Method for correcting misalignment of at least one shaft system - Patents.com

Abstract

The present invention relates to a method (100) for correcting misalignment of at least one shaft system (5, 5a, 5b) of a powertrain (3) on a test bench (1), in which at least one piezoelectric force sensor (4a, 4b, 4c, 4d) is arranged in a force path through which a force flow can be transmitted between a load unit (14; 14a, 14b) of the test bench (1) and the powertrain (3) or a drive unit (2) of the test bench (1) during the transmission of power via the shaft system (5; 5a, 5b) and which performs the following work steps: The present invention relates to a method (100) comprising a step (101) of performing a force measurement perpendicular to at least one plane (A, B; F) intersected by a rotation axis (D) of the axis system (5; 5a, 5b) and preferably at least substantially perpendicular to the rotation axis (D), a step (102) of analysing the measured values ​​or the measured value course of the force measurement in order to detect misalignment of the axis system (5; 5a, 5b), a step (103) of determining target values ​​for a position correction of the load unit (14; 14a, 14b) or the drive unit (2) in order to minimise the misalignment, and a step (105) of outputting the target values.

Description

[Technical field]

[0001] The present invention relates to a method for correcting misalignment of at least one shafting of a powertrain on a test bench, wherein at least one piezoelectric force sensor is arranged in a force path through which a force flow may be transmitted between a load unit of the test bench and a powertrain or a drive unit of the test bench during the transmission of power via the shafting. The present invention further relates to a test bench in which the method may be implemented. [Background technology]

[0002] Misalignment occurs due to assembly and manufacturing inaccuracies, settling phenomena, and thermal expansion, resulting in displacement of the rotor. Such displacement has a detrimental effect on the function and operational life of the rotor. Misalignment causes distorting forces on the rotor and its bearings, especially bending moments and compressive forces.

[0003] US Patent No. 5,399,633 discloses various test benches and measurement arrangements for detecting misalignments on a test bench using a piezoelectric force sensor, the contents of which are also incorporated herein by reference. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO / 2021 / 011982 Summary of the Invention [Problem to be solved by the invention]

[0005] The task of the present invention is to provide a test bench and a method for detection and / or correction of imbalance and / or misalignment of a powertrain shaft system during operation on a corresponding powertrain test bench. [Means for solving the problem]

[0006] This task is solved by the independent claims. Advantageous embodiments are claimed in the dependent claims.

[0007] A first aspect of the invention is a method for correcting misalignment of at least one shaft system of a powertrain on a test bench, comprising: at least one piezoelectric force sensor arranged in a force path through which a force flow can be transmitted between a load unit of the test bench and the powertrain or a drive unit of the test bench during the transmission of power via the shaft system; and comprising the following work steps: - performing force measurements in at least one plane and / or perpendicular to at least one plane intersected by the axis of rotation of the axis system, preferably at least substantially perpendicular to the axis of rotation; - analyzing the measured value progression of the force measurement to detect misalignment of the axis system; determining a target value for position correction of the load unit or the drive unit to minimize the misalignment; outputting a target value; The present invention relates to a method comprising:

[0008] A second aspect of the present invention is A load unit that can be connected to the shaft system under test; at least one piezoelectric force sensor arranged in a path of forces transmitted from a load unit of the test bench during the transmission of power by the shaft system and configured to perform force measurements in a plane and / or perpendicular to a plane intersected by the axis of rotation of the shaft system, preferably at least substantially perpendicular to the axis of rotation; means configured to perform a force measurement; and - means configured to analyze the force measurement values ​​or the measurement curves in order to detect misalignment of the axis system; means for determining a target value for a position correction of the load unit or the drive unit to minimize the misalignment; Means for outputting the target values, in particular an interface and A signal processing device having The present invention relates to a powertrain test bench comprising:

[0009] Further aspects of the invention relate to computer programs and computer readable media.Thus, the method according to the first aspect of the invention may be computer implemented.

[0010] A target value within the meaning of the present invention preferably specifies the direction and the amount by which the components to be aligned should be shifted and / or rotated. Moreover, the target value can also indicate the absolute value of the direction and position by which the components to be aligned should be shifted and / or rotated.

[0011] A shaft system within the meaning of the present invention comprises one or more rotatably connected shafts.

[0012] "Transmissible" within the meaning of the present invention preferably means "can be transmitted" or "has been transmitted".

[0013] A force flow within the meaning of the present invention is preferably 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 are accommodated by reaction forces and / or reaction moments. Preferably, the force flow is composed of forces, in particular lateral forces relative to the direction of rotation of an axis, and torques, in particular torques about the axis of rotation.

[0014] Power flow within the meaning of the present invention is preferably the path of power transmission in a mechanical system from the point of introduction to the point or points at which the power is taken off.

[0015] A piezoelectric measuring element within the meaning of the present invention preferably comprises a piezoelectric crystal and a charge dissipation or an electrical connection, respectively.

[0016] A mechanical unit within the meaning of the present invention is configured to convert energy, preferably kinetic energy, in particular rotational energy, into electrical energy or vice versa or to convert chemical energy into kinetic energy. A mechanical unit within the meaning of the present invention preferably comprises a housing.

[0017] A support device within the meaning of the present invention is preferably a device for supporting an element against forces acting on said element and / or against torques acting on said element. The support device is preferably configured to provide a so-called reaction force or bearing reaction force, respectively. A support device within the meaning of the present invention preferably serves to support a bearing device. Preferably, the support device is a bell housing, a powertrain housing or even a base plate.

[0018] Detection within the meaning of the present invention is preferably determination and / or quantification and / or localization and / or analysis.

[0019] Means within the meaning of the present invention may be designed as hardware and / or software, especially a processing unit, especially a digital processing unit, especially a microprocessor unit (CPU), preferably in data or signal connection to a memory or a bus system and / or having 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 capture input signals from the data bus and / or to send output signals to the data bus. The memory system may comprise one or more, especially different storage media, especially optical, magnetic, solid state and / or other non-volatile media. The program may be designed to embody or be capable of implementing the methods described herein, such that the CPU is able to execute the steps of such methods and thus to detect, among other things, imbalances and / or inconsistencies.

[0020] An incremental encoder within the meaning of the present invention is preferably capable of determining individual angle segments and / or a full revolution. In particular, an incremental encoder provides at least one pulse per revolution.

[0021] The invention is based, inter alia, on a technique for adjusting the misalignment of a powertrain shaft system on a test bench by means of force sensors, in particular force sensors provided for determining torques in a test run on the test bench. The use of the invention eliminates the need for further measuring methods or measuring instrumentation, in particular optical methods typically used in the prior art.

[0022] Above all, the shaft system does not have to be aligned externally, in other words separately away from the test bench. Instead, the detection of misalignments is performed directly on the test bench through the establishment of a frictional connection between a load unit, the so-called dyno, and a drive unit. The invention thus allows the alignment of the shaft system in the assembled state with all assembly inaccuracies, such as unequal screw weights, alignment errors, fit tolerances, and manufacturing errors such as eccentricity, asymmetry, density errors, etc.

[0023] In the case of a correction-required force measurement, the invention preferably utilizes piezoelectric measuring elements, which allow particularly more reliable measurements and, due to their stiffness, add only minor elasticity to the vibration system of the powertrain. The piezoelectric measuring elements are preferably permanently mounted on the test bench, whereby a physically uncontaminated measurement signal can then be recorded. In particular, the measuring elements can be supported by an intermediate plate or a base plate.

[0024] Since the physical "force" variables are directly captured, conclusions can be drawn regarding detrimental effects on mechanical components. Empirical methods of assessing the condition of machine units are not necessary. Based on the inventive determination of alignment errors, new standards for machine safety can therefore be developed. In addition to gravity, misalignments produce other spatially fixed forces or torques, in other words those that do not rotate with the rotational speed. The invention makes it possible to determine misalignments without additional vibration analysis.

[0025] If the alignment of the shaft system changes during operation, the invention makes it possible to detect this already on the test bench and for measures to be initiated, for example an emergency stop or load reduction, respectively, in order to prevent permanent damage to the powertrain or even the test bench.

[0026] Moreover, target values ​​for correcting the misalignment are inventively determined. An especially automated position correction of the load unit and / or the drive unit can be performed on the basis of these target values. The misalignment can thereby be minimized or even eliminated directly on the test bench. The target value determination significantly simplifies the configuration or calibration of the measurement arrangement, which up until now has been carried out mainly manually using optical methods. In particular, the time required therefor can be reduced by an order of magnitude. The possibility of automation also makes it possible to dispense with the use of highly qualified personnel for these tasks.

[0027] In one advantageous embodiment of the method, the following additional work steps are performed: determining a bending moment curve for the shaft system based on the force measurement values ​​or the measured value curves; determining a bending line of the shaft system based on the determined bending moment curve, taking into account in particular the boundary and connection conditions, wherein the target value is determined via the bending line; is carried out in determining the target value.

[0028] In a further advantageous embodiment, the method comprises the following working steps: checking whether a bending moment or bending moment curve for a shaft system exceeds a threshold value; iteratively repeating the method when the threshold has been exceeded or terminating the method when the threshold has not been exceeded. It further comprises:

[0029] An iterative process for optimizing the alignment of the shaft system on the basis of determined bending moments or bending moment curves allows a particularly precise determination of the target values.

[0030] In a further advantageous embodiment, the method comprises the following working steps: Disconnecting the frictional connection between the load unit and the drive unit, in particular by opening the shaft coupling. It further comprises:

[0031] Decoupling the frictional connection makes it particularly easy to change the position of the load unit and / or the drive unit.

[0032] In a further advantageous embodiment, the method comprises the following working steps: Varying the position of the load unit and / or the drive unit on the test bench based on the output target value. It further comprises:

[0033] Preferably, this position change is automated.More preferably, the test bench comprises for that purpose an adjustment device, which is configured to change the position of the load unit or the drive unit translationally and / or rotationally.

[0034] In a further advantageous embodiment, the method comprises the following working steps: Establishing a frictional connection between the load unit and the drive unit It further comprises:

[0035] Preferably, the frictional connection is restored following a position change of the load unit and / or the drive unit.

[0036] In a further advantageous embodiment of the method, the constants of the axis system specific to the test bench, in particular the product of the elasticity and resistance coefficients, are determined in order to calculate the bending line via two force measurements at different positions of the drive unit or the load unit.

[0037] This thereby enables the measurement arrangement to be calibrated without the material properties of the shaft system, in particular its stiffness, being known.

[0038] In a further advantageous embodiment of the method, the axis of rotation of the shaft system is the axis of rotation of an axis of the shaft system on which the force measurement is performed.

[0039] Preferably, the plane in which the force measurements are performed is defined by the bearing points of a system of axes on the mechanical unit on which the force sensor is supported. Even more preferably, the plane is defined by the point on which the force sensor is located.

[0040] In a further advantageous embodiment of the method, the force measurement is performed when the axis system is in a stationary or quasi-stationary state.

[0041] The stationary state of a shaft system within the meaning of the present invention preferably exists when the shaft system is not rotating.

[0042] A quasi-static state of the shaft system within the meaning of the present invention preferably exists when the shaft system rotates with an angular velocity at which the response time of the force sensor is relatively short with respect to the rate of change of the rotational position of the shaft system. In particular, the forces can be measured in such a way that they are not affected by dynamics. Preferably, the magnitude of the angular velocity is very small, so that its inertial mass has little or no effect, in particular so that to stop the shaft system requires a rotation angle range of about 90°, preferably about 70°, even more preferably about 15°, even more preferably about 10°, and most preferably less than about 5°. Preferably, there is no vibration of the shaft system in the quasi-static state.

[0043] As a result, the misalignment detection may be carried out subsequently in a stationary or quasi-stationary state of the shaft system, which makes it possible to determine the misalignment even before the actual test operation on the test bench, which makes it possible to prevent damage to the drive unit under test or to the test bench.

[0044] In a further advantageous embodiment of the method, the force measurements are monitored in that one or more measured values ​​are compared to a threshold value indicative of a critical shaft system load, and when the threshold value is exceeded, rotation of the shaft system is stopped or does not take place at all.

[0045] This also prevents damage to the drive unit under test or to the test bench.

[0046] In a further advantageous embodiment of the method, a plurality of piezoelectric sensors are provided in the force path and each force measurement of the piezoelectric sensors is monitored.

[0047] In a further advantageous embodiment of the method, a distinction is made during the analysis regarding misalignment between a parallel offset and / or an angular offset of the axis system.

[0048] Features and advantages described below in relation to a first aspect of the invention apply correspondingly to further aspects of the invention, and vice versa.

[0049] In one advantageous embodiment, the powertrain test bench additionally comprises an adjustment device configured to vary the position of the load unit translationally and / or rotationally, Powertrain test benches, especially signal processing devices, A means configured to control the adjustment device based on the output target value. It further comprises:

[0050] Further advantages and features emerge from the following description of preferred exemplary embodiments with reference to the drawings, which are at least partly schematic. [Brief description of the drawings]

[0051] [Figure 1a] A top view of the end face of the loading unit with the shaft of the loading unit protruding therefrom. [Figure 1b] FIG. 1b is a side view of the loading unit shown in FIG. [Figure 1c]2A and 2B show two top views of a measurement arrangement with a powertrain test bench and a first exemplary embodiment of a load unit according to FIGS. 1A and 1B, by means of which a method for correcting mismatches can be realized. [Diagram 2] 1 is an exemplary embodiment of a method for correcting misalignment. [Diagram 3] Four diagrams depicting the forces, bending moments, bend lines for angular misalignment, and bend lines for parallel misalignment of an axis system on a test bench. [Figure 4] 1 is a diagram with bend lines for parallel misalignment and bend lines for angular misalignment in the axial direction of the shaft system. [Diagram 5] FIG. 2 shows a top view of a measurement arrangement with a second exemplary embodiment of a powertrain test bench. [Figure 6] FIG. 2 shows a top view of a measurement arrangement with a third exemplary embodiment of a powertrain test bench. [Figure 7] FIG. 13 is a top view of a fourth exemplary embodiment of a powertrain test bench. [Figure 8] FIG. 8 is a detailed view of the powertrain test bench according to FIGS. 1, 5, 6 and 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] Figures 1a, 1b and 1c show three different views of a first exemplary embodiment of a powertrain test bench 1. Both the views of Figures 1a and 1b show only one load unit 14 of the powertrain test bench 1, while Figure 1c shows two views of a measurement arrangement with one of the load units 14 according to Figures 1a and 1b and one drive unit 2 to be tested.

[0053] The alignment of the individual views of FIG. 1a, FIG. 1b and FIG. 1c relative to each other occurs as a result of the depicted x, y and c coordinate axes of the reference system.

[0054] FIG. 1a shows a top view in the opposite direction of the z-axis on the end face of the loading unit 14, where the axis 5b of the loading unit 14 projects. FIG. 1b shows a side view along the x-axis of the loading unit according to FIG. 1a. The loading unit 14 is supported on a base or intermediate plate 10 by the measuring elements 4a, 4b, 4c, 4d of the force sensor. Preferably, the base or intermediate plate 10 supports the measuring elements 4a, 4b, 4c, 4d also in the horizontal direction. Preferably, an adjustment device 12a, 12, 12c is provided on the base or intermediate plate 10. It preferably has a first actuator 12a, a second actuator 12b and a third actuator 12c for pivoting about the x-axis and / or y-axis in order to shift the alignment of the base or intermediate plate 10 in the direction of the x-axis and / or y-axis and thus also the alignment of the loading unit 14.

[0055] In Fig. 1c, the drive unit 2 and the load unit 14 are each connected or connectable in a torque-transmitting manner to a shaft system, which for the sake of clarity is not fully depicted in this figure.

[0056] The left view of FIG. 1c shows a measurement arrangement in which the misalignment is strictly a parallel misalignment of the rotation axis D of the axis 5b of the loading unit 14 and the rotation axis D' of the axis 5a of the drive unit 2 in the x direction. The right view of FIG. 1c shows a measurement arrangement in which the misalignment is strictly an angular misalignment of the rotation axis D of the axis 5b of the loading unit 14 and the rotation axis D' of the axis 5a of the drive unit 2 about the y axis. Generally speaking, however, the misalignment appears as a superposition of an angular misalignment and a parallel misalignment. Moreover, the drive unit 2 can also additionally or alternatively be shifted in the y direction and / or pivoted about the x axis. Moreover, the measurement element can also be arranged on the drive unit 2 or in the axis system, as will be further explained below with reference to FIGS. 5, 6 and 7.

[0057] Different planes A, B, F, G, H are additionally marked in Fig. 1c. Plane A is a plane in which there are two measuring elements 4a, 4d aligned perpendicularly to the axis of rotation D of the loading unit 14 and arranged at the lower end of the loading unit 14 opposite the axis 5b of the loading unit 14. Plane B is a plane in which there are two measuring elements 4b, 4c aligned perpendicularly to the axis of rotation D of the loading unit 14 and arranged at the lower end of the loading unit 14 facing the axis 5b of the loading unit 14.

[0058] Plane G is aligned perpendicular to the axis of rotation D' of the drive unit 2 and is the plane in which lies a first bearing of the shaft 5a of the drive unit 2 arranged on the end of the drive unit 2 facing the axis 5b of the load unit 14. Plane H is aligned perpendicular to the axis of rotation D' of the drive unit 2 and is the plane in which lies a second bearing of the shaft 5a of the drive unit 2 arranged on the end of the drive unit 2 opposite the axis 5b of the load unit 14.

[0059] The right part of Fig. 1c shows the forces caused by the respective misalignments depicted in planes A, B and F. In planes A and B, the forces of vector A, B act on measuring elements 4a, 4b, 4c, 4d that support the load unit 14. In plane F, the force of vector F acts on a system of axes (not depicted).

[0060] The method makes it possible inter alia to simultaneously detect and then correct misalignments in both the xz-plane as well as the yz-plane.

[0061] Moreover, the test bench 1 preferably comprises a (not depicted) signal processing device 7. This is explained further below with reference to FIG.

[0062] FIG. 2 shows an exemplary embodiment of a method for correcting misalignment that can be used in the measurement arrangement described in FIGS. 1a-1c.

[0063] After installation of the measurement arrangement, it is preferably first calibrated. In particular a scaling factor or constant, in particular the product of the elastic and resistance coefficients, preferably the stiffness constant, of the axis system 5; 5a, 5b is determined for that purpose. This scaling factor or material constant preferably serves in the calculation of the bending line, as will be further explained below with reference to FIG. 3. More preferably, the scaling factor or material constant is determined by two force measurements, each at a different relative position of the drive unit 2 and the load unit 14.

[0064] In a first work step 101 of the method 100, a force measurement is performed in planes A, B and / or perpendicular to the planes A, B. The planes A, B are intersected by a rotation axis D of the axis 5b of the axis system 5; 5a, 5b, which is the axis of the loading unit 14. Preferably, the planes A, B are aligned at least substantially perpendicular to the rotation axis D. Preferably, the rotation axis D is the rotation axis of the axis 5b of the axis system 5; 5a, 5b, according to which the force measurement is performed, in other words the force is measured, as depicted in FIG. 1c.

[0065] More preferably, the force measurements are subsequently performed in a stationary or quasi-stationary state of the axis system 5; 5a, 5b. As explained above, this makes it possible to prevent damage to the measurement arrangement.

[0066] More preferably, the force measurements are continuously monitored. In particular, each last measured measurement is compared with a threshold value thereby indicating a critical axis system 5; 5a, 5b load. If this threshold value is exceeded, the rotation of the axis system 5; 5a, 5b is stopped or no rotation takes place. Furthermore, the method 100 is then preferably terminated. Preferably, as depicted in Fig. 7, there are multiple force sensors 4, 11 in the force path, and each force measurement of the force sensor 4, 11 is preferably monitored in this case.

[0067] Any constant circumferential lateral force indicates an angular offset in the axis system and can therefore be identified as a misalignment by the method of the present invention.

[0068] In a second work step 102, the measured values ​​or measured value curves of the force measurement are analyzed in order to detect misalignments of the axis system 5; 5a, 5b. Preferably, a distinction is made thereby regarding the misalignment between a parallel offset and / or an angular offset of the axis system 5; 5a, 5b.

[0069] In a third work step 103, a setpoint value for the position correction of the load unit 14 or the drive unit 2 is determined in order to minimize the misalignment. For that purpose, a bending moment or a bending moment curve for the axis system 5; 5a, 5b is determined in a first sub-step 103-1, preferably on the basis of the measured values ​​or measured value curves of the force measurement. In a second sub-step 103-2, preferably a bending line for the axis system 5; 5a, 5b is then determined on the basis of the determined bending moment or bending moment curve, taking into account the boundary conditions. A setpoint value for the position correction is then preferably determined using this bending line. Preferably, the misalignment is determined on the basis of the bending line w x It is smallest when (z) coincides with the axis of rotation D.

[0070] In a fourth work step 104, a check is made as to whether the bending moment or the bending moment curve for the axis system 5; 5a, 5b exceeds a threshold value. If the threshold value is exceeded, the method 100 continues and repeats. A setpoint value is output for this purpose in a fifth work step 105. Preferably, the output is made via the data interface 10 for the next work step. Alternatively or additionally, the setpoint value may be output to the user via the user interface 10.

[0071] When the threshold is no longer exceeded, the method 100 is preferably terminated in a ninth and final operational step 109 .

[0072] As the method 100 continues, the frictional connection between the load unit 14 and the drive unit 2 is preferably interrupted in a sixth work step 106, in particular by opening the (not depicted) couplings of the shaft system 5; 5a, 5b. The relative position of the two machine units 2, 14 with respect to each other can thereby be changed without counteracting forces.

[0073] In a seventh work step 107, the position of the load unit 14 and / or the drive unit 2 on the test bench is changed based on the output target value. This therefore results in reducing the mismatch.

[0074] In an eighth work step 108, the frictional connection between the load unit 14 and the drive unit 2 is then preferably restored. Preferably, the method 100 then starts again in the first work step 101. Alternatively, however, the method 100 can also be started again from the beginning after the previous work step.

[0075] With reference to FIGS. 3 and 4, an exemplary calculation of the target value based on the forces measured in planes A and B or in plane F is described below.

[0076] When a fixedly mounted drive unit 2 and a load unit 14 are mechanically connected via a shafting system, a friction connection is established which can be assumed to be a simplified bending beam (assuming a fixed / floating bearing shaft arrangement as depicted in Figures 1c and 3).

[0077] Depending on the location of the force flow measurements, in the illustrated case in planes A and B or in plane F, the bearing force vectors A and B or the misalignment force vector F can be calculated from the resultant moment equilibrium.

[0078] Force component F to determine misalignment x and F y and the force component F z and the instantaneous component M bx and M. by can be obtained in a manner known per se via a particular arrangement of the individual measuring elements 4a, 4b, 4c or preferred orientations of their piezoelectric elements.

[0079] Other methods for determining these parameters may also be used, for example the individual measuring elements 4a, 4b, 4c or the forces F1, .., F2 derived from the measurement signal, in other words the measured parameters. i Decomposition of the measurement signal, in particular the orthogonal decomposition.

[0080] For example, M to be determined z , F X , F Y The parameters are then the solution of a set of equations whereby equations such as: S1=a 11 M z +a 12 F x +a 13 F y S2=a 21 M z +a 22 F x +a 23 F y S3=a 31 M z +a 32 F x +a 33 F y SN=a N1 M z …

[0081] S1, S2, ...Si, ...SN are thereby the measurement signals of the individual measuring elements 4a, 4b, 4c, ...2, N. Each coefficient a depends on several factors, such as, for example, the respective position and respective preferred orientation of the measuring elements 4a, 4b, 4c, ...4i, 4N in the reference frame, the sensitivity of the respective measuring element 4a, 4b, 4c, ...,4i, ...N and possible signal losses due to force shunts through the fixing means.

[0082] Torque M z , the first lateral force component F x and the second lateral force component F yTo solve such a set of equations for , measurement signals from at least three measurement elements 4a, 4b, 4c with preferred directions aligned to be in a single plane are required. Moreover, at least two of the preferred directions do not need to be aligned parallel or anti-parallel.

[0083] For the illustrated general case of N=3, in other words with three measurement elements 4a, 4b, 4c, the solution of the set of equations depicted above is obvious. If further measurement elements are added to the measurement system 1, the set of equations becomes: z , F x , F y However, the measurement accuracy can be improved even further.

[0084] For N=4, four different sets of equations F(S1, S2, S3), F(S1, S2, S4), F(S1, S3, S4), F(S2, S3, S4) can be constructed. z , F x , F y The values ​​determined for may then be summed and averaged, in other words divided by 4 in the case of four measurement elements 4a, 4b, 4c, ..., 4i, ..., 4N. Similarly, an overdetermined set of equations F(S1, S2 ... , SN) may be constructed to be solved via a minimization problem.

[0085] Once a general solution is found for the set of equations, the parameters M z , F x , F y The calculation of can be reduced to a matrix multiplication, which provides three rows and as many columns as there are measurement signals S1, S2, S3, ... SN. The matrix elements or coefficients respectively represent the parameters M to be determined. z , F x , F y , which depicts the contribution of each of the individual sensors to

[0086]

number

[0087] Bending moment M bx and M. by can be determined via such decomposition as well.

[0088] The respective parameters M to be determined of the measurement signals S1, S2, ... Si, ... SN z , F x , F y requires knowledge of the positions and preferred directional orientations of the measurement elements 4a, 4b, 4c, . . . , 4i, . . . , 4N.

[0089] The geometrical parameters may be determined from a design drawing of the powertrain test bench 1 and from knowledge of the preferred orientations of the measurement elements 4a, 4b, 4c, . . . , 2i, . . . , 2N.

[0090] The orientation of the preferred direction of the measuring elements 4a, 4b, 4c, ..., 4i, ..., 4N may however also be determined by measuring the preferred direction using a calibration measurement. Preferably, the force sensor 4, 11 is clamped between two flat plates for that purpose. In a subsequent step, an external lateral force of known direction is applied. The preferred direction of the measuring elements 4a, 4b, 4c, ..., 4i, ..., 4N in the plane spanned by the preferred directions of the measuring elements 4a, 4b, 4c, ..., 4i, ..., 4N can be determined from the magnitude of the individual measuring signals S1, S2, ...Si, ...,SN with respect to the magnitude and direction of the introduced lateral force.

[0091] When the preferred orientation of the individual measuring elements 4a, 4b, 4c, ..., 4i, ..., 4N is known, the distance of the measuring elements 4a, 4b, 4c, ..., 4i, ..., 4N from the axis of rotation D determines the rotational speed of the defined torque M z and measuring the individual measurement signals S1, S2, . . . Si, . . . , SN.

[0092] Based on the determined forces A, B, and F, as depicted in Figure 3, the bending moment M by (z) can be determined as a function of the location in the direction of the axis of rotation D of the load unit 14, ie in the direction of the z-axis in the reference system shown.

[0093] Bending line w x (z) and bending moment M by (z) is then expressed as the following differential equation:

number

[0094] The differential equation is, in each case, the polynomial function w x (z) can be solved by the polynomial function w x (z) indicates the bending line. The corresponding polynomials w x (z) is then a set of coupled differential equations w for the multiple shaft sections 5a, 5b of the shaft system. x (z)”.

[0095] The scaling factor is the bending line w x This can be experimentally determined by specifying boundary conditions for (z). The cases depicted in Figs. 1c and 3 can be seen, for example, in x (0)=0 and w x (a) = 0. Additionally, the derivative for the angular misalignment about the bend line is zero in both cases at the point z = a + b, in other words, w' x(a+b)=0. The scaling factor may then be calculated through two force measurements at different relative alignments of the drive unit 2 and the load unit 14. Alternatively, however, the scaling factor may be estimated via FEM simulation of the axis system or measurement arrangement.

[0096] FIG. 4 shows two different bending lines w for a purely angular misalignment of the rotation axes D, D' from FIG. 1c (upper part of FIG. 4) and a purely parallel misalignment of the rotation axes D, D' from FIG. 1c (lower part of FIG. 4), determined via the depicted calculation method. x (z) In each case, the dotted lines indicate the bend lines at larger angular and parallel misalignments than the dashed lines.

[0097] Of course, the bend line y There may also be a parallel offset in the y direction resulting in a separate z-axis and an angular offset due to rotation about the x-axis. xy (z) may then be calculated by superposition, which is preferably the addition of bendlines which are vectors according to their orientation, and hence is a vector addition.

[0098] 5 to 7 show further exemplary embodiments of the powertrain test bench 1. Even if the arrangement of the force sensor or sensors in these exemplary embodiments deviates to some extent significantly from the arrangement depicted with respect to the first exemplary embodiment of FIG. 1, the calculation of the bending moments and bending lines of the powertrain can be reduced to the calculation method described above with reference to FIGS. 3 and 4.

[0099] 5 shows a second exemplary embodiment of a powertrain test bench 1, in which the detection of mismatches is possible in addition to the calibration or application test. Notably, the mismatches can be detected independently of the test bench operation.

[0100] Among other things, the powertrain test bench 1 comprises load units, or dynos 14a, 14b respectively, which are connectable in a rotatably fixed manner to the powertrain outputs as shown in FIG.

[0101] The powertrain test bench 1 preferably further comprises an incremental encoder 6 configured to measure the angle of rotation of the shaft system 5a, 5b. The function of the incremental encoder 6 is known from the prior art, inter alia it can determine the angle of rotation or the change in the angle of rotation and / or direction of the shaft system 5a, 5b photoelectrically, magnetically and / or by means of a sliding contact.

[0102] Moreover, the powertrain 1 preferably has a force sensor 4, which preferably comprises a plurality of piezoelectric measuring elements, i.e. three piezoelectric measuring elements 4a, 4b, 4c in Fig. 1. The measuring elements 4a, 4b, 4c are arranged on a measuring flange 12 in the exemplary embodiment according to Fig. 1, which may be part of the powertrain test bench 1 or the powertrain 3. Further preferably, strain gauges may also be used as measuring elements 4a, 4b, 4c.

[0103] The measurement flange connects a first shaft section 5a to a second shaft section 5b of the powertrain 3. The shafting 5a, 5b rotates about a rotation axis D, which is indicated in Figure 5 by a dashed / dotted line.

[0104] The drive unit 2 can both be a component of the powertrain test bench 1 or a component of the powertrain 3, depending on which components of the powertrain 3 are to be tested on the powertrain test bench 1.

[0105] 5, the power train 3 comprises a drive unit 2, a shaft system 5a, 5b, a differential 13 and a shaft segment (without reference numbers). The power flow can be transmitted from the drive unit 2 via the first shaft section 5a, the measurement flange 12, the first piezoelectric force sensor, the differential 13 and the shaft segment to the load units 14a, 14b.

[0106] The test bench 1 further comprises a support device 10, on which the entire drive test bench, the individual elements of the powertrain test bench 1 and / or even the powertrain 3 are mounted. The support device 10 can thereby comprise a mechanical structure for supporting the individual elements, for example, on the floor of a test bench hall. Further preferably, the support device 10 can comprise a base plate or be designed as such.

[0107] In the exemplary embodiment shown in FIG. 1, at least the drive unit 2 and the power units 14 a, 14 b are supported by a support device 10 .

[0108] The power flow, preferably generated by the drive unit 2, induces a force flow from the support device 10 through the drive unit 2, the power train 3 and the load units 14a, 14b to the support device 10 in the exemplary embodiment shown in Fig. 1. The support device 10 thereby provides respective reaction forces for supporting the drive unit 2 and the load units 14a, 14b.

[0109] The measuring elements 4a, 4b, 4c are preferably configured and designed to measure forces in the F-plane, in other words in a plane parallel to the xy-plane of the depicted reference system. The first force sensor 4 preferably comprises piezoelectric elements 4a, 4b, 4c utilizing the piezoelectric shear effect. In the illustrated exemplary embodiment, the force or the respective torque on the measuring flange 12 is introduced to the piezoelectric elements 4a, 4b, 4c via the end faces of the measuring elements 4a, 4b, 4c. The end faces of the piezoelectric elements 4a, 4b, 4c are thereby preferably frictionally connected to the surface of the measuring flange 12.

[0110] When there is a force on the measuring flange 12 in the x-direction and / or y-direction of the reference system, the piezoelectric measuring elements 4a, 4b, 4c therefore generate a corresponding measurement signal through the piezoelectric shear effect. The same applies when a torque acting in the z-direction is applied to the measuring flange 12.

[0111] Alternatively or additionally, the measuring elements 4a, 4b, 4c can realize a force measurement perpendicular to the first plane F. For that purpose, the measuring elements 4a, 4b, 4c preferably utilize the piezoelectric longitudinal or transverse effect. When the force is measured both in the first plane F as well as perpendicular thereto, there are preferably both measuring elements capable of measuring the force in the z direction as well as measuring elements capable of measuring the force in the x or xy plane. Further preferably, each of the measuring elements 4a, 4b, 4c comprises at least two piezoelectric elements connected in series with respect to the force flow, whereby the first piezoelectric element utilizes the piezoelectric shear effect and the second piezoelectric element utilizes the piezoelectric transverse or longitudinal effect.

[0112] FIG. 6 shows a third exemplary embodiment of a test bench 1, with the aid of which misalignments of the shaft system can be detected during test bench operation.

[0113] A substantial difference between the test bench 1 of the third exemplary embodiment from FIG. 6 and the test bench 1 of the second exemplary embodiment from FIG. 5 is that the force sensor 11 is not arranged in the power flow between the drive unit 2 and the load units 14a, 14b, but instead between the support device 10 and the drive unit 2.

[0114] Through this arrangement, the first force sensor 4 measures the reaction force that the support device 10 exerts on the drive unit 2 upon receiving a torque between the shaft system 5 and the drive unit 2 .

[0115] The force sensor 11 can thereby preferably be supported in the axial direction of the rotation axis D, as depicted in Fig. 6. However, the drive unit 2 can equally be supported laterally, downwards or upwards by the force sensor 11, as shown in the top view according to Fig. 1a, 1b or 7. Depending on how the piezoelectric measuring elements 11a, 11b, 11c engage with the drive unit 2, elements with a piezoelectric shear effect, elements with a piezoelectric longitudinal or transverse effect or elements with two different effects as explained above with reference to Fig. 5 are then employed.

[0116] Also, in the exemplary embodiment depicted in FIG. 6, the forces are preferably measured in planes C, D and / or perpendicular to planes G, H.

[0117] It is also possible to combine the second exemplary embodiment according to Fig. 5 with the third exemplary embodiment according to Fig. 6. For example, the second exemplary embodiment can therefore also have a measurement flange 12 on which a further piezoelectric force sensor is arranged. This second piezoelectric force sensor can then define a second plane F for measuring forces and / or moments.

[0118] Furthermore, there may be further piezoelectric force sensors for measuring the reaction forces on the load units 14a, 14b, which may also preferably support the respective load units 14a, 14b relative to a support device, in particular relative to the ground or base plate 10, so that the reaction forces between the load units 14a, 14b and the support device 10 can be measured in this case as well.

[0119] Compared to a direct measurement of the forces in the axis system 5 , the measurement of reaction forces according to FIG. 6 has the advantage that the respective force sensor 4 has no influence on the moment of inertia and momentum of the axis system 5 .

[0120] A fourth exemplary embodiment of a powertrain test bench, by means of which shaft system misalignments can be detected, is shown in FIG.

[0121] The powertrain 3, when applicable, comprises only one axle system 5 as well as one drive unit 2. In contrast to the first exemplary embodiment of the test bench according to Fig. 1, the reaction forces of both the load unit 14 as well as the drive unit 2 on the support device 10 are preferably measured for at least one measurement plane A, B on the load unit 14 and for at least one measurement plane G, H on the drive unit 2.

[0122] However, as in the case of the exemplary embodiments described in Figures 5 and 6, the powertrain 1 according to the first exemplary embodiment or according to the second exemplary embodiment may also comprise further elements, in particular gear mechanisms or differentials, axle segments, etc.

[0123] However, it may also be provided in this exemplary embodiment that each force sensor 4, 11 comprises two elements connected in series with respect to the force flow, such that two different measurement directions, in particular two mutually orthogonal measurement directions, are possible. In particular, these measurement directions may be aligned in the y-direction and the x-direction. Forces in the z-direction may be measured through a third piezoelectric element in the measuring element of the force sensor 4, 11.

[0124] FIG. 8 shows details of the powertrain test bench 1 according to FIG. 1, 5, 6 or 7 or a separate control unit arranged to control the powertrain test bench 1.

[0125] The signal processing device 7 comprises means 8 arranged for analyzing the measured values ​​or measured value profiles of the force measurement for the detection of misalignment of the axis system 5; 5a, 5b, means 9 for determining setpoint values ​​for the position correction of the load unit or the drive unit in order to minimize the misalignment, and means 10 for outputting the setpoint values, in particular an interface. Further preferably, the signal processing device 7 comprises means 15 for controlling the regulating device 12a, 12, 12c on the basis of the outputted setpoint values. The signal processing device 7 is signal-connected both to the measuring elements 4a, 4b, 4c of the force sensor as well as to the regulating device 12a, 12, 12c.

[0126] The exemplary embodiments described above are merely examples and are in no way intended to limit the scope of protection, application and configuration. Instead, the above description provides the skilled person with a guideline for implementing at least one exemplary embodiment, whereby various modifications may be made, in particular with regard to the function and arrangement of the components described, without departing from the scope of protection derived from the claims of the same and of equivalent combinations of features. In particular, the individual exemplary embodiments may be combined with one another, in particular with regard to the powertrain test bench or measurement arrangement. Thus, in particular, the exemplary embodiments of the powertrain test bench of Fig. 5, Fig. 6 and Fig. 7 may also comprise adjustment devices 12a, 12b, 12c. The sequence of work steps of the described method 100 may also deviate from the depicted one. In the same way, force measurements, in particular with respect to axes, may be realized through sensors based on strain gauges. [Explanation of symbols]

[0127] 1 Powertrain Test Bench 2 Drive unit 3. Powertrain 4. First Piezoelectric Force Sensor 4a, 4b, 4c Piezoelectric measuring elements 5, 5a, 5b axis system 6 Incremental Encoders 7 Signal Processing Devices 8, 9, 10, 15 Means of signal processing device 11 Second piezoelectric force sensor 12 Measurement flange 13 Differential / Gear Mechanism 14, 14a, 14b Load Unit

Claims

1. A method (100) for correcting misalignment of at least one shaft system (5, 5a, 5b) of a powertrain (3) on a test bench (1), comprising: At least one piezoelectric force sensor (4a, 4b, 4c, 4d) is arranged in a force path through which a force flow can be transmitted between a load unit (14; 14a, 14b) of the test bench (1) and a power train (3) or a drive unit (2) of the test bench (1) during the transmission of power via the shaft system (5; 5a, 5b), and is adapted to perform the following work steps: - performing (101) force measurements in at least one plane (A, B; F) and / or perpendicular to said at least one plane (A, B; F) intersected by a rotation axis (D) of said axis system (5; 5a, 5b) and preferably at least substantially perpendicular to said rotation axis (D); - analyzing (102) the force measurements or the measurement curves in order to detect any misalignment of the axis system (5; 5a, 5b), - determining (103) a target value for a position correction of said load unit (14; 14a, 14b) or of said drive unit (2) in order to minimize said misalignment; A step (105) of outputting the target value; A method (100).

2. The following additional work steps: - determining (103-1) a bending moment or a bending moment curve for the axis system (5; 5a, 5b) based on the measured values ​​or measured value courses of the force measurements; A step (103-2) of determining a bending line of the shaft system (5; 5a, 5b) based on the determined bending moment or bending moment curve, the target value being determined through the bending line; The method (100) of claim 1 , wherein the determining of the target value (103) is performed.

3. The following work steps: - a step (104) of checking whether a bending moment or a bending moment curve for said axis system (5; 5a, 5b) exceeds a threshold value; repeating (109) the method (100) iteratively if the threshold is exceeded or terminating the method (100) if the threshold is not exceeded. The method (100) of claim 1 or 2, further comprising:

4. The following work steps: a step (106) of separating the frictional connection between the load unit (14) and the drive unit (2), in particular by opening the couplings of the shaft system (5; 5a, 5b); The method (100) of any one of claims 1 to 3, further comprising:

5. The following work steps: A step (107) of varying the position of the load unit (14) and / or the drive unit (2) on the test bench based on the output target value. The method (100) of any one of claims 1 to 4, further comprising:

6. The following work steps: Establishing (108) a frictional connection between the load unit (14) and the drive unit (2). The method (100) of any one of claims 1 to 5, further comprising:

7. 7. The method (100) according to any one of claims 1 to 6, wherein constants of the axis system (5; 5a, 5b), in particular the product of the elastic and resistance coefficients, are determined for calculating a bending line through two force measurements for different positions of the drive unit (2) or the load unit (14).

8. 8. The method (100) according to any one of the preceding claims, wherein the axis of rotation (D) of the axis system (5; 5a, 5b) is the axis of rotation of an axis of the axis system (5; 5a, 5b) on which the force measurement is performed.

9. The method (100) according to any one of the preceding claims, wherein the force measurements are performed in a stationary or quasi-stationary state of the axis system (5; 5a, 5b).

10. 10. The method (100) according to any one of claims 1 to 9, wherein the force measurements are monitored in that one or more measurements are compared with a threshold value indicative of a critical shaft system (5; 5a, 5b) load, and when said threshold value is exceeded, rotation of the shaft system (5; 5a, 5b) is stopped or no rotation takes place.

11. The method (100) according to any one of the preceding claims, wherein a plurality of force sensors (4, 11) are provided in the path of force and each force measurement of the force sensors (4, 11) is monitored.

12. The method (100) according to any one of the preceding claims, wherein a distinction is made during the analysis regarding the misalignment between a parallel offset and / or an angular offset of the axis system (5; 5a, 5b).

13. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any one of claims 1 to 12.

14. A computer readable medium having stored thereon the computer program of claim 13.

15. A powertrain test bench (1), comprising: a load unit (14a, 14b) connectable to the shaft system (5; 5a, 5b) to be tested; at least one piezoelectric force sensor (4a, 4b, 4c, 4d) arranged in a path of forces whose flow is transmitted from and through the loading unit (14a, 14b) of the test bench (1) during the transmission of power through the axis system (5; 5a, 5b) and configured to perform force measurements in a plane (A, B; F) and / or perpendicular to said plane (A, B; F) intersected by a rotation axis (D) of the axis system (5; 5a, 5b), preferably at least substantially perpendicular to said rotation axis (D); - means (8) adapted to analyze the measured values ​​or measured value courses of said force measurements in order to detect any misalignment of said axis system (5; 5a, 5b); - means (9) for determining a setpoint for the position correction of said load unit or drive unit in order to minimize said misalignment; - means (10) for outputting said target values, in particular an interface A signal processing device (7) having A powertrain test bench (1).

16. the powertrain test bench (1) additionally comprises adjustment devices (12a, 12b, 12c) configured to change the position of the load units (14a, 14b) or the drive units (2) translationally and / or rotationally, The powertrain test bench (1), in particular the signal processing device (7), means (15) configured to control said regulating device (12) on the basis of said output target value; Further comprising: A powertrain test bench (1) according to claim 15.

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