KR20190015861A - The tilting algorithm for achieving high efficiency on wireless charging system - Google Patents

Abstract

The present invention relates to a method for detecting position relationship of a charging pad pair in a wireless charging system of an electric car and displacing the position relationship to optimal efficient positions. The objective of the method is to find optimal efficiency through low power signal input before real wireless charging, in other words, high power transmission. The method performs tilting of only pads, not overall movement of the car. The method measures resonance impedance of current displacement through low power signal transfer, and applies an efficiency calculation algorithm through a preregistered resonance frequency versus efficiency lookup table. A tilting mechanism device performs measurement, comparison and calculation of the resonance frequency and the physical displacement of the pads by driving an actuator. Therefore, the method can perform wireless charging with optimal efficiency in correspondence to states of the car (movement of a weight center, tilting and the like). If applied to an autonomous parking system, the present invention may provide technical advantages.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilting algorithm for a high-efficiency wireless charging system,

The present invention relates to electric vehicle technology, and more particularly, to a system for wirelessly charging a battery installed in a vehicle.

The electric vehicle charges the battery from external sources. A rechargeable AC power source, or a household power source. There must be cables and connectors physically connected to the power supply, which is sometimes inconvenient. A wireless charging system is known to replace this. The charging station is parked at a predetermined location to create a wireless charging environment. At this time, it is necessary to match the positions of the charging pad (Tx) of the charging station and the charging pad (Rx) of the vehicle.

Various prior arts have been proposed and are being actively researched, analyzed and discussed with respect to such wireless charging techniques. For example, Korean Patent No. 1364180 proposes a device for supplying electric power to an electric vehicle (Patent Document 1). Patent Document 1 discloses a technique of minimizing magnetic resistance by minimizing the gap between the power feeding core and the power collecting core (zero void), thereby maximizing the efficiency of power transmission. Although it is intended to achieve uniform power transmission using only a commercial frequency power source of 60 Hz without using a high frequency inverter and a regulator, there is a disadvantage that a design of a power supply coil and a current collecting coil must be newly changed.

International Publication No. WO2014 / 008300 proposes a wireless charging technique between a charging station and a paired vehicle (Patent Document 2). Patent Document 2 focuses on identification through communication between a vehicle and a charging station. However, the positional matching of the charging stations and the charging units of the vehicle, which are paired to perform the wireless charging, is vaguely described.

Whether using the technique of Patent Document 1, the technique of Patent Document 2, or other known or newly developed wireless charging technology, the user who drives the vehicle can operate the vehicle at a position suitable for wireless charging . At least a suitable location in terms of the charging station can be known in advance. If so, how important it is to guide and guide the driver to park at that location. This is related to the efficiency of the charge and is also a matter of safety.

However, even if the driver parked the electric car at the expected location in the charging station, there are still subtle problems affecting the charging efficiency. Not all vehicles are operated under the same conditions. For example, the center of gravity of the vehicle may be shifted or tilted because the air pressure of the front, rear, and right wheels is different. Also, the center of gravity of the vehicle may be moved or inclined by the occupant's position, the position, the load placed on the trunk, and the like, so that the geometric position of the vehicle-filled pad degrades its efficiency even if the vehicle is positioned for a predetermined maximum efficiency I could predict the problem. The tilting position of the transmission pad and the reception pad causes a spacing angle.

Therefore, the inventors of the present invention have studied and developed for a long time in order to solve the above-mentioned problems, and finally completed the present invention.

It is an object of the present invention to provide a method for searching for optimum charging efficiency in a geometrical positional relation between a charged Tx pad and an Rx pad. The point at which the method of the present invention is applied is after the driver has positioned the vehicle at the registration position and before the large-capacity power transmission from the charging station to the vehicle.

It is another object of the present invention to provide a new method of the present invention that should be simple and to find the optimum efficiency position relation as quickly as possible. By performing tilting of the transmitting pad and / or the receiving pad, rather than moving the vehicle as a whole, it tries to find the optimum efficiency point with minimal displacement.

On the other hand, other unspecified purposes of the present invention will be further considered within the scope of the following detailed description and easily deduced from the effects thereof.

In order to achieve the above object, a first aspect of the present invention is a method for detecting a positional relationship between a pair of charging pads in a wireless charging system of an electric vehicle and displacing the battery to an optimum efficiency position,

(a) when the charging Rx pad of the vehicle located in the charging station area is displaced, the charging station device performs a first signal power transmission preset via the charging Tx pad,

(b) The tilting mechanism device installed on the vehicle side senses the first signal received through the charging Rx pad of the vehicle, measures the resonance impedance, calculates the power transmission efficiency, compares it with a predetermined reference value S1,

(c1) when the power transmission efficiency is greater than the reference value (S1), tilting of the charging Rx pad is terminated, and high power transmission is performed from the charging station device to the vehicle side charging device,

(c2) is not greater than the reference value (S1), the charge Rx pad displacement of the step (a) is performed to continue the step (b) if the difference does not exceed the predetermined threshold,

(c3) if the difference is greater than a predetermined threshold, displacing the displacement of the charged Rx panel in the opposite direction and displacing then the charging station device performs a predetermined second signal power transmission through the charging Tx pad,

(d) The tilting mechanism device senses the second signal received through the charging Rx pad of the vehicle and measures the resonance impedance to calculate the power transmission efficiency and compares it with a preset reference value (S2)

(e1) when the electric power transmission efficiency in the step (d) is greater than the reference value (S2), the tilting of the charged Rx pad is terminated and the large electric power transmission is performed from the charging station device to the vehicle side charging device,

(e2) is not greater than the reference value (S2), the step (c2) is continued.

Preferably, the displacement of the filled Rx pad is made by displacement in the yaw and / or pitch directions by an actuator provided on the filled Rx pad.

A second aspect of the present invention is a method for controlling a charging station, comprising the steps of: (a) when a charging Tx pad of a charging station device is displaced relative to a vehicle located in a charging station area,

(b) The tilting mechanism device installed in the charging station device senses the first signal received through the charging Tx pad, measures the resonance impedance, calculates the power transmission efficiency, compares it with a predetermined reference value S1,

(c1) when the power transmission efficiency is greater than the reference value (S1), the tilting of the charging Tx pad is terminated, and then the charging station device performs the large power transmission to the vehicle side charging device,

(c2) is not greater than the reference value (S1), the charge Tx pad displacement of the step (a) is performed to continue the step (b) if the difference does not exceed the predetermined threshold value,

(c3) if the difference is greater than a predetermined threshold value, displacing the displacement of the charged Tx panel in the opposite direction to displace, then the vehicle-side device performs a predetermined second signal power transmission through the charged Rx pad,

(d) The tilting mechanism device senses the second signal received through the charging Tx pad of the vehicle, measures a resonance impedance, calculates a power transmission efficiency, compares the power transmission efficiency with a predetermined reference value (S2)

(e1) when the electric power transmission efficiency in the step (d) is larger than the reference value (S2), the tilting is terminated and the large electric power transmission is performed from the charging station device to the vehicle side charging device,

(e2) is not greater than the reference value (S2), the step (c2) is continued.

Preferably, the displacement of the charged Tx pad is made by a displacement in the yaw and / or pitch directions by an actuator provided on the charged Tx pad.

A third aspect of the present invention is a method for controlling a charging station device, comprising: before a charging station device performs a large power transmission through a pair of charging pads for an electric car stationary in a charging station area for wireless charging:

Frequency current signal is transmitted through the pair of charging pads and the power transmission efficiency is calculated by the resonance impedance measured through the signal transmission and is compared with a predetermined reference value to determine the charging Tx The geometric relationship of the pair of charging pads during the wireless charging is determined through a process of physically displacing by a tilting mechanism performed on either one of the pad and the charging Rx pad.

According to the principles of the present invention, the positional relationship of the charging pads can be optimized before charging the electric vehicle at the charging station. That is, the charging efficiency can be increased from the initial preliminary step for wireless charging. This effect has been realized by the present invention in an economical and rapid manner. It is more advantageous in the case of wireless charging according to autonomous parking of an electric vehicle.

On the other hand, even if the effects are not explicitly mentioned here, the effect described in the following specification, which is expected by the technical features of the present invention, and its potential effects are treated as described in the specification of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a conceptual configuration of a charging system showing a relationship between a charging station and a electric vehicle for wireless charging. FIG.
Figure 2 schematically shows a diagram of a configuration according to some preferred embodiments of the present invention.
3 is a diagram showing the principle of physical displacement of a charged Rx pad according to some preferred embodiments of the present invention.
4 is a graph showing the relationship between the physical displacement of the charged Rx pad and the resonant frequency according to some preferred embodiments of the present invention.
5 is a schematic view of an overall process according to a preferred embodiment of the present invention.
* The accompanying drawings illustrate examples of the present invention in order to facilitate understanding of the technical idea of the present invention, and thus the scope of the present invention is not limited thereto.

The present invention will now be described with reference to the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.

Figure 1 conceptually illustrates the basic spirit of the present invention. Wireless charging is based on the relationship between a charging station and an electric vehicle (EV). The charging station is comprised of a charging station device (100) and a charging station area (10). The EV 20 has a charging Rx pad 210 for receiving large power from the charging station 100 and supplying charging power to the built-in battery. In the case of wireless charging, the charging efficiency is greatly influenced by the position or spacing of the Tx pad 110 and the Rx pad 210, that is, the geometrical positional relationship of the pair of charging pads. First, the position of the charging pad is adjusted through the movement of the vehicle, and parking induction has an important technical meaning.

That is, as shown in FIG. 1 (a), the driver operates the electric vehicle (EV) 20 to enter the charging station area 10 and attempt parking. In order to perform wireless charging through the charging station device 100, the EV 20 must park at the matching position 50 for wireless charging. The geometric positional relationship between the charging Tx pad 110 of the charging station and the charging Rx pad 210 of the EV 20 is preset to the optimum efficiency range. The driver of the EV 20 can not know the optimum efficiency range, but the vehicle should be parked at the registration position 50 anyway to make the state as shown in Fig. 1 (b). Therefore, it is desirable that the wireless charging system induce parking so that it can park at the matching position. Conventionally, a method of guiding the driver to the driver by using a hardware means, or a method of maintaining the charging efficiency by performing impedance matching after power feeding has been used. In the present invention, the optimum efficiency is first obtained through a small signal before the large power transmission is performed in the power feeding device. Therefore, the resonance frequency and the impedance can be discriminated even while the EV 20 is running, and the parking induction can be performed so that the driver can perform optimal positioning.

However, even if parking is terminated at the registration station 50 of the charging station, as described above, there still remains a subtle problem affecting the charging efficiency. The deviation of the center of gravity of the vehicle due to the difference in the air pressure of the front and rear wheels, the position of the occupant, the number of persons, and the weight of the load placed on the trunk causes tilting of the pair of charging pads, Lt; / RTI > Therefore, since the geometrical positional relationship predicted by the optimum charging efficiency at the matching position 50 varies depending on the condition of the vehicle, the present invention is intended to readjust the geometrical positional relationship between the two pads designed with optimal charging efficiency. To this end, the charging Tx pad 110 or the charging Rx pad 210 may be displaced in the Yaw direction and / or the Pitch direction. That is, a tilting mechanism including an actuator may be installed in the charging station device or the vehicle-side device to make the displacement of the charging Tx pad 110 or the charging Rx pad 210.

The tilting mechanism of the present invention is characterized in that the tilting mechanism of the present invention includes a phase in which predetermined signal power transmission is performed through a pair of charging pads, a phase in which efficiency is determined with respect to a resonance frequency using a resonance impedance of a measured current position state, If necessary, the charging Tx pad 110 or the charging Rx pad 210 is physically displaced through the actuator stepwise.

Figure 2 schematically shows an electronic configuration according to some preferred embodiments of the present invention. Wireless charging is performed between the charging station device 100 and the EV side charging device 200. [ In the embodiment of FIG. 2, the geometric positional relationship of the pair of charging pads is determined through the physical displacement of the charging Rx pad 210 among the pair of charging pads.

The charging station device 100 connected to the AV power supply 1 supplied through the power system includes an AC-DC converter 101 and a DC-AC inverter 105. The AC-DC converter 101 converts AC power into DC power by applying a power factor correction circuit. The DC-AC inverter 105 converts the DC power to AC power for wireless-to-power supply and transfers power to the charging Tx pad 110. Such a wireless power supply system may use a known configuration known to those skilled in the art. In the present invention, a small signal is set in advance in the mechanism that the inverter 105 transmits electric power to the charging Tx pad 110. At this time, the small signal is a signal having a current level that can be confirmed by the Rx pad 210 injected from the Tx pad 110, and preferably a high frequency microcurrent of about several to several tens of mA.

As a result, the mechanism by which the AC power of the inverter 105 is transferred to the vehicle side via the charging Tx pad 110 is carried out in two stages. First, it is a preset signal power transmission. The small signal is sent first to find the optimal geometric positional relationship of the pair of charging pads and, if necessary, to drive the tilting mechanism device. Preferably, a small signal is injected into the input of the charging Tx pad 110 circuit, more preferably into the primary side power conversion circuit, and the secondary side charging Rx pad ( 210). It is preferable that the small signal injection is continuously injected every 200 ms after the EV enters the charging station region, for example. Then, it is determined whether the vehicle is in the optimal frequency band. Next, if you have found the optimal charging efficiency, then you will have a large power transfer for wireless charging. Although not shown, the charging station device 100 further includes a control unit for controlling the signal power transmission and a display unit for displaying the charging status.

The configuration and charging mechanism of the rectifier 220 and the battery 230 that rectify the charging power supplied through the charging Rx pad 210 of the EV side charging apparatus 200 are well known and will not be described in detail. In the present invention, a tilting mechanism device 250 for detecting and analyzing signal power transmission for parking guidance will be described.

The signal transmitted through the charge Rx pad 210 is sensed through the resonance frequency detection circuit 251 and the resonance impedance is measured. The controller 253 calculates the power transmission efficiency by using the measured resonance impedance and compares it with a predetermined reference value S1. Preferably, an algorithm for previously registering an efficiency look-up table with respect to the existing resonance frequency and comparing the measured resonance frequency with a preset reference value can be applied.

The actuator 255 of the till team mechanism device 250 then drives the charged Rx pad 210 to displace in the Yaw direction and / or the Pitch direction. More specifically, what algorithm the controller 253 drives the actuator 255 will be exemplified in the embodiment of FIG. However, how the charged Rx pad 210 performs the physical displacement will be exemplified in FIG.

FIG. 3 illustrates the tilting mechanism of the charged Rx pad 210 in the embodiment of FIG. The charging Tx pad 110 is fixed at the ground 11 of the charging station. On the other hand, the charging Rx pad 210 on the vehicle side is structured to be capable of physical displacement.

When the charging Rx pad 210 is connected to the vehicle side charging device frame 201, the actuators 215 and 215, the fixed ball 211, and the ball guide 213 mediate the connection. There is a gap (?) Ensuring a physical displacement between the vehicle body (21) and the charged Rx pad (210). As the actuators 215, 215 are physically displaced, the filled Rx pads 210 are also displaced.

The geometric positional relationship with the charged Tx pad 110 can be adjusted through the tilting mechanism of FIG. The charged Rx pad 210 can be displaced in the Yaw direction and in the Pitch direction through the driving of the actuators 215 and 215. [ It is possible to control the position of the charged Rx pad 210 by, for example, either one of the actuators 215 is raised and the other actuator 215 is driven down or driven in the opposite direction.

FIG. 4 is a graph showing the relationship between the tilting angle in the Yaw direction and the resonance frequency. The graph of FIG. 4 creates a lookup table for the resonance frequency determined by the Rx pad as a result of the small signal injection according to the tilting angle in the Yaw direction in the test bed state. There is a difference (Difference?) Between the immediately preceding value and the present value of the resonance frequency determined at the Rx stage after the injection of the high frequency small signal. This difference will change. The threshold value can be set as the difference between the resonance frequency at the position at the highest efficiency and the resonance frequency at the immediately preceding tilting position that is performed experimentally. Therefore, tilting is performed until the difference (DELTA) when the actual tilting mechanism is executed is smaller than the threshold value. This will be described again with reference to FIG.

The algorithm of the tilting mechanism of the present invention will be summarized through the flowchart of FIG. 5 once again through the configuration of the above embodiment.

The EV was parked at the matching position of the charging station area. Thus, before the charging station device makes a large power transfer, the initial displacement of the charging Rx pad of the vehicle has occurred (S10). Since the charged Rx pad can be displaced in the Yaw direction and the Pitch direction, some point on the charged Rx pad may have displacement coordinates. These displacement coordinates can have three-dimensional coordinates in the coordinate system.

The charging station device transmits a first signal power transmission, which is a preset high frequency micro-current through the charging Tx pad (S11).

Then, the tilting mechanism device installed on the vehicle side senses the first signal received through the charged Rx pad of the vehicle, measures the resonance impedance, and calculates Efficiency of Power Transfer (E1) (S12). Then, the tilting mechanism device compares the previously measured reference value S1 with the measured power transmission efficiency E1 (S13).

In step S13, if E1 is greater than S1, the tilting of the charged Rx pad is terminated (S14). The positional relationship of the pair of charging pads is determined, and a large power transmission is performed from the charging station device to the EV side charging device.

If E1 is not greater than S1 in step S13, the degree of the difference is determined (S15). If the difference does not exceed the predetermined threshold value, the process goes to step S10 to displace the charged Rx pad to repeat steps S11 to S13. If the difference is greater than the predetermined threshold value, The charged Rx pad is displaced in the direction opposite to the displacement (S20).

The charging station device transmits a second signal power transmission, which is a preset high-frequency micro-current through the charging Tx pad (S21). In some preferred embodiments, the second signal and the first signal may be the same. In another preferred embodiment, the second signal may be different from the first signal.

Then, as in the step S12, the tilting mechanism device senses the second signal received through the charging Rx pad and measures the resonance impedance to calculate the power transmission efficiency E2 (S22). Then, the tilting mechanism device compares the measured reference power value E2 with a preset reference value S2 (S23).

If E2 is greater than S2 in step S23, the tilting of the charged Rx pad is terminated (S24). The positional relationship of the pair of charging pads is determined, and a large power transmission is performed from the charging station device to the EV side charging device.

If E2 is not greater than S2 in step S23, the process proceeds to step S15.

Through this iterative process, the optimum efficiency point (tilting completion point for determining the geometric position relation of the charging pad pair) is found and the algorithm of the tilting mechanism device is terminated. The method of finding the optimal point is to find the inflection point of the graph according to each position. Meanwhile, the first signal and the second signal injected here are radio power transmission signals, and use a value that allows the power to be passed to the secondary side so that the resonance frequency detection circuit of the tilting mechanism device can sense the value.

[Other Modifications]

(1) (Embodiment 2) The embodiment (first embodiment) of Figs. 2 to 5 assumes the physical displacement of the charged Rx pad on the secondary side among the pair of charging pads. Therefore, the tilting mechanism device is installed on the vehicle side. Small signal injection was done on the primary side. However, contrary to this embodiment, it is possible to modify the position of the secondary-side charging Rx pad among the charging pad pairs and to find the optimum efficiency point while physically displacing the primary-side charging Tx pad. In this case, the small signal injection (the first signal power transmission and the second signal power transmission) may be transmitted to the primary side charging Rx pad through the secondary side charging Rx pad. That is, a small signal is transmitted from the vehicle to the charging station device. The basic principles and contents of the remaining configurations and processes are maintained at the same level as in the first embodiment. In this way, the technical idea of the present invention relating to the efficiency of wireless charging can be implemented in a charging station, which is an infrastructure, thereby reducing the burden of applying a new technology to a vehicle. However, infrastructure investment will require more investment. Chargers Tx Actuators that cause physical displacement of the pads must be installed in each charging station.

(2) (Third Embodiment) In the second embodiment, only the function of transmitting a small signal can be changed from the primary side to the secondary side by changing the function as in the first embodiment. The third embodiment can ensure versatility in various electric vehicles in carrying out the method of the present invention.

(3) (Fourth Embodiment) The above embodiments have been described focusing on any one of the pair of charging pads of the present invention, i.e., displacement of either the charging Tx pad or the charging Rx pad. In another embodiment of the present invention, the pad may be deformed into a configuration in which both pads are displaced together. More delicate displacement mechanisms are expected to be needed.

This method of the present invention is a technique for improving the efficiency of wireless charging from the viewpoint of physical displacement before wireless charging is performed for the EV that has been parked as a result. The charging efficiency improving scheme (parking guidance to the matching position) for the vehicle being parked and the wireless charging efficiency improvement when the non-contact charging power transmission is performed can be concurrently effected by the present invention. Especially, it is expected that the effect will be enhanced if it is linked with the autonomous parking system.

The scope of protection of the present invention is not limited to the description and the expression of the embodiments explicitly described in the foregoing. It is again to be understood that the present invention is not limited by the modifications or substitutions that are obvious to those skilled in the art.

Claims (5)

(a) when the charging Rx pad of the vehicle located in the charging station area is displaced, the charging station device performs a first signal power transmission preset via the charging Tx pad,
(b) The tilting mechanism device installed on the vehicle side senses the first signal received through the charging Rx pad of the vehicle, measures the resonance impedance, calculates the power transmission efficiency, compares it with a predetermined reference value S1,
(c1) when the power transmission efficiency is greater than the reference value (S1), tilting of the charging Rx pad is terminated, and high power transmission is performed from the charging station device to the vehicle side charging device,
(c2) is not greater than the reference value (S1), the charge Rx pad displacement of the step (a) is performed to continue the step (b) if the difference does not exceed the predetermined threshold,
(c3) if the difference is greater than a predetermined threshold, displacing the displacement of the charged Rx panel in the opposite direction and displacing then the charging station device performs a predetermined second signal power transmission through the charging Tx pad,
(d) The tilting mechanism device senses the second signal received through the charging Rx pad of the vehicle and measures the resonance impedance to calculate the power transmission efficiency and compares it with a preset reference value (S2)
(e1) when the electric power transmission efficiency in the step (d) is greater than the reference value (S2), the tilting of the charged Rx pad is terminated and the large electric power transmission is performed from the charging station device to the vehicle side charging device,
(e2) is not larger than the reference value (S2), the step (c2) is continued, and the positional relationship of the pair of charging pads in the wireless charging system of the electric vehicle is detected and shifted to the optimum efficiency position . The method according to claim 1,
Wherein the displacement of the charged Rx pad is made by a displacement in the yaw and / or pitch directions by an actuator provided on the charged Rx pad, detects the positional relationship of the pair of charging pads in the wireless charging system of the electric vehicle, . (a) when the charging Tx pad of the charging station device is displaced relative to the vehicle located in the charging station area, the vehicle-side device performs a first signal power transmission preset via the charging Rx pad,
(b) The tilting mechanism device installed in the charging station device senses the first signal received through the charging Tx pad, measures the resonance impedance, calculates the power transmission efficiency, compares it with a predetermined reference value S1,
(c1) when the power transmission efficiency is greater than the reference value (S1), the tilting of the charging Tx pad is terminated, and then the charging station device performs the large power transmission to the vehicle side charging device,
(c2) is not greater than the reference value (S1), the charge Tx pad displacement of the step (a) is performed to continue the step (b) if the difference does not exceed the predetermined threshold value,
(c3) if the difference is greater than a predetermined threshold value, displacing the displacement of the charged Tx panel in the opposite direction to displace, then the vehicle-side device performs a predetermined second signal power transmission through the charged Rx pad,
(d) The tilting mechanism device senses the second signal received through the charging Tx pad of the vehicle, measures a resonance impedance, calculates a power transmission efficiency, compares the power transmission efficiency with a predetermined reference value (S2)
(e1) when the electric power transmission efficiency in the step (d) is larger than the reference value (S2), the tilting is terminated and the large electric power transmission is performed from the charging station device to the vehicle side charging device,
(e2) is not larger than the reference value (S2), the step (c2) is continued, and the positional relationship of the pair of charging pads in the wireless charging system of the electric vehicle is detected and shifted to the optimum efficiency position . The method according to claim 1,
Wherein the displacement of the charged Tx pad is made by a displacement in the yaw and / or pitch direction by an actuator provided on the charged Tx pad, and detects the positional relationship of the pair of charging pads in the electric vehicle & . Before a charging station device makes a large power transfer through a pair of charging pads to an electric car stationed in the charging station area for wireless charging:
Frequency current signal is transmitted through the pair of charging pads and the power transmission efficiency is calculated by the resonance impedance measured through the signal transmission and is compared with a predetermined reference value to determine the charging Tx Characterized in that the geometric relationship of the pair of charging pads during wireless charging is determined through a process of physically displacing by a tilting mechanism applied to either of the pads and the charging Rx pad To detect the positional relationship of the pair of charging pads and to shift to the optimum efficiency position.

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