WO2015006824A1

WO2015006824A1 - Low-frequency magnetic field synchronisation for proximity detection systems

Info

Publication number: WO2015006824A1
Application number: PCT/AU2014/050124
Authority: WO
Inventors: Eric DE ZOETEN; Peter O'DONNELL
Original assignee: Industrea Mining Technology Pty Ltd
Priority date: 2013-07-15
Filing date: 2014-07-15
Publication date: 2015-01-22
Also published as: AU2014292821B2; AU2014292821A1

Abstract

A method of scheduling transmission of a magnetic field from an associated one of a plurality of systems used for magnetic field proximity detection, comprising: detecting one or more systems within a radio frequency (RF) awareness zone of another one or more of the plurality of systems; establishing an RF link between systems within the or each RF awareness zone; scheduling a magnetic field transmission for each of the systems connected by the RF link; and transmitting scheduling information to each respective system, using the RF link, to synchronise an associated magnetic field transmission prior to the connected systems moving into a region of magnetic field overlap.

Description

LOW-FREQUENCY MAGNETIC FIELD SYNCHRONISATION FOR PROXIMITY DETECTION SYSTEMS

RELATED A PP LI CATION

[0001] This application claims priority from Australian Patent Application AU 201 902606, the content of which is incorporated in entirety by reference.

TECHNICAL FIELD

[0002] The present invention relates to a system and a method of synchronisation of low-frequency magnetic fields for proximity detection systems, A proximity detection system may be used to locate, monitor, track, survey and/or map the position of persons and assets in possible explosive atmospheres in the rough operating conditions of mining, oil and gas industries, factories and warehouses.

^'BACKGROUND

[0003] In places such as milling, oil and gas rigs or factory buildings proximity detection systems are common. These systems can detect persons too close to danger spots or assets in danger of colliding, among other things. Often, these proximity detection systems use low frequency magnetic fields, as other traditional locating devices such as GPS may not: work effectively.

[0004] Various different systems have been developed, however when more than one low frequenc magnetic fields from different proximity detection systems overlap* the signals may be distorted or destroyed due t magnetic field summing.

[0005] For certain applications, multiple proximity systems can and will overlap. For example, whe multiple machines are within close proximity of each other. This can potentially defeat the proximity detection, potentially creatin a hazard as personnel are not detected around machinery or collision zones are not correctly identified due to the d torted magnetic field in the overlapping region. [0006] It may be desirable to provide a way for the proximity systems to be aware of each other and mitigate the magnetic field overlap problem.

[0007] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as. an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

BRIEF DESCRIPTION OF THE INVENTI ON

[0008] In accordance with an embodiment of the present invention, there is provided a method of scheduling transmission of a magnetic field from an associated one of a plurality of systems used for magnetic field proximity detection, comprising: detecting one or more systems within a radio frequency (RF) awareness zone of another one or more o the pluralit of systems; establishing an RF link between systems within the or each RF awareness ¾one; scheduling a magnetic field transmission for each of the systems conriected by the RF link; and transmitting scheduling information to each respective system, usin the RF link, to synchronise an associated magnetic field transmission prior to the connected systems moving int a region of magnetic field overlap

[0009] In an embodiment, the method further comprises: emitting a RF beacon message from one of the systems; detecting the RF beacon message at one or more of the other systems; and establishing the RF link between the emitting and detecting systems.

[0010] In an embodiment, the RF beacon message emitted from the or each system is uniquely tagged to a respecti ve one of the systems. fOOIl] in an embodiment, the method further comprise sequential transmission of an emit token over the RF link, following a scheduled transmission, to authorize magnetic field transmission fro a subsequent one of the systems. [0012] In an embodiment, each system has a predetermined time-out after receipt of the emit token, to ensure the magnetic Held transmission is confined to a scheduled transmission time,

[0013] In an embodiment, the scheduling information includes a list of systems identified in the or each RF awareness zone, associated with one or more of the systems, and scheduled time for magnetic field transmission for each system.

[0014] In an embodiment, wherein: the RF beacon message functions as a ranging signal.

[0015] I an embodiment, the RF link is established as an RF baekchannel for communications between the systems.

[0016] In an embodiment, the RF beacon signal associated with the or each system is emitted at fixed intervals.

[0017] In an embodiment, the method further includes transmitting handshake messages between the systems across the RF link, once an RF beacon signal is detected, to negotiate magnetic field transmission synchronization between the systems.

[0018] In an embodiment, the scheduling is determined on the basis of a transmission loop, with each system in the or each awareness zone being scheduled to sequentially transmit a magnetic field and, when all systems have completed trimsmission, the transmission loop is recommenced.

[0019] In accordance with another aspect, there is provided a network of systems for proximity detection, each system being configured to transmit magnetic field in accordance with the above described method.

[0020] In accordance with another aspect, there is provided a system for proximity detection having an emitter for generating a magnetic field, an RF antenna for transmitting an RF beacon signal and for establishing an RF link with one or more other systems, and a controller configured to synchronize magnetic field transmission, in accordance with the method, as described above. BRIEP DESCRIPTION OF FIGU RES

[00211 Example embodiments should become apparent from the following description, which is give by way of example only, of at least one preferred but non- limiting embodiment, described in connection with the accompanying drawings, in which:

[0022] Figure .1 is a, schematic view of an example of two proximity detection systems in a region of magnetic field overlap; and

[0023] Figure 2 is a schematic illustration of transmissions between the proximity^' detection systems.

DETAI LED DESCRIPTION

[0024] The following modes, given by way of example only, are described in order to provide a more precise understanding of the subject matter of a preferred embodiment or embodiments.

[0025] In the Figures, incorporated to illustrate features of an example embodiment, like reference numerals are used to identify like parts.

[0026] Referring to Figure 1, a schematic view is shown of an example of two proximity detection systems 1 , 4 moving towards each other. The first prox mity detection system 1 has a magnetic field 2 and a radi frequency (RF) awareness zone 3. Similarly, the second proximity detection system 4 has a magnetic field 5 and an RF awareness zone 6.

[0027] The two proximity detection systems 1, 4 approaching one another result in a magnetic field overlap region 7, with the bottom part of Figure 1 illustrating a distorted signal 8 in the overlapping region 7. Figure 1 also illustrates the combined system field 9, which is created, in accordance with the invention, by synchronising transmission of a magnetic field 10, from the first system 1, with transmissions of a magnetic field 1 1, from the second s stem 4.

[0028] Reletting to Figure 2, a schematic view of proximity detection systems 1 to n is shown. The first proximity detection system 1 includes a first controller 12, a magnetic field emitter 15 and a radio frequency (RF) antenna capable of sending and receiving information via radio frequency. The second proximity detection system 4 includes a second controller 13, a magnetic field emitter 15 and an RF antenna that communicates with the first controller 12 using the RF backchannel link 16. The proximity detection system 12 has an nth controller 14» a magnetic field emitter 15 and an RF antenna used, for the RF backchannel link 16.

[0029] The plot at the to of Figure 2 illustrates the synchronisation of the multiple systems 1 to n in a scheduleD transmission loop round robin 17, shown schematically. Use of the letter t denote the last; controller illustrates that there may be any number of systems in communication with one another and included in the round robin 17.

[0030] Referring again to Figure 1 , if the proximity detection systems 4 were to get close enough without synchronisation, the two magnetic fields 2, 5 would end up partially in the magnetic field overlap zone 7. This would result in a distorted signal 8. The present invention seeks to avoid thi by coordinating or synchronizing the magnetic fields so that only one magnetic field is being emitted at any given time.

[0031] The proximity systems 1, 4 are made aware of the presence of other proximity systems by the RF awareness zones 3, 6,. and the systems can be synchronised to avoid emitting magnetic fields 2, 5 at the same time. The use of the term "radio frequency" is intended to include any suitable frequency of electromagnetic waves capable of being used for communication, such as microwaves for example, provided they have a range greater than that of magnetic waves.

[0032] Using the RF awareness zones 3, 6, the closing proximity systems 1 , 4 recognise eac other and the synchronisation method is stalled. The synchronised combined system field 9 adds up the first system, field 1.0 and the second system field .1 .1. When synchronised, as only one magnetic field is being emitted at any given time, there is no interference of the magnetic fields with one another. This means that while each system 1, 4,,.. n, may not know the precise location of the surrounding systems, they can each safely operate their own proximity detection using the proximity sensor without the risk of interference from nearby systems. [0033] Time slicing of magnetic field emitters 15 allows each system 1 , 4, ... n, to emit its magnetic field in sequence, while never emitting at the same time as any other system, producing together a combined system field 9, A round robin scheduling 17 of emitters is used, with each system 1 , 4, ... n, taking its turn to emit its field, one after the other. Once all systems 1 , 4, ... n, have emitted their magnetic field, the loop repeats. This is a similar method to time-division multiple-access (TDMA) techniques.

[0034] With reference to both Figures 1 and 2, to achieve synchronisation, an RF backchannel 16 is used, where each proximity detection system 1, 4. ... n, can communicate with at least one other system when they are within the respective RF awareness zone 3, 6. As the RF awareness zones 3, 6 cover a larger area than the magnetic fields 2, 5, the synchronisation process will occur prior to any interference of the magnetic fields 2, 5. I this way the RF signals perform a ranging function, effectively notifying each other that they are. close prior to any danger of interference of the magnetic fields.

[0035] During normal use, each proximity detection system .1 , 4, ... n, transmits a beacon message at fixed intervals. When another system detects the beacon message, the two systems transmit a handshake message to each other to negotiate their field synchronisation. The- RF signals may be tagged to identify the signal source as part of the synchronisation algorithm and process.

[0036] As more systems ente the RF awareness "overlapping zone", they are added to the synchronisation negotiations. Each individual system 1 , 4, ... n, maintains a list of all other surrounding systems. In some situations not all RF awareness zones will overlap with all others, therefore preventin certain systems communicating directly with some of the other systems. Relaying scheduling information and communication algorithms allow the synchronisation to be maintained even in such situations.

[0037] After each system 1., 4_» ... n, completes emitting its magnetic field, it passes an "emit token" (via a message over the RF channel) to the next system. The "emit token" is passed around, to each system, where only the syste that, has the token can emit its magnetic field 2, 5. This process avoids overlapping magnetic fields, and allows continued operation of the proximity system 1, 4, ... n, eve when other proximity systems are close by.

[0038] if a system 1 , . 4, ... n, does not pass on the token within a predetermined timeout, it is removed from the list of ystem and the. token is automaiically "assumed" to be in the next system on the list. As- each system keeps the full synchronisation list, any particular syste going out of range allows the scheduling to continue for the remainin systems. This timeout process may continue until all other systems are out of range, at which point the system returns to normal operating mode.

[0039] Th maximum number of systems that can synchronise is limited by the maximum acceptable "loop time" for the proximity system. Where there are n systems in synchronisation, then the overall "loop time" is increased by a factor of a. Realistically, as magnetic fields only have limited effective range (typically less than 20 metres) there is a reasonable limit to the number of proximity systems than can physically fit within a space that allow their fields to overlap.

[0040] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

Claims

The Claims:

1, A method of scheduling transmission of a magnetic field from an associated one of a plurality of systems used for magnetic field proximity detection, comprising: detecting one or more systems within a radio frequency (RF) awareness zone of another one or more of the plurality of systems ; establishing an RF link between systems within the. or each. RF awareness mm; scheduling a magnetic field transmission for each of the systems connected by the RF link; and transmitting scheduling information to each respective system, using the RF Link, to synchronise an associated magnetic field transmission prior to the connected systems moving into a region of magnetic field Overlap,

2, A method of claim I. further comprising: emitting an RF beacon message from one of the systems; detecting the RF beacon message at one or more of the other systems; and establishing the RF link between the emitting and detecting systems.

3. The method of claim 2, wherein the RF beacon message emitted from the or each system is uniquely tagged, to a respective one of the systems .

4. The method of any one of claims 1 to 3, further comprising sequential transmission of an emit token over the RF link, following a scheduled transmission, to authorize magnetic field transmission from a subsequent one of the systems.

5, The method of claim 4, wherei each system has a predetermined time-out after receipt of the emit token, to ensure the magnetic field transmission is confined to a scheduled transmission time,

6, The method of claim 1, wherein the scheduling information includes a list of systems identified in the or each RF awareness zone, associated with one or more of the systems, and a scheduled time for magnetic field transmission for each system.

7, The method of claim 2, wherein the RF beacon message functions as a ranging signal.

8, The method of claim 1< wherein the RF link is established as an RF backchannel for communication between the systems.

9, The method of claim 3, wherein the RF beacon signal associated with the or each s stem is emitted at fi ed intervals,

10, The method of claim 9, further including transmitting handshake messages between the systems across the RF link, once an RF beacon signal is detected, to negotiate magnetic field transmission synchronization between the systems.

1 1 , The method of claim 1, wherein the scheduling is determined on the basis of a transmission loop, with each system in the or each RF awareness zone being scheduled to sequentially transmit a magnetic field and, when all systems have completed transmission, the transmission loop i recommenced.

12, A network of systems for piOximity detection, each system being configured to transmit a magnetic field in accordance with the method of claim 1.

13. A system for proximity detection having an emitter for generating a magnetic field. an RF antenna for transmitting an RF beacon signal and for establishing an RF link with one or more other systems, and a controller configured to synchronise magnetic field transmission, in accordance with the method of claim 1.

14. A plurality of proximity detection systems, each system having an emitter configured to generate a magnetic field, a radio frequency (RF) antenna configured to establish an RF link with one or more of the other proximity detection systems, and a controller to synchronise magnetic field transmissions o the plurality of proximity detection systems, configured so as to: detect one or more of the pluralit of proximit detection systems within an RF awareness zone of another one or more of the plurality of proximity detection systems; establish an RF link between the proximity detection systems within the or each awareness zone; schedule a magnetic field transmission for each of the system connected by an associated RF link; and transmit scheduling information to each respective proximit detection system, using the associated RF link, to synchronise magnetic field transmissions prior to the RF linked proximity detection systems moving into a region of magnetic field overlap.