Object detection system and object detection device

Abstract

To increase the distinctiveness of transmitted waves.SOLUTION: An object detection system as an example of the present disclosure includes a plurality of object detection devices arranged at a predetermined interval. Each of the plurality of object detection devices comprises: a transmission unit that transmits, at approximately the same time as other object detection devices, a transmission wave in which frequency modulation based on an initial signal of a frequency pattern that produces an amplitude greater than or equal to a predetermined value in a predetermined period, and a frequency modulation based on a plurality of chirp signals that vary in a frequency pattern different from the initial signal, including adjacent object detection devices, is applied in a mutually different manner; a reception unit that receives a reception wave as the returned transmission wave in response to reflection by the object; and a detection processing unit that detects information about the object on the basis of information acquired as a result of transmission and reception of the transmission wave and the reception wave.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an object detection system and an object detection device.

Background Art

[0002] Conventionally, a technique is known in which ultrasonic waves are transmitted as transmission waves, and reception waves as the transmission waves reflected by an object and returned are received, thereby detecting information about the object, such as the distance to the object.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology as described above, a system in which a plurality of object detection devices for detecting information about an object may be realized. In such a system, in order to detect information about an object in more detail, transmission waves may be transmitted substantially simultaneously (simultaneously and in parallel) from each of the plurality of object detection devices. In this case, in order to suppress interference and the like, it is desirable to enhance the discriminability of the transmission waves.

[0005] Therefore, one of the problems of the present disclosure is to provide an object detection system and an object detection device capable of enhancing the discriminability of transmission waves.

Means for Solving the Problems

[0006] An object detection system as an example of the present disclosure includes a plurality of object detection devices arranged at a predetermined interval. Each of the plurality of object detection devices is based on an initial signal having a frequency pattern in which an amplitude equal to or greater than a predetermined value is obtained in a predetermined period, followed by frequency modulation, and then a plurality of chirp signals that change in a frequency pattern different from the initial signal. As a combination of a first chirp signal with a monotonically increasing frequency and a second chirp signal with a monotonically decreasing frequency Transmits, substantially simultaneously with other object detection devices, a transmission wave subjected to frequency modulation such that the frequency modulation based on the chirp signal is performed in different manners including adjacent object detection devices. Having directivity within a predetermined range A transmission unit, Among the transmitted waves transmitted to a predetermined range A reception unit that receives a reception wave as a transmission wave returned in response to reflection by an object. Having directivity And a detection processing unit that detects information about an object based on the transmission wave, the reception wave, and information obtained as a result of transmission and reception of the transmission wave and the reception wave. According to this configuration, for example, after the transmission wave is modulated to a predetermined amplitude or more, modulation based on the chirp signal is performed. At this time, frequency modulation in different manners is performed among adjacent object detection devices. As a result, since it is modulated to a predetermined amplitude or more, from the beginning of the frequency modulation based on the chirp signal in the reception wave, the discrimination effect based on the chirp signal can be effectively utilized, and the signal-to-noise ratio can be improved. In addition, by performing frequency modulation in different manners among adjacent object detection devices, the discriminability of the transmission wave (reception wave) can be enhanced. Also, for example, the discriminability of the transmitted wave (received wave) can be easily enhanced by two chirp signals with simple waveforms.

[0008] Further, the transmission unit of the object detection system described above may perform, for example, frequency modulation based on a chirp signal so that each of the plurality of object detection devices changes in all different frequency patterns. According to this configuration, for example, the discriminability of the plurality of object detection devices can be further improved.

[0009] Further, the initial signal of the object detection system described above may perform, for example, frequency modulation that becomes the resonance frequency of the microphone of the object detection device. According to this configuration, for example, it is possible to transmit a transmission wave based on a chirp signal in a state where the amplitude of the transmission wave is efficiently increased, and it is possible to effectively improve the signal-to-noise ratio due to coding gain.

[0010] As an example of the present disclosure, an object detection device includes a plurality of chirp signals that change in a frequency pattern different from an initial signal following frequency modulation based on the initial signal of a frequency pattern that obtains an amplitude equal to or greater than a predetermined value within a predetermined period. As a combination of a first chirp signal with a monotonically increasing frequency and a second chirp signal with a monotonically decreasing frequency Frequency modulation based on these chirp signals is performed so as to be in different modes mutually including adjacent object detection devices, and a transmission wave is transmitted substantially simultaneously with other object detection devices. Having directivity within a predetermined range A transmission unit, Among the transmitted waves transmitted to the predetermined range A reception unit that receives a reception wave as the transmission wave returned in response to reflection by an object, Having directivity And a detection processing unit that detects information about an object based on information obtained as a result of transmission and reception of the transmission wave and the reception wave. According to this configuration, for example, after the transmission wave is modulated to a predetermined amplitude or more, modulation based on the chirp signal is performed. At this time, frequency modulation in different modes is performed mutually including adjacent object detection devices. As a result, since it is modulated to a predetermined amplitude or more, from the beginning of the frequency modulation based on the chirp signal in the reception wave, the discrimination effect based on the chirp signal can be effectively utilized, and the SNR can be improved. Further, by performing frequency modulation in different modes mutually including adjacent object detection devices, the discriminability of the transmission wave (reception wave) can be enhanced. Also, for example, the discriminability of the transmitted wave (received wave) can be easily enhanced by two chirp signals with simple waveforms.

Brief Description of Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0012] Hereinafter, embodiments and modifications of the present disclosure will be described with reference to the drawings. The configurations of the embodiments and modifications described below, as well as the actions and effects brought about by the configurations, are merely examples and are not limited to the following description.

[0013] FIG. 1 is an exemplary and schematic diagram showing the appearance of a vehicle 1 equipped with the object detection system according to the embodiment as viewed from above.

[0014] As shown in FIG. 1, the object detection system includes an ECU (Electronic Control Unit) 100 mounted inside a four-wheel vehicle 1 including a pair of front wheels 3F and a pair of rear wheels 3R, and object detection devices 201 to 208 mounted on the exterior of the vehicle 1.

[0015] In the example shown in FIG. 1, as an example, the object detection devices 201 to 204 are installed (arranged) at different positions at predetermined intervals in the vehicle width direction on, for example, the rear bumper at the rear end of the vehicle body 2 as the exterior of the vehicle 1. Also, the object detection devices 205 to 208 are installed (arranged) at different positions at predetermined intervals in the vehicle width direction on, for example, the front bumper at the front end of the vehicle body 2.

[0016] Here, in the present embodiment, the hardware configurations and functions of the object detection devices 201 to 208 are the same. Therefore, hereinafter, for simplicity, the object detection devices 201 to 208 may be collectively referred to as the object detection device 200. Also, the predetermined intervals between the object detection devices 200 can be appropriately adjusted according to the shape of the bumper or the like, and do not need to be exactly the same. Also, they may be displaced in the vertical direction.

[0017] Also, in the present embodiment, the installation position of the object detection device 200 is not limited to the example shown in FIG. 1. The object detection device 200 may be installed on at least one of the rear bumper and the front bumper, and may also be installed on the side surface of the vehicle body 2. Further, the object detection device 200 may be installed at any position among the rear bumper, the front bumper, and the side surface. Also, in the embodiment, the number of the object detection devices 200 is not limited to the example shown in FIG. 1. However, the technology of the embodiment is effective for a configuration in which a plurality of object detection devices 200 exist.

[0018] The object detection system according to the present embodiment performs transmission and reception of ultrasonic waves based on the configuration described below, and acquires information such as the time difference of the transmission and reception, thereby detecting information regarding an object (for example, the object O shown in FIG. 2 described later) including a human being existing around.

[0019] FIG. 2 is an exemplary and schematic block diagram showing the hardware configurations of the ECU 100 and the object detection device 200 of the object detection system according to the embodiment.

[0020] As shown in FIG. 2, the ECU 100 has a hardware configuration similar to that of a normal computer. More specifically, the ECU 100 includes an input / output device 110, a storage device 120, and a processor 130.

[0021] The input / output device 110 is an interface for realizing transmission and reception of information between the ECU 100 and the outside (the object detection device 200 in the example shown in FIG. 1).

[0022] The memory device 120 includes a main memory device such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and / or an auxiliary memory device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0023] The processor 130 controls various processes executed in the ECU 100. The processor 130 includes an arithmetic unit such as a CPU (Central Processing Unit), for example. By reading and executing a computer program stored in the memory device 120, the processor 130 realizes various functions such as parking assistance, for example.

[0024] On the other hand, as shown in FIG. 2, the object detection device 200 includes a transceiver 210 and a control unit 220. With these configurations, the object detection device 200 is configured as an in-vehicle sonar, which is an example of an in-vehicle sensor that detects the distance to an object existing around the vehicle 1.

[0025] The transceiver 210 has a vibrator 211 such as a piezoelectric element, and the vibrator 211 realizes transmission and reception of ultrasonic waves.

[0026] More specifically, the transceiver 210 transmits ultrasonic waves generated in response to the vibration of the vibrator 211 as transmission waves, and receives the vibration of the vibrator 211 caused by the ultrasonic waves transmitted as the transmission waves being reflected by an object existing outside and returning, as reception waves. In the example shown in FIG. 2, as objects that can reflect ultrasonic waves from the transceiver 210, a road surface RS and an object O installed on the road surface RS are exemplified.

[0027] In the example shown in FIG. 2, a configuration is illustrated in which both the transmission of the transmission wave and the reception of the reception wave are realized by a single transceiver 210 having a single vibrator 211. However, the technology of the embodiment is naturally applicable to a configuration in which the transmission-side configuration and the reception-side configuration are separated, such as a configuration in which the vibrator for transmitting the transmission wave and the vibrator for receiving the reception wave are provided separately.

[0028] The control unit 220 has a hardware configuration similar to that of a normal computer. More specifically, the control unit 220 includes an input / output device 221, a storage device 222, and a processor 223.

[0029] The input / output device 221 is an interface for realizing the transmission and reception of information between the control unit 220 and the outside (in the example shown in FIG. 1, the ECU 100 and the transceiver 210).

[0030] The storage device 222 includes a main storage device such as a ROM or a RAM, and / or an auxiliary storage device such as an HDD or an SSD.

[0031] The processor 223 controls various processes executed in the control unit 220. The processor 223 includes an arithmetic device such as a CPU, for example. The processor 223 realizes various functions by reading and executing a computer program stored in the storage device 222.

[0032] Here, the object detection device 200 according to the embodiment detects the distance to an object as information about the object by a technique called the so-called TOF (Time Of Flight) method. As will be described in detail below, the TOF method is a technique for calculating the distance to an object by considering the difference between the timing when the transmission wave is transmitted (more specifically, when the transmission starts) and the timing when the reception wave is received (more specifically, when the reception starts).

[0033] FIG. 3 is an exemplary and schematic diagram for explaining the outline of the technology used by the object detection device 200 according to the embodiment to detect the distance to an object.

[0034] In the example shown in FIG. 3, the time change of the signal level (for example, amplitude) of the ultrasonic wave transmitted and received by the object detection device 200 according to the embodiment is represented in a graph format. In the graph shown in FIG. 3, the horizontal axis corresponds to time, and the vertical axis corresponds to the signal level of the signal transmitted and received by the object detection device 200 via the transmitter / receiver 210 (vibrator 211).

[0035] In the graph shown in FIG. 3, the solid line L11 represents an example of an envelope (envelope waveform) that represents the time change of the signal level of the signal transmitted and received by the object detection device 200, that is, the degree of vibration of the vibrator 211. From this solid line L11, it can be read that when the vibrator 211 is driven to vibrate for a time Ta from the timing t0, the transmission of the transmission wave is completed at the timing t1, and then the vibration of the vibrator 211 continues while decaying due to inertia during the time Tb until the timing t2 is reached. Therefore, in the graph shown in FIG. 3, the time Tb corresponds to the so-called reverberation time.

[0036] The solid line L11 reaches a peak where the degree of vibration of the vibrator 211 exceeds (or is equal to) a predetermined threshold Th1 represented by the dashed-dotted line L21 at the timing t4 when a time Tp has elapsed from the timing t0 when the transmission of the transmission wave started. This threshold Th1 is a value preset to identify whether the vibration of the vibrator 211 is caused by the reception of the received wave as the transmission wave reflected by the object to be detected (for example, the object O shown in FIG. 2) and returned, or whether it is caused by the reception of the received wave as the transmission wave reflected by an object outside the detection target (for example, the road surface RS shown in FIG. 2) and returned.

[0037] Note that although FIG. 3 shows an example in which the threshold Th1 is set as a constant value that does not change with the passage of time, in the embodiment, the threshold Th1 may be set as a value that changes with the passage of time.

[0038] Here, vibrations having a peak exceeding (or equal to) the threshold Th1 can be regarded as being caused by the reception of a received wave as a transmitted wave reflected back by the object to be detected. On the other hand, vibrations having a peak below (or less than) the threshold Th1 can be regarded as being caused by the reception of a received wave as a transmitted wave reflected back by an object outside the detection target.

[0039] Therefore, it can be read from the solid line L11 that the vibration of the vibrator 211 at timing t4 is caused by the reception of a received wave as a transmitted wave reflected back by the object to be detected.

[0040] Note that in the solid line L11, after timing t4, the vibration of the vibrator 211 is attenuating. Therefore, timing t4 corresponds to the timing when the reception of the received wave as a transmitted wave reflected back by the object to be detected is completed, in other words, the timing when the transmitted wave last transmitted at timing t1 returns as a received wave.

[0041] Also, in the solid line L11, the timing t3 as the starting point of the peak at timing t4 corresponds to the timing when the reception of the received wave as a transmitted wave reflected back by the object to be detected starts, in other words, the timing when the transmitted wave first transmitted at timing t0 returns as a received wave. Therefore, in the solid line L11, the time ΔT between timing t3 and timing t4 is equal to the time Ta as the transmission time of the transmitted wave.

[0042] Based on the above, in order to obtain the distance to the object to be detected by the TOF method, it is necessary to obtain the time Tf between the timing t0 when the transmission wave starts to be transmitted and the timing t3 when the reception wave starts to be received. This time Tf can be obtained by subtracting the time ΔT equal to the transmission time Ta of the transmission wave from the time Tp which is the difference between the timing t0 and the timing t4 when the peak at which the signal level of the reception wave exceeds the threshold Th1 is reached.

[0043] The timing t0 when the transmission wave starts to be transmitted can be easily specified as the timing when the object detection device 200 starts operating, and the time Ta as the transmission time of the transmission wave is determined in advance by settings or the like. Therefore, in order to obtain the distance to the object to be detected by the TOF method, ultimately, it is important to specify the timing t4 when the peak at which the signal level of the reception wave exceeds the threshold Th1 is reached.

[0044] By the way, in a configuration where a plurality of object detection devices 200 are provided as in the above-described embodiment, in order to detect more detailed information about the objects existing in the surroundings, transmission waves may be transmitted from each of the plurality of object detection devices 200 substantially simultaneously (simultaneously and in parallel). In this case, in order to suppress interference and the like, it is desirable to enhance the distinguishability of the transmission waves.

[0045] Therefore, the embodiment realizes enhancing the distinguishability of the transmission waves by configuring the object detection device 200 as follows.

[0046] FIG. 4 is an exemplary and schematic block diagram showing the detailed configuration of the object detection device 200 according to the embodiment.

[0047] As shown in FIG. 4, in the embodiment, as the configuration on the transmission side, a plurality (for example, three) of transmission units 401, 403, and transmission unit 405 are provided, and as the configuration on the reception side, a plurality (for example, three) of reception units 402, 404, and reception unit 406 are provided.

[0048] Here, although FIG. 4 shows a state where the configuration on the transmission side and the configuration on the reception side are separated, such a mode of illustration is merely for convenience of explanation. Therefore, in the example shown in FIG. 4, for example, a combination of a transmission unit 401 and a reception unit 402, a combination of a transmission unit 403 and a reception unit 404, and a combination of a transmission unit 405 and a reception unit 406 each constitute one object detection device 200. However, as mentioned repeatedly above, the technology of the embodiment is naturally applicable to a configuration in which the configuration on the transmission side and the configuration on the reception side are separated.

[0049] Further, although FIG. 4 shows three configurations each on the transmission side and the reception side, in the embodiment, one more configuration each may be provided on the transmission side and the reception side so as to correspond to the four object detection devices 200 shown in FIG. 1.

[0050] In the embodiment, at least a part of the configuration shown in FIG. 4 is realized as a result of the cooperation between hardware and software. More specifically, it is realized as a result of the processor 223 of the object detection device 200 reading and executing a computer program from the storage device 222. However, in the embodiment, at least a part of the configuration shown in FIG. 4 may be realized by dedicated hardware (circuitry).

[0051] First, the configuration on the transmission side of the object detection device 200 will be described.

[0052] As shown in FIG. 4, the transmission unit 401 includes a wave transmitter 411, a carrier wave output unit 412, a modulation pattern determination unit 413, a multiplier 414, and an amplifier circuit 415.

[0053] Also, the transmission units 403 and 405 each include a wave transmitter 431 and a wave transmitter 451 similar to the wave transmitter 411. In FIG. 4, illustrations other than the wave transmitters 431 and 451 are omitted for space reasons, but the transmission units 403 and 405 have the same configuration as the transmission unit 401 also in parts other than the wave transmitters 431 and 451.

[0054] The transmitter 411 is composed of the aforementioned vibrator 211, and the vibrator 211 transmits a transmission wave corresponding to the transmission signal (after amplification) output from the amplifier circuit 415.

[0055] Here, in the embodiment, the transmitter 411 is configured to transmit a transmission wave substantially simultaneously with the transmitters 431 and 451 of other object detection devices 200 under the control of, for example, the ECU 100. Therefore, in the embodiment, it is necessary to attach identification information to the transmission wave in order to be able to identify the source of the transmission wave that has returned as the received wave.

[0056] Therefore, the embodiment generates a transmission wave encoded to include identification information by modulating a carrier wave, such as a sine wave, with a modulation pattern corresponding to the identification information to be attached to the transmission wave.

[0057] More specifically, the carrier wave output unit 412 outputs a carrier wave, such as a sine wave, which is the basis of the transmission wave. Then, the modulation pattern determination unit 413 determines a modulation pattern of the carrier wave corresponding to the identification information to be attached to the transmission wave. Then, the multiplier 414 multiplies the output from the modulation pattern determination unit 413 and the output from the carrier wave output unit 412 to modulate the carrier wave and generate a transmission wave encoded to include identification information.

[0058] In the embodiment, the modulation pattern of the carrier wave is determined using an initial signal and a plurality of chirp signals (for example, a first chirp signal and a second chirp signal). Here, the initial signal is a signal capable of performing frequency modulation so as to obtain an amplitude equal to or greater than a predetermined value within a predetermined period. The first chirp signal is, for example, a signal capable of performing frequency modulation by monotonically (more specifically, linearly) increasing from a first frequency to a second frequency within a predetermined period. The second chirp signal is, for example, a signal capable of performing frequency modulation by monotonically (more specifically, linearly) decreasing from the second frequency to the first frequency within a predetermined period.

[0059] The chirp signal patterns used in modulation patterns include, for example, a pattern in which a second chirp signal is used following a first chirp signal, or conversely, a pattern in which a first chirp signal is used following a second chirp signal. Also, the chirp signal patterns used in other modulation patterns include a pattern in which the first chirp signal is used again following the first chirp signal, a pattern in which the second chirp signal is used again following the second chirp signal, and the like. Further, the pattern of the chirp signal used in another modulation pattern may combine three or more chirp signals. When combining a plurality of chirp signals, a plurality of chirp signals with the upper and / or lower frequencies of each chirp signal changed or the duration changed may be combined. In this way, by combining a plurality of chirp signals, a plurality of types of modulation patterns can be easily generated. By modulating a carrier wave using such a plurality of modulation patterns, transmission waves having different characteristics (discriminability) can be easily generated.

[0060] By the way, when the ultrasonic wave is transmitted by the transmitter 411, the amplitude of the wave at the start of transmission is small, and for example, the amplitude is increased by transmitting the wave many times and adjusting the phase. Therefore, when simply modulating using a chirp signal, the frequency during the period when the amplitude of the wave is small (the period when the signal is weak) cannot be effectively utilized, so the SNR may deteriorate and the discriminability of the transmission wave may decrease.

[0061] Therefore, in this embodiment, frequency modulation is irregularly performed based on an initial signal and a chirp signal to generate a transmission wave, thereby improving the SNR by coding gain. Specifically, according to the impedance characteristics of the transmitter 411 (microphone), the frequency modulation (chirp) by pulse compression is variably changed irregularly on the time axis. For example, when the vibration (amplitude) of the transmitter 411 is small, the chirp is not started. First, for example, frequency modulation based on an initial signal with a frequency pattern that can obtain an amplitude equal to or greater than a predetermined amplitude in a predetermined period is performed. Preferably, for example, frequency modulation is performed so that the frequency becomes near the resonance frequency of the transmitter 411, and the carrier wave is transmitted. After the vibration (amplitude) becomes large to a certain extent, the chirp is started. As a result, fluctuations can be effectively utilized from the beginning of the modulation by the chirp signal, and the SNR can be improved.

[0062] FIG. 5 is an exemplary and schematic diagram showing a transmission chirp modulation pattern 10 of the object detection system according to the embodiment.

[0063] In FIG. 5, fm is the resonance frequency of the transmitter 411 (microphone), f1 is the lower limit frequency of the specific frequency band F set for the transmitter 411, and f2 is the upper limit frequency of the frequency band F.

[0064] As described above, in this embodiment, frequency modulation is irregularly performed based on an initial signal and a chirp signal to generate a transmission wave. In the case of FIG. 5, it is an example of the transmission chirp modulation pattern 10. First, modulation is performed with the initial signal W having a constant frequency near the resonance frequency fm. Then, after the vibration (amplitude) of the transmission wave becomes large to a certain extent, modulation is performed with the first chirp signal W1 (up chirp) that monotonically increases from the lower limit frequency f1 to the upper limit frequency f2, and subsequently, modulation with the second chirp signal W2 (down chirp) that monotonically decreases from the upper limit frequency f2 to the lower limit frequency f1 is performed. By transmitting the transmission wave modulated with such a transmission chirp modulation pattern 10, fluctuations can be effectively utilized from the start of the modulation by the chirp signal. In addition, by continuously performing modulation using a plurality of chirp signals, a highly discriminative transmission wave can be easily generated.

[0065] As shown in FIG. 1, in the case of the vehicle 1 of the present embodiment, four object detection devices 200 (201 to 204) are arranged at the rear end of the vehicle 1, and four object detection devices 200 (205 to 208) are arranged at the front end of the vehicle 1. Then, the object detection devices 201 to 204 are arranged in a state of approaching at a predetermined interval in the vehicle width direction and perform transmission and reception operations. Similarly, the object detection devices 205 to 208 are arranged in a state of approaching at a predetermined interval in the vehicle width direction and perform transmission and reception operations. In this case, in order for each object detection device 200 to accurately detect whether an object O (object) exists in the transmission direction of the transmission wave and, if the object O exists, the distance to the object O, it is necessary to accurately grasp from which object detection device 200 the received reception wave is transmitted. In this case, the transmission wave transmitted from the object detection device 200 needs to transmit transmission waves with different characteristics at least at adjacent (both adjacent) object detection devices 200.

[0066] For example, consider a case where the transmitted wave (received wave) is identified simply by using modulation with the first chirp signal W1 or the second chirp signal W2. For example, assume that the object detection device 205 transmits a transmitted wave modulated by the first chirp signal W1, the object detection device 206 transmits a transmitted wave modulated by the second chirp signal W2, the object detection device 207 transmits a transmitted wave modulated by the first chirp signal W1, and the object detection device 208 transmits a transmitted wave modulated by the second chirp signal W2. In this case, for example, when the object detection device 207 receives a received wave, it becomes difficult to identify whether the received wave is the transmitted wave transmitted by the object detection device 206 or the transmitted wave transmitted by the object detection device 208. In order to enable identification with this configuration, for example, the object detection device 205 transmits a transmitted wave modulated by the first chirp signal W1, and the object detection device 206 transmits a transmitted wave modulated by the second chirp signal W2. At that time, the transmission of the transmitted wave modulated by the first chirp signal W1 by the object detection device 207 and the transmission of the transmitted wave modulated by the second chirp signal W2 by the object detection device 208 are suspended, and after the reception of the received wave by the object detection device 205 and the object detection device 206 is completed, the object detection device 207 transmits a transmitted wave modulated by the first chirp signal W1, and the object detection device 208 transmits a transmitted wave modulated by the second chirp signal W2. That is, the object detection device 205 and the object detection device 207 cannot transmit the first chirp signal W1 simultaneously, and a processing waiting time is required.

[0067] On the other hand, as in the present embodiment, after transmitting a transmitted wave modulated near the resonance frequency fm with the initial signal W, by continuously performing modulation using a plurality of chirp signals, a transmitted wave with high discriminability can be easily transmitted in different modes for each object detection device 200.

[0068] For example, FIG. 6 is an exemplary and schematic diagram showing different transmission chirp modulation patterns that can be used when transmitting transmitted waves simultaneously from a plurality of object detection devices 200.

[0069] In the case of FIG. 6, the transmission chirp modulation pattern 12 indicated by the solid line is a pattern that, following the initial signal W, performs modulation by the first chirp signal W1 and then again performs modulation by the first chirp signal W1. Also, the transmission chirp modulation pattern 14 indicated by the dashed line is a pattern that, following the initial signal W, performs modulation by the first chirp signal W1 and the second chirp signal W2. Further, the transmission chirp modulation pattern 16 indicated by the dash-dotted line is a pattern that, following the initial signal WD1 which is slightly lower in frequency than the initial signal W, performs modulation by the second chirp signal W2 and the first chirp signal W1. Additionally, the transmission chirp modulation pattern 18 indicated by the double-dashed line is a pattern that, following the initial signal WD2 which is slightly lower in frequency than the initial signal WD1, performs modulation by the second chirp signal W2, then again performs modulation by the second chirp signal W2, and subsequently performs modulation by the first chirp signal W1.

[0070] In this way, adjacent object detection devices 200 can transmit easily and clearly distinguishable transmission waves by using different patterns of transmission chirp modulation patterns as described above. As a result, each object detection device 200 can perform transmission and reception simultaneously, and the measurement period by each object detection device 200 can be shortened. When detecting the object O using ultrasonic waves, usually, when there is a possibility that the object O exists, transmission and reception are repeated many times to confirm the presence or absence of the object O. As described above, in the configuration of this embodiment, since each object detection device 200 can transmit transmission waves (ultrasonic waves) substantially simultaneously, the confirmation time of the object O can be shortened.

[0071] Returning to FIG. 4, the amplifier circuit 415 amplifies the transmission signal output from the multiplier 414 and outputs the amplified transmission signal to the transmitter 411. In this way, in the embodiment, the configuration on the transmission side of the object detection device 200 transmits different transmission waves by modulation according to the transmission chirp modulation pattern.

[0072] Next, the configuration on the reception side of the object detection device 200 will be described.

[0073] As shown in FIG. 4, the receiving unit 402 includes a wave receiver 421, an amplification circuit 422, a filtering unit 423, an identification unit 424, and a plurality (for example, three) of signal processing systems 425A to 425C.

[0074] In addition, the receiving unit 404 and the receiving unit 406 each include a wave receiver 441 and a wave receiver 461 similar to the wave receiver 421. In FIG. 4, illustrations other than the wave receivers 441 and 461 are omitted for space reasons, but the receiving unit 404 and the receiving unit 406 have the same configuration as the receiving unit 402 even other than the wave receivers 441 and 461.

[0075] The wave receiver 421 is constituted by the vibrator 211 described above, and the vibrator 211 receives the transmitted wave reflected by the object as a received wave.

[0076] The amplification circuit 422 amplifies the received signal as a signal corresponding to the received wave received by the wave receiver 421.

[0077] The filtering unit 423 performs filtering processing on the received signal amplified by the amplification circuit 422. This filtering processing includes noise suppression and Doppler shift correction.

[0078] Here, in the embodiment, as described above, a plurality of distinguishable transmitted waves are substantially simultaneously transmitted from the plurality of transmitters 411, 431, and 451. Therefore, the received wave received by the wave receiver 421 is constituted by at least partially overlapping a plurality of waves corresponding to the plurality of transmitted waves transmitted from the plurality of transmitters 411, 431, and 451.

[0079] Therefore, in the embodiment, signal processing systems 425A to 425C are provided in the same number as the number of the transmitters 411, 431, and 451. Each of the signal processing systems 425A to 425C includes a correlation processing unit 426, an envelope processing unit 427, a threshold processing unit 428, and a detection processing unit 429. Based on these configurations, the signal processing systems 425A to 425C realize a function of specifying the relationship between the received wave received via the receiver 421 and the plurality of transmitted waves transmitted via the transmitters 411, 431, and 451, and a function of detecting information about an object based on the specified relationship.

[0080] The correlation processing unit 426 obtains a correlation value corresponding to the similarity of the identification information between the transmitted wave and the received wave based on the transmitted signal acquired from the configuration on the transmission side and the received signal that has undergone the filtering process by the filter processing unit 423. The correlation value is calculated based on a generally well-known correlation function or the like.

[0081] Then, the envelope processing unit 427 obtains the envelope of the waveform of the signal corresponding to the correlation value obtained by the correlation processing unit 426.

[0082] Then, the threshold processing unit 428 compares the value of the envelope obtained by the envelope processing unit 427 with a predetermined threshold value, and determines whether the identification information between the transmitted wave and the received wave is similar at a level equal to or higher than the predetermined level based on the comparison result.

[0083] Then, the detection processing unit 429 specifies the timing at which the similarity of the identification information between the transmitted wave and the received wave becomes a level equal to or higher than the predetermined level based on the processing result by the threshold processing unit 428, that is, the timing of reaching the peak at which the signal level of the received wave as the transmitted wave returned by reflection exceeds the threshold value (for example, the timing t4 shown in FIG. 2), and detects the distance to the object as information about the object by the TOF method.

[0084] Here, in the embodiment, the correlation processing unit 426 of the signal processing system 425A is configured to obtain a correlation value using the transmission signal acquired from the transmission unit 401. Therefore, the correlation value obtained by the correlation processing unit 426 of the signal processing system 425A is a value that reflects the similarity to the transmission wave transmitted from the transmitter 411.

[0085] Similarly, the correlation processing unit 426 of the signal processing system 425B is configured to obtain a correlation value using the transmission signal acquired from the transmission unit 403, and the correlation processing unit 426 of the signal processing system 425C is configured to obtain a correlation value using the transmission signal acquired from the transmission unit 405. Therefore, the correlation value obtained by the correlation processing unit 426 of the signal processing system 425B is a value that reflects the similarity to the transmission wave transmitted from the transmitter 431, and the correlation value obtained by the correlation processing unit 426 of the signal processing system 425C is a value that reflects the similarity to the transmission wave transmitted from the transmitter 451.

[0086] Accordingly, in the embodiment, the detection processing unit 429 of the signal processing system 425A specifies the timing at which the signal level of the received wave received by the receiver 421 exceeds the threshold value when the transmission wave transmitted from the transmitter 411 returns due to reflection and reaches a peak. Also, the detection processing unit 429 of the signal processing system 425B specifies the timing at which the signal level of the received wave received by the receiver 421 exceeds the threshold value when the transmission wave transmitted from the transmitter 431 returns due to reflection and reaches a peak, and the detection processing unit 429 of the signal processing system 425C specifies the timing at which the signal level of the received wave received by the receiver 421 exceeds the threshold value when the transmission wave transmitted from the transmitter 451 returns due to reflection and reaches a peak.

[0087] As described above, in the embodiment, using the three signal processing systems 425A to 425C, the timing at which the transmitted wave transmitted from the transmitter 411 returns due to reflection and is received by the receiver 421, the timing at which the transmitted wave transmitted from the transmitter 431 returns due to reflection and is received by the receiver 421, and the timing at which the transmitted wave transmitted from the transmitter 451 returns due to reflection and is received by the receiver 421 are appropriately specified. Then, based on the difference in the timing of each transmission and reception, the distance to the object is appropriately detected.

[0088] Based on the above configuration, the object detection system according to the embodiment detects information regarding an object (object O) by executing processing in the flow as shown in FIG. 7 below.

[0089] FIG. 7 is an exemplary and schematic flowchart showing a series of processes executed by the object detection system according to the embodiment to detect the distance to an object.

[0090] First, each object detection device 200 of the object detection system determines a pulse compression pattern from the band of the microphone (transceiver 210) by the modulation pattern determination unit 413 (S100).

[0091] Subsequently, the determined pulse compression pattern (transmission chirp modulation pattern) is assigned to each object detection device 200 (S102), and the preprocessing for object detection is completed.

[0092] Then, each object detection device 200 transmits a transmitted wave generated by modulating a carrier wave with the pulse compression pattern determined in S100 by the transceiver 210, and executes a process of receiving a received wave as a result of the transmitted wave returning due to reflection by the object (S104).

[0093] Then, each object detection device 200 executes an analysis of time-frequency characteristics by short-time FFT or a correlation process of obtaining a correlation value corresponding to the similarity of identification information between the transmitted wave and the received wave by the correlation processing unit 426 (S106).

[0094] Then, each object detection device 200 calculates the envelope (peak value, amplitude value) of the waveform of the signal corresponding to the correlation value obtained by the correlation processing unit 426 in the envelope processing unit 427 (S108).

[0095] Then, based on the comparison result between the correlation value (its envelope) and the threshold value, the detection processing unit 429 executes a ranging process for detecting the distance to the object for each object detection device 200 (S110). And when each object detection device 200 has not received a command indicating the end of the object detection process (No in S112), it returns to the process of S104, and at a predetermined cycle, executes the transmission process and reception process of the transmission wave (the wave modulated by the transmission chirp modulation pattern), and repeats the subsequent processes. Also, when a command indicating the end of the object detection process is received in S112 (Yes in S112), for example, when the ignition switch of the vehicle 1 is turned off, the process of this flow is terminated once.

[0096] As described above, the object detection system according to the embodiment includes a plurality of object detection devices 200. Therefore, the plurality of object detection devices 200 each have the same configuration and execute the processes according to the flowchart of FIG. 7 substantially simultaneously.

[0097] For example, in the embodiment, one of the plurality of object detection devices 200 includes a transmission unit 401, a reception unit 402, and a detection processing unit 429. The transmission unit 401 performs frequency modulation based on a plurality of chirp signals (W1, W2, etc.) that change in a frequency pattern different from the initial signal W following the frequency modulation based on the initial signal W of a frequency pattern that can obtain an amplitude equal to or greater than a predetermined value within a predetermined period, so that the frequency modulation is performed in a different manner for each other including adjacent object detection devices 200, and transmits the transmission wave substantially simultaneously with the other object detection devices 200. The reception unit 402 receives the reception wave as the transmission wave returned in response to the reflection by the object. The detection processing unit 429 detects information about the object based on the information obtained as a result of the transmission and reception of the transmission wave and the reception wave.

[0098] According to the above-described configuration, for example, after the transmission wave is modulated to a predetermined amplitude or more, modulation based on a chirp signal is performed. At this time, frequency modulation in different modes is performed mutually including the adjacent object detection device 200. As a result, since it is modulated to a predetermined amplitude or more, in the received wave, from the beginning of the frequency modulation based on the chirp signal, the discrimination effect based on the chirp signal can be effectively utilized, and the signal-to-noise ratio can be improved. Further, by performing frequency modulation in different modes mutually including the adjacent object detection device 200, the discriminability of the transmission wave (received wave) can be enhanced. As a result, in an environment where the low-speed safe driving support device of the vehicle 1 is used, collision avoidance from a long distance and collision avoidance immediately before a collision become easy. Further, since transmission and reception are performed only by frequency modulation, the circuit scale can be made smaller and the cost can be reduced compared to a combination with other modulation methods.

[0099] Further, the chirp signal that changes with a frequency pattern different from the above-described initial signal may be, for example, the first chirp signal W1 whose frequency monotonically increases or the second chirp signal W2 whose frequency monotonically decreases as shown in FIG. 5. According to this configuration, for example, the discriminability of the transmission wave (received wave) can be easily enhanced by two chirp signals having simple waveforms.

[0100] Further, the above-described transmission unit 401 may perform frequency modulation based on a chirp signal such that each of the plurality of object detection devices 200 changes with a different frequency pattern. According to this configuration, for example, the distinguishability of the plurality of object detection devices 200 can be further improved. In addition, the directivity of the object detection device 200 may be adjusted. For example, in FIG. 1, the reflected wave (received wave) of the transmission wave transmitted from the object detection device 205 may be receivable only by the object detection device 205 and the object detection device 206. Also, the reflected wave (received wave) of the transmission wave transmitted from the object detection device 208 may be receivable only by the object detection device 207 and the object detection device 208. In this case, the transmission wave transmitted from the object detection device 207 is not received by the object detection device 205. Similarly, the transmission wave transmitted from the object detection device 206 is not received by the object detection device 208. In such a case, the object detection device 205 and the object detection device 208 may transmit transmission waves by modulation based on the same transmission chirp modulation pattern. In this case, compared with the case of transmitting transmission waves by modulation based on all different transmission chirp modulation patterns, the number of patterns can be reduced, which can contribute to simplification of control.

[0101] Further, the above-described initial signal may perform frequency modulation to be the resonance frequency of the transmission unit 401 of the object detection device 200, for example. According to this configuration, for example, it becomes possible to transmit a transmission wave modulated based on a chirp signal with the amplitude of the transmission wave efficiently increased, and the improvement of the SN ratio due to the coding gain can be effectively performed.

[0102] In the above-described embodiment, the technology of the present disclosure is applied to a configuration for detecting information about an object by transmitting and receiving ultrasonic waves. However, the technology of the present disclosure can also be applied to a configuration for detecting information about an object by transmitting and receiving waves other than ultrasonic waves, such as sound waves, millimeter waves, or electromagnetic waves.

[0103] In the above-described embodiment, a configuration for detecting the distance to an object as information about the object is exemplified. However, the technology of the present disclosure can also be applied to a configuration for detecting only the presence or absence of an object as information about the object.

[0104] The embodiments and modifications of the present disclosure have been described above. However, the above-described embodiments and modifications are merely examples and are not intended to limit the scope of the invention. The novel embodiments and modifications described above can be implemented in various forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. The above-described embodiments and modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0105] 200, 201, 202, 203, 204 Object detection device 401, 403, 405 Transmission unit 402, 404, 406 Reception unit 426 Correlation processing unit 429 Detection processing unit

Claims

1. Comprising a plurality of object detection devices arranged at a predetermined interval, Each of the plurality of object detection devices, Following frequency modulation based on an initial signal of a frequency pattern that obtains an amplitude equal to or greater than a predetermined value within a predetermined period, as a plurality of chirp signals that change in a frequency pattern different from the initial signal, a first chirp signal whose frequency monotonically increases and a second chirp signal whose frequency monotonically decreases A transmission unit having a directivity within a predetermined range that transmits a transmission wave subjected to frequency modulation based on a combination so that the frequency modulation is in a different manner for each other including adjacent object detection devices, to other said object detection devices Substantially simultaneously, A receiving unit having a directivity for receiving a received wave as the transmitted wave that has returned in response to reflection by an object among the transmitted waves transmitted within the predetermined range, A detection processing unit that detects information about the object based on information obtained as a result of transmission and reception of the transmission wave and the reception wave, An object detection system comprising:

2. The object detection system according to claim 1, wherein the transmission unit performs frequency modulation based on the chirp signal so that each of the plurality of object detection devices changes in a different frequency pattern.

3. The object detection system according to claim 1 or claim 2, wherein the initial signal performs frequency modulation at a resonance frequency of a microphone of the object detection device.

4. Following frequency modulation based on an initial signal of a frequency pattern that obtains an amplitude equal to or greater than a predetermined value within a predetermined period, as a plurality of chirp signals that change in a frequency pattern different from the initial signal, a first chirp signal whose frequency monotonically increases and a second chirp signal whose frequency monotonically decreases A transmission unit having a directivity within a predetermined range that transmits a transmission wave subjected to frequency modulation based on a combination so that the frequency modulation is in a different manner for each other including adjacent object detection devices, to other said object detection devices Substantially simultaneously, A receiving unit having a directivity for receiving a received wave as the transmitted wave that has returned in response to reflection by an object among the transmitted waves transmitted within the predetermined range, A detection processing unit that detects information about the object based on information obtained as a result of transmission and reception of the transmission wave and the reception wave, An object detection device comprising:

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