Method for activating a vehicle function and associated device

Abstract

The invention relates to a method for activating a vehicle function by means of an activation device (D) according to a "hands-free" access device (SD) carried by a user (U) and provided with a magnetometer (M), the activation of the function is triggered by detecting the presence of the device in a predetermined area (Z1) around the vehicle (V) or in a passenger compartment (Z0) of the vehicle (V) and depending on a result of authentication of the device, the device comprises at least one external transceiver (A1) capable of transmitting outside the vehicle and one internal transceiver (A2) capable of transmitting in a passenger compartment (Z0) of the vehicle, the method comprising the following steps: a) detecting the presence of the device in a predetermined area (Z2); b) the access device (SD) continuously measures the amplitude (AM) of the magnetic field and the orientation (OR) of said magnetic field; c) comparing the measurements (AM, OR) with a predetermined amplitude curve (AMD) and an orientation curve (ORD); and d) activating the vehicle function (F1, F2) as a function of the result of the comparison.

Description

[Technical field]

[0001] The invention relates to a method for activating a function of a motor vehicle and an associated activation device. The invention is suitable in particular, but in no way in a limiting manner, for hands-free access to a function of a motor vehicle, namely the function of locking and unlocking an opening element of the motor vehicle. [Background Technology]

[0002] In motor vehicles, it is known practice to use vehicle function activation devices that are able to detect the presence of a hand or foot of a vehicle user, thereby allowing all or some of the vehicle's opening elements (e.g., doors or trunk) to be locked or unlocked. By way of example, the detection of the presence of a user's hand on or in front of a door handle, coupled with the identification of an identifier of a "hands-free" access device carried by the user, allows locking and unlocking of these opening elements.

[0003] "Hands-free" access systems for accessing motor vehicles allow an authorized user to lock and / or unlock the opening elements of his vehicle without physically pressing a button on the key. For this purpose, the vehicle recognizes a portable device such as a key fob or remote control or even a key carried by the user, and if the key fob or remote control or the key is located in a predetermined area around the vehicle or in the vehicle and is recognized as belonging to the vehicle, the vehicle automatically locks / unlocks its opening elements according to the user's intention, without the user having to physically manipulate the key.

[0004] To this end, when the user approaches the vehicle, communication is established via a wireless communication link between a “hands-free” access device (e.g. an electronic key fob or a smartphone) and a vehicle function activation device in order to authenticate the access device by means of its identifier.

[0005] To this end, the activation device comprises at least one radio frequency antenna allowing the reception of an identifier sent by the "hands-free" access device. The activation device is connected to the electronic computer or ECU (Electronic Control Unit) of the vehicle to which it transmits the identifier.

[0006] According to the prior art, the access device is typically an electronic key fob. The signal received by the antenna of the activation device (containing the identifier of the access device) is transmitted via RF (radio frequency) or LF (low frequency) waves. The precise location of the portable device around the vehicle is determined by measuring the strength of the LF signal received by the portable device (via the antenna and the electronic control unit) from the vehicle, these strength measurements being more generally referred to as RSSI (received signal strength indication) measurements. The strength measurements of each signal received by the portable device from each of the multiple LF antennas located on the vehicle V are received and analyzed by the on-board activation device, which thereby determines the location of the portable device relative to the LF antenna (i.e., relative to the vehicle) via triangulation.

[0007] Depending on the position of the portable device in the position area recognized by the vehicle, certain actions specific to the position area are automatically performed, namely early unlocking / locking or switching on the welcome lighting in the passenger compartment.

[0008] However, it is increasingly common to use a mobile phone to perform authentication functions, which avoids the need for a dedicated electronic key fob and thus limits the number of devices. Most mobile phones do not have RF or LF communication facilities. Therefore, there is a need to adapt a "hands-free" starting and / or access system for a vehicle so that the system can also communicate with other devices equipped with other communication standards (e.g., Ultra Wideband, or BLE (Bluetooth Low ), or Wi-Fi (Wireless Fidelity) communications), instead of using only radio and low-frequency (RF and LF) waves. In particular, ultra-wideband (UWB) is a radio modulation technology based on the transmission of pulses with very short duration (usually less than a nanosecond). As a result, the bandwidth can reach very high values.

[0009] When the access device is brought into proximity with the activation device (less than 2 m from the activation device) and recognizes the identifier received by the computer, coupled with the detection of the presence of the user's hand, locking or unlocking the vehicle doors is allowed.

[0010] A disadvantage of using a UWB communicator is that the location accuracy of the access device (mobile phone or key fob) is poorer than using prior art low frequency 125kHz communicators.

[0011] In fact, ultra-wideband is more sensitive to reflections and interference. Therefore, precise positioning involves providing the vehicle with six to eight UWB transceivers (four to six on the outside of the vehicle and two on the inside), so that three UWB transceivers are always visible to the access device, while according to the prior art, at low frequencies, a single visible transceiver is able to accurately locate the access device, and the vehicle is usually provided with three external antennas and 2 internal antennas to achieve the same positioning accuracy.

[0012] Increasing the number of UWB transceivers on a vehicle can result in undesirable additional costs for activating the devices.

[0013] The present invention proposes a method and a device for activating a vehicle function, which overcome the disadvantages of the prior art, in which case no additional costs are incurred for activating the device. [Summary of the invention]

[0014] The invention relates to a method for activating a vehicle function from a "hands-free" access device carried by a user and provided with a magnetometer, the activation of the function being triggered by detecting the presence of the device in a predetermined area around the vehicle or in the passenger compartment of the vehicle and according to the result of the authentication of the device, by means of an activation device comprising at least one external radio frequency transceiver capable of transmitting outside the vehicle and one internal radio frequency transceiver capable of transmitting in the passenger compartment (Z0) of the vehicle, the method being notable in that it comprises the following steps:

[0015] a. detecting the presence of the device in a predetermined area by means of radio frequency communication;

[0016] b. The access device continuously measures the magnitude of the magnetic field and the orientation of the magnetic field;

[0017] c. comparing the measurement results with a predetermined amplitude curve and orientation curve;

[0018] d. Activating a vehicle function based on the result of the comparison.

[0019] In one embodiment, the measurements are sent to the vehicle by means of radio frequency communication and the comparison is performed by the vehicle.

[0020] In another embodiment, the comparison is performed by the portable device and the results of the comparison are transmitted to the vehicle by means of radio frequency communication.

[0021] Radio frequency communications may involve high frequency or ultra high frequency communications.

[0022] In a further development of the invention, the access device is provided with an accelerometer, the measurement result of the magnetic field is corrected by a scalar product with a measurement result from the accelerometer, the scalar product is compared with a predetermined scalar product curve, and the vehicle function is activated depending on the result of the comparison.

[0023] The invention also relates to a "hands-free" access device for accessing a motor vehicle, said device being carried by the user and being provided with a magnetometer and being able to communicate with the vehicle by means of radio frequency communication, the notable features of this access device being that it is able to:

[0024] a. continuously measuring the magnitude of the magnetic field and the orientation of the magnetic field;

[0025] b. comparing the measurement results with a predetermined amplitude curve and orientation curve;

[0026] c. Activate vehicle functions based on the results of the comparison.

[0027] In one embodiment, the access device is capable of:

[0028] a. continuously measuring the magnitude of the magnetic field and the orientation of the magnetic field;

[0029] b. Sending the measurement results to the vehicle.

[0030] In a refinement of the invention, the "hands-free" access device for accessing a motor vehicle comprises an accelerometer (ACC), said device also being able to:

[0031] a. Continuously measure acceleration values;

[0032] b. Correcting the magnetometer measurement results by scalar product with the accelerometer measurement results;

[0033] c. comparing the value of the scalar product with a predetermined scalar product curve;

[0034] d. Activate vehicle functions based on the results of the comparison.

[0035] In another embodiment of the improvement of the present invention, the device comprises an accelerometer, the device further being capable of:

[0036] a. Continuously measure acceleration values;

[0037] b. Sending the measurement results to the vehicle.

[0038] The invention also relates to any activation device for activating a vehicle function, the activation of which is triggered by the detection of the presence of a "hands-free" access device carried by a user in a predetermined area around the vehicle or in the passenger compartment of the vehicle and according to the result of the authentication of said device, the activation device comprising at least one external antenna module for transmitting / receiving radio frequencies and one internal antenna for transmitting / receiving radio frequencies capable of being transmitted in the passenger compartment of the vehicle, the device communicating with the "hands-free" access device, characterized in that it is able to:

[0039] a. receiving a magnitude measurement of a magnetic field originating from the device and a magnetic field orientation measurement;

[0040] b. comparing the measurement results with a predetermined amplitude curve and orientation curve;

[0041] c. Activate vehicle functions based on the results of the comparison.

[0042] In an improved solution of the present invention, the device is capable of:

[0043] a. receiving a magnitude measurement of a magnetic field and an orientation measurement of a magnetic field and an acceleration measurement from the device;

[0044] b. Correct the magnetometer value by scalar product with the accelerometer value;

[0045] c. comparing the value of the scalar product with a predetermined scalar product curve;

[0046] d. Activating a vehicle function based on the result of the comparison.

[0047] The invention is applicable to any computer program product comprising program code instructions for performing the steps of the method according to any one of the features listed above, when said program is executed on a computer.

[0048] Finally, the invention relates to any motor vehicle comprising an activation device according to any one of the previously mentioned characteristics. [Drawings]

[0049] Further features and advantages of the present invention will become more clearly apparent on reading the following description. This is purely illustrative and must be read with reference to the accompanying drawings, in which:

[0050] [ Figure 1 ]: Figure 1 Schematically shows a motor vehicle comprising an activation device according to the invention;

[0051] [ Figure 2 ]: Figure 2 Schematically shows a hands-free access device according to a first embodiment of the present invention;

[0052] [ Figure 3 ]: Figure 3 schematically illustrates an activation device according to a second embodiment of the invention;

[0053] [ Figure 4 ]: Figure 4 is a flow chart showing an activation method according to the present invention;

[0054] [ Figure 5 ]: Figure 5 is a graph showing the variation in the amplitude of a magnetic field measured by an access device according to the distance between the device and a vehicle;

[0055] [ Figure 6 ]: Figure 6 is a graph showing the variation in orientation of a magnetic field vector measured by an access device according to the distance between the device and a vehicle;

[0056] [ Figure 7 ]: Figure 7 schematically illustrates the rotation of a magnetic field vector measured by a user carrying an access device as the device approaches a vehicle and then enters the interior of said vehicle;

[0057] [ Figure 8 ]: Figure 8 is a graph showing a change in the scalar product between a magnetic field vector and an acceleration vector as a function of time when a user carrying an access device approaches a vehicle and then enters a passenger compartment. [Specific implementation method]

[0058] Figure 1 A motor vehicle V is shown which comprises an activation device D according to the invention for activating a vehicle function.

[0059] Vehicle functions not only refer to functions such as locking or unlocking opening elements of the vehicle (doors or trunk), but also to switching on certain lighting in the vehicle (also called "welcome lighting") or even pre-adjusting the driver's seat when a user approaches.

[0060] When in the predetermined area Z1 (see Figure 1 ) and the user has been previously identified as being authorized to access the vehicle V.

[0061] The vehicle function may also be a “hands-free” start of the vehicle V, in which case the activation device D positions the access device precisely in the passenger compartment Z0 of the vehicle V beforehand.

[0062] More specifically, a "hands-free" access device SD (e.g., a smartphone) carried by a user communicates with an activation device D by means of radio frequency waves (e.g., high frequency or ultra-high frequency waves, such as ultra-wideband, Wi-Fi, BLE, etc.) in order to exchange an identifier of the access device with the activation device. The activation device D itself determines the position of the device SD relative to the vehicle V and verifies its identifier. Such methods for "hands-free" access to a vehicle V are known in the prior art and will not be described in further detail herein.

[0063] To this end, the activation device D comprises at least two transceivers: a radio frequency transceiver A1 capable of transmitting outside the vehicle in order to activate the unlocking / locking function or other functions that can be activated when the user approaches (preheating the seats, pre-adjusting the radio, seats, etc.); and an internal radio frequency transceiver A2 capable of transmitting in the passenger compartment Z0 of the vehicle in order to activate the hands-free starting function of the vehicle V.

[0064] The two transceivers A1 , A2 are electronically connected to a central control unit 10 , which is itself connected to a function activation device, ie a door unlocking / locking mechanism or a mechanism for starting the vehicle V or any other mechanism that activates a function.

[0065] The central control unit 10 comprises means for processing the information received by the transceiver, which means allow the central control unit to activate or deactivate vehicle functions, as is known to those skilled in the art.

[0066] The central control unit 10 also includes a processor 100 and a memory 101 (see Figure 3 ), the memory records instructions that allow the processor to be configured to perform certain specific processing operations, especially to implement the steps of the opening / closing method according to the embodiment described below.

[0067] The "hands-free" access device SD carried by the user is provided with a magnetometer M (see Figure 2 ), which measures the magnitude and direction of the Earth's magnetic field.

[0068] Of course, the device SD is able to communicate with the vehicle V by means of radio frequencies (HF or UHF) via transceivers A1, A2. To this end, the device is provided with suitable communication means ( Figure 2 ) and can send and receive data.

[0069] The access device SD also includes a processor 200 and a memory 201 (see Figure 3 ), the memory records instructions that allow the processor to be configured to perform certain specific processing operations, in particular, to implement the steps of the opening / closing method according to the embodiment described below.

[0070] In a first embodiment of the invention, the "hands-free" access device SD is also capable of:

[0071] a. continuously measuring the magnitude AM (also called the norm) and orientation OR of the vector of the magnetic field according to the three spatial dimensions of the magnetic field;

[0072] b. Compare the measurement results AM, OR with the predetermined amplitude curve AM D and orientation curve OR D Make comparisons;

[0073] c. Activate vehicle functions based on the results of the comparison.

[0074] The amplitude or norm of the magnetic field, AM, is given by the following equation:

[0075] [Mathematical formula 1]

[0076]

[0077] in:

[0078] is the vector of the Earth's magnetic field as sensed by the portable device.

[0079] AMx: is the magnetic field amplitude measured along the x-axis.

[0080] AMy: is the magnetic field amplitude measured along the y-axis.

[0081] AMz: is the magnetic field amplitude along the z-axis.

[0082] The orientation of the magnetic field OR corresponds to the magnetic field vector The angular coordinates of the three planes (XY, YZ, ZX) of the Cartesian coordinate system (0, x, y, z) and are represented by three angles θ, and α provides, namely:

[0083] [Mathematical formula 2]

[0084]

[0085] in:

[0086] α: is the angle of vector r on the XY plane.

[0087] β: is the angle of vector r on the YZ plane.

[0088] is the angle of vector r in the ZX plane.

[0089] This is Figure 6 was displayed in . Figure 6 The figure above shows the Cartesian coordinate system (0, x, y, z). The magnetic field vector As well as the amplitudes AMx, AMy, AMz of the field on the three axes x, y, z, and the angles α, β, α that the magnetic field vector makes with each of the three planes XY, YZ and ZX of the coordinate system.

[0090] To this end, the portable access device SD comprises (see Figure 2 ):

[0091] a. a device M0 for recording the amplitude AM and orientation OR of the magnetic field measured by the magnetometer M according to time t;

[0092] b. for comparing each of the curves thus recorded with a predetermined curve AM D , OR D Comparison devices M1, M2 for performing comparisons;

[0093] c. Means M3 for activating a vehicle function as a function of the results of the two comparisons.

[0094] The comparison means M1, M2 may be constituted by software means.

[0095] The activation means M3 may comprise a command sent to the activation device D which triggers one or more corresponding functions on the vehicle V.

[0096] In this first embodiment, the activation device D therefore receives an instruction to activate a vehicle function from an access device SD, which has previously processed the amplitude measurement results AM and the orientation measurement results OR of the magnetic field and has determined whether the access device SD is correctly located in a predetermined area Z1 around the vehicle V or in the passenger compartment Z0, in which the corresponding vehicle function can be activated.

[0097] In a second embodiment of the invention, the access device SD continuously measures the amplitude values ​​AM and the orientation values ​​OR of the magnetic field and transmits said measurements to the activation device D. In this second embodiment, the access device SD comprises only means M0 for recording said values.

[0098] In this second embodiment, the activation device D itself is able to:

[0099] a. Receiving the amplitude measurement result AM of the magnetic field and the orientation measurement result OR of the magnetic field from the device SD;

[0100] b. Compare the measurement results AM, OR with the predetermined amplitude curve AM D and orientation curve OR D Make comparisons;

[0101] c. Activate vehicle functions based on the results of the comparison.

[0102] To this end, in order to implement this second embodiment, the activation device D comprises:

[0103] a. For comparing the amplitude value AM and orientation value OR recorded according to time t with the predetermined amplitude curve AM D and orientation curve OR D The devices M1' and M2' for comparison;

[0104] b. Means M3 ′ for activating a vehicle function as a function of the results of the two comparisons.

[0105] The comparison means M1 ′, M2 ′ may be constituted by software means.

[0106] The activation device M3 ′ is connected to the various mechanisms present on the vehicle V for activating the functions.

[0107] In a development of the invention, the access device SD comprises an accelerometer ACC, and the measurement results AM, OR from the magnetometer are corrected by means of the values ​​of the accelerometer ACC. This is described below.

[0108] In a first improvement of the present invention, the access device SD is also capable of:

[0109] a. Continuously measure the acceleration value ACC;

[0110] b. Correct the measurement result AM of the magnetometer M by the measurement result of the accelerometer ACC through the scalar product;

[0111] c. Compare the value of the scalar product PSC with the predetermined scalar product curve PSC D Make comparisons;

[0112] d. Activate vehicle functions based on the results of the comparison.

[0113] To do this, accessing the device SD involves:

[0114] a. a device for measuring and recording the value of the accelerometer ACC;

[0115] b. means for multiplying the value of the magnetometer M by the value of the accelerometer ACC by a scalar product;

[0116] c. Used to compare the value of the scalar product PSC that changes over time with the predetermined scalar product curve PSC D A device for comparison between

[0117] d. Means for activating a vehicle function F1 , F2 as a function of the result of said comparison.

[0118] The above-mentioned means (not shown in the drawings) may be composed of software means.

[0119] In a second improvement of the invention, the access device SD is capable of:

[0120] a. Continuously measure the acceleration value ACC;

[0121] b. Send the measurement results to vehicle V.

[0122] In this second development of the invention, the vehicle V receives all the measurements originating from the magnetometer M and the accelerometer ACC of the access device SD, the activation device D being thus able to:

[0123] a. Receiving the amplitude measurement result AM of the magnetic field and the orientation measurement result OR of the magnetic field and the acceleration measurement result ACC from the device SD;

[0124] b. Use the value of the accelerometer ACC to correct the value of the magnetometer M through the scalar product;

[0125] c. Compare the value of the scalar product PSC with the predetermined scalar product curve PSC D Make comparisons;

[0126] d. Activating vehicle functions F1 , F2 depending on the result of the comparison.

[0127] To this end, activating the device D further comprises:

[0128] a. means for multiplying the value of the magnetometer M by the value of the accelerometer ACC by a scalar product;

[0129] b. Used to compare the value of the scalar product PSC that changes over time with a predetermined scalar product curve PSC D A device for comparison between

[0130] c. Means for activating a vehicle function F1 , F2 as a function of the result of said comparison.

[0131] The above-mentioned means (not shown in the drawings) may be composed of software means.

[0132] As previously mentioned, in the case of an activation device D capable of exchanging data with an access device SD by means of radio frequency communication, the activation device is capable of receiving data originating from the magnetometer M and the accelerometer ACC.

[0133] The scalar product is understood to mean the scalar product per unit time of the value of the magnetometer M at a given moment and the value of the accelerometer at the same moment. For a correct implementation of the invention, it is essential that the values ​​originating from the magnetometer and the accelerometer multiplied by the scalar product are synchronized, that is, they are measured at the same moment.

[0134] We will now describe Figure 4 The activation method shown in .

[0135] In a preliminary step (E0), the "hands-free" access device is detected in a predetermined area around the vehicle V, which may be a remote area Z2 located around the vehicle (see Figure 1 ). During this step, the access device SD and the vehicle V communicate with each other by means of high frequency or ultra-high frequency communication, the access device is authenticated and its relative position with respect to the vehicle V is determined. This preliminary step then allows the recording of the measurements originating from the magnetometer M to be triggered (step E1 ).

[0136] It should be noted that this step is optional and that, in fact, the portable device SD could continuously record the data originating from its magnetometer M; however, this solution is energy-consuming and it seems more reasonable to trigger such recording only when an access device SD is detected around the vehicle V, in the remote zone Z2 and therefore when the user may wish to activate a vehicle function.

[0137] During a first step E1 , the access device SD records amplitude measurements AM and orientation measurements OR of its integrated magnetometer M per unit time (e.g. ms) over a predetermined duration Δt (e.g. 0.5 s) with a sampling frequency of 50 Hz, i.e. a measurement every 20 ms over a duration of 0.5 s.

[0138] During the second step, the curve of the amplitude measurement results AM is compared with the predetermined curve AM D For comparison (see Figure 5 ).

[0139] More specifically, a check is performed to determine whether the amplitude value decreases over time, and whether the decrease is above a threshold value.

[0140] This is Figure 5 It was demonstrated in Figure 5 In the example, the amplitude value AM at the initial moment t0 at which recording begins has a first value AM1, and then at the first moment t1 after a few milliseconds or seconds, this value decreases to a second value AM2. If the difference ΔAM between these two values ​​AM1, AM2 is greater than a predetermined threshold S, for example S=70%, it is considered that the access device SD is approaching the vehicle V (step E2a).

[0141] In fact, the Applicant has discovered that the vehicle's body, which is mainly metallic, disturbs the values ​​of the Earth's magnetic field sensed by the magnetometer M integrated in the access device SD.

[0142] In this case, when the access device SD approaches the vehicle, the amplitude value AM of the Earth's magnetic field measured by the magnetometer integrated with said device decreases significantly.

[0143] Of course, this reduction stems from metallic interference from the vehicle body rather than local anomalies in the Earth's magnetic field.

[0144] Therefore, by measuring this change in the amplitude of the magnetic field, it is possible to detect that the access device SD is close to the vehicle V and is located in the predetermined zone Z1.

[0145] If the access device SD is brought close to the vehicle V to such an extent that the device is located in a predetermined zone Z1, a vehicle function F1 can be activated (step E4a), such as unlocking a door. The user is considered to be located in the zone Z1 when, for example, the amplitude change ΔAM exceeds a threshold value (e.g. greater than 70%). This indicates that the amplitude value AM has decreased by 70% within a predetermined duration Δt (e.g. between an initial instant t0 and a first instant t1).

[0146] The amplitude variation allows determining the distance of the device SD relative to the vehicle V, which is measured beforehand during a calibration phase, when a look-up table between amplitude and distance variation is established.

[0147] In a subsequent step, the curve of the magnetic field orientation measurement result OR is compared with the predetermined curve OR D A comparison is made (step E3a). More specifically, the orientation is the orientation of the magnetic field vector

[0148] The magnetometer M measures the magnetic field M in the three cardinal directions x, y, z (see Figure 6 ) and deduce the orientation of the magnetic field vector from this.

[0149] This is Figure 6 was displayed in . Figure 6 The three orientation angles θ, θ and θ of the magnetic field vector are shown according to time t. and the measurement results of α.

[0150] At the initial time t0 when recording begins, the angle values ​​are separated from each other and are stable, where the angle values is greater than the angle θ, which is greater than the angle α. In this configuration, the magnetic field vector Points to the Earth's magnetic north, such as Figure 7 shown.

[0151] A user U carrying an access device SD is located around a vehicle V, such as Figure 7 As shown in the letter "A" in the figure.

[0152] Then, at time t1, the values ​​of the three angles suddenly change, wherein the value of angle θ decreases significantly, and the value of angle α increases significantly. The values ​​of the two angles intersect. The value of angle α itself increases significantly.

[0153] Angle θ and This intersection point between the values ​​of Rotation occurs.

[0154] This is Figure 7 As shown in FIG. 1 , when the access device SD approaches the vehicle V (by Figure 7 The metal body of the vehicle V interferes with the orientation measurement of the magnetic field, and the magnetic field vector measured by the magnetometer M rotates itself. When a user carrying an access device SD enters the vehicle, the proximity of the metal body causes the magnetic field vector to rotate almost completely (as indicated by Figure 7 denoted by the letter “C” in FIG.

[0155] Similarly, this rotation of the magnetic field vector is "artificial" because it is produced by the metal of the vehicle, which distorts the measurements of the magnetometer M.

[0156] According to the invention, this rotation of the magnetic field means that it is possible to detect that a user carrying an access device has entered the interior of the vehicle V. In order to detect the rotation, for at least two of the three angles (e.g. θ and φ, e.g. Figure 6 For each angle in FIG. 1 , the absolute value of the orientation change ΔOR within a predetermined time duration (eg, between the initial time t0 and the time t1 ) needs to be greater than a threshold value T (eg, the threshold value is 45°).

[0157] Once the user U is in the vehicle, the rotation decays and slows down because the environment in the passenger compartment of the vehicle V is not magnetically stable. Once the portable device SD is placed in the passenger compartment, the rotation stops. In other words, when the user moves away from the vehicle V, the direction of the magnetic field vector changes with respect to the direction of the magnetic field vector.

[0158] In reality, the angular values ​​of the magnetic field vectors are each stable again, but they are different values ​​and are ordered differently from one another.

[0159] Therefore, the angle value θ is greater than the angle value The angle value Itself is greater than the angle value α.

[0160] The user U is then considered to be located in the passenger compartment Z0 and can activate a safety vehicle function F2 , such as starting the vehicle (step E5 a ).

[0161] In this first embodiment, when the amplitude curve and the orientation curve correspond to the detection of the user U in the predetermined area or the activation of a function is possible, the access device sends an instruction to the activation device D to activate the corresponding function.

[0162] In a second embodiment, as shown in the left branch of the flowchart, once recording of the amplitude measurements AM and orientation measurements OR of the magnetic field begins (step E1), said measurements are sent by the access device SD to the vehicle continuously or in groups of measurements (step E1b).

[0163] The vehicle V (more specifically the activation device D) then compares the curves of the amplitude measurement results AM and the orientation measurement results OR of the magnetic field with predetermined curves (step E2b, step E3b), as described above, to detect the user U approaching the vehicle in a predetermined area Z1 and activating the approach function F1 (step E4a), or to detect the user's entry into the passenger compartment and the user's position in the passenger compartment Z0 of the vehicle and activate the vehicle start function F2 (step E5a).

[0164] In this second embodiment of the activation method according to the invention, the activation device D processes data originating from the access device SD.

[0165] In a further development of the activation method according to the invention, the access device SD is provided with an accelerometer ACC (see Figure 2 ).pass Figure 4 The right branch of the method in shows this improvement.

[0166] In this embodiment, the measurements originating from the magnetometer M are corrected by the measurements originating from the accelerometer ACC. In practice, the accelerations experienced by the access device SD in three spatial dimensions may interfere with the measurements of the Earth's magnetic field. These interferences may make the proximity detection in the zone Z1 or the position of the user in the passenger compartment Z0 less precise when performed solely on the basis of the measurements of the magnetometer M.

[0167] The method proposes to determine the scalar product PSC between the magnetic field vector and the accelerometer vector (step E1d) according to the following equation and to use only the value of the scalar product PSC in order to detect the approach of an access device to the vehicle V or the entry of said device into the passenger compartment:

[0168] [Mathematical formula 3]

[0169]

[0170] as well as

[0171] [Formula 4]

[0172]

[0173] in:

[0174] AMx: is the magnetic field amplitude along the x-axis.

[0175] AMy: is the magnetic field amplitude along the y-axis.

[0176] AMz: is the magnetic field amplitude along the z-axis.

[0177] Accx: is the magnitude of acceleration along the x-axis.

[0178] Accy: is the magnitude of acceleration along the y-axis.

[0179] Accz: is the acceleration magnitude along the z-axis.

[0180] ω: is the magnetic field vector With the acceleration vector The angle between.

[0181] is the absolute value of the magnitude or norm of the magnetic field vector.

[0182] is the absolute value of the magnitude or norm of the acceleration vector.

[0183] Then the obtained scalar product PSC is compared with the predetermined scalar product curve PSC D Make a comparison.

[0184] This is Figure 8 was displayed in . Figure 8 shows that the magnetic field vector and the acceleration vector The scalar product PSC between them.

[0185] Until time t0 , a user carrying an access device SD approaches the vehicle V, which causes the value of the scalar product PSC to decrease to a first value PSC1 .

[0186] If the reduction ΔPSC of the scalar product value is greater than a first threshold T1 (for example equal to 50%), the access device SD is considered to be located in a predetermined zone Z1 around the vehicle V (step E2c) and the vehicle function F1 corresponding to the approach can be activated (step E4a).

[0187] Between time t0 and t1 , the user enters the vehicle V and the value of the scalar product PSC continues to decrease until it reaches a second threshold value PSC2 .

[0188] If the reduction in the scalar product value ΔPSC is greater than a second threshold value T2 (which is equal to 70%, for example) and this process occurs within a predetermined time window (in this case between times t0 and t1), the access device SD is considered to be located in a predetermined area Z0 of the vehicle V (step E3c) and the vehicle function F2 corresponding to the detection of the device SD being located in the passenger compartment can be activated (step E5a).

[0189] This improvement to the invention means that better precision can be achieved in terms of the position of the portable device SD, since the movements of the access device SD are thus correlated with the variations in the magnetic field sensed by the magnetometer M.

[0190] However, as mentioned above, it is important that the measurements originating from the magnetometer M and the accelerometer ACC, which are multiplied in a scalar product, are measured at the same instant.

[0191] Thus, according to the invention, the variations in the Earth's magnetic field sensed by the magnetometer M integrated in the portable access device SD are sufficient to determine the user's position in a predetermined area and to activate the corresponding vehicle function.

[0192] The present invention is particularly inventive because, unlike the prior art, it eliminates the need for multiple transceivers located around and within the vehicle.

[0193] In fact, according to the invention, only at least two radio frequency transceivers are required to activate all functions related to the proximity of users to the vehicle and / or their presence in the passenger compartment.

[0194] Therefore, the present invention has the advantages of being relatively cheap, easy to implement and reliable, thereby avoiding the disadvantages of the prior art.

Claims

1. A method for activating a vehicle function by means of an activation device (D) based on a "hands-free" access device (SD) carried by a user (U) and provided with a magnetometer (M), the activation of the function being triggered by detecting the presence of the device (U) in a predetermined zone (Z1) around a vehicle (V) or in the passenger compartment (Z0) of the vehicle (V) and based on the result of the authentication of the device, the activation device comprising at least one external radio frequency transceiver (A1) capable of transmitting outside the vehicle and one internal radio frequency transceiver (A2) capable of transmitting in the passenger compartment (Z0) of the vehicle, characterised in that the method comprises the following steps: a) detecting the presence of the device (SD) in a predetermined zone (Z2) by means of radio frequency communication; b) the access device (SD) continuously measures the amplitude (AM) of the magnetic field and the orientation (OR) of said magnetic field; c) comparing the measurement result (AM, OR) with a predetermined amplitude curve (AM D ) and orientation curve (OR D ) for comparison: i) whether the magnitude of the magnetic field decreases over time and whether the decrease in magnitude within a predetermined duration is greater than a threshold; or ii) whether a change in the orientation of the magnetic field over a predetermined duration corresponds to a rotation; d) Then, a vehicle function (F1, F2) is activated depending on the result of said comparison.

2. Activation method according to the preceding claim, characterized in that The measurements (AM, OR) are sent to the vehicle by means of radio frequency communication and the comparison is performed by the vehicle (V).

3. The activation method according to claim 1, characterized in that: The comparison is performed by the portable device (SD) and the result of the comparison is transmitted to the vehicle (V) by means of radio frequency communication.

4. The method for activating a vehicle function as claimed in any one of the preceding claims, characterized in that The radio frequency communication can involve high frequency or ultra high frequency communication.

5. The method for activating a vehicle function as claimed in any one of the preceding claims, characterized in that The access device (SD) is provided with an accelerometer (ACC), the measurement results (AM) of the magnetic field are corrected by a scalar product (PSC) with the measurement results originating from the accelerometer (ACC), and the scalar product (PSC) is compared with a predetermined scalar product curve (PSC). D ) for comparison and activating the vehicle function based on the result of the comparison.

6. A "hands-free" access device (SD) for accessing a motor vehicle (V), said device being carried by a user (U) and being provided with a magnetometer (M) and being able to communicate with the vehicle by means of radio frequency communication, characterised in that it is able to: a) continuously measuring the amplitude (AM) of a magnetic field and the orientation (OR) of said magnetic field; b) comparing the measurement result (AM, OR) with a predetermined amplitude curve (AM D ) and orientation curve (OR D ) for comparison; c) Activating vehicle functions ( F1 , F2 ) depending on the results of these comparisons.

7. A "hands-free" access device (SD) for accessing a motor vehicle, said device being carried by a user (U) and being provided with a magnetometer (M) and being able to communicate with the vehicle by means of radio frequency communication, characterised in that it is able to: a) continuously measuring the amplitude (AM) of a magnetic field and the orientation (OR) of said magnetic field; b) sending said measurement results to the vehicle (V).

8. A "hands-free" access device (SD) for accessing a motor vehicle according to claim 6, characterized in that The device comprises an accelerometer (ACC), the device being characterized in that the device is capable of: a) Continuously measure the acceleration value (ACC); b) correcting the measurement result (AM) of the magnetometer with the measurement result of the accelerometer (ACC) by a scalar product (PSC); c) comparing the value of the scalar product (PSC) with a predetermined scalar product curve (PSC D ) for comparison; d) activating the vehicle function ( F1 , F2 ) depending on the result of the comparison.

9. A "hands-free" access device (SD) for accessing a motor vehicle according to claim 7, characterized in that The device comprises an accelerometer (ACC), the device being characterized in that the device is capable of: a) Continuously measure the acceleration value (ACC); b) sending said measurement results to the vehicle (V).

10. An activation device (D) for activating a vehicle function, the activation of which is triggered by detecting the presence of a "hands-free" access device (SD) carried by a user (U) in a predetermined area (Z1) around a vehicle (V) or in the passenger compartment (Z0) of the vehicle (V) and based on the authentication result of the device, the activation device comprising at least one external antenna module (A1) for transmitting / receiving radio frequency, and an internal antenna (A2) for transmitting / receiving radio frequency that can be transmitted in the passenger compartment (Z0) of the vehicle, the device communicating with the "hands-free" access device, characterized in that The activation device is able to: a) receiving an amplitude measurement (AM) of a magnetic field and an orientation measurement (OR) of the magnetic field originating from the device; b) comparing the measurement result (AM, OR) with a predetermined amplitude curve (AM D ) and orientation curve (OR D ) for comparison; c) Activating vehicle functions ( F1 , F2 ) depending on the results of these comparisons.

11. An activation device (D) for activating a vehicle function, the activation of which is triggered by detecting the presence of a "hands-free" access device (SD) carried by a user (U) in a predetermined area (Z1) around a vehicle (V) or in the passenger compartment (Z0) of the vehicle (V) and based on the authentication result of the device (SD), the activation device comprising at least one external antenna module (A1) for transmitting / receiving radio frequency, and an internal antenna (A2) for transmitting / receiving radio frequency that can be transmitted in the passenger compartment (Z0) of the vehicle, the device communicating with the "hands-free" access device, characterized in that The activation device is able to: a) receiving an amplitude measurement (AM) of a magnetic field and an orientation measurement (OR) of the magnetic field and an acceleration measurement (ACC) originating from the device; b) correcting the value of the magnetometer (M) by means of a scalar product (PSC) with the value of the accelerometer (ACC); c) comparing the value of the scalar product (PSC) with a predetermined scalar product curve (PSC D ) for comparison; d) activating the vehicle function (F1, F2) depending on the result of the comparison.

12. A computer program product comprising program code instructions for executing the steps of the method according to any one of claims 1 to 5 when said program is executed on a computer.

13. A motor vehicle, characterized in that: The motor vehicle comprises an activation device (D) as claimed in any one of claims 10 or 11.

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