that gives a higher reception level. 2. The ultrasonic sensor according to claim 1, wherein the drive frequency adjusting means repeatedly performs stepwise adjustment of the drive frequency. 3. The object detected by the ultrasonic waves is a vehicle on a road surface, and the received signal used for the stepwise adjustment of the driving frequency is a road surface reflected wave of the ultrasonic waves. Item 3. The ultrasonic sensor according to Item 1 or 2. 4. An ultrasonic frequency control method of an ultrasonic sensor for detecting an object by ultrasonic waves, comprising: a reception level when an ultrasonic transmitter is driven at a predetermined drive frequency; and a predetermined step width for the drive frequency. The frequency adjustment amount is added and the reception level when the ultrasonic transmitter is driven is compared, and if the reception level when the frequency adjustment amount is added is higher, the frequency adjustment amount is added. When the drive frequency is set to a new drive frequency and the reception level when the frequency adjustment amount is added is lower, the reception level when the ultrasonic transmitter is driven at the predetermined drive frequency, and the drive If the reception level when the frequency adjustment is subtracted is higher than the reception level when the ultrasonic transmitter is driven by subtracting the frequency adjustment from the frequency, Ultrasonic frequency control method characterized by setting the driving frequency obtained by subtracting the frequency adjustment amount in the new driving frequency. 5. A computer program of an ultrasonic detector for detecting an object by ultrasonic waves, comprising: driving an ultrasonic transmitter at a predetermined driving frequency in a computer, and receiving the ultrasonic receiver at that time. Calculating the reflection distance of the ultrasonic wave from the received signal, confirming that it is a reflected wave from a predetermined object, the procedure of recording the reception level of the received signal in a memory, the ultrasonic transmitter to the drive frequency Driving by adding the frequency adjustment amount of a predetermined step width, calculating the reflection distance of the ultrasonic wave from the reception signal received by the ultrasonic receiver at that time, and confirming that it is a reflected wave from the object A procedure for comparing the reception level of the reception signal with the reception level recorded in the memory, and the reception level of the reception signal when the frequency adjustment is added to the drive frequency as a result of the comparison. When the frequency is higher, a procedure of setting a value obtained by adding the frequency adjustment amount to the drive frequency as a new drive frequency, and as a result of the comparison, when the reception level recorded in the memory is higher, The ultrasonic transmitter is driven by subtracting the frequency adjustment amount from the drive frequency, and the reflection distance of the ultrasonic wave is calculated from the reception signal received by the ultrasonic receiver at that time, and the reflected wave from the object is calculated. Make sure that
A step of comparing the reception level of the reception signal with the reception level recorded in the memory; and, as a result of the comparison, the reception level of the reception signal when the frequency adjustment amount is subtracted from the drive frequency is higher. Sometimes, a program for executing a procedure of setting a value obtained by subtracting the frequency adjustment amount from the drive frequency as a new drive frequency. 6. A storage medium recording the program according to claim 5.