How to Position a Vehicle

Abstract

The invention relates to a method for positioning a vehicle equipped with a mobile inductive charging device at a defined position relative to a stationary inductive charging device. The mobile or stationary inductive charging device has a first sensor winding with a first radial longitudinal direction and a second sensor winding with a second radial longitudinal direction. The first and second radial longitudinal directions are arranged at an angle of 70° to 110° to each other, preferably perpendicular to each other and at an angle of 35° to 55° to the vehicle longitudinal direction or a target vehicle longitudinal direction, preferably at an angle of 45° to the vehicle longitudinal direction or a target vehicle longitudinal direction. From the positioning signal, a first voltage signal is formed in the first sensor winding and a second voltage signal is formed in the second sensor winding. At least one first voltage signal is detected in a signal detection unit and the second voltage signal is detected in a signal detection unit. The evaluation unit converts the first voltage signal into a first digital signal, converts the second voltage signal into a second digital signal, processes and compares the first and second digital signals, the processing of the first and second digital signals includes a conversion into the frequency domain, and a directional deviation value between the vehicle longitudinal direction and the connection line from the stationary inductive charging device to the mobile inductive charging device is calculated from the comparison of the first and second digital signals.

Description

[Technical field]

[0001] The present invention relates to a method for positioning a vehicle according to the preamble of the independent claim.

[0002] DE 10 2014202747 A1 shows a device and a method for detecting the position deviation of a passive coil relative to the primary coil of an inductive charging system for a vehicle. In this case, two windings of a dual winding system for determining the position deviation are provided, which are arranged symmetrically with respect to the central axis of the vehicle by 45° each and offset from each other by 90° in one direction. In the two windings of the dual winding system, a voltage is induced by the magnetic field of the primary coil. The position deviation is determined by a simple comparison of the two induced voltages. However, a simple comparison of the two voltages in a given time domain is difficult to achieve high accuracy and large range for practical use.

[0003] US2016380488 discloses a method for determining the relative position of a wireless power transmitter to a wireless power receiver. Here, the relative position is determined by using a three-axis signal generator and a three-axis sensor. Therefore, the voltage strengths cannot be simply compared directly as is done in the double winding system according to DE102014202747. During signal processing, US2016380488 also uses Fourier transforms, in particular fast Fourier transforms.

[0004] The present invention aims to provide an improved or at least alternative embodiment of an inductive charging device of the type mentioned at the beginning.

[0005] A method is proposed herein for positioning a vehicle equipped with a mobile inductive charging device at a defined position relative to a stationary inductive charging device. The mobile or stationary inductive charging device has a first sensor winding with a first radial longitudinal direction and a second sensor winding with a second radial longitudinal direction. The first and second radial longitudinal directions are arranged at an angle of 70° to 110° to each other, preferably perpendicular to each other and at an angle of 35° to 55° to the vehicle longitudinal direction or the target vehicle longitudinal direction, preferably at an angle of 45° to the vehicle longitudinal direction or the target vehicle longitudinal direction. In this case, a first voltage signal is formed in the first sensor winding and a second voltage signal is formed in the second sensor winding from a positioning signal, preferably a positioning signal formed in the stationary or mobile inductive charging device. The first sensor winding has a first radial longitudinal direction and the second sensor winding has a second radial longitudinal direction. At least one first voltage signal is detected in a signal detection unit and at least one second voltage signal is detected in the signal detection unit and converted into a second digital signal. The first voltage signal is converted into a first digital signal and the second voltage signal is converted into a second digital signal by an evaluation unit, and the first digital signal and the second digital signal are processed and compared. The processing of the first digital signal and the second digital signal includes a conversion into the frequency domain. From the comparison of the first digital signal and the second digital signal, a directional deviation value between the vehicle longitudinal direction and the connecting line from the stationary inductive charging device to the mobile inductive charging device is calculated.

[0006] This offers the advantage that, unlike the prior art, a simple comparison of signals in the frequency domain is possible, whereas in DE 102014202747 A1 only a solution for the hardware structure is presented, but not the corresponding signal processing, whereas in US 2016380488 A1 a significantly more complex signal processing is required.

[0007] A vehicle charging system for inductive charging comprises at least one first inductive charging device, which is usually stationary, and a second charging device, which is usually mobile. The term "inductive charging device" is therefore used here only to represent one of at least two parts required for energy transmission for an inductive charging process. In an inductive charging process, an energy transmission winding generates an alternating magnetic field during energy transmission in the inductive charging device. The alternating magnetic field induces a voltage in another energy transmission winding of the other inductive charging device. The other inductive charging device is therefore used as a counter part in this particular charging process. Energy is transmitted wirelessly and is received by induction of a voltage.

[0008] A stationary inductive charging device is a non-moving part of a vehicle charging system, i.e., a part that does not move with the vehicle. The stationary inductive charging device may be preferably located on or at or within the bottom. In this case, the device may be a ground-mounted inductive charging device or an inductive charging device that is buried on or within the ground. The bottom may be a roadway, a parking lot floor, a garage floor, a parking structure, or a floor of another building. Alternatively, the stationary inductive charging device may be located on a wall, etc.

[0009] The device may be a stationary inductive charging device for a dynamic inductive charging process, in which the energy accumulator of the vehicle can be charged while the vehicle is moving, for example, in this case the stationary inductive charging device can extend along the roadway, below, in or on the roadway surface.

[0010] The mobile inductive charging device can be arranged on and / or in the vehicle. Very generally, a mobile inductive charging device is understood to be a part of a vehicle charging system that moves with the vehicle. The inductive charging device on and / or in the vehicle is therefore suitable for receiving a magnetic field and supplying electrical energy to an energy storage device of the vehicle, for example a battery or an accumulator in the vehicle. Basically, the vehicle charging system can also be used for bidirectional charging. In this case, the vehicle can also temporarily supply energy from the energy storage device to the power grid via the vehicle charging system.

[0011] In principle, the inductive charging device according to the invention can be used in any type of land vehicle, ship or aircraft with an electric or hybrid drive, in particular cars, buses and trucks.

[0012] For efficient energy transmission, the mobile inductive charging device must be positioned as accurately as possible relative to the stationary inductive charging device. That is, the mobile inductive charging device must be positioned in a defined position relative to the stationary inductive charging device. The defined position is preferably a set position that is considered to enable the energy transmission to take place as efficiently as possible. In this case, it can be considered in particular that the energy transmission windings of the two inductive charging devices are positioned opposite each other with the smallest possible distance from each other and with respect to the air gap between them. Since the two energy transmission windings do not generally need to be of the same size, it is also advantageous in this case to position the winding axes of the two energy transmission windings as symmetrical as possible in the up-down direction relative to each other. However, accurate positioning is often difficult or impossible for the driver without additional assistance in the form of a driver assistance system.

[0013] The positioning method according to the invention can be a fully automatic positioning method in which the vehicle is parked completely autonomously above the stationary inductive charging equipment, but it can also be that the positioning here is performed by a driver assistance system which shows the driver how he should steer his vehicle for optimal positioning relative to the stationary inductive charging equipment.

[0014] The positioning signal here is an alternating electromagnetic or magnetic field, which can induce a voltage signal in the sensor winding. Preferably, in this case, the positioning signal is transmitted or generated by a stationary inductive charging device at which the vehicle is positioned. The positioning signal here can be transmitted or generated directly from an energy transmission winding of the inductive charging device, or one or more further windings or other signal generating devices can be provided for this purpose. A power is preferably transmitted from the positioning signal, which is significantly lower than the power transmitted during the energy transmission.

[0015] The connection line from the stationary inductive charging device to the mobile inductive charging device takes into account in particular the defined mutual positions of the two inductive charging devices, which are targeted as described above, and in particular may extend between the two centers of the two energy transmission windings in the inductive charging device.

[0016] The first and / or second sensor winding can be located in or near a mobile or stationary inductive charging device. Very generally, a coil is defined here as a component that generates or receives a magnetic field. A coil may consist of a winding and any further elements, such as a magnetic core and a coil support. In this case, a winding is a device around which a current conductor is wound. A winding may consist of one or more turns, where a winding refers to one complete revolution of the conductor. Very generally, however, a winding may consist of less than one turn, i.e., for example, 0.5 turns. Of course, a non-integer number of windings is also possible, such as, for example, 2.5 turns.

[0017] The sensor winding according to the invention can be made in various forms, here having half a turn, one turn or preferably several turns. The conductor of such a sensor winding has a diameter of, for example, 0.01 mm. 2 ~2mm 2 The conductors here can be formed as Litz wires or as individual conductors or in other form, for example in the form of conductor tracks on a circuit board.

[0018] Generally, the windings extend in at least two dimensions about a winding axis. The winding axis is the axis about which the windings are wound. The main direction of extension perpendicular to the winding axis is referred to here as the radial longitudinal direction. That is to say, if the winding has a non-square rectangular cross section, the radial longitudinal direction extends along or parallel to the long sides of the rectangle. In a winding with an elliptical cross section, the radial longitudinal direction extends along or parallel to the main axis of the ellipse. The radial longitudinal direction of the sensor winding according to the invention may lie in a plane extending parallel to the ground.

[0019] Arranging the angles of the radial longitudinal directions so that the two radial longitudinal directions intersect at an angle of 70° to 110°, preferably perpendicularly, and each radial longitudinal direction is arranged at an angle of 35° to 55°, preferably 45°, relative to the vehicle longitudinal direction or the target vehicle longitudinal direction, is advantageous for maximum detection sensitivity and the simplest possible calculation of the position deviation between the vehicle and the stationary inductive charging device.

[0020] If the two angles between the respective radial longitudinal directions of the sensor windings and the vehicle longitudinal direction or the target vehicle longitudinal direction are approximately equal in magnitude, this means that the sensor windings are arranged symmetrically with respect to the direction of travel. This is particularly advantageous, since a symmetric arrangement of the sensor windings with respect to the direction of travel results in equal position deviations to the right or left, so that the corresponding ratio of the voltages induced in the sensor windings is also symmetrical, and therefore the position deviation can be calculated relatively simply from the induced voltages. If the two angles are 45°, then the two sensor windings will be at an angle of 90° to each other, which is ideal for optimal evaluation of the sensor signals.

[0021] The alternating magnetic field can induce an alternating voltage in the sensor windings, which in turn causes a current to flow in the conductors forming each sensor winding, where the alternating voltage induced in the first sensor winding is referred to as a first voltage signal and the alternating voltage induced in the second sensor winding is referred to as a second voltage signal.

[0022] In the signal detection unit, the positioning signal is received, for example, by an inductive charging device and is prepared so that it can be sampled in the analog / digital conversion unit. The signal detection unit here comprises circuits, where at least one circuit comprises the first sensor winding and another circuit comprises the second sensor winding. The circuits can comprise further components and are configured so that the voltage signal can be further processed with as little effort as possible.

[0023] The first voltage signal and / or the second voltage signal can be converted into a digital signal, for example in an analog / digital conversion unit. In this case, the analog signal is preferably sampled at a predefined sampling frequency. The analog / digital conversion unit can be part of the evaluation unit. For conversion into a digital signal, the voltage dropping across the first sensor winding or the voltage dropping across the second sensor winding does not necessarily have to be sampled directly in the analog / digital conversion unit. In this case, the respective voltage dropping across one or more further components of the same circuit as the first sensor winding or the second sensor winding can also be sampled.

[0024] The evaluation unit may include further elements for evaluating the digital signals. These may preferably be realized as logic blocks in a computing unit. The computing unit may be realized on one or more local electronic circuit devices, for example realized in the form of a microprocessor or a local controller, and / or may be part of a larger control device or central processing unit in the vehicle. Here, different logic blocks may also be realized on the same or different microprocessors or control devices.

[0025] In frequency transformation, a signal from a given time domain is mathematically transformed into the frequency domain. For a time-dependent signal, the evaluation shows how strong a certain frequency or a certain frequency range is present in the signal in the frequency domain. The evaluation in the frequency domain is advantageous here, in particular, because such an evaluation allows the frequency or frequency range of the positioning signal to be filtered, thus achieving a better signal-to-noise ratio and thus a larger range.

[0026] Here, preferably, a value can be determined from each of the two digital signals in the frequency domain, which preferably represents how much voltage is induced in each sensor winding, in particular at the excitation frequency of the positioning signal in each sensor winding.

[0027] When two correspondingly processed signals are compared, a directional deviation value between -1 and 1 can be determined, for example by subtracting the two values ​​and normalizing to the larger of the two values.

[0028] By comparing the two values ​​derived from the correspondingly processed signals, a description is obtained of the angle by which the vehicle longitudinal direction deviates from the vehicle direction towards the stationary inductive charging device. In this respect, the sensor device of the invention can also be called a rotation angle sensor. At least in a certain angle range, the angle by which the connecting line from the stationary inductive charging device to the mobile inductive charging device has rotated relative to the vehicle longitudinal direction is determined. Preferably, the orientation deviation value is proportional to the angle between the vehicle longitudinal direction and the connecting line from the stationary inductive charging device to the mobile inductive charging device.

[0029] The longitudinal direction of the vehicle is the direction in which the vehicle would move forward if it were driving straight, i.e. not going around curves. In most cases this is also the main direction of extension of the vehicle.

[0030] The stationary inductive charging equipment has a target vehicle longitudinal direction, which is the direction in which the vehicle longitudinal direction should be located after the positioning process is successfully completed.

[0031] Preferably, the positioning signal is formed in a stationary or mobile inductive charging device. In this case, the positioning signal is always formed in the inductive charging device, which does not include a sensor winding, respectively. If the positioning signal is formed in a stationary inductive charging device, the mobile inductive charging device includes a sensor winding. If the positioning signal is formed in a mobile inductive charging device, the stationary inductive charging device includes a sensor winding. The positioning signal can be formed, for example, by a coil or winding that generates an alternating magnetic field. The coil or winding can be an energy transmission winding that is provided for energy transmission in the mobile or stationary inductive charging device. Alternatively, the positioning signal can be formed by a separate winding or coil.

[0032] The transformation into the frequency domain is preferably realized by a discrete Fourier transform, in particular a fast Fourier transform (FFT). The discrete Fourier transform, or DFT for short, transforms a sampled signal in a given time domain into a discrete frequency signal by means of a Fourier transform. Here, the voltage signal induced in the sensor winding is discretely sampled. What is important here is the sampling frequency, which determines which frequencies are resolvable. The sampling frequency must be selected such that the relevant frequencies, here in particular the excitation frequency, are resolvable. A special optimized form of the discrete Fourier transform is the fast Fourier transform (FFT for short in English). The FFT is the most frequently realized form of the discrete Fourier transform, since the optimized algorithm minimizes the complexity and thus the computational costs.

[0033] Advantageously, the signal transformed into the frequency domain is filtered by a filter with a bandwidth B centered on the excitation frequency. The positioning signal formed by the stationary inductive charging device is formed by a predefined excitation frequency. The excitation frequency can be in the range 10 kHz to 150 kHz. Preferably, the excitation frequency is in the range 120 kHz to 145 kHz. Particularly preferably, the excitation frequency is in the range 120 kHz to 125 kHz or in the range 130 kHz to 145 kHz. For example, the excitation frequency may be 140 kHz. It is therefore not necessary to evaluate the entire induced voltage signal in the entire frequency domain, but only in the vicinity of the excitation frequency, which is sufficient. For this purpose, a digital filter can be used.

[0034] A digital filter is a mathematical function applied to a discrete signal in the frequency domain. Thus, the discrete frequency values ​​are limited to those of a certain pre-adjusted frequency band with a bandwidth B. The bandwidth may for example be in the order of 1 kHz. The frequency band is selected to include the excitation frequency, advantageously so that it is centered around the excitation frequency.

[0035] Preferably, the average direction deviation value is determined by forming an average value, in particular a moving average value, from a number of direction deviation values, in particular ten direction deviation values, determined at successive discrete time points. If no corresponding averaging is performed, large fluctuations in the direction deviation value occur, in particular in the case of large distances from the vehicle to the stationary inductive charging device. This is caused, among other things, by increased noise in the induced voltage signal. In particular, if the method is used as a driver assistance system and the direction deviation values ​​are displayed graphically, the range within which the driver can park with the indicated direction deviation value is limited by the increasing fluctuations with distance. When calculating the moving average value, the average value is always calculated from the last N values. That is to say, a new average value is not calculated for every T value per block, but rather the new value is added, the last value of the values ​​considered up to that point is deleted and the new average value is calculated directly. Instead of the block-by-block approach, the calculation here is carried out by moving average.

[0036] In a preferred embodiment, the first voltage signal, which is converted to a first digital signal in the evaluation unit, is the voltage drop directly across the first sensor winding, and the second voltage signal, which is converted to a second digital signal in the evaluation unit, is the voltage drop directly across the second sensor winding. In this case, the induced voltage is measured by direct measurement of the voltage induced in the first and second sensor windings. This is a very simple means of signal detection.

[0037] In a preferred alternative embodiment, the signal detection unit comprises a first oscillating circuit comprising at least a first sensor winding and a first capacitance and a second oscillating circuit comprising at least a second sensor winding and a second capacitance. The oscillating circuit comprises at least one inductance, for example in the form of a winding or coil, here preferably a sensor winding, a capacitance and a resonant frequency that depends on the magnitude of the capacitance and the inductance. In this case, it is advantageous if the resonant frequency of the first oscillating circuit and the second oscillating circuit is approximately equal to the frequency of the positioning signal, i.e. the oscillating circuits are tuned to the excitation frequency of the positioning signal. Each oscillating circuit is thus excited in resonance by the positioning signal. This allows the signal amplitude to be amplified. The measurement of the voltage induced in the oscillating circuit can be carried out, for example, via a voltage measurement in an analog / digital conversion unit that can be directly integrated in the oscillating circuit.

[0038] In one variant, the first oscillating circuit can have a first damping resistor and the second oscillating circuit can have a second damping resistor. The function of the damping resistor is to protect, for example, the sensor winding, parts of the analog / digital conversion unit or other parts from destruction by excessively high voltages or currents that may occur in the case of resonance. The damping resistor therefore reduces the quality of the oscillating circuit.

[0039] In a preferred alternative embodiment, the signal detection unit comprises a potential-free current measurement or a shunt measurement. In this variant, the induced voltage is not measured directly. Instead, the induced voltage can be determined indirectly via a potential-free current measurement. In this case, the Hall effect can be used, for example. Alternatively, a shunt measurement can be performed. Here, a voltage drop is measured across a shunt, from which the current is calculated. A shunt is a resistor, usually of low ohms, connected in series with a current circuit or a part of it. In this case, the current flows through the shunt and can be indirectly measured by measuring the voltage drop across the shunt. From this, the current is calculated according to Ohm's law. This measurement is called a shunt measurement. The shunt here can be a damping resistor at the same time or can be formed as a shunt and a damping resistor separated from each other.

[0040] The oscillatory circuit may alternatively measure the voltage drop across a sensor winding or capacitance.

[0041] In a preferred embodiment, the directional deviation value or the average directional deviation value or a value derived from the directional deviation value or the average directional deviation value is transmitted via a data interface to a bus system, preferably to a CAN bus or another calculation unit. As mentioned above, the directional deviation value is calculated from the ratio of the respective voltages induced in the sensor windings, which allows the determination of the directional deviation angle between the vehicle longitudinal direction and the direct connection line to the desired defined position. The evaluation unit can therefore directly transmit the directional deviation value or the average directional deviation value or can previously carry out further calculation or evaluation steps and transmit, for example, the directional deviation angle or other values ​​derived or calculated from the directional deviation value or the average directional deviation value. The transmission of the corresponding values ​​takes place via a data interface. The corresponding values ​​generally have a time-dependent course. A transmission to the bus system can then be carried out. A bus system is a system which is used to enable the transmission of data between individual subscribers in a network. The transmission of data takes place here according to a special protocol. A protocol which is often provided in vehicles is the CAN protocol. Here, "CAN" stands for "Controller Area Network" and the CAN bus is a field bus. As an alternative to the transfer to the bus system, the corresponding values ​​can also be transferred to a further computing unit, which can be physically connected to the evaluation unit or which does not have to be physically connected to the evaluation unit.

[0042] Preferably, the direction deviation value or the average direction deviation value or a value derived from the direction deviation value or the average direction deviation value is displayed on the direction display of the vehicle. The direction display can be displayed to the driver, for example, in the form of a pointer on a digital display. In this case, the pointer can be oriented directly in the direction in which the driver must steer the vehicle, thus allowing a very intuitive correction of the driving direction. If the pointer indicates straight ahead, the driver knows that he is steering his vehicle directly towards the stationary charging device. Alternatively or additionally, the direction deviation value or the average direction deviation value can be displayed as a numerical value.

[0043] Alternatively, the directional deviation value or the average directional deviation value can also not be displayed directly to the driver but can be further processed and used within the framework of an algorithm for an automated parking process or fully automated driving.

[0044] In an advantageous embodiment, the mobile inductive charging device and / or the stationary inductive charging device comprises at least one flux guide element and at least one energy transmission winding, the at least one flux guide element being suitable for guiding a magnetic field during energy transmission between the energy transmission winding of the mobile charging device and the energy transmission winding of the stationary inductive charging device, the first sensor winding and the second sensor winding being arranged around at least one of the at least one flux guide element.

[0045] The inductive charging device has an energy transmission winding capable of efficiently receiving a magnetic field from another energy transmission winding during a charging process or capable of transmitting a magnetic field to another energy transmission winding during a charging process, preferably capable of transmitting a power of 3 kW to 500 kW, preferably 3 kW to 50 kW. The energy transmission winding can be formed in various forms, for example from a high frequency Litz wire having a diameter of 0.5 mm to 10 mm, preferably made of copper.

[0046] The magnetic flux guide elements are suitable for guiding the magnetic field in a set manner. r >1, preferably μ r >50, particularly preferably μ rIt has a high magnetic permeability >100. The flux guide element is a magnetic core for the energy transfer winding. In particular in this case, the magnetic field acts in such a way that, due to the high magnetic permeability, as much magnetic flux as possible is transferred to the energy transfer winding. With the flux guide element, the energy transfer winding receives a larger magnetic flux under otherwise equal parameters than it would without the flux guide element. The flux guide element can be made of a ferromagnetic material or preferably a ferrite magnetic material, particularly preferably ferrite. The flux guide element can be made preferably plate-like (in the form of a planar core) and can be arranged in the inductive charging device on the opposite side of the energy transfer winding, i.e. on the side remote from the other inductive charging device.

[0047] By arranging the first and second sensor windings around at least one of the at least one flux guide elements, at least one of the at least one flux guide elements then assumes a double function: it serves as a magnetic core for the first and / or second sensor winding and also as a magnetic core or flux guide element for the energy transmission winding, so that a separate flux guide element for the sensor windings is not required, which leads to simplified manufacturing.

[0048] Arranging the sensor winding around the flux guide element means here that the flux guide element is at least partially surrounded by the sensor winding. The first and the second sensor winding can be arranged around the same flux guide element or around two different flux guide elements or each can also be arranged around several flux guide elements.

[0049] The two sensor windings can be arranged to surround only the flux guide element or elements, or may be arranged around further elements, e.g. an energy transmission winding and / or around a cooling device and / or a shielding device.

[0050] Preferably, the first and second radial longitudinal directions intersect in the area of ​​the surface developed by the energy transmission winding. The area of ​​the surface developed by the energy transmission winding is the surface developed by the energy transmission winding in a plane perpendicular to the winding axis. This means that inner areas of the energy transmission winding where no windings are present are implied, but not surfaces lying outside the energy transmission winding. The intersection of the two radial longitudinal directions of the sensor winding in the area of ​​the surface developed by the energy transmission winding does not necessarily mean that the sensor windings themselves intersect. It is also possible that the sensor windings only intersect in their extension.

[0051] Arranging the two sensor windings so that the two radial longitudinal directions intersect in the area of ​​the surface spread out by the energy transmission winding offers advantages in the evaluation of the two sensor signals.

[0052] Particularly preferably, the first radial longitudinal direction and the second radial longitudinal direction intersect at least approximately in the center of the energy transfer winding.Particularly preferably, the first radial longitudinal direction and the second radial longitudinal direction intersect at least approximately in the center of the energy transfer winding.

[0053] The center of the energy transmission winding is understood here to mean an area of ​​several centimeters around the geometric center of the energy transmission winding in a plane perpendicular to the winding axis. This is advantageous because in this case, both radial longitudinal directions of the two sensor windings are rotated by a predefined angle with respect to the vehicle longitudinal direction in a manner that is advantageous for optimal detection of position deviations between the vehicle and the stationary inductive charging device. Furthermore, this ensures that the sensor winding is positioned relative to the energy transmission winding in such a way that the lowest possible voltage is induced in the sensor winding during the energy transmission process.

[0054] In a preferred embodiment, the two sensor windings cross at least approximately in the center of the energy transmission winding, in which case the sensor windings cover a larger area and can induce more voltages, in which case there is no longer an actual crossing of the sensor windings, but only a crossing in the extension of the sensor windings.

[0055] In this embodiment, it is advantageous if both sensor windings are arranged point-symmetrically with respect to the centre of the energy transmission winding.

[0056] Preferably, the first radial longitudinal direction and the second radial longitudinal direction are at least approximately parallel to a main direction of magnetic field lines which are formed in the flux guide element in the area covered by the sensor winding during energy transmission.

[0057] The main direction of the magnetic field lines is the direction in which the magnetic field lines mainly extend at each location. In this case, it is not the exact extension characteristic of the magnetic field lines due to the sensor winding, but rather the radial longitudinal direction that is oriented in the extension direction of the magnetic field lines in the extension area of ​​the sensor winding. During the energy transfer from the stationary inductive charging device to the mobile inductive charging device, the magnetic field is guided in one or more flux guide elements. If the flux guide element or elements are designed in the form of a plate, during the charging process, a magnetic field with magnetic field lines that extend approximately radially relative to the energy transfer winding is generated in the flux guide element. Although a voltage is indeed induced in the sensor winding during the positioning process, from which the position deviation between the vehicle and the stationary inductive charging device is calculated, since the magnetic field is significantly higher during the charging process, it is important that the lowest possible voltage is induced in the sensor winding so that the component in question or adjacent components are not destroyed. With regard to the induced voltage, the magnetic field component perpendicular to the radial longitudinal direction of the sensor winding is important. Therefore, in a sensor winding arrangement in which the radial longitudinal direction of the sensor winding is ensured to be at least approximately parallel to the main direction of the magnetic field lines in the flux guide element during the charging process, no or only a small voltage is induced in the sensor winding.

[0058] Preferably, the stationary or mobile inductive charging device has at least two windings, where a first winding is an energy transmission winding and a second winding is a positioning signal winding. During the positioning process, the positioning signal is formed in the stationary or mobile inductive charging device by the positioning signal winding. Thus, the energy transmission winding is not used for positioning during the positioning process.

[0059] The positioning signal winding can transmit a positioning signal during the positioning process. For example, the positioning signal winding can generate an alternating magnetic field with a certain frequency based on an alternating voltage. In principle, the energy transmission winding can also transmit a positioning signal, but as proposed here, it is advantageous to use a separate positioning signal winding for generating the positioning signal. In particular, the positioning signal winding can generate a magnetic field that is suitable for positioning and allows a larger range in particular at the same power. The energy transmission winding is designed to be coupled as well as possible to the corresponding counter part. Thus, a vehicle generally does not have a large range for transmitting or receiving a magnetic field in the vehicle longitudinal direction or in the target vehicle longitudinal direction. However, this is important for the positioning process.

[0060] During positioning, the maximum possible power or magnetic field of the positioning signal is significantly limited. The maximum possible power or magnetic field of the positioning signal is significantly smaller than during the energy transfer process. During the positioning process, no vehicle is present on the stationary inductive charging device. Thus, for example, a person may be present on the stationary inductive charging device. In order for the magnetic field to be non-hazardous for people, a magnetic flux density of 27 μT or 6.25 μT, depending on the frequency range, must not be exceeded. With the proposed positioning signal winding, a positioning signal can be generated that maintains the limit or reference value and yet allows a high range.

[0061] In a preferred embodiment, the positioning signal winding is configured as a solenoid with a winding axis in the vehicle longitudinal direction or in the target vehicle longitudinal direction, the stationary or mobile inductive charging device has at least one flux guiding element, which is suitable for guiding a magnetic field during an energy transmission process between another inductive charging device and the energy transmission winding, and the positioning signal winding comprises at least one of the at least one flux guiding element.

[0062] Solenoids are also called cylindrical coils or solenoid coils. They can be wound in the form of a spiral or cylindrical spiral. In this case, however, the shape of the turns does not have to resemble a circle, but can for example resemble a square or a rectangle or a rectangle with rounded corners. The important difference with flat coils is that the turns do not lie in one plane, but extend along an axis. However, here it is entirely possible for two or more turns to extend parallel and thus lie in the same plane perpendicular to the axis.

[0063] When the positioning signal winding is in a mobile inductive charging device of a vehicle, the winding axis of the positioning signal winding is oriented in the vehicle longitudinal direction. When the positioning signal winding is in a stationary inductive charging device, the winding axis of the positioning signal winding is oriented in the target vehicle longitudinal direction.

[0064] In the proposed arrangement, the flux guide elements are responsible for guiding the magnetic field for energy transmission during the energy transmission process and for guiding the magnetic field for positioning during the positioning process, i.e. the flux guide elements here assume a double function, which is particularly advantageous, since this allows an efficient use of material and construction space.

[0065] By configuring the positioning signal winding as a solenoid with a winding axis in the vehicle longitudinal direction or in the target vehicle longitudinal direction, a magnetic field is generated with a main direction of magnetic field lines in the vehicle longitudinal direction or in the target vehicle longitudinal direction. On the one hand, this has the advantage that in this embodiment, a significantly larger range is possible for positioning than would be possible with the same power or the same magnetic field strength by the positioning signal generated by the energy transmission winding. Furthermore, such an orientation of the magnetic field is particularly well suited to allowing the simplest possible detection of position or angle deviations in the sensor winding.

[0066] Particularly preferably, the positioning signal winding is designed to have a particularly large extension in the driving plane and in a direction perpendicular to the vehicle longitudinal direction or the target vehicle longitudinal direction. For example, the positioning signal winding can extend over the entire width of the inductive charging device. This achieves a sufficiently homogeneous magnetic field with a main direction of magnetic flux in the vehicle longitudinal direction or the target vehicle longitudinal direction, and prevents or reduces local magnetic field buildups.

[0067] Preferred embodiments of the invention are illustrated in the drawings and explained in detail in the following description, in which identical reference numbers refer to identical or similar or functionally identical components. [Brief description of the drawings]

[0068] [Figure 1] FIG. 1 shows a highly simplified view of a vehicle equipped with an inductive charging device. [Diagram 2] FIG. 2 is a highly simplified plan view illustrating a vehicle equipped with an inductive charging device positioned above a stationary inductive charging device that transmits a positioning signal. [Diagram 3] FIG. 2 is a highly simplified block diagram showing a signal detection unit and an evaluation unit. [Figure 4] FIG. 2 is a block diagram showing an evaluation unit. [Diagram 5]FIG. 2 illustrates an embodiment of a signal detection unit. [Figure 6] FIG. 13 shows an alternative embodiment of the signal detection unit. [Figure 7] FIG. 13 illustrates another alternative embodiment of the signal detection unit. [Figure 8] FIG. 13 illustrates another alternative embodiment of the signal detection unit. [Figure 9] 1 is a cross-sectional view showing an inductive charging device for a vehicle. [Figure 10] FIG. 2 is a schematic diagram showing the directions of the windings. [Figure 11] FIG. 1 is a plan view showing an inductive charging device with a sensor winding. [Figure 12] FIG. 13 is a plan view showing an alternative inductive charging device with a sensor winding. [Figure 13] FIG. 1 is a plan view showing an inductive charging device equipped with a positioning signal winding. [Figure 14] FIG. 1 is a schematic diagram illustrating a vehicle charging system during a positioning process.

[0069] If the figures have reference numbers separated by a comma, this means that two descriptions apply to the specific referenced part. For example, in figure 1, 1a is shown, which means that this is an inductive charging device and furthermore a mobile inductive charging device.

[0070] In FIG. 1, a mobile inductive charging device 1, 1a is shown, which is arranged on a vehicle 2 having a battery 3 and is positioned above a stationary inductive charging device 1, 1b. During operation, energy can be transferred from the stationary inductive charging device 1b to the mobile inductive charging device 1a, thereby charging the battery 3. The mobile inductive charging device 1a and the stationary inductive charging device 1b are formed together or are part of a vehicle charging system 8. In this case, energy can be temporarily transferred from the mobile inductive charging device 1a to the stationary inductive charging device 1b. The stationary inductive charging device 1b, which is arranged on the ground in FIG. 1, may alternatively be buried in the roadway (not shown here). In a buried arrangement, the inductive charging device 1b may be covered by a certain layer of the roadway or may terminate flush with the roadway surface.

[0071] FIG. 2 shows a plan view of a vehicle 2 with a mobile inductive charging device 1a positioned above a stationary inductive charging device 1b, where the vehicle longitudinal direction 6 deviates from the direction towards the stationary inductive charging device 1b (the connection line 12 from the vehicle 2 to the stationary inductive charging device 1b) by a direction deviation value 17 or direction deviation angle 39.

[0072] The detection and evaluation of the sensor signal is shown diagrammatically in figure 3. The sensor signal, here a voltage signal, is detected in a signal detection unit 14 and evaluated in an evaluation unit 15.

[0073] The evaluation unit is shown diagrammatically in FIG. 4. From the positioning signal 40, a first voltage signal 13a is induced in a first sensor winding 9a (not shown) and a second voltage signal 13b is induced in a second sensor winding 9b (not shown). The two sensor windings 9a, 9b are part of a signal detection unit 14. The strength of each voltage signal, in particular the ratio of the two voltage signals to one another, indicates an estimate regarding the position, in particular the angular position of the vehicle relative to the stationary inductive charging device. Since the two sensor windings are arranged symmetrically with respect to the vehicle longitudinal direction 6, the directional deviation value 17 can be determined from the two voltage signals 13a and 13b with relatively little effort. The two voltage signals 13a and 13b are each sampled in an analog / digital conversion unit 16. The two sampled signals are then each evaluated separately in a calculation unit 19, which first includes a fast Fourier transform part 20. Here, the signals are efficiently converted into discrete signals in the frequency domain. A filter 21 then filters out only the frequency region centered on the excitation frequency of the positioning signal 40. This effectively filters out signal interferences, so that a much higher accuracy and thus a much larger range is achieved. A maximum value determination 22 is then performed in the filtered frequency band. Here, the two determined maxima 23 are compared with one another in a comparison unit 24. Here, a directional deviation value between -1 and 1 can be determined, for example, by subtracting the two maxima and normalizing to the larger of the two maxima. Finally, a moving average value is determined in an average value forming unit 25 from the plurality of directional deviation values ​​17. This compensates for fluctuations and thus results in a larger range. The average directional deviation value 18 is then graphically displayed in the exemplary directional display unit 26, here.

[0074] In Fig. 5, a simple implementation of the signal detection unit 14 with the evaluation unit 15 shown is shown. From the positioning signal 40, a voltage is induced in the two sensor windings 9a, 9b. In this case, the voltage induced in the first sensor winding 9a and in the second sensor winding 9b is measured directly. The first voltage signal 13a and the second voltage signal 13b are then respectively converted into digital signals in an analog / digital conversion unit 16 and further processed in a separate evaluation unit 15.

[0075] In Fig. 6 an alternative embodiment of the signal detection unit 14 with the illustrated evaluation unit 15 is shown. In contrast to the embodiment of Fig. 5, here an oscillating circuit 31 is used for signal detection. The oscillating circuit 31 here consists of each sensor winding 9, each capacitance 27 and each damping resistor 28. The damping resistor 28 can also be omitted as an option. The resonant frequency of the oscillating circuit is adjusted to the excitation frequency, i.e. to the frequency at which the corresponding positioning signal 40 is transmitted.

[0076] In Fig. 7, a further alternative embodiment of the signal detection unit 14 with the oscillating circuit 31 and the evaluation unit 15 is shown. Here again, the oscillating circuit 31 consists of each sensor winding 9, each capacitance 27 and each damping resistor 28. The damping resistor 28 is also optional. The resonant frequency of the oscillating circuit is also adjusted to the excitation frequency of the positioning signal 40 as above. However, unlike the example of Fig. 6, no voltage measurement is performed here, but the signal is determined via a potential-free current measurement 29.

[0077] Figure 8 shows, in an alternative embodiment, oscillating circuits 31 likewise shown in Figure 7. Here, however, the current in each oscillating circuit 31 is determined via a respective shunt 30 by means of a so-called shunt measurement.

[0078] In addition to the alternatives shown here, it is also possible to carry out voltage measurements directly at the two sensor windings 9 or at the two capacitances 27 (not shown).

[0079] 9 shows a side cross-sectional view of a mobile inductive charging device 1a, which includes a number of flux guide elements 5 and energy transmission windings 4, 4a, and is mounted on a vehicle 2. A corresponding arrangement is also possible if a stationary inductive charging device 1b is mounted, for example, on or in the ground (not shown).

[0080] Fig. 10 shows diagrammatically how directions in a winding, in particular the radial longitudinal direction 11 in the sensor winding here, are defined. In the example of Fig. 10, the winding is a cylindrical coil with five windings. The direction in which the windings are wound over one another is the winding axis 36. The coil has a non-square rectangular cross section here. The direction along the long side of the rectangle is referred to here as the radial longitudinal direction 11. In the case where the cross section is not rectangular but elliptical, the radial longitudinal direction 11 extends along the main axis of the ellipse.

[0081] FIG. 11 shows a plan view of an inductive charging device 1 according to the invention. The inductive charging device 1 can be a mobile inductive charging device 1a or a stationary inductive charging device 1b. In this embodiment, eight flux guide elements 5 are shown, which are arranged in a plane in the radial direction around the center 7 of the energy transmission winding 4. Narrow air gaps 32 are shown between the flux guide elements 5. The energy transmission winding 4, which is arranged below the flux guide elements 5 in this plan view, is indicated by dashed lines. The energy transmission winding 4 is here a flat coil 10. A first sensor winding 9a is arranged around one of the flux guide elements 5, and a second sensor winding 9b is arranged around the other one of the flux guide elements 5. The sensor windings are formed in this embodiment as cylindrical coils. The first sensor winding 9a is arranged axially symmetrically to the second sensor winding 9b in relation to the vehicle longitudinal direction 6. The first sensor winding 9a has a first radial longitudinal direction 11a and the second sensor winding 9b has a second radial longitudinal direction 11b. An angle 31 between the first radial longitudinal direction 11a and the longitudinal direction of the vehicle 6 is at least approximately equal to an angle 34 between the second radial longitudinal direction 11b and the longitudinal direction of the vehicle. The first radial longitudinal direction 11a and the second radial longitudinal direction 11b intersect or intersect at least approximately at the center 7 of the energy transmission winding 4. The first radial longitudinal direction 11a and the second radial longitudinal direction 11b extend radially outward from the center 7 of the energy transmission winding 4.

[0082] In the charging process, the vehicle 2 is positioned on the stationary inductive charging device 1b and energy is transferred to or from the mobile inductive charging device 1a to the stationary inductive charging device 1b. The flux guide element 5 then assumes the function of magnetic field guidance. Here, in the charging state, the magnetic field lines of the magnetic field run approximately in the radial direction. In FIG. 11, three magnetic field lines 35 are symbolically shown. Since the first radial longitudinal direction 11a and the second radial longitudinal direction 11b are likewise oriented in the radial direction and thus at least approximately parallel to the magnetic field lines 35, only a relatively low voltage or no voltage is induced in the first sensor winding 9a and the second sensor winding 9b here. This is important, since at high powers of energy transmission, destruction of the sensor windings would otherwise be more likely.

[0083] FIG. 12 shows a plan view of another embodiment of an inductive charging device 1 according to the invention. Here, four sensor windings are provided (a first sensor winding 9a, a second sensor winding 9b, a third sensor winding 9c and a fourth sensor winding 9d). Each sensor winding is arranged around another of the eight flux guide elements 5. Every two flux guide elements are located diagonally opposite to the center 7 of the energy transmission winding 4. The four sensor windings 9a, 9b, 9c, 9d together form a cross-shaped arrangement. Compared to FIG. 11, in this embodiment a larger area is covered by the sensor windings. At the same time, the area around the center 7 of the energy transmission winding remains free, so that the required mechanical support elements (not shown) can be arranged there. Each two of the sensor windings (e.g. the respective diagonally opposite windings) can be electrically connected in this case, for example in series. The sensor windings are here formed on a circuit board 37 in the form of conductor tracks 38. Alternatively, the sensor windings may be formed as Litz wire (not shown).

[0084] In Fig. 13 an inductive charging device 1 is shown with an energy transmission winding 4 and a number of flux guide elements 5. The energy transmission winding 4 is configured as a flat coil 10. A positioning signal winding 41 is arranged around the flux guide elements 5 and the energy transmission winding 4. The positioning signal winding 41 is configured as a solenoid 42. The positioning signal winding 41 is here arranged centrally and extending above the centre of the energy transmission winding 4.

[0085] FIG. 14a) shows a vehicle 2 with a vehicle longitudinal direction 6 and a mobile inductive charging device 1a during a positioning process in a target vehicle longitudinal direction 6a via a stationary inductive charging device 1b. The vehicle 2 drives directly towards the stationary inductive charging device 1b, so that the target vehicle longitudinal direction 6a is the same as the vehicle longitudinal direction. In addition to an energy transmission winding (not shown), a positioning signal winding 41 is also present in the mobile inductive charging device 1a. The positioning signal winding 41 has a winding axis 36 and a radial longitudinal direction 11. In addition to an energy transmission winding (not shown), the stationary inductive charging device 1b has two sensor windings 9a, 9b. The two windings each have one radial longitudinal direction 11a, 11b. The two windings are arranged symmetrically with respect to the target vehicle longitudinal direction 6a. Such an arrangement of the windings for positioning is particularly advantageous. The positioning signal winding 41 generates a very homogeneous magnetic field. A voltage is induced in the sensor windings 9a, 9b by the magnetic field of the positioning signal winding 41. As shown in the schematic diagram on the left, when the vehicle travels exactly perpendicular to the stationary inductive charging apparatus 1b, voltages of the same magnitude are induced in the two sensor windings 9a and 9b.

[0086] In FIG. 14 b) an embodiment is shown in which the positioning signal winding 41 is arranged in the stationary inductive charging device 1b and the sensor windings 9a, 9b are arranged in the mobile inductive charging device 1a. Otherwise, the operation of the embodiment is exactly the same. Here, the case is shown in which the vehicle 2 does not approach the stationary inductive charging device 1b perpendicularly, but rather with a deviation at an angle of about 45°. The vehicle longitudinal direction 6 and the connection line from the stationary inductive charging device to the mobile inductive charging device 12 are therefore positioned at a deviation angle 39 of 45° to each other. In this case, the positioning signal winding 41 generates a magnetic field that is positioned perpendicular to the first sensor winding 9a. This induces a maximum voltage. Furthermore, the magnetic field formed by the positioning signal winding 41 is approximately parallel to the second sensor winding 9b. Here, a minimum voltage or no voltage is induced. [Explanation of symbols]

[0087] 1 Inductive charging device 1a Mobile inductive charging device 1b Stationary inductive charging device 2 Vehicles 3 Vehicle Energy Storage Unit 4 Energy Transmission Winding 4a Energy transmission winding of a mobile inductive charging device 4b Energy transmission winding of stationary inductive charging device 5 Flux guide element 6 Vehicle longitudinal direction 6a Target vehicle longitudinal direction 7. Center of energy transmission winding 8 Vehicle Charging System 9 Sensor Winding 9a First sensor winding 9b Second sensor winding 9c Third sensor winding 9d Fourth sensor winding 10 Flat coil 11 Radial longitudinal direction 11a first radial longitudinal direction 11b Second radial longitudinal direction 12 Connection wire between stationary inductive charging equipment and mobile inductive charging equipment 13 Voltage Signal 13a First voltage signal 13b Second voltage signal 14 Signal Detection Unit 15 Evaluation Units 16 Analog / Digital Conversion Unit 17 Directional deviation value 18 Mean Directional Deviation 19 Computational Units 20 Fast Fourier Transform 21 Filters 22 Maximum value determination 23 Maximum 24 Comparison Units 25 Average value forming section 26 Direction display 27 Capacitance 28 Damping Resistor 29 Potential-free current measurement section 30 Shunt 31 Oscillatory Circuit 32 Air gap between flux guide elements 33 First Angle 34 Second Angle 35 Magnetic Field Lines 36 Winding axis 37 Circuit board 38 Conductor Path 39 Direction deviation angle 40 Positioning Signal 41 Positioning signal winding 42 Solenoid

Claims

1. A method for positioning a vehicle (2) equipped with a mobile inductive charging device (1a) at a defined position relative to a stationary inductive charging device (1b), comprising: The mobile inductive charging device (1a) or the stationary inductive charging device (1b) has a first sensor winding (9a) having a first radial longitudinal direction (11a) and a second sensor winding (9b) having a second radial longitudinal direction (11b), the first radial longitudinal direction (11a) and the second radial longitudinal direction (11b) are arranged at an angle of 70° to 110° to each other, preferably perpendicular to each other, and at an angle of 35° to 55° to the vehicle longitudinal direction (6) or the target vehicle longitudinal direction (6a), preferably at an angle of 45° to the vehicle longitudinal direction (6) or the target vehicle longitudinal direction (6a); a first voltage signal (13a) is generated in the first sensor winding (9a) from the positioning signal (40), and a second voltage signal (13b) is generated in the second sensor winding (9b); At least one said first voltage signal (13a) is detected in a signal detection unit (14), At least one second voltage signal (13b) is detected in a signal detection unit (14), an evaluation unit (15) converting the first voltage signal (13a) into a first digital signal and the second voltage signal (13b) into a second digital signal, and processing and comparing the first and second digital signals; processing the first digital signal and the second digital signal includes converting to a frequency domain; a directional deviation value (17) between the vehicle longitudinal direction (6) and a connection line (12) from the stationary inductive charging device (1b) to the mobile inductive charging device (1a) is calculated from a comparison of the first digital signal and the second digital signal; method.

2. 2. The method of claim 1, wherein the positioning signal (40) is generated in the stationary inductive charging device (1b) or the mobile inductive charging device (1a).

3. 3. The method according to claim 1, wherein the transformation into the frequency domain is realized by a discrete Fourier transform, in particular a fast Fourier transform (FFT).

4. 3. The method according to claim 1, wherein the signal transformed into the frequency domain is filtered by a filter (21) having a bandwidth B centered at the excitation frequency.

5. 3. The method according to claim 1, wherein the average directional deviation value (18) is determined by forming an average value, in particular a moving average value, from a plurality of directional deviation values ​​(17), in particular ten directional deviation values ​​(17), determined at successive discrete points in time.

6. the first voltage signal (13a) converted into a first digital signal in the evaluation unit (15) is directly the voltage drop across the first sensor winding (9a), the second voltage signal (13b) converted into a second digital signal in the evaluation unit (15) is directly the voltage drop across the second sensor winding (9b); 3. The method according to claim 1 or 2.

7. The signal detection unit (14) has a first oscillating circuit (31) including at least the first sensor winding (9a) and a first capacitance (27); The signal detection unit (14) has a second oscillating circuit (31) including at least the second sensor winding (9b) and a second capacitance (27).

3. The method according to claim 1 or 2.

8. 8. The method of claim 7, wherein the first oscillating circuit (31) comprises a first damping resistor (28) and the second oscillating circuit (31) comprises a second damping resistor (28).

9. 7. The method of claim 6, wherein the signal detection unit (14) comprises a potential-free current measurement unit (29) or a shunt measurement unit.

10. 3. The method according to claim 1, wherein the directional deviation value (17) or the average directional deviation value (18) or a value derived from the directional deviation value (17) or the average directional deviation value (18) is transmitted via a data interface to a bus system, preferably a CAN bus or another computing unit.

11. 3. The method according to claim 1, wherein the direction deviation value (17) or the average direction deviation value (18) or a value derived from the direction deviation value (17) or the average direction deviation value (18) is displayed on a direction display (26) of the vehicle (2).

12. The mobile inductive charging device (1a) and / or the stationary inductive charging device (1b) comprises at least one magnetic flux guide element (5) and at least one energy transmission winding (32), the at least one magnetic flux guide element (5) is suitable for guiding a magnetic field during energy transmission between the energy transmission winding (4a) of the mobile inductive charging device (1a) and the energy transmission winding (4b) of the stationary inductive charging device (1b), the first sensor winding (9a) and the second sensor winding (9b) are arranged around at least one of the at least one flux guide element (5); 3. The method according to claim 1 or 2.

13. 13. Method according to claim 12, characterized in that the first radial longitudinal direction (11a) and the second radial longitudinal direction (11b) intersect in the region of the surface developed by the energy transmission winding (4).

14. 14. The method of claim 13, wherein the first radial longitudinal direction (11a) and the second radial longitudinal direction (11b) intersect at least approximately at a center (7) of the energy transfer winding (4).

15. 13. The method according to claim 12, wherein the first radial longitudinal direction (11 a) and the second radial longitudinal direction (11 b) extend at least approximately parallel to a main direction of magnetic field lines (35) formed in the area of ​​the magnetic flux guide element (5) covered by the sensor winding during the energy transmission.

16. 3. The method according to claim 2, wherein the stationary inductive charging device (1b) or the mobile inductive charging device (1a) has at least two windings, a first winding being an energy transmission winding (4) and a second winding being a positioning signal winding (41).

17. The positioning signal winding (41) is formed as a solenoid (42) having a winding axis in the vehicle longitudinal direction (6) or the target vehicle longitudinal direction (6a), the stationary inductive charging device (1b) or the mobile inductive charging device (1a) comprises at least one magnetic flux guide element (5), which is suitable for guiding a magnetic field during an energy transmission process between another inductive charging device (1) and the energy transmission winding (4); the positioning signal winding (41) surrounds at least one of the at least one flux guide element (5); 17. The method of claim 16.

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