CN112677963A - Intelligent networking four-wheel independent steering and independent driving electric automobile emergency obstacle avoidance system - Google Patents

Abstract

The invention discloses an intelligent networking four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system, and aims to improve the obstacle avoidance capability of an electric vehicle by using a vehicle-to-vehicle interaction technology. The obstacle avoidance system can switch different obstacle avoidance modes according to the risk degree of collision between a vehicle and a front obstacle under three conditions of a vehicle-to-vehicle interaction module carried by the vehicle, namely under each condition of normal function, partial function obstacle occurrence and function failure. The vehicle can receive the motion information of other vehicles through the vehicle-to-vehicle interaction module so as to make a more reasonable obstacle avoidance decision; other vehicles can also receive the warning information sent by the vehicle, and favorable conditions are created for avoiding obstacles by the vehicle. Particularly, in an emergency situation that the vehicle cannot avoid collision through braking measures, the emergency obstacle avoidance system receives path planning information of other vehicles through the vehicle-to-vehicle interaction module, and judges whether the possibility of changing lanes and avoiding obstacles exists through the decision module, so that the collision risk is further reduced.

Description

Intelligent networking four-wheel independent steering and independent driving electric automobile emergency obstacle avoidance system

Technical Field

The invention belongs to the field of intelligent networked automobile safety, relates to an active anti-collision technology of vehicles, and particularly relates to an intelligent networked four-wheel independent steer-by-wire and independent drive-by-wire electric automobile emergency obstacle avoidance system.

Background

With the continuous maturation of the vehicle industry technology, vehicles are applied to aspects of human production and life. The more and more complex the vehicle driving requirements and road conditions, the higher the requirements for the design of the vehicle structure and control strategy are put forward. Therefore, a new type of four-wheel independent steering independent drive vehicle is proposed, which has better operability and flexibility compared to the conventional vehicle, and the design thereof represents the development direction of future unmanned vehicles and is one of the leading subjects in the field of intelligent vehicles at present. Compared with the traditional vehicle, the novel vehicle system with four wheels independently steered and independently driven mainly has the advantages of new control mode and driving mode. The four-wheel independent steering technology adds a new control degree of freedom for the control of the vehicle, so that the rear wheels can directly participate in the control of transverse motion when the vehicle turns, thereby not only reducing the lag generated by the steering force, but also independently controlling the motion trail and the posture of the vehicle and improving the control stability of the vehicle; the four-wheel independent driving technology controls the driving force of each tire in a direct or indirect mode through an independent motor or an independent braking system, so that the control and compensation of vehicle dynamics are realized, and the control precision and stability of the vehicle are improved.

Meanwhile, with the rapid increase of the automobile holding capacity, the incidence rate of traffic accidents is remarkably increased, resulting in a great amount of casualties and economic losses. The unmanned vehicle technology is also taken as a research focus by scientific research institutions at home and abroad, and is developed from military application to civilization. The internet of vehicles technology is a key technology in the research field of unmanned automobiles, and the internet of vehicles enables the unmanned automobiles not to be independent mobile vehicle individuals any more. Through the communication between the vehicles and the infrastructure, the interaction between the unmanned automobile and other vehicles, the interaction between the unmanned automobile and the infrastructure and between the unmanned automobile and human can be realized, and a huge information network is formed.

According to the statistics of road traffic accidents, collision accidents caused by the fact that the automobile cannot avoid the front obstacles in time account for a large proportion. Therefore, aiming at the four-wheel independent steering and independent driving electric automobile, an emergency obstacle avoidance method is designed by fully utilizing the maneuverability and flexibility of the electric automobile superior to the traditional automobile, so that the probability of collision accidents between the automobile and an obstacle is reduced, and the electric automobile is particularly necessary, and simultaneously conforms to the development trend of advanced driving assistance technology of unmanned vehicles. At present, the existing emergency obstacle avoidance system based on the four-wheel independent steering independent driving electric automobile has the following problems: 1) when the vehicles do not drive in the adjacent lanes on the two sides of the vehicle, lane changing and obstacle avoiding measures are considered, and the lane changing and obstacle avoiding possibility when other vehicles drive in the adjacent lanes is not considered; 2) the vehicle decision module selects obstacle avoidance measures only by acquiring relevant information through the vehicle sensing module, and the influence of surrounding traffic conditions on obstacle avoidance safety cannot be considered; therefore, there is still a great risk when taking obstacle avoidance measures. In view of the problems, the invention provides an intelligent networking four-wheel independent steer-by-wire and independent drive-by-wire electric vehicle emergency obstacle avoidance system, aiming at further improving the obstacle avoidance capability of a vehicle and reducing the possibility of collision accidents. The emergency obstacle avoidance system combines the vehicle-to-vehicle interaction technology in the vehicle networking technology, so that the vehicle can receive the motion information of other vehicles to make a more reasonable obstacle avoidance decision, and the other vehicles can also receive the warning information sent by the vehicle in the obstacle avoidance process, thereby creating favorable conditions for avoiding the obstacle of the vehicle, and further overcoming the defects of the existing four-wheel independent steering independent driving electric vehicle emergency obstacle avoidance system.

Disclosure of Invention

The invention aims to provide an intelligent networking four-wheel independent steer-by-wire and independent drive-by-wire electric vehicle emergency obstacle avoidance system, which improves the obstacle avoidance capability of a four-wheel independent steer independent drive electric vehicle by utilizing a vehicle-to-vehicle interaction technology, and further reduces the possibility of collision accidents between the vehicle and obstacles. In order to achieve the purpose, the technical scheme of the invention is as follows:

an intelligent networking four-wheel independent steer-by-wire and independent drive-by-wire electric vehicle emergency obstacle avoidance system comprises three obstacle avoidance modes; the whole system comprises a vehicle-to-vehicle interaction module, a sensing module, a decision module and an execution module; the obstacle avoidance system can switch different obstacle avoidance modes according to the collision risk degree between a vehicle and a front obstacle under three conditions of a vehicle-to-vehicle interaction module carried by the vehicle, namely under each condition of normal function, partial function obstacle occurrence and function failure; when partial functions of the vehicle-to-vehicle interaction module are obstructed, only one-way communication of the vehicle to other vehicles can be realized; the front wheel, the rear wheel, the left wheel and the right wheel of the vehicle respectively correspond to one hub motor, a control circuit of each hub motor is connected with the decision control module, and a four-wheel independent hydraulic braking system is adopted, so that the braking pressure of the four wheels can be independently controlled to meet different working condition requirements; and an electric control hydraulic system is adopted, so that the response speed is improved. The system can realize independent braking force control on each wheel, thereby effectively realizing the compensation of the yaw moment of the whole vehicle through the braking force control on a single wheel, and the effect is superior to that of the traditional electronic stability control system and traction control system.

The intelligent networking four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance method specifically comprises three obstacle avoidance modes, namely a first obstacle avoidance mode, a second obstacle avoidance mode and a third obstacle avoidance mode.

In the first obstacle avoidance mode in the technical solution, the control method includes the following steps:

(1) the current longitudinal speed v of the vehicle is collected by a sensing module_sThe longitudinal distance L between the vehicle and the front obstacle and the longitudinal distance L between the vehicle and the vehicle behind the vehicle_rAnd transmitting to the decision module;

(2) after the decision module inputs the relevant parameters, the minimum distance L required by the vehicle control module to control the vehicle to brake in a specific braking mode to a collision-free parking mode under the instruction of the decision module is calculated through a decision algorithm in the controller₁Shortest braking time t_b(ii) a Introducing an adjusting parameter a, and calculating the value of a by a decision module according to the current longitudinal speed of the vehicle;

1) when L > aL₁When the vehicle is in use, the emergency obstacle avoidance system does not work, and the vehicle is driven by a driver;

2) when L is₁＜L≤aL₁When the vehicle-mounted man-machine interaction system is used, a first-level warning is given to a driver to remind the driver to brake in advance; meanwhile, the decision module calculates the normal braking time t of the driver according to a corresponding calculation method_sIf the driver takes an emergency braking measure in time, at t_sIf the brake intensity of the vehicle reaches the maximum, the system does not take effect any more; if the driver is t after the first warning_sIf the braking is not started within the time or the braking strength of the vehicle does not reach the maximum, directly canceling the control authority of the driver on the vehicle accelerator pedal so as to avoid the misoperation of the driver to accelerate the vehicle, and simultaneously carrying out secondary warning on the driver through a vehicle-mounted human-computer interaction system; at the moment, the decision module recalculates the normal braking time t of the driver according to the corresponding calculation method_sIf the driver takes an emergency braking measure in time, at t_sThe brake intensity of the vehicle is maximized, and the system does not take effect any more; if the driver is t after the secondary warning_sIf the braking strength of the inner vehicle is not maximum, directly canceling all operation authorities of the driver, and sensing whether other vehicles exist behind the vehicle lane through a sensing module; when no vehicle exists behind, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module; when the rear part has the vehicle:

firstly, when the vehicle-to-vehicle interaction module is normal in function or partial function is obstructed, so that only one-way communication of the vehicle to other vehicles can be realized, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, and meanwhile, the vehicle-to-vehicle interaction module gives a warning to the rear vehicle to remind that an obstacle exists in the front of the rear vehicle and to pay attention to early braking or lane change, so that rear-end collision between the front vehicle and the rear vehicle during braking of the front vehicle is avoided;

secondly, when the vehicle-to-vehicle interaction module fails, the vehicle sensing module acquires the current longitudinal speed u of the rear vehicle_r：

When u is_rt_b＞(L₁+L_r) Then, the system is timely switched into a second obstacle avoidance mode;

when u is_rt_b≤(L₁+L_r) When the vehicle is braked, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module;

in a first obstacle avoidance mode, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module and comprises the following steps:

firstly, if the decision module makes a braking decision, L is more than or equal to L₁The vehicle can not collide with the barrier in the braking process, and the control module controls the front wheel and the rear wheel of the vehicle to have zero rotating angles in the braking process; if L is less than L₁In order to protect the life safety of a driver, the control module inputs a leftward turning angle delta to the front wheel of the vehicle so as to avoid the direct collision between the cockpit and the barrier; the unit of delta is degree, the size of delta depends on the distance between the vehicle and the obstacle at the moment when the decision module makes a braking decision, and the value is recorded as L_b(ii) a The shorter the distance between the vehicle and the obstacle is at the moment of making a braking decision by the decision making module, the shorter the time for the vehicle to collide with the obstacle is, and the shorter the time for avoiding the direct collision between the cockpit and the obstacle through the steering of the front wheel is; therefore, the designed and input front wheel steering angle value is increased along with the reduction of the distance between the vehicle and the obstacle when the decision module makes a braking decision, so that the direct collision between the cockpit and the obstacle is effectively avoided. The specific value taking method follows the following formula:

wherein, delta₀For a set initial value of the front wheel steering angle, alpha is an adjustment parameter, delta₀＞α；δ₀The specific value of alpha is determined by manufacturers according to the performance of an automobile steering system, the performance of a braking system, the space structure of a vehicle cab and the width of a vehicle;

when braking, the ABS system works normally, the braking system of the vehicle comprises two braking modes of hydraulic braking and hub motor braking, and the hub motor can provide motor braking torque through reverse rotation; the decision module reasonably calculates and distributes the braking force of the front wheel and the rear wheel to enable the front wheel and the rear wheel to be kept in a state close to locking but not locked at the same time, and the vehicle is controlled to brake in an electro-hydraulic composite braking mode so as to fully utilize the road surface adhesive force.

In the first obstacle avoidance mode, the specific method for reminding the driver of taking obstacle avoidance measures through the human-computer interaction system by the vehicle is as follows:

the specific method for the vehicle-mounted human-computer interaction system to give a first-level warning to the driver comprises the following steps: the control module controls the vehicle-mounted sound box to play voice with the maximum volume of 80%: the front part of the vehicle is provided with an obstacle, and a driver is asked to brake in time; controlling a vehicle-mounted man-machine interaction screen to display a flickering exclamation mark pattern, wherein the exclamation mark is red, the screen background is yellow, and the exclamation mark flickering frequency is f;

the specific method for the vehicle-mounted human-computer interaction system to carry out secondary warning on the driver comprises the following steps: the control module controls an air-conditioning air outlet right above the driver seat to convey cold air; controlling the vehicle-mounted sound to play voice at the maximum volume: please brake immediately; controlling a vehicle-mounted man-machine interaction screen to display a flickering exclamation mark pattern, wherein the exclamation mark is red, the screen background is yellow, and the exclamation mark flickering frequency is f;

thirdly, the frequency f of the flickering exclamation mark pattern displayed by the vehicle-mounted man-machine interaction screen is related to the real-time distance L between the vehicle and the obstacle, wherein the unit of f is Hertz, and the specific value taking method follows the following formula:

wherein L is the longitudinal distance between the vehicle and the front obstacle, L₁A minimum distance f required for a vehicle control module to control the vehicle to brake in a specific braking mode to a non-collision parking state under the instruction of a decision module₀The flicker frequency of the exclamation mark pattern when the real-time distance L between the vehicle and the obstacle approaches zero, beta is an adjusting parameter, f₀＞β；f₀The value of the sum beta can be obtained by a factory providing a corresponding human-computer interaction liquid crystal display screenThe home setting can also be set by the driver according to the driving habits and experiences of the driver; it can be seen that when the human-computer interaction system warns the driver, the frequency f of the blinking exclamation mark pattern displayed by the vehicle-mounted human-computer interaction screen gradually increases as the longitudinal distance between the vehicle and the front obstacle gradually decreases;

fourthly, after the vehicle-mounted human-computer interaction system carries out primary warning or secondary warning on the driver, if the driver carries out t after voice reminding_sTaking emergency braking measures within the time period to make the vehicle reach the maximum braking intensity, the system is no longer in effect, wherein t_sThe value taking method comprises the following steps:

the decision-making module establishes a database and collects the time from the beginning of the prompt of the driver receiving the emergency braking voice of the man-machine interaction platform in the daily driving process to the time of taking the emergency braking measure to enable the vehicle to reach the maximum braking strength; the collected time data is recorded as s₁,s₂,…s_nDetermining t by means of least squares_sThe value of (A) is as follows: let the error sum of squares

Substituting data s₁,s₂,…s_n(ii) a The decision module calculates s value when the R value is minimum, namely t in the warning process_sThe value of (a).

In the second obstacle avoidance mode in the technical solution, the control method includes the following steps:

(1) the current longitudinal speed v of the vehicle is collected by a sensing module_sThe longitudinal distance L between the vehicle and the front obstacle and the longitudinal distance L between the vehicle and the adjacent lane vehicle i_piThe transverse distance L of the center of mass of the vehicle relative to the left and right side boundaries of the obstacle_zl,L_zrAnd transmitting to the decision module;

(2) after the decision module inputs the relevant parameters, the minimum distance L required by the vehicle control module to control the vehicle to brake in a specific braking mode to a collision-free parking mode under the instruction of the decision module is calculated through a decision algorithm in the controller₁Shortest braking time t_bMinimum between left lane vehicle and host vehicleLongitudinal distance L_lminMinimum longitudinal distance L between right-side lane vehicle and host vehicle_rminMinimum safe lane-changing longitudinal distance L_s(ii) a Introducing an adjusting parameter b, and calculating the value of b by a decision module according to the current longitudinal speed of the vehicle;

when the sensing module fails to sense the obstacle in front in time or the obstacle suddenly appears to cause bL₁＜L≤L₁The sensing module senses whether other vehicles run in the adjacent lane of the vehicle;

1) when no other vehicles run in the adjacent lane of the vehicle on any side, the vehicle traction control system is closed, the wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and the wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment, so that lane changing and obstacle avoidance are realized; if no other vehicles run in the adjacent lanes on the two sides of the lane, the decision-making module selects a proper adjacent lane to implement lane change by a specific method;

2) when other vehicles run in the adjacent lanes on both sides of the vehicle, when L is equal to L_lmin≥L_rminSelecting a left lane as a target obstacle avoidance lane; when L is_lmin＜L_rminAnd selecting a right lane as a target obstacle avoidance lane, and simultaneously:

firstly, when the vehicle-to-vehicle interaction module is normal in function or partial function is in obstacle occurrence, so that only one-way communication of the vehicle to other vehicles can be realized, the vehicle sends a vehicle lane changing and obstacle avoiding intention and a target obstacle avoiding lane to vehicles on lanes on two sides through the vehicle-to-vehicle interaction module, the vehicles on the target obstacle avoiding lane provide a safe lane changing space for the vehicle by adopting a speed control method, the vehicle closes a vehicle traction control system, and the wheels on one side close to the available obstacle avoiding lane are controlled to brake through a decision module, and the wheels on one side far away from the obstacle avoiding lane are accelerated to drive so as to generate expected emergency yaw moment to realize lane changing and obstacle avoiding;

when the vehicle-to-vehicle interaction module fails:

the decision-making module judges whether the collision risk exists or not if the lane changing and obstacle avoiding are carried out according to the longitudinal distance between the vehicle and the adjacent lane vehicle;

when it is for the eyeAny vehicle i on the obstacle avoidance lane satisfies L_pi＞L_sWhen the vehicle is in use, the vehicle traction control system is closed, wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment, so that lane changing and obstacle avoidance are realized; wherein L is_sThe minimum safe lane changing longitudinal distance is set;

when any vehicle i exists on the target obstacle avoidance lane, L is enabled_pi≤L_sWhen the system is switched into a first obstacle avoidance mode in time, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, and collision loss is reduced as much as possible;

in the second obstacle avoidance mode, when the vehicle-to-vehicle interaction module fails, the decision module may determine the longitudinal distance L between the vehicle and the target obstacle avoidance lane vehicle according to the longitudinal distance L between the vehicle and the target obstacle avoidance lane vehicle_piLongitudinal distance L from minimum safe lane change_sThe size between: whether the vehicle has collision risk with the target obstacle avoidance lane vehicle or not when the vehicle changes lanes; wherein L is_sThe value of (a) can be determined by the longitudinal speed of the vehicle in the adjacent lane, the longitudinal speed of the vehicle, the predicted maximum lane change time of the vehicle and the longitudinal position of the vehicle in the adjacent lane relative to the vehicle; the specific calculation method is as follows:

l when the longitudinal position of the adjacent lane vehicle is in front of the vehicle_sThe calculation formula of (2) is as follows:

L_s＝v_st_{f max}-v_it_{f max}

l when the longitudinal position of the adjacent lane vehicle is behind the vehicle_sThe calculation formula of (2) is as follows:

L_s＝v_it_{f max}-v_st_{f max}

wherein v is_s,v_iThe current longitudinal speed, t, of the vehicle and the target obstacle avoidance lane vehicle i respectively_{f max}The calculation formula of the predicted maximum lane change time for the vehicle is as follows:

t_{f max}＝L/v_s

wherein L is the longitudinal distance between the vehicle and the front obstacle.

In a second obstacle avoidance mode, when other vehicles run in adjacent lanes on two sides and the vehicle-to-vehicle interaction module is normal in function, the method for controlling the speed adopted by the vehicle of the target obstacle avoidance lane to provide a safe lane change space for the vehicle comprises the following control processes:

the sensor module acquires the current longitudinal speed v of the vehicle i in the adjacent lane_iAnd the current longitudinal speed v of the vehicle_s；

When the adjacent lane vehicle i is positioned in front of the vehicle, if v_i≤cv_sThe vehicle i in the adjacent lane starts accelerating to cv at the maximum acceleration under the action of the decision module_sThen keeping constant speed running; if v is_i＞cv_sThe vehicle i in the adjacent lane keeps running at a constant speed at the current speed;

when the adjacent lane vehicle i is behind the vehicle, if v_i≥dv_sThe vehicle i in the adjacent lane starts to decelerate to dv with the maximum braking intensity under the action of the decision module_sThen keeping constant speed running; if v is_i＜dv_sThe vehicle i in the adjacent lane keeps running at a constant speed at the current speed;

wherein c and d are adjustment parameters; in the process of changing lanes and avoiding obstacles, the longitudinal speed v of the vehicle_sCan be considered approximately constant; controlling the values of the adjusting parameters c and d, and controlling the longitudinal speed of the vehicle in the adjacent lane in front of the vehicle to be always greater than the longitudinal speed of the vehicle when the vehicle changes lanes if c is greater than 1; the longitudinal speed of the vehicle in the adjacent lane behind the vehicle in the lane changing process of the vehicle can be controlled to be always smaller than the longitudinal speed of the vehicle when d is less than 1; thereby providing a safe lane change space for the vehicle;

in order to prevent the condition that the longitudinal speed of the vehicles in the adjacent lanes is too small or too large, the parameters c and d are adjusted by adopting a method of sectional value:

when the longitudinal speed v of the vehicle_sC is not more than 50km/h₂,d＝d₁；

When 50km/h < v_sWhen the value is less than 100km/h, the values of c and d follow the following formula:

when v is_sWhen the speed is more than or equal to 100km/h, c is c₁,d＝d₂；

Wherein:

c₁,c₂,d₁,d₂the specific value is set by a manufacturer according to the dynamic performance of the automobile.

In the third obstacle avoidance mode in the technical solution, the control method includes the following steps:

(1) the current longitudinal speed v of the vehicle is collected by a sensing module_sThe longitudinal distance L between the vehicle and the front obstacle, and the transverse distance L between the center of mass of the vehicle and the boundaries of the left side and the right side of the obstacle_zl,L_zrAnd transmitting to the decision module;

(2) after the decision module inputs the relevant parameters, the minimum distance L required by the vehicle control module to control the vehicle to brake in a specific braking mode to a collision-free parking mode under the instruction of the decision module is calculated through a decision algorithm in the controller₁Shortest braking time t_b(ii) a Introducing an adjusting parameter b, and calculating the value of b by a decision module according to the current longitudinal speed of the vehicle;

when the sensing module fails to sense the obstacle ahead in time or the obstacle suddenly appears to cause that L is less than or equal to bL₁The sensing module senses whether other vehicles run in the adjacent lane;

1) when no other vehicles run in the adjacent lanes, the electronic stability control system of the vehicle is closed, the wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and the wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment; meanwhile, the four-wheel independent steering mechanism is controlled to adopt a four-wheel different-direction steering mode, namely the steering direction of the rear wheels is opposite to that of the front wheels so as to reduce the steering radius and realize lane changing and obstacle avoidance; if no other vehicles run on the two sides of the lane, the decision-making module selects a proper adjacent lane to change lanes;

2) when other vehicles run on the adjacent lanes on the two sides;

firstly, when the vehicle-to-vehicle interaction module is in a normal function, each vehicle acquires the longitudinal speed, the longitudinal acceleration, the mass center abscissa, the mass center ordinate, the course angle, the lane changing intention of a driver and the straight-ahead intention of the driver of the vehicle through the self sensing module; the decision module of each vehicle selects a proper path planning method to obtain the possible path of each vehicle in the lane changing time of the vehicle by using the acquired information; if the vehicle is detected to have the intention of changing the lane of the driver, an objective function established based on the lane changing efficiency and the stability of the vehicle is adopted to obtain the optimal lane changing path of each vehicle; the vehicle receives the optimal lane changing path planned by other vehicles through a vehicle-to-vehicle interaction module, and judges whether the vehicle has the risk of collision with the adjacent lane vehicles at any time when the vehicle changes lanes by adopting a vehicle contour equation simultaneous solution method; further:

when the decision module judges that the vehicle has collision risks with vehicles on two adjacent lanes if the vehicle changes lanes to avoid the obstacle, the system timely switches to a first obstacle avoiding mode, and the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, so that collision loss is reduced as much as possible;

when the decision-making module judges that no collision risk occurs with the vehicle in the adjacent lane, the electronic stability control system of the vehicle is closed, the wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision-making module, and the wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment; meanwhile, the four-wheel independent steering mechanism is controlled to adopt a four-wheel different-direction steering mode, namely the steering direction of the rear wheels is opposite to that of the front wheels so as to reduce the steering radius and realize lane changing and obstacle avoidance; if the decision-making module judges that the vehicle has no collision risk with the vehicles on the adjacent two side lanes when the vehicle is subjected to lane changing and obstacle avoidance, the decision-making module selects a proper adjacent side lane to implement lane changing;

when partial functions of the vehicle-to-vehicle interaction module are obstructed, only one-way communication or function failure of the vehicle to other vehicles can be realized; at the moment, the distance between the vehicle and the barrier is close, and whether collision risks exist in the lane changing and obstacle avoiding measures cannot be judged, so that the lane changing measures are taken in a trade, and major accidents are easily caused; the system is timely switched into a first obstacle avoidance mode, and the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, so that collision loss is reduced as much as possible; if the vehicle-to-vehicle interaction module can realize one-way communication, the vehicle-to-vehicle interaction module reminds surrounding vehicles that the vehicle is about to be emergently braked and pays attention to deceleration and avoidance; if the vehicle-to-vehicle interaction module fails in function, the vehicle control module controls the vehicle to turn on the double flashing lamps, and simultaneously continuously whistles to remind surrounding vehicles to reduce the speed and avoid the vehicles.

In the third obstacle avoidance mode, after the vehicle obtains the motion information of the vehicle through the vehicle-mounted sensor, the method for determining the path of the vehicle and the adjacent vehicle comprises the following steps:

the method for selecting the vehicle to plan the path by the decision module comprises the following steps:

for the host vehicle, when eL₁＜L≤bL₁In the process, a quintic polynomial method is selected to plan the lane change path, and the quintic polynomial is smoother than the path planned by the cubic polynomial, so that the requirement on the stability of the vehicle is met more easily; when L is less than or equal to eL₁In the time, a cubic polynomial method is selected to plan the lane change path, and because the distance between the vehicle and the obstacle is smaller at the time, the possibility that the path planned by the cubic polynomial can successfully avoid collision is higher; wherein e is an adjusting parameter, e is more than 0 and less than b, and the specific value is set by a manufacturer according to the performance of the automobile steering system and the design condition of the stability structure of the automobile;

for the adjacent vehicle, judging whether the driver of the adjacent vehicle has the intention of changing the lane by a decision module; if the driver of the adjacent vehicle does not have the intention of changing lanes, the decision-making module plans a straight-going path of the adjacent vehicle according to the current speed of the adjacent vehicle acquired by the vehicle body sensor and the acceleration degree; if the drivers of the adjacent vehicles have the lane changing intention, the decision module selects a fifth-order polynomial to plan the lane changing path:

the expression of the vehicle track change trajectory planning model based on the cubic polynomial is as follows:

wherein x (t), y (t) are the transverse position and the longitudinal position of the vehicle in the geodetic coordinate system, u is the current longitudinal speed of the vehicle, and t is the current longitudinal speed of the vehicle₀，t₁Starting and ending times, m, for trajectory planning₀,m₁,m₂,m₃All coefficients are cubic polynomial interpolation functions;

the expression of the vehicle track change trajectory planning model based on the fifth-order polynomial is as follows:

in the formula, n₀,n₁,n₂,n₃,n₄,n₅All are coefficients of a quintic polynomial interpolation function;

secondly, after a track changing track model is obtained, the track changing time t is adjusted_f＝t₁-t₀The size of the obstacle avoidance path is obtained, and a series of possible lane changing and obstacle avoidance paths of the vehicle can be obtained;

determining the maximum yaw velocity and the maximum centroid slip angle when the vehicle changes lanes on the premise of meeting the vehicle stability according to the two-degree-of-freedom model of the vehicle:

the stability limit calculation method of the yaw rate is as follows:

therefore, the temperature of the molten steel is controlled,

the stable limit calculation method of the centroid slip angle is as follows:

therefore, the temperature of the molten steel is controlled,

wherein r represents yaw rate, F_yf,F_yrRespectively representing the lateral force of the front axle and the rear axle of the vehicle, wherein m is the mass of the whole vehicle, mu is the road surface adhesion coefficient, u is the longitudinal speed of the vehicle, beta is the mass center slip angle, C_αrRepresenting the cornering stiffness of the rear axle of the vehicle, a₀,b₀Respectively representing the distance between a front axle and a rear axle of the vehicle and the center of mass of the vehicle, wherein l is the wheelbase of the vehicle;

setting an objective function as follows for determining the optimal track change track of the vehicle:

in the formula, L_maxThe maximum lane changing longitudinal distance of the vehicle, u is the current longitudinal speed of the vehicle, and t_fR (t) is lane change time, beta (t) is yaw angular velocity and centroid side slip angle of the vehicle in the lane change process, and r_max,β_maxThe stable limit values of the yaw angular velocity and the centroid slip angle r obtained in the step three_min,β_minFor minimum yaw rate and centroid slip angle, w, of all lane change trajectories₁,w₂,w₃,w₄,w₅Is a weight coefficient; the first item of reaction lane change efficiency of the objective function and the second, third, fourth and fifth item of reaction lane change stability; the second term and the third term reflect the fluctuation conditions of the yaw velocity and the centroid slip angle in the lane changing process, and the fourth term and the fifth term reflect the influence of the maximum value of the yaw velocity and the centroid slip angle on the stability in the lane changing process;

setting different objective function solving constraint conditions for the vehicle and the adjacent vehicles; for the vehicle, under the emergency obstacle avoidance environment, the requirement on lane change efficiency is higher, so the weight occupied by the first item of the design objective function is higher, and the following are taken:

w₁＝0.6,w₂＝w₃＝w₄＝w₅＝0.1

meanwhile, the maximum lane changing longitudinal distance is the distance L between the vehicle and the front obstacle;

therefore, the corresponding constraint conditions are as follows:

for adjacent vehicles, emergency obstacle avoidance is not needed, and lane changing efficiency and lane changing stability need to be considered comprehensively, so the sum of the first weight and the last four weights of a design objective function is equal to obtain:

w₁＝0.5,w₂＝w₃＝w₄＝w₅＝0.125

meanwhile, the maximum lane changing distance is set to be L_lmaxThe specific value taking method comprises the following steps:

the decision-making module establishes a database to collect the time from the beginning of lane changing to the end of lane changing of the vehicle at different speeds; when the current speed of the adjacent vehicle i is u_iWhen L is_lmaxIs that the vehicle speed in the database is u_i-10km/h～u_iAverage value of the acquired track-changing time within the range of +10 km/h;

therefore, the corresponding constraint conditions are as follows:

substituting the constraint conditions into the objective function established in the step (iv) to solve to obtain the optimal lane change path of the vehicle at any speed;

after the adjacent vehicle decision module plans the path, the path information is sent to the vehicle through the vehicle-to-vehicle interaction module.

Further, the process that the vehicle decision module judges whether the collision risk with the adjacent lane vehicle exists when the optimal path planned by the vehicle carries out lane change and obstacle avoidance comprises the following steps:

the vehicle contour is regarded as an ellipse, and the collision problem between vehicles can be converted into the problem whether the vehicle and the vehicle elliptical contour intersect or not; the elliptical contour enlarges the area of the vehicle contour relative to the real vehicle contour, and the probability of misjudgment is smaller when collision risk judgment is carried out; meanwhile, the elliptic contour is easier to establish a corresponding mathematical model for calculation processing compared with the real vehicle contour, so that the speed of judging the collision risk by the decision module is increased; the center of the ellipse is provided with a vehicle mass center coordinate, the ellipse passes through four vertexes of the vehicle, and in order to enable the ellipse outline to better wrap the vehicle boundary, the short axial length of the ellipse is 1.2 times of the vehicle width; if the reference course angle of the vehicle is the orientation of the vehicle at the corresponding moment, a series of elliptical contours corresponding to time can be generated according to the reference track; for any vehicle, when the longitudinal speed is determined, for the reference trajectory determining the lane change time, the position coordinates of the four vertices of the vehicle at time t are calculated as follows:

the coordinates of the end points on the two sides of the minor axis of the elliptical profile are calculated as follows:

in the formula, τ_Hk,τ_iRespectively the lane changing time length of the vehicle and the lane changing time length, x, of the vehicle i in the adjacent lane_k1,...,4(t),y_k1,...,4(t) four vertex coordinates of the vehicle, x_k5,6(t),y_k5,6(t) coordinates of end points on both sides of the minor axis of the elliptical profile, l_H,w_HRespectively showing the length and width of the host vehicle,

is the heading angle, x_k(t),y_k(T) represents a centroid position of the host vehicle, T being a time interval;

the general expression of the ellipse equation can be set to the form:

Ax²+By²+2Cxy+Dx+Ey+F＝0

the system comprises a six-point coordinate simultaneous equation set, a six-point coordinate simultaneous equation set and a six-point coordinate simultaneous equation set, wherein A, B, C, D, E and F are undetermined coefficients of an elliptic equation;

secondly, after the vehicle acquires the planned paths of all adjacent vehicles through the vehicle-to-vehicle interaction module, solving the elliptical contour equations of all vehicles at any time t when the vehicle carries out lane changing according to the planned optimal path changing path; respectively determining an elliptic contour equation between the simultaneous vehicle and each adjacent vehicle, wherein if no real solution exists in the simultaneous equation set, the vehicle and the adjacent vehicle have no risk of collision; if any one group of the ellipse equations has a real solution, the vehicle and the adjacent vehicle have the risk of collision.

In the technical scheme, when the vehicle is ready to take lane changing and obstacle avoiding measures and the adjacent lanes at the two sides of the vehicle can be changed, the method for selecting the appropriate target obstacle avoiding lane by the decision module comprises the following steps:

firstly, the vehicle perception module collects the transverse distance L of the center of mass of the vehicle relative to the left and right side boundaries of the barrier_zl,L_zr；

II, judging by the vehicle decision module, if L_zl≤L_zrSelecting a left adjacent lane as a target lane changing lane; if L is_zl＞L_zrAnd selecting the adjacent lane on the right side as a target lane changing lane. Therefore, the transverse displacement in the lane changing process of the vehicle can be reduced, the lane changing time is shortened, and the collision risk is further reduced.

In the technical scheme, a distance comparison method is used as a basis for initially selecting an obstacle avoidance mode by an emergency obstacle avoidance system; wherein a and b are both adjustment parameters, a₁＜a＜a₂,b₁＜b＜b₂The specific value method of the parameters is as follows:

when the longitudinal speed v of the vehicle_sA is not more than 50km/h, a is a₁,b＝b₁；

When 50km/h < v_sWhen the speed is less than 100km/h,the values of a and b follow the following formula:

when v is_sA is more than or equal to 100km/h₂,b＝b₂；

Wherein, 1 < a₁,a₂＜2,0.5＜b₁,b₂And (3) the specific value is set by a manufacturer according to the performance of the automobile brake system.

After the vehicle adopts the lane changing and obstacle avoiding measures, the judgment basis of the emergency obstacle avoiding system for finishing the work is as follows:

when the vehicle takes the lane changing and obstacle avoiding measures in the second obstacle avoiding mode: the perception module perceives the transverse distance L between the vehicle mass center and the boundary of the barrier on the lane changing side of the vehicle in real time_zWhen L is sensed_zContinuously decreases to zero and then continuously increases to L_z＝l_HAt the moment of 2, the emergency obstacle avoidance system is closed in time, and the vehicle traction control system and the vehicle electronic stability system recover to work normally so as to ensure the stability of the vehicle;

when the vehicle takes the lane changing and obstacle avoiding measures in the third obstacle avoiding mode: the decision-making module establishes a linear equation which is parallel to the lane line and tangent to the boundary of the barrier at the lane changing side of the vehicle; calculating whether the ellipse outline equation and the linear equation have real number solutions in real time; when the calculation result is changed from the real number solution to the non-real number solution, the emergency obstacle avoidance system is closed in time, and the vehicle traction control system and the vehicle electronic stability system recover to work normally so as to ensure the stability of the vehicle;

meanwhile, if the vehicle-to-vehicle interaction module has normal functions, the position and the size of the barrier are marked and uploaded to a vehicle networking map, and other nearby vehicles are reminded to change lanes in advance to avoid the barrier.

Compared with the prior art, the invention has the beneficial effects that:

1) the system considers the possibility of lane changing and obstacle avoiding when other vehicles run in the adjacent lane of the vehicle, and under the emergency condition that the vehicle cannot avoid collision through braking measures, the emergency obstacle avoiding system combines the vehicle-to-vehicle interaction technology in the vehicle networking technology, so that the vehicle can receive path planning information of other vehicles, a more reasonable obstacle avoiding decision is made through the decision module, and the collision risk is further reduced.

2) The vehicle decision module acquires relevant information through the vehicle sensing module to select obstacle avoidance measures, and combines a vehicle-to-vehicle interaction technology in the vehicle networking technology, so that the vehicle can receive motion information of other vehicles to make a more reasonable obstacle avoidance decision; other vehicles can also receive warning information sent by the vehicle in the obstacle avoidance process, so that favorable conditions are created for the vehicle to avoid the obstacle, the obstacle avoidance capability of the vehicle is further improved, and the possibility of collision accidents is reduced.

Drawings

The invention is further described with reference to the accompanying drawings in which:

fig. 1 is a schematic diagram of the proposed emergency obstacle avoidance control system composition and work flow;

FIG. 2 is a schematic diagram of the information of the omni-directional distances between the host vehicle and other vehicles and between the host vehicle and obstacles;

fig. 3 is a control flow chart of a first obstacle avoidance mode;

fig. 4 is a control flow chart of a second obstacle avoidance mode;

fig. 5 is a flowchart of a third obstacle avoidance mode control;

FIG. 6 is a two degree of freedom kinematic model of a vehicle;

Detailed Description

The invention is further explained below with reference to the drawings.

As shown in fig. 1, the whole system comprises a vehicle-to-vehicle interaction module, a perception module, a decision module and an execution module; the decision module divides the emergency obstacle avoidance mode into a first obstacle avoidance mode, a second obstacle avoidance mode and a third obstacle avoidance mode. The working principle of the whole system is as follows: the vehicle-to-vehicle interaction module realizes direct communication between vehicles and has the capability of receiving and sending basic data of the vehicles; when the function of the vehicle-to-vehicle interaction module is normal or part of the function occursWhen an obstacle is present, the vehicle-to-vehicle interaction module can assist or directly participate in the realization of obstacle avoidance measures in different obstacle avoidance modes; under a first obstacle avoidance mode, the vehicle-to-vehicle interaction module can warn a vehicle behind the lane to avoid collision so as to prevent rear-end collision; under a second obstacle avoidance mode, the vehicle-to-vehicle interaction module can inform vehicles on adjacent lanes of the vehicle to adopt a speed control method to provide a safe lane changing space for the vehicle; in a third obstacle avoidance mode, the vehicle-to-vehicle interaction module can send respective path information planned by other vehicle decision modules to the vehicle, and the vehicle judges whether the vehicle has a collision risk in the lane changing and obstacle avoidance process through a corresponding algorithm in the decision modules; the sensing module acquires the motion information of the vehicle through the vehicle-mounted sensor, identifies lane line information through the camera, and acquires all-directional distance information between the vehicle and an obstacle or other vehicles through the radar; the vehicle motion information includes: the longitudinal speed, the longitudinal acceleration, the centroid abscissa, the centroid ordinate, the course angle, the lane changing intention of the driver and the straight-driving intention of the driver of the vehicle; the omnibearing distance information comprises a longitudinal distance L between the vehicle and a front obstacle and a longitudinal distance L between the vehicle and a vehicle behind the vehicle_rThe longitudinal distance L between the vehicle and the adjacent lane vehicle i_piThe transverse distance L of the center of mass of the vehicle relative to the left and right side boundaries of the obstacle_zl,L_zr(ii) a The specific measurement method of the omnidirectional distance information is shown in fig. 2; the decision module calculates the minimum distance L required by the vehicle control module to control the vehicle to brake in a specific braking mode to a collision-free parking mode under the instruction of the decision module according to the collected related information₁Shortest braking time t_bMinimum longitudinal distance L between vehicle on left lane of vehicle and vehicle_lminMinimum longitudinal distance L between right-side lane vehicle and host vehicle_rminThe lane changing intention of the driver of the adjacent lane vehicle i and the straight-going intention of the driver of the adjacent lane vehicle i; according to L, L₁According to the completeness of the function of the vehicle-to-vehicle interaction module, the emergency response condition of a driver and the traffic condition around the vehicle, the final obstacle avoidance mode and obstacle avoidance control are determinedA policy; in a third obstacle avoidance mode, if the vehicle-to-vehicle interaction module is normal in function, the vehicle decision module needs to plan a lane changing path of the vehicle according to a selected target lane changing and obstacle avoiding lane by adopting a proper algorithm, meanwhile, the vehicle-to-vehicle interaction module receives path planning information of other vehicles in the predicted lane changing time of the vehicle, and then a method based on vehicle elliptic contour equation simultaneous solution is adopted to analyze and calculate whether the risk of collision with other vehicles exists in the process of changing the lane and avoiding the obstacle of the vehicle; the execution module controls related execution mechanisms to complete the control strategy input by the decision module so as to realize the emergency obstacle avoidance process of the vehicle; the actuator includes: the four-wheel-hub motor type four-wheel steering system comprises four wheel hub motors, four-wheel independent steering mechanisms, an electric control hydraulic braking system and a human-computer interaction system; the human-computer interaction system comprises: the system comprises vehicle-mounted voice interaction equipment, a vehicle-mounted man-machine interaction liquid crystal display screen and an air conditioner air outlet; the air-conditioning air outlet is positioned on the top of the driver seat, and can convey cold air at a specific moment to prevent a driver from failing to respond to the prompt of a human-computer interaction system in time due to fatigue driving and take corresponding obstacle avoidance measures.

As shown in fig. 3, the first obstacle avoidance mode control process of the present invention is as follows:

firstly, the current longitudinal speed v of the vehicle is collected by a sensing module_sThe longitudinal distance L between the vehicle and the front obstacle and the longitudinal distance L between the vehicle and the vehicle behind the vehicle_rAnd transmitting to the decision module; then, after the decision module inputs the relevant parameters, the minimum distance L required by the vehicle control module to control the vehicle to brake in a specific braking mode to a collision-free parking mode under the instruction of the decision module is calculated through a decision algorithm in the controller₁Shortest braking time t_b(ii) a Introducing an adjusting parameter a, and calculating the value of a by a decision module according to the current longitudinal speed of the vehicle; further: when L > aL₁When the vehicle is in use, the emergency obstacle avoidance system does not work, and the vehicle is driven by a driver; when L is₁＜L≤aL₁When the vehicle-mounted man-machine interaction system is used, a first-level warning is given to a driver to remind the driver to brake in advance; meanwhile, the decision module calculates the normal braking time t of the driver according to a corresponding calculation method_sIf the driver takes an emergency braking measure in time, at t_sIf the brake intensity of the vehicle reaches the maximum, the system does not take effect any more; if the driver is t after the first warning_sIf the braking is not started within the time or the braking strength of the vehicle does not reach the maximum, directly canceling the control authority of the driver on the vehicle accelerator pedal so as to avoid the misoperation of the driver to accelerate the vehicle, and simultaneously carrying out secondary warning on the driver through a vehicle-mounted human-computer interaction system; at the moment, the decision module recalculates the normal braking time t of the driver according to the corresponding calculation method_sIf the driver takes an emergency braking measure in time, at t_sThe brake intensity of the vehicle is maximized, and the system does not take effect any more; if the driver is t after the secondary warning_sIf the braking strength of the inner vehicle is not maximum, directly canceling all operation authorities of the driver, and sensing whether other vehicles exist behind the vehicle lane through a sensing module; when no vehicle exists behind, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module; when the rear part has the vehicle: if the vehicle-to-vehicle interaction module is normal in function or partial function is obstructed, so that only one-way communication of the vehicle to other vehicles can be realized, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, and meanwhile, the vehicle-to-vehicle interaction module gives a warning to the rear vehicle to remind that an obstacle exists in the front of the rear vehicle and to pay attention to early braking or lane change, so that rear-end collision between the front vehicle and the rear vehicle during braking of the front vehicle is avoided; if the vehicle-to-vehicle interaction module fails, the vehicle sensing module acquires the current longitudinal speed u of the rear vehicle_rAnd simultaneously: when u is_rt_b＞(L₁+L_r) Then, the system is timely switched into a second obstacle avoidance mode; when u is_rt_b≤(L₁+L_r) When the vehicle is braked, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module;

in a first obstacle avoidance mode, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module and comprises the following steps:

firstly, if the decision module makes a braking decision, L is more than or equal to L₁When braking, the vehicle will not collide with the obstacle and is controlledThe module controls the turning angles of front and rear wheels of the vehicle to be zero; if L is less than L₁If the vehicle collides with the obstacle in the braking process, the control module inputs a leftward turning angle delta to the front wheel of the vehicle to protect the life safety of a driver so as to avoid the direct collision between the cockpit and the obstacle; the unit of delta is degree, the size of delta depends on the distance between the vehicle and the obstacle at the moment when the decision module makes a braking decision, and the value is recorded as L_b(ii) a The shorter the distance between the vehicle and the obstacle is at the moment of making a braking decision by the decision making module, the shorter the time for the vehicle to collide with the obstacle is, and the shorter the time for avoiding the direct collision between the cockpit and the obstacle through the steering of the front wheel is; therefore, the designed and input front wheel steering angle value is increased along with the reduction of the distance between the vehicle and the obstacle when the decision module makes a braking decision, so that the direct collision between the cockpit and the obstacle is effectively avoided. The specific value taking method follows the following formula:

wherein, delta₀For a set initial value of the front wheel steering angle, alpha is an adjustment parameter, delta₀＞α；δ₀The specific value of alpha is determined by manufacturers according to the performance of an automobile steering system, the performance of a braking system, the space structure of a vehicle cab and the width of a vehicle;

when braking, the ABS system works normally, the braking system of the vehicle comprises two braking modes of hydraulic braking and hub motor braking, and the hub motor can provide motor braking torque through reverse rotation; the decision module reasonably calculates and distributes the braking force of the front wheel and the rear wheel to enable the front wheel and the rear wheel to be kept in a state close to locking but not locked at the same time, and the vehicle is controlled to brake in an electro-hydraulic composite braking mode so as to fully utilize the road surface adhesive force.

In the first obstacle avoidance mode, the specific method for reminding the driver of taking obstacle avoidance measures through the human-computer interaction system by the vehicle is as follows:

the specific method for the vehicle-mounted human-computer interaction system to give a first-level warning to the driver comprises the following steps: the control module controls the vehicle-mounted sound box to play voice with the maximum volume of 80%: the front part of the vehicle is provided with an obstacle, and a driver is asked to brake in time; controlling a vehicle-mounted man-machine interaction screen to display a flickering exclamation mark pattern, wherein the exclamation mark is red, the screen background is yellow, and the exclamation mark flickering frequency is f;

the specific method for the vehicle-mounted human-computer interaction system to carry out secondary warning on the driver comprises the following steps: the control module controls an air-conditioning air outlet right above the driver seat to convey cold air; controlling the vehicle-mounted sound to play voice at the maximum volume: please brake immediately; controlling a vehicle-mounted man-machine interaction screen to display a flickering exclamation mark pattern, wherein the exclamation mark is red, the screen background is yellow, and the exclamation mark flickering frequency is f;

thirdly, the frequency f of the flickering exclamation mark pattern displayed by the vehicle-mounted man-machine interaction screen is related to the real-time distance L between the vehicle and the obstacle, wherein the unit of f is Hertz, and the specific value taking method follows the following formula:

wherein L is the longitudinal distance between the vehicle and the front obstacle, L₁A minimum distance f required for a vehicle control module to control the vehicle to brake in a specific braking mode to a non-collision parking state under the instruction of a decision module₀The flicker frequency of the exclamation mark pattern when the real-time distance L between the vehicle and the obstacle approaches zero, beta is an adjusting parameter, f₀＞β；f₀The value of beta can be set by a manufacturer providing a corresponding man-machine interaction liquid crystal display screen, and can also be set by a driver according to own driving habits and experiences; it can be seen that when the human-computer interaction system warns the driver, the frequency f of the blinking exclamation mark pattern displayed by the vehicle-mounted human-computer interaction screen gradually increases as the longitudinal distance between the vehicle and the front obstacle gradually decreases;

fourthly, after the vehicle-mounted human-computer interaction system carries out primary warning or secondary warning on the driver, if the driver carries out t after voice reminding_sTaking emergency braking measures within the time period to make the vehicle reach the maximum braking intensity, the system is no longer in effect, wherein t_sThe value taking method comprises the following steps: the decision-making module builds up a database of,collecting the time from the time when a driver receives the prompt of the man-machine interaction platform for emergency braking voice in the daily driving process to the time when the vehicle reaches the maximum braking strength by taking emergency braking measures; the collected time data is recorded as s₁,s₂,…s_nDetermining t by means of least squares_sThe value of (A) is as follows: let the error sum of squares

Substituting data s₁,s₂,…s_n(ii) a The decision module calculates s value when the R value is minimum, namely t in the warning process_sThe value of (a).

As shown in fig. 4, the second obstacle avoidance mode control process of the present invention is as follows:

firstly, the current longitudinal speed v of the vehicle is collected by a sensing module_sThe longitudinal distance L between the vehicle and the front obstacle and the longitudinal distance L between the vehicle and the adjacent lane vehicle i_piThe transverse distance L of the center of mass of the vehicle relative to the left and right side boundaries of the obstacle_zl,L_zrAnd transmitting to the decision module; then, after the decision module inputs the relevant parameters, the minimum distance L required by the vehicle control module to control the vehicle to brake in a specific braking mode to a collision-free parking mode under the instruction of the decision module is calculated through a decision algorithm in the controller₁Shortest braking time t_bMinimum longitudinal distance L between the left lane vehicle and the host vehicle_lminMinimum longitudinal distance L between right-side lane vehicle and host vehicle_rminMinimum safe lane-changing longitudinal distance L_s(ii) a Introducing an adjusting parameter b, and calculating the value of b by a decision module according to the current longitudinal speed of the vehicle; further: when the sensing module fails to sense the obstacle in front in time or the obstacle suddenly appears to cause bL₁＜L≤L₁The sensing module senses whether other vehicles run in the adjacent lane of the vehicle; when no other vehicles run in any adjacent lane on one side, the vehicle traction control system is closed, the wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and the wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment, so that the emergency yaw moment is generated, and the emergency yaw moment is realizedChanging the track and avoiding the barrier; if no other vehicles run in the adjacent lanes on the two sides of the lane, the decision-making module selects a proper adjacent lane to implement lane change by a specific method; when other vehicles run on the adjacent lanes on two sides, when L is equal to L_lmin≥L_rminSelecting a left lane as a target obstacle avoidance lane; when L is_lmin＜L_rminAnd selecting a right lane as a target obstacle avoidance lane, and simultaneously: when the vehicle-to-vehicle interaction module is normal in function or partial function is in obstacle, so that only one-way communication of the vehicle to other vehicles can be realized, the vehicle sends a vehicle lane changing and obstacle avoiding intention and a target obstacle avoiding lane to the vehicles on the lanes on two sides through the vehicle-to-vehicle interaction module, the vehicles on the target obstacle avoiding lane provide a safe lane changing space for the vehicle by adopting a speed control method, the vehicle closes a vehicle traction control system, wheels on one side close to the available obstacle avoiding lane are controlled to brake through a decision module, and wheels on one side far away from the obstacle avoiding lane are accelerated to drive so as to generate expected emergency yaw moment, so that lane changing and obstacle avoiding are realized; when the vehicle-to-vehicle interaction module fails, the decision module judges whether the collision risk exists or not if the lane changing and obstacle avoiding are carried out according to the longitudinal distance between the vehicle and the adjacent lane vehicle; the specific process comprises the following steps: when the L is satisfied for any vehicle i on the target obstacle avoidance lane_pi＞L_sWhen the vehicle is in use, the vehicle traction control system is closed, wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment, so that lane changing and obstacle avoidance are realized; wherein L is_sThe minimum safe lane changing longitudinal distance is set; when any vehicle i exists on the target obstacle avoidance lane, L is enabled_pi≤L_sWhen the system is switched into a first obstacle avoidance mode in time, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, and collision loss is reduced as much as possible;

in the second obstacle avoidance mode, when the vehicle-to-vehicle interaction module fails, the decision module may determine the longitudinal distance L between the vehicle and the target obstacle avoidance lane vehicle according to the longitudinal distance L between the vehicle and the target obstacle avoidance lane vehicle_piLongitudinal distance L from minimum safe lane change_sThe size between: whether the vehicle has collision risk with the target obstacle avoidance lane vehicle or not when the vehicle changes lanes;wherein L is_sThe value of (a) can be determined by the longitudinal speed of the vehicle in the adjacent lane, the longitudinal speed of the vehicle, the predicted maximum lane change time of the vehicle and the longitudinal position of the vehicle in the adjacent lane relative to the vehicle; the specific calculation method is as follows:

l when the longitudinal position of the adjacent lane vehicle is in front of the vehicle_sThe calculation formula of (2) is as follows:

L_s＝v_st_{f max}-v_it_{f max}

l when the longitudinal position of the adjacent lane vehicle is behind the vehicle_sThe calculation formula of (2) is as follows:

L_s＝v_it_{f max}-v_st_{f max}

wherein v is_s,v_iThe current longitudinal speed, t, of the vehicle and the target obstacle avoidance lane vehicle i respectively_{f max}The calculation formula of the predicted maximum lane change time for the vehicle is as follows:

t_{f max}＝L/v_s

wherein L is the longitudinal distance between the vehicle and the front obstacle.

In a second obstacle avoidance mode, when other vehicles run in adjacent lanes on two sides and the vehicle-to-vehicle interaction module is normal in function, the method for controlling the speed adopted by the vehicle of the target obstacle avoidance lane to provide a safe lane change space for the vehicle comprises the following control processes:

the sensor module measures the current longitudinal speed v of the adjacent lane vehicle i_iAnd the current longitudinal speed v of the vehicle_s；

When the adjacent lane vehicle i is positioned in front of the vehicle, if v_i≤cv_sThe vehicle i in the adjacent lane starts accelerating to cv at the maximum acceleration under the action of the decision module_sThen keeping constant speed running; if v is_i＞cv_sThe vehicle i in the adjacent lane keeps running at a constant speed at the current speed;

when the adjacent lane vehicle i is behind the vehicle, if v_i≥dv_sThe vehicle i in the adjacent lane starts to decelerate to the maximum braking intensity under the action of the decision moduledv_sThen keeping constant speed running; if v is_i＜dv_sThe vehicle i in the adjacent lane keeps running at a constant speed at the current speed;

wherein c and d are adjustment parameters; in the process of changing lanes and avoiding obstacles, the longitudinal speed v of the vehicle_sCan be considered approximately constant; controlling the values of the adjusting parameters c and d, and controlling the longitudinal speed of the vehicle in the adjacent lane in front of the vehicle to be always greater than the longitudinal speed of the vehicle when the vehicle changes lanes if c is greater than 1; the longitudinal speed of the vehicle in the adjacent lane behind the vehicle in the lane changing process of the vehicle can be controlled to be always smaller than the longitudinal speed of the vehicle when d is less than 1; thereby providing a safe lane change space for the vehicle; in order to prevent the condition that the longitudinal speed of the vehicles in the adjacent lanes is too small or too large, the parameters c and d are adjusted by adopting a method of sectional value:

when the longitudinal speed v of the vehicle_sC is not more than 50km/h₂,d＝d₁；

When 50km/h < v_sWhen the value is less than 100km/h, the values of c and d follow the following formula:

when v is_sWhen the speed is more than or equal to 100km/h, c is c₁,d＝d₂；

Wherein:

c₁,c₂,d₁,d₂the specific value is set by a manufacturer according to the dynamic performance of the automobile.

As shown in fig. 5, the third obstacle avoidance mode control process of the present invention is as follows:

firstly, the current longitudinal speed v of the vehicle is collected by a sensing module_sThe longitudinal distance L between the vehicle and the front obstacle, and the transverse distance L between the center of mass of the vehicle and the boundaries of the left side and the right side of the obstacle_zl,L_zrAnd transmitting to the decision module; then, the decision module is atAfter the relevant parameters are input, the minimum distance L required by the vehicle control module to control the vehicle to brake in a specific braking mode to a collision-free parking mode under the instruction of the decision module is calculated through a decision algorithm in the controller₁Shortest braking time t_b(ii) a Introducing an adjusting parameter b, and calculating the value of b by a decision module according to the current longitudinal speed of the vehicle; when the sensing module fails to sense the obstacle ahead in time or the obstacle suddenly appears to cause that L is less than or equal to bL₁The sensing module senses whether other vehicles run in the adjacent lane; further: when no other vehicles run in the adjacent lanes, the electronic stability control system of the vehicle is closed, the wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and the wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment; meanwhile, the four-wheel independent steering mechanism is controlled to adopt a four-wheel different-direction steering mode, namely the steering direction of the rear wheels is opposite to that of the front wheels so as to reduce the steering radius and realize lane changing and obstacle avoidance; if no other vehicles run on the two sides of the lane, the decision-making module selects a proper adjacent lane to change lanes; when adjacent lane in both sides all has other vehicles to travel, take different obstacle avoidance schemes based on car to car interaction module function sound degree: when the vehicle-to-vehicle interaction module is normal in function, each vehicle acquires the longitudinal speed, the longitudinal acceleration, the centroid abscissa, the centroid ordinate, the course angle, the lane changing intention of a driver and the straight-ahead intention of the driver of the vehicle through the self sensing module; the decision module of each vehicle selects a proper path planning method to obtain the possible path of each vehicle in the lane changing time of the vehicle by using the acquired information; if the vehicle is detected to have the intention of changing the lane of the driver, an objective function established based on the lane changing efficiency and the stability of the vehicle is adopted to obtain the optimal lane changing path of each vehicle; the vehicle receives the optimal lane changing path planned by other vehicles through a vehicle-to-vehicle interaction module, and judges whether the vehicle has the risk of collision with the adjacent lane vehicles at any time when the vehicle changes lanes by adopting a vehicle contour equation simultaneous solution method; further: when the decision module judges that the vehicle has collision risks with vehicles on two adjacent lanes if the vehicle changes lanes to avoid the barrier, the system timely switches to the first obstacle avoidanceIn the mode, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, so that the collision loss is reduced as much as possible; when the decision-making module judges that no collision risk occurs with the vehicle in the adjacent lane, the electronic stability control system of the vehicle is closed, the wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision-making module, and the wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment; meanwhile, the four-wheel independent steering mechanism is controlled to adopt a four-wheel different-direction steering mode, namely the steering direction of the rear wheels is opposite to that of the front wheels so as to reduce the steering radius and realize lane changing and obstacle avoidance; if the decision-making module judges that the vehicle has no collision risk with the vehicles on the adjacent two side lanes when the vehicle is subjected to lane changing and obstacle avoidance, the decision-making module selects a proper adjacent side lane to implement lane changing; when the function of the vehicle-to-vehicle interaction module is partially obstructed, so that only one-way communication or function failure of the vehicle to other vehicles can be realized; at the moment, the distance between the vehicle and the barrier is close, and whether collision risks exist in the lane changing and obstacle avoiding measures cannot be judged, so that the lane changing measures are taken in a trade, and major accidents are easily caused; the system is timely switched into a first obstacle avoidance mode, and the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, so that collision loss is reduced as much as possible; if the vehicle-to-vehicle interaction module can realize one-way communication, the vehicle-to-vehicle interaction module reminds surrounding vehicles that the vehicle is about to be emergently braked and pays attention to deceleration and avoidance; if the vehicle-to-vehicle interaction module fails in function, the vehicle control module controls the vehicle to turn on the double flashing lamps, and simultaneously continuously whistles to remind surrounding vehicles to reduce the speed and avoid the vehicles.

In the third obstacle avoidance mode, after the vehicle acquires the motion information of the vehicle through the vehicle-mounted sensor, the method for determining the path of the vehicle and the adjacent vehicle comprises the following steps:

the method for selecting the vehicle to plan the path by the decision module comprises the following steps:

for the host vehicle, when eL₁＜L≤bL₁In the process, a quintic polynomial method is selected to plan the lane change path, and the quintic polynomial is smoother than the path planned by the cubic polynomial, so that the requirement on the stability of the vehicle is met more easily; when L is less than or equal to eL₁Time of flight, selection of cubic polynomial methodPlanning the road path, wherein the distance between the vehicle and the barrier is smaller, so that the possibility that the path planned by the cubic polynomial can successfully avoid collision is higher; wherein e is an adjusting parameter, e is more than 0 and less than b, and the specific value is set by a manufacturer according to the performance of the automobile steering system and the design condition of the stability structure of the automobile; for the adjacent vehicle, judging whether the driver of the adjacent vehicle has the intention of changing the lane by a decision module; if the driver of the adjacent vehicle does not have the intention of changing lanes, the decision-making module plans a straight-going path of the adjacent vehicle according to the current speed of the adjacent vehicle acquired by the vehicle body sensor and the acceleration degree; if the drivers of the adjacent vehicles have the lane changing intention, the decision module selects a fifth-order polynomial to plan the lane changing path:

the expression of the vehicle track change trajectory planning model based on the cubic polynomial is as follows:

wherein x (t), y (t) are the transverse position and the longitudinal position of the vehicle in the geodetic coordinate system, u is the current longitudinal speed of the vehicle, and t is the current longitudinal speed of the vehicle₀，t₁Starting and ending times, m, for trajectory planning₀,m₁,m₂,m₃All coefficients are cubic polynomial interpolation functions;

the expression of the vehicle track change trajectory planning model based on the fifth-order polynomial is as follows:

in the formula, n₀,n₁,n₂,n₃,n₄,n₅All are coefficients of a quintic polynomial interpolation function;

secondly, after a track changing track model is obtained, the track changing time t is adjusted_f＝t₁-t₀The size of the obstacle avoidance path is obtained, and a series of possible lane changing and obstacle avoidance paths of the vehicle can be obtained;

determining the stable limit of the yaw velocity and the centroid yaw angle when the vehicle changes lanes on the premise of meeting the vehicle stability according to the two-degree-of-freedom model of the vehicle:

the stability limit calculation method of the yaw rate is as follows:

longitudinal speed v under vehicle body coordinate system in vehicle lane changing process_xApproximately equal to the longitudinal velocity u in the geodetic coordinate system, i.e.:

v_x≈u

according to the vehicle two-degree-of-freedom dynamic model shown in FIG. 6, the vehicle mass center slip angle and the yaw rate have the following relationship;

wherein β represents the centroid slip angle, F_yf,F_yrRespectively representing the lateral force applied to the front axle and the rear axle of the vehicle, m is the mass of the whole vehicle, u is the longitudinal speed of the vehicle, and delta_fRepresenting the front wheel steering angle, and assuming that the vehicle front left and right wheel steering angles are the same, r is the vehicle yaw rate;

further, when

Approaching zero, the vehicle dynamics are considered stable; neglecting tire longitudinal forces, the yaw-rate stability limit is as follows:

wherein mu is a road surface adhesion coefficient;

therefore, the temperature of the molten steel is controlled,

the stable limit calculation method of the centroid slip angle is as follows:

the calculation of the stable limit of the centroid slip angle relies on the research on the tire saturation characteristics, the tire saturation characteristics are deduced according to a classical brush model, and the expression of the brush model is as follows:

in the formula, alpha_f,α_rRespectively representing the slip angles, F, of the front and rear axles of the vehicle_zf,F_zrRespectively representing the vertical forces, C, of the front and rear axles of the vehicle_αf,C_αrRespectively representing the cornering stiffness of the front axle and the rear axle of the vehicle; with the brush model, alpha is assumed under a small angle_rThe stable range of (a) is as follows:

in the formula, a₀,b₀Respectively representing the distances of the front axle and the rear axle of the vehicle from the center of mass of the vehicle; the centroid slip angle stability limit is as follows:

therefore, the temperature of the molten steel is controlled,

in the formula, l is a vehicle wheel base;

setting an objective function as follows for determining the optimal track change track of the vehicle:

in the formula, L_maxThe maximum lane changing longitudinal distance of the vehicle, u is the current longitudinal speed of the vehicle, and t_fR (t) is lane change time, beta (t) is yaw angular velocity and centroid side slip angle of the vehicle in the lane change process, and r_max,β_maxThe stable limit values of the yaw angular velocity and the centroid slip angle r obtained in the step three_min,β_minFor changing track for allMinimum yaw rate and centroid slip angle in the trace, w₁,w₂,w₃,w₄,w₅Is a weight coefficient; the first item of reaction lane change efficiency of the objective function and the second, third, fourth and fifth item of reaction lane change stability; the second term and the third term reflect the fluctuation conditions of the yaw velocity and the centroid slip angle in the lane changing process, and the fourth term and the fifth term reflect the influence of the maximum value of the yaw velocity and the centroid slip angle on the stability in the lane changing process;

setting different objective function solving constraint conditions for the vehicle and the adjacent vehicles; for the vehicle, under the emergency obstacle avoidance environment, the requirement on lane change efficiency is higher, so the weight occupied by the first item of the design objective function is higher, and the following are taken:

w₁＝0.6,w₂＝w₃＝w₄＝w₅＝0.1

meanwhile, the maximum lane changing longitudinal distance is the distance L between the vehicle and the front obstacle;

therefore, the corresponding constraint conditions are as follows:

for adjacent vehicles, emergency obstacle avoidance is not needed, and lane changing efficiency and lane changing stability need to be considered comprehensively, so the sum of the first weight and the last four weights of a design objective function is equal to obtain:

w₁＝0.5,w₂＝w₃＝w₄＝w₅＝0.125

meanwhile, the maximum lane changing distance is set to be L_lmaxThe specific value taking method comprises the following steps:

the decision-making module establishes a database to collect the time from the beginning of lane changing to the end of lane changing of the vehicle at different speeds; when the current speed of the adjacent vehicle i is u_iWhen L is_lmaxIs that the vehicle speed in the database is u_i-10km/h～u_iAverage value of the acquired track-changing time within the range of +10 km/h;

therefore, the corresponding constraint conditions are as follows:

substituting the constraint conditions into the objective function established in the step (iv) to solve to obtain the optimal lane change path of the vehicle at any speed;

after the adjacent vehicle decision module plans the path, the path information is sent to the vehicle through the vehicle-to-vehicle interaction module.

Further, the process that the vehicle decision module judges whether the collision risk with the adjacent lane vehicle exists when the optimal path planned by the vehicle carries out lane change and obstacle avoidance comprises the following steps:

the vehicle contour is regarded as an ellipse, and the collision problem between vehicles can be converted into the problem whether the vehicle and the vehicle elliptical contour intersect or not; the elliptical contour enlarges the area of the vehicle contour relative to the real vehicle contour, and the probability of misjudgment is smaller when collision risk judgment is carried out; meanwhile, the elliptic contour is easier to establish a corresponding mathematical model for calculation processing compared with the real vehicle contour, so that the speed of judging the collision risk by the decision module is increased; the center of the ellipse is provided with a vehicle mass center coordinate, the ellipse passes through four vertexes of the vehicle, and in order to enable the ellipse outline to better wrap the vehicle boundary, the short axial length of the ellipse is 1.2 times of the vehicle width; if the reference course angle of the vehicle is the orientation of the vehicle at the corresponding moment, a series of elliptical contours corresponding to time can be generated according to the reference track; for any vehicle, when the longitudinal speed is determined, for the reference trajectory determining the lane change time, the position coordinates of the four vertices of the vehicle at time t are calculated as follows:

the coordinates of the end points on the two sides of the minor axis of the elliptical profile are calculated as follows:

in the formula, τ_Hk,τ_iRespectively the lane changing time length of the vehicle and the lane changing time length, x, of the vehicle i in the adjacent lane_k1,...,4(t),y_k1,...,4(t) four vertex coordinates of the vehicle, x_k5,6(t),y_k5,6(t) coordinates of end points on both sides of the minor axis of the elliptical profile, l_H,w_HRespectively showing the length and width of the host vehicle,

is the heading angle, x_k(t),y_k(T) represents a centroid position of the host vehicle, T being a time interval;

the general expression of the ellipse equation can be set to the form:

Ax²+By²+2Cxy+Dx+Ey+F＝0

the system comprises a six-point coordinate simultaneous equation set, a six-point coordinate simultaneous equation set and a six-point coordinate simultaneous equation set, wherein A, B, C, D, E and F are undetermined coefficients of an elliptic equation;

secondly, after the vehicle acquires the planned paths of all adjacent vehicles through the vehicle-to-vehicle interaction module, solving the elliptical contour equations of all vehicles at any time t when the vehicle carries out lane changing according to the planned optimal path changing path; respectively determining an elliptic contour equation between the simultaneous vehicle and each adjacent vehicle, wherein if no real solution exists in the simultaneous equation set, the vehicle and the adjacent vehicle have no risk of collision; if any one group of the ellipse equations has a real solution, the vehicle and the adjacent vehicle have the risk of collision.

In the technical scheme, when the vehicle is ready to take lane changing and obstacle avoiding measures and the adjacent lanes at the two sides of the vehicle can be changed, the method for selecting the appropriate target obstacle avoiding lane by the decision module comprises the following steps:

firstly, the vehicle perception module collects the transverse distance L of the center of mass of the vehicle relative to the left and right side boundaries of the barrier_zl,L_zr；

② this vehicleThe decision module makes a judgment if L is_zl≤L_zrSelecting a left adjacent lane as a target lane changing lane; if L is_zl＞L_zrAnd selecting the adjacent lane on the right side as a target lane changing lane. Therefore, the transverse displacement in the lane changing process of the vehicle can be reduced, the lane changing time is shortened, and the collision risk is further reduced.

In the technical scheme, a distance comparison method is used as a basis for initially selecting an obstacle avoidance mode by an emergency obstacle avoidance system; wherein a and b are both adjustment parameters, a₁＜a＜a₂,b₁＜b＜b₂The specific value method of the parameters is as follows:

when the longitudinal speed v of the vehicle_sA is not more than 50km/h, a is a₁,b＝b₁；

When 50km/h < v_sWhen the value is less than 100km/h, the values of a and b follow the following formula:

when v is_sA is more than or equal to 100km/h₂,b＝b₂；

Wherein, 1 < a₁,a₂＜2,0.5＜b₁,b₂And (3) the specific value is set by a manufacturer according to the performance of the automobile brake system.

After the vehicle adopts the lane changing and obstacle avoiding measures, the judgment basis of the emergency obstacle avoiding system for finishing the work is as follows:

when the vehicle takes the lane changing and obstacle avoiding measures in the second obstacle avoiding mode: the perception module perceives the transverse distance L between the vehicle mass center and the boundary of the barrier on the lane changing side of the vehicle in real time_zWhen L is sensed_zContinuously decreases to zero and then continuously increases to L_z＝l_HAt the moment of 2, the emergency obstacle avoidance system is closed in time, and the vehicle traction control system and the vehicle electronic stability system recover to work normally so as to ensure the stability of the vehicle;

when the vehicle takes the lane changing and obstacle avoiding measures in the third obstacle avoiding mode: the decision-making module establishes a linear equation which is parallel to the lane line and tangent to the boundary of the barrier at the lane changing side of the vehicle; calculating whether the ellipse outline equation and the linear equation have real number solutions in real time; when the calculation result is changed from the real number solution to the non-real number solution, the emergency obstacle avoidance system is closed in time, and the vehicle traction control system and the vehicle electronic stability system recover to work normally so as to ensure the stability of the vehicle;

meanwhile, if the vehicle-to-vehicle interaction module has normal functions, the position and the size of the barrier are marked and uploaded to a vehicle networking map, and other nearby vehicles are reminded to change lanes in advance to avoid the barrier.

Claims (10)

1. The utility model provides an urgent obstacle avoidance system of intelligent networking four-wheel independent steering and independent drive electric automobile which characterized in that: the obstacle avoidance system comprises three obstacle avoidance modes, namely a first obstacle avoidance mode, a second obstacle avoidance mode and a third obstacle avoidance mode; the whole system comprises a vehicle-to-vehicle interaction module, a sensing module, a decision module and an execution module; the system can switch different obstacle avoidance modes according to the collision risk degree of the vehicle and the front obstacle under three conditions of a vehicle-to-vehicle interaction module carried by the vehicle, namely under each condition of normal function, partial function obstacle and function failure; when partial functions of the vehicle-to-vehicle interaction module are obstructed, only one-way communication of the vehicle to other vehicles can be realized;

the vehicle-to-vehicle interaction module realizes direct communication between vehicles and has the capability of receiving and sending basic data of the vehicles; when the vehicle-to-vehicle interaction module is normal in function or part of functions are in obstacle avoidance, the vehicle-to-vehicle interaction module can assist or directly participate in the implementation of obstacle avoidance measures in different obstacle avoidance modes; under a first obstacle avoidance mode, the vehicle-to-vehicle interaction module can warn a vehicle behind the lane to avoid collision so as to prevent rear-end collision; under a second obstacle avoidance mode, the vehicle-to-vehicle interaction module can inform vehicles on adjacent lanes of the vehicle to adopt a speed control method to provide a safe lane changing space for the vehicle; in a third obstacle avoidance mode, the vehicle-to-vehicle interaction module can send respective path information planned by other vehicle decision modules to the vehicle, and the vehicle judges whether the vehicle has a collision risk in the lane changing and obstacle avoidance process through a corresponding algorithm in the decision modules;

the sensing module acquires the motion information of the vehicle through the vehicle-mounted sensor, identifies lane line information through the camera, and acquires all-directional distance information between the vehicle and an obstacle or other vehicles through the radar; the vehicle motion information includes: the longitudinal speed, the longitudinal acceleration, the centroid abscissa, the centroid ordinate, the course angle, the lane changing intention of the driver and the straight-driving intention of the driver of the vehicle; the omnibearing distance information comprises a longitudinal distance L between the vehicle and a front obstacle and a longitudinal distance L between the vehicle and a vehicle behind the vehicle_rThe longitudinal distance L between the vehicle and the adjacent lane vehicle i_piThe transverse distance L of the center of mass of the vehicle relative to the left and right side boundaries of the obstacle_zl,L_zr；

The decision module calculates the minimum distance L required by the vehicle control module to control the vehicle to brake in a specific braking mode to a collision-free parking mode under the instruction of the decision module according to the collected related information₁Shortest braking time t_bMinimum longitudinal distance L between vehicle on left lane of vehicle and vehicle_lminThe minimum longitudinal distance L between the vehicle on the right side lane of the vehicle and the vehicle_rminMinimum safe lane-changing longitudinal distance L_sThe lane changing intention of the driver of the adjacent lane vehicle i and the straight-going intention of the driver of the adjacent lane vehicle i; according to L, L₁According to the method, a proper obstacle avoidance mode is selected preliminarily, and a final obstacle avoidance mode and an obstacle avoidance control strategy are determined according to the functional completeness of a vehicle-to-vehicle interaction module, the emergency response condition of a driver and the traffic condition around the vehicle; in the third obstacle avoidance mode, if the vehicle-to-vehicle interaction module is normal in function, the vehicle decision module needs to plan the lane change path of the vehicle according to the selected target lane change and obstacle avoidance lane by adopting a proper algorithm, meanwhile, the vehicle-to-vehicle interaction module receives path planning information of other vehicles in the predicted lane change time of the vehicle, and then a method based on vehicle elliptic contour equation simultaneous solution is adopted to analyze and calculate whether the vehicle collides with other vehicles in the lane change and obstacle avoidance processThe risk of a crash;

the execution module controls a related execution mechanism to complete a control strategy input by the decision module so as to realize an emergency obstacle avoidance process of the vehicle; the actuator includes: the four-wheel-hub motor type four-wheel steering system comprises four wheel hub motors, four-wheel independent steering mechanisms, an electric control hydraulic braking system and a human-computer interaction system; the human-computer interaction system comprises: the system comprises vehicle-mounted voice interaction equipment, a vehicle-mounted man-machine interaction liquid crystal display screen and an air conditioner air outlet; the air-conditioning air outlet is positioned on the top of the vehicle above the driver seat, and can convey cold air at a specific moment so as to prevent a driver from failing to respond to the prompt of a human-computer interaction system in time due to fatigue driving;

the switching method of the three obstacle avoidance modes comprises the following processes:

(1) the first control method for the obstacle avoidance mode comprises the following processes:

1) when L > aL₁When the emergency obstacle avoidance system is not in use, the vehicle is driven by the driver, wherein a is an adjustment parameter, a₁＜a＜a₂The decision-making module calculates the value of a according to the current longitudinal speed of the vehicle;

2) when L is₁＜L≤aL₁When the vehicle-mounted man-machine interaction system is used, a first-level warning is given to the driver to remind the driver to brake in advance; meanwhile, the decision module calculates the normal braking time t of the driver according to a corresponding calculation method_sIf the driver takes emergency braking measures in time, the vehicle is driven at t_sWhen the internal braking strength reaches the maximum, the system does not take effect any more; if the driver is t after the first warning_sIf the braking is not started within the time or the braking strength of the vehicle does not reach the maximum, directly canceling the control authority of the driver on the vehicle accelerator pedal so as to avoid the misoperation of the driver to accelerate the vehicle, and simultaneously carrying out secondary warning on the driver through a vehicle-mounted human-computer interaction system; at the moment, the decision module recalculates the normal braking time t of the driver according to the corresponding calculation method_sIf the driver takes an emergency braking measure in time, at t_sThe brake intensity of the vehicle is maximized, and the system does not take effect any more; if the driver is t after the secondary warning_sIf the brake strength of the inner vehicle is not maximum, the full operation authority of the driver is directly cancelledSensing whether other vehicles exist behind the vehicle lane through a sensing module; when no vehicle exists behind, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module; when the rear part has the vehicle:

firstly, when the vehicle-to-vehicle interaction module is normal in function or partial function is obstructed, so that only one-way communication of the vehicle to other vehicles can be realized, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, and meanwhile, the vehicle gives a warning to a rear vehicle through the vehicle-to-vehicle interaction module to remind that an obstacle exists in the front of the rear vehicle and pay attention to early braking or lane change, so that rear-end collision between the vehicle and the rear vehicle during braking is avoided;

secondly, when the vehicle-to-vehicle interaction module fails, the vehicle sensing module acquires the current longitudinal speed u of the rear vehicle_r：

When u is_rt_b＞(L₁+L_r) Then, the system is timely switched into a second obstacle avoidance mode;

when u is_rt_b≤(L₁+L_r) When the vehicle is braked, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module;

(2) the second control method for the obstacle avoidance mode comprises the following processes:

when the sensing module fails to sense the obstacle in front in time or the obstacle suddenly appears to cause bL₁＜L≤L₁The sensing module senses whether other vehicles run in the adjacent lane of the vehicle, wherein b is an adjusting parameter, and b is₁＜b＜b₂The decision-making module calculates the value of b according to the current longitudinal speed of the vehicle;

1) when no other vehicles run in the adjacent lane of the vehicle on any side, the vehicle traction control system is closed, the wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and the wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment, so that lane changing and obstacle avoidance are realized; if no other vehicles run in the adjacent lanes on the two sides of the vehicle, the decision-making module selects a proper adjacent lane as an obstacle avoidance lane by a specific method;

2) when the adjacent lanes on both sides of the vehicle are all provided with other lanesWhen the vehicle is running, L_lmin≥L_rminSelecting a left lane as a target obstacle avoidance lane; when L is_lmin＜L_rminAnd selecting a right lane as a target obstacle avoidance lane, and simultaneously:

firstly, when the vehicle-to-vehicle interaction module is normal in function or partial function is in obstacle, so that only one-way communication of the vehicle to other vehicles can be realized, the vehicle sends a vehicle lane changing and obstacle avoiding intention and a target obstacle avoiding lane to the vehicles on the lanes on two sides through the vehicle-to-vehicle interaction module, the other vehicles on the target obstacle avoiding lane provide a safe lane changing space for the vehicle by adopting a speed control method, the vehicle closes a vehicle traction control system, and the wheels on one side close to the available obstacle avoiding lane are controlled to brake through a decision module and are accelerated to drive the wheels on one side far away from the obstacle avoiding lane so as to generate an expected emergency yaw moment and realize lane changing and obstacle avoiding;

when the vehicle-to-vehicle interaction module fails:

the decision-making module judges whether the vehicle has the risk of collision with the adjacent lane vehicle if the vehicle changes the lane and avoids the barrier according to the longitudinal distance between the vehicle and the adjacent lane vehicle;

when the L is satisfied for any vehicle i on the target obstacle avoidance lane_pi＞L_sWhen the vehicle is in use, the vehicle traction control system is closed, wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment, so that lane changing and obstacle avoidance are realized; wherein L is_sThe minimum safe lane changing longitudinal distance is set;

when any vehicle i exists on the target obstacle avoidance lane, L is enabled_pi≤L_sWhen the system is switched into a first obstacle avoidance mode in time, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, and collision loss is reduced as much as possible;

(3) the third control method for the obstacle avoidance mode comprises the following processes:

when the sensing module fails to sense the obstacle ahead in time or the obstacle suddenly appears to cause that L is less than or equal to bL₁The sensing module senses whether other vehicles run in the adjacent lane; wherein b is an adjustment parameter, b₁＜b＜b₂The decision-making module calculates the value of b according to the current longitudinal speed of the vehicle;

1) when no other vehicles run in the adjacent lane of the vehicle on any side, the electronic stability control system of the vehicle is closed, the wheels on one side close to the available obstacle avoidance lane are controlled to brake through the decision module, and the wheels on one side far away from the obstacle avoidance lane are accelerated and driven to generate an expected emergency yaw moment; meanwhile, the four-wheel independent steering mechanism is controlled to adopt a four-wheel different-direction steering mode, namely the steering direction of the rear wheels is opposite to that of the front wheels so as to reduce the steering radius and realize lane changing and obstacle avoidance; if no other vehicles run in the adjacent lanes on the two sides of the vehicle, the decision-making module selects a proper adjacent lane to implement lane change;

2) when other vehicles run on the adjacent lanes on the two sides of the vehicle;

firstly, when the vehicle-to-vehicle interaction module is in a normal function, each vehicle acquires the longitudinal speed, the longitudinal acceleration, the mass center abscissa, the mass center ordinate, the course angle, the lane changing intention of a driver and the straight-ahead intention of the driver of the vehicle through the self sensing module; the decision module of each vehicle selects a proper path planning method to obtain the possible path of each vehicle in the lane changing time of the vehicle by using the acquired information; if the vehicle is detected to have the intention of changing the lane of the driver, an objective function established based on the lane changing efficiency and the stability of the vehicle is adopted to obtain the optimal lane changing path of each vehicle; the vehicle receives the optimal lane changing path planned by other vehicles through a vehicle-to-vehicle interaction module, and then a method based on vehicle elliptic contour equation simultaneous solution is adopted to judge whether the vehicle has the risk of collision with the adjacent lane vehicle at any time when the vehicle changes lanes; further:

when the decision module judges that the vehicle changes lanes and the vehicles on the adjacent lanes on the two sides have collision risks, the system timely switches to a first obstacle avoidance mode, and the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, so that collision loss is reduced as much as possible;

when the decision-making module judges that the vehicle does not have collision risk with the vehicle on the adjacent lane at any side when the vehicle changes lanes, the electronic stability control system of the vehicle is closed, the wheels at one side close to the available obstacle avoidance lane are controlled to brake through the decision-making module, and the wheels at one side far away from the obstacle avoidance lane are accelerated and driven to generate expected emergency yaw moment; meanwhile, the four-wheel independent steering mechanism is controlled to adopt a four-wheel different-direction steering mode, namely the steering direction of the rear wheels is opposite to that of the front wheels so as to reduce the steering radius and realize lane changing and obstacle avoidance; if the decision-making module judges that the vehicle does not have collision risk with the vehicles on the adjacent two side lanes when the vehicle changes lanes, the decision-making module selects a proper adjacent side lane to implement lane changing through a specific method;

when partial functions of the vehicle-to-vehicle interaction module are obstructed, only one-way communication or function failure of the vehicle to other vehicles can be realized; the system is timely switched into a first obstacle avoidance mode, and the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module, so that collision loss is reduced as much as possible; if the vehicle-to-vehicle interaction module can realize one-way communication, the vehicle-to-vehicle interaction module reminds surrounding vehicles that the vehicle is about to be emergently braked and pays attention to deceleration and avoidance; if the vehicle-to-vehicle interaction module fails in function, the vehicle control module controls the vehicle to turn on the double flashing lamps, and simultaneously continuously whistles to remind surrounding vehicles to reduce the speed and avoid the vehicles.

2. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: in a first obstacle avoidance mode, the vehicle control module controls the vehicle to brake in a specific braking mode under the instruction of the decision module and comprises the following steps:

firstly, if the decision module makes a braking decision, L is more than or equal to L₁If the vehicle does not collide with the barrier in the braking process, the control module controls the front wheel and the rear wheel of the vehicle to have zero rotating angle in the braking process; if L is less than L₁When the vehicle collides with the obstacle in the braking process, the control module inputs a leftward turning angle delta to the front wheel of the vehicle so as to avoid direct collision between the cockpit and the obstacle; the unit of delta is degree, the size of delta depends on the distance between the vehicle and the obstacle at the moment when the decision module makes a braking decision, and the value is recorded as L_bThe specific value method follows the following formula:

wherein, delta₀For a set initial value of the front wheel steering angle, alpha is an adjustment parameter, delta₀＞α；δ₀The specific value of alpha is determined by manufacturers according to the performance of an automobile steering system, the performance of a braking system, the space structure of a vehicle cab and the width of a vehicle;

when braking, the ABS system works normally, the braking system of the vehicle comprises two braking modes of hydraulic braking and hub motor braking, and the hub motor can provide motor braking torque through reverse rotation; the decision module reasonably calculates and distributes the braking force of the front wheel and the rear wheel to enable the front wheel and the rear wheel to be kept in a state close to locking but not locked at the same time, and the vehicle is controlled to brake in an electro-hydraulic composite braking mode so as to fully utilize the road surface adhesive force.

3. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: in the first obstacle avoidance mode, the specific method for reminding the driver of taking obstacle avoidance measures through the human-computer interaction system by the vehicle is as follows:

the specific method for the vehicle-mounted human-computer interaction system to give a first-level warning to the driver comprises the following steps: the control module controls the vehicle-mounted sound box to play voice with the maximum volume of 80%: the front part of the vehicle is provided with an obstacle, and a driver is asked to brake in time; controlling a vehicle-mounted man-machine interaction screen to display a flickering exclamation mark pattern, wherein the exclamation mark is red, the screen background is yellow, and the exclamation mark flickering frequency is f;

the specific method for the vehicle-mounted human-computer interaction system to carry out secondary warning on the driver comprises the following steps: the control module controls an air-conditioning air outlet right above the driver seat to convey cold air; controlling the vehicle-mounted sound to play voice at the maximum volume: please brake immediately; controlling a vehicle-mounted man-machine interaction screen to display a flickering exclamation mark pattern, wherein the exclamation mark is red, the screen background is yellow, and the exclamation mark flickering frequency is f;

when the vehicle-mounted man-machine interaction screen displays the flickering exclamation mark pattern, the flickering frequency f depends on the real-time distance L between the vehicle and the obstacle, and the unit of f is Hertz, and the specific value taking method follows the following formula:

wherein f is₀The flicker frequency of the exclamation mark pattern when the real-time distance L between the vehicle and the obstacle approaches zero, beta is an adjusting parameter, f₀＞β；f₀The value of beta can be set by a manufacturer providing a corresponding man-machine interaction liquid crystal display screen, and can also be set by a driver according to own driving habits and experiences;

fourthly, after the vehicle-mounted human-computer interaction system carries out primary warning or secondary warning on the driver, if the driver carries out t after voice reminding_sTaking emergency braking measures within the time period to make the vehicle reach the maximum braking intensity, the system is no longer in effect, wherein t_sThe value taking method comprises the following steps:

the decision-making module establishes a database and collects the time from the beginning of the prompt of the driver receiving the emergency braking voice of the man-machine interaction platform in the daily driving process to the time of taking the emergency braking measure to enable the vehicle to reach the maximum braking strength; the collected time data is recorded as s₁,s₂,…s_nDetermining t by means of least squares_sThe value of (A) is as follows: let the error sum of squares

Substituting data s₁,s₂,…s_n(ii) a The decision module calculates s value when the R value is minimum, namely t in the warning process_sThe value of (a).

4. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: in the second obstacle avoidance mode, when the vehicle-to-vehicle interaction module fails, the decision module may determine the longitudinal distance L between the vehicle and the target obstacle avoidance lane vehicle according to the longitudinal distance L between the vehicle and the target obstacle avoidance lane vehicle_piLongitudinal distance L from minimum safe lane change_sThe size between: the vehicle changes lanesWhether the vehicle has collision risk with the target obstacle avoidance lane or not is judged; wherein L is_sThe value of (a) can be determined by the longitudinal speed of the vehicle in the adjacent lane, the longitudinal speed of the vehicle, the predicted maximum lane change time of the vehicle and the longitudinal position of the vehicle in the adjacent lane relative to the vehicle; the specific calculation method is as follows:

l when the longitudinal position of the adjacent lane vehicle is in front of the vehicle_sThe calculation formula of (2) is as follows:

L_s＝v_st_fmax-v_it_fmax

l when the longitudinal position of the adjacent lane vehicle is behind the vehicle_sThe calculation formula of (2) is as follows:

L_s＝v_it_fmax-v_st_fmax

wherein v is_s,v_iThe current longitudinal speed, t, of the vehicle and the target obstacle avoidance lane vehicle i respectively_fmaxThe calculation formula of the predicted maximum lane change time for the vehicle is as follows:

t_fmax＝L/v_s

wherein, L is the longitudinal distance between the vehicle and the front obstacle at the current moment.

5. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: in a second obstacle avoidance mode, when other vehicles run in adjacent lanes on two sides and the vehicle-to-vehicle interaction module is normal in function, the method for controlling the speed adopted by the vehicle of the target obstacle avoidance lane to provide a safe lane change space for the vehicle comprises the following control processes:

the sensor module measures the current longitudinal speed v of the vehicle i adjacent to the vehicle_iAnd the current longitudinal speed v of the vehicle_s；

When the adjacent lane vehicle i is positioned in front of the vehicle, if v_i≤cv_sThe vehicle i in the adjacent lane starts accelerating to cv at the maximum acceleration under the action of the decision module_sThen keeping constant speed running; if v is_i＞cv_sAdjacent lane vehicle i is presentThe vehicle speed keeps running at a constant speed;

when the adjacent lane vehicle i is behind the vehicle, if v_i≥dv_sThe vehicle i in the adjacent lane starts to decelerate to dv with the maximum braking intensity under the action of the decision module_sThen keeping constant speed running; if v is_i＜dv_sThe vehicle i in the adjacent lane keeps running at a constant speed at the current speed;

wherein c and d are adjustment parameters; in the process of changing lanes and avoiding obstacles, the longitudinal speed v of the vehicle_sCan be considered approximately constant; controlling the values of the adjusting parameters c and d, and controlling the longitudinal speed of the vehicle in the adjacent lane in front of the vehicle to be always greater than the longitudinal speed of the vehicle when the vehicle changes lanes if c is greater than 1; the longitudinal speed of the vehicle in the adjacent lane behind the vehicle in the lane changing process of the vehicle can be controlled to be always smaller than the longitudinal speed of the vehicle when d is less than 1; thereby providing a safe lane change space for the vehicle;

in order to prevent the condition that the longitudinal speed of the vehicles in the adjacent lanes is too small or too large, the parameters c and d are adjusted by adopting a method of sectional value:

when the longitudinal speed v of the vehicle_sC is not more than 50km/h₂,d＝d₁；

When 50km/h < v_sWhen the value is less than 100km/h, the values of c and d follow the following formula:

when v is_sWhen the speed is more than or equal to 100km/h, c is c₁,d＝d₂；

Wherein:

c₁,c₂,d₁,d₂the specific value is set by a manufacturer according to the dynamic performance of the automobile.

6. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: in a third obstacle avoidance mode, after the vehicle acquires the motion information of the vehicle through the vehicle-mounted sensor, the method for determining the path of the vehicle and the adjacent vehicle comprises the following steps:

the method for selecting the vehicle to plan the path by the decision module comprises the following steps:

for the host vehicle, when eL₁＜L≤bL₁Selecting a quintic polynomial method to plan the lane change path, and when L is less than or equal to eL₁Selecting a cubic polynomial method to plan a lane change path; wherein e is an adjusting parameter, e is more than 0 and less than b, and the specific value is set by a manufacturer according to the performance of the automobile steering system and the design condition of the stability structure of the automobile;

for the adjacent vehicle, judging whether the driver of the adjacent vehicle has the intention of changing the lane by a decision module; if the driver of the adjacent vehicle does not have the intention of changing lanes, the decision-making module plans a straight-going path of the adjacent vehicle according to the current speed of the adjacent vehicle acquired by the vehicle body sensor and the acceleration degree; if the drivers of the adjacent vehicles have the lane changing intention, the decision module selects a fifth-order polynomial to plan the lane changing path:

the expression of the vehicle track change trajectory planning model based on the cubic polynomial is as follows:

wherein x (t), y (t) are the transverse position and the longitudinal position of the vehicle in the geodetic coordinate system, u is the current longitudinal speed of the vehicle, and t is the current longitudinal speed of the vehicle₀，t₁Starting and ending times, m, for trajectory planning₀,m₁,m₂,m₃All coefficients are cubic polynomial interpolation functions;

the expression of the vehicle track change trajectory planning model based on the fifth-order polynomial is as follows:

in the formula, n₀,n₁,n₂,n₃,n₄,n₅All are coefficients of a quintic polynomial interpolation function;

secondly, after a track changing track model is obtained, the track changing time t is adjusted_f＝t₁-t₀The size of the obstacle avoidance path is obtained, and a series of possible lane changing and obstacle avoidance paths of the vehicle can be obtained;

determining the stable limit of the yaw velocity and the centroid yaw angle when the vehicle changes lanes on the premise of meeting the vehicle stability according to the two-degree-of-freedom model of the vehicle:

the stability limit calculation method of the yaw rate is as follows:

therefore, the temperature of the molten steel is controlled,

the stable limit calculation method of the centroid slip angle is as follows:

therefore, the temperature of the molten steel is controlled,

wherein r represents yaw rate, F_yf,F_yrRespectively representing the lateral force of the front axle and the rear axle of the vehicle, wherein m is the mass of the whole vehicle, mu is the road surface adhesion coefficient, u is the longitudinal speed of the vehicle, beta is the mass center slip angle, C_αrRepresenting the cornering stiffness of the rear axle of the vehicle, a₀,b₀Respectively representing the distance between a front axle and a rear axle of the vehicle and the center of mass of the vehicle, wherein l is the wheelbase of the vehicle;

setting an objective function as follows for determining the optimal track change track of the vehicle:

in the formula, L_maxThe maximum lane changing longitudinal distance of the vehicle, u is the current longitudinal speed of the vehicle, and t_fR (t) is lane change time, beta (t) is yaw angular velocity and centroid side slip angle of the vehicle in the lane change process, and r_max,β_maxThe stable limit values of the yaw angular velocity and the centroid slip angle r obtained in the step three_min,β_minFor minimum yaw rate and centroid slip angle, w, of all lane change trajectories₁,w₂,w₃,w₄,w₅Is a weight coefficient; the first item of reaction lane change efficiency of the objective function and the second, third, fourth and fifth item of reaction lane change stability; the second term and the third term reflect the fluctuation conditions of the yaw velocity and the centroid slip angle in the lane changing process, and the fourth term and the fifth term reflect the influence of the maximum value of the yaw velocity and the centroid slip angle on the stability in the lane changing process;

setting different objective function solving constraint conditions for the vehicle and the adjacent vehicles; for the vehicle, under the emergency obstacle avoidance environment, the requirement on lane change efficiency is higher, so the weight occupied by the first item of the design objective function is higher, and the following are taken:

w₁＝0.6,w₂＝w₃＝w₄＝w₅＝0.1

meanwhile, the maximum lane changing longitudinal distance is the distance L between the vehicle and the front obstacle;

therefore, the corresponding constraint conditions are as follows:

for adjacent vehicles, emergency obstacle avoidance is not needed, and lane changing efficiency and lane changing stability need to be considered comprehensively, so the sum of the first weight and the last four weights of a design objective function is equal to obtain:

w₁＝0.5,w₂＝w₃＝w₄＝w₅＝0.125

meanwhile, the maximum lane changing distance is set to be L_lmaxThe specific value taking method comprises the following steps:

the decision-making module establishes a database to collect the time from the beginning of lane changing to the end of lane changing of the vehicle at different speeds; when the current speed of the adjacent vehicle i is u_iWhen L is_lmaxIs that the vehicle speed in the database is u_i-10km/h～u_iAverage value of the acquired track-changing time within the range of +10 km/h;

therefore, the corresponding constraint conditions are as follows:

substituting the constraint conditions into the objective function established in the step (iv) to solve to obtain the optimal lane change path of the vehicle at any speed;

after the adjacent vehicle decision module plans the path, the path information is sent to the vehicle through the vehicle-to-vehicle interaction module.

7. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: in a third obstacle avoidance mode, the process that the vehicle decision module judges whether the vehicle has a collision risk with the adjacent lane vehicle when the vehicle changes lanes and avoids obstacles comprises the following steps:

the method comprises the following steps of (1) regarding a vehicle contour as an ellipse, taking a vehicle centroid coordinate from the center of the ellipse, enabling the ellipse to pass through four vertexes of a vehicle, and taking the short axial length of the ellipse as 1.2 times of the vehicle width in order to enable the ellipse contour to better wrap the vehicle boundary; if the reference course angle of the vehicle is the orientation of the vehicle at the corresponding moment, a series of elliptical contours corresponding to time can be generated according to the reference track; for any vehicle, when the longitudinal speed is determined, for the reference trajectory determining the lane change time, the position coordinates of the four vertices of the vehicle at time t are calculated as follows:

the coordinates of the end points on the two sides of the minor axis of the elliptical profile are calculated as follows:

in the formula, τ_Hk,τ_iRespectively the lane changing time length of the vehicle and the lane changing time length, x, of the vehicle i in the adjacent lane_k1,...,4(t),y_k1,...,4(t) four vertex coordinates of the vehicle, x_k5,6(t),y_k5,6(t) coordinates of end points on both sides of the minor axis of the elliptical profile, l_H,w_HRespectively showing the length and width of the host vehicle,

is the heading angle, x_k(t),y_k(T) represents a centroid position of the host vehicle, T being a time interval;

the general expression of the ellipse equation can be set to the form:

Ax²+By²+2Cxy+Dx+Ey+F＝0

the system comprises a six-point coordinate simultaneous equation set, a six-point coordinate simultaneous equation set and a six-point coordinate simultaneous equation set, wherein A, B, C, D, E and F are undetermined coefficients of an elliptic equation;

secondly, after the vehicle acquires the planned paths of all adjacent vehicles through the vehicle-to-vehicle interaction module, solving the elliptical contour equations of all vehicles at any time t when the vehicle carries out lane changing according to the planned optimal path changing path; respectively determining an elliptic contour equation between the simultaneous vehicle and each adjacent vehicle, wherein if no real solution exists in the simultaneous equation set, the vehicle and the adjacent vehicle have no risk of collision; if any one group of the ellipse equations has a real solution, the vehicle and the adjacent vehicle have the risk of collision.

8. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: when the vehicle is ready to adopt lane changing and obstacle avoiding measures and the adjacent lanes on the two sides of the vehicle can be changed, the method for selecting the appropriate target obstacle avoiding lane by the decision module comprises the following steps:

if L is_zl≤L_zrSelecting a left adjacent lane as a target lane changing lane; if L is_zl＞L_zrSelecting the adjacent lane at the right side as a target lane changing lane; wherein L is_zl,L_zrThe transverse distances of the center of mass of the vehicle relative to the boundaries of the left side and the right side of the obstacle are respectively.

9. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: adopting a distance comparison method as a basis for initially selecting an obstacle avoidance mode by an emergency obstacle avoidance system; wherein a and b are both adjustment parameters, a₁＜a＜a₂,b₁＜b＜b₂The specific value method of the parameters is as follows:

when the longitudinal speed v of the vehicle_sA is not more than 50km/h, a is a₁,b＝b₁；

When 50km/h < v_sWhen the value is less than 100km/h, the values of a and b follow the following formula:

when v is_sA is more than or equal to 100km/h₂,b＝b₂；

Wherein, 1 < a₁,a₂＜2,0.5＜b₁,b₂And (3) the specific value is set by a manufacturer according to the performance of the automobile brake system.

10. The intelligent networked four-wheel independent steering and independent driving electric vehicle emergency obstacle avoidance system of claim 1, wherein: after the vehicle adopts the lane changing and obstacle avoiding measures, the judgment basis of the emergency obstacle avoiding system for finishing the work is as follows:

when the vehicle takes the lane changing and obstacle avoiding measures in the second obstacle avoiding mode: the perception module perceives the transverse distance L between the vehicle mass center and the boundary of the barrier on the lane changing side of the vehicle in real time_zWhen L is sensed_zContinuously decreases to zero and then continuously increases to L_z＝l_HAt the moment of 2, the emergency obstacle avoidance system is closed in time, and the vehicle traction control system and the vehicle electronic stability system recover to work normally so as to ensure the stability of the vehicle;

when the vehicle takes the lane changing and obstacle avoiding measures in the third obstacle avoiding mode: the decision-making module establishes a linear equation which is parallel to the lane line and tangent to the boundary of the barrier at the lane changing side of the vehicle; calculating whether the ellipse outline equation and the linear equation have real number solutions in real time; when the calculation result is changed from the real number solution to the non-real number solution, the emergency obstacle avoidance system is closed in time, and the vehicle traction control system and the vehicle electronic stability system recover to work normally so as to ensure the stability of the vehicle;

meanwhile, if the vehicle-to-vehicle interaction module has normal functions, the position and the size of the barrier are marked and uploaded to a vehicle networking map, and other nearby vehicles are reminded to change lanes in advance to avoid the barrier.

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