Method for determining the functional status of a vehicle ultrasonic sensor

Abstract

A method for determining the functional state (FZ) of an ultrasonic sensor (2) for a vehicle (1) is disclosed, comprising: a) applying an electrical test signal (P) to the ultrasonic sensor (2) (S1); b) detecting an electrical response signal (A) from the ultrasonic sensor (2) (S2); c) determining a phase-frequency response (PF) including a phase angle (α) of the detected response signal (A) for the applied test signal (P) based on the excitation frequency (f) of the applied test signal (P) (S3); d) comparing a first phase angle (P1) below the resonance frequency (R) and a second phase angle (P2) above the resonance frequency (R) in at least the determined phase-frequency response (PF) with their respective expected phase angles (PE1, PE2) (S4); e) correcting the phase-frequency response (PF) determined based on the comparison (S5); and f) determining the functional state based on the corrected phase-frequency response (PFK). It includes a step (S6) of determining the state (FZ).

Description

Technology Field

[0001] The present invention relates to a method for determining the functional state of an ultrasonic sensor for a vehicle, a computer program product, a device, and a vehicle. Background Technology

[0002] Automotive ultrasonic sensors are designed to measure the distance to objects. In ultrasonic sensors, electroacoustic energy conversion occurs. Regardless of the physical principles of this energy conversion—which may be, above all, inherently mechanical induction, mechanical capacitance, mechanical limitation, magnetic limitation, or electrodeformability—any energy conversion element is susceptible to exposure to internally or externally induced changes; depending on the magnitude of such changes, this can lead to falsified measurement results or the failure of the entire sensor.

[0003] DE 10 2017 105 043 A1 describes a method in which an electrical test signal is generated and applied to an ultrasonic sensor, and at least one electrical characteristic parameter of the ultrasonic sensor affected by the electrical test signal is evaluated. Based on this evaluation, the transfer function of the ultrasonic sensor is determined and compared with a reference transfer function. Based on the comparison, the functional state of the ultrasonic sensor is determined. In particular, the transfer function is determined by an impedance frequency response, and the impedance frequency response (14) is provided to describe an electrical characteristic parameter (K) as a function of the phase angle (α) between the two, particularly as current and / or voltage.

[0004] Against this backdrop, the objective of the present invention is to provide an improved method for determining the functional state of an ultrasonic sensor for a vehicle.

[0005] According to the first aspect, a method for determining the functional state of an ultrasonic sensor for a vehicle is provided, and the method is,

[0006] a) a step of applying an electric test signal (P) to the ultrasonic sensor (2), and

[0007] b) a step of detecting an electrical response signal from an ultrasonic sensor, and

[0008] c) a step of determining a phase-frequency response including the phase angle of a detected response signal for an applied test signal (P) as a function of the excitation frequency of the applied test signal, and

[0009] d) a step of comparing a first phase angle (P1) below the resonant frequency and a second phase angle above the resonant frequency with each of the respective expected phase angles in at least the determined phase-frequency response, and

[0010] e) a step of correcting the phase-frequency response determined based on comparison, and

[0011] f) includes a step of determining the functional state based on the corrected phase-frequency response.

[0012] Ultrasonic sensors based on the resonance principle have a characteristic profile regarding the phase angle between the test signal and the response signal. Another finding is that the phase angle is less affected by transient effects than other electrical characteristic parameters such as voltage amplitude. Using the proposed method has the advantage of allowing the functional state of the ultrasonic sensor to be determined more reliably, as transient effects of the phase-frequency response can be compensated for.

[0013] For example, the functional state is the degree of contamination or freezing of the ultrasonic sensor's diaphragm or aging-related changes in diaphragm stiffness. Generally, the functional state may be related to any change in the mechanical properties of the ultrasonic sensor due to aging or other factors.

[0014] The ultrasonic sensor preferably comprises a diaphragm, a sound transducer element for vibration excitation and vibration detection (particularly a piezoelectric element), and a control and evaluation unit (particularly a microprocessor, e.g., an ASIC) configured to operate the sound transducer element for vibration excitation and vibration detection.

[0015] The vehicle can be an automobile, specifically a passenger car or a truck.

[0016] For example, the test signal is a harmonic signal, a step signal, a chirp signal, or a pulse signal. It is desirable that the applied test signal and the detected response signal be selected so as not to include an echo signal.

[0017] Preferably, the applied test signal contains current and the detected response signal contains voltage, but this situation may be reversed.

[0018] For example, the phase-frequency response may include an interval of -pi / 2 to +pi / 2.

[0019] The first and second phase angles in the test signal, or the frequencies underlying them, are selected in a manner that can fundamentally eliminate the associated transient effects. This means that even if transient effects occur around the resonant frequency, they do not affect the first and second phase angles or affect them only to a negligible degree. Therefore, the first and second phase angles allow for an undistorted comparison with the expected phase angles in each case (because transient effects can be suppressed). It is desirable for the expected phase angles to be stored in the ultrasonic sensor or the vehicle's data memory.

[0020] In particular, the correction involves a linear shift of the determined phase-frequency response. The correction may be associated with individual or all data points of the phase-frequency response.

[0021] According to one embodiment, the first and second phase angles are spaced apart from the resonant frequency by at least 20%, 30%, or 40% of the resonant frequency.

[0022] That is, the frequency of the test signal in which the first and second phase angles are detected is located at intervals from 0 to [resonant frequency - 20 to 40% × resonant frequency] and [resonant frequency + 20 to 40% × resonant frequency] to infinity. The inventors found that at the extreme frequencies selected from these values, transient effects do not occur or are negligible. That is, at the extreme frequencies, the operation of the ultrasonic sensor corresponds to a stationary state (i.e., a steady state). The expected phase angle also corresponds to the steady state. Thus, comparability is excellent. Furthermore, the correction factor determined from this comparison is reliable and can also be used to apply correction at the sampling point between the first phase angle and the second phase angle, as described below.

[0023] According to one embodiment, in step e), the first and second phase angles of the determined phase frequency response are corrected to their respective expected phase angles.

[0024] This means that the first phase angle and the second phase angle are mapped to the expected phase angle, respectively.

[0025] According to one embodiment, step e) includes correction of the phase-frequency response determined at a sampling point between a first phase angle and a second phase angle.

[0026] When mapping the first and second phase angles to the expected phase angle, a correction factor is determined. The correction at the sampling point is applied as a function of this correction factor. The phase-frequency response is generally affected by transient effects at the sampling point. Nevertheless, the stationary (steady-state) component of the signal can be reliably corrected using the correction factor.

[0027] According to additional embodiments, the correction performed at the first and second phase angles and / or sampling points is affine-linear.

[0028] This can improve the correction results.

[0029] According to an additional embodiment, in step f), the parameters of the state model of the ultrasonic sensor are determined using the corrected phase-frequency response, and the functional state is determined based on a comparison between the determined parameters and the expected parameters.

[0030] It is desirable for the state model to be a purely static model of the ultrasonic sensor. This means that transient effects are not taken into account. Such a model or its parameters can be calculated quickly. The predicted parameters are stored in the ultrasonic sensor or the vehicle's data memory. The parameters may represent, for example, the mechanical inertia, stiffness, or viscosity of the ultrasonic sensor or its individual components.

[0031] According to one embodiment, each expected phase angle and / or expected parameter is determined using a simulation model or a reference sensor.

[0032] Simulation models can be generated, in particular, in computer-aided design (CAD) programs. Specifically, simulation models can simulate the mechanical and / or thermodynamic behavior of ultrasonic sensors.

[0033] According to one embodiment, steps a) through f) are performed at the end of a production line where a vehicle including an ultrasonic sensor is manufactured, and / or at or immediately after each start of the vehicle.

[0034] The term "production line" refers to the production line of a vehicle manufacturer. "Starting a vehicle" means activating the functions necessary for driving, specifically turning on the ignition in the case of vehicles with internal combustion engines.

[0035] According to one embodiment, the ultrasonic sensor operates as a function of the detected functional state.

[0036] For example, vibration excitation of a sound transducer element occurs according to a determined functional state. Alternatively, the method by which an evaluation unit evaluates vibrations detected through the sound transducer element depends on the determined functional state. For example, distance detection or distance calculation for an ice-affected ultrasonic sensor (functional state: ultrasonic sensor is affected by ice) is performed differently compared to a state not affected by ice.

[0037] According to one embodiment, the state model has a first capacitor, a first inductor, and a first resistor connected in series with each other, and a second capacitor, a second inductor, and a second resistor connected in parallel.

[0038] This provides an accurate state model.

[0039] According to one embodiment, in step f), the correction is applied without using the amplitude-frequency response.

[0040] Since the amplitude-frequency response is relatively susceptible to unwanted transient effects, it can be advantageously eliminated.

[0041] According to one embodiment, in step f), the functional state is determined based on the corrected phase-frequency response and the detected temperature of the ultrasonic sensor or the vehicle environment.

[0042] By including temperature in the determination of the functional state, the results become more accurate.

[0043] Each "unit" (e.g., the control and evaluation unit or the unit referred to hereto below) may be implemented in hardware and / or software. If implemented in hardware, each unit may be in the form of, for example, a computer or a microprocessor. If implemented in software, each unit may be in the form of a computer program product, a function, a routine, an algorithm, a part of program code, or an executable object. Additionally, each unit mentioned herein may be in the form of a part of a vehicle's higher-level control system, such as a central control system and / or an ECU (Engine Control Unit).

[0044] A second aspect proposes a computer program product comprising instructions that cause the computer to perform the method described above when the program is executed by the computer.

[0045] Computer program products, such as computer program means, may be provided or transmitted as storage media, for example, such as memory cards, USB sticks, CD-ROMs, and DVDs, or in the form of files downloadable from a server on a network. This may be accomplished, for example, by transmitting a corresponding file containing the computer program product or computer program means over a wireless communication network.

[0046] According to a third aspect, a device for determining the functional state of an ultrasonic sensor for a vehicle is provided. This device includes

[0047] An excitation unit that applies an electrical test signal to the vehicle's ultrasonic sensor, and

[0048] A detection unit that detects an electrical response signal from an ultrasonic sensor, and

[0049] A determination unit that determines a phase-frequency response including the phase angle of a detected response signal for an applied test signal as a function of the excitation frequency of the applied test signal, and

[0050] A comparison unit that compares a first phase angle below the resonant frequency and a second phase angle above the resonant frequency with each of the respective expected phase angles in a determined phase-frequency response, and

[0051] A correction unit that corrects the phase-frequency response determined using comparison, and

[0052] It includes a determination unit for determining the functional state based on the corrected phase-frequency response.

[0053] According to the fourth aspect, a vehicle equipped with the aforementioned device is proposed.

[0054] The embodiments and features proposed for the first aspect apply equally to additional aspects, and vice versa.

[0055] Other possible embodiments of the present invention also include combinations of features or embodiments not explicitly mentioned above or below in connection with exemplary embodiments. In this case, those skilled in the art will add individual aspects as improvements or additions to each basic form of the present invention.

[0056] Further advantageous configurations and aspects of the present invention are the subject of the dependent claims and exemplary embodiments of the present invention described below. The present invention is described in more detail below based on preferred embodiments with reference to the accompanying drawings. Brief explanation of the drawing

[0057] FIG. 1 illustrates a plan view of a vehicle equipped with an ultrasonic sensor according to one embodiment. Figure 2 illustrates a device used in a vehicle. FIG. 3 illustrates a phase-frequency response according to one embodiment. FIG. 4 illustrates an equivalent circuit diagram according to one embodiment. FIG. 5 illustrates a flowchart according to one embodiment. Unless otherwise specified, identical or functionally identical elements in the drawings are provided using the same reference numerals. Specific details for implementing the invention

[0058] FIG. 1 illustrates a vehicle (1) designed, for example, in the form of a passenger car. The vehicle (1) includes an ultrasonic sensor (2), which may be part of a driver assistance system not illustrated in detail, and is used in particular to measure the distance between the vehicle (1) and an object (3). To this end, the ultrasonic sensor (2) emits ultrasonic waves (4), which are reflected by the object (3) and received back by the ultrasonic sensor (2). Based on the transmitted and received ultrasonic waves (4), the ultrasonic sensor (2) generates measurement data and transmits it to a central vehicle control unit (5) ("Electronic Control Unit"—also referred to as ECU for short). This can be done via a vehicle data bus.

[0059] Measurement data may change due to environmental influences, aging, or other factors. To measure distance as accurately as possible even when considering these factors, these influences must be entered into the distance measurement.

[0060] Accordingly, it is desirable that the functional state of the ultrasonic sensor (2) be determined at regular intervals, for example, while manufacturing the vehicle (1) at the end of the production line, and at the start or after starting each vehicle, i.e., after the onboard network is turned on. This functional state may be, for example, "the sensor is affected by ice" or "the piezoelectric element is aged." Generally, the functional state may consist of characterizing the ultrasonic sensor (2) or a part thereof by comparing it with an actual reference sensor (here, obtaining and comparing empirical values) or a simulation model (here, in the context of simulation, calculating and comparing values ​​using, for example, a CAD computer program).

[0061] To this end, the device (6) is provided at any other point of the vehicle control unit (5) or the vehicle (1). The device (6) is illustrated in more detail in FIG. 2 and may be implemented in hardware and / or software in the vehicle control unit (5). Alternatively, the device (6) and the ultrasonic sensor (2) may be formed within a common housing and / or at least partially on the same printed circuit board (PCB) and / or at least partially on the same microchip (in each case not illustrated).

[0062] The device (6) includes an excitation unit (61), which is designed to apply an electrical test signal (P) to an ultrasonic sensor (2), specifically a sound transducer element (not shown). This corresponds to method step S1 shown in FIG. 5.

[0063] The sound transducer element is, for example, a piezoelectric element. The transducer element acts on the diaphragm of the ultrasonic element (2) to generate vibrations based on a test signal (P). The test signal (P) includes, in particular, a time-dependent profile of current amplitude in the form of a chirp, for example.

[0064] Essentially, simultaneously with method step S1, the detection unit (62) of the device (6) detects the response signal (A) (Figs. 2 and 4) of the ultrasonic sensor (2) (see method step S2 of Fig. 5). According to an exemplary embodiment, this consists of a detected voltage that drops across the ultrasonic sensor (2), in particular, the sound transducer element.

[0065] Additionally, the device (6) includes a determination unit (63). This is designed to determine the phase frequency response (PF), indicated by the dashed line in FIG. 3, in step S3 (Fig. 5). This means that the relative phase angle (angle α (degrees), vertical coordinate in FIG. 3) between the test signal (P) and the response signal (A) is determined as a function of the frequency of the test signal P (also referred to as the “excitation frequency” here - f (in kHz), horizontal coordinate in FIG. 3). The excitation frequency includes an interval containing the resonant free frequency (R) (Fig. 3) of the ultrasonic sensor (2), in particular the diaphragm and sound transducer elements. In an exemplary embodiment, the resonant frequency (R) is 52 kHz, and the limits of the excitation interval (also referred to here as the “polar frequencies” Eu and Eo) are 30 kHz (Eu) at the lower limit and 90 kHz (Eo) at the upper limit. At the lower pole frequency (Eu) (e.g., 30 kHz), the phase-frequency response has a first phase angle (P1), and at the upper pole frequency (Eo), it has a second phase angle (P2). The first and second phase angles (P1, P2) and the pole frequencies underlying them are advantageously spaced apart from the resonance frequency (R) by 40% of their value. In this case, the distances to the pole frequencies (Eu and Eo) are 22 kHz and 38 kHz, respectively, both greater than 52 kHz x 40% = 20.8 kHz. The advantage is that the ratio of transient effects in the phase-frequency response at these pole frequencies is low. The amplitude-frequency response is advantageously not detected because it is much more sensitive to transients, but is not evaluated in any case.

[0066] The comparison unit (64) of the device (6) reads the first predicted phase angle (PE1) and the second predicted phase angle (PE2) from the data memory (7), which is likewise provided to the vehicle control unit (5), for example. The first and second phase angles (PE1, PE2) are preferably determined during the development of the ultrasonic sensor (2), or at least determined before the initial operation in the vehicle (1) for distance measurement. For example, these angles may be calculated using CAD or other simulation models or measured in a test using a reference sensor.

[0067] Then, in the method step (S4), the comparison unit (64) compares the first phase angle (P1) with the first predicted phase angle (PE1) and compares the second phase angle (P2) with the second predicted phase angle (PE2) to calculate the comparison result.

[0068] In the method step (S5), the correction unit (65) (Fig. 2) corrects the detected phase-frequency response (PF) based on the comparison result. According to an exemplary embodiment, an affine-linear transformation is determined to map a first phase angle (P1) to a first predicted phase angle (PE1) and a second phase angle (P2) to a second predicted phase angle (PE2). Based on this transformation (also referred to as a correction factor), the phase-frequency response (PF) is also proportionally corrected in an affine-linear manner at additional sampling points (S) between the pole frequencies Eu and Eo according to the location (i.e., frequency). For simplification, only one such sampling point is shown in Fig. 3. The phase angle (PS) at frequency (S) is mapped to the corrected phase angle (PSK). After correction at a plurality of additional sampling points (not shown), the corrected phase-frequency response (PFK) is obtained.

[0069] Additionally, the device (6) has a determination unit (66) (Fig. 2). This is designed to output a functional state (FZ) (Fig. 2) based on a corrected phase-frequency response (PFK) (method step (S6) of Fig. 5). For example, the functional state may be "sensor affected by ice". Alternatively, the functional state consists of one or more correction values ​​or similar values ​​and is used to correct distance data detected by the ultrasonic sensor (2) in the operation of the ultrasonic sensor (2) or the vehicle (1).

[0070] In particular, parameters of the state model (8) (here, equivalent circuit diagram) of the ultrasonic sensor (2) illustrated in FIG. 4 are determined. These are compared with expected parameters. In an exemplary embodiment, the state model (8) includes a capacitor (C1), an inductor (I1), and a resistor (R1) connected in series with respect to the test signal (P). Additionally, the state model (8) includes a capacitor (C2), an inductor (I2), and a resistor (R2) connected in parallel with respect to the test signal (P). Then, the determination unit (66) determines the parameters (C1, C2, I1, I2, R1, and R2) in such a way that a corrected phase frequency response (PFK) for the model is obtained. In an additional step, the determined parameters (C1, C2, I1, I2, R1, and R2) are compared with expected parameters (C1', C2', I1', I2', R1', and R2'). Based on the result of the comparison, the functional state (FZ) is determined. For example, the predicted parameters (C1', C2', I1', I2', R1', and R2') correspond to the ice influence state of the ultrasonic sensor (2). For example, the predicted parameters (C1', C2', I1', I2', R1', and R2') may be calculated using a CAD or other simulation model or measured in a test using a reference sensor. This is preferably done during the development phase of the ultrasonic sensor (2), or at least before initial operation in the vehicle (1) for distance measurement.

[0071] Preferably, the vehicle (1) includes a temperature sensor (9) that detects the temperature (T) of the vehicle environment (10). The detected temperature (T) is preferably used by a determination unit value (66) to further correct the determined parameters (C1, C2, I1, I2, R1 and R2). This correction can be performed, for example, using a lookup table or a conversion table. Then, by comparing with the expected parameters (C1', C2', I1', I2', R1' and R2'), the functional state (FZ) can be better determined.

[0072] Although the present invention has been described based on exemplary embodiments, it can be modified in many ways. Explanation of the symbols

[0073] 1 vehicle 2 ultrasonic sensors 3 objects 4 Ultrasound 5 Vehicle Control Unit 6 devices 61 Here Unit 62 detection units 63 Decision Units 64 comparison units 65 correction units 66 decision units 7 Data Memory 8-state model 9 temperature sensors 10 Vehicle Environment A response signal C1, C2 capacitors Eu, Eo extreme frequency f frequency FZ function status I1, I2 inductors P test signal P1, P2 phase angle PE1 Expected Phase Angle PE2 Expected Phase Angle PF Phase-Frequency Response PFK corrected phase-frequency response Phase angle of the PS sampling point Corrected phase angle of the PSK sampling point R resonance frequency R1, R2 resistors S sampling point T temperature α angle

Claims

Claim 1 A method for determining the functional state (FZ) of an ultrasonic sensor (2) for a vehicle (1), comprising: a) applying an electrical test signal (P) to the ultrasonic sensor (2) (S1); b) detecting an electrical response signal (A) from the ultrasonic sensor (2) (S2); c) determining a phase-frequency response (PF) including a phase angle (α) of the detected response signal (A) with respect to the applied test signal (P) as a function of the excitation frequency (f) of the applied test signal (P) (S3); d) comparing a first phase angle (P1) below the resonance frequency (R) and a second phase angle (P2) above the resonance frequency (R) in the determined phase-frequency response (PF) with their respective expected phase angles (PE1, PE2) (S4); e) correcting the determined phase-frequency response (PF) based on the comparison (S5); and f) the corrected phase-frequency A method comprising the step (S6) of determining the functional state (FZ) based on the response (PFK), wherein the first phase angle (P1) and the second phase angle (P2) are selected in a frequency range in which transient effects are eliminated. Claim 2 A method according to claim 1, characterized in that the first and second phase angles (P1, P2) are spaced apart from the resonant frequency (R) by at least 20%, 30%, or 40% of the resonant frequency (R). Claim 3 A method according to claim 1, characterized in that in step e), the first and second phase angles (P1, P2) of the determined phase-frequency response (PF) are corrected to the respective expected phase angles (PE1, PE2). Claim 4 A method according to claim 1, wherein step e) includes correction of the determined phase-frequency response (PF) at a sampling point (S) between the first and second phase angles (P1, P2). Claim 5 A method according to claim 4, wherein the correction applied at the first and second phase angles (P1, P2) and / or the sampling point (S) is affine-linear. Claim 6 A method according to claim 1, wherein in step f), the parameters (C1, C2, I1, I2, R1, R2) of the state model (8) of the ultrasonic sensor (2) are determined based on the corrected phase-frequency response (PFK), and the functional state (FZ) is determined based on a comparison of the determined parameters and the expected parameters (C1, C2, I1, I2, R1, R2). Claim 7 A method according to claim 6, wherein each of the above-mentioned expected phase angles (PE1, PE2) and / or the above-mentioned expected parameters (C1, C2, I1, I2, R1, R2) is determined using a simulation model or a reference sensor. Claim 8 A method according to claim 1, characterized in that steps a) to f) are performed at the end of a production line in which the vehicle (1) including the ultrasonic sensor (2) is manufactured, and / or at or immediately after each start of the vehicle (1). Claim 9 A method according to claim 1, wherein the ultrasonic sensor (2) is operated according to the determined functional state (FZ). Claim 10 A method according to claim 6, wherein the above-mentioned state model has a first capacitor (C1), a first inductor (I1), and a first resistor (R1) connected in series with each other, and a second capacitor (C2), a second inductor (I2), and a second resistor (R2) connected in parallel. Claim 11 A method according to claim 1, characterized in that in step f), the correction is performed without using an amplitude-frequency response. Claim 12 A method according to claim 1, wherein in step f), the functional state (FZ) is determined based on the corrected phase-frequency response (PFK) and the detected temperature (T) of the ultrasonic sensor (2) or the vehicle environment (10). Claim 13 A computer program stored on a computer-readable storage medium, comprising instructions that cause the computer to perform the method described in any one of claims 1 to 12 while the program is executed by the computer. Claim 14 A device for determining the functional state (FZ) of an ultrasonic sensor (2) for a vehicle (1), comprising: an excitation unit (61) for applying an electrical test signal (P) to the ultrasonic sensor (2); a detection unit (62) for detecting an electrical response signal (A) from the ultrasonic sensor (2); a determination unit (63) for determining a phase-frequency response (PF) including a phase angle (α) of the detected response signal (A) for the applied test signal (P) as a function of the excitation frequency (f) of the applied test signal (P); a comparison unit (64) for comparing a first phase angle (P1) below the resonance frequency (R) and a second phase angle (P2) above the resonance frequency (R) in the determined phase-frequency response (PF) with their respective expected phase angles (PE1, PE2); a correction unit (65) for correcting the determined phase-frequency response (PF) using the comparison; and based on the corrected phase-frequency response (PFK). A device comprising a determination unit (66) for determining the above functional state (FZ), wherein the first phase angle (P1) and the second phase angle (P2) are selected in a frequency range in which transient effects are eliminated. Claim 15 A vehicle (1) equipped with the device (6) described in paragraph 14.

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