阅读说明：本技术 一种铰接车辆转向控制方法及装置 (Steering control method and device for articulated vehicle ) 是由 王小娟 曹鹭萌 贾莉 郭建辉 于 2020-04-14 设计创作，主要内容包括：本发明涉及一种铰接车辆转向控制方法及装置,属于智能驾驶控制技术领域。其中方法包括：获取前车体和后车体的铰接角、以及障碍物信息；确定一个转向坐标系；根据铰接角确定前车体的转向半径和后车体的转向半径；根据前车体的转向半径确定最小半径；根据后车体的转向半径确定最大半径,以坐标原点为圆心,根据最小半径和最大半径确定为目标区域；将障碍物信息转换到转向坐标系,从而定位在目标区域中的障碍物或障碍物部分,进而进行铰接车辆的转向控制。本发明兼顾了障碍物对于不在一条直线上行驶的前车体和后车体的影响,保证了目标区域划分的准确,进而引导铰接车辆做出正确的行为决策,保证铰接车辆转向的安全性。(The invention relates to a steering control method and device for an articulated vehicle, and belongs to the technical field of intelligent driving control. The method comprises the following steps: acquiring the hinge angle of the front vehicle body and the rear vehicle body and the information of the obstacles; determining a steering coordinate system; determining the steering radius of the front vehicle body and the steering radius of the rear vehicle body according to the hinge angle; determining a minimum radius according to the steering radius of the front vehicle body; determining a maximum radius according to the steering radius of the rear vehicle body, and determining a target area according to the minimum radius and the maximum radius by taking the origin of coordinates as a circle center; the obstacle information is converted to a steering coordinate system to locate an obstacle or obstacle portion in the target area for steering control of the articulated vehicle. The invention gives consideration to the influence of the obstacles on the front vehicle body and the rear vehicle body which do not run on the same straight line, ensures the accuracy of target area division, further guides the articulated vehicle to make a correct behavior decision and ensures the steering safety of the articulated vehicle.)

1. An articulated vehicle steering control method, comprising the steps of:

1) when the articulated vehicle turns, acquiring articulation angles of a front vehicle body and a rear vehicle body and obstacle information; the obstacle information is all obstacle information in a vehicle coordinate system;

2) determining a steering coordinate system, wherein the origin of coordinates of the steering coordinate system is the intersection point of the transverse extension line of the center point of the front vehicle body and the transverse extension line of the center point of the rear vehicle body;

3) determining the steering radius of the front vehicle body and the steering radius of the rear vehicle body according to the hinge angle;

4) determining a minimum radius according to the steering radius of the front vehicle body; determining the maximum radius according to the steering radius of the rear vehicle body, and determining a fan ring area between a fan-shaped area swept by the minimum radius and a fan-shaped area swept by the maximum radius as a target area by taking the origin of coordinates as a circle center;

5) and converting the obstacle information to the steering coordinate system to locate an obstacle or obstacle portion in the target area for steering control of the articulated vehicle.

2. The articulated vehicle steering control method of claim 1, further comprising the steps of: and calculating the arc length between the obstacle or the boundary point of the obstacle part in the target area and the articulated vehicle, finding out a point corresponding to the minimum value of the arc length, and calculating the actual transverse distance and the actual longitudinal distance between the point and the articulated vehicle according to the arc length of the point.

3. The articulated vehicle steering control method of claim 2, wherein if the actual longitudinal distance is less than the lower longitudinal distance limit, controlling the articulated vehicle parking brake; if the actual transverse distance is greater than the lower limit of the transverse distance, the actual longitudinal distance is greater than the lower limit of the longitudinal distance, and the condition that the articulated vehicle runs on the road is met, controlling the articulated vehicle to avoid the obstacle and return; and if the actual transverse distance is greater than the lower limit of the transverse distance, the actual longitudinal distance is greater than the lower limit of the longitudinal distance, and the lane driving is not satisfied, controlling the articulated vehicle to avoid the obstacle and change the lane.

4. The articulated vehicle steering control method according to claim 1, wherein the calculation process of the steering radius of the front vehicle body and the steering radius of the rear vehicle body is:

R_f＝(L_f*cosγ+L_r)/(sinγ)；

R_r＝(L_f+L_r*cosγ)/(sinγ)；

wherein R _ f is the steering radius of the front vehicle body; r _ R is the steering radius of the rear vehicle body; l _ f is the distance from the center point of the front vehicle body to the hinge point; l _ r is the distance from the center point of the rear vehicle body to the hinge point; gamma is the articulation angle.

5. The articulated vehicle steering control method of claim 1, wherein the obstacle information is obtained by a lidar.

6. The articulated vehicle steering control method according to claim 1 or 4, characterized in that the minimum radius is the steering radius of the front vehicle body-front vehicle body width/2.

7. The articulated vehicle steering control method according to claim 1 or 4, wherein the maximum radius is the steering radius of the rear vehicle body + the rear vehicle body width/2.

8. An articulated vehicle steering control apparatus comprising a processor, a memory and a computer program stored in the memory and executable on the processor, the processor when executing the computer program implementing an articulated vehicle steering control method according to any of claims 1-7.

Technical Field

The invention relates to a steering control method and device for an articulated vehicle, and belongs to the technical field of intelligent driving control.

Background

As the leading field of science and technology, automatic driving is always a popular option for the development of science and technology at home and abroad, and along with the progress of technologies such as artificial intelligence and the like, automatic driving of automobiles gradually becomes a reality. The environment perception is used as a first link of automatic driving, the sensors are used for acquiring surrounding environment information such as roads, vehicle positions and obstacles, and the information is provided for the vehicle-mounted control center, so that the vehicle better simulates the perception capability of a human driver, understands the driving situation of the vehicle and the surrounding situation, makes correct driving behavior decisions, and realizes the automatic driving of the vehicle.

In the existing environment sensing module, the environment sensing technology based on the laser radar is generally applied. The method comprises the steps of scanning the surrounding environment by using a laser radar to obtain a large amount of point cloud data, processing the point cloud data to obtain characteristic quantities such as the position, the speed and the shape of a target obstacle, achieving information interaction between a vehicle and the surrounding environment, and guiding the vehicle to make a correct driving behavior decision. However, in the large amount of point cloud data, since many obstacle data are far from the vehicle and do not affect the traveling of the vehicle, in order to increase the calculation speed, it is necessary to divide the target area of the vehicle and to pick out only the obstacle point cloud data in the target area for calculation.

In the prior art, the vehicle target area is generally divided by identifying lane lines or other boundary information on a road, but the method cannot effectively filter the obstacle information under the condition of no lane line or road boundary information. Therefore, a vehicle head is taken as a coordinate origin, a target area of the vehicle is divided after calculation, and then obstacle data are screened, but for a large-sized vehicle such as an articulated vehicle, under the condition that the articulated vehicle is steered, the front vehicle body and the rear vehicle body of the articulated vehicle are not on the same straight line, the method cannot take account of the rear vehicle body, the error of division of the target area is large, the judgment of the vehicle is wrong, and the behavior decision requirement of the vehicle cannot be well met.

Disclosure of Invention

The method aims to provide a steering control method of an articulated vehicle, which is used for solving the problem that the conventional target area division method is inaccurate and causes misdecision of vehicle behavior; meanwhile, the articulated vehicle steering control device is also provided to solve the problem that the conventional target area division method is inaccurate and causes misdecision of vehicle behavior.

In order to achieve the above object, the present application provides a technical solution of a steering control method for an articulated vehicle, comprising the steps of:

1) when the articulated vehicle turns, acquiring articulation angles of a front vehicle body and a rear vehicle body and obstacle information; the obstacle information is all obstacle information in a vehicle coordinate system;

2) determining a steering coordinate system, wherein the origin of coordinates of the steering coordinate system is the intersection point of the transverse extension line of the center point of the front vehicle body and the transverse extension line of the center point of the rear vehicle body;

3) determining the steering radius of the front vehicle body and the steering radius of the rear vehicle body according to the hinge angle;

4) determining a minimum radius according to the steering radius of the front vehicle body; determining the maximum radius according to the steering radius of the rear vehicle body, and determining a fan ring area between a fan-shaped area swept by the minimum radius and a fan-shaped area swept by the maximum radius as a target area by taking the origin of coordinates as a circle center;

5) and converting the obstacle information to the steering coordinate system to locate an obstacle or obstacle portion in the target area for steering control of the articulated vehicle.

In addition, the present application also provides a technical solution of the articulated vehicle steering control apparatus, which includes a processor, a memory, and a computer program stored in the memory and operable on the processor, wherein the processor implements the technical solution of the articulated vehicle steering control method when executing the computer program.

The technical scheme of the articulated vehicle steering control method and the articulated vehicle steering control device has the beneficial effects that: according to the invention, when the articulated vehicle turns, a unified coordinate system of the front vehicle body and the rear vehicle body is established according to the central point of the front vehicle body and the central point of the rear vehicle body, the obstacle information is converted under the coordinate system, and meanwhile, the target area of the obstacle is divided under the coordinate system, so that the influence of the obstacle on the front vehicle body and the rear vehicle body which do not run on a straight line is considered, the accuracy of the division of the target area is ensured, the articulated vehicle is further guided to make a correct behavior decision, and the steering safety of the articulated vehicle is ensured.

Further, in the above method and apparatus for controlling steering of an articulated vehicle, in order to improve the accuracy of the steering control, the method further includes the steps of: and calculating the arc length between the obstacle or the boundary point of the obstacle part in the target area and the articulated vehicle, finding out a point corresponding to the minimum value of the arc length, and calculating the actual transverse distance and the actual longitudinal distance between the point and the articulated vehicle according to the arc length of the point.

Further, in the method and the device for controlling the steering of the articulated vehicle, if the actual longitudinal distance is smaller than the lower limit of the longitudinal distance, the articulated vehicle is controlled to stop and brake; if the actual transverse distance is greater than the lower limit of the transverse distance, the actual longitudinal distance is greater than the lower limit of the longitudinal distance, and the condition that the articulated vehicle runs on the road is met, controlling the articulated vehicle to avoid the obstacle and return; and if the actual transverse distance is greater than the lower limit of the transverse distance, the actual longitudinal distance is greater than the lower limit of the longitudinal distance, and the lane driving is not satisfied, controlling the articulated vehicle to avoid the obstacle and change the lane.

Further, in the above articulated vehicle steering control method and apparatus, in order to more accurately obtain the steering radius of the front vehicle body and the steering radius of the rear vehicle body, the calculation process of the steering radius of the vehicle body and the steering radius of the rear vehicle body is:

R_f＝(L_f*cosγ+L_r)/(sinγ)；

R_r＝(L_f+L_r*cosγ)/(sinγ)；

wherein R _ f is the steering radius of the front vehicle body; r _ R is the steering radius of the rear vehicle body; l _ f is the distance from the center point of the front vehicle body to the hinge point; l _ r is the distance from the center point of the rear vehicle body to the hinge point; gamma is the articulation angle.

Furthermore, in the articulated vehicle steering control method and device, in order to accurately obtain the information of the obstacle, the obstacle information is obtained through a laser radar.

Further, in the above-described articulated vehicle steering control method and apparatus, in order to determine the minimum radius simply and accurately, the minimum radius is equal to the steering radius of the front vehicle body — the front vehicle body width/2.

Further, in the above-described articulated vehicle steering control method and apparatus, in order to determine the maximum radius simply and accurately, the maximum radius is equal to the steering radius of the rear vehicle body + the rear vehicle body width/2.

Drawings

FIG. 1 is a flow chart of an articulated vehicle steering control method of the present invention;

FIG. 2 is a schematic view of the articulated vehicle of the present invention based on a steering coordinate system;

FIG. 3 is a schematic view of the target area of the present invention;

FIG. 4 is a schematic illustration of the target area of the present invention prior to cutting an obstacle;

FIG. 5 is a schematic view of the target area of the present invention after cutting the obstruction;

fig. 6 is a schematic structural view of the articulated vehicle steering control apparatus of the present invention.

Detailed Description

Articulated vehicle steering control method embodiment:

the articulated vehicle steering control method has the main concept that when the articulated vehicle is steered, the front vehicle body and the rear vehicle body are not on the same straight line, the target area of the whole vehicle can be accurately divided by establishing a unified coordinate system of the front vehicle body and the rear vehicle body, and the steering control safety of the articulated vehicle is improved.

Specifically, the articulated vehicle steering control method, as shown in fig. 1, includes the following steps:

1) when the articulated vehicle turns, the articulation angle of the front vehicle body and the rear vehicle body and the obstacle information are acquired.

In this step, the obstacle information is point cloud data obtained by scanning the surrounding environment with a laser radar, the point cloud data is processed to obtain information such as the position, speed, shape and the like of the obstacle, and the information is all obstacle information which can be scanned by the laser radar in a vehicle coordinate system (the vehicle coordinate system here may be a front vehicle body coordinate system, or a rear vehicle body coordinate system, and is set by an articulated vehicle);

the hinge angle γ of the front vehicle body and the rear vehicle body can be obtained by a rotation angle sensor, or can be calculated in real time in order that the hinge angle γ is more accurate, and the acquisition of the hinge angle γ is the prior art, and is not described in detail herein.

2) While step 1) is being carried out, a steering coordinate system is determined.

The steering coordinate system is a coordinate system unified by the front vehicle body and the rear vehicle body, and is obtained according to the coordinate system of the front vehicle body and the coordinate system of the rear vehicle body as shown in fig. 2, wherein the coordinate system o-x-y of the front vehicle body takes the central point of the front vehicle body as a coordinate origin o, the longitudinal running direction of the front vehicle body is a y axis, and the transverse running direction of the front vehicle body is an x axis; the coordinate system of the rear vehicle body takes the central point of the rear vehicle body as the origin of coordinates, the longitudinal running direction of the rear vehicle body is the y axis, and the transverse running direction of the rear vehicle body is the x axis; the coordinate origin o1 of the steering coordinate system o1-x1-y1 is the intersection point of the transverse extension line of the center point of the front vehicle body and the transverse extension line of the center point of the rear vehicle body; the line connecting the center point of the rear vehicle body with the origin of coordinates o1 forms an abscissa x1 and an ordinate y1 perpendicular to the abscissa x1 and oriented in the traveling direction of the articulated vehicle.

3) Determining the steering radius of the front vehicle body and the steering radius of the rear vehicle body according to the articulation angle obtained in the step 1).

In fig. 2, γ is a hinge angle between the front body and the rear body, N is a hinge point, L _ f is a distance from the front body to the hinge point, L _ R is a distance from the rear body to the hinge point, γ _ f is a heading angle of the front body, γ _ R is a heading angle of the rear body, and a steering radius R _ f of the front body and a steering radius R _ R of the rear body are calculated by a geometric relationship:

R_f＝(L_f*cosγ+L_r)/(sinγ)；

R_r＝(L_f+L_r*cosγ)/(sinγ)；

meanwhile, the coordinates (f _ cx, f _ cy) of the center point of the front vehicle body under the steering coordinate system and the coordinates (r _ cx, r _ cy) of the center point of the rear vehicle body under the steering coordinate system can be obtained by calculation:

f_cx＝R_f*cos(γ)；

f_cy＝R_f*sin(γ)；

r_cx＝R_r；

r_cy＝0。

4) determining a minimum radius according to the steering radius of the front vehicle body obtained in the step 3); determining the maximum radius according to the steering radius of the rear vehicle body obtained in the step 3), and determining a target area according to the minimum radius and the maximum radius.

The target area is an area where an obstacle affecting steering driving of the articulated vehicle is located, namely a range, and a boundary of the range needs to be found out to accurately divide the target area;

the boundary corresponds to the boundary of the area swept by the minimum radius and the maximum radius with the coordinate origin of the steering coordinate system as the origin when the articulated vehicle is steered, and the fan-shaped ring area between the fan-shaped area swept by the minimum radius and the fan-shaped area swept by the maximum radius is determined as the target area.

The maximum radius and the minimum radius can be obtained by calculation, as shown in fig. 3, where W _ f is the front vehicle body width and W _ R is the rear vehicle body width, and the minimum radius R _ in and the maximum radius R _ out corresponding to the target region are:

R_in＝R_f-W_f/2；

R_out＝R_r+W_r/2；

in the actual calculation process, the size of the sector ring area can be adjusted through the maximum radius and the minimum radius according to the actual scene.

5) Transforming the obstacle information acquired in step 1) to a steering coordinate system, thereby locating an obstacle or an obstacle portion in the target area.

In order to accurately perform the subsequent steps, the obstacle information is subjected to coordinate conversion from the vehicle coordinate system to the steering coordinate system, and the position information of the obstacle is usually subjected to coordinate conversion, for example: the coordinates of the obstacle in the vehicle coordinate system are (X, Y), the coordinates are converted into the coordinates (X _ o, Y _ o) in the steering coordinate system according to the kinematic relationship, and the conversion relationship is as follows:

when γ > 0, X _ o ═ X × sin (γ) -Y × cos (γ) + f _ cx;

y_o＝X*cos(γ)-Y*sin(γ)+f_cy；

when γ < 0, X _ o ═ X ═ sin (γ) + Y × cos (γ) + f _ cx;

y_o＝X*cos(γ)+Y*sin(γ)+f_cy。

in order to filter all the obstacle information obtained in step 1), locate the obstacle and the obstacle part in the target area, and divide the obstacle information under the steering coordinate system, the dividing idea is to find the intersection points of the curve equation of the target area and the straight line equation of the obstacle, and the intersection points are the dividing lines of the cutting, and the specific steps are as follows:

obtaining a curve equation of an inner ring and an outer ring of the target area by using the obtained minimum radius R _ in and the maximum radius R _ out and taking the coordinate origin of the steering coordinate as the center of a circle;

x²+y²＝R_in²；

x²+y²＝R_out²；

the inner circle corresponds to the curve A of the attached drawings 4 and 5, the outer circle corresponds to the curve B of the attached drawings 4 and 5, obs1, obs2, obs3, obs4 and obs5 in the graphs are obtained by the laser radar, the obstacle information in different shapes is obtained by the laser radar, each obstacle corresponds to 4 vertexes, a linear equation of 4 sides of the obstacle is obtained through the information of the four vertexes, and a straight line is determined by the two points, for example: point (x1, y1), point (x2, y2) defines the equation of a straight line:

(y-y2)/(y1-y2)＝(x-x2)/(x1-x2)；

and (3) solving the intersection point of the curves of the inner ring and the outer ring and the linear equation, and replacing the point outside the target area with the obtained intersection point so as to position the obstacle and the obstacle part in the target area. For example: the coordinates of the four vertices of the obstacle obs1 in the steering coordinate system are m1(-24,4), m2(-24,6), m3(-17,6), m4(-17,4), and the coordinates of the vertices of the obstacle obs1 portion in the target region are n1(-21.63,4), n2(-21.17,6), n3(-19.08,6), and n4(-19.6, 4).

6) Controlling the steering of the articulated vehicle in dependence on the obstacle or obstacle portion in the target area in step 5).

As shown in fig. 4 and 5, the shape of the obstacle is different and has a certain size, so it is necessary to find the closest point to the articulated vehicle in the obstacle, and the position information of the closest point is used as the basis for determining the vehicle steering control, specifically:

a. calculating obstacles or obstacles in a target areaThe portion of the boundary point is the arc length from the articulated vehicle, which is the arc length from the front body since the obstacle is generally in front of the articulated vehicle. The coordinates of a certain point in the steering coordinate system are (x _ o, y _ o), and the radius isTo illustrate the arc length solving process, the included angle theta between a certain point (x _ o, y _ o) and the front vehicle body is cos^-1(x _ o × R + y _ o × 0)/(R × R)), the arc length D ═ R × θ from the point to the front vehicle body;

b. finding out the point corresponding to the minimum value of the arc length after obtaining the arc lengths of all the boundary points from the articulated vehicle, and calculating the actual transverse distance L between the point and the articulated vehicle according to the arc length of the point_latActual longitudinal distance L_lon：

L_lon＝min(D)

L_lat＝R_min(D)-R_veh

Wherein: l is_latThe positive value indicates that the closest point of the obstacle is on the left side of the vehicle, and the negative value indicates that the closest point of the obstacle is on the right side of the vehicle.

c. According to the obtained actual transverse distance L_latAnd an actual longitudinal distance L_lonControlling the steering of the articulated vehicle, wherein the controlling of the steering of the articulated vehicle comprises parking braking, obstacle avoidance and lane change and obstacle avoidance and return;

setting the minimum transverse distance (i.e. the lower limit of the transverse distance) as Lat _ min, the minimum longitudinal distance (i.e. the lower limit of the longitudinal distance) as Lon _ min, if L_lon<Lon _ min, controlling the articulated vehicle to stop and brake; if L is_lon>Lon_minAnd L is_lat>Lat _ min, and controlling the articulated vehicle to avoid the obstacle and return when the vehicle runs on the road; if L is_lon>Lon _ min and L_lat>And controlling the articulated vehicle to avoid obstacles and change lanes when Lat _ min does not meet the driving of the lane.

In the foregoing embodiment, the first information of the obstacle is obtained by the laser radar in step 1), as another embodiment, the first information of the obstacle may also be obtained by using an ultrasonic sensor and an infrared sensor, which is not limited in the present invention.

In the above embodiment, the minimum radius and the maximum radius of the target area in step 4) are calculated according to the front vehicle body width and the rear vehicle body width, which can better meet the requirements of the vehicle.

In the above embodiment, in step 6), for accuracy of control, a point where the obstacle information is closest to the articulated vehicle is found out, as another embodiment, in the case that the obstacle is very small, one of the points of the obstacle may also be optionally selected as a basis for vehicle control, which is not limited by the present invention.

According to the invention, through unifying the coordinate systems of the front vehicle body and the rear vehicle body, the accurate division of the target area when the vehicle does not run on a straight line is solved, so that the vehicle is guided to make a correct behavior decision, and the safety of vehicle steering control is improved.

Articulated vehicle steering control apparatus embodiment:

an articulated vehicle steering control apparatus, as shown in fig. 6, includes a processor, a memory, and a computer program stored in the memory and executable on the processor, the processor implementing an articulated vehicle steering control method when executing the computer program.

The specific implementation process and effect of the articulated vehicle steering control method are described in the above embodiment of the articulated vehicle steering control method, and are not described herein again.

That is, the methods in the above articulated vehicle steering control method embodiments should be understood that the flow of the methods may be implemented by computer program instructions. These computer program instructions may be provided to a processor (e.g., a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus), such that the instructions, which execute via the processor, create means for implementing the functions specified in the method flow.

The processor referred to in this embodiment refers to a processing device such as a microprocessor MCU or a programmable logic device FPGA;

the memory of the present embodiment is used to store computer program instructions for implementing the articulated vehicle steering control method, and includes physical means for storing information, typically digitized information, and stored on a medium using electrical, magnetic, or optical means. For example: various memories for storing information by using an electric energy mode, such as RAM, ROM and the like; various memories for storing information by magnetic energy, such as hard disk, floppy disk, magnetic tape, magnetic core memory, bubble memory, and U disk; various types of memory, CD or DVD, that store information optically. Of course, there are other ways of memory, such as quantum memory, graphene memory, and so forth.

The articulated vehicle steering control device formed by the memory and the processor, which are used for storing computer program instructions formed by realizing the articulated vehicle steering control method, is realized by the processor executing corresponding program instructions in the computer, and the computer can be realized by a windows operating system, a linux system or other systems, for example, an android and an iOS system programming language in an intelligent terminal, a quantum computer-based processing logic realization and the like.

As another embodiment, the articulated vehicle steering control apparatus may further include other processing hardware, such as a database or a multi-level cache, a GPU, and the like, and the present invention does not specifically limit the structure of the articulated vehicle steering control apparatus.