Device and method for determining the power density spectrum of a vibration curve of an undamped mass on a movement path

Abstract

The invention relates to a device and a method for determining the power density spectrum of a vibration curve of an undamped mass on a movement path, in particular a route, wherein the movement path is specified (210); the movement path is divided into time windows, in particular in a sequence (214); an estimated power density spectrum of an estimated vibration curve of the undamped mass, in particular of a vehicle, is specified (216) for each time window on the basis of a specified power density spectrum of a vibration curve of the undamped mass, in particular of the vehicle, or of another undamped mass, in particular of another vehicle, said power density spectrum being assigned to the time window; the estimated vibration curve is determined (218) for each time window on the basis of the power density spectrum specified for the respective time window, in particular using an inverse fast Fourier transform of the specified power density spectrum; the vibration curve on the movement path is composed (220) of the estimated vibration curves determined for the respective time windows, in particular in the sequence; and the power density spectrum of the vibration curve on the movement path is determined (222) on the basis of the vibration curve on the movement path, in particular using a fast Fourier transform of the vibration curve on the movement profile.

Description

[0001] Description

[0002] title

[0003] Device and method for determining a power spectral density of a vibration profile of an undamped mass on a motion profile

[0004] State of the art

[0005] The invention relates to a device and a method for determining a power density spectrum of a vibration profile of an undamped mass on a motion profile.

[0006] To perform vibration load tests, for example on vehicle components, measurements are taken as a power spectral density spectrum. These measurements are compared with a standardized power spectral density spectrum or one defined by the manufacturer of, for example, the vehicle component or the vehicle to which the component belongs.

[0007] Disclosure of the invention

[0008] The device and method according to the independent claims provide a realistic power spectral density of the undamped mass for a vibration load test. This power spectral density is used, for example, for the vibration load test of a vehicle.

[0009] Assuming that the vehicle's wheels have negligible tire stiffness and damping, the power spectral density of the undamped mass characterizes vibrations caused by the vehicle's undamped mass being located in front of the vehicle's spring-damper system. The power spectral density for the vehicle's vibration test is estimated based on predefined power spectral density of the undamped mass vibration of the vehicle being tested, or based on predefined power spectral density of the undamped mass of another vehicle.

[0010] The power spectral density is estimated based on a predefined motion profile, or, in the case of a vehicle, a specific route. This estimated power spectral density enables a vibration load test without requiring any further measurements.

[0011] The method for determining a power spectral density of a vibration profile of an undamped mass on a motion profile, in particular a route profile, provides that the motion profile is specified, wherein the motion profile is divided into time windows, in particular in a sequence, wherein for each time window an estimated power spectral density of an estimated vibration profile of the undamped mass, in particular of a vehicle, is specified depending on a specified power spectral density of a vibration profile of the undamped mass, in particular of the vehicle, or of another undamped mass, in particular of another vehicle, assigned to the time window, wherein for each time window the estimated vibration profile is determined depending on the power spectral density specified for the respective time window, in particular by an inverse Fast Fourier Transform of the specified power spectral density.wherein the vibration profile on the motion profile is composed from the estimated vibration profiles determined for the respective time windows, in particular in the following order, and wherein the power spectral density of the vibration profile on the motion profile is determined depending on the vibration profile on the motion profile, in particular by a Fast Fourier Transform of the vibration profile on the motion profile.

[0012] It can be provided that for each time window, a mean estimated power spectral density and an extremal, in particular a minimum or maximum, estimated power spectral density are specified, wherein the power spectral density of the vibration profile is determined on the motion profile, which is composed of the estimated vibration profiles determined for the mean estimated power spectral densities for each time window, and wherein the power spectral density of the vibration profile on the motion profile is determined from the estimated vibration profiles determined for the extremal estimated power spectral densities for each time window. These power spectra are particularly well suited for the vibration load test.

[0013] It can be provided that the power spectral density of the vibration profile along the motion path is determined in at least two, preferably three, directions of vibration of the undamped mass of the vehicle, wherein the respective predetermined power spectral density is provided for the at least two, preferably three, directions, and the vibration profile along the route path is determined for the respective direction depending on the power spectral density spectra predetermined for the respective direction. This makes it possible to take the vibration in the respective direction into account during the vibration load test.

[0014] It can be provided that the movement path includes geographic positions, in particular those of a global satellite navigation system, wherein for at least one of the time windows, depending on at least one geographic position included in the movement path within the time window, a feature is determined that characterizes a surface irregularity and / or an environment, in particular a road, where the movement path takes place within the time window, wherein the estimated power spectra are each associated with a predefined feature that characterizes the surface irregularity and / or the environment for which the respective estimated power spectra are suitable, and wherein the estimated power spectra associated with the feature determined for the at least one time window is selected for that at least one time window. This results in the selection of an estimated power spectra that represents a feature suitable for the geographic position.It may be provided that a measurement database is made available, wherein the measurement database contains the estimated power spectral density spectra, wherein the respective power spectral density spectra in the measurement database are associated with a feature specified for the respective estimated power spectral density, and wherein the estimated power spectral density for the at least one time window is read from the measurement database depending on the feature determined for the at least one time window. The measurement database enables, in particular, rapid access to the required power spectral density spectra.

[0015] It may be provided that measurements of journeys with the vehicle or another vehicle or several other vehicles are provided, wherein the measurements each comprise a vibration profile measured during one of the journeys, wherein in each measurement a position of the vehicle during the journey on a route comprise a measurement of the vibration measured at that position, in particular at a steering knuckle of the vehicle, wherein the measured vibration profile is divided into time windows, in particular into time windows that overlap by 20% to 50%, wherein for each time window an estimated power spectral density is determined depending on the part of the measured vibration profile from the respective time window, wherein the time windows in the measurement database are each associated with a feature, wherein the feature associated with the respective time window characterizes the unevenness and / or the environment, in particular the road.for which the power spectral density spectrum estimated for the respective time window is suitable. This populates the measurement database based on measurements.

[0016] It can be provided that the measurement database includes several estimated power spectral densities associated with the same feature, wherein a mean power spectral density, in particular by determining the logarithmic mean of the several estimated power spectral densities, or an extremal power spectral density, in particular by determining the logarithmic variance of the several power spectral densities, is determined from the measurement database depending on the estimated power spectral densities associated with the same feature and stored in the measurement database associated with the same feature. This adds additional power spectral densities to the measurement database without additional measurements.

[0017] It may be provided that the characteristic for the at least one time window is determined based on a mean value, in particular a logarithmic mean value, which is defined for the geographical positions within the time window. The mean value identifies the at least one time window.

[0018] It may be provided that a database is made available, wherein the database comprises geographical positions, each geographical position being associated with the feature that characterizes the unevenness and / or the environment, in particular the road, at the respective position, wherein the feature associated with the respective geographical position is read from the database for that geographical position. This makes it possible to select an estimated power density spectrum that represents a feature appropriate to the geographical position.

[0019] The device for determining a power spectral density of a vibration profile of an undamped mass on a motion profile, in particular a route profile, is designed to carry out the method according to.

[0020] A computer program may be provided, wherein the computer program includes computer-readable instructions, the execution of which by a computer executes the procedure.

[0021] Further advantageous embodiments can be found in the following description and the drawing. The drawing shows:

[0022] Fig. 1 shows a schematic representation of a device for determining a power spectral density of a vibration profile of an undamped mass on a motion profile.

[0023] Fig. 2 shows a flowchart with steps of a method for determining a power spectral density of a vibration profile of an undamped mass on a motion profile. Figure 1 schematically depicts a device 100 for determining a power spectral density of a vibration profile of an undamped mass on a motion profile.

[0024] The device 100 is designed to perform a method for determining a power density spectrum of a vibration profile of an undamped mass on a motion profile.

[0025] The device 100 and the method are described using the example of determining a power spectral density of a vibration profile of an undamped mass of a vehicle along a route. The route includes geographical positions, in particular those of a global satellite navigation system. It can be provided that the route includes a vehicle speed associated with each position.

[0026] The device 100 and the method are not limited to application in the case of a route taken by the vehicle.

[0027] For example, the device 100 or the method can be configured for determining a power density spectrum of a vibration profile during the movement of a washing machine. The movement profile includes, for example, instead of a route profile, angular positions of a washing machine drum and a rotational speed profile and / or direction of rotation profile, assigned to each angular position.

[0028] The device 100 comprises at least one processor 102 and at least one memory 104.

[0029] The memory 104 stores, for example, instructions executable by at least one processor 102, the execution of which by the at least one processor 102 causes the device 100 to carry out the method.

[0030] Figure 2 shows a flowchart illustrating the steps of the procedure. This procedure determines power spectral density spectra for a vibration stress test. In this example, the procedure comprises a first part in which a measurement database containing estimated power spectral density spectra is provided. The second part of the procedure, in this example, provides the power spectral density for the vibration profile based on estimated power spectral density spectra from the measurement database.

[0031] The first part of the procedure comprises step 202.

[0032] Step 202 provides measurements of journeys.

[0033] The measurements are carried out in the field.

[0034] The measurements are carried out, for example, with the vehicle with which the vibration load test is to be performed.

[0035] The measurements are carried out, for example, with another vehicle or several other vehicles.

[0036] The measurements each include a vibration profile measured during one of the journeys.

[0037] The measurements include the vehicle's geographical position along a route. They also include a vibration profile of the undamped mass of the vehicle. The vibrations are measured, for example, at a steering knuckle.

[0038] In the measurements, each geographical position of the vehicle while driving on the route is assigned a measurement of the vibration measured at that geographical position.

[0039] In step 202, a database is provided that includes geographical positions and features. The features each characterize a feature and its surroundings at the respective geographical position.

[0040] Geographical positions are, for example, positions provided by a global satellite navigation system.

[0041] The geographical positions are each associated with a feature that characterizes the unevenness at the respective geographical position, and with a feature that characterizes the environment at the respective geographical position.

[0042] In this example, each geographic position in the database is assigned a feature that encompasses the roughness of the road on which the vehicle is located at that geographic position. An example of the feature that characterizes the roughness of the road is the International Roughness Index (IRI).

[0043] In this example, each geographic position in the database is assigned a characteristic that encompasses the surroundings of the road on which the vehicle is located at that geographic position. An example of a characteristic that defines the surroundings of the road is an environment index, which indicates, for example, whether the road is located in a city, outside a city, on a bridge, on a paved road, or on an unpaved road.

[0044] In this example, the IRI is a value increasing with roughness from 0 to 20. The environmental index is URBAN in this example, with a value of 1 for urban areas and 0 for rural areas. Other numerical values ​​are also possible. Only one IRI value and only one URBAN value are used per time window in this example. Similarly, only one IRI value and only one URBAN value are used for the power spectral density.

[0045] The first part of the procedure comprises step 204.

[0046] In step 204, for the respective measurements, the feature associated with the respective geographical position, which characterizes the unevenness at the respective geographical position, and the feature that characterizes the environment at the respective geographical position, are read from the database for the respective geographical position.

[0047] The first part of the procedure comprises step 206.

[0048] In step 206, the measured vibration profile of the respective measurement is divided into time windows.

[0049] The vibration profile is divided, for example, into immediately consecutive time windows. Alternatively, the vibration profile can be divided into time windows that overlap. For example, the vibration profile is divided into time windows that overlap by 20% to 50%.

[0050] In step 206, each time window is assigned a feature that characterizes an unevenness and a feature that characterizes an environment for which the vibration profile in the vibration load test is suitable.

[0051] The characteristic assigned to the respective time window that characterizes the unevenness is determined, for example, depending on a mean or median of the characteristics that characterize the unevenness, which are determined for the geographical positions in the time window.

[0052] The characteristic assigned to the respective time window that characterizes the environment is determined, for example, depending on a mean or median of the characteristics that characterize the environment and are defined for the geographical positions in the time window.

[0053] It may be provided that the set of features that characterize the unevenness, determined for the geographical positions in the time window, is assigned to the respective time window without averaging.

[0054] It may be provided that the set of features that characterize the environment, without averaging, is assigned to the respective time window, based on the geographical positions determined for the time window.

[0055] The first part of the procedure comprises step 208. In step 208, a measurement database is provided.

[0056] In step 208, for each time window, depending on the part of the measured vibration profile from the respective time window, an estimated power spectral density is determined and associated with the feature that characterizes the unevenness and the feature that characterizes the environment, and stored in the measurement database.

[0057] The measurement database can be configured to assign each estimated power density spectra to a category from a set of predefined categories. Each category represents a combination of a feature characterizing the unevenness with a feature characterizing the environment.

[0058] For example, the estimated power spectral spectra in the measurement database are associated with the respective feature that characterizes the unevenness and with the respective feature that characterizes the environment by assigning the respective estimated power spectral spectra to the category from the set of predefined categories that represents the respective combination.

[0059] The measurement database may contain multiple estimated power spectral density spectra of the same category. In one example, the power spectral density spectra of the same category are statistically evaluated. For instance, a logarithmic mean and logarithmic standard deviation of the power spectral density spectra are determined. An upper and lower bound of a confidence interval are then determined based on the logarithmic mean and logarithmic standard deviation. The logarithmic mean and logarithmic standard deviation define a distribution across the power spectral density spectra. It may be possible to derive a new estimated power spectral density within the confidence interval from this distribution across the power spectral density spectra.For example, the new estimated power spectral density, which is associated with the same combination of features, is stored in the measurement database with which the power spectral density spectra are associated, which are used to determine the distribution.

[0060] The second part of the procedure includes step 210.

[0061] In step 210, a route is specified.

[0062] The route includes geographical positions for a journey with a vehicle that will be used to perform the vibration load test.

[0063] In this example, the geographical positions are positions provided by the global satellite navigation system.

[0064] The second part of the procedure comprises step 212.

[0065] In step 212, the vehicle's speed is determined as it travels along the route.

[0066] The vehicle's speed is determined, for example, by simulating the journey along the route.

[0067] The second part of the procedure includes step 214.

[0068] In step 214, the route is divided into time windows. It may be possible to divide the route into time windows that are arranged in a sequence.

[0069] The second part of the procedure comprises step 216.

[0070] In step 216, an estimated power spectral density of an estimated vibration profile of the undamped mass is specified for each time window of the route. It may be provided that a mean estimated power spectral density and an extremal, in particular a minimum or maximum, estimated power spectral density are specified for each time window.

[0071] For example, for at least one of the time windows, depending on at least one geographical position that the movement path in the time window includes, a feature that characterizes an unevenness and a feature that characterizes an environment in which the movement path takes place in the time window.

[0072] In one example, the estimated power spectra are each associated with a given feature that characterizes the unevenness and with a feature that characterizes the environment for which the respective estimated power spectral density is suitable.

[0073] The estimated power density spectrum associated with the characteristics determined for at least one time window is selected for that at least one time window.

[0074] The respective estimated power spectral density is provided from the measurement database in the example.

[0075] The measurement database includes the estimated power density spectra.

[0076] The respective power spectral spectra are associated in the measurement database with the characteristics specified for the respective estimated power spectral spectra.

[0077] The estimated power spectral density for at least one time window is read from the measurement database, for example, depending on the characteristics determined for that at least one time window.

[0078] If the respective estimated power density spectrum in the measurement database is associated with a category from the set of predefined categories with the respective combination of the respective predefined characteristics, a combination of the characteristics determined for the at least one time window is assigned, for example, depending on the characteristics determined for the at least one time window, to a category from the set of predefined categories.

[0079] In the example, the estimated power spectral density is determined for the at least one time window that is assigned to the same category as the at least one time window.

[0080] The second part of the procedure includes step 218.

[0081] In step 218, the estimated vibration profile is determined for each time window depending on the power density spectrum specified for the respective time window.

[0082] In this example, the estimated vibration profile for each time window is determined by an inverse Fast Fourier Transformation of the power spectral density spectrum specified for the respective time window.

[0083] The second part of the procedure comprises step 220.

[0084] In step 220, the vibration profile along the route is compiled from the estimated vibration profiles determined for the respective time windows. If the order is predefined, the vibration profile is compiled from the estimated vibration profiles in that order.

[0085] The second part of the procedure includes step 222.

[0086] In step 222, a power density spectrum of the vibration profile along the route is determined depending on the vibration profile along the route.

[0087] The power spectral density of the vibration profile along the route is determined, for example, by a Fast Fourier Transform of the vibration profile along the route. Depending on the content of the measurement database, the estimated power spectral density for the route is determined differently.

[0088] If the measurement database is based on measurements taken from the vehicle with which the vibration load test is performed, it may be provided that the estimated power spectral density of the estimated vibration profile is determined depending on a predefined power spectral density of a vibration profile of the undamped mass of the vehicle, assigned to the respective time windows.

[0089] If the measurement database is based on measurements taken from a different vehicle or vehicles than the one used for the vibration load test, it may be provided that the estimated power spectral density of the estimated vibration profile is determined based on a predefined power spectral density of a vibration profile of another undamped mass of a different vehicle, assigned to the respective time windows.

[0090] If the measurement database is based on measurements originating from both the vehicle with which the vibration load test is performed and from another vehicle or several other vehicles, it may be provided that the estimated power spectral density of the estimated vibration profile is determined depending on at least one power spectral density of a vibration profile of the undamped mass of the vehicle and depending on at least one power spectral density of a vibration profile of another undamped mass of another vehicle, which are assigned to the respective time windows.

[0091] The vibration profiles and power spectra are described in the example for one direction of vibration. The method is preferably carried out separately for vibration profiles and power spectra for at least two, and preferably three, directions of vibration, particularly those perpendicular to each other.

[0092] The procedure was described using the example of a feature that characterizes the unevenness and a feature that characterizes the environment. It is possible to execute the procedure with only the feature that characterizes the unevenness or with only the feature that characterizes the environment.

Claims

Claims 1. Method for determining a power spectral density of a vibration profile of an undamped mass on a motion profile, in particular a route profile, characterized in that the motion profile is specified (210), wherein the motion profile is divided into time windows, in particular in a sequence (214), wherein for each time window an estimated power spectral density of an estimated vibration profile of the undamped mass, in particular of a vehicle, is specified depending on a specified power spectral density of a vibration profile of the undamped mass, in particular of the vehicle, or of another undamped mass, in particular of another vehicle, assigned to the time window (216), wherein for each time window the estimated vibration profile is determined depending on the power spectral density specified for the respective time window, in particular by an inverse Fast Fourier Transform of the specified power spectral density,is determined (218), wherein the vibration profile on the motion profile is composed from the estimated vibration profiles determined for the respective time windows, in particular in the sequence (220), and wherein the power spectral density of the vibration profile on the motion profile is determined depending on the vibration profile on the motion profile, in particular by a Fast Fourier Transform of the vibration profile on the motion profile (222).

2. Method according to claim 1, characterized in that for each time window a mean estimated power spectral density and an extremal, in particular a minimum or maximum, estimated power spectral density are specified (216), wherein the power spectral density of the vibration profile is determined on the motion profile (222), which is derived from the estimated power spectral density spectra determined for each time window. vibration profiles are composed (220), and the power spectral density of the vibration profile is determined on the motion profile (222), which is composed of the estimated vibration profiles determined for the extremal estimated power spectral density spectra per time window (220).

3. Method according to one of the preceding claims, characterized in that the power spectral density of the vibration profile on the motion profile is determined in at least two, preferably three directions of the vibration of the undamped mass of the vehicle (222), wherein the respective predetermined power spectral density is provided for the at least two, preferably three directions (216), and the vibration profile on the route profile is determined for the respective direction depending on the power spectral density spectra predetermined for the respective direction (220).

4. Method according to one of the preceding claims, characterized in that the movement profile includes geographical positions (210), in particular of a global satellite navigation system, wherein for at least one of the time windows, depending on at least one geographical position included in the movement profile in the time window, a feature is determined (216) which characterizes an unevenness and / or an environment, in particular a road, where the movement profile takes place in the time window, wherein the estimated power spectral spectra are each associated with a predetermined feature that characterizes the unevenness and / or the environment for which the respective estimated power spectral spectra are suitable, wherein the estimated power spectral spectra associated with the feature determined for the at least one time window is selected for the at least one time window.

5. Method according to one of the preceding claims, characterized in that a measurement database is provided (208), wherein the measurement database comprises the estimated power spectral spectra, wherein the respective power spectral spectra in the measurement database are defined by a feature specified for the respective estimated power spectral spectra. are associated, whereby the estimated power spectral density for the at least one time window is read from the measurement database depending on the feature determined for the at least one time window (216).

6. Method according to claim 4 or 5, characterized in that measurements of journeys with the vehicle or another vehicle or several other vehicles are provided (202), wherein the measurements each comprise a vibration profile measured during one of the journeys, wherein in each measurement a position of the vehicle during the journey with the vehicle on a route comprise a measured value of the vibration measured at the position, in particular at a steering knuckle of the vehicle, wherein the measured vibration profile is divided into time windows (206), in particular into time windows that overlap by 20% to 50%, wherein for each time window, depending on the part of the measured vibration profile, an estimated power spectral density is determined from the respective time window, wherein the time windows are each associated with a feature in the measurement database (208).wherein the feature associated with the respective time window characterizes the unevenness and / or the environment, in particular the road, for which the power density spectrum estimated for the respective time window is suitable.

7. Method according to claim 6, characterized in that the measurement database comprises several estimated power spectral spectra associated with the same feature, wherein a mean power spectral spectra, in particular by determining the logarithmic mean of the several estimated power spectral spectra, or an extremal power spectral spectral, in particular by determining the logarithmic variance of the several power spectral spectra, is determined from the measurement database depending on the estimated power spectral spectra associated with the same feature and is stored in the measurement database associated with the same feature (208).

8. Method according to claims 4 to 7, characterized in that the feature for the at least one time window depends on a mean value, in particular a logarithmic mean value determined for the geographical positions in the time window for certain characteristics (206).

9. Method according to one of claims 4 to 8, characterized in that a database is provided (202), wherein the database comprises geographical positions, wherein the geographical positions are each associated with the feature that characterizes the unevenness and / or the environment, in particular the road, at the respective position, wherein the feature associated with the respective geographical position is read from the database for the respective geographical position (204).

10. Device (100) for determining a power density spectrum of a vibration profile of an undamped mass on a motion profile, in particular a route profile, characterized in that the device (100) is configured to perform the method according to one of claims 1 to 9.

11. Computer program, characterized in that the computer program comprises computer-readable instructions, the execution of which by a computer performs the method according to one of claims 1 to 9.

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