Method for monitoring an electrical energy storage device on board a vehicle, monitoring device for an electrical energy storage device and motor vehicle

Abstract

Method (200) for monitoring an electrical energy storage device (105) on board a motor vehicle (100), wherein the energy storage device (105) is enclosed by means of an encapsulation (110), the method (200) comprising the following steps: - Sampling (205) an acoustic signal in the area of ​​the encapsulation (110); - Comparing (220) the sampled acoustic signal with a predetermined signal indicating damage to the encapsulation (110); and - Providing (225) a warning signal if the sampled acoustic signal matches the predetermined signal, wherein several characteristics of the sampled acoustic signal are compared with each predetermined threshold value, which corresponds to the characteristics of a predetermined signal and the warning signal is issued if - several characteristics of the sampled acoustic signal - correspond to predetermined characteristics of a predetermined signal or - each closer than predetermined to an assigned threshold value - and if, in addition, the signal strength of the sampled acoustic signal exceeds a predetermined threshold.

Description

[0001] The invention relates to an electrical energy storage device for a motor vehicle drive system, in particular the monitoring of the energy storage device with regard to mechanical damage.

[0002] In particular, the invention relates to a method for monitoring an electrical energy storage device on board a vehicle, a monitoring device for an electrical energy storage device and a motor vehicle.

[0003] A motor vehicle includes an electric drive system powered by energy from an electrical energy storage device. This energy storage device typically comprises a rechargeable battery made up of several cells and, due to its size and weight, is often located in the vehicle's underbody. A cell stores electrical energy in chemical form, generally comprising two electrodes and an electrolyte between them. Many different designs are known, ranging from solid electrolyte cells to redox flow cells, whose electrolyte is circulated during operation.

[0004] Chemical energy storage devices are typically mechanically encapsulated to prevent environmental pollution from leaking components and damage to the storage device from ingress. If the encapsulation is breached, air or water, for example, can penetrate the energy storage device and impair its functionality. Oxidation can reduce the energy storage device's capacity, and water ingress can create a fire hazard. An intruding object can cause an internal short circuit, leading to localized overheating and further damage to the storage device.

[0005] If another object strikes the vehicle horizontally, damage, including to the energy storage system's encapsulation, is usually easily visible. However, if the impact comes from underneath the vehicle, for example from a stone chip, the encapsulation can be damaged unnoticed.

[0006] DE 10 2014 201 162 A1 relates to a method for measuring mechanical vibrations with a piezoelectric sensor.

[0007] DE 102 06 351 A1 and DE 10 2012 023 393 A1 each relate to a method for the subsequent investigation of an acoustically recorded impact that occurred on a side body part of a vehicle during an accident.

[0008] DE 10 2014 018 055 A1 concerns a monitoring method for an energy storage device in which a structure-borne sound sensor measures an acoustic signal. The specific method of evaluating the acoustic signal is not described therein.

[0009] According to DE 10 2011 112 641 A1, knocking noises are generated on a battery using a hammer and acoustically evaluated.

[0010] DE 10 2013 000 867 A1 relates to a method for the electrical measurement of possible battery damage.

[0011] One of the problems underlying the invention is to improve the monitoring of an energy storage device on board a motor vehicle with regard to the integrity of its encapsulation, and to provide for this purpose an improved method for monitoring an electrical energy storage device on board a vehicle, an improved monitoring device for an electrical energy storage device, and a motor vehicle equipped therewith. The invention solves this problem by means of the subject matter of the independent claims. Dependent claims describe preferred embodiments.

[0012] An electrical energy storage device on board a motor vehicle is enclosed by means of a casing. According to a first aspect of the invention, a method for monitoring the electrical energy storage device comprises steps of scanning an acoustic signal in the area of ​​the casing; comparing the scanned acoustic signal with a predetermined signal indicating damage to the casing; and providing a warning signal if the scanned acoustic signal corresponds to the predetermined signal.

[0013] According to the invention, it is provided that - that several characteristics of the sampled acoustic signal are compared with predetermined threshold values, which correspond to the characteristics of a predetermined signal, and - that the warning signal is issued if - several characteristics of the sampled acoustic signal - correspond to predetermined characteristics of a predetermined signal or - each closer than predetermined to an assigned threshold value - and if, in addition, the signal strength of the sampled acoustic signal exceeds a predetermined threshold.

[0014] The warning signal can, for example, be an electrical or telecommunication signal, or a signal perceptible to a human, particularly acoustic, visual, or haptic. It has been recognized that a safety-relevant event that compromises the integrity of the enclosure can be associated with a characteristic noise that can be automatically detected and identified. This allows for simple and effective monitoring of the enclosure's integrity. In particular, an event that could compromise the enclosure's integrity can be detected by comparison. The warning signal is provided when damage or potential damage has occurred that would otherwise be difficult or impossible to detect. A safety-relevant event can be distinguished with a high degree of certainty from a non-safety-related event.

[0015] The predetermined signal indicates, in particular, damage to the encapsulation. Different types of damage are preferably assigned different predetermined signals. For example, a perforation, penetration, break, or rupture of the encapsulation can be detected. Furthermore, a rattling sound in the area of ​​the encapsulation can be detected, which can occur if a part of the encapsulation has become detached and the vehicle is subjected to vibrations, such as when driving over a bump. Preferably, different predetermined signals are also assigned to different points on the encapsulation where the acoustic signal is detected.

[0016] The comparison process involves determining whether several characteristics of the sampled acoustic signal match or exceed predetermined characteristics of a predefined signal. For example, one or more characteristics such as frequency, bandwidth, signal strength, or signal duration can be compared to predetermined threshold values. The threshold values ​​can be predefined, and a warning signal is emitted if several characteristics are closer than predefined to an assigned threshold or if they exceed the threshold—in either a positive or negative direction. The threshold values ​​can correspond to characteristics of a predefined signal, with the predefined signal being, for example, given preference. - as a combination of characteristics or also - as a representation of an acoustic recording may be the case.

[0017] According to the invention, the warning signal is only provided if the signal strength of the sampled acoustic signal exceeds a predetermined threshold. The signal strength can, for example, correspond to a sound pressure level that may depend on the force of an impact of an object on the encapsulation. A low-energy impact that does not compromise the integrity of the encapsulation will therefore not trigger the warning signal.

[0018] Preferably, the acoustic signal is automatically scanned and recognized.

[0019] Preferably, the sampled acoustic signal is compared with different predetermined signals that are assigned to different types of damage to the encapsulation.

[0020] Preferably, a spectrum of the sampled acoustic signal is compared with a spectrum of the predetermined signal. The spectrum is preferably limited to a predetermined frequency range and indicates signal strengths as a function of frequencies. The comparison can, for example, be parametric, so that a waveform representing the spectrum of the sampled acoustic signal can be compared with a waveform representing the predetermined signal.

[0021] Preferably, the signal strengths of the sampled acoustic signal are compared with the signal strengths of the predetermined signal in a predetermined number of distinct frequency ranges. For this purpose, mutually adjacent, disjoint frequency ranges can preferably be formed. The boundaries of the frequency ranges can be logarithmically distributed, and the signal strengths within the frequency ranges can be determined, in particular, by means of a Fourier transform, optionally discretely or using Fast Fourier. This allows for a rapid determination of the extent to which the sampled acoustic signal corresponds to the predetermined signal.

[0022] Furthermore, the frequency ranges can be specifically selected in areas that are highly informative for distinguishing between a safety-relevant and a safety-irrelevant event. This includes, in particular, frequency ranges in which only one of the events leads to relevant signal strengths, while the other does not. For example, road vibrations from a vehicle's chassis might be strongest in a lower frequency range, a safety-relevant event in a middle range, and a safety-irrelevant stone impact in an upper frequency range. Typical driving noises can occur in all frequency ranges. Determining signal strengths in all three frequency ranges can enable a clear differentiation.

[0023] Preferably, a correspondence between the sampled acoustic signal and the predetermined signal is determined if the sum of the squares of the signal strength deviations is less than a predetermined value. This procedure is also called the least-squares method and advantageously does not distinguish between positive and negative signal deviations. Large deviations are weighted particularly heavily by the squaring, so that the signals are only determined to correspond if a true correspondence exists.

[0024] Preferably, the time course of the sampled acoustic signal is compared with the time course of the predetermined signal. A short-time Fourier analysis can be performed for this purpose. For this, a sampled acoustic signal can be stored in a buffer memory, which is implemented, for example, as a ring buffer with a predetermined retention period (a "sliding window"). A sonogram of the sampled acoustic signal can then be graphically represented, providing an improved basis for comparison with the predetermined signal. The comparison described herein can then be performed using the predetermined signal, which is preferably available in a suitable format.

[0025] Optionally, multiple acoustic signals are sampled at different points on the encapsulation and each compared with corresponding predetermined signals. Sampling preferably occurs simultaneously or in a time-synchronized manner, so that multiple acoustic signals can be sampled for a single event, such as a rockfall on the encapsulation.

[0026] According to a second aspect of the invention, it comprises - a monitoring device for an electrical energy storage device that is enclosed by means of an encapsulation and installed on board a motor vehicle, - a sensor for scanning an acoustic signal in the area of ​​the encapsulation; - an interface for providing a warning signal; and - a processing facility.

[0027] The processing facility is designed to - to compare the sampled acoustic signal with a predetermined signal indicating damage to the encapsulation, comparing several characteristics of the sampled acoustic signal with predetermined threshold values ​​corresponding to characteristics of a predetermined signal; and furthermore, it is equipped to - to provide a warning signal via the interface if the sampled acoustic signal matches the predetermined signal, namely if - several characteristics of the sampled acoustic signal - correspond to predetermined characteristics of a predetermined signal or - each closer than predetermined to an assigned threshold value - and if, in addition, the signal strength of the sampled acoustic signal exceeds a predetermined threshold.

[0028] The processing device may include a programmable microcomputer or microprocessor. The monitoring device or the processing device is preferably configured to partially or completely execute a method described herein. For this purpose, the method may be in the form of a computer program product with program code that can run on the processing device or be stored on a computer-readable data carrier.

[0029] The monitoring device can increase safety on board the vehicle. Both contamination of the surrounding area by a medium leaking from the energy storage device through damaged encapsulation, and a defect in the energy storage device caused by an incoming medium or object, can be prevented at an early stage based on the sampled acoustic signal.

[0030] Preferably, the encapsulation covers an area between the energy storage device and the underside of the vehicle, with the sensor being located in this area. The encapsulation preferably surrounds the energy storage device on all sides and can be hermetically sealed. The encapsulation can be part of the energy storage device itself. Alternatively, the encapsulation can comprise a housing or a cover. By scanning the acoustic signal, specifically on a side of the encapsulation facing the ground, a likely event involving an external object striking or pressing against the encapsulation can be monitored particularly effectively. Such an event could include, for example, a stone impact, a vehicle running over an obstacle or animal, or the encapsulation coming to rest on the ground, for example, due to a large bump or step.

[0031] Preferably, the sensor is attached to the encapsulation and configured to detect structure-borne sound. This allows for improved suppression of acoustic signals transmitted via airborne sound. The detected acoustic signal can then be used to better identify the event acting on the encapsulation.

[0032] The processing device is preferably further configured to reduce energy exchange with the energy storage device, either to a predetermined level or to zero. For this purpose, the warning signal for switching off an electrical consumer, an electrical line, or the electrical storage device can be used in particular. The warning signal can also be issued to a person, in particular a driver of the motor vehicle, who can then initiate further measures.

[0033] According to another aspect of the invention, a motor vehicle comprises an electrical energy storage device enclosed by means of an encapsulation and a monitoring device described therein.

[0034] The invention will now be described in more detail with reference to the attached drawings, in which: Fig. 1 a motor vehicle; Fig. 2. A flowchart of a procedure for controlling a motor vehicle, and Fig. 3 example acoustic signals illustrated.

[0035] Fig. Figure 1 shows a motor vehicle 100, in particular a passenger car, which can be powered by electrical energy from an electrical energy storage device 105. An upper section shows a view of the motor vehicle 105 from below, and a lower section shows a side view, the views not necessarily relating to the same embodiment. The energy storage device 105 can be constructed in one piece or in multiple parts and is enclosed by a capsule 110, which is usually an integral part of the energy storage device 105. The capsule 110 can, for example, comprise a metal or plastic structure, which preferably ensures a seal between the energy storage device 105 and an environment, in particular with respect to a fluid such as air, moisture, or water vapor.The encapsulation 110 preferably extends between the energy storage device and a surface on which the motor vehicle 105 stands or drives, and further preferably also on sides and a side of the energy storage device 105 facing away from the surface.

[0036] A monitoring device 115 comprises at least one sensor 120 for scanning an acoustic signal, a processing device 125 and an interface 130 which may be connected to an output device 135.

[0037] The sensor 120 is preferably mounted in the area of ​​the encapsulation 110, particularly on a side of the encapsulation 110 facing the substrate. The sensor 120 can be configured as a microphone for detecting airborne sound or as a structure-borne sound sensor for detecting surface waves on the encapsulation 110. More preferably, the sensor 120 is limited to detection within a predetermined frequency range, which may be in the acoustic range. Multiple sensors 120 can also be provided, preferably arranged at different geometric locations within the area of ​​the encapsulation 110.

[0038] The sensor(s) 120 are connected to the processing unit 125, which may include a programmable microprocessor or microcontroller and is preferably connected to the interface 130. The processing unit 125 is configured to detect an acoustic signal by means of at least one of the sensors 120. This signal originates, in particular, from an event involving mechanical stress on the encapsulation 110 that could impair its integrity, especially its sealing. Such an event could include, for example, a stone impact, the underbody of the vehicle 105 contacting a surface, driving over or rolling over an object, or any intervention on the vehicle 100, for example, in a workshop.

[0039] The processing device 125 can temporarily store the sampled acoustic signal in a storage device 140, preferably storing only the signal from a predetermined, past time range in the storage device 140. The processing device 125 preferably compares the sampled acoustic signal with one or more predetermined signals, for example, with respect to its spectral composition, signal strength, or temporal profile. Speech recognition methods can be used for this comparison. In particular, a short-time Fourier transform (STFT) can be applied to the sampled signal, and the result can be compared with the result of a further such transformation of the predetermined signal. In one embodiment, the predetermined signal is already available in transformed form.The predetermined signal can also be stored in the storage device 140 or in a dedicated storage device.

[0040] The predetermined signal can indicate a breach of the integrity of the encapsulation 110, so that damage to the encapsulation 110 can be determined if the sampled acoustic signal bears sufficient resemblance to the predetermined signal. In this case, the processing unit 125 can output a warning signal via the interface 130, which can be directed, for example, to a driver of the motor vehicle 105 or to a system or subsystem on board the motor vehicle 105. In one embodiment, the system can also be influenced, in particular to reduce, limit, or terminate further charging of the energy storage device 105. The drive system of the motor vehicle 105 can be controlled or switched off accordingly. Similarly, the charging control of the energy storage device 105 can be controlled or switched off.

[0041] Fig. Figure 2 shows a flowchart of a method 200 for monitoring an electrical energy storage device 105. The method 200 is further preferably configured to run on a monitoring device 115 and, in particular, its processing unit 125. The method 200 can be executed cyclically, optionally even when the motor vehicle 100 is not in operation.

[0042] In step 205, an acoustic signal is sampled in the area of ​​the encapsulation 110 of the energy storage device 105. In step 210, a spectrum of the sampled signal can be determined. For this purpose, the signal strength of the sampled signal can be determined in one or more predetermined frequency ranges. Preferably, a Fourier transform is performed for this purpose. In one embodiment, a time evolution of the signal strengths in the predetermined frequency ranges and a predetermined time window is determined. In step 215, one of several predetermined signals can be selected with which the sampled signal is compared in step 220. Comparisons of the acoustic signal with several predetermined signals can also be performed.

[0043] The comparison can include determining whether one or more characteristics of the acoustic signal, such as a frequency-dependent signal strength curve, a time-dependent signal strength curve, or a signal duration, correspond to predetermined parameters. Correspondence can be determined if the characteristic falls below a predetermined distance from the predetermined parameter. If several characteristics are compared with their respective parameters, or if the comparison of a characteristic with a parameter comprises several individual determinations, the deviations found can be aggregated, for example, as the sum of the squares of the deviations, to obtain a simplified measure of correspondence. If the measure is below a predetermined threshold, correspondence can be determined.In another embodiment, one or more characteristics of the acoustic signal can also be checked for exceeding a predetermined threshold. A warning signal can be emitted if one or a predetermined number of the checked characteristics exceed their respective assigned threshold in a predetermined direction.

[0044] Depending on the result of the determination in step 220, a warning signal can be issued in step 225. The warning signal can be a general warning or a more specific request, for example, for further inspection of the energy storage device 105 or its encapsulation 110, or it can also influence the control of the motor vehicle 100.

[0045] Fig.Figure 3 shows a schematic, exemplary diagram 300 of a frequency analysis of a sampled acoustic signal. The horizontal axis represents a frequency (f), the vertical axis a signal strength (S), and the vertical axis a time (t). In a simplified embodiment, the temporal evolution of the sampled signal is not considered, and the representation is reduced to the plane facing the viewer, showing the signal strength and frequency.

[0046] Along the horizontal axis, a predetermined number of frequency ranges 305 are provided, in each of which the signal components of the sampled signal are determined according to their strength. The ranges preferably border each other and can be logarithmically distributed in their widths, such that a lower frequency range 305 may have a smaller absolute bandwidth than a higher frequency range. The distribution of the signal strengths across the frequency yields a spectrum 310, which can be characteristic of an acoustic signal sampled in the area of ​​the encapsulation 110 during an event acting on the encapsulation 110. When comparing two spectra 310 with each other, an absolute comparison of the signal strengths in corresponding frequency ranges 305 can be carried out, or the shape of a curve that connects the determined signal strengths can be compared with a corresponding curve of the other signal.

[0047] If the temporal profile of the sampled signal is also taken into account, then in particular the characteristics of a curve that connects the signal strengths along the time axis can be compared with a corresponding curve of the other signal. Reference sign 100 motor vehicles 105 electrical energy storage 110 encapsulation 115 Monitoring device 120 acoustic sensor (microphone) 125 Processing unit 130 interface 135 Dispensing device 140 storage device 200 procedures 205 samples acoustic signal 210 Determine spectrum 215 Select predetermined signal 220 equivalent? 225 Provide warning signal 300 Diagram 305 Frequency range 310 Spectrum

Claims

[1] Method (200) for monitoring an electrical energy storage device (105) on board a motor vehicle (100), wherein the energy storage device (105) is enclosed by means of an encapsulation (110), the method (200) comprising the following steps: - Sampling (205) an acoustic signal in the area of ​​the encapsulation (110); - Comparing (220) the sampled acoustic signal with a predetermined signal indicating damage to the encapsulation (110); and - Providing (225) a warning signal if the sampled acoustic signal matches the predetermined signal, wherein several characteristics of the sampled acoustic signal are compared with each predetermined threshold value, which corresponds to the characteristics of a predetermined signal and the warning signal is issued if - several characteristics of the sampled acoustic signal - correspond to predetermined characteristics of a predetermined signal or - each closer than predetermined to an assigned threshold value - and if, in addition, the signal strength of the sampled acoustic signal exceeds a predetermined threshold. [2] Method (200) according to claim 1, wherein the sampled acoustic signal is compared with a predetermined signal which - as a combination of predetermined characteristics or - as a representation of an acoustic recording is available. [3] Method (200) according to one of claims 1 or 2, wherein the acoustic signal is automatically sampled and detected. [4] Method (200) according to one of the preceding claims, wherein the sampled acoustic signal is compared with different predetermined signals which are associated with different damage to the encapsulation. [5] Method (200) according to one of the preceding claims, wherein a spectrum (310) of the sampled acoustic signal is compared with a spectrum (310) of the predetermined signal. [6] Method (200) according to claim 5, wherein a correspondence of the sampled acoustic signal with the predetermined signal is determined if a sum of squares of deviations of signal strengths is less than a predetermined value. [7] Method (200) according to one of the preceding claims, wherein a time course of the sampled acoustic signal is compared with a time course of the predetermined signal. [8] Method (200) according to one of the preceding claims, wherein several acoustic signals are sampled at different locations of the encapsulation (110) and each is compared with corresponding predetermined signals. [9] Monitoring device (115) for an electrical energy storage device (105) which is enclosed by means of an encapsulation (110) and is installed on board a motor vehicle (100), wherein the monitoring device (115) comprises the following: - a sensor (120) for scanning an acoustic signal in the area of ​​the encapsulation (110); - an interface (130) for providing a warning signal; and - a processing facility (125) which is equipped to, - to compare the sampled acoustic signal with a predetermined signal indicating damage to the encapsulation (110) and to compare several characteristics of the sampled acoustic signal with predetermined threshold values ​​corresponding to characteristics of a predetermined signal; and is further configured to, - to provide a warning signal via the interface (130) if the sampled acoustic signal corresponds to the predetermined signal, namely if - several characteristics of the sampled acoustic signal - correspond to predetermined characteristics of a predetermined signal or - each closer than predetermined to an assigned threshold value - and if, in addition, the signal strength of the sampled acoustic signal exceeds a predetermined threshold. [10] Monitoring device (115) according to claim 9, wherein the encapsulation (110) covers an area between the energy storage device (105) and an underside of the motor vehicle (100) and the sensor (120) is located in this area. [11] Monitoring device (115) according to claim 9 or 10, wherein the sensor (120) is attached to the encapsulation (110) and is configured to detect structure-borne sound. [12] Monitoring device (115) according to claim 9 or 10, wherein a microphone designed to detect airborne sound is used as the sensor (120). [13] Monitoring device (115) according to one of claims 9 to 12, wherein the processing device (125) is configured to reduce energy exchange with the energy storage device (105). [14] Motor vehicle (100), comprising - an electrical energy storage device (105) enclosed by means of an encapsulation (110), and - a monitoring device (115) according to any one of claims 9 to 13.

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