JP4421455B2 - Inclination angle measuring device - Google Patents

Description

  The present invention relates to an inclination angle measuring apparatus that measures an inclination angle of a vehicle using an ultrasonic sensor that transmits and receives ultrasonic waves, and more particularly, an inclination angle measuring apparatus of a phase difference detection system that detects a change in phase characteristics of an ultrasonic sensor. It is about.

Conventionally, in an apparatus that detects the presence or absence of an obstacle and an approximate distance by a reflected wave from the obstacle, such as an obstacle detection apparatus, the presence or absence of a direct wave detects whether the ultrasonic sensor is in a normal state ( For example, see Patent Document 1).
In addition, there is one that detects a foreign wave in the horn by detecting a reflected wave from a foreign substance attached in the horn of the ultrasonic sensor, and notifies the user of malfunction of the ultrasonic sensor due to the attachment of the foreign substance (for example, , See Patent Document 2).
Furthermore, there is also a device that constantly monitors the reverberation time of the ultrasonic sensor and detects that a foreign object has adhered to the ultrasonic sensor when the reverberation time exceeds a certain period. (For example, refer to Patent Document 3).

JP 2002-131428 A JP-A 63-27779 JP 63-33684 A

However, in the tilt angle detection device of the phase difference detection method, the characteristic change of the ultrasonic sensor itself affects the tilt angle due to foreign matter adhering to the surface of the ultrasonic sensor. There is a problem that the characteristic change of the ultrasonic sensor due to a very small amount of deposits in a state where the direct wave can be received cannot be detected only by detecting the presence or absence of the direct wave.
In addition, there has been a problem that the characteristic change of the ultrasonic sensor due to the adhered foreign matter cannot be detected only by detecting the presence or absence of the reflected wave as described in Patent Document 2.

  Furthermore, as described in Patent Document 3, the reverberation time of the ultrasonic sensor is constantly monitored, and when the reverberation time exceeds a certain period, it is detected that foreign matter has adhered to the ultrasonic sensor. In the case of an ultrasonic sensor integrated with transmission and reception, it is easy to determine the excitation period and the reverberation period of the ultrasonic sensor, but in the case of a separate ultrasonic sensor, only the reverberation period is detected from the received wave. However, it is difficult to detect the characteristic change of the ultrasonic sensor itself by checking the reverberation period.

  The present invention has been made to solve the above-described problems, and detects changes in the characteristics of an ultrasonic sensor due to a minute amount of deposits in a state where direct waves can be received, so that the inclination angle of a vehicle or the like can be reliably set. An object of the present invention is to obtain a tilt angle measuring device capable of measuring.

  The tilt angle measuring apparatus according to the present invention is provided with detection means for detecting a change in the phase characteristics of the ultrasonic sensor due to foreign matter adhering to the surface of the ultrasonic sensor, and includes a transmitting and receiving ultrasonic sensor for transmitting and receiving ultrasonic waves. There is no separate transmission / reception type, and the detection means detects the phase difference of the direct wave from the ultrasonic sensor and the storage means for storing the phase difference of the direct wave in a normal state of the ultrasonic sensor as a threshold. Phase change discriminating means for discriminating a change in the phase characteristic of the ultrasonic sensor by comparing the phase difference of the direct wave with a stored threshold value.

  According to the present invention, it is possible to detect a change in the characteristics of an ultrasonic sensor due to a minute amount of deposits in a state where direct waves can be received. Therefore, there is an effect that the foreign matter adhering to the surface of the ultrasonic sensor can be detected easily and reliably and the measurement accuracy of the inclination angle can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a phase difference detection type tilt angle measuring apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a phase difference detection type tilt angle measuring device according to Embodiment 1 of the present invention is attached to a vehicle rear portion (bumper 10), for example, with a predetermined interval, and electrical energy is converted into mechanical vibration energy. The transmission ultrasonic sensors 1 and 2 that transmit ultrasonic waves to the road surface 11, and the transmission ultrasonic sensors 1 and 2 so as to have the same distance from each other with a predetermined interval. Similarly, it is attached to the rear part of the vehicle (bumper 10) or the like, receives ultrasonic waves (reflected waves) transmitted from the ultrasonic sensors 1 and 2 and reflected on the road surface 11, and transmits the ultrasonic sensors 1, 2 for receiving the direct wave transmitted directly from the sensor 2 and converting the mechanical vibration energy into the electrical energy, and the ultrasonic sensor drive for the ultrasonic sensors 1 and 2 for transmission. A transmission circuit 5 as a transmission means for transmitting a signal, reception circuits 6 and 7 as reception means for receiving and amplifying electrical energy from the reception ultrasonic sensors 3 and 4, and these reception circuits 6 and 7, respectively. The ultrasonic sensors 1 to 4 that calculate the phase difference of the direct wave included in the received signal from the signal and store the calculated phase difference of the direct wave and a threshold value in a memory (not shown) as storage means in advance. The phase difference of the ultrasonic sensor is compared by comparing the phase difference of the direct wave in the normal state, and foreign matter (mud, ice, etc.) adheres to the surface of the ultrasonic sensors 1 to 4 based on the determination result. The phase-locked wave detection circuit 8 as a phase change determining means for determining the presence, the phase difference of reflected waves from the ultrasonic sensors 3 and 4 for reception, the transmission speed of ultrasonic waves, and the ultrasonic sensors 1, 2, 3 and 4 Based on the distance between the road surface 11 That comprises an arithmetic control circuit 9 as an arithmetic control unit for calculating the inclination angle of the vehicle. The phase-locked detection circuit 8 and the memory constitute detection means for detecting a change in the phase characteristic of the ultrasonic sensor due to a foreign substance that substantially adheres to the surface of the ultrasonic sensor.

First, the basic principle of the present invention will be described.
FIG. 2 shows normal electrical characteristics of the ultrasonic sensor alone, and FIG. 3 shows electrical characteristics when foreign matter (such as mud and ice) adheres to the surface of the ultrasonic sensor.
2 and 3 show the impedance characteristic a and the phase characteristic b of the ultrasonic sensors 1 to 4 with respect to the excitation AC waveform, and the ultrasonic sensors 1 to 4 have low impedance characteristics (resonance points). It is easy to generate transmitted sound pressure, easily receive ultrasonic waves at a point with high impedance characteristics (anti-resonance point) (high reception sensitivity), and have a phase change point between the resonance point and anti-resonance point I understand.

The tilt angle measuring device of the phase difference detection method detects the phase at the time of transmission / reception and calculates the tilt angle. From FIGS. 2 and 3, the ultrasonic sensors 1 to 4 are temporarily set at 20 kHz when normal and when foreign matter is attached. When the sensor is used, the phase changes greatly from about 30 degrees during normal operation to about -40 degrees during foreign object adhesion. By determining this difference, foreign object adhesion of the ultrasonic sensors 1 to 4 can be detected.
However, the phase difference of the reflected wave varies depending on the distance between the transmission / reception ultrasonic sensors 1 to 4 and the road surface 11, so a constant value is not selected. The characteristic change of the ultrasonic sensors 1 to 4 is detected by comparing the direct wave phase difference.

4 and 5 schematically show the case where the phase difference of the direct wave between the transmitting / receiving ultrasonic sensors 1 to 4 is used. In FIG. The direct wave d1 transmitted directly from the ultrasonic sensor 1 in addition to the ultrasonic wave (reflected wave r1) reflected from the road surface 11 by transmitting an ultrasonic wave (transmitted wave t1) from the ultrasonic sensor 1 for transmission. Similarly, with respect to the ultrasonic sensor 4 for reception, an ultrasonic wave (reflected wave) transmitted from the ultrasonic sensor 2 for transmission and reflected by the road surface 11 is transmitted from the ultrasonic sensor 2 for transmission. In addition to r2), there is a direct wave d2 transmitted directly from the ultrasonic sensor 2.
That is, from the ultrasonic sensors 1 and 2 for transmission, ultrasonic waves (transmission wave t) as shown in FIG. 5A are respectively transmitted toward the road surface 11, and from this road surface, FIG. The ultrasonic waves (reflected wave r) as shown in FIG. 6 are received by the receiving ultrasonic sensors 3 and 4, respectively. At the same time, the direct wave d as shown in FIG. Are transmitted and received between the ultrasonic sensors 3 and 4.

  Therefore, first, the phase difference of the direct wave d when the ultrasonic sensors 1 to 4 are normal is stored in advance in a memory (not shown) as an initial value (threshold value). That is, as shown in FIG. 5C from the ultrasonic sensors 1 and 2 for transmission to the ultrasonic sensors 3 and 4 for reception, the clock of the direct wave d is used as a reference clock, and FIG. The phase difference from the clock of the received waveform by the ultrasonic sensors 3 and 4 of the direct wave d with the ultrasonic sensors 1 to 4 in a normal state as shown in (d) is stored in the memory as the phase difference Pd1 (threshold value) at the normal time. Store in advance. Note that the phase difference of the direct wave d in a normal state of the ultrasonic sensors 1 to 4 is stored as an initial value (threshold value) in the product manufacturing process or measured before the actual use of the tilt angle. You may implement at the time of apparatus installation.

  When the reception waveform clock of the direct wave d as shown in FIG. 5E is received by the ultrasonic sensors 3 and 4 for reception, the phase difference Pd1 (reference phase difference between the received direct wave and the reference) In this case, since the phase difference of the direct wave shown in FIG. 5 (e) is a phase difference Pd2 having a value larger than the phase difference Pd1 that is the threshold, the reception waveform of the direct wave d at this time is It is determined that the phase difference is abnormal, and any one of the ultrasonic sensors 1 to 4 is regarded as a phase delayed due to adhesion of foreign matters such as mud and ice. The phase difference of the direct wave d is calculated by the phase-locked detection circuit 8 in this embodiment.

Next, the operation will be described with reference to the flowchart of FIG.
Now, when an ultrasonic sensor driving signal is sent from the transmitting circuit 5 to the transmitting ultrasonic sensors 1 and 2 (step ST1), the transmitting ultrasonic sensors 1 and 2 transmit the input driving signal. In response, electrical energy (electrical signal) is converted into mechanical vibration energy, and ultrasonic waves are transmitted as a transmission wave to the road surface 11. At this time, direct waves are transmitted from the transmitting ultrasonic sensors 1 and 2 to the receiving ultrasonic sensors 3 and 4, respectively (step ST2). The transmission waves from the transmission ultrasonic sensors 1 and 2 are reflected by the road surface 11 and received by the reception ultrasonic sensors 3 and 4 as reflected waves, respectively, and converted from mechanical vibration energy to electrical energy. At this time, the direct waves from the transmitting ultrasonic sensors 1 and 2 are also directly received by the receiving ultrasonic sensors 3 and 4 and converted from mechanical vibration energy to electrical energy (step ST3). The electrical energy from the reception ultrasonic sensors 3 and 4 is supplied to the reception circuits 6 and 7, amplified there, and supplied to the phase-locked detection circuit 8.

  The phase-locked wave detection circuit 8 calculates the phase difference of the direct wave included in the received signals from the receiving circuits 6 and 7 when detecting the adhesion of the foreign matter to the surfaces of the ultrasonic sensors 1 to 4 (step ST4). The calculated direct wave phase difference is compared with the threshold value representing the normal wave direct phase difference set in advance in the memory as described above to detect changes in the characteristics of the ultrasonic sensors 1 to 4 (step ST5). If the phase difference of the direct wave is within the threshold value and the characteristics of the ultrasonic sensors 1 to 4 are not changed, it is determined that no foreign matter is attached to the surface of the ultrasonic sensors 1 to 4 and the result is calculated. Output to the control circuit 9.

On the other hand, if the phase difference of the direct wave is outside the threshold value and the characteristics of the ultrasonic sensors 1 to 4 are changed, it is determined that a foreign substance is attached to the surface of the ultrasonic sensors 1 to 4 and that this is abnormal. Display or alarm (step ST6) and return to step ST4 to repeat the above operation. Then, after it is determined that no foreign matter is attached to the surface of the ultrasonic sensors 1 to 4 and is normal, the arithmetic control circuit 9 receives the normal reflected waves received by the receiving ultrasonic sensors 3 and 4. The vehicle inclination angle with respect to the road surface is measured based on the phase difference, the ultrasonic transmission speed, and the distance between the ultrasonic sensors (step ST7), and the series of processing operations is completed.

  In this way, in the present embodiment, the ultrasonic sensor in which the characteristic change of the ultrasonic sensor due to foreign matter adhering to the ultrasonic sensor surface is stored in advance as an initial value (threshold value) is in a normal state. Since the discrimination was made by comparing the phase difference of the direct wave with the calculated phase difference of the direct wave, the characteristic change of the ultrasonic sensor due to a minute amount of deposits in a state where the direct wave can be received can be detected, and reliably The inclination angle of the vehicle or the like can be measured, and the measurement accuracy can be improved.

Embodiment 2. FIG.
Note that when the phase-locked detection circuit 8 detects the phase difference of the direct wave, the number of pulses of the transmission wave from the transmission-side ultrasonic sensors 1 and 2 may be increased for continuous transmission. That is, when detecting the adhesion of the foreign matter of the ultrasonic sensors 1 to 4 by the direct wave phase difference, the transmission-side ultrasonic sensors 1 and 2 that are normally driven intermittently by the transmission circuit 5 may be continuously driven. As a result, the phase difference of the direct wave can be reliably detected, and the characteristic change of the ultrasonic sensor can be detected efficiently.

Embodiment 3 FIG.
In addition to the control period for detecting the tilt angle, a control period for detecting a change in the phase characteristics of the ultrasonic sensors 1 to 4 may be provided. The frequency does not matter. Thereby, the detection accuracy of the characteristic change of an ultrasonic sensor can be improved.

Embodiment 4 FIG.
Further, when detecting the characteristic change of the ultrasonic sensors 1 to 4, the output of the inclination angle measured by the arithmetic control circuit 9 may be stopped. That is, when it is determined that foreign matter is attached to the surface of the ultrasonic sensors 1 to 4 by detecting the phase difference of the ultrasonic sensor by detecting the phase difference of the direct wave, the arithmetic control circuit 9 Since the inclination angle measured in step 1 is not a normal value, the arithmetic control circuit 9 stops outputting the measured inclination angle until the characteristics of the ultrasonic sensors 1 to 4 return to normal. Thereby, an inclination angle can be measured correctly and a measurement precision can be improved.

Embodiment 5 FIG.
Further, the inclination angle measured by the arithmetic control circuit 9 may be corrected by using the phase difference of the direct wave detected by the phase synchronous detection circuit 8. That is, when the phase synchronization detection circuit 8 detects the phase difference of the direct wave and discriminates the change in the phase characteristics of the ultrasonic sensor, it is detected when the ultrasonic sensors 1 to 4 are found to have foreign matter attached. The inclination angle measured by the arithmetic control circuit 9 is corrected using the difference between the measured phase difference and the phase difference between the normal ultrasonic sensors 1 to 4. As a result, even when the ultrasonic sensors 1 to 4 are adhered to the foreign matter, the tilt angle can be measured in the arithmetic control circuit 9, and the measurement time can be shortened accordingly, and the tilt angle can be measured with high accuracy.

Embodiment 7 FIG.
As a means for preventing changes in the characteristics of the ultrasonic sensors 1 to 4 due to foreign matter adhering to the surface of the ultrasonic sensor from affecting the characteristics of the amplifier circuits included in the reception circuits 6 and 7 having the band-pass filter configuration, A buffer circuit may be provided between the ultrasonic sensor and the amplifier circuit.
FIG. 7 shows the case of the ultrasonic sensor 3 as an example. Normally, when a foreign object adheres to the surface of the ultrasonic sensor, the capacitor 3a, equivalent circuit resistance 3b and coil 3c, capacitor 3d, etc. of the ultrasonic sensor 3 are shown. The value changes and appears as a characteristic change of the ultrasonic sensor 3. Therefore, in the present embodiment, a high-impedance buffer circuit 12 is provided between the reception ultrasonic sensor 3 and the amplifier circuit 6 a of the reception circuit 6.

  Thus, when the ultrasonic sensor 3 for reception undergoes a characteristic change due to adhesion of a foreign substance, when the input impedance of the amplifier circuit 6a of the reception circuit 6 is low, the characteristic of the reception circuit 6 is affected, but as shown in FIG. Further, by providing the high impedance buffer circuit 12 between the reception ultrasonic sensor 3 and the reception circuit 6, mutual characteristics do not interfere with each other.

  FIG. 8 shows the transition of the frequency characteristics of the amplifier circuit 6a at this time. When there is no buffer circuit 12 between the receiving ultrasonic sensor 3 and the receiving circuit 6, the surface of the ultrasonic sensor 3 is shown. When a foreign object adheres to the antenna, the frequency characteristic changes between the characteristics f or g shown by the broken line in FIG. 8 according to the amount of the adhered foreign substance, but between the receiving ultrasonic sensor 3 and the receiving circuit 6. By providing the high-impedance buffer circuit 12, the mutual characteristics do not interfere with each other, and the frequency characteristics are fixed to the characteristic e indicated by the solid line in FIG. 8, and the tilt angle can be measured with higher accuracy.

In the above description, the high-impedance buffer circuit 12 is provided between the reception ultrasonic sensor 3 and the reception circuit 6. Of course, a high impedance is provided between the reception ultrasonic sensor 4 and the reception circuit 7. An impedance buffer circuit may be provided, which produces the same effect.
The technique of the seventh embodiment is not limited to the phase difference detection type tilt angle measuring apparatus using the transmission / reception separate type ultrasonic sensor of the first to fifth embodiments, but of course the transmission / reception of the sixth embodiment. The present invention can be similarly applied to the case of a phase difference detection type tilt angle measuring apparatus using a body type ultrasonic sensor, and the same effect is produced.

It is a block diagram which shows the structure of the inclination-angle measuring apparatus by Embodiment 1 of this invention. It is a figure which shows the electrical property of the ultrasonic sensor at the time of normal in the inclination-angle measuring apparatus by Embodiment 1 of this invention. It is a figure which shows the electrical property of the ultrasonic sensor at the time of the foreign material adhesion in the inclination angle measuring apparatus by Embodiment 1 of this invention. It is a schematic diagram for demonstrating the case where the phase difference of the direct wave between the ultrasonic sensors for transmission / reception is used in the inclination angle measuring apparatus by Embodiment 1 of this invention. It is a wave form diagram for demonstrating the case where the phase difference of the direct wave between the ultrasonic sensors for transmission / reception is used in the inclination angle measuring apparatus by Embodiment 1 of this invention. It is a flowchart for demonstrating operation | movement of the inclination-angle measuring apparatus by Embodiment 1 of this invention. It is a circuit block diagram which shows the principal part of the inclination-angle measuring apparatus by Embodiment 7 of this invention. It is a characteristic view for providing operation | movement description in the inclination angle measuring apparatus by Embodiment 7 of this invention.

Explanation of symbols

  1, 2 Transmission ultrasonic sensor, 3, 4 Reception ultrasonic sensor, 5 Transmission circuit, 6, 7 Reception circuit (amplifier circuit), 8 Phase synchronous detection circuit, 9 Operation control circuit, 10 Bumper, 11 Road surface, 12 Buffer circuit.

Claims (5)

A transmitting / receiving ultrasonic sensor that is attached to a vehicle and transmits an ultrasonic wave toward a road surface and a receiving ultrasonic sensor that receives the ultrasonic wave;
A second ultrasonic sensor that is attached to the vehicle and includes a transmission ultrasonic sensor that transmits ultrasonic waves toward the road surface and a reception ultrasonic sensor that receives the ultrasonic waves;
Based on the phase difference between the ultrasonic waves received by the first and second ultrasonic sensors, the transmission speed of the ultrasonic waves, and the distance between the first and second ultrasonic sensors, Arithmetic control means for measuring the inclination angle of the vehicle;
And detecting means for detecting a change in the phase characteristics of the first and the second foreign object by said first and second ultrasonic sensor attached to the surface of the ultrasonic sensor,
The detecting means is
The phase difference between the clock of the transmission wave transmitted directly from the transmission ultrasonic sensor to the reception ultrasonic sensor and the reference clock is defined as the phase difference of the direct wave, and the direct wave in the normal state of the ultrasonic sensor Storage means for storing the phase difference as a threshold;
A phase for detecting a phase difference of the direct wave of the ultrasonic sensor and comparing a phase difference of the detected direct wave with a threshold value stored in the storage unit to determine a change in the phase characteristic of the ultrasonic sensor. An inclination angle measuring device comprising: a change determining unit.   When detecting the phase difference between the clock of the transmission wave transmitted directly from the transmission ultrasonic sensor to the reception ultrasonic sensor and the reference clock, the transmission ultrasonic sensor is continuously driven by the transmission means, 2. The tilt angle measuring apparatus according to claim 1, wherein a transmission wave is continuously transmitted from the transmission ultrasonic sensor. 3. The tilt angle measuring apparatus according to claim 1, wherein a control period for detecting a change in phase characteristics of the ultrasonic sensor is provided in addition to the control period for detecting the tilt angle. Arithmetic control means, the first or second at characteristic change detecting the ultrasonic sensor, claim 1, characterized in that it stops the output of the measured angle of inclination of any one of claims of claims 3 Inclination angle measuring device. And ultrasonic sensors for reception, one of claims 1 of claim 4, characterized in that a buffer circuit of a high impedance between the receiving means for receiving ultrasonic waves from receiving credit ultrasonic sensor The tilt angle measuring device according to claim 1.

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