JP2010204033A - Radar device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent erroneous detection to an unneeded object without being influenced by the strength of reflection of different radio waves depending on objects. <P>SOLUTION: The difference between detection waveforms and reference waveforms is calculated (S5), and it is determined whether a differential signal having a strength of not less than a threshold S at distance h has been obtained. As a result, when the strength of the differential signal at distance h is not less than the threshold S, it is determined that the signal is a reflection from an unneeded object, such as manholes on a road, metal joints, or the like. When the strength of the differential signal at distance h is less than the threshold S, it is further determined whether time t required for detecting objects or time t for continuing to detect objects successively is not less than a threshold (L+B)/V according to vehicle speed V. As a result, in t≥(L+B)/V and t<(L+B)/V, normal alarm processing is performed and it is determined to be an erroneous detection of unneeded objects by instantaneous detection, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicular radar apparatus that transmits a radar wave to the outside of a vehicle, receives a reflected wave reflected by an object existing around the vehicle, and performs a ranging process.

  In general, radar uses electromagnetic waves, and the presence / absence and position of an object can be detected by capturing reflected waves of transmitted radio waves. When this radar apparatus is mounted on a vehicle, there is a possibility that an object that should not be recognized as an obstacle is erroneously detected as an obstacle due to the influence of clutter from the road surface.

  In order to deal with this, for example, in Patent Document 1, the road on which the vehicle is traveling is recognized by the navigation device, and when the road is a general road, the reflectance of the reflected wave of the object measured by the radar is the first threshold value. A technique is disclosed in which an object is extracted as an obstacle at the time described above, and when the road is an automobile-only road, the object is extracted as an obstacle when the reflectance of the reflected wave measured by the radar is equal to or higher than a second threshold higher than the first threshold. ing.

JP 2008-37361 A

  However, the technique disclosed in Patent Document 1 is mainly intended to prevent erroneous detection of manholes or the like on an automobile road where there is a low possibility that an object with low radio wave reflectance such as a pedestrian exists. Since the intensity of reflection of radio waves depends on the object, lowering the threshold value to detect pedestrians on ordinary roads also detects metal objects with particularly high reactivity such as manholes and joints.

  In particular, when trying to detect the surroundings of a vehicle in a wide range with a radar, it is necessary to use radio waves of a relatively low frequency, and it is difficult to control directivity, so it is possible to detect unnecessary objects. The sex becomes higher.

  The present invention has been made in view of the above circumstances, and provides a vehicular radar apparatus capable of preventing erroneous detection of an unnecessary object without being affected by the intensity of reflection of different radio waves depending on the object. It is aimed.

  In order to achieve the above object, a vehicle radar device according to the present invention is a vehicle radar device that performs a ranging process by receiving a reflected wave reflected by an object from a radar wave transmitted to the outside of the vehicle. Is filtered with a threshold of time according to the speed of the vehicle, the first filter that excludes processing for the reflected wave from the unnecessary object, and the reflected wave is filtered with the threshold of the reflection intensity at a predetermined distance, And a second filter that excludes processing for the reflected wave.

  According to the present invention, by using the first filter based on the time threshold according to the speed of the vehicle and the second filter based on the threshold of the reflection intensity at a predetermined distance, the reflection strength of the radio wave that varies depending on the object can be obtained. It is possible to prevent erroneous detection of unnecessary objects without being affected.

The block diagram of the radar device for vehicles concerning a 1st embodiment of the present invention. Same as above, explanatory diagram showing the arrangement of antennas on the car Same as above, explanatory diagram of differential waveform Same as above, explanatory diagram showing the detection process of metal objects laid on the road surface Same as above, an explanatory diagram showing the characteristics of the first filter Same as above, explanatory diagram of second filter for differential waveform Same as above, flowchart of object approach warning processing Explanatory drawing of the 2nd filter with respect to 2nd Embodiment of this invention with respect to a sampling waveform. Same as above, flowchart of object approach warning processing

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a vehicular radar apparatus (hereinafter simply referred to as “radar apparatus”) that is mounted on a vehicle such as an automobile and detects an object 200 existing around the vehicle to measure a distance. In the embodiment, it is a pulse radar device. The radar apparatus 1 includes a transmission antenna 2a, a reception antenna 2b, and a plurality of radar units 20, each including a signal processing circuit unit 5 that performs transmission / reception signal processing, and a distance measurement process by controlling each radar unit 20. The control unit 50 is mainly configured.

  Although FIG. 1 shows a transmission / reception antenna separation type device in which the transmission antenna 2a and the reception antenna 2b are separated, the transmission antenna 2a and the reception antenna 2b may be integrated.

  FIG. 2 shows an arrangement example of a plurality of radar units 20,... Of the radar apparatus 1 mounted on the automobile 100. Each radar unit 20 has two left and right corner portions inside the front bumper 101 and two left and right corner portions inside the rear bumper 102, two left and right portions below the front door 103 (inside the side sill spoiler), and a lower portion of the rear door 104 (side sill spoiler). (Inside) two places on the left and right, a total of eight places. The control unit 50 performs a ranging process while switching the radar units 20.

  The signal processing circuit unit 5 in each radar unit 20 includes a transmission circuit, a reception circuit, a sampling control circuit, and the like. In this circuit configuration, a transmission pulse of a predetermined frequency is generated by the transmission circuit based on the clock signal from the control unit 50, and a radar wave is transmitted from the transmission antenna 2a to the outside of the vehicle. Then, when the reflected wave reflected by the object is received by the receiving antenna 2b, the received wave is sampled by the receiving circuit.

  The reception wave is sampled using a known equivalent time sampling method. That is, a time sweep pulse delayed by a predetermined amount with respect to the transmission pulse by the sampling control circuit is generated and output to the reception circuit. In the receiving circuit, the received wave is sampled by the sample / hold based on the time sweep pulse. The sampling waveform at this time is a waveform obtained by expanding the waveform received by the receiving antenna 2b on the time axis (equivalent time sampling). The reception waveform sampled by the equivalent time is cut into high-frequency noise through a filter or the like, amplified to a predetermined output level, and input to the control unit 50.

  The control unit 50 is a central configuration of a ranging system using the radar unit 20. The control unit 50 includes a microprocessor and a peripheral circuit that outputs a clock signal and timing signal to the signal processing circuit unit 5, and an A / D conversion that converts an analog signal input from the signal processing circuit unit 5 into a digital signal. Equipment is provided.

  The control unit 50 supplies a clock signal and a timing signal to each signal processing circuit unit 5 and calculates a distance to an object existing outside the vehicle based on the received signal processed by each signal processing circuit unit 5. Processing is mainly performed. In the present embodiment, this distance measurement process is performed based on a differential waveform as shown by a solid line in FIG.

  That is, the control unit 50 holds the baseband waveform indicated by the alternate long and short dash line in FIG. 3 as the reference waveform. This reference waveform is a reflected waveform acquired in a situation where there is no object to be measured in the environment outside the vehicle.

  For example, the reflection waveform in a standard road surface condition where the object to be measured does not exist is acquired in advance by offline experiments or simulations, or the reflection waveform sampled during driving is acquired by statistical processing and controlled. It is stored and held in the memory in the unit 50. Then, the difference between the reference waveform read from the memory and the received waveform (the waveform indicated by the broken line in FIG. 3) acquired via the receiving antenna 2b and the signal processing circuit unit 5 is obtained, and the distance is measured based on the difference waveform. Do.

  The reception waveform in FIG. 3 shows data obtained by A / D converting the waveform for one frame (one period) with a resolution of 200 samples and 8 bits. The period of one frame is, for example, about 20 to 40 msec.

  In addition, as a received waveform, a raw waveform acquired via the receiving antenna 2b and the signal processing circuit unit 5 may be used. However, in order to reduce the influence of noise or the like, a waveform obtained by statistically processing a plurality of raw waveforms is used. You may make it handle as a received waveform.

  In this case, the radar apparatus 1 according to the present embodiment uses a radio wave with a relatively low frequency (for example, about 3 MHz) having a ranging range of about several meters when detecting an object around the vehicle. For this reason, the spread of the radio wave beam is large, and there is a possibility that metal objects having high reactivity such as manholes and joints on the road surface may be detected during traveling.

  For example, as shown in FIG. 4, consider a case where the radar unit 20 installed in a rear bumper at the rear of the vehicle detects a manhole 201 on the road surface. At this time, the effective beam detection width of the receiving antenna 2b is B, and the detection length (diameter) of the manhole 201 with respect to the traveling direction of the vehicle is L. First, as shown in FIG. 4A, when the vehicle body passes through the manhole 201 and enters the beam effective detection width B, the manhole 201 starts to be detected. Then, when the vehicle further advances from the stage of detection shown in FIG. 4B and exceeds the distance (L + B), the detection of the manhole 201 is finished.

At this time, assuming that the speed of the vehicle is V, a time t ₀ required to pass a distance (L + B) at which a valid signal can be acquired by the receiving antenna 2b is expressed by the following equation (1).
t ₀ = (L + B) / V (1)

Metal joints used in manholes and highway seams, etc. have a certain size (area), compared to vehicles, bicycles, pedestrians, etc. The detection time during traveling is considered to be extremely short. Therefore, the control unit 50 presets the time t ₀ according to the speed of the vehicle, and filters the received wave using the time t ₀ as a threshold, thereby excluding the processing for the reflected wave from the unnecessary object. A filter 50a is provided.

As shown in FIG. 5, the first filter 50 a is a software time filter that represents the relationship of the expression (1) with the vehicle speed V and the time t ₀ as axes, and is stored in the memory in the control unit 50. Is stored and retained. Then, by restricting the input sampling process in the control unit 50 to the shaded area in FIG. 5, the detection of unnecessary objects is prevented, and false alarms and the like due to instantaneous detection are eliminated.

  The effective beam detection width B in the equation (1) is determined in advance in consideration of the antenna characteristics and the frequency of the radar wave. In addition, the detection length L is approximately 0.5 to 1 m in the case of road manholes and metal joints.

For example, L = 0.6 m, When B = 0.8 m, the vehicle speed _{V = 100km / h, t 0} = 50.4msec, the vehicle speed 15km / h, the t ₀ = 336msec. Therefore, when the time required for detecting the object is equal to or less than t ₀ , the object detection process is not performed because the object is not to be detected. On the contrary, when the time required for detecting the object is t ₀ or more, or when the time for continuously detecting the object is t ₀ or more, the object detection processing is performed as the object to be detected. For example, alarm processing is performed. Further, t ₀ indicates that when a person or an object approaches the vehicle, the detection delay by the time filter can secure a distance that does not cause a practical problem with respect to the necessary alarm timing.

  Further, the control unit 50 includes a second filter 50b based on the reflection intensity factor of the object in addition to the first filter 50a based on the detection time factor, thereby reliably avoiding the detection of the unnecessary object. That is, generally, since a metal object has a higher reaction level than other objects, unnecessary objects such as manholes and joints that are metal objects on the road surface also have a high reaction level.

  Accordingly, the distance h at which the reflected wave is most picked up is set in advance by experiment or simulation from the positional relationship between the metal object on the road surface and the in-vehicle receiving antenna 2b. Then, a second filter 50b that filters the received wave according to whether or not the intensity of the reflected wave from the object at the time corresponding to the distance h is equal to or greater than a preset threshold and excludes the processing for the reflected wave from the unnecessary object is provided. As a reflection intensity filter, it is stored and held on a memory in the control unit 50b.

  In the present embodiment, waveform processing for determining the presence or absence of an object is performed based on the difference waveform. As shown in FIG. 6, as the difference waveform moves away from the object to be reflected, the waveform changes as follows: a solid line waveform → a broken line waveform → a one-dot chain line waveform in FIG. Therefore, a threshold value S for determining whether or not the object is an unnecessary object is provided as a reference value for the differential waveform in FIG. Then, as indicated by a circle in FIG. 6, when the intensity (amplitude) of the response of the differential waveform at the time corresponding to the distance h is greater than or equal to the threshold value S, it is determined that the reflection is from an unnecessary metal object such as a manhole. To exclude the processing for the corresponding waveform.

Thus, what should be originally recognized as an obstacle by performing equivalent delay processing based on the time t ₀ required to detect an unnecessary object according to the speed of the vehicle and the magnitude of the reaction of the object at a predetermined distance h It is possible to prevent erroneous detection of an object that is not.

  In addition, there is no restriction | limiting in particular in the order of filtering of the reflected wave by the 1st filter 50a and the 2nd filter 50b, which may be performed first. Moreover, these 1st, 2nd filters 50a and 50b are applied to the receiving antenna 2b of each radar unit 20 arrange | positioned around the vehicle.

  Next, an object approach warning program process using the above time filter and reflection intensity filter will be described with reference to the flowchart of FIG.

  First, in the first step S1, a reference signal is acquired and stored by processing a radar reception waveform in a standard road surface condition (a reference waveform stored in advance may be read from the memory). Then, after taking a predetermined interval in step S2, a radar signal is detected and stored in step S3.

  In the subsequent step S4, it is determined whether or not the current vehicle speed V exceeds a preset vehicle speed VL. The set vehicle speed VL is a vehicle speed at which an alarm process is performed by approaching an object during traveling. If V ≦ VL in step S4, the process returns to step S2. On the other hand, if V> VL, the process proceeds from step S4 to step S5, and the difference between the detected waveform and the reference waveform is calculated.

  In step S6, it is determined whether or not a difference signal having an intensity equal to or greater than the threshold value S at the distance h is obtained. As a result, when the intensity of the difference signal at the distance h is equal to or greater than the threshold value S, it is assumed that the reflection is from an unnecessary object such as a manhole or a metal joint on the road, and the process returns to step S2.

On the other hand, when the intensity of the difference signal at the distance h is less than the threshold value S, the process proceeds from step S6 to step S7, and the time t required to detect the object or the time t during which the object is continuously detected becomes the vehicle speed V. It is determined whether or not the corresponding threshold value t ₀ (= (L + B) / V) or more. As a result, when t ≧ t ₀ , the routine proceeds to step S8 where normal alarm processing is performed, and when an object is approaching, the alarm is turned on to warn the driver. In the case of t <t ₀ , it is determined in step S9 that it is an erroneous detection of an unnecessary object due to instantaneous detection, and the process returns to step S2 without outputting the alarm while maintaining OFF, and monitoring by the radar is continued.

  As described above, the radar apparatus 1 according to the present embodiment includes the first filter that filters the reflected wave from the object using the time required to detect the unnecessary object according to the vehicle speed as a threshold, and the reflection intensity at a predetermined distance. And a second filter that filters the reflected wave with a threshold value as a threshold, so that the detection performance for objects with low reflectivity of radio waves such as pedestrians is not sacrificed, and errors in metal objects such as manholes and joints on the road are detected. Detection can be reliably prevented.

Next, a second embodiment of the present invention will be described.
The second form is an example using a radar wave having a higher frequency than the first form. In the second mode, the configuration of the signal processing circuit unit 5 of the first mode is changed, and for example, a so-called FMCW (Frequency Modulated Continuous Wave) type circuit configuration that detects an object by transmitting and receiving a frequency-modulated continuous wave ( An FM modulated wave generator proportional to a triangular wave, a mixer that combines a part of a received wave and a transmitted wave from a reflector, and the like. Accordingly, the distance measuring process in the control unit 50 is changed.

  For example, when the radar frequency is set to about 3 GHz, a remarkable movement of a waveform peak capable of specifying the distance can be obtained in the received wave from the reflection object. Therefore, in the second embodiment, distance measurement can be performed with the amount of movement of the waveform in the time axis direction without depending on the waveform size, and it is not always necessary to use the differential waveform.

  In response to this change in distance measuring method, the same filter as in the first embodiment can be used as the first filter (time filter) 50a for preventing erroneous detection of unnecessary objects. On the other hand, as shown in FIG. 8, the second filter 50b used in the first embodiment is changed from a reflection intensity filter to a filter for the received waveform itself, and this filter is used to prevent erroneous detection of unnecessary objects.

  That is, as shown in FIG. 8, as the received waveform from the reflection object is farther away from the reflection object, the peak position θ changes as shown by the solid line waveform → the broken line waveform → the dashed line waveform in FIG. The distance can be measured based on this change. Accordingly, a threshold value S ′ for determining whether or not the object is an unnecessary object is provided, and when the waveform amplitude at the time of the distance h is smaller than the threshold value S ′ as shown by a circle in FIG. It is determined that no unnecessary metal object is detected. Conversely, when the waveform amplitude at the time of the distance h is equal to or greater than the threshold value S ′, the detection process is not performed because it is an unnecessary metal object such as a manhole.

  As shown in the flowchart of FIG. 9, the approach processing of the program in the second embodiment slightly changes the program processing of the first embodiment (see FIG. 7).

  In this program processing, the reference signal acquisition processing in step S1 and the difference calculation processing in step S5 in the first embodiment are unnecessary, the interval processing in step S2 is first performed, and then the radar signal detection in step S3 is performed. After the vehicle speed determination in step S4, the process proceeds to step S6-2, and it is determined whether or not a signal having a strength greater than or equal to the threshold value S 'is detected at the distance h.

  As a result, if a signal equal to or greater than the threshold value S ′ is detected at the distance h, it is assumed that the reflection is from an unnecessary object such as a manhole or a metal joint on the road, and the process returns to step S2. On the other hand, if the signal at the distance h is less than the threshold value S ′, the process proceeds from step S6-2 to step S7, and the time t by the time filter similar to that in the first embodiment is determined according to the vehicle speed V. Then, depending on the determination result, normal alarm processing in step S8 or alarm OFF processing based on erroneous detection determination in step S9 is performed.

  In the second mode, as in the first mode, it is possible to reliably prevent erroneous detection of metal objects such as manholes and joints on the road without sacrificing detection performance for objects with low radio wave reflectance such as pedestrians. can do.

DESCRIPTION OF SYMBOLS 1 Radar apparatus 20 Radar unit 50 Control unit 50a 1st filter 50b 2nd filter 100 Automobile 201 Manhole

Claims (3)

A radar device for a vehicle that performs a ranging process by receiving a reflected wave reflected by an object from a radar wave transmitted to the outside of the vehicle,
A first filter that filters the reflected wave with a threshold of time according to the speed of the vehicle and excludes processing for the reflected wave from an unnecessary object;
A vehicular radar apparatus, comprising: a second filter that filters the reflected wave with a threshold value of reflection intensity at a predetermined distance and excludes processing for the reflected wave from an unnecessary object.   The threshold value of the time in the first filter becomes shorter as the speed of the vehicle increases, and when the detection time of the object is less than or equal to the threshold value of the time, it is determined as the unnecessary object. The vehicular radar apparatus according to claim 1.   3. The vehicular radar apparatus according to claim 1, wherein the second filter determines that the object is an unnecessary object when the reflection intensity at the predetermined distance is equal to or greater than a threshold value. 4.

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