JP2017003347A - Object detection device and object detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an object detection device and an object detection method that can detect an object with high precision even when an antenna is small-sized.SOLUTION: An object detection device 100 comprises a radar sensor 4 which irradiates an object 2 with a radio wave and receives a reflected wave thereof, and a controller 5 which acquires a distance from the radar sensor to the object and an intensity of the reflected wave so as to detect whether the object is present. The controller detects whether the object is present over a peak search range wider than a detection and determination range of the object, detects a distance at which the intensity of the reflected wave is maximum when the object is detected, and determines that the object is present when the distance is equal to or shorter than a predetermined distance threshold within the detection and determination range of the object. An antenna which has wide directivity can be used since it is detected within the wide peak search range whether the object is present is detected, and the object can be detected with high precision since it is determined that the object is present when the distance at which the intensity of the reflected wave is maximum is within the detection and determination range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an object detection device and an object detection method for detecting the presence or absence of an object by irradiating an object with radio waves and receiving the reflected waves. For example, the present invention detects presence or absence of a vehicle in a vehicle compartment in a parking lot. It is applied to a vehicle detection device.

  As a vehicle presence detection device, for example, a loop coil type sensor disclosed in Patent Document 1 that detects the presence or absence of a vehicle by embedding a loop coil in a passenger compartment is known. However, since it is necessary to embed a loop coil in the ground, the construction work requires a lot of time and cost, and it may be difficult to install in a parking lot such as a building property.

On the other hand, what uses an infrared sensor or an ultrasonic sensor disclosed in Patent Document 2, for example, can install a sensor unit on a flap plate mounting portion or the like that prevents unauthorized removal of the vehicle. Therefore, the construction work can be shortened and the cost can be reduced, but these sensors are easily affected by the environment, such as sunlight, rain, wind, snow, indoor multiple reflection, and the like.
Thus, for example, Patent Document 3 proposes a radar system (millimeter wave radar) that is easy to install but hardly affected by the environment.

JP 2006-72437 A JP 2007-207206 A JP 2014-203340 A

  By the way, when an object detection device using a radar is used for detecting a vehicle in a parking lot, it is necessary to reduce the antenna directivity so as not to erroneously detect a vehicle in an adjacent vehicle compartment or a vehicle passing through a passage. There is. However, in order to reduce the directivity, the antenna size must be increased, and there is a risk of hindering when the antenna is built in the tire stopper or installed on the ceiling.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an object detection apparatus and an object detection method capable of detecting an object with high accuracy even when the antenna size is small. .

  The object detection apparatus of the present invention detects the presence or absence of an object by radiating a radio wave toward the object and receiving the reflected wave, and acquiring the distance from the radar sensor to the object and the intensity of the reflected wave. A control device, the control device detects the presence or absence of an object in a peak search range wider than the detection detection range of the object, and detects the distance where the intensity of the reflected wave is maximum when the object is detected, this distance Is determined to be present when it is equal to or smaller than a predetermined distance threshold within the object detection determination range.

  The object detection method of the present invention is a method for detecting the presence or absence of an object by irradiating an object with radio waves and receiving the reflected wave, and acquires the distance to the object and the intensity of the reflected wave. Detects the presence or absence of an object in a peak exploration range wider than the object detection determination range, detects the distance at which the intensity of the reflected wave is maximum when the object is detected, and this distance is a predetermined value within the object detection determination range. It is characterized in that it is determined that there is an object when it is less than or equal to the distance threshold.

  According to the present invention, since the presence / absence of an object is detected in a peak search range wider than the object detection determination range, a small antenna with wide directivity can be used. In addition, since the object is determined to be present when the distance at which the intensity of the reflected wave is maximum is equal to or less than a predetermined distance threshold within the detection determination range, an object outside the detection determination range is not detected, and an object within the detection determination range is detected. Can be detected with high accuracy. Moreover, even if a second harmonic or a third harmonic of the reflected wave is generated within the detection judgment range due to an object existing in the peak exploration range, the distance to the object where the intensity of the reflected wave is maximum is a predetermined distance. Since the threshold value is exceeded, it is possible to suppress erroneous detection or erroneous determination due to these effects.

  Therefore, when applied to an on-vehicle detection device in a parking lot, it can be easily built in a tire stopper or installed on a ceiling. In addition, it is possible to detect the vehicle in the vehicle compartment with high accuracy by suppressing erroneous detection of the vehicle in the adjacent vehicle compartment and the vehicle passing through the passage.

It is a block diagram which shows schematic structure of the object detection apparatus which concerns on embodiment of this invention. It is a flowchart which shows the algorithm of the object detection method which concerns on embodiment of this invention. It is a wave form diagram for demonstrating the method of calculating distance from the transmission wave and reception wave of a radar sensor. It is a top view for demonstrating the example which uses the object detection apparatus of this invention for the presence detection of a parking lot. FIG. 5 is a side view of FIG. 4. It is a flowchart which shows the algorithm in the case of using the object detection method of this invention for the presence detection of a parking lot. 7 is a waveform diagram showing the relationship between the reflected wave intensity threshold and the distance from the object detection device in the vehicle presence detection method of FIG. It is a figure which shows the in-vehicle determination range determined by the relationship between the intensity | strength of a reflected wave, and the distance from an object detection apparatus. When using the object detection method of this invention for the presence detection of a parking lot, it is a wave form diagram for demonstrating the influence of an interference wave, and its reduction. When using the object detection method of this invention for the presence detection of a parking lot, it is a wave form diagram for demonstrating the concrete other method of reducing an interference wave. It is a block diagram which shows the other schematic structure at the time of using the object detection apparatus of this invention for the presence detection of a parking lot. It is a wave form diagram for demonstrating the influence of the reflection in a housing | casing in the object detection apparatus of FIG. It is a wave form diagram for demonstrating the method to reduce the influence of reflection in a housing | casing, when using the object detection method of this invention for the presence detection of a parking lot. It is a flowchart which shows the other algorithm at the time of using the object detection method of this invention for the presence detection of a parking lot.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, an object detection apparatus 100 irradiates a radio wave from a transmission antenna 1 toward an object 2 to be detected and receives a reflected wave by a reception antenna 3. A control device (CPU) 5 that detects the presence or absence of the object 2 by acquiring the distance to the object 2 and the intensity of the reflected wave from the output IF (Intermediate Frequency) signal. Here, as the antennas 1 and 3, small antennas having wide directivity can be used.

  The control device 5 performs analog / digital conversion on the IF signal output from the radar sensor 4, processes the digital signal output from the A / D converter 6, and sends a control signal to the radar sensor 4. A processing unit 7 for outputting and controlling is included. The control device 5 is connected to a host device or a host device (not shown) via a host interface circuit (host I / F) 8. Data can be exchanged between the control device 5 and the host device or host device by wire or wireless. Then, an operating voltage is supplied to the radar sensor 4, the control device 5, and the upper interface circuit 8 from a power source 9 such as a commercial power source or a battery.

  Next, the object detection method in the above configuration will be described with reference to the flowchart of FIG. First, in order to detect the presence or absence of the object 2 in a peak search range wider than the detection determination range of the object 2, the control device 5 controls the radar sensor 4 to irradiate the object 2 from the transmission antenna 1 with radio waves. When the object 2 exists, the radio wave is reflected by the object 2 and the reflected wave is received by the receiving antenna 3. An IF signal including the distance of the reflection point and the intensity of the reflected wave is obtained from the delay time at this time. The IF signal is digitized by the A / D converter 6 in the control device 5 and input to the processing unit 7 for signal processing, thereby detecting the presence or absence of the object 2 within the peak search range (step S1). The processing unit 7 performs a fast Fourier transform (FFT) analysis on the digitized IF signal.

  The radar sensor 4 is an FM-CW (Frequency Modulated-Continuous Wave) system in this example, and transmits a radio wave whose frequency changes with time as shown by a solid line in FIG. 3 and receives a received wave shown by a broken line. The distance is calculated from the frequency difference Δf1, Δf2 with the transmission wave at that time. When the frequency difference between the transmitted wave and the received wave is small as indicated by Δf1, the time t1 until the reflected wave arrives is small, and when the frequency difference between the transmitted wave and the received wave is large as indicated by Δf2, the reflected wave It takes a long time t2 to reach. The frequency difference between the transmitted wave and the received wave can be expressed by the following equation.

Transmitted wave-received wave = beat signal (frequency)
The arrival time τ (seconds) is “τ = 2R / c”, where R is the distance until the radio wave radiated from the transmitting antenna 1 is reflected by the object 2 and reaches the receiving antenna 3, and c is the speed of light. Become.
Thus, since the frequency of the beat signal obtained from the near object 2 is low and the frequency of the beat signal obtained from the far object 2 is observed to be high, if the obtained beat signal is subjected to frequency analysis by a technique such as FFT analysis. , That distance is required.

  Then, it is determined whether or not the object 2 is present within the peak search range (step S2). If it is determined that the object 2 is present, the processing unit 7 detects the distance where the intensity of the reflected wave is maximum (step S3). On the other hand, if it is determined that there is no such information, it is notified to the host device via the host interface circuit 8 (step S4).

  In the next step S5, the processing unit 7 determines whether or not the distance at which the intensity of the reflected wave is maximum is equal to or less than a predetermined distance threshold. Here, the predetermined distance threshold is set to a predetermined distance to be detected within the detection determination range of the object 2. If the distance at which the intensity of the reflected wave is the maximum is not less than the distance threshold, the processing unit 7 determines that there is no object (step S6). If the distance is less than the distance threshold, the processing unit 7 determines whether or not the predetermined intensity threshold is exceeded. Is determined (step S7). This intensity threshold is set in consideration of the reflection intensity of the object 2 to be detected. If it is not equal to or greater than the predetermined intensity threshold, the processing unit 7 determines that there is no object (step S6), and if it is equal to or greater than the predetermined intensity threshold, it is determined that there is an object (step S8). And the determination result of these steps S6 and S8 is notified to a high-order apparatus and a high-order apparatus.

  In this way, by determining whether or not the distance at which the intensity of the reflected wave is maximum is equal to or less than a predetermined distance threshold, the reflection point within the wide peak search range is excluded, and the reflection within the detection determination range. You can determine if it is a point. In addition, by determining whether or not the maximum intensity of the reflected wave is greater than or equal to a predetermined intensity threshold, the influence of weak reflected waves within the detection determination range, such as second harmonic and third harmonic, is eliminated. , Can determine the presence or absence of objects.

  Therefore, according to this embodiment, since the presence or absence of the object 2 is detected in a peak search range wider than the detection determination range of the object 2, it is possible to use the small antennas 1 and 3 having a wide directivity. Further, the object 2 outside the detection determination range is not detected, and the object within the detection determination range can be detected with high accuracy. Furthermore, even if a reflected wave having a low intensity is generated in the detection determination range by an object existing in the peak search range, erroneous determination due to the influence can be suppressed.

[Application Example 1]
4 and 5 are a plan view and a side view, respectively, when the above-described object detection device is applied to the presence detection of a parking lot. Here, an example is shown in which the object detection device 100 is built in a tire stopper 120 installed on a road surface near an end in the passenger compartment 110. The tire stopper 120 is formed of a metal casing, and has a window 120a for radiating radio waves from the object detection device 100 on the surface where the vehicle 130 enters. A plate-like member such as resin is fitted into the window 120a so as to transmit radio waves, and the transmitting antenna 1 and the receiving antenna 3 are provided at positions corresponding to the window 120a. Since the antennas 1 and 3 are small antennas with wide directivity, the window 120a can be small, and the strength reduction of the tire stopper 120 can be reduced.

  Next, the presence detection algorithm will be described with reference to the flowchart of FIG. First, the control device 5 controls the radar sensor 4 to radiate radio waves from the transmitting antenna 1 toward the vehicle interior 110. The radio wave irradiation range is indicated by a fan-shaped area sandwiched between alternate long and short dash lines 141 and 142, and reaches the passage, the adjacent passenger compartment 111, or vehicles on both sides of the passenger compartment 110. The radio wave is reflected by the road surface of the parking lot or the vehicle 130, and the reflected wave is received by the receiving antenna 3. From the delay time at this time, the distance of the reflection point and the intensity of the reflected wave are obtained as an IF signal. The IF signal is digitized by the A / D converter 6 in the control device 5 and input to the processing unit 7 for processing, thereby obtaining the distance to the vehicle 130 and the intensity of the reflected wave (step S11).

  In the next step S12, the processing unit 7 determines whether or not the radio wave has been transmitted a preset number of times, here N times, and if not transmitted N times, the count value is incremented by 1 (N = N + 1) ( Step S13) and the acquisition of the distance and reflected wave intensity in step S11 are repeated up to N times.

If it is determined in step S12 that the radio wave has been transmitted N times, the processing unit 7 calculates an average value of distance and intensity (step S14). The average value can be calculated by adding the acquired distance and intensity and then dividing by N. However, each maximum value and minimum value are deleted, and the remaining average value is calculated to determine the presence or absence of the vehicle 130. As a result, it is possible to suppress the influence of the vehicle or the like moving in the passage, and to perform more accurate determination.
Of course, steps S12 to S14 may be omitted, and the distance to the vehicle 130 and the intensity of the reflected wave may be acquired only once (N = 1).

  Next, the processing unit 7 determines whether or not the average value of the distances is equal to or less than the first distance threshold L1 (step S15). Here, the first distance threshold L1 is a distance for setting the peak search range 140, and the presence or absence of the vehicle 130 is detected in the peak search range 140. If it is determined in step S15 that the average distance value is not equal to or less than the first distance threshold L1, the processing unit 7 determines that the vehicle is empty (step S16). When it is determined that the distance is equal to or less than the first distance threshold L1, the processing unit 7 detects the distance of the maximum intensity of the reflected wave (step S17).

  Subsequently, it is determined whether or not the maximum intensity distance of the reflected wave is equal to or smaller than the second distance threshold L2 (step S18). Here, the second distance threshold L2 is a predetermined distance to be detected in the passenger compartment 110 that is the detection determination range of the vehicle 130. For example, when the vehicle 130 enters the passenger compartment 110, the second distance threshold L2 is set to a distance at which a fan-shaped detection determination range 150 that can reliably detect this is set. If the maximum intensity distance is not less than or equal to the second distance threshold L2, the processing unit 7 determines that the distance is empty (step S16). If it is determined that the distance is the second distance threshold L2 or less, the processing unit 7 It is determined whether or not a predetermined intensity threshold is exceeded (step S19).

  This intensity threshold is set in consideration of the reflection intensity from the vehicle 130 in the passenger compartment 110. If it is not equal to or greater than the predetermined intensity threshold, the processing unit 7 determines that the vehicle is empty (step S16), and if it is equal to or greater than the predetermined intensity threshold, the processing unit 7 determines that the vehicle is present (step S20). And the determination result of said step S16, S20 is notified to the management apparatus of the parking lot which is a high-order apparatus (step S21).

  FIG. 7 is a waveform diagram showing the relationship between the reflected wave intensity threshold and the distance from the object detection device 100 in the on-vehicle detection method of FIG. A region surrounded by a one-dot chain line corresponds to the peak search range 140, and a region surrounded by a two-dot chain line corresponds to the detection determination range 150. When the vehicle 130 is present in the passenger compartment 110, a plurality of peaks are generated in the reflected wave obtained from the peak exploration range 140 that decreases as the distance from the object detection device 100 increases. These peaks are generated by superimposing, for example, a reflected wave from the road surface, a second harmonic, a third harmonic, and the like in addition to the reflected wave from the vehicle 130.

  The reason why the peak search range 140 is separated from the detection determination range (= in-vehicle determination range) 150 is to prevent the unnecessary peak components P1 and P2 in the peak search range 140 from determining that the vehicle is in the vehicle. These unnecessary peak components P1 and P2 are generated, for example, when the vehicle crosses the passage in front of the passenger compartment 110, so that it is not determined that the vehicle is in the vehicle. In FIG. 7, the intensity peak P <b> 3 of the reflected wave exists below the second distance threshold L <b> 2 in the detection determination range 150. Further, the intensity peak P3 of the reflected wave is equal to or greater than a predetermined intensity threshold Pth. Therefore, it is determined that the vehicle is present.

FIG. 8 shows the on-vehicle determination range determined by the relationship between the reflection intensity and the distance from the object detection device 100. A region where the distance from the object detection device 100 is near the second distance threshold L2 and the reflection intensity is maximum and the reflection intensity is higher than the predetermined intensity threshold Pth and is hatched to the right It is determined that the vehicle is in the vehicle.
The vehicle presence determination range is set in consideration of the distance detected for each vehicle body because the under-floor reflection of the vehicle body is received when the vehicle 130 stops.

  The distance at which the intensity of the reflected wave is maximum is determined using the second distance threshold L2, and the reflection points of the adjacent passenger compartment 111, the passenger compartments on both sides of the passenger compartment 110, and the passage are excluded. Thus, it is possible to determine whether the reflection point is in the passenger compartment 110 or not. In addition, by determining the maximum intensity of the reflected wave using a predetermined intensity threshold, the influence of the weak reflected wave peak in the detection determination range 150 in the own vehicle compartment 110 is removed, and the presence or absence of the vehicle 130 Can be determined.

  As described above, since the presence of the vehicle 130 is detected in the peak exploration range 140 wider than the detection determination range 150, the small antennas 1 and 3 having a wide directivity can be used. Therefore, it can be easily built in the tire stopper 120 or installed on the ceiling. Further, since the vehicle is determined to be present when the distance at which the intensity of the reflected wave is maximum is equal to or smaller than the second distance threshold L2 in the detection determination range 150, the vehicle outside the detection determination range 150 is not detected, and the detection determination is made. The vehicle 130 within the range 150 can be detected with high accuracy. Moreover, even if a second harmonic or a third harmonic of the reflected wave is generated in the detection determination range 150 by the vehicle existing in the peak exploration range 140, the distance at which the intensity of the reflected wave is maximum is the second distance. Since it becomes more than the threshold value L2, it can suppress misdetection and misjudgment by these influences.

[Second application example]
Usually, one object detection device (a vehicle presence detection device) is installed in each parking lot or for each of a plurality of vehicle compartments in a parking lot. In such a case, there is a possibility that the radio waves in the passenger compartment facing each other in the direction of the radio waves to be radiated may interfere with each other and be erroneously detected. For example, in FIG. 4, the object detection device in the passenger compartment 111 receives and misdetects the radio wave emitted from the object detection device 100 in the passenger compartment 110 or is emitted from the object detection device in the passenger compartment 111. There is a possibility that the object detection device 100 in the passenger compartment 110 receives radio waves and erroneously detects them. There is also a possibility of interference (interference) with other radars such as on-vehicle radars. In particular, when an interference wave having a small time shift with respect to the transmission wave is received, the interference wave and the reception wave cannot be distinguished from each other and erroneously detected.

  FIG. 9 is a waveform diagram for explaining the influence of an interference wave and its reduction when the object detection method of the present invention is used to detect the presence of a parking lot. FIG. 9A shows three states of a transmission wave, a reception wave, and an interference wave, and FIG. 9B shows an IF signal corresponding to each state of FIG. 9A. In the FM-CW system, a radio wave transmission period Δn and a non-transmission period (standby time) ΔN are normally repeated alternately, and the frequency of the radio wave is gradually increased during the transmission period Δn.

  As shown in the period Ta of FIG. 9A, when there is no interference and a received wave is obtained with a delay of a predetermined time with respect to the transmitted wave, it corresponds to the reflection point as shown in FIG. 9B. An IF signal Sa is obtained. On the other hand, as shown in the period Tb, when an interference wave is input with a time difference with respect to the transmission wave (when there is interference with almost the same timing as the reception wave), even if there is no vehicle, a broken line An IF signal Sb as shown is obtained. For this reason, an interference wave having substantially the same timing as the received wave causes erroneous detection. Moreover, since the period ΔN during which no radio wave is transmitted is a fixed value, the interference timing is maintained and interference occurs repeatedly.

  As shown in the period Tc, when an interference wave is input with a large time difference with respect to the transmission wave, the frequency of the IF signal Sc due to the interference is greatly shifted. In this case, since the frequency of the IF signal is converted into a distance in the FFT analysis, it can be ignored unless it is the target distance of the presence detection algorithm.

  If an interference wave with a constant frequency is received, an interference wave with a reverse frequency change, or an interference wave with a different frequency change slope, the beat signal of the interference wave is only momentarily. Since there is no interference, there is no problem in the FFT analysis.

  FIG.9 (c) is a wave form diagram for demonstrating the method to reduce an FM-CW interference wave, when using the object detection method of this invention for the presence detection of a parking lot. In the second application example, the radio wave non-transmission period (standby time) ΔN is randomly varied (ΔN + α) so that interference does not occur. Here, α is an arbitrary time. Thus, the frequency of the IF signal due to the interference is greatly shifted by intentionally shifting the timing of interference with the radio wave emitted from the object detection device in the opposite passenger compartment. As a result, the interference waves in the periods Tb and Tc are greatly shifted and can be ignored unless they are the target distance of the on-vehicle detection algorithm.

  FIG. 10 (a) shows another specific method for reducing the interference wave, and the object detection in the opposite passenger compartment is performed by combining the measurements with different waiting times ΔN multiple times (here, four times). The influence of interference with other radars such as on-vehicle radars or interference waves from the apparatus is removed. That is, the control device 5 controls the radar sensor 4 to irradiate the vehicle 130 with radio waves a plurality of times, and acquires the distance to the vehicle 130 and the intensity of the reflected wave. At this time, the object detection device that may interfere with the radio wave in the parking lot makes the waiting time ΔN from the transmission of the radio wave to the next transmission different. Then, the maximum value and minimum value of the acquired distance and reflected wave intensity are deleted, and the remaining average value is calculated to determine the presence or absence of the vehicle 130.

  In FIG. 10A, an interference wave as indicated by a one-dot chain line is superimposed on a transmission wave indicated by a solid line and a reception wave indicated by a broken line. However, the timings of the waiting times ΔT1, ΔT2, and ΔT3 from when a radio wave is transmitted until the next transmission are gradually increased. In this case, as shown in FIG. 10B, the detected peaks are the short distance peak of the interference wave, the reflection peak of the vehicle, the reflection peak of the vehicle, and the long distance peak of the interference wave. Therefore, the influence of the interference wave can be removed by setting the average of the values obtained by deleting the maximum value and the minimum value as the peak distance. Further, by changing the waiting time ΔN, even if there is a temporary interference, there is no repeated interference, and the temporary interference can be eliminated by deleting the maximum value and the minimum value.

[Third application example]
FIG. 11 is a block diagram showing another schematic configuration when the object detection device of the present invention is used for detection of the presence of a parking lot. Since the configuration of the object detection apparatus 100 is basically the same as that in FIG. 1, the same reference numerals are given to the same portions, and detailed descriptions thereof are omitted. This object detection device 100 is built in a housing (metal housing) 10, for example, a tire stopper 120. The casing 10 is provided with a window 10a for radiating radio waves, and radiates radio waves through the window 10a to receive reflected waves from the vehicle. A plate-like member such as resin is fitted into the window 10a so as to transmit radio waves.

  In the above configuration, the radar sensor 4 receives not only the vehicle reflection and the road surface reflected wave RF1 from the receiving antenna 3, but also the reflected wave RF2 generated by the inner surface reflection of the housing 10, and these reflected waves RF1 and RF2 are superimposed. Output an IF signal. For this reason, there is a possibility that the detection accuracy is lowered due to the influence of the reflected wave RF2.

  FIG. 12A is a waveform diagram of an IF signal when the passenger compartment is empty in the object detection device 100 of FIG. The object detection apparatus 100 reflects a reflected wave RF2 generated by reflection in the casing, that is, a radio wave radiated from the transmission antenna 1, by the metal casing 10 or a plate-like member fitted in the window 10a, and this is reflected by the reception antenna 3. The received state is shown. Thus, since the reflected wave RF2 generated by reflection in the casing is received even when the passenger compartment is empty, the in-vehicle IF signal is reflected wave RF2 generated by reflection in the casing in addition to the reflected wave RF1 from the vehicle and the road surface. Is a superimposed waveform.

  FIG. 12B shows the relationship between the in-casing reflection and the reflection intensity in the presence determination. In order to suppress erroneous detection and misjudgment due to the influence of reflection within the casing, the intensity threshold Pth of the reflection intensity must be set larger than the peak of the reflected wave RF2 due to reflection within the casing. In this way, when the reflection from the vehicle is smaller than the intensity threshold Pth, there is a risk of erroneous detection or erroneous determination. In addition, since the intensity of reflection in the housing varies due to individual differences in mass-produced products, the intensity threshold must be individually adjusted for accurate detection, and adjustment work takes time and money.

  Therefore, in the third application example, when the control device 5 determines that there is no vehicle, the intensity of the reflected wave (reflected wave RF2 generated by reflection in the housing) is stored as a reference value, and the presence / absence of the vehicle is determined. In addition, the stored reference value is subtracted from the intensity of the acquired reflected wave RF1. That is, the internal reflection waveform as shown in FIG. 13A is stored in the control device 5 as a reference value, and the difference from the received IF signal shown in FIG. ), The influence of reflection within the housing can be canceled and reduced.

As a result, as shown in FIG. 13D, the intensity of reflection within the housing is lowered, and the intensity threshold Pth can be set lower. As a result, it is possible to suppress the influence of the reflection in the housing and to widen the area for determining that the vehicle is present with hatching that is rising to the right.
Therefore, according to the configuration as described above, not only can erroneous detection due to the influence of reflection in the housing be suppressed, but also the reference waveform of reflection in the housing shown in FIG. The influence of individual differences can be reduced, and the strength threshold value Pth can be fixed.

[Fourth application example]
FIG. 14 is a flowchart showing another algorithm when the object detection method of the present invention is used for detecting the presence of a parking lot. The fourth application example is a combination of the first to third application examples described above. First, the control device 5 controls the radar sensor 4 to radiate radio waves from the transmitting antenna 1 toward the vehicle interior 110. The radio wave irradiation range is a peak search range that reaches a passage, an adjacent passenger compartment, or vehicles on both sides of the passenger compartment. The radio wave is reflected by the road surface of the parking lot or the vehicle 130, and the reflected wave is received by the receiving antenna 3. From the delay time at this time, the distance of the reflection point and the intensity of the reflected wave are obtained as an IF signal. The IF signal is digitized by the A / D converter 6 in the control device 5 and input to the processing unit 7 for processing, thereby obtaining the distance to the vehicle 130 and the intensity of the reflected wave (step S31).

  In the next step S32, interference countermeasures are taken by randomly changing the waiting time ΔN of radio waves (ΔN + α). Then, the processing unit 7 determines whether or not the radio wave has been transmitted a preset number of times, here N times (step S33). If not transmitted N times, the count value is incremented by 1 (N = N + 1) ( Step S34) and the acquisition of the distance and reflected wave intensity in step S31 are repeated up to N times.

  If it is determined in step S33 that the radio wave has been transmitted N times, the processing unit 7 calculates average values of distance and intensity, respectively (step S35). Each maximum value and minimum value are deleted, and the remaining average value is calculated, thereby suppressing the influence of the vehicle moving along the passage.

  In the subsequent step S36, the intensity of the reflected wave when it is determined that there is no vehicle is stored as a reference value, and the stored reference value is subtracted from the intensity of the acquired reflected wave when determining the presence or absence of the vehicle. In this way, the internal reflection is removed. And the presence or absence of a vehicle is determined in the state which removed the influence of interference countermeasures and reflection in a housing | casing (step S37). The determination of the presence or absence of the vehicle may be performed, for example, by executing steps S15 to S20 in the flowchart of FIG.

If it is determined in step S37 that the vehicle is present, it is determined whether or not the vehicle presence detection operation is completed (step S38), and the above-described operation is repeated until it is determined that the vehicle is present.
On the other hand, if it is determined in step S37 that the vehicle is empty, it is determined whether or not a predetermined time has elapsed (step S39). . When it is determined that a certain time has elapsed, the internal environment is updated (step S40), and the above-described operation is repeated until it is determined that the process has ended.

  According to the configuration as described above, the vehicle can be detected with higher accuracy by combining both interference countermeasures and suppression of influence by reflection within the housing. Further, since the environment in the housing is updated when a certain time elapses, it is possible to cope with a change in reflection within the housing caused by a change with time or distortion of a tire stop (metal housing) due to riding on the vehicle. In addition, since it is not necessary to individually adjust the intensity threshold due to individual differences in mass-produced products, the time and cost required for the adjustment work can be reduced.

In the fourth application example, the case where the first to third application examples of the object detection device are all combined has been described. However, depending on the characteristics and costs required in the surrounding environment of the parking lot, etc. Such application examples may be appropriately combined.
Further, in each of the application examples described above, an example in which the tire is built into the tire stop is shown, but it may be provided in the vehicle interior or the periphery of the vehicle interior, or may be installed on the ceiling or the like.
Furthermore, although the example applied to the presence detection of a parking lot was shown as an object detection apparatus, it is needless to say that it can be applied to detection of various other objects such as the presence detection of a train. In addition to distance information and intensity information, speed information may be acquired, and determination may be made in consideration of speed information.

  The configurations, operation procedures, and the like described in the above embodiments are merely schematically shown to the extent that the present invention can be understood and implemented. Therefore, the present invention is not limited to the described embodiments, and can be variously modified without departing from the scope of the technical idea shown in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Transmission antenna, 2 ... Object, 3 ... Reception antenna, 4 ... Radar sensor, 5 ... Control apparatus, 6 ... A / D converter, 7 ... Processing part, 8 ... High-order interface circuit, 9 ... Power supply, 10 ... Housing DESCRIPTION OF SYMBOLS 10a ... Window, 100 ... Object detection apparatus, 110 ... Vehicle compartment, 111 ... Adjacent vehicle compartment, 120 ... Tire stop, 130 ... Vehicle, 140 ... Peak search range, 150 ... Detection judgment range

Claims (8)

A radar sensor that radiates radio waves toward an object and receives the reflected wave, and a control device that detects the presence of an object by acquiring the distance from the radar sensor to the object and the intensity of the reflected wave,
The control device detects the presence or absence of an object in a peak exploration range wider than the detection detection range of the object, detects a distance where the intensity of the reflected wave is maximum when the object is detected, and this distance is the detection detection range of the object An object detection device that determines that there is an object when the distance is equal to or less than a predetermined distance threshold.   The control device determines that there is an object when the distance at which the intensity of the reflected wave is maximum is equal to or less than a predetermined distance threshold within the detection determination range of the object and the reflected wave is equal to or greater than a predetermined intensity threshold. Item 10. The object detection device according to Item 1.   The control device controls the radar sensor to irradiate the object to be detected a plurality of times, obtains the distance to the object and the intensity of the reflected wave, deletes the maximum value and the minimum value, The object detection apparatus according to claim 1, wherein the average value of the two is calculated to determine the presence or absence of an object.   The control device controls the radar sensor to irradiate the object to be detected a plurality of times at different time intervals, obtains the distance to the object and the intensity of the reflected wave, and sets the maximum value and the minimum value. The object detection apparatus according to claim 1, wherein the object detection device is deleted and the remaining average value is calculated to determine the presence or absence of an object.   The control device stores the intensity of the reflected wave when it is determined that there is no object as a reference value, and subtracts the stored reference value from the acquired intensity of the reflected wave when determining the presence or absence of the object. Item 5. The object detection device according to any one of Items 1 to 4.   The object to be detected is a vehicle, the detection detection range of the object is a cabin of a parking lot, the peak search range is a range in which a reflected wave from a vehicle in a passage and an adjacent vehicle compartment can be received, and the control device The object detection device according to any one of claims 1 to 5, which detects the presence or absence of a vehicle in a vehicle compartment in a parking lot. A method of detecting the presence or absence of an object by irradiating an object with radio waves and receiving the reflected wave,
Get the distance to the object and the intensity of the reflected wave,
Detect the presence or absence of an object in the peak search range wider than the object detection judgment range,
When the object is detected, the distance where the intensity of the reflected wave is maximum is detected.
An object detection method characterized by determining that an object is present when this distance is equal to or less than a predetermined distance threshold within an object detection determination range.   The distance at which the intensity of the reflected wave is maximum is equal to or smaller than a predetermined distance threshold within the object detection determination range, and the presence of an object is determined when the reflected wave is equal to or greater than a predetermined intensity threshold. Object detection method.