FR3044774A1 - METHOD USING POWER MEASUREMENTS FOR DETERMINING POSITIONING DATA BETWEEN TWO BODIES - Google Patents

Abstract

The method of use is associated with a system comprising a first body (1) having an orientation direction (2) and carrying at least two electronic nodes (3, 4) arranged in different positions at the first body (1). ), said system comprising a second body (5) associated with at least one electronic node (5e), said electronic nodes (3, 4) carried by the first body (1) and said at least one electronic node (5e) associated with the second body (5) being able to communicate with each other by radio links (7,6). The method comprises the following steps: an establishment step (E1), for each electronic node (3, 4) carried by the first body (1), of a radio link (6, 7) with said at least one electronic node associated with the second body (5), • a determination step (E2), for each established radio link (6, 7), of a reception parameter representative of a reception power associated with said established radio link, a step of determining (E3) a relative angle (α) between the orientation direction (2) of the first body (1) and a line (8) passing through the first body (1) and the second body (5). ) using the determined reception parameters.

Description

Method using power measurements to determine positioning data between two bodies

Field of the Invention [001] The invention relates to the field of radiolocation, especially in the context of body networks.

STATE OF THE ART [002] With the advent of intelligent instrumented clothing, the widespread use of personal digital equipment and radio / sensor technologies with very low consumption, the body networks (or "Body / Wearable Area Networks" in English) must to cover the needs of a variety of domains (multimedia, health, safety, sport, etc.). In addition, many emerging applications require the provision of accurate information on the position and / or orientation of mobile users. These applications concern, for example, indoor pedestrian navigation, the capture and analysis of team sports, the coordination of personnel, the detection of gestural control, or the detection of posture, etc. State-of-the-art solutions for estimating the arrival angle from narrow-band radio signals require a specific hardware architecture at the receiver, as well as a particular shaping of the receiver. signal transmitted accordingly. They are therefore not immediately compatible with conventional communication standards / devices such as Bluetooth or Wi-Fi and can not be implemented at the level of the mobile user, but preferably at the level of a user. infrastructure (eg base station, access point, or other). Moreover, most pedestrian radiolocation solutions are strongly penalized by the radio disturbances and obstructions generated by the body of the user of the radio devices himself and / or by external obstacles (eg non-visibility of radio inside).

OBJECT OF THE INVENTION [003] There is therefore a need to develop a new solution for developing at least one data relating to the orientation of the wearer, using in particular any type of signal, as well as a radio receiver architecture. conventional dedicated to communication.

[004] This need is solved by a method of using a system comprising a first body having an orientation direction and carrying at least two electronic nodes arranged in different positions at the first body, said system comprising a second body associated with at least one electronic node, said electronic nodes carried by the first body and said at least one electronic node associated with the second body being able to communicate with each other by radio links, said method comprising the following steps; a step of establishing, for each electronic node carried by the first body, a radio link with said at least one electronic node associated with the second body; a step of determining, for each established radio link, a reception parameter representative of the reception power associated with said established radio link; a step of determining a relative angle between the orientation direction of the first body and a straight line passing through the first body and the second body using the determined reception parameters.

[005] In a first case, said relative angle is determined by means of a deterministic association function linking said relative angle to the determined reception parameter values associated with said radio links, in particular to a difference value between the reception parameters. determined and expressed in decibels.

[006] For example, said deterministic function comprises parameters calculated from a predetermined and reproducible model linking the average power attenuation undergone for each radio link according to said relative angle and the position of the electronic node on the first body. and associated with said radio link.

[007] Said deterministic function can comprise parameters calculated from a dynamic observed empirically of reception parameters during a calibration phase associated with the first body.

[008] In particular, the calibration phase associated with the first body is to ensure a movement of the first body carrying said at least two electronic nodes to test a plurality of possible relative angles between the direction of orientation of said first body and a straight line. by the first body and a reference body so as to measure, for each tested relative angle, minimum and maximum differences between radio link standard reception parameters established between said at least two electronic nodes of the first body and an electronic node of the standard body .

[009] In particular, the deterministic function is an interpolation function calculated from the minimum and maximum differences between the standard receiving parameters measured empirically during the calibration phase for the different values of relative angles tested.

According to a second case, the step of determining the relative angle makes it possible to jointly determine a relative distance separating the first body from the second body.

In particular, the relative angle and the relative distance are obtained by solving a system of equations with two unknowns respectively formed by the relative angle and the relative distance, said system taking as input the determined reception parameters. and a parametric average attenuation model by radio link, of which a first parameter corresponding to the standard average attenuation at a reference distance, and a second parameter corresponding to an average attenuation coefficient, are also two functions dependent on the desired unknowns.

According to one embodiment, the system comprises a plurality of second bodies each associated with at least one electronic node and such that each second body forms a pair with the first body, said second bodies belonging to a fixed infrastructure, and: the establishment step is implemented for each second body, from which it follows that for each pair of radio links are formed between said electronic nodes carried by the first body of said pair and said at least one associated electronic node the second body of said pair; the step of determining a relative angle is implemented for each pair; said method comprises a step of determining an absolute position and / or an absolute angle of the first body within a frame of reference of the infrastructure comprising the plurality of second bodies from the determined relative angles associated with said pairs.

In particular, the step of determining the absolute angle and / or the absolute position comprises the use of an estimation function taking as input the known absolute positions of the second bodies within the frame of reference. infrastructure and each determined relative angle, said estimation function outputting said absolute angle and / or said absolute position.

In particular, the absolute angle corresponds to the angle formed between the direction of orientation of the first body and an invariant reference direction in the overall frame of the infrastructure, for example given by the Earth's magnetic north.

The estimation function may be such that the absolute angle and / or the absolute position are obtained as the iterative solution of a least squares problem involving an approximated and locally linearized form of a reference function. connecting the value of the angle relative to the absolute position of a second associated body, the absolute position of the first body and the absolute angle associated with the first body.

According to an additional embodiment, the system comprises a plurality of moving bodies each having an orientation direction and each carrying at least two electronic nodes arranged at different positions on said movable body, said first body and said second body. forming part of the plurality of moving bodies, and the method comprises for each mobile body and when said mobile body is in communication range with at least one other mobile body: a step of establishing, for each electronic node of said mobile body, a radio link with at least one electronic node of each other mobile body within communication range; a step of determining, for each established radio link, a reception parameter representative of the reception power associated with said established radio link; a step of determining a relative angle and a relative distance between said movable body and each mobile body of which at least one electronic node is within communication range of the electronic nodes of said mobile body from the determined reception parameters. Furthermore, the method comprises a step of implementing a cooperative function for estimating relative positions taking, at the input, determined relative angles and relative distances determined between moving bodies.

The cooperative function for estimating relative positions can take as input all of the determined relative angles of each of the moving bodies and the set of relative distances determined between moving bodies, alternatively the cooperative function for estimating relative positions. is implemented for each moving body and takes as input the relative angles and determined relative distances of said movable body relative to each other movable body in communication range.

The system may comprise a fixed infrastructure provided with at least two communicating elements whose absolute positions in the frame of reference of the infrastructure are known, and these absolute positions are injected into the cooperative position estimation function for this last gives the absolute positions of moving bodies within the frame of reference linked to the infrastructure.

The cooperative estimation function can implement a multidimensional positioning algorithm, or a cooperative tracking filter of Bayesian-type mobile body positions.

The invention also relates to a system comprising a first body carrying at least two electronic nodes arranged at distinct positions and having an orientation direction, said system comprising a second body associated with at least one electronic node adapted to communicating with the electronic nodes carried by the first body, said system comprises: a module configured to establish radio links between the two electronic nodes carried by the first body and said at least one electronic node associated with the second body; a module configured to measure reception parameters representative of the reception powers of each of the established radio links; and a module configured to exploit the measured reception parameters to establish a value of a relative angle between said first body orientation direction and a line through the first and second bodies

DESCRIPTION OF THE DRAWINGS The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and with reference to the drawings in which: FIG. 1 is a schematic illustration of FIG. a system according to an embodiment of the invention and provided with a first body and a second body, - Figure 2 schematically illustrates different steps of a method of using the system, - Figure 3 illustrates a difference in powers (received by two worn nodes) in decibels evolving as a function of time during a calibration phase, - Figure 4 illustrates the difference in power (received by two nodes carried) as a function of the relative angle from empirical data and according to a function of linear association and cubic association, - Figure 5 illustrates two curves of evolution of the relative angle (real and estimated) over time when the first body s e moves relative to a second fixed body, - Figure 6 schematically illustrates the interaction between two similar bodies, - Figure 7 schematically illustrates the displacement of a first movable body with respect to two second fixed bodies, - the figure 8 illustrates different steps according to a particular implementation of the method, - Figure 9 illustrates a plurality of moving bodies operating in the same environment, - Figure 10 illustrates steps according to a particular mode of implementation of the method.

In these figures, the same references are used to designate the same elements.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION [0023] In the remainder of this description, the features and functions well known to those skilled in the art are not described in detail.

Unexpected radio obstruction situations generally pose problems with radiolocation, detection of bodies and the deduction of their orientation. The person skilled in the art usually seeks to counteract these problems of obstruction, whether they are caused by the carrier of the mobile radio devices himself or by external obstacles in the environment. The method and the system described below propose instead to take advantage of a consequence of the attenuation caused by a carrier body of electronic nodes, also called radio nodes, on radio waves to determine at least one piece of information. relative angle between this body and another body, also carrier of radio node (s), and vis-à-vis which or which radio links are established.

An objective is to establish for a first body angular type information between the first body and a second body.

FIG. 1 illustrates a system comprising the first body 1 having an orientation direction 2 and carrying at least two electronic nodes 3, 4 arranged according to distinct positions at the first body 1. By "arranged according to distinct positions Is meant that these two electronic nodes 3, 4 are placed at different locations of the first body 1. In particular, the first body 1 having a front face 1a and a rear face 1b, one of the electronic nodes 3 is placed on the front face 1a of said first body 1 and the other electronic node 4 is placed on the rear face 1b of said first body 1.

The first body 1 can carry only two electronic nodes 3, 4 or more.

According to a preferred implementation, the first body 1 is likely to move. It can include an individual, such as a human being, who wants to follow, or who wants to retrieve information about his environment.

The orientation direction 2, or orientation vector, corresponds to the target direction or heading followed by the first body 1. When the first body 1 is a human, the orientation direction may be normal by relative to his torso and oriented according to the direction following the gaze of the individual.

When the first body 1 is a human being, the electronic nodes may be integrated into a garment worn by said first body 1, or fixed on the same garment. By "integrated in a garment" is meant that the electronic nodes can be buried in the garment. Of course, other options are possible, the electronic nodes being able to be secured by strap to said first body 1 or by hook and loop fastener.

Furthermore, this Figure 1 also shows that the system comprises a second body 5. The first body 1 can be movable relative to the second body 5. Alternatively, the first body 1 can be immobile and it is the second body 5 which moves in the environment of the first body 1. Yet alternatively the first and second bodies 1, 5 can be movable between them and each able to move. The second body 5 is associated with at least one electronic node 5e, this association is particularly such that the second body 5 carries said electronic node or that the latter is mounted on said second body 5. The electronic nodes 3, 4 carried by the first body 1 and said at least one electronic node 5e associated with the second body 5 are able to communicate with each other by radio links 6, 7. In other words, the electronic nodes 3, 4 carried by the first body 1 are distinct and said at least one The electronic node associated with said second body 5 is distinct from those carried by the first body 1. It is then understood that an electronic node may comprise the means necessary to transmit and / or receive a radio wave so as to form a corresponding radio link.

In particular, FIG. 2 illustrates a method of using the system and comprising an establishment step E1, for each electronic node 3, 4 carried by the first body, of a radio link 6, 7 with said minus an associated second body electronic node 5, that is to say the establishment of a radio link between each electronic node 3, 4 of the first body 1 and the electronic node 5e associated with the second body 5. In the illustrated example, the first body 1 comprises two electronic nodes 3, 4 which results in the establishment of two radio links 6, 7.

A radio link 6, 7 may be defined between a transmitter of a radio wave and a receiver of the radio wave.

The radio links can be established from the electronic node 5e associated with the second body 5 towards the electronic nodes 3, 4 carried by the first body 1, and in this case the electronic node 5e associated with the second body 5 comprises a transmitter a radio wave while the electronic nodes 3, 4 carried by the first body 1 each comprise a receiver of the electric radio wave. Alternatively, the radio links can be established from the electronic nodes 3, 4 carried by the first body 1 which then each comprise an emitter capable of transmitting towards said at least one electronic node 5e of the second body 5 which then comprises a receiver. Other combinations are also possible while remaining within the scope of the present invention, for example the electronic node 3 can be transmitter, the electronic node 4 can be receiver and the electronic node 5e can be both transmitter and receiver. Thus, each electronic node in the present description may include a transmitter and / or a receiver as appropriate.

It follows from the fact that the electronic nodes 3, 4 are arranged at distinct locations of the first body 1 that said first body 1 will cause different attenuations on said radio links 6, 7. It is this phenomenon that will be used to determine a relative angle between the first body 1 and the second body 5. The advantage is that such attenuation affects the power of the radio link seen by the receiver. The power of a radio link is easily measurable and available for the majority of communication protocols. In practice, the analog received power (in mW) is generally translated by an indicator taking an integer value on a discrete -unit- (or RSSI) scale reflecting linearly the level ( in dBm) of this same received power. In what follows, it will be sufficient to designate this measure as "received power" or "reception power" for the sake of simplicity. In other words, more generally, the terms "receive power" or "received power" used in the present text may be generalized to the terms (i.e., replaced by) "receive parameter representative of receive power" also more simply called "reception parameter", this reception parameter may be the analog power or an image of this analog power.

In this sense, the method may further comprise a determination step E2, for each established radio link 6, 7, a reception power associated with said established radio link. The reception power is of course the power of the radio link measured by the receiver. In other words, a determined reception power can be a measured reception power. Preferentially, the electronic nodes 3, 4 carried by the first body 1 being the receivers and the electronic node 5e associated with the second body 5 being the transmitter, the receiving powers are measured by the electronic nodes 3, 4.

Finally, the method may comprise a determination step E3 of a relative angle a between the orientation direction 2 of the first body 1 and a line 8 passing through the first body 1 and the second body 5 using the powers of determined reception. This line 8 is represented by dotted lines in FIG.

There are different solutions for determining this relative angle.

In a first case, said relative angle a is determined by means of a deterministic association function linking said angle relative to the determined reception power values associated with said radio links 6, 7, in particular to a difference value. between the reception powers determined and expressed in decibels (or their equivalents, in the form of received power indicators).

The deterministic function can take the form of a polynomial function of arbitrarily high degree.

According to an implementation of the first case, this deterministic function comprises parameters calculated from a predetermined and reproducible model linking the average attenuation in power undergone for each radio link as a function of said relative angle and the position of the electronic node (its position on the first body 1) carried by the first body 1 and associated with said radio link.

Alternatively, said deterministic function may comprise parameters calculated from an empirically observed dynamics of reception powers during a calibration phase associated with the first body 1. In particular, the calibration phase associated with the first body 1 consists of to ensure a movement (especially at least one complete rotation) of the first body 1 carrying said at least two electronic nodes 3, 4 to test a plurality of possible relative angles between the orientation direction 2 of said first body 1 and a straight line by the first body 1 and a reference body (this reference body can be the body 5 illustrated in FIG. 1 - in other words, it can be any other body between which and said first body a relative angle can be determined according to the method described) so as to measure, for each relative angle tested, minimum and maximum differences between receiving powers e heel of radio links established between said at least two electronic nodes 3, 4 of the first body 1 and an electronic node of the standard body. In this case, the deterministic function may be an interpolation function calculated from the minimum and maximum differences between the standard receiving powers measured empirically during the calibration phase for the different values of relative angles tested.

According to a particular example of the first case, the relative angle information a can be estimated by a by means of a deterministic and parametric function posed a priori (mapping in English language), y <- map (a) binding explicitly to the observed difference y [dB) of reception powers associated with electronic nodes 3, 4 on the front and rear faces of the first body 1, ie y [dB) = RSSBack [dB] -RSSFmnt [dB], with RSSBack [dB] the reception power in dB determined for the radio link associated with the electronic node, particularly located on the rear face of the first body 1 and RSSFmnt [dB] the reception power in dB determined for the radio link associated with the particular node This deterministic function can, for example, take the form of a polynomial function of arbitrarily high degree of the type map [a) = c0 + c1a + ... + cnan. In the example given in FIGS. 3 and 4, the parameters of this polynomial function (at orders 1 and 3, for illustration, with two general association functions - of form y (x) - superimposed on FIG. parameters are digital applications corresponding to the dynamics of the received power differences observed in FIG. 3) are adjusted to the dynamics observed for the power difference γ during the calibration phase illustrated in FIG. 3 consisting in determining power differences as a function of time related to the movement of the body 1 (for example aiming to establish only the maximum excursion for this difference for at least one complete rotation of the first body 1, for example an individual performing a turn on itself), using an interpolator arbitrary (for example a linear or cubic function between the minimum and maximum values, for the same illustration of Figure 3). It follows from the combination of FIGS. 3 and 4 the establishment of three empirical points P1, P2, P3 corresponding to the measured maximum reception power, to the 0, and to the measured maximum reception power. After calibration and in steady state, from the current measurements of the powers received at the nodes carried by the first body, the estimated current relative angle α is then determined as the solution of an equation of the y-map type [a) = 0 taking into account the empirical points determined above.

Figure 5 illustrates a test for validating the proper operation of the particular example given above. This FIG. 5 makes it possible to compare the result of an estimation of the relative angle α according to the invention (curve C1) from the difference of received powers observed at two compatible electronic nodes of the IEEE 802.15.4 standard. narrow at 2.4GHz and arranged on the front and rear faces of the first body 1 to the result delivered by a high-precision capture-optical reference system of the movement (curve C2) and this, for radio links with respect to a fixed transmitter of the second body belonging to a fixed infrastructure. These curves C1 and C2 represent the evolution of the relative angle of a mobile individual (forming the first body 1) with respect to the fixed infrastructure as a function of time and along a "natural" trajectory of the individual, whose absolute orientation (English language caption or "heading") within the infrastructure framework varies with time. It can be deduced from the study of this FIG. 5 that the method for determining the relative angle from a power difference is very close to what would be obtained with an expensive system of precision measurement.

It has been described above the interaction between a first body 1, in particular mobile, and a second body 5 forming part of a fixed infrastructure. This example is of course not limiting in the sense that the second body 5 can also be of the type of the first body 1 as shown in Figure 6 where the first and second bodies are formed by individuals. In the repository of the right individual, the latter can be the first body and the left individual can be the second body, and in the repository of the left individual, the roles can be reversed; say that the left individual can be the first body and the right individual can be the second body.

This first case makes it possible in particular to cover in a nonlimiting manner applications such as: • gestural control or secure procedures (such as, for example, permission to access a place and / or a content) on the basis of the orientation information of the individual, especially if the second body is fixed within the framework of an infrastructure and the first body is able to move towards this infrastructure; • Detection and / or classification of proximity social interactions, based on the relative orientation information between individuals.

According to a second case, the determination step E3 of the relative angle makes it possible to jointly determine a relative distance d separating the first body 1 from the second body 5. Here again the determined reception powers are used.

Preferably, the relative angle a and the relative distance d are obtained by solving a system of equations with two unknowns respectively formed by the relative angle a and the relative distance d, said system taking as input the powers determined reception and a parametric model of average attenuation by radio link G [a, d) (in the case of the example where one of the nodes is placed on the front face of the first body the parametric model is of type G [ a, d) and the other node being placed on the rear face of the body, the parametric model is of the type G (a + 180 °, ci)), of which a first parameter G0 (a), or where appropriate G0 (cr + 180 °), corresponding to the average standard attenuation at a reference distance, and a second parameter n (a), or where appropriate n (cr + 180 °), corresponding to an average attenuation coefficient, are also two functions depending on the unknowns sought. According to one implementation, it is understood that there is only one and the same function of a (defined for a node on the front panel). But depending on whether the radio node in question is placed on the front or rear face, the effective alpha angle passed as an argument to the function is alternately alpha or alpha + 180 ° (again, if we accept a single definition of a by individual, involving the vector "direction" -normal to the front face).

According to a particular example characterizing the average power attenuation for radio links between two equipped individuals (ie, from electronic nodes carried on a human body to other electronic nodes carried by another human body), we have: with:

from which it follows that by knowing RSSFmnt [dB] the reception power in dB determined for the radio link associated with the electronic node 3 located on the front face of the first body 1 and RSSBack [dB] the reception power in dB determined for the radio link associated with the electronic node 4 located on the rear face of the first body 1, the estimated relative angle a - corresponding to the relative angle to be determined - and the estimated relative distance d - corresponding to the relative distance to be determined - are the solutions of the following equations:

where PTx represents the transmitted power assumed to be identical on the two radio links (ie, the power presented at the input of the transmission antenna in the case of the example of the inter-individual attenuation model above involving two human bodies , or the radiated transmit power after the antenna in the case of an attenuation model between a human body and a fixed element of the infrastructure).

This second case preferably makes it possible to cover applications such as: • the gestural control or the secure procedures (for example authorization of access of place and / or content ...) on the basis of the orientation information and proximity of the individual, in particular by mobilizing at least the second body formed by a fixed element of an infrastructure; The detection and / or classification of proximity social interactions, on the basis of relative orientation information and relative distance between individuals (by mobilizing at least one radio link with respect to a second constituent body an individual then equipped with electronic nodes); Radar-like functions for detecting, positioning and tracking mobile active and cooperative elements around the first body (i.e. positioned in a frame of reference of the first body).

It has been described above means for determining a relative positioning between the first body 1 and the second body 5. Depending on the use case, it may also be advantageous to know absolute positioning data of the first body 1 in a determined frame of reference.

In a particular embodiment for addressing this problem of absolute positioning, the system comprises, as illustrated in FIG. 7, a plurality of second bodies 5a, 5b each associated with at least one electronic node 5e (which is own, that is to say that the nodes 5e of the second bodies are distinct), and so that each second body 5a, 5b forms a

couple in the first body 1. In the example of Figure 7, the system comprises two second bodies 5a, 5b, and there are two pairs (1; 5a) and (1; 5b). These second bodies 5a, 5b belonging to a fixed infrastructure 9, this fixed infrastructure 9 is linked to a repository within which the first body 1 will be placed and will be able to move / move. For example, the repository can be of the GPS "Global Positioning System" type in English language and can therefore be located anywhere since the positions of the "external" anchors are invariant in time within this global and absolute reference frame. . In other words, the first body 1, whose absolute position and absolute orientation are unknown, can be mobile with respect to the fixed infrastructure 9. For example, this infrastructure 9 can be linked to the walls of a room or room. 'a building. In the context of this particular embodiment, the method comprises (FIG. 8), the establishment step E1, described above, implemented for each second body 5a, 5b, from which it follows that for each couple of radio links are formed between said electronic nodes carried by the first body 1 of said pair and said at least one electronic node associated with the second body 5a, 5b of said pair. Of course, the determination step E2 described above is also implemented so that for each established radio link, an associated reception power is determined, for example by measurement. It should be understood here that, for each pair, a radio link is established between each electronic node carried by the first body 1 of said pair and said electronic node 5e associated with the second body 5 of said pair. In particular, for each pair it is said at least one electronic node 5e associated with the second body 5a, 5b of said pair which establishes the radio links with the electronic nodes 3, 4 carried by the first body 1 of said pair. Then, the determining step E3 of a relative angle a is implemented for each pair. It is thus obtained a relative angle for each pair. These relative angles can be obtained by the implementation of the first case described above or the second case described above. Finally, said method comprises a determination step E4 of an absolute position and / or an absolute angle β of the first body 1 within the frame of reference of the infrastructure comprising the plurality of second bodies 5a, 5b from relative angles. determined associated with said couples.

In particular, the determination step E4 of the absolute angle and / or of the absolute position comprises the use of an estimation function taking as input the known absolute positions of the second bodies 5a, 5b within of the infrastructure reference frame and each determined relative angle, said estimation function outputting said absolute angle and / or said absolute position.

The absolute positions of the second bodies 5a, 5b, and the absolute position of the first body 1 may correspond to Cartesian X and Y coordinates in a planar reference of the XY axis infrastructure shown in FIG. 7.

The absolute angle β corresponds to the angle formed between the orientation direction 2 of the first body 1 and an invariant reference direction 10 in the overall frame of the infrastructure, for example this reference direction 10 is given by the Earth's magnetic north. Direct knowledge of the absolute angle β (for itself) may be advantageous in guiding applications where headings need to be followed (for example, travel assistance for vulnerable people, such as the visually impaired or firefighters progressing). in a smoky building), but also more classically, to assist tracking-type navigation algorithms, where this information can be directly injected into the problem, either as an observation or as a "driving" element the prediction phase of the desired state (typically, the Cartesian coordinates and the associated speeds) According to an improvement of the embodiment, the estimation function is such that the absolute angle and / or the absolute position are obtained as the iterative solution of a least squares problem involving an approximated and locally linearized form of a d function. ference connecting the angle value relative to the absolute position (in particular of the coordinates xk, yk) of a second associated body, to the absolute position (in particular of the x, y coordinates) of the first body and to the associated absolute angle β to the first body 1. This reference function can in particular be implemented for each pair described above.

According to a particular example, the reference function is defined in the following manner:

With ak the relative angle between the first body 1 and another body for the pair of index k, β the absolute angle sought for the first body, xket yk the known coordinates of the second body of the corresponding pair, x and y the Absolute coordinates searched for the first body 1. This function is then linearized near an arbitrary point:

Which gives rise to the approximation:

where ^ 1 * 0 is the gradient of the function

evaluated at x0.

For all the K elements of the infrastructure, ie for the K couples, the inequality is formed as follows:

which gives rise, by identification to the system of equations (given here in matrix form):

Ax = b Where b is the K-dimensional column vector grouping all terms to the right of the equation in the previous equation. The solution ^ in the sense of the linearized least squares of such a system is given by: g ^ Â + l "o ù

is the pseudo-inverse matrix of Moore-Penrose of A.

In other words, starting with an initial condition xo, more or less distant from the true sought position x, a solution can be determined at one iteration.

according to the previous equation. It is quite obvious that the preceding solution can be generalized to an iterative solution aimed at refining the result, by giving itself an arbitrary stopping criterion (for example either a maximum number of iterations, or a limit on the variation of the solution from one iteration to another).

This particular embodiment makes it possible to cover single-user "pedestrian navigation" type applications by mobilizing K distinct pairs - with K the number of pairs which is greater than or equal to two - with respect to second bodies. fixed infrastructure. Furthermore, it is also understood that this embodiment makes it possible to jointly determine the absolute position and the absolute angle of the first body.

According to an additional embodiment, the system may comprise a plurality of movable bodies 11a, 11b, 11c, 11d each having an orientation direction 2 (in particular as defined above), as illustrated in FIG. 9. and comprising (each bearing) at least two electronic nodes 3, 4 arranged at different positions on said movable body 11a, 11b, 11c, 11d, said first body 1 and said second body 5 forming part of the plurality of moving bodies 11a, 11b, 11c, 11d. According to this embodiment, the method may comprise (FIG. 10) for each mobile body 11a, 11b, 11c, 11d and when said movable body 11a, 11b, 11c, 11d is in communication range with at least one other body mobile 11a, 11b, 11c, 11d (two mobile bodies are defined as being in communication range when their electronic nodes are capable of establishing a communication link between them): an establishment step E101, for each electronic node of said mobile body 11a, 11b, 11c, 11d, of a radio link with at least one electronic node of each other movable body 11a, 11b, 11c, 11d in communication range (that is, it follows from this step E101 establishing a radio link between each electronic node of said mobile body and at least one electronic node of each other mobile body within communication range); a determination step E102, for each established radio link, of a reception power associated with said established radio link; a determination step E103 of a relative angle α and a relative distance d between said movable body 11a, 11b, 11c, 11d and each movable body 11a, 11b, 11c, 11d of which at least one electronic node is at communication range of the electronic nodes of said mobile body from the determined reception powers (this relative angle and or the distance d being determined in the manner as previously described); and the method comprises a step E104 for implementing a cooperative function (in the sense of radiolocation, where it involves measurements between moving elements to be positioned) for estimating relative positions taking as input relative determined angles and relative distances determined between moving bodies. It is understood that the output of this cooperative position estimation function can give said positions of a moving body relative to the moving bodies of its vicinity.

In particular, the cooperative function for estimating relative positions can take as input the set of relative angles a determined of each of the moving bodies 11, 11b, 11c, 11d and the set of relative distances d determined between moving bodies 11a, 11b, 11c, 11d. This provides a global map of the set of moving bodies 11a, 11b, 11c, 11d in an environment where they evolve. Alternatively, the cooperative function for estimating relative positions is implemented for (and advantageously by) each movable body 11a, 11b, 11c, 11d and takes as input the relative angles and the determined relative distances of said movable body 11a, 11b 11c, 11d relative to each other movable body 11a, 11b, 11c, 11d with communication range. This allows for a given moving body to know the relative positions and orientations of the "visible" moving bodies of its close environment.

Furthermore, according to this embodiment, the system may comprise a fixed infrastructure 9 (FIG. 9) provided with at least two communicating elements 12, 13 whose absolute positions in the infrastructure reference system are known, and these absolute positions are injected into the cooperative function for estimating the positions so that the latter outputs the absolute positions of said moving bodies within the frame of reference related to the infrastructure. Relative distances and relative angles determined, it is sufficient to know in the plane two external anchoring positions (the absolute positions of the two communicating elements) and to ensure the mobile bodies connectivity comprising at least two radio links vis-à-vis -vis other bodies (moving body or communicating element). In this sense, to reset the relative positioning of the moving bodies in absolute positioning, it suffices that at least one of these mobile bodies has exchanged by radio links with the two communicating elements 12, 13 so that it has been determined for this purpose. at least one movable body of relative angles making it possible to go back to the absolute position value of said at least one moving body, in particular by using the previously described teachings. In this sense, to determine the absolute positions of the other moving bodies, the determined absolute position of said at least one moving body can be injected into the cooperative estimation function.

In particular, the cooperative position estimation function implements a multidimensional positioning algorithm or "MultiDimensional Scaling -MDS in English", or a cooperative tracking filter (of positions) of Bayesian type moving bodies. This algorithm, or this filter, can be used for the relative case and the absolute case of the cooperative estimation function.

The invention also relates to the system provided with the first body 1 carrying said at least two electronic nodes 3, 4 arranged at distinct positions on said first body 1 and having the orientation direction 2. Of course the system comprises the second body 5 whose said at least one associated electronic node is able to communicate with the electronic nodes 3, 4 carried by the first body 1. Furthermore, the system comprises a module 100 (Figure 1) configured to establish radio links 6 7 between the two electronic nodes 3, 4 carried by the first body 1 and the said at least one electronic node associated with the second body 5. Furthermore, the system comprises a module 101 configured to measure the reception powers of each of the radio links. established and a configured module 102 to exploit the measured reception powers to establish a value of the relative angle between said direction Orientation 2 and the straight line 8 passing through the first and second bodies 1, 5.

[0064] Concerning the processing of information, in particular given powers, many ways of concentrating this information with a view to processing them can be implemented, for example and in a non-exhaustive manner, one can have: a determination of the powers of reception at the first body and a concentration of the latter, via wireless links, at one of the electronic nodes of the first body which then performs the calculations to determine at least the relative angle, • a determination of the powers of reception at the first body and a concentration of the latter, via wireless links, at one of the electronic nodes of the first body which then transmits all these reception powers determined to an external server by wireless link to achieve calculations to determine at least the relative angle at the server level, • a determination of the powers of the reception at the first body then a concentration of the latter, via wire links, at one of the electronic nodes of the first body which then performs the calculations to determine at least the relative angle, • a determination of the receiving powers at the level of the first body and then a concentration of the latter, via wire links, at one of the electronic nodes of the first body which then transmits all these determined powers to an external server by wireless link to perform the calculations to determine at least the relative angle at the server level, • a determination of the reception powers at the first body and then a sharing thereof, via wireless links, to an external server to perform calculations to determine at less the relative angle at the server level, here each electronic node is able to establish a wireless link with the server p to directly transmit the reception power determined at said electronic node, • a determination of the reception powers at the first body and then a sharing thereof, via wireless links, to another first intermediate body which collects the information then who can return them to a server that then performs the calculations to determine an associated relative angle.

It is understood from what has been said above that the present invention is particularly applicable in the context of wireless body networks, and can offer a low cost solution, robust and accurate while requiring little or no needs in terms of calibration.

In particular, the relative angles will be determined preferentially at the level of the body concerned but may also be determined elsewhere (ie outside the carrier body) outside by a suitable server which can then return the calculated values of the relative angles carrier - or any other entity if he / she needs it. In other words, the module 101 configured to measure reception powers of each of the established radio links can be carried by the first body, and the configured module 102 to exploit the measured reception powers to establish a value of the angle relative between said orientation direction 2 and the straight line 8 passing through the first and second bodies 1, 5 can be carried by the first body or relocated so as to be remote from said first body 1.

Moreover, the solution implementing the determination of a relative angle from reception power measurements is robust to: • situations of radio irregularity (for example with respect to an incorrect orientation of the diagrams of antenna, calibration problems of the transmitted power, etc.) • the situations of obstructions and / or disturbances of the radio links (by an external obstacle) which then substantially substantially attenuate the at least two radio links making it possible to determine the relative angle, and is easy to implement as long as the communication standard allows the measurement of reception powers of the radio links.

According to the embodiment illustrated in Figure 6, the second body 5 is of the same type as the first body 1. The second body 5 then has an orientation direction and comprises at least two electronic nodes arranged in different positions. In this case, the establishment step E1, for each electronic node 3, 4 of the first body 1, of a radio link 6, 7 with the second body 5 is implemented for each electronic node of the second body 5.

Thus, to determine a relative angle, it can be used four radio links and thus four specific powers. Two estimates of relative angles can thus be carried out (i.e., an estimate per node of said second body). In this case, the line 8 passing through the first and second bodies 1, 5 can be calculated as the median arrival direction of the radio signal received at the nodes of the first body 1 vis-à-vis each node of said second body, determined from the two relative angles estimated.

It is understood that for a first body 1 given, especially when it is mobile, the determination of the relative angle, and where appropriate the relative distance with other bodies, the absolute position and the absolute angle can be implemented iteratively (if we want to refine the estimation from one iteration to another) and / or recursively (as in a filter-based solution where we can takes advantage of the dynamics of observation and estimation). Thus, it is possible to follow the evolution of the first body over time. This is particularly advantageous in navigation or radar applications. It is then possible to improve the tracking performance and pedestrian navigation experience (alone or in groups, whether they are coordinated or not ...), in particular by ensuring a better robustness with respect to the situations radio obstructions.

Preferably, in the present description it is considered the resolution of positioning problems in a two-dimensional environment (X coordinates, Y in a Cartesian coordinate system) and angular estimation in the azimuthal plane.

Although body-based examples having at least two electronic nodes have been given most often, the embodiments and cases presented may be extended to configurations comprising a larger number of electronic nodes. Without loss of generality, when the body has two nodes in the present description, it is preferentially nodes worn on the front of the body ("front" in English) and back ("back" in English). It has been mentioned previously the use of a difference of received powers (expressed in dB) to determine the relative angle. In the case of more than two radio links established between two bodies, for example when the first body comprises three or more electronic nodes, it is possible to set up a calculation law other than a simple difference in reception power which may also be 'apply. Another option is to form power differences according to the different possible pairs of nodes carried according to the methods described above (therefore, with a complexity since combinatorial), then to merge the angular results from each of these pairs (ex. preceding the calculation of an arithmetic mean, a weighted average, a median for the estimated final relative angle).

The present solutions are based on radio technologies and narrowband wireless communication protocols (preferably low power, low complexity and low cost in a context of body network) likely to be already standardized, which allows to avoid using specific hardware (typically network antennas for beamforming, co-located antennas and passive hybrid radio frequency couplers for sigma-delta receivers, or radio frequency mixers for demodulators type FMCW for "Frequency-Modulation Continuous-Wave" in English, etc ...).

Claims (17)

A method of using a system comprising a first body (1) having an orientation direction (2) and carrying at least two electronic nodes (3, 4) arranged in different positions at the first body (1). ), said system comprising a second body (5) associated with at least one electronic node (5e), said electronic nodes (3, 4) carried by the first body (1) and said at least one electronic node (5e) associated with the second body (5) being able to communicate with each other by radio links (7, 6), said method comprising the following steps: an establishment step (E1), for each electronic node (3, 4) carried by the first body (1), a radio link (6, 7) with said at least one electronic node associated with the second body (5), • a determination step (E2) for each established radio link (6, 7), a reception parameter representative of the reception power as associated with said established radio link, • a step of determining (E3) a relative angle (a) between the orientation direction (2) of the first body (1) and a line (8) passing through the first body (1 ) and the second body (5) using the determined reception parameters. 2. Method according to claim 1, characterized in that said relative angle (a) is determined by means of a deterministic association function linking said relative angle (a) to the determined reception parameter values associated with said radio links (6). , 7), in particular at a difference value between the reception parameters determined and expressed in decibel. 3. Method according to claim 2, characterized in that said deterministic function comprises parameters calculated from a predetermined and reproducible model linking the average attenuation in power undergone for each radio link according to said relative angle (a) and the position of the electronic node on the first body (1) and associated with said radio link. 4. Method according to claim 2, characterized in that said deterministic function comprises parameters calculated from a dynamic observed empirically receiving parameters during a calibration phase associated with the first body (1). 5. Method according to the preceding claim, characterized in that the calibration phase associated with the first body (1) is to ensure a movement of the first body (1) carrying said at least two electronic nodes (3, 4) to test a plurality possible relative angles between the direction of orientation of said first body (1) and a straight line passing through the first body (1) and a reference body so as to measure, for each relative angle tested, minimum and maximum differences between parameters IEC 60050 - International Electrotechnical Vocabulary - Details for IEV number 841-21-31 Electromagnetic binding standard reception between said at least two electronic nodes (3, 4) of the first body (1) and an electronic node of the standard body. 6. Method according to the preceding claim, characterized in that the deterministic function is an interpolation function calculated from the minimum and maximum differences between the standard reception parameters measured empirically during the calibration phase for the different values of relative angles tested. 7. Method according to claim 1, characterized in that the step of determining (E3) the relative angle (a) makes it possible to jointly determine a relative distance (d) separating the first body (1) from the second body (5). ). 8. Method according to the preceding claim, characterized in that the relative angle (a) and the relative distance (d) are obtained by solving a system of equations with two unknowns respectively formed by the relative angle (a) and the relative distance (d), said system taking as input the determined reception parameters and a radio-link average attenuation parametric model including a first parameter corresponding to the average standard attenuation at a reference distance, and a second parameter corresponding to an average attenuation coefficient, are also two functions dependent on the unknowns sought. 9. Method according to one of claims claims 1 to 8, characterized in that the system comprises a plurality of second bodies (5a, 5b) each associated with at least one electronic node (5e) and so that each second body (5a, 5b) forms a pair with the first body (1), said second bodies (5a, 5b) belonging to a fixed infrastructure (9), and in that: • the setting step (E1) is set implemented for each second body (5a, 5b), from which it follows that for each pair of radio links are formed between said electronic nodes (3, 4) carried by the first body (1) of said pair and said at least one electronic node associated with the second body (5a, 5b) of said pair, • the step of determining (E3) a relative angle (a) is implemented for each pair, • said method comprises a determining step (E4) an absolute position and / or an absolute angle of the first body (1) within a r ferential infrastructure comprising the plurality of second bodies (5a, 5b) from the determined relative angles associated with said couples. 10. Method according to the preceding claim, characterized in that the step of determining (E4) the absolute angle and / or the absolute position comprises the use of an estimation function taking as input known absolute positions. second bodies (5a, 5b) within the frame of reference of the infrastructure and each relative angle (a) determined, said estimation function giving as output said absolute angle and / or said absolute position. 11. Method according to one of claims 9 or 10, characterized in that the absolute angle (β) corresponds to the angle formed between the orientation direction of the first body (1) and a reference direction (10). invariant in the global frame of reference of the infrastructure, for example given by the terrestrial magnetic north. 12. The method of claim 10 or the combination of claims 10 and 11, characterized in that the estimation function is such that the absolute angle and / or the absolute position are obtained as the iterative solution of a problem in the sense least squares involving an approximated and locally linearized form of a reference function connecting the value of the angle relative to the absolute position of a second associated body, to the absolute position of the first body (1) and to the angle absolute associated with the first body (1). 13. The method of claim 1, characterized in that the system comprises a plurality of movable bodies (11a, 11b, 11c, 11d) each having an orientation direction (2) and each carrying at least two electronic nodes (3). 4) arranged at different positions on said movable body (11a, 11b, 11c, 11d), said first body (1) and said second body (5) forming part of the plurality of moving bodies, and in that the method comprises for each movable body (11a, 11b, 11c, 11d) and when said movable body (11a, 11b, 11c, 11d) is in communication with at least one other movable body (11a, 11b, 11c, 11d): an establishment step (E101), for each electronic node of said mobile body (11a, 11b, 11c, 11d), of a radio link with at least one electronic node of each other mobile body within range of communication, • a determination step (E102), for each established radio link, of a parameter receiving signal representative of the reception power associated with said established radio link, • a step of determining (E103) a relative angle and a relative distance between said movable body (11a, 11b, 11c, 11d) and each body mobile (11a, 11b, 11c, 11d) of which at least one electronic node is in communication range of the electronic nodes of said movable body (11a, 11b, 11c, 11d) from the determined reception parameters, and in that the method comprises a step (E104) of implementing a cooperative function for estimating relative positions taking, at the input, determined relative angles and determined relative distances between moving bodies. 14. The method as claimed in the preceding claim, characterized in that the cooperative function for estimating relative positions takes as input all the relative relative angles (a) determined of each of the moving bodies and the set of relative distances determined between moving bodies. or in that the cooperative function for estimating relative positions is implemented for each moving body and takes as input the relative angles and the determined relative distances of said movable body with respect to each other moving body in communication range. 15. The method of claim 13 or 14, characterized in that the system comprises a fixed infrastructure (9) provided with at least two communicating elements (12, 13) whose absolute positions in the frame of reference of the infrastructure are known, and in that these absolute positions are injected into the cooperative position estimating function for the latter to output the absolute positions of moving bodies within the frame of reference related to the infrastructure. 16. Method according to one of claims 13 to 15, characterized in that the cooperative estimation function implements a multidimensional positioning algorithm, or a cooperative tracking filter of Bayesian type moving body positions. 17. System comprising a first body (1) carrying at least two electronic nodes (3, 4) arranged at different positions and having an orientation direction (2), said system comprising a second body (5) associated with at least an electronic node (5e) able to communicate with the electronic nodes (3, 4) carried by the first body (1), characterized in that it comprises: • a module (100) configured to establish radio links between the two electronic nodes (3, 4) carried by the first body (1) and said at least one electronic node associated with the second body (5), • a module (101) configured to measure reception parameters representative of the reception powers of each established radio links (6, 7), and • a module (102) configured to exploit the measured reception parameters to establish a value of a relative angle (a) between said orientation direction (2) of the first co rps (1) and a straight line passing through the first and second bodies (1, 5).