Method for positioning a vehicle

Abstract

The invention relates to a method for positioning a vehicle having a mobile inductive charging device in a defined position in relation to a stationary inductive charging device. The mobile inductive charging device or the 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 radial longitudinal direction and the second radial longitudinal direction are arranged at an angle of between 70° and 110° in relation to one another, preferably perpendicularly in relation to one another, and at an angle of between 35° and 55° in relation to the longitudinal direction of the vehicle or to the target vehicle longitudinal direction, preferably at a 45° angle in relation to the longitudinal direction of the vehicle or in relation to the target vehicle longitudinal direction. A positioning signal generates a first voltage signal in the first sensor winding and a second voltage signal in the second sensor winding. The at least one first voltage signal is detected in a signal detection unit and the at least one second voltage signal is detected in a signal detection unit. An evaluation unit converts the first voltage signal into a first digital signal and the second voltage signal into a second digital signal and processes and compares the first digital signal and the second digital signal. Processing the first digital signal and the second digital signal includes transformation into the frequency range, and a direction deviation value between the longitudinal direction of the vehicle and the connecting line between the stationary inductive charging device and the mobile inductive charging device is calculated from the comparison of the first digital signal with the second digital signal.

Description

[0001]Method for positioning a vehicle The invention relates to a method for positioning a vehicle according to the preamble of the independent patent claim. DE 102014202747 A1 shows a device and a method for detecting a positional deviation of a passive coil relative to a primary coil of an inductive charging system for a vehicle. Two windings of a double winding system are provided for determining the positional deviation, and the two windings are arranged symmetrically, each offset by 45° in one direction relative to the center axis of the vehicle and offset by 90° to one another. A voltage is induced in each of the two windings of the double winding system by the magnetic field of the primary coil. The positional deviation is determined by a simple comparison of the two induced voltages.However, the simple comparison of the two voltages in the time domain makes it difficult to achieve high accuracy and range in practical terms. US 2016380488 A1 discloses a method for determining the relative position of a wireless power transmitter in relation to a wireless power receiver. The relative position is determined using a 3-axis signal generator and a 3-axis sensor. Therefore, a simple direct comparison of the voltage intensities is not possible, as is the case in the double-winding system of DE 102014202747 A1. During signal processing, US 2016380488 A1 also uses a Fourier transformation, in particular a fast Fourier transformation. The present invention addresses the problem of specifying improved or at least alternative embodiments for an inductive charging device of the type mentioned above.The present invention proposes a method for positioning a vehicle with a mobile inductive charging device in a defined position relative to a stationary inductive charging device. The mobile inductive charging device or the 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 radial longitudinal direction and the second radial longitudinal direction are arranged at an angle between 70° and 110° to one another, preferably perpendicular to one another and at an angle between 35° and 55° to the longitudinal direction of the vehicle or to the desired vehicle longitudinal direction, preferably at a 45° angle to the longitudinal direction of the vehicle or to the desired vehicle longitudinal direction.Here, a positioning signal, preferably a positioning signal generated in the stationary inductive charging device or in the mobile inductive charging device, generates a first voltage signal in a first sensor winding and a second voltage signal in a second sensor winding. The first sensor winding has a first radial longitudinal direction and the second sensor winding has a second radial longitudinal direction. The at least one first voltage signal is detected in a signal detection unit and the at least one second voltage signal is detected in a signal detection unit and converted into a second digital signal. An evaluation unit converts the first voltage signal into a first digital signal and the second voltage signal into a second digital signal and processes and compares the first digital signal and the second digital signal.The processing of the first digital signal and the second digital signal involves a transformation into the frequency domain. From the comparison of the first digital signal with the second digital signal, a directional deviation value between the longitudinal direction of the vehicle and the connecting line between the stationary inductive charging device and the mobile inductive charging device is calculated. Compared to the prior art, this offers the advantage of enabling a simple comparison of the signals in the frequency domain. In contrast, DE 102014202747 A1 only shows a solution for a hardware-based setup, but no corresponding signal processing, whereas US 2016380488 A1 requires significantly more complex signal processing. A vehicle charging system for inductive charging comprises at least a first, usually stationary, inductive charging device and a second, usually mobile, inductive charging device.The term "inductive charging device" therefore refers here to only one of at least two parts that are necessary for energy transfer during an inductive charging process. During the induction charging process, an energy transfer winding in an inductive charging device generates an alternating magnetic field during the energy transfer. This alternating magnetic field induces a voltage in another energy transfer winding of another inductive charging device. This additional inductive charging device thus serves as a counterpart for this specific charging process. The energy is transferred wirelessly and absorbed by induction of a voltage. A stationary inductive charging device is the non-mobile part of a vehicle charging system, i.e. the part that does not move with the vehicle. A stationary inductive charging device can preferably be located on, at, or in a floor.This can be an inductive charging device applied to the ground or an inductive charging device sunk into the ground or into the ground. A ground can be a roadway, a parking lot surface, a garage floor, a floor in a parking garage or another building. A stationary inductive charging device can alternatively be located on walls or the like. It is also possible for a stationary inductive charging device to be used for a dynamic inductive charging process. During a dynamic inductive charging process, an energy storage device of a vehicle can be charged while the vehicle is moving. For example, in this case the stationary inductive charging device can extend along the roadway under, in or on the road surface. A mobile inductive charging device can be arranged on and / or in a vehicle.In general terms, this refers to the part of a vehicle charging system that moves with the vehicle. An inductive charging device on and / or in the vehicle is therefore suitable for absorbing the magnetic field and making electrical energy available from an energy storage device in the vehicle, for example a battery or accumulator in the vehicle. In principle, a vehicle charging system can also be used for bidirectional charging. In this case, the vehicle can also temporarily feed energy from the energy storage device into the power grid via the vehicle charging system. In principle, an inductive charging device according to the invention can be used for any type of land, water, or aircraft that has an electric or hybrid drive. In particular, passenger cars, buses, and trucks are mentioned here.For efficient energy transfer, the mobile inductive charging device must be positioned as precisely as possible in relation to the stationary inductive charging device. The mobile inductive charging device must therefore be positioned in a defined position in relation to a stationary inductive charging device. The defined position is a predetermined position which preferably takes into account that energy transfer can take place with the highest possible efficiency. In particular, it can be taken into account that one energy transfer winding in each of the two inductive charging devices is positioned opposite one another with the smallest possible distance from one another and with regard to an air gap between them. Since both energy transfer windings generally do not have to be the same size, symmetrical positioning in which the winding axes of the two energy transfer windings lie as close to one another as possible is also advantageous.Precise positioning is often difficult or impossible for the driver without additional support in the form of a driver assistance system. The positioning method according to the invention can be a fully automatic positioning method in which the vehicle parks completely autonomously above the stationary inductive charging device. However, it is also possible for the positioning to be carried out by a driver assistance system, indicating to the driver how to steer the vehicle in order to optimally position it relative to the stationary inductive charging device. A positioning signal is an alternating electromagnetic or magnetic field that can induce a voltage signal in a sensor winding. The positioning signal is preferably emitted or generated by the stationary inductive charging device relative to which the vehicle is to be positioned.It is possible for the positioning signal to be transmitted or generated directly by an energy transmission winding of an inductive charging device, or for one or more additional windings or another signal generation device to be present for this purpose. The positioning signal preferably transmits power that is significantly lower than the power transmitted during energy transmission. The connecting line between the stationary inductive charging device and the mobile inductive charging device takes into account, in particular, the desired defined position of the two inductive charging devices relative to one another, as explained above. In particular, the connecting line can run between the two centers of the two energy transmission windings in the inductive charging devices. The first and / or the second sensor winding can be arranged in or near the mobile or stationary inductive charging device.In general terms, a coil is defined here as a component for generating or receiving a magnetic field. A coil can consist of a winding and optionally further elements such as a magnetic core and a coil carrier. A winding is a wound arrangement of a current conductor. A winding can consist of one or more turns, with one turn representing one full revolution of a conductor. In general, however, a winding can also consist of less than one turn, for example 0.5 turns. Of course, an incomplete number of turns, such as 2.5 turns, is also possible. A sensor winding according to the invention can be designed in different forms and can have half, one or preferably several turns. A conductor of such a sensor winding can, for example, have a cross-sectional area of ​​between 0.01 mm² and 2 mm².A conductor can be a stranded wire, a single conductor, or in another form, for example, in the form of conductor tracks on circuit boards. In general, a winding extends in at least two dimensions around a winding axis. The winding axis is the axis around which the winding is wound. The main extension direction perpendicular to the winding axis is referred to here as the radial longitudinal direction. For a winding with a rectangular (not square) cross-section, the radial longitudinal direction runs along or parallel to the longer side of the rectangle. For a winding with an elliptical cross-section, the radial longitudinal direction runs along or parallel to the main axis of the ellipse.The radial longitudinal direction of a sensor winding according to the invention can lie in a plane that extends parallel to the ground. An arrangement of the angles of the radial longitudinal directions such that the two radial longitudinal directions intersect at an angle between 70° and 110°, preferably perpendicular, and that the respective radial longitudinal direction is arranged at an angle of 35° - 55°, preferably 45°, to the longitudinal direction of the vehicle or to the desired vehicle longitudinal direction, is advantageous for the highest possible sensitivity during detection and the simplest possible calculation of the positional deviation between the vehicle and the stationary inductive charging device. If the two angles between the respective radial longitudinal direction of the sensor windings and the longitudinal direction of the vehicle or the desired vehicle longitudinal direction are approximately the same, this means that the sensor windings are arranged symmetrically to the direction of travel.This is particularly advantageous because the symmetrical arrangement of the sensor windings with respect to the direction of travel means that, with equally large positional deviations to the right or left, the corresponding ratios of the voltages induced in the sensor windings are also symmetrical. This makes it relatively easy to calculate the positional deviations from the induced voltages. If the two angles are 45º, the two sensor windings are at a 90º angle to each other, which is ideal for optimal evaluation of the sensor signals. An alternating magnetic field can induce an alternating voltage in a sensor winding, which in turn can cause a current to flow in the conductor from which the respective sensor winding is made. The alternating voltage induced in the first sensor winding is referred to here as the first voltage signal, and the alternating voltage induced in the second sensor winding is referred to as the second voltage signal.In a signal acquisition unit, the positioning signal is received, for example, from the inductive charging device and made available in such a way that it can be sampled in an analog-to-digital conversion unit. The signal acquisition unit here contains circuits, with at least one circuit containing the first sensor winding and another circuit containing the second sensor winding. The circuits can contain additional components and are designed so that the voltage signals can be further processed with the least possible effort. The first voltage signal and / or the second voltage signal can be converted into a digital signal, for example, in an analog-to-digital conversion unit. In this case, the analog signal is preferably sampled at a specific sampling frequency. The analog-to-digital conversion unit can be part of an evaluation unit.For conversion into a digital signal, the analog-to-digital conversion unit does not necessarily have to directly sample the voltage drop across the first sensor winding or the voltage drop across the second sensor winding. In this case, a voltage drop across one or more other components in the same circuit as the first sensor winding or the second sensor winding can also be sampled. An evaluation unit can contain additional elements for evaluating the digital signal. These can preferably be implemented as logical blocks in a computing unit. A computing unit can be implemented on one or more local electronic devices, which can be implemented, for example, in the form of microprocessors or local control units, and / or the computing unit can be part of a larger control unit or a central computing unit in the vehicle.Different logic blocks can be implemented on the same or different microprocessors or control units. In a frequency transformation, a signal is mathematically transformed from the time domain to the frequency domain. For a time-dependent signal, an evaluation in the frequency domain provides information about the strength of a certain frequency or frequency range in this signal. An evaluation in the frequency domain is advantageous here, particularly because it makes it possible to filter the frequency or frequency range of the positioning signal and thus achieve a better signal-to-noise ratio and thus a greater range. One value can then preferably be determined from each of the two digital signals in the frequency domain.This value preferably indicates how much voltage was induced in the respective sensor winding, in particular how much voltage was induced in the respective sensor winding at the excitation frequency of the positioning signal. By comparing the two correspondingly processed signals, 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. The ratio of the two values ​​derived from the correspondingly processed signals enables statements to be made about the angle by which the longitudinal direction of the vehicle deviates from the direction of the vehicle towards the stationary inductive charging device. In this respect, the present sensor arrangement can also be referred to as a rotation angle sensor.The angle by which the connecting line between the stationary inductive charging device and the mobile inductive charging device is rotated relative to the longitudinal direction of the vehicle is determined, at least within a specific angular range. The directional deviation value is preferably proportional to the angle between the longitudinal direction of the vehicle and the connecting line between the stationary inductive charging device and the mobile inductive charging device. The longitudinal direction of the vehicle is the direction in which the vehicle moves when driving straight ahead, i.e., when not cornering. This is usually also the main direction of extension of the vehicle. A stationary inductive charging device has a target vehicle longitudinal direction. This is the direction in which the longitudinal direction of the vehicle should be after a successful positioning process.The positioning signal is preferably generated in the stationary inductive charging device or in the mobile inductive charging device. In this case, the positioning signal is always generated in the inductive charging device, which in each case does not contain the sensor windings. If the positioning signal is generated in the stationary inductive charging device, the mobile inductive charging device contains the sensor windings. If the positioning signal is generated in the mobile inductive charging device, the stationary inductive charging device contains the sensor windings. The positioning signal can be generated, for example, by a coil or a winding that generates an alternating magnetic field. This can be a power transmission winding that is present for power transmission in the mobile inductive charging device or in the stationary inductive charging device.Alternatively, the positioning signal can also be generated by another winding or coil. The transformation into the frequency domain is preferably realized by a discrete Fourier transformation, in particular by a fast Fourier transformation (FFT). A discrete Fourier transformation (DFT for short) transforms a signal sampled in the time domain into a discrete frequency signal using a Fourier transformation. Here, the voltage signal induced in the sensor windings is discretely sampled. The sampling frequency is relevant here, as it determines which frequencies can be resolved. The sampling frequency must be selected so that the relevant frequencies, in this case in particular the excitation frequency, can be resolved. A special, optimized form of the discrete Fourier transformation is the fast Fourier transformation (FFT for short).Since the optimized algorithm minimizes complexity and thus computational effort, the FFT is the most commonly implemented form of discrete Fourier transformation. It is advantageous if the signal transformed into the frequency domain is filtered around the excitation frequency by a filter with a bandwidth B. The positioning signal generated by the stationary inductive charging device is generated with a specific excitation frequency. The excitation frequency can be in the range from 10 kHz to 150 kHz. The excitation frequency is preferably in the range from 120 kHz to 145 kHz. The excitation frequency is particularly preferably in the range between 120 kHz and 125 kHz or in the range between 130 kHz and 145 kHz. For example, the excitation frequency can be 140 kHz. It is therefore not necessary to evaluate the entire induced voltage signal over the entire frequency range; an evaluation close to the excitation frequency is sufficient.A digital filter can be used for this purpose. A digital filter is a mathematical function applied to the discrete signal in the frequency domain. The discrete frequency values ​​are thus limited to values ​​in a specific preset frequency band with the bandwidth B. The bandwidth can, for example, be on the order of 1 kHz. The frequency band is selected so that it contains the excitation frequency, advantageously so that it contains the excitation frequency in the middle. An averaged directional deviation value is preferably determined by calculating an average, in particular a moving average, from several directional deviation values, in particular from 10 directional deviation values ​​determined at discrete, consecutive points in time. Without appropriate averaging, the directional deviation values ​​fluctuate greatly, particularly over large distances between the vehicle and the stationary inductive charging device.The main cause of this is the increasing noise of the induced voltage signals. Particularly when the present method is used as a driver assistance system and the directional deviation value is displayed graphically, the range up to which the driver is able to park using the displayed directional deviation value is limited by the fluctuations that increase with distance. When calculating a moving average, the average of the last N values ​​is always calculated. This means that a new average is not calculated block by block for every T values; instead, if a new value is added, the last of the values ​​considered so far is discarded and a new average is calculated directly. Instead of a block-by-block procedure, this calculation is moving.In a preferred embodiment, the first voltage signal, which is converted into a first digital signal in the evaluation unit, is directly the voltage drop across the first sensor winding, and the second voltage signal, which is converted into a second digital signal in the evaluation unit, is directly the voltage drop across the second sensor winding. The induced voltage is measured by directly measuring the induced voltage at the first sensor winding and at the second sensor winding. This represents a very simple way of detecting the signal. In an alternative preferred embodiment, the signal detection unit has a first resonant circuit, which comprises at least the first sensor winding and a first capacitance, and a second resonant circuit, which comprises at least the second sensor winding and a second capacitance.An oscillating circuit contains at least one inductance, for example in the form of a winding or coil, preferably a sensor winding here, and a capacitance and has a resonant frequency which depends on the size of the capacitance and inductance. In the present case, it is advantageous if the resonant frequency of the first oscillating circuit and the second oscillating circuit is approximately the same as the frequency of the positioning signal, i.e. if the oscillating circuits are tuned to the excitation frequency of the positioning signal. Thus, the respective oscillating circuit is resonantly excited by the positioning signal. This can amplify the signal amplitude. The measurement of the voltages induced in the oscillating circuits can take place, for example, via a voltage measurement in an analog-to-digital conversion unit which can be integrated directly into the oscillating circuit.In one variant, the first resonant circuit can have a first damping resistor and the second resonant circuit can have a second damping resistor. The function of the damping resistors is, for example, to protect the sensor windings, components of the analog-to-digital conversion unit or other components from being damaged by excessively high voltages or currents that can occur in the event of resonance. The damping resistors thus reduce the quality of the resonant circuits. In a preferred alternative embodiment, the signal acquisition unit includes 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. The Hall effect, for example, can be utilized here. Alternatively, a shunt measurement can be performed.Here, the voltage drop across a shunt is measured, and the current is calculated from this. A shunt is a resistor, usually of low value, connected in series with a circuit or part of a circuit. Current can be measured indirectly by measuring the current flowing through the shunt and the voltage drop across the shunt. From this, the current is then calculated using Ohm's law. This measurement is called shunt measurement. A shunt can also be a damping resistor at the same time, or a shunt and a damping resistor can be implemented separately. In resonant circuits, it is also possible to measure the voltage drop across the sensor windings or the capacitors.In a preferred embodiment, the directional deviation value or the averaged directional deviation value or a value derived from the directional deviation value or the averaged directional deviation value is transferred via a data interface to a bus system, preferably to a CAN bus or to another computing unit. As explained above, a directional deviation value is calculated from the ratio of the voltages induced in the sensor windings and enables the determination of a directional deviation angle between the longitudinal direction of the vehicle and the direct connection to the desired defined position.It is therefore possible for the evaluation unit to directly transmit the directional deviation value or the averaged directional deviation value, or for further calculation or evaluation steps to take place beforehand and, for example, to transmit a directional deviation angle or other values ​​derived or calculated from the directional deviation value or the averaged directional deviation value. The corresponding value is transmitted via a data interface. A corresponding value generally has a time-dependent curve. It can be transmitted to a bus system. A bus system is a system that enables the transmission of data between the individual participants within a network. The transmission of the data is based on special protocols. A protocol frequently used in vehicles is the CAN protocol.“CAN” stands for “Controller Area Network,” and a CAN bus is a fieldbus. As an alternative to being passed on to a bus system, a corresponding value can also be passed on to another processing unit. The other processing unit may or may not be physically connected to the evaluation unit. Preferably, the directional deviation value, the averaged directional deviation value, or a value derived from the directional deviation value or the averaged directional deviation value is displayed on a direction indicator in the vehicle. The direction indicator can be shown to the driver, for example, in the form of a pointer on a digital display. The pointer can point directly in the direction the driver needs to steer the vehicle, allowing for very intuitive correction of the direction of travel. If the pointer points straight ahead, the driver knows that they are driving their vehicle directly toward the stationary inductive charging device.Alternatively or additionally, the directional deviation value or the averaged directional deviation value can be displayed as a numerical value. Alternatively, it is possible not to display the directional deviation value or the averaged directional deviation value directly to the driver, but to further process it and use it as part of an algorithm for an automated parking process or for fully automated driving. In an advantageous embodiment, the mobile inductive charging device and / or the stationary inductive charging device contains at least one flux guide element and at least one energy transfer winding. The at least one flux guide element is suitable for guiding a magnetic field during an energy transfer that takes place between an energy transfer winding of the mobile inductive charging device and an energy transfer winding of the stationary inductive charging device.The first sensor winding and the second sensor winding are arranged around at least one of the at least one flux guide element. An inductive charging device has an energy transfer winding which can efficiently receive a magnetic field from or transmit it to another energy transfer winding during the charging process. Power outputs of 3 kW to 500 kW, preferably 3 kW to 50 kW, can preferably be transmitted. An energy transfer winding can be designed in various forms and can, for example, consist of a high-frequency stranded wire with a diameter between 0.5 mm and 10 mm, preferably made of copper. A flux guide element is suitable for guiding a magnetic field in a predetermined manner. It has a high magnetic permeability with μr>1, preferably μ. r >50, particularly preferably μ r>100. The flux guiding element represents a magnetic core for the energy transmission winding. In particular, the magnetic field is influenced by the high permeability in such a way that the greatest possible magnetic flux is transmitted to the energy transmission winding. With a flux guiding element, the energy transmission winding absorbs a greater magnetic flux than without a flux guiding element, with otherwise identical parameters. A flux guiding element can be made of a ferromagnetic or preferably a ferrimagnetic material, particularly preferably a ferrite. A flux guiding element can preferably be plate-like - in the form of a planar core - and can be arranged in the inductive charging device on the side of the energy transmission winding which is facing away from the further inductive charging device. By arranging the first sensor winding and the second sensor winding around at least one of the at least oneFlux guiding elements, at least one of the at least one flux guiding elements assumes a dual function here. It acts as a magnetic core for both the first sensor winding and / or the second sensor winding, as well as a magnetic core or flux guiding element for the energy transmission winding. Thus, no separate flux guiding element is required for the sensor winding, which leads to simplified production. The arrangement of a sensor winding around a flux guiding element here means that at least a part of the flux guiding element is enclosed by a sensor winding. The first sensor winding and the second sensor winding can be arranged around the same flux guiding element or around two different flux guiding elements, or can each be arranged around several flux guiding elements. The two sensor windings can either be arranged around one or more flux guiding elements or also around additional elements, such asaround the energy transmission winding and / or around a cooling and / or shielding device. Preferably, the first radial longitudinal direction and the second radial longitudinal direction intersect in the area spanned by the energy transmission winding. The area spanned by the energy transmission winding refers to the area spanned by the energy transmission winding in the plane perpendicular to its winding axis. This explicitly also includes the inner area of ​​the energy transmission winding, in which no winding is present, but not the area located outside the energy transmission winding. The fact that the two radial longitudinal directions of the sensor windings intersect in the area spanned by the energy transmission winding does not necessarily mean that the sensor windings themselves intersect; it is also possible that they would only intersect in the extension. The two sensor windingsArranging them so that the two radial longitudinal directions intersect in the area spanned by the energy transmission winding offers advantages for the evaluation of the two sensor signals. Particularly preferably, the first radial longitudinal direction and the second radial longitudinal direction intersect at least approximately in the center of the energy transmission winding. It is particularly preferred that the first radial longitudinal direction and the second radial longitudinal direction intersect at least approximately in the center of the energy transmission winding. The center of the energy transmission winding refers here to the area a few centimeters around the geometric center of the energy transmission winding in the plane perpendicular to the winding axis. This is advantageous because the two radial longitudinal directions of the two sensor windings are rotated relative to the longitudinal direction of the vehicle by an angle that is sufficient for optimal detection of a positional deviation between the vehicle and the stationaryinductive charging device is advantageous. In addition, the sensor windings are arranged in relation to the energy transmission winding in such a way that the lowest possible voltages are induced in the sensor windings during the energy transmission process. In a preferred embodiment, the two sensor windings intersect at least approximately in the center of the energy transmission winding. In this embodiment, the sensor windings cover a larger area and more voltage can be induced. In this case, an actual intersecting of the sensor windings takes place, no longer just a intersecting in the extension of the sensor windings. It is advantageous if, in this embodiment, the two sensor windings are arranged point-symmetrically to the center of the energy transmission winding. Preferably, the first radial longitudinal direction and the second radial longitudinal direction are at least approximately parallel to the main direction of the magnetic field lines, whichduring energy transfer in the flux guide element, in the area covered by the sensor winding. The main direction of the magnetic field lines refers to the direction in which the magnetic field lines mainly extend at each location. The aim here is not to illustrate the exact course of the magnetic field lines through the sensor winding, but rather the radial longitudinal directions should be oriented according to the course of the magnetic field lines in the area where the sensor winding extends. During 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 one or more flux guide elements are plate-shaped, a magnetic field with magnetic field lines that run approximately radially in relation to the energy transfer winding is created in the flux guide elements during the charging process.Although a voltage is to be induced in the sensor windings during the positioning process in order to calculate a positional deviation between the vehicle and the stationary inductive charging device, the magnetic fields are significantly higher during the charging process and it is therefore important that as little voltage as possible is induced in the sensor windings to avoid damaging these or neighboring components. The field component perpendicular to the radial longitudinal direction of the sensor windings is relevant for the induced voltage. Therefore, with a sensor winding arrangement that ensures that the radial longitudinal direction of the sensor winding is at least approximately parallel to the main direction of the magnetic field lines in the flux guide elements during the charging process, no or only a small voltage is induced in the sensor winding. The stationary inductive charging device or the mobile inductive charging device preferably has at least two windings.wherein the first winding is a power transmission winding and the second winding is a positioning signal winding. During a positioning process, the positioning signal is generated by a positioning signal winding in the stationary inductive charging device or in the mobile inductive charging device. Thus, the power transmission winding is not used for positioning during a positioning process. A positioning signal winding can emit a positioning signal during a positioning process. For example, a positioning signal winding can generate an alternating magnetic field with a specific frequency due to an alternating voltage. In principle, an power transmission winding can also emit a positioning signal; however, it is advantageous, as proposed here, to use a separate positioning signal winding to generate a positioning signal. In particular, thePositioning signal windings generate magnetic fields that are more suitable for positioning and, in particular, enable a greater range with the same power. The energy transmission windings are designed to couple as well as possible with their counterparts. Therefore, they generally do not have a long range with regard to the transmission or reception of magnetic fields in the longitudinal direction of the vehicle or the desired vehicle longitudinal direction. However, this is crucial for a positioning process. During positioning, the maximum possible power or the maximum possible magnetic fields of the positioning signal are severely limited. They are significantly lower than is the case with an energy transmission process. During the positioning process, no vehicle is located on the stationary inductive charging device. Therefore, it is possible that, for example, a person on the stationary inductive charging deviceIn order for the magnetic fields to remain harmless to a person, they must not exceed flux densities of 27 µT or 6.25 µT, depending on the frequency range. With a proposed positioning signal winding, it is possible to generate positioning signals that comply with the limit values ​​or reference values ​​and still enable a long range. In a preferred embodiment, the positioning signal winding is designed as a solenoid with a winding axis in the longitudinal direction of the vehicle or the desired vehicle longitudinal direction, and the stationary inductive charging device or the mobile inductive charging device contains at least one flux guiding element, and the flux guiding element is suitable for guiding a magnetic field during an energy transfer process that takes place between another inductive charging device and the energy transfer winding, and the positioning signal winding encloses at least one of the at leasta flux guide element. A solenoid is also called a cylinder coil or solenoid coil. A solenoid can be wound in the form of a helix or a cylindrical spiral. However, the winding shape does not have to be circular, but can also have other shapes, such as square or rectangular, or even similar to a rectangle with rounded corners. The important difference to a flat coil is that the windings are not in one plane, but extend along an axis. However, two or more windings can also run parallel and thus be in the same plane perpendicular to the axis. If the positioning signal winding is located in a mobile inductive charging device of a vehicle, the winding axis of the positioning signal winding is aligned in the longitudinal direction of the vehicle. If the positioning signal winding is located in a stationary inductive charging deviceThe winding axis of the positioning signal winding is aligned in the desired vehicle longitudinal direction. In the proposed arrangement, the flux guide element guides a magnetic field for energy transfer during an energy transfer process and a magnetic field for positioning during a positioning process. The flux guide element thus performs a dual function, which is particularly advantageous because it allows for efficient use of material and installation space. The design of the positioning signal winding as a solenoid with a winding axis in the longitudinal direction of the vehicle or in the desired vehicle longitudinal direction generates a magnetic field with a main direction of the magnetic field lines in the longitudinal direction of the vehicle or in the desired vehicle longitudinal direction. This has the advantage, on the one hand, that this design enables a significantly greater range for positioning than is possible with a power transmission windinggenerated positioning signal at the same power or the same magnetic field strength. Furthermore, such an orientation of the magnetic field is also particularly well suited to enable the simplest possible detection of a positional deviation or an angular deviation in the sensor windings. Particularly preferably, the positioning signal winding is designed such that it has a particularly large extension in the travel plane and perpendicular to the longitudinal direction of the vehicle or to the desired vehicle longitudinal direction. For example, the positioning signal winding can extend over the entire width of an inductive charging device. Thus, a largely homogeneous magnetic field with a main direction of the magnetic flux in the longitudinal direction of the vehicle or the desired vehicle longitudinal direction is achieved, and local field increases are prevented or reduced. Preferred embodiments of the invention are illustrated in the drawings and are described in theThe following description explains this in more detail, wherein the same reference numerals refer to the same or similar or functionally identical components. It shows, schematically, Fig. 1 shows a highly simplified representation of a vehicle with an inductive charging device, Fig. 2 shows a highly simplified plan view of a vehicle with an inductive charging device that is to be positioned over a stationary inductive charging device that emits a positioning signal, Fig. 3 shows a highly simplified block diagram showing the signal acquisition unit and evaluation unit, Fig. 4 shows a block diagram of an evaluation unit, Fig. 5 shows an embodiment of a signal acquisition unit, Fig. 6 shows an alternative embodiment of a signal acquisition unit, Fig. 7 shows a further alternative embodiment of a signal acquisition unit, Fig. 8 shows a further alternative embodiment of a signal acquisition unit, Fig. 9 shows a sectional view of an inductive charging device.for a vehicle Fig.10 a schematic representation of the directions in a winding Fig.11 a top view of an inductive charging device with sensor windings Fig.12 a top view of an alternative inductive charging device with sensor windings Fig.13 a top view of an inductive charging device with positioning signal winding Fig.14 a schematic representation of a vehicle charging system during the positioning process If a part in the figures is designated with reference symbols separated by a comma, this means that both descriptions apply to the concrete designated part. In Fig.1, 1,1a means, for example: This is an inductive charging device and it is also a mobile inductive charging device. Fig.1 shows a mobile inductive charging device 1,1a, which is arranged on a vehicle 2 with 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 together form or are part of the vehicle charging system 8. 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 arranged on the ground in Fig.1 can alternatively be arranged sunk into the roadway (not shown here). In a sunk arrangement, the inductive charging device 1b can be covered by certain layers of the roadway or can be flush with the road surface. Fig.2 shows a plan view of a vehicle 2 with a mobile inductive charging device 1a, which is to be positioned above a stationary inductive charging device 1b, wherein here theLongitudinal direction of the vehicle 6 deviates from the direction toward the stationary inductive charging device 1b (connecting line 12 between vehicle 2 and the stationary inductive charging device 1b) by a directional deviation value 17 or a corresponding directional deviation angle 39. Fig. 3 shows a rough schematic of the detection and evaluation of the sensor signals. The sensor signals, here the voltage signals, are detected in a signal detection unit 14 and evaluated in an evaluation unit 15. Fig. 4 shows a schematic of the evaluation unit. The positioning signal 40 induces a first voltage signal 13a in a first sensor winding 9a (not shown) and a second voltage signal 13b in a second sensor winding 9b (not shown). The two sensor windings 9a, 9b are part of the signal detection unit 14. The intensity of the respective voltage signals and in particular the ratio of the two voltage signals to one another provides information about the position,in particular, the angular position of the vehicle in comparison to the stationary inductive charging device. Since the two sensor windings are arranged symmetrically to the longitudinal direction of the vehicle 6, a 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-to-digital conversion unit 16. The two sampled signals are then evaluated separately in a computing unit 19. The computing unit 19 initially contains a fast Fourier transformation 20. Here, the signals are efficiently transformed into a discrete signal in the frequency domain. A filter 21 then filters out only the frequency range around the excitation frequency of the positioning signal 40. This efficiently filters out signal interference, thus achieving significantly higher accuracy and therefore alsoRange is reached. A maximum determination 22 is then carried out in the filtered frequency band. The two maximum values ​​23 determined in this way are compared with each other in a comparison unit 24. For example, a directional deviation value between -1 and 1 can be determined by subtracting the two maximum values ​​and normalizing to the larger of the two maximum values. Finally, a moving average is determined from several directional deviation values ​​17 in an averaging unit 25. This compensates for fluctuations and thus enables an even greater range. The averaged directional deviation value 18 will now be graphically displayed on an exemplary direction display 26. Fig. 5 shows a simple possibility of a signal acquisition unit 14 with indicated evaluation unit 15. A positioning signal 40 induces a voltage in the two sensor windings 9a, 9b. The induced voltages at the firstSensor winding 9a and the second sensor winding 9b are measured directly. The first voltage signal 13a and the second voltage signal 13b are then converted into a digital signal in an analog-to-digital conversion unit 16 and further processed in the further evaluation unit 15. Fig. 6 shows an alternative embodiment of a signal acquisition unit 14 with an indicated evaluation unit 15. In contrast to the embodiment from Fig. 5, an oscillating circuit 31 is used for signal acquisition. The oscillating circuit 31 here consists of the respective sensor winding 9, a capacitance 27, and a damping resistor 28. The damping resistors 28 can optionally be omitted. The resonant frequency of the oscillating circuit is tuned to the excitation frequency, i.e., the frequency at which the corresponding positioning signal 40 was transmitted. Fig. 7 shows a further alternative embodiment of a signal acquisition unit 14 with an oscillating circuit 31 andwith indicated evaluation unit 15. Here, too, the resonant circuit 31 consists of the respective sensor winding 9, a capacitance 27 each, and a damping resistor 28 each. The damping resistors 28 are also optional. The resonant frequency of the resonant circuit is also tuned to the excitation frequency of the positioning signal 40. In contrast to the embodiment in Fig. 6, however, no voltage measurement is carried out here; instead, the signal is determined via a potential-free current measurement 29. Fig. 8 shows a further embodiment of an resonant circuit 31 as in Fig. 7. Here, however, the current in the respective resonant circuit 31 is determined via a shunt 30 by means of a so-called shunt measurement. In addition to the alternatives shown so far, it is also possible to perform a direct voltage measurement on the two sensor windings 9 or on the two capacitances 27 (not shown). Fig. 9 shows a lateral section through a mobile inductiveCharging device 1a, which includes several flux guiding elements 5 and a power transmission winding 4, 4a and is mounted on a vehicle 2. A corresponding arrangement is also possible for a stationary inductive charging device 1b, except that this is mounted, for example, on, at, or under a floor (not shown). Fig. 10 shows schematically how the directions, in particular the radial longitudinal direction 11, are defined in a winding, in particular in a sensor winding. The example in Fig. 10 is a cylindrical coil with five turns. The direction along which the winding was wound is the winding axis 36. The coil here has a rectangular, not square, cross-section. The direction along the longer side of the rectangle is called the radial longitudinal direction 11. If the cross-section is not rectangular, but elliptical, the radial longitudinal direction 11 runs along the main axis of the ellipse. Fig. 11 shows aTop view of an inductive charging device 1 according to the invention. This can be a mobile inductive charging device 1a or a stationary inductive charging device 1b. In the present exemplary embodiment, eight flux guiding elements 5 are shown, which are arranged radially around the center 7 of the energy transmission winding 4 in the plane. Narrow gaps 32 are between the flux guiding elements 5. The energy transmission winding 4, which is arranged below the flux guiding elements 5 with respect to this top view, is indicated by dashed lines. The energy transmission winding 4 is a flat coil 10 here. A first sensor winding 9a is arranged around one of the flux guiding elements 5, and a second sensor winding 9b is arranged around another flux guiding element 5. The sensor windings are designed here as cylindrical coils. The first sensor winding 9a is arranged axially symmetrically to the second sensor winding 9b with respect to the longitudinal direction of the vehicle 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. The angle 31 between the first radial longitudinal direction 11a and the longitudinal direction of the vehicle 6 is at least approximately equal to the 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 cross at least approximately in 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. During the charging process, the vehicle 2 is positioned above the stationary inductive charging device 1b, and energy is transferred to the mobile inductive charging device 1a or from the mobile inductive charging device 1a to the stationary inductive charging device 1b.The flux guide elements 5 assume the function of guiding the magnetic field. In the charging state, the field lines of the magnetic field within them run approximately radially. Three magnetic field lines 35 are symbolically indicated in Fig. 11. Since the first radial longitudinal direction 11a and the second radial longitudinal direction 11b are also radially aligned and thus at least approximately parallel to the magnetic field lines 35, relatively little or no voltage is induced in the first sensor winding 9a and the second sensor winding 9b. This is important, as the high power levels of the energy transfer could otherwise easily lead to the sensor windings being destroyed. Fig. 12 shows a plan view of another embodiment of an inductive charging device 1 according to the invention. Here, four sensor windings (a first sensor winding 9a, a second sensor winding 9b, a third sensor winding 9c, and a fourth sensor winding 9d) are shown.present. Each sensor winding is arranged around a different one of the eight flux guiding elements 5. Two of the flux guiding elements are located diagonally opposite each other with respect to the center 7 of the energy transmission coil 4. Together, the four sensor windings 9a, 9b, 9c, and 9d form a cross-shaped arrangement. Compared to Fig. 11, a larger area is covered with sensor windings here. At the same time, the area around the center 7 of the energy transmission winding remains free, so that the mechanically necessary support elements (not shown) can be arranged there. Two of the sensor windings at a time – for example, the diagonally opposite windings – can be electrically connected in series, for example. The sensor windings are designed here in the form of conductor tracks 38 on circuit boards 37. Alternatively, the sensor windings can also be designed as stranded wires (not shown). Fig. 13 shows an inductive charging device 1 with aEnergy transmission winding 4 and several flux guiding elements 5. The energy transmission winding 4 is designed as a flat coil 10. A positioning signal winding Error! Reference source could not be found. is arranged around the flux guiding elements 5 and around the energy transmission winding 4. The positioning signal winding 41 is designed as a solenoid 42. The positioning signal winding 41 is arranged centrally and runs across the center of the energy transmission winding 4. Fig. 14 a) shows a vehicle 2 with a longitudinal direction of the vehicle 6 with a mobile inductive charging device 1a during a positioning process above a stationary inductive charging device 1b with a desired vehicle longitudinal direction 6a. The vehicle 2 drives directly towards the stationary inductive charging device 1b and the desired vehicle longitudinal direction 6a is thus the same as the longitudinal direction of the vehicle 6. In the mobile inductive charging device 1a, in addition toThe energy transmission winding (not shown) also has a positioning signal winding 41. The positioning signal winding 41 has a winding axis 36 and a radial longitudinal direction 11. The stationary inductive charging device 1b has, in addition to the energy transmission winding (not shown), two sensor windings 9a and 9b. Both sensor windings each have a radial longitudinal direction 11a and 11b. Both sensor windings are arranged symmetrically to the desired vehicle longitudinal direction 6a. This arrangement of the windings is particularly advantageous for positioning. The positioning signal winding 41 generates a fairly homogeneous magnetic field. A voltage is induced in the sensor windings 9a and 9b by the magnetic field of the positioning signal winding 41. If the vehicle travels exactly perpendicularly towards the stationary inductive charging device 1b, as shown in the left sketch, an equal voltage is induced in both sensor windings 9a and 9b. Fig. 14 b) showsan embodiment in which the positioning signal winding 41 is arranged in the stationary inductive charging device 1b and the sensor windings 9a and 9b are arranged in the mobile inductive charging device 1a. The functionality of this embodiment is otherwise exactly the same. Shown here is a case in which the vehicle 2 does not approach the stationary inductive charging device 1b perpendicularly, but deviates from it at an angle of approximately 45°. The longitudinal direction of the vehicle 6 and the connecting line between the stationary inductive charging device and the mobile inductive charging device 12 are thus at a directional deviation angle 39 of 45°. In this case, the positioning signal winding 41 generates a magnetic field that is perpendicular to the first sensor winding 9a. A maximum voltage is induced here. The magnetic field generated by the positioning signal winding 41 is also approximately parallel to the secondSensor winding 9b. Minimal or no voltage is induced here. Reference numeral 1 Inductive charging device 1a Mobile inductive charging device 1b Stationary inductive charging device 2 Vehicle 3 Vehicle energy storage device 4 Energy transfer winding 4a Energy transfer winding in mobile inductive charging device 4b Energy transfer winding in stationary inductive charging device 5 Flux guide element 6 Longitudinal direction of the vehicle 6a Target vehicle longitudinal direction 7 Center of the energy transfer 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 Connecting line between the stationary inductive charging device and the mobile inductive charging device 13 Voltage signal 13a First voltage signal 13b Second voltage signal 14 Signal acquisition unitEvaluation unit Analog-digital conversion unit Directional deviation value Averaged directional deviation value Computation unit Fast Fourier transformation Filter Maximum determination Maximum value Comparison unit Averaging Directional indicator Capacitance Damping resistor Potential-free current measurement Shunt Resonant circuit Gap between flux guiding elements First angle Second angle Magnetic field line Winding axis Printed circuit board Conductive tracks Directional deviation angle Positioning signal Positioning signal winding Solenoid

Claims

Claims 1. A method for positioning a vehicle (2) with a mobile inductive charging device (1a) in a defined position relative to a stationary inductive charging device (1b), wherein - the mobile inductive charging device (1a) or the stationary inductive charging device (1b) has a first sensor winding (9a) with a first radial longitudinal direction (11a) and a second sensor winding (9b) with a second radial longitudinal direction (11b), - the first radial longitudinal direction (11a) and the second radial longitudinal direction (11b) are arranged at an angle between 70° and 110° to each other, preferably perpendicular to each other and at an angle between 35° and 55° to the longitudinal direction of the vehicle (6) or to the desired longitudinal direction of the vehicle (6a), preferably at a 45° angle to the longitudinal direction of the vehicle (6) or to the desired longitudinal direction of the vehicle (6a),- a positioning signal (40) in the first sensor winding (9a) generates a first voltage signal (13a) and in the second sensor winding (9b) a second voltage signal (13b), - that at least one first voltage signal (13a) is detected in a signal acquisition unit (14), - that at least one second voltage signal (13b) is detected in a signal acquisition unit (14), - an evaluation unit (15) converts the first voltage signal (13a) into a first digital signal and converts the second voltage signal (13b) into a second digital signal and processes and compares the first digital signal and the second digital signal, - the processing of the first digital signal and the second digital signal includes a transformation into the frequency domain, and - a directional deviation value (17) between the longitudinal direction of the vehicle (6) and the connecting line (12) between the stationary inductive charging device (1b) and the mobile inductive charging device (1a) is calculated from the comparison of the first digital signal with the second digital signal.

2. Method according to claim 1, wherein the positioning signal (40) is generated in the stationary inductive charging device (1b) or in the mobile inductive charging device (1a).

3. Method according to claim 1 or 2, wherein the transformation into the frequency domain is realized by a discrete Fourier transform, in particular by a fast Fourier transform (FFT). 4.A method according to any one of the preceding claims, characterized in that the signal transformed into the frequency domain is filtered by a filter (21) with a bandwidth B around the excitation frequency.

5. A method according to any one of the preceding claims, characterized in that an average directional deviation value (18) is determined by forming an average value, in particular a moving average value, from several, in particular 10, directional deviation values ​​(17) determined at discrete, successive time points.

6. A method according to any one of the preceding claims, characterized in that. - the first voltage signal (13a), which is converted into a first digital signal in the evaluation unit (15), is directly the voltage drop across the first sensor winding (9a), and - the second voltage signal (13b), which is converted into a second digital signal in the evaluation unit (15), is directly the voltage drop across the second sensor winding (9b).

7. Method according to any one of claims 1-5, characterized in that - the signal acquisition unit (14) has a first resonant circuit (31) comprising at least the first sensor winding (9a) and a first capacitor (27), and - the signal acquisition unit (14) has a second resonant circuit (31) comprising at least the second sensor winding (9b) and a second capacitor (27). 8.A method according to claim 7, characterized in that the first resonant circuit (31) has a first damping resistor (28) and the second resonant circuit (31) has a second damping resistor (28).

9. A method according to any one of claims 6-8, characterized in that the signal acquisition unit (14) includes a potential-free current measurement (29) or a shunt measurement.

10. A method according to any one of the preceding claims, characterized in that the directional deviation value (17) or the averaged directional deviation value (18) or a value derived from the directional deviation value (17) or from the averaged directional deviation value (18) is The value is transmitted via a data interface to a bus system, preferably a CAN bus or to another processing unit.

11. Method according to one of the preceding claims, characterized in that the direction deviation value (17) or the averaged direction deviation value (18) or a value derived from the direction deviation value (17) or from the averaged direction deviation value (18) is displayed on a direction indicator (26) in the vehicle (2). 12.A method according to one of the preceding claims, characterized in that – the mobile inductive charging device (1a) and / or the stationary inductive charging device (1b) comprises at least one flux guide element (5) and at least one energy transfer winding (32), – the at least one flux guide element (5) is suitable for guiding a magnetic field during an energy transfer which takes place between an energy transfer winding (4a) of the mobile inductive charging device (1a) and an energy transfer winding (4b) of the stationary inductive charging device (1b), and – 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).

13. A 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 area spanned by the energy transfer winding (4).

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

15. The method of any one of claims 12-144, characterized in that the first radial longitudinal direction (11a) and the second radial longitudinal direction (11b) are at least approximately parallel to the main direction of the magnetic field lines (35) that form during energy transfer in the flux guide element (5) in the area covered by the sensor winding.

16. The method of any one of claims 2-15, characterized in that the stationary inductive charging device (1b) or the mobile inductive charging device (1a) has at least two windings, wherein the first winding is an energy transfer winding (4) and the second winding is a positioning signal winding (41). 17.The method according to claim 16 is characterized in that - the positioning signal winding (41) is designed as a solenoid (42) with a winding axis in the longitudinal direction of the vehicle (6) or the intended longitudinal direction of the vehicle (6a) and - the stationary inductive charging device (1b) or the mobile inductive charging device (1a) contains at least one flux guidance element (5) and the flux guidance element (5) is suitable to guide a magnetic field during an energy transfer process which takes place between a further inductive charging device (1) and the energy transfer winding (4) and - the positioning signal winding (41) surrounds at least one of the at least one flux guidance elements (5).

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