Object detection device and object detection program

Abstract

To provide an object detection device and an object detection program for detecting an object using an ultrasonic sensor mounted on a vehicle, in which determination of freezing is performed much more suitably in order to realize good object detection.SOLUTION: An object detection device (6) detects an object using an ultrasonic sensor (5) mounted on a vehicle (V). The object detection device includes a freezing determination unit. The freezing determination unit determines that the ultrasonic sensor is in a frozen state when a prescribed freezing determination condition is established. The freezing determination condition includes the establishment of indirect wave proximity detection that an indirect wave itinerary time representing an elapsed time from a transmission time to a reception time of an ultrasonic wave transmitted from one of two ultrasonic sensors mounted on the same vehicle body component (V3) consisting of a first ultrasonic sensor (5a) and a second ultrasonic sensor (5b) and received by the other as an indirect wave is less than or equal to an indirect wave determination threshold.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an object detection device that detects objects using an ultrasonic sensor mounted on a vehicle, and an object detection program executed by such an object detection device. [Background technology]

[0002] There is known a device that uses an ultrasonic sensor to detect objects around a vehicle and performs vehicle control such as warning the occupants and driving assistance. In this type of device, if foreign matter such as snow or ice adheres to the surface of the ultrasonic sensor, the object detection may be impaired. Therefore, various proposals have been made to detect the occurrence of a stuck state and to reduce erroneous detection of objects due to the stuck state and interference with vehicle control caused by the erroneous detection.

[0003] For example, the driving assistance device described in Patent Document 1, when it is determined that an object is detected with time continuity equal to or greater than a predetermined standard based on object information from an ultrasonic sensor, determines that the object is an obstacle to be detected and starts driving assistance for the obstacle. Here, when the distance to the object based on the object information from the ultrasonic sensor is equal to or less than a predetermined distance and a snowy environment is detected, the driving assistance device changes the determination criterion for time continuity equal to or greater than a predetermined standard to a direction in which it becomes difficult to determine the object as an obstacle to be detected. This can reduce the disruption of driving assistance caused by snow adhering to the ultrasonic sensor. Specifically, it can lengthen (i.e., delay) the time until the object detected by the ultrasonic sensor is determined to be an obstacle to be detected. This can realize a more careful obstacle determination when it is considered that snow may be adhering to the ultrasonic sensor, thereby improving the reliability of driving assistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-89073 A Summary of the Invention [Problem to be solved by the invention]

[0005] As is clear from the above circumstances, in order to realize good object detection in this type of device, it is required to perform a better freezing determination. The present invention has been made in consideration of the above-mentioned circumstances and the like. [Means for solving the problem]

[0006] The object detection device (6) according to claim 1 is a device for detecting an object using an ultrasonic sensor (5) mounted on a vehicle (V), a freezing determination unit (64) that determines that the ultrasonic sensor is in a frozen state when a predetermined freezing determination condition is satisfied; The freezing judgment condition includes that indirect wave proximity detection is established in which an indirect wave travel time, which is the elapsed time between the transmission time and reception time of an indirect wave in which an ultrasonic wave transmitted from one of the two ultrasonic sensors, the first ultrasonic sensor (5a) and the second ultrasonic sensor (5b), which are mounted on the same vehicle body part (V3), is received by the other, is equal to or shorter than an indirect wave judgment threshold time. The object detection program according to claim 9 is a computer program executed by an object detection device (6) that detects an object using an ultrasonic sensor (5) mounted on a vehicle (V), The process executed by the object detection device includes a freezing determination process for determining that the ultrasonic sensor is in a frozen state when a predetermined freezing determination condition is satisfied, The freezing judgment condition includes that indirect wave proximity detection is established in which an indirect wave travel time, which is the elapsed time between the transmission time and reception time of an indirect wave in which an ultrasonic wave transmitted from one of the two ultrasonic sensors, the first ultrasonic sensor (5a) and the second ultrasonic sensor (5b), which are mounted on the same vehicle body part (V3), is received by the other, is equal to or shorter than an indirect wave judgment threshold time.

[0007] In addition, in each section of the application documents, each element may be given a reference symbol in parentheses. In this case, the reference symbol merely indicates an example of the correspondence between the element and the specific configuration described in the embodiment described later. Therefore, the present invention is not limited in any way by the description of the reference symbol. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an overall configuration of a vehicle equipped with an object detection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing the appearance of the vehicle shown in FIG. [Diagram 3] 3 is an enlarged cross-sectional view showing an outline of a mounting structure for the ultrasonic sensor shown in FIG. 2 to a vehicle body. [Figure 4] 2 is a block diagram showing an outline of a functional configuration of the object detection device shown in FIG. 1. [Diagram 5] 5 is a block diagram illustrating an example of a logic configuration of a freeze determination unit illustrated in FIG. 4. [Figure 6] FIG. 3 is a schematic diagram showing an overview of vibration transmission in a state in which two adjacent ultrasonic sensors shown in FIG. 2 are not frozen. [Figure 7] FIG. 4 is an enlarged cross-sectional view illustrating a schematic view of the ultrasonic sensor illustrated in FIG. 3 in a frozen state. [Figure 8] 3 is a schematic diagram showing an overview of vibration transmission in a state in which two adjacent ultrasonic sensors shown in FIG. 2 are both frozen. FIG. [Figure 9] 4 is a flowchart illustrating an example of the operation of the object detection device according to the embodiment of the present invention. [Figure 10] 4 is a flowchart illustrating an example of the operation of the object detection device according to the embodiment of the present invention. [Figure 11] 11 is a graph for explaining the indirect wave determination threshold time shown in FIG. 10. [Figure 12] 4 is a flowchart illustrating an example of the operation of the object detection device according to the embodiment of the present invention. [Figure 13]13 is a flowchart illustrating an example of an operation of an object detection device according to another embodiment of the present invention. [Figure 14] 13 is a flowchart illustrating an example of the operation of an object detection device according to still another embodiment of the present invention. [Figure 15] 13 is a flowchart illustrating an example of the operation of an object detection device according to still another embodiment of the present invention. [Figure 16] 5 is a block diagram illustrating another example of the logic configuration of the freeze determination unit illustrated in FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings as appropriate. Note that the configuration, functions, and implementation examples of the embodiments can be modified as appropriate. Therefore, multiple embodiments and variations may be described in the specification. In this case, in the following description, the same reference symbols will be given to parts that are identical or equivalent between one embodiment and another embodiment, between one embodiment and its variation, or between one variation and another variation. And, the preceding description of such parts may be appropriately applied to other embodiments or variations that follow, unless there is a technical contradiction or special additional explanation.

[0010] (Overall composition) 1 and 2, the vehicle V is a so-called four-wheeled vehicle, and includes a box-shaped vehicle body V1 formed into a substantially rectangular shape in a plan view. The concepts of "front", "rear", "left" and "right" in the vehicle V and the vehicle body V1 are as shown by arrows in FIG. 1 and FIG. 2. These directional concepts are based on the driver facing the direction of travel of the vehicle V while traveling forward. In the directional concepts shown by the arrows in the figures, the left-right direction corresponds to the "vehicle width direction", and the front-rear direction corresponds to the "vehicle overall length direction". With reference to FIG. 1, the vehicle overall length direction is parallel to the vehicle center line LC passing through the center of the vehicle body V1 in the vehicle width direction.

[0011] The vehicle body V1 is covered by a vehicle body panel V2, which is a vehicle body part. The vehicle body panel V2 is formed of a metal plate material. Furthermore, bumpers V3, which are vehicle body parts, are attached to the front and rear ends of the vehicle body V1. In this embodiment, the bumpers V3 are formed of a metal plate material.

[0012] The vehicle V is equipped with an in-vehicle system 1. The in-vehicle system 1 is a so-called driving assistance system or an automatic driving system, and is configured to be able to execute operations such as motion control of the vehicle V and output of an alarm to an occupant based on the detection result of an object around the vehicle V. The in-vehicle system 1 includes a vehicle speed sensor 2, a shift position sensor 3, a temperature sensor 4, a plurality of ultrasonic sensors 5, an object detection device 6, a notification unit 7, and a driving control unit 8. The vehicle speed sensor 2, the shift position sensor 3, the temperature sensor 4, and the plurality of ultrasonic sensors 5 are connected to the object detection device 6 so as to be able to communicate information or signals via a communication line such as an in-vehicle network. In addition, the notification unit 7 and the driving control unit 8 are connected to the object detection device 6 so as to be able to communicate information or signals via a communication line such as an in-vehicle network.

[0013] The vehicle speed sensor 2 is provided to generate an output corresponding to the traveling speed, i.e., vehicle speed, of the vehicle V. The shift position sensor 3 is provided to generate an output corresponding to the shift position of the vehicle V. The temperature sensor 4 is provided to generate an output corresponding to the outside air temperature, i.e., the temperature around the vehicle V. The temperature sensor 4 may be attached to the ultrasonic sensor 5 so as to generate an output corresponding to the internal temperature of the ultrasonic sensor 5.

[0014] The ultrasonic sensor 5 is configured to detect an object present in the external space around the vehicle V by transmitting and receiving ultrasonic waves. That is, the ultrasonic sensor 5 is configured to transmit an ultrasonic search wave toward the external space of the vehicle V and to detect the presence of the object and the distance to the object by receiving a received wave including a reflected wave of the search wave by the object. In this embodiment, the ultrasonic sensor 5 has a so-called integrated transmission and reception configuration. That is, each of the multiple ultrasonic sensors 5 is configured to be capable of transmitting a search wave toward the external space by itself and to receive ultrasonic waves propagated from the external space as a received wave.

[0015] A plurality of ultrasonic sensors 5 are attached to each of the front and rear bumpers V3. Specifically, as shown in FIG. 1, four ultrasonic sensors 5 are attached to the front bumper, which is the bumper V3 attached to the front of the vehicle body V1. Each of these ultrasonic sensors 5 is disposed at a different position at least in the vehicle width direction. More specifically, a first inner sensor 5a, a second inner sensor 5b, a first outer sensor 5c, and a second outer sensor 5d are attached to the front bumper. Similarly, four ultrasonic sensors 5 are attached to the rear bumper, which is the bumper V3 attached to the rear of the vehicle body V1. Note that, for the sake of simplicity of illustration and description, illustration and the following description of the four ultrasonic sensors 5 attached to the rear bumper are omitted.

[0016] The first inner sensor 5a and the second inner sensor 5b are disposed inward in the vehicle width direction, i.e., closer to the vehicle center line LC, than the first outer sensor 5c and the second outer sensor 5d, and are provided so as to transmit a search wave substantially forward. The first inner sensor 5a is disposed to the left of the vehicle center line LC. The second inner sensor 5b is disposed to the right of the vehicle center line LC. The first inner sensor 5a and the second inner sensor 5b are disposed symmetrically with respect to the vehicle center line LC. The first outer sensor 5c and the second outer sensor 5d are so-called corner sensors, and are attached to both ends of the front bumper in the vehicle width direction. The first outer sensor 5c and the second outer sensor 5d are disposed symmetrically with respect to the vehicle center line LC. The first outer sensor 5c is disposed at the left front corner of the vehicle body V1, and is provided so as to transmit a search wave substantially forward to the left. That is, the first inner sensor 5a is disposed between the first outer sensor 5c and the second inner sensor 5b in the vehicle width direction. The second outer sensor 5d is disposed at a right front corner of the vehicle body V1 and is arranged to transmit a search wave toward the substantially right front. That is, the second inner sensor 5b is disposed between the second outer sensor 5d and the first inner sensor 5a in the vehicle width direction.

[0017] The ultrasonic sensor 5 is also provided so as to be able to receive both direct and indirect waves. The "direct wave" refers to the received wave when the ultrasonic sensor 5 that transmitted the exploration wave is the same as the ultrasonic sensor 5 that received the received wave resulting from the exploration wave. On the other hand, the "indirect wave" refers to the received wave when the ultrasonic sensor 5 that transmitted the exploration wave is different from the ultrasonic sensor 5 that received the received wave resulting from the exploration wave. That is, for example, the first inner sensor 5a is provided so as to be able to receive a direct wave, which is a received wave resulting from the exploration wave transmitted by itself, and an indirect wave, which is a received wave resulting from the exploration wave transmitted by the adjacent second inner sensor 5b or first outer sensor 5c. The "received wave resulting from the exploration wave" includes not only the received wave of the exploration wave radiated into the external space around the vehicle V as a reflected wave from an object or road surface present in the external space, but also a non-reflected wave. The non-reflected wave includes, for example, a received wave when the exploration wave transmitted from a certain ultrasonic sensor 5 is received by itself or another ultrasonic sensor 5 without being reflected by an object in the external space. Specifically, non-reflected waves include, for example, received waves when an exploration wave emitted from one ultrasonic sensor 5 is not emitted into external space but is received by itself or another ultrasonic sensor 5 during a non-acoustic transmission process in which the exploration wave transmits inside the vehicle body V1 or an attachment to the vehicle body V1.

[0018] 3, the ultrasonic sensor 5 is mounted in a sensor mounting hole V4, which is a substantially circular through-hole provided in the bumper V3. The sensor mounting hole V4 is formed to penetrate the bumper V3 in the plate thickness direction by opening at a bumper outer surface V31 and a bumper inner surface V32, which are surfaces exposed with the plate thickness direction of the bumper V3 as the normal direction. The bumper outer surface V31 is the surface that faces the external space around the vehicle V, i.e., the outer surface. The bumper inner surface V32 is the back surface of the bumper outer surface V31, i.e., the inner surface.

[0019] The ultrasonic sensor 5 includes an ultrasonic microphone 51 and a bezel 52. The ultrasonic microphone 51 has a configuration in which an electromechanical energy conversion element such as a piezoelectric element is built inside a substantially cylindrical casing. The bezel 52 is a synthetic resin component constituting a mounting fixture for mounting the ultrasonic sensor 5 to the bumper V3, and includes a cylindrical portion 52a, a flange portion 52b, and a protruding portion 52c. The cylindrical portion 52a, the flange portion 52b, and the protruding portion 52c are integrally formed.

[0020] The tubular portion 52a is formed in a substantially cylindrical shape surrounding the ultrasonic microphone 51 having a substantially cylindrical outer shape. The inner diameter of the tubular portion 52a is set to be slightly larger than the outer diameter of the ultrasonic microphone 51. A substantially cylindrical anti-vibration rubber 53 is sandwiched between the ultrasonic microphone 51 and the tubular portion 52a. The anti-vibration rubber 53 is provided so that vibrations generated in the ultrasonic microphone 51 are not transmitted to the bezel 52.

[0021] The flange portion 52b extends radially outward from the axial end of the cylindrical portion 52a. The flange portion 52b is formed with an outer diameter larger than the diameter of the sensor mounting hole V4 so that the flange portion 52b faces the bumper outer surface V31 when the cylindrical portion 52a is inserted into the sensor mounting hole V4 and attached to the bumper V3. The protruding portion 52c extends radially outward from the cylindrical portion 52a at a position slightly spaced from the flange portion 52b in the axial direction. The protruding portion 52c has an outer diameter slightly smaller than the diameter of the sensor mounting hole V4 so that the protruding portion 52c is inserted into the sensor mounting hole V4. A rubber spacer 54 is fitted into the gap between the flange portion 52b and the protruding portion 52c. The spacer 54 is sandwiched between the flange portion 52b and the bumper V3 when the ultrasonic sensor 5 is attached to the bumper V3. That is, the spacer 54 is provided to suppress vibration transmission between the bezel 52 and the bumper V3.

[0022] Referring again to FIG. 1, the object detection device 6 is a device that detects an object present in an external space using the ultrasonic sensor 5 mounted on the vehicle V, and has a configuration as an in-vehicle microcomputer equipped with a CPU, ROM, RAM, non-volatile rewritable memory, etc. (not shown). CPU stands for Central Processing Unit. ROM stands for Read Only Memory. RAM stands for Random Access Memory. The non-volatile rewritable memory is a storage device that can rewrite information while the power is on, but holds information in an unrewritable manner while the power is off, such as a flash ROM or an EEPROM. EEPROM stands for Electronically Erasable and Programmable ROM. Thus, the object detection device 6 has a configuration as an object detection ECU. ECU stands for Electronic Control Unit. That is, the object detection device 6 is configured to detect objects around the vehicle V by causing each of the multiple ultrasonic sensors 5 to perform a transmission / reception operation at a predetermined timing when a predetermined detection operation execution condition is established, and receiving the object detection result from each of the multiple ultrasonic sensors 5. The configuration and operation of the object detection device 6 will be described in detail later.

[0023] The notification unit 7 is configured to notify the occupants, including the driver of the vehicle V, of information and give warnings by audio output and / or display. That is, the notification unit 7 is a collective term for display devices such as a meter panel, CID, and head-up display, and audio output devices such as speakers. CID stands for center information display. The notification unit 7 is provided to execute a notification operation according to the relative position and distance between the vehicle V and the obstacle when the object detection device 6 detects an obstacle. That is, the object detection device 6 is configured to notify the occupants of the object detection result using the ultrasonic sensor 5 by the notification unit 7, and to issue a warning to the occupants by the notification unit 7 as necessary.

[0024] The driving control unit 8 is an in-vehicle microcomputer for controlling the execution of a longitudinal vehicle motion control subtask and a lateral vehicle motion control subtask in the vehicle V, and includes a CPU, a ROM, a RAM, a non-volatile rewritable memory, and the like (not shown). The "longitudinal vehicle motion control subtask" includes starting, accelerating / decelerating, braking, and stopping. The "lateral vehicle motion control subtask" includes steering. That is, the driving control unit 8 has a configuration as a so-called automatic driving ECU or a driving assistance ECU. The driving control unit 8 is configured to execute vehicle motion control required for avoiding a collision with a detected object and reducing impact at the time of a collision, based on the object detection result by the object detection device 6.

[0025] (Object detection device) Fig. 4 shows part of the functional configuration realized by the CPU reading and executing a computer program from a ROM or a non-volatile rewritable memory in the object detection device 6. As shown in Fig. 4, the object detection device 6 includes, as its functional configuration, a reception state determination unit 61, a travel distance calculation unit 62, a temperature acquisition unit 63, and a freezing determination unit 64.

[0026] The reception state determination unit 61 is adapted to determine the reception state of the reception wave at each of the plurality of ultrasonic sensors 5. That is, the reception state determination unit 61 is adapted to acquire at least the reception state of the direct wave and the indirect wave and the travel time, i.e., TOF, from each of the plurality of ultrasonic sensors 5, and to determine the object detection state at each of the plurality of ultrasonic sensors 5. TOF is an abbreviation for Time of Flight. The travel distance calculation unit 62 is adapted to calculate the travel distance of the vehicle V between the reception timings of the reception waves at each of the plurality of ultrasonic sensors 5. The temperature acquisition unit 63 is adapted to acquire the ambient temperature of the ultrasonic sensor 5 based on the output of the temperature sensor 4. The freezing determination unit 64 is adapted to receive necessary information or signals from the reception state determination unit 61, the travel distance calculation unit 62, and the temperature acquisition unit 63, and to determine whether or not the ultrasonic sensor 5 is in a frozen state. That is, the freezing determination unit 64 is adapted to determine that the ultrasonic sensor 5 is in a frozen state when a predetermined freezing determination condition is established.

[0027] 5 shows an example of a logic configuration of the freezing determination unit 64 in this embodiment. In this embodiment, the freezing determination unit 64 determines that the ultrasonic sensor 5 is in a frozen state when a freezing determination is established in either the direct wave freezing determination 641 or the indirect wave freezing determination 642. That is, the freezing determination condition in this embodiment is that a freezing determination is established in either the direct wave freezing determination 641 or the indirect wave freezing determination 642. Details of the direct wave freezing determination 641 and the indirect wave freezing determination 642 will be described together in the operation overview described later.

[0028] (Operation overview) An overview of the operation of the in-vehicle system 1 having the above configuration will be described below. Hereinafter, the device configuration of the object detection device 6 according to this embodiment, and the process, method, and computer program executed thereby may be collectively referred to as "this embodiment."

[0029] The object detection device 6 starts an object detection operation when a predetermined detection operation execution condition is satisfied. The predetermined detection operation execution condition includes, for example, conditions related to the shift position and the vehicle speed. During the object detection operation, the object detection device 6 causes each of the ultrasonic sensors 5 to perform a transmission / reception operation. Specifically, the object detection device 6 sets the frequency and frequency modulation pattern of the search wave for each of the ultrasonic sensors 5, and controls the transmission / reception timing. That is, for example, for four ultrasonic sensors 5 mounted on the front bumper, the object detection device 6 switches between a transmission / reception sensor that performs both a transmission operation of transmitting a search wave and a reception operation of receiving a received wave, and a reception sensor that performs only a reception operation without performing a transmission operation, in a predetermined order and timing.

[0030] The object detection device 6 detects objects around the vehicle V based on the reception state of the waves received by each of the multiple ultrasonic sensors 5. Specifically, for example, when an object is present on the left front side of the vehicle V, it is possible to calculate the relative position and distance of the object with respect to the vehicle V by the principle of triangulation from the direct wave received by the first inner sensor 5a and the indirect wave received by the first outer sensor 5c, which are based on the exploration wave transmitted from the first inner sensor 5a.

[0031] Further, the object detection device 6 judges whether the ultrasonic sensor 5 is in a frozen state based on the reception state of the reception wave at each of the multiple ultrasonic sensors 5. Hereinafter, for the sake of simplicity of explanation, the freezing judgment in this embodiment will be described in detail using an example in which the first inner sensor 5a transmits a search wave to perform freezing judgment on the first inner sensor 5a and the first outer sensor 5c adjacent to each other. FIG. 6 is a schematic diagram for explaining the vibration transmission state at the mounting portion of the first inner sensor 5a and the first outer sensor 5c to the bumper V3 when both the first inner sensor 5a and the first outer sensor 5c are not frozen. FIG. 7 is a schematic diagram showing the state in which the ultrasonic sensor 5 shown in FIG. 3 is frozen. FIG. 8 is a schematic diagram corresponding to FIG. 6 when both the first inner sensor 5a and the first outer sensor 5c are frozen.

[0032] 6, in a non-frozen state, vibrations generated by the ultrasonic microphone 51 in the first inner sensor 5a, which is the source of the search wave, due to the emission of the search wave are absorbed by the vibration-proof rubber 53. In addition, a rubber spacer 54 having vibration-absorbing properties is sandwiched between the bezel 52 and the bumper V3. Therefore, in a non-frozen state, the transmission of vibrations from the ultrasonic microphone 51 to the bezel 52 and the bumper V3 is effectively suppressed.

[0033] FIG. 7 shows a state in which the portion of the ultrasonic sensor 5 facing the external space is covered with solid ice W due to freezing. In this state, the solid ice W bridges the ultrasonic microphone 51 and the metal bumper V3. This creates a path for vibration transmission within a solid between the ultrasonic microphone 51 and the bumper V3. FIG. 8 shows a state in which both the first inner sensor 5a and the first outer sensor 5c are frozen as described above and covered with solid ice W. As shown in FIG. 8, the first solid ice W1, which is the solid ice W covering the first inner sensor 5a, creates a vibration transmission path between the ultrasonic microphone 51 in the first inner sensor 5a and the bumper V3. Similarly, the second solid ice W2, which is the solid ice W covering the first outer sensor 5c, creates a vibration transmission path between the ultrasonic microphone 51 in the first outer sensor 5c and the bumper V3.

[0034] More specifically, referring to Fig. 8, a first solid transmission path Pa1 is generated from the ultrasonic microphone 51, which is the source of vibrations caused by the transmission of the search wave in the first inner sensor 5a, through the first fixed ice W1 to the bumper V3, and then from the bumper V3 through the first fixed ice W1 again to the ultrasonic microphone 51 in the first inner sensor 5a. The wave received by the first solid transmission path Pa1 corresponds to a "direct wave". In addition, a second solid transmission path Pa2 is generated from the ultrasonic microphone 51 in the first inner sensor 5a through the first fixed ice W1 to the bumper V3, from the bumper V3 to the second fixed ice W2, and then through the second fixed ice W2 to the ultrasonic microphone 51 in the first outer sensor 5c. The wave received by the second solid transmission path Pa2 corresponds to an "indirect wave".

[0035] A metal bumper V3 transmits vibrations more easily than a synthetic resin bumper. Furthermore, solid ice W transmits vibrations more easily than the air occupying the external space. Therefore, the vibrations are hardly attenuated during transmission through the first solid transmission path Pa1 and the second solid transmission path Pa2. For this reason, when both the first inner sensor 5a and the first outer sensor 5c are frozen, the first inner sensor 5a detects a direct wave from the first solid transmission path Pa1 with an intensity equal to or greater than the noise judgment threshold, and the first outer sensor 5c detects an indirect wave from the second solid transmission path Pa2 with an intensity equal to or greater than the noise judgment threshold.

[0036] Furthermore, the vibration transmission speed in the first solid transmission path Pa1 and the second solid transmission path Pa2 is higher than the vibration transmission speed in the first reflected wave transmission path Pb1 and the second reflected wave transmission path Pb2, which are transmission paths of the reflected wave by an object existing in the external space. The first reflected wave transmission path Pb1 is a transmission path of the reflected wave, which is a direct wave. The second reflected wave transmission path Pb2 is a transmission path of the reflected wave, which is an indirect wave. Therefore, the detection distance corresponding to the reflected wave from a very close object is calculated from the direct wave and indirect wave detected by freezing.

[0037] Therefore, in this embodiment, when direct wave proximity detection, which is a close distance detection by a direct wave, is established continuously, i.e., continuously, to a predetermined extent during a predetermined distance travel, the ultrasonic sensor 5 that receives the direct wave is determined to be in a frozen state. This is the direct wave freezing determination 641 shown in FIG. 5. The direct wave proximity detection is defined as a direct wave travel time, which is the elapsed time between the transmission time and the reception time of the direct wave, being equal to or less than the direct wave determination threshold time. The reason for the condition of "traveling a predetermined distance" is that in the case of normal close distance detection caused by a reflected wave from an object when an object actually exists, the distance to the object changes with the travel of the vehicle V, whereas in the case of freezing, the distance does not change with the travel of the vehicle V. In this way, by including the travel distance as a determination condition in the direct wave freezing determination 641, it is possible to effectively suppress erroneous determination.

[0038] In addition, in this embodiment, when an indirect wave proximity detection is established, which is a proximity detection by indirect waves in which an ultrasonic wave transmitted from one of the two ultrasonic sensors 5 is received by the other, it is determined that both the ultrasonic sensor 5 that is the source of the search wave in the indirect wave and the ultrasonic sensor 5 that received the indirect wave are in a frozen state. This is the indirect wave freezing judgment 642 shown in FIG. 5. Indirect wave proximity detection means that the indirect wave travel time, which is the elapsed time between the transmission time and the reception time of the indirect wave, is equal to or less than the indirect wave judgment threshold time. The indirect wave judgment threshold time may be the same as or different from the direct wave judgment threshold time, but it is preferable that it is a small value corresponding to "extreme proximity detection" that is about the detection limit or closer than this. In the indirect wave freezing judgment 642, unlike the direct wave freezing judgment 641, the travel distance is not included in the judgment conditions. This is because it is difficult to imagine the occurrence of such an extremely close detection by indirect waves except when frozen. Therefore, it is possible to quickly perform the freezing judgment without waiting for a predetermined travel distance.

[0039] 5, in this embodiment, when at least one of a direct wave freezing judgment 641 and an indirect wave freezing judgment 642 is satisfied, it is determined that a freezing state has occurred in at least one of the multiple ultrasonic sensors 5 mounted on the same bumper V3. This allows the freezing judgment to be performed more satisfactorily than in the past.

[0040] (Specific examples) A specific operation example according to this embodiment will be described below with reference to a flowchart. In the drawings and the following description in the specification, "step" will be abbreviated to "S". Also, the CPU provided in the object detection device 6 will be referred to simply as "CPU".

[0041] FIG. 9 shows an example of the process by the direct wave freezing decision 641, that is, the direct wave freezing decision process. In the flowchart shown in FIG. 9, first, in step 101, the CPU acquires the reception state of the received wave at each of the multiple ultrasonic sensors 5. Next, in step 102, the CPU determines whether or not a direct wave has been received at each of the multiple ultrasonic sensors 5. If a direct wave has not been received (i.e., step 102=NO), the CPU executes the process of step 103, and then temporarily ends the direct wave freezing decision process. In step 103, the CPU determines that the direct wave freezing decision is not established. On the other hand, if a direct wave has been received (i.e., step 102=YES), the CPU advances the process to step 104.

[0042] In step 104, the CPU judges whether the direct wave detection is a short-distance detection. If the direct wave detection is not a short-distance detection (i.e., step 104=NO), the CPU executes the process of step 103 to judge whether the direct wave freezing judgment is not established, and then temporarily ends the direct wave freezing judgment process. In contrast, if the direct wave detection is a short-distance detection (i.e., step 104=YES), the CPU advances the process to step 105.

[0043] In step 105, the CPU judges whether or not close-distance detection by direct waves is continuous in the same sensor. If close-distance detection by direct waves is not continuous in the same sensor (i.e., step 105=NO), the CPU executes the process of step 103 to judge whether the direct wave freezing judgment is not established, and then temporarily ends the direct wave freezing judgment process. In contrast, if close-distance detection by direct waves is continuous in the same sensor (i.e., step 105=YES), the CPU advances the process to step 106.

[0044] In step 106, the CPU judges whether the vehicle V has traveled a predetermined distance while the same sensor continues to detect close distances by direct waves. If the vehicle V has not traveled the predetermined distance (i.e., step 106=NO), the CPU executes the process of step 103 to judge that the direct wave freezing judgment is not satisfied, and then temporarily terminates the direct wave freezing judgment process. In contrast, if the vehicle V has traveled the predetermined distance (i.e., step 106=YES), the CPU advances the process to step 107.

[0045] In step 107, the CPU determines whether the detection distance, i.e., the distance measurement value, in successive close-distance detections by the same sensor using direct waves while driving a predetermined distance is constant, i.e., whether the amount of variation is within a predetermined range. If the distance measurement value is not constant (i.e., step 107=NO), the CPU executes the process of step 103 to determine that the direct wave freezing judgment is not established, and then temporarily terminates the direct wave freezing judgment process. In contrast, if the distance measurement value is constant (i.e., step 107=YES), the CPU executes the process of step 108, and then temporarily terminates the direct wave freezing judgment process. In step 108, the CPU determines that the direct wave freezing judgment is established.

[0046] Fig. 10 shows an example of the process by the indirect wave freezing decision 642, that is, the indirect wave freezing decision process. In the flowchart shown in Fig. 10, first, in step 201, the CPU acquires the reception state of the received waves at each of the plurality of ultrasonic sensors 5. Next, in step 202, the CPU judges whether or not an indirect wave has been received at each of the plurality of ultrasonic sensors 5. If an indirect wave has not been received (i.e., step 202 = NO), the CPU executes the process of step 203, and then temporarily ends the indirect wave freezing decision process. In step 203, the CPU judges that the indirect wave freezing decision is not established. On the other hand, if an indirect wave has been received (i.e., step 202 = YES), the CPU advances the process to step 204.

[0047] In step 204, the CPU judges whether the indirect wave detection is a short-distance detection. If the indirect wave detection is not a short-distance detection (i.e., step 204=NO), the CPU executes the process of step 203 to judge whether the indirect wave freezing judgment is not established, and then temporarily ends the indirect wave freezing judgment process. On the other hand, if the indirect wave detection is a short-distance detection (i.e., step 204=YES), the CPU advances the process to step 205.

[0048] In step 205, the CPU judges whether the indirect wave travel time is equal to or less than the indirect wave judgment threshold time THb. The indirect wave judgment threshold time THb will be described with reference to FIG. 11. In FIG. 11, the vertical axis indicates the indirect wave travel time, and the horizontal axis indicates the temperature. The straight line f1 indicates the acoustic indirect wave propagation characteristic when the indirect wave is a normal object reflected wave. In this way, the acoustic indirect wave propagation shows temperature dependency according to the temperature dependency of the sound speed. On the other hand, the straight line f2 indicates the non-acoustic vibration propagation characteristic when a bridge is formed between the ultrasonic microphone 51 and the metal bumper V3 due to the solid ice W or moisture. In this way, the non-acoustic vibration propagation does not show temperature dependency like the straight line f1. Therefore, in this specific example, the indirect wave judgment threshold time THb is set to a value between the straight lines f1 and f2. Specifically, the indirect wave judgment threshold time THb is set to a value equal to or less than the distance between two adjacent ultrasonic sensors 5 divided by the sound speed at 0°C. As shown in FIG. 11, the indirect wave determination threshold time THb may be set to a constant value independent of temperature, or may be set to vary with temperature.

[0049] If the indirect wave travel time exceeds the indirect wave determination threshold time THb (i.e., step 205=NO), the CPU executes the process of step 203 to determine whether the indirect wave freezing determination is true or false, and then temporarily ends the indirect wave freezing determination process. On the other hand, if the indirect wave travel time is equal to or less than the indirect wave determination threshold time THb (i.e., step 205=YES), the CPU executes the process of step 206, and then temporarily ends the indirect wave freezing determination process. In step 206, the CPU determines whether the indirect wave freezing determination is true or false.

[0050] FIG. 12 shows the final freezing judgment process based on the judgment results in the direct wave freezing judgment 641 and the indirect wave freezing judgment 642. In step 301, the CPU judges whether the direct wave freezing judgment is established or not. If the direct wave freezing judgment is established (i.e., step 301=YES), the CPU judges whether the final freezing judgment is established in step 302, and then temporarily ends the freezing judgment process. In contrast, if the direct wave freezing judgment is not established (i.e., step 301=NO), the CPU advances the process to step 303. In step 303, the CPU judges whether the indirect wave freezing judgment is established or not. If the indirect wave freezing judgment is established (i.e., step 303=YES), the CPU judges whether the final freezing judgment is established in step 302, and then temporarily ends the freezing judgment process. In contrast, if the indirect wave freezing judgment is not established (i.e., step 303=NO), the CPU judges whether the final freezing judgment is not established in step 304, and then temporarily ends the freezing judgment process.

[0051] Second Embodiment The second embodiment will be described below. In this embodiment, the content of the indirect wave freezing judgment 642 in the first embodiment is partially changed. That is, in this embodiment, the freezing judgment condition in the indirect wave freezing judgment 642 includes that the indirect wave proximity detection is established for a predetermined time or a predetermined number of times in addition to the indirect wave proximity detection being established similarly to the first embodiment. This makes it possible to effectively suppress the erroneous determination of a short-term indirect wave proximity detection due to raindrop collision in rainy weather as freezing. The content of the indirect wave freezing judgment process in this embodiment will be described below with reference to FIG. 13.

[0052] First, in step 401, the CPU acquires the reception state of the received waves at each of the multiple ultrasonic sensors 5. Next, in step 402, the CPU determines whether or not an indirect wave has been received at each of the multiple ultrasonic sensors 5. If an indirect wave has not been received (i.e., step 402=NO), the CPU executes the process of step 403 and then temporarily ends the indirect wave freezing determination process. In step 403, the CPU determines that the indirect wave freezing determination is not established. On the other hand, if an indirect wave has been received (i.e., step 402=YES), the CPU advances the process to step 404.

[0053] In step 404, the CPU judges whether the indirect wave detection is a short-distance detection. If the indirect wave detection is not a short-distance detection (i.e., step 404=NO), the CPU executes the process of step 403 to judge whether the indirect wave freezing judgment is not established, and then temporarily ends the indirect wave freezing judgment process. On the other hand, if the indirect wave detection is a short-distance detection (i.e., step 404=YES), the CPU advances the process to step 405.

[0054] In step 405, the CPU judges whether the indirect wave travel time is equal to or less than the indirect wave judgment threshold time THb. If the indirect wave travel time exceeds the indirect wave judgment threshold time THb (i.e., step 405=NO), the CPU executes the process of step 403 to judge that the indirect wave freezing judgment is not established, and then ends the indirect wave freezing judgment process. On the other hand, if the indirect wave travel time is equal to or less than the indirect wave judgment threshold time THb (i.e., step 405=YES), the CPU advances the process to step 406.

[0055] In step 406, the CPU judges whether or not indirect wave proximity detection has been established for a predetermined time or a predetermined number of times. If indirect wave proximity detection has not been established for a predetermined time or a predetermined number of times (i.e., step 406=NO), the CPU executes the process of step 403 to judge that the indirect wave freezing judgment has not been established, and then temporarily ends the indirect wave freezing judgment process. In contrast, if indirect wave proximity detection has been established for a predetermined time or a predetermined number of times (i.e., step 406=YES), the CPU executes the process of step 407, and then temporarily ends the indirect wave freezing judgment process. In step 407, the CPU judges that the indirect wave freezing judgment has been established.

[0056] Third embodiment The third embodiment will be described below. In this embodiment, the freezing judgment condition in the indirect wave freezing judgment 642 includes that the indirect wave proximity detection is established as in the first embodiment, and also that the indirect wave freezing judgment is established even if the transmission and reception are switched between two adjacent ultrasonic sensors 5. This makes it possible to effectively suppress erroneous judgments. The contents of the indirect wave freezing judgment process in this embodiment will be described below with reference to FIG. 14.

[0057] First, in step 501, the CPU executes an indirect wave freezing determination process in a case where one of two adjacent ultrasonic sensors 5 is a transmitting / receiving sensor and the other is a receiving sensor. Next, in step 502, the CPU executes an indirect wave freezing determination process by switching the transmitting / receiving sensor and the receiving sensor. The contents of the indirect wave freezing determination process in steps 501 and 502 are the same as those in the first or second embodiment described above.

[0058] Next, in step 503, the CPU determines whether the indirect wave freezing judgment is established in both step 501 and step 502. If both are established (i.e., step 503=YES), the CPU executes the process of step 504 and then temporarily ends the indirect wave freezing judgment process. In step 504, the CPU determines whether the indirect wave freezing judgment is established. In contrast, if at least one of them is not established (i.e., step 503=NO), the CPU executes the process of step 505 and then temporarily ends the indirect wave freezing judgment process. In step 505, the CPU determines whether the indirect wave freezing judgment is not established.

[0059] (Fourth embodiment) A fourth embodiment will be described below. In this embodiment, the freezing judgment conditions include that the indirect wave freezing judgment by the indirect wave approach detection is established and the temperature detected by the temperature sensor 4 is equal to or lower than the threshold temperature. The threshold temperature is, for example, 0°C. As shown in FIG. 11, when the temperature increases, the speed of sound propagating through the air increases, and the difference between the lines f1 and f2 decreases, making it difficult to distinguish. In addition, by making a freezing judgment only at 0°C or lower, it is possible to effectively avoid erroneous judgments that a freezing judgment is made in a water-retaining state rather than a frozen state.

[0060] Furthermore, in this embodiment, after the freezing determination is once established, if both the direct wave freezing determination and the indirect wave freezing determination are no longer established, the freezing determination is released.

[0061] Hereinafter, the contents of the freezing determination process in this embodiment will be described with reference to Fig. 15. First, in step 601, the CPU determines whether the temperature detected by the temperature sensor 4 is equal to or lower than the threshold temperature. If the temperature detected by the temperature sensor 4 exceeds the threshold temperature (i.e., step 601 = NO), the CPU determines in step 602 that the final freezing determination is not established, and then temporarily terminates the freezing determination process. On the other hand, if the temperature detected by the temperature sensor 4 is equal to or lower than the threshold temperature (i.e., step 601 = YES), the CPU advances the process to step 603.

[0062] In step 603, the CPU judges whether or not the direct wave freezing judgment is established. If the direct wave freezing judgment is not established (i.e., step 603=NO), the CPU advances the process to step 604. In step 604, the CPU judges whether or not the indirect wave freezing judgment is established. If either the direct wave freezing judgment or the indirect wave freezing judgment is established (i.e., step 603=YES or step 604=YES), the CPU judges whether the final freezing judgment is established in step 605, and then temporarily terminates the freezing judgment process. In contrast, if both the direct wave freezing judgment and the indirect wave freezing judgment are not established (i.e., step 603=NO and step 604=NO), the CPU judges whether the final freezing judgment is not established in step 602, and then temporarily terminates the freezing judgment process.

[0063] Fifth embodiment The fifth embodiment will be described below. In this embodiment, the freezing judgment condition is that both the indirect wave freezing judgment and the direct wave proximity detection are satisfied. That is, as shown in FIG. 16, the freezing judgment unit 64 outputs the final freezing judgment result by the logical product of the judgment result of the indirect wave freezing judgment 642 and the direct wave proximity detection 643. The direct wave proximity detection 643 is that the direct wave proximity detection is satisfied in the ultrasonic sensor 5 in which the indirect wave freezing judgment 642 is satisfied. When the indirect wave freezing judgment 642 is satisfied, there is a high possibility that the direct wave proximity detection is satisfied in the corresponding ultrasonic sensor 5, so the AND condition is used. This improves the reliability of the judgment and makes it possible to effectively suppress erroneous judgment. Note that the satisfaction condition of the direct wave proximity detection 643 in this embodiment, specifically, the detection distance condition, i.e., the judgment threshold time and the detection frequency, i.e., the number of consecutive or continuous times and the period, may be the same as or different from the direct wave freezing judgment 641. That is, for example, the freezing determination unit 64 may be configured to output a final freezing determination result regardless of the frequency of continuation or succession if a direct wave approach detection is established by the corresponding ultrasonic sensor 5 while the indirect wave freezing determination 642 is established. In other words, the freezing determination unit 64 shown in Fig. 16 may have an intermediate freezing determination condition between the OR condition of the direct wave freezing determination 641 and the indirect wave freezing determination 642 as in the first embodiment and the AND condition of the direct wave freezing determination 641 and the indirect wave freezing determination 642 as a modified example thereof.

[0064] (effect) The effects achieved by the above-described embodiment will be described below by categorizing them according to the configuration. Note that the following configurations (1) to (8) can be appropriately combined with each other as long as there is no technical contradiction or inconvenience.

[0065] (1) In the present invention, the freezing determination condition includes an indirect wave freezing determination condition. The indirect wave freezing determination condition includes the establishment of indirect wave proximity detection in which an indirect wave travel time, which is the elapsed time between the transmission time and reception time of an indirect wave in which an ultrasonic wave transmitted from one of two ultrasonic sensors 5 mounted on a bumper V3 as the same vehicle body part is received by the other, is equal to or shorter than an indirect wave determination threshold time. This makes it possible to quickly determine that both of these two ultrasonic sensors 5 are frozen without waiting for a predetermined driving distance.

[0066] (2) In the present invention, the indirect wave freezing determination condition includes that the indirect wave proximity detection continues for a predetermined time or a predetermined number of times, which effectively prevents a short-term indirect wave proximity detection caused by raindrop collision in rainy weather from being erroneously determined as freezing.

[0067] (3) In the present invention, the indirect wave freezing judgment condition includes that indirect wave proximity detection is established for both an indirect wave in which an ultrasonic wave transmitted from one of the two ultrasonic sensors 5 is received by the other, and an indirect wave in which an ultrasonic wave transmitted from one of the ultrasonic sensors 5 is received by itself. This makes it possible to effectively suppress erroneous judgments.

[0068] (4) In the present invention, the indirect wave determination threshold time THb is set to be equal to or less than the value obtained by dividing the distance between the two ultrasonic sensors 5 by the sound speed at 0° C. This allows the indirect wave freezing determination to be performed appropriately.

[0069] (5) In the present invention, the freezing determination conditions include that the indirect wave proximity detection is established and the outside air temperature is equal to or lower than a threshold temperature. This allows the indirect wave freezing determination to be performed appropriately. In addition, it is possible to effectively avoid erroneous determination that the object is frozen when it is not frozen but is in a water-retaining state.

[0070] (6) In the present invention, the freezing judgment condition includes that the indirect wave proximity detection is established and that the direct wave path time, which is the elapsed time between the transmission time and the reception time of the direct wave, is equal to or less than the direct wave judgment threshold time. This makes it possible to increase the reliability of the judgment.

[0071] (7) In the present invention, the above-described freezing determination is performed on the ultrasonic sensor 5 attached to the metallic bumper V3, which is a vehicle body part. This makes it possible to appropriately perform freezing determination on the ultrasonic sensor 5 attached to the metallic bumper V3, which is prone to vibration transmission.

[0072] (8) In the present invention, the freezing determination unit 64 cancels the determination that the ultrasonic sensor 5 is in a frozen state when the indirect wave proximity detection is not established and the direct wave proximity detection is not established. This makes it possible to effectively avoid erroneous cancellation of the freezing determination.

[0073] (Modification) The present invention is not limited to the above embodiment. Therefore, the above embodiment can be modified as appropriate. Representative modified examples will be described below. In the following description of the modified examples, differences from the above embodiment will be mainly described. In addition, the same reference numerals are used for parts that are the same or equivalent to each other in the above embodiment and the modified examples. Therefore, in the following description of the modified examples, the description of the above embodiment can be appropriately used for components having the same reference numerals as the above embodiment, unless there is a technical contradiction or special additional explanation.

[0074] The present invention is not limited to the specific device configurations shown in the above embodiments. That is, for example, the vehicle V is not limited to a four-wheeled vehicle. Specifically, the vehicle V may be a three-wheeled vehicle, or a six- or eight-wheeled vehicle such as a cargo truck.

[0075] The temperature sensor 4 is typically an outside air temperature sensor, an engine intake air temperature sensor, or the like, which is prepared for another system. However, the present invention is not limited to this embodiment. That is, the temperature sensor 4 may be built into the ultrasonic sensor 5.

[0076] The arrangement of the ultrasonic sensors 5 is not particularly limited. For example, the two ultrasonic sensors 5 that are the subject of the indirect wave freezing judgment may be attached to a metallic vehicle body panel V2. Each of the multiple ultrasonic sensors 5 may have the same mounting height and / or mounting elevation angle, or may have different mounting heights and elevation angles. Some of the multiple ultrasonic sensors 5 may be provided in the front grille. In addition, some of the functions of the object detection device 6 may be provided in the ultrasonic sensors 5.

[0077] In the above embodiment, the ECU is configured such that the CPU reads out the program from the ROM or the like and starts it. However, the present invention is not limited to such a configuration. That is, for example, the ECU may be a digital circuit configured to enable the above-mentioned operation, such as an ASIC such as a gate array. ASIC is an abbreviation for Application Specific Integrated Circuit.

[0078] In this way, each of the above functional configurations and methods may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, each of the above functional configurations and methods may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, each of the above functional configurations and methods may be realized by one or more dedicated computers configured by combining a processor and a memory programmed to execute one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitive tangible recording medium as instructions to be executed by a computer. In other words, each of the above functional configurations and methods may be expressed as a computer program including a procedure for realizing the same, or as a non-transitive tangible recording medium storing the program.

[0079] The program according to the present disclosure, which enables the execution of various operations, procedures, or processes described in the above embodiments, may be downloaded or upgraded via V2X communication by an in-vehicle communication device. Alternatively, such a program may be downloaded or upgraded via a terminal device provided in a manufacturing plant, a maintenance plant, a dealer, or the like of the vehicle V. The storage destination of such a program may be a memory card, an optical disk, a magnetic disk, or the like.

[0080] The present invention is not limited to the specific operation examples and processing modes shown in the above embodiment. Specifically, for example, in the above judgment process, "less than" and "less than" are interchangeable. Similarly, "more than" and "exceed" are interchangeable. Furthermore, expressions that indicate common or similar concepts, such as "detection," "detection," and "measurement," are interchangeable.

[0081] Needless to say, the elements constituting the above-mentioned embodiment are not necessarily essential, except when expressly stated as essential or when considered to be obviously essential in principle. Furthermore, when the numbers, values, quantities, ranges, etc. of the components are mentioned, the present invention is not limited to the specific numbers, except when expressly stated as essential or when clearly limited to a specific number in principle. Similarly, when the shapes, directions, positional relationships, etc. of the components are mentioned, the present invention is not limited to the shapes, directions, positional relationships, etc., except when expressly stated as essential or when clearly limited to a specific shape, direction, positional relationship, etc. in principle.

[0082] The modified examples are not limited to the above examples. Specifically, a plurality of the embodiments may be combined with each other. Also, a plurality of the modified examples may be combined with each other. Furthermore, all or a part of any of the embodiments and all or a part of any of the modified examples may be combined with each other. [Explanation of symbols]

[0083] 1. In-vehicle systems 4 Temperature Sensor 5 Ultrasonic Sensor 5a First inner sensor 5b Second inner sensor 51 Ultrasonic microphone 6. Object detection device 64 Freeze determination section V Vehicle V3 Bumper

Claims

1. An object detection device (6) that detects an object using an ultrasonic sensor (5) mounted on a vehicle (V), a freezing determination unit (64) that determines that the ultrasonic sensor is in a frozen state when a predetermined freezing determination condition is satisfied; The freezing determination condition includes that an indirect wave approach detection is established in which an indirect wave travel time, which is the elapsed time between a transmission time and a reception time of an indirect wave in which an ultrasonic wave transmitted from one of the first ultrasonic sensor (5a) and the second ultrasonic sensor (5b), which are two ultrasonic sensors attached to the same vehicle body part (V3), is received by the other, is equal to or shorter than an indirect wave determination threshold time. Object detection device.

2. The freezing determination condition includes that the indirect wave proximity detection continues for a predetermined period of time or a predetermined number of times. The object detection device according to claim 1 .

3. The freezing determination condition includes that the indirect wave proximity detection is established by both the indirect wave in which an ultrasonic wave transmitted from the first ultrasonic sensor is received by the second ultrasonic sensor and the indirect wave in which an ultrasonic wave transmitted from the second ultrasonic sensor is received by the first ultrasonic sensor. The object detection device according to claim 1 .

4. The indirect wave determination threshold time is set to be equal to or less than the distance between the first ultrasonic sensor and the second ultrasonic sensor divided by the speed of sound at 0°C. The object detection device according to claim 1 .

5. The freezing determination condition includes that the indirect wave proximity detection is established and the outside air temperature is equal to or lower than a threshold temperature. The object detection device according to claim 1 .

6. The freezing determination condition includes that the indirect wave proximity detection is established, and that the direct wave proximity detection is established in which a direct wave path time, which is the elapsed time between a transmission time and a reception time of a direct wave in which an ultrasonic wave transmitted from the first ultrasonic sensor is received by the first ultrasonic sensor, is equal to or shorter than a direct wave determination threshold time. The object detection device according to claim 1 .

7. The vehicle body part is a metal bumper. The object detection device according to claim 1 .

8. the freezing determination unit cancels the determination that the ultrasonic sensor is in a frozen state when the indirect wave proximity detection is not established and when a direct wave path time, which is the elapsed time between a transmission time and a reception time of a direct wave in which an ultrasonic wave transmitted from the first ultrasonic sensor is received by the first ultrasonic sensor, is equal to or shorter than a direct wave determination threshold time, thereby resulting in a direct wave proximity detection being not established. The object detection device according to claim 1 .

9. An object detection program executed by an object detection device (6) that detects an object using an ultrasonic sensor (5) mounted on a vehicle (V), The process executed by the object detection device includes a freezing determination process for determining that the ultrasonic sensor is in a frozen state when a predetermined freezing determination condition is satisfied, The freezing determination condition includes that an indirect wave approach detection is established in which an indirect wave travel time, which is the elapsed time between a transmission time and a reception time of an indirect wave in which an ultrasonic wave transmitted from one of the first ultrasonic sensor (5a) and the second ultrasonic sensor (5b), which are two ultrasonic sensors attached to the same vehicle body part (V3), is received by the other, is equal to or shorter than an indirect wave determination threshold time. Object detection program.

10. The freezing determination condition includes that the indirect wave proximity detection continues for a predetermined period of time or a predetermined number of times. The object detection program according to claim 9 .

11. The freezing determination condition includes that the indirect wave proximity detection is established by both the indirect wave in which an ultrasonic wave transmitted from the first ultrasonic sensor is received by the second ultrasonic sensor and the indirect wave in which an ultrasonic wave transmitted from the second ultrasonic sensor is received by the first ultrasonic sensor. The object detection program according to claim 9 .

12. The indirect wave determination threshold time is set to be equal to or less than the distance between the first ultrasonic sensor and the second ultrasonic sensor divided by the speed of sound at 0°C. The object detection program according to claim 9 .

13. The freezing determination condition includes that the indirect wave proximity detection is established and the outside air temperature is equal to or lower than a threshold temperature. The object detection program according to claim 9 .

14. The freezing determination condition includes that the indirect wave proximity detection is established, and that the direct wave proximity detection is established in which a direct wave path time, which is the elapsed time between a transmission time and a reception time of a direct wave in which an ultrasonic wave transmitted from the first ultrasonic sensor is received by the first ultrasonic sensor, is equal to or shorter than a direct wave determination threshold time. The object detection program according to claim 9 .

15. The vehicle body part is a metal bumper. The object detection program according to claim 9 .

16. The freezing determination process cancels the determination that the ultrasonic sensor is in a frozen state when the indirect wave proximity detection is not established and when a direct wave path time, which is the elapsed time between a transmission time and a reception time of a direct wave in which an ultrasonic wave transmitted from the first ultrasonic sensor is received by the first ultrasonic sensor, is equal to or shorter than a direct wave determination threshold time, thereby resulting in a direct wave proximity detection being not established. The object detection program according to claim 9 .

Images