JP2016191614A - Obstacle detection device, method of calculating humidity correction value, and method of determining ultrasonic wave reception threshold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an obstacle detection device capable of individually making correction for humidity conditions while minimizing an increase in size and cost of the device, and to provide a method of calculating a humidity correction value and a method of determining an ultrasonic wave reception threshold.SOLUTION: An obstacle detection device 100 calculates an outside air humidity correction value on the basis of: a travel distance of a vehicle measured based on an output of a vehicle speed sensor 30; a first time period (travel time t) it takes for an ultrasonic wave transmitted from an ultrasonic element 10 at a starting point of a travel distance measurement to be reflected by an obstacle and received by the ultrasonic element; a second time period (travel time t) it takes for an ultrasonic wave transmitted from the ultrasonic element 10 at a finishing point of the travel distance measurement to be reflected by the obstacle and received by the ultrasonic element; and temperature of outside air surrounding the vehicle detected by an outside air temperature sensor 50.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an obstacle detection device that detects a distance from an obstacle mounted on a vehicle, a humidity correction value calculation method thereof, and an ultrasonic wave reception threshold value determination method thereof.

  There is an obstacle detection device that transmits an ultrasonic wave, receives a reflected wave reflected by an obstacle, and acquires a distance to the obstacle based on the propagation time and sound velocity. In particular, a technique for mounting an obstacle detection device on a vehicle and preventing a collision between the vehicle and the obstacle or abnormal approach is widespread.

  When ultrasonic waves propagate in the air, the energy is attenuated according to the propagation distance. Since this attenuation is affected by environmental conditions such as temperature and humidity, the range in which the obstacle detection device can detect obstacles varies greatly depending on the outside air condition. Regarding the temperature, for example, the temperature around the vehicle can be acquired by a temperature sensor mounted on the vehicle. On the other hand, regarding humidity, a vehicle is generally not provided with a humidity sensor.

  Conventionally, ultrasonic detection can be performed automatically without using an additional sensor, etc., and ultrasonic detection can be performed accurately regardless of differences in the surrounding environment such as temperature and humidity. There is a proposal for an apparatus (see Patent Document 1). Patent Document 1 also describes that the humidity is estimated without using a humidity sensor to cope with a change in humidity (paragraph 0009 and the like).

Japanese Patent No. 5422744

  The technique disclosed in Patent Document 1 adjusts a reference threshold value for distinguishing between an ultrasonic reception signal and noise used for a calculation process of distance information according to environmental conditions such as temperature and humidity at that time. doing. For this reason, in the technique of patent document 1, it is not necessary to perform adjustment by temperature and adjustment by humidity separately.

  However, among various methods for detecting obstacles or measuring distances using ultrasonic waves, it is desirable to perform correction for each environmental condition. Specifically, there is a case where it is desired to separately perform correction based on temperature conditions and correction based on humidity conditions.

  Further, the method of estimating the humidity without using the humidity sensor shown in Patent Document 1 leads to an increase in size and cost of the ultrasonic sensor as shown in Paragraph 0009 of Patent Document 1. There is a fear. In addition, there are problems such as requiring calculation accuracy and processing capability of the control device.

  An object of the present invention is to provide an obstacle detection device, a humidity correction value calculation method, and an ultrasonic wave reception threshold value determination method capable of performing correction by humidity individually while suppressing increase in size and cost of the device. Is to provide.

  An obstacle detection device according to the present invention is provided in a vehicle and transmits and receives ultrasonic waves to detect obstacles around the vehicle, a vehicle speed sensor that detects the speed of the vehicle, and the vehicle periphery An outside air temperature sensor for detecting the temperature of the outside air, a moving distance of the vehicle measured based on an output of the vehicle speed sensor, and an ultrasonic wave transmitted by the ultrasonic sensor at the measurement start point of the moving distance is an obstacle And a second time until the ultrasonic wave transmitted by the ultrasonic sensor at the measurement end point of the movement distance is reflected and received by the obstacle, and And a controller that calculates a humidity correction value of the outside air based on the temperature of the outside air around the vehicle detected by the outside air temperature sensor.

  The humidity correction value calculation method of the present invention includes a moving distance measuring step for measuring a moving distance of the vehicle based on an output of a vehicle speed sensor that is provided in the vehicle and detects the speed of the vehicle, and a measurement start point of the moving distance. First time until the ultrasonic wave transmitted by the ultrasonic sensor provided in the vehicle is reflected by the obstacle and received, and the ultrasonic wave transmitted by the ultrasonic sensor at the measurement end point of the moving distance A humidity correction value of the outside air is calculated based on a second time until the sound wave is reflected by the obstacle and received and the temperature of the outside air around the vehicle detected by the outside temperature sensor provided outside the vehicle. And a humidity correction value calculating step.

  An ultrasonic wave reception threshold value determining method according to the present invention includes a moving distance measuring step that is provided in a vehicle and that measures a moving distance of the vehicle based on an output of a vehicle speed sensor that detects the speed of the vehicle. At a measurement start point, a first time until an ultrasonic wave transmitted by an ultrasonic sensor provided in the vehicle is reflected by an obstacle and received, and at the measurement end point of the moving distance, the ultrasonic sensor The humidity of the outside air based on the second time until the transmitted ultrasonic wave is reflected by the obstacle and received and the temperature of the outside air around the vehicle detected by the outside air temperature sensor provided outside the vehicle A humidity correction value calculating step for calculating a correction value, and a threshold value of the amplitude of the ultrasonic wave that is judged as an obstacle when the ultrasonic sensor receives the ultrasonic wave, using at least the calculated humidity correction value Having a threshold determination step of determining.

  ADVANTAGE OF THE INVENTION According to this invention, the correction | amendment by humidity conditions can be performed separately, suppressing the enlargement of an apparatus and the increase in cost.

The figure which shows the structural example of an obstacle detection apparatus The flowchart which shows an example of control of CPU in a humidity detection process The figure which shows the relationship between the movement distance of the vehicle and the flight time The figure for explaining threshold setting processing

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a diagram illustrating a configuration example of an obstacle detection apparatus 100 according to an embodiment of the present invention.

  As shown in FIG. 1, the obstacle detection apparatus 100 includes an ultrasonic element 10, a control unit 20, a vehicle speed sensor 30, a shift position sensor 40, and an outside air temperature sensor 50. The obstacle detection apparatus 100 is assumed to be attached to a vehicle such as a passenger car.

  The ultrasonic element 10 transmits an ultrasonic wave generated by a wave transmission unit 21 of the control unit 20 described later, and receives a reflected wave reflected by an object such as an obstacle around the vehicle. For example, electric power is generated in the piezoelectric element or the like included in the ultrasonic element 10 by the received reflected wave, and the ultrasonic element 10 outputs the magnitude of the electric power to the wave receiving unit 22 of the control unit 20 described later. Many conventional ultrasonic sensors including ultrasonic elements can detect obstacles at short distances of about 1 to 2 m. However, the obstacle detection apparatus 100 having the ultrasonic element 10 according to the present embodiment is an obstacle. The detectable distance may be longer than 3 m.

  In FIG. 1, as an example, the obstacle detection apparatus 100 is shown as having only one ultrasonic element 10, but the present invention is not limited to this. For example, two or more ultrasonic elements are included. You may have.

  The control unit 20 performs operation control of the obstacle detection device 100. The control unit 20 is configured by, for example, a microcontroller.

  As illustrated in FIG. 1, the control unit 20 includes a transmission unit 21, a reception unit 22, a CPU (Central Processing Unit) 23, a memory 24, and a communication unit 25.

  The wave transmission unit 21 generates and transmits an ultrasonic wave by vibrating a piezoelectric element (not shown) of the ultrasonic element 10 in a minute cycle based on the control of the CPU 23 described later.

  The wave receiving unit 22 receives a voltage signal generated by a piezoelectric element (not shown) of the ultrasonic element 10 that has received a reflected wave reflected by an obstacle or the like, and outputs the voltage signal to the CPU 23.

  The CPU 23 has an arithmetic processing function and performs various processes. Details of the processing performed by the CPU 23 will be described later. The ultrasonic element 10, the wave transmission unit 21, the wave reception unit 22, and the CPU 23 described above correspond to the ultrasonic sensor according to the present invention.

  The memory 24 stores various data used for each process performed by the CPU 23 in the control unit 20. The memory 24 reads out necessary data in response to a request from the CPU 23 and outputs it to the CPU 23.

  The communication unit 25 communicates with each component included in the vehicle, such as a vehicle speed sensor 30, a shift position sensor 40, and an outside air temperature sensor 50 described later. This communication is based on an in-vehicle network such as a CAN (Controller Area Network).

  The vehicle speed sensor 30 is attached to, for example, an axle connected to a vehicle wheel, and detects the rotational speed of the wheel. By processing the rotational speed of the wheel detected by the vehicle speed sensor 30 by the CPU 23 of the control unit 20 described above, it is possible to acquire information related to the speed and moving distance of the vehicle.

  The shift position sensor 40 detects the position of the shift lever of the vehicle. The shift position sensor 40 is attached to a transmission system of the vehicle, such as a gear box.

  The outside air temperature sensor 50 is attached to a part of the vehicle exposed to the outside of the vehicle, for example, near the front grille, etc., and detects the temperature outside the vehicle.

[Processing performed by CPU 23]
Hereinafter, details of the processing performed by the CPU 23 will be described. First, the CPU 23 performs an obstacle detection process for detecting a vehicle and obstacles around it by transmitting ultrasonic waves using the ultrasonic element 10 and receiving reflected waves. In this obstacle detection process, the CPU 23 generates a transmission instruction signal of a transmission ultrasonic wave with a minute cycle transmitted by the wave transmission unit 21, transmits the ultrasonic wave to the wave transmission unit 21, and is reflected by an obstacle or the like. This is a process of acquiring the voltage signal (received signal) of the received ultrasonic wave from the wave receiving unit 22 that has received the ultrasonic wave, and detecting the presence of an obstacle. In the obstacle detection device 100 of the present embodiment, the distance at which an obstacle can be detected by the ultrasonic wave transmitted by the ultrasonic element 10 is generally a short distance (for example, about 1 to 2 m) used for obstacle detection. It may be a long distance (for example, approximately 4 to 6 m, approximately 3 m or more and at most less than 10 m). Since the influence of ultrasonic attenuation due to environmental conditions such as humidity and temperature increases as the detectable distance increases, the obstacle detection apparatus 100 according to the present embodiment particularly increases the detectable distance. It is desirable to be used when

  When the CPU 23 detects an obstacle around the vehicle by the obstacle detection process, for example, the CPU 23 controls a brake control unit (not shown) and automatically applies the brake to prevent the vehicle from contacting the obstacle. You may make it cope with these.

  In the obstacle detection process, the received ultrasonic voltage signal acquired from the wave receiving unit 22 includes not only the ultrasonic wave reflected by the obstacle or the like but also a reflected wave from the road surface or the like as noise. Since the intensity of this noise is lower than that of a reflected wave from an obstacle or the like, it is possible to remove the noise by removing a value smaller than a predetermined threshold value from the voltage signal acquired from the wave receiving unit 22. it can. It is desirable that this threshold value be appropriately set according to the environment around the vehicle, for example, the temperature or humidity of the outside air. In this way, the CPU 23 performs a threshold setting process for suitably setting the threshold according to the temperature and humidity of the outside air.

  In performing the threshold setting process, the outside air temperature can be acquired by the outside temperature sensor 50, so the CPU 23 needs to perform a humidity detection process for detecting the humidity of the outside air using the ultrasonic element 10.

  As described above, the CPU 23 performs the obstacle detection process, the threshold setting process for accurately performing the obstacle detection process, and the humidity detection for acquiring the humidity of the outside air used in the threshold setting process. And processing.

[Humidity detection processing]
First, the details of the humidity detection process will be described below. FIG. 2 is a flowchart showing an example of the control of the CPU 23 in the humidity detection process.

  In step S <b> 100, the CPU 23 refers to the output result of the shift position sensor 40 and determines whether or not the shift lever is in “R (reverse)”. If it is determined that the shift lever is in “R”, the flow proceeds to step S101, and if not, the process of step S100 is repeated.

  Step S100 is a step for determining whether or not the CPU 23 starts the humidity detection process. The reason for determining whether or not the shift lever is in the “R” as an opportunity to start the humidity detection process is as follows. That is, for example, when the shift lever is put in “R” and the vehicle is going to back from now on, it is assumed that there are obstacles such as garage walls around the vehicle.

In step S101, CPU 23 obtains the information about the rotational speed of the wheel from the vehicle speed sensor 30, and calculates the velocity _{V 0} which vehicle at this point.

In step S102, CPU 23 has the current speed _{V 0} which vehicle calculated in step S101 is equal to or higher than a predetermined speed (e.g., 1km / h or the like). If the vehicle speed V ₁ is not less than the predetermined speed, the flow proceeds to step S103, the process is repeated in step S102 if not.

In step S103, CPU 23, from the ultrasonic element 10 is transmitting ultrasonic waves and receiving reflected waves, to measure the time t ₁ required for transmission and reception at this point. The time from when an ultrasonic wave is transmitted until it is reflected by an obstacle and received is hereinafter referred to as a flight time. Flight time t ₁ measured at the step S103 corresponds to an example of the first time according to the present invention.

In step S104, CPU 23 obtains the information about the rotational speed of the wheel from the vehicle speed sensor 30 again, and calculates the velocity _{V 1} of the vehicle at this point. In FIG. 2, it is described that the process of step S104 is executed after step S103, but it is desirable that the process of step S103 and the process of step S104 are performed simultaneously.

In step S105, CPU 23 determines whether the processing of steps S103 and S104 has passed a predetermined time _{t 0} from the end. The predetermined time _{t 0} is, for example, 0.1 seconds. In the present invention, the predetermined time t ₀ is not limited to 0.1 seconds, but the humidity is calculated by the vehicle speed sensor 30 as will be described later based on the distance traveled by the vehicle during the predetermined time t _0. It is desirable that the length is as long as the distance can be accurately calculated and as short as possible. If it is determined that the predetermined time t ₀ has elapsed after the processing of steps S103 and S104 has been completed, the slow proceeds to step S106, and if not, the processing of step S105 is repeated.

In step S106, CPU 23, from the ultrasonic element 10 is transmitted ultrasonic waves, measures the time of flight _{t 2} at this point (second time point). Time of flight t ₂ measured at the step S106 corresponds to an example of the second time according to the present invention.

In step S107, CPU 23 obtains the information about the rotational speed of the wheel from the vehicle speed sensor 30 again, and calculates the velocity _{V 2} of the vehicle at this point. In FIG. 2, it is described that the process of step S107 is executed after step S106. However, it is desirable that the process of step S106 and the process of step S107 are performed simultaneously.

In step S108, CPU 23 has a velocity _{V 1} of the acquired vehicle in step S104, the speed _{V 2} obtained in step S107, on the basis, from the time of step S103 until the time of step S107, i.e. the predetermined time _{t 0} vehicle calculates the moving distance L ₁ is a distance traveled between. The moving distance L ₁ may be calculated by, for example, adding a predetermined time t ₀ to the average value of the speeds V ₁ and V ₂ .

  In step S <b> 109, the CPU 23 uses the outside air temperature sensor 50 to acquire information related to the temperature T of outside air around the vehicle.

In step S110, CPU 23 has flying time _t 1 obtained in step S103 and step S106, _{t 2,} and acquired in step S109, the temperature T of the outside air around the vehicle at the time of the flight time _{t 1} and _{t 2} was measured based on estimates the moving distance L _2.

Based on the temperature T of the outside air around the vehicle at the time of measuring the time of flight t ₁ and t _2, details of a method of estimating the moving distance L _2. If the sound velocity c in the outside air around the vehicle at the time of measuring the flight times t ₁ and t ₂ is known, the moving distance L ₂ can be calculated as shown in FIG. FIG. 3 is a diagram showing the relationship between the moving distance of the vehicle and the flight time. As shown in FIG. 3, when there is an obstacle such as a wall behind the vehicle, the time until the ultrasonic wave transmitted from the ultrasonic element 10 of the vehicle is reflected by the obstacle and received is the flight time. t ₁ or t ₂ .

・・・（１） The speed of sound c is influenced by the temperature and humidity of the medium, in this case outside air around the vehicle. Specifically, the sound speed c is approximated by the following equation (1).

... (1)

In equation (1), c ₀ is the sound speed at a specific temperature and humidity, and is a fixed value (for example, 331.4 m / s). T is temperature (° C.). a is a correction coefficient related to temperature, and is a fixed value. H is humidity (g / m ³ ). b is a correction coefficient relating to humidity, which is a fixed value. These correction coefficients a and b may be stored in advance in the memory 24 or the like. To be precise, since the correction coefficient b relating to humidity includes variables such as atmospheric pressure and saturated water vapor pressure, the correction coefficient b is not a fixed value, but in this embodiment, it is obtained empirically for simplicity. Approximation is performed using a correction coefficient b which is a fixed value. The humidity correction value bH based on the correction coefficient b and the humidity H corresponds to the humidity correction value of the present invention.

・・・（２） When the sound speed c at the temperature T and the humidity H is calculated in this way, the moving distance L ₂ of the vehicle at the sound speed c when the flight times are t ₁ and t ₂ is given by the following equation (2). It is done.

... (2)

Expression (2) is obtained by integrating the time difference between the flight times t ₁ and t ₂ and the sound speed. As shown in FIG. 3, the flight times t ₁ and t ₂ are reciprocal times from when the ultrasonic waves are transmitted to when they are reflected and received. Therefore, in equation (2), 1 / 2 is done.

・・・（３） Thus, the travel distance L ₂ calculated from the flight times t ₁ and t ₂ and the temperature T is the distance traveled by the vehicle at the vehicle speeds V ₁ and V ₂ during the predetermined time t ₀ , that is, the travel distance L _1. Is equal to Therefore, in step S 111, CPU 23 calculates the humidity H from the travel distance _{L 1} and _{L 2.} Specifically, if L ₁ is substituted into the left side of the equation (2), only the humidity H becomes an unknown, so the humidity H can be calculated as in the following equation (3).

... (3)

[Threshold setting processing]
The CPU 23 performs a threshold setting process in step S112 based on the humidity H calculated in the humidity calculation process from steps S100 to S111. In the threshold value setting process, as described above, a process for setting a threshold value for removing noise to some extent from the voltage signal acquired from the wave receiving unit 22 is performed.

  FIG. 4 is a diagram for explaining the threshold setting process. FIG. 4A is an example of a voltage signal acquired by the wave receiving unit 22. As shown in FIG. 4B, the CPU 23 extracts a voltage value corresponding to the envelope component of the voltage signal acquired by the wave receiving unit 22, and sets a threshold value Th that satisfies a desired wave receiving sensitivity.

  Specifically, the threshold value Th may be set as follows. For example, the reception sensitivity of the ultrasonic element 10 is measured in advance under various temperature and humidity conditions, and a threshold value at which a desired reception sensitivity can be obtained for each temperature and humidity is checked and stored in the memory 24. In the threshold value setting process in step S112, the CPU 23 sets a suitable threshold value with reference to the memory 24 based on the outside air temperature T acquired in step S109 and the humidity H calculated in step S111. .

  In general, when the outside air is at low temperature and low humidity, the attenuation of the ultrasonic wave is small, the intensity of the ultrasonic wave received by the ultrasonic element 10 becomes strong, and the limit distance in the range where the obstacle can be detected becomes long. Further, if the outside air is hot and humid, the attenuation is large, the intensity of the ultrasonic wave received by the ultrasonic element 10 is weak, and the limit distance in the range in which an obstacle can be detected becomes short. For this reason, when the outside air is low temperature and low humidity, the threshold value may be set higher than in the case of high temperature and high pressure. By suitably setting the threshold value, the wave receiving sensitivity of the wave receiving unit 22 and the obstacle detection limit distance can be kept constant regardless of the temperature and humidity of the outside air.

  Instead of setting the threshold value based on the temperature T and the humidity H itself, the threshold value may be set based on the humidity correction value bH described above. That is, the humidity correction value bH may be calculated in step S111 described above, and the threshold value may be set based on this. In this case, instead of storing the threshold value for each humidity in the memory 24 in advance, the reception sensitivity of the ultrasonic element 10 with respect to various humidity correction values bH can be measured to obtain a suitable reception sensitivity. The threshold value may be checked and stored in the memory 24.

  As described above, the obstacle detection apparatus 100 according to the present embodiment is effective regardless of the detection distance of the obstacle by the ultrasonic wave, but is particularly effective when detecting a long distance (for example, 3 meters or more). Therefore, in the threshold setting process, the threshold may be adjusted in advance so that the limit distance of the detection range is at least 3 meters even when the outside air is hot and humid. On the other hand, if the outside air is low temperature and low humidity, if the received wave sensitivity is too good, it will not be possible to distinguish between reflections due to obstacles at a long distance and noise such as road surface reflections. It is desirable to adjust the value in advance.

  In step S113, the CPU 23 applies the threshold value Th set in step S113, and thereafter performs obstacle detection processing on the received signal from the ultrasonic element 10 using the threshold value Th.

As described above, the obstacle detection apparatus 100 according to the present embodiment has the vehicle movement distance measured based on the output of the vehicle speed sensor 30 and the ultrasonic wave transmitted by the ultrasonic element 10 at the measurement start point of the movement distance. The first time (flight time t ₁ ) until the sound wave is reflected by the obstacle and received, and the ultrasonic wave transmitted by the ultrasonic element 10 at the movement distance measurement end point is reflected and received by the obstacle. The humidity of the outside air is calculated based on the second time (flight time t ₂ ) until and the temperature of the outside air around the vehicle detected by the outside air temperature sensor 50.

Further, the obstacle detecting device 100 of this embodiment, a moving distance of the vehicle, the difference between the flight time t ₁ and time of flight t _2, the speed of the ultrasonic wave is obtained based on outside air temperature and the outside air The humidity of the outside air is calculated as being equal to the speed of sound determined based on the humidity of the outside air.

  With such a configuration, the obstacle detection apparatus 100 detects the humidity of the ambient air around the vehicle, which could not be detected conventionally because there is no sensor, from the moving distance of the vehicle acquired by the vehicle speed sensor 30 and two different places. Calculation is based on the travel distance of the vehicle calculated from the flight time to the obstacle and the sound speed. Therefore, in the obstacle detection device 100, the temperature and the humidity can be obtained individually while suppressing an increase in size and cost of the device.

  Also, the obstacle detection apparatus 100 according to the present embodiment uses at least the calculated humidity to determine a threshold value of the amplitude of the ultrasonic wave that is determined as an obstacle when the ultrasonic element 10 receives the ultrasonic wave. To do.

  With such a configuration, the obstacle detection apparatus 100 sets a threshold value higher than that in the case of high temperature and high pressure when the outside air is at low temperature and low humidity, for example. The limit distance for detecting obstacles by ultrasonic waves transmitted from the acoustic wave element 10 can be kept constant regardless of the temperature and humidity of the outside air.

  In the obstacle detection apparatus 100 of the present embodiment, the distance at which an obstacle can be detected by the ultrasonic wave transmitted by the ultrasonic element 10 is a short distance (for example, about 1 to 2 m) that is generally used for obstacle detection. It may be a long distance (for example, approximately 4 to 6 m, approximately 3 m or more and at most less than 10 m). In addition, since the influence of ultrasonic attenuation due to environmental conditions such as humidity and temperature increases as the detectable distance increases, the obstacle detection apparatus 100 according to the present embodiment particularly increases the detectable distance. It is desirable to be used when

  The obstacle detection apparatus 100 of the present embodiment further includes a shift position sensor 40 that detects the position of the shift lever of the vehicle, and the shift position sensor 40 is at a specific position, for example, “R (reverse)”. On the condition that this is detected, the CPU 23 starts calculating the humidity.

  In the above-described embodiment, the CPU 23 starts the humidity detection process on the condition that the shift lever is in “R (reverse)” in step S100 shown in FIG. However, the present invention is not limited to this, and if it is assumed that there are obstacles fixed around the vehicle, the humidity detection process is started on the condition that the shift lever is in another position. May be. Also, instead of starting the humidity detection process according to the position of the shift lever, the humidity detection process is started when triggered by some operation that is assumed to be an obstacle fixed around the vehicle. Also good.

  Further, in the above-described embodiment, the obstacle detection apparatus 100 calculates the humidity H, and corrects the threshold value of the sound wave amplitude by the threshold setting process using the value of the humidity H. It is not always necessary to calculate the humidity H itself. Since it is only necessary to obtain the humidity correction value bH for correcting at least the humidity condition, the entire humidity correction value bH may be obtained as one value without calculating the humidity H itself. Other calculation formulas may be used. In the present application, calculation of humidity is a concept included as an example of calculation of a humidity correction value.

  With such a configuration, the obstacle detection apparatus 100 has two different vehicle travel distances obtained by the vehicle speed sensor 30 as the humidity correction value of the ambient air around the vehicle, which could not be detected conventionally because there is no sensor. It can be calculated based on the moving distance of the vehicle calculated from the flight time to the obstacle measured from the place and the sound speed. Therefore, the obstacle detection apparatus 100 can individually perform correction based on the temperature condition and correction based on the humidity condition while suppressing an increase in the size and cost of the apparatus.

  The present invention is suitable for an obstacle detection device that detects an obstacle with ultrasonic waves, particularly an obstacle detection device having a long detection distance (for example, 3 meters or more).

DESCRIPTION OF SYMBOLS 100 Obstacle detection apparatus 10 Ultrasonic element 20 Control part 21 Transmission part 22 Wave reception part 23 CPU
24 memory 25 communication unit 30 vehicle speed sensor 40 shift position sensor 50 outside temperature sensor

Claims (7)

An ultrasonic sensor that is provided in the vehicle and detects an obstacle around the vehicle by transmitting and receiving ultrasonic waves;
A vehicle speed sensor for detecting the speed of the vehicle;
An outside temperature sensor for detecting the temperature of outside air around the vehicle;
The moving time of the vehicle measured based on the output of the vehicle speed sensor and the first time until the ultrasonic wave transmitted by the ultrasonic sensor at the measurement start point of the moving distance is reflected by an obstacle and received. A second time until the ultrasonic wave transmitted by the ultrasonic sensor is reflected and received by the obstacle at the measurement end point of the moving distance, and the outside air around the vehicle detected by the outside air temperature sensor. A control unit that calculates a humidity correction value of the outside air based on the temperature;
Obstacle detection device having The control unit is configured to measure a moving distance of the vehicle measured based on an output of the vehicle speed sensor and an ultrasonic wave transmitted from the ultrasonic sensor at a measurement start point of the moving distance until it is reflected by an obstacle and received. A first time, a second time until the ultrasonic wave transmitted by the ultrasonic sensor at the end of measurement of the moving distance is reflected and received by the obstacle, and the vehicle detected by the outside air temperature sensor Calculating the humidity of the outside air based on the temperature of the surrounding outside air,
The obstacle detection apparatus according to claim 1. The controller is
The velocity of the ultrasonic wave obtained based on the moving distance and the difference between the first time and the second time is determined based on the temperature of the outside air and the humidity of the outside air. The humidity correction value of the outside air is calculated as
The obstacle detection apparatus according to claim 1. The control unit determines a threshold value of the amplitude of the ultrasonic wave, which is determined as an obstacle when the ultrasonic sensor receives the ultrasonic wave, using at least the calculated humidity correction value.
The obstacle detection apparatus according to claim 1. A shift position sensor for detecting the positions of the two shift levers;
On the condition that the shift position sensor is detected at a specific position, the control unit starts calculating the humidity correction value.
The obstacle detection apparatus according to claim 1. A travel distance measuring step for measuring a travel distance of the vehicle based on an output of a vehicle speed sensor provided on the vehicle and detecting a speed of the vehicle;
At the measurement start point of the movement distance, the first time until the ultrasonic wave transmitted by the ultrasonic sensor provided on the vehicle is reflected by the obstacle and received, and at the measurement end point of the movement distance. Based on the second time until the ultrasonic wave transmitted by the ultrasonic sensor is reflected and received by the obstacle and the temperature of the outside air detected by the outside temperature sensor provided outside the vehicle. A humidity correction value calculating step of calculating a humidity correction value of the outside air;
A humidity correction value calculation method. A travel distance measuring step for measuring a travel distance of the vehicle based on an output of a vehicle speed sensor provided on the vehicle and detecting a speed of the vehicle;
At the measurement start point of the movement distance, the first time until the ultrasonic wave transmitted by the ultrasonic sensor provided on the vehicle is reflected by the obstacle and received, and at the measurement end point of the movement distance. Based on the second time until the ultrasonic wave transmitted by the ultrasonic sensor is reflected and received by the obstacle and the temperature of the outside air detected by the outside temperature sensor provided outside the vehicle. A humidity correction value calculating step of calculating a humidity correction value of the outside air;
A threshold value determining step for determining a threshold value of the amplitude of the ultrasonic wave, which is determined as an obstacle when the ultrasonic sensor receives the ultrasonic wave, using at least the calculated humidity correction value;
An ultrasonic wave reception threshold value determining method.

Images