A method, system, and vehicle for low-speed steering control of a four-wheel drive hub motor vehicle.

Abstract

This invention discloses a method, system, and vehicle for low-speed steering control of a four-wheel drive hub motor vehicle, relating to the field of vehicle steering control technology. The method involves: during low-speed steering of the vehicle, acquiring the accelerator pedal opening and steering wheel angle; determining the target speed of the hub motor with the highest rotational speed based on the accelerator pedal opening; identifying the outer front wheel hub motor as the hub motor during steering; determining the speed ratio between the outer front wheel hub motor and other wheel hub motors based on the steering wheel angle; and then, combining this with the target speed of the outer front wheel hub motor, determining the target speed of each hub motor; and controlling the operation of the four-wheel drive hub motors according to the target speeds to complete the low-speed turn. This invention employs four independently driven hub motors, and the speed and torque distribution of each hub motor can be achieved by directly controlling the output speed-torque difference of the motors through a controller, improving vehicle driving safety and avoiding potential instability during low-speed turns.

Description

Technical Field

[0001] This invention relates to the field of vehicle steering control technology, and in particular to a low-speed steering control method, system and vehicle for a four-wheel drive hub motor vehicle. Background Technology

[0002] Currently, traditional gasoline-powered vehicles and electric drive axle-mounted electric vehicles are powered by an engine or a single motor located in the front compartment / axle. They often require transmission mechanisms such as a gearbox, driveshaft, and differential to output power to the left and right wheels and drive them to rotate. Since a speed difference is required between the left and right wheels when turning, this speed difference is achieved using a differential. However, the application of a differential will greatly affect the safety and stability of the vehicle on low-friction surfaces, its ability to overcome obstacles, and its steering performance. For example, when the vehicle is turning, the speed difference between the inner and outer wheels will cause the vehicle to be unstable in steering. While a differential can allow for the speed difference between the inner and outer wheels, when the vehicle is driving on a low-friction surface, one wheel may lose traction due to insufficient road friction or other factors. In this case, the differential will automatically distribute all driving force to the wheel that has lost traction, while the other wheel that is working normally will not receive enough driving force. This will lead to vehicle instability and affect the vehicle's low-speed turning performance. Moreover, differentials require high-strength materials and manufacturing processes, resulting in high costs. Summary of the Invention

[0003] To address the shortcomings of the existing technology, this invention provides a low-speed steering control method, system, and vehicle for a four-wheel drive vehicle with hub motors. This vehicle utilizes hub motors for independent four-wheel drive. By directly controlling the output speed-torque difference of the hub motors through a controller, the speed-torque distribution of each hub motor can be achieved. This results in more accurate and rapid motor response, and torque can be arbitrarily distributed as needed, better meeting vehicle performance requirements and significantly increasing the safety of vehicles using hub motors. It effectively avoids potential driving instability during low-speed cornering. Furthermore, since the hub motors are directly controlled by the controller, no additional actuators or control components are required, leading to lower costs.

[0004] In a first aspect, the present invention provides a low-speed steering control method for a four-wheel drive hub motor vehicle.

[0005] A low-speed steering control method for a four-wheel drive hub motor vehicle, comprising:

[0006] During low-speed steering while driving a car, obtain the accelerator pedal opening and steering wheel angle;

[0007] Based on the accelerator pedal opening, the target speed of the hub motor with the highest rotational speed is determined; the hub motor with the highest rotational speed is the outer front wheel hub motor when turning.

[0008] Based on the steering wheel angle, the speed ratio of the outer front wheel hub motor to the other wheel hub motors is determined during steering. Then, combined with the target speed of the outer front wheel hub motor during steering, the target speed of each hub motor is determined. The four-wheel drive hub motors are controlled to operate according to the target speed to complete the low-speed turn of the car.

[0009] A further technical solution involves setting a steering wheel rotation clearance angle, comparing the steering wheel angle with the steering wheel rotation clearance angle, and considering that the car is driving straight if the steering wheel angle is less than or equal to the steering wheel rotation clearance angle, otherwise considering that the car is turning.

[0010] A further technical solution involves determining the speed ratio of the left front wheel hub motor to the other wheel hub motors when the car turns right. This ratio is then used to determine the target speed of the other wheel hub motors.

[0011] A further technical solution involves determining the speed ratio of the right front wheel hub motor to the other wheel hub motors when the car turns left. This ratio is then used to determine the target speed of the other wheel hub motors.

[0012] A further technical solution, based on the Ackerman steering model, analyzes and determines the relationship between the steering wheel angle and the speed ratio of the four-wheel drive hub motors; the relationship is as follows: when turning at low speed, the speed ratio of each hub motor to the left front wheel hub motor or the right front wheel hub motor is only related to the steering wheel angle and vehicle structural parameters, and is not related to the vehicle speed.

[0013] A further technical solution involves the following relationship between the steering wheel angle and the engine speed ratio:

[0014]

[0015]

[0016]

[0017]

[0018] In the above formula, ω i Let r be the angular velocity of the i-th wheel, where i = 1, 2, 3, 4, the first wheel is the left front wheel, and the second wheel is the right front wheel; i Let B be the rolling radius of the i-th wheel; L be the wheelbase; B1 and B2 are the intersections of the left and right front wheel kingpin axes with the ground, respectively; the distance between B1 and B2 is B; B3 and B4 are the projections of B1 and B2 onto the line connecting the left and right rear wheel connection points, respectively. i Let the projection of the center of the i-th wheel onto point B on the ground be... iThe distance; α and β are the steering angles of the left and right front wheels, respectively; For steering wheel angle; i w0 This is the steering system angle transmission ratio.

[0019] Secondly, the present invention provides a low-speed steering control system for a four-wheel drive hub motor vehicle.

[0020] A low-speed steering control system for a four-wheel drive hub motor vehicle is disclosed, which is used to drive the independent four hub motors of the vehicle to steer the vehicle. The system includes a steering controller, four independent hub motors for driving the rotation of the four wheels, and a motor controller for sending different speed commands to the four hub motors. The steering controller is electrically connected to each motor controller, a steering wheel, and an electronic accelerator pedal. The steering controller is used to execute the steps of the low-speed steering control method for a four-wheel drive hub motor vehicle as described in the first aspect.

[0021] Thirdly, the present invention also provides an electronic device, including a memory and a processor, and computer instructions stored in the memory and running on the processor, wherein the computer instructions, when executed by the processor, perform the steps of the method described in the first aspect.

[0022] Fourthly, the present invention also provides a computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the steps of the method described in the first aspect.

[0023] Fifthly, the present invention also provides a vehicle comprising the low-speed steering control system for a four-wheel drive hub motor vehicle as described in the second aspect, or achieving low-speed steering by employing the steps of the low-speed steering control method for a four-wheel drive hub motor vehicle as described in the first aspect.

[0024] The above one or more technical solutions have the following beneficial effects:

[0025] 1. This invention provides a low-speed steering control method, system, and vehicle for a four-wheel drive vehicle with hub motors. The vehicle utilizes hub motors for independent four-wheel drive. By directly controlling the output speed-torque difference of the hub motors through a controller, the speed-torque distribution of each hub motor can be achieved. This results in more accurate and rapid motor response, and torque can be arbitrarily distributed as needed, better meeting vehicle performance requirements. During steering, different motor controllers determine the target speed of each motor according to the relationship between the steering wheel angle and the speed ratio, thereby meeting vehicle performance requirements and significantly increasing the safety of vehicles using hub motors. This effectively avoids potential driving instability during low-speed cornering.

[0026] 2. This invention uses four-wheel independent drive hub motors, which are directly controlled by the controller. No additional actuators or control components are required, resulting in lower costs and easier implementation. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 This is an overall flowchart of the low-speed steering control method for a four-wheel drive hub motor vehicle according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of a four-wheel drive hub motor vehicle in an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the analysis results of the Ackermann steering model in an embodiment of the present invention. Detailed Implementation

[0031] It should be noted that the following detailed descriptions are exemplary and are intended only to describe specific embodiments and to provide further explanation of the invention, and are not intended to limit the scope of exemplary embodiments of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] Example 1

[0033] Considering that existing gasoline-powered vehicles and electric axle-driven electric vehicles often require transmission mechanisms such as gearboxes, drive shafts, and differentials to output power to the left and right wheels, their safety stability, obstacle-crossing ability, and steering performance are poor when driving on low-friction surfaces. Therefore, this embodiment proposes a low-speed steering control method for four-wheel drive in-wheel motor vehicles. The vehicle uses in-wheel motors for independent four-wheel drive, and the speed-torque difference of the in-wheel motors is directly controlled by a controller to achieve speed-torque distribution among the in-wheel motors, ensuring steering safety and stability when driving on low-friction surfaces. The low-speed steering control method for four-wheel drive in-wheel motor vehicles proposed in this embodiment is as follows: Figure 1 As shown, the specific steps include:

[0034] During low-speed steering while driving a car, obtain the accelerator pedal opening and steering wheel angle;

[0035] Based on the accelerator pedal opening, the target speed of the hub motor with the highest rotational speed is determined; the hub motor with the highest rotational speed is the outer front wheel hub motor when turning.

[0036] Based on the steering wheel angle, the speed ratio of the outer front wheel hub motor to the other wheel hub motors is determined during steering. Then, combined with the target speed of the outer front wheel hub motor during steering, the target speed of each hub motor is determined. The four-wheel drive hub motors are controlled to operate according to the target speed to complete the low-speed turn of the car.

[0037] The following content provides a more detailed description of the low-speed steering control method for four-wheel drive hub motor vehicles proposed in this embodiment.

[0038] like Figure 2 As shown, for the four-wheel drive hub motors, each hub motor is controlled by a motor controller, which can control each motor to achieve different speeds and torques. Based on this, the vehicle steering is analyzed. In this embodiment, the Ackerman steering model is used for analysis, such as... Figure 3 The analysis results shown are based on the Ackerman steering model, where the top side represents the direction of the car's movement and O is the steering center.

[0039] When the vehicle is turning at low speed, the slip angles of each tire are very small and can be ignored. Using the Ackerman steering model to analyze the four-wheel differential speed relationship, when the vehicle is turning right and the wheels are purely rolling, the Ackerman steering model shows that the speed ratio of each wheel to the speed of the first wheel (i.e., the left front wheel) or the second wheel (i.e., the right front wheel) is:

[0040]

[0041]

[0042]

[0043]

[0044] In the above formula, ω i Let r be the angular velocity of the i-th wheel, where i = 1, 2, 3, 4, the first wheel is the left front wheel, and the second wheel is the right front wheel; i Let L be the rolling radius of the i-th wheel; L is the wheelbase, which is the distance between B1B2 (i.e., the line connecting B1B2) and B3B4; B1 and B2 are the intersection points of the left and right front wheel kingpin axes with the ground, respectively; the distance between B1 and B2 is B; B3 and B4 are the projections of B1 and B2 onto the line connecting the left and right rear wheel connection points, respectively. i Let the projection of the center of the i-th wheel onto point B on the ground be... i The distance; α and β are the steering angles of the left and right front wheels, respectively; For steering wheel angle; i w0 This is the steering system angle transmission ratio.

[0045] Based on the Ackerman steering model, the relationship between the steering wheel angle and the speed ratio of the four-wheel drive hub motors was analyzed and determined. During low-speed steering, the speed ratio of each wheel to the speed of the first wheel (i.e., the left front wheel) or the second wheel (i.e., the right front wheel) is only related to the steering wheel angle. and vehicle structural parameters B, L, b i r i and i w0 It is related to, but not to, vehicle speed. Furthermore, if we consider the vehicle's structural parameters as constants, then the speed ratio... or Only the steering wheel angle The function, i.e. or Furthermore, during low-speed steering, different motor controllers determine the target speed of each motor according to the above function to meet the vehicle performance requirements and increase the safety of vehicles using hub motors.

[0046] Furthermore, in actual driving, it is necessary to consider both left and right turns. Specifically, during low-speed turning, the accelerator pedal opening and steering wheel angle are obtained. First, based on the accelerator pedal opening, the target speed ω of the highest-speed hub motor (which is actually the outer front wheel hub motor during turning) is determined. m，max Then, based on the above analysis and the steering wheel angle, determine the speed ratio of the outer front wheel hub motor to the other wheel hub motors during steering; finally, based on the target speed ω... m，max By determining the speed ratio, the target speed of each hub motor is determined, and the operation of the four-wheel drive hub motors is controlled according to the target speed to complete the low-speed turning of the car.

[0047] Considering both left and right turns, when the car turns right, the outer front wheel hub motor refers to the left front wheel hub motor. The speed ratio of the left front wheel hub motor to the other wheel hub motors is determined based on the steering wheel angle, and this ratio determines the target speed of the other wheel hub motors. When the car turns left, the outer front wheel hub motor refers to the right front wheel hub motor. The speed ratio of the right front wheel hub motor to the other wheel hub motors is determined based on the steering wheel angle, and this ratio determines the target speed of the other wheel hub motors. Preferably, a preset steering wheel rotation clearance angle is used. The steering wheel angle is compared with the steering wheel rotation clearance angle. If the steering wheel angle is less than or equal to the steering wheel rotation clearance angle, the car is considered to be driving straight; otherwise, the car is considered to be turning.

[0048] The above scheme can be expressed by the following formula:

[0049]

[0050] In the above formula, ω im,maxThis represents the target rotational speed of the hub motor of the i-th wheel. Based on the actual steering wheel angle φ determined through test calibration, the predetermined value can be found by looking up a table. The table is used to determine this. Considering the steering wheel's rotational clearance, when the steering wheel angle is not 0 but the vehicle is in a straight-line driving position (i.e., within the steering wheel rotational clearance range of [-ε, +ε]), it is still considered that the vehicle is driving straight.

[0051] Using the above method, the target speed of each motor can be determined based on the current accelerator pedal opening and steering wheel angle, thereby enabling vector control of the motor speed and torque to achieve safe and reliable low-speed turning of the car.

[0052] Example 2

[0053] This embodiment provides a low-speed steering control system for a four-wheel drive vehicle with hub motors, used to drive the independent hub motors of the four wheels of the vehicle to steer the vehicle. Figure 2 As shown, the system includes a steering controller, four independent hub motors for driving the rotation of the four wheels, and a motor controller for sending different speed commands to the four hub motors respectively. The steering controller is electrically connected to each motor controller, the steering wheel, and the electronic accelerator pedal. The steering controller is used to execute the steps in the low-speed steering control method for a four-wheel drive hub motor vehicle as described in Embodiment 1.

[0054] Furthermore, each hub motor is connected to the corresponding wheel via a reducer; each motor controller is electrically connected to the vehicle's battery, which supplies power to each motor controller.

[0055] Example 3

[0056] This embodiment provides an electronic device, including a memory and a processor, as well as computer instructions stored in the memory and running on the processor. When the processor executes the computer instructions, it completes the steps in the low-speed steering control method for a four-wheel drive hub motor vehicle as described above.

[0057] Example 4

[0058] This embodiment also provides a computer-readable storage medium for storing computer instructions, which, when executed by a processor, complete the steps in the low-speed steering control method for a four-wheel drive hub motor vehicle as described above.

[0059] Example 5

[0060] This embodiment also provides a vehicle, including the low-speed steering control system for a four-wheel drive hub motor vehicle as described in Embodiment 2, or achieving low-speed steering by adopting the steps of the low-speed steering control method for a four-wheel drive hub motor vehicle as described in Embodiment 1.

[0061] The steps and methods involved in Embodiments 2 to 5 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0062] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0063] The above description is only a preferred embodiment of the present invention. Although the specific implementation of the present invention has been described in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A low-speed steering control method for a four-wheel drive hub motor vehicle, characterized in that, include: During low-speed steering while driving a car, obtain the accelerator pedal opening and steering wheel angle; Based on the accelerator pedal opening, determine the target speed of the hub motor with the highest rotational speed; The highest speed hub motor is the outer front wheel hub motor when turning; Based on the steering wheel angle, the speed ratio of the outer front wheel hub motor to the other wheel hub motors is determined when turning. Then, combined with the target speed of the outer front wheel hub motor when turning, the target speed of each hub motor is determined. The four-wheel drive hub motors are controlled to operate according to the target speed to complete the low-speed turn of the car. When the car turns right, the outer front wheel hub motor refers to the left front wheel hub motor. At this time, the speed ratio of the left front wheel hub motor to the other wheel hub motors is determined according to the steering wheel angle, and the target speed of the other wheel hub motors is determined according to this speed ratio. When the car turns left, the outer front wheel hub motor refers to the right front wheel hub motor. At this time, the speed ratio of the right front wheel hub motor to the other wheel hub motors is determined according to the steering wheel angle, and the target speed of the other wheel hub motors is determined according to this speed ratio. Based on the Ackermann steering model, the relationship between steering wheel angle and the speed ratio of the four-wheel drive hub motors was analyzed and determined. The relationship is as follows: during low-speed steering, the speed ratio of each hub motor to the left front wheel hub motor or the right front wheel hub motor is only related to the steering wheel angle and vehicle structural parameters, and is independent of vehicle speed. The relationship between steering wheel angle and speed ratio is: , , ； , , ； ； ； In the above formula, For the first i Wheel angular velocity, i = 1,2,3,4, the first wheel is the left front wheel, and the second wheel is the right front wheel; For the first i Wheel rolling radius; L This refers to the wheelbase; , These are the intersections of the kingpin axles of the left and right front wheels with the ground. and Spacing is B , , They are respectively , The projection on the line connecting the left and right rear wheel connection points. For the first i The projection of the wheel's center onto the ground to point The distance; These are the steering angles of the left and right front wheels, respectively. Steering wheel angle; This is the steering system angle transmission ratio.

2. The low-speed steering control method for a four-wheel drive hub motor vehicle as described in claim 1, characterized in that, The system presets the steering wheel rotation clearance angle and compares the steering wheel angle with the steering wheel rotation clearance angle. If the steering wheel angle is less than or equal to the steering wheel rotation clearance angle, the car is considered to be driving straight; otherwise, the car is considered to be turning.

3. A low-speed steering control system for a four-wheel drive hub motor vehicle, used to drive the independent four-wheel hub motors of the vehicle to steer the vehicle, characterized in that, The system includes a steering controller, four independent hub motors for driving the rotation of the four wheels, and a motor controller for sending different speed commands to the four hub motors respectively. The steering controller is electrically connected to each motor controller, a steering wheel, and an electronic accelerator pedal. The steering controller is used to perform the steps of the low-speed steering control method for a four-wheel drive hub motor vehicle as described in any one of claims 1-2.

4. An electronic device, characterized in that, It includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, which, when executed by the processor, complete the steps of a low-speed steering control method for a four-wheel drive hub motor vehicle as described in any one of claims 1-2.

5. A computer-readable storage medium, characterized in that, Used to store computer instructions, which, when executed by a processor, complete the steps of a low-speed steering control method for a four-wheel drive hub motor vehicle as described in any one of claims 1-2.

6. A vehicle characterized in that, The method includes the low-speed steering control system for a four-wheel drive hub motor vehicle as described in claim 3, or the low-speed steering control method for a four-wheel drive hub motor vehicle as described in any one of claims 1-2, to achieve low-speed steering.

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