Object detection device

Abstract

This invention relates to an object detection device. The object detection device (1) includes: a drive signal generation unit (5) that generates a drive signal including frequency modulation; a first correlation filter (62) that performs correlation detection between the received signal and a first reference signal corresponding to the drive signal; a first determination unit (8) that determines whether the received wave is a reflected wave of a detection wave transmitted from a transmitting unit (40A) based on the correlation signal of the first correlation filter; a second correlation filter (63) that uses a signal corresponding to a portion of the drive signal as a second reference signal and performs correlation detection between the received signal and the second reference signal; a third correlation filter (64) that uses a signal including a portion of the drive signal with a frequency higher than the second reference signal as a third reference signal and performs correlation detection between the received signal and the third reference signal, wherein the third reference signal is a signal corresponding to a portion of the drive signal; and a second determination unit (9) that determines whether an object is within the detection range based on the correlation signals of the second and third correlation filters.

Description

Technical Field

[0001] This disclosure relates to an object detection device that detects objects by transmitting and receiving ultrasonic waves. Background Technology

[0002] In automatic parking systems used in vehicles such as automobiles, multiple ultrasonic sensors mounted on the vehicle's bumper detect obstacles. To improve the accuracy of such automatic parking systems, it is desirable to determine whether an obstacle is within the detection range. This determination may include, for example, determining whether it is a high object that could potentially come into contact with the vehicle body.

[0003] For example, Patent Document 1 proposes a technique for determining the height of an object using the difference in directivity based on frequency. Specifically, ultrasonic waves containing both higher and lower frequencies are transmitted as probe waves, and a bandpass filter is used to extract the amplitude components of the two frequencies from the received signal. The higher-frequency ultrasonic wave has a narrower directivity compared to the lower-frequency ultrasonic wave, so the height of the object can be determined by comparing the amplitudes of the two frequencies.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-98157

[0005] However, the object detection device described in Patent Document 1 lacks anti-interference functionality between sensors. Therefore, when increasing the transmission frequency of the detection wave, or when receiving transmission waves from other vehicles while facing or parallel to them, interference may prevent the accurate determination of the object's height.

[0006] As a method to prevent interference, for example, one method is to encode the probe wave by frequency modulation and determine whether the codes are consistent in the transmitted and received signals, that is, to determine whether the frequency modulation characteristics are consistent.

[0007] In the case of identifying the received wave through code, if the signal used for code identification and the signal used for height determination are sent separately, the number of detection waves required for one object detection process increases, thus reducing the execution frequency of the object detection process and reducing the object detection performance. Summary of the Invention

[0008] In view of the points illustrated above, this disclosure provides an object detection device capable of, for example, identifying the received wave and determining whether an object is within the detection range through a single transmission and reception.

[0009] In one aspect of this disclosure, an object detection device for detecting objects by transmitting and receiving ultrasonic waves comprises: a transmitting unit that transmits ultrasonic waves as a detection wave; a driving signal generating unit that generates a frequency-modulated driving signal for driving the transmitting unit; a receiving unit that receives ultrasonic waves and generates a received signal corresponding to the received ultrasonic waves; a first correlation filter that performs correlation detection between the received signal and a first reference signal corresponding to the driving signal and outputs a correlation signal; a first determination unit that determines, based on the correlation signal output by the first correlation filter, whether the ultrasonic wave received by the receiving unit is a reflected wave from the detection wave transmitted by the transmitting unit; a second correlation filter that uses a signal corresponding to a portion of the driving signal as a second reference signal, performs correlation detection between the received signal and the second reference signal, and outputs a correlation signal; a third correlation filter that uses a signal containing a portion of the driving signal with a frequency higher than the second reference signal as a third reference signal, performs correlation detection between the received signal and the third reference signal, and outputs a correlation signal, wherein the third reference signal is a signal corresponding to a portion of the driving signal; and a second determination unit that determines whether an object is within the detection range based on the correlation signals output by the second and third correlation filters.

[0010] In this way, the received wave is identified by correlation detection using a first reference signal corresponding to the drive signal. Furthermore, whether an object is within the detection range is determined by correlation detection using a second reference signal corresponding to a portion of the drive signal and a third reference signal containing a portion of the drive signal with a frequency higher than the second reference signal, wherein the third reference signal is a signal corresponding to a portion of the drive signal. Therefore, the identification of the received wave and the determination of whether an object is within the detection range can be achieved with a single transmission and reception.

[0011] Furthermore, the bracketed reference numerals attached to each component element are merely one example indicating the correspondence between that component element and the specific component elements described in the embodiments described later. Therefore, this disclosure is not intended to be limited by the description of the reference numerals in the accompanying drawings. Attached Figure Description

[0012] Figure 1 This is a block diagram of the object detection device according to the first embodiment.

[0013] Figure 2 This is a block diagram of the quadrature detector section included in the receiving signal processing unit.

[0014] Figure 3 It is a graph representing the frequency of the reference signal.

[0015] Figure 4 It is a block diagram of the quadrature detector unit included in the reference signal processing unit.

[0016] Figure 5 It is a block diagram of a correlation filter using a reference signal corresponding to the driving signal.

[0017] Figure 6 This is a block diagram of the vector rotation part and the addition part of the correlation filter.

[0018] Figure 7 It is a diagram showing the phase difference between the complex received signal and the complex reference signal.

[0019] Figure 8 This is a diagram showing the vector rotation of the complex received signal S1.

[0020] Figure 9 This is a diagram representing an example of the signal ΔS2 after vector rotation.

[0021] Figure 10 This is a diagram representing an example of the sum of signals ΔS1 and ΔS2 after vector rotation.

[0022] Figure 11 This is a diagram representing an example of the signal ΔS2 after vector rotation.

[0023] Figure 12 This is a diagram representing an example of the sum of signals ΔS1 and ΔS2 after vector rotation.

[0024] Figure 13 This is a block diagram of a correlation filter that uses the low-frequency components of a reference signal.

[0025] Figure 14 This is a block diagram of a correlation filter that uses the high-frequency components of a reference signal.

[0026] Figure 15 This is a flowchart of the object detection and processing.

[0027] Figure 16 This is a diagram representing an example of the relevant output.

[0028] Figure 17 This is a graph showing the relevant output when a probe wave is sent toward a high wall.

[0029] Figure 18 This is a graph showing the relevant output when a probe wave is sent toward a wheel wedge with a height of 10cm.

[0030] Figure 19 This is a graph showing the relevant output when a probe wave is sent toward a pole at a relatively high height.

[0031] Figure 20 This is a block diagram of the vector rotation section of the three correlation filters in the second embodiment.

[0032] Figure 21 This is a diagram showing the frequency of the reference signal in the third embodiment.

[0033] Figure 22 This is a block diagram of the object detection device according to the fourth embodiment.

[0034] Figure 23 It is a diagram showing the expansion of the frequency band through normalization and phase rotation.

[0035] Figure 24 This is a diagram showing the frequency of the reference signal in the fifth embodiment.

[0036] Figure 25 This is a graph representing the frequency of the reference signal in other implementations.

[0037] Figure 26 This is a graph representing the frequency of the reference signal in other implementations.

[0038] Figure 27 This is a graph representing the frequency of the reference signal in other implementations.

[0039] Figure 28 This is a graph representing the frequency of the reference signal in other implementations.

[0040] Figure 29 This is a graph representing the frequency of the reference signal in other implementations. Detailed Implementation

[0041] Hereinafter, embodiments of the present disclosure will be described based on the figures. Furthermore, in each of the following embodiments, the same reference numerals will be used to describe the identical or equivalent parts.

[0042] (First Implementation)

[0043] The first embodiment will be described. Figure 1 The object detection device 1 of this embodiment shown is configured to be mounted on a vehicle (not shown) to detect objects B around the vehicle. The vehicle on which the object detection device 1 is mounted will be referred to as "this vehicle". The vehicle (not shown) is, for example, an automobile.

[0044] The object detection device 1 detects objects by transmitting and receiving ultrasonic waves, and includes an ultrasonic sensor 2 and a control unit 3 that controls the operation of the ultrasonic sensor 2. The ultrasonic sensor 2 is configured to detect object B by transmitting a detection wave as an ultrasonic wave and receiving the reflected wave that is reflected by the detection wave.

[0045] The ultrasonic sensor 2 includes: a transceiver unit 4, a drive signal generation unit 5, a receive signal processing unit 6, a reference signal processing unit 7, a code determination unit 8, and a height determination unit 9. The transceiver unit 4 has a transmitting unit 40A and a receiving unit 40B. The transmitting unit 40A is configured to transmit a probe wave to the outside. The receiving unit 40B is configured to receive an ultrasonic wave containing a reflected wave from an object B that is reflected by the probe wave transmitted from the transmitting unit 40A.

[0046] The transceiver unit 4 includes a transducer 41, a transmitting circuit 42, and a receiving circuit 43. The transmitting unit 40A is composed of the transducer 41 and the transmitting circuit 42. The receiving unit 40B is composed of the transducer 41 and the receiving circuit 43.

[0047] The transducer 41 functions as a transmitter that sends probe waves outward and as a receiver that receives reflected waves, and is electrically connected to the transmitting circuit 42 and the receiving circuit 43. That is, the ultrasonic sensor 2 has a so-called transceiver integrated structure.

[0048] Specifically, the transducer 41 is configured as an ultrasonic microphone with built-in electromechanical energy conversion elements such as piezoelectric elements. The transducer 41 is positioned facing the outer surface of the vehicle so as to be able to transmit probe waves to the outside of the vehicle and receive reflected waves from the outside of the vehicle.

[0049] The transmitting circuit 42 is configured to drive the transducer 41 using an input drive signal, thereby causing the transducer 41 to emit a probe wave. Specifically, the transmitting circuit 42 includes a digital-to-analog conversion circuit, etc. That is, the transmitting circuit 42 is configured to generate a component input signal by performing signal processing such as digital-to-analog conversion on the drive signal output from the drive signal generation unit 5. The component input signal is an AC voltage signal used to drive the transducer 41. Furthermore, the transmitting circuit 42 is configured to apply the generated component input signal to the transducer 41 to excite the electromechanical energy conversion element in the transducer 41, thereby generating a probe wave.

[0050] The receiving circuit 43 is configured to generate a receiving signal corresponding to the result of the transducer 41 receiving the ultrasonic wave and output it to the receiving signal processing unit 6. Specifically, the receiving circuit 43 includes an amplification circuit and an analog-to-digital conversion circuit. That is, the receiving circuit 43 is configured to generate a receiving signal containing information related to the amplitude and frequency of the received wave by amplifying and performing analog-to-digital conversion on the element output signal output from the transducer 41. The element output signal is an AC voltage signal generated by the electromechanical energy conversion element provided in the transducer 41 through the reception of the ultrasonic wave.

[0051] As will be described later, the probe wave contains ultrasonic waves encoded through frequency modulation. The center frequency of the frequency modulation band of the probe wave is set to f.c The sampling frequency of the receiving circuit 43 is f c More than twice that of the driving signal. Furthermore, the sampling frequency of the received signal can be the same as or different from the sampling frequency of the driving signal.

[0052] The drive signal generation unit 5 is configured to generate a drive signal and output it to the transmitting circuit 42. The drive signal is used to drive the transducer 41 so that the probe wave is emitted from the transducer 41.

[0053] The drive signal generation unit 5 generates a drive signal corresponding to the frequency modulation state in the probe wave having a predetermined frequency modulation state. The drive signal generation unit 5 generates a drive signal to scan the frequency of the probe wave within a range including the resonant frequency of the transducer 41.

[0054] In this embodiment, the defined frequency modulation state includes up-chirp or down-chirp. Up-chirp is a frequency modulation state in which the frequency monotonically increases over time. Down-chirp is a frequency modulation state in which the frequency monotonically decreases over time.

[0055] The probe wave is encoded by frequency modulation of the driving signal. For example, an upper chirp represents code "1", and a lower chirp represents code "0". This code is used for the identification of the received wave.

[0056] The drive signal generation unit 5, the receiving signal processing unit 6, the reference signal processing unit 7, the code determination unit 8, and the height determination unit 9 are, for example, composed of a DSP programmed with functions such as drive signal generation, orthogonal detection (described later), correlation calculation, code determination, and height determination. DSP is an abbreviation for Digital Signal Processor.

[0057] The receiving signal processing unit 6 processes the received signal and performs correlation detection between the received signal and the reference signal. The receiving signal processing unit 6 includes: a quadrature detector 61, a correlation filter 62, a correlation filter 63, and a correlation filter 64.

[0058] The quadrature detector 61 performs quadrature detection on the received signal output from the receiving circuit 43 to generate a complex signal. For example... Figure 2 As shown, the quadrature detector 61 includes a multiplication unit 611, a low-pass filter 612, and a downsampling unit 613. Hereinafter, the low-pass filter 612 will be referred to as LPF612.

[0059] Multiplication unit 611 multiplies the received signal output from receiving circuit 43 by sin(2π·f) c ·t) and cos(2π·f c ·t), generating a complex signal. Here, t is time. sin(2π·f c ·t) and cos(2π·f cThe signal ·t) is input from the drive signal generation unit 5 to the multiplication unit 611. The multiplication unit 611 outputs the generated complex signal to the LPF 612.

[0060] The LPF612 removes high-frequency components from the complex signal output from the multiplication unit 611. The cutoff frequency of the LPF612 is input from the control unit 3, and is set based on the bandwidth of the transducer 41 and the scan frequency band of the drive signal. The complex signal after removing high-frequency components from the LPF612 is input to the downsampling unit 613.

[0061] The downsampling unit 613 downsamples the output signal of the LPF612. For example, the downsampling unit 613 samples the signal at a center frequency f... c The signal sampled twice was downsampled to the center frequency f. c The sampling frequency after downsampling can be set to be twice that of the center frequency f, based on the cutoff frequency of the LPF612. c It's twice as low.

[0062] The output signal of the downsampling unit 613 is input to correlation filters 62, 63, and 64. The complex signal output from the downsampling unit 613 is designated as the complex received signal. The complex received signal is composed of N signals sampled by the downsampling unit 613. N is an integer greater than or equal to 2. The N signals constituting the complex received signal are designated as signals S1 to S2 according to the sampling order. N .

[0063] Correlation filters 62, 63, and 64 perform correlation detection between the complex received signal generated by the quadrature detector 61 and the reference signals corresponding to the upper and lower chirps, respectively, and output the correlation signals. The reference signals used by correlation filters 62, 63, and 64 are respectively designated as the first reference signal, the second reference signal, and the third reference signal. Correlation filters 62, 63, and 64 are equivalent to the first correlation filter, the second correlation filter, and the third correlation filter, respectively.

[0064] The first reference signal corresponds to the drive signal and includes the same frequency modulation as the drive signal. The second and third reference signals are signals corresponding to a portion of the drive signal. The second reference signal includes the portion of the drive signal with a frequency lower than that of the third reference signal, and the third reference signal includes the portion of the drive signal with a frequency higher than that of the second reference signal. In this embodiment, the second and third reference signals are set as a portion of the first reference signal.

[0065] The correlation signal output from correlation filter 62 is input to code determination unit 8. The correlation signals output from correlation filters 63 and 64 are input to height determination unit 9. Details of correlation filters 62, 63, and 64 will be described later.

[0066] Figure 3This is a diagram representing an example of a reference signal. f RU It is the frequency of the first reference signal corresponding to the chirp, which, during time t1, originates from a frequency lower than the center frequency f. c The frequency f1 is higher than the center frequency f c The frequency f2 scan. RD It is the frequency of the first reference signal corresponding to the lower chirp, which is scanned from f2 to f1 during time t1.

[0067] f RL It is the frequency of the second reference signal, which is the frequency ratio f extracted from the first reference signal corresponding to the upper chirp. c The lower frequency range. f RH The frequency of the third reference signal is extracted from the first reference signal corresponding to the upper chirp at f. c The frequencies of the above portions. In f RL f RH In the diagram, solid lines represent the portions of the first reference signal used as the second and third reference signals, while dashed lines represent the portions of the first reference signal removed from the second and third reference signals. Thus, the second and third reference signals are respectively set as the first and second halves of the first reference signal corresponding to the upper chirp.

[0068] In this embodiment, the use of such a reference signal will be described. Furthermore, in... Figure 3 The diagram shows the second and third reference signals when the probe wave contains an upper chirp. When the probe wave contains a lower chirp, the second and third reference signals are the latter half and the first half of the first reference signal corresponding to the lower chirp, respectively.

[0069] The reference signal processing unit 7 processes the signal output from the drive signal generation unit 5 and outputs it to the receive signal processing unit 6. The signal output from the drive signal generation unit 5 to the reference signal processing unit 7 corresponds to the upper and lower chirps of the drive signal input to the transceiver unit 4, and this signal is set as a reference signal for identifying the code of the received signal. Furthermore, the drive signal generation unit 5 outputs the reference signal corresponding to the upper chirp and the reference signal corresponding to the lower chirp to the reference signal processing unit 7. In the receive signal processing unit 6, the reference signal processed by the reference signal processing unit 7 is used for correlation detection. Figure 1 As shown, the reference signal processing unit 7 includes an orthogonal detector 71.

[0070] The quadrature detector 71 performs quadrature detection on the reference signal output from the drive signal generation unit 5 to generate a complex signal. For example... Figure 4As shown, the quadrature detector 71 includes a multiplier 711, an LPF 712, and a downsampling unit 713. The multiplier 711, LPF 712, and downsampling unit 713 are configured with the same structure as the multiplier 611, LPF 612, and downsampling unit 613 of the quadrature detector 61.

[0071] That is, the multiplication unit 711 multiplies the reference signal by sin(2π·f). c ·t) and cos(2π·f c The LPF712 generates a complex signal by multiplying the complex signal output from the multiplication unit 711 and removing high-frequency components. Then, the downsampling unit 713 downsamples the output signal of the LPF712.

[0072] Furthermore, the downsampling unit 713 downsamples the received signal and the reference signal in the same manner using the downsampling frequency after downsampling. For example, the downsampling unit 613 downsamples the input signal to the center frequency f. c In the case of double sampling, the input signal is also downsampled to the center frequency f in the downsampling unit 713. c One times.

[0073] The output signal of the downsampling unit 713 is input to correlation filters 62, 63, and 64. The complex signal output from the downsampling unit 713 is designated as the complex reference signal. The complex reference signal, like the complex received signal, is composed of N signals. Following the sampling order, the N signals constituting the complex reference signal are designated as signals SR1 to SR2. N In the correlation filter 62, the signals S1 to S2 are processed. N The complex received signal and the signals SR1 to SR2 are constructed. N Correlation detection of the constructed complex reference signal.

[0074] As described above, in correlation filters 63 and 64, a portion of the first reference signal is used for correlation detection. Assume the driving signal contains an upper chirp. In this case, the portion of the complex reference signal generated by quadrature detection of the first reference signal corresponding to the upper chirp that corresponds to the second and third reference signals, i.e., the frequency ratio f... c The lower part and frequency in f c The above components are respectively input to correlation filters 63 and 64. For example, when N is even, signals SR1 to SR2... N / 2 The signal SR is input to the correlation filter 63. N / 2+1 ~SR N It is input into the correlation filter 64.

[0075] Then, in the correlation filter 63, the signals S1 to S2 are processed. N / 2 The complex received signal and the signals SR1 to SR2 are constructed.N / 2 The correlation detection is performed on the complex reference signal. Additionally, in the correlation filter 64, the correlation of signal S is performed. N / 2+1 ~S N The complex received signal and the signal SR constituted N / 2+1 ~SR N Correlation detection of the constructed complex reference signal.

[0076] Assume the driving signal contains a downchirp. In this case, the portion of the complex reference signal generated by quadrature detection of the first reference signal corresponding to the downchirp that corresponds to the second and third reference signals, i.e., the frequency ratio f, is... c The lower part and frequency in f c The above components are then input to correlation filters 63 and 64, respectively. For example, when N is even, the signal SR... N / 2+1 ~SR N The signals SR1 to SR2 are input to the correlation filter 63. N / 2 It is input into the correlation filter 64.

[0077] Then, in the correlation filter 63, the signal S is processed. N / 2+1 ~S N The complex received signal and the signal SR constituted N / 2+1 ~SR N The correlation detection is performed on the complex reference signal. Additionally, in the correlation filter 64, the correlation of signals S1 to S2 is performed. N / 2 The complex received signal and the signals SR1 to SR2 are constructed. N / 2 Correlation detection of the constructed complex reference signal.

[0078] A detailed explanation of the correlation filter 62 is provided. For example... Figure 5 As shown, the correlation filter 62 includes an upper chirped filter 620A and a lower chirped filter 620B. The upper chirped filter 620A performs correlation calculations between the upper chirped signal complex received signal and the complex reference signal. The lower chirped filter 620B performs correlation calculations between the lower chirped signal complex received signal and the complex reference signal.

[0079] One method for performing related calculations is to perform vector rotation on the complex received signals based on a reference signal and then add them together. The upper chirp filter 620A includes a reference signal holding unit 621, a vector rotation unit 622, an adder unit 623, and an amplitude conversion unit 624.

[0080] In the chirped filter 620A, a complex reference signal generated by quadrature detection of a reference signal corresponding to the chirped signal is input from the reference signal processing unit 7. The reference signal holding unit 621 is configured to hold and output the complex reference signal input from the reference signal processing unit 7, and individually output multiple signals constituting the complex reference signal. Specifically, the reference signal holding unit 621 individually outputs signals SR1 to SR2 output from the downsampling unit 713. N .

[0081] The vector rotation unit 622 performs vector rotation on the input signal. For example... Figure 6 As shown, the vector rotation unit 622 includes a matrix conversion unit 625, a received signal holding unit 626, and a multiplication unit 627.

[0082] The matrix conversion unit 625 will take the signals SR1 to SR2 output from the reference signal holding unit 621. N Convert to rotation matrix R1~R N Specifically, if the phase of signal SR1 is set to θ R1 Then, the rotation matrix R1 is generated as shown in the following formula.

[0083] [Formula 1]

[0084]

[0085] For rotation matrices R2~R N Also using signals SR2 to SR N phase θ R2 ~θ RN Similarly, it is generated. The matrix transformation unit 625 will be used with the generated rotation matrices R1 to R2. N The corresponding signals are individually output to the multiplication unit 627.

[0086] The receive signal holding unit 626 holds the complex received signal and outputs it to the multiplication unit 627. A complex received signal is input from the quadrature detector 61 to the receive signal holding unit 626, which then stores the input signals S1 to S27. N Individually output to the multiplication part 627.

[0087] The multiplication unit 627 calculates the correlation between the received signal and the first reference signal, which is equivalent to the first correlation calculation unit. Specifically, the multiplication unit 627 calculates the correlation between the received signal and the first reference signal and the first correlation calculation unit. N Multiply by signals S1 to S N The vector is used to generate signals ΔS1~ΔS, which take the phase difference between the received signal and the reference signal as the phase. N For example, such as Figure 7 As shown, if the phase difference between signal S1 and signal SR1 is set as Δθ1, and the amplitude of signal S1 is set as r1, then as follows Figure 8 As shown, the phase of signal ΔS1 is Δθ1, and its amplitude is r1. Furthermore, Figure 7 , Figure 8 And the following Figures 9-12 Signal S1 is shown on the complex plane. If the real part of signal S1 is set as I1 and the imaginary part as Q1, and the real part of signal ΔS1 is set as I1' and the imaginary part as Q1', then I1' and Q1' can be obtained by the following formula.

[0088] [Equation 2]

[0089]

[0090] Similarly, if signals S2 to S N With signals SR1~SR N The phase difference is set as Δθ2~Δθ N And the signals S2 to S N The amplitude is set to r2~r N Then the signal ΔS2~ΔS N The phase is Δθ2~Δθ N The amplitude is r2~r N According to signals S2 to S... N The real part I2~I N Imaginary part Q2~Q N And rotation matrices R2~R N Calculate the signal ΔS2~ΔS N The real part I2'~I N '、Imaginary part Q2'~Q N The multiplication unit 627 will convert signals ΔS1 to ΔS... N Individual outputs are sent to the addition section 623.

[0091] like Figure 6 As shown, the adder 623 includes an addition signal generation unit 628 and an averaging unit 629, and the signals ΔS1 to ΔS2 output from the multiplication unit 627 are... N The signal is input to the summing signal generation unit 628. The summing signal generation unit 628 adds the input signals, thereby performing correlation detection between the received signal and the reference signal.

[0092] If the signal ΔS1~ΔS N When added together, the amplitude increases when the correlation between the received signal and the reference signal is high, and decreases when the correlation is low. For example, as... Figure 8 , Figure 9 As shown, if the phases Δθ1 and Δθ2 of signals ΔS1 and ΔS2 are consistent, then as follows Figure 10 As shown, the amplitude is increased by adding signal ΔS2 to signal ΔS1. On the other hand, as... Figure 11As shown, if the phase Δθ2 of signal ΔS2 is significantly different from the phase Δθ1 of signal ΔS1, then as follows Figure 12 As shown, the amplitude is reduced by adding signal ΔS2 to signal ΔS1.

[0093] Thus, if the signal ΔS1~ΔS N The amplitude of the complex signal generated by the summation represents the correlation level between the received signal and the reference signal. The summation signal generation unit 628 transmits the summation signal ΔS1 to ΔS2 through the signals ΔS1 to ΔS2. N The complex signal generated by the summation of the two signals is output to the averaging section 629.

[0094] In addition, from Figures 7-12 It can be seen that the amplitude of the correlation signal varies not only with the correlation level between the received signal and the reference signal, but also with the amplitude of the received signal. The larger the amplitude of the received signal, the larger the amplitude of the correlation signal.

[0095] The averaging unit 629 averages the amplitude of the output signal from the summing signal generation unit 628 by dividing it by the number of signals being added, i.e., N. The complex signal averaged by the averaging unit 629 is then output to the amplitude conversion unit 624.

[0096] The amplitude conversion unit 624 converts the complex signal input from the averaging unit 629 into an amplitude signal. Specifically, the amplitude conversion unit 624 calculates the absolute value based on the real and imaginary parts of the complex signal and outputs the absolute value as the amplitude. The amplitude signal generated by the amplitude conversion unit 624 is output as a correlation signal to the code determination unit 8.

[0097] like Figure 5 As shown, the lower chirped filter 620B, like the upper chirped filter 620A, includes a reference signal holding section 621, a vector rotation section 622, an adder section 623, and an amplitude conversion section 624. The reference signal holding section 621 to the amplitude conversion section 624 of the lower chirped filter 620B are configured with the same structure as those of the upper chirped filter 620A.

[0098] However, in the down-chirped filter 620B, a complex reference signal generated by orthogonal detection of a reference signal corresponding to the down-chirped signal is input from the reference signal processing unit 7 to the reference signal holding unit 621, and correlation detection is performed between the complex received signal and the complex reference signal. Furthermore, the amplitude signal generated by the amplitude conversion unit 624 is output as a correlation signal to the code determination unit 8.

[0099] The correlation filters 63 and 64 are explained in detail. Figure 13 As shown, the correlation filter 63 includes: a reference signal holding unit 631, a vector rotation unit 632, an adder 633, and an amplitude conversion unit 634. Additionally, as... Figure 14 As shown, the correlation filter 64 includes: a reference signal holding unit 641, a vector rotation unit 642, an adder unit 643, and an amplitude conversion unit 644.

[0100] The reference signal holding section 631 to amplitude conversion section 634 of the correlation filter 63 and the reference signal holding section 641 to amplitude conversion section 644 of the correlation filter 64 are configured with the same structure as the reference signal holding section 621 to amplitude conversion section 624 of the upper chirped filter 620A.

[0101] However, in correlation filter 63, a complex reference signal corresponding to the second reference signal is input from reference signal processing unit 7, and correlation detection is performed between the complex received signal and the complex reference signal. Furthermore, in correlation filter 64, a complex reference signal corresponding to the third reference signal is input from reference signal processing unit 7, and correlation detection is performed between the complex received signal and the complex reference signal. Moreover, the amplitude signals generated by amplitude conversion units 634 and 644 are output as correlation signals to height determination unit 9.

[0102] The code determination unit 8 determines, based on the correlation signal output by the correlation filter 62, whether the ultrasonic wave received by the receiving unit 40B is a reflected wave of the probe wave transmitted by the transmitting unit 40A. The code determination unit 8 is equivalent to the first determination unit.

[0103] Specifically, the code determination unit 8 determines whether the code contained in the drive signal is consistent with the code contained in the received signal. Based on the correlation outputs of the upper chirp filter 620A and the lower chirp filter 620B, the code determination unit 8 calculates the peak value of the upper chirp correlation signal and the peak value of the lower chirp correlation signal. Then, the code determination unit 8 compares them, determines that the code corresponding to the larger one is contained in the received signal, and determines whether the code contained in the drive signal is consistent with the code contained in the received signal based on this determination result. The code determination unit 8 sends the code determination result to the control unit 3.

[0104] The height determination unit 9 determines whether an object is within the detection range based on the correlation signals output by the correlation filter 63 and the correlation signals output by the correlation filter 64. The height determination unit 9 is equivalent to the second determination unit. This detection range is set based on factors such as the probability of contact between an object outside the vehicle and the vehicle body. For example, for an object placed on the ground, it is set to enter the detection range if its height from the ground is greater than a predetermined value, and to leave the detection range if its height is less than the predetermined value. Furthermore, for an object protruding from the ceiling of the passageway, it is set to enter the detection range based on the size of the protrusion. In this embodiment, the determination of the height of an object placed on the ground is explained, but other criteria can also be used to determine whether an object is within the detection range.

[0105] The height determination unit 9 uses the directivity of ultrasound to determine the height of an object. The higher the frequency of the ultrasound, the narrower the directivity. That is, near the central axis of the probe wave's directivity, the amplitude of the probe wave is larger in both cases of lower and higher frequencies. Furthermore, at lower frequencies, the amplitude of the probe wave is also larger at locations further away from the central axis, resulting in a larger amplitude of the reflected wave from an object located at that position. Conversely, at higher frequencies, the amplitude of the probe wave is smaller at locations further away from the central axis, resulting in a smaller amplitude of the reflected wave from an object located at that position.

[0106] Furthermore, as mentioned above, the larger the amplitude of the received signal, the larger the amplitude of the correlated signal. Accordingly, in the correlation filter 63 using the second reference signal with a lower frequency, the amplitude of the correlation output is larger in both cases: when the object is near the central axis of the probe wave's directionality and when it is located far from the central axis. On the other hand, in the correlation filter 64 using the third reference signal with a higher frequency, the amplitude of the correlation output is larger when the object is near the central axis of the probe wave's directionality, but smaller when the object is located far from the central axis.

[0107] Therefore, by comparing the amplitude of the correlation output of correlation filter 63 with the amplitude of the correlation output of correlation filter 64, it is possible to determine whether an object is close to the central axis of the directionality of the detection wave. For example, if the amplitude of the correlation signal of correlation filter 63 is set to AL and the amplitude of the correlation signal of correlation filter 64 is set to AH, when AH / AL is greater than a threshold, the height determination unit 9 determines that the detected object is a high object that may come into contact with the vehicle body. On the other hand, when AH / AL is less than the threshold, the height determination unit 9 determines that the detected object is a low object. In addition, the height determination unit 9 can also compare AL and AH using other methods.

[0108] The control unit 3 is configured to connect to the ultrasonic sensor 2 via an onboard communication line to enable information communication, and to control the transmitting and receiving operations of the ultrasonic sensor 2. The control unit 3, as a sonar ECU, includes an onboard microcomputer (not shown) with a CPU, ROM, RAM, and non-volatile rewritable memory. ECU is an abbreviation for Electronic Control Unit. Non-volatile rewritable memory includes, for example, EEPROM and flash memory ROM. EEPROM is an abbreviation for Electronically Erasable and Programmable Read Only Memory.

[0109] As described above, the code determination unit 8 and the height determination unit 9 send code determination results and height determination results to the control unit 3. These determination results are used for obstacle reporting, automatic parking, and other processing.

[0110] The operation of object detection device 1 will be explained. Object detection device 1 repeatedly performs actions including... Figure 15 The object detection process shown is as follows. In this process, firstly, the control unit 3 sends a transmission instruction to the drive signal generation unit 5, and a detection wave is transmitted from the transducer 41 based on the drive signal generated by the drive signal generation unit 5. Then, if the transceiver unit 4 detects receipt of the ultrasonic signal, the object detection device 1 executes... Figure 15 The processing is shown.

[0111] First, in step S101, the quadrature detector 61 performs quadrature detection on the received signal output from the transceiver unit 4 to generate a complex received signal, which is then output to the correlation filters 62, 63, and 64. Additionally, the quadrature detector 71 performs quadrature detection on the reference signals output from the drive signal generation unit 5 corresponding to the upper and lower chirps, respectively, to generate complex reference signals, which are then output to the correlation filters 62, 63, and 64. At this time, the correlation filters 62, 63, and 64 are respectively input with the complex reference signals corresponding to the first, second, and third reference signals.

[0112] In the following step S102, the correlation filter 62 performs correlation detection between the complex received signal output from the quadrature detector 61 and the complex reference signal corresponding to the upper chirp, and outputs the correlation signal to the code determination unit 8. Additionally, the correlation filter 62 performs correlation detection between the complex received signal and the complex reference signal corresponding to the lower chirp, and outputs the correlation signal to the code determination unit 8.

[0113] Furthermore, correlation filter 63 performs correlation detection between the complex received signal and the complex reference signal corresponding to the second reference signal, and outputs the correlation signal to the height determination unit 9. Additionally, correlation filter 64 performs correlation detection between the complex received signal and the complex reference signal corresponding to the third reference signal, and outputs the correlation signal to the height determination unit 9.

[0114] In the following step S103, the code determination unit 8 detects peak values ​​from the correlation signals. Specifically, the code determination unit 8 detects peak values ​​from the upper-chirped correlation signal and the lower-chirped correlation signal output from the autocorrelation filter 62. For example, the code determination unit 8 compares the amplitude of the correlation signal with a threshold, and if there is a range in the correlation signal with an amplitude greater than the threshold, the maximum value within that range is taken as the peak value. Alternatively, the value at the center of that range can also be taken as the peak value.

[0115] In the following step S104, the code determination unit 8 determines whether the codes in the drive signal and the received signal are consistent. Specifically, the code determination unit 8 compares the peak value of the upper chirp correlation signal with the peak value of the lower chirp correlation signal. Furthermore, if the drive signal includes the upper chirp and the peak value of the upper chirp correlation signal is greater than the peak value of the lower chirp correlation signal, the code determination unit 8 determines that the codes are consistent. Similarly, if the drive signal includes the lower chirp and the peak value of the lower chirp correlation signal is greater than the peak value of the upper chirp correlation signal, the code determination unit 8 also determines that the codes are consistent. By ensuring code consistency in this way, an object is detected.

[0116] On the other hand, when the drive signal includes an upper chirp, and the peak value of the related signal of the upper chirp is below the peak value of the related signal of the lower chirp, the code determination unit 8 determines that the code is inconsistent. Additionally, when the drive signal includes a lower chirp, and the peak value of the related signal of the lower chirp is below the peak value of the related signal of the upper chirp, the code determination unit 8 also determines that the code is inconsistent.

[0117] If the code is determined to be consistent in step S104, the process moves to step S105; if the code is determined to be inconsistent, the process ends.

[0118] In step S105, the height determination unit 9 determines the height of the object based on the correlation outputs of the correlation filters 63 and 64. Specifically, the height determination unit 9 compares the amplitude ratio AH / AL with a predetermined threshold. If AH / AL is greater than the threshold, the detected object is determined to be a high-height object that may come into contact with the vehicle body. On the other hand, if the amplitude ratio AH / AL is less than the threshold, the height determination unit 9 determines that the detected object is a low-height object. After step S105, the process ends.

[0119] The range of the correlation signal used by the height determination unit 9 in the determination is set based on the correlation signal output by the correlation filter 62. Specifically, the range of amplitudes AL and AH used by the height determination unit 9 in the determination is set based on the time when the output of the correlation filter 62 reaches its peak.

[0120] For example, when transmitting a probe wave containing an upper chirp, the second reference signal used by correlation filter 63 is set to the first half of the first reference signal used by upper chirp filter 620A, and the third reference signal used by correlation filter 64 is set to the second half of the first reference signal. Therefore, if a reflected wave is received, the output of correlation filter 63 reaches its peak value before the output of upper chirp filter 620A, and the output of correlation filter 64 reaches its peak value after the output of upper chirp filter 620A.

[0121] Therefore, the height determination unit 9 uses the moment when the output of the chirped filter 620A reaches its peak value as a reference, and uses the amplitude of the output of the correlation filter 63 within the range up to the predetermined time as the amplitude AL. Additionally, the height determination unit 9 uses the amplitude of the output of the correlation filter 64 within the range up to the predetermined time as a reference, and uses that moment as a reference, as the amplitude AH.

[0122] When transmitting a probe wave containing a downchirped wave, the amplitude AL can be obtained by using the amplitude of the output of the downchirped filter 620B within the range up to a predetermined time, based on the time when the output of the downchirped filter 620B reaches its peak. Alternatively, the amplitude AH can be obtained by using the amplitude of the output of the correlation filter 64 within the range up to the predetermined time, based on that time.

[0123] like Figure 15 Once the processing is complete, the object detection result from the ultrasonic sensor 2 is sent to the control unit 3. This detection result includes the code determination result from the code determination unit 8 and the height determination result from the height determination unit 9. Additionally, the detection result may include, for example, the distance between the vehicle and the object determined by a Time-of-Flight (TOF) method. This distance calculation is performed, for example, in the code determination unit 8, but may also be performed by a calculation unit (not shown).

[0124] Assuming a probe wave containing an upper chirp is sent, two reflected waves are received at time intervals, and the results are obtained... Figure 16 The correlation output is as shown. In the upper chirped filter 620A, the amplitude of the correlation output is larger than the threshold in the range corresponding to the two reflected waves. Moreover, the maximum value in each range is set as the peak value of the output of the upper chirped filter 620A.

[0125] On the other hand, in the lower chirped filter 620B, the amplitude of the correlation output is smaller than the threshold in the range corresponding to the first reflected wave, so no peak value is detected. Additionally, in the range corresponding to the second reflected wave, the amplitude of the correlation output is larger than the threshold, but the peak value in this range is smaller than the peak value of the output of the upper chirped filter 620A. Therefore, in this case, for each of the two reflected waves, the codes are determined to be consistent in step S104, and an object is detected.

[0126] Moreover, in Figure 16 In the range corresponding to the first peak, the amplitude AL of the output of correlation filter 63 is approximately equal to the amplitude AH of the output of correlation filter 64. The amplitude calculated using this amplitude AL and AH is larger than the threshold value of AH / AL. Therefore, in step S105, the object detected based on the first reflected wave is determined to be a relatively high object that may come into contact with the vehicle body.

[0127] On the other hand, within the range corresponding to the second peak, the amplitude AL of the output of correlation filter 63 is larger than the amplitude AH of the output of correlation filter 64. The amplitude calculated using this amplitude AL and AH is smaller than the threshold value of AH / AL. Therefore, in step S105, it is determined that the object detected based on the second reflected wave is a low-height object.

[0128] Furthermore, as described above, when transmitting a probe wave containing an upper chirp, the output of correlation filter 63 reaches its peak value before the peak value of the output of upper chirp filter 620A. Additionally, the output of correlation filter 64 reaches its peak value after the peak value of the output of upper chirp filter 620A. Figure 16 In order to make the difference in amplitude easier to understand, the output of correlation filter 63 is shown at a time later than the actual time, and the output of correlation filter 64 is shown at a time earlier than the actual time.

[0129] Figures 17-19 This diagram shows the results of an experiment conducted by the inventors. In this experiment, various objects were placed in front of the ultrasonic sensor 2, and a probe wave containing an up-chirped wave was sent to detect the objects. Figures 17-19 The above figure shows the outputs of the upper chirped filter 620A and the lower chirped filter 620B. The solid line represents the output of the upper chirped filter 620A, and the dotted line represents the output of the lower chirped filter 620B. Figures 17-19 The following diagram shows the outputs of correlation filter 63 and correlation filter 64. The solid line represents the output of correlation filter 63, and the dotted line represents the output of correlation filter 64.

[0130] Figure 17 The outputs of correlation filters 62, 63, and 64 are shown when a relatively tall wall is positioned in front of the ultrasonic sensor 2. For example... Figure 17 As shown, the peak value of the output of the upper chirped filter 620A is larger than the peak value of the output of the lower chirped filter 620B. Therefore, the code is correctly determined to be consistent in step S104. Additionally, the amplitude of the output of the correlation filter 63 is smaller than the amplitude of the output of the correlation filter 64. Therefore, the amplitude ratio AH / AL is larger than the specified threshold, and the object is correctly determined to be taller in step S105.

[0131] Figure 18The outputs of correlation filters 62, 63, and 64 are shown when a 10cm high wheel wedge is positioned in front of the ultrasonic sensor 2. For objects with a relatively low height, such as the wheel wedge, the peak value of the output of the upper chirped filter 620A is larger than the peak value of the output of the lower chirped filter 620B, and the determination code is correctly obtained accordingly. In addition, the amplitude of the output of correlation filter 63 is larger than the amplitude of the output of correlation filter 64. Therefore, the amplitude ratio AH / AL is below the specified threshold, and the object is correctly determined to be a low-height object in step S105.

[0132] Figure 19 The outputs of correlation filters 62, 63, and 64 are shown when a relatively tall pole is positioned in front of the ultrasonic sensor 2. For objects with a small lateral width, such as the pole, the peak value of the output of the upper chirped filter 620A is larger than the peak value of the output of the lower chirped filter 620B, thus correctly determining the code. Furthermore, the amplitude of the output of correlation filter 63 is smaller than the amplitude of the output of correlation filter 64. Therefore, the amplitude is greater than the predetermined threshold (AH / AL), and the object is correctly determined to be tall in step S105. In this way, the code and height can be correctly determined for various objects.

[0133] As explained above, in this embodiment, code determination is performed using correlation detection of a first reference signal corresponding to the drive signal. Furthermore, a lower-frequency second reference signal and a higher-frequency third reference signal are extracted from the first reference signal, and height determination is performed using correlation detection of these second and third reference signals. Therefore, it is not necessary to send two signals for both code determination and height determination; both code and height can be determined with a single transmission and reception.

[0134] Furthermore, according to the above-described embodiments, the following effects can be obtained.

[0135] (1) The range of the correlation signal used by the height determination unit 9 in the determination is set based on the correlation signal output by the correlation filter 62. Due to the pulse compression effect of the correlation output of the correlation filter 62, the detection accuracy of the center of the reflected wave is improved. Therefore, by setting the range of the correlation signal in this way, the accuracy of height determination is improved.

[0136] (2) The range of the correlation signal used by the height determination unit 9 in the determination is set based on the time when the correlation signal output by the correlation filter 62 reaches its peak. Due to the pulse compression effect of the correlation output of the correlation filter 62, the detection accuracy of the center of the reflected wave is improved. Therefore, by setting the range of the correlation signal in this way, the accuracy of height determination is improved.

[0137] (Second Implementation)

[0138] The second embodiment will be described. This embodiment differs from the first embodiment in that the structures of the correlation filters 62, 63, and 64 are modified; otherwise, they are the same as in the first embodiment. Therefore, only the parts that differ from the first embodiment will be described.

[0139] In this embodiment, the correlation filters 62, 63, and 64 share a portion of the operational circuitry. Specifically, as shown... Figure 20 As shown, the vector rotation section 632 of the correlation filter 63 includes a matrix transformation section 635, a received signal holding section 636, and a multiplication section 637. The addition section 633 includes an addition signal generation section 638 and an averaging section (not shown). Similarly, the vector rotation section 642 of the correlation filter 64 includes a matrix transformation section 645, a received signal holding section 646, and a multiplication section 647. The addition section 643 includes an addition signal generation section 648 and an averaging section (not shown). The multiplication section 637 calculates the correlation between the received signal and the second reference signal, equivalent to a second correlation calculation section. The multiplication section 647 calculates the correlation between the received signal and the third reference signal, equivalent to a third correlation calculation section.

[0140] Furthermore, the reference signal holding units 631 and 641 are composed of a portion of the reference signal holding unit 621. The reference signal holding unit 631 is composed of the portion of the reference signal holding unit 621 that inputs, holds, and outputs a complex reference signal corresponding to the second reference signal. The reference signal holding unit 641 is composed of the portion of the reference signal holding unit 621 that inputs, holds, and outputs a complex reference signal corresponding to the third reference signal.

[0141] For example, assuming N is even, the first half of the first reference signal is set as the second reference signal, and the second half of the first reference signal is set as the third reference signal. In this case, the reference signal holding unit 631 holds and outputs signals SR1 to SR21 from the reference signal holding unit 621. N / 2 The reference signal holding unit 641 is composed of the reference signal holding unit 621 holding and outputting the signal SR. N / 2+1 ~SR N It is a component of [something].

[0142] Similarly, the matrix conversion unit 635, the received signal holding unit 636, and the multiplication unit 637 are each composed of a portion of the matrix conversion unit 625, the received signal holding unit 626, and the multiplication unit 627, respectively. Specifically, the matrix conversion unit 635 is composed of the portion of the matrix conversion unit 625 that converts the complex received signal corresponding to the second reference signal into a rotation matrix. Furthermore, the received signal holding unit 636 is composed of the portion of the received signal holding unit 626 that performs correlation detection with the second reference signal from the input, holding, and output complex received signals. Additionally, the multiplication unit 637 is composed of the portion of the multiplication unit 627 that multiplies the complex received signal output from the received signal holding unit 636 with the rotation matrix generated by the matrix conversion unit 635.

[0143] For example, in the above case, the matrix conversion unit 635 uses the input signals SR1 to SR2 from the matrix conversion unit 625. N / 2 Convert to rotation matrices R1~R N / 2 The output section is composed of the receiving signal holding section 636. Additionally, the receiving signal holding section 636 consists of the input, holding, and output signals S1 to S2 from the receiving signal holding section 626. N / 2 The multiplication unit 637 is composed of signals S1 to S2 from the received signal holding unit 636 in the multiplication unit 627. N / 2 With the rotation matrices R1 to R2 generated by the matrix transformation unit 635 N / 2 The components formed by multiplication.

[0144] Furthermore, the matrix conversion unit 645, the received signal holding unit 646, and the multiplication unit 647 are each composed of a portion of the matrix conversion unit 625, the received signal holding unit 626, and the multiplication unit 627, respectively. Specifically, the matrix conversion unit 645 is composed of the portion of the matrix conversion unit 625 that converts the complex received signal corresponding to the third reference signal into a rotation matrix. The received signal holding unit 646 is composed of the portions of the received signal holding unit 626 that handle the input, holding, and output received signals for correlation detection with the third reference signal. The multiplication unit 647 is composed of the portion of the multiplication unit 627 that multiplies the complex received signal output from the received signal holding unit 646 with the rotation matrix generated by the matrix conversion unit 645.

[0145] For example, in the above case, the matrix conversion unit 645 uses the input signal SR from the matrix conversion unit 625. N / 2+1 ~SR N Convert to rotation matrix R N / 2+1 ~R N The output section is also included. Additionally, the receive signal holding section 646 consists of the input, holding, and output signals S from the receive signal holding section 626. N / 2+1 ~S NThe multiplication unit 647 is composed of the signal S output from the received signal holding unit 646 in the multiplication unit 627. N / 2+1 ~S N The rotation matrix R generated by the matrix transformation unit 645 N / 2+1 ~R N The components formed by multiplication.

[0146] Thus, the multiplication units 627, 637, and 647 share the operational circuitry for performing related calculations; specifically, they share the operational circuitry for multiplying the complex received signal with the first, second, and third reference signals.

[0147] The multiplication unit 627, like in the first embodiment, individually outputs the signals ΔS1 to ΔS generated by multiplication. N Furthermore, for example, in the case described above, the signals ΔS1~ΔS N / 2 The signal ΔS is input to the summing signal generation unit 628 and the summing signal generation unit 638. N / 2+1 ~ΔS N The signal is input to the summing signal generation unit 628 and the summing signal generation unit 648.

[0148] The summing signal generation unit 638 adds the input signals and outputs the resulting complex signal to an averaging unit (not shown). This averaging unit averages the amplitude of the output signal from the summing signal generation unit 638 by dividing the sum of the summed signals. For example, in the case described above, the averaging unit divides the amplitude by N / 2. The averaged complex signal is then output to an amplitude conversion unit 634. The amplitude conversion unit 634, similar to the first embodiment, converts the input signal into an amplitude and outputs it as a correlation signal.

[0149] Similarly, the summing signal generation unit 648 sums the input signals and outputs the resulting complex signal to an averaging unit (not shown). This averaging unit averages the amplitude of the output signal from the summing signal generation unit 648 by dividing the sum of the summed signals. For example, in the case described above, the averaging unit divides the amplitude by N / 2. The averaged complex signal is then output to an amplitude conversion unit 644. The amplitude conversion unit 644, similar to the first embodiment, converts the input signal into an amplitude and outputs it as a correlation signal.

[0150] Furthermore, the related filters 63 and 64 share the summation circuitry of the upper chirped filter 620A and the lower chirped filter 620B. A circuit is provided between the multiplication unit 627 of the upper chirped filter 620A and the multiplication unit 627 of the lower chirped filter 620B and the summation signal generation units 638 and 648 to select the signals input to the summation signal generation units 638 and 648.

[0151] This circuit switches the signals input to the summing signal generation units 638 and 648 according to the drive signal. That is, when transmitting a probe wave containing an upper chirp, the signals ΔS1 to ΔS2 output from the multiplication unit 627 of the upper chirp filter 620A are... N The first half is input to the summing signal generation unit 638, and the second half is input to the summing signal generation unit 648. On the other hand, when transmitting a probe wave containing a down-chirped wave, the signals ΔS1 to ΔS1 output from the multiplication unit 627 of the down-chirped filter 620B are... N The first half is input to the summing signal generation unit 648, and the second half is input to the summing signal generation unit 638.

[0152] This embodiment achieves the same effects as the first embodiment because it has the same structure and operation as the first embodiment.

[0153] Furthermore, according to the above-described embodiments, the following effects can be obtained.

[0154] (1) The multiplication units 627, 637, and 647 share the operation circuit for multiplication. By changing the range of signal addition, the three correlation filters can be processed in parallel. Accordingly, the circuit for correlation detection calculation can be reduced, especially the multiplication unit which has a large circuit size, thus reducing the computational load and circuit size.

[0155] (Third Implementation)

[0156] The third embodiment will be described. This embodiment differs from the first embodiment in that the frequency of the reference signal is changed; otherwise, it is the same as the first embodiment. Therefore, only the parts that differ from the first embodiment will be described.

[0157] In this embodiment, the speed of the vehicle, measured by a speed sensor (not shown), is input to the ultrasonic sensor 2, and the frequency of the reference signal is corrected based on this speed. Specifically, as... Figure 21 As shown, the reference signal is the signal that shifts the drive signal to the high-frequency side.

[0158] Figure 21 The solid line represents the corrected reference signal, while the dotted line represents the original reference signal at the same frequency as the drive signal. Additionally, in f... RL f RH In the diagram, the double-dotted line represents the portion of the corrected first reference signal removed from the second and third reference signals. The displacement amount of the frequency is set according to the vehicle speed; the higher the vehicle speed, the greater the displacement.

[0159] This embodiment achieves the same effects as the first embodiment due to its identical structure and operation.

[0160] Furthermore, according to the above-described embodiments, the following effects can be obtained.

[0161] (1) The frequency of the reference signal is corrected according to the vehicle speed. Therefore, it is possible to suppress the reduction in code determination accuracy and the reduction in altitude determination accuracy caused by Doppler frequency shift.

[0162] (Fourth Implementation)

[0163] The fourth embodiment will be described. This embodiment adds a normalization and phase rotation configuration to the complex signal compared to the first embodiment. The rest is the same as the first embodiment, so only the parts that are different from the first embodiment will be described.

[0164] like Figure 22 As shown, the receiving signal processing unit 6 of this embodiment, in addition to the quadrature detector 61, correlation filter 62, correlation filter 63, and correlation filter 64, also includes a normalization unit 65 and a phase rotation unit 66. Furthermore, the reference signal processing unit 7, in addition to the quadrature detector 71, also includes a normalization unit 72 and a phase rotation unit 73. The drive signal generation unit 5, the receiving signal processing unit 6, the reference signal processing unit 7, the code determination unit 8, and the height determination unit 9 are, for example, composed of a DSP programmed with the aforementioned functions of drive signal generation, quadrature detection, correlation calculation, code determination, height determination, normalization (described later), and phase rotation.

[0165] The normalization unit 65 normalizes the complex received signal output from the quadrature detector 61 to keep the amplitude constant. For example... Figure 22 As shown, the complex received signal output from the quadrature detector 61 is input to the normalization unit 65.

[0166] The normalization unit 65 converts the complex received signal output from the quadrature detector 61 into amplitude. That is, the normalization unit 65 normalizes signals S1 to S2. N According to the real part I1~I N Imaginary part Q1~Q N Calculate the amplitude r1~r N For example, the amplitude r1 is r1 = √(I1) 2 +Q1 2 For amplitudes r2 to r N The same calculation is performed.

[0167] Then, the normalization part 65 is based on the amplitude r1~r N While maintaining the phase, the amplitude of the complex received signal input from the quadrature detector 61 is normalized and converted into a unit vector. Specifically, the normalization unit 65 divides the complex received signal by the original amplitude. That is, signals S1 to S2... N The real part I1~IN Converted to I1 / r1~I N / r N Imaginary part Q1~Q N Converted to Q1 / r1~Q N / r N .

[0168] Phase rotation unit 66 rotates the phase of the complex received signal. Phase rotation unit 66 is equivalent to the first phase rotation unit. The phase rotation unit 66 is input with the complex received signal normalized by normalization unit 65, and the complex received signal after phase rotation by phase rotation unit 66 is output to correlation filters 62, 63, and 64.

[0169] Specifically, the phase rotation unit 66 processes the input signal as follows: The real part of the normalized complex received signal is set as I', the imaginary part as Q', and the phase as θ, using I' = cosθ, Q' = sinθ, and cos²θ = 1 - 2sinθ. 2 Given θ and sin2θ = 2sinθcos, calculate cos2θ and sin2θ using I' and Q'. Then, set the real and imaginary parts of the new complex received signal to cos2θ and sin2θ respectively and output them.

[0170] In this embodiment, the signals S1 to S2 after normalization and phase rotation are as follows. N The signals are input to correlation filters 62, 63, and 64 for correlation detection with the complex reference signal. Furthermore, in the multiplication section 627 of the vector rotation section 622, I1 to I... N Q1~Q N And using I1 / r1~I N / r N Q1 / r1~Q N / r N Perform the calculations shown in Formula 2.

[0171] The phase rotation amount is an integer multiple, such as twice as described above, but the phase can also be rotated at other multiples. For example, in the phase rotation unit 66, two phase rotations of twice the value can be performed, outputting cos4θ = 1 - 2sinθ. 2 The signal whose phase is rotated four times, such as 2θ, sin4θ=2sin2θcos2θ.

[0172] Normalization unit 72 normalizes the complex reference signal output from quadrature detector 71 to keep the amplitude constant. Normalization unit 72 normalizes the complex reference signal using the same method as normalization unit 65. The complex reference signal normalized by normalization unit 72 is output to phase rotation unit 73.

[0173] Phase rotation unit 73 rotates the phase of the complex reference signal. Phase rotation unit 73 is equivalent to a second phase rotation unit. The phase rotation unit 73 is input with the complex reference signal normalized by normalization unit 72, and the complex reference signal with the phase rotated by phase rotation unit 73 is output to correlation filters 62, 63, and 64. Phase rotation is also performed in phase rotation unit 73 in the same way as phase rotation unit 66. By rotating the phase of the complex reference signal corresponding to the first reference signal using phase rotation unit 73, the phases of the complex reference signals corresponding to the second and third reference signals are also rotated.

[0174] The correlation filter 62 performs correlation detection between the phase-rotated complex received signal and the phase-rotated complex reference signal, and outputs the correlation signal. Specifically, the phase rotation unit 73 inputs the chirped and phase-rotated signals SR1 to SR2 corresponding to the chirped signal to the upper chirped filter 620A of the correlation filter 62. N Additionally, the phase rotation unit 73 inputs the normalized and phase-rotated signals SR1 to SR2 corresponding to the lower chirp filter 620B. N In the upper chirped filter 620A and the lower chirped filter 620B, correlation detection is performed between the normalized and phase-rotated complex received signal and the normalized and phase-rotated complex reference signal, and the correlation signal is output.

[0175] In addition, the correlation filter 63 receives the input normalized and phase-rotated signals SR1 to SR2. N The signal corresponds to the second reference signal. Furthermore, correlation detection is performed between this signal and the normalized and phase-rotated complex received signal, and a correlation signal is output. Additionally, the correlation filter 64 is input with the normalized and phase-rotated signals SR1 to SR2. N The signal corresponds to the third reference signal. Furthermore, correlation detection is performed between this signal and the normalized and phase-rotated complex received signal, and the correlation signal is output.

[0176] In the object detection processing of this embodiment, Figure 15In step S101, the quadrature detector 61 converts the received signal into a complex signal, the normalization unit 65 normalizes the complex received signal, and the phase rotation unit 66 performs phase rotation on the normalized complex received signal. Additionally, the quadrature detector 71 converts the reference signal into a complex signal, the normalization unit 72 normalizes the complex reference signal, and the phase rotation unit 73 performs phase rotation on the normalized complex reference signal. Then, in step S102, the correlation filters 62, 63, and 64 perform correlation detection between the phase-rotated complex received signal and the phase-rotated complex reference signal. In step S104, the code determination unit 8 performs code determination based on the correlation detection result, and in step S105, the height determination unit 9 performs height determination based on the correlation detection result.

[0177] Figure 23 This is a graph showing the changes in the frequency band of the complex received signal caused by normalization and phase rotation. Figure 23 In the diagram, the dashed line represents the amplitude of the complex received signal generated by the quadrature detector 61, the double-dash line represents the amplitude of the complex received signal normalized by the normalization unit 65, and the solid line represents the amplitude of the complex received signal after phase rotation by the phase rotation unit 66. Additionally, in... Figure 23 In the middle, f LPF It is the cutoff frequency of LPF612.

[0178] To detect obstacles with complex shapes such as vehicles and fences, it is desirable to shorten the signal width of the output of correlation filters 62, 63, and 64 to improve code determination accuracy and height determination accuracy. This signal width can be shortened by expanding the frequency band of the received signal.

[0179] The microphone used in transducer 41 in the vehicle sensor has a narrow frequency band. That is, when a microphone with such characteristics is used in transducer 41, although the transmit and receive sensitivity is high near the resonant frequency, the transmit and receive sensitivity is low at frequencies far from the resonant frequency.

[0180] Therefore, if the resonant frequency is set to f0, for example, f c If the chirp signal is sent in the manner of f0, then although f c The amplitude of the frequency components near f increases, but the amplitude of the components farther away from f increases. c The amplitude of the frequency components decreases, and only f can be fully utilized across the entire frequency band. c Nearby components. Therefore, as Figure 23 As shown by the dotted line, the actual bandwidth narrows, while the aforementioned signal width becomes longer. Therefore, when detecting obstacles with complex shapes, incorrect code decisions may be made. Furthermore, if based on signals S1 to S... NIf the difference in amplitude between frequencies is large, the results of related detections will be pulled toward the amplitude near the resonant frequency f0, which may lead to misjudgment of the code.

[0181] In contrast, if the received signal is normalized before the relevant detection, so that signals S1 to S2 are normalized... N If the amplitudes are consistent, the influence of the microphone's frequency characteristics can be reduced, such as Figure 23 As shown by the double-dotted line, the bandwidth of the received signal widens. Furthermore, by performing a phase rotation on the normalized complex received signal, as shown by the solid line, the apparent bandwidth widens further. Consequently, the signal width of the correlation output becomes shorter, improving both code determination accuracy and height determination accuracy.

[0182] This embodiment achieves the same effects as the first embodiment because it has the same structure and operation as the first embodiment.

[0183] Furthermore, according to the above-described embodiments, the following effects can be obtained.

[0184] (1) Before correlation detection, the phase of the complex received signal is rotated. As a result, the signal width of the correlation output is shortened, the resolution of the received wave is improved, and thus the accuracy of code determination and height determination is improved.

[0185] (Fifth Implementation)

[0186] The fifth embodiment will be described. This embodiment differs from the first embodiment in that it changes the reference signal, but otherwise remains the same. Therefore, only the parts that differ from the first embodiment will be described.

[0187] like Figure 24 As shown, the second reference signal in this embodiment is composed of a frequency ratio f in the first reference signal. c The lower part constitutes the third reference signal, which is composed of the frequency ratio f in the first reference signal. c The high portion is composed of, that is, the frequencies in the first reference signal removed from both the second and third reference signals, up to f. c The area near the second reference signal is separated from the minimum frequency of the third reference signal by the maximum frequency of the second reference signal.

[0188] This embodiment achieves the same effects as the first embodiment because it has the same structure and operation as the first embodiment.

[0189] Furthermore, according to the above-described embodiments, the following effects can be obtained.

[0190] (1) Make the frequency difference between the second and third reference signals larger than that in the first embodiment. The greater the frequency difference, the greater the difference in directivity, so the accuracy of altitude determination is improved.

[0191] (Other implementation methods)

[0192] Furthermore, this disclosure is not limited to the embodiments described above, and appropriate modifications can be made. Additionally, the above embodiments are not mutually exclusive; they can be appropriately combined, except where it is explicitly stated that they cannot be combined. Furthermore, in each of the above embodiments, the elements constituting the embodiment are not necessarily essential, except for those specifically stated as necessary or those explicitly considered necessary in principle.

[0193] Alternatively, the transducer 41 constituting the transmitting unit 40A and the transducer 41 constituting the receiving unit 40B can be set separately.

[0194] The frequencies of the second reference signal and the third reference signal may also partially overlap.

[0195] In the third to fifth embodiments, the correlation filters 62, 63, and 64 may share the multiplication unit, as in the second embodiment. In the fourth embodiment, the frequency of the reference signal may be corrected, as in the third embodiment. Figure 25 As shown, in the fifth embodiment, the frequency of the reference signal can also be corrected as in the third embodiment. In the fifth embodiment, the complex signal can also be normalized and its phase rotated as in the fourth embodiment.

[0196] like Figure 26 As shown, the bandwidth of the first reference signal can also be narrower than that of the driving signal. The S / N ratio of the components at both ends of the bandwidth in the received signal is lower, so by means of... Figure 26 The part corresponding to the reference signal is removed, thereby improving the accuracy of code determination.

[0197] The second and third reference signals can also partially share the frequency band with the first reference signal. For example, they can also be used. Figure 26 The first reference signal shown, and Figure 24 The second and third reference signals are shown. In this case, similar to the fifth embodiment, the height determination accuracy is also improved.

[0198] like Figure 27 As shown, it can also be modified as in the third embodiment. Figure 26 The frequency of the reference signal.

[0199] like Figure 28 As shown, an FSK signal that alternately repeats a signal at frequency f1 and a signal at frequency f2 can also be used as both the drive signal and the reference signal. FSK is an abbreviation for Frequency Shift Keying. Figure 28 f RThis is the frequency of the first reference signal. In the first embodiment, the correlation filter 62 is composed of two filters, one for upper chirp and one for lower chirp. However, when using such a drive signal, the correlation filter 62 is composed of a single filter. Figure 28 The correlation detection between the first reference signal and the received signal is shown. Furthermore, the second reference signal is composed of the portion of the first reference signal at frequency f1, and the third reference signal is composed of the portion of the first reference signal at frequency f2.

[0200] like Figure 29 As shown, an FSK signal consisting of four frequencies can also be used as both a drive signal and a reference signal. Figure 29 In the middle, the signals with frequency f2 are arranged in sequence, and the frequencies are larger than f1 and larger than f. c Small signals, frequency ratio f c The signal is larger than f2 and smaller than f2, and the signal has a frequency of f1. In this case, for example, the second reference signal is composed of the second and fourth signals of these four signals, and the third reference signal is composed of the first and third signals.

[0201] In the above embodiments, a reference signal output by the drive signal generation unit 5 is used, but a signal that is pre-calculated and recorded to correspond to the settings of the drive signal generation unit 5 may also be used.

[0202] The relevant calculation methods are not limited to vector rotation and summation of the complex received signals based on a reference signal. For example, methods can also be used to convert the complex received signal into a vector with amplitude r and phase θ, and then calculate the phase difference with the reference signal.

[0203] The method for correlation calculation is not limited to converting the received signal into a complex signal using orthogonal detection. For example, it can also be calculated using the correlation function between the received signal and a reference signal. By converting the calculated correlation signal into amplitude, the filter output can be obtained.

[0204] FFT can also be used to calculate related functions. FFT is an abbreviation for Fast Fourier Transform.

[0205] The drive signal generation unit, receive signal processing unit, reference signal processing unit, code determination unit, height determination unit, control unit, and methods described in this disclosure can also be implemented by a dedicated computer provided by a processor programmed to perform one or more functions embodied in a computer program and a memory. Alternatively, the drive signal generation unit, receive signal processing unit, reference signal processing unit, code determination unit, height determination unit, control unit, and methods described in this disclosure can also be implemented by a dedicated computer provided by a processor composed of one or more dedicated hardware logic circuits. Alternatively, the drive signal generation unit, receive signal processing unit, reference signal processing unit, code determination unit, height determination unit, control unit, and methods described in this disclosure can also be implemented by one or more dedicated computers composed of a processor programmed to perform one or more functions, a memory, and a processor composed of one or more hardware logic circuits. Furthermore, the computer program can also be stored as instructions to be executed by the computer on a non-transferable tangible recording medium that can be read by the computer.

Claims

1. An object detection device that detects objects by transmitting and receiving ultrasonic waves, comprising: The transmitting unit sends ultrasonic waves as detection waves. The drive signal generation unit generates a frequency-modulated drive signal for driving the aforementioned transmitting unit. The receiving unit receives ultrasonic waves and generates a receiving signal corresponding to the received ultrasonic waves. The first correlation filter performs correlation detection between the received signal and the first reference signal corresponding to the driving signal, and outputs the correlation signal. The first determination unit determines, based on the correlation signal output by the first correlation filter, whether the ultrasonic wave received by the receiving unit is a reflected wave of the probe wave transmitted by the transmitting unit. The second correlation filter takes the signal corresponding to a portion of the aforementioned driving signal as a second reference signal, performs correlation detection between the received signal and the second reference signal, and outputs the correlation signal. The third correlation filter takes the signal containing the portion of the driving signal with a frequency higher than the second reference signal as the third reference signal, performs correlation detection between the received signal and the third reference signal, and outputs a correlation signal, wherein... The aforementioned third reference signal is a signal corresponding to a portion of the aforementioned drive signal; as well as The second determination unit determines whether an object is within the detection range based on the correlation signal output by the second correlation filter and the correlation signal output by the third correlation filter.

2. The object detection device according to claim 1, wherein, The range of the correlation signal used by the second determination unit in the determination is set based on the correlation signal output by the first correlation filter.

3. The object detection device according to claim 2, wherein, The range of the correlation signal used by the second determination unit in the determination is set based on the time when the correlation signal output by the first correlation filter reaches its peak.

4. The object detection device according to any one of claims 1 to 3, wherein, The aforementioned first correlation filter includes a first correlation calculation unit that calculates the correlation between the received signal and the first reference signal. The second correlation filter described above includes a second correlation calculation unit that calculates the correlation between the received signal and the second reference signal. The aforementioned third correlation filter includes a third correlation calculation unit that calculates the correlation between the received signal and the third reference signal. The aforementioned first correlation calculation unit, the aforementioned second correlation calculation unit, and the aforementioned third correlation calculation unit share the same arithmetic circuit for performing correlation calculations.

5. The object detection device according to any one of claims 1 to 3, wherein, The aforementioned driving signals include an upper chirp signal whose frequency monotonically increases over time, or a lower chirp signal whose frequency monotonically decreases over time.

6. The object detection device according to any one of claims 1 to 3, wherein, The frequency of the first reference signal is corrected according to the speed of the vehicle equipped with the aforementioned transmitting unit and the aforementioned receiving unit.

7. The object detection apparatus according to any one of claims 1 to 3, wherein have: The first phase rotating part rotates the phase of the received signal; and The second phase rotation unit rotates the phases of the first reference signal, the second reference signal, and the third reference signal. The first correlation filter, the second correlation filter, and the third correlation filter respectively perform correlation detection between the received signal after phase rotation by the first phase rotation unit and the first reference signal, the second reference signal, and the third reference signal after phase rotation by the second phase rotation unit.

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