Object detection device

Abstract

Object detection device that detects an object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) using a distance measuring sensor (10) arranged at a predetermined height, wherein the object detection device emits a test wave towards an environment and receives a reflected wave of the test wave as detection information of the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b), wherein the object detection device comprises: a waveform acquisition section that acquires a reception time and a wave height value (Hp) of a wave reflected by the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b), wherein the wave height value (Hp) is defined as a value of a case in which a height (H) of the wave reflected by the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) reaches a maximum; a reference value calculation section that calculates a wave height value (Hp) of a wave reflected by a reference obstacle (41, 41a, 41b, 41c, 41d) as a reference value using the wave height value (Hp) obtained by the waveform acquisition section, wherein the reference obstacle is present at least at the predetermined height; a detection value calculation section that calculates a wave height value (Hp) of a wave reflected by a detection object (42, 42a, 42b) as a detection value using the wave height value (Hp) obtained by the waveform acquisition section, wherein the detection object (42, 42a, 42b) is a detection target; a reference distance calculation section which calculates a distance between the reference obstacle and the distance measuring sensor (10) as a reference distance using a reception time of the wave reflected by the reference obstacle, wherein the reception time of the wave reflected by the reference obstacle is obtained by the waveform acquisition section; a detection distance calculation section which calculates a distance between the detection object (42, 42a, 42b) and the distance measuring sensor (10) as a detection distance using a reception time of the wave reflected by the detection object (42, 42a, 42b), wherein the reception time of the wave reflected by the detection object (42, 42a, 42b) is obtained by the waveform acquisition section; a correction section that corrects the reference value and the detection value according to an attenuation factor that varies in response to a distance ratio of the reference distance to the detection distance; and a height calculation section that calculates a height of the detection object (42, 42a, 42b) in relation to the predetermined height according to the result of a comparison of the reference value corrected by the correction section with the detection value corrected by the correction section.

Description

TECHNICAL AREA

[0001] The present invention relates to an object detection device that detects a nearby object by emitting a test wave and receiving a wave reflected by the object. STATE OF THE ART

[0002] Proposals were made to equip a vehicle with a distance measuring sensor, such as an ultrasonic sensor, and to detect an object located near the vehicle, such as a vehicle ahead, a pedestrian, or an obstacle. It was also proposed to implement various control measures to improve vehicle safety, such as activating a braking device and issuing a warning to the driver, using the object detection results.

[0003] When a control measure is implemented to improve vehicle safety, a threshold value for the distance to an object near the vehicle must be adjusted according to the object's height before the control measure is executed. For example, comparing a case where a vehicle is parked along a wall with a case where the vehicle is parked along a curb, the vehicle can be parked closer to the curb than to the wall.

[0004] An object detection device of the type described above is described in JP 2002-350 540 A. If an object is present on one side of a road in relation to a curb, the object detection device described in JP 2002-350 540 A detects the presence of a low object, such as the curb, based on a reception time difference between reflected waves, respectively, reflected by the curb and the object.

[0005] DE 101 51 965 A1 discloses a method for operating a short-range detection system of a vehicle using an ultrasonic sensor that emits a test wave towards the environment and receives a reflected wave of the test wave as detection information of an object. An object height relative to the sensor height is determined, and this object height is determined based on the distance to a first object and a second object. SUMMARY OF THE INVENTION

[0006] If no object taller than a relatively low object, such as a curbstone, is present at a greater distance than the low object, then when the object detection device described in JP 2002-350 540 A detects the curbstone, it is unable to determine whether the detected object is a curbstone or a wall. Thus, according to the disclosure in JP 2002-350 540 A, a low object such as a curbstone can only be detected to a limited extent.

[0007] In light of the difficulties mentioned above, it is an object of the present invention to provide an object detection device capable of suitably calculating the height of a detection object located near a mobile object. This object is achieved by an object detection device having the features of claim 1. The dependent claims are directed to advantageous embodiments of the invention.

[0008] According to a first aspect of the present invention, an object detection device detects an object using a distance measuring sensor mounted at a predetermined height. The object detection device emits a test wave toward its surroundings and receives a reflected wave of the test wave as detection information about the object. The object detection device includes a waveform acquisition section, a reference value calculation section, a detection value calculation section, a reference distance calculation section, a detection distance calculation section, a correction section, and a height calculation section. The waveform acquisition section obtains a reception time and a wave height value of a wave reflected from the object. The wave height value is defined as the value of a case in which the height of the wave reflected from the object reaches a maximum.The reference value calculation section calculates a wave height value of a wave reflected from a reference obstacle as a reference value, using a wave height value obtained by the waveform acquisition section. The reference obstacle is present at least at the predetermined height. The detection value calculation section calculates a wave height value of a wave reflected from a detection object as a detection value, using a wave height value obtained by the waveform acquisition section. Here, the detection object is a detection target. The reference distance calculation section calculates a distance between the reference obstacle and the distance measuring sensor as a reference distance, using a reception time of the wave reflected from the reference obstacle. The reception time of the wave reflected from the reference obstacle is obtained by the waveform acquisition section.The detection distance calculation section calculates the distance between the detection object and the distance sensor as a detection distance using the reception time of the wave reflected from the detection object. The reception time of the wave reflected from the detection object is obtained by the waveform acquisition section. The correction section corrects the reference value and the detection value according to an attenuation value that varies in response to a distance ratio of the reference distance to the detection distance. The height calculation section calculates the height of the detection object relative to the predetermined height based on a comparison of the reference value, corrected by the correction section, with the detection value, also corrected by the correction section.

[0009] A wave reflected from an object located at the mounting height of the distance sensor returns directly to the distance sensor without being reflected off the ground or similar surfaces. In contrast, a wave reflected from an object located lower than the mounting height of the distance sensor will also be reflected off the ground either before or after reflection from the object, and the wave height value may be reduced due to this ground reflection. The configuration above accounts for this reduction in wave height. That is, according to the configuration above, an object located at the mounting height of the distance sensor is used as the reference obstacle, and the wave height value of a wave reflected from the reference obstacle is used as the reference value.The measured value, which is a wave height value of a detection target, is then compared to the reference value. Specifically, both the reference value and the measured value are corrected according to a change in the magnitude of an attenuation, which depends on the ratio between the reference distance and the measured distance. The height of the detected object relative to a predetermined height is calculated based on the result of comparing the corrected reference value with the corrected measured value.

[0010] Since the height of the detection target relative to the reference obstacle is calculated taking into account an attenuation level difference caused by a change in the position of the detection target relative to the distance measuring sensor, the height of the detection target can be determined with high accuracy.

[0011] Generally, the wave height of a reflected wave varies depending on changes in temperature or humidity. According to the configuration described above, the height of the detected object is calculated by comparing a measured value corresponding to the target with a reference value that is newly obtained with each measurement of the target. Thus, changes in temperature or humidity do not affect the measurement, and the height of the detected object can be calculated even more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and further problems, features and advantages of the present invention will become clear with reference to the following detailed description and the accompanying drawings. These show: Fig. 1 a view schematically showing an object detection device according to a first embodiment of the present invention; Fig. 2 a top view of a vehicle equipped with the object detection device; Fig. 3A a view showing a waveform of a test wave; Fig. 3B a view showing a waveform of a reflected wave; Fig. 4 a view showing a detailed waveform of a reflected wave; Fig. 5A a path of a wave reflected by an object that is higher than an installation position of a distance measuring sensor; Fig. 5B a path of a wave reflected by an object that is lower than the mounting position of the distance sensor; Fig. 6 a flowchart showing a process according to the first embodiment; Fig. 7 a subroutine demonstrating a reference obstacle extraction process according to the first embodiment; Fig. 8A a view showing a positional relationship between a vehicle, a front vehicle and a rear vehicle during a starting stage of parallel parking according to a second embodiment of the present invention; Fig. 8B a view showing a positional relationship between the vehicle, the front vehicle and the rear vehicle during parallel parking according to the second embodiment; Fig. 9 a flowchart showing a process according to the second embodiment; Fig. 10 a view showing vertical parking according to a third embodiment of the present invention; Fig. 11 a flowchart showing a process according to the third embodiment; and Fig. 12 a view showing a calculation method of a wave height value according to a fourth embodiment of the present invention. EXECUTIONAL FORMS FOR IMPLEMENTING THE INVENTION

[0013] The following describes various embodiments with reference to the drawings. The same or equivalent sections are designated with the same reference numerals in the drawings, and their descriptions are not repeated. (First embodiment)

[0014] Fig. Figure 1 shows a configuration of an object detection device according to the present embodiment. The object detection device is mounted on a vehicle and calculates the distance from the vehicle to an object located near the vehicle, for example, another vehicle or a road structure. The object detection device includes a distance measuring sensor 10 and an ECU 20 that controls the distance measuring sensor 10.

[0015] The distance measuring sensor 10 is provided, for example, by an ultrasonic sensor. The distance measuring sensor emits an ultrasonic wave with a frequency of 20 to 100 kHz as a test wave and receives a test wave that has reached an object and been reflected by the object as a reflected wave. The ECU 20 contains a microcomputer that includes a CPU, various memory components, an analog-to-digital converter, and so on. The CPU contained in the ECU 20 serves as a sensor control section 21, a distance calculation section 22, and a vehicle control section 23 by executing programs that have been pre-stored in the memory.

[0016] The sensor control section 21 transmits a control signal to the distance sensor 10 and obtains a wave height value of a reflected wave received by the distance sensor 10. The distance sensor 10 repeatedly emits a test wave at predetermined intervals (e.g., several milliseconds) for a predetermined duration as a single transmission in response to an instruction from the ECU 20. The distance calculation section 22 calculates a distance between the vehicle and the object from which a reflected wave is received by the distance sensor 10.The vehicle control section 23, based on a distance to the object near the vehicle calculated by the distance measuring sensor 10, performs controls on the vehicle's behavior, such as steering angle control or acceleration and deceleration control, and notifies the driver of the object's approach by activating or issuing an alarm.

[0017] Fig. Figure 2 is a top view of a vehicle 30 that has the object detection device. In the example of the Fig. 2. Four distance sensors 10 are mounted at predetermined distances from each other at both front and both rear ends of the vehicle 30, and two distance sensors 10 are mounted at predetermined distances from each other on the right and left side faces of the vehicle 30. Each of the distance sensors 10 is mounted at a predetermined height (approximately 45 to 60 cm from the ground). This height of 45 to 60 cm from the ground is similar to the height of a respective bumper mounted at the front and rear ends of the vehicle 30. Test waves are emitted radially from each distance sensor 10 into the vicinity of the vehicle 30, and some of the test waves reach a nearby object 40. A test wave that reaches the object 40 is reflected back to the distance sensor 10. The mounting positions of the distance sensors 10 on the vehicle 30, which are shown in Fig. The two shown are only examples, and the mounting positions can be changed in various ways.

[0018] Fig. 3A shows a waveform of a test wave, and Fig. Figure 3B shows a waveform of a reflected wave. Here, a waveform is defined as a shape formed by connecting each peak of a wave oscillating within a frequency range of 20 to 100 kHz. A test wave transmission starts at a transmission start time Ts and continues for a specified transmission duration Tb. The wave height H of a test wave increases from the transmission start time Ts. After the wave height reaches a maximum value, it is held at that maximum value for a predetermined time. When a predetermined time has elapsed since the wave height reached its maximum value, the wave height decreases, and the wave height becomes zero when the transmission duration Tb has elapsed since the transmission start time Ts.

[0019] A test wave reaches object 40 after a time interval corresponding to the distance between the distance sensor 10 and object 40. The test wave, having reached object 40, is reflected by object 40. The reflected wave reaches the distance sensor 10 after a time interval corresponding to the distance between the distance sensor 10 and object 40. The reflected wave reaches a peak value after a time interval equal to the transmission time Tb of the test wave since the reception start time Tx of the reflected wave. The distance between the distance sensor 10 and object 40 is determined by converting the difference between the transmission start time Ts of the test wave and the reception start time Tx of the reflected wave into a distance.The distance between the distance measuring sensor 10 and the object 40 can be calculated by subtracting the transmission start time Ts of the test wave from the reception start time Tx of the reflected wave, dividing the difference by two and multiplying half of the difference by a speed of sound.

[0020] A method for obtaining parameters of a reflected wave will be described in more detail below with reference to Fig. As described in section 4, it is generally difficult to determine the reception start time Tx of a reflected wave by identifying the point in time at which the wave height begins to increase from zero. Therefore, the reception start time Tx of the reflected wave is determined when the wave height exceeds a threshold value Hth (reception time T1). A maximum wave height is obtained after reception time T1. The above process can be carried out using a peak-holding process or similar method. The maximum value obtained in the manner described above is used as a wave height value Hp in the process of the present embodiment.

[0021] The wave height Hp of a reflected wave weakens with increasing propagation distance between the test wave and the reflected wave. Furthermore, the wave height Hp weakens due to reflection from nearby objects. Fig. Figure 5A shows a case in which a test wave is reflected by an object 41, for example a wall or another vehicle, which is higher than the mounting position of the distance measuring sensor 10. In contrast, Figure 5A shows... Fig. 5B a case in which a test wave is reflected by an object 42 that is lower than the mounting position of the distance measuring sensor 10. In Fig. 5A and Fig. 5B the distance measuring sensor 10 is able to obtain a reflected wave that reaches a receiving area 10a, which is highlighted and indicated by a dashed line in the respective figures.

[0022] As it is in Fig. As shown in Figure 5A, a test wave strikes object 41, which is higher than the mounting position of the distance measuring sensor 10, at essentially a right angle. In contrast, as shown in Figure 5A, the test wave strikes object 41 at a right angle. Fig. As shown in Figure 5B, a test wave does not strike object 42 at a right angle, as it is lower than the mounting position of the distance sensor 10. Thus, some of the test waves emitted by the distance sensor 10 reach object 42 after being reflected off the ground. The test waves are then reflected off object 42 and reach the distance sensor 10. Some of the test waves emitted by the distance sensor 10 reach object 42 directly. The test waves are also reflected off the ground after being reflected off object 42 and then reach the distance sensor 10.

[0023] Thus, a test wave reflected by object 42, which is lower than a wall, another vehicle, or similar object, is reflected more than once. The wave height value Hp is therefore small compared to a wave reflected only once by a wall, another vehicle, or similar object. Therefore, a wall, another vehicle, or similar object is defined as a reference obstacle. The object's height is then determined by comparing the wave height value Hp of the reference obstacle with the wave height value Hp of the detected object 42 (detection object) and determining the object's height relative to the reference obstacle.

[0024] Fig. Figure 6 shows a flowchart illustrating a sequence of processing procedures performed by the ECU 20 according to the present embodiment. The process in Fig. 6 is performed at a predetermined interval.

[0025] First, an instruction to transmit test waves and receive reflected waves is sent to the distance sensor 10 (S101). When the process in S101 ends, a test wave is transmitted by the distance sensor 10, and it is determined whether the wave height of a reflected wave exceeds the threshold value Hth (S102). The process in S102 is repeated in predetermined control cycles until the wave height exceeds the threshold value Hth (S102: Yes) or a predetermined time has elapsed (S102: No).

[0026] When the wave height exceeds the threshold value Hth (S102: Yes), a reception time T1 is obtained, and a distance from the distance measuring sensor 10 to an object is calculated (S103). Additionally, a wave height value Hp is obtained, which is a value in the case where the wave height reaches a maximum. During the above process, the ECU 20 serves as a waveform acquisition section. The calculated distance is referred to as a reference distance in a case where the object is used as a reference obstacle, and the ECU 20 serves as a reference distance calculation section. In a case where the object is an object (detection object) to be compared with the reference obstacle, the calculated distance is referred to as a detection distance, and the ECU 20 also serves as a detection distance calculation section.

[0027] The ECU 20 then serves as a correction section. The ECU 20 corrects the wave height value Hp by multiplying the wave height value Hp by a coefficient corresponding to the calculated distance (the reference distance or the detection distance) (S104). The coefficient used here is a value for correcting an attenuated component of the wave height value Hp. Here, the attenuation is caused by the distance to the object. The wave height value Hp is corrected to satisfy the assumption that the object is present at a certain distance. That is, the reference value and the detection value are corrected according to a change in the magnitude of an attenuation that depends on a ratio of the reference distance to the detection distance. The distance can be corrected in a case where the object is likely to be one that has reflected the wave that was previously received.The corrected distance and the corrected wave height value Hp are stored in a history memory section located in a memory of the ECU 20 (S105).

[0028] If, on the other hand, the wave height of the reflected wave does not exceed the threshold value Hth within a predetermined time period (S102: No), it can be determined that no object from which the test wave is reflected is being detected. Thus, non-detection information is stored in the history memory section. Even if the wave height of the reflected wave does not exceed the threshold value Hth, there is generally a wave reflected from another object of the same type. Therefore, the threshold value Hth, or the threshold value Hth corrected by a predetermined correction coefficient, can be used as an initial value or default value, and the initial value can be stored in the history memory section as the wave height value Hp.

[0029] The ECU 20 then serves as a grouping section. This means that a history is grouped according to a distance stored in the history memory section (S107). Reflected waves with calculated distances and detected azimuths that are close to each other are grouped as a set. That is, reflected waves that were likely reflected by the same object are grouped as a set. The azimuth of a reflected wave can be identified by determining which distance sensor 10 detected the reflected wave.

[0030] After grouping, a representative value of the wave height values ​​Hp is calculated for the grouped history (S108). To calculate the representative value, a mean of the wave height values ​​Hp in the same group stored in the history memory section is calculated, and the calculated mean is used as the representative value. The representative value may include a maximum and a minimum value in the group in addition to the mean. In cases where the maximum and minimum values ​​are used, they can be obtained after removing values ​​that deviate significantly from the mean using a mean filter or a Gaussian filter.

[0031] After calculating the representative value, a process is performed to extract a reference obstacle (S109). The reference obstacle is then compared to the representative value as the reference. ECU 20 serves as a data acquisition value calculation section by executing S108 and as a reference value calculation section by executing S109.

[0032] If the reference obstacle has been extracted (S110: Yes), the ECU 20 acts as a height calculation section. That is, it calculates a ratio or difference between the representative value and a reference value corresponding to the extracted reference obstacle. Then, for the object whose representative value was calculated, a height relative to the reference value is calculated based on the calculated ratio or difference between the representative value and the reference value, and the reference value specified as the height of the reference obstacle (S111). Subsequently, the sequence of processing procedures is terminated, and the ECU 20 waits until the next test wave transmission begins. If no reference obstacle is extracted (S110: No), the sequence of processing procedures is terminated, and the ECU 20 waits until the next test wave transmission begins.

[0033] The reference obstruction extraction process in S109 in the flowchart of the Fig. 6 is described in more detail below. The process shown in the flowchart of the Fig. Figure 7 shows a subroutine located in S109 of the Fig. 6 is executed.

[0034] First, using the grouped history, it is determined whether the object being detected contains a linear segment extending in a horizontal direction (S201). The process in S201 is carried out by determining whether a change in distance within a given group lies within a predetermined range. The reflection direction of a wave reflected from an object without a linear segment—that is, the reflection direction of a wave reflected from an object with an irregular or curved shape—varies, and the wave height value Hp decreases. As described above, the height of a detection target is calculated by comparing the wave height value Hp of a wave reflected from the reference obstacle with the wave height value Hp of a wave reflected from the detection target.Therefore, in a case where an object without a linear section in a horizontal direction is used as a reference obstacle, the calculated height of a comparison object relative to the reference obstacle may be higher than its actual height. Thus, an object with a linear section is used as the reference obstacle.

[0035] If it is determined that the object has a linear section, it is determined whether a wave height value Hp of the linear section is equal to or greater than a threshold value (S202). The threshold value is a preset value and is stored in a memory of ECU 20. If the wave height value Hp is less than the threshold value, the object has a linear section but may be an object that absorbs or scatters a test wave. If the object is used as a reference obstacle with such a probability, a calculated height of a comparison object relative to the reference obstacle may be higher than its actual height. If the wave height value Hp is less than the threshold value Hth, the object has a linear section but may be an object represented by a curb or vehicle stopper.If the object is a curb or a vehicle stopper, a reflected wave reaches the distance measuring sensor 10 after being reflected by the ground and the object. Accordingly, if the wave height value Hp of the linear section is less than the threshold value, the object is determined to be unsuitable as a reference obstacle.

[0036] If a wave height value Hp of the linear section is greater than the threshold (S202: Yes), it is determined whether the reference obstacle is registered in a list (S203). The list is used to temporarily store a history of reference obstacles extracted. The list is stored in memory on ECU 20. If it is determined that the reference obstacle is registered in the list (S203: Yes), the wave height value Hp is updated (S204). If it is determined that the reference obstacle is not registered in the list (S203: No), the reference obstacle is added to the list as a new entry (S205).

[0037] If the wave height value Hp of the linear section is less than the threshold (S202: No), in a case where a reference obstacle has already been registered in the list (S206), the reference obstacle is deleted from the list (S207) because the reference obstacle is unsuitable as a reference obstacle.

[0038] If the process ends in S204, S205 or S207, or if the result of the determination in S206 is negative, it is determined whether the reference obstacle is registered in the list (S208).

[0039] If it is determined that the reference obstacle is registered in the list (S208: Yes), a determination result is performed that provides information regarding the presence of the reference obstacle (S209). An average value of the reference obstacle registered in the list is calculated as the reference value (S210). The sequence of processing procedures then ends. If it is determined that no reference obstacle is registered in the list (S208: No), a determination result is performed that provides information regarding the absence of the reference obstacle (S211). The sequence of processing procedures then ends.

[0040] Due to the above configuration, the object detection device of the present embodiment achieves the following effects.

[0041] A wave reflected from an object located at the mounting height of the distance sensor 10 reaches the distance sensor 10 directly without being reflected by the ground or similar objects. In contrast, a wave reflected from an object located lower than the mounting height of the distance sensor 10 is also reflected by the ground either before or after reflection from the object, and the wave height value Hp may be reduced due to this reflection from the ground. The present embodiment takes such a reduction in the wave height value into account. That is, an object located at the mounting height of the distance sensor 10 is used as the reference obstacle, and the wave height value Hp of a reflected wave from the reference obstacle is used as the reference wave height value.By comparing a wave height value Hp of a detection target with the reference wave height value, the height of the detection target relative to the reference obstacle can be calculated with high accuracy.

[0042] The wave height value Hp is corrected by multiplying it by a value corresponding to the calculated distance, so that the distance to the reference obstacle is equal to the distance to the detection object. Even if the distance between the distance sensor 10 and the reference obstacle differs from the distance between the distance sensor 10 and the object 42 (the detection target), the height of the detection target 42 relative to the reference obstacle can be calculated. Here, the distance between the distance sensor 10 and the reference obstacle is determined upon detection of the reference obstacle, and the distance between the distance sensor 10 and the detection target 42 is determined upon detection of the object 42.

[0043] Generally, the wave height value Hp of a reflected wave varies under the influence of temperature and humidity. In the present embodiment, since the height of a detection object is calculated by comparing the reference value with the detection value obtained in response to each detection of the object, the height of the detection object can be calculated without being influenced by temperature and humidity.

[0044] In a case where an object extracted as the reference obstacle has an irregular or curved shape, the reflection direction varies, and the wave height value decreases. Therefore, if an object lacking a linear section is used as the reference obstacle, the calculated height of a comparison object relative to the reference obstacle will be greater than its actual height. In the present embodiment, when the reference obstacle is extracted, it is restricted to an object located at a distance within a predetermined range of variation. This avoids a situation where the calculated height of a comparison object relative to the reference obstacle is greater than its actual height. Consequently, the accuracy of object height detection can be improved. (Second embodiment)

[0045] An object detection device of the present embodiment has a similar overall configuration to the object detection device of the first embodiment. Here, the process of the first embodiment is used for parallel parking of a vehicle 30.

[0046] Fig. 8A and Fig. Figure 8B shows a case in which a process of the present embodiment is used, that is, a case in which the vehicle 30 is parked along a curb 42a in a space between a front vehicle 41a and a rear vehicle 41b. Fig. Figure 8A shows a positional relationship between vehicle 30, the front vehicle 41a and the rear vehicle 41b during a starting stage of parallel parking. Fig. Figure 8B shows a positional relationship between vehicle 30, the front vehicle 41a and the rear vehicle 41b during the execution of parallel parking.

[0047] When parallel parking is initiated, vehicle 30 passes a transverse position of the rear vehicle 41b and also a transverse position of a space between the front vehicle 41a and the rear vehicle 41b, reaching a transverse position of the front vehicle 41a and beginning its reverse movement. A distance sensor 10 determines the distance between vehicle 30 and a side surface of the front vehicle 41a and the distance between vehicle 30 and a side surface of the rear vehicle 41b. The side surfaces of the front vehicle 41a and the rear vehicle 41b are essentially flat and have linear shapes extending in a horizontal direction. Thus, both side surfaces can be suitable as reference obstacles.

[0048] When the vehicle 30 reverses, the distance between a rear end of the vehicle 30 and the curb 42a is detected by the distance measuring sensor 10. The height of the curb 42a can be estimated using the side surface of the front vehicle 41a and the side surface of the rear vehicle 41b, which were previously obtained as the reference obstacles, and also using a wave height value Hp of a wave reflected from the curb 42a.

[0049] Fig. Figure 9 shows a flowchart illustrating a sequence of processing procedures performed by the object detection device of the present embodiment. The process of the present embodiment is partially similar to the process of the first embodiment. Furthermore, in the present embodiment, the process of the first embodiment is repeated until parallel parking is initiated, and the process switches to the parallel parking process when parallel parking is initiated.

[0050] First, it is determined whether parallel parking is initiated (S301). Specifically, it is determined whether the front vehicle 41a and the rear vehicle 41b, which are parked at a predetermined distance or more from each other, are detected at transverse positions of the vehicle 30, and whether the direction of movement of the vehicle 30 changes from forward to reverse at a transverse position of the front vehicle 41a. If it is determined that parallel parking has not yet been initiated (S301: No), the process switches to the normal process (S302) performed in the first embodiment above, and then the process terminates.

[0051] If it is determined that parallel parking is or has been started (S301: Yes), the same processes as the processes in S101 to S108 of the first embodiment are repeated in S303 to S310. A wave height value Hp of a reflected wave from the curb 42a or similar, which is located within a space between the front vehicle 41a and the rear vehicle 41b, is obtained.

[0052] Subsequently, a reference obstacle extraction process is performed (S311). The process in S311 is carried out by executing a subroutine corresponding to S201 to S210 of the first embodiment. In this case, the front vehicle 41a and the rear vehicle 41b are selected as reference obstacles. That is, the presence of the front vehicle 41a and the rear vehicle 41b is detected in a determination in S301 of whether parallel parking is initiated. Since the front vehicle 41a and the rear vehicle 41b each have a side surface that is substantially linear, both the front vehicle 41a and the rear vehicle 41b are identified as suitable objects for reference obstacles. Then, the height of the curb 42a is calculated using the front vehicle 41a and the rear vehicle 41b as reference obstacles, and the sequence of processing procedures is terminated.

[0053] The above described a case in which the curb 42a is located within a space between the front vehicle 41a and the rear vehicle 41b. Note that the process of the present embodiment can also be carried out in a case in which a road structure other than the curb 42a, a wall, or the like is located within the space.

[0054] In the process described above, the height of the curb 42a is calculated after parallel parking has begun. Alternatively, the height of the curb 42a can be calculated before parallel parking begins. Specifically, reflected waves are obtained in the following order: waves reflected from the rear vehicle 41b, waves reflected from the curb 42a, and waves reflected from the front vehicle 41a as the vehicle 30 moves forward. Then, the height of the curb 42a is calculated using the front vehicle 41a and the rear vehicle 41b as reference obstacles. The front vehicle 41a, the rear vehicle 41b, and the height of the curb 42a are obtained in the manner described above and temporarily stored in a memory location of the ECU 20.When the direction of movement of the vehicle 30 changes from the forward direction to the reverse direction, the front vehicle 41a, the rear vehicle 41b and the height of the curb 42a, which are stored in the memory, are read out in order to carry out control based on the height and location of the curb 42a.

[0055] With the above configuration, the object detection device of the present embodiment achieves the following effects in addition to the effects achieved by the object detection device of the first embodiment.

[0056] When the vehicle 30 performs parallel parking, its approach distance changes depending on whether it is a curb 42a or a wall located on an inner section of the parking space. Thus, by using the process of the first embodiment to detect the height of an object located within the parking space, an approach distance to the object located within the parking space can be appropriately set for parallel parking. Furthermore, a wave reflected from the side surface of the front vehicle 41a and a wave reflected from the side surface of the rear vehicle 41b can be obtained in the case of parallel parking.Since the side surface of the front vehicle 41a and the side surface of the rear vehicle 41b have linear shapes, waves reflected from the side surfaces have suitable values ​​for calculating a reference value. Therefore, the height of the curb 42a or similar can be determined even more precisely. (Third embodiment)

[0057] An object detection device of the present embodiment has a similar overall configuration to the object detection device of the first embodiment. The process of the first embodiment is applied below for the vertical parking of a vehicle 30.

[0058] Fig. Figure 10 shows a case in which a process of the present embodiment is used, that is, a case in which the vehicle 30 performs perpendicular parking by reversing the vehicle 30 into a space between a left-hand vehicle 41c and a right-hand vehicle 41d until the vehicle 30 contacts a vehicle stopper 42b. Instead of the vehicle stopper 42b, a wall or similar may be arranged at an inner end of the parking space, and the vehicle 30 can reverse and be parked perpendicular to the wall.

[0059] When perpendicular parking is initiated, a side surface of the left vehicle 41c and a side surface of the right vehicle 41d are detected by a distance measuring sensor 10, which is attached to a side section of the vehicle 30. The height of the vehicle stopper 42b can be estimated using the side surfaces of the left vehicle 41c and the right vehicle 41d, obtained as described above, as reference obstacles and using a wave height value Hp of a wave reflected from a curb 42a.

[0060] Fig. Figure 11 shows a flowchart illustrating a sequence of processing procedures performed by the object detection device of the present embodiment. The process of the present embodiment is partially similar to the process of the first embodiment described above. Furthermore, in the present embodiment, the process of the first embodiment is repeated until perpendicular parking is initiated, and the process then switches to a perpendicular parking process when perpendicular parking is initiated.

[0061] First, it is determined whether perpendicular parking is or has been initiated (S401). It is determined that perpendicular parking is or has been initiated if a control condition of vehicle 30 is switched to reverse control and at least one of the left vehicle 41c and the right vehicle 41d is detected. If it is determined that perpendicular parking has not been initiated (S401: No), the process switches to a normal process (S402), which is the process executed in the first embodiment above, and the sequence of processing procedures is terminated.

[0062] If it is determined that vertical parking is initiated or has been initiated (S401: Yes), the same processes as those in S101 to S108 of the first embodiment in S403 to S410 are carried out. A wave height value Hp of a reflected wave from the vehicle stopper 42b or similar device is thus obtained.

[0063] Subsequently, a reference obstacle extraction process is performed (S411). The process in S411 is carried out by executing a subroutine corresponding to S201 to S210 of the first embodiment. Since the presence of the left vehicle 41c and the right vehicle 41d was already detected when a determination that perpendicular parking had started was performed in S401, and since the left vehicle 41c and the right vehicle 41d have side surfaces with essentially linear shapes suitable for reference obstacles, the left vehicle 41c and the right vehicle 41d are selected as reference obstacles. The same process can even be performed if only the left vehicle 41c or only the right vehicle 41d is detected.A height of the vehicle stopper 42b, which is found using the left vehicle 41c and the right vehicle 41d as reference obstacles, is calculated, and the sequence of processing procedures is terminated.

[0064] With the above configuration, the object detection device of the present embodiment achieves the following effects in addition to the effects achieved by the object detection device of the above first embodiment.

[0065] When vehicle 30 performs perpendicular parking, its approach distance is modified depending on whether the object within the parking space is the vehicle stop 42b or a wall. Thus, by applying the process of the first embodiment to enable the detection of the height of an object located within the parking space, an approach distance to an object in the inner section of the parking space can be appropriately adjusted during perpendicular parking. Furthermore, a wave reflected from the side surface of the left vehicle 41c and a wave reflected from the side surface of the right vehicle 41d can be obtained in the case of perpendicular parking. Since the side surfaces of the left vehicle 41c and the right vehicle 41d have linear shapes, the reflected waves from the side surfaces have values ​​suitable for calculating the reference values.Therefore, the height of the vehicle stopper 42b or similar can be determined even more precisely. (Fourth embodiment)

[0066] Each of the object detection devices of the first to third embodiments acquires a distance to an object located within a short distance. In some cases, the wave height of a received reflected wave exceeds a detectable maximum value. An object detection device of the present embodiment performs a process to estimate a wave height value Hp when the wave height of a received reflected wave exceeds a detectable maximum value. The ECU 20 serves as a wave height estimation section.

[0067] Fig. Figure 12 shows a waveform of a reflected wave when a wave height value Hp exceeds a detectable maximum value. Fig. Figure 12 shows a case where a wave height value is output as an upper limit Hsat if the actual wave height exceeds the detectable upper limit Hsat.

[0068] A first time point T1, at which a wave height exceeds a threshold value Hth, and a second time point T2, at which the wave height falls below the threshold value Hth, are obtained in order to calculate a wavelength value Tw, which indicates a time difference.

[0069] In Fig.In Figure 12, the X-axis represents time and the Y-axis represents wave height, and the waveform of a reflected wave is represented in an XY coordinate system. The fact that the time from a reception start time Tx until a wave height reaches a maximum is equal to a transmission time Tb is utilized in the present embodiment. A first right-angled triangle with vertices at one coordinate (Tx, 0), one coordinate (Tx + Tb, 0), and one coordinate (Tx + Tb, Hp), and a second right-angled triangle with vertices at one coordinate (Tx, 0), one coordinate (T1, 0), and one coordinate (T1, Hth) can be drawn based on the waveform. The first right-angled triangle and the second right-angled triangle have a similar shape. The first time T1 is also a value that is found by adding the transmission time Tb to the transmission start time Tx and subtracting half of the wavelength value Tw.

[0070] The ratio of two sides adjacent to the right angle is the same in both right-angled triangles. Therefore, using this fact, a wave height value Hp is calculated according to the following equation (1) using the threshold value Hth and the transmission time Tb, both of which are predetermined values, and the wavelength value Tw, which is a newly obtained value. (Tb−Tw / 2):Hth=Tb:Hp

[0071] With the above configuration, the object detection device of the present embodiment achieves the following effects.

[0072] For the process that uses a reflected wave, generally only the first time point T1, at which a wave height exceeds the threshold value Hth, is used. In contrast, the object detection devices of the first to third embodiments perform a process that requires a wave height value Hp in addition to the first time point T1. In the present embodiment, the value can be obtained by calculation even if a wave height value Hp exceeds the detectable upper limit Hsat. Even in a case where a wave height value Hp of a reflected wave exceeds the detectable upper limit Hsat during the process of the first to third embodiments, the height of an object can be determined. (Modifications)

[0073] In the respective embodiments described above, a wave height value is corrected according to a distance. However, a wave height value can also be corrected according to the direction in which a reflected wave is received. A wave height value of a test wave is attenuated when an angle increases with respect to an orientation of the distance measuring sensor 10. In other words, a wave height value of a wave reflected from an object not in the orientation of the distance measuring sensor 10 is smaller than a wave height value of a wave reflected from an object in the orientation of the distance measuring sensor 10. Taking such attenuation into account, a receiving direction of a reflected wave can be determined in order to correct a wave height value according to the determined direction.This means that the object detection device can also include a direction acquisition section that determines the receiving direction of a reflected wave relative to the orientation of a test wave. In this configuration, the correction section can correct a wave height value according to the receiving direction.

[0074] In the second embodiment above, it is determined whether parallel parking has been initiated, and a normal process, which is the same as in the first embodiment above, is carried out if it is determined that parallel parking has not yet been initiated. Similarly, in the third embodiment above, it can be determined whether perpendicular parking has been permitted, and a normal process, which is the same as in the first embodiment above, can be carried out if it is determined that perpendicular parking has not yet been initiated.Taking such characteristics into account, the second embodiment and the third embodiment can be combined to carry out a process corresponding to parallel parking or perpendicular parking when either parallel parking or perpendicular parking is started, and to carry out a normal process of the above first embodiment when neither parallel parking nor perpendicular parking has been started.

[0075] In the second embodiment described above, vehicle 30 is parked between the front vehicle 41a and the rear vehicle 41b. In the third embodiment described above, vehicle 30 is parked between the left vehicle 41c and the right vehicle 41d. Note that both embodiments can be used in a case where vehicle 30 is parked between columns or walls, or between a column or wall and another vehicle in a parking space. In such a case, columns and walls are objects that have a linear section and are therefore used as reference obstacles.

[0076] In the fourth embodiment above, the difference between the first time T1, at which a wave height exceeds the threshold Hth, and the second time T2, at which the wave height falls below the threshold Hth, is used as the wavelength value Tw. Alternatively, the difference between a time at which a wave height exceeds the upper limit Hsat and a time at which a wave height falls below the upper limit Hsat can also be used as the wavelength value Tw. In such a case, the upper limit Hsat is substituted for the threshold Hth in equation (1).

[0077] The above embodiments describe a case in which, according to one example, an ultrasonic wave is used as the test wave. Alternatively, other waves instead of an ultrasonic wave, for example, an acoustic wave or a radio wave, can be used as the test wave. In short, any wave that oscillates with a predetermined amplitude can be used as the test wave.

[0078] In the respective embodiments described above, the object detection device is arranged on the vehicle 30. Alternatively, the object detection device can be arranged on other mobile objects instead of a vehicle, for example, on an aircraft, a ship, or a robot. Furthermore, the object detection device can be arranged on a stationary object to measure a distance between the stationary object and an object near the stationary object, since multiple reflections may occur between the stationary object and a nearby object even when the object detection device is arranged on the stationary object. Additionally, the object detection device can be worn on or around a person to inform the individual of the approach of a nearby object.

[0079] Note that a flowchart or the processing of the flowchart of the present invention contains sections (also referred to as steps), each designated, for example, by S101. Furthermore, each section can be divided into several subsections, and several sections can be combined into a single section. Each of the sections thus configured can also be referred to as a circuit, device, module, or setup.

[0080] Any or any combination of sections described above can be achieved as (i) a software section in combination with a hardware unit (for example, a computer) or (ii) a hardware section which may or may not include a function of a device concerned; furthermore, the hardware section (for example, an integrated circuit, a hard-wired logic circuit) can be built within a microcomputer.

[0081] While the invention has been described with reference to its preferred embodiments, it is understood that the invention is not limited to these preferred embodiments and designs. The invention covers various modifications and equivalent arrangements. Furthermore, in addition to the preferred combinations and configurations, other combinations and configurations, including more, fewer, or a single element, are also possible within the scope of the invention.

Claims

[1] Object detection device which detects an object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) using a distance measuring sensor (10) arranged at a predetermined height, wherein the object detection device emits a test wave towards an environment and receives a reflected wave of the test wave as detection information of the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b), wherein the object detection device comprises: a waveform acquisition section that acquires a reception time and a wave height value (Hp) of a wave reflected by the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b), wherein the wave height value (Hp) is defined as a value of a case in which a height (H) of the wave reflected by the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) reaches a maximum; a reference value calculation section that calculates a wave height value (Hp) of a wave reflected by a reference obstacle (41, 41a, 41b, 41c, 41d) as a reference value using the wave height value (Hp) obtained by the waveform acquisition section, wherein the reference obstacle is present at least at the predetermined height; a detection value calculation section that calculates a wave height value (Hp) of a wave reflected by a detection object (42, 42a, 42b) as a detection value using the wave height value (Hp) obtained by the waveform acquisition section, wherein the detection object (42, 42a, 42b) is a detection target; a reference distance calculation section which calculates a distance between the reference obstacle and the distance measuring sensor (10) as a reference distance using a reception time of the wave reflected by the reference obstacle, wherein the reception time of the wave reflected by the reference obstacle is obtained by the waveform acquisition section; a detection distance calculation section which calculates a distance between the detection object (42, 42a, 42b) and the distance measuring sensor (10) as a detection distance using a reception time of the wave reflected by the detection object (42, 42a, 42b), wherein the reception time of the wave reflected by the detection object (42, 42a, 42b) is obtained by the waveform acquisition section; a correction section that corrects the reference value and the detection value according to an attenuation factor that varies in response to a distance ratio of the reference distance to the detection distance; and a height calculation section that calculates a height of the detection object (42, 42a, 42b) in relation to the predetermined height according to the result of a comparison of the reference value corrected by the correction section with the detection value corrected by the correction section. [2] Object detection device according to claim 1, which further comprises: a direction acquisition section that acquires a receiving direction of the wave reflected by the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) with respect to an orientation of the test wave, where the correction section corrects the reference value and the recorded value according to the direction of reception. [3] Object detection device according to claim 1 or 2, wherein The reference value calculation section calculates the reference value using the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) as the reference obstacle when the wave height value (Hp) of the wave reflected by the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) exceeds a predetermined threshold value (Hth), and the wave height value (Hp) of the wave reflected by the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) is obtained through the waveform acquisition section. [4] Object detection device according to one of claims 1 to 3, wherein the object detection device transmits several test waves in the direction of several objects (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b), the object detection device also has a grouping section that groups one or more of the objects (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) if the one or more objects (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) have distances to the distance measuring sensor (10) that are close to each other and azimuths with respect to the distance measuring sensor (10) that are close to each other, The reference value calculation section obtains an average of wave height values ​​(Hp) from one or more reference obstacles, which are grouped by the grouping section, as the reference value, and The acquisition value calculation section obtains an average of wave height values ​​(Hp) from one or more acquisition objects (42, 42a, 42b) that are grouped by the grouping section as the acquisition value. [5] Object detection device according to one of claims 1 to 4, wherein the reference value calculation section defines the object (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) which has a linear section extending in a horizontal direction as the reference obstacle. [6] Object detection device according to claim 4, wherein the reference value calculation section obtains the mean value by determining a part of the objects (40, 41, 41a, 41b, 41c, 41d, 42, 42a, 42b) that are arranged at intervals within a predetermined area to the distance measuring sensor (10) as a group of one or more reference obstacles. [7] Object detection device according to any one of claims 1 to 6, wherein the object detection device is arranged on a vehicle (30), and The reference value calculation section calculates the reference value using the object (41a, 41b, 41c, 41d) which has a height equal to or greater than the predetermined height and which is located close to the vehicle (30) as the reference obstacle. [8] Object detection device according to claim 7, wherein when the vehicle (30) is parked between two objects (41a, 41b, 41c, 41d) whose heights are equal to or greater than the predetermined height and which are spaced apart at a predetermined distance from each other, the reference value calculation section calculates the reference value using one of the two objects (41a, 41b, 41c, 41d) whose height is equal to or greater than the predetermined height as the reference obstacle. [9] Object detection device according to claim 7 or 8, wherein the object (41a, 41b, 41c, 41d) whose height is equal to or greater than the predetermined height is another vehicle. [10] Object detection device according to any one of claims 1 to 9, wherein an achievable upper limit is set with respect to the wave height value (Hp), The object detection device also includes a wave height estimation section that estimates the wave height value (Hp) when the wave height exceeds the attainable upper limit, and The wave height estimation section estimates the wave height value (Hp) based on a predetermined threshold (Hth), a first time (T1) at which the wave height exceeds the predetermined threshold (Hth), a second time (T2) at which the wave height falls below the predetermined threshold (Hth), and a transmission time (Tb) of the test wave.

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