CN114187755B - Vehicle formation control method - Google Patents
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Abstract
The invention provides a vehicle formation control method, which comprises the following steps: the formation collar vehicle enters a highway, road state data are obtained in real time, and a suggested speed is obtained according to the road state data and a speed-density relation model; the convoy vehicle travels at the recommended speed; when the formation leading vehicle receives a request for requesting the vehicle to apply for joining in the vehicle formation, judging whether the number of the vehicles in the vehicle formation is smaller than a preset value; if yes, the position information of the vehicle formation and the suggested speed are sent to the requesting vehicle; if not, the formation collar vehicle judges whether the number of vehicles in the vehicle formation is smaller than the optimal number of vehicles; if yes, the position information and the suggested speed of the vehicle formation are sent to the requesting vehicle; if not, refusing to request the vehicle to join in the vehicle formation; requesting vehicles to receive position information of the vehicle formation and suggested speed, and adding the vehicle formation. The vehicle formation control method can furthest improve the traffic capacity and the vehicle operation efficiency of the expressway.
Description
Technical Field
The invention relates to the technical field of vehicle driving, in particular to a vehicle formation control method.
Background
The traffic conditions of roads, particularly highways, are affected by vehicle driving, particularly vehicle formation, and the traffic conditions of the highways are affected more obviously during driving due to more vehicles. However, there is no better control method for vehicle formation at present, and the traffic capacity and the vehicle operation efficiency of the expressway cannot be ensured.
Disclosure of Invention
To achieve the above and other related objects, the present invention provides a vehicle formation control method, in which a formation vehicle in a vehicle formation includes a formation lead vehicle and a following vehicle, the vehicle formation control method including the steps of:
The method comprises the steps that a formation collar vehicle enters a highway, road state data are obtained in real time, and a suggested speed is obtained according to the road state data and a speed-density relation model;
The convoy vehicle travels at the suggested speed;
when the formation leading vehicle receives a request for requesting vehicles to apply for joining in a vehicle formation, judging whether the number of vehicles in the vehicle formation is smaller than a preset value; if yes, the position information of the vehicle formation and the suggested speed are sent to the request vehicle;
If not, the formation collar vehicle judges whether the number of vehicles in the vehicle formation is smaller than the optimal number of vehicles, and the optimal number of vehicles is larger than the preset value; if yes, the position information of the vehicle formation and the suggested speed are sent to the request vehicle; if not, rejecting the request vehicle to join the vehicle formation;
and the requesting vehicle receives the position information of the vehicle formation and adds the vehicle formation after the suggested speed.
Optionally, the road status data includes traffic density, lane occupancy and lane average speed.
Optionally, the formula for obtaining the suggested speed according to the road state data and the speed-density relation model is as follows:
Wherein v is a recommended speed, k is the actual traffic density of a road section received by the vehicle through the road test facility, v f is a free flow speed, k f is the maximum density of the free flow speed v f according to the actual calibration of different road sections, k j is the blocking density of the road section at the speed of 0 according to the actual calibration of different road sections, and m is the wave velocity coefficient: m is more than or equal to 0 and less than or equal to 1, and m can be according to the following and calibrating each road section respectively.
Optionally, the calculation formula of the optimal vehicle number is as follows:
Wherein N is the optimal number of vehicles, L is the total length of the vehicle formation, d is the distance between the formed vehicles, v is the recommended speed, v m is the average speed of the vehicles from the social vehicles to the target lane, a 1 is the speed from the start of the social vehicles to the target lane Acceleration in the process, a 2 is the speed of the social vehicleAcceleration to v m, x m is the distance between the social vehicle before lane change and the last formation vehicle in the vehicle formation, x n is the distance between the social vehicle when returning to the original lane and the formation pick-up vehicle in the vehicle formation, l is the length of the formation vehicle, and t 3 is the time when the social vehicle travels at the target vehicle at speed v m.
Optionally, in the vehicle formation, the distance between the current vehicle and the preceding vehicle is between a minimum safe distance and a maximum safe distance.
Optionally, when the front vehicle is stationary or in uniform motion, the formula of the minimum safe distance is as follows:
Wherein d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the front vehicle is found by the current vehicle, d 2 is the running distance of the front vehicle after the front vehicle is suddenly braked, d 0 is the minimum safe vehicle distance between the front vehicle and the current vehicle after the front vehicle is decelerated and stopped, t 1 is the time required for the braking force generated by the braking system to be linearly increased to the maximum value, a amax is the maximum braking acceleration of the current vehicle, v 1 is the speed of the current vehicle before the braking, and v 2 is the speed of the front vehicle under the stable running state;
When the front vehicle uniformly decelerates, the formula of the minimum safe distance is as follows:
wherein d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the front vehicle is found by the current vehicle, d 2 is the running distance of the front vehicle after the front vehicle is suddenly braked, d 0 is the time required for the minimum safe vehicle distance t 1 between the front vehicle and the current vehicle after the front vehicle is decelerated and stopped to be linearly increased to the maximum value, a amax is the maximum braking acceleration of the current vehicle, a bmax is the maximum braking acceleration of the front vehicle, v 1 is the speed of the current vehicle before braking, and v 2 is the speed of the front vehicle under the stable running state.
Optionally, the formula of the maximum safe distance is:
Wherein d max is the maximum safe distance, L 0 is the longitudinal distance between the lane changing vehicle and the rear vehicle in the vehicle formation when the lane changing vehicle is ready for lane changing, L A is the distance between the lane changing vehicle and the rear vehicle in the vehicle formation when the lane changing vehicle is in the center line of the lane where the vehicle formation is located, L B is the distance between the lane changing vehicle and the vehicle line when the lane changing vehicle is in the center line of the lane where the vehicle formation is located, v A is the speed of the vehicle in the formation when the lane changing vehicle is in the lane changing state, v B is the average speed of the vehicle on the lane borrowed by the lane changing vehicle in the lane changing state, and a is the maximum braking acceleration when the lane changing vehicle is in the lane changing state.
As described above, the vehicle formation control method of the present invention has the following advantageous effects: according to the vehicle formation control method, the recommended speed is obtained according to the road state data and the speed-density relation model, and whether the requested vehicle is allowed to join is judged according to the number of vehicles in the vehicle formation when the requested vehicle requests to join the vehicle formation, so that the number of vehicles in the vehicle formation is maintained within the optimal number of vehicles, the traffic capacity and the vehicle operation efficiency of the expressway can be improved to the maximum extent on the basis of ensuring the traffic safety of the road, the energy consumption of trucks is reduced, the frequent speed change and lane change of the vehicles are reduced, and adverse effects are caused on traffic flow.
Drawings
Fig. 1 and 2 are flowcharts of a vehicle formation control method according to the present invention.
Fig. 3 is a schematic diagram of taking a vehicle domain Δx, a vehicle number kΔx, a length Δx along a lane direction, an acceleration a of a vehicle domain movement, and a resultant force increment of a virtual force corresponding to the acceleration a in the vehicle domain movement in a single lane in the vehicle formation control method of the present invention.
FIG. 4 is a flow rate model relationship diagram of the speed-density relationship when the flow rate of the road reaches the maximum in the vehicle formation control method of the present invention; wherein the solid line indicates no congestion, the crisscrossed solid line is queuing dissipation, and the dotted line is queuing.
Fig. 5 is a schematic diagram of a social vehicle D lane change process in the vehicle formation control method of the present invention.
Fig. 6 is a graph showing acceleration over time during deceleration (or braking) of a vehicle in the vehicle formation control method of the present invention.
Fig. 7 is a diagram of a critical distance model in the vehicle formation control method of the present invention.
Fig. 8 is a schematic diagram of a lane change process performed by inserting a lane change vehicle into a vehicle formation in the vehicle formation control method of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The preferred embodiments in the following description are by way of example only and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
At present, no better control method is available for vehicle formation, and the traffic capacity and the vehicle operation efficiency of the expressway cannot be ensured.
Example 1
Referring to fig. 1, the present invention provides a vehicle formation control method, which includes the following steps:
s1: the method comprises the steps that a formation collar vehicle enters a highway, road state data are obtained in real time, and a suggested speed is obtained according to the road state data and a speed-density relation model;
s2: the convoy vehicle travels at the suggested speed;
S3: when the formation leading vehicle receives a request for requesting vehicles to apply for joining in a vehicle formation, judging whether the number of vehicles in the vehicle formation is smaller than a preset value; if yes, the position information of the vehicle formation and the suggested speed are sent to the request vehicle;
S4: if not, the formation collar vehicle judges whether the number of vehicles in the vehicle formation is smaller than the optimal number of vehicles, and the optimal number of vehicles is larger than the preset value; if yes, the position information of the vehicle formation and the suggested speed are sent to the request vehicle; if not, rejecting the request vehicle to join the vehicle formation;
S5: and the requesting vehicle receives the position information of the vehicle formation and adds the vehicle formation after the suggested speed.
According to the vehicle formation control method, the recommended speed is obtained according to the road state data and the speed-density relation model, and whether the requested vehicle is allowed to join is judged according to the number of vehicles in the vehicle formation when the requested vehicle requests to join the vehicle formation, so that the number of vehicles in the vehicle formation is maintained within the optimal number of vehicles, the traffic capacity and the vehicle operation efficiency of the expressway can be improved to the maximum extent on the basis of ensuring the traffic safety of the road, the energy consumption of trucks is reduced, the frequent speed change and lane change of the vehicles are reduced, and adverse effects are caused on traffic flow.
Example two
Referring to fig. 2 in conjunction with fig. 1, the road status data includes traffic density, lane occupancy, and lane average speed.
Optionally, the formula for obtaining the suggested speed according to the road state data and the speed-density relation model is as follows:
Wherein v is a recommended speed, k is the actual traffic density of a road section received by the vehicle through the road test facility, v f is a free flow speed, k f is the maximum density of the free flow speed v f according to the actual calibration of different road sections, k j is the blocking density of the road section at the speed of 0 according to the actual calibration of different road sections, and m is the wave velocity coefficient: m is more than or equal to 0 and less than or equal to 1, and m can be according to the following and calibrating each road section respectively.
Optionally, the calculation formula of the optimal vehicle number is as follows:
Wherein N is the optimal number of vehicles, L is the total length of the vehicle formation, d is the distance between the formed vehicles, v is the recommended speed, v m is the average speed of the vehicles from the social vehicles to the target lane, a 1 is the speed from the start of the social vehicles to the target lane Acceleration in the process, a 2 is the speed of the social vehicleAcceleration to v m, x m is the distance between the social vehicle before lane change and the last formation vehicle in the vehicle formation, x n is the distance between the social vehicle when returning to the original lane and the formation pick-up vehicle in the vehicle formation, l is the length of the formation vehicle, and t 3 is the time when the social vehicle travels at the target vehicle at speed v m.
Optionally, in the vehicle formation, the distance between the current vehicle and the preceding vehicle is between a minimum safe distance and a maximum safe distance.
Optionally, when the front vehicle is stationary or in uniform motion, the formula of the minimum safe distance is as follows:
Wherein d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the front vehicle is found by the current vehicle, d 2 is the running distance of the front vehicle after the front vehicle is suddenly braked, d 0 is the minimum safe vehicle distance between the front vehicle and the current vehicle after the front vehicle is decelerated and stopped, t 1 is the time required for the braking force generated by the braking system to be linearly increased to the maximum value, a amax is the maximum braking acceleration of the current vehicle, v 1 is the speed of the current vehicle before the braking, and v 2 is the speed of the front vehicle under the stable running state;
When the front vehicle uniformly decelerates, the formula of the minimum safe distance is as follows:
wherein d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the front vehicle is found by the current vehicle, d 2 is the running distance of the front vehicle after the front vehicle is suddenly braked, d 0 is the time required for the minimum safe vehicle distance t 1 between the front vehicle and the current vehicle after the front vehicle is decelerated and stopped to be linearly increased to the maximum value, a amax is the maximum braking acceleration of the current vehicle, a bmax is the maximum braking acceleration of the front vehicle, v 1 is the speed of the current vehicle before braking, and v 2 is the speed of the front vehicle under the stable running state.
Optionally, the formula of the maximum safe distance is:
Wherein d max is the maximum safe distance, L 0 is the longitudinal distance between the lane changing vehicle and the rear vehicle in the vehicle formation when the lane changing vehicle is ready for lane changing, L A is the distance between the lane changing vehicle and the rear vehicle in the vehicle formation when the lane changing vehicle is in the center line of the lane where the vehicle formation is located, L B is the distance between the lane changing vehicle and the vehicle line when the lane changing vehicle is in the center line of the lane where the vehicle formation is located, v A is the speed of the vehicle in the formation when the lane changing vehicle is in the lane changing state, v B is the average speed of the vehicle on the lane borrowed by the lane changing vehicle in the lane changing state, and a is the maximum braking acceleration when the lane changing vehicle is in the lane changing state.
In order to facilitate understanding of the technical solution of the present invention, some steps are described in detail below.
The suggested speed acquisition method is as follows:
In view of minimizing the impact of the entire road traffic conditions during the travel of the formation vehicles, it is desirable to control the speed of the formation vehicles, which should be variable with the variation of the road traffic conditions (herein mainly the traffic density). The speed is the optimal speed of the formation vehicle in the running process, and the calculation process is as follows:
Considering the traffic flow as movement under the action of certain virtual forces, and when the resultant force of the virtual forces is 0, the traffic flow moves at a uniform speed; when the combined forces of these virtual forces produce an increment-deltap, the traffic flow accelerates. As shown in fig. 3, a vehicle region Δx is taken in a single lane, the number of vehicles is kΔx, and the length thereof in the lane direction is Δx. The acceleration of the vehicle domain motion is a, the total force increment of the virtual force corresponding to the acceleration is-delta P, and according to Newton's second law, the vehicle domain motion comprises:
(kΔx)·a＝-ΔP
When the value of deltax is 0, Due toSo that
This equation is the differential equation of motion of the traffic flow without considering viscosity.
When the traffic flows reach a certain density, certain viscosity characteristics are presented due to mutual interference. It is assumed that there is no viscous drag in the traffic flow when v > v 1,k<k1; when v is less than or equal to v 1,k≥k1, viscous drag exists in the traffic flow.
After viscous drag is introduced, the stress condition of the vehicle domain is re-analyzed, and a motion differential equation describing viscous traffic flow can be obtained:
Wherein:
Is a viscous drag term.
So that it is possible to obtain:
assuming v is a function of k v=v (k), then:
substitution (3) can be obtained:
the two solutions are:
Or (b)
Namely:
The maximum density at the set velocity is the free flow velocity v f is k f; the blocking density at a speed of 0 is k j.
Typically, traffic flow has viscous drag in one density, speed range, and no viscous drag in another density, speed range, 0<k 1<kj,0<v1<vf.
① When v > v 1,k<k1, there is a formula (8):
The state point v=v f,k＝kf is in the range of v > v 1, and the above equation is integrated to obtain:
② When v < v 1,k>k1, there is a formula (8):
the state point v=0, k=k j is within v < v 1, and the above equation is integrated to obtain:
in summary, the velocity-density relationship is:
let state 1 be somewhere between [0, k j],[0,vf ], and v 1＝mvf, where m is the ratio of the maximum wave speed mv f to the design speed per hour, we call the wave speed coefficient: m is more than or equal to 0 and less than or equal to 1.
The traffic capacity of a road is limited, and the velocity-density relationship when the flow reaches the maximum is a constant flow model relationship, as shown in fig. 4, the velocities and densities corresponding to two points a and b on the constant flow curve are respectively:
and, maximum flow rate
When v > mv f, there is less interaction between the vehicles, and when v < mv f, there is interaction between the vehicles, so that there is:
Wherein: k f is the maximum density at free flow velocity v f, k j is the blocking density at velocity 0, m is the wave velocity coefficient, the ratio of the maximum wave velocity to the design velocity per hour.
The method for obtaining the optimal number of vehicles is as follows:
Considering the lane change requirement of the social vehicles running behind the formation vehicles, the length of the formation and the number of the formation vehicles need to be controlled, so that the social vehicles can return to the original lane in time after lane change to the greatest extent, the influence on adjacent lanes is reduced, and the whole road traffic efficiency is optimal. The calculation process of the optimal formation vehicle number is as follows:
the whole process of changing the social vehicle D into the following stages is divided into the following steps:
Stage 1: the lane changing operation is started when the distance between the social vehicle D and the end vehicle N of the formation vehicle is x m, the time taken from the start of the lane changing operation to the transition of the social vehicle D to the target lane is t 1, the acceleration is a 1, the in-process driving distance is x 1, the speed of the social vehicle D before the transition is v, and the speed of the social vehicle D when the lane is changed to the target lane is v V m is the average speed of the vehicle in the target lane;
stage 2: social vehicle D slave speed Accelerating to v m, wherein the time is t 2, the acceleration is a 2, and the driving distance in the process is x 2;
Stage 3: the social vehicle D keeps running at the speed v m for a period of time t 3(t3 which is a fixed value and is an adaptation time on the target lane until the distance from the formation vehicle 1 meets the minimum distance x n required for lane changing, and the running distance of the social vehicle D in the process is x 3;
The distance travelled by the formation queue in the whole process is x 0, and the total length of the formation vehicles is L.
The schematic diagram of the above process is shown in fig. 5.
So there are:
xm+L+x0+xn＝x1+x2+x3 (14)
Also, there are:
x0＝(t1+t2+t3)v (15)
x3＝vmt3 (18)
substituting equations (15), (16), (17), (18), (19), (20) into equation (14) yields a fleet vehicle total length of:
The length of the formation vehicles is l, and the distance between the formation vehicles is d:
So there are:
Nl+(N-1)d＝L
the optimal number of vehicles for the formation is thus found to be:
wherein L is the total length of the vehicle formation, d is the distance between the vehicles in the formation, (D i represents the distance between the ith vehicle and the previous vehicle in the formation), v is the recommended speed, v m is the average speed of the vehicles in the formation from the start of the change of the social vehicle D to the target lane, a 1 is the acceleration of the social vehicle D from the start of the change of the social vehicle D to the target lane stage 1, a 2 is the acceleration of the social vehicle D from the start of the change of the social vehicle D to the target lane stage 2, x m is the distance between the social vehicle before the change of the social vehicle and the last formed vehicle in the vehicle formation, x n is the distance between the social vehicle and the formation pick-up vehicle in the vehicle formation (i.e. the formed vehicle 1 in the vehicle formation) when the social vehicle returns to the original lane, l is the length of the formed vehicle, and the value is equal to(L i represents the length of the ith vehicle in the formation), t 3 is the time the social vehicle is traveling at the target vehicle speed v m.
The minimum safe distance acquisition method comprises the following steps:
Because the vehicles in formation driving have different motion states in the driving process, when the speed of the current vehicle changes drastically, the motion state of the following vehicle changes, for example: when the front vehicle is in emergency braking or decelerating running, the following vehicle is caused to brake with great acceleration, and in order to ensure the running safety of the vehicles in the formation, the minimum safety distance between two vehicles in the formation is calculated as follows:
the acceleration of the vehicle during deceleration (or braking) is plotted as a function of time according to the time map of the vehicle versus the run-flat process as shown in fig. 6.
T 1: and a braking force increasing stage. The braking force generated by the braking system is linearly increased to the maximum value, the elapsed time is t 1, the following is made Where a max is the maximum braking acceleration, the resulting vehicle speed at the braking force increase phase is expressed as:
the distance travelled in time t 1 is:
t 2: and (3) continuing the braking phase. The braking process mainly focuses on a continuous braking stage, the braking force is stable in the process, the acceleration of the vehicle is kept unchanged, and the vehicle performs uniform deceleration motion.
In the continuous braking phase, the vehicle speed at the time t 1 For initial speed, then a uniform deceleration motion is performed during this period until the vehicle speed is reduced to a safe following speed v 2, so the distance travelled by the vehicle from the beginning of period t 2 to the deceleration to v 2 is:
t 3: and a braking stop stage. The brake is released, and the braking force gradually decreases along with the gradual release of the brake pedal. It is considered that the braking force linearly decreases in this process, and the braking time in the brake releasing stage is recorded as t 3, the vehicle braking force exists but the vehicle is stationary in the brake releasing stage, the vehicle braking distance does not increase, and only the driver performs a process of eliminating the braking effect in the braking operation.
To sum up, from the time the vehicle finds a hazard (beginning at time t 1) until the vehicle speed decreases to v 2, the distance travelled by the vehicle is the total braking distance of the vehicle:
in the calculation formula of the total braking distance, the time t 1 is the braking force increasing stage. In this stage, the action time is different due to the different vehicle conditions and driver conditions, but the stage time is shorter, wherein The term is small and therefore negligible, i.e. the braking stop phase is regarded as a very short period of constant motion. Finally, the total braking distance is obtained:
Because the vehicles in formation driving have different motion states in the driving process, when the speed of the front vehicle is changed drastically, the motion state of the following vehicle is changed, and when the front vehicle is braked urgently or runs at a reduced speed, the following vehicle is braked with great acceleration; when the vehicle is accelerating, there is basically no danger to the following vehicle, so this situation is not considered. Thus, a critical distance model is established as shown in fig. 7.
dmin＝d1-d2+d0
Wherein d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the current vehicle finds the front vehicle and adopts deceleration braking, d 2 is the running distance of the front vehicle suddenly adopting braking, and d 0 is the minimum safe vehicle distance between the front vehicle and the current vehicle after the current vehicle decelerates and stops.
(1) Stationary or uniform movement of the front vehicle
The rear vehicle (i.e., the current vehicle) detects that the front vehicle is moving at a constant velocity of v 2 and if v 1＜＜v2 is present, the collision risk does not occur. If v 1>v2 exists, the distance between the front and rear vehicles is continuously reduced until the distance is smaller than a certain critical value, and at the moment, the possibility of rear-end collision is increased, so that the rear vehicle needs to implement deceleration operation until the front and rear vehicles are at a safe workshop distance, and the rear vehicle and the front vehicle keep running at the same speed. If no collision still occurs when the relative speed of the two vehicles is zero, the danger is relieved. The front vehicle being stationary can be regarded as belonging to the special case where the front vehicle is at a constant speed of zero, i.e. v 2＝0,d2 = 0. The distance of the rear vehicle continuously decelerating and driving in the process of decelerating and driving to the same speed as the front vehicle and the distance of the front vehicle uniformly driving are respectively as follows:
and because:
so that:
Wherein d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the front vehicle is found by the current vehicle, d 2 is the running distance of the front vehicle after the front vehicle is suddenly braked, d 0 is the minimum safe vehicle distance between the front vehicle and the current vehicle after the front vehicle is decelerated and stopped, t 1 is the time required for the braking force generated by the braking system to be linearly increased to the maximum value, a amax is the maximum braking acceleration of the current vehicle, v 1 is the speed of the current vehicle before the braking, and v 2 is the speed of the front vehicle under the stable running state.
In particular, if the rear vehicle speed is equal to the front vehicle speed, i.e., v 1＝v2, then the minimum safe distance between the rear vehicle and the front vehicle is d 0.
(2) Uniform deceleration movement of front vehicle
If the front vehicle encounters a red light or a speed limit sign and needs to run at a reduced speed, the rear vehicle detects that the front vehicle continuously decelerates, and the rear vehicle brakes to keep a safe driving distance. Since the preceding vehicle is subjected to uniform deceleration movement in preparation, and the following vehicle starts corresponding braking action after the preceding vehicle is subjected to braking deceleration, the preceding vehicle does not consider the braking system delay time in the process. Let the maximum braking acceleration of the front vehicle be a bmax.
Where d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the front vehicle is found by the current vehicle, d 2 is the running distance of the front vehicle after the front vehicle is suddenly braked, d 0 is the time required for the minimum safe vehicle distance t 1 between the front vehicle and the current vehicle after the front vehicle is decelerated and stopped to be linearly increased to the maximum value, a amax is the maximum braking acceleration of the current vehicle, a bmax is the maximum braking acceleration of the front vehicle, v 1 is the speed of the current vehicle before braking, and v 2 is the speed of the front vehicle in a stable running state.
In particular, if the rear vehicle speed is equal to the front vehicle speed, i.e., v 1＝v2, the minimum safe distance between the rear vehicle and the front vehicle is
The method for obtaining the maximum safe distance comprises the following steps:
To prevent other vehicles from being inserted into the queue in society, it is necessary to control the distance between the vehicles in the queue. And after the B vehicles enter the queue after lane change, the distance from the B vehicles to the A vehicles of the formation is L 1, and then L 1 is the maximum safety distance between the formation vehicles. The calculation process is as follows:
As shown in fig. 7, vehicle a represents a formation vehicle, vehicle B represents a social other vehicle attempting to change lane insertion into a train, and it is assumed that the speed of vehicle a is v A and the average speed of the lane in which vehicle B is located is v B when vehicle B changes lane.
The following analysis is performed on the lane change vehicle B before and after lane change:
lane-changing vehicle B is ready to make a lane change at a longitudinal distance L 0 between two vehicles A, B.
The distance of the movement of the B vehicle in the time from the lane change of the B vehicle to the center line of the lane where the A vehicle is located is as follows:
the distance of the movement of the vehicle A in the time from the lane change of the vehicle B to the lane center line of the vehicle A is as follows:
The distance of the longitudinal movement of the B vehicle at time t 0 is:
After the B vehicles complete lane changing, the distance between the two vehicles is as follows:
Wherein: d max is the maximum safe distance, L 0 is the longitudinal distance between the lane changing vehicle B and the rear vehicle A in the vehicle formation, L A is the distance between the lane changing vehicle B and the movement of the rear vehicle A in the vehicle formation in the time from the lane changing vehicle B to the center line of the lane where the vehicle formation is located, L B is the distance between the lane changing vehicle B and the movement of the lane changing vehicle B in the time from the lane changing vehicle B to the center line of the lane where the vehicle formation is located, v A is the speed of the vehicle formation when the lane changing vehicle B changes lanes, v B is the average speed of the vehicle on the lane borrowed by the lane changing vehicle B, and a is the maximum braking acceleration when the lane changing vehicle B changes lanes.
In summary, in order to prevent other external vehicles from entering the formation, d < d max needs to be satisfied.
The invention provides a vehicle formation control method. As shown in fig. 2, the method of the present invention comprises: when the formation collar vehicles enter the expressway, road state data (mainly referred to as traffic density k, lane occupancy and average lane dividing speed) sent by a road side unit in real time are obtained; after the formation collar vehicle receives the information, the suggested speed v under the current road state can be obtained by combining the road speed-density relation model, and the vehicle can run at the suggested speed v; the method comprises the steps that in the process that trucks apply for joining in formation, after the formation collar vehicle receives request information, the number of vehicles in a queue is judged, when the number of the vehicles in the queue is smaller than 2, position information, suggested speed and the like of the formation vehicles are sent to the requesting vehicles, the requesting vehicles receive the information and join in formation, and meanwhile, a certain distance d is kept between the requesting vehicles and the front vehicles according to a safe distance model; when the number of vehicles in the queue is more than or equal to 2, after receiving the request information, the formation collar calculates the optimal number N of vehicles in the cargo vehicle formation according to the current speed v of the formation vehicles, the average speed v m of other lanes, the safety distance x m before lane change, the safety distance x n after lane change, the adaptation time t 3 on the target lane, the formation vehicle distance d, the formation vehicle length l and the like, and meanwhile, the optimal number N of vehicles in the cargo vehicle formation is compared with the number N of vehicles in the queue at the moment; if N is more than or equal to N, the formation leading vehicle sends information to the requesting vehicle, and the joining is refused; if N is less than N, allowing joining, and simultaneously transmitting position information, suggested speed and the like of the formation vehicle to the requesting vehicle by the formation lead vehicle; requesting the vehicle to receive information, and joining in formation based on a certain strategy; in the running process of all the formation vehicles, information such as the speed, the position and the like of the front vehicles in the queue can be obtained in real time, and the distance between the current vehicle and the front vehicle is controlled to be between the minimum safety distance and the maximum safety distance by combining the safety distance model. The intelligent control system can furthest improve the traffic capacity and the vehicle operation efficiency of the expressway on the basis of ensuring the traffic safety of the road by intelligently controlling the number of the formation vehicles, the speed of the vehicles and the safety distance between the vehicles.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (6)
1. A vehicle formation control method, characterized in that a formation vehicle in a vehicle formation includes a formation lead vehicle and a following vehicle, the vehicle formation control method comprising the steps of:
the formation collar vehicle enters the expressway, road state data are obtained in real time, and a formula for obtaining the suggested speed according to the road state data and the speed-density relation model is as follows:
wherein v is a recommended speed, k is the actual traffic density of a road section received by the vehicle through the road test facility, v f is a free flow speed, k f is the maximum density of the free flow speed v f according to the actual calibration of different road sections, k j is the blocking density of the road section at the speed of 0 according to the actual calibration of different road sections, and m is the wave velocity coefficient: m is more than or equal to 0 and less than or equal to 1, and m is according to each calibrating road sections respectively;
The convoy vehicle travels at the suggested speed;
when the formation leading vehicle receives a request for requesting vehicles to apply for joining in a vehicle formation, judging whether the number of vehicles in the vehicle formation is smaller than a preset value; if yes, the position information of the vehicle formation and the suggested speed are sent to the request vehicle;
If not, the formation collar vehicle judges whether the number of vehicles in the vehicle formation is smaller than the optimal number of vehicles, and the optimal number of vehicles is larger than the preset value; if yes, the position information of the vehicle formation and the suggested speed are sent to the request vehicle; if not, rejecting the request vehicle to join the vehicle formation;
and the requesting vehicle receives the position information of the vehicle formation and adds the vehicle formation after the suggested speed.
2. The vehicle formation control method according to claim 1, characterized in that: the road state data includes traffic density, lane occupancy, and lane average speed.
3. The vehicle formation control method according to claim 2, characterized in that: the calculation formula of the optimal vehicle number is as follows:
Wherein N is the optimal number of vehicles, L is the total length of the vehicle formation, d is the distance between the formed vehicles, v is the recommended speed, v m is the average speed of the vehicles from the social vehicles to the target lane, a 1 is the speed from the start of the social vehicles to the target lane Acceleration in the process, a 2 is the speed of the social vehicleThe speed is accelerated to v m, x m is the distance between the social vehicle before lane change and the last formation vehicle in the vehicle formation, x n is the distance between the social vehicle and the formation pick-up vehicle in the vehicle formation when the social vehicle is returned to the original lane, l is the length of the formation vehicle, and t 3 is the time when the social vehicle travels at the speed v m in the target lane.
4. The vehicle formation control method according to claim 1, characterized in that: in the vehicle formation, the distance between the current vehicle and the preceding vehicle is between the minimum safe distance and the maximum safe distance.
5. The vehicle formation control method according to claim 4, characterized in that: when the front vehicle is stationary or moves at a uniform speed, the formula of the minimum safety distance is as follows:
Wherein d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the front vehicle is found by the current vehicle, d 2 is the running distance of the front vehicle after the front vehicle is suddenly braked, d 0 is the minimum safe vehicle distance between the front vehicle and the current vehicle after the front vehicle is decelerated and stopped, t 1 is the time required for the braking force generated by the braking system to be linearly increased to the maximum value, a amax is the maximum braking acceleration of the current vehicle, v 1 is the speed of the current vehicle before the braking, and v 2 is the speed of the front vehicle under the stable running state;
When the front vehicle uniformly decelerates, the formula of the minimum safe distance is as follows:
wherein d min is the minimum safe distance, d 1 is the running distance of the front vehicle after the front vehicle is found by the current vehicle, d 2 is the running distance of the front vehicle after the front vehicle is suddenly braked, d 0 is the time required for the minimum safe vehicle distance t 1 between the front vehicle and the current vehicle after the front vehicle is decelerated and stopped to be linearly increased to the maximum value, a amax is the maximum braking acceleration of the current vehicle, a bmax is the maximum braking acceleration of the front vehicle, v 1 is the speed of the current vehicle before braking, and v 2 is the speed of the front vehicle under the stable running state.
6. The vehicle formation control method according to claim 4, characterized in that: the formula of the maximum safe distance is as follows:
Wherein d max is the maximum safe distance, L 0 is the longitudinal distance between the lane changing vehicle and the rear vehicle in the vehicle formation when the lane changing vehicle is ready for lane changing, L A is the distance between the lane changing vehicle and the rear vehicle in the vehicle formation when the lane changing vehicle is in the center line of the lane where the vehicle formation is located, L B is the distance between the lane changing vehicle and the vehicle line when the lane changing vehicle is in the center line of the lane where the vehicle formation is located, v A is the speed of the vehicle in the formation when the lane changing vehicle is in the lane changing state, v B is the average speed of the vehicle on the lane borrowed by the lane changing vehicle in the lane changing state, and a is the maximum braking acceleration when the lane changing vehicle is in the lane changing state.
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| CN115273450B (en) * | 2022-08-19 | 2023-10-17 | 北京航空航天大学 | A lane-changing method for vehicles entering a formation in a connected autonomous driving environment |
| CN116820080B (en) * | 2023-01-05 | 2024-04-30 | 北京交通大学 | Method and system for scheduling formation operation of highway automatic driving truck |
| CN115953890B (en) * | 2023-03-13 | 2023-05-26 | 山东科技大学 | Vehicle dynamic loose formation method based on real-time online navigation map |
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