Method for detecting and taking into account magnetic influences on vibration sensors of a balancing machine

Abstract

In a method for detecting magnetic influences on vibration sensors (a, b, c, d) of a balancing machine, a first and a second vibration sensor (a, b, c, d) are provided on a bearing stand (1, 3) for receiving a rotor (2). The vibration sensors (a, b, c, d), arranged symmetrically on the bearing stands (1, 3) with respect to a central axis of the bearing stand (1, 3), detect vibrations caused by the rotor (2) in the same measuring direction and transmit these as a voltage signal to an evaluation unit. The evaluation unit can determine an imbalance value as the product of the mass and distance from a rotational axis of the rotor (2), as well as the angular position on the rotor (2). Any influences on the first vibration sensor (a, b, c, d) are detected by the second vibration sensor (a, b, c, d) with a phase shift of 2α.The influences are captured by comparing the voltage signals of the vibration sensors (a, b, c, d) or the voltage signals as voltage over time, in particular as vibration vectors in magnitude and phase, especially computationally, or by calculating the imbalance for each vibration sensor (a, b, c, d) from the measured voltage signals and combining them.

Description

[0001] The invention relates to a method for detecting and taking into account magnetic influences on vibration sensors of a balancing machine. The invention further relates to a balancing machine for carrying out the method.

[0002] Balancing machines for measuring rotor imbalance are known. The rotor can be mounted in bearing stands. To detect vibrations originating from the driven rotor, moving coils, for example, can be used as vibration sensors, the output signal of which is then processed. During an imbalance measurement, the bearing bridge of the balancing machine is set into vibration according to the rotor imbalance, causing the moving coil to move within the magnetic field and thus inducing a voltage in the coil, which is then amplified in a subsequent voltage amplifier.

[0003] From DE 11 27 599 A a balancing machine with two moving coils functioning as vibration sensors is known, wherein the disclosed design allows for the elimination of interfering vibrations.

[0004] DE 12 37 807 B describes a balancing machine with a foundation-fixed bearing stand and a bearing component, e.g., a bearing bridge, which is supported against it in a way that allows vibration, and which supports the rotor to be balanced. The sensor can be attached to the rigid bearing stand base in such a way that the sensor does not move in the direction of vibration, while the actuating rod is supported against the vibrating bearing bridge. For this purpose, the actuating rod is guided outwards through the permanent magnet and, in its installed position, is supported against the rigid bearing stand base via a lever mechanism.

[0005] Several sources of error exist in imbalance measurement. Individual errors can be detected and compensated for by adding test weights. Other influences, resulting from mechanical deformation of the rotor due to the axial mounting, are difficult to detect and compensate for. Often, measurements must be performed at different rotational speeds, which is time-consuming and impractical.

[0006] DE 10 2012 107 590 B4 describes a method for determining the influence of the machine environment on the measurement accuracy of a vibration-measuring balancing machine. In this method, a measurement signal acquired with the drive of the balancing machine stationary from at least one vibration sensor of the balancing machine is combined with a predetermined speed signal, and an unbalance reference value describing the environmental influence is calculated from the combined signals using the signal evaluation method of the balancing machine.

[0007] US Patent 3,164,995 A discloses a method for reducing interference, in which an additional sensor is provided on the device for determining imbalance, with which absolute vibrations of the frame are detected. The two sensors, which are designed as moving-coil sensors, are arranged coaxially one behind the other and attached to each other. The first sensor has a sensor element in the form of the moving-coil rod, which is connected to the vibrating bearing component for the rotor, the balancing bridge. The second sensor has a sensor mass that is matched to the design of the device and the rotor under investigation. The measurement signal emitted by the second sensor is proportional to the vibrations of the frame and thus to the interference vibrations of the sensor housing, and is superimposed on the signal emitted by the first sensor.

[0008] US Patent 5,209,116 A discloses a method for reducing interference in unbalance measurement, in which a simulation mass with the same weight as the rotor under investigation is arranged adjacent to the vibrating bearing component for the rotor. The vibrations of the bearing component are detected by a first pair of sensors arranged between it and the frame, while the vibrations of the simulation mass are detected by a second pair of sensors, also arranged between the simulation mass and the frame. The first pair of sensors detects unbalance-induced and interference-induced vibrations, while the second pair detects vibrations between the simulation mass (which is stationary due to its inertial mass) and the frame as interference vibrations. The signals from both pairs of sensors are superimposed and processed for evaluation.

[0009] The problem, however, is that measurement errors occur when a magnetic or magnetizable rotor passes close to a vibration sensor, such as a moving coil. A magnetized rotor induces a voltage in the cable of a vibration sensor, proportional to the speed at which it passes the cable. When measuring with a moving coil, this effect is significantly greater if it is not adequately shielded. A disadvantage of shielding, however, is that its effect is difficult to detect. Such magnetic influences affect the measurement and are essentially indistinguishable from the rotor imbalance being measured.

[0010] To detect similar error influences, measurements can be taken at two or more rotational speeds, and a computational correction can be performed based on the frequency response. In particular, the imbalance can be separated from the magnetic force, as the imbalance force increases quadratically with rotational speed, while the magnetic force is independent. However, such methods are complex and not very practical.

[0011] From JP 2005-188 951 A, a dynamic balancing test machine is known in which the test specimen is mounted on flat, thin piezoelectric elements, in particular PVDF film sensors, via support elements. It is further described that magnetic influences on vibration sensors can have a disruptive effect, but this can be countered by using piezoelectric sensors, thus reducing the influence of magnetized rotors.

[0012] The object of the invention is therefore to provide a method by which such magnetic influences on sensors can be detected.

[0013] The problem is solved by the features of claim 1. Preferred embodiments are described in the dependent claims.

[0014] The object of the invention is achieved by providing a method for detecting magnetic influences on vibration sensors of a balancing machine, in which a first and a second vibration sensor, arranged symmetrically to a central axis of the bearing stand for receiving a rotor, detect vibrations caused by the rotor in the same measuring direction and transmit them as a voltage signal to an evaluation unit, which determines an imbalance amount as the product of mass and distance from a rotational axis of the rotor, as well as the angular position on the rotor, wherein influences on the first vibration sensor are detected by the second vibration sensor with a phase shift of 2α, in which the influence on the vibration sensors is detected by the voltage signals of the vibration sensors in analog or digital form.In particular, vibration vectors can be compared in magnitude and phase, or the imbalance can be calculated for each vibration sensor from the measured voltage signals and combined. This method simplifies imbalance measurement, as it eliminates the need to run through multiple, potentially high, rotational speeds. Moreover, any magnetic influences on the measurement, which previously remained largely undetected, can now be identified.

[0015] In accordance with the invention, it is advantageous to distinguish between an in-phase and an out-of-phase influence on the vibration sensors. The in-phase influence is characterized by an additional voltage signal with the same sign measured by the vibration sensors, and the out-of-phase influence by a measured voltage signal with opposite signs. The terms "effect" and "influence" can be used interchangeably within the meaning of the invention.

[0016] The evaluation unit is connected to the vibration sensors for data exchange. This connection can be either wireless or wired. The evaluation unit can be integrated into a balancing machine and, for example, be designed as a computer or processing unit with appropriate interfaces on which programs or apps can be installed. It can also be a retrofittable processing unit or one that can be connected to a balancing machine, such as a computer or tablet.

[0017] In a preferred embodiment of the method, a measurement quality q can be achieved by q=|g||h| The unbalances are calculated using g = a + b and h = a - b, where a represents the imbalances calculated from the measured voltage signals of the first vibration sensor and b represents the imbalances calculated from the measured voltage signals of the second vibration sensor. The measurement can be considered reliable, and advantageously, no magnetic influence is present, if q >> 1. If q is large, i.e., q >> 1, then the unbalance measurement is, in principle, reliable. If the magnitudes of g and h are similar, or if the resulting value of q is less than a definable limit, such as 10, then a measurement error is likely. Advantageously, the limit can be freely defined. The advantage of directly using the quotient as a quality characteristic is that the sensor angle α does not necessarily need to be entered.

[0018] Furthermore, a method is preferred in which measurement quality is ensured by means of an imbalance tolerance. qT=T|h| The unbalance tolerance T is calculated, where the permissible residual unbalance for a rotor to be measured is defined, and h is calculated using the formula h = a - b, where a represents the unbalances calculated from the measured voltage signals of the first vibration sensor and b represents the unbalances calculated from the measured voltage signals of the second vibration sensor. The unbalance tolerance T, i.e., a permissible residual unbalance, can also be used to determine the measurement quality, so that the error component is not given undue attention at small measured values. The permissible residual unbalance is advantageously predefined by the manufacturer.

[0019] In a preferred embodiment, the method enables the automatic correction of the detected measurement error. This involves calculating a corrected imbalance value with u=12 (g - ih tan α) for an in-phase influence and u=12 (g + ih cot α) is calculated for an out-of-phase influence, with g = a + b and h = a - b, where a represents the imbalances calculated from the measured voltage signals of the first vibration sensor and b represents the imbalances calculated from the measured voltage signals of the second vibration sensor. The cotangent can be calculated using cot α = cos α / sin α.

[0020] Furthermore, the invention relates to a balancing machine for carrying out the previously described method, comprising bearing stands for receiving a rotor and two vibration sensors mounted on a bearing stand, which are arranged symmetrically spaced from a central axis of the bearing stand and are designed to detect vibrations caused by the rotor. The machine also includes an evaluation unit to which the vibration sensors are connected for data exchange and which is configured to carry out the method. The method can be implemented as a sequence, particularly as a computer program, within the evaluation unit. Based on the method according to the invention, the balancing machine can perform a precise determination of the imbalance, whereby magnetic influences on the vibration sensors can be detected and compensated for. Moving coils are particularly suitable as vibration sensors.

[0021] To perform a measurement in two planes, two vibration sensors can be provided on each of two bearing stands.

[0022] The quality, and especially the robustness, of the process can be influenced by the position of the vibration sensors. Particularly in the case of out-of-phase influence, it is advantageous to arrange two vibration sensors on a bearing stand at an angle 2α of approximately 90° to each other. For out-of-phase influence, it is advantageous if the angle 2α is as close as possible to 90°, i.e., if the vibration sensors are positioned approximately opposite each other at the level of the rotor's axis of rotation. Furthermore, it is advantageous if two vibration sensors on a bearing stand are arranged at an angle 2α of ≤ 45° to each other. For in-phase influence, it is advantageous if α becomes very small, i.e., if both sensors are positioned close to each other below the axis of rotation.

[0023] The invention is explained in more detail below with reference to an embodiment of the invention, which is illustrated in the drawing. The drawing shows... Fig. 1 horizontal bearing stand with symmetrical moving coil construction and rotor and Fig. 2 Arrangement of two bearing stands in a horizontal machine.

[0024] There are numerous measured signal components in the sensor signals that are not causally related to the imbalance. 1. For example, only the first order is used, i.e., a narrowband frequency component that is rigidly determined by the rotation. All other signal components are filtered out from the outset. 2. Furthermore, an unbalance calibration is performed, which can lead to measurement errors if applied to other rotors or different rotational speeds. These errors can be corrected or detected by checking or readjusting the unbalance indicator using test weights. This is a scaling or angular error, resulting from the transmission behavior of the sensors to the unbalance indicator, which is detected by applying test unbalances. 3. The most problematic influences are those that could not be distinguished from imbalance using known methods. They cannot be detected by test imbalances and are therefore incorrectly attributed to rotor imbalance.

[0025] Such fault influences, in particular magnetic influences, can be detected and corrected using the method according to the invention.

[0026] Measured signal components from the sensors that originate from the rotational movement of the rotor, but are not caused by the centrifugal force effect of the imbalance, include, for example, mechanical deformations of the shaft, forces and deformations caused by the axial support of the rotor when the stop rolls against the rotor, and magnetic influences of the rotor on the sensor signal.

[0027] Centrifugal force and imbalance influences lead to vibration displacements at the measuring points of a "hard measuring" balancing machine, which increase quadratically with the rotational speed; therefore, the vibration displacement x is proportional to the imbalance u times the rotational speed n squared: x ~ un 2 .

[0028] Mechanical deformations at the bearing stand due to a bent shaft lead to vibration amplitudes that are constant at every rotational speed. Therefore, they have a different transmission factor compared to the effect of imbalance when measured at two different rotational speeds. Such influences can only be distinguished from imbalance measurements if measurements are taken at two different speeds. The same applies to magnetic forces.

[0029] A magnetized rotor induces a voltage in the cable of a vibration sensor, proportional to the speed at which it passes the cable. When measuring with a vibration transducer, especially a moving coil, the effect is significantly greater if it is not adequately shielded. Even a seemingly non-magnetized rotor, such as a simple steel disc or a compressor wheel, where the operator would not expect an obvious magnetic effect, can still lead to inaccurate measurements.

[0030] Measuring at multiple rotational speeds and subsequently separating the imbalance from the frequency response has major disadvantages: - This is a special procedure that is only used when the operator is familiar with the effects. - It means a significantly greater effort to start up at multiple speeds. - It may be necessary to calibrate the machine several times, i.e., to perform at least three test runs per speed before an imbalance measurement result is available. - It is not always possible to reach a higher speed, or if the procedure requires it, the question arises as to why measurements are not taken directly at a higher speed where the imbalance force dominates and the error is generally reduced. Higher rotational speeds can pose a safety risk. - The rotor can deform at higher speeds and thus has a different state of imbalance. - The balancing machine can be operated near its natural resonance, which makes the measurement less accurate.

[0031] These are all reasons why it is advantageous to detect measurement errors directly during a measurement at a fixed rotational speed.

[0032] Fig. Figure 1 shows a horizontal bearing stand 1 with an integrated rotor 1 from an axial view. A second bearing stand 3 can be added, as shown in Fig. As indicated in point 2, the procedure is also present. The method is first described for measurements in a single plane.

[0033] An imbalance u causes a voltage signal in the vibration sensor a, which is detected by an evaluation unit and processed digitally. The evaluation unit's computer registers the signal and displays the imbalance magnitude as the product of mass times distance from the axis of rotation and the angular position on the rotor 2. The same process can be performed for sensor b, which is arranged symmetrically and vertically mirrored to the central axis. For the purposes of this invention, the term "sensor" is used for the sake of simplicity to refer to a vibration sensor.

[0034] Since both sensors a and b are mounted in the same measuring direction, but with opposite signs, they measure the same signal in terms of magnitude, but with the opposite sign, or a phase shift of 180° relative to the rotor angle. The transfer factor of sensor a and sensor b to the imbalance is a complex quantity with magnitude and angle. Depending on which sensor a or b is used to indicate the imbalance, the transfer factor has approximately the same magnitude, but the phase is opposite. Small differences in sensor sensitivity result in slightly different magnitudes of the transfer factor.

[0035] The factors are generally determined using so-called calibration or balancing runs, by adding a known test imbalance to the unknown imbalance of rotor 2 and determining the signal change factor per imbalance from vectorial difference calculation of both measurement results.

[0036] If, in addition to the machine's movement due to the imbalance force, there is another effect in the vibration signal, e.g., caused by the induction of a voltage when a magnetic pole passes sensor a, b, then it causes a change in the signal in both sensors a, b, but offset by the angle 2α. In the Fig. Sensor b will first measure an effect, and sensor a will measure it at a time when rotor 2 has rotated further by the angle 2α. This means that such an effect has a phase shift of 2α, not 180°.

[0037] It should be noted that the described effect has a local impact directly on sensor a, b, while the imbalance affects the entire bearing stand 1 and thus generates a signal that is largely independent of the sensor position.

[0038] Two mechanisms of impact can be distinguished: 1. The interfering effect causes a voltage with opposite sign when passing sensors a and b. 2. The sensors supply an additional voltage of the same sign.

[0039] Effect (1) is referred to as an out-of-phase effect and (2) as an in-phase effect within the meaning of the invention.

[0040] To indicate the fault, the signals from both sensors a and b can be combined: once added and once subtracted. This can be done using various methods: 1. Analog, based on the sensor signal 2. Digital as a time signal from sensor a, b or after first-order calculation 3. After the unbalance calibration, i.e., the unbalance is determined separately for each sensor a, b and both values ​​are combined.

[0041] The advantage is that this eliminates small differences in the sensor constants.

[0042] The fundamental difference is that, according to point 3, both components have different signs, i.e., adding the sensor signals corresponds to subtracting the imbalance values ​​and vice versa.

[0043] The following equations are formulated using the 3rd method, but can be transferred to the other two methods.

[0044] Let u be the imbalance that would be measured if no disturbances were present, and v be a false imbalance caused by the described effect. Both quantities are complex numbers, meaning they have magnitude and angle, while the false imbalance v is unknown. The imbalance measurements of the individual sensors a, b are as follows for the out-of-phase effect: a=u+veiα b=u+ve−iα, or the second equation for the in-phase effect is: b=u−ve−iα.

[0045] A combination of g and h is introduced, as follows: g=a+b, h=a−b so is g=2u+v(eiα+e−iα) h=v(eiα−e−iα) or g=2u+2v cos α h=2v i sin α Error indication

[0046] The first application of the preferred method can be to display a measurement error; thus, a display and quantification takes place.

[0047] The imbalance can be calculated from each of the sensors a, b, or from the combination g as U ≈ g / 2. The error v is neglected in this calculation.

[0048] The measurement quality q can be derived from the ratio of the values ​​of g to h: q=|g||h|

[0049] If q is large, i.e., q ≈ 1, then the imbalance measurement is essentially reliable. If the magnitudes of g and h are similar, then a measurement error is present. The advantage of directly using the quotient as a quality characteristic is that the sensor angle α does not need to be entered.

[0050] The measurement error, or the error percentage, can be displayed in the evaluation unit, or a warning can be issued only if it exceeds a defined amount, e.g., 10%. For this purpose, it is advantageous if the evaluation unit simultaneously includes a control unit, a display such as a screen, and input devices such as a touchscreen, or combinations thereof.

[0051] Alternatively, the unbalance tolerance T can be used, i.e., basically a permissible residual unbalance, so that too much attention is not paid to the error component in the case of small measured values: qT=T|h| Error correction

[0052] The measurement error can also be corrected automatically, especially if the angle α is known. Generally, the angle is always known, as sensors a and b are usually permanently installed and therefore the angle is predetermined by the design. However, depending on the bearing diameter of rotor 2, the height on the machine can vary, and thus so can the angle α. To correct this, the angle α can be calculated from distances, such as the currently set bearing height and the rotor diameter, as well as the position of sensors a and b. Alternatively, a mean angle can be defined and stored in the evaluation unit of the balancing machine.

[0053] The corrected imbalance value for the out-of-phase effect can be calculated directly from g and h: u=12(g+ih cot α)

[0054] With the cotangent cot α = cos α / sin α.

[0055] Accordingly, the corrected imbalance for the in-phase effect is: u=12(g+ih tan α) robustness

[0056] The robustness of a preferred method can be influenced by the position of sensors a, b: For the antiphase effect, it is advantageous if the angle α is as close as possible to 90°, i.e., if the sensors a, b are approximately opposite each other at the height of the rotation axis of the rotor 2. For the in-phase effect, it is advantageous if the angle α is very small, i.e., both sensors a, b are positioned close to each other below the rotation axis of the rotor 2.

[0057] It is preferred that the error rate is automatically corrected by using g or is approximately good enough so that no correction calculation is necessary.

[0058] It is preferred that, at favorable angles, the error is automatically corrected, but both sensors a and b may be necessary. With only one sensor a or b, the error may be present in its full magnitude.

[0059] It has been advantageously found that, in most common balancing machines, the installation of a second sensor a, b at an angle α in the middle range, i.e., around 45°, is beneficial. In these cases, the correction calculation can be performed and the imbalance difference h is not excessively increased.

[0060] The method advantageously serves to detect magnetic influences on vibration sensors (a, b, c, d) of a balancing machine, comprising a first and a second vibration sensor (a, b, c, d) mounted on a bearing stand (1, 3) for supporting a rotor (2). The vibration sensors (a, b, c, d), arranged symmetrically on the bearing stands (1, 3) with respect to a central axis of the bearing stand (1, 3), detect vibrations caused by the rotor (2) in the same measuring direction and transmit these as a voltage signal to an evaluation unit. The evaluation unit can determine the amount of imbalance as the product of the mass and distance from a rotational axis of the rotor (2), as well as the angular position on the rotor (2). Any influences on the first vibration sensor (a, b, c, d) are detected by the second vibration sensor (a, b, c, d) with a phase shift of 2α.The influences are captured by comparing the voltage signals of the vibration sensors (a, b, c, d) or the voltage signals as voltage over time, in particular as vibration vectors in magnitude and phase, especially computationally, or by calculating the imbalance for each vibration sensor (a, b, c, d) from the measured voltage signals and combining them.

[0061] There are three advantageous methods for calculating an imbalance: • Conventional calculation based on the measurement signals of a vibration sensor, e.g., a moving coil or multiple moving coils. Only the plausibility of the measured value can be displayed. • Complete correction of measurement errors caused in particular by magnetic influences using the previously described procedure for imbalance correction. Input of the angle α may be necessary. • Arrangement of the vibration sensor, e.g., a moving coil at an angle α of approximately 90° in the case of an out-of-phase effect. Here, for example, g can be used to calculate the imbalance, as described above, whereby any error is essentially corrected "automatically" without requiring any software adjustment. The use of g can also mean that any measurement signals are added analogously (i.e., only a wiring adjustment is necessary). The angle α does not necessarily have to be entered into the balancing machine's software for this configuration.

[0062] The illustrated embodiment can also be applied to measurements on two planes, which is schematically represented in Fig.Figure 2 is shown. Normally, balancing machines measure imbalances in two planes on the rotor 2, perpendicular to the axis of rotation and at a certain axial distance from each other. The planes in which the imbalance is to be calculated and displayed are usually not the same as the planes of the bearings, i.e., the bearing stands 1, 3 in which the sensors are located. In the example shown, two bearing stands 1, 3 are provided, each with two vibration sensors a, b and c, d.

[0063] For a rigid rotor, imbalances in two known planes can be converted into two other planes using lever ratios. This involves linearly combining the imbalances of the two planes, for example, by multiplying them with a 2x2 matrix. The coefficients of the matrix contain only length ratios of the axial distances between the planes (see, for example, Hatto Schneider: Balancing Technology, Springer).

[0064] To perform the correction of the imbalance according to a preferred method, the imbalances can first be transformed from the general planes to the planes of the bearing stands 1, 3, corrected there, and then transformed back to the display planes.

[0065] The method according to the invention, or the preferred balancing machine, has numerous advantages over known devices or methods. For example, known arrangements cannot detect or correct magnetic influence. Using the method according to the invention, which can be easily implemented in existing evaluation units, reliable measurement of magnetic influence is possible. Furthermore, the quality of the imbalance measurement can be easily quantified, which in turn simplifies operation.

Claims

[1] Method for detecting and taking into account magnetic influences on vibration sensors (a, b, c, d) of a balancing machine, in which a first and a second vibration sensor (a, b, c, d) arranged symmetrically to a central axis of the bearing stand (1, 3) on a bearing stand (1, 3) for receiving a rotor (2) detect vibrations caused by the rotor (2) in the same measuring direction and transmit them as a voltage signal to an evaluation unit, which determines an imbalance amount as the product of mass and distance from an axis of rotation of the rotor (2), as well as the angular position on the rotor (2), wherein influences on the first vibration sensor (a, b, c, d) are detected with a phase shift of 2α by the second vibration sensor (a, b, c, d), in which the influence on the vibration sensors (a, b, c, d) is detected by the voltage signals of the vibration sensors (a, b, c, d) in analog or digital form,in particular as vibration vectors in magnitude and phase, or the imbalance is calculated for each vibration sensor (a, b, c, d) from the measured voltage signals and the calculated imbalances are combined with each other. [2] Method according to claim 1, characterized by that the procedure achieves a measurement quality q through q=|g||h| with g = a + b and h = a - b, is calculated, where a represents the imbalances calculated from the measured voltage signals of the first vibration sensor and b represents the imbalances calculated from the measured voltage signals of the second vibration sensor, and where there is no magnetic influence when q >> 1. [3] Method according to claim 1, characterized by that in the procedure a measurement quality is achieved by means of an imbalance tolerance T by qT=T|h| is calculated, wherein the imbalance tolerance T is defined as the permissible residual imbalance for a rotor (2) to be measured and h is calculated using the formula h = a - b, where a represents the imbalances calculated from the measured voltage signals of the first vibration sensor and b represents the imbalances calculated from the measured voltage signals of the second vibration sensor. [4] Method according to claim 1, characterized by that a corrected imbalance value with u=12(g−ih tan α) (g - ih tan α) for an in-phase influence and u=12(g+ih cot α) (g + ih cot α) is calculated for an antiphase influence, with g = a + b and h = a - b, where a represents the imbalances calculated from the measured voltage signals of the first vibration sensor and b represents the imbalances calculated from the measured voltage signals of the second vibration sensor. [5] Balancing machine for carrying out the method according to one of the preceding claims, with bearing stands (1, 3) for receiving a rotor (2) and with two vibration sensors (a, b, c, d) attached to a bearing stand (1, 3), which are arranged symmetrically spaced apart from a central axis of the bearing stand (1, 3) and are designed to receive vibrations caused by the rotor (2), with an evaluation unit to which the vibration sensors (a, b, c, d) are connected for data exchange and which is set up for carrying out the method. [6] Balancing machine according to claim 5, characterized by that the balancing machine comprises two bearing stands, each with two vibration sensors. [7] Balancing machine according to claim 5 or 6, characterized by , that two vibration sensors are arranged on a bearing stand at an angle 2α of approximately 90° to each other. [8] Balancing machine according to claim 5 or 6, characterized by , that two vibration sensors are arranged on a bearing stand at an angle 2α of ≤ 45° to each other.

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