JP2011174735A - Driving support apparatus and obstacle detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving support apparatus using a general ultrasonic sensor, and correctly measuring and announcing a distance between a vehicle and an obstacle even if a temperature is changed. <P>SOLUTION: The driving support apparatus includes: a first measurement unit for detecting signals received by a plurality of the ultrasonic sensors attached to the vehicle, for calculating first time information until an ultrasonic wave directly propagated from one of the first and second adjacent ultrasonic sensors to the other is received by the other, and for measuring a propagation speed of the ultrasonic wave based on information on a distance between the first and second ultrasonic sensors and the first time information; a second measurement unit for calculating second time information until the ultrasonic wave emitted from a plurality of the ultrasonic sensors and reflected by the obstacle is received, and for measuring a distance between the obstacle based on the measured propagation speed of the ultrasonic wave and the second time information; and a warning unit for generating a warning when the distance between the vehicle and the obstacle is within a preset distance. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a driving support apparatus and an obstacle detection method for detecting and notifying obstacles around a moving body using an ultrasonic sensor installed on the moving body such as a vehicle.

  Conventionally, for the purpose of driving support of a vehicle, a plurality of ultrasonic sensors are attached to the vehicle to detect obstacles around the vehicle, and the presence or absence of the obstacle is notified to a display, a speaker, etc., and the vehicle collides with or collides with the obstacle. There is an obstacle detection device that avoids this.

  In such an obstacle detection device, an ultrasonic wave is transmitted from the ultrasonic sensor toward the periphery of the vehicle, and when there is an obstacle, the ultrasonic wave reflected by the obstacle is received by the sensor to check the presence or absence of the obstacle. The driver is notified when an obstacle approaches the vehicle. For example, it is suitable for parking assistance when parking in a garage or the like while backing the vehicle.

  By the way, in the obstacle detection device described above, it is necessary to detect the distance from the obstacle with high accuracy. However, the ultrasonic sensor changes the propagation speed of the sound wave due to changes in ambient temperature, atmospheric pressure, etc. An error may occur in the distance to the object, and the object may actually collide with the obstacle without being able to be notified accurately even though it is approaching the obstacle.

  In order to eliminate such problems, there is a technology to measure the distance more accurately by attaching a temperature sensor to the vehicle and compensating for the propagation speed of the ultrasonic wave according to the temperature change, but a temperature sensor or the like is required. This is disadvantageous in terms of cost.

  Patent Document 1 discloses an ultrasonic sensor device that prevents deterioration of detection accuracy due to adhesion of water droplets or dust or a temperature change when an ultrasonic sensor is mounted on a vehicle. However, in the example of Patent Document 1, a plurality of receiving elements are integrated on the same substrate for one transmitting element, and the distance to the obstacle is determined from the time difference between the average time values of one transmitting signal and the plurality of receiving signals. It is an arithmetic operation, and it is necessary to use a special ultrasonic sensor.

JP 2006-242650 A

  In the conventional obstacle detection device, it is necessary to detect the distance from the obstacle with high accuracy. However, the ultrasonic sensor changes the transmission speed of the sound wave due to changes in ambient temperature, atmospheric pressure, etc. In some cases, an error may occur in the distance, and it may not be possible to report accurately even though the obstacle is actually approaching. In the example of Patent Document 1, it is necessary to use a special ultrasonic sensor having a plurality of receiving elements for one transmitting element, which is not practical.

  In view of such circumstances, the present invention uses a general ultrasonic sensor to accurately measure the distance between a vehicle and an obstacle even when there is a temperature change and the like and an obstacle An object is to provide an object detection method.

  The driving support device of the present invention according to claim 1 is attached to a vehicle, a plurality of ultrasonic sensors that transmit and receive ultrasonic waves, a detection circuit that detects and outputs signals received by the plurality of ultrasonic sensors, Using the output signal of the detection circuit, the first ultrasonic wave directly propagated from one of the adjacent first and second ultrasonic sensors to the other of the plurality of ultrasonic sensors is received by the other. A first measurement unit that calculates time information of 1 and measures a propagation speed of an ultrasonic wave based on distance information between the first and second ultrasonic sensors and the first time information; and the detection Using the output signal of the circuit, the second time information until receiving the ultrasonic wave emitted from the plurality of ultrasonic sensors and reflected by the obstacle is calculated, and the propagation speed of the measured ultrasonic wave and the first time are calculated. Measure the distance to the obstacle based on the time information of 2. Characterized by comprising a second measuring section, and a warning unit for issuing an alarm when the distance between the vehicle and the obstacle has become within a preset distance to.

  According to a fourth aspect of the present invention, there is provided a driving support apparatus according to the present invention, an ultrasonic sensor that is attached to a vehicle and transmits / receives ultrasonic waves, a reflector disposed in the vehicle at a predetermined distance from the ultrasonic sensor, A detection circuit that detects and outputs a signal received by the ultrasonic sensor, and an ultrasonic wave directly propagated from the ultrasonic sensor to the reflection plate is reflected by the reflection plate using an output signal of the detection circuit. First time information until the ultrasonic sensor is received is calculated, and the ultrasonic propagation velocity is measured based on the distance information between the ultrasonic sensor and the reflector and the first time information. And calculating the second time information until the ultrasonic wave emitted from the ultrasonic sensor and reflected by the obstacle is received using the output signal of the first measurement unit and the detection circuit. Ultrasonic propagation speed and the second time A second measurement unit that measures a distance to the obstacle based on information; and a warning unit that issues an alarm when the distance between the vehicle and the obstacle is within a preset distance. It is characterized by that.

  According to a sixth aspect of the present invention, there is provided an obstacle detection method according to the present invention, wherein a plurality of ultrasonic sensors that transmit and receive ultrasonic waves are attached to a vehicle, signals received by the plurality of ultrasonic sensors are detected, and the plurality of ultrasonic waves are detected. Calculating first time information until an ultrasonic wave directly propagated from one of the adjacent first and second ultrasonic sensors to the other of the sensors is received by the other, and the first and second Based on the distance information between the ultrasonic sensors and the first time information, the propagation speed of the ultrasonic waves is measured, and using the detected signals, the ultrasonic waves are emitted from the plurality of ultrasonic sensors and reflected by an obstacle. Second time information until ultrasonic waves are received is calculated, and a distance to the obstacle is measured based on the measured propagation speed of the ultrasonic waves and the second time information.

  Furthermore, the obstacle detection method of the present invention according to claim 8 is characterized in that an ultrasonic sensor for transmitting and receiving ultrasonic waves is attached to a vehicle, a reflector is arranged on the vehicle at a predetermined distance from the ultrasonic sensor, A signal received by the ultrasonic sensor is detected, and first time information until the ultrasonic wave directly propagated from the ultrasonic sensor to the reflecting plate is reflected by the reflecting plate and received by the ultrasonic sensor is obtained. Calculate, measure the propagation speed of the ultrasonic wave based on the distance information between the ultrasonic sensor and the reflector and the first time information, and use the detected signal to be emitted from the ultrasonic sensor. Second time information until the ultrasonic wave reflected by the obstacle is received is calculated, and the distance to the obstacle is measured based on the measured propagation speed of the ultrasonic wave and the second time information. It is characterized by that.

  According to the embodiment of the present invention, the distance to the obstacle can be accurately measured even if the ambient temperature changes, and accurate driving assistance can be provided to the driver.

The block diagram which shows the structure of the driving assistance device which concerns on one Embodiment of this invention. Operation | movement explanatory drawing of the driving assistance device which concerns on the same embodiment. The top view which shows the attachment position of the ultrasonic sensor to the vehicle which concerns on the embodiment. The signal waveform diagram explaining operation | movement of the driving assistance device which concerns on the same embodiment. The signal waveform diagram explaining operation | movement when there exists a temperature change. The flowchart explaining operation | movement of the driving assistance apparatus which concerns on the same embodiment. The top view which shows the attachment position of the ultrasonic sensor and reflector in the vehicle which concerns on other embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a driving support apparatus 100 according to an embodiment of the present invention. 1, the driving support apparatus 100 includes a sensor group 10 including a plurality of ultrasonic transceivers 11, 12..., A transmission / reception / detection circuit 20, a signal processing unit 30, a memory 40, and a warning unit 50. The ultrasonic transceivers 11, 12,... Include a transmitter that emits an ultrasonic signal and a receiver that receives an incident ultrasonic signal. In the following description, the ultrasonic transceiver is referred to as an ultrasonic sensor.

  The ultrasonic sensors 11, 12,... Are attached to, for example, a rear bumper of the vehicle or a side surface of the vehicle, emit ultrasonic signals to obstacles around the vehicle, and the emitted ultrasonic signals are reflected by the obstacles. When received by the ultrasonic sensors 11, 12,. The transmission / reception / detection circuit 20 generates an ultrasonic signal and transmits it from the ultrasonic sensors 11, 12,..., And receives and detects the ultrasonic signals received by the ultrasonic sensors 11, 12,. Further, the detected signal is waveform-shaped with a predetermined threshold and supplied to the signal processing unit 30.

  The signal processing unit 30 is configured by, for example, a microprocessor (microcomputer), sets the above-described threshold value, and processes the waveform-shaped output signal from the transmission / reception / detection circuit 20 to obtain distance information between the obstacle and the vehicle. Is calculated. The memory 40 stores threshold information and time information calculated by the signal processing unit 30.

  The warning unit 50 includes a sound generation unit such as a speaker (or buzzer), and notifies the driver by sound when an obstacle approaches the vehicle within a predetermined distance. In addition to notifying by voice, a display unit such as a display may be provided to display a warning on the display.

  In this embodiment, ultrasonic signals are emitted from the ultrasonic sensors 11 and 12 to obstacles around the vehicle, and the emitted ultrasonic signals are reflected by the obstacles and received by the ultrasonic sensors 11 and 12 again. Measure the round trip propagation time. Then, the distance from the obstacle is measured based on this time information. Among the plurality of ultrasonic sensors 11, 12,..., An ultrasonic wave directly propagated from an adjacent sensor is received, and the current temperature is measured. An ultrasonic propagation velocity is calculated, and accurate distance information is calculated based on the propagation velocity.

  Hereinafter, the operation for measuring the distance between the vehicle and the obstacle will be described. FIG. 2 shows a case where the vehicle 1 is parked in the garage while being backed. For example, when the vehicle 1 is put back into the garage, the driver may not know the distance to the wall 2 or the object 3 placed in the garage and may collide. For this reason, by emitting ultrasonic waves from a plurality of ultrasonic sensors provided on the rear or side surface of the vehicle 1, receiving ultrasonic waves reflected from the wall 2 or the object 3 by the ultrasonic sensors, and processing the received signals. When the vehicle 1 approaches an obstacle (wall 2 or object 3), the driver is notified.

  FIG. 3 is a plan view showing the arrangement of the ultrasonic sensors with respect to the vehicle 1. In FIG. 3, for example, ultrasonic sensors 11 and 12 are installed on a rear bumper of the vehicle 1 by a predetermined distance (L0). Ultrasonic sensors 13 and 14 are installed on the side of the vehicle 1. Then, an ultrasonic signal is emitted from the ultrasonic sensors 11 to 14 to the surroundings of the vehicle 1, and the ultrasonic signals reflected by the obstacles (the wall 2 and the object 3) are received by the ultrasonic sensors 11 to 14. Yes.

  L is the distance from the ultrasonic sensor to the measurement object (obstacle), T is the time until the ultrasonic wave emitted from the ultrasonic sensor is reflected by the measurement object and returns to the ultrasonic sensor, and in the gas The distance L can be obtained by the following equation (1), where C is the propagation speed (sound speed) of the ultrasonic wave.

L = T · C / 2 (1)
However, it is known that the propagation speed C (m / sec) of the ultrasonic wave in the gas changes depending on the gas temperature and becomes slower as the temperature decreases. On the other hand, ultrasonic waves have the property of being easily transmitted through the air along the solid surface, and the ultrasonic sensors 11 and 12 installed on the bumper of the vehicle for distance measurement are no exception, and ultrasonic waves are transmitted through the air along the bumper surface. Propagates. As a result, the two adjacent sensors (for example, the ultrasonic sensors 11 and 12) directly receive each other's transmission waves.

  Therefore, the present invention is characterized in that the ultrasonic wave propagating along the bumper surface is used to calculate the ultrasonic wave propagation velocity corresponding to the actual temperature and to correct the distance to the obstacle. Hereinafter, a description will be given with reference to FIGS. 4 and 5. 4 and 5, a case will be described in which ultrasonic waves are transmitted and received from two adjacent ultrasonic sensors 11 and 12 among a plurality of ultrasonic sensors.

  4A shows an ultrasonic wave (transmission wave S1) transmitted from the ultrasonic sensor 11 and an ultrasonic wave (reflected wave S2) reflected by the obstacle after the transmission wave S1 is reflected by the obstacle. ) Shows the signal waveform. At the same time, the ultrasonic wave directly propagated from the adjacent ultrasonic sensor 12 is transmitted through the air along the bumper surface of the vehicle, and the signal waveform of the ultrasonic wave (propagation wave S3) received by the ultrasonic sensor 11 is shown. . The level of the propagation wave S3 is sufficiently smaller than the level of the reflected wave S2.

  FIG. 4B shows a detection signal by the transmission / reception / detection circuit 20. Detection is performed by half-wave rectifying the received raw waveform. The detection signal includes components of the transmission wave S1, the reflected wave S2, and the propagation wave S3. FIG. 4C shows a pulse output obtained by shaping the waveform by setting the first threshold value TH1 for the detection signal (b). The noise component can be removed by setting the threshold TH1 and detecting a signal equal to or higher than the threshold TH1.

  In FIG. 4C, the detection pulse corresponding to the transmission wave S1 is S11, and the detection pulse corresponding to the reflected wave S2 is S21. As can be seen from FIG. 4B, since the propagation wave S3 is equal to or less than the threshold value TH1, the propagation wave S3 is removed as noise in FIG. 4C.

  The time from the generation of the pulse S11 to the generation of the pulse S21 is T1. Usually, by measuring this time T1, the distance between the vehicle and the obstacle can be measured based on the equation (1). However, since the propagation speed of the ultrasonic wave in the gas changes depending on the gas temperature, it is necessary to accurately grasp the propagation speed of the ultrasonic wave at the current temperature. Therefore, waveform shaping is performed by lowering the threshold as shown in FIG.

  FIGS. 5A, 5B, and 5C show the same signal waveforms as in FIG. 4, but show a state in which the threshold is lowered from TH1 to TH2. When the threshold value TH2 is lowered to a value at which the component of the propagation wave S3 can be detected, detection pulses S11, S21, and S31 of the transmission wave S1, the reflected wave S2, and the propagation wave S3 are obtained as shown in FIG. Can do. The time from the generation of the pulse S11 to the generation of the pulse S21 is T2, and the time from the generation of the pulse S11 to the generation of the pulse S31 is T3 (T3 <T2).

  On the other hand, since the distance L0 between the ultrasonic sensor 11 and the ultrasonic sensor 12 (the length transmitted through the bumper edge, not the straight line distance) is unchanged, the signal processing unit 30 is based on the time T3 and the distance L0. The ultrasonic wave propagation velocity C0 at the current temperature is calculated by the following equation (2).

C0 = L0 / T3 (2)
Therefore, assuming that the actual distance L1 to the obstacle is the ultrasonic wave propagation velocity C0 at the current temperature and the time T1 in FIG. 4C, the distance L1 is expressed by the following equation (3). Can be calculated.

L1 = T1 · C0 / 2 (3)
Thus, the signal processing unit 30 is configured to receive the ultrasonic waves directly propagated from one of the adjacent first and second ultrasonic sensors (11, 12) to the other among the plurality of ultrasonic sensors. A first measurement unit that calculates time information T3 and measures ultrasonic propagation velocity C0 based on distance information (L0) between the first and second ultrasonic sensors (11, 12) and time information T3. Configure.

  Further, the signal processing unit 30 calculates time information T1 until receiving ultrasonic waves emitted from a plurality of ultrasonic sensors (11, 12,...) And reflected by an obstacle, and the measured ultrasonic propagation velocity C0. And a second measuring unit that measures the distance to the obstacle based on the time information T1.

  The time T1 from the generation of the detection pulse S11 to the generation of the detection pulse S21 when the threshold value is TH1 and the time T2 from the generation of the detection pulse S11 to the generation of the detection pulse S21 when the threshold value is TH2 are substantially equal. The distance L1 to the obstacle may be calculated using the time T2. In this case, the detection threshold is always set to a low level TH2. However, when the threshold value is switched between TH1 and TH2, the times T1 and T2 slightly deviate from each other. Therefore, it may be more accurate to calculate the distance L1 from the obstacle based on the time T1 at the threshold value TH1. it can.

  Further, the case where the propagation speed of the ultrasonic wave becomes slow due to the temperature change is shown by the dotted line waveforms in FIGS. 5B and 5C. When the temperature of ultrasonic waves decreases, the propagation speed in the gas decreases. For this reason, the detection pulses of the reflected wave S2 and the propagation wave S3 are also delayed as indicated by S22 and S32, and the time T2 from the generation of the transmission wave S1 to the reception of the reflection wave S2 and the reception of the propagation wave S3. The time T3 is also delayed and becomes T2 ′ and T3 ′. Further, the time T1 from the generation of the transmission wave S1 when the threshold value is TH1 to the reception of the reflected wave S2 is also a delay T1 '(not shown).

  However, since the distance L0 between the ultrasonic sensor 11 and the ultrasonic sensor 12 is unchanged, the ultrasonic wave propagation velocity C0 ′ when the temperature changes is expressed by the following (4) based on the time T3 ′ and the distance L0. ).

C0 ′ = L0 / T3 ′ (4)
Therefore, when the actual distance L1 to the obstacle is defined, the following equation (5) can be calculated based on the ultrasonic wave propagation velocity C0 ′ and the time T1 ′ at the current temperature.

L1 = T1 ′ · C0 ′ / 2 (5)
Conversely, when the ambient temperature increases, the propagation speed of the ultrasonic wave increases, and accordingly, the distance from the obstacle can be measured accurately.

  Information on the distance L0 between the two adjacent sensors 11 and 12 (the length that traveled through the bumper edge, not the straight line distance) and the information on the detection thresholds TH1 and TH2 are stored in the memory 40 in advance, It is read as needed when measuring the distance. Time information T1 and T3 measured by setting the threshold values TH1 and TH2 can also be stored in the memory 40. Moreover, although the ultrasonic sensors 11 and 12 were described in the above description, ultrasonic waves are emitted from all the sensors 11 to 14 installed in the vehicle 1 in synchronization.

  FIG. 6 is a flowchart showing the operation of the driving support apparatus. In FIG. 6, step S1 indicates ACC on (engine start), and initialization is performed in step S2. After step S3, in step S4, the normal detection threshold (first threshold TH1) is set. In step S5, information (time information T1) is acquired from the ultrasonic sensors 11 and 12 when the first threshold value TH1 is set.

  In the next step S6, the second detection threshold TH2 is set, and time information T3 until the propagation wave S3 from the adjacent ultrasonic sensor is received is measured. In step S7, the ultrasonic sensor 11 and 12 are measured. The distance information L0 is acquired. In step S8, the ultrasonic wave propagation velocity C0 at the current temperature is measured based on the acquired distance information L0 and time information T3. In step S9, the distance between the vehicle and the obstacle is calculated based on the time information T1 acquired in step S5 and the propagation velocity C0 measured in step S8.

  In step S10, a warning output process is performed when the distance from the obstacle is equal to or smaller than a preset distance, and a warning sound is generated or a warning is displayed. Thereafter, the process between step S11 and step S3 is repeated, while the vehicle engine is running, the distance to the obstacle is measured and a warning is given, and the process is terminated in step S12 when the engine is stopped.

  Thus, in the embodiment of the present invention, the propagation speed of the ultrasonic wave corresponding to the current ambient temperature can always be measured in real time, and the distance to the obstacle can be accurately measured. In addition, since ultrasonic waves from adjacent ultrasonic sensors are received and the actual ultrasonic wave propagation speed is measured, there is no need to use an extra detection element such as a temperature sensor. Can be suppressed.

  Next, a second embodiment of the present invention will be described. In the first embodiment, the example in which the ultrasonic wave propagation velocity at the current temperature is measured using two adjacent ultrasonic sensors (for example, the sensors 11 and 12) is described. In the second embodiment, one ultrasonic sensor is used. The ultrasonic wave propagation speed is measured using an ultrasonic sensor and a reflector.

  FIG. 7 is a plan view showing the arrangement of the ultrasonic sensor and the reflecting plate with respect to the vehicle 1. For example, a reflection plate 60 is provided in the rear bumper of the vehicle 1 instead of the ultrasonic sensor 12, and the ultrasonic sensor 11 is installed at a predetermined distance (L 0) away from the reflection plate 60. Ultrasonic sensors 13 and 14 are installed on the side of the vehicle 1.

  Then, an ultrasonic signal is emitted from the ultrasonic sensors 11, 13, and 14 to the surroundings of the vehicle, and the ultrasonic signal reflected by the obstacle (the wall 2 or the object 3) is received by the ultrasonic sensors 11, 13, and 14. I am doing so. Further, in FIG. 7, the ultrasonic wave transmitted from the ultrasonic sensor 11 travels in the air along the bumper surface of the vehicle 1, hits the reflection plate 60 and is reflected, and the reflected ultrasonic wave is received by the ultrasonic sensor 11. I have to.

  Since the distance L0 between the ultrasonic sensor 11 and the reflecting plate 60 (the length that travels through the bumper edge, not the linear distance) is unchanged, the ultrasonic waves emitted from the ultrasonic sensor 11 are reflected by the reflecting plate 60 and again. Assuming that the round trip time until reception by the ultrasonic sensor 11 is T4, the ultrasonic wave propagation velocity C1 at the current temperature can be calculated by the following equation (6) based on the time T4 and the distance L0. .

C1 = 2 · L0 / T4 (6)
Therefore, when the time from when the ultrasonic wave emitted from the ultrasonic sensor 11 is reflected by the obstacle until it is received again by the ultrasonic sensor 11 is T1, the actual distance L1 to the obstacle is expressed by Equation (6). Based on the obtained ultrasonic wave propagation velocity C1 and time T1, it can be calculated by the following equation (7).

L1 = T1 · C1 / 2 (7)
Since the ultrasonic sensor 11 propagates the ultrasonic wave generated by itself through the bumper edge to the reflection plate 60 and further receives the ultrasonic wave reflected by the reflection plate 60, the ultrasonic level at the time of reception is attenuated. However, reflected waves can be detected by setting the threshold value well. If the threshold is lower than the threshold TH2 in FIG. 5B, the ultrasonic wave reflected by the reflector 60 can be detected. Therefore, the ultrasonic wave propagation speed at the current temperature can be measured using one ultrasonic sensor, and the circuit configuration can be simplified.

  As described above, according to the present invention, the distance to the obstacle can be accurately measured even when the ambient temperature changes, and accurate driving assistance can be provided to the driver.

  In the above description, the example in which the ultrasonic wave propagation speed is measured by the ultrasonic sensors 11 and 12 has been described. However, the ultrasonic sensor 11 installed in front of the vehicle and the ultrasonic sensor 13 installed in the side (or the ultrasonic sensor). The ultrasonic wave propagation speed may be measured using the ultrasonic sensor 12 and the ultrasonic sensor 14). Moreover, although the example which installed the ultrasonic sensors 11 and 12 in the back of a vehicle and detected the obstruction of a vehicle back was demonstrated, it installs an ultrasonic sensor in the front of a vehicle and detects an obstruction in the front of a vehicle. May be. Various modifications can be made without departing from the scope of the claims.

DESCRIPTION OF SYMBOLS 100 ... Driving assistance apparatus 1 ... Vehicle 2, 3 ... Obstacle 10 ... Ultrasonic sensor group 11, 12, 13, 14 ... Ultrasonic sensor 20 ... Transmission / reception / detection circuit 30 ... Signal processing part (microcomputer)
40 ... Memory 50 ... Warning section 60 ... Reflector

Claims (8)

A plurality of ultrasonic sensors attached to the vehicle for transmitting and receiving ultrasonic waves;
A detection circuit for detecting and outputting signals received by the plurality of ultrasonic sensors;
Using the output signal of the detection circuit, the first ultrasonic wave directly propagated from one of the adjacent first and second ultrasonic sensors to the other of the plurality of ultrasonic sensors is received by the other. A first measurement unit that calculates time information of 1 and measures ultrasonic wave propagation speed based on the distance information between the first and second ultrasonic sensors and the first time information;
Using the output signal of the detection circuit, second time information is calculated until the ultrasonic wave emitted from the plurality of ultrasonic sensors and reflected by the obstacle is received, and the propagation speed of the measured ultrasonic wave and A second measuring unit for measuring a distance to the obstacle based on the second time information;
And a warning unit that issues a warning when the distance between the vehicle and the obstacle is within a preset distance. The detection circuit sets a first detection threshold for the detection signal, detects the first ultrasonic wave directly propagated from one of the first and second ultrasonic sensors to the other, and Detecting a second ultrasonic wave reflected by the obstacle by setting a second detection threshold value higher than the first detection threshold value;
The first measuring unit measures the first time information based on the detected first ultrasonic wave, and the second measuring unit is based on the detected second ultrasonic wave. The driving support device according to claim 1, wherein the second time information is measured.   2. The storage unit according to claim 1, further comprising a storage unit that stores information on the first and second detection threshold values, wherein the detection circuit sets the detection threshold value based on information read from the storage unit. Driving assistance device. An ultrasonic sensor attached to a vehicle and transmitting and receiving ultrasonic waves;
A reflector disposed in the vehicle at a predetermined distance from the ultrasonic sensor;
A detection circuit for detecting and outputting a signal received by the ultrasonic sensor;
Using the output signal of the detection circuit, first time information until the ultrasonic wave directly propagated from the ultrasonic sensor to the reflecting plate is reflected by the reflecting plate and received by the ultrasonic sensor is calculated. A first measurement unit that measures the propagation speed of the ultrasonic wave based on the distance information between the ultrasonic sensor and the reflector and the first time information;
Using the output signal of the detection circuit, second time information is calculated until the ultrasonic wave emitted from the ultrasonic sensor and reflected by the obstacle is received, and the propagation speed of the measured ultrasonic wave and the first time are calculated. A second measuring unit that measures the distance to the obstacle based on the time information of 2;
And a warning unit that issues a warning when the distance between the vehicle and the obstacle is within a preset distance. The detection circuit sets a first detection threshold with respect to the detection signal, detects reflected ultrasonic waves from the reflector received by the ultrasonic sensor, and exceeds the first detection threshold. Set a high second detection threshold to detect ultrasound reflected by the obstacle;
The first measurement unit measures the first time information based on the reflected ultrasonic wave from the reflector, and the second measurement unit also receives the ultrasonic wave reflected by the obstacle. The driving support device according to claim 4, wherein the second time information is measured. Attach multiple ultrasonic sensors that transmit and receive ultrasonic waves to the vehicle,
Signals received by the plurality of ultrasonic sensors are detected, and ultrasonic waves directly propagated from one of the adjacent first and second ultrasonic sensors to the other of the plurality of ultrasonic sensors are received by the other. Calculate the first time information until
Measuring the propagation velocity of the ultrasonic wave based on the distance information between the first and second ultrasonic sensors and the first time information;
Using the detected signals, calculate second time information until receiving ultrasonic waves emitted from the plurality of ultrasonic sensors and reflected by an obstacle,
An obstacle detection method, comprising: measuring a distance to the obstacle based on the measured ultrasonic propagation velocity and the second time information. A first detection threshold is set for the detection signal to detect the first ultrasonic wave directly propagated from one of the first and second ultrasonic sensors to the other;
Detecting a second ultrasonic wave reflected by the obstacle by setting a second detection threshold value higher than the first detection threshold value;
Measuring the first time information based on the detected first ultrasonic wave;
The obstacle detection method according to claim 6, wherein the second time information is measured based on the detected second ultrasonic wave. Install an ultrasonic sensor to send and receive ultrasonic waves to the vehicle,
A reflector is arranged at a predetermined distance from the ultrasonic sensor in the vehicle,
A first time from detection of the signal received by the ultrasonic sensor until the ultrasonic wave directly propagated from the ultrasonic sensor to the reflector is reflected by the reflector and received by the ultrasonic sensor Calculate information,
Measure the ultrasonic wave propagation speed based on the distance information between the ultrasonic sensor and the reflector and the first time information,
Using the detected signal, calculate second time information until receiving the ultrasonic wave emitted from the ultrasonic sensor and reflected by the obstacle,
An obstacle detection method, comprising: measuring a distance to the obstacle based on the measured ultrasonic propagation velocity and the second time information.

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