CN115857482A

CN115857482A - Deadlock prevention method based on key points and trolley control system

Info

Publication number: CN115857482A
Application number: CN202111115691.6A
Authority: CN
Inventors: 朱兆辉; 吴海贤
Original assignee: Shanghai Fast Warehouse Automation Technology Co ltd
Current assignee: Shanghai Fast Warehouse Automation Technology Co ltd
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2023-03-28

Abstract

The invention provides a deadlock prevention method based on key points, which comprises the following steps: s11: when a request for adding key points to a trolley is received, adding the trolley to a candidate set of key points through a processor; s12: when a plurality of trolleys exist in the candidate set, comparing every two trolleys, and evaluating the preferred trolleys for the trolleys with overlapped residual paths based on the number of conflicts of each trolley and the distance from each trolley to a key point; s13: locking the optimized trolley to a key point, selecting an avoidance point and controlling the optimized trolley to move to the avoidance point; s14: when the optimized trolley passes through the key point, locking is released and the optimized trolley is deleted from the candidate set; s15: repeating the steps S11-S14 until all the trolleys in the candidate set pass through the key points; wherein the number of carts that coincide with the remaining path of a cart is the number of collisions for that cart. By identifying and marking the key points, the invention can control the traffic of the key points under the condition of multiple vehicles so as to prevent deadlock and avoid collision, thereby realizing conflict-free and efficient operation of the AGV.

Description

Deadlock prevention method based on key points and trolley control system

Technical Field

The present disclosure relates to the field of automated guided vehicles, and more particularly, to a deadlock prevention method based on a key point, a cart control system, and a computer-readable storage medium.

Background

With the development and popularization of technologies such as robots and internet of things, an intelligent logistics warehouse using an Automated Guided Vehicle (AGV) gains the favor of enterprises with high efficiency operation efficiency. According to a specific application scenario, the scale of an Automatic Guided Vehicle System AGVS (automated Guided Vehicle System) varies from a single System to dozens or even hundreds of systems, the System road network is more and more complex, and two major problems of collision and deadlock mainly exist. For example, in the case of distributed AGV control, after the path planning algorithm (such as a-x algorithm) is completed by the AGV, or in the case of centralized AGV control, because of factors such as actual field or operation, deadlock conditions such as AGV path overlapping are likely to occur. Past warehouse designers often adopt a one-way map mode to avoid the problem, but the over-conservative map design strategy causes the AGV to need to detour by a longer distance to reach the destination, and the performance of the AGVS is limited. On the premise of ensuring higher operation efficiency of AGVS, how to put forward an effective traffic control strategy ensures that the system is not paralyzed due to collision and deadlock, ensures the operational orderliness and high efficiency of the AGV traffic control system, and has important significance.

The statements in this background section merely disclose technology known to the inventors and do not, of course, represent prior art in the art.

Disclosure of Invention

In view of one or more of the existing drawbacks, the present invention provides a method for deadlock prevention based on key points, comprising:

s11: adding, by a processor, a cart to a candidate set of keypoints when a cart add keypoint request is received;

s12: when a plurality of trolleys exist in the candidate set, comparing every two trolleys, and evaluating the preferred trolley through a processor on the basis of the number of conflicts of each trolley and the distance from each trolley to the key point for the trolley with the overlapped residual paths;

s13: locking the optimized trolley to the key point, selecting an avoidance point through a processor, and controlling the optimized trolley to go to the avoidance point;

s14: after the optimized trolley passes through the key point, locking is released through a processor and deleted from the candidate set;

s15: repeating the steps S11-S14 until all the trolleys in the candidate set pass through the key point;

and the number of the trolleys which are overlapped with the residual path of one trolley is the conflict number of the trolley.

According to an aspect of the invention, further comprising: scanning according to the map edge relation, and setting path points meeting the following conditions as key points:

the total number of the outgoing edges and the incoming edges is more than or equal to 3;

the outgoing edge is more than or equal to 2; and

at least one adjacent waypoint is in the roadway.

According to an aspect of the present invention, wherein the step S12 further comprises:

s121: for the trolleys with overlapped residual paths, calculating the conflict number of each trolley, and adding the trolley with the largest conflict number into the optimal conflict set;

s122: selecting the trolleys in the unloaded state for all the trolleys in the preferred conflict set, and adding the trolleys in the unloaded state to a second conflict set;

s123: and calculating the Manhattan distance of each trolley to the key point for all trolleys in the second conflict set, and selecting the trolley with the shortest Manhattan distance as the preferred trolley.

According to an aspect of the invention, further comprising: when one trolley remains in the candidate set, controlling the one trolley to pass through the key point.

According to an aspect of the invention, further comprising: and when two trolleys remain in the candidate set and the remaining paths of the two trolleys do not coincide, controlling the two trolleys to pass through the key point in sequence.

According to an aspect of the present invention, wherein the step S13 further comprises: and setting path points meeting the following conditions as avoidance points:

adjacent to the key point and having a depth of 1;

the edge-out direction of the key point is positioned, and the key point does not conflict with the driving direction of other trolleys; and

no other vehicles go to avoid.

According to an aspect of the present invention, wherein the step S13 further comprises: and after the avoidance point is selected, calculating and splicing the path from the current position of the preferred trolley to the avoidance point and the path from the avoidance point to the terminal point of the preferred trolley, and updating the path of the preferred trolley.

According to an aspect of the present invention, wherein the step S13 further comprises: and when the avoidance point meeting the conditions does not exist or is positioned on the remaining path of the preferred trolley, controlling the preferred trolley to continuously run along the remaining path.

According to one aspect of the invention, the method further comprises the following steps: and in the running process of the trolley, when a next key point is detected or an obstacle exists in a first preset distance, setting the obstacle as an impassable point, and replanning a path.

According to an aspect of the invention, further comprising: and in the running process of the trolley, when the fact that the trolley in the idle state exists in the condition that the distance from the last key point is smaller than the second preset distance or the distance from the terminal point is smaller than the third preset distance is detected, the trolley in the idle state is triggered to run away from the residual path of the trolley.

The invention also relates to a trolley control system comprising:

a plurality of small cars are arranged on the base,

a scheduling unit, in communication with the plurality of carts, configured to perform the deadlock prevention method according to any one of claims 1-10.

According to an aspect of the invention, the scheduling unit further comprises:

a locking management module configured to manage locking requests and release locking requests of the plurality of carts;

a path planning module configured to perform path planning on the plurality of carts; and

and the deadlock prevention module is coupled with the locking management module and the path planning module and is configured to control the trolleys to release deadlock, avoid barriers and trigger the trolleys in an idle state to drive away.

According to one aspect of the invention, wherein the trolley is an automated guided transport vehicle.

The invention also relates to a computer-readable storage medium comprising computer-executable instructions stored thereon which, when executed by a processor, implement the deadlock prevention method as described above.

According to the technical scheme, by identifying and marking the key points, traffic control can be performed on the key points under the condition of multiple vehicles so as to prevent deadlock and avoid collision, and conflict-free and efficient operation of the AGV is realized. The main process is as follows: 1. identifying key points in the map which may generate conflicts; 2. sensing key point positions which are about to pass by the trolley; 3. sensing that a fixed obstacle in front of the trolley bypasses; 4. sensing that an idle vehicle in front of the trolley drives away; 5. controlling the passing sequence of the trolleys at the key point positions; 6. and selecting the trolley to be avoided to the position near the key point for avoiding.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to be construed as limiting the disclosure. In the drawings:

FIG. 1 is a flow diagram of a method for deadlock prevention based on key points according to one embodiment of the invention;

FIG. 2A is a diagram illustrating a determination key point according to a first embodiment of the present invention;

FIG. 2B is a diagram illustrating a second embodiment of the present invention;

FIG. 2C is a diagram illustrating a third embodiment of determining key points;

FIG. 3A is a diagram illustrating a fourth embodiment of the invention for calculating collision distances;

FIG. 3B is a diagram illustrating a fifth embodiment of the invention for calculating collision distances;

FIG. 3C is a diagram illustrating the computation of collision distances according to a sixth embodiment of the present invention;

FIG. 4 is a flowchart of step S12 of a deadlock prevention method according to an embodiment of the invention;

FIG. 5 is a diagram illustrating a deadlock prevention method according to a seventh embodiment of the invention;

FIG. 6 is a diagram illustrating a deadlock prevention method according to an eighth embodiment of the present invention;

FIG. 7 is a diagram illustrating a deadlock prevention method according to a ninth embodiment of the present invention;

fig. 8 shows a schematic view of obstacle avoidance in a tenth embodiment of the invention;

fig. 9 shows a schematic obstacle avoidance diagram according to an eleventh embodiment of the invention;

fig. 10 shows an idle vehicle avoidance schematic diagram according to a twelfth embodiment of the invention;

fig. 11 shows an idle vehicle avoidance schematic diagram according to a thirteenth embodiment of the invention;

fig. 12 is a schematic diagram illustrating an idle vehicle avoidance in a fourteenth embodiment of the present invention;

fig. 13 is a schematic diagram showing avoidance of an idle vehicle according to a fifteenth embodiment of the invention;

FIG. 14 is a block diagram of a cart control system according to one embodiment of the present invention.

Detailed Description

In the following, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the description of the present invention, it should be noted that unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection, either mechanically, electrically, or in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly above and obliquely above the second feature, or simply meaning that the first feature is at a lesser level than the second feature.

The following disclosure provides many different embodiments or examples for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize applications of other processes and/or uses of other materials.

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it should be understood that they are presented herein only to illustrate and explain the present invention and not to limit the present invention.

FIG. 1 illustrates a method for deadlock prevention based on key points according to an embodiment of the present invention, where the method 10 for deadlock prevention comprises the following steps:

in step S11, when a cart add keypoint request is received, the cart is added to the candidate set of keypoints by the processor. When the system is started, aiming at the imported map elements, according to the map edge relation, the path points or the reversing points are traversed, and the points meeting certain conditions are set as key points. When a cart (automated guided vehicle) approaches the keypoint, the cart may issue a request to add the keypoint.

According to a preferred embodiment of the present invention, the deadlock prevention method 10 further comprises: scanning according to the map edge relation, and setting path points meeting the following conditions as key points: (a 1) the total number of outgoing edges and incoming edges is greater than or equal to 3; (a 2) the edge is more than or equal to 2; (a 3) at least one adjacent waypoint is in the roadway. For example, whether a path point a is a key point is judged, wherein an outgoing edge of the point a is a path direction taking the point a as a starting point and other path points as end points; the edge of the point A is a path direction taking other path points as a starting point and the point A as an end point. The condition (a 1) and the condition (a 2) can be determined based on the outgoing edge and the incoming edge of the point a. Preferably, point a may select a particular waypoint, such as a turnaround point (i.e. a waypoint that allows the loaded vehicle to change direction), but without regard to the memory point and its associated egress and ingress edges.

Regarding the condition (a 3), it may be determined whether the point a has at least one adjacent waypoint (e.g., point B) in the roadway by: (b1) The number of the path points adjacent to the point B is less than that of the path points adjacent to the point A; (b 2) satisfies one of the following conditions: the number of path points adjacent to the point B is 1; or the number of the path points adjacent to the point B is 2, and the two adjacent path points and the point B form a non-right angle; or, the number of path points adjacent to the point B is 3, and a non-straight angle is formed after the point A is removed. Because the car (e.g., AGV) can only move between the waypoints or the turning points along the manhattan distance, the total number of outgoing and incoming edges of the point a is 4 at most regardless of the double passage, and the total number of outgoing and incoming edges of the point B can be determined to be 2 or 3 based on the condition (B1), in which case the point B may be located in a roadway (e.g., an intersection or a t-intersection) or may be in close proximity to a path boundary (e.g., a corner or a wall) and the latter needs to be further excluded in combination with the condition (B2).

How to judge the point a as the key point is described below by way of example.

Fig. 2A is a schematic diagram of determining key points according to a first embodiment of the present invention, in which black solid lines are path boundaries (e.g., walls or shelves), and each square represents a path point or a direction-changing point. First, since the number of outgoing sides of point a is 2, the number of incoming sides is 1, and the total number of outgoing and incoming sides is 3, point a satisfies the conditions "(a 1) the total number of outgoing and incoming sides is 3 or more", and "(a 2) the number of outgoing sides is 2 or more". Continuously judging whether the point B adjacent to the point A is in the roadway: the points adjacent to the point B are the point A and the point C, and the number of the points adjacent to the point B is 2; the dots adjacent to the point A are the point B, the point D and the point E, the number of dots adjacent to the point A is 3, the point B satisfies the condition "(B1) the number of dots adjacent to the point B is smaller than the number of dots adjacent to the point A", however, the point A, the point B and the point C form a right angle, so the point B does not satisfy the condition "(B2) the number of dots adjacent to the point B is 2, and the two adjacent dots and the point B form a non-right angle". That is, point B is not in the lane, point B does not satisfy the condition "(a 3) point B adjacent to point a is in the lane", and therefore point a does not satisfy all the conditions to become the key point, and point a is not the key point.

Fig. 2B is a schematic diagram of determining key points according to the second embodiment of the present invention, in which black solid lines are path boundaries (e.g., walls or shelves), and each square represents a path point or a direction-changing point. First, since the number of outgoing sides of point a is 2, the number of incoming sides is 2, and the total number of outgoing and incoming sides is 4, point a satisfies the condition "(a 1) the total number of outgoing and incoming sides is 3 or more" and "(a 2) the total number of outgoing and incoming sides is 2 or more". And continuously judging whether the point B adjacent to the point A is in the roadway: the points adjacent to the point B are the point A, the point C and the point D, and the number of the points adjacent to the point B is 3; points adjacent to the point a are the point B, the point E, the point F and the point H, the number of points adjacent to the point a is 4, the point B satisfies the condition "(B1) the number of points adjacent to the point B is smaller than the number of points adjacent to the point a", however, the point B, the point C and the point D form a straight angle after the point a is removed, so the point B does not satisfy the condition "(B2) the total number of points adjacent to the point B is 3, and a non-straight angle is formed after the point a is removed. That is, point B is not in the lane, point B does not satisfy the condition "(a 3) point B adjacent to point a is in the lane", and therefore point a does not satisfy all the conditions to become the key point, and point a is not the key point.

In the above two embodiments, the situation that the keypoint is close to the path boundary is excluded, and fig. 2C shows a schematic diagram of determining the keypoint in the third embodiment of the present invention, where a black thick solid line is the path boundary (e.g., a wall or a shelf), and each square represents a path point or a direction change point. First, since the number of outgoing sides of point a is 3, the number of incoming sides is 1, and the total number of outgoing and incoming sides is 4, point a satisfies the conditions "(a 1) the total number of outgoing and incoming sides is 3" or more, and "(a 2) the number of outgoing sides is 2" or more. Then, continuously judging whether the point B adjacent to the point A is in the roadway: the points adjacent to the point B are the point A and the point C, and the number of the points adjacent to the point B is 2; the points adjacent to the point a are the point B, the point D, the point E and the point F, the number of points adjacent to the point a is 4, the point B satisfies the condition "(B1) the number of points adjacent to the point B is smaller than the number of points adjacent to the point a", and the point a, the point B and the point C form a straight angle, so the point B satisfies the condition "(B2) the number of points adjacent to the point B is 2, and the two adjacent points and the point B form a non-right angle". That is, point B is in the lane, and point B satisfies the condition "(a 3) point B adjacent to point a is in the lane", and therefore point a satisfies all the conditions to become the key points, and point a is the key point.

How to judge the key points is described above by three embodiments, and all the key points in the map are scanned based on the above conditions. The keypoints are usually path points where collisions may occur, and in general, the following path points are all identified as keypoints: intersections of crossroads, intersections of tees, and intersections of culmination intersections.

For each keypoint, a candidate set of keypoints may be set. During the cart's run, the next keypoint on its path may be retrieved and a request to add a keypoint may be issued so that the cart is added to the candidate set of keypoints. In addition, the candidate set of each key point is dynamically adjusted, and the candidate set of the key point can be added when the trolley applies for adding the key point; after the car passes the keypoint, it may be deleted from the candidate set of keypoints.

In step S12: and when a plurality of trolleys exist in the candidate set, comparing every two trolleys, and evaluating the preferred trolleys through the processor on the basis of the number of conflicts of each trolley and the distance from each trolley to the key point for the trolleys with the coincident residual paths. Wherein, the preferred trolley is the trolley which can pass the key point preferentially. When there are multiple cars in the candidate set, two problems need to be solved: how to calculate the collision distance to the collision path and how to solve the deadlock problem in advance.

Taking the car AGV1 as an example, starting from the front-most locking point of the AGV1, the next key point in the remaining path, for example, key point A1, is found. The locking point is a path point or a reversing point for forbidding other AGVs to enter so as to ensure that the AGV can enter or pass through safely.

After finding the next key point A1, the AGV1 sends a request to add to the key point A1, and after monitoring the request, the scheduling unit adds the AGV1 to the candidate set of the key point A1, and deletes the AGV1 from the candidate sets of other key points.

For all the trolleys in the candidate set of the key point A1, based on the paths of all the trolleys, pairwise grouping and comparing the path coincidence condition to calculate the collision distance (hereinafter referred to as collision distance) to the collision path. For example, a certain group includes a car AGV1 and a car AGV2, and obtains the current positions and remaining paths of the AGVs 1 and 2, if the remaining path of the AGV2 passes through the key point A1 and then needs to pass through the current position of the AGV1, and the path from the key point A1 to the current position of the AGV1 of the AGV2 coincides with the path from the current position of the AGV1 to the key point, the collision distance of the AGVs 1 is 0; otherwise, the collision distance of the AGV1 is the manhattan distance from the current position of the AGV1 to the key point A1. If the collision distance of the AGV2 is also 0, the residual paths of the AGV1 and the AGV2 are overlapped, and deadlock can be caused when the vehicle continues to run according to the current path. Generally, since the key point A1 has at least 3 adjacent path points, the third path point not on the two vehicle paths can be used as an avoidance point, and after a preferred vehicle is selected from the candidate set, the path of the preferred vehicle is changed, and the preferred vehicle is controlled to travel to the path point for avoiding deadlock.

Fig. 3A is a schematic diagram illustrating a collision distance calculation according to a fourth embodiment of the present invention, where the current positions of AGVs 2 and 1 and a key point A1 are shown, where the remaining path of AVG2 is P2, the remaining path of AGV1 is P1, and the remaining path P2 and the remaining path P1 form two collision paths CP1 and CP2 on two sides of the key point A1. After the AGV2 passes through the key point A1 for the first time, the AGV2 needs to pass through the current position of the AVG1, that is, the remaining path P2 and the remaining path P1 form a collision path CP1 on the side of the key point A1, and then the collision distance of the AGV1 is 0; after the AGV1 passes through the key point A1 for the first time, the AGV1 needs to pass through the current position of the AVG2, the remaining path P1 and the remaining path P2 form a collision path CP2 on the other side of the key point A1, and then the collision distance of the AGV2 is 0.

Fig. 3B is a schematic diagram illustrating the calculation of the collision distance according to the fifth embodiment of the present invention, and the diagram illustrates the current positions of AGVs 2 and 1 and a key point A1, where the remaining path of AVG2 is P2, the remaining path of AGV1 is P1, and the remaining path P2 and the remaining path P1 form a collision path CP on the side of the key point A1. After the AGV2 passes through the key point A1 for the first time, the AGV2 needs to pass through the current position of the AVG1, and then the conflict distance of the AGV1 is 0; the AGV1 does not need to pass through the current position of the AVG2 after passing through the key point A1 for the first time, and the collision distance of the AGV2 is the manhattan distance to the key point A1.

FIG. 3C is a diagram illustrating the computation of collision distances according to a sixth embodiment of the present invention; the present positions of AGV2 and AGV1 and the key point A1 are shown in the figure, where the remaining path of AVG2 is P2, the remaining path of AGV1 is P1, and the remaining path P2 and the remaining path P1 form a conflict path CP. The AGV2 does not pass through the current position of the AVG1 after passing through the key point A1 for the first time, and then the collision distance of the AGV1 is the Manhattan distance reaching the key point A1; the AGV1 does not pass through the current position of the AVG2 after passing through the key point A1 for the first time, and the collision distance of the AGV2 is the manhattan distance to the key point A1.

How to calculate the collision distance of two vehicles is described above by three embodiments. According to the method, all trolleys in the candidate set are compared pairwise to obtain all conflict distances.

According to a preferred embodiment of the present invention, wherein said step S12 further comprises:

in step S121: and for the trolleys with coincided residual paths, calculating the collision number of each trolley, and adding the trolley with the highest collision number into the preferred collision set. And the number of the trolleys which are overlapped with the residual path of one trolley is the conflict number of the trolley. Taking AGV1 and AVG2 as examples, the trolleys that overlap with the remaining path of AGV1, i.e. the trolleys with collision distance of 0, are taken as the collision set 1 of AGV1, and the number of trolleys in the collision set 1 is the collision number of AGV 1; and taking the trolleys which are overlapped with the residual paths of the AGV2, namely the trolleys with the collision distance of 0 as a collision set 2 of the AGV2, wherein the number of the trolleys in the collision set 2 is the collision number of the AGV2. And by analogy, calculating the conflict number of each trolley, and adding the trolley with the largest conflict number to the preferred conflict set.

In step S122: and selecting the trolleys in the unloaded state for all trolleys in the preferred conflict set, and adding the trolleys in the unloaded state to the second conflict set. If the preferred conflict set includes multiple carts, for example, the conflict number of multiple carts is the same in step S121, the comparison of the cart carrying status is continued. At this time, the load is not considered, and only whether the load is carried or not is considered. The cart in which it is not loaded is added to the second conflict set. Further, if there is only one cart in the preferred conflicting set, then that cart is the preferred cart.

In step S123: and calculating the Manhattan distance of each trolley to the key point A1 for all trolleys in the second conflict set, and selecting the trolley with the shortest Manhattan distance as the preferred trolley. If there are more cars in the second collision set, for example, the number of collisions is the same and none of them are loaded, the manhattan distance from the car to the key point A1 is continuously compared, and the nearest car is selected as the preferred car. Furthermore, if there is only one cart in the second conflicting set, then that cart is the preferred cart.

The above selection of the car that needs to pass through the key point A1 preferentially through steps S121-S123 presupposes that there are a plurality of cars in the candidate set and that a deadlock is expected to occur in the future.

According to a preferred embodiment of the present invention, the deadlock prevention method 10 further comprises: when one trolley remains in the candidate set, the one trolley is controlled to pass through the key point.

According to a preferred embodiment of the present invention, the deadlock prevention method 10 further comprises: and when two trolleys remain in the candidate set and the remaining paths of the two trolleys do not coincide, controlling the two trolleys to pass through the key points in sequence.

After the preferred cart is evaluated, it is also considered that: after passing through the key point A1, the trolley continues to run according to the rest path, or the path is changed, and the trolley temporarily goes to an avoidance point to avoid.

In step S13: locking the optimized trolley to the key point, selecting an avoidance point through a processor, and controlling the optimized trolley to go to the avoidance point. After the preferred trolleys are evaluated, the selection of the current round is finished, and the rest trolleys are left for the next round of selection of the preferred trolleys. The preferred cart is then locked to key point A1, while the next waypoint, i.e., avoidance point, to which the preferred cart is heading needs to be determined.

According to a preferred embodiment of the present invention, wherein step S13 further comprises: and setting path points meeting the following conditions as avoidance points: (c 1) adjacent to the keypoint, and having a depth of 1; (c2) The edge-out direction of the key point is positioned, and the key point does not conflict with the driving direction of other trolleys; and (c 3) avoiding other trolleys without going to the other trolleys.

For example, the AGV1 and the AGV2 having collision distances of 0 each select the preferred car AGV1 in step S12, and first, obtain a driving direction which does not collide with the AGV1 and the AGV2 as an available direction; then, obtaining idle path points with the depth of 1 around the key point A1 in the available direction as candidate points, wherein the depth of 1 represents that the distance between the path point and the key point A1 is 1 code point, namely the minimum distance unit on the map; then, acquiring path points which can be reached by the AGV1 in the candidate points, do not block the AGV2 and do not have the selection of the preferred trolleys in other candidate sets; finally, one of the points is selected as an avoidance point for the AGV1.

According to a preferred embodiment of the present invention, wherein step S13 further comprises: after the avoidance point is selected, calculating and splicing the path from the current position of the preferred trolley to the avoidance point and the path from the avoidance point to the terminal point of the preferred trolley, and updating the path of the preferred trolley. Continuing to take the AGV1 and the AGV2 whose collision distances are both 0 as an example, after the AGV1 reaches the avoidance point through the key point A1, if the updated path still needs to pass through the key point A1, the AGV1 can continue to compete for the key point A1, that is, participate in the evaluation of the preferred car in the next round of candidate set. At this time, the collision distance of the AGV1 is manhattan distance to the key point A1, the collision distance of the AGV2 is 0, and if only the AGV1 and the AGV2 exist in the candidate set, the AGV2 in the current round of evaluation is the preferred car, and can be locked and pass through the key point A1.

According to a preferred embodiment of the present invention, the step S13 further comprises: and when the avoidance points meeting the conditions do not exist or are positioned on the remaining path of the preferred trolley, controlling the preferred trolley to continuously run along the remaining path. Continuing taking the AGV1 and the AGV2 with collision distances both equal to 0 as an example, after the AGV1 reaches the avoidance point through the key point A1, if the updated path does not need to pass through the key point A1 again, the AGV can continue to travel along the remaining path. At this time, there is only AGV2 in the candidate set, and AGV2 is the preferred car, and can lock and pass through the key point A1.

In step S14: after the preferred cart passes the keypoint, the lock is released by the processor and removed from the candidate set. For example, if the AGV1 locks the key point A1, only the AGV1 can pass through, and no other car can enter or pass through, so after the AGV1 passes through, the lock needs to be released so that the other car can continue to compete or pass through the key point A1.

In step S15: and repeating the steps S11-S14 until all the trolleys in the candidate set pass through the key point. After the optimized trolley of the current round is locked and passes through the key point, if a new trolley is applied to be added into the candidate set of the key point A1, updating the candidate set, and continuing the next round of selection; otherwise, continuing to perform the next round of selection based on the remaining trolleys in the candidate set until the quantity of the trolleys in the candidate set of the key point A1 is 0.

In summary, the deadlock prevention method 10 is introduced through steps S11 to S15, and path points that may generate collisions are scanned as key points; when the trolley is about to pass through the key point, the trolleys are controlled to pass through in sequence based on the conflict number, the loading condition and the conflict distance of all the trolleys in the candidate set, and the trolleys go to the avoidance point to avoid or continue to leave the path, so that the deadlock condition is solved in advance. The following is further described by way of example.

EXAMPLE seven

As shown in fig. 5, the carts AGV1 and AGV2 are about to pass through the same intersection. And adding the vehicle to the key point candidate set of the intersection in the forward driving process of the AGV2. During the forward driving process of the AGV1, the AGV1 also applies for adding the candidate set, so that two trolleys exist in the candidate set, and the evaluation of the preferred trolleys is started: since the conflict distances of AGVs 1 and 2 are both not 0, i.e. the conflict numbers are both 0, if one of them is unloaded, the unloaded trolley is the preferred trolley, otherwise, the preferred trolley is evaluated based on the distance to the key point. As shown in fig. 5, for example, AGV1 is located 3 distances from the key point and AGV2 is located 1 distance from the key point, AGV2 is the preferred cart because AGV2 is closer to the key point. When the AGV2 reaches the position near the crossroad and successfully applies for key point locking, the AGV2 preferentially passes through the crossroad, then releases the locking, continues to drive the remaining path, and simultaneously the processor deletes the remaining path from the candidate set. In the next round of evaluation, if only AGV1 remains in the candidate set, then AGV1 is the preferred cart, and can lock and pass through the key point, release the lock by the processor, and delete it from the candidate set. This embodiment is the case where there is no conflict between cars.

Example eight

As shown in fig. 6, the AGV1 and the AGV2 are about to pass through the same intersection, and the AGV2 needs to pass through the current position of the AGV1 after turning. And adding the vehicle to the key point candidate set of the intersection in the forward driving process of the AGV2. During the forward driving process of the AGV1, applying for adding to the candidate set, wherein two trolleys exist in the candidate set, and the evaluation of the preferred trolleys is started: and calculating the collision distance, wherein the collision distance of the AGV1 is 0, the collision distance of the AGV2 is the Manhattan distance to the key point, the collision number of the AGV1 is 1, the collision number of the AGV2 is 1, the collision number of the AGV1 is 0, the collision number of the AGV1 is more than the collision number of the AVG2, and the AGV1 is the preferred trolley. When the AGV1 reaches the position near the crossroad and successfully applies for key point locking, the AGV1 preferentially passes through the crossroad, then releases the locking, continues to drive the remaining path, and simultaneously the processor deletes the remaining path from the candidate set. At the next round of review, only AGVs 2 remain in the candidate set, then AGVs 2 are the preferred carts and may be locked and pass through the key points, released by the processor and deleted from the candidate set. This embodiment anticipates that deadlocks will occur and resolves ahead of time.

Example nine

As shown in fig. 7, the AGV1 and the AGV2 are about to pass through the same intersection, the AGV2 needs to pass through the current position of the AGV1 after turning, and the AGV1 also needs to pass through the current position of the AGV2 after turning. And adding the vehicle to the key point candidate set of the intersection in the forward driving process of the AGV2. During the forward driving process of the AGV1, applying for adding to the candidate set, wherein two trolleys exist in the candidate set, and the evaluation of the preferred trolleys is started: and calculating the collision distance, wherein the collision distances of the AGV1 and the AGV2 are both 0, the collision number of the AGV1 is 1, the collision number of the AGV2 is also 1, if one of the AGVV is not loaded, the unloaded trolley is the preferred trolley, otherwise, the preferred trolley is evaluated based on the distance to the key point. For example, as shown in fig. 7, AGV1 reaches the key point a distance of 3 and AGV2 reaches the key point a distance of 1, AGV2 is the preferred cart because AGV2 is closer to the key point. Determining an avoidance point for the AGV2 to avoid: the traveling directions of the AGVs 1 and 2 are not available, and a path point with the depth of 1 at the upward or rightward direction of the intersection is an available point, for example, an upper point is selected as an avoidance point.

The update path of AGV2 is: current position → key point of intersection → avoidance point above intersection → key point of intersection → target position. When the AGV2 reaches the vicinity of the crossroad and successfully applies for the key point locking, the AGV2 preferentially passes through the crossroad and then releases the locking, and meanwhile, the processor deletes the locking from the candidate set.

And (4) because the updated path of the AGV2 still passes through the key point of the crossroad, the AGV2 reappears and adds the key point into the candidate set, the candidate set is updated, and the trolleys participating in the next round of evaluation are the AGV1 and the AGV2. And calculating the collision distance, wherein the collision distance of the AGV1 is 0, the collision distance of the AGV2 is the Manhattan distance to the key point, the collision number of the AGV1 is 1, the collision number of the AGV2 is 1, the collision number of the AGV1 is 0, the collision number of the AGV1 is more than the collision number of the AVG2, and the AGV1 is the preferred trolley. When the AGV1 reaches the position near the crossroad and successfully applies for key point locking, the AGV1 preferentially passes through the crossroad, then releases the locking, continues to drive the remaining path, and simultaneously the processor deletes the remaining path from the candidate set. If only AGVs 2 remain in the candidate set, then AGVs 2 are the preferred carts and may be locked down and pass through the key points, released by the processor and deleted from the candidate set. This embodiment anticipates that a ring deadlock will occur and is resolved in advance.

The deadlock prevention method 10 is described in detail above by the seventh, eighth, and ninth embodiments. According to the technical scheme, by identifying and marking the key points, traffic control can be performed on the key points under the condition of multiple vehicles so as to prevent deadlock and avoid collision, and conflict-free and efficient operation of the AGV is realized.

According to a preferred embodiment of the present invention, the deadlock prevention method 10 further comprises: and in the running process of the trolley, setting the barrier as an impassable point and replanning a path when a next key point is detected or the barrier exists in the first preset distance. The first preset distance is, for example, 10 code points. The obstacles are for example: manually locking path points, fault locking path points, shelves, offline trolleys, abnormal-state trolleys, error trolleys and the like.

Fig. 8 shows a schematic diagram of obstacle avoidance according to a tenth embodiment of the present invention, in which the AGV1 travels in two lanes, finds an obstacle on the current lane during traveling, sets the obstacle as an unreachable path point, and bypasses the lane.

Fig. 9 shows an obstacle avoidance diagram according to an eleventh embodiment of the present invention, where the vehicle AGV1 travels in a single lane, finds an obstacle on a current lane during traveling, sets the obstacle as an unreachable path point, and bypasses from the outside of the single lane.

According to a preferred embodiment of the present invention, the deadlock prevention method 10 further comprises: in the running process of the trolley, when the trolley in the idle state exists in the condition that the distance from the last key point is smaller than the second preset distance or the distance end point is smaller than the third preset distance, the trolley in the idle state is triggered to run away from the residual path of the trolley. The second preset distance is, for example, 10 code points, the third preset distance is, for example, 10 code points, and the second preset distance and the third preset distance may not be equal. When the trolley in the idle state is triggered to avoid, the target avoiding point is not on the future path of the current trolley.

Fig. 10 shows a schematic diagram of idle vehicle avoidance according to a twelfth embodiment of the present invention, where a car AGV1 goes to a point d, finds an idle car AGV2 during a driving process, applies for the idle car AGV2 to avoid to a scheduling unit, and the AGV2 receives an avoidance task, selects a nearest reachable point a that is not on a path of the car AGV1, and goes to avoid. The trolley AGV1 reaches point d.

Fig. 11 shows a schematic diagram of idle vehicle avoidance according to a thirteenth embodiment of the present invention, where the car AGV1 travels to point d and finds an idle car AGV2 during traveling. And the AGV2 receives the avoidance task and selects a nearest reachable point e which is not on the path of the AGV1. At this time, the key point candidate set of the T-junction comprises AGV1 and AGV2, the collision distance is calculated, the collision distance of the AGV2 is 0, the collision distance of the AGV1 is the Manhattan distance reaching the key point, the collision number of the AGV2 is 1, the collision number of the AGV1 is 0, and the AGV2 is the preferred trolley, and the preferred trolley can be locked and can go to the e point through the key point. After waiting for the AGV2 to pass through near the intersection, the AGV1 is locked again and goes to the point d through the key point. The embodiment is an avoidance strategy of key points of the same dead-end.

Fig. 12 shows a schematic diagram of idle vehicle avoidance according to a fourteenth embodiment of the present invention, where the car AGV1 goes to a point d, and an idle car AGV2 is found during driving. And the AGV2 receives the avoidance task and selects a nearest reachable point e which is not on the path of the AGV1. AGV2 reaches point e and dodges, and AGV1 reaches point d.

Fig. 13 shows a schematic diagram of avoidance of a fifteen-embodiment idle vehicle, where the car AGV1 travels to a point d, and an idle car AGV2 is found during traveling. And the AGV2 receives the avoidance task and selects a nearest reachable point e which is not on the path of the AGV1. AGV2 reaches point e and dodges, and AGV1 reaches point d. This embodiment is a dead end avoidance strategy.

The present invention also relates to a trolley control system 20, as shown in fig. 14, comprising:

a plurality of trolleys (21) are provided,

a scheduling unit 22, in communication with the plurality of carts 21, is configured to perform the deadlock prevention method 10 as described above.

According to a preferred embodiment of the present invention, the scheduling unit 22 further comprises:

a lock management module 221 configured to manage lock requests and release lock requests of the plurality of carts 21;

a path planning module 222 configured to plan a path of the plurality of vehicles 21; and

a deadlock prevention module 223, coupled to the locking management module 221 and the path planning module 222, configured to control the plurality of trolleys 21 to release deadlocks, avoid obstacles, and trigger the trolleys 21 in an idle state to drive away.

According to a preferred embodiment of the invention, said trolley 21 is an automated guided vehicle.

The present invention also relates to a computer-readable storage medium comprising computer-executable instructions stored thereon which, when executed by a processor, implement the deadlock prevention method 10 as described above.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A deadlock prevention method based on key points comprises the following steps:

s12: when a plurality of trolleys exist in the candidate set, comparing every two trolleys, and evaluating the preferred trolley through a processor on the basis of the number of conflicts of each trolley and the distance from each trolley to the key point for the trolley with the overlapped residual path;

2. The deadlock prevention method of claim 1, further comprising: scanning according to the map edge relation, and setting path points meeting the following conditions as key points:

the outgoing edge is more than or equal to 2; and

at least one adjacent waypoint is in the roadway.

3. The deadlock prevention method according to claim 1, wherein the step S12 further comprises:

4. The deadlock prevention method according to claim 1, further comprising: and when one trolley in the candidate set is remained, controlling the one trolley to pass through the key point.

5. The deadlock prevention method of claim 1, further comprising: and when two trolleys remain in the candidate set and the remaining paths of the two trolleys do not coincide, controlling the two trolleys to pass through the key point in sequence.

6. The deadlock prevention method according to any one of claims 1 to 5, wherein the step S13 further comprises: and setting path points meeting the following conditions as avoidance points:

adjacent to the key point and having a depth of 1;

no other trolleys go to avoid.

7. The deadlock prevention method according to claim 6, wherein the step S13 further comprises: after the avoidance point is selected, calculating and splicing the path from the current position of the preferred trolley to the avoidance point and the path from the avoidance point to the terminal point of the preferred trolley, and updating the path of the preferred trolley.

8. The deadlock prevention method according to claim 6, wherein the step S13 further comprises: and when the avoidance point meeting the conditions does not exist or is positioned on the remaining path of the preferred trolley, controlling the preferred trolley to continuously run along the remaining path.

9. The deadlock prevention method of claim 7, further comprising: and in the running process of the trolley, when a next key point is detected or an obstacle exists in a first preset distance, setting the obstacle as an impassable point, and replanning a path.

10. The deadlock prevention method of claim 7, further comprising: and in the running process of the trolley, when the fact that the trolley in the idle state exists in the condition that the distance from the last key point is smaller than the second preset distance or the distance from the terminal point is smaller than the third preset distance is detected, the trolley in the idle state is triggered to run away from the residual path of the trolley.

11. A cart control system, comprising:

a plurality of small cars are arranged on the base,

12. The cart control system of claim 11, the dispatch unit further comprising:

13. The cart control system of claim 11 or 12, wherein the cart is an automated guided vehicle.

14. A computer-readable storage medium comprising computer-executable instructions stored thereon which, when executed by a processor, implement the deadlock prevention method of any one of claims 1-10.