GB2558182A

GB2558182A - Autonomous guided vehicle system

Info

Publication number: GB2558182A
Application number: GB1612986.8A
Authority: GB
Inventors: Dominik Moczek Aleksander
Original assignee: A Tech Fabrications Ltd
Current assignee: A Tech Fabrications Ltd
Priority date: 2016-07-27
Filing date: 2016-07-27
Publication date: 2018-07-11
Anticipated expiration: 2036-07-27
Also published as: GB2558182B; GB201612986D0

Abstract

An autonomous guided vehicle system has a guidance track 109 for guiding autonomous vehicles and at least one autonomous guided vehicle 101. The guidance track 109 includes a control section (fig 3) for conveying control information to the autonomous guided vehicle 101, and the control section includes a predetermined number of control blocks (302-309, fig 3), each control block being selectively magnetised to encode the control information. The autonomous guided vehicle 101 comprises a magnetic sensor 108 to detect a magnetic state of each control block and communicate this to a control unit coupled to the magnetic sensor 108, the control unit arranged to control the autonomous guided vehicle 101 to perform a command associated with the control information.

Description

(54) Title of the Invention: Autonomous guided vehicle system Abstract Title: Autonomous guided vehicle system (57) An autonomous guided vehicle system has a guidance track 109 for guiding autonomous vehicles and at least one autonomous guided vehicle 101. The guidance track 109 includes a control section (fig 3) for conveying control information to the autonomous guided vehicle 101, and the control section includes a predetermined number of control blocks (302-309, fig 3), each control block being selectively magnetised to encode the control information. The autonomous guided vehicle 101 comprises a magnetic sensor 108 to detect a magnetic state of each control block and communicate this to a control unit coupled to the magnetic sensor 108, the control unit arranged to control the autonomous guided vehicle 101 to perform a command associated with the control information.

101

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109

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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Control block magnetic state	Command
00000000	Continue moving in current direction of travel
10000000	Turn around and move in opposite direction
01000000	Perform forklift pick up action
11000000	Perform forklift drop off action
00100000	Turn left for predetermined time T ignoring guidance track
10100000	Turn right for predetermined time T ignoring guidance track
01100000	Proceed straight for pre determined time T ignoring guidance track
11100000	Turn off AGV function

Fig 4

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501

Direction of travel A

503

Direction of travel B

509

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Fig 6b

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/U1 \ 702

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_	V

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Fig 9

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Fig 10

Application No. GB1612986.8

RTM

Date :23 January' 2017

Intellectual

Property

Office

The following terms are registered trade marks and should be read as such wherever they occur in this document:

Teflon

Intellectual Property Office is an operating name of the Patent Office www.gov.uk/ipo

Autonomous Guided Vehicle System

Technical Field

The present invention relates to systems for controlling autonomous guided vehicles, and in particular systems in which autonomous guided vehicles follow guidance tracks and perform various commands.

Background

In many environments, for example factories and warehouses, vehicles are employed to perform various tasks. For example, vehicles may be used to move items under production from one production line to another, to move completed items from a production line to a storage location or to move items from a storage location to a distribution point.

Forklift trucks, human operated vehicles provided with a moveable “forklift” unit, are well known for this purpose. Alternatively or additionally, in certain environments, autonomous, or semi-autonomous guided vehicles are used. Such autonomous guided vehicles (AGVs) move around an environment without requiring human control to direct their movement, for example by following a guidance track. Such AGVs provide an advantage in that they do not require a human operator to control them when they are operating autonomously. As well as moving autonomously, certain AGVs can perform various tasks autonomously, such as picking up particular items (e.g. loaded pallets), moving them to another location, and then setting them down.

Such AGVs can greatly improve efficiency and productivity in certain environments.

However, conventional techniques for implementing such AGVs rely on complex on-board processors which are provided with complex control programs. In some examples, such AGVs are programmed to perform certain tasks at certain locations. To achieve this, an AGV tracks its location (for example monitoring a guidance track for a particular location marker) and then when it is detected that the AGV is at the relevant location, the task is performed.

Such AGV implementation techniques have a number of drawbacks. The use of complex processors means the cost and power consumption of such AGVs is typically high and “troubleshooting” an AGV which is operating incorrectly can be difficult and time consuming. Moreover, conveying new control information to such AGVs, for example changing the action that an AGV performs at a particular location, or programming an AGV to perform a new action at a particular location, can require the AGV to be reprogrammed which can be a time-consuming and complex task, particularly if this has to be done with several AGVs.

Summary of the Invention

In accordance with a first aspect of the invention, there is provided an autonomous guided vehicle system comprising a guidance track for guiding autonomous vehicles and at least one autonomous guided vehicle. The guidance track includes at least one control section for conveying control information to the autonomous guided vehicle, said control section comprising a predetermined number of control blocks, each control block being selectively magnetised to encode the control information. The autonomous guided vehicle comprises a magnetic sensor arranged to detect a magnetic state of each control block and communicate this to a control unit coupled to said magnetic sensor, said control unit arranged to control the autonomous guided vehicle to perform a command associated with the control information.

Optionally, the guidance track is magnetised with a first magnetic polarity and each control block is selectively magnetised with one of the first magnetic polarity, a second magnetic polarity opposite the first magnetic polarity, or no magnetic polarity.

Optionally, the control blocks are positioned adjacent to one another forming a control block section and the magnetic sensor detects the magnetic state of each control block as the AGV moves along the guidance track.

Optionally, the control section further comprises a marker block of a predetermined magnetic state positioned ahead of the control block section, and the control unit is arranged to identify the presence of the control block section responsive to the magnetic sensor detecting the marker block.

Optionally, the marker block is of a predetermined length, said predetermined length indicating a predetermined length of the control blocks of the control section, and the control unit is arranged to determine the predetermined length of the control blocks from the detection by magnetic sensor of the marker block, and control a control block reading operation of the control blocks by the magnetic sensor in accordance with the determined predetermined length of the control blocks.

Optionally, the marker block and the control block section are separated by an unmagnetised separation region of a predetermined length.

Optionally, each control section is formed from a section of track running substantially parallel to a main section of the guidance track.

Optionally, each control section is connected at a first and/or second end to the main section of the guidance track.

Optionally, the control information is associated with a command for the autonomous guided vehicle to perform a predefined movement and/or perform a predefined action.

Optionally, the predefined movement is in a predefined direction at a predefined speed.

Optionally, the predefined action comprises a forklift action of a forklift unit of the autonomous guided vehicle.

Optionally, the autonomous guided vehicle comprises at least one fork leg comprising a fork leg magnetic sensor and the guidance track further comprises at least one fork leg guidance track section for guiding the fork leg of the autonomous guided vehicle during the forklift action.

Optionally, the autonomous guided vehicle comprises two fork legs, each comprising a fork leg magnetic sensor and the fork leg guidance track section comprises two fork leg guidance tracks for guiding the fork legs of the autonomous guided vehicle during the forklift action.

Optionally, the magnetic sensor comprises an array of a plurality of individual magnetic sensors.

Optionally, each magnetic sensor communicates a detection signal to the control unit if it detects the guidance track, and the control unit thereby determines a position of the guidance of track at a given time based on which of one or more of the individual magnetic sensors are currently detecting the tape.

Optionally, when determining the position of the guidance track, the control unit responds to the detection signal from individual magnetic sensors currently detecting the guidance track, and detection signals from N number of magnetic sensors either side of the individual magnetic sensors currently detecting guidance track. Optionally, N is 1.

Optionally, the magnetic sensor is shaped such that a first plurality of peripheral magnetic sensors and a second plurality of peripheral magnetic sensors trail a third plurality of central magnetic sensors.

Optionally, the third plurality of central magnetic sensors are disposed along a substantially straight central cross section of the magnetic sensor and the first and second plurality of peripheral magnetic sensors are disposed respectively along two end sections of the magnetic sensor, the central cross section and two end sections configured to form a flattened V shape.

In accordance with a second aspect of the invention there is provided an autonomous guided vehicle for use in a system according to the first aspect.

In accordance with certain aspects of the invention, an autonomous guided vehicle system is provided in which a guidance track includes one or more control sections. The control sections have encoded thereon control information which can be read by an AGV. Accordingly, the guidance track itself is used to convey control information to an AGV. This means that an AGV does not need to track its location and does not need to associate a location with a particular command, rather it simply responds to the control information as it encounters it on the guidance track. As a result, control electronics provided with an AGV can be greatly simplified, and in some examples can be implemented without using any control processors at all. This can reduce the cost and power consumption of an AGV considerably. Further, the command that an AGV performs at a particular location can be easily changed simply by changing the magnetic state of the relevant control blocks. In certain applications this can be readily achieved by simply applying a magnet to the relevant part of the control section of the guidance track. This can greatly simplify the process of updating the tasks performed by an AGV.

Various further aspects and features of the invention are defined in the claims.

Brief Description of Figures

Certain embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

Figure 1 provides a simplified schematic diagram of an autonomous guided vehicle (AGV) system;

Figure 2 provides a simplified schematic diagram of a guidance track in accordance with certain embodiments of the invention;

Figure 3 shows a portion 301 of a control section of a guidance track in accordance with certain embodiments of the invention;

Figure 4 provides a table providing example control information that can be encoded in control blocks of a control section of guidance track in accordance with certain embodiments of the invention;

Figure 5 provides a schematic diagram showing a portion of guidance track in accordance with certain embodiments of the invention;

Figure 6a provides a schematic diagram of a magnetic sensor array in accordance with certain embodiments of the invention;

Figure 6b provides a schematic diagram depicting progression of an AGV around a sharp corner in accordance with certain embodiments of the invention;

Figure 7 provides a schematic diagram of an AGV arranged in accordance with certain embodiments of the invention;

Figure 8 provides a schematic diagram showing a portion of guidance track including fork guidance tracks in accordance with certain embodiments of the invention;

Figure 9 provides a schematic diagram of an AGV arranged in accordance with certain embodiments of the invention, and

Figure 10 provides a schematic diagram of a control system of an AGV in accordance with examples of the invention.

In the drawings like reference numerals refer to like parts. 5

Detailed Description

Figure 1 provides a simplified schematic diagram of an autonomous guided vehicle (AGV) system. The system includes an AGV 101. The AGV 101 includes a main body 102 housing motors, batteries and a control unit, a steerable drive wheel 103 and non-steering wheels

104. The steerable drive wheel typically includes a driving motor for turning the drive wheel to propel the AGV 101 along, and a turning motor for changing the orientation of the steerable drive wheel for steering the AGV 101. The AGV 101 further includes a fork lift unit 105 comprising two spaced arms 106, 107 which can be raised and lowered and used to lift, carry and place down items such as storage pallets. The AGV 101 further includes a magnetic sensor array 108. The system further includes a metallic guidance track 109. The guidance track 109 includes a suitable metallic material which has been magnetised and can therefore be detected by the magnetic sensor array 108 of the AGV 101.

Typically, the magnetic guidance track comprises an outer protective material including Teflon and polyurethane and a metallic inner that comprises ferrite powder, neodymium powder and iron powder.

Although not shown in Figure 1, in certain embodiments, the AGV has fitted various further stabilising wheels, for example swivel wheels mounted at the corners of the AGV.

Detection signals, generated by the magnetic sensor array 108 as it passes over the guidance track 109, are used by the control unit of the AGV 101 to generate guidance control signals which are used to control the steerable drive wheel 103 so that the AGV 101 can follow the magnetic guidance strip. The guidance control signals control the speed and orientation (for steering) of the drive wheel by controlling the driving motor and the turning motor.

The guidance track 109 includes control sections on which control information is encoded. This information is encoded by selectively magnetising certain parts (blocks) of the guidance track in accordance with a specific magnetic state (e.g. a specific magnetic polarity). The magnetic field of a control section is detected by the magnetic sensor array 108 of the AGV 101 as the magnetic sensor array passes over the control section. Corresponding detection signals are generated by the magnetic sensor array 108 which correspond to the encoded control information and these detection signals are received by the control unit and used to generate command control signals which are used to control the steerable drive wheel in conjunction with the fork lift unit to perform various actions For example, the control information may encode instructions to perform actions such as stop, spin 90 degrees, move forward one metre, drop forks move backward one metre, spin 90 degrees to return to the original position and resume following the magnetic strip 109. In this way, the AGV 101 can perform various tasks such as moving pallets from one location to another.

Typically, the main sections of the guidance track, i.e. the sections used for guiding the AGV around the track, are magnetised with a first polarity, e.g. with a north pole on the side of the guidance track facing the AGV and the south pole on the side of the guidance track facing the floor/ground. Such a polarity is referred to as a “north polarity”.

In certain examples, the magnetised blocks of the control sections are polarised, selectively, with the first polarity, no polarity or a second polarity which is opposite the first polarity. Thus, if the first polarity is a north polarity, the second polarity is a “south polarity” i.e. with a south pole on the side of the guidance track facing the AGV and the north pole on the side of the guidance track facing the floor/ground.

During operation, the AGV depicted in Figure 1 generally travels along the guidance track in the direction indicated by arrow 110. When performing an operation using the fork lift unit 105, the AGV reverses, fork unit first, off the track and into the relevant position and performs a pick up or set down operation. The AGV then returns to the magnetic guidance track and continues along it.

Figure 2 provides a simplified schematic diagram of a guidance track 201 in accordance with certain embodiments of the invention. The guidance track 201 is shown from above and as can be seen forms a loop. At two points 202, 203 in the loop, the guidance track 201 splits into parallel tracks which provide two control sections 204, 205 of the guidance track as discussed above. Each control section 204, 205 is thus formed from a section of track running next to a main section of the guidance track. In the example depicted in Figure 2, each control section is connected at both ends to the main section of the guidance track. However, in certain examples, the control section may be connected to the main section of the guidance track at only one end or not connected to the main section of the guidance track at all.

In certain embodiments, for example as depicted in Figure 2, the control sections are the same width as the main sections of the guidance track. However, in other embodiments, the control sections may be wider than the main sections of the guidance track.

The distance of the control sections 204, 205 from the main section of the guidance track can be any suitable distance and is typically determined by the width of the magnetic sensor of the AGV. In certain examples, the main section of the guidance track and the control sections are separated by a gap of between 10mm to 15mm. As will be appreciated, Figure 2 is schematic and is not to scale in particular with regard to the gap between the main section of guidance track and the control sections.

Each control section 204, 205 has encoded thereon control information which is described further with reference to Figure 3.

In certain embodiments, the magnetic sensor array of the AGV comprises a number of individual magnetic sensors, for example Hall effect sensors, in a linear array.

In such examples, the control unit of the AGV controls the steering of the AGV by turning the steerable drive wheel in dependence on which of the magnetic sensors of the array detect the presence of the guidance track. For example if sensors of the array to the left of the array detect the guidance track then the steerable drive wheel turns to the left. If sensors of the array to the right of the array detect the guidance track then the steerable drive wheel turns to the right.

Further, with reference to Figure 2, by providing a linear array of magnetic sensors the control unit of the AGV can respond to detection signals relating both to the main section of the guidance track and the parallel control section. In this way the control unit of the AGV can use detection signals for guidance purposes from the main section and detection signals for control information purposes from the control section of the guidance track.

As described above, in certain embodiments the main sections of the guidance track are magnetised with a north polarity for guiding the AGV around the track and the control blocks of the control sections are selectively magnetised with a south polarity, north polarity or no polarity. In certain such embodiments, the individual magnetic sensors are arranged to detect and distinguish between the magnetic field emanating from a part of the track magnetised with a north polarity and part of the track magnetised a south polarity. The detection signal output from each sensor can indicate if a north polarity magnetic field is detected or a south polarity magnetic field is detected.

Figure 3 shows a portion 301 of a control section of the guidance track in accordance with certain embodiments of the invention. The control section includes a predetermined number of control blocks. These control blocks are positioned adjacent to each other and together form a control block section. Each control block bears information by being of a predetermined magnetic state, for example, as mentioned above by being magnetized with one of a first polarity, the opposite polarity of the first polarity (the second polarity) or with no specific pole at all (unmagnetised).

Control blocks can be magnetized by bringing a suitable magnet or electromagnet into close vicinity with the block. This permanently magnetises the control block.

A “north” polarisation can be achieved with a north pole being generated on the upward facing side of the track and a south pole on the downward facing side of the track. A “south” polarisation can be achieved with a south pole being generated on the upward facing side of the track and the north pole on the downward facing side of the track.

The portion 301 of the control section shown in Figure 3 includes eight control blocks 302, 303, 304, 305, 306, 307, 308, 309. As will be understood, in other implementations more control blocks or fewer control blocks can be used. Typically, each of the control blocks is of the same predetermined length Li.

The polarity, or absence of a pole, of the magnetic field of each control block is detected by the magnetic sensor array of the AGV as it moves over the control section of the guidance track. Corresponding detection signals are generated and sent to the control unit of the AGV.

In this way, based on the magnetic state of each control block one of several possible instruction codes can be conveyed to the control unit of the AGV. In certain examples, this can be an n-bit instruction code, where n is the number of control blocks in the control section.

Figure 4 provides a table showing a number of instruction codes, each instruction code associated with a specific command. If a control block is magnetised with a first polarity (e.g. a north polarity) or is unmagnetised, this corresponds to a “0”. If a control block is magnetised with a second polarity, opposite the first polarity, (e.g. a south polarity of the first polarity is a north polarity), then this corresponds to a “1”.

Thus, with reference to Figure 4, assuming that the first polarity is north and the second polarity is thus south, in the event that all of the control blocks are either unmagnetised or magnetised with a north polarity, this corresponds to an instruction code of “00000000” which when received by the control unit causes the control unit to control the AGV to continue moving along the guidance track in its current direction.

In the event that a first control block is magnetised with a south polarity and the remaining control blocks are either unmagnetised or magnetised with a north polarity, this corresponds to an instruction code of “10000000” which when received by the control unit causes the control unit to control the AGV to turn around and proceed along the guidance track in the opposite direction to the direction it was traveling in before encountering the control section.

In the event that a second control block is magnetised with a south polarity and the remaining control blocks are either unmagnetised or magnetised with a north polarity, this corresponds to an instruction code of “01000000” which when received by the control unit causes the control unit to control the AGV to perform a forklift pick up action. This action could comprise the steps of turning 90 degrees left or right; proceed forward a set distance; pick up a pallet; raise the forks; retreat back to the previous position, and continue in the previous direction of travel.

In the event that a first and second control block are magnetised with a south polarity and the remaining control blocks are either unmagnetised or magnetised with a north polarity, this corresponds to an instruction code of “11000000” which when received by the control unit causes the control unit to control the AGV to perform a forklift set-down action. This action could comprise the steps of turning 90 degrees to the left or right; proceed forward a set distance; lower the forks to set down a pallet; retreat back to the previous position, and continue in the previous direction of travel.

In the event that a third control block is magnetised with a south polarity and the remaining control blocks are either unmagnetised or magnetised with a north polarity, this corresponds to an instruction code of “00100000” which when received by the control unit causes the control unit to control the AGV to turn left and proceed for a predetermined period of time T, for example 0.8 seconds, and during this period ignore the position of the guidance track. In the event that a first and third control block are magnetised with a south polarity and the remaining control blocks are either unmagnetised or magnetised with a north polarity, this corresponds to an instruction code of “10100000” which when received by the control unit causes the control unit to control the AGV to turn right and proceed for a predetermined period of time T, for example 0.8 seconds, and during this period ignore the guidance track.

In the event that a second and third control block are magnetised with a south polarity and the remaining control blocks are either unmagnetised or magnetised with a north polarity, this corresponds to an instruction code of “01100000” which when received by the control unit causes the control unit to control the AGV to proceed in its current straight direction for a predetermined period of time T, for example 0.8 seconds, and during this period ignore the position of the guidance track (however, the sensor array ceases detecting the guidance track altogether, the control unit is arranged to stop the AGV).

In the event that a first, second and third control block are magnetised with a south polarity and the remaining control blocks are either unmagnetised or magnetised with a north polarity, this corresponds to an instruction code of “11100000” which when received by the control unit causes the control unit to turn the AGV off.

As will be understood, the use of eight control blocks means that up to 256 instructions codes can be used.

As can be seen from Figure 3, the portion of the control section 301 also includes a marker block 310. The marker block 310 is of a predetermined magnetic state, typically opposite to the main section of the guidance track used for guiding the AGV. Thus if the main section of the track is polarised with a north pole, the marker block 310 is magnetised with a south pole. The marker block 310 extends over a predetermined length Lm. The marker block 310 is separated from the beginning of the control blocks (i.e. the beginning of the control block section) by a separation region 311 which typically, is not magnetized with a specific pole, i.e. is unmagnetised.

When the AGV travels in the direction indicated by the arrow shown in Figure 3, it first encounters the marker block 310 of the control section. From this, the control unit of the AGV identifies the presence of the control block section ahead. Responsive to this, the control unit can initiate a control block reading mode which is described in further detail below.

Firstly, the control unit, based on signals from the magnetic sensor array, determines the length Lm of the marker block 310. The guidance track, and in particular the control sections are arranged such that the length of the marker block Lm is related to the predetermined length of the control blocks in accordance with a predetermined relationship, that is, the control unit of the AGV can determine from the length of the marker block 310 what the length Li of each information block will be. For example, the length Li of each information block may be the same as the length Lm of the marker block, e.g. length of Lm = Li.

The length Ls of the separation region 311 is predetermined, for example, half the length of the marker block, e.g. the length of Ls is ¹Λ Lm.

Figure 3 is schematic and not to scale, particularly in relation to the size of the different blocks.

Once the AGV has passed over the marker block 310, the length of the separation region 311 and the length of each information block is known. Further, the total number of information blocks (e.g. eight) is also known and stored in the control unit of the AGV. With this information (the length Lm of the marker block 310, the length Ls of the separation region 311) and by monitoring the speed of the AGV along the guidance track (which is typically maintained at a constant speed whilst the AGV passes over the control blocks), the AGV control unit can perform a control block reading operation in which it calculates when the magnetic sensor array is positioned over a particular control block. In this way, the control unit can determine when it is over a particular control block and can thus determine the magnetic polarity of that block. In certain embodiments, to increase the accuracy of the control block reading operation, the control unit can determine the polarity of a control block when it calculates the magnetic sensor array is over a central region of each control block. This minimises the effect of the magnetic field of any adjacent control blocks.

Once the magnetic sensor array has passed over all of the control blocks the complete encoded instruction code is received by the control unit. The control unit then ceases the control block reading operation and performs the command associated with the encoded instruction code. In certain examples, the command is carried out a predetermined period of time after the last (e.g. eighth) control block is read or after the AGV has moved a predetermined distance from the las control block. Alternatively, the AGV can be equipped with a sensor arranged to detect a mark positioned adjacent the guidance track and after the control section. The sensor and mark can be provided by any suitable means, for example an optical sensor and an optical mark, upon detection of the mark by the sensor, the control unit control the AGV to perform the command.

Once the magnetic polarity of all of the blocks from the control section is determined, the control unit determines what control information has been encoded.

In certain embodiments, control sections of the guidance track are arranged such that information can be conveyed to an AGV irrespective of the direction of approach of the AGV. An example of this is explained in more detail with reference to Figure 5.

Figure 5 provides a schematic diagram (not to scale) showing a portion of the guidance track 501 including a control section 502 and main section 503 of the guidance track. The control section 503 may be connected at either end 504, 505 to the main section 503.

The control section 502 includes a first marker block and control block section 506 as described above with reference to Figure 3. As will be understood, an AGV traveling in a first direction indicated by arrow A will encounter the first marker block and control block section 506 and control information will be conveyed to the AGV as described above.

The control section 502 includes a second marker block and control block section 507, again, as described above with reference to Figure 3. However, as can be seen from Figure 5, the second marker block and control block section 507 is arranged in a reverse layout to the first marker block and control block section 506.

As will be understood, an AGV traveling in a first direction indicated by arrow A will encounter the first marker block and control block section 506 and control information will be conveyed to the AGV as described above.

In embodiments in which control sections are arranged as shown in Figure 5, after the AGV has performed its actions and if it is continuing in the same direction (i.e. the direction of travel indicated by arrow A) the control unit of the AGV is arranged to stop reading the control section 502 for a predetermined length 508 after the eighth (i.e. last) control block of the first marker block and control block section 504. Along this predetermined length of track 508 is where the second marker block and control block section 507 are located.

In this way, an AGV traveling in the direction of travel indicated with arrow A will receive the necessary control information from the control blocks of the first marker block and control block section 506, perform the necessary functions, and if it is continuing in the original direction of travel, will ignore any control information from the second marker block and control block section 507.

The same applies if an AGV is traveling in a direction indicated by arrow B. That is, the AGV responds to the control information from the second marker block and control block section 507 and then does not respond to any control information from blocks over a predetermined length 509 which ensures that the controls blocks of the first marker block and control block section 506 are ignored.

Typically the predetermined distances 508 and 509 are the same.

As will be understood, this means that a system can be arranged in which AGVs can approach a control section from either direction and still receive relevant control information.

Figure 6a provides a schematic diagram showing a magnetic sensor array 601 viewed from above in use and in accordance with certain examples of the invention.

In certain examples, the magnetic sensor is shaped such that a first plurality of peripheral magnetic sensors and a second plurality of peripheral magnetic sensors trail a third plurality of central magnetic sensors. Accordingly, the magnetic sensor can be formed in a flattened “V” shape, or a general arc shape.

In one example, the magnetic sensor array 601 comprises a cross section 602, a first end section 603 and a second end section 604. The first end section 603 and the second end section 604 are disposed at an angle relative to the cross section 602 such that the magnetic sensor array 601 generally has a flattened “V” shape. The angle a between the outer edge of each end section and the plane of the cross section is typically an acute angle, for example between 25 and 30 degrees.

Disposed along the length of the magnetic sensor array are a plurality of individual magnetic sensors. In Figure 6a, the magnetic sensor array 601 includes 44 individual magnetic sensors. Each magnetic sensor is connected to the control unit

In certain examples, the output of each magnetic sensor is such that a first output is generated if the main section of the guidance track, polarised with a first polarisation (e.g. north) is detected. A second output is generated if the opposite polarity (e.g. south, typically used in the control sections to indicate a “1”) is detected. To achieve this, the sensors can be arranged in any suitable way. In certain examples, each sensor has two output lines. A first line is high if a magnetic field of the first polarity is detected, a second line is high if a magnetic field of the opposite polarity is detected. In examples in which the main sections of the guidance track are magnetised with a north polarity and the control blocks of the control section are magnetised with a south pole to indicate a “1”, the first line is high if a north pole is detected and low if a south pole or no pole is detected. The second line is high if a south pole is detected and low if no pole or a north pole is detected.

The flattened V shape of the magnetic sensor array, and specifically the arrangement of the angled first end section and angled second end section, is such that the AGV can turn sharper corners than would be possible if the magnetic sensor array was simply of a generally straight configuration. For example if the guidance track included a corner that turned sharply at, for example, substantially 90 degrees to the left, when encountering the corner, the momentum of the AGV may be such that the cross section 602 would pass off the guidance track before the magnetic sensors could detect the corner and the control unit could respond. However, by virtue of the configuration of the first end section 603, and specifically its angle relative to the cross section 602, the magnetic sensors on the first end section 603 will pass over the section of the guidance track that has turned to the left and the AGV will thus continue to detect the guidance track and can turn the corner appropriately. This concept is depicted in Figure 6b which shows the progression of the AGV by virtue of the position of the magnetic sensor array 609 as it encounters a sharp left hand corner of the guidance track 610 as described above.

As mentioned above, the control unit of the AGV is arranged to turn the steerable drive wheel depending on which of the individual magnetic sensors detects the guidance track.

An example of this is depicted in Figure 6a. If the control unit detects a signal from a magnetic sensor indicating that it detects the main section of the guidance track (for example if the first line from a magnetic sensor is high indicating a north pole is detected) then it controls the turning motor to turn the steerable drive wheel either left or right. Figure 6a depicts the magnetic sensor from “above” thus if sensors from the left of the magnetic sensor array detect the guidance track then the control unit controls the turning motor to turn the steerable drive wheel left, and if sensors from the right of the magnetic sensor array detect the guidance track then the control unit controls the turning motor to turn the steerable drive wheel right. This concept is shown in Figure 6a, by either the letter “L” or the letter “R” on each magnetic sensor.

As can be seen from Figure 6a, the magnetic sensors of the cross section have two “centre points”: a first “centre point” 605 and a second “centre point” 606. The magnetic sensor directly to the left of the centre points 605, 606 causes the AGV to steer to the left and the magnetic sensor directly to the right of the centre points 605, 606 causes the AGV to steer to the right.

The provision of two centre points ensures that the AGV is never steered so as to maintain a driving position directly on top of the guidance track. Instead the AGV is steered slightly to one side of the guidance track.

In certain examples, the degree to which the AGV steers to the left or the right is different depending on which magnetic sensor is currently detecting the magnetic guidance track. The further the magnetic sensor that detects the magnetic guidance track is from one of the centre points, the more the steerable drive wheel is turned to steer.

In certain examples, this is achieved by the control unit controlling the turning motor with a PWM signal. The closer the magnetic sensor currently detecting the guidance track is to one of the centre points, the closer the duty cycle of the PWM signal generated by the control unit is to 50%.

If a magnetic sensor detects the guidance track and is a magnetic sensor that causes the AGV to steer to the left, then the duty cycle of the generated PWM signal is less than 50%. The further the detecting magnetic sensor is from one of the centre points the closer the correspondingly generated duty of the PWM signal is to 15%. If the control unit determines that the left most magnetic sensor 607 has detected the guidance track, then the PWM generated by the control unit is 15%. This turns the steerable drive wheel a maximum leftward amount.

If a magnetic sensor detects the guidance track and is a magnetic sensor that causes the AGV to steer to the right, then the duty cycle of the generated PWM signal is greater than 50%. The further from one of the centre points the closer the duty cycle of the generated PWM signal is to 85%. If the control unit determines that the right most magnetic sensor 608 has detected the guidance track, then the PWM generated by the control unit is 85%. This turns the steerable drive wheel a maximum rightward amount.

In the event that two magnetic sensors detect the guidance track at the same time, the control unit is arranged to control the turning motor with a duty cycle that is a value between the duty cycle values associated with two the magnetic sensors. For example, if a sensor associated with a duty cycle of 43% and a sensor associated with a duty cycle of 45% both detect the guidance track then the control unit is arranged to output a PWM signal of 44%.

In certain examples, the sensor array includes a control mechanism which is arranged such that during operation, under certain conditions, the control unit only responds to signals from specific magnetic sensors. Specifically, when determining the position of the guidance track, the control unit responds to the detection signal from individual magnetic sensors currently detecting the guidance track, and detection signals from a certain number of magnetic sensors either side of the individual magnetic sensors currently detecting guidance track.

For example, if at a given moment in time, none of the magnetic sensors are currently detecting a magnetic pole of the first polarity (e.g. a north pole), this indicates that none of the magnetic sensors are currently detecting the guidance track and the control unit is arranged to read the output signals from all of the magnetic sensors indicative of the presence of a magnetic pole of the first polarity (e.g. north pole). For example, the control unit may read the first output line of all of the magnetic sensors

As soon as one of the magnetic sensors detects a magnetic pole of the first polarity (e.g. a north pole), then the control unit is arranged to read the output signal indicative of the presence of a magnetic pole of a first polarity (e.g. north pole) from that magnetic sensor and the output signal indicative of the presence of a magnetic pole of a first polarity (e.g. north pole) from a number of sensors, n, adjacent to that magnetic sensor. Typically n is one. Therefore, in certain examples if previously none of the magnetic sensors detect the guidance track and then the first line of a magnetic sensor goes high, the control unit reads from that magnetic sensor and reads the first line of the magnetic sensors either side of that sensor. The first lines of all of the other magnetic sensors are ignored.

If two or more adjacent magnetic sensors both detect the guidance track, e.g. if the first line of two adjacent magnetic sensors is high, then the control unit operates as described above, that is for the left most magnetic sensor currently detecting the guidance track, the n magnetic sensors to its left are read (as noted above, typically n is one therefore only the magnetic sensor directly to its left is read) and the n magnetic sensors to its right are read. As n is typically one, then this is typically the other magnetic sensor which is currently detecting the guidance track so this is read by the control unit anyway. Similarly, for the right most magnetic sensor currently detecting the guidance track, the n magnetic sensors to its right are read (as noted above, typically n is one therefore only the magnetic sensor directly to its right is read) and the n magnetic sensors to its left are read. As n is typically one, then this is typically the other magnetic sensor which is currently detecting the guidance track so this is read by the control unit anyway.

In certain examples, a similar technique is used for reading from magnetic sensors detecting a magnetic pole of the second polarity (e.g. a south pole), used to encode instruction codes in the control blocks.

In such examples, the control unit is arranged to read the output signal indicative of the presence of a magnetic pole of a second polarity (e.g. south pole) from a number of magnetic sensors, Y, either side of the magnetic sensors currently detecting the magnetic pole of the first polarity (e.g. north pole).

The number Y is typically set based on the spacing between the main section of the guidance track and the control section, e.g. two. For example, if a given magnetic sensor is being read by the control unit and the first output line of that sensor is high indicating the detection of the guidance track, then the control unit is arranged to read the second output lines of the two magnetic sensors directly to the left of the given magnetic sensor and the second output of the two magnetic sensors directly to the right of the magnetic sensor currently detecting the guidance track.

In certain examples, the control unit can contain two separate modules, a first module for reading signals from the magnetic sensors relating to the position of the guidance track (e.g. the output of the first lines of the magnetic sensors that are being selectively read) and a second module for reading signals from the control blocks (e.g. the output of the second lines of the magnetic sensors that are being selectively read).

In certain examples, the control unit can be arranged to control the speed of the driving motor based on which of the magnetic sensors is currently detecting the guidance track. More specifically, the further the magnetic sensor is from the centre of the magnetic sensor

07 17 array, the slower the speed of the driving motor. This can be implemented in any suitable way. For example, if the control unit determines that any of the five left-most or five right-most magnetic sensors detect the guidance track, then the control unit controls the driving motor to drive at a predetermined slowest speed. If any of five sensors immediately to the right of the five left-most sensors detect the guidance track or if any of five sensors immediately to the left of the five right-most sensors detect the guidance track, then the control unit controls the driving motor to drive at a predetermined intermediate speed. If any of the other magnetic sensors (i.e. therefore being sensors a designated “middle” of the sensor array) detect the guidance track, the control unit controls the driving motor to drive at a predetermined maximum io speed.

Figure 7 provides a schematic diagram of an AGV arranged in accordance with certain embodiments of the invention. The AGV shown in Figure 7 corresponds to that shown in Figure 1 except each spaced arm of the fork lift unit includes a wheel unit 701,702. The view 15 of the AGV of Figure 7 is the reverse of the view of the AGV in Figure 1. Each wheel unit 701, 702 includes one or more steerable wheels. In the example shown in Figure 7, each wheel unit 701,702 includes two wheels. Further, each fork leg includes a fork leg magnetic sensor array 703, 704. The fork leg magnetic sensor arrays correspond to the examples of the magnetic sensor arrays described above, e.g. comprising a plurality of magnetic sensors e.g. 20 Hall effect sensors, disposed in a linear array. However, each fork leg magnetic sensor array typically comprises fewer Hall effect sensors, for example six, than the examples of the magnetic sensor array described above which are arranged to generate both control information for the steerable drive wheel and to detect encoded control information. Further, each fork leg magnetic sensor array is typically straight in shape, e.g. substantially rectangular 25 rather than a more complex shape such as the flattened V shape for the main magnetic sensor described above.

The magnetic sensors on each fork leg magnetic sensor array are arranged to output a high signal if a guidance track is detected. Although both fork legs are provided with a magnetic sensor array, typically, the control unit only reads from one magnetic sensor array at any one time. The output is received by the control unit and is used to control a servo motor in each wheel unit. In keeping with the operation of the magnetic sensor array described above, if a central magnetic sensor of a fork leg magnetic sensor detects a guidance track, then the control unit controls the servo motors to maintain the steerable wheels of the wheel units in their current position. Additionally, if no fork guidance track is detected, then the control unit controls the servo motors to maintain the steerable wheels of the wheel units in a “straight22

07 17 ahead” position. On the other hand, if a magnetic sensor to the left of the fork leg magnetic sensor detects the guidance track, then the control unit generates a signal which causes the servo motors to turn the steerable wheels such that the fork legs are steered leftward. Similarly, if a magnetic sensor to the right of the fork leg magnetic sensor detects the guidance track, then the control unit generates a signal which causes the servo motor to turn the steerable wheels such that the fork legs are steered rightward. In certain examples, this can be achieved by associating different magnetic sensors with different PWM duty cycles as described above.

The sensors depicted in Figure 7 are positioned towards a distal end of each leg. However, in other embodiments, the fork leg sensors can be placed in other suitable positions that will enable the wheel units 701,702 to be steered.

As described above, in certain examples the AGV proceeds around the guidance track in the direction indicated by arrow 705. When the AGV reaches a control section, the control section may have encoded thereon instructions for the AGV to perform a forklift pick up operation. Typically, this may involve the AGV making a turn (e.g. a 90 degree to turn) so that the forklift unit faces a pick up area off to one side of the guidance track. The AGV then proceeds a predetermined distance to the pick-up area and performs a pick up operation to pick up an object. The AGV then reverses back onto the guidance track and continues along the guidance track, normally to a set down location where a set down operation is performed.

The pick-up operation may typically require the AGV to insert the fork legs of the forklift unit into suitable fork leg receiving holes of an object to be picked up, for example fork leg receiving holes of a pallet. This may require the fork legs to be positioned within a predetermined accuracy tolerance, for example horizontally within a tolerance of approximately 3mm.

In accordance with examples of the invention in which the AGV is provided with fork leg magnetic sensor arrays and steerable wheel units, the guidance track can include one or more additional magnetic guidance tracks (fork leg guidance tracks) for the forks to follow to improve the accuracy with which the pick-up operation is performed.

One or more fork leg guidance tracks can be provided.

Typically, the fork leg guidance tracks are magnetised with a magnetic pole which is opposite of that of the magnetic pole of the main guidance track. For example, if the main guidance track is magnetised with a first magnetic polarity, e.g. a north pole, then the fork leg guidance tracks are magnetised with a magnetic pole of an opposite polarity, e.g. a south pole. The fork leg magnetic sensor arrays are typically arranged to detect only this second magnetic polarity, thus they do not detect the main guidance track. This is explained further with reference to Figure 8

Furthermore, in certain embodiments, the fork leg guidance tracks are magnetised such that the magnetic field produced is weaker than that of the main guidance track. In this way, it is not detected by the main magnetic sensor array used to steer the AGV. In order to detect the weaker field, in certain embodiments, the fork leg sensors are positioned lower (closer to the floor) than the main magnetic sensor.

Figure 8 provides a schematic diagram showing a portion of guidance track 801 and a portion of a control section 802. The control section 802 has encoded thereon control information for performing a forklift pick up operation. As soon as this control information is received and decoded by the control unit, the control unit begins reading from one of the fork leg magnetic sensor arrays and begins to perform the pick operation by turning 90 degrees, as indicated by arrow 803, and thereby facing a pick up area 804 off to one side of the guidance track. The AGV then proceeds, forklift unit first, a predetermined distance, as indicated by arrow 805 to the pick-up area 804. As can be seen from Figure 8, two fork leg guidance tracks 806, 807 are provided leading up to the pick-up area 804. The fork leg magnetic array that the control unit is reading from detects the corresponding fork leg guidance tracks which, as described above enable the fork legs and thus the forklift unit to be guided to the pick-up area and to ensure that each fork leg is correctly inserted into a fork leg receiving space 808, 809.

In certain examples, as depicted for example in Figure 8, each fork leg guidance track 806, 807 is provided with converging lead-in sections 810. As will be understood, these converging lead-in sections are positioned such that if the AGV is misaligned slightly after performing a turning action, each fork leg magnetic array will detect a converging lead-in section and be guided to the main section of the fork leg guidance track.

Figure 9 provides a schematic diagram of an AGV corresponding to Figure 7, except depicting an AGV that has performed a pick up operation and picked up an object 901. As will be understood, in order of the AGV to pick up an object, the fork legs must elevate. In certain examples, in order to ensure that the wheel units 702, 703 maintain contact with the floor/ground when the fork legs are in an elevated position they are arranged to descend from the fork legs. This can be appreciated by comparing Figure 7 with Figure 9. In certain examples, the wheel units can descend from the fork legs be by virtue of a gravity operated hinge mechanism.

In certain embodiments described above, both fork legs are provided with magnetic sensor arrays and the control unit can select which fork leg sensor array to read from. This can be based on any suitable criteria, for example which fork sensor detects the fork guidance track first.

However, in other embodiments, only one fork leg is provided with a magnetic sensor array.

It will be understood that AGVs in accordance with examples of the invention can be fitted with any suitable forklift unit with one or more fork legs.

AGVs in accordance with certain examples of the invention are not provided with forklift units but are instead provided with alternative functional units. For example, an AGV may be provided with a towing mechanism allowing a trailer or a train of trailers to be towed behind the AGV. In certain examples, a robotic unit, such as a robotic arm unit may be provided on an AGV for performing more complex tasks than a conventional fork lift unit. Specific instructions can be conveyed to the AGV for the robotic unit using the techniques described above. In certain embodiments, AGVs may be provided with extended forklift units such as “stacker” units as are known in the art.

AGVs arranged in accordance with certain examples of the invention may include additional features for assisting safe and efficient movement around environments such as factories and warehouses. Such additional features may include proximity sensors, such as ultrasonic proximity sensors and/or infrared proximity sensors arranged to detect nearby obstacles such as objects obstructing the intended path of the AGV or people, for example walking across or close to the guidance track. In such embodiments, the sensors may be connected to the control unit and arranged to generate a signal if an obstacle is detected. In some examples, this signal may additionally indicate the proximity of the detected the obstacle. The control unit can control the movement of the AGV accordingly, for example slowing the speed of the driving motor if the proximity sensors indicate an obstacle within a threshold proximity or stopping the AGV altogether if an obstacle is detected within very close proximity of the AGV.

As will be understood, in certain implementations, multiple AGVs, as described above, may operate on a guidance track.

In such examples, techniques can be deployed to ensure that AGVs encountering each other travelling in opposite directions on the same stretch of track will not collide. Such techniques can involve proximity sensors as described above. Techniques can be deployed such that AGVs detecting the presence of other AGVs on the guidance track are arranged to briefly move off the track to travel around each other. For more complex guidance track arrangements, traffic control systems are contemplated.

In certain examples, a guidance track may include one or more charging points. If an AGV detects that its battery is low and it passes a charging point it is arranged to perform an action, based for example on an instruction code encoded on a control section, to connect to the charging point.

In certain examples, an AGV may be provided with manual override functionality allowing an operator to control the movement of the AGV directly, for example via a control panel mounted on the AGV or by other means known in the art, such as via a wired or wireless remote control arrangement.

Figure 10 provides a schematic diagram of the control system of an AGV in accordance with certain examples of the invention.

A control unit 1001 is connected to a main magnetic sensors array 1002 and a left fork leg magnetic sensor array 1003 and a right fork leg magnetic sensor array 1004. The control unit 1001 is coupled to a driving wheel motor 1005 and a turning motor 1006 for driving and turning a steerable drive wheel as described above. The control unit 1001 is also coupled to a left fork leg servo motor 1007 for steering wheels of a wheel unit of left fork leg and a right fork leg servo motor 1008 for steering wheels of a wheel unit of right fork leg. The control unit is also connected to a proximity sensor 1009.

Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and/or steps are mutually exclusive. The invention is not restricted to any details of any foregoing embodiments. The invention extends to any novel one, or novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

1. An autonomous guided vehicle system comprising a guidance track for guiding autonomous vehicles and at least one autonomous guided vehicle, said guidance track including at least one control section for conveying control information to the autonomous guided vehicle, said control section comprising a predetermined number of control blocks, each control block being selectively magnetised to encode the control information, wherein the autonomous guided vehicle comprises a magnetic sensor arranged to detect a magnetic state of each control block and communicate this to a control unit coupled to said magnetic sensor, said control unit arranged to control the autonomous guided vehicle to perform a command associated with the control information.

2. An autonomous guided vehicle system according to claim 1, wherein the guidance track is magnetised with a first magnetic polarity and each control block is selectively magnetised with one of the first magnetic polarity, a second magnetic polarity opposite the first magnetic polarity, or no magnetic polarity.

3. An autonomous guided vehicle system according to claim 1 or 2, wherein the control blocks are positioned adjacent to one another forming a control block section and the magnetic sensor detects the magnetic state of each control block as the AGV moves along the guidance track.

4. An autonomous guided vehicle system according to claim 3, wherein the control section further comprises a marker block of a predetermined magnetic state positioned ahead of the control block section, and the control unit is arranged to identify the presence of the control block section responsive to the magnetic sensor detecting the marker block.

5. An autonomous guided vehicle system according to claim 4, wherein the marker block is of a predetermined length, said predetermined length indicating a predetermined length of the control blocks of the control section, and the control unit is arranged to determine the predetermined length of the control blocks from the detection by magnetic sensor of the marker block, and control a control block reading operation of the control blocks by the magnetic sensor in accordance with the determined predetermined length of the control blocks.

6. An autonomous guided vehicle system according to claim 5, wherein the marker block and the control block section are separated by an unmagnetised separation region of a predetermined length.

7. An autonomous guided vehicle system according to any previous claim, wherein each control section is formed from a section of track running substantially parallel to a main section of the guidance track.

8. An autonomous guided vehicle system according to claim 7, wherein each control section is connected at a first and/or second end to the main section of the guidance track.

9. An autonomous guided vehicle system according to any previous claim, wherein the control information is associated with a command for the autonomous guided vehicle to perform a predefined movement and/or perform a predefined action.

10. An autonomous guided vehicle system according to claim 9, wherein the predefined movement is in a predefined direction at a predefined speed.

11. An autonomous guided vehicle system according to claim 9 or 10, wherein the predefined action comprises a forklift action of a forklift unit of the autonomous guided vehicle.

12. An autonomous guided vehicle system according to claim 11, wherein the autonomous guided vehicle comprises at least one fork leg comprising a fork leg magnetic sensor and the guidance track further comprises at least one fork leg guidance track section for guiding the fork leg of the autonomous guided vehicle during the forklift action.

13. An autonomous guided vehicle system according to claim 12, wherein the autonomous guided vehicle comprises two fork legs, each comprising a fork leg magnetic sensor and the fork leg guidance track section comprises two fork leg guidance tracks for guiding the fork legs of the autonomous guided vehicle during the forklift action.

14. An autonomous guided vehicle system according to any previous claim, wherein the magnetic sensor comprises an array of a plurality of individual magnetic sensors.

15. An autonomous guided vehicle system according to claim 14, wherein each magnetic sensor communicates a detection signal to the control unit if it detects the guidance track, and the control unit thereby determines a position of the guidance of track at a given time based on which of one or more of the individual magnetic sensors are currently detecting the tape.

16. An autonomous guided vehicle system according to claim 15, wherein, when determining the position of the guidance track, the control unit responds to the detection signal from individual magnetic sensors currently detecting the guidance track, and detection signals from N number of magnetic sensors either side of the individual magnetic sensors currently detecting guidance track.

17. An autonomous guided vehicle system according to claim 16, wherein N is 1.

18. An autonomous guided vehicle system according to any of claims 14 to 17, wherein the magnetic sensor is shaped such that a first plurality of peripheral magnetic sensors and a second plurality of peripheral magnetic sensors trail a third plurality of central magnetic sensors.

19. An autonomous guided vehicle system according to claim 18, wherein the third plurality of central magnetic sensors are disposed along a substantially straight central cross section of the magnetic sensor and the first and second plurality of peripheral magnetic sensors are disposed respectively along two end sections of the magnetic sensor, the central cross section and two end sections configured to form a flattened V shape.

20. An autonomous guided vehicle for use in a system according to any of claims 1 to 19.

21. An autonomous guided vehicle system or autonomous guided vehicle as hereinbefore described with reference to the drawings.

Intellectual

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Application No: GB1612986.8 Examiner: Dr EP Plummer