Method for adjusting a piezoelectric torque sensor

Abstract

The present invention relates to a method for adjusting a piezoelectric torque sensor of a measuring device, preferably part of a test stand, for determining a torque applied to a test piece based on a force flow, the measuring device having a piezoelectric torque sensor and a second torque sensor based on a different measurement principle and configured to continuously detect static torque, the measuring device being configured such that both torque sensors measure torque within the force flow, a target measurement signal of the piezoelectric torque sensor is determined based on the torque measurement by the second torque sensor, and the detected measurement signal of the piezoelectric torque sensor is adjusted and output based on the determined target measurement signal.

Description

[Technical Field]

[0001] The present invention relates to a method for adjusting a measuring device for determining a torque applied to a test piece, preferably a piezoelectric torque sensor of a test stand, the measuring device comprising a piezoelectric torque sensor. [Background technology]

[0002] When developing and controlling motors, in particular internal combustion engines or electric machines, it is important to know the torque at the motor shaft as accurately as possible, especially during test bench operation.

[0003] For this purpose, it is known from the prior art to use measuring systems with strain gauges or piezoelectric sensors.

[0004] Strain gauges and similar measuring elements are commonly used to measure static forces, but due to their construction, measuring systems equipped with these types of measuring elements generally have too long a response time for measuring dynamic force curves.

[0005] A piezoelectric torque sensor has a piezoelectric element that generates a voltage based on the piezoelectric effect when a force is applied to the piezoelectric element.

[0006] It is based on the principle that a voltage is generated in a piezoelectric element when it is elastically deformed. The deformation of the piezoelectric element creates microscopic dipoles inside the elementary cells of the piezoelectric element. The sum of the electric fields connected to the microscopic dipoles in all elementary cells of the piezoelectric element results in a voltage that can be measured microscopically when a deformation or force is applied. The charge transfer is usually measured using a charge-to-voltage converter, also called a charge amplifier.

[0007] Piezoelectric measuring elements or the measurement principle of piezoelectric elements can be used to measure instantaneous forces occurring at a certain frequency. However, for measuring forces over a relatively long period of time, such as steady-state forces, the measurement principle of piezoelectric elements is not very suitable because the measurement signal is subject to temporal drift. Therefore, piezoelectric elements are suitable for measuring dynamic tension, compression, and shear forces. Piezoelectric elements have a wide dynamic range and are rigid, allowing high dynamic forces to be measured simultaneously with high resolution. Due to their structure, piezoelectric sensors have very high natural frequencies and therefore have little effect on the system to be measured.

[0008] Patent document 1 discloses a measuring device for determining forces and / or torques in a torque-transmitting shaft, the bearing device, in particular its output shaft and / or input shaft, being supported by a machine formed by torque transmission in the shaft, the measuring device having at least two, preferably three or four, piezoelectric elements and a fixing device, the fixing device being configured to support the piezoelectric elements so that forces, in particular shear forces, between the bearing device and a supporting device for supporting the bearing device can be measured using the piezoelectric elements. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2019 / 144172 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention aims to expand the measurement spectrum of a measuring device for measuring torque, which comprises a piezoelectric torque sensor. In particular, it aims to provide a method for adjusting the piezoelectric torque sensor of the measuring device with respect to the low frequency range of torque oscillations and a test stand, which method makes it possible to carry out such an adjustment. [Means for solving the problem]

[0011] This problem is solved by the teaching of the independent claims. Advantageous embodiments are set forth in the dependent claims.

[0012] A first aspect of the present invention relates to a method for adjusting a piezoelectric torque sensor of a measuring device, preferably part of a test stand, for determining a torque applied to a test piece based on a force flow, the measuring device having a piezoelectric torque sensor and a second torque sensor based on a different measurement principle and configured to continuously detect static torque, the measuring device being configured such that both torque sensors measure torque within the force flow, a target measurement signal of the piezoelectric torque sensor is determined based on the torque measurement by the second torque sensor, and the detected measurement signal of the piezoelectric torque sensor is adjusted and output based on the determined target measurement signal.

[0013] A second aspect of the invention relates to a test stand for a machine, preferably an electric machine, for measuring dynamic torque, the test stand comprising a piezoelectric torque sensor and a second torque sensor based on a different measurement principle and configured to continuously detect the static component of torque, both torque sensors being configured to measure torque in a force flow at the test stand and arranged at the test stand.

[0014] A third aspect of the invention relates to a measuring device for a machine, preferably an electric machine, for measuring dynamic torque, the measuring device comprising a piezoelectric torque sensor and a second torque sensor based on a different measurement principle and configured to continuously detect the static component of the torque, both torque sensors being constructed and arranged to measure torque within only one force flow.

[0015] Preferably, the measuring device and / or test stand is designed to test specimens at high rotational speeds of greater than about 10,000 U / min, preferably greater than about 35,000 U / min, most preferably greater than about 100,000 U / min.

[0016] The measurement spectrum in the present invention is preferably a frequency range in which meaningful measurements can be performed using a measurement device.

[0017] The test specimen in the present invention is preferably the machine to be tested or the whole consisting of the machine to be tested and the shaft and / or shaft assembly. Preferably, the elements of the test specimen are connected to each other so that they cannot rotate.

[0018] In the present invention, adjustment preferably refers to setting or correcting the measured value indicated by the measuring device so that the deviation from the reference value of a reference instrument forming the target value is as small as possible. Typically, a measuring device is adjusted during calibration if the measurement error between the measurement indication of the measuring device and the reference instrument is unacceptably large. During adjustment according to the present invention, drift in the signal of a piezoelectric torque sensor is corrected using the signal of a sensor configured to continuously detect static torque. Further deviations caused by other effects, for example, in a frequency range of vibration frequencies different from the frequency range of vibration frequencies considered during adjustment, are preferably not detected by adjustment according to the present invention.

[0019] A force flow in the sense of the present invention is the path of a force and / or torque in a mechanical system from the point of application, in particular the point of introduction, to one or more points where the force and / or torque is absorbed by a reaction force and / or reaction torque. Preferably, the force flow is made up of forces, in particular forces transverse to the direction of rotation of the shaft, and torques, in particular torques around the axis of rotation.

[0020] Power flow in the present invention is the path of transmission of power in a mechanical system from the point of input to one or more points where the power is removed.

[0021] The quasi-steady frequency range in the present invention preferably includes vibration frequencies at which measurements can be performed by both torque sensors at equilibrium. In particular, in such equilibrium, there are no significant measurement differences at each measurement position due to vibrations on the test stand, and the response time of the second torque sensor is relatively small relative to the rate of change of torque. In such a state, measurement drift of the piezoelectric torque sensor also occurs, unlike measurements at higher frequencies.

[0022] The means of the present invention may be implemented using hardware and / or software techniques and may in particular comprise a processing device, in particular a digital device, in particular a microprocessor (CPU), preferably in data or signal connection with a memory or a bus system, and / or one or more programs or program modules. The CPU may be configured to process instructions implemented as a program stored in the memory system, to detect input signals from the data bus, and / or to send output signals to the data bus. The memory system may comprise one or more, in particular different, storage media, in particular optical, magnetic, solid-state, and / or other non-volatile media. The program may embody or implement the method described herein, and the CPU may be provided to execute the steps of the method.

[0023] The measuring flange according to the invention is preferably a torque sensor having two flanges between which an applied torque can be measured.

[0024] The present invention is based on the recognition that, while maintaining a sufficient distance to possible natural vibration or resonance modes of the test stand assembly, adjustment of a piezoelectric torque sensor can be performed using a second torque sensor placed in the same force flow as the piezoelectric torque sensor.

[0025] In this case, a reference signal is measured by a second torque sensor in the force flow in which the piezoelectric torque sensor also measures torque. A target measurement signal of the piezoelectric torque sensor is calculated based on the reference signal. The target measurement signal can be used to adjust the measurement signal of the piezoelectric torque sensor. The adjusted measurement signal can be output to a user or via a data interface for further data processing.

[0026] Piezoelectric torque sensors can measure dynamic torque components with high accuracy. However, the piezoelectric element's relatively large signal drift can cause the piezoelectric torque sensor to detect low-frequency torque components inaccurately. The second torque sensor, on the other hand, measures static torque components at low-frequency torque but cannot capture high-frequency signal components. Low-frequency operating conditions are especially relevant when the test specimen has a vibration frequency below 10 Hz. Test stands typically have natural frequencies in the 50-80 Hz range. Therefore, to eliminate the effects of natural frequencies, adjustments should be performed when the vibration frequency does not exceed 10 Hz.

[0027] The measuring device according to the present invention can be used to periodically or continuously adjust or readjust such piezoelectric torque sensors, which allows accurate measurement of torques at frequencies below 1 Hz, and thus allows steady-state force or torque measurements to be made.

[0028] Thus, thanks to the invention, the measurement spectrum of the piezoelectric torque sensor can be extended into the low frequency vibration range, in particular into the static range.

[0029] In an advantageous embodiment of the method, the setpoint measurement signal of the piezoelectric torque sensor is further determined on the basis of a shaft rotation speed measurement, by which different moments of inertia in various parts of the powertrain or test specimen can be taken into account during the adjustment.

[0030] In a further advantageous embodiment of the method, the target measurement signal of the piezoelectric torque sensor is determined using the following equation:

[0031]

number

[0032] M Piezo_cal is the target measurement signal, and M W is the torque measured by a second torque sensor on a shaft or shaft assembly that is non-rotatably connected to or is a component of the test specimen, and J W is the moment of inertia of the shaft or shaft assembly that is connected to the test specimen (5) or is a component of the test specimen (5) so as not to rotate, and J UUT is the moment of inertia of the test specimen,

number

[0033] The inventors have realised that using this relatively simple equation, in particular the equation that forms the basis of the model, it is possible to determine a reliable value for the target measurement signal of the piezoelectric torque sensor that corresponds closely to the actual value of the torque at the measurement location.

[0034] In a further advantageous embodiment of the method, a model of the measurement signal / target measurement signal control process is generated based on the detected measurement signal and the simultaneously determined target measurement signal, and the detected measurement signal is adjusted using the model after generation, which allows for an adjustment as a function of the rotational speed without further measurements.

[0035] In a further advantageous embodiment of the method, the model is based on a transfer function, the parameters of which are determined by comparing a measurement signal detected by means of a piezoelectric torque sensor with a target measurement signal determined on the basis of torque measurements by means of a second torque sensor during tests on a test stand of a test specimen, thereby providing for easy adjustment.

[0036] In a further advantageous embodiment of the method, a piezoelectric torque sensor measures the reaction torque at at least one support point of the test specimen, thereby determining the corresponding applied torque. Correspondingly, in an advantageous embodiment of the test stand, the piezoelectric torque sensor is configured and arranged so that the force flow between the test specimen and a support device for supporting the test specimen can be measured. Again, ultimately, the reaction torque used to support the test specimen is determined. By averaging the torque on the test specimen based on the reaction torque, it is not necessary to perform measurements on rotating elements of the test specimen to determine the torque. This prevents a measurement device that may be present on a rotating element, such as a measurement flange, from changing the moment of inertia of the measurement assembly or introducing elasticity into the measurement assembly.

[0037] The advantages and features described above in relation to the first aspect of the invention correspondingly apply to the second aspect of the invention, and vice versa.

[0038] Advantageously, the test stand comprises a loading device, in particular a dynamometer or brake, for applying a load to the test specimen.By means of the dynamometer, dynamic measurements can be carried out on the test stand.

[0039] In a further advantageous embodiment, the test stand has a gear mechanism, in particular a boost gear mechanism, arranged in the force flow between the loading device and the test object, the piezoelectric torque sensor being arranged to detect torque on the side of the force flow relative to the gear mechanism on which the test object can be arranged, and the second torque sensor being arranged to detect torque on the side of the force flow relative to the gear mechanism on which the loading device is arranged.

[0040] The present invention is particularly advantageous in test stand assemblies with gear mechanisms, since a piezoelectric torque sensor is preferably arranged on the side of the force flow that rotates at a high rotational speed. Here, high-frequency vibrations generated by the gear mechanism can be determined using the piezoelectric torque sensor. In contrast, a second torque sensor with a different structure, in particular a strain gauge assembly, measures torque on the side of the gear mechanism that rotates at a lower rotational speed. This allows measurements at low vibration frequencies of torque, so-called quasi-steady or steady-state measurements, to be performed. In particular, the force flow is transformed from a low-dynamic force flow to a high-dynamic force flow. This transformation also transforms the low-frequency components of torque vibrations. Arranging a second torque sensor on the side of the gear mechanism that rotates at a higher rotational speed is particularly disadvantageous because torques with high vibration frequencies cannot be determined using a second torque sensor that is not based on such a piezoelectric measurement principle. However, the equation is also valid for the relationship between the torque measured by the second torque sensor and the target measurement signal of the piezoelectric torque sensor, as further shown above.

[0041] In a further advantageous embodiment of the method, the shaft assembly has a gear mechanism, the second torque sensor is arranged in a part of the shaft assembly that rotates at a lower rotational speed relative to the gear mechanism, and the piezoelectric torque sensor is arranged in a part of the shaft assembly that rotates at a higher rotational speed relative to the gear mechanism. The present invention is particularly advantageous in this embodiment, because torque vibrations occurring in the part of the shaft assembly that has a higher rotational speed and that have a very high vibration frequency can be well determined by the piezoelectric torque sensor.

[0042] In a further advantageous embodiment, the test stand has a speed sensor provided and arranged for measuring the number of revolutions with respect to the test specimen.

[0043] In a further advantageous embodiment of the test stand, the gear mechanism having at least one shaft forms a shaft assembly, and the speed sensor is arranged to detect the number of rotations on the side of the shaft assembly on which the loading device is arranged relative to the gear mechanism.

[0044] In a further advantageous embodiment of the test stand, the measurement principle of the second torque sensor is based on strain gauges, which are preferably measuring flanges. Strain gauge-based torque sensors are particularly well suited for steady-state and quasi-steady-state or low-frequency measurements of torque or torque-based forces.

[0045] In a further advantageous embodiment, the test specimen and the loading device, and, if present, the gear mechanism, are supported on the same base.

[0046] In a further advantageous embodiment, the test stand comprises adjustment means for continuously adjusting the piezoelectric torque sensor, wherein the torque detected by the piezoelectric torque sensor can be adjusted by the adjustment means using the model.

[0047] Further features and advantages will become apparent from the following description of exemplary embodiments, which refers to the drawings in which: FIG. [Brief explanation of the drawings]

[0048] [Figure 1] 1 shows an embodiment of a test stand having a piezoelectric torque sensor and a second torque sensor. [Figure 2] FIG. 10 is a block diagram illustrating a method for adjusting piezoelectric torque. [Figure 3] FIG. 1 illustrates an example of a control process for adjusting the measurement signal of a piezoelectric torque sensor. DETAILED DESCRIPTION OF THE INVENTION

[0049] FIG. 1 shows an embodiment of a test stand 1 for testing machines.

[0050] In the following, the invention will be explained on the basis of a test bench 1 for testing an electric machine 5. However, it will be clear to a person skilled in the art that the described embodiments can also be applied to other types of machines, in particular electromechanical or chemomechanical energy converters.

[0051] The test stand 1 preferably comprises a dynamometer 7, by means of which a load, in particular a driving torque or a braking torque, can be applied to the electric machine to be tested.

[0052] The illustrated test stand 1 is preferably used for testing electric machines that operate at relatively high rotational speeds, preferably above 10,000 rpm, more preferably above 35,000 rpm, and most preferably above 100,000 rpm, during normal operation. This is the case, for example, of an electric drive for a compressor, such as a turbocharger, or an electric drive motor for an electric vehicle. Such high rotational speeds cannot be supplied or accommodated by the dynamometer 7. Therefore, the test stand 1 preferably includes a gear mechanism 8, in particular a so-called boost gear mechanism, which converts the rotational speeds on the shaft sections 10b, 10c, which non-rotatingly connect the dynamometer 7 with the boost gear mechanism 8, to higher rotational speeds. This higher, converted rotational speed is transmitted to the electric machine 5 to be tested via the shaft section 10a, which non-rotatingly connects the boost gear mechanism 8 with the electric machine 5 to be tested. Conversely, the rotational speed supplied by the electric machine 5 to be tested is converted via the boost gear mechanism 8 to a speed and torque range in which the dynamometer 7 is operable.

[0053] The gear mechanism 8 together with the various shafts or shaft portions 10a, 10b, 10c form a shaft assembly. The test specimen is formed either by the electric machine 5 alone or by the electric machine 5 and at least partly the shaft assembly, depending on which component is to be tested.

[0054] 1, the dynamometer 7, the boost gear 8, and the electric machine 5 to be tested are mounted on the same base 11. In this case, the electric machine 5 to be tested is supported relative to the base 11 by a support device 6. In this case, the support device 6 provides a reaction force for the electric machine 5 to be tested, and the reaction force is used to support the flow of power and the flow of output between the electric machine 5 to be tested and the dynamometer 7.

[0055] In this regard, the support device 6 is preferably configured so that the electric machine 5 to be tested can be attached to the side, in particular the end face, on which the shaft of the electric machine 5 is arranged or on which the shaft portion 10a can be coupled to the shaft of the electric machine, as shown in FIG. 1. This arrangement offers the advantage that the torque sensor 3 can be arranged between the support device 6 and the electric machine 5 to be tested so that a large portion of the torque acting on the electric machine 5 to be tested is applied to the piezoelectric torque sensor 3, as shown in FIG. 1. In particular, this arrangement minimizes or eliminates the shunting of forces that do not pass through the piezoelectric torque sensor 3. Preferably, for this type of support of the electric machine 5 to be tested by the piezoelectric torque sensor 3 and the support device 6, both the piezoelectric torque sensor 3 and the support device 6 have a passage for the shaft or shaft or shaft portion 10a of the electric machine 5 to be tested. This passage is preferably formed as an opening.

[0056] However, the electric machine 5 to be tested can also be mounted in different ways, for example on the side facing away from the base 11, in a suspended manner or on another side of the electric machine 5 to be tested. Details regarding the support of the electric machine 5 to be tested shown in FIG. 1 and further support possibilities as well as the determination of the reaction force using the piezoelectric torque sensor 3 can be taken from the initially mentioned patent application WO 2007 / 024990.

[0057] The boost gear mechanism 8 divides the test stand assembly of the test stand 1 into two sides I and II. On the first side I, where the electric machine 5 to be tested is located, the shaft assembly rotates at a higher rotational speed and a lower torque is applied to the shaft assembly. Therefore, this part of the shaft assembly will be referred to herein as the first part I of the shaft assembly.

[0058] On the other output side of the boost gear mechanism 8, designated second side II, shaft portions 10b, 10c rotate at a lower speed and higher torque. Typically, the gear ratio of the boost gear mechanism 8 is from about 3:1 to about 10:1. Accordingly, this portion of the shaft assembly is also designated herein as second portion II of the shaft assembly.

[0059] The shaft assembly or power train, preferably consisting of the electric machine 5, shaft sections 10a, 10b, 10c, boost gear mechanism 8 and dynamometer 7, is a system capable of vibrating. Natural modes of resonance or vibration are typically greater than 50 Hz, depending on the structure of the test stand 1 and the electric machine 5 to be tested.

[0060] To determine the torque acting on the electric machine to be tested based on the force flow from or to the dynamometer 7, the test stand 1 has a piezoelectric torque sensor 3. In this case, the torque sensor 3 preferably does not directly determine the torque applied to the electric machine to be tested 5 through the shaft section 10a, but indirectly determines the reaction torque by means of which the electric machine to be tested 5 is supported on the support device 6. Furthermore, the test stand 1 has a second torque sensor 4, which is not based on the piezoelectric measurement principle but measures torque using a different measurement principle. In this case, so-called strain gauges, as are generally known from the prior art, are preferably used. Preferably, the second torque sensor 4 is configured as a measurement flange and measures the torque between both shaft sections 10b and 10c.

[0061] The arrangement of both torque sensors shown in Figure 1 is particularly advantageous for the adjustment of the piezoelectric torque sensor 3, since the second part II of the shaft assembly, which rotates at a lower rotational speed, experiences less vibration and therefore measurements using the second torque sensor 4 using strain gauges are more accurate. This means that sensors based on strain gauges are only suitably suited for dynamic measurements.

[0062] In contrast, the piezoelectric torque sensor 3 is located on the first part I of the shaft assembly, directly on the electric machine 5 to be tested, where the applied torque is also to be determined. By placing the piezoelectric torque sensor directly on the test piece, high accuracy in the measurement of the applied torque is obtained.

[0063] For determining the rotational speed of the shaft assembly, in particular in the region of the second part II of the shaft assembly, a speed sensor 9 is arranged, which is able to determine the rotational speed. In Fig. 1, the speed sensor 9 determines the rotational speed of the shaft of the dynamometer 7 and the rotational speed of the shaft parts 10b and 10c. Thus, through the selected gear ratio of the boost gear mechanism 8, it is also possible to infer the rotational speed of the first part I of the shaft assembly.

[0064] The torque M measured using the second torque sensor 4 W and the rotation speed ω measured using the speed sensor 9 W and, based on this, the friction torque M caused in particular by the bearing and / or the boost gear mechanism 8 R , the moment of inertia of the shaft assembly J W , as well as the moment of inertia J of the electrical machine 5 to be tested UUT Considering the target measurement signal M Piezo_cal can be determined, which will be explained in more detail below in connection with the method 100 according to the present invention for tuning a piezoelectric torque sensor.

[0065] At the same time, the piezoelectric torque sensor 3 is used to measure the actual measurement signal M of the torque being applied to the piezoelectric torque sensor 3. Piezo can be measured.

[0066] In order to carry out a calibration of the actual measurement signal of the piezoelectric torque sensor 3, the test stand 1 further preferably comprises adjustment means 12. The adjustment means 12 are preferably part of the data processing system of the test stand 1, but can also be part of an external data processing system. PiezoAfter being calibrated, the piezoelectric torque sensor 3 can be adjusted by the adjustment means 12, preferably using a model stored in the adjustment means 12 for the calibration or adjustment, which model will also be described in more detail further below in connection with the method 100.

[0067] 2 is a block diagram of an embodiment of a method 100 for adjusting a piezoelectric torque sensor of a measurement device 2. Preferably, such a measurement device 2 is part of a test stand 1, as described above in connection with FIG.

[0068] The adjustment of the piezoelectric torque sensor 3 is carried out on an operational test stand, for which purpose a torque is applied to the dynamometer 7 through the shaft assembly by means of the electric machine 5 to be tested, or vice versa from the dynamometer 7 to the electric machine 5 to be tested.

[0069] Preferably, during adjustment, the test stand 1 operates at a relatively low rotational speed of the shaft assembly, with the rotational speed of the second part II of the shaft assembly being preferably less than 50 rpm. For rotational speeds within this magnitude range, low torque vibration frequencies of less than about 10 Hz, preferably less than about 5 Hz, more preferably less than about 1 Hz, depending on the structure of the test stand 1 and the test specimen, are expected.

[0070] The frequency range of this vibration frequency is selected so as to be at a distance from the resonant frequency or natural mode of the entire system consisting of the test stand 1 and the test object, which is typically around 50 Hz.

[0071] More preferably, the frequency range of vibration frequencies suitable for this adjustment is isolated using a frequency filter, in particular using a Fourier analysis, in which case the rotation speed during test stand operation is not important for the adjustment.

[0072] During operation, the piezoelectric torque sensor 3 measures 101a the torque applied to the electric machine 5 to be tested. As already mentioned in connection with FIG. 1, the piezoelectric torque sensor 3 preferably detects the reaction force by means of which the electric machine 5 to be tested is supported on the support device 6. In contrast, the second torque sensor 4 detects 101b the torque in the shaft assembly, relatively far from the electric machine 5 to be tested. In the case of a test stand 1 or test specimen having a gear mechanism 8 as shown in FIG. 1, the second torque sensor 4 is preferably arranged in region II of the shaft assembly where lower rotational speeds prevail.

[0073] Torque M by the second torque sensor 4 W Measurement and rotation speed ω by speed sensor 9 W Based on the measurement and Piezo_cal is calculated 102. Preferably, the target measurement signal is determined using the following equation:

[0074]

number

[0075] However, also in principle, the torque M measured by the second torque sensor 4 W Only approximately, in some cases, the friction torque M R Considering the target measurement signal M Piezo_cal can be used to determine

[0076] The determined target measurement signal M Piezo_cal Based on this, the detected measurement signal M Piezo is corrected 103. More preferably, the corrected measurement signal is output 104.

[0077] The measurement signal M detected by the piezoelectric torque sensor 3 Piezo The correction of is preferably performed in the measurement signal / target measurement signal control process.

[0078] An example of such a control process is shown in FIG.

[0079] Preferably, the target measurement signal M Piezo_cal is compared with the measurement signal M Piezo The correction value thus determined, preferably at a relatively low frequency of torque oscillations, is valid for the entire measurement range, in particular also at a relatively high frequency of torque oscillations.

[0080] In a preferred embodiment, furthermore, based on the measurement of the second torque sensor 4, a target measurement signal M is calculated as a function of the torque oscillation frequency. Piezo_cal A model can be created that can be used in determining

[0081] Essentially, the control process shown in FIG. 3 operates by generating a target measurement signal M Piezo_cal represents the above equation for calculating

[0082] Shaft rotation speed ω W is derived over time and multiplied by the sum of the moment of inertia of the shaft assembly and the moment of inertia of the electrical machine 5 to be tested. In particular, the friction torque M exists as a function of the rotation speed n and the gear ratio T. R and the above-mentioned product is the torque M measured using the second torque sensor 4. W The calculated signal is passed through a low pass filter LP to obtain the target measurement signal M Piezo_cal This target measurement signal M Piezo_cal is the measurement signal M, corrected based on the previous adjustment and also passed through the low-pass filter LP Piezo Preferably, the illustrated low-pass filters LP have the same characteristics, in particular the same dynamics, limit frequencies, order and type. By using a low-pass filter, vibration frequencies suitable for conditioning the measurement signal of the piezoelectric torque sensor can be isolated.

[0083] This difference is fed to the integrator 1 / s. If the calculated acceleration of the shaft rotation is lower than the limit value Limit, the previous adjustment is replaced by a new value S in the integrator 1 and the measurement signal M measured by the piezoelectric torque sensor 3 is Piezo It is used to correct for.

[0084] By taking into account the limit value Limit on the rotational acceleration, it is ensured that adjustment changes are only made up to a certain vibration frequency.

[0085] The above-described embodiments are merely examples and should not limit the scope of protection, applications, and structures. Rather, the above description provides a guide for a person skilled in the art to realize at least one embodiment, and various modifications can be made, particularly with respect to the function and arrangement of the described components, without departing from the scope of protection that is evident from the claims of these equivalent feature combinations. In particular, the individual embodiments can be combined with each other. [Explanation of symbols]

[0086] 1 test stand 2. Measuring equipment 3 Piezoelectric torque sensor 4 Second torque sensor 5. Electrical Machinery 6 Support device 7 Dynamometer 8 Gear mechanism 9 Speed ​​Sensor 10a, 10b, 10c shaft 11. Base 12 Adjustment means

Claims

1. 1. A method (100) for adjusting a piezoelectric torque sensor (3) of a measurement device (2) for determining a torque applied to a test piece (5) based on a force flow, the measurement device (2) having a piezoelectric torque sensor (3) and a second torque sensor (4) based on a different measurement principle and configured for continuously detecting static torque, the measurement device (2) being configured such that both torque sensors measure torque within the force flow (101 a, 101 b), a target measurement signal of the piezoelectric torque sensor (3) is determined (102) based on the torque measurement by the second torque sensor (4), and the detected measurement signal of the piezoelectric torque sensor is adjusted (103) and output (104) based on the determined target measurement signal.

2. The method (100) of claim 1, wherein the measuring device (2) is part of a test stand (1).

3. 3. The method (100) according to claim 1 or 2, wherein the determination of the target measurement signal of the piezoelectric torque sensor (3) is performed in a quasi-stationary frequency range of the oscillation frequency of the torque in the measuring device.

4. 4. The method (100) according to claim 3, wherein the determination of the target measurement signal of the piezoelectric torque sensor (3) is performed in a frequency range below 50 Hz.

5. 4. The method (100) of claim 3, wherein the determination of the target measurement signal of the piezoelectric torque sensor (3) is performed in a frequency range between 5 Hz and 50 Hz.

6. 6. The method (100) according to claim 1, wherein the determination of the target measurement signal of the piezoelectric torque sensor (3) is performed in a frequency range of torque vibration frequencies in which no natural vibration modes or resonance modes occur in the measurement environment.

7. 7. The method according to claim 6, wherein the measuring device is part of a test stand, and the determination of the target measurement signal of the piezoelectric torque sensor is performed in a frequency range of torque vibration frequencies in which no natural vibration modes or resonance modes occur on the test stand.

8. 7. The method (100) according to claim 6, wherein the determination of the target measurement signal of the piezoelectric torque sensor (3) is performed at a torque oscillation frequency below 20 Hz.

9. 7. The method (100) according to claim 6, wherein the determination of the target measurement signal of the piezoelectric torque sensor (3) is performed at a torque oscillation frequency below 10 Hz.

10. 10. The method (100) according to any one of claims 3 to 9, wherein the tuning is performed while the test body (5) is in operation and the torque is isolated in a desired frequency range using a frequency filter.

11. 11. The method (100) of claim 10, wherein the tuning is performed while the test body (5) is in motion and the torque is isolated in a desired frequency range using Fourier analysis.

12. 12. The method (100) according to any one of claims 1 to 11, wherein the target measurement signal of the piezoelectric torque sensor (3) is further determined on the basis of a rotational speed measurement on the test piece.

13. The target measurement signal of the piezoelectric torque sensor (3) is calculated based on the following equation: [Equation 1] where M Ｐｉｅｚｏ＿ｃａｌ is the target measurement signal, and M Ｗ is the torque measured by the second torque sensor (4) on a shaft (10a, 10b, 10c) or shaft assembly that is connected to the test body (5) in a rotationally fixed manner or is a component of the test body (5), and J Ｗ is the moment of inertia of the shaft (10a, 10b, 10c) or the shaft assembly which is connected to the test body (5) in a rotationally non-rotating manner or which is a component of the test body (5), and J ＵＵＴ is the moment of inertia of the test specimen (5), [Equation 2] is the time derivative of the measured rotational speed of the shaft (10a, 10b, 10c) or the shaft assembly which is non-rotationally connected to the test body (5) or which is a component of the test body (5), and M Ｒ The method (100) of any one of claims 1 to 12, wherein is the friction torque.

14. M Ｒ The method (100) of claim 13, wherein ∇ is the friction torque caused by the bearings and / or gear mechanism (8).

15. 15. The method (100) according to claim 13 or 14, wherein the shaft assembly has a gear mechanism (8), the second torque sensor (4) is arranged in a part (II) that rotates at a lower rotational speed relative to the gear mechanism (8), and the piezoelectric torque sensor (3) is arranged in a part (I) that rotates at a higher rotational speed relative to the gear mechanism (8).

16. 16. The method (100) according to any one of claims 1 to 15, wherein the piezoelectric torque sensor (3) measures a reaction torque at at least one support point of the test body (5) to determine the torque applied to the test body (5).

17. A computer program comprising instructions which, when executed by a computer, cause the computer to perform the steps of the method (100) of any one of claims 1 to 16.

18. A computer readable medium having stored thereon the computer program of claim 17.

19. A test stand (1) for a machine for measuring dynamic torque, the test stand (1) having a piezoelectric torque sensor (3), an adjustment means (12) configured to adjust the piezoelectric torque sensor (3), and a second torque sensor (4) based on a different measurement principle and configured to continuously detect a static component of torque, both torque sensors (3, 4) being configured to measure torque in a force flow at the test stand (1) and arranged on the test stand (1).

20. 20. The test bench (1) of claim 19, wherein the piezoelectric torque sensor (3) is configured and arranged so that a force can be measured within a force flow between a test specimen (5) and a support device (6) for supporting the test specimen (5).

21. 21. Test stand (1) according to claim 19 or 20, comprising a loading device (7) for applying a load to the test specimen (5).

22. 22. A test bench (1) according to claim 21, wherein the loading device (7) is a dynamometer or a brake.

23. 23. A test bench (1) as claimed in claim 21 or 22, comprising a gear mechanism (8) arranged in the force flow between the loading device (7) and the test specimen (5), wherein the piezoelectric torque sensor (3) is arranged to detect torque on a side (I) of the force flow relative to the gear mechanism (8) on which the test specimen (5) can be arranged, and the second torque sensor (4) is arranged to detect torque on a side (II) of the force flow relative to the gear mechanism (8) on which the loading device (7) is arranged.

24. 24. A test stand (1) according to claim 23, wherein the gear mechanism (8) is a boost gear mechanism.

25. 25. Test stand (1) according to any one of claims 19 to 24, wherein the measurement principle of the second torque sensor (4) is based on strain gauges.

26. 26. Test stand (1) according to claim 25, wherein the second torque sensor (4) is a measuring flange.

27. 27. A test stand (1) according to any one of claims 19 to 26, wherein the test stand (1) is a test stand (1) for an electric machine.

28. 27. A test stand (1) according to any one of claims 19 to 26, wherein the test stand (1) is configured to carry out a method according to any one of claims 1 to 16.

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