Method for detecting an imbalance in the operation of a drive unit

Abstract

The invention relates to a method (100) for detecting an imbalance in the operation of a drive unit (10) by means of a detection unit (11), the drive unit (10) comprising at least one shaft (12) and at least one electric machine (13), wherein the electric machine (13) is operatively connected to the shaft (12) in such a way that the shaft (12) can be driven by the electric machine, the method comprising the following steps: - performing (110) a frequency analysis of an operating signal (S) of the drive unit (11), in order to break down the operating signal (S) into its frequency components (Fi), wherein the operating signal (S) is characteristic of a curve of an operating parameter (N) of the electric machine (12) over time (t), - determining (120) an amplitude mean value (A) for at least one frequency component (Fi) of the operating signal (S), - calculating (130) an amplitude deviation (∆A) between the amplitude mean value (A) and an amplitude reference value (Aref), which in particular is specific to the relevant frequency component, - determining an imbalance status of the shaft (11) based on the amplitude deviation (∆A).

Description

[0001] Description

[0002] title

[0003] Method for detecting an imbalance during operation of a drive unit

[0004] The invention relates to a method for detecting an imbalance during operation of a drive unit, a detection unit for detecting an imbalance during operation of a drive unit, a detection system, a computer program product, a computer-readable storage medium and a data carrier signal according to the appended claims.

[0005] State of the art

[0006] Drive units, particularly those used to drive turbocompressors, are operated at high speeds in numerous applications. To minimize frictional losses on the shaft (drive shaft) of a drive unit, plain bearings or, preferably, aerodynamic gas bearings, especially air bearings, are often used. Aerodynamic gas bearings, in particular, are sensitive to imbalance in the drive unit shaft guided in the bearing. If such an imbalance occurs on the shaft during operation of the drive unit, it can result in vibrations, a reduction in performance, or even bearing damage. This can endanger the operation of the drive unit or lead to total failure of the drive unit.

[0007] In this context, it is known that drive units are checked for imbalance during production, especially before delivery, using additional measuring technology. Due to the costs associated with such measurement technology, continuous monitoring during operation is not carried out. Operational imbalances are therefore usually not detected early and regularly lead to significant damage or failure of the affected drive units.

[0008] Disclosure of the invention

[0009] Within the scope of the present invention, a method for detecting an imbalance during operation of a drive unit, a detection unit for detecting an imbalance during operation of a drive unit, a detection system, a computer program product, a computer-readable storage medium, and a data carrier signal are proposed. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings.In this case, features and details which are described in connection with the method according to the invention naturally also apply in connection with the recognition unit according to the invention and / or in connection with the recognition system according to the invention and / or in connection with the computer program product according to the invention and / or in connection with the computer-readable storage medium according to the invention and / or in connection with the data carrier signal according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made reciprocally.

[0010] The invention presented serves in particular to detect an imbalance occurring during operation of a drive unit on a shaft of the drive unit at an early stage in order to be able to effectively avoid potential consequential damage, wherein the detection of the imbalance should preferably be realized with the simplest possible means or at the lowest possible cost.

[0011] According to a first aspect, the present invention relates to a method for detecting an imbalance in the operation of a drive unit by a detection unit, the drive unit comprising at least one shaft and at least one electric machine, wherein the electric machine is operatively connected to the shaft such that the shaft can be driven by the electric machine, the method comprising: carrying out a frequency analysis of an operating signal of the drive unit, in particular of the electric machine, to decompose the operating signal into its frequency components, wherein the operating signal is characteristic of a course of an operating parameter of the drive unit over time, in particular by an analysis unit of the detection unit,

[0012] Determining an amplitude mean value for at least one, in particular exactly one, frequency component of the operating signal, in particular by the analysis unit of the detection unit,

[0013] Calculating an amplitude deviation between the mean amplitude value and an amplitude reference value specific in particular for the relevant frequency component and / or the relevant operating point, in particular by an evaluation unit of the detection unit,

[0014] Determining an unbalance status of the shaft based on the amplitude deviation, in particular by an evaluation unit of the detection unit.

[0015] It can advantageously be provided that the aforementioned method steps are carried out in the order specified above. Additionally or alternatively, the method can preferably be designed as a computer-implemented method.

[0016] The method according to the invention makes use of the effect identified within the scope of the present invention, namely that the mean amplitude of at least one frequency component of a speed signal of a shaft changes as a function of an imbalance present on the shaft. In this respect, on the basis of an amplitude deviation relating to the specific frequency component, which represents a measure of the deviation between the mean amplitude and an amplitude reference value, it can be detected whether or not there is an imbalance on the shaft of the drive unit. The method according to the invention therefore offers the advantage that an imbalance on a shaft of a drive unit can be detected reliably, at an early stage, and also in a simple and efficient manner during operation of the drive unit. If an imbalance is detected, further measures, such as switching off the drive unit, can be initiated in order to prevent consequential damage orto avoid a total failure of the drive unit.

[0017] In this case, the operating signal is to be understood as a profile of an operating parameter of the drive unit, in particular of the electric machine, over time. In other words, the operating signal comprises a plurality of operating parameter values ​​of the drive unit, in particular of the electric machine, recorded chronologically in succession. In particular, an operating parameter is to be understood here as a parameter that characterizes a current operating state or operating point of the drive unit.

[0018] It can be provided within the scope of the invention that the operating signal is a phase current signal, wherein in particular the phase current signal is characteristic of the course of the phase current of at least one phase of the electrical machine over time. In particular, the phase current signal can be characteristic of the course of the phase current of at least two or exactly two, in particular at least three or exactly three, phases, particularly preferably all phases, of the electrical machine over time. In particular with field-oriented control, a conclusion can be drawn from the course of the phase currents about the current speed of the shaft of the drive unit, a torque currently applied to the shaft and / or a current power of the drive unit.

[0019] Within the scope of the invention, it can be provided that the operating signal is a speed signal, wherein the speed signal is preferably characteristic of a speed profile of the shaft of the drive unit over time. In other words, it can be provided that the speed signal comprises a plurality of chronologically successively recorded speed values ​​of the shaft of the drive unit.

[0020] It can be provided within the scope of the invention that the operating signal is a torque signal, wherein the torque signal is preferably characteristic of a curve of a torque applied to the shaft of the drive unit over time. In other words, it can be provided that the torque signal comprises a plurality of chronologically successive recorded torque values ​​of the shaft of the drive unit. It can be provided within the scope of the invention that the operating signal is a power signal, wherein the power signal is preferably characteristic of a curve of a power of the drive unit over time. In other words, it can be provided that the power signal comprises a plurality of chronologically successive recorded power values ​​of the drive unit.

[0021] Within the scope of the invention, it can be provided that a drive unit is designed to drive a turbocompressor or as a turbocompressor. In other words, it can be provided that at least one compressor impeller is arranged on the shaft so that rotation of the shaft can be transferred to the compressor impeller. The compressor impeller can preferably be designed as a radial compressor impeller. A turbocompressor can preferably be used to compress a refrigerant in an air conditioning system, in particular in a vehicle, and / or as an air compressor in a fuel cell, in particular in a vehicle. Additionally or alternatively, at least one turbine impeller can be arranged on the shaft so that rotation of the shaft can be transferred to the turbine impeller.In particular, it can be provided that at least one compressor impeller and at least one turbine impeller are arranged on the shaft, so that rotation of the shaft can be transmitted to the compressor impeller and the turbine impeller. The compressor impeller and the turbine impeller can preferably be arranged at opposite ends of the shaft.

[0022] Carrying out a frequency analysis can preferably comprise carrying out a Fourier transformation, in particular a fast Fourier transformation (FFT). The Fourier transformation allows the operating signal to be converted from the time domain into the frequency domain and thus to be examined for its composition of different frequency components. The frequency analysis can preferably be combined with filtering, in particular bandpass filtering, in order to isolate those frequency components which are of interest for further analysis. If the mean amplitude is to be determined, for example, only for one frequency component, e.g. the second harmonic, the remaining frequency components of the operating signal can be removed or at least greatly attenuated by applying filtering, in particular bandpass filtering. Different orfluctuating amplitude values. To identify an imbalance status, it has proven advantageous to average the respective amplitude values ​​for a frequency component and thus calculate a mean amplitude value specific to the respective frequency component, which serves as the basis for further evaluation.

[0023] Based on the mean amplitude value, which is specific in particular for a frequency component and / or an operating point, an amplitude deviation between the mean amplitude value and an amplitude reference value, which is specific in particular for the respective frequency component, can be determined. It can preferably be provided that the amplitude reference value characterizes a state of the drive unit in which no or essentially no (insignificant) imbalance is present on the shaft of the drive unit. In other words, the amplitude reference value represents an average amplitude value of an oscillation with the frequency of the respective frequency component, which can be observed provided the drive unit is in a normal, in particular fault-free, operating state.In the present case, an insignificant imbalance is understood to mean an imbalance that is considered to be so small that the safe and reliable operation of the drive unit is not endangered.

[0024] Accordingly, an imbalance status of the drive unit shaft can be determined based on the amplitude deviation. This makes it possible to characterize whether the drive unit is in a normal operating condition or whether a fault, in particular in the form of an imbalance on the drive unit shaft, is present. Preferably, the imbalance status can be characteristic of whether or not an imbalance, in particular a harmful imbalance, is present on the shaft. A harmful or significant imbalance is to be understood as an imbalance that is considered harmful with regard to the safe and reliable operation of the drive unit.

[0025] In particular, a negative imbalance status may indicate that there is no imbalance or essentially no imbalance on the drive unit shaft. This may, for example, also include an imbalance that is so slight that it can be considered harmless. Additionally or alternatively, a positive imbalance status may indicate that there is an imbalance, particularly a harmful one, on the shaft, in particular an imbalance that is considered harmful with regard to the safe and reliable operation of the drive unit.

[0026] Determining the imbalance status can preferably comprise a comparison of the amplitude deviation with a, in particular predefined, threshold value. Thus, it can preferably be provided that if the amplitude deviation is less than or equal to the threshold value, no or no significant imbalance is detected on the shaft. In other words, an amplitude deviation that is less than or equal to the threshold value is preferably characteristic of no or only an insignificant imbalance on the shaft. In particular, however, exceeding the threshold value due to the amplitude deviation can be interpreted as indicating that a, in particular harmful, imbalance is present on the shaft.

[0027] Within the scope of the invention, it is conceivable for the determination of an amplitude mean value to be carried out for at least one, in particular precisely one, frequency component. In other words, it can optionally be provided that the determination of the amplitude mean value, as well as the subsequent calculation of an amplitude deviation and the determination of an imbalance status of the shaft based thereon, are carried out for only one frequency component.

[0028] Within the scope of the invention, it can be provided that the mean amplitude value is determined for at least one, in particular exactly one, frequency component, wherein the frequency of this frequency component is an integer multiple, in particular twice, a fundamental frequency of the electrical machine. In other words, it can be provided that the mean amplitude value is determined for at least one, in particular exactly one, harmonic of a fundamental frequency of the electrical machine. A harmonic is an oscillation whose frequency is an integer multiple of a fundamental frequency, in particular a fundamental frequency of the electrical machine. Within the scope of the invention, it has been shown that an unbalance-related change in the mean amplitude value is particularly pronounced in the second harmonic, i.e. a frequency component whose frequency is twice a fundamental frequency of the electrical machine.In this respect, it is particularly preferred according to the invention that the mean amplitude value is determined for a frequency component, wherein the frequency of this frequency component is twice a fundamental frequency of the electrical machine.

[0029] Within the scope of the invention, it can be provided that a fundamental frequency of the electrical machine is an excitation frequency, in particular a synchronous frequency, of the electrical machine. In the case of synchronous machines in particular, the speed is controlled by controlling the stator coils with an alternating voltage whose frequency is adapted. For this purpose, the drive unit or the electrical machine can comprise a frequency converter which is designed to convert an alternating voltage from a mains frequency to the desired frequency for controlling the stator coils. By controlling the stator coils with an alternating voltage, a stator rotating field is generated in the stator of the electrical machine which rotates at a speed that is dependent on the frequency of the alternating voltage (synchronous speed or synchronous frequency). This rotating field ultimately drives the rotor of the electrical machine orthe drive unit's shaft, with the rotor speed being coupled to the synchronous speed of the rotating field generated in the stator. For example, if a rotating field is generated in the stator of the electric machine that rotates at 2000 Hz (120,000 rpm), the speed of the electric machine's rotor or the drive unit's shaft will also be set to 2000 Hz (120,000 rpm), since the speed of the electric machine's rotor is coupled to the synchronous frequency of the rotating field generated in the stator of the electric machine.

[0030] Within the scope of the present invention, it can further be provided that the operating signal, in particular the speed signal, power signal and / or torque signal, is determined from a phase current signal of the electrical machine, wherein the phase current signal is characteristic of the course of the phase current of at least one phase of the electrical machine over time. In particular, the phase current signal can be characteristic of the course of the phase current of at least two or exactly two, in particular at least three or exactly three, phases, particularly preferably all phases, of the electrical machine over time. The speed control of electrical machines, in particular synchronous machines, is regularly carried out on the basis of field-oriented control. In this type of control, the phase currents in the electrical machine, in particular in a frequency converter of the electrical machine, are recorded.Based on the phase current curve, a position of the rotor of the electric machine as well as its speed and / or a current torque or current power of the electric machine or drive unit can then be determined, in particular based on a model. This offers the advantage that, to determine the operating signal or to provide the operating signal as a speed signal and / or torque signal and / or power signal, a sensor system that is often already present in electric machines, in particular synchronous machines, can be used. In particular, therefore, no additional components or sensors need to be integrated into the electric machine to carry out the method according to the invention.

[0031] Alternatively or additionally, it can be provided that the operating signal is detected or provided by at least one sensor, wherein the sensor is designed for a, in particular time-resolved, detection of an operating parameter of the drive unit. The speed sensor can preferably be designed as a contactless, in particular optical, speed sensor. In particular, it can be provided that the speed signal is detected or provided by at least one speed sensor, wherein in particular the speed sensor is designed for a, in particular time-resolved, detection of a speed of the shaft of the drive unit or of a rotor of the electric machine. Preferably, at least one speed sensor can be designed as a contactless, in particular optical, speed sensor.

[0032] Additionally or alternatively, it is conceivable that the procedure also includes:

[0033] Interpolating the operating signal to generate a uniform sampling rate of the operating signal, in particular by an analysis unit of the detection unit.

[0034] The interpolation of the operating signal, in particular the speed signal and / or the torque signal and / or the power signal and / or the phase current signal, can preferably be carried out before the frequency analysis of the operating signal.

[0035] In particular, in field-oriented control of the speed of an electrical machine, especially a synchronous machine, the time-dependent acquisition of the phase currents (and thus the time-dependent acquisition of the speed values ​​and / or torque values ​​and / or power values ​​and / or phase current values) is regularly performed synchronously with the control loop. This can result in non-equidistant time intervals between the discrete phase current or operating parameter values. By interpolating the operating signal to a uniform sampling rate, runtime effects can be taken into account in the sampling. Furthermore, an operating signal with a constant sampling rate can always be provided, even with a changing control frequency.

[0036] Furthermore, it can optionally be provided that a temporal progression of the amplitude deviation is taken into account when determining the unbalance status, in particular by the evaluation unit of the detection unit. This has the advantage of reducing the risk of a false alarm. In particular, it is conceivable that an unbalance status is only determined to the effect that a, in particular harmful, imbalance is present on the shaft (positive unbalance status) if the amplitude deviation has repeatedly, in particular within a specified period of time, exceeded a, in particular predefined, threshold value. This can be avoided in the case of a merely brief increase in the amplitude deviation from being immediately determined that a harmful imbalance is present on the shaft and further measures, such as switching off the drive unit, are taken.

[0037] Within the scope of the invention, it is conceivable that at least one amplitude reference value is characteristic of at least one, in particular exactly one, frequency component and / or of at least one, in particular exactly one, operating point of the drive unit and / or of at least one or exactly one operating parameter of the drive unit. In particular, it is conceivable that the amplitude reference value is characteristic of the operating parameter that is also the subject of the operating signal. Since the amplitude variables vary depending on the respective frequency component, it can be ensured that the amplitude deviations calculated on the basis of the amplitude reference value represent a reliable basis for determining the imbalance status. The amplitude variable for a given frequency component can also vary depending on an operating point of the drive unit.In this respect, the reliability of the method can be improved by selecting operating-point-specific amplitude reference values. At least one amplitude reference value can preferably be determined in a factory condition or after balancing the drive unit. In other words, at least one amplitude reference value can be determined in a condition of the drive unit in which no or no significant imbalance is present on the drive unit shaft.

[0038] At least one operating point can preferably be defined by at least one of the following specifications:

[0039] Speed ​​of the drive unit shaft,

[0040] Ambient temperature,

[0041] Ambient pressure,

[0042] Mass flow which is passed through the drive unit, in particular at least one compressor impeller and / or turbine impeller of the drive unit.

[0043] Furthermore, within the scope of the invention, it can be provided that at least one of the following is included:

[0044] Detecting at least one operating signal of the drive unit, in particular by the drive unit and / or the detection unit,

[0045] Providing at least one operating signal of the electrical machine to the detection unit, in particular to a communication unit of the detection unit,

[0046] Transmitting at least one unbalance status to at least one user and / or at least one mobile device and / or at least one, in particular central, computer, in particular in conjunction with a time stamp, wherein the time stamp is preferably characteristic of the time of determining the unbalance status, in particular by a communication unit of the detection unit,

[0047] Generating a control command to switch off the drive unit depending on the imbalance of the shaft, in particular by an evaluation unit of the detection unit,

[0048] Transmitting a control command to the drive unit, in particular by a communication unit of the detection unit, storing at least one amplitude deviation and / or at least one unbalance status on a, in particular non-volatile, data memory of the detection unit, in particular in conjunction with a time stamp, wherein the time stamp is preferably characteristic of the time of the calculation or determination of the amplitude deviation and / or the unbalance status.

[0049] By transmitting an imbalance status to at least one user, a mobile device, or a central computer, those responsible can be alerted to the occurrence of an imbalance at an early stage. Accordingly, measures can be taken early on to ensure continued operation of the drive unit and effectively prevent serious consequential damage.

[0050] The generation of a control command can, in particular, be intended to shut down the drive unit if an imbalance occurs on the drive unit's shaft. This can prevent consequential damage and allow the drive unit to be serviced and subsequently put back into operation at a relatively low cost.

[0051] Storing the amplitude deviation or the imbalance status allows for chronological tracking of the relevant data. In particular, this simplifies the consideration of the temporal progression of the amplitude deviation.

[0052] According to a second aspect of the present invention, a detection unit is provided for detecting an imbalance during operation of a drive unit. The detection unit preferably comprises at least one, in particular exactly one, analysis unit, in particular for analyzing an operating signal of the drive unit. In particular, the analysis unit can be designed to perform a frequency analysis and / or bandpass filtering of the operating signal and / or to determine an amplitude mean value of at least one frequency component. Additionally or alternatively, the detection unit preferably comprises at least one, in particular exactly one, evaluation unit, in particular for evaluating at least one amplitude mean value determined by the analysis unit.Particularly preferably, it can be provided that the recognition unit is operated according to a method according to the first aspect of the present invention, in particular a method according to one of claims 1 to 5.

[0053] With regard to a recognition unit according to the invention, the same advantages arise as have already been described with regard to a method according to the invention.

[0054] Within the scope of the invention, it can be provided that at least one detection unit has at least one communication unit. At least one communication unit can comprise at least one communication interface, in particular at least one wireless or wired communication interface, preferably at least one WLAN, Bluetooth, LAN and / or mobile radio interface. At least one communication interface can be used to provide an operating signal to the detection unit and / or to transmit control commands or other information such as an imbalance status. The transmission can be made to the drive unit and / or a user and / or at least one mobile device and / or at least one, in particular central, computer.At least one communication unit can be brought into a communication connection, in particular a bidirectional one, with at least one analysis unit and / or evaluation unit, preferably to transmit data and / or information, such as an operating signal. At least one detection unit, in particular at least one analysis unit and / or at least one evaluation unit and / or at least one communication unit, can comprise means for data processing. The means for data processing can preferably comprise at least one processor, at least one main memory, and / or at least one, in particular non-volatile, data memory.

[0055] According to a third aspect of the present invention, a detection system is provided. The detection system comprises at least one, in particular precisely one, drive unit, which comprises at least one shaft and at least one electric machine, wherein the electric machine is operatively connected to the shaft such that the shaft can be driven by the electric machine. Furthermore, the detection system comprises a detection unit for detecting an imbalance during operation of the drive unit. Preferably, it can be provided that the detection unit is designed according to the second aspect of the present invention, in particular according to claim 6.

[0056] With regard to a recognition system according to the invention, the same advantages arise as have already been described with regard to a method according to the invention and / or a recognition unit according to the invention.

[0057] In the present case, it can be provided that at least one detection unit is integrated into a drive unit. In other words, it is conceivable that at least one detection unit forms a structural unit with a drive unit. Additionally or alternatively, it is conceivable that at least one detection unit is spatially separated from a drive unit. In particular, at least one detection unit can be implemented, at least partially, by a computer, in particular a central one. This results in the advantage of centralized and efficient monitoring of one or more drive units.

[0058] Within the scope of the invention, it can advantageously be provided that at least one electrical machine is designed as a synchronous machine, in particular a three-phase and / or permanent magnet machine. For this type of electrical machine, the use of a method according to the invention or a detection unit according to the invention has proven particularly reliable and effective.

[0059] Within the scope of the invention, it can be provided that at least one electrical machine and / or at least one detection unit comprises at least one current sensor for detecting a phase current of the electrical machine, in particular of a frequency converter of the electrical machine. Preferably, the temporal profile of at least one phase current can be detected by at least one current sensor, wherein, in particular, a temporal profile of the rotational position of the shaft of the drive unit and / or a temporal profile of the speed of the shaft of the drive unit can be determined based on the temporal profile of the phase current.

[0060] Additionally or alternatively, it can be provided that at least one drive unit and / or at least one detection unit comprises at least one speed sensor for detecting a speed of the shaft. At least one speed sensor can preferably be designed as a contactless, in particular optical, speed sensor.

[0061] According to a fourth aspect of the present invention, a computer program product is provided, wherein the computer program product comprises instructions which cause a recognition unit, in particular a recognition unit according to the second aspect of the present invention and / or claim 6, to execute a method according to the first aspect of the present invention, in particular according to one of claims 1 to 5.

[0062] According to a fifth aspect of the present invention, a computer-readable storage medium is provided, wherein a computer program product according to the fourth aspect of the present invention, in particular according to claim 10, is stored on the computer-readable storage medium.

[0063] According to a sixth aspect of the present invention, a data carrier signal is provided, wherein the data carrier signal transmits a computer program product according to the fourth aspect of the present invention, in particular according to claim 10.

[0064] With regard to a computer program product according to the invention and / or a computer-readable storage medium according to the invention and / or a data carrier signal according to the invention, the same advantages arise as have already been described with regard to a method according to the invention and / or a recognition unit according to the invention and / or a recognition system according to the invention.

[0065] Further advantages, features, and details of the invention will become apparent from the following description, in which several embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0066] Fig. 1 is a schematic view of a method, Fig. 2 is a schematic view of a recognition unit,

[0067] Fig. 3 is a schematic view of a drive unit,

[0068] Fig. 4 is a schematic view of a detection system,

[0069] Fig. 5 is a schematic view of a speed signal and

[0070] Fig. 6 is a schematic view of an amplitude mean value of a frequency component.

[0071] In the following figures, identical reference numerals are used for the same technical features, even for different embodiments.

[0072] Fig. 1 shows a schematic view of a method 100 for detecting an imbalance during operation of a drive unit 10 by a detection unit 11, the drive unit 10 comprising at least one shaft 12 and at least one electric machine 13, wherein the electric machine 13 is operatively connected to the shaft 12 such that the shaft 12 can be driven by the electric machine 13, the method 100 comprising:

[0073] Carrying out 110 a frequency analysis of an operating signal S of the drive unit 10, for decomposing the operating signal S into its frequency components Fi, wherein the operating signal S is characteristic of a profile of an operating parameter N of the shaft 12 over time t, Determining 120 an amplitude mean value A for at least one frequency component Fi of the operating signal S,

[0074] Calculating 130 an amplitude deviation AA between the mean amplitude value A and an amplitude reference value A, which is specific in particular for the relevant frequency component re f,

[0075] Determining 140 an unbalance status of the shaft 12 based on the amplitude deviation AA.

[0076] In the present case, the operating signal S is designed as a speed signal S of the shaft 12, wherein the speed signal S is characteristic of a profile of the speed N of the shaft 12 over time t. Furthermore, Fig. 2 shows a schematic view of a detection unit 11 for detecting an imbalance during operation of a drive unit 10. The detection unit 11 comprises an analysis unit 11.1 as well as an evaluation unit 11.2 and a communication unit 11.3.

[0077] The analysis unit 11.1 is designed to perform a frequency analysis and / or bandpass filtering of a rotational speed signal S of the shaft 12 of a drive unit 10 and also to calculate an amplitude mean value A for at least one frequency component Fi. The evaluation unit 11.2 is designed to evaluate at least one amplitude mean value A and, based thereon, to determine an imbalance status of the shaft 11. Preferably, the communication unit 11.3 can at least be designed to provide a rotational speed signal S to the detection unit 11.

[0078] Fig. 3 further shows a schematic representation of a drive unit 10. The drive unit 10 comprises a shaft 12 and also an electric machine 13, wherein the electric machine 13 is operatively connected to the shaft 12 such that the shaft 12 can be driven by the electric machine 13.

[0079] The electric machine 13 comprises a stator 14 and a rotor 15. Both the stator and the rotor can comprise at least one winding or multiple windings. The rotor 15 of the electric machine is embodied here as a portion of the shaft 12.

[0080] The drive unit 10 is designed here to drive a turbocompressor. Accordingly, at least one compressor impeller 16 is arranged on the shaft 12, wherein the compressor impeller 16 is designed as a radial compressor impeller or a compressor impeller of radial design.

[0081] Fig. 4 shows a schematic view of a detection system 50. The detection system 50 comprises at least one drive unit 10, which includes at least one shaft 12 and at least one electric machine 13, wherein the electric machine 13 is operatively connected to the shaft 12 such that the shaft 12 can be driven by the electric machine 13. Furthermore, the detection system 50 comprises a detection unit 11 for detecting an imbalance during operation of the drive unit 10.

[0082] In the present case, the recognition unit 10 of the recognition system 50 is spatially separated from the drive unit 10 and is formed at least partially by a, in particular central, computer.

[0083] Fig. 4 shows a schematic curve of a speed signal S, wherein the speed signal S is characteristic of a curve of the speed N of the shaft 12 of the drive unit 10 over time t.

[0084] By applying frequency analysis and bandpass filtering, the speed signal S can be decomposed into its frequency components Fi or reduced to the frequency components Fi relevant for further analysis. This converts the speed signal from the time domain to the frequency domain, where the amplitude of the respective frequency components can be plotted.

[0085] This is illustrated by way of example in Fig. 5, where only an average amplitude value A for a frequency component F2 is shown. In this case, the average amplitude value shown is specific for a frequency component F2, where the frequency of the respective frequency component F2 is an integer multiple, in this case twice, of a fundamental frequency, in this case the excitation frequency, of the electrical machine 13. Thus, the frequency component F2 corresponds to the second harmonic of the fundamental frequency of the electrical machine 13.

[0086] Based on the mean amplitude value A determined for the frequency component F2 of the second harmonic, an amplitude deviation AA is subsequently calculated between the mean amplitude value A and a reference amplitude value A re f is determined. The amplitude reference value A characterizes re f a state of the drive unit 10 in which no or essentially no (insignificant) imbalance is present on the shaft 12 of the drive unit 10.

[0087] Accordingly, an imbalance status of the shaft 12 of the drive unit 10 can be determined based on the amplitude deviation AA. This makes it possible to characterize whether the drive unit 10 is in a normal operating state or whether a fault, in particular in the form of an imbalance on the shaft 12 of the drive unit 10, is present.

Claims

Claims 1 . Method (100) for detecting an imbalance during operation of a drive unit (10) by a detection unit (11), the drive unit (10) comprising at least one shaft (12) and at least one electric machine (13), wherein the electric machine (13) is operatively connected to the shaft (12) such that the shaft (12) can be driven by the electric machine (13), the method (100) comprising: Carrying out (110) a frequency analysis of an operating signal (S) of the drive unit (10) to decompose the operating signal (S) into its frequency components (Fi), wherein the operating signal (S) is characteristic of a course of an operating parameter (N) of the electrical machine (12) over time (t), Determining (120) an amplitude mean value (A) for at least one frequency component (Fi) of the operating signal (S), Calculating (130) an amplitude deviation (AA) between the mean amplitude value (A) and an amplitude reference value (A re f), Determining (140) an unbalance status of the shaft (11) based on the amplitude deviation (AA).

2. Method (100) according to claim 1, characterized in that the determination (120) of the mean amplitude value (A) is carried out for a frequency component whose frequency is an integer multiple, in particular twice, of a fundamental frequency of the electrical machine (12).

3. Method (100) according to one of the preceding claims, characterized in that the operating signal (S) is determined from a phase current signal of the electrical machine (12), wherein the phase current signal is characteristic of the course of the phase current of at least one phase of the electrical machine over time (t).

4. Method (100) according to one of the preceding claims, characterized in that it additionally comprises: Interpolating the operating signal (S) to generate a uniform sampling rate of the operating signal (S).

5. Method (100) according to one of the preceding claims, characterized in that in determining the unbalance status, a temporal course of the amplitude deviation (AA) is taken into account, in particular by the evaluation unit (11.2) of the detection unit (11).

6. Detection unit (11) for detecting an imbalance during operation of a drive unit (10), preferably comprising at least one analysis unit (11.1) and at least one evaluation unit (11.2), wherein the detection unit (11) is operated according to a method (100) according to one of the preceding claims.

7. Detection system (50) comprising at least one drive unit (10), the drive unit (10) comprising at least one shaft (11) and at least one electric machine (12), wherein the electric machine (12) is operatively connected to the shaft (11) such that the shaft (11) can be driven by the electric machine (12), the detection system (50) further comprising a detection unit (10) for detecting an imbalance during operation of the drive unit (10) according to claim 6.

8. Detection system (50) according to claim 7, characterized in that that the electrical machine is designed as a synchronous machine, in particular a three-phase and / or permanent magnet machine.

9. Detection system (50) according to one of claims 7 or 8, characterized in that at least one current sensor for detecting a phase current of at least one phase of the electrical machine and / or at least one speed sensor for detecting a speed (N) of the shaft (11) is included.

10. A computer program product comprising instructions causing a recognition unit (11) according to claim 6 to carry out method steps according to a method (100) according to any one of claims 1 to 5.

11. A computer-readable storage medium on which a computer program product according to the preceding claim is stored.

12. A data carrier signal carrying a computer program product according to claim 10.

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