Ultrasonic generator, transducer, and object detection device

Abstract

An ultrasound generator of the embodiment of the preset invention comprises: a vibrator provided with a piezoelectric body that vibrates from the piezoelectric effect when an AC voltage is applied and thereby generates ultrasonic waves, at least two electrodes provided along the surface of the piezoelectric body in positions that differ in height, and counter electrodes provided in positions opposing the at least two electrodes; and a control unit that, upon receiving an ultrasound generation instruction that contains information on directivity of ultrasonic waves that are generated, performs control to select from the at least two electrodes and the counter electrodes a combination, corresponding to the directivity in the ultrasound generation instruction, of a voltage-applying electrode which is an electrode to which an AC voltage is applied, and a ground electrode which is an electrode that is made ground potential, and to apply an AC voltage to the voltage-applying electrode to generate ultrasound.

Description

Technical Field

[0001] The present disclosure relates to an ultrasonic generator, a vibrator, and an object detection device.

Background Art

[0002] Conventionally, there has been a technique of applying an alternating voltage to a piezoelectric body to cause vibration by the piezoelectric effect and generate ultrasonic waves. Also, assuming that object detection is performed based on the reflected wave of the generated ultrasonic wave, it is meaningful to change the directivity of the ultrasonic wave in the height direction (vertical direction).

[0003] To change the directivity of ultrasonic waves in the height direction, for example, there is a method of using a plurality of vibrators.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using a plurality of vibrators to change the directivity of ultrasonic waves in the height direction, there is a problem that the cost increases.

[0006] Therefore, one of the problems of the present disclosure is to provide an ultrasonic generator, a vibrator, and an object detection device that can change the directivity of generated ultrasonic waves in the height direction at a low cost.

Means for Solving the Problems

[0007] An example of an ultrasonic generator in this disclosure includes a piezoelectric body that vibrates by the piezoelectric effect to generate ultrasonic waves when an AC voltage is applied, and a transducer having two or more electrodes provided at different heights on the surface of the piezoelectric body and a counter electrode provided at a position opposite to the two or more electrodes, and a control unit that, upon receiving an ultrasonic generation instruction including information on the directivity of the ultrasonic waves to be generated, selects a combination from the two or more electrodes and the counter electrode of a voltage application electrode which applies an AC voltage and a ground electrode which is set to ground potential, corresponding to the directivity in the ultrasonic generation instruction, and applies an AC voltage to the voltage application electrode to generate ultrasonic waves. This configuration allows for changing the vertical directivity of the ultrasound using a single transducer, thus reducing costs.

[0008] Furthermore, an example of a transducer in this disclosure comprises a piezoelectric body that vibrates by the piezoelectric effect and generates ultrasonic waves when an AC voltage is applied, and two or more electrodes provided at different heights on the surface of the piezoelectric body and a counter electrode provided at a position opposite to the two or more electrodes, wherein the directivity of the generated ultrasonic waves differs depending on the selected combination of a voltage application electrode, which is an electrode to which an AC voltage is applied, and a ground electrode, which is an electrode to which the ground potential is maintained. This configuration allows for changing the vertical directivity of the ultrasound using a single transducer, thus reducing costs.

[0009] Furthermore, an object detection device as an example of the present disclosure comprises a transmitting unit that transmits ultrasonic waves using a transducer, a receiving unit that receives reflected waves of the ultrasonic waves using the transducer, and a control unit. The transducer comprises a piezoelectric body that vibrates by the piezoelectric effect and generates ultrasonic waves when an AC voltage is applied, and two or more electrodes provided at different heights on the surface of the piezoelectric body and a counter electrode provided at a position opposite to the two or more electrodes. When the control unit receives an ultrasonic wave generation instruction that includes information on the directivity of the ultrasonic waves to be generated, it selects a combination from the two or more electrodes and the counter electrode of a voltage application electrode, which is an electrode to which an AC voltage is applied, and a ground electrode, which is an electrode to which an AC voltage is set to ground potential, corresponding to the directivity in the ultrasonic wave generation instruction, and applies an AC voltage to the voltage application electrode to generate ultrasonic waves. This configuration allows for changing the vertical directivity of the ultrasound using a single transducer, thus reducing costs. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram of the external appearance of a vehicle equipped with the object detection system of the embodiment, viewed from above. [Figure 2] Figure 2 is a schematic block diagram showing the general hardware configuration of the ECU and object detection device of the embodiment. [Figure 3] Figure 3 is a schematic diagram showing an overview of the oscillator of the embodiment. [Figure 4] Figure 4 is an explanatory diagram of the directivity of the ultrasonic waves generated from the transducer of the embodiment. [Figure 5] Figure 5 is an explanatory diagram of the detection range by ultrasonic waves generated from the transducer of the embodiment. [Figure 6] Figure 6 is an explanatory diagram illustrating the overview of the technology used by the object detection device of this embodiment to detect the distance to an object. [Figure 7] Figure 7 is a schematic block diagram illustrating the detailed configuration of the object detection device according to the embodiment. [Figure 8] Figure 8 shows the directional correspondence information of the embodiment. [Figure 9] Figure 9 is a flowchart showing the first process performed by the object detection system of the embodiment. [Figure 10] Figure 10 is a flowchart showing the second process performed by the object detection system of the embodiment. [Figure 11] Figure 11 is a flowchart showing the third process performed by the object detection system of the embodiment. [Modes for carrying out the invention]

[0011] The embodiments of this disclosure will be described below with reference to the drawings. The configurations of the embodiments described below, as well as the functions and effects brought about by such configurations, are merely examples, and the present invention is not limited to the following description.

[0012] Figure 1 is a schematic diagram of the external appearance of a vehicle equipped with the object detection system of the embodiment, viewed from above. The object detection system of the embodiment is an in-vehicle sensor system that transmits and receives ultrasonic waves and uses the time difference between such transmission and reception to detect information about objects in the surroundings (for example, obstacle O shown in Figure 2, which will be described later).

[0013] More specifically, as shown in Figure 1, the object detection system of the embodiment comprises an ECU (Electronic Control Unit) 100 as an in-vehicle control device and object detection devices 201 to 204 as in-vehicle sonar. The ECU 100 is mounted inside a four-wheeled vehicle 1, which includes a pair of front wheels 3F and a pair of rear wheels 3R, while the object detection devices 201 to 204 are mounted on the exterior of the vehicle 1.

[0014] In the example shown in FIG. 1, as an example, the object detection devices 201 to 204 are installed at different positions at the rear end (rear bumper) of the vehicle body 2 as the exterior of the vehicle 1. However, the installation positions of the object detection devices 201 to 204 are not limited to the example shown in FIG. 1. For example, the object detection devices 201 to 204 may be installed at the front end (front bumper) of the vehicle body 2, may be installed at the side surface of the vehicle body 2, or may be installed at two or more of the rear end, the front end, and the side surface.

[0015] In the embodiment, the hardware configurations and functions of the object detection devices 201 to 204 are the same. Therefore, hereinafter, for the sake of simplicity of explanation, the object detection devices 201 to 204 are collectively referred to as "object detection device 200" (an example of an ultrasonic wave generating device). Further, in the embodiment, the number of the object detection devices 200 is not limited to four as shown in FIG. 1.

[0016] FIG. 2 is a block diagram schematically showing the schematic hardware configuration of the ECU 100 and the object detection device 200 of the embodiment.

[0017] 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.

[0018] The input / output device 110 is an interface for realizing the transmission and reception of information between the ECU 100 and the outside (in the example shown in FIG. 1, the object detection device 200).

[0019] The storage device 120 includes a main storage device such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and / or an auxiliary storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0020] The processor 130 is responsible for various processes performed in the ECU 100. The processor 130 includes an arithmetic unit such as a CPU (Central Processing Unit). The processor 130 realizes various functions by reading and executing computer programs stored in the storage device 120.

[0021] On the other hand, as shown in Figure 2, the object detection device 200 includes a transducer 210 and a control unit 220.

[0022] The transducer 210 includes a transducer 211 (an example of an ultrasonic sensor) made of a piezoelectric element and the like, and a switching unit 212, and the transducer 211 transmits and receives ultrasonic waves.

[0023] More specifically, the transducer 210 transmits ultrasonic waves generated in response to the vibration of the transducer 211 as a transmitted wave, and receives the vibration of the transducer 211 caused by the ultrasonic waves transmitted as a transmitted wave being reflected back by an external object as a received wave (reflected wave). In the example shown in Figure 2, an obstacle O placed on the road surface RS is exemplified as an object that reflects ultrasonic waves from the transducer 210.

[0024] Here, Figure 3 is a schematic diagram showing an overview of the transducer 211 of the embodiment. The following description assumes that the transducer 211 is installed in the vehicle 1. The transducer 211 comprises a front electrode 4, wiring 5, piezoelectric element 6, rear electrode 7, and wiring 8.

[0025] The front electrode 4 is an example of two or more electrodes provided at different heights (vertical positions) on the surface of the piezoelectric body 6. The front electrode 4 comprises front electrodes 4a and 4b. The front electrodes 4a and 4b are electrically insulated from each other.

[0026] The wiring 5 includes wiring 5a connected to the front electrode 4a and wiring 5b connected to the front electrode 4b.

[0027] When an AC voltage is applied to the piezoelectric element 6, it vibrates due to the piezoelectric effect and generates ultrasonic waves.

[0028] The rear electrode 7 is a counter electrode provided on the surface of the piezoelectric element 6 at a position opposite to the front electrodes 4a and 4b.

[0029] Wiring 8 is connected to the rear electrode 7.

[0030] The processor 223 then selects the voltage application electrode and the ground electrode from the front electrodes 4a and 4b and the rear electrode 7, and controls the directivity of the generated ultrasonic waves by adjusting the frequency, phase, and amplitude of the applied AC voltage (details will be described later).

[0031] Returning to Figure 2, the control unit 220 has a hardware configuration similar to that of a typical computer. More specifically, the control unit 220 includes an input / output device 221, a storage device 222, and a processor 223.

[0032] The input / output device 221 is an interface for transmitting and receiving information between the control unit 220 and external devices (the ECU 100 and the transducer 210 in the example shown in Figure 1).

[0033] The storage device 222 includes a main memory such as ROM or RAM, and / or an auxiliary storage device such as an HDD or SSD. The storage device 222 stores, for example, directional information 230. The directional information 230 is an example of correspondence information between the combination of the voltage application electrode (the electrode to which an AC voltage is applied) and the ground electrode (the electrode that is set to ground potential) among the front electrodes 4a, 4b and rear electrode 7, the frequency, phase, and amplitude of the applied AC voltage, and the directionality of the generated ultrasound. Note that the frequency, phase, and amplitude are not all essential, and some or all of them may be omitted.

[0034] Here, Figure 8 shows the directional information 230 of the embodiment. In the directional information 230, for each directional information, which is information about the direction and spread of the ultrasonic output, the combination of the voltage application electrode and the ground electrode is associated with the frequency, phase, and amplitude of the applied AC voltage. For example, if the combination of the voltage application electrode and the ground electrode is different, the way the voltage is applied to the piezoelectric body 6 will be different, and the location where the piezoelectric body 6 vibrates will be different, so the directionality of the ultrasonic waves generated from the piezoelectric body 6 will also be different. Note that there may be multiple ground electrodes or there may be one. Also, electrodes that are neither the voltage application electrode nor the ground electrode are kept in an insulated state. Furthermore, the directionality of the ultrasonic waves generated from the piezoelectric body 6 will also differ depending on the frequency, phase, and amplitude of the applied AC voltage.

[0035] Furthermore, the output direction of the ultrasonic waves generated from the transducer 211 is approximately the direction indicated by symbol D in Figure 3. Here, Figure 4 is an explanatory diagram of the directivity of the ultrasonic waves generated from the transducer of the embodiment. Depending on the combination of the voltage application electrode and the ground electrode, and the frequency, phase, and amplitude of the applied AC voltage, the output direction of the ultrasonic waves generated from the piezoelectric body 6 can change in various directions in the height direction, as exemplified by symbols D1 to D3. The way in which the ultrasonic waves spread can also change in various ways. And, for example, directivity correspondence information 230 as shown in Figure 8 can be created in advance through experiments.

[0036] Returning to Figure 2, the processor 223 is responsible for various processes executed in the control unit 220. The processor 223 includes an arithmetic unit such as a CPU. The processor 223 realizes various functions by reading and executing computer programs stored in the memory device 222.

[0037] For example, when the processor 223 receives an ultrasonic generation instruction from the ECU 100, which includes information on the directivity of the ultrasonic waves to be generated, it refers to the directivity-corresponding information 230, selects a combination from the front electrodes 4a, 4b and the rear electrode 7 of a voltage application electrode, which is an electrode to which an AC voltage is applied, and a ground electrode, which is an electrode to which an AC voltage is applied, corresponding to the directivity in the ultrasonic generation instruction, and also determines the frequency, phase, and amplitude, and applies an AC voltage to the voltage application electrode to generate ultrasonic waves.

[0038] Furthermore, the processor 223 calculates the distance to the object that reflected the ultrasound based on the timing of when the ultrasound was transmitted by the transmitter and the timing of when the reflected ultrasound was received by the receiver. If the distance changes over time, the processor 223 changes the vertical directivity of the ultrasound transmitted by the transmitter based on the directivity change information, which has a set degree of change in the vertical direction of directivity according to the distance (details will be described later).

[0039] Furthermore, the processor 223 acquires information on the change in intensity of the reflected wave while changing the vertical directivity of the ultrasonic waves transmitted by the transmitter, and calculates the height of the object that reflected the ultrasonic waves based on the change information (details will be described later).

[0040] When the combination of the voltage application electrode and the ground electrode is determined, the switching unit 212, in accordance with instructions from the processor 223, switches the wiring 5a, 5b, and 8 corresponding to the voltage application electrode to the power supply, switches the wiring corresponding to the ground electrode to the ground, and further switches the other wiring to an insulated state.

[0041] The object detection device 200 of this embodiment detects the distance to an object using a technique known as the Time of Flight (TOF) method. The TOF method is a technique that calculates the distance to an object by considering the difference between the timing when the transmitted wave is sent (more specifically, when it begins to be transmitted) and the timing when the received wave is received (more specifically, when it begins to be received).

[0042] Here, Figure 5 is an explanatory diagram of the detection range by ultrasonic waves generated from the transducer 211 of the embodiment. When the transducer 210 is installed in front of the vehicle 1, the detection range by ultrasonic waves generated from the transducer 211 can be switched in the height direction, as shown in regions R1 and R2.

[0043] Furthermore, Figure 6 is an explanatory diagram illustrating the overview of the technology used by the object detection device 200 of the embodiment to detect the distance to an object. More specifically, Figure 6 is a diagram illustrating and schematicly showing the time change in the ultrasonic signal level (e.g., amplitude) transmitted and received by the object detection device 200 of the embodiment in graphical form. In the graph shown in Figure 6, 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 transducer 210 (transducer 211).

[0044] In the graph shown in Figure 6, the solid line L11 represents an example of an envelope that shows the time change in the signal level of the signal transmitted and received by the object detection device 200, that is, the degree of vibration of the oscillator 211. From this solid line L11, it can be seen that the oscillator 211 is driven and vibrates for a time Ta from timing t0, so that the transmission of the transmitted wave is completed at timing t1, and then for a time Tb until timing t2, the vibration of the oscillator 211 due to inertia continues while decaying. Therefore, in the graph shown in Figure 6, time Tb corresponds to the so-called reverberation time.

[0045] The solid line L11 indicates that at timing t4, a time Tp has elapsed from timing t0, when the transmission of the transmitted wave begins, the degree of vibration of the oscillator 211 reaches a peak that exceeds a predetermined threshold Th1, represented by the dashed line L21. This threshold Th1 is a value that is pre-set to distinguish whether the vibration of the oscillator 211 is caused by the reception of a transmitted wave that has been reflected back by the object being detected (for example, the obstacle O shown in Figure 2), or by the reception of a transmitted wave that has been reflected back by an object not being tested (for example, the road surface RS shown in Figure 2).

[0046] Although Figure 6 shows an example where the threshold Th1 is set as a constant value that does not change over time, in this embodiment, the threshold Th1 may be set as a value that changes over time.

[0047] Here, vibrations with peaks exceeding the threshold Th1 can be considered to be caused by the reception of received waves that have been reflected back by the object being detected. On the other hand, vibrations with peaks below the threshold Th1 can be considered to be caused by the reception of received waves that have been reflected back by objects other than the object being detected.

[0048] Therefore, the solid line L11 indicates that the vibration of the oscillator 211 at timing t4 was caused by the reception of the received wave, which was a transmitted wave reflected back by the object being detected.

[0049] In the solid line L11, the vibration of the oscillator 211 is attenuated from timing t4 onwards. Therefore, timing t4 corresponds to the timing when the reception of the received wave, which has been reflected back by the object being detected, is completed; in other words, the timing when the last transmitted wave at timing t1 returns as a received wave.

[0050] Furthermore, in the solid line L11, timing t3, which is the starting point of the peak at timing t4, corresponds to the timing when reception of the received wave, which is the transmitted wave reflected back by the detected object, begins. In other words, it corresponds to the timing when the transmitted wave initially sent at timing t0 returns as the received wave. Therefore, in the solid line L11, the time ΔT between timing t3 and timing t4 is equal to the time Ta, which is the transmission time of the transmitted wave.

[0051] Based on the above, in order to determine the distance to the object to be detected using the TOF method, it is necessary to find the time Tf between the timing t0 when the transmitted wave begins to be sent and the timing t3 when the received wave begins to be received. This time Tf can be obtained by subtracting a time ΔT, which is equal to the transmission time Ta of the transmitted wave, from the time Tp, which is the difference between timing t0 and timing t4 when the signal level of the received wave reaches a peak exceeding the threshold Th1.

[0052] Furthermore, when determining whether an object reflecting ultrasound is the object to be detected (for example, obstacle O shown in Figure 2) or an object not to be sampled (for example, road surface RS shown in Figure 2), it may be desirable to change the directivity of the ultrasound generated from the transducer 211 in the height direction.

[0053] However, using multiple ultrasonic sensors to control the directivity of ultrasound presents a problem in terms of cost. Therefore, in this embodiment, low cost is achieved by controlling the directivity of ultrasound with a single ultrasonic sensor (transducer 211).

[0054] In Figure 6, the solid line L11 corresponds to the case where the detection range of the transducer 210 is region R2 in Figure 5. The dashed line L12 corresponds to the case where the detection range of the transducer 210 is region R1 in Figure 5. By changing the vertical directivity of the generated ultrasonic waves in this way, the signal level of the reflected waves from objects changes, which in turn allows for improved object detection accuracy and calculation of object height.

[0055] Figure 7 is a schematic block diagram illustrating the detailed configuration of the object detection device 200 of the embodiment. Note that in Figure 7, the transmitting side configuration (transmitter) and the receiving side configuration (receiver) are shown separately; however, this representation is solely for explanatory purposes. Therefore, in this embodiment, as described above, both the transmission of the transmitting wave and the reception of the receiving wave are realized by a single transducer 210. However, the technology of this embodiment is also applicable to configurations where the transmitting side configuration and the receiving side configuration are separated.

[0056] Furthermore, in the embodiment, at least a portion of the configuration shown in Figure 7 is realized as a result of cooperation between hardware and software, more specifically, 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 portion of the configuration shown in Figure 7 may be realized by dedicated hardware (circuitry).

[0057] First, let's briefly explain the configuration of the transmitting side of the object detection device 200.

[0058] As shown in Figure 7, the object detection device 200 comprises, on the transmitting side, a transmission control unit 430, a transmitter 411, a code generation unit 412, a carrier output unit 413, a multiplier 414, and an amplification circuit 415.

[0059] The transmitter 411 is composed of the aforementioned oscillator 211, and the oscillator 211 transmits a transmission wave corresponding to the transmission signal output (amplified) from the amplification circuit 415.

[0060] In this embodiment, the transmitter 411 transmits the transmission wave after encoding it to include identification information of a predetermined code length, based on the configuration described below.

[0061] The code generation unit 412 generates a pulse signal corresponding to the code of a bit sequence consisting of, for example, a sequence of 0s or 1s. The length of the bit sequence corresponds to the code length of the identification information attached to the transmission signal. The code length is set to a length that allows the transmission waves transmitted from each of the four object detection devices 200 shown in Figure 1 to be distinguished from each other.

[0062] The carrier output unit 413 outputs a carrier wave as the signal to which identification information is to be added. For example, the carrier output unit 413 outputs a sine wave of a predetermined frequency as the carrier wave.

[0063] The multiplier 414 modulates the carrier wave by multiplying the output from the code generation unit 412 and the output from the carrier wave output unit 413 to add identification information. The multiplier 414 then outputs the modulated carrier wave, to which the identification information has been added, to the amplifier circuit 415 as the transmission signal that will form the basis of the transmission wave. In this embodiment, the modulation method may be one or more combinations of several commonly known modulation methods, such as amplitude modulation or phase modulation.

[0064] The amplification circuit 415 amplifies the transmission signal output from the multiplier 414 and outputs the amplified transmission signal to the transmitter 411.

[0065] Also referring to Figure 3, when the transmission control unit 430 (processor 223) receives an ultrasonic generation instruction from the ECU 100, which includes information on the directivity of the ultrasonic waves to be generated, it refers to the directivity correspondence information 230 and selects a combination of voltage application electrode and ground electrode corresponding to the directivity in the ultrasonic generation instruction from the electrodes of the front electrodes 4a, 4b and the rear electrode 7, and determines the frequency, phase, and amplitude. Then, according to the combination of voltage application electrode and ground electrode in the transmitter 411 (transducer 211), the transmission control unit 430 controls the switching unit 212 to switch the wiring 5a, 5b, and 8 that corresponds to the voltage application electrode to the power supply, switch the wiring that corresponds to the ground electrode to the ground, and further switch the other wiring to an insulated state.

[0066] With this configuration, in this embodiment, the transmission control unit 430, switching unit 212, code generation unit 412, carrier output unit 413, multiplier 414, amplification circuit 415, and transmitter 411 are used to transmit a transmission wave (ultrasound) to which predetermined identification information is attached, and to control the directivity of the transmission wave.

[0067] Next, we will briefly describe the configuration of the receiving side of the object detection device 200.

[0068] As shown in Figure 7, the object detection device 200 includes, as a receiver, a receiver 421, an amplification circuit 422, a filter processing unit 423, a correlation processing unit 424, an envelope processing unit 425, a threshold processing unit 426, and a detection processing unit 427.

[0069] The receiver 421 is composed of the aforementioned transducer 211, and the transducer 211 receives the transmitted wave reflected by an object as a received wave.

[0070] The amplification circuit 422 amplifies the received signal, which corresponds to the received wave received by the receiver 421.

[0071] The filter processing unit 423 applies filtering to the received signal amplified by the amplification circuit 422 to reduce noise. In this embodiment, the filter processing unit 423 may acquire information regarding the frequency of the transmitted signal and further apply frequency correction to the received signal to match the frequency of the transmitted signal (for example, correction using a bandpass filter that allows a specific frequency to pass through, or correction for frequency transitions due to Doppler shift).

[0072] The correlation processing unit 424 obtains a correlation value corresponding to the similarity of the identification information between the transmitted wave and the received wave, based on, for example, the transmitted signal obtained from the transmitting side configuration and the received signal after filtering by the filter processing unit 423. The correlation value can be obtained based on a generally well-known correlation function or the like.

[0073] The envelope processing unit 425 determines the envelope of the signal waveform corresponding to the correlation value obtained by the correlation processing unit 424.

[0074] The threshold processing unit 426 compares the envelope value obtained by the envelope processing unit 425 with a predetermined threshold value.

[0075] Based on the comparison results from the threshold processing unit 426, the detection processing unit 427 identifies the timing at which the signal level of the received wave reaches a peak exceeding the threshold (timing t4 shown in Figure 6), and detects the distance to the object using the TOF method.

[0076] Based on the above configuration, the object detection system of the embodiment performs the processing shown in Figure 9. The series of processes shown in Figure 9 are repeatedly executed, for example, at a predetermined control cycle. Figure 9 is a flowchart showing the first process performed by the object detection system of the embodiment.

[0077] As shown in Figure 9, first, in S11, when the transmission control unit 430 (Figure 7) receives an ultrasonic generation instruction from the ECU 100 that includes information on the directivity of the ultrasonic waves to be generated, it refers to the directivity correspondence information 230 and selects a combination of voltage application electrode and ground electrode from the electrodes of the front electrodes 4a, 4b and the rear electrode 7 that corresponds to the directivity in the ultrasonic generation instruction. According to this combination, it controls the switching unit 212 to switch the wiring 5a, 5b, and 8 that corresponds to the voltage application electrode to the power supply, switch the wiring that corresponds to the ground electrode to the ground, and further switch the other wiring to an insulated state.

[0078] Next, in S12, the transmitter 411 of the object detection device 200 transmits a transmission wave to which predetermined identification information has been assigned. At that time, the frequency, phase, and amplitude corresponding to the ultrasonic wave generation instruction in the directional information 230 are used.

[0079] Next, in S13, the receiver 421 of the object detection device 200 receives a reflected wave (received wave) corresponding to the transmitted wave transmitted in S12. Then, the correlation processing unit 424 of the object detection device 200, for example under the control of the ECU 100, obtains a correlation value corresponding to the similarity of the identification information between the transmitted wave and the received wave.

[0080] Next, in S14, after processing by the envelope processing unit 425 and the threshold processing unit 426, the detection processing unit 427 detects the distance to the object using the TOF method.

[0081] Thus, according to the object detection device 200 of this embodiment, by using a transducer 211 configured as shown in Figure 3, selecting a combination of the voltage application electrode and the ground electrode from the front electrodes 4a, 4b and the rear electrode 7, and by adjusting the frequency, phase, and amplitude, the directivity of the ultrasound in the height direction can be changed with a single transducer 211, resulting in low costs. In other words, a transducer needs to be of a certain size or larger in order to vibrate, but in conventional technology, when multiple transducers are used to control the directivity of the ultrasound in the height direction, it becomes necessary to use multiple transducers of a certain size or larger, which increases costs. On the other hand, according to the technology of this embodiment, the directivity of the ultrasound can be controlled with a single transducer 211, resulting in low costs.

[0082] Furthermore, by changing the height-directivity of the generated ultrasound, it is possible to detect low-profile objects with high precision, and to identify the direction of arrival of ultrasound and suppress its effects with high precision when multipath (multiple propagation paths) occurs.

[0083] Furthermore, the directivity in the height direction of the ultrasound can be changed by referring to the specific directional information 230 (Figure 8).

[0084] Furthermore, since the vertical directivity of the ultrasound can be controlled, useful information can be obtained by controlling the ultrasound's directivity, for example, when it is necessary to determine whether a reflected wave is a reflection from the road surface or a reflection from an obstacle. If the reflected wave can be identified, the time spent on subsequent processing, such as filtering out unnecessary information (reflections from the road surface), can be reduced.

[0085] Next, Figure 10 is a flowchart showing the second process performed by the object detection system of the embodiment. Steps S21 to S24 are the same as steps S11 to S14 in Figure 9.

[0086] After step S24, in step S25, the processor 223 determines whether the distance has changed. If yes, proceed to step S26; otherwise, return to step S22.

[0087] In step S26, the processor 223 changes the vertical directivity of the ultrasonic waves transmitted by the transmitter based on the directivity change information, which is set to change the degree of change in the vertical direction of directivity according to the distance.

[0088] In this way, for example, when detecting a low-profile object on the ground and the distance to the object gradually decreases, the directivity of the ultrasound can be gradually changed downwards to maintain the intensity of the reflected waves from the object and thus maintain the accuracy of object detection.

[0089] Next, Figure 11 is a flowchart showing the third process performed by the object detection system of the embodiment. This series of processes calculates the height of an object that reflected ultrasound by acquiring information on the change in intensity of the reflected wave while changing the directivity of the ultrasound in the height direction. Steps S31 to S34 are the same as steps S11 to S14 in Figure 9.

[0090] After step S34, in step S35, the processor 223 determines whether a predetermined condition has been met. If Yes, the process proceeds to step S37; otherwise, it proceeds to step S36. This predetermined condition is for determining whether sufficient information on the change in intensity of the reflected wave has been acquired. For example, it may be, but is not limited to, acquiring a first predetermined number of times or more of high-intensity reflected waves and / or acquiring a second predetermined number of times or more of low-intensity reflected waves.

[0091] In step S36, the processor 223 changes the directivity in the height direction based on a predetermined algorithm. Then, the process returns to step S32.

[0092] In step S37, the processor 223 calculates the height of the object that reflected the ultrasonic waves based on the information about the change in the intensity of the reflected waves.

[0093] In this way, for example, if the height of an object is unknown when it is detected, the height of the object can be calculated by changing the directivity in the height direction of the generated ultrasound while recognizing the change in the intensity of the reflected wave.

[0094] Although embodiments of this disclosure have been described above, these embodiments are merely examples and are not intended to limit the scope of the invention. The embodiments described above can be implemented in various forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The embodiments described above are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0095] For example, in the embodiment described above, the front electrode 4 was divided into two rectangular sections, both as a whole and as individual electrodes, but it is not limited to this. The whole and individual electrodes may have shapes other than rectangles (triangles, circles, etc.), and the number of divisions may be three or more.

[0096] Alternatively, the rear electrode 7 may be divided into two or more electrodes.

[0097] Furthermore, the directional correspondence information 230 (correspondence relationship information) may be stored in an external storage device of the object detection device 200.

[0098] Furthermore, the transducer 211 may generate two or more directional ultrasonic waves simultaneously. In this case, the control unit 220 controls the generation of two or more directional ultrasonic waves with different frequencies and phases, and when an ultrasonic wave is detected via the transducer 210 immediately afterward, it identifies which of the two or more directional ultrasonic waves the detected ultrasonic wave was reflected from, based on the difference in frequency and phase. By simultaneously transmitting ultrasonic waves with two or more directions and identifying the original ultrasonic wave upon reception, it is possible to suppress, for example, the rapid decrease in signal strength due to multipath interference that occurs in obstacles with multiple reflection points.

[0099] [Summary of this embodiment] This embodiment comprises at least the following configurations.

[0100] The ultrasonic generator comprises a piezoelectric body 6 that vibrates by the piezoelectric effect to generate ultrasonic waves when an AC voltage is applied, and a transducer 211 having two or more electrodes (front electrodes 4a, 4b) provided at different heights on the surface of the piezoelectric body 6 and a counter electrode (rear electrode 7) provided at a position opposite to the two or more electrodes, and a control unit 220 that, upon receiving an ultrasonic generation instruction including information on the directivity of the ultrasonic waves to be generated, selects a combination of a voltage application electrode, which is an electrode to which an AC voltage is applied, and a ground electrode, which is an electrode to which the voltage application electrode is set to ground potential, from the two or more electrodes and the counter electrode, corresponding to the directivity in the ultrasonic generation instruction, and performs control to generate ultrasonic waves by applying an AC voltage to the voltage application electrode.

[0101] This configuration allows the vertical directivity of the ultrasound to be changed with a single transducer 211, thus reducing costs.

[0102] Furthermore, the ultrasonic generator described above also includes a storage unit (memory device 222) that stores correspondence information (directivity correspondence information 230) between the combination of a voltage-applying electrode and a ground electrode among two or more electrodes and a counter electrode, and the directivity of the generated ultrasonic waves. The control unit 220 controls the generation of ultrasonic waves by referring to the correspondence information. This configuration is preferable.

[0103] This configuration allows the directivity of the ultrasound in the vertical direction to be changed by referring to the correspondence information described above.

[0104] Furthermore, an example of the transducer 211 in this disclosure comprises a piezoelectric body 6 that vibrates by the piezoelectric effect and generates ultrasonic waves when an AC voltage is applied, and two or more electrodes provided at different heights on the surface of the piezoelectric body 6 and two or more counter electrodes provided at positions opposite to the two or more electrodes, wherein the directivity of the generated ultrasonic waves differs depending on the selected combination of a voltage application electrode which is an electrode to which an AC voltage is applied and a ground electrode which is an electrode that is at ground potential.

[0105] This configuration allows the vertical directivity of the ultrasound to be changed with a single transducer 211, thus reducing costs.

[0106] Furthermore, an object detection device 200 as an example of the present disclosure includes a transmitting unit that transmits ultrasonic waves by a transducer 211, a receiving unit that receives reflected ultrasonic waves by the transducer 211, and a control unit 220. The transducer 211 includes a piezoelectric body 6 that vibrates by the piezoelectric effect and generates ultrasonic waves when an AC voltage is applied, and two or more electrodes provided at different heights on the surface of the piezoelectric body 6 and counter electrodes provided at positions opposite to the two or more electrodes. When the control unit 220 receives an ultrasonic wave generation instruction that includes information on the directivity of the ultrasonic waves to be generated, it selects a combination from the two or more electrodes and the counter electrodes of a voltage application electrode, which is an electrode to which an AC voltage is applied, and a ground electrode, which is an electrode to which an AC voltage is set to ground potential, corresponding to the directivity in the ultrasonic wave generation instruction, and applies an AC voltage to the voltage application electrode to generate ultrasonic waves.

[0107] This configuration allows the vertical directivity of the ultrasound to be changed with a single transducer 211, thus reducing costs.

[0108] Furthermore, the object detection device 200 described above further includes a storage unit (memory device 222) that stores correspondence information between the combination of a voltage-applying electrode and a ground electrode among two or more electrodes and a counter electrode, and the directivity of the generated ultrasonic waves. The control unit 220 controls the generation of ultrasonic waves by referring to the correspondence information. This configuration is preferable.

[0109] This configuration allows the directivity of the ultrasound in the vertical direction to be changed by referring to the correspondence information described above.

[0110] Furthermore, in the object detection device 200 described above, the control unit 220 calculates the distance to the object that reflected the ultrasonic waves based on the timing when the ultrasonic waves are transmitted by the transmitting unit and the timing when the reflected ultrasonic waves are received by the receiving unit. If the distance changes over time, the control unit changes the vertical directivity of the ultrasonic waves transmitted by the transmitting unit based on the directivity change information, which is set to change the degree of change in the vertical direction of directivity according to the distance. This configuration is preferable.

[0111] With this configuration, when the distance changes over time, the directivity of the ultrasound in the vertical direction can be changed according to the distance, for example, to maintain the intensity of the reflected waves from the object and thus maintain the accuracy of object detection.

[0112] Furthermore, in the object detection device 200 described above, the control unit 220 acquires information on the change in intensity of the reflected wave while changing the directivity in the height direction of the ultrasonic waves transmitted by the transmitting unit, and calculates the height of the object that reflected the ultrasonic waves based on the change information. This configuration is preferable.

[0113] With this configuration, by changing the vertical directivity of the generated ultrasound and recognizing the change in the intensity of the reflected wave, it is possible to calculate the height of the object that reflected the ultrasound.

[0114] Furthermore, the effects of the dependent claims and embodiments are additional effects separate from the effects of the independent claims. [Explanation of Symbols]

[0115] 1...Vehicle, 4...Front electrode, 5...Wiring, 6...Piezoelectric element, 7...Rear electrode, 8...Wiring, 100...ECU, 200...Object detection device, 210...Transmitter / receiver, 211...Vibrator, 212...Switching unit, 220...Control unit, 221...Input / output device, 222...Memory device, 223...Processor, 230...Directional information

Claims

1. An object detection device comprising: a transmitting unit that transmits ultrasonic waves using a transducer; a receiving unit that receives reflected ultrasonic waves using the transducer; and a control unit, The aforementioned oscillator is The device comprises a piezoelectric body that vibrates due to the piezoelectric effect and generates ultrasonic waves when an AC voltage is applied, and two or more electrodes provided at different heights on the surface of the piezoelectric body, and counter electrodes provided at positions opposite to the two or more electrodes. The control unit, When an ultrasonic generation instruction is received that includes information on the directivity of the ultrasonic waves to be generated, the system selects a combination from the two or more electrodes and the counter electrode of a voltage-applying electrode, which is an electrode to which an AC voltage is applied, and a ground electrode, which is an electrode to which an AC voltage is set to ground potential, corresponding to the directivity in the ultrasonic generation instruction, and applies an AC voltage to the voltage-applying electrode to generate ultrasonic waves. Based on the timing at which the ultrasonic waves were transmitted by the transmitting unit and the timing at which the reflected ultrasonic waves were received by the receiving unit, the distance to the object that reflected the ultrasonic waves is calculated. An object detection device that, if the aforementioned distance changes over time, changes the vertical directivity of the ultrasonic waves transmitted by the transmitting unit according to the aforementioned distance.

2. The system further comprises a storage unit that stores information on the correspondence between the two or more electrodes and the counter electrodes, specifically the combination of the voltage-applying electrode and the ground electrode, and the directivity of the generated ultrasonic waves. The object detection device according to claim 1, wherein the control unit performs control to generate the ultrasonic waves by referring to the correspondence information.

3. The control unit is The object detection device according to claim 1, wherein information on the change in intensity of the reflected wave is acquired while changing the directivity in the height direction of the ultrasonic waves transmitted by the transmitting unit, and the height of the object that reflected the ultrasonic waves is calculated based on the change information.

4. The object detection device according to claim 1, wherein, if the distance decreases over time, the vertical directivity of the ultrasonic waves transmitted by the transmitting unit is changed downward according to the distance.

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