Driving device and driving method

Abstract

A drive signal generating unit (34) generates a drive signal for driving an ultrasonic transmitter (2) based on a basic signal in which unit frequency signals corresponding to the respective codes in the code string are arranged in a time series. The preceding unit frequency signal of two unit frequency signals adjacent in the time series in the basic signal is set as a first unit frequency signal, and the succeeding unit frequency signal is set as a second unit frequency signal. A target value of the transmission frequency is set as a target frequency. When the drive signal generating unit switches the first unit frequency signal and the second unit frequency signal in a discontinuous switching state different from a continuous switching state in which the target frequency corresponding to the first unit frequency signal changes continuously to the target frequency corresponding to the second unit frequency signal at approximately the same rate of change, the frequency of at least a switching portion in the second unit frequency signal is shifted in the same direction as the frequency change direction from the first unit frequency signal to the second unit frequency signal, the switching portion including the portion immediately after the start.

Description

Technical Field

[0001] The present invention relates to a device and a method for driving an ultrasonic transmitter with an ultrasonic transmission frequency. Background Art

[0002] There are known devices that use ultrasonic sensors to detect objects. When such devices are mounted on a vehicle for obstacle detection, the detection accuracy of the object may be reduced due to interference or the like. Interference may be generated, for example, when an ultrasonic sensor mounted on the vehicle receives an ultrasonic wave transmitted from an ultrasonic sensor mounted on another vehicle that exists around the vehicle. Alternatively, interference may be generated, for example, when one of a plurality of ultrasonic sensors mounted on the vehicle receives an ultrasonic wave transmitted from another ultrasonic sensor.

[0003] In addition, an ultrasonic multi-sensor array is disclosed in Patent Document 1. The ultrasonic multi-sensor array described in Patent Document 1 has at least two transmission units and at least one reception unit, and the plurality of transmission units can operate in parallel.

[0004] In the ultrasonic multi-sensor array described in Patent Document 1, ultrasonic pulses are encoded in order to enable parallel operation. Specifically, in order to encode each pulse in a plurality of transmitting units that operate simultaneously, the frequency of the carrier signal is linearly modulated. That is, the frequency of the carrier signal of the first transmitting unit increases linearly during the pulse duration. On the other hand, the frequency of the carrier signal of the second transmitting unit decreases linearly during the pulse duration.

[0005] Patent Document 1: German Patent Application Publication No. 10106142

[0006] By using the technology disclosed in Patent Document 1, the ultrasonic sensor mounted on the vehicle can identify whether the received wave is a reflected wave of its own transmitted wave. Specifically, the above identification can be performed based on whether the same frequency change as the frequency change of its own transmitted wave is included in the received wave. If the desired identification accuracy is obtained, the above-mentioned interference problem can be solved. Summary of the invention

[0007] However, in the above-mentioned object detection using the transmission and reception of ultrasonic waves, further improvement in recognition accuracy is required. The present invention is made in view of the above-mentioned exemplified situation, etc. That is, the present invention provides, for example, a device structure and method that can improve recognition accuracy compared with the past.

[0008] According to one aspect of the present invention, a driving device for driving an ultrasonic transmitter having an ultrasonic transmission frequency includes:

[0009] The drive signal generating unit is configured to generate a drive signal for driving the ultrasonic transmitter based on a basic signal in which unit frequency signals are arranged in time series, wherein the unit frequency signals are frequency signals corresponding to each of the codes in a code string formed by a plurality of codes.

[0010] When the preceding unit frequency signal of the two unit frequency signals adjacent in time series in the basic signal is set as the first unit frequency signal and the succeeding unit frequency signal is set as the second unit frequency signal, and the target value of the transmission frequency is set as the target frequency, the drive signal generating unit shifts the frequency of at least the switching part of the second unit frequency signal in the same direction as the frequency change direction from the first unit frequency signal to the second unit frequency signal when the first unit frequency signal and the second unit frequency signal are switched in a discontinuous switching state different from a continuous switching state, and in the continuous switching state, the target frequency corresponding to the first unit frequency signal to the target frequency corresponding to the second unit frequency signal continuously changes at approximately the same rate of change, and the switching part includes the part immediately after the start.

[0011] According to another aspect of the present invention, a driving method for driving an ultrasonic transmitter:

[0012] generating a driving signal for driving the ultrasonic transmitter based on a basic signal in which unit frequency signals are arranged in time series, wherein the unit frequency signals are frequency signals corresponding to each of the codes in a code string formed by a plurality of codes,

[0013] When the preceding unit frequency signal of the two unit frequency signals adjacent in time series in the basic signal is set as the first unit frequency signal and the succeeding unit frequency signal is set as the second unit frequency signal, and the target value of the transmission frequency is set as the target frequency, in the generation of the drive signal, when the first unit frequency signal and the second unit frequency signal are switched in a discontinuous switching state different from a continuous switching state, the frequency of at least the switching part of the second unit frequency signal is shifted in the same direction as the frequency change direction from the first unit frequency signal to the second unit frequency signal, and in the continuous switching state, the target frequency corresponding to the first unit frequency signal to the target frequency corresponding to the second unit frequency signal continuously changes at approximately the same rate of change, and the switching part includes the part immediately after the start.

[0014] In addition, in each column of the application document, each element is sometimes marked with a parenthesized reference numeral. However, the above reference numerals are only a specific example of the correspondence between the element and the specific unit described in the embodiment described later. Therefore, the present invention is not limited by the description of the above reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a block diagram showing a schematic configuration of an object detection device including a driving device according to an embodiment.

[0016] Figure 2A Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of transmission and reception in an example of a driving signal output by a driving signal generating unit shown in FIG.

[0017] Figure 2B Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of transmission and reception in another example of the drive signal output by the drive signal generating unit shown.

[0018] Figure 3 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0019] Figure 4 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0020] Figure 5 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0021] Figure 6 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0022] Figure 7 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0023] Figure 8 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0024] Fig. 9 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0025] Fig.10 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0026] Fig.11 Yes means Figure 1 FIG. 1 is a timing chart of frequency characteristics of another example of a drive signal output by the drive signal generating unit.

[0027] Fig.12 This is a time chart showing an example of a code string including four codes.

[0028] Fig.13 is a timing chart showing another example of a code string including four codes.

[0029] Fig.14 This is a time chart showing another example of a code string including four codes.

[0030] Fig.15 This is a time chart showing another example of a code string including four codes.

[0031] Fig.16 This is a time chart showing another example of a code string including four codes.

[0032] Fig.17 This is a time chart showing another example of a code string including four codes.

[0033] Fig.18 This is a timing chart showing an example of an ideal FSK signal.

[0034] Fig.19 It means Fig.18 Corresponding timing diagram of an example of an actual FSK signal. DETAILED DESCRIPTION

[0035] (Implementation Method)

[0036] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In addition, if various modifications that can be applied to an embodiment are inserted in the middle of a series of descriptions related to the embodiment, it is possible to hinder the understanding of the embodiment. Therefore, the modifications are collectively recorded after the description of the embodiment.

[0037] Reference Figure 1The object detection device 1 is configured to be mounted on a vehicle V as a mobile body, so as to detect an object B around the vehicle V. Hereinafter, the state in which the object detection device 1 is mounted on the vehicle V is referred to as a "vehicle-mounted state". In addition, hereinafter, the vehicle V equipped with the object detection device 1 according to the present embodiment is referred to as a "host vehicle".

[0038] The object detection device 1 has a structure as a so-called sonar, that is, an ultrasonic sensor. Specifically, the object detection device 1 is configured to transmit a transmission wave as an ultrasonic wave toward the outside. In addition, the object detection device 1 is configured to detect a surrounding object B by receiving a reflected wave caused by the object B of the transmission wave transmitted to the outside, and obtain distance measurement information corresponding to the object B.

[0039] The object detection device 1 includes a transceiver 2, a drive device 3, and a determination device 4. In the present embodiment, the object detection device 1 is configured by supporting the transceiver 2, the drive device 3, and the determination device 4 by a single sensor housing (not shown).

[0040] That is, the object detection device 1 has an integrated transceiver structure including a transceiver 2 having an ultrasonic transmission frequency and a receiving frequency. The transceiver 2 is configured to function as an ultrasonic transmitter that transmits transmission waves to the outside, and as an ultrasonic receiver that receives reception waves including reflection waves of the transmission waves of the object B.

[0041] Specifically, the transceiver 2 has a transmitting unit 20A and a receiving unit 20B. In addition, the transceiver 2 has a transducer 21. The transmitting unit 20A and the receiving unit 20B are configured to use a common transducer 21 to respectively realize a transmitting function and a receiving function. The transducer 21 has a structure as a resonant ultrasonic microphone, in which an electrical-mechanical energy conversion element such as a piezoelectric element is built into a microphone housing of a substantially cylindrical shape.

[0042] When mounted on a vehicle, the transducer 21 is arranged to be located at a position facing the outer surface of the vehicle so as to be able to transmit a transmission wave to the outside of the vehicle and to be able to receive a reflected wave from the outside of the vehicle. Specifically, when mounted on a vehicle, the transducer 21 is mounted on the outer panel member V1 in such a manner that the transceiver surface 21a is exposed to the outer space of the vehicle from a through hole, i.e., an assembly hole V2, of the outer panel member V1 formed in the vehicle. The outer panel member V1 is, for example, a bumper or a vehicle body panel, and is formed of a plate material made of synthetic resin or metal. The transceiver surface 21a is the outer surface of the microphone housing in the transducer 21, and is arranged to function as a transmission surface for transmitting waves and a reception surface for receiving waves.

[0043] The transceiver 2 includes a transducer 21, a transmission circuit 22, and a reception circuit 23. The transducer 21 is electrically connected to the transmission circuit 22 and the reception circuit 23. The transmission unit 20A is composed of the transducer 21 and the transmission circuit 22. The reception unit 20B is composed of the transducer 21 and the reception circuit 23.

[0044] The transmission circuit 22 is configured to drive the transducer 21 based on the input drive signal, so that the transducer 21 transmits a transmission wave having a frequency corresponding to the frequency of the drive signal. Hereinafter, the frequency of the drive signal is referred to as the "drive frequency". In addition, hereafter, the frequency of the transmission wave is referred to as the "transmission frequency". In contrast, hereafter, the frequency of the reception wave is referred to as the "reception frequency".

[0045] Specifically, the transmission circuit 22 has a digital / analog conversion circuit and the like. That is, the transmission circuit 22 is configured to generate an element input signal by performing signal processing such as digital / analog conversion on the drive signal output from the drive signal generation unit 34. The element input signal is an AC voltage signal for driving the transducer 21. Moreover, the transmission circuit 22 is configured to apply the generated element input signal to the transducer 21 to drive the electrical-mechanical energy conversion element in the transducer 21, thereby exciting the transceiver surface 21a and transmitting the transmission wave to the outside.

[0046] The receiving circuit 23 is configured to generate a receiving signal corresponding to the reception result based on the receiving wave of the transducer 21 and output it to the receiving signal processing unit 41. Specifically, the receiving circuit 23 has an amplifier circuit and an analog / digital conversion circuit. That is, the receiving circuit 23 is configured to generate a receiving signal by performing signal processing such as amplification and analog / digital conversion on the element output signal output by the transducer 21. The element output signal is an AC voltage signal generated by the electrical-mechanical energy conversion element provided in the transducer 21 when the transceiver surface 21a is excited by the reception of the receiving wave. In addition, the receiving circuit 23 is configured to output the generated receiving signal containing information related to the amplitude and frequency of the receiving wave to the receiving signal processing unit 41.

[0047] In this way, the transceiver 2 is configured to transmit a transmission wave through the transducer 21 and receive a reflected wave from the object B as a received wave, thereby generating a received signal corresponding to the distance between the transducer 21 and the object B and the receiving frequency. Hereinafter, the received wave when the transceiver 2 receives the reflected wave of the transmission wave transmitted by itself is referred to as a "regular wave". In contrast, the received wave caused by the transmission wave from other devices is referred to as an "irregular wave" below. "Other devices" also include other transceivers 2 mounted on the own vehicle.

[0048] The driving device 3 driving the transceiver 2 is configured to control the transmission state of the transmission wave from the transceiver 2. In the present embodiment, the driving device 3 is provided in a control circuit (not shown) that controls the overall object detection operation in the object detection device 1. The driving device 3 includes a transmission control unit 31, a code generation unit 32, a basic signal generation unit 33, a drive signal generation unit 34, and a temperature acquisition unit 35.

[0049] The transmission control unit 31 is configured to determine the waveform and transmission timing of the transmission wave by controlling the overall operation of the driving device 3. That is, the transmission control unit 31 determines the code string assigned to the transmission wave, that is, the transmission code string. The "code string" is formed by a plurality of codes. Specifically, the code string has, for example, the following structure: a plurality of the three codes "1", "0", and "-1" are arranged like "1, -1". In the present embodiment, the transmission control unit 31 selects one of the predetermined plurality of code strings as the transmission code string.

[0050] The code generation unit 32 is configured to output the transmission code string determined by the transmission control unit 31 to the basic signal generation unit 33. Specifically, the code generation unit 32 outputs the code string "1, 0" when the transmission control unit 31 determines the transmission code string to be "code string F1", and outputs the code string "1, 1" when the transmission control unit 31 determines the transmission code string to be "code string F2".

[0051] The basic signal generating unit 33 is configured to generate a basic signal corresponding to the transmitted code string and output it to the driving signal generating unit 34. The basic signal is a signal in which unit frequency signals are arranged in a time series. The unit frequency signal is a frequency signal corresponding to each of the multiple codes in the transmitted code string. A "frequency signal" is a signal indicating a frequency modulation method, that is, a frequency change method with the passage of time. Specifically, for example, as a unit frequency signal corresponding to the code "1", a frequency increase signal whose frequency increases within a prescribed time is set. In addition, as a unit frequency signal corresponding to the code "-1", a frequency decrease signal whose frequency decreases within a prescribed time is set. And, as a unit frequency signal corresponding to the code "0", a CW signal whose frequency is constant within a prescribed time is set. CW is the abbreviation of continuous waveform. A CW signal is also called a CF signal. CF is the abbreviation of continuous frequency.

[0052] The drive signal generating unit 34 is configured to generate a drive signal based on the control signal received from the transmission control unit 31 and the basic signal generated by the basic signal generating unit 33. The drive signal is a signal for driving the transceiver 2, i.e., the transmitting unit 20A, to transmit a transmission wave from the transducer 21, and is, for example, a pulse signal having a frequency within the ultrasonic frequency band. A specific example of the drive signal will be described in the column of the operation overview described later.

[0053] The control signal generated and output by the transmission control unit 31 includes waveform correction information for determining the final waveform of the drive signal and a timing signal for controlling the transmission timing of the transmission wave. That is, the drive signal generation unit 34 generates the drive signal based on the frequency signal generated by correcting the basic signal according to the waveform correction information corresponding to the code offset mode in the transmission code string determined by the transmission control unit 31. The details of the waveform correction information are described in the column of the action summary described later. In addition, the drive signal generation unit 34 is configured to output the drive signal toward the transmission unit 20A at a specified timing based on the timing signal.

[0054] The temperature acquisition unit 35 is provided to acquire the operating temperature of the object detection device 1, ie, the transceiver 2. Specifically, the temperature acquisition unit 35 receives the detection value of the outside air temperature detected by the outside air temperature sensor (not shown) mounted on the vehicle V via the in-vehicle network (not shown).

[0055] The temperature acquisition unit 35 is configured to output the acquired operating temperature to the transmission control unit 31. The transmission control unit 31 sets the waveform correction information based on the acquired operating temperature. The details of setting the waveform correction information according to the operating temperature will be described in the section of the operation overview described later.

[0056] The determination device 4 is configured to execute, based on the received signal, a detection determination process of the object B. Specifically, the determination device 4 includes a received signal processing unit 41 and an object detection unit 42 .

[0057] The receiving signal processing unit 41 is configured to generate an amplitude signal and a receiving frequency signal by performing processing such as FFT on the receiving signal. FFT is the abbreviation of Fast Fourier Transform. The amplitude signal is a signal corresponding to the amplitude of the received wave. The receiving frequency signal is a frequency signal in the received wave, that is, a signal corresponding to the receiving frequency. In other words, the receiving frequency signal is a signal corresponding to a waveform pattern related to coding in the received signal. In addition, the receiving signal processing unit 41 is configured to output the generated amplitude signal and the receiving frequency signal to the object detection unit 42.

[0058] The object detection unit 42 is configured to detect the object B based on the amplitude signal and the received frequency signal acquired from the received signal processing unit 41. Specifically, the object detection unit 42 determines whether the received wave is a regular wave based on a predetermined reference signal and the acquired received frequency signal. In addition, when the received wave is a regular wave, the object detection unit 42 detects the presence of the object B and the distance between the transducer 21 and the object B based on the acquired amplitude signal.

[0059] (Action Summary)

[0060] Hereinafter, an outline of the operation based on the configuration of the present embodiment will be described together with typical operation examples and effects achieved by the configuration with reference to the drawings.

[0061] If the specified object detection conditions are met, the object detection device 1 starts the object detection operation. The object detection conditions include, for example, that the vehicle's travel speed is within a specified range, that the vehicle's gear position is a travel gear position that includes reverse travel, etc. If the object detection conditions are not met, the object detection device 1 ends the object detection operation.

[0062] When the object detection operation starts, first, the transmission control unit 31 determines the code string to be assigned to the transmission wave, that is, the transmission code string. In addition, the transmission control unit 31 outputs the determination result of the transmission code string to the code generation unit 32. The code generation unit 32 outputs the transmission code string determined by the transmission control unit 31 to the basic signal generation unit 33. The basic signal generation unit 33 generates a basic signal corresponding to the transmission code string output from the code generation unit 32, and outputs it to the drive signal generation unit 34.

[0063] Specifically, for example, when the transmission control unit 31 determines the transmission code string to be "code string F1", the code generation unit 32 outputs the code string "1, 0" as the transmission code string. Then, the basic signal generation unit 33 generates a basic signal corresponding to the code string "1, 0". The above-mentioned basic signal is formed by arranging the unit frequency signal corresponding to the code "1" of the start bit, that is, the frequency increase signal, and the unit frequency signal corresponding to the code "0" of the second bit, that is, the CW signal, in a time series.

[0064] If the object detection condition is satisfied, the transmission control unit 31 determines the arrival of the transmission timing at a predetermined period. The predetermined period is, for example, a period of several hundred milliseconds. The arrival determination of the transmission timing is performed using a timing method such as a timer not shown. If the transmission timing arrives, the transmission control unit 31 outputs a control signal to the drive signal generating unit 34. That is, the transmission control unit 31 controls the output of the drive signal from the drive signal generating unit 34 to the transceiver 2.

[0065] When the basic signal and the control signal are input, the drive signal generating unit 34 generates a drive signal and outputs it to the transmitting unit 20A, i.e., the transmitting circuit 22. The transmitting circuit 22 drives the transducer 21 based on the input drive signal. Then, the transducer 21 transmits an ultrasonic wave, i.e., a transmission wave, of a frequency corresponding to the frequency of the drive signal toward the outside of the vehicle. Thus, the transmission wave is transmitted at a predetermined transmission timing.

[0066] During the specified receivable period in the object detection operation, the object detection device 1 performs the receiving operation. In the structure of the present embodiment of the integrated transmission and reception type, the receivable period is the period between the end of the transmission of the transmission wave and the next transmission timing that comes immediately thereafter, excluding the quiet zone caused by the influence of the echo, etc. During the receivable period, the transducer 21 outputs an AC voltage signal corresponding to the amplitude and frequency of the received wave, that is, an element output signal.

[0067] The receiving circuit 23 generates a receiving signal by performing signal processing such as amplification and analog / digital conversion on the element output signal. The receiving signal processing unit 41 generates an amplitude signal and a receiving frequency signal by performing processing such as FFT on the receiving signal. The receiving signal processing unit 41 outputs the generated amplitude signal and receiving frequency signal to the object detection unit 42.

[0068] The drive signal is frequency modulated corresponding to each code in the transmission code string determined by the transmission control unit 31. The frequency of the transmission wave, that is, the transmission frequency, corresponds to the frequency of the drive signal, that is, the driving frequency. Therefore, the transmission frequency has a frequency change corresponding to the time change of the driving frequency as a feature corresponding to the identification. Therefore, when the received wave is a regular wave, the received frequency should have the same characteristics as the transmission frequency with respect to the frequency modulation method. In addition, the "frequency modulation method" also includes no modulation, that is, CW.

[0069] Therefore, the object detection unit 42 determines whether the received wave is a regular wave based on the received frequency signal output from the received signal processing unit 41. Specifically, the object detection unit 42 compares the received frequency signal corresponding to the waveform pattern in the received signal with the reference signal corresponding to the transmission code string determined by the transmission control unit 31. In this way, it is possible to identify whether the received wave is a regular wave, that is, a reflected wave of its own transmission wave. When the received wave is a regular wave, the object detection unit 42 detects the presence of the object B and the distance between the transducer 21 and the object B based on the amplitude signal output from the received signal processing unit 41.

[0070] As described above, the transmission wave is encoded to provide identification. In addition, as the encoding method, a multi-bit encoding is used in which a code corresponding to the frequency modulation method is associated with each bit. Therefore, according to the object detection device 1 involved in this embodiment and the object detection method executed by it, it is possible to improve the recognition accuracy compared with the past.

[0071] Figure 2A Indicates the time variation of the driving frequency and receiving frequency corresponding to the code string "1, 0". Figure 2A In , the horizontal axis t represents time. Figure 2A In the time diagram on the upper side of FIG. , the vertical axis fD represents the driving frequency. In addition, the dotted line represents the target frequency, that is, the target value of the transmission frequency. Figure 2A In the lower time chart, the vertical axis fR represents the reception frequency. Figure 2B Indicates the time changes of the driving frequency and the receiving frequency corresponding to the code string "1, 1". Figure 2B The meaning of the vertical and horizontal axes in Figure 2A same.

[0072] In addition, the transceiver 2 having the transducer 21 as a resonant ultrasonic microphone has the same characteristics as a bandpass filter. That is, the frequency band that can be well transmitted and received by the transceiver 2 is substantially limited to a width of ±several % centered on the resonant frequency fC. Therefore, a predetermined transmission and reception frequency band is set for the transceiver 2.

[0073] The above-mentioned transmission and reception frequency band is a range of S=0 to Sb[dB] when the output or sensitivity is set to S and S=0[dB] at the resonant frequency fC. That is, the frequency range in which the transceiver 2 can perform good transmission and reception, that is, the transmission and reception frequency band, is a frequency band of S=0 to Sb[dB] between the upper limit frequency fH and the lower limit frequency fL. Sb is typically, for example, -3[dB]. The sensitivity is the sensitivity when the transceiver 2 is used as a receiver. In addition, such a transmission and reception frequency band can also be called a "resonance band", "-3dB band" or "3dB band". fL<fC<fH. fL-fC≈fC-fH.

[0074] Therefore, in this embodiment, the target frequency corresponding to the code "1" is set as follows Figure 2A and Figure 2B As shown by the dotted line to the upper right in the figure, the target frequency corresponding to the code "-1" is set to be a "down chirp" that linearly increases from the lower limit frequency fL to the upper limit frequency fH over time. On the other hand, the target frequency corresponding to the code "-1" is set to be a "down chirp" that linearly decreases from the upper limit frequency fH to the lower limit frequency fL over time. In addition, the target frequency corresponding to the code "0" is set to be constant at the resonant frequency fC.

[0075] Therefore, the unit frequency signal corresponding to the code "1", that is, the frequency increase signal, has a frequency characteristic in which the driving frequency increases from the lower limit frequency fL toward the upper limit frequency fH. On the other hand, the unit frequency signal corresponding to the code "-1", that is, the frequency reduction signal, has a frequency characteristic in which the driving frequency decreases from the upper limit frequency fH toward the lower limit frequency fL. In addition, the unit frequency signal corresponding to the code "0", that is, the CW signal, has a frequency characteristic in which the driving frequency becomes constant at the resonant frequency fC.

[0076] In addition, in the resonance type transceiver 2, the frequency tracking performance is poor at the driving frequency far from the resonance frequency fC. Figure 2A as well as Figure 2B As shown, when the start bit is different from the code "0", the driving frequency is set to be constant at the resonance frequency fC during the period from the pre-burst start time ts before the first start time ts1 to the first start time ts1. The first start time ts1 is the start time of the first unit frequency signal U1 corresponding to the start bit. That is, before the first unit frequency signal U1 starting with the driving frequency far from the resonance frequency fC is driven, the transceiver 2 is driven at the resonance frequency fC for a short time. Thereby, the frequency tracking performance can be improved.

[0077] Furthermore, in the present embodiment, the frequency increase signal corresponding to the code "1" has a rectangular wave frequency characteristic that changes in a step-like manner from the lower limit frequency fL to the upper limit frequency fH. On the other hand, the frequency reduction signal corresponding to the code "-1" has a rectangular wave frequency characteristic that changes in a step-like manner from the upper limit frequency fH to the lower limit frequency fL. Thus, the frequency tracking performance can be improved.

[0078] Specifically, in Figure 2A In the example shown, in the first unit frequency signal U1 as a frequency increase signal, the driving frequency is set to a constant frequency, that is, the lower limit frequency fL, during the period from the first start moment ts1 to the first intermediate moment tm1 before the first end moment te1. The first end moment te1 represents the end moment of the first unit frequency signal U1. On the other hand, during the period from the first intermediate moment tm1 to the first end moment te1, the driving frequency is set to a constant frequency, that is, the upper limit frequency fH. Moreover, at the first intermediate moment tm1 between the first start moment ts1 and the first end moment te1, the driving frequency changes in a step-like manner from the lower limit frequency fL to the upper limit frequency fH. As a result, the actual transmission frequency characteristics are as follows. Figure 2A As shown by the middle dotted line, the frequency characteristic is close to the target that the frequency increases linearly with the passage of time.

[0079] In addition, Figure 2AIn the example shown, the time interval from the first start time ts1 to the first intermediate time tm1 in the first unit frequency signal U1 is set to be substantially equal to the time interval from the first intermediate time tm1 to the first end time te1. In addition, the second start time ts2 and the second end time te2 respectively represent the start time and the end time of the second unit frequency signal U2 corresponding to the second bit. In this embodiment, the first end time te1 and the second start time ts2 are substantially consistent.

[0080] (Frequency offset processing)

[0081] exist Figure 2A In the example shown, at the first end time te1 of the code switching, that is, the second start time ts2, the target frequency changes discontinuously from the upper limit frequency fH to the resonant frequency fC. The target frequency thereafter is constant at the resonant frequency fC. Correspondingly, in the basic signal, the second unit frequency signal U2 is set so that the frequency becomes constant at the resonant frequency fC from the second start time ts2 to the second end time te2. The time interval from the second start time ts2 to the second end time te2 is set to be the same as the time interval from the first start time ts1 to the first end time te1.

[0082] Therefore, in Figure 2A In the example of the code string "1, 0" shown, the basic signal has the following frequency characteristics. Specifically, the basic signal is formed by arranging the rectangular wave-shaped first unit frequency signal U1 that changes stepwise from the lower limit frequency fL to the upper limit frequency fH at the first intermediate moment tm1 and the CW wave-shaped second unit frequency signal U2 that is constant at the resonant frequency fC in a time series. Therefore, in the second unit frequency signal U2 of the CW signal corresponding to the code "0", the driving frequency should be constant at the resonant frequency fC during the period from the second starting moment ts2 to the second ending moment te2.

[0083] However, in the resonant transceiver 2, the follow-up performance of the switching of the driving frequency is poor. That is, even if you want to change the transmission frequency, the transmission frequency does not switch instantly but changes gradually. The frequency change rate at this time depends on the characteristics of the transducer 21 and the transmission circuit 22. Therefore, if the driving frequency during the period from the second start time ts2 to the second end time te2 is set constant at the resonance frequency fC, the actual transmission frequency and reception frequency are as follows: Figure 2A Specifically, due to the influence of the frequency change in the rising region T1 where the start bit frequency rises, the frequency overshoots in the bit switching region T2, and gradually approaches the resonance frequency fC in the subsequent convergence region T3.

[0084] By gradually approaching the resonant frequency fC from the overshoot frequency, as shown in Figure 2A As shown by the dotted line in the lower time diagram in , a waveform pattern with a reduced frequency appears in the convergence area T3. If the above-mentioned waveform pattern with a reduced frequency is mistakenly judged as a "down chirp", that is, the code "-1", the recognition accuracy is reduced. Alternatively, since it takes time for the slope of the frequency change to flatten like a CW signal, the signal length per bit becomes longer. If the signal length becomes longer, it is difficult to increase the number of bits per unit time, and the changes in the code pattern that can be set are also limited.

[0085] Therefore, the driving device 3 involved in this embodiment and the driving method executed by the same shift the driving frequency of the switching part including the switching part immediately after the second start time ts2 in the second unit frequency signal U2 to the low frequency side compared with the original driving frequency, that is, the resonant frequency fC. The direction of the frequency shift is the same direction as the frequency change direction from the first unit frequency signal U1 to the second unit frequency signal U2 at the first end time te1, that is, the second start time ts2. The frequency signal of the driving frequency is constituted by the frequency signal of the shifted part between the shifted moments ts2-tm2 in the basic signal and the frequency signal of the part between the unshifted moments ts1-te1 and the moments tm2-te2 in the basic signal.

[0086] Specifically, if Figure 2A As shown in the upper time chart in FIG. 1 , the device and method according to the present embodiment correct the driving frequency toward the low frequency side in the time period from the second start time ts2 to the second intermediate time tm2 in the second unit frequency signal U2. Figure 2A In the example shown, the time period from the second start time ts2 to the second intermediate time tm2 is the portion of the second unit frequency signal U2 immediately after the second start time ts2.

[0087] According to this embodiment, Figure 2A As shown by the solid line in the lower time diagram in , the frequency overshoot in the bit switching area T2 is suppressed as much as possible. As a result, the frequency change in the second bit is flattened early. Therefore, the accuracy of pattern matching is improved. In addition, by making the signal length of each bit as short as possible, the number of bits per unit time can be increased, and the changes in the code pattern that can be set are increased. Therefore, when a plurality of sonars are mounted in the vehicle V, a unique code that does not overlap with each other can be assigned to each sonar, and it is easy to identify which sonar is sending the signal in the reception judgment. Therefore, according to this embodiment, the recognition can be improved compared with the past.

[0088] Figure 2BThis is an example of a code string "1, 1". In this example, the target frequency corresponding to the code "1" of the start position rises linearly from the lower limit frequency fL to the upper limit frequency fH over time. The target frequency corresponding to the code "1" of the next second position also rises linearly from the lower limit frequency fL to the upper limit frequency fH over time. At the first end time te1 of the code switching, that is, the second start time ts2, the target frequency changes discontinuously from the upper limit frequency fH to the lower limit frequency fL.

[0089] As described above, the frequency characteristics of the target frequency corresponding to the code "1" of the starting position and the frequency characteristics of the target frequency corresponding to the code "1" of the next second position are exactly the same. Therefore, the first unit frequency signal U1 corresponding to the code "1" of the starting position and the second unit frequency signal U2 corresponding to the code "1" of the next second position should originally become exactly the same waveform. Specifically, the driving frequency in the second unit frequency signal U2 from the second starting time ts2 to the second intermediate time tm2 should originally be constant at the lower limit frequency fL, similar to the driving frequency in the first unit frequency signal U1 from the first starting time ts1 to the first intermediate time tm1.

[0090] However, when the second unit frequency signal U2 is set to have the same waveform as the first unit frequency signal U1, the actual transmission frequency and reception frequency are as follows: Figure 2B Specifically, since the tracking performance of the switching of the driving frequency in the resonant transceiver 2 is poor, the frequency drop in the frequency drop region T4 after the frequency switching becomes smaller. As a result, the frequency rise or the rise gradient in the second bit frequency rise region T5 becomes smaller. Therefore, in the second bit, it is difficult to obtain the frequency change of the specified amount corresponding to the code "1" whose frequency changes in the "up chirp" shape. That is, the characteristics of the received signal become smaller.

[0091] Therefore, the device and method involved in this embodiment at least shift the driving frequency of the switching part including the switching part immediately after the second start time ts2 in the second unit frequency signal U2 to the low frequency side compared with the original driving frequency, that is, the lower limit frequency fL. The direction of the frequency shift is the same direction as the frequency change direction from the first unit frequency signal U1 to the second unit frequency signal U2 at the first end time te1, that is, the second start time ts2. Specifically, the device and method correct the driving frequency to the low frequency side in the time period from the second start time ts2 to the second intermediate time tm2 in the second unit frequency signal U2.

[0092] According to this embodiment, Figure 2BAs shown by the solid line in the lower time diagram in , the frequency decrease amount in the frequency decrease area T4 becomes larger. Therefore, the frequency increase amount or the increase gradient in the second bit frequency increase area T5 becomes larger. Therefore, in the second bit, the frequency change of the specified amount corresponding to the code "1" whose frequency changes in the shape of "up chirp" can be well obtained. That is, the characteristics of the received signal can be increased. Therefore, the accuracy of pattern matching is improved.

[0093] In this way, sometimes the first unit frequency signal U1 in front and the second unit frequency signal U2 in the back of the two unit frequency signals adjacent in time series in the basic signal are switched in a discontinuous switching state different from the continuous switching state. The continuous switching state is a state in which the first unit frequency signal U1 and the second unit frequency signal U2 are switched in a manner in which the target frequency changes continuously from the target frequency corresponding to the first unit frequency signal U1 to the target frequency corresponding to the second unit frequency signal U2 at approximately the same rate of change. For example, in the case of the discontinuous switching state, the target frequency changes discontinuously. Alternatively, in the case of the discontinuous switching state, the rate of change of the target frequency, i.e., the gradient, changes, so that the target frequency changes in a "broken line" shape. In the case of the discontinuous switching state, the drive signal generating unit 34 causes the frequency of at least the switching portion of the second unit frequency signal U2 to shift in the same direction as the frequency change direction from the first unit frequency signal U1 to the second unit frequency signal U2, and the switching portion is a portion immediately after the start.

[0094] Specifically, in Figure 2A In the example shown, the target frequency corresponding to the first unit frequency signal U1 rises linearly from the lower limit frequency fL toward the upper limit frequency fH. On the other hand, the target frequency corresponding to the second unit frequency signal U2 is constant at the resonant frequency fC. The switch from the first unit frequency signal U1 to the second unit frequency signal U2 is performed in a manner that the corresponding target frequency changes discontinuously from the upper limit frequency fH to the resonant frequency fC. In addition, the gradient of the target frequency before and after the target frequency changes discontinuously from the upper limit frequency fH to the resonant frequency fC is also different. Therefore, the first unit frequency signal U1 and the subsequent second unit frequency signal U2 are switched in a discontinuous switching state.

[0095] Therefore, the drive signal generating unit 34 shifts the drive frequency toward the lower frequency side than the original resonant frequency fC in the time period from the second start time ts2 to the second intermediate time tm2 in the second unit frequency signal U2. The frequency shift direction at this time is the same direction as the frequency change direction from the first unit frequency signal U1 to the second unit frequency signal U2 at the first end time te1 and the second start time ts2, that is, the frequency reduction direction from the upper limit frequency fH toward the resonant frequency fC.

[0096] Similarly, in Figure 2B In the example shown, the target frequency corresponding to the first unit frequency signal U1 rises linearly from the lower limit frequency fL toward the upper limit frequency fH. Similarly, the target frequency corresponding to the second unit frequency signal U2 rises linearly from the lower limit frequency fL toward the upper limit frequency fH. The switch from the first unit frequency signal U1 to the second unit frequency signal U2 is performed in a manner that the corresponding target frequency changes discontinuously from the upper limit frequency fH to the lower limit frequency fL. Therefore, the first unit frequency signal U1 and the subsequent second unit frequency signal U2 are switched in a discontinuous switching state.

[0097] Therefore, the drive signal generating unit 34 shifts the drive frequency toward the low frequency side compared to the original lower limit frequency fL in the time period from the second start time ts2 to the second intermediate time tm2 in the second unit frequency signal U2. The frequency shift direction at this time is the same direction as the frequency change direction from the first unit frequency signal U1 to the second unit frequency signal U2 at the first end time te1 and the second start time ts2, that is, the frequency reduction direction from the upper limit frequency fH toward the lower limit frequency fL.

[0098] In the existing structure represented by the disclosure of patent document 1, the frequency change rate depends on the sensor characteristics, and the frequency does not switch instantly but changes gradually. Therefore, in a shorter signal length, the characteristics of the received signal become smaller and high recognition cannot be obtained, that is, shortening the signal length is limited. On the other hand, even if the signal length is extended to increase the characteristics and improve the recognition performance, it is difficult to increase the number of bits per unit time as described above. Specifically, for example, only a 1-bit code can be transmitted. 8 to 12 sonars are mounted in a vehicle V, so it is difficult to identify a 1-bit code well. In contrast, according to the device and method involved in this embodiment, the switching of two codes adjacent in time series can be performed quickly and well. Therefore, it is possible to suppress overshoot in CW waves, or to increase the characteristics of the received signal in chirp waves. In addition, the signal length per 1 bit can be shortened. Therefore, it is possible to form a transmission wave encoded by arranging multiple frequency patterns of the same or different frequency in time series with good recognition. Therefore, according to this embodiment, a device structure and method that can improve recognition accuracy compared with the past are provided.

[0099] In the resonance type transceiver 2, the frequency characteristics of transmission and reception including the resonance frequency fC and the transmission and reception frequency band vary according to the temperature. Therefore, in this embodiment, the drive signal generating unit 34 sets the frequency characteristics according to the operating temperature of the transceiver 2. Figure 2A as well as Figure 2BThat is, the temperature acquisition unit 35 acquires the operating temperature of the object detection device 1, that is, the transceiver 2, and outputs it to the transmission control unit 31. The transmission control unit 31 sets the waveform correction information according to the acquired operating temperature.

[0100] Specifically, in Figure 2A In the example shown, the transmission control unit 31 sets the time interval from the second start time ts2 to the second intermediate time tm2 in the second unit frequency signal U2 according to the operating temperature. In addition, the transmission control unit 31 sets the offset amount, i.e., the correction amount, of the driving frequency from the resonant frequency fC in the time period from the second start time ts2 to the second intermediate time tm2 according to the operating temperature. Figure 2B In the example shown, the transmission control unit 31 sets a correction amount, which is a deviation amount of the drive frequency from the lower limit frequency fL in the time period from the second start time ts2 to the second intermediate time tm2, based on the operating temperature.

[0101] According to the device and method of this embodiment, the influence of the operating temperature on the frequency waveform of the transmission wave can be reduced as much as possible, thereby further improving the recognition accuracy compared with the past.

[0102] (Multi-bit processing)

[0103] In the above use Figure 2A and Figure 2B In the description of the operation overview, the switching of the start bit and the second bit in the code string is mainly described. The following describes the specific processing for the code string with more than 3 bits.

[0104] A code of three or more digits can be assigned to the transmission wave. By encoding the transmission wave with a plurality of digits of three or more digits, the number of changes in the code pattern that can be set can be further increased, and thus the recognition accuracy can be improved compared with the past.

[0105] (Specific example 1)

[0106] Figure 3 to Figure 5 This shows an example of encoding the transmission wave using a 4-bit code string. Figure 3 to Figure 5 In , fT represents the target frequency and fD represents the driving frequency. Figure 3 to Figure 5 In the time diagram of the driving frequency fD shown in the lower middle side, the unit basic signal before the offset, that is, before the correction, is represented by the thick dotted line. In addition, on the time t on the horizontal axis, t0 represents the start time of the start bit, which is Figure 2AThe first start time ts1 in corresponds to ts2. t1 represents the end time of the start bit and the start time of the second bit. Similarly, t2 represents the end time of the second bit and the start time of the third bit, t3 represents the end time of the third bit and the start time of the fourth bit, and t4 represents the end time of the fourth bit.

[0107] exist Figure 3 to Figure 5 In the example shown, the target frequency corresponding to the code "1" has a frequency characteristic of "up chirp" that rises linearly and monotonically. On the other hand, the target frequency corresponding to the code "-1" has a frequency characteristic of "down chirp" that decreases linearly and monotonically. In addition, the target frequency corresponding to the code "0" has a frequency characteristic of CW wave.

[0108] Correspondingly, the unit frequency signal corresponding to the code "1", i.e., the frequency increase signal, has a frequency characteristic of "up chirp" in which the driving frequency increases linearly and monotonically. On the other hand, the unit frequency signal corresponding to the code "-1", i.e., the frequency decrease signal, has a frequency characteristic of "down chirp" in which the driving frequency decreases linearly and monotonically. In addition, the unit frequency signal corresponding to the code "0", i.e., the CW signal, has a frequency characteristic of a CW wave in which the driving frequency becomes constant.

[0109] exist Figure 3 In the example shown, the transmission wave is encoded by the code string "-1, 1, -1, 1". In this case, the target frequency corresponding to the start bit decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. The target frequency corresponding to the second bit increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. The target frequency corresponding to the third bit decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. The target frequency corresponding to the fourth bit increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC.

[0110] Correspondingly, in the basic signal, the first unit frequency signal U1 decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. In addition, the second unit frequency signal U2 increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. In addition, the third unit frequency signal U3 decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. In addition, the fourth unit frequency signal U4 increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. The basic signal is formed by arranging the first unit frequency signal U1, the second unit frequency signal U2, the third unit frequency signal U3 and the fourth unit frequency signal U4 in this order in a time series. Without performing frequency offset processing, the basic signal is roughly consistent with the frequency signal representing the frequency characteristics in the drive signal.

[0111] At time t1, the target frequency corresponding to the start position is the lower limit frequency fL. In addition, at time t1, the target frequency corresponding to the second position is the lower limit frequency fL. Therefore, the target frequency changes continuously at time t1. However, the change direction of the target frequency corresponding to the start position and the change direction of the target frequency corresponding to the second position are opposite directions. Therefore, at time t1, the target frequency changes in a "broken line" shape. That is, the first unit frequency signal U1 and the subsequent second unit frequency signal U2 are switched in a discontinuous switching state.

[0112] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the second unit frequency signal U2 in a frequency increase direction opposite to the frequency change in the constant direction, i.e., the decreasing direction, in the first unit frequency signal U1. Specifically, the transmission control unit 31 outputs waveform correction information to the drive signal generating unit 34 so as to bias the entire second unit frequency signal U2 having an "up-chirp" frequency characteristic toward the high frequency side.

[0113] At time t2, the target frequency corresponding to the second position is the resonant frequency fC. In addition, at time t2, the target frequency corresponding to the third position is the resonant frequency fC. Therefore, the target frequency changes continuously at time t2. However, the change direction of the target frequency corresponding to the second position and the change direction of the target frequency corresponding to the third position are in opposite directions. Therefore, at time t2, the target frequency changes in a "broken line" shape. Therefore, the second unit frequency signal U2 and the subsequent third unit frequency signal U3 are switched in a discontinuous switching state.

[0114] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the third unit frequency signal U3 in a frequency reduction direction opposite to the frequency change in the constant direction, i.e., the rising direction, in the second unit frequency signal U2. Specifically, the transmission control unit 31 outputs waveform correction information to the drive signal generating unit 34 so as to bias the entire third unit frequency signal U3 having a frequency characteristic of "down chirp" toward the low frequency side.

[0115] At time t3, the target frequency corresponding to the third digit is the lower limit frequency fL. In addition, at time t3, the target frequency corresponding to the fourth digit is the lower limit frequency fL. Therefore, the target frequency changes continuously at time t3. However, the change direction of the target frequency corresponding to the third digit and the change direction of the target frequency corresponding to the fourth digit are in opposite directions. Therefore, at time t3, the target frequency changes in a "broken line" shape. Therefore, the third unit frequency signal U3 and the subsequent fourth unit frequency signal U4 are switched in a discontinuous switching state.

[0116] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the fourth unit frequency signal U4 in a frequency rising direction opposite to the frequency change in the constant direction, i.e., the decreasing direction, in the third unit frequency signal U3. Specifically, the sending control unit 31 outputs waveform correction information to the drive signal generating unit 34 so as to bias the entire fourth unit frequency signal U4 having an "up-chirp" frequency characteristic toward the high frequency side.

[0117] exist Figure 4 In the example shown, the transmission wave is encoded by the code string "-1, 1, 0, 0". In this case, the target frequency corresponding to the start bit decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. The target frequency corresponding to the second bit increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. The target frequencies corresponding to the third and fourth bits are constant at the resonant frequency fC.

[0118] Correspondingly, in the basic signal, the first unit frequency signal U1 decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. In addition, the second unit frequency signal U2 increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. In addition, the third unit frequency signal U3 and the fourth unit frequency signal U4 are constant at the resonant frequency fC. The basic signal is formed by arranging the first unit frequency signal U1, the second unit frequency signal U2, the third unit frequency signal U3 and the fourth unit frequency signal U4 in this order in a time series.

[0119] The setting status of the start bit and the target frequency in the second bit is the same as Figure 3 The example shown is the same. Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the second unit frequency signal U2 in the frequency rising direction opposite to the frequency change in the decreasing direction in the first unit frequency signal U1. Specifically, the transmission control unit 31 outputs the waveform correction information that biases the entire second unit frequency signal U2 having the frequency characteristic of "up chirp" toward the high frequency side to the drive signal generating unit 34.

[0120] At time t2, the target frequency corresponding to the second position is the resonant frequency fC. In addition, at time t2, the target frequency corresponding to the third position is the resonant frequency fC. Therefore, the target frequency changes continuously at time t2. However, the change gradient of the target frequency corresponding to the second position is a positive value that is not 0, while the change gradient of the target frequency corresponding to the third position is 0. Therefore, at time t2, the target frequency changes in a "broken line" shape. Therefore, the second unit frequency signal U2 and the subsequent third unit frequency signal U3 are switched in a discontinuous switching state.

[0121] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the third unit frequency signal U3 in a frequency reduction direction opposite to the frequency change in the rising direction in the second unit frequency signal U2. Specifically, the sending control unit 31 outputs waveform correction information that shifts the frequency of the switching portion between moments t2 and tm in the third unit frequency signal U3 in a frequency reduction direction to the drive signal generating unit 34. The shifted frequency is the lower limit frequency fL at moment t2, and rises from the lower limit frequency fL in an "upward chirp" shape between moments t2 and tm. The time interval between moments t2 and tm is set according to the operating temperature, etc.

[0122] At time t3, the target frequency corresponding to the third position is the resonant frequency fC. In addition, at time t3, the target frequency corresponding to the fourth position is the resonant frequency fC. Moreover, the frequency gradient of the third unit frequency signal U3 and the frequency gradient of the fourth unit frequency signal U4 near time t3 are both 0 and equal. Therefore, the third unit frequency signal U3 and the subsequent fourth unit frequency signal U4 are switched in a continuous switching state.

[0123] Therefore, the drive signal generating unit 34 does not shift the frequency of the fourth unit frequency signal U4. In other words, the transmission control unit 31 does not correct the frequency pattern of the fourth unit frequency signal U4.

[0124] exist Figure 5 In the example shown, the transmission wave is encoded by the code string "-1, 1, 1, -1". In this case, the target frequency corresponding to the start bit decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. The target frequency corresponding to the second bit increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. The target frequency corresponding to the third bit increases linearly and monotonically from the resonant frequency fC to the upper limit frequency fH. The target frequency corresponding to the fourth bit decreases linearly and monotonically from the upper limit frequency fH to the resonant frequency fC.

[0125] Correspondingly, in the basic signal, the first unit frequency signal U1 decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. In addition, the second unit frequency signal U2 increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. In addition, the third unit frequency signal U3 increases linearly and monotonically from the resonant frequency fC to the upper limit frequency fH. In addition, the fourth unit frequency signal U4 decreases linearly and monotonically from the upper limit frequency fH to the resonant frequency fC. The basic signal is formed by arranging the first unit frequency signal U1, the second unit frequency signal U2, the third unit frequency signal U3, and the fourth unit frequency signal U4 in this order in a time series.

[0126] The setting status of the start bit and the target frequency in the second bit is the same as Figure 3 and Figure 4The example shown is the same. Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the second unit frequency signal U2 in the frequency rising direction opposite to the frequency change in the decreasing direction in the first unit frequency signal U1. Specifically, the transmission control unit 31 outputs the waveform correction information that biases the entire second unit frequency signal U2 having the frequency characteristic of "up chirp" toward the high frequency side to the drive signal generating unit 34.

[0127] At time t2, the target frequency corresponding to the second position is the resonant frequency fC. In addition, at time t2, the target frequency corresponding to the third position is the resonant frequency fC. Therefore, the target frequency changes continuously at time t2. Moreover, the frequency gradient of the second unit frequency signal U2 and the frequency gradient of the third unit frequency signal U3 near time t2 are both 0 and equal. Therefore, the second unit frequency signal U2 and the subsequent third unit frequency signal U3 are switched in a continuous switching state.

[0128] Therefore, the drive signal generation unit 34 does not shift the frequency of the third unit frequency signal U3. In other words, the transmission control unit 31 does not correct the frequency pattern of the third unit frequency signal U3.

[0129] At time t3, the target frequency corresponding to the third digit is the upper limit frequency fH. In addition, at time t3, the target frequency corresponding to the fourth digit is the upper limit frequency fH. Therefore, the target frequency changes continuously at time t3. However, the change direction of the target frequency corresponding to the third digit and the change direction of the target frequency corresponding to the fourth digit are in opposite directions. Therefore, at time t3, the target frequency changes in a "broken line" shape. Therefore, the third unit frequency signal U3 and the subsequent fourth unit frequency signal U4 are switched in a discontinuous switching state.

[0130] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the fourth unit frequency signal U4 in a frequency reduction direction opposite to the frequency change in the rising direction in the third unit frequency signal U3. Specifically, the sending control unit 31 outputs waveform correction information to the drive signal generating unit 34 so as to bias the entire fourth unit frequency signal U4 having a frequency characteristic of "down chirp" toward the low frequency side.

[0131] (Specific example 2)

[0132] Figure 6 to Figure 8 Yes Figure 3 to Figure 5 The driving frequency waveform in the example shown is changed to Figure 2A as well as Figure 2B The same waveform as shown in the example is plotted. In addition, Figure 6 and Figure 3 correspond, Figure 7 and Figure 4 correspond, Figure 8 and Figure 5 In addition, Figure 6 to Figure 8 In the time chart of the driving frequency fD shown in the lower middle portion, a waveform corresponding to the target value of the transmission frequency fT is indicated by a dotted line.

[0133] exist Figure 6 In the example shown, the transmission wave is encoded by the code string "-1, 1, -1, 1". Figure 3 The example shown is the same. Figure 6 to Figure 8 In the example shown, the drive signal generating unit 34 changes the CW wave-shaped drive frequency in steps, thereby generating a transmission wave whose transmission frequency changes in an "up chirp" shape. Similarly, the drive signal generating unit 34 changes the CW wave-shaped drive frequency in steps, thereby generating a transmission wave whose transmission frequency changes in a "down chirp" shape.

[0134] Specifically, if Figure 6 As shown, in the basic signal, the first unit frequency signal U1 and the third unit frequency signal U3 are constant at the lower limit frequency fL. On the other hand, the second unit frequency signal U2 and the fourth unit frequency signal U4 are constant at the resonant frequency fC. The basic signal is formed by arranging the first unit frequency signal U1, the second unit frequency signal U2, the third unit frequency signal U3 and the fourth unit frequency signal U4 in this order in a time series.

[0135] That is, the target frequency corresponding to the start position decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. The target frequency corresponding to the second position increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. Correspondingly, in the basic signal, the first unit frequency signal U1 is set constant at the lower limit frequency fL. In addition, the second unit frequency signal U2 is set constant at the resonant frequency fC.

[0136] and Figure 3 In the example shown, at time t1, the target frequency changes in a "zigzag" shape. That is, the first unit frequency signal U1 and the subsequent second unit frequency signal U2 are switched in a discontinuous switching state.

[0137] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the second unit frequency signal U2 in the frequency rising direction in the same direction as the frequency change from the first unit frequency signal U1 to the second unit frequency signal U2. Specifically, the sending control unit 31 outputs waveform correction information that biases the entire second unit frequency signal U2 toward the high frequency side to the drive signal generating unit 34.

[0138] The target frequency corresponding to the second position increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. The target frequency corresponding to the third position decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. Correspondingly, in the basic signal, the second unit frequency signal U2 is set constant at the resonant frequency fC. In addition, the third unit frequency signal U3 is set constant at the lower limit frequency fL.

[0139] and Figure 3 In the example shown, at time t2, the target frequency changes in a "broken line" shape. Therefore, the second unit frequency signal U2 and the subsequent third unit frequency signal U3 are switched in a discontinuous switching state.

[0140] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the third unit frequency signal U3 in the same frequency reduction direction as the frequency change from the second unit frequency signal U2 to the third unit frequency signal U3. Specifically, the sending control unit 31 outputs waveform correction information that biases the entire third unit frequency signal U3 toward the low-frequency side to the drive signal generating unit 34.

[0141] The target frequency corresponding to the third position decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. The target frequency corresponding to the fourth position increases linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. Correspondingly, in the basic signal, the third unit frequency signal U3 is set constant at the lower limit frequency fL. In addition, the fourth unit frequency signal U4 is set constant at the resonant frequency fC.

[0142] and Figure 3 In the example shown, at time t3, the target frequency changes in a "broken line" shape. Therefore, the third unit frequency signal U3 and the subsequent fourth unit frequency signal U4 are switched in a discontinuous switching state.

[0143] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the fourth unit frequency signal U4 in the frequency rising direction in the same direction as the frequency change from the third unit frequency signal U3 to the fourth unit frequency signal U4. Specifically, the sending control unit 31 outputs waveform correction information that biases the entire fourth unit frequency signal U4 toward the high frequency side to the drive signal generating unit 34.

[0144] exist Figure 7 In the example shown, the transmission wave is encoded with the code string "-1, 1, 0, 0". Figure 4 The example shown is the same.

[0145] like Figure 7As shown, in the basic signal, the first unit frequency signal U1 is constant at the lower limit frequency fL. On the other hand, the second unit frequency signal U2 is constant at the resonant frequency fC. In addition, the third unit frequency signal U3 and the fourth unit frequency signal U4 are constant at the resonant frequency fC. The basic signal is formed by arranging the first unit frequency signal U1, the second unit frequency signal U2, the third unit frequency signal U3 and the fourth unit frequency signal U4 in this order in a time series.

[0146] and Figure 4 In the example shown, at time t1, the target frequency changes in a "zigzag" shape. That is, the first unit frequency signal U1 and the subsequent second unit frequency signal U2 are switched in a discontinuous switching state.

[0147] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the second unit frequency signal U2 in the frequency rising direction in the same direction as the frequency change from the first unit frequency signal U1 to the second unit frequency signal U2. Specifically, the sending control unit 31 outputs waveform correction information that biases the entire second unit frequency signal U2 toward the high frequency side to the drive signal generating unit 34.

[0148] and Figure 4 In the example shown, at time t2, the target frequency changes in a "broken line" shape. Therefore, the second unit frequency signal U2 and the subsequent third unit frequency signal U3 are switched in a discontinuous switching state.

[0149] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the third unit frequency signal U3 in the same frequency reduction direction as the frequency change from the second unit frequency signal U2 to the third unit frequency signal U3. Specifically, the sending control unit 31 outputs waveform correction information that biases the entire third unit frequency signal U3 toward the low-frequency side to the drive signal generating unit 34.

[0150] and Figure 4 In the example shown, at time t3, the target frequency changes continuously with the same gradient. Therefore, the third unit frequency signal U3 and the subsequent fourth unit frequency signal U4 are switched in a continuous switching state. Therefore, the drive signal generating unit 34 does not shift the frequency for the fourth unit frequency signal U4. That is, the sending control unit 31 does not correct the frequency pattern of the fourth unit frequency signal U4.

[0151] exist Figure 8 In the example shown, the transmission wave is encoded by the code string "-1, 1, 1, -1". The target frequency in this case is Figure 5 The example shown is the same.

[0152] like Figure 8As shown, in the basic signal, the first unit frequency signal U1 is constant at the lower limit frequency fL. In addition, the second unit frequency signal U2 is constant at the resonant frequency fC. In addition, the third unit frequency signal U3 is constant at the upper limit frequency fH. In addition, the fourth unit frequency signal U4 is constant at the resonant frequency fC. The basic signal is formed by arranging the first unit frequency signal U1, the second unit frequency signal U2, the third unit frequency signal U3 and the fourth unit frequency signal U4 in this order in a time series.

[0153] and Figure 5 In the example shown, at time t1, the target frequency changes in a "zigzag" shape. Therefore, the first unit frequency signal U1 and the subsequent second unit frequency signal U2 are switched in a discontinuous switching state.

[0154] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the second unit frequency signal U2 in the frequency rising direction in the same direction as the frequency change from the first unit frequency signal U1 to the second unit frequency signal U2. Specifically, the sending control unit 31 outputs waveform correction information that biases the entire second unit frequency signal U2 toward the high frequency side to the drive signal generating unit 34.

[0155] and Figure 5 Similarly, in the example shown, at time t2, the target frequency changes continuously with the same gradient. Therefore, the second unit frequency signal U2 and the subsequent third unit frequency signal U3 are switched in a continuous switching state. Therefore, the drive signal generating unit 34 does not shift the frequency for the third unit frequency signal U3. That is, the sending control unit 31 does not correct the frequency pattern of the third unit frequency signal U3.

[0156] and Figure 5 In the example shown, at time t3, the target frequency changes in a "broken line" shape. Therefore, the third unit frequency signal U3 and the subsequent fourth unit frequency signal U4 are switched in a discontinuous switching state.

[0157] Therefore, the drive signal generating unit 34 shifts the frequency of at least the switching portion in the fourth unit frequency signal U4 in the same direction as the frequency change from the third unit frequency signal U3 to the fourth unit frequency signal U4. Specifically, the sending control unit 31 outputs waveform correction information that biases the entire fourth unit frequency signal U4 toward the low-frequency side to the drive signal generating unit 34.

[0158] As mentioned above, in Figure 6 to Figure 8 In the example shown, the driving frequency waveform is set to a rectangular wave shape that changes in steps. This allows the desired transmission frequency change in the resonance type transceiver 2 to be realized in as short a time as possible, thereby shortening the signal length per bit as much as possible.

[0159] (Concrete example 3)

[0160] Fig. 9 Yes Figure 3 The frequency shift method in the example shown is changed. Fig. 9 In the example shown, the frequency of the portion other than the switching portion in the unit frequency signal is not shifted, but the frequency of the switching portion is shifted.

[0161] That is, the drive signal generating unit 34 does not shift the frequency of the portion other than the switching portion in the second unit frequency signal U2, but shifts the frequency of the switching portion. The switching portion is the portion between time t1 and tm1. On the other hand, the portion other than the switching portion is the portion between time tm1 and t2.

[0162] Similarly, the drive signal generating unit 34 shifts the frequency of the switching portion between the time t2 and tm2 in the third unit frequency signal U3, and does not shift the frequency of the portion other than the switching portion. In addition, the drive signal generating unit 34 shifts the frequency of the switching portion between the time t3 and tm3 in the fourth unit frequency signal U4, and does not shift the frequency of the portion other than the switching portion.

[0163] In the above structure and method, the switching of two codes adjacent in time sequence can also be performed quickly and well. Therefore, the characteristics of the received signal can be increased. In addition, by shortening the signal length of each 1 bit as much as possible, the number of bits per unit time can be increased, thereby increasing the changes of the code pattern that can be set. Therefore, the recognition accuracy can be improved compared with the past.

[0164] (Concrete example 4)

[0165] Fig.10 Yes Figure 4 The frequency offset method in the example shown is changed. Figure 4 In the example shown, the frequency pattern after the shift is set to be an "up chirp" shape that rises linearly and monotonically over time. Fig.10 In the example shown, the frequency pattern after the shift is set to a fixed frequency signal without temporal frequency variation.

[0166] That is, the drive signal generating unit 34 sets the frequency of the portion between the time t1 and tm1 in the second unit frequency signal U2 after the shift to a fixed frequency without temporal frequency change. Similarly, the drive signal generating unit 34 sets the frequency of the portion between the time t2 and tm2 in the third unit frequency signal U3 after the shift to a fixed frequency without temporal frequency change. Thus, the desired transmission frequency change in the resonant type transceiver 2 can be achieved in as short a time as possible, and the signal length per bit can be shortened as much as possible.

[0167] (Concrete example 5)

[0168] Fig.11 Yes Fig. 9 The frequency offset method in the example shown is changed. Fig.11 In the example shown, the greater the difference between the offset frequency and the resonant frequency fC, the longer the duration of the switching portion where the frequency is offset is set. That is, the drive signal generating unit 34 sets the duration "tm1-t1" of the switching portion between the time t1-tm1 in the second unit frequency signal U2 so that the greater the difference between the offset frequency and the resonant frequency fC, the longer the duration "tm1-t1". The resonant frequency fC is equivalent to the center frequency in the frequency band fC to fH of the basic signal.

[0169] Specifically, if we refer to Fig.11 , the difference between the shifted frequency of the portion between time t2-tm2 in the third unit frequency signal U3 and the resonant frequency fC is greater than the difference between the shifted frequency of the portion between time t1-tm1 in the second unit frequency signal U2 and the resonant frequency fC. Therefore, the duration "tm2-t2" of the switching portion in the third unit frequency signal U3 is set to be longer than the duration "tm1-t1" of the switching portion in the second unit frequency signal U2. Thus, the desired transmission frequency change in the resonant transceiver 2 can be achieved in as short a time as possible, and the signal length per bit can be shortened as much as possible.

[0170] (Concrete example 6)

[0171] like Figure 6 to Figure 11 As shown, the drive signal generating unit 34 preferably sets the shifted frequency to a frequency different from the resonance frequency fC. This can achieve a desired transmission frequency change in the resonance type transceiver 2 in as short a time as possible, and can shorten the signal length per bit as much as possible.

[0172] Specifically, for example, in Fig.11In the example shown, the target frequency decreases linearly from the resonant frequency fC to the lower limit frequency fL between time t0 and t1, and increases linearly from the lower limit frequency fL to the resonant frequency fC between time t1 and t2. Around time t1, the target frequency changes from decreasing to increasing at the lower limit frequency fL far from the resonant frequency fC.

[0173] As described above, the resonance-type transceiver 2 has poor tracking performance for switching of the driving frequency. Therefore, when changing the transmission frequency from a frequency away from the resonance frequency fC toward the resonance frequency fC, it is difficult to obtain sufficient tracking performance by simply moving the target value toward the resonance frequency fC. Therefore, in this case, it is necessary to make the actual driving frequency excessively shifted in the direction in which the frequency is desired to be changed compared to the predetermined value in the basic signal.

[0174] Therefore, the drive signal generation unit 34 shifts the drive frequency from a predetermined value on the lower frequency side than the resonant frequency fC in the basic signal before the shift to a higher frequency side than the resonant frequency fC during the time period t1-tm1. That is, the transmission control unit 31 outputs waveform correction information in which the frequency after the shift is on the "opposite side" of the resonant frequency fC relative to the frequency before the shift.

[0175] (Variation Example)

[0176] The present invention is not limited to the above-mentioned embodiment. Therefore, the above-mentioned embodiment can be appropriately changed. Below, representative modified examples are described. In the following description of the modified examples, the differences from the above-mentioned embodiment are mainly described. In addition, in the above-mentioned embodiment and the modified examples, the same or equivalent parts are marked with the same figure numerals. Therefore, in the description of the following modified examples, with respect to the constituent elements with the same figure numerals as those in the above-mentioned embodiment, as long as there is no technical contradiction or special additional description, the description in the above-mentioned embodiment can be appropriately cited.

[0177] The vehicle V equipped with the object detection device 1 is not limited to an automobile. In addition, the object detection device 1 is not limited to a vehicle-mounted structure mounted on the vehicle V. Therefore, specifically, for example, the object detection device 1 can also be mounted on a ship or an aircraft.

[0178] The object detection device 1 is not limited to Figure 1 As shown in the figure, each of the transceivers 2 and the drive device 3 is provided. That is, the object detection device 1 may also include a plurality of transceivers 2. In this case, the drive device 3 may also be configured to perform drive control of the plurality of transceivers 2. Alternatively, the transceiver 2 and the drive device 3 may also be provided in a one-to-one relationship.

[0179] The object detection device 1 is not limited to a structure of an integrated transmitter and receiver. That is, the object detection device 1 is not limited to a structure capable of transmitting and receiving ultrasonic waves through a single transducer 21. Therefore, for example, a transmitting transducer 21 electrically connected to a transmitting circuit 22 and a receiving transducer 21 electrically connected to a receiving circuit 23 may be arranged in parallel. In other words, the transmitting unit 20A and the receiving unit 20B may each include a transducer 21. In this case, the transmitting unit 20A and the receiving unit 20B may also be supported by respective sensor housings.

[0180] By using triangulation of multiple transducers 21, it is sometimes possible to detect the two-dimensional position of object B relative to the vehicle. In this case, for example, a transmission wave having the same frequency characteristics, i.e., a code arrangement, can be emitted from each of the multiple transducers 21 mounted on the vehicle. At this time, the "regular wave" becomes a reception wave when the reflection wave of the transmission wave transmitted from the vehicle is received by the vehicle. In contrast, the "irregular wave" becomes a reception wave when the reflection wave of the transmission wave transmitted from other vehicles is received by the vehicle. As a result, the influence caused by interference between multiple vehicles can be well suppressed.

[0181] According to the present invention, the time per bit can be shortened, and more code patterns can be transmitted than before. Therefore, for example, different code patterns can be assigned to the multiple transducers 21 mounted on the vehicle. Thus, transmission waves having different frequency characteristics, i.e., code arrangements, can be emitted from each of the multiple transducers 21 mounted on the vehicle. Thus, strict distinction between direct waves and indirect waves is facilitated, and thus erroneous recognition caused by the influence of multiple reflections can be well suppressed.

[0182] The structures of the transmission circuit 22, the reception circuit 23 and other parts are not limited to the specific examples shown in the above-mentioned embodiment. That is, for example, a digital / analog conversion circuit may be provided in the drive signal generation part 34 instead of the transmission circuit 22. That is, the drive signal may be the element input signal itself for the transducer 21.

[0183] All or part of the drive device 3 may be provided outside a sensor housing (not shown) supporting the transceiver 2 in the ultrasonic sensor. That is, for example, all or part of the drive device 3 may be provided in a so-called sonar ECU electrically connected to the ultrasonic sensor. ECU is an abbreviation of Electronic Control Unit.

[0184] The code string may be changeable or unchangeable. That is, for example, the transmission control unit 31 may be configured to change the code string assigned to the transmission wave when the object detection unit 42 detects interference. Specifically, for example, when the object detection unit 42 detects interference, the transmission control unit 31 may select a code string different from the code string currently selected as the transmission code string as a new transmission code string. Alternatively, the transmission control unit 31 may use a random number or the like to cause the code generation unit 32 to generate a code string each time the object detection device 1 is started.

[0185] Alternatively, the drive signal generating unit 34 may be configured to output only one drive signal SD to one transceiver 2. In this case, specifically, for example, the drive signal generating unit 34 in the object detecting device 1 mounted on the vehicle only outputs the drive signal SD corresponding to the 3-digit code "110". In addition, the drive signal generating unit 34 in the object detecting device 1 mounted on another vehicle only outputs the drive signal SD corresponding to the 3-digit code "100". Furthermore, the drive signal generating unit 34 in the object detecting device 1 mounted on another other vehicle only outputs the drive signal SD corresponding to the 3-digit code "111". In this case, the code generating unit 32 can be omitted.

[0186] When a plurality of transceivers 2 are provided, the drive signal generating unit 34 may be configured to input a drive signal SD having a different code arrangement to each of the plurality of transceivers 2. Specifically, for example, when two transceivers 2 are provided, a drive signal SD corresponding to a 3-bit code of "110" may be input to one, and a drive signal SD corresponding to a 3-bit code of "100" may be input to the other.

[0187] fC may be a center frequency in the transmission / reception frequency band between the upper limit frequency fH and the lower limit frequency fL. In this case, the center frequency may be a frequency different from the resonance frequency of the transceiver 2 .

[0188] The code string and the frequency characteristics corresponding thereto are not limited to the above-mentioned specific examples. Figure 12 to Figure 17 Another example of a code string having a 4-bit code is shown.

[0189] Fig.12 Indicates that Figure 3 The code string shown is “-1, 1, -1, 1” and the reversed code string is “1, -1, 1, -1”. Fig.13 Indicates that Figure 5 The code string shown is “-1, 1, 1, -1”, and the reversed code string is “1, -1, -1, 1”. Fig.14 Represents the code string "1, -1, 0, 1".

[0190] The predetermined frequency in the case of code "0" corresponding to the CW signal is not limited to the resonance frequency fC. That is, for example, Fig.15 The first unit frequency signal U1 corresponding to the start bit "1" in the code string "1, 0, -1, 0" shown in the figure rises linearly and monotonically from the resonant frequency fC to the upper limit frequency fH. Therefore, the second unit frequency signal U2 corresponding to the second bit code "0" is set to be constant at the upper limit frequency fH in a manner continuous with the frequency at the end time in the previous first unit frequency signal U1.

[0191] On the other hand, the third unit frequency signal U3 corresponding to the third bit "-1" decreases linearly and monotonically from the upper limit frequency fH to the resonant frequency fC. Therefore, the fourth unit frequency signal U4 corresponding to the fourth bit code "0" is set to be constant at the resonant frequency fC in a manner continuous with the frequency at the end time in the previous third unit frequency signal U3.

[0192] Likewise, Fig.16 The first unit frequency signal U1 corresponding to the start bit "1" in the code string "-1, 0, 1, 0" shown in the figure decreases linearly and monotonically from the resonant frequency fC to the lower limit frequency fL. Therefore, the second unit frequency signal U2 corresponding to the second bit code "0" is set to be constant at the lower limit frequency fL in a manner continuous with the frequency at the end time in the previous first unit frequency signal U1.

[0193] On the other hand, the third unit frequency signal U3 corresponding to the third bit "1" rises linearly and monotonically from the lower limit frequency fL to the resonant frequency fC. Therefore, the fourth unit frequency signal U4 corresponding to the fourth bit code "0" is set to be constant at the resonant frequency fC in a manner continuous with the frequency at the end time in the previous third unit frequency signal U3.

[0194] The starting frequency of the start bit is not limited to the resonance frequency fC. Fig.17 As shown, the starting frequency of the start bit may also be the lower limit frequency fL. Alternatively, the starting frequency of the start bit may also be the upper limit frequency fH. Alternatively, the starting frequency of the start bit may also be a frequency different from the upper limit frequency fH, the resonance frequency fC, and the lower limit frequency fL.

[0195] like Figure 3 to Figure 17 As shown, in a preferred example, the start bit has a certain frequency modulation other than "0", that is, a CW wave. Thus, the recognition is improved. However, the present invention is not limited to the above-mentioned method. That is, for example, the start bit may also be "0", that is, a CW wave.

[0196] In the above embodiment, an example of encoding based on three codes "-1", "0" and "1" is shown. However, the present invention is not limited to the above encoding method. That is, for example, "10", "11" and "01" can be used instead of "-1", "0" and "1". The code "-1" corresponds to the code "10". The code "0" corresponds to the code "11". The code "1" corresponds to the code "01".

[0197] In each of the above-mentioned specific examples, the drive device 3 changes the target frequency linearly. However, the present invention is not limited to the above-mentioned method. That is, for example, the drive device 3 may change the target frequency in a curve. Alternatively, the drive device 3 may change the target frequency in a step-like manner.

[0198] Fig.18 This is an example of an ideal FSK signal used in sonar. FSK is the abbreviation of Frequency Shift Keying. Fig.19 Representation and Fig.18 An example of the corresponding actual FSK signal. Fig.18 as well as Fig.19 In the figure, td represents the bit determination time, Tb represents the bit determination period, C1, C2, C3 and C4 represent the start bit, the second bit, the third bit and the fourth bit respectively.

[0199] As mentioned above, sonar is resonant, so the frequency does not switch suddenly. Fig.18 as well as Fig.19 As shown, the FSK signal in the sonar generates a frequency slope, i.e., a conversion rate, when the frequency is switched. The maximum value of the absolute value of the conversion rate depends on the characteristics of the transducer 21 and the transceiver circuit. In addition, an overshoot occurs at the beginning of the upper limit frequency fH and the lower limit frequency fL as the bit determination frequency. Therefore, it is necessary to set the conversion rate and the bit length after the overshoot in consideration of the sonar characteristics.

[0200] In FSK, it is important to improve the conversion rate and not change the frequency within the frequency range of fH and fL at the position determination point. That is, by increasing the conversion rate and quickly forming a constant frequency state between the upper limit frequency fH and the lower limit frequency fL as the position determination frequency, the signal length can be shortened. Therefore, the present invention can also be well applied to FSK. The "target frequency" in this case is Fig.18 The frequency signal shown represents the waveform of an ideal FSK signal. In addition, the bit determination frequency is not limited to the upper limit frequency fH and the lower limit frequency fL. That is, the bit determination frequency only needs to be within the above-mentioned transmission and reception frequency band.

[0201] The frequency conversion is not limited to FFT, but can also be DFT. As its installation method, multiple BPFs for each frequency can be prepared to detect the frequency. DFT is the abbreviation of Discrete Fourier Transform. BPF is the abbreviation of Band-pass Filter. In addition, the frequency can also be measured based on the interval between the zero-crossing time of the AC receiving signal and the threshold.

[0202] In the transmission process corresponding to one code string, when there are multiple frequency switching parts where frequency shift processing should be performed, frequency shift processing may not be performed on all of them. That is, if frequency shift processing is performed at least once in the transmission process corresponding to one code string, then of course this method is included in the present invention.

[0203] The above-mentioned functional structures and methods may also be implemented by a special-purpose computer, which is provided by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the above-mentioned functional structures and methods may also be implemented by a special-purpose computer provided by using one or more special-purpose hardware logic circuits to constitute a processor. Alternatively, the above-mentioned functional structures and methods may also be implemented by one or more special-purpose computers, which are composed of a combination of a processor and a memory programmed to execute one or more functions, and a processor composed of one or more hardware logic circuits.

[0204] Specifically, the drive device 3 is not limited to a structure having a well-known microcomputer having a CPU or the like. That is, the whole or a part of the drive device 3 may also be a structure having a digital circuit configured to realize the above-mentioned functions, such as an ASIC or FPGA such as a gate array. ASIC is the abbreviation of Application Specific Integrated Circuit. FPGA is the abbreviation of Field Programmable Gate Array.

[0205] In addition, the computer program may also be stored as an instruction executed by a computer in a non-transitional physical storage medium that can be read by a computer. That is, the device or method involved in the present invention may also be expressed as a computer program including steps for implementing the above-mentioned functions or methods, or a non-transitional physical storage medium storing the program.

[0206] Regarding the elements constituting the above-mentioned embodiments, except for the cases that are specifically indicated as necessary and the cases that are clearly considered to be necessary in principle, etc., they are of course not necessarily necessary. In addition, in the case of the number, value, amount, range, etc. of the constituent elements, except for the cases that are specifically indicated as necessary and the cases that are clearly limited to a specific number in principle, etc., the present invention is not limited to the specific number. Similarly, in the case of the shape, direction, positional relationship, etc. of the constituent elements, except for the cases that are specifically indicated as necessary and the cases that are limited to a specific shape, direction, positional relationship, etc. in principle, the present invention is not limited to the shape, direction, positional relationship, etc.

[0207] The modification examples are not limited to the above-mentioned examples. In addition, a plurality of modification examples may be combined with each other. Furthermore, all or part of the above-mentioned embodiment and all or part of the modification examples may be combined with each other.

Claims

1. A driving device for driving an ultrasonic transmitter having an ultrasonic transmission frequency, wherein: The driving device comprises: a drive signal generating unit configured to generate a drive signal for driving the ultrasonic transmitter based on a basic signal in which unit frequency signals are arranged in time series, the unit frequency signals being frequency signals corresponding to each of the codes in a code string formed of a plurality of codes; as well as a transmission control unit configured to control output of the drive signal from the drive signal generating unit to the ultrasonic transmitter, When the preceding unit frequency signal of the two unit frequency signals adjacent in time series in the basic signal is set as the first unit frequency signal and the succeeding unit frequency signal is set as the second unit frequency signal, and the target value of the transmission frequency is set as the target frequency, the drive signal generating unit shifts the frequency of at least a switching portion of the second unit frequency signal in the same direction as the frequency change direction from the first unit frequency signal to the second unit frequency signal when the first unit frequency signal and the second unit frequency signal are switched in a discontinuous switching state different from a continuous switching state, and in the continuous switching state, the target frequency corresponding to the first unit frequency signal to the target frequency corresponding to the second unit frequency signal continuously changes at approximately the same rate of change, and the switching portion includes the portion immediately after the start.

2. The driving device according to claim 1, wherein: The drive signal generating unit shifts the frequency of the second unit frequency signal in a direction opposite to a frequency change in the first unit frequency signal that causes a frequency change in a constant direction with the passage of time.

3. The driving device according to claim 1, wherein: The drive signal generating unit does not shift the frequency of a portion other than the switching portion in the second unit frequency signal, but shifts the frequency of the switching portion.

4. The driving device according to claim 3, wherein: The drive signal generating unit sets the duration of the switching portion so that the duration becomes longer as the difference between the frequency after the shift and the center frequency in the frequency band of the basic signal increases.

5. The driving device according to any one of claims 1 to 4, wherein: The drive signal generating unit sets the shifted frequency to a fixed frequency without temporal frequency variation.

6. The driving device according to any one of claims 1 to 4, wherein: The drive signal generating unit sets a frequency shift method according to an operating temperature of the ultrasonic transmitter.

7. A driving method, which is a driving method for driving an ultrasonic transmitter having an ultrasonic transmission frequency, wherein: generating a driving signal for driving the ultrasonic transmitter based on a basic signal in which unit frequency signals are arranged in time series, wherein the unit frequency signals are frequency signals corresponding to each of the codes in a code string formed of a plurality of codes, When the preceding unit frequency signal of the two unit frequency signals adjacent in time series in the basic signal is set as the first unit frequency signal and the succeeding unit frequency signal is set as the second unit frequency signal, and the target value of the transmission frequency is set as the target frequency, in the generation of the drive signal, when the first unit frequency signal and the second unit frequency signal are switched in a discontinuous switching state different from a continuous switching state, the frequency of at least the switching part of the second unit frequency signal is shifted in the same direction as the frequency change direction from the first unit frequency signal to the second unit frequency signal, and in the continuous switching state, the target frequency corresponding to the first unit frequency signal to the target frequency corresponding to the second unit frequency signal continuously changes at approximately the same rate of change, and the switching part includes the part immediately after the start.

8. The driving method according to claim 7, wherein: In generating the driving signal, the frequency of the second unit frequency signal is shifted in a direction opposite to a frequency change in the first unit frequency signal that changes in frequency in a constant direction with the passage of time.

9. The driving method according to claim 7, wherein: In generating the driving signal, the frequency of a portion other than the switching portion in the second unit frequency signal is not shifted, while the frequency of the switching portion is shifted.

10. The driving method according to claim 9, wherein: In the generation of the driving signal, the duration of the switching portion is set so that the duration becomes longer as the difference between the frequency after the shift and the center frequency in the frequency band of the basic signal becomes larger.

11. The driving method according to any one of claims 7 to 10, wherein: In the generation of the driving signal, the frequency after the shift is set to a fixed frequency without temporal frequency variation.

12. The driving method according to any one of claims 7 to 10, wherein: In generating the driving signal, a frequency shift method is set according to an operating temperature of the ultrasonic transmitter.

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