Diagnostic method for a heating system of an electric drive battery of an electric or hybrid vehicle.

Abstract

Diagnostic method for a heating system of an electric drive battery of an electric or hybrid vehicle. Diagnostic method for a heating system (1) of an electric drive battery (2) of an electric or hybrid vehicle (100), the heating system (1) comprising a first switch controlled (4) by a control unit (3), the diagnostic method comprising the following steps: - determination of a value for the setpoint duty cycle of the first controlled switch (4), - determination, by another method, of a value for the duty cycle actually applied by the first controlled switch, - comparison of the value for the setpoint duty cycle of the first controlled switch and the value for the duty cycle actually applied by the first controlled switch, - in case of discrepancy, signaling of the discrepancy and / or deactivation of the heating device (9). Figure 1.

Description

Title of the invention: Method for diagnosing a heating system of an electric drive battery of an electric or hybrid vehicle.

[0001] The invention relates to a method for diagnosing a heating system of an electric drive battery in an electric or hybrid vehicle. The invention also relates to a diagnostic device for a heating system of an electric drive battery in an electric or hybrid vehicle. The invention further relates to an automotive heating system comprising such a diagnostic device. The invention also relates to a motor vehicle comprising such a diagnostic device and / or such a heating system. The invention further relates to a computer program implementing the aforementioned method. Finally, the invention relates to a recording medium on which such a program is recorded.

[0002] In battery-based energy storage systems, maintaining a certain level of performance over a wide temperature range is essential. However, the electrochemical composition of battery cells does not allow for this absolute performance maintenance. A phenomenon is particularly noticeable at low temperatures, where chemical reactions slow down. Therefore, and in order to promote cell durability, the battery's charging or discharging power is limited by a control unit (BMS for Battery Management System). This control unit, equipped with a software program, then transmits the maximum power the battery can handle over a multiplexed network (CAN: control area network) to a supervisory control unit of an electrical system (HEVC: hybrid and electric vehicle controller), which may be insufficient to meet the vehicle driver's needs.

[0003] To solve this problem, one technical solution consists of equipping the drive battery of the electric or hybrid vehicle (plug-in or not) with a heating device, in particular a heating mat thermally connected to the battery. This heating device is electrically powered by the drive battery itself or by another battery and is equipped, for example, with a resistive component that increases the temperature of the battery coolant by Joule heating.

[0004] The heating power is determined by the BMS computer according to the operating conditions identified by the supervisor computer, which include, for example: - cold load, - cold driving - Pre-conditioning the vehicle in anticipation of starting a taxiing mission...

[0005] This heating system, while efficient in meeting customer expectations, is not without risk. The main danger is overheating of the drive battery, which can occur particularly in the event of a control system failure. Indeed, a heating element continuously supplied by the battery would continue to raise the temperature of the cells via the coolant, which could damage them or even cause a fire in the battery.

[0006] The object of the invention is to provide a method for diagnosing a heating system and a diagnostic device that improves upon devices and methods known in the prior art. In particular, the invention provides simple and robust means for detecting a risk of overheating of a vehicle's drive battery caused by a faulty heating system.

[0007] According to the invention, a method allows for the diagnosis of a heating system of an electric drive battery of an electric or hybrid vehicle, the heating system comprising: - a heating device, in particular an electric resistance heating device, - a power supply battery for the heating device, - a control unit for the electrical power supplying the heating device, and - a first switch controlled by the computer to supply the pulse width modulation heating device from the power supply battery and applying a duty cycle setpoint control of the first controlled switch. The diagnostic process includes, in particular periodically or from time to time, the following steps: - determination, in particular by consulting the computer, at a given moment, of a value for the duty cycle of the control setpoint of the first controlled switch, - determination, by another method, in particular by measurement and / or calculation and / or estimation, at that given instant, of a value of the duty cycle actually applied by the first controlled switch, - comparison of the value of the setpoint duty cycle of the first controlled switch and the value of the duty cycle actually applied by the first controlled switch, - in case of discrepancy between the value of the setpoint duty cycle of the first controlled switch and the value of the actual duty cycle applied by the first controlled switch, signaling of the discrepancy and / or deactivation of the heating device.

[0008] The deactivation step may include opening a second controlled switch.

[0009] The signaling step may include a display on an interface and / or the emission of an acoustic signal.

[0010] Preferably, there is a discrepancy when the value of the control setpoint duty cycle of the first controlled switch and the value of the duty cycle actually applied by the first controlled switch differ by more than a predefined adjustable threshold, for example typically around 10% to 15% of the value of the control setpoint duty cycle of the first controlled switch.

[0011] The step of determining a value for the duty cycle actually applied by the first controlled switch may include: - a measurement of the voltage across the terminals of the heating device, - a measurement of the voltage across the terminals of the power supply battery, and - a calculation of the ratio of the two voltages.

[0012] The ratio of the two voltages can be considered as equal to the duty cycle actually applied by the first controlled switch.

[0013] The step of determining a value for the duty cycle actually applied by the first controlled switch may include: - an analysis of the voltage changes across the terminals of the first controlled switch, - a determination of the first duration of the phases in which the voltage is at a first value and a determination of the second duration of the phases in which the voltage is at a second value greater than the first value, and - a calculation of the ratio of the first duration to the sum of the first and second durations.

[0014] The ratio of durations can be considered as equal to the duty cycle actually applied by the first controlled switch.

[0015] The invention also relates to a diagnostic device for a heating system of an electric drive battery in an electric or hybrid vehicle. The diagnostic device may include hardware and / or software components implementing the method defined above, in particular hardware and / or software components designed to implement the method defined above.

[0016] The invention also relates to a heating system comprising a diagnostic device defined above.

[0017] The invention also relates to a motor vehicle comprising a heating system as defined above and / or a diagnostic device as defined above.

[0018] According to the invention, a computer program product comprises program code instructions recorded on a computer-readable medium to implement the steps of the process defined above when said program runs on a computer

[0019] According to the invention, a computer program product downloadable from a communication network and / or recorded on a data medium readable by a computer and / or executable by a computer, is characterized in that it includes instructions which, when the program is executed by the computer, lead the latter to implement the process defined above.

[0020] According to the invention, a computer-readable data recording medium on which a computer program is recorded includes program code instructions for implementing the method defined above.

[0021] According to the invention, a computer-readable recording medium includes instructions which, when executed by a computer, lead the computer to implement the process defined above.

[0022] The invention also relates to a signal from a data carrier, carrying the computer program product defined previously.

[0023] The attached drawing represents, by way of example, an embodiment of a motor vehicle according to the invention and an execution method of a diagnostic process according to the invention.

[0024] Fig. 1 is a schematic representation of an embodiment of a motor vehicle according to the invention.

[0025] The [Fig.2] is a flowchart of an execution method of a diagnostic process according to the invention.

[0026] An embodiment of a motor vehicle 1 according to the invention is described below with reference to [Fig. 1].

[0027] The motor vehicle 100 is, for example, a passenger car or a commercial vehicle. However, the vehicle may be of any type. The motor vehicle may have an electric motor or a hybrid motor (plug-in or not). Consequently, the vehicle includes an electric drive battery 2.

[0028] The motor vehicle 100 includes a heating system 1 for the drive battery 2.

[0029] The vehicle may also include a user interface 200 enabling in particular the emission of visual and / or audible and / or acoustic signals to a user.

[0030] The heating system 1 comprises: - a heating device 9, in particular an electric resistance heating device, such as a resistance-based heating mat, - a power supply battery 2 for the heating device, preferably consisting of the drive battery 2 itself, but which may also consist in whole or in part of another auxiliary battery, - a control unit 3 for managing the electrical power supplying the heating device 9, and - a first switch controlled 4 by the computer 3 to power the heating device 9 in pulse width modulation (PWM) by applying a duty cycle to the first controlled switch 4 from the power supply battery 2. Due to thermal inertia, slow switching can be allowed in the range [1 Hz; 100 Hz].

[0031] As shown in [Fig.1], in one embodiment, the heating system 1 mainly comprises a series arrangement of: - the battery 2, - the controlled switch 4, and - the heating device 9.

[0032] The controlled switch 4 is driven by the control unit 3. The controlled switch is, for example, a power transistor 4. The control unit 3 uses operating and environmental data from the battery 2 to determine the heating power required to warm the battery 2. Based on this, the control unit defines a control signal for the controlled switch 4, enabling the heating device 9 to be electrically powered so that it delivers the necessary heating power to warm the battery 2. As previously mentioned, the control of the controlled switch 4 is performed using pulse-width modulation to modulate the heating power. The duty cycle of such control determines the heating power.

[0033] The control device 9 is therefore electrically powered via alternating phases of switching the activation and deactivation (ON / OFF) states of the controlled switch. A transistor-type controlled switch can be controlled via a voltage applied between a gate and an emitter, which creates a conduction channel between a collector and an emitter, allowing electrons to pass through and thus closing the circuit (battery, heating device).

[0034] Preferably, the heating system 1 includes a capacitor 7 connected in parallel with the heating device 9. This capacitor 7 allows the smoothing of the fluctuations of the voltage Uh across the terminals of the heating device 9 during the switching of the controlled switch 4.

[0035] Preferably, the heating system 1 includes a coil 6 connected in series with the heating device 9. This coil 6 makes it possible to smooth out the fluctuations in the current passing through the heating device 9 and capacitor 7 assembly during the switching of the controlled switch 4.

[0036] Preferably, the heating system 1 includes a diode 5 to prevent current reversal in the heating device 9. This diode 5 is connected between the controlled switch and ground, with the anode connected to ground and the cathode connected to the controlled switch 4.

[0037] Preferably, the heating system 1 includes a controlled switch 8 for disconnecting the heating device 9 from its power supply in the event of a risk or malfunction being detected. The controlled switch 8 is preferably also controlled by the control unit 3. Such a controlled switch 8 is, for example, positioned in series between the heating device 9 and the controlled switch 4, particularly as close as possible to the heating device 9. In any case, the controlled switch 8 can be placed anywhere it can deactivate the heating device 9 even if the controlled switch 4 is held in a closed state, particularly in the event of a malfunction.

[0038] The heating system 1 further includes a diagnostic device 30. The diagnostic device 30 advantageously includes, for example, elements for measuring voltage at different points in the heating system.

[0039] For example, in a first embodiment, the diagnostic device 30 comprises: - a voltage measurement element 10 across the terminals of the heating device 9, and - a voltage measurement element 12, 13 across the terminals of the battery 2.

[0040] For example, in a second embodiment, the diagnostic device 30 includes an element 13, 14 for measuring the voltage across the terminals of the controlled switch 4.

[0041] The diagnostic device 30 further includes an analysis module 31, for example contained in the computer 3, allowing the measured voltages to be analyzed using the elements mentioned previously.

[0042] The voltage measurement elements may include or consist of wires connecting points in the electrical circuit to terminals of the computer 3, in particular input terminals of the measurement element.

[0043] The diagnostic device 30 preferably comprises all the elements enabling the control or implementation of the diagnostic process that is the subject of the invention. In particular, the elements may be of the hardware type or of the software type. Preferably, the diagnostic process is implemented in real time. By "process implemented in real time", we mean here that the process allows a diagnosis to be made from state data of the heating control system that is no more than a few minutes or a few seconds old, for example less than one second.

[0044] An embodiment of a method for operating a heating system as previously mentioned is described below with reference to [Fig. 2]. Such an operating method can also be viewed as a method for operating a motor vehicle.

[0045] In such an execution mode, after a possible update step S100, one or more iterations of the steps described below are implemented.

[0046] In a first step SI 10, the current Irqt to flow in the controlled switch 4 to electrically supply the heating device 9 is determined. This determination is ensured for example by the computer 3 which takes into account the operating conditions of the drive battery 2 and deduces a need for heating or thermal input, and consequently the current Irqt necessary for this thermal input.

[0047] In a second step S120, a duty cycle aref of the control setpoint of the controlled switch 4 is calculated. This calculation establishes the duty cycle aref necessary to obtain the current Irqt determined in the first step. This calculation is, for example, implemented by the computer 3. Considering the maximum supply current Imax of the heating device 9 when the drive battery 2 is directly connected to the heating device 9, the following relationship is obtained: aref = Irqt / Imax As seen previously, this duty cycle aref represents a time ratio of the durations of the conduction and non-conduction phases of the controlled switch 4. The duty cycle aref is 1 when the controlled switch 4 is permanently closed and is 0 when the controlled switch 4 is permanently open.

[0048] This value of the duty cycle of the control setpoint aref of the first controlled switch 4 can be directly used in the diagnostic procedure described below. Thus, in the diagnostic procedure, a determination at a given time of a value of the duty cycle of the control setpoint of the first controlled switch 4 can be carried out by using the aref value calculated during the last step S120, i.e. by consulting the computer 3.

[0049] In a third step S130, in particular the computer 3, controls the controlled switch 4 with the duty cycle determined or calculated in the second step 120.

[0050] In a fourth step S10, a diagnostic procedure is implemented which is detailed below.

[0051] Finally, at the end of step S10, we loop back to step S110.

[0052] The implementation of step S10 can be carried out at each iteration of the steps S110, S120, S130. Alternatively, step S10 can be implemented only during certain iterations of steps S10, S120, and S130. In any case, this implementation of step S10 is carried out, for example: - periodically, that is to say at a given time interval or period, or - from time to time, in particular at the request of a user or at the request of the computer 3 or at the request of a third-party system embedded in the vehicle 100.

[0053] A method of executing step S10 of diagnosing the operation of the heating system 1 is described in more detail below. The diagnosis focuses more specifically on the operation of the controlled switch 4, in particular on the correct implementation of the duty cycle controlled by the computer 3.

[0054] In a first substep S140, the voltage Uh across the terminals of the heating device 9 is measured. This measurement is, for example, performed by the control unit 3 via measuring elements 10 and 11. The voltage across the battery terminals Ubatt is also measured. This measurement is, for example, performed by the control unit 3 via measuring elements 12 and 13.

[0055] In a second substep S150, an effective duty cycle of the cores (or the one actually applied by the controlled switch 4) is calculated from the measurements of substep S140. This calculation is performed, for example, by the computer 3, in particular by the analysis module 31, according to the following formula: cores = Uh / Ubatt Thus, in this step S150, we determine, by another method, in particular by measurement and / or calculation, at a given instant, a value of the duty cycle ratio actually applied by the first controlled switch 4.

[0056] In a third substep S160, an absolute value of the difference between the effective duty cycle and the control setpoint duty cycle is calculated and compared to a threshold e. As an alternative to calculating an absolute value of the difference and comparing it to a threshold, a percentage error between the effective duty cycle and the control setpoint duty cycle can also be calculated and compared to an error threshold. If the absolute value of the difference or the error is less than a threshold, the process loops back to step S10. Conversely, if the absolute value of the difference or the error is greater than or equal to the threshold, the process proceeds to step S170. These calculations and comparisons are preferably performed by the computer 3, in particular by the analysis module 31. Thus, in substep S160, the value of the duty cycle is compared the setpoint of the first controlled switch 4 and the value of the duty cycle actually applied by the first controlled switch 4.

[0057] In a fourth substep S170, the discrepancy between the actual duty cycle and the control setpoint duty cycle is signaled to a user via an interface 200, by a visual or audible signal, or to a third-party system of the motor vehicle and / or the heating device 9 is deactivated. To perform this deactivation, the controlled switch 8 can be opened. The signaling can be controlled by the control unit 3. The deactivation can also be controlled by the control unit 3. Thus, in substep S170, in the event of a discrepancy between the value of the control setpoint duty cycle of the first controlled switch 4 and the value of the duty cycle actually applied by the first controlled switch 4, the discrepancy is signaled and / or the heating device 9 is deactivated.

[0058] Thus, more generally, the following steps are implemented in the diagnostic procedure: - determination, in particular by consulting the calculator 3, at a given moment, of a value for the duty cycle of the control setpoint of the first controlled switch 4, - determination, by another method, in particular by measurement and / or calculation, at that given instant, of a value of the duty cycle actually applied by the first controlled switch 4, - comparison of the value of the setpoint duty cycle of the first controlled switch 4 and the value of the duty cycle actually applied by the first controlled switch 4, - in case of discrepancy between the value of the duty cycle setpoint of the first controlled switch 4 and the value of the duty cycle actually applied by the first controlled switch 4, signaling of the discrepancy and / or deactivation of the heating device 9.

[0059] Regardless of the embodiment or variant, for example, a discrepancy is considered to exist when: - the value of the duty cycle setpoint of the first controlled switch, and - the value of the duty cycle actually applied by the first controlled switch, differ by more than a predefined adjustable error threshold, typically around 10% to 15% of the control setpoint duty cycle value.

[0060] In the execution mode described above, the step of determining a value for the duty cycle actually applied by the first controlled switch 4 comprises: - a measurement of the voltage across the terminals of the heating device 9, - a measurement of the voltage across the terminals of the power supply battery 2, and - a calculation of the ratio of the two voltages. Furthermore, the ratio of the two voltages is considered to be equal to the duty cycle actually applied by the first controlled switch.

[0061] However, alternatively, another determination is possible. For example, the step of determining a value for the duty cycle actually applied by the first controlled switch may include: - an analysis of the voltage changes across the terminals of the first controlled switch 4, - a determination of the first duration of the phases in which the voltage is at a first value and a determination of the second duration of the phases in which the voltage is at a second value greater than the first value, and - a calculation of the ratio of the first duration to the sum of the first and second durations. Furthermore, we can then consider that the ratio of the durations is equal to the duty cycle actually applied by the first controlled switch.

[0062] Thanks to the solutions described above, a diagnosis of the pulse width modulation control of the heating device 9 makes it possible to locate a malfunction at the level of the electrical control part and the replacement of the controlled switch 4 can therefore be considered before that of the heating device 9, which greatly reduces after-sales service costs.

[0063] Another advantage is the elimination of the need for additional sensors. Indeed, all the parameters used in the diagnostic procedure are already available in motor vehicles. This also reduces the cost, physical size, and algorithmic complexity that would be incurred by the use of additional sensors.

[0064] Finally, another advantage is the simplicity of software implementation. Only a few arithmetic and logical operations are required, resulting in low consumption of computing resources.

[0065] In the embodiment described above, the heating of the drive battery 2 is ensured by itself by powering the heating device 9. Alternatively, the heating of the drive battery 2 can be ensured by an auxiliary battery providing the power supply to the heating device 9.

[0066] In this document, the notion of "given instant" should not be interpreted very strictly. There may be slight time delays between steps S130 and S140, for example a few milliseconds, or even a few tens of milliseconds.

Claims

Demands

1. A method for diagnosing a heating system (1) of an electric drive battery (2) of an electric or hybrid vehicle (100), the heating system (1) comprising: - a heating device (9), in particular an electric resistance heating device, - a power supply battery (2) for the heating device, - a control unit (3) for controlling the electrical power supply to the heating device (9), and - a first switch controlled (4) by the control unit (3) to supply the heating device (9) by pulse-width modulation from the power supply battery (2) and by applying a duty cycle setpoint for the control of the first controlled switch (4), the diagnostic method comprising, in particular periodically or from time to time, the following steps: - determining, in particular by consulting the control unit (3), at a given time,- a value of the duty cycle setpoint of the first controlled switch (4), - determination, by another method, in particular by measurement and / or calculation and / or estimation, at that given instant, of a value of the duty cycle actually applied by the first controlled switch, - comparison of the value of the duty cycle setpoint of the first controlled switch and the value of the duty cycle actually applied by the first controlled switch, - in the event of a discrepancy between the value of the duty cycle setpoint of the first controlled switch and the value of the duty cycle actually applied by the first controlled switch (4), signaling of the discrepancy and / or deactivation of the heating device (9).

2. Diagnostic method according to claim 1, characterized in that the deactivation step includes the opening of a second controlled switch (8).

3. Diagnostic method according to claim 1 or 2, characterized in that the signaling step includes a display on an interface (200) and / or the emission of an acoustic signal.

4. Diagnostic method according to any one of claims 1 to 3, characterized in that there is a discrepancy when the value of the control setpoint duty cycle of the first controlled switch and the value of the duty cycle actually applied by the first controlled switch differ by more than a predefined adjustable threshold, for example typically around 10% to 15% of the value of the control setpoint duty cycle of the first controlled switch.

5. Diagnostic method according to any one of the preceding claims, characterized in that the step of determining a value of the duty cycle actually applied by the first controlled switch (4) comprises: - a measurement of the voltage across the terminals of the heating device (9), - a measurement of the voltage across the terminals of the power supply battery (2), and - a calculation of the ratio of the two voltages.

6. Diagnostic method according to the preceding claim, characterized in that the ratio of the two voltages is considered to be equal to the duty cycle actually applied by the first controlled switch (4).

7. Diagnostic method according to any one of the preceding claims, characterized in that the step of determining a value of the duty cycle actually applied by the first controlled switch comprises: - an analysis of the evolutions of the voltage across the terminals of the first controlled switch (4), - a determination of the first duration of the phases in which the voltage is at a first value and a determination of the second duration of the phases in which the voltage is at a second value greater than the first value, and - a calculation of the ratio of the first duration to the sum of the first and second durations.

8. Diagnostic method according to the preceding claim, characterized in that the ratio of the durations is considered to be equal to duty cycle actually applied by the first controlled switch.

9. Diagnostic device (30) for a heating system (1) of an electric drive battery (2) of an electric or hybrid vehicle (100), the diagnostic device (30) comprising hardware (3, 31, 10, 11, 12, 13, 14) and / or software elements implementing the method according to any one of claims 1 to 8, in particular hardware (3, 31, 10, 11, 12, 13, 14) and / or software elements designed to implement the method according to any one of claims 1 to 8.

10. Heating system (1) comprising a diagnostic device (30) according to the preceding claim.

11. Motor vehicle (100) comprising a heating system (1) according to the preceding claim and / or a diagnostic device (30) according to claim 9.

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