Road unevenness detection by evaluating the operating current of an electric vehicle drive unit

Abstract

The present invention provides a method for determining the state of a roadway on which a vehicle with an electric drive is traveling, by detecting an operating current of the electric drive, calculating at least one current variation in the operating current, identifying roadway irregularities based on the current variations, generating a signal that reproduces the location of the current variation and / or the roadway irregularity, and outputting the location or the roadway irregularity as a roadway irregularity location. Furthermore, a corresponding computer program product is described.

Description

[Technical Field]

[0001] Driving over unevenness in the roadway can reduce comfort and cause wear and tear on the vehicle's undercarriage. It is known to detect unevenness, such as potholes, in order to be able to warn the vehicle before the pothole occurs and, in some cases, to adapt the chassis to the pothole or other unevenness ahead.

[0002] It is known from DE 10 2014 214 729 A1 to determine potholes using height or inertial sensors, which involve additional costs in terms of hardware.

[0003] The object of the present invention is to provide a cost-effective possibility for detecting roadway irregularities.

[0004] This problem is solved by the subject matter of the independent claims. Further characteristics, features, embodiments and advantages can be obtained from the dependent claims and the description.

[0005] The proposed method involves detecting roadway irregularities based on current fluctuations in an electric traction drive. It has been recognized that driving over roadway irregularities causes torque changes in the drive when driving over relatively deep roadway irregularities, such as potholes, and when exiting roadway irregularities that are higher than the roadway defect. The former causes a temporary torque drop, while the latter causes a torque peak. These torque changes can be detected in the current flowing through the electric drive during operation based on the electric drive's electric motor characteristics (generating power, reaction of torque changes to the drive's operating current). This allows roadway irregularities to be estimated by determining the current fluctuations. This allows roadway irregularities, and possibly their associated locations (roadway irregularity locations), to be detected cost-effectively. This can also be used to adapt the drive or chassis operating parameters in preparation for roadway irregularities, and in particular to create a database of locations where roadway irregularities exist (roadway irregularity locations).

[0006] A method for determining the state of a roadway is described. A vehicle with an electric drive travels on the roadway. The electric drive is a traction drive in this case. The operating current of the electric drive is detected. This can be achieved by measuring or otherwise calculating the operating current within the framework of a motor closed-loop or motor open-loop control of the electric drive. Actual current values ​​of the motor control can be sent as signals that represent the operating current, which form the basis for calculating at least one current fluctuation. The operating current can be determined as a phase current of the electric machine of the electric drive or as the operating direct current of an inverter that supplies the electric machine (or also based on a quantity in the motor open-loop or motor closed-loop control). The operating current can be determined by incorporating a closed-loop or open-loop controlled variable in the motor open-loop or motor closed-loop control. The current fluctuations can be calculated by detecting fluctuations in the control error of the motor closed-loop control (characterizing roadway roughness), or based on the target / actual difference in the motor closed-loop control, or based on harmonics in the operating current (characterizing roadway roughness).Since the open-loop or closed-loop controlled variables are linked to the operating current or partially or completely reproduce it, they can also be referred to as operating currents in terms of detection.

[0007] At least one current fluctuation occurring in the operating current is determined. This current fluctuation is caused by the passage of roadway irregularities. Here, the current fluctuation does not refer to a change in the current that generates a rotating magnetic field. Instead, it refers only to a fluctuation relative to a target operating current. Here, the target operating current can be a (polyphase) phase current (AC) or a DC current for supplying an inverter. The current fluctuation refers to a deviation of the current from its target profile, i.e., a deviation from the target rotating current flowing as a phase current in the drive electric machine or from the DC current supplied to the inverter. Thus, the current fluctuation is a change relative to the phase AC current or its sinusoidal profile, or a change in the inverter's supply DC current. The current or current fluctuation can be measured using a current sensor (shunt, Hall element, measuring transformer, etc.) or similar. The current fluctuations can be determined in particular by high-pass filtering of the operating current and by correlation with signal shapes that are characteristic of the effect of traversed roadway irregularities on the operating current of the electric drive.

[0008] Based on the current fluctuation, it is determined that the vehicle is traveling over a roadway unevenness at the time of the current fluctuation. Based on the current fluctuation, it is determined that a roadway unevenness exists, and the roadway unevenness, in particular its thickness, or a quantity characterizing the roadway as uneven (roadway quality) is output. This can be used to correspondingly configure the chassis (regardless of the location of the occurrence), to configure the driving mode (e.g., accelerator pedal sensitivity or sport mode vs. eco mode), and / or to display user-detectable information indicating the roadway unevenness and possibly its thickness or quality. Based on the current fluctuation, it is determined, in particular, that the vehicle is located at a roadway unevenness. The location where the vehicle was or is located at the time of the current fluctuation corresponds to the location of the current fluctuation. The location of the occurrence can be determined by a (preferably global) location method, in particular a satellite-assisted and / or mobile radio network-assisted location method. Here, a signal reproducing the location of the current fluctuation is generated. This signal may include location data, in particular global location data or location data on a road in a map display. This signal reproduces at least the location of occurrence, and can also reproduce the strength and / or length (duration) of the current fluctuation, or the thickness of the roadway irregularity. This signal or the location of occurrence reproduced therefrom is output as the roadway irregularity location. In other words, this signal corresponds to the location of occurrence of the roadway irregularity location, and can also reproduce the quality and / or quantity of the roadway irregularity. Therefore, in this case, a signal that reproduces the location of occurrence of the current fluctuation is generated and output. This signal can be output as a database entry.

[0009] The location of the occurrence is preferably output to a database, in which the location of the occurrence is stored, preferably together with other data characterizing the roadway unevenness (thickness, length, size...). The database may be located in the vehicle, in particular in the vehicle's navigation device. The database may also be located in a mobile device configured to perform navigation functions.

[0010] Preferably, the mobile device combines navigation functionality with a database.

[0011] This allows the navigation device or navigation function to display the navigation data combined with the entries in the database. The database may also be provided external to the vehicle, for example as a database accessible to a navigation device in the vehicle. The navigation device calls up the entries in the database and preferably combines these entries with the navigation data (or navigation display) of the navigation device. Such a navigation device may be a device that is fixedly integrated into the vehicle (and configured for corresponding communication) or may be a mobile device that is configured for corresponding communication and configured to perform the navigation function (e.g. in the form of application software).

[0012] Preferably, the duration (the duration between two successive current fluctuations or the path equivalent to the duration) or the intensity and / or shape of the current fluctuations is determined, from which a quality or quantity characteristic of the current fluctuations can be derived, which can in particular be stored or output as a signal in association with the location of the roadway irregularity.

[0013] In particular, the duration (time or path equivalent between two successive current fluctuations) and / or shape can be compared with a preset duration and / or shape. Preferably, a similarity value is calculated during the comparison, which is a measure of the similarity between the determined duration and / or shape and a preset duration and / or shape. Different thicknesses can be predefined, and the preset thickness that has the greatest similarity to the determined thickness can be determined. Correlation in the time domain or frequency domain can be used to determine the similarity, and the correlation result reproduces the similarity. It is also possible to determine the similarity, particularly the similarity value, by vectorial similarity or based on a neural network. The similarity value reproduces the strength of the similarity and increases with the strength of the similarity.

[0014] Preferably, the location of the occurrence is output only if the similarity value is above a pre-set boundary, thereby filtering out road irregularities that are incorrectly detected as being true.

[0015] In some embodiments, a current change associated with a change in target speed received via the operating interface is subtracted from the operating current before calculating the current change. Because this change in target speed (corresponding to the target acceleration) is known, the current change can be subtracted from the determined operating current by subtraction. Furthermore, because the current change caused by such a change in target speed has a much smaller edge steepness than the current change resulting from roadway irregularities, the proportion of the current change resulting from the change in target speed can be suppressed by high-pass filtering or the like.

[0016] It can be specified that at least one current fluctuation in the operating current is determined, a signal is generated, and / or the location of the current fluctuation is output only when the current fluctuation is determined at a vehicle speed above a preset speed threshold. In other words, if the vehicle speed does not exceed the preset speed threshold, the current fluctuation is not detected as a roadway irregularity. This speed threshold can be, for example, 5 km / h or 2 km / h.

[0017] This prevents curbing when exiting or entering a parking space from being incorrectly detected as a roadway irregularity.

[0018] The at least one current variation in the operating current is preferably determined by calculating the amplitude and / or edge steepness and / or frequency content as characteristics of the current variation.

[0019] This characteristic is mapped to torque variations that are the cause of current fluctuations in the electric drive due to road irregularities. In particular, the amplitude and / or edge steepness and / or frequency content are mapped to the strength of the current fluctuations and thus to the thickness of the road irregularities. Preferably, the road condition, in particular the road irregularity characteristics, are determined based on the torque variations. In particular, the depth, thickness and / or length of the road irregularities are taken into account as road irregularity characteristics.

[0020] The current fluctuations can be mapped to road conditions or roadway irregularity characteristics using a mapping of the representation of the current fluctuations as a time signal or in frequency space, preferably outputting the location of occurrence along with the road condition. This mapping maps the current fluctuations or their characteristics (amplitude, duration, edge steepness) to the quantity or quality of roadway irregularities.

[0021] Preferably, the mapping maps the current fluctuations as a frequency domain representation. This maps the frequency domain representation of the current fluctuations to the quality or quantity of roadway irregularities. The frequency domain representation may be a full or partial spectral representation of the current fluctuations, in particular the amplitude of one or more frequency components of the current fluctuations. Furthermore, the current fluctuations can be mapped in the time domain. Furthermore, the current fluctuations can be mapped by a neural network. A neural network (or a system generally configured for machine learning) can reproduce the relationship between road conditions (or roadway irregularity characteristics) and the current fluctuations occurring in the drive unit due to the road conditions.

[0022] Furthermore, a method for operating a vehicle's electric drive depending on the road condition or roadway irregularities is proposed. The method specifies determining a driving route. A roadway irregularity warning is output before reaching a roadway irregularity determined according to the method of any one of claims 1 to 9 or an occurrence location determined according to the method of any one of claims 1 to 9. Alternatively or additionally, the vehicle's electric drive or chassis can be configured for roadways with large irregularities, for example by increasing spring elasticity and / or reducing the maximum drive power. Furthermore, if the occurrence location is reached at a speed higher than the minimum speed, i.e., at a speed that is too high and therefore not adapted to the roadway irregularity, a vehicle wear counter can be incremented, thereby increasing vehicle wear.

[0023] A computer program product configured to implement the method is described. The computer program product has an input interface (function header or the like) for values ​​that represent the time course of an operating current. The computer program product has a program section that determines the time variations in these values. The input interface is configured to pass these values ​​to the program section. The computer program product has an output interface (function header or the like) that outputs an occurrence value that characterizes the actual occurrence of the variation, or an occurrence position of the variation as the actual position of the vehicle at the time of the occurrence of the variation. The program section is configured to pass the occurrence value or occurrence position to the output interface. A computing device configured to implement the method may be provided. The computing device may be configured as a processor and associated program memory, the program memory storing a computer program that, when running on the processor, implements the method.

Claims

1. 1. A method for identifying a condition of a roadway on which a vehicle having an electric drive travels, comprising: - detecting the operating current of said electric drive; - calculating at least one current variation in said operating current; - generating a signal that reproduces the location of the current fluctuations; - outputting the location of the occurrence as a roadway irregularity location and / or outputting a quantity characterizing the roadway irregularity.

2. 2. The method of claim 1, further comprising outputting the location of the occurrence to a database located inside or outside the vehicle and storing the location in the database.

3. 3. The method according to claim 1, further comprising: determining the duration and / or the strength and / or shape of the current fluctuations; comparing the duration and / or the strength and / or the shape with a predetermined duration and / or shape; determining a similarity value that is a measure of the similarity between the determined duration and / or shape and the predetermined duration and / or shape; and outputting the occurrence position only if the similarity value exceeds a predetermined boundary.

4. 4. The method according to claim 1, further comprising subtracting from the operating current a current change associated with a change in target speed received via an operating interface before the calculation of the current variation.

5. 5. The method according to claim 1, further comprising determining at least one current fluctuation in the operating current, generating the signal, and / or outputting the occurrence position only if the current fluctuation is determined at a speed of the vehicle that exceeds a preset speed threshold.

6. 6. The method according to claim 1, wherein the determination of the at least one current fluctuation in the operating current is specified by calculating amplitude and / or edge steepness and / or frequency content as features of the current fluctuation, and mapping the features to torque changes occurring in the electric drive that are the cause of the current fluctuation.

7. The method according to claim 6 , further comprising determining road conditions, in particular road roughness characteristics, based on the torque variations.

8. 8. The method according to claim 1, further comprising mapping the current fluctuations to road conditions using a mapping of a representation of the current fluctuations as a time signal or in frequency space, and outputting the location of occurrence together with the road conditions.

9. 9. The method of claim 8, wherein the mapping is a mapping that maps the current fluctuations as a frequency domain representation and / or a mapping that maps the current fluctuations using a neural network, the neural network reproducing a relationship between road conditions and current fluctuations occurring in the drive unit due to the road conditions.

10. 10. A method for operating an electric drive of a vehicle depending on road conditions, the method determining a driving route and outputting a road unevenness warning before reaching an occurrence location outputted in accordance with a method according to any one of claims 1 to 9, and / or setting the electric drive or chassis of the vehicle for roadways with large unevenness, and / or counting up a vehicle wear counter if the occurrence location is driven at or above a minimum speed.

11. 11. A computer program product configured to implement the method according to any one of claims 1 to 10, the computer program product having an input interface for values ​​representing the time course of an operating current and a program section for determining the time variations in said values, the computer program product further having an output interface for outputting an occurrence value characterizing an actual occurrence of said variation or the occurrence position of said variation as the actual position of the vehicle at the time of said occurrence of said variation.

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