Source: https://patents.google.com/patent/EP2504662B1/en
Timestamp: 2020-04-06 15:52:39
Document Index: 168532369

Matched Legal Cases: ['art 400', 'art 500', 'art 400', 'art 400', 'art 400', 'art 400', 'art 500', 'art 500', 'art 500', 'art 500', 'art 600', 'art 600', 'art 700', 'art 700', 'art 600', 'art 700', 'art 700', 'art 700', 'art 400', 'art 400', 'art 500', 'art 400', 'art 500', 'art 400', 'art 500']

EP2504662B1 - Positioning a device relative to a magnetic signal source - Google Patents
Positioning a device relative to a magnetic signal source Download PDF
EP2504662B1
EP2504662B1 EP09851744.4A EP09851744A EP2504662B1 EP 2504662 B1 EP2504662 B1 EP 2504662B1 EP 09851744 A EP09851744 A EP 09851744A EP 2504662 B1 EP2504662 B1 EP 2504662B1
EP09851744.4A
EP2504662A4 (en
EP2504662A1 (en
Paul Mikael Kamppi
2009-11-24 Application filed by Nokia Technologies Oy filed Critical Nokia Technologies Oy
2009-11-24 Priority to PCT/US2009/006293 priority Critical patent/WO2011065931A1/en
2012-10-03 Publication of EP2504662A1 publication Critical patent/EP2504662A1/en
2017-07-12 Publication of EP2504662A4 publication Critical patent/EP2504662A4/en
2018-11-21 Publication of EP2504662B1 publication Critical patent/EP2504662B1/en
US 6 686 881 B1 describes an identification and tracking system for a mobile object using magnetic fields generated by separate magnetic field sources. The respective magnetic fields are detected at the object and used for determining its position relative to the magnetic field sources.
In a first aspect of the present invention, a method is disclosed, comprising the steps of appended claim 1.
In this first aspect of the present invention, furthermore an apparatus is disclosed, as defined in appended claim 13. Said apparatus may for instance be said device, or a part thereof.
In this first aspect of the present invention, furthermore an apparatus is disclosed, comprising at least one processor; and at least one memory including computer program code as defined in claim 12. Said computer program code may for instance at least partially represent software and/or firmware for said processor. Non-limiting examples of said memory are a RAM or ROM that is accessible by said processor. Said apparatus may for instance be said device, or a part thereof. According to the first aspect of the present invention, a magnetic signal is detected at a device. Said device may for instance be a positioning device that is configured to determine its position. Said determined position may then be indicated to a user of said device, or provided to another apparatus for further processing. An example of said device is a hand-held electronic device, for instance a mobile phone, or a mobile navigation unit.
Said magnetic signal may for instance comprise a magnitude and/or a direction of a magnetic flux density or of a magnetic field strength. Said magnetic signal may for instance be a sinusoidal signal. As a further example, said magnetic signal may be a signal with a constant magnitude. It stems from a magnetic signal source, which may for instance be an artificial magnetic signal source (in contrast to the Earth's magnetic poles). The magnetic signal source has been installed in an environment in which said device (and thus also the user carrying said device) is to be positioned by said positioning process. A non-limiting example of such a magnetic signal source is a coil arrangement (i.e. one or more coils, for instance a pair of Helmholtz coils) driven by a current, which may for instance be a time-variant current, such as for instance a sinusoidal current, or a time-invariant current, such as for instance a constant (DC) current. Said magnetic signal source may produce said magnetic signal in a stationary or quasi-stationary manner, i.e. said magnetic signal source may not act as an antenna. This may for instance be achieved when the dimensions of the components of the magnetic signal source (for instance one or more coils) are much smaller (for instance by a factor of 10 or less) than a quarter of the wave-length of a signal that drives said magnetic signal source (such as for instance a current that drives said one or more coils) . Said magnetic signal may not be accompanied by an electric signal. Said magnetic signal may not be the magnetic component of an electro-magnetic signal (such as for instance a travelling electro-magnetic wave emitted by an antenna).
Positioning process information is available, which is used in said positioning process. Therein, positioning process information is information on a detected magnetic signal, and/or information determined based on said detected magnetic signal, and/or identity information determined based on data measured to detect said detected magnetic signal.
As further non-limiting examples, the positioning process information may comprise one or more parameters or characteristics of said detected magnetic signal, for instance its frequency, modulation pattern, magnitude and/or direction, or information contained in said magnetic signal itself, for instance information that has been included (e.g. coded) into said magnetic signal. For instance, the position of the magnetic source that produced the detected magnetic signal may be included into the magnetic signal, for instance explicitly (as coordinate values, e.g. geodetic coordinates), or implicitly (for instance by assigning the magnetic signal source an identifier, e.g. a number, so that the position of the magnetic signal source can be identified based on the identifier).aid positioning process information may additionally or alternatively comprise information on a movement direction of the user of the device, which movement direction may for instance be gathered by a process that controls the activation of said magnetic signal source and may then be included into said magnetic signal.
As further non-limiting examples, said positioning process information may comprise information that is determined based on data measured to detect said detected magnetic signal (for instance measurement data that is obtained by measuring a magnetic characteristic over a period of time to detect the magnetic signal) . Therein, said information may be determined based on said measured data alone, or also based on further information, such as for instance reference data pertaining to the magnetic signal source that produced the detected magnetic signal, allowing deriving of, for instance, a movement direction and/or a step length of a user and/or allowing identification of a magnetic signal source that produced the detected magnetic signal.
Triggering production of the magnetic signal by the user or device approaching or passing the magnetic signal source may also be advantageous since the area in which the magnetic signal is detectable at the device can be confined to a limited area or substantially a single position. Detection of the magnetic signal at the device may then be considered indicative of the device being located in this limited area or at this position. For instance, if the magnetic signal source is mounted in a corridor, a first light barrier before the magnetic signal source and a second light source behind the magnetic signal source may be used to turn on and off the production of the magnetic signal, respectively, when a user walks through the first and second light barrier. The limited area is then the area between the first and second light barrier. Equally well, in this scenario, a single light barrier at the magnetic signal source may be used, and a user passing this light barrier may then, due to the detection of the magnetic signal (the production of which is triggered by passing the light barrier) at the user' s device, be considered at the position of the magnetic signal source.
Therein, the detection of the magnetic signal at the device may be considered to be independent of the way of triggering the production of the magnetic signal; in other words, the device may only have to be capable of detection of the magnetic signal, whereas the triggering of the production of the magnetic signal can be implemented in many different ways, for instance as appropriate in the respective environment in which the magnetic signal source is installed (for instance, near an automatic door, a switch coupled to the automatic door may be user to trigger production of the magnetic signal by a magnetic signal source that is located near the automatic door, whereas for a different magnetic source, for instance a light barrier or a contact switch on the floor may be used) .
According to an embodiment of the first aspect of the present invention, detecting said magnetic signal at said device is part of the method according to the first aspect of the present invention. Consequently, the apparatuses according to the first aspect of the present invention then comprise means for detecting said magnetic signal or are caused to detect said magnetic signal. Alternatively, said detecting of said magnetic signal may not be part of said method according to the first aspect of the present invention, and said apparatuses according to the first aspect of the present invention may then not comprise means for detecting or may not be caused to detect said magnetic signal. They may then for instance receive information on or from said detected magnetic signal from another apparatus. This other apparatus may for instance be a part of said device.
For instance, if only one magnetic signal source is (known to be) installed in the environment, the magnetic signal may be necessarily associated with this single magnetic signal source and/or with the position of said magnetic signal source. If several magnetic signal sources are (known to be) installed in the environment, and if the magnetic signals produced by these magnetic signal sources are all the same (for instance all sinusoids with the same frequency), a detected magnetic signal may be associated with its producing magnetic signal source and/or the position of this magnetic signal source based on additional information, such as coarse information on a current position of the device, or a last known position of the device, for instance combined with map information. Said position of said device may then for instance be determined by assuming that - since the device is detecting the magnetic signal - the position of the device and the position of the magnetic signal source are substantially the same.
It may also be the case that at least two magnetic signal sources may be installed in said environment, that said at least two magnetic signal sources may be configured to produce different magnetic signals, respectively, and that said positioning process may be capable of differentiating between said different magnetic signals when associating said detected magnetic signal with said position of said magnetic signal source that produced said detected magnetic signal. Said magnetic signals may then for instance differ in their frequencies, and/or may be modulated differently (for instance by using Frequency Shift Keying (FSK) or any other type of modulation) . Each magnetic signal source may then for instance produce a unique magnetic signal, so that the magnetic signals may be unambiguously associated with their magnetic signal sources and their respective positions. Said positioning process may then for instance use information (such as a table) on an association of the different magnetic signals and the positions of their respective magnetic signal sources.
In a second aspect of the present invention, a method is disclosed, comprising producing, at a magnetic signal source that is installable in an environment, a magnetic signal that is detectable by a device, wherein positioning process information that is at least one of information on a detected magnetic signal, information determined based on said detected magnetic signal and identity information determined based on data measured to detect said detected magnetic signal is useable in a positioning process that is for positioning said device in said environment.
In this second aspect of the present invention, furthermore a computer-readable medium is disclosed, having a computer program according to the second aspect of the present invention stored thereon. The computer-readable medium may have the same properties that have already been described with respect to the computer-readable medium according to the second aspect of the present invention. Said processor may for instance be comprised in said magnetic signal source. In this second aspect of the present invention, furthermore an apparatus is disclosed, configured to perform the method according to the second aspect of the present invention. Said apparatus may for instance be the magnetic signal source, or a part thereof.
In this second aspect of the present invention, furthermore an apparatus is disclosed, comprising means for producing, at a magnetic signal source that is installable in an environment, a magnetic signal that is detectable at a device, wherein positioning process information that is at least one of information on a detected magnetic signal, information determined based on said detected magnetic signal and identity information determined based on data measured to detect said detected magnetic signal is useable in a positioning process that is for positioning said device in said environment. Said apparatus may for instance be said magnetic signal source, or a part thereof.
In this second aspect of the present invention, furthermore an apparatus is disclosed, comprising at least one processor; and at least one memory including computer program code, said at least one memory and said computer program code configured to, with said at least one processor, cause said apparatus at least to produce, at a magnetic signal source that is installable in an environment, a magnetic signal that is detectable by a device, wherein positioning process information that is at least one of information on a detected magnetic signal, information determined based on said detected magnetic signal and identity information determined based on data measured to detect said detected magnetic signal is useable in a positioning process that is for positioning said device in said environment. Said computer program code may for instance at least partially represent software and/or firmware for said processor. Non-limiting examples of said memory are a RAM or ROM that is accessible by said processor. Said apparatus may for instance be said magnetic signal source, or a part thereof.
In a third aspect of the present invention, a system is disclosed, comprising at least one magnetic signal source installed in an environment and comprising means for producing a magnetic signal; and at least one apparatus comprising means for using, in a positioning process, positioning process information that is at least one of information on a detected magnetic signal detected at a device, information determined based on said detected magnetic signal and identity information determined based on data measured to detect said detected magnetic signal, wherein said positioning process is for positioning said device in said environment.
In this third aspect of the present invention, furthermore a system is disclosed, comprising at least one magnetic signal source installed in an environment and configured to produce a magnetic signal; and at least one apparatus comprising at least one processor and at least one memory including computer program code, said at least one memory and said computer program code configured to, with said at least one processor, cause said apparatus at least to use, in a positioning process, positioning process information that is at least one of information on a detected magnetic signal detected at a device, information determined based on said detected magnetic signal and identity information determined based on data measured to detect said detected magnetic signal, wherein said positioning process is for positioning said device in said environment.
A schematic illustration of an embodiment of a system according to the present invention;
a schematic block diagram of an embodiment of an apparatus in a device to be positioned according to the present invention;
a schematic block diagram of a further embodiment of an apparatus in a device to be positioned according to the present invention;
a schematic illustration of an embodiment of a tangible storage medium according to the present invention;
a flowchart of an embodiment of a method according to the present invention to be performed by the apparatus of Fig. 2a;
a flowchart of an embodiment of a method according to the present invention to be performed by the apparatus of Fig. 2b;
a schematic block diagram of an embodiment of an apparatus in a magnetic signal source according to the present invention;
a flowchart of an embodiment of a method according to the present invention to be performed by the apparatus of Fig. 5;
a flowchart of a further embodiment of a method according to the present invention to be performed by the apparatus of Fig. 5;
a schematic illustration of an example of an environment in which magnetic signal sources according to the present invention have been installed to support a positioning of a device;
a schematic illustration of a set of Helmholtz coils that serve as an example of a magnetic signal source according to the present invention;
a schematic illustration of an example of measurement data containing a magnetic signal according to the present invention;
a schematic illustration of examples of measurement data and reference data pertaining to a magnetic signal produced by a magnetic signal source; and
a schematic illustration of a set-up in which a movement direction of a user/device is determined based on a detected direction of a magnetic flux density or magnetic field strength produced by a magnetic signal source.
Fig. 2a is a schematic block diagram of an embodiment of an apparatus 4 that implements device 3 of Fig. 1 or forms a component thereof (for instance a module thereof). Apparatus 4 comprises a positioning processor 40 with program memory 41 and main memory 42. Positioning processor 40 is configured to use positioning process information in a positioning process. To this end, positioning processor 40 may for instance execute a computer program that is stored in program memory 41. Main memory 42 is used by positioning processor 40 as a working memory. Positioning processor 40 is further configured to operate a positioning process that targets positioning of device 3 (see Fig. 1) in an environment. To this end, positioning processor 40 interfaces with one or more positioning sensors 45. Examples of such positioning sensors 45 are a GNSS sensor, and/or a unit for angle-based positioning (e.g. a DoA/DoD unit) and/or a DR unit. Further non-limiting examples for positioning sensor 45 are sonic/sonar, infrared or radar sensors, or a camera or a WLAN-based positioning unit. Based on information from the positioning sensors 45, positioning processor 40 conducts the positioning process to determine the position of device 3. Apparatus 4 may further comprise a user interface 43, for instance to receive commands from a user and/or to present a result of the positioning process to the user.
Generally speaking, this positioning process information comprises information on a detected magnetic signal, and/or information determined based on said detected magnetic signal and/or identity information determined based on data measured to detect said detected magnetic signal.
Such positioning process information may for instance comprise a representation of the magnetic signal itself, or information included in the magnetic signal (like for instance an identifier of the magnetic signal source that produced the magnetic signal, or a position of the magnetic signal source), information on a parameter or characteristic of the detected magnetic signal (like for instance its frequency, modulation pattern, magnitude or direction), or the bare information that a magnetic signal has been detected at all, to name but a few non-limiting examples. Optionally, unit 44 may further comprise a reference data memory 442. Therein, for instance replicas of magnetic signals to be detected may be stored as a basis for the comparison performed by processor 441.
Fig. 2b is a schematic block diagram of a further embodiment of an apparatus 5 that implements device 3 of Fig. 1 or forms a component thereof (for instance a module thereof).
Apparatus 5 comprises a multi-purpose processor 50, which combines some or all of the functionality of positioning processor 40 and processor 441 of apparatus 4 of Fig. 2a. Generally speaking, multi-purpose processor 50 thus is configured to use positioning process information in a positioning process, and is further configured to detect the magnetic signal in measurement data that is provided by magnetometer 54 of apparatus 5. Multi-purpose processor 50 is further capable of determining/deriving positioning process information based on the measurement data provided by magnetometer 54, and also based on further data, such as for instance reference data that may be stored in main memory 52, which may further be used as working memory by multi-purpose processor 50, for instance for storing measurement data obtained from magnetometer 54. Equally well, there may be a dedicated reference data memory as in apparatus 4 of Fig. 2a. Multi-purpose processor 50 further interfaces with a program memory that stores program code that is executed by multi-purpose processor 50, and with one or more positioning sensors 55 that provide further information for the positioning process. Apparatus 5 may further comprise an optional user interface 53 for receiving user inputs and/or for outputting information to a user.
Fig. 3 is a schematic illustration of an embodiment of a tangible storage medium 60 according to the present invention. This tangible storage medium may for instance form program memory 41 of the apparatus 4 of Fig. 2a or program memory 51 of apparatus 5 of Fig. 2b. It may for instance be embodied as RAM or ROM memory, but equally well as a removable memory. Tangible storage medium 60 comprises a computer program 61, which in turn comprises program code 62. This program code may for instance implement the methods of the flowchart 400 of Fig. 4a or of the flowchart 500 of Fig. 4b that may be executed when computer program 61 is run on positioning processor 41 of apparatus 4 of Fig. 2a or on multi-purpose processor 50 of apparatus 5 of Fig. 2b. Fig. 4a is a flowchart 400 of an embodiment of a method according to the present invention. This flowchart 400 may for instance be comprised as computer program 61 in tangible storage medium 60, which may in turn represent program memory 41 of apparatus 4 of Fig. 2a, so that flowchart 400 would then be executed by positioning processor 40.
In a step 401 of flowchart 400, positioning process information is received. This positioning process information comprises information on a detected magnetic signal, and/or information determined based on a detected magnetic signal, and/or identity information determined based on data measured to detect a detected magnetic signal. With respect to apparatus 4 of Fig. 2a, this information would thus be received by positioning processor 40 from unit 44.
In a step 402, the received positioning process information is used in a positioning process. With respect to apparatus 4 of Fig. 2a, this positioning process would be performed by positioning processor 40.
Fig. 4b is a flowchart 500 of an embodiment of a method according to the present invention. This flowchart 500 may for instance be comprised as computer program 61 in tangible storage medium 60, which may in turn represent program memory 51 of apparatus 5 of Fig. 2b, so that flowchart 500 would then be executed by multi-purpose processor 50.
In a step 501 of flowchart 500, measurement data is received. With reference to apparatus 5 of Fig. 2b, this measurement data would be provided by magnetometer 54 to multi-purpose processor 50.
In a step 502, the magnetic signal is detected based on an analysis of the received measurement data. In the context of apparatus 5 of Fig. 2b, this would be performed by multi-purpose processor 50.
In a step 503, positioning process information is produced. In the context of apparatus 5 of Fig. 2b, this would also be performed by multi-purpose processor 50.
Producing identity information determined based on data measured to detect the detected magnetic signal, for instance by comparing measurement data from a magnetometer with reference data related to a magnetic signal source to determine a movement direction and/or step length of a user and/or to identify the magnetic signal source that produced the detected magnetic signal.
In a step 504, the produced positioning process information is used in a positioning process. In the context of apparatus 5 of Fig. 2b, this would also be performed by multi-purpose processor 50.
Fig. 6a is a flowchart 600 of an embodiment of a method according to the present invention. This flowchart 600 may for instance be implemented as computer program 61 of tangible storage medium 60 of Fig. 3, which in turn may represent program memory 71 of apparatus 7 of Fig. 5 and thus may be executed by processor 7.
Fig. 6b is a flowchart 700 of a further embodiment of a method according to the present invention. This flowchart 700 may for instance be implemented as computer program 61 of tangible storage medium 60 of Fig. 3, which in turn may represent program memory 71 of apparatus 7 of Fig. 5 and thus may be executed by processor 7.
In contrast to flowchart 600 of Fig. 6a, in the flowchart 700 of Fig. 6b, switching events received from switching units (such as for instance switching units 74 of apparatus 7 of Fig. 5) are used to trigger production of the magnetic signal.
An exemplary example of a switch-on event is a user entering a light barrier that is installed at the magnetic source. An exemplary example of a switch-off event is the user leaving the light barrier. The magnetic signal would then only be produced during the time when the light barrier is obstructed.
In the following, application of the present invention in the context of an indoor positioning system will be described as a non-limiting example. It should however be noted that the present invention is equally well applicable in outdoor positioning or in mixed outdoor/indoor scenarios.
Accordingly, Fig. 7 is a schematic illustration of an example of an indoor environment 8 in which such a hybrid positioning system can be deployed. The indoor environment comprises a large lecture hall 80, in which angle-based positioning works quite well, and a couple of adjacent corridors 81, where angle-based positioning does not work well, since the signals from the ceiling-mounted antenna arrays are obstructed. In these corridors 81, thus DR positioning is preferred. An example of angle-based positioning that may be applied here is direction of departure (DoD) positioning, where the device 3 acts as receiving unit that estimates the direction of departure of the signals transmitted from an antenna array that may for instance be mounted at a ceiling of lecture hall 80 (for instance to assure line-of-sight propagation towards the device 3) . The signals from the multiple antenna elements of this antenna array are not sent at the same time instant, but switched sequentially. The device 3 then knows the order in which the antenna elements have sent the signals, and - using knowledge on the antenna pattern of the antenna array - the direction of departure of the signals transmitted from the antenna array can be obtained. Based on this and on knowledge on the position of the antenna array, the position of the device 3 can be calculated at device 3.
The set of Helmholtz coils 9 comprises two coils 90 and 91, respectively, which are fed with the same current I (in the same sense of direction in each of the coils 90 and 91, as shown in Fig. 8) . In the present example, current I is a sine wave with a frequency of 40 Hz, to name but an example. Each coil 90 and 91 has a radius R, wherein the spacing between both coils 90 and 91 is also chosen to be equal to R. This has the effect that the magnetic flux density caused by the current flowing through the coils 90 and 91 is substantially uniform between the two coils 90 and 91. In Fig. 8, this magnetic flux density is, at least within the cylinder spanned around the x-axis by the radius R, parallel to the x-axis.
The magnitude of the magnetic flux density in the center region (near the x-axis) of the midplane between both coils 90 and 91 is then given as: B = 4 5 3 / 2 μ 0 nI R ,
Wherein µ 0 is the permeability constant (1.26 × 10-6 T m/A) and n is the number of turns of each coil 90 and 91.
For the Helmholtz coils 90, 91 used for the magnetic gates 82 in the transitions of environment 8 of Fig. 7, a radius (and distance) of R=0.2 m was used. Since the frequency of the sinusoidal current I flowing through the Helmholtz coils 90, 91 was chosen to be 40 Hz, it is noted that the wavelength associated with the 40 Hz frequency is λ=7.5 × 106 m, i.e. the dimensions (R=0.2 m) of the Helmholtz coils are very small compared to the wavelength λ, so that the Helmholtz coils 90, 91 do not act as an antenna. The magnetic field produces by the Helmholtz coils 90, 91 can thus be considered as a quasi-stationary field.
To finally obtain a magnetic gate 82 as deployed in the environment 8 of Fig. 7, the Helmholtz coils 90, 91 are further furnished with a microcontroller (corresponding to processor 70 of apparatus 7 of Fig. 5, e.g. Microchip PIC 16F690 flash-based 8-bit CMOS microcontroller), a power supply (e.g. a 4.5 V dry-cell battery), and a power amplifier (e.g. National Semiconductor LM4861 audio power amplifier with shutdown mode). The latter three components together can be considered to form the coils unit 73 of the apparatus 5 of Fig. 7. Furthermore, as switching unit (see unit 74 of apparatus 5 of Fig. 7), a light barrier is used, which is implemented by an infrared emitting diode positioned in the centre of coil 90 (e.g. Wishay TSAL6200 940 nm infrared diode) and an infrared receiver module (e.g. Wishay TSOP4838 IR receiver module) positioned in the centre of coil 91, so that the infrared emitting diode and the infrared receiver module face each other and form a light barrier. When this light barrier is interrupted, for instance by a user of the device passing the transition at which the magnetic gate 82 is mounted, the microcontroller then triggers production of the magnetic field by feeding a current into coils 90, 91 (see step 702 of the flowchart 700 of Fig. 6b). When the light barrier is no longer obstructed, production of the magnetic field is terminated (see step 704 of the flowchart 700 of Fig. 6b) . In the present embodiment, with the sinusoidal magnetic signal having a frequency of 40 Hz, the period of the magnetic signal is 25 ms. As long as the device/user is passing the light barrier slowly, detection of a single period of the magnetic signal at the device 3 is possible. If the speed of passing the light barrier increases so that the obstruction time of the light barrier is below 25 ms, proper detection of the magnetic signal at the device 3 may no longer possible. To combat this, the frequency of the magnetic signal may be increased, or the radius of the coils 90, 91 may be increased, or the mechanism that switched the production of the magnetic signal on and off may be modified, for instance by using two light barriers before and behind the magnetic gate 82 with a sufficiently large spacing to allow several periods of the magnetic signal to be produced even when the user/device quickly passes the magnetic gate 82.
Returning to the example of an environment 8 of Fig. 7, the magnetic gates 82 and the magnetic signals produced by them may be used in the positioning process (see step 402 of the flowchart 400 of Fig. 4a and step 505 of the flowchart of Fig. 4b) in different ways. For instance, the following non-limiting set of use-cases may be imagined:
The positioning process information o to be used in step 402 of the flowchart 400 of Fig. 4a and in step 504 of flowchart 500 of Fig. 4b may then for instance be the bare information that a magnetic signal has been detected at all (i.e. without any further information on this magnetic signal).
In one embodiment, the position of the magnetic gate 82 that produced the magnetic signal detected at the device 3 is included in the detected magnetic signal and then is considered as the current position of the device 3. The positioning process information to be used in step 402 of the flowchart 400 of Fig. 4a and in step 504 of flowchart 500 of Fig. 4b may then for instance be the position of the magnetic gate 82 only.
The positioning process information to be used in step 402 of the flowchart 400 of Fig. 4a and in step 504 of flowchart 500 of Fig. 4b may then for instance be the information on characteristics of the detected magnetic signal (e.g. its frequency, if different magnetic gates 82 are differentiated by different frequencies of their magnetic signals) or on the identifier included therein (if different magnetic gates 82 are differentiated by different identifiers in their respective magnetic signals) or on an magnetic gate identifier determined based on comparing measurement data against reference data.
The movement direction of the device (or its user) is used in the positioning process, for instance as information for a DR process. This movement direction can for instance be determined based on the data measured to detect the detected magnetic signal and on reference data related to the magnetic gate 82 that produced the detected magnetic signal. Alternatively, this movement direction can for instance be determined based on a detected direction of the magnetic flux density or field strength of the magnetic gate and an estimated movement direction of the device, both in the coordinate system of the magnetometer, and a known direction of the magnetic flux density or field strength in the coordinate system used by the positioning process.
Use-case C can of course be combined with any of use-cases A and B (or both) described above, but can equally well be applied solely.
In the following, the detection of the magnetic signal as performed by processor 441 of unit 44 of apparatus 4 of Fig. 2a and by multi-purpose processor 50 of apparatus 5 of Fig. 2b will be explained in more detail.
Fig. 9 is a diagram 10 with an example of data measured to detect a magnetic signal according to the present invention. Diagram 10 shows the magnetic field measured at device 3 (see Fig. 1) with a 3-axis magnetometer (see unit 440 of apparatus 4 of Fig. 2a and unit 54 of apparatus 5 of Fig. 2b) along the x-, y- and z-axis of a three-dimensional coordinate system when device 3 passes, during a period of 25 s, a magnetic gate 82 (see Fig. 7) that is embodied as described with reference to Fig. 8 above, i.e. is equipped with a light barrier that causes the magnetic gate 82 to produce a sinusoidal magnetic signal with a frequency of 40 Hz only when the light barrier is obstructed. Therein, the measurement curves are denoted by reference numeral 102 for the x-axis, 100 for the y-axis and 101 for the z-axis.
The curves 100-102 represent three vector components (x, y, z) of a 3-axis (triaxial) magnetometer. All of them exhibit a periodic pattern that is a result of changes in the magnetometer's alignment relative to the Earth's magnetic field. As a result of the walking movement, the angle between the Earth's magnetic field and the three axes of the magnetometer changes and thus, each of the magnetometer axes detects a varying magnetic field.
The magnetic signal can for instance be detected from the measurement curve 102, which represents the measurement data provided by the magnetometer 440 to processor 441 of apparatus 4 in Fig. 2b and by magnetometer 54 to multi-purpose processor 50 of apparatus 5 in Fig. 2b), by correlation with a replica of the magnetic signal transmitted by the magnetic gate 82, in this case a 40 Hz sinusoidal signal. Such a replica may be stored in a reference memory (such as memory 442 of apparatus 4 of Fig. 2a or main memory 52 of apparatus 5 of Fig. 2b), or may be generated on-the-fly.
Therein, diagrams 121 and 122 represent reference measurements (only with respect to one axis) that have been performed with respect to a specific magnetic gate as a basis for later comparison and have been stored in a reference memory (such as memory 442 of apparatus 4 of Fig. 2a or main memory 52 of apparatus 5 of Fig. 2b), for instance together with the respective movement direction and optionally further parameters such as an identification of the magnetic gate and/or the position of the magnetic gate and/or information on the magnetic signal produced by the magnetic gate (e.g. its frequency or modulation scheme) and/or information on the length to which the reference measurement pertains.
The comparison of measurement data comprising an actually detected magnetic signal and the reference data may either be performed in a way that first the magnetic gate 82 that produced the detected magnetic signal is determined (for instance based on characteristics of the magnetic signal, such as for instance its frequency, if different frequencies are used to differentiate between different magnetic gates 82, or based on an identifier comprised in the magnetic signal), and then comparing the detected magnetic signal with the reference data that is available for this magnetic gate 82. Equally well, a detected magnetic signal may be directly compared with the reference data of all magnetic gates 82. This may however be computationally more expensive. If the length of the reference measurement is known (for instance stored together with the reference data), a pattern matching approach can be used in a similar fashion to calibrate the user's step length for the traversed distance. To this end, in addition to the measured reference data for a magnetic gate (and the further information such as the walking direction during the reference measurement, etc.), the length of the collected measurement is stored as well, e.g. in meters. The reference data could then for instance represent a path starting at a pre-defined distance (e.g. 5 meters) before the gate and ending at a pre-defined distance (e.g. 5 meters) after the gate.
Since the length of the reference measurement in meters around the gate is known exactly, the step length of the person passing by the gate can be determined by analyzing the 'Doppler shift' between the actually measured signal and the reference signal when knowing the step occurrences (i.e. how many steps a user took when walking the path from the pre-defined distance before the gate to the pre-defined distance behind the gate).
As reference data for the identification of a magnetic gate, either several sets of data pertaining to measurements performed with respective different movement directions towards this gate, or only one set of data pertaining to a measurement with one movement direction towards this gate may be provided, whereas in the latter case, for instance movement-direction-dependent symetries may be exploited (for instance the fact that, if only two opposite movement directions are possible, such as for instance in a narrow floor, the two associated sets of reference data are mirrored versions of each other).
In Fig. 11, a user 132 (shown from above) is passing a magnetic gate that is formed by a pair of coils 130 and 131 and produces a magnetic flux density (or magnetic field strength) 134. The user is equipped with a device 133 that is to be positioned, and which comprises a magnetometer that uses a coordinate system 135, with x-axis 135-1 and y-axis 135-2 (for the sake of simplicity of presentation, only a two-dimensional coordinate system is shown here, whereas in practice, also a three-dimensional coordinate system could be applied) . This coordinate system 135 will be denoted as "sensor coordinate system" in the following.
As will be described in more detail below, device 133 is capable of estimating a movement direction of the user/device, which movement direction is indicated by arrow 137. This movement direction is however only available in the sensor coordinate system 135, which is decoupled from the coordinate system of the environment in which user 132 is to be positioned and which is used by the positioning process. This latter coordinate system will be termed "positioning coordinate system" in the following.
Device 133 is also capable of detecting at least the direction 136 of the magnetic flux density 134 produced by the coils 130 and 131, also in the sensor coordinate system 135, and to determine the angle ϕ 138 between the estimated movement direction 137 and the detected direction 134 of the magnetic flux density.
Now, if the direction of the magnetic flux density 134 is known in the positioning coordinate system, the estimated movement direction of the user/device can be transferred from the sensor coordinate system 135 to the positioning coordinate system by applying the angle ϕ 138 accordingly. This can be accomplished by storing the direction of the magnetic flux density 134 in the positioning coordinate system, for instance together with further information on the magnetic gate (such as for instance a position or identifier of the magnetic gate).
An approach to estimate the movement direction 137 of a user/device in the sensor coordinate system 135 can be derived from publication "Personal Positioning based on Walking Locomotion Analysis with Self-Contained Sensors and Wearable Camera" in Proceedings of the Second IEEE and ACM International Symposium on Mixed and Augmented Reality, 2003, Oct. 7-10, 2003, pages 103- 112.
(c) to circuits, such as a microprocessor (s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.
This definition of 'circuitry' applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a positioning device.
The invention has been described above by means of embodiments, which shall be understood to be non-limiting examples. In particular, it should be noted that there are alternative ways and variations of implementing the invention which are obvious to a skilled person in the art and can be implemented without deviating from the scope of the appended claims. It should also be understood that the sequence of all method steps presented above is not mandatory, also alternative sequences may be possible.
- using, in a positioning process, positioning process information that is at least one of information on a detected magnetic signal, information determined based an said detected magnetic signal and identity information determined based on data measured to detect said detected magnetic signal, said identity information identifying a magnetic signal source,
wherein said detected magnetic signal is produced by the magnetic signal source installed in an environment and detected at a device,
wherein said positioning process is for positioning said device in said environment, and
wherein said positioning process information used in the positioning process is at least said identity information and said identity information is used in said positioning process to trigger a switching between at least two different positioning modes.
The method according to claim 1, further comprising detecting said magnetic signal at said device.
The method according to any of the claims 1 or 2, wherein said data measured to detect said detected magnetic signal is measurement data obtained by measuring a magnetic characteristic over a period of time to detect said magnetic signal, and wherein said information determined based on said data measured to detect said detected magnetic signal is a movement direction of said device that is determined based on a comparison of said measurement data and reference data related to said magnetic signal source.
The method according to any of the claims 1-3, wherein said data measured to detect said detected magnetic signal is measurement data obtained by measuring a magnetic characteristic over a period of time to detect said magnetic signal, and wherein said information determined based on said data measured to detect said detected magnetic signal is an identification of said magnetic signal source that produced said detected magnetic signal, said identification being determined based on a comparison of said measurement data and reference data related to said magnetic signal source.
The method according to claim 4, further comprising determining said identification.
The method according to any of the claims 1-5, wherein said magnetic signal comprises a direction of a magnetic flux density or of a magnetic field strength produced by said magnetic signal source, wherein said detected magnetic signal comprises a detected direction of said magnetic flux density or of said magnetic field strength, and wherein said positioning process information is a movement direction of said device in said environment determined based on an estimated movement direction of said device in a sensor coordinate system relative to said detected direction in said sensor coordinate system and an knowledge on an absolute direction of said magnetic flux density or said magnetic field strength in said environment.
The method according to claim 6, further comprising determining said movement direction of said device in said environment.
The method according to any of the claims 1-7, wherein said positioning process information is used in said positioning process to associate said detected magnetic signal with a position of said magnetic signal source that produced said detected magnetic signal, so that a position of said device is determinable at least partially based an said position of said magnetic signal source.
The method according to claim 8, wherein at least two magnetic signal sources are installed in said environment, wherein said at least two magnetic signal sources are configured to produce different magnetic signals, respectively, and wherein said positioning process is capable of differentiating between said different magnetic signals when associating said detected magnetic signal with said position of said magnetic signal source that produced said detected magnetic signal, wherein said magnetic signal comprises a magnitude and/or a direction of a magnetic flux density or of a magnetic field strength.
The method according to any of the claims 1-9,
wherein one of said at least two different positioning modes is based on dead reckoning, and/or one of the at least two different positioning modes is angle-based positioning or a GNSS based positioning mode.
The method according to any of the claims 1-10, wherein said magnetic signal source comprises a pair of Helmholtz coils.
- program code for performing the method according to at least one of the claims 1-11, when said computer program is executed on a processor.
- means for using, in a positioning process, positioning process information that is at least one of information on a detected magnetic signal, information determined based on said detected magnetic signal and identity information determined based on data measured to detect said detected magnetic signal, said identity information identifying a magnetic signal source,
wherein said detected magnetic signal is produced by the magnetic signal source installed in an environment and detected at a device, wherein said positioning process is for positioning said device in said environment, and
wherein said positioning process information used in the positioning process is at least said identity information and said
identity information is used in said positioning process to trigger a switching between at least two different positioning modes.
The apparatus according to claim 13, further configured to perform the method of at least one of the claims 2-11.
- at least one apparatus according to any of the claims 13 or 14, and
- at least one magnetic signal source installed in the environment and comprising means for producing the magnetic signal.
EP09851744.4A 2009-11-24 2009-11-24 Positioning a device relative to a magnetic signal source Active EP2504662B1 (en)
EP2504662A1 EP2504662A1 (en) 2012-10-03
EP2504662A4 EP2504662A4 (en) 2017-07-12
EP2504662B1 true EP2504662B1 (en) 2018-11-21
EP09851744.4A Active EP2504662B1 (en) 2009-11-24 2009-11-24 Positioning a device relative to a magnetic signal source
ES (1) ES2710624T3 (en)
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2009-11-24 EP EP09851744.4A patent/EP2504662B1/en active Active
2009-11-24 CN CN200980163344.1A patent/CN102741653B/en active IP Right Grant
2009-11-24 US US13/511,362 patent/US20120232838A1/en not_active Abandoned
2009-11-24 WO PCT/US2009/006293 patent/WO2011065931A1/en active Application Filing
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US20120232838A1 (en) 2012-09-13
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WO2011065931A1 (en) 2011-06-03
ES2710624T3 (en) 2019-04-26
CN104296750B (en) 2017-05-03 Zero speed detecting method, zero speed detecting device, and pedestrian navigation method as well as pedestrian navigation system
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