OBJECT DETECTION DEVICE

Abstract

An object detection device (10) which is implemented on a movable body (30), comprising an object detection sensor (20) which emits a search wave (25) and receives a reflected wave (26) of the search wave (25) as detection information of an object (50) and detects the object (50) present in the surroundings of the movable body (30) on the basis of the detection information, wherein the object detection sensor (20) receives the reflected wave (26) within a predetermined object detection period (Td) after the search wave (25) is transmitted, the object detection device (10) includes: a distance calculating section which calculates a distance (D) between the movable body (30) and the object (50) based on a time at which the reflected wave (26) is received; a speed detecting section which detects a speed (V) of the movable body (30); a frequency detection section which, in a period in which the speed (V) of the movable body (30) is continuously equal to or greater than a vehicle speed threshold (Vth), detects a first occurrence frequency (CA) with which the calculated distance (D) within a predetermined first disturbance detection period (T1) in the object detection period (Td) is equal to or less than a distance threshold (Dth), and the frequency detection section detects a second occurrence frequency (CB) of a reception signal received during a noise detection period (Tn), wherein the noise detection period (Tn) is different from a transmission period (Tb) of the search wave (25) and the object detection period (Td) and is within a transmission period of the search wave (25); and a fault determination section which determines a presence of occurrence of a fault when the first occurrence frequency (CA) is equal to or greater than a first fault determination threshold (CAth) before the first fault determination period (T1) has elapsed, and the disturbance determination section determines a presence of occurrence of a disturbance when the second occurrence frequency (CB) detected by the frequency detection section within a disturbance determination period (T2) is equal to or greater than a threshold value (CBth).

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based on and claims priority from prior Japanese Patent Application No. 2014-215094 filed on October 22, 2014, the disclosure of which is incorporated herein by reference. BACKGROUND (TECHNICAL FIELD)

[0002] The invention relates to an object detection device which detects peripheral objects. (Related prior art)

[0003] Conventionally, techniques have been proposed in which a positioning sensor, such as an ultrasonic sensor, is installed in a host vehicle to detect objects present in the surroundings of the host vehicle, including a preceding vehicle, a pedestrian, and an obstacle. Furthermore, based on the detection results, various controls are performed to improve the driving safety of the host vehicle, such as operating the brake unit and alerting the driver (see, for example, JP 2014 - 89077 A).Furthermore, DE 44 33 957 A1 discloses a method for ultrasonic obstacle detection, in which in successive measuring cycles an ultrasonic pulse (SE) is emitted by at least one ultrasonic transmitter unit and then ultrasonic waves are detected by an associated ultrasonic receiver unit and the detected ultrasonic waves are evaluated to detect obstacles reflecting ultrasonic waves, wherein during the evaluation, evaluation echograms are obtained from echograms measured in the successive measuring cycles by an evaluation in which, in order to obtain a new evaluation echogram from a previous one, the echo envelope amplitudes of the previous evaluation echogram are increased at points where the amplitudes of the newly measured echogram are higher than a predetermined threshold value and are decreased at points where they are lower than a predetermined threshold value.US 5 319 611 A DE discloses a method for determining distance data in a time-of-flight distance measuring system based on emitting energy emissions and analyzing echoes resulting from the emissions. DE 11 2010 005 571 B4 relates to an obstacle detection device that improves time intervals for detecting an obstacle by using ultrasonic sensors mounted in a front and rear area and on the right and left sides of a vehicle without reducing the reliability of detecting an obstacle existing around the vehicle. DE 199 24 755 A1 discloses an ultrasonic-based distance detection device with a disturbance determination device.

[0004] In the object detection device disclosed in JP 2014-89077 A, a plurality of positioning sensors are installed in the host vehicle to calculate the position of an object in the vehicle width direction according to the triangulation principle. Furthermore, when the position of the object in the vehicle width direction is within a range of the vehicle width, it is determined that the object is detected. When the position of the object in the vehicle width direction is not within the range of the vehicle width, it is determined that the object is not detected. According to the control, the object present at a position where the probability of contact with the host vehicle is lower is prevented from being erroneously detected.

[0005] In a case where an object is detected using positioning sensors, the object may be detected due to the influence of external environments such as snow, rain, and mutual interaction with a sensor of another vehicle. In this case, there is a risk that control to prevent contact with the detected object may be executed in an undesired manner, or that control to prevent contact may not be executed even though it should or must be executed. SHORT DESCRIPTION

[0006] The object of the present invention is achieved by the object detection device according to the independent claim. The dependent claims are directed to advantageous developments of the invention.

[0007] An embodiment provides an object detection device that can accurately detect a situation in which the reliability of detection information of an object decreases due to the influence of external environments.

[0008] An embodiment provides an object detection device according to claim 1. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The attached drawings show: Fig. 1 is a drawing showing a schematic configuration of an object detecting device; Fig. 2 is a drawing for explaining a method for calculating a position of an object; Fig. 3 a drawing representing a search wave and a reflected wave on the time axis; and Fig. 4 is a flowchart showing a procedure of a fault detection process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Various embodiments will be described below with reference to the accompanying drawings. Throughout the drawings, components that are identical or similar to others are given the same reference numerals to omit unnecessary explanation.

[0011] An embodiment in which an object detection device installed in a mobile body is embodied will be described with reference to the drawings. The object detection device according to the present embodiment is an in-vehicle device installed in a vehicle, which is a mobile body. The object detection device receives detection information about an object from a positioning sensor serving as an object detection sensor for detecting an object (for example, another vehicle, a road structure, or the like) present in the vicinity of the vehicle. First, the schematic configuration of an object detection system for a vehicle according to the present embodiment will be described with reference to Fig. 1 explained.

[0012] In Fig. 1, a positioning sensor 20 is, for example, an ultrasonic sensor and has a function of transmitting ultrasonic waves with wavelengths of 20 to 100 kHz as search waves and receiving the search waves reflected from an object as reflected waves. In the present embodiment, four sensors are mounted on the front portion (for example, the front bumper) of a vehicle 30 at predetermined intervals so as to be arranged in the vehicle width direction perpendicular to the traveling direction of the vehicle 30. More specifically, the positioning sensor 20 includes two center sensors (a first center sensor 21 and a second center sensor 22) mounted near a center line 31 of the vehicle width and at symmetrical positions with respect to the center line 31, and corner sensors 23, 24 arranged at the left corner and right corner of the vehicle 30, respectively.Note that the tracking sensors 20 are also arranged at the rear part (e.g., the rear bumper) of the vehicle 30. However, since the mounting positions and functions of the tracking sensors 20 of the rear part are the same as those of the tracking sensors 20 of the front part, explanations thereof are omitted.

[0013] In each of the positioning sensors 20, a direct detection area 40 is defined as an area in which reflected waves (direct waves) of the search waves emitted therefrom can be received. The positioning sensors 20 are mounted such that the direct detection areas 40 of the adjacent two positioning sensors 20 overlap. It is noted that in Fig. 1, only direct detection areas 41, 42 of the two center sensors 21, 22 are shown. However, the direct detection areas 40 are also set for corner sensors 23, 24. Moreover, the direct detection areas 40 of the adjacent two sensors overlap. A threshold value of the amplitude of a reflected wave is set in the locating sensors 20. When the locating sensor 20 receives a reflected wave with the amplitude equal to or greater than the threshold value, the locating sensor 20 transmits detection information, including the time at which the locating sensor 20 receives the reflected wave, to an ECU (electronic control unit) 10 serving as the object detection device.

[0014] The ECU 10 is mainly configured by a microcomputer including a CPU and various memories. The ECU 10 determines the presence or absence of an object 50 in the vicinity of the vehicle based on the detection information of the object 50 received from the tracking sensors 20. More specifically, the ECU 10 outputs a control signal to the tracking sensors 20 to instruct the tracking sensors 20 to emit ultrasonic waves from each of the tracking sensors 20 at predetermined emission periods (for example, at intervals of several hundred ms). Furthermore, the ECU 10 determines whether or not an object is present in the vicinity of the vehicle based on the detection information of the object 50 received from the tracking sensors 20.If it is determined that an object 50 is present in the vicinity of the vehicle, the ECU 10 performs steering wheel control or deceleration control of the vehicle 30 as contact avoidance control, or outputs a notification to the driver of the vehicle 30 by means of a warning sound so that the vehicle 30 does not come into contact with the object 50.

[0015] The location sensors 20 transmit ultrasonic waves from the sensors 21 to 24 in a predetermined order at predetermined intervals in accordance with the transmission command received from the ECU 10. In the present embodiment, the first center sensor 21 first transmits ultrasonic waves in accordance with the command from the ECU 10, then the second center sensor 22 transmits ultrasonic waves, and finally the two corner sensors 23, 24 transmit ultrasonic waves. Note that the sensors 21 to 24 transmit search waves at intervals so as not to interfere with each other.

[0016] The ECU 10 calculates a position (coordinates) of the object 50 relative to the vehicle 30 based on the triangulation principle using the object detection information received from the positioning sensors 20. According to the triangulation principle, as is known, coordinates of a measurement point are calculated from a known distance between two points and distances between the known two points and the measurement point. Based on this principle, the ECU 10 calculates an estimated position of the object 50 in the vehicle width direction using the distance between the two positioning sensors 20 whose direct detection areas 40 overlap with each other and the distances between the positioning sensors 20 and the object 50.

[0017] Fig. Fig. 2 is a drawing for explaining a method for calculating the detected position of the object 50 and shows the two center sensors 21, 22 and the object 50 positioned in front of the center sensors 21, 22 in a plan view. It is noted that in Fig. 2, the first center sensor 21 is a direct detection sensor that transmits a search wave and receives a direct wave. The second center sensor 92 is an indirect detection sensor that receives a reflected wave (indirect wave) of the ultrasonic wave transmitted by another sensor. The direct detection sensor and the indirect detection sensor are two sensors that perform triangulation.

[0018] The ECU 10 provides a coordinate system in which the X-axis is a straight line connecting the two center sensors 21, 22, and the Y-axis is a straight line passing through the center of the first center sensor 21 and the second center sensor 22 and is perpendicular to the X-axis. The ECU 10 calculates an X-coordinate (x) and a Y-coordinate (y) of the coordinate system as a detection position of the object 50. More specifically, the ECU 10 causes the direct detection sensor (the first center sensor 21 in Figure 2) to transmit the search wave 25. Then, when the first center sensor 21 receives the reflected search wave 25 as the direct wave 26, the ECU 10 calculates the distance L1 between the first center sensor 21 and the object 50 based on the received direct wave 26.Moreover, when the second center sensor 22 receives the reflected search wave 25 as the indirect wave 26, the ECU 10 calculates the distance L2 between the second center sensor 92 and the object 50 based on the received indirect wave 27.

[0019] The distance between the origin O, which is the intersection point of the X-axis and the Y-axis, and the first sensor 21, and the distance between the origin O and the second sensor 22, which are distances d, are equal to each other and are stored in advance in the ECU 10. Furthermore, the ECU 10 calculates the time period between the time the first center sensor 21 transmits the search wave 25 and the time the first center sensor 21 receives the direct wave 26 as a first time period t1, and calculates the time period between the time the first sensor 21 transmits the search wave 25 and the time the second sensor 22 receives the indirect wave 27 as a second time period t2. In this case, the value obtained by multiplying the first time period t1 by the speed of sound is twice the first distance L1.The value obtained by multiplying the second time period t2 by the speed of sound is the sum of the first distance L1 and the second distance L2. The ECU 10 calculates the coordinates (x, y) of the object 50 by performing a calculation based on triangulation using the distance 2d between the center sensors 21 and 22, the first time period t1, and the second time period t2.

[0020] It is noted that in Fig. 2, an example is explained in which the first center sensor 21 is a direct detection sensor and the second center sensor 22 is an indirect detection sensor. However, all combinations of two sensors that are adjacent to each other among the four sensors 21 to 24 result in combinations of the direct detection sensor and the indirect detection sensor. Thus, the detection position of the object can be calculated not only by the combination of the first center sensor 21 and the second center sensor 22, but also by all other combinations, by means of the principle of triangulation using the direct detection sensor and the indirect detection sensor. Furthermore, with respect to the location sensors 20 of the rear part of the vehicle, the detection position of the object present in the vicinity of the vehicle is also calculated by the principle of triangulation from all the combinations of the two sensors that are adjacent to each other.

[0021] The ECU 10 sets a reliability level determination counter N, which serves as an indicator indicating a probability of the presence of an object based on the frequency with which the location sensor 20 detects the same object. In the present embodiment, the reliability level determination counter N is incremented and decremented for each of the sensors. If the frequency of detecting the same object by the same sensor is higher, the counter value is set to a larger value (to correspond to a higher reliability level). Then, when the reliability level determination counter N exceeds a threshold value, it is determined that the object to be controlled is present in the surroundings of the vehicle 30, thereby allowing the contact avoidance control to intervene.

[0022] In addition, if it is determined that the object detected during the last calculation period and the object detected during the current calculation period are different from each other, the reliability level determination counter N is reset. The reliability level determination counter N corresponds to a reliability of an object.

[0023] Fig. Figure 3 is a drawing representing waveforms of the search wave 25 and the reflected wave 26 on the time axis. It is noted that Fig. 3 shows a transmission period of the search wave 25 in a sensor 20. The sensor 20 starts transmitting the search wave 25 at a transmission start time ts. During a constant time period Tb, the sensor 20 continuously transmits the search wave 25. Moreover, when the transmitted search wave 25 is reflected by the object 50, the sensor 20 receives a reflected wave 26 at a time tx, by which the time period corresponding to the distance from the object 50 has elapsed, within a predetermined object detection period Td (for example, several tens of ms) after the search wave 25 is transmitted. It is noted that as the distance between the vehicle 30 and the object 50 increases, the time period between the start time tw of the object detection period Td and the reception time tx of the reflected wave 26 becomes longer.The object detection time period Td is a reception time period of the reflected wave 26 for detecting the presence or absence of the object 50 which may become an obstacle to the vehicle 30.

[0024] In the present embodiment, a noise detection period Tn is set during a transmission period determined with respect to the transmission period of the search wave 25, during a period different from the object detection period Td and the transmission period Tb of the search wave 25. The ECU 10 performs a noise detection process based on the presence and absence of a reception signal (noise signal) within the noise detection period Tn. More specifically, as shown in Fig. 3, the noise detection period Tn is defined as a predetermined period immediately before the transmission start time Ts of the search wave 25. If a reception signal with an amplitude equal to or greater than a threshold is detected within the noise detection period Tn, it is determined that noise is present. Note that the transmission period determined with respect to the transmission period of the search wave 25 is a period between the time when a sensor 20 transmits the search wave 25 and the time when the same sensor 20 transmits the next search wave 25.

[0025] If snow or rain comes into contact with the positioning sensor 20, the sensor 20 may detect an extremely short distance. Furthermore, if snow or rain comes into contact with a sensor surface of the positioning sensor 20, or if mutual interference with a sensor of another vehicle is caused, noise may occur. When the extremely short detection distance and the generation of noise are due to the external environment such as snow, rain, and mutual interference with a sensor of another vehicle, the extremely short detection distance and noise are often continuously generated as long as the external environment remains unchanged.

[0026] Therefore, in the present embodiment, the frequency of occurrence of interference signals at the same time within the transmission period determined with respect to the transmission period of the search wave 25 is detected to determine the presence or absence of interference based on the occurrence frequency. Specifically, (1) a reflected wave detected during a predetermined short-distance detection period Th (see Fig. 3) including the start time tw of the object detection period Td, or (2) a noise signal received during the noise detection period Tn is assumed to be a noise signal to detect the frequency (frequency of occurrence) of noise signals within a predetermined detection period. Then, when the frequency of occurrence of noise signals becomes equal to or greater than a threshold value, it is determined that noise is present.

[0027] Next, the procedure of a failure detection process according to the present embodiment will be described with reference to FIG. Fig. 4. This process is performed by the ECU 10 at predetermined calculation periods (for example, periods shorter than the emission period of the search wave of the sensor 20 (for example, intervals of several milliseconds to several tens of milliseconds)). It is noted that in the present embodiment, the Fig. 4 is performed for each sensor to determine the presence or absence of a fault in each sensor.

[0028] In Fig.4, the ECU 10 determines whether or not it is currently in the object detection period Td in step S101. If it is in the object detection period Td, the process proceeds to step S102, in which the sensor 20 receives a reflected wave, and the ECU 10 determines whether or not a detection distance D calculated based on the received reflected wave is equal to or smaller than a detection distance threshold Dth (for example, several tens of cm). More specifically, the ECU 10 determines whether or not the center sensors 21, 22 mounted on the front part of the vehicle 30 have received the reflected wave. If a negative determination is made in step S102, the current routine is terminated. If an affirmative determination is made in step S102, the process proceeds to step S103.

[0029] In step S103, the ECU 10 determines whether the speed (vehicle speed V) of the vehicle 30 is equal to or greater than a distance detection permission vehicle speed Vth (for example, several tens of km / h). Note that the vehicle 30 is provided with a vehicle speed sensor 32. Herein, a detection value of the vehicle speed sensor 32 is used as the vehicle speed V.

[0030] If V≥Vth, the process proceeds to step S104, in which the ECU 10 increments a distance determination counter CA by a predetermined value (for example, one). In the subsequent step S105, the ECU 10 determines whether or not the distance determination counter CA is equal to or greater than a first disturbance determination threshold value CAth. If CA<CAth, the process proceeds to step S107, in which the ECU 10 determines whether or not a disturbance determination period T1 based on the detection distance has elapsed. As the disturbance determination period T1, a period of time is set by defining as a starting point a time when it is initially determined that the detection distance D calculated based on the reflected wave is equal to or smaller than the determination distance threshold value Dth after the distance determination counter CA is reset.The time span lies between the starting point and the time at which a predetermined period of time has elapsed.

[0031] If it is determined in step S107 that the abnormality determination period T1 has not elapsed, the routine is stopped. On the other hand, if it is determined that the abnormality determination period T1 has elapsed, the process proceeds to step S108, in which the ECU 10 resets the distance determination counter CA, and then the routine is terminated. In this case, during the abnormality determination period T1, the frequency of occurrence of a state in which the detection distance D is extremely short is lower. Therefore, the ECU 10 does not determine that a abnormality has occurred. Note that if it is determined that the speed V is lower than the distance determination permission vehicle speed Vth, the ECU 10 similarly resets the distance determination counter CA in step S108.

[0032] In contrast, if the distance detection counter CA has become equal to or greater than the first abnormality detection threshold value CAth before the abnormality detection period T1 elapses, an affirmative determination is made in step S105. Then, the process proceeds to step S106, in which the ECU 10 determines that a abnormality exists.

[0033] If it is determined in step S101 that it or the ECU 10 is not in the object detection period Td, the process proceeds to step S109. In step S109, the ECU 10 determines whether or not it is currently in the noise detection period Tn. If it is in the noise detection period Tn, the process proceeds to step S110, in which the ECU 10 determines whether or not a noise signal is being received. If no noise signal is being received, the routine is stopped.

[0034] In contrast, if a noise signal is received during the noise detection period Tn, the process proceeds to step S111, in which the ECU 10 increments a noise determination counter CB by a predetermined value (for example, one). In the subsequent step S112, the ECU 10 determines whether or not the noise determination counter CB is equal to or greater than a second disturbance determination threshold CBth. If CB < CBth, the process proceeds to step S114, in which the ECU 10 determines whether or not a disturbance determination period T2 based on the noise has elapsed. As the disturbance determination period T2, a period is set by defining as a start point a time when it is initially determined that a noise signal is received during the noise detection period Tn after the noise determination counter CB is reset.The time span lies between the starting point and the time at which a predetermined period of time has elapsed.

[0035] In step S114, if it is determined that the failure determination period T2 has not elapsed, the routine is stopped. Conversely, if it is determined that the failure determination period T2 has elapsed, the process proceeds to step S115, where the noise determination counter CB is reset, and then the routine is terminated. If the noise determination counter CB becomes equal to or greater than the second failure determination threshold CBth before the failure determination period T2 elapses, an affirmative determination is made in step S112, and then the process proceeds to step S113, where it is determined that a failure is present.

[0036] In a situation where the influence of external environmental factors such as snow, rain, and mutual interference with a sensor of another vehicle is exerted, the reliability of detection information of an object obtained by the location sensor 20 becomes lower. Therefore, in the present embodiment, when it is determined that there is a disturbance in step S106 or step S113, the threshold value of the reliability level determination counter N for allowing the contact avoidance control to intervene is increased or changed to be increased. Therefore, in a situation where the reliability of the detection information of an object obtained by the location sensor 20 is lower, the required number of detections until the control intervenes is increased.

[0037] In accordance with the above-described embodiment, the following outstanding advantages can be obtained.

[0038] The occurrence frequency of noise signals at the same time within a predetermined transmission period, determined with respect to the transmission period of the search wave 25, is detected to determine the presence or absence of noise based on the detected occurrence frequency. The location sensor 20 may detect an extremely short distance or generate noise due to being affected by external environmental factors such as snow, rain, and mutual interference with a sensor of another vehicle. Moreover, if the extremely short detection distance and the generation of noise are due to the external environment, the extremely short detection distance and the generation of noise will often continue as long as the external environment remains unchanged.By focusing on these points, the above configuration can separate the presence or absence of external environmental influences from actual obstacles. As a result, the situation in which the reliability of an object's detection information is deteriorating due to the influence of external environmental influences can be accurately determined.

[0039] More specifically, as an aspect of interference detection, the reflected wave received during the short-distance detection period Th, defined within a period including the start time tw of the object detection period Td during the transmission period determined with respect to the transmission period of the search wave 25, is regarded as an interference signal, and the presence or absence of interference is determined from the occurrence frequency of the interference signal. If snow or rain comes into contact with the location sensor 20, the sensor 20 may detect an extremely short distance. Moreover, if snow or rain is a cause, the extremely short detection distance is frequently caused. By focusing on these points, the above configuration can accurately determine where the reliability of object detection information decreases due to the influence of snow or rain.

[0040] Furthermore, as another aspect of noise determination, a reception signal received during the noise detection period Tn determined within a period different from the transmission period Tb of the search wave 25 and the object detection period Td during the transmission period determined with respect to the transmission period of the search wave 25 is regarded as a noise signal, and the presence or absence of noise is determined from the occurrence frequency of the noise signal. When snow or rain comes into contact with the positioning sensor 20, or mutual interference with a sensor of another vehicle is caused, noise may occur. Furthermore, when snow, rain, or mutual interference with a sensor of another vehicle is a cause, noise is frequently generated.By focusing on these points, the above configuration can accurately detect the situation where the reliability of the detection information of an object is lowered due to the influence of snow, rain, or mutual interference with a sensor of another vehicle.

[0041] In the interference detection process based on the detection distance D, interference detection is performed under the condition that the vehicle speed V is equal to or greater than the distance detection permission vehicle speed Vth (for example, several tens of km / h). According to the configuration, signals due to external environments and actual obstacles can be accurately separated, thus preventing the detection of an object from being missed.

[0042] Using the center sensors 21, 22 provided at the front of the vehicle, interference detection is performed based on the detection distance D. While the influence of snow or rain is greater for the sensor mounted at the front of the vehicle, the influence is relatively smaller for the sensor mounted at the rear or corner of the vehicle 30. Therefore, when interference detection is performed based on the detection distance D by the sensor mounted at the rear or corner of the vehicle, it may be considered that separation from actual obstacles may not be sufficiently performed.Furthermore, in a case of the corner sensors 23, 24, an obstacle may be present near (for example, within several tens of cm) the vehicle 30, and the actual obstacle and the external environment are difficult to separate. Considering these points, the above configuration can perform interference detection with high accuracy while preventing omission of detection of an actual obstacle. (Other embodiments)

[0043] The invention is not limited to the above embodiments and can be implemented as follows.

[0044] In the above embodiments, when it is determined that there is a disturbance by at least one of the disturbance determination based on the detection distance and the disturbance determination based on noise, the threshold value of the reliability level determination counter N is increased. Alternatively, when it is determined that there is a disturbance by both the disturbance determination based on the detection distance and the disturbance determination based on noise, it may be finally determined that there is a disturbance. Then, the threshold value of the reliability level determination counter N may be increased or changed to be increased.

[0045] In the above embodiments, the detection counters CA, CB are set for each of the detection distance-based disturbance detection and the noise-based disturbance detection to compare the disturbance detection thresholds CAth and CBth with each other. Alternatively, a common counter may be provided for both the detection distance-based disturbance detection and the noise-based disturbance detection to compare the sum of the number of times a state where the detection distance is extremely short and the number of times noise is generated with a detection threshold, thereby performing the disturbance detection.

[0046] In the above embodiments, the disturbance determination may be performed based on a noise signal under the condition that the speed of the vehicle 30 is equal to or greater than a threshold value (noise determination permission vehicle speed). Note that the noise determination permission vehicle speed may be the same as the distance determination permission vehicle speed Vth, or may be different from the distance determination permission vehicle speed Vth.

[0047] In the above embodiments, when it is determined that a disturbance exists, the threshold value of the reliability level determination counter N is changed to increase it. However, another configuration may be used if it is difficult to allow the contact avoidance control to intervene. For example, when it is determined that a disturbance exists, the amount of increase of the reliability level determination counter N obtained when the object 50 is detected may be smaller than when it is not determined that a disturbance exists.

[0048] In the above embodiments, the disturbance determination is performed based on the detection distance under the condition that the vehicle speed V is equal to or greater than the distance determination permission vehicle speed Vth. However, regardless of whether the vehicle condition is satisfied, the disturbance determination may be performed based on the detection distance.

[0049] In the above embodiments, the time periods between a starting point, which is a time point at which it is initially determined that a noise signal is received after the detection counter is reset, and the time at which a predetermined time has elapsed, are set as the noise detection time periods T1, T2. However, for example, the detection counter may be reset every time a predetermined time has elapsed to perform the noise detection process by defining a time period at the end of which the detection counter is reset as the noise detection time periods T1, T2.

[0050] In the above embodiments, the time period between the time at which it is determined that an interference signal is being received and the time at which a predetermined period of time has elapsed is defined as the interference detection periods T1, T2. Instead, the time period at the end of which the number of transmissions of the search wave 25 becomes the predetermined frequency may be defined as the interference detection periods T1, T2.

[0051] In the above embodiments, when a plurality of positioning sensors 20 determine that a malfunction exists, it can be conclusively determined that a malfunction exists, and, for example, the threshold value of the reliability level determination counter N can be increased, thereby making it difficult for the contact avoidance controller to intervene. If external environmental factors such as snow and rain are causes, the probability that another sensor also determines that a malfunction exists is higher. Therefore, according to the above configuration, the presence or absence of a malfunction can be determined more accurately.

[0052] In the above embodiments, a case is described where the location sensors 20 serving as object detection sensors are provided at the front and rear of the vehicle 30. However, the position where the sensors are mounted is not limited to this. For example, instead of or in addition to the front and rear of the vehicle 30, the sensors may be provided on the right and left side surfaces.

[0053] In the above embodiments, a configuration including an ultrasonic sensor that detects an object using ultrasonic waves as search waves is adopted for the positioning sensor 20. However, a sensor that transmits a search wave and receives reflected waves of the transmitted search waves to detect an object may be adopted. For example, a millimeter-wave radar, a laser radar, or the like that detects an object using electromagnetic waves as the search waves may be used.

[0054] In the above embodiments, an object detection device installed in a vehicle is described as an example. However, for example, the object detection device may be installed in a moving body such as a railway vehicle, a ship, an aircraft, and a robot.

[0055] Aspects of the embodiments described above are summarized below.

[0056] An embodiment provides an object detection device according to claim 1.

[0057] For example, the positioning sensor may detect an extremely short distance or generate noise due to external environments such as snow, rain, and mutual interference with a sensor of another vehicle. Furthermore, when the extremely short detection distance and noise generation are due to external environments, the extremely short detection distance and noise generation often continue as long as the external environment lasts. Focusing on these points, in the above configuration, an occurrence frequency of a noise signal at the same time within a predetermined transmission period determined with respect to a transmission period of the search wave is detected to determine the presence or absence of noise based on the detected occurrence frequency.The above configuration can separately detect the presence or absence of external environmental influences and actual obstacles. As a result, the situation in which the reliability of object detection information decreases due to the influence of external environmental conditions can be accurately determined.

[0058] It is to be understood that the invention is not limited to the configurations described above, but that any and all modifications, variations or equivalents that may occur to those skilled in the art are to be considered as falling within the scope of the invention.

Claims

[1] An object detection device (10) mounted on a movable body (30), comprising an object detection sensor (20) which emits a search wave (25) and receives a reflected wave (26) of the search wave (25) as detection information of an object (50) and detects the object (50) present in the vicinity of the movable body (30) on the basis of the detection information, wherein the object detection sensor (20) receives the reflected wave (26) within a predetermined object detection period (Td) after the search wave (25) is transmitted, the object detection device (10) includes: a distance calculating section which calculates a distance (D) between the movable body (30) and the object (50) based on a time at which the reflected wave (26) is received; a speed detecting section which detects a speed (V) of the movable body (30); a frequency detection section which, in a period in which the speed (V) of the movable body (30) is continuously equal to or greater than a vehicle speed threshold (Vth), detects a first occurrence frequency (CA) with which the calculated distance (D) within a predetermined first disturbance detection period (T1) in the object detection period (Td) is equal to or less than a distance threshold (Dth), and the frequency detection section detects a second occurrence frequency (CB) of a reception signal received during a noise detection period (Tn), wherein the noise detection period (Tn) is different from a transmission period (Tb) of the search wave (25) and the object detection period (Td) and is within a transmission period of the search wave (25); and a fault determination section which determines a presence of occurrence of a fault when the first occurrence frequency (CA) is equal to or greater than a first fault determination threshold (CAth) before the first fault determination period (T1) has elapsed, and the disturbance determination section determines a presence of occurrence of a disturbance when the second occurrence frequency (CB) detected by the frequency detection section within a disturbance determination period (T2) is equal to or greater than a threshold value (CBth). [2] The object detection device (10) according to claim 1, wherein the object detection sensor (20) is an ultrasonic sensor which emits an ultrasonic wave as the search wave (25).

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