Method of operating an ultrasonic sensor, computer program product, ultrasonic sensor system and vehicle

Abstract

A method for operating an ultrasonic sensor (2) comprising a membrane (3) and an exciter element (4); the method comprising: obtaining (S1) calibration data from a storage unit (9) storing the calibration data, the calibration data comprising a first frequency response (FR1) of the ultrasonic sensor in a sending direction (SD) as a function of a membrane excitation frequency at different membrane temperatures and a second frequency response (FR2) of the ultrasonic sensor in a receiving direction (RD) as a function of a membrane vibration frequency at different membrane temperatures; determining (S2) a current membrane temperature; determining (S3) a sensitivity of the ultrasonic sensor using the first and second frequency responses at the current membrane temperature; and controlling (S4) a current provided to the exciter element and / or a gain of the ultrasonic sensor based on a difference between the determined sensitivity and a pre-stored sensitivity.

Description

Technical Field

[0001] The present invention relates to a method for operating an ultrasonic sensor, a computer program product, an ultrasonic sensor system, and a vehicle having such an ultrasonic sensor system. Background Technology

[0002] Ultrasonic sensors can be used in vehicles to determine the distance between the vehicle and objects located around it. Such ultrasonic sensors may include a housing and an ultrasonic diaphragm disposed in an opening in the housing. The ultrasonic sensor can be used to measure the distance to objects in the vehicle's environment based on a pulse-echo method. In this process, the ultrasonic diaphragm is excited by an exciter element attached thereto, emitting energy in the form of an ultrasonic signal. The exciter element then detects the vibration of the ultrasonic diaphragm caused by the echo signal returning from the vehicle's environment. The distance to the object is determined based on the signal propagation time. This measurement is used, for example, by parking assist systems in motor vehicles. It is known that temperature affects the sensitivity of ultrasonic sensors.

[0003] DE 10 2012 002979A1 illustrates an ultrasonic sensor according to the above description. A temperature-dependent oscillator is used as the exciter element to compensate for the signal propagation time according to the ambient temperature of the ultrasonic sensor.

[0004] In DE 10 2009 039 083 A1, the ambient temperature of the ultrasonic sensor is determined by observing the ultrasonic vibration of the membrane and comparing it with a reference value.

[0005] The ultrasonic sensor described in DE 10 2012 215 493 A1 includes a temperature sensor. Different thresholds are set for different temperature values ​​measured by the temperature sensor, and echo signals are identified above said thresholds.

[0006] In US2007 / 0157728 A1, temperature compensation is based on ambient temperature. Summary of the Invention

[0007] One object of the present invention is to improve the method of operating an ultrasonic sensor.

[0008] According to a first aspect, a method for operating an ultrasonic sensor is provided, particularly a method for operating an ultrasonic sensor for a vehicle. The ultrasonic sensor includes a diaphragm and an exciter element for exciting the diaphragm and / or detecting vibrations of the diaphragm. The method includes:

[0009] The calibration data is obtained from the storage unit storing the calibration data, which includes information about the first frequency response of the ultrasonic sensor (in particular the membrane) in the transmitting direction according to the membrane excitation frequency at different membrane temperatures and information about the second frequency response of the ultrasonic sensor (in particular the membrane) in the receiving direction according to the membrane vibration frequency at different membrane temperatures.

[0010] Determine the current membrane temperature;

[0011] The sensitivity of the ultrasonic sensor (the determined sensitivity) is determined using the first frequency response and the second frequency response at the current membrane temperature; and

[0012] The current supplied to the exciter element and / or the gain of the ultrasonic sensor are controlled based on the difference between the determined sensitivity and the pre-stored sensitivity.

[0013] Controlling the current supplied to the exciter element and / or the gain of the ultrasonic sensor allows for adjustment of the ultrasonic sensor's sensitivity to a given signal path. Specifically, the sensitivity can be modified to approach or reach a pre-stored sensitivity, which can be a target sensitivity. Advantageously, the sensitivity can be adjusted in a temperature-dependent manner, thereby improving the accuracy of sensitivity adjustment. The temperature dependence of the transfer function in the transmission direction and / or the temperature dependence of the transfer function in the receiving direction can be compensated separately. Robust temperature compensation is achieved across the entire film temperature spectrum.

[0014] Ultrasonic sensors can be used in vehicles to determine the distance between the vehicle and objects located around it. Vehicles can be passenger vehicles, such as cars, trucks, buses, trains, airplanes, etc. Ultrasonic sensors can also be part of parking assistance systems in motor vehicles.

[0015] An ultrasonic sensor may include a housing and an ultrasonic diaphragm (also referred to as a "diaphragm") disposed in an opening in the housing. The ultrasonic sensor can be used to measure the distance to objects in a vehicle environment based on a pulse-echo method. In this process, the ultrasonic diaphragm is excited by an exciter element attached thereto, emitting energy in the form of an ultrasonic signal. The exciter element then detects the vibration of the ultrasonic diaphragm, which originates from the echo signal returned from an object in the vehicle environment. The distance to the object is determined based on the signal propagation time.

[0016] The temperature of the membrane (also known as "membrane temperature") alters its properties, thus affecting the sensitivity of an ultrasonic sensor. In other words, the transfer function of an ultrasonic sensor (expressed as gain over a frequency range) changes with temperature.

[0017] To calibrate the ultrasonic sensor, the temperature of the membrane is determined. The membrane temperature can be determined through calculation, especially when a temperature sensor is not directly attached to the membrane. The membrane temperature is membrane-specific and does not correspond to ambient temperature, room temperature, or the temperature around the ultrasonic sensor. Determining the precise temperature of the membrane allows for better compensation for the temperature dependence of membrane properties. Advantageously, the temperature dependence of sensitivity can be compensated for.

[0018] The expression "current temperature" refers to the actual or true temperature of the membrane at a specific point in time. The current temperature does not need to be continuously determined. Instead, it can be determined at predetermined time intervals, such as every minute, every few minutes, etc.

[0019] The steps of obtaining calibration data, determining the current temperature, determining the determined sensitivity, and / or controlling the current supplied to the exciter element and / or the gain of the ultrasonic sensor are preferably part of the calibration process (calibration phase) of the ultrasonic sensor, which is performed before the ultrasonic sensor is used in the operation process (operation phase).

[0020] Calibration data can be pre-stored data in a storage unit. Information about the first frequency can be stored as different curves or tables for each temperature. Information about the second frequency can be stored as different curves or tables for each temperature. Preferably, calibration data is determined individually for each ultrasonic sensor. The calibration data can be specific to the corresponding ultrasonic sensor and / or specific to the signal path (described further below). This increases the accuracy of determining and adjusting sensitivity.

[0021] The first frequency response of an ultrasonic sensor in the transmission direction, as a function of the membrane excitation frequency (which depends on the membrane excitation frequency), indicates how the transfer function of the ultrasonic sensor varies with frequency and temperature in the transmission direction. In the transmission direction, the transfer function indicates how the membrane's output varies with the excitation frequency from the exciter element. The first frequency response can be expressed in decibels (dB), or dimensionlessly, if the first frequency response is divided by the reference frequency response at room temperature, as described below. Frequency can be expressed in Hertz or kilohertz (Hz or kHz), and temperature can be expressed in degrees Celsius (°C). The transmission direction is the direction in which the ultrasonic sensor emits the ultrasonic signal.

[0022] The second frequency response of an ultrasonic sensor in the receiving direction, as a function of the membrane excitation frequency (which depends on the membrane excitation frequency), indicates how the transfer function of the ultrasonic sensor varies with frequency and temperature in the receiving direction. In the receiving direction, the transfer function indicates how the signal received at the exciter element varies with the membrane's vibration frequency. The second frequency response can be expressed in decibels (dB), or dimensionlessly, if the second frequency response is divided by the reference frequency response at room temperature, as described below. Frequency can be expressed in Hertz or kilohertz (Hz or kHz), and temperature in degrees Celsius (°C). The receiving direction is the direction in which the ultrasonic sensor receives ultrasonic signals, particularly echoes from ultrasonic signals previously emitted by the membrane and reflected back by an object.

[0023] The first frequency response at the current membrane temperature preferably includes a frequency-dependent first frequency response corresponding to the determined current membrane temperature (e.g., stored as a curve or table in calibration data). The second frequency response at the current membrane temperature preferably includes a frequency-dependent second frequency response corresponding to the determined current membrane temperature (e.g., stored as a curve or table in calibration data).

[0024] The sensitivity of an ultrasonic sensor is specifically the integral of the difference between the transfer function in the transmitting direction (represented by a first frequency response) and the transfer function in the receiving direction (represented by a second frequency response) multiplied by a predetermined weighting factor, which is performed over the entire (frequency) bandwidth or over the (frequency) bandwidth of interest for the sensitivity.

[0025] The determined sensitivity can be the current sensitivity of the ultrasonic sensor. In other words, the determined sensitivity can be the sensitivity of the ultrasonic sensor at a given point in time and at a given (e.g., current) film temperature.

[0026] The pre-stored sensitivity can be a predetermined sensitivity of the ultrasonic sensor or a sensitivity pre-stored in, for example, a storage unit or different storage devices. The pre-stored sensitivity can be a target sensitivity. The target sensitivity is preferably the same for several or all signal paths, particularly for multiple or all ultrasonic sensors of the same type. Having the same target sensitivity for multiple signal paths and / or ultrasonic sensors is advantageous because all these sensors will output the same signal when detecting the same object at the same distance. This then facilitates the analysis of the signals output by multiple ultrasonic sensors.

[0027] The current can be modified by a control unit that changes the current supplied to the exciter element based on the difference between a determined sensitivity and a pre-stored sensitivity. The current supplied to the exciter element instructs how the exciter element should excite the membrane. The ultrasonic signal output by the ultrasonic sensor can vary with the current. Changing the current modifies the output of the ultrasonic sensor, thereby modifying its sensitivity. Preferably, the current is adjusted to compensate for the difference between the determined sensitivity and the pre-stored sensitivity. In particular, in the current control step, the difference between the determined sensitivity and the pre-stored sensitivity is reduced. The "current control" step preferably includes current modification (adjustment).

[0028] For example, the greater the difference between the determined sensitivity and the pre-stored sensitivity, the greater the current modification in the "control" step. Preferably, the amount of current adjustment is proportional to the difference between the determined sensitivity and the pre-stored sensitivity. The amount of current adjustment can be provided by a model stored as a table, graph, etc. In particular, the model can indicate that a gain of X dB (corresponding to a given change in sensitivity) can be achieved by a change in Y amperes.

[0029] In an arrangement with multiple ultrasonic sensors, modifying the current supplied to the exciter element of the first ultrasonic sensor alters the signal received by any of the ultrasonic sensors from the first ultrasonic sensor. Therefore, modifying the current does not allow adjustment of the sensitivity of a single signal path, but only of multiple signal paths (one signal path corresponds to the path from transmitter to receiver). Modifying the current typically allows for coarse adjustment of the sensitivity.

[0030] Gain, particularly digital gain. Modifying the gain corresponds to multiplying the amplitude of the output signal of the ultrasonic sensor, i.e., the received signal, by a predetermined constant. The (digital) gain of the ultrasonic sensor, particularly the gain of a single signal path, can be directly adjusted by a gain adjustment section (which can be an ASIC) in the control unit. The ultrasonic signal output by the ultrasonic sensor can vary with the gain. Changing the gain can modify the output of the ultrasonic sensor, thereby modifying its sensitivity. Preferably, the gain is adjusted to compensate for the difference between the determined sensitivity and the pre-stored sensitivity. In particular, in the step of controlling the gain, the difference between the determined sensitivity and the pre-stored sensitivity is reduced. The step of "controlling the gain" preferably includes modifying (adjusting) the gain.

[0031] For example, the greater the difference between the determined sensitivity and the pre-stored sensitivity, the greater the amount of gain modification in the "control" step. Preferably, the amount of gain adjustment is proportional to the difference between the determined sensitivity and the pre-stored sensitivity. The amount of gain adjustment can be provided by a model stored as a table, curve, etc. In particular, the model can indicate that a change in sensitivity in M ​​Hz can be achieved by a change in N dB.

[0032] The gain can be modified individually for each signal path. As a result, gain adjustment allows for fine-tuning of the sensitivity of each ultrasonic sensor, especially for each signal path.

[0033] Any sensitivity of an ultrasonic sensor can be achieved through gain adjustment alone. However, significant gains modifications (e.g., exceeding 3 dB) negatively increase noise. Compensating for the difference between the determined sensitivity and the pre-stored sensitivity using both current and gain allows for sensitivity adjustment with sufficient amount (using current adjustment) and sufficient precision (using gain adjustment) while maintaining low noise. When the control steps involve controlling the current and controlling the gain, controlling the current is preferably performed before controlling the gain.

[0034] According to one embodiment, the current supplied to the exciter element and / or the gain of the ultrasonic sensor are controlled to compensate for the difference between the determined sensitivity and the pre-stored sensitivity.

[0035] Specifically, the current supplied to the exciter element and / or the gain of the ultrasonic sensor are controlled such that if the first and second frequency responses are remeasured after adjusting the current supplied to the exciter element and / or the gain of the ultrasonic sensor, the new determined sensitivity based on the new measurement results of the first and second frequency responses will be closer to the pre-stored sensitivity than the determined sensitivity determined before adjusting the current supplied to the exciter element and / or the gain of the ultrasonic sensor.

[0036] According to another embodiment, the method further includes controlling the membrane excitation frequency and / or detection frequency region, in which the ultrasonic sensor is configured to detect membrane vibration based on obtained calibration data and a determined current membrane temperature.

[0037] Therefore, the temperature dependence of the transfer function in the transmission direction and / or the temperature dependence of the transfer function in the reception direction can be compensated separately in a frequency-dependent manner. Advantageously, the temperature dependence of the film excitation frequency and / or detection frequency regions can be compensated separately.

[0038] The step of controlling the membrane excitation frequency and / or detection frequency is preferably part of the calibration process of the ultrasonic sensor, which is performed before the ultrasonic sensor is used during operation.

[0039] The membrane excitation frequency can be the frequency at which the exciter element excites the membrane to emit an ultrasonic signal.

[0040] Controlling the membrane excitation frequency can correspond to controlling and / or changing the excitation frequency of the exciter element that excites the membrane. Preferably, the membrane excitation frequency is controlled such that, for the current membrane temperature, the sensitivity of the ultrasonic sensor in the transmission direction is maximized. In particular, the membrane excitation frequency is modified to match the excitation frequency with the highest first frequency response for the current temperature. The operation of the ultrasonic sensor in the transmission direction is thus improved, and in particular optimized.

[0041] The detection frequency region can be the area where the ultrasonic sensor is currently set to detect the received echo signal. Specifically, the exciter element can convert the signal received at the membrane into an electrical signal. The exciter element may include a filter that selects only the signal within a specific detection frequency region.

[0042] Controlling the detection frequency range can correspond to controlling and / or changing the detection frequency range of the current detection signal of the exciter element. Preferably, the detection frequency range is controlled such that the sensitivity of the ultrasonic sensor in the receiving direction is maximized for the current membrane temperature. In particular, the detection frequency range is modified to include and / or match the excitation frequency with the highest second frequency response for the determined current temperature. The operation of the ultrasonic sensor in the receiving direction is thus improved, and in particular optimized.

[0043] According to another embodiment, determining the determined sensitivity includes calculating the integral of the difference between a first frequency response and a second frequency response at the current membrane temperature multiplied by a frequency-related weighting factor, the integral being performed over the frequency bandwidth of interest.

[0044] In other words, the sensitivity is calculated by performing the following integral: ∫[FR1(f)–FR2(f)]*h(f)df, where f is the frequency, FR1(f) is the frequency-dependent first frequency response, FR2(f) is the frequency-dependent second frequency response, and h(f) is the frequency-dependent weighting factor. The weighting factor is pre-calculated for the bandwidth of interest. For example, the bandwidth of interest corresponds to the low chirp (44–50 kHz) or high chirp (52–58 kHz) range of the ultrasonic sensor. The weighting factor can be different for different bandwidths of interest.

[0045] According to another embodiment,

[0046] The first frequency response of an ultrasonic sensor is its first frequency response to a predetermined signal path in the transmission direction.

[0047] The second frequency response of the ultrasonic sensor is the second frequency response of the ultrasonic sensor to the predetermined signal path in the receiving direction, and

[0048] Determining the sensitivity of an ultrasonic sensor corresponds to determining the sensitivity of a predetermined signal path.

[0049] A signal path specifically corresponds to the path from the transmitter to the receiver (either a transmitter and receiver within the same ultrasonic sensor or between a transmitter and receiver from different ultrasonic sensors). A membrane that transmits ultrasonic signals can form a transmitter. A membrane that receives ultrasonic signals can form a receiver.

[0050] According to another embodiment, the method further includes:

[0051] Calibration data are empirically determined by measuring the frequency response of the ultrasonic sensor in the transmitting direction while changing the membrane excitation frequency, and performing these measurements at different membrane temperatures, and / or by measuring the second frequency response of the ultrasonic sensor in the receiving direction while changing the membrane vibration frequency, and performing these measurements at different membrane temperatures.

[0052] To determine the frequency response in the transmission direction, a measuring microphone placed at a predetermined distance from the ultrasonic sensor can be used. The microphone detects the intensity of the ultrasonic signal emitted by the membrane in the transmission direction. The microphone detects the ultrasonic signal intensity as the excitation frequency of the membrane varies within a predetermined frequency range, particularly as it varies continuously or incrementally. This frequency scan or variation can be repeated at different temperatures, for example, using a climate chamber. The ultrasonic signal intensities detected at different frequencies and temperatures can correspond to or be used to determine a first frequency response.

[0053] To determine the frequency response in the receiving direction, a loudspeaker placed at a predetermined distance from the ultrasonic sensor can be used. The loudspeaker can emit a reference ultrasonic signal simulating an echo, which is received by the diaphragm in the receiving direction. While the frequency of the reference ultrasonic signal emitted by the loudspeaker varies, particularly continuously, within a predetermined frequency range, an exciter element detects the intensity of the ultrasonic signal detected at the diaphragm. This frequency scan can be repeated at different temperatures, for example, using a climate chamber. The ultrasonic intensities detected at different frequencies and temperatures can correspond to a second frequency response, or be used to determine the second frequency response.

[0054] According to another embodiment, during the empirical determination of calibration data, the membrane excitation frequency and / or membrane vibration frequency vary between 10 kHz and 100 kHz, particularly between 40 and 70 kHz, and particularly between 42 and 62 kHz.

[0055] The membrane excitation frequency and / or membrane vibration frequency can be varied continuously, particularly by performing a frequency sweep. Alternatively, the frequency response can be measured only for discrete values ​​of the membrane excitation frequency and / or membrane vibration frequency, for example, in increments of 1, 2, or 5 kHz. Calibration data may include information on a first and / or second frequency response for various membrane excitation frequencies and / or membrane vibration frequencies, particularly between 40 and 70 kHz, and more particularly between 42 and 62 kHz.

[0056] According to another embodiment, the calibration data includes information on a first frequency response and / or a second frequency response at various temperatures between -40°C and 90°C or between -30°C and 80°C, wherein the various temperatures are in increments of 5°C or 10°C.

[0057] During the empirical determination of calibration data, the aforementioned frequency response measurements can be performed for different temperatures within the aforementioned range and increments.

[0058] According to another embodiment, the steps of determining the current temperature of the membrane and controlling the current supplied to the exciter element, the gain of the ultrasonic sensor, the membrane excitation frequency and / or the detection frequency range are performed multiple times during the operation phase of the ultrasonic sensor, particularly on the same ultrasonic sensor.

[0059] The operation phase can be a period during which the ultrasonic sensor is used to determine the distance to an object, especially when it is not switched off. Specifically, the ultrasonic sensor can be recalibrated to maintain good sensor sensitivity when the membrane temperature changes. The same calibration data can be used for each calibration, thus reducing calibration work.

[0060] According to another embodiment, the steps of determining the current temperature of the membrane and controlling the current supplied to the exciter element, the gain of the ultrasonic sensor, the membrane excitation frequency and / or the detection frequency range are performed at regular time intervals during the operation phase of the ultrasonic sensor, particularly every minute, two minutes, five minutes or ten minutes.

[0061] These steps can also be performed twice per hour, once per hour, etc. It is advantageous to perform the steps of determining the current membrane temperature, controlling the current supplied to the exciter elements, the gain of the ultrasonic sensor, the membrane excitation frequency, and / or the detection frequency range at regular intervals, because the calibration of the ultrasonic sensor can be adjusted as the current temperature changes. This allows for maintaining high sensitivity of the ultrasonic sensor.

[0062] According to another embodiment, the calibration data is stored as a table in the storage unit.

[0063] It is convenient to store calibration data in a table because it requires very little storage space.

[0064] According to a further embodiment,

[0065] For each different membrane temperature, the first frequency response includes the ratio of the frequency response of the ultrasonic sensor in the transmission direction at the predetermined membrane temperature to the frequency response of the ultrasonic sensor in the transmission direction at room temperature; and / or

[0066] For each different membrane temperature, the second frequency response includes the ratio of the frequency response of the ultrasonic sensor in the receiving direction at the predetermined membrane temperature to the frequency response of the ultrasonic sensor in the receiving direction at room temperature.

[0067] Room temperature can represent the membrane temperature at 20°C.

[0068] According to a second aspect, a computer program product including instructions is provided, which, when executed by a computer, cause the computer to perform a method according to the first aspect or an embodiment of the first aspect.

[0069] Computer program products, such as computer program devices, can be implemented as memory cards, USB sticks, CD-ROMs, DVDs, or files that can be downloaded from a server on a network. For example, such files can be provided by transmitting files including computer program products from a wireless communication network.

[0070] According to a third aspect, an ultrasonic sensor system is provided. The ultrasonic sensor system includes:

[0071] An ultrasonic sensor, comprising a membrane and an actuator element for exciting the membrane and / or for detecting vibrations of the membrane;

[0072] A storage unit is used to store calibration data, which includes information about a first frequency response of the ultrasonic sensor in the transmitting direction at different membrane temperatures, depending on the membrane excitation frequency, and information about a second frequency response of the ultrasonic sensor in the receiving direction at different membrane temperatures, depending on the membrane vibration frequency.

[0073] Temperature determination unit, used to determine the current temperature of the membrane;

[0074] A sensitivity determination unit is used to determine the sensitivity of the ultrasonic sensor (the determined sensitivity) using a first frequency response and a second frequency response at the current membrane temperature; and

[0075] The control unit is used to control the current supplied to the exciter element and / or the gain of the ultrasonic sensor based on the difference between the determined sensitivity and the pre-stored sensitivity.

[0076] The storage unit, temperature determination unit, sensitivity determination unit, and / or control unit can be implemented as hardware and / or software. The temperature determination unit, sensitivity determination unit, and / or control unit can be housed in a single ASIC (Application-Specific Integrated Circuit). The ultrasonic sensor system can be configured to perform the method according to the first aspect or an embodiment of the first aspect. The embodiments and features described with reference to the method of the first aspect, with necessary modifications in detail, are applicable to the ultrasonic sensor system according to the third aspect.

[0077] According to a fourth aspect, a vehicle is provided that includes an ultrasonic sensor system according to a third aspect for determining the distance to an obstacle (or object).

[0078] The embodiments and features described with reference to the ultrasonic sensor system in the third aspect are applicable to vehicles according to the fourth aspect, with necessary modifications.

[0079] Other possible embodiments or alternative solutions of the present invention also include combinations of features described above or below with respect to the embodiments (not expressly mentioned herein). Those skilled in the art can also add individual or separate aspects and features to the most basic form of the invention. Attached Figure Description

[0080] Other embodiments, features, and advantages of the invention will become apparent from the accompanying drawings, the following description, and the dependent claims, in which:

[0081] Figure 1 A vehicle including an ultrasonic sensor system is shown;

[0082] Figure 2 It shows Figure 1 Ultrasonic sensor system;

[0083] Figure 3 The empirical determination of the frequency response in the transmission direction is shown;

[0084] Figure 4 The ratio of the first frequency response at -40°C to the first frequency response at room temperature is shown to depend on the relationship between frequencies;

[0085] Figure 5 An example of calibration data including information about the first frequency response is shown;

[0086] Figure 6 The empirical determination of the frequency response in the receiving direction is shown;

[0087] Figure 7 An example of calibration data including information about the second frequency response is shown;

[0088] Figure 8A method for operating an ultrasonic sensor according to a first embodiment is shown;

[0089] Figure 9 An example table showing how to adjust the current supplied to the exciter element and / or the gain of the ultrasonic sensor is shown; and

[0090] Figure 10 A method for operating an ultrasonic sensor according to a second embodiment is shown.

[0091] In the accompanying drawings, unless otherwise stated, the same reference numerals denote the same or functionally equivalent elements. Detailed Implementation

[0092] Figure 1 A vehicle 100, including an ultrasonic sensor system 1, is shown. Vehicle 100 is a car. Figure 1 Oriented in the right-hand side of the vehicle 100, the ultrasonic sensor system 1 is located on the right-hand side of the vehicle 100. The ultrasonic sensor system 1 is configured to determine the distance to obstacles or objects on the right side of the vehicle 100. Knowing the distance to these obstacles or objects is particularly useful for assisting the driver in parking and / or when the vehicle 100 is partially or fully autonomously driven.

[0093] exist Figure 2 The ultrasonic sensor system 1 is shown in more detail below. The ultrasonic sensor system 1 includes a housing 15 made of plastic material. On one side of the ultrasonic sensor system 1 (in... Figure 2 (on the lower side of the orientation), the housing 15 includes an opening 17 in which the ultrasonic diaphragm 3 is disposed. The diaphragm 3 is configured to transmit and receive ultrasonic signals.

[0094] The membrane 3 has an actuator element 4 connected thereto, which is a piezoelectric element. The actuator element 4 is configured to receive an electrical signal with a specific current and mechanically excite the membrane 3 accordingly. Furthermore, the actuator element 4 is configured to receive vibrations from the membrane 3 and convert them into electrical signals. The membrane 3 and the actuator element 4 form an ultrasonic sensor 2.

[0095] The ultrasonic sensor 2 uses a dual-chirped broadband signal. To ensure that the signal amplitude remains constant over the temperature range of the membrane 3, the behavior of the transfer function over the temperature range must be properly modeled. This is explained below.

[0096] Within the ultrasonic sensor system 1, the ultrasonic sensor system 1 also includes a printed circuit board (PCB) 7 on which a control unit 8, a storage unit 9, a temperature determination unit 11, and a sensitivity determination unit 18 are arranged. Units 8, 9, 11, and 18 can be embedded in an ASIC. The functions of these units 8, 9, 11, and 18 will be described below. The PCB 7 is connected to the exciter element 4 via contact elements 6 to transmit electrical signals to and / or receive electrical signals from it. Figure 2 In the example, contact element 6 is a wire.

[0097] Storage unit 9 is configured to store calibration data. The calibration data indicates how the ultrasonic sensor 2 responds to different membrane excitation frequencies in the transmitting direction SD at different temperatures, and how the ultrasonic sensor 2 responds to different membrane vibration frequencies in the receiving direction RD at different temperatures. (Refer to...) Figures 3 to 7 The content of the calibration data is described and determined empirically.

[0098] Figure 3 The settings for empirically determining the frequency response of ultrasonic sensor 2 in the transmission direction SD are shown. This empirical determination is used to determine the first frequency response FR1 included in the calibration data, as will be described below. The first frequency response FR1 is frequency-dependent.

[0099] like Figure 3 As shown, microphone 16 is placed in front of ultrasonic sensor system 1 at a distance d from ultrasonic sensor system 1. Microphone 16 is oriented in the propagation path of ultrasonic signal 10 emitted by diaphragm 3 along the transmission direction SD. Figure 3 The device is placed in a climate chamber (not shown) to change the temperature of membrane 3.

[0100] Microphone 16 is used to determine the intensity (e.g., in decibels) of the ultrasonic signal 10 arriving at microphone 16, while simultaneously changing the excitation frequency of diaphragm 3 by altering the electrical signal of exciter element 4. In other words, the frequency response FR of ultrasonic sensor 2 in the transmission direction SD is measured as a function of temperature and frequency. This measurement is repeated individually for each ultrasonic sensor 2 at different temperatures (in this example, between -40°C and 80°C, in increments of 20°C). Figure 3 In the example, the frequency varies continuously between 42 and 62 kHz.

[0101] As a result, for each discrete temperature value, the following was obtained: Figure 4 The curve shown. Figure 4 This is the curve for -40℃. In detail, Figure 4The ratio of the first frequency response FR1 (FR1(-40℃)) at -40℃ to the first frequency response FR1 (FR1(RT)) of membrane 3 at room temperature RT is shown as a function of the excitation frequency of membrane 3. This ratio is shown on the vertical axis and is dimensionless, while the excitation frequency is shown on the horizontal axis and is expressed in kHz. Here, "room temperature" RT refers to the membrane temperature of 20℃.

[0102] exist Figure 4 In the diagram, different curves represent four different measurements of FR1(-40℃) / FR1(RT), as a function of the membrane excitation frequency. The dashed line represents the median of the curve, 14.

[0103] Figure 5 This median value 14 of FR1(T) / FR1(RT) for each discrete temperature measured is shown. Figure 5 The graph shown represents the first frequency response FR1 of the ultrasonic sensor 2 in the transmission direction SD, and is stored in the storage unit 9 as part of the calibration data.

[0104] A similar empirical determination can be performed to determine the second frequency response FR2 on the receiving direction RD. For this purpose, the following method is used: Figure 6 Experience settings. For example... Figure 6 As shown, the speaker 12 is placed in front of the ultrasonic sensor system 1 at a distance d from the ultrasonic sensor system 1 (distance d can be equal to or different from the distance d). Figure 3 The distance d). The loudspeaker 12 is oriented such that the ultrasonic reference signal 13 emitted by the loudspeaker 12 along the receiving direction RD reaches the diaphragm 3 of the ultrasonic sensor system 1. Figure 3 The device is placed in a climate chamber (not shown) to change the temperature of membrane 3.

[0105] When the frequency of the reference signal 13 is changed by the loudspeaker 12, the electrical signal emitted by the exciter element 4 in response to the vibration of the diaphragm 3 upon receiving the reference signal 13 is analyzed to determine the intensity (e.g., in decibels) of the ultrasonic signal 13 arriving at the exciter element 4, thereby changing the diaphragm vibration frequency. In other words, the second frequency response FR2 of the ultrasonic sensor 2 in the receiving direction RD is measured as a function of temperature and frequency. For each individual ultrasonic sensor, this measurement is repeated at different temperatures (in this example, between -40°C and 80°C, in increments of 20°C). Figure 6 In the example, the frequency varies continuously between 42 and 62 kHz.

[0106] Similar to Figure 4 and Figure 5 , Figure 6 The experimental results Figure 7The second frequency response FR2 shown is stored in storage unit 9 as part of the calibration data. In detail, Figure 7 The median 14 of the ratio of the second frequency response FR2(FR2(T)) of sensor 2 as a function of frequency in the receiving direction at one of the discrete temperatures to the second frequency response FR2(FR2(RT)) in the receiving direction at room temperature (20°C) is shown.

[0107] For each ultrasonic sensor 2, the empirical determination of the first and second frequency responses FR1, FR2 is performed only once to determine its own calibration data. The stored calibration data can be directly used to calibrate the ultrasonic sensor 2 to consistently improve its sensitivity. See below for reference. Figure 8 Describe the calibration of ultrasonic sensor 2 using ultrasonic sensor system 1.

[0108] In detail, Figure 8 In step S1, calibration data is obtained from storage unit 9. Specifically, control unit 8 retrieves calibration data, which here includes data from... Figure 5 and 7 The curve graph.

[0109] This can be performed after, during, or before step S1. Figure 8 In step S2, the temperature determination unit 11 determines the current temperature of the membrane 3. This can be done through mathematical methods and / or using a temperature sensor. The determined temperature of the membrane 3 is then sent to the control unit 8.

[0110] In step S3, the sensitivity determination unit 18 uses the first frequency response FR1 and the second frequency response FR2 at the current membrane temperature to calculate the determined sensitivity of the ultrasonic sensor 2. Specifically, the sensitivity determination unit 18 calculates the integral of the difference between the first frequency response FR1 and the second frequency response FR2 at the current membrane temperature, multiplied by a weighting factor. This integral is performed over the frequency bandwidth of interest, for example, between 44 and 50 kHz (low channel chirp).

[0111] In other words, at the current membrane temperature determined in step S2, the membrane stored in [the membrane] is used. Figure 5 and 7 Based on the calibration data, the sensitivity determination unit 18 calculates the determined sensitivity as ∫(FR1(f)–FR2(f))*h(f)df, where f is the frequency, FR1(f) and FR2(f) correspond to the first and second frequency responses FR1 and FR2 and explicitly indicate their frequency dependence, and h(f) is a weighting factor. The weighting factor is pre-calculated for the bandwidth of interest.

[0112] In step S4, the control unit 8 calculates the sensitivity at 900Hz. Then, the control unit 8 adjusts the current supplied to the exciter element 4 and / or the gain of the ultrasonic sensor 2 to compensate for the difference between the sensitivity determined in step S3 and the pre-stored sensitivity. In other words, the control unit 8 adjusts the current supplied to the exciter element 4 and / or the gain of the ultrasonic sensor 2 to reduce the difference between the sensitivity of the ultrasonic sensor 2 and the pre-stored sensitivity.

[0113] If the sensitivity determined from step S3 is lower than the preset sensitivity, the control unit 8 increases the current to the exciter element 4, resulting in an increase in sensitivity. Similarly, if the sensitivity determined from step S3 is higher than the preset sensitivity, the control unit 8 decreases the current to the exciter element 4, resulting in a decrease in sensitivity.

[0114] To tune the sensitivity more precisely, the control unit 8 then individually adjusts (increases or decreases) the gain of each signal path of the ultrasonic sensor 2 by directly changing the settings of the gain adjustment unit set in the control unit 8.

[0115] Therefore, the sensitivity of the ultrasonic sensor 2 is adjusted to reduce the difference between the sensitivity of the ultrasonic sensor 2 and the pre-stored sensitivity, preferably until the sensitivity of the ultrasonic sensor 2 and the pre-stored sensitivity become equal to each other.

[0116] To adjust the current and / or gain, the control unit 8 can refer to the data stored in the storage unit 9 and... Figure 9 The table shown in the image. Figure 9 The table indicates the amount of modification to the current and / or gain performed by the control unit 8 based on the sensitivity determined from step S3. Figure 9 In the example, the target sensitivity (pre-stored sensitivity) is 1000Hz (1kHz).

[0117] Figure 9 The table is for each of the determined sensitivity values ​​determined in step S3. Figure 9 The left column indicates the amount of current modification and / or gain modification that the control unit 8 should perform to achieve the target sensitivity.

[0118] By observing how modifications to the current and / or gain supplied to the exciter element 4 alter the first and second frequency responses FR1 and FR2, and thus change the sensitivity of the ultrasonic sensor 2, the pre-determined... Figure 9 The table.

[0119] In the example above where the control unit 8 determines the sensitivity to be 900Hz in step S3, the current is adjusted by increasing the current by 0 (zero) mA and the gain is adjusted by increasing the current by 1 dB to achieve the target sensitivity of 1000Hz.

[0120] Figure 10 Another embodiment of a method for operating an ultrasonic sensor 2 is shown, which can be performed using the ultrasonic sensor 2. Steps S1-S4 are consistent with reference. Figure 8 The steps S1-S4 described are the same.

[0121] In step S5, the control unit 8 uses the membrane temperature obtained from the temperature determination unit 11 and the calibration data received from the storage unit 9 to control the ultrasonic sensor 2. Specifically, the control unit 8 controls the excitation frequency of the membrane 3 such that it matches the first frequency response FR1 at the determined temperature of the membrane 3. Figure 5 The highest frequency. Therefore, high sensitivity of the ultrasonic sensor 2 is achieved in the transmission direction SD.

[0122] Furthermore, the control unit 8 controls the detection frequency range of the ultrasonic device 2 such that it matches or includes the second frequency response FR2 at a defined temperature on the membrane 3. Figure 5 The highest frequency. Therefore, high sensitivity of the ultrasonic sensor 2 is achieved in the receiving direction RD.

[0123] Although the invention has been described with reference to preferred embodiments, it will be apparent to those skilled in the art that modifications can be made in all embodiments. For example, instead of storing the first and second frequency responses FR1, FR2 as graphs, they can be stored as tables, such as including only the highest frequency response for each temperature in the calibration data. Empirical determination of the first and second frequency responses FR1, FR2 can be performed using more or fewer different ultrasonic sensors 2 at different frequencies and / or temperature ranges and / or with different frequency and / or temperature increments.

[0124] Figure Labels

[0125] 1. Ultrasonic sensor system

[0126] 2. Ultrasonic sensor

[0127] 3. Membrane

[0128] 4. Actuator Components

[0129] 5. Internal

[0130] 6 Contact elements

[0131] 7 Printed Circuit Board

[0132] 8 Control Unit

[0133] 9 storage units

[0134] 10 Ultrasonic signal

[0135] 11 Temperature determination unit

[0136] 12 speakers

[0137] 13 Reference Signal

[0138] 14 median

[0139] 15. Outer shell

[0140] 16 microphones

[0141] 17 Opening

[0142] 18 Sensitivity Determination Unit

[0143] 100 vehicles

[0144] d Distance

[0145] FR1 First Frequency Response

[0146] FR2 Second Frequency Response

[0147] RD receiving direction

[0148] RT room temperature

[0149] SD transmission direction

[0150] S1-S5 method steps.

Claims

1. A method for operating an ultrasonic sensor (2), the ultrasonic sensor (2) comprising a diaphragm (3) and an exciter element (4) for exciting the diaphragm (3) and / or for detecting vibrations of the diaphragm (3); the method comprising: (S1) Calibration data is obtained from the storage unit (9) storing calibration data, the calibration data including information about the first frequency response (FR1) of the ultrasonic sensor (2) in the transmitting direction (SD) according to the membrane excitation frequency at different membrane temperatures and information about the second frequency response (FR2) of the ultrasonic sensor (2) in the receiving direction (RD) according to the membrane vibration frequency at different membrane temperatures. Determine (S2) the current membrane temperature; The sensitivity of the ultrasonic sensor (2) is determined (S3) by using the first frequency response (FR1) and the second frequency response (FR2) at the current membrane temperature; and The current supplied to the exciter element (4) and / or the gain of the ultrasonic sensor (2) are controlled (S4) based on the difference between the determined sensitivity and the pre-stored sensitivity.

2. The method according to claim 1, wherein, Control the current supplied to the exciter element (4) and / or the gain of the ultrasonic sensor (2) to compensate for the difference between the determined sensitivity and the pre-stored sensitivity.

3. The method according to claim 1 or 2, further comprising: Based on the obtained calibration data and the determined current membrane temperature, the membrane excitation frequency is controlled (S5) and / or the ultrasonic sensor (2) is set to a detection frequency range for detecting the vibration of the membrane (3).

4. The method according to claim 1 or 2, wherein, The sensitivity determined in (S3) includes calculating the integral of the difference between the first frequency response and the second frequency response at the current membrane temperature multiplied by a frequency-related weighting factor, the integral being performed over the frequency bandwidth of interest.

5. The method according to claim 1 or 2, wherein, The first frequency response (FR1) of the ultrasonic sensor (2) is the first frequency response of the ultrasonic sensor (2) in the transmission direction (SD) of the predetermined signal path. The second frequency response (FR2) of the ultrasonic sensor (2) is the second frequency response of the ultrasonic sensor (2) in the receiving direction (RD) of the predetermined signal path, and The sensitivity of the ultrasonic sensor (2) is determined (S3) to correspond to the sensitivity of the predetermined signal path.

6. The method according to claim 1 or 2, further comprising: The calibration data are empirically determined by measuring the first frequency response (FR1) of the ultrasonic sensor (2) in the transmitting direction (SD) while changing the membrane excitation frequency, and performing these measurements at different membrane temperatures, and / or by measuring the second frequency response (FR2) of the ultrasonic sensor (2) in the receiving direction (RD) while changing the membrane vibration frequency, and performing these measurements at different membrane temperatures.

7. The method according to claim 6, wherein, During the empirical determination of calibration data, the membrane excitation frequency and / or the membrane vibration frequency varied between 40 and 70 kHz.

8. The method according to claim 1 or 2, wherein, The calibration data includes information on the first frequency response (FR1) and / or the second frequency response (FR2) at various temperatures between -40°C and 90°C.

9. The method according to claim 3, wherein, The steps of determining the current membrane temperature and controlling the current output of the exciter element (4), the gain of the ultrasonic sensor, the membrane excitation frequency and / or the detection frequency range are performed multiple times during the operation phase of the ultrasonic sensor.

10. The method according to claim 9, wherein, During the operation phase of the ultrasonic sensor, steps are performed at regular time intervals to determine the membrane temperature and to control the current output by the exciter element (4), the gain of the ultrasonic wave, the membrane excitation frequency, and / or the detection frequency range.

11. The method according to claim 1 or 2, wherein, The calibration data is stored as a table in the storage unit (9).

12. The method according to claim 1 or 2, wherein, For each different membrane temperature, the first frequency response (FR1) includes the ratio of the frequency response (FR) of the ultrasonic sensor (2) in the transmission direction (SD) at the predetermined membrane temperature to the frequency response (FR) of the ultrasonic sensor (2) in the transmission direction (SD) at room temperature; and / or For each different membrane temperature, the second frequency response (FR2) includes the ratio of the frequency response (FR) of the ultrasonic sensor (2) in the receiving direction (RD) at the predetermined membrane temperature to the frequency response (FR) of the ultrasonic sensor (2) in the receiving direction (RD) at room temperature.

13. The method according to claim 7, wherein, During the empirical determination of calibration data, the membrane excitation frequency and / or the membrane vibration frequency varied between 42 and 62 kHz.

14. The method according to claim 8, wherein, The various temperatures are in increments of 10°C.

15. A computer program product comprising instructions that, when a computer executes the program, cause the computer to perform the method according to any one of the preceding claims.

16. An ultrasonic sensor system (1), comprising: An ultrasonic sensor (2) includes a membrane (3) and an exciter element (4) for exciting the membrane (3) and / or for detecting the vibration of the membrane (3). Storage unit (9) for storing calibration data, the calibration data including information about the first frequency response (FR1) of the ultrasonic sensor (2) in the transmitting direction (SD) according to the membrane excitation frequency at different membrane temperatures, and information about the second frequency response (FR2) of the ultrasonic sensor (2) in the receiving direction (RD) according to the membrane vibration frequency at different membrane temperatures; Temperature determination unit (11) is used to determine the current membrane temperature; Sensitivity determination unit (18) is used to determine the sensitivity of the ultrasonic sensor using a first frequency response (FR1) at the current membrane temperature and a second frequency response (FR2) at the current membrane temperature; and Control unit (8) is used to control the current supplied to the exciter element (4) and / or the gain of the ultrasonic sensor (2) based on the difference between the determined sensitivity and the pre-stored sensitivity.

17. A vehicle (100) comprising an ultrasonic sensor system (1) according to claim 16 for determining the distance to an obstacle.

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