DE102018209660A1 - Method and device for determining the positioning of the coils of an inductive charging system - Google Patents

Abstract

A device (507) for determining position information relating to a secondary coil (121) of a secondary unit (120) relative to a primary coil (111) of a primary unit (110) is described. The primary unit (110) comprises a reception coil (211), which is set up to detect a measurement signal (520) with respect to a magnetic measurement field (410) generated by a transmission coil (201) of the secondary unit (120). The device (507) is set up to generate a compensation signal (612) for a magnetic charging field (400) present in a direct vicinity of the receiving coil (211). In addition, the device (507) is set up to compensate, based on the compensation signal (612), at least partially for an influence of the charging field (400) on the measurement signal (520) detected by the reception coil (211) in order to provide a compensated measurement signal (620). Furthermore, the device (507) is set up to determine a signal strength (610) of the measuring field (410) on the receiving coil (211) on the basis of the compensated measurement signal (620), and position information in relation to a signal based on the signal strength (610) Determine the position of the secondary coil (121) relative to the primary coil (111).

Description

The invention relates to a method and a device for determining the positioning or the alignment of a secondary coil relative to the primary coil of an inductive charging system, in particular for charging the energy store of a vehicle.

Vehicles with an electric drive have an electrical energy store in which electrical energy for operating an electrical machine of the vehicle can be stored. The vehicle's energy storage device can be charged with electrical energy from a power supply network. For this purpose, the energy store is coupled to the power supply network in order to transfer the electrical energy from the power supply network into the energy store of the vehicle. The coupling can be wired (via a charging cable) and / or wireless (using an inductive coupling between a charging station and the vehicle).

One approach to the automatic, wireless, inductive charging of the energy store of the vehicle is that electrical energy is transmitted to the energy store from the floor to the underbody of the vehicle via magnetic induction via the underbody clearance. A primary coil on the ground generates a magnetic charging field that induces a charging current on a secondary coil of the vehicle.

For energy-efficient charging, the highest possible coupling factors between the primary coil and the secondary coil are advantageous. If a vehicle is parked in an imprecise manner in a parking position, the coils may be offset laterally and thus the coupling factor of the inductive coupling system comprising the primary coil and the secondary coil may be reduced.

In order to support the positioning of a vehicle over a primary coil, one or more transmitter coils of the vehicle can generate a magnetic positioning or measuring field, which can be detected by one or more receiving coils of the charging station. The position of the vehicle relative to the primary coil can then be determined on the basis of the field strengths of the measuring field recorded on the one or more receiving coils.

It can happen that the position of the vehicle relative to the primary coil changes during an ongoing inductive charging process (e.g. because the vehicle rolls away). This can lead to a reduction in the coupling factor and thus to a reduction in the energy efficiency of the charging process. Furthermore, the safety of the inductive charging system can be impaired, especially if there is a relatively large offset between the primary coil and the secondary coil (e.g. because an area above the primary coil is accessible to people).

The present document deals with the technical problem of enabling a precise determination of the positioning of a secondary coil relative to a primary coil in an efficient manner even during an inductive charging process.

The task is solved in each case by the independent claims. Advantageous embodiments include described in the dependent claims. It is pointed out that additional features of a claim dependent on an independent claim without the features of the independent claim or only in combination with a subset of the features of the independent claim can form a separate invention that is independent of the combination of all features of the independent claim can be made the subject of an independent claim, a divisional application or a late application. This applies in the same way to the technical teachings described in the description, which can form an invention that is independent of the features of the independent claims.

According to one aspect, a device for determining position information relating to a secondary coil of a secondary unit (for example a vehicle) relative to a primary coil of a primary unit (for example a floor unit) is described. The primary coil is set up to generate a magnetic charging field in order to transmit electrical energy to the secondary coil (for example to charge the energy store of a vehicle). Furthermore, the primary unit comprises at least one reception coil, which is set up to detect a measurement signal with respect to a magnetic measurement field generated by a transmission coil of the secondary unit. The magnetic measuring field can be superimposed by a magnetic charging field, the energy of the charging field being significant (for example by the factor 5 . 10 . 100 or more) can be above the energy of the measuring field. As a result, the positioning of the secondary coil based on the measuring field can be falsified, in particular during a charging process.

The device is set up to generate a compensation signal for a magnetic charging field that is present in the direct vicinity of the receiving coil. The compensation signal is dependent on the charging field frequency of the Charging field generated. The device can be part of the primary unit, or at least connected to the primary unit via a data connection. If the charging field is generated by the primary unit itself, the charging field frequency can be determined directly. If the charging field is generated by a further primary unit, the charging field frequency can be transmitted to the device via a communication link (for example via radio).

The detected measurement signal can comprise an interference signal (possibly only) dependent on the charging field and a useful signal (possibly only) dependent on the measuring field. The energy of the interference signal can be significantly higher (e.g. by a factor of 5, 10, 100 or more) than the energy of the useful signal.

The device can in particular be set up to set the phase of the compensation signal as a function of the detected measurement signal, in particular in such a way that a distance measure (e.g. the difference) between the phase of the detected measurement signal and the phase of the compensation signal is reduced, in particular minimized. Coordination of the phases of the compensation signal and the detected measurement signal provides a reliable approximation of the phase of the charging field (or the interference signal) in particular when the energy of the interference signal is significantly higher than the energy of the useful signal.

As an alternative or in addition, the device can be set up to set the amplitude of the compensation signal as a function of the detected measurement signal, in particular in such a way that the difference or another distance measure between the amplitude of the compensation signal and the amplitude of the detected measurement signal is reduced, in particular minimized. Coordinating the amplitudes of the compensation signal and the detected measurement signal provides a reliable approximation of the amplitude of the charging field (or the interference signal) when the energy of the interference signal is significantly higher than the energy of the useful signal.

The device is further configured to use the compensation signal to at least partially compensate for the influence of the charging field on the measurement signal detected by the reception coil in order to provide a compensated measurement signal. The device can be set up to subtract the compensation signal from the detected measurement signal in order to determine the compensated measurement signal. As a result of the compensation of the influence of the compensation signal, it can be caused that the energy portion of the useful signal in the compensated measurement signal is greater than the energy portion of the useful signal in the detected measurement signal. The signal strength of the measuring field at the receiving coil can then be determined with increased accuracy on the basis of the compensated measuring signal. In particular, the signal strength of the compensated measurement signal or a frequency component of the compensated measurement signal can be determined in order to determine the signal strength of the measurement field.

The device thus makes it possible to determine the signal strength of a measuring field for determining the position of a secondary coil relative to a primary coil with increased accuracy. Furthermore, the device can be set up to determine position information in relation to the position of the secondary coil relative to the primary coil on the basis of the signal strength determined. The accuracy of the position determination can thus be increased (even during an ongoing inductive charging process).

The device can comprise a compensation coil which is magnetically coupled to the receiving coil, in particular via a common ferromagnetic coil core. The device can be set up to generate a magnetic compensation field in the vicinity of the receiving coil by means of the compensation coil and as a function of the compensation signal (for example by means of a current through the compensation coil that depends on the compensation signal), so that the magnetic charging field in the vicinity of the Receiving coil is at least partially compensated. In this way, the influence of the inductive charging field can be compensated for directly at the receiving coil, so that saturation effects of a coil core of the receiving coil can be avoided. Furthermore, a reduced design of electronic components of the device is made possible.

The device can comprise an amplifier which is set up to amplify the compensated measurement signal instead of the detected measurement signal. The amplifier can be an input amplifier on the receiving coil. The compensation can thus take place before the amplification of the measurement signal, so that the design of electronic components of the device can be reduced.

The device can be set up to modulate the compensated measurement signal with a modulation signal (for example with a square-wave signal) in order to provide a modulated measurement signal. The modulation signal can have a modulation frequency that depends on (or corresponds to) the charging field frequency of the magnetic charging field present in the immediate vicinity of the receiving coil. Furthermore, the device can be set up to transmit the modulated measurement signal by means of a Filter (bandpass) filters in order to extract a frequency component of the modulated measurement signal. The filter (in particular a cutoff frequency of the filter) can depend on the measuring field frequency of the measuring field (and possibly on the charging field frequency). The amplitude of the extracted frequency component can (possibly alone) depend on the measuring field (and in particular not on the loading field). The signal strength of the measuring field at the receiving coil can then be determined with particularly high accuracy on the basis of the extracted frequency component.

According to a further aspect, a further device for determining position information relating to a secondary coil of a secondary unit (for example a vehicle) relative to a primary coil of a primary unit (for example a floor unit) is described. The primary coil is set up to generate a magnetic charging field in order to transmit electrical energy to the secondary coil (for example to charge the energy store of a vehicle). Furthermore, the primary unit comprises at least one reception coil, which is set up to detect a measurement signal with respect to a magnetic measurement field generated by a transmission coil of the secondary unit. As already explained above, the magnetic measuring field can be superimposed by a magnetic charging field, the energy of the charging field being significant (for example by the factor 5 . 10 . 100 or more) can be above the energy of the measuring field. As a result, the positioning of the secondary coil based on the measuring field can be falsified, in particular during a charging process.

The device is set up to modulate a measurement signal detected by or derived from the reception coil with a modulation signal in order to provide a modulated measurement signal. The modulation signal has a modulation frequency that depends on the charging field frequency of a magnetic charging field that is present in the immediate vicinity of the receiving coil. The modulation signal can comprise or be a square wave signal. In this case, the device can be set up to determine the modulated measurement signal in an efficient manner by periodically reversing the sign of the measurement signal (according to the modulation frequency).

The acquired or derived (e.g. compensated) measurement signal can comprise an interference signal dependent on the charging field and a useful signal dependent on the measuring field. The energy of the interference signal can be significantly higher (e.g. by a factor of 5, 10, 100 or more) than the energy of the useful signal.

The modulated measurement signal can be filtered using a (bandpass) filter in order to extract a frequency component of the modulated measurement signal. The filter can depend on the measuring field frequency of the measuring field. The modulation frequency can be equal to the charging field frequency. Alternatively, the modulation frequency can be equal to the charging field frequency times a rational factor not equal to one. In this way, the distance between different frequency components of the modulated measurement signal can be increased, and thus the accuracy of the extraction of a frequency component can be increased. In particular, the modulation frequency can be such that the frequency spacing between the extracted frequency component and a directly adjacent frequency component of the modulated measurement signal is greater than the frequency spacing between the measuring field frequency and the charging field frequency, in particular by a factor of 2, 3, 5, 10 or more.

The extracted frequency component is preferably selected in such a way that, apart from the modulation signal, the extracted frequency component depends only on the useful signal. Consequently, the signal strength of the measuring field at the receiving coil can be determined with high accuracy on the basis of the extracted frequency component. The device can also be set up to determine precise position information in relation to the position of the secondary coil relative to the primary coil on the basis of the signal strength.

As already explained above, the primary unit of an inductive charging system can be arranged next to a further primary unit of a further charging system. The magnetic charging field present in the immediate vicinity of the receiving coil of the primary unit can then be generated by the further primary unit. A device described in this document can be set up, in particular via a wireless communication link, to receive frequency information relating to the charging field frequency of the magnetic charging field, which is generated by the further primary unit. In this way, malfunctions of an adjacent charging process can be compensated for by positioning on an inductive charging system.

The filter for extracting the frequency component can have a bandwidth that makes it possible to extract the relevant frequency component of the modulated measurement signal for all possible charging field frequencies from a predefined charging field frequency range (e.g. between 8 kHz and 90 kHz). This enables an efficient extraction of the relevant frequency component.

According to a convention, it can be provided that a measuring field is to be generated by the transmitting unit during a charging process (for example in order to continuously Position of the secondary coil relative to the primary coil). A device described in this document can be set up to determine on the basis of the determined signal strength of the measuring field whether a measuring field is generated by the transmitting unit or not. Furthermore, the device can be set up to cause the primary unit to prevent the generation of the magnetic charging field if it is determined that no measuring field is generated by the transmitting unit. A measuring field can thus be used to interrupt a charging process. In particular, a secondary unit can thus be enabled to interrupt a charging process in an efficient and reliable manner (without using an additional communication connection).

A device described in this document can be set up to determine a current value of the charging field frequency (e.g. based on an oscillator for controlling the primary coil or for controlling a further primary coil of an adjacent charging system). The operation of the device can then be adapted as a function of the current value of the charging field frequency. In particular, the frequency of a compensation signal and / or a modulation signal can be adapted. Furthermore, the cutoff frequency of a filter can be adjusted to extract a frequency component. This enables flexible adaptation to the operation of a charging system.

A device described in this document can be set up to determine the compensation signal, the compensated measurement signal, the modulated measurement signal and / or the signal strength of the measurement field in an efficient and precise manner at least partially or completely by means of analog hardware.

A device described in this document can be set up to determine signal strengths of the measuring field on a plurality of receiving coils and / or signal strengths of the measuring fields of a plurality of transmitting coils. Based on the signal strengths, position information can then be determined in relation to the position of the secondary coil relative to the primary coil (e.g. using a triangulation method). In this way, the position of a secondary coil can be determined with increased accuracy.

A device described in this document can be set up to determine the signal strength of at least one measuring field on the receiving coil that was generated by a transmitting coil that is arranged on a further secondary unit (e.g. on a further secondary unit of an adjacent charging system). This signal strength can then also be taken into account when determining the position information. In this way, the position of a secondary coil can be determined with increased accuracy.

According to a further aspect, a primary unit, in particular a base unit, for an inductive charging system is described, which comprises at least one of the devices described in this document for determining position information.

According to a further aspect, an inductive charging system is described which comprises the primary unit described in this document.

According to a further aspect, a method for determining position information relating to a secondary coil of a secondary unit relative to a primary coil of a primary unit is described. The method comprises generating a compensation signal for a magnetic charging field that is present in a direct environment of the receiving coil, the compensation signal being generated as a function of the charging field frequency of the charging field. In addition, the method comprises determining a compensated measurement signal by at least partially compensating an influence of the charging field on the measurement signal detected by the receiving coil by means of the compensation signal. Furthermore, the method includes determining, based on the compensated measurement signal, a signal strength of the measurement field at the reception coil. In addition, the method may include determining, based on the signal strength, position information in relation to a Position of the secondary coil relative to the primary coil.

According to a further aspect, a further method for determining position information relating to a secondary coil of a secondary unit relative to a primary coil of a primary unit is described. The method comprises modulating a measurement signal detected by or derived from the reception coil with a modulation signal in order to provide a modulated measurement signal, the modulation signal having a modulation frequency that depends on the charging field frequency of a magnetic charging field that is present in the immediate vicinity of the receiving coil. In addition, the method comprises filtering the modulated measurement signal by means of a filter in order to extract a frequency component of the modulated measurement signal, the filter depending on the measurement field frequency of the measurement field. Furthermore, the method includes determining, based on the extracted frequency component, a signal strength of the measuring field at the receiving coil. Furthermore, the method can include determining, based on the signal strength, position information in relation to a position of the secondary coil relative to the primary coil.

According to a further aspect, a software (SW) program is described. The SW program can be set up to run on a processor and thereby perform one of the methods described in this document.

According to a further aspect, a storage medium is described. The storage medium can comprise a software program which is set up to be executed on a processor and thereby to carry out one of the methods described in this document.

It should be noted that the methods, devices and systems described in this document can be used both alone and in combination with other methods, devices and systems described in this document. Furthermore, any aspect of the methods, devices and systems described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways.

• 1 beispielhafte Komponenten eines induktiven Ladesystems;
• 2 beispielhafte Sende- und Empfangsspulen zur Ermittlung der relativen Positionierung zwischen einem Fahrzeug und einer Ladestation;
• 3a beispielhafte Sende- und Empfangsspulen in einer Seitenansicht;
• 3b beispielhafte Sende- und Empfangsspulen in einer schematischen Darstellung;
• 3c beispielhafte Sende- und Empfangsspulen in einer Draufsicht;
• 4a ein beispielhaftes Messfeld einer Sendespule und ein beispielhaftes Ladefeld einer Primärspule;
• 4b beispielhafte Parameter eines Messfeldes und eines Ladefeldes;
• 5a eine beispielhafte Signalverarbeitung zur Ermittlung der Signalstärke eines Messfeldes;
• 5b ein beispielhaftes überlagertes Messsignal an einer Empfangsspule;
• 6a eine beispielhafte Vorrichtung zur Kompensation des Ladefeldes;
• 6b ein beispielhaftes kompensiertes Messsignal einer Empfangsspule;
• 7a eine beispielhafte Vorrichtung zur Extraktion einer Messsignal-Frequenzkomponente aus einem Messsignal;
• 7b beispielhafte Frequenzkomponenten eines Messsignals;
• 7c beispielhafte Frequenzkomponenten eines modulierten Messsignals;
• 8a eine beispielhafte Vorrichtung zur Kompensation des Ladefeldes;
• 8b eine weitere beispielhafte Vorrichtung zur Kompensation des Ladefeldes; und
• 9a und 9b Ablaufdiagramme von beispielhaften Verfahren zur Ermittlung der Positionierung einer Primärspule und einer Sekundärspule.

The invention is described in more detail below on the basis of exemplary embodiments. Show

• 1 exemplary components of an inductive charging system;
• 2 exemplary transmission and reception coils for determining the relative positioning between a vehicle and a charging station;
• 3a exemplary transmission and reception coils in a side view;
• 3b exemplary transmission and reception coils in a schematic representation;
• 3c exemplary transmission and reception coils in a plan view;
• 4a an exemplary measuring field of a transmitter coil and an exemplary charging field of a primary coil;
• 4b exemplary parameters of a measuring field and a charging field;
• 5a an exemplary signal processing for determining the signal strength of a measuring field;
• 5b an exemplary superimposed measurement signal on a receiving coil;
• 6a an exemplary device for compensation of the charging field;
• 6b an exemplary compensated measurement signal of a receiving coil;
• 7a an exemplary device for extracting a measurement signal frequency component from a measurement signal;
• 7b exemplary frequency components of a measurement signal;
• 7c exemplary frequency components of a modulated measurement signal;
• 8a an exemplary device for compensation of the charging field;
• 8b another exemplary device for compensation of the charging field; and
• 9a and 9b Flow diagrams of exemplary methods for determining the positioning of a primary coil and a secondary coil.

As stated at the beginning, the present document deals with the efficient and precise determination of the positioning and / or the orientation of the secondary coil of a vehicle relative to the primary coil of a base unit of an inductive charging system. In this context shows 1 a vehicle 100 with an energy storage 103 for electrical energy (e.g. with a rechargeable battery 103 ). The vehicle 100 includes a secondary coil 121 in the vehicle underbody, with the secondary coil 121 via a rectifier (as part of the secondary electronics 123 ) with the energy storage 103 connected is. The secondary coil 121 is typically part of a so-called "Wireless Power Transfer" (WPT) vehicle unit 120 or secondary unit 120 ,

The secondary coil 121 the WPT vehicle unit 120 can over a primary coil 111 be positioned with the primary coil 111 for example on the floor of a garage. The primary coil 111 is typically part of a so-called WPT floor unit 110 or primary unit 110 or charging station 110 , The primary coil 111 is with a power supply 113 connected. The power supply 113 may include a radio frequency generator or inverter that has an AC (Alternating Current) current in the primary coil of the WPT ground unit 110 generated, whereby a magnetic field (in particular a magnetic charging field or a charging magnetic field) is induced. The magnetic charging field can have a frequency from a predefined charging field frequency range. The charging field frequency of the electromagnetic charging field can be in the range of 80-90 kHz (in particular at 85 kHz).

With sufficient magnetic coupling between the primary coil 111 the primary unit 110 and secondary coil 121 the secondary unit 120 about the underbody clearance 130 the magnetic charging field creates a corresponding voltage and thus also a current in the secondary coil 121 induced. The induced current in the secondary coil 121 is rectified by the rectifier and in the energy store 103 saved. So electrical energy can be wireless from the power supply 113 to energy storage 103 of the vehicle 100 be transmitted. The charging process can be done in the vehicle 100 by a charging control unit (as part of the secondary electronics 123 ) being controlled. The charging control device can be set up for this purpose, for example wirelessly (for example via WLAN), with the primary unit 110 to communicate.

To the greatest possible field strengths of the magnetic charging field for bridging the underbody clearance 130 to be able to manufacture, resonant systems can be used. Both the primary coil 111 as well as the secondary coil 121 integrated in resonant circuits via the primary coil 111 and the secondary coil 121 are coupled together. In particular, the primary unit is in a primary resonant circuit 110 due to a relatively low coupling factor between the primary coil 111 and secondary coil 121 typically relatively high primary currents are used to generate a magnetic charging field with sufficient field strength.

2 shows an exemplary vehicle 100 with one or more transmitter coils 201 . 202 . 203 , with the transmitter coils 201 . 202 . 203 are set up, a (measuring) magnetic field or a magnetic measuring field 221 to create. On a floor unit 110 (commonly referred to as a charging station or primary unit) are one or more receiving coils 211 . 212 . 213 arranged, which are set up the measuring field 221 (which in 4a with the reference sign 410 is designated) a transmitter coil 201 . 202 . 203 to feel. In particular, from each receiving coil 211 . 212 . 213 the field strength of a measuring field 221 at the respective position of the receiving coils 211 . 212 213 be determined. Through a receiving coil 211 An actual field strength value can thus be determined, which is the value of the field strength of the measuring field 221 at the position of the receiving coil 211 displays. The value of the field strength of the measurement field 221 as a function of time is also referred to in this document as a measurement signal.

In the run-up to a positioning process, a map can be recorded, which is for a specific combination of vehicle 100 and charging station 110 (ie for a specific charging system) Reference field strength values as a function of the relative positioning between the vehicle 100 and charging station 110 or between the secondary coil 121 and primary coil 111 displays. The reference field strength value for a specific relative position (ie for a specific offset value of the offset between the primary coil 111 and secondary coil 121 ) can be the value of the field strength of the measuring field 221 at the position of the receiving coil 211 display when the vehicle 100 located at the specific relative position. The relative position can include a relative distance in the plane (X coordinates and Y coordinates). Furthermore, the relative position can include a relative distance in height (Z coordinates) (for example with different loads). In addition, the relative position can be a rotation or orientation between the vehicle 100 and floor unit 110 include. The characteristic diagram can thus display reference field strength values as a function of x, y and possibly z and / or the rotation or orientation. In particular, a reference curve of the reference field strength values as a function of x, y and possibly z and / or the rotation or orientation can be provided as a characteristic diagram. The map or the reference curve can be measured in advance for a charging system.

During a positioning process, the actual field strength value (for example the amplitude of a measurement signal) can now be compared with the reference field strength values from the predetermined characteristic diagram. In particular, the relative position can be determined, by means of which a (for example mean square) deviation between the actual field strength value and a reference field strength value from the predetermined characteristic map is reduced, in particular minimized. The relative position then shows the actual relative position 222 between the transmitter coil 201 and the receiving coil 211 on. If the position of the transmitter coil 201 (e.g. relative to the vehicle 100 ) and the position of the receiving coil 211 (e.g. relative to the floor unit 110 ) are known, can from the actual relative position 222 between the transmitter coil 201 and the receiving coil 211 the corresponding actual relative position 222 between secondary coil 121 and primary coil 111 be determined.

As in 2 can illustrate several different pairs of transmit coils 201 . 202 . 203 and receiving coils 211 . 212 . 213 be used. For each of these pairs, a characteristic diagram or a reference curve can be determined, which shows the reference field strength values on a receiving coil 211 . 212 . 213 as a function of the relative position or the offset. For example, from the transmitter coil 201 generated measuring field 221 by N receiving coils 211 . 212 . 213 recorded at different positions. Through each of the N receiving coils 211 . 212 . 213 an actual field strength value can be determined so that N actual field strength values are available. Furthermore, for each receiving coil 211 . 212 . 213 a map can be provided. The actual relative position 222 can then be determined by mean square) deviation between the N actual field strength values and N reference field strength values from the N characteristic maps or the N reference curves is reduced, in particular minimized.

Furthermore Q can transmit coils 201 . 202 . 203 used the Q measuring fields 221 produce. The measuring fields 221 can by N receiving coils 211 . 212 . 213 be received. N x Q maps or reference profiles can be provided for the N x Q pairs. Furthermore, during a positioning process, N x Q actual field strength values can be recorded, which can be compared with the N x Q characteristic diagrams or reference profiles by the actual relative position 222 to determine. By using multiple transmit coils 201 . 202 . 203 and / or receiving coils 211 . 212 . 213 the accuracy of the position determination can be increased. In particular, possible ambiguities due to symmetry in a map or in a reference curve can be eliminated.

There can thus be between pairs of Q transmit coils 201 . 202 . 203 and N receiving coils N x Q measurements are taken to determine N x Q actual field strength values.

Characteristic maps (in particular field strength measurement fields) or reference courses of the reference field strength values can be determined in advance for the N x Q pairs. These maps or reference profiles can be used for a specific charging system (ie for a specific combination of vehicle type 100 and floor unit 110 ) are recorded.

3a shows exemplary transmission coils 202 . 203 of a vehicle 100 and exemplary receiving coils 211 . 213 a floor unit 110 in a front view. Also shows 3a an exemplary evaluation unit or evaluation device 300 a floor unit 110 , Furthermore shows 3b an exemplary transmitter coil 201 and exemplary receiving coils 211 . 213 in a corresponding Cartesian coordinate system, the x-axis being the x-axis of the vehicle 100 and the z axis of the z or vertical axis of the vehicle 100 equivalent. 3c shows two transmitter coils 201 . 202 and four receiving coils 211 . 212 . 213 . 214 in a top view.

When positioning a vehicle 100 there may be an offset between the primary coil 111 and the secondary coil 121 exist in the x direction and / or in the y direction. Furthermore, depending on the loading of the vehicle 100 there is a different distance in the z direction.

4a shows field lines of the loading field 400 that from the primary coil 111 is generated. Furthermore shows 4a a field line of the measuring field 221 . 410 by a transmitter coil 202 is generated. Out 4b it can be seen that during a charging process, that of a receiving coil 211 detected magnetic field of an overlay from the charging field 400 and the measuring field 410 equivalent.

4b illustrates typical field strength values or flux density values and frequencies of the charging field 400 and the measuring field 410 (see the points 401 . 411 in the amplitude / frequency diagram 4b) , The loading field 400 typically has a flux density in the range of 2mT during the measurement field 410 one by the factor 10 . 100 or more smaller flux density in the range of 10µT. On the other hand, the frequencies of both magnetic fields are 400 . 410 relatively close to each other (e.g. at 85kHz for the charging field 400 and at 115kHz for the measuring field 410 ).

A magnetic measuring field is thus generated during a charging process 410 essentially from the magnetic charging field 400 covers, so that the field strength or the flux density of the measuring field 410 not easily by means of a receiving coil 211 can be measured. Thus, based on the in the 2a to 3c described coils 201 . 202 . 203 and / or receiving coils 211 . 212 . 213 . 214 not easily positioning the secondary coil 121 relative to the primary coil 111 be monitored during a charging process.

5a illustrates an example of signal processing with which a precise determination of the field strength or the flux density of a measuring field can also be carried out during a charging process 410 is made possible. It shows 5a especially as with a PFC (Power Factor Correction) unit 505 and an inverter 506 an alternating current can be generated from electrical energy from a supply network by means of the primary coil 111 a loading bay 400 to create. The loading field 400 poses for a receiving coil 211 an interference signal 500 On the other hand, that represents a transmitter coil 201 generated measuring field 410 for a receiving coil 211 a useful signal 510 represents the interference signal 500 shows the charging field frequency 501 on, and the useful signal 510 shows the measuring field frequency 511 of the measuring field 510 on.

From a receiving coil 211 thus becomes a sum signal 520 (also referred to in this document as a measurement signal) that detects an overlay from the useful signal 510 and the interference signal 500 shown. Exemplary useful, interference and sum signals 510 . 500 . 520 are in 5b shown.

5a also shows a device 507 that is set up based on the charging field frequency 501 the useful signal 510 from the sum signal 520 to extract. In other words, it can be an approximated useful signal 512 are determined, the most accurate approximation of the useful signal 510 equivalent. The approximated useful signal 512 can then in an evaluation unit 508 can be evaluated, for example by actual field strength values or the signal strength of the measuring field 410 to investigate.

6a illustrates an exemplary device 507 with which from a receiving coil 211 detected sum signal 520 can be processed to an approximated useful signal 512 . 610 to investigate. In particular, by the in 6a shown device 507 at least partially the interference signal 500 be compensated for by a compensated sum signal or measurement signal 620 to investigate.

The device 507 includes a signal generator 601 which is set up a compensation signal 603 to generate that the charging field frequency 501 having. In one phase unit 602 can the phase of the compensation signal 603 be adjusted (especially to the phase of the charging field 400 or the interference signal 500 be adjusted) and in an amplitude unit 608 can determine the amplitude of the (possibly phase-shifted) compensation signal 607 can be adjusted (especially to the amplitude of the charging field 400 or the interference signal 500 be adjusted).

The phase unit 602 is set up, the compensation signal 603 postponed (in units 606 ) to a (phase shifted) compensation signal 607 to generate. The delay may occur 8t 605 in a comparison unit 604 can be determined, which is set up the sum signal 520 with the (phase shifted) compensation signal 607 to compare. For this purpose, in the comparison unit 604 a distance measure between the phase of the sum signal 520 and the (phase shifted) compensation signal 607 determined and reduced, in particular minimized.

In the amplitude unit 608 can by means of the units 613 the amplitude of the sum signal 520 and the amplitude of a (amplified or damped) compensation signal 612 be determined. The units 613 can be set up the respective signals 520 . 612 rectify and / or filter using a low-pass filter. The amplitude of the sum signal 520 and the amplitude of the (amplified or damped) compensation signal 612 can in a comparison unit 611 be compared. Based on the comparison, the gain / damping factor 614 can be determined on the (possibly phase-shifted) compensation signal 603 . 607 is to be applied to by the reinforcement unit 609 the (amplified or attenuated) compensation signal 612 provide. The gain / damping factor 614 are determined in such a way that the amplitude of the (amplified or damped) compensation signal 612 as close as possible to the amplitude of the sum signal 520 lies.

It can therefore be a (amplified or damped and phase-shifted) compensation signal 612 be provided that in the sum signal 520 included interference signal 500 approximated (eg with a deviation of 2% or less). The compensation signal 612 can from the sum signal 520 be subtracted to the compensated sum signal 620 provide.

6b shows an exemplary useful signal 510 , an exemplary sum signal 620 and an exemplary compensated interference signal 600 (resulting from the difference between the interference signal 500 and the compensation signal 612 results). How out 6b can be seen, assign the useful signal 510 and the compensated interference signal 600 comparable amplitudes. As a result, the field strength or the flux density of the measuring field 410 with increased accuracy based on the compensated sum signal or measurement signal 620 be determined. In particular, in an evaluation unit 508 . 614 based on the compensated sum signal 620 the amplitude 610 of the useful signal 510 be determined. The charging field frequency 501 and / or a reference signal 603 with the charging field frequency 501 be taken into account.

As explained above, the (compensated) sum signal 520 . 620 an interference component 701 at the charging field frequency 501 and a useful component 711 at the measuring field frequency 511 on (see 7b) , Because the charging field frequency 501 and the measuring field frequency 511 typically relatively close to each other (e.g. at 85kHz vs. 115kHz), the useful component 711 typically not in a reliable and precise manner using a bandpass filter directly from the (compensated) sum signal 520 . 620 be extracted.

7a shows an exemplary evaluation device 614 , which is set up, the (compensated) sum signal 520 . 620 superimposed with a modulation signal to a modulated sum signal 720 to generate, which has at least one frequency component that does not depend on the amplitude of the (compensated) interference signal 500 . 600 (and only on the amplitude of the useful signal 510 ) depends, and which is relatively far in frequency from another frequency component of the modulated sum signal 720 is removed, so the modulated sum signal 720 in more efficient and precise Way through a bandpass filter 702 can be extracted.

A square wave signal with the charging field frequency can be used as the modulation signal 501 be used. The superimposition of the (compensated) sum signal 520 . 620 with the modulation signal can in a modulation unit 704 respectively. The superposition with a modulation signal with the charging field frequency 501 can be used as a synchronous demodulation of the useful signal 510 from the (compensated) interference signal 510 . 610 to be viewed as. 7c illustrates different frequency components of the modulated sum signal 720 , In particular shows 7c a frequency component 712 at 30kHz, which is not dependent on the amplitude of the (compensated) interference signal 500 . 600 depends. This frequency component 712 has a relatively large distance to the nearest component at 140kHz. So a filter 702 with the in 7c frequency response shown 706 used to be the frequency component 712 and thus a modulated useful signal 710 to extract. The amplitude 610 of the useful signal 510 can by one unit 613 based on the modulated useful signal 710 determined and in one measuring unit 703 be measured.

The in the 6a and 7a described processing of a detected sum signal 520 can be done by analog hardware. Alternatively or in addition, digital signal processing can take place.

A square-wave signal can be described by the following series, where ω = 2πf is the angular frequency and f is the frequency of the square-wave signal (in particular the charging field frequency 501 ). Here, h can have the value 1 if the modulation signal is a rectangle with the amplitude 1. $$f\left(t\right)=\frac{4H}{\pi }\left[\text{sin}\left(\omega t\right)+\frac{1}{3}\text{sin}\left(3\omega t\right)+\frac{1}{5}\text{sin}\left(5\omega t\right)+...\right]$$

wobei ω_Nutz die der Messfeldfrequenz 511 entsprechende Kreisfrequenz ist, wobei a_Nutz die Amplitude 610 des Nutzsignals 510 ist, wobei astörRed die Amplitude des (kompensierten) Störsignals 500, 600 ist, wobei ω_StörRed die Kreisfrequenz des (kompensierten) Störsignals 500, 600 ist und wobei φ eine Phase des (kompensierten) Störsignals 500, 600 ist. Dabei sind ω und ω_StörRed typischerweise identisch, da das Modulationssignal und das Störsignal 500, 560 bevorzugt vom selben Oszillator abgeleitet sind.The (compensated) sum signal 520 . 620 can be described as $$\text{s}\left(\text{t}\right)={\text{a}}_{\text{Nutz}}*\text{sin}\left({\mathrm{\omega }}_{\text{Nutz}}\text{t}\right)+{\text{a}}_{\text{StörRed}}*\text{sin}\left({\mathrm{\omega }}_{\text{StörRed}}\text{t +}\mathrm{\phi }\right)$$

where ω _Uses that of the measuring field frequency 511 is the corresponding angular frequency, where a _{Nutz is} the amplitude 610 of the useful signal 510 , where astörRed is the amplitude of the (compensated) interference signal 500 . 600 , where ω _{StörRed is} the angular frequency of the (compensated) interference signal 500 . 600 and where φ is a phase of the (compensated) interference signal 500 . 600 is. Here ω and ω _{StörRed are} typically identical, since the modulation signal and the interference signal 500 . 560 are preferably derived from the same oscillator.

The modulated sum signal 720 results from a convolution of the above-mentioned signals and / or from the relationship: sin (x) * sin (y) = (cos (xy) -cos (x + y)) / 2 for the individual spectral components of the sum signal 720 and the square wave signal with the charging field frequency 501 , where x is the right-hand signal and y is the (compensated) sum signal 520 . 620 are. It can thus be determined that the extracted frequency component 712 has the amplitude a ₀ * a _Nutz / 2, with a ₀ = 4h / π. Thus, from the amplitude of the extracted frequency component 712 or the extracted useful signal 710 the amplitude in a precise manner 610 of the useful signal 510 be determined.

8a illustrates another device 507 to compensate for the magnetic charging field 400 when determining the position of a secondary coil 121 relative to a primary coil 111 , By means of a reception coil 211 is a sum signal 520 detected. Furthermore, a compensation signal 612 determined (such as in connection with 6a set forth). The compensation signal 612 can at least partially to the sensor of the receiving coil 211 be fed back (e.g. to an amplifier 802 of the sensor, for example a resonance capacitor 801 comprises). As a result, a compensated sum signal can already be sent to the sensor 620 (With a reduced amplitude) are generated, which makes it possible to reduce the design of electronic components.

8b illustrates the feedback of a compensation signal 612 directly to the receiving coil 211 , In particular, based on the compensation signal 612 by means of a compensation coil 811 a magnetic compensation field is generated that the charging field 400 in the vicinity of the receiving coil 211 at least partially compensated for, so that's effectively from the receiving coil 211 detected magnetic field is reduced and thus saturation of a ferrite core of the receiving coil 211 can be avoided.

Alternatively or in addition to the use of a modulation signal, the charging field frequency 501 , a modulation signal can be used which is one of the charging field frequency 501 derived frequency. For example, the modulation signal can have a frequency that is the charging field frequency 501 times corresponds to a rational number (e.g. 3/2). So the distance between a frequency component to be extracted 712 and an adjacent frequency component, increasing the filter used 702 can be further simplified and / or made more selective. It can also be used at a different frequency 501 of the loading field 400 and / or at a different frequency 511 of the measuring field 410 generate a modulated sum signal that with a relatively simple filter 702 can be processed further.

Different methods are thus described, which are used to reduce the through a loading field 400 caused interference signal 500 (eg used in combination). In particular, the oscillator frequency 501 the energy transfer a compensation signal 612 can be derived from the received sensor signal with approximately the same phase position and amplitude 520 can be deducted. This can be done in the received sensor signal (ie in the sum signal 520 ) contained interference signal 500 be reduced.

The remaining (compensated) sum signal 620 can be multiplied by a square wave signal (with the period of energy transfer). This multiplication corresponds to synchronous demodulation with the interference signal 500 , With this synchronous demodulation and a downstream bandpass filter 702 can the interference signal 610 be further reduced in an efficient manner, so that a precise signal strength measurement with reduced falsification by the interference signal 610 becomes possible.

As in the 8a and 8b shown, the interference signal 510 can already be reduced at the sensor. Overriding of the sensing path can thus be prevented. An alternative method for synchronous demodulation can also be used. In particular, the interference suppression can be improved by a suitable choice of the demodulation frequency and, if necessary, to a specific measuring field frequency 511 can be adjusted for positioning.

The methods described in this document can be applied to variable energy transfer frequencies 501 be adjusted. The charging field frequency is adjusted 501 typically relatively slow. The change in the charging field frequency 501 can when generating the compensation signal 612 , when generating the modulation signal and / or when filtering by means of a filter 702 be taken into account. As an alternative to adapting the filter 702 can suppress the interference signal by a suitable choice of the (de) modulation frequency 500 for the entire possible frequency range of the charging field frequency 501 (e.g. from 81 to 90 kHz).

The measuring field frequency 511 can have different values. Possibly. can be the values of one or more measuring field frequencies 511 via radio connection (e.g. via WLAN) from the secondary unit 120 to the primary unit 110 be transmitted. So an adjustment of the filter 702 depending on the respective measuring field frequency 511 respectively.

Possibly. An adjacent charging system can sense an adjacent parking / positioning process (even during an active charging process). The distance between the floor coils of the different floor units 110 each other is fixed and can be made known to the systems. This allows a neighboring station to position a vehicle 100 support with additional sensor signals. Especially due to the relatively large distance between the primary systems 111 to each other, there are relatively large relative angles and thus precise data for determining the position.

The presence of a sensor signal (in particular a useful signal 510 ) on the one or more receiving coils 211 can be made a condition for energy transfer. So that has a secondary system 120 by switching off the position signal (ie the useful signal 510 ) the possibility of switching off a charging field regardless of data transmission (e.g. WLAN) 400 to force.

During the positioning process of a vehicle 100 (if there is no energy transmission) the interference signal can be caused by the measures described 500 , which is caused by the energy transmission of a neighboring system, can be suppressed. The possible charging field frequency 501 A neighboring system is typically in a relatively narrow frequency range (for example 81-90 kHz) and can be provided in a precise manner, for example via data communication (for example WLAN). In addition, the exact interference signal can be obtained via a PLL (phase-lock loop) circuit 500 be determined.

9a shows a flow diagram of an exemplary method 900 for determining position information relating to a secondary coil 121 a secondary unit 120 relative to a primary coil 111 a primary unit 110 , Here is the primary coil 111 set up a magnetic charging field 400 to generate electrical energy to the secondary coil 121 transferred to. The primary unit 110 comprises at least one receiving coil 211 , which is set up a measurement signal 520 regarding one from a transmitter coil 201 the secondary unit 120 generated magnetic measuring field 410 capture.

The procedure 900 includes generating or determining 901 a compensation signal 612 for one, in the immediate vicinity of the receiving coil 211 present magnetic charging field 400 , The magnetic charging field 400 from the primary coil 111 and / or from an adjacent further primary coil 111 to be generated. The compensation signal 612 becomes dependent on the charging field frequency 501 of the loading field 400 generated.

The procedure also includes 900 investigating 902 a compensated measurement signal 620 by at least partially compensating for an influence of the charging field 400 to that from the receiving coil 211 recorded measurement signal 520 by means of the compensation signal 612 , In particular, the compensation signal 612 from the detected measurement signal 620 subtracted from. Alternatively or additionally, a compensation coil can be used 811 based on the compensation signal 612 a magnetic compensation field is generated that the magnetic charging field 400 in the vicinity of the receiving coil 211 and / or in a coil core of the receiving coil 211 at least partially wiped out.

The method further comprises 900 investigating 903 , based on the compensated measurement signal 620 , a signal strength 610 of the measuring field 410 on the receiving coil 211 , The signal strength 610 of the measuring field 410 due to the reduced influence of the loading field 400 can be determined with increased accuracy.

The procedure can also 900 investigating 904 , based on signal strength 610 , position information related to a position of the secondary coil 121 relative to the primary coil 111 include.

9b shows a flowchart of a further method 910 for determining position information relating to a secondary coil 121 a secondary unit 120 relative to a primary coil 111 a primary unit 110 , Here is the primary coil 111 set up a magnetic charging field 400 to generate electrical energy to the secondary coil 121 transferred to. The primary unit 110 comprises at least one receiving coil 211 , which is set up a measurement signal 520 regarding one from a transmitter coil 201 the secondary unit 120 generated magnetic measuring field 410 capture.

The procedure 910 includes modulating 911 one from the receiving coil 211 detected or a measurement signal derived therefrom 520 . 620 with a modulation signal to a modulated measurement signal 720 provide. The modulation signal has a modulation frequency that is different from the charging field frequency 501 one, in the immediate vicinity of the receiving coil 211 present magnetic charging field 400 depends. The magnetic charging field 400 can from the primary coil 111 and / or from an adjacent further primary coil 111 to be generated.

The procedure also includes 910 filtering 912 of the modulated measurement signal 720 using a (bandpass) filter 702 to a (single and / or isolated) frequency component 712 of the modulated measurement signal 720 to extract. The filter 702 , especially a frequency response 706 of the filter 702 , can depend on the measuring field frequency 511 of the measuring field 410 depend.

The method further comprises 910 investigating 913 , based on the extracted frequency component 712 , a signal strength 610 of the measuring field 410 on the receiving coil 211 , The energy of the extracted frequency component 712 is preferably amplified or exclusively by the energy of the measuring field 410 (and possibly on the energy of the modulation signal). Thus the signal strength 610 of the measuring field 410 can be determined with increased accuracy.

The procedure can also 910 investigating 914 , based on signal strength 610 , position information related to a position of the secondary coil 121 relative to the primary coil 111 include.

The measures described in this document can cause the interference signal caused by an energy transmission 500 can be suppressed in an efficient and precise manner (for example by means of a hardware circuit). Thus, a magnetic field can be measured 410 based positioning system can also be used during an inductive charging process. The measures described can thus avoid the installation of additional sensors (and the associated costs or the associated installation space). In addition, the sensitivity and accuracy and the range of a positioning process can be increased by the measures described (in particular by improved filtering of the useful signal 510 and the suppression of interference or noise).

The present invention is not restricted to the exemplary embodiments shown. In particular, it should be noted that the description and the figures are only intended to illustrate the principle of the proposed methods, devices and systems.

Claims (20)

Device (507) for determining position information relating to a secondary coil (121) of a secondary unit (120) relative to a primary coil (111) of a primary unit (110); wherein the primary coil (111) is configured to generate a magnetic charging field (400) in order to transmit electrical energy to the secondary coil (121); wherein the primary unit (110) comprises at least one reception coil (211) which is set up to provide a measurement signal (520) with respect to a magnetic generated by a transmission coil (201) of the secondary unit (120) Measuring field (410); wherein the device (507) is set up to - generate a compensation signal (612) for a magnetic charging field (400) present in a direct vicinity of the receiving coil (211); wherein the compensation signal (612) is generated as a function of a charging field frequency (501) of the charging field (400); - on the basis of the compensation signal (612) at least partially compensate for an influence of the charging field (400) on the measurement signal (520) detected by the reception coil (211) in order to provide a compensated measurement signal (620); - on the basis of the compensated measuring signal (620) to determine a signal strength (610) of the measuring field (410) on the receiving coil (211); and - on the basis of the signal strength (610), determine position information with respect to a position of the secondary coil (121) relative to the primary coil (111). Device (507) according to Claim 1 The device (507) is set up to set a phase of the compensation signal (612) as a function of the detected measurement signal (520), in particular in such a way that a distance measure between a phase of the detected measurement signal (520) and the phase of the compensation signal (612 ) is reduced. Device (507) according to one of the preceding claims, wherein the device (507) is set up to set an amplitude of the compensation signal (612) as a function of the detected measurement signal (520), in particular such that a difference between the amplitude of the compensation signal (612 ) and an amplitude of the detected measurement signal (520) is reduced. The device (507) according to any one of the preceding claims, wherein - The detected measurement signal (520) comprises an interference signal (500) dependent on the charging field (400) and a useful signal (510) dependent on the measuring field (410); and - The device (507) is set up to subtract the compensation signal (612) from the detected measurement signal (520) in order to determine the compensated measurement signal (620), so that an energy component of the useful signal (510) in the compensated measurement signal (620) is greater is as an energy component of the useful signal (510) in the detected measurement signal (520). The device (507) according to any one of the preceding claims, wherein - The device (507) comprises a compensation coil (811) which is magnetically coupled to the receiving coil (211), in particular via a common ferromagnetic coil core; and - The device (507) is set up by means of the compensation coil (811) and depending on the compensation signal (612) to generate a magnetic compensation field in the vicinity of the receiving coil (211), so that the magnetic charging field (400) in the vicinity of the Receiving coil (211) is at least partially compensated. Device (507) according to one of the preceding claims, wherein the device (507) comprises an amplifier (802) which is set up to amplify the compensated measurement signal (620) instead of the detected measurement signal (520). Device (507) according to one of the preceding claims, wherein the device (507) is set up - Modulate the compensated measurement signal (620) with a modulation signal to provide a modulated measurement signal (720); wherein the modulation signal has a modulation frequency which depends on the charging field frequency (501) of the magnetic charging field (400) present in the immediate vicinity of the receiving coil (211); - filtering the modulated measurement signal (720) by means of a filter (702) in order to extract a frequency component (712) of the modulated measurement signal (720); wherein the filter (702) depends on a measuring field frequency (511) of the measuring field (410); and - Determine the signal strength (610) of the measuring field (410) on the receiving coil (211) on the basis of the extracted frequency component (712). Device (507) for determining position information relating to a secondary coil (121) of a secondary unit (120) relative to a primary coil (111) of a primary unit (110); wherein the primary coil (111) is configured to generate a magnetic charging field (400) in order to transmit electrical energy to the secondary coil (121); wherein the primary unit (110) comprises at least one receiving coil (211), which is set up to detect a measurement signal (520) relating to a magnetic measurement field (410) generated by a transmission coil (201) of the secondary unit (120); the device (507) being set up to - modulate a measurement signal (520, 620) detected by or derived from the reception coil (211) with a modulation signal in order to provide a modulated measurement signal (720); wherein the modulation signal has a modulation frequency which depends on a charging field frequency (501) of a magnetic charging field (400) present in a direct vicinity of the receiving coil (211); - filtering the modulated measurement signal (720) by means of a filter (702) in order to extract a frequency component (712) of the modulated measurement signal (720); wherein the filter (702) depends on a measuring field frequency (511) of the measuring field (410); - on the basis of the extracted frequency component (712) to determine a signal strength (610) of the measuring field (410) on the receiving coil (211); and - on the basis of the signal strength (610) determine position information in relation to a position of the secondary coil (121) relative to the primary coil (111). Device (507) according to Claim 8 , wherein the modulation signal comprises or is a square wave signal. Device (507) according to one of the Claims 8 to 9 , wherein the modulation frequency - is equal to the charging field frequency (501); - is equal to the charging field frequency (501) times a rational factor not equal to one; is such that a frequency distance between the extracted frequency component (712) and a directly adjacent frequency component of the modulated measurement signal (720) is greater than a frequency distance between the measuring field frequency (511) and the charging field frequency (501), in particular by a factor of 2, 3, 5, 10 or more. Device (507) according to one of the Claims 8 to 10 The device (507) is set up to determine the modulated measurement signal (720) by periodically reversing a sign of the measurement signal (520, 620). Device (507) according to one of the Claims 8 to 11 , wherein the filter (702) has a bandwidth that makes it possible to extract the frequency component (712) of the modulated measurement signal (720) for all possible charging field frequencies (501) from a predefined charging field frequency range. The device (507) according to any one of the preceding claims, wherein - The primary unit (110) is arranged next to a further primary unit (110); - The magnetic charging field (400) present in the direct vicinity of the receiving coil (211) is generated by the further primary unit (110); and - The device (507) is set up, in particular via a wireless communication link, to receive frequency information relating to the charging field frequency (501) of the magnetic charging field (400), which is generated by the further primary unit (110). Device (507) according to one of the preceding claims, wherein according to a convention, a measuring field (410) is to be generated by the transmission unit (201) during an ongoing charging process; the device (507) being set up, - determine on the basis of the signal strength (610) whether or not a measuring field (410) is generated by the transmitting unit (201); and - to cause the primary unit (111) to prevent generation of the magnetic charging field (400) if it is determined that no measuring field (410) is generated by the transmitting unit (201). Device (507) according to one of the preceding claims, wherein the device (507) is set up - to determine a current value of the charging field frequency (501); and - Adapt an operation of the device (507) depending on the current value of the charging field frequency (501). Device (507) according to one of the preceding claims, wherein the device (507) is set up to compensate the signal (612), the compensated measurement signal (620), the modulated measurement signal (720) and / or the signal strength (610) by means of analog hardware determine. Device (507) according to one of the preceding claims, wherein the device (507) is set up - to determine signal strengths (610) of the measuring field (410) on a plurality of receiving coils (211, 212, 213, 214) and / or signal strengths (610) of the measuring fields (410) of a plurality of transmitting coils (201, 202, 203); and - Determine position information in relation to the position of the secondary coil (121) relative to the primary coil (110) on the basis of the signal strengths (610). Device (507) according to one of the preceding claims, wherein the device (507) is set up - to determine the signal strength (610) of at least one measuring field (410) on the receiving coil (201), which was generated by a transmitting coil (201, 202, 203) which is arranged on a further secondary unit (120); and - Take this signal strength (610) into account when determining the position information. Method (900) for determining position information relating to a secondary coil (121) of a secondary unit (120) relative to a primary coil (111) of a primary unit (110); wherein the primary coil (111) is configured to generate a magnetic charging field (400) in order to transmit electrical energy to the secondary coil (121); wherein the primary unit (110) comprises at least one receiving coil (211), which is set up to detect a measurement signal (520) relating to a magnetic measurement field (410) generated by a transmission coil (201) of the secondary unit (120); the method (900) comprising - generating (901) a compensation signal (612) for a magnetic charging field (400) present in a direct vicinity of the receiving coil (211); wherein the compensation signal (612) in Is generated as a function of a charging field frequency (501) of the charging field (400); - Determining (902) a compensated measurement signal (620) by at least partially compensating for an influence of the charging field (400) on the measurement signal (520) detected by the receiving coil (211) by means of the compensation signal (612); - Determining (903), on the basis of the compensated measurement signal (620), a signal strength (610) of the measurement field (410) on the reception coil (211); and - determining (904), based on the signal strength (610), position information in relation to a position of the secondary coil (121) relative to the primary coil (111). Method (910) for determining position information relating to a secondary coil (121) of a secondary unit (120) relative to a primary coil (111) of a primary unit (110); wherein the primary coil (111) is configured to generate a magnetic charging field (400) in order to transmit electrical energy to the secondary coil (121); wherein the primary unit (110) comprises at least one receiving coil (211), which is set up to detect a measurement signal (520) relating to a magnetic measurement field (410) generated by a transmission coil (201) of the secondary unit (120); the method comprising (910) - modulating (911) a measurement signal (520, 620) detected by the reception coil (211) or derived therefrom with a modulation signal in order to provide a modulated measurement signal (720); wherein the modulation signal has a modulation frequency which depends on a charging field frequency (501) of a magnetic charging field (400) present in a direct vicinity of the receiving coil (211); - filtering (912) the modulated measurement signal (720) by means of a filter (702) in order to extract a frequency component (712) of the modulated measurement signal (720); wherein the filter (702) depends on a measuring field frequency (511) of the measuring field (410); - determining (913), on the basis of the extracted frequency component (712), a signal strength (610) of the measuring field (410) on the receiving coil (211); and - Determining (914), based on the signal strength (610), position information in relation to a position of the secondary coil (121) relative to the primary coil (111).

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