Object detection system

Abstract

An object detection system (1) includes an acoustic wave generating device (10) that generates an acoustic wave by being heated by electric power, and a processing circuit (30) that performs an object detection process that detects an object in an object space using the acoustic wave from the acoustic wave generating device (10). The object detection process includes a setting process, a wave transmission process, and a determination process. In the setting process, a search range corresponding to a distance to an object in the object space is set. In the wave transmission process, the acoustic wave generating device (10) is controlled so that the acoustic wave generating device (10) generates an acoustic wave at a target sound pressure that is associated with the search range set in the setting process. In the determination process, a received wave signal that indicates an acoustic wave received by a received wave device (20) that receives the acoustic wave from the object space is acquired from the received wave device (20), and it is determined, based on the received wave signal, whether an object is present in the search range.

Description

Technical Field

[0001] This disclosure generally relates to object detection systems. More specifically, this disclosure relates to object detection systems that utilize sound waves for object detection. Background Technology

[0002] Patent Document 1 discloses an object detection device (object detection system). The object detection device of Patent Document 1 uses multiple ultrasonic sensors to detect objects existing around a moving body based on reflected waves (echoes) received by the ultrasonic sensors (receiving devices). The ultrasonic sensors generate ultrasonic waves from an oscillator and generate a received signal along with the vibration of the oscillator.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-105703 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The closer the object, the larger the reflected wave; the farther the object, the smaller the reflected wave. To detect distant objects, increasing the sound pressure level of the ultrasound can be considered. However, if the sound pressure level of the ultrasound increases, the influence of the direct sound (direct wave) caused by the ultrasound generated by the transducer directly incident on the ultrasound sensor becomes greater, making it more difficult to detect objects at close range.

[0008] This disclosure provides an object detection system that can expand the detection range of objects.

[0009] Technical solutions for solving the problem

[0010] One aspect of this disclosure is an object detection system comprising: a sound wave generating device that generates sound waves by heating when energized; and a processing circuit that performs object detection processing to detect objects in an object space using the sound waves from the sound wave generating device. The object detection processing includes a setting process, a wave transmission process, and a determination process. In the setting process, a search range for objects in the object space is set. In the wave transmission process, the sound wave generating device is controlled to generate sound waves with a target sound pressure level, the target sound pressure level being associated with the search range set in the setting process. In the determination process, a received signal representing the sound waves received by the receiving device is obtained from a receiving device that receives sound waves from the object space, and a determination is made based on the received signal to determine whether an object exists within the search range.

[0011] Invention Effects

[0012] The method disclosed herein can expand the detection range of objects. Attached Figure Description

[0013] Figure 1 This is a block diagram illustrating a structural example of an object detection system according to one implementation method.

[0014] Figure 2 yes Figure 1 The circuit diagram of the acoustic wave generator in the object detection system is shown.

[0015] Figure 3 yes Figure 1 The timing diagram shows the operation of the driving and adjusting switching elements in the object detection system.

[0016] Figure 4 It is a waveform diagram showing the relationship between the driving signal and the received signal.

[0017] Figure 5 This is a diagram illustrating the magnitude of the reflected wave.

[0018] Figure 6 yes Figure 1 The flowchart shows the operation of the object detection system.

[0019] Figure 7 This is a block diagram of the structure of the sound wave generating device in Modified Example 1.

[0020] Figure 8 This is a block diagram of the structure of the sound wave generating device in Modified Example 2. Detailed Implementation

[0021] (Implementation Method)

[0022] [1. Summary]

[0023] Figure 1 This is a block diagram illustrating a structural example of the object detection system 1 according to this embodiment. The object detection system 1 is capable of detecting objects in an object space using sound waves. For example, the object detection system 1 is used to detect objects such as obstacles in a moving body. Examples of moving bodies include vehicles such as cars, unmanned aerial vehicles such as drones, and autonomous mobile robots. An example of an autonomous mobile robot is a cleaning robot.

[0024] like Figure 1 As shown, the object detection system 1 includes: a sound wave generator 10, which generates sound waves by heating up when energized; and a processing circuit 30, which performs object detection processing to detect objects in an object space using the sound waves from the sound wave generator 10. The object detection processing includes setting processing ( Figure 6 S11, S16-S19), wave transmission processing ( Figure 6S12) and decision processing ( Figure 6 (S13, S14). In the setting process, the search range for objects in the object space is set. In the wave transmission process, the sound wave generating device 10 is controlled to generate sound waves with a target sound pressure level, and the target sound pressure level is associated with the search range set in the setting process. In the determination process, a received signal representing the sound waves received by the receiving device 20 is obtained from the receiving device 20 that receives sound waves from the object space, and the presence of an object in the search range is determined based on the received signal.

[0025] Figure 1 The object detection system 1 can set the sound pressure of the sound wave output from the sound wave generator 10 to a target sound pressure that is correlated with the search range of the object in the target space. In other words, the sound pressure of the sound wave can be set according to the distance to the object. Therefore, by increasing the target sound pressure, the reflected wave from the object can be increased, thereby enabling the detection of more distant objects. On the other hand, by decreasing the target sound pressure, the influence of direct sound on the receiving device 20 can be reduced, thereby enabling the detection of closer objects. As described above, the object detection system 1 can expand the detection range of objects.

[0026] [2. Details]

[0027] The object detection system 1 will now be described with reference to the accompanying drawings. Figure 1 As shown, the object detection system 1 includes a sound wave generator 10, a wave receiver 20, and a processing circuit 30.

[0028] [2-1. Sound wave generating device]

[0029] Figure 1 The sound wave generating device 10 includes a sound wave source 11, a drive circuit 12, an adjustment circuit 13, and a control circuit 14.

[0030] The sound source 11 generates sound waves by heating up when energized. More specifically, the sound source 11 is a thermally excited element that generates sound waves by heating air. The sound source 11 is a so-called thermoelectric sound generator. The sound source 11 includes, for example, a heating element, a substrate, a pair of electrodes, and an insulating layer. The heating element is a resistive element that heats up by allowing current to flow through it. The heating element is disposed on the substrate, for example, so that it is in contact with air. The air surrounding the heating element expands or contracts according to the temperature change of the heating element. This generates air pressure waves, i.e., sound waves. The insulating layer suppresses heat conduction from the heating element to the substrate. The pair of electrodes are electrodes for allowing current to flow from the outside of the sound source 11 to the heating element. The pair of electrodes are disposed on both sides of the heating element. The sound source 11 may also have a conventionally known structure, therefore a detailed description of the sound source 11 is omitted.

[0031] Figure 2This is a circuit diagram illustrating an example of the structure of the sound wave generator 10. (Example:) Figure 2 As shown, the sound source 11 is electrically connected between the DC power supply V1 and ground.

[0032] The DC power supply V1 includes various power circuits and / or batteries. These power circuits may include, for example, an AC / DC converter, a DC / DC converter, a regulator, and a battery. The voltage of the DC power supply V1 is, for example, 5V.

[0033] The drive circuit 12 supplies power to the sound source 11, causing the sound source 11 to generate sound waves. For example... Figure 2 As shown, the drive circuit 12 includes a capacitor C1, a drive switching element T1, and a resistor R1.

[0034] Capacitor C1 is used to supply power to the sound source 11. Capacitor C1 is electrically connected between the DC power supply V1 and the connection point of the sound source 11 and ground. Capacitor C1 is, for example, an electrolytic capacitor or a ceramic capacitor.

[0035] A driving switch element T1 is used to drive the sound wave source 11 by controlling the power supply to it. The driving switch element T1 is electrically connected between the sound wave source 11 and ground. The driving switch element T1 is, for example, an n-type MOSFET. When the driving switch element T1 is turned on, power is supplied to the sound wave source 11. Figure 2 As shown by arrow A1, current flows from capacitor C1 to sound source 11, supplying power to sound source 11. If the drive switching element T1 is open, no power is supplied to sound source 11. By turning the drive switching element T1 on and off, sound source 11 generates sound waves. In this disclosure, a "sound wave" is a periodic sine wave. In contrast, a "series of sound waves" is a multi-period sine wave.

[0036] Resistor R1 forms an overcurrent protection element electrically connected between capacitor C1 and DC power supply V1. Resistor R1 limits the current flowing directly from DC power supply V1 to sound source 11. Resistor R1 prevents excessive heating of sound source 11. The resistance value of resistor R1 is, for example, 50Ω or more and 5kΩ or less.

[0037] In the drive circuit 12, current flows from capacitor C1 to sound source 11, supplying power to sound source 11. Therefore, the sound pressure of the sound wave output from sound source 11 depends on the voltage V2 between the two ends of capacitor C1.

[0038] The adjustment circuit 13 adjusts the sound pressure of the sound wave from the sound wave generator 10 by adjusting the voltage V2 across capacitor C1 in the drive circuit 12. Figure 2As shown, the adjustment circuit 13 includes an inductor L1, an adjustment switching element T2, and a diode D1. The inductor L1 is electrically connected between the DC power supply V1 and the capacitor C1. Figure 2 In this circuit, inductor L1 is electrically connected between resistor R1 (which serves as an overcurrent protection element) and DC power supply V1. Adjustment switch T2 is electrically connected in parallel with the series circuit of inductor L1 and DC power supply V1. Adjustment switch T2 is, for example, an n-type MOSFET. Inductor L1, DC power supply V1, and adjustment switch T2 form a closed loop. If adjustment switch T2 is turned on, energy is stored in inductor L1. Figure 2 As shown by arrow A2, current flows through the closed loop of DC power supply V1, inductor L1, and adjusting switch element T2, accumulating energy in inductor L1. If the adjusting switch element T2 changes from closed to open, an induced electromotive force is generated in inductor L1. Therefore, as shown by arrow A3, current flows from inductor L1 to capacitor C1, charging capacitor C1. Figure 2 The adjustment circuit 13 can charge capacitor C1, thereby allowing adjustment of the voltage V2 across capacitor C1. The energy stored in inductor L1 is adjusted by regulating the period during which the switching element T2 is on. Diode D1 is electrically connected between inductor L1 and capacitor C1. Specifically, the anode of diode D1 is electrically connected to inductor L1, and the cathode of diode D1 is electrically connected to capacitor C1. Diode D1 reduces the possibility of current flowing from capacitor C1 to inductor L1, thus preventing accidental discharge of capacitor C1.

[0039] The control circuit 14 is configured to control the drive circuit 12 and the adjustment circuit 13. The control circuit 14 may include, for example, an oscillator for outputting the drive signals S1 and S2, described later. The control circuit 14 may be, for example, an integrated circuit such as an FPGA (field-programmable gate array). While controlling the switching of the drive switching element T1 of the drive circuit 12 to generate sound waves from the sound source 11, the control circuit 14 also controls the adjustment circuit 13 to make the voltage V2 across the capacitor C1 of the drive circuit 12 a value corresponding to the target sound pressure level.

[0040] The control circuit 14 controls the switching (on / off) of the drive element T1 of the drive circuit 12. By controlling the drive element T1 of the drive circuit 12, the control circuit 14 executes the action of generating sound waves from the sound source 11. Figure 1As shown, the control circuit 14 outputs a drive signal S1 to control the switching of the drive switching element T1. In this embodiment, the drive switching element T1 is a MOSFET, and the drive signal S1 is input to the gate of the drive switching element T1. During the period when the drive signal S1 is high, the drive switching element T1 is turned on. During the period when the drive signal S1 is low, the drive switching element T1 is turned off. Figure 2 In the diagram, the drive signal S1 is represented as a DC power supply.

[0041] Control circuit 14 controls the switching (on / off) of the adjustment switching element T2 of adjustment circuit 13. By controlling the adjustment switching element T2 of adjustment circuit 13, control circuit 14 adjusts the voltage V2 across capacitor C1 in drive circuit 12. Figure 1 As shown, the control circuit 14 outputs a drive signal S2 to control the switching of the adjustment switching element T2. In this embodiment, the adjustment switching element T2 is a MOSFET, and the drive signal S2 is input to the gate of the adjustment switching element T2. During the period when the drive signal S2 is high, the adjustment switching element T2 is turned on. During the period when the drive signal S2 is low, the adjustment switching element T2 is turned off. Figure 2 In the diagram, the drive signal S2 is represented as a DC power supply.

[0042] Next, refer to Figure 3 The control circuit 14 controls the drive circuit 12 and the adjustment circuit 13 in detail. Figure 3 This is a timing diagram illustrating the operation of the sound wave generating device 10.

[0043] Control circuit 14 outputs drive signal S1 to drive switching element T1 to control drive circuit 12 to generate sound waves from sound source 11. For example... Figure 3 As shown, the drive signal S1 is a pulse signal (impact signal). The pulse width of the drive signal S1 can be set to, for example, 2μs to 25μs. In the drive signal S1, the pulse width corresponds to the on-time T1on of the drive switching element T1. The on-time T1on is the period during which the drive switching element T1 is turned on. During the on-time T1on, current flows from the capacitor C1 to the sound source 11, supplying power to the sound source 11.

[0044] During the on-time T1on, power is supplied to the sound source 11 from the capacitor C1 and sound waves are output from the sound source 11. The control circuit 14 starts during the on-time T1on (e.g., Figure 3Before time t21, the voltage V2 across capacitor C1 is adjusted by adjustment circuit 13. Control circuit 14 outputs drive signal S2 to adjustment switch element T2 to control adjustment circuit 13 in adjusting voltage V2 across capacitor C1. In this embodiment, adjustment switch element T2 is turned on during the on-time of drive switch element T1 (T1on), and simultaneously switches to on-time with drive switch element T1.

[0045] exist Figure 3 In the example of drive signal S2, three drive signals S2-1 to S2-3 are shown. Figure 3 As shown, drive signals S2-1 to S2-3 are pulse train signals. Specifically, the pulse widths of drive signals S2-1 to S2-3 correspond to the on-time T2on of the adjusting switch element T2. The on-time T2on is the period during which the adjusting switch element T2 is on. The on-time T2on of drive signals S2-1 to S2-3 are different. The on-time T2on of drive signal S2-1 is from time t11 to time t12, the on-time T2on of drive signal S2-2 is from time t11 to time t13 (later than time t12), and the on-time T2on of drive signal S2-3 is from time t11 to time t14 (later than time t13). During the on-time T2on, current flows from the DC power supply V1 to the inductor L1, where energy is stored. After the on-time T2on, the adjusting switch element T2 is turned off. When the adjusting switch element T2 is turned off, current flows from inductor L1 to capacitor C1, and capacitor C1 is charged. Therefore, the voltage V2 across capacitor C1 can be adjusted by the length of the on-time T2on. Under drive signals S2-1 to S2-3, the voltage V2 across capacitor C1 becomes the lowest under drive signal S2-1, and the voltage V2 across capacitor C1 becomes the highest under drive signal S2-3.

[0046] like Figure 3 As shown, the control circuit 14 switches the adjustment switch element T2 from on to off before the on-time T1on of the drive switch element T1. Therefore, the voltage V2 across the capacitor C1 can be set to a voltage corresponding to the on-time T2on of the adjustment switch element T2.

[0047] [2-2. Wave receiving device]

[0048] The receiving device 20 receives the sound wave and outputs the received signal representing the sound wave to the processing circuit 30. Figure 1The receiving device 20 includes multiple (two in the illustrated example) microphones 21, multiple (two in the illustrated example) amplifier circuits 22, multiple (two in the illustrated example) filters 23, an AD converter 24, and a control circuit 25.

[0049] Microphone 21 is an acoustic-to-electrical conversion element that converts sound waves into electrical signals. If microphone 21 receives a sound wave, it outputs a received signal in analog form representing the received sound wave. Microphone 21 is used to detect sound waves reflected by an object after being output from sound source 11. Amplifier circuit 22 amplifies and outputs the received signal in analog form from microphone 21. Filter 23 allows signals in the passband containing the frequency band of the sound wave to pass through. Filter 23 is, for example, a bandpass filter. AD converter 24 converts the received signal in analog form, which has passed through filter 23, into a received signal in digital form and outputs it to control circuit 25. Microphone 21, amplifier circuit 22, filter 23, and AD converter 24 can also be conventionally known structures, therefore detailed descriptions are omitted.

[0050] Control circuit 25 controls AD converter 24, causing AD converter 24 to output the received signal in digital form to control circuit 25. Control circuit 25 outputs the received signal in digital form from AD converter 24 to processing circuit 30. Control circuit 25 is, for example, an integrated circuit such as an FPGA. Alternatively, control circuit 14 and control circuit 25 can be integrated into a single chip. For example, control circuit 14 and control circuit 25 can also be implemented by a single FPGA.

[0051] [2-3. Processing Circuit]

[0052] The processing circuit 30 is a circuit that controls the operation of the object detection system 1. The processing circuit 30 can be implemented, for example, by a computer system containing one or more processors (microprocessors) and one or more memories. The function of the processing circuit 30 is achieved by executing programs through one or more processors.

[0053] The processing circuit 30 performs object detection processing, which uses sound waves from the sound wave generator 10 to detect objects in the object space. The object detection processing includes setting processing, wave transmission processing, and judgment processing.

[0054] In the setting process, a search range for objects in the object space is set. The object space is the space of objects that are detected. Multiple search ranges can be set, relating to a range of minimum to maximum distances to objects pre-defined in the object space. In this embodiment, the distance to the object is, for example, the distance from the sound wave generator 10 to the object. The search range is the range of objects in the object space that are detected. The search range is determined by the range of distances to the object. As described above, multiple search ranges can be set in the object space, and these multiple search ranges are ranges with different distances from each other. Multiple search ranges may also partially overlap, but it is preferable that one search range is not contained within another. For example, the multiple search ranges include a first search range, a second search range, and a third search range. The first search range is closest to the sound wave generator 10 among the first to third search ranges. The third search range is furthest from the sound wave generator 10 among the first to third search ranges. The second search range is farther from the sound wave generator 10 than the first search range and closer to the sound wave generator 10 than the third search range. In other words, the first search range is the near-range search range, the second search range is the medium-range search range, and the third search range is the far-range search range. Near-range is, for example, a distance of a few centimeters from the object. Far-range is, for example, a distance of a few meters from the object. The method for setting the search range in the settings process will be explained in "[4. Setting the Search Range in Settings Process]" later.

[0055] In the wave transmission process, the sound wave generating device 10 is controlled to generate a sound wave with a target sound pressure level, which is correlated with a search range set in the setting process. More specifically, in the wave transmission process, the voltage V2 across capacitor C1 is adjusted by the adjustment circuit 13 so that the sound pressure of the sound wave from the sound wave generating device 10 becomes the target sound pressure level, and the drive switching element T1 of the drive circuit 12 is driven to generate a sound wave from the sound wave source 11. In the wave transmission process, for example, the processing circuit 30 sends a command to the control circuit 14, whereby the control circuit 14 executes the control of the drive circuit 12 and the adjustment circuit 13. The establishment of the correlation between the search range and the target sound pressure level will be explained later in "[3. Establishment of Correlation between Search Range and Target Sound Pressure Level]".

[0056] In the determination process, a received signal representing the sound waves received by the receiving device 20 is acquired from the receiving device 20 that receives sound waves from the object space. For example, the received signal in digital form from the receiving device 20 is acquired in the determination process. If an object exists in the object space, the sound waves from the object space include a reflected wave (also called an echo) at the object from the sound wave output from the sound wave generator 10. In the determination process, the presence of an object in the object space is determined based on the acquired received signal. In this embodiment, in the determination process, if the determination value based on the received signal is above a threshold, it is determined that an object exists. The determination value is, for example, the magnitude (amplitude) of the received signal. The threshold is used to determine whether the sound wave represented by the received signal contains a reflected wave. That is, the case where the determination value based on the received signal is above the threshold is the case where a reflected wave at the object is detected. In the determination process, if it is determined that an object exists within the search range, the distance to the object is determined based on the received signal. In the determination process, for example, the distance to the object is calculated using TOF (Time of Flight) technology based on the time difference between the moment when the sound wave is output from the sound wave generator 10 (transmission time) and the moment when the reflected wave is detected at the object (reception time). Since conventionally known techniques can be applied to the detection of objects using sound waves and the determination of distances to objects, detailed explanations are omitted.

[0057] [3. Establishing a correlation between the search range and the target sound pressure level]

[0058] Figure 4 This is a timing diagram showing the relationship between the drive signal S1 and the received signals R1 and R2 in a comparative example object detection system without adjustment circuit 13. Figure 4 In this context, Vth is the threshold used in the decision-making process. The received signal R1 corresponds to the case where the object is at close range, and the received signal R2 corresponds to the case where the object is at a distance. Figure 4 In the receiving signals R1 and R2, a direct sound wave RW10 is generated because the sound wave output from the sound wave generator 10 via the drive signal S1 directly enters the receiving device 20. To prevent false detection due to the magnitude of the direct sound wave RW10 exceeding a threshold Vth, a blind zone is set. The blind zone is set after the wave transmission process. For example, the blind zone is the period from the time t31 when the drive signal S1 is output to the time t32 when the magnitude of the direct sound wave RW10 does not exceed the threshold Vth. In the determination process, during the blind zone, the presence of an object is not determined based on the received signals. The received signal R1 contains a reflected wave RW11 from a nearby object, and the received signal R2 contains a reflected wave RW12 from a distant object. Figure 4It is clear that the closer an object is, the earlier the received time of the reflected wave from the object is detected. When a blind zone is set, objects cannot be detected at distances where the reception time falls within the blind zone. Therefore, to detect objects at closer distances, the blind zone should ideally be short. The greater the sound pressure of the sound wave output from the sound wave generator 10, the greater the size and length of the direct sound RW10. That is, the period during which the size of the direct sound RW10 exceeds the threshold Vth varies depending on the sound pressure of the sound wave output from the sound wave generator 10. Therefore, if the sound pressure of the sound wave output from the sound wave generator 10 is reduced, shortening the period during which the size of the direct sound RW10 exceeds the threshold Vth, the blind zone can also be shortened. Therefore, to detect objects at close distances, the sound pressure of the sound wave should ideally be low. Furthermore, according to... Figure 4 It is clear that if an object is close, the reflected wave from the object is larger, and if the object is far away, the reflected wave from the object is smaller. Even when a reflected wave from an object actually exists, in the determination process, if the magnitude of the reflected wave is below the threshold Vth, it is determined that no object exists. That is, for distances where the magnitude of the reflected wave is below the threshold Vth, object detection cannot be performed. Here, if the sound pressure of the sound wave output from the sound wave generator 10 is increased, the reflected wave can be made larger. Therefore, in order to detect objects at a distance, the sound pressure of the sound wave is preferably larger. In this way, in order to detect objects at a close distance, the sound pressure of the sound wave is preferably smaller, so as to shorten the period during which the magnitude of the direct sound RW10 becomes above the threshold Vth. On the other hand, in order to detect objects at a distance, the sound pressure of the sound wave is preferably larger, so as to extend the distance during which the magnitude of the reflected wave becomes above the threshold Vth. Considering the above aspects, the farther the search range is from the sound wave generator 10, the larger the target sound pressure is set. Regarding the first search range to the third search range, the target sound pressure associated with the first search range is the smallest, and the target sound pressure associated with the third search range is the largest. Furthermore, if the target sound pressure increases, the period during which the direct sound RW10 becomes above the threshold Vth becomes longer. Therefore, the farther the search range is from the sound wave generator 10, the longer the blind zone is set. Regarding the first to third search ranges, the blind zone associated with the first search range is the shortest, and the blind zone associated with the third search range is the longest.

[0059] Figure 5 This is an illustration of the magnitude of the reflected wave. When a sound wave with a given sound pressure is output from the sound wave generator 10, if an object is present in the first search range, a reflected wave RW1 is obtained; if an object is present in the second search range, a reflected wave RW20 is obtained; and if an object is present in the third search range, a reflected wave RW30 is obtained. The farther the object is from the sound wave generator 10, the smaller the magnitude of the reflected wave. Figure 5In this context, Vth is the threshold used in the decision-making process. The magnitude of the reflected wave RW1 is sufficiently large compared to the threshold Vth, but the magnitude of the reflected wave RW30 is only slightly larger than the threshold Vth. When measuring distance from the moment the sound wave is output from the sound wave generator 10 until the moment a reflected wave exceeding the threshold Vth is detected, the longer the distance to the object, the smaller the magnitude of the reflected wave. Therefore, the longer the distance to the object, the greater the impact of the error, and the lower the object detection accuracy. Further reducing the threshold Vth can reduce the impact of the error, but it may also lead to the misdetection of noise that is not a reflected wave as a reflected wave.

[0060] In this embodiment, a target sound pressure level is set such that the magnitude of the reflected wave from the object is greater than or equal to a predetermined value. This predetermined value is larger than a threshold value Vth. In particular, the predetermined value is preferably larger than the threshold value Vth to a degree that it is not affected by errors. For example, when a sound wave with a given sound pressure level is output from the sound wave generating device 10, the predetermined value corresponds to the magnitude of the reflected wave RW1 from an object within the first search range. In the second search range, a target sound pressure level is set such that a reflected wave RW2 with a magnitude of the predetermined value and larger than the reflected wave RW20 is obtained. In the third search range, a target sound pressure level is set such that a reflected wave RW3 with a magnitude of the predetermined value and larger than the reflected wave RW30 is obtained. By setting target sound pressure levels for multiple search ranges in this way, the same threshold value Vth can be used for different search ranges, and the influence of distance-related errors and the possibility of false detections due to noise can be reduced, thereby improving the object detection accuracy.

[0061] [4. Setting the search range during processing]

[0062] In the setting process, a search range is selected from multiple search ranges. For example, in the setting process, the search range closest to the sound wave generator 10 among multiple search ranges is selected as the initial search range. In the setting process, if the determination process determines that no object exists, the search range is changed. In the setting process, if the determination process determines that no object exists, the search range is changed so that the search range is further away from the sound wave generator 10. That is, in the setting process, the search range is changed from near to far from the sound wave generator 10. In the setting process, if the search range where the determination process determines that no object exists is farthest from the sound wave generator 10, the search range is changed so that the search range is closer to the sound wave generator 10. For example, in the setting process, the search range closest to the sound wave generator 10 is selected from multiple search ranges. In the setting process, if the distance to the object is determined by the determination process, the search range is set based on the distance to the object determined in the determination process. That is, setting the search range based on the distance to the object increases the probability of detecting the object. Furthermore, objects can be tracked in the object space.

[0063] [5. Action]

[0064] Next, refer to Figure 6 The operation of the object detection system 1 will be explained, particularly the operation of the object detection system 1 during object detection processing. In the following explanation, the multiple search ranges are the first to third search ranges described above. In the setting process, the first search range, which is the search range closest to the sound wave generator 10, is selected as the initial search range (S11). In the wave transmission process, the sound wave generator 10 is controlled to generate a sound wave with a target sound pressure level, and the target sound pressure level is associated with the first search range set in the setting process (S12). Then, the presence of an object in the first search range is determined by the determination process (S13).

[0065] If an object exists in the first search range (S13; Yes), the distance to the object is determined by the determination process (S14). In the setting process, the search range is set based on the distance to the object determined in the determination process (S16). For example, in the setting process, a search range containing the distance to the object determined in the determination process is selected from multiple search ranges. Then, in the wave transmission process, the sound wave generating device 10 is controlled so that it generates a sound wave with a target sound pressure, and the target sound pressure is associated with the search range set in the setting process (S12). If no object exists in the first search range (S13; No), the search range is changed in the setting process. First, in the setting process, it is determined whether the search range where the determination process determines that no object exists is farthest from the sound wave generating device 10 (S17). Since the current search range is the first search range (S17: No), the search range is changed in the setting process so that the search range is farthest from the sound wave generating device 10 (S18). In the setup process, the search range is changed from the first search range to the second search range. Then, S12 and S13 are executed.

[0066] If an object exists in the second search range (S13; Yes), executes S14 and S16. If no object exists in the second search range (S13; No), in the setting process, it is determined whether the search range where the determination process determined that no object exists is furthest from the sound wave generator 10 (S17). Since the current search range is the second search range (S17: No), in the setting process, the search range is changed so that the search range is farther away from the sound wave generator 10 (S18). In the setting process, the search range is changed from the second search range to the third search range. Then, executes S12 and S13.

[0067] If an object exists in the third search range (S13; Yes), execute S14 and S16. If no object exists in the third search range (S13; No), in the setting process, determine whether the search range where the determination process determined that no object exists is furthest from the sound wave generator 10 (S17). Since the current search range is the third search range (S17: Yes), in the setting process, change the search range so that it is closer to the sound wave generator 10 (S19). In the setting process, change the search range from the third search range to the first search range. Then, execute S12 and S13.

[0068] In this way, the object detection system 1 performs object detection while changing the search range through setting processing. The object detection system 1 can set the sound pressure of the sound wave output from the sound wave generator 10 to a target sound pressure associated with the search range of the object in the object space. That is, the sound pressure of the sound wave can be set according to the distance to the object. Therefore, by increasing the target sound pressure, the reflected wave from the object can be increased, thereby enabling the detection of more distant objects. On the other hand, by decreasing the target sound pressure, the influence of direct sound on the receiving device 20 can be reduced, thereby enabling the detection of closer objects. As described above, the object detection system 1 can expand the object detection range.

[0069] [6. Effects, etc.]

[0070] The object detection system 1 described above includes: a sound wave generating device 10 that generates sound waves by heating up when energized; and a processing circuit 30 that performs object detection processing to detect objects in an object space using the sound waves from the sound wave generating device 10. The object detection processing includes: a setting process that sets a search range for objects in the object space; a wave transmission process that controls the sound wave generating device 10 to generate sound waves with a target sound pressure level, the target sound pressure level being associated with the search range set in the setting process; and a determination process that acquires received signals R1 and R2 representing the sound waves received by the receiving device 20 from the receiving device 20 receiving the sound waves from the object space, and determines whether an object exists based on the received signals R1 and R2. With this structure, the object detection range can be expanded.

[0071] In the object detection system 1, the farther the search range is from the sound wave generator 10, the greater the target sound pressure. This structure allows for an expanded detection range for objects.

[0072] In object detection system 1, during the determination process, if the magnitude of the received signal is above the threshold Vth, an object is determined to exist. This structure simplifies the object detection process.

[0073] In object detection system 1, the target sound pressure is set such that the magnitudes of the reflected waves RW1, RW2, and RW3 from the object are greater than a predetermined value larger than the threshold Vth. Based on this structure, the influence of distance-related errors and the possibility of false detections due to noise can be reduced, thereby improving the accuracy of object detection.

[0074] In object detection system 1, during the determination process, the presence of an object is not determined based on the received signals R1 and R2 within the blind zone set after the wave transmission process. The blind zone is set according to the search range set in the setting process. According to this structure, false detection caused by the magnitude of the direct sound RW10 exceeding the threshold Vth can be prevented, while also expanding the object detection range.

[0075] In object detection system 1, the further the search range is from the sound wave generator 10, the longer the blind zone is set. According to this structure, false detection caused by the magnitude of the direct sound RW10 exceeding the threshold Vth can be prevented, while also expanding the detection range of objects.

[0076] In object detection system 1, during the setting process, if the determination process determines that no object exists, the search range is changed. This structure increases the likelihood of detecting an object.

[0077] In the object detection system 1, during the setting process, if the determination process determines that no object exists, the search range is changed so that the search range is moved away from the sound wave generator 10. This structure increases the likelihood of detecting an object.

[0078] In the object detection system 1, during the setting process, if the search range determined by the determination process to be the furthest from the sound wave generator 10 where no object exists, the search range is changed so that it is closer to the sound wave generator 10. This structure increases the likelihood of detecting an object.

[0079] In object detection system 1, during the determination process, if an object is determined to exist, the distance to the object is determined based on the received signals R1 and R2. Based on this structure, the distance to the object can be obtained.

[0080] In object detection system 1, during the setting process, if the distance to the object is determined by the decision process, the search range is set based on the distance to the object determined in the decision process. This structure increases the likelihood of detecting the object.

[0081] In the object detection system 1, the sound wave generating device 10 includes: a drive circuit 12 having a capacitor C1 charged by a DC power supply V1 and a drive switching element T1 that supplies power from the capacitor C1 to a sound wave source 11 that generates sound waves by heating when energized; and an adjustment circuit 13 that adjusts the sound pressure of the sound wave from the sound wave generating device 10 by adjusting the voltage V2 across the capacitor C1 in the drive circuit 12. During wave transmission, the voltage V2 across the capacitor C1 is adjusted by the adjustment circuit 13 to make the sound pressure of the sound wave from the sound wave generating device 10 the target sound pressure, thereby driving the drive switching element T1 in the drive circuit 12 to generate sound waves from the sound wave source 11. With this structure, the sound pressure of the sound wave output from the sound wave generating device 10 can be easily adjusted.

[0082] In the object detection system 1, the adjustment circuit 13 includes: an inductor L1 electrically connected between a DC power supply V1 and a capacitor C1; and an adjustment switch element T2 electrically connected in parallel with the series circuit of the inductor L1 and the DC power supply V1. The adjustment circuit 13 adjusts the voltage V2 across the capacitor C1 by adjusting the on-time T2on of the adjustment switch element T2. This structure simplifies the circuit configuration.

[0083] In the object detection system 1, the adjustment circuit 13 has a diode D1, the anode of which is electrically connected to an inductor L1, and the cathode of which is electrically connected to a capacitor C1. This structure reduces the possibility of current flowing from the capacitor C1 to the inductor L1, thus accidentally discharging the capacitor C1.

[0084] In the object detection system 1, the adjustment switch element T2 is switched on during the period when the drive switch element T1 is switched on, and it switches on simultaneously with the drive switch element T1. Based on this structure, the adjustment of the sound pressure level of the sound wave becomes easy.

[0085] (Modified Example)

[0086] The embodiments disclosed herein are not limited to the embodiments described above. Various modifications can be made to the embodiments described above, depending on the design, etc., as long as the objectives of this disclosure are achieved. Hereinafter, variations of the embodiments described above are given. The variations described below can be appropriately combined and applied.

[0087] [1. Variation Example 1]

[0088] Figure 7 This is a circuit diagram of a structural example of the sound wave generator 10A, as shown in Modification 1. The sound wave generator 10A includes a sound wave source 11, a drive circuit 12A, and an adjustment circuit 13A. Like the sound wave generator 10, the sound wave generator 10A also includes a control circuit 14, but... Figure 7The diagram of control circuit 14 is omitted.

[0089] The drive circuit 12A has a drive switching element T1 that supplies power to a sound source 11 from a given capacitor. The sound source 11 heats up and generates sound waves when energized. The drive switching element T1 controls the power supply to the sound source 11. The drive switching element T1 is connected between the sound source 11 and ground. If the drive switching element T1 is on, power is supplied to the sound source 11. If the drive switching element T1 is off, no power is supplied to the sound source 11. By turning the drive switching element T1 on / off, the sound source 11 generates sound waves. The drive switching element T1 is, for example, an n-type MOSFET.

[0090] The adjustment circuit 13A adjusts the sound pressure of the sound wave from the sound wave generator 10 by selecting at least one of a plurality of capacitors C1-1 to C1-3 (hereinafter referred to as C1 in the drawing) that are charged by a plurality of DC power supplies V1-1 to V1-3 (hereinafter collectively referred to as V1) with different voltages as a given capacitor. Figure 7 As shown, the adjustment circuit 13A includes multiple capacitors C1-1 to C1-3 and a switching circuit 131.

[0091] Multiple capacitors C1-1 to C1-3 are charged by multiple DC power supplies V1-1 to V1-3 with different voltages. Capacitor C1 is used to supply power to the sound source 11. Capacitor C1 is electrically connected between the connection point of the DC power supply V1 and the sound source 11 and ground. Capacitor C1 is charged by the DC power supply V1. Capacitor C1 is, for example, an electrolytic capacitor or a ceramic capacitor.

[0092] Switching circuit 131 selects a power source from a plurality of capacitors C1 to supply power to sound source 11. More specifically, switching circuit 131 electrically connects at least one of the plurality of capacitors C1 to sound source 11, such that sound wave generating device 10A generates sound waves with a target sound pressure level associated with a search range set in the setting process. For example, capacitor C1-1 and DC power supply V1-1 are used to achieve a target sound pressure level associated with a first search range. Capacitor C1-2 and DC power supply V1-2 are used to achieve a target sound pressure level associated with a second search range. Capacitor C1-3 and DC power supply V1-3 are used to achieve a target sound pressure level associated with a third search range.

[0093] like Figure 7As shown, the switching circuit 131 includes multiple (three in the illustrated example) switches SW1-1 to SW1-3 (hereinafter referred to collectively as SW1). The multiple switches SW1-1 to SW1-3 are electrically connected between the sound source 11 and the multiple capacitors C1-1 to C1-3. In the switching circuit 131, one of the multiple switches SW1-1 to SW1-3 is set to ON, and the others are set to OFF. Thus, one of the multiple capacitors C1-1 to C1-3 is electrically connected to the sound source 11.

[0094] Control circuit 14 controls the switching circuit 131 of drive circuit 12A and adjustment circuit 13A. Control circuit 14 controls the switch SW1 of switching circuit 131, thereby electrically connecting at least one of the plurality of capacitors C1 to sound source 11, so that sound wave generating device 10A generates sound wave with target sound pressure, the target sound pressure being associated with a search range set in the setting process.

[0095] When the object detection system 1 is equipped with a sound wave generator 10A, the processing circuit 30 controls the control circuit 14 of the sound wave generator 10A to perform the following wave transmission process. In the wave transmission process, the adjustment circuit 13A selects a capacitor C1 corresponding to the target sound pressure from a plurality of capacitors C1 as a given capacitor, and drives the drive switching element T1 of the drive circuit 12A to generate a sound wave from the sound wave source 11.

[0096] In this way, the object detection system 1 can set the sound pressure of the sound wave output from the sound wave generator 10A to a target sound pressure that is correlated with the search range of the object in the object space. That is, the sound pressure of the sound wave can be set according to the distance to the object. Therefore, by increasing the target sound pressure, the reflected wave from the object can be increased, thereby enabling the detection of more distant objects. On the other hand, by decreasing the target sound pressure, the influence of direct sound on the receiving device 20 can be reduced, thereby enabling the detection of closer objects. As described above, the object detection system 1 can expand the detection range of objects.

[0097] In the object detection system 1 described above, the sound wave generating device 10A includes: a drive circuit 12A having a drive switching element T1 that supplies power from a given capacitor C1 to a sound wave source 11 that generates sound waves by heating when energized; and an adjustment circuit 13A that adjusts the sound pressure of the sound wave from the sound wave generating device 10A by selecting at least one of a plurality of capacitors C1 charged by a plurality of DC power supplies V1 with different voltages as the given capacitor C1. In the wave transmission process, the adjustment circuit 13A selects a capacitor C1 corresponding to the target sound pressure from the plurality of capacitors C1 as the given capacitor C1, and drives the drive switching element T1 of the drive circuit 12A to generate sound waves from the sound wave source 11. With this structure, the sound pressure of the sound wave output from the sound wave generating device 10A can be easily adjusted.

[0098] [2. Variation Example 2]

[0099] Figure 8 This is a circuit diagram of the structure of the sound wave generator 10B, which is a modified example 2. The sound wave generator 10B includes multiple (three in the illustrated example) sound wave sources 11-1 to 11-3 (hereinafter collectively referred to as 11), a drive circuit 12, and an adjustment circuit 13B. The sound wave generator 10B, like the sound wave generator 10, includes a control circuit 14, but... Figure 8 The diagram of control circuit 14 is omitted.

[0100] Multiple sound wave sources 11-1 to 11-3 are electrically connected between the DC power supply V1 and ground. For example... Figure 8 As shown, multiple sound wave sources 11-1 to 11-3 are connected in parallel.

[0101] The drive circuit 12 includes a capacitor C1 charged by a DC power supply V1 and a drive switching element T1 that supplies power from the capacitor C1 to a given sound source 11. A given sound source 11 is selected from a plurality of sound sources 11-1 to 11-3. The drive circuit 12 supplies power to the given sound source 11, causing the given sound source 11 to generate sound waves. Furthermore, the drive circuit 12 includes a resistor R1. The resistor R1 constitutes an overcurrent protection element electrically connected between the capacitor C1 and the DC power supply V1.

[0102] The adjustment circuit 13B adjusts the sound pressure level of the sound wave from the sound wave generating device 10B by selecting at least one of the plurality of sound wave sources 11-1 to 11-3 as a given sound wave source 11. For example... Figure 8As shown, the adjustment circuit 13B selects the destination of the power supply from the capacitor C1 from a plurality of sound wave sources 11-1 to 11-3. More specifically, the adjustment circuit 13B electrically connects at least one of the plurality of sound wave sources 11-1 to 11-3 to the capacitor C1, such that the sound wave generating device 10B generates a sound wave with a target sound pressure level associated with a search range set in the setting process. For example, sound wave source 11-1 is used to achieve a target sound pressure level associated with a first search range. Sound wave source 11-2 is used to achieve a target sound pressure level associated with a second search range. Sound wave source 11-3 is used to achieve a target sound pressure level associated with a third search range.

[0103] like Figure 8 As shown, the adjustment circuit 13B includes multiple (three in the illustrated example) switches SW2-1 to SW2-3 (hereinafter referred to collectively as SW2). The multiple switches SW2-1 to SW2-3 are electrically connected between the multiple sound wave sources 11-1 to 11-3 and the capacitor C. In the adjustment circuit 13B, one of the multiple switches SW2-1 to SW2-3 is set to ON, and the others are set to OFF. Thus, one of the multiple sound wave sources 11-1 to 11-3 is electrically connected to the capacitor C1.

[0104] Control circuit 14 controls drive circuit 12 and adjustment circuit 13B. Control circuit 14 controls switch SW2 of adjustment circuit 13B to electrically connect at least one of the plurality of sound wave sources 11 to capacitor C1, so that sound wave generating device 10B generates sound wave with target sound pressure, the target sound pressure being associated with a search range set in the setting process.

[0105] When the object detection system 1 is equipped with a sound wave generator 10B, the processing circuit 30 controls the control circuit 14 of the sound wave generator 10B to perform the following wave transmission process. In the wave transmission process, the adjustment circuit 13B selects a sound wave source 11 corresponding to the target sound pressure from a plurality of sound wave sources 11 as a given sound wave source 11, and drives the drive switching element T1 of the drive circuit 12 to generate a sound wave from the given sound wave source 11.

[0106] In this way, the object detection system 1 can set the sound pressure of the sound wave output from the sound wave generator 10B to a target sound pressure that is correlated with the search range of the object in the object space. That is, the sound pressure of the sound wave can be set according to the distance to the object. Therefore, by increasing the target sound pressure, the reflected wave from the object can be increased, thereby enabling the detection of more distant objects. On the other hand, by decreasing the target sound pressure, the influence of direct sound on the receiving device 20 can be reduced, thereby enabling the detection of closer objects. As described above, the object detection system 1 can expand the detection range of objects.

[0107] In the object detection system 1 described above, the sound wave generating device 10B includes: a plurality of sound wave sources 11, each of which heats up when energized and generates sound waves with different sound pressures; a drive circuit 12, having a capacitor C1 charged by a DC power supply V1 and a drive switching element T1 that supplies power from the capacitor C1 to a given sound wave source 11; and an adjustment circuit 13B, which adjusts the sound pressure of the sound wave from the sound wave generating device 10B by selecting at least one of the plurality of sound wave sources 11 as the given sound wave source 11. In the wave transmission process, the adjustment circuit 13B selects a sound wave source 11 corresponding to the target sound pressure from the plurality of sound wave sources 11 as the given sound wave source 11, and drives the drive switching element T1 of the drive circuit 12 to generate a sound wave from the given sound wave source 11. According to this structure, the sound pressure of the sound wave output from the sound wave generating device 10B can be easily adjusted.

[0108] [3. Other variations]

[0109] In one variation, in the sound wave generating device 10, the control circuit 14 may also output a drive signal S1 to the drive switching element T1 in order to control the drive circuit 12 to generate a series of sound waves from the sound wave source 11. The switching frequency of the drive switching element T1 corresponds to the frequency of the series of sound waves. The switching frequency of the drive switching element T1 is, for example, 20 kHz or higher. The switching frequency of the drive switching element T1 is, for example, 150 kHz or lower.

[0110] In Modification 1, the number of DC power supplies V1 and the number of capacitors C1 are not particularly limited. Adjustment circuit 13A can also connect two or more capacitors C1 to the sound source 11 as needed. In Modification 1, multiple capacitors C1 are connected in parallel with the sound source 11, but they can also be connected in series with the sound source 11. In this case, the number of capacitors C1 connected in series can be changed by switching circuit 131, thereby adjusting the voltage applied to the sound source 11. The structure of Modification 1 can also be applied to sound wave generating device 10 and sound wave generating device 10B.

[0111] In Modification 2, the number of sound wave sources 11 is not particularly limited. The adjustment circuit 13B can also connect two or more sound wave sources 11 to the capacitor C1 as needed. In Modification 2, multiple sound wave sources 11 are connected in parallel with the capacitor C1, but they can also be connected in series with the capacitor C1. In this case, the number of multiple sound wave sources 11 connected in series can be changed by adjusting the adjustment circuit 13B, thereby adjusting the sound pressure. The structure of Modification 2 can also be applied to the sound wave generating device 10 and the sound wave generating device 10A.

[0112] In a variation, other overcurrent protection components can be used instead of resistor R1. Examples of overcurrent protection components include current fuses, fusible resistors, and bimetallic components. However, overcurrent protection components are not always necessary.

[0113] (Way)

[0114] As can be seen from the above embodiments and variations, this disclosure includes the following methods. Hereinafter, reference numerals are used in parentheses only to illustrate the correspondence with the embodiments.

[0115] The first method is an object detection system (1), comprising: a sound wave generating device (10; 10A; 10B) that generates sound waves by being powered on; and a processing circuit (30) that performs object detection processing to detect objects in an object space using sound waves from the sound wave generating device (10; 10A; 10B). The object detection processing includes: a setting process that sets a search range for the object in the object space; a wave transmission process that controls the sound wave generating device (10; 10A; 10B) to generate sound waves with a target sound pressure level, the target sound pressure level being associated with the search range set in the setting process; and a determination process that obtains a received signal (R1, R2) representing the sound waves received by the received device (20) from a receiving device (20) receiving sound waves from the object space, and determines whether the object exists based on the received signal (R1, R2). This method can expand the detection range of objects.

[0116] The second method is an object detection system (1) based on the first method. In the second method, the farther the search range is from the sound wave generating device (10; 10A; 10B), the greater the target sound pressure. According to this method, the detection range of the object can be expanded.

[0117] The third method is an object detection system (1) based on the second method. In the third method, during the determination process, if the magnitude of the received signal (R1, R2) is above a threshold (Vth), it is determined that the object exists. According to this method, the object detection process can be simplified.

[0118] The fourth method is an object detection system (1) based on the third method. In the fourth method, the target sound pressure is set such that the magnitude of the reflected waves (RW1, RW2, RW3) from the object is greater than a predetermined value larger than the threshold (Vth). According to this method, the influence of distance-related errors and the possibility of false detections due to noise can be reduced, thereby improving the object detection accuracy.

[0119] The fifth method is an object detection system (1) based on the fourth method. In the fifth method, during the determination process, the presence of the object is not determined based on the received signals (R1, R2) within the blind zone set after the wave transmission process. The blind zone is set according to the search range set in the setting process. According to this method, false detection caused by the magnitude of the direct sound (RW10) exceeding the threshold (Vth) can be prevented, while also expanding the object detection range.

[0120] The sixth method is an object detection system (1) based on the fifth method. In the sixth method, the longer the search range is from the sound wave generating device (10; 10A; 10B), the longer the blind zone is set. According to this method, false detection caused by the magnitude of the direct sound (RW10) exceeding the threshold (Vth) can be prevented, while also expanding the detection range of the object.

[0121] The seventh method is an object detection system (1) based on any one of the methods 1 to 6. In the seventh method, during the setting process, if the determination process determines that the object does not exist, the search range is changed. According to this method, the probability of detecting an object can be increased.

[0122] The eighth method is an object detection system (1) based on the seventh method. In the eighth method, during the setting process, if the determination process determines that the object does not exist, the search range is changed so that the search range is moved away from the sound wave generating device (10; 10A; 10B). According to this method, the probability of detecting an object can be increased.

[0123] The ninth method is an object detection system (1) based on the eighth method. In the ninth method, during the setting process, if the search range where the determination process determines that the object does not exist is furthest from the sound wave generating device (10; 10A; 10B), the search range is changed so that the search range is closer to the sound wave generating device (10; 10A; 10B). According to this method, the probability of detecting an object can be increased.

[0124] The tenth method is an object detection system (1) based on any one of the methods 1 to 9. In the tenth method, during the determination process, if the presence of the object is determined, the distance to the object is determined based on the received signals (R1, R2). According to this method, the distance to the object can be obtained.

[0125] The 11th method is an object detection system (1) based on the 10th method. In the 11th method, during the setting process, if the distance to the object is determined by the determination process, the search range is set based on the distance to the object determined in the determination process. According to this method, the probability of detecting an object can be increased.

[0126] The 12th method is an object detection system (1) based on any one of the 1st to 11th methods. In the 12th method, the sound wave generating device (10) includes: a drive circuit (12) having a capacitor (C1) charged by a DC power supply (V1) and a drive switching element (T1) that supplies power from the capacitor (C1) to a sound wave source (11) that generates sound waves by heating up when energized; and an adjustment circuit (13) that adjusts the sound pressure of the sound wave from the sound wave generating device (10) by adjusting the voltage (V2) between the two ends of the capacitor (C1) of the drive circuit (12). In the wave transmission process, the voltage (V2) between the two ends of the capacitor (C1) is adjusted by the adjustment circuit (13) so that the sound pressure of the sound wave from the sound wave generating device (10) becomes the target sound pressure, and the drive switching element (T1) of the drive circuit (12) is driven to generate sound waves from the sound wave source (11). According to this method, the sound pressure of the sound wave output from the sound wave generator (10) can be easily adjusted.

[0127] The 13th method is an object detection system (1) based on the 12th method. In the 13th method, the adjustment circuit (13) includes: an inductor (L1) electrically connected between the DC power supply (V1) and the capacitor (C1); and an adjustment switch element (T2) electrically connected in parallel with the series circuit of the inductor (L1) and the DC power supply (V1). The adjustment circuit (13) adjusts the voltage (V2) across the capacitor (C1) by the on-time (T2on) of the adjustment switch element (T2). According to this method, the circuit structure can be simplified.

[0128] The 14th method is an object detection system (1) based on the 13th method. In the 14th method, the adjustment circuit (13) has a diode (D1), the anode of which is electrically connected to the inductor (L1), and the cathode of which is electrically connected to the capacitor (C1). According to this method, the possibility of the capacitor (C1) accidentally discharging due to current flowing from the capacitor (C1) to the inductor (L1) can be reduced.

[0129] The 15th method is an object detection system (1) based on the 13th or 14th method. In the 15th method, the adjustment switch element (T2) is turned on during the on-time (Tlon) of the drive switch element (T1), and simultaneously switches on with the drive switch element (T1). According to this method, the adjustment of the sound pressure of the sound wave becomes easier.

[0130] The 16th method is an object detection system (1) based on any one of the 1st to 11th methods. In the 16th method, the sound wave generating device (10A) includes: a drive circuit (12A) having a drive switching element (T1) that supplies power from a given capacitor (C1) to a sound wave source (11) that generates sound waves by heating up when energized; and an adjustment circuit (13A) that adjusts the sound pressure of the sound wave from the sound wave generating device (10A) by selecting at least one of a plurality of capacitors (C1) charged by a plurality of DC power supplies (V1) with different voltages as the given capacitor (C1). In the wave transmission process, the adjustment circuit (13A) selects a capacitor (C1) corresponding to the target sound pressure from the plurality of capacitors (C1) as the given capacitor (C1), and drives the drive switching element (T1) of the drive circuit (12A) to generate sound waves from the sound wave source (11). According to this method, the sound pressure of the sound wave output from the sound wave generator (10A) can be easily adjusted.

[0131] The 17th method is an object detection system (1) based on any one of the 1st to 11th methods. In the 17th method, the sound wave generating device (10B) includes: a plurality of sound wave sources (11), each of which heats up by being energized and generates sound waves with different sound pressures; a drive circuit (12) having a capacitor (C1) charged by a DC power supply (V1) and a drive switching element (T1) for supplying power from the capacitor (C1) to a given sound wave source (11); and an adjustment circuit (13B) for adjusting the sound pressure of the sound wave from the sound wave generating device (10B) by selecting at least one of the plurality of sound wave sources (11) as the given sound wave source (11). In the wave transmission process, the adjustment circuit (13B) selects a sound wave source (11) from the plurality of sound wave sources (11) that corresponds to the target sound pressure as the given sound wave source (11), and drives the drive switching element (T1) of the drive circuit (12) to generate a sound wave from the given sound wave source (11). In this manner, the sound pressure of the sound wave output from the sound wave generator (10B) can be easily adjusted.

[0132] The 18th method is an object detection system (1) based on any one of the 12th to 17th methods. In the 18th method, during the wave transmission process, a series of sound waves are generated from the sound wave generating device (10; 10A; 10B) by switching the driving switching element (T1), and the switching frequency of the driving switching element (T1) is 20 kHz or higher. According to this method, the object detection accuracy can be improved.

[0133] Industrial availability

[0134] This disclosure can be applied to sound wave generating devices. Specifically, this disclosure can be applied to object detection systems that use sound waves to detect objects.

[0135] Explanation of reference numerals in the attached figures

[0136] 1: Object detection system;

[0137] 10, 10A, 10B: Sound wave generating device;

[0138] 11: Sound wave source;

[0139] 12, 12A: Drive circuit;

[0140] 13, 13A, 13B: Adjustment circuit;

[0141] V1: DC power supply;

[0142] V2: Voltage between the two terminals;

[0143] C1: Capacitor;

[0144] T1: Switching element for driving;

[0145] T1on: During connection period;

[0146] L1: Inductor;

[0147] T2: Adjustment switching element;

[0148] T2on: During connection period;

[0149] D1: Diode;

[0150] 20: Wave receiving device;

[0151] 30: Processing circuit;

[0152] R1, R2: Received signal;

[0153] RW1, RW2, RW3: Reflected waves.

Claims

1. An object detection system, comprising: A sound wave generating device that generates heat and produces sound waves by being powered on; and The processing circuit performs object detection processing, which uses sound waves from the sound wave generator to detect objects in the object space. The object detection process includes: The settings process defines the search range for the objects in the object space. The sound wave generator is controlled to generate a sound wave with a target sound pressure level, the target sound pressure level being correlated with a search range set in the setting process; and The determination process involves acquiring a received signal representing the sound waves received by the receiving device from the object space, and determining whether the object exists based on the received signal. The farther the search range is from the sound wave generating device, the greater the target sound pressure level. In the determination process, if the magnitude of the received signal is above a threshold, it is determined that the object exists. The target sound pressure level is set such that the magnitude of the reflected wave from the object is greater than or equal to a predetermined value above the threshold. In the determination process, within the blind zone set after the wave transmission process, the presence of the object is not determined based on the received wave signal. The blind zone is set according to the search range set in the setting process. The higher the target sound pressure level, the longer the blind zone is set.

2. The object detection system according to claim 1, wherein, In the setting process, if the determination process determines that the object does not exist, the search range is changed.

3. The object detection system according to claim 2, wherein, In the setting process, if the determination process determines that the object does not exist, the search range is changed so that the search range is moved away from the sound wave generating device.

4. The object detection system according to claim 3, wherein, In the setting process, if the search range where the object is determined to not exist is furthest from the sound wave generating device, the search range is changed so that the search range is closer to the sound wave generating device.

5. The object detection system according to any one of claims 1 to 4, wherein, In the determination process, if the existence of the object is determined, the distance to the object is determined based on the received wave signal.

6. The object detection system according to claim 5, wherein, In the setting process, if the distance to the object is determined by the determination process, the search range is set based on the distance to the object determined in the determination process.

7. The object detection system according to any one of claims 1 to 4, wherein, The sound wave generating device includes: The drive circuit includes a capacitor charged by a DC power supply and a drive switching element that supplies power from the capacitor to a sound wave source that heats up and generates sound waves when energized; and The adjustment circuit adjusts the sound pressure level of the sound waves from the sound wave generator by adjusting the voltage across the capacitor in the drive circuit. In the wave transmission process, The voltage across the capacitor is adjusted by the adjustment circuit so that the sound pressure of the sound wave from the sound wave generator becomes the target sound pressure. The driving switching element of the driving circuit is used to generate sound waves from the sound wave source.

8. The object detection system according to claim 7, wherein, The adjustment circuit has: An inductor, electrically connected between the DC power supply and the capacitor; and The adjusting switching element is electrically connected in parallel with the series circuit of the inductor and the DC power supply. The adjustment circuit adjusts the voltage across the capacitor by controlling the on / off period of the adjustment switching element.

9. The object detection system according to claim 8, wherein, The adjustment circuit has diodes. The anode of the diode is electrically connected to the inductor. The cathode of the diode is electrically connected to the capacitor.

10. The object detection system according to claim 8 or 9, wherein, The adjustment switch element is turned on during the period when the drive switch element is turned on, and switches to be turned on simultaneously with the drive switch element.

11. The object detection system according to any one of claims 1 to 4, wherein, The sound wave generating device includes: A drive circuit having a drive switching element that supplies power from a sound wave source that heats up and generates sound waves when a given capacitor pair is energized. as well as The adjustment circuit adjusts the sound pressure of the sound waves from the sound wave generator by selecting at least one of a plurality of capacitors, each charged by a plurality of DC power supplies with different voltages, as the given capacitor. In the wave transmission process, The adjustment circuit selects a capacitor from the plurality of capacitors that corresponds to the target sound pressure as the given capacitor. The driving switching element of the driving circuit is used to generate sound waves from the sound wave source.

12. The object detection system according to any one of claims 1 to 4, wherein, The sound wave generating device includes: Multiple sound wave sources generate heat and produce sound waves with different sound pressures when energized. A drive circuit having a capacitor charged by a DC power supply and a drive switching element for supplying power from the capacitor to a given sound wave source. as well as The adjustment circuit adjusts the sound pressure level of the sound wave from the sound wave generating device by selecting at least one of the plurality of sound wave sources as the given sound wave source. In the wave transmission process, The adjustment circuit selects the sound source corresponding to the target sound pressure from the plurality of sound sources as the given sound source. The driving switching element of the driving circuit is driven to generate sound waves from the given sound wave source.

13. The object detection system according to claim 7, wherein, In the wave transmission process, a series of sound waves are generated from the sound wave generating device by switching the drive switching element. The switching frequency of the drive switching element is 20kHz or higher.

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