OBJECT DETECTION DEVICE

Abstract

Object detection device (1) designed to detect an environmental object (B), the object detection device (1) comprising: a drive signal generating unit (3) arranged to generate a drive signal that drives a transmitting unit including a transmitter (20A) that transmits transmission waves to the outside; a control unit (4) arranged to control an output of the drive signal transmitted from the drive signal generating unit (3) to the transmitting unit; and a receiving circuit (23) which generates a reception signal in dependence on a reception state of a receiver (20B) which receives reflection waves of the transmission waves reflected at the object (B), wherein the drive signal generating unit (3) is designed to generate the drive signal whose frequency changes stepwise such that its frequency is a first frequency in a first period and its frequency is a second frequency, which is different from the first frequency, in a second period following the first period; the control unit (4) is designed to set the first frequency and the second frequency such that a resonance frequency of the transmitting unit lies between the first frequency and the second frequency, and to identify, based on a width of a frequency change of a characteristic curve of the frequency of the reception signal, whether reception waves are the reflection waves of the transmission waves transmitted by the object detection device (1); and the receiving circuit (23) is designed to generate the received signal whose frequency increases or decreases following a frequency change of the transmitted waves, wherein the frequency change occurs in response to the stepwise frequency change of the drive signal.

Description

Technical field

[0001] The present invention relates to an object detection device designed to detect environmental objects. State of the art

[0002] An object detection device using an ultrasonic sensor is known. In the case where this type of object detection device is mounted on a vehicle to detect obstacles, interference may lead to a deterioration in detection accuracy. For example, interference may be generated when an ultrasonic sensor mounted on another vehicle in the vicinity of the own vehicle emits ultrasonic waves, and the ultrasonic sensor mounted on the own vehicle receives these ultrasonic waves. In other cases, interference may be generated, for example, when one of a plurality of ultrasonic sensors mounted on the own vehicle receives ultrasonic waves emitted by another of the ultrasonic sensors.

[0003] DE 101 06 142 A1 discloses an ultrasonic multi-sensor array. The ultrasonic multi-sensor array disclosed in DE 101 06 142 A1 includes at least two transmitting units and at least one receiving unit. Note that some of the transmitting units can be operated in parallel. According to the ultrasonic multi-sensor array, ultrasonic pulses are encoded so that they are suitable for parallel operation. In particular, the frequency of the carrier wave signal is linearly modulated for each pulse encoding in the transmitting units operated in parallel. In other words, the frequency of the carrier wave signal of the first transmitting unit is linearly increased during the pulse duration or pulse period. On the other hand, the frequency of the carrier wave signal of the second transmitting unit is decreased during the pulse duration or pulse period.

[0004] DE 10 2005 033 462 A1 and JP 2012-168 122 A each disclose an object detection device configured to detect a surrounding object, the object detection device comprising: a drive signal generation unit configured to generate a drive signal that drives a transmitting unit including a transmitter that emits transmission waves to the outside; a control unit configured to control an output of the drive signal transmitted from the drive signal generation unit to the transmitting unit;and a receiving circuit that generates a received signal depending on a receiving state of a receiver that receives reflection waves of the transmission waves reflected by the object, wherein the drive signal generating unit is configured to generate the drive signal whose frequency changes stepwise, and the drive signal generating unit is configured to generate the drive signal whose frequency is a first frequency in a first period and whose frequency is a second frequency, different from the first frequency, in a second period following the first period.; Summary of the invention

[0005] When the technique disclosed in DE 101 06 142 A1 is used, the ultrasonic sensor mounted on the own vehicle is capable of identifying whether the received waves are reflection waves of the ultrasonic waves emitted by the own ultrasonic sensor. Specifically, the identification is performed based on whether the received waves contain a frequency change that is the same as the frequency change of the ultrasonic waves emitted by the own ultrasonic sensor. Thus, the interference problem described above can be solved.

[0006] The transmitting unit, which includes a transducer used for an oscillator that emits ultrasonic waves, has a predetermined resonant frequency. If the driving frequency deviates from the resonant frequency, the tracking performance of the transmitting unit deteriorates. However, even if the driving frequency is linearly increased or decreased similarly to the technique described in DE 101 06 142 A1, it is difficult to achieve a desired width of frequency change of the transmitted waves. Therefore, it is difficult to obtain desired identification characteristics.

[0007] The present invention was conceived in view of the problems described above. The present invention provides a configuration capable of appropriately solving the problem of interference by improving the identification characteristic of the transmission waves.

[0008] A first aspect of the present invention relates to an object detection device having the features of independent claim 1.

[0009] According to the invention, the control signal generation unit generates the control signal for controlling the transmitting unit. The transmitting unit is controlled by the control signal, whereby the transmission waves are emitted from the transmitter to the outside.

[0010] Many researchers concerning the present invention have discovered characteristics according to which the frequency of the transmission waves approaches a predetermined frequency when the transmission unit is driven at a predetermined frequency different from the resonance frequency.

[0011] With these characteristics, the drive signal generating unit changes the drive frequency stepwise or incrementally between a predetermined first frequency and a predetermined second frequency.

[0012] According to the object detection device of the present invention, the driving frequency changes rapidly, and the tracking performance of the transmitting unit is improved. Thus, a desired width of frequency change of the transmitting waves is obtained, and a desired identification characteristic is obtained. Accordingly, it is possible to provide a configuration capable of appropriately solving the problem of interference by improving an identification characteristic with respect to the transmitting waves.

[0013] Note that reference numerals in parentheses may be provided for the respective elements. However, these reference numerals represent only one example of a relationship between the elements and specific devices described in the embodiments described later. Therefore, the above reference numerals are not intended to limit the present invention. Short description of the drawings Fig. 1 is a block diagram showing an overall configuration of an object detection device according to an embodiment. Fig. 2A is a timing chart showing frequency characteristics of a first example of a drive signal generated by a drive signal generating unit according to Fig. 1 is generated. Fig. 2B is a graph showing characteristics of a reception signal corresponding to the drive signal that Fig. 2A shown frequency characteristics. Fig. 2C is a timing chart showing a frequency characteristic of a drive signal of a comparative example. Fig. 2D is a graph showing characteristics of a received signal corresponding to the drive signal that controls the Fig. 2C has the frequency characteristic shown. Fig. 3 is a graph showing a state in which the resonance frequency of the Fig. 1 shown transmitter unit changes depending on the ambient temperature. Fig. 4A is a timing chart showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to a second example. Fig. 4B is a timing diagram showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to the second example. Fig. 5A is a timing chart showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to a third example. Fig. 5B is a timing diagram showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to the third example. Fig. 6A is a timing chart showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to a fourth example. Fig. 6B is a timing chart showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to the fourth example. Fig. 7A is a timing chart showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to a fifth example. Fig. 7B is a timing chart showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to the fifth example. Fig. 8A is a timing chart showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to a sixth example. Fig. 8B is a timing chart showing frequency characteristics of a drive signal supplied from the Fig. 1 shown drive signal generating unit, according to the sixth example. Fig. 9 is a timing chart showing a frequency characteristic of a drive signal supplied from the Fig. 1, according to a modification example. Fig. 10 is a timing chart showing a frequency characteristic of a drive signal supplied from the Fig. 1, according to another modification example. Description of the embodiments

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Since various modification examples applicable to an embodiment may obscure the understanding of the embodiments if described in the course of explaining the embodiments, these modification examples will be described after the description of the embodiments. configuration

[0015] According to Fig. 1, an object detection device 1 is mounted on, for example, a vehicle, not shown, and is configured to detect an object B in the vicinity of the vehicle. The vehicle on which the object detection device 1 according to the present embodiment is mounted is hereinafter referred to as an own vehicle.

[0016] According to the present embodiment, the object detection device 1 has an ultrasonic sensor configuration. In other words, the object detection device 1 is configured to transmit transmission waves as ultrasonic waves to the outside of the own vehicle. Furthermore, the object detection device 1 is configured to receive reflection waves of the transmission waves reflected by the object B, from which the distance to the object B is determined and obtained. Specifically, the object detection device 1 includes a transceiver unit 2, a drive signal generation unit 3, a control unit 4, and a temperature acquisition unit 5.

[0017] According to the present embodiment, the object detection device 1 is configured to realize a transmission-reception function via a single transceiver unit 2. In other words, the single transceiver unit 2 includes a single transducer 21. Furthermore, the transceiver unit 2 includes a transmitter 20A and a receiver 20B. The transmitter 20A and the receiver 20B share the common transducer 21, thus providing both a transmission function and a reception function.

[0018] The transceiver unit 2 specifically includes the transducer 21, a transmitting circuit 22, and a receiving circuit 23. The transmitter 20A includes the transducer 21 and the transmitting circuit 22. Furthermore, the receiver 20B includes the transducer 21 and the receiving circuit 23.

[0019] The transducer 21 is electrically connected to the transmitting circuit 22 and the receiving circuit 23. The transducer 21 functions as a transmitter that transmits transmitted waves to the outside and as a receiver that receives reflected waves. Specifically, the transducer 21 is configured as an ultrasonic microphone including an electromechanical energy conversion element such as a piezoelectric element. The transducer 21 is arranged facing the outer surface of the vehicle and is capable of transmitting transmitted waves to the outside of the vehicle and receiving reflected waves from the outside of the vehicle.

[0020] The transmission circuit 22 is configured to drive the transducer 21 based on the received drive signal, thereby causing the transducer 21 to emit transmission waves in an ultrasonic frequency band. Specifically, the transmission circuit 22 includes a digital-to-analog conversion circuit or the like. That is, the transmission circuit 22 applies digital-to-analog conversion or the like to the drive signal output from the drive signal generation unit 3 and applies the resulting AC voltage to the transducer 21.

[0021] The receiving circuit 23 generates a received signal depending on the reception state of the ultrasonic waves at the transducer 21 and outputs the generated received signal to the control unit 4. Specifically, the receiving circuit 23 includes an amplifier circuit and an analog-to-digital conversion circuit, or the like. In other words, the receiving circuit 23 is configured to apply an amplification process and analog-to-digital conversion to the voltage signal received from the transducer 21 to generate and output the received signal depending on the amplitude of the received ultrasonic waves.

[0022] Thus, the transceiver unit 2 is configured such that the transducer 21 as a transceiver transmits the transmission waves and receives reflection waves of the transmission waves transmitted by the transducer itself, thereby generating the reception signal depending on the distance to the object B.

[0023] The drive signal generation unit 3 is arranged to generate a drive signal that drives the transmitter 20A. The drive signal serves as a signal for driving the transmitter 20A to cause the transducer 21 to emit the transmission waves. The drive signal is, for example, a pulse signal in the ultrasonic frequency band. The drive signal generation unit 3 is configured to generate a drive signal whose frequency changes stepwise. A specific example of the drive signal will be described later.

[0024] The control unit 4 is configured to control the output of the drive signal transmitted from the drive signal generating unit 3 to the transmitter 20A and to process a reception signal output from the receiver 20B. Specifically, the control unit 4 is configured to output a control signal to the drive signal generating unit 3, thereby controlling a transmission state of the transmission waves from the transmitter 20A. Specifically, the control unit 4 controls the frequency of the drive signal generated by the drive signal generating unit 3 and the output timing. Furthermore, the control unit 4 is configured to receive the reception signal from the receiver circuit 23 while controlling the operation of the receiver circuit 23, thereby detecting the presence of the object B and the distance between the transducer 21 and the object B.

[0025] Furthermore, the control unit is configured to change the frequency of the drive signal depending on a change in the ambient temperature acquired by the temperature acquisition unit 5. The ambient temperature refers to a temperature in the vicinity of the transceiver 2, i.e., the transducer 21, and is typically a vehicle exterior temperature. The temperature acquisition unit 5 is configured to acquire information corresponding to the ambient temperature. Specifically, the temperature acquisition unit 5 is configured to receive the output signal of a temperature sensor, such as an exterior temperature sensor (not shown), mounted on the vehicle itself and output the reception result to the control unit 4. overall operation

[0026] Hereinafter, an overall operation of a configuration according to the present embodiment and effects and advantages obtained by the configuration will be described with reference to the drawings.

[0027] According to the Fig. In the configuration of the present embodiment shown in FIG. 1, the control unit 4 outputs the control signal to the drive signal generation unit 3. Then, the drive signal generation unit 3 generates the drive signal and outputs the drive signal to the transmitter 20A. With this drive signal, the transmitter 20A is driven. In other words, the transmission circuit 22 excites the transducer 21. Thus, the transducer 21 serves as a transmitter that transmits transmission waves to the outside of the object detection device 1, that is, to the outside of the own vehicle. The excitation frequency of the transducer 21 depends on the frequency of the drive signal.

[0028] In the case where the reflection waves reflected by the object B are received by the transducer 21 serving as a receiver, the receiving circuit 23 generates the reception signal depending on the reception state of the ultrasonic waves at the transducer 21 and outputs the generated reception signal to the control unit 4. Thus, the object B is detected. The distance between the transducer 21 and the object B is obtained. First special example

[0029] Fig. Figure 2A shows a specific example of the drive signal. The frequency of the drive signal is referred to as the drive frequency. Fig. 2A, the horizontal axis t indicates time, and the vertical axis f indicates the driving frequency.

[0030] A transmission start time ts indicates a start time of the drive signal output, a transmission end time te indicates the end time of the drive signal output, and an intermediate time tm indicates a time between the transmission start time ts and the transmission end time te. A period from the transmission start time ts to the intermediate time tm is referred to as the first period T1. Furthermore, a period from the intermediate time tm to the transmission end time te is referred to as the second period T2.

[0031] Note that fs indicates a start frequency and fe indicates an end frequency. The start frequency fs is a drive frequency at the transmission start time ts. The end frequency fe is a drive frequency at the transmission end time te. The maximum frequency fmax indicates a maximum value of the drive frequency. The minimum frequency fmin indicates a minimum value of the drive frequency. The center frequency fc is a mean value between the maximum frequency fmax and the minimum frequency fmin. In addition, fr indicates a resonant frequency of the transmitter 20A. Typically, the resonant frequency substantially coincides with the resonant frequency of the transducer 21.

[0032] Here, an example is shown in which the drive frequency changes discretely such that the drive frequency changes stepwise or incrementally. In particular, in the present example, the start frequency fs is equal to the minimum frequency fmin, and the end frequency fe is equal to the maximum frequency. Furthermore, in the present example, the drive frequency is kept constant at the minimum frequency fmin during a first period T1 from the transmission start time ts to the intermediate time tm. Furthermore, the drive frequency is kept constant at the maximum frequency fmax during a second period T2 from the intermediate time tm to the transmission end time te. According to the present example, the drive frequency increases discretely from the minimum frequency fmin to the maximum frequency fmax at the intermediate time tm. The start frequency fs corresponds to a first frequency and the end frequency corresponds to a second frequency.

[0033] According to the present example, the drive signal generation unit 3 generates the drive signal in which the frequency in the first period T1 is the minimum frequency fmin, and the frequency in the second period T2 subsequent to the first period T1 is the maximum frequency fmax, which is different from the minimum frequency fmin. Furthermore, in the present example, the drive signal generation unit 3 generates the drive signal in which the center frequency fc is equal to the resonance frequency fr. In other words, the difference between the resonance frequency fr and the minimum frequency fmin as a drive frequency during the first period T1 is equal to the difference between the resonance frequency fr and the maximum frequency fmax as a drive frequency during the second period T2. Thus, in the present example, the first period T1 is equal to the second period T2.

[0034] Specifically, according to the present example, the control unit 4 sets or controls the drive frequency and its output timing as follows. The starting frequency fs is set to coincide with the minimum frequency fmin. In the first period T1, the drive frequency is kept constant at the minimum frequency fmin. The drive frequency is set to discretely increase from the minimum frequency fmin to the maximum frequency fmax at the intermediate time tm, which is the end time of the first period T1 and the start time of the second period T2. In the second period T2 following the intermediate time tm, the drive frequency is kept constant at the maximum frequency fmax. The ending frequency fe is set to coincide with the maximum frequency fmax.The center frequency fc between the minimum frequency fmin and the maximum frequency fmax is set to coincide with the resonance frequency fr.

[0035] Fig. 2B is a graph showing characteristics of the received signal corresponding to the drive signal that Fig. 2A shown frequency characteristics. In Fig. 2B, the reception start time tr1 is a time at which the reflected waves of the transmission waves corresponding to the transmission start time ts are received. The reception end time tr2 is a time at which the reflected waves of the transmission waves corresponding to the transmission end time te are received. In addition, Va indicates an amplitude of the received signal, and f indicates a reception frequency, that is, the frequency of the received signal.

[0036] A comparison example is in the Fig. 2C and Fig. 2D, where the drive frequency is increased linearly from the minimum frequency fmin to the maximum frequency fmax. Fig. 2C shows frequency characteristics or the frequency characteristic of the control signal according to Fig. 2A. Fig. 2D shows properties or characteristics of the received signal according to Fig. 2B. In the Fig. 2B and Fig. 2D, the frequency change width Δf is a difference between the maximum frequency and the minimum frequency of the reception signal during a period from the reception start time tr1 to the reception end time tr2, having a value corresponding to the identification characteristic.

[0037] The transmitter 20A, which includes the transducer 21 used for an oscillator that transmits ultrasonic waves, has a predetermined resonance frequency fr. The transducer 21, as an ultrasonic resonance microphone, has characteristics similar to a bandpass filter. That is, the frequency band in which the transmitter 20A is capable of properly transmitting / receiving ultrasonic waves is limited to ± a few percent of the width of the resonance frequency fr. The farther the driving frequency is from the resonance frequency fr, the worse the tracking performance of the transmitter 20A.

[0038] A curve that Fig. 3 is drawn by a solid line, shows a sensitivity-frequency characteristic at the ambient temperature of 25 degrees Celsius when the transducer 21 is used as a receiver. In Fig. 3, the vertical axis S indicates the sensitivity, and the horizontal axis f indicates the frequency. The sensitivity of 0 dB corresponds to the maximum value of the intensity of the transmitted waves. The frequency band Δfb, which is Fig. 3 indicates a sensitivity range from 0 to Sb [dB], with the sensitivity at the resonance frequency fr being equal to 0 [dB]. The frequency band Δfb in which the transmitter 20A is capable of properly transmitting / receiving ultrasonic waves ranges from the lower cutoff frequency fd to the upper cutoff frequency fu, which corresponds to the sensitivity from 0 to Sb [dB]. For example, the sensitivity Sb is typically -3 [dB]. The minimum frequency fmin is regularly set at the lower cutoff frequency fd or close to the lower cutoff frequency fd. Similarly, the maximum frequency fmax is regularly set at the upper cutoff frequency fu or in the vicinity of the upper cutoff frequency fu.

[0039] In this regard, according to the comparative example, the resonance frequency fr is set to the center frequency fc, which is between the minimum frequency fmin and the maximum frequency fmax, and the drive frequency is linearly increased from the minimum frequency fmin toward the maximum frequency fmax. Note that the minimum frequency fmin as the start frequency fs and the maximum frequency fmax as the end frequency fe are values ​​farthest from the resonance frequency fr. Thus, the tracking performance of the transmitter 20A deteriorates significantly near the transmission start time ts and the transmission end time te.

[0040] Accordingly, in the case of the comparative example, a desired width of the frequency change of the transmission waves is difficult to achieve. As shown in Fig. 2D, it is thus difficult to obtain a sufficiently large value for the frequency change width Δf in the received signal that indicates a suitable identification characteristic.

[0041] On the other hand, various researchers regarding the present invention have discovered characteristics according to which the frequency of the transmission waves approaches a predetermined frequency when the transmitter 20A is driven at a predetermined frequency different from the resonance frequency fr. According to the present invention, the drive signal generation unit 3 changes the drive frequency stepwise between a first predetermined frequency and a second predetermined frequency according to these characteristics.

[0042] According to the present invention, the driving frequency changes rapidly, and the tracking capability of the transmitter 20A is improved. Thus, a desired width of the frequency change of the transmission waves is obtained. As shown in Fig. 2B, a sufficiently large value for the frequency change width Δf in the received signal can be obtained, indicating a suitable identification characteristic. That is, a desired identification characteristic is obtained. Thus, according to the configuration described above, the identification characteristic of the transmitted waves is improved, thereby solving the problem of interference.

[0043] Note that the effects and advantages described above also apply to a case where the drive signal has a frequency change pattern opposite to that in Fig. 2A. According to this drive signal, the start frequency fs is equal to the maximum frequency fmax, and the end frequency fe is equal to the minimum frequency fmin. In addition, the drive frequency is constant at the maximum frequency fmax during the first period T1 from the transmission start time ts to the intermediate time tm. Furthermore, the drive frequency is constant at the minimum frequency fmin during the second period T2 from the intermediate time tm to the transmission end time te. In addition, the drive frequency is discretely decreased from the maximum frequency fmax to the minimum frequency fmin at the intermediate time tm.

[0044] Now the resonance frequency fr varies depending on the ambient temperature. A curve that Fig. 3, indicated by a dotted line, shows the frequency characteristic of the sensitivity at an ambient temperature of -10 degrees Celsius. Furthermore, a curve indicated by a dot-dash line shows the frequency characteristic of the sensitivity at an ambient temperature of 50 degrees Celsius. Thus, the resonance frequency fr decreases in association with a temperature increase in the ambient temperature range expected for an on-vehicle object detection device 1.

[0045] In this regard, the object detection device 1 according to a configuration of the present embodiment includes the temperature acquisition unit 5 that acquires information about the ambient temperature. Furthermore, the control unit 4 changes the drive frequency depending on a change in the ambient temperature. Specifically, the control unit 4 corrects the start frequency fs, the end frequency fe, the minimum frequency fmin, and the maximum frequency fmax based on the ambient temperature. Thus, the identification property can be further improved regardless of a change in the ambient temperature. Second special example

[0046] Fig. Figure 4A shows another specific example of the control signal. Fig. The example shown in Figure 4A concerns a case where the frequency level of the example shown in Fig. 2A. The output timing of the control signal, i.e. the change timing of the control frequency, in the example of Fig. 4A is the same as in the example of Fig. 2A. As it is in Fig. 4A, the center frequency fc may differ from the resonance frequency fr. The same applies to the Fig. 4B, in which the drive frequency is discretely reduced from the maximum frequency fmax to the minimum frequency fmin at the intermediate time tm. Third special example

[0047] Fig. Figure 5A shows another specific example of the control signal. As shown in Fig. As shown in Figure 5A, the starting frequency fs and the minimum frequency fmin can be set to be lower than the lower limit frequency fd. Furthermore, the ending frequency fe and the maximum frequency fmax can be set to be higher than the upper limit frequency fu.

[0048] In other words, the control unit 4 sets the starting frequency fs and the minimum frequency fmin outside the frequency band Δfb. Furthermore, the control unit 4 sets the final frequency fe and the maximum frequency fmax outside the frequency band Δfb.

[0049] However, in the case where a deviation between the lower limit frequency fd, the start frequency fs, and the minimum frequency fmin is too large, the tracking performance of the transmitter 20A deteriorates. Similarly, in the case where a deviation between the upper limit frequency fu, the end frequency fe, and the maximum frequency fmax is too large, the tracking performance of the transmitter 20A deteriorates. Thus, these deviations should be set to a lower or minimum limit at which a suitable or good identification characteristic can still be achieved. Specifically, for example, the start frequency fs, the end frequency fe, the minimum frequency fmin, and the maximum frequency fmax are set such that the sensitivity is in a range of -3.1 to -3.5 [dB].

[0050] As described above, in the case where the driving frequency is set outside the frequency band Δfb as shown in Fig. 3, the problem arises that sensitivity can deteriorate significantly due to temperature changes. In this case, changing the drive frequency depending on the ambient temperature, i.e., correcting the drive frequency, would be particularly important.

[0051] Note that the effects and advantages described above are also obtained in the case where the driving frequency is discretely reduced from the maximum frequency fmax to the minimum frequency fmin at the intermediate time tm, as shown in Fig. 5B is shown. Fourth special example

[0052] Fig. Figure 6A shows another specific example. Fig. The example shown in Figure 6A concerns a case where the time of the intermediate time tm of the Fig. 4A is different. In other words, according to the example shown in Fig. In the example shown in Figure 6A, the starting frequency fs, i.e., the minimum frequency fmin, has a larger difference from the resonance frequency fr than the ending frequency fe, i.e., the maximum frequency fmax. As described above, with a large difference between the drive frequency and the resonance frequency fr, the tracking capability of the transmitter 20A deteriorates.

[0053] For this reason, the Fig. 6A, the first period T1 corresponding to the minimum frequency fmin is set longer than the second period T2. In other words, the control unit 4 sets the first period T1 corresponding to the drive frequency with the larger difference from the resonance frequency fr to be longer than the second period, among the first period T1 and the second period T2. Thus, the identification property can be further improved.

[0054] Note that the effects and advantages described above also apply to a case where the drive frequency is discretely reduced from the maximum frequency fmax to the minimum frequency fmin at the intermediate time tm. Fifth special example

[0055] Fig. 7A and Fig. 7B show another specific example of the control signal. As shown in Fig. 7A, a third period T3 may be provided as an output period of an intermediate frequency fi between the first period T1 having the minimum frequency fmin and the second period T2 as the output period of the maximum frequency fmax.

[0056] In the example of Fig. 7A, the intermediate frequency fi, corresponding to the third frequency, is set to a frequency between the minimum frequency fmin and the maximum frequency fmax. In this case, the drive frequency is discretely increased from the minimum frequency fmin to the intermediate frequency fi at the first intermediate time tm1. Subsequently, the drive frequency is discretely increased from the intermediate frequency fi to the maximum frequency fmax at the intermediate time tm2.

[0057] In the Fig. In the example shown in Figure 7A, the drive frequency is kept constant at the start frequency fs, i.e., the minimum frequency fmin, in the first period T1 from the transmission start time ts to the first intermediate time tm1. Furthermore, the drive frequency is kept constant at the intermediate frequency fi in the third period T3 from the first intermediate time tm1 to the second intermediate time tm2. Thereafter, the drive frequency is kept constant at the end frequency fe, i.e., the maximum frequency fmax.

[0058] As it is in Fig. 7B, a third period T3 may be provided as an output period of the intermediate frequency fi between the first period T1 as an output period of the maximum frequency fmax and the second period T2 as an output period of the minimum frequency fmin. Fig. In the example shown in Figure 7B, the intermediate frequency fi is defined as lying between the maximum frequency fmax and the minimum frequency fmin.

[0059] Thus, the control signal generating unit 3 generates in the Fig. 7A and Fig. 7B, the drive signal is adjusted such that its frequency in the third period T3 between the first period T1 and the second period T2 becomes the intermediate frequency fi, which is different from the start frequency fs and the end frequency fe. Note that the intermediate frequency fi in the examples shown in Fig. 7A and Fig. 7B may be the same as the center frequency fc or may be different from the center frequency fc. Similarly, in the examples shown in Fig. 7A and Fig. In the examples shown in Figure 7B, the intermediate frequency fi may be the same as the resonant frequency fr or may be different from the resonant frequency fr. Sixth special example

[0060] Fig. 8A and Fig. 8B shows another example of the control signal. Fig. 8A is an example of a case where the intermediate frequency fi in the Fig. 7A is shifted to a side further away from the resonance frequency to the maximum frequency fmax, that is, to a high-frequency side. Fig. The example shown in Figure 8B is a case where the intermediate frequency fi is in the Fig. 7B is further shifted to a side away from the resonance frequency to the minimum frequency fmin, that is, to a low frequency side.

[0061] In particular, the control signal generating unit 3 generates in the Fig. 8A and Fig. 8B, the control unit 4 adjusts the drive signal such that its frequency in the third period T3 between the first period T1 and the second period T2 becomes an intermediate frequency fi that is different from the start frequency fs and the end frequency fe. The control unit 4 adjusts the start frequency fs, the end frequency fe, and the intermediate frequency fi such that the intermediate frequency fi is shifted from the resonant frequency fr in the direction in which the end frequency fe exists, and the intermediate frequency fi has a greater difference from the resonant frequency fr than the end frequency fe.

[0062] According to the present example, a change magnitude of the driving frequency at the first intermediate time tm1 can be set larger than the end time of the first period T1. Therefore, the tracking performance of the transmitter 20A can be further improved. Modifications

[0063] The present invention is not limited to the above-described embodiments. Thus, the above-described embodiments can be appropriately modified. Typical modification examples will be described below. In the explanation of the following modification examples, configurations different from the above-described embodiment will be mainly described. In addition, in the above-described embodiments and the modification examples, the same reference numerals are used for the same or equivalent portions. Thus, in the explanation of the following modification examples, for elements having the same reference numerals as in the above-described embodiment, the explanation of the above-described embodiment also applies unless there is a technical inconsistency or additional explanation is given.

[0064] The object detection device 1 is not limited to an on-vehicle device, i.e., a device mounted on the vehicle. In other words, the object detection device 1 can be mounted on ships or flying objects.

[0065] As it is in Fig. 1, the object detection device 1 may include the transceiver unit 2 and the drive signal generation unit 3 as a respective single unit. Alternatively, the object detection device 1 may include multiple transceivers 2.

[0066] In the case where two transceivers 2 are arranged, the object detection device 1 is designed to allow the transceivers 2 to be supplied with control signals of different waveforms. For example, in the case where two transceivers 2 are arranged, the Fig. 4A is fed to a transceiver 2, and the control signal shown in Fig. The control signal shown in Figure 4B is supplied to the other transceiver 2. Thus, the transmission waves are appropriately or correctly identified by the respective transceivers 2.

[0067] The drive signal generation unit 3 may be configured to select a drive signal waveform from among a plurality of drive signal waveforms shown in the specific examples described above and output the selected drive signal. In other words, the control unit 4 may be configured to receive a selection command input to an input section not shown and select the drive signal waveform based on the received selection command. Thus, even in a case where a plurality of object detection devices 1 according to the present embodiment are mounted on the own vehicle or on a plurality of vehicles, the transmission waves from the respective object detection devices 1 can be properly identified.

[0068] The object detection device 1 is not limited to a configuration capable of transmitting / receiving ultrasonic waves through a single transducer 21. A transducer 21 for transmitting, electrically connected to the transmitting circuit 22, and a transducer 21 for receiving, electrically connected to the receiving circuit 23, may be provided in parallel.

[0069] The configurations of the respective sections in the transmitting circuit 22 and the receiving circuit 23 are not limited to the specific examples described above. For example, a digital-to-analog conversion circuit may be provided in the drive signal generating unit 3 instead of the transmitting circuit 22.

[0070] The drive signal waveform is not limited to the specific examples described above. In the specific examples described above, the drive frequency is kept constant in the first period T1 and the second period T2, respectively. However, the present invention is not limited to this configuration.

[0071] In the Fig. 2A, for example, the starting frequency fs may be closer to the resonance frequency fr than the minimum frequency fmin. That is, the driving frequency may be modulated according to a downward chirp modulation in the first period T1. The ending frequency fe may be closer to the resonance frequency fr than the maximum frequency fmax. In particular, the driving frequency may be downward chirp modulated in the second period T2. The same applies to the Fig. 4A to 8A. Here, in the example shown in Fig. 5A, the starting frequency fs may preferably be lower than the lower limit frequency fd. Furthermore, the ending frequency fe may preferably be equal to or greater than the upper limit frequency fu.

[0072] Similarly, in the examples shown in the Fig. 4B to 8B, the starting frequency fs can be set closer to the resonance frequency fr than the maximum frequency fmax. That is, the driving frequency can be up-chirped in the first period T1. Furthermore, the final frequency fe can be set closer to the resonance frequency fr than the minimum frequency fmin. In particular, the driving frequency can be up-chirped in the second period T2. Here, the starting frequency fs can be set in the range shown in Fig. 5A, the final frequency may preferably be equal to or greater than the upper limit frequency fu. Furthermore, the final frequency fe may preferably be equal to or less than the lower limit frequency fd.

[0073] The frequency change is not limited to a discrete change. As is the case, for example, in Fig. As shown in Figure 9, the drive frequency in the third period T3 can be changed linearly. Alternatively, the drive frequency can be changed according to an S-curve.

[0074] Furthermore, it goes without saying that in the embodiment described above, the elements constituting the embodiment are not necessarily indispensable, except in the case where it is clearly stated that the element is essential and in the case where the element is clearly considered essential in principle. When numerical values ​​such as the number, numerical value, size, range, etc. of the constituent elements of the embodiment are mentioned, they are particularly limited to a specific number only when it is specifically stated as essential. The number is not limited to a specific number except in certain cases. When referring to the shape, direction, positional relationship, etc. of components, the shape, position, etc. are not in principle limited to a specific shape, direction, positional relationship, etc. unless otherwise stated.There are no restrictions on relationships between them.

[0075] The modification examples are not limited to the examples described above. Furthermore, multiple modification examples can be combined with each other. Furthermore, all or part of the above-described embodiment can be combined with all or part of the respective modification examples.

Claims

[1] Object detection device (1) designed to detect an environmental object (B), the object detection device (1) comprising: a drive signal generating unit (3) arranged to generate a drive signal that drives a transmitting unit including a transmitter (20A) that transmits transmission waves to the outside; a control unit (4) arranged to control an output of the drive signal transmitted from the drive signal generating unit (3) to the transmitting unit; and a receiving circuit (23) which generates a reception signal in dependence on a reception state of a receiver (20B) which receives reflection waves of the transmission waves reflected at the object (B), wherein the drive signal generating unit (3) is designed to generate the drive signal whose frequency changes stepwise such that its frequency is a first frequency in a first period and its frequency is a second frequency, which is different from the first frequency, in a second period following the first period; the control unit (4) is designed to set the first frequency and the second frequency such that a resonance frequency of the transmitting unit lies between the first frequency and the second frequency, and to identify, based on a width of a frequency change of a characteristic curve of the frequency of the reception signal, whether reception waves are the reflection waves of the transmission waves transmitted by the object detection device (1); and the receiving circuit (23) is designed to generate the received signal whose frequency increases or decreases following a frequency change of the transmitted waves, wherein the frequency change occurs in response to the stepwise frequency change of the drive signal. [2] The object detection device (1) according to claim 1, wherein the control unit (4) is configured to set the first frequency and the second frequency to frequencies outside a frequency band of the transmitter (20A). [3] The object detection device (1) according to claim 1 or 2, wherein the control unit (4) is configured to set one period of the first period and the second period to be longer than the other period of them, the one period having a frequency between the first frequency and the second frequency, the one frequency having a larger difference from the resonance frequency than the frequency of the other period. [4] Object detection device (1) according to one of claims 1 to 3, wherein the drive signal generating unit (3) is designed to generate the drive signal whose frequency in a third period between the first period and the second period is a third frequency that differs from the first frequency and the second frequency; and the control unit (4) is designed to set the first frequency, the second frequency and the third frequency such that the third frequency is shifted from the resonant frequency in the same shift direction in which the second frequency is shifted from the resonant frequency, and the third frequency has a greater difference from the resonant frequency than the second frequency. [5] The object detection device (1) according to claim 1, wherein a transducer (21) having functions of the transmitter (20A) and the receiver (20B) is used to provide a transmission function and a reception function of the object detection device (1).

Images