FR3003355A1 - METHOD FOR REPORTING A MOTOR VEHICLE IN RELATION TO A PARKING AREA, AND METHOD FOR ASSISTING PARKING OF A MOTOR VEHICLE IN A PARKING AREA - Google Patents

Abstract

The invention relates to a method of locating a motor vehicle (10) with respect to a parking area (20), comprising the steps of: a) transmitting a magnetic field (Brad) by means of a first transmission means magnetic field (21) provided in the parking area, b) measuring the values of two non-parallel components (Bx / Rm, Bz / Rm) of the magnetic field by means of a magnetic field measuring means (12) provided for in edge of the motor vehicle, and c) locate the motor vehicle with respect to the parking area by means of calculation means adapted to determine a relative positioning value between the motor vehicle and the parking area, from, on the one hand, measured values of the components and, on the other hand, a predetermined map which corresponds to each set of component values a relative positioning value between the motor vehicle and the parking area. t.

Description

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention relates generally to the field of motor vehicles. It relates more particularly to a method of locating a motor vehicle with respect to a parking area for a motor vehicle using magnetic means. It also relates to a method of assisting the parking of a motor vehicle in a parking area using such a tracking method. Finally, it relates to a motor vehicle and a parking area for the implementation of such a method. BACKGROUND ART In many situations, it is useful or necessary, indeed indispensable, to pinpoint the position of a motor vehicle with respect to a parking area, for example during parking maneuvers or when the motor vehicle must be parked. position at a specific location in the parking area.

For this, a first solution already implemented on certain motor vehicles (known as automated park assist function) is to use ultrasonic sensors that scan the parking area and to detect any obstacles whose positions by report to the parking area are known.

This first solution therefore requires that the parking area be delimited by obstacles located above the ground, such as poles or other vehicles. Thus, it is not possible to locate the position of the motor vehicle relative to the parking area if it is isolated or if adjacent parking areas are free. In addition, the accuracy of a system comprising ultrasonic sensors can degrade depending on external conditions such as weather conditions. A second solution is to use one or more video sensors coupled to an image processing system. Document EP2202132A2 discloses, for example, a method of locating a motor vehicle with respect to a parking area, according to which an image of a painted target is acquired by means of a lateral camera system arranged on the motor vehicle. on the ground inside the parking area and the relative position of the motor vehicle is deduced from the processing of this image and the recognition of the shape of the acquired image of the target. Nevertheless, even if the solutions based on video sensors have very high precision, they are very expensive for the automotive field. In addition, the performance of this type of solution may be degraded depending on the weather conditions (rain, fog), or illumination conditions (spurious reflections, low light, glare from the headlights of another motor vehicle towards the video sensor). OBJECT OF THE INVENTION In order to overcome the aforementioned drawbacks of the state of the art, the present invention proposes a method of locating a motor vehicle with respect to an inexpensive motor vehicle parking area that can be used. easily, and which has high performance even when external conditions, including weather, are bad or unfavorable.

Thus, according to the invention, the tracking method comprises the following steps: a) emitting a magnetic field by means of at least a first magnetic field emission means provided respectively in the parking area or on board the motor vehicle , b) measuring the values of at least two non-parallel components of said transmitted magnetic field by at least one magnetic field measuring means respectively provided on board said motor vehicle or in said parking area, and c) locating said motor vehicle with respect to said parking area by means of calculation means adapted to determine at least one relative positioning value between said motor vehicle and said parking area from, on the one hand, said measured values of the components of the magnetic field, and on the other hand, a predetermined map that maps to each set of component values of said cha mp magnetic, a relative positioning value between said motor vehicle and said parking area. Thus, the tracking method according to the invention implements means for transmitting and measuring the magnetic field which are partly in the parking area and partly on board the motor vehicle. As a result, the tracking method eliminates the use of elements located above the ground, which limits the risk of degradation. In addition, these magnetic means have the advantage of being inexpensive, compact, and also offer, when used in combination, a good positioning accuracy. Finally, these magnetic means are insensitive to poor weather conditions (rain, fog) and can operate regardless of the illumination conditions. Other nonlimiting and advantageous features of the registration method according to the invention are the following: the predetermined mapping used in step c) comprises a database register with at least two entries formed by said at least two components of the magnetic field, and an output formed by said relative positioning value; the predetermined mapping used in step c) comprises a mathematical function or an algorithm that associates, with each set of values of the components of said magnetic field, said relative positioning value; in step a), said magnetic field is emitted, on the one hand, along a first main transmission axis by said first magnetic field emission means, and on the other hand, along a second main axis; by means of a second magnetic field emission means, and in step c), two relative positioning values are determined, namely the relative position and orientation of the motor vehicle with respect to the transmission area. parking; said first magnetic field emission means and said second magnetic field emission means emit a time or frequency multiplexed magnetic field. The tracking method according to the invention can be advantageously exploited to position the motor vehicle on a predetermined path and assist parking this motor vehicle. Thus, the invention also proposes a method of assisting the parking of a motor vehicle in a parking area comprising the following successive operations: (i) locating said motor vehicle with respect to said parking area by means of a method register according to the invention; (ii) determining a trajectory to be followed by the motor vehicle to reach the parking area; (iii) determining a steering wheel angle setpoint for the motor vehicle to follow said trajectory; (iv) automatic steering of the motor vehicle according to said steering wheel angle instruction or indication to a driver of said motor vehicle of said steering wheel angle setpoint. Advantageously, the second operation (ii) and the third operation (iii) are carried out thanks to the calculation means used for locating the motor vehicle during the first operation (i). Preferably, during the operation (iii), a vehicle speed setpoint is also determined for the motor vehicle to follow the trajectory determined during the operation (ii), and during the operation (iv), the automatic steering is also performed according to said vehicle speed setpoint or an indication of said vehicle speed setpoint is given to the driver of the motor vehicle. The invention also proposes a motor vehicle comprising at least one magnetic field measuring means adapted to implement step b) of a tracking method according to the invention and calculation means adapted to implement step c) of said registration method. In this configuration, the magnetic field emission means are then provided in the parking area. Advantageously, the magnetic field emission means provided in the parking area are buried in the parking area, so as to leave blank the surface of the parking area and to prevent these means of emission magnetic field does not degrade when the motor vehicle passes over the parking area. Advantageously, the motor vehicle comprises a measuring means which is a bi-axis magnetometer. Preferably, the motor vehicle comprises several measuring means which are tri-axis magnetometers, said tri-axis magnetometers being adapted to measure three distinct components of the magnetic field emitted by the magnetic field emission means located in the area. parking. The use of one or more tri-axis magnetometers makes it possible to improve the accuracy of the relative position and orientation of the motor vehicle with respect to the parking area.

More preferably, the parking area comprises a transmission means which is a bi-axis coil, adapted to emit a magnetic field along two main axes of emission. Even more preferably, the parking area comprises one or more transmission means which are tri-axis coils. The use of bi-axis or tri-axis coils makes it possible to emit a magnetic field whose distribution / topology is more complex, further improving tracking accuracy. The invention also proposes a parking area comprising at least one magnetic field measuring means suitable for implementing step b) of the aforementioned identification method and calculation means adapted to implement step c). of this tracking method. In this configuration, the magnetic field emission means are then provided on board the motor vehicle. DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description with reference to the accompanying drawings, given by way of non-limiting example, will make it clear what the invention consists of and how it can be achieved. In the accompanying drawings: - Figure 1 is a schematic view of a motor vehicle and a parking area adapted to implement a tracking method according to a first embodiment of the invention; FIG. 2 is a schematic view of a coil of a non-contact charging terminal of the parking area of FIG. 1; FIG. 3 is a map of a component Bx of the magnetic field emitted by the coil of FIG. 2; FIG. 4 is a map of a component Bz of the magnetic field emitted by the coil of FIG. 2; FIG. 5 is a schematic view of a motor vehicle and a parking area adapted to implement a tracking method according to a second embodiment of the invention; - Figure 6 is a schematic view of a tri-axis coil buried in the parking area of Figure 5; FIG. 7 is a diagrammatic view of an iso-intensity line of the magnetic field emitted by one of the circular turns of the triaxial coil of FIG. 6 and of the magnetic field measurement axes of FIG. bi-axis magnetometer; FIG. 8 is a schematic view of the iso-intensity lines of the magnetic fields emitted by two coils of perpendicular axes; Fig. 9 is a schematic view showing the location of the possible positions of a magnetometer with respect to the field lines of a coil of Fig. 8; FIG. 10 is a curve for determining the orientation of a magnetometer as a function of a component of the magnetic field; FIG. 11 is a graph showing the temporal variations of a first magnetic field emitted by a first coil; FIG. 12 is a curve representing the temporal variations of a second magnetic field emitted by a second coil; FIG. 13 is a graph showing the temporal variations of the magnetic field resulting from the superposition of the first magnetic field of FIG. 11 and the second magnetic field of FIG. 12; FIG. 14 is a curve representing the Fourier transform of the magnetic field resulting from FIG. 13; - Figure 15 is a schematic view of a motor vehicle and a parking area adapted to implement a tracking method 30 according to a third embodiment of the invention; FIG. 16 is a schematic view of a tri-axis coil buried in the parking area of FIG. 15; FIG. 17 is a schematic view of a motor vehicle illustrating the kinematic model used in a parking assistance method according to the invention; FIG. 18 is a diagrammatic view of the parking area and the tri-axis coil of FIG. 6 showing the iso-intensity toruses of the magnetic fields emitted by the coil of the contactless charging terminal of FIG. parking area and by the tri-axis coil. As a preliminary, it will be noted that identical or similar elements of the different embodiments of the invention will, as far as possible, be referenced by the same reference signs and will not be rewritten each time.

FIGS. 1, 5 and 15 show three embodiments of a motor vehicle 10 and a parking area 20 for a motor vehicle designed to implement a method of locating the motor vehicle 10 with respect to the parking area 20 according to the invention. In these embodiments, the motor vehicle 10 is a vehicle with electric propulsion whose electric motor is supplied with electrical energy from a storage battery (not shown) housed in the motor vehicle 10. In order to recharge this accumulator battery, the motor vehicle 10 comprises an induction charging terminal 11 which is fixed on the underside (not shown) of the motor vehicle 10, so that it is located outside the motor vehicle 10 and that it faces the ground on which the motor vehicle 10 circulates or parks. The receiving load terminal 11 comprises a primary coil (not shown) here of substantially circular shape and of diameter compatible with a mounting on a motor vehicle. In the case of a motor vehicle, the diameter is 30 centimeters on average. The receiving load terminal 11 has a center 10C (see FIGS. 1, 15). As is well shown in Figures 1, 5 and 15, the parking area 20 is here defined by a ground mark 20A, here of rectangular shape. The parking area 20 comprises an inductive emitter charging terminal 21 which is here fixed on the ground, inside the parking area 20. In the same manner as the receiving charging terminal 11, the terminal of transmitting charge 21 comprises a secondary coil here of substantially circular shape and of diameter substantially equal to that of the primary coil of the receiving load terminal. This secondary coil 21B comprises a planar circular coil (see Figure 2) in which an electric current can flow. The operation of this secondary coil 21B will be described in the following. The transmitting charging terminal 21 is powered and controlled by an electronic power supply and control box 22 which is here located in the parking area 20, within the zone delimited by the floor mark 20A, and which is connected to the local electrical network 23. Alternatively, the power supply and electronic control box could be for example located outside the parking area. The power supply and electronic control box 22 is preferably buried under the parking area 20, so that it does not flush with the ground surface. Alternatively, the power supply and electronic control box could be designed to be fixed on the ground, in or out of the parking area. To recharge its storage battery, the motor vehicle 10 must be located in the parking area 20, inside the floor mark 20A, so that its receiving charge coil 11 is located above of the charging charging terminal 21. During this charging, the emitting charging terminal 21 is powered and controlled by the power supply and electronic control unit 22 so that a charging electric power is transmitted by induction of the charging terminal. transmitting load 21 to the receiving load terminal 11 for the charge of the storage battery of the motor vehicle 10. In order to maintain a satisfactory electric charging power transmission capacity, it is desirable that the primary coil of the terminal 30 receiving load 11 and the secondary coil 21B of the emitter charging terminal 21 are positioned approximately in line with each other. Indeed, if the misalignment of the axes of the two coils is greater than a certain misalignment tolerance, the transmission efficiency becomes low and it becomes unprofitable to recharge the motor vehicle 10 by induction. In the various embodiments shown in FIGS. 1, 5 and 15, where the receiving load terminal 11 and the transmitting charging terminal 21 each have a diameter of 30 cm, the misalignment tolerance of the axes of the two terminals charging 11, 21 when charging is about 10 to 15 centimeters. The present invention thus aims at enabling the motor vehicle 10 to be placed in the parking area 20 in such a way that the two coils are correctly oriented.

According to a particularly advantageous characteristic of the invention, the tracking method comprises the following steps: a) emitting a magnetic field by means of at least a first magnetic field emission means provided respectively in the parking area or on board of the motor vehicle, b) measuring the values of at least two non-parallel components of said transmitted magnetic field by at least one magnetic field measurement means provided on board said motor vehicle (in the case where the first transmission means of magnetic field is provided in the parking area) or in said parking area (in the case where the first magnetic field emission means 20 is provided on board the motor vehicle), and c) locate said motor vehicle relative to at said parking area by means of calculation means adapted to determine at least one relative positioning value between said automobile vehicle e and said parking area, from, on the one hand, said measured values of the components of the magnetic field and, on the other hand, a predetermined mapping which maps to each set of component values of said magnetic field. , a relative positioning value between said motor vehicle and said parking area. In other words, in step a), by means of at least a first magnetic field emission means, a magnetic field is generated at any point in the space around the first field emission means magnetic, especially in the near environment surrounding the parking area 20 and the motor vehicle 10. Then, in step b), this magnetic field is detected and measured by the magnetic field measuring means, this detection in two non-parallel directions to measure at least two non-parallel components of the emitted magnetic field. Finally, in a third step c), on the one hand, the measurement of the components of the magnetic field carried out in step b), and on the other hand, a predetermined mapping of the emitted magnetic field is used. This predetermined mapping represents a priori knowledge of the emitted magnetic field. More specifically, it contains information on the distribution of this magnetic field around the first magnetic field emission means, in the near environment around the parking area 20 or the motor vehicle 10. Thus, by measuring the values of the components of the emitted magnetic field and knowing a priori the relative positioning value between the vehicle 10 and the parking area 20 associated with these values, it is possible, according to the tracking method of the invention, to locate the motor vehicle 10 with respect to the parking area 20. In a first embodiment described with reference to FIGS. 1 to 4, the relative positioning value is constituted by the value of the distance of the motor vehicle 10 from 20. In the second and third embodiments described with reference to FIGS. 5 to 14 and 15 to 16, the values of pos The relative relative values determined are the values of the relative position and orientation of the motor vehicle 10 with respect to the parking area 20. In order to specify, in the rest of this description, how the various embodiments of the method of locating will be implemented, will be associated first of all with the vehicle 10 a vehicle reference system Rv defined by: - a vehicle reference point 10C, and 30 - three vehicle axes 10X, 10Y, 10Z which are here perpendicular between them in pairs and intersect at the vehicle reference point 10C, a longitudinal axis 10X, a transverse axis 10Y, and a vertical axis 10Z. In the same way, parking area 20 is associated with a parking reference frame Rs defined by: - a parking reference point 20C, and - three parking axes 20X, 20Y, 20Z which are also perpendicular to each other at two. two and intersect at reference point 20C, including a longitudinal axis 20X, a transverse axis 20Y, and a vertical axis 20Z.

It will be considered in the following description that the parking area 20 defines a substantially horizontal plane, parallel to the parking plane defined by the two parking axes 20X, 20Y. Without limitation and for the sake of simplification, it will be considered in the following description that the two vehicle axes 10X, 10Y form a vehicle plane which is horizontal and parallel to the parking plane defined by the two parking axes 20X, 20Y. In these three embodiments shown in Figures 1, 5 and 15, the first magnetic field emission means, respectively referenced 21B, 24, 241 is located in the parking area 20.

This first magnetic field emission means 21B; 24; 241 is a magnetic field source that emits, when powered by an electric current, a magnetic field in space. Correspondingly, as shown in FIGS. 1, 5, and 15, the first magnetic field measuring means referenced 12 in FIGS. 1 and 5 and 121 in FIG. 15 is provided on board the motor vehicle 10. It will be seen later in the description that this first magnetic field measuring means 12; 121 makes it possible to measure the values of at least two non-parallel components of the magnetic field B'd emitted by the first magnetic field emission means 21; 24; 241 located in the parking area 20. We will now describe how the predetermined mapping of step c) of the registration process is obtained and how it can be exploited for the implementation of the method according to the invention.

In the parking reference frame Rs of the parking area 20, Bx / Rs, By / R5, BZ / Rs will be the three components of the magnetic field Brdd emitted by the first magnetic field emission means 21; 24; 241 along the three parking axes 20X, 20Y, and 20Z. Mapping the magnetic field B'd emitted by a magnetic field emission means at any point of a space around said magnetic field emission means, in a predetermined radius, then consists of a means which allows to determine, at each point of this space, the components of the magnetic field Brad with a good precision.

In practice, it is unfortunately not possible to measure the magnetic field B'd at any point in space but only in a limited number of particular points, these particular points forming a mesh, regular or not, of the space. To establish this mapping, it will be possible for example to use a magnetic field sensor 10. This mapping can also be established theoretically, by modeling the locations. At the conclusion of this theoretical or experimental determination, for a plurality of points P of the space (of coordinates X / Rs, Y / Rs, Z / Rs in the reference frame of the parking area Rs) is known) , the values of the two nonparallel components Bx / Rs (P) and BziRs (P). Thus, by inverting these functions, a predetermined map is obtained which maps, for each set of values of the non-parallel components Bx / R, and Bz / R, of the magnetic field B'd, the distance 20 or the position and the relative orientation of the motor vehicle 10 relative to the parking area 20. It will be understood, with reference to the various embodiments shown in Figures 1 to 16, that it is useful to exploit the data on the magnetic field B'd, to get them in shape for later use. Two options can then be chosen. The first option is to store this data in a table. Thus, the previously predetermined map may comprise a database register with at least two inputs formed by the two nonparallel components Bx / Rs (P) and Bz / Rs (P) of the magnetic field Brad determined in the plurality of points. P of space. This database register will correspond to each pair of inputs, an output formed by the distance Dy / 5 between the motor vehicle 10 and the parking area 20, or by the relative position and orientation of the motor vehicle 10 in relation to the parking area 20.

Thus, by measuring the two nonparallel components Bx / R, and Bz / R, of the transmitted magnetic field Brad, and by reporting the values of these components in this database register, it is possible to read at the output the value the distance between the motor vehicle 10 and the parking area 20 (in the first embodiment of the invention), that is to say the values of the relative position and orientation of the motor vehicle 10 with respect to the area parking station 20 (in the second and third embodiments of the invention). The second option for formatting the data of the predetermined map is to analytically approximate the data of this map. Thus, the predetermined map may comprise a mathematical function or an algorithm which associates, with each set of values of the nonparallel components Bx / R, and Bz / R, of the magnetic field Brad, namely the distance, the position and the relative orientation of the motor vehicle 10 with respect to the parking area 20. When the predetermined mapping comprises a mathematical function, it is preferably a two-variable mathematical function, namely the values of the non-parallel components Bx / R, and Bz / R, magnetic field Brad. This function associates with these two values, either the value of the distance, or the values of the relative positions and orientation of the motor vehicle 10 with respect to the parking area 20. When the predetermined cartography comprises an algorithm, the latter admits input variables, including non-parallel components Bx / R, and Bz / R, of the magnetic field Brad. By numerical calculation, the algorithm then outputs either the value of the distance or the values of the relative position and orientation of the motor vehicle 10 with respect to the parking area 20 corresponding to the values of the two non-parallel components. In practice, the first option using a database register is not preferred since the use of such a register requires the use of expensive, often expensive, data storage computing means. Thus, in the various embodiments of the tracking method described with reference to FIGS. 1 to 16, the predetermined cartography will comprise an algorithm that associates, with each set of values, nonparallel components Bx / R, and Bz / R, of the field magnetic B'd, the distance (in the first embodiment of the invention), or the relative position and orientation (in the second and third embodiments of the invention) of the motor vehicle 10 relative to the parking area 20. There is shown in Figure 1 a first embodiment of the motor vehicle 10 and the parking area 20 with which it is possible to implement the first embodiment of the tracking method according to the invention. According to this first embodiment, the relative positioning value between the motor vehicle 10 and the parking area 20 is constituted by the data of the distance D, between the motor vehicle 10 and the parking area 20.

Here the distance D ',, between the motor vehicle 10 and the parking area 20 will be defined as being equal to the (Euclidean) distance between the parking reference point 20C and the projection of the vehicle reference point 10C on the parking plan defined by the two parking axes 20X, 20Y.

In other words, if we note, in the parking reference frame Rs, respectively X \ they and Yvis the coordinates of the vehicle reference point 10C respectively on the parking axis 20X and the parking axis 20Y, then the distance Dv ,, is equal to ((Xv1s) 2 (y \ 1s) 2) 112. In this embodiment, a part of the equipment dedicated to the non-contact load, in particular the emitter charging terminal 21 and the electronic power supply and control box 22, is used for the implementation of the tracking method. . In particular, the first magnetic field emission means, which makes it possible to emit the magnetic field B'd, comprises the secondary coil 21B of the emitter charging terminal 21 of the parking area 20. According to this first embodiment embodiment, in step a) of the tracking method, a magnetic field Brad is emitted through the secondary coil 21B of the emitter charging terminal 21 provided in the parking area 20. For this, the power supply box and electronic control 22 sends an electric current into the secondary coil 21B, which generates a magnetic field around the emitter charging terminal 21, near the parking area 20. It will be specified here that the intensity of the magnetic field B d transmitted by the secondary coil 21B during the tracking method according to the invention is much lower, for example ten times lower than the magnetic field B'd emitted during a charging phase of the motor vehicle 10. FIG. 3 and FIG. 4 show the Bx / R and Bz / R components of the magnetic field B'd emitted by the secondary coil 21B along the parking area axes 20X and 20Z. It is important to point out, at this stage of the description, that the results presented in Figures 3 and 4 are theoretical results, in that they were obtained here by numerical simulation by modeling the magnetic field emission B'd emitted by the secondary coil 21B in space. In general, the magnetic field Brad emitted by the first magnetic field emission means is a non-uniform magnetic field, that is to say that the different components Bx, By, and Bz of this magnetic field vary in size. function of the position considered in space. Since the axes 20X and 20Z are mutually perpendicular, the two components Bx and Bz constitute two non-parallel components of the magnetic field B-ad emitted by the secondary coil 21B. In step b) of the registration method, the values of the two non-parallel components Bx / R and BZ / Rv of the magnetic field B'd emitted by the field measurement means 25 are measured in the vehicle reference frame Rv. magnet 12 provided on board the motor vehicle 10, as shown in Figure 1. In this first embodiment, the first magnetic field measuring means is formed of a magnetometer. In general, a magnetometer is a magnetic field measuring device comprising a magnetic field sensor responsive to one or more components of a magnetic field, expressed in Tesla (T). From the measurement of these components, the intensity of the measured magnetic field is reconstructed. The magnetometer 12 fitted to the motor vehicle 10 shown in FIG. 1 is here a bi-axis magnetometer. It will be understood that the magnetometer 12 is adapted to measure two non-parallel components of a magnetic field. For simplicity, it will be considered here that the bi-axis magnetometer 12 of the motor vehicle 10 is centered on the vehicle reference point 10C and is oriented so that its two axes 12X, 12Z are respectively parallel to the longitudinal axis 10X and the transverse axis 10Z of the motor vehicle 10. The two axes 12X, 12Z of the magnetometer 12 are here perpendicular to each other and correspond to the two non-parallel axes in which the magnetometer 12 of the motor vehicle 10 measures the two non-parallel components of the magnetic field Bx / Rv and Bz / Rv in the reference frame of the vehicle R. It will be considered that the component BX / Rv, respectively the component BZ / Rv, corresponds to the component Bx of the magnetic field along the axis 12X of the magnetometer 12, respectively to the Bz component of the magnetic field along the 12Z axis of the magnetometer 12, these two components being measured at the magnetometer reference point 12C. The two axes 12X, 12Z of the magnetometer 12 here define a magnetometer plane which is parallel to the parking plane defined by the two parking axes 20X, 20Z. During step c), the distance D ',, separating the motor vehicle 10 from the parking area 20, that is to say the distance between the center of the emitting charging coil 21C, is calculated. and the center of the receiver charging coil 11C. For this purpose, the distance associated with the inputs whose values are equal to the values of the two non-parallel components BX / Rv and Bz / R measured by the magnetometer 12 is read in the map. Thus, the measurement made by the magnetometer 12 on board the motor vehicle 10 provides a measurement which is an image of the magnetic field Brad emitted by the secondary coil of the emitter charging terminal 21 located in the parking area 20. Knowing a priori this magnetic field B d and passing through a calibration step, the measurement made by the magnetometer 12 is connected to the distance between the magnetometer 12 and the secondary coil, and thus at the distance Dv, separating the motor vehicle 10 from the area parking 20.

As will be explained later, this distance can be used in various ways, including to emit a sound at a frequency depending on this distance, to inform the driver of the vehicle. However, even if this configuration with a secondary coil 21B and a bi-axis magnetometer 12 is sufficient to determine the distance between the motor vehicle 10 and the parking area 20, it does not make it possible to completely determine the position and the relative orientation. the magnetometer 12 with respect to this secondary coil 21. There is shown in FIG. 5 a second embodiment of the motor vehicle 10 and the parking area 20 by means of which it is possible to implement the second embodiment of the invention. tracking method according to the invention. According to this second embodiment, two relative positioning values between the motor vehicle 10 and the parking area 20 are determined in step c) of the registration method. These two relative positioning values between the motor vehicle 10 and the parking area 20 are constituted by the relative position and orientation data between the motor vehicle 10 and the parking area 20. By relative position, will hear the coordinates (x / 5, Yv / s) of the vehicle reference center 10C in the reference frame of the parking area R. By relative orientation, we will hear the angle 0, /, that forms the longitudinal axis 10Y of motor vehicle 10 with the longitudinal axis 20X of the parking area 20. Compared to the first embodiment shown in FIG. 1, the parking area 20 comprises, in this second embodiment, a trilateral coil. axis 24 separate from the emitter charging terminal 21, and a control system 25 (see Figure 5). Alternatively, the separate coil of the emitter charging terminal 30 could for example be a bi-axis coil. Nevertheless, the use of a bi-axis coil leads to less accurate relative positioning measurements than with a tri-axis coil. As shown in FIG. 6, the tri-axis coil 24 comprises: a first magnetic field emission means comprising a first circular turn 24B traversed by a first electric current, and a second magnetic field emission means having a second circular turn 24A traversed by a second electric current. a third magnetic field emission means comprising a third circular turn 24D traversed by a third electric current. The circular turns 24B, 24A, 24D are here planar, circular and centered all three on the same coil reference center 24C. They are associated with a reel reference Rb centered on the coil reference center 24C and having three coil axes 24X, 24Y, 24Z which are here perpendicular to each other in pairs and intersect at the coil reference point 24C, one of which longitudinal axis 24X, a transverse axis 24Y, and a vertical axis 24Z. The first circular turn 24B is of revolution about the vertical axis 24Z of the coil 24 while the second circular turn 24A is of revolution about the longitudinal axis 24X of the coil 24 and the third circular turn 24D is of revolution around the transverse axis 24Y of the coil 24. It will be considered that, by construction, the relative position and orientation of the reel repository Rb with respect to the parking area reference Rs are perfectly known. In step a) of the registration method according to the second embodiment of the invention, a magnetic field Brad is emitted along a first main transmission axis 24Z by virtue of the first magnetic field emission means 24B and according to a second main transmission axis 24X through the second magnetic field emission means 24A.

More precisely, the magnetic field Brad emitted by the bi-axis coil 24 is the superposition of a first magnetic field Bradl emitted by the first circular turn 24B and a second magnetic field Brad, 2 emitted by the second circular turn 24B. Advantageously, in this second embodiment of the invention, the different magnetic field emission means used emit a magnetic field that is multiplexed in time or in frequency. It will be understood that: - either the different magnetic field emitting means emit successively in time individual magnetic fields so that the magnetometer 12 of the motor vehicle 10 can successively measure non-parallel components of the individual magnetic field emitted by each means The magnetic field emission means emit individual magnetic fields at different frequencies so that, by signal processing, the magnetometer 12 is able to distinguish the measurement signal from the magnetic field emitter. measuring the individual magnetic field emitted by a first magnetic field emitting means of the measurement signal from the measurement of the individual magnetic field emitted by a second magnetic field emission means 10. This last case is that represented in FIGS. 11 to 14. FIG. 11 shows the variations of a value representative of an individual magnetic field Bram emitted (here its intensity) by the first circular turn 24B as a function of the time t. It is observed that the magnetic field Brad, 1 emitted has a certain periodicity. In the same way, in FIG. 12, the variations of a value representative of an individual magnetic field Brad 2 emitted (here its intensity) by the emitter charging terminal 21 as a function of time t are represented. It is also observed that the emitted magnetic field has another periodicity, the frequency fo of the individual magnetic field Brad, o emitted by the emitting charging terminal 21 being greater than the frequency f1 of the individual magnetic field Brad, 1 emitted by the first turn circular 24B. Although not shown, the individual magnetic fields Brad, 2, Brad, 3 emitted by the second circular turn 24A and by the third circular turn 24D are also periodic respectively at frequencies f2 and f3. FIG. 13 shows the intensity 1 (Brad) of the total magnetic field Brad (sum of the individual magnetic fields Brad, 0, Brad, 1, Brad, 2 and Brad, 3) emitted by all the field emission means magnetic, namely the emitter charging terminal 21 and the three circular turns 24A, 24B, 24D as a function of time t. In Figure 13, it is difficult to detect a periodicity. By using a Fourier transform (see FIG. 14), it will nonetheless be possible to isolate each of the individual magnetic fields Brad, O, Brad, Brad, Brad, emitted at frequencies f0, f1, f2 and f3 different from each other. so that the control system 25 can distinguish each of the individual magnetic fields Brad.07Brad, 1 Brad, 2, Brad.3, these generating peaks PFO, PF1, PF2, and PF3 in the frequency spectrum TF of the transform of Fourier. Thus configured, the first and second circular turns 24B, 24A thus each emit a magnetic field Brad, 1, Brad, 2 of which part of the field lines 24L is shown in FIG. 8. In step b) of the tracking method the bi-axis magnetometer 12 of the motor vehicle 10 measures the two non-parallel components Bx, O, Rv and By, O / Rv of the magnetic field emitted by the transmitting charging terminal 20. As for the first preceding embodiment described in FIG. 1 to 4, depending on the intensity 1 (Brad, o) of the individual magnetic field Brad, 0 emitted by emitter charging terminal 21 and measured by the magnetometer 12, it is possible to determine the distance between the magnetometer 12 and the reference center 20C of the secondary coil 21B. Similarly, the dual-axis magnetometer 12 of the automobile vehicle 10 also measures the two nonparallel components of the individual magnetic fields Brad, l, Brad, 2, Brad, 3 emitted by the first, second and third circular turns 24B, 24A, 24D of the tri-axis coil 24 located in the parking area 20. The distance between the magnetometer 12 and the reference center 24C of the tri-axis coil 24 is then determined. The distances previously determined are known from FIG. some precision. Thus, as shown in FIG. 18, two tori 21T and 24T are obtained in which the possible position of the magnetometer 12 of the motor vehicle 10 is determined. The motor vehicle 10 is then at the intersection of these two toroids 21T, 24T namely, either 24-21A or 24-21B (see Figure 18). By analyzing the respective signs of the non-parallel components of the individual magnetic fields measured by the magnetometer 12, the zone in which the magnetometer 12 is located is determined. In general, the position of the magnetometer 12 with respect to the emitting charging terminal is determined. 21 and the tri-axis coil 24 as being the position of the centroid of the previously determined zone. In order to determine the relative orientation of the magnetometer 12 with respect to the emitter charging terminal 21 and the tri-axis coil 24, consider, for example, the magnetic field lines 24L such as those shown in FIG. magnetic field lines 24 are the field lines of the individual magnetic field B'd, 3 emitted by the third circular turn 24D of the tri-axis coil 24. The angle em / b is introduced, which is the angle of rotation of the magnetometer 12 in the parking space reference frame Rs. In other words, the angle emib is the angle oriented between the axis 12X of the magnetometer 12 and the axis 24X of the tri-axis coil 24.

From FIG. 7, it is also possible to calculate the emib angle that the magnetometer 12 has with respect to the radius 24R joining the coil reference center 24C and the reference point of the vehicle by the formula: tan ern / b = ( BY, 3 / Rv) / (BX, 3 / Rv). As shown in FIG. 8, the possible angle θp 'of the magnetometer 12 with respect to the coil center 24C is also introduced. This possible angle apos is between apos, min and OEpos, max (see Figure 9). We then note: - Bx, 3 / Rv and BY, 3 / Rv the non-parallel components of the individual magnetic field Brad, 3 emitted by the third circular turn 24D, respectively along the axis 12X of the magnetometer 12X and along the axis 12Y magnetometer 12Y, and - Bx, 3 / Rb and BY, 3 / Rb the non-parallel components of the individual magnetic field Brad, 3 emitted by the third circular turn 24D respectively along the axis 24X and the axis 24Y of the coil 24. The components Bx, 3 / Rv and Bx, 3 / Rv of the individual magnetic field B rad, 3 emitted by the third circular turn 24D and measured by the magnetometer 12 at the vehicle reference point 10C: Bx, 3 are determined. / Rv EST = 5i n (em / b ± OEpos) * Bx, 3 / Rb + COS (Orn / b ± Ctpos) * BY, 3 / Rb By, 3 / Rv EST = COS (Orn / b ± OEpos) * BX, 3 / Rb - S ill (ern / b ± OEpos) * BY, 3 / Rb 30 The value of the angle Omit, is the value that minimizes, in least squares sense, the following equation: (BX, 3 / RV EST - BX, 3 / Rv) 2 (By, 3, RV_EST By, 3, RV) 2. Then, the analysis of the signs of the non-parallel components Bx, 3 / Rv and By, 3 / Rv makes it possible to reduce the search domain. 3 0 0 3 3 5 5 22 Knowing the terminals of ap ', in particular the lower limit OEpos.min and the upper limit apos, max, we can draw the values of nonparallel components Bx, 3 / Rv and By, 3 / Rv for the different possible points according to the angle apos. FIG. 10 shows the curve obtained for Bx, 3, R, as a function of the possible angle% os. Now, using the actual measurement of Bx, 3, R, measured by the magnetometer 12, the previous curve (see FIG. 10) is used to determine the angle apos corresponding to the relative position of the magnetometer 12 with respect to the coil. tri-axis 24. We obtain directly and simultaneously the relative position and orientation of the magnetometer 12 of the motor vehicle 10 relative to the coil 24 of the parking area 20. There is shown in Figure 15 a third embodiment of the motor vehicle 10 and the parking area 20 through which it is possible to implement the third embodiment of the tracking method according to the invention. According to this third embodiment, two relative positioning values between the motor vehicle 10 and the parking area 20 are determined in step c) of the tracking method, namely the position data and the relative orientation of the vehicle. In this preferred embodiment, the parking area 20 comprises a set of magnetic field emission means 240 which is associated with a coil reference frame Rb defined by a motor vehicle 10 relative to the parking area 20. 240C coil reference center, and the three 240X 240Y, 240Z coil oriented axes. As before, the relative position and orientation of the reel repository Rb with respect to the parking area reference Rs is assumed to be known by construction. As is well shown in FIG. 15, the set of magnetic field emission means 240 here comprises three triaxial coils 241, 242, 243 which are each driven by the control system 25. As shown in FIG. each tri-axis coil 241, 242, 243 comprises three circular turns A, B, D, which are flat and centered at the same coil reference point 240C and whose main emission axes are two to two perpendicular to each other . In addition, these main transmission axes are parallel to the 240X, 240Y, 240Z coil oriented axes.

The relative position and orientation of each of the tri-axis coils 241, 242, 243 with respect to the coil reference frame Rb of the set of magnetic field emission means 240 are known by construction. It is therefore the same with respect to the reference of parking area R ,. Advantageously, as for the second embodiment, each of the tri-axis coils 241, 242, 243 emits a magnetic field which is multiplexed in time or frequency. In this third embodiment, and as clearly shown in FIG. 15, the motor vehicle 10 comprises a set of magnetic field measurement means 120 provided on board said motor vehicle 10 to which is associated a magnetometer reference frame R, defined by the magnetometer reference center 12C, and the three non-parallel 12X, 12Y, 12Z magnetometer axes. More precisely, the set of magnetic field measurement means 120 here comprises three triaxial magnetometers 121, 122, 123 capable of measuring three components of a magnetic field in three non-parallel directions. It will be considered here that the three measurement directions of the tri-axis magnetometers 121, 122, 123 are identical and parallel to the magnetometer axes 12X, 12Y, 12Z which are themselves respectively parallel to the three vehicle axes 10X, 10Y, 10Z (see figure 16). The possibility of measuring a third non-parallel component, here the Bz / R component, in the vehicle reference system R, makes it possible to improve the accuracy of the determination of the relative position and orientation of each of the three triaxial magnetometers. 121, 122, 123 with respect to all of the magnetic field emitting means 240. Thus, the determination of the relative position and orientation of the motor vehicle 10 with respect to the parking area 20, step c) of the registration method is also improved. It can indeed be operated according to a method homologous to that described with reference to the second embodiment of the invention, and by comparing the results obtained with the different magnetometers so as to determine a finer approximation of the position and the orientation of the motor vehicle in relation to the parking area.

According to one variant, the registration method may implement N magnetometers, bi-axis or tri-axis, and M coils, bi-axes or tri-axes. We then obtain M x N measuring points. These multiple measurements make it possible to improve the overall accuracy of the calculation of position and orientation. The easiest way to use these measurement points and find the relative position of the motor vehicle relative to the parking area is to determine their center of gravity. A method of assisting the parking of the motor vehicle 10 in the parking area 20 will now be described with reference to FIGS. 15 and 17, this parking assistance method using the tracking method as it is implemented. in this third embodiment. This parking assistance method makes it possible, for example, to drive the motor vehicle 10 to the parking area 20 so that the receiving charging terminal 11 and the transmitting charging terminal 21 are positioned one above the other. other, before carrying out a charging operation of the accumulator batteries of the motor vehicle 10 by induction. It will be considered here that at the beginning of the parking assistance method, the motor vehicle 10 is located at least partially outside the parking area 20, so that the two charging terminals 11, 21 are not located one above the other. In addition, at the end of the parking assistance method, the motor vehicle 10 is positioned and oriented with respect to the parking area 20 so that the receiving load terminal center 11C is located substantially vertically. from the transmitting charging terminal center 21C.

Between the beginning and the end of the parking assistance method, the motor vehicle 10 will therefore follow a path between an initial position and an end position. In a first operation (operation i), the motor vehicle 10 of FIG. 15 is first identified with respect to the parking area 20 by the marking method previously described. After this first operation (i), the initial relative position and orientation of the motor vehicle 10 with respect to the parking area 20 are precisely determined. The trajectory that the motor vehicle 10 should follow is then determined to reach the parking area 20. This trajectory, theoretical and ideal, can be characterized by the data of a plurality of vectors, said state vectors Ek of the motor vehicle 10 at the instant tk which can be written in the form: kk = (Xv / s, k, Yv / s, k, Ovis, k), where Xv / s, k, Yv / s, k are respectively the coordinates, along the longitudinal axis 20X and the transverse axis 20Y of the parking area 20, of the vehicle reference center 10C and ev / s, k is the orientation of the motor vehicle 10 relative to the parking area In other words, if the motor vehicle 10 follows the determined trajectory to reach the parking area 20, then its vehicle reference center 10C, at each instant tk, is located at the point of coordinates xvis, k, Yv / s, k in the parking space reference R, and the angle made by the vehicle X axis 10X with the X parking axis 20X is equal to eV / 5k. A "bicycle" model is then introduced for the motor vehicle 10, as shown in FIG. 17.

In this model, it is considered that the motor vehicle 10 has only two equivalent fictitious wheels 10F spaced by the wheelbase 10E of the motor vehicle 10, of value B and that it moves so that its two fictitious wheels 10F follow a movement rolling without slipping off the ground. Note that this assumption is valid at low speed, which is the case during a parking maneuver. This classic "bicycle" model makes it possible to reduce the motor vehicle movement equations 10 and to linearize said equations so that a Kalman filter can be used. We are here at a previous moment tk-1 for which we assume that the state vector kk-i = (Xv / 5, k-1, Yv / s, k-1, ev / 5, k-1) is known. - We also note Vk_i and tk-1, respectively the vehicle speed 10V and the equivalent wheel angle 10D (see Figure 17). By coupling the determination of the relative position (xv / s, k-tYv / s, ki) and orientation (ev / sk-i) of the motor vehicle 10 with respect to the parking area 20 with the acquisition by proprioceptive sensors of the motor vehicle 10 giving the vehicle speed Vk_i and the flywheel angle (1) k-1, it is indeed possible to establish a Kalman filter.

Indeed, from the proprioceptive data (Vk_i, (1) k-1) and the state vector kk_i at time tk_i, it is possible to predict, at the instant following tk, an estimated state vector Ekik-i = (Xv / s, k1k-1, Yv / s, kik-1,0v / s, kik-1) by the following relations: xv / s, kik-i = Xv / s, k-1 [ Vk-1 * COS (O k-1 ± 4k-1) * (tk tk-1)] Yv / s, kik-1 = Yv / s, k-1 [Vk-1 * Sin (Ov / s, k -1 ± 4) k-1) * (tk tk-1) 1 () screws, kik-1 = () screws, k-1 [Vk-1 * sin () * (tk-tk_i)] / B In a second so-called updating step, the determination is made, at time tk, of the relative position (xvis, k, Yvis, k) and orientation (ews, k) of the motor vehicle 10 with respect to the parking area 20 for calculating the state kkik at time tk by the formula: kkik = kk1k-1 Kk * (kktk1k-1).

In a known manner, the term Kk is the optimal Kalman gain (or covariance matrix of the error) which arbitrates between the estimated state kkik_i and the measured state kk at the instant tk. This gain notably takes into account the modeling of the sensor error. In other words, the gain of Kalman Kk makes it possible to say whether one prefers to privilege the determination of the state vector kk at time tk by the calculation (Kk = 0) (see equations above) or by the measure (Kk = 1) magnetometers 121, 122, 123. Thus, in a third step of the parking assistance method, the steering wheel angle 10D required is determined so that the motor vehicle 10 follows said path. In other words, the flywheel angle ck is chosen so that the state vector kkik calculated at each instant tk is as close as possible to the state vector kk determined along the trajectory of the motor vehicle 10 Advantageously, during this third operation (iii), the vehicle speed Vk is also determined so that the motor vehicle 10 follows said trajectory. In a fourth step (iv) of the parking assistance method, the motor vehicle 10 is automatically driven by imposing on the latter the desired steering wheel angle 10D so as to be as close to the vehicle as possible. ideal trajectory. Alternatively, an indication could for example be given to the driver of the motor vehicle relative to the steering wheel angle to be used to follow the path. Advantageously, during the fourth operation (iv), the automatic control is also performed according to the vehicle speed 10V. In another variant, it may be preferred, for example, to also give an indication of the vehicle speed to the driver of the motor vehicle.

Claims (10)

REVENDICATIONS1. Method for marking a motor vehicle (10) with respect to a parking area (20) for a motor vehicle, characterized in that it comprises the steps of: a) emitting a magnetic field (B'd) by means of at least one first magnetic field emission means (21, 24B, 241) respectively provided in the parking area (20) or on board the motor vehicle (10), b) measuring the values of at least two components (Bx / Rv, Bz / Rv) non-parallel of said magnetic field (B'd) emitted by at least one magnetic field measuring means (12, 121) respectively provided on board said motor vehicle (10) or in said area parking (20), and c) locating said motor vehicle (10) relative to said parking area (20) by means of calculation adapted to determine at least one relative positioning value (Dy ',; xv, s , yv, s, ev, $) between said motor vehicle (10) and said parking area (20) from, on the one hand, said measured values of the components (Bx / Rv, Bz / Rv) of the magnetic field (B-ad) and, on the other hand, a predetermined mapping which maps to each set of component values (Bx / Rv, Bz / Rv) of said magnetic field (B'd), a relative positioning value between said motor vehicle (10) and said parking area (20). 2. The method according to claim 1, wherein the predetermined map used in step c) comprises a database register with at least two inputs formed by said at least two components (Bx / Rv, Bz / Rv). magnetic field (Brad), and an output formed by said relative positioning value (Dvis; xv / s, Yv / s, ev / s). 3. A method of identification according to claim 1, wherein the predetermined mapping used in step c) comprises a mathematical function or an algorithm that associates, with each set of values of the components (13,, Rv, BÉRv) of said magnetic field. (Bi-ad), said relative positioning value (Dv / s; xv / s, Yvis, ev / s). 4. A method of marking according to any one of the preceding claims, wherein: in step a), said magnetic field (B'd) is emitted, on the one hand, along a first main transmission axis ( 24Z) by means of said first magnetic field emission means (24B), and secondly, according to a second main transmission axis (24X) by means of a second magnetic field emission means (24A), and in step c), two relative positioning values are determined, namely the relative position and orientation of the motor vehicle (10) relative to the parking area (20). The method of claim 4, wherein said first magnetic field transmitting means (24B) and said second magnetic field transmitting means (24A) emit a multiplexed magnetic field (Brad, l, Brad, 2) in time or frequency. 6. A parking assistance method for a motor vehicle (10) in a parking area (20) comprising the following successive operations: (i) locating said motor vehicle (10) with respect to said parking area (20); ) by means of a registration method according to one of claims 4 or 5; (ii) determining the path to be followed by the motor vehicle (10) to reach the parking area (20); (iii) determining a steering wheel angle setpoint (10D) for the motor vehicle (10) to follow said path; (iv) automatic steering of the motor vehicle (10) according to said flywheel angle setpoint (10D) or indication to a driver of said automobile vehicle (10) of said flywheel angle setpoint (10D). 7. The parking assistance method according to claim 6, wherein: during operation (iii), a vehicle speed setpoint (10V) is also determined so that said motor vehicle (10) follows said trajectory, and - during operation (iv), the automatic control is also performed according to said vehicle speed instruction (10V) or an indication of said vehicle speed instruction (10V) is given to the driver of the motor vehicle (10). 8. Motor vehicle (10) comprising at least one magnetic field measuring means (12, 121) adapted to implement step b) of the marking method according to one of claims 1 to 5 and calculating means adapted to implement step c) of said tracking method. The motor vehicle (10) of claim 8, wherein said magnetic field measuring means (12) is a bi-axis magnetometer. 10. Parking area comprising at least one magnetic field measuring means adapted to implement step b) of a registration method according to one of claims 1 to 5 and calculation means adapted to implement step c) of said registration method.