CN114771526B - Longitudinal vehicle speed control method and system for automatic lane changing - Google Patents

Longitudinal vehicle speed control method and system for automatic lane changing Download PDF

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CN114771526B
CN114771526B CN202210395665.1A CN202210395665A CN114771526B CN 114771526 B CN114771526 B CN 114771526B CN 202210395665 A CN202210395665 A CN 202210395665A CN 114771526 B CN114771526 B CN 114771526B
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longitudinal
vehicle
automatic
planning
speed
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CN114771526A (en
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谯睿智
贺勇
孔周维
邱利宏
任凡
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Chongqing Changan Automobile Co Ltd
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Chongqing Changan Automobile Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
    • B60W30/18—Propelling the vehicle
    • B60W30/18009—Propelling the vehicle related to particular drive situations
    • B60W30/18163—Lane change; Overtaking manoeuvres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2552/00—Input parameters relating to infrastructure
    • B60W2552/53—Road markings, e.g. lane marker or crosswalk
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2554/00—Input parameters relating to objects
    • B60W2554/40—Dynamic objects, e.g. animals, windblown objects
    • B60W2554/402—Type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2554/00—Input parameters relating to objects
    • B60W2554/40—Dynamic objects, e.g. animals, windblown objects
    • B60W2554/404—Characteristics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2554/00—Input parameters relating to objects
    • B60W2554/40—Dynamic objects, e.g. animals, windblown objects
    • B60W2554/404—Characteristics
    • B60W2554/4041—Position
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2554/00—Input parameters relating to objects
    • B60W2554/80—Spatial relation or speed relative to objects
    • B60W2554/802—Longitudinal distance
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Traffic Control Systems (AREA)
  • Control Of Driving Devices And Active Controlling Of Vehicle (AREA)

Abstract

The invention discloses a longitudinal vehicle speed control method and a longitudinal vehicle speed control system for automatic lane changing, wherein the method comprises the following steps of S1, acquiring surrounding environment information of a vehicle; s2, judging whether to start automatic channel changing, if so, executing the next step; s3, judging whether an automatic channel changing safety condition is met according to surrounding environment information, if so, starting channel changing, otherwise, executing the next step; s4, longitudinally planning a target space for automatic channel changing according to surrounding environment information to obtain a plurality of feasible longitudinal planning schemes; s5, deciding an optimal scheme from a plurality of feasible longitudinal planning schemes; s6, generating a longitudinal control instruction according to the optimal scheme, and checking whether the book meets the automatic channel changing safety condition after the longitudinal control instruction is executed; s7, executing the longitudinal control instruction and starting channel changing. According to the invention, the longitudinal planning problem of automatic lane changing is accurately modeled, the nonlinear optimization is utilized to solve the accurate solution, and the accuracy and the success rate of planning are greatly improved through the real-time verification of constraint.

Description

Longitudinal vehicle speed control method and system for automatic lane changing
Technical Field
The invention belongs to the technical field of automatic driving, and particularly relates to a longitudinal vehicle speed control method and system for automatic lane changing.
Background
With the development of artificial intelligence technology, multi-sensor fusion technology and control decision technology, the demand for automatic driving automobiles is also increasing. According to the use scene, technical ability, etc. of the automatic driving car, it can be classified into L1 to L5 without grades. Where L2 is advanced driving assistance, L3 is conditional automatic driving, L4 is full automatic driving of a defined area, and L5 is full automatic driving.
The industry is currently focusing on mass production of L2-L3 level autopilot technology, which is mainly aimed at limited autopilot capability in urban expressway and expressway scenes. The vehicle has the main functions of lane centering running, vehicle self-adaptive cruising, vehicle automatic lane changing and the like.
For point-to-point automatic driving tasks of structured roads such as expressways, the automatic driving system is required to have the capabilities of automatic ramp up and down, automatic switching and interactive driving, automatic overtaking and lane changing and the like besides basic lane centering and vehicle self-adaptive cruising. Wherein the automatic overtaking lane changing function refers to when the navigation path is opened: (1) When the vehicle runs on the lane and the vehicle flow speed of the adjacent lane is high, the vehicle can automatically execute the overtaking lane changing instruction so as to improve the overall passing efficiency; (2) The lane is automatically changed to a lane which can enter and exit the ramp or enter and exit the interchange, so that the driving of the next stage can be completed.
In the scene of automatic lane changing, there may be a situation that the target lane and the vehicle of the lane occupy the lane changing space of the vehicle, and at this time, the system is required to automatically perform longitudinal decision planning and adjust the vehicle speed so as to smoothly and safely complete the lane changing action.
The Chinese patent CN202110604908.3 discloses an automatic driving longitudinal planning method, a system and a vehicle for creating a lane change condition, and describes a method for creating a safe lane change condition through active acceleration and deceleration, wherein the method traverses all possible acceleration and deceleration schemes to find a feasible scheme so as to meet the safe lane change condition. However, by using the traversal method, the solving precision is rough, and meanwhile, along with the complexity of the constraint problem, the feasible solution is difficult to obtain.
Disclosure of Invention
In order to solve the problems, the invention provides a longitudinal vehicle speed control method and a longitudinal vehicle speed control system for automatic lane changing, which are used for accurately modeling a longitudinal planning problem of automatic lane changing, solving an accurate solution by utilizing nonlinear optimization, and greatly improving the planning precision and success rate through real-time verification of constraint.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a longitudinal vehicle speed control method for automatic lane changing comprises the following steps,
S1, acquiring surrounding environment information of a vehicle;
s2, judging whether to start automatic channel changing, if so, executing the next step;
s3, judging whether an automatic channel changing safety condition is met according to surrounding environment information, if so, starting channel changing, otherwise, executing the next step;
S4, longitudinally planning a target space for automatic channel changing according to surrounding environment information to obtain a plurality of feasible longitudinal planning schemes;
s5, deciding an optimal scheme from a plurality of feasible longitudinal planning schemes;
s6, generating a longitudinal control instruction according to the optimal scheme, and checking whether the book meets the automatic channel changing safety condition after the longitudinal control instruction is executed;
s7, executing the longitudinal control instruction and starting channel changing.
As optimization, the surrounding environment information comprises surrounding vehicle target information and lane line information which are acquired in real time through an on-vehicle sensor, and a corresponding relation is established between the vehicle target information and the lane line information; the vehicle target information comprises the position, speed and type of surrounding vehicles; the lane line information comprises lane line coefficients, lengths and types.
As optimization, the automatic lane change safety conditions comprise that the relative longitudinal distance between the vehicle and the target vehicle is larger than a preset distance, and the relative vehicle speed is smaller than a preset vehicle speed.
As an optimization, step S4 includes,
S401, searching target spaces of all the replaceable channels according to surrounding environment information;
S402, determining a front vehicle and a rear vehicle for each target space;
S403, using the vehicle as acceleration and deceleration and uniform motion, and establishing a nonlinear optimization model for uniform motion by a front vehicle and a rear vehicle;
s404, solving the model, and obtaining an optimal solution corresponding to each target space as a feasible longitudinal planning scheme.
As an optimization, step S403 includes,
S4031, setting a longitudinal speed adjustment time length of the vehicle and a planned acceleration and deceleration speed a 1, wherein the time length comprises an acceleration and deceleration time length t 1 and a constant speed time length t 2;
S4032, setting a safety constraint condition,
t1,t2≥0 (1)
amin≤a1≤amax (2)
Tmin≤t1+t2≤Tmax (3)
Wherein w 1/w2/w3 is three weight coefficients of the performance index related to driving style, a h is the current acceleration and deceleration of the vehicle,For the longitudinal distance from the host vehicle to the front vehicle at time (t 1+t2), V front is the front vehicle speed,/>For the longitudinal distance from the rear vehicle to the host vehicle at time (t 1+t2), V rear is the rear vehicle speed,/>For the longitudinal distance from the host vehicle to the host vehicle before the host vehicle lane at the time (t 1+t2), V hostfront speed of the host vehicle before the host vehicle lane,/>The speed of the vehicle at the moment (T 1+t2), T dis is a safe time interval calibration quantity, and T vel is a safe relative speed calibration quantity;
S4033, setting a performance index f (a 1,t1,t2) related to a 1,t1,t2, introducing a weight coefficient related to driving style, calculating a 1,t1,t2 value when f (a 1,t1,t2) is minimum on the premise of meeting the safety constraint condition,
min f(a1,t1,t2)＝(t1+t2)w1+(t1a1)2w2+(ah-a1)2w3 (10)
The calculation model is that,
In step S404, the model is solved according to a sequential quadratic programming algorithm, a 1,t1,t2 corresponding to each target space is calculated, and the optimal value f (a 1,t1,t2) when the flag bit and the performance index are minimum is output.
In step S5, the minimum longitudinal planning scheme is selected from the plurality of optimal values f (a 1,t1,t2) as the optimal scheme.
As an optimization, step S6, comprising,
S601, calculating accumulated time t from the moment of obtaining the optimal scheme, and taking expected acceleration and deceleration a t as a longitudinal control instruction:
s602, checking whether the longitudinal control instruction meets a safety constraint condition after execution is completed;
S603, if yes, continuing to output a longitudinal control instruction a t, otherwise, returning to S4 for re-planning;
S604, judging that t is more than or equal to t 1+t2, if yes, finishing longitudinal speed regulation, returning to the step S2, judging whether the current moment meets the automatic channel switching safety condition, and if not, returning to the step S601 to generate a longitudinal control instruction of the next period; if not, the vertical control command a t is continuously output.
Based on the method, the invention also provides a longitudinal vehicle speed control system for automatic lane changing, which comprises,
The environment sensing system is used for acquiring surrounding environment information of the vehicle;
The upper-layer action decision system is used for making a decision on automatic channel switching, outputting an automatic channel switching instruction and scheduling tasks of each stage of automatic channel switching;
the longitudinal planning system is used for planning a plurality of feasible longitudinal planning schemes by combining surrounding environment information;
The longitudinal decision system is used for deciding an optimal longitudinal planning scheme from a plurality of feasible longitudinal planning schemes;
And the longitudinal control system is used for issuing the optimal longitudinal planning scheme to the executor for control execution and checking the automatic lane change safety condition by combining the surrounding environment information.
Compared with the prior art, the invention has the following advantages:
The invention obtains environmental information by using sensors such as the angle radar, the camera and the like of the mass production, carries out longitudinal decision planning of automatic lane changing, and has reliable and mature hardware scheme and controllable cost. The calculation method based on the nonlinear optimization algorithm is mature, is easy to be transplanted to the environment of the embedded controller for operation, and meets the performance requirement of vehicle-mounted calculation. The longitudinal decision result is close to the intention of the driver, and the user experience is good. The longitudinal decision style can be calibrated through weight parameters, and the conservative, common, aggressive and other driver styles can be reflected well.
Drawings
FIG. 1 is a block diagram of an overall architecture of the present invention;
FIG. 2 is an overall design of the present invention;
FIG. 3 is a basic timing diagram of the present invention.
Detailed Description
The invention will be further described with reference to the drawings and examples.
Examples: referring to fig. 1, the following steps are exemplified by lane change to the left unless otherwise specified.
A longitudinal vehicle speed control method for automatic lane changing comprises the following steps,
S1, acquiring surrounding environment information of the vehicle.
Specifically, information (including position, speed, type) of a surrounding vehicle and other targets is acquired, and information (including lane line coefficients, length, type) of surrounding lane lines corresponds to the vehicle targets on each lane. As shown in fig. 2, the host vehicle is HV, the host vehicle is right front target 1, left front target 3, right front target 4, left side target 7, right side target 8, left rear target 9, right rear target 10, and right rear target 11.
S2, judging whether to start automatic channel changing, if so, executing the next step.
Specifically, if the upper-layer action decision system outputs an instruction that the host vehicle needs to actively change lanes to the left, it needs to determine whether the states of the target No. 1, the target No. 3, the target No. 7 and the target No. 9 meet the safety conditions of lane change of the host vehicle. Here, the target No. 3 is taken as a front vehicle, and the host vehicle is taken as a rear vehicle (similarly, when the target No. 9 and the host vehicle are judged, the host vehicle is the front vehicle, and the target No. 9 is the rear vehicle).
S3, judging whether an automatic channel changing safety condition is met according to surrounding environment information, if so, starting channel changing, otherwise, executing the next step;
Specifically, the automatic lane change safety conditions comprise,
1. The relative longitudinal distance between the front car and the rear car is required to be larger than or equal to a certain value:
Slong≥Vrear*Tdis (16)
S long is the absolute longitudinal distance from the rear vehicle to the front vehicle, V rear is the speed of the rear vehicle, T dis is the safety time interval calibration quantity, and generally 0.2-0.5 is taken according to the speed;
2. The relative speed of the front vehicle and the rear vehicle is less than or equal to a certain value:
S long is the absolute longitudinal distance from the rear vehicle to the front vehicle, V front is the speed of the front vehicle, V rear is the speed of the rear vehicle, T vel is the safety relative vehicle speed standard quantity, and generally 5-6 is taken according to the speed;
If the channel changing safety condition is met, directly executing the channel changing, otherwise executing the next step.
S4, carrying out longitudinal planning on the automatic lane change target space according to surrounding environment information, and obtaining a plurality of feasible longitudinal planning schemes. The step S4 includes the steps of,
S401, searching target spaces of all the replaceable channels according to surrounding environment information;
S402, determining a front vehicle and a rear vehicle for each target space; for lane changing to the left, all obstacles of the left lane are traversed and all lane changing spaces are found. For example, if all of the 3,7,9 targets exist, the lane change space of the host vehicle has the following types: (1) lane changing to the rear of the No. 9 target; (2) lane changing to the middle of targets No. 7 and No. 9; (3) lane changing to the middle of the targets No.3 and No. 7; and (4) switching to the front of the target No. 3. Thus, 4 lane changing spaces can be obtained, and one lane changing space is corresponding to the front vehicle and the rear vehicle. For example, in lane change space 2, the front vehicle is the target No. 7, and the rear vehicle is the target No. 9. If there is no front or rear car (lane change space 1 or 4), then both the virtual one distance and the speed are absolutely safe for the front and rear car target attribute (e.g., the front/rear car speed is comparable to the own car, the front/rear car distance is more than 1000 meters from the own car).
S403, the vehicle is taken as acceleration and deceleration and uniform motion, and a nonlinear optimization model is established for the uniform motion of the front vehicle and the rear vehicle. As shown in fig. 3, taking the lane change space (2) as an example, defining a front vehicle as a No. 7 target, a rear vehicle as a No. 9 target, and a front vehicle of the own vehicle as a No. 1 target, modeling the problem: the maximum time for the host vehicle to adjust the speed of the host vehicle in the host lane does not exceed a certain time T max during the active lane change; the speed of the vehicle is adjusted into two stages at most: acceleration and deceleration actions and a uniform speed stage, wherein the acceleration and deceleration a min≤a1≤amax of the acceleration and deceleration actions stage and the uniform speed stage acceleration a 2 =0 are that the acceleration and deceleration t 1 time is firstly carried out and then the uniform speed t 2,t1,t2 is more than or equal to 0; the longest and shortest time T max/Tmin,Tmin≤(t1+t2)≤Tmax for the host vehicle to adjust the speed of the host vehicle in the host lane during active lane change; predicting that the automatic channel changing safety condition needs to be met after the acceleration and deceleration and uniform speed stages of t 1+t2; the target vehicle is processed according to the uniform motion model. The following nonlinear optimal programming can be obtained:
S4031, setting a longitudinal speed adjustment time length of the vehicle and a planned acceleration and deceleration speed a 1, wherein the time length comprises an acceleration and deceleration time length t 1 and a constant speed time length t 2;
S4032, setting a safety constraint condition,
S4032, setting a safety constraint condition,
t1,t2≥0 (1)
amin≤a1≤amax (2)
Tmin≤t1+t2≤Tmax (3)
Wherein w 1/w2/w3 is three weight coefficients of the performance index related to driving style, a h is the current acceleration and deceleration of the vehicle,For the longitudinal distance from the host vehicle to the front vehicle at time (t 1+t2), V front is the front vehicle speed,/>For the longitudinal distance from the rear vehicle to the host vehicle at time (t 1+t2), V rear is the rear vehicle speed,/>For the longitudinal distance from the host vehicle to the host vehicle before the host vehicle lane at the time (t 1+t2), V hostfront speed of the host vehicle before the host vehicle lane,/>The speed of the vehicle at the moment (T 1+t2), T dis is a safe time interval calibration quantity, and T vel is a safe relative speed calibration quantity;
S4033, setting a performance index f (a 1,t1,t2) related to a 1,t1,t2, introducing a weight coefficient related to driving style, calculating a 1,t1,t2 value when f (a 1,t1,t2) is minimum on the premise of meeting the safety constraint condition,
min f(a1,t1,t2)＝(t1+t2)w1+(t1a1)2w2+(ah-a1)2w3 (10)
The vehicle is a uniform acceleration and uniform motion calculation model, and the target vehicle is a uniform motion calculation model which is as follows:
S404, solving the model, and obtaining an optimal solution corresponding to each target space as a feasible longitudinal planning scheme. The performance index of formula (1) includes three indices: (1) the total time is the shortest; (2) the absolute value of the speed change of the own vehicle is minimum; (3) The absolute value of the difference between the planned acceleration and deceleration and the current acceleration and deceleration of the vehicle is minimum. By adjusting the weights, it can be decided whether the style is aggressive or comfortable. The equations (5) (7) (9) represent the relative distance safety conditions among the automatic lane change safety conditions, and the equations (6) (8) (10) represent the relative vehicle speed safety conditions among the automatic lane change safety conditions.
The problem is a nonlinear optimization problem that can be solved using a corresponding mathematical algorithm, such as a sequential quadratic programming algorithm (SQP).
For each lane-change space, a corresponding a 1,t1,t2 is calculated, and if a feasible optimal solution satisfying the constraint exists, a flag bit and an optimal value f are output (a 1,t1,t2). And if no feasible solution exists, outputting a corresponding flag bit.
S5, deciding an optimal scheme from a plurality of feasible longitudinal planning schemes; and selecting the minimum longitudinal planning scheme from a plurality of optimal values f (a 1,t1,t2) as an optimal scheme.
S6, generating a longitudinal control instruction according to the optimal scheme, and checking whether the book meets the automatic channel changing safety condition after the longitudinal control instruction is executed; s601, calculating accumulated time t from the moment of obtaining the optimal scheme, and taking expected acceleration and deceleration a t as a longitudinal control instruction:
S602, due to the existence of control errors and the change of surrounding target states, whether the currently output instruction still meets the safety constraint condition after execution is completed is checked in each period of control output, and the calculation model is as follows:
S front,Vfront,Srear,Vrear,Shostfront,Vhostfront in the above formula is the target state corresponding to the current t moment. t' 1,t′2 is t 1,t2 according to the time after t correction:
S603, if yes, continuing to output a longitudinal control instruction a t, otherwise, returning to S4 for re-planning;
S604, judging that t is more than or equal to t 1+t2, if yes, finishing longitudinal speed regulation, returning to the step S2, judging whether the current moment meets the automatic channel switching safety condition, and if not, returning to the step S601 to generate a longitudinal control instruction of the next period; if not, the vertical control command a t is continuously output. Specifically, because the conditions of safe channel change may be satisfied before the speed regulation is longitudinally completed due to the existence of the control error and the change of the surrounding target state, the judgment condition in the step A2 is referred to determine whether the current time satisfies the safe condition of automatic channel change, if yes, the channel change is directly executed, and if not, the step S601 is returned to generate the longitudinal control instruction of the next period.
S7, executing the longitudinal control instruction and starting channel changing.
Based on the method, the invention also provides a longitudinal vehicle speed control system for automatic lane changing, which comprises,
The environment sensing system is used for acquiring surrounding environment information of the vehicle; the information of the targets such as the surrounding environment vehicles, the lane line information, the navigation path and the like are acquired by utilizing various sensors mounted on the vehicle.
The upper-layer action decision system is used for making a decision on automatic channel switching, outputting an automatic channel switching instruction and scheduling tasks of each stage of automatic channel switching;
the longitudinal planning system is used for planning a plurality of feasible longitudinal planning schemes by combining surrounding environment information; and acquiring target information, and respectively corresponding the targets to the driving lane and the adjacent lanes of the vehicle according to the lane line information. And according to the target information, constructing a nonlinear optimization problem, constructing performance indexes by using factors such as the acceleration and deceleration, the acceleration and deceleration change, the execution time and the like, and calculating a plurality of feasible longitudinal planning schemes with optimal performance indexes under the condition of meeting safety constraint.
The longitudinal decision system is used for deciding an optimal longitudinal planning scheme from a plurality of feasible longitudinal planning schemes;
And the longitudinal control system is used for issuing the optimal longitudinal planning scheme to the executor for control execution and checking the automatic lane change safety condition by combining the surrounding environment information.
The invention obtains environmental information by using sensors such as the angle radar, the camera and the like of the mass production, carries out longitudinal decision planning of automatic lane changing, and has reliable and mature hardware scheme and controllable cost. The calculation method based on the nonlinear optimization algorithm is mature, is easy to be transplanted to the environment of the embedded controller for operation, and meets the performance requirement of vehicle-mounted calculation. The longitudinal decision result is close to the intention of the driver, and the user experience is good. The longitudinal decision style can be calibrated through weight parameters, and the conservative, common, aggressive and other driver styles can be reflected well.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the technical solution, and those skilled in the art should understand that modifications and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the present invention, and all such modifications and equivalents are included in the scope of the claims.

Claims (6)

1. A longitudinal vehicle speed control method for automatic lane changing is characterized by comprising the following steps,
S1, acquiring surrounding environment information of a vehicle;
s2, judging whether to start automatic channel changing, if so, executing the next step;
S3, judging whether an automatic channel changing safety condition is met according to surrounding environment information, if so, starting channel changing, otherwise, executing the next step; the automatic lane change safety conditions comprise that the relative longitudinal distance between the vehicle and the target vehicle is greater than a preset distance, and the relative vehicle speed is less than a preset vehicle speed;
s4, longitudinally planning a target space for automatic channel changing according to surrounding environment information to obtain a plurality of feasible longitudinal planning schemes; in particular to the preparation method of the composite material,
S401, searching target spaces of all the replaceable channels according to surrounding environment information;
S402, determining a front vehicle and a rear vehicle for each target space;
S403, using the vehicle as acceleration and deceleration and uniform motion, and establishing a nonlinear optimization model for uniform motion by a front vehicle and a rear vehicle;
In particular to the preparation method of the composite material,
S4031, setting a longitudinal speed adjustment time length of the vehicle and a planned acceleration and deceleration speed a 1, wherein the time length comprises an acceleration and deceleration time length t 1 and a constant speed time length t 2;
S4032, setting a safety constraint condition,
t1,t2≥0 (1)
amin≤a1≤amax (2)
Tmin≤t1+t2≤Tmax (3)
Wherein w 1/w2/w3 is three weight coefficients of the performance index related to driving style, a h is the current acceleration and deceleration of the vehicle,For the longitudinal distance from the host vehicle to the front vehicle at time (t 1+t2), V front is the front vehicle speed,/>For the longitudinal distance from the rear vehicle to the host vehicle at time (t 1+t2), V rear is the rear vehicle speed,/>For the longitudinal distance from the host vehicle to the host vehicle before the host vehicle lane at the time (t 1+t2), V hostfront speed of the host vehicle before the host vehicle lane,/>The speed of the vehicle at the moment (T 1+t2), T dis is a safe time interval calibration quantity, and T vel is a safe relative speed calibration quantity;
S4033, setting a performance index f (a 1,t1,t2) related to a 1,t1,t2, introducing a weight coefficient related to driving style, calculating a 1,t1,t2 value when f (a 1,t1,t2) is minimum on the premise of meeting the safety constraint condition,
minf(a1,t1,t2)＝(t1+t2)w1+(t1a1)2w2+(ah-a1)2w3 (10)
The calculation model is that,
S404, solving the model, and obtaining an optimal solution corresponding to each target space as a feasible longitudinal planning scheme;
s5, deciding an optimal scheme from a plurality of feasible longitudinal planning schemes;
s6, generating a longitudinal control instruction according to the optimal scheme, and checking whether the book meets the automatic channel changing safety condition after the longitudinal control instruction is executed;
s7, executing the longitudinal control instruction and starting channel changing.
2. The method for controlling the longitudinal vehicle speed of automatic lane changing according to claim 1, wherein the surrounding environment information comprises surrounding vehicle target information and lane line information acquired in real time by an on-vehicle sensor, and the vehicle target information and the lane line information are in a corresponding relation; the vehicle target information comprises the position, speed and type of surrounding vehicles; the lane line information comprises lane line coefficients, lengths and types.
3. The method according to claim 1, wherein in step S404, the model is solved according to a sequential quadratic programming algorithm, a 1,t1,t2 corresponding to each target space is calculated, and an optimal value r (a 1,t1,t2) when the flag bit and the performance index are minimum is output.
4. A longitudinal vehicle speed control method for automatic lane changing according to claim 3, wherein in step S5, the minimum longitudinal planning scheme is selected from a plurality of optimal values f (a 1,t1,t2) as the optimal scheme.
5. A longitudinal vehicle speed control method for automatic lane changing according to any one of claims 1 to 4, wherein step S6 comprises,
S601, calculating accumulated time t from the moment of obtaining the optimal scheme, and taking expected acceleration and deceleration a t as a longitudinal control instruction:
s602, checking whether the longitudinal control instruction meets a safety constraint condition after execution is completed;
S603, if yes, continuing to output a longitudinal control instruction a t, otherwise, returning to S4 for re-planning;
S604, judging that t is more than or equal to t 1+t2, if yes, finishing longitudinal speed regulation, returning to the step S2, judging whether the current moment meets the automatic channel switching safety condition, and if not, returning to the step S601 to generate a longitudinal control instruction of the next period; if not, the vertical control command a t is continuously output.
6. A system for implementing the longitudinal vehicle speed control method for automatic lane changing according to any one of claims 1 to 5, comprising,
The environment sensing system is used for acquiring surrounding environment information of the vehicle;
The upper-layer action decision system is used for making a decision on automatic channel switching, outputting an automatic channel switching instruction and scheduling tasks of each stage of automatic channel switching;
the longitudinal planning system is used for planning a plurality of feasible longitudinal planning schemes by combining surrounding environment information;
The longitudinal decision system is used for deciding an optimal longitudinal planning scheme from a plurality of feasible longitudinal planning schemes;
And the longitudinal control system is used for issuing the optimal longitudinal planning scheme to the executor for control execution and checking the automatic lane change safety condition by combining the surrounding environment information.
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