METHOD FOR MONITORING THE HEALTH STATUS OF AN ELECTRIC OR HYBRID VEHICLE BATTERY USING WAVES

Abstract

The invention relates to a method for monitoring the state of an electric or hybrid vehicle battery, the battery comprising a wave emitter and a wave receiver, the method comprising the following steps: - a step of emitting a first wave by the wave emitter, the wave receiver receiving a first signal; - a step of emitting a second wave by the wave emitter, the wave receiver receiving a second signal; - a step of calculating a value by cross-correlation, for a given instant, between the first signal and the second signal; - a step of comparing, so as to determine the state of the battery, between the calculated value and a predetermined value. Figure 1

Description

Title of the invention: METHOD FOR MONITORING THE HEALTH STATUS OF AN ELECTRIC OR HYBRID VEHICLE BATTERY BY MEANS OF WAVES

[0001] The invention relates to electric vehicles, that is to say, those equipped with at least one battery for storing electrical energy intended for their propulsion. This includes vehicles with a single means of electric propulsion, as well as hybrid vehicles incorporating at least one mode of electric propulsion.

[0002] A method for monitoring the state of a vehicle battery is known from patent application DE102014218699A1. The method comprises the emission of a surface wave onto the battery by a wave emitter. A signal, corresponding to the surface wave modified by its passage through the battery, is received by a battery receiver. Subsequently, the received signal is compared to a predetermined reference signal. In this way, the method extracts information about the state of the battery.

[0003] However, in some cases the predetermined reference signal does not reflect the current state of the battery, and the comparison between the received signal and the predetermined reference signal leads to an error in interpreting the battery's state. For example, if a battery is functional but in a different state than the battery was in at the time the calibration test that generated the predetermined reference signal is performed, and if the received signal deviates sufficiently from the reference signal, the battery is incorrectly interpreted as faulty, resulting in sudden battery failures and safety hazards.

[0004] The objective of the present invention is to overcome these drawbacks and to increase the reliability and lifespan of batteries for electric or hybrid vehicles, as well as to reduce the complexity of battery monitoring systems and their costs.

[0005] To achieve this objective, the invention proposes a method for monitoring the state of an electric or hybrid vehicle battery, the battery comprising a wave emitter and a wave receiver, the method comprising the following steps: - a step of propagation of a first wave, the first wave being emitted by the wave emitter, the wave receiver receiving a first signal transmitted and / or reflected in the battery; - a propagation stage of a second wave, the second wave being emitted by the wave emitter, the wave receiver receiving a second signal transmitted and / or reflected in the battery; - a step to calculate a cross-correlation value, for a given instant, between the first signal and the second signal, using the following formula, \ _ T00 4 cttj / iù A is a first continuous function expressing the 1 (T 1 — (tT )at first signal, B* is a second continuous function expressing the second signal, the second function being conjugate and T is the given instant; - a comparison step between the calculated cross-correlation value and a first predetermined cross-correlation value, in order to determine the state of the battery.

[0006] Such a method, in addition to providing an additional means of battery monitoring, adapts to the current state of the battery, contributing to faster and more reliable detection of any potential battery fault. Furthermore, the method allows for real-time signal processing, greater accuracy in fault detection, and more precise differentiation between faults.

[0007] In its general definition, the invention provides for such a wave emitter and such a wave receiver. However, it is also conceivable to provide two, or even three, such wave emitters and such wave receivers in order to improve the detection of possible battery faults.

[0008] Advantageously, the wave emitter is configured to emit Rayleigh waves with a frequency between 1 MHz and 100 MHz.

[0009] Due to their structure, Rayleigh waves propagate on the surface of the battery in such a way as to detect more accurately surface variations of the battery and defects on the battery.

[0010] Advantageously, the wave emitter is configured to emit Lamb waves, inside the battery, having a frequency between 100 kHz and 1 MHz.

[0011] Due to their structure, Lamb waves propagate within the battery, particularly through thin plates and layered structures, for example, lithium-ion battery materials. In this way, internal variations in the materials, such as delaminations, internal cracks, and density changes caused by chemical degradation within the battery, are detected more accurately.

[0012] Advantageously, the method includes a step of emitting a signal alerting of a fault, when the calculated value is less than a second predetermined distance value.

[0013] Advantageously, the method includes a step of acquiring the relative position of the wave emitter with respect to the wave receiver by a position sensor when a fault is detected.

[0014] This makes it possible to determine the location of a possible defect by knowing the relative position of the wave emitter with respect to the wave receiver.

[0015] Advantageously, the process comprises the following steps: - a step of measuring a current intensity value of the battery; - an activation step of the first wave emission step by the wave emitter when the measured current intensity value is greater than a predetermined current intensity value.

[0016] This allows a first measurement to be taken automatically, for example when the vehicle starts.

[0017] The invention also relates to a computer program comprising program code instructions for executing the steps of a process as defined above, when the program is running on a computer.

[0018] The invention also relates to an assembly comprising an electric or hybrid vehicle battery, a wave transmitter, a wave receiver and an electronic control unit, the control unit comprising the means for acquisition, processing by software instructions stored in a memory as well as the control means required for the implementation of a computer program as defined above.

[0019] In practice, the electronic control unit is a battery management system, also called a BMS. Battery management systems are already commonly used in hybrid and electric vehicles. The battery management system includes a software instruction processing means, such as a digital signal processor configured to rapidly process digital operations on signals. Furthermore, the control means is, in practice, a user interface.

[0020] The invention further relates to an electric or hybrid vehicle comprising an assembly as defined above.

[0021] The invention will be further detailed by describing a non-limiting embodiment, and based on the accompanying figures in which: - [Fig.l] schematically illustrates an assembly according to one embodiment of the present invention; - [Fig.2] illustrates a flowchart representing the steps of a method for monitoring the state of a battery according to an embodiment of the present invention.

[0022] As illustrated [Fig. 1], according to one embodiment of the invention, a battery 10 comprising a wave emitter 20 is shown. In practice, the battery 10 is, for example, a lithium-ion battery. Furthermore, a wave receiver 30 is configured to receive the waves reflected and / or transmitted by the battery 10.

[0023] It is planned, for example, to integrate the wave emitter 20 and the wave receiver 30 respectively into a first piezoelectric cell and a second piezoelectric cell.

[0024] Alternatively, the wave emitter 20 and the wave receiver 30 are ultrasonic cells.

[0025] Figure 2 illustrates a flowchart of a method for monitoring the state of battery 10, its steps being described below.

[0026] In a propagation step of a first wave El, the first wave is emitted by the wave emitter 20, the wave receiver 30 receiving a first signal transmitted and / or reflected in the battery 10.

[0027] When the transmitter is configured to emit Rayleigh waves, the transmitter is advantageously located on the surface of the battery 10. Rayleigh waves typically have a frequency between 1 MHz and 100 MHz.

[0028] When the transmitter is configured to emit Lamb waves, the transmitter is advantageously located inside the battery 10. Lamb waves typically have a frequency between 100 kHz and 1 MHz.

[0029] In a propagation step of a second wave E2, the second wave is emitted by the wave emitter 20, the wave receiver 30 receiving a second signal transmitted and / or reflected in the battery 10.

[0030]

[0031]

[0032] In a calculation step E3, a cross-correlation value, for a given instant, between the first signal and the second signal, is calculated using the following formula, "...L", where A is a first continuous function expressing the first signal in time form, B* is a second continuous function expressing the second signal in time form, the second function being conjugate and T is the given instant. We can also consider calculating a cross-correlation value, for a given frequency, between the first signal and the second signal, calculated using the following formula: F( f î) - J +°°Aœ)df™1 is a First continuous function expressing the first signal in frequency form, B* is a second continuous function expressing the second signal in frequency form, the second function being conjugate and w is the given frequency. In a comparison step E4, the calculated value and a first predetermined cross-correlation value are compared in order to determine the health status of battery 10.

[0033] Generally, the first predetermined cross-correlation value is chosen such that the greater the difference between the first predetermined cross-correlation value and the calculated value, the more the battery 10 is considered to have a significant number of defects, for example, by choosing a first predetermined value of zero. Thus, such a comparison indicates the health status of the battery 10.

[0034] The method advantageously includes a step of emitting a signal alerting to a fault, when the calculated cross correlation value is less than a second predetermined value.

[0035] The method further advantageously includes a step of acquiring the relative position of the wave emitter 20 with respect to the wave receiver 30 by a position sensor when a fault is detected.

[0036] The process advantageously comprises: - a step of measuring a current intensity value of the battery 10; - an activation step of the emission step of the first wave by the wave emitter 20 when the measured current intensity value is greater than a predetermined current intensity value.

Claims

Demands

1. Method for monitoring the health status of a battery (10) of an electric or hybrid vehicle, the battery (10) comprising a wave emitter (20), the method comprising the following steps: - a step of propagating a first wave (E1), the first wave being emitted by the wave emitter (20), a wave receiver (30) receiving a first signal transmitted and / or reflected in the battery (10); - a step of propagating a second wave (E2), the second wave being emitted by the wave emitter (20), the wave receiver (30) receiving a second signal transmitted and / or reflected in the battery (10);- a calculation step (E3) of a cross-correlation value, for a given instant, between the first signal and the second signal, by the following formula, pT( t) B* (t T)dt™ is a first continuous function expressing the first signal in time form, B* is a second continuous function expressing the second signal in time form, the second function being conjugate and T is the given instant; - a comparison step (E4) between the calculated cross-correlation value and a first predetermined cross-correlation value, so as to determine the health status of the battery (10).;

2. A method according to claim 1, characterized in that the wave emitter (20) is configured to emit Rayleigh waves having a frequency between 1 MHz and 100 MHz.

3. A method according to claim 1, characterized in that the wave emitter (20) is configured to emit Lamb waves, inside the battery (10), having a frequency between 100 kHz and 1 MHz.

4. A method according to any one of claims 1 to 3, characterized in that it comprises a step of emitting a signal alerting of a fault, when the calculated cross-correlation value is less than a second predetermined cross-correlation value.

5. A method according to claim 4, characterized in that it comprises a step of acquiring the relative position of the wave emitter (20) relative to the wave receiver (30) by a position sensor when a fault is detected.

6. A method according to any one of claims 1 to 5, characterized in that the method comprises the following steps: - a step of measuring a current intensity value of the battery (10); - a step of activating the first wave emission step by the wave emitter (20) when the measured current intensity value is greater than a predetermined current intensity value.

7. Computer program comprising program code instructions for carrying out the steps of a process according to any one of claims 1 to 6, when the program is running on a computer.

8. Assembly comprising an electric or hybrid vehicle battery (10), a wave transmitter (20), a wave receiver (30) and an electronic control unit, the control unit comprising the means for acquisition, processing (40) by software instructions stored in memory as well as the control means (50) required for the implementation of a computer program according to claim 7.

9. Electric or hybrid vehicle comprising an assembly according to claim 8.

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