Normal stress sensor system

Abstract

The present invention relates to a normal stress sensor system having at least one normal stress sensor (1) with a first carrier (10a) having a resonator (13c) at a natural frequency that depends, preferably at least in a substantially linear manner, on a mechanical normal stress to be captured, with a second carrier (10b) that is spaced apart from the first carrier (10a) along a longitudinal axis (X), and with a connecting element (11) which is compressible, preferably along the longitudinal axis (X), and connects the first carrier (10a) and the second carrier (10b) to one another in a manner spaced apart from one another along the longitudinal axis (X), wherein the resonator (13c) is spaced apart from the second carrier (10b) by an air gap (14) of the dimension (A) along the longitudinal axis (X), and wherein the resonator (13c) is designed such that mechanical normal stresses (F) acting on the connecting element (11) change the natural frequencies of the resonator (13c), and with at least one control unit which is designed to excite the resonator (13c) of the normal stress sensor (1) to oscillate at the natural frequencies thereof and to capture the oscillations thereof, wherein the control unit is also designed to determine the mechanical normal stresses (F) from the captured oscillations of the resonator (13c).

Description

[0001] Description

[0002] Normal voltage sensor system

[0003] The present invention relates to a normal voltage sensor system according to claim 1, a normal voltage sensor for use in such a normal voltage sensor system according to claim 14 and a control unit for use in such a normal voltage sensor system according to claim 15.

[0004] To measure mechanical normal and shear stresses, the transducers must be integrated into the component in such a way that they can capture the force flow to be measured. If this force flow is inhomogeneous, flat sensors are usually required. Elastomer-based pressure measuring foils, which are inserted into the component for one measurement at a time, map the distribution of the maximum stresses through color changes. However, this is usually inaccurate, cannot be recorded electronically, and requires the installation, removal, and evaluation of an unused pressure measuring foil for each measurement, making this method of recording normal and shear stresses unattractive.

[0005] With the help of electronic pressure transducers, normal stress distributions can be measured continuously and electronically. For example, a matrix of piezoresistive transducers provides the data for a spatially resolved image. Alternatively, dielectric elastomer sensors (DES) can be used to measure mechanical normal stresses. However, with the exception of dielectric elastomer sensors, such known sensors are only partially suitable for measuring mechanical stresses in elastomeric bodies because the dielectric elastomer sensors cannot track relatively large strains. Furthermore, piezoresistive pressure transducers are expensive, so they are preferably used for discontinuous measurements.

[0006] From DE 10 2020 216 234 A1 a device for detecting mechanical normal stresses in an elastomer component is known, comprising an elastomer component, at least one normal stress sensor, wherein the normal stress sensor has at least one resonator whose natural frequency is dependent, preferably at least substantially linearly, on the mechanical normal stresses to be detected, wherein at least the resonator is embedded in the elastomer component in such a way that mechanical normal stresses acting on the elastomer component can change the natural frequency of the resonator, and at least one control unit which is designed to excite the resonator to oscillate at its natural frequency and to detect its oscillations, wherein the control unit is further designed to determine the mechanical normal stresses of the elastomer component from the detected oscillations of the resonator.

[0007] In other words, a normal force sensor for elastomeric components is described, which consists of a so-called symmetrical microwave stripline designed as a resonator. Along the longitudinal axis, above and below each conductor strip, there is a dielectric, which is covered on its outer surface with a conductive layer and is electrically connected to ground potential. The normal force to be measured compresses the stripline along the longitudinal axis and thus reduces the distance between the centrally arranged conductor strip and the two outer ground surfaces along the longitudinal axis, which changes the wave impedance and return loss of the arrangement. During the force measurement, the stripline is connected to an impedance spectrometer, which evaluates the wave impedance and return loss and calculates the measurement result from this.

[0008] The disadvantage of the device of DE 10 2020 216 234 A1 is that in this way only the average normal stress can be recorded, which acts in the center of the surface of the normal stress sensor.

[0009] From DE 10 2021 206 816.2 (unpublished) discloses a normal stress sensor system having at least one normal stress sensor having at least one first resonator with a first natural frequency which is dependent on a first mechanical normal stress to be detected, having at least one second resonator with a second natural frequency which is dependent on a second mechanical normal stress to be detected, wherein the normal stress sensor is designed to be arranged between two objects in such a way that mechanical normal stresses acting between the objects can change the natural frequencies of the resonators, and having at least one control unit which is designed to excite the resonators of the normal stress sensor to oscillate at their natural frequencies and to detect their oscillations, wherein the control unit is further designed to determine the mechanical normal stresses from the detected oscillations of the resonators.In the standard voltage sensor described in DE 102021 206 816.2, a resonant conductor structure is located between two conductive surfaces that are electrically connected to ground potential. The space between the resonator and the ground surfaces is filled with an elastomeric dielectric.

[0010] Applications in which the standard voltage will be measured by sensors will include future braking systems in which the traditional hydraulic components are to be replaced by electromechanical components (dry brakes). During braking, the driver determines the level of braking force by applying force to the brake pedal. Electronic control regulates the force with which a brake disc or brake drum is braked to this target value. Control requires fast and accurate measurement of the currently effective braking force.

[0011] For this purpose, sensors for measuring braking force within electromechanical brakes are currently being developed. These sensors are based on different measuring principles, such as pressure measurement in a compressible container containing a hydraulic medium, or a load cell based on piezoresistive strain gauges. Normal stress sensors or a normal stress sensor system as described in DE 10 2021 206 816.2 can also be used for this purpose.

[0012] However, the requirements for operating a force sensor or a standard tension sensor within such a brake are extreme. These requirements include the absorption of high forces, high operating temperatures, fast measurement without hysteresis, small installation space, and low cost.

[0013] The described state-of-the-art solutions only partially meet these requirements. For example, a hydraulic sensor has a inherent latency due to the required pressure accumulator, while the load cell has a comparably high height. The force sensor or the microwave-based standard stress sensor described in DE 10 2021 206 816.2 exhibits a recovery behavior due to the elastomers used, which can lead to hysteresis and aging-related changes in the dielectric constant.

[0014] An object of the present invention is to provide a force sensor or a normal stress sensor which has the above-mentioned

[0015] It is intended to meet all the requirements at all, and at least better than previously known. In particular, all of the above-mentioned requirements should be met together, preferably as effectively as possible. At the very least, an alternative to known methods for measuring normal stresses should be created.

[0016] The object is achieved according to the invention by a standard voltage sensor system having the features according to claim 1, by a standard voltage sensor having the features according to claim 14, and by a control unit having the features according to claim 15. Advantageous further developments are described in the subclaims.

[0017] Thus, the invention relates to a normal stress sensor system with at least one normal stress sensor with a first carrier with a resonator with a natural frequency which is dependent, preferably at least substantially linearly, on a mechanical normal stress to be detected, with a second carrier which is spaced from the first carrier along a longitudinal axis, and with a connecting element, preferably compressible along the longitudinal axis, which connects the first carrier and the second carrier to one another at a distance from one another along the longitudinal axis, wherein the resonator is spaced from the second carrier along the longitudinal axis by an air gap of the same size and wherein the resonator is designed such that mechanical normal stresses acting on the connecting element change the natural frequencies of the resonator, and with at least one control unit which is designedto excite the resonator of the normal stress sensor to oscillate at its natural frequencies and to detect its oscillations, wherein the control unit is further configured to determine the mechanical normal stresses from the detected oscillations of the resonator.

[0018] In other words, according to the invention, instead of a symmetrical arrangement and preferably a symmetrical stripline, an asymmetrical arrangement and preferably an asymmetrical stripline is used by using an air gap instead of a dielectric between the resonator of the first carrier and the second carrier. This avoids the corresponding disadvantages described above.

[0019] This allows the mechanical normal stresses of a resonator to be detected by sensors. The resonator can thus detect mechanical normal stresses in the form of compressive and / or tensile forces. These forces influence the resonator's vibration behavior in such a way that the vibration behavior of the resonator can be characteristic of the acting mechanical normal stresses. If the resonator is then excited to vibrate and the vibration behavior of the resonator is recorded and evaluated, conclusions can be drawn about the applied mechanical normal stresses. This allows mechanical normal stresses to be continuously detected by sensors.

[0020] Making the connecting element compressible, for example from an elastomeric material or soft metal, can increase the sensitivity of the sensor detection, since larger changes in the size of the air gap can be caused with the same force.

[0021] A particular advantage here is that such a resonator can be manufactured easily, quickly, precisely, and / or robustly, for example, by vulcanization, printing, or gluing. Such a resonator can also be designed to be relatively flat. Furthermore, such a resonator or a corresponding standard stress sensor can be provided as a simple component at a relatively low cost.

[0022] According to one aspect of the invention, the resonator is part of a

[0023] Microstrip line. A microstrip line, or stripline (English: microstrip), refers to a specific class of electrical waveguide for use in the high-frequency range. It consists of one or more thin, conductive strips, preferably applied to a dielectric. This could represent a concrete implementation possibility.

[0024] According to a further aspect, the resonator of the standard voltage sensor is designed as a high-frequency resonator. A high-frequency resonator is understood to be a resonator that can operate in the frequency range of high-frequency oscillations. This refers to frequencies in the range of 1 to 300 GHz.

[0025] The advantage of this is that such high frequencies have correspondingly short wavelengths, allowing the resonator to be realized with comparatively small dimensions. This allows the comparatively small resonator to be integrated into a very small standard voltage sensor.

[0026] Another advantage is that, due to the high frequency, no interaction can occur between the electromagnetic field of the resonator and the surrounding material itself, which could have a negative effect on its functionality.

[0027] Another advantage is that, due to its high operating frequency, the resonator can be very sensitive to the measured value signal and thus to normal force or pressure. This can increase measurement sensitivity.

[0028] According to a further aspect, the resonator of the normal stress sensor is designed to be elastic, preferably as a conductive liquid. This allows the resonator to flexibly adapt to the movements of the objects between which the normal stresses are to be measured, thereby detecting the mechanical normal stresses comparatively accurately. Due to its elastic design, the resonator or the corresponding normal stress sensor can also follow significantly greater strains than rigid transducers.

[0029] According to a further aspect, the resonator of the normal stress sensor is arranged in a ring around the longitudinal axis. This can promote the most uniform possible arrangement of the resonator relative to the axis of the normal stresses to be detected along the longitudinal axis and allow the same normal stresses to act uniformly on the resonator and thus be detected equally by them.

[0030] According to a further aspect, a preferably elastic dielectric, preferably as a component of a microstrip line, is arranged between the first carrier and the resonator of the standard voltage sensor. This can represent a simple way to implement the resonator with the properties and advantages described here. Configuring the dielectric of the standard voltage sensor to be elastic can also enable the dielectric to implement the corresponding properties described above.

[0031] According to a further aspect, a first electrically conductive conductor layer, preferably as a first ground plane and / or as a component of a microstrip line, is arranged between the first carrier and the resonator of the standard voltage sensor. In this way, the ground plane is at the reference potential for the electric field lines of the electromagnetic field. This ensures defined conditions in the strip line. The ground plane preferably comprises or even consists of a material with high electrical conductivity.

[0032] According to a further aspect, the second carrier has a second electrically conductive conductor layer, preferably as a second ground plane. This allows the corresponding properties and advantages described above to also be applied to the second carrier.

[0033] According to a further aspect, the first carrier and / or the second carrier is / are formed as a preferably elastic carrier layer, preferably as a carrier film. This can facilitate implementation, particularly as a flexible design.

[0034] According to a further aspect, the first carrier comprises a first electrical insulator, preferably a first electrically insulating film, and the second carrier comprises a second electrical insulator, preferably a second electrically insulating film. In this way, the insulating layers separate the reference potential from the undefined potential of the metal body on which the resonators are mounted.

[0035] According to a further aspect, the resonator of the normal stress sensor is designed to extend over a large area, with the resonator's planar extension plane being perpendicular to the direction of the mechanical normal stresses. This can make it possible to implement the resonators with a sufficiently elongated extension while maintaining a compact design. This can promote large-area sensory detection of the mechanical normal stresses, which can improve the quality of the sensor-detected values.

[0036] According to a further aspect, the control unit is designed to excite the resonator of the normal stress sensor to oscillate at its natural frequency using broadband pulses, to record their impulse responses, and to determine the mechanical normal stresses from the recorded impulse responses. This can represent an operating mode that excites the resonators to oscillate at their respective natural frequency and to record or receive the corresponding signals from the resonators. According to a further aspect, the control unit is designed to continuously excite the resonator of the normal stress sensor to oscillate at its natural frequency using oscillations of variable frequency, to record its oscillations, to determine the transmission parameters from the resonance frequency of the recorded oscillations, and to determine the mechanical normal stresses from the determined transmission parameters.This can represent an alternative mode of operation to excite the resonator to oscillate at its natural frequency and to detect or receive the corresponding signals from the resonators.

[0037] The present invention also relates to a standard voltage sensor for use in a standard voltage sensor system as described above. This provides a standard voltage sensor for implementing a standard voltage sensor system as described above and utilizing its properties and advantages.

[0038] The present invention also relates to a control unit for use in a standard voltage sensor system as described above. This allows a control unit to be created to implement the device described above and utilize its properties and advantages. The control unit can also be used universally, e.g., for similar devices or measuring systems, with appropriate adaptation of the software implementation of the previously described functions to the respective application.

[0039] Normal stress sensor systems according to the invention can be used particularly in elastomer components such as belts, air springs, hoses, straps, bearings, etc., as well as in measurement technology in general. An exemplary embodiment and further advantages of the invention are explained below in conjunction with the following figure. It shows:

[0040] Fig. 1 is a schematic sectional view of a normal stress sensor according to the invention along the longitudinal axis.

[0041] The above-mentioned figure is described in cylindrical coordinates with a longitudinal axis X, a radial direction perpendicular to the longitudinal axis X (not shown), and a circumferential direction (not shown) running around the longitudinal axis X. The longitudinal axis X, the radial direction, and the circumferential direction can collectively be referred to as spatial directions or cylindrical spatial directions.

[0042] A standard stress sensor 1 according to the invention comprises a first carrier 10a and a second carrier 10b along the longitudinal axis X, which are spaced apart from one another along the longitudinal axis X. The first carrier 10a is designed as a first carrier layer 10a or as a first carrier foil 10a, and the second carrier 10b is designed as a second carrier layer 10b or as a second carrier foil 10b. Both carriers 10a, 10b are fixedly connected to one another along the longitudinal axis X by a compressible connecting element 11.

[0043] Facing each other along the longitudinal axis X, a first electrical insulator 12a in the form of a first electrically insulating film 12a is arranged on the first carrier 10a and a second electrical insulator 12b in the form of a second electrically insulating film 12b is arranged on the second carrier 10b.

[0044] A microstrip line 13 is arranged on the first electrical insulator 12a and faces the second electrical insulator 12b along the longitudinal axis X. The microstrip line 13 has, starting from the first electrical insulator 12a, in this order along the longitudinal axis X, a first electrically conductive conductor layer 13a in the form of a first ground plane 13a, a flexible dielectric 13b, and a resonator 13c. The resonator 13c is formed using printed electrically conductive ink. A second electrically conductive conductor layer 15 in the form of a second ground plane 15 is arranged opposite the resonator 13c along the longitudinal axis X. The resonator 13c and the second ground plane 15 are spaced apart from one another along the longitudinal axis X by an air gap 14 with a dimension A.

[0045] The normal stress sensor 1, together with a control unit (not shown), forms a normal stress sensor system. The control unit can excite the resonator 13a of the normal stress sensor 1 to oscillate at the respective natural frequency using an alternating electric field or its field lines E, and these oscillations can be detected by the control unit 1. From the detected oscillations of the resonator 13a, the control unit can determine the mechanical normal stresses F along the longitudinal axis X.

[0046] In other words, if the dimension A of the air gap 14, the distance between the second ground plane 14 and the resonator 13a, is reduced by the applied normal stress F, this affects the natural frequency of the resonator 13a, i.e., the natural frequency is detuned. This can be detected or recognized by the control unit, and the applied mechanical normal stress F along the longitudinal axis X can be determined from this.

[0047] List of reference symbols (part of the description)

[0048] A Dimension of the air gap 14

[0049] E Field lines of the alternating electric field

[0050] F mechanical normal stresses along the longitudinal axis X

[0051] X Longitudinal axis

[0052] I Normal voltage sensor

[0053] 10a first carrier; first carrier layer; first carrier film

[0054] 10b second carrier; second carrier layer; second carrier film

[0055] II (compressible) connecting element

[0056] 12a first electrical insulator; first electrically insulating film

[0057] 12b second electrical insulator; second electrically insulating film

[0058] 13 microstrip line

[0059] 13a first electrically conductive conductor layer; first ground plane

[0060] 13b Dielectric

[0061] 13c Resonator

[0062] 14 Air gap

[0063] 15 second electrically conductive conductor layer; second ground plane

Claims

Patent claims 1. Normal stress sensor system with at least one normal stress sensor (1) with a first carrier (10a) with a resonator (13c) with a natural frequency which is dependent, preferably at least substantially linearly, on a mechanical normal stress to be detected, with a second carrier (10b) which is spaced from the first carrier (10a) along a longitudinal axis (X), and with a connecting element (11), preferably compressible along the longitudinal axis (X), which connects the first carrier (10a) and the second carrier (10b) at a distance from one another along the longitudinal axis (X), wherein the resonator (13c) is spaced from the second carrier (10b) along the longitudinal axis (X) by an air gap (14) of dimension (A), and wherein the resonator (13c) is designed such that mechanical normal stresses (F) acting on the connecting element (11) determine the natural frequencies of the resonator (13c). change, and with at least one control unit,which is designed to excite the resonator (13c) of the normal stress sensor (1) to oscillate at its natural frequencies and to detect its oscillations, wherein the control unit is further designed to determine the mechanical normal stresses (F) from the detected oscillations of the resonator (13c).

2. Normal voltage sensor system according to claim 1, wherein the resonator (13c) is part of a microstrip line (13).

3. Normal voltage sensor system according to claim 1 or 2, wherein the resonator (13c) of the normal voltage sensor (1) is designed as a high-frequency resonator (13c).

4. Normal voltage sensor system according to one of the preceding claims, wherein the resonator (13c) of the normal voltage sensor (1) is elastic, preferably as a conductive liquid.

5. Normal stress sensor system according to one of the preceding claims, wherein the resonator (13c) of the normal stress sensor (1) is arranged in a ring around the longitudinal axis (X).

6. Normal voltage sensor system according to one of the preceding claims, wherein a preferably elastic dielectric (13b), preferably as a component of a microstrip line (13), is arranged between the first carrier (10a) and the resonator (13c) of the normal voltage sensor (1).

7. Normal voltage sensor system according to one of the preceding claims, wherein a first electrically conductive conductor layer (13a), preferably as a first ground surface (13a) and / or as a component of a microstrip line (13), is arranged between the first carrier (10a) and the resonator (13c) of the normal voltage sensor (1).

8. Normal voltage sensor system according to claim 7, wherein the second carrier (10b) has a second electrically conductive conductor layer (15), preferably as a second ground surface (15).

9. Normal voltage sensor system according to one of the preceding claims, wherein the first carrier (10a) and / or the second carrier (10b) is / are designed as a preferably elastic carrier layer (10a, 10b), preferably as a carrier film (10a, 10b). Normal stress sensor system according to one of the preceding claims, wherein the first carrier (10a) has a first electrical insulator (12a), preferably a first electrically insulating film (12a), and wherein the second carrier (10b) has a second electrical insulator (12a), preferably a second electrically insulating film (12a). Normal stress sensor system according to one of the preceding claims, wherein the resonator (13c) of the normal stress sensor (1) is designed to extend flatly, wherein the resonator (13c) is oriented with its flat plane of extension perpendicular to the direction of the mechanical normal stresses (F).Normal stress sensor system according to one of the preceding claims, the control unit is designed to excite the resonator (13c) of the normal stress sensor (1) to oscillate at its natural frequency using broadband pulses, to record the pulse responses thereof, and to determine the mechanical normal stresses (F) from the recorded pulse responses. Normal stress sensor system according to one of the preceding claims, wherein the control unit (2) is designed to continuously excite the resonator (13c) of the normal stress sensor (1) to oscillate at its natural frequency using oscillations of variable frequency, to record the oscillations thereof, to determine the transmission parameters from the resonance frequency of the recorded oscillations, and to determine the mechanical normal stresses (F) from the determined transmission parameters.

14. A normal voltage sensor (1) for use in a normal voltage sensor system according to one of claims 1 to 13.

15. A control unit for use in a normal voltage sensor system according to one of claims 1 to 13.

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