Measuring device and method for measuring forces and / or torques in an object under investigation made of ferromagnetic material

Abstract

Measuring device (1) for measuring forces and / or torques present in an object of investigation (2) made of ferromagnetic material, comprising a. comprising a magnetoelastic sensor i. a first coil unit (3) configured to generate a magnetic field (B1, B2) which extends at least partially outside the sensor and penetrates at least a partial area of ​​the object under investigation (2), wherein the first coil unit (3) comprises a transmitting coil (7), ii. a second coil unit (4) configured to detect response signals induced by the generated magnetic field (B1, B2) in the object under investigation (2), wherein the response signals reflect local magnetic field changes in the object under investigation (2), wherein the second coil unit (4) comprises two pairs of coils surrounding the transmitting coil (7), each pair of coils having two opposing receiving coils (9) relative to the circumference of the transmitting coil (7), iii. a ferrite core arrangement comprising a first ferrite core (8) and second ferrite cores (10) distributed around the first ferrite core (8), wherein the ferrite cores (8, 10) are arranged on a common ferrite base plate (11), and wherein the ferrite cores (8, 10) are shaped in the manner of a rod cylinder and extend perpendicular to the base plate (11) from a cylindrical base arranged on the base plate (11); b. several capacitive distance sensors (5) which form an integrated unit with the magnetoelastic sensor and are configured to detect distance values ​​(A) present between the measuring device (1) and the object under investigation (2) at different spatial locations; c. an evaluation unit (6) which is set up for this purpose i. to determine measurement signals based on response signals received from the second coil unit (4) and which are proportional to the forces and / or torques present in the object under investigation (2), and ii. to calculate an average distance value from the distance values ​​(A) recorded at the different spatial locations and to use the average distance value to compensate for fluctuations in the measurement signals resulting from a dynamic distance variation between the measuring device (1) and the object under investigation (2), namely signal attenuations and / or signal amplifications; wherein the transmitting coil (7) and the receiving coils (9) are arranged on a common coil carrier, wherein the coil carrier has recesses by virtue of which the coil carrier can be plugged over the ferrite cores (8, 10), and wherein the recesses are formed in the area of ​​the respective coil centers in the coil carrier, wherein, based on object information available for the object of investigation (2), an adapted signal amplification or signal attenuation of the measurement signals can be preselected in the sense of a coarse adjustment, and wherein the measuring device (1) is set up to variably amplify and / or attenuate the measurement signals proportional to the forces and / or torques present in the object of investigation (2) in the sense of a fine adjustment.

Description

[0001] The present invention relates to a measuring device and a method for measuring forces and / or torques present in a test object made of ferromagnetic material.

[0002] The measuring device proposed by the present invention includes, among other things, a magnetoelastic sensor. It is well known in the prior art to use such sensors for the non-destructive measurement of torques and / or forces in objects made of ferromagnetic material. Such sensors are based on the inverse magnetostrictive effect, i.e., the effect by which ferromagnetic materials experience a change in magnetic susceptibility when mechanical stresses occur. Since mechanical stresses are induced not only by tensile and compressive forces but also by torsion, the inverse magnetostrictive effect can also be used for torque measurement, for example, to measure the torque of a shaft without contact. If a magnetic field is applied in a ferromagnetic layer of an object under investigation, e.g.,When a wave is induced, a response signal is generated in the layer, depending on the applied voltages. This signal can be detected via suitable receiving coils. Since the response signal is influenced by the voltages occurring in the ferromagnetic material, the forces and / or torques present in the object under investigation can be deduced from the response signal. The detected electrical signal depends primarily on the distance between the magnetoelastic sensor and the object under investigation, as well as on the temperature of the ferromagnetic material.

[0003] Several different sensors are known from the prior art that utilize the magnetoelastic effect to measure torques or forces of ferromagnetic objects without contact. Magnetoelastic sensors are generally characterized by high accuracy.

[0004] As already mentioned, the signals detected by a magnetoelastic sensor depend strongly on the distance between the sensor and the object under investigation or measurement. EP 2 769 192 B1 discloses a sensor that takes the distance between the object under investigation and the sensor into account. The torsion and torque sensor described therein comprises a magnetoelastic force sensor with a sensor head having a ferrite core with a central leg and four outer legs surrounding the central leg. A transmitting coil generating a magnetic field is arranged on the central leg, and magnetic field sensors for measuring a magnetic flux caused by the magnetic field of the transmitting coil in a measured object are arranged on the outer legs.Furthermore, the force sensor described therein has a detection device for acquiring an electrical quantity representing the inductance of the transmitting coil or uniquely related to it, wherein the magnetoelastic force sensor also includes a device for determining the distance of the sensor head from the object being measured from the electrical quantity. In the device described therein, information about the distance between the sensor and the object under investigation is thus extracted from data on the coil inductance of the transmitting coil.

[0005] Accordingly, the present invention is based on the objective of providing a measuring device and a method for measuring forces and / or torques present in a test object made of ferromagnetic material, with which a reliable, accurate and flexible measurement of forces and / or torques in said test object is ensured, in particular also during its dynamic movement relative to the measuring device, taking into account a variable distance between the test object and the measuring device. Accordingly, the stated objective is achieved by using the measuring device for measuring forces and / or torques present in a test object made of ferromagnetic material.

[0006] The aforementioned problem is solved by a measuring device having the features of claim 1, by a method having the features of claim 4, and by using the measuring device having the features of claim 5.

[0007] The measuring device proposed by the invention is—as already mentioned—a measuring device for measuring forces and / or torques present in a test object made of ferromagnetic material. The measuring device initially comprises a magnetoelastic sensor. The latter has a first coil unit configured to generate a magnetic field that extends at least partially outside the sensor and penetrates at least a portion of the test object. The magnetic field is generated by applying an electrical voltage, for example, alternating current (Maxwell's equations). Furthermore, the magnetoelastic sensor comprises a second coil unit configured to detect response signals induced in the test object by the generated magnetic field, the response signals reflecting local magnetic field changes within the test object.Despite the advantageous embodiments described later, the geometry and shape of the first and second coil units are not fundamentally fixed. Thus, the number of individual coils underlying the coil units, their geometry, spatial arrangement, coil material, number of turns, etc., can vary.

[0008] The detection of magnetic field changes present in the object under investigation, resulting from magnetic field changes generated by the first coil unit, forms the basis of the magnetoelastic measurement principle and is well-known in the prior art. The local magnetic field changes in the object under investigation can be measured by the second coil unit, since these changes generate voltages in the coil unit, which can then be measured as an electrical quantity.

[0009] Furthermore, the measuring device comprises at least one capacitive distance sensor, which forms an integrated unit with the magnetoelastic sensor and is configured to detect distance values ​​between the measuring device and the object under investigation. "Integrated" unit means that the magnetoelastic sensor and the distance sensor can be arranged in a common housing.

[0010] Compared to the prior art, such a distance sensor enables the direct measurement of the distance between the measuring device and the object under investigation. Compared to indirect distance determination, the distance can be determined more precisely and reliably with a dedicated distance sensor. As already indicated by the term "at least one" distance sensor, several distance sensors can easily be integrated into the measuring device. This allows the distance to be precisely determined at multiple relative positions of the measuring device to the object under investigation. This is particularly advantageous when the distance between the measuring device and the object under investigation changes with respect to the dimensions (i.e., the length or width) of the measuring device.To account for such distance variations during measurement, it can be advantageous to distribute several distance sensors across the measuring range of the measuring device. Alternatively, a single distance sensor can be provided, configured to determine distances at multiple locations. For example, the distance sensor can be implemented as capacitive sensor surfaces on an end face of the measuring device.

[0011] The measuring device also includes an evaluation unit designed to determine measurement signals based on response signals received from the second coil unit. These signals are proportional to the forces and / or torques present in the object under investigation. Values ​​proportional to these forces and / or torques can be determined from the electrical voltages induced in the second coil unit (induced by the locally changing magnetic fields in the object). By appropriately converting or scaling the acquired signals (e.g., with respect to the specific object under investigation), a differential voltage or a digital signal proportional to the forces and / or torques can be output.The measurement signals obtained in this way can be further processed in a raw data format, or alternatively converted directly into force and / or torque values.

[0012] Furthermore, the evaluation unit is designed to compensate for fluctuations in the measurement signals resulting from dynamic variations in the distance between the measuring device and the object under investigation, such as signal attenuation and / or signal amplification. If, for example, a certain distance between the measuring device and the object under investigation leads to an attenuation of the measurement signals that exceeds a predefined value, it may be necessary to amplify the corresponding measurement signals depending on the measured distance. Similarly, it may be necessary to selectively attenuate the measurement signals if they are stronger than a predefined limit. This signal amplification or attenuation can be automated, for example, via a routine operated by the evaluation unit.

[0013] The distance values ​​mentioned refer to the distance between the measuring device and the object under test, or the size of any air gap present there (the magnetoelastic measuring method described here is a non-contact measuring principle). For a planar object under test, it will generally suffice to determine a single distance value between a surface of the measuring device facing the object under test and a surface of the object. However, in the case of objects under test with a non-planar surface (for example, a shaft with a cylindrical surface profile), a varying distance between the measuring device and the object under test can exist along one or more spatial directions within the area of ​​the measuring device.Accordingly, it can be advantageous to determine distance values ​​at multiple positions (this can be achieved, for example, by providing several distance sensors or by using a single distance sensor capable of measuring distances at multiple locations). From distance values ​​determined at different spatial locations, the evaluation unit can calculate an average distance value, which can then be used to compensate for dynamic distance variations. This can also be done directly based on individual distance values. With the proposed measuring device, distance values ​​can be measured in real time and thus incorporated into the evaluation or determination of the forces or torques present in the object under investigation.

[0014] The evaluation unit can be a microcontroller, an ASIC, an FPGA, or a similar component. The evaluation unit can also provide a data processing unit in the form of a portable computing unit.

[0015] It is also conceivable that the evaluation unit is a mobile device, a portable computer, etc., connected to the measuring device via a signal connection. This signal connection can be wireless or wired.

[0016] The necessity of the aforementioned measurement signal compensation arises from the fact that the distance between the measuring device and the object under test (i.e., the air gap width) has an inversely proportional effect on the signals detectable by the second coil unit (e.g., on the differential output voltage of the second coil unit). The greater the distance, the weaker the detectable signals. As described later, the second coil unit can have several receiving coils combined in a differential or crossed coil configuration. Such a coil arrangement can compensate for measurement signal errors due to angular changes between the measuring device and the object under test, but not for changes in the distance or air gap width. The measuring device proposed by the invention provides a remedy for this.

[0017] Further advantageous embodiments are specified in the dependent claims. It should be emphasized at this point that all of the advantageous embodiments of the measuring device described in the dependent claims and below are also included in the subject matter of the method according to the invention. Accordingly, the embodiment variants described in the context of the measuring device according to the invention can also be possible embodiments of the method according to the invention.

[0018] According to a first advantageous embodiment of the invention, the first coil unit comprises a transmitting coil arranged on a first ferrite core. By applying an alternating electrical voltage, the transmitting coil generates a magnetic field that at least partially penetrates the object under investigation, particularly a near-surface region. Preferably, the measuring device is held in a fixed position during the generation of the magnetic field. The transmitting coil can be a cylindrical coil wound with a plurality of turns around the ferrite core. The number of turns depends on the required coil quality factor and excitation frequency. In particular, it can be provided that the coil is not wound directly onto the ferrite core, but rather that an electrically insulating intermediate layer, for example made of plastic, is provided between the coil and the ferrite core.This prevents unwanted short circuits. The transmitting coil is coupled to an electrical circuit that provides the necessary voltage to generate the magnetic field. Specifically, the transmitting coil is part of an electrical resonant circuit, such as a series resonant circuit. The series resonant circuit can be kept in resonance via phase locking or a resonator circuit. The setting of the resonant frequency depends on the coil's quality factor (i.e., in particular, the coil material used and the diameter of the coil wire), as well as the number of turns. It should also be noted that the resonant frequency can depend on other factors, such as the air gap between the object under investigation and the measuring device or the coil units.The individual turns of the transmitting coil do not necessarily have to be arranged one above the other in a vertical direction parallel to the first ferrite core (stacked arrangement); rather, the required turns can also be arranged next to each other in a plane perpendicular to the ferrite core.

[0019] According to a further advantageous embodiment of the invention, the second coil unit can comprise two pairs of coils surrounding the transmitting coil, each pair having two opposing receiving coils relative to the circumference of the transmitting coil. The second coil unit can thus be configured as a cross-coil arrangement. With such an arrangement of the receiving coils, the angular dependence between the measuring device and the object under investigation can be compensated. The receiving coils are advantageously each arranged on a second ferrite core. In such a configuration or arrangement of the receiving coils, for example, two separate signals are received from the two receiving coil pairs, with each signal being assigned to one receiving coil pair (i.e., providing a combination of signals from two receiving coils).It is also possible to provide a greater number of receiving coil pairs than two, for example four receiving coil pairs (8 coils), six receiving coil pairs (12 coils), eight receiving coil pairs (16 coils), etc.

[0020] According to a further embodiment of the invention, both the transmitting coil and the receiving coils can be arranged on a common substrate (e.g., a PCB). For example, the coils can be printed onto the substrate, milled into it, or etched into it. In the latter two cases, the substrate initially comprises a metallic surface, from which the metal surface is removed according to a predetermined coil geometry. Furthermore, the substrate can have recesses by virtue of which it can be placed over the first and second ferrite cores. The ferrite cores thus protrude through the coil substrate, while the coils are arranged on the substrate. The recesses are formed in the area of ​​the respective coil centers in the coil substrate. This design enables simple and quick replacement of the coils, for example, in the case of a necessary inductance adjustment, etc.

[0021] According to a further advantageous embodiment of the invention, the first ferrite core and the second ferrite cores can be arranged on a common ferrite base plate, forming a common ferrite core assembly. The ferrite core assembly can, for example, be a single-piece component and manufactured by casting. The first ferrite core and the second ferrite cores can be shaped like rod cylinders and extend perpendicularly to the base plate from a cylindrical base arranged on the base plate. The second ferrite cores are arranged around the first ferrite core; in cross-section, the second ferrite cores can be arranged in a square or rectangular pattern around the first ferrite core. In this case, the second ferrite cores would form the corners of a square or rectangle, respectively.The individual rod cylinders (of the first ferrite core and the second ferrite cores) have an outer cylindrical surface. Besides the one-piece construction of the ferrite core assembly, it can also be composed of individual ferrite cores and a ferrite base plate, which are glued or screwed together.

[0022] In an advantageous embodiment, the transmitting coil and the receiving coils can be cylindrical coils surrounding an outer surface of the first ferrite core and the second ferrite core, respectively. As already mentioned, the coils are not in direct contact with the ferrite cores, but rather are arranged on an electrical insulator surrounding the ferrite cores or on a common carrier board (see above). The insulator can be, for example, a plastic sheath, an adhesive, or an insulating varnish. Generally, arranging the coils (both the transmitting and receiving coils) on ferrite cores is advantageous with regard to increasing the coil inductance and improving high-frequency magnetic properties. Ferrite is a soft magnetic material with a relatively high magnetic saturation flux density and / or high magnetic permeability.This allows, for example, the magnetic flux generated by a coil (especially the transmitting coil) to be focused and guided with minimal loss. Referring to the previously mentioned arrangement of the coils on a common carrier board, it should be noted that up to 100 turns (or even more) are applied to the carrier board (e.g., a PCB) for each coil, for example, in the form of 10 layers with 10 turns each. The individual turns can therefore comprise several layers.

[0023] According to a further advantageous embodiment of the invention, the device can be configured to variably amplify and / or attenuate the measurement signals proportional to the forces and / or torques present in the object under investigation. The measurement signals can be amplified or attenuated either by the evaluation unit or an associated data processing unit, or by a separate preamplifier unit. It can be provided that the signals received by the individual receiving coils, or combined signals, are amplified or attenuated.

[0024] When using a cross-coil arrangement, the signals received by each pair of receiving coils (this signal can already be a combined signal from the individual coils assigned to the respective receiving coil pair) can be amplified or attenuated (for example, by suitable preamplifier units) before being fed to the evaluation unit, where further amplification (e.g., digital) can be performed as part of data processing or preparation. With a combination of the received signals prior to variable amplification or attenuation, these signals can be combined in any permutation; that is, the selection of the receiving coils providing the combined signals can be flexibly chosen.

[0025] In another variation, variable gain and / or attenuation can refer to a dynamic adjustment of the measurement gain (of the received signals), which is specifically based on the nature (material), size, shape, and type of the object being measured, and in particular on the expected magnitude of the required signal gain or attenuation. This allows for the pre-selection of a suitable signal gain or attenuation for different objects, based on the available object information. Based on this initial coarse setting, further amplification can be performed as a fine-tuning adjustment, depending on the actual signal strength. This procedure can be carried out at the pre-amplification stage as well as at the stage of subsequent (including digital) amplification.Dynamic measurement amplification can also be used to take into account and compensate for a dynamically changing air gap size (i.e., a dynamically changing distance between the measuring device and the object under investigation).

[0026] The difference between the signals provided by the two pairs of receiving coils, or between other combined and provided differential signals, is proportional to the mechanical forces or torques present in the object under test. However, this only applies if the distance between the measuring device and the object under test is static or constant. By incorporating the distance values ​​measured capacitively by the distance sensor (especially the distance values ​​between the object under test and the receiving coils), the signal can be dynamically corrected or compensated. This enables the output of a compensated measurement signal, allowing precise signal values ​​to be obtained even in the presence of dynamic movements between the measuring device and the object under test, values ​​that are proportional to the forces and / or torques present in the object under test.

[0027] As mentioned at the outset, the invention also proposes a method for measuring forces and / or torques present in a test object made of ferromagnetic material. The method is carried out using the measuring device described above, and the steps described below are performed.

[0028] In a first process step (a.), the measuring device is initially positioned at a distance relative to a test object made of ferromagnetic material. Depending on the size or geometry of the test object, it may happen that the end face of the measuring device facing the test object and the surface of the test object are not parallel to each other. This can be the case, in particular, with test objects that have a round cross-section. When positioning the measuring device, it can be fixed in a suitable holding fixture relative to the (possibly moving) test object. Alternatively, it is also conceivable to position the measuring device on a moving unit (e.g., a movable xy or xyz measuring table) and move it relative to the test object (for example, to take measurements at different positions of the test object).An arrangement on a handling device that moves in three-dimensional space (e.g. a robot arm) or a handling device designed in the style of a delta robot is also conceivable.

[0029] In process step b, a magnetic field is generated using the first coil unit. This field extends at least partially outside the sensor and penetrates at least a portion of the object under investigation. In an alternative procedure, the penetration depth can be adjusted by varying the distance of the measuring device relative to the object. Alternatively, the measuring device can be moved relative to the object in a defined incremental sequence, i.e., the distance can be varied. Using this approach, forces and / or torques can be determined at different depths within the object. It is even possible to generate depth profiles of the forces and / or torques present in the object.

[0030] In process step c., the following sub-steps are performed at a predefinable number of measurement times: i. Detection of response signals induced in the object under investigation by the generated magnetic field using the second coil unit, wherein the response signals reflect local magnetic field changes in the object under investigation, ii. Recording of distance values ​​between the measuring device and the object under investigation.

[0031] Regarding the possible advantageous configurations for sub-steps i. and ii., reference is made to the preceding explanations.

[0032] In process step d., the following sub-steps are carried out using the evaluation unit: i. Determining measurement signals based on response signals received from the second coil unit, and proportional to the forces and / or torques present in the object under investigation, and ii. using the distance values: Compensating for fluctuations in the measurement signals resulting from a dynamic variation in distance between the measuring device and the object under investigation, for example signal attenuation and / or signal amplification.

[0033] Regarding the possible advantageous configurations of sub-steps i. and ii. (of process step d.), reference is made to the preceding explanations.

[0034] Further embodiments of the present invention will become apparent from the figures and the following description of the figures. These are intended to enable a person skilled in the art to carry out the invention. For example: Fig. 1 in a schematic side view the measuring device according to the invention in an arrangement relative to an object under investigation; Fig. 2 in a schematic top view the measuring device according to the invention, from which the geometry of the ferrite core arrangement and the arrangement of the receiving and transmitting coils can be seen; Fig. 3 in a schematic top view the measuring device according to the invention, from which a possible geometry of the capacitive distance sensor in relation to the ferrite core arrangement emerges; Fig. 4 a schematic representation of one of the circuit diagrams underlying the measuring device; Fig. 5 a first application example in which the measuring device or the method according to the invention can be used; Fig. 6 a second application example in which the measuring device or the method according to the invention can be used; Fig. 7 a third application example in which the measuring device or the method according to the invention can be used.

[0035] The Fig. Figure 1 shows the measuring device according to the invention in a schematic side view. As described above, the measuring device 1 is designed to measure the forces and / or torques present in a test object 2 made of ferromagnetic material. As shown in the figure, the measuring device 1 can be arranged at a distance from the test object 2 for carrying out the measurement. Depending on the geometry or arrangement of the test object 2, the distance values ​​A between the measuring device 1 and the test object 2 can vary along the length or width of the test object 2. In the example shown, the Fig. 1. The distance between an end face of the measuring device 1 facing the object 2 and the object 2 increases from left to right. Such a variation in distance can occur particularly with objects 2 that have convexly curved surfaces.

[0036] A key component of the measuring device 1 is a magnetoelastic sensor. This sensor initially comprises a first coil unit 3, which is configured to generate a magnetic field B1, B2 that extends at least partially outside the sensor and penetrates at least a portion of the object under investigation 2. The direction of the generated magnetic fields B1, B2 depends, among other things, on the distance of the ferromagnetic object under investigation 2. The magnetic fields B1, B2 can be adjusted via the first coil unit 3 such that they penetrate the object under investigation 2 at different points even with a varying distance A. As the Fig. As can also be seen in Figure 1, the first coil unit 3 comprises a transmitting coil 7 wound around a first ferrite core 8. However, the coil 7 is usually not wound directly onto the core 8, but rather onto a spacer or electrical insulator provided between the ferrite core 8 and the coil 7.

[0037] Furthermore, the magnetoelastic sensor comprises a second coil unit 4, which is configured to detect response signals induced by the generated magnetic field B1, B2 in the object under investigation 2, wherein the response signals reflect local magnetic field changes in the object under investigation 2. The second coil unit 4 has two coil pairs surrounding the transmitting coil 7, each coil pair having two opposing receiving coils 9 with respect to the circumference of the transmitting coil 7. The receiving coils 9 are each arranged on second ferrite cores 10. The arrangement of the transmitting coil 7 or the receiving coils 9 or of the first ferrite core 8 and the second ferrite cores 10 is particularly advantageous due to the Fig. 2. The ferrite cores 8, 10 are arranged on a ferrite base plate 11 and provide a ferrite core arrangement.

[0038] Another one in the Fig. The component of the measuring device 1 shown in Figure 1 is a capacitive distance sensor 5, which forms an integrated unit with the magnetoelastic sensor and is configured to detect distance values ​​A between the measuring device 1 and the object under investigation 2. The capacitive distance sensor 5 generates different capacitive fields K1, K2 (depending on the distance A to the object under investigation 2). Based on this, the distance A between the measuring device 1 and the object under investigation 2 can be determined via the distance sensor 5. As shown in the Fig. As shown in Figure 3, the distance sensor 5 can be disc-shaped and form part of an end face of the measuring device 1.

[0039] A further component of the measuring device is an evaluation unit 6, which is configured, on the one hand, to determine measurement signals based on response signals received from the second coil unit 4 and which are proportional to the forces and / or torques present in the object under investigation 2. On the other hand, the evaluation unit 6 is configured, using the distance values ​​A, to compensate for fluctuations in the measurement signals resulting from a dynamic variation in distance between the measuring device 1 and the object under investigation 2, for example, signal attenuations and / or signal amplifications. Further details on the evaluation unit 6 are described below. Fig. 4 explained.

[0040] The Fig. Figure 2 illustrates, in a schematic top view, the geometry and structure of the measuring device 1 according to the invention, from which the geometry of the ferrite core arrangement and the arrangement of the receiving and transmitting coils are evident. In the present example, the measuring device 1 has a round cross-sectional shape. The second ferrite cores 10 are clearly distributed around a centrally arranged first ferrite core 8. For example, the second ferrite cores 10 can be arranged in a square pattern around the first ferrite core 8. The same applies to the receiving coils 9 in relation to the transmitting coil 7.

[0041] The Fig. Section 4 refers to an exemplary circuit diagram that can form the basis of the measuring device 1. An essential component of the circuit diagram or the measuring device is the evaluation unit 6, the more detailed functions of which will be discussed below. Together with the transmitting coil 7 and the distance sensor 5, the receiving coils 9 form a probe head 11 of the measuring device 1. The transmitting coil 11 can be coupled to a transmitting coil resonant circuit. Components of the transmitting coil resonant circuit can include, for example, a driver 12 and a resonant frequency shifter 13. The resonant frequency of the transmitting coil can be set or adjusted via this shifter. The receiving coils 9, or coil pairs formed by them, are connected to the evaluation unit 6 via preamplifiers 14, 15. The preamplifiers transmit amplified or attenuated differential signals DM1, DM2 to the evaluation unit 6.The signals received by the receiving coils 9 can be amplified via the preamplifiers 14 and 15. Combined signals from several receiving coils 9 can also be amplified by the preamplifiers 14 and 15. The preamplifiers 14 and 15 can also attenuate the signals received by the coils.

[0042] As already mentioned, the evaluation unit 6 can be implemented as a microcontroller, ASIC, FPGA, or similar electronic components. Components of the evaluation unit can include, in particular, an input and scaling unit 16, which allows, for example, user-defined scaling (amplification or attenuation) to be specified. The resulting signal amplification or attenuation can be performed digitally within the evaluation unit 6. Alternatively, the relevant information is passed on to the preamplifiers 14 and 15. Furthermore, the evaluation unit 6 includes a distance compensation unit 17, which compensates the measured signals with respect to a distance value A determined by the calculated distance values. This also essentially involves adjusting the received signal intensities.

[0043] Furthermore, an additional object-specific scaling unit 18 may be provided, which allows a preliminary scaling with regard to signal amplification or signal attenuation based on characteristic data of the object 2.

[0044] The evaluation unit 6 can also include a storage unit 19 and a range-to-gain conversion unit 20. The latter can be used to specify further amplification conditions by the user.

[0045] Regarding the measurement procedure or the process flow according to the invention, reference is made to the introductory description.

[0046] In the Fig. Figures 5 to 7 show possible applications of the measuring device 1 according to the invention or of the measuring method. For example, the measuring device 1, formed from the probe head 11 and the evaluation unit 6, can be used to measure forces on steel connecting parts 21, 22.

[0047] Such connecting elements 21, 22 can be subjected to a force F (in this case, the connecting element 22), which can lead to the generation of magnetoelastically detectable forces in the connected steel connecting element 21. Examples of applications where such steel connecting elements 21, 22 are connected include lever assemblies, scales, or wheel suspensions. The figure schematically illustrates a shaft 24 rotating about an axis of rotation 23. The measuring device mentioned above can be used to measure torques occurring in the shaft. An exemplary application area could be motor steel shafts. The present invention allows for torque determination in the case of eccentric shaft rotation, low-tolerance shaft surfaces, or non-circular shaft surfaces. Fig.Figure 7 shows another application example, namely the determination of torque with the measuring device 1 according to the invention on a hollow shaft gearbox output side of an industrial robot arm 25. The probe head 11 and the evaluation unit 6 of the measuring device 1 are located directly in the motor control unit 26 and enable real-time torque measurements as well as control of the robot arm 25 based thereon. Reference symbol list 1 measuring device 2. Object of investigation 3 first coil unit 4 second coil unit 5 capacitive distance sensors 6 evaluation unit 7 Transmitting coil 8 first ferrite core 9 Receiving coil 10 second ferrite core 11 Sample head 12 drivers 13 Resonance frequency shifters 14 preamplifiers 15 preamplifiers 16 Input and scaling unit 17 Distance compensation unit 18 scale units 19 storage units 20 Range-to-Gain Conversion Unit 21 steel connecting part 22 steel connecting part 23 Rotation axis 24 wave 25 robot arm 26 Engine control unit A distance value B1 Magnetic field B2 Magnetic field DM1 Differential signal DM2 differential signal K1 capacitive field K2 capacitive field

Claims

[1] Measuring device (1) for measuring forces and / or torques present in an object of investigation (2) made of ferromagnetic material, comprising a. comprising a magnetoelastic sensor i. a first coil unit (3) configured to generate a magnetic field (B1, B2) which extends at least partially outside the sensor and penetrates at least a partial area of ​​the object under investigation (2), wherein the first coil unit (3) comprises a transmitting coil (7), ii. a second coil unit (4) configured to detect response signals induced by the generated magnetic field (B1, B2) in the object under investigation (2), wherein the response signals reflect local magnetic field changes in the object under investigation (2), wherein the second coil unit (4) comprises two pairs of coils surrounding the transmitting coil (7), each pair of coils having two opposing receiving coils (9) relative to the circumference of the transmitting coil (7), iii. a ferrite core arrangement comprising a first ferrite core (8) and second ferrite cores (10) distributed around the first ferrite core (8), wherein the ferrite cores (8, 10) are arranged on a common ferrite base plate (11), and wherein the ferrite cores (8, 10) are shaped in the manner of a rod cylinder and extend perpendicular to the base plate (11) from a cylindrical base arranged on the base plate (11); b. several capacitive distance sensors (5) which form an integrated unit with the magnetoelastic sensor and are configured to detect distance values ​​(A) present between the measuring device (1) and the object under investigation (2) at different spatial locations; c. an evaluation unit (6) which is set up for this purpose i. to determine measurement signals based on response signals received from the second coil unit (4) and which are proportional to the forces and / or torques present in the object under investigation (2), and ii. to calculate an average distance value from the distance values ​​(A) recorded at the different spatial locations and to use the average distance value to compensate for fluctuations in the measurement signals resulting from a dynamic distance variation between the measuring device (1) and the object under investigation (2), namely signal attenuations and / or signal amplifications; wherein the transmitting coil (7) and the receiving coils (9) are arranged on a common coil carrier, wherein the coil carrier has recesses by virtue of which the coil carrier can be plugged over the ferrite cores (8, 10), and wherein the recesses are formed in the area of ​​the respective coil centers in the coil carrier, wherein, based on object information available for the object of investigation (2), an adapted signal amplification or signal attenuation of the measurement signals can be preselected in the sense of a coarse adjustment, and wherein the measuring device (1) is set up to variably amplify and / or attenuate the measurement signals proportional to the forces and / or torques present in the object of investigation (2) in the sense of a fine adjustment. [2] Measuring device (1) according to claim 1, characterized by that the ferrite core assembly is a one-piece component. [3] Measuring device (1) according to one of the preceding claims, characterized by , that the transmitting coil (7) and the receiving coils (9) are cylindrical coils that surround an outer surface of the first ferrite core (8) and the second ferrite cores (10), respectively. [4] Method for measuring forces and / or torques present in a test object (2) made of ferromagnetic material using a measuring device (1) according to one of claims 1 to 3, wherein the measuring device (1) comprises a magnetoelastic sensor having a first and second coil unit (3, 4), several capacitive distance sensors (5) and an evaluation unit (6), comprising the following steps: a. Arranging the measuring device (1) at a distance relative to a test object (2) made of ferromagnetic material; b. using the first coil unit (3): generating a magnetic field (B1, B2) which extends at least partially outside the sensor and penetrates at least a part of the object under investigation (2). c. at a predefinable number of measurement points: i. Detection of response signals induced by the generated magnetic field (B1, B2) in the object under investigation (2) using the second coil unit (4), wherein the response signals reflect local magnetic field changes in the object under investigation (2), ii. Recording distance values ​​(A) between the measuring device (1) and the object under investigation (2) at different spatial locations; d. using the evaluation unit (6): i. Determining measurement signals based on response signals received from the second coil unit (4) and proportional to the forces and / or torques present in the object under investigation (2), and ii. Calculating an average distance value from the distance values ​​(A) recorded at the different spatial locations and using the average distance value: Compensating for fluctuations in the measurement signals resulting from a dynamic distance variation between the measuring device (1) and the object under investigation (2), namely signal attenuations and / or signal amplifications, whereby, based on object information available for the object under investigation (2), an adapted signal amplification or signal attenuation of the measurement signals is pre-selected in the sense of a coarse adjustment, and wherein, with the measuring device (1), the measurement signals proportional to the forces and / or torques present in the object under investigation (2) are variably amplified and / or attenuated in the sense of a fine adjustment. [5] Use of a measuring device (1) designed according to one of claims 1 to 3 for measuring forces and / or torques present in an object of investigation (2) made of ferromagnetic material, for example a rotating shaft or a moving steel connecting element, wherein the object of investigation (2) moves continuously or discontinuously relative to the measuring device (1), and wherein measurement signal fluctuations resulting from the movement or associated distance variations between the measuring device (1) and the object of investigation (2), namely signal attenuations and / or signal amplifications, are compensated.

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