OBJECT DETECTION SYSTEM AND OBJECT DETECTION METHOD

Abstract

To provide an object detection system with which it is possible to detect an entity and eliminate virtual images under an environment where a plurality of reflection objects exist around a vehicle, even while the vehicle remains halted.SOLUTION: The present invention finds a plurality of candidates for an object position on the basis of a first signal that indicates a time when a reflected wave of a transmitted wave of a first distance sensor is received by the first distance sensor and a second signal that indicates a signal when a reflected wave of a transmitted wave of a second distance sensor is received by the second distance sensor, finds a logic signal that indicates a time when the reflected wave of the transmitted wave of the first distance sensor should be received by the second distance sensor and / or a logic signal that indicates a time when the reflected wave of the transmitted wave of the second distance sensor should be received by the first distance sensor, when it is assumed that an object exists for each of the plurality of candidates, and identifies a position of the object on the basis of a third signal that indicates a time when the reflected wave of the transmitted wave of the first distance sensor is received by the second distance sensor, a fourth signal that indicates a time when the reflected wave of the transmitted wave of the second distance sensor is received by the first distance sensor, and the logic signals.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an object detection system and an object detection method that detect the positions of a plurality of objects around a vehicle using a plurality of distance sensors. [Background technology]

[0002] Sonar devices that use ultrasonic waves are distance sensors that calculate the distance to an object based on the length of time between the time the transmitted wave is sent and the time the reflected wave is received. However, ultrasonic waves are usually sent in a wide range, so it is not easy to determine the direction of an object. The direction of an object can be determined by sending a transmitted wave in a narrow range and scanning while changing the transmission direction, but since scanning a wide range takes time, it is not practical to use this method in in-vehicle sonar, which needs to detect objects quickly even when moving at high speed.

[0003] For this reason, it is common for on-board sonar to use two or more sonars to calculate the object's position through triangulation. However, while this method is effective when there is only one object, when there are multiple objects, it creates a false image, making it impossible to pinpoint the object's position.

[0004] The object detection method of Patent Document 1 is known as a conventional technique for solving this problem. For example, the abstract of the document states that "to provide an object detection method and an object detection device capable of detecting an object with high reliability without installing a new laser device," and states that the solution is "an object detection method in a vehicle having at least two distance sensors 1 and 2, in which the relative position of an object detected within an overlapping range of the detection areas of the distance sensors 1 and 2 is determined by a triangulation method, and the apparent object generated by the triangulation method is obtained by dynamically observing the detected object." In other words, Patent Document 1 shows a method of eliminating apparent objects (virtual images) by repeating triangulation while moving the vehicle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-159680 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the object detection method of Patent Document 1 distinguishes between real objects and virtual images while the vehicle is moving, and therefore cannot eliminate virtual images when the vehicle is stopped, making it difficult to use the method for preventing false starts, for example.

[0007] Therefore, an object of the present invention is to provide an object detection system and an object detection method that can detect real objects and eliminate virtual images even when the vehicle is stopped in an environment where there are multiple reflective objects around the vehicle. [Means for solving the problem]

[0008] In order to achieve the above object, an object detection system mounted on a vehicle includes a first distance sensor and a second distance sensor that are installed in front of the vehicle and transmit a transmission wave to an object and receive a reflected wave reflected by the object, and an object detection device that detects a position of the object based on output signals from the first distance sensor and the second distance sensor, the object detection device determining a plurality of candidates for the position of the object based on a first signal indicating a time when the first distance sensor receives a reflected wave of the first distance sensor reflected by the object and a second signal indicating a time when the second distance sensor receives a reflected wave of the second distance sensor reflected by the object, and For each of the complements, at least one of a theoretical signal indicating a time when the reflected wave of the transmission wave of the first distance sensor should be received by the second distance sensor, when it is assumed that the object is present, or a theoretical signal indicating a time when the reflected wave of the transmission wave of the second distance sensor should be received by the object, is obtained, and the object detection system identifies the position of the object based on a third signal indicating a time when the reflected wave of the transmission wave of the first distance sensor reflected by the object is received by the second distance sensor, a fourth signal indicating a time when the reflected wave of the transmission wave of the second distance sensor reflected by the object is received by the first distance sensor, and the theoretical signal. Effect of the Invention

[0009] By using the present invention, it is possible to correctly recognize the position of a reflecting object without moving the vehicle in an environment where there are multiple reflecting objects, thereby improving the accuracy of functions such as preventing false starts, and realizing a safe and reliable driving assistance system. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with an object detection system according to an embodiment of the present invention; [Diagram 2] Schematic diagram of reflected wave reception times for left and right sonars [Diagram 3] Principle diagram of how a virtual image is calculated using waves reflected from multiple reflectors [Figure 4]FIG. 2 is an explanatory diagram of a processing procedure of an object detection device according to an embodiment of the present invention; [Figure 5A] Schematic diagram of the distances of the left sonar, reflectors, and right sonar paths [Figure 5B] Schematic diagram of the distances of the right sonar, reflectors, and left sonar paths [Figure 6] Comparison of reflected wave reception time after synchronization error correction and calculated reflected wave reception time [Figure 7] Illustration of synchronization error between left and right sonar DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An object detection system 10 according to an embodiment of the present invention will now be described with reference to the drawings.

[0012] <Overall Configuration of Object Detection System 10> FIG. 1 is a schematic diagram of a vehicle 1 equipped with an object detection system 10 according to the present embodiment. In the figure, 11L and 11R are left and right sonars that transmit and receive ultrasonic waves and are installed on the left and right sides of the front of the vehicle 1, and 12 is an object detection device that calculates the position of a reflecting object 2 around the vehicle 1 based on information from each sonar. Specifically, the object detection device 12 is a computer unit that includes a calculation device such as a CPU, a storage device such as a semiconductor memory, and hardware such as a communication device. The calculation device executes a program loaded into the storage device to realize the functions of each process in FIG. 4, but the following description will be given while omitting such well-known techniques as appropriate.

[0013] Here, L in Figure 1 La is the distance from the left sonar 11L to the reflector 2a, L Lb is the distance from the left sonar 11L to the reflector 2b, L Ra is the distance from the right sonar 11R to the reflector 2a, L Rb is the distance from the right sonar 11R to the reflector 2b.

[0014] In this object detection system 10, the left sonar 11L transmits ultrasonic waves as transmission waves in accordance with an instruction from the object detection device 12, and receives the reflected waves R from the reflecting object 2 at a time T L In FIG. 1, since there are two reflectors 2, the left sonar 11L measures the time T LaL and the time T when the reflected wave R from the reflecting object 2b is received. LbL The object detection device 12 measures the reflected waves R and transmits them to the object detection device 12. At this time, the object detection device 12 instructs the right sonar 11R to receive the reflected waves R as well, so the right sonar 11R also receives the reflected waves R from the reflecting objects 2a and 2b due to the transmitted waves from the left sonar 11L, and transmits the reflected waves R to the object detection device 12. LaR , T LbR is transmitted to the object detection device 12.

[0015] Next, the right sonar 11R transmits ultrasonic waves as transmission waves in accordance with an instruction from the object detection device 12, and receives the reflected waves R at a time T R In FIG. 1, since there are two reflectors 2, the right sonar 11R measures the time T RaR and the time T when the reflected wave R from the reflecting object 2b is received. RbR The object detection device 12 measures the reflected wave R and transmits it to the object detection device 12. At this time, the object detection device 12 instructs the left sonar 11L to receive the reflected wave R as well, so the left sonar 11L also receives the reflected wave R from the reflecting objects 2a and 2b due to the transmitted wave from the right sonar 11R, and transmits the reflected wave R to the object detection device 12. RaL , T RbL is transmitted to the object detection device 12.

[0016] <How to calculate the distance to the reflecting object from the time the reflected wave is received> Here, an example of the reflected wave reception time of each sonar will be described with reference to FIG. 2. The origin of FIG. 2(a) is the time when the left sonar 11L transmits a transmission wave, and the time T LaL , T LbL is the time when the transmission wave of the left sonar 11L is reflected by the reflecting objects 2a and 2b and returns to the left sonar 11L. Similarly, the origin of FIG. 2(b) is the time when the transmission wave of the right sonar 11R is transmitted, and time T RbR , TRaR is the time it takes for the transmitted wave from the right sonar 11R to be reflected by the reflecting objects 2b and 2a and return to the left sonar 11L.

[0017] Left sonar 11L to two time T LaL , T LbL When the object detection device 12 receives the ultrasonic wave, it can determine that there are two reflecting objects 2 in front of the vehicle 1, and calculates the distance to each reflecting object by taking into account the speed of ultrasonic waves (sound speed V). Note that the sound speed V increases or decreases depending on the temperature of the air through which the ultrasonic waves propagate, but by referring to the temperature indicated by a digital thermometer connected to the object detection device 12, the object detection device 12 can calculate the sound speed V in the current environment. Using the sound speed V calculated in this way, the distance L from the left sonar 11L to the reflecting object 2a can be calculated using the following formulas 1 and 2. La and the distance L from the left sonar 11L to the reflector 2b Lb can be calculated.

[0018]

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[0019]

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[0020] It is.

[0021] Similarly, two time periods T from right sonar 11R RbR , T RaR When the right sonar 11R receives the signal, the object detection device 12 calculates the distance L from the right sonar 11R to the reflecting object 2a using the following equations 3 and 4. Ra and the distance L from the right sonar 11R to the reflector 2b Rb can be calculated.

[0022]

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[0023]

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[0024] Since simultaneous transmission of ultrasonic waves from the two sonars causes interference, the object detection device 12 manages the transmission times of the left sonar 11L and the right sonar 11R so that they transmit ultrasonic waves with a time difference. However, if a transmission method that takes interference reduction or removal into consideration, such as a chirp signal using frequency modulation or a spread spectrum method using a spread code, is selectable, it is also possible for the left sonar 11L and the right sonar 11R to transmit simultaneously.

[0025] <The principle behind the creation of virtual images> The time T for each sonar measurement LaL , T LbL , T RbR , T RaR When the sonar receives the signal, the object detection device 12 calculates the distance L from each sonar to the two reflecting objects 2a and 2b by using the above formulas 1 to 4. La , L Lb , L Ra , L Rb However, it is not possible to identify the actual positions of the two reflecting objects 2a and 2b.

[0026] That is, the first combination in which reflectors 2a and 2b exist at the two black circles in FIG. 3 (a distance L from the left sonar 11L) La The arc (solid line) and the distance L from the right sonar 11R Ra The first reflector 2 exists at the intersection of the arcs (solid lines) of the left sonar 11L at a distance L Lb The arc (dashed line) and the distance L from the right sonar 11R Rb The second combination (distance L La Arc (solid line) and distance L Rb The first reflector 2 exists at the intersection of the arcs (dashed lines) of and the distance L Lb Arc (dashed line) and distance L RaSince none of the combinations (combinations in which a second reflecting object 2 exists at the intersection of the arcs (solid lines)) is inconsistent with triangulation, one of them (specifically, the second combination) cannot be determined to be a virtual image 3 and rejected.

[0027] In this way, if it is not possible to distinguish between the combination of the positions of real reflectors 2 and the combination of the positions of virtual images 3, if the output of the object detection device 12 is used as is for false start prevention control or emergency automatic braking control, the virtual image 3 of the reflector 2 that is actually on the roadside may be mistaken for the reflector 2 that is in front of the vehicle 1, which may induce unnecessary braking, or conversely, the real reflector 2 in front of the vehicle 1 may be mistaken for the virtual image 3 of the reflector 2 that is on the roadside, which may result in a collision with the real reflector 2.

[0028] <Procedure for eliminating virtual images> Therefore, in the object detection system 10 of this embodiment, when multiple reflectors 2 exist, a correct combination corresponding to the actual position of the reflector 2 is identified from multiple candidates that are not inconsistent with the triangulation method, thereby making it possible to prevent misidentification of the position of the reflector 2. An example of a processing procedure by this object detection system 10 is shown in FIG.

[0029] First, in step S1L, ultrasonic waves are transmitted from the left sonar 11L in response to a command from the object detection device 12. Next, in step S2L, the left sonar 11L receives a reflected wave R corresponding to the transmitted wave from the left sonar 11L, and in step S3R, the right sonar 11R receives a reflected wave R corresponding to the transmitted wave from the left sonar 11L.

[0030] Similarly, in step S1R, ultrasonic waves are transmitted from the right sonar 11R in response to a command from the object detection device 12. Next, in step S2R, the right sonar 11R receives a reflected wave R in response to the transmitted wave from the right sonar 11R, and in step S3L, the left sonar 11L receives a reflected wave R in response to the transmitted wave from the right sonar 11R.

[0031] In step S4L, the reflected wave extraction / distance calculation unit of the object detection device 12 detects the reflected wave R from the signal obtained in step S2L, and calculates the distance from the left sonar 11L to the reflecting object 2a or 2b based on the interval between the transmission time of the transmitted wave and the reception time of the reflected wave (Equation 1, Equation 2).

[0032] Similarly, in step S4R, the reflected wave extraction / distance calculation unit of the object detection device 12 detects the reflected wave R from the signal obtained in step S2R, and calculates the distance from the right sonar 11R to the reflecting object 2a or 2b based on the interval between the transmission time of the transmitted wave and the reception time of the reflected wave (Equation 3, Equation 4).

[0033] On the other hand, in step S5R, the reflected wave extraction / distance calculation unit of the object detection device 12 detects the reflected wave R from the signal obtained in step S3R, and calculates the distance L (FIG. 5A) which is the sum of the distance from the left sonar 11L to the reflecting object 2a and the distance from the reflecting object 2a to the right sonar 11R based on the interval between the transmission time of the transmitted wave and the reception time of the reflected wave. LaR In this step, the distance L is calculated, which is the sum of the distance from the left sonar 11L to the reflector 2b and the distance from the reflector 2b to the right sonar 11R. LbR Also requested.

[0034] Similarly, in step S5L, the reflected wave extraction / distance calculation unit of the object detection device 12 detects the reflected wave from the signal obtained in step S3L, and calculates the distance L (FIG. 5B) which is the sum of the distance from the right sonar 11R to the reflecting object 2a and the distance from the reflecting object 2a to the left sonar 11L based on the interval between the transmission time of the transmitted wave and the reception time of the reflected wave. RaL In this step, the distance L is calculated, which is the sum of the distance from the right sonar 11R to the reflector 2b and the distance from the reflector 2b to the left sonar 11L. RbL Also requested.

[0035] In step S6, the reflected wave combination creation unit of the object detection device 12 creates a combination of reflected waves using the outputs of steps S4L and S4R. For example, if there are two reflecting objects 2a and 2b in front of the vehicle 1 as shown in FIG. 1, two reflected waves R are detected in the processes of steps S4L and S4R (see FIG. 2(a) and (b)). Therefore, four distances L calculated using the reception times of the reflected waves R are calculated as follows: La , L Lb , L Ra , L Rb is used to create the reflected wave combination. In this case, the distance L La Arc and distance L Ra A pair of arcs with distance L Lb Arc and distance L Rb The pair of arcs with distance L La Arc and distance L Rb A pair of arcs with distance L Lb Arc and distance L Ra Let the pair of arcs in be the second combination.

[0036] In step S7, the reflecting object position calculation unit of the object detection device 12 calculates the theoretical position of the reflecting object 2 from the combination created in step S6 and the distance information. La Arc and distance L Ra The intersection point of the arc and the distance L Lb Arc and distance L Rb The intersection point of the two circular arcs is calculated and is set as the first theoretical position of the reflectors 2a and 2b (the two black circles in FIG. 3). La Arc and distance L Rb The intersection point of the arc and the distance L Lb Arc and distance L RaThe positions of the intersections of the arcs are calculated and set as the second theoretical positions of the reflectors 2a and 2b (the two white circle positions in FIG. 3). Note that in FIG. 3, the first theoretical position (the two black circle positions in FIG. 3) is the correct position of the reflectors 2a and 2b, and the second theoretical position (the two white circle positions in FIG. 3) is the position of the virtual images 3a and 3b, but in this step, both theoretical positions are set as candidate positions of the reflector 2 without determining which theoretical position is correct.

[0037] In step S8, the received wave theoretical value calculation unit of the object detection device 12 calculates the theoretical value of the time when the reflected wave R in response to the transmission wave from the left sonar 11L is received by the right sonar 11R (see FIG. 5A), and the theoretical value of the time when the reflected wave R in response to the transmission wave from the right sonar 11R is received by the left sonar 11L (see FIG. 5B). This calculation is performed for all position candidates using the position candidates of the reflecting objects 2a, 2b obtained in step S7, and the positions and sound speed V of each sonar that are given in advance. The calculation in this step determines the calculated reflected wave reception time (time T a1 , T b1 ) and the calculated reflected wave reception time from the second theoretical position (time T a2 , T b2 ) is calculated.

[0038] In step S9, the time synchronization error correction unit of the object detection device 12 outputs a time signal that eliminates the synchronization error ΔT between the left sonar 11L and the right sonar 11R based on the outputs of steps S5L and S5R. Since the left sonar 11L and the right sonar 11R are independent devices, their respective built-in timers manage the time. The object detection device 12 issues instructions to synchronize the managed times of both built-in timers, but a slight synchronization error ΔT occurs between both built-in timers due to delays in the time synchronization instructions and changes over time.

[0039] When the reflected wave R from the transmitted wave of the left sonar 11L is received by the left sonar 11L, and when the reflected wave R from the transmitted wave of the right sonar 11R is received by the right sonar 11R, no synchronization error occurs between the transmission time and the reception time because transmission and reception are performed within the same device, but when the reflected wave R from the transmitted wave of the left sonar 11L is received by the right sonar 11R (FIG. 5A) or when the reflected wave R from the transmitted wave of the right sonar 11R is received by the left sonar 11L (FIG. 5B), the transmitting and receiving sonars are different, so there is an effect of a synchronization error between the two sonars. Therefore, the object detection device 12 corrects the synchronization error using the following method.

[0040] The distance L from when the left sonar 11L transmits to when it is reflected by the reflector 2a and received by the right sonar 11R LaR (Fig. 5A) and the distance L from the right sonar 11R until the transmission wave is reflected by the reflecting object 2a and received by the left sonar 11L. RaL (Figure 5B) simply follows the same route in the opposite direction, so the distance is the same, i.e., L LaR =L RaL Therefore, if there is no synchronization error ΔT between the left and right sonars, the transmission and reception time T LaR and the transmission and reception time T RaL should also be the same.

[0041] Figure 7 is a graph illustrating the time at which each sonar receives reflected wave R in the environments of Figures 5A and 5B when the built-in timer of the right sonar 11R is delayed by a synchronization error ΔT compared to the built-in timer of the left sonar 11L.

[0042] FIG. 7(a) shows the time T LaL 7(b) shows the time T before correction when the reflected wave of the left sonar 11L is received by the right sonar 11R under the same environment. LaR ' and True Time T LaR In this example, the built-in timer of the right sonar 11R on the receiving side is slower than the built-in timer of the left sonar 11L on the transmitting side by a synchronization error ΔT, so the uncorrected time T detected using the built-in timer of the right sonar 11R on the receiving side is LaR' is the true time T based on the transmission time of the left sonar 11L. LaR Therefore, as shown in the following equation 5, the time before correction T LaR By adding the synchronization error ΔT to the distance L LaR True time T, which corresponds to the value obtained by dividing by the speed of sound V LaR can be calculated.

[0043]

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[0044] FIG. 7(c) shows the time T RaR 7(d) shows the time T before correction when the reflected wave of the right sonar 11R is received by the left sonar 11L under the same environment. RaL ' and True Time T RaL In this example, the built-in timer of the left sonar 11L on the receiving side is faster than the built-in timer of the right sonar 11R on the transmitting side by a synchronization error ΔT, so the uncorrected time T detected using the built-in timer of the left sonar 11L on the receiving side is RaL ' is the true time T based on the transmission time of the right sonar 11R. RaL Therefore, as shown in the following equation 6, the time before correction T RaL By subtracting the synchronization error ΔT from RaL True time T, which corresponds to the value obtained by dividing by the speed of sound V RaL can be calculated.

[0045]

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[0046] Time T in Equation 5 LaR is the time T in Eq. RaLis obtained by subtracting the synchronization error ΔT. Therefore, by calculating the average value of both, the reception time of the reflected wave R in the absence of the synchronization error ΔT can be calculated regardless of the size of the synchronization error ΔT, and therefore in this step, this average value is output as the corrected reception time of the reflected wave.

[0047] In step S10, the difference calculation unit of the object detection device 12 calculates the difference between the calculated reflected wave reception time and the corrected reflected wave reception time using the output of step S8 and the output of step S9. An example of the difference calculation in this step will be described with reference to FIG.

[0048] FIG. 6(a) shows the reflected waves R from the actual reflecting objects 2a and 2b in the environment of FIG. 1, which were synchronously corrected in step S9. a , R b Reception time (time T a , T b 6(b) and (c) show the calculated reflected wave reception times (time T a1 , T b1 ) and the calculated time of reception of the reflected wave from the second theoretical position (the two white circles in Figure 3) (time T a2 , T b2 ).

[0049] In this step, by comparing the actual measured value of the reflected wave reception time in Figure 6(a) with the theoretical values ​​of the reflected wave reception time in Figures 6(b) and (c), it is determined which of the first theoretical position and the second theoretical position is the more reliable candidate.

[0050] Therefore, the reliability of the first theoretical position (the two black circle positions in Figure 3), which is the first candidate for the reflector position, is calculated, for example, using the following equation 7, and the reliability of the second theoretical position (the two white circle positions in Figure 3), which is the second candidate for the reflector position, is calculated, for example, using the following equation 8.

[0051]

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[0052]

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[0053] As is clear from FIG. 6, if δ, which is the difference between the actual measurement value (FIG. 6(a)) and the theoretical value (FIGS. 6(b)(c)), is small, it is considered that the actual measurement value and the theoretical value have a high similarity, and therefore the smaller calculation result of Equation 7 and Equation 8 is determined to be the candidate with a higher reliability. Therefore, in the example of FIG. 6, the first theoretical position with the smaller δ is determined to be more likely to be the actual position of the reflecting object 2. Note that Equation 7 and Equation 8 are only one example of a formula for calculating reliability, and for example, the sum of absolute values ​​can be used instead of the sum of squares.

[0054] Through the above processes, in this step, the candidate with the highest reliability is selected from among the multiple reflecting object position candidates, and the position of the reflecting object corresponding to that candidate is output as the position of the reflecting object 2.

[0055] According to the object detection system of the present embodiment described above, in an environment where a plurality of reflecting objects are present, the position of the reflecting object can be correctly recognized without moving the vehicle, and the accuracy of the erroneous start prevention function, etc. can be improved, thereby realizing a safe and reliable driving assistance system. Note that, although the object detection system using sonar has been exemplified above, the present invention may be applied to an object detection system using other types of distance sensors such as millimeter wave radar and LiDAR instead of sonar. [Explanation of symbols]

[0056] 1 vehicle, 10 Object detection systems, 11 Sonar, 11L Left Sonar, 11R Right Sonar, 12 Object detection device, 2, 2a, 2b reflective objects, 3a, 3b virtual image

Claims

1. An object detection system mounted on a vehicle, a first distance sensor and a second distance sensor that are installed in front of the vehicle and transmit a transmission wave to an object and receive a reflected wave reflected by the object; an object detection device that detects a position of the object based on output signals of the first distance sensor and the second distance sensor, The object detection device includes: determining a plurality of candidates for the position of the object based on a first signal indicating a time at which the first distance sensor receives a reflected wave of the transmission wave of the first distance sensor reflected by the object and a second signal indicating a time at which the second distance sensor receives a reflected wave of the transmission wave of the second distance sensor reflected by the object; For each of the plurality of candidates, at least one of a theoretical signal indicating a time when the second distance sensor should receive a reflected wave of the first distance sensor reflected by the object, and a theoretical signal indicating a time when the first distance sensor should receive a reflected wave of the second distance sensor reflected by the object, assuming that the object is present; a position of the object is identified based on a third signal indicating a time when the second distance sensor receives a reflected wave of the first distance sensor reflected by the object, a fourth signal indicating a time when the first distance sensor receives a reflected wave of the second distance sensor reflected by the object, and the theoretical signal; and correcting a synchronization error between a built-in timer of the first distance sensor and a built-in timer of the second distance sensor; correcting the synchronization error by calculating an average value of the third signal and the fourth signal; An object detection system, comprising: a processor for processing the object; a processor for processing the object; and a processor for processing the object;

2. 2. The object detection system according to claim 1, The object detection device includes: Calculating a first distance, which is a distance between the first distance sensor and the object, by dividing a multiplication result of the first signal and the sound speed by two; Calculating a second distance, which is a distance between the second distance sensor and the object, by dividing a multiplication result of the second signal and the sound speed by two; An object detection system, comprising: a point of intersection between an arc of the first distance from the first distance sensor and an arc of the second distance from the second distance sensor, the point of intersection being a candidate for the position of the object.

3. 1. An object detection method for detecting an object using a first distance sensor and a second distance sensor installed in a front portion of a vehicle, comprising: outputting a first signal indicating a time at which the first distance sensor receives a reflected wave from the object due to a transmitted wave from the first distance sensor; outputting a second signal indicating a time at which the second distance sensor receives a reflected wave from the object due to a transmitted wave from the second distance sensor; outputting a third signal indicating a time when a reflected wave from the object, which is a transmission wave from the first distance sensor, is received by the second distance sensor; outputting a fourth signal indicating a time when the first distance sensor receives a reflected wave from the object, the reflected wave being transmitted by the second distance sensor; Calculating a first distance, which is a distance between the first distance sensor and the object, by dividing the first signal by twice the speed of sound; Calculating a second distance, which is a distance between the second distance sensor and the object, by dividing the second signal by twice the speed of sound; determining an intersection of an arc of the first distance from the first distance sensor and an arc of the second distance from the second distance sensor as a candidate for the position of the object; obtaining at least one of a theoretical signal indicating a time when a wave transmitted from the first distance sensor should be reflected by the object and received by the second distance sensor, when it is assumed that the object is present among the candidates, and a theoretical signal indicating a time when a wave transmitted from the second distance sensor should be reflected by the object and received by the first distance sensor; calculating an average value of the third signal and the fourth signal; calculating a reliability of the candidate object location based on the average value and the theoretical signal; 1. An object detection method comprising:

Images