Object detection device

Abstract

Object detection device mounted on a vehicle for detecting an object outside the vehicle, wherein the object detection device comprises: a transmitting / receiving device (1) configured to transmit an ultrasonic wave as a probe wave, wherein the ultrasonic wave contains an identification code to distinguish between the ultrasonic wave and ultrasonic waves transmitted by other devices, to receive an ultrasonic wave and to output a signal responsive to the received wave, a first filter (5, 6) and a second filter (5, 7) configured to filter the output signal of the transmit / receive device, wherein the first filter and the second filter have different characteristics, an amplitude detection device (10) configured to detect a reflected wave based on amplitude information contained in an output signal of the first filter, and a signal determination device (11) configured to determine, based on identification code information contained in an output signal of the second filter, whether the received wave is a reflected wave of the probe wave or not, wherein The bandwidth of the first filter is narrower than that of the second filter.

Description

BACKGROUND Technical area

[0001] The present disclosure relates to an object detection device. Related technology

[0002] An object detection device to be mounted on a vehicle for detecting obstacles by transmitting and receiving ultrasonic waves, as disclosed in EP 2 373 434 B1, uses a known technique which changes the frequency of a probe wave over time and compares the frequency of the probe wave with frequencies of received waves, thereby avoiding interference between ultrasonic waves transmitted by the vehicle carrying the device and other vehicles moving around the vehicle carrying the device.

[0003] However, the object detection device disclosed in EP 2 373 434 B1 uses a resonant microphone to transmit and receive ultrasonic waves. With such an object detection device, the waveform of a received signal can vary in a manner similar to that of the probe wave at the start and end times of reception. Therefore, a method of identifying received waves solely by frequency comparison can be subject to a reduction in object detection accuracy.

[0004] The inventors have demonstrated that detecting peaks in the amplitude of a received wave based on gradients or similar characteristics of the amplitude of the received wave, and comparing frequencies of the probe wave and the received wave within a time range at each peak value of the amplitude or close to it, can improve the identification accuracy of the received wave.

[0005] An amplitude waveform generated from the received signal is used to capture the propagation time and peak amplitude of the ultrasonic wave. When generating the amplitude waveform, it is desirable to use a narrow bandwidth (BW) filter to reduce the influence of superposition from noise and multiple ultrasonic waves.

[0006] Meanwhile, a frequency waveform generated from the received signal is used to compare the frequencies of the probe wave and the received wave. When generating the frequency waveform, it is desirable to use a wide-bandwidth (BW) filter to reduce the loss of frequency modulation information. To further reduce the loss of frequency information, it is desirable to use a filter that complements the frequency response of the resonant microphone. Similarly, when changing the phase or amplitude, rather than the frequency, to transmit a probe wave, and when comparing phase change patterns or similar characteristics of the probe wave and the received wave, it is desirable to use a wide-band BW filter.

[0007] Accordingly, if the amplitude waveform used to detect amplitude peaks and the frequency waveform used to compare frequency change patterns are generated using the same filter, the detection accuracy of either the peaks or the amplitude pattern may decrease. Such a reduction in detection accuracy can lead to a decrease in the detection accuracy of the received waves. There is room for improvement in the identification accuracy of the received waves.

[0008] From DE 101 06 142 A1, a method for operating an ultrasonic multisensor array, in particular a parking aid for a motor vehicle, is also known. The multisensor array comprises at least two transmitter units arranged along the circumference of the motor vehicle for emitting ultrasonic pulses into a monitoring area and at least one receiver unit for receiving ultrasonic pulses reflected from an object in the monitoring area. Several transmitter units can be operated in parallel and simultaneously emit ultrasonic pulses coded to each other. It is proposed that, for encoding purposes, the carrier signals of the ultrasonic pulses for the individual simultaneously operated transmitter units are frequency-modulated differently, at least during the pulse duration, and that the received coded ultrasonic pulses are assigned by the at least one receiver unit to the individual simultaneously operated transmitter units based on the encoding. Brief description

[0009] The object of the present invention is to provide an object detection device that can increase the identification accuracy of a received wave.

[0010] The problem is solved by the subject matter of the main claim. Advantageous further developments are specified in the dependent claims.

[0011] According to the invention, the first and second filters are each associated with the amplitude determination device and the signal determination device, respectively, which enables the generation of amplitude information and identification code information using filters whose characteristics are suitable for the intended application. Accordingly, this configuration can increase the detection accuracy of amplitude and identification code peaks and thereby improve the identification accuracy of the received wave. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the accompanying drawings: is Fig. 1 a block diagram of an object detection device according to a first embodiment, is Fig. 2 a block diagram of a receiving circuit, is Fig. 3. A block diagram of a signal processing device, is Fig. 4. An example of filter characteristics with different BWs, is Fig. 5. An example of filter characteristics with different Q values, is Fig. 6 a block diagram of an amplitude generation device and an amplitude determination device, is Fig. 7 a block diagram of a frequency generation device, is Fig. 8. An example of an amplitude waveform and a frequency waveform based on a comparison example. is Fig. 9 an example of an amplitude waveform and a frequency waveform according to the first embodiment, Fig. 10 is an example of filter characteristics according to another embodiment and Fig. Figure 11 is an example of filter characteristics according to yet another embodiment. DESCRIPTION OF SPECIFIC EXECUTION FORMS

[0013] With reference to the accompanying drawings, several embodiments of the present invention are described below. Essentially common elements or steps in the embodiments are designated with the same numbers and are not described redundantly. First embodiment

[0014] A first embodiment is now described. An object detection device of the present embodiment is an ultrasonic sonar device. The object detection device is mounted on a vehicle and detects an object outside the vehicle.

[0015] As in Fig. As shown in Figure 1, the object detection device includes a microphone 1, a transmission circuit 2, a signal generation device 3, and a control device 4. The object detection device also includes a receiving circuit 5, a signal processing device 6, a signal processing device 7, an amplitude generation device 8, an amplitude determination device 9, a frequency generation device 10, and a signal determination device 11.

[0016] The control device 4, the signal processing device 6, and the like are configured as a known microcomputer containing a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), an I / O unit, and the like, and perform various types of processing, such as arithmetic processing, according to programs stored in the ROM or similar. The ROM and RAM can be tangible, non-temporary, computer-readable media. The control device 4, or similar, can be configured as an application-specific integrated circuit (ASIC) containing a signal processing circuit.

[0017] The object detection device includes, for example, microphone 1 and a plurality of sensors located on various parts of the vehicle, as well as the CPU (i.e., a processor) of the ECU. Elements that are in Fig. The components shown in 1, with the exception of microphone 1, can be located in the sensors or in the processor.

[0018] Microphone 1 is configured to transmit and receive ultrasonic waves and output signals corresponding to the received waves. Microphone 1 serves as a transmit / receive device. It is mounted on an exterior surface of the vehicle and transmits ultrasonic waves, which are probe waves for detecting objects, towards the vehicle's exterior. Specifically, microphone 1 incorporates a piezoelectric element (not shown) containing a piezoelectric layer positioned between two opposing electrodes.

[0019] The two electrodes are connected to the transmission circuit 2. When an alternating current (AC) voltage is applied by the transmission circuit 2 and the piezoelectric layer deforms or changes its shape, ultrasonic waves are transmitted from the microphone 1 to the outside of the vehicle.

[0020] The transmission circuit 2 amplifies an input signal and outputs the amplified signal. The signal generator 3, which generates a pulse signal, is connected to the transmission circuit 2. The transmission circuit 2 converts a pulse signal input from the signal generator 3 into an alternating current signal, amplifies it, and then applies its alternating voltage to the microphone 1.

[0021] The signal generator 3 produces a pulse signal with an identification code for identifying an ultrasonic wave in response to a wave transmission instruction from the control device 4. This identification code is intended to identify a reflected wave of a probe wave transmitted by the microphone 1 and ultrasonic waves transmitted by other object detection devices. Identifying a received wave using such an identification code enables simultaneous measurement at multiple microphones, which can lead to increased measurement reliability and reduce the measurement cycle time.

[0022] The identification code represents a pattern of amplitude, frequency, phase, or similar characteristics. The signal generation device 3 of the present embodiment generates a pulse signal containing a chirp signal whose frequency changes over time in a predetermined pattern. Thus, a probe wave, which is an ultrasonic wave with a chirp signal whose frequency changes over time in a predetermined pattern, is transmitted from the microphone 1.

[0023] Chirp signals contain an upward chirp signal, represented by the code '0', and a downward chirp signal, represented by the code '1'. The upward chirp signal is a signal whose frequency increases over time. The downward chirp signal is a signal whose frequency decreases over time.

[0024] The two electrodes of the piezoelectric element contained in microphone 1 are also connected to the receiver circuit 5. A voltage generated between the two electrodes when the piezoelectric layer changes upon receiving an ultrasonic wave through microphone 1 is fed into the receiver circuit 5.

[0025] The receiving circuit 5 performs processing, such as amplification, noise reduction, and A / D conversion, on an output signal from the microphone 1. As in Fig. As shown in Figure 2, the receiving circuit 5 includes a DC distance device 12, a terminal protection circuit 13, an amplifier 14 and a bandpass filter (BPF) 15, an amplifier 16, and an A / D converter (ADC) 17. The output signal of the microphone 1 is fed into the DC distance device 12.

[0026] The DC removal device 12 is configured to remove an offset component from the output signal of microphone 1 to protect the subsequent stage from excessive DC current. The DC removal device 12 includes a low-pass filter (LPF) and a high-pass filter (HPF) with fixed characteristics. An output signal from the DC removal device 12 is fed into the terminal protection circuit 13.

[0027] The terminal protection circuit 13 is configured to define an upper limit for the signal size, thereby protecting the subsequent stage from excessively large inputs. An output signal from the terminal protection circuit 13 is amplified by the amplifier 14 and then fed into the BPF 15.

[0028] The BPF 15 is an analog filter for removing noise from input signals. The BPF 15 can be configured as a combination of an LPF and an HPF. The characteristic of the BPF 15 can complement the frequency characteristic of the microphone 1. The center frequency, bandwidth, and complementary characteristic of the BPF 15 are variable and can be set by an input signal from the control unit 4. The output signal of the BPF 15 is amplified by the amplifier 16, converted into a digital signal by the ADC 17, and then fed into the signal processing units 6 and 7. The gain of the amplifier 16, the sampling rate of the ADC 17, and a reference clock for measuring propagation delay are set by an input signal from the control unit 4.

[0029] The receiving circuit 5 can have a different configuration. For example, a plurality of amplifiers 16 can be provided, or the amplifier 16 can be followed by the BPF 15.

[0030] Each of the signal processing units 6 and 7 is configured to perform processing, such as amplification or noise reduction, on an output signal from the receiving circuit 5. Signal processing unit 6 serves as the first filter, and signal processing unit 7 serves as the second filter. As shown in Fig. As shown in Figure 3, the signal processing unit 6 contains a BPF 18 and an amplitude offset correction unit 19.

[0031] The BPF 18 is a digital filter for removing noise from input signals. The BPF 18 complements the frequency response of microphone 1. The center frequency, bandwidth, and complementary characteristics of the BPF 18 can be varied and set by an input signal from the control unit 4. An output signal from the BPF 18 is fed into the amplitude offset correction unit 19.

[0032] The amplitude offset correction device 19 is configured to amplify an input signal from the BPF 18 and to correct an amplitude offset. The gain and the magnitude of the amplitude offset correction of the amplitude offset correction device 19 are set by an input signal from the control device 4. An output signal from the amplitude offset correction device 19 is fed into the amplitude generation device 8.

[0033] As in Fig. As shown in Figure 3, the signal processing unit 7 contains a BPF 20 and an amplitude offset correction unit 21. The amplitude offset correction unit 21 of the signal processing unit 7 has a similar configuration to the amplitude offset correction unit 19 of the signal processing unit 6.

[0034] The BPF 20 of signal processing unit 7 has a characteristic that differs from that of the BPF 18 of signal processing unit 6. More specifically, the bandwidth of BPF 20 is larger than that of BPF 18. For example, BPFs 18 and 20 are biquadratic filters with the same center frequency, as shown in Fig. As shown, the BW of the BPF 20 can be larger than that of the BPF 18, or as in Fig. As shown, the BPF 20 has a larger inverse characteristic than the BPF 19, which complements the frequency characteristic of microphone 1.

[0035] In the Fig. A dashed line indicates a threshold value that defines the gain of each filter. A passband of the filter is a region where the gain is above the threshold value. The characteristic of each of the BPFs 18 and 20 is set such that the majority of frequencies in a region where the frequency of the probe wave changes fall within the passband of the filter.

[0036] When the complementary characteristic of the filter is increased to obtain an M-shaped gain curve, signals with certain frequencies are amplified. The synthesis of the filter characteristic and the characteristic of microphone 1, as shown in Fig. As shown, this can reduce signal amplification. As in Fig. As shown in Figure 5, the characteristic of each of the BPFs 18, 20 is set such that the majority of the frequencies of the range in which the frequency of the probe wave changes falls into a passband of the synthesized property of filter and microphone 1.

[0037] The signal, which is input from the receiving circuit 5 into the signal processing unit 7, is processed by the BPF 20 to have an amplitude offset amplified and corrected by the amplitude offset correction unit 21 and then input into the frequency generation unit 10.

[0038] As in Fig. As shown in Figure 6, the amplitude generation device 8 includes an amplitude converter 22 and a low-pass filter (LPF) 23. The amplitude converter 22 extracts amplitude information from an output signal of the signal processing device 6 and generates an amplitude waveform of the received wave. The amplitude waveform generated by the amplitude converter 22 is smoothed by the LPF 23 and then fed into the amplitude determination device 9. A characteristic of the LPF 23 is set by an input signal from the control device 4.

[0039] The amplitude determination device 9 measures a travel time and an amplitude value of the reflected wave based on the amplitude waveform generated by the amplitude generation device 8. As in Fig. As shown in Figure 6, the amplitude determination device 9 includes a threshold determination device 24, a timer 25 and a peak detection device 26.

[0040] The threshold determination device 24 determines whether the amplitude of the received wave is greater than a predetermined amplitude threshold, based on the amplitude waveform generated by the amplitude generation device 8. The amplitude threshold is set by an input signal from the control device 4. The threshold determination device 24 measures a wavelength of the amplitude waveform.

[0041] A result of the determination, which is carried out by the threshold determination device 24, is entered into the timer 25 and the peak detection device 26. The timer 25 measures a transit time, which is the time interval from the transmission of a probe wave from the microphone 1 until the threshold determination device 24 determines the amplitude of the received wave that is greater than the amplitude threshold, and then outputs a measurement result to the control device 4.

[0042] The peak detection device 26 is configured to detect the amplitude of the received wave. The peak detection device 26 receives a determination result from the amplitude determination device 25 and the amplitude waveform generated by the amplitude generation device 8 via the amplitude determination device 25, and thereby detects peaks of the amplitude of the received wave from the amplitude waveform.

[0043] For example, the peak detection device 26 captures a portion of the amplitude waveform where the absolute value of a gradient of the amplitude waveform is equal to or less than a predetermined value, and is thus identified as the peak of the amplitude. The peak detection device 26 calculates a residual sum of squares between a reference waveform stored in the control device 4 and the amplitude waveform of the received wave, and captures a portion of the amplitude waveform as the peak of the amplitude when the residual sum of squares is equal to or less than a predetermined value.

[0044] The peak detection device 26 measures a peak amplitude value that is greater than the amplitude threshold. The peak detection device 26 sends a result of the amplitude peak detection, the peak amplitude value, the result of the determination by the amplitude determination device 25, the wavelength and other data to the control device 4.

[0045] As in Fig. As shown in Figure 7, the frequency generation unit 10 includes a phase-difference converter 27 and a frequency converter 28. The phase-difference converter 27 mixes a pulse signal generated by the signal generation unit 3 and an input signal from the signal processing unit 7 to extract phase difference information from the input signal. The phase difference information is fed into the signal determination unit 11 and the frequency converter 28. A reference clock, which the phase-difference converter 27 uses for conversion, is supplied by the control unit 4.

[0046] The frequency converter 28 calculates a frequency of the received wave based on the frequency of the pulse signal generated by the signal generation unit 3 and the phase difference input of the phase difference converter 27, thus generating a frequency waveform. The frequency waveform generated by the frequency converter 28 is transmitted to the signal detection unit 11.

[0047] The signal determination device 11 is configured to determine, based on code information contained in the output signal of the signal processing device 7, whether the received wave is a reflected wave of the probe wave or not. As described above, the signal generation device 3 of the present embodiment generates a pulse signal whose frequency changes over time, as indicated in the identification code. If a frequency change pattern corresponding to the identification code is detected from the frequency waveform, the signal generation device 11 determines that the frequency waveform of the received wave contains the same identification code as the transmitted wave.

[0048] For example, reference waveforms corresponding to code '0' and code '1' are input from the control unit 4 into the signal determination unit 11. The signal determination unit 11 calculates a residual sum of squares between each of the reference waveforms and the frequency waveform of the received wave. If the residual sum of squares between the reference waveform corresponding to code '0' and the frequency waveform of the received wave is equal to or less than a predetermined threshold, the signal determination unit 11 determines that the frequency waveform of the received wave contains code '0'. If the residual sum of squares between the reference waveform corresponding to code '1' and the frequency waveform of the received wave is equal to or less than the predetermined threshold, the signal determination unit 11 determines that the frequency waveform of the received wave contains code '1'.

[0049] For example, reference waveforms corresponding to code '0' and code '1' are input from the controller 4 into the signal identification device 11. If a frequency change pattern similar to the frequency change pattern of code '0' is detected in the frequency waveform, the signal identification device 11 determines that the frequency waveform of the received wave contains code '0'. If a frequency change pattern similar to the frequency change pattern of code '1' is detected in the frequency waveform, the signal identification device 11 determines that the frequency waveform of the received wave contains code '1'.

[0050] Poor responsiveness of microphone 1 to the input signal can lead to a frequency difference between a pulse signal generated by the signal generation device 3 and a signal output by microphone 1 upon receiving a reflected wave of the probe wave. More precisely, when microphone 1 receives a reflected wave of the probe wave, the frequency of microphone 1's output signal changes over time similarly to the pulse signal, having initially changed inversely or more slowly than the pulse signal. Thus, the frequency of a reference frequency waveform or frequency change pattern input by the control device 4 to the signal determination device 11 changes over time in the manner described above.

[0051] The result of the amplitude peak detection is transmitted from the amplitude determination device 9 to the signal determination device 11. When an amplitude peak of the received wave is detected from the amplitude waveform of the received wave, the signal determination device 11 recognizes an identification code. For example, if a residual sum of squares between the frequency waveform of the received wave and the reference waveform reaches or falls below a predetermined value within a predetermined time range, including the time during which the amplitude peaks occur, the signal determination device 11 determines that the received wave contains the identification code corresponding to the reference waveform, and then a result of the determination performed by the signal determination device 11 is transmitted to the control device 4.

[0052] The control unit 4 determines, based on information transmitted by the amplitude determination unit 9 and the signal determination unit 11, whether an object is present within a detection range. Upon receiving a result of this determination, the control unit 4 sends a notification to the vehicle's driver. For example, in response to a detection distance, the control unit 4 sets a detection duration. If, within this duration, the threshold determination unit 24 determines that the amplitude is greater than the amplitude threshold, and the signal determination unit 11 determines that the received wave is a reflected wave of the probe wave, the control unit 4 determines that an object is within the detection range.

[0053] The amplitude determination device 9 and the signal determination device 11 measure the delay times of the respective signal processing devices 6, 7, and similar components and transmit these to the control device 4. The delay time of each filter varies with the BW (signal processing unit) and the Q-value, etc., which can lead to a delay time difference between BPF 18 and BPF 20. Thus, the control device 4, which selects information to be used for determination in response to a difference between the delay times, can increase the determination accuracy.

[0054] The operation of the object detection device will now be described. After the control unit 4 sends a transmission instruction to the signal generation unit 3, the signal generation unit 3 initiates the generation of a pulse signal. The transmission circuit 2 converts the pulse signal generated by the signal generation unit 3 into an alternating current signal, and the transmission circuit 2 applies an alternating voltage to the microphone 1, so that a probe wave is transmitted from the microphone 1. The pulse signal that the signal generation unit 3 generates in response to the transmission instruction from the control unit 4 contains a frequency change pattern that corresponds to an identification code for identifying an ultrasonic wave. Thus, a probe wave with the identification code is transmitted from the microphone 1.

[0055] Subsequently, the control unit 4, which sends a reception instruction to the signal processing units 6, 7, the receiving circuit 5 and the signal processing units 6, 7, performs processing, such as amplification, filtering, A / D conversion and the like, on an output signal from the microphone 1. Thus, an amplitude waveform and a frequency waveform are generated by the amplitude generation unit 8 and the frequency generation unit 10, respectively.

[0056] The BPF 18 of the signal processing unit 6 has a narrow bandwidth, which allows the signal processing unit 6 to remove a significant amount of noise and thus prevent distortion of the amplitude waveform generated by the amplitude generation unit 8. The BPF 20 of the signal processing unit 7 has a wide bandwidth, which allows the signal processing unit 7 to reduce the loss of frequency information and thus facilitate the recognition of an identification code from the frequency waveform generated by the frequency generation unit 10.

[0057] When the waveforms are generated by the amplitude generation unit 8 and the frequency generation unit 10, the amplitude determination unit 9 compares the amplitude of the received wave with the amplitude threshold, and then the signal determination unit 11 identifies the received wave. Based on the determination results of the amplitude determination unit 9 and the signal determination unit 11, the control unit 4 determines whether an object is present within a detection range and notifies the vehicle driver upon receiving a determination result from the control unit 4. The object detection device repeatedly performs this ultrasonic wave transmission and reception processing.

[0058] In a configuration where, for example, a common and wide filter is used in both signal processing for amplitude waveform generation and signal processing for frequency waveform generation, an amplitude waveform and a frequency waveform are generated from a signal with many high-frequency components. In such a configuration, an identification code can be easily recognized from the frequency waveform. However, the amplitude waveform can be distorted by the presence of noise, so that multiple peaks can be detected, which can reduce the recognition accuracy of the identification code.

[0059] For example, assuming that, as in Fig. As shown in Figure 8, if two peaks of the amplitude are detected within a time interval in which the amplitude is large, processing is performed to detect an identification code for each of the two peaks of the frequency waveform. For example, if a probe wave is transmitted with a downward chirp signal corresponding to the identification code "1", not only a downward chirp signal corresponding to the identification code "1" but also an upward chirp signal corresponding to the identification code "0" can be detected from the received wave with a reflected wave. In the lower diagram of Fig. Figure 8 shows the dashed, dotted line as a reference waveform corresponding to the downward chirp signal and the dashed, two-dotted line as a reference waveform corresponding to the upward chirp signal.

[0060] Conversely, reducing the filter's bandwidth can reduce distortion of the amplitude waveform. However, it can become difficult to derive an identification code from the frequency waveform.

[0061] In the present embodiment, separate filters, i.e., BPFs 18 and 20, are used in the signal processing for amplitude waveform generation and in the signal processing for frequency waveform generation, with the bandwidth of BPF 18 being set narrower than that of BPF 20. This configuration can reduce distortions of the amplitude waveform caused by noise.

[0062] With this configuration, as in Fig. As shown, a single peak of the amplitude is captured within a time interval in which the amplitude of the received wave is large. For example, with a probe wave transmitted with a downward chirp signal corresponding to the identification code "1", only a downward chirp signal corresponding to the identification code "1" is captured from the received wave, including any reflected wave. In the lower diagram of Fig. Figure 9 shows the dashed dotted line as a reference waveform that corresponds to the downward chirp signal.

[0063] Additionally, a wide bandwidth of the BPF 20 facilitates the capture of an identification code from the frequency waveform.

[0064] As described above, in the present embodiment, separate filters are used in the signal processing for amplitude waveform generation and in the signal processing for frequency waveform generation, so that the characteristics of each filter are suitable for generating the amplitude waveform and for generating the frequency waveform, respectively. This configuration can increase the detection accuracy of an amplitude peak and an identification code of the received wave, and thus improve the detection accuracy of the received wave. Modifications

[0065] The present invention is not limited to the foregoing embodiment, but can be appropriately modified within the scope of the claims.

[0066] In an alternative embodiment, the microphone 1 can contain a microphone for transmitting and a microphone for receiving.

[0067] In the first embodiment, a transit time is measured using a time at which the amplitude exceeds the amplitude threshold. In an alternative embodiment, a transit time can be measured using a time at which the amplitude reaches its peak. In such an embodiment, a limitation of the BW of the BPF 18 can prevent a reduction in the measurement accuracy of the transit time that may be caused by distortions of the amplitude waveform, which can be caused by noise.

[0068] In the first embodiment, the signal processing units 6, 7, which serve as first and second filters respectively, are connected to the receiving circuit 5. In an alternative embodiment, two receiving circuits 5 can be provided, one of which is connected to the signal processing unit 6 and the other to the signal processing unit 7. In a further alternative embodiment, the receiving circuit 5 can contain the signal processing units 6, 7, so that the receiving circuit 5 contains two BPFs 15, each with different characteristics corresponding to the characteristics of the respective signal processing units 6, 7.

[0069] In the first embodiment, the characteristics of the BPFs 15, 18, 20 are set by input signals from the control unit 4. In an alternative embodiment, these characteristics can be fixed.

[0070] In the first embodiment, each identification code corresponds to a different chirp signal whose frequency changes over time. In an alternative embodiment, each identification code can correspond to a different probe wave modulated by a different modulation type. For example, amplitude shift keying, which changes the amplitude, or phase shift keying, which changes the phase, can be used. On / off keying or similar functions can be used as amplitude shift keying. Binary phase shift keying with phases of 0° and 180° or quadrature phase shift keying with phases of 0°, 90°, 180°, and 270° can be used as phase shift keying. In a further embodiment, a plurality of frequencies can be selected from the resonant band of microphone 1, and each of the selected frequencies can be assigned a different code.

[0071] In an alternative embodiment, the properties of the BPFs 18, 20 can be adjusted in response to an identification code contained in a pulse signal generated by the signal generation device 3, so that the properties of these filters are suitable for the frequencies represented by the identification code. This configuration can increase the detection accuracy.

[0072] In an alternative embodiment, both the first filter and the second filter can contain LPF instead of BPF, or HPF instead of BPF. In another alternative embodiment, as in Fig. As shown in Figure 10, the first filter and the second filter can contain the LPF and the HPF respectively, or vice versa, instead of the BPF. Fig. The low-pass filter (LPF) indicated by the solid line forms the first filter. The high-pass filter (HPF) indicated by the dashed / dotted line forms the second filter. Increasing the Q value of each LPF and HPF can provide complementary characteristics to the frequency response of microphone 1, as shown by the dashed / dotted line in [reference]. Fig. This shows that in an alternative embodiment, the Q-value of the LPF and the HPF can be increased.

[0073] In such an embodiment, where the LPF and the HPF are combined as described above, the cutoff frequency of one or both of the filters, LPF and HPF, can be changed. Each of the filters, first filter and second filter, can be configured as a combination of one or both, or of the LPF and the HPF with the BPF. In an alternative embodiment, the BPF and a notch filter can be combined to complement the characteristics of microphone 1.

[0074] In an alternative embodiment, the BPF 18, 20 can be configured not to have complementary characteristics to the frequency characteristic of the microphone 1, or only the BPF 20 can be configured to have a complementary characteristic to the frequency characteristic of the microphone 1.

[0075] In the first embodiment, the control unit 4 selects information that is used to perform a determination in response to a difference between the delay times. In an alternative embodiment, the timing of the transmission of a determination result from the amplitude determination unit 9 or the signal determination unit 11 to the control unit 4 can be adjusted in response to the difference between the delay times.

[0076] The frequency of a reflected wave is Doppler-shifted as a function of the relative velocity of an object relative to microphone 1. The signal detection device 11 can be configured to measure the magnitude of the Doppler shift and correct the filter characteristics based on this magnitude.

[0077] For example, the magnitude of the inverse characteristics of BPF 18, 20 can be changed in response to the magnitude of the Doppler shift. In an alternative embodiment, the BW of BPF 18 can be changed in response to the magnitude of the Doppler shift. More specifically, BW1 = BW0 + f shift , where BW0 and BW1 represent BWs before and after the correction, respectively, and f shift This represents the magnitude of the Doppler shift. Such a change in the BW (Body Value) can reduce the influence of the Doppler shift on the amplitude determination. In a further alternative embodiment, the BW of the BPF 20 can be changed in response to the magnitude of the Doppler shift.

[0078] In an alternative embodiment, the center frequency of the BPF 18 can be changed in response to the magnitude of the Doppler shift. More specifically, f c1 = f c0 + f shift, where fc0 and fc1 represent the center frequency of BPF 18 before and after correction, respectively. Such a change in the center frequency of BPF 18 can prevent the attenuation of the amplitude waveform due to an offset between the frequency of the received wave and a bandwidth of BPF 18, and thus increase the measurement accuracy of the amplitude of the received wave. In another alternative embodiment, the center frequency of BPF 20 can be changed in response to the magnitude of the Doppler shift. In yet another alternative embodiment, both the center frequency and the bandwidth of each of BPFs 18 and 20 can be changed.

[0079] The timing of the changes in the characteristics BPFS 18, 20 in response to the magnitude of the Doppler shift can be immediately after the signal determination device 11, which determines that the received wave is a reflected wave of the probe wave. This timing can be after the control device 4 has determined that an object is within a detection range and before the subsequent probe wave is transmitted.

[0080] The most recently measured Doppler shift magnitude at a given time, or the average of multiple previously measured Doppler shift magnitudes, can be used as the Doppler shift magnitude, which is a measure of the correction magnitude of the filter characteristics. In an alternative embodiment, a relative velocity of the object with respect to the vehicle can be calculated based on the history of multiple past measured distances, a measurement cycle period, a vehicle speed, and similar parameters. The Doppler shift magnitude can then be estimated based on this calculated relative velocity.

[0081] In an alternative embodiment, the amplitude detection device 9 and the signal detection device 11 can measure the background noise and, if the magnitude of the background noise is greater than a predetermined noise level, narrow the bandwidth or reduce the complementary characteristic of each of the BPFs 18, 20. Conversely, if the magnitude of the background noise is equal to or less than a predetermined noise level, the bandwidth can be reduced. Furthermore, in such an alternative embodiment, the amplitude detection device 9 and the signal detection device 11 can narrow the bandwidth and reduce the complementary characteristic of each of the BPFs 18, 20. In another alternative embodiment, the frequency generation device 10 can detect the background noise frequency. The amplitude detection device 9 and the signal detection device 11 can narrow the bandwidth of each of the BPFs 18, 20 to avoid the detected background noise frequency.This configuration can increase the noise reduction rate and prevent a reduction in the determination accuracy of the amplitude determination device 9 caused by noise.

[0082] The noise threshold can be set in response to a noise level measured by monitoring the output signal of microphone 1 before the object detection processing begins. In an alternative embodiment, the signal determination device 11 can monitor the degree of matching between the frequency waveform of the received wave and the frequency pattern represented by the ultrasonic wave identification code and set the noise threshold in response to the background noise level when the degree of matching is equal to or less than a predetermined value.

Claims

[1] Object detection device mounted on a vehicle for detecting an object outside the vehicle, wherein the object detection device comprises: a transmitting / receiving device (1) configured to transmit an ultrasonic wave as a probe wave, wherein the ultrasonic wave contains an identification code to distinguish between the ultrasonic wave and ultrasonic waves transmitted by other devices, to receive an ultrasonic wave and to output a signal responsive to the received wave, a first filter (5, 6) and a second filter (5, 7) configured to filter the output signal of the transmit / receive device, wherein the first filter and the second filter have different characteristics, an amplitude detection device (10) configured to detect a reflected wave based on amplitude information contained in an output signal of the first filter, and a signal determination device (11) configured to determine, based on identification code information contained in an output signal of the second filter, whether the received wave is a reflected wave of the probe wave or not, wherein The bandwidth of the first filter is narrower than that of the second filter. [2] Object detection device according to claim 1, wherein the amplitude determination device or the signal determination device is configured to correct a delay time difference between the first filter and the second filter caused by a difference in characteristics between them. [3] Object detection device according to claim 1 or 2, wherein one or both of the bandwidths, bandwidth of the first filter and bandwidth of the second filter, are changed based on the magnitude of a Doppler shift of the reflected wave with respect to the probe wave. [4] Object detection device according to one of claims 1 to 3, wherein one or both of the center frequencies, center frequency of the first filter and center frequency of the second filter, are changed on the basis of an amount of a Doppler shift of the reflected wave with respect to the probe wave. [5] Object detection device according to claim 3 or 4, wherein the magnitude of a Doppler shift is estimated based on a relative velocity of the object with respect to the vehicle. [6] Object detection device according to any one of claims 1 to 5, wherein when the noise quantity greater than a predetermined value is measured, one or both of the bandwidths, bandwidth of the first filter and bandwidth of the second filter, become narrower compared to before the noise quantity greater than the predetermined value is measured. [7] Object detection device according to any one of claims 1 to 6, wherein the second filter has a complementary characteristic to a frequency characteristic of the transmitting / receiving device, and the first filter has a lower complementary characteristic to the frequency characteristic of the transmitting / receiving device than the second filter. [8] Object detection device according to claim 7, wherein one or both of the complementary characteristics, complementary characteristic of the first filter and complementary characteristic of the second filter, are changed in their magnitude based on the magnitude of a Doppler shift of the reflected wave with respect to the probe wave. [9] Object detection device according to claim 8, wherein the magnitude of a Doppler shift is estimated based on a relative velocity of the object with respect to the vehicle. [10] Object detection device according to one of claims 7 to 9, wherein when the noise quantity which is greater than a predetermined value is measured, one or both of the complementary characteristics, complementary characteristic of the first filter and complementary characteristic of the second filter, are reduced compared to before the noise quantity which is greater than the predetermined value is measured.

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