Exit judgement method for lane keeping assist function based on curvature of curve

Abstract

An exit judgment method for a lane keeping assist function based on the curvature of a curve, comprising: on the basis of the curvature of a curve, calculating a timeout exit time threshold value, a vehicle attitude stabilization time threshold value and a driver takeover torque threshold value, the curvature of the curve being obtained on the basis of a driving image containing a lane line acquired by a vehicle-mounted sensing device; and if any one of a timeout judgment condition, a stabilization judgement condition and a driver takeover judgment condition is satisfied at present, exiting the lane keeping assist function, wherein when the activation duration of the lane keeping assist function exceeds the timeout exit time threshold value, the timeout judgment condition is satisfied, when the vehicle is kept in a stable state for a duration exceeding the vehicle attitude stabilization time threshold value, the stabilization judgment condition is satisfied, and when a steering torque of a driver exceeds the driver takeover torque threshold value, the driver takeover judgment condition is satisfied.

Description

A method for determining the exit of lane keeping assist function based on curve curvature CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The embodiments of this application are based on the Chinese patent application with application number 202311555821.7 and application date November 17, 2023, and claim the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into the embodiments of this application as a reference. Technical Field

[0002] The present invention relates to the field of assisted driving technology, and in particular to a method for determining an exit of a lane keeping assist function based on curve curvature. Background Art

[0003] Lane Keeping Assist (LKA) is a short-term intervention function. The system only intervenes when the vehicle deviation criteria are met. This system intervention does not involve long-term vehicle control. When the system's exit control conditions are met, such as when the vehicle returns to the center position and shows no signs of deviation, Lane Keeping Assist will automatically exit control, returning control to the driver. This raises the question of when to switch system control to driver control. The timing of the system's exit significantly impacts the user experience and safety of the function, especially in curved roads. The greater the curvature of the curve, the longer the Lane Keeping Assist function should remain in control after activation, and the exit judgment mechanism should be more stringent. Otherwise, after releasing control, the vehicle can easily drift out of its lane again in the curve.

[0004] The prior art provides a vehicle decision-making and control method and device that balances safety and stability. The method comprises: obtaining the road surface parameters of the current lane, the driving state parameters of the current vehicle, and the driving state parameters of an obstructing vehicle, where the obstructing vehicle is a vehicle traveling in the current lane or a target lane; determining a lane change decision for the current vehicle based on the road surface parameters, the driving state parameters of the current vehicle, and the driving state parameters of the obstructing vehicle; and controlling the current vehicle to change lanes to the target lane based on the lane change decision. This method makes lane change decisions based on the road surface parameters of the current lane and the driving state of the vehicle, providing appropriate lane change decisions for different road conditions, avoiding unsafe situations such as vehicle skidding, and improving the stability of the vehicle's lane change process while ensuring vehicle safety.

[0005] The above-mentioned prior art has the following drawbacks: it only proposes driver takeover as the condition for exiting the lateral assist function, without addressing exit conditions such as system control timeout or vehicle posture stabilization. This can result in the lane keeping assist function controlling the vehicle for extended periods of time, failing to intervene when necessary and exit promptly after correction is complete, thus minimizing the impact on the driver. Furthermore, the exit criteria proposed in the first technique are not tied to curved road conditions, making it less adaptable to curves. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for determining the exit of a lane keeping assist function based on curve curvature, so as to improve the user experience of the assisted driving function.

[0007] To solve the above technical problems, the present invention provides a technical solution: establishing linear relationships between curve curvature and the timeout exit time threshold, vehicle attitude stabilization time threshold, and driver takeover torque threshold, respectively, so that the timeout exit time threshold, vehicle attitude stabilization time threshold, and driver takeover torque threshold increase with increasing curve curvature; calculating the timeout exit time threshold, vehicle attitude stabilization time threshold, and driver takeover torque threshold based on the curve curvature;

[0008] If any of the timeout judgment conditions, stability judgment conditions, and driver takeover judgment conditions are currently met, the lane keeping assist function is exited;

[0009] The timeout judgment condition is: the lane keeping assist function is on for a duration exceeding the timeout exit threshold; the stability judgment condition is:

[0010] The vehicle maintains a stable state for a duration exceeding a vehicle attitude stability time threshold, wherein the vehicle stability is determined based on the lateral distance between the vehicle and the lane line and the deviation angle between the vehicle heading angle and the tangent line of the lane line;

[0011] The driver takeover judgment condition is: the driver steering torque exceeds the driver takeover torque threshold.

[0012] As a second aspect of the present invention, the present invention provides an exit judgment device for a lane keeping assist function, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the above-described exit judgment method for the lane keeping assist function based on curve curvature is implemented.

[0013] As a third aspect of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned method for determining the exit of the lane keeping assist function based on curve curvature.

[0014] As a fourth aspect of the present invention, the present invention provides a lane keeping assist system, comprising the above-mentioned lane keeping assist function exit judgment device, and further comprising:

[0015] The vehicle-mounted sensor device is used to obtain a driving image containing lane lines and transmit the driving image to the image processing device;

[0016] an image processing device for acquiring the curvature of a curve in a driving image provided by an on-board sensor device, and transmitting the curvature of the curve to an exit determination device for a lane keeping assist function;

[0017] a vehicle stability determination device, configured to determine whether the vehicle is in a stable state based on the lateral distance between the vehicle and the lane line and the deviation angle between the vehicle's heading angle and the tangent line of the lane line, and transmit the vehicle stability determination result to the lane keeping assist function exit determination device;

[0018] A driver steering torque acquisition device, used to acquire the driver's steering torque and transmit it to the exit judgment device of the lane keeping assist function;

[0019] a timing device for obtaining the duration of the lane keeping assist function being on and the duration of the vehicle maintaining a stable state, and transmitting the information to the lane keeping assist function exit determination device;

[0020] The lane keeping assist function exit judgment device determines whether to exit the lane keeping assist function based on the received curve curvature, the driver's steering torque, the vehicle stability judgment result, the activation duration of the lane keeping assist function, and the duration of the vehicle maintaining a stable state.

[0021] As a fifth aspect of the present invention, the present invention provides an assisted driving system, including the lane keeping assist system described above.

[0022] As a sixth aspect of the present invention, the present invention provides an automobile provided with the above-mentioned assisted driving system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic diagram of vehicle stability determination parameters according to a first embodiment of the present invention;

[0024] FIG2 is a schematic diagram of a method for determining an exit of a lane keeping assist function based on curve curvature according to a first embodiment of the present invention. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0026] Example 1:

[0027] Referring to FIG2 , a method for determining when to exit a lane keeping assist function based on curve curvature includes the following steps:

[0028] S1. Calculate the timeout exit threshold, vehicle attitude stabilization time threshold, and driver takeover torque threshold based on the curve curvature; the curve curvature is obtained based on the driving image containing lane lines (preview time) obtained by the on-board sensor device (front-view camera); the greater the curve curvature, the greater the timeout exit threshold, vehicle attitude stabilization time threshold, and driver takeover torque threshold.

[0029] The calculation process of the exit time threshold T1 is as follows;

[0030]

[0031] Where T0 is the preset timeout exit threshold in the straight road, Crv is the curvature of the curve, and Crv max is the maximum curve curvature supported by the assisted driving system, T crv Add the timeout exit coefficient to the preset curve.

[0032] The calculation process of the vehicle attitude stabilization time threshold T2 is as follows;

[0033]

[0034] Where T0 ' is the preset vehicle attitude stabilization time threshold in the straight road, T crv ' Add the vehicle attitude stabilization time coefficient to the preset curve.

[0035] Driver takeover torque threshold Trq takeover The calculation process is as follows;

[0036]

[0037] Where Trq takeover0 is the preset driver takeover torque threshold in a straight road, and Trqtakeover_crv is the preset driver takeover torque coefficient superimposed on the curve.

[0038] 1 , which illustrates an application scenario of an embodiment of the present invention, when a vehicle is located in a curve with a certain curvature, a method for determining the stability of the vehicle is as follows;

[0039] Calculate the lane width value LaneWide;

[0040]

[0041] In the above formula, LaneWide max LaneWide minare the maximum lane width and minimum lane width allowed by the lane keeping assist function, and LaneWide0 is the lane width measurement value obtained based on the driving image containing lane lines obtained by the on-board sensor device.

[0042] Calculate the horizontal distance threshold Dist ' ;

[0043]

[0044] In the above formula, Dist max 、Dist min They are the preset maximum and minimum values ​​of the horizontal distance threshold respectively.

[0045] when and When , the vehicle is judged to be in a stable state; is the deviation angle, Dist is the lateral distance, is the preset deviation angle threshold, is a preset lateral distance threshold; the deviation angle is obtained based on the driving image containing lane lines obtained by the on-board sensor device.

[0046] Deviation angle ,The lateral distance Dist is defined as follows;

[0047] The sensor coordinate system is established with the installation position of the vehicle-mounted sensor device used to obtain driving images as the origin. The sensor coordinate system takes the vehicle's driving direction as the positive direction of the x-axis, the horizontal direction perpendicular to the x-axis and toward the right side of the vehicle as the positive direction of the y-axis, and the vertical upward direction as the positive direction of the z-axis. The distance from the intersection of the y-axis and the lane line to the origin is the lateral distance Dist. The tangent of the lane line is drawn at the intersection of the y-axis and the lane line. The angle between the tangent and the x-axis is the deviation angle. .

[0048] S2. If any one of the timeout judgment condition, the stability judgment condition, and the driver takeover judgment condition is currently met, the lane keeping assist function is exited.

[0049] When the Lane Keeping Assist function remains active for longer than the timeout threshold, the timeout condition is met (defined as Exit_flg1 > 0). The timeout condition is set based on the following: Since Lane Keeping Assist falls under Level 2 intelligent driving, the driver has control of the vehicle. Therefore, a maximum control time threshold should be set to ensure that the system exits after a certain period of control, and the system should not control the steering wheel for extended periods. The curvature of the lane line during the preview time is detected by the forward-looking camera. The timeout threshold, T1, varies with the curvature of the curve; as the curvature increases, the timeout threshold should increase.

[0050] When the vehicle maintains a stable state for a period exceeding the vehicle attitude stability time threshold, the stability condition is met (defined as Exit_flg2 > 0). The stability condition is set based on the following: if the vehicle drifts to one side of the lane and the Lane Keeping Assist function is activated, the Lane Keeping Assist function will control the vehicle's steering to bring it back to the center of the lane, preventing the vehicle from drifting out. This state should be maintained for a period of time to minimize the vehicle from drifting out of the lane again after control is released. The holding time T2 varies with the curvature of the curve; as the curvature increases, it should be appropriately extended.

[0051] When the driver's steering torque exceeds the driver takeover torque threshold, the driver takeover judgment condition is met (defined as Exit_flg3>0). The takeover judgment condition is set based on the following: Because driver control takes priority in L2 assisted driving, the system should exit control when it recognizes that the driver wants to take over the vehicle. This is done by using the torque sensor to identify the driver's steering torque Trq. When the driver's steering torque Trq exceeds the driver takeover steering torque threshold, the system should exit. The driver takeover steering torque threshold should change with the curvature of the curve; as the curvature increases, the driver takeover steering torque threshold should increase.

[0052] The vehicle stability is determined based on the lateral distance between the vehicle and the lane line and the deviation angle between the vehicle heading angle and the tangent line of the lane line.

[0053] Example 2:

[0054] The principles adopted in this embodiment are substantially the same as those in the first embodiment. Based on the first embodiment, this embodiment further provides a lane keeping assist system, including a lane keeping assist function exit determination device, the device being configured to execute the lane keeping assist function exit determination method based on curve curvature described in the first embodiment, and further comprising:

[0055] The vehicle-mounted sensor device is used to obtain driving images containing lane markings and transmit the driving images to the image processing device. The vehicle-mounted sensor device is a forward-looking camera, etc.

[0056] The image processing device is used to obtain the curvature of the curve in the driving image provided by the on-board sensor device and transmit the curve curvature to the lane keeping assist function's exit determination device. The greater the curve curvature, the higher the timeout exit threshold, the vehicle posture stabilization time threshold, and the driver takeover torque threshold. The calculation of the curve curvature is a conventional technique, primarily using image processing to obtain an image of the curve, and then calculating the curvature based on the curve's geometry.

[0057] The vehicle stability state judgment device is used to judge whether the vehicle is in a stable state based on the lateral distance between the vehicle and the lane line and the deviation angle between the vehicle heading angle and the tangent of the lane line, and transmit the vehicle stability state judgment result to the exit judgment device of the lane keeping assist function.

[0058] The method for determining the stable state of the vehicle is as follows:

[0059] Calculate the lane width value LaneWide;

[0060]

[0061] In the above formula, LaneWide max LaneWide min are the maximum lane width and minimum lane width allowed by the lane keeping assist function, and LaneWide0 is the lane width measurement value obtained based on the driving image containing lane lines obtained by the on-board sensor device.

[0062] Horizontal distance threshold ;

[0063]

[0064] In the above formula, Dist max 、Dist min They are the preset maximum and minimum values ​​of the horizontal distance threshold respectively.

[0065] when and When , the vehicle is judged to be in a stable state; is the deviation angle, Dist is the lateral distance, is the preset deviation angle threshold, is the preset lateral distance threshold; the deviation angle is obtained based on the driving image containing lane lines obtained by the vehicle-mounted sensor device; the deviation angle ,The lateral distance Dist is defined as follows;

[0066] The sensor coordinate system is established with the installation position of the vehicle-mounted sensor device used to obtain driving images as the origin. The sensor coordinate system takes the vehicle's driving direction as the positive direction of the x-axis, the horizontal direction perpendicular to the x-axis and toward the right side of the vehicle as the positive direction of the y-axis, and the vertical upward direction as the positive direction of the z-axis. The distance from the intersection of the y-axis and the lane line to the origin is the lateral distance Dist. The tangent of the lane line is drawn at the intersection of the y-axis and the lane line. The angle between the tangent and the x-axis is the deviation angle. .

[0067] The driver steering torque acquisition device is used to acquire the driver's steering torque and transmit it to the exit judgment device of the lane keeping assist function.

[0068] The timing device is used to obtain the duration of the lane keeping assist function being on and the duration of the vehicle maintaining a stable state, and transmit the information to the lane keeping assist function exit judgment device.

[0069] The lane keeping assist function exit judgment device determines whether to exit the lane keeping assist function based on the received curve curvature, the driver's steering torque, the vehicle stability judgment result, the activation duration of the lane keeping assist function, and the duration of the vehicle maintaining a stable state.

[0070] Specifically, the calculation process of the exit time threshold T1 is as follows;

[0071]

[0072] Where T0 is the preset timeout exit threshold in the straight road, Crv is the curvature of the curve, and Crv max is the maximum curve curvature supported by the assisted driving system, T crv Add the timeout exit coefficient to the preset curve.

[0073] The calculation process of the vehicle attitude stabilization time threshold T2 is as follows;

[0074]

[0075] Where T0 ' is the preset vehicle attitude stabilization time threshold in the straight road, T crv ' Add the vehicle attitude stabilization time coefficient to the preset curve.

[0076] Driver takeover torque threshold Trq takeover The calculation process is as follows;

[0077]

[0078] Where Trq takeover0 is the preset driver takeover torque threshold in a straight road, and Trqtakeover_crv is the preset driver takeover torque coefficient superimposed on the curve.

[0079] The lane keeping assist function is exited if any one of the timeout judgment condition, stability judgment condition and driver takeover judgment condition is currently met.

[0080] When the Lane Keeping Assist function remains active for longer than the timeout threshold, the timeout condition is met (defined as Exit_flg1 > 0). The timeout condition is set based on the following: Since Lane Keeping Assist falls under Level 2 intelligent driving, the driver has control of the vehicle. Therefore, a maximum control time threshold should be set to ensure that the system exits after a certain period of control, and the system should not control the steering wheel for extended periods. The curvature of the lane line during the preview time is detected by the forward-looking camera. The timeout threshold, T1, varies with the curvature of the curve; as the curvature increases, the timeout threshold should increase.

[0081] When the vehicle maintains a stable state for a period exceeding the vehicle attitude stability time threshold, the stability condition is met (defined as Exit_flg2 > 0). The stability condition is set based on the following: if the vehicle drifts to one side of the lane and the Lane Keeping Assist function is activated, the Lane Keeping Assist function will control the vehicle's steering to bring it back to the center of the lane, preventing the vehicle from drifting out. This state should be maintained for a period of time to minimize the vehicle from drifting out of the lane again after control is released. The holding time T2 varies with the curvature of the curve; as the curvature increases, it should be appropriately extended.

[0082] When the driver's steering torque exceeds the driver takeover torque threshold, the driver takeover judgment condition is met (defined as Exit_flg3>0). The takeover judgment condition is set based on the following: Because driver control takes priority in L2 assisted driving, the system should exit control when it recognizes that the driver wants to take over the vehicle. This is done by using the torque sensor to identify the driver's steering torque Trq. When the driver's steering torque Trq exceeds the driver takeover steering torque threshold, the system should exit. The driver takeover steering torque threshold should change with the curvature of the curve; as the curvature increases, the driver takeover steering torque threshold should increase.

[0083] The vehicle stability is determined based on the lateral distance between the vehicle and the lane line and the deviation angle between the vehicle heading angle and the tangent line of the lane line.

[0084] The above method and system are applicable to a vehicle controller for a lane keeping assist function.

[0085] Based on the above system, the present invention also provides an exit judgment device for a lane keeping assist function, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the above-mentioned method for judging the exit of the lane keeping assist function based on curve curvature is implemented.

[0086] Based on the above system, the present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the above-mentioned method for determining the exit of the lane keeping assist function based on curve curvature is implemented.

[0087] Based on the above system, the present invention also provides an assisted driving system, including the lane keeping assist system described above.

[0088] The present invention also provides a car equipped with the above-mentioned auxiliary driving system.

[0089] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for judging the exit of a lane keeping assist function based on curve curvature, including: Respectively establish linear relationships between curve curvature and timeout exit time threshold, vehicle attitude stability time threshold, and driver takeover torque threshold, so that when the curve curvature is larger, the timeout exit time threshold, vehicle attitude stability time threshold, and driver takeover torque threshold increase accordingly; calculate the timeout exit time threshold, vehicle attitude stability time threshold, and driver takeover torque threshold according to the curve curvature. If any one of the current timeout judgment condition, stability judgment condition, and driver takeover judgment condition is satisfied, then exit the lane keeping assist function. The timeout judgment condition is: the opening duration of the lane keeping assist function exceeds the timeout exit time threshold. The stability judgment condition is: the vehicle maintains a stable state and the duration exceeds the vehicle attitude stability time threshold, and the vehicle stable state is judged according to the lateral distance between the vehicle and the lane line and the deviation angle between the vehicle heading angle and the tangent of the lane line. The driver takeover judgment condition is: the driver's steering torque exceeds the driver takeover torque threshold.

2. The method for determining the exit of the lane keeping assist function based on the curve curvature according to claim 1, wherein: The calculation process of the exit time threshold T1 is as follows; Wherein, T0 is the timeout exit time threshold in the preset straight road, Crv is the curve curvature, and Crv max is the maximum curve curvature supported by the assisted driving system, and T crv is the preset curve superposition timeout exit time coefficient.

3. The method for judging the exit of the lane keeping assistance function based on the curve curvature according to claim 1, wherein: The calculation process of the vehicle attitude stability time threshold T2 is as follows; Where, T0 ’ is the vehicle attitude stability time threshold in the preset straight road, Crv is the curve curvature, and Crv max is the maximum curve curvature supported by the assisted driving system, and T crv ’ is the preset curve superposition vehicle attitude stability time coefficient.

4. The method for judging the exit of the lane keeping assistance function based on the curve curvature according to claim 1, wherein: Driver takeover torque threshold Trq takeover The calculation process is as follows; where Trq takeover0 is the driver takeover torque threshold in the preset straight road, Crv is the curve curvature, and Crv max is the maximum curve curvature supported by the assisted driving system, and Trqtakeover_crv is the preset curve superposition driver takeover torque coefficient.

5. The method for judging the exit of the lane keeping assist function based on the curve curvature according to claim 1, wherein: The method for judging the stable state of the vehicle is as follows; Calculate the calculated value of the lane width LaneWide; In the above formula, LaneWide max and LaneWide min are respectively the maximum lane width and the minimum lane width allowed by the lane keeping assist function, and LaneWide0 is the lane width measurement value obtained from the driving image containing lane lines acquired by the vehicle-mounted sensing device; Calculate the horizontal distance threshold Dist ’ ; In the above formula, Dist max and Dist min are respectively the maximum and minimum values of the preset horizontal distance threshold; When And When it is determined that the vehicle is in a stable state; among which is the deviation angle, Dist is the lateral distance, is a preset deviation angle threshold, Dist ' is a preset lateral distance threshold; the deviation angle is obtained from the driving image containing lane lines acquired by the vehicle-mounted sensing device; the deviation angle The lateral distance Dist is defined as follows; Taking the installation position of the vehicle-mounted sensing device for obtaining driving images as the origin, a sensing coordinate system is established. In the sensing coordinate system, the positive direction of the x-axis is the vehicle driving direction, the positive direction of the y-axis is the horizontal direction perpendicular to the x-axis and towards the right side of the vehicle, and the positive direction of the z-axis is the vertically upward direction; the distance from the intersection of the y-axis and the lane line to the origin is the lateral distance Dist, and at the intersection position of the y-axis and the lane line, a tangent to the lane line is made, and the angle between this tangent and the x-axis is the deviation angle 。 6. A device for judging the exit of a lane keeping assist function, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, it implements the method for judging the exit of the lane keeping assist function based on curve curvature according to any one of claims 1-5.

7. A computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the method for judging the exit of the lane keeping assist function based on curve curvature according to any one of claims 1-5.

8. A lane keeping assist system, including the device for judging the exit of the lane keeping assist function according to claim 6, and further including: An in-vehicle sensing device, configured to acquire a driving image containing lane lines and transmit the driving image to an image processing device; An image processing device, configured to acquire the curvature of a curve in the driving image according to the driving image provided by the in-vehicle sensing device and transmit the curve curvature to the device for judging the exit of the lane keeping assist function; A vehicle stable state judging device, configured to judge whether the vehicle is in a stable state according to the lateral distance between the vehicle and the lane line and the deviation angle between the vehicle heading angle and the tangent of the lane line, and transmit the vehicle stable state judgment result to the device for judging the exit of the lane keeping assist function; A driver steering torque acquisition device, configured to acquire the driver's steering torque and transmit it to the device for judging the exit of the lane keeping assist function; A timing device, configured to acquire the opening duration of the lane keeping assist function and the duration of the vehicle maintaining a stable state, and transmit them to the device for judging the exit of the lane keeping assist function; The lane keeping assist function exit determination device determines whether to exit the lane keeping assist function based on the received curve curvature, driver steering torque, vehicle stability state determination result, lane keeping assist function activation duration, and vehicle stable state duration.

9. An assisted driving system, comprising the lane keeping assist system according to claim 8.

10. A vehicle, provided with the assisted driving system according to claim 9.

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