阅读说明：本技术 一种自主泊车控制方法及装置 (Autonomous parking control method and device ) 是由 周文立 李秦 王博 林志超 于 2020-03-27 设计创作，主要内容包括：本发明提供了一种自主泊车控制方法,应用于自动泊车系统的车端,包括步骤：步骤S10,周期性地获得目标剩余距离、当前车速的信息；步骤S11,确定当前车速所处的速度区间,选择对应的目标车速确定策略,并结合预设最大车速、预设加速度及预设减速度,获得目标车速信息；步骤S12,根据所述获得的目标车速,确定对汽车进行制动或驱动控制,使所述汽车的速度达到所述获得的目标车速,并最终使汽车位于目标位置。本发明还可以对目标车速进行滤波处理,同时提供了相应的装置。实施本发明,可以实现高精度停车,并提高用户的使用体验。(The invention provides an autonomous parking control method, which is applied to a vehicle end of an automatic parking system and comprises the following steps: step S10, periodically obtaining the information of the target remaining distance and the current vehicle speed; step S11, determining the speed interval of the current speed, selecting a corresponding target speed determination strategy, and combining a preset maximum speed, a preset acceleration and a preset deceleration to obtain target speed information; and step S12, according to the obtained target speed, determining to brake or drive the automobile, so that the speed of the automobile reaches the obtained target speed, and finally enabling the automobile to be located at the target position. The invention can also carry out filtering processing on the target vehicle speed and simultaneously provides a corresponding device. By implementing the invention, high-precision parking can be realized, and the use experience of a user is improved.)

1. An autonomous parking control method is applied to a vehicle end of an automatic parking system, and is characterized by comprising the following steps:

step S10, periodically obtaining the information of the target remaining distance and the current vehicle speed;

step S11, determining the speed interval of the current speed, selecting a corresponding target speed determination strategy, and combining a preset maximum speed, a preset acceleration and a preset deceleration to obtain target speed information;

and step S12, according to the obtained target speed, determining to brake or drive the automobile, so that the speed of the automobile reaches the obtained target speed, and finally enabling the automobile to be located at the target position.

2. The method of claim 1, wherein the step S11 further comprises:

in step S110, when the current vehicle speed is zero, the first comparison value d2 is calculated according to the following formula:

d2＝Vmax^2/2/Accel+Vmax^2/2/Decel

the method comprises the following steps that Vmax is a preset maximum speed, Accel is a preset acceleration, and Decel is a preset deceleration;

step S111, comparing the target remaining distance with a predetermined lowest distance threshold value d1 and a second comparison value d 2;

step S112, when the comparison result shows that the target remaining distance is smaller than the preset minimum distance threshold value d1, determining the target vehicle speed as zero;

when the comparison result is that the target remaining distance is greater than the predetermined lowest distance threshold value d1 and is less than or equal to the first comparison value d2, the target vehicle speed Vset0 is calculated according to the following formula:

vset0 ═ sqrt (2 × tgtdit/(1/Accel + 1/Decel)); wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is greater than the first comparison value d2, determining the target vehicle speed as the preset maximum vehicle speed.

3. The method of claim 1, wherein the step S11 further comprises:

step S113, when the current vehicle speed is greater than zero and less than or equal to the preset maximum vehicle speed, respectively calculating a second comparison value d3 and a third comparison value d4 according to the following formulas:

d3＝Vnow^2/2/Decel

d4＝(Vmax^2-Vnow^2)/2/Accel+Vmax^2/2/Decel

wherein Vnow is the current vehicle speed, Vmax is the preset maximum vehicle speed, Accel is the preset acceleration, and Decel is the preset deceleration;

step S114, comparing the current target remaining distance with the second comparison value d3 and a third comparison value;

step S115, when the comparison result shows that the target remaining distance is greater than the third comparison value d4, determining the target vehicle speed as a preset maximum vehicle speed;

when the comparison result is that the target remaining distance is less than or equal to the third comparison value d4 and greater than the second comparison value d3, the target vehicle speed Vset0 is calculated according to the following formula.

Vset0＝sqrt(2*(tgtDist+Vnow^2/2/Accel)/(1/Accel+1/Decel))

Wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is smaller than the second comparison value d3, determining the target vehicle speed as zero.

4. The method of claim 1, wherein the step S11 further comprises:

step S116, when the current vehicle speed is greater than or equal to the preset maximum vehicle speed, a fourth comparison value d5 is calculated according to the following formula:

d5＝Vnow^2/2/Decel

wherein Vnow is the current vehicle speed, and Decel is the preset deceleration;

step S117, comparing the target remaining distance with the fourth comparison value d 5;

step S118, when the comparison result is that the target remaining distance is greater than the fourth comparison value d5, determining the target vehicle speed as the preset maximum vehicle speed; otherwise, the target vehicle speed is determined to be zero.

5. The method according to any one of claims 1 to 4, wherein the step S11 further comprises:

after the target vehicle speed is obtained, whether the following conditions are met or not is further judged, and if all the conditions are met, the target vehicle speed is forced to be zero:

the target vehicle speed obtained this time is greater than zero;

the target vehicle speed obtained in the previous period is zero;

the target remaining distance of the previous period is greater than the target remaining distance of the current period;

the difference between the target remaining distance of the previous cycle and the target remaining distance of the current cycle is smaller than a predetermined fifth comparison value d 6;

the current vehicle speed is at least larger than the target vehicle speed by a preset sixth comparison value; and

the current vehicle speed is greater than zero.

6. The method according to claim 5, wherein the step S12 specifically includes:

after the target vehicle speed is determined, when the target vehicle speed is greater than zero, performing drive control according to the target vehicle speed and the current vehicle speed, and controlling the vehicle to accelerate to the determined target vehicle speed; when the target speed is zero, performing braking control according to the target remaining distance and the current speed, and controlling the automobile to decelerate to the determined target speed;

and after the automobile reaches the target speed, entering the next control period, and repeating the steps S10 to S11 to finally enable the automobile to be located at the target position.

7. An autonomous parking control device provided at a vehicle end of an automatic parking system, comprising:

the automobile information obtaining unit is used for periodically obtaining the information of the target remaining distance and the current speed;

the target vehicle speed determining unit is used for determining a speed interval where the current vehicle speed is located, selecting a corresponding target vehicle speed determining strategy, and combining a preset maximum vehicle speed, a preset acceleration and a preset deceleration to obtain target vehicle speed information;

and the parking control unit is used for determining to brake or drive the automobile according to the obtained target speed, so that the speed of the automobile reaches the obtained target speed, and finally the automobile is positioned at the target position.

8. The apparatus according to claim 7, wherein the target vehicle speed determination unit further includes:

a first calculation unit for calculating a first comparison value d2 according to the following formula when the current vehicle speed is zero:

d2＝Vmax^2/2/Accel+Vmax^2/2/Decel

the method comprises the following steps that Vmax is a preset maximum speed, Accel is a preset acceleration, and Decel is a preset deceleration;

a first comparing unit for comparing the target remaining distance with a predetermined lowest distance threshold d1 and a second comparison value d 2;

a first comparison result processing unit for determining the target vehicle speed as zero when the comparison result of the first comparison unit is that the target remaining distance is less than a predetermined minimum distance threshold value d 1;

when the comparison result is that the target remaining distance is greater than the predetermined lowest distance threshold and is less than or equal to the first comparison value d2, the target vehicle speed Vset0 is calculated according to the following formula:

vset0 ═ sqrt (2 × tgtdit/(1/Accel + 1/Decel)); wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is greater than the first comparison value d2, determining the target vehicle speed as the preset maximum vehicle speed.

9. The apparatus according to claim 7, wherein the target vehicle speed determination unit further includes:

a second calculating unit, configured to calculate a second comparison value d3 and a third comparison value d4 according to the following formulas when the current vehicle speed is greater than zero and less than or equal to a preset maximum vehicle speed:

d3＝Vnow^2/2/Decel

d4＝(Vmax^2-Vnow^2)/2/Accel+Vmax^2/2/Decel

wherein Vnow is the current vehicle speed, Vmax is the preset maximum vehicle speed, Accel is the preset acceleration, and Decel is the preset deceleration;

a second comparing unit, configured to compare the current target remaining distance with the second comparison value d3 and a third comparison value;

the second comparison result processing unit is used for determining the target vehicle speed as the preset maximum vehicle speed when the comparison result of the second comparison unit is that the target remaining distance is greater than the third comparison value d 4;

when the comparison result is that the target remaining distance is less than or equal to the third comparison value d4 and greater than the second comparison value d3, the target vehicle speed Vset0 is calculated according to the following formula.

Vset0＝sqrt(2*(tgtDist+Vnow^2/2/Accel)/(1/Accel+1/Decel))

Wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is smaller than the second comparison value d3, determining the target vehicle speed as zero.

10. The apparatus according to claim 7, wherein the target vehicle speed determination unit further includes:

a third calculating unit for calculating a fourth comparison value d5 according to the following formula when the current vehicle speed is greater than or equal to a preset maximum vehicle speed:

d5＝Vnow^2/2/Decel

wherein Vnow is the current vehicle speed, and Decel is the preset deceleration;

a third comparing unit for comparing the target remaining distance with a fourth comparison value d 5;

a third comparison result processing unit, configured to determine the target vehicle speed as the preset maximum vehicle speed when the comparison result of the third comparison unit is that the target remaining distance is greater than the fourth comparison value d 5; otherwise, the target vehicle speed is determined to be zero.

11. The apparatus according to any one of claims 7 to 10, wherein the target vehicle speed determination unit further includes:

and the filtering unit is used for further judging whether the following conditions are met after the target vehicle speed is obtained, and if all the conditions are met, the target vehicle speed is forced to be zero actually:

the target vehicle speed obtained this time is greater than zero;

the target vehicle speed obtained in the previous period is zero;

the target remaining distance of the previous period is greater than the target remaining distance of the current period;

the difference between the target remaining distance of the previous period and the target remaining distance of the current period is smaller than a preset fifth comparison value;

the current vehicle speed is at least larger than the target vehicle speed by a preset sixth comparison value; and

the current vehicle speed is greater than zero.

12. The apparatus according to claim 11, wherein the parking control unit specifically includes:

the control unit is used for carrying out drive control according to the target speed and the current speed when the target speed is greater than zero, and controlling the automobile to accelerate to the determined target speed; when the target speed is zero, performing braking control according to the target remaining distance and the current speed, and controlling the automobile to decelerate to the determined target speed;

and the triggering unit is used for sending a triggering message to the target speed determining unit after the automobile reaches the target speed so as to enter the next control period and finally enable the automobile to be positioned at the target position.

Technical Field

The invention relates to the field of vehicle control in automatic driving, in particular to an autonomous parking control method and device applied to a vehicle end of an automatic parking system.

Background

The autonomous parking is a technical scheme provided for solving the last kilometer in automatic driving, and the highly automated autonomous parking is composed of a field end, a vehicle end and a cloud end. Wherein, the control of the vehicle end part is divided into transverse control and longitudinal control. In the longitudinal control, a more common control interface adopts a target residual distance tgtdit and a maximum vehicle speed Vmax. For example, the upper layer path tracking controller makes a request that the target residual distance tgtdit is equal to 4 meters and the maximum vehicle speed Vmax is equal to 2 km/h. This requires that the vehicle be moved 4 meters and the maximum speed of the vehicle during the movement is no more than 2 km/h.

In the prior art, some planning schemes exist, for example, in the above example, the current vehicle speed is directly and rapidly controlled to 2km/h, and then when the target remaining distance reaches a threshold (for example, 2 meters), the vehicle is decelerated through braking, so that parking is completed; or in other arrangements, the parking position is adjusted by frequent accelerations and decelerations. However, in actual use, it is found that the existing schemes plan the target speed more coarsely, do not consider the magnitude of the current vehicle speed, and have poor user experience in situations such as multiple acceleration and sudden braking.

Disclosure of Invention

The invention aims to provide an autonomous parking control method and device, which can realize high-precision parking and improve the use experience of a user.

The technical scheme adopted by the invention is that an autonomous parking control method is provided and is applied to a vehicle end of an automatic parking system, and the method comprises the following steps:

step S10, periodically obtaining the information of the target remaining distance and the current vehicle speed;

step S11, determining the speed interval of the current speed, selecting a corresponding target speed determination strategy, and combining a preset maximum speed, a preset acceleration and a preset deceleration to obtain target speed information;

and step S12, according to the obtained target speed, determining to brake or drive the automobile, so that the speed of the automobile reaches the obtained target speed, and finally enabling the automobile to be located at the target position.

Wherein the step S11 further includes:

in step S110, when the current vehicle speed is zero, the first comparison value d2 is calculated according to the following formula:

d2＝Vmax^2/2/Accel+Vmax^2/2/Decel

the method comprises the following steps that Vmax is a preset maximum speed, Accel is a preset acceleration, and Decel is a preset deceleration;

step S111, comparing the target remaining distance with a predetermined lowest distance threshold value d1 and a second comparison value d 2;

step S112, when the comparison result shows that the target remaining distance is smaller than the preset minimum distance threshold value d1, determining the target vehicle speed as zero;

when the comparison result is that the target remaining distance is greater than the predetermined lowest distance threshold and is less than or equal to the first comparison value d2, the target vehicle speed Vset0 is calculated according to the following formula:

vset0 ═ sqrt (2 × tgtdit/(1/Accel + 1/Decel)); wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is greater than the first comparison value d2, determining the target vehicle speed as the preset maximum vehicle speed.

Wherein the step S11 further includes:

step S113, when the current vehicle speed is greater than zero and less than or equal to the preset maximum vehicle speed, respectively calculating a second comparison value d3 and a third comparison value d4 according to the following formulas:

d3＝Vnow^2/2/Decel

d4＝(Vmax^2-Vnow^2)/2/Accel+Vmax^2/2/Decel

wherein Vnow is the current vehicle speed;

step S114, comparing the current target remaining distance with the second comparison value d3 and a third comparison value;

step S115, when the comparison result shows that the target remaining distance is greater than the third comparison value d4, determining the target vehicle speed as a preset maximum vehicle speed;

when the comparison result is that the target remaining distance is less than or equal to the third comparison value d4 and greater than the second comparison value d3, the target vehicle speed Vset0 is calculated according to the following formula.

Vset0＝sqrt(2*(tgtDist+Vnow^2/2/Accel)/(1/Accel+1/Decel))

Wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is smaller than the second comparison value d3, determining the target vehicle speed as zero.

Wherein the step S11 further includes:

step S116, when the current vehicle speed is greater than or equal to the preset maximum vehicle speed, a fourth comparison value d5 is calculated according to the following formula:

d5＝Vnow^2/2/Decel

wherein Vnow is the current vehicle speed, and Decel is the preset deceleration;

step S117, comparing the target remaining distance with the fourth comparison value d 5;

step S118, when the comparison result is that the target remaining distance is greater than the fourth comparison value d5, determining the target vehicle speed as a preset maximum vehicle speed; otherwise, the target vehicle speed is determined to be zero.

Wherein the step S11 further includes:

after the target vehicle speed is obtained, whether the following conditions are met or not is further judged, and if all the conditions are met, the target vehicle speed is forced to be zero:

the target vehicle speed Vset0 obtained this time is greater than zero;

the target vehicle speed Vset1Last obtained in the previous cycle is zero;

the target residual distance tgtDist of the previous period is greater than the target residual distance tgtdit of the current time;

the difference between the target residual distance tgtDist of the previous period and the current target residual distance tgtdit is smaller than a predetermined fifth comparison value d 6;

the current vehicle speed is at least larger than the target vehicle speed by a preset sixth comparison value v 2; and

the current vehicle speed Vnow is greater than zero.

After the target vehicle speed is determined, when the target vehicle speed is greater than zero, performing drive control according to the target vehicle speed and the current vehicle speed, and controlling the vehicle to accelerate to the determined target vehicle speed; when the target speed is zero, performing braking control according to the target remaining distance and the current speed, and controlling the automobile to decelerate to the determined target speed;

and after the automobile reaches the target speed, entering the next control period, and repeating the steps S10 to S11 to finally enable the automobile to be located at the target position.

Accordingly, another aspect of the present invention provides an autonomous parking control apparatus, disposed at a vehicle end of an automatic parking system, including:

the automobile information obtaining unit is used for periodically obtaining the information of the target remaining distance and the current speed;

the target vehicle speed determining unit is used for determining a speed interval where the current vehicle speed is located, selecting a corresponding target vehicle speed determining strategy, and combining a preset maximum vehicle speed, a preset acceleration and a preset deceleration to obtain target vehicle speed information;

and the parking control unit is used for determining to brake or drive the automobile according to the obtained target speed, so that the speed of the automobile reaches the obtained target speed, and finally the automobile is positioned at the target position.

Wherein the target vehicle speed determination unit further includes:

a first calculation unit for calculating a first comparison value d2 according to the following formula when the current vehicle speed is zero:

d2＝Vmax^2/2/Accel+Vmax^2/2/Decel

the method comprises the following steps that Vmax is a preset maximum speed, Accel is a preset acceleration, and Decel is a preset deceleration;

a first comparing unit for comparing the target remaining distance with a predetermined lowest distance threshold d1 and a second comparison value d 2;

a first comparison result processing unit for determining the target vehicle speed as zero when the comparison result of the first comparison unit is that the target remaining distance is less than a predetermined minimum distance threshold value d 1;

when the comparison result is that the target remaining distance is greater than the predetermined lowest distance threshold and is less than or equal to the first comparison value d2, the target vehicle speed Vset0 is calculated according to the following formula:

vset0 ═ sqrt (2 × tgtdit/(1/Accel + 1/Decel)); wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is greater than the first comparison value d2, determining the target vehicle speed as the preset maximum vehicle speed.

Wherein the target vehicle speed determination unit further includes:

a second calculating unit, configured to calculate a second comparison value d3 and a third comparison value d4 according to the following formulas when the current vehicle speed is greater than zero and less than or equal to a preset maximum vehicle speed:

d3＝Vnow^2/2/Decel

d4＝(Vmax^2-Vnow^2)/2/Accel+Vmax^2/2/Decel

wherein Vnow is the current vehicle speed;

a second comparing unit, configured to compare the current target remaining distance with the second comparison value d3 and a third comparison value;

the second comparison result processing unit is used for determining the target vehicle speed as the preset maximum vehicle speed when the comparison result of the second comparison unit is that the target remaining distance is greater than the third comparison value d 4;

when the comparison result is that the target remaining distance is less than or equal to the third comparison value d4 and greater than the second comparison value d3, the target vehicle speed Vset0 is calculated according to the following formula.

Vset0＝sqrt(2*(tgtDist+Vnow^2/2/Accel)/(1/Accel+1/Decel))

Wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is smaller than the second comparison value d3, determining the target vehicle speed as zero.

Wherein the target vehicle speed determination unit further includes:

a third calculating unit for calculating a fourth comparison value d5 according to the following formula when the current vehicle speed is greater than or equal to a preset maximum vehicle speed:

d5＝Vnow^2/2/Decel

wherein Vnow is the current vehicle speed, and Decel is the preset deceleration;

a third comparing unit for comparing the target remaining distance with a fourth comparison value d 5;

a third comparison result processing unit, configured to determine the target vehicle speed as the preset maximum vehicle speed when the comparison result of the third comparison unit is that the target remaining distance is greater than the fourth comparison value d 5; otherwise, the target vehicle speed is determined to be zero.

Wherein the target vehicle speed determination unit further includes:

and the filtering unit is used for further judging whether the following conditions are met after the target vehicle speed is obtained, and if all the conditions are met, the target vehicle speed is forced to be zero actually:

the target vehicle speed Vset0 obtained this time is greater than zero;

the target vehicle speed Vset1Last obtained in the previous cycle is zero;

the target residual distance tgtDist of the previous period is greater than the target residual distance tgtdit of the current time;

the difference between the target residual distance tgtDist of the previous period and the current target residual distance tgtdit is smaller than a predetermined fifth comparison value d 6;

the current vehicle speed is at least larger than the target vehicle speed by a preset sixth comparison value v 2; and

the current vehicle speed Vnow is greater than zero. The parking control unit specifically comprises:

the control unit is used for carrying out drive control according to the target speed and the current speed when the target speed is greater than zero, and controlling the automobile to accelerate to the determined target speed; when the target speed is zero, performing braking control according to the target remaining distance and the current speed, and controlling the automobile to decelerate to the determined target speed;

and the triggering unit is used for sending a triggering message to the target speed determining unit after the automobile reaches the target speed so as to enter the next control period and finally enable the automobile to be positioned at the target position.

The embodiment of the invention has the following beneficial effects:

the invention provides an autonomous parking control method and device, which can quantitatively calculate and solve a target vehicle speed by inputting a target remaining distance and a maximum vehicle speed and combining the current vehicle speed so as to realize high-precision parking;

meanwhile, according to the invention, different speed intervals are set for the current vehicle speed, each speed interval adopts a corresponding target vehicle speed calculation mode, and meanwhile, the target vehicle speed is subjected to filtering processing, so that frequent switching between drive control and brake control can be avoided, appropriate acceleration and deceleration can be obtained, the acceleration or deceleration process of parking is comfortable, and the use experience of a user is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.

Fig. 1 is a main flow diagram of an embodiment of an autonomous parking control method according to the present invention;

fig. 2 is a detailed flowchart corresponding to the first speed interval in step S11 in fig. 1;

FIG. 3 is a graph of a velocity profile corresponding to FIG. 2;

fig. 4 is a detailed flowchart corresponding to the second speed interval in step S11 in fig. 1;

FIG. 5 is a graph of the velocity profile corresponding to FIG. 4;

fig. 6 is a detailed flowchart corresponding to the third speed interval in step S11 in fig. 1;

FIG. 7 is a graph of a velocity profile corresponding to FIG. 6;

FIG. 8 is a flow chart of a corresponding embodiment of the method of the present invention;

fig. 9 is a schematic structural diagram of an autonomous parking control apparatus according to the present invention;

FIG. 10 is a schematic view showing the construction of a target vehicle speed determining unit shown in FIG. 9;

fig. 11 is a schematic structural diagram of the parking control unit in fig. 9.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.

Fig. 1 is a main flow chart of an embodiment of an autonomous parking control method according to the present invention, which is combined with fig. 2 to 8; in this embodiment, the autonomous parking control method is applied to a vehicle end of an automatic parking system, and the method includes the following steps:

step S10, periodically obtaining the information of the target remaining distance and the current vehicle speed; it is understood that the target remaining distance can be obtained by combining the automobile with an autonomous parking control system, and the current vehicle speed can be obtained by an on-board speed sensor; in one embodiment, the periodicity may be set to acquire every 20 ms.

Step S11, determining the speed interval of the current speed, selecting a corresponding target speed determination strategy, and combining a preset maximum speed, a preset acceleration and a preset deceleration to obtain target speed information;

in the present embodiment, the current vehicle speed is divided into three speed intervals, one of which is zero speed; the speed is greater than zero and less than the preset maximum speed; thirdly, the speed is greater than or equal to the preset maximum speed; when the current vehicle falls into different speed intervals, different target vehicle speed determination strategies are adopted respectively, specifically the following steps are respectively adopted:

as shown in fig. 2 and 3, in a specific example, the step S11 further includes:

in step S110, when the current vehicle speed is zero, the first comparison value d2 is calculated according to the following formula:

d2＝Vmax^2/2/Accel+Vmax^2/2/Decel

the method comprises the following steps that Vmax is a preset maximum speed, Accel is a preset acceleration, and Decel is a preset deceleration;

in one embodiment, the predetermined acceleration Accel may be 0.10m/s 2. The preset deceleration Decel may be 0.10m/s 2. The numerical value is used for people in the vehicle to feel that the acceleration and the deceleration are smooth and comfortable, so that the speed change of the vehicle is small, and the speed control is not easy to overshoot.

Step S111, comparing the target remaining distance with a predetermined lowest distance threshold value d1 and a second comparison value d 2; in one example, the d1 may take the value of 100 mm. Since the autonomous parking system generally requires the distance controller to finally achieve an accuracy of 100mm, d1 may be set to be less than or equal to this value. Step S112, when the comparison result shows that the target remaining distance is smaller than the preset minimum distance threshold value d1, determining the target vehicle speed as zero;

when the comparison result is that the target remaining distance is greater than the predetermined lowest distance threshold and is less than or equal to the first comparison value d2, the target vehicle speed Vset0 is calculated according to the following formula:

vset0 ═ sqrt (2 × tgtdit/(1/Accel + 1/Decel)); wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is greater than the first comparison value d2, determining the target vehicle speed as the preset maximum vehicle speed.

A velocity profile for the situation shown in fig. 2 is shown in fig. 3, where the vertical axis represents velocity and the horizontal axis represents time, and the area enclosed by the line segment and the horizontal axis may be equivalent to the remaining distance value.

When the target residual distance tgtdit is large, the future speed plan V-t line will be a trapezoid (i.e. the area enclosed by the line segments a, b, c, d and the horizontal axis), the height of the trapezoid is the maximum vehicle speed Vmax, and the slopes of the two waists of the trapezoid are determined by the preset acceleration Accel and the preset deceleration Decel.

When the target residual distance tgtdit is reduced to the critical value d2, the V-t line is changed from a trapezoid to a triangle (i.e. the area formed by the line segments a, b, f and the horizontal axis), the height of the triangle is the maximum vehicle speed Vmax, and the slopes of the two waists of the triangle are determined by the preset acceleration Accel and the preset deceleration Decel. When the target remaining distance tgtdit is larger than d2, the target speed Vset0 takes the maximum vehicle speed Vmax.

When the target residual distance tgtdit continues to decrease, the area of the triangle surrounded by the V-t line continues to decrease (e.g. the area formed by the line segments a and e and the horizontal axis), the slopes of the two waists of the triangle are determined by the preset acceleration Accel and the preset deceleration Decel, and the height Vset of the triangle is smaller than the maximum vehicle speed Vmax, so the Vset0 can be calculated by using the above formula.

When the target residual distance tgtdit continues to decrease, the area enclosed by the V-t line tends to zero. When the area is smaller than the minimum distance threshold d1, it is considered that the vehicle position accuracy has reached the requirement, and control ends.

As shown in fig. 4 and 5, in a specific example, the step S11 further includes:

step S113, when the current vehicle speed is greater than zero and less than or equal to the preset maximum vehicle speed, respectively calculating a second comparison value d3 and a third comparison value d4 according to the following formulas:

d3＝Vnow^2/2/Decel

d4＝(Vmax^2-Vnow^2)/2/Accel+Vmax^2/2/Decel

wherein Vnow is the current vehicle speed;

step S114, comparing the current target remaining distance with the second comparison value d3 and a third comparison value;

step S115, when the comparison result shows that the target remaining distance is greater than the third comparison value d4, determining the target vehicle speed as a preset maximum vehicle speed;

when the comparison result is that the target remaining distance is less than or equal to the third comparison value d4 and greater than the second comparison value d3, the target vehicle speed Vset0 is calculated according to the following formula.

Vset0＝sqrt(2*(tgtDist+Vnow^2/2/Accel)/(1/Accel+1/Decel))

Wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is smaller than the second comparison value d3, determining the target vehicle speed as zero.

The velocity profile for the situation shown in fig. 4 is shown in fig. 5. Specifically, the method comprises the following steps:

when the target residual distance tgtdit is large, the figure enclosed by the V-t lines is an unfilled corner trapezoid (i.e. the area enclosed by the line segments a, b, c and d and the horizontal axis). The height of the trapezoid is the maximum vehicle speed Vmax, and the slopes of the two waists of the trapezoid are determined by the preset acceleration Accel and the preset deceleration Decel.

When the target residual distance tgtdit is reduced to a critical value (a third comparison value d4), the V-t line is changed from a unfilled corner trapezoid to a unfilled corner triangle (i.e. an area enclosed by the line segments a, b, e and the horizontal axis), the height of the triangle is the maximum vehicle speed Vmax, and the slopes of the two waists of the triangle are determined by the preset acceleration Accel and the preset deceleration Decel. The third comparison value d4 can be calculated by the formula; therefore, when the target remaining distance tgtdit is greater than d4, the target speed Vset0 takes the maximum vehicle speed Vmax.

When the target remaining distance tgtdit continues to decrease, the area of the triangle surrounded by the V-t line continues to decrease, and when the target remaining distance tgtdit decreases to the critical value (second comparison value d3), the triangle is an area surrounded by the line segment g and the horizontal axis, so that the height thereof becomes the current vehicle speed Vnow. The slope of the triangle waist line is determined by the preset deceleration Decel. Therefore, the second comparison value d3 can be calculated by the formula;

when the target residual distance tgtdit is between d3 and d4, the height of the unfilled triangle (i.e., the area enclosed by the line segments a and f and the horizontal axis) enclosed by the V-t lines is Vset0, and the slopes of the two waists are determined by the preset acceleration Accel and the preset deceleration Decel. Vset0 can be calculated using the formula previously described;

when the target residual distance tgtdit continues to decrease, the area of the triangle surrounded by the V-t line continues to decrease, and the current vehicle speed Vnow point cannot be changed, so the deceleration slope is increasingly large (such as a line segment h), and the required braking strength is increasingly large. Vset0 is determined to be 0 and braking control is requested.

As shown in fig. 6 and 7, in a specific example, the step S11 further includes:

step S116, when the current vehicle speed is greater than or equal to the preset maximum vehicle speed, a fourth comparison value d5 is calculated according to the following formula:

d5＝Vnow^2/2/Decel

wherein Vnow is the current vehicle speed, and Decel is the preset deceleration;

step S117, comparing the target remaining distance with the fourth comparison value d 5;

step S118, when the comparison result is that the target remaining distance is greater than the fourth comparison value d5, determining the target vehicle speed as a preset maximum vehicle speed; otherwise, the target vehicle speed is determined to be zero.

The velocity plan curve for the situation shown in fig. 6 is shown in fig. 7, in particular:

when the target residual distance tgtdit is large, the figure enclosed by the V-t lines is a polygonal trapezoid (i.e. the area enclosed by the line segments a, b, c and the horizontal axis). The height of the trapezoid is the maximum vehicle speed Vmax, and the slopes of the two waists of the trapezoid are determined by the preset acceleration Accel and the preset deceleration Decel.

When the target remaining distance tgtdit decreases to the critical value (the fourth comparison value d5), the V-t line becomes a triangle (i.e., an area where the line segment ad and the horizontal axis enclose). The slope of the triangle waist is determined by the preset deceleration Decel. The fourth comparison value d5 can be calculated using the formula described above. Therefore, when the target remaining distance tgtdit is greater than d5, the target speed Vset0 takes the maximum vehicle speed Vmax.

When the target residual distance tgtdit continues to decrease, the area of the triangle surrounded by the V-t line continues to decrease, and the current vehicle speed Vnow point cannot be changed, so the deceleration slope is increasingly large (such as the line segment e or f), and the braking strength is required to be increasingly large. Therefore, Vset0 at this time is determined to be 0, and braking control is requested.

In a specific example, the step S11 further includes:

after the target vehicle speed is obtained, whether the following conditions are met or not is further judged, and if all the conditions are met, the target vehicle speed is forced to be zero:

condition 1: the target vehicle speed Vset0 obtained this time is greater than zero; when this condition is satisfied, this control is referred to as drive control.

Condition 2: the target vehicle speed Vset1Last obtained in the previous cycle is zero; when this condition is satisfied, the previous control is the brake control.

Condition 3: the target residual distance tgtDist of the previous period is greater than the target residual distance tgtdit of the current time;

condition 4: the difference between the target residual distance tgtDist of the previous period and the current target residual distance tgtdit is smaller than a predetermined fifth comparison value d 6; in one embodiment, the value of d6 may be 111 mm. Since the vehicle speed is 20km/h at a control period of 20ms, the vehicle can move 111mm within one control period. The speed limit is 10km/h in the autonomous parking. When the difference between the last target residual distance tgtditlast and the target residual distance tgtDist is smaller than 111mm, it indicates that the residual distance is in a continuously decreasing state, which indicates that the present period and the previous period are likely to belong to the distance control of "the same time (i.e., in the same path)".

Condition 5: the current vehicle speed is at least larger than the target vehicle speed by a preset sixth comparison value v 2; in one embodiment, v2 may take the value of 0.3km/h, because the accuracy of the commonly used PID (proportional-integral-derivative controller) speed control is around 0.3 km/h. The target vehicle speed Vset0 is equal to the maximum vehicle speed Vmax in some conditional branches, while the actual vehicle speed Vnow should never exceed the maximum vehicle speed Vmax. The control strategy should be biased towards braking control when the current vehicle speed Vnow is greater than the difference between the target vehicle speed Vset0 minus v2, i.e. the current vehicle speed is relatively high and well suited for braking control.

And the current vehicle speed Vnow is greater than zero. If it is already 0, no braking control is required.

It is understood that, in the present embodiment, the definition of the "same time" distance control is as follows: in autonomous parking, the trajectory followed by the vehicle consists of a plurality of paths. When the vehicle tracks a certain path, the target residual distance tgtdit is gradually changed to 0 from the length of the path as the vehicle travels. When the next path is tracked, the target residual distance tgtdit is suddenly changed from 0 to the length of the next path. Distance control in the same path is referred to as "same time" distance control.

Through the filtering process of the target vehicle speed, the too frequent switching between the braking and the driving control can be avoided.

And step S12, according to the obtained target speed, determining to brake or drive the automobile, so that the speed of the automobile reaches the obtained target speed, and finally enabling the automobile to be located at the target position.

In a specific embodiment, the step S12 specifically includes:

after the target vehicle speed is determined, when the target vehicle speed is greater than zero, performing drive control according to the target vehicle speed and the current vehicle speed, and controlling the vehicle to accelerate to the determined target vehicle speed; in a specific example, the braking control is performed based on the remaining distance tgtdit and the current vehicle speed Vnow. For example, the relationship between the remaining distance tgtdit, the current vehicle speed Vnow, and the braking strength may be calibrated in advance and stored in a mapping table. In actual use, the remaining distance tgtdit and the current vehicle speed Vnow are input, that is, the braking strength can be obtained by looking up a table and output. Data in the table are obtained by adopting real vehicle test calibration in advance, so that the control effect can be improved.

When the target speed is zero, performing braking control according to the target remaining distance and the current speed, and controlling the automobile to decelerate to the determined target speed; in a specific example, a PID (proportional-integral-derivative controller) can be used for speed control, which is simple and easy to implement.

And after the automobile reaches the target speed, entering the next control period, and repeating the steps S10 to S11 to finally enable the automobile to be located at the target position.

A flow chart of a specific embodiment of the method of the present invention is shown in fig. 8, wherein the steps can be understood with reference to the foregoing description.

Accordingly, as shown in fig. 9, which shows a schematic structural diagram of an autonomous parking control device provided by the present invention, and together with fig. 10 and fig. 11, in the present embodiment, an autonomous parking control device 1 is provided at a vehicle end of an automatic parking system, and includes:

an automobile information obtaining unit 10 for periodically obtaining information of a target remaining distance and a current speed;

the target vehicle speed determining unit 11 is configured to determine a speed interval in which the current vehicle speed is located, select a corresponding target vehicle speed determining strategy, and obtain target vehicle speed information by combining a preset maximum vehicle speed, a preset acceleration and a preset deceleration;

and the parking control unit is used for determining to brake or drive the automobile according to the obtained target speed, so that the speed of the automobile reaches the obtained target speed, and finally the automobile is positioned at the target position.

Specifically, in an actual example, the target vehicle speed determination unit 11 further includes:

a first calculation unit 110 for calculating a first comparison value d2 according to the following formula when the current vehicle speed is zero:

d2＝Vmax^2/2/Accel+Vmax^2/2/Decel

the method comprises the following steps that Vmax is a preset maximum speed, Accel is a preset acceleration, and Decel is a preset deceleration;

a first comparing unit 111 for comparing the target remaining distance with a predetermined lowest distance threshold d1 and a second comparison value d 2;

a first comparison result processing unit 112, configured to determine the target vehicle speed as zero when the comparison result of the first comparison unit is that the target remaining distance is smaller than a predetermined minimum distance threshold d 1;

when the comparison result is that the target remaining distance is greater than the predetermined lowest distance threshold and is less than or equal to the first comparison value d2, the target vehicle speed Vset0 is calculated according to the following formula:

vset0 ═ sqrt (2 × tgtdit/(1/Accel + 1/Decel)); wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is greater than the first comparison value d2, determining the target vehicle speed as the preset maximum vehicle speed.

Specifically, in an actual example, the target vehicle speed determination unit 11 further includes:

a second calculating unit 113, configured to calculate a second comparison value d3 and a third comparison value d4 according to the following formulas when the current vehicle speed is greater than zero and less than or equal to a preset maximum vehicle speed:

d3＝Vnow^2/2/Decel

d4＝(Vmax^2-Vnow^2)/2/Accel+Vmax^2/2/Decel

wherein Vnow is the current vehicle speed;

a second comparing unit 114, configured to compare the current target remaining distance with the second comparison value d3 and a third comparison value;

a second comparison result processing unit 115, configured to determine the target vehicle speed as a preset maximum vehicle speed when the comparison result of the second comparison unit is that the target remaining distance is greater than the third comparison value d 4;

when the comparison result is that the target remaining distance is less than or equal to the third comparison value d4 and greater than the second comparison value d3, the target vehicle speed Vset0 is calculated according to the following formula.

Vset0＝sqrt(2*(tgtDist+Vnow^2/2/Accel)/(1/Accel+1/Decel))

Wherein tgtdit is the target residual distance;

and when the comparison result shows that the target remaining distance is smaller than the second comparison value d3, determining the target vehicle speed as zero.

Specifically, in an actual example, the target vehicle speed determination unit 11 further includes:

a third calculating unit 116 for calculating a fourth comparison value d5 according to the following formula when the current vehicle speed is greater than or equal to the preset maximum vehicle speed:

d5＝Vnow^2/2/Decel

wherein Vnow is the current vehicle speed, and Decel is the preset deceleration;

a third comparing unit 117 for comparing the target remaining distance with a fourth comparison value d 5;

a third comparison result processing unit 118 for determining the target vehicle speed as the preset maximum vehicle speed when the comparison result of the third comparison unit is that the target remaining distance is greater than the fourth comparison value d 5; otherwise, the target vehicle speed is determined to be zero.

Specifically, in an actual example, the target vehicle speed determination unit 11 further includes:

a filter unit 119 configured to further determine whether or not the following conditions are satisfied after the target vehicle speed is obtained, and if all the conditions are satisfied, force the target vehicle speed to be substantially zero:

the target vehicle speed Vset0 obtained this time is greater than zero;

the target vehicle speed Vset1Last obtained in the previous cycle is zero;

the target residual distance tgtDist of the previous period is greater than the target residual distance tgtdit of the current time;

the difference between the target residual distance tgtDist of the previous period and the current target residual distance tgtdit is smaller than a predetermined fifth comparison value d 6;

the current vehicle speed is at least larger than the target vehicle speed by a preset sixth comparison value v 2; and

the current vehicle speed Vnow is greater than zero.

Specifically, in a practical example, the parking control unit 12 specifically includes:

the control unit 120, when the target vehicle speed is greater than zero, performs drive control according to the target vehicle speed and the current vehicle speed, and controls the vehicle to accelerate to the determined target vehicle speed; when the target speed is zero, performing braking control according to the target remaining distance and the current speed, and controlling the automobile to decelerate to the determined target speed;

and the triggering unit 121 is configured to send a triggering message to the target vehicle speed determining unit after the vehicle reaches the target vehicle speed, so as to enter a next control cycle, and finally, locate the vehicle at the target position.

For more details, reference may be made to the preceding description of fig. 1-8.

The embodiment of the invention has the following beneficial effects:

the invention provides an autonomous parking control method and device, which can quantitatively calculate and solve a target vehicle speed by inputting a target residual distance tgtDist and a maximum vehicle speed Vmax and combining a current vehicle speed Vnow so as to realize high-precision parking;

meanwhile, according to the invention, different speed intervals are set for the current vehicle speed, each speed interval adopts a corresponding target vehicle speed calculation mode, and meanwhile, the target vehicle speed is subjected to filtering processing, so that frequent switching between drive control and brake control can be avoided, appropriate acceleration and deceleration can be obtained, the acceleration or deceleration process of parking is comfortable, and the use experience of a user is improved.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, apparatus, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.