Battery pack mechanical state detection method and device

Abstract

The embodiment of the application discloses a battery pack mechanical state detection method and device, relates to the technical field of new energy vehicles, and is convenient for realizing low-cost real-time monitoring and judging the mechanical state of a battery pack, so that the occurrence of mechanical abuse of the battery pack is avoided. The method comprises the following steps: sampling the acceleration of the battery pack in a first time period according to a predetermined sampling frequency to obtain a discrete acceleration signal; converting the discrete acceleration signal from a time domain to a frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal; and determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal. The application is suitable for the new energy vehicle battery pack health state monitoring scene.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy vehicles, and particularly relates to a battery pack mechanical state detection method and device. BACKGROUND

[0002] With the development of new energy vehicles, the self-ignition phenomenon of new energy vehicles has also attracted attention from all walks of life. Research shows that the main reasons for the self-ignition of the battery pack are as follows: mechanical abuse, production defects, electrical abuse, high temperature environment, etc. The above factors are not isolated from each other, but are coupled and interacted with each other. For example, the battery pack is subjected to high-speed collision, which causes the battery pack to be extruded and deformed, the battery modules are extruded and pierced, short-circuited, or the bottom is subjected to impact and strong jolt during driving, which causes the joint to be loose, damaged and short-circuited, etc. All of the above may occur at the same time, and further cause the battery pack to be self-ignited when the new energy vehicle is charging or conducting.

[0003] At present, many new energy vehicle enterprises and three-electricity system suppliers begin to strengthen the research work on the safety technology of power batteries in order to improve the safety of new energy vehicles and the product competitiveness. At present, the research work mainly focuses on how to solve the influence of production abuse, electrical abuse and high temperature environment on the self-ignition of the battery pack. For example, through the combination of thermal event parameters such as temperature, temperature rise rate, SOC, voltage drop, current, gas concentration and gas pressure, the change of the thermal event parameters in the whole process is detected to determine whether there is a thermal runaway risk.

[0004] For the influence of mechanical abuse on the battery pack, the inventors found in the process of realizing the present application that: at present, the recognition of mechanical abuse is generally in the form of X-ray scanning, ultrasonic nondestructive testing, etc., which has high cost and is not convenient for forming real-time monitoring and judgment of the mechanical state of the battery pack. SUMMARY

[0005] Therefore, the embodiments of the present application provide a battery pack mechanical state detection method and device, which is convenient for realizing low-cost real-time monitoring and judgment of the mechanical state of the battery pack, so as to avoid the occurrence of mechanical abuse of the battery pack.

[0006] In order to achieve the above application purpose, the following technical scheme is adopted:

[0007] In a first aspect, the embodiments of the present application provide a battery pack mechanical state detection method, which comprises the following steps:

[0008] sampling the acceleration of the battery pack in a first time period at a predetermined sampling frequency to obtain a discrete acceleration signal;

[0009] converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal;

[0010] determine the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal.

[0011] In combination with the first aspect, in a first implementation manner of the first aspect, the converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal comprises: converting the discrete acceleration signal from the time domain to the frequency domain based on a discrete Fourier transform to calculate the amplitude-frequency characteristic of the acceleration signal.

[0012] In combination with the first aspect or the first implementation manner of the first aspect, in a second implementation manner of the first aspect, the converting the discrete acceleration signal from the time domain to the frequency domain based on a discrete Fourier transform to calculate the amplitude-frequency characteristic of the acceleration signal comprises: calculating the amplitude-frequency characteristic of the acceleration signal according to an acceleration amplitude-frequency characteristic calculation formula

[0013] calculating the amplitude-frequency characteristic of the acceleration signal; wherein ACC(k) represents an amplitude value corresponding to a sampling frequency of (k) represents an amplitude value corresponding to a sampling frequency of

[0014] In combination with the first or second implementation manner of the first aspect, in a third implementation manner of the first aspect, the determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal comprises: comparing the amplitude-frequency characteristic of the acceleration signal with a battery pack calibration amplitude-frequency characteristic to determine the mechanical state of the battery pack in the first time period; or,

[0015] calculating a ratio of the amplitude-frequency characteristics of adjacent sampling points of the acceleration signal;

[0016] comparing the ratio of the amplitude-frequency characteristics with a battery pack calibration ratio of adjacent sampling point amplitude-frequency characteristics to determine the mechanical state of the battery pack in the first time period; or,

[0017] normalizing the amplitude value of the amplitude-frequency characteristic of the acceleration signal to uniformly map the amplitude value to the interval [0, 1] to obtain a normalized amplitude-frequency characteristic curve; the normalized amplitude-frequency characteristic curve contains a corresponding relationship between the frequency and the amplitude value of the acceleration signal;

[0018] comparing the amplitude value of the normalized amplitude-frequency characteristic curve with a battery pack calibration amplitude value at the corresponding frequency to determine the mechanical state of the battery pack in the first time period.

[0019] In a fourth implementation form of the first aspect, in any of the first to third implementation forms of the first aspect, the converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal comprises:

[0020] performing an integral operation on the discrete acceleration signal to obtain a discrete velocity signal;

[0021] performing a discrete Fourier transform on the velocity signal to generate an amplitude-frequency characteristic of the velocity signal;

[0022] the determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal comprises determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the velocity signal.

[0023] In a fifth implementation form of the first aspect, in any of the first to fourth implementation forms of the first aspect, after obtaining the discrete acceleration signal, the method further comprises: performing filtering processing on the discrete acceleration signal to obtain a reconstructed discrete acceleration signal.

[0024] In a second aspect, an embodiment of the present application provides a battery pack mechanical state detection device, comprising: a sampling unit configured to sample acceleration of a battery pack in a first time period at a predetermined sampling frequency to obtain a discrete acceleration signal;

[0025] a time-frequency conversion unit configured to convert the discrete acceleration signal from the time domain to the frequency domain to obtain an amplitude-frequency characteristic of the acceleration signal;

[0026] a state determination unit configured to determine a mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal.

[0027] In a first implementation form of the second aspect, the converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal comprises: converting the discrete acceleration signal from the time domain to the frequency domain based on a discrete Fourier transform to calculate the amplitude-frequency characteristic of the acceleration signal.

[0028] In a second implementation form of the second aspect, in the first implementation form of the second aspect, the time-frequency conversion unit is specifically configured to calculate the amplitude-frequency characteristic of the acceleration signal according to an acceleration amplitude-frequency characteristic calculation formula.

[0029] calculating the amplitude-frequency characteristic of the acceleration signal; wherein A n represents a corresponding amplitude value when the sampling frequency is f, n represents the ordinal number of a sampling point in the first time period, T is a sampling point time interval, N is a physical quantity related to a calculation capability of a master control unit, and j is an imaginary unit.

[0030] The battery pack mechanical state detection method and device provided by the embodiment of the present application can reflect the vibration change condition of the battery pack mechanical structure, because when the battery pack mechanical structure is in failure, damage or fatigue damage, the vibration parameters of the sensitive point, such as the amplitude, will change obviously or new components will appear. Therefore, after obtaining the amplitude-frequency characteristic of the acceleration signal, the embodiment of the present application can determine whether the mechanical state of the battery pack is healthy according to the amplitude-frequency characteristic of the acceleration signal. Compared with the existing X-ray scanning, ultrasonic non-destructive testing and other battery pack mechanical state detection schemes, the technical scheme provided by the embodiment of the present application is convenient for realizing low-cost real-time monitoring and determining the mechanical state of the battery pack, thereby avoiding the occurrence of the mechanical abuse of the battery pack. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0032] Figure 1 The flowchart of the battery pack mechanical state detection method according to an embodiment of the present application;

[0033] Figure 2 The structural schematic block diagram of the battery pack mechanical state detection device according to an embodiment of the present application;

[0034] Figure 3 The acceleration curve diagram collected by the new energy vehicle in a certain time period according to an embodiment of the present application;

[0035] Figure 4 The amplitude-frequency characteristic curve of the acceleration signal in the frequency domain corresponding to the acceleration curve diagram in the time domain; Figure 3

[0036] Figure 5 The speed amplitude-frequency characteristic curve according to an embodiment of the present application;

[0037] Figure 6 The structural schematic block diagram of the battery pack mechanical state detection device according to another embodiment of the present application; DETAILED DESCRIPTION

[0038] ​The embodiments of the present application will be described in detail below with reference to the drawings.

[0039] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0040] The battery pack is subjected to collision, resulting in extrusion deformation of the battery pack, mutual extrusion between the battery modules to form puncture and short circuit, or the bottom is subjected to impact and strong jolt during driving, resulting in joint loosening, damage and short circuit, etc. Mechanical abuse is one of the important reasons for causing the mechanical state of the battery pack to change, and thus thermal runaway and self-ignition occur. However, the current means for detecting the mechanical state of the battery pack mainly includes X-ray or ultrasonic nondestructive testing, which has high cost and is difficult to form a system for real-time monitoring of the mechanical state of the battery pack on the vehicle.

[0041] The battery pack mechanical state detection method provided by the embodiments of the present application is based on the relationship between the mechanical abuse, vibration frequency (amplitude) and mechanical state of the battery pack mechanical structure obtained by creative research. The amplitude-frequency characteristics in the frequency domain are obtained by converting the acceleration signal in the time domain. According to the amplitude-frequency characteristics, the mechanical state of the battery pack can be judged and detected. The cost is low, and it is convenient to realize real-time monitoring of the mechanical state of the battery pack on the vehicle.

[0042] Embodiment one

[0043] Figure 1 It is an embodiment flow diagram of the battery pack mechanical state detection method of the present application. Please refer to Figure 1 The battery pack mechanical state detection method provided by the embodiments of the present application is suitable for the new energy vehicle battery pack health state monitoring scene, which includes the following steps:

[0044] S110, sampling the acceleration of the battery pack in a first time period according to a predetermined sampling frequency to obtain a discrete acceleration signal.

[0045] Please refer to Figure 2 In the present embodiment, a plurality of acceleration sensors can be arranged in the battery pack, and the acceleration sensors are used to collect the acceleration of the battery pack.

[0046] The acceleration sensors can be arranged at different position points in the battery pack, and the acceleration sensors are used to collect the acceleration information of different positions of the battery pack in real time.

[0047] The main control unit of the vehicle can sample the acceleration from the acceleration sensor in real time according to a predetermined sampling frequency to obtain a series of discrete acceleration signals, such as Figure 3As shown in the figure, the acceleration change curve in the time domain is obtained. It should be noted that the sampled acceleration signal is a series of discrete values. When the sampling interval is small enough, it can be regarded as Figure 3 The curve shown.

[0048] The sampling representation of acc(t) is shown in Equation 1.

[0049]

[0050] Where f s is the sampling frequency, T is the sampling period, n represents the ordinal number of the sampling point in the first time period. For example, if it is the sampling point of the first frame, then n=1, and acc(t) represents the acceleration value collected in the first sampling period (first sampling); if it is the sampling point of the second frame, then n=2, and acc(t) represents the acceleration value collected in the second sampling period (second sampling), and so on.

[0051] Furthermore, the main control unit can calculate the amplitude-frequency characteristics of the mechanical structure at each position of the battery pack based on the acceleration information at different positions. Please refer to the following for a specific solution for calculating the amplitude-frequency characteristics.

[0052] In some embodiments, after obtaining the discrete acceleration signal, the method further includes: performing filtering processing on the discrete acceleration signal to obtain a reconstructed discrete acceleration signal.

[0053] For example, the specific filtering method can be mean filtering, and the mean filtering calculation is shown in the following formula: L is a mean filter parameter, which in this embodiment represents the number of sampling points involved in the calculation.

[0054] Of course, other filtering methods may also be used, such as median filtering, but they will not be described in detail here to highlight the innovative purpose of the present invention.

[0055] S120 : Convert the discrete acceleration signal from the time domain to the frequency domain to obtain an amplitude-frequency characteristic of the acceleration signal.

[0056] In this embodiment, the time domain signal can be converted into a frequency domain signal through a Fourier transform. Specifically, converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal includes: converting the discrete acceleration signal from the time domain to the frequency domain based on a discrete Fourier transform, and calculating the amplitude-frequency characteristic of the acceleration signal.

[0057] In some embodiments, the discrete acceleration signal is converted from the time domain to the frequency domain based on discrete Fourier transform, and the amplitude-frequency characteristic of the acceleration signal is calculated, which includes: according to the acceleration amplitude-frequency characteristic calculation formula The amplitude-frequency characteristic of the acceleration signal is calculated, wherein ACC(k) represents the amplitude value corresponding to the kth sampling point in the first time period, n represents the serial number of the sampling point in the first time period, T is a sampling point time interval, N is a physical quantity related to the computing capacity of the master unit, for example, if the processor (CPU) running cycle is 500 ms and the sampling frequency is 2 KHz, that is, 2 data points per ms, then the calculation formula of N is N=500*2=1000; according to the different computing capacity of the processor, the value of N can be calculated according to the above calculation formula; and j is an imaginary unit.

[0058] In S130, the mechanical state of the battery pack in the first time period is determined according to the amplitude-frequency characteristic of the acceleration signal.

[0059] The battery pack mechanical state detection method provided by the embodiment of the application is based on the relationship between the vibration characteristic (generally represented by amplitude) of the mechanical structure of the battery pack and the mechanical state found in engineering practice, and the amplitude-frequency characteristic (representing the relationship between the vibration amplitude and the frequency) of the acceleration signal in the predetermined length monitoring time period is obtained by converting the collected time domain acceleration signal into a frequency domain amplitude signal, which can reflect the vibration change condition of the mechanical structure of the battery pack. When the mechanical structure of the battery pack fails, is damaged or has fatigue damage, the vibration parameter of the corresponding sensitive point, for example, the amplitude, will change obviously or new components will appear.

[0060] Therefore, the technical scheme provided by the embodiment of the application can determine whether the mechanical state of the battery pack is healthy according to the amplitude-frequency characteristic of the acceleration signal after obtaining the amplitude-frequency characteristic of the acceleration signal, which is convenient for realizing low-cost real-time monitoring and determining the mechanical state of the battery pack, thereby avoiding the occurrence of mechanical abuse of the battery pack.

[0061] In the embodiment, the amplitude-frequency characteristic of the acceleration signal is obtained, that is, the amplitude-frequency characteristic of the mechanical vibration of the battery pack. When the mechanical state of the battery pack changes or mechanical abuse occurs, the amplitude-frequency characteristic of the mechanical vibration of the battery pack will change compared with the amplitude-frequency characteristic when the battery pack is in a safe state. When the change exceeds a certain threshold, the mechanical state and the mechanical abuse condition of the battery pack can be detected and identified.

[0062] There are many schemes for specifically determining the mechanical state and the mechanical abuse condition of the battery pack according to the obtained amplitude-frequency characteristic, some of which are listed below to help understanding.

[0063] ​In some embodiments, the determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal comprises: comparing the amplitude-frequency characteristic of the acceleration signal with a battery pack calibration amplitude-frequency characteristic to determine the mechanical state of the battery pack in the first time period.

[0064] In other embodiments, the determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal can be: normalizing the amplitude of the amplitude-frequency characteristic of the acceleration signal, uniformly mapping the amplitude to the interval [0, 1] to obtain a normalized amplitude-frequency characteristic curve; the normalized amplitude-frequency characteristic curve comprises a corresponding relationship between the frequency and the amplitude of the acceleration signal.

[0065] The normalized amplitude-frequency characteristic curve comprises a corresponding relationship between the frequency and the amplitude of the acceleration signal.

[0066] The normalized amplitude-frequency characteristic curve comprises a corresponding relationship between the frequency and the amplitude of the acceleration signal.

[0067] Alternatively, in some embodiments, the determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal can be: calculating the ratio of the amplitude-frequency characteristics of adjacent sampling points of the acceleration signal; wherein the calculation formula is The normalized amplitude-frequency characteristic curve comprises a corresponding relationship between the frequency and the amplitude of the acceleration signal.

[0068] In addition, the scheme for determining the mechanical state of the battery pack according to the amplitude-frequency characteristic can also have other variations, for example, the difference between the amplitude-frequency characteristics of adjacent sampling points is compared with a calibration threshold to determine; or the variance or expected value of the amplitude of the amplitude-frequency characteristic of each sampling point is compared with a calibration threshold to determine, etc. Since there are many variations, it cannot be enumerated. However, no matter what variation of the amplitude-frequency characteristic is used to determine the mechanical state of the battery pack, the basic technical concept is to determine the mechanical state of the battery pack based on the amplitude-frequency characteristic of the acceleration signal, and any variation derived from this technical concept is within the protection scope of the present application.

[0069] In some embodiments, the converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal comprises: performing an integral operation on the discrete acceleration signal to obtain a discrete velocity signal; and performing a discrete Fourier transform on the velocity signal to generate the amplitude-frequency characteristic of the velocity signal.

[0070] wherein the formula for performing an integral operation on the acceleration signal to obtain the velocity is:

[0071]

[0072] The formula for performing a discrete Fourier transform on the above equation to obtain the amplitude-frequency characteristic of the velocity is:

[0073]

[0074] It can be understood that, for each segment of sample point data, the calculated is the relationship between the mechanical vibration amplitude (amplitude) and the frequency at different positions of the battery pack, i.e., the amplitude-frequency characteristic.

[0075] In this embodiment, while judging whether the mechanical state of the battery pack is healthy and the mechanical abuse condition according to the amplitude-frequency characteristic of the mechanical vibration of the battery pack in the frequency domain, the mechanical state of the battery pack can also be scored or graded by the deviation degree of the amplitude signal of the mechanical vibration of the battery pack in the frequency domain calculated in real time from the preset amplitude signal, so as to realize the quantitative evaluation of the mechanical state of the battery pack and provide important data support for subsequent safety disposal measures of the mining area.

[0076] It can be understood that the factors of the thermal runaway and spontaneous combustion of the battery pack are sometimes not determined by a single factor, but are caused by the interaction of multiple factors. For example, the interaction of high temperature environment, electrical abuse and mechanical abuse. Therefore, in order to accurately evaluate the health state of the battery pack, in some embodiments, after obtaining the discrete acceleration signal, the method further comprises: calculating and determining the cumulative damage degree of the battery pack in the first time period according to the discrete acceleration signal.

[0077] In this embodiment, the calculation method of the cumulative damage degree of the battery pack in the first time period can refer to the related content of the invention patent application with the patent application number 202210530481.1. In order to highlight the innovation of the present application, the specific description will not be repeated.

[0078] After the determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristic of the acceleration signal, the method further comprises:

[0079] determining whether the mechanical state exceeds a first health index threshold; the first health index threshold can be set according to the relationship between the mechanical state and the health degree of the battery pack during the actual operation of the vehicle.

[0080] If yes, it is determined whether to send a safety warning or a power-off signal according to the accumulated damage degree and the current mechanical state.

[0081] In this embodiment, in order to avoid the occurrence of battery pack thermal runaway and self-ignition events caused by the comprehensive influence of multiple factors, it is determined whether to send a safety warning or a power-off signal by further combining the historical accumulated damage degree after detecting that the mechanical state exceeds the first health index threshold. This can be closer to the real situation of vehicle thermal runaway, and the battery pack monitoring effectiveness is higher.

[0082] Similarly, in order to avoid the thermal runaway and self-ignition events caused by the comprehensive action of mechanical abuse and high temperature factors, in some embodiments, the method further comprises: collecting temperature information of the battery pack.

[0083] After determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristics of the acceleration signal, the method further comprises:

[0084] determining whether the mechanical state exceeds a first health index threshold; if yes, it is determined whether to send a safety warning or a power-off signal according to the temperature information and the current mechanical state.

[0085] In this embodiment, in order to avoid the occurrence of battery pack thermal runaway and self-ignition events caused by the comprehensive influence of multiple factors, it is determined whether to send a safety warning or a power-off signal by further combining the temperature factor of the battery pack after detecting that the mechanical state exceeds the first health index threshold. This can be closer to the real situation of vehicle thermal runaway, and effectively reduces the occurrence of thermal runaway and self-ignition events.

[0086] Of course, it can also be determined whether to send a safety warning or a power-off signal according to the mechanical abuse, the accumulated damage degree and the temperature, so as to reduce the occurrence of thermal runaway.

[0087] In summary, compared with the battery pack mechanical detection scheme of X-ray and probe, the battery pack mechanical state detection method provided by the embodiment of the application can effectively identify the mechanical abuse condition of the battery pack caused by strong jolt, collision damage, joint loosening and the mechanical state of the battery pack by collecting acceleration signals at different positions of the battery pack, converting the collected time domain signals into frequency component signals (amplitude), and using the relationship between the vibration characteristics of the mechanical structure and the mechanical state. This scheme has low cost, and is convenient for realizing real-time detection and judgment on vehicles, and has good real-time performance and flexibility.

[0088] Embodiment two

[0089] Please refer to Figure 2 and Figure 6 As shown in the figure, based on the same technical concept as in Embodiment One, the present application also provides a battery pack mechanical state detection device, comprising: a sampling unit 210, configured to sample the acceleration of the battery pack within a first time period at a predetermined sampling frequency, to obtain a discrete acceleration signal;

[0090] Wherein, the acceleration sensor array can be placed inside the battery pack, and the master control unit (processor) can be arranged inside the battery pack or at other positions of the vehicle. The acceleration sensor is connected to the master control unit through a wire or wireless transmission mode. The sampling unit of the master control unit samples the acceleration signal from the acceleration sensor at a predetermined sampling frequency.

[0091] A time-frequency conversion unit 220 is configured to convert the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal.

[0092] A state determination unit 230 is configured to determine the mechanical state of the battery pack within the first time period according to the amplitude-frequency characteristic of the acceleration signal.

[0093] The time-frequency conversion unit 220 is specifically configured to convert the discrete acceleration signal from the time domain to the frequency domain based on the discrete Fourier transform, and calculate the amplitude-frequency characteristic of the acceleration signal.

[0094] In some embodiments, the time-frequency conversion unit 220 is specifically configured to calculate the amplitude-frequency characteristic of the acceleration according to the acceleration amplitude-frequency characteristic calculation formula

[0095] The amplitude-frequency characteristic of the acceleration signal is calculated; wherein ACC(k) represents the amplitude corresponding to the sampling frequency at the point k, n represents the ordinal number of the sampling point within the first time period, T is the sampling point time interval, N is a physical quantity related to the computing capacity of the master control unit, and j is the imaginary unit.

[0096] The battery pack mechanical state detection device provided by the embodiments of the present application can be used to execute Figure 1 The method embodiment shown in the figure, the implementation principle and technical effects are similar to those of Embodiment One, and will not be described here in detail. Please refer to each other.

[0097] It can be understood that Figure 2The detection device shown is also applicable to performing the step flow in other embodiments in Embodiment One, for example, determining the mechanical state of the battery pack in the first time period according to comparison between the amplitude-frequency characteristic of the acceleration signal and the calibration amplitude-frequency characteristic of the battery pack. For brevity of description, reference can be made to the relevant description in Embodiment One, and the remaining embodiments will not be described herein.

[0098] For each embodiment provided by the present application, since it is basically similar to the method embodiment, the description is relatively simple, the technical solutions and technical effects are basically the same, and reference can be made to the relevant description in Embodiment One.

[0099] It should be noted that, in this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0100] For the convenience of description, the above battery pack mechanical state detection device is described in various functional units / circuits / modules respectively according to functions. Of course, the functions of the units / modules can be implemented in the same or multiple software and / or hardware when implementing the present application.

[0101] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, can include the processes of the above-mentioned embodiment methods. The storage medium can also be a magnetic disc, an optical disc, a read-only memory (ROM), a random access memory (RAM), etc.

[0102] The above description is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for detecting the mechanical state of a battery pack, characterized in that: The method comprises the steps of: Sampling the acceleration of the battery pack within a first time period according to a predetermined sampling frequency to obtain a discrete acceleration signal; Converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal; determining a mechanical state of the battery pack within a first time period based on an amplitude-frequency characteristic of the acceleration signal; Converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal includes: converting the discrete acceleration signal from the time domain to the frequency domain based on discrete Fourier transform, and calculating the amplitude-frequency characteristic of the acceleration signal; Among them, according to the acceleration amplitude-frequency characteristic calculation formula The amplitude-frequency characteristic of the acceleration signal is calculated; wherein, Indicates the sampling frequency is The corresponding amplitude at the first time period is n, n represents the ordinal number of the sampling point in the first time period, T is the time interval between the sampling points, and N is a physical quantity related to the computing power of the main control unit. Is the identifier of the imaginary part.

2. The detection method according to claim 1, wherein Determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristics of the acceleration signal includes: determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristics of the acceleration signal and the calibrated amplitude-frequency characteristics of the battery pack; or Normalizing the amplitude of the amplitude-frequency characteristic of the acceleration signal, uniformly mapping the amplitude to the interval [0, 1], and obtaining a normalized amplitude-frequency characteristic curve; the normalized amplitude-frequency characteristic curve includes a correspondence between the frequency and amplitude of the acceleration signal; Determining a mechanical state of the battery pack within a first time period by comparing the amplitude of the normalized amplitude-frequency characteristic curve with a calibrated amplitude of the battery pack at a corresponding frequency; Alternatively, the ratio of the amplitude-frequency characteristics of the acceleration signals at adjacent sampling points is calculated; The mechanical state of the battery pack in the first time period is determined by comparing the ratio of the amplitude-frequency characteristic with the calibrated ratios of the amplitude-frequency characteristics of adjacent sampling points of the battery pack.

3. The detection method according to claim 1, wherein include: Converting the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal includes: performing an integration operation on the discrete acceleration signal to obtain a discrete velocity signal; Performing discrete Fourier transform on the speed signal to generate an amplitude-frequency characteristic of the speed signal; Determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristics of the acceleration signal includes: determining the mechanical state of the battery pack in the first time period according to the amplitude-frequency characteristics of the speed signal.

4. The detection method according to claim 1, wherein After obtaining the discrete acceleration signal, the method further includes: performing filtering processing on the discrete acceleration signal to obtain a reconstructed discrete acceleration signal.

5. The detection method according to claim 1, wherein The method further comprises: After obtaining the discrete acceleration signal, the method further includes: calculating and determining the cumulative damage degree of the battery pack in the first time period based on the discrete acceleration signal; After determining the mechanical state of the battery pack within the first time period according to the amplitude-frequency characteristic of the acceleration signal, the method further includes: determining whether the mechanical state exceeds a first health index threshold; If so, a comprehensive determination is made as to whether to issue a safety warning or a power-off signal based on the degree of accumulated damage and the current state of the machine; or, The method further includes: collecting temperature information of the battery pack; After determining the mechanical state of the battery pack within the first time period according to the amplitude-frequency characteristic of the acceleration signal, the method further includes: determining whether the mechanical state exceeds a first health index threshold; If so, a comprehensive judgment is made based on the temperature information and the current mechanical state whether to issue a safety warning or a power-off signal.

6. A battery pack mechanical state detection device, characterized in that: include: a sampling unit, configured to sample the acceleration of the battery pack within a first time period at a predetermined sampling frequency to obtain a discrete acceleration signal; a time-frequency conversion unit, configured to convert the discrete acceleration signal from the time domain to the frequency domain to obtain the amplitude-frequency characteristic of the acceleration signal; a state determining unit, configured to determine a mechanical state of the battery pack within a first time period according to an amplitude-frequency characteristic of the acceleration signal; The time-frequency conversion unit is specifically used to convert the discrete acceleration signal from the time domain to the frequency domain based on discrete Fourier transform, and calculate the amplitude-frequency characteristics of the acceleration signal; wherein, according to the acceleration amplitude-frequency characteristic calculation formula The amplitude-frequency characteristic of the acceleration signal is calculated; wherein, Indicates the sampling frequency is The corresponding amplitude at the first time period is n, n represents the ordinal number of the sampling point in the first time period, T is the time interval between the sampling points, and N is a physical quantity related to the computing power of the main control unit. Is the identifier of the imaginary part.

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