System for inductively transmitting power from a primary device to a secondary device, primary device, and method for operating such a system

Abstract

The invention relates to a system (10) for inductively transmitting power, comprising a primary device (100), a secondary device (200), and a control unit (120), wherein the primary device (100) is designed to transmit power to a secondary oscillating circuit of the secondary device (200) in an inductive manner via a primary oscillating circuit during the power transmission, and the control unit (120) is designed to detect secondary power data of the secondary device (200) and determine primary target power data using the detected secondary power data and a power characteristic. The control unit (120) is additionally designed to detect primary power data of the primary device (100) and detect a foreign object using a comparison between the primary target power data and the primary power data. The power characteristic comprises reference target power data based on reference secondary power data. The invention additionally relates to a method for operating such a system.

Description

[0001] 38875.TUR.P110PC S / Wi / js 1 / 36 System for inductive power transmission from a primary device to a secondary device, primary device and method for operating such a system The present invention relates to a system for inductive power transmission from a primary device to a secondary device, to a primary device and to a method for operating a system for inductive power transmission. It therefore lies in the technical field of contactless power transmission (wireless power transfer) and inductive couplers. Systems are known in which inductive power transmission between a primary device (transmitter) and a secondary device (receiver) takes place via an electromagnetic field. An important parameter when using such inductive couplers is the axial offset between the transmitter and the receiver, i.e. in particular the distance between transmitter and receiver in the axial direction.Knowledge of this parameter allows, for example, a more precise estimation of the power to be applied on the transmitter side in order to transfer a specific target power to the receiver side by induction. The object of the present invention is to provide a system for inductive power transmission, a primary device and a method for operating such a system, wherein the axial offset between transmitter and receiver can be determined in a particularly simple manner. This object is achieved according to the invention by a system, a primary device and a method having the features of the independent claims. Advantageous embodiments are specified in the dependent claims. 38875.TUR.P110PC S / Wi / js 2 / 36 The object is then achieved by a system for inductive power transmission, which comprises a primary device and a secondary device as well as a control unit.The primary device is configured to inductively transmit power to a secondary resonant circuit of the secondary device via a primary resonant circuit during power transmission. The control unit is configured to record secondary power data of the secondary device and a frequency parameter of the primary device. The control unit is further configured to determine an actual distance between the primary device and the secondary device based on the recorded secondary power data and the frequency parameter using a distance characteristic map. The distance characteristic map comprises reference secondary power data as a function of reference frequency parameters and as a function of reference distances. The invention therefore uses a distance characteristic map to be able to determine the distance between the primary and secondary device based on the frequency parameter and the recorded secondary power data.In particular, an axial offset is assumed, i.e. a distance between transmitter and receiver that is essentially only pronounced in one axial direction, without, for example, a simultaneous lateral offset or an angular deviation that would result in the primary and secondary devices not being directly aligned. Such deviations can be taken into account or modeled in further embodiments of the system. In one embodiment, the frequency parameter of the primary device relates to a primary frequency of the primary device, wherein in particular the primary intermediate circuit of the primary device is operated with a predetermined constant primary voltage. In a further embodiment, the secondary performance data relates to a secondary voltage 38875.TUR.P110PC S / Wi / js 3 / 36 induced in a secondary intermediate circuit of the secondary device and / or a secondary current supplied from the secondary intermediate circuit of the secondary device.In particular, the distance characteristic map represents a relationship between the frequency parameter, in particular the primary frequency of the primary device set for power transmission, and the transmitted secondary power, in particular the secondary voltage of the secondary device, at different distances between the primary device and the secondary device. Depending on the recorded values ​​of the frequency parameter and the secondary power data, it can then be determined which distance this combination of values ​​corresponds to. The distance characteristic map is, in particular, independent of the primary current strength set for the primary device. In this way, the distance between the primary and secondary devices can be determined without, for example, variations in the primary current strength having a disruptive effect, such as if a foreign object is present that absorbs part of the inductively transmitted power, which in turn leads to a higher required primary current strength.When defining the axis of an axial offset, it can be assumed that the primary device and the secondary device each have field distributions that are formed in such a way that maximum inductive power transfer is possible when the primary device and the secondary device are arranged one above the other along a defined axis. For example, the primary resonant circuit and the secondary resonant circuit have coils that each have a longitudinal axis; for optimal inductive coupling, it can then be provided that these longitudinal axes are to be arranged one above the other. For example, the coils of the primary resonant circuit and the secondary resonant circuit are arranged in the extension of their respective coil longitudinal axes. It can be provided that the 38875.TUR.P110PC S / Wi / js 4 / 36 Longitudinal axes of the coils correspond to the longitudinal axes of the respective devices, i.e. the primary device and the secondary device; however, this is generally not mandatory. In a further example, lobe-shaped distributions of the electromagnetic field of the primary device and the secondary device are assumed, so that maximum inductive power transmission can occur when the lobes of the transmitter and receiver are arranged one above the other. In one embodiment of the system, the control unit is comprised by the primary device. In further embodiments, it can be comprised by the secondary device or be designed as an external control unit, for example as a control module of a higher-level control system. The primary and secondary power data are recorded in a manner known per se using suitable sensors. The measured values ​​can be transmitted to the control unit in various ways.In a further embodiment, the control unit is configured to acquire the secondary performance data via an IO-Link connection. Other types of data connections can be provided alternatively or additionally. The data connection can exist between a primary interface of the primary device and a secondary interface of the secondary device. The IO-Link or other data connection can exist between the primary device and the secondary device, particularly if the control unit is included in the primary device. In this case, primary performance data can be transferred directly from a sensor to the control unit, and the secondary performance data can be transferred to the control unit via an IO-Link connection or another data connection. 38875.TUR.P110PC S / Wi / js 5 / 36 In a further embodiment of the system, a data connection, in particular for transmitting the secondary power data to the primary device, can be implemented by modulating a data transmission signal onto the electromagnetic field for inductive power transmission, thereby enabling, in particular, data transmission from the primary device to the secondary device. In a further development, the distance characteristic map can be determined using a distance reference measurement, wherein, during the distance reference measurement, actual secondary power data of the secondary device is measured as a function of the frequency parameter of the primary device for a plurality of reference distances within a predetermined operating range between the primary device and the secondary device.In particular, the distance characteristic map comprises individual characteristic curves for different distances, which describe the relationship between the frequency parameter and the secondary performance data. It can further be provided that the parameters of a function are determined by means of a compensation calculation, which then corresponds to a characteristic curve of the distance characteristic map or which represents the course of the entire distance characteristic map. In a further embodiment, the individual characteristic curves of the distance characteristic map can be determined by means of a regression analysis, in particular a linear or polynomial curve fitting, as functions of the measured secondary performance data as a function of the frequency parameter. In particular, a compensation calculation is carried out using the least squares (LS) method. 38875.TUR.P110PC S / Wi / js 6 / 36 For example, the fit determines the parameters of an nth-degree polynomial, such as first-degree for a linear curve, second-degree for a parabola, or third-degree for a hyperbolic function. The specified operating range can, for example, relate to a specific interval of distances as well as power and / or frequency ranges within which the inductive power transfer between the primary device and the secondary device operates. In particular, the frequency parameter here is a primary frequency that characterizes the electromagnetic field generated by the primary device for inductive power transfer. For example, the primary frequency is generated by the control unit, such as the frequency of a square-wave signal. The resonant circuit of the primary device is alternately controlled via power switches in the amplifier circuit.This creates an alternating current in the front coil, which in turn creates an alternating electromagnetic field. The frequency of the alternating electromagnetic field corresponds to the frequency output by the control unit. In one method for determining the distance characteristic map, a distance reference measurement is carried out, wherein actual secondary power data of the secondary device is measured as a function of a primary frequency of the primary device for a plurality of reference distances within a predetermined operating range between the primary device and the secondary device. For example, a primary frequency of the primary device is measured, which is adjusted at a fixed, predetermined primary voltage so that a specific reference secondary power is obtained at the secondary device. This measurement is carried out at a fixed distance for a plurality of values ​​of the 38875.TUR.P110PC S / Wi / js 7 / 36 reference secondary power, so that a curve is created that shows the relationship between the controlled primary frequency and the secondary power for a constant distance. The individual characteristic curves are determined for different reference distances between the primary and secondary devices, so that a dependence of the primary frequency to be controlled on the distance is also determined. The reference distances are selected within a predetermined working range between the primary device and the secondary device. The individual characteristic curves determined for different reference distances can be combined to form the distance characteristic map. A compensation calculation can then be carried out for each of the curves obtained in this way in order to obtain the parameters of a function, for example a linear or other approximate curve, which can then be used as a power characteristic curve.Furthermore, parameters of a function representing the distance characteristic map can also be determined by means of compensation calculations. In particular, the control unit is further configured to generate an output or a control signal depending on the determined actual distance. For example, a specific distance can be output in this way. Furthermore, depending on the determined actual distance, a parameter of the inductive power transmission can be determined, such as a suitable current and / or voltage from the primary device in order to transmit a specific power over this distance to the secondary device. Such a target value can also be used to monitor the integrity of the inductive power transmission and, for example, to detect foreign objects. 38875.TUR.P110PC S / Wi / js 8 / 36 A foreign object, in particular an at least partially metallic object, is deemed to be detected, for example, if its presence is determined within a transmission range of the system. The transmission range is in particular a space in the vicinity of the primary device within which a significant inductive power transfer to a metallic foreign object takes place, in particular in such a way that a significant heating of the foreign object can occur. In one embodiment, the control unit is further configured to determine primary target power data based on the recorded secondary power data and the determined actual distance using a power characteristic curve. The control unit is further configured to record primary power data of the primary device and to detect a foreign object based on a comparison of the primary target power data with the primary power data.The power characteristic curve comprises reference target power data as a function of reference secondary power data as well as as a function of reference distances. The power characteristic curve is particularly specific for a certain axial offset or axial distance between the primary device and the secondary device. In an additional embodiment, the position of the devices relative to one another can also be taken into account, such as an angle of the devices relative to one another and / or a radial offset. By taking into account the dependence of the power characteristic curve on the actual distance between the primary and secondary devices, the primary target power data can be determined more precisely. The control unit can also be configured to generate and output a switching signal when a foreign object is detected, for example to stop the inductive power transmission through the primary device or to reduce the primary power to a predetermined value. 38875.TUR.P110PC S / Wi / js 9 / 36 This exploits, among other things, the knowledge that the presence of a foreign object - especially a metallic foreign object - in the area of ​​inductive power transmission leads to a portion of the primary power supplied by the primary device being dissipated, for example by heating the foreign object. In order to still achieve a specified secondary power, a correspondingly higher primary power must be set. The system is then intended to use the resulting deviation from the "target" value of the primary power to detect the presence of a foreign object. If a foreign object is present in the area of ​​power transmission, a higher primary power must therefore be supplied in order to provide the same specified secondary power of the secondary device.A performance curve is then used, which indicates a relationship between the secondary performance data received from the secondary device and the primary target performance data to be adjusted by the primary device. The performance curve is determined in a reference situation in which it can be ensured that no relevant foreign object is present. By comparing the actually adjusted primary performance data with the primary target performance data according to the performance curve, a deviation can be determined, for example, which is then compared to a threshold value. If the deviation exceeds the threshold value, it is assumed that a foreign object is present.The control unit can now be configured to generate a control signal when a foreign object is detected, for example to stop the inductive power transmission through the primary device or to reduce the primary power to a predetermined value. Alternatively or additionally, a warning signal can be issued. A threshold value used for evaluating the comparison between the primary power data and the primary target power data can, for example, be fixed. It can also be determined as a predetermined percentage of the primary target power data, for example as a percentage of a primary target current, so that the threshold value for a permissible deviation is greater the larger a parameter value of the primary target power data is.Foreign object detection occurs dynamically, i.e., at different distances between the primary and secondary devices, as well as at different transmitted power levels. Since this system detects foreign objects more precisely than conventional systems – even in a situation where lower power is to be transmitted to the secondary device – heating of metallic objects can be avoided across the entire power and distance range of the inductive coupler system. The associated hazard potential is significantly minimized. The primary and secondary power data within the meaning of the invention relate to the electrical power of the primary and secondary devices, respectively. Accordingly, relevant parameters include, in particular, current and / or voltage. The power value is the product of current and voltage.For example, the secondary performance data includes a secondary voltage and / or a secondary current; the product of these parameters results in particular in the electrical power inductively transferred to the secondary device. In particular, the parameters output by an intermediate circuit of the secondary device are taken into account. The primary performance data can also include a primary voltage and / or a primary current; the product of these parameters results in particular in the power that is applied by the primary device during the inductive power transfer to the secondary device. In particular, the parameters output by an intermediate circuit of the primary device are taken into account. In one embodiment of the system, the primary performance data relates to a primary current in a primary intermediate circuit of the primary device.In particular, the primary intermediate circuit of the primary device can be operated with a predetermined constant primary voltage. Furthermore, the secondary power data can relate to a secondary voltage induced in a secondary intermediate circuit of the secondary device and a secondary current supplied from the secondary intermediate circuit of the secondary device. In one embodiment, it is provided that the primary device is operated with a predetermined primary voltage. In such a case, it may be sufficient for the primary power data recorded by the control unit to include a primary current. In particular, the primary voltage then does not need to be recorded specifically; it can also be assumed to be constant for the evaluation. In particular, it can be provided that during the inductive power transmission - with the primary voltage kept essentially constant - the primary current is regulated such that predetermined secondary power data are obtained.In further examples, the primary-side voltage can also be regulated. In particular, the primary-side power, i.e. the product of input current and voltage, is then a controlled variable. The determined primary target power data also relate in particular to a primary target current. 38875.TUR.P110PC S / Wi / js 12 / 36 The system's control unit therefore determines the primary target power data using a power characteristic curve and based on the recorded secondary power data as well as the distance between transmitter and receiver. For example, a primary target current is determined, whereby it is particularly assumed that a certain primary voltage is fixed. The power characteristic curve can be stored in a memory connected to the control unit, for example for a specific type or model of the system.In one embodiment, the power characteristic curve can be determined based on at least one power reference measurement or based on a plurality of power reference measurements. During the power reference measurement, actual primary power data of the primary device are measured as a function of a plurality of reference secondary power data of the secondary device. For example, the reference secondary power data can comprise a plurality of parameter values ​​of the secondary power data, which are distributed, in particular, equidistantly within an interval. For the power reference measurement, for example, the system or a system of the same type without a foreign body can be measured, wherein, for a predetermined primary voltage, the primary frequency of the primary device is controlled such that a primary current strength is set as a manipulated variable in order to obtain specific values ​​of the secondary power output at the intermediate circuit of the secondary device.In the example, these determined values ​​of the secondary power can be arranged equidistantly within an interval; the interval in which the power reference measurements are carried out can correspond to an operating range of the electrical power inductively transmitted by the system. 38875.TUR.P110PC S / Wi / js 13 / 36 In particular, during such a power reference measurement, the reference primary power data are determined based on the measured actual primary power data. The data measured during the power reference measurement can, for example, be filtered, smoothed and / or processed by averaging. In a further development, during the power reference measurement, the actual primary power data are further measured as a function of a plurality of reference distances within a predetermined operating range between the primary device and the secondary device.Thus, specific power characteristics are determined for the respective distance. In one embodiment, the power characteristics are determined using a regression analysis, in particular a linear or polynomial curve fit, as a function of the measured actual primary power data as a function of the reference secondary power data. In particular, a compensation calculation is carried out using the least squares (LS) method. For example, the fitting determines the parameters of an nth-degree polynomial, for example, first-degree for a linear curve. The invention further relates to a primary device for inductively transmitting power to a secondary device, wherein the primary device comprises a control unit and a primary device interface.The control unit is configured to detect a frequency parameter of the primary device and, via the primary device interface, to detect secondary power data of a secondary device coupled to the primary device for inductive power transmission. The control unit is further configured to use the detected secondary power data and the frequency parameter to determine an actual distance between the primary device and the secondary device 38875.TUR.P110PC S / Wi / js 14 / 36 using a distance characteristic map. The distance characteristic map includes reference secondary power data as a function of reference frequency parameters and as a function of reference distances. The primary device is, in particular, a primary device for the system described above. Corresponding developments are therefore conceivable.In the method for operating a system for inductive power transmission from a primary device to a secondary device, a frequency parameter of the primary device and secondary power data of the secondary device are recorded during the inductive power transmission. Based on the recorded secondary power data and the frequency parameter, an actual distance between the primary device and the secondary device is determined using a distance characteristic map. The distance characteristic map includes reference secondary power data as a function of reference frequency parameters and as a function of reference distances. The method is particularly designed to operate the system described here. It therefore has the same advantages and can be further developed in the manner described here. Further details and advantages of the invention will now be explained in more detail with reference to the exemplary embodiments illustrated in the drawings. In the drawings: Fig.1 shows a schematic representation of an embodiment of a system for inductive power transmission; Fig. 2 shows an embodiment of the method for operating a system for inductive power transmission; Fig. 3 shows an example of recorded data from a power reference measurement at different distances; 38875.TUR.P110PC S / Wi / js 15 / 36 Fig. 4 shows an example of a power characteristic curve determined based on the recorded data; Fig. 5 shows a schematic representation of an embodiment of a functional principle for inductive power transmission; Fig. 6 shows an example of recorded data from a distance reference measurement; Fig. 7 shows an example of power characteristics determined based on the recorded data; and Fig. 8 shows an example of fitted characteristics of a distance characteristic map. With reference to Fig.Figure 1 explains an embodiment of a system 10 for inductive power transmission and for detecting a metallic object in the electromagnetic field between a primary device 100, here a transmitter 100, and a secondary device 200, here a receiver 200, during contactless power transmission. The system 10 comprises the primary device 100 and the secondary device 200. In the embodiment, the primary device 100 comprises a single coil 104 located in a (primary) resonant circuit for inductive energy transmission between the coupled primary device 100 and secondary device 200, with the primary device 100 assuming the role of the transmitter 100. It further comprises a control unit 107 for adjusting the load- and distance-dependent resonant circuit frequency, as well as a voltage converter 101 with a constant output voltage and a voltage intermediate circuit 102 for adjusting the input voltage to the resonant circuit voltage.The primary device 100 further comprises an amplifier 103, in particular a “current-mode Class-D amplifier,” for adapting the control signals of the control unit 107 to the resonant circuit with the single coil 104, as well as a current measuring unit 106 between the voltage intermediate circuit 102 and an amplifier 103. 38875.TUR.P110PC S / Wi / js 16 / 36 The primary device 100 further comprises a voltage measuring unit 105 on the voltage intermediate circuit 102 and an evaluation and control unit 107 for controlling the voltage converter 101 and the amplifier 103. The primary device 100 further comprises an interface for data transmission 108 between a coupled primary device 100 and secondary device 200, wherein in particular an IO-Link method can be used to operate a data connection with the secondary device 200.The secondary device 200 also includes a single coil 204 located in a (secondary) resonant circuit for inductive energy transfer between the coupled primary device 100 and the secondary device 200, with the secondary device 200 assuming the role of the receiver 200. The secondary device further includes a rectifier 203 with a voltage intermediate circuit 202 for storing the received energy. The secondary device 200 also comprises a voltage converter 201 for adapting the intermediate circuit voltage to the output voltage and a current measuring unit 206 between the voltage intermediate circuit 202 and the voltage converter 201. The secondary device 200 further comprises a voltage measuring unit 205 on the voltage intermediate circuit 202 and an interface for data transmission 208 between the secondary device 200 and the primary device 100 coupled thereto for data purposes. With reference to Fig. 2, a method for operating the system 10 explained above with reference to Fig. 1 is further explained.The method is used in particular to detect a foreign object in the range of the electromagnetic field during inductive power transmission. 38875.TUR.P110PC S / Wi / js 17 / 36 During the power transmission between primary device 100 and secondary device 200, the intermediate circuit voltage induced in secondary device 200 (secondary voltage, ^) is measured cyclically, in the present example at intervals of Δt = 10 ms. ^^^ ) and the current provided from the intermediate circuit 202 of the secondary device 200 (secondary current, ^ ^^^) are recorded. These values ​​are transmitted via interface 208 to the corresponding interface 108 of the primary device 100. In the exemplary embodiment, a data connection according to IO-Link is used, but another type of data transmission can also be selected, in particular wired or wireless. For example, the data transmission can also be carried out by modulating a carrier signal onto the transmitted electrical power, so that the data and the electrical power are transmitted via the same channel. From the values ​​thus recorded, the current power (^ ^^^ = ^ ^^^ ∙ ^ ^^^ ) of the secondary device 200 is determined. Furthermore, in this step S1, the current primary current ^ ^^^ In step S2, the acquired data is averaged or smoothed over a specific time interval. This results in averaged values ​​for the primary current ^^^^_^^^ and for the secondary power ^ ^^^ _^^^ . In this example, a distance ^ between the primary 100 and the secondary device 200 is assumed, which lies within a working range of 0 mm to 7 mm. Furthermore, the example assumes a load current ^ ^^^ of the secondary device 200 in a range of 0 mA to 750 mA. In other examples, other ranges for the distance ^ and load current ^ ^^^ be provided. 38875.TUR.P110PC S / Wi / js 18 / 36 In the event that there is no foreign metallic object in the electromagnetic field between the primary and secondary device, a relationship – in a first approximation linear – results between the input current in the resonant circuit of the primary device (primary current, ^ ^^^ ) and the secondary output power of the intermediate circuit of the secondary device (secondary power, ^ ^^^ = ^ ^^^ ∙ ^ ^^^This ratio is specified by means of a power characteristic curve, which is stored in the evaluation and control unit 107 of the primary device 100 and evaluated by it. The power characteristic curve has approximately the following form: In a step S3, a cyclic calculation of the "target" primary current (target primary current, ^ ^^^_^^^^ ) for the resonant circuit of the primary device 100 on the basis of an averaged, i.e. smoothed, recorded output power of the intermediate circuit 202 of the secondary device 200 (averaged secondary power, ^ ^^^_^^^ ). This means that the target primary current ^ ^^^_^^^^ which should be adjusted according to the power characteristic curve in order to achieve a certain (average) secondary power ^ ^^^_^^^ This enables an accurate evaluation of the actually measured and averaged input current ^ ^^^_^^^into the resonant circuit of the primary device 100 and the current calculated "target" input current ^ ^^^_^^^^ into the resonant circuit of the primary device 100. A metallic foreign object in the electromagnetic field between the primary device 100 and the secondary device 200 during inductive power transmission leads to the dissipation of power, for example, by heating the foreign object. This power is provided by the transmitter 100 but not received by the receiver 200. The primary current ^ ^^^_^^^ must therefore exceed the calculated “target” 38875.TUR.P110PC S / Wi / js 19 / 36 input current ^ ^^^_^^^^ in order to still provide a certain secondary power. In a step S4, the calculated primary target input current ^ ^^^_^^^^ a maximum permissible input current ^ ^^^_^^^ which, for example, determines the calculated target input current ^ ^^^_^^^^ by a certain percentage x%: The actually measured primary current ^ ^^^_^^^is operated with the maximum permissible input current ^ ^^^_^^^ compared and when exceeded, that is at this threshold, that is at ^ ^^^_^^^ ≥ ^ ^^^_^^^ , there is an unacceptable deviation of the actual averaged input current in the resonant circuit of the primary device 100. From this, it is concluded, in particular, that a foreign object is present. In a step S6, a corresponding output is then generated, such as a warning message and / or a switching signal that, for example, interrupts the inductive power transmission. If the threshold value is not exceeded, that is, , no output is generated in step S7. Alternatively, an output can be generated to indicate that no foreign object was detected. The method is repeated in the loop after the specified interval Δt. The deviation between the measured and the calculated input current in the resonant circuit of the primary device 100 can be evaluated regardless of which operating ranges are specified for the transmittable power 38875.TUR.P110PC S / Wi / js 20 / 36 and / or the distance between the primary device 100 and the secondary device 200. The method can, for example, be applied for higher secondary powers (approximately > 18 W) and / or larger distances (approximately > 7 mm). For this purpose, in particular the power characteristic curve should be determined over the entire operating ranges used for distance and / or secondary power.The method is therefore easily adaptable for different operating ranges of the secondary power and distances, in particular by using power characteristics for corresponding operating ranges. The method enables early detection of metallic deposits, for example on the front cap of one of the primary 100 and / or secondary devices 200. This allows maintenance and cleaning work on the coupler system to be designed in such a way that wear and tear and energy consumption are reduced. The reliable and rapid detection of foreign objects also reduces the danger posed by heated metallic objects in the electromagnetic field between the primary 100 and secondary device 200 during inductive power transmission. The method for dynamic foreign object detection is explained again below in different terms. The method is based on the functional relationship between the input current (^. ^^^_^^^^) into the resonant circuit of the primary device 100 without foreign object and its control in order to at a given primary voltage (^ ^^^ ) a certain secondary output voltage (^ ^^^_^^^^ ) and a secondary output current (^^^^_^^^^ ll) at the voltage intermediate circuit 202 of the secondary device 200 without a foreign object. Fct. 1 shows the aforementioned functional relationship: 38875.TUR.P110PC S / Wi / js 21 / 36 ^ ^^^_^^^^ [A] Input current into the resonant circuit of the primary device without foreign object ^ ^^^_^^^^ [V] Voltage at the intermediate circuit capacitor of the secondary device without foreign object ^ ^^^_^^^^ [A] Current from the intermediate circuit capacitor of the secondary device without foreign object ^ ^^^_^^^^ [W] Output power from the intermediate voltage circuit of the secondary device without foreign object The following equation Gl.1 can be used to transform the function Fkt.1: ^ ^^^_^^^^ = ^ ^^^_^^^^ ∙ ^ ^^^_^^^^ Eq.1 ^ ^^^_^^^^[W] Output power from the intermediate voltage circuit of the secondary device without foreign object (205, 206) This results in the following relationship for the function Fct.2: ^ ^^^_^^^^ = ^(^ ^^^_^^^^ ) Fct.2 Since the voltage converter 101 of the primary device 100 has a constant output voltage (^ ^^^ ) at the voltage intermediate circuit 102, the output voltage (^ ^^^ ) are not considered in the following for the exemplary embodiment. With reference to Fig. 3 and Fig. 4, measurements for determining a power characteristic are explained as examples. For the sake of clarity, Fig. 3 shows measurements for distances ^ of 0 mm, 3 mm, and 7 mm between the mutually facing cover caps of the primary 100 and secondary device 200; however, measurements were taken and evaluated at closer intervals. The measurements of the regulated actual primary current ^ ^^^_^^^^ were also carried out in a range of secondary output power ^^^^_^^^^ from about 1 W to about 20 W. This is a measurement of the relationship between ^ ^^^_^^^^ = ^(^ ^^^_^^^^ ) over ^ from 0 mm to 7 mm. The exemplary method for dynamic foreign object detection assumes that the functional relationship specified in function Fct. 2 can be well approximated as a linear characteristic curve. For this purpose, based on the measured functional characteristics shown in Fig. 3 for the dependent variable ^ ^^^_^^^^ from function Fct. 2, at each point of the curve, the measured maximum value ^^^^_^^^^_^^^= ^(^^^^_^^^^_^^^) of all considered functional characteristics is used. The distance dependence of the relationship is thus avoided by using as relevant points of the power characteristic the values ​​for each value of the secondary power ^ ^^^_^^^^ the highest measured values ​​^ ^^^_^^^^evaluated. In Fig. 3, these maximum values ​​^^^^_^^^^_^^^ are indicated as a dashed line d_max. The resulting function characteristic curve is then linearized by determining the parameters of a linear fit function using a best-fit calculation, in particular using the least squares method. The slope (^) and the shift constant (^) of the linearized function characteristic curve are stored as parameters. In further embodiments, a different function can be used for the fit, such as an n-th order polynomial. 38875.TUR.P110PC S / Wi / js 23 / 36 In Fig. 4, the maximum values ​​^^^^_^^^^_^^^ are shown as points d_max and the linearized function ^^^^_^^^^_^^^ continuous curve d_max_lin. For the maximum values The following applies to the functional characteristic curves from Fct.2 over the distances ^ from 0 mm to 7 mm: ^^^^_^^^^_^^^[A] Maximum input current into the resonant circuit of the primary device without foreign object ^^^^_^^^^_^^^[W] Minimum output power from the intermediate voltage link of the secondary device without foreign object The following equation Eq.2 also applies: ^^^^_^^^^_^^^= ^^^^_^^^^_^^^∙ ^^^^_^^^^_^^^Eq.2 ^^^^_^^^^_^^^[V] Minimum voltage at the intermediate circuit capacitor of the secondary device without foreign object ^^^^_^^^^_^^^[A] Minimum current from the intermediate circuit capacitor of the secondary device without foreign object The “minimum” voltage or current of the intermediate circuit capacitor of the secondary device is understood to be the respective values ​​which are at least valid for a given primary current ^ ^^^_^^^^ ′ can be obtained. This means that the minimum secondary power achieved ^^^^_^^^^_^^^in the secondary device and the maximum primary current used for this purpose ^ ^^^_^^^^′. This determines the power characteristic curve so that sufficient reserves are provided to achieve the desired power through inductive power transmission. To linearize function Fct. 3, a fit to an equation as given in Eq. 3 is performed: ^ ^^^_^^^^′ [A] Linearized maximum input current into the resonant circuit of the primary device without foreign object (106) ^ [V-1] Slope of the function Fct.3 (here: 0.053) ^ [A] Displacement constant of the function Fct.3 (here: 0.2245) Fig. 4 shows an example of the linearized functional characteristic curve of Fct. 3 for the measured maximum values ​​at distances ^ from 0 mm to 7 mm. A maximum and linearized power characteristic curve for ^^^^_^^^^_^^^= ^(^^^^_^^^^_^^^) over ^ from 0 mm to 7 mm is shown using a compensation calculation. If a metallic foreign object is located in the electromagnetic field between the primary and secondary devices during power transmission, this creates an inadmissible deviation from the input current into the resonant circuit of the primary device calculated on the basis of Fct. 3 (^ ^^^_^^^^ ′) and is therefore identified as a foreign object. To calculate the maximum permissible input current into the resonant circuit of the primary device, the following applies: ^ ^^^_^^^ = ^^^^_^^^^ ′ + ^ ^^^_^^^^ ′ ∙ ^% Eq.4 ^ ^^^_^^^ [A] Maximum permissible input current into the resonant circuit of the primary device 38875.TUR.P110PC S / Wi / js 25 / 36 ^ ^^^_^^^^ ′ [A] Linearized maximum input current into the resonant circuit of the primary device without foreign object ^% [-] Percentage specified, permissible deviation of the linearized maximum input current into the resonant circuit of the primary device without foreign object As is clear from the above description, there is a relationship between the primary side input power ^ ^^^ , to which the input current ^ ^^^ and the input voltage kept constant in the example ^ ^^^ , and the secondary output power ^ ^^^ , to which the output current ^ ^^^ and the output voltage ^ ^^^ contribute, and the distance ^ between primary 100 and secondary device 200. Simply put, the more input power ^ ^^^be used to achieve the same secondary output power ^ ^^^to be achieved, the greater the distance ^ is. In the procedure illustrated in Fig. 4, the power characteristic curve is constructed such that the distance ^ is not taken into account for the comparison with a threshold value of the maximum permissible input current of the primary device. However, there is a dependency between the target primary power data on the transmitter side, the achieved secondary power data on the receiver side, and the distance between the transmitter and receiver. In a further embodiment, it is therefore provided that the axial distance ^ between the transmitter and the receiver is determined and taken into account in order to determine the target primary power or the maximum permissible primary current. For this purpose, the appropriate power characteristic curve is determined using a power characteristic map that includes power characteristics for different values ​​of the distance ^. In particular, the measurements of the values ​​of the regulated actual primary current ^ shown in Fig. 3^^^_^^^^ depending on the secondary 38875.TUR.P110PC S / Wi / js 26 / 36 output power ^ ^^^_^^^^at different distances ^ evaluated. For each distance ^ or for a specific range of distances, a separate power characteristic curve is determined using a compensation calculation and fitted to an n-th order polynomial or another suitable function using a compensation calculation. The power characteristic curves recorded for different distances ^ now form a distance characteristic map. In order to evaluate this distance characteristic map, the required secondary output power and the distance ^ must be recorded. The power characteristic curve matching the distance ^ is then determined and based on this power characteristic curve the target primary power data is determined, in this example the maximum primary input current, whereby a fixed primary input voltage is assumed. The determination of the axial distance between the primary device and the secondary device is explained below with reference to Fig. 5.The system 500 shown here essentially corresponds to the system already explained above with reference to Fig. 1. Therefore, it will not be described in detail again. The system 500 for inductive power transmission comprises a primary device 600 and a secondary device 700. The control unit is not shown separately here, but is intended to be included in the primary device 600. During an inductive power transmission, a control 607 of the primary device 600 is supplied by a source 510 with a primary current ^. ^^^ The control 607 then provides a pulse width modulated signal ^ ^^^ready to drive an oscillating circuit 504. In this way, a primary-side frequency of 105.0 to 129.5 kHz is achieved in the exemplary embodiment. 38875.TUR.P110PC S / Wi / js 27 / 36 Power is transferred 540 from the primary-side oscillating circuit 604 to a secondary-side oscillating circuit 704. In parallel, data transfer 530 is implemented between the primary device 600 and the secondary device 700, with an IO-Link connection being provided in the example; in further exemplary embodiments, other data connections can be provided alternatively or additionally. The alternating voltage induced in the oscillating circuit 704 of the secondary device 700 depends on the distance ^ between the primary device 600 and the secondary device 700. By means of this induced alternating voltage, a rectifier 707 then generates a direct voltage ^ ^^^generated. As soon as power is delivered from the secondary device 700 to a load 520, a measurable secondary current flows from the intermediate circuit capacitor ^ ^^^ . The current values ​​for the secondary current ^ ^^^ and the secondary voltage ^ ^^^ are measured and transmitted via data transmission 530 to the primary device 600. Within the limits of the frequency of the PWM control signal ^ ^^^ the primary device 600 regulates the intermediate circuit voltage ^ ^^^ of the secondary device 700, to a desired value, in the embodiment 24 V. The graph shown in Fig. 6 illustrates an example of a functional relationship between the frequency of the PWM control signal ^ ^^^ of the primary device 600 and the intermediate circuit voltage ^ ^^^ of the secondary device 700. Furthermore, the graph shown in Fig. 7 illustrates an example of a functional relationship between the frequency of the PWM control signal ^ ^^^of the 38875.TUR.P110PC S / Wi / js 28 / 36 primary device 600 and the secondary current ^ ^^^ of the secondary device 700. This graph shows curves of measurements at different distances ^, here 0 mm, 2 mm and 4 mm. To better evaluate these curves, the secondary power ^ is plotted on the x-axis. ^^^ = ^ ^^^ ∙ ^ ^^^ and on the y-axis the value of ^ ^^^ ∙ ^ ^^^ ∙ ^, where the factor ^ = ^ ∙ ^ ^ with a constant ^ = 30 and a parameter ^ = ^ ^^^ = ^ ^^^ ∙ ^ ^^^ with the exponent ^ = −1. This results in the following transformation for the values ​​of the y-axis in this example: ^ ^^^ ∙ ^ ^^^ ∙ ^ That is, the curves shown in Fig. 7 show the relationship of the value ^ ^^^ / ^ ^^^ depending on the secondary power ^ ^^^for different distances ^. In a further step, the curves measured for the distances ^ can be fitted using a fitting calculation, for example, determining the parameters of a third-order polynomial. In the example, the constants ( ^1, ^2, ^3, ^4 ) for a polynomial of the form: The course of such characteristic curves for the distances ^ between 0 mm and 7 mm is shown as an example in Fig. 8. In the exemplary embodiment, these characteristic curves for various distances ^ form the distance characteristic field. 38875.TUR.P110PC S / Wi / js 29 / 36 To determine a distance between the transmitter 100, 600 and the receiver 200, 700, the primary frequency ^ ^^^ of the primary device 100, 600 and the secondary power obtained from the intermediate circuit of the secondary device 200, 700 ^ ^^^ In particular, the secondary performance ^ ^^^via the data connection 530, such as an IO-Link connection, from the secondary device 200, 700 to the primary device 100, 600. It can now be determined which of the characteristic curves of the distance characteristic map the measured value pair is closest to. The corresponding distance ^ is then output and can be used, for example, in foreign body detection. In further embodiments, the characteristic curves of the distance characteristic map can be formed in other ways. The basic idea here is that the characteristic curves represent a relationship between the primary frequency ^ ^^^ of the primary device 100, 600 and the secondary power obtained from the intermediate circuit of the secondary device 200, 700 ^ ^^^for different distances ^. These parameters are recorded during the inductive power transmission, and a test is carried out to determine which characteristic curve the recorded pair of values ​​most closely corresponds to. The corresponding distance ^ can then be specified.

[0002] 38875.TUR.P110PC S / Wi / js 30 / 36 List of reference symbols 10 System 100 Primary device; transmitter 101 Voltage converter 102 Voltage intermediate circuit; primary intermediate circuit 103 Amplifier 104 Single coil 105 Voltage measuring unit 106 Current measuring unit 107 Evaluation and control unit 108 Primary interface; interface (data transmission) 110 Input 120 Output 130 Data transmission 140 Power transmission 200 Secondary device; receiver 201 Voltage converter 202 Voltage intermediate circuit; secondary intermediate circuit 203 Rectifier 204 Single coil 205 Voltage measuring unit 206 Current measuring unit 207 Evaluation and control unit 208 Secondary interface; Interface (data transmission) 500 System 510 Source 520 Load 530 Data connection 540 Power transmission 600 Primary device 38875.TUR.P110PC S / Wi / js 31 / 36 604 Primary resonant circuit 607 Control 700 Secondary device 704 Secondary resonant circuit 707 Rectifier d Distance S1, S2, S3, S4, S5, S6, S7 Step

Claims

38875.TUR.P110PC S / Wi / js 32 / 36 Patent claims 1. System (10) for inductive power transmission, comprising - a primary device (100) and a secondary device (200); and - a control unit (120); - wherein the primary device (100) is configured to inductively transmit power to a secondary resonant circuit of the secondary device (200) during the power transmission via a primary resonant circuit; wherein - the control unit (120) is configured to detect secondary power data of the secondary device (200) and a frequency parameter of the primary device (100); wherein - the control unit (120) is further configured to determine an actual distance between the primary device (100) and the secondary device (200) using a distance characteristic map based on the detected secondary power data and the frequency parameter; where - the distance map includes reference secondary power data as a function of reference frequency parameters and as a function of reference distances. 2.System (10) according to claim 1, characterized in that the frequency parameter of the primary device (100) relates to a primary frequency of the primary device (100); and / or that the secondary power data relates to a secondary voltage induced in a secondary intermediate circuit (202) of the secondary device (200) and / or a secondary current supplied from the secondary intermediate circuit (202) of the secondary device (200). 38875.TUR.P110PC S / Wi / js 33 / 36 3. System (10) according to one of the preceding claims, characterized in that the control unit (120) is comprised by the primary device (100); and / or that the control unit (120) is configured to acquire the secondary performance data via an IO-Link connection.

4. System (10) according to one of the preceding claims, characterized in that the distance characteristic map can be determined based on a distance reference measurement; wherein, during the distance reference measurement, actual secondary performance data of the secondary device (200) are measured as a function of the frequency parameter of the primary device (100) for a plurality of reference distances within a predetermined operating range between the primary device (100) and the secondary device (200). 5.System (10) according to claim 4, characterized in that characteristic curves of the distance characteristic map are determined by means of a regression analysis, in particular a linear or polynomial curve fitting, as functions of the measured secondary power data as a function of the frequency parameter.

6. System (10) according to one of the preceding claims, characterized in that the control unit (120) is further configured to determine primary target power data on the basis of the acquired secondary power data and the determined actual distance by means of a power characteristic curve; wherein the power characteristic curve comprises reference target power data as a function of reference secondary power data and as a function of reference distances; wherein. 38875.TUR.P110PC S / Wi / js 34 / 36 the control unit (120) is further configured to acquire primary performance data of the primary device (100) and to detect a foreign object based on a comparison of the primary target performance data with the primary performance data.

7. System (10) according to claim 6, characterized in that the performance characteristic curve can be determined based on a performance reference measurement; wherein, during the performance reference measurement, actual primary performance data of the primary device (100) are measured as a function of a plurality of reference secondary performance data of the secondary device (200). 8.A primary device (100) for inductive power transmission from the primary device (100) to a secondary device (200), comprising - a control unit (120) and a primary device interface (108); wherein - the control unit (120) is configured to detect a frequency parameter of the primary device (100) and, via the primary device interface (108), to detect secondary power data of a secondary device (200) coupled to the primary device (100) for inductive power transmission; and - wherein the control unit (120) is further configured to determine an actual distance between the primary device (100) and the secondary device (200) based on the detected secondary power data and the frequency parameter by means of a distance characteristic map; - wherein the distance characteristic map comprises reference secondary power data as a function of reference frequency parameters and as a function of reference distances. 9.Method for operating a system (10) for inductive power transmission from a primary device (100) to a secondary device (200); wherein. 38875.TUR.P110PC S / Wi / js 35 / 36 - during the inductive power transmission, a frequency parameter of the primary device (100) and secondary power data of the secondary device (200) are recorded; and - based on the recorded secondary power data and the frequency parameter, an actual distance between the primary device (100) and the secondary device (200) is determined by means of a distance characteristic map; wherein - the distance characteristic map comprises reference secondary power data as a function of reference frequency parameters and as a function of reference distances.

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