Ultrasonic sensor control device, ultrasonic sensor

Abstract

To provide an ultrasonic sensor control device capable of suppressing an influence of direct waves of ultrasonic waves transmitted from a transmission device of an ultrasonic sensor.SOLUTION: An ultrasonic sensor control device 100 for controlling an ultrasonic sensor device for transmitting and receiving ultrasonic waves includes: a transmission control part 111; a reception part 112; and a device control part 113. The transmission control part 111 controls transmission of transmission ultrasonic waves at a first frequency via the ultrasonic sensor device. The reception part 112 receives reception ultrasonic waves via the ultrasonic sensor device. The device control part 113 controls the ultrasonic sensor device such that a transmission frequency of transmission ultrasonic waves and a reception frequency of reception ultrasonic waves become predetermined frequencies. The device control part 113 changes a reception frequency to a frequency differing from a first frequency during a first period at least including a transmission period of transmission ultrasonic waves.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic sensor control device and an ultrasonic sensor. [Background technology]

[0002] Conventionally, ultrasonic systems are known that measure the distance to an object by generating ultrasonic waves and measuring the time it takes for the reflected waves to return from the object. Furthermore, a method for reducing the influence of direct waves from an ultrasonic transmitter has been proposed for this ultrasonic system. Patent Document 1 discloses an ultrasonic sensor device that includes an ultrasonic transmitter that emits ultrasonic waves and an ultrasonic receiver that receives the ultrasonic waves. The ultrasonic sensor device disclosed in Patent Document 1 reduces the influence of reverberation from direct waves by using a threshold signal for the ultrasonic sound pressure and a mask signal for a mask period. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-156281 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the ultrasonic sensor device disclosed in Patent Document 1, it is necessary to adjust the threshold and mask period according to the distance to the expected object. Therefore, if there is an error or change in the setting of the threshold or mask period for the distance to the object, the accuracy of the distance measurement will decrease.

[0005] In view of the above circumstances, an object of the present invention is to provide an ultrasonic sensor control device that can suppress the influence of direct waves of ultrasonic waves transmitted from a transmitting device of an ultrasonic sensor. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, an ultrasonic sensor control device according to one aspect of the present embodiment is an ultrasonic sensor control device that controls an ultrasonic sensor device that transmits and receives ultrasonic waves, and includes a transmission control unit that controls the transmission of transmitted ultrasonic waves at a first frequency via the ultrasonic sensor device, a receiving unit that receives received ultrasonic waves via the ultrasonic sensor device, and a device control unit that controls the ultrasonic sensor device so that the transmission frequency of the transmitted ultrasonic waves and the reception frequency of the received ultrasonic waves become predetermined frequencies, and the device control unit changes the reception frequency so that the reception frequency becomes a frequency different from the first frequency during a first period that includes at least the transmission period of the transmitted ultrasonic waves.

[0007] An ultrasonic sensor according to another aspect of this embodiment includes an ultrasonic sensor device having a vibrating membrane that transmits and receives ultrasonic waves by vibration of the vibrating membrane, a transmission control unit that controls the transmission of transmitted ultrasonic waves at a first frequency via the ultrasonic sensor device, a receiving unit that receives received ultrasonic waves via the ultrasonic sensor device, and a device control unit that controls the ultrasonic sensor device so that the transmission frequency of the transmitted ultrasonic waves and the reception frequency of the received ultrasonic waves become predetermined frequencies, and the device control unit changes the reception frequency so that the reception frequency becomes a frequency different from the first frequency during a first period that includes at least the transmission period of the transmitted ultrasonic waves. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an ultrasonic sensor control device that can suppress the influence of direct waves of ultrasonic waves transmitted from a transmitting device of an ultrasonic sensor. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the configuration of an ultrasonic sensor control device according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating an example of the configuration of the ultrasonic sensor device according to the first embodiment. [Figure 3A] FIG. 3A is a diagram illustrating an example of frequency information according to the first embodiment. [Figure 3B] FIG. 3B is a diagram showing an example of transmission information and reception information according to the first embodiment. [Figure 4] FIG. 4 is a diagram for explaining the relationship between the control voltage and the frequency. [Figure 5A] FIG. 5A is a diagram for explaining a direct wave and reverberation in an ultrasonic sensor. [Figure 5B] FIG. 5B is a timing chart for explaining the processing in the ultrasonic sensor according to the first embodiment. [Figure 6] FIG. 6 is a flowchart illustrating an example of processing performed by the ultrasonic sensor control device according to the first embodiment. [Figure 7] FIG. 7 is a timing chart for explaining the processing in the ultrasonic sensor according to the second embodiment. [Figure 8] FIG. 8 is a flowchart illustrating an example of processing performed by the ultrasonic sensor control device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, this embodiment will be described with reference to the drawings. In the drawings described below, identical or similar parts are designated by identical or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and planar dimensions of each component may differ from the actual relationship. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Furthermore, it goes without saying that the drawings may include parts with different dimensional relationships and ratios.

[0011] Furthermore, the embodiments described below are merely examples of devices and methods for embodying the technical ideas, and do not specify the materials, shapes, structures, arrangements, etc. of the components. Various modifications can be made to the present embodiments within the scope of the claims.

[0012] A specific aspect of this embodiment is as follows.

[0013] <1> An ultrasonic sensor control device that controls an ultrasonic sensor device that transmits and receives ultrasonic waves, comprising: a transmission control unit that controls the transmission of transmitted ultrasonic waves at a first frequency via the ultrasonic sensor device; a receiving unit that receives received ultrasonic waves via the ultrasonic sensor device; and a device control unit that controls the ultrasonic sensor device so that the transmission frequency of the transmitted ultrasonic waves and the reception frequency of the received ultrasonic waves become predetermined frequencies, wherein the device control unit changes the reception frequency so that the reception frequency becomes a frequency different from the first frequency during at least a first period that includes a transmission period of the transmitted ultrasonic waves.

[0014] <2> The first period is a period including a transmission period of the transmitted ultrasonic wave and a second period after the transmission period ends. <1> The ultrasonic sensor control device according to claim 1.

[0015] <3> The second period is a predetermined period after the end of the transmission period, and is a period until the reverberation of the transmitted ultrasonic waves falls below a predetermined sound pressure. <2> The ultrasonic sensor control device according to claim 1.

[0016] <4> the device control unit changes the transmission frequency to a frequency different from the first frequency during a third period after the transmission period ends. <1> ~ <3> 10. The ultrasonic sensor control device according to claim 9, wherein:

[0017] <5> the device control unit sets a frequency different from the first frequency by changing the natural frequency of a vibration membrane provided in a transmitting device and / or a receiving device of the ultrasonic sensor device to a frequency that does not resonate with the first frequency. <1> ~ <4> 10. The ultrasonic sensor control device according to claim 9, wherein:

[0018] <6> an ultrasonic sensor comprising: an ultrasonic sensor device having a vibrating membrane that transmits and receives ultrasonic waves by vibration of the vibrating membrane; a transmission control unit that controls the transmission of transmitted ultrasonic waves at a first frequency via the ultrasonic sensor device; a receiving unit that receives received ultrasonic waves via the ultrasonic sensor device; and a device control unit that controls the ultrasonic sensor device so that the transmission frequency of the transmitted ultrasonic waves and the reception frequency of the received ultrasonic waves become predetermined frequencies, wherein the device control unit changes the reception frequency so that the reception frequency becomes a frequency different from the first frequency during a predetermined period that includes at least a transmission period of the transmitted ultrasonic waves.

[0019] (First embodiment) The configuration of an ultrasonic sensor 10 according to the first embodiment will be described with reference to FIG. 1. The ultrasonic sensor 10 according to the first embodiment includes an ultrasonic sensor control device 100 and an ultrasonic sensor device 200. The ultrasonic sensor 10 is a sensor that can transmit ultrasonic waves via the ultrasonic sensor device 200 and also receive ultrasonic waves via the ultrasonic sensor device 200. The ultrasonic sensor 10 is used, for example, in a ranging system that can measure the distance to an object by measuring the time of flight (TOF) between transmitting ultrasonic waves and receiving the reflected waves from the object. The ultrasonic sensor control device 100 will be described in detail below.

[0020] FIG. 2 shows an example of the configuration of an ultrasonic sensor device 200 used in the ultrasonic sensor 10. The ultrasonic sensor device 200 is an ultrasonic sensor device including a transmitting device 210 that transmits ultrasonic waves and a receiving device 230 that receives ultrasonic waves, and is configured by, for example, a transducer using the piezoelectric effect. In this embodiment, the transducer includes a piezoelectric element on each of the transmitting and receiving sides. On the transmitting side, the transducer applies a drive voltage to the piezoelectric element to vibrate the piezoelectric element, causing a vibrating membrane (not shown) in contact with the transmitting device 210 to vibrate, thereby generating a transmitted ultrasonic wave. On the receiving side, the piezoelectric element vibrates based on the vibration of the vibrating membrane (not shown), and the reception of a received ultrasonic wave of a predetermined frequency is detected by sensing an electrical signal generated by the vibration of this piezoelectric element.

[0021] The transmitting device 210 is configured as a vibrating body including a pair of electrodes, a piezoelectric film (not shown) sandwiched between the pair of electrodes, and a vibrating membrane. The example shown in FIG. 2 is a view seen from above in a direction perpendicular to the plane on which the transmitting device 210 and the receiving device 230 of the ultrasonic sensor device 200 are arranged, and shows the upper electrode, which is the uppermost of the pair of electrodes. The transmitting device 210 is configured in a stacked form in which the piezoelectric film (not shown) is sandwiched between the upper electrode and the lower electrode from above and below. The vibrating membrane is in contact with the lower electrode. That is, in this embodiment, the transmitting device 210 is configured in a stacked form in which the upper electrode, the piezoelectric film, the lower electrode, and the vibrating membrane are stacked in this order.

[0022] The pair of electrodes are formed using a thin film of a conductive metal such as platinum, molybdenum, iridium, or titanium. As described above, one electrode (upper electrode) is located above the piezoelectric film and connected to an electrode pad portion 211, which is a circuit pattern for applying a drive voltage to the upper electrode. Similarly, the other electrode (lower electrode) is located below the piezoelectric film and is electrically connected via wiring to an electrode pad portion 211 for the transmitting device 210, which is a circuit pattern for applying a drive voltage to the lower electrode.

[0023] The piezoelectric film is made of, for example, lead zirconate titanate (PZT). In addition to lead zirconate titanate, aluminum nitride (AlN), zinc oxide (ZnO), lead titanate (PbTiO3), or the like can also be used for the piezoelectric film.

[0024] The vibrating membrane is made of a thin film and is configured to be displaceable in the direction of the film thickness, that is, in the direction normal to the vibrating membrane.

[0025] A driving voltage (V_tx) sent from the ultrasonic sensor control device 100 is applied to the upper electrode and lower electrode of the transmitting device 210 via the electrode pad portion 211 of the transmitting device 210. In response to the driving voltage (V_tx) sent to the transmitting device 210, the piezoelectric element and the diaphragm vibrate, generating a transmitted ultrasonic wave.

[0026] Similar to the transmitting device 210, the receiving device 230 is configured as a vibrating body including a pair of electrodes, a piezoelectric film (not shown) sandwiched between the pair of electrodes, and a vibrating membrane. The receiving device 230 is configured in a stacked form in which the piezoelectric film (not shown) is sandwiched between an upper electrode and a lower electrode from above and below. The vibrating membrane is in contact with the lower electrode. That is, in this embodiment, the receiving device 230 is configured in a stacked form in which the upper electrode, the piezoelectric film, the lower electrode, and the vibrating membrane are stacked in this order.

[0027] When an ultrasonic wave of a predetermined frequency reaches the vibration membrane of the receiving device 230, a potential difference occurs between the upper electrode and the lower electrode of the receiving device 230, generating a predetermined voltage (V_rx). By detecting this voltage (V_rx), it becomes possible to receive the ultrasonic wave. The generated voltage (V_rx) is sent to the ultrasonic sensor control device 100 via the electrode pad part 231 of the receiving device 230.

[0028] In this embodiment, a signal (electrical signal) is generated between the electrodes of the receiving device 230 due to the positive piezoelectric effect, and the ultrasonic sensor control device 100 extracts this signal. In other words, the electrodes are used as a vibration sensor for sensing the electrical signal. Generally, the receiving frequency at which a vibration sensor is most sensitive is the resonant frequency of the vibrating body that serves as the sensing device. The system can achieve the most sensitive and comfortable state in response to external input by adjusting the resonant frequency of the vibrating body itself, which serves as the vibration sensor.

[0029] The ultrasonic sensor device 200 also includes a transmission frequency adjustment unit 220 that adjusts the transmission frequency of the transmitted ultrasonic waves transmitted from the transmitting device 210, and a reception frequency adjustment unit 240 that sets the reception frequency of the ultrasonic waves that can be received by the receiving device 230.

[0030] The transmission frequency adjustment unit 220 applies a predetermined voltage sent from the ultrasonic sensor control device 100 to the electrodes provided in the transmission frequency adjustment unit 220, thereby deforming the transmission frequency adjustment unit 220 and setting the frequency of the ultrasonic waves transmitted from the transmitting device 210.

[0031] Similarly, the receiving frequency adjustment unit 240 applies a predetermined voltage sent from the ultrasonic sensor control device 100 to the electrodes provided in the receiving frequency adjustment unit 240, thereby deforming the receiving frequency adjustment unit 240 and setting the frequency of the receiving ultrasonic waves that can be received by the receiving device 230.

[0032] By applying a predetermined voltage to the transmission frequency adjustment unit 220 and the reception frequency adjustment unit 240, it is possible to change the physical characteristics, such as the effective size and hardness, of the vibrating body including the piezoelectric element and the vibrating membrane. In this way, the ultrasonic sensor control device 100 can change the resonance frequency (natural frequency) of the vibrating body. In other words, by changing the natural frequency of the vibrating membranes provided in the transmitting device 210 and the receiving device 230 to a frequency that does not resonate with a certain frequency, it is possible to set a frequency different from this certain frequency as the transmission frequency and the reception frequency.

[0033] Returning to FIG. 1 , the ultrasonic sensor control device 100 will be described. The ultrasonic sensor control device 100 includes a control unit 110 and a storage unit 120. The ultrasonic sensor control device 100 may be configured as a general-purpose microcomputer including a CPU (central processing unit, control unit 110), a memory (storage unit 120), an input / output unit (not shown), and the like. In this case, a computer program for causing the microcomputer to function as the ultrasonic sensor control device 100 may be installed in the microcomputer. By executing the computer program, the microcomputer functions as multiple information processing circuits included in the ultrasonic sensor control device 100. Note that in this embodiment, an example is shown in which the multiple information processing circuits included in the ultrasonic sensor control device 100 are realized by software. However, it is also possible to configure the information processing circuits by providing dedicated hardware for executing each of the information processes described below. Alternatively, the multiple information processing circuits may be configured as separate hardware. Details of the control unit 110 will be described later.

[0034] The storage unit 120 is composed of a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, etc., and stores "frequency information," "transmission information," and "reception information." Specifically, the storage unit 120 stores the "frequency information" shown in FIG. 3A and the "transmission information" and "reception information" shown in FIG. 3B. The "frequency information," "transmission information," and "reception information" stored in the storage unit 120 may be configured as physically or logically separated areas in a single storage device. Alternatively, the storage unit 120 for each data may be configured to be provided in multiple physically different storage devices.

[0035] The "frequency information" stored in the storage unit 120 stores ultrasonic frequencies that the ultrasonic sensor 10 can handle. Specifically, the stored frequencies are ultrasonic frequencies that can be received by the receiving device 230 of the ultrasonic sensor device 200 and transmitted by the transmitting device 210. The frequency values ​​stored in the "frequency information" are set to a value that does not cause interference, taking into account factors such as Doppler shift and reception characteristics. For example, in the example shown in FIG. 3A, the first frequency, second frequency, and third frequency columns of the "frequency information" store 40 kHz, 45 kHz, and 50 kHz, which are separated by 5 kHz, respectively. The ultrasonic sensor control device 100 selects a frequency stored in the "frequency information" and transmits and receives ultrasonic waves.

[0036] Furthermore, the "frequency information" stores corresponding control voltages for realizing the first frequency, the second frequency, and the third frequency. In the example shown in FIG. 3A, 0 V, 3 V, and 6 V are stored as voltages corresponding to the first frequency, the second frequency, and the third frequency, respectively. For example, to apply the first frequency to the transmission ultrasound transmitted by the transmitting device 210, a voltage of 0 V is applied to the electrode pad section 221 of the transmission frequency adjustment section 220. Similarly, to apply the second frequency or the third frequency to the transmission ultrasound transmitted by the transmitting device 210, a voltage of 3 V or 6 V is applied to the electrode pad section 221 of the transmission frequency adjustment section 220.

[0037] FIG. 4 is a diagram illustrating the frequency characteristics for each control voltage. In FIG. 4, frequency waveforms F1, F2, and F3 show the frequency characteristics when the voltages are 0 V, 3 V, and 6 V, respectively. In this embodiment, the frequency at which the amplitude of frequency waveform F1 is maximum is referred to as the first frequency and has a value of 40 kHz. Similarly, the frequency at which the amplitude of frequency waveform F2 is maximum is referred to as the second frequency and has a value of 45 kHz. Furthermore, the frequency at which the amplitude of frequency waveform F3 is maximum is referred to as the third frequency and has a value of 50 kHz. As shown in FIG. 4, the characteristics of the waveform indicating the frequency amplitude differ depending on the corresponding control voltage.

[0038] Furthermore, the "frequency information" stores information about "distance measurement frequencies" that indicate which frequencies are used for distance measurement for each frequency set in the "frequency information." Here, the frequencies that fall under the "distance measurement frequencies" are the transmission frequencies of the ultrasonic waves transmitted by the ultrasonic sensor 10 and the reception frequencies that can be received as reflected waves from an object. In the example shown in FIG. 3A, a "○" is stored in the column for the frequency that falls under the "distance measurement frequencies." In this embodiment, the "distance measurement frequency" is, for example, the first frequency.

[0039] This "distance measurement frequency" can be set in advance, and may be configured, for example, by the user via an input / output unit of the ultrasonic sensor control device 100. Furthermore, this "distance measurement frequency" may be set to a frequency different from the first frequency to avoid interference with the ultrasonic frequencies of other systems. Even in this case, the "distance measurement frequency" may be configured to be set by the user via an input / output unit of the ultrasonic sensor control device 100.

[0040] The "transmission information" shown in Fig. 3B stores information related to the "transmission status" and "transmission frequency" of the transmitted ultrasonic waves from the transmitting device 210. The "transmission status" stores the transmission status of the transmitted ultrasonic waves from the transmitting device 210, such as before transmission, during transmission, or completed transmission. Furthermore, the "transmission frequency" stores the transmission frequency to be transmitted if before transmission, the transmission frequency being transmitted if during transmission, and the transmitted transmission frequency if transmission has completed. The example shown in Fig. 3B shows a state in which transmitted ultrasonic waves with a transmission frequency of a first frequency are being transmitted.

[0041] The "reception information" shown in FIG. 3B stores information related to the "reception status" and "reception frequency" of the received ultrasound in the receiving device 230. The "reception status" stores information related to whether or not the received ultrasound has been received, for example. Furthermore, the "reception frequency" stores the reception frequency that can be received by the receiving device 230. In the example shown in FIG. 3B, the reception frequency that can be received is the second frequency, and the reception status indicates that the received ultrasound has not yet been received.

[0042] Next, a description will be given of the functions of the control unit 110 of the ultrasonic sensor control device 100 shown in Fig. 1. The control unit 110 includes a transmission control unit 111, a receiving unit 112, and a device control unit 113 as its functions.

[0043] The transmission control unit 111 controls the transmission of the transmitted ultrasonic waves from the transmitting device 210. Specifically, the transmission control unit 111 causes the transmitting device 210 to transmit the transmitted ultrasonic waves at the "transmission frequency" of the "transmission information" (FIG. 3B) stored in the storage unit 120. The transmission control unit 111 also updates the "transmission status" of the transmission information stored in the storage unit 120 according to the transmission status of the transmitted ultrasonic waves.

[0044] The receiving unit 112 receives the received ultrasonic waves via the receiving device 230, and stores reception information relating to the received ultrasonic waves in the storage unit 120. Specifically, the receiving unit 112 receives the received ultrasonic waves via the receiving device 230 at the "reception frequency" of the "reception information" (FIG. 3B) stored in the storage unit 120, and stores content indicating "received" in the "reception status" of the reception information stored in the storage unit 120.

[0045] The device control unit 113 controls the transmission frequency adjustment unit 220 and the reception frequency adjustment unit 240 based on the "frequency information" (FIG. 3A) stored in the storage unit 120. In this embodiment, the first frequency is a frequency that can be received by the receiving device 230 and that corresponds to the transmitted ultrasonic waves transmitted by the transmitting device 210 and the received ultrasonic waves that are reflected waves of the transmitted ultrasonic waves. That is, in this embodiment, the frequency used for distance measurement by the ultrasonic sensor 10 (distance measurement frequency) is assumed to be the first frequency, and the following description will be given assuming that the frequency used for distance measurement by the ultrasonic sensor 10 is the first frequency. Note that the configuration of this embodiment is not limited to the first frequency, and the second frequency or the third frequency may be used as the frequency used for distance measurement by the ultrasonic sensor 10 (distance measurement frequency) to prevent interference with other systems.

[0046] In addition, the device control unit 113 can set the transmission frequency and reception frequency to a frequency different from the first frequency by changing the natural frequency of the diaphragm provided in the transmitting device 210 and / or the receiving device 230 to a frequency that does not resonate with the first frequency.

[0047] The processing of the ultrasonic sensor control device 100 according to the first embodiment will be described using Figures 5A and 5B. Figure 5A is a diagram for explaining the influence of a direct wave on an ultrasonic sensor of a comparative example to which this embodiment is not applied. Also, Figure 5B is a diagram for explaining the processing when the ultrasonic sensor control device 100 according to the first embodiment is applied.

[0048] In the comparative example shown in Fig. 5A, during the period from time T1 to time T2, the transmission control unit 111 outputs (applies) to the transmitting device 210 a drive voltage (V_tx) for driving the transmitting device 210. By outputting the drive voltage (V_tx) from the transmission control unit 111 to the transmitting device 210, a pulse wave as shown in "transmitted ultrasonic wave" is transmitted during the period from time T1 to time T3 in Fig. 5A. Note that in the comparative example shown in Fig. 5A, reverberation of the transmitted ultrasonic wave exists during the period from time T2 to time T3.

[0049] The transmitted ultrasonic waves between time T1 and time T3 are transmitted through the circuit board, reflected by a nearby housing, etc., and appear as direct waves in the received ultrasonic waves. The time it takes for the reflected waves to return after being reflected from the target varies depending on the distance to the target. The direct wave described above is generated in a fixed environment, and the time it takes to reach the receiving device 230 is almost constant. The vibration of the received ultrasonic wave is detected by the vibrating membrane of the receiving device 230, and the voltage appearing on V_rx is sent to the ultrasonic sensor control device 100. As a result, in the comparative example shown in FIG. 5A, the receiving device 230 receives the direct wave from time T1 to time T3. That is, the receiving device 230 receives the received ultrasonic wave at an earlier timing than the reflected ultrasonic wave received from time T4 to time T5. This results in an erroneous distance measurement in the comparative example shown in FIG. 5A, which does not apply this embodiment. Note that in the comparative example shown in FIG. 5A, the voltage (Vc_tx) for adjusting the transmission frequency of the transmitted ultrasonic wave is 0 V, and ultrasonic waves with a first frequency of 40 kHz are transmitted. Furthermore, in the comparative example shown in FIG. 5A, the voltage (Vc_rx) for adjusting the reception frequency of the received ultrasonic wave is 0 V, and ultrasonic waves with a first frequency of 40 kHz are received.

[0050] In the example of the ultrasonic sensor control device 100 according to the first embodiment shown in FIG. 5B, a predetermined voltage is applied to the voltage (Vc_rx) for adjusting the reception frequency of the received ultrasonic waves during the period up to time T3. In the example shown in FIG. 5B, the predetermined voltage is 3 V, and the reception frequency of the received ultrasonic waves is a second frequency (45 kHz). That is, during the period up to time T3, the reception frequency is set so that the receiving device 230 can receive the received ultrasonic waves of the second frequency, which is different from the first frequency, which is the frequency of the transmitted ultrasonic waves transmitted from the transmitting device 210. The period from time T1 to time T3 is a period that includes at least the transmission period of the transmitted ultrasonic waves. This period that includes at least the transmission period of the transmitted ultrasonic waves corresponds to the first period. Furthermore, the period from time T2 to time T3 is a predetermined period after the transmission of the transmitted ultrasonic waves, and is the period until the reverberation of the transmitted ultrasonic waves falls below a predetermined sound pressure. This predetermined period after the transmission of the transmitted ultrasonic waves corresponds to the second period.

[0051] In the period from time T1 to time T3 shown in FIG. 5B, the waveform of the received ultrasonic wave does not appear in V_rx, which indicates reception of the reception frequency. That is, it can be seen that the receiving device 230 does not receive the received ultrasonic wave in the period from time T1 to time T3. As a result, in the example shown in FIG. 5B, the transmitted ultrasonic wave transmitted in the period from time T1 to time T2 is received as a reflected wave in the period from time T4 to time T5. That is, in the example shown in FIG. 5B, it is shown that the ultrasonic sensor control device 100 can correctly measure the distance to the target.

[0052] (Outline of processing flow of ultrasonic sensor control device 100) Next, the flow of processing (ultrasonic sensor control method) in the ultrasonic sensor control device 100 will be shown using the flowchart shown in Figure 6. In the flowchart shown in Figure 6, processing also ends when the power is turned off or an interrupt to end processing is issued. In addition, in the following explanation of the flowchart, content that is the same as that described above in the explanation of the ultrasonic sensor control device 100 will be omitted or simplified. Note that, in determining each period, a timeout period measured by a timer (not shown) may be set, and processing may end with a timeout interrupt after the timeout period has elapsed.

[0053] In step S601, the device control unit 113 sets the transmission frequency to a first frequency. Specifically, the device control unit 113 sets the voltage (Vc_tx) of the transmission frequency adjustment unit 220 to the voltage of the first frequency (0 V). Note that the ultrasonic sensor device 200 in this embodiment transmits ultrasonic waves with a frequency of 40 kHz (ultrasonic waves of the first frequency) when the voltage (Vc_tx) of the transmission frequency adjustment unit 220 is 0 V.

[0054] In step S602, the device control unit 113 sets the reception frequency to the second frequency. Specifically, the device control unit 113 sets the voltage (Vc_rx) of the reception frequency adjustment unit 240 to the voltage of the second frequency (3 V). Note that the ultrasonic sensor device 200 in this embodiment is capable of receiving ultrasonic waves with a frequency of 45 kHz (ultrasonic waves of the second frequency) when the voltage (Vc_rx) of the reception frequency adjustment unit 240 is 3 V.

[0055] In step S603, the transmission control unit 111 starts transmitting the transmission ultrasonic waves. Specifically, the transmission control unit 111 applies a predetermined voltage to the transmitting device 210 of the ultrasonic sensor device 200, thereby transmitting the transmission ultrasonic waves from the transmitting device 210. In the example of Fig. 6, the ultrasonic waves transmitted in step S603 are ultrasonic waves of a first frequency of 40 kHz.

[0056] In step S604, the control unit 110 determines whether the transmission period of the transmitted ultrasonic waves has ended. Specifically, the control unit 110 determines whether the transmission period that has been determined in advance and stored in the storage unit 120 of the ultrasonic sensor control device 100 has ended. This transmission period may be configured to be set by the user via an input / output unit of the ultrasonic sensor control device 100. Alternatively, a value determined according to the characteristics of the ultrasonic sensor device 200 may be stored in advance in the storage unit 120 and used.

[0057] In step S604, if the control unit 110 determines that the transmission period of the transmitted ultrasonic waves has ended (step S604: YES), the process proceeds to step S605. On the other hand, in step S604, if the control unit 110 determines that the transmission period of the transmitted ultrasonic waves has not ended (step S604: NO), the process returns to step S603. That is, the control unit 110 repeats the process from step S603 until the transmission period ends.

[0058] In step S605, the control unit 110 determines whether a predetermined period has elapsed since the end of the transmission period. Note that this predetermined period includes a period during which reverberation of the transmitted ultrasonic waves exists. In step S605, if the control unit 110 determines that the predetermined period has elapsed (step S605: YES), the process proceeds to step S606. On the other hand, in step S605, if the control unit 110 determines that the predetermined period has not elapsed (step S605: NO), the process returns to step S605. That is, the control unit 110 repeats the process of step S605 from the end of the transmission period until the predetermined period has elapsed.

[0059] In step S606, the device control unit 113 sets the reception frequency to the first frequency. Specifically, the device control unit 113 sets the voltage (Vc_rx) of the reception frequency adjustment unit 240 to the voltage of the first frequency (0 V). It is assumed that the ultrasonic sensor device 200 in this embodiment can receive ultrasonic waves with a frequency of 40 kHz (ultrasonic waves of the first frequency) at (0 V). In other words, the device control unit 113 sets the voltage to a frequency that can receive ultrasonic waves transmitted from the ultrasonic sensor device 200 at the first frequency.

[0060] In step S607, the control unit 110 determines whether the reception period of the received ultrasonic waves has ended. The reception period of the received ultrasonic waves is determined in advance and stored in the storage unit 120. This reception period may be configured to be set by the user via an input / output unit of the ultrasonic sensor control device 100. Alternatively, a value determined according to the characteristics of the ultrasonic sensor device 200 may be stored in advance in the storage unit 120 and used.

[0061] In step S607, if the control unit 110 determines that the reception period of the received ultrasonic waves has ended (step S607: YES), the process proceeds to step S608. On the other hand, in step S607, if the control unit 110 determines that the reception period of the received ultrasonic waves has not ended (step S607: NO), the process returns to step S607. That is, the control unit 110 repeats the process of step S607 until the reception period ends.

[0062] In step S608, the control unit 110 determines whether the processing of the ultrasonic sensor control device 100 has ended. Specifically, it determines whether the processing of distance measurement in the ultrasonic sensor control device 100 has ended. In step S608, if the control unit 110 determines that the processing of the ultrasonic sensor control device 100 has ended (step S608: YES), the processing of the ultrasonic sensor control device 100 ends. On the other hand, in step S608, if the control unit 110 determines that the processing of the ultrasonic sensor control device 100 has not ended (step S608: NO), the processing returns to step S602, and the processing from step S602 is repeated.

[0063] As described above, the ultrasonic sensor control device 100 that controls the ultrasonic sensor device that transmits and receives ultrasonic waves according to the first embodiment includes a transmission control unit 111, a receiving unit 112, and a device control unit 113. The transmission control unit 111 controls the transmission of transmitted ultrasonic waves at a first frequency via the ultrasonic sensor device. The receiving unit 112 receives received ultrasonic waves via the ultrasonic sensor device. The device control unit 113 controls the ultrasonic sensor device so that the transmission frequency of the transmitted ultrasonic waves and the reception frequency of the received ultrasonic waves become predetermined frequencies. The device control unit 113 changes the reception frequency to a frequency different from the first frequency during at least a first period that includes a transmission period of the transmitted ultrasonic waves.

[0064] This allows the ultrasonic sensor control device 100 to suppress the influence of the direct waves of the ultrasonic waves transmitted from the transmitting device 210 of the ultrasonic sensor 10.

[0065] Furthermore, the first period in the ultrasonic sensor control device 100 according to the first embodiment is a period that includes the transmission period of the transmitted ultrasonic waves and the second period after the transmission period ends. This enables the ultrasonic sensor control device 100 to suppress the influence of the direct wave of the ultrasonic waves transmitted from the transmitting device 210 of the ultrasonic sensor 10, and further reduces the influence of reverberation of the transmitted ultrasonic waves transmitted from the transmitting device 210.

[0066] Furthermore, the second period in the ultrasonic sensor control device 100 according to the first embodiment is a predetermined period after the transmission period ends, and is a period until the reverberation of the transmitted ultrasonic waves falls below a predetermined sound pressure. This allows the ultrasonic sensor control device 100 to more reliably reduce the influence of reverberation of the transmitted ultrasonic waves transmitted from the transmitting device 210.

[0067] Furthermore, the device control unit 113 of the ultrasonic sensor control device 100 according to the first embodiment changes the natural frequency of the vibrating membrane provided in the transmitting device 210 and / or the receiving device 230 of the ultrasonic sensor device 200 to a frequency that does not resonate with the first frequency. That is, the device control unit 113 changes the natural frequency of the vibrating membrane provided in the transmitting device 210 and / or the receiving device 230 to a frequency that does not resonate with the first frequency, thereby making it possible to set a frequency different from the first frequency. In this way, the ultrasonic sensor control device 100 according to the first embodiment can suppress the influence of direct waves and reverberation of ultrasonic waves transmitted from the transmitting device 210 in the ultrasonic sensor 10 having a vibrating membrane.

[0068] (Second embodiment) As described above, one specific embodiment has been described, but the above-described embodiment is merely an example and is not intended to limit the scope of the embodiment. For example, the above-described embodiment exemplified a configuration in which the reception frequency of received ultrasonic waves is switched to a frequency different from the transmission frequency during the transmission period of the transmitted ultrasonic waves and during a predetermined period after the transmission period. Here, a configuration different from the first embodiment will be described for an ultrasonic sensor control device 100 according to a second embodiment in which the transmission frequency of the transmitted ultrasonic waves is changed after the transmission period of the transmitted ultrasonic waves to a frequency different from the transmission frequency of the transmitted ultrasonic waves transmitted during the transmission period.

[0069] FIG. 7 shows an example of a timing chart relating to the processing of transmitting and receiving ultrasonic waves in the ultrasonic sensor 10 according to the second embodiment. As shown in FIG. 7, in the second embodiment, at time T1, the transmission control unit 111 starts outputting a drive voltage (V_tx) to the transmitting device 210. At time T2, the transmission control unit 111 ends outputting the drive voltage (V_tx) to the transmitting device 210. At this time T2, when the output of the drive voltage (V_tx) from the transmission control unit 111 to the transmitting device 210 ends, a voltage of the second frequency (3 V) is applied to the voltage (Vc_tx) of the transmission frequency adjustment unit 220. In other words, the frequency of the transmitted ultrasonic waves is changed from the first frequency to the second frequency. During the period from time T2 to time T3, reverberation of the transmitted ultrasonic waves remains, but the frequency of the reverberation during this period is the second frequency, which is different from the first frequency, which is the receiving frequency after time T2. Therefore, the receiving unit 112 does not receive the reverberation of the direct wave from the transmitting device 210 during the period from time T2 to time T3.

[0070] At time T2, voltage (Vc_tx) of transmission frequency adjuster 220 is changed to the voltage (3 V) for the second frequency, and then, after a predetermined period has elapsed, voltage (Vc_tx) of transmission frequency adjuster 220 returns to the voltage (0 V) for the first frequency. This predetermined period may be, for example, until the next transmission of the transmission frequency from transmitting device 210. Note that the predetermined period from when voltage (Vc_tx) of transmission frequency adjuster 220 is changed to the voltage (3 V) for the second frequency at time T2 until when it returns to the voltage (0 V) for the first frequency corresponds to the third period.

[0071] Furthermore, in the second embodiment, the voltage (Vc_rx) of the reception frequency adjuster 240 is changed from the voltage (3 V) corresponding to the second frequency to the voltage (0 V) corresponding to the first frequency at time T2. In the second embodiment, reception ultrasonic waves of the first frequency can be received at time T2, but as described above, the voltage (Vc_tx) corresponding to the transmission frequency of the transmission frequency adjuster 220 is changed to the voltage (3 V) corresponding to the second frequency at time T2. Therefore, after time T2, the receiving device 230 does not receive reverberation. This makes it possible to receive reception ultrasonic waves immediately after transmitting the transmission ultrasonic waves, and therefore enables more accurate distance measurement of close-range objects, for example, without being affected by reverberation.

[0072] (Outline of processing flow of ultrasonic sensor control device 100) Next, the flow of processing (ultrasonic sensor control method) in the ultrasonic sensor control device 100 according to the second embodiment will be shown using the flowchart shown in FIG. 8. In the flowchart shown in FIG. 8, processing also ends when the power is turned off or an interrupt to end processing is issued. In the following description of the flowchart, the same content as that described above in the description of the ultrasonic sensor control device 100 will be omitted or simplified. Note that, in determining each period, a timeout period measured by a timer (not shown) may be set, and processing may end with a timeout interrupt after the timeout period has elapsed.

[0073] In step S801, the device control unit 113 sets the transmission frequency to a first frequency. Specifically, the device control unit 113 sets the voltage (Vc_tx) of the transmission frequency adjustment unit 220 to the voltage of the first frequency (0 V). Note that the ultrasonic sensor device 200 in this embodiment transmits ultrasonic waves with a frequency of 40 kHz (ultrasonic waves of the first frequency) when the voltage (Vc_tx) of the transmission frequency adjustment unit 220 is 0 V.

[0074] In step S802, the device control unit 113 sets the reception frequency to the second frequency. Specifically, the device control unit 113 sets the voltage (Vc_rx) of the reception frequency adjustment unit 240 to the voltage of the second frequency (3 V). Note that the ultrasonic sensor device 200 in this embodiment is capable of receiving ultrasonic waves with a frequency of 45 kHz (ultrasonic waves of the second frequency) when the voltage (Vc_rx) of the reception frequency adjustment unit 240 is 3 V.

[0075] In step S803, the transmission control unit 111 starts transmitting the transmission ultrasonic wave. Specifically, the transmission control unit 111 applies a predetermined voltage to the transmitting device 210 of the ultrasonic sensor device 200, thereby transmitting the transmission ultrasonic wave from the transmitting device 210. In the example of Fig. 8, the ultrasonic wave transmitted in step S803 is an ultrasonic wave of a first frequency of 40 kHz.

[0076] In step S804, the control unit 110 determines whether the transmission period of the transmitted ultrasonic waves has ended. Specifically, the control unit 110 determines whether the transmission period previously set in the storage unit 120 of the ultrasonic sensor control device 100 has ended. In step S804, if the control unit 110 determines that the transmission period of the transmitted ultrasonic waves has ended (step S804: YES), the process proceeds to step S805. On the other hand, in step S804, if the control unit 110 determines that the transmission period of the transmitted ultrasonic waves has not ended (step S804: NO), the process returns to step S803. That is, the control unit 110 repeats the process from step S803 until the transmission period ends.

[0077] In step S805, the device control unit 113 sets the transmission frequency to the second frequency. Specifically, the device control unit 113 sets the voltage (Vc_tx) of the transmission frequency adjustment unit 220 to the voltage of the third frequency (3 V). Note that, when the voltage (Vc_tx) of the transmission frequency adjustment unit 220 is 3 V, the ultrasonic sensor device 200 in this embodiment transmits ultrasonic waves with a frequency of 45 kHz (ultrasonic waves of the second frequency).

[0078] In step S806, the device control unit 113 sets the reception frequency to the first frequency. Specifically, the device control unit 113 sets the voltage (Vc_rx) of the reception frequency adjustment unit 240 to the voltage of the first frequency (0 V). Note that the ultrasonic sensor device 200 in this embodiment is capable of receiving ultrasonic waves with a frequency of 40 kHz (ultrasonic waves of the first frequency) when the voltage (Vc_rx) of the reception frequency adjustment unit 240 is 0 V.

[0079] In step S807, the control unit 110 determines whether the reception period of the received ultrasonic waves has ended. The reception period of the received ultrasonic waves is determined in advance and stored in the storage unit 120. This reception period may be configured to be set by the user via an input / output unit of the ultrasonic sensor control device 100. Alternatively, a value determined according to the characteristics of the ultrasonic sensor device 200 may be stored in advance in the storage unit 120 and used.

[0080] In step S807, if the control unit 110 determines that the reception period of the received ultrasonic waves has ended (step S807: YES), the process proceeds to step S808. On the other hand, in step S807, if the control unit 110 determines that the reception period of the received ultrasonic waves has not ended (step S807: NO), the process returns to step S807. That is, the control unit 110 repeats the process of step S807 until the reception period ends.

[0081] In step S808, the control unit 110 determines whether the processing of the ultrasonic sensor control device 100 has ended. Specifically, it determines whether the processing of distance measurement in the ultrasonic sensor control device 100 has ended. In step S808, if the control unit 110 determines that the processing of the ultrasonic sensor control device 100 has ended (step S808: YES), the processing of the ultrasonic sensor control device 100 ends. On the other hand, in step S808, if the control unit 110 determines that the processing of the ultrasonic sensor control device 100 has not ended (step S808: NO), the processing returns to step S801, and the processing from step S801 is repeated.

[0082] As described above, the device control unit 113 of the ultrasonic sensor control device 100 according to the second embodiment changes the transmission frequency to a frequency different from the first frequency during the third period after the end of the transmission period. This allows the ultrasonic sensor control device 100 to more reliably reduce the influence of reverberation on the transmitted ultrasonic waves transmitted from the transmitting device 210.

[0083] As described above, the device control unit 113 of the ultrasonic sensor control device 100 according to the second embodiment changes the reception frequency to the first frequency during the third period after the transmission period ends. This makes it possible to reliably receive the reflected wave while suppressing the effects of the direct wave and reverberation, even when the reflected wave arrives in a short time period in a distance measurement system for short distance measurement. As a result, by using the ultrasonic sensor 10 according to the second embodiment, it is possible to realize a more accurate distance measurement system.

[0084] In the second embodiment shown in FIG. 7, the transmission frequency is changed to the second frequency (45 kHz) at time T2, and the reception frequency until time T2 is the second frequency (45 kHz). However, this configuration does not limit the embodiment. For example, the transmission frequency may be changed to the third frequency (50 kHz) at time T2. Alternatively, the reception frequency until time T2 may be the third frequency (50 kHz). In this way, by using multiple frequencies other than the ranging frequency (first frequency), it is possible to further suppress the effects of direct waves and reverberation.

[0085] In the second embodiment shown in FIG. 7 , the voltage (Vc_rx) of the reception frequency adjuster 240 is changed from the voltage of the second frequency (3 V) to the voltage of the first frequency (0 V) at time T2. However, the embodiment is not limited to this configuration. For example, the voltage (Vc_rx) of the reception frequency adjuster 240 may be changed from the voltage of the second frequency (3 V) to the voltage of the first frequency (0 V) at time T3. By changing the voltage of the reception frequency adjuster 240 at the timing when the time has elapsed since the transmission frequency was changed at time T2 until it became stable, the influence of reverberation in the receiving device 230 can be reduced. Furthermore, the timing of the change in the voltage of the reception frequency adjuster 240 is not limited to time T2 or time T3. For example, the change may be made later than time T3 depending on the environment in which the ultrasonic sensor control device 100 is used. For example, a configuration in which the timing of voltage change in reception frequency adjuster 240 is time T3 can be realized by providing a process for allowing a wait time (lapse) to elapse between steps S805 and S806 in the flowchart shown in FIG. 8. This wait time may be, for example, 100 μs, which corresponds to four cycles of 400 kHz. Furthermore, this wait time is not limited to the embodiment, and may be set to a time shorter or longer than 100 μs. For example, in a distance measuring device for long-distance measurement, it takes time for a reflected wave to arrive, so a configuration can be used in which the effects of reverberation are further reduced.

[0086] (Other embodiments) The above-described embodiment is merely an example of an embodiment, and therefore, the present embodiment is not limited to the above-described embodiment, and various modifications can be made to other embodiments depending on the design, etc., as long as they do not deviate from the technical concept of the present embodiment.

[0087] Furthermore, the scope of this embodiment includes a computer program (ultrasonic sensor control program) that causes a computer to execute the processing in the ultrasonic sensor control device 100 described above, and a computer-readable recording medium on which the program is recorded. Any type of computer-readable recording medium may be used. Furthermore, the computer program is not limited to being recorded on the recording medium, and may be transmitted via a telecommunications line, a wireless or wired communication line, a network such as the Internet, or the like. [Explanation of symbols]

[0088] 10 Ultrasonic Sensor 100 Ultrasonic sensor control device 111 Transmission control section 112 Receiving unit 113 Device control unit 120 Storage section 200 Ultrasonic Sensor Device 210 Transmitting Device 220 Transmission frequency adjustment unit 230 receiving device 240 Receiving frequency adjustment unit 211, 221, 231, 241 Electrode pad section

Claims

1. An ultrasonic sensor control device that controls an ultrasonic sensor device that transmits and receives ultrasonic waves, a transmission control unit that controls transmission of ultrasonic waves at a first frequency via the ultrasonic sensor device; a receiving unit that receives ultrasonic waves via the ultrasonic sensor device; a device control unit that controls the ultrasonic sensor device so that a transmission frequency of the transmitted ultrasonic wave and a reception frequency of the received ultrasonic wave are predetermined frequencies; The device control unit changes the reception frequency so that the reception frequency is different from the first frequency during at least a first period including a transmission period of the transmitted ultrasonic wave.

2. The ultrasonic sensor control device according to claim 1 , wherein the first period includes a transmission period of the transmitted ultrasonic waves and a second period after the transmission period ends.

3. 3. The ultrasonic sensor control device according to claim 2, wherein the second period is a predetermined period after the end of the transmission period, and is a period until reverberation of the transmitted ultrasonic waves falls below a predetermined sound pressure.

4. The ultrasonic sensor control device according to any one of claims 1 to 3, wherein the device control unit changes the transmission frequency to a frequency different from the first frequency during a third period after the transmission period ends.

5. The device control unit sets a frequency different from the first frequency by changing the natural frequency of a vibrating membrane provided in a transmitting device and / or a receiving device of the ultrasonic sensor device to a frequency that does not resonate with the first frequency. An ultrasonic sensor control device according to any one of claims 1 to 4.

6. an ultrasonic sensor device that includes a vibrating membrane and transmits and receives ultrasonic waves by vibration of the vibrating membrane; a transmission control unit that controls transmission of ultrasonic waves at a first frequency via the ultrasonic sensor device; a receiving unit that receives ultrasonic waves via the ultrasonic sensor device; a device control unit that controls the ultrasonic sensor device so that a transmission frequency of the transmitted ultrasonic wave and a reception frequency of the received ultrasonic wave are predetermined frequencies, The device control unit changes the reception frequency so that the reception frequency is different from the first frequency during a predetermined period that includes at least a transmission period of the transmitted ultrasonic waves.

Images