EP3092507A1

EP3092507A1 - System and method for locating an object

Info

Publication number: EP3092507A1
Application number: EP15700847.5A
Authority: EP
Inventors: Matthieu MUTZ; Stéphane Mutz
Original assignee: Blinksight
Current assignee: Blinksight
Priority date: 2014-01-06
Filing date: 2015-01-06
Publication date: 2016-11-16
Also published as: WO2015101674A1; US10698074B2; US20160327630A1; FR3016220B1; FR3016220A1

Abstract

The present invention relates to a system for locating a mobile element, characterized in that it comprises: - at least one beacon (1) emitting radio messages; - at least one relay (2) capable of emitting a second message with a known lag following the receipt of a first message originating from said at least one beacon (1); - at least one sensor (3) capable of measuring in a local time base the instants of arrival of the messages originating from said at least one beacon (1) and at least one relay (2); - at least one position computer, that can be central or onboard each sensor, capable of determining the position of a mobile element on the basis of the arrival time information; the mobile element being able to be a beacon (1), a relay (2) or a sensor (3).

Description

SYSTEM AND METHOD FOR LOCATING AN OBJECT

GENERAL TECHNICAL FIELD

The context of this invention is that of the location of a mobile object within an area covered by an ad hoc infrastructure. Of particular interest here are applications requiring the precise localization of an object within an enclosure or a covered building or an open-air site delimited by an enclosure.

Indeed, while GPS or mobile phone networks nowadays make it possible to know easily and with a relatively satisfactory accuracy the position of objects on a planetary scale or a very wide geographical area, the use of these technologies are not appropriate for location inside a building or at the scale of a delimited industrial site.

We are particularly interested in a solution that combines a small footprint (size, weight), good location accuracy, and minimal energy consumption.

STATE OF THE ART

Mobile telephone systems, such as those known from documents US-A-2009/061899, US-A-2012/208523, WO 2010/123291 and US-A-7 738 836, certainly allow an outside location. of a building, but with a precision of the order of 50 to 100 meters, which is insufficient to locate an object inside a building or enclosure.

WO 99/49333 discloses a system employing Ultra Wide Band radio frequency pulse modulation techniques.

The authors of WO 99/49333 provide a solution for knowing the position of an object using time-of-flight measurements of an Ultra Wide Band radio pulse train.

In a first implementation, the authors of WO 99/49333 describe a system employing a so-called active receiver associated with the object whose position is desired, which responds to a request from an ultra-wideband pulse transmitter by retransmitting itself a series of pulses. The transmitter then determines the distance between itself and the receiver by first measuring the time delay of the signal retransmitted by the receiver relative to the initially transmitted signal. This first implementation has the defect of requiring a response from the receiver, so an additional complexity of the latter. The use of the ultra wideband radio channel is also extended.

The authors of WO 99/49333 also present a second implementation, called passive receiver, in which a single exchange is necessary and where we are interested in the instant of reception by the receiver of a pulse train transmitted at a time known by the transmitter. As stated by the authors, this solution has the major disadvantage of requiring the existence of a common time base between the transmitter and the receiver.

Also included in the description of the IEEE 802.15.4a standard, in particular in the appendices Dl .3.1, Dl .3.2 and D1.4, references to location systems. The latter implement distance measurement techniques by estimating the round trip time between two devices, as presented in WO 99/49333, or TDOA multilateration by measuring the difference in arrival time of the same device. radio message to a plurality of receivers.

Direct flight time measurement systems as presented in WO 99/49333 or in Annexes Dl .3.1 and Dl .3.2 of the IEEE 802.15.4a standard, require the use of transceivers at each end of the IEEE 802.15.4a standard. link. The complexity and the cost of the location function and the amount of energy consumed are thus increased.

TDOA systems overcome this constraint, but pose the problem of fine synchronization of receiver timebases to achieve satisfactory accuracy. For example, to achieve a location measurement accuracy of 10 cm, the basics of Several receivers must be maintained at all times in phase with a precision of the order of 100 ps. Such a synchronization is in practice difficult to achieve and requires for example the use of controlled distribution devices of a common clock to all receivers TDOA system, for example in the form of a wired network.

In order to propose a solution more adapted to the problematic posed, one looks for a system and a process which is able to locate an object inside an enclosure with a precision of localization of the order of 10 cm. In addition, it is sought to obtain a system that minimizes the implementation complexity, which minimizes the number of radio exchanges required, which does not have the synchronization and / or clock distribution constraints of the TDOA systems and which is the most versatile possible.

PRESENTATION OF THE INVENTION

The present invention relates to a system for locating a mobile element characterized in that it comprises:

. at least one beacon transmitting radio messages;

. at least one relay capable of transmitting a second message with a known delay following receipt of a first message from said at least one beacon;

. at least one sensor capable of measuring in its own time base the arrival times of the messages from said at least one beacon and at least one relay;

. at least one position calculator, which can be central or on board with each sensor, capable of determining the position of a mobile from the arrival time information;

the mobile element can be a beacon, a relay or a sensor.

The invention makes it possible to measure the difference in arrival time between a direct path of a beacon to a sensor and one or more indirect paths involving re-transmission with a known delay by one or more relays. By its operating principle, this invention operates in a similar way to that of a TDOA system but does not require a fine alignment of the time bases of several sensors since only one time base is used to perform the measurements of different times. arrival at the same sensor.

Compared to direct flight time measurement systems, the present invention has a reduced complexity of the beacon that requires the use of a transmitter only, and the target that requires the use of a receiver only. For each of these two elements, the complexity is reduced, as well as the necessary expenditure in energy.

Finally, the present invention allows great flexibility and is also suitable for the case where one seeks to locate an object, for example to determine the position of a pallet in a warehouse.

According to other advantageous and nonlimiting features of the invention:

. the location system comprises a central sequencer having a radio transmitter and each beacon contains a radio receiver adapted to receive messages transmitted by said central sequencer.

. the locating system comprises a plurality of sensors all connected by a telecommunication means to a position calculator.

. the telecommunication means is for example wired Ethernet or WI-FI type and the position calculator is a computer server.

According to a second aspect, the invention relates to a method for locating a mobile element, characterized in that it comprises steps of:

(a) Transmitting by at least one beacon of a message Ml;

(b) Receiving said message M1 by at least one relay and sending a message M2 with a known delay with respect to receiving the message M1 by said at least one relay;

(c) Receiving said messages M1 and M2 by at least one sensor and

(d) Determining the position of a mobile carrying the beacon, the relay or the sensor, from the arrival time information. According to other advantageous and nonlimiting features of the invention:

. the message M l emitted in step (a) by a tag includes in its data the identification of the tag.

. the message M l emitted in step (a) comprises a time marker for identifying the transmission time in the time base of the beacon and / or the time of reception of the message in the time base of the relay or of the sensor. This marker may for example be a start of packet delimiter or a specific bit in a packet header.

. the message M2 emitted in step (b) by a relay includes in its data the identification of the relay as well as that of the beacon whose message M1 has triggered the message M2 for this relay.

. the message M2 emitted in step (b) by a relay includes a time marker for identifying the transmission time in the time base of the relay and / or the time of reception of the message in the time base of the sensor . This marker may for example be a start of packet delimiter or a specific bit in a packet header.

. the delay between receiving a message M l emitted in step (a) and sending a message M2 emitted in step (b) by a relay is of the same order of magnitude as the processing time messages M l or M2.

The invention also relates to beacons, relays and sensors, as such, involved in the implementation of the system and / or process mentioned above.

PRESENTATION OF FIGURES

Other features and advantages of the present invention will appear on reading the following description of a preferred embodiment. This description will be given with reference to the appended drawings in which: Figure 1 is a diagram of a first embodiment of the invention having a fixed beacon, a fixed relay and a mobile sensor;

FIG. 2 is a diagram of a second embodiment of the invention having several fixed beacons, a fixed relay and a mobile sensor;

FIG. 3 is a diagram of a message transmitted by a beacon according to one embodiment of the invention;

FIG. 4 is a message transmission and reception diagram implemented by a location system according to the first embodiment of the invention;

FIG. 5 is a diagram of a message transmitted by a relay according to one embodiment of the invention;

FIG. 6 is a message transmission and reception diagram according to one embodiment of the invention making it possible to avoid collisions between the beacon and relay messages, and

FIG. 7 is a diagram of a third embodiment of the invention having several fixed beacons, a fixed relay and a mobile sensor, synchronized by a central sequencer, in particular to ensure time multiplexing,

FIG. 8 is a diagram of an Ultra Wide Band pulse transmitter according to an embodiment of the invention,

FIG. 9 is a diagram of an Ultra Wide Band pulse receiver according to an embodiment of the invention,

FIG. 10 is a diagram of an Ultra Wide Band pulse-transceiver according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

According to one embodiment of the invention, there is provided a system for locating a mobile element inside an enclosure, characterized in that it comprises: at least one beacon (1, 11, 12, 13) capable of transmitting at least a first radio message (M l, M il, M 12, M 13) inside the enclosure;

at least one relay (2, 21, 22) capable of transmitting a second message (M2, M21, M22) inside the enclosure with a known delay (D) following the reception of the first message (M 1, M il, M 12, M 13) from said at least one beacon (1, 11, 12, 13);

at least one sensor (3) capable of measuring in a local time base the arrival times of the messages coming from said at least one beacon (1, 11, 12, 13) and at least one relay (2, 21, 22); ) inside the enclosure;

at least one position calculator (5) capable of determining the position of a movable element, which is one of the beacon (1, 11, 12, 13), the relay (2, 21, 22) and the sensor (3), from at least arrival time information and positions, known by the computer (5), from the other of the beacon (1, 11, 12, 13), the relay (2, 21 , 22) and the sensor (3);

the beacon having at least one ultra-wideband radio pulse transmitter for transmitting the first message (Ml, M il, M 12, M 13), the relay having at least one ultra-wideband radio pulse receiver for receiving the first message ( M l, M il, M 12, M 13) and an Ultra Wide Band radio pulse transmitter for transmitting the second message (M2, M21, M22),

the sensor having at least one Ultra Wide Band pulse type radio receiver for receiving the first message (M1, M11, M12, M13) and the second message (M2, M21, M22).

Thanks to the invention, a strong temporal accuracy is obtained for measuring the times inside an enclosure. This temporal accuracy can be of the order of 100 ps or less. Thus, the location accuracy of the movable element inside an enclosure may be a few centimeters, for example 10 cm or less than 10 cm, or a much better accuracy than mobile phone systems providing a location accuracy greater than 10 meters.

Indeed, mobile telephone systems, such as those known from the aforementioned documents US-A-2009/061899, US-A-2012/208523, WO 2010/123291 and US-A-7 738 836, show frames and subframes with a width of about 10 MHz.

On the contrary, the communication mode involving, according to the embodiment indicated above, a beacon, a relay and a sensor having Ultra Wide Band pulse transmitters and receivers makes it possible both to obtain a higher bandwidth. or equal to 500 MHz, so that the dimensional accuracy of location is less than or equal to 10 cm, for example greater than or equal to 3 cm and less than or equal to 10 cm.

In addition, compared to systems of the state of the art, the invention overcomes the need for complicated clock synchronization to be implemented between several sensors or base stations. Thus, the invention requires fewer sensors and fewer base stations than the state of the art, especially with respect to systems where the messages transmitted by a mobile transmitter must be received by two or three base stations that determine the location. of the issuer. Thanks to the invention, the relay does not need a high clock accuracy. For example, if the delay D is equal to 1 ms, a clock precision of 0.1 ppm of the relay can introduce less than 100 ps of measurement error.

The enclosure may be a closed or delimited or fenced enclosure. The enclosure may be a building, for example a covered building, or a building bounded by walls and a roof. The enclosure can be a warehouse or a store. The enclosure may be an open-air site, bounded horizontally by a physical boundary. The enclosure may be an outdoor facility on a defined geographical area, such as a stadium, a station, an airport, a subway station or an underground transport station or an underground site. The enclosure may be an industrial site or a factory. According to the invention, the movable element is one of the beacon, the relay and the sensor.

According to one embodiment of the invention, the mobile element is the beacon or an object carrying the beacon.

According to one embodiment of the invention, the mobile element is the relay or an object carrying the relay.

According to one embodiment of the invention, the movable element is the sensor or an object carrying the sensor.

According to one embodiment of the invention, the system for locating a mobile element inside an enclosure comprises a central sequencer (4) having a radio transmitter and each beacon (1, 11, 12, 13) contains a radio receiver adapted to receive messages transmitted by said central sequencer.

According to one embodiment of the invention, the system for locating a mobile element inside an enclosure comprises several sensors (3) all connected by a telecommunication means to the remote position calculator.

According to one embodiment of the invention, the telecommunication means is FiiFi Ethernet or WI-FI and the position calculator is a computer server.

According to one embodiment of the invention, the computer (5) can be central and remote from each sensor.

According to one embodiment of the invention, the computer (5) is embedded on the sensor.

According to one embodiment of the invention, said delay (D) is known by the position calculator (5), which is able to determine the position of the mobile element from at least said delay (Di- Next a mode embodiment of the invention, there is provided a method for locating a movable element inside an enclosure, characterized in that it comprises steps of:

(a) Emitting by at least one beacon (1, 11, 12, 13) of at least one first message (M l, M il, M12, M 13) inside the enclosure; (b) Reception of said first message (Ml, M il, M 12, M 13) by at least one relay (2, 21, 22) inside the enclosure and transmission, inside the enclosure a second message (M2, M21, M22) with a known delay (D) with respect to the reception of the first message (M1, M11, M12, M13) by said at least one relay (2, 21, 22 );

(c) Reception, within the enclosure, of said messages (M1, M1, M12, M13, M2, M21, M22) by at least one sensor (3) and measures, in a timebase local arrival times messages from said at least one beacon (1, 11, 12, 13) and at least one relay (2, 21, 22) within the enclosure;

(d) determining, by a position calculator (5), the position of the mobile element carrying the beacon, the relay or the sensor, starting from at least the arrival time information and the positions known by the calculator (5), others among the beacon (1, 11, 12, 13), the relay (2, 21, 22) and the sensor (3),

According to one embodiment of the invention, the first message

(M l, M il, M 12, M 13) transmitted in step (a) comprises a time marker for identifying the transmission time in the time base of the beacon and / or the instant of reception the first message (Ml, M il, M 12, M 13) in the time base of the relay or the sensor.

According to one embodiment of the invention, the second message

(M2, M21, M22) transmitted in step (b) comprises a time marker for identifying the transmission instant of the second message (M2, M21, M22) in the time base of the relay and / or the moment of receipt of second message (M2, M21, M22) in the time base of the sensor and / or the delay between the instant of reception of the first message (M l, M il, M 12, M 13) and the instant of emission of the second message (M2, M21, M22) in the relay's own timebase.

According to one embodiment of the invention, the marker present in the messages (Ml, M il, M 12, M 13) transmitted in step (a) and / or the marker present in the messages (M2, M21, M22 ) issued in step (b) is a particular field of the message. For example, it may be a field defining the end of a synchronization header or a specific bit of a packet header.

According to one embodiment of the invention, the first message (M 1, M 1, M 12, M 13) transmitted in step (a) by the beacon includes in its data the identification of the beacon.

According to one embodiment of the invention, the second message (M2, M21, M22) transmitted in step (b) by the relay includes in its data the identification of the relay and that of the tag that triggered the retransmission.

According to one embodiment of the invention, the delay (D) between the reception of the first message (M l, M il, M 12, M 13) transmitted in step (a) and the transmission of the second message ( M2, M21, M22) transmitted in step (b) by the relay is at least equal to the processing time of the first and / or second message, and as much as possible of the same order of magnitude as the processing time of the first and / or second message and / or second message.

According to one embodiment of the invention, said delay (D) is known by the position calculator (5), which is capable of determining the position of the movable element from at least said delay (D). For example, the delay (D) is programmed in the computer (5) or determined during an initial calibration phase.

According to one embodiment of the invention, there is provided a radio message transmission beacon for implementing the system as described above and / or the method as described above, characterized in that the tag has at least one Ultra Wide Pulse radio transmitter Band (100) for periodically sending a message (Ml, M il, M 12, M 13) comprising a time marker for identifying the transmission time in a time base of the beacon.

According to one embodiment of the invention, there is provided a relay for receiving and transmitting radio messages for implementing the system as described above and / or the method as described above, characterized in that it comprises:

at least one ultra-wide band radio pulse receiver (200) for receiving a first message (Ml, M il, M 12, M 13) from a beacon and comprising a time marker making it possible to precisely identify the instant of reception of the message (M l, M il, M 12, M 13) by said ultra wide band radio pulse receiver,

at least one Ultra Wide Band radio transmitter (100) for transmitting the second message (M2, M21, M22) comprising in its data the first message (M l, M il, M 12, M 13) and comprising a marker time for identifying the instant of transmission of the second message (M2, M21, M22) in a relay time base,

the delay between the reception of the first message (M 1, M 1 1, M 12, M 13) and the transmission of the second message (M2, M21, M22) being known to a certain extent in a timebase of the relay.

According to one embodiment of the invention, there is provided a radio message reception sensor for implementing the system as described above and / or the method as described above, characterized in that it comprises :

at least one ultra wide band pulse type radio receiver (200) for receiving a first message (M l, M il, M 12, M 13) transmitted from a beacon and a second message (M2, M21, M22) issued from a relay, and

a unit for measuring, in a local time base, the arrival times of the first message (M l, M il, M 12, M 13) coming from the beacon and / or the second message (M2, M21, M22); ) from the relay. As represented in FIGS. 1 and 2, the invention comprises one or more beacons 1, 11, 12 or 13. Each beacon 1, 11, 12 or 13 consists of at least one ultra-wide band radio pulse transmitter. adapted to transmit a first message M l, Mi l, M 12 or M 13.

The invention further comprises one or more relays 2, 21 or 22.

Each relay comprises at least one ultra-wide band radio pulse receiver, an ultra wide band radio pulse transmitter and a device for triggering the transmission of a second radio message M2, M21 or M22 with a delay D predetermined by report at the instant of reception of the first message M l, M il, M 12 or M 13 by the receiver.

The invention comprises at least one sensor 3 which captures the first message M 1, M 1, M 12 or M 13 and the second message M2, M21 or M22. Each sensor 3 is equipped with at least one ultra-wide band pulse radio receiver, a local time base and a device for measuring, according to the local time base, the arrival times of the messages M 1. , Mi1, M12, M13 and / or M2, M21, M22.

Finally, the invention further comprises one or more position calculation devices 5, diagrammatically in FIGS. 1 and 2. From the data contained in the messages M1, M1, M12 or M13 and M2, M21 or M22. , measured arrival times and data known to be known on the position of the beacons and / or the relays and / or the sensors, a calculator makes it possible to provide an estimate of the position of the mobile to be located, said mobile being able to be a beacon, a relay or a sensor.

Each beacon 1, 11, 12 or 13 transmits, via its radio transmitter, a first radio message M l, M il, M 12 or M 13, represented in FIG. 3, comprising among others a time marker allowing a receiver adapted to accurately determine the instant of reception of said marker in the message M l, M il, M 12 or M 13 in a local time base to the receiver when it is received. The message M l, M il, M12 or M 13 may further contain for example a data area containing an identifier making it possible to uniquely determine the identity of the beacon 1, 11, 12 or 13 having transmitted the message Ml, M il, M 12 or M 13.

In what follows, the term "measuring the moment of arrival of the radio message" is used to measure the time, in a local time base, of the device concerned, of the exact moment of reception of the marker contained in the message. received radio message.

In the embodiment shown in FIG. 4, the message M 1 transmitted by a beacon 1 at a time t 0 is assumed.

The message M l is received by a sensor 3 with a delay T _B c linked to the flight time of the radio waves between the beacon 1 and the sensor 3. The sensor then measures the instant of arrival t 1 of this message M 1 in its own time base.

Almost simultaneously, the message M l emitted by the beacon 1 is also received by a relay 2 with a delay T _BR linked to the flight time of the radio waves from the beacon 1 to the relay 2. The message M 1 is received by relay 2 at time t2. This reception will then trigger the transmission by relay 2 of a second message M2 after a known delay D with respect to the instant t2 of receiving the message M1 by relay 2. The message M2 comprises among others a time marker to accurately determine the reception time by a receiver. It may also comprise a data zone containing, for example, a first identifier making it possible to uniquely determine the identity of the beacon 1 having sent the first message M1 at the origin of this second message M2, and / or a second identifier to uniquely determine the identity of relay 2, as shown in FIG.

In particular embodiments of the invention, the message M2 may further comprise information characterizing the time t 2 for receiving the message M 1 in the time base specific to the relay 2 and / or information characterizing the delay D.

The delay D is thus specified so that the marker present in the message M2 emitted by the radio transmitter of the relay 2 is emitted exactly with a delay D with respect to the reception by the receiver Relay radio 2 of the marker present in the message M l. The delay D is expressed relative to the local time base of the relay.

The message M2 is received by the sensor 3 with a delay T _RC linked to the flight time of the radio waves from the relay 2 to the sensor 3. The latter determines the time of reception t3 by its radio receiver in its own time base.

If we omit a possible frequency offset of the time bases of the relay 2 and the sensor 3, we obtain the following equation:

t3 - tl = T _BR + D + T _RC - T _BC

The delay D is chosen so that it is greater than the maximum flight time of the radio waves from the beacon 1 to the sensor 3 or from the beacon 1 to the relay 2.

The delay D is for example of the same order of magnitude as the duration of reading, writing and transmission messages M l and M2.

In a particular embodiment of the invention given here by way of example in FIG. 4, the duration of the first message M 1 is, for example, 0.6 ms, that of the second message M2 is 1 ms and the duration D is also 1 ms. In this same embodiment, the maximum range achievable by a radio communication is 60 meters and the maximum measurable flight time is 200 ns.

The contribution of relay 2 to the arrival time difference measurement error t3 - t1 is essentially in the delay D. It is not necessary for the time base of relay 2 to be perfectly in phase at every moment with that of the beacon 1 or the sensor 3. It is relatively easy to obtain an accuracy of 100 ps over a delay D of 1 ms, which limits the relative contribution of the relay 2 to a position error of 3 cm.

As a result of receiving a first message M 1 and a second message M2, a sensor 3 forms, for each first message M 1 followed by a second message M 2, a pair (t 1, t 3) describing the times of respective arrival of the first message M l and the second message M2 in its local time base. Where appropriate, these pairs can be increased to include the identity of beacon 1 and / or that of relay 2, for example as a quadruplet (1; 2; tl; t3).

In addition, if the message M2 contains the information t2 characterizing the instant of receipt of the message M l by the relay 2 according to its own time base, this information t2 may also be retained by the sensor 3, for example in the form of triplets (t1; t2; t3) or quintuplets (1; 2; tl; t2; t3).

This information, for example the pairs (t1; t3), the triplets (t1; t2; t3), the quadruplets (1; 2; tl; t3) or the quintuplets (1; 2; t1; t2; t3) are transmitted to a position calculation unit 5. This uses among other things the times t1 and t3, the knowledge of the delay D, as well as known parameters known to the system for estimating the position of a mobile. For example, if the position of the beacons 1, 1 1, 12, 13 and relays 2, 21, 22 is known to the system, the position calculator will use the knowledge of the respective positions of the beacons 1, 1 1, 12, 13 and relays 2, 21, 22 to determine the location of the sensors 3, this case corresponding to the embodiment where the movable element is the sensor or an object bearing the sensor. The calculations performed in the position calculation unit 5 are similar to those performed in a similar unit of a TDOA type system.

If several relays 2 are within range of the same beacon 1, they can each transmit a message M2 consecutively upon receipt of the message M l. Assuming that the sensor 3 is itself within reception range of this plurality of relays 2, it will receive multiple messages M2 and capture a plurality of arrival times t3. It will therefore transmit a plurality of information, for example quintuplets (1; 2; t1; t2; t3), to the position calculator 5, the identity of the relays 2 and the times t2 and t3 being different for each such quintuplet .

To allow for a simple implementation, an Ultra Wide Band Pulse radio receiver such as that integrated in Relay 2 or Sensor 3 is generally capable of receiving a single radio that time. It is important for the optimal operation of the invention to ensure proper sequencing of operations.

In the case where there are in the same system several beacons 1, 11, 12 or 13 within the communication range of the same relay 2 or the same sensor 3, it is suggested to guarantee that the messages M 1 emitted by each beacon 1, 11, 12 or 13 do not collide with each other.

For example, a Time Division Multiplex Access (TDMA) method can be implemented.

In the embodiment of which the diagram is exposed FIG.

6 and the general diagram is illustrated in FIG. 7, a central sequencer 4 is added to the system in order to avoid collisions between the different messages. This central sequencer 4 has a radio transmitter, which may be other than Ultra Wide Band radio pulse. Each beacon 11, 12 and 13 also then contains a radio receiver able to receive messages from the global sequencer 4. In the case where there are several relays 21 and 22 within the same system, as explained in FIG. it is suggested to ensure that messages M21 and M22 do not collide with each other.

For example, a different delay D may be assigned statically or dynamically to each relay 21 and 22 of the system so that, if several relays 21 and 22 receive the same message M11, M12 or M13, each message M21 and M22 can be transmitted in turn. In this case, the relay 2, 21, 22 can communicate the delay D used in the data area of the message M2.

In another implementation of the invention, it can be ensured that a single relay 21 or 22 has its receiver turned on at a given instant, for example using a TDMA type system as described above. This ensures that a single message M21 or M22 is transmitted following a message Mi l, M 12 or M 13.

In a particular embodiment of the invention, one is interested in the location of a mobile element in a building or a speaker. For example, we want to locate a vehicle or mobile terminal in a warehouse.

According to this embodiment, the coverage area is equipped with at least one beacon 1 whose position is assumed to be known and at least one relay 2 whose position is also assumed to be known.

Since the position of the beacons 1 and the relays 2 is known, the flight time of a beacon 1 to a relay 2 is therefore also assumed to be known. For example, the latter can be determined by calculation from the positions of the beacon and relay or determined empirically.

The sensor 3 is here associated with a moving object whose position in the building or an enclosure is to be determined. For example, the sensor 3 is integrated with a vehicle or a mobile terminal whose position in the building or the enclosure is to be determined.

The sensor 3 is assumed within communication range of the beacons 1 and the relays 2. Several moving objects all equipped with a sensor 3 can be in the coverage area, the following description is then generalized for each sensor 3 in the system. .

According to this mode of implementation and the general operating principle of the invention, each beacon 1 in turn transmits a radio message M 1 containing at least one single position marker. The message M 1 may further include an identifier for uniquely determining the identity of the tag 1.

Each message M l emitted by a beacon 1 is sensed almost simultaneously with the difference in flight time by a sensor 3, which measures the time t1 of receiving the message M 1 in its own time base, and by a relay 2. The relay 2 then transmits with a delay D a second message M2 containing at least one unique marker position. The message M2 may furthermore contain in a data zone a first identifier making it possible to uniquely determine the identity of the tag 1 having transmitted the first message M1 at the origin of the second message M2, and / or a second identifier for uniquely determining the identity of the relay 2 transmitting the second message M2. There may be several relays 2. Each message M2 is picked up by the sensor 3 which determines the time of reception t3 by its receiver in its local time base. The sensor 3 then forms, for each message M 1 followed by a message M2, a pair (t 1, t 3) describing the respective arrival times of the first message M 1 and the second message M 2 in its local time base. If necessary, these pairs can be increased to include the identity of the beacon 1 and / or that of the relay 2, for example in the form of a quadruplet (1; 2; tl; t3).

According to this mode of implementation of the invention, the mobile can also embark a position calculation unit 5. The pairs (t1; t3) or the quadruplets (1; 2; t1; t3) are communicated from the sensor 3 to the position calculation unit 5.

For each pair of first message M 1 followed by a second message M2 received by a sensor 3 from a beacon 1 via a relay 2, the position calculation unit 5 knows an estimate of the time t1 of arrival of first message M l to the sensor 3, an estimate of the time t3 of arrival of the second message M2 to the sensor 3, the position of the beacon 1, the position of the relay 2, an estimation of the flight time of the message M l from 1 to 2 and an estimate of the response time D of relay 2.

According to this mode of operation, the measurements t1 and t3 can thus be connected to two unknowns: d (l, 3) the distance from the beacon 1 to the sensor 3, and d (2, 3) the distance from the relay 2 to the sensor 3 If we consider the measurements associated with several beacons 1 for the same sensor 3 and the same relay 2, the position calculation unit 5 can then determine an estimate of the position of the mobile associated with the sensor 3.

For example and without losing in genericity, we present here the case shown in Figure 2 of the location in the plane of a moving object associated with a sensor 3 of unknown position (x; y) from three position markers 11 (xl; yl), 12 position (x2; y2) and 13 position (x3; y3) and a single position relay 2 (0; 0) in any orthonormal frame. The beacon 11 transmits a message Mil received at a time t11 by the sensor 3 and relayed by the relay 2 in a message M21 and received at a time t13 by the sensor 3. Similarly, the beacon 12 transmits an M12 message received at a moment t21 by the sensor 3 and relayed by the relay 2 into a message M22 received by the sensor 3 at a time t23. Finally, the beacon 13 transmits a message M13 received at a time t31 by the sensor 3 and relayed by the relay 2 into a message M23 received by the sensor 3 at a time t33.

For more legibility in the calculations, we will name the tags 11, 12 and

13 respectively Bl, B2 and B3 or Bi, with i = 1, 2 or 3. Relay 2 will be named R and the sensor marked 3 in Figure 2 will be called C.

The distance d (Bi, R), for i integer between 1 and 3, between Bi and R is assumed to be known. Likewise, the flight time T _BI R between Bi and R is known for example by construction or by empirical measurement.

So :

d (Bi, R) = xi ² + yi ² = c. T _BiR

We can write in a similar way:

d (Bi, C = - xi) ² + (y - yi) ² = c. T _BiC

We then

d (Bl, R) d (R, C) d (B1, C)

tl3 -tll = + D +

CC

d (B2, R) d (R, C) d (B2, C)

t23 - t21 = + D +

c c c

d (B3, R) d (R, C) d (B3, C)

t33 - t31 = + D +

CC

We then ask:

Or, after substitution:

By moving into quadratic form and reorganizing it comes

Proceeding by successive differences, we can then eliminate the terms in square root:

x.2.x2 + y.2.y2- x2 ² - y2 ² x.2.xl + y.2.yl- xl ² - 0 = c.Atl - c.At2 - - +

c.At2 c.Atl

x, 2.x3 + y.2.y3- x3 ² - y3 ² x.2.xl + y.2.yl- xl ² - yl ²

0 = c.Atl - c.At - c.At3 c.Atl

It comes then that (x; y) is a solution of:

A system of equations for a larger number of degrees of freedom or for a larger number of beacons can also be derived similarly.

Similarly, we can generalize the previous example in the case of the re-transmission of messages of one or more tags by several relays.

It is then easy to solve such a system of equations by analytical methods or by more robust numerical methods.

In a variant of the present embodiment of the invention, it is possible for example to replace the preceding linearization by the use of an EKF or UKF type Kalman filter capable of solving a nonlinear equation system. In another embodiment of the invention, the mobile element is the tag or an object bearing the tag.

For example, one is interested in the location of an object, which can be an article of a store, which can be other than a telephone, in a building or an enclosure. For example, and without losing in generality, the aim here is to locate a pallet in a warehouse in order to know its location on a plane.

Each object to locate has a tag. For example, the tag is in the form of an active tag attached to the object of interest. Each beacon 1 periodically sends a first message M l. Each beacon therefore includes, in addition to its ultra wide band pulse radio transmitter, a local time base. For example, a tag 1 may be configured to issue a message M 1 twice a second.

In this embodiment, the message M 1 comprises, in addition to the time stamp for determining the instant of reception, a data zone containing an identifier for uniquely determining the identity of the tag 1 and information allowing to determine the time t0 transmission of the message M l in a time base local to the tag 1.

The coverage area, for example the warehouse in the illustration given above, is equipped with at least one relay 2 of known position. More precisely, as many relays are installed as necessary to allow each beacon 1 to be within communication range of at least as many relays as degrees of freedom to be solved by the location system. For example, in the case of a location in the plane, it will be ensured that at any possible position a beacon 1 is able to communicate with at least two relays.

The messages M 1 from the tags 1 associated with the objects to be located are transformed into messages M2 by the relays 2 as described above. For example, the messages M2 comprise, in addition to the time marker used to determine the arrival time, a first piece of information allowing the identification of the tag 1, a second information to determine the identity of the relay 2, a third piece of information for determining the transmission time t0 of the first message M l in the time base local to the tag 1, and a fourth piece of information making it possible to determine the delay D applied by relay 2 for retransmission of the message M l in the message M2.

The coverage area is also equipped with at least one known positional access point. Each access point comprises at least one sensor 3. More particularly, it will install as many access points or sensors 3 as necessary so that in any possible position a beacon 1 can communicate with at least one sensor 3.

More precisely, the position of the relays 2 and sensors 3 is chosen so that when a beacon 1 can communicate with a relay 2 and a sensor 3, then a communication can also be established between the relay 2 and the sensor 3.

According to this mode of operation, the flight time of a message M2 from a relay 2 to a sensor 3 is assumed to be known. For example, this flight time can be determined deterministically from the distance from relay 2 to sensor 3 or empirically.

In this embodiment, the sensors 3 are interconnected by any communication means, for example by a computer network of Ethernet or Wi-Fi type.

Still according to this embodiment, the system has at least one position calculation unit 5, for example in the form of a computer server connected to the network of the sensors 3.

According to the invention, each sensor 3 receives, on successive reception of a first message M 1 and a second message M2 associated with it, the respective arrival times t 1 and t 3 of the first message M 1 and the second message M2. .

For each message pair M 1 followed by an associated message M2, each sensor 3 transmits a reading addressed to the position calculation unit 5. Such a record includes, for example, among others an identifier making it possible to uniquely determine the identity of sensor 3, the information used to determine the time t0 transmission of the message M l in the time base local to the tag 1, the respective arrival times tl and t3 respective messages M l and M2 to the sensor 3 in its own time base, the identification of the beacon 1 having transmitted the first message M 1 and that of the relay 2 having transmitted the second message M2 in response to the first message M 1 and the delay D used by the relay 2 to transmit the message M2 after receiving the message Ml.

The position calculation unit 5 collects the different readings transmitted by the sensors 3.

In one possible embodiment, the position of each beacon 1 is determined using an EKF or UKF type Kalman filter associated with the beacon 1. The readings received from the sensors 3 are grouped by beacon identifier. 1 and ordered by tO increasing time. For a message M 1 transmitted at tO given, at least an estimate of the time t1 of reception of the first message M1 by a sensor 3 of identity and known position, the identity and the position of a relay 2 having transmitted an associated message M2, the moment of reception t3 of the message M2 by the same sensor 3, the delay D of retransmission of the message M2 by 2, the flight time of the relay 2 to the sensor 3.

The Kalman filter can then be updated to estimate the position of the tag 1 at time t0. Indeed, knowing an estimate (x;) _t of the position of the beacon 1 at a time t less than t0 and a model of the evolution of this position between t and tO, the Kalman filter can determine the position ( x; y) _t0 likely from beacon 1 to time tO through the observation equation:

d (2; 3) d (1; 2) d (1; 3)

At = £ 3 - tl - D - = - -

c c c

with d (l; 2) the Euclidean distance from beacon 1 to relay 2, d (l; 3) the Euclidean distance from beacon 1 to sensor 3, the known D delay and the known flight time from relay 2 to the sensor 3.

The preceding embodiments can be generalized in the case of a system that includes at least one assumed position tag. known and at least one position sensor assumed to be known. The system would further include one or more relays whose position is to be determined, which corresponds to the embodiment where the moving element is the relay or an object carrying the relay.

According to one embodiment, the format of the Ultra Wide Band M1 or M2 pulse radio message as shown in FIG. 3 is as follows:

- Synchronization header containing periodic repetitions of a predetermined sequence of pulses present or absent, positive or negative transposed in frequency around a carrier;

- Start of packet marker represented by a known sequence of pulses (present or absent, positive or negative) transposed in frequency around a carrier, and easily differentiable from the synchronization header;

- Data field in the form of a modulated pulse train.

In one embodiment, the time stamp for identifying the exact time of transmission and / or arrival of a message is the boundary between the end of the packet start delimiter and the beginning of the data field.

According to one embodiment, the synchronization header is formed by periodic repetitions of a prescribed symbol, which may itself be formed by a prescribed sequence of pulses (of which for example + 1 denoting a positive pulse, 0 denoting the absence of impulse, and -1 denoting a negative impulse). The synchronization header is for example formed by 1024 periodic repetitions of a symbol formed by the following sequence of pulses: -1 0 0 0 0 + 1 0 -1 0 + 1 + 1 + 1 0 + 1 - 1 0 0 0 + 1 -1 + 1 + 1 + 1 0 0 -1 + 1 0 -1 0 0. The pulses forming the symbols of Εη-head synchronization given above as an example being for example issued to a ternary rate of 10 to 500 Mega pulses per second, for example 31.25 Mega pulses per second. The packet start marker may for example be itself formed by a succession of symbols (for example 8 symbols) of identical format to those of Εη-synchronization head, but may be present or absent, of normal or inverted polarity. For example, the sequence 0 + 1 0 -1 + 1 0 0 -1 can be used to form such a start marker of packet (+ 1 designating a symbol of format identical to those of ΓΕη-head synchronization given previously as for example, 0 denoting a total absence of pulse for the duration of a symbol, and -1 denoting a symbol similar to those used for Εη-synchronization head but the polarity of the pulses has been reversed).

The data field can for example be made by position modulation of a pulse train in a given time window. For example, if we associate with each bit of a binary message to transmit a time window of for example 100 ns to 10 ms, for example 8 ps, we can determine that a bit at 0 will be represented by the presence of a pulse train in the first half of said window, while a bit at 1 will be identified by the presence of a pulse train in the second half of said window. Said pulse train may for example be formed by a pseudo-random succession of 1 to 512 pulses, for example 128 pulses, positive or negative, at a rate of 100 Mega-imulsions per second to 1 Giga-pulses per second, for example of 500 Mega pulses per second, the pseudo-random sequence being known to the transmitter and receiver and reset at each message start.

According to one embodiment, in FIG. 8, a transmitter 100 Ultra Wide Pulse Band comprises:

A digital modulator 101 (for example a digital processor) making it possible to form a ternary flux (comprising, for example, ternary frames); A digital-to-analog converter 102 for shaping pulses from the ternary flux into an Ultra Wide band pulse signal in baseband;

A mixer 103 for transposing the Ultra Wideband pulse signal in baseband into an Ultra Wide Band pulse-frequency radio signal;

A radiofrequency local oscillator 104 supplying a central frequency necessary for the frequency transposition operation of the mixer 103;

A power amplifier 105 for the radiofrequency signal Ultra Large impulse band;

An antenna 106 for radiating the radio frequency signal Ultra Wide Pulse band (sending the message M l or M2),

- A first reference clock 107.

This transmitter 100 is for example present in the beacon 1.

The transmitter of the relay 2 may include elements similar to those of the transmitter 100 of the beacon 1.

The radio frequency oscillator 104 may be generated from the main reference clock 107 through a phase locked loop. The frequency of the radio frequency oscillator 104 is for example 3 to 10 GHz and that of the main reference clock from 100 MHz to 1 GHz, for example 500 MHz.

The flow rate of the ternary flux (+ 1, 0 or -1) at the output of the digital modulator 101 is, for example, of a ternary sample every 500 ps at 2 ns, for example 2 ns, ie a flow rate of 100 Mega ternary samples per second to 2 Giga ternary samples per second, for example 500 Mega ternary samples per second.

The reconstruction filter of the digital / analog converter 102 is for example of low-pass type with a cutoff frequency of 400 MHz.

According to one embodiment, in FIG. 9, a Receiver 200 Ultra Wide Pulse Band comprises: An antenna 201 for receiving the radio signal Ultra Wide Band impulse (reception of the message M l or M2),

A low noise amplifier (LNA) 202;

A mixer 203 for transforming the output signal 206 of the amplifier 202 into a baseband signal 207 comprising an in-phase component and a quadrature component;

A radiofrequency oscillator 204 for supplying the reference signal 205 to the mixer 203;

A baseband amplifier 208 for each of the in-phase and quadrature components of the output signal 207 of the mixer 203;

An analog / digital converter 209 for each of the in-phase and quadrature outputs 210 of the baseband amplifier 208;

A digital signal processing unit 211, comprising for example a digital processor.

According to one embodiment, the analog / digital converter 209 and the digital signal processing unit 211 operate synchronously on a second local reference clock 212.

The radio frequency oscillator 204 may be created by multiplication from a second local clock reference 212, for example using a phase locked loop.

This receiver 200 is for example present in the sensor 3. The receiver of the relay 2 may comprise elements similar to those of the receiver 200.

In one embodiment, the steps of receiving in the digital signal processing unit 211 include:

- Frequency synchronization of the clocks of the receiver with those of the transmitter;

- Symbol synchronization by correlation with the known sequence of the synchronization header;

- Acquisition of a channel impulse response; - Searching the start frame delimiter;

- Search time marker to identify the exact time of arrival of messages

According to one embodiment of the invention, the digital processing unit 211 has a permanent counter operating at a rate of 1 increment with each cycle of the second local clock reference 212, and the unit 211 captures the value said counter when receiving the time marker present in the messages M 1 and M2. The value of this counter is then considered as that of the instant t1, t2 or t3 in the local timebase of the receiver 200. For example, the dynamics of the counter can be 32-bits.

According to one possible embodiment of the invention, the digital processing unit 211 integrates channel impulse response analysis capabilities by oversampling and interpolation to enable the arrival time to be identified with a resolution less than that of a sample.

Relay 2 implements a reception chain and a transmission chain as described above, that is to say a transmitter 100 and a receiver 200 as described above.

The functions of reference clocks 107 and 212 and radiofrequency oscillators 104 and 204 may be shared or left independent. There can therefore be a single reference clock 107, 212 for the transmitter 100 and the receiver 200 in the relay 2. There can therefore be a single radio frequency oscillator 104, 204 for the transmitter 100 and the receiver 200 in the relay 2.

A counter 213 and / or a delay line 213 may be provided between the digital signal processing unit 211 and the digital modulator 101. This counter 213 and / or this delay line 213 serves, for example, to create the delay D in FIG. the message M2.

Relay 2 may have only one antenna 106, 201 if it also has a transmit / receive antenna switch, or two separate antennas 106 and 201.

Claims

claims

1. System for locating a mobile element inside an enclosure, characterized in that it comprises:

at least one beacon (1, 11, 12, 13) capable of transmitting at least a first radio message (M l, M i l, M 12, M 13) inside the enclosure;

at least one sensor (3) capable of measuring in a local time base the arrival times of the messages coming from said at least one beacon (1, 11, 12, 13) and at least one relay (2, 21, 22) inside the enclosure;

at least one position calculator (5), able to determine the position of a movable element, which is one of the beacon (1, 11, 12, 13), the relay (2, 21, 22) and the sensor (3), from at least the arrival time information and positions, known by the computer (5), from the other of the beacon (1, 11, 12, 13), the relay (2, 21, 22) and the sensor (3);

the beacon having at least one ultra-wideband radio pulse transmitter for transmitting the first message (M l, M il, M12, M13), the relay having at least one ultra-wideband radio pulse receiver for receiving the first message (M 1, M il, M 12, M 13) and an Ultra Wide Band radio pulse transmitter for transmitting the second message (M2, M21, M22),

the sensor having at least one Ultra Wide Band pulse type radio receiver for receiving the first message (M l, M il, M 12, M 13) and the second message (M2, M21, M22).

2. System for locating a mobile element inside an enclosure according to claim 1, characterized in that it comprises a central sequencer (4) having a radio transmitter and in that each beacon (1 , 11, 12, 13) and / or each relay (2, 21, 22) contains a radio receiver adapted to receive messages transmitted by said central sequencer.

3. System for locating a mobile element inside an enclosure according to one of claims 1 or 2, characterized in that it comprises a plurality of sensors (3) all connected by a telecommunication means to the computer of remote position.

4. System for locating a mobile element inside an enclosure according to claim 3, characterized in that the telecommunication means is of the wired Ethernet or WI-FI type and that the position calculator is a computer server. .

5. System for locating a mobile element inside an enclosure according to one of claims 1 or 2, characterized in that the computer (5) is embedded on the sensor.

6. System for locating a mobile element inside an enclosure according to one of claims 1 to 5, characterized in that said delay (D) is known by the position calculator (5), which is capable of determining the position of the movable element from at least said delay (D).

7. A method of locating a mobile element inside an enclosure, characterized in that it comprises steps of:

(a) Emitting by at least one beacon (1, 11, 12, 13) of at least one first message (M l, Mi l, M 12, M 13) inside the enclosure;

(b) Receiving said first message (Ml, M il, M 12, M 13) by at least one relay (2, 21, 22) inside the enclosure and transmitting, inside the enclosure, a second message (M2, M21, M22) with a known delay (D) with respect to the reception of the first message (Ml, M il, M 12, M 13) by said minus one relay (2, 21, 22);

the beacon having at least one Ultra Wide Band radio transmitter for transmitting the first message (Ml, M i l, M 12, M 13), the relay having at least one Ultra Wide pulse radio receiver

Band for receiving the first message (M l, M i l, M 12, M 13) and an Ultra Wide Band radio transmitter for transmitting the second message (M2, M21, M22),

the sensor having at least one radio receiver of the pulse type Ultra

Wide band for receiving the first message (M l, M i l, M 12, M 13) and the second message (M2, M21, M22).

8. A method of locating a movable element inside an enclosure according to claim 7, characterized in that the first message (Ml, M il, M 12, M 13) transmitted in step (a) includes a time marker for identifying the transmission time in the time base of the beacon and / or the reception time of the first message (M 1, Mi 1, M 12, M 13) in the time base of the beacon. relay or sensor.

9. A method of locating a mobile element inside an enclosure according to one of claims 7 and 8, characterized in that the second message (M2, M21, M22) transmitted in step (b). has a time marker for identifying the transmission time of the second message (M2, M21, M22) in the relay time base and / or the reception time of the second message (M2, M21, M22) in the time base of the sensor and / or the delay between the instant of reception of the first message (Ml, M il, M 12, M 13) and the instant of transmission of the second message (M2, M21, M22) in the timebase own relay.

10. A method of locating a mobile element inside an enclosure according to claim 7, characterized in that the first message (Ml, M il, M 12, M 13) issued in step (a). by the tag has in its data the identification of the tag.

11. A method of locating a mobile element inside an enclosure according to one of claims 7 or 8, characterized in that the second message (M2, M21, M22) issued in step (b). by the relay includes in its data the identification of the relay and that of the beacon that triggered the retransmission.

12. A method of locating a mobile element inside an enclosure according to one of claims 7 to 9, characterized in that the delay (D) between the reception of the first message (Ml, M il, M 12, M13) transmitted in step (a) and the transmission of the second message (M2, M21, M22) transmitted in step (b) by the relay is at least equal to the processing time of the first and / or second message, and as much as possible of the same order of magnitude as the processing time of the first and / or second message.

13. A method for locating a mobile element inside an enclosure according to one of claims 7 to 12, characterized in that said delay (D) is known by the position calculator (5), which is capable of determining the position of the movable element from at least said delay (D).

Radio message transmitting beacon for implementing the system according to one of claims 1 to 6 and / or the method according to one of claims 7 to 13, characterized in that the beacon comprises least one ultra-wide band radio pulse transmitter for periodically transmitting a message (Ml, M il, M 12, M 13) comprising a time marker for identifying the moment of transmission in a time base of the beacon.

Radio transmitting and receiving relay for implementing the system according to one of Claims 1 to 6 and / or the method according to one of Claims 7 to 13, characterized in that it comprises :

at least one Ultra Wide Band pulse radio receiver for receiving a first message (Ml, M i l, M 12, M 13) from a beacon,

at least one ultra wide band pulse radio transmitter for transmitting the second message (M2, M21, M22) comprising in its data the first message (M l, M il, M 12, M 13) and comprising a time marker allowing identify the instant of transmission of the second message (M2, M21, M22) in a time base of the relay,

the delay between the reception of the first message (M l, M i l, M 12, M 13) and the transmission of the second message (M2, M 21, M 22) being known to a certain extent in a timebase of the relay.

16. radio message receiving sensor for implementing the system according to one of claims 1 to 6 and / or the method according to one of claims 7 to 13, characterized in that it comprises:

at least one ultra wide band pulse type radio receiver for receiving a first message (M l, M il, M 12, M 13) transmitted from a beacon and a second message (M2, M21, M22) transmitted from a relay, and

a unit for measuring in a local time base the arrival times of the first message (Ml, M il, M 12, M 13) originating from the beacon and / or the second message (M2, M21, M22) from the relay.