EP4307986A1

EP4307986A1 - Device for tracking a person by using contextualised activity measurements

Info

Publication number: EP4307986A1
Application number: EP22711249.7A
Authority: EP
Inventors: Derek Hill; Nicolas DEFRANOUX
Original assignee: Panoramic Digital Health
Current assignee: Panoramic Digital Health
Priority date: 2021-03-14
Filing date: 2022-03-13
Publication date: 2024-01-24
Also published as: FR3120514A1; US20240163643A1; WO2022194719A1; FR3120514B1

Abstract

Device (1) for monitoring the status of a user in an environment, comprising: ‐ a mobile module (10), which is intended to be worn by the user and comprises an activity sensor and a processing unit for producing a status signal (S_s) from an activity signal generated by the activity sensor; ‐ beacons (20), which are distributed in the environment and are designed to send a transmission signal (S_e) to the mobile module (10) via a short-range wireless connection; the device being characterised in that: - the processing unit (15) is designed to produce a position signal (S_p) on the basis of at least one distance between the mobile module and a beacon; ‐ the transmission unit (16) is designed to transmit the status signal (S_s) and the position signal (S_p) to the central unit (30).

Description

Title: Device for tracking a person using contextualized activity measures

TECHNICAL FIELD The technical field of the invention is the tracking of a person by using measurements of activities carried out by the person coupled with information on the position of the person inside a building.

PRIOR ART

Common connected objects benefit from connectivity technologies that can be leveraged in health-related applications. An example of a recent application relates to applications making it possible to detect proximity to a person who later turns out to be infected with a virus. This type of application has proven to be particularly effective in countries where it was widely used, for example in South Korea.

Furthermore, there is a growing demand for home care, this demand coming from both patients and health authorities, in order to optimize the length of stay in a hospital environment. The maintenance at home, or in non-hospital infrastructures, of certain sick people, or those suffering from a disability, or the elderly presupposes that appropriate monitoring be envisaged. We are witnessing a rapid development of connected devices, making it possible to transmit data related to the physical or physiological activity of people from their place of residence, whether it is a private home or a business structure. specialized reception.

It is also known that conventional geolocation systems, for example of the GPS type, can be unreliable when one is inside a building. In addition, the consumption of this type of device is high, which requires a high capacity battery or frequent recharging. To date, the location information of a person is hardly used in devices allowing the transmission of physiological data of a person.

The documents US20160379476 and WO2020198090 describe devices intended to be worn by a person, with the objective of monitoring the activity carried out by the person, in particular at home. The invention falls within this framework. It proposes an improved device, the implementation of which makes it possible to remotely monitor a change in the state of a user, and taking account of his position, in particular the position inside a building.

DISCLOSURE OF THE INVENTION

A first object of the invention is a device for monitoring the state of a user, the user occupying an environment, the device comprising:

- a mobile module, intended to be carried by the user;

- beacons, distributed in the environment, configured to send a transmission signal to the mobile module by a short-range wireless link; the nomadic module comprising:

- A short-range wireless link unit, configured to receive at least one transmission signal emitted by at least one beacon, and preferably a plurality of transmission signals respectively emitted by a plurality of beacons;

- a telemetry unit, configured to estimate, at different measurement instants, a distance between the nomadic module and each beacon whose transmission signal is received by the nomadic module;

- at least one user activity sensor, configured to establish an activity signal representative of user activity at each measurement instant;

- a processing unit, configured to generate a status signal from at least one activity signal measured by the activity sensor;

- a transmission unit, configured to transmit the status signal to a central unit; the device being characterized in that:

- the processing unit is configured to establish a position signal as a function of at least one distance estimated by the telemetry unit, at each measurement instant, the position signal being representative of a position of the user in relation to the environment;

- the transmission unit is configured to transmit the status signal and the position signal established, at each measurement instant, to the central unit, so as to allow storage, by the central unit, of the signal d state and of the position signal established at each instant of measurement.

The activity sensor may comprise at least:

- a motion sensor; - And/or a cardiac activity sensor;

- and/or a muscle activity sensor;

- and/or a brain activity sensor;

- and/or a blood pressure sensor; - And/or a sensor of an analyte.

According to one embodiment, at least one beacon is a privacy beacon, the device being programmed such that when the nomadic module, receiving a transmission signal emitted by the privacy beacon, is placed at a distance of the privacy beacon less than a threshold distance, no status signal is transmitted by the mobile module to the central unit. The telemetry unit is preferably configured to estimate a distance between the nomadic module and at least one beacon according to an intensity or a power of the transmission signal sent by the beacon to the nomadic module.

The telemetry unit is preferably configured to estimate several distances between the nomadic module and respectively several beacons according to transmission signals transmitted respectively by each beacon to the nomadic module. The processing unit can then be configured such that the position signal corresponds to a position of the nomadic module with respect to several beacons. According to one possibility, the position signal is or comprises a list of estimated distances between the nomadic module and each beacon.

According to one embodiment, the processing unit is configured to: - estimate a state of the user, among several predetermined states, from at least one activity signal established by the activity sensor;

- generating the status signal based on the estimated user status.

The state of the user can be representative of a physical activity practiced by the user at the moment of measurement, or of a state of stress of the user at the moment of measurement, or of a state physiological of the user at the moment of measurement.

According to one embodiment, the status signal corresponds to the activity signal, possibly preprocessed, resulting from the activity sensor or from each activity sensor. The status signal can be obtained by associating or by combining the activity signal resulting from different activity sensors. The status signal may be equal to the activity signal. The short-range link can in particular be a link whose range is less than 50 meters or 30 meters.

According to one embodiment: - at least one beacon comprises an ambient sensor, configured to measure a temperature and/or a sound level and/or a light level;

- the beacon is configured to transmit an ambient signal, depending on the measurement performed by the ambient sensor, to the nomadic module;

- the processing unit is programmed to assign an ambient level, depending on the ambient signal, to each status signal.

According to this embodiment, the central unit collects, at each measurement instant, the position signal, the status signal and the ambient level.

A second object of the invention is a method for monitoring a state of a user of a device according to the first object of the invention, the user being placed in an environment, the user carrying the nomadic module of the device, several beacons of the device being distributed in the environment, the method comprising, in at least one instant of measurement: a) measurement of an activity of the user, using an activity sensor of the module nomadic; b) generating a status signal from the activity measured by one or each activity sensor; c) estimating a distance between the nomadic module and at least one beacon; d) from the distance or from each distance resulting from c), determination of a position signal representative of a position of the user in the environment; e) transmission of the status signal and of the position signal of the user, determined at each instant of measurement, to a central unit.

The central unit is different from the mobile module.

At least one beacon can be fixed in the environment. Preferably, several beacons are distributed in a fixed manner in the environment.

According to one possibility, a beacon can be carried by a third person, different from the user.

According to one possibility,

- the environment includes an object, likely to be in contact with the user or manipulated by the user;

- at least one beacon is attached to the object.

According to one possibility, at least one beacon is a privacy beacon, the device being programmed such that when the nomadic module, communicating with the privacy beacon, is placed at a distance from the privacy beacon of less than a threshold distance, no status signal is transmitted by the mobile module to the central unit. According to one possibility,

- at least one beacon comprises an ambient sensor, configured to measure a temperature and/or a sound level and/or a light level,

- the beacon is configured to transmit, to the nomadic module, an ambient signal, depending on the measurement made by the ambient sensor;

- the processing unit is programmed to assign an ambient level, depending on the ambient signal, to the status signal transmitted to the central unit.

The central unit can be present in the environment or remote from the environment. The environment is preferably a place intended to be inhabited by the user. It can be a workplace. The environment preferably corresponds to all or part of a residential building or a building intended for a work activity.

Other characteristics of the first and second object of the invention are found in the appended claims.

A third object of the invention is a measurement system, comprising: several devices according to the first object of the invention, the devices being intended to be worn respectively by different users; a central unit, configured to receive the status signal and the position signal respectively established, at each measurement instant, for the different users; the central unit being programmed to: take into account a predetermined task;

• from the status and position signals transmitted to the central unit, selection, for each user, of measurement times during which each user performs said task, the measurement times selected for each user forming at least one range time specific to each user; · for each user, processing status signals and/or position signals in each time range selected for said user, so as to characterize the activity of each user when the latter performs said predetermined task. According to this embodiment, preferably, only the signals transmitted to the central unit during the time range specific to each user are used to characterize the activity of the user for the task taken into account.

The third aspect of the invention can be implemented simultaneously by considering respectively different tasks performed by each user. The invention will be better understood on reading the description of the embodiments presented, in the remainder of the description, in connection with the figures listed below.

FIGURES

Figure IA schematizes the main components of a device according to the invention.

FIG. 1B shows an example of distribution of beacons in an environment, the environment being a dwelling.

FIG. 2A shows an activity signal produced by an accelerometer when the user moves around in a large room. In FIG. 2A, the abscissa axis corresponds to time (unit: millisecond ms) and the ordinate axis corresponds to acceleration (unit: mg or milli-g).

FIG. 2B shows an activity signal produced by an accelerometer when the user moves around in a small room. In FIG. 2B, the abscissa axis corresponds to time (unit: millisecond ms) and the ordinate axis corresponds to acceleration (unit: mg or milli-g)

FIG. 3 schematizes the main steps of a method for implementing the device shown in FIG. 1A.

FIG. 4A represents a power of a signal emitted by a beacon and received by a nomadic module. The abscissa axis corresponds to time (unit: seconds) and the ordinate axis corresponds to the power received by the mobile module (unit: dBm).

FIG. 4B represents an estimation of a distance between the nomadic module and the beacon, the distance being calculated according to the signal represented in FIG. 4A. The abscissa axis corresponds to time (unit: seconds) and the ordinate axis corresponds to estimated distance (unit: mm).

FIGS. 5A to 5E are boxplots (usually designated by the Anglo-Saxon term box plot) showing the variability of an average gait cycle period (usually designated by the Anglo-Saxon term step time), measured by nomad modules respectively carried by two test users: user 1 and user 2. The abscissa axis designates the user and the ordinate axis corresponds to a time unit (ms). FIGS. 6A to 6C are also boxplots representing a variability of a time to sit on a chair, or “sit time” (FIG. 6A), of a time to get up from a chair “stand time” (FIG. 6B) or a duration for sitting down and getting up “sit to stand time” (FIG. 6C). In each figure, the abscissa axis designates the type of chair. 1: chair height 39.5 cm - 2: chair height 51.5 cm - 3: chair height 59.5 cm - 4: all chairs combined. On each y-axis, the unit is milliseconds. FIG. 7A illustrates a path taken by a user in an environment comprising two beacons referenced 20i and 202.

FIG. 7B shows the estimated distance between the mobile module carried by the user and the beacon 20i. The ordinate axis corresponds to the distance (unit: mm). The abscissa axis corresponds to time (unit: second).

FIG. 7C represents a power of a signal emitted by beacon 20i and received by the nomadic module. The abscissa axis corresponds to time (unit: seconds) and the ordinate axis corresponds to the power received by the mobile module (unit: dBm).

FIGS. 7D, 7E and 7F are measurements resulting respectively from an accelerometer, a gyroscope and a magnetometer integrated into the nomadic module. In each figure, the ordinate axis represents the quantity measured (units: milli-g for figure 7D, degrees per second (dps) for figure 7E and Gauss (Gs) for figure 7F). On each of these figures, the abscissa axis corresponds to time (unit: second).

FIG. 8A illustrates different positions of a nomad module with respect to a beacon, a distance between the nomad module and the beacon having been measured in each position.

Figure 8B shows the estimated distances between the mobile module and the beacon (curve a - left ordinate axis - unit mm), as well as the power of the signal received by the mobile module (curve b - right ordinate axis - unit dBs). Curve c represents the actual distances. The abscissa axis represents time (second unit).

FIGS. 9A to 9F are boxplots representing a variability in the duration of movements performed by a test user. The user carried out the movements normally or while carrying a load of 5 kg. In each figure, the abscissa axis corresponds to the user's configuration (1: normal configuration; 2: configuration with load port). The y-axis corresponds to the duration (unit: ms).

FIG. 9A corresponds to an average period of walking, without contextualization, the test user evolving in two different rooms.

FIG. 9B corresponds to a duration for getting up from a chair, without contextualization, the user using two different chairs.

FIG. 9C corresponds to an average period of walking, the measurements being contextualized, the test user evolving in the same room.

FIG. 9D corresponds to an average walking period, the measurements being contextualized, the test user evolving in the same room, different from the room corresponding to FIG. 9C. FIG. 9E corresponds to a duration for getting up from a chair, the measurements being contextualized, the test user using the same chair.

FIG. 9F corresponds to a duration for getting up from a chair, the measurements being contextualized, the test user using the same chair, different from the chair corresponding to FIG. 9E.

FIG. 10 represents a measurement of the distance between two beacons as a function of time.

DESCRIPTION OF PARTICULAR EMBODIMENTS

Figure IA schematizes the three main components of a device according to the invention. The device 1 comprises a mobile module 10, intended to be carried by a user. The nomadic module can for example be arranged in contact with the body of the user, by being for example held by a bracelet or an armband. The nomadic module 10 can be integrated into a watch.

The nomadic module 10 is intended to communicate, by a short-range wireless link, with a beacon 20, and preferably with several beacons 20. By short-range link is meant a link established, generally by radio wave, within a range of a few tens of meters: without obstacles, the range is less than 50 meters or even 30 meters. It may be, for example, a communication by radio wave at ultra high frequency (UHF), for example of the Bluetooth type, or, preferably, a communication of the low-power Bluetooth type, usually designated by the acronym BLE , meaning “Bluetooth Low Energy”. Such a protocol is the subject of a standard published by the Bluetooth SIG (Bluetooth Special Interest Group). Alternatively, the link can be of the ZigBee type, which, like the Bluetooth or Bluetooth Low Energy link, uses radio waves at the 2.4 GHz frequency.

The nomad module 10 comprises a wireless link unit 11, intended to communicate, via the short-range wireless link, with beacons 20 located within the range of the nomad module. The wireless link unit 11 is connected to an antenna 12, presenting a reception diagram. In known manner, the reception diagram corresponds to an angular variation in the reception sensitivity of the antenna. Generally, the reception diagram of an antenna is not isotropic.

The device comprises at least one beacon 20, and preferably several beacons 20, distributed in an environment. The environment is a space, generally covered, that the user is likely to occupy. It may for example be a dwelling, or a place of work, or a collective dwelling, for example a nursing home or an establishment intended for the reception of the elderly. The environment can include spaces outdoors, such as a garden. However, one intended use of the invention is within a building, where Global Positioning System (GPS) positioning may malfunction or not be fully operational.

Each beacon 20 comprises a transmission unit 21, intended to transmit a transmission signal S _e to the nomad module 10, according to the short-term wireless link on the basis of which the nomad module 10 communicates. The transmission unit 21 is connected to an antenna 22, intended to transmit or receive a signal. Like the antenna 12 equipping the nomadic module, the antenna 22 of each beacon 20 is characterized by a transmission/reception diagram, generally non-isotropic.

The mobile module can advantageously comprise an orientation unit 12', intended to estimate an orientation of the mobile module, and more precisely an orientation of the antenna 12. The orientation unit 12' can implement an accelerometer, in order to to estimate the orientation of the antenna. Advantageously, the orientation unit 12' comprises a magnetometer combined with the accelerometer. The accelerometer can belong to an activity sensor 14 described below. The orientation of the antenna can be used by the telemetry unit 13 so as to improve the estimation of the distance. Indeed, the reception sensitivity of the antenna 12 varies angularly, the orientation of the antenna can be used to take into account a variation in sensitivity in the estimation of the distance.

The nomadic module 10 also comprises a telemetry unit 13, configured to estimate, at different measurement instants, a distance between the nomadic module 10 and at least one beacon 20, or even each beacon 20 located within the range of the nomadic module 10. Each distance between the mobile module 10 and a beacon 20 is estimated on the basis of a measurement of the power of the transmission signal emitted by the beacon 20 and received by the mobile module. It is known that the power of the signal received by a receiver of a radio wave allows an estimation of the distance between the transmitter of the radio wave (in this case the beacon 20) and the receiver of the radio wave ( in this case the nomadic module 10), according to the expression:

,P-RSSI\ d=10 10XJV>(1) where: d is the estimate of the distance between the beacon 20 and the nomadic module 10;

P is a power of the signal transmitted by the beacon (dB); N is a constant, usually between 2 and 4, the value of which can be adjusted by the orientation unit 12'.

RSSI, meaning "Received Signal Strength Indicator", corresponds to the strength of the signal emitted by the antenna and received by the mobile module (dB).

The nomadic module 10 includes at least one activity sensor 14. The activity sensor 14, or each activity sensor 14, is configured to measure an activity of the user and emit an activity signal S _a representative of user activity. The activity sensor can be chosen from:

- A motion sensor, for example of the gyrometer or accelerometer or magnetometer type;

- a cardiac activity sensor, for example a sensor operating according to the principle of photoplethysmography, a technique usually implemented on sports watches;

- a muscle activity sensor, for example an electromyography sensor;

- a cerebral activity sensor, for example an Electroencephalography (EEG) type sensor;

- a blood pressure sensor, for example a sensor based on pulse wave velocity;

- an electrodermal activity sensor, configured to measure an impedance of the skin, in particular during the occurrence of a stressful situation;

- a temperature sensor;

- an atmospheric pressure sensor;

- a sensor of an analyte, for example a glucose sensor, the concentration of certain molecules being able to be detected by photoacoustic method or by the analysis of a bodily fluid, for example sweat. It can also be a biochemical sensor.

The or each activity sensor 14 is preferably non-invasive and non-intrusive in the body of the user. Each activity sensor 14 can in particular implement an optical or acoustic or electrical or electrochemical method.

The atmospheric pressure sensor can make it possible to identify particular tasks carried out by the user, for example going up or down a staircase. Advantage is then taken of a detection of a variation in the atmospheric pressure measured by the sensor to determine a variation in the altitude of the user. The term “activity” can correspond to a physical activity of the user, or to a physiological activity of the user: it can be a cardiac activity, a muscular activity, a neurological activity. It can also be a psychological activity, for example the occurrence of a stressful situation for the user, or the occurrence of a state of drowsiness. It may also be an activity representative of a state considered to be pathological: for example the appearance of tremors or akinesia in a user suffering from Parkinson's disease.

The activity signal emitted by each activity sensor 14 can be monodimensional or multidimensional. When the activity sensor is an accelerometer or a gyrometer or a magnetometer, the activity signal is usually three-dimensional.

The mobile module 10 also comprises a processing unit 15, configured to process the activity signal established by the or each activity sensor 14 so as to establish a status signal S _s of the user. According to one possibility, the processing unit can perform simple signal processing operations, for example amplification and/or shaping and/or digitization. The status signal S _s then corresponds to the activity signal S _a , or to each activity signal, resulting from the processing. According to another possibility, the processing unit 15 can be programmed to interpret the activity signal S _a , or each activity signal, so as to estimate a state of the user from among several predetermined states. The state signal S _s then corresponds to the estimated state of the user. User status can be selected from:

- an active state (user performing regular movements) or resting state, similar to sleep;

- a type of movement carried out by the user: walking, passage from the seated position to the standing position, passage from the standing position to the seated position, passage from the lying position to the standing position, passage from the standing position to the lying down, tremors, walking on stairs, rolling over, running, jumping, falling;

- a symptomatic state: tremors, agitation, disordered movements;

- a state of stress.

The state signal S _s can also be or comprise a characteristic of a movement of the user, for example an average time period between two consecutive steps, or a speed of movement, or a speed of execution of a movement particular. It may for example be a time or frequency characteristic. The status signal S _s is generated by the processing unit 15, from one or more activity signals S _a resulting respectively from one or more activity sensors 14. The processing unit 15 can implement a classification algorithm. The classification algorithm can be a supervised artificial intelligence algorithm, having been the subject of learning, for example a decision tree type algorithm.

The processing unit 15 can be composed of analog or digital circuits. It may comprise a microprocessor, in particular during the implementation of the classification algorithm described above.

The processing unit 15 can also estimate a position of the user from the distance between the nomadic module and each beacon. By position is meant a position of the user in the environment in which the beacons 20 are distributed. This may for example be a room occupied by the user.

The mobile module 10 also includes a transmission unit 16. The transmission unit 16 is configured to transmit the status signal, resulting from the processing unit 15, to a central unit 30 described below.

In addition to a transmission unit 21 connected to an antenna 22, each beacon 20 can advantageously include an orientation unit 22', intended to establish an orientation of the antenna 22 of the beacon 20. This is to take into account account an angular variability of the transmission power of the antenna 22, in the estimation of the distance by the telemetry unit 13 of the nomadic module.

Each beacon 20 can also include an ambient sensor 24, intended to measure information relating to an ambient parameter, at the position occupied by the beacon. The ambient parameter can be chosen from: the temperature and/or a sound level and/or a luminosity. Depending on the selected ambient parameter, the ambient sensor 24 can be a thermometer, or a microphone or a photodetector.

The mobile module 10 is configured to be connected to a central unit 30. The central unit 30 is intended to receive signals transmitted by the mobile module 10. These are in particular status signals and information relating to the position of the user at different measurement instants. The central unit 30 comprises a memory, making it possible to memorize the signals received, over time, by the mobile module, or by different mobile modules used simultaneously. The central unit 30 may comprise a microprocessor, for the analysis of the stored signals. When the state signal S _s is formed by each activity signal S _a , possibly pre-processed, the classification of the state of the user can be carried out at the level of the central unit 30 from the signal d status transmitted by the mobile module 10.

The transmission of signals between the mobile module 10 and the central unit 30 is preferably carried out by a long-range wireless link, for example Wifi or by a mobile telephone network, for example of the 3G, 4G or 5G type.

FIG. 1B represents an example of distribution of beacons 20 in an environment which corresponds to a habitat occupied by a user U. The environment has been schematized in the form of a horizontal plane. Beacons 20 are distributed in different rooms, intended to be occupied by the user: bedroom, living room, kitchen, toilets. The central unit 30 is placed in the entrance. In other configurations, the central unit 30 is located remotely, for example in a data storage and analysis center, collecting the status signals transmitted by the mobile modules of different users. The tags 20 are generally attached to particular rooms, or to particular objects. For example, a beacon can be fixed on a chair or on a table, or on a particular household appliance. Preferably, certain beacons are placed in a fixed manner in the environment.

In FIG. 1B, the user U is seated and carries the mobile module 10. A mobile beacon 20 _m has been shown, carried by a third person, in the kitchen. It is a mobile beacon, attached to a person other than the user: medical personnel or someone from the family circle. In the case of collective housing, the third person may be another occupant of the collective housing.

In FIG. 1B, a privacy beacon 20 _p has also been shown, located in the bathroom. When the mobile module is positioned close to the privacy beacon 20 _p , the sending of data to the central unit 30 is interrupted. The use of a privacy beacon guarantees that the user's privacy is preserved in certain, so-called “private” parts of the habitat, in which the user does not want his state to be determined and analyzed. A 20 _p privacy beacon can be placed in the toilet, in a bathroom or in a bedroom. The use of a privacy beacon 20 _p is an important element for the acceptability of the use of the device 1 by the user.

An important aspect of the device is the ability to measure data, representative of the user's daily activity, in a closed or partly closed environment, while assigning these data a position signal S _p , representative of a position of the user in the environment. Indeed, the inventors consider that the activity of the user can vary according to his position in a given environment. The association between signals, representative of the activity of the user, translating his state, and the location of the user in the environment, makes it possible to obtain data acquired in a particular context. We are talking about contextualized data. The data, when it is contextualized, that is to say associated with a position of the user, has less dispersion, and is easier to analyze.

FIGS. 2A and 2B represent an acceleration signal, measured by an accelerometer worn by a user moving respectively in a large room and in a small room. The abscissa axis corresponds to the time (unit ms) and the ordinate axis corresponds to the norm of the acceleration. It is observed that although coming from the same sensor, the signals measured by the accelerometer do not have the same characteristics. Thus, the average periods of the user's steps in the large room and in the small room are respectively 587 milliseconds and 658 ms. Thus, the average time period of the steps can form a status signal, characterizing the activity of the user. This example shows that the status signal varies according to the position of the user, and more precisely according to the room occupied by the user.

In order to obtain a more detailed analysis of the activity of the user, it is understood that it is preferable to dissociate the signals grouped according to the position of the user, in this case the room occupied by the user. . Thus, the association of information relating to the position of the user makes it possible to reduce the variability of relevant information for tracking the user.

FIG. 3A schematizes the main steps of a method for implementing the device 1 previously described. The implementation of the method assumes that the position of the beacons 20 is known: each beacon is thus assigned to a room, or to an object, or to a person. Each beacon is assigned an identifier of its own. Two different tags have two different identifiers. It is preferable that several tags are fixed in the environment.

Step 100: Acquisition of activity signals.

During this step, each activity sensor 14 of the mobile module 10 generates an activity signal S _a at a measurement instant. It may for example be an accelerometer signal and a heart rate signal. Step 110: Generation of a status signal.

From the activity signal S _a generated by each activity sensor 14, the processing unit 15 establishes a status signal S _s of the user. In general, the state signal S _s characterizes the activity of the user. According to a first possibility, the state signal S _s corresponds to a set formed by each activity signal S _a emitted by each activity sensor 14, possibly after application of a treatment of the type filtering, shaping, amplification , scanning. The processing unit 15 can be configured to extract characteristics from each activity signal S _a , for example average, variance, or other statistical indicators, detection of peaks, peak to peak distance, minimum, maximum, a dominant frequency, a time period of a movement performed by the user. The status signal S _s can comprise characteristics extracted from each activity signal S _a . According to this possibility, the state signal S _s brings together the activity signals S _a measured by each activity sensor 14, and/or characteristics of the activity signals S _a measured by each activity sensor. According to a second possibility, the processing unit 15 is programmed to implement a classification algorithm, so as to estimate a state of the user, among several predetermined states, as previously described. The classification algorithm may be based on features extracted from each activity signal. In this case, the state signal S _s is representative of the state of the user. Step 120: measurement of distances between the nomad module and at least one beacon, and preferably each beacon located within the range of the nomad module.

During this step, the telemetry unit 13 of the nomadic module 10 estimates a distance between the module and each beacon 20 placed within range of the short-term link of the wireless link unit 11. As previously mentioned, the distance is estimated on the basis of an intensity of a transmission signal S _e emitted by the beacon and picked up by the nomadic module. In order to refine the measurement of the distance, the respective orientations of the antennas 22, 12 of the beacon and of the nomadic module, with respect to the vertical, can be taken into account, by using an accelerometer present in the beacon and in the module nomad 10. This allows a comparison of the transmission/reception diagrams, so as to take account of variations in the transmission power (at the level of the beacon) and of the reception sensitivity (at the level of the nomad module 10). When several beacons 20 are within range of the nomadic module 10, the transmission signal S _e addressed by each beacon includes the identifier of the beacon, so as to obtain a list of distances between the nomadic module 10 and each beacon 20. L The identifier also makes it possible to identify the type of beacon: fixed beacon, beacon attached to an object, beacon carried by a person, or privacy beacon.

According to a first possibility, each beacon 20 transmits a transmission signal S _e , comprising its identifier, according to a regular frequency. In this case, the mobile module periodically receives the transmission signal S _e , and the telemetry unit 13 determines the distance between the beacon and the mobile module from the transmission signal S _e .

According to another possibility, when an activity sensor 14 detects a significant variation in an activity signal, the wireless link unit 11 of the nomadic module 10 transmits a link signal to each beacon. Each beacon having detected the link signal generated by the mobile module emits a transmission signal S _e , the latter being detected by the antenna 12 of the mobile module and transmitted to the telemetry unit 13. This possibility is considered less energy consuming by the nomadic module, and more energy consuming for the beacon. This possibility is preferred because the mobile module must be as compact as possible. Beacon compactness requirements are reduced.

FIGS. 4A and 4B represent respectively a time evolution of the RSSI power of a transmission signal S _e emitted by a beacon 20 and detected by a nomadic module 10 as well as of the distance estimated from the power, according to the expression (1). In Figs. 4A and 4B, the abscissa axis corresponds to time (seconds) and the ordinate axis corresponds to RSSI (unit dBm) and distance (unit: mm). dBm is power in decibels relative to a reference value of 1 milliwatt (mW).

Most beacons 20 are fixed and can therefore be connected to large capacity batteries or directly to the electrical network. Preference will be given to the embodiments according to which the electrical consumption of the nomadic module is minimized, to the detriment of the beacons.

According to one possibility, the emission signal S _e emitted by the beacon 20 comprises a component representative of the level of an ambient parameter measured by the ambient sensor 24: as previously indicated, it may be a value temperature, a brightness value or an ambient sound level value: the value of the ambient parameter is transmitted to the processing unit 15 of the mobile module. Indeed, the activity of the user can be sensitive to such an ambient parameter.

As mentioned in connection with Figure IB, a 20 _m beacon can be worn by a third person likely to interact with the user. The measurement of the distance between the beacon carried 20 _m and the nomadic module 10 constitutes an indication that the user is interacting with the person wearing the beacon. His behavior is likely to be influenced by the presence of the person. Thus, the proximity of a third person is relevant data, which can be considered as an ambient parameter, in the same way as the temperature or the luminosity or the sound level, and allowing to contextualize measurements of activity and the user status signal S _s generated by the processing unit 15.

Step 130: determining a position of the user

During step 130, the processing unit 15 determines a position of the user in the environment considered, as a function of the distance, or, and preferably, as a function of several distances respectively measured between the nomadic module 10 and each beacon 20 considered to be stationary in the environment. The position of the beacons 20 is then stored in the processing unit 15. The determination of the position of the user results from a confrontation between the measured distances and the position of each beacon, with the exception of a possible beacon range 20 _m . The position of the user can be determined by implementing a triangulation algorithm. Thus, the position of the user is preferably determined with respect to different beacons 20, the latter being considered as fixed in the user's environment.

When a beacon is attached to an immobile object, or which can be considered as such, a single measured distance makes it possible to estimate the position of the user. Thus, when the user is seated on a chair on which a beacon is fixed, the position of the user can be determined when the distance between the beacon, fixed on the chair, and the nomadic module, is less than a certain threshold .

The position of the user, resulting from step 130, may be such that the user is located within a delimited privacy perimeter, in which it is not desirable that the activity or the state of the user are memorized and analyzed by the central unit 30. This corresponds for example to the bathroom, represented in FIG. 1B, or to a bedroom. The presence of the user in the privacy perimeter is detected when the distance between the privacy beacon 20 _p is less than a predetermined threshold value. The position of the user in the privacy perimeter can be confirmed by other distances between other beacons, in particular fixed beacons, for example by implementing a triangulation algorithm.

According to a variant, the estimation of the position of the user is carried out at the level of the central unit 30. In this case, the position signal, transmitted with the status signal S _s , can comprise a list of distances estimated between the mobile module and a beacon, preferably several beacons, in particular fixed in the user's environment.

At the end of step 130, a position signal S _p is available, representative of the position of the user in the environment. It is either an estimated position, for example a room in which the user is located, or a distance or a list of distances allowing an estimation of the position.

Step 140

During step 140, the transmission unit transmits, to the central unit 30, the status signal S _s and the position signal S _p of the user at each measurement instant. Any ambient parameters can be assigned to the status signal S _s , such as the temperature, the luminosity, the ambient sound level, or the presence of a third person wearing a beacon with a range of 20 _m . The state signal S _s is thus contextualized, in the sense that it is representative not only of the activity of the user, but also of the conditions under which this activity is carried out: position and/or level of ambiance.

According to one possibility, the position and status signals are stored in a memory of the mobile module 10 and transmitted sequentially to the central unit 30, for example according to a determined frequency.

Steps 100 to 140 are repeated, each iteration making it possible to obtain a state signal S _s and a position signal S _p of the user, and possibly a value of an ambient parameter (presence of a person , temperature, etc. at a measurement instant. Steps 100 to 140 can be repeated continuously, or as long as nomadic module 10 is considered active. To this end, the mobile module 10 can execute a step 90, allowing the mobile module 10 to pass between a standby state and an active state.

In order to minimize the energy consumption of the nomadic module 10, the latter can enter a standby mode when no activity, or significant variation in activity, is detected by an activity sensor 14. When a variation activity is detected, the processing unit 15 can "wake up" the main components of the nomadic module, so as to activate the wireless communication with beacons and perform distance calculations. The processing unit 15 can implement an algorithm, for example a supervised learning artificial intelligence algorithm, to switch the nomadic module from the standby state to the active state, on the basis of signals coming from activity sensors 14, and in particular signals representative of a motor activity of the user.

The data transmitted to the central unit 30 is intended for user monitoring. It can be a follow-up of a convalescence, or a follow-up of the evolution of a state of health. When the data transmitted is representative of an abnormal situation, the central unit 30 can detect the occurrence of an emergency situation and emit an alert signal. An abnormal situation may be excessive tremor, a prolonged immobile position in a position, in the environment occupied by the user, and not intended for rest, a sudden acceleration to a position corresponding to a staircase, which may indicate a fall, or an increase in the heart rate while the user is located in a position corresponding to a place of rest, for example an armchair or a bed. An alert situation may correspond to a lack of distance measurement, the fixed beacons located in the habitat being out of the range of the nomadic module, reflecting a potential exit of the user outside his habitat.

Experimental trials

Figures 5A-5E show example data from trials in which two test users were asked to perform motor tasks. Test users wore a nomadic module, as previously described, on their belt. Users moved through a test environment consisting of two rooms. A first room was small. A second room was larger. Test users moved around the environment. The mobile module of each test user made it possible to locate the room occupied by the user, so as to separate the data measured according to the room occupied by each user.

The users wore a mobile module comprising an STM32L433 microcontroller (ST Microelectronics), connected to a Fanstel BC832 BLE link unit, as well as an inertial unit LSM6DSOX (ST Microelectronics). This type of inertial unit has a circuit making it possible to execute an algorithm for interpreting the activity signals measured. In this application, the circuit of the inertial unit has been programmed to estimate the period of a walking cycle, usually designated by the Anglo-Saxon term Step Time. Thus, in this example, the state signal S _s was the duration of the walk cycle.

FIGS. 5A to 5E represent walking cycle times (ordinate axis - unit ms) determined for each test user (abscissa axis), and this respectively in the large room, the large room with three obstacles, the small room, the small room with two obstacles, as well as in all configurations. FIGS. 5A to 5D are representative of contextualized status signals, that is to say assigned to a position of the user (large room, large room with obstacles, small room, small room with obstacles), while the FIG. 5E corresponds to non-contextualized data, that is to say without taking into account the position of the user.

In each figure, the state signals have been represented in the form of a “box plot”, usually referred to as a “box-plot”, mentioning the median, the quartiles and the extrema. Each extremum corresponds respectively to the first quartile decreased by 1.5 times the interquartile range, as well as to the third quartile increased by 1.5 times the interquartile range. It is observed that the contextualized data (FIGS. 5A to 5D) are less dispersed than the non-contextualized data (FIG. 5E). Thus, an important aspect of the invention is to be able to transmit signals representative of the user, but also the context in which the signals were acquired, in particular the position and possibly other environmental factors. This makes it possible to significantly reduce the variability of the data: the characterization of the user is then more precise. In addition, it is observed that the median value of the gait cycle varies according to the room in which the user moves: the smaller and/or more crowded the room, the more the duration of the gait cycle increases.

In the present case, by analyzing the contextualized data, by linking them to the room in which the user was moving, it is easier to detect a change in the user's symptoms, a worsening of the symptoms being able to result in a reduction in walking cycle. A variation is more easily detectable when the variability of the measurements is low.

The invention allows a detailed analysis of the evolution of the symptoms of a patient in-situ, that is to say in his place of residence. Test sessions are thus avoided, carried out in a hospital environment, in a standardized environment, which corresponds to current practice for patients suffering from Parkinson's disease. By implementing the invention, the follow-up of the patient can be carried out from motricity data acquired at his home and contextualized, i.e. grouped according to the position of the user. In this example, the user's position corresponds to the room occupied by the user.

Figures 6A-6C illustrate another example of use, in which a test user was asked to sit and stand on different chairs, of different heights. FIGS. 6A to 6C respectively represent the durations for sitting down, getting up and the durations of a sit-stand cycle, this type of duration being usually referred to as “sit to stand time”. In each figure, the ordinate axis corresponds to the calculated duration and the abscissa axis corresponds to the height of the chair (unit ms). In each figure, the abscissa axis designates the type of chair. 1: chair height 39.5 cm - 2: chair height 51.5 cm - 3: chair height 59.5 cm - 4: all chairs combined (no contextualization). The data is presented in the form of boxplots, as described in connection with Figures 5A through 5E. We observe that depending on the type of chair, the median value varies, as does the variability. The contextualization of the data, namely the position of the user on a chair of known height, allows a better precision of the analysis. This example can be implemented by arranging different beacons on different chairs. The user's position relative to a chair is determined by a simple distance measurement. The occupied chair corresponds to the beacon closest to the user.

FIGS. 7A to 7F illustrate a distance measurement test as well as measurements resulting from activity sensors 14 during a course followed by a user. During this test, the user has traveled between two beacons 20i, 20 ₂ . The course extended between a 20i beacon and a table T, passing through two chairs C1, C2. The second beacon 2(¾ was placed on the table T. During the course, the user sat down on the chairs C1, C2, on the way there and on the way back. In FIG. 7A, the arrows in solid lines and in dotted lines respectively represent the outward path, from the beacon 20i to the table T, as well as the return path.

FIG. 7B represents the distance measured by the nomadic module with respect to the first beacon 20i. The nomadic module 10 was carried in front of the user. We observe the masking effect of the user, which leads to overestimating the distance relative to the first beacon 20i during the outward journey. The body of the user forms a screen resulting in an attenuation of the transmission signal S _e between the beacon 20i and the nomadic module, which induces the masking effect. This masking effect can be mitigated by using multiple tags. FIG. 7C shows the power of the signal emitted by the first beacon and received by the mobile module, as a function of time. FIGS. 7D, 7E and 7F represent the signals measured by the accelerometer, the gyrometer and the magnetometer of the mobile module, as a function of time (axis of abscissas: s). FIGS. 7A to 7F illustrate the ability of the device to simultaneously measure different distances, while measuring activity signals according to a high temporal frequency.

Figures 8A and 8B are an illustration of the masking effect induced by the user's body. In FIG. 8A, the beacon is materialized by a star. The user U, provided with the module, has turned on himself, as represented in FIG. 8A, according to sequences of duration equal to 15 seconds. The double arrow represents the distance between the beacon and the nomadic module 10 in each situation represented in FIG. 8A. In each configuration, the real distance between the beacon and the mobile module has been indicated. In FIG. 8B, the evolution of the RSSI power received by the mobile module has been represented (curve b) and the distance estimated from the power RSSI (curve a), by implementing expression (1), and this as a function of time (axis of abscissas - unit s). In FIG. 8B, the real distance has also been represented (curve c), the latter being schematized by horizontal lines. These figures illustrate the masking effect of the user, in particular between 45 s and 60 s, which results in an overestimation of the distance, the overestimation being around 1 meter. These measurements show that the distance between a beacon and the nomadic module can be estimated with an uncertainty of 1 m. It is not a precise measurement, but it is sufficient to evaluate a position of the user in a habitat, and in particular to identify the room occupied by the user. By combining several distances respectively between different beacons and the nomadic module, the measurement uncertainty can be reduced, for example by implementing a triangulation algorithm.

FIGS. 9A to 9F illustrate durations measured while a test user performed different tasks, with or without a 5 kg weight carried by the user, and this in different rooms: room 1 and room 2. Room 1 included a first type of chair, and Exhibit 2 had a second type of chair. The fact of carrying a weight corresponds to a simulation of a deterioration in the state of health of the user. We measured the step time (period of the gait cycle) as well as the time between a sitting position and a standing position (sit to stand time).

Figures 9A, 9C, and 9D illustrate step time measurements, while Figures 9B, 9E, and 9F depict time measurements from sitting to standing. Figures 9A and 9B are established from non-contextualized data: it concerns all of the measures. FIGS. 9D to 9F are established from contextualized data, that is to say attached to user position information, in this case the room occupied by the user. Figures 9C and 9E correspond to part 1, while Figures 9D and 9F correspond to part 2. In each figure, the abscissa axis corresponds to the user's configuration (1: normal configuration; 2: configuration that the user is carrying the 5 kg load). In each figure, the y-axis corresponds to the duration (unit: ms)

A statistical analysis of the data represented in FIGS. 9A to 9F shows the effect of a contextualization of the data on the detection of a change in the state of health of the user. The main statistical results are represented in tables 1 and 2 (for step time - duration of the gait cycle) as well as 3 and 4 (for sit to stand time - duration between sitting and standing). We observe that the variability of the measurements is lower when the latter are contextualized. A consequence of the lower variability is a decrease in the sample size to distinguish symptom onset. By sample size, we mean the minimum size of the sample allowing the latter to be characterized with a predetermined level of confidence.

When the measures are contextualized, the sample size is reduced, due to the lower variability of the measures. This makes it possible to identify more precisely, and earlier, a change in the state of the user.

Table 1

Table 2

Table 3 Table 4 The invention can be applied to other types of situations, a few examples of application being now described.

The ability to correlate activity measurements with the presence of a third person can be exploited in the study of autism: indeed, the inventors consider that the activity of an autistic child varies when the child is alone or when the child is in the presence of a third person. The invention makes it possible to contextualize this, by assigning, to activity measurements, the presence of a third person as an ambiance parameter.

During convalescence, for example following a viral episode, a person may present symptoms of fatigue, including reduced physical activity and difficulty performing daily tasks. The invention makes it possible to follow the movement of a user, between different rooms, which makes it possible to estimate the degree of fatigue of the user, from the data transmitted to the central unit.

For an elderly subject, the invention makes it possible to attach beacons to everyday objects, or in everyday parts, which allows monitoring of the person's activity. The objects can be an appliance, a shower, a bed, or the steering wheel of a car.

In the context of clinical trials, the invention makes it possible to detect and study the reactions of a participant, for example in terms of heart rate or temperature. The invention allows a significant reduction in the variability of the measurements carried out on the user, for example the measurements representative of a physiological state. Such a reduction in variability allows for more rapid detection of changes in the condition of the clinical trial user.

Thus, the device according to the invention can be implemented simultaneously on different users. This makes it possible to determine, on each user, time ranges during which the user is considered to be performing the same task. For example, it is possible to determine, for each user, time periods during which the user is seated, or lying down, or performs a particular motor task, for example getting up, sitting down, or climbing stairs, or walking in line. right. The invention makes it possible to select, for each user, time slots during which the user performs said task. This makes it possible to collect data concerning the activity of each user, representative of the task considered, during the time periods selected for each user. During the selected time slots, each user is considered to be performing the same task. As a result, the measured data exhibits reduced variability. This allows more accurate analysis of user activity, as the data pertains to user activity performing a specific task. It will be understood that this improves the statistical representativeness of the signals measured (state signal and position signal), since these are signals measured while each user performs the same task. The measured data is therefore more comparable. For example, it is possible to collect data representative of a movement in a straight line, or data representative of a transition from a standing position to a sitting or lying position, of users who have previously undergone the same surgical intervention, for example adding a prosthesis. The invention makes it possible to collect data from a large number of users performing the same task, and this in their natural environment, for example at their home. This allows individual tracking of each user or the drawing up of comparisons between different users performing the same task.

Data collected while users are placed in the same context is more representative. They lead to a more precise statistical analysis, because of their lower variability.

A possible application concerns the follow-up of patients suffering from a degenerative disorder, such as Parkinson's disease. The invention allows collection of data, for example data characteristic of mobility, of different users placed in the same context. For example, it is possible to select the data measured (state signal, position signal) on users moving about in a spacious room, for example a hallway or a living room. Thus, it is possible to collect contextualized data while each user evolves in an environment that is familiar to him. This is an alternative to the usual follow-up methods, during which patients with Parkinson's disease undergo tests in a hospital setting. The invention makes it possible to deport data collection to the user's home, while controlling variability. The taking into account of contextualized data makes it possible to acquire data relating to the patient on a daily basis. This allows for better user tracking. This can help assess the effect of a treatment, whether it is a desired effect or a side effect.

In addition, acquiring data relating to a user's activity in a familiar environment can avoid biases that can affect measurements when the user is in a hospital setting. In this type of medicalized environment, the user may not behave naturally. According to such an embodiment, the central unit 30 is configured to receive position signals S _p and status signals S _s from different users. The central unit 30 is then programmed to analyze the position signals and/or the status signals so as to select, for each user, measurement instants during which each user carries out a previously defined task. The selected measurement instants define, for each user, different measurement time ranges. This makes it possible to define, for different users, different measurement time ranges, during which the users are considered to perform the same task. The data relating to the activity of the users, during the time ranges selected, are therefore comparable and lend themselves more to a statistical analysis by considering only the state signals S _s and/or position signals S _p transmitted by each user , during each selected time range. It is understood that the time ranges assigned to a user can be different from the time ranges assigned to another user.

The central unit 30 can then be programmed to characterize the activity of each user when the latter performs said predetermined task. According to this embodiment, the central unit 30 and the measurement device form a system for monitoring different users, each user being equipped with a device 1 as previously described.

Such an embodiment can be implemented by simultaneously considering different tasks of the user, and a selection, for each user, of time ranges respectively assigned to each task.

As previously mentioned, most beacons 20 are distributed in a fixed manner and form a network of beacons. According to one embodiment, at least one beacon, and preferably each beacon, is configured to estimate the distance separating it from one or more other beacons. Each beacon 20 is configured to emit an identification signal comprising a digital identifier of said beacon. The power of the identification signal emitted by a beacon 20, and detected by another beacon, makes it possible to estimate a distance between the two beacons. A beacon 20, or even each beacon, can be configured to transmit, to the nomadic module 10, relative positioning data S20 of other beacons comprising:

- an identification of the other beacons, called neighboring beacons;

- information representative of the distance between the beacon considered and the neighboring beacons: it may be a power of the identification signal emitted by each neighboring beacon or distances calculated on the basis of the power of the identification signal . The relative positioning data S20 are contained in the transmission signal S _e transmitted by each beacon 20 to the nomadic module 10 during step 120.

The nomadic module 10 receives, from at least one beacon 20, or from each beacon, the relative positioning data S ₂ o as previously defined. The relative positioning data S ₂ o are transmitted to the central unit 30. The collection of relative positioning data S ₂₀ , by the central unit 30, makes it possible to detect any displacement of a beacon 20 with respect to a position reference previously recorded for said beacon. According to this embodiment, the central unit 30 has a reference map, according to which each beacon 20 occupies a reference position. The relative positioning data S ₂ o make it possible to compare the distances between each beacon with reference distances, which correspond to the distances between the beacons when the latter occupy their reference position. Such an embodiment makes it possible to identify a modification of a position of a beacon relative to the reference position. In such a case, the emission signals S _e emitted by the beacon whose position has been modified are considered invalid or doubtful. A beacon position verification action can also be initiated. Such an embodiment makes it possible to improve the reliability of the device, by ensuring that each beacon indeed occupies a reference position which has been previously assigned to it. According to this embodiment, the central unit 30 is programmed to: receive data representing the relative positioning of the various beacons; from the data received, comparing the position of each beacon with the reference configuration according to which each beacon occupies the reference position assigned to it.

The reference configuration can be initialized during an initialization phase. According to this embodiment, the central unit and the measuring device form a user monitoring system.

FIG. 10 represents an experimental test, during which the distance between two beacons was measured as a function of time. The abscissa axis corresponds to time, each increment x of the abscissa axis corresponds to 10 seconds, and the ordinate axis corresponds to the distance between the two beacons, expressed in the form of an RSSI power of the exchanged signal between the two beacons - unit: dBm. During this test, the distance was measured by a first beacon, which remained fixed. The distance was measured taking into account a power of the identification signal emitted by the second beacon, as described in connection with expression (1). Before the x=900 coordinate and after the x=1050 coordinate, the distance between the two beacons was fixed and equal to 3.5 meters Between x=900 and x=1050, the second beacon was temporarily moved closer to a distance of 1 meter, which results in an increase in RSSI power.

According to one embodiment, during step 140, the communication between the mobile module 10 and the central unit 30 is carried out according to a protocol allowing transmission, by the mobile module, of the data stored in the mobile module (in particular the position signals S _p and the state signals S _s acquired as a function of time), and possibly data S20 relating to the relative positioning of the beacons. The amount of data to be transmitted may be high, while user monitoring must be maintained.

Also, the nomadic module 10 must be configured to receive, as regularly as possible, a transmission signal S _e from the beacons 20. As previously indicated, the transmission signal S _e transmitted by each beacon 20 comprises an identifier of said tag. The power of the transmission signal makes it possible to estimate the distance between the beacon 20 and the nomadic module 10. The estimation of the distance possibly takes into account the orientation of the beacon and the orientation of the nomadic module, so as to compare the transmission diagrams of the beacon and reception of the mobile module. The transmission signal S _e emitted by each beacon 20 can also comprise an ambient parameter as well as relative positioning data S20 of the neighboring beacons.

The nomadic module 10 must also be configured to transmit, to the central unit 30, the status signal S _s , the position signal S _p and possibly the relative positioning data S20 emitted by one or more beacons 20. The transmission should be as regular as possible.

The use of a nomadic module 10 able to operate simultaneously according to a transmission mode and a reception mode can be envisaged. However, this increases the cost and energy consumption of the nomadic module. In order to limit the cost and consumption of the nomadic module, a clever solution is to use a “single-mode” nomadic module that can operate alternately either in transmission mode or in reception mode. This presupposes the implementation of a specific protocol alternately managing the transmission and reception of data by the nomadic module. The inventors estimate that the duration of reception of emission signals S _e , emitted by the beacons 20, is a few seconds, for example 2 seconds. The data transmission time (S _s , S _p , S20) from the nomadic module to the central unit 30 can be longer, for example by a few minutes. During the transmission period, the nomadic module 10 cannot receive transmission signals S _e emitted by beacons 20. The position information of the user in the environment, allowing the contextualization of the activity of the user, are lost. It is therefore necessary to manage, for the nomadic module 10:

- Periods of reception of the emission signals S _e , emitted by the beacons 20, short and which must be as frequent as possible, for example every second, and, more generally, several times per minute. The reception of the transmission signals S _e is performed by the wireless link unit 11.

- Periods of data transmission, to the central unit 30, long, and which can be performed at a slower frequency than the reception of the transmission signals S _e , for example once or several times per hour. Data transmission is performed by the transmission unit 16.

Knowing that when the mobile device 10 is monomode, the transmission and reception periods cannot be performed simultaneously.

It is preferable to limit the effect of the transmission of data, to the central unit, on the frequency of reception of transmission signals S _e from beacons. Also, the nomadic module 10 can be configured to transmit the position signal S _p , the status signal S _s and any relative positioning data S20 according to a so-called slow frequency, which is at least 10 times slower or at least 100 times slower than the reception frequency of the emission signals S _e emitted by the beacons 20.

The data transmission/reception protocol by the nomadic module 10 can be configured so that during each transmission sequence to the central unit 30, when the duration of the transmission exceeds a predetermined duration, for example 30 seconds or 1 minute, the transmission is interrupted. Following the interruption of the transmission, the nomadic module 10 switches from the transmission mode to the reception mode, so as to receive transmission signals S _e emitted by the beacons. After at least one reception sequence, the nomadic module 10 switches from reception mode to transmission mode, so that the transmission of data (S _s , S _p , S ₂ o) to the central unit is continued. In general, when the transmission of data to the central unit exceeds the predetermined duration, the transmission is interrupted, so as to allow reception of transmission signals S _e , coming from the beacons. Following the reception of the data, the transmission of the data to the central unit 30 is resumed.

According to this protocol, the transmission of data is segmented into different time segments, so as to allow reception of at least one transmission signal S _e emitted by at least one beacon 20 between two consecutive time segments. The duration of each time segment can be a few seconds or a few tens of seconds.

The invention can also be used in the world of work, in particular for monitoring the activity of operators, so as to optimize routes, or monitoring isolated workers. The objective may then be to improve operator safety.

Claims

1. Device (1) for monitoring the state of a user, the user occupying an environment, the device comprising: a mobile module (10), intended to be worn by the user;

- beacons (20), distributed in the environment, configured to send a transmission signal (S _e ) to the nomadic module (10) by a short-range wireless link; the nomadic module comprising: a short-range wireless link unit (11), configured to receive at least one transmission signal (S _e ) emitted by at least one beacon; a telemetry unit (13), configured to estimate, at different measurement instants, a distance between the nomad module and each beacon whose transmission signal is received by the nomad module; at least one user activity sensor (14), configured to establish an activity signal (S _a ) representative of user activity at each measurement instant; a processing unit (15), configured to generate a status signal (S _s ) from at least one activity signal measured by the activity sensor;

- a transmission unit (16), configured to transmit the status signal (S _s ) to a central unit (30); the device being such that: the processing unit (15) is configured to establish a position signal (S _p ) as a function of at least one distance estimated by the telemetry unit (13), at each measurement instant , the position signal (S _p ) being representative of a position of the user with respect to the environment;

- the transmission unit (16) is configured to transmit the status signal (S _s ) and the position signal (S _p ) established, at each measurement instant, to the central unit (30), in such a way to allow storage, by the central unit, of the status signal and of the position signal established at each instant of measurement; the device being characterized in that at least one beacon (20 _p ) is a privacy beacon, the device being programmed such that when the nomadic module (10), receiving a transmission signal (S _e ) emitted by the privacy beacon (20 _p ), is disposed at a distance from the privacy beacon less than a threshold distance, no status signal is transmitted by the nomadic module (10) to the central unit (30 ).

2. Device according to claim 1, wherein the activity sensor (14) comprises at least: a motion sensor; and/or a cardiac activity sensor; - and/or a muscle activity sensor; and/or a brain activity sensor;

- and/or a blood pressure sensor;

- And/or a sensor of an analyte.

3. Device according to any one of the preceding claims, wherein at least one beacon (20 _p ) is a privacy beacon, the device being programmed such that when the nomadic module (10), receiving a signal from emission (S _e ) emitted by the privacy beacon (20 _p ), is placed at a distance from the privacy beacon less than a threshold distance, no status signal is transmitted by the nomadic module (10) to the central unit (30).

4. Device according to any one of the preceding claims, in which the telemetry unit (13) is configured to estimate a distance between the nomadic module (10) and at least one beacon (20) as a function of an intensity or a power of the transmission signal (S _e ) addressed by the beacon to the nomadic module.

5. Device according to claim 4, in which: the mobile module comprises an orientation unit (12'), configured to estimate an orientation of the mobile module; the telemetry unit takes into account an orientation of the nomad module to estimate the distance and each beacon whose transmission signal is received by the nomad module.

6. Device according to any one of the preceding claims, in which the telemetry unit (13) is configured to estimate several distances between the nomadic module (10) and respectively several beacons (20) according to transmission signals ( S _e ) transmitted respectively by each beacon to the nomadic module.

7. Device according to claim 6, wherein the processing unit (15) is configured such that the position signal (S _p ) corresponds to a position of the nomadic module (10) with respect to several beacons.

8. Device according to any one of the preceding claims, in which the unit of processing (15) is configured to: estimate a state of the user, among several predetermined states, from at least one activity signal (S _a ) established by the activity sensor (14);

- generating the state signal (S _s ) according to the state of the estimated user.

9. Device according to claim 8, in which the state of the user is representative of a physical activity practiced by the user at the time of measurement, or of a state of stress of the user at the time of measurement. instant of measurement, or of a physiological state of the user at the instant of measurement.

10. Device according to any one of claims 1 to 7, in which the status signal (S _s ) corresponds to the activity signal (S _a ), optionally preprocessed, resulting from the activity sensor or from each sensor d activity (14).

11. Device according to any one of the preceding claims, in which the short-range link is a link whose range is less than 50 meters or 30 meters.

12. Device according to any one of the preceding claims, in which: - at least one beacon comprises an ambient sensor (24), configured to measure a temperature and/or a sound level and/or a light level; the beacon (20) is configured to transmit an ambient signal, depending on the measurement performed by the ambient sensor, to the nomadic module (10);

- the processing unit (15) is programmed to assign an ambient level, depending on the ambient signal, to each status signal.

13. Device according to any one of the preceding claims, in which: at least one beacon is configured to receive an identification signal emitted by at least one other beacon, the power of said identification signal depending on a distance between the two beacons; - said beacon is configured to emit a transmission signal (S _e ) comprising a relative positioning signal (S20), the relative positioning signal being determined from a power of each identification signal received by the other beacon;

- the mobile module (10) is configured to transmit the relative positioning signal (S20) to the central unit (30).

14. Device according to any one of the preceding claims, in which: the mobile module is configured to switch between

• a reception mode, in which the short-range wireless link unit (11) receives at least one transmission signal (S _e ) transmitted by at least one beacon (20);

• a transmission mode, in which the transmission unit (16) transmits the status signal (S _s ) and the position signal (S _p ) established, at each measurement instant, to the central unit ( 30) ; the mobile module being configured so that:

• when the duration of the transmission mode exceeds a predetermined duration, the transmission mode is interrupted, so as to allow switching from the transmission mode to the reception mode;

• following the reception of at least one transmission signal (S _e ), the module switches from the reception mode to the transmission mode, so as to continue the transmission to the central unit.

15. Method for monitoring a state of a user of a device (1) according to any one of the preceding claims, the user being placed in an environment, the user carrying the nomadic module (10) of the device , several beacons (20) of the device being distributed in the environment, the method comprising, in at least one instant of measurement: a) measurement of an activity of the user, using an activity sensor (14) nomadic module; b) generation of a status signal (S _s ) from the activity measured by one or each activity sensor; c) estimating a distance between the nomadic module and at least one beacon; d) from the distance or from each distance resulting from c), determination of a position signal (S _p ) representative of a position of the user in the environment; e) transmission of the status signal (S _a ) and of the position signal (S _p ) of the user, determined at each measurement instant, to a central unit; the method being such that at least one beacon (20 _p ) is a privacy beacon, the device being programmed such that when the nomadic module (10), communicating with the privacy beacon (20 _p ), is disposed at a distance from the privacy beacon less than a threshold distance, no status signal (S _s ) is transmitted by the nomadic module (10) to the central unit (30).

16. Method for monitoring a state of a plurality of users, each user using a device according to any one of claims 1 to 14, each user being placed in an environment, each user carrying the nomadic module (10) of the device, several beacons (20) of the device being distributed in the environment of each user, the method comprising, for each user, at different measurement instants: a) measurement of an activity of the user, using an activity sensor (14) of the mobile module; b) generation of a status signal (S _s ) from the activity measured by one or each activity sensor; c) estimating a distance between the nomadic module and at least one beacon; d) from the distance or from each distance resulting from c), determination of a position signal (S _p ) representative of a position of the user in the environment; e) transmission of the status signal (S _a ) and of the position signal (S _p ) of the user, determined at each measurement instant, to a central unit; the method comprising, following the performance of steps a) to e), for different users, and at different measurement instants: taking into account a predetermined task; from the status and position signals transmitted to the central unit, selection, for each user, of measurement times during which each user performs said task, the measurement times selected for each user forming at least one time range specific to each user;

- for each user, processing status signals and/or position signals in each time range selected for said user, so as to characterize the activity of each user when the latter performs said predetermined task.

17. Method according to claim 15 or claim 16 in which at least one beacon is fixed in the environment.

18. Method according to any one of claims 15 to 17, wherein at least one beacon (20 _m ) is carried by a third person, different from the user.

19. Method according to any one of claims 15 to 18, in which: the environment includes an object, likely to be in contact with the user or manipulated by the user;

- at least one beacon is attached to the object.

20. Method according to any one of claims 15 to 19, in which: - at least one beacon (20) comprises an ambient sensor (24), configured to measure a temperature and/or a sound level and/or a light level, the beacon is configured to transmit, to the nomadic module (10), an ambient signal, depending on the measurement made by the ambient sensor;

- the processing unit (15) is programmed to assign an ambient level, depending on the ambient signal, to the status signal (S _s ) transmitted to the central unit (30).

21. Method according to any one of claims 15 to 20, in which the central unit is present in the environment or remote from the environment.