Ultrasonic phase array sensor

Abstract

The invention relates to an ultrasonic phase array sensor with a multilayer structure (108), wherein at least a first layer (108.1) comprises a membrane (104), at least a second layer (108.2) a piezoelectric substrate (106) and at least a third layer (108.3) several electrical contacts (102), wherein the electrical contacts (102) are applied independently of one another on a surface (110) of the piezoelectric substrate (106).

Description

Technical area

[0001] The invention relates to an ultrasonic phased array sensor comprising a membrane, a piezoelectric substrate and a plurality of electrical contacts, wherein the electrical contacts are applied independently of one another on a surface of the piezoelectric substrate. State of the art

[0002] The measuring principle of ultrasonic parking sensors is based on acoustic waves. These are emitted into the inaudible range and reflected by an obstacle. An ultrasonic parking sensor receives the reflected signal, and the electronics evaluate the signal using a time measurement (time of flight). All ultrasonic parking sensors use a piezoelectric element to convert electrical energy into acoustic energy. However, this single element limits the parking sensor's application to one direction of sound radiation. Other physical effects, such as lidar or radar, could also be used for parking sensors. However, ultrasound enables very cost-effective production of parking sensors.

[0003] To expand the sensor range of ultrasound sensors, ultrasound phased array sensors are already being used in medicine (AS Savoia, "Design, Fabrication, Characterization, and System Integration of a 1-D PMUT Array for Medical Ultrasound Imaging," 2021 IEEE International Ultrasonics Symposium (IUS), p. 4, 2021). These are based on a combination of individual ultrasound transducer arrays. By controlling the individual ultrasound transducers in a phase-shifted manner, the radiation direction of the ultrasound can be changed. This makes it possible to scan a volume with an ultrasound phased array sensor and even perform acoustic imaging. Air-coupled ultrasound phased array sensors are not yet commercially available according to the current state of the art. To date, there are only research projects in this field (Jäger, D. Großkurth, M. Rutsch, A. Unger, R. Golinske, H. Wang, S. Dixon, K. Hofmann, and M.Kupnik, “Aircoupled 40-kHz ultrasonic 2D-phased array based on a 3D-printed waveguide structure,” 2017 IEEE International Ultrasonics Symposium (IUS), pp. 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), p. 4, 2020; E. Verreycken, W. Daems, and J. Steckel, "Passive Acoustics." Steckel, "Passive Acoustic Sound Source Tracking in 3D Using Distributed Microphone Arrays," 2018 International Conference on Indoor Positioning and Indoor Navigation (IPIN), p. 4, 2018) and startups (Toposens, Toposens, 2022, https: / / toposens.com / autonomous-parking / ). Commercial use of these systems in the automotive sector is still pending.All of these systems are based on the interconnection of multiple piezoelectric ultrasonic transducers. Since the cost of the sensor scales with the number of ultrasonic transducers, these approaches are not suitable for a cost-effective parking sensor. Furthermore, these systems are too large for the automotive sector and cannot be manufactured compactly.

[0004] Electrode separation is currently only used for 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), p. 4, 2019). Comb electrodes allow waves to be transmitted or received only at selected areas of the piezoelectric substrate. These SAWs are used to construct high-frequency filters or delay elements, which are not part of this invention.

[0005] The invention presented here also differs significantly from PMUTs (piezoelectric machined ultrasonic transducers) (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), p. 4, 2021, AS Savoia, “Design, Fabrication, Characterization, and System Integration of a 1-D PMUT Array for Medical Ultrasound Imaging,” 2021 IEEE International Ultrasonics Symposium (IUS), p. 4, 2021), as it does not use clean room processes, thus saving costs. Disclosure of the invention

[0006] The functions of an ultrasonic phased array sensor are simulated with a single piezo element (hereinafter referred to as the piezoelectric substrate) to create a novel parking sensor. Instead of irradiating the entire piezoelectric substrate with a large-area electrode, the electrode is isolated to excite individual areas of the piezoelectric substrate to vibrate. This represents a compact and cost-effective solution.

[0007] According to the invention, an ultrasonic phased array sensor is proposed, comprising a multi-layer structure, wherein at least a first layer has a membrane, at least a second layer has a piezoelectric substrate and at least a third layer has a plurality of electrical contacts, wherein electrical contacts are applied independently of one another on a surface of the piezoelectric substrate.

[0008] A membrane is a layer that acts as a separating layer between the medium to be measured and the sensor. In ultrasonic phased array sensors, a membrane is used to transmit or receive ultrasonic waves. The membrane acts, for example, as an ultrasonic transducer, converting mechanical vibrations into electrical signals.

[0009] An electrical contact comprises a connection or terminal used to establish electrical signals between the piezoelectric material and an electronic circuit that controls the ultrasonic phased array sensor. For example, an electrical contact is suitable for generating, detecting, or processing electrical signals based on the piezoelectric properties of a substrate. These electrical contacts can be attached to the piezoelectric substrate, for example, in the form of wires, contact pins, or solder connections.

[0010] Within the scope of the inventive solution, several areas of the piezoelectric substrate are provided with electrical contacts, whereby the electrical contacts can be controlled independently of one another. This allows the contacted areas to be electrically controlled independently of one another, and the direction of the ultrasonic emission can be controlled. Furthermore, the independent control of the contact surfaces by electrical contacts significantly increases the sensor's detection range. This allows, for example, the height classification of obstacles to be performed.

[0011] The use of a piezoelectric substrate proposed within the scope of the invention is an essential component of an ultrasonic phased array sensor. A material exhibiting a piezoelectric property is used. The piezoelectric property enables a material to generate an electrical charge when subjected to mechanical stress or deformation, and conversely, to undergo mechanical deformation when an electrical voltage is applied. For example, when generating ultrasonic waves, the piezoelectric substrate deforms due to the piezoelectric property when an electrical voltage is applied, and this deformation generates ultrasonic waves, which propagate as sound waves.When the ultrasonic waves hit an object, they are reflected back to the piezoelectric substrate. The reflected ultrasonic waves cause further deformation of the piezoelectric substrate, which is then converted into an electrical voltage. For example, the electrical voltage can be measured and evaluated to obtain information about an object, such as the distance of an object from the ultrasonic sensor.

[0012] In an advantageous development of the ultrasonic phased array sensor proposed according to the invention, the membrane is mechanically connected to the piezoelectric substrate.

[0013] A mechanical connection, as defined by the invention, is understood to mean that at least two components are physically connected to one another. A mechanical connection of a piezoelectric substrate to a membrane includes various joining methods such as anodic bonding or adhesive bonding, mechanical fastening, or thermal bonding. The connection locally excites the membrane to vibrate and emits ultrasound in the open medium.

[0014] In an advantageous development of the ultrasonic phased array sensor proposed according to the invention, a radiation angle can be varied by a phase shift.

[0015] A radiation angle is the angular range within which a radiation source, such as an ultrasonic phased array sensor, radiates into the surrounding space or is received by it. The radiation angle is a specific angle between a major radiation axis, a principal axis, the radiation source, and a boundary of the irradiated area. The radiation angle can be measured in degrees, for example, and represented in polar coordinates, for example in the case of ultrasonic phased array sensors. The radiated sound pressure level is normalized to the maximum (normalized sound pressure level (dB)). Due to the phase shift between the array elements, the radiation direction changes.

[0016] In an advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, a radiation direction can be controlled by phase shift.

[0017] According to the invention, a phase shift is understood as a targeted adjustment of the temporal orientation of the emitted or detected ultrasonic waves between the individual components of an ultrasonic grating. Changing this phase shift can be used, for example, to direct, focus, and control the radiation characteristics of a sensor's ultrasonic waves. For example, precise focusing can improve spatial resolution.

[0018] The phase shift of the individual electrical contacts is achieved by electronics. This includes at least one function generator that oscillates a resonance of the electrical contact. The function generator then controls several phase shifters (phi_1, phi_2, phi_3), which change the phase of the control signal. The outputs of the phase shifters are electrically connected to the individual electrical contacts. This causes each electrical contact to oscillate with a different phase, and the resulting radiation direction of the ultrasonic phased array sensor can be changed.

[0019] A radiation direction, as defined by the invention, is a targeted alignment of the ultrasonic waves emitted by the sound source of an ultrasonic phased array sensor. The radiation direction allows the energy flow of the ultrasonic waves to be precisely controlled, thus significantly impacting the sensor's performance and flexibility. The radiation direction can be controlled by a combination of radiation angle and phase shift. If, for example, the radiation angle is changed in such a way that the spatial propagation direction of the emitted energy is altered, the phase shift results in a combination of ultrasonic waves that results in amplification in the desired radiation direction.

[0020] For example, the ultrasonic phased array sensor can be installed in a vehicle's shock absorber, allowing the radiation direction to be manipulated. This allows, for example, an ultrasonic signal to be emitted at different angles.

[0021] 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 phase shift.

[0022] The solution according to the invention allows, for example, sound to be emitted in a straight direction when a constant alternating voltage is applied. Furthermore, the emission direction of the ultrasonic phased array sensor can be varied, for example, by introducing an electrical phase shift. This allows an obstacle to be acoustically detected, scanned, and, for example, an obstacle height measurement to be performed.

[0023] For example, an ultrasonic phased array sensor can be installed in a vehicle's shock absorber to measure the height of an obstacle. The ultrasound is first emitted in a straight line toward an obstacle. Direct radiation ensures a maximum echo from the obstacle. To measure the height of the obstacle, the angle of the ultrasound radiation is increased until the ultrasound misses the obstacle. Once the ultrasound has passed the obstacle, a minimal received signal is detected, and the height of the obstacle can be estimated.

[0024] In an advantageous development of the ultrasonic phased array sensor proposed according to the invention, the ultrasonic phased array sensor can be designed in a variety of geometric shapes: round, rectangular, elliptical, triangular or square.

[0025] In an advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the number of electrical contacts can be selected as desired.

[0026] 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 areas, wherein each area or several individual areas can be controlled separately.

[0027] In a further advantageous embodiment of the ultrasonic phased array sensor proposed according to the invention, the membrane offers protection against environmental influences, wherein the membrane comprises a moisture-resistant and dust-resistant material.

[0028] Furthermore, the invention relates to the use of the ultrasonic phased array sensor for automotive applications, wherein the ultrasonic phased array sensor is designed as a parking sensor. Advantages of the invention

[0029] The ultrasonic phased array sensor according to the invention uses a piezoelectric substrate as an insert, which is divided into several regions.

[0030] This allows these areas to be electrically controlled independently of one another and the direction of the ultrasound radiation to be directed.

[0031] The ultrasonic phased array sensor according to the invention significantly increases the field of view (FOV) of the sensor. This allows a larger area or volume to be detected within a limited detection range. This provides a greater detection range than the state of the art, for example, in safety-critical applications such as autonomous driving or parking, where complete environmental detection is essential.

[0032] Furthermore, the increased detection range of the ultrasonic phased array sensor enables early detection of obstacles before they enter the immediate detection zone. The increased detection range also reduces the number of required sensors. Furthermore, the increased detection range of an ultrasonic phased array sensor according to the invention enables flexible sensor placement, thus reducing overall system complexity.

[0033] In addition, it is possible to perform height classification of obstacles. Height classification allows for more accurate parking space detection, as the sensor monitors not only the horizontal position of a parking space but also the height of the available space. When parking, height classification helps detect obstacles such as poles, curbs, or neighboring objects, allowing the vehicle to park and exit without collisions.

[0034] This invention increases safety when parking. For example, a child directly in front of, next to, or behind the vehicle can be more easily detected. The same applies to animals such as dogs, cats, and the like.

[0035] The invention is one of the most cost-effective options for an ultrasonic phased array sensor. Because only one piezoelectric substrate is required, both manufacturing and material costs are very low compared to systems with multiple piezoelectric substrates.

[0036] Because the invention disclosed has a wide reception range (FoV) compared to the prior art, the number of ultrasonic parking sensors required in vehicles can be reduced. For example, for larger vehicles (station wagons, coupes, and others), one sensor could be installed in the center and two more at the corners of the front or rear of the vehicle. Small cars could be equipped with just one central sensor to further reduce costs.

[0037] Current ultrasonic parking sensors repeatedly experience false detections due to strong acoustic echoes from the ground. Especially in parking garages with duplex parking spaces or on roadways with rough surfaces, the sensor responds even when there is no obstacle present. This invention solves this problem by allowing the direction of the reflection to be checked for plausibility. This increases the overall reliability of ultrasonic parking sensors and reduces false detections. Short description of the drawings

[0038] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0039] They show: Fig. 1 a schematic representation of an ultrasonic phased array sensor in cross section, Fig. 2 a schematic representation of an ultrasonic phased array sensor, Fig. 3 a schematic representation of a sound pressure level diagram, Fig. 4 is a schematic diagram of a phase shifter connected to an ultrasonic phase array sensor, Fig. 5 a schematic representation of the radiation direction of a vehicle-mounted ultrasonic phased array sensor and Fig. 6 a schematic representation of a height obstacle measurement. Embodiments of the invention

[0040] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0041] Fig. 1 shows a schematic representation of an ultrasonic phased array sensor 200 in cross section 100, which comprises a multilayer structure 108. The Fig. The multilayer structure 108 shown in Figure 1 comprises a first layer 108.1 formed from a membrane 104. A second layer 108.2 comprises a piezoelectric substrate 106, and a third layer 108.3 comprises four electrical contacts 102, wherein the electrical contacts 102 are applied at a distance 112 from one another on a surface 110 of the piezoelectric substrate 106.

[0042] On a surface 110 of the piezoelectric substrate 106, alternatively to Fig. 1, for example, further electrical contacts 102 can be applied, wherein the distance 112 can be selected variably.

[0043] Fig. 2 shows a schematic representation of an ultrasonic phased array sensor 200. The Fig. The ultrasonic phased array sensor 200 shown in Figure 2 has a geometric shape 202, wherein the geometric shape 202 has a circular base area. Furthermore, the ultrasonic phased array sensor 200 has a multilayer structure 108. The illustrated multilayer structure 108 has a first layer 108.1, which is formed from a membrane 104. A second layer 108.2 has a piezoelectric substrate 106, and a third layer 108.3, the inner layer, has three electrical contacts 102. The Fig. The three electrical contacts 102 shown in Figure 2 have different shapes.

[0044] For example, the geometric shape 202 of the piezoelectric substrate 106 can be square, rectangular, round, or elliptical. The number of electrical contacts 102 can also be increased or decreased as desired.

[0045] Fig. 3 shows a schematic representation of a sound pressure level diagram 300. The sound pressure level diagram 300 has an X-axis representing the normalized sound pressure level X in [dB] and a Y-axis representing the angle in degrees, where the angle represents a directional characteristic Y of the ultrasonic phased array sensor 200. Furthermore, the sound pressure level diagram 300 shows four curve lines 304, where each individual curve line 304 represents a sound pressure level for a specific angle of an ultrasonic beam.

[0046] Based on the Fig. Figure 3 shows a beam variation from 0° (straight ahead) to 30° in 10° increments. These are only exemplary beam angles to illustrate the function.

[0047] The curves 304 are displayed in polar coordinates. This allows for a particularly clear representation of the directional characteristic. The curve 304 corresponds to a single lobe.

[0048] For example, the gradient lines 304 in Fig. 3 illustrates a change in the radiation direction 608 of ultrasound caused by a phase shift among electrical contacts 102. Each illustrated line 304 corresponds to a different radiation direction 608 in the diagram.

[0049] Fig. Figure 4 shows a schematic representation of a phase shifter 400 connected to an ultrasonic phase array sensor 200. The Fig. The ultrasonic phased array sensor 200 shown in Figure 4 has the geometric shape 202 of a circular base. Furthermore, the ultrasonic phased array sensor 200 has a multilayer structure 108. The illustrated multilayer structure 108 has a first layer 108.1, which is formed from a membrane 104. A second layer 108.2 has a piezoelectric substrate 106, and a third layer 108.3, the inner layer, has three electrical contacts 102. The Fig. The three electrical contacts 102 shown in Figure 4 have different shapes. Furthermore, Fig. 4 shows an electronics system 402. The electronics system 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 outputs of the phase shifters 404, 406, 408 are electrically connected to the individual electrical contacts 102 of the ultrasonic phased array sensor 200.

[0050] A function generator 410 has a capacitance that can oscillate at the resonance of an electrical contact 102. Furthermore, the function generator 410 feeds several phase shifters 404, 406, and 408, which change the phase of the control signal. In this way, each electrical contact 102 is resonated with a different phase, and the resulting radiation direction 608 of the ultrasonic phased array sensor 200 can be changed.

[0051] For example, targeted control of sound radiation can be achieved through a phase shift, which allows, for example, the direction in which the ultrasound is emitted to be controlled and adjusted. The ability to direct the ultrasound specifically at a specific area or obstacle 602 represents an advantageous control option. A phase shift using multiple phase shifters 404, 406, and 408 can lead to better imaging, for example, imaging of an obstacle height.

[0052] Fig. 5 shows a schematic representation of the radiation direction 608 of an ultrasonic phased array sensor 200 mounted on a vehicle 502. The ultrasonic phased array sensor 200 is mounted on a bumper 504. Furthermore, three radiation directions are shown: an upward radiation direction 506, a straight radiation direction 508, and a downward radiation direction 510.

[0053] For example, a radiation direction 608 of an ultrasound emitted by an ultrasonic phased array sensor 200 can be manipulated using an ultrasonic phased array sensor 200. In this way, a variety of radiation angles can be generated.

[0054] Fig. 6 shows a schematic representation of a height obstacle measurement with the representation of a straight radiation 600.1 onto an obstacle 602 and a curved radiation 600.2 around an obstacle 602. Fig. 6 further schematically shows the radiation direction 608 of an ultrasonic phased array sensor 200 mounted on a vehicle 502. The ultrasonic phased array sensor 200 is mounted on or in a bumper 504.

[0055] An example of this is the integration of one or more ultrasonic phased array sensors 200 into the bumper 504 of a vehicle 502. The ultrasound is transmitted directly toward an obstacle 602 (linear emission 600.1). Due to the linear emission 600.1, a maximum echo is received from the obstacle 602. To measure the height of the obstacle 602, the angle of the emission direction 608 of the ultrasound is increased until it misses the obstacle 602. Once the ultrasound has passed the obstacle 602, only a minimal received signal is detected, and the height of the obstacle 602 can be estimated.

[0056] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of expert practice. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] AS Savoia, “Design, Fabrication, Characterization, and System Integration of a 1-D PMUT Array for Medical Ultrasound Imaging,” 2021 IEEE International Ultrasonics Symposium (IUS), p. 4, 2021

[0003] Jäger, D. Großkurth, M.rutsch, A. Unger, R. Golinske, H. Wang, S. Dixon, K. Hofmann and M. Kupnik, “Aircoupled 40-kHz ultrasonic 2D-phased array based on a 3D-printed waveguide structure,” 2017 IEEE International Ultrasonics Symposium (IUS), p.. 4, 2017

[0003] G. Allevato, M. Rutsch, J. Hinrichs, M. Pesavento und M. Kupnik, „Embedded Air-Coupled Ultrasonic 3D Sonar System with GPU Acceleration,“ 2020 IEEE SENSORS, S. 4, 2020

[0003] G. Allevato, M. Rutsch, J. Hinrichs, E. Sarradj, M. Pesavento und M. Kupnik, „Spiral Air-Coupled Ultrasonic Phased Array for High Resolution 3D Imaging“, 2020 IEEE International Ultrasonics Symposium (IUS), S. 4, 2020

[0003] E. Verreycken, W. Daems und 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), S. 4, 20018

[0003] Y.-n. YIN, W. WANG, Y.-n. JIA, X.-f. XUE und 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), S. 4, 2019

[0004] 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), S. 4, 2021, A. S. Savoia, „Design, Fabrication, Characterization, and System Integration of a 1-D PMUT Array for Medical Ultrasound Imaging,“ 2021 IEEE International Ultrasonics Symposium (IUS), S. 4, 2021

[0005]

Claims

[1] Ultrasonic phased array sensor (200) comprising a multi-layer structure (108), wherein at least a first layer (108.1) has a membrane (104), at least a second layer (108.2) has a piezoelectric substrate (106) and at least a third layer (108.3) has a plurality of electrical contacts (102), wherein electrical contacts (102) are applied independently of one another on a surface (110) of the piezoelectric substrate (106). [2] The ultrasonic phased array sensor (200) of claim 1, wherein the diaphragm (104) is mechanically connected to the piezoelectric substrate (106). [3] Ultrasonic phased array sensor (200) according to one of the preceding claims, wherein a radiation angle can be varied by a phase shift. [4] Ultrasonic phased array sensor (200) according to one of the preceding claims, wherein a radiation direction (608) is controllable by phase shift. [5] The ultrasonic phased array sensor (200) of claim 3, wherein the ultrasonic phased array sensor (200) comprises obstacle height measurement by phase shifting. [6] Ultrasonic phased array sensor (200) according to one of the preceding claims, wherein the ultrasonic phased array sensor (200) is designed in a variety of geometric shapes (202), namely round, rectangular, elliptical, triangular or square. [7] Ultrasonic phased array sensor (200) according to one of the preceding claims, wherein the number of electrical contacts (102) can be selected as desired. [8] Ultrasonic phased array sensor (200) according to one of the preceding claims, wherein the electrical contacts (102) are divided into individual, electrically separated regions, each region or several individual regions being separately controllable. [9] An ultrasonic phased array sensor (200) according to any preceding claim, wherein the membrane (104) provides protection against environmental influences, the membrane (104) comprising a moisture-resistant and dust-resistant material. [10] Use of the ultrasonic phased array sensor (200) according to one of the preceding claims in automotive applications, wherein the ultrasonic phased array sensor (200) is designed as a parking sensor.

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