Measuring arrangement, measuring device, test bench, and, method for determining a torque loss of an electrical machine with a rotor by means of a measuring arrangement

Description

/ 23 MEASURING ARRANGEMENT, MEASURING DEVICE, TEST BENCH, AND METHOD FOR DETERMINING THE TORQUE LOSS OF AN ELECTRIC MACHINE WITH A ROTOR BY MEANS OF A MEASURING ARRANGEMENT

[001] The invention relates to a measuring arrangement having an electric machine with a rotor and a measuring device for determining a torque loss of the electric machine, wherein the measuring device has a clamping device and at least one piezoelectric element, preferably at least three, in particular four, piezoelectric elements, each with a preferred direction, wherein the clamping device supports at least one piezoelectric element.

[002] The resistance or load torque Mw applied to an electric machine in motor operation is composed of a drive torque Ma and a torque loss Mv that counteracts the drive torque. The torque loss is caused, in particular, by air friction, bearing friction and, depending on the electric machine, by brush friction and / or electric eddy currents.

[003] Document WO 2018 / 046296 A1 describes a method for distinguishing an electromechanical actuator unit, wherein a value for a torque loss of the electromechanical actuator unit is determined based on a quiescent current, the difference between the first value and the second value for the voltage induced in the electric motor and the mass inertia of the electromechanical actuator unit.

[004] Document WO 2019 / 144171 A1 also describes a measuring system for determining a moment of force and / or torque on a torque transmission shaft, wherein the measuring system has at least three, in particular at least four, piezoelectric elements, each with a preferred direction, which are arranged in different positions around a rotational geometric axis of the shaft in a transmitted force flow. Petition 870250085575, dated 09 / 22 / 2025, p. 15 / 48 / 23 through the axis in such a way that a force of the force flow, in particular exclusively, acts on the piezoelectric elements, wherein the preferred directions are each parallel or in a single plane that is intercepted by the rotational geometric axis, and wherein the preferred direction of at least two, in particular at least three, of the piezoelectric elements is neither parallel nor antiparallel to each other.

[005] Document WO 2019 / 144172 A1 also describes a measuring device for determining a force and / or torque on a torque transmission shaft, which is mounted by means of a bearing device, in particular in a machine whose output and / or input shaft is formed by the torque transmission shaft, wherein the measuring device is arranged on a torque transmission shaft, wherein the measuring device has at least two, preferably three or four, piezoelectric elements in a clamping device, wherein the clamping device carries the piezoelectric elements and is designed in such a way that a force, in particular the shear force, between the bearing device and the support device for supporting the bearing device can be measured by means of the piezoelectric elements.

[006] An object of the invention is to provide an improved measurement arrangement for determining the torque loss of an electric machine. In particular, it is an object of the invention to be able to determine the torque loss Mv without measuring electrical parameters of the electric machine.

[007] This object is resolved by the precept of independent claims. Advantageous designs are claimed in the dependent claims.

[008] A first aspect of the invention relates to a measuring arrangement that has an electric machine with a rotor and a measuring device for determining a torque loss of the electric machine.

[009] in which the measuring device has a device of Petition 870250085575, dated 22 / 09 / 2025, p. 16 / 48 / 23 fixing and at least one piezoelectric element, preferably at least three, in particular four, piezoelectric elements, each with a preferred direction, wherein the fixing device supports the at least one piezoelectric element and mounts the electric machine by means of the at least one piezoelectric element in such a way that at least the shear forces between the electric machine and the fixing device can be measured by means of the at least one piezoelectric element, wherein the preferred direction or directions are each parallel to or in a single plane, wherein a geometric axis of rotation of the rotor intersects the plane at an angle between 45° and 135°, preferably between 85° and 95°, more preferably at least essentially perpendicularly, and wherein the rotor rotates freely.

[0010] A second aspect of the invention relates to a method for determining the torque loss of an electric machine with a rotor, wherein the electric machine is mounted on a measuring device in such a way that an axial torque can be measured on the machine and wherein the rotor rotates freely, comprising the following working steps: • Initially operate the machine in such a way that the rotor reaches a predefined speed; • Secondly, operate the machine at rest when the preset speed is reached, at which point a signal from the measuring device representing the axial torque on the machine is monitored; • Identify a jump in the signal; and • Determine the magnitude of the jump, where the magnitude indicates the torque loss of the electrical machine.

[0011] A third aspect of the invention relates to a measuring device for determining the torque loss of an electric machine with Petition 870250085575, dated 09 / 22 / 2025, page 17 / 48 / 23 a rotor, in which the machine is mounted on a measuring device in such a way that an axial torque on the machine can be measured and in which the rotor rotates freely, comprising: • means for controlling the operation of the machine, configured to initially operate the machine in such a way that the rotor reaches a predefined rotational speed and then operate the machine at rest; • means for monitoring a signal from the measuring device representing the axial torque of a machine; • means to identify a jump in the signal; and • means to determine the magnitude of the jump, where the magnitude indicates the torque loss of the electrical machine.

[0012] A fourth aspect of the invention relates to a test bench.

[0013] To rotate freely, in the sense of the invention, preferably means not loaded by an external load.

[0014] A piezoelectric element within the meaning of the invention has at least one piezoelectric crystal and contacts for electrical connection to it. Preferably, the piezoelectric element is designed as a sensor with other components, such as a housing. Furthermore, a piezoelectric crystal preferably exhibits a piezoelectric effect.

[0015] A preferred direction within the meaning of the invention indicates the loading direction of the piezoelectric element, in particular by means of a shear force on its end face, in which the strongest voltage is generated in the piezoelectric crystal of the piezoelectric element. The preferred direction is also called the polarization direction.

[0016] An axial torque in the sense of the invention is preferably the torque applied to the rotor of a machine.

[0017] In operation at rest, in the sense of the invention, the current Petition 870250085575, dated 22 / 09 / 2025, page 18 / 48 / 23 of control preferably does not cause either drive torque or brake torque. In addition, the control current is preferably switched off.

[0018] A means in the sense of the invention may be implemented in hardware and / or software and may comprise, in particular, a particularly digital processing unit, in particular a microprocessor unit (CPU), which is connected by means of data or signals, in particular digitally, to a memory system and / or bus, and / or to one or more programs or program modules. The CPU may be designed to process commands implemented as a program stored in a memory system, detect input signals from a data bus and / or output signals to a data bus.A memory system may comprise one or more storage media, in particular different media, in particular optical, magnetic, solid-state and / or other non-volatile media. The program may be designed in such a way that it incorporates or is capable of executing the methods described herein, so that the CPU can execute the steps of such methods.

[0019] The invention is based on the approach of determining the torque loss of an electric machine by means of a reaction torque to support the electric machine, setting the drive torque Ma of the electric machine to zero.

[0020] According to the invention, this is achieved by first allowing the machine to rotate freely at a predefined speed and then abruptly switching the electric machine to standby mode while maintaining a constant speed. This results in a jump in the torque acting on rotor 4, which corresponds to the axial reaction torque of the motor.

[0021] The measuring arrangement according to the invention allows measuring the torque loss of an electric machine directly, without the need to provide a load on the rotor. In other words, the moment of inertia of the rotor mass is not distorted by a measuring device that rotates with Petition 870250085575, dated 09 / 22 / 2025, page 19 / 48 / 23. This allows the torque loss of the electric machine to be determined with much greater precision.

[0022] According to the invention, electrical parameters such as voltages and induced currents of the electric motor do not need to be measured to determine torque loss. In this respect, the invention has the advantage that torque loss cannot be influenced by any measurement. Furthermore, it is not necessary to calculate any torque loss from electrical measurements based on physical relationships. The method according to the invention for determining torque loss is also significantly more accurate than such a calculation.

[0023] Furthermore, the measuring arrangement according to the invention can be implemented on test benches, which are much simpler in terms of design than, for example, when using a torque flange based on strain gauges. According to the invention, no loading machine is required. In addition, there is no need to install speed ramps.

[0024] The use of piezoelectric elements as measuring elements in the measuring device allows for a particularly precise determination of the jump in the signal. Piezoelectric elements allow for highly dynamic measurements, so they can reproduce the change in the signal from the value before the jump to the value after the jump with particular accuracy.

[0025] By mounting the electric machine using at least one piezoelectric element, it is also possible to measure a reaction torque to the axial torque acting on the rotor without performing measurements on the rotor itself. Piezoelectric elements are particularly suitable for mounting in this application because they have very high rigidity and sensitivity to highly dynamic vibrations.

[0026] In principle, it is possible to support the electric machine using only a single piezoelectric element and to support support points. Petition 870250085575, dated 09 / 22 / 2025, page 20 / 48 / 23 additional elements using other support elements. However, part of the power flow does not pass through the piezoelectric elements, but through the other support elements. Therefore, it is advantageous to use more piezoelectric elements to support the electric machine. In particular, it is advantageous to use two, three, or even four piezoelectric elements and then support the electric machine exclusively through the piezoelectric elements, so that all the power flow generated by the electric machine passes through the piezoelectric elements. This achieves a particularly high measurement accuracy.

[0027] According to the invention, the preferred direction or directions are parallel to or in a single plane, and the geometric axis of rotation of the rotor intersects the plane at an angle between 45° and 135°, preferably between 85° and 95°, more preferably at least essentially perpendicular. Thus, the motor is supported on the clamping device through its end face. This arrangement makes it particularly easy to determine the torque loss using piezoelectric shear elements as piezo elements. In particular, the measurement signals of individual piezoelectric elements can be calculated together in a particularly easy way to determine force components.

[0028] At least essentially within the meaning of the invention, this preferably means an angle range of + / -1°.

[0029] In an advantageous design of the measuring arrangement, the piezoelectric elements are arranged, each in different positions around a geometric axis of rotation of the electric machine rotor. This allows the electric machine to be supported in a particularly advantageous way in the clamping device, preferably without the use of other support elements, so that the electric machine is supported exclusively by piezoelectric elements.

[0030] In a further advantageous design of the measuring arrangement, the measuring device additionally comprises a pre-device. Petition 870250085575, dated 09 / 22 / 2025, page 21 / 48 / 23 tensioning and first pre-tensioning elements, wherein at least one piezoelectric element can be pre-tensioned or is pre-tensioned between the clamping device and the pre-tensioning device by means of the first pre-tensioning elements in such a way that at least one piezoelectric element is forcibly fixed, and wherein the electric machine is rotationally fixed to the pre-tensioning device.

[0031] Applying a pre-tension using a pre-tensioning device allows electrical machines to be changed in the measuring device without affecting the calibration of the measuring device. Piezoelectric elements must always be pre-tensioned to exhibit the desired linear behavior. However, each pre-tensioning and discharge can lead to a change in the power flow and therefore a change in the calibration of the measuring device. Thanks to the pre-tensioning device, the system only needs to be pre-tensioned once and the calculation can always remain the same. This allows electrical machines, in particular, to be changed quickly.

[0032] If no pre-tensioning device is available, the piezoelectric elements are fixed directly between the motor 2, in particular its housing, and the fixing device 5 in a forced manner.

[0033] In a further advantageous design of the measuring arrangement, the electric machine is fixed to the clamping device and is supported by at least one piezoelectric element in such a way that the at least one piezoelectric element is forcibly fixed.

[0034] This keeps the piezoelectric elements in position and eliminates the need for calibration when changing machines.

[0035] In a further advantageous design of the measuring arrangement, the clamping device or the pre-tensioning device has a recess in which a shaft of the electric machine can be accommodated and / or guided. Petition 870250085575, dated 09 / 22 / 2025, page 22 / 48 / 23 through it, in which preferably one side of the electric machine, where the shaft emerges, is facing the clamping device and / or the pre-tensioning device.

[0036] In a further advantageous design of the measuring arrangement, the geometric axis of rotation is oriented at least essentially vertically during the intended use of the measuring arrangement.

[0037] In a further advantageous design of the measuring arrangement, the clamping device or the electric machine is supported exclusively by at least one piezoelectric element.

[0038] As a result, all the relevant force flow passes through the piezoelectric element(s). This leads to particularly high measurement accuracy.

[0039] In a further advantageous design of the measuring arrangement, the preferred direction of at least one piezoelectric element is, in each case, oriented at least essentially tangentially to a direction of rotation of the rotor. This also allows the torque loss of the electric machine to be calculated in a simple manner.

[0040] In a further advantageous design of the measuring arrangement, the at least one piezoelectric element has a first subelement and a second subelement, by means of which shear forces can be measured in each case, wherein a preferred direction of the first subelement is aligned at least essentially perpendicular to a preferred direction of the second subelement, wherein the subelements are arranged along their end faces relative to each other, wherein a measurement of the first subelement and a measurement of the second subelement are taken into account in the signals of the measuring device.

[0041] This means that the measuring device is not sensitive to the preferred direction alignment of the two sub-elements. In other words, as long as their relative alignment matches the defined alignment, the Petition 870250085575, dated 22 / 09 / 2025, p. 23 / 48 / 23 two sub-elements can be arranged in any way in the clamping device, where a complete measuring signal is always available. This greatly simplifies the installation of the measuring device and avoids errors in determining a torque loss due to misalignment in one or more preferred directions.

[0042] In a further advantageous design of the measuring arrangement, the piezoelectric elements have a first sub-element and / or a second sub-element, by means of which a shear force can be measured, and a third sub-element, by means of which a compressive force can be measured, wherein the sub-elements are arranged along their end faces relative to each other, wherein a measurement of the first sub-element and / or the second sub-element and a measurement of the third sub-element are taken into account in the signal of the measuring device. This type of piezoelectric element allows measuring both shear and compressive forces.

[0043] In a further advantageous design of the measuring arrangement, the measuring device further comprises means that are designed to measure desired measured variables, in particular a torque about the geometric axis of rotation and / or forces acting parallel to the plane, taking into account a respective angle between the preferred direction or directions of at least one piezoelectric element and tangents to the direction of rotation of the rotor at the location or locations of at least one piezoelectric element. Taking into account the orientation of the preferred direction, the torque loss can be calculated with particular accuracy.

[0044] In a further advantageous design of the measuring arrangement, the measuring device further comprises means that are designed to determine desired measured variables, in particular a torque about the geometric axis of rotation and / or forces acting parallel to the plane, by means of a system of equations, in particular a linear system. Petition 870250085575, dated 09 / 22 / 2025, page 24 / 48 / 23 of equations, based on measurements of at least one piezoelectric element.

[0045] Using a system of equations, the torque loss can be determined with particular precision. In particular, the preferred directions of the piezoelectric elements do not need to be precisely aligned, since the respective contribution of the piezoelectric elements to different force components can be taken into account in the linear system of equations.

[0046] In another advantageous design of the measuring arrangement, the clamping device has recesses in which a piezoelectric element is arranged in each case. This allows the measuring device to be designed to be particularly compact. In addition, the piezoelectric elements are protected because the recess acts as a housing.

[0047] In another advantageous design of the measuring arrangement, the clamping device and the pre-tensioning device are formed in two parts and the pre-tensioning device has two half-shells to accommodate the electric machine, wherein the measuring device further comprises second pre-tensioning elements by means of which the two half-shells can be pre-tensioned against each other so that a frictional connection can be produced between the pre-tensioning device and the electric machine.

[0048] This makes it particularly easy to connect the electric machine to the measuring device. In particular, no fastening means, such as screws or mounting holes, are required in an electric machine housing.

[0049] In a further advantageous design of the measuring arrangement, the clamping device is designed as a clamping plate, in particular a base plate, which is mounted on a test bench during its intended use, and / or the pre-tensioning device is a pre-tensioning plate. The plates are particularly well suited for supporting the Petition 870250085575, dated 09 / 22 / 2025, page 25 / 48 / 23 piezoelectric elements.

[0050] Other advantages and features are evident from the following description in conjunction with the figures. The following figures show, at least in part schematically: Figure 1 shows a partially transparent top view of a first exemplary embodiment of a measurement arrangement for determining the torque loss of an electric machine; Figure 2 shows a partially transparent side view of the measuring arrangement according to Figure 1; Figure 3 shows a partially transparent top view of a second exemplary embodiment of the measurement arrangement for determining the torque loss of an electric machine; Figure 4 shows a partially transparent top view of a third exemplary embodiment of the measurement arrangement for determining the torque loss of an electric machine; Figure 5 shows a partially transparent side view of the measuring arrangement according to Figure 4; Figure 6 shows an alternative embodiment of a piezoelectric element; Figure 7 shows another alternative embodiment of a piezoelectric element; Figure 8 shows a diagram illustrating the time curve of the rotor's angular velocity, the torque acting on the rotor, and the control current as a function of time; Figure 9 shows another diagram illustrating the control current and the torque Mz applied again to the rotor as a function of time; Figure 10 shows a block diagram of a method for determining the torque loss of an electric machine; and Petition 870250085575, dated 09 / 22 / 2025, page 26 / 48 / 23 Figure 11 shows an example of a system for determining torque loss.

[0051] Figures 1 and 2 illustrate a first exemplary embodiment of a measuring arrangement 1 for determining a torque loss of an electric machine 2. Figure 2 is a partially transparent side view of the measuring arrangement 3 of Figure 1.

[0052] The electric machine 2 is preferably a motor with a rotating shaft 9, which has a rotor 4 that rotates on the rotating shaft 9 around a geometric axis of rotation 7.

[0053] Measuring arrangement 1 has a measuring device 3 for measuring torques. Measuring device 3 preferably has a clamping device 5 and a pre-tensioning device 8. Between the clamping device 5 and the pre-tensioning device 8 are arranged piezoelectric elements 6i, 6ii, 6iii and 6iv, which are fixed and pre-tensioned by means of pre-tensioning elements, in particular screws (not shown). Piezoelectric elements 6i to 6iv are preferably piezoelectric measuring elements that utilize the piezoelectric shear effect. This means that the piezoelectric elements measure shear forces Fs,ia Fs,iv acting in a plane in which piezoelectric elements 6i to 6iv are arranged.

[0054] In the exemplary embodiment shown in figures 1 and 2, the motor 2 is fixed in a fixed rotational manner in the pretensioning device 8. Thus, the torques acting on the shaft 9 or on the rotor 4 are transmitted through the housing of the motor 2 to the pretensioning device 8. The fixing device 5 is preferably mounted so that it cannot rotate, so that these moments cause the shear forces Fs,ia Fs,iv in the piezoelectric elements 6i to 6iv.

[0055] The electric motor 2 is freely suspended. This means that the rotor 4 is rotating freely, that is, it is not loaded. Petition 870250085575, dated 09 / 22 / 2025, p. 27 / 48 14 / 23 external. This is common to all exemplary modalities of measurement arrangement 1.

[0056] As can be seen in figure 2, the measuring elements 6i to 6iv are received at least partially in recesses in the mounting plate 5.

[0057] Preferably, the pre-tensioning device 8, which is designed as a pre-tensioning plate in figure 2, has a recess through which the shaft 9 of the motor 2 can be guided. Preferably, the mounting device 5, which is designed as a mounting plate in figure 2, also has such a recess.

[0058] The force components measured by the piezoelectric elements 6i to 6iv are shown in Figure 1. These are the force components in the Y direction Fy, the force component in the X direction Fxe, and the axial torque about the geometric axis of rotation 7 Mz. As shown in Figure 1, the preferred directions of the piezoelectric elements, indicated by the vector arrows Fsj to Fs,iV of the measured shear forces, are aligned tangentially to a direction of rotation of the rotor 4 about the geometric axis of rotation 7.

[0059] In this case, the axial torque Mz acting on motor 2 can be easily calculated using the following equation: Mz - (-Fs,i + Fi,» - Fs.m + Fí.iv) * R where R is the distance between the piezoelectric elements 6i to 6iv and the geometric axis of rotation 7 of the rotor 4.

[0060] The signals in front of the measured shear forces result from the respective alignment of the preferred direction of the piezoelectric elements 6i to 6iv. The measured shear forces Fsj to Fs,iV are calculated from the measurement signals Si, Sü, Sm, Sm, which are preferably specified in picocoulombs, and a respective sensor sensitivity, which is preferably specified in N / pC.

[0061] In the equation above, the respective angle β between the directions Petition 870250085575, dated 09 / 22 / 2025, page 28 / 48 / 23. The preferred angles of the piezoelectric elements 6i to 6iv and the respective tangent at the location of the piezoelectric element 6i to 6iv to the direction of rotation of rotor 4 play an important role. This angle β specifies what proportion of a measured shear force Fs should be attributed to the tangential direction and, therefore, to the torque Mz.

[0062] The tangential force Ft is obtained from the shear force Fs according to the following equation: Ft = Fs · cos β

[0063] In the first exemplary embodiment of the measurement arrangement 1 shown in Figures 1 and 2, the angle β = 0° for piezoelectric elements 6ii and 6iv and β = 180° for piezoelectric elements 6i and 6iii. However, the individual piezoelectric elements 6i to 6iv can also be positioned as desired. As described above, this means that not all the force is measured in the tangential direction, but only a proportional force Ft according to the equation above. To calculate the torque Mz according to the equation above, the measured tangential component of the force F must be recalculated to 100% using a weighting factor. For example, for β = 45°, Ft = 0.707 · Fs. Therefore, the measured tangential force Ft would have to be multiplied by 1.293 to compensate for the missing sign components.

[0064] To ensure that a complete measurement signal is always available, piezoelectric elements 6i can also be used, which have two sub-elements 6i-1, 6i-2 arranged adjacent to each other on their end faces. For this purpose, the preferred direction of the individual sub-elements 6i-1, 6i-2 should be perpendicular, as indicated in Figure 6 by the measurable shear force vectors Fsi-1, Fsi-2. The magnitude of the shear force in the tangential direction is given by the projected length of the sum vector in the tangential direction.

[0065] This design of piezoelectric elements 6i to 6iv, therefore, always generates a measurement signal Si that corresponds to that of a single Petition 870250085575, dated 09 / 22 / 2025, p. 29 / 48 16 / 23 piezoelectric element whose preferred direction would be oriented tangentially to the direction of rotation of rotor 4.

[0066] As an alternative to the equation above for calculating the torque Mz, a system of equations, in particular a linear system of equations, can also be used to calculate the force components Fx, Fy and the torque component Mz in the plane formed by the position of the piezoelectric elements 6i, 6ii, 6iii, 6iv. The system of linear equations can be summarized in matrix form and represented as follows: Mz\ {CU - CIcia / 51Fx = ; ·.. ; SnF7 / \C3i - C3ÍP / \S}

[0067] The individual matrix coefficients can be determined by calibration measurements using measuring device 3, which are preferably performed after piezoelectric elements 6i to 6iv have been pre-tensioned.

[0068] Figure 3 shows a second exemplary embodiment of a measuring arrangement 1. In contrast to the first exemplary embodiment of the measuring arrangement 1, the second exemplary embodiment has only the clamping device 5, which is designed as a clamping plate.

[0069] A pre-tensioning device in the form of an additional plate is not provided in the second embodiment. Instead, a motor housing or motor 2 is arranged directly on the piezoelectric elements 6i to 6iv. The motor housing or motor 2 is pre-tensioned with the mounting plate 5 in such a way that a friction connection is formed between the motor housing or motor 2 itself, on the one hand, and between the piezoelectric elements 6i to 6iv and the mounting plate 5, on the other hand. In this way, shear forces can also be applied to the piezoelectric elements 6i to 6iv in this exemplary embodiment.

[0070] A third exemplary modality of an arrangement of Petition 870250085575, dated 09 / 22 / 2025, p. 30 / 48 / 23: The measurement to determine the torque loss of an electrical machine is explained with reference to figures 4 and 5:

[0071] In this exemplary embodiment, both the clamping devices 5a, 5b and the pre-tensioning device 8a, 8b are designed in two parts. The clamping device has a first clamping plate 5a and a second clamping plate 5b, which are spaced by an opening 10. The pre-tensioning device has a first half-shell 8a and a second half-shell 8b. The first half-shell 8a is arranged on the first clamping plate 5a by means of two piezoelectric elements 6iii, 6iv and is fixed to the first clamping plate 5a by means of pre-tensioning elements (not shown). The second half-shell 8b is also arranged on the second clamping plate 5b by means of two piezoelectric elements 6i, 6ii. They are also fastened to each other by means of fasteners (not shown), so that shear forces can be introduced into the piezoelectric elements 6i, 6ii by means of a friction connection.

[0072] Figure 5 shows a side view of the measuring arrangement 1 according to Figure 4. As can be seen from Figure 5, the motor 2 can be fixed by means of two half-shells 8a, 8b.

[0073] The half-shells 8a, 8b are preferably designed so that they can fix the electric motor 2 by means of a friction connection. For this purpose, the half-shells 8a, 8b each have a shoulder 11a, 11b by means of which the motor 2 can be fixed. For fixing, the measuring device 3 preferably has other fixing means (not shown) with which the first fixing plate 5a and the second fixing plate 5b and therefore also the first half-shell 8a and the second half-shell 8b can be pre-tensioned against each other. These fixing elements are also preferably designed as screw means.

[0074] A gap (without a reference mark) between the two socks Petition 870250085575, dated 09 / 22 / 2025, p. 31 / 48 / 23 shells 8a, 8b, but also the gap 10 between the first fixing plate 5a and the second fixing plate 5b can be designed so that the shaft 9 can also be accommodated here.

[0075] The three exemplary embodiments shown in figures 1 to 5 have in common that the motor 2 is arranged with one of its end faces on the measuring device 3. However, the measuring principle according to the invention, which is explained in more detail below, also works if the motor 2 is arranged with the other end face facing the measuring device 3.

[0076] The pre-tensioning device 8 can also be designed as a motor-specific adapter plate. In addition, additional plates can be mounted on the pre-tensioning plate 8, which are designed as motor-specific adapter plates. This reduces the setup times for the measuring arrangement 1 in which the motor 2 is installed on the measuring device.

[0077] Although all three exemplary embodiments shown in Figures 1 to 5 illustrate that the geometric axis of rotation 7 of rotor 4 is oriented perpendicularly to a plane defined by piezoelectric elements 6i to 6iv or their preferred directions, the geometric axis of rotation 7 may also be aligned at an angle to this plane, provided it intersects the defined plane. Preferably, the geometric axis of rotation 7 intersects the plane at an angle between 45° and 135°. If the geometric axis of rotation is not oriented perpendicularly to the plane, the orientation must be taken into account in the equation above for the calculation of torque Mz by means of appropriate geometric factors. Thus, an oblique position of the geometric axis of rotation 7 with respect to the aforementioned plane also requires a redefinition of the coefficients of the calibration matrix or the coefficients of the aforementioned system of equations.

[0078] To also measure a normal force FN,i, it can be predicted Petition 870250085575, dated 09 / 22 / 2025, page 32 / 48 / 23, which, in addition to two overlapping sub-elements 6ii-1, 6ii-2; 6iii-1, 6iii-2; 6i-1, 6i2; 6iv-1, 6iv-2, provides third sub-elements 6ii-3, 6iii-3, 6i-3, 6iv-3, as shown in Figure 7. The overlapping sub-elements 6ii-1, 6ii-2; 6iii-1, 6iii-2; 6i-1, 6i-2; 6iv-1, 6iv-2 must have preferred directions arranged at right angles to each other.

[0079] Also in this case, the shear force Ftna in the tangential direction to the direction of rotation of rotor 4 results from the projected length of the sum vector in the tangential direction.

[0080] In all exemplary embodiments of the measurement arrangement shown, any number of piezoelectric elements 6i to 6iv can be installed. However, it should be noted that the pre-tensioning plate and / or the electric motor 2 must be supported in at least three positions to achieve a stable position. For this reason, if there are fewer than three piezoelectric elements 6i to 6iv, one or two additional contact elements must be provided. However, this leads to force deviations, which impair the measurement accuracy of the measuring device 2. In particular, these proportionally reduce the force flow through the existing piezoelectric element or piezoelectric elements 6i to 6iv. Furthermore, the additional support elements can lead to non-linearities.

[0081] Figures 8 to 10 below describe an exemplary embodiment of a method for determining the torque loss of an electric machine 2 with a rotor 4.

[0082] In this method, the measuring arrangements as described in relation to Figures 1 to 7 can be used. In principle, however, it is also possible to use a different measuring arrangement 1 and a different measuring device 3 with which the torque loss can also be determined using method 100. In particular, measuring devices 3 that have other measuring elements instead of piezoelectric elements can be used. Furthermore, other geometric arrangements are also Petition 870250085575, dated 09 / 22 / 2025, pp. 33 / 48 20 / 23 possible, both in relation to measuring device 3 and in relation to measuring arrangement 1 as a whole.

[0083] As described at the beginning, the rotor 4 of an electric motor 2 is accelerated by interaction in a magnetic field. The drive torque Ma is applied. At the same time, torque losses Mvse counteract this drive torque Ma.

[0084] When rotor 4 is accelerated, the acceleration is counteracted by a torque generated by the moment of inertia of the mass J of rotor 4. Here, the following applies: Mz = / φ : Mz = Ma - Mv = / <p

[0085] According to the equation, during an acceleration or braking process of rotor 4, the drive torque Manão can be distinguished from the torque loss Mv.

[0086] At a constant angular velocity (Φ = 0), the following applies: Ma- Mv= 0

[0087] If motor 2 is now operated at idle speed so that rotor 4 stops by inertia, an operation called “free deceleration”, the drive torque Ma = 0. Thus, the measured axial torque Mz = -Mv applies.

[0088] Standby operation can be achieved by disconnecting the motor from the power supply or by interrupting the control current.

[0089] The axial torque Mzdo rotor 4 reacts according to a jump response because only the torque loss Mvestá is present at the moment when the idle operation begins. This jump response is also shown in the diagram in Figure 8, along with the control current I curve over time.

[0090] The axial torque jump response Mz can be measured as the Petition 870250085575, dated 09 / 22 / 2025, pages 34 / 48 21 / 23 reaction torque in motor 2, in particular by means of one of the examples of a measurement arrangement 1 shown.

[0091] At the moment when the drive torque becomes zero, the rotational speed of rotor 4 begins to decrease, as shown in the diagram in figure 8.

[0092] The use of piezoelectric elements is particularly suitable for this measurement, as they are particularly good at measuring dynamic forces.

[0093] Figure 9 shows another diagram in which actual measurements of the control current I and axial torque Mz are performed on a real measurement arrangement 1 according to the first exemplary embodiment shown.

[0094] The measured braking torque Mvé is 0.5 Nm. The area shown in the diagram as control current I corresponds to three periodic phase currents with amplitudes of approximately 40 A. They drop to 0 at the free deceleration point. The axial torque signal Mzé is filtered through a low-pass filter at approximately 500 Hz. The step response of the axial torque Mzé is obtained from the linear adjustments of the torque signal Mzé before and after free deceleration, which are shown as lines. A block diagram of the exemplary embodiment of method 100 for determining a torque loss of an electric machine 2 with a rotating shaft 4 is shown in Figure 8.

[0095] As explained above, the electric motor 2 is mounted on the measuring device 1 so that it can rotate freely and, in particular, no load machine is connected to the free-rotating rotor 4 or its shaft 9.

[0096] In a first work stage 101, motor 2 is operated by means of a control current I such that rotor 4 reaches a predefined speed. Motor 2 is accelerated to the predefined speed. Petition 870250085575, dated 09 / 22 / 2025, page 35 / 48 / 23 independently, that is, by the acceleration torque Magerado in engine 2.

[0097] Three-phase sinusoidal currents are preferably used as control currents, depending on the type of motor 2.

[0098] Once the preset speed is reached, motor 2 should preferably continue to be operated at a constant speed.

[0099] In a second working stage 102, the motor 2 is then operated at idle speed. Preferably, the control current I is switched off, in particular interrupted, for this purpose. For this purpose, it is preferable to use a switch or relay.

[00100] In a third working step 103, the signal is filtered by means of a low-pass filter, which preferably has a cutoff frequency of 500 Hz. This allows a low-frequency signal to be detected from a highly dynamic measurement signal, such as that generated by piezoelectric elements 6i to 6iv.

[00101] In a fourth step of work 104, a jump in the filtered signal is identified.

[00102] Depending on the jump position, the signal is fitted in a first section before the identified jump and in a second section after the jump in a fifth work step 105.

[00103] Based on the signal sections adjusted before and after the jump, the magnitude of the jump is determined in a sixth working step 106. This jump quantity corresponds to the axial torque Mz of rotor 4 at the moment of free deceleration, that is, when motor 2 switches to standby mode and therefore to the negative torque loss Mv at this moment. Preferably, the torque loss Mv is sent to an interface.

[00104] Figure 11 shows a module 1000 for determining a torque loss of a measuring device 3, in particular by means of one of the exemplary embodiments of the measuring arrangements 1. Petition 870250085575, dated 09 / 22 / 2025, page 36 / 48 / 23

[00105] Module 1000 has means 1001 for controlling the operation of machine 2, which are designed to initially operate machine 2 in such a way that rotor 4 reaches a predefined speed and then operate the machine at rest speed. Additionally, module 1000 has means 1002 for monitoring a signal from measuring device 3, which represents the axial torque in machine 2. Furthermore, module 1000 has means 1004 for identifying a jump in the signal and means 1006 for determining the amount of the jump, where the amount indicates the torque loss of the electric machine 2. Additionally, optional means 1003 for filtering the signal and means 1005 for adjusting the signal may be provided.

[00106] It should be noted that the exemplary embodiments are merely examples that do not limit the scope of protection, applications, or structure in any way. Instead, the preceding description provides those skilled in the art with guidance for implementing at least one exemplary embodiment, in which various modifications, particularly with respect to the function and arrangement of the described components, can be made without departing from the scope of protection as defined by the claims and these equivalent combinations of features. Petition 870250085575, dated 09 / 22 / 2025, pp. 37 / 48

Claims

1 / 5 CLAIMS 1. Measuring arrangement (1), characterized in that it has an electric machine (2) with a rotor (4) and a measuring device (3) for determining the torque loss of the electric machine (2), wherein the measuring device (3) has a clamping device (5) and at least one piezoelectric element (6i, 6ii, 6iii, 6iv), preferably at least three, in particular four, piezoelectric elements, each with a preferred direction, wherein the clamping device (5) supports at least one piezoelectric element (6i, 6ii, 6iii, 6iv) and mounts the electric machine by means of at least one piezoelectric element (6i, 6ii, 6iii, 6iv) such that at least the shear forces between the electric machine (2) and the clamping device (5) can be measured by means of at least one piezoelectric element (6i, 6ii, 6iii, 6iv), wherein the preferred direction or directions are each parallel to, or in a single plane,wherein a geometric axis of rotation (7) of the rotor (4) intersects the plane at an angle between 45° and 135°, preferably between 85° and 95°, more preferably at least essentially perpendicular, and wherein the rotor (4) rotates freely.

2. Measuring arrangement (1) according to claim 1, characterized in that the measuring device (3) has more than one piezoelectric element (6i, 6ii, 6iii, 6iv), wherein the piezoelectric elements (6i, 6ii, 6iii, 6iv) are arranged, each one, in different positions around the geometric axis of rotation (7) of the rotor (4) of the electric machine (2).

3. Measuring arrangement (1) according to claim 1 or 2, characterized in that the measuring device (2) further comprises a pre-tensioning device (8) and first pre-tensioning elements, wherein at least one piezoelectric element (6i, 6ii, 6iii, 6iv) can be pre-tensioned or is pre-tensioned between the clamping device (5) and the pre-tensioning device (8) by means of the first pre-tensioning elements such that at least one piezoelectric element (6i, 6ii, 6iii, 6iv) is forcibly fixed, and wherein the electric machine (2) is rotationally fixed to the pre-tensioning device (8).

4. Measuring arrangement (1) according to any one of claims 1 to 3, characterized in that the electric measuring machine (2) is fixed to the fixing device (5) and is supported by at least one piezoelectric element (6i, 6ii, 6iii, 6iv) such that the at least one piezoelectric element (6i, 6ii, 6iii, 6iv) is forcibly fixed.

5. Measuring arrangement (1) according to any one of claims 1 to 4, characterized in that the clamping device (5) or the pre-tensioning device (8) has a recess in which a shaft (9) of the electric machine (2) can be accommodated and / or guided through it, wherein preferably one side of the electric machine (2), in which the shaft (9) emerges, is facing the clamping device (5) and / or the pre-tensioning device (8).

6. Measuring arrangement (1) according to any of the preceding claims, characterized in that the geometric axis of rotation (7) is oriented at least essentially vertically during the intended use of the measuring arrangement (1).

7. Measuring arrangement (1) according to any of the preceding claims, characterized in that the clamping device (5) or the electric machine (2) is supported exclusively by at least one piezoelectric element (6i, 6ii, 6iii, 6iv).

8. Measurement arrangement (1) according to any of the preceding claims, characterized in that the preferred direction of at least one piezoelectric element (6i, 6ii, 6iii, 6iv) is oriented at least essentially tangentially to a direction of rotation of the shaft.

9. Measurement arrangement (1) in accordance with any of Petition 870250085575, dated 22 / 09 / 2025, p. 39 / 48 3 / 5 previous claims, characterized in that at least one piezoelectric element (6i, 6ii, 6iii, 6iv) has a first subelement (6i-1, 6ii-1, 6iii-1, 6iv-1) and a second subelement (6i-2, 6ii-2, 6iii-2, 6iv-2), through which shear forces can be measured in each case, wherein a preferred direction of the first subelement (6i-1, 6ii-1, 6iii-1, 6iv-1) is at least essentially perpendicular to a preferred direction of the second subelement (6i-2, 6ii-2, 6iii-2, 6iv-2), wherein the two subelements (6i-1, 6i-2; 6ii-1; 6ii-2; 6iii-1, 6iii-2; 6iv-1, 6iv-2) are arranged along their end faces relative to each other.

10. Measurement arrangement (1) according to any of the preceding claims, characterized in that the at least one piezoelectric element (6i, 6ii, 6iii, 6iv) comprises a first subelement (6i-1, 6ii-1, 6iii-1, 6iv-1) and / or a second subelement (6i-2, 6ii-2, 6iii-2, 6iv-2), by means of which a shear force can be measured, and a third subelement (6i-3, 6ii-3, 6iii-3, 6iv-3), by means of which a compressive force can be measured, wherein the subelements (6i1, 6i-2, 6i-3; 6ii-1; 6ii-2, 6ii-3; 6iii-1, 6iii-2, 6iii-3; 6iv-1, 6iv-2, 6iv-3) are arranged along their end faces relative to each other.

11. Measuring arrangement (1) according to any of the preceding claims, characterized in that the measuring device (3) further comprises means that are designed to measure desired measured variables, in particular a torque about the geometric axis of rotation (7) and / or forces acting parallel to the plane, taking into account a respective angle between the preferred direction or directions of at least one piezoelectric element (6i, 6ii, 6iii, 6iv) and tangent to the direction of rotation of the rotor (4) at the location or locations of at least one piezoelectric element (6i, 6ii, 6iii, 6iv).

12. Measurement arrangement (1) according to any of the preceding claims, characterized in that the measurement device (3) further comprises means that are arranged to determine desired measured variables, in particular a torque about the geometric axis of rotation and / or forces acting parallel to the plane, by means of a system of equations, in particular a linear system of equations, based on measurements of at least one piezoelectric element (6i, 6ii, 6iii, 6iv).

13. Measuring arrangement (1) according to any of the preceding claims, characterized in that the clamping device has recesses in which a piezoelectric element is arranged in each case.

14. Measuring arrangement (1) according to any of the preceding claims, characterized in that the clamping device (5a, 5b) and the pre-tensioning device (8a, 8b) are designed in two parts and the pre-tensioning device (8a, 8b) has two half-shells (8a, 8b) to accommodate the electric machine (2), wherein the measuring device (3) further comprises second pre-tensioning elements by means of which the two half-shells (8a, 8b) can be pre-tensioned against each other so that a friction connection can be produced between the pre-tensioning device (8a, 8b) and the electric machine (2).

15. Measuring device (3), characterized in that it determines a torque loss of an electric machine with rotor (4), in particular for use in a measuring arrangement as defined in any of the preceding claims, wherein the machine (2) is mounted on a measuring device (3) such that an axial torque can be measured on the machine (2) and wherein the rotor (4) rotates freely, comprising: means (1001) for controlling the operation of the machine (2), configured to initially operate the machine (2) such that the rotor (4) reaches a predefined rotational speed and then operate the machine at rest; means (1002) for monitoring a signal from the measuring device (3) representing the axial torque on the machine (2); means for identifying (1004) a jump in the signal; and means for determining (1006) the amount of the jump, wherein the amount indicates the torque loss of the electric machine (2).

16. Test bench, characterized in that it has a measuring arrangement as defined in any one of claims 1 to 14 and / or a measuring device as defined in claim 15.

17. Method for determining the torque loss of an electric machine with a rotor (4) by means of a measuring arrangement (1) as defined in any one of claims 1 to 14, characterized in that it comprises the following working steps: firstly, operate (101) the machine (2) such that the rotor (4) reaches a predefined speed; secondly, operate (102) the machine (2) at rest when the predefined speed is reached, wherein a signal from the measuring device (3) representing the axial torque in the machine (2) is monitored; secondly, identify (104) a jump in the signal; and determine (106) the amount of the jump, wherein the amount indicates the torque loss of the electric machine (2). Petition 870250085575, dated 22 / 09 / 2025, pp. 42 / 48

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