Ultrasonic phased array sensor

Abstract

The invention relates to an ultrasonic phased array sensor (200), comprising a multi-layer structure (108), at least one first layer (108.1) having a membrane (104), at least one second layer (108.2) having a piezoelectric substrate (106), and at least one third layer (108.3) having a plurality of electrical contacts (102), the electrical contacts (102) are applied independently of one another on a surface (110) of the piezoelectric substrate (106).

Description

Technical Field

[0001] The invention relates to an ultrasonic phase array sensor having a diaphragm, a piezoelectric substrate and a plurality of electrical contacts, wherein the electrical contacts are applied independently of one another on the surface of the piezoelectric substrate. Background Art

[0002] The measuring principle of ultrasonic parking sensors is based on sound waves.

[0003] These sound waves are radiated into the inaudible range and reflected at obstacles. The ultrasonic parking sensor receives the reflected signal again and the electronics evaluate it by means of a time measurement (time of flight). In order to convert electrical energy into sound energy, piezoelectric elements are used in all ultrasonic parking sensors. However, these individual elements limit the area of ​​use of the parking sensor to the direction of the sound radiation. Other physical effects, such as lidar or radar, can also be used for parking sensors. However, ultrasound allows very cost-effective production of parking sensors.

[0004] In order to expand the sensor area of ​​ultrasonic sensors, ultrasonic phased array sensors have been used in medicine (ASSavoia, "Design, Fabrication, Characterization, and System Integration of a1-D PMUT Array for Medical Ultrasound Imaging", 2021 IEEE International Ultrasonics Symposium (IUS), page 4, 2021). These ultrasonic phased array sensors are based on the merging of single ultrasonic transducer arrays. By manipulating the individual ultrasonic transducer arrays in a phase-shifted manner, the radiation direction of the ultrasound waves can be changed. This makes it possible to scan volumes with the aid of ultrasonic phased array sensors and even perform acoustic imaging. According to today's prior art, air-coupled ultrasonic phased array sensors are not yet commercially available. So far, there are only research projects in this field ( D. Groβkurth, M. Rutsch, A. Unger, R. Golinske, H. Wang, S. Dixon, K. Hofmann, and M. Kupnik, “Aircoupled 40-kHz ultrasonic 2D-phasedarray based on a 3D-printed waveguide structure”, 2017 IEEE International Ultrasonics Symposium(IUS), page 4, 2017; G. Allevato, M. Rutsch, J. Hinrichs, M. Pesavento, and M. Kupnik, "Embedded Air-Coupled Ultrasonic 3D Sonar System with GPU Acceleration", 2020 IEEE SENSORS, p. 4, 2020; G. Allevato, M. Rutsch, J. Hinrichs, E. Sarradj, M. Pesavento, and M. Kupnik, “Spiral Air-Coupled Ultrasonic Phased Array for High Resolution 3D Imaging”, 2020 IEEE International Ultrasonics Symposium (IUS), page 4, 2020; E. Verreycken, W. Daems and J. Steckel, “Passive Akustik”. Steckel, “Passive Acoustic Sound Source Tracking in 3D Using Distributed Microphone Arrays”, 2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN), page 4, 20018) and start-ups (Toposens, Toposens, 2022, https: / / toposens.com / autonomous-parking / ). The commercial use of these systems in the automotive field has not yet arrived. All of these systems are based on the interconnection of multiple piezoelectric ultrasonic transducers. Since the cost of the sensor is proportional to the number of ultrasonic transducers, these solutions cannot be considered for cost-effective parking sensors. In addition, these systems are too large for the automotive field and cannot be produced compactly.

[0005] At present, electrode separation is only used in the case of surface acoustic waves (SAW) (Y.-n.YIN, W.WANG, Y.-n.JIA, X.-f.XUE and Y.LIANG, "Development of A Surface Acoustic Wave Delay Line Device for Sensing ICE", 2019 13th Symposium on Piezoelectric, Acoustic Waves and Device Applications (SPAWDA), page 4, 2019). Through comb electrodes, waves are emitted or received only on selected areas of the piezoelectric substrate. These SAWs are used to construct high-frequency filters or delay elements, which are not part of the present invention.

[0006] The invention proposed here is also significantly different from PMUT (piezoelectric, machined ultrasonic transducer) (S. Sadeghpour, E. Zilonova, J. D'Hooge and M. Kraft, "A Novel 6 MHz Phased Array Piezoelectric Micromachined Ultrasound Transducer (pMUT) with 128 Elements for Medical Imaging", 2021 IEEE International Ultrasonics Symposium (IUS), page 4, 2021, ASSavoia, "Design, Fabrication, Characterization, and System Integration of a 1-D PMUT Array for Medical Ultrasound Imaging", 2021 IEEE International Ultrasonics Symposium (IUS), page 4, 2021) because no clean room process is used here and therefore costs are saved. Summary of the invention

[0007] The function of an ultrasonic phased array sensor with a single piezoelectric element (hereinafter referred to as a piezoelectric substrate) is simulated to realize a novel parking sensor. In this case, the entire piezoelectric substrate with large-area electrodes is not irradiated, but the electrodes are isolated in order to excite individual areas of the piezoelectric substrate to vibrate. This constitutes a compact and cost-effective solution.

[0008] According to the present invention, an ultrasonic phased array sensor is proposed, which includes a multilayer structure, wherein at least one first layer has a diaphragm, at least one second layer has a piezoelectric substrate, and at least one third layer has a plurality of electrical contacts, wherein the electrical contacts are applied independently of one another on the surface of the piezoelectric substrate.

[0009] The diaphragm is a layer that serves as a separation layer between the medium to be measured and the sensor. In ultrasonic phase array sensors, a diaphragm is used in order to emit or receive ultrasonic waves. For example, the diaphragm is used as an ultrasonic transducer for converting mechanical vibrations into electrical signals.

[0010] The electrical contacts have a connection portion or attachment end for establishing an electrical signal between the piezoelectric material and an electronic circuit that controls the ultrasonic phased array sensor. For example, the electrical contacts are suitable for generating, detecting or processing electrical signals based on the piezoelectric properties of the substrate. The electrical contacts can be mounted on the piezoelectric substrate, for example in the form of leads, contact pins or soldered connections.

[0011] In the framework of the solution according to the invention, a plurality of regions of the piezoelectric substrate are provided with electrical contacts, wherein the electrical contacts can be controlled independently of one another. As a result, the regions connected by the contacts can be electrically controlled independently of one another and the direction of the ultrasonic radiation can be controlled. In addition, by independently controlling the contact surface via the electrical contacts, the detection area of ​​the sensor is significantly increased. On this basis, for example, a height classification of obstacles can be performed.

[0012] The use of a piezoelectric substrate proposed within the framework of the present invention is an important component of an ultrasonic phase array sensor. In this case, a material with piezoelectric properties is used. The piezoelectric property enables the material to generate an electric charge under mechanical load or deformation and, in turn, to undergo mechanical deformation under the application of a voltage. For example, in the case of generating ultrasonic waves, when a voltage is applied, the piezoelectric substrate deforms due to the piezoelectric property, and this deformation generates ultrasonic waves that propagate as sound waves. When the ultrasonic waves hit an object, these ultrasonic waves are reflected onto the piezoelectric substrate, wherein the reflected ultrasonic waves cause further deformation of the piezoelectric substrate, which is converted into a voltage. In this way, for example, the voltage can be measured and analyzed in order to obtain information about the object, for example, information about the distance between the object and the ultrasonic sensor.

[0013] In an advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the diaphragm is mechanically connected to the piezoelectric substrate.

[0014] A mechanical connection in the sense of the present invention is understood to mean that at least two structural elements are physically connected to each other. The mechanical connection of the piezoelectric substrate to the diaphragm includes different joining methods, such as anodic bonding or gluing, mechanical fastening or thermal bonding. The connection excites the diaphragm to vibrate locally and emits ultrasonic waves in the free medium.

[0015] In an advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the radiation angle can be varied by a phase shift.

[0016] The radiation angle is the angular range in which a radiation source, for example a radiation source of an ultrasonic phase array sensor, radiates into the surrounding space or is received by the surrounding space. The radiation angle is a certain angle between the main radiation axis, the main axis, of the radiation source and the boundary of the irradiated area. The radiation angle can be measured, for example, in degrees and can be shown, for example, in polar coordinates in an ultrasonic phase array sensor. The radiated sound pressure level is standardized (normiert) based on the maximum value (normalized sound pressure level (dB)). Due to the phase shift between the array elements, a change in the radiation direction occurs.

[0017] In an advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the radiation direction can be controlled by a phase shift.

[0018] According to the invention, a phase shift is understood to be a targeted adjustment of the temporal orientation of the emitted or detected ultrasound waves between the individual components of the ultrasound grid. A change in the phase shift can be used, for example, to steer, focus and control the ultrasound waves of the sensor in terms of their radiation characteristics. For example, by precise focusing, the spatial resolution can be improved.

[0019] The phase shift of each electrical contact is achieved by an electronic device. The electronic device comprises at least one function generator, which puts the resonance of the electrical contact into vibration. Then, a plurality of phase shifters (Phi_1, Phi_2, Phi_3) are controlled by the function generator, which change the phase of the control signal. The output of the phase shifter is electrically connected to each electrical contact. As a result, each electrical contact vibrates with a different phase, and the resulting radiation direction of the ultrasonic phase array sensor can be changed.

[0020] The radiation direction in the sense of the present invention is the targeted orientation of the ultrasonic waves emitted by the sound source of the ultrasonic phase array sensor. The energy flow of the ultrasonic waves can be precisely controlled by the radiation direction and thus a significant influence on the efficiency and flexibility of the sensor can be achieved. The control of the radiation direction can be achieved by a combination of the radiation angle and the phase shift. For example, if the radiation angle is changed in such a way that a change in the spatial propagation direction of the emitted energy is achieved, the phase shift leads to the realization of the following combination of the ultrasonic waves: the combination causes amplification in the desired radiation direction.

[0021] Thus, for example, an ultrasonic phased array sensor can be installed in a bumper of a vehicle, wherein the radiation direction can be controlled. Thus, for example, ultrasonic signals can be radiated at different angles.

[0022] In an advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the ultrasonic phased array sensor comprises an obstacle height measurement by means of a phase shift.

[0023] By means of the solution according to the invention, it is possible, for example, to radiate sound in a straight line direction with the same applied AC voltage. In addition, for example, by introducing an electrical phase shift, the radiation direction of the ultrasonic phase array sensor can be changed. Thus, obstacles can be acoustically identified, scanned and, for example, obstacle height measurements can be performed.

[0024] For example, an ultrasonic phased array sensor for obstacle height measurement can be installed in the bumper of a vehicle. Here, the ultrasonic wave is first radiated straight onto the obstacle. Through direct radiation, the maximum echo is received from the obstacle. Now, in order to measure the height of the obstacle, the angle of the ultrasonic wave radiation is increased until the ultrasonic wave misses the obstacle. Once the ultrasonic wave has passed the obstacle, the minimum received signal is detected and the height of the obstacle can be estimated.

[0025] In an advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the ultrasonic phased array sensor can be embodied in a plurality of geometric shapes: circular, rectangular, elliptical, triangular or square.

[0026] In an advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the number of electrical contacts can be selected arbitrarily.

[0027] In a further advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the electrical contacts are divided into individual, electrically separated regions, wherein each region or a plurality of individual regions can be individually actuated.

[0028] In a further advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the membrane provides protection against environmental influences, wherein the membrane comprises a moisture-proof and dust-proof material.

[0029] Furthermore, the invention relates to the use of an ultrasonic phased array sensor for automotive applications, wherein the ultrasonic phased array sensor is designed as a parking sensor.

[0030] Advantages of the present invention

[0031] In the ultrasonic phase array sensor according to the present invention, a piezoelectric substrate is used as an insert, and the piezoelectric substrate is divided into a plurality of regions, so that the regions can be electrically controlled independently of each other, and the radiation direction of the ultrasonic wave can be steered.

[0032] The ultrasonic phased array sensor according to the invention significantly increases the detection field (FOV) of the sensor. As a result, larger areas or volumes can be detected within a limited detection area. Thus, for example, in safety-critical applications requiring complete environmental detection, such as autonomous driving or parking, an increased detection field is provided compared to the prior art.

[0033] In addition, by the increased detection area of ​​the ultrasonic phased array sensor, obstacles can be identified early before they enter the direct detection area. In addition, by the increased detection area, the number of required sensors can be reduced. In addition, the increased detection area of ​​the ultrasonic phased array sensor according to the present invention enables flexible sensor placement and thus reduces the overall system complexity.

[0034] In addition, it is possible to carry out a height classification of obstacles. With the help of the height classification, a more accurate recognition of the parking space can be achieved, because the sensor not only monitors the horizontal position of the parking space, but also the height of the available space. When parking, the height classification helps to identify obstacles such as electric poles, curb edges or adjacent objects, so that parking in and out can be carried out without collision.

[0035] The invention described increases safety when parking. Thus, for example, children who are directly in front of, beside or behind the vehicle can be better identified. The same also applies to animals such as dogs and cats.

[0036] The invention is one of the cost-effective possibilities for ultrasonic phased array sensors. Since only one piezoelectric substrate is required, both the manufacturing costs and the material costs in production are very low compared to systems with multiple piezoelectric substrates.

[0037] Due to the wide reception area (FoV) of the invention shown compared to the prior art, the number of ultrasonic parking sensors required in a vehicle can be reduced. For example, for larger vehicles (station wagons, coupes and other vehicles), one sensor can be mounted centrally and two additional sensors can be mounted on the front or rear corners of the vehicle. Small vehicles can be equipped with only one centrally located sensor in order to further reduce costs.

[0038] With current ultrasonic parking sensors, false detections often occur due to strong acoustic echoes from the ground. In particular, in parking garages with multiple parking spaces or on driveways with rough surfaces, the sensor responds even though there are no obstacles. With the invention described, this problem can be solved because the direction of the reflection can be checked for plausibility. This improves the reliability of the ultrasonic parking sensor overall and reduces false detections. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Embodiments of the present invention are explained in more detail with reference to the drawings and the following description.

[0040] The accompanying drawings show:

[0041] Figure 1 A schematic diagram showing a cross section of an ultrasonic phase array sensor,

[0042] Figure 2 A schematic diagram showing an ultrasonic phase array sensor,

[0043] Figure 3 A schematic diagram showing a graph of sound pressure levels,

[0044] Figure 4 A schematic diagram showing a phase shifter attached to an ultrasonic phase array sensor,

[0045] Figure 5 A schematic diagram showing the radiation direction of an ultrasonic phase array sensor mounted on a vehicle,

[0046] Figure 6 Schematic diagram showing height obstacle measurement. DETAILED DESCRIPTION

[0047] In the following description of embodiments of the invention, identical or similar elements are denoted by the same reference numerals, wherein a repeated description of these elements is omitted in individual cases. The figures merely schematically illustrate the subject matter of the invention.

[0048] Figure 1 A schematic diagram of a cross section 100 of an ultrasonic phased array sensor 200 is shown, the cross section including a multi-layer construction 108 . Figure 1The illustrated multilayer structure 108 has a first layer 108.1, which is formed by a membrane 104. A second layer 108.2 has a piezoelectric substrate 106, and a third layer 108.3 has four electrical contacts 102, wherein the electrical contacts 102 are applied to a surface 110 of the piezoelectric substrate 106 at a distance 112 from one another.

[0049] Alternative Figure 1 For example, further electrical contacts 102 may be applied to surface 110 of piezoelectric substrate 106 , wherein distance 112 may be selected in a variable manner.

[0050] Figure 2 A schematic diagram of an ultrasonic phased array sensor 200 is shown. Figure 2 The ultrasonic phased array sensor 200 shown has a geometry 202, wherein the geometry 202 has a circular bottom surface. In addition, the ultrasonic phased array sensor 200 has a multilayer structure 108. The multilayer structure 108 shown has a first layer 108.1, which is formed by a diaphragm 104. The second layer 108.2 has a piezoelectric substrate 106, and the third layer 108.3, i.e. the inner layer, has three electrical contacts 102. Figure 2 The three electrical contacts 102 shown have different shapes.

[0051] For example, the geometric shape 202 of the piezoelectric substrate 106 may be square, rectangular, circular, or elliptical. The number of electrical contacts 102 may also be increased or decreased arbitrarily.

[0052] Figure 3 The diagram 300 shows a schematic diagram of a sound pressure level. The sound pressure level diagram 300 has an X-axis which shows a standardized sound pressure level X in [dB] and a Y-axis which shows an angle in degrees, wherein the angle represents a directional characteristic Y of the ultrasonic phased array sensor 200. Furthermore, the sound pressure level diagram 300 shows four curves 304, wherein each individual curve 304 shows the sound pressure level for a specific angle of the ultrasonic beam.

[0053] according to Figure 3 The variation of the radiation from 0° (linearly) to 30° is shown in 10° steps. These are merely exemplary radiation angles to illustrate the function.

[0054] The variation line 304 is shown in polar coordinates. This allows a particularly good representation of the directional characteristic. The variation line 304 corresponds to a single-lobe variation.

[0055] For example, Figure 3The change lines 304 in Graph 1 show a change in the radiation direction 608 of the ultrasound waves, which change is caused by a phase shift between the electrical contacts 102. In this case, each of the change lines 304 shown in the graph corresponds to a different radiation direction 608.

[0056] Figure 4 A schematic diagram of a phase shifter 400 is shown, which is attached to the ultrasonic phase array sensor 200. Figure 4 The ultrasonic phased array sensor 200 shown has a circular base geometry 202. In addition, the ultrasonic phased array sensor 200 has a multilayer structure 108. The multilayer structure 108 shown has a first layer 108.1, which is formed by a diaphragm 104. The second layer 108.2 has a piezoelectric substrate 106, and the third layer 108.3, i.e., the inner layer, has three electrical contacts 102. Figure 4 The three electrical contacts 102 shown have different shapes. Figure 4 4 shows an electronic device 402. The electronic device 402 includes a function generator 410, a phase shifter Phi_1 404, a phase shifter Phi_2 406, and a phase shifter Phi_3 408. The output ends of the phase shifters 404, 406, 408 are electrically connected to the respective electrical contacts 102 of the ultrasonic phase array sensor 200.

[0057] The function generator 410 has a capacitor that can vibrate in resonance with the electrical contact 102. In addition, the function generator 410 feeds a plurality of phase shifters 404, 406, 408, which change the phase of the control signal. In this way, each electrical contact 102 with a different phase is placed in resonance, and the resulting radiation direction 608 of the ultrasonic phase array sensor 200 can be changed.

[0058] In this way, for example, a targeted control of the sound radiation can be achieved by phase shifting, in which case, for example, the direction in which the ultrasound is radiated can be controlled and adjusted. The ability to specifically direct the ultrasound toward a specific area or obstacle 602 is an advantageous control possibility. The phase shifting performed by a plurality of phase shifters 404, 406, 408 can lead to better imaging, for example, imaging of the height of an obstacle.

[0059] Figure 5 A schematic diagram showing radiation directions 608 of an ultrasonic phased array sensor 200 mounted on a vehicle 502 is shown. The ultrasonic phased array sensor 200 is mounted on a bumper 504. In addition, three radiation directions are shown, namely an upward radiation direction 506, a straight radiation direction 508, and a downward radiation direction 510.

[0060] For example, the radiation direction 608 of the ultrasonic waves radiated by the ultrasonic phased array sensor 200 can be controlled by means of the ultrasonic phased array sensor 200. In this way, a plurality of radiation angles can be generated.

[0061] Figure 6 A schematic diagram of a height obstacle measurement is shown with a schematic diagram of a radiation 600 . 1 to a straight line onto an obstacle 602 and a schematic diagram of a radiation 600 . 2 of an arc around the obstacle 602 . Figure 6 Furthermore, a radiation direction 608 of an ultrasonic phase array sensor 200 mounted on the vehicle 502 is schematically shown. The ultrasonic phase array sensor 200 is mounted on or in the bumper 504.

[0062] An example of this is the integration of one or more ultrasonic phase array sensors 200 into the bumper 504 of the vehicle 502. The ultrasonic wave is sent directly in the direction of the obstacle 602 (straight line radiation 600.1). The maximum echo from the obstacle 602 is received by the straight line radiation 600.1. In order to measure the height of the obstacle 602, the angle of the radiation direction 608 of the ultrasonic wave is increased until the ultrasonic wave misses the obstacle 602. Once the ultrasonic wave has passed the obstacle 602, only the smallest received signal is still detected and the height of the obstacle 602 can be estimated.

[0063] The invention is not limited to the embodiments described herein and the aspects emphasized therein. On the contrary, numerous modifications within the scope of a person skilled in the art can be realized within the scope given by the claims.

Claims

1. An ultrasonic phased array sensor (200), comprising a multilayer structure (108), wherein: At least one first layer (108.1) has a diaphragm (104), at least one second layer (108.2) has a piezoelectric substrate (106), and at least one third layer (108.3) has a plurality of electrical contacts (102), wherein the electrical contacts (102) are applied independently of one another on a surface (110) of the piezoelectric substrate (106).

2. The ultrasonic phase array sensor (200) according to claim 1, wherein: The diaphragm (104) is mechanically connected to the piezoelectric substrate (106).

3. The ultrasonic phase array sensor (200) according to any one of the preceding claims, wherein: The radiation angle can be changed by phase shifting.

4. The ultrasonic phase array sensor (200) according to any one of the preceding claims, wherein: The radiation direction (608) can be controlled by phase shifting.

5. The ultrasonic phase array sensor (200) according to claim 3, wherein: The ultrasonic phased array sensor (200) includes obstacle height measurement by phase shifting.

6. The ultrasonic phase array sensor (200) according to any one of the preceding claims, wherein: The ultrasonic phased array sensor (200) is implemented in a plurality of geometric shapes (202), namely circular, rectangular, elliptical, triangular or square.

7. The ultrasonic phase array sensor (200) according to any one of the preceding claims, wherein: The number of electrical contacts (102) can be selected arbitrarily.

8. The ultrasonic phase array sensor (200) according to any one of the preceding claims, wherein: The electrical contact (102) is divided into individual, electrically isolated regions, wherein each region or a plurality of individual regions can be individually actuated.

9. The ultrasonic phased array sensor (200) according to any one of the preceding claims, wherein the diaphragm (104) provides protection against environmental influences, wherein: The membrane (104) comprises a moisture-proof and dust-proof material.

10. Use of the ultrasonic phase array sensor (200) according to any one of the preceding claims in automotive applications, wherein: The ultrasonic phased array sensor (200) is configured as a parking sensor.

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