US20190317202A1 - Ultrasonic sensor - Google Patents

Ultrasonic sensor Download PDF

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Publication number
US20190317202A1
US20190317202A1 US16/306,977 US201716306977A US2019317202A1 US 20190317202 A1 US20190317202 A1 US 20190317202A1 US 201716306977 A US201716306977 A US 201716306977A US 2019317202 A1 US2019317202 A1 US 2019317202A1
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Prior art keywords
amplitude
waves
judgement
ultrasonic sensor
interval
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US16/306,977
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English (en)
Inventor
Mitsuyasu Matsuura
Taketo Harada
Tetsuya Aoyama
Yu Koyama
Takuya Nomura
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Denso Corp
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Denso Corp
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Assigned to DENSO CORPORATION reassignment DENSO CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NOMURA, TAKUYA, AOYAMA, TETSUYA, HARADA, TAKETO, KOYAMA, Yu, MATSUURA, MITSUYASU
Assigned to DENSO CORPORATION reassignment DENSO CORPORATION CORRECTIVE ASSIGNMENT TO CORRECT THE CORRESPONDENT NAME PREVIOUSLY RECORDED ON REEL 047869 FRAME 0440. ASSIGNOR(S) HEREBY CONFIRMS THE CORRECTION OF CORRESPONDENT NAME FROM KNOBBE, MARTENS, OLSEN & BEAR, LLP TO KNOBBE, MARTENS, OLSON & BEAR, LLP. Assignors: NOMURA, TAKUYA, AOYAMA, TETSUYA, HARADA, TAKETO, KOYAMA, Yu, MATSUURA, MITSUYASU
Publication of US20190317202A1 publication Critical patent/US20190317202A1/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/93—Sonar systems specially adapted for specific applications for anti-collision purposes
    • G01S15/931—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/523—Details of pulse systems
    • G01S7/526—Receivers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/4409—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison
    • G01N29/4427—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison with stored values, e.g. threshold values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/93—Sonar systems specially adapted for specific applications for anti-collision purposes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004—Means for monitoring or calibrating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/523—Details of pulse systems
    • G01S7/526—Receivers
    • G01S7/527—Extracting wanted echo signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/01—Indexing codes associated with the measuring variable
    • G01N2291/014—Resonance or resonant frequency
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004—Means for monitoring or calibrating
    • G01S2007/52007—Means for monitoring or calibrating involving adjustment of transmitted power
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004—Means for monitoring or calibrating
    • G01S2007/52009—Means for monitoring or calibrating of sensor obstruction, e.g. dirt- or ice-coating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/93—Sonar systems specially adapted for specific applications for anti-collision purposes
    • G01S15/931—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G01S2015/937—Sonar systems specially adapted for specific applications for anti-collision purposes of land vehicles sensor installation details

Definitions

  • the present disclosure relates to an ultrasonic sensor that transmits ultrasonic waves as probe waves, and acquires reflected waves that are reflected from objects in the surroundings, with the reflected waves including detection waves.
  • ultrasonic sensors have been implemented which transmit ultrasonic waves as probe waves, receive reflected waves that are reflected from an object, and detect the distance of the object.
  • ultrasonic sensor when foreign matter such as water or the like adheres to a transmitter/receiver which performs transmission of the probe waves and reception of the detection waves, there is a danger that errors will arise in the calculated distances of objects, or an object may be judged to exist where it does not, or it may be judged that there is no object when an object actually does exist.
  • An ultrasonic sensor which judges when there is foreign matter adhering to the transmitter/receiver is disclosed in PTL 1.
  • judgement as to whether or not there is foreign material adhering to the transmitter/receiver is made by using a time point at which an amplitude falls below a set threshold value.
  • the present disclosure is intended to overcome the above problem, having a main objective of providing an ultrasonic sensor which can accurately judge when there is foreign matter adhering to the surface of a transmitter/receiver.
  • the present disclosure relates to an ultrasonic sensor that transmits probe waves which are ultrasonic waves and acquires detection waves including reflected waves that are reflected from surrounding objects, and includes a transmitter/receiver that transmits the probe waves and acquires the detection waves, a detection wave processing section that executes processing for passing a predetermined band of frequencies which include the frequency of the probe waves, an amplitude measurement section which measures the amplitude of the detection waves, and a judgement section that judges the adherence of foreign matter on the transmitter/receiver, based on a relationship between a time axis and values of the amplitude of the detection waves during a reverberation interval which follows the termination of transmitting the probe waves.
  • the frequency of a reverberation which is produced following termination of transmitting the probe waves, will be close to the frequency of the probe waves. In that case, even when processing for passing a prescribed band of frequencies is executed by the detection wave processing section on the detection waves, in acquiring the amplitude of the reverberation, the detection waves will not be readily attenuated. On the other hand, if there is foreign matter adhering to the transmitter/receiver, then the frequency of the reverberation that is produced following termination of transmitting the probe waves will differ from the frequency of the probe waves.
  • FIG. 1 is a configuration diagram of an ultrasonic sensor
  • FIG. 2 shows waveforms for a case in which foreign matter does not adhere to a transmitter/receiver, with (a) being the waveform of frequency and (b) being the waveform of amplitude;
  • FIG. 3 shows waveforms for a case in which foreign matter adheres to the transmitter/receiver, with (a) being the waveform of frequency and (b) being the waveform of amplitude;
  • FIG. 4 is a flow chart of processing executed by the ultrasonic sensor
  • FIG. 5 is a diagram for describing processing relating to a second embodiment, for the case in which foreign matter does not adhere to the transmitter/receiver;
  • FIG. 6 is a diagram for describing processing relating to the second embodiment, for the case in which foreign matter adheres to the transmitter/receiver;
  • FIG. 7 is a diagram for describing processing relating to a third embodiment, for the case in which foreign matter does not adhere to the transmitter/receiver;
  • FIG. 8 is a diagram for describing processing relating to the third embodiment, for the case in which foreign matter adheres to the transmitter/receiver;
  • FIG. 9 is a diagram for describing processing relating to a fourth embodiment, for the case in which foreign matter does not adhere to the transmitter/receiver;
  • FIG. 10 is a diagram for describing processing relating to the fourth embodiment, for the case in which foreign matter adheres to the transmitter/receiver;
  • FIG. 11 is a diagram for describing processing relating to a fifth embodiment, for the case in which foreign matter does not adhere to the transmitter/receiver.
  • FIG. 12 is a diagram for describing processing relating to the fifth embodiment, for the case in which foreign matter adheres to the transmitter/receiver.
  • the present embodiment of an ultrasonic sensor is installed on a mobile body such as a vehicle or the like.
  • An object detection system which includes the ultrasonic sensor that transmits probe waves in each of prescribed control periods, receives reflected waves that are reflected from an object in the surroundings of the mobile body, and measures the time duration between transmission and reception, for thereby obtaining the distance between the mobile body and the object.
  • FIG. 1 is a configuration diagram of an ultrasonic sensor 10 of the present embodiment.
  • the ultrasonic sensor 10 is connected for communication with an ECU 20 which controls respective functions of the vehicle, with the ultrasonic sensor 10 being controlled based on commands from the ECU 20 , and transmitting detection results to the ECU 20 .
  • a control section 11 communicates with the ECU 20 , and executes control for transmitting probe waves which are ultrasonic waves, based on commands from the ECU 20 , while also transmitting to the ECU 20 the detection results of detection waves that include reflected waves. At that time, the ECU 20 notifies the control section 11 of the frequency of the probe waves, and the control section 11 drives a transmitter/receiver 12 such as to transmit ultrasonic waves having that frequency.
  • the transmitter/receiver 12 is of known type, being equipped with a piezoelectric element and a drive circuit which supplies drive power to the piezoelectric element, with the drive power being supplied by the transmitter/receiver 12 to the piezoelectric element by means of control signals from the control section 11 , for transmitting probe waves that are ultrasonic waves.
  • the transmitter/receiver 12 in addition receives, as detection waves, reflected waves that are reflected from objects in the surroundings, and also receives other ultrasonic waves as detection waves.
  • the detection waves received by the transmitter/receiver 12 are inputted to the detection wave processing section 13 as voltages.
  • a detection wave processing section 13 performs filter processing of the detection waves. Specifically, filter processing of the detection waves is executed using a bandpass filter having a passband that can pass a band of frequencies which include the frequency of the probe waves, attenuating the amplitude of detection waves that are at frequencies other than those of the band of frequencies passed by the bandpass filter. The reason for this is that, when probe waves are reflected from an object and the reflected waves are acquired as detection waves, the frequency of the reflected waves will be close to the frequency of the probe waves, while detection waves having a different frequency have a high possibility of being noise.
  • the detection wave processing section 13 inputs the voltage value to an amplitude measurement section 14 , after filter processing.
  • the amplitude measurement section 14 measures the amplitude of the acquired detection waves. Specifically, to acquire the amplitude, a value of voltage that is obtained based on the detection waves is converted to the amplitude. In detecting the amplitude, an upper limit value is determined for the voltage that can be acquired, and if the acquired voltage has a value exceeding the upper limit, the amplitude is made the upper limit value Amax.
  • the amplitude that is measured by the amplitude measurement section 14 will be explained referring to FIGS. 2 and 3 , based also on the frequency of the detection waves.
  • the frequencies shown in FIGS. 2( a ) and 3( a ) are obtained, for example, by taking the points at which the voltage changes from positive to negative as zero crossing points, and calculating the inverse of the period between the zero crossing points as a frequency.
  • the frequency count values in the diagrams show the measured numbers of reference waves between the zero crossing points of the detection waves. That is to say, if the value of the frequency count becomes large, this signifies that the time between the zero crossing points becomes longer and that the frequency becomes lower.
  • FIGS. 2( b ) and 3( b ) show connected amplitudes that are maximum positive values for the respective frequencies, that is to say, these diagrams show the result of envelope detection.
  • the detection wave processing section 13 performs processing for attenuating waves having frequencies other than those of the prescribed frequency band of the bandpass filter.
  • the amplitude will be attenuated by the bandpass filter, and the amplitude will be reduced by comparison with the case in which there is no adherence of foreign matter, as shown in FIG. 3( b ) .
  • the amplitude is not possible to determine whether the amplitude has become small due to adhering foreign matter, or has become small due to the fact that the reverberation interval has ended. However, if the amplitude remains above a prescribed value during a prescribed range of time, then it is judged that there is adhering foreign matter.
  • the foreign matter may include snow, water, mud, etc., while the expression “adhering” can signify a condition in which water is flowing on the surface of the transmitter/receiver 12 .
  • a first threshold value Ath 1 and a second threshold value Ath 2 which is smaller than the first threshold value Ath 1 , are set.
  • the specific values of the first threshold value Ath 1 and the second threshold value Ath 2 are determined through experiment, and are set by a threshold value setting section 15 and inputted to a timer section 16 .
  • the timer section 16 measures, as a first interval ⁇ T 1 , an interval for which the amplitude is higher than the first threshold value Ath 1 , and measures, as a second interval ⁇ T 2 , an interval for which the amplitude is higher than the second threshold value Ath 2 .
  • the amplitude may momentarily fall below the first threshold value Ath 1 , due to errors in detecting the amplitude, etc., even when there is no foreign matter adhering to the transmitter/receiver 12 .
  • the amplitude may in some cases momentarily fall below the second threshold value Ath 2 , when there is foreign matter adhering to the transmitter/receiver 12 , even during the reverberation interval.
  • a judgement section 17 calculates the time that elapses from the point at which the amplitude falls below the first threshold value Ath 1 until it falls below the second threshold value Ath 2 . Specifically, the judgement section 17 acquires the first interval ⁇ T 1 and the second interval ⁇ T 2 from the timer section 16 , and subtracts the first interval ⁇ T 1 from the second interval ⁇ T 2 . A decision is then made as to whether or not the calculated interval is a value that is greater than a prescribed value. If the calculated value is greater than the prescribed value, then it can be said that the amplitude in the reverberation interval has remained above the prescribed value during a time interval that is within the prescribed range. Hence, the judgement result is transmitted to the control section 11 .
  • control section 11 acquires a judgement result from the judgement section 17 indicating that there is adherence of foreign matter
  • processing is then executed for notifying this to a driver of the vehicle.
  • the judgement result is transmitted to the ECU 20 , and the driver of the vehicle is notified by use of a display apparatus, etc., installed in the vehicle.
  • the processing which is executed when it is judged that there is foreign matter adhering to the transmitter/receiver 12 is not limited to this example, and it would be equally possible to execute various other forms of processing.
  • the processing sequence executed by the ultrasonic sensor 10 will be described referring to the flow chart of FIG. 4 .
  • the processing of the flow chart of FIG. 4 is executed repetitively at each of prescribed sampling periods.
  • step S 101 the detection waves are acquired, and then in step S 102 , the amplitude is measured.
  • step S 103 a decision is made as to whether or not the time measurement of the first interval ⁇ T 1 is in progress. It is possible to judge in this way whether or not the value of the first interval ⁇ T 1 is zero.
  • Step S 103 can be performed by judging whether the value of the first interval ⁇ T 1 is not zero, or by judging a flag which indicates that the time measurement of the first interval ⁇ T 1 is in progress.
  • step S 104 a decision is made as to whether or not the time measurement of the second interval ⁇ T 2 is in progress.
  • step S 104 can be performed by judging whether the value of the second interval ⁇ T 2 is not zero, or by judging a flag which indicates that the time measurement of the second interval ⁇ T 2 is in progress.
  • step S 104 If there is a negative decision in step S 104 , that is to say, the time measurement of the second interval ⁇ T 2 is not in progress, processing then proceeds to step S 105 , in which a decision is made as to whether the amplitude measured in step S 102 is higher than the first threshold value Ath 1 . As described above, processing proceeds to step S 105 if a negative decision is reached in both step S 103 and step S 104 , so that reaching a positive decision in step S 105 is limited to the case in which the amplitude exceeds the first threshold value Ath 1 for the first time after transmitting of the probe waves has started.
  • a negative decision in step S 105 is reached in an interval which extends from the start of transmitting the probe waves until the amplitude reaches the first threshold value Ath 1 , or in an interval which follows the time at which the amplitude falls below the second threshold value Ath 2 , that is to say, an interval which follows the end of the of the reverberation interval.
  • step S 105 If there is a positive decision in step S 105 , that is to say, if it is judged that the amplitude exceeds the first threshold value Ath 1 , then the time measurement of the first interval ⁇ T 1 and the second interval ⁇ T 2 is started, and the processing sequence is then ended.
  • Step S 106 in the processing sequence is executed at time point t 1 shown in FIGS. 2 and 3 .
  • the processing sequence is ended directly.
  • step S 103 If there is a positive decision in step S 103 , that is to say, in a case in which the time measurement of the first interval ⁇ T 1 is in progress, then processing proceeds to step S 107 , in which a decision is made as to whether or not the amplitude exceeds the first threshold value Ath 1 . If there is a positive decision in step S 107 , that is to say, the amplitude that has been measured in step S 102 is greater than first threshold value Ath 1 , then processing proceeds to step S 108 , in which the first interval ⁇ T 1 and second interval ⁇ T 2 are incremented. That is to say, the time measurement of the first interval ⁇ T 1 and second interval ⁇ T 2 is continued. Step S 108 of the processing sequence is executed in an interval that extends from after time point t 1 until time point t 2 , shown in FIGS. 2 and 3 . The processing sequence is then ended.
  • step S 107 If there is a negative decision in step S 107 , that is to say, if the amplitude that was measured in step S 102 is less than the first threshold value Ath 1 , then processing proceeds to step S 109 .
  • step S 109 the value of the first interval ⁇ T 1 is stored in temporary memory, and in the succeeding step S 110 , incrementing of the second interval ⁇ T 2 is performed. The time measurement of the second interval ⁇ T 2 is continued, while ending the time measurement of the first interval ⁇ T 1 .
  • Step S 110 of the processing sequence is executed in the next sampling period after time point t 2 , shown in FIGS. 2 and 3 . The processing sequence is then ended.
  • step S 104 If there is a positive decision in step S 104 , that is to say, if the time measurement of the first interval ⁇ T 1 has ended and the time measurement of the second threshold value Ath 2 is in progress, then processing proceeds to step S 111 , in which a decision is made as to whether or not the amplitude is greater than the second threshold value Ath 2 . If there is a positive decision in step S 111 , that is to say, if the amplitude measured in step S 102 is greater than the second threshold value Ath 2 , then processing proceeds to step S 112 , in which incrementing of the second interval ⁇ T 2 is performed. That is to say, the time measurement of the second interval ⁇ T 2 is continued. Step S 112 of the processing sequence is executed in an interval that extends from after the next sampling period following time point t 2 , shown in FIGS. 2 and 3 , up to time point t 3 . The processing sequence is then ended.
  • step S 113 the value of first interval ⁇ T 1 that has been temporarily stored in memory is subtracted from the value of the second interval ⁇ T 2 whose time measurement has been completed, and a decision is made as to whether the resultant value is greater than a prescribed value. That is to say, a decision is made as to whether or not the length of the interval for which the amplitude is less than the first threshold value Ath 1 and above the second threshold value Ath 2 is greater than a prescribed value.
  • Step S 113 of the processing sequence is executed in the next sampling period following time point t 3 , shown in FIGS. 2 and 3 .
  • step S 113 If there is a positive decision in step S 113 , that is to say, if the length of the interval for which the amplitude is less than the first threshold value Ath 1 and above the second threshold value Ath 2 is greater than the prescribed value, then processing proceeds to step S 114 , and a judgement is made as to whether or not there is foreign matter adhering to the surface of the transmitter/receiver 12 . The processing sequence is then ended. However, if there is a negative decision in step S 113 , then the processing sequence is ended directly.
  • the ultrasonic sensor 10 of the present embodiment provides the following effects.
  • the frequency of a reverberation that is produced following the transmitting of the probe waves becomes different from the frequency of the probe waves. If filter processing is performed by the detection wave processing section 13 at that time, then since detection waves that are at frequencies outside the passband of the filter will become attenuated, the amplitude will be reduced. For that reason it can be considered that if the amplitude is greater than the first threshold value Ath 1 , then the frequency during the reverberation interval is close to the frequency when transmitting the probe waves, while if the amplitude is smaller than the second threshold value Ath 2 then it can be considered that the reverberation interval has ended.
  • the interval is the reverberation interval and that the frequency in that interval deviates from that of the probe waves.
  • the time interval which elapses from the point at which the amplitude falls below the first threshold value Ath 1 until it falls below the second threshold value Ath 2 is acquired, and by judging whether or not that interval is longer than a prescribed interval, a decision can be made as to whether or not the frequency during the reverberation interval deviates from the frequency of the probe waves.
  • an accurate judgement can be made as to whether or not there is foreign matter adhering to the transmitter/receiver 12 .
  • the present embodiment differs from the first embodiment with respect to a part of the processing executed by the judgement section 17 .
  • the judgement section 17 acquires a number of times that local maximums of the amplitude are attained in a prescribed interval following the time at which the amplitude falls below the first threshold value Ath 1 .
  • This number of occurrences of local maximums is taken to be the number of times that the amplitude changes from an increasing to a decreasing condition. It should be noted that if the amplitude, after having once increased then remains constant, and thereafter decreases, then this can be taken as being a single occurrence of a local maximum value.
  • the judgement section 17 compares the counted number of local maximums of the amplitude with a predetermined value. If the number of local maximums is greater than the predetermined value, then it is judged that there is adherence of foreign matter.
  • FIGS. 5 and 6 The processing applied to the amplitude with the present embodiment will be described referring to FIGS. 5 and 6 .
  • FIGS. 5 and 6 the positions where there are local maximums are surrounded by dashed lines.
  • the time at which the amplitude falls below the first threshold value Ath 1 is time point t 11 at which the reverberation interval ends.
  • the amplitude thereafter continues to decrease, and a condition is reached at which it is hardly possible to detect the amplitude. For that reason, in a prescribed interval beginning from time point t 11 and elapsing at time point t 12 , the acquired number of local maximums of the amplitude becomes small.
  • time point t 11 at which the amplitude falls below the first threshold value Ath 1 is the time at which transmitting the probe waves is ended. Since the interval of attenuation following time point at which the amplitude falls below the first threshold value Ath 1 is a continuation of the reverberation interval, the amplitude repetitively increases and decreases in the vicinity of a certain value. For that reason, the acquired number of local maximums attained by the amplitude becomes large during a prescribed interval which extends from time point t 11 and elapses when a certain time point t 12 is reached.
  • the ultrasonic sensor 10 of the present embodiment provides the following effects, in addition to effects similar to those provided by the ultrasonic sensor 10 of the first embodiment.
  • the present embodiment differs from the first embodiment with respect to a part of the processing executed by the judgement section 17 .
  • the judgement section 17 provides a prescribed period in the reverberation interval, and obtains the number of times that local maximum value of amplitude are attained during that prescribed period.
  • the prescribed period is set such as to include at least part of the reverberation interval, and with the present embodiment, the prescribed period commences when the transmitting of the probe waves is ended.
  • the processing for obtaining the number of times that local maximum value of amplitude are attained are the same as for the second embodiment, so that specific description is omitted.
  • time point t 21 is the start of an interval in which the number of local maximums is counted and which ends at time point t 22 .
  • time point t 22 is the start of an interval in which the number of local maximums is counted and which ends at time point t 22 .
  • the locations of the local maximums are enclosed by dashed lines.
  • the amplitude will generally be maintained close to an upper limit value Amax during the reverberation interval, and will become attenuated when the reverberation interval terminates. For that reason, the number of local maximums that are obtained in the interval from t 21 to t 22 will become small.
  • the ultrasonic sensor 10 of the present embodiment provides the following effects, in addition to effects similar to those provided by the ultrasonic sensor 10 of the first embodiment.
  • an upper limit value Amax is provided for the value that can be obtained, and if the actual amplitude is greater than the upper limit value Amax, processing is executed for setting the amplitude of the detection waves as the upper limit value Amax. If there is no foreign matter adhering to the transmitter/receiver 12 , then since the attenuation of the amplitude of the detection waves during the reverberation interval is small, the amplitude becomes the upper limit value Amax. Hence, the number of local maximums of the amplitude becomes small.
  • the attenuation of the amplitude of the detection waves during the reverberation interval will be relatively great, so that the amplitude becomes smaller than Amax.
  • the number of local maximums of the amplitude will become greater than for the case in which no foreign matter adheres, so that a judgement can be made as to whether or not there is adherence of foreign matter, from the number of these local maximums.
  • the present embodiment differs from the first embodiment with respect to a part of the processing executed by the judgement section 17 .
  • the processing executed by the judgement section 17 of the present embodiment will be described referring to FIGS. 9 and 10 .
  • the judgement section 17 obtains an area S that is enclosed by the envelope which extends from the point at which the amplitude falls below the first threshold value Ath 1 up to the point at which it falls below the second threshold value Ath 2 . Specifically, the amplitudes at each of respective sampling periods are accumulated, and the cumulative value is set as the area S.
  • the judgement section 17 judges whether or not the calculated area S is greater than a prescribed value. If the area S is greater than the prescribed value, then it is judged that there is matter such as water adhering to the transmitter/receiver 12 , and that judgement result is notified to the control section 11 .
  • the ultrasonic sensor 10 of the present embodiment provides the following effects, in addition to effects similar to those provided by the ultrasonic sensor 10 of the first embodiment.
  • the frequency during the reverberation interval becomes changed, and the duration of the interval from the point at which the amplitude falls below the first threshold value Ath 1 up to the point at which it falls below the second threshold value Ath 2 becomes increased.
  • the area S enclosed by the envelope of amplitudes will become larger.
  • the present embodiment differs from the above embodiments with respect to a part of the processing executed by the judgement section 17 .
  • the processing executed by the judgement section 17 of the present embodiment will be described referring to FIGS. 11 and 12 .
  • the judgement section 17 provides a plurality of prescribed intervals which follow the point at which the amplitude falls below the first threshold value Ath 1 .
  • the judgement section 17 next calculates the amounts of change in the areas S 1 ⁇ S 4 .
  • the average of the amounts of change between the areas S 1 ⁇ S 4 may be used, or the difference could be obtained between the area S 1 having the largest value and the area S 4 having the smallest value, or the differences between the areas that are mutually preceding and succeeding could be obtained, and the largest one of these differences used.
  • a decision can be made as to whether there is adherence of foreign matter, by comparing the value of the amount of change in area with a prescribed value, and determining that there is adherence of foreign matter if the value of the amount of change in area is greater than the prescribed value.
  • the prescribed intervals can extend from time point at which the probe waves are terminated, as with the third embodiment. In that case, if there is no adherence of foreign matter, the amplitude will greatly decrease when the reverberation interval ends, so that if the change in area is small, it can be judged that there is adherence of foreign matter.
  • the ultrasonic sensor 10 of the present embodiment provides the following effects, in addition to effects similar to those provided by the ultrasonic sensor 10 of the first embodiment.
  • the amplitude during the reverberation interval becomes attenuated.
  • a decision can be made as to whether there is foreign matter adhering to the transmitter/receiver 12 .
  • the present embodiment differs from the above embodiments with respect to a part of the processing executed by the judgement section 17 .
  • the judgement section 17 compares a part of the detection waves with a reference waveform, which has been predetermined.
  • the reference waveform is a waveform that has been measured beforehand in a case in which there is no foreign matter adhering to the transmitter/receiver 12 . If the correlation between the waveform of the detection waves and the reference waveform is obtained and the correlation value is greater than a prescribed value, then since it can be said that the shape of the waveform of the detection waves is close to that of the reference waveform, it is judged that there is no foreign matter adhering to the transmitter/receiver 12 .
  • the correlation value is smaller than the prescribed value, then since it can be said that the shape of the waveform of the detection waves deviates from that of the reference waveform, it is judged that there is foreign matter adhering to the transmitter/receiver 12 .
  • the reference waveform a waveform which is measured beforehand in a condition in which there is no foreign matter adhering to the transmitter/receiver 12
  • a waveform for the case in which there is foreign matter adhering to the transmitter/receiver 12 it would be equally possible to use, as the reference waveform, a waveform for the case in which there is foreign matter adhering to the transmitter/receiver 12 .
  • the ultrasonic sensor 10 of the present embodiment provides effects that are similar to those provided by the ultrasonic sensor 10 of the first embodiment.
  • the detection wave processing section 13 is provided with two bandpass filters having respectively different widths of passband.
  • the center frequency of each of these bandpass filters is the frequency of the detection waves.
  • the bandpass filter having the narrower one of the passbands is referred to as the first bandpass filter
  • the bandpass filter having the wider passband is referred to as the second bandpass filter.
  • the detection wave processing section 13 executes, in parallel, processing for passing the acquired detection waves through the first bandpass filter and through the second bandpass filter.
  • the processing of the flow chart shown in FIG. 4 is applied to the detection waves that have passed through the first bandpass filter and have passed through the second bandpass filter, respectively, with the interval during which the amplitude is smaller than the first threshold value Ath 1 and is greater than the second threshold value Ath 2 being respectively obtained for these, that is to say, the value resulting from subtracting the first interval ⁇ T 1 from the second interval ⁇ T 2 is obtained.
  • the respective calculated values are then compared, and a decision is made as to whether or not there is foreign matter adhering to the transmitter/receiver 12 .
  • the amplitudes of the respective detection waves which pass through the bandpass filters will not become readily attenuated, irrespective of which of the filters is passed through.
  • the value obtained by subtracting the first interval ⁇ T 1 from the second interval ⁇ T 2 will be substantially the same for the detection waves that are passed by the first bandpass filter and the detection waves that are passed by the second bandpass filter.
  • the detection waves that pass through the first bandpass filter will have a relatively high degree of attenuation in amplitude, while the degree of amplitude attenuation of the detection waves that pass through the second bandpass filter will be relatively small.
  • the value obtained by subtracting the first interval ⁇ T 1 from the second interval ⁇ T 2 will be greater for the detection waves that are passed by the second bandpass filter.
  • the ultrasonic sensor 10 of the present embodiment provides effects that are similar to those provided by the ultrasonic sensor 10 of the first embodiment, and also provides the following effects.
  • the judgement conditions are set as a first condition, and a second condition which is whether or not a frequency deviates from the frequency of the probe waves, with the first condition and the second condition being used in judging whether or not foreign matter is adhering to the transmitter/receiver 12 .
  • the second condition it would be equally possible for the second condition to include a requirement relating to time, for each of the above embodiments.
  • the time measurement of the first interval ⁇ T 1 and the second interval ⁇ T 2 is started on condition that the amplitude falls below the first threshold value Ath 1 .
  • commence the time measurement of the first interval ⁇ T 1 and the second interval ⁇ T 2 at time point of commencement of transmitting the probe waves.
  • time measurement of the first interval ⁇ T 1 and the second interval ⁇ T 2 is performed, and the difference between the measured values is obtained.
  • the judgement as to whether or not there is adhering foreign matter can be performed by comparing the measured value of time with a prescribed value.
  • bandpass filters are used; however, it would be equally possible to use band-stop filters instead. Furthermore, since the frequency becomes lower if there is foreign matter adhering to the transmitter/receiver 12 , it would be equally possible to use detection waves that have been passed through a high-pass filter, in the processing for judging whether or not there is adhering foreign matter. This is similarly true for the fifth embodiment, where it would be equally possible to use high-pass filters or band-stop filters having respectively different passbands.
  • the number of local maximums of the amplitude is obtained during a predetermined interval which commences when the amplitude becomes less than the first threshold value Ath 1 .
  • that interval, in which the amplitude is less than the first threshold value Ath 1 and is greater than the second threshold value Ath 2 is longer when there is foreign matter adhering to the transmitter/receiver 12 than when there is no adhering foreign matter.
  • the amplitude will generally decrease monotonically from the point at which it becomes less than the first threshold value Ath 1 until it becomes less than the second threshold value Ath 2 , so that the possibility of producing maximum values is low.
  • judgement can accurately be made as to whether or not foreign matter is adhering to the transmitter/receiver 12 , by obtaining the number of local maximums of the amplitude during the interval in which the amplitude is less than the first threshold value Ath 1 and is greater than the second threshold value Ath 2 .
  • the second embodiment instead of obtaining the number of local maximums, it would be equally possible to perform the judgement as to adhering foreign matter on the transmitter/receiver 12 by using the highest-magnitude one of the local maximums, or by using the average magnitude of the local maximums, etc. If there is no foreign matter adhering to the transmitter/receiver 12 , then since in that case the point at which the amplitude becomes less than the first threshold value Ath 1 is the termination of the reverberation interval, the amplitude will continue to become attenuated thereafter, until a condition is reached where it can hardly be detected. For that reason, the maximum amplitude will be small.
  • the point at which the amplitude becomes less than the first threshold value Ath 1 is the termination of transmitting the probe waves, and the amplitude will repetitively increase and decrease during the reverberation interval thereafter, so that there will be relatively large maximum values of the amplitude.
  • a decision can be made as to whether foreign matter is adhering to the transmitter/receiver 12 , from the maximum value of the amplitude during a predetermined interval that follows the point at which the amplitude becomes less than the first threshold value Ath 1 .
  • the third embodiment instead of using the number of local maximums, it would be equally possible to judge whether foreign matter is adhering to the transmitter/receiver 12 by using the highest one of the local maximums of the amplitude, or by using the average of the local maximums, etc. Since the attenuation of the amplitude during the reverberation interval will be relatively small if no foreign matter is adhering to the transmitter/receiver 12 , there will be a relatively large maximum value of the amplitude during that interval, while if there is foreign matter adhering to the transmitter/receiver 12 then there will be a relatively high degree of attenuation of the amplitude during the reverberation interval, so that the maximum value of the amplitude will be relatively small. Hence, a decision can be made as to whether foreign matter is adhering to the transmitter/receiver 12 , from the maximum value of the amplitude during a predetermined interval that follows the termination of transmitting the probe waves.
  • processing is performed using bandpass filters, in parallel, having respectively different passbands.
  • bandpass filters which have respectively different transmission intervals, for example a preceding and a succeeding transmission interval.
  • two bandpass filters having respectively different passbands are used; however, it would be equally possible to use three or more bandpass filters.
  • the detection waves passed by a bandpass filter could be compared with the detection waves passed by a high-pass filter, or compared with the detection waves passed by a band-stop filter.
  • the ultrasonic sensor 10 of the embodiments is installed on a mobile body such as a vehicle; however, the ultrasonic sensor 10 is not limited to such installation, and could be installed on a stationary object such as a road structure or the like.

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DE112017002853T5 (de) 2019-02-14

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