Vehicle transverse motion control method and system

Abstract

The invention provides a vehicle transverse motion control method and a vehicle transverse motion control system. The vehicle transverse motion control method comprises the steps that a feedback rotation angle is calculated based on an LQR algorithm; calculating a feed-forward rotation angle based on preview tracking control; and adding the feedback rotation angle and the feedforward rotation angle to obtain a front wheel rotation angle original value which is used for participating in vehicle transverse motion control. Through the configuration, on one hand, the advantages of simple calculation and less calculation resource occupation of the LQR algorithm and the preview tracking control algorithm can be played, and on the other hand, the control effect can be effectively improved by combining the calculation results of the LQR algorithm and the preview tracking control algorithm. The vehicle transverse motion control system is hardware for operating the control method. Both of the two can solve the problem that in the prior art, a vehicle transverse movement online control method cannot meet the requirements of actual application scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle kinematics control, and in particular to a vehicle lateral motion control method and system. Background Art

[0002] Lane centering and command lane change (or lever lane change) are comfort assistance functions in the L2 ADAS assisted driving system. These two functions control the lateral deviation movement of the vehicle based on the lane line information perceived by the camera and assist the driver in steering the steering wheel. In the lane centering function, the system controls the vehicle trajectory to track the center line of the lane and drive along the center of the lane; in the command lane change function, after the driver activates the steering lever trigger function, the system controls the vehicle to move laterally to the left or right adjacent lane when it determines that there is no risk of collision with obstacles in the adjacent lanes. After completing the lane change, the vehicle drives in the center of the corresponding lane. The lateral motion control of the assisted driving system generally uses the position deviation and orientation angle deviation of the vehicle relative to the reference line (or lane centerline) from the camera perception processing module as feedback, and uses the front wheel angle or steering wheel angle as the control output. The commonly used control methods have the following shortcomings and challenges:

[0003] (1) Using the actual position deviation and heading angle deviation as feedback, the deviation is adjusted to 0 through PID control. The main disadvantage is that the PID parameters are difficult to adjust, and multiple sets of PID parameters are required to cover the full speed range. In addition, the control targets of the position deviation and the heading angle deviation conflict with each other. The process of reducing the position deviation will inevitably increase the heading angle deviation, making it difficult to cope with large deviation conditions.

[0004] (2) The pure tracking algorithm based on the kinematic model of a two-wheeled bicycle and the geometric relationship of the preview point position is not applicable to high-speed conditions and conditions with large lateral deviations due to the relatively simplified kinematic model. It is also unable to eliminate the steady-state control deviation and has poor lane centering performance.

[0005] (3) The control based on the dynamic model of two-wheeled bicycles has high requirements on the accuracy of vehicle dynamic parameters (lateral stiffness, moment of inertia, etc.). Model mismatch caused by inaccurate parameters or simplified system model will lead to problems such as steering and steering wheel control oscillation, affecting the control effect. If the MPC (model predictive control) model predictive control method is adopted, its optimization solution process requires a lot of calculation, while the controller computing and storage resources are limited, which is not suitable for online control.

[0006] (4) In the lane centering application scenario, the center line of the ego vehicle lane is directly used as the control reference line. If the command lane change application scenario directly uses the center line of the target lane as the reference line, the initial lateral deviation is large, and the above control method is difficult to cope with. If a transition trajectory is used to switch from the center line of the ego vehicle lane to the center line of the target lane, a path planning algorithm needs to be added, which increases the complexity of the algorithm.

[0007] In summary, the online control method of vehicle lateral motion in the prior art cannot meet the needs of actual application scenarios. Summary of the invention

[0008] The object of the present invention is to provide a vehicle lateral motion control method and a vehicle lateral motion control system to meet the needs of vehicle lateral motion online control application scenarios.

[0009] In order to solve the above technical problems, the present invention provides a vehicle lateral motion control method, the vehicle lateral motion control method comprising:

[0010] The feedback steering angle is calculated based on the LQR algorithm; wherein the control deviation in the LQR algorithm is: the lateral deviation of the vehicle relative to the center line of the lane, the rate of change of the lateral deviation of the vehicle relative to the center line of the lane, the heading angle deviation of the vehicle relative to the center line of the lane, and the rate of change of the heading angle deviation of the vehicle relative to the center line of the lane.

[0011] A feedforward angle is calculated based on preview tracking control; the feedforward angle is calculated based on kinematic geometric relationship.

[0012] The feedback steering angle and the feedforward steering angle are added together to obtain an original value of the front wheel steering angle.

[0013] And, calculating the actual steering wheel angle based on the original value of the front wheel angle.

[0014] Optionally, the step of calculating the feedback angle based on the LQR control method includes: determining a scaling factor based on an operating state and kinematic parameters of the vehicle, wherein the operating state is one of the following states: a lane centering state and a command lane change state; and calculating the feedback angle by multiplying the feedback gain matrix in the LQR algorithm, the scaling factor and the control deviation and then adding them together.

[0015] Optionally, the step of determining the scaling factor based on the operating state and the kinematic parameters of the vehicle includes: if the operating state is the command lane change state, judging whether the lateral position deviation of the current vehicle is less than a preset deviation threshold according to the kinematic parameters; if so, using the first scaling factor; otherwise, using the second scaling factor.

[0016] If the motion state is the lane centering state, a third scaling factor is used.

[0017] The first scaling factor is smaller than the second scaling factor, and the third scaling factor is smaller than the second scaling factor.

[0018] Optionally, the step of calculating the feedback turning angle based on the LQR control method includes: judging the operating state based on a turn signal and an enable signal of a lane change instruction or a lane centering function.

[0019] Optionally, the step of calculating the feedforward angle based on preview tracking control includes:

[0020] A feature point coordinate sequence of a target lane boundary line or a curve coefficient of a fitting curve is obtained based on a camera; wherein the target lane boundary line includes lane boundary lines on both sides of the following lanes: a current lane, a left lane, and a right lane.

[0021] Based on the target lane boundary line, a lane center line is calculated.

[0022] Select a preview point in front of the center line of the lane.

[0023] And, the feedforward angle is calculated based on the vehicle wheelbase, the relative distance between the preview point and the vehicle, and the deviation angle between the preview point and the vehicle.

[0024] Optionally, the step of selecting a preview point in front of the center line of the lane includes: selecting the preview point based on the current vehicle speed and the curvature of the center line of the lane, the faster the vehicle speed, the farther the preview point is, and the greater the curvature of the center line of the lane, the closer the preview point is.

[0025] Optionally, the step of calculating the feedback angle based on the LQR algorithm includes:

[0026] The original lateral deviation of the vehicle relative to the center line of the lane is acquired based on the camera, and the lateral deviation e1 is obtained after limiting the original lateral deviation and its change slope.

[0027] The vehicle's orientation angle deviation e2 relative to the lane centerline is obtained based on the camera.

[0028] The rate of change of the lateral deviation of the vehicle relative to the center line of the lane is obtained based on the product of the vehicle speed and e2

[0029] And, the rate of change of the vehicle's heading angle deviation relative to the lane centerline is obtained based on the product of the vehicle speed and the lane centerline curvature minus the yaw rate

[0030] Optionally, the step of calculating the actual steering wheel angle based on the original value of the front wheel angle includes:

[0031] The first steering wheel angle control amount is calculated using the original value of the front wheel angle and the current steering wheel angle.

[0032] If the amplitude and the change rate of the first steering wheel angle control value are both within a preset range, the actual steering wheel angle is calculated directly using the first steering wheel angle control value.

[0033] Furthermore, if the amplitude or the rate of change of the first steering wheel angle control amount is not within the preset range, the first steering wheel angle control amount is limited to obtain a second steering wheel angle control amount, and the actual steering wheel angle is calculated based on the second steering wheel angle control amount.

[0034] Optionally, the vehicle lateral motion control method further includes:

[0035] Determine whether to activate the lateral control function based on vehicle status, external input commands and environmental perception status.

[0036] If the judgment result is activation, the actual steering wheel angle is output to control the vehicle movement.

[0037] And, if the judgment result is inactive, the actual steering wheel angle is not output.

[0038] In order to solve the above technical problems, the present invention further provides a vehicle lateral motion control system, the vehicle lateral motion control system comprising:

[0039] LQR feedback calculation module: used to calculate the feedback angle based on the LQR algorithm; wherein the control deviation in the LQR algorithm is: the lateral deviation of the vehicle relative to the center line of the lane, the rate of change of the lateral deviation of the vehicle relative to the center line of the lane, the heading angle deviation of the vehicle relative to the center line of the lane, and the rate of change of the heading angle deviation of the vehicle relative to the center line of the lane.

[0040] Preview pure tracking feedforward module: the feedforward angle is calculated based on the preview tracking control; the feedforward angle is calculated based on the kinematic geometric relationship.

[0041] An output module: used to obtain an original value of a front wheel steering angle based on the addition of the feedback steering angle and the feedforward steering angle; and used to calculate an actual steering wheel steering angle based on the original value of the front wheel steering angle.

[0042] Compared with the prior art, the present invention provides a vehicle lateral motion control method and a vehicle lateral motion control system, wherein the vehicle lateral motion control method includes: calculating the feedback angle based on the LQR algorithm; calculating the feedforward angle based on the preview tracking control; adding the feedback angle and the feedforward angle to obtain the original value of the front wheel angle, which is used to participate in the vehicle lateral motion control. With such a configuration, on the one hand, the advantages of the LQR algorithm and the preview tracking control algorithm in terms of simple calculation and less computing resources can be brought into play; on the other hand, combining the calculation results of the two can effectively improve the control effect. The vehicle lateral motion control system is the hardware for running the above control method. Both can solve the problem that the online control method for vehicle lateral motion in the prior art cannot meet the needs of actual application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0044] Figure 1 is a flow chart of a vehicle lateral motion control method according to an embodiment of the present invention;

[0045] Figure 2 is a schematic diagram of a control deviation according to an embodiment of the present invention;

[0046] Figure 3 It is a schematic diagram of the bicycle dynamics model;

[0047] Figure 4 Schematic diagram of geometric relationship of preview feedforward control of one embodiment of the present invention;

[0048] Figure 5 is a structural block diagram of a vehicle lateral motion control system according to an embodiment of the present invention;

[0049] Figure 6 This is the actual vehicle test result of the vehicle lateral motion control method according to one embodiment of the present invention under the following working conditions;

[0050] Figure 7 is a first actual vehicle test result of a vehicle lateral motion control method according to an embodiment of the present invention under a second working condition;

[0051] Figure 8 This is the second actual vehicle test result of the vehicle lateral motion control method according to one embodiment of the present invention under working condition 2.

[0052] in:

[0053] 1-left lane boundary line; 2-right lane boundary line; 3-lane center line; 4-feature point; 5-vehicle; 6-corresponding point; 7-center point; 8-tangent line; 9-parallel line; 10-preview point.

[0054] 20-Vehicle lateral motion control system; 21-Lane change process identification module; 22-Target lane line selection module; 23-LQR feedback deviation and gain coefficient calculation module; 24-LQR feedback item scaling coefficient selection module; 25-Pre-aiming pure tracking feedforward module; 26-LQR feedback calculation module; 27-Output module. DETAILED DESCRIPTION

[0055] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0056] As used in the present invention, the singular forms "one", "an" and "the" include plural objects, the term "or" is generally used to include the meaning of "and / or", the term "several" is generally used to include the meaning of "at least one", and the term "at least two" is generally used to include the meaning of "two or more". In addition, the terms "first", "second" and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "the proximal end" and "the distal end" generally refer to two corresponding parts, which include not only the endpoints, and the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. In addition, as used in the present invention, an element disposed on another element generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two elements, and the connection, coupling, cooperation or transmission between the two elements may be direct or indirect through an intermediate element, and cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element may be in any orientation such as inside, outside, above, below or on one side of another element, unless otherwise clearly indicated in the content. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] The core idea of ​​the present invention is to provide a vehicle lateral motion control method and a vehicle lateral motion control system to meet the needs of vehicle lateral motion online control application scenarios.

[0058] The following description is given with reference to the accompanying drawings.

[0059] Please refer to Figure 1 The present invention provides a vehicle lateral motion control method, the vehicle lateral motion control method comprising:

[0060] S10, calculating the feedback angle based on the LQR algorithm.

[0061] S20, calculating a feedforward angle based on preview tracking control; the feedforward angle is calculated based on a kinematic geometric relationship.

[0062] S30, the feedback steering angle and the feedforward steering angle are added to obtain an original value of the front wheel steering angle.

[0063] And, S40, calculating the actual steering wheel angle based on the original value of the front wheel angle.

[0064] In step S10, the control deviation in the LQR algorithm is: the lateral deviation of the vehicle relative to the lane centerline e1, the rate of change of the lateral deviation of the vehicle relative to the lane centerline The vehicle's angular deviation from the center line of the lane, e2, and the rate of change of the vehicle's angular deviation from the center line of the lane

[0065] Please refer to Figure 2 In the figure, XY represents the ground coordinate system, and Vx-Vy represents the vehicle body coordinate system. Figure 2 The left lane boundary line 1 and the right lane boundary line 2 are shown, as well as the lane center line 3 calculated based on the two, and the lane center line 3 is an imaginary line. In one embodiment, the left lane boundary line 1 and the right lane boundary line 2 are represented by a plurality of feature points 4, and can also be represented by curve fitting. The vehicle 5 has a center point 7, and there is a point on the lane center line 3 corresponding to the center point 7 (the corresponding method can be the intersection of the center point 7 along the y-axis of the vehicle body coordinate system and the lane center line 3, or other reasonable corresponding methods), which can be called the corresponding point 6. The difference between the corresponding point 6 and the center point 7 is the lateral deviation e1 of the vehicle relative to the lane center line. A tangent line 8 of the lane center line 3 can be made through the corresponding point 6, and the tangent line 8 is translated to pass through the center point 7 to obtain a parallel line 9. The angle formed by the x-axis of the vehicle body coordinate system and the parallel line 9 is the orientation angle deviation e2 of the vehicle relative to the lane center line. And are the first-order derivatives of e1 and e2 respectively. It can be understood that the above content only introduces the physical meaning of control deviation. In the actual control process, how to measure these physical quantities will use other methods.

[0066] According to the principle of LQR control, the control quantity output by LQR feedback control, that is, the feedback angle δ fbk Calculate according to the following formula: fbk =-K T *err.

[0067] Among them, the control deviation Feedback gain matrix K = [k1 k2 k3 k4] T , by selecting reasonable Q matrix and R matrix values, the linear quadratic Riccati equation is solved offline to obtain K, which is stored in the controller.

[0068] The above process can be calculated according to the standard LQR algorithm. The general process is as follows: solve the minimum value of the J cost function.

[0069]

[0070] Where J is the cost function optimized by LQR, and LQR needs to obtain the minimum cost. In the cumulative cost in the formula, the terminal state is not considered. The cost that needs to be optimized is the integral accumulation of the deviation of the system state and the control amount (front wheel angle). A and B in the system equation are obtained from the vehicle dynamics model and parameters; the weight matrices R and Q are adjustable and can be set and calibrated according to actual conditions.

[0071] According to the HJB condition, the Riccati equation can be obtained:

[0072]

[0073] And solve the optimal control rate:

[0074] u * (t) = -Q -1 (t)B T (y)P(t)x(t)=-K(t)x(t)

[0075] When the vehicle speed is constant or approximately constant, K can be considered constant, so an offline calculation can be performed. The table of the corresponding relationship between the vehicle speed and the gain coefficient can be calculated offline and stored in the controller, and can be obtained by looking up the table by the vehicle speed when the function is running.

[0076] The A and B matrices can be Figure 3 To understand, Figure 3 This is a schematic diagram of the bicycle dynamics model of a vehicle. The symbols in the figure have a unified definition in the field of vehicle dynamics, so they are not described here. The key parameters are introduced as follows: δ f is the front wheel steering angle, that is, the angle between the front wheel direction and the longitudinal axis of the vehicle; α fand α r are the sideslip angles of the front and rear wheels, i.e. the angle between the front and rear wheel speed directions and the wheels. β is the sideslip angle at the center of mass.

[0077] The system equation is as follows:

[0078]

[0079]

[0080] u(t)=[δ f ]

[0081] In this embodiment, different from the prior art, based on the feedback gain matrix K, adjustable scaling coefficients w1-w4 are further added to facilitate flexible adjustment of the proportion of each feedback item according to actual application conditions. The feedback angle is calculated as follows:

[0082]

[0083] W=[w1w2w3w4] is called a scaling factor.

[0084] Specifically, the step of calculating the feedback angle based on the LQR control method includes: determining a scaling factor based on an operating state and kinematic parameters of the vehicle, wherein the operating state is one of the following states: a lane centering state and a command lane change state; and calculating the feedback angle by multiplying the feedback gain matrix in the LQR algorithm, the scaling factor and the control deviation and then adding them together.

[0085] Furthermore, the step of determining the scaling factor based on the operating state and the kinematic parameters of the vehicle includes: if the operating state is the command lane change state, judging whether the lateral position deviation of the current vehicle is less than a preset deviation threshold according to the kinematic parameters; if so, using the first scaling factor; otherwise, using the second scaling factor.

[0086] If the motion state is the lane centering state, a third scaling factor is used.

[0087] The first scaling factor is smaller than the second scaling factor, and the third scaling factor is smaller than the second scaling factor.

[0088] The "less than" here should be understood in a broad sense. For example, the sum is less than, the weighted sum is less than, or the final control effect is less than, all of which can be considered as falling within the scope of "less than".

[0089] In a specific embodiment, the dominant feedback item is selected by setting scaling coefficients w1 to w4 under different degrees of deviation and different vehicle speeds. For the lane centering function, the initial lateral deviation is small, and the control target is to converge the lateral deviation to zero. The influence of the heading angle is not significant, and a better centering effect can be obtained by mainly using the lateral deviation e1 feedback. For the command lane change function, since the initial lateral deviation e1 is large, the lane line heading angle e2 will increase in the process of controlling the steering to reduce e1. If only the lateral deviation e1 is used as feedback, overshoot is likely to occur, which is manifested as the vehicle entering the target lane at a larger angle when entering the lane change, but the steering wheel returns to the center line late, and the steering wheel is turned in the opposite direction after crossing the center line of the target lane, resulting in a more abrupt lane change process. When the vehicle speed is high, the steering wheel will not have time to return to the center line, and the vehicle may run out of the target lane. In addition to the angle deviation e2, the deviation of the heading angle is also reflected in the lateral deviation change rate The higher the speed, the more you turn the car towards the corner. The greater the impact, this scheme mainly selects the lateral deviation e1 and its change rate The heading angle deviation e2 is used as feedback during the lane change process. The influence of the steering angle in e2 plays a "damping" role, so that the steering wheel can be returned to the center position in time during the lane changing process, and overshoot will not occur, making the lane changing process smoother.

[0090] Therefore, for the lane changing process, the lateral deviation e1 is used for judgment. If e1 is lower than the preset movement threshold (taken as 0.4m), W takes the value [0.5; 0; 0.1; 0]; if e1 is higher than the preset movement threshold, W takes the value [0.5; 0.5; 0.6; 0]. For lane centering, W takes the value [0.5; 0; 0.1; 0]. The functional differences between lane centering and command lane change are met by different values ​​of the scaling coefficient. In other embodiments, the preset movement threshold and the specific values ​​of W may also be different from this example.

[0091] In a specific embodiment, the step of calculating the feedback angle based on the LQR control method includes: judging the operating state based on a turn signal, and an enable signal of a lane change command or lane centering function, etc. The driver's steering intention and command are obtained through the turn signal, and the lateral control condition is divided into lane change and lane centering.

[0092] The step of calculating the feedforward angle based on preview tracking control comprises:

[0093] A feature point coordinate sequence of a target lane boundary line or a curve coefficient of a fitting curve is obtained based on a camera; wherein the target lane boundary line includes lane boundary lines on both sides of the following lanes: a current lane, a left lane, and a right lane.

[0094] Based on the target lane boundary line, a lane center line is calculated.

[0095] Select a preview point in front of the center line of the lane.

[0096] And, the feedforward angle is calculated based on the vehicle wheelbase, the relative distance between the preview point and the vehicle, and the deviation angle between the preview point and the vehicle.

[0097] The feature point coordinate sequence can be referenced Figure 2 A curve fitting scheme may be, for example, to fit the curve using a cubic polynomial, and then retain the coefficients of the polynomial for subsequent operations.

[0098] The geometric relationship of preview feedforward control is as follows: Figure 4 shown. Figure 4 In the formula, R represents the turning radius, α represents the deviation angle between the preview point 10 and the vehicle, ld is the relative distance between the preview point and the vehicle, and L is the wheelbase of the vehicle. Figure 4 We can calculate δ fwd =arctan(L / R), R=l d / 2sinα. Among them, δ fwd represents the feedforward angle.

[0099] Furthermore, the step of selecting the preview point in front of the lane centerline includes: selecting the preview point based on the current vehicle speed and the curvature of the lane centerline, the faster the vehicle speed, the farther the preview point is, the greater the curvature of the lane centerline, the closer the preview point is. The specific preview point selection details can be set according to actual needs, for example, proportional to the vehicle speed and inversely proportional to the curvature, or only positively correlated with the vehicle speed but not linearly, etc.

[0100] Specifically, the step of calculating the feedback angle based on the LQR algorithm includes:

[0101] Based on the camera, the original lateral deviation of the vehicle relative to the center line of the lane is obtained. When the lateral control is switched from the lane centering function to the command lane change function, the reference center line is switched from the current lane to the adjacent lane, and the original lateral deviation undergoes a step jump, which will cause a sudden change in the steering wheel angle or an excessive rate of change in the angle. By limiting the change slope of the lateral deviation, the jump of the lateral deviation e1 input to the algorithm during the transition process is avoided, and when the e1 sensed by the camera is greater than the preset upper limit, the preset upper limit is taken as e1. That is, the lateral deviation e1 is obtained after limiting the original lateral deviation and its change slope.

[0102] The vehicle's orientation angle deviation e2 relative to the lane centerline is obtained based on the camera.

[0103] The rate of change of the lateral deviation of the vehicle relative to the center line of the lane is obtained based on the product of the vehicle speed and e2 That is, Among them, v represents the vehicle speed.

[0104] And, the rate of change of the vehicle's heading angle deviation relative to the lane centerline is obtained based on the product of the vehicle speed and the lane centerline curvature minus the yaw rate That is, Where k represents the lane centerline curvature and ω represents the yaw rate.

[0105] In addition, to ensure steering comfort and safety, before the front wheel angle is converted into the steering wheel angle output, the amplitude and change rate of the steering wheel angle control value are also limited. That is, the step of calculating the actual steering wheel angle based on the original value of the front wheel angle includes:

[0106] The first steering wheel angle control amount is calculated using the original value of the front wheel angle and the current steering wheel angle.

[0107] If the amplitude and the change rate of the first steering wheel angle control value are both within a preset range, the actual steering wheel angle is calculated directly using the first steering wheel angle control value.

[0108] Furthermore, if the amplitude or the rate of change of the first steering wheel angle control amount is not within the preset range, the first steering wheel angle control amount is limited to obtain a second steering wheel angle control amount, and the actual steering wheel angle is calculated based on the second steering wheel angle control amount.

[0109] It is also necessary to determine whether the actual steering wheel angle is involved in the final vehicle motion control based on the lateral control enabling conditions. It is mainly determined based on the current vehicle state, whether the driver turns on the function, the environmental perception state, etc., and comes from the external enabling condition judgment module. Lateral control can only be enabled when the driver turns on this function, the vehicle is in a controlled state, and the lane lines are clear and complete. The steering wheel angle is output only after the lateral control is enabled, otherwise the lateral control function is not activated.

[0110] That is, the vehicle lateral motion control method further includes:

[0111] Determine whether to activate the lateral control function based on vehicle status, external input commands and environmental perception status.

[0112] If the judgment result is activation, the actual steering wheel angle is output to control the vehicle movement.

[0113] And, if the judgment result is inactive, the actual steering wheel angle is not output.

[0114] This embodiment further provides a vehicle lateral motion control system 20, and the vehicle lateral motion control system 20 includes:

[0115] Lane change process identification module 21: used to obtain turn signal signals, and enable signals of command lane change or lane centering functions, and determine the current operating state of the vehicle based on the signals. Specifically, in the command lane change operating state, the driver's turn signal is used as the start of the lane change process to trigger the command lane change lateral control. If the vehicle changes lanes to the left, the moment when the vehicle crosses the left lane line, enters the left lane and completes the centering is the end time of the lane change process; if the vehicle changes lanes to the right, the moment when the vehicle crosses the right lane line, enters the right lane and completes the centering is the end time of the lane change process. When the vehicle crosses the left lane line, it is marked by the lateral distance of the left lane line perceived by the camera suddenly changing from near zero to close to the lane width, and at the same time, the distance of the right lane line suddenly changes from close to the lane width to near zero; when the vehicle crosses the right lane line, it is marked by the opposite change trend of the left and right lane lines. The vehicle completes the centering in the corresponding lane, and it is marked by the lateral position deviation e1 and the heading angle deviation e2 decreasing and remaining within the set threshold.

[0116] Target lane line selection module 22: When the vehicle is in the command lane change state, it is used to select the corresponding target lane boundary line as the information input for lateral control according to the lane change direction (left or right) indicated by the turn signal. For left lane change, the left lane line and the left left lane line perceived by the camera are selected as the target lane line; for right lane change, the right lane line and the right right lane line are selected as the target lane line. If the lane change process is not entered or the lane change crosses the lane line, the default is lane centering, and the left and right lane lines of the vehicle are selected as the target lane lines. The corresponding lane center line can be calculated based on the selected lane lines on both sides.

[0117] The LQR feedback deviation and gain coefficient calculation module 23 is used to obtain the control deviation, store the gain coefficient (which can also be understood as a vehicle speed-gain coefficient comparison table) and output it to the LQR feedback calculation module 26.

[0118] The LQR feedback item scaling factor selection module 24 is used to determine the scaling factor based on the operating state and the kinematic parameters of the vehicle and output it to the LQR feedback calculation module 26 .

[0119] Preview pure tracking feedforward module 25: calculates the feedforward angle based on preview tracking control; the feedforward angle is calculated based on kinematic geometric relationship.

[0120] LQR feedback calculation module 26: used to calculate the feedback angle based on the LQR algorithm; the calculation method can refer to the above content.

[0121] Output module 27: used to obtain the original value of the front wheel angle based on the addition of the feedback angle and the feedforward angle; and used to calculate the actual steering wheel angle based on the original value of the front wheel angle.

[0122] The vehicle lateral motion control system further includes a lateral control enabling module (not shown), which determines whether to activate the lateral control function based on the vehicle state, external input commands and environmental perception state. The lateral control can only be enabled when the driver turns on this function, the vehicle is in a controlled state, and the lane lines are clear and complete. The lateral control enabling signal can be lateral control inactive or active. The lateral control activation includes two situations: lane centering function enabling or command lane change function enabling. If the judgment result is active, the output module 27 is driven to output the actual steering wheel angle to control the vehicle movement; and if the judgment result is inactive, the output module 27 is driven not to output the actual steering wheel angle.

[0123] This embodiment was applied to a real vehicle and tested, which proved the beneficial effect of this embodiment. The specific test conditions and test results are as follows.

[0124] Working condition 1: Lane centering condition: The vehicle is traveling at a speed of 40 km / h along a road with clear lane markings, and the lane centering function is activated.

[0125] The test results are as follows Figure 6 shown. Figure 6 In the figure, the green line is the lane centering enable signal. At t2 (indicated by the purple vertical line in the figure), it jumps from 0 to 1, and the lane centering control begins. The red line is the target lane centerline deviation. After t2, the lane centering control begins. The large fluctuation of the lane centerline deviation in the initial stage gradually decreases after the centering control. The absolute value of the lane centerline deviation continues to remain at around 0.1m, which is a small value and is significantly smaller than the initial deviation. It can be considered that it has been kept near the lane centerline.

[0126] Working condition 2: Command lane change working condition test, the vehicle is traveling at a speed of 40 km / h, moving along a road with clear lane markings, and the lane centering function is activated; the driver turns on the turn signal and the vehicle changes lanes.

[0127] The test results are as follows Figure 7 and Figure 8 As shown. Figure 7 The change of lateral deviation is shown. Figure 8 The figure shows the change of the heading angle deviation. At t1 and t2 (indicated by the purple vertical lines in the figure, the former is t1 and the latter is t2), the right turn and left turn signals are turned on respectively, and the center line of the right or left lane is selected as the target.

[0128] Figure 7In the figure, the green line is the lane centering enable signal, which remains at 1, and the red line is the target lane centerline deviation, which jumps at t1 and t2. After t1 and t2, the target lane is the adjacent lane, and the lane centerline deviation becomes the adjacent lane centerline deviation. The smallest absolute value between it and a fixed value threshold is taken as e1, which is used as the state input of the controller, and the vehicle starts to turn to reduce the deviation. After the absolute value of the lane centerline deviation drops below the fixed value threshold, it gradually decreases, and the vehicle enters the target lane. The absolute value of the lane centerline deviation gradually decreases, and after it remains within 0.4m, it can be considered that the vehicle remains in the target lane.

[0129] Figure 8 In the figure, the green line is the lane centering enable signal, which remains at 1; the light blue line is the target lane centerline angle (in radians). After t1 and t2, the lane centerline deviation becomes the adjacent lane centerline deviation, the vehicle starts to turn, and the absolute value of the target lane centerline angle increases. After the vehicle enters the target lane, the target lane becomes the current lane, the lane centering function returns the vehicle to the center, and the absolute value of the target lane centerline angle decreases. During the entire lane change process, the lane centerline angle is maintained within a small range, indicating that the lane change process is relatively smooth.

[0130] from Figure 6 to Figure 8 It can be seen from the content that this embodiment has achieved better control effect in vehicle lateral motion control.

[0131] In summary, this embodiment provides a vehicle lateral motion control method and a vehicle lateral motion control system. The vehicle lateral motion control method includes: calculating the feedback angle based on the LQR algorithm; calculating the feedforward angle based on the preview tracking control; adding the feedback angle and the feedforward angle to obtain the original value of the front wheel angle, which is used to participate in the vehicle lateral motion control. With such a configuration, on the one hand, the advantages of the LQR algorithm and the preview tracking control algorithm in terms of simple calculation and low computing resource usage can be brought into play; on the other hand, combining the calculation results of the two can effectively improve the control effect. The vehicle lateral motion control system is the hardware for running the above control method. Both can solve the problem that the online control method for vehicle lateral motion in the prior art cannot meet the needs of actual application scenarios.

[0132] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A vehicle lateral motion control method, characterized in that: The vehicle lateral motion control method comprises: The feedback angle is calculated based on the LQR algorithm; wherein the control deviation in the LQR algorithm is: the lateral deviation of the vehicle relative to the center line of the lane, the rate of change of the lateral deviation of the vehicle relative to the center line of the lane, the heading angle deviation of the vehicle relative to the center line of the lane, and the rate of change of the heading angle deviation of the vehicle relative to the center line of the lane; Calculating a feedforward angle based on preview tracking control; the feedforward angle is calculated based on a kinematic geometric relationship; The feedback steering angle and the feedforward steering angle are added to obtain an original value of the front wheel steering angle; and, The actual steering wheel angle is calculated based on the original value of the front wheel angle.

2. The vehicle lateral motion control method according to claim 1, characterized in that: The step of calculating the feedback angle based on the LQR control method comprises: determining a scaling factor based on an operating state and kinematic parameters of the vehicle, wherein the operating state is one of the following states: a lane centering state and a commanded lane change state; and, The feedback gain matrix in the LQR algorithm, the scaling factor and the control deviation are multiplied and then added to calculate the feedback angle.

3. The vehicle lateral motion control method according to claim 2, characterized in that: The step of determining the scaling factor based on the operating state and the kinematic parameters of the vehicle comprises: If the running state is the command lane change state, judging whether the lateral position deviation of the current vehicle is less than a preset deviation threshold value according to the kinematic parameters, and if so, using the first scaling factor, otherwise, using the second scaling factor; If the motion state is the lane centering state, using a third scaling factor; The first scaling factor is smaller than the second scaling factor, and the third scaling factor is smaller than the second scaling factor.

4. The vehicle lateral motion control method according to claim 2, characterized in that: The step of calculating the feedback turning angle based on the LQR control method includes: judging the operating state based on a turn signal and an enable signal of a lane change instruction or a lane centering function.

5. The vehicle lateral motion control method according to claim 1, characterized in that: The step of calculating the feedforward angle based on preview tracking control comprises: Acquire a feature point coordinate sequence of a target lane boundary line or a curve coefficient of a fitting curve based on a camera; wherein the target lane boundary line includes lane boundary lines on both sides of the following lanes: a current lane, a left lane, and a right lane; Calculating a lane centerline based on the target lane boundary line; Selecting a preview point ahead of the lane centerline; and, The feedforward turning angle is calculated based on the vehicle wheelbase, the relative distance between the preview point and the vehicle, and the deviation angle between the preview point and the vehicle.

6. The vehicle lateral motion control method according to claim 5, characterized in that: The step of selecting a preview point in front of the lane centerline includes: selecting the preview point based on the current vehicle speed and the curvature of the lane centerline, the faster the vehicle speed, the farther the preview point is, and the greater the curvature of the lane centerline, the closer the preview point is.

7. The vehicle lateral motion control method according to claim 1, characterized in that: The step of calculating the feedback angle based on the LQR algorithm comprises: Acquire the original lateral deviation of the vehicle relative to the center line of the lane based on the camera, and obtain the lateral deviation e1 after limiting the original lateral deviation and its change slope; Obtaining the vehicle's orientation angle deviation e2 relative to the lane centerline based on the camera; The rate of change of the lateral deviation of the vehicle relative to the center line of the lane is obtained based on the product of the vehicle speed and e2 as well as, The rate of change of the vehicle's heading angle deviation relative to the lane centerline is obtained by subtracting the yaw rate from the product of the vehicle speed and the lane centerline curvature.

8. The vehicle lateral motion control method according to claim 1, characterized in that: The step of calculating the actual steering wheel angle based on the original value of the front wheel angle comprises: Calculate a first steering wheel angle control value using the original value of the front wheel angle and the current steering wheel angle; If the amplitude and the change rate of the first steering wheel angle control value are both within a preset range, directly using the first steering wheel angle control value to calculate the actual steering wheel angle; and, If the amplitude or the change rate of the first steering wheel angle control amount is not within the preset range, the first steering wheel angle control amount is limited to obtain a second steering wheel angle control amount, and the actual steering wheel angle is calculated based on the second steering wheel angle control amount.

9. The vehicle lateral motion control method according to claim 1, characterized in that: The vehicle lateral motion control method further includes: Determine whether to activate the lateral control function based on the vehicle status, external input commands and environmental perception status; If the judgment result is activation, outputting the actual steering wheel angle to control the vehicle movement; and, If the judgment result is inactive, the actual steering wheel angle is not output.

10. A vehicle lateral motion control system, characterized in that: The vehicle lateral motion control system comprises: LQR feedback calculation module: used to calculate the feedback angle based on the LQR algorithm; wherein the control deviation in the LQR algorithm is: the lateral deviation of the vehicle relative to the center line of the lane, the rate of change of the lateral deviation of the vehicle relative to the center line of the lane, the heading angle deviation of the vehicle relative to the center line of the lane, and the rate of change of the heading angle deviation of the vehicle relative to the center line of the lane; Preview pure tracking feedforward module: calculates the feedforward angle based on preview tracking control; the feedforward angle is calculated based on kinematic geometric relationship; An output module: used to obtain an original value of a front wheel steering angle based on the addition of the feedback steering angle and the feedforward steering angle; and used to calculate an actual steering wheel steering angle based on the original value of the front wheel steering angle.

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