A steering control method and device for a vehicle

Abstract

The application provides a steering control method and device of a vehicle, and belongs to the technical field of vehicle control. The method comprises the following steps: when a preset steering assistance activation condition is met, obtaining a target yaw angular velocity and an actual yaw angular velocity of a target vehicle; determining a target yaw torque based on the target yaw angular velocity and the actual yaw angular velocity; obtaining a target demand torque of the target vehicle; determining target torques of each wheel based on the target yaw torque and the target demand torque, the target torques of each wheel being used to generate a driving torque difference of left and right wheels of the target vehicle; and controlling motors corresponding to each wheel to output torques according to the target torques corresponding to each wheel, so as to assist the target vehicle to steer. The application generates a yaw moment through a driving torque difference to assist steering, and realizes the reduction of a turning radius without relying on brake intervention, thereby improving the maneuverability and passing efficiency under a low-speed large-turning-angle working condition.

Description

Technical Field

[0001] This application relates to the field of vehicle control technology, and in particular to a vehicle steering control method and device. Background Technology

[0002] With the development of electric vehicle technology, distributed drive vehicles have attracted attention due to their ability to drive each wheel independently. In low-speed turning scenarios such as narrow curves and parking, traditional vehicles typically rely on the braking system to apply braking force to the inner wheels to generate yaw moment, assisting in steering and reducing the turning radius. However, this braking-intervention-based steering assistance method causes a decrease in vehicle speed during turning due to the intervention of braking force, affecting driving smoothness and passability. Furthermore, multiple adjustments are required to complete turns or U-turns in narrow spaces, limiting maneuverability. Therefore, a vehicle steering control method is urgently needed to solve the aforementioned technical problems. Summary of the Invention

[0003] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. This summary section is not intended to limit the key features and essential technical features of the claimed technical solutions, nor is it intended to determine the scope of protection of the claimed technical solutions.

[0004] This application aims to address the technical problem of reduced vehicle speed and poor maneuverability caused by traditional braking intervention methods in low-speed steering scenarios. The method, when preset steering assist activation conditions are met, acquires the target yaw rate and actual yaw rate of the target vehicle, determines the target yaw torque based on the difference between the two, and then distributes the target torque to each wheel in conjunction with the target torque requirement, creating a driving torque difference between the left and right wheels. This controls each motor to output corresponding torque to assist vehicle steering. This achieves steering assist without relying on braking intervention, avoids speed loss during steering, reduces the turning radius, and improves throughput in low-speed, large-angle conditions.

[0005] Firstly, this application proposes a vehicle steering control method, the method comprising: When the preset steering assist activation conditions are met, the target yaw rate and actual yaw rate of the target vehicle are obtained. The target yaw torque is determined based on the target yaw rate and the actual yaw rate. Obtain the target torque requirement of the target vehicle, where the target torque requirement is used to characterize the longitudinal drive torque requirement of the target vehicle. Based on the target yaw torque and the target required torque, the target torque of each wheel is determined. The target torque of each wheel is used to generate a driving torque difference between the left and right wheels of the target vehicle. The motors corresponding to each wheel are controlled to output torque according to the target torque of each wheel, so as to assist the target vehicle in steering.

[0006] In some implementations, obtaining the target yaw rate of the target vehicle includes: Calculate the initial yaw rate based on the target vehicle's current front wheel steering angle, current rear wheel steering angle, current vehicle speed, and current wheelbase; Determine the yaw rate limit based on the road surface adhesion coefficient and the current vehicle speed; Based on the yaw rate limit value, the initial yaw rate is limited to obtain the target yaw rate.

[0007] In some implementations, the target yaw torque is determined based on the target yaw rate and the actual yaw rate, including: Calculate the difference between the target yaw rate and the actual yaw rate to obtain the yaw rate error; The target yaw torque is obtained by controlling the yaw rate error using a proportional-integral-derivative controller.

[0008] In some implementations, obtaining the target torque requirement of the target vehicle includes: The target torque required is queried from the preset first mapping relationship, which corresponds to the combination of the current accelerator pedal opening and the current vehicle speed of the target vehicle. The first mapping relationship is used to characterize the correspondence between the combination of accelerator pedal opening and vehicle speed and the required torque.

[0009] In some implementations, obtaining the target torque requirement of the target vehicle includes: From the preset candidate mapping relationships, find the second mapping relationship corresponding to the current driving mode of the target vehicle; The target torque demand is queried from the second mapping relationship, which corresponds to the combination of the current accelerator pedal opening and the current vehicle speed of the target vehicle. Different driving modes correspond to different candidate mapping relationships. The second mapping relationship is used to characterize the correspondence between the combination of accelerator pedal opening and vehicle speed and the demand torque.

[0010] In some implementations, obtaining the target torque requirement of the target vehicle includes: When the target vehicle is detected to be in drive or reverse gear and neither the accelerator nor the brake pedal is pressed, it is determined that the target vehicle is in a creeping state. In crawl mode, obtain the preset crawl target speed; Based on the target creep speed and the current speed, the creep torque is calculated by the proportional-integral controller and determined as the target required torque.

[0011] In some implementations, the target torque for each wheel is determined based on the target yaw torque and the target required torque, including: Based on the front axle longitudinal torque distribution coefficient and the target required torque of the target vehicle, determine the front axle base torque and the rear axle base torque. Obtain the target vehicle's current track width, current tire radius, front axle yaw torque distribution coefficient, and rear axle yaw torque distribution coefficient, wherein the sum of the front axle yaw torque distribution coefficient and the rear axle yaw torque distribution coefficient is 1; The difference in drive torque between the left and right front axle wheels is determined based on the target yaw torque, the front axle yaw torque distribution coefficient, the current tire radius, and the current track width. The difference in drive torque between the left and right rear axle wheels is determined based on the target yaw torque, the rear axle yaw torque distribution coefficient, the current tire radius, and the current track width. Based on the base torque of the front axle and the difference in drive torque between the left and right front wheels, determine the target torque of the left front wheel and the target torque of the right front wheel; Based on the base torque of the rear axle and the difference in drive torque between the left and right rear wheels, the target torques for the left and right rear wheels are determined.

[0012] In some implementations, when the target vehicle turns left, the target torque of the left front wheel is less than the target torque of the right front wheel, and the target torque of the left rear wheel is less than the target torque of the right rear wheel; when the target vehicle turns right, the target torque of the left front wheel is greater than the target torque of the right front wheel, and the target torque of the left rear wheel is greater than the target torque of the right rear wheel.

[0013] In some implementations, the preset steering assist activation conditions include: The target vehicle's current steering wheel angle is greater than or equal to a preset steering angle threshold, the target vehicle's current speed is less than or equal to a preset speed threshold, the target vehicle's current gear is either forward or reverse, the target vehicle's current battery state of charge is greater than or equal to a preset state of charge threshold, and the target vehicle's preset safety functions are inactive.

[0014] In some implementations, after determining the target yaw torque based on the target yaw rate and the actual yaw rate, the method further includes: Obtain the distance between obstacles surrounding the target vehicle and the target vehicle; When the distance to the obstacle is less than the preset safe distance threshold, a limit coefficient is determined based on the obstacle distance, wherein the limit coefficient is positively correlated with the obstacle distance; The product of the target yaw torque and the limiting coefficient is determined as the corrected target yaw torque; Based on the target yaw torque and the target required torque, determine the target torque for each wheel, including: Based on the corrected target yaw torque and target required torque, the target torque for each wheel is determined.

[0015] In some implementations, the method further includes determining the target torque for each wheel before determining the target torque for each wheel based on the target yaw torque and the target required torque: Obtain the current vertical load on each wheel and the current road surface adhesion coefficient; Based on the current vertical load and current road adhesion coefficient of each wheel, determine the maximum available torque of each wheel; For each wheel, the target torque of the wheel is limited to the maximum available torque of the wheel and the preset maximum motor torque.

[0016] In some implementations, after determining the maximum available torque for each wheel based on the current vertical load and current road adhesion coefficient for each wheel, the method further includes: Based on the current tire temperature of each wheel, a temperature correction factor is determined for each wheel, where the temperature correction factor is negatively correlated with the current tire temperature. For each wheel, the product of the wheel's maximum available torque and the wheel's temperature correction factor is determined as the wheel's corrected maximum available torque.

[0017] In some implementations, a temperature correction factor for each wheel is determined based on the current tire temperature of each wheel, including: For each wheel, when the current tire temperature of the wheel is less than or equal to the first preset temperature threshold, the temperature correction coefficient of the wheel is determined to be the first preset coefficient. When the current tire temperature of the wheel is greater than or equal to the second preset temperature threshold, the temperature correction coefficient of the wheel is determined to be the second preset coefficient, wherein the second preset temperature threshold is greater than the first preset temperature threshold and the second preset coefficient is less than the first preset coefficient. When the current tire temperature of the wheel is greater than the first preset temperature threshold and less than the second preset temperature threshold, the temperature correction coefficient of the wheel is determined by interpolation calculation of the first preset coefficient and the second preset coefficient.

[0018] In some embodiments, after controlling the motors corresponding to each wheel to output torque according to the target torque of each wheel, the method further includes: While controlling the motors corresponding to each wheel to output torque according to the target torque of each wheel, the activation status of each preset safety function of the target vehicle is monitored. When any preset safety function is detected to be activated, stop controlling each motor to output torque according to the target torque of each wheel, and control each motor to restore the torque output to the normal driving state.

[0019] Secondly, this application proposes a vehicle steering control device, the device comprising: The condition judgment module is used to obtain the target yaw rate and actual yaw rate of the target vehicle when the preset steering assist activation conditions are met. The yaw torque module is used to determine the target yaw torque based on the target yaw angular velocity and the actual yaw angular velocity. The demand torque module is used to obtain the target demand torque of the target vehicle, wherein the target demand torque is used to characterize the longitudinal drive torque demand of the target vehicle. The torque distribution module is used to determine the target torque of each wheel based on the target yaw torque and the target required torque. The target torque of each wheel is used to create a driving torque difference between the left and right wheels of the target vehicle. The motor control module is used to control the motors corresponding to each wheel to output torque according to the target torque of each wheel, so as to assist the target vehicle in steering.

[0020] Thirdly, this application proposes an electronic device comprising: a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor executes the computer program stored in the memory to implement the steps of the vehicle steering control method of any of the first aspects described above.

[0021] Fourthly, this application also proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the steering control method for any vehicle according to the first aspect.

[0022] Fifthly, this application also proposes a computer program product, including a computer program that, when executed by a processor, implements the steps of the steering control method for any vehicle according to the first aspect.

[0023] In summary, the vehicle steering control method provided in this application acquires a target yaw rate and an actual yaw rate when preset steering assist activation conditions are met. The target yaw rate characterizes the driver's steering intention and expected yaw motion, providing a target value for torque control that reflects the driver's needs and preventing the system from blindly outputting torque, causing the steering response to deviate from the driver's expectations. Based on the target yaw rate and the actual yaw rate, a target yaw torque is determined, making the target yaw torque characterize the magnitude and direction of the expected yaw moment under the current steering state. A target required torque is acquired to characterize the longitudinal drive torque demand of the entire vehicle, ensuring that the vehicle meets basic drive requirements during steering assist and preventing abnormal vehicle power response caused by insufficient or excessive longitudinal drive during steering assist. Based on the target yaw torque and the target required torque, the target torque of each wheel is determined, and the target torque of each wheel is used to generate a drive torque difference between the left and right wheels. This drive torque difference generates a yaw moment acting on the vehicle body, providing steering assist torque without triggering braking system intervention, thereby avoiding speed loss due to braking intervention. By controlling the motors corresponding to each wheel to output torque according to the target torque corresponding to each wheel, the vehicle can be assisted to complete steering by driving torque difference while maintaining vehicle speed, thereby reducing the turning radius and improving maneuverability and passability under low-speed and large-angle conditions. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit this specification. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic flowchart illustrating a vehicle steering control method provided in an embodiment of this application; Figure 2 A schematic diagram of the process for obtaining the target yaw rate provided in an embodiment of this application; Figure 3 A schematic diagram of the process for determining the target yaw torque provided in an embodiment of this application; Figure 4 A schematic diagram of a process for obtaining the target required torque provided in an embodiment of this application; Figure 5 A schematic diagram illustrating another process for obtaining the target required torque, provided in an embodiment of this application; Figure 6 A schematic diagram illustrating another process for obtaining the target required torque, provided in an embodiment of this application; Figure 7 A flowchart illustrating the process of determining the target torque for each wheel, provided for an embodiment of this application; Figure 8 A schematic diagram of the process for correcting the target yaw torque provided in an embodiment of this application; Figure 9 A flowchart illustrating the process of limiting the target torque of each wheel, provided for an embodiment of this application; Figure 10 This is a schematic diagram illustrating the process of temperature-corrected target torque for each wheel, provided in an embodiment of this application. Figure 11 A schematic diagram illustrating the process of stopping torque output provided in an embodiment of this application; Figure 12 A schematic diagram of the structure of a vehicle steering control device provided in an embodiment of this application; Figure 13 This is a schematic diagram of the structure of a vehicle steering control electronic device provided in an embodiment of this application. Detailed Implementation

[0025] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such objects can be interchanged where appropriate so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. Furthermore, "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or device that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices. The technical solutions in the embodiments of this application will now be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them.

[0026] This application relates to the field of vehicle control technology, and the technical terms involved in this application are explained below.

[0027] The distributed drive vehicle described in this application refers to a vehicle configuration where each wheel is equipped with an independent power source, commonly including hub motor drive and wheel-side motor drive. Unlike traditional centralized drive vehicles that distribute power to the left and right wheels via a differential, each wheel of a distributed drive vehicle can independently control the magnitude and direction of its driving torque. This configuration provides greater freedom in vehicle dynamics control.

[0028] The torque vector control described in this application refers to a control technology that generates a desired yaw moment by independently distributing and adjusting the driving torque of each wheel of a vehicle, thereby improving vehicle handling stability. This technology utilizes the independently controllable torque of each wheel in a distributed drive architecture, applying differentiated driving torques between different wheels to generate a rotational torque around the vehicle's vertical axis. Compared to traditional electronic stability control systems that generate yaw moment based on braking force differences, torque vector control can adjust the yaw moment without reducing the vehicle's total driving force.

[0029] The yaw rate described in this application is a physical quantity characterizing the angular velocity of a vehicle about its vertical axis, measured in radians per second or degrees per second. This parameter reflects the yaw motion state of the vehicle during steering and is a key indicator for evaluating vehicle steering response and handling stability. In vehicle dynamics control, yaw rate is typically used as a controlled variable, and the control algorithm tracks the target value desired by the driver.

[0030] The yaw moment in this application refers to the moment acting on a vehicle about its vertical axis, causing the vehicle to yaw. During steering, the vehicle requires an appropriate yaw moment to achieve the driver's steering intention. Yaw moment can be generated in various ways, including applying different longitudinal forces (driving or braking forces) to the left and right wheels, actively changing the steering angle of the front or rear wheels, etc.

[0031] The road adhesion coefficient of this application is a dimensionless parameter characterizing the maximum available friction between the tire and the road surface. Its value depends on factors such as road material, road conditions (dryness and wetness), and tire characteristics. This coefficient affects the maximum driving torque and braking force borne by each wheel of the vehicle and is used to constrain torque distribution control.

[0032] The vertical load in this application refers to the force perpendicular to the road surface borne by each wheel of the vehicle, the magnitude of which depends on factors such as vehicle mass distribution, static load, and dynamic load transfer. During vehicle acceleration, braking, or cornering, the vertical load of each wheel will be redistributed due to inertial forces, thereby affecting the adhesion and maximum available driving torque of each wheel.

[0033] The vehicle steering control method provided in this application can be applied to various low-speed, large-angle turning scenarios. In narrow urban streets, vehicles need to complete right-angle turns or U-turns within limited road width, which traditionally often requires multiple adjustments to pass. In parking lot scenarios, vehicles need to complete exiting or entering parking spaces within the narrow space between the parking space and surrounding vehicles, placing high demands on the vehicle's steering agility and handling precision. In off-road extrication scenarios, vehicles travel on unpaved roads with complex and variable road adhesion conditions, requiring control of the driving force of each wheel to prevent wheel slippage and improve traction. Furthermore, the method of this application is also applicable to low-speed scenarios such as narrow U-turns in busy urban areas and complex terrain. The characteristics of these scenarios are low vehicle speed, large steering wheel angles, and high requirements for vehicle steering agility and traction efficiency, making a torque vectoring-based steering assist control strategy suitable.

[0034] Please see Figure 1 This is a flowchart illustrating a vehicle steering control method provided in an embodiment of this application, which may specifically include: S110. When the preset steering assist activation conditions are met, obtain the target yaw rate and actual yaw rate of the target vehicle.

[0035] The target vehicle is a distributed drive vehicle, with each wheel of the target vehicle having its own independently driven motor. Each motor can independently control the magnitude and direction of the driving torque for its corresponding wheel. Preset steering assist activation conditions are used to determine whether the current operating condition of the target vehicle is suitable for entering steering assist mode. This steering assist mode refers to the control mode provided in this application embodiment, which, when the preset conditions are met, acquires the target yaw rate and the actual yaw rate, determines the target yaw torque based on the deviation between the two, and distributes the target torque to each wheel in combination with the target required torque to form a driving torque difference between the left and right wheels. Finally, it controls each motor to output the corresponding torque to assist in vehicle steering.

[0036] For example, during vehicle operation, it determines whether preset steering assist activation conditions are met. When the conditions are met, it acquires the target yaw rate and the actual yaw rate. The target yaw rate is a desired value calculated based on the vehicle's current motion state and the driver's input, representing the yaw motion state the driver hopes the vehicle will achieve through steering. The actual yaw rate is the real value detected in real time by an inertial measurement unit installed on the vehicle, representing the vehicle's actual yaw motion state at the current moment. Acquiring these two parameters provides torque control with a target value reflecting the driver's needs and a feedback value reflecting the vehicle's actual response, allowing the control process to adjust based on the deviation between the expectation and the reality.

[0037] S120. Determine the target yaw torque based on the target yaw rate and the actual yaw rate.

[0038] For example, a target yaw rate and an actual yaw rate are compared to determine the degree of deviation between the vehicle's current yaw motion state and the driver's desired state. This deviation reflects the amount by which the vehicle's steering response deviates from the driver's intention. Based on this deviation, a target yaw torque is calculated using a control algorithm. This target yaw torque characterizes the magnitude and direction of the yaw moment that needs to be applied to the vehicle body to make the vehicle's actual yaw motion approximate the driver's desired yaw motion. When the actual yaw rate is less than the target yaw rate, it indicates understeer, requiring an increase in yaw moment to enhance steering response; when the actual yaw rate is greater than the target yaw rate, it indicates oversteer, requiring a decrease in yaw moment to suppress oversteer.

[0039] S130, Obtain the target torque required by the target vehicle.

[0040] The target required torque characterizes the longitudinal drive torque requirement of the target vehicle. This target required torque represents the driver's demand for longitudinal drive force and is used to characterize the total longitudinal drive torque required by the vehicle under the current driving operation. This required torque varies with the driver's acceleration and the vehicle's driving state. During steering assistance, the vehicle needs to provide yaw moment assistance while maintaining its responsiveness to the driver's longitudinal drive demand, avoiding any impact on the vehicle's normal acceleration or creep performance due to the introduction of steering assistance torque.

[0041] S140. Based on the target yaw torque and the target required torque, determine the target torque of each wheel. The target torque of each wheel is used to generate a driving torque difference between the left and right wheels of the target vehicle.

[0042] For example, under the premise of ensuring that the sum of the driving torque output by each wheel meets the target torque requirement, a driving torque difference is generated between the left and right wheels on the same axle. This driving torque difference generates a yaw moment acting on the vehicle body. The direction and magnitude of this yaw moment are consistent with the target yaw torque.

[0043] Optionally, for any axle, when the direction of the target yaw torque indicates that the vehicle needs to turn left, the target torque of the right wheel of that axle is greater than the target torque of the left wheel; when the direction of the target yaw torque indicates that the vehicle needs to turn right, the target torque of the left wheel of that axle is greater than the target torque of the right wheel.

[0044] S150 controls the motors corresponding to each wheel to output torque according to the target torque corresponding to each wheel, so as to assist the target vehicle in steering.

[0045] For example, the target torque corresponding to each wheel is sent to the drive motor corresponding to that wheel, and each motor is controlled to output torque according to the target torque value it receives. Driven by the target torque, a driving torque difference is generated between the left and right wheels. This torque difference forms a yaw moment acting on the vehicle. The direction of this yaw moment is consistent with the steering direction desired by the driver, thus adding a yaw moment component to the vehicle's original steering response, assisting the vehicle in completing the steering operation. In this process, since the yaw moment originates from the differentiated distribution of driving torque rather than the application of braking force, the vehicle's total driving power is not lost, and the vehicle speed is maintained, thereby reducing the turning radius while maintaining the vehicle's passability.

[0046] In summary, the vehicle steering control method provided in this application acquires a target yaw rate and an actual yaw rate when preset steering assist activation conditions are met. The target yaw rate characterizes the driver's steering intention and expected yaw motion, providing a target value for torque control that reflects the driver's needs and preventing the system from blindly outputting torque, causing the steering response to deviate from the driver's expectations. Based on the target yaw rate and the actual yaw rate, a target yaw torque is determined, such that the target yaw torque characterizes the magnitude and direction of the expected yaw moment under the current steering state. A target required torque is acquired to characterize the longitudinal drive torque demand of the entire vehicle, ensuring that the vehicle meets basic drive requirements during steering assist and preventing abnormal vehicle power response caused by insufficient or excessive longitudinal drive during steering assist. Based on the target yaw torque and the target required torque, the target torque of each wheel is determined, and the target torque of each wheel is used to generate a drive torque difference between the left and right wheels. This drive torque difference generates a yaw moment acting on the vehicle body, providing steering assist torque without triggering braking system intervention, thereby avoiding speed loss due to braking intervention. By controlling the motors corresponding to each wheel to output torque according to the target torque corresponding to each wheel, the vehicle can be assisted to complete steering by driving torque difference while maintaining vehicle speed, thereby reducing the turning radius and improving maneuverability and passability under low-speed and large-angle conditions.

[0047] In some embodiments, the preset steering assist activation conditions include: The target vehicle's current steering wheel angle is greater than or equal to a preset steering angle threshold, the target vehicle's current speed is less than or equal to a preset speed threshold, the target vehicle's current gear is either forward or reverse, the target vehicle's current battery state of charge is greater than or equal to a preset state of charge threshold, and the target vehicle's preset safety functions are inactive.

[0048] The aforementioned preset steering angle threshold, preset vehicle speed threshold, and preset charge threshold can all be obtained through corresponding bench tests or vehicle calibration tests based on the actual configuration and performance requirements of the target vehicle. This application does not impose specific numerical limitations on these values. For example, the preset steering angle threshold can be calibrated based on the transmission ratio of the vehicle's steering system and the desired timing of steering assist intervention; the preset vehicle speed threshold can be calibrated based on the vehicle's handling stability requirements under low-speed conditions; and the preset charge threshold can be calibrated based on the battery system's discharge characteristics and power output capability. The specific values ​​of each of the above preset values ​​can be determined by those skilled in the art through a limited number of experiments based on actual application scenarios and design requirements.

[0049] For example, the system acquires the current steering wheel angle of the target vehicle. When this steering wheel angle is greater than or equal to a preset angle threshold, it indicates that the driver has a clear steering intention, such as in situations requiring a sharp turn in narrow bends or parking scenarios. Simultaneously, the system acquires the current vehicle speed. When this current speed is less than or equal to a preset speed threshold, it indicates that the vehicle is in a low-speed driving state suitable for activating steering assistance, avoiding intervention at high speeds that could affect driving safety. The system also acquires the current gear of the target vehicle. When the current gear is forward or reverse, it indicates that the vehicle is in a drivable driving gear, where the steering assistance function has practical application needs. Furthermore, the system acquires the current state of charge (SBC) of the target vehicle. When this SBC is greater than or equal to a preset charge threshold, it indicates that the power battery has sufficient energy reserves to support the additional torque output requirements during steering assistance, preventing a decrease in vehicle power performance due to insufficient battery power. It is also necessary to obtain the activation status of the target vehicle's preset safety functions. When all these preset safety functions are inactive, it indicates that the vehicle is currently in a stable driving state, and the intervention of the steering assist function will not conflict with the vehicle's existing safety control strategy. When all the above conditions are met, it is determined that the target vehicle meets the preset steering assist activation conditions. At this point, the target yaw rate and the actual yaw rate can be obtained, and subsequent steering assist control steps can be executed.

[0050] It should be noted that the preset safety functions include at least one of the following: vehicle stability control, automatic parking, hill descent control, automatic emergency braking, adaptive cruise control, and automatic parking. These safety functions control the vehicle's safety from different dimensions, such as vehicle attitude stability, parking brake maintenance, hill speed control, emergency collision avoidance, longitudinal speed following, and automatic parking operation. While these functions are active, their respective control logics independently output braking or driving forces to maintain the vehicle's safety. If the steering assist torque of this application is added at this time, it may have unpredictable coupling effects on the vehicle's actual response. Therefore, when any of the aforementioned preset safety functions is active, the steering assist function is disabled.

[0051] Please see Figure 2 This is a schematic diagram of the process for obtaining the target yaw rate according to an embodiment of this application, which may specifically include: S210. Calculate the initial yaw rate based on the target vehicle's current front wheel angle, current rear wheel angle, current vehicle speed, and current wheelbase.

[0052] For example, the current front wheel angle and current rear wheel angle of the target vehicle reflect the steering angle desired by the driver through the steering wheel input and the steering angle of the vehicle's rear wheels, the current vehicle speed is used to characterize the current longitudinal speed of the vehicle, and the current wheelbase characterizes the geometric distance between the front and rear axles of the vehicle.

[0053] Based on the current front wheel steering angle, current rear wheel steering angle, current vehicle speed, and current wheelbase, the initial yaw rate is calculated using a vehicle dynamics model. The formula for this calculation is as follows:

[0054] Where, γ des V is the initial yaw rate. x Current vehicle speed l Where is the current wheelbase, K is the stability factor, and δ f δ is the current front wheel steering angle. r The formula represents the current rear wheel steering angle. It reflects the driver's desired yaw direction by the difference between the front and rear wheel steering angles. It characterizes the vehicle's response to steering input at different speeds by using the ratio of vehicle speed and wheelbase, as well as corrections for stability factors, thereby obtaining the initial yaw rate corresponding to the current vehicle state.

[0055] S220. Based on the road surface adhesion coefficient and the current vehicle speed, determine the yaw rate limit.

[0056] The coefficient of friction reflects the maximum available adhesion between the tire and the road surface. Its value affects the maximum lateral acceleration the vehicle can withstand, while the current vehicle speed determines the upper limit of the yaw rate that the vehicle can achieve under given road surface adhesion conditions. The formula for calculating the yaw rate limit is as follows: γ lim =0.85×μg / V x Where, γ lim Here, μ is the yaw rate limit, g is the road adhesion coefficient, and V is the gravitational acceleration. xThe current vehicle speed is 0.85, which is a preset calibration coefficient used to leave a certain safety margin based on the theoretical limit value, so as to avoid the control target exceeding the physical feasible range. This limit value represents the maximum yaw rate that the vehicle can safely reach under the current road conditions and vehicle speed. When the yaw rate expected by the driver exceeds this limit value, if it is not limited, it may cause the vehicle to exceed the adhesion limit and become unstable.

[0057] S230. Based on the yaw rate limit value, the initial yaw rate is limited to obtain the target yaw rate.

[0058] For example, the initial yaw rate is limited according to the yaw rate limit value to obtain the target yaw rate. The limiting method is to take the smaller of the absolute value of the initial yaw rate and the absolute value of the yaw rate limit value as the absolute value of the target yaw rate, that is: γ target =min{|γ des |,|γ lim |} Where, γ target Let γ be the target yaw rate. des Let γ be the initial yaw rate. lim This is the yaw rate limit value. This limiting process ensures that the target yaw rate does not exceed the safe upper limit allowed by the current road conditions and vehicle speed. When the initial yaw rate input by the driver is within the safe range, the limiting process retains the initial value, allowing the vehicle to respond according to the driver's actual intention. When the initial yaw rate input by the driver exceeds the safe upper limit, the limiting process restricts the target yaw rate to the yaw rate limit value, avoiding outputting an expected value beyond the physically feasible range, and preventing wheel slippage or vehicle instability caused by torque distribution commands exceeding the tire adhesion limits.

[0059] Please see Figure 3 This is a flowchart illustrating the process of determining the target yaw torque according to an embodiment of this application, which may specifically include: S310. Calculate the difference between the target yaw rate and the actual yaw rate to obtain the yaw rate error.

[0060] S320: The yaw rate error is controlled by a proportional-integral-derivative controller to obtain the target yaw torque.

[0061] For example, the target yaw rate is the desired yaw rate calculated based on the vehicle's current motion state and the driver's steering input, representing the yaw motion state the driver hopes the vehicle will achieve through the current steering operation. The actual yaw rate is the vehicle's actual yaw rate value detected by the inertial measurement unit, representing the vehicle's true yaw motion response at the current moment. Subtracting the actual yaw rate from the target yaw rate gives the yaw rate error. A positive error indicates that the vehicle's current actual yaw response is less than the driver's expectation, and the vehicle is in an understeer state. A negative error indicates that the vehicle's current actual yaw response is greater than the driver's expectation, and the vehicle is in an oversteer state. The absolute value of this error reflects the degree of deviation between the driver's expectation and the actual response.

[0062] The Proportional-Integral-Derivative (PID) controller is an algorithm that controls based on the time-varying nature of system error. Its control output is obtained by a weighted sum of three parts: a proportional term, an integral term, and a derivative term. The proportional term multiplies the current yaw rate error by a preset proportional gain coefficient, producing an instantaneous control output proportional to the current error magnitude, used to quickly respond to deviations between the driver's steering input and the actual response. The integral term multiplies the cumulative yaw rate error over time by a preset integral gain coefficient, producing a control output to eliminate steady-state residual error. When a small yaw rate deviation persists for an extended period, the integral term gradually increases the control output until the deviation is eliminated. The derivative term multiplies the rate of change of the yaw rate error over time by a preset derivative gain coefficient, producing a control output to suppress the trend of error change. When the rate of change of the error is large, the derivative term outputs a larger inverse control output to suppress drastic fluctuations in the yaw rate. The target yaw torque is obtained by adding the three control outputs above. This target yaw torque is adjusted according to the change of yaw rate error, so that the actual yaw rate of the vehicle continuously approaches the target yaw rate.

[0063] In summary, this embodiment calculates the yaw rate error by measuring the difference between the target yaw rate and the actual yaw rate. The sign of this error represents understeer and oversteer, respectively, and the absolute value of the error reflects the degree of deviation between the driver's expectation and the actual response. The target yaw torque is obtained by performing a weighted calculation of the proportional, integral, and derivative terms on the yaw rate error using a proportional-integral-derivative controller. The proportional term generates a control quantity in real time based on the current error magnitude to quickly respond to deviations. The integral term accumulates historical errors to eliminate steady-state residual deviations. The derivative term makes proactive adjustments based on the error change trend to suppress drastic fluctuations in yaw rate. The synergistic effect of these three terms ensures that the target yaw torque adjusts with changes in error, guaranteeing that the actual yaw rate of the vehicle approaches the target value, thereby improving steering response speed and accuracy.

[0064] Please see Figure 4 This is a schematic diagram of a process for obtaining the target required torque according to an embodiment of this application, which may specifically include: S410. Query the target torque required corresponding to the combination of the current accelerator pedal opening and the current vehicle speed of the target vehicle from the preset first mapping relationship, wherein the first mapping relationship is used to characterize the correspondence between the combination of accelerator pedal opening and vehicle speed and the required torque.

[0065] For example, the preset first mapping relationship is a pre-calibrated two-dimensional data table stored in the vehicle controller. This mapping relationship uses accelerator pedal opening and vehicle speed as two input dimensions and the required torque as the output dimension. During vehicle operation, the current accelerator pedal opening is detected by the accelerator pedal position sensor, and the current vehicle speed is calculated by the wheel speed sensor or the vehicle controller. Both are used as query indices and input into the first mapping relationship. For different combinations of accelerator pedal opening and vehicle speed, the first mapping relationship sets corresponding required torque values. Accelerator pedal opening reflects the driver's subjective intention regarding the vehicle's driving force output, and vehicle speed reflects the vehicle's current longitudinal motion state. At the same vehicle speed, the larger the accelerator pedal opening, the greater the corresponding required torque. At the same accelerator pedal opening, the gain of the required torque with speed at lower vehicle speeds is greater than the gain of the required torque with speed at higher vehicle speeds, allowing the vehicle to obtain a more sensitive torque response during low-speed start-up and a smoother torque response at high speeds to avoid over-driving. By querying the mapping relationship between the current accelerator pedal opening and the current vehicle speed, the required torque that matches the current operating conditions is obtained as the target required torque.

[0066] In summary, the accelerator pedal opening in this embodiment reflects the driver's subjective demand for vehicle driving force, ensuring that the target torque changes instantly with the driver's acceleration operation, thus maintaining consistency between the vehicle's power response and the driver's intention. By jointly querying vehicle speed and accelerator pedal opening, the same accelerator pedal opening corresponds to different torque demands at different vehicle speeds. This avoids wheel slippage due to excessive torque demand at high speeds or sluggish start-up due to insufficient torque demand at low speeds. The queried target torque demand is adapted to the current driving conditions, satisfying the driver's driving needs while maintaining smooth driving torque output.

[0067] Please see Figure 5 This is a schematic diagram of another process for obtaining the target torque requirement provided in an embodiment of this application, which may specifically include: S510. From the preset candidate mapping relationships, find the second mapping relationship corresponding to the current driving mode of the target vehicle.

[0068] S520. Query the target torque demand corresponding to the combination of the current accelerator pedal opening and the current vehicle speed from the second mapping relationship. Different driving modes correspond to different candidate mapping relationships. The second mapping relationship is used to characterize the correspondence between the combination of accelerator pedal opening and vehicle speed and the demand torque.

[0069] For example, the vehicle controller pre-stores multiple candidate mapping relationships, each corresponding to a driving mode. The candidate mapping relationships for different driving modes are independently calibrated, representing the correspondence between the combination of accelerator pedal opening and vehicle speed and the required torque in different driving modes. During vehicle operation, the current driving mode is actively set by the driver via a mode selection switch or automatically determined by the vehicle based on driving conditions. The driving modes include at least Sport mode and Eco mode, with different driving modes corresponding to different torque response characteristic requirements.

[0070] The system searches for a mapping relationship that matches the current driving mode from multiple candidate mapping relationships and identifies this mapping relationship as the second mapping relationship. In the second mapping relationship, corresponding required torque values ​​are set for different combinations of accelerator pedal opening and vehicle speed. The current accelerator pedal opening and current vehicle speed are input as query indexes into the second mapping relationship to obtain the required torque that matches the combination of the current driving mode, current accelerator pedal opening, and current vehicle speed. This required torque is then identified as the target required torque.

[0071] In summary, this application embodiment, by pre-setting multiple candidate mapping relationships in the vehicle and assigning different candidate mapping relationships to different driving modes, allows the same combination of accelerator pedal opening and vehicle speed to correspond to different required torques in different driving modes, satisfying the driver's differentiated needs for vehicle power response characteristics in different driving scenarios. In Sport mode, the required torque in the second mapping relationship has a larger gain with the change of accelerator pedal opening, giving the vehicle a more aggressive acceleration response to match the driving needs of a sporty style. In Eco mode, the required torque in the second mapping relationship has a smaller gain with the change of accelerator pedal opening, giving the vehicle a smoother torque output to reduce energy consumption. By finding the corresponding second mapping relationship for the current driving mode and then querying the target required torque corresponding to the combination of the current accelerator pedal opening and vehicle speed, the determined target required torque is adapted to the driving mode selected by the driver, ensuring that the vehicle's power response characteristics conform to the style settings of the current driving mode while meeting the driver's driving needs.

[0072] Please see Figure 6 This is a schematic diagram of another process for obtaining the target required torque provided in an embodiment of this application, which may specifically include: S610: When it is detected that the target vehicle is currently in drive or reverse gear and neither the accelerator pedal nor the brake pedal is depressed, it is determined that the target vehicle is in a creeping state.

[0073] For example, the vehicle detects the current gear position, accelerator pedal position, and brake pedal position during driving. When the current gear is detected to be drive or reverse, it indicates that the vehicle is drivable. When the accelerator pedal is not depressed and the brake pedal is not depressed, it indicates that the driver is not currently applying an active acceleration or braking command to the vehicle. When both of the above conditions are met simultaneously, the vehicle is determined to be in a creep state. Creep state is an operating state set up by a distributed drive vehicle to simulate the low-speed coasting characteristics of a traditional automatic transmission vehicle under idling conditions when the driver does not actively request driving or braking force. In this state, the vehicle can generate a small amount of driving torque to maintain low-speed driving without relying on the driver's accelerator pedal input, making it convenient for the driver to achieve low-speed movement of the vehicle by slight control of the brake pedal in scenarios such as parking and following other vehicles in congested traffic.

[0074] S620, in creep mode, obtains the preset creep target speed.

[0075] The creep target speed is a pre-calibrated fixed speed value, which represents the stable driving speed that the vehicle is expected to maintain in creep mode. Its value is usually set in a low speed range.

[0076] The S630 calculates the creep torque based on the target creep speed and the current speed using a proportional-integral controller, and determines the creep torque as the target required torque.

[0077] For example, the proportional-integral (PI) controller calculates the control quantity based on the change in vehicle speed error over time. The vehicle speed error is the difference between the target creep speed and the current vehicle speed. The proportional term multiplies the current vehicle speed error by a preset proportional gain coefficient, generating an instantaneous control output proportional to the magnitude of the current vehicle speed error. When the current vehicle speed is lower than the target creep speed, the proportional term outputs a positive torque to drive the vehicle to accelerate. The integral term multiplies the cumulative value of the vehicle speed error over time by a preset integral gain coefficient, generating a control output used to eliminate the residual error in steady-state vehicle speed. When the vehicle is traveling in an environment with changing resistance, such as on a slope, the integral term continuously increases the control quantity until the current vehicle speed reaches the target creep speed. The control outputs of the proportional and integral terms are added together to obtain the creep torque, which is then determined as the target required torque.

[0078] In summary, this embodiment of the application determines that the vehicle is in a creeping state by detecting that the current gear is either forward or reverse and that neither the accelerator pedal nor the brake pedal is depressed. This allows the vehicle to maintain low-speed driving by outputting a small amount of driving torque even when the driver does not actively request driving force, reducing the driver's workload in low-speed driving scenarios. A preset creeping target speed is obtained as the speed control target, providing a following target value for the proportional-integral controller. The proportional-integral controller calculates the creeping torque based on the creeping target speed and the current speed. The proportional term ensures that the creeping torque increases instantly as the speed error increases, ensuring that the vehicle responds quickly to recover the target speed when starting or encountering resistance. The integral term continuously accumulates small residual speed errors and adjusts the creeping torque accordingly until the speed error is eliminated, ensuring that the vehicle can stably maintain a creeping target speed under different gradients and load conditions. The calculated creep torque is determined as the target required torque, so that the vehicle can maintain a stable low speed without relying on the accelerator pedal input in creep mode. This makes it easier for the driver to control the vehicle speed using only the brake pedal in scenarios such as parking, moving in narrow spaces, and following other vehicles in congested traffic.

[0079] Please see Figure 7 This is a flowchart illustrating the process of determining the target torque for each wheel according to an embodiment of this application, which may specifically include: S710. Based on the front axle longitudinal torque distribution coefficient and target required torque of the target vehicle, determine the front axle base torque and rear axle base torque.

[0080] For example, the front axle longitudinal torque distribution coefficient of the target vehicle is obtained. Optionally, this front axle longitudinal torque distribution coefficient is a pre-calibrated value, ranging from 0 to 1, used to characterize the distribution ratio of the target torque demand between the front and rear axles. Based on this front axle longitudinal torque distribution coefficient and the target torque demand, the base torque of the front axle and the base torque of the rear axle are calculated using the following formula: T front_base =p×T total T rear_base =(1-p)×T total Among them, T front_base T is the base torque of the front axle, p is the longitudinal torque distribution coefficient of the front axle, and T is the base torque of the front axle. total For the target torque requirement, T rear_base This refers to the rear axle base torque. The front axle base torque is used to characterize the sum of the longitudinal drive torques distributed to the two front axle wheels, and the rear axle base torque is used to characterize the sum of the longitudinal drive torques distributed to the two rear axle wheels.

[0081] S720: Obtain the target vehicle's current track width, current tire radius, front axle yaw torque distribution coefficient, and rear axle yaw torque distribution coefficient, wherein the sum of the front axle yaw torque distribution coefficient and the rear axle yaw torque distribution coefficient is 1.

[0082] Here, the current track width is the distance between the center points of the left and right wheels of the target vehicle; the current tire radius is the rolling radius of each wheel of the target vehicle; and both the front axle yaw torque distribution coefficient and the rear axle yaw torque distribution coefficient are pre-calibrated fixed values, with the sum of the two coefficients being 1. The front axle yaw torque distribution coefficient characterizes the proportion of the target yaw torque allocated to the difference in driving torque between the left and right front axle wheels, while the rear axle yaw torque distribution coefficient characterizes the proportion of the target yaw torque allocated to the difference in driving torque between the left and right rear axle wheels.

[0083] S730 determines the difference in drive torque between the left and right front axles based on the target yaw torque, the front axle yaw torque distribution coefficient, the current tire radius, and the current track width.

[0084] The formula for calculating the difference in drive torque between the left and right front axle wheels is: ΔT front =(q f ×M z ×r) / (w / 2) Where, ΔT front The difference in drive torque between the left and right front wheels, q f M is the front axle yaw torque distribution coefficient. z Let r be the target yaw torque, w be the current tire radius, and w / 2 be half of the current wheelbase (i.e., the distance from the center point of the left and right wheels to the longitudinal centerline of the vehicle). This formula means that the portion of the target yaw torque allocated to the front axle is equal to the yaw moment generated by the difference in driving torque between the left and right front axle wheels. This yaw moment is equal to the difference in driving force obtained by dividing the difference in driving torque between the left and right front axle wheels by the current tire radius, multiplied by half of the current wheelbase.

[0085] S740 determines the difference in drive torque between the left and right rear axles based on the target yaw torque, the rear axle yaw torque distribution coefficient, the current tire radius, and the current track width.

[0086] The formula for calculating the difference in drive torque between the left and right rear axles is: ΔT rear =(q r ×M z ×r) / (w / 2) Where, ΔT rear q represents the difference in drive torque between the left and right rear wheels. rThis is the rear axle yaw torque distribution coefficient. The formula means that the portion of the target yaw torque distributed to the rear axle is equal to the yaw moment generated by the difference in drive torque between the left and right rear axle wheels. This yaw moment is equal to the difference in drive force obtained by dividing the difference in drive torque between the left and right rear axle wheels by the current tire radius, multiplied by half of the current wheelbase.

[0087] S750, based on the base torque of the front axle and the difference in drive torque between the left and right front wheels, determines the target torque of the left front wheel and the target torque of the right front wheel.

[0088] For example, the target torque for the left front wheel is equal to half of the base torque of the front axle minus the difference in drive torque between the left and right front wheels; the target torque for the right front wheel is equal to half of the base torque of the front axle plus the difference in drive torque between the left and right front wheels. The calculation formula is as follows: Front left wheel (FL): T FL =T front_base / 2-ΔT front Right front wheel (FR): T FR =T front_base / 2+ΔT front Among them, T FL T represents the target torque for the left front wheel. FR T represents the target torque for the right front wheel. front_base The base torque of the front axle is ΔT. front This represents the difference in driving torque between the left and right front axle wheels. Half of the base front axle torque represents a reference value for evenly distributing the longitudinal driving torque of the front axle to the left and right front wheels. The difference in driving torque between the left and right front axle wheels is a signed value superimposed on this reference value. When this difference is positive, the target torque for the left front wheel decreases from the reference value, while the target torque for the right front wheel increases from the reference value, creating a driving torque difference where the left side is smaller than the right side. This driving torque difference generates a yaw moment in the first direction on the vehicle. When this difference is negative, the target torque for the left front wheel increases from the reference value, while the target torque for the right front wheel decreases from the reference value, creating a driving torque difference where the left side is larger than the right side. This driving torque difference generates a yaw moment in the second direction on the vehicle.

[0089] S760, based on the rear axle base torque and the difference in drive torque between the left and right rear wheels, determines the target torque for the left rear wheel and the target torque for the right rear wheel.

[0090] For example, the target torque for the left rear wheel is equal to half of the base torque of the rear axle minus the difference in drive torque between the left and right rear wheels; the target torque for the right rear wheel is equal to half of the base torque of the rear axle plus the difference in drive torque between the left and right rear wheels. The calculation formula is as follows: Left rear wheel (RL): T RL =T rear_base / 2-ΔT rear Right rear wheel (RR): T RR =T rear_base / 2+ΔT rear Among them, T RL T is the target torque for the left rear wheel. RR T represents the target torque for the right rear wheel. rear_base The base torque of the rear axle is ΔT. rear This represents the difference in drive torque between the left and right rear wheels. Half of the base torque of the rear axle represents a reference value for evenly distributing the longitudinal drive torque of the rear axle to the left and right rear wheels. The difference in drive torque between the left and right rear wheels is a signed value superimposed on this reference value. When the difference is positive, the target torque for the left rear wheel decreases from the reference value, and the target torque for the right rear wheel increases from the reference value, creating a drive torque difference where the left side is smaller than the right side. This drive torque difference generates a yaw moment in the first direction on the vehicle. When the difference is negative, the target torque for the left rear wheel increases from the reference value, and the target torque for the right rear wheel decreases from the reference value, creating a drive torque difference where the left side is larger than the right side. This drive torque difference generates a yaw moment in the second direction on the vehicle.

[0091] Specifically, the signs of the torque differences between the left and right front axle and rear axle are kept consistent, ensuring that the yaw moments generated by the front and rear axles are in the same direction and act together on the vehicle to produce the total target yaw torque. The first and second directions of the target yaw torque are opposite, corresponding to the vehicle's left and right turning directions, respectively. When the target vehicle turns left, the direction of the target yaw torque is the first direction, and both the torque differences between the left and right front axle and rear axle are positive, with the target torque for the left front wheel being less than that for the right front wheel, and the target torque for the left rear wheel being less than that for the right rear wheel. When the target vehicle turns right, the direction of the target yaw torque is the second direction, and both the torque differences between the left and right front and rear axle are negative, with the target torque for the left front wheel being greater than that for the right front wheel, and the target torque for the left rear wheel being greater than that for the right rear wheel.

[0092] In summary, this embodiment of the application allocates the target required torque into a front axle base torque and a rear axle base torque through a front axle longitudinal torque distribution coefficient. This allows the distribution ratio of the total required torque between the front and rear axles to be calibrated according to the vehicle's drive configuration, thereby adapting the distribution of base torque to the vehicle's drive characteristics. By obtaining the front and rear axle yaw torque distribution coefficients and setting their sum to 1, the target yaw torque is distributed to the front and rear axles according to a preset ratio. Based on the target yaw torque, yaw torque distribution coefficients, tire radius, and track width, the driving torque difference between the left and right wheels of the front and rear axles is calculated respectively. Using half the track width as a lever arm, the yaw moment is converted into a driving force difference, and then the driving force difference is converted into a driving torque difference using the tire radius. This establishes a clear numerical correspondence between the yaw moment requirement and the driving torque difference between the left and right wheels of each axle. The target torque for each wheel is determined by superimposing half of the base torque as a reference value and the difference in driving torque between the left and right wheels. This ensures that the target torque of each wheel accurately achieves the torque difference between the left and right wheels while meeting the overall longitudinal drive requirements. This torque difference is converted into a yaw moment acting on the vehicle through the interaction between the tires and the ground. This yaw moment generates a steering assist torque while driving the vehicle forward or backward. Moreover, the generation of this steering assist torque does not depend on the intervention of the braking system. Thus, the vehicle can be assisted in steering without losing speed, reducing the turning radius and improving the passability under low-speed, large-angle conditions.

[0093] Please see Figure 8 This is a schematic flowchart of the process for correcting the target yaw torque provided in an embodiment of this application. After step S120, it may specifically include: S810: Obtain the distance between the obstacles around the target vehicle and the target vehicle.

[0094] For example, obstacle distance is detected by radar sensors or camera sensors installed on the target vehicle. The target vehicle is equipped with multiple obstacle detection sensors, which are distributed at different locations on the target vehicle to cover the space around the vehicle. Each sensor detects obstacles within its respective detection range and outputs the corresponding distance value.

[0095] Optionally, after acquiring the distance values ​​output by each sensor, a minimum obstacle distance is determined from these values. This minimum obstacle distance characterizes the closest distance between the target vehicle and obstacles in any direction in the surrounding environment at the current moment, reflecting the size of the target vehicle's operable space in the current spatial environment. The smaller the minimum obstacle distance, the narrower the space around the target vehicle, and the yaw moment that needs to be applied during steering should be reduced accordingly to avoid collisions between the vehicle and obstacles during steering.

[0096] S820. When the distance to the obstacle is less than the preset safe distance threshold, a limit coefficient is determined based on the obstacle distance, wherein the limit coefficient is positively correlated with the obstacle distance.

[0097] Optionally, the minimum obstacle distance can be compared with a preset safe distance threshold. When the minimum obstacle distance is less than the preset safe distance threshold, it indicates that the target vehicle is too close to surrounding obstacles. Assisting the steering based on the current target yaw torque could lead to a collision between the vehicle and the obstacle, requiring a reduction in the target yaw torque. In this case, a limiting coefficient is determined based on the minimum obstacle distance. This limiting coefficient is positively correlated with the minimum obstacle distance; that is, the smaller the minimum obstacle distance, the smaller the limiting coefficient, and vice versa. The limiting coefficient ranges from 0 to 1. When the minimum obstacle distance is zero, the limiting coefficient is zero; when the minimum obstacle distance is equal to the preset safe distance threshold, the limiting coefficient is 1.

[0098] The aforementioned preset safety distance threshold can be obtained through on-site testing based on the overall dimensions of the target vehicle, the sensor detection range, and the desired safety redundancy. During the calibration process, parameters such as the target vehicle's body width, wheelbase, and minimum turning radius are assessed by conducting steering tests at different distances to evaluate the required safety distance between the vehicle and obstacles, as well as the driver's collision avoidance reaction time, thereby determining the preset safety distance threshold. This application does not specify a particular numerical value for this threshold.

[0099] S830. The product of the target yaw torque and the limiting coefficient is determined as the corrected target yaw torque.

[0100] For example, the target yaw torque is multiplied by a constraint coefficient, and the product is determined as the corrected target yaw torque. Since the constraint coefficient is less than or equal to 1, the corrected target yaw torque is less than or equal to the original target yaw torque, thus reducing the target yaw torque. When the minimum obstacle distance is greater than or equal to a preset safe distance threshold, the constraint coefficient is set to 1, and the target yaw torque remains unchanged.

[0101] S840: Based on the corrected target yaw torque and target required torque, determine the target torque for each wheel.

[0102] For example, the corrected target yaw torque is smaller than the original target yaw torque. Based on the corrected target yaw torque, the differences in driving torque between the left and right front axle wheels and the left and right rear axle wheels, calculated accordingly, are also reduced. This results in a corresponding reduction in the driving torque differences between the left and right front wheels and between the left and right rear wheels. The reduced driving torque difference means a smaller torque difference between the left and right wheels, leading to a corresponding reduction in the actual yaw moment generated by the vehicle. This reduces the vehicle's steering amplitude, thus preventing collisions with obstacles due to oversteering in confined spaces. When the minimum obstacle distance returns to a safe range (greater than or equal to a preset safe distance threshold), the limiting coefficient returns to 1, the corrected target yaw torque equals the original target yaw torque, and the vehicle resumes normal steering assist response.

[0103] In summary, this embodiment of the application obtains the distances to obstacles in all directions around the target vehicle and determines the minimum obstacle distance from these distances. It senses the obstacle distance in the narrowest direction within the space surrounding the vehicle, and this minimum distance reflects the maximum risk of the vehicle colliding with an obstacle in the current environment. By comparing the minimum obstacle distance with a preset safe distance threshold, a safety limiting function is activated when the minimum distance is less than the threshold. This ensures that intervention only occurs when the vehicle is too close to an obstacle in any direction, maintaining normal steering assist response when the distance is sufficient, and avoiding unnecessary intervention that could affect steering efficiency. By determining a limiting coefficient based on the minimum obstacle distance, and ensuring that the limiting coefficient is positively correlated with the minimum obstacle distance, the reduction in yaw torque increases as the minimum distance decreases. The reduction gradually increases as the vehicle approaches the obstacle and gradually decreases as the vehicle moves away from the obstacle, preventing abrupt changes in yaw torque due to sudden changes in the limiting coefficient, which could lead to abrupt steering actions. The corrected target yaw torque is obtained by multiplying the target yaw torque by the limiting coefficient. The corrected target yaw torque decreases as the limiting coefficient decreases, thereby proportionally reducing the difference in driving torque between the left and right wheels of each wheel calculated based on the corrected value. Ultimately, the yaw moment actually generated by the vehicle decreases smoothly as the distance to the minimum obstacle shortens, maintaining the largest possible steering assistance effect while ensuring that the vehicle does not collide with obstacles in any direction.

[0104] Please see Figure 9 This is a flowchart illustrating the process of limiting the target torque of each wheel according to an embodiment of this application. Before step S140, it may specifically include: S910: Obtain the current vertical load on each wheel and the current road surface adhesion coefficient.

[0105] For example, the current vertical load of each wheel is calculated using the longitudinal and lateral accelerations detected by the inertial measurement unit installed on the vehicle.

[0106] The formula for calculating the vertical load on the right front wheel is:

[0107] The formula for calculating the vertical load on the left front wheel is:

[0108] The formula for calculating the vertical load on the right rear wheel is:

[0109] The formula for calculating the vertical load on the left rear wheel is:

[0110] in, m veh For the overall vehicle quality, g It is the acceleration due to gravity. b This is the distance from the center of mass to the rear axle. a This is the distance from the center of gravity to the front axle. l wheelbase and a and b The sum of them equals l. a x For longitudinal acceleration, a y For lateral acceleration, h COG For the height of the vehicle's center of gravity, w This refers to the wheel track.

[0111] In the above formula, the first two terms represent the load transfer due to longitudinal acceleration, and the last two terms represent the load transfer due to lateral acceleration. The sum of these two terms yields the actual vertical load on each wheel under the current acceleration and turning conditions. When longitudinal acceleration is positive, the vehicle is accelerating, and the load is transferred from the front axle to the rear axle. When longitudinal acceleration is negative, the vehicle is decelerating, and the load is transferred from the rear axle to the front axle. When lateral acceleration is positive, the vehicle is turning left, and the load is transferred from the left wheel to the right wheel. When lateral acceleration is negative, the vehicle is turning right, and the load is transferred from the right wheel to the left wheel.

[0112] S920: Determine the maximum available torque for each wheel based on the current vertical load and current road adhesion coefficient of each wheel.

[0113] Optionally, the current method for calculating the road surface adhesion coefficient is as follows:

[0114] in, μ The current road surface adhesion coefficient, a x For longitudinal acceleration, a yis the lateral acceleration. This calculation method estimates the current road surface adhesion capability based on the ratio of the actual resultant acceleration generated between the tire and the road surface during vehicle motion to the gravitational acceleration. The greater the resultant acceleration generated during vehicle acceleration or turning, the higher the road surface adhesion coefficient, indicating the greater the adhesion force provided by the road surface.

[0115] S930. For each wheel, limit the target torque of the wheel within the maximum available torque of the wheel and the preset maximum motor torque.

[0116] Exemplarily, for each wheel, multiply the current vertical load by the current road surface adhesion coefficient to obtain the maximum driving force that each wheel can bear under the current road surface condition. Multiply the maximum driving force by the tire radius to obtain the maximum available torque of each wheel. The calculation formula for the maximum available torque is: T max-raw,xx =μ×F Z,xx ×r wherein, xx represents the identifier of each wheel of the vehicle, xx when it takes fl it represents the left front wheel, xx when it takes fr it represents the right front wheel, xx when it takes rl it represents the left rear wheel, xx when it takes rr it represents the right rear wheel; r is the current tire radius. The maximum available torque represents the upper limit value of the driving torque output by each wheel under the current vertical load distribution and current road surface adhesion conditions. When the target torque of a certain wheel exceeds this upper limit value, the adhesion force between the wheel and the road surface is insufficient to transmit the driving force corresponding to the target torque, and the wheel will spin.

[0117] After determining the maximum available torque of each wheel, for each wheel, obtain the maximum motor torque of the drive motor corresponding to the wheel, and limit the target torque of each wheel within the maximum available torque of the wheel and the maximum motor torque corresponding to the wheel, that is, take the minimum value among the target torque, the maximum available torque and the maximum motor torque as the final target torque of the wheel.

[0118] It should be noted that the preset maximum motor torque is a fixed torque limit value pre-calibrated and stored in the vehicle controller. This limit value is determined by the physical output capability of the drive motor itself corresponding to each wheel, and the maximum motor torques corresponding to the four wheels are the same.

[0119] In summary, this embodiment of the application obtains longitudinal and lateral acceleration through an inertial measurement unit and calculates the vertical load on each wheel by combining vehicle parameters such as vehicle mass, center of gravity position, center of gravity height, and wheelbase. This ensures that the calculation of the vertical load considers the forward-backward load transfer caused by longitudinal acceleration or deceleration and the left-right load transfer caused by lateral acceleration or turning. The vertical load on each wheel is updated according to changes in the vehicle's motion state, ensuring that the calculation of the maximum available torque is always based on the current actual load distribution. The road adhesion coefficient is calculated using longitudinal and lateral acceleration, and is updated according to changes in road conditions. On low-adhesion roads, the maximum available torque of each wheel is reduced overall to prevent wheel slippage; on high-adhesion roads, the maximum available torque of each wheel is increased overall to fully utilize road adhesion. By limiting the target torque to within the maximum available torque and the maximum motor torque, the final output target torque is constrained by both road adhesion conditions and the physical capabilities of the motor, avoiding wheel slippage due to the target torque exceeding the adhesion limit or motor overload due to exceeding the motor's capabilities, thus ensuring drive stability during steering assistance.

[0120] In some embodiments, updating the current road surface adhesion coefficient includes: When the accelerator pedal position is greater than the preset pedal position threshold, the absolute value of the front wheel angle is less than the preset angle threshold, the vehicle speed is greater than the preset vehicle speed threshold, and the rate of change of both longitudinal acceleration and lateral acceleration is less than the preset rate of change threshold, the vehicle is determined to be in a stable acceleration condition. At this time, the road adhesion coefficient can be calculated and updated based on the detected values ​​of longitudinal acceleration and lateral acceleration.

[0121] The above conditions define the applicable scenarios for the adhesion coefficient update. The accelerator pedal position threshold ensures the vehicle is in an active acceleration state rather than a coasting or braking state. The front wheel steering angle threshold ensures the vehicle is in a near-straight-line driving state to avoid interference from lateral acceleration during cornering on the adhesion coefficient estimation. The vehicle speed threshold eliminates interference when the vehicle is stationary or at extremely low speeds. The acceleration rate of change threshold ensures the vehicle is in a steady-state acceleration state rather than a transient impact condition. When any of the above conditions are not met, the adhesion coefficient update calculation is not performed, and the road adhesion coefficient uses either the factory default value or the historical stored value. The factory default value is used when the vehicle starts, and this default value is set according to the high adhesion coefficient of dry asphalt roads, allowing the vehicle to perform torque control based on high adhesion capability during the initial stage. If the vehicle has met the adhesion coefficient update conditions and successfully calculated the road adhesion coefficient during historical driving, this calculated value is stored in the controller as a historical value. In conditions where the update conditions are not met, the road adhesion coefficient continues to use this historical stored value, allowing the vehicle to still perform torque limiting based on the most recently updated adhesion coefficient in low-speed or cornering conditions where adhesion coefficient estimation is not possible.

[0122] Please see Figure 10 This is a schematic diagram of the process for temperature-corrected target torque of each wheel provided in an embodiment of this application. After step S920, it may specifically include: S1010. Determine the temperature correction factor for each wheel based on the current tire temperature of each wheel.

[0123] For example, when a tire operates under high load for extended periods or delivers high torque on a high-traction surface, the rubber material and tire carcass structure inside the tire accumulate heat due to repeated compression and rebound deformation, causing the tire temperature to gradually rise. When the tire temperature rises to a certain level, the viscoelastic properties of the tire rubber material change, the rubber softens, and the adhesion between the tire and the road surface decreases. Continuing to drive at the original maximum usable torque will lead to increased tire slippage and accelerated tire wear. Therefore, it is necessary to adjust the maximum usable torque based on the current tire temperature of each wheel.

[0124] For each wheel, when the current tire temperature is less than or equal to a first preset temperature threshold, it indicates that the tire temperature is within the normal operating range, and the temperature correction coefficient is determined as the first preset coefficient. When the current tire temperature is greater than or equal to a second preset temperature threshold, it indicates that the tire temperature has risen to a level that significantly affects adhesion, and the temperature correction coefficient is determined as the second preset coefficient. The second preset temperature threshold is greater than the first preset temperature threshold, and the second preset coefficient is less than the first preset coefficient. When the current tire temperature is greater than the first preset temperature threshold and less than the second preset temperature threshold, it indicates that the tire temperature is in the transition range between normal temperature and overheating temperature. In this case, the temperature correction coefficient is determined by interpolation calculation of the first and second preset coefficients, so that the temperature correction coefficient continuously decreases from the first preset coefficient to the second preset coefficient as the tire temperature increases.

[0125] Optionally, the first preset temperature threshold is 80℃, the second preset temperature threshold is 120℃, the first preset coefficient is 1, and the second preset coefficient is 0.5.

[0126] S1020. For each wheel, the product of the wheel's maximum available torque and the wheel's temperature correction coefficient is determined as the wheel's corrected maximum available torque.

[0127] For example, for each wheel, the maximum available torque of that wheel is multiplied by its temperature correction factor, and the product is determined as the corrected maximum available torque of that wheel. Since the temperature correction factor takes a first preset value when the tire temperature is within the normal operating range, a second preset value after the tire temperature enters the overheating range, and decreases as the temperature rises within the transition range, the corrected maximum available torque remains unchanged when the tire temperature is below the first preset temperature threshold, and decreases to the original maximum available torque multiplied by the second preset factor when the tire temperature is above the second preset temperature threshold, decreasing as the tire temperature rises within the transition range. The corrected maximum available torque replaces the original maximum available torque and is used for limiting the target torque of each wheel, updating the target torque limitation from the original physically calculated value to the value corrected for tire temperature.

[0128] In summary, this embodiment sets a first preset temperature threshold and a second preset temperature threshold, dividing the tire temperature into a normal operating range, a transition range, and an overheating range. Within the normal operating range, the temperature correction coefficient is the first preset coefficient. Within the overheating range, the temperature correction coefficient is reduced to the second preset coefficient to decrease the maximum usable torque. Within the transition range, interpolation is used to make the temperature correction coefficient change with increasing temperature. The corrected maximum usable torque is obtained by multiplying the maximum usable torque by the temperature correction coefficient. This corrected maximum usable torque decreases with increasing tire temperature in both the transition and overheating ranges. As the tire temperature rises, the maximum usable torque decreases accordingly, limiting the upper limit of the target torque and preventing further increases in tire temperature due to continuous high torque output, which would exacerbate thermal degradation and wear.

[0129] Please see Figure 11 This is a schematic diagram of the process for stopping torque output provided in an embodiment of this application. After step S150, it may specifically include: S1110. During the process of controlling the motors corresponding to each wheel to output torque according to the target torque of each wheel, monitor the activation status of each preset safety function of the target vehicle. S1120. When any preset safety function is detected to be activated, stop controlling each motor to output torque according to the target torque of each wheel, and control each motor to restore the torque output to the normal driving state.

[0130] For example, during the process of controlling the motors corresponding to each wheel to output torque according to the target torque of each wheel, the activation status of each preset safety function of the target vehicle is monitored. Each preset safety function includes at least one of the following: vehicle stability control, automatic parking, hill descent control, automatic emergency braking, adaptive cruise control, and automatic parking. These safety functions operate independently and have a higher control priority than steering assist. When any preset safety function is detected to be activated, it indicates that the vehicle has entered a condition requiring the intervention of a specific safety control strategy, and the yaw torque generated by the steering assist function may conflict with the currently executed safety function control command. In this case, the control of each motor to output torque according to the target torque of each wheel is stopped, the current torque vector distribution control logic is canceled, and each motor is controlled to resume torque output under normal driving conditions. Torque output under normal driving conditions means that the motor outputs according to the required torque input by the driver's accelerator pedal, without adding the torque difference between the left and right wheels used to generate yaw torque. By monitoring the activation status of preset safety functions and immediately exiting steering assist control and resuming normal driving output when any safety function is activated, it is ensured that there is no superposition conflict between the steering assist function and the various safety functions.

[0131] In summary, this embodiment monitors the activation status of each preset safety function during the operation of the steering assist function. This allows the vehicle to immediately identify changes in control priority when a safety function intervenes, preventing unpredictable coupling responses caused by the superposition of steering assist torque and safety function control commands. When any preset safety function is activated, the steering assist torque output is immediately stopped and the vehicle returns to normal driving mode. This ensures that the control commands of the safety function are not interfered with by the steering assist torque, maintaining the independent control of the vehicle's attitude and trajectory by the safety function, and guaranteeing the vehicle's safety under extreme or dangerous conditions.

[0132] In some embodiments, the exit conditions for the agile steering feature include: During the activation of the Agile Steering function, the vehicle continuously monitors various exit conditions. When the driver actively disables the Agile Steering function via the human-machine interface, it indicates that the driver no longer subjectively needs steering assistance, and the vehicle immediately exits the Agile Steering mode and stops torque vectoring. When the vehicle speed exceeds a preset speed threshold, it indicates that the vehicle has left the low-speed steering scenario. Continuing to apply yaw torque at high speeds may affect the vehicle's lateral stability. At this time, the Agile Steering function is automatically disengaged, and the torque of each wheel is restored to normal driving conditions. When the vehicle shifts to Park or Neutral, the vehicle has exited the driving state and no longer needs steering assistance; the Agile Steering function automatically disengages. When the battery state of charge is lower than a preset charge threshold, the available battery power is insufficient to support the additional yaw torque output demand. Maintaining the Agile Steering function may lead to over-discharge of the battery or insufficient power. At this time, the Agile Steering function is automatically disengaged to protect the battery system. When any of the following functions is activated: Vehicle Stability Control, Auto Hold, Hill Descent Control, Automatic Emergency Braking, Adaptive Cruise Control, or Automatic Parking, that function is executing independent safety control commands. To avoid conflicts between steering assist torque and safety function control commands, Agile Steering immediately disengages and returns to normal driving mode. The above disengagement conditions are related by an OR logic, meaning that meeting any one of them triggers the disengagement of Agile Steering.

[0133] In some embodiments, the steering control method provided in this application is applied to a steering control system of a distributed drive vehicle. This system includes a vehicle controller, a torque vector control module, a braking system, a drive system, a battery system, a steering system, an inertial measurement unit, an intelligent driving system, and a human-machine interface. The vehicle controller, as the control unit of this system, establishes signal transmission links with the braking system, drive system, battery system, steering system, inertial measurement unit, intelligent driving system, and human-machine interface, respectively, for receiving status signals uploaded by each subsystem and issuing control commands. The torque vector control module is integrated within the vehicle controller or interacts with the vehicle controller as an independent functional unit, for calculating the target torque for each wheel based on the signals received by the vehicle controller.

[0134] The signals uploaded by the braking system to the vehicle controller include vehicle stability control status, automatic parking status, hill descent control status, automatic emergency braking status, brake pedal status, vehicle speed, wheel speeds, and braking forces of each wheel. Based on these signals, the vehicle controller determines whether the vehicle stability control, automatic parking, hill descent control, and automatic emergency braking functions are active, thus determining the activation and deactivation conditions for the agile steering function. Simultaneously, the vehicle controller sends single-wheel braking force requests and vehicle stability control interaction requests to the braking system. Upon receiving these requests, the braking system arbitrates the response, achieving coordinated control of braking and drive.

[0135] The signals uploaded by the drive system to the vehicle controller include gear position, accelerator pedal position, drive force of each motor, and torque limits of each motor. The vehicle controller determines the availability of the agile steering function based on the gear position and obtains the driver's longitudinal drive requirements based on the accelerator pedal position. The vehicle controller sends target torque requests to each wheel to the drive system, and the drive system controls each motor to output the corresponding torque based on the received target torque requests.

[0136] The signals uploaded by the battery system to the vehicle controller include the battery power curve and the battery state of charge (SOC). The vehicle controller determines the available power under the current SOC based on the battery power curve and whether the agile steering function is available based on the SOC. When the SOC is below a preset threshold, the vehicle controller determines that the agile steering function is unavailable and grays out the agile steering function button via the human-machine interface. When calculating the target torque for each wheel, the vehicle controller limits the total torque output based on the battery power curve to ensure that the total torque output does not exceed the power range currently available from the battery.

[0137] The steering system sends signals to the vehicle controller including steering wheel angle, front wheel angle, and rear wheel angle. The vehicle controller determines the driver's steering intention based on the steering wheel angle and calculates the target yaw rate based on the front and rear wheel angles.

[0138] The signals uploaded by the inertial measurement unit to the vehicle controller include longitudinal acceleration, lateral acceleration, vertical acceleration, and yaw rate. The vehicle controller adjusts the torque distribution to each wheel in real time based on the deviation between the yaw rate and the target yaw rate, so that the actual yaw rate is close to the target yaw rate.

[0139] The signals uploaded by the intelligent driving system to the vehicle controller include driving function status, parking function status, intelligent driving enable status, and obstacle distance. Obstacle distance includes the distance to obstacles around the vehicle. The vehicle controller adjusts the target yaw torque based on the obstacle distance information uploaded by the intelligent driving system, reducing the target yaw torque when the obstacle distance is less than a preset safe distance threshold. The vehicle controller also sends the agile steering operating status and function status to the intelligent driving system, which uses these signals to determine whether the agile steering function is working and available.

[0140] The human-machine interface (HMI) includes a settings interface and a display interface. The settings interface features a toggle button for the agile steering function, with both "off" and "on" options. The HMI receives a function availability signal from the vehicle controller. When the vehicle controller determines that the agile steering function is unavailable, the HMI grays out the toggle button and prevents the user from activating it. When the vehicle controller determines that the agile steering function is available, the HMI highlights the toggle button and allows the user to activate it. The display interface shows turning path information and obstacle distance information after the function is activated. The turning path information is graphically displayed as the expected trajectory of the target vehicle, and the obstacle distance information is displayed numerically and graphically as the real-time distance between the target vehicle and obstacles. The HMI displays a function description below the function name and shows the corresponding reason for unavailability when the user attempts to operate the function after it has been grayed out. The agile steering function is off by default. When the vehicle is powered off after the driver activates the agile steering function, this activation state is not remembered; the agile steering function is restored to the off state upon the next power-on.

[0141] The technical solution of this application will be further described in detail below through specific embodiments.

[0142] Example 1: Right-angle turn on a narrow city street The vehicle is making a right-angle turn on a narrow street. The driver activates the agile steering function through the human-machine interface, at which point the vehicle speed has dropped below the preset speed threshold. The vehicle controller detects that the steering wheel angle has exceeded the preset angle threshold, determines that the driver intends to make a right-angle turn, meets the preset steering assist activation conditions, and activates the agile steering function.

[0143] The vehicle controller calculates the target yaw rate based on the current front wheel steering angle, current vehicle speed, and current wheelbase. It then limits the initial yaw rate according to a yaw rate limit value to obtain the target yaw rate. The vehicle controller acquires the actual yaw rate detected by the inertial measurement unit (IMU), calculates the difference between the target yaw rate and the actual yaw rate to obtain the yaw rate error, and uses a proportional-integral-derivative (PID) controller to perform control calculations on the yaw rate error to obtain the target yaw torque. If the distance between the vehicle and the right-side wall is detected to be 0.8 meters, which is less than a preset safe distance threshold, the vehicle controller determines a limiting coefficient based on this distance. The target yaw torque is multiplied by the limiting coefficient to obtain the corrected target yaw torque, reducing the yaw torque to avoid a collision between the vehicle's right side and the wall.

[0144] The vehicle controller acquires the accelerator pedal opening and current vehicle speed, and queries the preset first mapping relationship for the target torque required corresponding to the combination of the current accelerator pedal opening and current vehicle speed. The vehicle controller acquires the current vertical load and current road adhesion coefficient of each wheel to determine the maximum available torque for each wheel. Based on the front axle longitudinal torque distribution coefficient and the target torque required, the vehicle controller determines the base torque of the front axle and the base torque of the rear axle. Based on the corrected target yaw torque, the front axle yaw torque distribution coefficient, the current tire radius, and the current track width, the vehicle controller determines the driving torque difference between the left and right front wheels. Based on the corrected target yaw torque, the rear axle yaw torque distribution coefficient, the current tire radius, and the current track width, the vehicle controller determines the driving torque difference between the left and right rear wheels. Based on the driving torque differences between the front and rear wheels, the vehicle controller determines the target torque for the left front wheel, right front wheel, left rear wheel, and right rear wheel. At this point, the left front and left rear wheels apply a smaller torque, while the right front and right rear wheels apply a larger torque. This creates a driving torque difference between the left and right wheels, which generates a counterclockwise yaw moment to assist the vehicle in turning to the left. The vehicle controller controls the motors corresponding to each wheel to output torque according to the target torque of each wheel.

[0145] The steering control method described in this application allows the vehicle to complete right-angle turns in narrow streets without the need for multiple forward and backward adjustments. The human-machine interface displays the vehicle's turning path and the distance to the right-side wall. When the distance is less than a preset alarm distance threshold, a voice alarm is issued to remind the driver to pay attention to safety.

[0146] Example 2: Parking and exiting the parking lot The vehicle is attempting to exit a parking space in a narrow lane. The driver activates the agile steering function via the human-machine interface and engages reverse gear. At this point, the vehicle speed has dropped below a preset speed threshold. The vehicle controller detects that the steering wheel angle has exceeded a preset angle threshold, determines that the driver intends to reverse out of the parking space, and meets the preset steering assist activation conditions, thus activating the agile steering function.

[0147] The vehicle controller calculates the target yaw rate based on the current front wheel angle, current vehicle speed, and current wheelbase. It then limits the initial yaw rate according to a yaw rate limit value to obtain the target yaw rate. The actual yaw rate detected by the inertial measurement unit is acquired, and the difference between the target yaw rate and the actual yaw rate is calculated to obtain the yaw rate error. This error is then controlled by a proportional-integral-derivative (PID) controller to obtain the target yaw torque. The intelligent driving system detects an obstacle distance of 1.2 meters between the vehicle and the vehicle on its left, and an obstacle distance of 1.5 meters between the vehicle and the vehicle behind. Since these obstacle distances are all less than a preset safe distance threshold, the vehicle controller determines the minimum obstacle distance from these distances. Based on this minimum obstacle distance, a limit coefficient is determined. The target yaw torque is multiplied by the limit coefficient to obtain the corrected target yaw torque, ensuring that the vehicle maintains a safe distance from surrounding vehicles during exiting the parking area.

[0148] The vehicle is detected to be in reverse gear, with neither the accelerator nor brake pedals depressed, indicating it is in a creeping state. The vehicle controller acquires a preset creeping target speed and calculates the creeping torque using a proportional-integral controller based on the target speed and current speed, defining this creeping torque as the target torque requirement. The vehicle controller acquires the current vertical load and road adhesion coefficient for each wheel to determine the maximum available torque for each wheel. Based on the front axle longitudinal torque distribution coefficient and the target torque requirement, the vehicle controller determines the base torque for the front and rear axles. Based on the corrected target yaw torque, the front axle yaw torque distribution coefficient, the current tire radius, and the current track width, the vehicle controller determines the difference in drive torque between the left and right front axles. Similarly, based on the corrected target yaw torque, the rear axle yaw torque distribution coefficient, the current tire radius, and the current track width, the vehicle controller determines the difference in drive torque between the left and right rear axles. The vehicle controller determines the target torques for the left front wheel, right front wheel, left rear wheel, and right rear wheel based on the torque differences between the left and right front axle and rear axle. At this point, the left front and left rear wheels apply a larger torque, while the right front and right rear wheels apply a smaller torque. This creates a torque difference between the left and right wheels, generating a clockwise yaw moment to assist the vehicle in turning to the right rear. The vehicle controller then controls the motors corresponding to each wheel to output torque according to the target torque for each wheel.

[0149] The steering control method described in this application allows the vehicle to complete exit maneuvers in narrow lanes without the need for multiple reversing adjustments. The human-machine interface displays the vehicle's turning path and distances to surrounding vehicles, and issues a voice alert when the distance is less than a preset warning threshold, thus improving driving safety.

[0150] Please see Figure 12 This is a schematic diagram of the structure of a vehicle steering control device 20 provided in an embodiment of this application. The device includes: The condition judgment module 1221 is used to obtain the target yaw rate and the actual yaw rate of the target vehicle when the preset steering assist activation condition is met. Yaw torque module 1222 is used to determine the target yaw torque based on the target yaw angular velocity and the actual yaw angular velocity; The demand torque module 1223 is used to obtain the target demand torque of the target vehicle, wherein the target demand torque is used to characterize the longitudinal drive torque demand of the target vehicle. The torque distribution module 1224 is used to determine the target torque of each wheel based on the target yaw torque and the target required torque, wherein the target torque of each wheel is used to generate a driving torque difference between the left and right wheels of the target vehicle. The motor control module 1225 is used to control the motors corresponding to each wheel to output torque according to the target torque corresponding to each wheel, so as to assist the target vehicle in steering.

[0151] In some embodiments, the condition judgment module 1221 includes: The initial yaw angle calculation submodule is used to calculate the initial yaw rate based on the target vehicle's current front wheel steering angle, current rear wheel steering angle, current vehicle speed, and current wheelbase. The yaw rate limit calculation submodule is used to determine the yaw rate limit value based on the road surface adhesion coefficient and the current vehicle speed; The target yaw angle determination submodule is used to limit the initial yaw angle based on the yaw angle velocity limit value to obtain the target yaw angle velocity.

[0152] In some embodiments, the yaw torque module 1222 includes: The yaw rate error calculation submodule is used to calculate the difference between the target yaw rate and the actual yaw rate, and obtain the yaw rate error. The target yaw torque determination submodule is used to perform control calculations on the yaw angular velocity error through a proportional-integral-derivative controller to obtain the target yaw torque.

[0153] In some embodiments, the demand torque module 1223 includes: The first demand torque submodule is used to query the target demand torque corresponding to the combination of the current accelerator pedal opening and the current vehicle speed from the preset first mapping relationship. The first mapping relationship is used to characterize the correspondence between the combination of accelerator pedal opening and vehicle speed and the demand torque.

[0154] In some embodiments, the demand torque module 1223 includes: The second mapping relationship submodule is used to find the second mapping relationship corresponding to the current driving mode of the target vehicle from the preset candidate mapping relationships; The second demand torque submodule is used to query the target demand torque corresponding to the combination of the current accelerator pedal opening and the current vehicle speed from the second mapping relationship. Different driving modes correspond to different candidate mapping relationships. The second mapping relationship is used to characterize the correspondence between the combination of accelerator pedal opening and vehicle speed and the demand torque.

[0155] In some embodiments, the demand torque module 1223 includes: The creep state determination submodule is used to determine that the target vehicle is in a creep state when it is detected that the current gear of the target vehicle is forward or reverse and neither the accelerator pedal nor the brake pedal is pressed. The creep speed acquisition submodule is used to acquire the preset creep target speed in creep mode; The demand torque determination submodule is used to calculate the creep torque based on the creep target speed and the current speed through a proportional-integral controller, and determine the creep torque as the target demand torque.

[0156] In some embodiments, the torque distribution module 1224 includes: The base torque determination submodule is used to determine the base torque of the front axle and the base torque of the rear axle based on the front axle longitudinal torque distribution coefficient and the target required torque of the target vehicle. The vehicle parameter acquisition submodule is used to acquire the target vehicle's current track width, current tire radius, front axle yaw torque distribution coefficient, and rear axle yaw torque distribution coefficient, wherein the sum of the front axle yaw torque distribution coefficient and the rear axle yaw torque distribution coefficient is 1. The front axle drive torque difference submodule is used to determine the drive torque difference between the left and right front axle wheels based on the target yaw torque, the front axle yaw torque distribution coefficient, the current tire radius, and the current track width. The rear axle drive torque difference submodule is used to determine the drive torque difference between the left and right rear axle wheels based on the target yaw torque, the rear axle yaw torque distribution coefficient, the current tire radius, and the current track width. The front wheel target torque submodule is used to determine the target torque of the left front wheel and the target torque of the right front wheel based on the base torque of the front axle and the difference in drive torque between the left and right front wheels. The rear wheel target torque submodule is used to determine the target torque of the left rear wheel and the target torque of the right rear wheel based on the base torque of the rear axle and the difference in drive torque between the left and right rear wheels.

[0157] In some embodiments, when the target vehicle turns left, the target torque of the left front wheel is less than the target torque of the right front wheel, and the target torque of the left rear wheel is less than the target torque of the right rear wheel; when the target vehicle turns right, the target torque of the left front wheel is greater than the target torque of the right front wheel, and the target torque of the left rear wheel is greater than the target torque of the right rear wheel.

[0158] In some embodiments, the condition judgment module 1221 includes: The activation condition judgment submodule is used when the target vehicle's current steering wheel angle is greater than or equal to a preset steering angle threshold, the target vehicle's current speed is less than or equal to a preset speed threshold, the target vehicle's current gear is forward or reverse, the target vehicle's current battery charge state is greater than or equal to a preset charge threshold, and the target vehicle's preset safety functions are inactive.

[0159] In some embodiments, the vehicle steering control device 1220 further includes: The obstacle distance acquisition module is used to acquire the distance between obstacles around the target vehicle and the target vehicle. The restriction coefficient acquisition module is used to determine the restriction coefficient based on the obstacle distance when the obstacle distance is less than a preset safe distance threshold. The restriction coefficient is positively correlated with the obstacle distance. The corrected torque determination module is used to determine the corrected target yaw torque by multiplying the target yaw torque by the limiting coefficient. The torque distribution module 1224 includes: The target torque correction submodule is used to determine the target torque for each wheel based on the corrected target yaw torque and the target required torque.

[0160] In some embodiments, the vehicle steering control device 1220 further includes: The wheel parameter acquisition module is used to obtain the current vertical load of each wheel and the current road surface adhesion coefficient. The wheel maximum torque determination module is used to determine the maximum available torque of each wheel based on the current vertical load and the current road adhesion coefficient of each wheel. The wheel torque limiting module is used to limit the target torque of each wheel to within the maximum available torque of the wheel and the preset maximum motor torque.

[0161] In some embodiments, the vehicle steering control device 1220 further includes: The temperature correction module is used to determine the temperature correction coefficient for each wheel based on the current tire temperature of each wheel. The temperature correction coefficient is negatively correlated with the current tire temperature. The temperature-corrected torque module is used to determine the corrected maximum available torque of each wheel by multiplying the wheel's maximum available torque by the wheel's temperature correction coefficient.

[0162] In some embodiments, the temperature correction module includes: The first correction submodule is used to determine the temperature correction coefficient of each wheel as the first preset coefficient when the current tire temperature of the wheel is less than or equal to the first preset temperature threshold. The second correction submodule is used to determine the temperature correction coefficient of the wheel as the second preset coefficient when the current tire temperature of the wheel is greater than or equal to the second preset temperature threshold. The second preset temperature threshold is greater than the first preset temperature threshold, and the second preset coefficient is less than the first preset coefficient. The linear correction submodule is used to determine the temperature correction coefficient of the wheel by interpolating the first preset coefficient and the second preset coefficient when the current tire temperature of the wheel is greater than the first preset temperature threshold and less than the second preset temperature threshold.

[0163] In some embodiments, the vehicle steering control device 1220 further includes: The activation status monitoring module is used to monitor the activation status of each preset safety function of the target vehicle during the process of controlling the motors corresponding to each wheel to output torque according to the target torque of each wheel. The drive torque control module is used to stop controlling the torque output of each motor according to the target torque of each wheel when any preset safety function is detected to be activated, and to control each motor to restore the torque output of each motor to the normal drive state.

[0164] Please see Figure 13 This application also provides an electronic device 1300, including a memory 1310, a processor 1320, and a computer program 1311 stored in the memory 1310 and running on the processor. When the processor 1320 executes the computer program 1311, it implements the steps of a vehicle steering control method.

[0165] Since the electronic device described in this embodiment is the device used to implement the vehicle steering control device in the embodiments of this application, those skilled in the art will understand the specific implementation methods and various variations of the electronic device in this embodiment based on the methods described in the embodiments of this application. How the electronic device implements the methods in the embodiments of this application will not be described in detail here. Any device used by those skilled in the art to implement the methods in the embodiments of this application falls within the scope of protection of this application.

[0166] In practice, when the computer program 1311 is executed by the processor, it can implement any of the embodiments corresponding to the first aspect.

[0167] Based on the same inventive concept, embodiments of this application provide a computer-readable storage medium storing computer program instructions, which, when loaded and executed by a processor, implement the steps of the vehicle steering control method described above.

[0168] Based on the same inventive concept, this application provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the vehicle steering control method described above.

[0169] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0170] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

[0171] Although preferred embodiments have been described in this specification, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications beyond the scope of this specification.

[0172] Obviously, those skilled in the art can make various modifications to this specification without departing from its spirit and scope. Therefore, this specification also intends to include any modifications that fall within the scope of the claims and their equivalents.

Claims

1. A vehicle steering control method, characterized in that, The method includes: When the preset steering assist activation conditions are met, the target yaw rate and actual yaw rate of the target vehicle are obtained. The target yaw torque is determined based on the target yaw rate and the actual yaw rate. Obtain the target required torque of the target vehicle, wherein the target required torque is used to characterize the longitudinal drive torque requirement of the target vehicle. Based on the target yaw torque and the target required torque, the target torque of each wheel is determined, and the target torque of each wheel is used to generate a driving torque difference between the left and right wheels of the target vehicle. The motors corresponding to each wheel are controlled to output torque according to the target torque corresponding to each wheel, so as to assist the target vehicle in steering.

2. The method according to claim 1, characterized in that, The acquisition of the target yaw rate of the target vehicle includes: Calculate the initial yaw rate based on the target vehicle's current front wheel angle, current rear wheel angle, current vehicle speed, and current wheelbase; Based on the road surface adhesion coefficient and the current vehicle speed, determine the yaw rate limit value; Based on the yaw rate limit value, the initial yaw rate is limited to obtain the target yaw rate.

3. The method according to claim 1, characterized in that, Determining the target yaw torque based on the target yaw rate and the actual yaw rate includes: The difference between the target yaw rate and the actual yaw rate is calculated to obtain the yaw rate error; The target yaw torque is obtained by controlling the yaw rate error using a proportional-integral-derivative controller.

4. The method according to claim 1, characterized in that, The step of obtaining the target torque requirement of the target vehicle includes: The target torque required is queried from the preset first mapping relationship, which corresponds to the combination of the current accelerator pedal opening and the current vehicle speed of the target vehicle. The first mapping relationship is used to characterize the correspondence between the combination of accelerator pedal opening and vehicle speed and the required torque.

5. The method according to claim 1, characterized in that, The step of obtaining the target torque requirement of the target vehicle includes: From the preset candidate mapping relationships, find the second mapping relationship corresponding to the current driving mode of the target vehicle; The target torque demand is queried from the second mapping relationship, which corresponds to the combination of the current accelerator pedal opening and the current vehicle speed of the target vehicle. Different driving modes correspond to different candidate mapping relationships. The second mapping relationship is used to characterize the correspondence between the combination of accelerator pedal opening and vehicle speed and the torque demand.

6. The method according to claim 1, characterized in that, The step of obtaining the target torque requirement of the target vehicle includes: When it is detected that the target vehicle is currently in drive or reverse and neither the accelerator pedal nor the brake pedal is depressed, it is determined that the target vehicle is in a creeping state. In the creeping state, a preset creeping target speed is obtained; Based on the target creep speed and the current speed, the creep torque is calculated by the proportional-integral controller, and the creep torque is determined as the target required torque.

7. The method according to claim 1, characterized in that, The step of determining the target torque for each wheel based on the target yaw torque and the target required torque includes: Based on the front axle longitudinal torque distribution coefficient of the target vehicle and the target required torque, determine the front axle base torque and the rear axle base torque; Obtain the current wheel track, current tire radius, front axle yaw torque distribution coefficient, and rear axle yaw torque distribution coefficient of the target vehicle, wherein the sum of the front axle yaw torque distribution coefficient and the rear axle yaw torque distribution coefficient is 1; Based on the target yaw torque, the front axle yaw torque distribution coefficient, the current tire radius, and the current wheel track, determine the difference in drive torque between the left and right front axle wheels; Based on the target yaw torque, the rear axle yaw torque distribution coefficient, the current tire radius, and the current wheel track, determine the difference in drive torque between the left and right rear axle wheels; Based on the base torque of the front axle and the difference in drive torque between the left and right front wheels, the target torque of the left front wheel and the target torque of the right front wheel are determined. Based on the base torque of the rear axle and the difference in drive torque between the left and right rear wheels, the target torque of the left rear wheel and the target torque of the right rear wheel are determined.

8. The method according to claim 7, characterized in that, When the target vehicle turns left, the target torque of the left front wheel is less than the target torque of the right front wheel, and the target torque of the left rear wheel is less than the target torque of the right rear wheel; when the target vehicle turns right, the target torque of the left front wheel is greater than the target torque of the right front wheel, and the target torque of the left rear wheel is greater than the target torque of the right rear wheel.

9. The method according to claim 1, characterized in that, The preset steering assist activation conditions include: The target vehicle's current steering wheel angle is greater than or equal to a preset steering angle threshold, the target vehicle's current speed is less than or equal to a preset speed threshold, the target vehicle's current gear is either forward or reverse, the target vehicle's current battery state of charge is greater than or equal to a preset state of charge threshold, and the target vehicle's preset safety functions are inactive.

10. The method according to claim 1, characterized in that, After determining the target yaw torque based on the target yaw rate and the actual yaw rate, the method further includes: Obtain the distance between the obstacles surrounding the target vehicle and the target vehicle; When the distance to the obstacle is less than a preset safe distance threshold, a restriction coefficient is determined based on the obstacle distance, wherein the restriction coefficient is positively correlated with the obstacle distance; The product of the target yaw torque and the limiting coefficient is determined as the corrected target yaw torque; The step of determining the target torque for each wheel based on the target yaw torque and the target required torque includes: Based on the corrected target yaw torque and the target required torque, the target torque for each wheel is determined.

11. The method according to claim 1, characterized in that, Before determining the target torque for each wheel based on the target yaw torque and the target required torque, the method further includes: Obtain the current vertical load on each wheel and the current road surface adhesion coefficient; Based on the current vertical load and the current road adhesion coefficient of each wheel, determine the maximum available torque of each wheel; For each wheel, the target torque of the wheel is limited to the maximum available torque of the wheel and the preset maximum motor torque.

12. The method according to claim 10, characterized in that, After determining the maximum available torque for each wheel based on the current vertical load and the current road adhesion coefficient for each wheel, the method further includes: Based on the current tire temperature of each wheel, a temperature correction factor is determined for each wheel, wherein the temperature correction factor is negatively correlated with the current tire temperature; For each wheel, the product of the wheel's maximum available torque and the wheel's temperature correction factor is determined as the wheel's corrected maximum available torque.

13. The method according to claim 10, characterized in that, The determination of the temperature correction factor for each wheel based on its current tire temperature includes: For each wheel, when the current tire temperature of the wheel is less than or equal to a first preset temperature threshold, the temperature correction coefficient of the wheel is determined to be the first preset coefficient. When the current tire temperature of the wheel is greater than or equal to the second preset temperature threshold, the temperature correction coefficient of the wheel is determined to be the second preset coefficient, wherein the second preset temperature threshold is greater than the first preset temperature threshold, and the second preset coefficient is less than the first preset coefficient; When the current tire temperature of the wheel is greater than the first preset temperature threshold and less than the second preset temperature threshold, the temperature correction coefficient of the wheel is determined by interpolation calculation of the first preset coefficient and the second preset coefficient.

14. The method according to claim 1, characterized in that, After controlling the motors corresponding to each wheel to output torque according to the target torque of each wheel, the method further includes: During the process of controlling the motors corresponding to each wheel to output torque according to the target torque of each wheel, the activation status of each preset safety function of the target vehicle is monitored. When any of the preset safety functions is detected to be activated, the control of each motor to output torque according to the target torque of each wheel is stopped, and each motor is controlled to resume torque output in normal driving state.

15. A steering control device for a vehicle, characterized in that, The device includes: The condition judgment module is used to obtain the target yaw rate and actual yaw rate of the target vehicle when the preset steering assist activation conditions are met. A yaw torque module is used to determine the target yaw torque based on the target yaw angular velocity and the actual yaw angular velocity; The demand torque module is used to obtain the target demand torque of the target vehicle, wherein the target demand torque is used to characterize the longitudinal drive torque demand of the target vehicle. The torque distribution module is used to determine the target torque of each wheel based on the target yaw torque and the target required torque, and the target torque of each wheel is used to generate a driving torque difference between the left and right wheels of the target vehicle. The motor control module is used to control the motors corresponding to each wheel to output torque according to the target torque corresponding to each wheel, so as to assist the target vehicle in steering.

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