JP2016080651A - Reception time estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reception time estimation device capable of accurately estimating a reception time.SOLUTION: A reception time estimation device 20 estimates a time starting to receive a wave as an estimation reception time in the case that the wave transmitted with a predetermined time is received as one transmission opportunity, and includes: first acquisition means for acquiring a first time having exceeded a first threshold value in which a crest value of the received wave is a predetermined value; second acquisition means for acquiring a second crest value as the crest value of the wave and a second time in association therewith at the predetermined timing during a period, after the first time, until the crest value of the wave increases and reaches a peak value; and reception time estimation means for calculating a time in which the crest value of the wave changes from zero as the estimation reception time on the basis of the first threshold value, the second crest value, the first time, and the second time.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a reception time estimation device that receives a wave transmitted with a predetermined time as a transmission opportunity and detects a reception start time of the received wave.

  There is an object detection device using a distance measuring sensor such as an ultrasonic sensor as a device that receives a wave transmitted with a predetermined time as a transmission opportunity and performs processing using the reception start time of the received wave. The object detection apparatus irradiates an object with an exploration wave such as an ultrasonic wave and receives a reflected wave that is an exploration wave reflected by the object. Then, the positions of the distance measuring sensor and the object are calculated based on the time when reception is started. At this time, a detection threshold for the reflected wave is provided, and the time when the peak value of the reflected wave exceeds the detection threshold is the reception time, and the detection time is obtained using the propagation time obtained by subtracting the transmission time of the exploration wave from the reception time. The distance to an object that is In general, since the reflected waveform includes noise, the detection threshold is set so that the reception time is not erroneously determined due to the noise. That is, if the detection threshold value is lowered, the rate at which noise exceeds the detection threshold value increases, and as a result, there is an increased risk of erroneous detection that an object is present even when the object is not present.

  On the other hand, if the detection threshold is increased, the rate at which noise exceeds the detection threshold decreases, but it takes time from the start of reception of the reflected wave until the peak value exceeds the detection threshold, and the propagation time is measured longer. . As a result, a difference between the calculation result of the distance to the object and the actual distance occurs. At this time, the closer the distance to the object whose position is to be detected, the greater the ratio of error to that distance.

  Incidentally, as an object detection apparatus using an ultrasonic sensor, there is an object detection apparatus described in Patent Document 1. The object detection device described in Patent Literature 1 uses a rising threshold value and a peak threshold value, and receives a time that exceeds the rising threshold value when the peak value of the reflected wave exceeds the rising threshold value after exceeding the rising threshold value. It is time. Based on the reception time, the distance between the vehicle and the object is calculated.

JP 2002-350540 A

  In the object detection device described in Patent Document 1, since the reception start time is not determined only when the peak value of the reflected wave exceeds the first threshold, the noise resistance performance can be improved. However, depending on the material and shape of the object to be detected, it may take time until the peak value of the reflected wave exceeds the first peak value after the reception of the reflected wave is started. In this case, if the time when the peak value of the reflected wave exceeds the first threshold is estimated as the reception time of the reflected wave, a deviation from the actual reception time occurs.

  The present invention has been made to solve the above-described problems, and a main object of the present invention is to provide a reception time estimation device capable of accurately estimating a reception time.

  The present invention relates to a reception time estimation device that estimates a time at which reception of a wave is started as an estimated reception time when a wave transmitted with a predetermined time as a transmission opportunity is received. A first acquisition means for acquiring a first time that is a time when the peak value of the first wave exceeds a first threshold value that is a predetermined value; and after the first time, the peak value of the wave is increased. A second acquisition means for acquiring a second peak value that is the peak value of the wave and a second time associated therewith at a predetermined timing within a period until the peak value is reached, a first threshold value, Reception time estimating means for calculating, as an estimated reception time, a time at which the wave peak value changes from zero based on the two peak values, the first time, and the second time.

  When a wave transmitted with a predetermined time as one transmission opportunity is received, the waveform of the received wave can generally approximate a triangle. And the apex whose height is zero in the approximate triangle corresponds to the point where the peak value is zero, and it can be estimated that it is the time when the wave reception is started. In this regard, if two parameters in the waveform are acquired with the above configuration, the point at which the peak value becomes zero is calculated as the estimated reception time using the two parameters. Therefore, the estimated reception time can be made closer to the actual reception time.

  In addition, since the estimated reception time is the time before the first time, not the first time that is the time that exceeded the first threshold, the first threshold is set to a high value that is not affected by noise. can do. Therefore, it is possible to accurately calculate the estimated reception time while ensuring noise resistance performance.

It is a figure which shows the outline | summary of the object detection apparatus which concerns on 1st Embodiment. It is a top view of the vehicle carrying an object detection apparatus. (A) is a figure which shows the waveform of an exploration wave, (b) is a figure which shows the waveform of a reflected wave. It is a figure which shows the calculation method of the estimated reception time in 1st Embodiment. It is a flowchart which shows the process of 1st Embodiment. It is a figure which shows the calculation method of the estimated reception time in 2nd Embodiment. It is a flowchart which shows the process of 2nd Embodiment. It is a figure which shows the calculation method of the estimated reception time in 3rd Embodiment. It is a flowchart which shows the process of 3rd Embodiment. It is a figure which shows the calculation method of the estimated reception time in 4th Embodiment. It is a flowchart which shows the process of 4th Embodiment. It is a figure which shows the calculation method of the estimated reception time in 5th Embodiment. It is a flowchart which shows the process of 5th Embodiment.

<First Embodiment>
Hereinafter, a first embodiment in which a reception time estimation device is embodied as an object detection device will be described with reference to the drawings.

  FIG. 1 shows a configuration of an object detection apparatus according to the present embodiment. The object detection device is a device that is mounted on a vehicle and calculates the distance between the vehicle and other objects such as other vehicles and road structures that exist around the vehicle. The ECU 20 is configured to be controlled.

  The distance measuring sensor 10 is an ultrasonic sensor, for example, and has a function of transmitting an ultrasonic wave of 20 to 100 kHz as an exploration wave and a function of receiving an exploration wave reflected by reaching an object as a reflected wave. Yes. The ECU 20 includes a microcomputer, which includes a CPU, various memories, an A / D converter, and the like. The CPU included in the ECU 20 realizes a function as the sensor control unit 21, a function as the distance calculation unit 22, and a function as the vehicle control unit 23 by a program stored in the memory.

  The sensor control unit 21 transmits a control signal to the distance measuring sensor 10 and acquires the peak value of the reflected wave received by the distance measuring sensor 10. At this time, the distance measuring sensor 10 repeatedly transmits the exploration wave at a predetermined interval (for example, every several milliseconds) with a predetermined time as one transmission opportunity based on an instruction from the ECU 20. The distance calculation unit 22 calculates the distance between the vehicle and the object based on the reflected wave received by the distance measuring sensor 10. The vehicle control unit 23 controls the behavior of the vehicle, such as steering angle control and acceleration / deceleration control, based on the distance from the object around the vehicle calculated by the distance measuring sensor 10, and alerts the driver. To notify the approach of an object.

  FIG. 2 is a top view of the vehicle 30 on which the object detection device is mounted. The distance measuring sensors 10 are attached at predetermined intervals, for example, four each before and after the vehicle 30 and two each on the left and right side surfaces of the vehicle 30. Each distance measuring sensor 10 is attached to, for example, a predetermined height (about 45 to 60 cm from the ground) of a bumper provided before and after the vehicle 30. The exploration wave is transmitted radially from the distance measuring sensor 10 to the surroundings of the vehicle 30, and a part thereof reaches surrounding objects. The exploration wave that reaches the object is reflected to the distance measuring sensor 10 as a reflected wave. Note that the mounting position of the distance measuring sensor 10 shown in FIG. 2 with respect to the vehicle 30 is merely an example, and various changes can be made.

  FIG. 3 shows the waveforms of the exploration wave and the reflected wave. In this specification, a shape connecting the vertices of a wave that vibrates at a frequency of 20 to 100 kHz is defined as a waveform.

  The exploration wave starts to be transmitted at the transmission start time Ts and continues to be transmitted for a certain transmission time Tb. At this time, the peak value H of the exploration wave starts increasing from the transmission start time Ts, and after the peak value H reaches the maximum value, the peak value H is maintained for a predetermined time. After the peak value H reaches the maximum value, attenuation of the peak value H is started after a lapse of a predetermined time, and the peak value H becomes zero at the time when the transmission time Tb has elapsed from the transmission start time Ts.

  The exploration wave reaches the object after a time corresponding to the distance between the distance measuring sensor 10 and the object has elapsed. The exploration wave that has reached the object is reflected by the object to become a reflected wave, and reaches the distance measurement sensor 10 after a time corresponding to the distance between the distance measurement sensor 10 and the object has elapsed. At this time, the peak value is obtained after a time equal to the search wave transmission time Tb has elapsed from the reception start time Tx of the reflected wave. Then, the distance between the distance measurement sensor 10 and the object is obtained by converting the difference between the transmission start time Ts of the exploration wave and the reception start time Tx of the reflected wave into a distance. At this time, if the value obtained by subtracting the search wave transmission start time Ts from the reflected wave reception start time Tx is divided by 2 and multiplied by the sound speed, the distance between the distance measuring sensor 10 and the object can be calculated.

  By the way, as shown in FIG. 4, the peak value H of the reflected wave starts to rise at the reception start time Tx, and the time change rate of the peak value H increases with time. Subsequently, the time change rate of the peak value H becomes substantially constant, and the peak value H rises linearly. In the vicinity of the peak value, the time change rate of the peak value H decreases with time, and reaches the peak value when the time change rate becomes zero. Therefore, it can be said that the shape up to the peak value of the reflected wave is a shape similar to a triangle in which the part where the peak value H rises linearly is part of the long side.

  Here, the first peak value H1 which is the peak value H in the range (straight line part) in which the peak value H increases linearly, and the peak value H of the straight part and larger than the first peak value H1. A second peak value H2 that is a high value H is set. Also, the time when the first peak value H1 is reached is the first time T1, and the time when the second peak value H2 is reached is the second time T2. In addition, the time is taken as the X axis, the peak value H is taken as the Y axis, the waveform of the reflected wave is expressed from the XY coordinate system, and the coordinates (T0, 0) of the common vertex are determined. At this time, the first right triangle having the coordinates (T0,0), the coordinates (T1, H1), and the coordinates (T1,0) as the vertices, the coordinates (T0,0), the coordinates (T2, H2), and the coordinates A second right triangle with the vertex (T2, 0) can be drawn on the waveform. The first right triangle and the second right triangle are similar. The coordinate of the vertex is a point where the peak value H becomes zero, and the X coordinate is an estimated reception time T0 at which it can be estimated that reception of the reflected wave is started.

Therefore, if the values of the first peak value H1, the second peak value H2, the first time T1, and the second time T2 can be obtained, the ratio of the lengths of the two sides sandwiching the right angle of the right triangle becomes equal. Then, the estimated reception time T0 can be calculated by the following equation (1).
(T1-T0): H1 = (T2-T0): H2 (1)

  Therefore, in the present embodiment, the estimated reception time T0 is calculated on the assumption that the rising waveform of the reflected wave includes a portion that can be approximated to a triangle. That is, a first threshold value Hth1 and a second threshold value Hth2 that is larger than the first threshold value Hth1 are set for the peak value H, and the time when the peak value H exceeds the first threshold value Hth1 is set to the first time. Obtained as T1, and the time when the peak value H exceeds the second threshold Hth2 is obtained as the second time T2. Then, the estimated reception time T0 is calculated using the first threshold value Hth1, the second threshold value Hth2, the first time T1, and the second time T2.

  At this time, the first threshold value Hth1 is higher than the peak value of general noise, and the second threshold value Hth2 is experimentally obtained as the peak value of the reflected wave reflected from the object in the search range. Value. The first threshold value Hth1 and the second threshold value Hth2 are set in advance and stored in the memory of the ECU 20. The peak value H is measured for a time longer than the reciprocal of the frequency in one control cycle, and the maximum value in one control cycle is acquired as the peak value H.

That is, with respect to the above equation (1), the estimated reception time T0 is calculated by the following equation (2) using the first threshold value Hth1 as the first peak value H1 and the second threshold value Hth2 as the second peak value H2. To do.
(T1-T0): Hth1 = (T2-T0): Hth2 (2)

  FIG. 5 is a flowchart showing distance calculation processing according to the present embodiment. First, time measurement is started with the start of transmission of the exploration wave (S101), and it is determined whether or not the peak value H of the reflected wave is equal to or greater than the first threshold value Hth1 (S102). If the peak value H of the reflected wave is less than the first threshold value Hth1 (S102: NO), the time is added (S103). The processing of S102 and S103 is continued until the peak value H of the reflected wave becomes equal to or higher than the first threshold value Hth1. On the other hand, if it is determined that the peak value H of the reflected wave is equal to or greater than the first threshold value Hth1 (S102: YES), the ECU 20 functions as the first acquisition unit and acquires the time as the first time T1 (S104). .

  Subsequently, it is determined whether or not the peak value H of the reflected wave is equal to or greater than the second threshold value Hth2 (S105). If the peak value H of the reflected wave is less than the second threshold value Hth2 (S105: NO), the time is added (S106). On the other hand, if it is determined that the peak value H of the reflected wave is greater than or equal to the second threshold value Hth2 (S105: YES), the ECU 20 functions as a second acquisition unit and acquires the time as the second time T2 (S107). .

  Then, the estimated reception time T0 is calculated by the above equation (2) using the acquired first time T1 and second time T2 and the first threshold value Hth1 and second threshold value Hth2 which are predetermined values. (S108). At this time, the ECU 20 functions as reception time estimating means. Finally, using the calculated estimated reception time T0, the distance between the distance measuring sensor 10 and the object is calculated (S109), and a series of processing ends.

  In this embodiment, since the time measurement is started when the transmission of the exploration wave is started, the distance between the distance measuring sensor 10 and the object can be obtained from the estimated reception time T0. And the distance between the distance measuring sensor 10 and the object may be obtained by a value obtained by subtracting the transmission start time Ts of the exploration wave from the estimated reception time T0.

  In addition, since a certain offset occurs between the calculated estimated reception time T0 and the actual reception start time Tx, the calculated estimated reception time T0 may be corrected by the offset.

  With the above configuration, the object detection device according to the present embodiment has the following effects.

  When the value of the first threshold value Hth1 is set to a value that is not affected by noise and it is determined that reception of the reflected wave has started at the time when the peak value H becomes the first threshold value Hth1, the actual reception start time Tx As a result, the distance detection accuracy decreases. The influence of this decrease in detection accuracy becomes more significant as the distance between the distance measuring sensor 10 and the object is smaller. That is, the distance calculation error increases for a short-distance object that is required to calculate the distance more accurately.

  In this respect, in the present embodiment, the waveform of the reflected wave is approximated as a triangle, and the peak value H is zero by using the first threshold value Hth1 and the second threshold value Hth2, and the first time T1 and the second time T2. A certain time is estimated as the estimated reception time T0. For this reason, the difference between the reception start time Tx and the estimated reception time T0 is reduced, and the distance between the distance measurement sensor 10 and the object can be obtained more accurately.

Second Embodiment
The object detection device according to the present embodiment has the same overall configuration as the object detection device according to the first embodiment, and the processing for obtaining the estimated reception time T0 is partially different.

FIG. 6 shows the principle of calculating the estimated reception time T0 in this embodiment. In the present embodiment, the first threshold value Hth1 is used as in the first embodiment, but the second threshold value Hth2 is not used, and the predetermined time ΔT has elapsed since the first time T1 when the peak value H exceeded the first threshold value Hth1. Later, the second peak value H2 is acquired. Then, the estimated reception time T0 is calculated by the following equation (3) using the first threshold value Hth1, the second peak value H2, the first time T1, and the predetermined time ΔT with respect to the above equation (1). .
(T1-T0): Hth1 = (T1 + ΔT−T0): H2 (3)

  FIG. 7 is a flowchart showing distance calculation processing according to the present embodiment. First, in S201 to S204, the same processing as the processing according to S101 to S104 of the first embodiment is performed, and the first time T1 is acquired. Subsequently, it is determined whether or not a predetermined time ΔT has elapsed from the first time T1 (S205). If the predetermined time ΔT has not elapsed since the first time T1 (S205: NO), the time is added (S206). On the other hand, if it is determined that the predetermined time ΔT has elapsed from the first time T1 (S205: YES), the ECU 20 functions as the second acquisition means, and acquires the peak value H at that time as the second peak value H2 ( S207).

  Then, the estimated reception time T0 is calculated by the above equation (3) using the acquired first time T1 and second peak value H2, and the first threshold value Hth1 and the predetermined time ΔT that are predetermined values. (S208). At this time, the ECU 20 functions as reception time estimating means. Finally, using the calculated estimated reception time T0, the distance between the distance measuring sensor 10 and the object is calculated (S209), and the series of processing ends.

  With the above configuration, the object detection device according to the present embodiment has the following effects in addition to the effects exhibited by the object detection device according to the first embodiment.

  When the second threshold value Hth2 is also used in addition to the first threshold value Hth1, the peak value H of the reflected wave is low and the peak value of the peak value H of the reflected wave is It may be lower than 2 threshold value Hth2. In this regard, in the present embodiment, the second threshold value Hth2 is not provided, and the second peak value H2 after the lapse of the predetermined time ΔT from the first time T1 is used, so that the peak value H of the reflected wave has the first threshold value Hth1. If it exceeds, the estimated reception time T0 can be calculated.

<Third Embodiment>
The object detection device according to the present embodiment has the same overall configuration as the object detection device according to the first embodiment, and the processing for obtaining the estimated reception time T0 is partially different.

FIG. 8 shows the principle of calculating the estimated reception time T0 in this embodiment. In the present embodiment, the first threshold value Hth1 is used as in the first embodiment, but the second threshold value Hth2 is not used, and the peak value Hp, which is the value when the peak value H becomes maximum, is acquired. Then, the estimated reception time T0 is calculated using the fact that the time from the estimated reception time T0 until the peak value H reaches the peak value Hp is equal to the transmission time Tb of the exploration wave. That is, the estimated reception time T0 is calculated by the following equation (4) using the first threshold value Hth1, the peak value Hp, the first time T1, and the transmission time Tb with respect to the above equation (1).
(T1-T0): Hth1 = Tb: Hp (4)

  FIG. 9 is a flowchart showing distance calculation processing according to the present embodiment. First, in S301 to S304, the same processing as that in the first embodiment is performed to obtain the first time T1.

  Subsequently, it is determined whether or not the peak value H has reached a peak (S305). In S305, the peak value H is acquired and held for each control period, and the peak value H is compared with the peak value H in the previous control period. At this time, if the peak value H is larger than the peak value H of the previous control cycle, it is determined that the peak value Hp is not reached (S305: NO), and the determination of S305 is performed again in the next control cycle. On the other hand, if it is determined that the peak value H is a peak (S305: YES), the ECU 20 functions as the second acquisition unit, and acquires the peak value H of the previous control cycle of the control cycle as the peak value Hp (S306). ).

  Then, the estimated reception time T0 is calculated by the above equation (4) using the acquired first time T1 and peak value Hp, and the first threshold value Hth1 and transmission time Tb, which are predetermined values (S307). . At this time, the ECU 20 functions as reception time estimating means. Finally, using the calculated estimated reception time T0, the distance between the distance measuring sensor 10 and the object is calculated (S308), and a series of processing ends.

  With the above configuration, the object detection apparatus according to the present embodiment has the following effects in addition to the effects exhibited by the object detection apparatus according to the first embodiment.

  When the second threshold value Hth2 is also used in addition to the first threshold value Hth1, the peak value Hp of the reflected wave peak value H becomes low depending on the material of the object reflecting the exploration wave, etc. It may be lower than the second threshold value Hth2. In this regard, in the present embodiment, since the peak value Hp is used without providing the second threshold value Hth2, the estimated reception time T0 can be calculated if the peak value H of the reflected wave exceeds the first threshold value Hth1.

<Fourth embodiment>
The object detection device according to the present embodiment has the same overall configuration as the object detection device according to the first embodiment, and the processing for obtaining the estimated reception time T0 is partially different.

  FIG. 10 shows the principle of calculating the estimated reception time T0 in this embodiment. In the present embodiment, as in the first embodiment, the first threshold value Hth1 is used, but the second threshold value Hth2 is not used, and the processing for obtaining the peak value H is performed every predetermined time ΔT. The processing for obtaining the peak value H is performed for a section that can be approximated to a straight line, that is, a section where the rate of increase of the peak value H is constant, and the estimated reception time T0 is calculated using the highest peak value H in that section. To do. FIG. 10 shows an example in which the second to fifth peak values H2 to H5 are acquired each time a predetermined time ΔT elapses after the peak value H exceeds the first threshold value Hth1 at the first time T1. The time when the fifth peak value H5 is acquired is the time obtained by adding 4ΔT to the first time T1. At this time, the fourth peak value H4 is an interval that can be approximated to a straight line, and the fifth peak value H5 is outside the interval that can be approximated to a straight line. Therefore, the fourth peak value H4 and the time when the fourth peak value H4 is acquired are used for calculating the estimated reception time T0.

Then, the estimated reception time T0 is calculated by the following equation (5) using the acquired first time T1, the nth peak value Hn, and the predetermined time ΔT with respect to the above equation (1).
(T1-T0): Hth1 = (T1 + (n−1) ΔT−T0): Hn (5)

  FIG. 11 is a flowchart showing distance calculation processing according to the present embodiment. First, in S401 to S404, the same processing as that in the first embodiment is performed to acquire the first time T1.

  Subsequently, the addition of the number n of acquisitions of the crest value H is started (S405), and it is determined whether or not a time n times the predetermined time ΔT has elapsed from the first time T1 (S406). If n times the predetermined time ΔT has not elapsed since the first time T1 (S406: NO), the time is added (S407). On the other hand, if it is determined that a time n times the predetermined time ΔT has elapsed from the first time T1 (S406: YES), the (n + 1) peak value H (n + 1), which is the peak value H at that time, is acquired. (S408). At this time, the ECU 20 functions as a second acquisition unit.

  Subsequently, it is determined whether or not the acquired peak value H is the second peak value H2 (S409). Here, only the first threshold value Hth1 and the second peak value H2 cannot determine whether or not the increase rate of the peak value H is constant, so the process of S409 is performed.

  If it determines with it being the 2nd peak value H2 (S409: YES), the number of acquisition n will be added (S410) and it will transfer to the process which acquires the 3rd peak value H3. On the other hand, if it is determined that it is not the second peak value H2 (S409: NO), the (n + 1) th increase rate ΔH (n + 1), which is the difference between the (n + 1) th peak value H (n + 1) and the nth peak value Hn. ) Is calculated (S411). Then, it is determined whether or not the difference between the (n + 1) th increase rate ΔH (n + 1) and the nth increase rate ΔHn is a value that can be approximated to zero (S412).

  When the difference between the (n + 1) th increase rate ΔH (n + 1) and the nth increase rate ΔHn is a value that can be approximated to zero (S412: YES), since the increase rate of the peak value H is constant, the acquisition is performed. The number of times n is added (S410), and the peak value H after a predetermined time ΔT is acquired. On the other hand, if the difference between the (n + 1) th increase rate ΔH (n + 1) and the nth increase rate ΔHn is not a value that can be approximated to zero (S412: NO), the (n + 1) th peak value H (n + 1) is obtained. Since the increase rate of the peak value H is decreasing with time, the estimated reception time T0 is calculated by the above equation (5) using the nth peak value Hn (S413). At this time, the ECU 20 functions as reception time estimating means. Finally, using the calculated estimated reception time T0, the distance between the distance measuring sensor 10 and the object is calculated (S414), and the series of processing ends.

  With the above configuration, the object detection device according to the present embodiment has an effect similar to that of the second embodiment.

<Fifth Embodiment>
The object detection device according to the present embodiment has the same overall configuration as the object detection device according to the first embodiment, and the processing for obtaining the estimated reception time T0 is partially different.

  FIG. 12 shows the principle of calculating the estimated reception time T0 in this embodiment. In the present embodiment, similarly to the fourth embodiment, the first threshold value Hth1 is used, and the peak value H is acquired every predetermined time ΔT. In addition, the process of acquiring the peak value H is performed up to the vicinity of the peak value.

  Then, the function f (T), which is a function of the time T, is obtained from the first threshold value Hth1, the predetermined time ΔT, and the obtained first time T1, and the second to (n + 1) th peak values H2 to H (n + 1). Ask. And the estimated reception time T0 is calculated | required using the value which substituted the estimated reception time T0 into the function f (T) becomes zero.

  FIG. 13 is a flowchart showing processing according to the present embodiment. In S501 to S508, processing similar to the processing in S401 to S408 of the fourth embodiment is performed, and the first time T1 and the second to (n + 1) peak values H2 to H (n + 1) are acquired. At this time, the ECU 20 functions as a first acquisition unit and a second acquisition unit. Subsequently, whether or not the (n + 1) peak value H (n + 1) is a peak value is determined by the same processing as S305 of the third embodiment (S509).

  If it is determined that the (n + 1) peak value H (n + 1) is not a peak value, the number of acquisitions n is added (S510), and the peak value H after a predetermined time ΔT is acquired. On the other hand, if it is determined that the (n + 1) peak value H (n + 1) is the peak value, the first to (n + 1) peak values H1 to H (n + 1), the first time T1, and the predetermined time ΔT are used. Thus, the function f (T) is obtained (S512). At this time, the ECU 20 functions as a waveform estimation unit. Then, using the fact that the function f (T0) is zero, the estimated reception time T0 is calculated (S512). At this time, the ECU 20 functions as reception time estimating means. Finally, using the calculated estimated reception time T0, the distance between the distance measuring sensor 10 and the object is calculated (S513), and a series of processing ends.

  The function f (T) may be any function that can approximate the shape of the reflected wave, and can be approximated by a polynomial function, a square root function, a sine function, or the like.

  In addition, although the function f (T) is obtained using the peak value H up to the vicinity of the peak value, the slope of a section that can be approximated to a straight line may be approximated using a plurality of peak values H. In this case, the function f (T) is a linear function.

  With the above configuration, the object detection device according to the present embodiment has an effect similar to that of each of the above embodiments.

<Modification>
In each of the above embodiments, an example in which the reception time estimation device is embodied as an object detection device is shown, but the reception time estimation device can be used in addition to the object detection device. For example, the present invention can be applied to a device that receives a wave such as a radio wave transmitted from another device and performs processing based on the reception time.

  In each of the above embodiments, an example using an ultrasonic wave as the exploration wave is illustrated, but a wave other than the ultrasonic wave, for example, a sound wave, a radio wave, or the like can be used as the exploration wave.

  In each of the above embodiments, the object detection device is mounted on the vehicle 30, but the mounting target may be a moving body other than the vehicle, for example, an airplane, a ship, a robot, or the like. Further, it may be mounted on a fixed object, and may be used to measure the distance between the fixed object and an object around the fixed object. In addition, it may be worn or carried by a person, and can also be used to inform a person of the approach of a surrounding object.

In the third embodiment, the first reception time T1 and the peak value Hp are acquired to calculate the estimated reception time T0. However, the processing may be partially changed as follows. That is, the peak value Hp is acquired, and the peak time Tp that is the time when the peak value Hp is acquired is acquired. Then, using the fact that the time from the reception start time Tx to the peak time Tp is equal to the transmission time Tb, the estimated reception time T0 is calculated by the following equation (6). In other words, the ECU 20 includes a peak time acquisition unit that acquires the peak time Tp, and a reception time estimation unit that calculates the estimated reception time T0 based on the transmission time Tb and the acquired peak time Tp. . In this case, the process of acquiring the peak value Hp and the peak time Tp may be started on condition that the first threshold value Hth1 is exceeded, and the first time T1 may not be acquired.
T0 = Hp−Tb (6)

  20 ... ECU.

Claims (8)

A reception time estimation device (20) for estimating a time at which reception of a wave is started as an estimated reception time when receiving a wave transmitted with a predetermined time as a transmission opportunity,
First acquisition means for acquiring a first time that is a time at which a peak value of a received wave exceeds a first threshold that is a predetermined value;
The second peak value that is the peak value of the wave is associated with the second peak value at a predetermined timing after the first time and within a period from when the peak value of the wave increases until reaching the peak value. Second acquisition means for acquiring a second time to be transmitted;
Based on the first threshold value, the second peak value, the first time, and the second time, a reception time estimation that calculates a time when the peak value of the wave changes from zero as the estimated reception time A reception time estimation device comprising: means. The second peak value is a second threshold value that is a predetermined value;
The second time is a time when the peak value of the wave exceeds the second threshold,
The reception time estimation according to claim 1, wherein the reception time estimation means calculates the estimated reception time based on the first threshold and the second threshold and the acquired first time and the second time. apparatus. The second acquisition means acquires the second peak value at a second time after a predetermined time has elapsed from the first time,
The reception time estimation device according to claim 1, wherein the reception time estimation means calculates the reception time based on the first threshold value, the second peak value, the first time, and the predetermined time. .   The reception time estimation device according to claim 3, wherein the second acquisition means acquires the peak value of the wave a plurality of times, and sets the maximum peak value among the peak values acquired a plurality of times as the second peak value. .   The reception time estimation apparatus according to claim 4, wherein the second acquisition means acquires the second peak value on condition that the increase rate of the peak value is constant. The wave is a reflected wave in which a transmitted exploration wave is reflected by an object,
The second acquisition means acquires a peak value of a value at which the peak value of the reflected wave is maximum as the second peak value, and a transmission time that is a time from the start of transmission of the exploration wave to the end of transmission As the second time,
The reception time estimation device according to claim 1, wherein the reception time estimation means calculates the estimated reception time based on the first threshold value, the peak value, the first time, and the transmission time. . Waveform estimation means for estimating the waveform of the wave based on the first threshold value, the second peak value, the first time, and the second time;
The second acquisition means acquires the second peak value and the second time a plurality of times every predetermined time from the first time,
The reception time estimation apparatus according to claim 1, wherein the reception time estimation unit calculates the estimated reception time based on the estimated waveform.   The reception time estimation apparatus according to claim 7, wherein the waveform estimation unit approximates the waveform by a function.

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