JP2015055599A - Object detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology of efficiently detecting a reflection wave received from an object.SOLUTION: An object detection device orthogonally demodulates a receiving signal received from a transducer unit by use of a reference signal corresponding to a transmission signal, to obtain an I signal and a Q signal. On the basis of the I signal and the Q signal, a phase θ and an amplitude A of the receiving signal with respect to the reference signal are calculated (S210). The object detection device calculates a phase difference Δθ which is a difference of phase θ from a previous value at each time (S220), and calculates a standard deviation σ of the phase difference Δθ in each of periods of time length corresponding to a wave transmission time Te (S240). When the standard deviation σ is less than a reference value σ(Yes in S250), the process proceeds to S260 on the assumption that the receiving signal in the period is a signal to be detected, which shows characteristics of a reflection wave of an object to be detected. When the standard deviation σ is equal to or larger than the reference value σ(No in S250), a main unit enters S280 on the assumption that the receiving signal in the evaluation period is noise.

Description

  The present invention relates to an object detection apparatus that detects an object using a search wave.

  2. Description of the Related Art Conventionally, an object detection device that detects an object by transmitting a survey wave and receiving a reflected wave is known. Specifically, an apparatus that transmits a burst wave using ultrasonic waves as an exploration wave and estimates the distance to a forward object based on the time required from the transmission of the exploration wave to the reception of the reflected wave is known. .

  In this object detection device, for example, a sine wave having a predetermined frequency is transmitted as a burst wave for a certain period of time, and the received signal of the reflected wave is orthogonally demodulated using a reference signal having a frequency synchronized with the burst wave (Patent Literature). 1).

  When the relative velocity with the front object is zero, the Doppler shift does not occur, so the frequencies of the exploration wave and the reflected wave basically match, and the phase (phase difference) of the received signal with respect to the reference signal is A constant value is taken according to the path length from transmission to reception. Accordingly, the complex vector corresponding to the demodulated signal after the removal of the high frequency component is directed in a certain direction on the complex plane (IQ plane).

  On the other hand, noise is not determined in a fixed direction in the complex plane. In the conventional apparatus, using such a phenomenon, a vector sum obtained by vector addition of complex vectors is calculated so that the vector sum of reflected waves appears with a larger value than the vector sum of noise. And based on this vector sum, reception of a reflected wave is detected and the distance to a front object is estimated.

JP 2005-249770 A

  By the way, the above-described method for calculating the vector sum and estimating the distance to the front object has the following problems. That is, when the relative speed with respect to the front object is not zero, the frequency of the reflected wave with respect to the exploration wave changes under the influence of the Doppler shift.

  For a reflected wave having a frequency different from that of the exploration wave (reference signal), the phase of the received signal with respect to the reference signal changes with time in accordance with the frequency difference. That is, when the relative speed with respect to the front object is not zero, the complex vector corresponding to the demodulated signal after high frequency component removal rotates on the complex plane at an angular velocity corresponding to the frequency difference caused by the Doppler shift.

  Therefore, unless correction for removing the influence of the Doppler shift is performed on the phase of the complex vector, the complex vector corresponding to the reflected wave cannot be directed in a certain direction on the complex plane, and the S / N ratio is increased. Improved, it is impossible to accurately detect the reception of the reflected wave and estimate the distance to the front object.

  Therefore, according to the prior art, for each of a plurality of speed bands that can be taken as relative speeds with respect to the front object, the complex vector phase is corrected by the amount corresponding to the speed band, thereby correcting the complex vector complex by Doppler shift. The rotation on the plane is suppressed. According to this technique, the vector sum of the velocity band that matches the relative velocity with the front object that caused the reflected wave is emphasized among the vector sums obtained for each velocity band, and shows a large value. Based on the vector sum indicating the large value, reception of the reflected wave is detected.

  However, according to this technique, it is necessary to calculate a vector sum for each speed band. That is, the reception of the reflected wave cannot be detected efficiently. The present invention has been made in view of such problems, and an object of the present invention is to provide a technique capable of efficiently detecting reception of a reflected wave even in a situation where a relative speed is generated.

  The object detection apparatus of the present invention includes transmission / reception means, generation means, detection means, change amount calculation means, and determination means. The transmission / reception means transmits an exploration wave having a predetermined frequency and receives an incoming wave. The generating means generates a reference signal having a frequency corresponding to the exploration wave.

  The detecting means detects the phase of the received signal with respect to the reference signal based on the reference signal and the received signal from the transmitting / receiving means. The change amount calculating means calculates the amount of change per unit time of the phase detected by the detecting means.

  The discriminating unit discriminates, as the detection target signal, a signal indicating the characteristic of the reflected wave of the exploration wave generated by the detection target object from the received signal based on the distribution of the change amount calculated by the change amount calculating unit. . For example, the object detection device detects an object based on the detection target signal determined by the determination unit.

  The reception signal from the transmission / reception unit includes dark noise of the transmission / reception unit in addition to the reception signal of the reflected wave generated by the detection target object corresponding to the exploration wave. Here, the distribution of the change amount corresponding to the received signal corresponding to the noise is a distribution having no regularity. On the other hand, the distribution of the amount of change corresponding to the received signal of the reflected wave generated by the object to be detected is compared with noise even in an environment where the relative position and the relative speed change between the object and the object detection device. Show a strong regularity.

  Therefore, as in the present invention, if the detection target signal is determined based on the distribution of the change amount calculated by the change amount calculation means, the reception of the reflected wave generated by the object to be detected can be detected with high accuracy. It is possible to detect an object with high accuracy while suppressing the influence of noise.

  Specifically, the determination unit may be configured to determine a received signal during a period in which the variation in variation is less than a reference as a detection target signal. In addition, the determination unit calculates a statistical value related to the distribution of the change amount in the period corresponding to this time length in a unit of time length corresponding to the time from when the transmission / reception unit starts transmitting the search wave to when it ends. Based on the calculated statistical value, it may be configured to determine whether or not the received signal in this period is a detection target signal.

  As a value representing “variation in variation” and “statistical value regarding variation distribution”, variance or standard deviation of variation can be cited as an example. For example, the discriminating means may be configured to calculate the variance or standard deviation of the change amount as the statistical value and discriminate the received signal during the period in which the calculated variance or standard deviation is less than the reference as the detection target signal. If the discrimination means is configured in this way, the detection target signal can be discriminated with high accuracy by a simple procedure.

  In other words, the detection means may be configured to detect the amplitude of the received signal in addition to the phase of the received signal. The object detection device may be configured to include a reception detection unit that detects reception of the reflected wave generated by the detection target object on condition that the sum of the amplitudes of the detection target signals exceeds a threshold value. By detecting the reception of the reflected wave in this way, it is possible to detect the reception of the reflected wave of interest with high accuracy while suppressing the influence of noise.

  As another example, the object detection device may be configured to include an adding unit and a setting unit. The adding means calculates a vector sum obtained by vector addition of the complex vectors of the received signal at each time in the period when the received signal is determined as the detection target signal. The “complex vector of the received signal” referred to here is a sine wave complex vector indicating the amplitude and phase corresponding to the amplitude and phase of the received signal (phase with respect to the reference signal).

  Prior to calculating the vector sum, the adding means corrects the phase of the complex vector at each time, and calculates the vector sum obtained by vector addition of the complex vectors at each time after the phase correction.

  On the other hand, the setting means sets the amount of phase correction by the adding means. The setting means sets a correction amount corresponding to the shift amount of the phase caused by the Doppler shift as the correction amount of the phase of the complex vector at each time based on the temporal change of the phase detected by the detection means.

  This object detection apparatus can be provided with means for detecting reception of a reflected wave generated by an object to be detected based on the vector sum calculated by the addition means as reception detection means. Specifically, provided is a reception detection unit that detects reception of a reflected wave generated by an object to be detected on condition that the magnitude of the vector sum calculated by the addition unit exceeds a preset threshold value. Can do.

  According to this object detection device, the influence of the Doppler shift can be suppressed, the vector sum corresponding to the detection target signal can be enhanced, the S / N ratio is improved, and the detection target object in which the relative speed is generated The reflected wave from can be detected with high accuracy.

  The detection means may be configured to perform quadrature demodulation on the received signal using the reference signal and detect the phase and amplitude of the demodulated signal as the phase and amplitude of the received signal. If the object detection device is configured as described above, reception of the reflected wave generated by the detection target object can be detected with high accuracy by using the quadrature demodulation technique.

It is a block diagram showing the structure of an object detection apparatus. It is the functional block diagram which showed the function implement | achieved by the main unit. It is a flowchart showing the transmission / reception process which a main unit performs. It is a flowchart showing the correction | amendment compression process which a main unit performs. It is a graph group in which the change in the phase θ of the received signal when receiving the reflected wave from the detection target object is shown in the upper stage, and the change in the phase θ of the received signal corresponding to noise is shown in the lower stage. It is the graph which showed the probability density function of phase difference (DELTA) (theta). It is a figure explaining rotation and vector sum of a complex vector of a received signal on a complex plane. It is a flowchart showing the object detection process which a main unit performs. It is a flowchart showing the abnormality detection process which a main unit performs. It is the graph which illustrated in the upper stage the phase change of the received signal at the time of normal with no foreign object adhering to a vibration surface, and illustrated in the lower stage the phase change of the received signal at the time of abnormality with the foreign object adhesion on a vibration surface. It is the flowchart which showed a part of correction | amendment compression process, Comprising: It is the flowchart which showed the phase correction procedure of the modification.

Embodiments of the present invention will be described below with reference to the drawings.
The object detection apparatus 1 of the present embodiment shown in FIG. 1 is mounted on a vehicle such as an automobile, transmits an ultrasonic burst wave BW as an exploration wave, and receives the reflected wave, thereby positioning in the exploration wave transmission direction. The relative distance D and the relative speed V of the object to be moved are detected.

  The object detection apparatus 1 includes a transmission signal generation unit 10, a reference signal generation unit 20, a transmission / reception unit 30, an A / D (analog / digital) converter 40, a phase shifter 50, a multiplier 60, 65, low-pass filters 70 and 75, and a main unit 80.

  The transmission signal generation unit 10 generates a burst pulse signal having a predetermined angular frequency ω as a transmission signal based on a control signal from the main unit 80. The transmission signal generation unit 10 generates, for example, a sine wave burst pulse signal as a transmission signal. The burst pulse signal generated by the transmission signal generation unit 10 is input to the reference signal generation unit 20 and also input to the transmission / reception unit 30.

  The reference signal generation unit 20 generates a sine wave signal synchronized with the angular frequency ω of the burst pulse signal input from the transmission signal generation unit 10 as a reference signal, and this reference signal is supplied to the phase shifter 50 and the multiplier 60. input. Specifically, a sine wave signal having an angular frequency ω that matches the burst pulse signal is input to the phase shifter 50 and the multiplier 60 as a reference signal. The reference signal generation unit 20 constitutes a quadrature demodulation circuit (in other words, a phase detection circuit) together with the phase shifter 50, the multipliers 60 and 65, and the low-pass filters 70 and 75.

  The transmission / reception wave unit 30 transmits a burst wave BW having a predetermined angular frequency ω based on the transmission signal from the transmission signal generation unit 10 as an exploration wave, while receiving an incoming wave (reflected wave). / D converter 40 to input. The transmission / reception unit 30 is configured as an ultrasonic sensor. As an ultrasonic sensor, a sensor that transmits an ultrasonic wave based on a transmission signal using a piezoelectric element and converts an incoming wave into an electric signal (reception signal) is known. The ultrasonic sensor has a resonance frequency, and the transmission signal generation unit 10 inputs a burst pulse signal having an angular frequency ω corresponding to the resonance frequency to the transmission / reception unit 30.

  The A / D converter 40 converts the received signal input from the transmission / reception unit 30 into a digital signal and inputs the digital signal to the multipliers 60 and 65. In addition to the received signal, the multiplier 60 receives the reference signal from the reference signal generation unit 20 without passing through the phase shifter 50. The reference signal from the reference signal generation unit 20 is input to the multiplier 65 after being changed by the phase shifter 50 by the phase (−π / 2).

  Therefore, when the reference signal is represented by a function f (t) = cos (ωt) with the time t as a variable and the received signal is represented by a function g (t) = A · cos (ω1 · t + φ), a multiplier From 60, a signal corresponding to the function h1 (t) = A · cos (ω1 · t + φ) · cos (ωt) is output. On the other hand, from the multiplier 65, a signal corresponding to the function h2 (t) = A · cos (ω1 · t + φ) · cos (ωt−π / 2) = − A · cos (ω1 · t + φ) · sin (ωt). Is output.

  The output signal from the multiplier 60 is input to the low-pass filter 70, and after the high frequency component is removed, it is output as an I signal that is an in-phase component of the received signal. The function h1 (t) includes the equation h1 (t) = A · cos (ω1 · t + φ) · cos (ωt) = (A / 2) · {cos {(ω1 + ω) t + φ} + cos {(ω1-ω) T + φ}} holds. As can be understood from this, the I signal is output as a signal corresponding to the function I (t) = (A / 2) · cos {(ω1−ω) · t + φ}.

  On the other hand, the output signal from the multiplier 65 is input to the low-pass filter 75 to remove high frequency components, and then output as a Q signal that is a quadrature component of the received signal. The function h2 (t) includes the equation h2 (t) = − A · cos (ω1 · t + φ) · sin (ωt) = (− A / 2) · {sin {(ω1 + ω) t + φ} −sin {(ω1 −ω) · t + φ}} holds. As can be understood from this, the Q signal is output as a signal corresponding to the function Q (t) = (A / 2) · sin {(ω1−ω) · t + φ}.

  The I signal and the Q signal as demodulated signals obtained by orthogonal demodulation with respect to the received signal using the reference signal generation unit 20, the phase shifter 50, the multipliers 60 and 65, and the low-pass filters 70 and 75 are input to the main unit 80. Is done.

  The main unit 80 detects reception of the reflected wave of the exploration wave generated from the detection target object based on the I signal and the Q signal. As an example of the detection target object, an object that may collide with the host vehicle can be given as an example.

  Next, the configuration of the main unit 80 will be described. The main unit 80 of this embodiment includes a CPU 81 that executes processes according to various programs, a ROM 83 that stores the various programs, and a RAM 85 that is used as a work area when the CPU 81 executes the processes. The main unit 80 implements various functions by causing the CPU 81 to execute processing according to the program stored in the ROM 83. In the present specification, the processing executed by the CPU 81 will be described with the main unit 80 as the operating subject.

  The main unit 80 functions as the transmission / reception processing unit 110, the correction compression processing unit 120, the object detection processing unit 130, and the abnormality detection processing unit 140 illustrated in FIG. However, the main unit 80 is not a combination of a general-purpose computer (microcomputer) and a program, but dedicated hardware that functions as a transmission / reception processing unit 110, a correction compression processing unit 120, an object detection processing unit 130, and an abnormality detection processing unit 140. A configuration including a circuit may be employed.

  The main unit 80 functions as the transmission / reception processing unit 110 by repeatedly executing the transmission / reception processing shown in FIG. When the main unit 80 starts transmission / reception processing, the main unit 80 controls the transmission signal generation unit 10 to cause the transmission signal generation unit 10 to generate a pulse burst signal, and to cause the transmission / reception wave unit 30 to transmit an exploration wave (burst wave BW) ( S110). On the other hand, the value of the demodulated signal (the value of the I signal and the Q signal at each time) based on the received signal input from the transmission / reception unit 30 during a certain period determined as the reception processing period from the end of transmission is stored in the memory (RAM 85). (S120).

  Hereinafter, the values of the I signal and the Q signal are expressed as an I value and a Q value, respectively. Furthermore, the time length (the width of the burst wave BW) from the transmission start time to the transmission end time of the exploration wave (burst wave BW) is expressed as a transmission time Te. The reception processing period for accumulating the I value and the Q value is set to a time longer than the time required for the exploration wave to be reflected back to the detection target object.

  The main unit 80 further performs the correction compression processing shown in FIG. 4 to function as the correction compression processing unit 120 and sequentially calculate the reception power P. Specifically, when the burst wave BW is transmitted by the execution of S110, the main unit 80 starts the correction compression process after a specified time has elapsed from the end of transmission of the burst wave BW. Repeatedly until the reception processing period ends.

  The specified time after the end of transmission of the burst wave BW corresponds to the reverberation period. As is well known, the transmission / reception unit 30 which is an ultrasonic sensor is affected by the sneak wave of the burst wave BW transmitted by itself even if the input of the burst pulse signal from the transmission signal generation unit 10 is stopped. Vibrate for a while. After the burst pulse signal input is stopped (that is, after transmission of the burst wave), the main unit 80 performs the correction compression process after the lapse of the specified time estimated as the reverberation period until the vibration due to the influence of the sneak wave ends. To start.

When the correction compression process is started, the main unit 80, among the I value and Q value at each time sequentially written to the memory (RAM 85) by S120, the I [N] and Q [ N], the phase θ [N] = atan (Q [N] / I [N]) and the amplitude A [N] = (I [N]) of the received signal (specifically, demodulated signal) at this latest time ² + Q [N] ² ) ^1/2 is calculated (S210). The phase θ [N] corresponds to the phase of the received signal with respect to the reference signal.

  Further, the main unit 80 calculates the phase difference Δθ [N] = θ [N] −θ [N−1], which is the amount of change from the previous value of the phase θ [N] (S220). The previous phase θ [N−1] corresponds to the phase one calculation cycle Ts before the phase θ [N], and corresponds to the phase calculated in the previous S210. This calculation cycle (execution cycle of correction compression processing) Ts corresponds to the cycle (2π / ω) of the burst pulse signal.

  Thereafter, the main unit 80 stores the calculated phase θ [N], amplitude A [N], and phase difference Δθ [N] in the RAM 85 (S230). Further, the phase differences Δθ [N] and Δθ [N−1] at each time from the phase difference Δθ [N] at the latest time (current time) to the phase difference Δθ [1] before the predetermined period accumulated in the RAM 85. ,... Δ [1] is used to calculate the standard deviation σ of the phase difference Δθ over a predetermined period (S240). The time length of the predetermined period for which the standard deviation σ is calculated coincides with the transmission time Te. Hereinafter, the predetermined period for which the standard deviation σ is calculated is expressed as an evaluation period.

Thereafter, the main unit 80 determines whether or not the standard deviation σ of the evaluation period is less than a predetermined reference value σ _R (S250), and determines that the standard deviation σ is less than the reference value σ _R. (Yes in S250), the received signal in the evaluation period is regarded as a detection target signal indicating the characteristics of the reflected wave from the detection target object, and the process proceeds to S260. On the other hand, when the main unit 80 determines that the standard deviation σ is equal to or greater than the reference value σ _R (No in S250), the main unit 80 regards the received signal in the evaluation period as noise, and proceeds to S280. Note that the object detection apparatus 1 can be configured to execute only S210 to S230 in the entire correction compression process until the data of the phase difference Δθ [n] corresponding to the transmission time Te is accumulated.

Here, the reason why the received signal in the evaluation period is regarded as the detection target signal indicating the characteristic of the reflected wave from the detection target object when the standard deviation σ is less than the reference value σ _R will be described. In the environment where the relative speed between the detection target object and the object detection device 1 (the host vehicle) is zero, when the wave transmission / reception unit 30 receives a reflected wave generated by the search wave reflecting the detection target object, Since no Doppler shift occurs, there is no frequency difference between the reference signal and the received signal. Accordingly, when the reflected wave is received, the phase θ calculated in S210 theoretically takes a constant value, and the phase difference Δθ indicates zero.

On the other hand, in an environment where the relative speed between the detection target object and the object detection apparatus 1 is not zero, a Doppler shift occurs, and thus a frequency difference occurs between the reference signal and the reception signal. Due to this, since the phase θ of the received signal with respect to the reference signal changes, the phase difference Δθ indicates a value that is not zero when the reflected wave is received. However, when the relative speed is constant, the Doppler frequency f _d is constant, so that the phase θ changes linearly as shown in the upper part of FIG. 5, and the phase difference Δθ theoretically has a constant value. take.

  Since the relative speed changes depending on the acceleration / deceleration of the vehicle, the phase difference Δθ actually changes, but the time required to transmit and receive the exploration wave is an extremely short time of about several tens of milliseconds, Changes in the relative distance and relative speed of the vehicle that occur at the transmission time Te are negligible and can be ignored. Therefore, when the received signal is a reflected wave from the object to be detected, the probability density function of the phase difference Δθ shows a sharp peak as shown by the solid line in FIG. 6, and the standard deviation σ of the phase difference Δθ is small. Indicates the value.

On the other hand, when the received signal is noise, the phase difference Δθ varies greatly because there is no regularity in the change of the phase θ as shown in the lower part of FIG. As a result, the probability density function of the phase difference Δθ when the received signal is noise shows a gradual peak as shown by a broken line in FIG. 6, and the standard deviation σ corresponds to the reflected wave of the detection target object. It shows a value that is basically larger than the standard deviation σ. In the present embodiment, using such a phenomenon, when the standard deviation σ is less than the reference value σ _R , the received signal is regarded as a detection target signal indicating the characteristics of the reflected wave from the detection target object.

When the standard deviation σ is less than the reference value σ _R , and the process proceeds to S260, the main unit 80 causes the complex vector A [n] · exp {iθ [n] of the received signal (demodulated signal) at each time in the evaluation period. ]} (N = 1,..., N) is converted into a complex vector A [n] · exp {iθ [N]} (n = 1,..., N) to correct the phase of the received signal. The symbol i here is an imaginary symbol.

  The complex vector A [n] · exp {iθ [n]} of the received signal is rotated with time on the complex plane under the influence of the Doppler shift as shown by the broken line in FIG. Then, by replacing the phase θ [n] with the phase θ [N], the phase θ [n] is corrected by the Doppler shift, and the complex vector A [n] · exp {iθ [n]} ( n = 1,..., N) corrects the complex vector so that it does not rotate on the complex plane due to the influence of the Doppler shift.

Thereafter, the main unit 80 proceeds to S270, and adds the vector of the complex vector A [n] · exp {iθ [N]} (n = 1,..., N) after phase correction at each time in the evaluation period. The complex vector sum _Asum of the received signal is calculated.

When the process in S270 is completed, the main unit 80 proceeds to S290. Note that the complex vector indicated by the solid line in FIG. 7 illustrates the complex vector sum _Asum of the received signal.

On the other hand, when the standard deviation σ is equal to or larger than the reference value σ _R , the main unit 80 moves to S280 and does not perform phase correction, but performs complex vector A [n] · exp {iθ [ n]} (n = 1,..., N) are added as vectors to calculate a complex vector sum _Asum of the received signals. Thereafter, the process proceeds to S290.

After shifting to S290, the main unit 80, the absolute value squared of the vector sum A _sum calculated in S270 or S280 | ^2, received power P of the received signal at the evaluation period = | | A _sum calculated as ² | A _sum. Thereafter, the correction compression process is temporarily terminated. The main unit 80 repeatedly executes the correction compression processing with such contents until the reception processing period ends.

Incidentally, from the mathematical understanding, the absolute value square of the vector sum A _sum calculated in S270 | A _sum | ^2, the amplitude A of the received signal at each time in the evaluation period [n] (n = 1, ..., N) of Matches the square of the sum.

Therefore, in the correction compression process, if it is determined that the standard deviation σ is less than the reference value σ _R (Yes in S250), the process of S260 is not performed, and in S270, the amplitude A of the received signal at each time in the evaluation period The sum of [n] (n = 1,..., N) may be calculated, and in S290, the square of the _sum may be calculated as received power P = | A _sum | ² of the received signal in the evaluation period.

  In addition, the main unit 80 functions as the object detection processing unit 130 by executing the object detection process shown in FIG. 8 every time the correction compression process (S290) is executed, and based on the received power P, the detection target object The reception of the reflected wave from is detected.

  When the object detection process is started, the main unit 80 determines whether or not the reception power P calculated in the correction compression process has exceeded a predetermined threshold value TH. That is, it is determined whether or not the reception power P has changed so as to cross the threshold value TH from below to above (S310). If a negative determination is made (No in S310), the object detection process is temporarily terminated.

On the other hand, when determining that the received power P has exceeded the threshold value TH (Yes in S310), the main unit 80 detects the reception of the reflected wave from the detection target object, and from the average value Δθ _Ave of the phase difference Δθ in the evaluation period. based on the Doppler frequency f _d is calculated, to calculate the relative velocity V of the detection target object for the object detecting device 1 (vehicle) (S320).

  Further, based on the elapsed time Tp from the transmission time of the exploration wave to the reception detection time of the reflected wave when the received power P exceeds the threshold TH and the propagation velocity C of the exploration wave, the detection object As the relative distance D, a distance D = C · Tp / 2 from the object detection apparatus 1 to the detection target object is calculated (S330).

  Thereafter, the main unit 80 provides object detection information describing the calculated relative velocity V and relative distance D to an electronic control unit (ECU) that performs vehicle control (brake control, etc.) through in-vehicle LAN communication ( S340), the object detection process is terminated.

  In addition, the main unit 80 functions as the abnormality detection processing unit 140 by executing the abnormality detection process shown in FIG. 9 during the reverberation period before the start of the correction compression process, and the transmission / reception unit 30 (ultrasonic sensor). Detects that foreign matter such as water droplets has adhered to the vibration surface of.

  The reason for detecting that a foreign object has adhered to the vibration surface of the wave transmitting / receiving unit 30 by the abnormality detection process is as follows. That is, in a state where foreign matters such as water droplets are attached to the vibration surface, characteristics such as directivity of the transmission / reception unit 30 change and the reception power P is the threshold value TH even though the reception signal is noise. The initial value TH0 may be exceeded. In such a state, if the threshold value TH = the initial value TH0, the object is detected in the object detection process even though the received signal is noise. In addition, the vibration surface is difficult to vibrate due to the foreign matter, the amplitude of the received signal is lowered, and the object is difficult to detect.

  Such an object detection process is not preferable because it naturally detects a detection target object that does not exist or makes it difficult to detect a detection target object to be detected. In this embodiment, for this reason, it is detected that a foreign object has adhered to the vibration surface of the wave transmitting / receiving unit 30 by executing an abnormality detection process.

  Specifically, in the abnormality detection process, an abnormality in which a foreign object adheres to the vibration surface of the transmission / reception unit 30 is detected based on the phase change amount δ of the received signal (demodulated signal) during the reverberation period. When foreign matter is attached to the vibration surface, the characteristics of the vibration surface change, and therefore the phase change of the received signal (demodulation signal) during the reverberation period differs from that at normal time as shown in FIG. The upper part of FIG. 10 shows a phase change of a reception signal (demodulation signal) at a normal time when no foreign matter is attached to the vibration surface, and the lower part of FIG. The phase change of (demodulated signal) is shown.

According to the present embodiment, the object detection device 1 stores the phase change amount δ during the reverberation period in a normal state in which no foreign matter is attached to the vibration surface as the standard value δ _s in the ROM 83. The standard value δ _s is stored in the ROM 83 before the object detection device 1 is shipped. However, the standard value δ _s can be learned and updated in the object detection device 1. In this case, the object detection device 1 can store the learning value of the standard value δ _s in the flash memory as the ROM 83.

Based on the standard value δ _s stored in the ROM 83, the main unit 80 detects an abnormality in which foreign matter is attached to the vibration surface of the wave transmitting / receiving unit 30.
When the abnormality detection process shown in FIG. 9 is started, the main unit 80 receives the received signal (demodulated signal) at each time of the reverberation period based on the I value and Q value of the received signal at each time of the reverberation period accumulated in the RAM 85. ) Phase θ [m] and amplitude A [m] (m = 1,..., M) are calculated and stored in the RAM 85 (S410).

  Here, the phase θ and amplitude A of the received signal at the start point of the reverberation period are expressed by phase θ [1] and amplitude A [1], and the phase θ and amplitude A of the received signal at the end point of the reverberation period are expressed as phase θ. [M] and amplitude A [M].

  The main unit 80 further calculates the phase difference Δθ [m + 1] = θ [m + 1] −θ [m] (m = 1,..., M−1) from the previous value of the phase θ [m + 1] of the received signal at each time. Calculate and store in the RAM 85 (S410). Thereafter, the main unit 80 calculates the average value of the phase difference Δθ in the reverberation period as the phase change amount δ in the reverberation period according to the following equation (S420).

When this process is completed, the main unit 80 calculates an error E = | δ−δ _s | from the standard value δ _s of the phase change amount δ calculated in S420 (S425), and the error E is determined in advance. It is determined whether it is less than or equal to the upper limit value (S430). If the error E is less than or equal to the upper limit value (Yes in S430), it is determined that no abnormality has occurred that foreign matter adheres to the vibration surface of the transmission / reception unit 30 (S440), and the threshold value used in the object detection process TH is set to an initial value TH0 (S450), and the abnormality detection process is terminated.

  On the other hand, when the error E exceeds the upper limit (No in S430), the main unit 80 determines that an abnormality in which foreign matter adheres to the vibration surface of the transmission / reception unit 30 has occurred (S460), and the object The threshold value TH used in the detection process is set to a correction value TH1 determined as a value larger than the initial value TH0 (S470), and the abnormality detection process ends. In this way, when there is an abnormality in which foreign matter adheres to the vibration surface, if the threshold value TH is set to a value larger than the initial value TH0, the received power P becomes the threshold value even though the received signal is noise. The possibility that the detection target object is erroneously detected due to exceeding TH can be suppressed.

The configuration of the object detection device 1 according to the present embodiment has been described above. According to the present embodiment, when the reception signal from the transmission / reception unit 30 is noise (including circuit noise), the reference signal of the reception signal is compared with the case where the reflected wave from the detection target object is received. Focusing on the large variation in the change in phase θ with respect to the received signal, the received signal (detection target signal) indicating the characteristics of the reflected wave from the detection target object is discriminated from the received signal. Specifically, in the time length unit corresponding to the transmission time Te, the standard deviation σ of the phase difference Δθ in the evaluation period corresponding to the time length is calculated, and the standard deviation σ is less than the reference value σ _R. In this case, it is determined that the received signal is a detection target signal.

  Therefore, according to the present embodiment, the detection target signal can be discriminated from the received signal with high accuracy, and the reception of the reflected wave of the exploration wave generated by the object to be detected can be detected with high accuracy. . As a result, according to the present embodiment, the relative distance D and the relative speed V with respect to the detection target object can be calculated with high accuracy.

  In particular, according to the present embodiment, since the detection target signal is determined based on the variation in the phase difference Δθ, as in the prior art, for each speed band that can be taken as a relative speed with respect to the detection target object, according to the speed band. It is not necessary to perform an inefficient phase correction that corrects the phase of the complex vector by a certain amount.

In other words, in the prior art, after performing phase correction on the complex vector of the received signal, the vector sum of the complex vector after phase correction is calculated, and reflection is performed on the condition that the magnitude of this vector sum exceeds the threshold value. The reception of the wave was detected. On the other hand, according to this embodiment, the _sum of the amplitudes _Asum of the detection target signals (according to the above embodiment, the square of the sum of amplitudes | _Asum | ² ) exceeds the threshold value. The effect similar to that of the prior art can be efficiently obtained by detecting reception.

  Further, according to the present embodiment, when an abnormality in which foreign matter is attached to the vibration surface is detected and the abnormality is detected, the threshold value TH is set to a value TH1 larger than the initial value TH0. Therefore, it is possible to suppress erroneous detection of an object due to adhesion of a foreign object, and it is possible to configure a highly accurate object detection device 1.

[Modification 1]
In the abnormality detection process of the above-described embodiment, when it is determined that an abnormality in which foreign matter adheres to the vibration surface of the transmission / reception unit 30 (S460), the threshold value TH is set to a value TH1 that is greater than the initial value TH0. (S470).

  However, in S470, instead of setting the threshold value TH to a value larger than the initial value TH0, the object detection operation may be prohibited. That is, the object detection apparatus 1 may be configured to stop executing the correction compression process and the object detection process after the reverberation period ends. In addition, the object detection apparatus 1 may be configured to perform a notification operation to the effect that an abnormality has occurred to a vehicle occupant through a warning lamp or the like instead of executing the correction compression process and the object detection process. Of course, the object detection apparatus 1 can be configured to notify the abnormality while performing the correction compression process and the object detection process.

[Modification 2]
In the correction compression processing of the above embodiment, the received power P is calculated even in an environment where the standard deviation σ is equal to or greater than the reference value σ _R. However, there is a high possibility that the reception power P (S290) when the standard deviation σ is equal to or larger than the reference value σ _R takes a small value. Further, when the standard deviation σ is equal to or larger than the reference value σ _R , there is a very high possibility that the received signal is noise.

Therefore, in S290, the received power P when the standard deviation σ is equal to or larger than the reference value σ _R may be calculated as zero formally. In other words, if the standard deviation σ is greater than or equal to the reference value σ _R , the correction compression process is configured so that the reception power P is formally calculated as zero in S290 without executing the process in S280. Can be done.

As a similar modification, when the standard deviation σ is equal to or greater than the reference value σ _R , the object detection device 1 is configured to not execute the object detection process based on the received power P in the evaluation period corresponding to the standard deviation σ. May be.

[Modification 3]
In S260 of the above embodiment, the complex vector A [n] · exp {iθ [n]} (n = 1,..., N) at each time in the evaluation period is converted into the complex vector A [n] · exp {iθ [N. ]} (N = 1,..., N) to perform phase correction of the received signal. However, the phase correction in S260 may be performed as shown in FIG. FIG. 11 is a flowchart specifically showing the processing of S261 and S263 corresponding to another example of S260.

In S261, the correction amount of the phase θ [n] (n = 1,..., N) at each time in the evaluation period is set to {θ _d · (N−n)}. As the value θ _d , an average value of the phase difference Δθ in the evaluation period can be used. In S263, the complex vector A [n] · exp {iθ [n]} (n = 1,..., N) of the received signal (demodulated signal) at each time is converted into A [n] · exp {i (θ [N] + θ _d · (N−n))} to correct the phase θ of the complex vector by the Doppler shift.

Even if the phase correction is performed in this way, it is possible to suppress the influence of the Doppler shift and to emphasize the reception signal of the reflected wave from the detection target object when calculating the reception power P, and to detect the detection target with high accuracy. The reception of the reflected wave from the object can be detected. In addition, the value θ _d may not be an average value as long as it is a representative value of the phase difference Δθ. For example, the value θ _d of the set {Δθ [N], Δθ [N−1],. The median value can be adopted.

[Modification 4]
In S420 of the above embodiment, the average value of the phase differences Δθ in the reverberation period was calculated as the phase change amount δ. However, as the phase change amount δ, the difference between the start phase θ [1] and the end phase θ [M] in the reverberation period can be calculated according to the following equation.

In this case, the ROM 83 has the standard value δ _s as the start phase θ [1] and the end phase θ [M] in the reverberation period in an environment where no foreign matter is attached to the vibration surface of the transmission / reception unit 30. The standard value of the difference can be stored.

[Modification 5]
In S420 of the above embodiment, the average value of the phase difference Δθ in the reverberation period is calculated as the phase change amount δ in the reverberation period. However, as the phase change amount δ, the total value of the phase differences Δθ in the reverberation period can be calculated according to the following equation. In this case, the ROM 83, as a standard value [delta] _s, and stores the sum value of the phase difference Δθ in the reverberation period in an environment where foreign matter is not attached to the vibrating surface of the wave transceiver unit 30.

The total value of the phase difference Δθ in the reverberation period described above is the difference δ = θ between the phase θ [1] of the start point and the phase θ [M] of the end point in the reverberation period calculated as the phase change amount δ in Modification 4. At first glance, [M] −θ [1]. However, the phase θ calculated using the I value and the Q value is limited to the range of 0 to 2π. That is, when the phase θ changes in excess of 2π during the reverberation period, the phase change information δ of Modification 4 does not show information on the phase change of 2π or more.

  On the other hand, according to the fifth modification, the phase difference Δθ is calculated in a time unit sufficiently shorter than the time length of the reverberation period, and the total value thereof is calculated. Therefore, the phase change amount δ has a phase of 2π or more. Change information appears. According to the fifth modification, information on a phase change of 2π or more can be included in the phase change amount δ, and adhesion of a foreign object can be detected more appropriately.

[Other Embodiments]
The present invention is not limited to the above-described embodiments including modifications, and can take various forms. For example, in S240, the variance σ ² is calculated instead of the standard deviation σ, and in S250, it is determined whether or not the variance σ ² is less than a predetermined reference value σ _R ^2. May be configured.

  Moreover, only one object detection device 1 may be provided in one vehicle, or a plurality of object detection devices 1 may be provided. When a plurality of object detection devices 1 are provided in one vehicle, the abnormality detection process can be configured as a process of correcting the threshold values TH of all the object detection devices 1 mounted on the own vehicle to the value TH1 in S470. . In this case, the plurality of object detection devices 1 can be mounted in the vehicle so as to be capable of bidirectional communication with each other. That is, the system including a plurality of object detection devices of the present invention includes a threshold correction unit that corrects the threshold TH in all the object detection devices 1 when an abnormality is detected in at least one of the plurality of object detection devices 1. The configuration may be provided.

  In addition, the object detection device 1 is not limited to an automobile, and can be mounted on, for example, a mobile robot. Alternatively, it can be configured as a portable object detection device. Moreover, the object detection apparatus 1 is not limited to what transmits an ultrasonic wave as a search wave, It can be comprised using various search waves. In addition, the object detection apparatus 1 may be configured not to execute the object detection process or the abnormality notification process. For example, if the object detection device 1 makes an affirmative determination in S250 of the correction compression process, the object detection device 1 may be configured to detect an object and notify the user to that effect.

[Correspondence]
Finally, the correspondence between terms will be described. The transmission / reception unit 30 corresponds to an example of a transmission / reception unit, and the reference signal generation unit 20 corresponds to an example of a generation unit. The functions realized by S210 and S410 executed by the quadrature demodulation circuit and the main unit 80 correspond to an example of functions realized by the detection means.

  The functions realized by S220 and S410 executed by the main unit 80 correspond to examples of functions realized by the change amount calculating means, and the functions realized by S240 and S250 are functions realized by the determining means. Corresponds to an example. The function realized by S310 executed by the main unit 80 corresponds to an example of the function realized by the reception detection unit.

  In addition, the function realized by S263 and S270 executed by the main unit 80 corresponds to an example of the function realized by the adding unit, and the function realized by S261 is an example of the function realized by the setting unit. Correspond.

  The function realized by S320 executed by the main unit 80 corresponds to an example of the function realized by the speed estimation unit, and the function realized by S330 corresponds to an example of the function realized by the distance estimation unit. To do.

  In addition, the function realized by S420 to S430 executed by the main unit 80 corresponds to an example of the function realized by the abnormality detection unit, and the function realized by S470 is a function realized by the threshold correction unit. This corresponds to an example.

DESCRIPTION OF SYMBOLS 1 ... Object detection apparatus, 10 ... Transmission signal generation unit, 20 ... Reference signal generation unit, 30 ... Transmission / reception unit, 40 ... A / D converter, 50 ... Phase shifter, 60, 65 ... Multiplier, 70, 75 ... low pass filter, 80 ... main unit, 81 ... CPU, 83 ... ROM, 85 ... RAM, 110 ... transmission / reception processing unit, 120 ... correction compression processing unit, 130 ... object detection processing unit, 140 ... abnormality detection processing unit, BW ... Burst wave.

Claims (12)

An object detection device (1) comprising:
Transmitting / receiving means (30) for transmitting an exploration wave having a predetermined frequency and receiving an incoming wave;
Generating means (20) for generating a reference signal having a frequency corresponding to the exploration wave;
Detecting means (50, 60, 65, 70, 75, 80, S210, S410) for detecting the phase of the received signal with respect to the reference signal based on the reference signal and the received signal from the transmitting / receiving means;
A change amount calculating means (80, S220, S410) for calculating a change amount per unit time of the phase detected by the detecting means;
Based on the distribution of the variation calculated by the variation calculation means, a signal indicating the characteristic of the reflected wave of the exploration wave generated by the detection target object is determined as a detection target signal from the received signal. Discrimination means (80, S240, S250);
An object detection apparatus comprising: The object detection apparatus according to claim 1, wherein the determination unit determines, as the detection target signal, the reception signal during a period in which variation in the change amount is less than a reference. The discriminating unit calculates a statistical value related to the distribution of the change amount in a period corresponding to the time length in a time length unit corresponding to a time from when the transmission / reception unit starts transmission of the exploration wave to when it ends. Then, based on the calculated statistical value, it is determined whether or not the received signal in this period is the detection target signal. The determination means calculates a variance or standard deviation of the change amount as the statistical value, and determines the received signal in a period in which the calculated variance or the standard deviation is less than a reference as the detection target signal. The object detection device according to claim 3. The detection means detects the amplitude of the reception signal in addition to the phase of the reception signal,
The object detection device further includes:
Reception detection means (80, S310) for detecting reception of the reflected wave generated by the detection target object on condition that the sum of the amplitudes of the detection target signals exceeds a threshold value
The object detection device according to any one of claims 1 to 4, wherein the object detection device is provided. The detection means detects the amplitude of the reception signal in addition to the phase of the reception signal,
The object detection device further includes:
A sine wave indicating the amplitude and phase corresponding to the amplitude and phase of the received signal at each time as a complex vector of the received signal at each time of the period when the received signal is determined as the detection target signal A vector sum obtained by vector addition of the complex vectors, wherein the phase of the complex vector at each time is corrected, and the complex at each time after the phase correction is calculated as the vector sum. Adding means (80, S263, S270) for calculating a vector sum obtained by vector addition,
A means for setting a correction amount of the phase by the adding means, and a Doppler shift as the correction amount of the phase of the complex vector at each time based on a temporal change of the phase detected by the detection means Setting means (80, S261) for setting a correction amount corresponding to the phase shift amount caused by
Reception detection means (80, S310) for detecting reception of the reflected wave generated by the detection target object on condition that the magnitude of the vector sum calculated by the addition means exceeds a preset threshold value. )When,
The object detection device according to any one of claims 1 to 4, wherein the object detection device is provided. The detection means performs quadrature demodulation on the received signal using the reference signal, and detects the phase and amplitude of the demodulated signal as the phase and amplitude of the received signal. The object detection apparatus described. Speed estimation means (80, S320) for estimating a relative speed of the object that caused the reflected wave based on a temporal change in the phase of the reflected wave detected by the reception detection means.
The object detection apparatus according to any one of claims 5 to 7, further comprising: The elapsed time from the transmission of the exploration wave to the reception of the reflected wave for the reflected wave detected by the reception detection unit is specified, and based on the elapsed time, the object up to which the reflected wave is generated is determined. Distance estimation means for estimating relative distance (80, S330)
The object detection apparatus according to claim 5, further comprising: The amount of change in the phase that occurs in the phase detected by the detection means during a predetermined period after the transmission of the exploration wave by the transmission / reception means accompanying reception of the sneak wave of the exploration wave, the transmission / reception Standard value storage means (83) for storing a standard change amount which is a standard value of the change amount generated when the means is operating normally;
Abnormality detection means for detecting an operation abnormality of the transmission / reception means based on a difference between the change amount in the predetermined period after the transmission of the exploration wave of the phase detected by the detection means and the standard change amount is completed. (80, S420 to S430),
The object detection apparatus according to claim 5, further comprising: Threshold value correcting means (80, S470) for correcting the threshold value when the abnormality is detected by the abnormality detecting means.
The object detection device according to claim 10, further comprising: The object detection apparatus according to claim 11, wherein the threshold correction unit corrects the threshold in a direction to increase the threshold.