Steer-by-wire system safety control method and storage medium

Abstract

The invention discloses a safety control method for a steer-by-wire system, which comprises the following steps of: S1, respectively calibrating an upper turning middle position and a lower turning middle position, and calculating an upper turning angle deviation alpha 1 and a lower turning angle deviation alpha 1 in real time; s2, acquiring a current vehicle speed V; s3, an alignment judgment threshold T0, a safety boundary A and a safety boundary B are preset, and A is larger than T0 and smaller than B; s4, when alpha1 is larger than T0 and smaller than A, entering a degradation state 1, limiting the maximum vehicle speed to be smaller than or equal to V1, calculating an angle offset in real time according to the steering direction, and enabling a down-turning request angle to be equal to (steering wheel turning angle beta + / -angle offset) / a transmission coefficient; s5, when alpha1 is larger than or equal to A and smaller than B, entering a degradation state 2, limiting the maximum vehicle speed to be smaller than or equal to V2, and introducing a dynamic coefficient changing along with V on the basis of the angle offset, so that the correction rate at the low speed is higher than the correction rate at the high speed; and S6, when alpha1 is larger than or equal to B, manual driving is forbidden, and intelligent driving forcibly takes over or executes safe parking. According to the method, a driver is allowed to take over in a speed limiting mode in the scene that the upper rotation angle and the lower rotation angle are not aligned, yaw impact caused by one-time correction can be avoided, and both the correction speed and the high-speed stability can be considered.

Description

TECHNICAL FIELD

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

[0002] The steer-by-wire system structure is shown in Figure 1 , which is divided into an upper turning steering wheel, a lower turning rack, and left and right wheels, and there is no mechanical connection between the upper turning and the lower turning. The driver controls the rotation of the upper turning steering wheel, and then calculates the request angle of the lower turning (lower turning request angle = upper turning steering wheel rotation angle / transmission coefficient) according to the steering wheel rotation angle. The rack moves left and right to control the rotation of the wheels. The alignment of the angle of the steering wheel is particularly important. Only when the angle of the steering wheel is aligned can the driver safely control the vehicle to turn.

[0003] In the human driving scenario and the intelligent driving scenario, the steering wheel angle alignment function is required. In the human driving scenario, only when the steering wheel angle is aligned can the vehicle enter the human driving and be driven. When the driver leaves the driving position, the angle needs to be aligned again to ensure that the steering wheel angles of the upper and lower turns of the steer-by-wire are aligned. In the intelligent driving scenario, since the upper and lower turns of the steer-by-wire can be independently controlled, the lower turn can independently perform the intelligent driving function to control the vehicle to turn. The steering wheel of the upper turn does not necessarily rotate with the lower turn. If the driver intervenes to control the steering at this time, the steering wheel needs to be aligned with the lower turn first, and then the driver can take over the control of the steering to control the whole vehicle. In addition, the game mode is a special mode. In this mode, the driver can play games while sitting in the car. The upper turning steering wheel will provide a simulated hand feeling (adapted to the game scene). At this time, the upper turning steering wheel rotates, and the lower turn does not rotate with the upper turning steering wheel. After exiting the game mode, the game alignment needs to be completed before entering the human driving mode. In the intelligent driving scenario, the game mode can be activated at any time. When the intelligent driving exits, the driver needs to take over. The alignment function must be executed first. After the alignment is completed, the intelligent driving can exit and enter the human driving.

[0004] However, in some special situations, the driver needs to control the vehicle urgently. Although the angles of the upper and lower turns are not aligned at this time, the alignment function can be allowed to be inactivated to enter the state of urgent vehicle control, and the vehicle steering control is realized with the angle deviation to reduce the degree of harm.

[0005] In summary, the existing technology has the following technical problems to be solved:

[0006] 1. The existing technology must complete "center calibration + angle alignment" in advance to enter the human driving, and cannot immediately take over in an emergency.

[0007] 2. If the up-turn center position is not calibrated or the up-down turn angle deviation exists in the prior art, the system directly reports a fault and exits the manual driving, and the vehicle may stall or fail to turn;

[0008] 3. The control scheme of the prior art has no gradual correction strategy in the alignment process, and directly prohibits manual driving when the deviation is large, lacking a "controllable with disease" degradation mechanism;

[0009] 4. The control scheme of the prior art does not distinguish between deviation size and vehicle speed, and cannot balance "correction speed" and "high-speed stability". SUMMARY

[0010] A series of simplified concepts are introduced in the summary section, which are simplifications of the prior art in the art, which will be described in further detail in the detailed description section. The summary section of the present application does not mean to attempt to limit the key features and necessary technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0011] The technical problem to be solved by the present application is to provide a steer-by-wire system safety control method that allows the driver to take over in an emergency and ensures vehicle controllability when the up-turn-down turn angle is not aligned.

[0012] Another technical problem to be solved by the present application is to provide a steer-by-wire system safety control method that dynamically selects a "speed limit + active correction" strategy according to the deviation size and vehicle speed, gradually eliminating the deviation and ensuring driving safety.

[0013] Still another technical problem to be solved by the present application is to provide a steer-by-wire system safety control method that automatically triggers intelligent driving takeover or safe parking when the up-turn-down turn angle deviation is too large to be manually driven, avoiding risk spillover.

[0014] To solve the above technical problems, the steer-by-wire system safety control method provided by the present application, the steer-by-wire system includes a mechanically disconnected up-turn steering wheel assembly and a down-turn actuator, comprising the following steps:

[0015] S1, calibrate the up-turn center position and the down-turn center position respectively, and calculate the up-down turn angle deviation a1 in real time;

[0016] S2, obtain the current vehicle speed V;

[0017] S3, preset the alignment determination threshold T0, the safety boundary A, and the safety boundary B, and T0

[0018] S4, when |α1| > T0 and |α1| < A, enter degraded state 1: limit maximum speed ≤ V1, and calculate angle offset in real time according to steering direction, so that the steering angle = (steering wheel angle β ± angle offset) / transmission coefficient, and angle offset decreases with the increase of V;

[0019] S5, when |α1| ≥ A and |α1| < B, enter degraded state 2: limit maximum speed ≤ V2, and introduce a dynamic coefficient that changes with V based on angle offset, so that the correction rate at low speed is higher than that at high speed;

[0020] S6, when |α1| ≥ B, prohibit manual driving, and force to take over or execute safe parking by intelligent driving.

[0021] Preferably, the safety control method of the steer-by-wire system is further improved, and the dynamic coefficient includes a decay coefficient DecreaseFactor and an amplification coefficient IncreaseFactor.

[0022] Preferably, the safety control method of the steer-by-wire system is further improved, and the decay coefficient DecreaseFactor monotonically increases with vehicle speed V, and the amplification coefficient IncreaseFactor monotonically decreases with vehicle speed V.

[0023] Preferably, the safety control method of the steer-by-wire system is further improved, and angle offset is linearly attenuated to zero in (α1 / angle offset) periods.

[0024] Preferably, the safety control method of the steer-by-wire system is further improved, and the maximum value of the transmission coefficient is limited to: upshift remaining stroke / downshift remaining stroke.

[0025] Preferably, the safety control method of the steer-by-wire system is further improved, when the downshift actuator reaches the mechanical end, the steering wheel in the upshift direction enters the virtual end synchronously and provides a reverse torque.

[0026] Preferably, the safety control method of the steer-by-wire system is further improved, when the vehicle speed is less than the vehicle speed threshold and |α1| > T0, the driver is allowed to drive at low speed by engaging the gear in the limp mode.

[0027] If the vehicle speed is less than the vehicle speed threshold, it means that the vehicle is not started at this time, and the safety state at this time is to alarm the driver, or not to allow the gear to be engaged until the steering wheel is aligned, or the vehicle is set to the limp mode, and the gear can be engaged only when the limp mode is turned on. Another situation is that the vehicle is in the process of driving, and the vehicle speed is greater than the threshold at this time, and the vehicle needs to be driven with an angle deviation at this time.

[0028] Preferably, the safety control method of the steer-by-wire system is further improved, V1=120km / h, V2=10km / h.

[0029] The application provides a computer readable storage medium internally storing a computer program, the computer program is executed to implement the steps of the safety control method of the steer-by-wire system.

[0030] The working process and principles of the application are described as follows.

[0031] The application establishes the upper and lower turning common angle reference through "median calibration", calculates the deviation alpha1 in real time and compares with the three-level threshold (T0, A, B), forms a "gradient degradation" strategy, in the degradation state 1 and 2, adopts "beta+ offset" feedforward compensation + dynamic coefficient feedback, makes the actual lower turning angle of each cycle additional correction delta alpha1, gradually swallows the initial deviation, reduces the offset and the change amplitude of decrease factor / increase factor at high speed, ensures the stability of vehicle yaw, increases the correction amount at low speed, shortens the alignment time, if the deviation exceeds the safety boundary B, it is considered that the single stroke is insufficient, the driver cannot complete the full range steering, the system refuses to drive and triggers the intelligent driving safety parking.

[0032] The application can at least achieve the following technical effects.

[0033] 1. The application still allows the driver to take over in a speed-limited manner in the misalignment scene, solves the rigid defect that "must be aligned to drive" in the background technology.

[0034] 2. The application decomposes the large deviation into multiple driving cycles through "offset + dynamic coefficient" double-parameter adjustment, avoids the yaw impact caused by one-time correction.

[0035] 3. The three-level threshold and two-level speed limit of the application are combined, so that the risk is always constrained in the "controllable window", and the "correction speed" and "high speed stability" are considered.

[0036] 4. The application forces the intelligent driving to take over when the deviation is too large, fills the blank of "man driving cannot be safely controlled". BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings are intended to illustrate the general characteristics of the methods, structures, and / or materials used in specific exemplary embodiments of the invention, supplementing the description in the specification. However, the drawings are schematic diagrams not drawn to scale and may not accurately reflect the precise structural or performance characteristics of any of the given embodiments. The drawings should not be construed as limiting or restricting the range of numerical values ​​or properties covered by exemplary embodiments of the invention. The invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0038] Figure 1 This is a schematic diagram of an existing steer-by-wire system.

[0039] Figure 2 This is a schematic diagram of the control flow of the present invention.

[0040] Figure 3 This is a diagram illustrating the deviation of the up and down rotation angle of the drive-by-wire system. Figure 1 .

[0041] Figure 4 This is a schematic diagram of the correction for the deviation of the up and down rotation angle of the drive-by-wire system.

[0042] Figure 5 This is a diagram illustrating the deviation of the up and down rotation angle of the drive-by-wire system. Figure 2 . Detailed Implementation

[0043] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can fully understand other advantages and technical effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and various details in this specification can also be applied based on different viewpoints, with various modifications or changes made without departing from the overall design concept of the invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. The following exemplary embodiments of the present invention can be implemented in many different forms and should not be construed as being limited to the specific embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the technical solutions of these exemplary embodiments to those skilled in the art. It should be understood that when an element is referred to as "connected" or "combined" to another element, the element can be directly connected or combined to the other element, or there may be intermediate elements. The difference is that when an element is referred to as "directly connected" or "directly combined" to another element, there are no intermediate elements. Throughout the drawings, the same reference numerals always denote the same elements.

[0044] First embodiment;

[0045] refer to Figure 2As shown, the present invention provides a safety control method for a steer-by-wire system. The steer-by-wire system includes an upward-turning steering wheel assembly and a downward-turning actuator that are not mechanically connected, and includes the following steps:

[0046] S1, respectively calibrate the midpoint of the upward rotation and the midpoint of the downward rotation, and calculate the deviation α1 of the upward and downward rotation angles in real time;

[0047] S2, obtain the current vehicle speed V;

[0048] S3, preset alignment judgment threshold T0, safety boundary A, safety boundary B, and T0 < A < B;

[0049] S4, when |α1|>T0 and |α1|<A, enter the downgrade state 1: limit the maximum vehicle speed ≤V1, and calculate the angle offset in real time according to the steering direction, so that the downturn request angle = (steering wheel angle β± angle offset) / transmission coefficient, and the angle offset decreases as V increases;

[0050] The principle behind this step is explained as follows: When the deviation between the vertical and horizontal steering angles exceeds the alignment threshold but is less than the safety boundary A, it is considered that there is a slight misalignment between the vertical and horizontal steering angles. Therefore, the system enters degraded state 1, issues a warning to the driver, and limits the vehicle speed to less than 120 km / h. At this time, the left and right travel of the upward steering is asymmetrical. The process... Figure 3 Taking the angle deviation to the right as an example, the schematic diagram of steer-by-wire is as follows: Figure 2 As shown, there is an angular deviation of α1 between upturn and downturn. The travel distance for upturn and right turn is less than the total travel distance for upturn / 2. Because the total travel distance for right turn is relatively small, in order to ensure that the steering wheel can reach the mechanical end point when turning upturn and also when turning downturn, it is necessary to calculate the maximum transmission coefficient for right turn (maximum transmission coefficient for right turn = remaining total travel distance for upturn and right turn / remaining total travel distance for downturn and right turn). When calculating the requested angle for downturn, the transmission coefficient used must not exceed this maximum transmission coefficient. Although steering control is performed with an angular deviation at this time, active correction can be made during the driver's steering process to compensate for the calculated requested angle for downturn and reduce the angular deviation between upturn and downturn.

[0051] Initially, there is an angular deviation of α1 between upturn and downturn. The driver turns the steering wheel to the right by an angle of β. At this point, the uncompensated downturn request angle σ0 is calculated as: Steering wheel rotation angle β / Transmission coefficient. To achieve active correction of the angular deviation, the compensated downturn request angle σ1 is calculated as: (Steering wheel rotation angle β + Angle offset) / Transmission coefficient. The angle offset value decreases with increasing vehicle speed, and the maximum value of the transmission ratio is limited. Through this compensation correction method, the angular deviation between upturn and downturn can be reduced. The reduced angular deviation value α1offset = (σ1 - σ0) * Transmission coefficient = Angle offset. After α11 / α1offset cycles, the angular deviation between upturn and downturn is completely corrected, meaning the angle offset linearly decays to zero over (α1 / Angle offset) cycles.

[0052] When the driver turns left, due to the rightward deviation of the up-and-down turning angle, the actual downward turning angle requested for the same steering wheel rotation angle is reduced, thus reducing the up-and-down turning angle deviation. Therefore, the downward turning angle requested after left turn compensation = (steering wheel rotation angle - angle offset) / transmission coefficient.

[0053] S5, when |α1|≥A and |α1|<B, enter the downgrade state 2: limit the maximum vehicle speed to ≤V2, and introduce a dynamic coefficient that varies with V on the basis of the angle offset, so that the correction rate at low speed is higher than the correction rate at high speed;

[0054] The principle behind this step is explained as follows: If there is a significant angular deviation in the up and down turns of the drive-by-wire system (greater than safety boundary A, less than safety boundary B), it enters degraded state 2, and the vehicle speed is limited to less than 10 km / h. Again, taking a rightward angular deviation as an example, such as... Figure 5 , ​ As shown, when the driver turns right, the calculated compensated downward turn request angle is = (actual steering wheel rotation angle for upward turn + angle offset) / (transmission coefficient * DecreaseFactor). Here, DecreaseFactor is less than or equal to 1. The higher the vehicle speed, the larger DecreaseFactor becomes. Furthermore, "transmission coefficient * DecreaseFactor" has a maximum value limit. The maximum transmission coefficient for right turn is = the remaining total travel distance for upward right turn / the remaining total travel distance for downward right turn.

[0055] When the driver turns left, the compensated downward turn request angle = (actual steering wheel rotation angle - angle offset) / (transmission coefficient * increaseFactor), where increaseFactor is greater than or equal to 1, and the higher the vehicle speed, the smaller increaseFactor is.

[0056] When calculating the compensated downturn request angle, in addition to correcting the deviation between the upturn and downturn angles using the angle offset, the Decrease Factor and Increase Factor of the transmission coefficient are introduced to increase the angle correction magnitude per cycle. This allows for faster correction of the upturn and downturn angle deviations at lower vehicle speeds. At higher vehicle speeds, a slower and more stable correction of the angle deviation is required. Because the upturn and downturn are separated in steer-by-wire, when the downturn reaches the mechanical end point, the upturn enters the virtual end point. The determination method is that if the compensated downturn request angle = total downturn travel / 2, then the upturn synchronously enters the end point, providing a reverse end force to prevent the driver from overshooting this end point.

[0057] S6, when |α1|≥B, manual driving is prohibited, and intelligent driving will forcibly take over or execute a safe stop.

[0058] If the up and down turning angles of the drive-by-wire system have a significant angular deviation (greater than safety boundary B), it is determined that the single-sided travel is too short, posing a safety risk. In this case, the intelligent driving system will take over to align the angles or bring the vehicle to a safe stop. While compensating for the up and down turning angle deviations, the system will continuously monitor whether the angle deviation has been compensated. If the angle deviation compensation is complete, and it is determined that there are no further angular deviations in the up and down turns, the alarm will be canceled, and the system will return to normal driving mode.

[0059] Further explanations of the angle offset, Decrease Factor, and Increase Factor are as follows;

[0060] 1. Angle offset

[0061] When the driver turns the steering wheel, the system adds or subtracts an additional angle value to dynamically reduce the angular deviation between up and down turns.

[0062] If the deviation is to the right, when the driver turns the steering wheel to the right, the system will add a positive offset to the steering wheel angle;

[0063] When turning the steering wheel to the left, the system will subtract an offset; this allows the steering actuator to turn "a little more" or "a little less," gradually approaching the steering wheel angle and reducing the deviation.

[0064] The magnitude of the offset decreases as vehicle speed increases (the correction is more gentle at high speeds);

[0065] ffset will gradually decay until the bias is completely corrected.

[0066] 2. Decrease Factor

[0067] When turning right, the system applies a factor to the transmission coefficient attenuation scaling to accelerate angle correction.

[0068] When the angle deviation is large (entering downgrade state 2); and the driver turns the steering wheel to the right;

[0069] When the system calculates the downturn request angle, it multiplies the transmission coefficient by DecreaseFactor (≤1) to make the actual downturn angle larger, thereby eliminating the deviation more quickly.

[0070] The lower the vehicle speed, the smaller the Decrease Factor (the faster the correction);

[0071] The higher the vehicle speed, the larger the DecreaseFactor (the slower the correction, ensuring stability);

[0072] There is a maximum limit to prevent exceeding the mechanical travel.

[0073] 3. Increase Factor

[0074] When turning left, the system amplifies and scales the transmission coefficient by a factor that is also used to speed up the angle correction.

[0075] When the angle deviation is large (entering degraded state 2), and the driver turns the steering wheel to the left, the system will multiply the transmission coefficient by the increase factor (≥1), making the actual downward turning angle smaller, thus pulling back to alignment faster.

[0076] The lower the vehicle speed, the larger the Increase Factor (the faster the correction);

[0077] The higher the vehicle speed, the smaller the increase factor (the correction is slower, ensuring stability);

[0078] Also limited by the maximum transmission coefficient to prevent mechanical impact.

[0079] Second embodiment;

[0080] The present invention provides a computer-readable storage medium having a computer program stored therein, which, when executed, is used to implement the steps of the safety control method for the steer-by-wire system described in the first embodiment.

[0081] The computer-readable medium includes both permanent and non-permanent, removable and non-removable media, which can store information by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include non-transitory computer-readable media, such as modulated data signals and carrier waves.

[0082] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will also be understood that, unless expressly defined herein, terms such as those defined in a general dictionary shall be interpreted as having the meaning consistent with their meaning in the relevant field context, and not as having an idealized or overly formal meaning.

[0083] The present invention has been described in detail above through specific embodiments and examples, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A safety control method for a steer-by-wire system, the steer-by-wire system comprising an upper steering wheel assembly and a lower steering actuator without mechanical connection, characterized in that, The method comprises the following steps: S1, respectively calibrate the upper and lower turning midpoints, and calculate the upper and lower turning angle deviation α1 in real time; S2, obtain the current vehicle speed V; S3, preset the alignment determination threshold T0, the safety boundary A, and the safety boundary B, and T0 S4, when |α1| > T0 and |α1| < A, enter the degraded state 1: limit the maximum vehicle speed ≤V1, and calculate the angle offset in real time according to the steering direction, so that the lower turning request angle = (steering wheel turning angle β ± angle offset) / transmission coefficient, and the angle offset decreases with the increase of V; S5, when |α1| ≥ A and |α1| < B, enter the degraded state 2: limit the maximum vehicle speed ≤V2, and introduce a dynamic coefficient that changes with V on the basis of the angle offset, so that the correction rate at low speed is higher than that at high speed; S6, when |α1| ≥ B, prohibit manual driving, and force to take over or execute safe parking by intelligent driving.

2. The drive-by-wire steering system safety control method according to claim 1, characterized by: The dynamic coefficient comprises a decay coefficient DecreaseFactor and an amplification coefficient IncreaseFactor.

3. The drive-by-wire steering system safety control method of claim 2, wherein: The decay coefficient DecreaseFactor monotonically increases with the vehicle speed V, and the amplification coefficient IncreaseFactor monotonically decreases with the vehicle speed V.

4. The drive-by-wire steering system safety control method of claim 1, wherein: The angle offset linearly decays to zero at (α1 / angle offset) periods.

5. A safety control method for a steer-by-wire system according to any one of claims 1 to 4, characterized in that: The maximum value of the transmission coefficient is limited to: upper turning remaining stroke / lower turning remaining stroke.

6. A safety control method for a steer-by-wire system according to any one of claims 1 to 4, characterized in that: When the lower turning actuator reaches the mechanical end, the upper turning steering wheel synchronously enters the virtual end and provides a reverse torque.

7. The drive-by-wire steering system safety control method of claim 1, wherein: When the vehicle speed < vehicle speed threshold and |α1| > T0, the driver is allowed to drive at low speed through the limp mode.

8. The drive-by-wire steering system safety control method of claim 1, wherein: V1 = 120 km / h, V2 = 10 km / h.

9. A computer-readable storage medium, characterized in that: The computer program is stored in the internal storage, and when executed, is used to realize the steps of the safety control method of the steer-by-wire system according to any one of claims 1-8.

Images