A steer-by-wire vehicle control method, system, and medium

Abstract

The application relates to a kind of drive-by-wire steering vehicle control method, system and medium, it relates to vehicle control technical field, the method includes obtaining steering wheel angle, vehicle speed and gear information;According to the gear information, it is judged whether the vehicle is in reverse gear state;When the vehicle is in reverse gear state and vehicle speed is lower than preset threshold value, steering ratio is adjusted to negative steering ratio;According to the negative steering ratio and the steering wheel angle, front wheel target angle is calculated;And control steering actuator is steered according to the front wheel target angle, so that the steering direction of steering wheel and the actual steering direction of vehicle body are kept consistent.The application can significantly reduce the operation difficulty of driver by realizing the consistency mapping of the steering direction of steering wheel and the actual steering direction of vehicle body in reverse gear state, improves the intuitiveness and accuracy of reversing operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle control, in particular to a steer-by-wire vehicle control method, system and medium. BACKGROUND

[0002] In traditional vehicles, the steering wheel is directly connected to the steering wheel through a complex mechanical mechanism, which means that there is a fixed proportional relationship between the steering angle of the steering wheel and the steering angle of the wheels. This mechanically determined steering ratio is always positive, that is, the steering wheel is turned to the left, and the wheels are turned to the left, regardless of whether the vehicle is moving forward or backward. Steer-by-wire is a new type of automobile steering system that completely eliminates the physical mechanical connection between the steering wheel and the wheels, and completely transmits the driver's steering intention through electrical signals, which is processed by the control unit and directly driven by the motor to drive the steering execution mechanism. The vehicle equipped with steer-by-wire can completely decouple the mechanical connection between the steering wheel and the wheels, and instead realize intelligent steering mapping by the electronic control unit.

[0003] In reverse gear state, the direction of the steering wheel is opposite to the actual steering direction of the vehicle body, for example, when the driver turns the steering wheel counterclockwise, the tail of the vehicle will be offset to the left, that is, the vehicle body actually retreats in a clockwise direction. This direction control logic is completely different from that in forward gear, making it difficult for many drivers, especially novice drivers, to quickly establish an accurate sense of direction when reversing, and often requiring a long period of practice and training to gradually form a conditioned reflex to achieve smooth direction judgment and operation. When reversing or turning around in a narrow road, the driver often cannot adjust the vehicle body to the desired position through a single steering operation, so it is often necessary to switch between forward and reverse gears and adjust the steering wheel to gradually correct the vehicle body posture through multiple operations. SUMMARY

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a steer-by-wire vehicle control method, system and medium, which can significantly reduce the operation difficulty of the driver and improve the intuitiveness and accuracy of the reversing operation by realizing the consistency mapping of the steering direction of the steering wheel and the actual steering direction of the vehicle body in reverse gear state.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions.

[0006] In a first aspect, the present application provides a steer-by-wire vehicle control method, which adopts the following technical solutions:

[0007] A steer-by-wire vehicle control method, comprising:

[0008] obtaining the steering wheel angle, the vehicle speed and the gear information;

[0009] determining whether the vehicle is in a reverse gear state according to the gear information;

[0010] adjusting the steering ratio to a negative steering ratio when the vehicle is in the reverse gear state and the vehicle speed is lower than a preset threshold value;

[0011] calculating a front wheel target angle according to the negative steering ratio and the steering wheel angle; and

[0012] controlling a steering actuator to steer according to the front wheel target angle, so that the steering direction of the steering wheel is consistent with the actual steering direction of the vehicle body.

[0013] Further, in the above-mentioned steer-by-wire vehicle control method, the calculating of the front wheel target angle according to the negative steering ratio and the steering wheel angle comprises:

[0014] calculating an initial front wheel angle according to a speed-adaptive angle gain and the steering wheel angle;

[0015] multiplying the initial front wheel angle by a negative steering ratio sign factor to obtain the front wheel target angle; and

[0016] performing amplitude limitation and rate limitation on the front wheel target angle.

[0017] Further, 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 function relationship, so that the steering sensitivity is higher at low speed and the steering sensitivity is lower at high speed.

[0018] Further, in the above-mentioned steer-by-wire vehicle control method, the adjusting of the steering ratio to the negative steering ratio comprises:

[0019] determining a target steering ratio sign factor, wherein the target steering ratio sign factor is negative one when in the reverse gear state and the target steering ratio sign factor is positive one when in the forward gear state;

[0020] performing smooth transition processing on the current steering ratio sign factor by a low-pass filter to avoid jitter near zero speed; and

[0021] adjusting the steering ratio sign factor to negative one only when the vehicle is in the reverse gear state and the absolute value of the vehicle speed is less than or equal to the preset threshold value.

[0022] Further, in the above-mentioned steer-by-wire vehicle control method, when the vehicle is in the reverse gear state and the steering ratio is set to the negative steering ratio, the vehicle speed is limited within the preset threshold value.

[0023] Further, in the above-mentioned steer-by-wire vehicle control method, further comprising:

[0024] obtaining a current yaw rate of the vehicle;

[0025] calculating a desired yaw rate according to the steering wheel angle, so that the desired yaw rate has the same sign as the steering wheel angle;

[0026] calculating a deviation between the desired yaw rate and the actual yaw rate; and

[0027] performing closed-loop correction on the front wheel target angle according to the deviation, to ensure consistency between the steering direction of the steering wheel and the actual steering direction of the vehicle body.

[0028] Further, in the above-mentioned steer-by-wire vehicle control method, the closed-loop correction on the front wheel target angle according to the deviation comprises calculating a correction amount by a proportional-integral controller, and superimposing the correction amount on the front wheel target angle.

[0029] Further, in the above-mentioned steer-by-wire vehicle control method, the method further comprises:

[0030] calculating a predicted trajectory according to the current steering wheel angle and the vehicle speed;

[0031] displaying the predicted trajectory and the reversing image on a vehicle-mounted display screen, so that the predicted trajectory is consistent with the actual vehicle trajectory; and

[0032] when a sensor failure or an actuator fault is detected, immediately setting the steering ratio sign factor to positive one and reducing the maximum steering angle limit.

[0033] Further, in the above-mentioned steer-by-wire vehicle control method, the calculation of the predicted trajectory comprises calculating the vehicle position and heading angle change trajectory in a preset future time by a numerical integration method based on a bicycle model, using the current steering wheel angle, the vehicle speed and the wheelbase parameter.

[0034] In a second aspect, the present application provides a steer-by-wire vehicle control system, which adopts the following technical solution:

[0035] an information acquisition module, configured to acquire a steering wheel angle, a vehicle speed and gear information;

[0036] a gear judgment module, configured to judge whether the vehicle is in a reverse gear state according to the gear information;

[0037] a steering ratio adjustment module, configured to adjust the steering ratio to a negative steering ratio when the vehicle is in the reverse gear state and the vehicle speed is lower than a preset threshold value;

[0038] an angle calculation module, configured to calculate a front wheel target angle according to the negative steering ratio and the steering wheel angle; and

[0039] a steering control module, configured to control a steering actuator to steer according to the front wheel target angle, so that the steering direction of the steering wheel is consistent with the actual steering direction of the vehicle body.

[0040] In a third aspect, the present application provides a readable storage medium, which adopts the following technical solution:

[0041] A readable storage medium, the readable storage medium stores computer instructions, and the computer instructions are executed by a processor to implement the vehicle control method according to any one of the above first aspect.

[0042] Compared with the prior art, the present application has at least one of the following beneficial technical effects:

[0043] The vehicle control method of the present application can realize the consistency of the steering direction of the steering wheel and the actual steering direction of the vehicle body by adjusting the steering ratio to a negative steering ratio in the reverse gear state, thereby significantly improving the driving experience. This scheme can effectively solve the problem of confusion in the traditional reversing operation, so that the driver can more intuitively control the steering of the vehicle when reversing, reducing the learning cost and operation errors, especially for novice drivers, which can greatly shorten the adaptation time. At the same time, this method can also reduce the multiple correction operations in complex working conditions such as U-turn in narrow road or reversing into the garage, improve the accuracy and efficiency of the reversing operation, and reduce the safety risk caused by incorrect steering judgment. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0045] Figure 1 A flowchart of a steer-by-wire vehicle control method is shown.

[0046] Figure 2 A flowchart of a front wheel target steering angle calculation method is shown.

[0047] Figure 3 A flowchart of a steering ratio adjustment method is shown.

[0048] Figure 4 A flowchart of a closed-loop correction method based on yaw rate feedback is shown.

[0049] Figure 5 A principle diagram showing that the steering direction of the steering wheel and the actual steering direction of the vehicle body are consistent is shown.

[0050] Figure 6 A timing diagram of the operation of a traditional vehicle in a narrow road U-turn scenario is shown.

[0051] Figure 7 A timing diagram of the operation of the embodiment of the application in a narrow road U-turn scenario is shown.

[0052] Figure 8 A timing diagram of the operation of a conventional vehicle in a reversing into a garage scenario is shown.

[0053] Figure 9 A timing diagram of the operation of the embodiment of the application in a reversing into a garage scenario is shown.

[0054] Figure 10 A timing diagram of the operation of a conventional vehicle in a side parking scenario is shown.

[0055] Figure 11 A timing diagram of the operation of the embodiment of the application in a side parking scenario is shown.

[0056] Figure 12 A block diagram of a steer-by-wire vehicle control system is shown. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application. In addition, it should be understood that the specific implementation manners described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0058] It should be noted that the description order of the following embodiments is not used to limit the preferred order of the embodiments of the present application. In addition, the description of each embodiment in the following embodiments has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0059] The execution order of the method steps described in the embodiments of the present application can be executed in the order described in the specific implementation manners, or the execution order of each step can be adjusted on the premise of solving the technical problems according to actual needs, which is not listed one by one here.

[0060] The present application will be further described in detail below with reference to the drawings.

[0061] With reference to Figure 1 The embodiment of the present application provides a steer-by-wire vehicle control method 100, which is used for realizing the consistency of the steering direction of a steering wheel and the actual steering direction of a vehicle body in a reverse gear state. The method 100 processes the steering intention of a driver through an electronic control unit, completely decouples the mechanical connection relationship between the steering wheel and the wheels, and realizes intelligent steering mapping.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] After the step 110 of maintaining the positive steering ratio, the method 100 enters a step 116 of calculating a front wheel target steering angle according to the positive steering ratio and the steering wheel steering angle. After the step 112 of adjusting to the negative steering ratio, the method 100 enters a step 114 of calculating the front wheel target steering angle according to the negative steering ratio and the steering wheel steering angle. Both calculation paths are based on the same core mapping formula, with the difference being the value of the sign factor S_eff.

[0068] It is pointed out that the numerical value of the speed adaptive angle gain K(v) in the positive steering ratio and the negative steering ratio is not limited here, i.e. in other embodiments, different angle gain parameters can be set for the positive steering ratio mode and the negative steering ratio mode according to different vehicle characteristics, driving habits or operation scene requirements. For example, in the negative steering ratio mode, the angle gain can be appropriately increased to improve the sensitivity of the reversing operation, or customized adjustment can be made through the vehicle-mounted human-machine interface according to the personal preference of the driver. In addition, the function form of the angle gain can also adopt other mathematical models, such as linear function, piecewise function or lookup table mode, to meet the steering response characteristic requirements in specific application scenarios.

[0069] After the step 116, the method 100 enters a step 120 of controlling the steering actuator to steer according to the front wheel target steering angle. After the step 114, it enters a step 118 of also controlling the steering actuator to steer according to the front wheel target steering angle, but at this time it is ensured that the steering direction of the steering wheel is consistent with the actual steering direction of the vehicle body. The steering actuator drives the front wheels to steer through the motor, realizing accurate angle control.

[0070] In the negative steering ratio mode, when the driver wants to move the vehicle head to the left while reversing, the driver turns the steering wheel to the left, the control unit recognizes that the vehicle is in the reverse gear state, and sends an instruction to the steering execution motor to drive the front wheels to turn to the right, thereby realizing the movement of the vehicle head to the left. From the perspective of the driver, the operation logic is completely consistent with that when driving forward, eliminating the reverse thinking and operation burden required by traditional reversing.

[0071] Reference Figure 2 The embodiment of the present application also provides a front wheel target steering angle calculation method 200 for calculating the front wheel target steering angle according to the negative steering ratio and the steering wheel steering angle. The method 200 realizes accurate steering angle calculation through a plurality of continuous steps, ensuring the accuracy and safety of steering control.

[0072] As shown in Figure 2 The method 200 starts from a step 202 of acquiring the steering wheel steering angle and the current vehicle speed. The steering wheel steering angle θ_sw is a direct embodiment of the steering intention of the driver, and together with the current vehicle speed v, it constitutes the basic input parameters for steering angle calculation. Real-time acquisition of these parameters provides data support for subsequent speed adaptive processing.

[0073] The method 200 proceeds to step 204 to calculate a speed-adaptive angle gain according to the vehicle speed. The angle gain κ(v) is calculated by an exponential function: κ(v) = κ_min + (κ_max - κ_min)·exp(-|v|^p / v0^p). In the formula, κ_max is the maximum angle gain, taking a value of about 0.07 rad / rad; κ_min is the minimum angle gain, taking a value of about 0.04 rad / rad; v0 is the characteristic speed, taking a value of about 4 m / s; and p is the adjustment parameter, taking a value of about 2. Through the exponential function relationship, the adaptive adjustment characteristic of higher steering sensitivity at low speed and lower steering sensitivity at high speed is realized.

[0074] In step 206, the method 200 calculates an initial front wheel angle according to the steering wheel angle and the speed-adaptive angle gain. The initial front wheel angle δ_raw is calculated by the formula δ_raw = κ(v)·θ_sw. The calculation process combines the steering input of the driver with the speed-related gain factor to form a basic front wheel angle command.

[0075] In step 208, the method 200 multiplies the initial front wheel angle by a negative steering ratio sign factor. The sign factor S_eff is determined according to the gear position and vehicle speed conditions, taking a value of -1 in the reverse gear and low speed conditions, and taking a value of +1 in other conditions. Through the multiplication operation, the front wheel angle considering the gear characteristics is obtained.

[0076] In step 210, the method 200 obtains a front wheel target angle δ_cmd from the multiplication result. The front wheel target angle comprehensively considers the driver's intention, vehicle speed characteristics and gear state, providing a basic value for subsequent limit processing.

[0077] In step 212, the method 200 limits the amplitude of the front wheel target angle. The amplitude limit uses the formula |δ_cmd|≤ δ0·exp(-λ|v|), where δ0 is the reference maximum angle, taking a value of about 0.65 rad, and λ is the speed attenuation coefficient, taking a value of about 0.07 s / m. The limit ensures that the angle amplitude is within a safe range, preventing excessive angle from causing the vehicle to lose control.

[0078] In step 214, the method 200 limits the rate of change of the front wheel target angle. The rate of change limit uses the formula |dδ / dt| ≤ δ̇_max, where δ̇_max is the maximum angular velocity limit, taking a value of about 20 degrees per second. The limit controls the rate of change of the angle, avoiding sharp changes in the angle that adversely affect vehicle stability.

[0079] The method 200 outputs the final front wheel target steering angle in step 216. The front wheel target steering angle after the amplitude limiting and rate limiting processing has safety and executability, and can be directly used for generating control instructions of the steering execution mechanism. The final steering angle value ensures that the steering operation is within the physical constraints and safety requirements.

[0080] Referring to Figure 3 , the embodiment of the present application also provides a steering ratio adjustment method 300 for adjusting the steering ratio to a negative steering ratio. The method 300 realizes stable switching of the steering ratio between positive and negative values by determining the target steering ratio sign factor, smoothing transition processing, and conditional judgment, etc., to avoid the jitter phenomenon near zero speed.

[0081] As Figure 3 shown, the method 300 starts in step 302 to obtain the current gear information. The gear information g includes forward gear D, reverse gear R, neutral gear N, and parking gear P, etc. The gear information is detected in real time by a gear sensor and transmitted to the control unit. The gear information provides a basis for determining the target steering ratio sign factor.

[0082] The method 300 continues to step 304 to determine whether the current gear is in reverse. The determination step is a logical determination by comparing the current gear information with the reverse gear identifier. When the determination result is reverse, the method 300 enters step 306; when the determination result is non-reverse, the method 300 enters step 308.

[0083] In step 306, the 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 characteristic in the reverse gear state, providing a basis for realizing consistency between the steering direction of the steering wheel and the actual steering direction of the vehicle body. In step 308, the method 300 sets the target steering ratio sign factor S_tar to positive one, which is applicable to non-reverse states such as forward gear, neutral gear, and parking gear.

[0084] The two branch paths converge in step 310, and the method 300 performs smoothing transition processing on the current steering ratio sign factor by a low-pass filter. The smoothing transition processing is realized by a first-order low-pass filter, and the differential equation is dS_eff / dt = (S_tar·M(v) - S_eff) / τ_s. In the equation, S_eff is the current effective steering ratio sign factor, S_tar is the target steering ratio sign factor, M(v) is a threshold function, and τ_s is a smoothing transition time constant.

[0085] The smooth transition time constant τ s is set to 0.2 seconds, which controls the speed of the transition of the steering ratio sign factor from the current value to the target value. By setting this time constant, abrupt changes of the steering ratio sign factor near zero speed are avoided, preventing steering chattering phenomena due to sign factor jumps. The implementation of the low-pass filter ensures the smoothness and stability of the steering ratio switching process.

[0086] The method 300 evaluates in step 312 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. The preset threshold value v en is set to 15 km / h, which corresponds to about 4.2 m / s. The threshold function M(v) plays a role in this step, taking the value 1 when |v| ≤ v en and the value 0 when |v| > v en.

[0087] When the conditions of step 312 are met, the method 300 enters step 314, adjusting the steering ratio sign factor to -1. This adjustment is only performed under the double condition that the vehicle is in reverse gear and the absolute value of the vehicle speed is less than or equal to the preset threshold value, ensuring the safety and applicability of the activation of the negative steering ratio.

[0088] When the conditions of step 312 are not met, the method 300 enters step 316, maintaining the steering ratio sign factor as positive one. This maintenance operation is applicable to the case where the vehicle speed exceeds the preset threshold value, at which time the steering ratio sign factor is automatically returned to positive one, ensuring the stability and safety of steering at high speed.

[0089] The product S tar · M(v) of the threshold function M(v) and the target steering ratio sign factor S tar plays a conditional control role in the low-pass filter. When the vehicle is in reverse and the vehicle speed is below the threshold value, this product is -1, driving the effective steering ratio sign factor S eff to transition to -1. When the vehicle speed exceeds the threshold value or the vehicle is not in reverse, this product is positive one or zero, driving the effective steering ratio sign factor S eff to return to positive one.

[0090] The steering ratio adjustment method 300 realizes stable switching between positive and negative steering ratios through the combined strategy of gear priority, low-speed threshold, and smooth transition. Gear priority ensures that the steering ratio adjustment is consistent with the driver's gear selection intention; the low-speed threshold ensures that the negative steering ratio is only activated under safe low-speed conditions; and the smooth transition ensures that the switching process does not adversely affect vehicle control. Figure 1

[0091] Reference Figure 4 ​This 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] The method 400 performs a closed-loop correction to the front wheel target steering angle in step 412 according to the calculated yaw rate error. The closed-loop correction is based on the yaw rate approximation formula of the 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 error can be converted to a correction amount for the front wheel steering angle.

[0098] The closed-loop correction calculates the correction amount Δδ through a proportional-integral controller. The calculation of the correction amount uses the formula Δδ=K_ψ(v)·(ψ̇_des-ψ̇_act), where K_ψ(v) is the speed-dependent proportional-integral controller gain. The gain coefficient is calculated using the formula K_ψ(v)=0.25 / (1+0.1|v|) to achieve a speed-adaptive control characteristic. The calculated correction amount Δδ is superimposed on the front wheel target steering angle to form the final corrected front wheel target steering angle δ_final=δ_cmd+Δδ.

[0099] The method 400 ensures the consistency of the steering direction of the steering wheel and the actual steering direction of the vehicle body in step 414. Through the aforementioned expected yaw rate calculation, error analysis, and closed-loop correction process, this step verifies that the corrected front wheel target steering angle can produce a vehicle body steering response consistent with the steering direction of the steering wheel. This consistency verification is based on the sign relationship of the yaw rate to ensure that the goal of sign(ψ̇_act)=sign(θ_sw) is achieved.

[0100] The proportional-integral controller design takes into account the vehicle dynamics and response time requirements. The proportional control part provides immediate correction response, and the integral control part eliminates steady-state error. The speed-adaptive characteristic of the controller gain K_ψ(v) ensures that appropriate control performance can be achieved at different vehicle speeds, avoiding the problems of slow response at low speed or excessive response at high speed.

[0101] The closed-loop correction method 400 achieves the accuracy and robustness of steering control through yaw rate feedback. The calculation of the expected yaw rate ensures accurate expression of the steering intention; the error calculation provides a quantitative evaluation of the control error; and the proportional-integral controller achieves effective elimination of the error. The entire closed-loop control process ensures that the steer-by-wire vehicle can maintain the consistency of the steering direction of the steering wheel and the actual steering direction of the vehicle body under various working conditions.

[0102] Reference Figure 5, the steering direction of the steering wheel and the actual steering direction of the vehicle body are consistent by comparing the traditional steering mode and the negative steering ratio mode. In the traditional forward gear state, when the steering wheel rotates counterclockwise, the vehicle turns counterclockwise, and the steering direction of the steering wheel and the actual steering direction of the vehicle body are directly corresponding. After adopting negative steering ratio in the reverse gear state, when the steering wheel rotates counterclockwise, the vehicle also turns counterclockwise, eliminating the need for reverse thinking in the traditional reverse operation.

[0103] The realization principle of negative steering ratio is based on the adjustment of the steering ratio sign factor S_eff. In the reverse gear and low speed condition, the sign factor takes the value of-1, so that the sign relationship in the front wheel target angle δ_cmd = S_eff · κ(v) · θ_sw changes. When the driver turns the steering wheel to the left, the negative sign factor makes the front wheel actually turn to the right, but due to the backward movement of the vehicle, the whole vehicle body presents the effect of turning to the left, which is consistent with the steering intention of the driver.

[0104] Referring to Figures 6 to 11 , wherein Figure 6 and Figure 7 are the U-turn scene in narrow road, the comparison between non-drive-by-wire (positive steering ratio) and drive-by-wire (positive and negative steering ratio switching). Figure 8 and Figure 9 are the reverse parking scene, the comparison between non-drive-by-wire (positive steering ratio) and drive-by-wire (positive and negative steering ratio switching). Figure 10 and Figure 11 are the side parking scene, the comparison between non-drive-by-wire (positive steering ratio) and drive-by-wire (positive and negative steering ratio switching). Based on the schematic diagram of each scene, the drive-by-wire vehicle control method described in the embodiment of the application reduces the multiple correction operations in complex working conditions such as U-turn in narrow road or reverse parking, for example Figure 6 the steering wheel needs to be turned 2400° in Figure 7 only 800°. Figure 8 1600° is needed, Figure 9 800° is needed. Figure 10 , 11 is to embody a standard side parking working condition, the consistency mapping of the steering direction of the steering wheel and the actual steering direction of the vehicle body is realized in the reverse gear state, without the need for reverse thinking, which can significantly reduce the operation difficulty of the driver.

[0105] The simplified control method reduces the complexity of decision branches through the merging processing of conditional judgments. By integrating the evaluation of gear state and vehicle speed threshold into a single decision point through double conditional judgments, the execution efficiency of the control logic is improved. When the condition is not met, the steering ratio is automatically maintained as a positive value, ensuring that the steering characteristics in the conventional driving mode are not affected.

[0106] Further, the implementation of the prediction trajectory calculation and display and safety fallback logic described in the embodiments of the present application includes key links such as trajectory prediction, display synchronization, and fault handling. The calculation of the predicted trajectory is based on a bicycle model, uses the current steering wheel angle, vehicle speed, and wheelbase parameters, and calculates the vehicle position and heading angle change trajectory within a preset time in the future through a numerical integration method.

[0107] The predicted trajectory calculation uses a system of differential equations to describe the time evolution of the vehicle motion state. The position change equation is 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, v is the vehicle speed, and ψ is the vehicle 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 front wheel target angle.

[0108] The numerical integration method uses the 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 5 seconds in the future. Through this numerical integration process, the vehicle's position trajectory point sequence (x_i, y_i, ψ_i) within the prediction time range is calculated, where i represents the time step index. This trajectory point sequence constitutes the geometric description of the predicted trajectory.

[0109] When displaying the reversing image and the predicted trajectory on the vehicle display screen, the consistency between the predicted trajectory and the actual vehicle trajectory is achieved through coordinate transformation and image superposition. The world coordinate system position of the predicted trajectory is converted to display screen pixel coordinates through perspective transformation and superimposed on the real-time image obtained by the reversing camera. The color and thickness of the trajectory line are gradually changed according to the time distance, with the recent trajectory displayed as a thicker bright line and the long-term trajectory displayed as a thinner dark line.

[0110] The real-time update frequency of the predicted trajectory is synchronized with the control period to ensure that the trajectory display can timely reflect the changes in the steering wheel angle. When the driver adjusts the steering wheel position, the predicted trajectory is updated on the display screen accordingly, providing the driver with immediate path preview information. This synchronization mechanism ensures the consistency between the predicted trajectory and the actual vehicle trajectory.

[0111] The safety fallback logic is activated immediately when a sensor failure or actuator fault is detected. Fault detection includes abnormal steering wheel angle sensor signal, missing vehicle speed sensor data, interrupted gear sensor communication, 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.

[0112] The reduction of the maximum steering angle limit is achieved by modifying the magnitude limit parameter δ_0. In normal conditions, δ_0 is set to about 0.65 radian, while in fault mode, δ_0 is reduced to 0.3 radian, which is equivalent to reducing the maximum steering angle from about 37 degrees to about 17 degrees. This limit reduction ensures the conservatism and safety of vehicle steering in fault state, avoiding excessive steering angle leading to vehicle out of control.

[0113] The embodiment of the application further discloses a steer-by-wire vehicle control system.

[0114] With reference to Figure 12 , the steer-by-wire vehicle control system 500 adopts a modular architecture design, and realizes consistent control of the steering direction of the steering wheel and the actual steering direction of the vehicle body in the reverse gear state. The steer-by-wire vehicle control system 500 includes a plurality of functional modules connected through information flow and control flow between the modules to form a complete steering control solution.

[0115] As shown in Figure 12 , the steer-by-wire vehicle control system 500 includes an information acquisition module 502 for acquiring steering wheel angle, vehicle speed and gear information. The information acquisition module 502 realizes data acquisition function through a variety of sensor interfaces, including a steering wheel angle sensor interface, a vehicle speed sensor interface and a gear sensor interface. The steering wheel angle θ_sw is measured by a high-precision rotary encoder with a resolution of 0.1 degrees; the vehicle speed v is obtained by a wheel speed sensor or a GPS module, and the update frequency is 100 Hz; the gear information g is read from the transmission control unit through the CAN bus.

[0116] The steer-by-wire vehicle control system 500 further includes a gear judgment module 504 for judging whether the vehicle is in the reverse gear state according to the gear information. The gear judgment module 504 receives the gear information from the information acquisition module 502 and determines the current gear state through logical comparison operation. The judgment logic of the gear judgment module 504 includes the recognition of the reverse gear R, the forward gear D, the neutral gear N and the parking gear P, and generates a Boolean type reverse gear state flag signal. The judgment result provides a decision basis for the subsequent steering ratio adjustment.

[0117] The steer-by-wire vehicle control system 500 includes a steering ratio adjustment module 506 for adjusting the steering ratio to a negative steering ratio when the vehicle is in the reverse gear state and the vehicle speed is lower than a preset threshold value. The steering ratio adjustment module 506 receives the vehicle speed information from the information acquisition module 502 and the reverse gear state judgment result from the gear judgment module 504. The steering ratio adjustment module 506 internally implements a threshold function M(v) and a low-pass filter, and realizes smooth adjustment of the steering ratio sign factor through the differential equation dS_eff / dt = (S_tar·M(v) - S_eff) / τ_s.

[0118] The preset threshold value v_en of the steering ratio adjustment module 506 is set to 4.2 m / s, corresponding to a speed limit of 15 km / h. When the vehicle is in reverse gear and the absolute value of the vehicle speed is less than the 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 s to ensure the stability of the steering ratio switching process. The module also includes a manual driver active switching option, allowing the driver to manually activate or disable the negative steering ratio function through the vehicle-mounted human-machine interface.

[0119] The steer-by-wire vehicle control system 500 includes a steering angle calculation module 508 for calculating the front wheel target steering angle based on the negative steering ratio and the steering wheel steering angle. The steering angle calculation module 508 receives the steering wheel steering angle and vehicle speed information from the information acquisition module 502, as well as the 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.

[0120] The steering angle calculation module 508 internally includes an amplitude limiter and a rate limiter to ensure that the calculated front wheel target steering angle is within a safe range. The amplitude limitation uses 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 limitation uses the formula |dδ / dt| ≤ δ̇_max, where δ̇_max is the maximum angular velocity limit. The module also implements a closed-loop correction function with yaw rate feedback, which accurately adjusts the front wheel target steering angle through a proportional-integral controller.

[0121] The steer-by-wire vehicle control system 500 includes a steering control module 510 for controlling the steering execution mechanism to steer according to the front wheel target steering angle, so that the steering direction of the steering wheel is consistent with the actual steering direction of the vehicle body. The steering control module 510 receives the front wheel target steering angle from the steering angle calculation module 508 and controls the movement of the steering execution mechanism through a motor driver. The steering control module 510 implements position closed-loop control to ensure that the actual front wheel steering angle δ_act accurately tracks the target steering angle δ_cmd.

[0122] The steering control module 510 also implements a steering wheel road feel torque feedback function, which generates a steering wheel touch torque through a 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 a steering wheel angle proportional coefficient, with a value of about 0.6 newton-meters per radian; K_Δ is a steering angle deviation proportional coefficient, with a value of about 0.8 newton-meters per radian; B_θ is a steering wheel angular velocity damping coefficient, with a value of about 0.03 newton-meters per radian per second; and R is the current steering ratio. This torque feedback ensures that the driver can still obtain a consistent touch experience as traditional steering in the negative steering ratio mode.

[0123] The information flow connection relationship between the modules embodies the data processing flow of the system. The information acquisition module 502 as the data source provides basic sensor data to the gear judgment module 504, the steering ratio adjustment module 506, and the steering angle calculation module 508. The judgment result of the gear judgment module 504 is transmitted to the steering ratio adjustment module 506 for determination of the steering ratio sign factor. The output of the steering ratio adjustment module 506 is transmitted to the steering angle calculation module 508 to participate in the calculation of the front wheel target steering angle. The calculation result of the steering angle calculation module 508 is transmitted to the steering control module 510 for control of the steering actuator.

[0124] The control flow connection relationship embodies the control logic flow of the system. The reverse gear state judgment of the gear judgment module 504 triggers the sign factor adjustment of the steering ratio adjustment module 506; the change of the sign factor of the steering ratio adjustment module 506 drives the steering angle calculation module 508 to recalculate the front wheel target steering angle; and the target steering angle update instruction of the steering angle calculation module 508 adjusts the actuator position of the steering control module 510. This control flow ensures a complete control link from gear change to steering response.

[0125] The configuration method of the 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 is a basic geometric parameter, and its typical value range is 2.5 to 3.2 meters according to the specific vehicle model setting. The gain factors κ_max and κ_min represent the maximum and minimum angle gains, respectively, which are adjusted according to the steering characteristics requirements of the vehicle model, with κ_max typically ranging from 0.05 to 0.10 rad / rad, and κ_min typically ranging from 0.02 to 0.06 rad / rad.

[0126] The time constant parameters include a smoothing transition time constant τ s and a yaw rate control time constant, which are calibrated according to the dynamic response characteristics of the vehicle model. The typical value range of τ s is 0.1 to 0.5 seconds, and a smaller time constant is suitable for sports vehicles, and a larger time constant is suitable for comfortable vehicles. The angular velocity limit parameter δ̇_max is set according to the performance and safety requirements of the steering actuator, and the typical value range is 10 to 30 degrees per second.

[0127] The configuration of the calibration parameters is realized through an on-board diagnostic interface or a special calibration tool. The calibration process includes parameter download, function verification, and performance test steps. The parameter download writes the vehicle model specific calibration data into the non-volatile memory of the control unit; the function verification confirms the working state of each module under the new parameters; and the performance test evaluates the response characteristics of the entire system under actual driving conditions. This calibration method ensures the applicability and performance consistency of the steer-by-wire vehicle control system 500 on different vehicle models.

[0128] The embodiment of the present application also discloses a readable storage medium.

[0129] A readable storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the steer-by-wire vehicle control method in any one of the above embodiments. The computer readable storage medium can include any entity or device capable of carrying the computer program, a recording medium, a U disk, a mobile hard disk, 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 can be in the form of source code, object code, an executable file, or some intermediate form, etc. The computer readable storage medium can include any entity or device capable of carrying the computer program code, a recording medium, a U disk, a mobile hard disk, 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.

[0130] Any process or method descriptions or any other information described herein in the flowchart form can be understood as representing at least one of the steps of an associated computer program product, wherein the respective step can be implemented as computer usable program code to be executed by a processor. The respective steps can therefore represent a portion of an algorithm that can be implemented as computer usable program code to be executed by a processor. The program code can be written in any suitable programming language, including compiled or interpreted languages, and can include computer executable instructions that implement the various processes described herein. The program code can be executed using a single processing or multiprocessor computer system, or it can be executed using multiple, connected computer systems, each of which can be implemented using one or more processors.

[0131] The logic and / or steps represented in flow diagrams or otherwise described herein, for example, can be considered as a sequence of executable instructions, and can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions, or a combination of the above. The logic and / or steps can also be implemented in programmable logic or electronic hardware, including but not limited to programmable logic devices or arrays, application-specific integrated circuits, or other hardware using combinatorial logic.

[0132] The above embodiments are only used to illustrate the technical solutions of the present application, not limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

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 front wheel steering angle based on the negative steering ratio and the steering wheel angle, including calculating the initial front wheel steering angle based on the steering wheel angle and the speed-adaptive angle gain; The target front wheel steering angle is obtained by multiplying the initial front wheel steering angle by the negative steering ratio sign factor; The target steering angle of the front wheel is subject to amplitude and rate of change limits; as well as The steering actuator is controlled 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; The speed-adaptive angle gain κ(v) is adjusted according to the current vehicle speed according to a preset function relationship, which is: κ(v) = κ_min + (κ_max - κ_min) / (1 + (|v| / v0)^p), where κ_max and κ_min are the maximum angle gain and minimum angle gain, respectively, v0 is the characteristic speed, and p is the adjustment parameter.

2. 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.

3. The steer-by-wire vehicle control method according to claim 2, 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.

4. 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.

5. The steer-by-wire vehicle control method according to claim 4, 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.

6. 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.

7. The steer-by-wire vehicle control method according to claim 6, 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.

8. 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, including calculating the initial front wheel angle based on the steering wheel angle and the speed-adaptive angle gain. The target front wheel steering angle is obtained by multiplying the initial front wheel steering angle by the negative steering ratio sign factor; The target steering angle of the front wheel is subject to amplitude and rate of change limits; 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; The speed-adaptive angle gain κ(v) is adjusted according to the current vehicle speed according to a preset function relationship, which is: κ(v) = κ_min + (κ_max - κ_min) / (1 + (|v| / v0)^p), where κ_max and κ_min are the maximum angle gain and minimum angle gain, respectively, v0 is the characteristic speed, and p is the adjustment parameter.

9. 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 1-7.

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