JP2012237625A - Object distance detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detection accuracy of distance to an object.SOLUTION: An object distance detection device 10 includes: a distance detection part 25 which detects time difference from time when electromagnetic waves are transmitted by a transmission part 11a of a radar device 11 to time when reflected waves are received by a reception part 11b, and calculates distance from a vehicle to an object on the basis of the time difference; a maximum value estimation part 24 which estimates the maximum value (estimated peak voltage Vpeak) of reception intensity according to inclinations on the increment side and the decrement side of the reception intensity in waveform F of reception intensity distribution on a two-dimensional orthogonal coordinate plane showing correspondence between the time difference and the reception intensity of the reflected waves; and a distance correction part 26 which corrects the distance calculated by the distance detection part 25 on the basis of time width (estimated pulse width W) in which the reception intensity in the waveform F of the reception intensity distribution is equal to or more than a voltage threshold Vth, and the maximum value (estimated peak voltage Vpeak).

Description

  The present invention relates to an object distance detection device.

  Conventionally, for example, when measuring the distance to the reflection point based on the time difference between the emission time of the transmission wave using laser light and the reception time of the reflected wave, the reflected wave is reflected in the correspondence between the reception intensity of the reflected wave and the time difference. A distance measuring device is known that corrects a measurement error caused by a difference in received intensity of reflected waves by correcting a time difference based on a time width during which the received intensity is greater than a predetermined threshold (see, for example, Patent Document 1). ).

JP-A-9-236661

By the way, according to the distance measuring device according to the above-described prior art, the time width is shortened when the received intensity of the reflected wave is weak, and the time width is lengthened when the received intensity of the reflected wave is strong. The time difference is corrected.
However, the correspondence relationship between the received intensity of the reflected wave and the time width varies depending on the object that emits the reflected wave. For example, when the received intensity of the reflected wave is weak, the time width becomes longer or the received intensity of the reflected wave is lower. There is a possibility that the time width is shortened when the time is strong, and there is a possibility that appropriate correction cannot be performed.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an object distance detection device capable of improving the accuracy of detection of the distance to an object.

  In order to solve the above problems and achieve the object, an object distance detection device according to claim 1 of the present invention is a transmission means for transmitting an electromagnetic wave toward a predetermined area from a vehicle (for example, in the embodiment). A transmitting unit 11a), a receiving unit (for example, the receiving unit 11b in the embodiment) that receives a reflected wave reflected by an object in the predetermined area, and the transmitting unit. The time difference detecting means (for example, the distance detecting unit 25 in the embodiment) for detecting the time difference from the time when the electromagnetic wave is transmitted to the time when the reflected wave is received by the receiving means, and the time difference detecting means Object distance detection comprising: distance calculation means for calculating the distance from the vehicle to the object based on the detected time difference (for example, the distance detection unit 24 in the embodiment also serves as) A curve on a two-dimensional orthogonal coordinate plane showing a correspondence relationship between the time difference detected by the time difference detection means and the reception intensity of the reflected wave received by the reception means (for example, an embodiment) In the reception strength distribution waveform F) at the reception strength distribution waveform F) according to the slope of the reception strength increase side and the slope of the reception strength decrease side (for example, the estimated peak in the embodiment) Maximum value estimating means for estimating the voltage Vpeak) (for example, the maximum value estimating unit 24 in the embodiment) and the reception intensity in the curve is equal to or greater than a predetermined threshold (for example, the voltage threshold Vth in the embodiment). Correction for correcting the distance calculated by the distance calculation unit based on a time width (for example, the estimated pulse width W in the embodiment) and the maximum value estimated by the maximum value estimation unit And a stage (e.g., distance correction section 26 in the embodiment).

  Further, in the object distance detection device according to the second aspect of the present invention, the time difference detection means receives the reflected wave having the reception intensity equal to or greater than the predetermined threshold from the time when the electromagnetic wave is transmitted by the transmission means. The time difference up to a predetermined time is detected, and the distance calculation means calculates the distance based on the time difference when the reception intensity is the predetermined threshold among the time differences detected by the time difference detection means.

According to the object distance detection device of the first aspect of the present invention, the distance calculated based on the time difference from the time when the electromagnetic wave is transmitted to the time when the reflected wave is received is calculated as the time difference and the reception intensity of the reflected wave. The accuracy of the distance can be improved by correcting based on the maximum value of the reception intensity of the reception intensity distribution indicating the correspondence and the time width in which the reception intensity is equal to or greater than the predetermined threshold.
For example, when the maximum input voltage of the AD converter that samples the output of the receiving means is smaller than the maximum value of the received intensity of the reflected wave, the maximum value of the received intensity cannot be directly detected. Even in this case, it is possible to accurately estimate the maximum value of the received intensity according to the slope of the received intensity on the increasing side and decreasing side in the curve indicating the correspondence between the time difference and the received intensity of the reflected wave.

  Furthermore, according to the object distance detection device according to the second aspect of the present invention, the distance calculated for the reflected wave whose reception intensity is a predetermined threshold is determined by the time width and the maximum value where the reception intensity is equal to or greater than the predetermined threshold. By correcting, the detection accuracy of the distance to the reflection point can be improved.

It is a block diagram of the object distance detection apparatus which concerns on embodiment of this invention. It is a figure which shows the example of the waveform F of the receiving intensity distribution detected by the object distance detection apparatus which concerns on embodiment of this invention, the estimated pulse width W, and the estimated peak voltage Vpeak. The product M (= Vpeak × W) of the distance correction value C (M, L), the distance L (Tofup), the estimated peak voltage Vpeak, and the estimated pulse width W stored in the object distance detecting device according to the embodiment of the present invention. It is a figure which shows the example of the data which show a corresponding relationship. It is a figure which shows the example of the correspondence of the various objects which are the detection targets of the object distance detection apparatus which concerns on embodiment of this invention, the estimated peak voltage Vpeak, and the estimated pulse width W. It is a figure which shows the example of the waveform F of the receiving intensity distribution detected by the object distance detection apparatus which concerns on embodiment of this invention, the estimated pulse width W, and the estimated peak voltage Vpeak. It is a figure which shows the example of the waveform F of the receiving intensity distribution detected by the object distance detection apparatus which concerns on embodiment of this invention, the estimated pulse width W, and the estimated peak voltage Vpeak. It is a figure which shows the example of the waveform F of the receiving intensity distribution detected by the object distance detection apparatus which concerns on embodiment of this invention, the estimated pulse width W, and the estimated peak voltage Vpeak. Data indicating a correspondence relationship between the distance correction value C (M) stored in the object distance detection device according to the embodiment of the present invention and the product M (= Vpeak × W) of the estimated peak voltage Vpeak and the estimated pulse width W It is a figure which shows the example of.

Hereinafter, an object distance detection apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.
An object distance detection device 10 according to the present embodiment is mounted on, for example, a vehicle and includes a radar device 11 and a processing device 12 as shown in FIG.

The radar apparatus 11 includes a transmission unit 11a and a reception unit 11b, and divides a detection target region set in the external environment of the vehicle (for example, ahead of the traveling direction of the vehicle) into a plurality of angular regions, and each angular region is divided into a plurality of angular regions. A transmission signal of an electromagnetic wave such as an infrared laser or a millimeter wave is transmitted from the transmission unit 11a so as to scan.
And the reflected signal of the reflected wave produced by each outgoing signal being reflected by the object (for example, another vehicle, a structure, a road surface, etc.) in the detection object field outside a vehicle, a pedestrian, etc. is received by receiving part 11b. Receive.
Then, a signal related to the transmission signal and the reflection signal is output to the processing device 12.

  For example, as illustrated in FIG. 1, the processing device 12 includes an AD converter 21, a reception intensity distribution detection unit 22, a pulse width detection unit 23, a maximum value estimation unit 24, a distance detection unit 25, and a distance correction unit 26. And is configured.

The AD converter 21 samples the output of the reception unit 11b after the electromagnetic wave is transmitted from the transmission unit 11a of the radar apparatus 11 (that is, a signal indicating the reception intensity of the reflected wave received by the reception unit 11b) at a predetermined constant cycle. Then, the analog value of the reception intensity (for example, voltage) of the reflected wave received by the receiving unit 11b is converted into a digital value.
The AD converter 21 performs AD conversion for each input voltage of an analog value obtained by sampling the output of the receiving unit 11b at a predetermined constant period, for example, as each data point P of the output voltage shown in FIG. Outputs the digital output voltage.

Note that the AD converter 21 has a predetermined input upper limit voltage Vup and an input lower limit voltage with respect to an input voltage capable of performing appropriate AD conversion, and has an input voltage that is greater than or equal to the input lower limit voltage and less than or equal to the input upper limit voltage Vup. On the other hand, an output voltage having a digital value corresponding to the analog value of the input voltage is output.
On the other hand, for an input voltage larger than the input upper limit voltage Vup, for example, as in each data point P of the output voltage shown in FIG. 2, the digital value of the input upper limit voltage Vup is uniform regardless of the analog value of the input voltage. Is output.

The reception intensity distribution detection unit 22 detects a reception intensity distribution by a plurality of data points P as shown in FIG.
For example, the reception intensity distribution detection unit 22 indicates the time indicating the output timing of the AD converter 21 (that is, the time difference from the time when the electromagnetic wave is transmitted by the transmission unit 11a to the time when the reflected wave is received by the reception unit 11b) X It is obtained by sampling by the AD converter 21 on a two-dimensional orthogonal coordinate plane having the coordinate axis and the output voltage of the AD converter 21 (that is, the reception intensity (for example, voltage) of the reflected wave received by the receiving unit 11b) as the Y coordinate axis. The distribution of a plurality of data points P to be detected is detected.
FIG. 2 also shows an example of the estimated waveform D of the received intensity of the reflected wave received by the receiving unit 11b in accordance with the emission intensity design value of the transmitting unit 11a of the radar apparatus 11.

The pulse width detection unit 23 is a predetermined value smaller than the input lower limit voltage of the AD converter 21 and lower than the input upper limit voltage Vup, for example, in the waveform F of the received intensity distribution by the plurality of data points P on the two-dimensional orthogonal coordinate plane. A time width in which the reception intensity is equal to or higher than a predetermined voltage threshold Vth is detected with respect to the voltage threshold Vth.
More specifically, in the waveform F, the time (rise timing) Toup of the coordinate point A corresponding to the predetermined voltage threshold Vth on the increase side of the reception intensity (that is, voltage) and the decrease side of the reception intensity (that is, voltage). The time width between the time (falling timing) Tofdn of the coordinate point B corresponding to the predetermined voltage threshold Vth is detected as the estimated pulse width W.

The local maximum estimator 24 corresponds to the inclination on the increase side of the reception intensity and the inclination on the decrease side of the reception intensity in the waveform F of the reception intensity distribution by the plurality of data points P on the two-dimensional orthogonal coordinate plane. Then, the maximum value (estimated peak voltage Vpeak) of the reception intensity is estimated.
More specifically, the tangent line LA at the coordinate point A corresponding to the predetermined voltage threshold value Vth on the increase side of the reception strength (that is, voltage) and the predetermined voltage threshold value Vth on the decrease side of the reception strength (that is, voltage). The intersection point Q with the tangent line LB at the coordinate point B to be detected is detected, and the reception intensity (that is, voltage) corresponding to this intersection point Q is detected as the maximum value of the reception intensity (estimated peak voltage Vpeak).

  The distance detection unit 25 is based on the reception intensity distribution detected by the reception intensity distribution detection unit 22 and the time when the reflected wave is received by the reception unit 11b from the time when the electromagnetic wave is transmitted by the transmission unit 11a (transmission time) (reception) A time difference up to (time) is detected, and a distance L from the vehicle to the object (that is, the reflection point of the reflected wave) is calculated based on this time difference.

  For example, based on the output of the AD converter 21, the distance detection unit 25 is an output obtained by sampling the AD converter 21 with respect to the output of the reception unit 11b after the electromagnetic wave is transmitted by the transmission unit 11a of the radar apparatus 11. Depending on whether or not there is a time difference from the transmission time to the reception time.

Further, for example, the distance detection unit 25 calculates the time difference from the time when the electromagnetic wave is transmitted by the transmission unit 11a of the radar apparatus 11 to the time when the reflected wave whose reception intensity (that is, voltage) is equal to or higher than the predetermined voltage threshold Vth is received. To detect.
Then, the distance detection unit 25, for example, the time difference when the reception intensity (that is, voltage) is the predetermined voltage threshold Vth (that is, the time difference with respect to the time (rise timing) Toup of the coordinate point A in the reception intensity distribution shown in FIG. ) To calculate the distance L from the vehicle to the object (that is, the reflection point of the reflected wave).

  The distance correction unit 26 is configured to detect a distance L detected by the distance detection unit 25 based on the estimated pulse width W detected by the pulse width detection unit 23 and the estimated peak voltage Vpeak detected by the maximum value estimation unit 24, for example, The distance L (Tofup) based on the time difference when the reception intensity (that is, voltage) is the predetermined voltage threshold Vth (that is, the time difference with respect to the time (rise timing) Toup of the coordinate point A in the reception intensity distribution shown in FIG. 2) is corrected. To do.

The distance correction unit 26 is, for example, a predetermined distance corresponding to at least the estimated peak voltage Vpeak and the estimated pulse width W as data of a predetermined map created in advance for the distance correction coefficient C used for correcting the distance L (Tofup). Data of the correction value coefficient C is stored.
For example, the predetermined distance correction coefficient C shown in FIG. 3 changes according to the product M (= Vpeak × W) of the estimated peak voltage Vpeak and the estimated pulse width W and the distance L (Tofup), and the product M or the distance L ( With the increase in Tofup), the trend is increasing.

  Then, the distance correction unit 26 corrects the distance L (Tofup) detected by the distance detection unit 24 using the distance correction coefficient C (M, L), for example, as shown in the following formula (1). The subsequent distance L (TOF) is calculated.

  In the above formula (1), the product M (= Vpeak × W) of the estimated peak voltage Vpeak and the estimated pulse width W is proportional to the reflected energy (that is, the energy of the reflected wave received by the receiving unit 11b). The correction unit 26 performs correction in consideration of the area and shape of the detection target (that is, an object that emits a reflected wave, a pedestrian, or the like) in addition to the distance L (Tofup).

  In other words, various detection objects that emit reflected waves are, for example, shown in FIG. 4 according to the reception intensity of the reflected waves, that is, the estimated peak voltage Vpeak, and the depth of the point (reflection point) on the detection object, that is, the estimated pulse width W. It has a distribution characteristic as shown in FIG.

For example, in FIG. 4, for pedestrians, the estimated peak voltage Vpeak is weak and the estimated pulse width W is slightly wider, and for the oncoming vehicle, the estimated peak voltage Vpeak is weak and the estimated pulse width W is slightly Narrow.
Further, for example, the estimated peak voltage Vpeak is strong and the estimated pulse width W is wide for a signboard, and the estimated peak voltage Vpeak is strong and the estimated pulse width W is further widened for a large vehicle.

  For example, as illustrated in FIG. 4, the distance correction unit 26 uses an estimated peak voltage Vpeak and an estimated pulse width W that change according to various detection objects to control various detection objects. The distance to the nearest point (nearest point) from the required vehicle can be detected with high accuracy.

  The object distance detection apparatus 10 according to the present embodiment has the above-described configuration. Next, an operation example of the object distance detection apparatus 10 will be described.

  For example, with respect to the oncoming vehicle RA existing in front of the vehicle S shown in FIG. 5, the waveform FA1 of the reflected wave having the reflection point at the front grille and the headlight of the oncoming vehicle RA and the hood of the oncoming vehicle RA A waveform F obtained by synthesizing the waveform FA2 and the like by a reflected wave having a reflection point at the periphery is detected. Then, the estimated pulse width W1 and the estimated peak voltage Vpeak1 are detected for this waveform F.

Further, for example, for the preceding vehicle RB existing in front of the vehicle S shown in FIG. 6, a waveform FB1 based on a reflected wave having a reflection point at the periphery of the rear end reflector of the preceding vehicle RB, and a rear body portion of the preceding vehicle RB. A waveform F obtained by combining a waveform FB2 and the like by a reflected wave having a reflection point in the periphery of the signal is detected. Then, an estimated pulse width W2 (> W1) and an estimated peak voltage Vpeak2 (> Vpeak1) are detected for the waveform F.
In this case, as the estimated pulse width W2 and the estimated peak voltage Vpeak2 increase as compared with the oncoming vehicle RA shown in FIG. 5, the accuracy of the distance L decreases (that is, the variation in the positional accuracy increases). Therefore, the correction according to the larger product M (= Vpeak2 × W2) is performed, thereby suppressing the variation in position accuracy.

Further, for example, for the large vehicle RC existing in front of the vehicle S shown in FIG. 7, a plurality of waveforms FC1, FC2,. A combined waveform F is detected. An estimated pulse width W3 (> W2) and an estimated peak voltage Vpeak3 (> Vpeak2) are detected for this waveform F.
In this case, as the estimated pulse width W3 and the estimated peak voltage Vpeak3 increase as compared with the preceding vehicle RB shown in FIG. 6, the accuracy of the distance L decreases (that is, the variation in positional accuracy increases). Therefore, the correction according to the larger product M (= Vpeak3 × W3) is performed, thereby suppressing the variation in position accuracy.

  As described above, according to the object distance detection device 10 according to the present embodiment, the time when the reflected wave is received by the receiving unit 11b from the time (transmitting time) when the electromagnetic wave is transmitted by the transmitting unit 11a of the radar device 11 ( By correcting the distance L calculated based on the time difference until the (reception time) based on the estimated peak voltage Vpeak and the estimated pulse width W, the accuracy of the distance L can be improved.

  In addition, for example, the input upper limit voltage Vup of the AD converter 21 is received by the receiving unit 11b due to being smaller than an analog input voltage obtained by sampling the output of the receiving unit 11b at a predetermined constant period. Even if it is not possible to directly detect the maximum value of the reception intensity of the reflected wave, the maximum value of the reception intensity (in accordance with the slope of the reception intensity distribution waveform F on the increase side and decrease side of the reception intensity ( The estimated peak voltage Vpeak) can be estimated with high accuracy.

In the above-described embodiment, the distance correction coefficient C is changed according to the product M (= Vpeak × W) and the distance L (Tofup), but is not limited to this. For example, as shown in FIG. The distance correction coefficient C may change only according to the product M (= Vpeak × W).
For example, in the data of the predetermined distance correction coefficient C shown in FIG. 8, as the product M (= Vpeak × W) increases, the increase rate of the distance correction coefficient C changes to a decreasing tendency, and the distance correction coefficient C increases. Has changed.

10 Object Distance Detection Device 11a Transmission Unit (Transmission Unit)
11b Receiver (Receiving means)
24 local maximum estimation unit (local maximum estimation means)
25 Distance detector (time difference detector, distance calculator)
26 Distance correction unit (correction means)

Claims (2)

A transmission means for transmitting electromagnetic waves toward a predetermined area from the vehicle;
Receiving means for receiving the reflected wave reflected by the object in the predetermined area, the electromagnetic wave transmitted by the transmitting means;
A time difference detecting means for detecting a time difference from a time when the electromagnetic wave is transmitted by the transmitting means to a time when the reflected wave is received by the receiving means;
An object distance detection device comprising distance calculation means for calculating a distance from the vehicle to the object based on the time difference detected by the time difference detection means;
A slope on the increase side of the reception intensity in a curve on a two-dimensional orthogonal coordinate plane showing a correspondence relationship between the time difference detected by the time difference detection means and the reception intensity of the reflected wave received by the reception means; Maximum value estimation means for estimating a maximum value of the reception strength according to the slope on the decrease side of the reception strength;
Correction means for correcting the distance calculated by the distance calculation means based on a time width in which the received intensity in the curve is equal to or greater than a predetermined threshold and the maximum value estimated by the maximum value estimation means; An object distance detection device comprising: The time difference detection means detects the time difference from the time when the electromagnetic wave is transmitted by the transmission means to the time when the reflected wave having the reception intensity equal to or greater than the predetermined threshold is received,
The object according to claim 1, wherein the distance calculation unit calculates the distance based on the time difference when the reception intensity is the predetermined threshold among the time differences detected by the time difference detection unit. Distance detection device.

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