PRIMARY ASSEMBLY FOR USE IN A WIRELESS POWER TRANSMISSION SYSTEM,

POSITIONING SYSTEM, AND METHOD OF DETERMINING A DISTANCE BETWEEN A PRIMARY ASSEMBLY AND A SECONDARY ASSEMBLY

The present invention refers to the field of wireless power transmission. In such systems, a primary assembly and a secondary assembly should be aligned and therefore, the position and orientation of the secondary assembly relative to the primary assembly should be known.

In a primary assembly of a system of wireless power transmis ^¬ sion, a transmission coil or a system of transmission coils can be provided. In a secondary assembly, a reception coil or a plurality of reception coils can be provided. Electromag ^¬ netic power such as magnetic power can be transferred from the primary assembly to the secondary assembly by induction from a primary coil of the primary assembly. If the secondary assembly having the secondary coil is in the vicinity of the primary coil, then the secondary coil can receive the

magnetic power and convert it to electric energy. Utilizing such systems, electric power can be transferred wirelessly, e.g. to charge battery of a wireless communication device or the battery of an electric vehicle.

To reduce transmission losses, the primary assembly and the secondary assembly should be aligned with respect to each other .

The primary assembly can be an assembly solidly mounted to a fixed position, e.g. a charging position at a parking area. The secondary assembly can be mounted to the electric vehicle and electrically connected to the vehicle's circuitry.

Thus, for optimal power transfer, the positioning of the sec- ondary assembly in the vicinity of the primary assembly, e.g. directly above the primary assembly, is wanted and a possible misalignment should be as small as possible.

The corresponding positioning system may operate simultane- ously with the wireless power transfer operation and should be immune to its presence.

From the patent publications WO 2016/099807 Al and US

2015/0094887 Al, positioning systems utilizing radar trans- ceivers or transmission coils are known.

However, known systems are either complex and strongly increase manufacturing costs or not very accurate. Thus, what is wanted is a positioning system that is relia ^¬ ble, accurate and producible with low additional costs.

To that end, a primary assembly for use in a wireless power transmission system, a positioning system, and a method of determining a distance between a primary assembly and a sec ^¬ ondary assembly are provided in the independent claims. De ^¬ pendent claims provide preferred embodiments.

The primary assembly can be used in a wireless power trans- mission system. The primary assembly comprises a first an ^¬ tenna and a second antenna. The first antenna is provided to determine a distance between the first antenna and a circuit component of a secondary assembly. The secondary assembly may be used for or may be part of a wireless power transmission system. The second antenna is provided to determine a dis ^¬ tance between the second antenna and the circuit component of the secondary assembly.

The number of antennas is not limited. The primary assembly can have further antennas .

The primary assembly may be the assembly of a wireless power transmission system that is localized at a fixed position, e.g. at a parking area. The primary assembly may be the transmitting part of a wireless power transmission system.

The secondary assembly may be the assembly that is used for receiving transmitted energy and can be connected to or be a part of an electric vehicle or, in general, an electrical de ^¬ vice that should be provided with energy without the need for a cable connection. Thus, the primary assembly can be a ground assembly and the secondary assembly can be a vehicle assembly.

The circuit component of the secondary assembly and the first antenna and the second antenna of the primary assembly should work together to determine the distance between the primary assembly and the secondary assembly. If the distance between the primary assembly and the secondary assembly is known, then the corresponding wireless power transmission system can determine whether electromagnetic power can be transferred from the primary assembly to the secondary assembly or not. Further, if the distance is known, then measures can be performed to bring the secondary assembly to the primary assembly. In general, if the distance between the circuit component of the secondary assembly and the first antenna of the primary assembly is known, then it is clear that the primary assembly is located on a spherical surface around the secondary assem ^¬ bly. To be more precise: if the distance between the circuit component of the secondary assembly and the first antenna of the primary assembly is known and if the distance between the circuit component of the secondary assembly and the second antenna of the primary assembly is known, then the circuit component of the secondary assembly is at an intersection of a first spherical surface around the first antenna of the primary assembly and a second spherical surface of the second antenna of the primary assembly.

If it is assumed that the primary assembly is at a fixed lo ^¬ cation at a parking area and the secondary assembly is mounted to an electric vehicle that drives on a road and moves in two dimensions, then the position of the circuit component of the secondary assembly can be limited to two in ^¬ tersecting points of two circles around the first antenna and the second antenna, respectively.

Thus, it is possible that the primary assembly further com- prises a third antenna that is provided to determine a dis ^¬ tance between the third antenna and the circuit component of the secondary assembly.

With the knowledge of the distance between the circuit compo- nent of the secondary assembly and the third antenna of the primary assembly, the exact position of the circuit component of the secondary assembly can be determined. Compared to conventional positioning systems, the provision of two or three coils at the primary assembly and an addi ^¬ tional circuit component at the secondary assembly allows a high precision at low costs and a high reliability.

It is possible that the antenna or the antennas of one of the assemblies selected from the primary assembly and the second ^¬ ary assembly emits a signal while the antenna or the antennas of the respective other assembly receives the transmitted signal.

Thus, it is possible that the first antenna and the second antenna and - if present, the third antenna - are reception antennas and the circuit component of the secondary assembly is a transmission antenna.

When the transmission antenna, e.g. of the secondary assembly, iteratively emits a signal that is received by the an ^¬ tennas of the primary assembly, then the distance between the secondary assembly (to be more precise: the antenna of the secondary assembly) and the primary assembly can be monitored iteratively .

The signal can be an electromagnetic signal.

The distance between the circuit component of the secondary assembly and the antennas of the primary assembly can be de ^¬ termined by evaluating the signal strength at the position of the respective reception antenna.

It is possible that the first antenna and the second antenna comprise a resonance circuit. The respective resonance cir- cuit of an antenna can include an inductive element and a ca- pacitive element. The inductive element and the capacitive element can be electrically connected, e.g. in series or in parallel to each other.

Also, the circuit component of the secondary assembly can comprise a resonance circuit having an inductive element and a capacitive element connected in series or in parallel. The inductivity of the inductive elements and the capacity of the capacitive elements can be chosen to set the resonance frequencies of the corresponding resonance circuits to a com ^¬ mon value. The resonance frequency can be between 50 kHz and 50 MHz, e.g. 125 kHz .

The signal transmitted by the circuit component of the sec ^¬ ondary assembly can be a square wave signal.

It is possible that the primary assembly further comprises a first rectifier, a second rectifier and an evaluation

circuit. The first rectifier is electrically connected to the first antenna and to the evaluation circuit, the second rectifier is electrically connected to the second antenna and to the evaluation circuit. The rectifier is provided to transmit a first signal and a second signal to the evaluation circuit . It is possible that the primary assembly comprises one rectifier per antenna. The rectifier can receive an electric signal provided by the respective antennas. The rectifier can rectify each electric signal and provides the rectified signal to the evaluation circuit .

The electromagnetic energy of an electromagnetic signal is mainly proportional to the square of the voltage induced by the antenna. Further, the electromagnetic power received by an antenna is mainly reciprocal to the square value of the distance between the transmitter and the receiver. Thus, a voltage provided from a reception antenna to the rectifier is mainly reciprocal to the distance between the corresponding reception antenna and the circuit component of the secondary assembly emitting the signal. Correspondingly, the rectified signal is a measure for the corresponding distance that is submitted to the evaluation circuit. Utilizing triangulation or similar methods based on the knowledge concerning the distances between the circuit components of the secondary assembly and each antenna of the primary assembly, the evaluation circuit can determine the distance between the circuit component of the secondary assembly and the primary assembly .

Correspondingly, it is possible that the first signal is a voltage signal that is a measure for the distance between the first antenna and the circuit element of the secondary assem ^¬ bly and the second signal is a voltage signal that is a meas ^¬ ure for the distance between the second antenna and the cir ^¬ cuit element of the secondary assembly.

It is possible that the primary assembly is provided for use in a wireless power transmission system comprising a primary coil provided to transmit electromagnetic power to a secondary coil. The secondary coil is the receiving coil of the system. The secondary coil may be part of the secondary assembly. Or the secondary assembly and the secondary coil may be parts of a reception system being part of the wireless power transfer system.

A positioning system comprises a primary assembly, e.g. as described above, and a secondary assembly, e.g. as described above. Thus, the secondary assembly can have an antenna as a circuit element and a secondary coil provided to receive electromagnetic power from the primary assembly or to

transmit electromagnetic power to the primary assembly.

Thus, the terminology is such that the primary coil is associated with the primary assembly and the secondary coil is associated with the secondary assembly. One possible function of the primary coil is to transmit power to the secondary coil. However, the opposite direction is also possible: the secondary coil can be used to transmit power to the primary coil, too.

If the positioning system notifies that the distance between the primary assembly and the secondary assembly is suffi ^¬ ciently small, then the power transfer from the primary as- sembly, which may be a ground assembly, to the secondary as ^¬ sembly, which may be a vehicle assembly, can be started.

It is possible that the positioning system and/or the second ^¬ ary assembly comprise a fifth antenna and/or a sixth antenna in the secondary assembly.

By evaluating distances between additional antennas of the secondary assembly and the antennas of the primary assembly, not only the distance between the secondary assembly and the primary assembly but also the orientation of the secondary assembly relative to the primary assembly can be determined. This is especially useful if information obtained from the positioning system shall be used to navigate the secondary assembly to the primary assembly because then, an optimal di ^¬ rection to navigate the secondary assembly to the primary as ^¬ sembly can be determined. A method of determining a distance between a primary assembly of a wireless power transmission system and a secondary assembly of the wireless power trans ^¬ mission system comprises the steps:

- transmitting a first signal from a circuit component of the secondary assembly,

- receiving the first signal with a first antenna of the pri ^¬ mary assembly,

- receiving the first signal with a second antenna of the primary assembly,

- determining a first distance between the circuit component of the secondary assembly and the first antenna by evaluating the signal strength of the first signal at the position of the first antenna,

- determining a second distance between the circuit component of the secondary assembly and the second antenna by evaluat- ing the signal strength of the first signal at the position of the second antenna.

- determining the position and orientation of a secondary coil based on the first and the second distance and the angle of two directions. Of course, if the primary assembly has one or more additional antennas and if the secondary antenna has one or more addi ^¬ tional antennas, then additional steps of transmitting, re ^¬ ceiving and evaluating can be performed.

In particular, it is preferred that the primary assembly has four antennas to increase redundancy and to improve evalua ^¬ tion of the distances. It is possible that the method further comprises the steps:

- receiving the first signal with a third antenna of the pri ^¬ mary assembly,

- determining a third distance between the circuit component of the secondary assembly and the third antenna by evaluating the signal strength of the first signal at the position of the third antenna,

- determining the distance between the primary assembly and the secondary assembly by evaluating the first distance, the second distance, and the third distance.

Thus, by utilizing triangulation by the evaluation circuit, the precise distance between the transmission antenna of the secondary assembly and the primary assembly can be determined while only circuit components need to be added to the assem- blies that increase manufacturing costs to a small amount.

Working principles and details of preferred embodiments are explained and provided by the schematic figures. In the figures:

FIG. 1 shows a possible arrangement of a vehicle assembly near a ground assembly. shows the relevant distances between the circuit component of the vehicle assembly and the antennas of the ground assembly. shows voltage signals provided at a specified time. shows the vehicle assembly at the position of the ground assembly. shows the temporal development of the voltage sig ^¬ nals during an approach. shows a vehicle assembly comprising three antennas. shows the final state where the vehicle assembly is not only brought to the position of the ground as ^¬ sembly but also aligned with the ground assembly. shows a possible composition of circuit elements in a series resonance circuit. shows a possible arrangement of circuit elements in a parallel resonance circuit. shows the working principle of the rectifier and the evaluation circuit.

FIG. 11 shows an embodiment of the ground assembly with

four antennas . FIG. 1 shows a typical initial state of a secondary assembly realized by a vehicle assembly VA in the vicinity of a pri ^¬ mary assembly realized by a ground assembly GA. The position ^¬ ing system shall help bringing the vehicle assembly VA to the ground assembly GA. It is assumed that the vehicle assembly VA is mounted to a vehicle that can be moved in two dimen ^¬ sions, that is in the xy-plain. The vehicle assembly VA may have a secondary coil SC and the ground assembly GA may have a primary coil PC. The primary coil PC and the secondary coil SC should be utilized to transmit magnetic power from the ground assembly GA to the vehicle assembly VA, e.g. to charge the vehicle's battery. To that end, the secondary coil must be brought to and aligned to the primary coil PC. The vehicle assembly VA has a first antenna VAAl that can continuously or iteratively emit an electromagnetic signal. The ground assembly GA has a first antenna GAA1, a second an ^¬ tenna GAA2 and a third antenna GAA3. Each of the antennas of the ground assembly GA receives the signal or the signals transmitted by the antenna VAAl of the vehicle assembly VA. By evaluating the signal, e.g. by evaluating the signal strength at the corresponding position of the reception antenna, the distance between the vehicle assembly VA and the ground assembly GA can be determined.

FIG. 2 shows the relevant distances of the positioning system PS, i.e. a first distance between the antenna of the vehicle assembly VA and the first antenna of the ground assembly GA. The second distance D2 is the distance between the antenna of the vehicle assembly VA and the second antenna of the ground assembly GA, and the third distance D3 is the distance be ^¬ tween the antenna of the vehicle assembly and the third re ^¬ ception antenna of the ground assembly GA. FIG. 3 illustrates corresponding voltage levels that corre ^¬ spond to the distances Dl, D2, D3 in FIG. 2. The maximum voltage is limited by the shortest possible distance between the transmission antenna of the vehicle assembly and the re ^¬ ception antenna of the ground assembly.

FIG. 4 illustrates a final position of the vehicle assembly VA directly over the ground assembly GA after guiding an electric vehicle to its charging position. However, the orientation of the vehicle can still be improved.

FIG. 5 shows the corresponding temporal development of volt ^¬ age signals from an initial time Tl to the final time T2. The vehicle is moved towards the ground assembly in such a way that the determined distance is reduced. The final position may be reached when the sum of the voltage signals has reached a maximum. FIG. 6 shows a vehicle assembly VA having three transmission antennas. With two or more transmission antennas at the vehi ^¬ cle assembly site, not only the distance between the vehicle assembly and the ground assembly GA can be determined. Fur ^¬ ther, the orientation of the vehicle assembly VA relative to the ground assembly GA can be determined. Thus, as a conse ^¬ quence thereof, FIG. 7 shows a final stage of an approach process where the vehicle assembly is precisely positioned over the ground assembly and where the vehicle assembly is precisely arranged relative to the ground assembly. By evalu- ating the distances between each of the antennas of the vehi ^¬ cle assembly and each of the antennas of the ground assembly, a precise determination of the position and a precise determination of the orientation can be obtained. FIG. 8 shows possible details of a preferred transmission or reception antenna having an inductive element IE a capacitive element CE and a resistive element RE in the antenna A. The inductive element IE and the capacitive element CE are electrically connected in series and form a series resonance circuit .

FIG. 9 shows an alternative preferred embodiment of a recep- tion or a transmission antenna A where the inductive element IE and the capacitive element CE are electrically connected in parallel to form the parallel resonance circuit. The parallel circuit is connected in series with a resistive element .

The inductances of the inductance elements of the antennas and the capacities of the capacitive elements of the antennas are chosen such that the corresponding resonance frequency of the resonance circuit matches a common resonance frequency that may be around 125 kH.

FIG. 10 shows further details of the ground assembly GA hav ^¬ ing a rectifier R and an evaluation circuit EC. The rectifier R receives information, e.g. voltage information, from the antennas of the ground assembly GA and provides corresponding distance information that may be encoded as a voltage to the evaluation circuit EC. The evaluation circuit EC may comprise amplifiers and integrated circuits to perform the necessary calculations to convert voltage information to distance in- formation that can be provided to a routing system that leads the vehicle to the ground assembly. FIG. 11 shows a preferred embodiment where the ground assem ^¬ bly GA has four reception antennas.

The assemblies and the positioning system and the methods de scribed above are not limited to the stated technical de ^¬ tails. Assemblies can comprise further circuit elements. The positioning system can comprise further assemblies and circuit elements and the methods can comprise further steps.

List of reference signs

A: antenna

CE : capacitive element

Dl, D2, D3 distances

EC: evaluation circuit

GA: ground assembly/primary assembly

GAAi, 2, 3, 4- first, second, third, fourth antenna of the ground assembly

IE: inductive element

PC: primary coil

PS: positioning system

R: rectifier

RE: resistive element

SC: secondary coil

Tl : first time

T2 : second, later time

V: voltage

Vi,2,3: voltages received by antennas of the ground assembly

VA: vehicle assembly/secondary assembly

VAA1 : first antenna of the vehicle assembly

VAA2, VAA3 : a second and a third antenna of the vehicle assembly