A Pure Electric Four-Wheel Drive Torque Distribution Method, System and Vehicle

Abstract

The present invention provides a pure electric four-wheel drive torque distribution method, system and vehicle. Based on the efficiency of the front and rear electric drive systems, zero torque power loss, the torque control accuracy of the electric drive system and the change of the voltage at the electric drive end, the four-wheel drive torque distribution coefficient is calculated. And by means of looking up the four-wheel drive torque distribution coefficient, the influence of the continuous change of the voltage during vehicle driving on the four-wheel drive torque distribution coefficient can be simulated, and the influence of the continuous change of the voltage at the electric drive end on the four-wheel drive torque distribution coefficient during the actual driving process of the vehicle can be simulated.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicles, and relates to a pure electric four-wheel drive torque distribution method, system and vehicle. Background Technique

[0002] The statements in this part only provide background technical information related to the present invention, and do not necessarily constitute prior art.

[0003] At present, the energy consumption requirements for pure electric vehicles are getting higher and higher. There are two sets of drive systems for the front and rear electric drives in pure electric four-wheel drive, and the vehicle weight increases compared with two-wheel drive. Moreover, since both the front and rear electric drives can drive, there are situations where the front drive or the rear drive drives alone or the front and rear drives drive simultaneously during actual driving. When the front drive or the rear drive drives alone, there will be a zero-torque drag loss. When the front and rear drives drive simultaneously, the target torques of the front and rear drives need to be reasonably distributed according to the vehicle demand torque. Otherwise, it is easy to cause high energy consumption of pure electric four-wheel drive. Therefore, it is necessary to optimize the energy consumption of pure electric four-wheel drive through a reasonable four-wheel drive torque distribution strategy.

[0004] As the inventor understands, some researchers have conducted relevant research, but there are certain disadvantages in all of them. Taking Chinese Patent CN 110843551 A as an example, it provides a control strategy in a four-wheel drive torque distribution method, mainly considering the system efficiency difference between the front and rear electric drives. Under a certain torque demand, the front motor output torque Tf and the rear motor output torque Tr under the optimal system efficiency are calculated based on the efficiency function to calculate the front-wheel drive torque distribution coefficient λ, where λ = T f / (T f +T r ). However, this invention does not consider the influence of the efficiency change under different voltages of the front and rear electric drives on the torque distribution coefficient, nor does it consider the influence of zero-torque power loss and actual torque control accuracy on the torque distribution coefficient.

[0005] Taking Chinese Patent CN 112026532 A as an example, it provides a control strategy in a pure electric four-wheel drive torque distribution control method that considers the system efficiency difference between the front and rear electric drives, zero-torque loss, and the influence of the efficiency change caused by voltage change on the torque distribution coefficient. However, it does not consider the influence of torque control accuracy on the four-wheel drive torque distribution coefficient. When considering the influence of voltage change on the torque distribution coefficient, when the voltage of the power battery is higher than a certain value, torque distribution is performed according to the efficiency map of high voltage; when the voltage of the power battery is within a certain range, torque distribution is performed according to the efficiency map of medium voltage; when the voltage of the power battery is lower than a certain value, torque distribution is performed according to the efficiency map of low voltage. The torque distribution coefficient does not change continuously completely according to the voltage change. Summary of the Invention

[0006] To solve the above problems, the present invention proposes a pure electric four-wheel drive torque distribution method, system and vehicle. Based on the efficiency of the front and rear electric drive systems, zero-torque power loss, torque control accuracy of the electric drive system, and changes in the terminal voltage of the electric drive, the four-wheel drive torque distribution coefficient is calculated. And by looking up the four-wheel drive torque distribution coefficient, the influence of the continuous change of the voltage during vehicle driving on the four-wheel drive torque distribution coefficient can be simulated, and the influence of the continuous change of the terminal voltage of the electric drive on the four-wheel drive torque distribution coefficient during the actual driving process of the vehicle can be simulated.

[0007] According to some embodiments, the present invention adopts the following technical solutions:

[0008] A pure electric four-wheel drive torque distribution method, comprising the following steps:

[0009] Obtain the working mode and determine the throttle characteristics corresponding to the mode;

[0010] According to the throttle characteristics, combined with the torque capabilities and torque control accuracy thresholds of the front and rear electric drive assemblies at different voltages, determine the torque range of the electric drive assembly and the range of the front-wheel drive torque distribution coefficient to be calculated at the set voltage;

[0011] According to the electric drive assembly efficiency data at different voltages, and the zero-torque drag power loss data of the front and rear electric drive assemblies, determine the optimal torque distribution coefficient map at the set voltage;

[0012] Determine the optimal torque distribution coefficient map at other voltages;

[0013] According to the current voltage of the electric drive terminal, the required rotational speed and torque at the output end, find the optimal torque distribution coefficient in the torque distribution coefficient map;

[0014] Judge whether the optimal torque distribution coefficient meets the torque range of the electric drive assembly at the current voltage. If not, re-determine the torque distribution coefficient. Otherwise, judge whether it meets the vehicle stability. If so, form the torque control instructions for the front and rear motors. Otherwise, form the control instructions according to the torques of the front and rear motors calculated by the vehicle stability system or the vehicle controller.

[0015] As an alternative implementation, the specific process of determining the torque range of the electric drive assembly at the set voltage to be calculated includes determining the torque range of the electric drive assembly corresponding to the torque distribution map to be calculated at the set voltage according to the maximum torque in the throttle characteristics; where the maximum value in the throttle characteristics is determined according to the maximum torque values corresponding to the front and rear drive assemblies at different rotational speeds or vehicle speeds.

[0016] As an alternative implementation, the specific process of determining the range of the front-wheel drive torque distribution coefficient at the set voltage to be calculated includes:

[0017] When the absolute value of the vehicle's required torque is less than the sum of the absolute values of the torque control accuracy thresholds of the front and rear motors in the low-torque region multiplied by the gear ratio, the torque distribution coefficient is determined based on the minimum power loss corresponding to the two coefficients of 0 or 1 for the front-wheel drive torque distribution coefficient.

[0018] As an alternative implementation, the specific process of determining the range of the front-wheel drive torque distribution coefficient to be calculated at the set voltage includes:

[0019] When the absolute value of the vehicle's required torque is greater than the sum of the absolute values of the torque control accuracy thresholds of the front and rear motors in the low-torque region multiplied by the gear ratio;

[0020] According to the torque control accuracies of the front and rear drives, the range of the front-wheel drive torque distribution coefficient to be calculated is adjusted. The range of the front-wheel drive torque distribution coefficient is a discrete torque distribution coefficient range at set intervals within [absolute value of the front motor torque accuracy threshold * gear ratio / torque at the output end of a certain electric drive assembly, 1].

[0021] As an alternative implementation, the specific process of determining the optimal torque distribution coefficient map at the set voltage includes:

[0022] Based on the efficiency test data of the front and rear electric drive systems at the set voltage, calculate the power loss when controlling with different front-wheel drive torque distribution coefficients at the corresponding points of the rotational speed and torque at the output end of a specific electric drive assembly of the vehicle. By comparing the calculation results, find the torque distribution coefficient K0 with the minimum power loss;

[0023] Then calculate the power loss when the rear drive drives alone and when the front drive drives alone. Additionally, consider the power loss of zero-torque drag of the front drive and the power loss of zero-torque drag of the rear drive. Compare the power losses at these two torque distribution coefficients with the power losses at the discrete torque distribution coefficients calculated in the previous step to find the torque distribution coefficient K1' with the minimum power loss;

[0024] Compare the minimum torque distribution coefficient K1' with the absolute value of the front motor torque accuracy threshold * gear ratio / torque at the output end of a certain electric drive assembly. (Except when the torque distribution coefficient is 0), take the maximum value of the two to obtain the optimal torque distribution coefficient K2';

[0025] When calculating the required torques of the front and rear drives based on the obtained optimal torque distribution coefficient K2', it is necessary to determine whether the required torques of the front and rear drives are within their torque output capabilities. If so, the optimal torque distribution coefficient K2' does not need to change; if not, the torque distribution coefficient needs to be re-determined according to the above three steps. At this time, the power loss at the torque distribution coefficient may be the second smallest value or other values (not the minimum value because the value of K2' has been excluded) until the optimal torque distribution coefficient K1 is found;

[0026] Then, when calculating the corresponding points of the rotational speed and torque at the output end of other specific electric drive assemblies, follow the above three steps to obtain the torque distribution coefficients K2, K3, K4... Kn with the optimal power loss;

[0027] Calculate the above optimal torque distribution coefficients K1, K2, K3, K4... Kn to obtain the optimal torque distribution coefficient map within the output torque range of the front and rear electric drive assembly systems under the set voltage.

[0028] As an alternative implementation, the specific process of determining the optimal torque distribution coefficient map at other voltages includes: following the calculation process of the optimal torque distribution coefficient map at the set voltage, changing the voltage value, and calculating at least the optimal torque distribution coefficient maps including the minimum operating voltage, rated voltage, and maximum operating voltage of the electric drive system.

[0029] As an alternative implementation, the specific process of forming the front and rear motor torque control commands includes, according to the optimal torque distribution coefficient map under different working conditions, corresponding to the working conditions of the electric drive assembly at different voltages, rotational speeds, and torques, obtaining the torque distribution coefficient of the front drive according to the current voltage, rotational speed, and torque requirements, and then calculating the motor demand torques of the front and rear drives, and using this torque as the torque control commands for the front and rear motors.

[0030] A pure electric four-wheel drive torque distribution system includes:

[0031] A first determination module, configured to obtain the working mode, determine the throttle characteristics corresponding to the mode, and according to the throttle characteristics, in combination with the torque capabilities and torque control accuracy thresholds of the front and rear electric drive assemblies under different voltages, determine the torque range of the electric drive assembly and the range of the front drive torque distribution coefficient to be calculated at the set voltage;

[0032] A second determination module, configured to determine the optimal torque distribution coefficient map with the optimal power loss at the set voltage according to the efficiency data of the electric drive assembly at the determined voltage and the zero-torque drag power loss data of the front and rear electric drive assemblies;

[0033] A third determination module, according to the range of the front drive torque distribution coefficient of the first determination module and the optimal torque distribution coefficient map obtained by the second determination module, compares and determines the optimal torque distribution coefficient map at the set voltage;

[0034] A fourth determination module, configured to determine the optimal torque distribution coefficient map at other voltages;

[0035] A search module, configured to search for the optimal torque distribution coefficient in the torque distribution coefficient map according to the current voltage, output end demand rotational speed, and torque of the electric drive end;

[0036] A judgment module is configured to judge whether vehicle stability is satisfied. If so, front and rear motor torque control instructions are formed; otherwise, control instructions are formed according to the front and rear motor torques calculated by the vehicle stability system or the vehicle controller.

[0037] A terminal device includes a processor and a computer-readable storage medium. The processor is used to implement each instruction; the computer-readable storage medium is used to store multiple instructions, and the instructions are adapted to be loaded and executed by the processor to perform the steps in the above method.

[0038] A pure electric four-wheel drive vehicle includes the above system or terminal device, or distributes the front and rear motor torques by adopting the above method.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] In addition to considering the efficiency of the front and rear electric drive systems, zero-torque power loss, and the influence of voltage changes on the electric drive system, the four-wheel drive torque distribution strategy of the present invention also considers the influence of the torque control accuracy of the electric drive system on the four-wheel drive torque distribution coefficient, and also finds the four-wheel drive torque distribution coefficient through voltage interpolation, so that the front and rear drive torque distribution coefficients change with the voltage change at the electric drive end.

[0041] When considering the influence of the voltage change at the electric drive end on the four-wheel drive torque distribution, although the torque distribution coefficient is calculated according to the efficiency test map at several discrete voltages, the present invention interpolates the four-wheel drive torque distribution coefficients at several voltages of the electric drive end in real time through the voltage interpolation method, so as to simulate the influence of the continuous voltage change at the electric drive end on the four-wheel drive torque distribution coefficient during the actual driving process of the vehicle and optimize the energy consumption of the pure electric four-wheel drive vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0043] Figure 1 It is a distribution flowchart of an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0045] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0046] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0047] The present invention provides a pure electric four-wheel drive torque distribution method. When formulating the four-wheel drive torque distribution strategy, factors such as the front and rear electric drive system efficiencies at different voltages, the zero-torque power losses of the front and rear electric drives, and the torque control accuracies of the front and rear electric drives are fully considered to control the front and rear electric drive systems to participate in driving with appropriate torques, so as to achieve the purpose of optimizing the vehicle energy consumption.

[0048] If the output torque of the front motor is T f and the output torque of the rear motor is T r , then the front-wheel drive torque distribution coefficient K is calculated as follows: λ = T f / (T f +T r ). If the front-wheel drive torque distribution coefficient is λ, correspondingly, the rear-wheel drive torque distribution coefficient is 1 - λ. The two are corresponding relationships, so only the front-wheel drive torque distribution coefficient is separately mentioned in the following scheme descriptions. Those skilled in the art should know that after the front-wheel drive torque distribution coefficient is determined, the rear-wheel drive torque distribution coefficient is naturally determined.

[0049] As Figure 1 shown, the specific method includes:

[0050] In the first step, first consider the mode selected by the user. According to the Pedal map corresponding to the selected mode by the user and the external characteristics of the electric drive assembly at a certain voltage, determine the torque range of the electric drive assembly corresponding to the torque distribution map to be calculated at the certain voltage.

[0051] Then, according to the influence of the torque control accuracies of the front and rear drive motors on the torque distribution coefficient, determine the range of the front-wheel drive torque distribution coefficient to be calculated.

[0052] Specifically, it is divided into two cases. The first case: when the absolute value of the vehicle demand torque is less than the sum of the absolute values of the torque control accuracy thresholds of the front and rear motors in the low-torque region multiplied by the speed ratio.

[0053] At this time, the front-wheel drive torque distribution coefficients to be calculated are only 0 and 1. Determine the torque distribution coefficient according to the minimum power loss corresponding to the two coefficients of the front-wheel drive torque distribution coefficient 0 or 1 (the corresponding rear-wheel drive torque distribution coefficients are 1 or 0).

[0054] The second case: when the absolute value of the vehicle's required torque is greater than the sum of the absolute values of the torque control accuracy thresholds of the front and rear motors in the low-torque region multiplied by the gear ratio.

[0055] At this time, it is necessary to adjust the range of the front-wheel drive torque distribution coefficient to be calculated according to the torque control accuracy of the front and rear drives. When not considering the torque control accuracy of the motor, the range of the front-wheel drive torque distribution coefficient to be calculated is [0, 0.01…0.99, 1], including 0 and 1, and the discrete points between 0 and 1 can be spaced 0.01. In other embodiments, it can also be other values.

[0056] In this embodiment, 0.01 is taken as an example for illustration. After considering the torque control accuracy of the motor, the range of the front-wheel drive torque distribution coefficient to be calculated is [absolute value of the front motor torque accuracy threshold * gear ratio / required torque at the output end of a certain electric drive assembly, …, 0.99, 1].

[0057] To ensure the clarity of the solution, as a typical embodiment for illustration, if the torque control accuracy of a certain front and rear drive motors is ±3 N·m when it is below 100 N·m, and ±3% when it is above 100 N·m, if it is necessary to calculate the optimal torque distribution coefficient at a specific electric drive assembly output speed of 200 rpm and a torque of 200 N·m, and the reduction ratios of the front and rear drive assemblies are both 10, the range of the front-wheel drive torque distribution coefficient calculated at this time is [3 * 10 / 200 = 0.15, 0.16…0.99, 1].

[0058] Similarly, taking the above example to illustrate the necessity of considering the torque control accuracy of the motor, if it is necessary to calculate the optimal torque distribution coefficient at a specific electric drive assembly speed of 200 rpm and a torque of 200 N·m, if through calculation, the power loss is the smallest when the front-wheel drive torque distribution coefficient is 0.05, but when the front-wheel drive torque distribution coefficient is 0.05, it is necessary for the front-wheel drive to output 200 * 0.05 / 10 = 1 N·m. At this time, if considering the front-wheel drive motor torque control accuracy of ±3 N·m when it is below 100 N·m, the actual output torque of the motor at this time is 1 ± 3 N·m, that is, the torque output range is between -2 N·m and 4 N·m. At this time, the front-wheel drive output torque may be negative, which seriously does not match the positive driving torque required by the vehicle. Therefore, the required torques of the front and rear drive motors need to consider the torque control accuracy of the front and rear drive motors. And the range of the front-wheel drive torque distribution coefficient to be calculated after considering the torque control accuracy may be narrower than the range from 0 to 1.

[0059] Next, according to the efficiency test data of the front and rear electric drive systems under a certain voltage, the power loss when controlling with different front-wheel drive torque distribution coefficients can be calculated at a specific electric drive assembly output speed and torque corresponding point of the vehicle. By comparing the calculation results, the torque distribution coefficient K0 with the minimum power loss can be found.

[0060] When calculating the power losses at torque distribution coefficients of 0 and 1 (these two torque distribution coefficients represent rear-wheel drive alone and front-wheel drive alone respectively), correspondingly, it is also necessary to additionally consider the zero-torque drag power losses of the front-wheel drive and the zero-torque drag power losses of the rear-wheel drive. Then, the power losses at these two torque distribution coefficients are compared with the power losses at the discrete torque distribution coefficients between 0 and 1 obtained in the previous step to find the torque distribution coefficient K1' with the minimum power loss. The minimum torque distribution coefficient K1' is then compared with the value of (absolute value of the front motor torque accuracy threshold * reduction ratio / torque at the output end of a certain electric drive assembly). (Except when the torque distribution coefficient is 0), the maximum value of the two is taken to obtain the optimal torque distribution coefficient K2';

[0061] When calculating the required torques of the front-wheel drive and the rear-wheel drive according to the obtained optimal torque distribution coefficient K2', it is necessary to determine whether the required torques of the front-wheel drive and the rear-wheel drive are within their torque output capabilities. If so, the optimal torque distribution coefficient K2' does not need to change; if not, it is necessary to re-determine the torque distribution coefficient according to the above three steps. At this time, the power loss at the torque distribution coefficient may be the second smallest value or other values (not the minimum value because the value of K2' has been excluded) until the optimal torque distribution coefficient K1 is found;

[0062] Then, at other specific corresponding points of the output end speed and torque of the electric drive assembly, find the torque distribution coefficients K1, K2, K3, K4... Kn with the minimum power loss. It should be noted that these specific corresponding points of the output end speed and torque of the electric drive assembly refer to the discrete points within the output capabilities of the front and rear electric drives and within the Pedal map torque range corresponding to different modes. After calculating the optimal torque distribution coefficients at these discrete points, the optimal torque distribution coefficient map of the front and rear electric drive assembly systems at a certain voltage is obtained.

[0063] After obtaining the optimal torque distribution coefficient map of a certain voltage of the front and rear electric drive assembly systems, calculate the optimal torque distribution coefficient map at another voltage according to the above process.

[0064] Finally, obtain the optimal torque distribution coefficient map including at least three voltages. The three voltages at least include the minimum working voltage, the rated voltage, and the maximum working voltage of the electric drive system to better cover the entire working range of the electric drive system.

[0065] After the above calculations are completed, the optimal torque distribution coefficient map of the vehicle under different working conditions is obtained, which can correspond to the working conditions at different voltages, speeds, and torques of the electric drive assembly. According to the current voltage, speed, and torque requirements, the torque distribution system of the front-wheel drive is obtained, and then the required torques of the front and rear motors are calculated. This torque is used as the torque control command for the front and rear motors.

[0066] It should also be noted that the front and rear motor control torques calculated by this process are valid when there are no problems with vehicle body stability. When vehicle body stability problems occur, the front and rear drive motor required torques calculated by the vehicle electronic stability system controller or the VCU controller (vehicle controller) should be used as the final control commands.

[0067] The overall process of the present invention will be described below with a typical embodiment:

[0068] It is necessary to determine the torque range of the electric drive assembly corresponding to the torque distribution coefficient map at a certain voltage and the range of the front-drive torque distribution coefficient to be calculated according to the Pedal map corresponding to different modes, the front and rear motor control accuracy thresholds, and other parameters of the vehicle and its components. The Pedal map corresponding to different modes means that if the driving mode selected by the user is different, the corresponding Pedal map will also be different. Among them, the Pedal map is calibration data, which is determined according to the torque output ranges of the front and rear drive assemblies and drivability, and represents the torque requirements at different throttle openings and different speeds (or vehicle speeds). The main function of the Pedal map here is to determine the torque range of the electric drive assembly corresponding to the torque distribution coefficient map at a certain voltage according to the maximum torque of the Pedal map; the front and rear motor control accuracy thresholds, and other parameters of the vehicle and its components are used to determine the range of the front-drive torque distribution coefficient to be calculated.

[0069] If it is currently necessary to determine the torque distribution coefficients of the front and rear drive systems of a certain vehicle model to control the front and rear motors, the maximum torque output requirement of the electric drive assembly corresponding to the Pedal map in the ECO mode selected by the user is 5500 N·m. Although the maximum output capabilities of the front and rear electric drive ends calculated according to the capabilities of the front and rear motors at 630V voltage are 7000 N·m, the finally determined torque range of the electric drive assembly at 630V voltage is from -5500 N·m to 5500 N·m. In addition, for the torque distribution coefficient map of the front and rear drive systems, if the torque control accuracy of the front and rear drive motors is ±3 N·m when it is below 100 N·m, and ±3% when it is above 100 N·m, and the reduction ratios of the front and rear drive assemblies are both 10, if it is necessary to calculate the optimal torque distribution coefficient at the point of 200 rpm and 200 N·m of the output end of a specific electric drive assembly in the torque distribution coefficient map of the front and rear drive systems, the range of the front-drive torque distribution coefficient calculated at this time is [3×10 / 200 = 0.15, 0.16…0.99 1].

[0070] In the second step, the optimal torque distribution coefficient at a certain voltage is determined based on the electric drive assembly efficiency data at different voltages and the zero-torque drag power loss data of the front and rear electric drive assemblies. The electric drive assembly efficiency data at different voltages are the efficiency test data of the electric drive assembly, and should include at least the test data at three voltages (rated voltage of the electric drive assembly, minimum operating voltage, maximum operating voltage); the zero-torque drag power loss data of the front and rear electric drive assemblies are mainly used to calculate the corresponding power loss when the front-wheel drive torque distribution coefficient is 0 or 1.

[0071] The calculation formula is as follows:

[0072] 1. When the vehicle is driving:

[0073]

[0074]

[0075]

[0076] 2. When the vehicle is performing regenerative braking:

[0077]

[0078]

[0079]

[0080] In the formula:

[0081] P r_drag and P f_drag respectively represent the power losses corresponding to zero-torque output of the rear-wheel drive and front-wheel drive assemblies, which are positive values, with the unit of kW;

[0082] T r and T f respectively represent the output torques of the rear-wheel drive and front-wheel drive assemblies, with the unit of N·m;

[0083] n represents the output speeds of the rear-wheel drive and front-wheel drive assemblies. Since according to the example, the reduction ratios of the front and rear drives are both 10, the output speeds of the rear-wheel drive and front-wheel drive assemblies are the same, with the unit of rpm;

[0084] η r and η f respectively represent the efficiency functions of the rear-wheel drive and front-wheel drive assemblies. In actual calculation, the efficiency test data can be used instead of the function;

[0085] Front-wheel drive torque distribution coefficient.

[0086] According to the above formula, it is possible to calculate that when driving or during energy recovery, P lossThe minimum value (i.e., min(P loss )) corresponds to λ. This λ is the optimal torque distribution coefficient at the point of the output speed of 200 rpm and torque of 200 N·m of a specific electric drive assembly in the torque distribution coefficient map of the front and rear drive systems.

[0087] In the third step, according to the above process, calculate the optimal torque distribution coefficients at the points of the output speed and torque of a specific electric drive assembly in the torque distribution coefficient maps of other front and rear drive systems. After all these points are calculated, the optimal torque distribution coefficient map at 630 V is obtained.

[0088] In the fourth step, according to the above process, calculate the optimal torque distribution coefficient maps at the other two voltages, the lowest 530 V and the highest 730 V.

[0089] Of course, if there is efficiency data at other voltages, the torque distribution coefficient map with the minimum power loss can also be obtained according to the above process for at least voltages other than these three voltages.

[0090] In the fifth step, determine whether there is a problem with the vehicle body stability. If there is a problem with the vehicle body stability, control the output torques of the front and rear electric drive systems according to the torques of the front and rear drive motors calculated by the vehicle electronic stability system or the torques of the front and rear drive motors calculated by the VCU. If there is no problem with the vehicle body stability, control the output torques of the front and rear electric drive systems according to the torque distribution coefficients calculated according to the above process.

[0091] The present invention also provides the following product embodiments:

[0092] A pure electric four-wheel drive torque distribution system, comprising:

[0093] A first determination module, configured to obtain a working mode, determine the throttle characteristics corresponding to the mode, and according to the throttle characteristics, in combination with the torque capabilities of the front and rear motors and the torque control accuracy threshold, determine the torque range of the electric drive assembly and the range of the front-wheel drive torque distribution coefficient at a set voltage that needs to be calculated;

[0094] A second determination module, configured to determine the torque distribution coefficient map with the optimal power loss at a set voltage according to the efficiency data of the electric drive assembly at the determined voltage and the zero-torque drag power loss data of the front and rear electric drive assemblies;

[0095] A third determination module, according to the range of the front-wheel drive torque distribution coefficient of the first determination module and the optimal torque distribution coefficient map obtained by the second determination module, compares and determines the optimal torque distribution coefficient map at the set voltage;

[0096] A fourth determination module, configured to determine the optimal torque distribution coefficient maps at other voltages;

[0097] A search module configured to find an optimal torque distribution coefficient in a torque distribution coefficient map according to the current voltage at the electric drive end, the required rotational speed at the output end, and the torque.

[0098] A judgment module configured to judge whether vehicle stability is satisfied. If so, front and rear motor torque control instructions are formed; otherwise, control instructions are formed according to the front and rear motor torques calculated by the vehicle stability system or the vehicle controller.

[0099] A terminal device includes a processor and a computer-readable storage medium. The processor is used to implement each instruction; the computer-readable storage medium is used to store multiple instructions, and the instructions are adapted to be loaded and executed by the processor to perform the steps in the above method.

[0100] A pure electric four-wheel drive vehicle includes the above system or terminal device, or distributes the front and rear motor torques by using the above method.

[0101] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0102] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0103] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0104] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable apparatus to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable apparatus provide steps for realizing the functions specified in one process or multiple processes and / or blocks Figure 1 one process or multiple processes and / or blocks Figure 1 or steps for realizing the functions specified in one block or multiple blocks.

[0105] The foregoing are only preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0106] Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, such description is not intended to limit the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A pure electric four-wheel drive torque distribution method, characterized in that, it includes the following steps: Obtain the working mode and determine the throttle characteristics corresponding to the mode; According to the throttle characteristics, combined with the torque capabilities and torque control precision thresholds of the front and rear electric drive assemblies under different voltages, determine the torque range of the electric drive assembly and the range of front-wheel drive torque distribution coefficients to be calculated at the set voltage; According to the efficiency data of the electric drive assembly under different voltages and the zero-torque drag power loss data of the front and rear electric drive assemblies, determine the optimal torque distribution coefficient map at the set voltage; Determine the optimal torque distribution coefficient map at other voltages; According to the current voltage at the electric drive end, the required speed and torque at the output end, find the optimal torque distribution coefficient in the torque distribution coefficient map; Based on the front and rear electric drive torque control commands determined according to the optimal torque distribution coefficient, judge whether the vehicle stability is satisfied. If so, form the front and rear motor torque control commands; otherwise, form the control commands according to the front and rear motor torques calculated by the vehicle stability system or the vehicle controller; The specific process of determining the optimal torque distribution coefficient map at the set voltage includes: According to the efficiency test data of the front and rear electric drive systems at the set voltage, calculate the power loss when the vehicle is controlled according to different front-wheel drive torque distribution coefficients at a specific corresponding point of the output speed and torque of the electric drive assembly. By comparing the calculation results, find the torque distribution coefficient K0 with the minimum power loss; When calculating the power loss at torque distribution coefficients of 0 and 1, it is also necessary to additionally consider the zero-torque drag power loss of the front-wheel drive or the zero-torque drag power loss of the rear-wheel drive. Then, compare the power losses at these two torque distribution coefficients with the power losses at the discrete torque distribution coefficients between 0 and 1 calculated in the previous step to find the torque distribution coefficient K1' with the minimum power loss; Compare the minimum torque distribution coefficient K1' with the absolute value of the front motor torque precision threshold * speed ratio / torque at a certain electric drive assembly output end. Except when the torque distribution coefficient is 0, take the maximum value of the two to obtain the optimal torque distribution coefficient K2'; When calculating the required torques of the front-wheel drive and rear-wheel drive according to the obtained optimal torque distribution coefficient K2', it is necessary to determine whether the required torques of the front-wheel drive and rear-wheel drive are within their torque output capabilities. If so, the optimal torque distribution coefficient K2' does not need to change; if not, it is necessary to re-determine the torque distribution coefficient according to the above three steps. At this time, the power loss at the torque distribution coefficient may be the second smallest value or other values until the optimal torque distribution coefficient K1 is found; Then calculate the power loss when controlled according to different front-wheel drive torque distribution coefficients at another specific corresponding point of the output speed and torque of the electric drive assembly. By comparing the calculation results, find the optimal torque distribution coefficients K1, K2, K3, K4... Kn; When all the optimal torque distribution coefficients at these discrete points are calculated, the optimal torque distribution coefficient map of the front and rear electric drive assembly systems at a certain voltage is obtained.

2. A pure electric four-wheel drive torque distribution method according to claim 1, characterized in that, The specific process of determining the torque range of the electric drive assembly at the set voltage to be calculated includes determining the torque range of the electric drive assembly corresponding to the torque distribution map at the set voltage to be calculated according to the maximum torque in the throttle characteristic.

3. A pure electric four-wheel drive torque distribution method as claimed in claim 1, characterized in that the specific process of determining the range of the front-wheel drive torque distribution coefficient at the set voltage to be calculated includes: When the absolute value of the vehicle demand torque is less than the sum of the absolute values of the torque control accuracy thresholds of the front and rear motor low torque regions multiplied by the speed ratio, the torque distribution coefficient is determined according to the minimum power loss corresponding to the two coefficients of 0 or 1 of the front-wheel drive torque distribution coefficient.

4. A pure electric four-wheel drive torque distribution method as claimed in claim 1, characterized in that the specific process of determining the range of the front-wheel drive torque distribution coefficient at the set voltage to be calculated includes: When the absolute value of the vehicle demand torque is greater than the sum of the absolute values of the torque control accuracy thresholds of the front and rear motor low torque regions multiplied by the speed ratio; According to the torque control accuracies of the front and rear drives, the range of the front-wheel drive torque distribution coefficient to be calculated is adjusted. The range of the front-wheel drive torque distribution coefficient is a discrete torque distribution coefficient range at set intervals of [absolute value of the motor torque accuracy threshold * speed ratio / torque at the output end of a certain electric drive assembly, 1].

5. A pure electric four-wheel drive torque distribution method as claimed in claim 1, characterized in that the specific process of determining the optimal torque distribution coefficient map at other voltages includes: according to the calculation process of the optimal torque distribution coefficient map at the set voltage, changing the voltage value, and calculating at least the optimal torque distribution coefficient maps including the minimum working voltage, rated voltage and maximum working voltage of the electric drive system.

6. A pure electric four-wheel drive torque distribution method as claimed in claim 1, characterized in that The specific process of forming the front and rear motor torque control commands includes, according to the optimal torque distribution coefficient map under different working conditions, corresponding to the working conditions of the electric drive assembly at different voltages, speeds and torques, obtaining the torque distribution coefficient of the front-wheel drive according to the current voltage, speed and torque requirements, and then calculating the motor demand torques of the front and rear drives. This torque is used as the torque control command for the front and rear motors.

7. A pure electric four-wheel drive torque distribution system, characterized in that it includes: A first determination module, configured to obtain the working mode, determine the throttle characteristic corresponding to the mode, and according to the throttle characteristic, in combination with the torque capabilities and torque control accuracy thresholds of the front and rear electric drive assemblies at different voltages, determine the torque range of the electric drive assembly and the range of the front-wheel drive torque distribution coefficient at the set voltage to be calculated; A second determination module, configured to determine the optimal torque distribution coefficient map at the set voltage according to the efficiency data of the electric drive assembly at the determined voltage and the zero-torque drag power loss data of the front and rear electric drive assemblies; A third determination module, according to the range of the front-wheel drive torque distribution coefficient of the first determination module and the optimal torque distribution coefficient map obtained by the second determination module, compares and determines the optimal torque distribution coefficient map at the set voltage; A fourth determination module, configured to determine the optimal torque distribution coefficient map at other voltages; A search module, configured to search for an optimal torque distribution coefficient in a torque distribution coefficient map according to the current voltage at the electric drive end, the required rotational speed at the output end, and the torque. A judgment module, configured to judge whether vehicle stability is satisfied. If so, front and rear motor torque control instructions are formed; otherwise, control instructions are formed according to the front and rear motor torques calculated by the vehicle stability system or the vehicle controller. The specific process of determining the optimal torque distribution coefficient map at a set voltage includes: According to the efficiency test data of the front and rear electric drive systems at the set voltage, calculate the power loss when the vehicle is controlled according to different front-wheel drive torque distribution coefficients at specific rotational speed and torque corresponding points at the output end of the electric drive assembly. By comparing the calculation results, find the torque distribution coefficient K0 with the minimum power loss. When calculating the power loss at torque distribution coefficients of 0 and 1, it is also necessary to additionally consider the zero-torque drag power loss of the front-wheel drive or the zero-torque drag power loss of the rear-wheel drive. Then, compare the power losses at these two torque distribution coefficients with the power losses at the discrete torque distribution coefficients between 0 and 1 calculated in the previous step to find the torque distribution coefficient K1' with the minimum power loss. Compare the minimum torque distribution coefficient K1' with the absolute value of the front motor torque accuracy threshold * speed ratio / torque at the output end of a certain electric drive assembly. Except when the torque distribution coefficient is 0, take the maximum value of the two to obtain the optimal torque distribution coefficient K2'. When calculating the required torques of the front-wheel drive and the rear-wheel drive according to the obtained optimal torque distribution coefficient K2', it is necessary to determine whether the required torques of the front-wheel drive and the rear-wheel drive are within their torque output capabilities. If so, the optimal torque distribution coefficient K2' does not need to change; if not, it is necessary to re-determine the torque distribution coefficient according to the above three steps. At this time, the power loss at the torque distribution coefficient may be the second smallest value or other values until the optimal torque distribution coefficient K1 is found. Then, calculate the power loss when the vehicle is controlled according to different front-wheel drive torque distribution coefficients at another specific rotational speed and torque corresponding point at the output end of the electric drive assembly. By comparing the calculation results, find the optimal torque distribution coefficients K1, K2, K3, K4... Kn. When all the optimal torque distribution coefficients at these discrete points are calculated, the optimal torque distribution coefficient map of the front and rear electric drive assembly systems at a certain voltage is obtained.

8. A terminal device Characterized in that it includes a processor and a computer-readable storage medium. The processor is used to implement each instruction; the computer-readable storage medium is used to store multiple instructions, and the instructions are adapted to be loaded and executed by the processor to perform the steps in the pure electric four-wheel drive torque distribution method according to any one of claims 1-6.

9. A pure electric four-wheel drive vehicle Characterized in that it includes the pure electric four-wheel drive torque distribution system according to claim 7 or the terminal device according to claim 8, or distributes the front and rear motor torques by using the pure electric four-wheel drive torque distribution method according to any one of claims 1-6.

Images