WO2017141370A1 - Object detection apparatus, object detection method, and object detection program - Google Patents

Abstract

An object detection apparatus (10) is mounted on a mobile body (100). A radiation unit (131) radiates an acoustic signal generated through superposition of a plurality of waves different in frequency by an acoustic signal output apparatus (21) mounted on the mobile body (100). A reception unit (132) receives a reflection wave signal generated as a result of the acoustic signal, which has been radiated from the radiation unit (131) mounted on the mobile body (100), being reflected on an object. A detection unit (116) detects the object present around the mobile body (100) by calculating a correlation value between a reference signal and a reception signal, the reception signal being the reflection wave signal received by the reception unit (132).

Description

Object detection apparatus, object detection method, and object detection program

This invention relates to a technique for detecting an object existing around a moving body.

As a technique for detecting an object existing around a moving body, for example, there is a technique for detecting surrounding vehicles existing around the vehicle. By detecting an object around the moving body, it is possible to control the moving body so as to avoid a collision with the detected object.

Patent Document 1 describes that an object is detected using an ultrasonic sensor.

Special table 2013-518333 gazette

When detecting an object using an acoustic signal, such as when using an ultrasonic sensor, if at least one of the moving object and the object is moving, a frequency shift called a Doppler shift occurs, and the object is detected. The accuracy will drop.
An object of the present invention is to make it possible to accurately detect an object using an acoustic signal even when a Doppler shift occurs.

The object detection device according to the present invention is:
A reception unit that receives a reflected wave signal generated by reflecting an acoustic signal radiated from a moving object, which is an acoustic signal composed of a plurality of waves having different frequencies,
And a detection unit that detects the object by calculating a correlation value between the reception signal and a reference signal using the reflected wave signal received by the reception unit as a reception signal.

In the present invention, an object is detected using an acoustic signal formed by superposing a plurality of waves having different frequencies. Thereby, even if a Doppler shift occurs, an object can be detected with high accuracy.

The block diagram when the object detection apparatus 10 which concerns on Embodiment 1 is mounted in a mobile body. FIG. 3 is an explanatory diagram of a situation between the moving body 100 according to the first embodiment and the object 200 existing around the moving body 100. 3 is a flowchart showing an overall operation of the object detection apparatus 10 according to the first embodiment. 5 is a flowchart showing the operation of step ST1 according to the first embodiment. Explanatory drawing of the transmission signal generation method which concerns on Embodiment 1. FIG. Explanatory drawing of the transmission signal generation method which concerns on Embodiment 1. FIG. 6 is a flowchart showing the operation of step ST2 according to the first embodiment. 6 is a flowchart showing the operation of step ST3 according to the first embodiment. Explanatory drawing of relative distance d and Doppler shift amount which concerns on Embodiment 1. FIG. Explanatory drawing of relative distance d and Doppler shift amount which concerns on Embodiment 1. FIG. Explanatory drawing of the cross correlation function which concerns on Embodiment 1. FIG. The block diagram of the object detection apparatus 10 which concerns on the modification 1. FIG. The block diagram of the object detection apparatus 10 which concerns on the modification 2. FIG. FIG. 3 is a configuration diagram of an object detection device 10 according to a second embodiment. Explanatory drawing of the condition of the mobile body 100 which concerns on Embodiment 2, and the object 200 which exists around the mobile body 100. FIG. 10 is a flowchart showing the operation of step ST2 according to the second embodiment. 10 is a flowchart showing the operation of step ST3 according to the second embodiment. FIG. 6 is a configuration diagram of an object detection device 10 according to a third embodiment. Explanatory drawing of the condition of the mobile body 100 which concerns on Embodiment 3, and the object 200 which exists around the mobile body 100. FIG. 10 is a flowchart showing the operation of step ST1 according to the third embodiment. 10 is a flowchart showing the operation of step ST3 according to the third embodiment. FIG. 6 is a configuration diagram of an object detection apparatus 10 according to a fourth embodiment. 10 is a flowchart showing an overall operation of the object detection apparatus 10 according to the fourth embodiment.

Embodiment 1 FIG.
*** Explanation of configuration ***
With reference to FIG. 1, an example in which the object detection apparatus 10 according to Embodiment 1 is mounted on a moving body will be described.
The object detection device 10 is a computer mounted on the moving body 100. In the first embodiment, it is assumed that the moving body 100 is a vehicle. However, the moving body 100 may be another type such as a ship. In addition, as a mounting form for mounting the object detection device 10, it is mounted in a removable or separable form even if it is integrated with the moving body 100 or other illustrated components in a form that is integrated or inseparable. May be.
The object detection device 10 includes hardware including a processor 11, a storage device 12, an audio interface 13, and an in-vehicle interface 14. The processor 11 is connected to other hardware via the system bus and controls these other hardware.

The processor 11 is an IC (Integrated Circuit) that performs processing. Specific examples of the processor 11 are a CPU (Central Processing Unit), a DSP (Digital Signal Processor), and a GPU (Graphics Processing Unit).

The storage device 12 includes a memory 121 and a storage 122. The memory 121 is, for example, a RAM (Random Access Memory). The storage 122 is an HDD (Hard Disk Drive) as a specific example. The storage 122 may be a portable storage medium such as an SD (Secure Digital) memory card, a CF (CompactFlash), a NAND flash, a flexible disk, an optical disk, a compact disk, a Blu-ray (registered trademark) disk, or a DVD.

The audio interface 13 is a device for connecting the acoustic signal output device 21 and the acoustic signal input device 22 mounted on the moving body 100 to the system bus via the audio bus. As a specific example, the audio interface 13 is a USB (Universal Serial Bus), IEEE 1394, or HDMI (registered trademark, High-Definition Multimedia Interface) terminal.
The acoustic signal output device 21 is a device that outputs an acoustic signal. As a specific example, the acoustic signal output device 21 is a device including a D / A (digital / analog) converter, a signal amplifier, and a radiation device. The D / A converter is a device that converts a digital signal including transmission signal waveform information transmitted from the audio interface 13 via the audio bus into an analog signal that is an electrical signal. The signal amplifier is a device that amplifies the transmission signal converted into an analog signal by the D / A converter. The radiation device is a device that radiates a transmission signal, which is an analog signal amplified by a signal amplifier, as an acoustic signal. As a specific example, the radiation device is a speaker. The radiating device is not limited to a speaker, but may be a device that can radiate an analog signal having a plurality of frequency peaks. For example, the radiating device may be a device in which a plurality of ultrasonic sensors having different resonance frequencies are assembled.
The acoustic signal input device 22 is a device that collects an acoustic signal including a reflected wave reflected by an object from the acoustic signal radiated from the acoustic signal output device 21. As a specific example, the acoustic signal input device 22 is a device including a collection device, a signal amplifier, and an A / D (analog / digital) converter. The collection device is a device that converts an acoustic signal from the outside of the device into an analog signal that is an electrical signal and collects the signal. The signal amplifier is a device that amplifies the analog signal collected by the collecting device. The A / D converter is a device that converts the analog signal amplified by the signal amplifier into a digital signal including received signal waveform information and transmits the digital signal to the audio interface 13 via the audio bus. The collection device is a microphone as a specific example. The collecting device is not limited to a microphone, but may be any device that can collect acoustic signals having a plurality of frequency peaks. For example, the collecting device may be a device in which a plurality of ultrasonic sensors having different resonance frequencies are assembled.

The in-vehicle interface 14 is a device for connecting the vehicle information ECU 23 and the sensor ECU 24 mounted on the moving body 100 to the system bus via the in-vehicle bus. The in-vehicle interface 14 is, as a specific example, a USB, IEEE 1394, or HDMI (registered trademark) terminal. The in-vehicle bus is, as a specific example, a CAN (Control Area Network).
The vehicle information ECU 23 is a device that acquires information such as time and the speed of the moving body 100.
The sensor ECU 24 is a device that acquires external environment information, which is information about the environment outside the moving body 100 such as temperature and wind speed. External environment information is used to correct the acoustic velocity V _s. Therefore, temperatures as external environment information is not limited to wind speed, humidity, atmospheric pressure, specific heat, may be any parameters available for the correction of density such acoustic velocity V _s.

The object detection device 10 includes, as functional components, a time synchronization unit 111, a transmission signal generation unit 112, a reception signal generation unit 113, a vehicle signal generation unit 114, an environmental signal generation unit 115, a detection unit 116, A radiation unit 131, a reception unit 132, a time acquisition unit 141, a vehicle information acquisition unit 142, and an environment information acquisition unit 143 are provided.
The functions of the time synchronization unit 111, the transmission signal generation unit 112, the reception signal generation unit 113, the vehicle signal generation unit 114, the environment signal generation unit 115, and the detection unit 116 are realized by software. The storage 122 of the storage device 12 stores a program that realizes the function of each unit realized by software. This program is read into the memory 121 by the processor 11 and executed by the processor 11.
The functions of the radiation unit 131 and the reception unit 132 are realized by the audio interface 13.
The functions of the time acquisition unit 141, the vehicle information acquisition unit 142, and the environment information acquisition unit 143 are realized by the in-vehicle interface 14.

Information, data, signal values, and variable values indicating the results of processing of the functions of the respective units of the object detection device 10 are stored in the memory 121, the register in the processor 11, or the cache memory. In the following description, it is assumed that information, data, signal values, and variable values indicating the processing results of the functions of the respective units of the object detection apparatus 10 are stored in the memory 121.

It is assumed that a program for realizing each function realized by software is stored in the storage device 12. However, this program may be stored in a portable storage medium such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a Blu-ray (registered trademark) disk, or a DVD.

In FIG. 1, only one processor 11 is shown. However, a plurality of processors 11 may be provided, and a plurality of processors 11 may execute programs that realize each function in cooperation with each other.

*** Explanation of operation ***
With reference to FIG. 2 to FIG. 10, the operation of the object detection apparatus 10 according to the first embodiment will be described.
The operation of the object detection apparatus 10 according to the first embodiment corresponds to the object detection method according to the first embodiment. The operation of the object detection apparatus 10 according to the first embodiment corresponds to the processing of the object detection program according to the first embodiment.

With reference to FIG. 2, the situation of the moving body 100 according to Embodiment 1 and the object 200 existing around the moving body 100 will be described. In the first embodiment, the object 200 is a vehicle that travels in front of the moving body 100.
FIG. 2 shows a moving body 100 on which an acoustic signal output device 21 and an acoustic signal input device 22 are installed, and an object 200. In FIG. 2, the acoustic signal output device 21 and the acoustic signal input device 22 are disposed at positions close to each other on the front side of the moving body 100.
In this situation, the shortest path length from the acoustic signal output device 21 to the object 200 and the shortest path length from the reflected wave generation source to the acoustic signal input device 22 are almost equal to the distance d. The generation source of the reflected wave is a position where the transmission signal output from the acoustic signal output device 21 reaches the object 200 in the shortest time.
Further, as shown in FIG. 2, the mobile 100 is traveling at a speed _{v s,} the object 200 travels at a speed _{v o.} In this situation, the object detection apparatus 10 detects the object 200 and estimates the relative distance d and the relative speed Δv = v _o −v _s .

** Overall operation **
The overall operation of the object detection apparatus according to the first embodiment will be described with reference to FIG.
As a premise of the process shown in FIG. 3, as shown in FIG. 1, the time synchronization unit 111 generates a synchronization signal based on the time acquired by the time acquisition unit 141 from the vehicle information ECU 23, and receives the transmission signal generation unit 112 and the reception. The signal is transmitted to the signal generator 113, the vehicle signal generator 114, and the environment signal generator 115.

In the radiation processing of step ST1, the transmission signal generation unit 112 transmits a transmission signal to the radiation unit 131 every predetermined time T seconds based on the synchronization signal transmitted by the time synchronization unit 111. When the transmission signal is transmitted from the transmission signal generation unit 112, the radiating unit 131 transmits the received transmission signal to the acoustic signal output device 21. The acoustic signal output device 21 radiates the received transmission signal as an acoustic signal.

In the reception process of step ST2, the reception unit 132 receives a reception signal that is an acoustic signal converted into a digital signal by the acoustic signal input device 22. In the reception signal received by the reception unit 132, when the object 200 exists around the moving body 100, the acoustic signal (transmission signal) radiated by the acoustic signal output device 21 in step ST1 is reflected by the object 200. The signal component corresponding to the reflected wave generated by is included. The received signal may contain noise other than the signal component corresponding to the reflected wave.
The reception signal generation unit 113 transmits the reception signal for the latest T seconds received by the reception unit 132 to the detection unit 116 every fixed time T1 seconds. Here, the time T1 is equal to or less than the time T.
In addition, the vehicle signal generation unit 114 acquires the speed of the moving body 100 via the vehicle information acquisition unit 142 and transmits it to the detection unit 116.
The environment signal generation unit 115 acquires external environment information via the environment information acquisition unit 143 and transmits the external environment information to the detection unit 116.
The reception signal generation unit 113, the vehicle signal generation unit 114, and the environment signal generation unit 115 are synchronized with the timing at which transmission of the transmission signal is started in step ST1, based on the synchronization signal transmitted by the time synchronization unit 111. Works.

In the detection process of step ST3, the detection unit 116 detects the object 200 present around the moving body 100 based on the reception signal transmitted by the reception signal generation unit 113 in step ST2.
In addition, when the object 200 is detected, the detection unit 116 converts the speed transmitted by the vehicle signal generation unit 114 in step ST2 and the external environment information transmitted by the environment signal generation unit 115 together with the reception signal. Based on this, the relative distance d and the relative speed Δv of the object 200 are estimated.

** Detailed operation of step ST1 **
With reference to FIG. 4, the operation of step ST1 according to the first embodiment will be described in detail.
In the elapsed time determination process in step ST11, the transmission signal generation unit 112 measures the elapsed time from the transmission time at which the previous transmission signal was transmitted, based on the synchronization signal transmitted by the time synchronization unit 111.
If T seconds have elapsed from the transmission time, the transmission signal generation unit 112 proceeds to step ST12, and if T seconds have not elapsed from the transmission time, the transmission signal generation unit 112 executes step ST11 again.

In the transmission process of step ST12, the transmission signal generation unit 112 reads a signal waveform stored in the memory 121 in advance, and transmits the read signal waveform to the radiation unit 131 as a transmission signal. And the radiation | emission part 131 radiates | transmits a transmission signal as an acoustic signal via the acoustic signal output device 21. FIG.

Here, the transmission signal radiated as an acoustic signal is a signal configured by superposing a plurality of waves having different frequencies. The transmission signal is preferably a signal obtained by superposing a plurality of waves whose frequencies increase according to the geometric sequence. The transmission signal is desirably a signal obtained by superposing a plurality of waves having different initial phases for each frequency.
The frequency of each wave that is a component of the transmission signal is preferably in the frequency band of sound waves or low-frequency ultrasonic waves, specifically in the range of 16 kHz to 100 kHz. That is, it is desirable that the acoustic signal as the transmission signal is a signal obtained by superimposing a plurality of waves having a frequency within one of the frequency bands of the sound wave and the low frequency ultrasonic wave.

When not only detecting the object 200 in step ST3 but also estimating the relative distance d and the relative speed Δv between the moving body 100 and the object 200, the transmission signal includes the first signal and the phase of the first signal. And a second signal obtained by inverting.

Specifically, the transmission signal includes q (≧ 2) types of frequency components, the frequency increases in a geometric series, and the frequency and the initial phase correspond one-to-one. A signal is available. That is, as a specific example, the signal u (t, T ₀ ) shown in Equation 1 can be used as the transmission signal.

Here, p (> 0) is a constant corresponding to the bandwidth. f ₀ (> 0) is a constant representing the lowest frequency. T ₀ (> 0) is a constant related to the initial phase. a _k is a constant corresponding to the amplitude of each frequency.
This signal has frequencies f ₀ , p ^{1 / q} f ₀ , p ^{2 / q} f ₀ ^,. . . , P ^{(q−1) / q} f ₀ and p ^{1 / q} times. In this signal, the initial phase at the frequency (p ^{k / q} f ₀ ) for each integer k is 2πT ₀ · p ^{k / q} f ₀ , and the frequency and the initial phase have a one-to-one correspondence.

Further, as the transmission signal, a signal whose frequency is continuously distributed within a certain bandwidth can be used. This corresponds to reducing the frequency increase rate p ^{1 / q} until the peak of each frequency cannot be distinguished on the frequency amplitude characteristic in the signal u (t, T ₀ ).

Further, as a transmission signal, a frequency characteristic equivalent to that of the original signal u (t, T ₀ ), such as a signal obtained by cutting out a partial section of the signal u (t, T ₀ ) with a window function, and overlapping of the cut out signals. A signal having As a specific example, assuming that a rectangular window that cuts out the section t ₁ ≦ t ≦ t ₂ is rect [t ₁ , t ₂ ], the number obtained by superimposing the two signals shown in Equation 2 and the two signals shown in Equation 2 The signal w (t) shown in FIG. 3 can also be used as a transmission signal.

In the above description, the transmission signal generation unit 112 uses the signal waveform read from the memory 121 as the transmission signal. However, in step ST12, the transmission signal generation unit 112 may generate a signal waveform and use it as a transmission signal.
As a specific example, when the signal u (t, T ₀ ) is used, as shown in FIG. 5, the object detection device 10 stores a plurality of sine wave waveforms as constituent elements of the transmission signal in the memory 121. Remember. In step ST12, the transmission signal generation unit 112 reads a sine wave waveform having a plurality of frequencies from the memory 121, and adds the read sine wave waveforms having the plurality of frequencies to generate a signal waveform that becomes a transmission signal. To do. In FIG. 5, k = 0,. . . , Q−1, f _k = p ^{k / q} f0 and φ _k = 2πf _k T ₀ .
Further, when a signal having a continuously distributed frequency is used as a transmission signal, the object detection apparatus 10 stores a signal waveform such as white noise or pink noise in the memory 121 as a reference waveform as shown in FIG. deep. Then, in step ST12, the transmission signal generation unit 112 reads the reference waveform from the memory 121, and passes the read reference waveform through a bandpass filter having a reference bandwidth as a pass band, thereby generating a signal waveform that becomes a transmission signal. Generate. The passband f is, for example, f ₀ ≦ f ≦ f _q−1 . In this case, the transmission signal generation unit 112 may perform various other signal processing such as changing the frequency phase characteristics through the all-pass filter on the signal waveform after passing as necessary. The object detection apparatus 10 stores information such as a random number seed necessary for generating the reference waveform in the memory 121 instead of the reference waveform, and the transmission signal generation unit 112 is stored in the memory 121 in step ST12. A reference waveform may be generated from the obtained information.

** Detailed operation of step ST2 **
With reference to FIG. 7, the operation of step ST2 according to the first embodiment will be described in detail.
In the reception process of step ST21, the reception unit 132 stores the reception signals for the latest T seconds among the reception signals constantly collected by the acoustic signal input device 22 based on the synchronization signal transmitted by the time synchronization unit 111. Remember it. Specifically, the reception unit 132 writes the reception signal collected by the acoustic signal input device 22 to the memory 121 and erases the reception signal that has passed T seconds from the collection from the memory 121.

In the elapsed time determination process in step ST22, the reception signal generation unit 113 measures the elapsed time from the transmission time at which the previous reception signal was transmitted based on the synchronization signal transmitted by the time synchronization unit 111.
The reception signal generation unit 113 advances the process to step ST23 when T1 seconds have elapsed from the transmission time, and returns the process to step ST21 when T1 seconds have not elapsed since the transmission time.

In the transmission process of step ST <b> 23, the reception signal generation unit 113 reads the reception signal for the latest T seconds stored in the memory 121 and transmits the read reception signal to the detection unit 116.
At this time, the vehicle signal generation unit 114 acquires the speed of the moving body 100 via the vehicle information acquisition unit 142 and transmits it to the detection unit 116.
In addition, the environment signal generation unit 115 acquires external environment information via the environment information acquisition unit 143 and transmits the external environment information to the detection unit 116.

** Detailed operation of step ST3 ***
With reference to FIG. 8, the operation of step ST3 according to the first embodiment will be described in detail.
In the correlation processing in step ST31, the detection unit 116 calculates cross-correlation functions for the reception signal transmitted by the reception signal generation unit 113 in step ST2 and each of at least two types of reference signals.
In the first embodiment, it is assumed that two types of reference signals 1 and 2 are stored in the memory 121. Then, the detection unit 116 reads the two types of reference signals 1 and 2 from the memory 121 and calculates a cross-correlation function for each of the received signal and the reference signals 1 and 2. The detection unit 116 writes the calculated cross-correlation functions in the memory 121.

The reference signal may be a signal that has a peak in the cross-correlation function with the received signal. As a specific example, a transmission signal can be used as a reference signal. At this time, an ideal reception signal when the Doppler shift does not occur has a signal waveform similar to a signal obtained by delaying the transmission signal by a time due to the relative distance. For this reason, the cross-correlation function between the reference signal and the received signal is a peak of the auto-correlation function of the transmission signal shifted by the delay time. In addition, when a Doppler shift occurs, the peak position is further shifted accordingly.
The reference signal is not limited to the transmission signal, and a signal having a frequency characteristic equivalent to that of the transmission signal can be used. As a specific example, when the transmission signal is the signal w (t) shown in Equation 3, in addition to the signal w (t) that is the transmission signal, the signal u (t, T ₀ ) and the signal U ( t), the signal V (t) shown in Equation 4 can be used as a reference signal.

In the peak determination process in step ST32, the detection unit 116 determines whether or not there is a peak in each cross-correlation function calculated in step ST31.
Specifically, the detection unit 116 reads each cross-correlation function calculated in step ST31 from the memory 121. Then, the detection unit 116 specifies, as a peak, the time at which the value of each cross-correlation function is higher than the surrounding value by a reference value or more. The detection unit 116 determines that there is a peak when there is a time specified as a peak, and determines that there is no peak when there is no time specified as a peak.
If there is a peak, the detection unit 116 proceeds to step ST34, and if there is no peak, the process proceeds to step ST35.

Note that the detection unit 116 calculates a cross-correlation function in step ST31, determines the presence of a peak, writes the determination result to the memory 121, and reads the determination result from the memory in step ST32 to determine whether a correlation peak exists. It may be determined. Here, the determination result is a peak position when a peak is present, and a flag indicating that no peak is present when no peak is present, that is, no object is detected. In this way, the usage amount of the memory 121 can be reduced.

In the sound speed calculation process in step ST33, the detection unit 116 calculates the sound speed in parallel with step ST31 and step ST32.
Specifically, the sound velocity V _s (m (meter) / s (second)) of dry air at 1 atm can be approximated as V _s = 331.5 + 0.61T _p . Here, T _p is the Celsius temperature. Therefore, the detection unit 116 calculates the sound speed by substituting the air temperature indicated by the external environment information into the approximate expression. When the wind is blowing, the wind speed is added to or subtracted from the sound speed. Therefore, the detection unit 116 calculates the sound speed using the wind speed indicated by the external environment information.
In addition, the detection part 116 is good also considering a sound speed as a constant like 340 m / s. The detecting unit 116 may measure the speed of sound V _s by such sensor.

In the first calculation process of step ST34, the detection unit 116 determines that the object 200 is detected around the moving body 100 because the peak exists in step ST32, and the relative distance d between the moving body 100 and the detected object 200 is detected. Is estimated. In addition, the detection unit 116 estimates the Doppler shift rate ρ.
The detection unit 116 estimates the relative distance d and the Doppler shift rate ρ by determining how much the maximum peak position of the cross-correlation function between the received signal and the reference signal is shifted from the standard peak position. The detection unit 116 writes the estimated values of the relative distance d and the Doppler shift rate ρ in the memory 121.

A method for estimating the relative distance d will be described.
As a specific example, consider the case where the signal w (t) shown in Equation 3 is used as a transmission signal and the signal U (t) shown in Equation 4 is used as a reference signal.
At this time, as shown in FIG. 9, if the Doppler shift does not occur, that is, if ρ = 1, the received signal y (t) is delayed by a time (d + d) / V _s corresponding to the relative distance. Here, in the situation of FIG. 2, the transmission path until the transmission signal is received is as follows: acoustic signal output device 21 → object 200 (source of reflected wave) → acoustic signal input device 22. Therefore, the path length is d + d.
However, as shown at the bottom of FIG. 9, the signal expands and contracts when a Doppler shift occurs. FIG. 9 shows a case where ρ> 1. Therefore, as shown in FIG. 10, the maximum peak position _{ty, U} of the cross-correlation function between the received signal y (t) and the reference signal U (t) is the transmission signal w (t) and the reference signal U (t). as the maximum peak position t _w, relative to the _U of the cross-correlation function between, shifted by the sum of the minute amount and the Doppler shift of the time delay corresponding to the relative distance. Therefore, the shift amount Δt _U is expressed by Equation 5.

Further, if the signal V (t) shown in Equation 4 is used as a reference signal, the maximum peak position _{ty, V} of the cross-correlation function between the reception signal y (t) and the reference signal V (t) is the transmission signal w. Shift is performed in the same manner as the maximum peak position _{ty, U} with reference to the maximum peak position _{tw, V} of the cross-correlation function between (t) and the reference signal V (t). However, as shown in the lowermost stage of FIG. 9, the signal expansion and contraction occurs at equal distances from side to side with respect to the signal center. Equally reverse. Therefore, the shift amount Δt _V is expressed by Equation 6.

Therefore, the peak shift caused by the Doppler shift can be canceled by taking the average of the respective peak shift amounts as shown in Equation 7, and a time delay amount Δt ⁻ corresponding to the relative distance can be obtained.

Therefore, the detection unit 116 estimates the relative distance d using Equation 8.

A method for estimating the Doppler shift rate will be described.
As a specific example, consider the case where the signal w (t) shown in Equation 3 is used as a transmission signal and the signal U (t) and signal V (t) shown in Equation 4 are used as reference signals.
As described above, the peak shift caused by the Doppler shift has the same distance and the opposite direction, and the peak shift caused by the relative distance has the same distance and the same direction regardless of the reference signal. For this reason, the peak shift caused by factors other than the Doppler shift can be canceled by taking the difference between the respective peak shift amounts.
Therefore, the distance between the maximum peak position _{ty, U} and the maximum peak position _{ty, V} is expressed by Equation 9. Here, as shown in FIG. _{10, t w, V -t w} , a U = 2T _i.

Therefore, when this is solved with respect to the Doppler shift rate ρ, the following equation is obtained. The detection unit 116 estimates the Doppler shift rate ρ using Equation 10.

In the specific example described above, two types of signals U (t) and signals V (t) having symmetrical waveforms are used as reference signals. In addition, a signal w (t) in which the signal U (t) and the signal V (t) are arranged at the same distance from the origin is used as a transmission signal. Then, by using these reference signals and transmission signals, the Doppler shift or the peak shift caused by the time delay corresponding to the relative distance d was canceled.
However, the transmission signal may be a signal including the first signal and the second signal obtained by inverting the first signal. In this case, the reference signal may be a signal including the first signal component and a signal including the second signal. If such a transmission signal and a reference signal are used, the Doppler shift or the peak shift caused by the time delay corresponding to the relative distance d can be canceled.
However, it is desirable that components other than the component included in the reference signal in the transmission signal are signals that do not hinder the cross-correlation peak detection. The signal that does not interfere with the cross-correlation peak detection is, for example, a signal that is uncorrelated with each reference signal.
As a specific example, a signal obtained by separating two types of reference signals, the signal U (t) and the signal V (t) by a known different time around the origin of the time axis, can be used as a transmission signal. A signal including a signal other than the signal w (t) can also be used as a transmission signal.

In the non-detection process of step ST35, it is assumed that the detection unit 116 does not detect the object 200 around the moving body 100 because no peak exists in step ST32. The detection unit 116 writes a flag indicating that the object 200 is not detected in the memory 121, or stores a special value when the object 200 is not detected as an estimated value of the relative distance d and the relative speed Δv. 121 is written.

In the second calculation process of step ST36, the detection unit 116 estimates the relative speed Δv between the moving body 100 and the object 200 from the estimated value of the Doppler shift rate ρ estimated in step ST34. The detection unit 116 writes the estimated value of the relative speed Δv in the memory 121.

A method for estimating the relative speed Δv will be described.
In the situation shown in FIG. 2, the Doppler shift rate ρ is expressed by Equation 11.

When Equation 11 is solved for the velocity v _o , the relative velocity Δv = v _o −v _s becomes Equation 12.

Therefore, the detection unit 116 substitutes the value of the velocity _{v s} and the sound velocity _{V s} of the moving body 100 to the number 12 to estimate the relative velocity Delta] v.

Here, the detection unit 116 calculates the relative speed Δv by using the speed v _s transmitted by the vehicle signal generation unit 114 in step ST2 and the sound speed V _s calculated in step ST33.
In addition, when the relationship of V _s >> v _s is established between the velocity v _s of the moving body 100 and the sound velocity Vs, the relative velocity Δv can be approximated as in Expression 13. However, by using the velocity v _s transmitted by the vehicle signal generation unit 114 at step ST2, the it is possible to estimate the relative velocity Δv more accurately.

In the output process of step ST38, when the object 200 is detected, the detection unit 116 uses the estimated value of the relative distance d estimated in step ST34 and the estimated value of the relative speed Δv estimated in step ST36. Read from the memory 121. Then, the detection unit 116 outputs the estimated values of the read relative distance d and relative speed Δv.
On the other hand, when the object 200 is not detected, the detection unit 116 reads the flag written in the memory 121 in step ST35 or the estimated values of the relative distance d and the relative speed Δv. Then, the detection unit 116 outputs the read flag or estimated values of the relative distance d and the relative speed Δv.

*** Effects of Embodiment 1 ***
As described above, the object detection apparatus 10 according to Embodiment 1 uses a signal configured by superimposing a plurality of waves having different frequencies as a transmission signal. Thereby, since the S / N ratio (signal to noise ratio) in the correlation processing can be improved, the object 200 at a long distance can be detected. Further, the relative distance d and the relative speed Δv between the moving body 100 and the object 200 can be estimated.

The effect of using a signal formed by superposing a plurality of waves having different frequencies as a transmission signal will be described.
As an apparatus for detecting the object 200 using sound waves, an ultrasonic sensor is known and may be mounted on a moving object for the purpose of detecting an obstacle at a short distance. Here, the ultrasonic sensor transmits and receives a signal having a single frequency component such as 40 kHz. More precisely, the ultrasonic sensor transmits and receives a signal including a frequency component of several percent before and after the center frequency with a single frequency as the center frequency. Therefore, a signal that can be used as a transmission signal is a pulse signal with a single frequency or a signal (amplitude modulation signal, phase modulation signal, frequency modulation signal) whose amplitude, phase, frequency, etc. are modulated by a specific code.
When using a pulse signal as the transmission signal, for example, a method is used in which the time when the amplitude of the reception signal exceeds a certain threshold is regarded as the reception time, and the relative distance from the time and speed of sound required for transmission / reception to the obstacle is used. It is done. While this method does not require complicated signal processing, it has a drawback of being vulnerable to noise.

In some cases, a signal having a different frequency, amplitude, phase, or the like assigned to a code pattern such as a modulated signal (M-sequence (maximum length sequence)) is used as a transmission signal. In this case, as shown in FIG. 11, the cross-correlation function shown in the equation 14 between the received signal and the transmitted signal is calculated, and the time required for transmission / reception is obtained from the deviation of the maximum peak position. Is used. FIG. 11 shows a case where a frequency modulation signal is used as a transmission signal.

While this method can improve the S / N ratio by correlation processing, the S / N ratio is improved according to the code length, so that the signal length becomes long to measure a long distance. There is. Furthermore, when at least one of the moving body 100 and the object 200 is moving, a frequency shift due to the Doppler effect (hereinafter referred to as Doppler shift) occurs, so that the frequency modulation signal is not suitable for correlation processing.

On the other hand, when a signal formed by superposing a plurality of waves having different frequencies is used as a transmission signal, the S / N ratio can be improved as compared with the case of using a single frequency signal even if the signal length is the same. That is, the object 200 at a long distance can be detected while suppressing an increase in signal length. Further, the reception time can be obtained from the maximum peak position of the cross-correlation function, the relative distance d can be estimated, and the Doppler shift amount can also be estimated from the peak position deviation amount.

Further, the object detection apparatus 10 according to Embodiment 1 uses a signal obtained by superimposing a plurality of waves whose frequencies increase according to a geometric sequence as a transmission signal. Thereby, the object 200 at a long distance can be detected with higher accuracy. In addition, the relative distance d and the relative speed Δv between the moving body 100 and the object 200 can be estimated with higher accuracy.

The effect of using, as a transmission signal, a signal in which a plurality of waves whose frequencies increase according to a geometric sequence will be superimposed will be described.
The Doppler shift works in a multiplicative way. That is, all frequency components are increased or decreased at the same magnification. Therefore, an ideal received signal is obtained by using an attenuation rate α (<1) due to air, a Doppler shift rate ρ, a relative distance d between the moving body 100 and the object 200, and a sound velocity V _s. ρ (t−2d) / V _s ).
For this reason, by using a signal in which each frequency increases in a geometric series, even when a Doppler shift occurs, the overlap between the frequency amplitude characteristics of the transmission signal and the reception signal increases. Therefore, a large peak tends to occur in the cross-correlation function between the transmission signal and the reception signal. As a result, the object 200 can be detected with high accuracy, and the relative distance d and the relative speed Δv between the moving body 100 and the object 200 can be estimated with high accuracy.

The object detection apparatus 10 according to Embodiment 1 uses a signal obtained by superimposing a plurality of waves having different initial phases for each frequency as a transmission signal. Thereby, the object 200 at a long distance can be detected with higher accuracy. In addition, the relative distance d and the relative speed Δv between the moving body 100 and the object 200 can be estimated with higher accuracy.

The effect of using a signal obtained by superposing a plurality of waves having different initial phases for each frequency as a transmission signal will be described.
When Doppler shift occurs, if the frequency and initial phase have a one-to-one correspondence, and the same frequency component is included in the transmitted signal and the received signal, the phase corresponding to that frequency is the same for both To do. For this reason, the peak positions of the cross-correlation functions corresponding to the respective frequencies coincide with each other, and a large peak is easily formed. As a result, the object 200 can be detected with high accuracy, and the relative distance d and the relative speed Δv between the moving body 100 and the object 200 can be estimated with high accuracy.

The object detection apparatus 10 according to the first embodiment uses a signal obtained by superimposing a plurality of waves having a frequency within either frequency band of a sound wave and a low-frequency ultrasonic wave as a transmission signal. Thereby, the object 200 at a long distance can be detected with higher accuracy. In addition, the relative distance d and the relative speed Δv between the moving body 100 and the object 200 can be estimated with higher accuracy.

The effect of using any frequency band of a sound wave and a low frequency ultrasonic wave is demonstrated.
The sound wave radiated into the air is gradually attenuated by the influence of the viscosity of the air. At this time, the energy density is proportional to exp (−2αz), assuming that the air attenuation constant α and the propagation distance z of the sound wave. According to the literature (Koichi Yoshihisa, “Calculation of Air Absorption in Outdoor Sound Propagation (ISO 9613-1)”, Noise Control, Vol. 21, No. 3, pp. 130-135 (1997)). Since α is approximately proportional to the square of the frequency, the higher the frequency, the greater the attenuation. For this reason, signals in a high frequency band such as 40 kHz, 200 kHz, and 400 kHz, which are frequencies often used in an object detection device using sound waves, such as an ultrasonic sensor, are not suitable for detecting an object at a long distance. The object detection apparatus 10 can detect an object 200 at a long distance by suppressing attenuation of energy by using a sound wave in a frequency band lower than this as a transmission signal.

However, signals in the frequency band below 16 kHz are generally within the human audible range. Therefore, it is desirable not to use a frequency band of less than 16 kHz from the viewpoint of health and noise problems.

In the case of a short distance of about several meters or less, the object 200 can be detected not only within the range of 16 kHz to 40 kHz but also using a signal in a higher frequency band. Therefore, the object detection apparatus 10 uses sound waves or low frequency ultrasonic waves in the range of 16 kHz to 100 kHz.

In addition, the object detection apparatus 10 according to Embodiment 1 calculates the sound speed V _{s based} on the external environment information acquired via the environment information acquisition unit 143. Thereby, the relative speed Δv between the moving body 100 and the object 200 can be calculated with high accuracy.

*** Other configurations ***
<Modification 1>
In the first embodiment, the object detection apparatus 10 has many functions in order to increase the detection accuracy of the object 200 and to increase the estimation accuracy of the relative distance d and the relative speed Δv between the moving body 100 and the object 200. With components. However, as a first modification, the functional components may be simplified although there is a possibility that the accuracy may be slightly reduced as compared with the first embodiment. The first modification will be described with respect to differences from the first embodiment.

With reference to FIG. 12, the structure of the object detection apparatus 10 which concerns on the modification 1 is demonstrated.
The object detection device 10 includes hardware including a processor 11, a storage device 12, and an audio interface 13.
The object detection apparatus 10 includes a time synchronization unit 111, a detection unit 116, and a reception unit 132 as functional components. The reception unit 132 receives a reception signal including a reflected wave reflected by an object from the acoustic signal output device 21 mounted on the moving body 100 via the acoustic signal input device 22 mounted on the moving body 100. And accept. The time synchronization unit 111 synchronizes the operations of the acoustic signal output device 21 and the acoustic signal input device 22, and enables time measurement until the sound wave emitted from the acoustic signal output device 21 is received by the acoustic signal input device 22. To do. The detection unit 116 detects the object 200 based on the reception signal received by the reception unit 132 and estimates the relative distance d and the relative speed Δv between the moving body 100 and the object 200.

Note that the object detection apparatus 10 may have some hardware and functions shown in FIG. 1 added to the configuration shown in FIG.

<Modification 2>
In the first embodiment, the functions of the time synchronization unit 111, the transmission signal generation unit 112, the reception signal generation unit 113, the vehicle signal generation unit 114, the environment signal generation unit 115, and the detection unit 116 are software. Was realized. However, as a second modification, the functions of these units may be realized by hardware. The second modification will be described with respect to differences from the first embodiment.

With reference to FIG. 13, the structure of the object detection apparatus 10 which concerns on the modification 2 is demonstrated.
When the functions of the respective units are realized by hardware, the object detection device 10 includes a processing circuit 15 instead of the processor 11 and the storage device 12. The processing circuit 15 is a dedicated electronic circuit that realizes the functions of each unit of the object detection device 10 and the function of the storage device 12.

The processing circuit 15 is assumed to be a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, a logic IC, a GA (Gate Array), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array). Is done.
The function of each part may be realized by one processing circuit 15, or the function of each part may be realized by being distributed to a plurality of processing circuits 15.

<Modification 3>
As a third modification, some functions of the time synchronization unit 111, the transmission signal generation unit 112, the reception signal generation unit 113, the vehicle signal generation unit 114, the environment signal generation unit 115, and the detection unit 116 are hard. It may be realized by hardware, and other functions may be realized by software. That is, some of the functions of the object detection device 10 may be realized by hardware, and other functions may be realized by software.

The processor 11, the storage device 12, the audio interface 13, the in-vehicle interface 14, and the processing circuit 15 are collectively referred to as “processing circuitries”. That is, the function of each part is realized by a processing circuit.

<Modification 4>
In the first embodiment, as shown in FIG. 2, the acoustic signal output device 21 and the acoustic signal input device 22 are arranged at positions close to each other on the front side of the moving body 100 and are objects that are vehicles traveling in front of the moving body 100. An example of detecting 200 has been described. However, the present invention is not limited to this, and the acoustic signal output device 21 and the acoustic signal input device 22 are arranged at close positions on the rear side of the moving body 100 to detect the object 200 that is a vehicle traveling behind the moving body 100. You can also Further, the acoustic signal output device 21 and the acoustic signal input device 22 may be arranged on both the front side and the rear side of the moving body 100 to detect the object 200 that is a vehicle traveling forward and backward.
Further, the object 200 is not limited to a vehicle, and may be other types such as a pedestrian and a building-like structure whose moving speed is equal to or lower than the sound speed.

Even if the acoustic signal output device 21 and the acoustic signal input device 22 are not close to each other, the acoustic signal input device 22 generates a reflected wave generated by reflecting the output signal radiated from the acoustic signal output device 21 to the object 200. It only needs to be arranged at a position where it can be collected.
In the situation shown in FIG. 2, one acoustic signal input device 22 is disposed on the front side of the moving body 100. However, the number of acoustic signal input devices 22 is not limited to one and may be two or more. When a plurality of acoustic signal input devices 22 are arranged, the detection unit 116 synthesizes estimation results for reception signals collected by the acoustic signal input devices 22.
To summarize the estimation results is to take the average of the respective estimated values as a specific example. Thereby, estimation accuracy can be improved.

Embodiment 2. FIG.
When the object 200 is positioned on the oblique side of the moving body 100, the relative velocity Δv estimated from the received signal from one acoustic signal input device 22 becomes an oblique component of the relative velocity Δv of the object 200.
The second embodiment is different from the first embodiment in that the object 200 is detected using at least two acoustic signal input devices 22. Thus, in the second embodiment, it is possible to estimate the relative speed Δv even when the object 200 is located obliquely to the moving body 100. In the second embodiment, this different point will be described.

*** Explanation of configuration ***
With reference to FIG. 14, the structure of the object detection apparatus 10 which concerns on Embodiment 2 is demonstrated.
The object detection device 10 includes at least two acoustic signal input devices 22. In the second embodiment, the object detection device 10 includes an acoustic signal input device 22A and an acoustic signal input device 22B.
Further, the object detection device 10 includes a reception unit 132 corresponding to each acoustic signal input device 22. In the second embodiment, the object detection device 10 includes a reception unit 132A corresponding to the acoustic signal input device 22A and a reception unit 132B corresponding to the acoustic signal input device 22B.

*** Explanation of operation ***
The operation of the object detection apparatus 10 according to the second embodiment will be described with reference to FIGS. 15 to 17.
The operation of the object detection apparatus 10 according to the second embodiment corresponds to the object detection method according to the second embodiment. The operation of the object detection apparatus 10 according to the second embodiment corresponds to the processing of the object detection program according to the second embodiment.

With reference to FIG. 15, the situation of the moving body 100 according to Embodiment 2 and the object 200 existing around the moving body 100 will be described. In the second embodiment, the object 200 is a vehicle that runs on the left side of the moving body 100.
FIG. 15 shows a moving body 100 in which an acoustic signal output device 21 and two acoustic signal input devices 22 are installed on the left side, and an object 200. In FIG. 15, the acoustic signal input device 22 </ b> A is disposed at a position close to the acoustic signal output device 21, and the acoustic signal input device 22 </ b> B is disposed at a position away from the acoustic signal output device 21.
In this situation, an acoustic signal output device 21 and an audio signal input device 22A, between the acoustic signal input device 22B is the distance d _12. Also, the shortest path length and the shortest path length from the acoustic signal output device 21 to the object 200, the source of the reflected wave to the acoustic signal input device 22A are both becomes substantially equal distance d _1. The generation source of the reflected wave is a position where the transmission signal output from the acoustic signal output device 21 reaches the object 200 in the shortest time. Further, the shortest path length to the audio signal input device 22B from the source of the reflected wave is a distance d _2.
Further, the angles formed by the acoustic signal output device 21 and the acoustic signal input device 22A and the reflected wave generation source are almost equal to θ ₁ . Further, the angle between the acoustic signal input unit 22B and the source of the reflected wave becomes theta _2. Note that the angle is defined counterclockwise with 0 ° for the front of the moving body 100 and 180 ° for the rear.
Further, as shown in FIG. 15, the moving body 100 travels at a speed _{v s,} the object 200 travels at a speed _{v o.} In this situation, the relative distance d ₁ and the relative distance d ₂ and the relative speed Δv = v _o −v _s are estimated.

Since the overall operation and the detailed operation in step ST1 are the same as those in the first embodiment, description thereof is omitted.

** Detailed operation of step ST2 **
With reference to FIG. 16, the operation in step ST2 according to the second embodiment will be described in detail.
The process of step ST22 is the same as the process of step ST22 of FIG.

In the reception process of step ST21B, the reception unit 132A stores the reception signal 1 for the latest T seconds in the memory 121 among the reception signals 1 that are always collected by the acoustic signal input device 22A. Similarly, the reception unit 132B stores the reception signal 2 for the latest T seconds in the memory 121 among the reception signals 2 that are always collected by the acoustic signal input device 22B.

In the transmission process of step ST23B, the reception signal generation unit 113 reads the reception signals 1 and 2 for the latest T seconds stored in the memory 121, and transmits the read reception signals 1 and 2 to the detection unit 116. At this time, the vehicle signal generation unit 114 acquires the speed of the moving body 100 via the vehicle information acquisition unit 142 and transmits it to the detection unit 116. Similarly, the environment signal generation unit 115 acquires external environment information via the environment information acquisition unit 143 and transmits the external environment information to the detection unit 116.

** Detailed operation of step ST3 **
With reference to FIG. 17, the operation in step ST3 according to the second embodiment will be described in detail.
The processing from step ST32 to step ST33 is the same as the processing from step ST32 to step ST33 in FIG. Moreover, the process of step ST35 is the same as the process of step ST35 of FIG.

In the correlation process in step ST31B, the detection unit 116 calculates a cross-correlation function for each of the reception signals 1 and 2 transmitted by the reception signal generation unit 113 in step ST2 and each of at least two types of reference signals 1 and 2. To do.
In the second embodiment, it is assumed that two types of reference signals 1 and 2 are stored in the memory 121. Then, the detection unit 116 reads the two types of reference signals 1 and 2 from the memory 121 and calculates a cross-correlation function for each of the received signals 1 and 2 and each of the reference signals 1 and 2. The detection unit 116 writes the calculated cross-correlation functions in the memory 121.

In the first calculation process of step ST34B, the detection unit 116 estimates the relative distance d between the moving body 100 and the detected object 200 and the Doppler shift rate ρ. The detection unit 116 writes the estimated values of the relative distance d and the Doppler shift rate ρ in the memory 121.

A method for estimating the relative distance d will be described.
The detection unit 116 calculates the average peak shift amount according to Equation 7 for each of the received signals 1 and 2 by the same process as the process of step ST34 in FIG. Using the average peak shift amount Δt ₁ ⁻ calculated for the received signal ₁ and the average peak shift amount Δt ₂ ⁻ calculated for the received signal 2, the detection unit 116 calculates the relative distance d ₁ , to estimate the d _2.

Here, with respect to the relative distance d _1, the transmission path to the transmission signal is received, the audio signal output device 21 → the object 200 (the source of the reflected wave) → acoustic signal input device 22A. Therefore, the path length is d ₁ + d ₁ . Therefore, the estimated value of the relative distance d ₁ is calculated by 1/2 a value obtained by converting the time required for transmission and reception distance.
Regarding the relative distance d ₂ , since the transmission path until the transmission signal is received is the acoustic signal output device 21 → the object 200 (source of reflected wave) → the acoustic signal input device 22B, the path length is d. a ₁ + _{d 2.} Therefore, estimates of the relative distance d ₂ is calculated by subtracting the relative distance d ₁ from the value obtained by converting the time required for transmission and reception distance.

A method for estimating the Doppler shift rate ρ will be described.
The detection unit 116 estimates the Doppler shift rate ρ according to Equation 10 for each of the received signals 1 and 2 by the same process as the process of step ST34 of FIG. In the situation shown in FIG. 15, an estimate of the Doppler shift rate [rho calculated from the received signals collected by the audio signal input unit 22A and [rho _1, were calculated from the received signals collected by the audio signal input device 22B Doppler the estimated value of the shift rate ρ and ρ _2.

In the second calculation process in step ST36B, detector 116, along with the estimates from the estimated value [rho ₁ of the Doppler shift rate estimated [rho relative speed Delta] v ₁ in step ST34B, estimating the relative velocity Delta] v ₂ from the estimated value [rho ₂ To do.

A method for estimating the relative speed Δv will be described.
In the situation shown in FIG. 15, the estimated values ρ ₁ and ρ ₂ are each expressed by Expression 16.

Here, the values of cos θ ₁ and cos θ ₂ can be calculated based on the principle of triangulation from the triangles of three sides d ₁₂ , d ₁ , and d ₂ in FIG. The distance d ₁₂ because of the distance between the acoustic signal input unit 22A and the acoustic signal input unit 22B, a known value. Further, the relative distance d ₁ and the relative distance d ₂ can be used an estimate of the calculated relative distance in step ST34B.
Therefore, the detection unit 116 calculates cos θ ₁ and cos θ ₂ by Expression 17 from the values of the distance d ₁₂ , the relative distance d _1, and the relative distance d ₂ .

The detection unit 116 substitutes the velocity v _s of the moving body 100, the sound velocity V _s, and the calculated values of cos θ ₁ and cos θ _{2 in} the respective equations of the estimated values ρ ₁ and ρ ₂ of Equation 16, and the velocity Solve for _vo . Thus, the detection unit 116 obtains the acoustic signal input device 22A, the estimated value Delta] v ₁ relative velocity Δv ₌ v o -v _s corresponding to each 22B, a Delta] v _2.

In the overall processing in step ST37B, the detection unit 116 estimates the relative speed Δv by integrating the estimated values Δv ₁ and Δv ₂ corresponding to the acoustic signal input devices 22A and 22B estimated in step ST36B.
Specifically, in Embodiment 2, the detection unit 116 estimates the relative speed Δv by calculating the average of the estimated values Δv ₁ and Δv ₂ . The detection unit 116 writes the estimated relative speed Δv in the memory 121.
Note that the detection unit 116 performs a method of setting the mode of the distribution of the estimated values Δv ₁ and Δv ₂ as a relative velocity Δv, or performs an outlier determination process, and calculates the relative velocity Δv using only an estimation result that is not an outlier. The relative speed Δv may be calculated by another method such as.

In the output process of step ST38B, when the object 200 is detected, the detection unit 116 calculates the estimated values of the relative distances d ₁ and d ₂ estimated in step ST34B and the relative velocity Δv estimated in step ST37B. The estimated value is read from the memory 121. Then, the detection unit 116 outputs the estimated values of the read relative distances d ₁ and d ₂ and the relative speed Δv.
On the other hand, when the object 200 is not detected, the detection unit 116 reads the flag written in the memory 121 in step ST35 or the estimated values of the relative distances d ₁ and d ₂ and the relative speed Δv. Then, the detecting unit 116 outputs the read flag or the estimated values of the relative distances d ₁ and d ₂ and the relative speed Δv.

In step ST38B, the detection unit 116 may calculate the relative position coordinates of the object 200 from the estimated relative distance values d ₁ and d ₂ and the known distance d _{12 according} to the principle of triangulation and output the calculated coordinates. .

*** Effects of Embodiment 2 ***
As described above, the object detection apparatus 10 according to Embodiment 2 applies the principle of triangulation to estimation results obtained from a plurality of received signals. Thereby, even when the object 200 exists on the side of the moving body 100 and the transmission path of the transmission signal has an angle, the relative distance d and the relative speed Δv can be estimated.
When the object 200 is present beside the moving body 100, the relative distance d and the relative speed can be obtained by arranging one acoustic signal input device 22 on the side of the moving body 100 as in the first embodiment. Δv can be estimated.

*** Other configurations ***
<Modification 5>
In the second embodiment, as shown in FIG. 15, two acoustic signal input devices 22 </ b> A and 22 </ b> B are arranged on the left side of the moving body 100. Thereby, the object 200 existing on the left side of the moving body 100 is detected. As a fifth modification, two acoustic signal input devices 22 may be arranged on the right side of the moving body 100 to detect the object 200 present on the right side of the moving body 100. Alternatively, two acoustic signal input devices 22 may be disposed on both the left and right sides of the moving body 100 to detect the object 200 present on both the left and right sides of the moving body 100.

<Modification 6>
In the second embodiment, two acoustic signal input devices 22 are arranged. However, as a sixth modification, three or more acoustic signal input devices 22 may be arranged.
When three or more acoustic signal input devices 22 are arranged, the detection unit 116 estimates the relative distance d and the Doppler shift rate ρ for each acoustic signal input device 22 in step ST34B. Further, in step ST36B to step ST37B, the detection unit 116 calculates the relative speed Δv corresponding to each acoustic signal input device 22, and integrates the calculated relative speed Δv.
By using three or more acoustic signal input devices 22, triangulation is performed a plurality of times, and the estimation accuracy between the relative velocity Δv and the relative position coordinates of the object 200 can be increased.

Embodiment 3 FIG.
At a distance where the reflected wave reflected by the object 200 and the direct sound transmitted from the acoustic signal output device 21 and not reflected by the object 200 overlap, the cross-correlation function does not peak and the object 200 may not be detected. .
The third embodiment is different from the second embodiment in that the object 200 is detected using at least two acoustic signal output devices 21. As a result, in the third embodiment, the cross-correlation function has a peak even at a distance where the reflected wave and the direct sound overlap, and the object 200 can be detected with high accuracy. In the third embodiment, this different point will be described.

*** Explanation of configuration ***
With reference to FIG. 18, the structure of the object detection apparatus 10 which concerns on Embodiment 3 is demonstrated.
The object detection device 10 includes at least two acoustic signal output devices 21. In the third embodiment, the object detection device 10 includes an acoustic signal output device 21A and an acoustic signal output device 21B.
Further, the object detection device 10 includes a radiation unit 131 corresponding to each acoustic signal output device 21. In the third embodiment, the object detection device 10 includes a radiation unit 131A corresponding to the acoustic signal output device 21A and a radiation unit 131B corresponding to the acoustic signal output device 21B.

*** Explanation of operation ***
The operation of the object detection apparatus 10 according to the third embodiment will be described with reference to FIGS.
The operation of the object detection apparatus 10 according to the third embodiment corresponds to the object detection method according to the third embodiment. The operation of the object detection apparatus 10 according to the third embodiment corresponds to the processing of the object detection program according to the third embodiment.

Referring to FIG. 19, the situation of moving body 100 according to Embodiment 3 and object 200 existing around moving body 100 will be described. In the third embodiment, the object 200 is a vehicle traveling on the left side of the moving body 100.
FIG. 19 shows a moving body 100 in which two acoustic signal output devices 21 and two acoustic signal input devices 22 are installed on the left side, and an object 200. In FIG. 19, the acoustic signal input device 22A is disposed at a position close to the acoustic signal output device 21A, and the acoustic signal input device 22B is disposed at a position close to the acoustic signal output device 21B.
In this situation, between the acoustic signal output device 21A and the audio signal input device 22A, the audio signal output device 21B and the audio signal input unit 22B is the distance _{d 12.} Further, the shortest path length from the acoustic signal output device 21A to the object 200 and the shortest path length from the reflected wave generation source of the transmission signal output from the acoustic signal output device 21A to the acoustic signal input device 22A are almost all. The distance d _A1 is equal. The shortest path length to the audio signal input device 22B from the source of the reflected wave, the distance d _A2. In addition, the shortest path length from the acoustic signal output device 21B to the object 200 and the shortest path length from the reflected wave generation source of the transmission signal output from the acoustic signal output device 21B to the acoustic signal input device 22B are almost all. The distance is equal to d _B1 . The shortest path length from the reflected wave generation source to the acoustic signal input device 22A is the distance _dB2 .
Further, the angles formed by the acoustic signal output device 21A and the acoustic signal input device 22A and the generation source of the reflected wave of the transmission signal output from the acoustic signal output device 21A are substantially equal to θ _A1 . The angle formed between the acoustic signal input device 22B and the generation source of the reflected wave is θ _A2 . In addition, the angles formed by the acoustic signal output device 21B and the acoustic signal input device 22B and the generation source of the reflected wave of the transmission signal output from the acoustic signal output device 21B are substantially equal to θ _B1 . The angle formed by the acoustic signal input device 22A and the source of the reflected wave is θ _B2 .
Further, as shown in FIG. 19, the moving body 100 travels at a speed _{v s,} the object 200 travels at a speed _{v o.} In this situation, the relative distance d ₁ and the relative distance d ₂ and the relative speed Δv = v _o −v _s are estimated.

Since the overall operation and the detailed operation in step ST2 are the same as those in the second embodiment, description thereof is omitted.

** Detailed operation of step ST1 **
Referring to FIG. 20, the operation of step ST1 according to Embodiment 3 will be described in detail.
The process of step ST11 is the same as the process of step ST11 of FIG.

In the transmission process of step ST12C, the transmission signal generation unit 112 reads a signal waveform stored in advance in the memory 121, and transmits the read signal waveform to the radiation units 131A and 131B as a transmission signal. The radiating units 131 </ b> A and 131 </ b> B radiate the transmission signal as an acoustic signal via the acoustic signal output device 21. Here, the transmission signal radiated from the radiating unit 131A is referred to as a transmission signal A, and the transmission signal radiated from the radiating unit 131B is referred to as a transmission signal B.
Here, the transmission signals A and B transmitted from the acoustic signal output devices 21A and 21B are different signals. Specifically, the transmission signals A and B are uncorrelated with each other. That is, no peak appears in the cross-correlation function between the transmission signals A and B.

** Detailed operation of step ST3 **
With reference to FIG. 21, the operation of step ST3 according to Embodiment 3 will be described in detail.
The processing from step ST32 to step ST33 is the same as the processing from step ST32 to step ST33 in FIG. Moreover, the process of step ST35 is the same as the process of step ST35 of FIG.

In the correlation process of step ST31C, the detection unit 116 performs the reception signals 1 and 2 transmitted by the reception signal generation unit 113 in step ST2 and at least four types of reference signals A1, A2, B1, and B2, respectively. Calculate the cross-correlation function. The reference signals A1 and A2 are two types of reference signals corresponding to the transmission signal A. The reference signals B1 and B2 are two types of reference signals corresponding to the transmission signal B.
In the third embodiment, it is assumed that four types of reference signals A1, A2, B1, and B2 are stored in the memory 121. Then, the detection unit 116 reads four types of reference signals A1, A2, B1, and B2 from the memory 121, and calculates cross-correlation functions for the received signals 1 and 2 and the reference signals A1, A2, B1, and B2, respectively. calculate. The detection unit 116 writes the calculated cross-correlation functions in the memory 121.
That is, the detection unit 116 calculates the number of acoustic signal output devices 21 (two) × the number of acoustic signal input devices 22 (two) × 2 = 8 cross-correlation functions.

Here, both the received signal 1 and the received signal 2 are a mixture of a reflected wave corresponding to the transmission signal A and a reflected wave corresponding to the transmission signal B. At this time, since the transmission signal A and the transmission signal B are uncorrelated with each other, calculating the cross-correlation function with the reference signals A1 and A2 for the reception signals 1 and 2 respectively corresponds to the reflected wave of the transmission signal A. Only the correlation peak stands. Similarly, when the cross-correlation function between the received signals 1 and 2 and the reference signals B1 and B2 is calculated, only a correlation peak corresponding to the reflected wave of the transmission signal B is generated.
Therefore, even when the direct sound of the transmission signal A overlaps with the reflected wave of the transmission signal B and when the direct sound of the transmission signal B overlaps with the reflected wave of the transmission signal A, by calculating the cross-correlation function, Only peaks corresponding to the respective reflected waves can be extracted. Therefore, the relative distance d and the relative speed Δv corresponding to the transmission signals A and B can be estimated.

In the first calculation process in step ST34C, the detection unit 116 estimates the relative distance d and the Doppler shift rate ρ for each of the transmission signals A and B by the same process as in step ST34B in FIG. The detection unit 116 writes the estimated values of the relative distance d and the Doppler shift rate ρ in the memory 121.
Here, the estimated values of the relative distance d from each acoustic signal input device 22 to the object 200 corresponding to the transmission signal A are respectively estimated values d _A1 and d _A2, and the estimated values of the Doppler shift rate ρ are respectively estimated values ρ. _A1, and ρ _A2. Further, the estimated values of the relative distance d from each acoustic signal input device 22 to the object 200 corresponding to the transmission signal B are respectively estimated values d _B1 and d _B2, and the estimated values of the Doppler shift rate ρ are respectively estimated values ρ _B1. , Ρ _B2 .

In the second calculation process in step ST36C, the detection unit 116 estimates the relative speed Δv _A1 from the estimated value ρ _A1 of the Doppler shift rate ρ estimated in step ST34C by the same process as in step ST36B in FIG. estimating the relative velocity Delta] v _A2 from the value [rho _A2, it estimates the relative velocity Delta] v _B1 from the estimated value [rho _B1, estimates the relative velocity Delta] v _B2 from the estimated value [rho _B2.

A method for estimating the relative speed Δv will be described.
In the situation shown in FIG. 19, the estimated values ρ _A1 , ρ _A2 , ρ _B1 , and ρ _B2 are each expressed by Equation 18.

Detector 116, similar to the values of cos [theta] ₁ and cos [theta] ₂ in step ST36B shown in FIG. 17, based on the principle of trilateration to compute the number 19 the value of cos [theta] _A1 and cos [theta] _A2 and cos [theta] _B1 and cos [theta] _B2 .

The detecting unit 116 calculates the velocity v _s of the moving body 100, the sound velocity V _s, and the calculated values of cos θ _A1 , cos θ _A2 , cos θ _B1, and cos θ _{B2 from} the estimated values ρ _A1 , ρ _A2 , ρ of Equation 18. _{B1, ρ B2} is assigned to each of the equation, solving for velocity _{v o.} Thus, detector 116, the transmission signal A, B and the acoustic signal input device 22A, the relative speed corresponding to each combination of the 22B Δv ₌ v o -v _s estimate _{Δv A1, Δv A2, Δv B1} , Δv _{Get B2} .

In the overall process of step ST37C, the detection unit 116 combines the estimated values d _A1 and d _B1 estimated in step ST34C to estimate the relative distance d ₁ , and the estimated values d _A2 and d _B2 to estimate the distance _{d 2.} In addition, the detection unit 116 estimates the relative speed Δv by combining the estimated values Δv _A1 , Δv _A2 , Δv _B1 , Δv _B2 estimated in step ST36C.
Specifically, in Embodiment 3, the detecting unit 116 calculates the average of the estimated values d _A1 and d _B2 to estimate the relative distance d ₁ and calculates the average of the estimated values d _A2 and d _B2. by estimates a relative distance d _2. In addition, the detection unit 116 estimates the relative velocity Δv by calculating the average of the estimated values Δv _A1 , Δv _A2 , Δv _B1 , Δv _B2 . The detection unit 116 writes the estimated relative speed Δv in the memory 121.
Note that the detection unit 116 performs a method of setting the mode of the distribution of the estimated values Δv _A1 , Δv _A2 , Δv _B1 , Δv _B2 as a relative velocity Δv, or performs an outlier determination process, and uses only an estimation result that is not an outlier. The relative speed Δv may be calculated by another method such as calculating the relative speed Δv.

In the output process of step ST38C, when the object 200 is detected, the detection unit 116 reads the estimated values of the relative distances d ₁ and d _{2 and} the estimated value of the relative velocity Δv estimated in step ST37C from the memory 121. . Then, the detection unit 116 outputs the estimated values of the read relative distances d ₁ and d ₂ and the relative speed Δv.
On the other hand, when the object 200 is not detected, the detection unit 116 reads the flag written in the memory 121 in step ST35 or the estimated values of the relative distances d ₁ and d ₂ and the relative speed Δv. Then, the detecting unit 116 outputs the read flag or the estimated values of the relative distances d ₁ and d ₂ and the relative speed Δv.

In step ST38C, the detection unit 116 may calculate and output the relative position coordinates of the object 200 from the estimated relative distance values d ₁ and d ₂ and the known distance d _{12 according} to the principle of triangulation. .

*** Effects of Embodiment 3 ***
As described above, the object detection apparatus 10 according to Embodiment 3 detects the object 200 using a plurality of transmission signals. Thereby, even in the distance where the reflected wave and the direct sound overlap, the cross-correlation function has a peak, and the object 200 can be detected with high accuracy.

*** Other configurations ***
<Modification 7>
In the third embodiment, as shown in FIG. 19, two acoustic signal output devices 21 </ b> A and 21 </ b> B and two acoustic signal input devices 22 </ b> A and 22 </ b> B are arranged on the left side of the moving body 100. Thereby, the object 200 existing on the left side of the moving body 100 is detected. As a seventh modification, two acoustic signal output devices 21 and two acoustic signal input devices 22 may be arranged on the right side of the moving body 100 to detect the object 200 present on the right side of the moving body 100. Further, two acoustic signal output devices 21 and two acoustic signal input devices 22 are arranged on the left and right sides of the moving body 100 to detect the object 200 existing on both the left and right sides of the moving body 100. Good.

<Modification 8>
In the third embodiment, two acoustic signal output devices 21 are arranged. However, as a modified example 8, three or more acoustic signal output devices 21 may be arranged.
When three or more acoustic signal output devices 21 are arranged, the detection unit 116 estimates the relative distance d and the Doppler shift rate ρ for each acoustic signal output device 21 in step ST34C. In step ST36C, the detection unit 116 calculates the relative speed Δv corresponding to each acoustic signal output device 21. In step ST37C, the detection unit 116 combines the calculated relative distance d and relative speed Δv.

<Modification 9>
In the third embodiment, two acoustic signal output devices 21 that radiate different transmission signals are arranged. However, as a ninth modification, a transmission signal obtained by superimposing uncorrelated signals from one acoustic signal output device 21 may be transmitted. As a result, as in the third embodiment, the cross-correlation function has a peak even at the distance where the reflected wave and the direct sound overlap, and the object 200 can be detected with high accuracy.
Note that the degree of decorrelation does not necessarily have to be completely uncorrelated, as long as it satisfies the detection accuracy or measurement performance required for the object detection apparatus 10.

Embodiment 4 FIG.
In the first to third embodiments, it has been described that the object 200 existing around the moving body 100 is detected. The fourth embodiment is different from the first to third embodiments in that the moving body 100 is controlled based on the detected result. In the fourth embodiment, this different point will be described.
In the fourth embodiment, a case where a function is added to the first embodiment will be described. However, it is possible to add functions to the second and third embodiments.

*** Explanation of configuration ***
With reference to FIG. 22, the structure of the object detection apparatus 10 which concerns on Embodiment 4 is demonstrated.
In FIG. 22, functional components other than the detection unit 116 are mainly omitted for easy understanding.
The in-vehicle interface 14 is connected to the vehicle control ECU 25. The vehicle control ECU 25 is a device that controls control devices such as a brake, an accelerator, and a steering wheel.

The object detection apparatus 10 includes a control unit 117 as a functional component. The function of the control unit 117 is realized by software, similar to the detection unit 116 and the like.

*** Explanation of operation ***
With reference to FIG. 23, operation | movement of the object detection apparatus 10 which concerns on Embodiment 4 is demonstrated.
The operation of the object detection apparatus 10 according to the fourth embodiment corresponds to the object detection method according to the fourth embodiment. The operation of the object detection apparatus 10 according to the fourth embodiment corresponds to the processing of the object detection program according to the fourth embodiment.

In the object detection process in step ST41, the object detection device 10 detects the object 200 existing around the moving body 100 and estimates the relative distance d and the relative speed Δv by the method described in the first embodiment.

In the control process of step ST42, when the object 200 is detected in step ST41, the control unit 117 sends a control signal for controlling the moving body 100 based on the output relative distance d and relative speed Δv to the in-vehicle interface 14. To the vehicle control ECU 25. Thereby, the control unit 117 controls the operation of the moving body 100.
As a specific example, when the object 200 is detected in front of the moving body 100, the relative distance d is within the reference distance, and the relative speed Δv is equal to or higher than the reference speed, the moving body 100 collides with the object 200. Therefore, the control unit 117 transmits a control signal for controlling the brake to the vehicle control ECU 25. Thereby, the brake is controlled, the moving body 100 is decelerated, and the moving body 100 is prevented from colliding with the object 200.
As another specific example, when the lane is changed, the object 200 in the lateral direction is detected, and if there is no object 200 at the planned destination location, the steering wheel is controlled so that the lane is changed. Control the handle etc. so that it does not change. This prevents the object 200 from colliding with the lane change.

<Modification 10>
In the second to fourth embodiments, as in the first embodiment, the functions of the respective units of the object detection device 10 are realized by software. However, as in the second modification of the first embodiment, the function of each unit of the object detection device 10 may be realized by hardware. As in the third modification of the first embodiment, the object detection device 10 may have some functions realized by hardware and other functions realized by software.

The embodiment of the present invention has been described above. You may implement combining some of these embodiment and modifications. Any one or several of them may be partially implemented. In addition, this invention is not limited to the above embodiment and modification, A various change is possible as needed.

As a specific example, the first embodiment has described that the object 200 existing in the front-rear direction of the moving body 100 is detected. In the second and third embodiments, the detection of the object 200 that exists in the left-right direction of the moving body 100 has been described. These may be combined so that the object 200 existing in the front-rear and left-right directions of the moving body 100 can be detected.
Further, the acoustic signal output device 21 and the acoustic signal input device 22 may be arranged on the bottom side of the moving body 100 to detect the object 200 present on the road surface on which the moving body 100 travels. Further, the acoustic signal output device 21 and the acoustic signal input device 22 may be arranged on the upper side of the moving body 100 to detect the object 200 existing on the upper side of the moving body 100.

10 object detection device, 11 processor, 12 storage device, 111 time synchronization unit, 112 transmission signal generation unit, 113 reception signal generation unit, 114 vehicle signal generation unit, 115 environment signal generation unit, 116 detection unit, 12 storage device, 121 Memory, 122 storage, 13 audio interface, 131 radiation unit, 132 reception unit, 14 in-vehicle interface, 141 time acquisition unit, 142 vehicle information acquisition unit, 143 environment information acquisition unit, 15 processing circuit, 21 acoustic signal output device, 22 acoustic Signal input device, 23 vehicle information ECU, 24 sensor ECU, 100 moving body, 200 object.

Claims (15)

1. A reception unit that receives a signal of a reflected wave, which is an acoustic signal composed of a superposition of a plurality of waves having different frequencies, and is generated when the acoustic signal radiated from a moving object is reflected by an object;
   An object detection apparatus comprising: a detection unit that detects the object by calculating a correlation value between the reception signal and a reference signal using the reflected wave signal received by the reception unit as a reception signal.
2. The object detection apparatus according to claim 1, wherein the acoustic signal is a signal obtained by superposing a plurality of waves whose frequencies increase according to a geometric progression.
3. The object detection device according to claim 1, wherein the acoustic signal is a signal obtained by superimposing a plurality of waves having different initial phases for each frequency.
4. The object detection apparatus according to any one of claims 1 to 3, wherein the acoustic signal is a signal obtained by superimposing a plurality of waves having a frequency within a frequency band of either a sound wave or a low-frequency ultrasonic wave.
5. 5. The object detection device according to claim 1, wherein the acoustic signal is a signal including a first signal and a second signal obtained by inverting the first signal. 6.
6. The detection unit calculates a correlation value between the received signal and each of the reference signal U (t) and the reference signal V (t), which are the reference signals, thereby calculating the distance between the moving body and the object, The object detection apparatus according to claim 1, wherein at least one of a relative speed between the moving body and the object is estimated.
7. The detection unit includes a shift amount Δt _U with respect to a reference position of a peak position of a correlation value between the received signal and the reference signal U (t), and a peak of a correlation value between the received signal and the reference signal V (t). A time delay amount Δt ⁻ corresponding to a relative distance is calculated by a sum (Δt _U + Δt _V ) of a shift amount Δt _V with respect to a reference position of the position, and the moving body and the object are calculated from the calculated time delay amount Δt ^−. The object detection apparatus according to claim 6, wherein the distance is estimated.
8. The detection unit includes a shift amount Δt _U with respect to a reference position of a peak position of a correlation value between the received signal and the reference signal U (t), and a peak of a correlation value between the received signal and the reference signal V (t). A Doppler shift amount s is calculated from a difference (Δt _V −Δt _U ) between a position and a shift amount Δt _V with respect to a reference position, and a relative speed between the moving body and the object is estimated from the calculated Doppler shift amount s. Item 7. The object detection device according to Item 6.
9. The object detection device includes, as the reception unit, a reception unit A and a reception unit B that receive signals of the reflected waves received at different positions of the moving body,
   The detection unit receives a reflected wave signal received by the reception unit A as a reception signal A, and receives the distance d ₁ between the moving body and the object based on the reception signal A and the reception unit B. Using a reflected wave signal as a received signal B, the distance d ₂ between the moving body and the object based on the received signal B is calculated, and at the same time, the Doppler is based on at least one of the received signal A and the received signal B. the shift amount s by calculating, from said receiving unit a and the distance d ₁₂ between the receiving unit B and the distance d ₁ and the distance d ₂ between the Doppler shift amount s, the moving body and said object The object detection apparatus according to claim 6, wherein the relative speed of the object is estimated.
10. The detection unit calculates a Doppler shift amount s ₁ based on the reception signal A and a Doppler shift amount s ₂ based on the reception signal B as the Doppler shift amount s, and the reception unit A and the reception unit the relative speed Δv1 calculates the distance d ₁₂ between B and the distance d ₁ and the distance d ₂ from the Doppler shift amount s ₁ Tokyo, the distance d ₁₂ between the receiving unit B and the receiving unit a said distance relative velocity Δv2 calculated from d ₁ and the distance d ₂ between the Doppler shift amount s ₂ Prefecture, from said relative speed Δv1 the relative velocity Δv2 Prefecture, estimates the relative velocity between the moving body and the object and The object detection apparatus according to claim 9.
11. The object detection device further includes:
    A radiation unit A that radiates an acoustic signal A as the acoustic signal, and a radiation unit B that radiates an acoustic signal B different from the acoustic signal A as the acoustic signal,
    The detection unit includes, for each of the reference signal for the acoustic signal A and the reference signal for the acoustic signal B, a relative distance between the moving body and the object, and between the moving body and the object. The object detection apparatus according to claim 9, wherein at least one of the relative velocity is estimated.
12. 12. The detection unit according to claim 6, wherein the detection unit estimates at least one of a distance between the moving body and the object and a relative speed between the moving body and the object using the speed of the moving body. The object detection apparatus of any one of Claims.
13. The detection unit calculates a sound speed that is a speed of the acoustic signal from external environment information about an environment outside the mobile object, and uses the calculated sound speed to calculate a distance between the mobile object and the object. The object detection apparatus according to claim 6, wherein at least one of a relative speed between the moving body and the object is estimated.
14. The reception unit provided in the moving body is an acoustic signal configured by superimposing a plurality of waves having different frequencies, and receives a reflected wave signal reflected from the object by the acoustic signal radiated from the moving body,
    An object detection method in which a processor detects the object by calculating a correlation value between the received signal and a reference signal using a reflected wave signal received by the receiving unit as a received signal.
15. When an acoustic signal composed of a superposition of a plurality of waves having different frequencies and a reflected wave signal generated by reflection of an acoustic signal radiated from a moving object on an object is received,
    An object detection program for causing a computer to execute a detection process for detecting the object by calculating a correlation value between the reception signal and a reference signal using a reflected wave signal received by the reception process as a reception signal.

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