Method for arranging at least three strain gauges on a planar component, in particular a resilient planar component

Abstract

The invention relates to a method for arranging at least three strain gauges (1, 2, 3) on a planar component (4, 6, 7), in particular a resilient planar component, which has at least one geometric and / or mechanical symmetry (S1, S2), in order to clearly determine a position and magnitude of a locally limited force (F), in particular point force, acting on the component (4, 6, 7).

Description

[0001] Method for arranging at least three strain sensors on a, in particular elastic, plate-shaped component

[0002] Technical area

[0003] The invention relates to a method for arranging at least three strain sensors on a, in particular elastic, plate-shaped component which has at least one geometric and / or mechanical symmetry, for unambiguously determining a position and magnitude of a locally limited, in particular point-like, force on the component.

[0004] State of the art

[0005] If a plate-shaped component has various symmetries (mirror, rotational symmetries, etc.) with regard to the distribution of material properties, component geometry and boundary conditions, etc., an ambiguous identification of the load position can occur if a locally limited point force acts on the component.

[0006] Description of the invention

[0007] The object of the invention is to create a method with which a reproducible, unambiguous determination of the position and magnitude of a locally limited force acting on a plate-shaped component is possible.

[0008] The invention solves the problem by the features of claim 1.

[0009] By forming a mathematical model for each strain sensor at least from a plate model, in particular a Kirchhoff plate model, based on an elastic plate theory of the component, from a sensor model for the electromechanical property of the strain sensor in question and from the geometric arrangement of the strain sensor in question on the component, it may be possible to find a unique solution that depends on the arrangement of the strain sensors with respect to the geometric and / or mechanical symmetry of the component.For this purpose, an estimation method is used for each mathematical model in order to calculate the solutions for each mathematical model under the specification of a locally limited, in particular point-like, force on the component that is the same for all mathematical models. Subsequently, all calculated solution values ​​of the solutions of the mathematical models are compared with each other to determine whether the solutions of the mathematical models essentially agree in a single solution value of the calculated solution values.

[0010] This makes it possible to determine whether a clear determination of the position and magnitude of a locally limited force acting on the component is possible.

[0011] If there is a multiple match, it can be concluded that the current arrangement of the strain sensors does not allow for a clear determination of the position and magnitude of the force.

[0012] However, if this agreement exists at just one point, it is certain that the entirety of the component (distribution of material properties, component geometry, boundary conditions, etc.) and all strain sensors used (position, length and orientation, type) no longer exhibits any symmetries. The geometric and / or mechanical symmetry of the component as a whole is thus canceled out because the agreement of all models in a solution value recognizes that the symmetries of the entirety of all sensors do not coincide with the symmetries of the component. The strain sensors thus enable a clear and reproducible determination of the position and magnitude of the force on the component. Furthermore, the method according to the invention is easy to handle and, after application, ensures an exact measurement of the position and magnitude of the force.Preferably, in the case of this lack of agreement, the geometric arrangement of at least one strain sensor of the strain sensors on the component is changed until this agreement results in an unambiguous determination of the position and magnitude of the force on the component.

[0013] Additionally or alternatively, at least one strain sensor can be replaced by another, in particular one with a different geometric design, strain sensor until this agreement results in a clear determination of the position and magnitude of the force on the component.

[0014] Thus, using the method according to the invention, the arrangement of the strain sensors can always reproducibly lead to a clear determination of the position and magnitude of the force on the component.

[0015] The method can be further facilitated if the strain sensors are arranged on the component, each with the longitudinal extension, in such a way that for at least one, in particular for each, geometric and / or mechanical symmetry on the component, at least one strain sensor of the strain sensors has an asymmetrical course with its longitudinal extension in relation to this geometric or mechanical symmetry.

[0016] If, for example, the component has several geometric and / or mechanical symmetries, the above can be achieved if, for each geometric and / or mechanical symmetry on the measuring object, a strain sensor of the strain sensors is arranged in such a way that its longitudinal extension has an asymmetrical course with respect to a symmetry of the geometric and / or mechanical symmetries.

[0017] The above can be achieved, for example, if an arranged strain sensor of the strain sensors exhibits an asymmetrical profile with respect to a mirror symmetry as the geometric symmetry of the component. It is also conceivable for an arranged strain sensor of the strain sensors to exhibit an asymmetrical profile with respect to a rotational symmetry as the geometric and / or mechanical symmetry of the component. This can reliably break a rotational symmetry of the component.

[0018] Preferably, an arranged strain sensor of the strain sensors has an asymmetrical course with respect to a point symmetry as geometric and / or mechanical symmetry of the component in order to break this symmetry.

[0019] Preferably, the longitudinal extension of a strain sensor of the strain sensors runs along the geometric and / or mechanical axis or plane of symmetry of the component. This arrangement along a symmetry enables, for example, more uniform sensitivity, particularly with respect to possible force loads that may be randomly distributed across the surface.

[0020] If the strain sensors are provided with a substantially linear, in particular straight, longitudinal extension on the component, this can further facilitate the arrangement of the strain sensors.

[0021] For this purpose, strain sensors preferably have a straight path, allowing them to be easily applied, laid, or clamped during the manufacturing process. Curved paths along optimal paths are possible, however, and increase the accuracy of the evaluation. Furthermore, linear strain sensors monitor the component over a comparatively large area and average out interference effects, which can further improve the sensitivity of the strain sensors.

[0022] Preferably, the strain sensor comprises at least one elasto-resistive wire, which can further increase the reliability and / or accuracy of the measurement data acquisition. For example, the plate-shaped component is a protective plate for a transaction battery or a base plate of this transaction battery.

[0023] Short description of the drawing

[0024] The figures illustrate the subject matter of the invention in more detail using several exemplary embodiments.

[0025] Fig. 1 shows a plate-shaped component with a first arrangement of three strain sensors,

[0026] Fig. 1 a Views of three solutions of three mathematical models, each containing a sensor model of a strain sensor, for the first arrangement shown in Fig. 1,

[0027] Fig. 1 b shows the calculated solution values ​​of the solutions shown in Fig. 1a,

[0028] Fig. 2 shows the plate-shaped component of Fig. 1 with a second arrangement of the three strain sensors according to a first embodiment of the invention, Fig. 2a shows views of three solutions of three mathematical models, each containing a sensor model of a strain sensor, for a second arrangement of these strain sensors on a plate-shaped component,

[0029] Fig. 2b is a representation of the calculated solution values ​​of the solutions shown in Fig. 2a,

[0030] Fig. 3 shows a third arrangement of three strain sensors according to the invention on a rotationally symmetrical and plate-shaped component according to a second embodiment of the invention and

[0031] Fig. 4 shows a fourth arrangement according to the invention of three strain sensors on a mirror-symmetrical, circular and plate-shaped component according to a third embodiment of the invention.

[0032] Way of carrying out the invention According to Figures 1 and 2, strain sensors 1, 2, 3 can be seen which are arranged on a mirror-symmetrical and rectangular component 4, specifically on the upper side 4a of this component 4. The component 4 has two symmetries S1 and S2, namely mirror symmetries, as can be seen in Figures 1 and 2. In addition, the component 4 is, for example, elastic, but can also have elastic-plastic properties during deformation, also depending on the magnitude of the mechanical load. For example, this component 4 is a protective plate for a transaction battery or a base plate of this transaction battery.

[0033] According to Figures 1a, 1b and 2a, 2b, the method for arranging three strain sensors 1, 2, 3 on an upper side 4a of a plate-shaped component 4 is illustrated.

[0034] Thus, it can be seen from Fig. 1 a and 1 b that with the first geometric arrangement of the strain sensors 1, 2 and 3 shown in Fig. 1 and the geometric symmetry S1, S2 of the elastic component 4, a load position, namely a vertical load with a point-like force F, cannot be clearly determined.

[0035] On the other hand, according to the second arrangement of the strain sensors 1, 2 and 3 according to Fig. 2 according to the invention, a clear determination of the position and magnitude of the locally limited point-like force F on the component 4 is possible.

[0036] This is made possible according to the invention in that for each strain sensor 1, 2, 3 a mathematical model is formed at least from a plate model, namely Kirchhoff's plate model, based on an elastic plate theory of the component, from a sensor model for the electromechanical property of the respective strain sensor 1, 2, 3 and from the geometric arrangement of the respective strain sensor 1, 2, 3 on the component 4. Thus, for example, the respective mathematical model is composed of at least these parts: the plate model, the respective sensor model and the geometric arrangement of the respective sensor 1, 2, 3. Further parts are conceivable. The solutions A, C and B1 or B2 for the three mathematical models are shown in Fig. 1a and 2a. In order to calculate these solutions A, B1, B2 and C, an estimation method is used for each mathematical model.Using the estimation method, the possible positions of this force F are calculated for each mathematical model and its solutions A, B1, B2 or C, assuming a locally limited point force F acting on the component 4 that is the same for all mathematical models. The resulting solution values ​​W(A), W(B1), W(B2) and W(C) of the solutions A, B1, B2 and C can be seen in Fig. 1 b and 2b.

[0037] All calculated solution values ​​W(A), W(B1 ), W(B2) and W(C) of the solutions A, B1 , B2, C of the mathematical models are now compared with each other.

[0038] As can be seen in Fig. 1 b for this arrangement of the strain sensors 1 , 2 , 3 according to Fig. 1, the calculated solution values ​​W(A), W(B1 ) and W(C) have two common intersection points 5. The solutions A, B1 and C of the mathematical models therefore do not agree on a single solution value 5 of the calculated solution values ​​W(A), W(B1 ) and W(C). An unambiguous determination of the position and magnitude of the force F on the component 4 is therefore not possible. This is because the strain sensors 1 , 2 , 3 arranged according to Fig. 1 with their respective longitudinal extension do not have an asymmetric course with regard to all geometric or mechanical symmetries S1 , S2 of the component 4.

[0039] However, according to the invention, a unique solution is given if a single solution value results, as shown below:

[0040] As shown in Fig. 2b for the arrangement according to the invention according to Fig. 2, there is a match in a single solution value 5 that is common to all solutions A, B2, C of the mathematical models. This makes it possible to unambiguously determine the position and magnitude of the force F on the component 4. This is because the entirety of component 4 and strain sensors 1, 2, 3 no longer have any symmetries. The second and third strain sensors 2 and 3 break the two mirror symmetries S1, S2 of component 4, which results in unambiguousness. In order to achieve this unambiguous solution, a change must be made to the arrangement of the strain sensors 1, 2, 3 on the component 4 according to Fig. 1. This change can take place in a separate method step. Starting from Fig. 1, this change is achieved by changing the arranged second strain sensor 2 in the arrangement, as shown in Fig. 2.

[0041] Generally speaking, the strain sensors 1, 2, 3, each with the longitudinal extension L1, L2, L3, are arranged on the component 4 in such a way that for each geometric and / or mechanical symmetry S1, S2 on the component 4, at least one strain sensor 1, 2 or 3 of the strain sensors 1, 2, 3, with its longitudinal extension L1, L2, L3, has an asymmetrical course with respect to this geometric or mechanical symmetry S1, S2.

[0042] With this change in the arrangement of the second strain sensor 2, the second and third strain sensors 2, 3 of the strain sensors 1, 2, 3 now exhibit an asymmetrical profile with respect to the two geometric mirror symmetries S1, S2 of the component 4. This enables a clear determination of the position and magnitude of the force F on the component 4, as can be seen in the single solution value 5 in Fig. 2b.

[0043] Fig. 3 shows an inventive arrangement of three strain sensors on a doubly rotationally symmetrical, plate- and rhomboid-shaped component 6 according to a second exemplary embodiment. The third strain sensor 3 breaks the two symmetries S1, S2 of component 6, thereby providing unambiguous determination of the position and magnitude of the locally limited, point-like force F acting on component 6.

[0044] This uniqueness is also given in the third embodiment according to Fig. 4. On this rotationally symmetric component 7 with infinitely many rotational and mirror symmetries, the strain sensors 1 and 2 lead to a double mirror or rotational symmetry, which is broken by the third strain sensor 3 of the strain sensors 1, 2, 3.

[0045] As can also be seen from all embodiments according to the invention according to Fig. 2, 3 and 4, several strain sensors run along a geometric axis of symmetry S1, S2 of the respective component 4, 6, 7. Thus, the strain sensor 1 runs along the geometric axis of symmetry S1 of the component 4, the strain sensors 1, 2 run along the geometric axis of symmetry S1 of the component 6 and the strain sensors 1, 2 run along the geometric axis of symmetry S1 of the component 7.

[0046] All strain sensors 1, 2, 3 are designed as elasto-resistive wires. The strain sensors 1, 2, 3 are provided on the respective component 4, 6, 7 with a substantially linear longitudinal extension, with the first and second strain sensors 1, 2 extending straight. This considerably simplifies the arrangement of the strain sensors 1, 2, 3.

[0047] It goes without saying that the solutions of the mathematical models, especially when using estimation methods that provide approximate solutions, are often not exactly the same in a single solution value. A person skilled in the art understands that small deviations may occur and lie within a narrow tolerance range. Therefore, a person skilled in the art will consider the comparison, in accordance with their expertise, to be a substantial match.

[0048] In general, it is noted that "in particular" can be translated into English as "more particularly." A feature preceded by "in particular" is to be considered an optional feature that can be omitted and thus does not constitute a limitation, for example, of the claims. The same applies to "vorzugsweise," translated into English as "preferably."

Claims

Patent claims:

1. Method for arranging at least three strain sensors (1, 2, 3) on a, in particular elastic, plate-shaped component (4, 6, 7), which has at least one geometric and / or mechanical symmetry (S1, S2), for the unambiguous determination of a position and magnitude of a locally limited, in particular point-like, force (F) on the component (4, 6, 7), in which the strain sensors (1, 2, 3) are arranged with a longitudinal extension on the component (4, 6, 7) are arranged geometrically, for each strain sensor (1, 2, 3) a mathematical model at least comprising a plate model, in particular a Kirchhoff plate model, based on an elastic plate theory of the component (4, 6, 7), a sensor model for the electromechanical property of the respective strain sensor (1, 2, 3) and the geometric arrangement of the respective strain sensor (1, 2, 3) is formed on the component (4, 6, 7), an estimation method is used for each mathematical model in order to calculate the solutions (A, B1, B2, C) for each mathematical model, specifying a locally limited, in particular point-like, force (F) on the component (4, 6, 7) that is the same for all mathematical models, and then all calculated solution values (W(A to C)) of the solutions (A, B1, B2, C) of the mathematical models are compared with one another to determine whether the solutions of the mathematical models essentially agree in a single solution value (W(A to C)) of the calculated solution values (W(A to C)).

2. Method according to claim 1, characterized in that in the case of this lack of agreement, the geometric arrangement of at least one strain sensor (1, 2 or 3) of the strain sensors (1, 2, 3) on the component (4, 6, 7) is changed and / or at least one strain sensor (1, 2, 3) is replaced by another, in particular differently geometrically designed, strain sensor (1, 2, 3), until this agreement results in a clear determination of the position and magnitude of the force (F) on the component (4, 6, 7).

3. Method according to claim 1 or 2, characterized in that the strain sensors (1, 2, 3) are arranged on the component (4, 6, 7) with their respective longitudinal extensions in such a way that for at least one, in particular for each, geometric and / or mechanical symmetry (S1, S2) on the component (4, 6, 7), at least one strain sensor (1, 2 or 3) of the strain sensors (1, 2, 3) has an asymmetrical course with its longitudinal extension in relation to this geometric or mechanical symmetry (S1, S2).

4. Method according to claim 3, characterized in that an arranged strain sensor (1, 2 or 3) of the strain sensors (1, 2, 3) has an asymmetrical course with respect to a mirror symmetry as geometric and / or mechanical symmetry (S1, S2) of the component (4, 6, 7).

5. Method according to one of claims 3 to 4, characterized in that an arranged strain sensor (1, 2 or 3) of the strain sensors (1, 2, 3) has an asymmetrical course with respect to a rotational symmetry as geometric and / or mechanical symmetry (S1, S2) of the component (4, 6, 7).

6. Method according to one of claims 3 to 5, characterized in that an arranged strain sensor (1, 2 or 3) of the strain sensors (1, 2, 3) has an asymmetrical course with respect to a point symmetry as geometric and / or mechanical symmetry (S1, S2) of the component (4, 6, 7).

7. Method according to one of claims 3 to 6, characterized in that an arranged strain sensor (1, 2 or 3) of the strain sensors (1, 2, 3) runs with its longitudinal extension along the geometric and / or mechanical axis or plane of symmetry of the component (4, 6, 7).

8. Method according to one of claims 1 to 7, characterized in that the strain sensors (1, 2, 3) are provided with a substantially linear, in particular straight, longitudinal extension on the component (4, 6, 7).

9. Method according to one of claims 1 to 8, characterized in that the strain sensor (1, 2, 3) has at least one elasto-resistive wire.

10. Method according to one of claims 1 to 9, characterized in that the plate-shaped component (4, 6, 7) is a protective plate for a transaction battery or a base plate of this transaction battery.

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