Steer-by-wire vehicle control method and system and medium

Abstract

The invention relates to a steer-by-wire vehicle control method and system and a medium, and relates to the technical field of vehicle control. The method comprises the steps that the steering angle of a steering wheel, the vehicle speed and gear information are obtained; judging whether the vehicle is in a reverse gear state or not according to the gear information; when the vehicle is in the reverse gear state and the vehicle speed is lower than a preset threshold value, the steering ratio is adjusted to be a negative steering ratio; calculating a front wheel target turning angle according to the negative steering ratio and the steering wheel turning angle; and controlling a steering execution mechanism to steer according to the front wheel target turning angle, so that the steering direction of a steering wheel is consistent with the actual steering direction of a vehicle body. Consistent mapping of the steering direction of the steering wheel and the actual steering direction of the vehicle body is achieved in the reverse gear state, the operation difficulty of a driver can be remarkably reduced, and the intuition and accuracy of reversing operation are improved.

Description

Technical Field

[0001] This invention relates to the field of vehicle control technology, and in particular to a steer-by-wire vehicle control method, system, and medium. Background Technology

[0002] In traditional vehicles, the steering wheel is directly connected to the steering wheels via a complex mechanical mechanism. This means there is a fixed proportional relationship between the steering wheel's rotation angle and the wheel's steering angle. This mechanically determined steering ratio is always positive; that is, turning the steering wheel to the left results in the wheels turning to the left, regardless of whether the vehicle is moving forward or backward. Steer-by-wire is a new type of automotive steering system that completely eliminates the physical mechanical connection between the steering wheel and the wheels. It transmits the driver's steering intentions entirely through electrical signals, which are then processed by the control unit and directly driven by a motor to activate the steering actuator. Vehicles equipped with steer-by-wire can completely decouple the mechanical connection between the steering wheel and the wheels, instead relying on an electronic control unit to achieve intelligent steering mapping.

[0003] In reverse gear, the steering wheel direction is opposite to the actual turning direction of the vehicle. For example, when the driver turns the steering wheel counterclockwise, the rear of the vehicle will shift to the left, meaning the vehicle is actually reversing clockwise. This steering control logic is completely different from that in forward gear, making it difficult for many drivers, especially novice drivers, to quickly develop an accurate sense of direction when reversing. It often requires a considerable amount of practice and training to gradually develop a conditioned reflex and achieve smooth directional judgment and operation. When making a U-turn or reversing in narrow roads, drivers often cannot adjust the vehicle to the ideal position with a single steering operation, frequently resulting in understeer or oversteer. In such cases, it is necessary to switch between forward and reverse gears, and then adjust the steering wheel, gradually correcting the vehicle's posture through multiple operations. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a steer-by-wire vehicle control method, system and medium, which can significantly reduce the difficulty of operation for the driver and improve the intuitiveness and accuracy of reversing operation by achieving a consistent mapping between the steering wheel direction and the actual steering direction of the vehicle body in reverse gear.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] In a first aspect, the present invention provides a steer-by-wire vehicle control method, which adopts the following technical solution: A steer-by-wire vehicle control method, comprising: Obtain information on steering wheel angle, vehicle speed, and gear position; Determine whether the vehicle is in reverse gear based on the gear information; When the vehicle is in reverse gear and the speed is below the preset threshold, the steering ratio will be adjusted to a negative steering ratio. Calculate the target steering angle of the front wheels based on the negative steering ratio and the steering wheel angle; and The steering actuator is controlled to steer according to the target turning angle of the front wheels, so that the steering wheel direction is consistent with the actual steering direction of the vehicle body.

[0007] Furthermore, in the above-mentioned steer-by-wire vehicle control method, the step of calculating the target front wheel steering angle based on the negative steering ratio and the steering wheel angle includes: The initial front wheel angle is calculated based on the adaptive angle gain of the steering wheel angle and speed. The target front wheel steering angle is obtained by multiplying the initial front wheel steering angle by the negative steering ratio sign factor; and The target steering angle of the front wheel is subject to amplitude and rate of change limits.

[0008] Furthermore, in the above-mentioned steer-by-wire vehicle control method, the speed-adaptive angle gain is adjusted according to the current vehicle speed according to a preset functional relationship, so that the steering sensitivity is higher at low speeds and lower at high speeds.

[0009] Furthermore, in the above-mentioned steer-by-wire vehicle control method, adjusting the steering ratio to a negative steering ratio includes: Determine the target steering ratio sign factor, where the target steering ratio sign factor is negative one in reverse gear and positive one in forward gear; The current steering ratio sign factor is smoothed using a low-pass filter to avoid jitter near zero speed; and The steering ratio sign factor will be adjusted to negative one only when the vehicle is in reverse gear and the absolute value of the vehicle speed is less than or equal to a preset threshold.

[0010] Furthermore, in the above-mentioned steer-by-wire vehicle control method, when the vehicle is in reverse gear and the steering ratio is set to a negative steering ratio, the vehicle speed is limited to the preset threshold value.

[0011] Furthermore, the aforementioned steer-by-wire vehicle control method also includes: Obtain the vehicle's current yaw rate; Calculate the desired yaw rate based on the steering wheel angle, so that the desired yaw rate and the steering wheel angle have the same sign; Calculate the deviation between the desired yaw rate and the actual yaw rate; and The target steering angle of the front wheels is corrected in a closed loop based on the deviation to ensure consistency between the steering wheel direction and the actual steering direction of the vehicle body.

[0012] Furthermore, in the above-mentioned steer-by-wire vehicle control method, the step of performing closed-loop correction of the front wheel target angle based on the deviation includes calculating the correction amount through a proportional-integral controller and superimposing the correction amount onto the front wheel target angle.

[0013] Furthermore, the aforementioned steer-by-wire vehicle control method also includes: The predicted trajectory is calculated based on the current steering wheel angle and vehicle speed; The reversing image and the predicted trajectory are displayed on the in-vehicle display screen, ensuring that the predicted trajectory matches the actual vehicle trajectory; and When a sensor failure or actuator malfunction is detected, the steering ratio sign factor is immediately set to positive one, and the maximum steering angle limit is reduced.

[0014] Furthermore, in the above-mentioned steer-by-wire vehicle control method, the calculation and prediction trajectory includes, based on a bicycle model, using the current steering wheel angle, vehicle speed, and wheelbase parameters, calculating the trajectory of the vehicle's position and heading angle changes within a preset time period through numerical integration.

[0015] Secondly, the present invention provides a steer-by-wire vehicle control system, which adopts the following technical solution: The information acquisition module is used to acquire information such as steering wheel angle, vehicle speed, and gear position. The gear position determination module is used to determine whether the vehicle is in reverse gear based on the gear position information. The steering ratio adjustment module is used to adjust the steering ratio to a negative steering ratio when the vehicle is in reverse gear and the vehicle speed is below a preset threshold. The steering angle calculation module is used to calculate the target steering angle of the front wheels based on the negative steering ratio and the steering wheel angle; and The steering control module is used to control the steering actuator to steer according to the target turning angle of the front wheels, so that the steering direction of the steering wheel is consistent with the actual steering direction of the vehicle body.

[0016] Thirdly, the present invention provides a readable storage medium, which adopts the following technical solution: A readable storage medium storing computer instructions that, when executed by a processor, implement the vehicle control method as described in any one of the first aspects above.

[0017] In summary, compared with the prior art, the present invention includes at least one of the following beneficial technical effects: The steer-by-wire vehicle control method of this invention achieves a consistent mapping between the steering wheel direction and the actual vehicle direction by adjusting the steering ratio to a negative steering ratio in reverse gear, thereby significantly improving the driving experience. This solution effectively solves the problem of confusing directional feedback in traditional reversing operations, allowing drivers to control the vehicle's steering more intuitively while reversing, reducing learning costs and operational errors, especially for novice drivers, significantly shortening the adaptation time. Simultaneously, this method also reduces the need for multiple corrections in complex situations such as U-turns on narrow roads or reversing into parking spaces, improving the accuracy and efficiency of reversing operations and reducing safety risks caused by incorrect steering judgments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart of a steer-by-wire vehicle control method is shown.

[0020] Figure 2 A flowchart of a method for calculating the target steering angle of the front wheels is shown.

[0021] Figure 3 A flowchart of a steering ratio adjustment method is shown.

[0022] Figure 4 A flowchart of a closed-loop correction method based on yaw rate feedback is shown.

[0023] Figure 5 The diagram illustrates the principle that the steering wheel direction should align with the actual steering direction of the vehicle body.

[0024] Figure 6 The diagram shows the timing sequence of a traditional vehicle making a U-turn on a narrow road.

[0025] Figure 7 The diagram illustrates the timing of operations in a narrow road U-turn scenario according to an embodiment of the present invention.

[0026] Figure 8 The diagram shows the timing sequence of operations for a traditional vehicle reversing into a parking space.

[0027] Figure 9 The diagram illustrates the timing sequence of operations in a reverse parking scenario according to an embodiment of the present invention.

[0028] Figure 10 The diagram shows the timing sequence of operations for a traditional vehicle in a side parking scenario.

[0029] Figure 11 The diagram shows the operation timing of an embodiment of the present invention in a side parking scenario.

[0030] Figure 12 A block diagram of a steer-by-wire vehicle control system is shown. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0032] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments of this application. Furthermore, the descriptions of each embodiment in the following embodiments have their own emphasis; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0033] The method steps described in this embodiment of the invention can be executed in the order described in the specific implementation, or the execution order of each step can be adjusted according to actual needs, provided that the technical problem can be solved. These are not listed one by one here.

[0034] The present invention will be further described in detail below with reference to the accompanying drawings.

[0035] Reference Figure 1 This invention provides a steer-by-wire vehicle control method 100 to achieve consistency between the steering wheel direction and the actual vehicle steering direction in reverse gear. This method 100 processes the driver's steering intention through an electronic control unit, completely decoupling the mechanical connection between the steering wheel and the wheels to achieve intelligent steering mapping.

[0036] like Figure 1 As shown, method 100 begins at step 102, acquiring steering wheel angle, vehicle speed, and gear information. The steering wheel angle θ_sw is measured in radians, with a positive value for left turns. The vehicle speed v is measured in meters per second, with positive values ​​for forward and negative values ​​for reverse. Gear information g includes states such as forward (D), reverse (R), neutral (N), and parking (P). This information is collected in real-time by corresponding sensors, providing basic data for subsequent steering control decisions.

[0037] Method 100 continues to step 104, determining whether the vehicle is in reverse gear based on the gear information. In step 106, a decision branch is made based on the gear determination result. When the vehicle is not in reverse gear, Method 100 proceeds to step 110, maintaining a positive steering ratio. When the vehicle is in reverse gear, Method 100 proceeds to step 108, further determining whether the vehicle speed is below a preset threshold.

[0038] In step 108, the absolute value of the vehicle speed is evaluated to determine if it is less than or equal to a preset threshold. This preset threshold is set at 15 kilometers per hour, corresponding to approximately 4.2 meters per second. When the vehicle speed exceeds this threshold, a positive steering ratio is maintained to ensure steering stability at high speeds. When the vehicle speed falls below the threshold, method 100 proceeds to step 112, allowing the user to adjust the steering ratio to a negative steering ratio. In this case, the vehicle speed is limited to the preset threshold, ensuring that the negative steering ratio is only activated under safe low-speed conditions.

[0039] Step 112 adjusts the steering ratio towards a negative steering ratio by modifying the steering ratio sign factor S_eff(g,v). In reverse gear and at low speed, the sign factor S_eff is -1, while in forward gear or at high speed, it is +1. This sign factor, together with the speed-adaptive angle gain κ(v), forms the core mapping relationship: δ_cmd = S_eff(g,v) · κ(v) · θ_sw, where δ_cmd is the target steering angle of the front wheels.

[0040] The speed-adaptive angle gain κ(v) is adjusted according to the current vehicle speed based on a preset functional relationship, calculated as κ(v) = κ_min + (κ_max - κ_min) / (1 + (|v| / v0)^p). In this formula, κ_max and κ_min represent the maximum and minimum angle gains, respectively, v0 is the characteristic speed, and p is the adjustment parameter. This functional relationship enables adaptive adjustment, resulting in higher steering sensitivity at low speeds and lower steering sensitivity at high speeds.

[0041] After step 110, which maintains a positive steering ratio, method 100 proceeds to step 116, calculating the target front wheel steering angle based on the positive steering ratio and the steering wheel angle. After step 112, which adjusts to a negative steering ratio, method 100 proceeds to step 114, calculating the target front wheel steering angle based on the negative steering ratio and the steering wheel angle. Both calculation paths are based on the same core mapping formula, differing only in the value of the sign factor S_eff.

[0042] It should be noted that the value of the speed-adaptive angle gain κ(v) in both the positive and negative steering ratios is not limited here. That is, in other implementations, different angle gain parameters can be set for the positive and negative steering ratio modes respectively, based on different vehicle characteristics, driving habits, or operational scenario requirements. For example, in the negative steering ratio mode, the angle gain can be appropriately increased to improve the sensitivity of reversing operations, or it can be customized through the vehicle's human-machine interface according to the driver's personal preferences. Furthermore, the functional form of the angle gain can also adopt other mathematical models, such as linear functions, piecewise functions, or lookup tables, to meet the steering response characteristic requirements of specific application scenarios.

[0043] Method 100 proceeds to step 120 after step 116, controlling the steering actuator to steer according to the target front wheel angle. After step 114, it proceeds to step 118, similarly controlling the steering actuator to steer according to the target front wheel angle, but this time ensuring that the steering wheel direction matches the actual vehicle steering direction. The steering actuator drives the front wheels via a motor, achieving precise angle control.

[0044] In negative steering ratio mode, when the driver wants the car to move to the left while reversing, they turn the steering wheel to the left. The control unit recognizes that the vehicle is in reverse gear and sends a command to the steering motor, driving the front wheels to turn to the right, thus moving the car to the left. From the driver's perspective, the operating logic is completely consistent with that of forward driving, eliminating the reverse thinking and operational burden required for traditional reversing.

[0045] Reference Figure 2 This invention also provides a method 200 for calculating the target steering angle of the front wheels, used to calculate the target steering angle of the front wheels based on the negative steering ratio and the steering wheel angle. This method 200 achieves accurate steering angle calculation through multiple consecutive steps, ensuring the accuracy and safety of steering control.

[0046] like Figure 2 As shown, method 200 begins at step 202, obtaining the steering wheel angle and current vehicle speed. The steering wheel angle θ_sw, as a direct reflection of the driver's steering intention, together with the current vehicle speed v, constitutes the basic input parameters for angle calculation. Real-time acquisition of these parameters provides data support for subsequent speed adaptive processing.

[0047] Method 200 continues to step 204, calculating the speed-adaptive angle gain based on vehicle speed. This angle gain κ(v) is calculated using an exponential function: κ(v) = κ_min + (κ_max - κ_min)·exp(-|v|^p / v0^p). In this formula, κ_max is the maximum angle gain, approximately 0.07 radians per radian; κ_min is the minimum angle gain, approximately 0.04 radians per radian; v0 is the characteristic speed, approximately 4 meters per second; and p is the adjustment parameter, approximately 2. Through this exponential function relationship, an adaptive adjustment characteristic is achieved, with higher steering sensitivity at low speeds and lower steering sensitivity at high speeds.

[0048] In step 206, method 200 calculates the initial front wheel steering angle based on the steering wheel angle and the speed-adaptive angle gain. The initial front wheel steering angle δ_raw is calculated using the formula δ_raw = κ(v) · θ_sw, which combines the driver's steering input with the speed-related gain coefficient to form the basic front wheel steering angle command.

[0049] In step 208, method 200 multiplies the initial front wheel steering angle by a negative steering ratio sign factor. The sign factor S_eff is determined based on the gear and vehicle speed conditions, taking a value of -1 under reverse and low speed conditions, and a value of +1 under other conditions. Through this multiplication operation, the front wheel steering angle considering gear characteristics is obtained.

[0050] In step 210, method 200 obtains the target front wheel steering angle δ_cmd from the result of the multiplication operation. This target front wheel steering angle comprehensively considers the driver's intention, vehicle speed characteristics, and gear status, providing a basic value for subsequent restriction processing.

[0051] In step 212, method 200 limits the amplitude of the target front wheel steering angle. The amplitude limit is calculated using the formula |δ_cmd|≤ δ0·exp(-λ|v|), where δ0 is the reference maximum steering angle, approximately 0.65 radians; and λ is the speed decay coefficient, approximately 0.07 seconds per meter. This limit ensures that the steering angle amplitude is within a safe range, preventing excessive steering angles from causing the vehicle to lose control.

[0052] In step 214, method 200 limits the rate of change of the target front wheel steering angle. The rate of change limit is set using the formula |dδ / dt| ≤ δ̇_max, where δ̇_max is the maximum angular velocity limit, approximately 20 degrees per second. This limit controls the rate of change of steering angle, preventing abrupt changes in steering angle from adversely affecting vehicle stability.

[0053] In step 216, method 200 outputs the final target front wheel steering angle. The target front wheel steering angle, after amplitude and rate-of-change limiting, possesses both safety and executability, and can be directly used to generate control commands for the steering actuator. This final steering angle value ensures that steering operations are performed within physical constraints and safety requirements.

[0054] Reference Figure 3 This invention also provides a steering ratio adjustment method 300 for adjusting the steering ratio to a negative steering ratio. This method 300 achieves stable switching of the steering ratio between positive and negative values ​​through steps such as determining the target steering ratio sign factor, smooth transition processing, and condition judgment, avoiding jitter near zero speed.

[0055] like Figure 3 As shown, method 300 begins at step 302, acquiring the current gear information. The gear information g includes states such as drive (D), reverse (R), neutral (N), and parking (P), which are detected in real-time by the gear position sensor and transmitted to the control unit. This gear information provides the basis for subsequent determination of the target steering ratio sign factor.

[0056] Method 300 continues to step 304, determining whether the current gear is reverse. This determination step makes a logical judgment by comparing the current gear information with the reverse gear indicator. When the determination result is reverse gear, method 300 proceeds to step 306; when the determination result is not reverse gear, method 300 proceeds to step 308.

[0057] In step 306, method 300 sets the target steering ratio sign factor S_tar to negative one. This setting ensures that the steering ratio sign factor has a negative value in reverse gear, providing a basic condition for achieving consistency between the steering wheel steering direction and the actual steering direction of the vehicle body. In step 308, method 300 sets the target steering ratio sign factor S_tar to positive one, applicable to non-reverse gear states such as forward, neutral, and parking gear.

[0058] The two branch paths converge in step 310, and method 300 performs a smooth transition processing on the current steering ratio sign factor using a low-pass filter. This smooth transition processing is implemented using a first-order low-pass filter, and the differential equation is dS_eff / dt = (S_tar·M(v) - S_eff) / τ_s. In this equation, S_eff is the current effective steering ratio sign factor, S_tar is the target steering ratio sign factor, M(v) is the threshold function, and τ_s is the smooth transition time constant.

[0059] The smooth transition time constant τ_s is set to 0.2 seconds. This time constant controls the speed at which the steering ratio sign factor transitions from its current value to the target value. By setting this time constant, abrupt changes in the steering ratio sign factor near zero speed are avoided, preventing steering jitter caused by sudden changes in the sign factor. The implementation of a low-pass filter ensures the smoothness and stability of the steering ratio switching process.

[0060] In step 312, method 300 evaluates whether the vehicle is in reverse gear and whether the absolute value of the vehicle speed is less than or equal to a preset threshold value. This preset threshold value, v_en, is set to 15 kilometers per hour, corresponding to approximately 4.2 meters per second. The threshold function M(v) plays a role in this step; when |v| ≤ v_en, M(v) takes the value 1; when |v| > v_en, M(v) takes the value 0.

[0061] When the conditions of step 312 are met, method 300 proceeds to step 314, adjusting the steering ratio sign factor to negative one. This adjustment is performed only under the dual conditions that the vehicle is in reverse gear and the absolute value of the vehicle speed is less than or equal to a preset threshold value, ensuring the safety and applicability of enabling the negative steering ratio.

[0062] If the condition in step 312 is not met, method 300 proceeds to step 316, maintaining the steering ratio sign factor at positive one. This maintenance operation is applicable when the vehicle speed exceeds a preset threshold value. At this time, the steering ratio sign factor automatically returns to positive one, ensuring steering stability and safety at high speeds.

[0063] The product of the threshold function M(v) and the target steering ratio sign factor S_tar, S_tar·M(v), plays a conditional control role in the low-pass filter. When the vehicle is in reverse gear and the vehicle speed is below the threshold, the product is -1, driving the effective steering ratio sign factor S_eff towards negative one. When the vehicle speed exceeds the threshold or the vehicle is not in reverse gear, the product is positive one or zero, driving the effective steering ratio sign factor S_eff back towards positive one.

[0064] This steering ratio adjustment method 300 achieves stable switching between positive and negative steering ratios through a combination of strategies including gear priority, low-speed threshold, and smooth transition. Gear priority ensures that the steering ratio adjustment aligns with the driver's gear selection. Figure 1 To ensure that the low-speed threshold ensures that the negative steering ratio is only activated under safe low-speed conditions; and that the smooth transition ensures that the switching process does not adversely affect vehicle control.

[0065] Reference Figure 4This invention also provides a closed-loop correction method 400 based on yaw rate feedback to further ensure the consistency between the steering wheel direction and the actual steering direction of the vehicle body. This method 400 achieves precise adjustment of the target steering angle of the front wheels by acquiring the current yaw rate of the vehicle, calculating the desired yaw rate, analyzing the deviation, and performing closed-loop correction.

[0066] like Figure 4 As shown, method 400 begins at step 402, acquiring the vehicle's current yaw rate. The yaw rate ψ̇ represents the vehicle's rotational angular velocity about its vertical axis, measured in radians per second. This parameter is acquired in real-time via a gyroscope sensor or a vehicle dynamics sensor, reflecting the vehicle's actual steering response state. Accurate acquisition of the yaw rate provides a practical feedback signal for subsequent closed-loop control.

[0067] Method 400 continues to step 404 to obtain the steering wheel angle. The steering wheel angle θ_sw, as a direct reflection of the driver's steering intention, together with the yaw rate signal, constitutes the input parameters for closed-loop control. This angle information is acquired in real time through the steering wheel angle sensor, providing basic data for calculating the desired yaw rate.

[0068] In step 406, method 400 calculates the desired yaw rate based on the steering wheel angle. The desired yaw rate ψ̇_des is calculated based on the formula ψ̇_des = k_ψ(v)·θ_sw, where k_ψ(v) is the speed-related yaw rate gain coefficient. This gain coefficient is calculated using the formula k_ψ(v) = k_ψ0 / (1 + (|v| / v_ψ)^q), where k_ψ0 is the reference gain, approximately 0.7 radians per second; v_ψ is the characteristic velocity, approximately 3 meters per second; and q is the adjustment parameter, approximately 2.

[0069] In step 408, method 400 ensures that the desired yaw rate and the steering wheel angle have the same sign. This step verifies the sign relationship between the desired yaw rate ψ̇_des and the steering wheel angle θ_sw through a sign consistency check. When the steering wheel is turned to the left (θ_sw > 0), the desired yaw rate is positive; when the steering wheel is turned to the right (θ_sw < 0), the desired yaw rate is negative. This sign consistency ensures that the steering intention matches the direction of the desired response.

[0070] In step 410, method 400 calculates the deviation between the desired yaw rate and the actual yaw rate. The deviation is calculated using the formula Δψ̇ = ψ̇_des - ψ̇_act, where ψ̇_act is the vehicle's current actual yaw rate. This deviation reflects the difference between the desired steering response and the actual steering response, providing a control error signal for closed-loop correction.

[0071] In step 412, method 400 performs a closed-loop correction on the target front wheel steering angle based on the calculated deviation. This closed-loop correction is based on the approximate formula for the yaw rate of a bicycle model: ψ̇ ≈ (v / L)·tan(δ), where v is the vehicle speed, L is the wheelbase, and δ is the front wheel steering angle. Through this approximation, the yaw rate deviation can be converted into a correction amount for the front wheel steering angle.

[0072] The closed-loop correction calculates the correction amount Δδ using a proportional-integral (PI) controller. The correction amount is calculated using the formula Δδ = K_ψ(v)·(ψ̇_des - ψ̇_act), where K_ψ(v) is the speed-dependent PPI controller gain. This gain coefficient is calculated using the formula K_ψ(v) = 0.25 / (1 + 0.1|v|) to achieve speed-adaptive control characteristics. The calculated correction amount Δδ is then superimposed on the target front wheel steering angle to form the final corrected target front wheel steering angle δ_final = δ_cmd + Δδ.

[0073] In step 414, method 400 ensures the consistency between the steering wheel direction and the actual steering direction of the vehicle body. Through the aforementioned calculation of the desired yaw rate, deviation analysis, and closed-loop correction processing, this step verifies that the corrected front wheel target steering angle can produce a vehicle body steering response consistent with the steering wheel direction. This consistency verification is based on the sign relationship of the yaw rate, ensuring that the objective of sign(ψ̇_act) = sign(θ_sw) is achieved.

[0074] The proportional-integral (PI) controller is designed with vehicle dynamics and response time requirements in mind. The proportional control section provides an immediate corrective response, while the integral control section eliminates steady-state errors. The speed-adaptive nature of the controller gain K_ψ(v) ensures appropriate control performance under different vehicle speeds, avoiding problems such as slow response at low speeds or overly aggressive response at high speeds.

[0075] This closed-loop correction method 400 achieves both precision and robustness in steering control through yaw rate feedback. The calculation of the desired yaw rate ensures accurate expression of steering intent; deviation calculation provides a quantitative assessment of control error; and the proportional-integral controller effectively eliminates the error. The entire closed-loop control process ensures that the steer-by-wire vehicle maintains consistency between the steering wheel direction and the actual vehicle steering direction under various operating conditions.

[0076] Reference Figure 5This demonstration compares the traditional steering mode and the negative steering ratio mode to illustrate the principle that the steering wheel's direction of turn aligns with the vehicle's actual steering direction. In traditional forward gear, turning the steering wheel counter-clockwise results in the vehicle turning counter-clockwise, maintaining a direct correspondence between the steering wheel's direction and the vehicle's actual steering direction. In reverse gear, using a negative steering ratio, the vehicle also turns counter-clockwise when the steering wheel is turned, eliminating the need for reverse thinking in traditional reversing operations.

[0077] The principle behind negative steering ratio is based on adjusting the steering ratio sign factor S_eff. In reverse gear and at low speed, the sign factor is -1, changing the sign relationship in the front wheel target steering angle δ_cmd = S_eff · κ(v) · θ_sw. When the driver turns the steering wheel to the left, the negative sign factor causes the front wheels to actually turn to the right, but due to the vehicle's reverse motion, the overall vehicle body appears to be turning to the left, consistent with the driver's steering intention.

[0078] Reference Figures 6 to 11 ,in Figure 6 and Figure 7 A comparison of non-drive-by-wire (positive steering ratio) and drive-by-wire (positive and negative steering ratio switching) systems for U-turns on narrow roads. Figure 8 and Figure 9 A comparison of non-drive-by-wire (positive steering ratio) and drive-by-wire (positive and negative steering ratio switching) systems for a reverse parking scenario. Figure 10 and Figure 11 For parallel parking scenarios, a comparison is made between non-steerable (positive steering ratio) and steerable (positive / negative steering ratio switching) methods. Based on the schematic diagrams of various scenarios, it can be seen that the steerable vehicle control method described in this embodiment of the invention reduces the number of correction operations in complex conditions such as U-turns on narrow roads or reversing into parking spaces. Figure 6 The steering wheel needs to be turned 2400°. Figure 7 Only 800° is needed. Figure 8 Requires 1600° Figure 9 800° is required. Figure 10 The number 11 demonstrates that in a standard parallel parking situation, the steering wheel direction and the actual steering direction of the vehicle are consistent in reverse gear, eliminating the need for reverse thinking and significantly reducing the difficulty of operation for the driver.

[0079] This simplified control method reduces the complexity of decision branches by merging conditional judgments. By integrating the evaluation of gear position and vehicle speed threshold into a single decision point through dual conditional judgments, the execution efficiency of the control logic is improved. When the conditions are not met, the steering ratio is automatically maintained at a positive value, ensuring that the steering characteristics in normal driving mode are not affected.

[0080] Furthermore, the implementation of the predicted trajectory calculation and display, as well as the safety rollback logic, described in this embodiment of the invention includes key steps such as trajectory prediction, display synchronization, and fault handling. The predicted trajectory is calculated based on a bicycle model, using the current steering wheel angle, vehicle speed, and wheelbase parameters, and employing a numerical integration method to calculate the vehicle's position and heading angle changes within a preset time period.

[0081] The predicted trajectory calculation uses a system of differential equations to describe the time evolution of the vehicle's motion state. The position change equations are dx / dt = v·cos(ψ) and dy / dt = v·sin(ψ), where x and y represent the vehicle's position coordinates in the horizontal and vertical directions, respectively, v is the vehicle speed, and ψ is the vehicle's heading angle. The heading angle change equation is dψ / dt = (v / L)·tan(δ_cmd), where L is the wheelbase and δ_cmd is the target steering angle of the front wheels.

[0082] The numerical integration method employs a fourth-order Runge-Kutta algorithm to solve the system of differential equations. The integration time step is set to 0.1 seconds, and the prediction time range is set to the next 5 seconds. Through this numerical integration process, the sequence of vehicle position trajectory points (x_i, y_i, ψ_i) within the prediction time range is calculated, where i represents the time step index. This sequence of trajectory points constitutes the geometric description of the predicted trajectory.

[0083] When displaying the reversing image and predicted trajectory on the in-vehicle display screen, the consistency between the predicted trajectory and the actual vehicle trajectory is achieved through coordinate transformation and image overlay. The world coordinate system position of the predicted trajectory is converted into pixel coordinates on the display screen through perspective transformation and overlaid on the real-time image captured by the reversing camera. The color and thickness of the trajectory lines are gradually processed according to the time distance, with recent trajectories displayed as thicker, brighter lines and distant trajectories displayed as thinner, darker lines.

[0084] The predicted trajectory is updated in real-time in sync with the control cycle, ensuring that the trajectory display promptly reflects changes in the steering wheel angle. When the driver adjusts the steering wheel position, the predicted trajectory is updated accordingly on the display, providing the driver with an immediate preview of the path. This synchronization mechanism ensures consistency between the predicted trajectory and the actual vehicle trajectory.

[0085] The safety rollback logic activates immediately upon detecting sensor failure or actuator malfunction. Fault detection includes various conditions such as abnormal steering wheel angle sensor signal, missing vehicle speed sensor data, gear position sensor communication interruption, and steering actuator response timeout. When any fault condition is detected, the control unit immediately sets the steering ratio sign factor to positive one and reduces the maximum steering angle limit.

[0086] The reduction in the maximum steering angle limit is achieved by modifying the amplitude limit parameter δ_0. Under normal operating conditions, δ_0 is approximately 0.65 radians. In fault mode, δ_0 is reduced to 0.3 radians, which is equivalent to reducing the maximum steering angle from approximately 37 degrees to approximately 17 degrees. This reduction in limit ensures the conservatism and safety of vehicle steering in fault conditions, preventing excessive steering angles from causing loss of vehicle control.

[0087] This invention also discloses a steer-by-wire vehicle control system.

[0088] Reference Figure 12 The steer-by-wire vehicle control system 500 described in this embodiment of the invention adopts a modular architecture design to achieve consistent control between the steering wheel direction and the actual steering direction of the vehicle body in reverse gear. This steer-by-wire vehicle control system 500 includes multiple functional modules, which are connected through information and control flows to form a complete steering control solution.

[0089] like Figure 12 As shown, the steer-by-wire vehicle control system 500 includes an information acquisition module 502 for acquiring steering wheel angle, vehicle speed, and gear information. This information acquisition module 502 performs data acquisition through various sensor interfaces, including a steering wheel angle sensor interface, a vehicle speed sensor interface, and a gear position sensor interface. The steering wheel angle θ_sw is measured using a high-precision rotary encoder with a resolution of 0.1 degrees; the vehicle speed v is acquired through a wheel speed sensor or a GPS module, with an update frequency of 100 Hz; and the gear position information g is read from the transmission control unit via the CAN bus.

[0090] The steer-by-wire vehicle control system 500 also includes a gear position determination module 504, used to determine whether the vehicle is in reverse gear based on gear position information. This gear position determination module 504 receives gear position information from the information acquisition module 502 and determines the current gear position through logical comparison operations. The determination logic of the gear position determination module 504 includes the identification of states such as reverse (R), drive (D), neutral (N), and parking (P), and generates a Boolean-type reverse gear status flag signal. This determination result provides a decision-making basis for subsequent steering ratio adjustments.

[0091] The steer-by-wire vehicle control system 500 includes a steering ratio adjustment module 506, which adjusts the steering ratio to a negative steering ratio when the vehicle is in reverse gear and the vehicle speed is below a preset threshold. The steering ratio adjustment module 506 receives vehicle speed information from the information acquisition module 502 and the reverse gear status determination result from the gear position determination module 504. Internally, the steering ratio adjustment module 506 implements a threshold function M(v) and a low-pass filter, and smoothly adjusts the steering ratio sign factor through the differential equation dS_eff / dt = (S_tar·M(v) - S_eff) / τ_s.

[0092] The preset threshold value v_en of the steering ratio adjustment module 506 is set to 4.2 meters per second, corresponding to a vehicle speed limit of 15 kilometers per hour. When the vehicle is in reverse gear and the absolute value of the vehicle speed is less than this threshold value, the target steering ratio sign factor S_tar is set to -1; otherwise, it is set to +1. The smooth transition time constant τ_s is set to 0.2 seconds to ensure the stability of the steering ratio switching process. This module also includes a manual driver-active switching option, allowing the driver to manually activate or deactivate the negative steering ratio function through the onboard human-machine interface.

[0093] The steer-by-wire vehicle control system 500 includes a steering angle calculation module 508, used to calculate the target steering angle of the front wheels based on the negative steering ratio and the steering wheel angle. This steering angle calculation module 508 receives steering wheel angle and vehicle speed information from the information acquisition module 502, and a steering ratio sign factor from the steering ratio adjustment module 506. The steering angle calculation module 508 implements the core mapping relationship δ_cmd = S_eff(g,v) · κ(v) · θ_sw, where the speed-adaptive angle gain κ(v) is dynamically adjusted according to the vehicle speed.

[0094] The steering angle calculation module 508 includes an amplitude limiter and a rate of change limiter to ensure that the calculated target steering angle of the front wheels is within a safe range. The amplitude limit is set using the formula |δ_cmd| ≤ δ_0·exp(-λ|v|), where δ_0 is the reference maximum steering angle and λ is the speed attenuation coefficient. The rate of change limit is set using the formula |dδ / dt| ≤ δ̇_max, where δ̇_max is the maximum angular velocity limit. This module also implements a closed-loop correction function for yaw rate feedback, precisely adjusting the target steering angle of the front wheels through a proportional-integral controller.

[0095] The steer-by-wire vehicle control system 500 includes a steering control module 510, which controls the steering actuator to steer according to the target front wheel angle, ensuring that the steering wheel direction matches the actual vehicle steering direction. The steering control module 510 receives the target front wheel angle from the angle calculation module 508 and controls the movement of the steering actuator via a motor driver. The steering control module 510 implements closed-loop position control, ensuring that the actual front wheel angle δ_act accurately tracks the target angle δ_cmd.

[0096] The steering control module 510 also implements steering wheel road feel torque feedback, generating steering wheel tactile torque through the torque feedback formula T_fb = K_θ·θ_sw + K_Δ·(θ_sw - δ_act·R) + B_θ·θ̇_sw. In this formula, K_θ is the steering wheel angle proportionality coefficient, with a value of approximately 0.6 Nm / radian; K_Δ is the angle deviation proportionality coefficient, with a value of approximately 0.8 Nm / radian; B_θ is the steering wheel angular velocity damping coefficient, with a value of approximately 0.03 Nm / s / radian; and R is the current steering ratio. This torque feedback ensures that the driver can still obtain a tactile experience consistent with traditional steering even in negative steering ratio mode.

[0097] The information flow connections between the modules reflect the system's data processing workflow. The information acquisition module 502, acting as the data source, provides basic sensor data to the gear selection module 504, steering ratio adjustment module 506, and angle calculation module 508. The gear selection result from the gear selection module 504 is passed to the steering ratio adjustment module 506 for determining the steering ratio sign factor. The output of the steering ratio adjustment module 506 is passed to the angle calculation module 508 for calculating the target front wheel steering angle. The calculation result from the angle calculation module 508 is passed to the steering control module 510 for controlling the steering actuator.

[0098] The control flow connections reflect the system's control logic. The reverse gear determination by the gear position determination module 504 triggers the sign factor adjustment by the steering ratio adjustment module 506; the change in the sign factor by the steering ratio adjustment module 506 drives the steering angle calculation module 508 to recalculate the target steering angle of the front wheels; the target steering angle update command from the steering angle calculation module 508 instructs the steering control module 510 to adjust the actuator position. This control flow ensures a complete control link from gear position change to steering response.

[0099] The configuration method of vehicle-specific calibration parameters allows the steer-by-wire vehicle control system 500 to adapt to the characteristics of different vehicle models. The wheelbase L, as a basic geometric parameter, is set according to the specific vehicle model, with a typical range of 2.5 to 3.2 meters. Gain factors κ_max and κ_min represent the maximum and minimum angular gain, respectively, and are adjusted according to the steering characteristics required by the vehicle model. κ_max typically ranges from 0.05 to 0.10 radians per radian, and κ_min typically ranges from 0.02 to 0.06 radians per radian.

[0100] The time constant parameters include the smooth transition time constant τ_s and the yaw rate control time constant, which are calibrated according to the dynamic response characteristics of the vehicle model. The typical range of τ_s is 0.1 to 0.5 seconds; smaller time constants are suitable for sporty vehicles, while larger time constants are suitable for comfort vehicles. The angular velocity limit parameter δ̇_max is set according to the performance and safety requirements of the steering actuator, with a typical range of 10 to 30 degrees per second.

[0101] The calibration parameters are configured via the on-board diagnostic interface or a dedicated calibration tool. The calibration process includes parameter download, functional verification, and performance testing. Parameter download writes vehicle-specific calibration data into the non-volatile memory of the control unit; functional verification confirms the operating status of each module under the new parameters; and performance testing evaluates the response characteristics of the entire system under real-world driving conditions. This calibration method ensures the applicability and performance consistency of the steer-by-wire vehicle control system 500 across different vehicle models.

[0102] This invention also discloses a readable storage medium.

[0103] A computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the steer-by-wire vehicle control method described in any of the above embodiments. The computer-readable storage medium may include any entity or device capable of carrying a computer program, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), and a software distribution medium, etc. The computer program includes computer program code. The computer program code may be in the form of source code, object code, an executable file, or some intermediate form, etc. The computer-readable storage medium may include any entity or device capable of carrying computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), and a software distribution medium, etc.

[0104] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0105] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus or device (such as a computer-based system, a system including a processing module or other system that can fetch and execute instructions from, an instruction execution system, apparatus or device).

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 the present invention.

Claims

1. A steer-by-wire vehicle control method, characterized in that, include: Obtain information on steering wheel angle, vehicle speed, and gear position; Determine whether the vehicle is in reverse gear based on the gear information; When the vehicle is in reverse gear and the speed is below the preset threshold, the steering ratio will be adjusted to a negative steering ratio. Calculate the target steering angle of the front wheels based on the negative steering ratio and the steering wheel angle; as well as The steering actuator is controlled to steer according to the target turning angle of the front wheels, so that the steering wheel direction is consistent with the actual steering direction of the vehicle body.

2. The steer-by-wire vehicle control method according to claim 1, characterized in that, The calculation of the target front wheel steering angle based on the negative steering ratio and the steering wheel angle includes: The initial front wheel angle is calculated based on the adaptive angle gain of the steering wheel angle and speed. The target front wheel steering angle is obtained by multiplying the initial front wheel steering angle by the negative steering ratio sign factor; and The target steering angle of the front wheel is subject to amplitude and rate of change limits.

3. The steer-by-wire vehicle control method according to claim 2, characterized in that, The speed-adaptive angle gain is adjusted according to the current vehicle speed based on a preset function relationship, resulting in higher steering sensitivity at low speeds and lower steering sensitivity at high speeds.

4. The steer-by-wire vehicle control method according to claim 1, characterized in that, The process of adjusting the steering ratio to a negative steering ratio includes: Determine the target steering ratio sign factor, where the target steering ratio sign factor is negative one in reverse gear and positive one in forward gear; The current steering ratio sign factor is smoothed using a low-pass filter to avoid jitter near zero speed; and The steering ratio sign factor will be adjusted to negative one only when the vehicle is in reverse gear and the absolute value of the vehicle speed is less than or equal to a preset threshold.

5. The steer-by-wire vehicle control method according to claim 4, characterized in that, When the vehicle is in reverse gear and the steering ratio is set to a negative steering ratio, the vehicle speed is limited to the preset threshold value.

6. The steer-by-wire vehicle control method according to claim 1, characterized in that, Also includes: Obtain the vehicle's current yaw rate; Calculate the desired yaw rate based on the steering wheel angle, so that the desired yaw rate and the steering wheel angle have the same sign; Calculate the deviation between the expected yaw rate and the actual yaw rate; as well as The target steering angle of the front wheels is corrected in a closed loop based on the deviation to ensure consistency between the steering wheel direction and the actual steering direction of the vehicle body.

7. The steer-by-wire vehicle control method according to claim 6, characterized in that, The closed-loop correction of the front wheel target steering angle based on the deviation includes calculating the correction amount through a proportional-integral controller and superimposing the correction amount onto the front wheel target steering angle.

8. The steer-by-wire vehicle control method according to claim 1, characterized in that, Also includes: The predicted trajectory is calculated based on the current steering wheel angle and vehicle speed; The reversing image and the predicted trajectory are displayed on the in-vehicle display screen, so that the predicted trajectory is consistent with the actual vehicle driving trajectory. as well as When a sensor failure or actuator malfunction is detected, the steering ratio sign factor is immediately set to positive one, and the maximum steering angle limit is reduced.

9. The steer-by-wire vehicle control method according to claim 8, characterized in that, The calculated predicted trajectory includes a bicycle model, using the current steering wheel angle, vehicle speed, and wheelbase parameters, to calculate the trajectory of the vehicle's position and heading angle changes within a preset time period using a numerical integration method.

10. A steer-by-wire vehicle control system, characterized in that, include: The information acquisition module is used to acquire information such as steering wheel angle, vehicle speed, and gear position. The gear position determination module is used to determine whether the vehicle is in reverse gear based on the gear position information. The steering ratio adjustment module is used to adjust the steering ratio to a negative steering ratio when the vehicle is in reverse gear and the vehicle speed is below a preset threshold. The steering angle calculation module is used to calculate the target steering angle of the front wheels based on the negative steering ratio and the steering wheel angle; as well as The steering control module is used to control the steering actuator to steer according to the target turning angle of the front wheels, so that the steering direction of the steering wheel is consistent with the actual steering direction of the vehicle body.

11. A readable storage medium, characterized in that, The readable storage medium stores computer instructions that, when executed by a processor, implement the vehicle control method as described in any one of claims 1-9.

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