CN113311698B - Lane keeping control method, control device and vehicle - Google Patents
Lane keeping control method, control device and vehicle Download PDFInfo
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Abstract
The invention provides a lane keeping control method, a control device and a vehicle, wherein the lane keeping control method comprises the following steps: setting control parameters of a linear quadratic controller; determining the pre-aiming distance of the vehicle according to the speed of the vehicle; determining the state error feedback quantity and the road curvature compensation quantity of the vehicle according to the pre-aiming distance and the lane line information of the lane where the vehicle is located; determining the state error control quantity of the vehicle according to the control parameters and the state error feedback quantity; and controlling the vehicle to steer according to the state error control quantity and the road curvature compensation quantity. Therefore, a proper pre-aiming point can be continuously determined in the driving process of the vehicle according to different vehicle speeds, and the control compensation can be calculated and controlled by combining the pre-aiming distance and the relevant parameters of the lane line, so that the robustness of a lane keeping control algorithm is improved, the accurate automatic control of vehicle steering is realized, the vehicle can be quickly and accurately aligned under different vehicle speeds and different states, and the vehicle is ensured to drive along the center of the lane.
Description
Technical Field
The invention relates to the technical field of vehicles, in particular to a lane keeping control method, a control device and a vehicle.
Background
The lane keeping control can actively detect the transverse deviation of the vehicle during running, calculate an expected steering command in real time according to the lane line information identified by the camera and control the vehicle to run along the center of a lane. The system can reduce the burden of a driver, improve the driving comfort and reduce the occurrence of traffic accidents.
In the related art, the current lane keeping control is widely designed based on a kinematic model, as shown in fig. 1, by setting multi-point previews with different distances and distances, a PID control method is adopted to synthesize the weight coefficients of different previewing points to obtain a control quantity, but the method mainly has the following problems:
1) The stability of the high-speed running of the vehicle is difficult to ensure based on a kinematic model;
2) The PID controller is difficult to meet the design requirements of adopting a vehicle dynamic model;
3) The multi-point preview method has more controller parameters and is difficult to adjust the parameters to achieve the optimal effect.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art or the related art.
To this end, a first aspect of the invention provides a lane keeping control method.
The second aspect of the invention also provides a control device.
A third aspect of the invention also provides a vehicle.
The fourth aspect of the present invention also provides a readable storage medium.
In view of this, a first aspect of the present invention proposes a lane keeping control method including: setting control parameters of a linear quadratic controller; determining the pre-aiming distance of the vehicle according to the speed of the vehicle; determining the state error feedback quantity and the road curvature compensation quantity of the vehicle according to the pre-aiming distance and the lane line information of the lane where the vehicle is located; determining the state error control quantity of the vehicle according to the control parameters and the state error feedback quantity; and controlling the vehicle to steer according to the state error control quantity and the road curvature compensation quantity.
The lane keeping control method provided by the invention sets the control parameters of a linear quadratic form (LQR) controller, adaptively calculates the pre-aiming distance through the current speed of the vehicle, further determines the pre-aiming point, and calculates the State Error Feedback (SEF) and the road curvature compensation of the vehicle by combining the pre-aiming distance and the lane line information of the vehicle relative to the lane lines at the two sides of the lane. And determining the state error control quantity when the vehicle runs by using the control parameters and the state error feedback quantity. And finally, compensating the state error control quantity by using the road curvature compensation quantity to obtain the final steering wheel angle so as to control the vehicle to steer. According to the lane keeping control method provided by the invention, on the basis of the feedback control of the state error at the preview position, a proper preview point can be continuously determined in the vehicle driving process according to different vehicle speeds, so that the vehicle can be conveniently tracked at a certain single preview point in the driving direction, the control compensation can be calculated and controlled by combining the preview distance and the parameters related to the lane line, and the robustness of a lane keeping control algorithm is improved. And then realize accurate vehicle steering automatic control for the vehicle all can be fast, accurately return under different speed of a motor vehicle, different states, avoid the vehicle adaptive control in-process to appear the line ball, deviate lane scheduling problem, guarantee that the vehicle goes along lane center, alleviate driver's burden, promote driving comfort, and reduce the emergence of traffic accident.
According to the lane keeping control method provided by the invention, the following additional technical characteristics can be provided:
in the above technical solution, further, determining the preview distance of the vehicle according to the speed of the vehicle includes: determining the preview time according to the speed; and determining the preview distance according to the product of the preview time and the speed.
In the technical scheme, the speed of the vehicle is used for selecting proper preview time so as to predict the running condition of the vehicle in a period of time in the future, the product of the speed of the vehicle and the preview time is calculated to obtain a preview distance, and a proper transverse preview point (a certain point in the running direction of the vehicle) is continuously designed in the running process of the vehicle. On the one hand, a single preview point is selected for tracking in a speed self-adaptive mode of the vehicle, so that the preview point is guaranteed to be more consistent with the current driving condition of the vehicle, the applicability of the preview point is improved, and required parameters are effectively reduced on the basis of the real-time control precision of transverse control. On the other hand, the vehicle speed is used as a correction term to control the vehicle steering, the calculation accuracy and precision are high for a scene with a high speed, and the requirements of the vehicle in a low-speed and high-speed motion scene are met.
In the above technical solution, further, determining the preview time according to the speed includes: taking the first preview time as a preview time based on the speed being less than a first speed threshold; calculating a preview time according to the first preview time and the second preview time based on the speed being greater than or equal to a first speed threshold and less than or equal to a second speed threshold; and taking the second preview time as the preview time based on the speed being greater than the second speed threshold.
In the technical scheme, the size relation between the speed of the vehicle and a first speed threshold value and a second speed threshold value is compared, and the appropriate preview time is set according to the size relation. Specifically, if the speed is smaller than a first speed threshold value, which indicates that the current speed of the vehicle is smaller, a first large preview time is selected as preview time; if the speed is greater than the second speed threshold value, the current speed of the vehicle is larger, and a second smaller preview time is selected as preview time; and if the speed is between the first speed threshold and the second speed threshold, namely the speed is greater than or equal to the first speed threshold and is less than or equal to the second speed threshold, calculating the preview time according to the first preview time and the second preview time. I.e. the greater the speed of the vehicle, the smaller the preview time. Therefore, the preview time can be dynamically adjusted, different preview points can be adaptively calculated by utilizing different vehicle speeds, and the accuracy of vehicle transverse offset control is further improved.
Further, the preview time is calculated according to the first preview time and the second preview time, and the following formula is adopted:
wherein, t pre For preview time, V 1 Is a first speed threshold, V 2 Is a second speed threshold, the first speed threshold is less than the second speed threshold, t premax Is the first preview time, t premin The first preview time is greater than the second preview time.
It is understood that the first preview time and the second preview time can be set according to the model of the vehicle, the control precision requirement, etc., for example, the first preview time is the maximum preview time allowed by the system, and the second preview time is the minimum preview time allowed by the system.
In the above technical solution, further, determining a state error feedback quantity and a road curvature compensation quantity of the vehicle according to the pre-aiming distance and lane line information of a lane where the vehicle is located, includes: determining a center line coefficient of a lane according to lane line information; determining road curvature and state error feedback quantity of the vehicle according to the center line coefficient and the pre-aiming distance; determining a road curvature compensation quantity according to the road curvature and the target parameters of the vehicle; wherein the target parameters of the vehicle include: the speed of the vehicle, the mass of the vehicle, the moment of inertia of the vehicle about the z-axis, the distance from the front axle of the vehicle to the center of mass, the distance from the rear axle of the vehicle to the center of mass, the cornering stiffness of the front wheels of the vehicle, the cornering stiffness of the rear wheels of the vehicle.
In the technical scheme, the lane line information comprises a left lane line fitting coefficient and a right lane line fitting coefficient. And determining the center line coefficient of the lane according to the lane line information so as to analyze the position of the vehicle in the lane. The center line coefficient is used for representing the center position of the lane, the center line of the lane is also a lane symmetrical line, and the distance from the center line of the lane to lane lines (a left lane line and a right lane line) on two sides of the lane is the same. And determining the road curvature of the expected track, namely the road curvature of the track from the vehicle to the pre-aiming point, and the state error feedback quantity according to the center line coefficient and the pre-aiming distance. And finally, calculating the road curvature compensation quantity according to the road curvature and the target parameters of the vehicle, and comprehensively considering the uncertain influence of the road curvature and the target parameters of the vehicle to achieve the purpose of tracking the expected running track with high reliability and high precision. On the other hand, the state error feedback quantity and the road curvature are calculated only through the parameters related to the lane lines, the calculation algorithm is simplified, the target parameters of the vehicle and the lane line information are easy to obtain, and the application range is wide.
Specifically, a center line coefficient of the lane is determined according to the lane line information, and the following formula is adopted:
wherein, c 0l 、c 1l 、c 2l 、c 3l As left lane line fitting coefficient, c 0r 、c 1r 、c 2r 、c 3r Is the right lane line fitting coefficient, c 0 、c 1 、c 2 、c 3 Is the center line coefficient of the lane.
In any of the above technical solutions, further, a state error feedback amount is determined according to the center line coefficient and the preview distance, and the following formula is adopted:
e y ＝c 0 +c 1 x pre +c 2 x pre 2 +c 3 x pre 3 ；
e ψ ＝arctan(c 1 +2c 2 x pre +3c 3 x pre 2 )；
determining the road curvature of the vehicle according to the center line coefficient and the pre-aiming distance, and adopting the following formula:
wherein, c 0 、c 1 、c 2 、c 3 Is the center line coefficient of the lane, e y Is a lateral position deviation of the vehicle,
is the rate of change of lateral position deviation of the vehicle, e ψ Is the deviation of the heading angle of the vehicle,
is the heading angle deviation change rate of the vehicle, X is the state error feedback quantity, X pre And T is the pre-aiming distance, T is the control period of the vehicle, rho is the curvature of the road, n is the current control period, and n-1 is the previous control period.
In the technical scheme, the state error is updated and fed back to the control gain, so that the transverse control effect is more accurate.
In any of the above technical solutions, further, the road curvature compensation amount is determined according to the road curvature and the target parameter of the vehicle, and the following formula is adopted:
wherein, delta sw_c For road curvature compensation, R d Is the radius of curvature, m is the mass of the vehicle, V x As the speed of the vehicle, I z Is the moment of inertia of the vehicle about the z-axis, l f Is the distance from the front axle of the vehicle to the center of mass, l r Is the distance of the rear axle of the vehicle to the center of mass, C f For the cornering stiffness of the front wheels of the vehicle, C r For cornering stiffness of the rear wheel of the vehicle, L = L f +l r 。
In the technical scheme, the road curvature of the expected track is adopted to perform feedforward compensation on the road curvature.
In any of the above solutions, further, the control parameters of the linear quadratic controller include a first weighting matrix Q and a second weighting matrix R; q = diag [ Q = d 1 ，0，q 3 ，0]；R＝[r](ii) a Wherein r is a fixed amount, q 1 、q 3 Are variables.
In this embodiment, q 1 、q 3 And r are three control parameters respectively, r is set as a fixed value, q 1 、q 3 Is a variation, and q 1 、q 3 Is related to the speed of the vehicle. Thus only for q 1 、q 3 And r, designing a linear quadratic controller by using the three control parameters, optimizing the control model, and adopting a linear adjustment method for a weight matrix of the control parameters of the linear quadratic controller.
Determining a control gain of the vehicle according to a vehicle dynamics model, and adopting the following formula:
K＝[k 1 、k 2 、k 3 、k 4 ]；
K＝lqr(A，B，Q，R)；
wherein, A and B are matrixes of a vehicle dynamics model, K is an optimal control gain convergence matrix (control gain) calculated by MATLAB, and K is 1 、k 2 、k 3 、k 4 The four elements in the control gain convergence matrix are respectively, Q is a first weighting matrix, and R is a second weighting matrix.
In any of the above technical solutions, further, determining a state error control amount of the vehicle according to the control parameter and the state error feedback amount includes: determining a vehicle dynamic model according to the control parameters and the target parameters of the vehicle; determining a control gain of the vehicle according to the vehicle dynamics model; and determining the state error control quantity according to the product of the control gain and the state error feedback quantity.
In the technical scheme, a vehicle dynamic model is determined according to the control parameters and the target parameters of the vehicle, the optimal control gain is determined by using the vehicle dynamic model, and errors in calculation of the control gain through the position relation between the vehicle and the vehicle road are avoided. And determining the state error control quantity according to the product of the control gain and the state error feedback quantity.
It is understood that a plurality of preview points can be set to synthesize the state error control quantity through weighting coefficients.
In any of the above solutions, further, controlling the vehicle steering according to the state error control amount and the road curvature compensation amount includes: acquiring the steering transmission ratio of the vehicle; calculating the product of the sum of the state error control quantity and the road curvature compensation quantity and the steering transmission ratio to obtain the steering wheel angle of the vehicle; and controlling the vehicle to steer according to the steering wheel angle.
In the technical scheme, the expected steering wheel angle is obtained by summing the state error control quantity and the road curvature compensation quantity and multiplying the sum by the steering transmission ratio, and the steering wheel angle is output to the steer-by-wire system to control the steering of the vehicle, realize lane keeping and ensure that the vehicle can still completely eliminate the steady-state error when uncertain parameters exist.
According to a second aspect of the present invention, there is also provided a control apparatus comprising: a memory storing a program or instructions; and a processor connected with the memory, wherein the processor implements the lane keeping control method of the first aspect when executing the program or the instructions. Therefore, the control device has all the beneficial effects of the lane keeping control method provided by the first aspect, and redundant description is omitted to avoid redundancy.
According to a third aspect of the present invention, there is provided a vehicle including the control apparatus set forth in the second aspect. Therefore, the vehicle has all the beneficial effects of the control device provided by the second aspect, and redundant description is not repeated for avoiding repetition.
According to a fourth aspect of the present invention, there is provided a readable storage medium having stored thereon a program or instructions which, when executed by a processor, performs the lane-keeping control method set forth in the first aspect. Therefore, the readable storage medium has all the beneficial effects of the lane keeping control method provided by the first aspect, and redundant description is omitted for avoiding redundancy.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 illustrates a schematic diagram of a lateral motion control logic for a related art autonomous vehicle;
FIG. 2 shows one of the flow diagrams of a lane keeping control method according to one embodiment of the invention;
FIG. 3 is a second schematic flow chart of a lane keeping control method according to an embodiment of the invention;
FIG. 4 is a third flowchart of a lane-keeping control method according to an embodiment of the invention;
FIG. 5 is a fourth flowchart illustrating a lane keeping control method according to an embodiment of the present invention;
FIG. 6 shows a fifth flowchart of a lane keeping control method according to an embodiment of the present invention;
FIG. 7 shows a sixth flowchart of a lane keeping control method according to an embodiment of the present invention;
FIG. 8 illustrates a lane keeping control logic diagram in accordance with an exemplary embodiment of the present invention;
fig. 9 shows a schematic block diagram of a control device of an embodiment of the present invention.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.
A lane-keeping control method, a control apparatus, and a vehicle according to some embodiments of the invention will be described below with reference to fig. 2 to 9.
Example 1:
as shown in fig. 2, according to an embodiment of the present invention, there is provided a lane-keeping control method including:
102, setting control parameters of a linear quadratic controller;
106, determining a state error feedback quantity and a road curvature compensation quantity of the vehicle according to the pre-aiming distance and the lane line information of the lane where the vehicle is located;
and step 110, controlling the vehicle to steer according to the state error control quantity and the road curvature compensation quantity.
In this embodiment, control parameters of a Linear Quadratic (LQR) controller are set, and at the same time, a pre-aiming distance is adaptively calculated by a current speed of the vehicle, so as to determine a pre-aiming point, and a State Error Feedback (SEF) and a road curvature compensation amount of the vehicle are calculated in combination with the pre-aiming distance and lane information of the vehicle with respect to lane lines on both sides of a lane. And determining the state error control quantity when the vehicle runs by using the control parameters and the state error feedback quantity. And finally, compensating the state error control quantity by using the road curvature compensation quantity to obtain a final steering wheel angle so as to control the vehicle to steer. The lane keeping control method provided by the invention can continuously determine a proper pre-aiming point in the driving process of the vehicle according to different vehicle speeds on the basis of the feedback control of the state error at the pre-aiming position, is convenient for the tracking of a certain single pre-aiming point of the vehicle in the driving direction, can calculate, control and compensate by combining the pre-aiming distance and the parameters related to the lane line, and improves the robustness of a lane keeping control algorithm. And then realize accurate vehicle steering automatic control for the vehicle all can be fast, accurately return under different speed of a motor vehicle, different states, avoid the vehicle adaptive control in-process to appear the line ball, deviate lane scheduling problem, guarantee that the vehicle goes along lane center, alleviate driver's burden, promote driving comfort, and reduce the emergence of traffic accident.
Specifically, the speed of the vehicle may be collected by a speed sensor in the vehicle. The lane line information can be obtained by camera recognition.
Further, the control parameters of the linear quadratic controller include a first weighting matrix Q and a second weighting matrix R; q = diag [ Q ] 1 ，0，q 3 ，0]；R＝[r](ii) a Wherein q is 1 、q 3 And r is three control parameters, r is a fixed quantity, q 1 、q 3 Is a variable, q 1 、q 3 Is related to the speed of the vehicle. Thus only for q 1 、q 3 And r, designing a linear quadratic controller according to the three control parameters, and optimizing the control model, wherein a weight matrix of the control parameters of the linear quadratic controller adopts a linear adjustment method.
It is understood that the first weighting matrix Q may also be a pair of Q 1 、q 2 、q 3 、q 4 Design was performed, i.e. Q = diag [ Q ], [ Q ] 1 ，q 2 ，q 3 ，q 4 ]。
Example 2:
as shown in fig. 3, according to an embodiment of the present invention, there is provided a lane-keeping control method including:
and step 212, controlling the vehicle to steer according to the state error control quantity and the road curvature compensation quantity.
In the embodiment, the speed of the vehicle is used for selecting the appropriate preview time so as to predict the running condition of the vehicle in a future period of time, and the product of the speed of the vehicle and the preview time is calculated to obtain the preview distance so as to continuously design the appropriate preview point (a certain point in the running direction of the vehicle) in the running process of the vehicle. On the one hand, a single preview point is selected for tracking in a speed self-adaptive mode of the vehicle, the preview point is guaranteed to better accord with the current driving condition of the vehicle, and required parameters are effectively reduced on the basis of improving the applicability of the preview point and the real-time control precision of transverse control. On the other hand, the vehicle steering is controlled by using the vehicle speed as a correction term, the calculation accuracy and precision are higher for a scene with higher speed, and the requirements of the vehicle in a low-speed and high-speed motion scene are met.
Specifically, the preview distance is determined according to the product of preview time and speed, and the following formula is adopted:
x pre ＝t pre ×V x ；
wherein, t pre For preview time, V x Speed of the vehicle, x pre Is the pre-aiming distance.
It will be appreciated that the method of designing the preview point may be a high order fit to the vehicle speed.
Further, comparing the speed of the vehicle with a first speed threshold and a second speed threshold, and setting a suitable preview time according to the size relationship, wherein the following formula is specifically adopted:
wherein, t pre For preview time, V 1 Is a first speed threshold value, V 2 Is a second speed threshold, the first speed threshold is less than the second speed threshold, t premax Is the first preview time, t premin The first preview time is greater than the second preview time.
In the embodiment, if the speed is smaller than a first speed threshold value, which indicates that the current speed of the vehicle is smaller, a first large preview time is selected as preview time; if the speed is greater than the second speed threshold value, the current speed of the vehicle is larger, and a second smaller preview time is selected as preview time; and if the speed is between the first speed threshold and the second speed threshold, namely the speed is greater than or equal to the first speed threshold and is less than or equal to the second speed threshold, calculating the preview time according to the first preview time and the second preview time. I.e. the greater the speed of the vehicle, the smaller the preview time. Therefore, the preview time can be dynamically adjusted, different preview points can be calculated by utilizing different vehicle speeds in a self-adaptive manner, and the accuracy of vehicle transverse deviation control is improved.
It is understood that the first preview time and the second preview time can be set according to the model of the vehicle, the control precision requirement, etc., for example, the first preview time is the maximum preview time allowed by the system, and the second preview time is the minimum preview time allowed by the system.
Example 3:
as shown in fig. 4, according to an embodiment of the present invention, there is provided a lane-keeping control method including:
and step 314, controlling the vehicle to steer according to the state error control quantity and the road curvature compensation quantity.
Wherein the target parameters of the vehicle include: the speed of the vehicle, the mass of the vehicle, the moment of inertia of the vehicle about the z-axis, the distance from the front axle of the vehicle to the center of mass, the distance from the rear axle of the vehicle to the center of mass, the cornering stiffness of the front wheels of the vehicle, the cornering stiffness of the rear wheels of the vehicle.
In this embodiment, the lane line information includes a left lane line fitting coefficient and a right lane line fitting coefficient. And determining the center line coefficient of the lane according to the lane line information so as to analyze the position of the vehicle in the lane. The center line coefficient is used for representing the center position of the lane, the center line of the lane is also a lane symmetrical line, and the distance from the center line of the lane to lane lines (a left lane line and a right lane line) on two sides of the lane is the same. And determining the road curvature of the expected track, namely the road curvature of the track from the vehicle to the pre-aiming point, and the state error feedback quantity according to the center line coefficient and the pre-aiming distance. And finally, calculating the road curvature compensation amount according to the road curvature and the target parameters of the vehicle, on one hand, comprehensively considering the uncertain influence of the road curvature and the target parameters of the vehicle, and performing feedforward compensation on the road curvature by adopting the road curvature of the expected track so as to achieve the purpose of tracking the expected running track with high reliability and high precision. On the other hand, the state error feedback quantity and the road curvature are calculated only through the parameters related to the lane lines, the calculation algorithm is simplified, the target parameters of the vehicle and the lane line information are easy to obtain, and the application range is wide.
Specifically, the center line coefficient of the lane is determined according to the lane line information, and the following formula is adopted:
wherein the content of the first and second substances,c 0l 、c 1l 、c 2l 、c 3l as left lane line fitting coefficient, c 0r 、c 1r 、c 2r 、c 3r Is the right lane line fitting coefficient, c 0 、c 1 、c 2 、c 3 Is the center line coefficient of the lane.
Further, according to the center line coefficient and the pre-aiming distance, determining the state error feedback quantity, and adopting the following formula:
e y ＝c 0 +c 1 x pre +c 2 x pre 2 +c 3 x pre 3 ；
e ψ ＝arctan(c 1 +2c 2 x pre +3c 3 x pre 2 )；
determining the road curvature of the vehicle according to the center line coefficient and the pre-aiming distance, and adopting the following formula:
wherein, c 0 、c 1 、c 2 、c 3 Is the center line coefficient of the lane, e y Is a lateral position deviation of the vehicle,
is the rate of change of lateral position deviation of the vehicle, e ψ Is the deviation of the heading angle of the vehicle,
is the heading angle deviation change rate of the vehicle, X is the state error feedback quantity, X pre And T is the pre-aiming distance, T is the control period of the vehicle, rho is the curvature of the road, n is the current control period, and n-1 is the previous control period.
In any of the above technical solutions, further, the road curvature compensation amount is determined according to the road curvature and the target parameter of the vehicle, and the following formula is adopted:
wherein, delta sw_c For road curvature compensation, R d Is the radius of curvature, m is the mass of the vehicle, V x As the speed of the vehicle, I z Is the moment of inertia of the vehicle about the z-axis,/ f Is the distance from the front axle of the vehicle to the center of mass, l r Is the distance of the rear axle of the vehicle to the center of mass, C f Cornering stiffness of the front wheels of the vehicle, C r For cornering stiffness of rear wheels of a vehicle, L = L f +l r 。
Example 4:
as shown in fig. 5, according to an embodiment of the present invention, there is provided a lane-keeping control method including:
and step 414, controlling the vehicle to steer according to the state error control quantity and the road curvature compensation quantity.
In this embodiment, a vehicle dynamics model is determined from the control parameters and the target parameters of the vehicle, with which an optimal control gain is determined. And determining the state error control quantity according to the product of the control gain and the state error feedback quantity. Specifically, the vehicle dynamics model includes: a matrix A and a matrix B;
where m is the mass of the vehicle, V x As the speed of the vehicle, I z Is the moment of inertia of the vehicle about the z-axis,/ f Is the distance from the front axle of the vehicle to the center of mass, l r Is the distance of the rear axle of the vehicle to the center of mass, C f Cornering stiffness of the front wheels of the vehicle, C r Is the cornering stiffness of the rear wheels of the vehicle.
Determining a control gain of the vehicle according to a vehicle dynamics model, and adopting the following formula:
K＝[k 1 、k 2 、k 3 、k 4 ]；
K＝lqr(A，B，Q，R)；
where K is an optimal control gain convergence matrix (control gain) calculated by MATLAB, and K is 1 、k 2 、k 3 、k 4 Four elements in the control gain convergence matrix, respectively.
Determining the state error control quantity according to the product of the control gain and the state error feedback quantity, and adopting the following formula:
δ sw_b ＝-KX；
wherein, delta sw_b X is a state error control quantity, and X is a state error feedback quantity.
It can be understood that a plurality of preview points can be set to synthesize the state error control quantity through the weighting coefficient.
Example 5:
as shown in fig. 6, according to an embodiment of the present invention, there is provided a lane-keeping control method including:
502, setting control parameters of a linear quadratic controller;
and step 514, controlling the vehicle to steer according to the steering wheel angle.
In the embodiment, the expected steering wheel angle is obtained by summing the state error control quantity and the road curvature compensation quantity and multiplying the sum by the steering transmission ratio, and the steering wheel angle is output to the steer-by-wire system to control the vehicle to steer, so that lane keeping is realized, and the vehicle can be ensured to completely eliminate the steady-state error when uncertain parameters exist.
The steering wheel angle of the vehicle is obtained by the following formula:
δ sw ＝(δ sw_b +δ sw_c )×i；
wherein, delta sw Is the steering wheel angle, delta sw_b Is a state error control quantity, delta sw_c And i is a steering transmission ratio for the road curvature compensation quantity.
Example 6:
as shown in fig. 7, according to an embodiment of the present invention, there is provided a lane-keeping control method including:
606, setting an LQR matrix;
and step 620, judging whether the process is finished or not, if so, finishing the process, and if not, entering step 614.
In this embodiment, as shown in fig. 8, an optimal control gain is calculated through a vehicle dynamics model, at the same time, a lane line information extracted by a camera is used, different pre-aiming points are adaptively calculated according to different vehicle speeds, a state error feedback quantity is calculated, a linear quadratic optimal control (LQR) design controller is adopted, a feedforward compensation quantity is given by obtaining a road curvature through the lane line information, an error control quantity is obtained by multiplying the optimal control gain and the state error feedback quantity, then a feedforward compensation quantity is calculated on the road curvature through the lane line information, a final control quantity is obtained by summing the error control quantity and the feedforward compensation quantity, a steering wheel ratio is multiplied to obtain a desired angle of the steering wheel, and the angle is issued to a steer-by-wire system through a can bus to realize reliable lane keeping control, thereby reducing the burden of a driver, improving driving comfort and reducing the occurrence of traffic accidents.
Wherein, the LQR matrix is set as follows: the control parameters involved in the LQR controller include a weighting matrix Q and a weighting matrix R, specifically Q = diag [ Q1,0, Q3,0], R = [ R ], i.e., Q1, Q3, and R are 3 parameters in total.
Calculating a vehicle dynamics matrix: and calculating correlation matrixes A and B of a vehicle dynamics model of the controlled object according to overall parameters (target parameters) of the whole vehicle, wherein the vehicle dynamics model adopts dynamics and is designed only aiming at q1, q3 and r.
Calculating a control gain: calculating the optimal control gain K = K according to a vehicle dynamics model 1 、k 2 、k 3 、k 4 。
Calculating a preview point: actual speed V fed back according to wheel speed (speed of vehicle) of vehicle x Calculating the horizontal pre-aiming point (pre-aiming distance) x in real time pre ＝t pre ×V x Wherein, t pre Calculated by the following formula. Specifically, the preview point is calculated by multiplying the speed fed back by the vehicle by the preview time, and the long preview time is adopted at low speed and the short preview time is adopted at high speed.
Updating lane line coefficient calculation: and calculating lane center line coefficients according to the left lane line and the right lane line sensed by the camera.
Updating state error feedback quantity: calculating the transverse position deviation e according to the lane central line information y Rate of change of lateral position deviation
Course angle deviation e ψ Rate of change of course angular deviation
And obtaining the state error feedback quantity X.
e y ＝c 0 +c 1 x pre +c 2 x pre 2 +c 3 x pre 3 ；
e ψ ＝arctan(c 1 +2c 2 x pre +3c 3 x pre 2 )；
Calculating a state error control quantity: multiplying the optimal control gain and the state error feedback quantity to calculate the state error control quantity delta sw_b 。
δ sw_b ＝-KX；
Calculating the road curvature compensation quantity: calculating to obtain the road curvature compensation delta according to the lane center line coefficient sw_c The state error control quantity and the road turning radius are calculated only by the parameters related to the lane lines.
Calculating the steering wheel angle: the error feedback control quantity and the road curvature compensation quantity are summed and multiplied by a steering wheel ratio (steering transmission ratio, related to a driving device of the steering wheel) to obtain a final steering wheel angle delta sw And the steering wheel angle is sent to a steer-by-wire system through the can bus, so that lane keeping is realized.
δ sw ＝(δ sw_b +δ sw_c )×i。
Example 7:
as shown in fig. 9, an embodiment according to a second aspect of the present invention proposes a control device 900, including: a memory 902 and a processor 904. A processor, memory 902 storing a program or instructions; the processor 904 is connected to the memory 902, and the processor 904 executes the program or the instructions to implement the lane-keeping control method according to the embodiment of the first aspect. Therefore, the control device 900 has all the advantages of the lane keeping control method provided in the first embodiment, and redundant description is omitted to avoid redundancy.
Example 8:
an embodiment according to a third aspect of the invention proposes a vehicle comprising the control device proposed in the embodiment of the second aspect. Therefore, the vehicle has all the beneficial effects of the control device provided by the embodiment of the second aspect, and redundant description is not repeated for avoiding repetition.
Example 9:
an embodiment according to a fourth aspect of the present invention proposes a readable storage medium having stored thereon a program or instructions which, when executed by a processor, performs the lane-keeping control method proposed by an embodiment of the first aspect. Therefore, the readable storage medium has all the beneficial effects of the lane keeping control method provided in the embodiment of the first aspect, and redundant description is omitted to avoid redundancy.
In the present invention, the term "plurality" means two or more unless explicitly defined otherwise. The terms "mounted," "connected," "fixed," and the like are to be construed broadly and include, for example, fixed connections, detachable connections, or integral connections; "coupled" may be direct or indirect through an intermediary. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description of the present specification, the description of "one embodiment," "some embodiments," "specific embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A lane keep control method characterized by comprising:
setting control parameters of a linear quadratic controller;
determining a pre-aiming distance of a vehicle according to the speed of the vehicle;
determining the state error feedback quantity and the road curvature compensation quantity of the vehicle according to the pre-aiming distance and the lane line information of the lane where the vehicle is located;
determining a state error control quantity of the vehicle according to the control parameter and the state error feedback quantity;
controlling the vehicle to steer according to the state error control quantity and the road curvature compensation quantity;
the controlling the vehicle steering according to the state error control amount and the road curvature compensation amount includes:
acquiring a steering transmission ratio of the vehicle;
calculating the product of the sum of the state error control quantity and the road curvature compensation quantity and the steering transmission ratio to obtain the steering wheel angle of the vehicle;
and controlling the vehicle to steer according to the steering wheel angle.
2. The lane keep control method of claim 1, wherein said determining a preview distance of the vehicle based on the vehicle's speed comprises:
determining a preview time according to the speed;
and determining the preview distance according to the product of the preview time and the speed.
3. The lane keep control method of claim 2, wherein said determining a preview time based on said speed comprises:
based on the speed being less than a first speed threshold, taking a first preview time as the preview time;
taking a second preview time as the preview time based on the speed being greater than a second speed threshold;
calculating the preview time from the first preview time and the second preview time based on the speed being greater than or equal to the first speed threshold and less than or equal to the second speed threshold;
wherein the first speed threshold is less than the second speed threshold, and the first preview time is greater than the second preview time.
4. The lane-keeping control method of claim 1, wherein the determining a state error feedback amount and a road curvature compensation amount of the vehicle based on the pre-line-of-sight distance and lane line information of a lane in which the vehicle is located includes:
determining a center line coefficient of the lane according to the lane line information;
determining the road curvature of the vehicle and the state error feedback quantity according to the center line coefficient and the pre-aiming distance;
determining the road curvature compensation quantity according to the road curvature and the target parameters of the vehicle;
wherein the target parameters of the vehicle include: the speed, the mass of the vehicle, the moment of inertia of the vehicle about the z-axis, the distance from the front axis to the center of mass of the vehicle, the distance from the rear axis to the center of mass of the vehicle, the cornering stiffness of the front wheels of the vehicle, the cornering stiffness of the rear wheels of the vehicle.
5. The lane-keeping control method according to claim 1,
the control parameters comprise a first weighting matrix Q and a second weighting matrix R;
Q＝diag[q 1 ，0，q 3 ，0]；
R＝[r]；
wherein r is a fixed amount, q 1 、q 3 Are variables.
6. The lane keep control method according to claim 1, wherein the determining the state error control amount of the vehicle based on the control parameter and the state error feedback amount includes:
determining a vehicle dynamic model according to the control parameters and the target parameters of the vehicle;
determining a control gain for the vehicle based on the vehicle dynamics model;
determining the state error control quantity according to the product of the control gain and the state error feedback quantity;
wherein the control gain of the vehicle is determined according to the vehicle dynamics model using the following formula:
K＝[k 1 、k 2 、k 3 、k 4 ]；
K＝lqr(A，B，Q，R)；
wherein A and B are matrixes of the vehicle dynamics model, K is control gain, and K is 1 、k 2 、k 3 、k 4 Four elements in the control gain, Q is a first weighting matrix, and R is a second weighting matrix.
7. The lane keep control method according to claim 4,
and determining the state error feedback quantity according to the center line coefficient and the pre-aiming distance, and adopting the following formula:
e y ＝c 0 +c 1 x pre +c 2 x pre 2 +c 3 x pre 3 ；
e ψ ＝arctan(c 1 +2c 2 x pre +3c 3 x pre 2 )；
determining the road curvature of the vehicle according to the center line coefficient and the pre-aiming distance, and adopting the following formula:
determining the road curvature compensation quantity according to the road curvature and the target parameters of the vehicle, and adopting the following formula:
wherein, c 0 、c 1 、c 2 、c 3 Is the center line coefficient, e y Is a lateral position deviation of the vehicle,
is the rate of change of lateral position deviation of the vehicle, e ψ Is the deviation of the course angle of the vehicle,
is the course angle deviation change rate of the vehicle, X is the state error feedback quantity, X pre For the pre-sight distance, T is the control period of the vehicle, ρ is the road curvature, δ sw_c N is the current control period, n-1 is the previous control period, R is the road curvature compensation quantity d Is the radius of curvature, m is the mass of the vehicle, V x As the speed of the vehicle, /) f Is the distance from the front axle of the vehicle to the center of mass,/ r Is the distance of the rear axle of the vehicle to the center of mass, C f Cornering stiffness of the front wheels of the vehicle, C r For cornering stiffness of the rear wheel of the vehicle, L = L f +l r ，K 3 To control one element in the gain convergence matrix.
8. A control device, characterized by comprising:
a memory storing a program or instructions;
a processor connected with the memory, the processor implementing the lane-keeping control method of any one of claims 1 to 7 when executing the program or the instructions.
9. A vehicle characterized by comprising the control apparatus according to claim 8.
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