JP3036109B2 - Travel control method for mobile robot system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a travel control method in a mobile robot system including a plurality of mobile robots and a control station for controlling the mobile robots.

[0002]

2. Description of the Related Art In recent years, with the development of factory automation (FA), various systems of this type have been developed and put into practical use. In this mobile robot system, the control station instructs each mobile robot to a destination and an operation to be performed at the destination by radio or wire. The mobile robot, which has received an instruction from the control station, automatically travels to and arrives at the instructed place, performs the instructed work at that place, and waits for the next instruction at that place when the work is completed.

In this type of system, how to prevent collision between automatically traveling robots is a major problem. As one method for solving this problem, it is conceivable to stop another robot while one mobile robot is traveling. However, in the case of this method, although the possibility of collision is extremely reduced, the traveling efficiency of the robot is extremely deteriorated, and there is no point in causing a plurality of mobile robots to travel.

Accordingly, the applicant of the present application has filed Japanese Patent Application No. Hei.
No. 959 has proposed a mobile robot system in which each mobile robot makes a reservation for traveling and avoids collision between the mobile robots. Hereinafter, an outline of the mobile robot system will be described. In this system, a node is set at each base of a traveling path on which each mobile robot travels. Each mobile robot detects a node, and measures a moving distance from a node that has passed the last node, thereby grasping its own location and traveling on a traveling path. In addition, the mobile robot stores a table of the distance between each node, and refers to this table when traveling toward a target node (hereinafter, referred to as a target node), so that the mobile robot moves from the current position to the target node. Each node included in the fixed distance X and the first node outside the fixed distance X are always obtained. Then, the mobile robot transmits to the control station a travel reservation request for the travel route formed by the obtained nodes. The control station that has received the travel reservation request transmits a message permitting the received travel reservation request to the mobile robot when the travel of the travel path is not permitted to another mobile robot. Then, the mobile robot receiving this message travels on the permitted traveling route,
Proceed to the target node.

[0005]

However, in the above-described mobile robot system, the following disadvantages may occur. FIG. 8 illustrates the first case, and FIG. 9 illustrates the second case. First, as shown in FIG. 8, the mobile robot R1
From the node # 8 to the left in the drawing. In this case, the mobile robot R1 moves from the current position # 4 in the moving direction to the first node # 5 outside the fixed distance X.
Is transmitted to the control station, and the request is granted. Similarly, the mobile robot R2 has a node #
The request for travel reservation up to 6 is transmitted to the control station, and this request is also permitted. However, when the mobile robots R1 and R2 move in accordance with these permissions, they both enter a running path where there is no escape. In this case, in order to avoid a collision, the mobile robot R2 must return to the node # 7 and proceed to another traveling path, and perform a time loss for calculating the avoidance operation by calculation and the avoidance operation. This causes a time loss. Next, as shown in FIG. 9, it is assumed that when the mobile robot R2 is working in a dead end, a mobile robot R1 having a node in the dead end as a target node has entered.
In this case, the mobile robot R1 has the exit node # 5 of the dead end.
A ride is reserved and the permission is given, resulting in a deadlock condition. The present invention has been made in view of the above circumstances, and provides a traveling control method in a mobile robot system in which a collision between mobile robots can be prevented at an early stage, and a time loss required for collision avoidance is minimized. The purpose is to do.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a mobile robot comprising a plurality of mobile robots and a control station for controlling the mobile robots, wherein each mobile robot travels while detecting a node provided on a travel path. In the system, the control station provides the mobile robot with a work node consisting of a target node corresponding to a work point and a type of work to be performed at the work point. For the control station, if the current position, or if there is a target node within a certain distance from the node to pass, or the current position, or a branch node where the node to pass is connected to a dead end, When the destination node is in the dead end, a travel reservation to the destination node is requested, and a certain distance is set from the current position or the node to be passed. If there is no destination node in the release within,
Requesting a travel reservation to the first branch node exceeding the predetermined distance toward the destination node, wherein the control station is configured to perform the travel reservation if the requested node is an entrance or exit of a dead end; If the target node of the mobile robot requesting the reservation is in the dead end, there is no other mobile robot in the dead end, and the requested node permits another mobile robot to make a travel reservation. The travel reservation is permitted only when the node is not the node that has made the travel reservation, and when the node for which the travel reservation has been requested is not an entrance or exit of a blind alley, the node is not a node that has permitted travel reservation to another mobile robot. The travel reservation is permitted.

[0007]

According to the above method, since the request for travel reservation of each mobile robot is made in units of branch nodes, it is not possible for the mobile robots to encounter each other on the travel path between the branch nodes. Further, when a mobile robot exists in a dead end, and another mobile robot having a target node in the dead end proceeds, a request for travel reservation by the other mobile robot to a node at an entrance / exit of the dead end is rejected. You. Therefore, the mobile robot in the dead end can get out of the dead end.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a mobile robot system to which a traveling control method according to an embodiment of the present invention is applied will be described with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the mobile robot system. In this figure, C is a control station, the configuration of which is shown in FIG. R1 to Rn are mobile robots, the configuration of which is shown in FIG. The control station 1 and each of the mobile robots R1 to Rn are wirelessly connected.
The mobile robot Rk (k = 1 to n) moves along a magnetic tape attached to the floor of a predetermined traveling path, and is provided at an appropriate interval on the traveling path. Node is set. Each of these nodes has a node mark affixed to the floor, and each mobile robot Rk
Is provided with a detector for detecting this node mark.

Next, the configuration of the control station C will be described. In FIG. 2, reference numeral 1 denotes a CPU (Central Processing Unit), and reference numeral 2 denotes a program memory storing programs executed by the CPU 1. One of the programs executed by the CPU 1 is a reservation availability determination program that determines whether or not to permit a reservation when a travel reservation request is issued from each mobile robot Rk. FIG. 4 shows the flow of the reservation availability determination program. Reference numeral 3 denotes a collision table, in which a collision data block is stored for each combination (#j, #k) of adjacent nodes existing on the traveling road. Here, the content of the collision data block will be described. For example, assume that the mobile robot has moved from node #j to node #k or vice versa. As a result of this movement, in order to avoid a collision, a new node where another mobile robot must not exist is generated. The number of such nodes and the total number of such nodes are written in the collision data block. The details of the collision data block are described in Japanese Patent Application No. 1-130959. Reference numeral 4 denotes a map memory, which stores coordinates of each node, data indicating a node type, numbers of other nodes connected to the node, distances to the other nodes, and the like. Reference numeral 5 denotes a data memory for storing data. Here, a partial storage area of the data memory 5 is used as a reserve table for managing travel reservations from each mobile robot. This reserve table is made up of storage slots corresponding to the nodes on the travel path. When permitting travel reservation from the mobile robot Rk,
For each storage slot corresponding to each node in the permitted travel route and for each storage slot corresponding to each node where no other mobile robot must be present in order for the mobile robot Rk to pass these nodes, R
The number “k” of k is written. Reference numeral 6 denotes an operation unit, and 7 denotes a communication device. The communication device 7 transmits the data supplied from the CPU 1 on a carrier having a predetermined frequency. The carrier wave carrying this data is received by the mobile robots R1 to Rn.

Next, the mobile robot Rk will be described.
In FIG. 3, reference numeral 11 denotes a CPU, and 12 denotes a program memory storing programs executed by the CPU 11. Reference numeral 13 denotes a data memory for storing data, 14 denotes an operation unit, 15 denotes a communication device, and 16 denotes a map memory in which the same data as the map memory 4 in the control station C is stored. A traveling control device 17 receives traveling data (destination data, traveling speed data, and the like) supplied from the CPU 11, controls a driving motor while detecting a magnetic tape and a node mark on the floor surface by a magnetic sensor, The mobile robot runs toward the target node. Also, based on the output of the encoder attached to the axle, always detect the distance from the last node passed to the current position,
The current position data indicating the distance is output to the CPU 11. Reference numeral 18 denotes an arm control device which receives a work program number supplied from the CPU 11, reads a work program of that number from an internal memory when the mobile robot arrives at a work node, and reads a work program of the robot program according to the read program. ) To control the work.

Hereinafter, the operation of the mobile robot system will be described. (Operation Example 1) On the traveling road shown in FIG.
It is assumed that work to be performed has occurred. At this time, assuming that the mobile robot R1 having no work is waiting at the node # 2, a work instruction including a work point code specifying the node # 7 and a work program number is transmitted from the control station C to the mobile robot R1. Is done. Mobile robot R1
CPU 11 stores the received work point code and program number in the data memory 13, and then searches for a traveling route to the target node # 7. This route search is performed by a conventionally known vertical search method or the like. By this route search, for example, # 3 → # 4 → # 5 → # 6 →
It is assumed that the route # 7 has been searched. The CPU 11 sequentially accumulates the travel distance of the searched route from the starting point node # 2 toward the destination node # 7 based on the distance between the nodes stored in the map memory 16 and exceeds the predetermined distance X. Find the first node. In the case shown in FIG. 5, since the first node exceeding the fixed distance X is the branch node # 3, the CPU 11 transmits the node number of the node # 3 and a travel reservation request to the control station C. The CPU 1 of the control station C
According to the flow shown in FIG. 4, it is determined whether or not permission is given to the reservation request for all the received node numbers (in this case, only node # 3). In this case, since the node # 3 is a normal branch node, the process proceeds to step S4.
All the node numbers stored in the collision data block corresponding to the node set (# 2, # 3) in the collision table 3 are read. Then, it is determined whether or not there is at least one reserved node among the nodes corresponding to these node numbers. If not reserved, that is, if the contents of the storage slots corresponding to these nodes in the reserve table are all “0”, the robot number “1” is written into each of those storage areas. In this way, route # 2 → # 3 is reserved, and CP of control station C is
The number of node # 3 and the reservation completion code are transmitted from U1 to mobile robot R1. The mobile robot R1 receives the reservation completion code from the control station C,
Proceed to node # 3. Thereafter, the mobile robot R1
Every time the predetermined time elapses, data indicating the current state of the robot (running, waiting, working, etc.) and the current position is transmitted to the control station C. The CPU 1 in the control station C constantly monitors the current position data sent from the mobile robot R1 and refers to the map memory 4 to determine whether the mobile robot R1 has passed the node # 3. When it is determined that the mobile robot R1 has passed the node # 3, the reservation of the route # 1 → # 2 is released. That is, the robot number “1” written in the reserve table at the time of reservation of route # 1 → # 2 is returned to “0”. on the other hand,
The CPU 11 of the mobile robot R1 constantly monitors the distance left before passing the node # 3 based on the current position data and the distance between the nodes stored in the map memory 16. Then, the CPU 11 makes a new travel reservation before the mobile robot R1 passes through the node # 3. In this case, the first node exceeding the distance X from the node # 3 toward the target node # 7 is # 4, but this node # 4 is not a branch node. Accordingly, the requesting node in this case is the node # 6, and the CPU 11 transmits the nodes up to the requesting node # 6, that is, the nodes # 4 and #.
The control station C transmits the node numbers of # 5 and # 6 and the travel reservation request.
Send to

The control station C determines whether or not reservation is possible for each received node number according to the flow shown in FIG.
In this case, similarly to the above-described determination on the travel reservation up to the node # 3, the determination regarding any of the nodes is performed in step S4. And all nodes #
Only when there is no possibility of collision with another mobile robot when the reservation is permitted for # 4, # 5, and # 6, travel reservation of the mobile robot R1 is permitted, and nodes # 4, # 5, and # 5 in the reserve table are allowed. The number "1" is written to each storage slot corresponding to # 6 and to each storage slot corresponding to a node where no other mobile robot should exist when the mobile robot R1 passes through these nodes. Then, the reservation completion code is transmitted to the mobile robot R1. On the other hand, if any one of the nodes # 4, # 5, and # 6 cannot permit the reservation, for example, as shown in FIG. 6, the other mobile robot R2 performs the work in the node # 6. If all nodes # 4,
A reservation refusal code is transmitted from the control station C to the mobile robot R1 for rejecting the reservation for # 5 and # 6. Then, the mobile robot R1 may be instructed to temporarily wait at the node # 3, or may be instructed to select another route.
An instruction for performing the collision avoidance operation is given from the control station C to the mobile robot R1.

When the reservation up to the request node # 6 is permitted, the mobile robot R1 proceeds toward the node # 6. Then, as described above, before passing through the node # 6,
Make a new travel reservation. In this case, since the target node # 7 is within the range of the distance X from the node # 6, the request node of the mobile robot R1 is the node # 7, and the mobile robot R
No. 1 issues a travel reservation request to node # 7.

The control station C follows the flow shown in FIG.
It is determined whether the travel reservation for the request node # 7 from the mobile robot R1 is permitted. In this case, since the request node # 7 is the target node, it is determined in step S1 whether or not the travel reservation is possible. If the reservation is possible, the reservation up to the destination node # 7 is permitted,
A reservation completion report is transmitted to the mobile robot R1. As a result, the mobile robot R1 advances to the target node # 7 and performs the specified work.

(Operation Example 2) In FIG. 5, the mobile robot R1 waiting at the node # 2 receives the node # in the dead end.
It is assumed that a work instruction to perform a work is given at 22. As a result, the mobile robot R1 moves to the destination node # 2.
The travel route search up to # 2 is performed, and for example, by this route search, # 3 → # 4 → # 5 → # 6 → # 15 → # 21 →
The route # 22 is searched. As in the case of the operation example 1, the mobile robot R1 first transmits a travel reservation to the branch node # 3 to the control station C, and when this is permitted by the control station C, the mobile robot R1 moves to the node # 3. Go forward. Next, the mobile robot R1 makes a travel reservation to the next branch node # 6 before passing through the node # 3, and when this is permitted by the control station C, the node # 6.
Continue to. And before reaching node # 6,
A third travel reservation is made. In the case shown in FIG. 5, node #
Since it is the first branch node # 15 exceeding the distance X from 6 toward the target node # 22, the mobile robot R1 transmits a request for travel reservation to the node # 15 to the control station C.

The control station C determines whether or not reservation is possible according to the flow shown in FIG. In this case, since the node # 15 is a branch node on the dead end, the process proceeds to step S2, and a primary determination is made as to whether a travel reservation up to the node # 15 is possible. If it is determined in this primary determination that a travel reservation up to node # 15 is possible, step S is further performed.
Proceeding to 21, a secondary determination is made as to whether the target node of the mobile robot R1 is in a dead end connected to the branch node # 15. If the result of the secondary determination is “YES”, the flow proceeds to step S22, and a tertiary determination is made as to whether or not another mobile robot exists in the dead end connected to the branch node # 15. If the result of the tertiary determination is “NO”, traveling reservation to the node # 15 is permitted for the mobile robot R1. Further, for example, when another mobile robot R2 exists in the dead end as shown in FIG. 7, the result of the tertiary determination is “YES”, and the traveling reservation to the node # 15 for the mobile robot R1 is not permitted. Therefore,
The mobile robot R1 waits at the node # 6 until the mobile robot R2 goes out of the blind alley. On the other hand, if the result of the determination in step S21 is "NO", that is, if the target node of the mobile robot R1 is not in the dead end, the control station C permits the mobile robot R1 to make a travel reservation to the node # 15. When traveling to the node # 15 is permitted, the mobile robot R1 proceeds to the node # 15. Then, before reaching node # 15, a fourth travel reservation is made. In the case shown in FIG. 5, the first node exceeding the distance X from the node # 15 toward the destination node # 22 is the node # 21, which is a node in the dead end. Accordingly, the mobile robot R1 transmits a request for a travel reservation to the target node # 22 to the control station C.
In this case, the control station C determines whether the reservation is possible or not in step S3 in FIG. As long as the system is normal, reservation for travel to the destination node in this dead end is permitted. However, if it is determined in this determination that the reservation cannot be made, the control station C considers that some abnormality has occurred in the system and issues a warning.

[0017]

As described above, according to the present invention, a plurality of mobile robots and a control station for controlling these mobile robots are provided, and each mobile robot detects a node provided on a traveling path. In the traveling mobile robot system, the control station, for the mobile robot,
A task instruction including a target node corresponding to the work point and a type of work to be performed at the work point is provided, and the mobile robot to which the work instruction is given is presently located or going to pass to the control station. If there is a target node within a certain distance from the target node, or if the current position or the node to be passed is a branch node connected to a dead end, and the target node is within the dead end, the target node is reached. If there is no destination node within a certain distance from the current position or the node to be passed, a travel reservation to the first branch node exceeding the certain distance is requested to the destination node. In addition, the control station is adapted to execute the case where the node for which the travel reservation is requested is an entrance / exit of a blind alley, and the object of the mobile robot requesting the travel reservation is determined. If the mobile node is in the dead end, there is no other mobile robot in the dead end and the requested node is not a node that has permitted travel reservation to another mobile robot. If travel reservation is permitted and the node that has requested the travel reservation is not the entrance of a dead end, the travel reservation is permitted only if the node is not a node that has permitted travel reservation to another mobile robot. Therefore, the collision between the mobile robots is prevented at an early stage, and there is an effect that a time loss for performing the operation of avoiding the collision is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a mobile robot system to which a traveling control method according to one embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a control station C in the same system.

FIG. 3 is a block diagram showing a configuration of a mobile robot Rk in the same system.

FIG. 4 is a flowchart showing an operation of the control station C for determining whether or not a travel reservation can be made in the system.

FIG. 5 is a diagram showing an operation example in the system.

FIG. 6 is a diagram showing an operation example in the system.

FIG. 7 is a diagram showing an operation example in the system.

FIG. 8 is a diagram showing an operation example in a conventional mobile robot system.

FIG. 9 is a diagram showing an operation example in a conventional mobile robot system.

[Explanation of symbols]

 C: Control station, R1 to Rn: Mobile robot.

Claims (1)

(57) [Claims] 1. A mobile robot system comprising a plurality of mobile robots and a control station for controlling these mobile robots, wherein each mobile robot travels while detecting a node provided on a travel path, wherein the control station comprises: To the mobile robot, a work instruction including a target node corresponding to a work point and a type of work to be performed at the work point is provided. The mobile robot to which the work instruction is provided is provided with a current position to the control station. Or the target node is within a certain distance from the node to be passed, or the current position or the node to be passed is a branch node connected to the dead end, and the target node is in the dead end. In this case, a travel reservation to the destination node is requested, and there is no destination node within a certain distance from the current location or the node to be passed. In this case, a request is made for a travel reservation up to the first branch node exceeding the certain distance toward the destination node, wherein the control station has a case where the node that has requested the travel reservation is an entrance to a dead end, If the target node of the mobile robot requesting the travel reservation is in the dead end, there is no other mobile robot in the dead end, and the requested node is sent to another mobile robot. The travel reservation is permitted only when the node is not the node that has permitted the travel reservation, and when the node that has requested the travel reservation is not the entrance of the dead end, the node that has permitted the travel reservation to another mobile robot. A travel control method in the mobile robot system, wherein the travel reservation is permitted only when the travel reservation is not satisfied.