METHOD FOR MONITORING THE DRIVE TORQUE OF AN ELECTRIC TRACTOR

Description

[0001] The present invention claims priority from French application No. 2204959 filed on 24.05.2022.

[0002] The field of the invention relates to a method for monitoring the motor torque of an electric traction machine of an electrified vehicle.

[0003] In the automotive industry, vehicle manufacturers integrate monitoring functions to ensure the proper operation of the electric traction motor. Specifically, one of these functions involves continuously monitoring the torque produced by the electric motor's rotor by measuring it and comparing it to the specified torque target. If a significant deviation is detected, an alert is triggered, and the electric motor is reconfigured into a degraded mode.

[0004] The prior art document FR2904108A1 describes a low-cost device for determining the operating characteristics of an electric motor. It allows, in particular, the determination of the motor's direction of rotation and variations in operating speed or torque. This device has a beneficial application in vehicle window motors for detecting when the window is pinched by an obstacle.

[0005] Regarding the electric traction machine, in an effort to optimize its components and efficiency, extend its lifespan, and reduce its cost, the focus was on optimizing the electric machine with respect to torque accuracy requirements in the forward direction of the vehicle compared to the reverse direction. Consequently, the torque accuracy achieved by the traction machine's rotor in forward motion is greater than that achieved in reverse. Documents WO 2021 / 141053 A1, US11040673B2, DE112020001169T5, and FR3043604A1 describe similar methods for monitoring the torque of an electric vehicle motor.

[0006] There is a need to improve the torque monitoring function of an electric traction machine to ensure optimal performance and increase the level of torque control requirements. A further objective of the invention is to improve fault diagnostics and prevent unnecessary alerts and reconfigurations of the electric traction machine in a motor vehicle. Another objective is to provide a lower-cost electric machine while simultaneously improving operational safety.

[0007] More specifically, the invention relates to a method for monitoring the motor torque of an electric traction machine in an electrified vehicle, comprising determining the torque difference between a torque setpoint transmitted to the electric machine and the torque produced by the electric machine's rotor, and determining whether the rotor rotates in the forward or reverse direction of the vehicle. According to the invention, the method includes comparing the torque difference to a first threshold when the rotor rotates in the forward direction and comparing the torque difference to a second threshold when the rotor rotates in the reverse direction, and activating a reconfiguration of the electric machine based on the result of the comparison.The second threshold has a higher torque value than the first threshold, which reduces the design requirements for reverse and lowers the cost of the electric machine.

[0008] According to one variant, the process also includes ordering a first reconfiguration of the electric machine if the deviation is greater than the first threshold in the forward direction for at least a first period.

[0009] According to one variant, the first duration is equal to 450 milliseconds.

[0010] According to a variant of the first reconfiguration, the process involves storing an initial fault code in a first state, signaling a fault, and stopping the electrical machine. The first state is a so-called permanent state.

[0011] According to one variant, the process also includes ordering a second reconfiguration of the electric machine if the deviation is greater than the second threshold in the reverse direction for at least a second duration.

[0012] According to one variant, the second duration is equal to 100 milliseconds.

[0013] According to a variant of the second reconfiguration, the process involves storing a second fault code in the first state, signaling a fault, and stopping the electrical machine. The first state is a so-called permanent state.

[0014] According to one variant, the process further includes, in the event of activation of the first or second reconfiguration and detection of a vehicle shutdown command, the command to re-establish the operation of the electrical machine, the cessation of the signaling, and the storage of the first or second fault code in a second state. The second state is a so-called transient state.

[0015] According to one variant, the first threshold is equal to 50 Nm and the second threshold is equal to 60 Nm

[0016] An electrified vehicle is also envisaged comprising an electric traction machine and a control unit for the electric traction machine in which the control unit is configured to implement the monitoring method according to any one of the preceding embodiments.

[0017] We also envision a computer program product comprising instructions which, when the program is executed by a computer of the electric traction machine, lead the latter to implement any one of the embodiments of the method of monitoring the motor torque according to the invention.

[0018] Using two torque monitoring thresholds with distinct values, differentiating between forward and reverse operation of the electric machine, allows for optimization of the electric machine design in the direction of rotation corresponding to the forward movement of the VHL. This monitoring method reduces the cost of the electric machine due to less demanding design requirements in the reverse direction.

[0019] Other features and advantages of the present invention will become more apparent upon reading the following detailed description, which includes embodiments of the invention given by way of non-limiting examples and illustrated by the accompanying drawings, in which: [ Fig.1 [ ] schematically represents a powertrain of an electrified motor vehicle configured to implement the method according to the invention. ] Fig.2 ] represents a preferred embodiment of the monitoring method according to the invention.

[0020] The invention applies to electrified vehicles, in particular all-electric motor vehicles and hybrid vehicles. More specifically, the invention relates to a method for monitoring the torque of the electric traction motor of an electrified vehicle.

[0021] In figure 1 , an example of an electrified vehicle powertrain 1 intended to implement the invention has been schematically represented. The powertrain 1 comprises a control unit 16, designated by the acronym eVCU for "Electric Vehicle Control Unit" in English, supervisor or the acronym ECU for "Electronic Control Unit", an electric traction machine 10 powered by a traction battery system 14, and a traction chain of a motor torque CR transmitted by the rotor of the electric machine 10 to the wheels of the vehicle.

[0022] Typically, for a 100% electric drive vehicle, the drivetrain includes a reduction gear 11 mechanically connected to the rotor and a mechanical transmission 12 of the motor torque to each drive wheel of the vehicle. Other transmission architectures are conceivable for the monitoring method according to the invention, particularly for hybrid architectures.

[0023] Furthermore, it is planned, but not shown on the figure 1 , an on-board charger for the battery system 14, a charging socket box intended to connect the vehicle to an external power source, for example a domestic socket, a fixed domestic station (commonly called a "Wallbox" in English), a charging station at a motorway service station designed for this purpose, or a mobile charging station.

[0024] The traction battery system 14 is intended to power the traction machine 10 of the vehicle. It includes electrical energy storage means 142. In the context of the invention, the voltage of the traction battery system 14 may be 48V or higher, 400 volts according to the preferred embodiment (between 350 volts and 450 volts), 800 volts (between 700 volts and 900 volts), or even higher. The battery 142 comprises energy storage elements including electrochemical cells, for example, lithium-ion cells.

[0025] The battery system 14 also includes a management computer 141 (designated by the acronym BMS for "Battery Management System" or TBCU for "Traction Battery Control Unit") adapted to supervise the specific parameters of the battery 142 in cooperation with current and voltage sensors, such as the state of charge SOC ("State of Charge"), the open circuit voltage OCV ("Open Circuit Voltage") expressed in Volts, the charging current expressed in Amperes, the state of health SOH ("State of Health"), the voltage or the temperature of the battery 142.

[0026] Furthermore, the supervisory control unit 16 monitors the electric traction machine 10 and the traction battery system 14, among other things. The control unit 16 has the function of centralizing the data collected from the vehicle and transmitting it to other vehicle computers via a data communication bus 15, for example, of the CAN type.

[0027] More specifically, the supervisory computer 16 continuously determines the torque setpoint to be applied to the wheels and the DC torque setpoint to be applied by the electric machine 10 at the rotor output. For example, the DC torque setpoint can be determined from the wheel torque setpoint and the gear ratio of the gearbox 11. The DC torque setpoint to be applied is transmitted via the communication bus 15 to the traction electric machine 10.

[0028] The computer 16 includes, stored in memory, a map 161 delivering a torque setpoint value to the wheel as a function of the following parameters 162: the direction of travel of the vehicle AV / AR from a sensor on the gear lever, the depressment of the accelerator and brake pedals ENF and the speed of the vehicle VIT, received for example from a trajectory control computer.

[0029] More specifically, the traction electric machine 10 includes a microprocessor-based, memory-equipped integrated circuit computer 13, configured for controlling the electric machine 10, designated by the term MCU for "Machine Control Unit." In this example, the traction electric machine 10 is a permanent magnet synchronous machine. The computer 13 generates and transmits a current command to an electrical converter. The current command is determined from a mapping stored in the computer 13's memory, which provides the necessary amount of current that the converter must draw from the high-voltage electrical grid in response to the requested torque command, based on the high-voltage grid voltage and the temperature of the traction electric machine 10's stator.This converter takes current from the voltage network supplied by the battery system 14 to power the poles of the stator of the electric traction machine 10.

[0030] In particular, the computer 13 includes a monitoring module 131 whose function is to implement the motor torque monitoring method according to the invention. For its operation, the module 131 continuously determines the achieved torque CR during its operation. As is known per se, the achieved torque CR is determined from the mechanical power Pm supplied to the transmission chain by the rotor according to the relation Pm = Cr * W, which power Pm is calculated from the electrical power Pe at the input of the electric machine 10 and a predetermined efficiency coefficient Rd of the electric machine 10. And, W is the instantaneous rotational speed of the rotor, expressed for example in rpm.

[0031] In particular, the efficiency coefficient Rd is measured on the test bench for each speed step, torque step, voltage step, supply current step, and stator temperature step. A map of the Rd values ​​is learned on the test bench and stored in the memory of the computer 13 so that the latter can determine the Rd coefficient at any given time during the operation of the electrical machine 10.

[0032] In addition, the computer 13 is capable of continuously determining during its operation, by measurement or reception, the following operating parameters: the voltage U across the terminals of the electrical machine 10, the current drawn I by the electrical machine 10, the rotational speed W of the rotor and the temperature of the stator.

[0033] Thus, the monitoring module 131 continuously calculates the achieved torque CR according to the following formula and the recorded efficiency map: CR=U*I*Rd / W

[0034] Furthermore, the monitoring module 131 continuously determines the DC torque setpoint during operation. The DC torque setpoint is received by the control unit 13 via the communication bus 15.

[0035] Furthermore, the monitoring module 131 continuously determines the deviation EC between the actual torque and the setpoint torque CC according to the following formula: EC = abs(CR - CC), where abs() is the absolute value function. The monitoring module 131 is configured in memory with at least two torque thresholds S1 and S2, and two predetermined durations D1 and D2. S1 and D1 correspond specifically to torque monitoring in forward motion, and S2 and D2 specifically to monitoring in reverse motion. S1 is an acceptability criterion for torque deviation in forward motion, and S2 is an acceptability criterion for torque deviation in reverse motion. S2 has a higher torque value than S1 because a larger torque deviation is permitted in reverse. D1 and D2 are the maximum acceptable durations for an EC deviation when this deviation exceeds S1 or S2. D1 and D2 have distinct values.

[0036] Furthermore, the monitoring module 131 is capable of activating a reconfiguration of the electric machine 10 in the event of detection of a torque anomaly in forward or reverse operation. The reconfiguration consists of operating a degraded mode of the electric machine. For example, the reconfiguration imposes a maximum torque limit or completely prevents the supply of torque. According to the invention, at least two reconfiguration modes are provided: a first mode in forward operation and a second mode in reverse operation. Moreover, each reconfiguration mode can be deactivated according to deactivation conditions specific to each mode. Examples of conditions will be described in figure 2 .

[0037] Furthermore, for the purposes of the monitoring process, the control unit 16 collects information relating to anomalies detected by the electric traction machine 10 in order to transmit it to another centralized control unit (not shown in figure 1 designated by the acronym BSI for Intelligent Service Box. In this non-limiting example, the BSI and the control unit 16 communicate via a second communication bus, of the CAN type. More specifically, the BSI is responsible for recording a diagnostic and alert log that can be consulted by after-sales services. A fault is recorded in the BSI's memory as a fault code representing the severity level and status of the fault. A fault can be recorded in a permanent state (i.e., the fault is still active) or in a transient state (the fault is no longer detected, but the event remains recorded in the log history).

[0038] In figure 2 A diagram is described representing a preferred embodiment of the algorithm for the method of monitoring the motor torque of an electric traction machine for an electrified vehicle according to the invention. With reference to the figure 1 The process is implemented by the monitoring module 131, in this example the computer 13 of the electric machine 10. However, this is not mandatory; the monitoring module 131 could be external to the computer 13, while still being coupled to it. In this latter case, it could itself be configured as a dedicated computer including, for example, a dedicated program. Consequently, the monitoring module, according to the invention, can be implemented as software modules, electronic circuits, or hardware, or a combination of electronic circuits and software modules.

[0039] In an initial step 21, the vehicle is started and the electric motor is switched on. The gear selector is, for example, in the forward or reverse position. The driver presses the brake or accelerator pedal. The vehicle is moving at a given speed VIT.

[0040] In a second step 22, the monitoring module 131 calculates the deviation EC between the actual torque CR and the torque setpoint CC. The torque setpoint CC and the actual torque CR are determined by the monitoring module 131 in accordance with the description of the figure 1 .

[0041] In a third step 23, the monitoring module determines the direction of travel of the vehicle (forward / reverse) by selecting the specific threshold value for that direction from among the values ​​S1 and S2 stored in the monitoring module's memory. The direction of travel is preferably determined from information provided by a piezometric sensor on the electric traction machine, which detects the direction of rotation of the rotor.

[0042] In a fourth step 24, the monitoring module compares the EC deviation with the value S1 if the electric machine rotor is rotating in the positive direction of forward torque (AV). Furthermore, if the EC deviation is greater than S1, the monitoring module checks whether this EC deviation remains greater than S1 for a duration D greater than the duration D1. In this non-limiting example, S1 is equal to 50 Nm and D1 is equal to 450 milliseconds. D1 can be equal to values ​​lower or higher than these.

[0043] At a fifth stage 25, if EC is greater than S1 for a duration D exceeding the duration D1, the monitoring module activates a first reconfiguration mode MR1 for the electric traction machine. The first reconfiguration mode MR1 consists of shutting down the electric traction machine (preventing the supply of torque), recording a fault code in non-volatile memory, also known as read-only memory or reprogrammable read-only memory (ROM or EPROM), and communicating this fault code to the vehicle's eVCU control unit for diagnostic purposes. This fault code indicates a failure to maintain the specified torque of the electric traction machine in forward motion. Furthermore, the electric traction machine's control unit requests that a "stop" indicator light be illuminated on the instrument panel and a message be displayed to vehicle users, informing them that a problem has occurred in the traction system.The fault code is recorded in a so-called permanent state, indicating that the anomaly is present.

[0044] This first reconfiguration mode MR1 can be deactivated at a sixth deactivation step 26 when a first deactivation condition is detected. Failure to comply with the forward torque setpoint is considered a critical anomaly. Therefore, the first deactivation condition is intervention by a technical service on the electric machine, including checking the diagnostic log and clearing the non-volatile memory of the electric machine's control unit. Once the intervention is performed, the process returns to the initial step 20 and enters a verification loop.

[0045] Furthermore, at step 24, as long as the EC deviation remains below the threshold S1 or is greater than S1 for a duration D less than D1, the process returns to the initial step 20 and returns to a verification loop.

[0046] Returning to step 23, if reverse gear (AR) is detected, in a seventh step 27, the monitoring module compares the EC deviation with the value S2. The electric machine's rotor rotates in the negative direction of reverse gear (AR). Furthermore, if the EC deviation is greater than S2, the monitoring module checks whether this EC deviation remains greater than S2 for a duration D greater than D2. In this non-limiting example, S2 is equal to 60 Nm and D2 is equal to 100 milliseconds. S2 must be greater than S1. D2 can be equal to values ​​lower or higher than S1.

[0047] At stage 28, if EC is greater than S2 for a duration D exceeding D2, the monitoring module activates a second reconfiguration mode, MR2, for the electric motor. This second reconfiguration mode, MR2, involves shutting down the electric motor (preventing torque supply), recording a fault code in non-volatile memory, and communicating this fault code to the vehicle's eVCU control unit for diagnostic purposes. This fault code indicates a failure to meet the specified torque requirements of the electric motor in reverse. Furthermore, the electric motor control unit illuminates a "stop" warning light on the instrument panel and displays a message alerting vehicle users that a problem has occurred in the drivetrain. The fault code is stored in a permanent state, indicating that the fault is present.In this preferred embodiment, the MR2 mode differs from the MR1 mode by its deactivation condition 29.

[0048] More specifically, the second MR2 reconfiguration mode can be deactivated at a ninth deactivation step 29 when a second deactivation condition is detected. Failure to meet the torque target in reverse is considered less critical than in forward gear. Therefore, the second deactivation condition is the detection of a vehicle shutdown event, also known as "ignition off," triggered by the activation of a key or the vehicle's start / stop button.

[0049] This condition, known as "ignition off," allows the vehicle to exit reconfiguration mode MR2. The process then returns to the initial step 20, and the vehicle is again authorized to restart. In this case, the electrical machine control unit (ECU) initiates a rehabilitation procedure 30 for the electrical machine. This procedure involves turning off the "stop" indicator light and the fault message, allowing the electrical machine to operate, and storing the fault code in a second, transient state in the ECU's non-volatile memory for diagnostic purposes. The transient state indicates that the fault no longer exists and serves to record the event for later analysis. At the initial step 20, the process returns to a verification loop.

[0050] However, it is envisaged as an alternative that the second deactivation condition 29 is the intervention of a technical service, identical to the first condition 26. The fault code remains in a permanent state and the electric traction machine remains stopped until the technical intervention.

[0051] As an optional variant, to avoid immobilizing the vehicle even if a fault is detected while driving forward, step 26 allows the vehicle to exit reconfiguration mode upon detection of a vehicle shutdown command event, known as "ignition cut-off." The process then returns to the initial step 20, and the vehicle is again authorized to move. This variant, not shown in figure 1 , includes a rehabilitation step of the traction machine identical to step 30 before returning to the initial step 20.

Claims

1. Method for monitoring the motor torque of an electric traction machine (10) of an electrified vehicle, comprising determining (22) a torque deviation (EC) between a torque setpoint (CC) transmitted to the electric machine and a torque actually produced (CR) by a rotor of the electric machine (10), and determining (23) whether the rotor rotates in a forward driving direction or a reverse driving direction of the vehicle, characterized in that it comprises comparing (24) the torque deviation (EC) with a first threshold (S1) when the rotor rotates in the forward driving direction, and comparing (27) the torque deviation (EC) with a second threshold (S2) when the rotor rotates in the reverse driving direction, and activating a reconfiguration (25, 28) of the electric machine (10) depending on a result of the comparison (24, 27), the second threshold (S2) having a value greater than the first threshold (S1).

2. Monitoring method according to claim 1, characterized in that it further comprises controlling a first reconfiguration (25) of the electric machine (10) if the deviation (EC) is greater than the first threshold (S1) in the forward driving direction (AV) for at least a first duration (D1).

3. Monitoring method according to claim 2, characterized in that the first duration (D1) is equal to 450 milliseconds.

4. Monitoring method according to claim 2 or 3, characterized in that the first reconfiguration (25) comprises storing a first fault code in a first state, signaling a fault, and stopping the electric machine (10).

5. Monitoring method according to any one of claims 1 to 4, characterized in that it further comprises controlling a second reconfiguration (28) of the electric machine (10) if the deviation (EC) is greater than the second threshold (S2) in the reverse driving direction (AR) for at least a second duration (D2).

6. Monitoring method according to claim 5, characterized in that the second duration (D2) is equal to 100 milliseconds.

7. Monitoring method according to claim 5 or 6, characterized in that the second reconfiguration (28) comprises storing a second fault code in the first state, signaling a fault, and stopping the electric machine.

8. Monitoring method according to any one of claims 2 to 7, characterized in that it further comprises, in the event of activation of the first reconfiguration (25) or the second reconfiguration (28) and upon detection of a vehicle shutdown command, controlling a rehabilitation (30) of operation of the electric machine (10), stopping the signaling, and storing the first or second fault code in a second state.

9. Monitoring method according to any one of claims 1 to 8, characterized in that the first threshold (S1) is equal to 50 N·m and the second threshold (S2) is equal to 60 N·m.

10. Electrified vehicle comprising an electric traction machine (10) and a control unit (13) of the electric traction machine (10), characterized in that the control unit (13) is configured to implement the monitoring method according to any one of claims 1 to 9.