Four-wheel-drive torque distribution method for front-rear dual-motor automobile without wheel speed sensor

Abstract

The invention discloses a four-wheel-drive torque distribution method for a front-rear double-motor automobile without a wheel speed sensor, which comprises the following steps: acquiring the rotating speed of a front motor and the rotating speed of a rear motor, calculating the proportion of the rotating speed of the front motor and the rotating speed of the rear motor, and judging whether the proportion is within a preset range or not; if the proportion is within the preset range, it is judged that the automobile does not slip, and four-wheel-drive torque distribution based on the optimal efficiency is conducted through a genetic algorithm; and if the proportion is out of the preset range, it is judged that the automobile slips, and four-wheel-drive torque distribution is conducted through sliding mode control. A genetic algorithm global optimization objective function is combined with a fuzzy sliding mode control dynamic adjustment rule, the technical problem that a traditional single control method cannot give consideration to dynamic response speed and global optimality during dual-motor torque distribution is solved, high-precision rotating speed difference tracking is achieved, and meanwhile it is ensured that the system always approaches the optimal working point; and the overall energy efficiency and stability are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wheel speed sensorless vehicles, and in particular relates to a method for distributing torque of a four-wheel drive vehicle with front and rear dual motors without wheel speed sensors. Background Art

[0002] With the development of four-wheel drive technology in electric vehicles, precise torque distribution is crucial to vehicle stability, energy efficiency, and driving experience. Traditional solutions rely on wheel speed sensors to monitor each wheel's status in real time. However, these sensors increase cost, failure rate, and system complexity, and their reliability is particularly reduced in harsh environments.

[0003] Existing wheel speed sensorless solutions mostly distribute torque based on a fixed ratio. In the process of implementing the present invention, the inventors found that the existing technology has at least the following problems:

[0004] 1. Dynamic and steady-state contradiction: Although a single control method (such as pure sliding mode) has a fast response, it is difficult to achieve optimal energy consumption;

[0005] 2. Insufficient robustness: Fixed allocation rules or simplified models are prone to instability when the road surface changes suddenly. Summary of the Invention

[0006] The purpose of the embodiments of the present application is to address the problems existing in the prior art and provide a method for distributing torque to a four-wheel drive vehicle with front and rear dual motors without wheel speed sensors.

[0007] According to a first aspect of an embodiment of the present application, a method for distributing torque to a front and rear dual-motor four-wheel drive vehicle without wheel speed sensors is provided, comprising:

[0008] S1: Obtaining the front motor speed and the rear motor speed, calculating the ratio of the front motor speed to the rear motor speed, and determining whether the ratio is within a predetermined range;

[0009] S2: If the ratio is within a predetermined range, it is determined that the vehicle is not slipping, and four-wheel drive torque distribution based on optimal efficiency is performed using a genetic algorithm;

[0010] S3: If the ratio is outside the predetermined range, it is determined that the vehicle is slipping, and the four-wheel drive torque is distributed using adaptive sliding film control.

[0011] Furthermore, in step S2, the four-wheel drive torque distribution based on the best efficiency is performed by a genetic algorithm, specifically:

[0012] (1) Generate an initial first population based on the minimum / maximum torque coefficient of the front axle drive motor;

[0013] (2) Calculate the sum of the loss power corresponding to each individual in the first population, thereby obtaining the fitness of each individual, where the sum of the loss power of the individual is inversely proportional to the fitness;

[0014] (3) determining whether an end condition is satisfied, and if so, outputting a front axle motor torque coefficient and a rear axle motor torque coefficient corresponding to the most efficient individual in the current second population, wherein the sum of the front axle motor torque coefficient and the rear axle motor torque coefficient is equal to 1; if not, continuing the execution;

[0015] (4) Randomly select two individuals from the first population, compare their fitness, and add the individual with the larger fitness to the second population. Repeat the selection until the number of individuals in the second population reaches the predetermined population size.

[0016] (5) For each individual i in the second population, a random number r1 of 0 to 1 is generated. If the random number r1 is less than the crossover probability, the crossover is triggered, that is, the individual i is randomly weighted and fused with the next individual (i+1) to generate an offspring i', which replaces the original parent i;

[0017] (6) For each individual j in the second population obtained in step (5), generate a random number r2 between 0 and 1. If the random number r2 is less than the mutation probability, trigger the mutation, that is, perform Gaussian approximate mutation on the individual j, and shift the individual j by r2 multiplied by 10% Gaussian perturbation (0.1×(maximum torque coefficient-minimum torque coefficient)), and return to step (3);

[0018] Among them, the predetermined population size, maximum number of generations, minimum / maximum torque coefficient of the front axle drive motor, crossover probability, and mutation probability are all obtained through calibration.

[0019] Furthermore, in step S3, the four-wheel drive torque distribution is performed using adaptive sliding film control, specifically:

[0020] The speed of the rear axle motor is converted by the transmission ratio of the transmission system and the difference between it and the speed of the front axle motor is used to obtain the sliding surface;

[0021] When the front axle motor torque changes, the torque change sgn(s)·ΔT is added to the rear axle motor torque based on the sign of the sliding surface, where s is the sliding surface, sgn is the sign function, and ΔT is the torque adjustment step size.

[0022] The changed torque is compared with the total torque sent by the VCU, converted into the front and rear axle motor torque coefficients and then distributed.

[0023] Furthermore, an allowable error range is added at the sliding mode equilibrium point, that is, the sliding mode surface s=0 to set a dead zone to avoid the front and rear axle motor torques from oscillating back and forth, wherein the allowable error range is determined by calibration.

[0024] Furthermore, the torque adjustment step size is inferred using fuzzy rules, specifically:

[0025] Based on the sliding surface s and the sliding surface change rate ds, the torque adjustment step ΔT is obtained through fuzzy control using predetermined fuzzy rules.

[0026] According to a second aspect of an embodiment of the present application, a computer program product is provided, comprising a computer program / instruction, which implements the method described in the first aspect when executed by a processor.

[0027] According to a third aspect of the embodiments of the present application, there is provided an electronic device, including:

[0028] one or more processors;

[0029] a memory for storing one or more programs;

[0030] When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in the first aspect.

[0031] According to a fourth aspect of an embodiment of the present application, a computer-readable storage medium is provided, on which computer instructions are stored. When the instructions are executed by a processor, the steps of the method described in the first aspect are implemented.

[0032] The technical solutions provided by the embodiments of the present application may have the following beneficial effects:

[0033] It can be seen from the above embodiments that the present application combines the global optimization objective function of the genetic algorithm with the dynamic adjustment rules of the fuzzy sliding mode control, overcoming the technical problem that the traditional single control method cannot take into account both dynamic response speed and global optimality when distributing the torque of the dual motors. It achieves high-precision speed difference tracking while ensuring that the system always approaches the optimal operating point, thereby improving overall energy efficiency and stability.

[0034] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0036] Figure 1 The present invention is a flowchart showing a method for distributing torque to a four-wheel drive vehicle with front and rear dual motors without wheel speed sensors according to an exemplary embodiment.

[0037] Figure 2 The figure is a flow chart showing a genetic algorithm for solving the optimal torque according to an exemplary embodiment.

[0038] Figure 3The present invention is a block diagram of a four-wheel drive torque distribution device for a front and rear dual-motor vehicle without wheel speed sensors according to an exemplary embodiment.

[0039] Figure 4 The figure is a schematic diagram of an electronic device according to an exemplary embodiment. DETAILED DESCRIPTION

[0040] Exemplary embodiments are described in detail herein, with examples illustrated in the accompanying drawings. When the following description refers to the drawings, identical numerals in different drawings represent identical or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with this application.

[0041] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0042] It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0043] Figure 1 FIG. 1 is a flow chart showing a method for distributing torque between front and rear dual-motor four-wheel drive vehicles without wheel speed sensors according to an exemplary embodiment. Figure 1 As shown, this method is applicable to vehicles with dual front and rear motor drive, no central differential and no wheel speed sensors, and can include the following steps:

[0044] S1: Obtaining the front motor speed and the rear motor speed, calculating the ratio of the front motor speed to the rear motor speed, and determining whether the ratio is within a predetermined range;

[0045] S2: If the ratio is within a predetermined range, it is determined that the vehicle is not slipping, and four-wheel drive torque distribution based on optimal efficiency (OE) is performed using a genetic algorithm;

[0046] In this step, the optimal torque can be solved by genetic algorithm, that is, the torque distribution coefficient of the front and rear axle motors that minimizes the power loss of the front and rear axle motors under the current speed conditions can be calculated, such as Figure 2 As shown, specifically:

[0047] (1) Encoding the minimum / maximum torque coefficients of the front axle drive motor into floating-point numbers and generating an initial first population. In this embodiment, since the coefficients themselves are floating-point numbers, no processing is required during encoding. A number of arbitrary points are randomly selected between the minimum / maximum torque coefficients. The set of these points is the initial population, and the number of selected points is the predetermined population size.

[0048] (2) Calculate the sum of the loss power corresponding to each individual in the first population, thereby obtaining the fitness of each individual, where the sum of the loss power of the individual is inversely proportional to the fitness;

[0049] Among them, the power loss P Loss The calculation formula is:

[0050]

[0051] Where n is the motor speed, T is the motor torque, and eta is the motor electric efficiency.

[0052] (3) determining whether an end condition is satisfied, and if so, outputting a front axle motor torque coefficient and a rear axle motor torque coefficient corresponding to the most efficient individual in the current second population, wherein the sum of the front axle motor torque coefficient and the rear axle motor torque coefficient is equal to 1; if not, continuing the execution;

[0053] (4) Randomly select two individuals from the first population, compare their fitness, and add the individual with the larger fitness to the second population. Repeat the selection until the number of individuals in the second population reaches the predetermined population size.

[0054] (5) For each individual i in the second population, a random number r1 of 0 to 1 is generated. If the random number r1 is less than the crossover probability, the crossover is triggered, that is, the individual i is randomly weighted and fused with the next individual (i+1) to generate an offspring i', which replaces the original parent i;

[0055] (6) For each individual j in the second population obtained in step (4), generate a random number r2 between 0 and 1. If the random number r2 is less than the mutation probability, trigger the mutation, that is, perform Gaussian approximate mutation on the individual j, and shift the individual j by r2 multiplied by 10% Gaussian perturbation (0.1×(maximum torque coefficient-minimum torque coefficient)), and return to step (3);

[0056] Among them, the predetermined population size, maximum number of generations, minimum / maximum torque coefficient of the front axle drive motor, crossover probability, and mutation probability are all obtained through calibration.

[0057] S3: If the ratio is outside the predetermined range, it is determined that the vehicle is slipping, and adaptive fuzzy sliding mode control (AFSMC) is used to distribute the four-wheel drive torque;

[0058] Specifically, the speed of the rear axle motor is converted into a speed comparable to that of the front axle motor through the transmission ratio. The ratio is Where i R is the total reduction ratio of the rear axle motor, i F is the total reduction ratio of the front axle motor, i Trans is the gear ratio of the current gear of the transmission. The sliding surface is used to force the system state to slide along a predetermined trajectory, suppress disturbances, and ensure rapid convergence and robustness. Since the front and rear axle motor speeds are adjusted according to the above ratio during normal driving, the sliding surface is designed to be s = k·n R -n F , where n F is the front axle motor speed, n R is the rear axle motor speed, and k is the proportional coefficient previously converted using the transmission ratio. At the same time, an allowable error range is added at the sliding mode equilibrium point (s=0) to set the dead zone. The allowable error range can be determined by calibration to avoid oscillation of the front and rear axle motor torques. When the front axle motor torque changes, the torque change is sgn(s)·ΔT, which is added to the rear axle motor, where sgn is the sign function and ΔT is the torque adjustment step. The changed torque is compared with the total torque sent by the VCU, converted into the front and rear axle motor torque coefficients, and then distributed. When the front motor speed increases, the sliding mode surface is negative, the torque change is negative, the front axle motor reduces torque, and the slip tendency is reduced. The same applies in reverse.

[0059] In this step, fuzzy rules can also be used to infer the torque adjustment step size, specifically:

[0060] Based on the sliding surface s and the sliding surface change rate ds, the torque adjustment step ΔT is obtained through the fuzzy control toolbox of MATLAB and predetermined fuzzy rules, wherein the membership function can select a triangular membership function (simple calculation and strong real-time performance).

[0061] Table 1 below shows the fuzzy rules (expert experience). By introducing fuzzy rules, the sliding mode control can enhance robustness and improve noise resistance.

[0062] Table 1

[0063]

[0064] This table is used in the decision-making process of the torque fuzzy controller: the torque adjustment step is dynamically calculated based on the sliding surface and the sliding surface change rate. It belongs to the core rule base of fuzzy reasoning.

[0065] NB (Negative Big), NS (Negative Small), ZO (Zero), PS (Positive Small), and PB (Positive Big) stand for Negative Big, Negative Small, Zero, Positive Small, and Positive Big, respectively. NB indicates a very large negative error and requires rapid reverse correction; NS indicates a slightly lower error and requires fine-tuning in the negative direction; ZO indicates a perfect zero bound; PS indicates a slightly lower error and requires fine-tuning in the positive direction; and PB indicates a very large positive error and requires rapid reverse correction.

[0066] The entire table represents a robust control strategy based on dynamic errors: the larger the deviation, the stronger the compensation until the system returns to equilibrium.

[0067] Among them, the outputs of steps (2) and (3) both need to use the Ramp function to avoid torque mutations caused by controller switching.

[0068] It should be noted that steps (2) and (3) obtain the front axle motor torque coefficient and the rear axle motor torque coefficient. The total torque sent by the VCU needs to be distributed according to their respective coefficients, that is, the front axle motor torque = front axle motor torque coefficient * total torque, the rear axle motor torque = rear axle motor torque coefficient * total torque, and the front axle motor torque coefficient + rear axle motor torque coefficient = 1.

[0069] This method aims to improve the ability of vehicles without wheel speed sensors to escape from difficult driving conditions and reduce system energy consumption. When the wheels are not slipping, even if the specifications of the front and rear dual motors and the transmission ratios of the front and rear drivetrains differ, the ratio of their speeds is essentially fixed, and the normalized speed difference is essentially constant. When a wheel slips, the motor load decreases, and the speed increases significantly. If the ratio of the front and rear motor speeds exceeds the error range of the fixed ratio, the system switches to SMC control, reducing the torque of that motor while compensating the other motor. The strong robustness of SMC improves the vehicle's adaptability to complex road conditions and its ability to escape from difficult driving. If the ratio of the front and rear motor speeds is within the error range of the fixed ratio, the system switches to OE control to reduce energy consumption.

[0070] Corresponding to the aforementioned embodiment of the method for distributing torque between front and rear dual-motor vehicles with four-wheel drive without wheel speed sensors, the present application also provides an embodiment of a device for distributing torque between front and rear dual-motor vehicles with four-wheel drive without wheel speed sensors.

[0071] Figure 3 This is a block diagram of a front and rear dual-motor four-wheel drive torque distribution device for a vehicle without wheel speed sensors according to an exemplary embodiment. Figure 3, the apparatus may include:

[0072] a ratio calculation module 21 for obtaining the front motor speed and the rear motor speed, calculating the ratio of the front motor speed to the rear motor speed, and determining whether the ratio is within a predetermined range;

[0073] an efficiency-optimizing distribution module 22 for determining that the vehicle is not slipping if the ratio is within a predetermined range, and performing four-wheel drive torque distribution based on efficiency optimization through a genetic algorithm;

[0074] The sliding film control distribution module 23 is configured to determine that the vehicle is slipping if the ratio is outside a predetermined range, and to distribute the four-wheel drive torque using sliding film control.

[0075] Regarding the apparatus in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0076] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to the partial description of the method embodiments. The device embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present application scheme. A person of ordinary skill in the art can understand and implement it without paying any creative work.

[0077] Accordingly, the present application also provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the above-mentioned front and rear dual-motor four-wheel drive torque distribution method for a wheel speed sensorless vehicle.

[0078] Accordingly, the present application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned method for distributing torque between front and rear dual-motor vehicles with no wheel speed sensors. Figure 4 As shown in the figure, it is a hardware structure diagram of a device with data processing capability for a front and rear dual-motor four-wheel drive torque distribution device without wheel speed sensor provided by an embodiment of the present invention, except Figure 4 In addition to the processor, memory, and network interface shown, any device with data processing capabilities in which the apparatus in the embodiment is located may also include other hardware, generally based on the actual functions of the device with data processing capabilities, which will not be described in detail.

[0079] Accordingly, the present application also provides a computer-readable storage medium having computer instructions stored thereon, which, when executed by a processor, implement the above-mentioned method for distributing torque to the front and rear dual-motor four-wheel drive vehicle without wheel speed sensors. The computer-readable storage medium may be an internal storage unit of any device with data processing capabilities as described in any of the aforementioned embodiments, such as a hard disk or memory. The computer-readable storage medium may also be an external storage device, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), an SD card, a flash card (Flash Card), etc. equipped on the device. Furthermore, the computer-readable storage medium may also include both an internal storage unit and an external storage device of any device with data processing capabilities. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capabilities, and may also be used to temporarily store data that has been output or is to be output.

[0080] Those skilled in the art will readily conceive of other embodiments of the present application after considering the specification and practicing the contents disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of this application and include common knowledge or customary techniques in the art that are not disclosed in this application.

Claims

1. A method for distributing torque on a four-wheel drive vehicle with dual motors and no wheel speed sensors, characterized in that: include: S1: Obtaining the front motor speed and the rear motor speed, calculating the ratio of the front motor speed to the rear motor speed, and determining whether the ratio is within a predetermined range; S2: If the ratio is within a predetermined range, it is determined that the vehicle is not slipping, and four-wheel drive torque distribution based on optimal efficiency is performed using a genetic algorithm; S3: If the ratio is outside the predetermined range, it is determined that the vehicle is slipping, and the four-wheel drive torque is distributed using adaptive sliding film control.

2. The method according to claim 1, characterized in that In step S2, the four-wheel drive torque distribution based on the best efficiency is performed by a genetic algorithm, specifically: (1) Generate an initial first population based on the minimum / maximum torque coefficient of the front axle drive motor; (2) Calculate the sum of the loss power corresponding to each individual in the first population, thereby obtaining the fitness of each individual, where the sum of the loss power of the individual is inversely proportional to the fitness; (3) determining whether an end condition is satisfied, and if so, outputting a front axle motor torque coefficient and a rear axle motor torque coefficient corresponding to the most efficient individual in the current second population, wherein the sum of the front axle motor torque coefficient and the rear axle motor torque coefficient is equal to 1; if not, continuing the execution; (4) Randomly select two individuals from the first population, compare their fitness, and add the individual with the larger fitness to the second population. Repeat the selection until the number of individuals in the second population reaches the predetermined population size. (5) For each individual i in the second population, a random number r1 of 0 to 1 is generated. If the random number r1 is less than the crossover probability, the crossover is triggered, that is, the individual i is randomly weighted and fused with the next individual (i+1) to generate an offspring i', which replaces the original parent i; (6) For each individual j in the second population obtained in step (5), generate a random number r2 between 0 and 1. If the random number r2 is less than the mutation probability, trigger the mutation, that is, perform Gaussian approximate mutation on the individual j, and shift the individual j by r2 multiplied by 10% Gaussian perturbation (0.1×(maximum torque coefficient-minimum torque coefficient)), and return to step (3); Among them, the predetermined population size, maximum number of generations, minimum / maximum torque coefficient of the front axle drive motor, crossover probability, and mutation probability are all obtained through calibration.

3. The method according to claim 1, characterized in that In step S3, the four-wheel drive torque distribution is performed using adaptive sliding film control, specifically: The speed of the rear axle motor is converted by the transmission ratio of the transmission system and the difference between it and the speed of the front axle motor is used to obtain the sliding surface. When the front axle motor torque changes, the torque change sgn(s)·ΔT is added to the rear axle motor torque based on the sign of the sliding surface, where s is the sliding surface, sgn is the sign function, and ΔT is the torque adjustment step size. The changed torque is compared with the total torque sent by the VCU, converted into the front and rear axle motor torque coefficients and then distributed.

4. The method according to claim 3, characterized in that An allowable error range is added at the sliding mode equilibrium point, i.e., the sliding mode surface s=0, to set a dead zone to avoid oscillation of the front and rear axle motor torques. The allowable error range is determined by calibration.

5. The method according to claim 3, characterized in that The torque adjustment step size is inferred using fuzzy rules, specifically: Based on the sliding surface s and the sliding surface change rate ds, the torque adjustment step ΔT is obtained through fuzzy control using predetermined fuzzy rules.

6. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the method according to any one of claims 1 to 5 is implemented.

7. An electronic device, characterized in that: include: one or more processors; a memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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