Wireless power transfer system

Abstract

To provide a wireless power supply system that does not require adjustment or control for the position and angle of a power supply coil and a power reception coil when power is supplied to a rotating object, has a simple structure, and can always supply power wirelessly without interruption irrespective of the manner in which the power reception coil rotates with respect to the power supply coil.　Provided is a system for wirelessly supplying power to a rotating power supply object using PT symmetry, wherein: each of a power supply coil 11 and a power reception coil 21 is a solenoid-type or helical-type coil having magnetic poles at both ends; and when the power reception coil 21 is rotated with respect to the power supply coil 11, the power supply coil 11 and the power reception coil 21 are arranged so that a rotation center O of the power reception coil 21 approaches either one of two magnetic poles (201, 202) at the two ends of the power reception coil 21.

Description

[Technical Field] 【0001】 This invention relates to a wireless power supply system for a rotating power supply target that utilizes Parity-Time symmetry (hereinafter referred to as "PT symmetry"). [Background technology] 【0002】 There have been several known technologies for contactless wireless power transfer, including electromagnetic induction and magnetic resonance methods. Of these, electromagnetic induction wireless power transfer technology is used, for example, to charge mobile phones, and has coils arranged vertically, essentially acting as an electrical transformer, where electricity flows when the power supply coil and power receiving coil are in close contact. 【0003】 However, electromagnetic induction wireless power transfer technology has several problems: it cannot achieve a large distance between the power supply coil and the power receiving coil, and even a slight misalignment or separation between the two coils prevents both charging and power supply. Therefore, it is difficult to apply to artificial devices installed inside the human body, such as artificial hearts, and it is also difficult to apply to devices that rotate in multiple directions or have axial misalignment, such as robotic arms. 【0004】 Furthermore, magnetic resonance wireless power transfer technology was developed at an American university around 2006-2007, and because it allows for a greater distance between the power transfer coil and the power receiving coil compared to electromagnetic induction, it is approaching a level close to practical application. However, it has a sensitivity that prevents transmission unless the distance between the power transfer coil and the power receiving coil is kept constant; transmission is impossible if they get closer or further away than that distance, or if there is an angle between them. Therefore, this also presents a problem in that it is difficult to apply to artificial devices attached inside the human body, such as artificial hearts, or devices that rotate in multiple directions or have axial misalignment, such as robotic arms. 【0005】 In order to solve such problems, for example, Patent Document 1 discloses a non-contact power supply system using a magnetic resonance method, which includes a control device having a function of adjusting the positional relationship and angle between a power supply coil and a power receiving coil, so as to stably supply power to an artificial heart or the like. 【0006】 Also, for example, Patent Document 2 discloses a technique for realizing rotation and bending in a non-contact power supply type rotary module used in a robot. In a multi-joint robot having a first arm and a second arm, two non-contact power supply portions are provided to facilitate operations such as attachment and addition of the arms. 【Prior Art Documents】 【Patent Documents】 【0007】 【Patent Document 1】 International Publication No. 2018 / 150678 【Patent Document 2】 Japanese Unexamined Patent Application Publication No. 2020 - 106985 【Patent Document 3】 Japanese Unexamined Patent Application Publication No. 2022 - 121324 【Patent Document 4】 Japanese Patent Application Publication No. 2014 - 532296 【Patent Document 5】 Japanese Unexamined Patent Application Publication No. 2009 - 164293 【Non-Patent Documents】 【0008】 【Non-Patent Document 1】 Sid Assawaworrarit, Xiaofang Yu & Shanhui Fan, “Robust wireless power transfer using a nonlinear parity-time-symmetric circuit”, Nature, 15 JUNE 2017, volume 546, p.387 - 390 【Non-Patent Document 2】 Xianglin Hao, Ke Yin, Jianlong Zou, Ruibin Wang, Yuangen Huang, Xikui Ma & Tianyu Dong, “Frequency-Stable Robust Wireless Power Transfer Based on High-Order Pseudo-Hermitian Physics”, Phys. Rev. Lett. 2023, 130, 077202 [Non-Patent Document 3] H. Ishida, T. Kyoden, and H. Furukawa, “Application of parity-time symmetry to low-frequency wireless power transfer system”, IEEJ J. Ind. Appl., 2022, vol.11, no.1, pp.59-68 [Overview of the project] [Problems that the invention aims to solve] 【0009】 However, in contactless power supply systems using magnetic resonance, such as those shown in Patent Document 1, the power transmission equipment must be large and complex because it is necessary to adjust the distance between the power supply coil and the power receiving coil to be constant, and to adjust the angle to be constant. Furthermore, the control unit of the power transmission equipment must be constantly subjected to high-level control, such as adjusting the relative positions and angles between the coils. In addition, there is the problem that these high-level control functions stop when the batteries are replaced. 【0010】 Furthermore, in contactless power supply systems for robot arms, such as those shown in Patent Document 2, there was a problem in that power could not be supplied at a certain rotation angle when supplying or receiving power to a rotating object. Also, since it is not possible for the tip of a single arm to bend in any direction and rotate 360 ​​degrees in any direction, there was a problem that a complex multi-jointed structure would be required if rotation in any direction of 360 degrees was desired. 【0011】 This invention was made to solve the above-mentioned problems, and aims to provide a wireless power supply system that does not require adjustment or control of the position or angle of the power supply coil and power receiving coil when supplying power to a rotating object, has a simple structure, and can always supply power wirelessly without interruption regardless of how much the power receiving coil rotates relative to the power supply coil. [Means for solving the problem] 【0012】 To achieve the above objective, this invention provides a wireless power supply system for a rotating power supply target that utilizes parity-time symmetry (hereinafter referred to as "PT symmetry"), wherein the power supply coil provided in the power supply circuit and the power receiving coil provided in the power receiving circuit are solenoid-type or helical-type coils having magnetic poles at both ends, and as a means of maintaining the PT symmetry and keeping the transmitted power constant while wirelessly supplying power when the power receiving coil is rotated relative to the power supply coil, the power supply coil and the power receiving coil are arranged such that the rotation center of the power receiving coil is near one of the two magnetic poles at both ends of the power receiving coil. [Effects of the Invention] 【0013】 According to the wireless power supply system of this invention, in wireless power supply utilizing PT symmetry, when supplying power to a rotating object, the power supply coil and the receiving coil are arranged so that the rotation center of the receiving coil is near one of the two magnetic poles at both ends of the receiving coil. This eliminates the need for adjustment or control of the position and angle of the power supply coil and the receiving coil, and the structure is simple. Furthermore, it is possible to maintain uninterrupted transmission and high transmission efficiency regardless of how much the receiving coil rotates relative to the power supply coil, thus enabling constant wireless power supply. [Brief explanation of the drawing] 【0014】 [Figure 1] This is an explanatory diagram showing the schematic configuration of the power supply coil and power receiving coil used in the wireless power supply system utilizing PT symmetry in Embodiment 1 of this invention. [Figure 2] This diagram shows the positional relationship between coils in a wireless power transfer system utilizing PT symmetry, where the rotation center O is located in the center of the receiving coil for a rotating power supply target. [Figure 3] This figure shows the relationship between the rotation angle θ and the magnetic coupling coefficient km for the coil arrangement shown in Figure 2. [Figure 4] This figure shows the positional relationship between coils in a wireless power supply system utilizing PT symmetry according to Embodiment 1 of this invention, when the rotation center O is located at one of the two magnetic poles at both ends of a solenoid-type receiving coil in a rotating power supply target. [Figure 5] This figure shows the relationship between the rotation angle θ and the magnetic coupling coefficient km for the coil arrangement shown in Figure 4. [Figure 6] This graph shows the relationship between the rotation angle of the two coils (a power supply coil and a power receiving coil) used in a wireless power transfer system and the transmitted power. [Figure 7] This is an explanatory diagram showing an example of a general configuration of a wireless power supply system. [Figure 8]Figure 2 shows an example of an experimental graph illustrating the relationship between the magnetic coupling coefficient km, the critical magnetic coupling coefficient kmc, and the transmitted power when the receiving coil is rotated around its central point. [Figure 9] This graph shows experimental results of the transmitted power as a function of the rotation angle of the two coils (the power supply coil and the power receiving coil) in the coil arrangement shown in Figure 4. [Figure 10] This is a schematic perspective view showing one specific example (an example in which the coils are arranged axially) of a magnetic field resonance type wireless power supply system utilizing PT symmetry in Embodiment 1 of this invention, in which the power supply coil and power receiving coil are built into a robot arm. [Figure 11] This invention, in Embodiment 1, describes a wireless power supply system using magnetic resonance that utilizes PT symmetry, specifically a case where a relay is included and the power supply coil and power receiving coil are built into a robot arm, applied to a robot arm with two joints. [Figure 12] This is a schematic perspective view showing another specific example (an example in which the coils are arranged in the rotational direction) of a magnetic field resonance type wireless power supply system utilizing PT symmetry in Embodiment 1 of this invention, in which the power supply coil and power receiving coil are built into a robot arm. [Figure 13] This is an explanatory diagram showing an example of the schematic configuration of a power supply coil and a power receiving coil used in a wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention. [Figure 14] This is an explanatory diagram showing another example of the schematic configuration of the power supply coil and power receiving coil used in a wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention. [Figure 15] This is an explanatory diagram showing yet another example of the schematic configuration of the power supply coil and power receiving coil used in a wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention. [Figure 16] Figure 15 is a schematic perspective view showing the coil structure for a wireless power supply device. [Figure 17]This figure shows the positional relationship between coils in a wireless power supply system utilizing PT symmetry according to Embodiment 2 of this invention, when the rotation center O is located at one of the two magnetic poles at both ends of the double spiral type receiving coil shown in Figure 13, for a rotating power supply target. [Figure 18] This figure shows the positional relationship between coils in a wireless power supply system utilizing PT symmetry according to Embodiment 2 of this invention, when the rotation center O is located on one of the two magnetic poles at both ends of the hybrid type receiving coil shown in Figure 15, for a rotating power supply target. [Figure 19] Figure 15 is a schematic perspective view showing one specific example of a magnetic field resonance type wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention, in which a hybrid type power supply coil and power receiving coil, as shown, are mounted on the wall surface of a metal robot arm. [Figure 20] This is an explanatory diagram showing an example of the schematic configuration of a power supply coil and a power receiving coil used in a wireless power supply system utilizing PT symmetry in Embodiment 3 of this invention. [Figure 21] This figure shows the positional relationship between coils in a wireless power supply system utilizing PT symmetry according to Embodiment 3 of this invention, when the rotation center O is located at one of the two magnetic poles at both ends of the solenoid-type receiving coil shown in Figure 20, for a rotating power supply target. [Figure 22] Figure 20 is a schematic perspective view showing one specific example of a magnetic field resonance type wireless power supply system utilizing PT symmetry in Embodiment 3 of this invention, in which a hybrid type power supply coil and a solenoid type power receiving coil are mounted on the wall surface of a metal robot arm. [Modes for carrying out the invention] 【0015】 This invention relates to a wireless power supply system for a rotating power supply target that utilizes Parity-Time symmetry (hereinafter referred to as "PT symmetry"). The embodiments of this invention will be described in detail below with reference to the drawings. 【0016】 First, let's explain wireless power transfer technology. There are already several known wireless power transfer technologies, such as electromagnetic induction and magnetic resonance. Of these, electromagnetic induction wireless power transfer technology is used, for example, to charge mobile phones. The coils are arranged vertically, and in other words, it works on a principle similar to a transformer, so power can only be transmitted when the distance (transmission distance) between the power supply coil and the power receiving coil is very short. 【0017】 However, electromagnetic induction wireless power transfer technology has a problem in that the transmission distance is short, only a few millimeters, so it is not possible to place a large distance between the power supply coil and the power receiving coil. Furthermore, if the positions of the power supply coil and the power receiving coil are even slightly misaligned or separated, neither charging nor power supply is possible. In other words, it is susceptible to positional errors, making it difficult to apply to artificial devices attached inside the human body, such as artificial hearts, or devices that rotate in multiple directions or have axial misalignment, such as robotic arms. 【0018】 Furthermore, magnetic resonance wireless power transfer technology has a long transmission distance of several centimeters to several meters, allowing for a larger distance between the power supply coil and the power receiving coil compared to electromagnetic induction, bringing it closer to practical application. However, it is sensitive to positional deviations; power cannot be transmitted unless the distance between the power supply coil and the power receiving coil is kept constant. If the distance is too close or too far, or if an angle is introduced, the transmission efficiency decreases, making it impossible to deliver the necessary power. In other words, this method is also susceptible to positional deviations, making it difficult to apply to devices that rotate in multiple directions or have axial misalignment (rotating power supply targets), such as robot arms. 【0019】 Furthermore, Patent Document 1 discloses a wireless power supply system that uses magnetic resonance technology and includes a control device that has the function of adjusting the positional relationship and angle between the power supply coil and the power receiving coil, thereby supplying stable power to an artificial heart assist device and the like. According to this system, even if the position shifts up or down by a few centimeters due to the movement of the human body, the control device will adjust the parameters accordingly each time to compensate for the positional shift. 【0020】 However, this type of system requires functions to adjust the distance between the power supply coil and the power receiving coil to be constant, and to adjust the angle to be constant. This results in a large and complex control device (external equipment such as power transmission equipment), and the need to constantly perform sophisticated control such as adjusting the relative positions and angles between the coils places a heavy load on the control unit of the control device (external equipment such as power transmission equipment). Furthermore, there was a problem in that the sophisticated control functions would stop when the batteries supplying power to the external equipment were replaced. 【0021】 Therefore, there is a strong desire for a wireless power supply system that eliminates the need for adjustment or control of the position and angle of the power supply coil and power receiving coil for a rotating power supply target, and that can supply power wirelessly without interruption regardless of how much the power receiving coil rotates relative to the power supply coil. Various wireless power supply methods have been repeatedly experimented with and tested, but currently, none have been found that are suitable for practical use. 【0022】 Here, one wireless power transfer method is a technology called wireless power transfer that utilizes Parity-Time symmetry (hereinafter referred to as "PT symmetry"). In a wireless power transfer system that utilizes PT symmetry, even if the transmission distance changes or if there is a misalignment between the power supply coil and the power receiving coil, the transmitted power will always remain constant as long as PT symmetry is preserved. In other words, a wireless power transfer system that utilizes PT symmetry replaces the AC power source in conventional magnetic resonance wireless power transfer technology with an inverter that behaves electrically similarly to a negative resistor, that is, an inverter that behaves as a negative resistor. 【0023】 This is a known technique, as disclosed in, for example, Patent Document 3, but to explain it in more detail, an inverter that behaves as a negative resistor is an inverter whose switching frequency and voltage amplitude are not fixed in advance, and which has a circuit configuration in which the switching frequency is determined by the apparent resonant frequency of the wireless power supply circuit as seen from the output terminal of the inverter, and is an inverter in which the switching frequency follows changes in the apparent resonant frequency of the wireless power supply circuit, which may change due to changes in the transmission distance or positional displacement of the coil, with a fast response speed. Here, the wireless power supply circuit is a circuit that includes the transmitting side resonant circuit, the receiving side resonant circuit, and all circuits connected thereafter. Furthermore, the apparent resonant frequency means the actual resonant frequency that takes into account the interaction between the transmitting side resonant circuit and the receiving side resonant circuit, since they interact with each other. 【0024】 However, conventional wireless power transfer systems utilizing PT symmetry are driven at high frequencies of around 1-3 MHz, requiring the use of air-core coils for both the power transfer and receiving coils. This necessitates large coil dimensions, limiting the range of applicable applications. Specifically, the coils in conventional wireless power transfer systems utilizing PT symmetry were approximately 60 cm in diameter (see Non-Patent Literature 1). Furthermore, due to the high frequency, placing metallic objects (conductive objects) around the power transfer and receiving coils resulted in reduced transmission efficiency due to eddy current losses generated by these conductive objects. Therefore, this technology could not be applied to rotating power transfer targets. 【0025】 One of the applicants for the present invention has invented a wireless power supply device utilizing PT symmetry, which solves the problems of conventional wireless power supply systems utilizing PT symmetry. This device uses a low frequency of 100 kHz or less, resulting in less reduction in transmission efficiency even when metal objects are placed nearby, and can maintain high transmission efficiency even when there are changes in transmission distance or misalignment of the coils. Furthermore, the power supply coil and power receiving coil can be miniaturized, making it suitable for use in various applications. This invention was filed in 2021 (see Patent Document 3). 【0026】 Furthermore, the present invention was arrived at through repeated experiments and trial and error, applying the technology of the wireless power supply device utilizing PT symmetry described in the prior application, Patent Document 3, to wireless power supply to a rotating power supply target. In this embodiment of the invention, a robot arm will be used as an example of a rotating power supply target. 【0027】 When considering power supply to a robot arm as a rotating power source, it is desirable to supply power to the tips of the arm's joints to enable various fine tasks. In this case, it is desirable that the arm receiving the power bends in multiple directions and rotates itself. This "rotation" makes wired power supply via a cord difficult. Furthermore, when tilting in multiple directions, wireless power supply using coils wound around a cylinder is not possible. 【0028】 Therefore, in this embodiment of the invention, assuming the use of solenoid coils or helical coils having magnetic poles at both ends for both the power supply coil and the power receiving coil, we will sequentially explain the structure and circuitry invented through repeated trial and error experiments to ensure that wireless power supply to a power supply target (robot arm) that bends in multiple directions and rotates itself is always possible. Although detailed explanations of solenoid-type coils and helical-type coils are omitted as they are well known coils, in this embodiment of the invention, a coil that is coupled by a spatial magnetic field generated in the radial direction of the coil is called a solenoid-type coil, and a coil that is coupled by a magnetic field generated in the axial direction of the coil is called a helical-type coil. 【0029】 Embodiment 1. Figure 1 is an explanatory diagram showing the schematic configuration of the power supply coil 11 and the power receiving coil 21 used in a wireless power supply system utilizing PT symmetry in Embodiment 1 of the present invention. As shown in Figure 1(a), both the power supply coil 11 provided in the power supply circuit and the power receiving coil 21 provided in the power receiving circuit are solenoid-type coils in which windings (e.g., Litz wire) 111 and 211 are wound around magnetic cores 100 and 200 made of a soft magnetic material such as ferrite. The shape of the coil used in wireless power supply is often a spiral-shaped, circular single spiral coil (or pancake-shaped coil). The fact that this coil is a solenoid-type coil or a helical-type coil with magnetic poles at both ends is also one of the features of Embodiment 1 of the present invention. By using a solenoid-type coil or a helical-type coil with a soft magnetic material as the core in this way, it is possible to make a small coil, so it is possible to install it inside a small power supply target. 【0030】 Furthermore, as shown in Figure 1(b), the magnetic core 100 (or 200) has approximately rectangular parallelepiped-shaped magnetic poles 101, 102 (or 201, 202) at both ends, that is, at both ends other than the portion where the winding 111 (or 211) is wound (the portion enclosed by the dashed line in Figure 1(b)), where the winding is not wound. These magnetic poles 101, 102, 201, 202 are formed such that the area of ​​the opposing faces of the power supply coil 11 and the power receiving coil 21 facing each other (the area of ​​the ends of the upper (back) side of Figure 1(b)) is larger than the area of ​​the other faces of the magnetic poles. This makes it possible to increase the magnetic coupling coefficient when the power supply coil 11 and the power receiving coil 21 face each other, which has the effect of making it possible to increase the transmission distance of the coils and widening the allowable range of coil misalignment. 【0031】 Here, we will explain the magnetic coupling coefficient between two coils. When the distance or angle between two coils changes, or when the position of the coils changes, the magnetic coupling coefficient k between the two coils changes. m The magnetic coupling coefficient k between the two coils changes. mThe magnetic coupling coefficient k decreases as the transmission distance between the two coils increases, and also decreases when the displacement between the coils increases. Conversely, as the distance between the two coils decreases, the magnetic coupling coefficient k decreases. m It becomes larger, and when they get close enough to almost touch, it approaches 1. That is, the magnetic coupling coefficient k m It can take values ​​between 0 and 1. 【0032】 Thus, in the wireless power supply system utilizing PT symmetry in the embodiment of this invention, the power supply coil 11 and the power receiving coil 21 used are solenoid-type coils or helical-type coils having magnetic poles at both ends, respectively. Furthermore, the embodiment of this invention presents a means for always providing wireless power while maintaining a constant transmitted power by preserving PT symmetry when rotating the power receiving coil relative to the power supply coil. 【0033】 Figure 2 shows the positional relationship between coils in a wireless power transfer system utilizing PT symmetry, where the rotation center O is located in the center of the receiving coil in a rotating power transfer target. Figure 3 shows the rotation angle θ and magnetic coupling coefficient k for the coil arrangement shown in Figure 2. m This figure shows the relationship between the two. In conventional robot arms, as shown in Figure 2, the rotation center O of the power receiving coil 21 is generally located near the center of the power receiving coil 21. Here, in Figure 2, the state in which the axis 11L of the power supply coil 11 and the axis 21L of the power receiving coil 21 are parallel is defined as a rotation angle of 0 degrees, and the angle between the two axes is defined as the rotation angle θ (the same applies in Figure 4, which will be described later). 【0034】 In Figure 2, the dashed line shows the receiving coil before rotation. Before rotation, the axis 11L of the supply coil 11 and the axis of the receiving coil (the dashed receiving coil does not have a symbol or axis shown) are parallel. The solid line shows the receiving coil 21 after it has been rotated by an angle θ around its center. 【0035】 In the case of the coil arrangement shown in FIG. 2, that is, when the rotation center O is near the center of the power receiving coil 21, at an angle (here, 90 degrees of rotation angle) between the rotation angles θ of the power supply coil 11 and the power receiving coil 21, the magnetic coupling coefficient k m is found to be 0 (zero) (see FIG. 3). Thus, when the magnetic coupling coefficient k m becomes 0 (zero), even if wireless power supply using PT symmetry is employed, power supply becomes impossible. Therefore, since a robot arm that can rotate 360 degrees cannot always be powered and moved, in order to cause complex movements, the magnetic coupling coefficient k m must not become 0 (zero), that is, in this case, a multi-joint robot arm that moves within a range that does not reach plus or minus 90 degrees is required. 【0036】 To solve this problem, the applicant of the present application devised a coil arrangement such that the magnetic coupling coefficient k m does not become 0 (zero) at any rotation angle, and through repeated experiments and trial and error, arrived at the present invention so as to be applicable to wireless power supply to a rotating power supply target. 【0037】 Thus, an example of a coil arrangement such that the magnetic coupling coefficient k m does not become 0 (zero) at any rotation angle θ is shown in FIG. 4. FIG. 4 is a diagram showing the positional relationship between the coils when the rotation center O is at one of the two magnetic poles at both ends of a solenoid-type power receiving coil in a rotating power supply target in the wireless power supply system using PT symmetry of Embodiment 1 of this invention. Further, FIG. 5 is a diagram showing the relationship between the rotation angle θ and the magnetic coupling coefficient k m for the coil arrangement shown in FIG. 4. 【0038】 As with Figure 2, the dashed line in Figure 4 represents the receiving coil before rotation. Before rotation, the axis 11L of the supply coil 11 and the axis of the receiving coil (the dashed receiving coil does not have a symbol or axis shown) are parallel. The solid line represents the receiving coil 21 after it has been rotated by an angle θ around one of the two magnetic poles at both ends of the receiving coil 21 (magnetic pole 202 in the example shown in Figure 4). 【0039】 The use of the term "near the magnetic pole" here means that the rotation center O is not located near the center (central part) of the receiving coil 21 as shown in Figure 2, but rather at a position off-center from the center of the receiving coil 21. It could be at the very ends of the magnetic poles (201, 202) at both ends of the receiving coil 21, or it could be around the center of the magnetic poles (201, 202). This is the definition given by the term "near the magnetic pole." In other words, looking at the receiving coil 21 as a whole, it means that the rotation center O is located at a position shifted to the vicinity of the magnetic poles (201, 202) at both ends. The same applies to Embodiments 2 and 3. 【0040】 Specifically, Figure 4 shows the positional relationship of the coil when the rotation center O is located on one of the two magnetic poles (201, 202) at both ends of the receiving coil 21, and Figure 5 shows the rotation angle θ and magnetic coupling coefficient k in the positional relationship of the coil in Figure 4. m This shows the relationship. Here, although the way it changes differs somewhat depending on the shape of the coil and the position of the center of rotation, as the rotation angle θ increases, the magnetic coupling coefficient k increases accordingly. m The tendency for the coefficient to decrease is common to both Figure 2 and Figure 4. However, in the case of the coil positional relationship shown in Figure 4, that is, when the rotation center O is near one of the two magnetic poles (201, 202) at both ends of the receiving coil 21, the magnetic coupling coefficient k is as shown in Figure 5. mThe rotation angle at which the value becomes 0 (zero) can be eliminated. In this state, by utilizing PT symmetry, the transmitted power can be kept constant at any rotation angle θ. 【0041】 Thus, by arranging the power supply coil 11 and the power receiving coil 21 such that the rotation center of the power receiving coil 21 is near one of the two magnetic poles (201, 202) at both ends of the power receiving coil 21, the magnetic coupling coefficient k is maintained at any rotation angle θ when the power receiving coil 21 is rotated relative to the power supply coil 11. m Since it never becomes 0 (zero), it is possible to preserve PT symmetry and always provide wireless power while keeping the transmission power constant. 【0042】 Here, to reiterate, existing wireless power transfer technologies will be explained. Wireless power transfer using magnetic fields includes electromagnetic induction and magnetic resonance. Figure 6 is a graph showing the relationship between the rotation angle of the two coils (transmission coil and receiving coil) used in a wireless power transfer system and the transmitted power. Figure 6(a) shows the case of electromagnetic induction, and Figure 6(b) shows the case of magnetic resonance. 【0043】 In the case of electromagnetic induction, the magnetic coupling coefficient k m As the rotation angle decreases, the amount of power that can be transmitted (transmission power) also decreases. Therefore, the relationship between the rotation angle of the two coils and the transmission power is as shown in the graph in Figure 6(a): the transmission power is greatest when the rotation angle is 0 (zero), and decreases as the rotation angle increases. 【0044】 In the case of magnetic resonance, a specific magnetic coupling coefficient k m When the value is such that the power supply circuit and the power receiving circuit resonate and become strongly coupled, a specific magnetic coupling coefficient k m The transmitted power is maximized at a specific value. Therefore, the relationship between the rotation angle of the two coils and the transmitted power is as shown in the graph in Figure 6(b): the transmitted power is greatest at a certain rotation angle, and decreases as the rotation angle deviates from that value. 【0045】 Thus, in both methods, the common point is that the transmitted power changes when the rotation angle changes. In practical applications, it is necessary to supply a constant power to the load (equipment) attached to the receiving side, so it is undesirable for the transmitted power to change with the rotation angle. Therefore, it is necessary to control the power in some way so that the transmitted power remains constant. 【0046】 Here, we will explain the system configuration of the wireless power transfer system. Figure 7 is an explanatory diagram showing an example of the schematic configuration of a wireless power transfer system. Figure 7(a) shows a typical system configuration when power control is performed using existing technology. Figure 7(b) shows an example of a system configuration when PT symmetry is utilized (without a repeater), and Figure 7(c) shows another example of a system configuration when PT symmetry is utilized (with a repeater). 【0047】 If power control is performed using existing methods, the system configuration shown in Figure 7(a) is a possible example. This system configuration requires sensors to detect voltage and current values ​​in the power supply and power receiving circuits, wireless communication equipment to feed back the detected values ​​from the receiving side to the power control unit on the power supply side, and a computer in the power control unit to perform calculations based on the detected values. However, if the angular velocity of rotation is high, power control will not be able to keep up with that speed, so power control is expected to be difficult with this configuration. 【0048】 Factors that reduce the response speed of power control include the time delays that occur in the aforementioned wireless communication equipment and computers. If power control could be performed without using communication equipment or computers, the response speed could be improved. Therefore, this invention utilizes a physical law called PT symmetry. As mentioned above, by utilizing PT symmetry, the transmitted power is affected by the magnetic coupling coefficient k as a physical phenomenon. mThis creates a state that is unaffected by these factors. Therefore, the transmitted power remains constant even when the rotation angle changes, thus achieving the objective. This method does not require the aforementioned communication equipment or computers, and in the case of no repeater, the system configuration shown in Figure 7(b) enables power control with a fast response speed. 【0049】 Furthermore, as described in Non-Patent Document 2, PT symmetry can be preserved even when a relay coil is placed between the power supply coil in the power supply circuit and the power receiving coil in the power receiving circuit. In practice, a capacitor is connected to the relay coil, forming a resonant circuit. If this resonant circuit is called a repeater, a system configuration including the repeater shown in Figure 7(c) can also be considered. This configuration is envisioned when applying wireless power supply using PT symmetry to a multi-joint robot arm, as will be described later. Note that a condition for a resonator is that the natural resonant frequency of the repeater matches the natural resonant frequencies of the power supply circuit and the power receiving circuit. Here, the natural resonant frequency is the resonant frequency of the resonator alone. 【0050】 Next, we will explain the limit value (critical angle) of the rotation angle. When the magnetic coupling coefficient becomes smaller than a certain value, PT symmetry is no longer preserved; that is, there exists a limit (critical) magnetic coupling coefficient at which PT symmetry can be preserved. Thus, the condition for the preservation of PT symmetry is the magnetic coupling coefficient k. m The critical magnetic coupling coefficient k indicates the limit value (critical value) of the limit. mc There is a critical magnetic coupling coefficient k. mc The formula and theoretical explanation are publicly known, as described in, for example, Patent Document 3 and Non-Patent Document 3, so a detailed explanation will be omitted here. 【0051】 And, as mentioned above, if PT symmetry is conserved, the magnetic coupling coefficient k m Even if the rotation angle changes, the transmitted power remains constant, but the magnetic coupling coefficient k m The critical magnetic coupling coefficient k mcIf the value falls below this level, PT symmetry cannot be preserved, making it difficult to maintain a constant transmission power. In actual systems, the magnetic coupling coefficient k m The critical magnetic coupling coefficient k mc If the value falls below this level, the transmission power drops significantly, making wireless power transfer practically impossible. 【0052】 Figure 8 shows the magnetic coupling coefficient k with respect to the rotation angle θ when the receiving coil shown in Figure 2 is rotated around its central point. m , critical magnetic coupling coefficient k mc、 Figure 8 is a graph showing experimental results illustrating the relationship between transmitted power and transmission power. Specifically, Figure 8 is a graph showing the relationship between transmitted power and magnetic coupling coefficient with respect to the rotation angle of the two coils (a power supply coil and a power receiving coil) shown in Figure 2, with the horizontal axis representing the rotation angle and the vertical axis representing the transmitted power and magnetic coupling coefficient. 【0053】 In the example shown in Figure 8, as indicated by the dashed line in the graph, the critical magnetic coupling coefficient k mc The critical magnetic coupling coefficient k is 0.039. mc k is a unique value in each system and is a constant. On the other hand, the magnetic coupling coefficient k m k is a variable, and the magnetic coupling coefficient is k. m The coefficient of power tends to decrease with increasing rotation angle θ of the two coils. In the graph, the black circles ● represent the experimental results of the transmitted power, and the solid line represents the magnetic coupling coefficient k. m This shows the numerical calculation results. 【0054】 In the example shown in Figure 8, the rotation angle θ of the two coils is around 70 degrees, and the magnetic coupling coefficient k m The critical magnetic coupling coefficient k mc This matches. In this case, the magnetic coupling coefficient k m The critical magnetic coupling coefficient k mc Up to a rotation angle of 70 degrees, where the value becomes larger than θ, PT symmetry is preserved, and the transmitted power is maintained at an approximately constant value (about 18W in this example). After that, when the rotation angle θ exceeds 70 degrees, the magnetic coupling coefficient k m The critical magnetic coupling coefficient k mcBecause it takes a value smaller than this, PT symmetry cannot be preserved, and the transmission power drops significantly. 【0055】 In practical applications, it is desirable to maximize the critical angle. If PT symmetry can be preserved at any rotation angle θ, the transmitted power can be kept constant even when the receiving coil is rotated 360 degrees. This enables wireless power supply to a continuously rotating power source. However, apart from this invention, there have been no successful examples of continuous power supply over 360 degrees using a pair of solenoid coils or helical coils. 【0056】 Thus, by using a power supply coil 11 and a power receiving coil 21 consisting of a pair of solenoid coils or helical coils, installation space is reduced, which is an advantage as it makes it suitable for applications such as robot arms. Another advantage is that it can handle simultaneous movement of two rotation axes (11L and 21L). 【0057】 Next, regarding methods for increasing the critical angle, we will discuss the rotation angle θ and magnetic coupling coefficient k shown in Figures 3 and 5 above. m This will be explained using a graph of the relationship. As shown by the dashed line in Figure 3, if the arrangement of the two coils is as in Figure 2, then the critical magnetic coupling coefficient k mc If k is 0.1, then PT symmetry can be preserved up to a rotation angle of 44 degrees. In other words, the critical magnetic coupling coefficient k mc The critical angle when is 0.1 is 44 degrees. Furthermore, since this graph is symmetric with respect to negative rotation angles, PT symmetry is actually preserved within a range of ±44 degrees (88 degrees total). 【0058】 Furthermore, as shown by the dashed line in Figure 3, if the critical magnetic coupling coefficient k mc If k becomes 0.05, then PT symmetry will be preserved up to ±66 degrees (132 degrees total). Therefore, in order to increase the critical angle, the critical magnetic coupling coefficient k, which is inversely proportional to the critical angle, must be considered. mc You just need to make it smaller. 【0059】 Critical magnetic coupling coefficient k mc Methods for reducing the critical angle will be discussed later, but one way to increase the critical angle is the magnetic coupling coefficient k m The goal is to keep this value as large as possible. This can be achieved by the coil arrangement. This is the coil arrangement shown in Figure 4, but please refer to Figure 5, which is a graph of the case when the rotation center O is on one of the magnetic poles (201 or 202) of the receiving coil 21. 【0060】 In the case of the coil arrangement shown in Figure 4, if we assume the critical magnetic coupling coefficient k mc If it is 0.05 (the dashed line in Figure 5), then the magnetic coupling coefficient k is at any angle. m The critical magnetic coupling coefficient k mc Because it does not fall below this value, it becomes possible to preserve PT symmetry up to ±180 degrees (360 degrees in total), allowing the receiving coil to rotate continuously. 【0061】 As described above, the critical angle can be increased by the arrangement (positional relationship) of the power supply coil 11 and the power receiving coil 21. Specifically, the coil arrangement shown in Figure 2, where the rotation center O is in the center of the power receiving coil 21, results in the narrowest critical angle, while the arrangement shown in Figure 4, where the rotation center O is on one of the magnetic poles (201 or 202) of the power receiving coil 21, results in the widest critical angle. 【0062】 In other words, as shown in Figure 4, if the power supply coil 11 and the power receiving coil 21 are arranged such that the rotation center O of the power receiving coil 21 is near one of the two magnetic poles (201, 202) at both ends of the power receiving coil 21, the critical angle can be increased, and the range of rotation angles and transmission distances in which PT symmetry can be preserved can be expanded. Therefore, when the power receiving coil 21 is rotated relative to the power supply coil 11, it becomes possible to always wirelessly supply power while preserving PT symmetry and maintaining a constant transmission power. 【0063】 Next, we will explain the results of experimental verification using a real device with a system configuration without a repeater that utilizes PT symmetry as shown in Figure 7(b), referring to Figure 9. Figure 9 shows the magnetic coupling coefficient k with respect to the rotation angle when the receiving coil shown in Figure 4 is rotated around one of the two magnetic poles at both ends. m , critical magnetic coupling coefficient k mc、 This is a graph showing experimental results illustrating the relationship with transmitted power. 【0064】 Specifically, Figure 9 is a graph showing the relationship between the transmission power and the magnetic coupling coefficient with respect to the rotation angle of the two coils (a power supply coil and a power receiving coil) shown in Figure 4. The horizontal axis represents the rotation angle, and the vertical axis represents the transmission power and the magnetic coupling coefficient. The dashed line in the graph represents the critical magnetic coupling coefficient k. mc The result is (=0.039), with the black circle ● representing the experimental result of the transmission power and the solid line representing the numerical calculation result of the magnetic coupling coefficient. 【0065】 As shown in Figure 9, the experimental results confirmed that the transmitted power remained almost constant over ±180 degrees (360 degrees in total). Furthermore, the magnetic coupling coefficient k was maintained at all rotation angles θ. m The critical magnetic coupling coefficient k mc The value did not fall below (=0.039), confirming that constant transmission power was achieved as a result of the preservation of PT symmetry over 360 degrees. Furthermore, it was confirmed that constant transmission power was maintained even when the coil was continuously rotated more than one full turn. To date, there have been no examples of rotation over 360 degrees using a pair of solenoid coils or helical coils (examples of successful continuous power supply). 【0066】 As described above, we were able to confirm, not only through logical consideration but also through experimentation, that the present invention is effective and offers significant advantages. 【0067】 Here, as an example of the application of the present invention, we will explain that it can be applied to various types of robot arms. The joints of a robot arm may have degrees of freedom for multi-axis rotation. Figure 10 is a schematic perspective view showing one specific example (an example in which the coils are arranged axially) of a magnetic field resonance type wireless power supply system utilizing PT symmetry in Embodiment 1 of this invention, in which the power supply coil and power receiving coil are built into a robot arm. 【0068】 Figure 10(a) shows a configuration where a forearm containing a power receiving coil 21 is connected to an upper arm containing a power supply coil 11, allowing the forearm from the elbow (joint) onward to rotate 360 ​​degrees relative to the upper arm. Figure 10(b) shows that the forearm can rotate 360 ​​degrees relative to the fixed upper arm in the plane indicated by the arrow. Figure 10(c) shows that it can rotate 360 ​​degrees on another plane as well. Similarly, Figure 10(d) shows that it can rotate 360 ​​degrees on another plane. In other words, the forearm can rotate 360 ​​degrees in all directions. Figure 10(e) shows the configuration when it is incorporated into a robot arm with a hand-like gripping part at its tip. 【0069】 As shown in Figure 10, we assume a scenario where a pair of coils is placed at the elbow joint of the robot, and power is supplied from the upper arm to the forearm via wireless power transfer. Since the forearm is oriented in various directions depending on the situation, the magnetic coupling coefficient k between the coils is considered. m It becomes impossible to keep it constant. Therefore, it is difficult to keep the transmitted power constant with existing technology. Thus, there is no invention of a method or apparatus for wirelessly transmitting constant power using a single set of coils in a system that rotates simultaneously in multiple axes. However, in this apparatus that preserves PT symmetry, the magnetic coupling coefficient k m Even if the critical magnetic coupling coefficient k changes, mc As long as it does not fall below a certain level, the transmitted power can always be kept constant regardless of the direction or angle of the arm. 【0070】 Therefore, using the device of the present invention, it becomes possible to wirelessly transmit a constant power in various orientations that can be assumed as rotation axes of a robot arm, as shown in Figures 10(a) to (e). Furthermore, a constant power can be achieved even when multiple axes of rotation are performed simultaneously. The coil arrangement common to all assumed rotation directions is that the power supply coil and the power receiving coil are positioned such that the rotation center of the power receiving coil is near one of the two magnetic poles at both ends of the power receiving coil. 【0071】 Other anticipated applications include wireless power transfer while preserving PT symmetry in two-joint or multi-joint robot arms and multi-joint robots, using the repeater made of the aforementioned repeater coil and capacitor. Figure 11 shows a specific example of a magnetic field resonance type wireless power transfer system utilizing PT symmetry in Embodiment 1 of this invention, in which the power supply coil and power receiving coil are built into the robot arm, and is applied to a two-joint robot arm with a repeater. 【0072】 Thus, even in the case of a multi-joint robot arm with three or more arms connected, as shown in Figure 11, wireless power supply is possible by placing a relay equipped with a resonator in the middle, and it can be bent in all directions and rotated 360 degrees (it can even perform movements involving 360-degree rotation), thus improving convenience. However, according to the present invention, wireless power supply is always possible even for power supply targets that involve 360-degree rotation, so for example, in the case of a robot arm, there is no need to make it multi-jointed, and it can be bent in all directions and rotated 360 degrees with just one joint, which has the advantage of simplifying the structure of the arm. 【0073】 Furthermore, in the example shown in Figure 10, the coil is arranged in the direction of the axis (rotation axis) of the robot arm (the receiving coil 21 is arranged so that the axis of the coil is in the same direction as or parallel to the axis (rotation axis) of the robot arm). However, similar effects can be obtained even if the coil is arranged in the direction of rotation of the robot arm (the receiving coil 21 is arranged so that the axis of the coil is perpendicular to the axis (rotation axis) of the robot arm), as shown in Figure 12. Figure 12 is a schematic perspective view showing another specific example (an example in which the coils are arranged in the rotation direction) in which the power supply coil and the power receiving coil are built into the robot arm in a magnetic field resonance type wireless power supply system utilizing PT symmetry in Embodiment 1 of this invention. 【0074】 Figure 12(a) shows the device built into a robot arm with a hand-like gripping part at its tip, and Figure 12(b) is a magnified view of a portion of Figure 12(a). Compared with Figure 10(e), it can be seen that the arrangement of the coils is different, but even with the arrangement shown in Figure 12, the power supply coil 11 and the power receiving coil 21 are positioned such that the rotation center of the power receiving coil 21 is near one of the two magnetic poles (201, 202) at both ends of the power receiving coil 21. 【0075】 As described above, according to the wireless power supply system of Embodiment 1 of this invention, in wireless power supply utilizing PT symmetry, when supplying power to a rotating object, the power supply coil and the power receiving coil are arranged such that the rotation center of the power receiving coil is near one of the two magnetic poles at both ends of the power receiving coil. This eliminates the need for adjustment or control of the position and angle of the power supply coil and the power receiving coil, and the structure is simple. Furthermore, it is possible to maintain high transmission efficiency without interruption, regardless of how much the power receiving coil rotates relative to the power supply coil, thus enabling constant wireless power supply. 【0076】 In Embodiment 1 of this invention, a robot arm was described as an example of a rotating power supply target. However, it is not limited to robot arms. It can be applied to any rotating target that requires wireless power supply, such as a multi-jointed arm stand with a light bulb, camera, monitor, etc., mounted at its tip. 【0077】 Furthermore, while Embodiment 1 of this invention was described as having a receiving coil rotating relative to the power supply coil (this pattern is thought to be the most common), it is not necessarily limited to this pattern, and can also be applied to powered devices in which the power supply coil rotates relative to the power receiving coil. That is, as a means of always providing wireless power while preserving PT symmetry and keeping the transmitted power constant when rotating the power supply coil relative to the power receiving coil, the power supply coil and the receiving coil may be arranged such that the rotation center of the power supply coil is near one of the two magnetic poles at both ends of the power supply coil. 【0078】 Embodiment 2. Figure 13 is an explanatory diagram showing an example of the schematic configuration of the power supply coil 31 and power receiving coil 41 used in a wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention, and is called a double spiral coil. In wireless power supply devices, a coil called a "DD coil" or "double D coil," which has two coils spirally wound on a magnetic plate, is known to increase the transmission distance and have high magnetic flux generation efficiency (see, for example, Figure 5 of Patent Document 4, Patent Document 5, etc.). Furthermore, the DD coil (double D coil) is used as the highest-performing coil for electromagnetic coils when transmitting high power, such as in wireless power supply to electric vehicles. Here, the term "double spiral coil" will be used consistently. 【0079】 Figure 13(a) shows the state in which the power supply coil 31 provided in the power supply circuit and the power receiving coil 41 provided in the power receiving circuit are facing each other, and Figure 13(b) is a side view of the power supply coil 31 and power receiving coil 41 shown in Figure 13(a) oriented horizontally, with the side where the power supply coil 31 and power receiving coil 41 face each other facing upwards. As shown in Figures 13(a) and (b), both the power supply coil 31 provided in the power supply circuit and the power receiving coil 41 provided in the power receiving circuit are double spiral coil structures in which two planar spiral coils 311 and 312, and 411 and 412, which form a double spiral by spiral winding (e.g., Litz wire), are arranged in a double configuration on top of magnetic cores 100 and 200 made of a soft magnetic material such as ferrite. Then, the unwinding portions near the center of each of the planar spiral coils 311, 312, 411, and 412 become the magnetic poles 101, 102, 201, and 202. 【0080】 Here, the coil structure shown in Embodiment 1 and the coil structure shown in Embodiment 2 are the same in that they are the general configurations of the power supply coil and power receiving coil used in a wireless power supply system utilizing PT symmetry. When supplying power to a rotating object, the power supply coil and power receiving coil are arranged so that the rotation center of the power receiving coil is near one of the two magnetic poles at both ends of the power receiving coil. This eliminates the need for adjustment or control of the position and angle of the power supply coil and power receiving coil, and the structure is simple. Furthermore, it is possible to maintain uninterrupted transmission and high transmission efficiency regardless of how much the power receiving coil rotates relative to the power supply coil, thus enabling power to be supplied wirelessly at all times. 【0081】 However, in Embodiment 1, the power supply coil in the power supply circuit and the power receiving coil in the power receiving circuit were solenoid-type or helical-type coils having magnetic poles at both ends. However, as shown in Figures 10 to 12, when applied to a robot arm, if the robot arm is made only of metal that blocks magnetic fields, magnetic flux leaks from the back of each coil, preventing a proper loop from forming, which can reduce the magnetic coupling coefficient and prevent the wireless power transfer from being effective. 【0082】 In other words, when a power supply coil and a power receiving coil, as shown in Figure 4 of Embodiment 1, are installed inside or around the rotating object, if there is a metal plate on the back of each coil (the side that is not facing the power supply coil and the power receiving coil), that is, if the rotating object is entirely made of metal, magnetic flux will leak from the back of each coil, preventing the magnetic flux from looping properly. This causes the alternating magnetic field to strike the metal plate, resulting in eddy current losses. It has been found that these eddy current losses not only reduce power transmission efficiency but also prevent the preservation of PT symmetry. In short, Embodiment 1 is effective when the material of the rotating object is not metal, such as plastic, but if the rotating object is entirely made of metal, the wireless power supply may not be effective. 【0083】 Therefore, in this second embodiment, the power supply coil provided in the power supply circuit and the power receiving coil provided in the power receiving circuit are each double spiral type (Figure 13) or hybrid type (see Figures 14 and 15 described later) coils having magnetic poles at both ends. In this case, even if there is metal on the back of the coil, the proportion of magnetic flux that self-loops on the back of the coil is very small. As a result, it was confirmed that when rotating the power receiving coil relative to the power supply coil, or when rotating the power supply coil relative to the power receiving coil, PT symmetry can be preserved and wireless power can always be supplied while keeping the transmitted power constant. 【0084】 Figure 14 is an explanatory diagram showing another example of the schematic configuration of the power supply coil 31 and power receiving coil 41 used in the wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention, and is a type of what is called a hybrid coil. Similar to the double spiral type shown in Figure 13, Figure 14 is a coil structure in which two planar spiral coils 311 and 312 and 411 and 412 that constitute a double spiral are arranged slightly apart on top of magnetic cores 100 and 200 made of a soft magnetic material such as ferrite, and solenoid-shaped coil windings 111 and 211 are arranged between these two coils (311 and 312, 411 and 412) in the same manner as in Figure 4 in Embodiment 1, with the magnetic cores 100 and 200 as the axis. Furthermore, in this coil structure as well, the unwinding portions near the center of each of the planar spiral coils 311, 312, 411, and 412 become the magnetic poles 101, 102, 201, and 202. 【0085】 Figure 15 is an explanatory diagram showing yet another example of the schematic configuration of the power supply coil 31 and power receiving coil 41 used in a wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention, and is also a type of hybrid coil. In Figure 15, two spiral coils 321 and 322, 421 and 422 (stepped spiral coils 321 and 322, 421 and 422 constituting a double spiral) are wound diagonally from the top to the bottom of magnetic cores 100 and 200 made of a soft magnetic material such as ferrite, and the two coils 321 and 322, 421 and 422 are arranged slightly apart, and between the two coils (321 and 322, 421 and 422), a solenoid-shaped coil winding 111 and 211 is arranged in the same manner as in Figure 14, wound around the magnetic cores 100 and 200 as an axis. Furthermore, in this coil structure as well, the unwinding portions near the center of each stepped spiral coil 321, 322, 421, and 422 become the magnetic poles 101, 102, 201, and 202. 【0086】 Furthermore, Figure 16 is a schematic perspective view showing the coil structure for the wireless power supply device shown in Figure 15, and only the power supply coil 31 is shown. In other words, Figure 15(b) is a side view of Figure 16 as seen from the direction of arrow A. As shown in Figure 16, the magnetic core 100 is a magnetic material with a roughly rectangular parallelepiped shape, having a length from left to right, the longest side being in the X-axis direction, a depth, the second longest side being in the Y-axis direction, and a thickness from top to bottom, the shortest side being in the Z-axis direction. Note that the directions of the X, Y, and Z axes are only shown in Figure 16 and are omitted in Figures 13 to 15, but the X, Y, and Z axes are defined in the same way as in Figure 16 in Figures 13 to 15. That is, the explanation of top and bottom, such as top and bottom, refers to whether it is the positive or negative side in the Z-axis direction, with the side where the power supply coil and the power receiving coil face each other being considered top. 【0087】 Furthermore, the use of "approximately" in phrases like "a magnetic material with an approximate rectangular prism shape" means that it doesn't have to be a strict rectangular prism; for example, the corners of the rectangular prism shape might be slightly rounded, or the intersecting edges might be slightly angled rather than right angles. In other words, as long as the overall shape is roughly rectangular, it doesn't have to be a perfect rectangular prism. 【0088】 Here, two spiral coils 321 and 322, and 421 and 422 constitute a double spiral coil. In Figure 16, of the two stepped spiral coils 321 and 322, coil 321 is positioned on the left and coil 322 is positioned on the right. The left coil 321 has a step in the Z-axis direction such that the inside of coil 321 (the side closer to the right coil 322) is above the magnetic core 100 (positive side in the Z-axis direction), and the outside (the side furthest from the right coil 322) is below the magnetic core 100 (negative side in the Z-axis direction). Similarly, the right coil 322 has a step in the Z-axis direction such that the inside of coil 322 (the side closer to the left coil 321) is above the magnetic core 100 (positive side in the Z-axis direction), and the outside (the side furthest from the left coil 321) is near the bottom of the magnetic core 100 (negative side in the Z-axis direction). 【0089】 These two stepped spiral coils 321 and 322 are positioned slightly apart in the X-axis direction, and between these two spiral coils 321 and 322, a single coil winding (solenoid coil) 111,211 is positioned around the magnetic core 100 as its axis, wound multiple times so that the coils do not overlap in the Y-axis and Z-axis directions. 【0090】 The coil structures shown in Figures 14 and 15 are coil structures conceived by the applicant as an application of Figure 13, and are also disclosed in the applicant's international patent application: PCT / JP2023 / 44946. These coil structures, which include both a double spiral coil and a solenoid coil, will be referred to as "hybrid coils." 【0091】 Generally, the coils used for wireless power transfer are often spiral-shaped, circular single spiral coils (or pancake-shaped coils). However, one of the features of Embodiment 2 of the present invention is that the coil shape is a double spiral coil or a hybrid coil with magnetic poles at both ends. By using a double spiral coil or a hybrid coil with a soft magnetic material as the core, it is possible to make a small coil, which makes it possible to install it inside a small power supply target. 【0092】 However, as mentioned above, in Embodiment 1, the power supply coil in the power supply circuit and the power receiving coil in the power receiving circuit were solenoid-type or helical-type coils having magnetic poles at both ends. However, as shown in Figures 10 to 12, when applied to a robot arm, if the robot arm is made only of metal that blocks magnetic fields, magnetic flux leaks from the back of the coil, preventing it from looping properly, which can reduce the magnetic coupling coefficient and prevent the wireless power supply from being effective. 【0093】 Therefore, in this embodiment 2, the power supply coil provided in the power supply circuit and the power receiving coil provided in the power receiving circuit are each double spiral type or hybrid type coils having magnetic poles at both ends. In this case, even if there is metal on the back of the coil, the proportion of magnetic flux that self-loops on the back of the coil is very small. As a result, it was confirmed that when rotating the power receiving coil relative to the power supply coil, or when rotating the power supply coil relative to the power receiving coil, PT symmetry can be preserved and wireless power supply can always be performed while keeping the transmitted power constant. 【0094】 Figure 17 shows the positional relationship between coils in a wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention, when the rotation center O is located at one of the two magnetic poles at both ends of the double spiral type receiving coil shown in Figure 13, for a rotating power supply target. Similar to Figure 4 of Embodiment 1, the magnetic coupling coefficient k is also constant in the double spiral type coil shown in Figure 13 at any rotation angle θ. m An example of a coil arrangement that does not result in 0 (zero) is shown in Figure 17. Note that in Figure 17, unlike in Figure 4, the power supply coil 31 is shown in the foreground and the power receiving coil 41 is shown in the background, and the power receiving coil is assumed to rotate relative to the power supply coil. 【0095】 Then, similar to Figure 4 in Embodiment 1, the state in which the axis 31L of the power supply coil 31 and the axis 41L of the power receiving coil 41 are parallel is defined as a rotation angle of 0 degrees, and the angle between the two axes is defined as the rotation angle θ (the same applies to Figure 18, which will be described later). Also, in Figure 17, the dashed line shows the power receiving coil before rotation, and before rotation, the axis 31L of the power supply coil 31 and the axis of the power receiving coil (the dashed power receiving coil does not have a symbol or axis shown). Furthermore, the power receiving coil 41 shown by the solid line is the power receiving coil 41 after being rotated by a rotation angle θ around one of the two magnetic poles at both ends of the power receiving coil 41 (in the example shown in Figure 17, magnetic pole 202) (the same applies to Figure 18, which will be described later). 【0096】 Here, although not shown in the diagram, in the case of the coil positional relationship shown in Figure 17, that is, when the rotation center O is near one of the two magnetic poles (201, 202) at both ends of the receiving coil 41, the magnetic coupling coefficient k is the same as in Figure 5 in Embodiment 1. m The rotation angle at which the value becomes 0 (zero) can be eliminated. In this state, by utilizing PT symmetry, the transmitted power can be kept constant at any rotation angle θ. 【0097】 Thus, by arranging the power supply coil 31 and the power receiving coil 41 such that the rotation center of the power receiving coil 41 is near one of the two magnetic poles (201, 202) at both ends of the power receiving coil 41, the magnetic coupling coefficient k is maintained at any rotation angle θ when the power receiving coil 41 is rotated relative to the power supply coil 31. m Since it never becomes 0 (zero), it is possible to preserve PT symmetry and always provide wireless power while keeping the transmission power constant. 【0098】 Figure 18 shows the positional relationship between coils in a wireless power supply system utilizing PT symmetry in Embodiment 2 of this invention, when the rotation center O is located at one of the two magnetic poles at both ends of the hybrid type receiving coil shown in Figure 15, for a rotating power supply target. In the hybrid type coil shown in Figure 15, the magnetic coupling coefficient k is also constant at any rotation angle θ. m An example of a coil arrangement that does not result in 0 (zero) is shown in Figure 17. 【0099】 As with Figures 2, 4, and 17, the dashed line in Figure 18 represents the receiving coil before rotation. Before rotation, the axis 31L of the supply coil 31 and the axis of the receiving coil (the dashed receiving coil does not have a symbol or axis shown) are parallel. The solid line represents the receiving coil 41 after it has been rotated by an angle θ around one of the two magnetic poles at both ends of the receiving coil 41 (in the example shown in Figure 18, magnetic pole 202). 【0100】 Here, although the illustration is omitted, in the case of the coil positional relationship shown in Figure 18, that is, when the rotation center O is near one of the two magnetic poles (201, 202) at both ends of the receiving coil 41, the magnetic coupling coefficient k is the same as in Figure 5 in Embodiment 1. m The rotation angle at which the value becomes 0 (zero) can be eliminated. In this state, by utilizing PT symmetry, the transmitted power can be kept constant at any rotation angle θ. 【0101】 Thus, by arranging the power supply coil 31 and the power receiving coil 41 such that the rotation center of the power receiving coil 41 is near one of the two magnetic poles (201, 202) at both ends of the power receiving coil 41, the magnetic coupling coefficient k is maintained at any rotation angle θ when the power receiving coil 41 is rotated relative to the power supply coil 31. m Since it never becomes 0 (zero), it is possible to preserve PT symmetry and always provide wireless power while keeping the transmission power constant. 【0102】 In other words, as shown in Figures 17 and 18, Embodiment 2 of this invention is characterized in that, similar to Embodiment 1 shown in Figure 4, the rotation center of the receiving coil is located near one of the two magnetic poles at both ends of the receiving coil. 【0103】 Furthermore, by arranging the power supply coil 31 and the power receiving coil 41 such that the rotation center of the power receiving coil 41 is near one of the two magnetic poles (201, 202) at both ends of the power receiving coil 41, the magnetic coupling coefficient k is maintained at any rotation angle θ when the power receiving coil 41 is rotated relative to the power supply coil 31. m Since it never becomes 0 (zero), it is possible to preserve PT symmetry and always provide wireless power while keeping the transmission power constant. 【0104】 Figure 19 is a schematic perspective view showing one specific example of a magnetic field resonance type wireless power supply system utilizing PT symmetry in Embodiment 2 of the present invention, in which the hybrid type power supply coil and power receiving coil shown in Figure 15 are mounted on the wall surface of a metal robot arm. In Figure 19, the robot arm that is the object of rotation is made entirely of metal, and the hybrid type power supply coil and power receiving coil shown in Figure 15 are arranged on the wall surface of the metal robot arm such that the rotation center of the power receiving coil is near one of the magnetic poles. 【0105】 In Figure 19, the power supply coil 31 is fixed to the robot arm 5, and the power receiving coil 41 is fixed to the robot arm 6. However, since the power receiving coil 41 needs to be mounted facing the power supply coil 31, the figure shows the power receiving coil 41 fixed to a coil mounting frame 7 attached to the robot arm 6. Normally, the hybrid coil shown in Figure 15 uses a coil winding type for winding and fixing the coil, but in Figure 19, the coil winding type is omitted in order to make it easier to understand that the hybrid power supply coil 31 and power receiving coil 41 shown in Figure 15 are mounted. 【0106】 When the object to be rotated is not made solely of metal, that is, when it is made of materials other than metal, such as resin, or when metal is used in part, PT symmetry could be preserved even when the coil was embedded in the object to be rotated (robot arm), as shown in Figures 10 to 12 of Embodiment 1. However, when the object to be rotated is made solely of metal, embedding the coil would completely enclose the surroundings in metal, which could make it impossible to preserve PT symmetry. In such cases, as shown in Figure 19, the power supply coil and power receiving coil from Embodiment 2 can be attached to the wall surface of the robot arms 5 and 6, which are the objects to be rotated, thereby ensuring that PT symmetry is preserved and wireless power supply can always be performed. Experimental results in this specific example confirmed that PT symmetry can be preserved and wireless power supply can be performed efficiently even when a metal robot arm is rotated. 【0107】 As described above, according to the wireless power supply system of Embodiment 2 of this invention, similar to Embodiment 1, in wireless power supply utilizing PT symmetry, when supplying power to a rotating object, the power supply coil and the power receiving coil are arranged such that the rotation center of the power receiving coil is near one of the two magnetic poles at both ends of the power receiving coil. This eliminates the need for adjustment or control of the position and angle of the power supply coil and the power receiving coil, and the structure is simple. Furthermore, it is possible to maintain high transmission efficiency without interruption, regardless of how much the power receiving coil rotates relative to the power supply coil, thus enabling constant wireless power supply. 【0108】 In Embodiment 2 of this invention, a robot arm was used as an example of a rotating power supply target, but it is not limited to a robot arm. It can be applied to any rotating object that requires wireless power supply, such as a multi-jointed arm stand with a light bulb, camera, monitor, etc., mounted at its tip. Furthermore, according to Embodiment 2, compared to Embodiment 1, even if the rotating power supply target is made only of metal, PT symmetry can be preserved and wireless power supply can be performed efficiently. 【0109】 Furthermore, although Embodiment 2 of this invention was described as having a receiving coil rotating relative to the power supply coil (this pattern is thought to be the most common), it is not necessarily limited to this pattern, and can also be applied to powered devices in which the power supply coil rotates relative to the power receiving coil. That is, as a means of always providing wireless power while preserving PT symmetry and keeping the transmitted power constant when rotating the power supply coil relative to the power receiving coil, the power supply coil and the receiving coil may be arranged such that the rotation center of the power supply coil is near one of the two magnetic poles at both ends of the power supply coil. 【0110】 Embodiment 3. Figure 20 is an explanatory diagram showing an example of the schematic configuration of the power supply coil 31 and power receiving coil 21 used in a wireless power supply system utilizing PT symmetry in Embodiment 3 of this invention. In Figure 20, the power supply coil 31 is a hybrid type coil as described in Figures 15 and 16 of Embodiment 2, and the power receiving coil 21 is a solenoid type coil as described in Embodiment 1. Thus, the power supply coil and the power receiving coil do not necessarily have to be the same shape, and Embodiment 3 is a combination of Embodiment 1 and Embodiment 2. 【0111】 In other words, Embodiment 3 is an example of a pattern in which one of the power supply coil or power receiving coil is a solenoid type or helical type coil as described in Embodiment 1, and the other is a double spiral type or hybrid type coil as described in Embodiment 2. 【0112】 As shown in Figure 20, the power supply coil 31 in the power supply circuit may be a double spiral type or hybrid type coil having magnetic poles at both ends, and the power receiving coil 21 in the power receiving circuit may be a solenoid type or helical type coil having magnetic poles at both ends, or conversely, the power supply coil may be a solenoid type or helical type coil having magnetic poles at both ends, and the power receiving coil may be a double spiral type or hybrid type coil having magnetic poles at both ends. 【0113】 Figure 21 shows the positional relationship between coils in a wireless power supply system utilizing PT symmetry in Embodiment 3 of this invention, when the rotation center O is located on one of the two magnetic poles at both ends of the solenoid-type receiving coil 21 shown in Figure 20, for a rotating power supply target. Similar to Figure 4 of Embodiment 1 and Figures 17 and 18 of Embodiment 2, the magnetic coupling coefficient k is also constant for the power supply coil and receiving coil shown in Figure 20 at any rotation angle θ. mAn example of a coil arrangement that does not result in 0 (zero) is shown in Figure 21. In Figure 21, as in Figures 17 and 18, the power supply coil 31 is shown in the foreground and the power receiving coil 21 is shown in the background, and it is assumed that the power receiving coil 21 rotates relative to the power supply coil 31. 【0114】 Then, similar to Figure 4 of Embodiment 1 and Figures 17 and 18 of Embodiment 2, the state in which the axis 31L of the power supply coil 31 and the axis 21L of the power receiving coil 21 are parallel is defined as a rotation angle of 0 degrees, and the angle between the two axes is defined as the rotation angle θ. Also, in Figure 21, the dashed line shows the power receiving coil before rotation, and before rotation, the axis 31L of the power supply coil 31 and the axis of the power receiving coil (the dashed power receiving coil does not have a symbol or axis shown) are parallel. Furthermore, the solid line shows the power receiving coil 21 after it has been rotated by a rotation angle θ around one of the two magnetic poles at both ends of the power receiving coil 21 (in the example shown in Figure 21, magnetic pole 202). 【0115】 Here, although the diagram is omitted, in the case of the coil positional relationship shown in Figure 21, that is, when the rotation center O is near one of the two magnetic poles (201, 202) at both ends of the receiving coil 21, the magnetic coupling coefficient k is the same as in Figure 5 in Embodiment 1. m The rotation angle at which the value becomes 0 (zero) can be eliminated. In this state, by utilizing PT symmetry, the transmitted power can be kept constant at any rotation angle θ. 【0116】 Thus, by arranging the power supply coil 31 and the power receiving coil 21 such that the rotation center of the power receiving coil 21 is near one of the two magnetic poles (201, 202) at both ends of the power receiving coil 21, the magnetic coupling coefficient k is maintained at any rotation angle θ when the power receiving coil 21 is rotated relative to the power supply coil 31. m Since it never becomes 0 (zero), it is possible to preserve PT symmetry and always provide wireless power while keeping the transmission power constant. 【0117】 In other words, as shown in Figure 21, Embodiment 3 of this invention is characterized in that, similar to Embodiment 1 shown in Figure 4 and Embodiment 2 shown in Figures 17 and 18, the rotation center of the receiving coil is located near one of the two magnetic poles at both ends of the receiving coil. 【0118】 Furthermore, by arranging the power supply coil 31 and the power receiving coil 21 such that the rotation center of the power receiving coil 21 is near one of the two magnetic poles (201, 202) at both ends of the power receiving coil 21, the magnetic coupling coefficient k is maintained at any rotation angle θ when the power receiving coil 21 is rotated relative to the power supply coil 31. m Since it never becomes 0 (zero), it is possible to preserve PT symmetry and always provide wireless power while keeping the transmission power constant. 【0119】 Here, we will explain the advantages of using a solenoid or helical coil as one of the power receiving coils and a double spiral or hybrid coil as the other, as in this Embodiment 3. First, solenoid or helical coils have the advantage of being lightweight overall because they have a simple structure and require fewer turns. Furthermore, by using a double spiral or hybrid coil as the other coil, as explained in Embodiment 2, even if the rotating object is entirely made of metal and there is metal on the back of the coil, the magnetic flux leaking from the back of the double spiral or hybrid coil is not very large. 【0120】 Figure 22 is a schematic perspective view showing one specific example of a magnetic field resonance type wireless power supply system utilizing PT symmetry in Embodiment 3 of the present invention, in which the hybrid type power supply coil and solenoid type power receiving coil shown in Figure 20 are mounted on the wall surface of a metal robot arm. In Figure 22, the robot arm that is the object of rotation is made of metal only, and the back surface of the hybrid type power supply coil 31 shown in Figure 20 is positioned on the wall surface of the metal robot arm 5, while the solenoid type power receiving coil 21 is positioned on the wall surface of the robot arm 6 that rotates relative to the robot arm 5, facing the power supply coil 31 attached to the robot arm 5, and the rotation center of the power receiving coil 21 is positioned near one of the magnetic poles of the power receiving coil 21. 【0121】 Furthermore, in Figure 22, the power receiving coil 21 is fixed to the robot arm 6. However, since the power receiving coil 21 needs to be mounted facing the power supply coil 31, the figure shows the power receiving coil 21 fixed to a coil mounting frame 7 attached to the robot arm 6, similar to the power receiving coil 41 in Figure 19. 【0122】 When the object to be rotated is not made solely of metal, that is, when it is made of materials other than metal, such as resin, or when metal is used in part, PT symmetry could be preserved even when the coil was built into the robot arm that is the object to be rotated, as shown in Figures 10 to 12 of Embodiment 1. However, when the object to be rotated is made solely of metal, building in the coil would completely enclose the surroundings in metal, making it impossible to preserve PT symmetry. In such cases, as shown in Figure 22, the power supply coil and power receiving coil from Embodiment 3 can be attached to the wall surface of the robot arm that is the object to be rotated, thereby reducing weight and preserving PT symmetry, enabling wireless power supply at all times. Experimental results in this specific example confirmed that PT symmetry can be preserved and wireless power supply can be efficiently performed even when a metal robot arm is rotated. 【0123】 In other words, as in this embodiment 3, when one of the power supply coils and power receiving coils used in a wireless power supply system utilizing PT symmetry is a solenoid type or helical type coil, and the other is a double spiral type or hybrid type coil, the overall weight of the coils can be reduced. Furthermore, even if the rotating object is made of metal and there is metal on the back of the double spiral type or hybrid type coil, it is possible to maintain PT symmetry and always provide wireless power while keeping the transmitted power constant. 【0124】 As described above, according to the wireless power supply system of Embodiment 3 of this invention, similar to Embodiments 1 and 2, in wireless power supply utilizing PT symmetry, when supplying power to a rotating object, the power supply coil and the power receiving coil are arranged such that the rotation center of the power receiving coil is near one of the two magnetic poles at both ends of the power receiving coil. This eliminates the need for adjustment or control of the position and angle of the power supply coil and the power receiving coil, and the structure is simple. Furthermore, it is possible to maintain high transmission efficiency without interruption regardless of how much the power receiving coil rotates relative to the power supply coil, thus enabling constant wireless power supply. 【0125】 Furthermore, in Embodiment 3 of this invention, the rotating power supply target is not limited to a robot arm, but can be applied to any rotating object that requires wireless power supply, such as a multi-joint arm stand with a light bulb, camera, monitor, etc., mounted at its tip. Also, according to Embodiment 3, compared to Embodiment 1, even if the rotating power supply target is made only of metal, PT symmetry can be preserved and wireless power supply can be performed efficiently. Moreover, according to Embodiment 3, compared to Embodiment 2, there is the advantage that the overall weight can be reduced by using a solenoid type or helical type coil for either the power supply coil or the power receiving coil. 【0126】 Furthermore, although Embodiment 3 of this invention was described as having the receiving coil rotate relative to the supplying coil (this pattern is thought to be the most common), it is not necessarily limited to this pattern, and can also be applied to powered devices in which the supplying coil rotates relative to the receiving coil. That is, as a means of always providing wireless power while preserving PT symmetry and keeping the transmitted power constant when the supplying coil rotates relative to the receiving coil, the supplying coil and the receiving coil may be arranged such that the rotation center of the supplying coil is near one of the two magnetic poles at both ends of the supplying coil. 【0127】 Furthermore, within the scope of the present invention, it is possible to freely combine each embodiment, modify any component of each embodiment, or omit any component in each embodiment. [Industrial applicability] 【0128】 The wireless power supply system of this invention can be applied to various power supply targets that involve rotation, such as robot arms and multi-joint arm stands. [Explanation of Symbols] 【0129】 11,31 Power supply coil Axles of power supply coils 11L and 31L 21,41 Power receiving coil Axial lines of the 21L and 41L receiving coils. 100,200 magnetic cores 101,102,201,202 magnetic pole 111,211 Winding (Solenoid coil) 311, 312, 411, 412 Planar spiral coils that form a double spiral. 321, 322, 421, 422 Stepped spiral coils that make up a double spiral 5,6 Robot Arm 7. Fixing frame for coil mounting

Claims

[Claim 1] A wireless power supply system for a rotating power supply target that utilizes Party-Time symmetry (hereinafter referred to as "PT symmetry"), The power supply coil in the power supply circuit and the power receiving coil in the power receiving circuit are solenoid-type or helical-type coils having magnetic poles at both ends. As a means of always providing wireless power while preserving the PT symmetry and keeping the transmitted power constant when rotating the power receiving coil relative to the power supply coil, The power supply coil and the power receiving coil are positioned such that the rotation center of the power receiving coil is near one of the two magnetic poles located at both ends of the power receiving coil. A wireless power supply system characterized by the following features. [Claim 2] A wireless power supply system for a rotating power supply target that utilizes Party-Time symmetry (hereinafter referred to as "PT symmetry"), The power supply coil in the power supply circuit and the power receiving coil in the power receiving circuit are solenoid-type or helical-type coils having magnetic poles at both ends. As a means of always providing wireless power while preserving the PT symmetry and keeping the transmitted power constant when rotating the power supply coil relative to the power receiving coil, The power supply coil and the power receiving coil are positioned such that the rotation center of the power supply coil is near one of the two magnetic poles located at both ends of the power supply coil. A wireless power supply system characterized by the following features. [Claim 3] A wireless power supply system for a rotating power supply target that utilizes Party-Time symmetry (hereinafter referred to as "PT symmetry"), The power supply coil in the power supply circuit and the power receiving coil in the power receiving circuit are each double spiral type or hybrid type coils having magnetic poles at both ends. As a means of always providing wireless power while preserving the PT symmetry and keeping the transmitted power constant when rotating the power receiving coil relative to the power supply coil, The power supply coil and the power receiving coil are positioned such that the rotation center of the power receiving coil is near one of the two magnetic poles located at both ends of the power receiving coil. A wireless power supply system characterized by the following features. [Claim 4] A wireless power supply system for a rotating power supply target that utilizes Party-Time symmetry (hereinafter referred to as "PT symmetry"), The power supply coil in the power supply circuit and the power receiving coil in the power receiving circuit are each double spiral type or hybrid type coils having magnetic poles at both ends. As a means of always providing wireless power while preserving the PT symmetry and keeping the transmitted power constant when rotating the power supply coil relative to the power receiving coil, The power supply coil and the power receiving coil are positioned such that the rotation center of the power supply coil is near one of the two magnetic poles located at both ends of the power supply coil. A wireless power supply system characterized by the following features. [Claim 5] A wireless power supply system for a rotating power supply target that utilizes Party-Time symmetry (hereinafter referred to as "PT symmetry"), One of the coils in the power supply circuit (power supply coil) and the power receiving circuit (power receiving coil) is a solenoid-type or helical-type coil with magnetic poles at both ends, and the other coil is a double-spiral-type or hybrid-type coil with magnetic poles at both ends. As a means of always providing wireless power while preserving the PT symmetry and keeping the transmitted power constant when rotating the power receiving coil relative to the power supply coil, The power supply coil and the power receiving coil are positioned such that the rotation center of the power receiving coil is near one of the two magnetic poles located at both ends of the power receiving coil. A wireless power supply system characterized by the following features. [Claim 6] A wireless power supply system for a rotating power supply target that utilizes Party-Time symmetry (hereinafter referred to as "PT symmetry"), One of the coils in the power supply circuit (power supply coil) and the power receiving circuit (power receiving coil) is a solenoid-type or helical-type coil with magnetic poles at both ends, and the other coil is a double-spiral-type or hybrid-type coil with magnetic poles at both ends. As a means of always providing wireless power while preserving the PT symmetry and keeping the transmitted power constant when rotating the power supply coil relative to the power receiving coil, The power supply coil and the power receiving coil are positioned such that the rotation center of the power supply coil is near one of the two magnetic poles located at both ends of the power supply coil. A wireless power supply system characterized by the following features.

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