Self-calibrated UWB modules for a vehicle access system

Abstract

Set (100) of at least two UWB modules (1101; 1102; 1103; 1104), wherein each UWB module comprises a respective transmission and reception unit, a respective time-stamping unit, and a respective signal processing unit. Each UWB module is capable of calculating a current distance value between said UWB module and a badge. Each UWB module is further capable of calculating a calibration distance value, using bidirectional communication with the other UWB modules, a time-of-flight calculation and the calculation of a difference between a measured distance and an actual distance between two UWB modules. Figure 2

Description

Title of the invention: Self-calibrating UWB modules for a vehicle access system Technical field

[0001] The invention relates to the field of vehicle access systems.

[0002] A vehicle access system is installed on a motor vehicle. It is capable of exchanging information with at least one badge worn by a user wishing to access said vehicle, so as to be able to authenticate and locate this user. State of the art

[0003] In a manner known per se, a vehicle access system typically comprises: - a central computer; - long-range transmission and reception means, advantageously based on so-called BLE technology, for “Bluetooth Low Energy”, and cooperating with the central computer to remotely locate and authenticate a user carrying a badge authorized to access the vehicle; - medium-range transmission and reception means, advantageously based on the so-called UWB technology, for “Ultra-Wide Band”, and cooperating with the central computer to locate the authenticated user, and to control certain functions of the vehicle when depending on the position of the user (for example lighting of the vehicle upon entering a first perimeter, then unlocking of the openings upon entering a second perimeter narrower than the first perimeter); and - where appropriate, short-range presence detection means, capable of detecting the immediate proximity of the authenticated user, and cooperating with the central computer to control at least one vehicle opening unlocking function.

[0004] Throughout the text, the term UWB (for the English “ultra-wide band”), or ultra-wide band, refers to a low-energy, wide-spectral radiofrequency signal. In particular, a UWB radiofrequency signal is defined by a ratio of the bandwidth divided by the central frequency which is greater than or equal to 20%, or by a bandwidth of 250 MHz or more.

[0005] The medium-range transmission and reception means comprise in particular a set of UWB modules, intended to be positioned, in use, in predetermined locations on the vehicle.

[0006] Each UWB module preferably comprises: - a transmission and reception unit, configured to transmit a UWB badge interrogation signal, and to receive in return a UWB badge response signal; - a timestamp unit, configured to store timestamp data, relating to times of transmission of the badge interrogation signal and reception of the badge response signal; and - a signal processing unit, configured to calculate a current distance value between said UWB module and the badge, using said timestamp data.

[0007] In a manner known per se, each badge response signal further incorporates timestamp data stored at the badge. This allows the signal processing unit to accurately determine a radiofrequency signal propagation time between the UWB module and the badge, even if the clocks of the badge and the UWB module are not perfectly synchronized.

[0008] In any event, the signal processing unit is configured to determine a radiofrequency signal propagation time between the UWB module and the badge, called time of flight. This time of flight makes it possible to determine a current value of distance between the UWB module and the badge, these two quantities being linked by the speed of light in a vacuum, or more particularly the speed of a radio wave in air.

[0009] We have in particular: dmes=c*At+dcai, with dmes the current distance value between the UWB module and the badge; c the speed of light in a vacuum; At the said flight time; and dcai a calibration distance specific to the UWB module and linked in particular to slight delays introduced by the UWB module itself.

[0010] In a known manner, the calibration distance dcai is calculated in the factory, before installation of the UWB module on the vehicle, and stored in a memory, within said UWB module. In use, the calibration distance dcai is used by the signal processing unit, to calculate current distance values ​​between said UWB module and the badge.

[0011] In use, each of the UWB modules determines a current distance value to the badge. These several distance values ​​are transmitted to the central computer, which determines the position of the badge by a triangulation calculation.

[0012] An objective of the present invention is to propose a solution for improving the accuracy of determining the position of the badge. Statement of the invention

[0013] This objective is achieved with a set of at least two (preferably at least three) modules called UWB modules, in which each UWB module comprises a respective transmission and reception unit, a respective time-stamping unit, and a respective signal processing unit, and in each UWB module: - the transmitting and receiving unit is configured to transmit and receive ultra-wideband radiofrequency signals, in particular to transmit a badge interrogation signal, and to receive in return a badge response signal from a badge; - the timestamping unit is configured to store first timestamping data, relating to times of transmission of the badge interrogation signal and reception of the badge response signal; and - the signal processing unit is configured to use said first timestamp data to calculate a first current time-of-flight value, corresponding to a radiofrequency signal propagation time between said UWB module and the badge, and to then calculate a current distance value between said UWB module and the badge

[0014] According to the invention, in each UWB module: - the transmission and reception unit is further configured to transmit a UWB module interrogation signal, to at least one of the three other UWB modules, and to receive in return at least one UWB module response signal (from at least one of the three other UWB modules); - the timestamp unit is configured to store second timestamp data, relating to times of transmission of the UWB module interrogation signal and reception of the UWB module response signal; - the signal processing unit is configured to use said second timestamp data to calculate at least one second current time-of-flight value, each corresponding to a radiofrequency signal propagation time between said UWB module and a respective one of the three other UWB modules, and to then deduce therefrom at least one current distance value between said UWB module and said other UWB module, called measured distance; - the signal processing unit comprises a memory, storing at least one real deviation value, each corresponding to a real distance value between said UWB module and a respective one of the three other UWB modules; and - the signal processing unit is configured to calculate the value of a calibration distance, using the at least one measured deviation and the at least one actual deviation value.

[0015] In other words, each UWB module is capable of: - calculating a current distance value between said UWB module and a badge, using two-way communication with said badge; and - calculate the value of a calibration distance, using two-way communication with other UWB modules, time-of-flight calculation and calculation of a difference between a measured distance and an actual distance between two UWB modules.

[0016] Thus, each UWB module is capable of self-calibrating, i.e. calculating itself the calibration distance value associated with the distance calculations that it performs.

[0017] The self-calibration according to the invention does not impose any particular conditions, such as a connection to an external calibration device during a maintenance operation. In other words, the self-calibration according to the invention is capable of being repeated as many times as desired over time. It is thus possible to update, throughout the lifetime of the UWB modules, their respective calibration distances. It is thus possible to take into account, in the distance calculations provided by each UWB module, a possible drift in the calibration distance associated with said UWB module. Said drift may be due to the effects of aging and wear of the materials, to slight shifts in the physical positions of the elements of the module, etc.

[0018] At each instant, the calibration distance used to calculate a distance using the UWB module is therefore as close as possible to a real calibration distance value. The error in the distance calculation is therefore minimized, and consequently the error in determining the position of the badge.

[0019] The invention thus offers a solution for improving the accuracy of determining the position of the badge, in a system determining the position of the badge using distance measurements provided by each of the UWB modules of the assembly according to the invention.

[0020] Self-calibration uses at least one other of the UWB modules present on the vehicle, each of these UWB modules being arranged in a fixed and known location on the vehicle. Thus, self-calibration does not require the addition of additional dedicated elements. Compactness, as well as manufacturing costs, are thus optimized.

[0021] Finally, the self-calibration is carried out in a completely autonomous manner by each UWB module. In particular, the self-calibration does not involve any additional data exchange between a UWB module and the central computer, in comparison with the prior art. The invention can thus be implemented using a central computer identical to those of the prior art, without any adaptation being necessary.

[0022] In particular, each UWB module is capable of carrying out self-calibration on its own initiative, at predetermined times (for example each time it switches from a standby mode to an active mode).

[0023] Two UWB modules may exchange several UWB module interrogation signals and several UWB module response signals. In addition or alternatively, the sending of the interrogation signal may be preceded by the reception of a wake-up signal, originating from the UWB module with which a two-way communication tional is then established.

[0024] Preferably, each UWB module response signal incorporates so-called additional timestamp data, stored and then incorporated into the signal at the UWB module emitting said response signal. Each UWB module is then capable of: - extract this additional timestamp data from the response signal it receives, and - also use this additional timestamp data, to calculate the second current flight time value.

[0025] The additional time stamp data advantageously relates to a time interval between the reception of a UWB module interrogation signal and the return sending of a UWB module response signal, within the same UWB module. It is thus possible to accurately determine a propagation time between two UWB modules, even if their respective clocks are not perfectly synchronized.

[0026] Preferably, in each UWB module, the signal processing unit is configured to calculate the value of the calibration distance, using a difference between the measured deviation and the actual deviation value.

[0027] Advantageously, in each UWB module: - said memory stores several real difference values, which correspond respectively to the real difference values ​​between said UWB module and each of the other UWB modules; - said UWB module is configured to calculate several measured deviations, which correspond to respective distance values ​​between said UWB module and each of the other UWB modules; and - said UWB module is configured to calculate the value of a calibration distance, using respective differences between a measured deviation and a corresponding real deviation value, and by combining said differences.

[0028] In each UWB module, the signal processing unit is configured to store said calibration distance value, and to use the latter during subsequent calculations of a current distance value between said UWB module and the badge.

[0029] In each UWB module, the signal processing unit can be configured to: - determine an initial calibration distance value, then use the latter as a calibration distance value, during subsequent calculations of a current distance value between said UWB module and the badge; then - determine at least one updated calibration distance value, and then use the latter as the calibration distance value, during subsequent calculations of a current value of distance between said UWB module and the badge.

[0030] Advantageously, each UWB module has a so-called conventional operating mode, in which it is configured to provide at least one current distance value relative to a badge, and a so-called self-calibration operating mode, in which it is configured to provide a calibration distance value, each UWB module further comprising a control unit configured to control a switch of the UWB module to the self-calibration mode.

[0031] Advantageously, in each UWB module, the signal processing unit is configured to compare the value of a calibration distance with a predetermined threshold value, and to generate an alert signal when the value of a calibration distance is greater than said threshold value.

[0032] In each UWB module, the signal processing unit can be configured to: - detect a defective module among the UWB modules of the set, by comparing, with a predetermined threshold, a difference in absolute value between the measured deviation and the corresponding real deviation value; and - control the deactivation of the UWB module identified as being defective, when the presence of a defective module has been detected among the UWB modules in the set.

[0033] The invention also covers a user location system, intended to be integrated within a motor vehicle, and comprising an assembly according to the invention, the system further comprising a central computer, connected to each of the UWB modules of the assembly, and configured to: - receive, from each respective one of said UWB modules, a current value of distance between said UWB module and the badge; and - calculate, using said current distance values, a current position of the badge relative to said vehicle.

[0034] Preferably, said central computer is further configured to control locking and / or unlocking of at least one opening of the motor vehicle, in particular as a function of at least one current position of the badge relative to said vehicle.

[0035] The system according to the invention may further comprise the badge, the badge being intended to be worn by a user wishing to access the motor vehicle, and the badge comprising a memory storing an authentication code.

[0036] The invention also relates to a vehicle comprising an assembly according to the invention.

[0037] The invention also relates to a method implemented in each UWB module of an assembly according to the invention, the method comprising the following steps: a / transmission of the UWB module interrogation signal, to at least one of the other three UWB modules, and for receiving in return the at least one UWB module response signal; b / storage of the second timestamp data, relating to times of transmission of the UWB module interrogation signal and reception of the UWB module response signal; c / using the second timestamp data, calculating the second current time-of-flight value, corresponding to a radiofrequency signal propagation time between said UWB module and a respective one of the three other UWB modules, and using said second current time-of-flight value to calculate the corresponding measured deviation; d / calculation of a difference between the measured deviation and the corresponding actual deviation value, to obtain a calibration distance value; then e / use of said calibration distance value to then calculate at least one current distance value between said UWB module and a badge.

[0038] Advantageously, steps a / to d / are implemented several times during the lifetime of the assembly according to the invention, and step e / is each time implemented using the last calculated calibration distance value.

[0039] The method according to the invention may further comprise: - a step of detecting a defective module among the UWB modules of the set, by comparing, with a predetermined threshold, a difference in absolute deviation between the measured deviation and the corresponding real deviation value; and - a step of controlling a deactivation of the UWB module identified as being defective, when the presence of a defective module has been detected among the UWB modules of the set. Description of the figures

[0040] Other characteristics and advantages of the invention will become apparent upon reading the description which follows. This is purely illustrative and should be read in conjunction with the appended drawings in which:

[0041] [Fig-1] [Fig.l] schematically illustrates an assembly and a system according to the invention, integrated within a motor vehicle;

[0042] [Fig.2] [Fig.2] schematically illustrates the assembly of [Fig.l], and, for one of the UWB modules of the assembly, the two-way communications existing with the other UWB modules of the assembly;

[0043] [Fig.3] [Fig.3] schematically illustrates a UWB module in an assembly according to the invention; and

[0044] [Fig.4] [Fig.4] schematically illustrates a method implemented within a UWB module in an assembly according to the invention.

[0045] Detailed description of at least one embodiment

[0046] First of all, with reference to [Fig. 1] and in a schematic manner, an assembly 100 according to the invention is described.

[0047] The assembly 100 is composed of several UWB modules, or anchors, here four UWB modules referenced 110i, 1102, 1103 and 1104.

[0048] In use, the four UWB modules are integrated on a motor vehicle 10, shown in [Fig.l] in dotted lines and in a top view. The four UWB modules are more particularly arranged respectively at the four corners of the motor vehicle 10 (the four corners being defined on a representation of the vehicle in top view).

[0049] Each of the four UWB modules will be described in more detail below.

[0050] [Fig.l] also illustrates a central computer 200, on board the motor vehicle 10, and a badge 300, intended to be worn by a user wishing to access the interior of the motor vehicle 10.

[0051] In use, each of the four UWB modules 110i, 1102, 1103 and 1104 is capable of exchanging UWB type radiofrequency signals with the badge 300. The bidirectional communication between the badge 300, and each respective one of the UWB modules 110i, 1102, 1103 and 1104, is symbolized in [Fig.l] by respective arrows 1011, 1012, 1013, 1014.

[0052] This exchange of signals allows each UWB module to determine its distance to the badge 300, by a time-of-flight calculation. Each of the UWB modules transmits this distance to the central computer 200, which determines, by triangulation, the position of the badge 300 relative to the vehicle 10. The UWB modules 110i, 1102, 1103 and 1104 thus form, with the computer 200, a location system. Where appropriate, the location system can be defined as also incorporating the badge 300.

[0053] The badge 300 may be a dedicated device, or be formed by a smartphone equipped with a dedicated application. In any event, the badge 300 is configured to receive, process and transmit UWB radiofrequency signals, allowing the UWB modules to calculate flight times to said badge.

[0054] Advantageously, the badge 300 further comprises a memory, which stores an authentication code capable of being recognized at the central computer 200.

[0055] Advantageously, the badge 300 is further configured to transmit and receive radiofrequency signals of a technology other than UWB, in particular the BLE long-range radiofrequency transmission technology. This long-range transmission can be used for an exchange of data relating to the authentication code mentioned above.

[0056] The central computer 200 is on board the vehicle 10. It comprises elements such as at least one processor with one or more memories. It is configured to exchange data with, at least, each of the four UWB modules 110i, 1102, 1103 and 1104.

[0057] The central computer 200 can have many functionalities other than the sole location of the badge 300. For example, it can be configured to control a locking and / or an unlocking of at least one opening of the motor vehicle 10, in particular as a function of at least one current position of the badge 300 and an authentication code transmitted by the latter. In other words, the central computer 200 and the four UWB modules 110i, 1102, 1103 and 1104 then belong to a vehicle access system, preferably a passive type system.

[0058] According to the invention, and as illustrated in [Fig.2], each of the four UWB modules 110 1, 1102, 1103 and 1104 is further capable of exchanging UWB type radiofrequency signals with each of the three other UWB modules. In particular: - the first UWB module 1101 is capable of exchanging UWB signals with each of the three UWB modules 1102, 1103 and 1104; - the second UWB module 1102 is capable of exchanging UWB signals with each of the three UWB modules 110i, 1103 and 1104; - the third UWB module 1103 is capable of exchanging UWB signals with each of the three UWB modules 1102, 110i and 1104; and - the fourth UWB module 1104 is capable of exchanging UWB signals with each of the three UWB modules 1102, 1103 and 110i.

[0059] In [Fig.2], the two-way communication between the second UWB module 1102 and each of the three UWB modules 110i, 1103 and 1104 is shown using the three arrows 102i, 1023, 1024.

[0060] [Fig.3] then illustrates, schematically, a UWB module 110i=ij2,3Or4 of the assembly 100 according to the invention.

[0061] Each UWB module 11 Oj, 2, 3 or 4 of the assembly 100 according to the invention comprises: - a unit 11 li=i,2> 3 or 4 of emission and reception; - a timestamp unit 112i=iT 2,3 or 4; and - a signal processing unit 113i=i,2,3or4-

[0062] The transmission and reception unit llli=i,2,3 or 4 is configured to transmit and receive UWB type radiofrequency signals. For this, it comprises in particular an electronic oscillator and at least one radiofrequency antenna, capable of converting an electrical signal into a radiofrequency signal, and vice versa.

[0063] Here, the transmission and reception unit llli=i,2,3or4 is configured more particularly for: - emit at least one badge interrogation signal, to a badge such as badge 300 of [Fig.l]; - receive at least one badge response signal, originating in use from a badge having received said badge interrogation signal; - transmit at least one UWB module interrogation signal, referenced SE(i) in [Fig.3], where i relates to the transmitting UWB module; and - receiving at least one UWB module response signal, referenced SR(i, j) in [Fig.3], where i relates to the UWB module transmitting the interrogation signal and j relates to the UWB module transmitting the response signal.

[0064] In other words, in addition to their capacity to exchange signals with the badge, the UWB modules of the assembly according to the invention are connected in a network.

[0065] The badge interrogation signal and the badge response signal are not shown in [Fig.3], and correspond to the UWB signals emitted by the prior art UWB modules.

[0066] The UWB module interrogation signal is a UWB radio frequency signal. It can be sent in turn towards each of the three other UWB modules. Alternatively, the UWB module interrogation signal is sent simultaneously in several spatial directions, so that it can be received by each of the three other UWB modules.

[0067] The UWB module interrogation signal may have similar characteristics to the badge interrogation signal, the difference being that: - when transmitting the badge interrogation signal, the other UWB modules are placed in a mode in which they do not react to the reception of such a signal, while - upon transmission of the UWB module interrogation signal, the other UWB modules are placed in a mode in which they react to the reception of such a signal.

[0068] The UWB module response signal is a UWB radio frequency signal. It may be similar to a badge response signal. The UWB module response signal is transmitted by another of the UWB modules of the assembly according to the invention, upon reception of the UWB module interrogation signal.

[0069] Thus, in each UWB module, the transmission and reception unit llli=i,2,3or4 is capable of: - to receive at least one UWB module response signal from another of the UWB modules in the set, but also - to transmit such a UWB module response signal, upon receipt of a UWB module interrogation signal from another of the UWB modules in the set.

[0070] In other words, in each UWB module, the transmission and reception unit ll11=i,2,3 or 4 is capable of carrying out bidirectional communication with the other UWB modules. This bidirectional communication involves the exchange of at least one interrogation signal and one response signal. There may also be a signal of wake-up, sent by one UWB module to another UWB module to establish two-way communication.

[0071] In practice, the transmission and reception unit 1 lli=i,2,3OU4 can receive, simultaneously or not, a UWB module response signal coming from each of the three other UWB modules in the set.

[0072] The time stamping unit 112,-, 2.3<>u4 is connected to the transmission and reception unit llli=i,2,3or4. It is configured to store: - first timestamp data, relating to times of transmission of the badge interrogation signal and reception of the badge response signal (as in the UWB modules of the prior art); and - second timestamp data, relating to times of transmission of a UWB module interrogation signal, denoted SE(i), and of reception of a UWB module response signal, denoted SR(i, j), transmitted by another of the UWB modules and in response to the reception of the signal SE(i).

[0073] The second timestamp data may relate to the respective times of receipt of the UWB module response signal from each of the three other UWB modules.

[0074] The time stamping unit 1 12,,2,3 or 4 may have its own memory, in which the time stamp data is stored. Alternatively, it writes data directly into the signal processing unit 113i=i,2,3 or 4.

[0075] In any event, the signal processing unit 113i=ij2,3Or4 is connected to the time-stamping unit 112i=i,2> 3 OR4, so as to be able to receive the first and second time-stamping data.

[0076] Advantageously, at least part of the second timestamp data may be encoded, or incorporated, in a UWB module response signal transmitted by said module.

[0077] The signal processing unit 113i=i,2,3 OR4 is configured to be able to implement a first signal processing as well as a second signal processing. It advantageously comprises at least one microcontroller.

[0078] In an advantageous embodiment, the transmission and reception unit 11 li=i,2,3OU4, the time-stamping unit 1 12i r 2,3Ou4 and the signal processing unit 113i=i,2,3ou4 are integrated together on the same printed circuit. This eliminates the need for connection cables between these elements, which could cause additional delays.

[0079] The first signal processing is similar to what exists in the prior art. It consists of: - use the first timestamp data, to calculate a first current value of flight time between the UWB module 110; and a badge such as the badge 400 of [Fig.l], the first current value of flight time corresponding to a duration of radiofrequency signal propagation between said UWB module 110; and the badge; then - using said time of flight, calculating a current distance value between said UWB module 110; and the badge.

[0080] Advantageously, the calculation of the first current time-of-flight value also uses additional timestamp data extracted from the badge response signal. This data preferably relates to time intervals between a signal reception and a signal transmission, at the badge.

[0081] In a manner known per se, the current distance value is given by: dB(t)=At;(t)*c + dca;, with dB(t) the distance value between said UWB module 110; and the badge, at time t; c the speed of light in a vacuum; Ati(t) the first time-of-flight value, at time t; and dcai a predetermined calibration distance., associated with the UWB 110 module;.

[0082] The calibration distance dca; is a value specific to the UWB module 110; considered. It generally takes a non-zero value, in particular due to the different time delays which can be introduced within said UWB module.

[0083] The second signal processing is original. It consists of: - using the second timestamp data, to calculate at least a second current time-of-flight value between the UWB module 110; and one of the three other UWB modules. Each second current time-of-flight value corresponds to a radiofrequency signal propagation time between said UWB module 110; and one of the three other UWB modules; then - using the at least one time of flight, calculating at least one current distance value between said UWB module 110; one of the three other UWB modules. Each current distance value is called measured distance.

[0084] Advantageously, the calculation of the second current time-of-flight value also uses additional timestamp data, extracted from the UWB module response signal. These additional timestamp data preferably relate to time intervals between an interrogation signal reception and a response signal transmission, at the UWB module sending said response signal. For this, each UWB module is configured both to incorporate such data into a UWB module response signal that it sends, and to extract such data from a UWB module response signal that it receives.

[0085] The second signal processing may include calculating a plurality of second current time-of-flight values, respectively between the UWB module 110; and each of the three other UWB modules. It may then include calculating a plurality of current distance values, respectively between the UWB module 110; and each of the three other UWB modules.

[0086] The signal processing unit 113i=i,2> 3 OU4 comprises a memory, not specifically shown in [Fig.3], and storing at least one real deviation value. Each real deviation value corresponds to the real distance value between said UWB module 110;, and a respective one of the three other UWB modules. These real deviation values ​​are known data, linked to the physical locations of the UWB modules, under the conditions of use. In practice, these are the real distances between the UWB modules when they are mounted on a motor vehicle. The real deviation values ​​may be standard data, common to all vehicles of the same model. Alternatively, a preliminary step of measuring said real deviation values ​​on a particular motor vehicle may be provided, and storing said measurements in the signal processing unit 113i=ij2,3Ou4 of said vehicle.

[0087] The signal processing unit 113i=i,2,3OU4 is further configured to calculate a value of the calibration distance dcai, using the at least one measured deviation, and the at least one actual deviation value.

[0088] The value of the calibration distance dcai is a function in particular of at least one difference ôj, such that: ôj = ER(j) - At2(t ; j)*c, with ER(j) the real distance from the other UWB module of index j; c the speed of light in vacuum; and At2(t; j) the second time-of-flight value, obtained at time t and using a signal from the UWB module of index j, where At2(t; j)*c corresponds to the real difference value between the UWB module 110; and the UWB module 110j.

[0089] The value of the calibration distance dcai is for example an arithmetic mean of the ôj, obtained for each of the three other UWB110j modules, and where appropriate for different measurement times. The mean can be weighted, for example to give more weight to the real deviations least susceptible to error, etc.

[0090] In practice, each UWB 110i r 2,3 or 4 module advantageously has two operating modes (in addition to a standby mode): - a so-called “classic” mode, in which it is configured to provide at least one current distance value relative to a badge; and - a so-called “self-calibration” mode, in which it is configured to provide a calibration distance value.

[0091] Preferably, each UWB module 110i=i,2,3 or 4 is capable of initiating itself a switch to the self-calibration mode. In particular, each UWB module 110i i.2,3 or 4 is capable of initiating itself the communication with the other UWB modules followed by subsequent steps ultimately making it possible to determine a value of the calibration distance dcai. In other words, each UWB module 110i i 2,3 or 4 is capable of initiating the implementation of the steps of the method according to the invention, as described below with reference to [Fig.4]. Each UWB module 110,-,. 2. i<>u4 is able to carry out this switching on its own initiative, without external request, in particular from a central computer or an external calibration device, or a smartphone.

[0092] To carry out this switching, each UWB module 110, , 2.3 or 4 advantageously comprises a respective control unit 114,-, 2.1 <>„4- Each control unit 114 i=i,2,3 or 4 is configured to initiate the implementation of the steps of the method according to the invention, at predetermined times, for example each time the motor vehicle is started.

[0093] In each UWB module, the control unit is therefore configured to control the implementation of the following steps, at predetermined times: - transmission of at least one UWB module interrogation signal and reception of at least one UWB module response signal, by the transmission and reception unit; - storing second corresponding timestamp data, using the timestamp unit; - using the signal processing unit, calculating at least a second current time-of-flight value, then at least one corresponding measured deviation, and finally a value of a calibration distance.

[0094] We then describe, with reference to [Fig.4], the steps of the method according to the invention, implemented at the level of each UWB module 110; of the assembly according to the invention.

[0095] In a first step 401, a UWB module interrogation signal is transmitted as described above. This step 401 is implemented using the transmission and reception unit llli=i,2,3or4.

[0096] In a second step 402, at least one UWB module response signal is received as described above. This step 402 is implemented using the transmission and reception unit 111 i=i,2,3 or 4.

[0097] These steps 401 and 402 can be repeated several times.

[0098] In a third step 403, the second timestamp data is stored. as described above, relating to the times of signal transmission in step 401 and signal reception in step 402. This step 403 is implemented using the timestamp unit I I2,-, 2. î<>u4- It can be implemented at the same time as steps 401 and 402. In [Fig.4], the second timestamp data is denoted Ti.

[0099] In a fourth step 404, at least one second current time-of-flight value is calculated, as described above. This step 404 is implemented using the signal processing unit 1 13, ,. 2>3 or 4. In [Fig. 4], the at least one time-of-flight value thus calculated is denoted At.

[0100] In a fifth step 405, at least one measured deviation is calculated as described above. This step 405 is implemented using the signal processing unit 113 i=i,2,3or4- In [Fig.4], the at least one measured deviation thus calculated is denoted Em.

[0101] In a sixth step 406, the difference between at least one measured deviation Em, and a corresponding real deviation value Er as described above is calculated, and a calibration distance value is deduced therefrom, as described above. This step 406 is implemented using the signal processing unit 113,-,. 2. i<>u4- In [Fig.4], the calibration distance value is denoted dca;.

[0102] The method then comprises a step, not shown, of updating the value of a constant.

[0103] This value dca; is then used to update the value of a constant, stored in the signal processing unit I 13,-,.2.1,,,,4 and used as a calibration distance to calculate a current distance value between the UWB module 110; and a badge. Thus, subsequent calculations of a distance to a badge will be based on the calibration distance value calculated using steps 401 to 406 described above.

[0104] Advantageously, a new calibration distance value can be calculated several times during the lifetime of each UWB module. Each time, this new calibration distance value is used to update the value of said constant. This ensures that the effect of aging of each module is taken into account over time.

[0105] The invention is not limited to the examples described above, and also includes many other variants, for example with a different number of UWB modules in the module assembly. For example, the assembly may comprise only two UWB modules, each installed in use on a respective B-pillar of the vehicle. According to another variant, the assembly may comprise more than four UWB modules, with, in use, one UWB module on each corner of the vehicle and one or more UWB modules in the center or on a B-pillar of the vehicle.

[0106] It may be noted that a large increase in the calibration distance may indicate a malfunction of at least one of the UWB modules. In advantageous variants, in each UWB module, the signal processing unit is configured to: - detecting a defective module among the UWB modules of the set, by comparing, with a predetermined threshold, a difference in absolute deviation between the measured deviation and the corresponding actual distance value; and - control the deactivation of the UWB module identified as being defective, when the presence of a defective module has been detected among the UWB modules in the set.

[0107] In practice, a UWB module can control its own deactivation, or the deactivation of a third-party module.

[0108] For example, a UWB module, noted A, calculates a measured deviation EAb, respectively E ac, relative to a second UWB module, noted B, respectively a third UWB module, noted C.

[0109] If Eab is very far from the actual value of distance between modules A and B (beyond a first predetermined threshold), while EAC is quite close to the actual value of distance between modules A and C (below a second predetermined threshold, distinct from or identical to the first predetermined threshold), then it is considered that module B is dysfunctional and module A controls the deactivation of module B.

[0110] If Eab is very far from the actual value of distance between modules A and B (beyond a first predetermined threshold), and EAC is also very far from the actual value of distance between modules A and C (beyond a second predetermined threshold, distinct from or identical to the first predetermined threshold), then it can be considered that module A itself is dysfunctional, and module A deactivates.

[0111] The deactivation of a UWB module is advantageously accompanied by the emission of an alert signal, intended to inform the user of the vehicle that maintenance is necessary.

Claims

1. Claims Set (100) of at least two modules called UWB modules (110; ; 1102; 1103; 1104; 110i) for a user location system intended to be integrated within a motor vehicle, in which each UWB module is intended to be positioned, in use, at a predetermined location on a motor vehicle, and comprises a respective transmission and reception unit (11 h), a respective timestamping unit (112;), and a respective signal processing unit (113; ), and in each UWB module: - the transmission and reception unit (111;) is configured to transmit and receive ultra-wideband radiofrequency signals, in particular to transmit a badge interrogation signal, and to receive in return a badge response signal from a badge (300); - the timestamping unit (112;) is configured to store first timestamping data, relating to times of transmission of the badge interrogation signal and reception of the badge response signal; and - the signal processing unit (113;) is configured to use said first timestamp data to calculate a first current time-of-flight value, corresponding to a radiofrequency signal propagation time between said UWB module and the badge (300), and to then calculate a current distance value between said UWB module and the badge (300); characterized in that, in each UWB module (110; ; 1102; 1103; 1104; HO;): - the transmission and reception unit (111;) is further configured to transmit a UWB module interrogation signal (SE(i)), to at least one of the three other UWB modules, and to receive in return at least one UWB module response signal (SR(i, j)); - the timestamp unit (112;) is configured to store second timestamp data (Ti), relating to times of transmission of the UWB module interrogation signal (SE(i)) and reception of the UWB module response signal (SR(i, j)); - the signal processing unit (113;) is configured to use said second timestamp data to calculate at least one second current time-of-flight value (At), each corresponding to a radiofrequency signal propagation time between said UWB module and a respective one of the three other UWB modules, and to then deduce therefrom at least one current distance value between said UWB module and said other UWB module, called measured deviation (Em); - the signal processing unit (113;) comprises a memory, storing at least one actual deviation value (Er), each corresponding to an actual distance value between said UWB module and a respective one of the three other UWB modules; and - the signal processing unit (113;) is configured to calculate the value of a calibration distance (dca;), using the at least one measured deviation (Em) and the at least one actual deviation value (Er).

2. Assembly (100) according to claim 1, characterized in that, in each UWB module (110; ; 1102; 1103; 1104; 110;), the signal processing unit (113;) is configured to calculate the value of the calibration distance (dca;), using a difference between the measured deviation (Em) and the actual deviation value (Er).

3. Assembly (100) according to claim 1 or 2, characterized in that, in each UWB module (110; ; 1102; 1103; 1104; 110;): - said memory stores several actual deviation values, which correspond respectively to the actual deviation values ​​between said UWB module and each of the other UWB modules; - said UWB module is configured to calculate several measured deviations, which correspond to respective distance values ​​between said UWB module and each of the other UWB modules; and - said UWB module is configured to calculate the value of a calibration distance, using respective differences between a measured deviation and a corresponding actual deviation value, and by combining said differences.

4. Assembly (100) according to any one of claims 1 to 3, characterized in that, in each UWB module (110; ; 1102; 1103; 1104; 110;), the signal processing unit (113;) is configured to store said calibration distance value (dcal), and to use the latter during subsequent calculations of a current distance value between said UWB module and the badge (300).

5. Assembly (100) according to claim 4, characterized in that, in each UWB module (110; ; 1102; 1103; 1104; 110;), the signal processing unit (113;) is configured to: - determine an initial calibration distance value, then use the latter as a calibration distance value, during subsequent calculations of a current distance value between said UWB module and the badge (300); then - determining at least one updated calibration distance value, then using the latter as a calibration distance value, during subsequent calculations of a current distance value between said UWB module and the badge (300).

6. Assembly (100) according to any one of claims 1 to 5, characterized in that each UWB module (110i; 1102; 1103; 1104; 110;) has a so-called conventional operating mode, in which it is configured to provide at least one current distance value relative to a badge (300), and a so-called self-calibration operating mode, in which it is configured to provide a calibration distance value (dca;), each UWB module further comprising a control unit (114;), configured to control a switch of the UWB module to the self-calibration mode.

7. Assembly (100) according to any one of claims 1 to 6, characterized in that in each UWB module (110i; 1102; 1103; 1104; 110;), the signal processing unit (113;) is configured to compare the value of a calibration distance (dca;) with a predetermined threshold value, and to generate an alert signal when the value of a calibration distance is greater than said threshold value.

8. Assembly (100) according to any one of claims 1 to 7, characterized in that in each UWB module (110; ; 1102; 1103; 1104; 110;), the signal processing unit (113;) is configured to: - detect a defective module among the UWB modules (110; ; 1102; 1103; 1104; 110;) of the assembly, by comparing, with a predetermined threshold, a difference in absolute value between the measured deviation (Em) and the corresponding actual deviation value (Er); and - control the deactivation of the UWB module identified as being defective, when the presence of a defective module among the UWB modules (110; ; 1102; 1103; 1104; 110;) of the assembly (100) has been detected.

9. User location system, intended to be integrated within a motor vehicle (10), and comprising an assembly (100) according to any one of claims 1 to 8, characterized in that it further comprises a central computer (200), connected to each of the UWB modules (110; ; 1102; 1103; 1104; 110;) of the assembly (100), and configured to: - receiving, from each respective one of said UWB modules, a current distance value between said UWB module and the badge (300); and - calculating, using said current distance values, a current position of the badge (300) relative to said vehicle.

10. System according to claim 9, characterized in that said central computer (200) is further configured to control locking and / or unlocking of at least one opening of the motor vehicle (10), in particular as a function of at least one current position of the badge (300) relative to said vehicle (10).

11. System according to claim 10, characterized in that it further comprises the badge (300), the badge being intended to be worn by a user wishing to access the motor vehicle (10), and comprising a memory storing an authentication code.

12. Vehicle (10) comprising an assembly (100) according to any one of claims 1 to 8.

13. Method implemented in each UWB module (110i; 1102; 1103; 1104; 110;) of an assembly (100) according to any one of claims 1 to 8, characterized in that it comprises the following steps: a / transmission (401) of the UWB module interrogation signal (SE(i)), to at least one of the three other UWB modules, and reception (402) in return of the at least one UWB module response signal (SR(i,j)); b / storage (403) of the second time stamp data (Ti), relating to times of transmission of the UWB module interrogation signal and reception of the UWB module response signal;c / using the second timestamp data, calculating (404) the second current time-of-flight value (At), corresponding to a radiofrequency signal propagation time between said UWB module and a respective one of the three other UWB modules, and using (405) said second current time-of-flight value to calculate the corresponding measured deviation (Em); d / calculating a difference (406) between the measured deviation (Em) and the corresponding actual deviation value (Er), to obtain a calibration distance value (dcai); then e / using said calibration distance value to then calculate at least one current distance value between said UWB module and a badge.;

14. Method according to claim 13, characterized in that steps a / to d / are implemented several times during the lifetime of the assembly (100) according to any one of claims 1 to 7, and in that step e / is each time implemented using the last calculated calibration distance value.

15. Method according to claim 13 or 14, characterized in that it further comprises: - a step of detecting a defective module among the UWB modules (110i; 1102; 1103; 1104; 110;) of the set (100), by comparing, with a predetermined threshold, a difference in absolute deviation between the measured deviation (Em) and the corresponding real deviation value (Er); and - a step of controlling a deactivation of the UWB module identified as being defective, when the presence of a defective module among the UWB modules (110i; 1102; 1103; 1104; 110;) of the set (100) has been detected.

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