Method for controlling an electric all-wheel drive train of a motor vehicle, method for creating a characteristic map for controlling an electric all-wheel drive train of a motor vehicle, and motor vehicle

Abstract

The invention relates to a method for controlling an electric all-wheel drive train of a motor vehicle, in which a total torque currently desired by the driver and to be implemented and a current axle speed of the motor vehicle are determined (V1) by means of an electronic computing device, a motor torque to be provided for achieving the total torque of respective electric traction machines of the motor vehicle is determined (V2) using a specified characteristic map, and the respective electric traction machines are individually controlled (V3) in order to initiate the process of the determined respective motor torque being provided by means of the respective electric traction machine, respective motor torques to be individually provided by all of the electric traction machines of the motor vehicle being specified in the characteristic map for different combinations of total torques and axle speeds of the motor vehicle desired by the driver.

Description

[0001] Method for controlling an electric all-wheel drive system of a motor vehicle, method for creating a characteristic map, and motor vehicle

[0002] The invention relates to a method for controlling an electric all-wheel drive train of a motor vehicle, a method for creating a characteristic map and a motor vehicle.

[0003] US Patent 2012 / 0059562 A1 discloses a method for generating a torque map for the operation of a vehicle's all-wheel drive system. The method involves a model that describes how an electronic control unit of the all-wheel drive system, located within the vehicle, processes data received from one or more sensors or vehicle subsystems. The model is executed on a computing device, which simulates the operation of the vehicle's all-wheel drive system control unit. The computing device acquires data from a controller area network (CAN) located within the vehicle and data from the vehicle describing the wheel torque while simulating the operation of the electronic control unit. A raw torque value is generated by the computing device from the CAN and wheel torque data.The raw torque value is used to generate a torque value that is linked to an engine speed and intake air value derived from data acquired by the Controller Area Network.

[0004] Furthermore, a method is known from US 2023 / 0046751 A1 which uses drivetrain actuators for one or more individual wheels of a

[0005] 24-0925 ABZ EXA 24.09.2024 Electric vehicles can be implemented and enable the connection and disconnection of at least part of the axle and wheel from a torque-supplying electric motor. A decoupled wheel and axle have less friction and a lower rotational mass than a wheel and axle connected to an electric motor.

[0006] The object of the present invention is to provide a solution by which a motor vehicle with an electric all-wheel drive system can be operated particularly efficiently and with low computing power.

[0007] This problem is solved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the dependent claims, the description, and the figures. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0008] The invention relates to a method for controlling an electric all-wheel drive system of a motor vehicle, in particular a passenger car. The all-wheel drive system is configured to drive all wheels of the motor vehicle. Thus, the torque available for driving the motor vehicle can be distributed to all wheels of the motor vehicle as needed by means of the all-wheel drive system. In this electric all-wheel drive system, the total torque available for driving the motor vehicle is provided by at least one electric traction motor. The motor vehicle can therefore be driven by electrical energy from the at least one electric traction motor.

[0009] The procedure involves using an electronic computing device, in particular an electronic computing device of the motor vehicle, to determine the total torque to be implemented as currently requested by the driver and the current axle speed of the motor vehicle.

[0010] 24-0925 ABZ EXA 24.09.2024 The vehicle axle speed is the same for all axles of the motor vehicle, and thus, for example, for the front and rear axles. The total torque desired by the driver is the torque that is to act on the motor vehicle as a whole, whereby the total torque desired by the driver can be determined, in particular, by means of user input from the driver. The driver thus specifies, via user input, the total torque with which, in his opinion, the motor vehicle should be driven.

[0011] The method further provides that, using an electronic computing device and a predefined characteristic map, the motor torque required to achieve the total torque of the respective electric traction motors of the vehicle is determined. For example, the vehicle can comprise two electric traction motors, one of which is assigned to each axle of the vehicle. In other words, the vehicle can be driven at its front axle by a first electric traction motor and at its rear axle by a second electric traction motor.The characteristic map is thus used to determine how large the first motor torque to be provided by the first electric traction motor and how large the second motor torque to be provided by the second electric traction motor must be in order to ensure that the vehicle is driven with the total torque desired by the driver.

[0012] The method further provides for the individual control of each electric traction motor to trigger the provision of the determined respective engine torque by each electric traction motor. For example, the vehicle can include a control unit configured to individually control the respective electric traction motors. The first electric traction motor is thus controlled in such a way that it provides the first engine torque, and the second electric traction motor is controlled in such a way that it provides the second engine torque. The characteristic map contains values ​​for different combinations of total torques requested by the driver and the respective axle speeds of the vehicle.

[0013] 24-0925 ABZ EXA 24.09.2024 specifies the motor torques to be individually provided to all electric traction motors of the vehicle. This means that the characteristic map takes into account how many electric traction motors the vehicle has and which of the electric traction motors are configured to drive which axle of the vehicle. Thus, for different combinations of total torques desired by the driver and the respective axle speeds of the vehicle as input data, the characteristic map specifies which electric traction motor of the vehicle is to provide which motor torque for this specific combination of input data.The characteristic map enables a particularly simple distribution of the total torque to be delivered by the vehicle to the respective electric traction motors, without the need for complex calculations, simply based on the input data using the available characteristic map. The distribution of the total torque to be provided to the respective electric traction motors can thus be dynamically determined depending on the level of the total torque to be provided and the axle speed, without requiring significant computing power.

[0014] In a possible further development of the invention, it is provided that the characteristic map is used to determine a portion of the desired total torque to be set, which is to be individually provided by the respective traction motors. For example, the characteristic map can provide a percentage value for the distribution of the total torque to be implemented among the respective electric traction motors as a result value. For example, for a given combination of input data, the characteristic map can indicate that a first percentage of the total torque desired by the driver is to be provided by a first of the electric traction motors, and the remainder of the total torque to be implemented by the driver is to be provided by the second electric traction motor of the vehicle.For example, the characteristic map can provide a percentage value describing what proportion of the total torque desired by the driver is to be implemented by the electric traction motor assigned to the front axle of the vehicle. By specifying only the proportions of the desired total torque to be implemented by the respective electric traction motors, it can be ensured that the total torque delivered by all electric traction motors of the vehicle is as high as necessary.

[0015] 24-0925 ABZ EXA 24.09.2024 Torque is provided so that the total torque to be implemented by the driver is effective in the motor vehicle.

[0016] In another possible embodiment of the invention, the total torque desired by the driver is determined based on the accelerator pedal position of the vehicle. The system thus determines how far the driver has depressed the accelerator pedal and, based on this pedal position, calculates the desired total torque. This total torque can be determined based on either the accelerator pedal position or the vehicle's current speed. The driver can then specify the desired total torque particularly easily and intuitively via the accelerator pedal.

[0017] In a further possible embodiment of the invention, it is provided that if a predetermined operating parameter lies outside a predetermined operating range, the control of all traction motors of the motor vehicle is carried out independently of the characteristic map according to a stored control preset. This operating parameter can be, for example, the speed of the motor vehicle, the ambient temperature of the motor vehicle, the temperature of at least one traction battery of the motor vehicle which is configured to provide electrical energy for at least one electric traction motor of the motor vehicle, or the temperature of at least one of the electric traction motors.The motor speed specified by the characteristic map, which is to be individually provided by the respective electric traction motors, can therefore be overridden as soon as at least one specified operating parameter lies outside the specified operating range assigned to that operating parameter. For example, if the specified operating parameter lies outside the specified operating range, such as the outside temperature being outside a specified temperature range, it can be specified that, regardless of the axle speed and the level of total torque desired by the driver, the proportions of the total torque to be provided by the respective electric traction motors each correspond to a specified standard value. This applies provided that all specified operating parameters are within their respective assigned specified ranges.

[0018] 24-0925 ABZ EXA 24.09.2024 Within the operating range for the respective operating parameter, the distribution of the shares of the total torque to be provided by the respective electric traction motors, as well as the torque to be applied by the driver, can be dynamically determined based on the characteristic map. This enables particularly safe operation of the vehicle, even in the vehicle's peripheral operating ranges.

[0019] The invention further relates to a method for creating a characteristic map for controlling an electric all-wheel drive system of a motor vehicle. In this method, for creating the characteristic map, various combinations of a total torque of the motor vehicle desired by the driver and an axle speed of the motor vehicle are assigned, as input data, the respective motor torques to be individually provided by all electric traction motors of the motor vehicle. In other words, for each combination of input data in the characteristic map, the respective motor torque to be provided by each electric traction motor is defined. The respective motor torques to be provided by all electric traction motors can be the same or different from one another.In particular, the process involves creating a characteristic map for a vehicle type, which includes all vehicles that have the same type and number of electric traction motors and the same arrangement of these motors relative to the respective driven axles. Individual characteristic maps can be created for different vehicle types. In other words, the characteristic map can be created and then made available for all vehicles of a common vehicle type. Therefore, the characteristic map is not intended to be created individually for each vehicle; rather, it is intended that the characteristic map can be used for all vehicles of a common vehicle type. This allows a particularly large number of vehicles to be equipped with a very small number of different characteristic maps.

[0020] In a possible further development of the invention, it is provided that for the respective combination of input data, the motor torque to be provided individually by the respective electric traction machines is additionally dependent on estimated losses of the respective electric traction machine and of an inverter assigned to this electric traction machine, as well as of one of these

[0021] 24-0925 ABZ EXA 24.09.2024 is selected for the transmission assigned to the electric traction motor. This takes into account the losses occurring in the respective electric traction motors, as well as in the inverters and transmissions assigned to them, when considering the motor torques stored in the characteristic map, which are to be provided individually by the respective electric traction motors. This ensures that the vehicle is driven with the specified total torque when all traction motors provide the assigned motor torque determined from the characteristic map.

[0022] In a further possible embodiment of the invention, it is provided that, for the respective combination of input data, the individual control is selected depending on the desired maximum power output and / or low-loss power transmission from the respective electric traction motor to the wheels of the vehicle and / or minimum energy consumption. The target variable is thus specified: the vehicle is to be driven with maximum power output and / or with particularly low losses and / or with minimal energy consumption, and the characteristic map is created or adapted accordingly. This ensures that, as a result of controlling the vehicle based on the characteristic map, the vehicle can be driven according to the objective set when creating the characteristic map, and thus with maximum power output and / or particularly low losses and / or minimal energy consumption.

[0023] In a further possible embodiment of the invention, the characteristic map is provided for use in a large number of motor vehicles. Thus, the characteristic map can be created once and then used in the large number of vehicles. This makes it possible to control the respective all-wheel drive systems of the large number of vehicles particularly easily based on the characteristic map. This eliminates the need to create the characteristic map individually for each vehicle.

[0024] The invention further relates to a motor vehicle, in particular a motor car, especially a passenger car, with a storage device in which a characteristic map is stored, which is generated in a method as already described in connection with the method for creating a characteristic map for controlling an electric motor vehicle.

[0025] 24-0925 ABZ EXA 24.09.2024, which describes an all-wheel drive system of a motor vehicle, has been created. Furthermore, the motor vehicle includes an electronic computing unit configured to control all of the vehicle's electric traction motors according to a map. The motor vehicle can thus perform a procedure similar to that already described in connection with the procedure for controlling an electric drive system of a motor vehicle. This allows the electric all-wheel drive system of the motor vehicle to be controlled dynamically, particularly easily and quickly, depending on the total torque set by the driver and the current axle speed of the motor vehicle.

[0026] Further features of the invention may become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0027] The drawing shows in the single figure (Fig. 1) a process scheme for a method for controlling an electric all-wheel drive train of a motor vehicle.

[0028] Figure 1 shows a process diagram for a method for controlling an electric all-wheel drive system of a motor vehicle. The method comprises three process steps, V1 to V3. In the first process step, V1, an electronic computer in the motor vehicle determines the total torque currently requested by the driver and the current axle speed of the motor vehicle as input data. Specifically, the total torque requested by the driver is selected based on the accelerator pedal position of the motor vehicle. In the second process step, V2, the electronic computer uses a predefined characteristic map to determine the motor torque to be provided by the respective electric traction motors of the motor vehicle to achieve the total torque.In other words, the input data is used to determine, based on the characteristic map for each electric traction motor of the motor vehicle, how high the output can be using the respective motor.

[0029] 24-0925 ABZ EXA 24.09.2024 The characteristic map specifies the motor torque to be provided by each electric traction motor for different combinations of total torque and axle speeds requested by the driver. This map allows, in particular, the determination of the proportion of the desired total torque to be set that must be provided individually by each traction motor.

[0030] As part of process step V3, it is provided that all electric traction machines of the motor vehicle are controlled according to the motor torque to be provided by the respective electric traction machine, as determined on the basis of the characteristic map, in particular by means of a control unit of the motor vehicle.

[0031] The characteristic map was created using a process in which, for the creation of the map, the respective motor torques to be individually provided by all electric traction motors of the vehicle were assigned as input data to various combinations of total vehicle torques to be achieved by the driver and the respective axle speeds of the vehicle. For each combination of input data, the motor torque to be individually provided by the respective electric traction motors can also be selected depending on the estimated losses of the respective electric traction motor, as well as of an inverter and / or a transmission assigned to the respective electric traction motor.

[0032] Furthermore, it may be specifically provided that, for each combination of input data, the individual control is selected depending on the desired maximum power output and / or the desired low-loss power transmission from the respective electric traction motor to the vehicle's wheels and / or the desired minimum energy consumption. The resulting characteristic map can then be made available for use in a large number of vehicles.

[0033] 24-0925 ABZ EXA 24.09.2024 It is possible that if a specified operating parameter lies outside a specified operating range, the control of all traction machines will be carried out independently of the characteristic map based on a stored predefined control setting.

[0034] The described method is based on the understanding that torque distribution in all-wheel drive systems is often hardcoded to the individual axles of a vehicle. This means that the vehicle decides whether or not to engage all-wheel drive. If all-wheel drive is engaged, a load is distributed across the vehicle's axles with a fixed torque distribution. This fixed torque distribution is not necessarily the most efficient method for propelling the vehicle in all-wheel drive mode. Electrically powered vehicles have various components, such as electric motors, inverters, and transmissions, that transfer energy and can therefore also cause losses. To minimize these losses, intelligent axle control is essential.

[0035] The fundamental principle of the invention is to create a characteristic map that enables optimized control of the vehicle axles. This map describes a relationship between various parameters, such as the current axle speed of the vehicle, the total torque requested by the driver (derived from the vehicle's pedal position), and optionally, the instantaneous torque supplied by the respective electric traction motors as input data, with individual motor torques to be provided by each traction motor. Taking into account the losses in the respective traction motor (which can also be referred to as an electric motor), the inverter, and the transmission, the characteristic map provides the most efficient control for individual wheels and axles of the vehicle.This ensures optimal power transmission, maximizing vehicle performance while minimizing energy consumption.

[0036] The characteristic map specifies a precise torque distribution to the axles, particularly to all traction motors of the vehicle, thereby optimizing the efficiency of the all-wheel drive system. The characteristic map can form the core of a control logic and allows for the consideration of performance parameters.

[0037] 24-0925 ABZ EXA 24.09.2024 of the respective electric traction machine and direct inputs from the driver via the accelerator pedal, individual inverters and thus to control individual axles of the motor vehicle as efficiently as possible via respective electric traction machines.

[0038] The sophisticated interplay of these aspects contributes to optimal energy utilization within the all-wheel drive system. The pre-generated map can be directly loaded into the vehicle. This enables the vehicle to react adaptively to a wide variety of driving situations without requiring complex calculations while driving. This approach relieves the burden on onboard computing resources and ensures that the efficiency of the electric all-wheel drive system can be maintained at a consistently high level. The described concept offers an elegant and innovative solution for significantly improving the vehicle's range and energy consumption.

[0039] One of the main advantages of the described method is a significant increase in energy efficiency, as the sophisticated control system ensures optimal distribution of the total torque requested by the driver to the different axles of the vehicle. This leads to reduced energy consumption and thus contributes to an extended vehicle range. Furthermore, no onboard calculations are required for the method. By performing a complex calculation of the characteristic map in advance and implementing the completed map in the vehicle, particularly its electronic computing unit, complex and computationally intensive real-time processes during driving are eliminated. This can reduce the system load on the vehicle and increase the lifespan and reliability of the vehicle's onboard electronics.A further benefit of the method arises from the scalability and adaptability of the aforementioned technology. Since the map can be individually developed for each vehicle model, it can be easily adapted to a wide variety of vehicle types and drive configurations.

[0040] Finally, the ease of integrating the pre-calculated map into the existing vehicle enables a cost-effective and time-efficient implementation of an efficient all-wheel-drive control system. This offers manufacturers a lucrative opportunity to bring their vehicles up to the latest technological standards. Furthermore,

[0041] 24-0925 ABZ EXA 24.09.2024 Furthermore, the increased energy efficiency of the motor vehicle supports efforts towards environmentally friendly and sustainable mobility by reducing the energy consumption and thus the ecological footprint of the motor vehicle. Overall, the invention demonstrates how efficient all-wheel drive torque distribution can be implemented.

[0042] 24-0925 ABZ EXA 24.09.2024 Reference List

[0043] V1 to V3 respective process steps

[0044] 24-0925 ABZ EXA 24.09.2024

Claims

Patent claims 1. Method for controlling an electric all-wheel drive train of a motor vehicle, in which an electronic computing device determines a total torque to be implemented by the driver and a current axle speed of the motor vehicle (V1), a motor torque to be provided by the respective electric traction machines of the motor vehicle to achieve the total torque is determined using a predefined map (V2), and the respective electric traction machines are individually controlled (V3) to trigger the provision of the determined respective motor torque by the respective electric traction machine, wherein the respective motor torques to be provided individually by all electric traction machines of the motor vehicle are specified in the map for different combinations of total torques and axle speeds of the motor vehicle desired by the driver.

2. Method according to claim 1, characterized in that a proportion of the desired total torque to be set is determined by means of the characteristic map, which is to be provided individually by means of the respective traction machine (V2).

3. Method according to claim 1 or 2, characterized in that the total torque desired by the driver is determined as a function of an accelerator pedal position of the motor vehicle (V1).

4. Method according to one of the preceding claims, characterized in that if a predetermined operating parameter lies outside a predetermined operating range, the control of all traction machines is carried out independently of the characteristic map according to a stored specification for the control. 24-0925 ABZ EXA 24.09.2024 5. Method for creating a characteristic map for controlling an electric all-wheel drive train of a motor vehicle, in which, for the creation of the characteristic map, respective different combinations of a total torque of the motor vehicle to be achieved by the driver and an axle speed of the motor vehicle are assigned as input data, respectively motor torques to be individually provided by all electric traction machines of the motor vehicle.

6. Method according to claim 5, characterized in that, for the respective combination of input data, the motor torque to be provided individually by the respective electric traction machines is additionally selected depending on estimated losses of the respective electric traction machine as well as of an inverter and a gearbox associated with the respective electric traction machine.

7. Method according to claim 5 or 6, characterized in that for the respective combination of input data, the individual control is selected depending on a maximum power to be achieved and / or a low-loss power transmission to be achieved from the respective electric traction machine to the wheels of the motor vehicle and / or a minimum energy consumption to be achieved.

8. Method according to one of claims 5 to 7, characterized in that the characteristic map is provided for programming in a large number of motor vehicles.

9. Motor vehicle, comprising a storage device in which a characteristic map is stored which has been created in a method according to one of claims 5 to 8, and with an electronic computing device which is configured to perform a 24-0925 ABZ EXA 24.09.2024 To control all electric traction motors of the motor vehicle depending on the characteristic map. 24-0925 ABZ EXA 24.09.2024

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