In-situ turning control method and system for dual-motor-driven vehicle

Abstract

The invention provides an in-situ turning-around control method for a dual-motor-driven vehicle, and the method comprises the steps: responding to an in-situ turning-around instruction, and if the current state of the vehicle meets a preset safety starting condition, generating and executing a cooperative control instruction; adjusting the cooperative control instruction according to the real-time motion state of the vehicle to maintain stable rotation of the vehicle; when the in-situ turning process is close to the end, a smooth exit strategy is executed; wherein the cooperative control instruction comprises one or more of a steering instruction used for controlling the steering angles of the front wheel and the rear wheel, a torque instruction used for controlling the front axle motor and the rear axle motor to output driving force in opposite directions, and a braking instruction used for controlling the braking force of each wheel. According to the invention, a common dual-motor four-wheel-drive platform is utilized, and in-situ turning is realized by cooperatively controlling an existing actuator, so that the system cost and complexity are effectively reduced, and the maneuverability, safety and operation convenience of the vehicle in a narrow space are improved.

Description

Technical Field

[0001] This application relates to the field of vehicle control technology, and in particular to a control system for electric or hybrid vehicles, specifically a method and system for controlling U-turns in place for dual-motor driven vehicles. Background Technology

[0002] The ability to make a U-turn on the spot can greatly improve a vehicle's maneuverability in confined spaces. Current technologies mostly rely on in-wheel motors with four-wheel independent drive or multi-wheel independent steering systems capable of extreme turning angles. These solutions have significant drawbacks: in-wheel motors increase unsprung mass, affecting suspension performance, and are costly and pose durability challenges; complex large-angle steering systems face barriers in mechanical design, control algorithms, and cost. These factors make it difficult for existing technologies to be widely adopted in mainstream passenger vehicles.

[0003] Therefore, there is an urgent need for a technical solution that can achieve the function of turning around on the spot based on a more widely used front and rear dual-motor four-wheel drive vehicle platform (i.e., the front and rear axles are each driven by a motor), so as to improve the vehicle's flexibility in a more cost-effective and reliable way. Summary of the Invention

[0004] This application aims to solve at least one of the technical problems existing in the prior art mentioned above, and proposes a method and system for controlling U-turns on the spot for dual-motor driven vehicles. This technology does not rely on hub motors or extreme steering angle designs, and can achieve safe, stable and smooth U-turns on the spot by coordinating the control of the vehicle's existing steering system, drive system and braking system.

[0005] In a first aspect, embodiments of this application provide a method for controlling a U-turn in place for a dual-motor driven vehicle, including:

[0006] In response to a U-turn command, if the vehicle's current state meets the preset safety activation conditions, a cooperative control command is generated and executed.

[0007] Adjust the coordinated control commands according to the real-time motion status of the vehicle to maintain stable vehicle rotation;

[0008] As the process of turning around in place nears its end, a smooth exit strategy is executed;

[0009] The coordinated control commands include one or more of the following: steering commands for controlling the steering angles of the front and rear wheels, torque commands for controlling the output of opposite driving forces by the front and rear axle motors, and braking commands for controlling the braking force of each wheel.

[0010] Furthermore, determine whether the vehicle's current state meets the preset safety activation conditions, including determining one or more of the following:

[0011] The vehicle speed is below or equal to a speed threshold;

[0012] The steering wheel angle is within a neutral range;

[0013] The vehicle is in drive and the accelerator pedal opening is less than a threshold value.

[0014] The vehicle's powertrain, braking system, and steering system are functioning correctly.

[0015] The current road surface adhesion coefficient is below an adhesion threshold.

[0016] Furthermore, generating steering commands includes:

[0017] Calculate the target front wheel steering angle and the target rear wheel steering angle required to make the vehicle rotate around its center or a point near the center.

[0018] Furthermore, the coordinated control commands are adjusted based on the real-time motion status of the vehicle, including:

[0019] Based on wheel slip ratio information, braking force is applied to target wheels whose slip ratio exceeds a first threshold.

[0020] Based on the vehicle's lateral acceleration information, when the lateral acceleration exceeds the second threshold, the driving torque and / or braking torque are adjusted to reduce it.

[0021] Furthermore, smooth exit strategies include:

[0022] The output torque of the control drive motor gradually decreases to zero;

[0023] The braking force of the control braking system is gradually released to zero.

[0024] Furthermore, it also includes:

[0025] During the execution of the cooperative control command, the effect of steering input on wheel steering is limited or cut off.

[0026] Secondly, embodiments of this application provide a U-turn control system capable of implementing any of the foregoing U-turn control methods, comprising:

[0027] The execution module includes the steering system, drive system, and braking system;

[0028] The control module is used to receive the U-turn command, determine the start conditions, calculate the control parameters, and control the execution module to work together to achieve a U-turn in place.

[0029] Furthermore, the control module includes:

[0030] The function trigger condition judgment module is used to detect and judge one or more of the following: vehicle speed, steering wheel angle, vehicle gear, accelerator pedal opening, system fault status and road surface adhesion coefficient, in order to determine whether the current state of the vehicle meets the preset safety activation conditions.

[0031] The active steering cooperative control module is used to calculate and control the steering angles of the front and rear wheels;

[0032] Torque distribution module, used to calculate and distribute driving torque and / or braking torque;

[0033] The smoothness control module is used to control the output torque and brake force release as the turn-around process nears its end.

[0034] Furthermore, the torque distribution module also includes:

[0035] The slip ratio control submodule calculates the slip ratio based on the wheel speed and triggers braking.

[0036] The lateral acceleration control submodule adjusts the torque distribution based on IMU data.

[0037] Furthermore, the control module is also used for:

[0038] During the U-turn function, the steering system enters a mode in which steering input does not change the actual steering angle of the wheels.

[0039] This application provides a method and system for controlling U-turns on the spot in a dual-motor driven vehicle. This technology does not rely on hub motors or extreme steering angle designs. It only utilizes a common dual-motor four-wheel drive platform and achieves safe, stable and smooth U-turns on the spot by coordinating the control of the vehicle's existing steering system, drive system and braking system. This effectively reduces system cost and complexity and improves the vehicle's maneuverability, safety and ease of operation in narrow spaces. Attached Figure Description

[0040] Figure 1 The core flowchart of a U-turn control method for a dual-motor driven vehicle provided in this application embodiment;

[0041] Figure 2 A detailed flowchart of a method for controlling a U-turn in place for a dual-motor driven vehicle, provided in an embodiment of this application;

[0042] Figure 3 A diagram illustrating the mechanical analysis model for a U-turn in place, provided in an embodiment of this application.

[0043] Figure 4 This is a schematic diagram of the module structure of a U-turn control system for a dual-motor driven vehicle, provided in an embodiment of this application. Detailed Implementation

[0044] To enable those skilled in the art to better understand the technical solutions of this application, exemplary embodiments of this application are described below with reference to the accompanying drawings, including various details of the embodiments of this application to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. Similarly, for clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description. Unless otherwise specified, the various embodiments of this application and the features within those embodiments can be combined with each other.

[0045] As used herein, the term “and / or” includes any and all combinations of one or more of the associated enumerated entries. The terminology used herein is for describing particular embodiments only and is not intended to limit the application. As used herein, the singular forms “a” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated features, integrals, steps, operations, elements, and / or components is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded. Terms such as “connected” or “linked” are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect.

[0046] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It should also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art and this application, and will not be interpreted as having an idealized or overly formal meaning, unless expressly so defined herein.

[0047] Definition of key technical terms:

[0048] (1) U-turn: refers to the process of making a vehicle rotate around its center point or a fixed point without moving its position, thereby achieving a complete change of vehicle direction (usually a 180° turn).

[0049] (2) IMU: Inertial Measurement Unit, is a sensor used to measure the motion state of an object. It is usually composed of an accelerometer, a gyroscope and a magnetometer. It can measure the acceleration, angular velocity and magnetic field strength of an object, thereby calculating the object's attitude, position and velocity.

[0050] U-turn technology is a feature that allows a vehicle to turn on the spot, primarily used for parking and getting out of difficult situations in confined spaces. This technology achieves a U-turn with zero turning radius by controlling the vehicle to rotate around its geometric center. The benefits of U-turn technology include significantly improved vehicle agility and handling, especially in space-constrained environments. It helps drivers quickly adjust the vehicle's direction, reducing the hassle of reversing and multiple turns, thus improving driving efficiency and safety.

[0051] Existing U-turn technology generally relies on independently controllable hub motors. However, the use of hub motors increases unsprung mass, affecting suspension response and comfort. Furthermore, the design and manufacturing are more complex, resulting in higher costs. Currently, this technology is only used in high-performance cars or concept cars and is not suitable for ordinary four-wheel drive vehicles.

[0052] This application aims to propose a U-turn control technology applicable to ordinary four-wheel drive vehicles with dual motors on the front and rear axles. This technology establishes coordinated vehicle control by integrating the angle control of the rear-wheel active steering system, the torque distribution of the drive motor, and the braking force distribution of the braking system. After detecting the driver's activation of the U-turn command, the control unit will execute the following technical path: using a high-precision steering motor to drive the front wheels to achieve a large angle deflection of ±45° and the rear wheels to achieve an angle deflection of ±10°. Combined with wheel speed sensors and torque distribution algorithms, the drive torque of the four wheels is dynamically adjusted to form a rotational torque around the geometric center of the vehicle. At the same time, a slip ratio real-time monitoring module is introduced, and the controller automatically optimizes the torque output intensity to reduce the tire slip ratio to within a safe threshold while ensuring steering efficiency.

[0053] The U-turn control technology proposed in this application is a comprehensive technical solution aimed at achieving efficient and safe U-turns for vehicles. It achieves the U-turn function by coordinating the control of the drive system, braking system, and steering system. In a specific embodiment, the U-turn control system for a dual-motor driven vehicle provided in this application mainly includes an execution module and a control module, as referenced... Figure 4 .

[0054] The execution module includes: a front-wheel active steering system, a rear-wheel active steering system, a drive system, and an integrated electro-hydraulic braking system.

[0055] Front wheel active steering system: After receiving a U-turn command, it disconnects the steering wheel from the front wheel steering and executes the target steering angle of the front wheels calculated by the controller.

[0056] Rear-wheel active steering system: After receiving a U-turn command, it executes the target steering angle of the rear wheels calculated by the controller.

[0057] Drive system: After receiving the command to turn around in place, it executes the target output torque of the front and rear motors calculated by the controller.

[0058] Integrated electro-hydraulic braking system: After receiving the command to turn around on the spot, it executes the wheel cylinder braking pressure calculated by the controller.

[0059] The control module includes a controller. The controller primarily comprises four key control modules: a function trigger condition judgment module, an active steering coordination control module, a torque distribution module, and a ride comfort control module. The following is a detailed description of each control module.

[0060] 1. Function trigger condition judgment module

[0061] Upon receiving a request to make a U-turn, the system dynamically determines the activation conditions for the U-turn function based on a series of vehicle status parameters to ensure that the vehicle performs the function in a safe and appropriate state. Specific determination conditions include one or more of the following:

[0062] Speed ​​threshold detection: The system monitors vehicle speed in real time, and the U-turn function is only allowed to be activated when the vehicle speed is less than or equal to 5 km / h.

[0063] Driver Operation Status Detection: This detection primarily focuses on steering wheel angle, vehicle gear position, and accelerator pedal opening. The steering wheel angle must be within ±5° of the neutral position to ensure the vehicle initially maintains a straight-line driving state. Simultaneously, the vehicle must be in D gear, and the accelerator pedal opening must be less than 10%.

[0064] System fault status detection: A comprehensive inspection of the powertrain, braking, and steering systems is performed via the CAN bus to ensure that these critical systems are free of fault codes. Only when all these systems are functioning normally can the vehicle perform a U-turn.

[0065] Road surface adhesion coefficient estimation: Based on wheel speed sensors and IMU sensors, the road surface adhesion coefficient is calculated. When the road surface adhesion coefficient is less than 0.3, it is permissible to perform a U-turn in place. This avoids excessive road surface adhesion coefficient, which would increase the friction between the tires and the ground, accelerate tire wear, and may also place an excessive load on the vehicle's steering and power systems.

[0066] 2. Active steering and cooperative control module

[0067] This module is primarily responsible for precisely controlling the steering of the vehicle's front and rear wheels and locking the steering wheel. The specific control strategy is as follows:

[0068] The front and rear wheel angles are calculated based on the mechanical analysis model of a U-turn in place and the optimization algorithm.

[0069] Front wheel steering control adjusts the front wheel steering angle to the target angle θ1 (θ1∈[-45°,+45°]) through the front wheel active steering system.

[0070] Rear wheel steering control, through the rear wheel active steering system, adjusts the rear wheel steering angle to the target angle θ2 (θ2∈[-10°,+10°]).

[0071] To prevent the driver from interfering with the normal operation of the steering system while the vehicle is making a U-turn, the system will electronically disconnect the steering wheel from the wheels.

[0072] 3. Torque Distribution Module

[0073] This module dynamically calculates the wheel slip ratio based on information such as the vehicle's wheel speed and lateral acceleration, and rationally allocates braking and driving torques to ensure the stability and safety of the vehicle during a U-turn. Specific control measures are as follows:

[0074] Slip ratio control: Based on the wheel speed sensor to measure the speed of the four wheels, when the slip ratio of a single wheel is greater than 25%, the system will apply braking torque to the wheel with high slip ratio through active braking to reduce its slip ratio and ensure the stability of the vehicle when turning.

[0075] Lateral acceleration control: The system uses an IMU sensor to measure the vehicle's lateral acceleration. When the lateral acceleration is greater than 0.01g, the system will actively brake to control the lateral acceleration to be less than 0.01g, preventing dangerous situations such as skidding or rollover caused by excessive lateral acceleration during U-turns.

[0076] Drive torque distribution: The optimal drive torque is calculated based on the mechanical model of turning in place. The front axle motor outputs positive torque, and the rear wheel motor outputs negative torque.

[0077] 4. Smoothness control module

[0078] When the vehicle approaches the target rotation angle, for example, when 30° remains, the system activates a slow-reverse strategy to ensure smoothness when the vehicle terminates the U-turn operation. The specific control method is as follows:

[0079] Motor torque decay: The output torque of the motor decays exponentially, as expressed by the following formula:

[0080] ;

[0081] Where k represents the attenuation coefficient, a constant greater than zero that determines the rate of torque attenuation (unit: 1 / second, 1 / s). The larger the value of k, the faster the torque attenuates. T0 represents the initial torque, referring to the motor's output torque value (unit: N·m) at the instant the smooth exit strategy starts (t=0). T(t) represents the motor torque at the current moment, referring to the actual output torque value of the motor at any time t after the smooth exit strategy starts (unit: N·m). t represents time, referring to the time elapsed since the smooth exit strategy started (unit: seconds, s). e represents the natural constant, a mathematical constant, approximately equal to 2.71828.

[0082] Braking pressure gradient release: The braking force is released using a linear curve, with a pressure change rate ≤3 MPa / s.

[0083] The mechanical analysis model diagram for turning around in place is shown below. Figure 3 As shown.

[0084] ;

[0085] ;

[0086] In this diagram, F1 represents the front-wheel drive force, which is the traction force (unit: Newtons, N) provided by the front axle motor acting on the front wheels. F2 represents the rear-wheel drive force, which is the traction force (unit: Newtons, N) provided by the rear axle motor acting on the rear wheels; its direction is usually opposite to F1 to achieve rotation in place. α represents the front wheel steering angle, which is the angle of deflection of the front wheels relative to the vehicle's longitudinal axis (unit: ° or rad). β represents the rear wheel steering angle, which is the angle of deflection of the rear wheels relative to the vehicle's longitudinal axis (unit: ° or rad). L represents the wheelbase, which is the distance between the center points of the front and rear axles (unit: meters, m). f represents rolling friction resistance, which is the sum of the rolling friction forces generated between the four tires and the ground when the vehicle is rotating (unit: Newtons, N); it is the main external force hindering rotation. b represents the track width, which is the distance between the center points of the left and right wheels on the same axle (unit: meters, m). The approximate lever arm is used to estimate the resistance moment arm of rolling friction resistance f about the vehicle's center point O. Figure 3 Point O is the geometric center.

[0087] The working principle of this U-turn control system for dual-motor driven vehicles is as follows: the driver initiates a request via the central control screen, and the request signal is sent to the controller. The controller's condition judgment module then collects and analyzes the vehicle status data. If any safety condition is not met, the driver is notified of the reason and the system exits the control system.

[0088] If all conditions are met, the controller's collaborative control calculation module calculates the required front wheel steering angle, rear wheel steering angle, and target torque for the front and rear motors based on the mechanical model. Subsequently, the control module instructs the steering system to actuate, directing the drive motors to output equal but opposite torques, creating a torque couple that rotates the vehicle. The braking system, based on real-time monitoring results, intervenes with braking on individual wheels with excessive slip to maintain stability.

[0089] When the vehicle rotates close to the target angle or the driver releases the accelerator, the ride comfort control module intervenes, controlling the motor torque to decrease exponentially. At the same time, the braking pressure is released linearly until the vehicle comes to a smooth stop, completing the U-turn.

[0090] refer to Figure 1 and Figure 2 In another embodiment, a method for controlling a U-turn in place for a dual-motor driven vehicle may specifically include the following steps.

[0091] S101. The driver can activate the U-turn function on the central control screen, select the U-turn angle, or stop the U-turn by releasing the accelerator.

[0092] S102. After receiving a U-turn request, determine the conditions for enabling the U-turn function. If the conditions are not met, exit the function and indicate the unmet status. If the conditions are met, execute the subsequent steps.

[0093] S103, the controller calculates the front and rear wheel rotation angles, the front and rear motor driving forces, and the braking force of each wheel.

[0094] S104: The front and rear wheel active steering systems execute the target steering angle, the front and rear motors execute the target driving torque, and the hydraulic braking system executes the target braking force.

[0095] S105. Determine whether the U-turn is about to stop or the accelerator pedal opening is 0. If not, continue to S104; if so, proceed to the next step.

[0096] S106, the motor torque decreases slowly, and the braking force is released slowly.

[0097] Specific technical details of an embodiment of a U-turn control method for a dual-motor driven vehicle can be found in the aforementioned specific embodiment of a U-turn control system for a dual-motor driven vehicle, and will not be repeated here.

[0098] Overall, the beneficial effects of the technical solution of this application compared with the prior art include:

[0099] 1. Low cost and high applicability: Based on the mainstream dual-motor four-wheel drive platform design, it makes full use of existing actuators, without the need for additional expensive hardware, resulting in low cost and easy promotion.

[0100] 2. High security: Through multi-dimensional pre-activation condition judgment and real-time process monitoring, a complete safety boundary is constructed, effectively preventing function misuse and vehicle instability.

[0101] 3. Good stability: Through closed-loop control based on slip ratio and lateral acceleration, torque distribution is dynamically adjusted, which actively ensures the stability of the turning process.

[0102] 4. Excellent smoothness: The specialized exit strategy ensures a smooth and seamless process throughout the entire process of function initiation, execution and termination, enhancing driving and riding comfort.

[0103] 5. Extremely simple operation: Simplifying complexity, drivers can trigger complex operations through a single interface, greatly reducing the operational burden.

[0104] The flowcharts or block diagrams in the accompanying drawings illustrate the architecture, functionality, and / or operation of possible implementations of systems, methods, and / or computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0105] Exemplary embodiments have been disclosed herein, and while specific terminology has been used, it is used and should be interpreted only in a general illustrative sense and is not intended to be limiting. In some embodiments, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of this application as set forth by the appended claims.

Claims

1. A method for controlling a U-turn in place for a dual-motor driven vehicle, characterized in that, include: In response to a U-turn command, if the vehicle's current state meets the preset safety activation conditions, a cooperative control command is generated and executed. Adjust the coordinated control commands according to the real-time motion status of the vehicle to maintain stable vehicle rotation; As the process of turning around in place nears its end, a smooth exit strategy is executed; The coordinated control commands include one or more of the following: steering commands for controlling the steering angles of the front and rear wheels, torque commands for controlling the output of opposite driving forces by the front and rear axle motors, and braking commands for controlling the braking force of each wheel.

2. The method for controlling a U-turn in place according to claim 1, characterized in that, Determine whether the vehicle's current state meets the preset safety activation conditions, including determining one or more of the following: The vehicle speed is below or equal to a speed threshold; The steering wheel angle is within a neutral range; The vehicle is in drive and the accelerator pedal opening is less than a threshold value. The vehicle's powertrain, braking system, and steering system are functioning correctly. The current road surface adhesion coefficient is below an adhesion threshold.

3. The method for controlling a U-turn in place according to claim 1, characterized in that, Generating steering instructions includes: Calculate the target front wheel steering angle and the target rear wheel steering angle required to make the vehicle rotate around its center or a point near the center.

4. The method for controlling a U-turn in place according to claim 1, characterized in that, Adjusting collaborative control commands based on the vehicle's real-time motion status, including: Based on wheel slip ratio information, braking force is applied to target wheels whose slip ratio exceeds a first threshold. Based on the vehicle's lateral acceleration information, when the lateral acceleration exceeds the second threshold, the driving torque and / or braking torque are adjusted to reduce it.

5. The method for controlling a U-turn in place according to claim 1, characterized in that, Smooth exit strategies include: The output torque of the control drive motor gradually decreases to zero; The braking force of the control braking system is gradually released to zero.

6. The method for controlling a U-turn in place according to claim 1, characterized in that, Also includes: During the execution of the cooperative control command, the effect of steering input on wheel steering is limited or cut off.

7. A U-turn control system capable of implementing the U-turn control method according to any one of claims 1-6, characterized in that, include: The execution module includes the steering system, drive system, and braking system; The control module is used to receive the U-turn command, determine the start conditions, calculate the control parameters, and control the execution module to work together to achieve a U-turn in place.

8. The on-the-spot U-turn control system according to claim 7, characterized in that, The control module includes: The function trigger condition judgment module is used to detect and judge one or more of the following: vehicle speed, steering wheel angle, vehicle gear, accelerator pedal opening, system fault status and road surface adhesion coefficient, in order to determine whether the current state of the vehicle meets the preset safety activation conditions. The active steering cooperative control module is used to calculate and control the steering angles of the front and rear wheels; Torque distribution module, used to calculate and distribute driving torque and / or braking torque; The smoothness control module is used to control the output torque and brake force release as the turn-around process nears its end.

9. The in-situ U-turn control system according to claim 8, characterized in that, The torque distribution module also includes: The slip ratio control submodule calculates the slip ratio based on the wheel speed and triggers braking. The lateral acceleration control submodule adjusts the torque distribution based on IMU data.

10. The on-the-spot U-turn control system according to claim 7, characterized in that, The control module is also used for: During the U-turn function, the steering system enters a mode in which steering input does not change the actual steering angle of the wheels.

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