Patent Publication Number: US-2023133877-A1

Title: Ultrasonic sensor control device, ultrasonic sensor, and ultrasonic sensor control method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority benefit of Japanese Patent Application No. JP 2021-177478 filed in the Japan Patent Office on Oct. 29, 2021. Each of the above-referenced applications is hereby incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present disclosure relates to an ultrasonic sensor control device, an ultrasonic sensor, and an ultrasonic sensor control method. 
     In the past, in an ultrasonic wave system that measures a distance to a target object by measuring a time from the generation of an ultrasonic wave to the returning of the wave after being reflected by the target object, a method has been proposed for avoiding interference from an ultrasonic wave transmitted from another system. Japanese Patent Laid-Open No. 2020-60410 (hereinafter, referred to as Patent Document 1) discloses an acoustic wave processing device having a function for avoiding interference from an ultrasonic wave transmitted from another system. The acoustic wave processing device disclosed in Patent Document 1 transmits ultrasonic waves with characteristics (patterns) based on the phase difference, burst wave interval, burst duration, and amplitude level ratio of the two ultrasonic waves transmitted successively. Thus, interference from an ultrasonic wave transmitted from another system is prevented. 
     SUMMARY 
     However, there is a limit to the characteristics (patterns) provided to the ultrasonic waves to be transmitted, and a case is conceivable in which ultrasonic waves are transmitted with identical characteristics (patterns) when identical systems are used. Sufficient studies have hitherto not been made regarding a mechanism for cancelling crosstalk in a case where interference (crosstalk) from an ultrasonic wave transmitted from another system occurs, and therefore, there is a possibility that erroneous distance measurement may be performed when the interference from the ultrasonic wave of the other system occurs. 
     In view of circumstances as described above, it is desirable to provide an ultrasonic sensor control device that can easily cancel crosstalk in an ultrasonic sensor. 
     An ultrasonic sensor control device according to an example of the present embodiment includes a transmission control section configured to control a transmitting device configured to transmit a transmission ultrasonic wave, a receiving section configured to receive a reception ultrasonic wave, a frequency determining section configured to determine a result of comparing a reception frequency that is a frequency of the reception ultrasonic wave received by the receiving section and that is a frequency capable of being received by the receiving section, with a transmission frequency of the transmission ultrasonic wave that is transmitted under the control of the transmission control section, and a frequency switching section configured to change the transmission frequency and the reception frequency on the basis of a result of the determination by the frequency determining section. 
     An ultrasonic sensor according to another example of the present embodiment includes an ultrasonic sensor device configured to transmit and receive an ultrasonic wave, a transmission control section configured to control transmission of a transmission ultrasonic wave via the ultrasonic sensor device, a receiving section configured to receive a reception ultrasonic wave via the ultrasonic sensor device, a frequency determining section configured to determine a result of comparing a reception frequency that is a frequency of the reception ultrasonic wave received by the receiving section and that is a frequency capable of being received by the receiving section, with a transmission frequency of the transmission ultrasonic wave that is transmitted under the control of the transmission control section, and a frequency switching section configured to change the transmission frequency and the reception frequency on the basis of a result of the determination by the frequency determining section. 
     An ultrasonic sensor control method according to yet another example of the present embodiment includes controlling a transmitting device configured to transmit a transmission ultrasonic wave, receiving a reception ultrasonic wave from a receiving device, determining a result of comparing a reception frequency that is a frequency of the received reception ultrasonic wave and that is a frequency capable of being received via the receiving device, with a transmission frequency of the transmission ultrasonic wave, and changing the transmission frequency of the transmission ultrasonic wave and the reception frequency on the basis of a result of the determination based on the comparison between the reception frequency and the transmission frequency. 
     According to the present disclosure, it is possible to provide an ultrasonic sensor control device that can easily cancel crosstalk of an ultrasonic sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram illustrating a configuration of an ultrasonic sensor control device according to a first embodiment; 
         FIG.  2    is a diagram illustrating an example of frequency information, transmission information, and reception information according to the first embodiment; 
         FIG.  3 A  is a timing diagram of assistance in explaining a state of crosstalk in an ultrasonic sensor; 
         FIG.  3 B  is a timing diagram of assistance in explaining processing in the ultrasonic sensor control device according to the first embodiment; 
         FIG.  4    is a flowchart illustrating an example of processing performed by the ultrasonic sensor control device according to the first embodiment; 
         FIG.  5    is a block diagram illustrating a configuration of an ultrasonic sensor control device according to a second embodiment; 
         FIG.  6    is a diagram illustrating an example of frequency information, transmission information, and reception information according to the second embodiment; 
         FIG.  7 A  is a timing diagram of assistance in explaining a state of crosstalk in an ultrasonic sensor; 
         FIG.  7 B  is a timing diagram of assistance in explaining processing in the ultrasonic sensor control device according to the second embodiment; 
         FIG.  7 C  is a timing diagram of assistance in explaining processing in the ultrasonic sensor control device according to the second embodiment; 
         FIG.  8    is a block diagram illustrating a configuration of an ultrasonic sensor control device according to a third embodiment; 
         FIG.  9    is a diagram illustrating an example of frequency information, transmission information, and reception information according to the third embodiment; 
         FIG.  10 A  is a timing diagram of assistance in explaining a state of crosstalk in an ultrasonic sensor; 
         FIG.  10 B  is a timing diagram of assistance in explaining processing in the ultrasonic sensor control device according to the third embodiment; and 
         FIG.  11    is a flowchart illustrating an example of processing performed by the ultrasonic sensor control device according to the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With regard to the time length ratio, the number of pulses, the polarities, and/or other features in timing diagrams illustrated in drawings, it is needless to say that some of them may be different from actual ones. 
     In addition, embodiments illustrated in the following are examples of devices and methods for embodying technical concepts, and the material, shape, structure, arrangement, or other configuration of each constituent part is not limited to the one described below. Various changes can be made to the present embodiment in claims. 
     One specific example of the present embodiment is as follows. 
     &lt;1&gt; An ultrasonic sensor control device including a transmission control section configured to control a transmitting device configured to transmit a transmission ultrasonic wave, a receiving section configured to receive a reception ultrasonic wave, a frequency determining section configured to determine a result of comparing a reception frequency that is a frequency of the reception ultrasonic wave received by the receiving section and that is a frequency capable of being received by the receiving section, with a transmission frequency of the transmission ultrasonic wave that is transmitted under the control of the transmission control section, and a frequency switching section configured to change the transmission frequency and the reception frequency on the basis of a result of the determination by the frequency determining section. 
     &lt;2&gt; The ultrasonic sensor control device according to &lt;1&gt;, in which the frequency determining section determines whether or not the reception frequency of the reception ultrasonic wave received by the receiving section and the transmission frequency are different from each other, in a predetermined period of time before a timing of transmission of the transmission ultrasonic wave, and when the frequency determining section determines that the reception frequency and the transmission frequency are the same, the frequency switching section switches the transmission frequency and the reception frequency to a frequency different from the frequency scheduled to be transmitted. 
     &lt;3&gt; The ultrasonic sensor control device according to &lt;1&gt;, in which the receiving section receives a plurality of the reception ultrasonic waves from a plurality of receiving devices configured to receive the plurality of reception ultrasonic waves, the frequency determining section determines whether or not the reception frequency of the reception ultrasonic wave received by the receiving section and the transmission frequency are different from each other, in a predetermined period of time before a timing of transmission of the transmission ultrasonic wave, and when the frequency determining section determines that the reception frequency and the transmission frequency are the same, the frequency switching section switches the transmission frequency and a plurality of reception frequencies of the plurality of reception ultrasonic waves to a frequency different from the frequencies capable of being received by the plurality of receiving devices at a time point of the determination by the frequency determining section. 
     &lt;4&gt; The ultrasonic sensor control device according to &lt;1&gt;, in which the receiving section receives a plurality of the reception ultrasonic waves from a plurality of receiving devices configured to receive the plurality of reception ultrasonic waves, the frequency determining section determines whether or not the reception frequency of the reception ultrasonic wave received by the receiving section and the transmission frequency are different from each other, in a predetermined period of time before a timing of transmission of the transmission ultrasonic wave, and when the frequency determining section determines that the reception frequency and the transmission frequency are the same, the frequency switching section switches the transmission frequency and a plurality of reception frequencies of the plurality of reception ultrasonic waves to a frequency that is included in frequencies capable of being received by the plurality of receiving devices at a time point of the determination by the frequency determining section and that is different from the reception frequency of the reception ultrasonic wave received by the receiving section. 
     &lt;5&gt; The ultrasonic sensor control device according to &lt;1&gt;, in which the transmission control section controls the transmitting device such that the transmitting device successively transmits a first transmission ultrasonic wave of a first transmission frequency and a second transmission ultrasonic wave of a second transmission frequency, the receiving section receives a first reception ultrasonic wave and a second reception ultrasonic wave from a plurality of receiving devices configured to receive a plurality of the reception ultrasonic waves, the frequency determining section determines a result of comparing a first reception frequency of the first reception ultrasonic wave and a second reception frequency of the second reception ultrasonic wave with the first transmission frequency and the second transmission frequency, and when the first reception frequency is different from the first transmission frequency or when the second reception frequency is different from the second transmission frequency, the frequency switching section switches the first transmission frequency, the second transmission frequency, the first reception frequency, and the second reception frequency to frequencies different from the first transmission frequency and the second transmission frequency. 
     &lt;6&gt; The ultrasonic sensor control device according to &lt;1&gt;, in which the transmission control section controls a plurality of the transmitting devices such that the transmitting devices transmit a first transmission ultrasonic wave of a first transmission frequency and a second transmission ultrasonic wave of a second transmission frequency simultaneously, the receiving section receives a first reception ultrasonic wave and a second reception ultrasonic wave from a plurality of receiving devices configured to receive a plurality of the reception ultrasonic waves, the frequency determining section determines a result of comparing a first reception frequency of the first reception ultrasonic wave and a second reception frequency of the second reception ultrasonic wave with the first transmission frequency and the second transmission frequency, and when the first reception frequency and the second reception frequency are the same frequency as either the first transmission frequency or the second transmission frequency and when the first reception ultrasonic wave and the second reception ultrasonic wave are not received in same timing, the frequency switching section switches the first transmission frequency, the second transmission frequency, the first reception frequency, and the second reception frequency to frequencies different from the first transmission frequency and the second transmission frequency. 
     &lt;7&gt; An ultrasonic sensor including an ultrasonic sensor device configured to transmit and receive an ultrasonic wave, a transmission control section configured to control transmission of a transmission ultrasonic wave via the ultrasonic sensor device, a receiving section configured to receive a reception ultrasonic wave via the ultrasonic sensor device, a frequency determining section configured to determine a result of comparing a reception frequency that is a frequency of the reception ultrasonic wave received by the receiving section and that is a frequency capable of being received by the receiving section, with a transmission frequency of the transmission ultrasonic wave that is transmitted under the control of the transmission control section, and a frequency switching section configured to change the transmission frequency and the reception frequency on the basis of a result of the determination by the frequency determining section. 
     &lt;8&gt; An ultrasonic sensor control method including controlling a transmitting device configured to transmit a transmission ultrasonic wave, receiving a reception ultrasonic wave from a receiving device, determining a result of comparing a reception frequency that is a frequency of the received reception ultrasonic wave and that is a frequency capable of being received via the receiving device, with a transmission frequency of the transmission ultrasonic wave, and changing the transmission frequency of the transmission ultrasonic wave and the reception frequency on the basis of a result of the determination based on the comparison between the reception frequency and the transmission frequency. 
     First Embodiment 
     A configuration of an ultrasonic sensor  10  according to a first embodiment will be described with reference to  FIG.  1   . The ultrasonic sensor  10  includes an ultrasonic sensor control device  100  and an ultrasonic sensor device  200 . The ultrasonic sensor  10  in the present embodiment is a sensor that can transmit an ultrasonic wave and that can also receive the ultrasonic wave. The ultrasonic sensor  10  is used in, for example, a distance measuring system that can measure a distance to a target object by measuring a time from the transmission of an ultrasonic wave to the returning of the wave after being reflected by the target object (time of flight (TOF)). 
     The ultrasonic sensor control device  100  includes a receiving section  111 , a frequency determining section  112 , a frequency switching section  113 , a transmission control section  114 , and a storage unit  120 . The ultrasonic sensor device  200  is an ultrasonic sensor device including a receiving device  210  that receives an ultrasonic wave and a transmitting device  220 . The ultrasonic sensor device  200  has, for example, a transducer utilizing a piezoelectric effect. When a predetermined voltage is applied to the transmitting device  220 , a piezoelectric vibrator (not illustrated) included in the transmitting device  220  is vibrated and made to generate an ultrasonic wave. In addition, when the ultrasonic wave of a predetermined frequency reaches the receiving device  210 , a predetermined voltage occurs in a piezoelectric vibrator (not illustrated) of the receiving device  210 , and the receiving device  210  can receive the ultrasonic wave through detection of the voltage. 
     The receiving section  111  receives the reception ultrasonic wave via the receiving device  210 , and stores reception information related to the reception ultrasonic wave in the storage unit  120 . Specifically, the receiving section  111  receives the reception ultrasonic wave via the receiving device  210  at a reception frequency included in the reception information stored in the storage unit  120 , and stores the contents indicating “received,” as a reception state included in the reception information stored in the storage unit  120 . 
     The frequency determining section  112  determines whether or not a transmission ultrasonic wave has been transmitted, on the basis of a transmission state included in transmission information stored in the storage unit  120 . In addition, on the basis of a transmission frequency included in the transmission information and the reception frequency included in the reception information, the transmission information and the reception information being stored in the storage unit  120 , the frequency determining section  112  compares the reception frequency of the reception ultrasonic wave and the transmission frequency of the transmission ultrasonic wave with each other, and determines whether or not the reception frequency and the transmission frequency are the same. 
     Incidentally, in the present specification, a case where the “frequencies are the same” is not limited to a case where the frequencies as targets for the determination are completely the same, and includes a case where the frequencies as targets for the determination are the same within a predetermined range. For example, in a case where measurement specifications of the ultrasonic sensor  10  are set such that “a speed relative to a measurement target object is ±5 km/h under the conditions where a sound source frequency is 40 kHz and an operating temperature is −20° C. to 60° C.,” a frequency range is as follows. Specifically, with respect to the frequency of 40 kHz, the lowest reception frequency of the wave returned after being reflected by the target object is 39,653.5 Hz (with the distance increasing at 5 km/h at a time of −20° C.). Similarly, the highest reception frequency of the wave returned after being reflected by the target object is 40,303.0 Hz (with the distance decreasing at 5 km/h at a time of +60° C.). Incidentally, in both of these cases, suppose that a significant figure is 0.1 Hz, that a sound source tolerance is 0, and that the speed of sound is (331.5+0.61T) m/s (T is an atmospheric temperature). That is, in a case where the frequency as a target for the determination is 40 kHz and where the frequency as a target for the comparison is in a range of 39,653.5 to 40,303.0 Hz, for example, the frequency determining section  112  determines that the “frequencies are the same.” Note that the predetermined range in the frequency determination is not limited to the values in the above-described example, and differs according to the measurement specifications of the ultrasonic sensor  10  and the value of the target frequency. 
     When the frequency determining section  112  determines that the frequencies are the same, the frequency switching section  113  switches and changes the transmission frequency included in the transmission information and the reception frequency included in the reception information, the transmission information and the reception information being stored in the storage unit  120 , to a different frequency. That is, when the frequency determining section  112  determines that the reception frequency and the transmission frequency are the same in a predetermined period of time before a timing of transmission of the transmission ultrasonic wave from the transmitting device  220 , the frequency switching section  113  switches and changes the transmission frequency of the transmission ultrasonic wave to a frequency different from the frequency scheduled to be transmitted. Incidentally, in the present embodiment, the predetermined period of time is a period of time from the starting of the ultrasonic sensor control device  100  to the timing of transmission of the transmission ultrasonic wave by the transmitting device  220 . In addition, suppose that the predetermined period of time can be set as desired. For example, in a case where crosstalk from an ultrasonic wave transmitted from another device is desired to be determined more accurately, this predetermined period of time may be set longer than a default (initially set) period. 
     The transmission control section  114  controls the transmission of the transmission ultrasonic wave from the transmitting device  220 . Specifically, the transmission control section  114  causes the transmitting device  220  to transmit the transmission ultrasonic wave at the transmission frequency included in the transmission information stored in the storage unit  120 . In addition, after the transmission of the transmission ultrasonic wave, the transmission control section  114  changes the transmission state included in the transmission information stored in the storage unit  120 , to “transmitted.” 
     The storage unit  120  includes a read only memory (ROM), a random access memory (RAM), or a hard disk, for example. The storage unit  120  stores “frequency information,” “transmission information,” and “reception information.” Specifically, the storage unit  120  stores information illustrated in  FIG.  2   . Incidentally, the “frequency information,” the “transmission information,” and the “reception information” stored in the storage unit  120  may be configured as regions provided in one storage device and divided from one another physically or logically. Alternatively, a configuration in which storage units  120  of the respective pieces of data are provided in a plurality of physically different storage devices may be adopted. 
     Frequencies of ultrasonic waves that can be handled in the ultrasonic sensor  10  are stored in the “frequency information” in the storage unit  120 . Specifically, frequencies at which the receiving device  210  of the ultrasonic sensor device  200  can receive the ultrasonic wave and at which the transmitting device  220  of the ultrasonic sensor device  200  can transmit the ultrasonic wave are stored. In addition, the values of the frequencies stored in the “frequency information” are assumed to be separated from one another to a degree that crosstalk does not occur in consideration of a Doppler shift, reception characteristics, and other characteristics. For example, in the example illustrated in  FIG.  2   , the fields of a first frequency, a second frequency, and a third frequency in the “frequency information” store, as the values of the frequencies, 45 kHz, 50 kHz, and 55 kHz each separated from another by 5 kHz. The ultrasonic sensor control device  100  selects a frequency stored in the “frequency information” to transmit and receive an ultrasonic wave. 
     Information related to the transmission ultrasonic wave that is transmitted via the transmitting device  220  is stored in the “transmission information” in the storage unit  120 . Specifically, a “transmission state” indicating whether or not the transmission ultrasonic wave has been transmitted from the transmitting device  220  is stored. As the “transmission state,” information indicating “before transmission” is stored before the transmission ultrasonic wave is transmitted from the transmitting device  220 . In addition, as the “transmission state,” information indicating “transmitted” is stored after the transmission ultrasonic wave is transmitted from the transmitting device  220 . 
     In addition, information related to the transmission frequency is stored in the “transmission information.” As the transmission frequency in the “transmission information,” the frequency scheduled to be transmitted is stored before the transmission ultrasonic wave is transmitted from the transmitting device  220 . In addition, as the transmission frequency in the “transmission information,” the frequency of the transmission ultrasonic wave actually transmitted is stored after the transmission ultrasonic wave is transmitted from the transmitting device  220 . 
     Information related to the reception ultrasonic wave received via the receiving device  210  is stored in the “reception information” in the storage unit  120 . Specifically, a “reception state” indicating whether or not the reception ultrasonic wave is received by the receiving device  210  is stored. As the “reception state,” information indicating “not received” is stored before the reception ultrasonic wave is received from the receiving device  210 . In addition, as the “reception state,” information indicating “received” is stored after the reception ultrasonic wave is received from the receiving device  210 . 
     In addition, information related to the reception frequency is stored in the “reception information.” The frequency of the reception ultrasonic wave that can be received from the receiving device  210  is stored as the reception frequency in the “reception information.” That is, the reception frequency in the “reception information” is a frequency capable of being received by the receiving device  210 . 
     Here, processing performed by the ultrasonic sensor control device  100  will be described with reference to timing diagrams of  FIG.  3 A  and  FIG.  3 B . In the timing diagrams illustrated in  FIG.  3 A  and  FIG.  3 B , a difference between frequencies of ultrasonic waves is schematically represented by using graphic patterns and reference signs UF 1  and UF 2 . Incidentally, suppose that UF 1  denotes the first frequency of an ultrasonic wave and that UF 2  denotes the second frequency of an ultrasonic wave. In subsequent timing diagrams, the difference between frequencies of ultrasonic waves are schematically represented as in  FIG.  3 A  and  FIG.  3 B . 
     Suppose in  FIG.  3 A  and  FIG.  3 B  that the first frequency (UF 1 ), for example, is set as the transmission frequency and reception frequency at a time of a start of the ultrasonic sensor control device  100 . That is, the ultrasonic sensor control device  100  transmits an ultrasonic wave of the first frequency (UF 1 ), receives the wave reflected by a target object at the first frequency (UF 1 ), and thus measures a distance to the target object. 
     Suppose in  FIG.  3 A  that the transmitting device  220  transmits an ultrasonic wave at time T 2 , the transmitted ultrasonic wave is reflected by the target object, and the reflected ultrasonic wave is received by the receiving device  210  at time T 4 . Meanwhile, suppose in  FIG.  3 A  that another device which is different from the ultrasonic sensor control device  100  transmits an ultrasonic wave, and the transmitted ultrasonic wave is received by the receiving device  210  at the first frequency (UF 1 ) at time T 1  and time T 3 . The other device in the present embodiment is not limited to another ultrasonic sensor  10 , and may be a distance measuring system using another ultrasonic sensor using a frequency of an ultrasonic wave close to that handled by the ultrasonic sensor  10  or may be a repelling device for use against animal damage, for example. 
     In this case, in the example illustrated in  FIG.  3 A , the ultrasonic sensor control device  100  recognizes the ultrasonic wave received by the receiving device  210  at time T 3 , as the ultrasonic wave transmitted from the transmitting device  220  at time T 2  and then reflected by the target object. The target ultrasonic wave should be received at time T 4 , but the different ultrasonic wave is erroneously received at time T 3 . Thus, a time from the transmission of the ultrasonic wave from the transmitting device  220  to the reception of the ultrasonic wave is shortened. That is, the ultrasonic sensor may not perform distance measurement accurately. 
     On the other hand, in the example illustrated in  FIG.  3 B , when an ultrasonic wave of the first frequency is received by the receiving device  210  at time T 1 , the frequency determining section  112  determines that the ultrasonic wave of the first frequency (UF 1 ) as the transmission frequency is received in a timing before the transmitting device  220  transmits the ultrasonic wave (time T 2 ). 
     On the basis of the result of the determination by the frequency determining section  112 , the frequency switching section  113  switches the transmission frequency and the reception frequency to the second frequency (UF 2 ) different from the first frequency (UF 1 ). Consequently, in the example illustrated in  FIG.  3 B , no ultrasonic wave of the first frequency (UF 1 ) is received at time T 3  as the ultrasonic wave transmitted from the transmitting device  220 . In addition, an ultrasonic wave of the second frequency (UF 2 ) can be received correctly at time T 4 . It is thus possible to cancel crosstalk from another device and perform accurate distance measurement in the distance measuring system using the ultrasonic sensor control device  100 . 
     Outline of Processing Flow of Ultrasonic Sensor Control Device  100   
     Next, a flow of processing in the ultrasonic sensor control device  100  (ultrasonic sensor control method) will be illustrated with reference to a flowchart of  FIG.  4   . A series of operations of the ultrasonic sensor control device  100  illustrated in the flowchart of  FIG.  4    is started when the ultrasonic sensor control device  100  is started, and the processing is ended in response to the transmission of a transmission ultrasonic wave. Further, the processing in the flowchart illustrated in  FIG.  4    is also ended in response to the turning off of the power or a processing termination interrupt. In addition, in the following description of the flowchart, the same contents as described in conjunction with the foregoing ultrasonic sensor control device  100  will be omitted or described in a simplified manner. 
     In step S 401 , the transmission control section  114  determines whether or not it is a timing of transmission of a transmission ultrasonic wave. When the transmission control section  114  determines in step S 401  that it is the timing of transmission of a transmission ultrasonic wave (step S 401 : YES), the processing proceeds to step S 406 . When the transmission control section  114  determines in step S 401  that it is not the timing of transmission of a transmission ultrasonic wave (step S 401 : NO), on the other hand, the processing proceeds to step S 402 . 
     In step S 402 , the receiving section  111  determines whether or not a reception ultrasonic wave is received. Specifically, the receiving section  111  determines whether or not a reception ultrasonic wave is received at the reception frequency included in the reception information stored in the storage unit  120 . When the receiving section  111  determines in step S 402  that a reception ultrasonic wave is received (step S 402 : YES), the processing proceeds to step S 403 . When the receiving section  111  determines in step S 402  that no reception ultrasonic wave is received (step S 402 : NO), on the other hand, the processing returns to step S 401  to repeat the processing from step S 401 . That is, until the timing of transmission of a transmission ultrasonic wave, the processing of step S 401  and step S 402  is repeated to determine whether or not a reception ultrasonic wave is received. When the timing of transmission of a transmission ultrasonic wave comes first, the transmission control section  114  transmits the transmission ultrasonic wave in step S 406  to be described later. When a reception ultrasonic wave is received first, on the other hand, processing from step S 403  to be described later on down is performed. 
     In step S 403 , the frequency determining section  112  determines whether or not the transmission ultrasonic wave is yet to be transmitted. Specifically, in step S 403 , the frequency determining section  112  determines whether or not the transmission ultrasonic wave is yet to be transmitted, on the basis of the transmission state included in the transmission information stored in the storage unit  120 . When the frequency determining section  112  determines in step S 403  that the transmission ultrasonic wave is yet to be transmitted (step S 403 : YES), the processing proceeds to step S 404 . When the frequency determining section  112  determines in step S 403  that the transmission ultrasonic wave is not yet to be transmitted, that is, the transmission ultrasonic wave has been transmitted (step S 403 : NO), on the other hand, the processing returns to step S 401  to repeat the processing from step S 401 . 
     In step S 404 , the frequency determining section  112  determines whether or not the reception frequency of the reception ultrasonic wave and the transmission frequency of the transmission ultrasonic wave scheduled to be transmitted are the same. Specifically, the frequency determining section  112  determines whether or not the reception frequency of the reception ultrasonic wave and the transmission frequency of the transmission ultrasonic wave are the same, on the basis of the transmission frequency in the transmission information and the reception frequency in the reception information, the transmission information and the reception information being stored in the storage unit  120 . When the frequency determining section  112  determines in step S 404  that the reception frequency of the reception ultrasonic wave and the transmission frequency of the transmission ultrasonic wave are the same (step S 404 : YES), the processing proceeds to step S 405 . When the frequency determining section  112  determines in step S 404  that the reception frequency of the reception ultrasonic wave and the transmission frequency of the transmission ultrasonic wave are not the same (step S 404 : NO), on the other hand, the processing returns to step S 401  to repeat the processing from step S 401 . 
     In step S 405 , the frequency switching section  113  changes the transmission frequency of the transmission ultrasonic wave and the reception frequency of the reception ultrasonic wave. Specifically, the frequency switching section  113  switches and changes the transmission frequency in the transmission information and the reception frequency in the reception information, the transmission information and the reception information being stored in the storage unit  120 , to a different frequency. The processing then returns to step S 401  to repeat the processing from step S 401 . 
     In step S 406 , the transmission control section  114  transmits the transmission ultrasonic wave. Specifically, in step S 406 , the transmission control section  114  causes the transmitting device  220  to transmit the transmission ultrasonic wave at the transmission frequency included in the transmission information stored in the storage unit  120 . In addition, after the transmission of the transmission ultrasonic wave, the transmission control section  114  changes the transmission state included in the transmission information stored in the storage unit  120 , to “transmitted.” 
     As described above, the ultrasonic sensor control device  100  according to the first embodiment includes the transmission control section  114  configured to control the transmitting device configured to transmit a transmission ultrasonic wave, the receiving section  111  configured to receive a reception ultrasonic wave, the frequency determining section  112 , and the frequency switching section  113 . The frequency determining section  112  determines a result of comparing a reception frequency that is a frequency of the reception ultrasonic wave received by the receiving section  111  and that is a frequency capable of being received by the receiving section  111 , with a transmission frequency of the transmission ultrasonic wave that is transmitted under the control of the transmission control section  114 . In addition, the frequency switching section  113  changes the transmission frequency and the reception frequency on the basis of a result of the determination by the frequency determining section  112 . 
     With this configuration, the ultrasonic sensor control device  100  determines the result of comparing the transmission frequency of the transmission ultrasonic wave and the reception frequency of the reception ultrasonic wave with each other. It is thus possible to easily determine ultrasonic wave crosstalk from another device, and also easily cancel the crosstalk from the other device by changing the transmission frequency and the reception frequency. 
     In addition, in the first embodiment, the frequency determining section  112  determines whether or not the reception frequency of the reception ultrasonic wave received by the receiving section  111  and the transmission frequency are different from each other, in a predetermined period of time before the timing of transmission of the transmission ultrasonic wave. When it is determined that the reception frequency and the transmission frequency are the same, the frequency switching section  113  switches the transmission frequency and the reception frequency to a frequency different from the frequency scheduled to be transmitted. 
     With this configuration, in a case of using the ultrasonic sensor  10  according to the first embodiment, for example, the ultrasonic wave expected to cause crosstalk can be determined in advance, and with the use of a frequency of an ultrasonic wave different from the ultrasonic wave expected to cause crosstalk, the ultrasonic sensor  10  can transmit the ultrasonic wave and receive the reflected wave. That is, the processing of determining and cancelling crosstalk from another device can be performed efficiently before actual distance measurement, and in the actual distance measurement, erroneous measurement due to the crosstalk can be prevented. 
     Second Embodiment 
     One concrete embodiment has been described above. However, the foregoing embodiment is illustrative, and does not limit embodiments. For example, the foregoing embodiment illustrates an example in which the transmission frequency of the transmission ultrasonic wave and the reception frequency of the reception ultrasonic wave are determined before the transmission of the transmission ultrasonic wave, and the transmission frequency and the reception frequency are changed when the transmission frequency and the reception frequency are the same. Here, description will be further made regarding a configuration, focusing on the difference from the configuration of the first embodiment, of an ultrasonic sensor control device  100  according to a second embodiment that receives a plurality of reception ultrasonic waves and that determines the transmission frequency of the transmission ultrasonic wave and the reception frequencies of the plurality of reception ultrasonic waves. 
       FIG.  5    is a diagram illustrating a general configuration of an ultrasonic sensor  10  according to the second embodiment. As illustrated in  FIG.  5   , the configuration of the ultrasonic sensor  10  according to the second embodiment is different from that of the first embodiment in that the ultrasonic sensor device  200  includes a plurality of receiving devices  210 . 
       FIG.  6    illustrates “frequency information,” “transmission information,” and “reception information” stored in the storage unit  120  of the ultrasonic sensor control device  100  according to the second embodiment. As illustrated in  FIG.  6   , the “reception information” stored in the storage unit  120  of the ultrasonic sensor control device  100  according to the second embodiment is different from that of the first embodiment in that reception states and reception frequencies for the plurality of receiving devices  210  are stored. 
     Processing performed by the ultrasonic sensor control device  100  according to the second embodiment will be described with reference to timing diagrams illustrated in  FIGS.  7 A to  7 C . 
     Suppose in  FIGS.  7 A to  7 C  that the first frequency (UF 1 ), for example, is set as the transmission frequency at a time of a start of the ultrasonic sensor control device  100 . Further, suppose that the first frequency (UF 1 ), the second frequency (UF 2 ), and the third frequency (UF 3 ) are set as the respective reception frequencies for a first receiving device, a second receiving device, and a third receiving device. In addition, the ultrasonic sensor control device  100  transmits an ultrasonic wave of the first frequency (UF 1 ), the wave reflected by a target object is received by the first receiving device at the first frequency (UF 1 ), and thus, the ultrasonic sensor control device  100  measures a distance to the target object. 
     Suppose in  FIG.  7 A  that the transmitting device  220  transmits an ultrasonic wave at time T 4 , the transmitted ultrasonic wave is reflected by the target object, and the first receiving device receives the reflected ultrasonic wave at time T 8 . Meanwhile, suppose in  FIG.  7 A  that another device which is different from the ultrasonic sensor control device  100  transmits an ultrasonic wave, and the first receiving device receives the ultrasonic wave at the first frequency (UF 1 ) at time T 1  and time T 5 . 
     In this case, in the example illustrated in  FIG.  7 A , the ultrasonic wave received by the first receiving device at time T 5  is recognized as the ultrasonic wave transmitted from the transmitting device  220  at time T 4  and then reflected by the target object. The target ultrasonic wave should be received at time T 8 , but the different ultrasonic wave is erroneously received at time T 5 . Thus, a time from the transmission of the ultrasonic wave from the transmitting device  220  to the reception of the ultrasonic wave is shortened. That is, distance measurement is performed erroneously. 
     On the other hand, in the example illustrated in  FIG.  7 B , ultrasonic waves of the first frequency (UF 1 ), the second frequency (UF 2 ), and the third frequency (UF 3 ) are received by the first receiving device, the second receiving device, and the third receiving device, respectively, at time T 1 , time T 2 , and time T 3 . In this case, the frequency determining section  112  in the second embodiment determines that the ultrasonic wave of the first frequency (UF 1 ) as the transmission frequency is received by the first receiving device in a timing before the transmitting device  220  transmits the ultrasonic wave. 
     On the basis of the result of the determination by the frequency determining section  112 , the frequency switching section  113  switches the transmission frequency and the reception frequency for the first receiving device to a frequency different from the first frequency (UF 1 ). Here, in the second embodiment, the second and third receiving devices other than the first receiving device also receive the ultrasonic waves of the second frequency (UF 2 ) and the third frequency (UF 3 ). Therefore, in a case where the transmission frequency of the transmission ultrasonic wave is switched to the second frequency (UF 2 ) or the third frequency (UF 3 ), which is a frequency different from the first frequency (UF 1 ), a reception ultrasonic wave is erroneously received at time T 6  or time T 7 . 
     Therefore, in the second embodiment, the frequency switching section  113  switches the frequency to a frequency different from the reception frequencies for the plurality of receiving devices  210 . For example, in the example illustrated in  FIG.  7 B , the frequency of the transmission ultrasonic wave and the reception frequency for the first receiving device are switched to a fourth frequency (UF 4 ). Consequently, in the example illustrated in  FIG.  7 B , no ultrasonic wave of the first frequency (UF 1 ) is received at time T 5 . In addition, an ultrasonic wave of the fourth frequency (UF 4 ) can be received correctly at time T 8 . It is thus possible to eliminate erroneous reception and perform correct distance measurement in the distance measuring system using the ultrasonic sensor control device  100 . 
     In addition, in the ultrasonic sensor control device  100  in the second embodiment, the frequency switching section  113  may switch the transmission frequency and the reception frequency for the first receiving device to a reception frequency that is included in the reception frequencies for the plurality of receiving devices  210  and at which no reception ultrasonic wave is received. For example, in the example illustrated in  FIG.  7 C , the third receiving device does not receive any reception ultrasonic wave before the transmission of the transmission ultrasonic wave from the transmitting device  220 . Hence, in the example illustrated in  FIG.  7 C , the frequency of the transmission ultrasonic wave and the reception frequency for the first receiving device are switched to the third frequency (UF 3 ) which is not received by the third receiving device. Consequently, in the example illustrated in  FIG.  7 C , no ultrasonic wave of the first frequency (UF 1 ) is received at time T 5 . In addition, an ultrasonic wave of the third frequency (UF 3 ) can be received correctly at time T 8 . It is thus possible to eliminate erroneous reception and perform correct distance measurement in the distance measuring system using the ultrasonic sensor control device  100 . 
     As described above, the receiving section  111  of the ultrasonic sensor control device  100  in the second embodiment receives a plurality of reception ultrasonic waves from the plurality of receiving devices  210  configured to receive the plurality of reception ultrasonic waves. In addition, the frequency determining section  112  determines whether or not the reception frequency of the reception ultrasonic wave received by the receiving section  111  and the transmission frequency are different from each other, in a predetermined period of time before a timing of transmission of the transmission ultrasonic wave. Further, when it is determined that the reception frequency and the transmission frequency are the same, the frequency switching section  113  switches the transmission frequency and a plurality of reception frequencies to a frequency different from the frequencies capable of being received by the plurality of receiving devices  210  at a time point of the determination in the frequency determining section  112 . 
     With this configuration, the ultrasonic sensor  10  according to the second embodiment can detect the plurality of frequencies capable of being received by the plurality of receiving devices  210 . Consequently, erroneous reception of ultrasonic waves originating from other systems can be reduced more. A more accurate distance measuring system can thus be realized. 
     Further, the receiving section  111  of the ultrasonic sensor control device  100  in the second embodiment receives a plurality of reception ultrasonic waves from the plurality of receiving devices  210  configured to receive the plurality of reception ultrasonic waves. In addition, the frequency determining section  112  determines whether or not the reception frequency of the reception ultrasonic wave received by the receiving section  111  and the transmission frequency are different from each other, in a predetermined period of time before a timing of transmission of the transmission ultrasonic wave. Further, when it is determined that the reception frequency and the transmission frequency are the same, the frequency switching section  113  may switch the transmission frequency and a plurality of reception frequencies to a frequency that is included in frequencies capable of being received by the plurality of receiving devices at a time point of the determination in the frequency determining section and that is different from the reception frequency of the reception ultrasonic wave received by the receiving section. 
     With this configuration, the ultrasonic sensor  10  according to the second embodiment can detect the plurality of frequencies capable of being received by the plurality of receiving devices  210 . In addition, this configuration can reduce the number of applicable frequencies. Consequently, erroneous reception of ultrasonic waves originating from other systems can be reduced more. A more accurate distance measuring system can thus be realized. 
     Third Embodiment 
     A third embodiment will next be described. Note that, in the following description, when the same reference signs as in the first embodiment and/or the second embodiment are used, identical configurations to those of the first embodiment and/or the second embodiment are illustrated, and the preceding description is referred to unless particular description is made. Here, a plurality of transmission ultrasonic waves are transmitted, and timings of reception of a plurality of reception ultrasonic waves are determined. A configuration of an ultrasonic sensor  10  according to the third embodiment will be described focusing on the difference from the configuration (configurations) of the first embodiment and/or the second embodiment. 
       FIG.  8    is a diagram illustrating a general configuration of the ultrasonic sensor  10  according to the third embodiment. As illustrated in  FIG.  8   , the configuration of the ultrasonic sensor  10  according to the third embodiment is different from that (those) of the first embodiment and/or the second embodiment in that the ultrasonic sensor device  200  includes a plurality of transmitting devices  220  and a plurality of receiving devices  210 . 
       FIG.  9    illustrates “frequency information,” “transmission information,” and “reception information” stored in the storage unit  120  of the ultrasonic sensor control device  100  according to the third embodiment. As illustrated in  FIG.  9   , the “transmission information” stored in the storage unit  120  of the ultrasonic sensor control device  100  according to the third embodiment is different from that of the second embodiment in that transmission states and transmission frequencies for the plurality of transmitting devices  220  are stored. 
     In addition, as illustrated in  FIG.  9   , the “transmission information” and the “reception information” stored in the storage unit  120  of the ultrasonic sensor control device  100  according to the third embodiment are different from those of the first and second embodiments in that items of transmission times and reception times are included. In the example illustrated in  FIG.  9   , “timing A” indicated as a transmission time denotes the transmission time of an ultrasonic wave transmitted by a first transmitting device. In addition, “timing A+time B” indicated as a transmission time denotes the transmission time of an ultrasonic wave transmitted by a second transmitting device, and denotes a time after “time B” has elapsed from “timing A.” In addition, “timing C” and “timing D” denote the respective times at which a first receiving device and a second receiving device receive ultrasonic waves. 
     Processing performed by the ultrasonic sensor control device  100  according to the third embodiment will be described with reference to timing diagrams illustrated in  FIG.  10 A  and  FIG.  10 B . 
     Suppose in  FIG.  10 A  and  FIG.  10 B  that a first frequency (UF 1 ) and a second frequency (UF 2 ), for example, are set as the respective transmission frequencies for the first transmitting device and the second transmitting device at a time of a start of the ultrasonic sensor control device  100 . In addition, suppose that a first frequency (UF 1 ) and a second frequency (UF 2 ) are set as the respective reception frequencies for the first receiving device and the second receiving device. Moreover, the ultrasonic sensor control device  100  transmits transmission ultrasonic waves of the first frequency (UF 1 ) and the second frequency (UF 2 ) from the first transmitting device and the second transmitting device. Then, the wave reflected by a target object is received by the first receiving device at the first frequency (UF 1 ) or received by the second receiving device at the second frequency (UF 2 ). A distance to the target object is thus measured. Note that the respective transmission frequencies of the transmission ultrasonic waves transmitted from the first transmitting device and the second transmitting device correspond to a first transmission frequency and a second transmission frequency. Similarly, the respective reception frequencies received by the first receiving device and the second receiving device correspond to a first reception frequency and a second reception frequency. 
     Further, the third embodiment compares transmission order of the transmission ultrasonic waves transmitted from the first and second transmitting devices, with reception order of the reflected waves received by the first and second receiving devices, and thus determines whether there is signal crosstalk from another ultrasonic sensor system. Note that the transmission ultrasonic wave transmitted from the first transmitting device corresponds to a first transmission ultrasonic wave. In addition, the transmission ultrasonic wave transmitted from the second transmitting device corresponds to a second transmission ultrasonic wave. Similarly, the reception ultrasonic wave received by the first receiving device corresponds to a first reception ultrasonic wave. In addition, the reception ultrasonic wave received by the second receiving device corresponds to a second reception ultrasonic wave. 
     For example, in the example illustrated in  FIG.  10 A , the ultrasonic sensor  10  transmits the transmission ultrasonic waves in order of the first frequency (UF 1 ) and the second frequency (UF 2 ) from the first and second transmitting devices at time T 1  and time T 2 . Here, when there is no signal crosstalk from another ultrasonic sensor, the first and second receiving devices receive the reflected waves in order of the first frequency (UF 1 ) and the second frequency (UF 2 ). However, in the example illustrated in  FIG.  10 A , an ultrasonic wave of the second frequency (UF 2 ) is received first at time T 3 . The ultrasonic sensor  10  according to the present third embodiment can recognize the occurrence of crosstalk in the ultrasonic wave of the second frequency (UF 2 ). 
     The processing performed by the ultrasonic sensor  10  according to the third embodiment will further be described with reference to  FIG.  10 B . For example, the ultrasonic sensor  10  in the third embodiment may not receive (not use, as received signals) the reception ultrasonic waves received at times T 3  to T 5  in  FIG.  10 B . Thereafter, the frequency switching section  113  changes the transmission frequencies for the first and second transmitting devices to a third frequency (UF 3 ) and a fourth frequency (UF 4 ), for example. At time T 6  and time T 7 , ultrasonic waves of the third frequency (UF 3 ) and the fourth frequency (UF 4 ) are transmitted from the first and second transmitting devices. 
     Thereafter, at time T 8  and time T 9 , the first and second receiving devices receive the respective reception ultrasonic waves of the third frequency (UF 3 ) and the fourth frequency (UF 4 ). The reception order of the ultrasonic waves of the third frequency (UF 3 ) and the fourth frequency (UF 4 ) received by the first and second receiving devices is the same as the transmission order of the transmission ultrasonic waves of the third frequency (UF 3 ) and the fourth frequency (UF 4 ) transmitted by the first and second transmitting devices at time T 6  and time T 7 . Hence, processing such as distance measurement can be performed by using the reception ultrasonic waves of the third frequency (UF 3 ) and/or the fourth frequency (UF 4 ) in the ultrasonic sensor  10  in the third embodiment. 
     Outline of Processing Flow of Ultrasonic Sensor Control Device  100   
     Next, a flow of processing in the ultrasonic sensor control device  100  (ultrasonic sensor control method) according to the third embodiment will be illustrated with reference to a flowchart illustrated in  FIG.  11   . A series of operations of the ultrasonic sensor control device  100  illustrated in the flowchart of  FIG.  11    is started when the ultrasonic sensor control device  100  is started, and the processing is ended in response to the transmission of transmission ultrasonic waves. In addition, the processing in the flowchart illustrated in  FIG.  11    is also ended in response to the turning off of the power or a processing termination or time-out interrupt. In addition, in the following description of the flowchart, the same contents as described in conjunction with the foregoing ultrasonic sensor control device  100  will be omitted or described in a simplified manner. 
     In step S 1101 , the transmission control section  114  controls the transmitting device  220  such that the transmitting device  220  transmits transmission ultrasonic waves of a plurality of transmission frequencies in predetermined order (predetermined combination). The plurality of transmission ultrasonic waves are thus transmitted from the plurality of transmitting devices  220 . 
     In step S 1102 , the receiving section  111  determines whether or not a plurality of reception ultrasonic waves are received. When the receiving section  111  determines in step S 1102  that a plurality of reception ultrasonic waves are received (step S 1102 : YES), the processing proceeds to step S 1103 . When the receiving section  111  determines that no reception ultrasonic waves are received in step S 1102  (step S 1102 : NO), on the other hand, the processing returns to step S 1102 . That is, the processing of step S 1102  is repeatedly performed until a plurality of reception ultrasonic waves are received. Incidentally, in a state in which a plurality of reception ultrasonic waves are not received normally due to an abnormality in the ultrasonic sensor  10 , for example, the processing illustrated in  FIG.  11    may be ended by a time-out interrupt or other operations after a predetermined period of time elapses. 
     In step S 1103 , the frequency determining section  112  determines whether or not the received reception ultrasonic waves are received in a predetermined combination. Here, the predetermined combination is, for example, the transmission order of the transmission ultrasonic waves transmitted from the first transmitting device and the second transmitting device. When the frequency determining section  112  determines in step S 1103  that the received reception ultrasonic waves are received in the predetermined combination (step S 1103 : YES), the processing proceeds to step S 1105 . When the frequency determining section  112  determines in step S 1103  that the received reception ultrasonic waves are not received in the predetermined combination (step S 1103 : NO), on the other hand, the processing proceeds to step S 1104 . 
     In step S 1104 , the frequency switching section  113  changes the transmission frequencies of the transmission ultrasonic waves and the reception frequencies of the reception ultrasonic waves. Specifically, the frequency switching section  113  switches and changes, to different frequencies, the transmission frequencies in the transmission information regarding the plurality of transmitting devices  220  and the reception frequencies in the reception information regarding the plurality of receiving devices  210 , the transmission information and the reception information being stored in the storage unit  120 . 
     In step S 1105 , the transmission control section  114  transmits transmission ultrasonic waves. Specifically, in step S 1105 , the transmission control section  114  causes the plurality of transmitting devices  220  to transmit the transmission ultrasonic waves in predetermined order at the transmission frequencies in the transmission information stored in the storage unit  120 . In addition, after the transmission of the transmission ultrasonic waves, the transmission control section  114  changes the transmission states included in the transmission information regarding the plurality of transmitting devices  220  stored in the storage unit  120 , to “transmitted.” 
     As described above, an example has been illustrated in which the frequency determining section  112  of the ultrasonic sensor  10  in the foregoing third embodiment determines the reception order of the ultrasonic waves of the reception frequencies received by the first and second receiving devices, according to the transmission order of the ultrasonic waves of the transmission frequencies transmitted from the first and second transmitting devices. In the third embodiment, a configuration in which ultrasonic waves are transmitted or received simultaneously, for example, instead of in the transmission order or the reception order described above may also be adopted. For example, transmission ultrasonic waves of different transmission frequencies may simultaneously be transmitted from the first and second transmitting devices, and the frequency determining section  112  may determine whether or not the reception ultrasonic waves received by the first and second receiving devices are received simultaneously. Note that, in this case, when the frequency determining section  112  determines whether or not the reception ultrasonic waves received by the first and second receiving devices are received simultaneously, the reception ultrasonic waves received by the first and second receiving devices do not need to be received perfectly simultaneously. The frequency determining section  112  may determine whether or not the reception ultrasonic waves received by the first and second receiving devices are received simultaneously with a margin of a predetermined period of time provided. 
     As described above, the transmission control section  114  of the ultrasonic sensor  10  in the third embodiment controls the transmitting device  220  such that the transmitting device  220  successively transmits a first transmission ultrasonic wave of the first transmission frequency and a second transmission ultrasonic wave of the second transmission frequency. Further, the receiving section  111  receives a first reception ultrasonic wave and a second reception ultrasonic wave from the plurality of receiving devices  210  configured to receive a plurality of the reception ultrasonic waves. In addition, the frequency determining section  112  determines a result of comparing the first reception frequency of the first reception ultrasonic wave and the second reception frequency of the second reception ultrasonic wave with the first transmission frequency and the second transmission frequency. Moreover, when the first reception frequency is different from the first transmission frequency or when the second reception frequency is different from the second transmission frequency, the frequency switching section  113  switches the first transmission frequency, the second transmission frequency, the first reception frequency, and the second reception frequency to frequencies different from the first transmission frequency and the second transmission frequency. 
     With this configuration, the ultrasonic sensor  10  according to the third embodiment can determine whether or not there is crosstalk from another device, on the basis of the predetermined combination of the transmission frequencies and the reception frequencies. That is, in the third embodiment, the processing of determining and cancelling ultrasonic wave crosstalk from another device can efficiently be performed even after the transmission of the transmission ultrasonic waves from the transmitting devices  220 , and erroneous measurement due to the crosstalk can be prevented in actual distance measurement. 
     In addition, the transmission control section  114  of the ultrasonic sensor  10  in the third embodiment controls the transmitting devices  220  such that the transmitting devices  220  successively transmit a first transmission ultrasonic wave of the first transmission frequency and a second transmission ultrasonic wave of the second transmission frequency. In addition, the receiving section  111  receives a first reception ultrasonic wave and a second reception ultrasonic wave from the plurality of receiving devices  210  configured to receive a plurality of the reception ultrasonic waves. In addition, the frequency determining section  112  determines a result of comparing the first reception frequency of the first reception ultrasonic wave and the second reception frequency of the second reception ultrasonic wave with the first transmission frequency and the second transmission frequency. Further, when the first reception frequency and the second reception frequency are the same frequency as either the first transmission frequency or the second transmission frequency and when the first reception ultrasonic wave and the second reception ultrasonic wave are not received in the same timing, the frequency switching section  113  may switch the first transmission frequency, the second transmission frequency, the first reception frequency, and the second reception frequency to frequencies different from the first transmission frequency and the second transmission frequency. 
     With this configuration, the ultrasonic sensor  10  according to the third embodiment can determine whether or not there is crosstalk from another device, on the basis of the predetermined combination of the transmission frequencies and the reception frequencies. That is, in the third embodiment, the processing of determining and cancelling ultrasonic wave crosstalk from another device can efficiently be performed even after the transmission of the transmission ultrasonic waves from the transmitting devices  220 , and erroneous measurement due to the crosstalk can be prevented in actual distance measurement. 
     Other Embodiments 
     It is to be noted that the foregoing embodiments are an example of embodiments to be implemented. Therefore, it is needless to say that the present embodiment is not limited to the foregoing embodiments, and even in other embodiments, various changes can be made according to design or other requirements within a scope not deviating from technical concepts according to the present embodiment. 
     A method has been illustrated in which the ultrasonic sensor  10  in the foregoing third embodiment determines whether or not there is crosstalk, on the basis of the predetermined order (combination) of the plurality of transmission ultrasonic waves and the plurality of reception ultrasonic waves. For example, a predetermined code may be generated according to the combination of the transmission order of the plurality of transmission ultrasonic waves, and whether or not reception ultrasonic waves are received in the receiving devices  210  in the order of the predetermined code may be determined. For example, the transmission of an ultrasonic wave from the first transmitting device is represented by “0,” and the transmission of an ultrasonic wave from the second transmitting device is represented by “1.” In this case, when the transmission of ultrasonic waves from the first and second transmitting devices is performed four consecutive times, codes having 14 patterns, that is, “0001” to “1110” excluding “0000” and “1111,” can be generated. Further, when the number of times of transmission of ultrasonic waves from the first and second transmitting devices is increased, the number of applicable codes is also increased, so that even when systems of the same kind are used, for example, crosstalk can be prevented. 
     In addition, as described above, in the ultrasonic sensor control device  100  in the foregoing embodiment, the frequency determining section  112  compares the reception frequency of a reception ultrasonic wave and the transmission frequency of a transmission ultrasonic wave with each other, and determines whether or not the reception frequency and the transmission frequency are the same. The foregoing embodiment does not limit the configuration of the embodiment. For example, a configuration in which, with the use of an ultrasonic sensor  10  capable of changing a frequency characteristic, the frequency characteristic of the ultrasonic sensor  10  is changed on the basis of a result of reception determination may be applied to the ultrasonic sensor control device  100 . In addition, a configuration in which a plurality of ultrasonic sensors  10  using some dedicated frequencies determine the frequencies and change and use the frequencies may be adopted. Further, a configuration in which, with an ultrasonic sensor  10  capable of transmitting and receiving ultrasonic waves of frequencies in a wider range, the ultrasonic sensor control device  100  can selectively use a plurality of different frequencies practically by changing a driving waveform of the ultrasonic wave or applying a plurality of methods for analyzing received waveforms may be adopted. 
     In addition, a computer program (ultrasonic sensor control program) for causing a computer to perform the processing in the foregoing ultrasonic sensor control device  100  and a computer readable recording medium on which the program is recorded are included in the scope of the present embodiment. Here, any kind of the computer readable recording medium is available. Further, the above-described computer program is not limited to the program recorded on the above-described recording medium, and may be transmitted via a telecommunication line, a wireless or wire communication line, or a network typified by the Internet, for example.