Acceleration sensors for torque estimation

Abstract

The invention relates to an assembly having a transmission which has at least one planetary stage, one or more one-dimensional acceleration sensors (103) which are attached to a ring gear (101) of the planetary stage and are oriented, with their respective measuring direction, radially with respect to the ring gear, and a computing device; wherein the computing device is designed to receive accelerations measured by the one or more acceleration sensors (103), to predict one or more accelerations (103) which are applied to one or more of the acceleration sensors (103), in each case in the measuring direction (105), on the basis of one or more hypothetical drive torques which are present at an input shaft of the transmission; and to determine the one or more hypothetical drive torques in such a way that the predicted accelerations correspond to the measured accelerations.

Description

[0001] ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24

[0002] Acceleration sensors for torque estimation

[0003] The invention relates to an arrangement according to the preamble of claim 1, a method using such an arrangement and a corresponding computer program.

[0004] Virtual sensors are known from the prior art. The measured values ​​of virtual sensors are determined by simulation based on the values ​​of real sensors. For example, "Validation of a Wind Turbine Gearbox Strain Simulation Model in Service to Virtual Sensing" (J. Bosmans, M. Kirchner, J. Croes and W. Desmet; Springer Nature 87, pp. 107-117) describes virtual torque sensors for the input shaft of a wind turbine. Their virtual measured values ​​are determined based on physically existing strain gauges attached to a ring gear of the gearbox. Virtual measured values ​​from the virtual torque sensors can be determined via simulation and correlated with the measured values ​​of the strain gauges in a virtual model of the gearbox.

[0005] The invention is based on the objective of improving the determination of input torques of a gearbox compared to the prior art. This objective is achieved by an arrangement according to claim 1, a method according to the independent method claim, and a computer program also claimed. Preferred embodiments are included in the dependent claims and will become apparent from the following description and the figures.

[0006] The arrangement according to the invention comprises a gearbox, one or more acceleration sensors and a computing device.

[0007] The gearbox is preferably a wind turbine gearbox. The gearbox has at least one planetary stage with a ring gear. The ring gear must be rotationally fixed, meaning it cannot rotate relative to the gearbox housing. This is advantageous with regard to the mounting of the acceleration sensors. In particular, the ring gear can be fixed in the housing and / or be part of the housing. For a rotationally fixed ring gear, a [ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24]

[0008] A planet carrier, preferably non-rotatably connected to an input shaft of the gearbox and / or forming the input shaft as a single unit, and a sun gear belonging to the same planetary stage, rotatable relative to the housing. The axes of rotation of the planet carrier and the sun gear then coincide with a central axis of the ring gear.

[0009] The one or more accelerometers are one-dimensional accelerometers. They are designed to measure accelerations along exactly one spatial direction. In this case, the accelerometers are mounted on the ring gear. This allows them to measure the accelerations of the ring gear at their mounting location. MEMS are preferably used as accelerometers. Highly sensitive DC accelerometers are particularly suitable.

[0010] The acceleration sensors are radially aligned with their respective measuring directions relative to the central axis of the ring gear. The measuring direction of each sensor is therefore orthogonal to the central axis of the ring gear and intersects it.

[0011] The computing device is connected to one or more accelerometers via a signal conductor. The computing device is thus configured to receive signals from the one or more accelerometers. These signals encode the accelerations measured by the one or more accelerometers.

[0012] The accelerations of the ring gear, and thus the accelerations measured by the one or more acceleration sensors, depend on the application of a constant or time-varying drive torque to the input shaft. When the input shaft is subjected to a drive torque, the entire transmission rolls around its longitudinal axis due to the compliance of the transmission bearings. Furthermore, the torque transmission within the transmission causes elastic deformations of the ring gear. Both the rolling motions of the transmission and the elastic deformations of the ring gear are measured as accelerations by the one or more acceleration sensors. ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24

[0013] The computing device is designed to predict the accelerations measured by one or more acceleration sensors as a function of one or more hypothetical drive torques applied to the input shaft. These hypothetical drive torques are characterized by the fact that they are neither measured nor determined by measurement. Instead, they can be arbitrarily defined as input for a calculation or simulation.

[0014] Preferably, the computing device predicts the accelerations measured by the one or more accelerometers using a virtual model of the gearbox that replicates the gearbox's physical behavior. A combination of two individual models has proven particularly suitable. A first model simulates the kinematic behavior of the gearbox as a whole, especially its rolling motions. The second model is a finite element model that simulates the elastic deformations of the ring gear.

[0015] Finally, the computing device is designed to determine the one or more hypothetical drive torques applied to the input shaft of the transmission in such a way that the predicted one or more accelerations correspond to the one or more measured and received accelerations. Accelerations are considered to correspond if they are identical or if their deviation does not exceed a predetermined threshold, which, in particular, remains constant during the process step of predicting the one or more accelerations.

[0016] If the accelerations match, it can be assumed that the hypothetical one or more drive torques determined according to the invention correspond to the one or more drive torques actually applied to the input shaft. Expensive and damage-prone sensors mounted on the drive shaft for directly measuring the drive torques are therefore rendered obsolete by the invention. Compared to strain gauges, the predictive accuracy of the one or more accelerations is improved by the use of acceleration sensors. ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24

[0017] The determination of one or more hypothetical drive torques can be achieved iteratively. In this process, the one or more drive torques are iteratively changed or adjusted until the predicted one or more accelerations match the measured accelerations.

[0018] Preferably, the computing device is configured to determine a directional component of the acceleration due to gravity in the accelerations measured by the accelerometers. If the directional component of the acceleration due to gravity changes, the computing device, according to a further refinement, calculates a corresponding tilt of each accelerometer that is the cause of the change. Specifically, the computing device is further developed to determine a tilt of at least one accelerometer that is the cause of a change in the directional component of the acceleration due to gravity contained in the measured acceleration of at least one accelerometer. The determination of the tilt can be carried out computationally or by simulation.

[0019] Tilting of an accelerometer refers to a change in the angular position of the accelerometer resulting from its rotation perpendicular to its measuring direction. When one or more drive torques are applied to the input shaft, the rolling motion of the transmission causes the accelerometer to tilt around the central axis of the ring gear. This tilting is superimposed on tilting caused by the elastic deformation of the ring gear.

[0020] In addition to the one or more accelerations, a tilting of the at least one specified acceleration sensor is also predicted as a function of the one or more hypothetical drive torques. The one or more hypothetical drive torques are determined in such a way that not only do the predicted accelerations correspond to the measured accelerations, but also the predicted ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24

[0021] Tilt with the calculated tilt. This can also be implemented iteratively. The one or more hypothetical drive torques are iteratively changed or adjusted until the predicted tilt matches the calculated tilt. Tilts are considered to match if they are identical or if their deviation does not exceed a predetermined threshold, which, in particular, remains constant during the prediction step of the one or more tilts.

[0022] By taking the determined tilt into account in addition to the measured one or more accelerations, as required by further training, the accuracy of determining the one or more hypothetical drive torques is improved.

[0023] To simplify the prediction of accelerations and / or tilts, the arrangement is preferably further developed such that the one or more acceleration sensors are uniformly distributed around the circumference of the ring gear. With a uniform distribution around the circumference of the ring gear, each acceleration sensor is equidistant from its neighboring accelerometers – measured directly or via the circumference of the ring gear. In particular, the acceleration sensors can be arranged in a common cross-sectional plane, that is, in a plane orthogonal to the central axis of the ring gear and intersecting the ring gear.

[0024] In a preferred embodiment, one or more acceleration sensors are mounted on an outer circumferential or cylindrical surface of the ring gear. This is advantageous because the outer circumferential surface is subjected to the accelerations to be measured and is therefore particularly easily accessible.

[0025] Preferably, the arrangement is further developed such that the one or more acceleration sensors are arranged outside a vertical first longitudinal section plane of the ring gear and / or outside a second longitudinal section plane of the ring gear that is oriented orthogonally to the first longitudinal section plane. This is from ZF Friedrichshafen AG, file 304275, Friedrichshafen, 2024-06-24

[0026] An advantage is that when an acceleration sensor is arranged within the first longitudinal section plane or within the second longitudinal section plane, the sensor's sensitivity to tilting is minimal. Therefore, the improved arrangement of one or more acceleration sensors is preferably combined with the above-described improvement of the computing device for determining the one or more drive torques in accordance with the predicted tilting and the calculated tilting.

[0027] A particularly simple implementation of the process steps performed by the computing device results when, according to a preferred embodiment, eight acceleration sensors are present. According to this embodiment, exactly eight of the acceleration sensors described above are mounted on the ring gear.

[0028] A method according to the invention comprises the method steps described above, which can be carried out by the computing device of the arrangement according to the invention.

[0029] A computer program according to the invention implements the method according to the invention. The computer program thus comprises instructions that cause the computing device of the arrangement described above to execute the method according to the invention when the computer program is executed by the computing device. The computer program can be contained within the computing device, stored on a storage medium outside the computing device, or encoded in one or more transmittable or transmitted signals. In particular, the computer program can be a computer program product, that is, a tradable unit or a unit that serves the purpose of transferring ownership of the computer program. The computer program can be in the form of hardware-implemented circuit logic, not only as software. ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24

[0030] Preferred embodiments are shown in the figures. Matching reference numerals denote identical or functionally equivalent features. In detail, the figures show...

[0031] Fig. 1 shows a ring gear with acceleration sensors; and

[0032] Fig. 2 shows a schematic representation of the tilting of a sensor.

[0033] The ring gear 101 of a planetary gear stage shown in Fig. 1 is provided with a total of eight accelerometers 103 on its outer circumferential surface. These are one-dimensional accelerometers, each with exactly one measuring direction 105.

[0034] The acceleration sensors 103 are designed to measure accelerations exclusively along their respective measuring direction 105. Since they are mounted on the ring gear 101, they measure accelerations at the corresponding points on the ring gear 101.

[0035] The measuring directions 105 are each aligned orthogonally to the outer circumferential surface of the ring gear 101. They each run along a straight line contained in a cross-sectional plane of the ring gear 101 – which is identical to the plane of Fig. 1 – and intersect a central axis 107 of the ring gear 101.

[0036] With a beam 109 extending horizontally from the central axis 109 within the aforementioned cross-sectional plane, the measuring directions 105 of the accelerometers 103 each enclose an angle 11 that is not divisible by 45°. This ensures that any change in the directional component of the acceleration due to gravity acting on each sensor 103 in the measuring direction 105 when the respective sensor is tilted is sufficiently large and thus measurable with sufficient accuracy. For example, the eight angles 111 of the accelerometers 103 are 5°, 50°, 95°, 140°, 185°, 230°, 275°, and 320°. ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24

[0037] Figure 2 shows an example of an accelerometer 101 in its resting state (shown with a dashed line) and in its tilted state. The angle 111 changes by a tilt angle 201 due to the tilting.

[0038] In its resting state, the accelerometer 101 experiences a directional component g' of the gravitational acceleration g. The following applies: g' = gx sin(0)

[0039] 6 denotes angle 1 1 1.

[0040] For a directional component g" acting on the accelerometer in the tilted state, with a as the tilt angle, the following applies: g" = gx sin(0 — er)

[0041] This results in the following for the difference between the two directional components g" ~ g'

[0042] = gx sin(0 — er) — g X sin(0)

[0043] = gx [sin(0) cos(cr) — sin 0] — gx sin(0)

[0044] « gx [sin(0) — er cos(0)] — gx sin(0)

[0045] « — gx er x cos((0))

[0046] Finally, one obtains g' - g" a ~ - gx cos(0) ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24

[0047] Reference mark

[0048] 101 Ring gear

[0049] 103 Accelerometer

[0050] 105 Measuring direction

[0051] 107 Central axis

[0052] 109 beam

[0053] 111 angles

[0054] 201 tilt angle

Claims

ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24 Patent claims 1. Arrangement comprising a transmission having at least one planetary stage, one or more one-dimensional acceleration sensors (103) attached to a ring gear (101) of the planetary stage and radially aligned with their respective measuring direction relative to the ring gear, and a calculating device; wherein the calculating device is configured, - to receive accelerations measured by the one or more acceleration sensors (103), - to predict one or more accelerations (103) with which one or more of the acceleration sensors (103) are subjected in the measuring direction (105) depending on one or more hypothetical drive torques applied to an input shaft of the transmission; and - to determine the one or more hypothetical driving torques in such a way that the predicted accelerations match the measured accelerations.

2. Arrangement according to claim 2; characterized in that the calculating device is designed, - determine, based on a change in the directional component of the acceleration due to gravity contained in the measured acceleration of at least one acceleration sensor (103), a tilting of the at least one acceleration sensor (103) that is the cause of the change, - to predict tilting of the at least one acceleration sensor (103) depending on the one or more drive torques, and - to determine the one or more drive torques in such a way that the predicted tilting matches the calculated tilting.

3. Arrangement according to one of the preceding claims; characterized in that the one or more acceleration sensors (103) are distributed uniformly over the circumference of the ring gear (101). ZF Friedrichshafen AG File 304275 Friedrichshafen 2024-06-24 4. Arrangement according to one of the preceding claims; characterized in that the one or more acceleration sensors (103) are attached to an outer circumferential surface of the ring gear (101).

5. Arrangement according to one of the preceding claims; characterized in that the one or more acceleration sensors (103) are arranged outside a vertical first longitudinal section plane of the ring gear (101) and / or outside a second longitudinal section plane of the ring gear (101) that is aligned orthogonally to the first longitudinal section plane.

6. Arrangement according to one of the preceding claims; characterized in that the acceleration sensors (103) are present exactly eight times.

7. Method using an arrangement according to one of the preceding claims; characterized in that the computing device of the arrangement - receives one or more accelerations measured by the acceleration sensors (103), - predicts one or more accelerations with which one or more of the acceleration sensors (103) are subjected in the measuring direction (105) depending on one or more drive torques applied to an input shaft of the transmission; and - which determines one or more drive torques such that the predicted accelerations match the measured accelerations.

8. Computer program with instructions for causing the computing device of an arrangement according to one of claims 1 to 6 to execute a method according to the preceding claim.

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