CN105974925A - AGV trolley driving control method and system - Google Patents

Abstract

The present invention relates to a control method and system for running AGV cars. The system includes a central control unit for controlling each AGV car. The central control unit sends dispatch instructions to the control units on each AGV car, and controls the movement of the AGV car. The car is equipped with a sensor for detecting obstacles. The obstacle signal collected by the sensor is sent to the control unit. The control unit makes a judgment based on the obstacle signal. The control unit sends a control command to control the moving speed of the AGV car. The time point and length of time, so as to establish an obstacle database. The database sets a threshold for the occurrence of obstacles according to the location and frequency of obstacles, and the number of obstacles in a certain section is more or less than the set When the threshold is reached, when the AGV car travels to this road section, the control unit controls the speed of the car to ensure that obstacles can pass smoothly, avoid conflicts, and ensure the effective operation of the entire AGV system.

Description

AGV trolley driving control method and system

technical field

The present invention relates to the technical field of AGV trolleys, in particular to a control method and system for driving AGV trolleys.

Background technique

AGV automatic navigation car is a kind of only transportation equipment that can automatically complete the loading, unloading and transportation of goods under the condition of dispatching system or manual instructions. Therefore, AGV automatic navigation car is widely used in logistics sorting warehouses. The navigation control system mainly consists of magnetic guidance, inertial guidance, laser guidance, etc. Among them, inertial guidance and laser guidance are far less widely used than magnetic guidance due to their weak anti-interference ability. However, with the introduction of flexible manufacturing systems, the production lines of enterprises have become more complex, and the demand for materials has become more flexible and changeable. There are multiple AGVs arranged on the magnetic track in the entire warehouse. The travel of multiple AGVs is controlled by the control unit of the system. At the intersection of the magnetic guide rails, there will be obstacles on the magnetic guide rails for AGV cars with different running speeds on the magnetic guide rails. The obstacles are mainly pedestrians or other moving objects in the warehouse. The above-mentioned moving obstacles often shuttle from the magnetic track of the AGV trolley. When the AGV trolley encounters the above-mentioned obstacles, it is generally difficult to Adjustment, the AGV car will collide with obstacles, so the driving safety and stability of the magnetically guided multi-AGV poses a huge challenge.

Contents of the invention

The purpose of the present invention is to provide a method and system for controlling the travel of AGVs, which can adjust the travel of AGVs, avoid conflicts caused by the travel of AGVs, and improve the safety and stability of multi-AGV travel.

In order to achieve the above purpose, the technical scheme adopted in the control method of AGV trolley driving is:

The method includes the following steps:

A control method for AGV trolley travel, the method includes the following steps:

a), establish an electronic map of the AGV trolley walking on the magnetic track, and determine the current position of the trolley;

b) Install a sensor for detecting obstacles on the AGV car, and record the time point t1 when the sensor detects the obstacle;

c), when the sensor on the AGV trolley detects that the obstacle leaves, and records the time point t2 when the sensor detects that the obstacle leaves, and calculates the existence time D=t2-t1 of the obstacle;

d) Record the number of times Ct of obstacles appearing on a road section L and within a certain period of time TD, the number of times C that the AGV car passes through the road section L within the time period TD, calculate the total time T for the AGV car to appear obstacles, and set The frequency threshold Pf of obstacles appearing on this road section;

Then, the probability of failure in this road section L is P=Ct/C; the average duration of obstacles in this road section L is Ta=T/Ct,

When P≥Pf, it is predicted that there will be obstacles in the time period TD and the road section L, and the control unit sends a control command to the AGV car, and adjusts the speed of the AGV car so that the AGV car executes the deceleration command;

When P≤Pf, it is predicted that there will be no obstacles in this time period TD and this road section L, and the AGV car will drive at a normal speed;

When P=0, the AGV car runs normally.

The present invention also has the following features:

When P≥Pf, the control unit sends a control command to the AGV car, so that the AGV car travels at a speed of S=Scur*P*k, where Scur is the driving speed of the AGV car before finding an obstacle, and k is a proportional coefficient; so that When the AGV car travels near the obstacle, the obstacle has left the path of the AGV car.

When P≤Pf, if the sensor detects an obstacle or receives the traffic congestion in the road ahead through the broadcast, it will drive according to the situation when P≥Pf.

In order to achieve the above purpose, the technical solution adopted by the control system of AGV trolley driving is:

The system includes a central control unit for controlling each AGV car. The central control unit sends scheduling instructions to the control unit on each AGV car and controls the movement of the AGV car. The AGV car is equipped with sensors for detecting obstacles. The obstacle signal is sent to the control unit, the control unit makes a judgment according to the obstacle signal, and the control unit sends a control command to control the moving speed of the AGV trolley.

The present invention also has the following features:

An emergency stop switch is arranged on the AGV trolley, and the emergency stop switch is used to control the power-off and power-on of the driving mechanism of the AGV trolley.

A limit switch is arranged in the middle of the fork of the AGV trolley, and the limit switch is used to control the power-off and power-on of the driving mechanism of the AGV trolley.

Compared with the prior art, the technical effect of the present invention is: use the electronic map automatically generated by the AGV car to judge the location of the AGV car, then let the AGV car run on the magnetic track, and use the sensor to collect the time of the existence of obstacles point and length of time, so as to establish an obstacle database. The database sets a threshold for the occurrence of obstacles according to the location and frequency of the obstacles. The number of obstacles in a certain section is more or less than the set When the threshold is reached, when the AGV car travels to this road section, the control unit controls the speed of the car to ensure that obstacles can pass smoothly, avoid conflicts, and ensure the effective operation of the entire AGV system.

Description of drawings

Fig. 1 is a logic block diagram of the control system for AGV trolley driving;

Fig. 2 is a schematic diagram of an electronic map of an AGV trolley;

Figure 3 is a schematic diagram of the state of two AGV cars traveling in the same direction;

Figure 4 is a schematic diagram of the state of multiple AGV cars arriving at the same intersection at the same time;

Fig. 5 is a schematic diagram of a state where a non-moving obstacle appears on the path of the AGV trolley;

Figure 6 is a hybrid control structure diagram of the AGV trolley;

Fig. 7 is a structural diagram of an AGV trolley;

Figure 8 is a control structure diagram of the combination of centralization and separate self-control modes of the AGV trolley.

detailed description

In conjunction with Fig. 1 to Fig. 8, the present invention is described further:

Firstly, the control method of AGV trolley is elaborated in detail:

A control method for AGV trolley travel, the method includes the following steps:

a), establish the electronic map that AGV dolly 10 walks on the magnetic track, determine the current position of dolly;

b) Install a sensor 20 for detecting obstacles on the AGV trolley 10, and record the time point t1 when the sensor 20 detects the obstacle; the obstacle is mainly a movable pedestrian or item in the warehouse, a movable obstacle Objects walk on the magnetic track that the AGV trolley 10 runs.

c), when the sensor 20 on the AGV dolly 10 detects that the obstacle leaves, and records the time point t2 when the sensor 20 detects that the obstacle leaves, calculates the existence time D=t2-t1 of the obstacle;

d), record the number of times Ct of obstacles on a certain road section L and in a period of time TD, the number of times C that the AGV car 10 passes through the road section L in this section of time TD, and calculate the total time T of obstacles in the AGV car 10, Set the frequency threshold Pf of obstacles appearing on this road section; the above-mentioned obstacles are on all road sections in the entire warehouse, and the time of encountering obstacles is D1, D2, D3..., then the total time T for the AGV car 10 to appear obstacles =D1+D2+D3....

Then, the probability of failure in this road section L is P=Ct/C; the average duration of obstacles in this road section L is Ta=T/Ct,

When P≥Pf, it is predicted that obstacles will appear in the time period TD and the road section L, and the control unit 30 sends a control command to the AGV car 10, and adjusts the speed of the AGV car 10, so that the AGV car 10 executes the deceleration command;

When P≤Pf, it is predicted that there will be no obstacles in the time period TD and the road section L, and the AGV trolley 10 will travel at a normal speed;

When P=0, the AGV trolley 10 runs normally.

As shown in Figure 2, let the AGV car 10 run normally on the magnetic track, use the electronic map automatically generated by the AGV car 10, and the coordinate positioning device on the AGV car 10 can judge the position of the AGV car 10, and the AGV car 10 generates The electronic map of the AGV can determine which path the AGV car 10 is driving on, and then let the AGV car 10 run on the magnetic track, use the sensor to collect the signal of the obstacle and the signal of the obstacle, and use the AGV car 10. The recorder records the time point and length of time when obstacles exist, thereby establishing an obstacle database. The database sets a frequency threshold Pf for the occurrence of obstacles based on the location and frequency of obstacles. When the number of occurrences is more or less than the set frequency threshold Pf, when the AGV car 10 travels to the road section, the control unit 30 controls the speed of the AGV car 10 to ensure that obstacles can pass smoothly, avoid conflicts, and ensure that the entire AGV The trolley 10 is located in the warehouse and can run stably;

The above-mentioned obstacle may be the AGV trolley 10 itself traveling in a straight line, or it may be a pedestrian or article passing through the magnetic guide rail, or a conflict generated when multiple AGV trolleys 10 are located at the intersection;

Combined with Figure 3, two AGV cars 10 are traveling in the same direction, but the speed of the AGV car 10 at the rear is greater than that of the AGV car 10 in front, so there will be AGV cars 10 at the rear catching up with the AGV in front within a limited time In the case of the car 10, in this case the rear AGV car 10 must negotiate with the front AGV car 10, or the front AGV car 10 speeds up, or the rear AGV car 10 slows down, when the speed adjustment cannot meet the collision-free Conditions, the AGV car 10 at the rear can only choose to stop and wait, and continue to run after the situation permits. The actual mode of operation in this case is that the AGV car 10 at the rear first broadcasts the information that the operation is blocked, and the AGV car 10 in front on the same path receives the information and then conducts point-to-point negotiation with the AGV car 10 at the rear;

Combined with Figure 4, multiple AGVs 10 arrive at the same intersection at the same time, and a situation of competing for the intersection occurs. In this case, the AGVs 10 will negotiate according to the set strategy to determine the order of passing the intersection in turn;

In special cases, referring to Figure 5, there is an immovable obstacle on the path originally planned to run by the AGV car 10. This may be an unknown object in the external environment, or it may be another AGV car that stops there and does not run. 10;

If the AGV car 10 can judge in advance that there is an obstacle on a certain path, it needs to avoid that path segment through the path planning algorithm. If it cannot be avoided, or it is not known in advance that there is such an obstacle, it will not pass until it reaches this point. If the sensor 20 finds an obstacle, the AGV car 10 first expects that this is a stopped AGV car 10, broadcasts the obstacle information, expects to get a response from the object in front, and lets it move to release the path segment. If there is no result in the communication, the AGV car 10 can only choose to stop and wait, and broadcast the information that the obstacle cannot be processed, and feed back this situation to the monitoring system of the host computer in real time. The system administrator can detect the abnormal situation in time and carry out relevant processing.

As a preferred solution of the present invention, when P≥Pf, the control unit 30 sends a control command to the AGV car 10, so that the AGV car 10 travels at the speed S=Scur*P*k, where Scur is the AGV car 10 before finding an obstacle The driving speed, k is a proportional coefficient; so that when the AGV car 10 travels near the obstacle, the obstacle has left the path of the AGV car 10 travel.

When P≦Pf, it refers to the situation shown in the drawing. If the sensor 20 detects an obstacle or receives the congested section of the road ahead through the broadcast, it will drive according to the situation when P≧Pf.

The following is a detailed description of the control system of the AGV trolley:

The system includes a central control unit 40 for controlling each AGV trolley 10. The central control unit 40 sends a scheduling command to the control unit 30 on each AGV trolley 10, and controls the movement of the AGV trolley 10. The AGV trolley 10 is provided with a device for detecting obstacles. The sensor 20 of the object, the obstacle signal collected by the sensor 20 is sent to the control unit 30, the control unit 30 makes a judgment according to the obstacle signal, and the control unit 30 sends a control command to control the moving speed of the AGV trolley 10.

When running into a more urgent situation, the AGV car 10 is provided with an emergency stop switch, which is used to control the power-off and power-on of the driving mechanism of the AGV car 10, and the emergency switch can make the AGV car 10 stop quickly.

Aiming at the problem that the AGV trolley 10 cannot stop when encountering obstacles when loading pallets, a limit switch is added in the middle of the fork of the AGV trolley 10 to ensure the safety of the AGV trolley 10 for loading and unloading.

The above-mentioned sensor 20 is an infrared obstacle detector, so that the AGV trolley 10 has the function of detecting obstacles. And when the AGV car 10 encounters an emergency during driving and an obstacle is found, the AGV car 10 can be decelerated and stopped to prevent the AGV car 10 from colliding with the obstacle, thereby greatly improving the safety of the AGV car 10 traveling.

As shown in FIG. 6 and FIG. 8 , since the AGV uses the central control unit 40 in the flexible manufacturing system to adopt centralized control over each AGV trolley 10, multiple machines send multiple requests to the central control unit 40 in a cycle mode, resulting in a deadlock in the dispatching system. Defects that lock phenomenon and increase system load. Therefore, the control model adopts a combination of centralization and separate self-control.

As shown in FIG. 7 , the central control unit 40 issues scheduling tasks, and each AGV car 10 has its own perception system, communication system, decision-making system, and execution system, which can be based on the external conditions it perceives, including environmental information obtained by various sensors. And the information obtained by communicating with other AGV trolleys 10, infers the next action according to its own decision-making system.

Because each AGV car 10 in the system can perform calculations and decision-making by itself, there is no need for the central control unit 40 to perform unified calculation and analysis work, so the system usually adopts a distributed control structure to distribute calculation tasks to each AGV car 10, each AGV 10 can perform point-to-point or point-to-multipoint information exchange without forwarding through the central route, so the communication load is also averaged.

Claims (6)

1. The control method of AGV dolly travel, is characterized in that: method comprises the steps: a), establish the electronic map of AGV trolley (10) walking on the magnetic track, determine the current position of trolley; b), a sensor (20) for detecting obstacles is set on the AGV trolley (10), and the time point t1 when the sensor (20) detects the obstacle is recorded; c), when the sensor (20) on the AGV trolley (10) detects that the obstacle leaves, and record sensor (20) detects the time point t2 when the obstacle leaves, and calculates the existence time D=t2-t1 of the obstacle; d), record the number of times Ct of obstacles on a certain road section L and in a period of time TD, the number of times C that the AGV dolly (10) passes through the road section L in the time TD, and calculate the number of times that the AGV dolly (10) has obstacles For the total duration T, set the frequency threshold Pf of obstacles appearing on this road section; Then, the failure probability P=Ct/C of this road section L; the average duration of obstacles appearing in this road section L is Ta=T/Ct, when P≥Pf, then it is predicted that within this time period TD and this road section L will When an obstacle appears, the control unit (30) sends a control command to the AGV car (10), and adjusts the speed of the AGV car (10), so that the AGV car (10) executes a deceleration command; When P≤Pf, it is predicted that there will be no obstacles in this time period TD and this road section L, and the AGV trolley (10) will travel at a normal speed; When P=0, the AGV trolley (10) runs normally. 2. The control method of AGV trolley traveling according to claim 1, characterized in that: when P≥Pf, the control unit (30) sends a control command to the AGV trolley (10), so that the AGV trolley (10) follows the speed S =Scur*P*k travels, wherein Scur is the travel speed of the AGV car (10) before finding the obstacle, and k is a proportional coefficient; so that when the AGV car (10) travels to the vicinity of the obstacle, the obstacle has left the AGV car (10) The path of travel. 3. The AGV trolley driving control method according to claim 1 or 2, characterized in that: when P≤Pf, if the sensor (20) detects an obstacle or receives congestion in the front section through broadcast, then according to P≥Pf Driving under the condition of Pf. 4. The control system for AGV trolley travel is characterized in that: the system includes a central control unit (40) for controlling each AGV trolley (10), and the central control unit (40) sends dispatch instructions to each AGV trolley (10) The control unit (30) controls the movement of the AGV trolley (10), the AGV trolley (10) is provided with a sensor (20) for detecting obstacles, and the obstacle signal collected by the sensor (20) is sent to the control unit (30) , the control unit (30) judges according to the obstacle signal, and the control unit (30) issues a control command to control the moving speed of the AGV trolley (10). 5. The control system for traveling the AGV trolley according to claim 4, characterized in that: the AGV trolley (10) is provided with an emergency stop switch, and the emergency stop switch is used to control the disconnection of the driving mechanism of the AGV trolley (10). Electricity and electrification. 6. The control system for traveling the AGV trolley according to claim 4, characterized in that: a limit switch is arranged in the middle of the fork of the AGV trolley (10), and the limit switch is used to control the driving mechanism of the AGV trolley (10) power off and on.