Vehicle automatic lane changing control method

Abstract

The present invention relates to the field of vehicle automatic driving technology, and in particular to a vehicle automatic lane change control method. A vehicle automatic lane change control method, through environmental perception equipment and combined inertial navigation to perceive the driving environment and current movement conditions around the vehicle, the decision control unit integrates environmental information and driving information to determine whether the vehicle meets the lane change conditions, if the lane change conditions are met, then the torque control command is output, and the operation execution unit is operated to make the vehicle stably drive along the planned target trajectory, automatically complete the lane change action, so as to improve driving safety and reduce the driver's operating burden. The automatic lane change control method of the present invention plans the optimal lane change trajectory and the reasonable time required to complete the lane change when the surrounding environment of the vehicle permits. At the same time, the lateral and longitudinal stability of the vehicle is considered to ensure that the vehicle implements lane changes under different road conditions, prevent the vehicle from deviating from the target trajectory, and meet the comfort of the automatic lane change experience.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle automatic driving, and in particular to a vehicle automatic lane changing control method. Background Art

[0002] At present, the vehicle automatic lane change control method is generally as follows: first, using the lane line information of the vehicle, multiple cubic spline curves (or Bezier curves) are fitted as a family of feasible motion trajectories for automatic lane change; then, according to the boundary conditions, a specific optimization algorithm (such as A* algorithm, Lattice algorithm, etc.) is used to calculate an optimal target motion trajectory; then, the sensors of the autonomous vehicle are used to collect the lateral position of the vehicle, the yaw angle of the vehicle, and other information; then, based on the above target trajectory and the position information of the autonomous vehicle, the lateral position deviation and the yaw angle deviation of the autonomous vehicle are calculated; finally, the desired EPS steering angle or EPS torque is calculated for the lateral position deviation and yaw angle deviation of the autonomous vehicle through a specific algorithm (PID control, LQR control, etc.).

[0003] The above-mentioned vehicle automatic lane change control method is only applicable to ideal road conditions. In rainy and snowy weather, when the road is slippery, the vehicle is prone to instability and deviates from the target trajectory during the automatic lane change process, so the lateral and longitudinal stability of the vehicle needs to be considered. Therefore, the vehicle needs to change lanes when driving autonomously. When the surrounding environment of the vehicle allows, choosing an optimal lane change trajectory and designing a reasonable lane change completion time have become the key to a comfortable automatic lane change experience. Summary of the invention

[0004] The technical problem to be solved by the present invention is: in order to solve the problems existing in the prior art in the above-mentioned background technology, a vehicle automatic lane change control method is provided.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a vehicle automatic lane change control method, which senses the driving environment and current motion situation around the vehicle through an environmental sensing device and a combined inertial navigation system, and a decision control unit combines environmental information and driving information to determine whether the vehicle meets the lane change conditions. If the lane change conditions are met, a torque control command is output to make the vehicle stably drive along the planned target trajectory and automatically complete the lane change action;

[0006] The specific steps include:

[0007] S1. Lane recognition: Identify the left lane line of the vehicle through the environment perception device y l , right lane line y r , and the right outer lane marking on the adjacent lane on the right yrr ;

[0008] S2. Lane line confidence judgment: Calculate the lane line type, confidence, validity and effective distance to judge the lane line quality and further evaluate whether it can be used for control decision-making;

[0009] S3, target trajectory extraction: obtaining actual lane line information through step S1, processing the actual lane line information, and then extracting the target trajectory of the vehicle traveling in the lane according to the road environment;

[0010] S4, judging the driver's intention: The automatic lane change system judges whether the driver is in the active driving state. If the driver is in the active driving state, the lane change will not be performed. In other cases, the lane change will be performed from the left or right lane according to the surrounding environment;

[0011] S5, target path planning: Assume that the current lane of the vehicle is located at a distance of 100 meters from point O. ALC AO Point A of ALC , start planning the lane change trajectory. The lane change path is divided into two sections. First, plan the first driving curve section OO' and calculate the lateral offset of the planned lane change trajectory ALC AO And the ordinate of the planned path x and the horizontal axis y ; Secondly, plan the second driving curve segment O'O'' and calculate the lateral offset of the vehicle relative to the center line of the lane at this time ALC AO ′;

[0012] S6. Optimize the planned path: first calculate the lateral speed of the planned path v y and the lateral acceleration of a uniformly moving vehicle a y , and then calculate the upper limit of the lateral acceleration during steering a y max , the lower limit of longitudinal acceleration a xLim and acceleration limit a Lim , and finally calculate the shortest time to complete the lane change T sLim ;

[0013] S7, collision detection: Use sensors to detect whether there are obstacles around. If yes, return to step S5 to re-plan the target path. If no, start lane change action;

[0014] S8, Lane Change Control: First calculate the torque applied by the lateral deviation control on the EPS steering gearTorq LatErr , and then calculate the torque applied by the yaw angle deviation control to the EPS steering gear Torq HdAngle , and then calculate the feedforward compensation torque Torq fwd Finally, add the above three to get the final steering torque Torq total .

[0015] Furthermore, in step S1, the left lane line y l The calculation formula is: (i),

[0016] Right lane line y r The calculation formula is: (ii),

[0017] Right outer lane marking y rr The calculation formula is: (iii);

[0018] In formula (i), l 0 is the lateral distance of the left lane line relative to the vehicle, l 1 is the yaw angle of the left lane line, l 2 is the curvature of the left lane line, l 3 is the curvature change rate of the left lane line; in formula (ii), r 0 is the lateral distance of the right lane line relative to the vehicle, l 1 is the yaw angle of the right lane line, r 2 is the curvature of the right lane line, r 3 is the curvature change rate of the right lane line; in formula (iii), r r0 is the lateral distance of the right outer lane line relative to the vehicle, r r1 is the yaw angle of the right lane line, r r2 is the curvature of the right lane line, r r3 is the curvature change rate of the right lane line.

[0019] Furthermore, the lateral offset of the lane change trajectory planned in step S5 ALC AO The calculation formula is:

[0020] (1),

[0021] In formula (1), AO is the distance that the vehicle deviates from the center line of the lane at point O, and its calculation formula is:

[0022] (2),

[0023] Lane width is the lane width, which is calculated as:

[0024] (3),

[0025] T delta It is the timer from the start of the lane change to the end of the lane change, and its calculation formula is:

[0026] (4),

[0027] In formula (4), ΔT It is the operation cycle of the controller calling the automatic lane change algorithm software. k Is a natural number, which refers to the time from the start of the lane change to the end of the lane change k operation cycles, T s is the time required to complete the lane change;

[0028] Assume that the vehicle's speed when planning to change lanes is V O , and assuming that the vehicle maintains a constant speed during the entire lane change process, the ordinate of the planned path is x The calculation formula is:

[0029] (5),

[0030] The horizontal coordinate of the planned path y The calculation formula is:

[0031] (6);

[0032] The lateral offset of the vehicle relative to the lane centerline ALC AO ′ The calculation formula is:

[0033] (7).

[0034] Furthermore, the lateral speed of the path planned in step S6 is v y The calculation formula is:

[0035] (8),

[0036] Substituting formula (1) into formula (8), we get:

[0037] (9),

[0038] The lateral acceleration of a uniformly moving vehicle a y The calculation formula is:

[0039] (10),

[0040] Consider the longitudinal speed of the general vehicle movement during high-speed driving v o Relatively large, and the lateral speed v y＜＜ v o , so formula (10) is simplified to:

[0041] (11),

[0042] In formula (11), R is the turning radius. When a vehicle changes lanes on a curved road, the actual turning curvature of the vehicle is calculated as follows:

[0043] (12),

[0044] (13),

[0045] In formula (12) and formula (13), A 2 is the curvature of the road on which the vehicle is located. For a road with equally reliable left and right lane lines, the curvature is A The calculation formula for 2 is:

[0046] (14),

[0047] ρ is the road curvature of the planned cosine curve, and its calculation formula is:

[0048] (15),

[0049] From equations (5) and (6), we can get:

[0050] (16),

[0051] For formula (16), y Taking the first-order derivative, we get:

[0052] (17),

[0053] For formula (16), y Taking the second-order derivative, we get:

[0054] (18),

[0055] Consider the general longitudinal speed during high-speed driving v o Relatively large, and the lateral speed v y＜＜ v o , so formula (17) is simplified to:

[0056] (19),

[0057] According to formula (18) and formula (15), we can get:

[0058] (20),

[0059] Substituting formula (20) into formula (13), we get:

[0060] (twenty one),

[0061] Substituting equation (21) into equation (11), we get:

[0062] (twenty two),

[0063] Formula (22) can be simplified to:

[0064] (twenty three),

[0065] If the curvature of the lane change is large, you need to consider A 2 on the lateral acceleration, and then calculate the limit of lateral acceleration during steering, specifically:

[0066] when When a y Get the extreme value, so when A 2>0 and When the lateral acceleration is limited during turning a y max The calculation formula is:

[0067] (twenty four),

[0068] or A 2<0 and When , the lateral acceleration reaches the extreme value, and the calculation formula is:

[0069] (25),

[0070] In formula (25), the positive and negative signs only indicate whether the direction of acceleration is to the left or to the right.

[0071] Furthermore, the acceleration limit value is calculated in step S6 a Lim The road adhesion system needs to be considered μ and the acceleration due to gravity ɡ ,

[0072] For low adhesion road surfaces, when μ<0.3, the acceleration limit value a Lim The calculation formula is:

[0073] (26),

[0074] For roads with adhesion coefficient μ>=0.3, the acceleration limit value a Lim The calculation formula is:

[0075] (27),

[0076] During lane change, acceleration ≤ acceleration limit a Lim , that is:

[0077] (28),

[0078] In formula (28), a x is the longitudinal acceleration, under the condition of uniform vehicle speed, a x ≈0,

[0079] Lateral acceleration limit a y Lim Not greater than the acceleration limit a Lim , from which we can conclude:

[0080] (28').

[0081] Furthermore, the shortest time to complete the lane change is calculated in step S6. T sLim When changing lanes, first consider whether the lane change conditions are met, specifically:

[0082] like , indicating that the road curvature is too large at this time, and the lane change condition is not met, so the lane change is not performed;

[0083] like , and then calculate the minimum time required to complete the lane change;

[0084] Further judgment:

[0085] when A When 2>0, that is, the road itself is curved to the right:

[0086] if , that is, the road curvature satisfies , at this time, the vehicle can maintain a constant speed to complete the lane change, and calculate the minimum time required to complete the lane change T S , the calculation formula is:

[0087] (29),

[0088] In this case, the minimum time to complete the lane change is T sLim The calculation formula is:

[0089] (30),

[0090] when A When 2 < 0, that is, the road itself is curved to the left:

[0091] if , that is, the road curvature satisfies , at this time, the vehicle can maintain a constant speed to complete the lane change, and calculate the minimum time required to complete the lane change T S , the calculation formula is:

[0092] (31),

[0093] In this case, the minimum time to complete the lane change T sLim The calculation formula is:

[0094] (32),

[0095] In the actual lane changing process, a certain safety margin needs to be taken into account, and the time required to complete the lane change should be appropriately extended. Taking the safety factor η>1.0, we get:

[0096] (33),

[0097] Considering that the vehicle usually does not change lanes at a constant speed but at a variable speed, it is assumed that the limit of the longitudinal acceleration during the variable speed movement is a x Lim ,So:

[0098] (34),

[0099] (34′),

[0100] Substituting equation (34) into equation (24) or equation (25), we can obtain the minimum time required for the speed change motion to complete the lane change: T sLim .

[0101] Furthermore, the torque of the EPS steering gear implemented by the lateral deviation control in step S8 is calculated. Torq LatErr , specifically:

[0102] (a) Calculate the expected lateral displacement ALC AO ,

[0103] (b) Measure the actual lateral displacement value: The offset of the vehicle in the lane is measured by the environmental perception device and calculated using the following formula:

[0104] (35),

[0105] (c) Calculate the lateral deviation error value. The calculation formula is:

[0106] (36),

[0107] (d) Control of lateral deviation: The torque of the EPS steering gear applied by the lateral deviation control is calculated using the control algorithm. The calculation formula is:

[0108] (37).

[0109] Furthermore, the torque of the EPS steering gear implemented by the yaw angle deviation control in step S8 is calculated. Torq HdAngle , specifically:

[0110] (I) Calculate the desired yaw angle ALC A1 , the calculation formula is:

[0111] (38),

[0112] The longitudinal speed v x = v O , lateral speed v y According to formula (4), the following formula is obtained:

[0113] (39),

[0114] (II) Calculate the actual yaw angle: The actual yaw angle of the vehicle in the lane measured by the environment perception device is calculated using the following formula:

[0115] (40),

[0116] (III) calculating the yaw angle error value;

[0117] (41),

[0118] (IV) Control of lateral deviation: The torque applied to the EPS steering gear by yaw angle deviation control is calculated using a control algorithm. The calculation formula is:

[0119] (42),

[0120] Furthermore, the feedforward compensation torque is calculated in step S8 Torq fwd , specifically:

[0121] (A) Calculate the road curvature of the planned path: The curvature of the planned path calculated according to formula (13) ρ When a vehicle changes lanes on a curved road, the actual curvature of the vehicle is calculated to obtain ALC A2 ;

[0122] (B) Calculate the feedforward compensation torque using the following formula:

[0123] (43),

[0124] In formula (43), ɡ (ALC A2 ） is a function of the curvature of the target trajectory,

[0125] (C) Calculate the final steering torque Torq total , the calculation formula is:

[0126] (44).

[0127] Furthermore, the environmental perception device in step S1 includes a front-view camera, a side-view camera, a rear-view camera, a forward millimeter-wave radar, a corner millimeter-wave radar and a GPS; the control algorithm in step S8 includes a pid control algorithm, an LQR control algorithm and an MPC control algorithm.

[0128] Beneficial effects of the present invention: The automatic lane change control method of the present invention plans the optimal lane change trajectory and the reasonable time required to complete the lane change when the vehicle's surrounding environment permits. At the same time, it takes into account the lateral and longitudinal stability of the vehicle to ensure that the vehicle can change lanes under different road conditions, prevent the vehicle from deviating from the target trajectory, and meet the comfort of the automatic lane change experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0129] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0130] Figure 1 It is a control principle diagram for realizing the vehicle automatic lane changing control method of the present invention.

[0131] Figure 2 It is a schematic diagram of target path planning in the vehicle automatic lane changing control method of the present invention. DETAILED DESCRIPTION

[0132] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0133] like Figure 1 As shown in the figure, the method for realizing the automatic lane change control of a vehicle requires a vehicle instrument, ESP (vehicle stability program), an integrated machine (ADAS function controller), a sensor, an EMS (engine control system), a BCM (body controller), EPS (power steering), a CGW (vehicle gateway) and an IMU sensor (inertial sensor). The vehicle instrument displays information such as the request, the activation status and the set vehicle speed of the ADAS function (such as ALC (automatic lane change function) / LKA (lane keeping assist) / ACC (adaptive cruise control)); ESP is used to control the acceleration and deceleration of the vehicle; the integrated machine is used to realize the lateral and longitudinal fusion control of the vehicle (such as the lane keeping function); the sensor recognizes the external environmental information and sends the external environmental information to the ADAS controller; the EMS is used to provide power; the BCM transmits the body status to the ACC function controller; the EPS is used to realize the lane keeping and lane changing functions of the vehicle; the CGW is used to realize the communication function between CAN and the vehicle Ethernet; the IMU sensor includes the measurement of longitudinal acceleration, lateral acceleration, yaw angular velocity, etc.

[0134] There is no specific requirement for the sensor used in the vehicle automatic lane change control method of this embodiment, as long as it can collect vehicle information in the external environment. For example, some systems only have forward radar installed but no corner radar, and the lateral control function is implemented in the ADAS function controller.

[0135] The vehicle automatic lane changing control method of this embodiment senses the driving environment and current motion conditions around the vehicle through environmental sensing equipment and combined inertial navigation. The decision control unit combines environmental information with driving information to determine whether the vehicle meets the lane changing conditions. If the lane changing conditions are met, a torque control command is output to allow the vehicle to stably travel along the planned target trajectory and automatically complete the lane changing action.

[0136] The specific steps include:

[0137] S1. Lane recognition: Lane recognition is one of the key technologies of the automatic lane change system (ALC). Lane recognition is responsible for detecting and outputting the control parameters required by the automatic lane change system (ALC), including lane curvature, vehicle position relative to the lane, and heading relative to the lane. Since road scenes are easily affected by many factors such as weather, lighting, and road traffic environment, lane recognition requires both accuracy, real-time performance, and robustness.

[0138] like Figure 2 As shown, the left lane line of the vehicle is identified by the environmental perception device y l , right lane line y r , and the right outer lane marking on the adjacent lane on the right y rr ,

[0139] Left lane line y l The calculation formula is: (i),

[0140] Right lane line y r The calculation formula is: (ii),

[0141] Right outer lane marking y rr The calculation formula is: (iii);

[0142] The left lane line information is obtained through the vehicle's camera: In formula (i), l 0 is the lateral distance of the left lane line relative to the vehicle (the right side is defined as positive here), l 1 is the yaw angle of the left lane line, l 2 is the curvature of the left lane line (the right curvature is defined as positive here), l 3 is the curvature change rate of the left lane line; in formula (ii), r 0 is the lateral distance of the right lane line relative to the vehicle, r 1 is the yaw angle of the right lane line, r 2 is the curvature of the right lane line,r 3 is the curvature change rate of the right lane line; in formula (iii), r r0 is the lateral distance of the right outer lane line relative to the vehicle, r r1 is the yaw angle of the right lane line, r r2 is the curvature of the right lane line, r r3 is the curvature change rate of the right lane line.

[0143] S2. Confidence judgment of lane lines: Calculate the lane line type, confidence, validity and effective distance to judge the quality of the lane line and further evaluate whether it can be used for control decision-making. When the confidence of the lane line recognition is low or the effective distance of the lane line is short, the automatic lane change function is suppressed.

[0144] S3, target trajectory extraction: obtain the actual lane line information through step S1, process the actual lane line information, and then extract the target trajectory of the vehicle in the lane according to the road environment. After the ALC control is completed, the vehicle should be on the target trajectory, which is generally the center line of the lane. Appropriate offsets can be made for curves, single-side approach to guardrails and other road conditions. Figure 2 As shown, the target trajectory when the lane change is completed is the center line of the right lane.

[0145] S4. Determine the driver's intention: In order to avoid excessive interference of the system with the driver's operation and cause trouble to the driver during driving, the automatic lane change system (ALC) needs to determine whether the driver is in an active driving state through the turn signal lever, steering wheel torque, corner signal, accelerator pedal signal, brake pedal signal, gear position signal, etc., so as to determine whether the system function needs to be suppressed. In the decision-making process of the autonomous driving vehicle, if the vehicle speed is less than the cruise setting speed for more than a certain time (this time can be calibrated, the variable is ALC_LowSpd _Time), it means that the lane is crowded and the front vehicle is blocking the vehicle's travel. At the same time, according to the surrounding environment of the vehicle, it can be judged that the lane can be changed to overtake from the left or right lane.

[0146] S5. Target path planning: In order to make the planned path feasible and ensure that the vehicle can stably track the target trajectory, it is necessary to consider the vehicle's dynamic factors during path planning to ensure the real-time nature of path planning and the comfort of vehicle driving. The ALC system activates the lane change function at least 500m before the latest lane change point and waits for an opportunity to complete the lane change action; the lane change point should be within the interval of the dotted lane line (lane change is prohibited on the solid line); the lane change scene should meet the lane change conditions and should comply with the requirements of traffic regulations.

[0147] There are potential risks in changing lanes. The system should change lanes safely when the lane change conditions are met. If the traffic scenario cannot support safe lane changes and the lane change waiting time ALC_Holdon_Time is exceeded, the system should abandon the lane change, re-update the navigation route and plan the driving route or prompt the driver to take over.

[0148] When the vehicle is at a distance from point O ALC AO When the vehicle reaches point A, it starts planning the lane change trajectory. The lane change path planning is divided into two steps. First, the vehicle is planned to drive from point O to point O'. Before changing lanes (i.e. ), plan the first driving curve segment OO', and calculate the lateral offset of the planned lane change trajectory ALC AO And the ordinate of the planned path x and the horizontal axis y ;

[0149] (1),

[0150] In formula (1), A O is the distance that the vehicle deviates from the center line of the lane at point O, and its calculation formula is:

[0151] (2),

[0152] Lane width is the lane width, which is calculated as:

[0153] (3),

[0154] T delta It is the timer from the start of the lane change to the end of the lane change, and its calculation formula is:

[0155] (4),

[0156] In formula (4), ΔT It is the operation cycle of the controller calling the automatic lane change algorithm software. k Is a natural number, which refers to the time from the start of the lane change to the end of the lane change k operation cycles, T s is the time required to complete the lane change;

[0157] Assume that the vehicle's speed when planning to change lanes is V O , and assuming that the vehicle maintains a constant speed during the entire lane change process, the ordinate of the planned path is x The calculation formula is:

[0158] (5),

[0159] The horizontal coordinate of the planned path y The calculation formula is:

[0160] (6);

[0161] Secondly, the plan is to drive from point O' to point O", after the vehicle changes to the right lane (corresponding to time ), plan the second driving curve segment O'O''. When the vehicle passes the O' point, the left and right lane line equations perceived by the camera installed on the vehicle will change. Relatively speaking, the new left lane line perceived by the camera is transformed into yr, and the new right lane line perceived by the camera is transformed into yrr. Relative to the objects perceived by the camera at point O, they are translated by a lane line width. Therefore, this corresponds to the lateral offset relative to the vehicle. ALC AO ′, the calculation formula is as follows:

[0162] (7).

[0163] S6. Optimize the planned path: There is a parameter in the planned path above T s , that is, the time required for the transformation to complete. Here, we calculate T s The preferred value of; first calculate the lateral speed of the planned path v y , the calculation formula is:

[0164] (8),

[0165] Substituting formula (1) into formula (8), we get:

[0166] (9),

[0167] The lateral acceleration of a uniformly moving vehicle a y The calculation formula is:

[0168] (10),

[0169] Consider the longitudinal speed of the general vehicle movement during high-speed driving v o Relatively large, and the lateral speed v y＜＜ vo , so formula (10) is simplified to:

[0170] (11),

[0171] In formula (11), R is the turning radius. When a vehicle changes lanes on a curved road, the actual turning curvature of the vehicle is calculated as follows:

[0172] (12),

[0173] (13),

[0174] In formula (12) and formula (13), A 2 is the curvature of the road on which the vehicle is located. For a road with equally reliable left and right lane lines, the curvature is A The calculation formula for 2 is:

[0175] (14),

[0176] ρ is the road curvature of the planned cosine curve, and its calculation formula is:

[0177] (15),

[0178] From equations (5) and (6), we can get:

[0179] (16),

[0180] For formula (16), y Taking the first-order derivative, we get:

[0181] (17),

[0182] For formula (16), y Taking the second-order derivative, we get:

[0183] (18),

[0184] Consider the general longitudinal speed during high-speed driving v o Relatively large, and the lateral speed v y＜＜ v o , so formula (17) is simplified to:

[0185] (19),

[0186] According to formula (18) and formula (15), we can get:

[0187] (20),

[0188] Substituting formula (20) into formula (13), we get:

[0189] (twenty one),

[0190] Substituting equation (21) into equation (11), we get:

[0191] (twenty two),

[0192] Formula (22) can be simplified to:

[0193] (twenty three),

[0194] If the curvature of the lane change is large, you need to consider A 2 on the lateral acceleration, and then calculate the limit of lateral acceleration during steering, specifically:

[0195] when When a y Get the extreme value, so when A 2>0 and When the lateral acceleration is limited during turning a y max The calculation formula is:

[0196] (twenty four),

[0197] or A 2<0 and When , the lateral acceleration reaches the extreme value, and the calculation formula is:

[0198] (25),

[0199] In formula (25), the positive and negative signs only indicate whether the direction of acceleration is to the left or to the right.

[0200] Then calculate the acceleration limit value a Lim , the road adhesion system needs to be considered μ and the acceleration due to gravity ɡ ,

[0201] For low adhesion road surfaces, when μ<0.3, the acceleration limit value a Lim The calculation formula is:

[0202] (26),

[0203] For the road surface with adhesion coefficient μ>=0.3, for lane change path planning, the lateral and longitudinal acceleration and deceleration of the vehicle should not be too large. Excessive acceleration and deceleration will reduce the comfort of the occupants. Here, the acceleration limit value is set to 0.3g (g refers to the acceleration due to gravity, which is generally 9.8 m / s 2 ), acceleration limit value a Lim The calculation formula is:

[0204] (27),

[0205] During lane change, acceleration ≤ acceleration limit a Lim , that is:

[0206] (28),

[0207] Based on this, the minimum time required for lane change is solved. In formula (28), a x is the longitudinal acceleration, under the condition of uniform vehicle speed, a x ≈0;

[0208] Lateral acceleration limit a y Lim Should not exceed the acceleration limit a Lim , from which we can conclude:

[0209] (28'),

[0210] Then, determine whether the current road conditions meet the lane change conditions. , indicating that the road curvature is too large at this time, and the lane change condition is not met, so the lane change is not performed;

[0211] like , and then calculate the minimum time required to complete the lane change;

[0212] Further judgment:

[0213] when A When 2>0, that is, the road itself is curved to the right:

[0214] if , that is, the road curvature satisfies , at this time, the vehicle can maintain a constant speed to complete the lane change, and calculate the minimum time required to complete the lane change T S , the calculation formula is:

[0215] (29),

[0216] In this case, the minimum time to complete the lane change is T sLim The calculation formula is:

[0217] (30),

[0218] when A When 2 < 0, that is, the road itself is curved to the left:

[0219] if , that is, the road curvature satisfies , at this time, the vehicle can maintain a constant speed to complete the lane change, and calculate the minimum time required to complete the lane change T S , the calculation formula is:

[0220] (31),

[0221] In this case, the minimum time to complete the lane change T sLim The calculation formula is:

[0222] (32),

[0223] In the actual lane changing process, a certain safety margin needs to be taken into account, and the time required to complete the lane change should be appropriately extended. Taking the safety factor η>1.0, we get:

[0224] (33),

[0225] Finally, calculate the shortest time to complete the lane change when the vehicle changes speed T sLim ; Considering that the vehicle does not change lanes at a constant speed, but at a variable speed, it is assumed that the limit of the longitudinal acceleration during the variable speed movement is a x Lim ,So:

[0226] (34),

[0227] and (34′),

[0228] Substituting equation (34) into equation (24) or equation (25), we can obtain the minimum time required for the speed change motion to complete the lane change: T sLim .

[0229] S7, Collision Detection: Based on the longitudinal and lateral accelerations and road adhesion conditions, the required collision force to complete the lane change is calculated. TS , so that when the vehicle is at point O, it can plan Figure 2 If there are no obstacles on this planned route through the detection of sensors such as cameras and radars, the path planning is successful and the lane change can be performed.

[0230] S8, Lane Change Control: First calculate the torque applied by the lateral deviation control on the EPS steering gear Torq LatErr , specifically:

[0231] (a) Calculate the expected lateral displacement ALC AO ,

[0232] (b) Measure the actual lateral displacement value: The offset of the vehicle in the lane is measured by the environmental perception device and calculated using the following formula:

[0233] (35),

[0234] (c) Calculate the lateral deviation error value. The calculation formula is:

[0235] (36),

[0236] (d) Control of lateral deviation: The torque of the EPS steering gear applied by the lateral deviation control is calculated using the control algorithm. The calculation formula is:

[0237] (37).

[0238] Then calculate the torque applied to the EPS steering gear by the yaw angle deviation control Torq HdAngle , specifically:

[0239] (I) Calculate the desired yaw angle ALC A1 , the calculation formula is:

[0240] (38),

[0241] The longitudinal speed v x = v O , lateral speed v y According to formula (4), the following formula is obtained:

[0242] (39),

[0243] (II) Calculate the actual yaw angle: The actual yaw angle of the vehicle in the lane measured by the environment perception device is calculated using the following formula:

[0244] (40),

[0245] (III) calculating the yaw angle error value;

[0246] (41),

[0247] (IV) Control of lateral deviation: The torque applied to the EPS steering gear by yaw angle deviation control is calculated using a control algorithm. The calculation formula is:

[0248] (42),

[0249] Then calculate the feedforward compensation torque Torq fwd , specifically:

[0250] (A) Calculate the road curvature of the planned path: The curvature of the planned path calculated according to formula (13) ρ When a vehicle changes lanes on a curved road, the actual curvature of the vehicle is calculated to obtain ALC A2 ;

[0251] (B) Calculate the feedforward compensation torque using the following formula:

[0252] (43),

[0253] In formula (43), ɡ (ALC A2 ） is a function of the curvature of the target trajectory,

[0254] (C) Calculate the final steering torque Torq total , the calculation formula is:

[0255] (44).

[0256] Finally, the practical EPS assist torque also requires the calculation of the upper and lower limits of the EPS execution torque, as well as filtering and rising and falling rate limits to eliminate sudden changes. These sudden changes may be caused by the perceived lateral deviation of the lane line and the sudden change of the yaw angle. Since the output EPS execution torque part includes the difference in yaw angle multiplied by a specific constant, for example, if the yaw angle suddenly changes from -1 degree to +1 degree, the output EPS execution torque is bound to change suddenly.

[0257] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A vehicle automatic lane change control method, characterized in that: The driving environment and current motion conditions around the vehicle are sensed through environmental sensing equipment and combined inertial navigation. The decision control unit combines environmental information with driving information to determine whether the vehicle meets the lane change conditions. If the conditions are met, a torque control command is output to make the vehicle drive stably along the planned target trajectory and automatically complete the lane change action. The specific steps include: S1. Lane recognition: Identify the left lane line of the vehicle through the environment perception device y l , right lane line y r , and the right outer lane marking on the adjacent lane on the right y rr ; S2. Lane line confidence judgment: Calculate the lane line type, confidence, validity and effective distance to judge the lane line quality and further evaluate whether it can be used for control decision-making; S3, target trajectory extraction: obtaining actual lane line information through step S1, processing the actual lane line information, and then extracting the target trajectory of the vehicle traveling in the lane according to the road environment; S4, judging the driver's intention: The automatic lane change system judges whether the driver is in an active driving state. If the driver is in an active driving state, the automatic lane change system will not change lanes to overtake. In other cases, the automatic lane change system will change lanes to overtake from the left or right lane according to the surrounding environment; S5, target path planning: Assume that the current lane of the vehicle is located at a distance of 100 meters from point O. ALC AO At point A, the lane change trajectory is planned. The lane change path is divided into two sections. First, the first driving curve section OO' is planned, and the lateral offset of the planned lane change trajectory is calculated. ALC AO And the ordinate of the planned path x and the horizontal axis y ; Next, plan the second driving curve segment O'O'' and calculate the lateral offset of the vehicle relative to the lane centerline at this time. ALC AO ′; S6. Optimize the planned path: first calculate the lateral speed of the planned path v y and the lateral acceleration of a uniformly moving vehicle a y , and then calculate the limit of lateral acceleration during steering a ymax , longitudinal acceleration limit a xLim and acceleration limit a Lim , and finally calculate the shortest time to complete the lane change T sLim ; S7, collision detection: Use sensors to detect whether there are obstacles around. If yes, return to step S5 to re-plan the target path. If no, start lane change action; S8, Lane Change Control: First calculate the torque applied by the lateral deviation control on the EPS steering gear Torq LatErr , and then calculate the torque applied by the yaw angle deviation control to the EPS steering gear Torq HdAngle , and then calculate the feedforward compensation torque Torq fwd Finally, add the above three to get the final steering torque Torq total ; The left lane line in step S1 y l The calculation formula is: （i）， Right lane line y r The calculation formula is: (ii), Right outer lane marking y rr The calculation formula is: (iii); In formula (i), l 0 is the lateral distance of the left lane line relative to the vehicle, l 1 is the yaw angle of the left lane line, l 2 is the curvature of the left lane line, l 3 is the curvature change rate of the left lane line; in formula (ii), r 0 is the lateral distance of the right lane line relative to the vehicle, r 1 is the yaw angle of the right lane line, r 2 is the curvature of the right lane line, r 3 is the curvature change rate of the right lane line; In formula (iii), r r0 is the lateral distance of the right outer lane line relative to the vehicle, r r1 is the yaw angle of the right lane line, r r2 is the curvature of the right lane line, r r3 is the curvature change rate of the right lane line; The lateral offset of the lane change trajectory planned in step S5 ALC AO The calculation formula is: （1）， In formula (1), A O is the distance that the vehicle deviates from the center line of the lane at point O, and its calculation formula is: （2）， Lane width is the lane width, which is calculated as: （3）， T delta It is the timer from the start of the lane change to the end of the lane change, and its calculation formula is: （4）， In formula (4), ΔT It is the operation cycle of the controller calling the automatic lane change algorithm software. k Is a natural number, which refers to the time from the start of the lane change to the end of the lane change k operation cycles, T s is the time required to complete the lane change; Assume that the vehicle's speed when planning to change lanes is V O , and assuming that the vehicle maintains a constant speed during the entire lane change process, the ordinate of the planned path is x The calculation formula is: (5)， The horizontal coordinate of the planned path y The calculation formula is: （6）； The lateral offset of the vehicle relative to the lane centerline ALC AO ′ The calculation formula is: （7）。 2. The vehicle automatic lane change control method according to claim 1, characterized in that: The lateral speed of the path planned in step S6 v y The calculation formula is: （8）， Substituting formula (1) into formula (8), we get: （9）， The lateral acceleration of a uniformly moving vehicle a y The calculation formula is: （10）， Consider the longitudinal speed of the general vehicle movement during high-speed driving v o Relatively large, and the lateral speed v y＜＜ v o , so formula (10) is simplified to: （11）， In formula (11), R is the turning radius. When a vehicle changes lanes on a curved road, the actual turning curvature of the vehicle is calculated as follows: （12）， （13）， In formula (12) and formula (13), A 2 is the curvature of the road on which the vehicle is located. For a road with equally reliable left and right lane lines, the curvature is A The calculation formula for 2 is: （14）， ρ is the road curvature of the planned cosine curve, and its calculation formula is: （15）， From equations (5) and (6), we can get: （16）， For formula (16), y Taking the first-order derivative, we get: （17）， For formula (16), y Taking the second-order derivative, we get: （18）， Consider the general longitudinal speed during high-speed driving v o Relatively large, and the lateral speed v y＜＜ v o , so formula (17) is simplified to: （19）， According to formula (18) and formula (15), we can get: （20）， Substituting formula (20) into formula (13), we get: （21）， Substituting equation (21) into equation (11), we get: （22）， Formula (22) can be simplified to: （23）， If the curvature of the lane change is large, you need to consider A 2 on the lateral acceleration, and then calculate the limit of lateral acceleration during steering, specifically: when When a y Get the extreme value, so when A 2>0 and When the lateral acceleration is limited during turning a ymax The calculation formula is: （24）， or A 2<0 and When , the lateral acceleration reaches the extreme value, and the calculation formula is: （25）， In formula (25), the positive and negative signs only indicate whether the direction of acceleration is to the left or to the right.

3. The vehicle automatic lane change control method according to claim 2, characterized in that: The acceleration limit value is calculated in step S6. a Lim The road adhesion system needs to be considered μ and the acceleration due to gravity ɡ , For low adhesion road surfaces, when μ<0.3, the acceleration limit value a Lim The calculation formula is: （26）， For roads with adhesion coefficient μ>=0.3, the acceleration limit value a Lim The calculation formula is: （27）， During lane change, acceleration ≤ acceleration limit a Lim , that is: （28）， In formula (28), a x is the longitudinal acceleration, under the condition of uniform vehicle speed, a x ≈0, Lateral acceleration limit a y Lim Not greater than the acceleration limit a Lim , from which we can conclude: （28’）。 4. The vehicle automatic lane change control method according to claim 3, characterized in that: The shortest time to complete the lane change is calculated in step S6 T sLim When changing lanes, first consider whether the lane change conditions are met, specifically: like , indicating that the road curvature is too large at this time, and the lane change condition is not met, so the lane change is not performed; like , and then calculate the minimum time required to complete the lane change; Further judgment: when A When 2>0, that is, the road itself is curved to the right: if , that is, the road curvature satisfies , at this time, the vehicle can maintain a constant speed to complete the lane change, and calculate the minimum time required to complete the lane change T S , the calculation formula is: （29）， In this case, the minimum time to complete the lane change is T sLim The calculation formula is: （30）， when A When 2 < 0, that is, the road itself is curved to the left: if , that is, the road curvature satisfies , at this time, the vehicle can maintain a constant speed to complete the lane change, and calculate the minimum time required to complete the lane change T S , the calculation formula is: （31）， In this case, the minimum time to complete the lane change is T sLim The calculation formula is: （32）， In the actual lane changing process, a certain safety margin needs to be taken into account, and the time required to complete the lane change should be appropriately extended. Taking the safety factor η>1.0, we get: （33）， Considering that the vehicle usually does not change lanes at a constant speed but at a variable speed, it is assumed that the limit of the longitudinal acceleration during the variable speed movement is a x Lim ,So: （34）， and (34′), Substituting equation (34) into equation (24) or equation (25), we can obtain the minimum time required for the speed change motion to complete the lane change: T sLim .

5. The vehicle automatic lane change control method according to claim 2, characterized in that: The torque of the EPS steering gear implemented by the lateral deviation control in step S8 is calculated. Torq LatErr , specifically: (a) Calculate the expected lateral displacement ALC AO , (b) Measuring the actual lateral displacement value: The offset of the vehicle in the lane is measured by the environmental perception device and calculated using the following formula: （35）， (c) Calculate the lateral deviation error value using the following formula: （36）， (d) Control of lateral deviation: The torque of the EPS steering gear applied by the lateral deviation control is calculated using the control algorithm. The calculation formula is: （37）。 6. The vehicle automatic lane change control method according to claim 5, characterized in that: The torque of the EPS steering gear implemented by the yaw angle deviation control in step S8 is calculated. Torq HdAngle , specifically: (I) Calculate the desired yaw angle ALC A1 , the calculation formula is: （38）， The longitudinal speed v x = v O , lateral speed v y According to formula (4), the following formula is obtained: （39）， (II) Calculate the actual yaw angle: The actual yaw angle of the vehicle in the lane measured by the environment perception device is calculated using the following formula: （40）， (III) Calculate the yaw angle error value; （41）， (IV) Control of lateral deviation: The torque applied to the EPS steering gear by the yaw angle deviation control is calculated using a control algorithm. The calculation formula is: （42）。 7. The vehicle automatic lane change control method according to claim 6, characterized in that: In step S8, the feedforward compensation torque is calculated. Torq fwd , specifically: (A) Calculate the road curvature of the planned path: The curvature of the planned path calculated according to formula (13) ρ When a vehicle changes lanes on a curved road, the actual curvature of the vehicle is calculated to obtain ALC A2 ; (B) Calculate the feedforward compensation torque using the following formula: （43）， In formula (43), ɡ(ALC A2 ） is a function of the curvature of the target trajectory, (C) Calculate the final steering torque Torq total , the calculation formula is: （44）。 8. The vehicle automatic lane change control method according to claim 6, characterized in that: The environmental perception device in step S1 includes a front-view camera, a side-view camera, a rear-view camera, a forward millimeter-wave radar, a corner millimeter-wave radar and a GPS; the control algorithm in step S8 includes a pid control algorithm, an LQR control algorithm and an MPC control algorithm.

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