Vehicle assembly including a radar sensor and a layer arrangement

Abstract

The invention relates to a vehicle-to-vehicle assembly, said vehicle assembly being configured to detect a target object in the environment of said vehicle, comprising: - a radar sensor comprising at least one transmitting antenna configured to emit radar waves and at least two receiving antennas configured to receive returning radar waves which are reflected from said target object, - a layer arrangement comprising: (i) a primary layer disposed opposite said radar sensor and comprising an output surface (S1) for the returning radar waves, and (ii) at least one secondary layer comprising an input surface for the returning radar waves, and (iii) at least one predetermined non-planar shape present in the primary layer or in at least one secondary layer,- characterized in that said primary layer output surface is calculated as a function of said at least one predetermined shape such that return waves reach said at least two receiving antennas with the same angle of incidence regardless of the position of the target object.

Description

Title of the invention: Vehicle assembly comprising a radar sensor and a layer arrangement

[0001] The present invention relates to a vehicle assembly. It finds a particular but non-limiting application in the detection of an object located in the environment of a motor vehicle.

[0002] A vehicle assembly configured to detect an object in the environment of a vehicle, comprises, in a manner known to those skilled in the art: - a radar sensor comprising at least one transmitting antenna configured to transmit radar waves and at least two receiving antennas configured to receive return radar waves which are reflected on an object, said radar sensor being configured to measure a phase difference between the return radar waves arriving at each receiving antenna, - an arrangement of layers comprising at least one layer arranged opposite said radar sensor.

[0003] The arrangement of layers forms an illuminated logo or forms layers of a projector including the exit glass, or layers of a rear light including the exit glass.

[0004] A disadvantage of this state of the art is that if the exit glass of the headlight or the rear light of the vehicle has a significant curvature, this creates calculation errors on the angular position of the object. The same is true if the illuminated logo has a relief. Indeed, for certain targets, the return radar waves may not reach the two receiving antennas for certain angles of incidence. Consequently, either the target is not detected, or several targets may be confused.

[0005] In this context, the present invention aims to propose a vehicle assembly which makes it possible to solve the mentioned drawback.

[0006] To this end, the invention proposes a vehicle assembly for a vehicle, said vehicle assembly being configured to detect a target object in the environment of said vehicle and comprising: - a radar sensor comprising at least one transmitting antenna configured to transmit radar waves and at least two receiving antennas configured to receive return radar waves which are reflected on said target object, - an arrangement of layers comprising: (i) a primary layer disposed opposite said radar sensor and comprising an exit surface for return radar waves, and (ii) at least one secondary layer comprising an entry surface for return radar waves, and (iii) at least one predetermined non-planar shape present in the primary layer or in at least one secondary layer, - characterized in that said output surface of the primary layer is calculated as a function of said at least one predetermined shape so that return waves reach said at least two receiving antennas with the same angle of incidence whatever the position of the target object.

[0007] According to non-limiting embodiments, said vehicle assembly may further comprise one or more additional characteristics taken alone or in all technically possible combinations, among the following.

[0008] According to a non-limiting embodiment, said primary layer and said at least one secondary layer are combined into a single layer.

[0009] According to a non-limiting embodiment, said primary layer and said at least one secondary layer are distinct and have a different refractive index.

[0010] According to a non-limiting embodiment, said output surface of the primary layer is calculated according to the equation A(u, 0) = A(u, L) for any angle u located inside the field of vision of said radar sensor and L the distance between said at least two receiving antennas.

[0011] According to a non-limiting embodiment, the shape of said output surface is determined by a finite difference method.

[0012] According to a non-limiting embodiment, said phase difference measured by said radar sensor is corrected by a correction function of a processing unit of the vehicle.

[0013] According to a non-limiting embodiment, the arrangement of layers forms a logo or layers of a projector or a rear light.

[0014] According to a non-limiting embodiment, the predetermined shape is a relief formed of flat or conical surfaces.

[0015] According to a non-limiting embodiment, the output surface of the primary layer is partly flat and comprises a part set back or raised relative to said flat part configured to compensate for an offset induced by said predetermined shape to said phase difference which exists between the return radar waves arriving at each receiving antenna.

[0016] According to a non-limiting embodiment, the primary layer has a primary refractive index, and said arrangement of layers comprises two secondary layers each with a secondary refractive index and a tertiary refractive index respectively, one of which comprises the entry surface of the returning radar waves and having the tertiary refractive index, said entry surface being in part parallel to said exit surface and the tertiary refractive index being the same as the primary refractive index.

[0017] According to a non-limiting embodiment, the predetermined shape is curved and is a smooth surface.

[0018] There is further provided an arrangement of layers arranged opposite a radar sensor, said radar sensor comprising at least one transmitting antenna configured to transmit radar waves and at least two receiving antennas configured to receive return radar waves which are reflected on a target object, said arrangement of layers comprising: - (i) a primary layer arranged opposite said radar sensor and comprising an exit surface for return radar waves, - (ii) at least one secondary layer comprising an entry surface for return radar waves, - at least one predetermined non-planar shape present in the primary layer or in at least one secondary layer, - characterized in that said output surface of the primary layer is calculated as a function of said at least one predetermined shape of said input surface so that return waves reach said at least two receiving antennas with the same angle of incidence whatever the position of the target object.

[0019] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures:

[0020] [Fig-1] is a schematic view of a vehicle assembly, said assembly of vehicle comprising a radar sensor and an arrangement of layers, according to a non-limiting embodiment of the invention,

[0021] [Fig.2] is a schematic view of two return radar waves corresponding to a radar wave emitted by the radar sensor of the vehicle assembly of [Fig.l] which arrive at the layer arrangement of the vehicle assembly of [Fig.l], said layer arrangement comprising a first layer and a second layer, the first layer and the second layer being distinct, according to a first non-limiting variant embodiment of a first non-limiting embodiment,

[0022] [Fig.3] is a schematic view of two return radar waves corresponding to a radar wave emitted by the radar sensor of the vehicle assembly of [Fig.l] arriving at the layer arrangement of the vehicle assembly of [Fig.l], said layer arrangement comprising a first layer and a second layer, the first layer and the second layer being distinct, according to a second non-limiting variant embodiment of a first non-limiting embodiment,

[0023] [Fig.4] is a schematic view of two return radar waves corresponding to a radar wave emitted by the radar sensor of the vehicle assembly of [Fig.l] which arrive at the layer arrangement of the vehicle assembly of [Fig.l], said layer arrangement comprising a first layer, a second layer and a third layer, the first layer, the second layer and the third layer being distinct, according to a second non-limiting embodiment,

[0024] [Fig.5] is a schematic view of two return radar waves corresponding to a radar wave emitted by the radar sensor of the vehicle assembly of [Fig.l] which arrive at the arrangement of layers of the vehicle assembly of [Fig.l], said arrangement of layers comprising a first layer, a second layer, the first layer and the second layer being merged, according to a third non-limiting embodiment,

[0025] [Fig.6] is a figure allowing to explain a calculation of an exit surface of the layer arrangement of the vehicle assembly of [Fig.l] as a function of an entry surface of said layer arrangement, for a layer arrangement comprising a first layer, a second layer, the first layer and the second layer being merged, according to a non-limiting embodiment.

[0026] Identical elements, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.

[0027] The vehicle assembly 1 of a vehicle 2 according to the invention is described with reference to Figures 1 to 6. In a non-limiting embodiment, the vehicle 2 is a motor vehicle. By motor vehicle is meant any type of motorized vehicle. This embodiment is taken as a non-limiting example in the remainder of the description. In the remainder of the description, the vehicle 2 is thus otherwise called motor vehicle 2. The motor vehicle 2 comprises a processing unit 21. In a non-limiting embodiment, this processing unit 21 is integrated into the radar sensor 10 described below. In the non-limiting example, it is outside the radar sensor 10 and the vehicle assembly 1.

[0028] The vehicle assembly 1 is configured to detect an object 3, otherwise called target 3, in the environment of the motor vehicle 2. As illustrated in [Fig.l], the vehicle assembly 1, otherwise called vehicle arrangement 1, comprises: - a radar sensor 10 configured to transmit / receive radar waves RI, R2 respectively, - a layer arrangement 12.

[0029] These elements are described below.

[0030] The radar sensor 10 is described below. As illustrated in [Fig.l], the radar sensor 10 is arranged opposite the layer arrangement 12. In a non-limiting embodiment, the radar sensor 10 is a millimeter wave radar sensor (between 24GHz and 300GHz) or hyperfrequency radar sensor (between 300MHz and 81GHz) or microwave radar sensor (between 1GHz and 300GHz). In a non-limiting embodiment, the sensor radar 10 operates at a radar frequency between 76GHz and 81GHz. In a non-limiting embodiment, the radar waves RI are emitted over a frequency band between 100MHz and 5GHz. Thus, in a non-limiting example, if the radar sensor 10 operates at a radar frequency of 77GHz, i.e. a wavelength X of 3.95mm, with a frequency band of 1GHz, the radar sensor 10 will operate over a frequency band of 76.5GHZ to 77.5GHz. The radar waves RI will thus be emitted over the frequency range 76.5GHZ to 77.5GHz, i.e. a wavelength range X of 3.87mm to 3.92mm. Thus, in another non-limiting example, if the radar sensor 10 operates at a radar frequency of 78.5 GHz with a frequency band of 5 GHz, the radar sensor 10 will operate on a frequency band of 76 GHz to 81 GHz. The radar waves RI will thus be emitted on the frequency range 76 GHz to 81 GHz, i.e. a wavelength range X of 3.701 mm to 3.945 mm.

[0031] As illustrated in [Fig.l], the radar sensor 10 has a field of view FOV. The emitted radar waves RI arrive with an angle of incidence 0' on the layer arrangement 12. In a non-limiting embodiment, the angle of incidence 0' is between 0° and +-30°. The field of view FOV thus varies between -30° and +30°. The center of the field of view FOV is an angle of 0° relative to the longitudinal axis of the vehicle, otherwise called the vehicle axis Ax. In another non-limiting embodiment, the field of view FOV thus varies between -90° and +45°. The center of the field of view FOV is an angle of -45° relative to the vehicle axis Ax and the angle of incidence 0' of the radar waves RI on the layer arrangement 12 remains close to 0° (the vehicle assembly 1 then being positioned at approximately 45° from the vehicle axis Ax).

[0032] In a non-limiting embodiment, the radar sensor 10 is arranged at the level of a headlight, a rear light or an illuminated or non-illuminated logo of the motor vehicle 2.

[0033] The radar sensor 10 is configured to scan the external environment of the motor vehicle 2, thanks to the emission of radar waves RL. As illustrated in [Fig.l], the radar sensor 10 thus comprises: - at least one transmitting antenna 100 configured to transmit radar waves RI, otherwise called primary radar waves RI, or transmitted radar waves RI, - at least two receiving antennas 101 configured to receive radar waves R2, otherwise called secondary radar waves R2 or return radar waves R2.

[0034] The radar sensor 10 further comprises at least one transmitter 103 configured to generate the primary radar waves RI and at least one receiver 104 configured to process the secondary radar waves R2 received in return. In a non-limiting embodiment, a single electronic component can be used for both the transmitting and receiving functions. There will thus be one or more transmitters / receivers called " transceiver » in English. Said transmitter 103 generates primary radar waves RI which are subsequently emitted by the transmitting antenna 100, which when they encounter an object 3 (here a pedestrian in the non-limiting example illustrated) in the external environment of the motor vehicle 2 are reflected on said object 3. The radar waves thus reflected are waves transmitted in return to the radar sensor 10. These are the secondary radar waves R2 received by the receiving antennas 101. These are radar waves retransmitted in the direction of the radar sensor 10. The radar sensor 10 is configured to measure the phase difference A <p entre les ondes radars de retour r2 arrivant sur chaque antenne réceptrice 101. on rappelle que la propagation des est régie par loi snell-descartes. dans un mode réalisation non limitatif, primaires ri et secondaires sont radio fréquence. le capteur radar 10 comprend une pluralité d’émetteurs 103 récepteurs 104.

[0035] l’antenne émettrice 100, autrement appelée configurée pour émettre générées l’émetteur 103. les antennes réceptrices 101, appelées configurées recevoir communiquer au récepteur 104 qui traite suite. il existe déphasage aq>, otherwise called phase difference Aq>, between the secondary radar waves R2 received by the receiving antennas 101 which makes it possible to deduce therefrom the angular position Pos of the object 3 relative to the motor vehicle 2, object 3 which is located in the external environment of the motor vehicle 2. The radar sensor 10 is thus configured to measure this phase difference Aq> between the secondary radar waves R2 arriving at each receiving antenna 101. In non-limiting embodiments, the antennas 100, 101 are patch antennas or slot antennas.

[0036] In a non-limiting embodiment, the antennas 100, 101, the transmitter 103 and the receiver 104 are arranged on a printed circuit board 105. In a non-limiting embodiment, the printed circuit board is a rigid printed circuit board otherwise called PCBA (“Printed Circuit Board Assembly” in English) or a flexible printed circuit board, otherwise called “Flexboard” in English.

[0037] The radar sensor 10 further comprises an electronic control unit 106 configured to control the transmitter 103 and the receiver 104. Since a radar sensor is known to those skilled in the art, it is not described in further detail here.

[0038] The layer arrangement 12 is described below. As illustrated in Figures 2 to 5, it comprises: - a primary layer 121, and - at least one secondary layer 122.

[0039] In non-limiting embodiments, the arrangement of layers 12 forms an illuminated or non-illuminated logo, or forms layers of a headlight or a rear light of the motor vehicle 2, such as the exit window, or the exit window and a decorative part called a mask.

[0040] The primary layer 121 is arranged opposite the radar sensor 10 and comprises an exit surface SI for the return radar waves R2. In a non-limiting embodiment, the primary layer 121 is made of plastic. The exit surface SI forms a diopter between the material of the primary layer 121 (which comprises a refractive index ni) and the air (of refractive index nO).

[0041] Said secondary layer 122 comprises an entry surface S2 for the return radar waves R2. The return radar waves R2 arrive at the entry surface S2 with an angle of incidence 0. The angle of incidence 0 corresponds to a refracted angle [3. The angle of incidence 0 varies depending on where the return radar wave R2 meets the entry surface S2. Thus, in the figures, a first return radar wave R2 is shown with an angle of incidence 00 and a second return radar wave R2 is shown with an angle of incidence 0. The entry surface S2 forms a diopter between the material of the secondary layer 122 (which comprises a refractive index n2) and the air (of refractive index nO).

[0042] In a first non-limiting embodiment of FIGS. 2 to 4, the primary layer 121 and said at least one secondary layer 122 are distinct and have a respective refractive index n1, n2 that is different.

[0043] In a second non-limiting embodiment illustrated in [Fig. 5], the primary layer 121 and said at least one secondary layer 122 are merged into a single layer and thus form only a single layer.

[0044] It will be noted that the secondary layer 122 comprises a predetermined shape 124. This is a 3D shape. This predetermined shape 124 is imposed by automobile manufacturers, often for stylistic reasons, and is therefore linked to the motor vehicle 2.

[0045] In a first non-limiting embodiment, the predetermined shape 124 is a relief formed by flat or conical surfaces (illustrated in Figures 3 or 4) of a logo. The logo is thus in relief. The logo is illuminated or not. In the non-limiting example of Figures 3 and 4, the relief 124 is a trapezoidal shape. In another non-limiting example not illustrated, the relief 124 may be a pyramidal shape. In a first non-limiting variant embodiment illustrated in [Fig. 3], said predetermined shape 124 is part of the input surface S2 of the secondary radar waves R2. In a second non-limiting variant embodiment illustrated in [Fig. 4], said predetermined shape 124 is not part of the input surface S2 of the secondary radar waves R2.

[0046] In a second non-limiting embodiment, the predetermined shape 124 is a smooth surface (illustrated in FIGS. 2 or 5) of a rear light or a headlight. By smooth, it is meant that it does not have an angle, that it is without relief, namely that it has no roughness.

[0047] Three non-limiting embodiments of the arrangement of layers 12 are described below with reference respectively to Figures 2, 3, to [Fig.4] and finally to [Fig.5].

[0048] In a first non-limiting embodiment illustrated in Figures 2 and 3, the arrangement of layers 12 comprises two layers including: - a primary layer 121, and - a secondary layer 122, the primary layer 121 and the secondary layer 122 being distinct.

[0049] According to this first non-limiting embodiment, the primary layer 121 and the secondary layer 122 are adjacent and delimited by a junction surface 126.

[0050] In a first non-limiting variant embodiment illustrated in [Fig. 2], the secondary layer 122 has a predetermined shape 124 of smooth surface. In a non-limiting example, the smooth surface is curved. In this case the angle of incidence 00 is generally different from the angle of incidence 0 for two return radar waves R2 which arrive at the input surface S2 at different locations. The secondary layer 122 thus comprises a radius of curvature R. In this case, in a non-limiting embodiment, the arrangement of layers 12 is a rear light or a headlight. The primary layer 121 is a substrate which makes it possible to support the secondary layer 122, and the secondary layer 122 is an exit glass of the rear light or the headlight. The predetermined shape 124 is part of the input surface S2 of the secondary radar waves R2.

[0051] In a second non-limiting variant embodiment illustrated in [Fig. 3], the secondary layer 122 has a predetermined shape 124 which is a relief. In a non-limiting example, the relief 124 is trapezoidal in shape. In this case, in a non-limiting embodiment, the layer arrangement 12 is a logo. According to the second non-limiting variant embodiment, the junction surface 126 follows the shape of the input surface S2. It therefore extends parallel to the input surface S2. The predetermined shape 124 is part of the input surface S2 of the secondary radar waves R2. In this case, the angle of incidence 00 is generally different from the angle of incidence 0 for two return radar waves R2 which arrive at the input surface S2 at different locations.

[0052] In a second non-limiting embodiment illustrated in [Fig.4], the arrangement of layers 12 comprises: - a primary layer 121, - a first secondary layer 122a, - a second secondary layer 122b, the primary layer 121, the first secondary layer 122a and the second secondary layer 122b being distinct.

[0053] In this case, in a non-limiting example, the layer arrangement 12 is a logo. In this case, the primary layer 121 is an optical layer which also serves as a support for the first secondary layer 122a, the first secondary layer 122a is a film, and the second secondary layer 122b is an output glass. The input surface S2 of the return radar waves R2 is part of the second secondary layer 122b.

[0054] The first secondary layer 122a is disposed between the primary layer 121 and the second secondary layer 122b. The primary layer 121 and the first secondary layer 122a are adjacent and delimited by a joining surface 126. The first secondary layer 122b and the second secondary layer 122b are adjacent and delimited by a joining surface 127.

[0055] The first secondary layer 122a comprises a predetermined shape 124a. The second secondary layer 122a comprises a predetermined shape 124b identical to that 124a of the first secondary layer 124a. The predetermined shape 124a extends along the joining surface 126. The predetermined shape 124b extends along the joining surface 127. In a non-limiting embodiment, the predetermined shapes 124a and 124b are reliefs. In a non-limiting example, these reliefs 124a, 124b have a trapezoidal shape. The joining surface 127 follows the joining surface 126. It therefore extends parallel to the joining surface 126, and the reliefs 124a, 124b are arranged directly opposite one another. It will be noted that none of the predetermined shapes 124a, 124b is part of the input surface S2.

[0056] The primary layer 121 has a primary refractive index n1. The first secondary layer 122a has a secondary refractive index n2. The second secondary layer 122b has a tertiary refractive index n3. The input surface S2 is partly parallel to the output surface S1, and the tertiary refractive index n3 is the same as the primary refractive index n1. This allows the returning radar waves R2 to exit the output surface S1 with the same angle of incidence a=a0, a as that 00, 0 respectively when they arrive at the input surface S2, which allows for a partly flat output surface S1. This subsequently allows for phase shift compensation described later.

[0057] As illustrated in [Fig.4], in a non-limiting embodiment, the input surface S2 is planar. In this case the angle of incidence 00 is equal to the angle of incidence 0 for two return radar waves R2 which arrive on the input surface S2 at different locations.

[0058] In a third non-limiting embodiment illustrated in [Fig.5], the arrangement of layers 12 comprises: - a primary layer 121, - a secondary layer 122, the primary layer 121 and the secondary layer 122 being merged.

[0059] The input surface S2 is not parallel to the output surface SI.

[0060] In a non-limiting variant embodiment illustrated in [Fig. 5] the predetermined shape 124 is a smooth surface. In a non-limiting example, the smooth surface is curved and has a radius of curvature R. In this case, in a non-limiting embodiment, the arrangement of layers 12 which therefore comprises only one layer is an outlet glass of a rear light or a headlight. In another non-limiting variant embodiment not illustrated the predetermined shape 124 is a relief. In this case, the same figure as [Fig. 3] is obtained without junction surface 126 and n2=n1.

[0061] The output surface SI of the primary layer 121 is calculated as a function of the input surface S2 so that the return waves R2 reach the two receiving antennas 101 with the same angle of incidence a whatever the position of the target object 3.

[0062] In order to determine the shape of the output surface SI, the following calculations are carried out. It will be noted that the calculations are made in a horizontal plane comprising the receiving antennas 101. Indeed, the radar sensor 10 considered determines the azimuth of the target objects 3 and not their elevation and therefore has a field of view FOV of low elevation. The input surface S2, the output surface SI and the predetermined shape 124 are assumed to have zero curvatures and must in practice have low curvatures in vertical sections perpendicular to the AZ-AY plane of [Fig.6]. In other words, they are assumed to be in their useful part surfaces which are cylindrical with an axis perpendicular to the AZ-AY plane and of any cross section.

[0063] We pose: - g: the shape of the output surface SI that we are looking for, with g a function such that all the points of the output surface SI have coordinates (y, z=g(y)) in the Ay-Az frame. - f: the predetermined form 124, with f a function such that all the points of the predetermined form 124 have coordinates (y, z=f(y)) in the Ay-Az frame. - d real number which is any distance.

[0064] We set yl, y 2 as homogeneous functions at coordinates along the horizontal axis AY perpendicular to the vehicle axis Ax, and A as the solutions of the following equations.

[0065] Let yl(u, d) be the solution to the equation '

[0066] [Math.l] g(y)tan(w) -y+d = 0

[0067] yl is thus the solution to an equation which involves g.

[0068] we set w as an angle:

[0069] [Math.2] w(u. d) = arcsin^sin^w + arctan^(y (“, d)) ) ) ) -arctan^(y (w, d) j )

[0070] Let then y2(u, d) be the solution to the equation: [Math.3] y (“4) f(y)tan(w(«, d) ) -y-—^tan(w(w, d) ) +yi(w, d) =0

[0071] we pose:

[0072] [Math.4] A(w, d) = arcsin(n.sin^w(w, d) +arctan^ (y?(«, d) ) ) ) ) -arctan^ (y?(n, d) ) )

[0073] Since f (which describes the predetermined form 124) is fixed, g is the solution, when it exists, of A(u, 0) = A(u, L) (differential equation) for all angles u lying inside the field of view FOV of the radar sensor 10.

[0074] To solve the equation A(u, 0)= A(u, L), in non-limiting embodiments, a finite difference method or the finite element method, or a step-by-step method, is used. A practical method for solving the equation of the finite difference method type is described below.

[0075] In practice we calculate 0^= A(a0, 0) and N= A(a, L) as follows.

[0076] To explain the calculations, we refer to [Fig.6] which represents the antennas receiving antennas 101 of the radar sensor 10 and the layer arrangement 12, in which the primary layer 121 and the secondary layer 122 are merged and therefore have a refractive index nl=n2. For the calculations, the receiving antennas 101 are considered to be point-like. They are separated from each other by a distance L. A Y, Z reference frame is used where Z is parallel to the line of sight of the radar sensor 10 with the AY axis perpendicular to the AZ axis. One of the receiving antennas 101 is on an abscissa y = 0, the other being at an abscissa y = -L. [Fig.6] illustrates a return radar wave R21, otherwise called primary return radar wave R21, which arrives at the receiving antenna 101 with abscissa y = -L, noted 101(a0, -L) and another return radar wave R22, otherwise called secondary return radar wave R22, which arrives at the other receiving antenna 101 with abscissa y = 0, noted 101(a, 0).

[0077] For the various calculations below, the following notations are used: - g: the shape of the output surface SI that we are looking for, - f: the predetermined form 124, - ON: the angle of a return radar wave R21 arriving at the input surface S2 relative to a vertical parallel to the Z axis, the orientation of ON being given by the arrow in the figure indicating said angle, - N: the angle of the other return radar wave R22 arriving at the input surface S2 relative to a vertical parallel to the Z axis, the orientation of N being given by the arrow in the figure indicating said angle. This angle N is called the angle of incidence of the target object 3, or target angle, - aO: the angle of the primary return radar wave R21 which arrives at the receiving antenna 101(a0, -L) relative to a vertical parallel to the Z axis, aO being oriented as ON and N, - a: the angle of the secondary return radar wave R22 which arrives at the receiving antenna 101,(a, 0) relative to a vertical parallel to the Z axis, with a0=a, a being oriented as ON and N, - aO: the angle of the primary return radar wave R21 which arrives on the output surface SI relative to a vertical parallel to the Z axis, aO being oriented as ON and N. The return radar wave R21 is that which arrives on a first receiving antenna 101, - a: the angle of the secondary return radar wave R22 on the output surface SI relative to a vertical parallel to the Z axis, a being oriented as ON and N. The other return radar wave R22 is the one that arrives at the second receiving antenna 101, - [110: the path, otherwise called optical path, traveled by the primary return radar wave R21 between the output surface SI and the receiving antenna 101 (aO, -L), in other words in the figure it is the distance along the primary return radar wave R21 between the output surface SI and the receiving antenna 101 (aO, -L). This path is traveled in the air, - [120: the path, otherwise called optical path, traveled by the primary return radar wave R21 between the input surface S2 and the output surface SI, in other words in the figure it is the distance along the primary return radar wave R21 between the input surface S2 and the output surface SL This path is traveled in the primary layer 121 (merged with the secondary layer 122), - [it: the path, otherwise called optical path, traveled by the secondary return radar wave R22 between the output surface SI and the receiving antenna 101 (a, 0), in other words in the figure it is the distance along the secondary return radar wave R22 between the output surface SI and the receiving antenna 101 (a, 0). This path is traveled in the air, - [12: the path, otherwise called optical path, traveled by the secondary return radar wave R22 between the input surface S2 and the output surface SI, in other words in the figure it is the distance along the secondary return radar wave R22 between the input surface S2 and the output surface SI. This path is traveled in the primary layer 121 (merged with the secondary layer 122), - p3: the path taken by the secondary return radar wave R22 between the perpendicular common to the two return radar waves R21, R22 and starting from the first point of contact with the entry surface S2. This path is taken in the air. In other words, p.3 is the path difference of the return radar waves R21 and R22 to return to an identical phase reference for the two return radar waves R21 and R22, namely the phase difference Aq>= 0.

[0078] Let z=f(y) be an equation of the input surface S2 and z=g(y) an equation of the output surface SI in the reference frame AY, AZ centered on the receiving antenna 101 of greatest y (here y=0) of a pair of receiving antennas 101. f is known because it is the predetermined form 124 conventionally imposed by the manufacturers as indicated previously. We are looking for g. If the output surface SI is well formed so that the return radar waves R21, R22 arrive at the receiving antennas 101, then we have ON N = for all y of the support of g, for the same angle a. It will be noted that the support of g is the set of abscissas y for which the function g is defined.

[0079] This means that the rays R21 and R22 come from the same target object 3 and form the same plane wave. Otherwise, if the output surface SI is not well arranged, then N ON. This means that the return radar waves R21 and R22 do not come from the same target object 3. And the radar sensor 10 can then be misled and detect a false target object 3.

[0080] We denote by f' and g' the derivatives of the functions f and g. We have:

[0081] [Math.5] a = arctan(^ )

[0082] And

[0083] [Math.6] z, z, . (sin(a+arctan(g'(y))) j a = - arctan ( g ( y ) ) + arcsm (------y—— /

[0084] We have q2 solution of:

[0085] [Math.7] g(y) +p2cos(a) =f(y+p2sin(a))

[0086] So:

[0087] [Math. 8] K = - arctan (f' (y + g2sin (a))) + arcsin (n2sin (a+ arctan (f' (y + g2sin (a)))))

[0088] This formula is referenced formula [1]. In addition, we have qlO solutions of:

[0089] [Math.9] plOcos(a) = g((il0sin(a) -L)

[0090] With L the gap (or distance) between the two receiving antennas 110. We have:

[0091] [Math. 10] n (sin(a+mvtan(g(plOsin(a>L))) \ a0 = - arctan (g (g 1 Ostn (a) - L)) + arcsin (------------------ /

[0092] In addition, we have a solution of:

[0093] [Math. 11] g(plOsin(a) -L) +p20cos(a0) = f(pl0sin(a) -L + p20sin(a0) )

[0094] So we get:

[0095] [Math. 12] KO = - arctan(f ( plOsin(a ) -L + p20sin(a0) ) )

[0096] + arcsin (n2sin ('0 + arctan (f (p 1 Osin (a) - L + p20sin ('0)))))

[0097] We see that if g is known, we can verify the condition N = ON for all y.

[0098] Conversely, this condition N = ON makes it possible to determine g.

[0099] In a non-limiting embodiment, g is determined, approximately, by a finite difference type method. A non-limiting example of a finite difference type method is described below.

[0100] We choose a finite subset of abscissas yl to ym (i.e. yi, with i = 1 to m, m integer) of the support of g and we look for the values ​​gi=g(yi). This allows us to do a sampling, in other words a discretization. For this we must choose an approximation g'i of the derivative of g in yi. In a non-limiting embodiment, the approximation g'i is equal to:

[0101] [Math. 13]

[0102] g' allows to find the direction of the normal to the surface of SI for a given abscissa y, direction which is needed to calculate the propagation of the return radar waves R2 through the arrangement of layers 12.

[0103] Thus, using this formula, we choose the values ​​of gi until we approach N = ON. We thus solve for all the points gi chosen the equation A(u, 0)=A(u, L) described previously. In other words, we minimize N - ON for all the points yi. g will thus be known for all the values ​​of gi thus chosen.

[0104] Then with the chosen values ​​gi, which correspond to points gi on the support of g, we interpolate the function g between the points gi and g'i on the abscissas yi.

[0105] In a non-limiting variant embodiment, g and g' may be approximated by piecewise linear functions passing through the points (yi, gi) and the points (yi, g'i). In another non-limiting variant embodiment, g and g' may be approximated by spline curves or any other interpolation basis.

[0106] We can then, for any set of values ​​gi, verify the condition N = ON for all yi.

[0107] Estimating g then comes down to finding the set {gi, i=l to m] which best allows us to verify the condition N = ON for all yi.

[0108] By choosing a metric M, this amounts to an optimization problem on a finite set of variables (here gi), a problem for which there are many known optimization algorithms. In non-limiting embodiments, simulated annealing or linear search methods (called "Line Search" in English) can be used, for which a starting point is taken as a parallel to the imposed input surface. We thus take the gi of a surface parallel to the input surface S2 to begin the optimization.

[0109] In a non-limiting embodiment, the metric M is the sum of the absolute values ​​of the difference between ON and N for all yi (i=l to m, m integer). We thus have,

[0110] [Math. 14] Lm

[0111] We must minimize this metric which depends on all the points yi. Indeed, to find the values ​​of gi, we must thus minimize this metric M.

[0112] If the abscissas yi are regularly spaced on a finite support, gi tends towards g(yi) when m tends towards infinity. In other words, if we have sampled with a constant step, we converge towards the solution if we have many points yi. We have gi which is the discretized and approximate solution, and g(yi) the exact solution. It will be noted that the minimum number m of points yi to achieve a given precision depends on the approximations (namely the g'i), the interpolations made and the metric M chosen. In another non-limiting embodiment, the metric M is the square root of the sum of the squared differences between ON and N for all yi (i=l to m, m integer).

[0113] Thus, we find the shape g of the output surface SI which allows the return radar waves R2 to reach the 2 receiving antennas 101. Thus, the radar sensor 10 will not see a false target object 3.

[0114] It will be noted that the same reasoning can be applied for an arrangement of layers in which the primary layer 121 and said at least one secondary layer 122 are distinct, and for any arrangement of layers 12 comprising a primary layer 121 and several secondary layers 122.

[0115] It will be noted that due to the predetermined shape 124 of the secondary layer 122, the phase difference Aq> measured by the radar sensor 10 between two return radar waves R2 does not follow the classic formula of radar sensors 10 Aq>0=2jr.L.sin(a) / X, but a more complex law following. For a target located in the angular direction N relative to the axis of the radar sensor 10 represented by AZ in [Fig.6], the radar sensor 10 will measure the following phase shift Aq>: [Math. 15] _ u3+n2(u2-(.i20)+u 1-u 10 HAS <p = 2tt---;——-----

[0116] cette formule est référencée [2]. la mesure de l’azimut la cible déduit du déphasage aq>according to the classical formula will thus be erroneous since the phase shift Aq> does not follow the classical formula.

[0117] We have:

[0118] [Math. 16] pl = ^y2 + g(y)2

[0119] [Math. 17] g3 = sin (KO - arctan ()) ^ / (f(y2) -f(y20))2+ (y2-y20)2

[0120] With

[0121] [Math. 18] y2 = y + p2sin(a)

[0122] [Math. 19] y20 = p 1 Osin (a) - L + p20si n (aO)

[0123] The radar sensor 10 will thus provide an angle of incidence of the target object 3, otherwise called target angle ea(y):

[0124] [Math.20] ea(yj =arcsin\2n£ / *K

[0125] This formula is referenced formula [3].

[0126] To correct this erroneous measurement, in a non-limiting embodiment, the processing unit 21 is configured to apply a correction function fl to the angle of incidence ea(y) to correct the error due to the phase difference Aq> measured by the radar sensor 10.

[0127] With formula [1], we know f, f'. a and p2 are functions of g. g is known for a given y. The processing unit 21 therefore knows how to calculate N(y) as described previously. With formula [2], Aq> is a function of g and f. The processing unit 21 therefore knows how to calculate Aq>(y) and therefore calculate the target angle ea(y) (formula [3]) which will be provided by the radar sensor 10. The processing unit 21 will thus provide the correction function fl(EA) = N(ea '(EA)), where EA is an angular position of the target returned by the radar and fl(EA) the true azimuth of this target.

[0128] In a non-limiting embodiment, the processing unit 21 is further configured to calculate the angular position Pos of a target object 3 from the phase difference Aq> after correction.

[0129] It will be noted that the element 12 generally creates for a given target of azimuth N a phase difference Aq> between the secondary radar waves R2 arriving at each receiving antenna 101 different from that which would exist in the absence of said element 12 or if it were composed solely of layers with parallel plane faces, a phase difference which would then be ^g _ 7^81^. The real phase difference Aq> is given by the preceding formula [2]. The radar sensor 10 will calculate N on the basis of the phase difference Aq>0. If it can be ensured that Aq>-Aq>0=0 modulo 2ir (compensation), the radar will indeed measure N without needing to use the function fl. The compensation can be carried out by modifying the optical path that one of the return radar waves R2 must travel when arriving at one of the two receiving antennas 101. The modification of the optical path to be carried out is equal to: c=(((Aq>-Aq>0)+n*27r) / 2jr)*X, with n being a relative integer.In the case where a segment of the output surface SI after calculation is plane or conical (straight line segment in section in the figures), the optical path can be modified by shifting (translating) this segment according to the direction of the R2 wave which crosses it by a length equal to (1-nl) x c.

[0130] In a first non-limiting embodiment, when the output surface SI is partly planar ([Fig. 3] and [Fig. 4]), the output surface SI of the primary layer 121 is arranged so as to compensate for said offset. The compensation makes it possible to reduce the optical path of the return radar waves R2 for one of the two receiving antennas 101. Thus, the arrangement of the last diopter represented by the output surface SI through which the return radar waves R2 pass makes it possible to compensate for the offset. For this purpose, the output surface SI comprises a part 125, called the compensating part 125, arranged at the location where one of the return radar waves R2 passes through said output surface SL. Thanks to this arrangement of the part 125, the offset is thus compensated. This part is an additional phase shift correction zone. The output surface SI is partly flat and includes the portion 125 which is recessed or raised relative to the flat portion.Namely, the part 125 enters the material of the primary layer 121 or projects relative to the flat part of the output surface SL. Said recessed or raised part 125 is arranged so as to be in the path of one of the return radar waves R2 which arrives at one of the two receiving antennas 101 of said radar sensor 10. The optical path of this return radar wave R2 is thus modified so that the offset between the phase difference Aq> between the return radar waves R2 arriving at each receiving antenna 101 and the phase difference Aq>0 allowing the radar to calculate the exact azimuth angle N is compensated.

[0131] Thus, in the non-limiting embodiment illustrated in [Fig. 3], the part 125 is in relief and trapezoidal in shape in section. It will be noted that the part of the surface of dotted SI output delimits the SI output surface at the same location as part 125 if there is no compensation and therefore if part 125 does not exist.

[0132] Thus, in the non-limiting embodiment illustrated in [Fig.4], the portion 125 is in relief and in the shape of a rectangle in section. It will be noted that the portion of the exit surface SI in dotted lines delimits the exit surface SI at the same location as the portion 125 if there is no compensation and therefore if the portion 125 does not exist. The entry surface S2 of the second secondary layer 122b is parallel to the exit surface SI, including the portion 125. It will be noted that the illustrated case takes into account the fact that nl=n3.

[0133] It will be noted that if there are several secondary layers 122, an equivalent refractive index is defined for the calculation of the phase difference Aq>. Thus, these different secondary layers 122 will be seen as a single homogeneous secondary layer, and the part 125 will be adjusted according to this homogeneous secondary layer.

[0134] In a second non-limiting embodiment, when the output surface SI is continuous and not flat, namely continuous and curved ([Fig.2] and [Fig.5]), the offset is compensated by a compensation function of the processing unit 21. Indeed, in this case, compensation cannot be made by modifying the output surface SI by means of a part 125.

[0135] Thus, either the offset is corrected at the physical level by creating a discontinuous surface for the output surface SI using the part 125 and adjusting the depth 125, or it is done digitally by the processing unit 21.

[0136] Of course, the description of the invention is not limited to the embodiments described above and to the field described above. Thus, in another non-limiting embodiment, the radar sensor 10 comprises more than one transmitting antenna 100 and more than two receiving antennas 101. Thus, in another non-limiting embodiment, the arrangement of layers 12 comprises more than two secondary layers 122. Thus, the arrangement of layers 12 may comprise other secondary layers 122. Thus, in non-limiting examples, the other secondary layers 122 are a diffusing layer, and / or a reflective layer, and / or an opaque layer, in the visible light range.Thus, in another non-limiting embodiment, instead of a correction function fl calculated by the processing unit 21, a calibration can be carried out before using the radar sensor 10 in order to obtain a correction table which will be used by the processing unit 21. The calibration will be carried out by placing a target object 3 at different predetermined angles and looking at the values ​​of these angles measured by the radar sensor 10, values ​​having an error due to the predetermined shape 124 of the secondary layer 122. Thus, in a non-limiting example, the correction table will thus comprise the values ​​of the predetermined angles and the corresponding values ​​of the angles measured by the radar sensor 10, and the unit . processing unit 21 will thus calculate the difference in values ​​to be applied for the correction. In another non-limiting example, the correction table will include the values ​​of the predetermined angles and the corresponding correction values ​​to be applied.

[0137] Thus, the invention described presents in particular the following advantages: - it allows the calculation of the angular position Pos of a target object 3 not to be impacted by a 3D shape of a layer in the layer arrangement 12, - it prevents the radar sensor 10 from detecting false target objects, - it allows to correct the measurement errors by the radar sensor 10 of the phase shift Aq>.

Claims

Claims

1. Vehicle assembly (1) for a vehicle (2), said vehicle assembly (1) being configured to detect a target object (3) in the environment of said vehicle (2) and comprising: - a radar sensor (10) comprising at least one transmitting antenna (100) configured to transmit radar waves (RI) and at least two receiving antennas (101) configured to receive return radar waves (R2) which are reflected on said target object (3), said radar sensor (10) being configured to measure a phase difference (Aq>) between the return radar waves (R2) arriving at each receiving antenna (101), - a layer arrangement (12) comprising: (i) a primary layer (121) arranged opposite said radar sensor (10) and comprising an exit surface (SI) for the return radar waves (R2), and (ii) at least one secondary layer (122) comprising an entry surface (S2) return radar waves (R2),and (iii) at least one predetermined non-planar shape (124) present in the primary layer (121) or in at least one secondary layer (122), said output surface (SI) of the primary layer (121) being calculated as a function of said at least one predetermined shape (124) so that return waves (R2) reach said at least two receiving antennas (101) with the same angle of incidence (a) whatever the position of the target object (3), characterized in that the predetermined shape (124) is a relief formed of planar surfaces, in which the output surface (SI) of the primary layer (121) is partly planar and comprises a part (125) recessed or raised relative to said planar part configured to compensate for an offset induced by said predetermined shape (124) at said phase difference (Aq>) which exists between the return radar waves (R2) arriving at each receiving antenna (101).,

2. Vehicle assembly (1) according to claim 1, wherein said primary layer (121) and said at least one secondary layer (122) are merged into a single layer.

3. Vehicle assembly (1) according to claim 1, wherein said primary layer (121) and said at least one secondary layer (122) are distinct and have a different refractive index (ni, n2).

4. Vehicle assembly (1) according to any one of the preceding claims, wherein the shape of said output surface (SI) is determined by a finite difference method.

5. Vehicle assembly (1) according to any one of the preceding claims, wherein said phase difference (Aq>) measured by said radar sensor (10) between the return radar waves (R2) arriving at each receiving antenna (101) is corrected by a correction function (fl) of a processing unit (21) of the vehicle (2).

6. A vehicle assembly (1) according to any preceding claim, wherein the arrangement of layers (12) forms a logo or layers of a headlamp or taillight.

7. Vehicle assembly (1) according to any one of the preceding claims, wherein the primary layer (121) has a primary refractive index (ni), and said layer arrangement (12) comprises two secondary layers (122a, 122b) each with a secondary refractive index (n2) and a tertiary refractive index (n3) respectively, one of which (122b) comprises the entrance surface (S2) of the returning radar waves (R2) and has the tertiary refractive index (n3), said entrance surface (S2) being partly parallel to said exit surface (SI) and the tertiary refractive index (n3) being the same as the primary refractive index (ni).

8. Arrangement of layers (12) arranged opposite a radar sensor (10), said radar (10) being arranged at a headlight, a rear light or a logo, illuminated or not, of a motor vehicle (2), said radar sensor (10) comprising at least one transmitting antenna (100) configured to transmit radar waves (RI) and at least two receiving antennas (101) configured to receive return radar waves (R2) which are reflected on a target object (3), said arrangement of layers (12) comprising: - (i) a primary layer (121) arranged opposite said radar sensor (10) and comprising an output surface (SI) for the return radar waves (R2), - (ii) at least one secondary layer (122) comprising an input surface (S2) for the return radar waves (R2), - at least one predetermined non-planar shape (124) present in the primary layer (121) or in at least one secondary layer (122), - characterized in that said output surface (SI) of the primary layer (121) is calculated as a function of said at least one predetermined shape (124) of said input surface (S2) so that return waves (R2) reach said at least two receiving antennas (101) with the same angle of incidence (a) regardless of the position of the target object (3), and in that the predetermined shape (124) is a relief formed of flat surfaces, in which the output surface (SI) of the primary layer (121) is partly flat and comprises a part (125) recessed or raised relative to said flat part configured to compensate for an offset induced by said predetermined shape (124) to said phase difference (Aq>) which exists between the return radar waves (R2) arriving at each receiving antenna (101).

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