Power receiving device and power control method

Abstract

To improving the power transmission efficiency from a power transmission device by suppressing occurrence of magnetic saturation in the power receiving device in water even when the outer circumference of the housing is surrounded by a magnetic material.SOLUTION: The power receiving device is capable of moving underwater and has a housing whose outer circumference is surrounded by a magnetic material. The power receiving device has a power receiving unit that receives the power transmitted wirelessly from a power transmission device and a storage battery. The power receiving device includes: a power supply unit for charging the storage battery based on the power received by the power receiving unit; a power detection unit that repeatedly detects the power value of the power supply unit that is in operation; and a power receiving processor that determines the control current value for operating the power supply unit based on a comparison result between the power value detected by the power detection unit and the power value that is previously detected by the power detection unit, and controls the operation of the power supply unit based on the determined control current value.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to a power receiving device and a power control method. [Background technology]

[0002] Patent Document 1 discloses a power transmission device (e.g., an underwater base station) that transmits power contactlessly underwater between a power receiving device (e.g., an underwater vehicle) using a magnetic resonance method. This power transmission device includes a power transmission resonance coil, a balloon, and a balloon control mechanism. The power transmission resonance coil transmits power contactlessly to the power receiving resonance coil of the power receiving device using a magnetic field resonance method. The balloon contains the power transmission resonance coil. The balloon control mechanism displaces water between the power transmission resonance coil and the power receiving resonance coil by expanding the balloon when power is transmitted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-015901 A Summary of the Invention [Problem to be solved by the invention]

[0004] When it is assumed that power is transmitted from a power transmitting device to a power receiving device underwater, aluminum, which is a weakly magnetic material (non-magnetic material), is generally used for the housing of an underwater vehicle (i.e., a power receiving device) such as an autonomous underwater vehicle (AUV: Autonomous Underwater Vehicle). When a power receiving coil is formed by winding wire around the side of this housing, the inductance decreases due to the conductivity of aluminum, which is a weakly magnetic material, and the Q value decreases. To solve this problem, a configuration in which the outer periphery of the housing of the power receiving device is surrounded by a magnetic body made of a ferromagnetic material makes it possible to reduce eddy current loss and increase power transmission efficiency.

[0005] However, when the above-mentioned configuration is adopted, as the power received by the power receiving device increases, the effect of reducing eddy current loss is hindered by the phenomenon of magnetic saturation of the magnetic material, resulting in a problem of a decrease in the efficiency of power transmission to the power receiving device. In particular, when wirelessly feeding power to a power receiving device underwater (e.g., underwater), the impedance of the power source in the power receiving device is likely to fluctuate due to the impedance of the rechargeable battery mounted in the power receiving device, or fluctuations in the coil coupling coefficient based on the position-free nature of the power receiving device as a moving body, making it difficult to find conditions that do not cause the above-mentioned magnetic saturation.

[0006] The present disclosure has been devised in consideration of the conventional situation described above, and provides a power receiving device and a power control method that suppresses the occurrence of magnetic saturation in the power receiving device underwater, even when the outer periphery of the housing is surrounded by a magnetic material, and improves the transmission efficiency of power from the power transmitting device. [Means for solving the problem]

[0007] The present disclosure provides a power receiving device that is movable underwater and has a housing whose outer periphery is surrounded by a magnetic material, the power receiving device including a power receiving unit that receives power wirelessly transmitted from a power transmitting device, a power supply unit that has a storage battery and charges the storage battery based on the power received by the power receiving unit, and a power detection unit that repeatedly detects a power value during operation of the power supply unit. a current detection unit that repeatedly detects a current value during operation of the power supply unit; a power receiving side processor that determines a control current value for operating the power supply unit based on a comparison result between a power value detected by the power detection unit and a power value previously detected by the power detection unit, and controls the operation of the power supply unit based on the determined control current value. The power receiving processor determines the control current value based on the current value detected by the current detection unit in accordance with either a case where the power value increases when the control current value is increased or a case where the power value decreases when the control current value is increased. The present invention provides a power receiving device.

[0008] The present disclosure also provides a power control method performed by a power receiving device that is movable underwater and has a housing whose outer periphery is surrounded by a magnetic material, the method comprising: receiving power wirelessly transmitted from a power transmitting device; charging a storage battery based on the received power in a power supply unit having the storage battery; and repeatedly detecting a power value during operation of the power supply unit; Repeatedly detecting a current value during operation of the power supply unit;A control current value for operating the power supply unit is determined based on a result of comparing the detected power value with a previously detected power value, and the operation of the power supply unit is controlled based on the determined control current value. The control current value is determined based on the detected current value in response to either a case where the power value increases when the control current value is increased, or a case where the power value decreases when the control current value is increased. The present invention provides a power control method. Effect of the Invention

[0009] According to the present disclosure, even when the outer periphery of the housing is surrounded by a magnetic material, the occurrence of magnetic saturation in the power receiving device underwater can be suppressed, and the transmission efficiency of power from the power transmitting device can be improved. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a usage environment in which an underwater power supply system according to a first embodiment is installed; [Figure 2A] FIG. 1 is a perspective view showing an example of the external appearance of an underwater vehicle; [Figure 2B] 2A and a partially enlarged cross section of the underwater vehicle as viewed from the direction of the arrow FF in FIG. [Figure 2C] FIG. 2A shows a cross section of the underwater vehicle as viewed from the direction of the arrows GG in FIG. 2A and an enlarged portion of the cross section. [Diagram 3] FIG. 1 is a diagram showing an example of a hardware configuration of an underwater power supply system according to a first embodiment; [Figure 4] A block diagram showing an example of a functional configuration of a power receiving processor [Diagram 5] Graph showing an example of characteristics showing changes in impedance with respect to load current in a power receiving device [Figure 6] Graph showing an example of characteristics showing transition of coil current with respect to impedance in a power receiving device [Figure 7] Graph showing an example of characteristics showing a transition of load power with respect to load current in a power receiving device [Figure 8] 1 is a flowchart showing an example of an operation procedure for power control of a power receiving device according to a first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, with reference to the drawings as appropriate, an embodiment specifically disclosing a power receiving device and a power control method according to the present disclosure will be described in detail. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Note that the attached drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] Fig. 1 is a diagram illustrating a schematic example of a usage environment in which an underwater power supply system 1000 according to the first embodiment is installed. The underwater power supply system 1000 has a power transmitting device 100, a power receiving device 200, and a plurality of coils CL (see Fig. 3). The power transmitting device 100 transmits power to the power receiving device 200 wirelessly (i.e., without contact) via the plurality of coils CL according to a magnetic resonance method. The number of coils CL to be arranged is n (n: an integer of 2 or more) and is arbitrary.

[0013] The coil CL is formed, for example, in a ring shape and insulated by being covered with a resin cover. The coil CL is formed, for example, by a cab-tire cable, a helical coil, or a spiral coil. A helical coil is a ring-shaped coil wound in a helical shape not in the same plane but along the direction of power transmission by the magnetic resonance method. A spiral coil is a ring-shaped coil formed in a spiral shape in the same plane. The use of a spiral coil makes it possible to make the coil CL thinner. The use of a helical coil makes it possible to secure a large space inside the wound coil CL. Note that FIG. 1 shows an example of a spiral coil.

[0014] The coil CL used for power transmission includes a power transmitting coil CLA and a power receiving coil CLB. The power transmitting coil CLA is a primary coil. The power receiving coil CLB is a secondary coil. The coil CL may include at least one relay coil CLC (Booster Coil) arranged between the power transmitting coil CLA and the power receiving coil CLB. The relay coil CLC is an example of a power transmitting coil. When there are multiple relay coils CLC, the relay coils CLC are arranged substantially parallel to each other, and more than half of the openings formed by the relay coils CLC overlap. The interval between the multiple relay coils CLC is, for example, equal to or greater than the radius of the relay coil CLC. The relay coil CLC assists the power transmission by the power transmitting coil CLA.

[0015] The power transmitting coil CLA is provided in the power transmitting device 100 (see FIG. 3). The power receiving coil CLB is provided in the power receiving device 200 (see FIG. 3). The relay coil CLC may be provided in the power transmitting device 100, in the power receiving device 200, or separately from the power transmitting device 100 and the power receiving device 200. A part of the relay coil CLC may be provided in the power transmitting device 100, and another part may be provided in the power receiving device 200.

[0016] The power transmitting device 100 may be partially installed on the ship 50, or may be disposed in another location (e.g., a power supply facility 1200 installed on land). The power receiving device 200 may be set in a mobile underwater vehicle 70 (e.g., a submarine, a bottom drilling machine), or may be installed in a fixedly installed underwater facility (e.g., a seismometer, a surveillance camera, a geothermal generator). In FIG. 1, a submarine is illustrated as an example of the underwater vehicle 70. Each coil CL is disposed underwater (e.g., in the sea).

[0017] The underwater vehicle 70 may be, for example, a Remotely Operated Vehicle (ROV), an Unmanned Underwater Vehicle (UUV), or an Autonomous Underwater Vehicle (AUV).

[0018] A part of the vessel 50 is above the water surface 90 (e.g., sea surface), i.e., above the water, and another part of the vessel 50 is below the water surface 90, i.e., underwater (e.g., under the sea). The vessel 50 is movable on the water (e.g., above sea), and can freely move to, for example, a data acquisition location on the water (e.g., above sea). A power cable 280 connects the power transmitting device 100 installed on the vessel 50 to the power transmitting coil CLA. The power cable 280 is connected to a driver 151 (see FIG. 3) in the power transmitting device 100 via a connector on the water.

[0019] The underwater vehicle 70 can travel underwater and freely move to a predetermined data acquisition point based on instructions from the ship 50. The instructions from the ship 50 may be transmitted by communication via each coil CL or by other communication methods.

[0020] The coils CL are arranged at equal intervals, for example. The distance between adjacent coils CL (coil interval) is, for example, 5 m. The coil interval is, for example, about half the diameter of the coil CL. Considering the attenuation of the magnetic field strength underwater (for example, under the sea), the transmission frequency is, for example, 40 kHz or less and preferably less than 10 kHz. In addition, when transmitting power at a transmission frequency of 10 kHz or more, it is necessary to perform a predetermined simulation based on the provisions of the Radio Law, and this work can be omitted when the frequency is less than 10 kHz. Note that the lower the transmission frequency, the longer the power transmission distance, the larger the coil CL, and the longer the coil interval. Note that the transmission frequency may be a frequency higher than 40 kHz, for example, when a communication signal is superimposed.

[0021] The transmission frequency is determined based on coil characteristics such as the inductance of the coil CL, the diameter of the coil CL, and the number of turns of the coil CL. The diameter of the coil CL is, for example, several meters to several tens of meters. The larger the diameter of the coil CL, that is, the larger the wire diameter of the coil CL, the smaller the electrical resistance in the coil CL and the smaller the power loss. The power transmitted through the coil CL is, for example, 50 W or more, and may be in the order of kW.

[0022] The power transmission device 100 may also include one or more bobbins bn around which the wire of the coil is wound. The material of the bobbins bn is a non-conductive or weakly magnetic material (e.g., resin such as polyvinyl chloride, acrylic, or polyester). The material of the bobbins bn may have dielectric properties. For example, if polyvinyl chloride is used as the material of the bobbins bn, it is inexpensive, easy to obtain, and easy to process. By making the bobbins bn non-conductive, the power transmission device 100 can suppress the magnetic field generated by the alternating current flowing through the coil CL from being absorbed by the bobbins bn. In FIG. 1, a power supply station including a bobbin bn10 floating in water and a power supply station including a bobbin bn11 arranged on the seabed are installed to perform underwater power supply (e.g., undersea power supply).

[0023] In the power supply station including the bobbin bn10, a power transmission coil CLA11 and a relay coil CLC11 are wound and arranged around the outer circumference of the cylindrical bobbin bn10. A power cable 280 is connected to the power transmission coil CLA11, and power is supplied from a ship 50 moored on the sea via the power cable 280. The power cable 280 supports this power supply station in a floating state in the sea. In the floating state, openings on both sides of the cylindrical bobbin bn10 may face horizontally. The underwater vehicle 70 may enter the entrance of the floating power supply station in the horizontal direction and receive power while remaining inside the bobbin bn10.

[0024] The power supply station including the bobbin bn11 is fixed to the top of two pillars 1101 embedded in the seabed 910. The entrance of this power supply station may face horizontally. In the power supply station, the power transmitting coil CLA12 is wound around the cylindrical bobbin bn11, but the relay coil CLC is not arranged. For example, a power cable 280A laid on the seabed 910 may be connected to the power transmitting coil CLA12, and power may be supplied from the power supply facility 1200 via the power cable 280A. The underwater vehicle 70 may enter the entrance of the power supply station installed on the seabed 910 in the horizontal direction and receive power while remaining inside the bobbin bn11.

[0025] Here, a magnetic body (see below) is provided so as to cover the entire outer periphery of the housing of the underwater vehicle 70 according to embodiment 1. This is for the purpose of reducing eddy current loss in the underwater vehicle 70 (in other words, the power receiving device 200) and increasing the efficiency of power transmission from the power transmitting device 100.

[0026] Next, the positional relationship between the underwater vehicle 70 and the magnetic body will be described with reference to Figures 2A to 2C. Figure 2A is a perspective view showing a typical example of the appearance of the underwater vehicle 70. Figure 2B is a diagram showing a cross section of the underwater vehicle 70 as viewed from the direction of the arrow FF in Figure 2A, and an enlarged portion of a portion thereof. Figure 2C is a diagram showing a cross section of the underwater vehicle 70 as viewed from the direction of the arrow GG in Figure 2A, and an enlarged portion of a portion thereof.

[0027] The underwater vehicle 70 has a structure including a core 850 which is a magnetic material having high magnetic permeability (i.e., a ferromagnetic material) and a power receiving coil CLB arranged to wind around the core 850. The core 850 may be composed of a housing of the underwater vehicle 70 (e.g., a weakly magnetic material 851 such as aluminum) and a magnetic material (e.g., ferrite 852) wound around the housing. The core 850 may be formed by attaching a magnetic material to the side surface of a cylindrical weakly magnetic material that imitates the housing of the underwater vehicle 70. The magnetic material may be formed in a cylindrical shape so as to fit along the side surface of the cylindrical weakly magnetic material, or may be formed in a sheet shape so as to be attached to the side surface of the weakly magnetic material. The magnetic material is not limited to being attached to the side surface of the cylindrical weakly magnetic material (e.g., the side surface of the housing of the underwater vehicle 70), but may also be attached to the front surface (e.g., the front surface of the housing of the underwater vehicle 70) and the back surface (e.g., the back surface of the housing of the underwater vehicle 70). For the cylindrical weak magnetic body, for example, aluminum is used, which is light, rust-resistant, and easy to cut. The weak magnetic body is not limited to aluminum, and may be stainless steel, titanium, resin, or the like. As an example of the magnetic material, in the first embodiment, ferrite 852 having a thickness of 2 mm is used. Since ferrite does not easily conduct electricity, it generates little heat even when a magnetic field is generated, does not rust, and is easy to handle. The magnetic material (ferromagnetic material) is not limited to ferrite, and silicon steel plate, permalloy, or the like may also be used. Ferromagnetic materials have a higher magnetic permeability than weak magnetic materials.

[0028] When the core 850 is provided inside the power receiving coil CLB, the magnetic field generated by the power transmitting coil CLA or the relay coil CLC is concentrated inside the ferrite 852 forming the core 850, and the generated magnetic field generates a magnetic flux inside the ferrite 852. As a result, in the underwater vehicle 70, many magnetic field lines are concentrated inside the power receiving coil CLB, suppressing a decrease in the efficiency of power transmission from the power transmitting device 100.

[0029] When the underwater vehicle 70 enters inside the relay coil CLC and reaches a position where the relay coil CLC and the power receiving coil CLB face each other on approximately the same plane, wireless power supply starts underwater. Note that the same applies when the underwater vehicle 70 enters inside the power transmitting coil CLA from the power transmitting coil CLA side instead of the relay coil CLC, and wireless power supply starts underwater when the power transmitting coil CLA and the power receiving coil CLB reach a position where they face each other on approximately the same plane.

[0030] The receiving coil CLB is formed by sealing, for example, 10 turns of electric wire 856 with a covering material 855. The covering material 855 may be any material having insulating properties, elasticity, and weather resistance, and rubber may be used here. The underwater vehicle 70 is integrated by mounting the formed receiving coil CLB on the outer periphery of the core 850. An adhesive may be applied to the contact surface between the outer periphery of the core 850 and the covering material 855 of the receiving coil CLB to prevent them from being separated. Note that the core 850 and the receiving coil CLB may be integrated by a method other than bonding with an adhesive.

[0031] 3 is a diagram showing an example of a hardware configuration of the underwater power supply system 1000 according to Embodiment 1. As described above, the underwater power supply system 1000 includes the power transmitting device 100, the power receiving device 200, and a plurality of coils CL.

[0032] The power transmitting device 100 includes an AC power source 110, an ADC (AC / DC converter) 120, a power transmitting processor 130, and a power transmitting circuit 150.

[0033] The ADC 120 converts AC power supplied from an AC power source 110, which is an example of a power source for power transmission, into DC power. The converted DC power is sent to the power transmission circuit 150.

[0034] The power transmitting processor 130 is configured using, for example, a CPU (Central Processing Unit), and controls the operations of the various components of the power transmitting device 100 (for example, the AC power supply 110, the ADC 120, and the power transmitting circuit 150).

[0035] The power transmitting circuit 150 includes a driver 151, a resonant circuit 152, and a matching circuit 153. The driver 151 converts the DC power from the ADC 120 into an AC voltage of a predetermined frequency (e.g., a pulse waveform). The resonant circuit 152 includes a capacitor CA and a power transmitting coil CLA, and generates an AC voltage of a sine wave waveform from the AC voltage of the pulse waveform from the driver 151. The power transmitting coil CLA resonates at a predetermined resonant frequency in response to the AC voltage applied from the driver 151. The power transmitting coil CLA is impedance-matched to the output impedance of the power transmitting device 100 by the matching circuit 153.

[0036] The frequency of the AC voltage obtained by the conversion by the driver 151 corresponds to the transmission frequency of the power transmission between the power transmitting device 100 and the power receiving device 200, and corresponds to the resonance frequency. The transmission frequency may be set based on the Q value of each coil CL, for example.

[0037] Although not shown in FIG. 3, the power transmitting device 100 may further include a communication device (not shown) for data communication. The communication device has, for example, a PLC adapter compatible with PLC (Power Line Communication) communication, and a modulation / demodulation circuit for modulating or demodulating communication data communicated with the power receiving device 200. The modulation / demodulation circuit may be provided in the PLC adapter. For example, the communication device transmits control information from the power transmitting device 100 to the power receiving device 200 via the PLC adapter (not shown) and the coil CL. For example, the communication device receives data from the power receiving device 200 to the power transmitting device 100 via the coil CL and the PLC adapter. This data includes, for example, data of the exploration results obtained by the underwater exploration or bottom exploration by the underwater vehicle 70. The communication device can quickly communicate data with the underwater vehicle 70 (in other words, the power receiving device 200) while the underwater vehicle 70 is performing operations such as data collection.

[0038] The power receiving device 200 includes a power receiving circuit 210 , a power supply circuit 220 , a power receiving side processor 230 , a power sensor 240 , and a current sensor 250 .

[0039] The power receiving circuit 210 includes a rectifier circuit 211, a resonant circuit 212, and a matching circuit 213. The rectifier circuit 211 converts AC power induced in the power receiving coil CLB into DC power. The resonant circuit 212 includes a capacitor CB and a power receiving coil CLB, and receives AC power transmitted from the power transmitting coil CLA. The power receiving coil CLB is impedance-matched to the input impedance of the power receiving device 200 by the matching circuit 213.

[0040] The power supply circuit 220 includes a DC / DC power supply circuit 221, a constant current circuit 222, and a secondary battery 223 as an example of a storage battery. The DC / DC power supply circuit 221 constitutes a power supply circuit using one or more general-purpose circuit components (e.g., a DC / DC converter) as a power supply for charging the secondary battery 223 in the underwater power supply system 1000, and supplies the DC power from the power receiving circuit 210 to the constant current circuit 222 by stepping up or stepping down the DC power based on a control signal from the power receiving side processor 230. The constant current circuit 222 supplies a constant charging current to the secondary battery 223 according to the type of the secondary battery 223 based on the power supply voltage supplied from the DC / DC power supply circuit 221, thereby controlling the charging or discharging of the secondary battery 223. The secondary battery 223 stores the power transmitted from the power transmitting device 100. The secondary battery 223 is, for example, a lithium ion battery.

[0041] The power receiving side processor 230 is configured using, for example, a CPU, and controls the operation of each part (for example, the power receiving circuit 210, the power supply circuit 220, the power sensor 240, and the current sensor 250) of the power receiving device 200. The power receiving side processor 230 executes periodic interrupt processing for periodically controlling the charging current from the constant current circuit 222 to the secondary battery 223 (see Figs. 5 to 8). The periodic interrupt processing is executed, for example, every 10 ms. The power receiving side processor 230 will be described in detail later with reference to Fig. 4.

[0042] The power sensor 240 detects the power corresponding to the power supply voltage supplied to the constant current circuit 222 of the power supply circuit 220 from the DC / DC power supply circuit 221 in synchronization with the timing of the above-mentioned periodic interrupt process, and sends it to the power receiving side processor 230.

[0043] The current sensor 250 detects the current (that is, the charging current) supplied to the secondary battery 223 by the constant current circuit 222 of the power supply circuit 220 in synchronization with the timing of the above-mentioned periodic interrupt process, and sends it to the power receiving side processor 230.

[0044] Although not shown in FIG. 3, the power receiving device 200 may further include a communication device (not shown) for data communication. This communication device has, for example, a PLC adapter compatible with PLC communication, and a modulation / demodulation circuit for modulating or demodulating communication data communicated with the power transmitting device 100. This modulation / demodulation circuit may be provided in the PLC adapter. For example, the communication device receives control information from the power transmitting device 100 to the power receiving device 200 via the coil CL and the PLC adapter. For example, the communication device transmits data from the power receiving device 200 to the power transmitting device 100 via the PLC adapter and the coil CL. This data includes, for example, data of the exploration results obtained by the underwater exploration or bottom exploration by the underwater vehicle 70. The communication device can quickly communicate data with the ship 50 (in other words, the power transmitting device 100) while the underwater vehicle 70 is performing operations such as data collection.

[0045] The relay coil CLC, like the power transmitting coil CLA and the power receiving coil CLB, configures a resonant circuit together with the capacitor CC. That is, in this embodiment, the resonant circuits are arranged in multiple stages underwater, and power is transmitted by the magnetic resonance method.

[0046] Here, power transmission from the power transmitting device 100 to the power receiving device 200 will be briefly described with reference to FIG.

[0047] In the resonant circuit 152 of the power transmitting device 100, when a current flows through the power transmitting coil CLA of the power transmitting device 100, a magnetic field is generated around the power transmitting coil CLA. The oscillation of the generated magnetic field is transmitted to a resonant circuit including the relay coil CLC that resonates at the same frequency as the resonant frequency in the resonant circuit 152.

[0048] In the resonant circuit including the relay coil CLC, a current is excited in the relay coil CLC due to the oscillation of the magnetic field, and a magnetic field is generated around the relay coil CLC. The oscillation of the generated magnetic field is transmitted to the resonant circuit including the other relay coil CLC that resonates at the same frequency as the resonant frequency in the resonant circuit 152, and to the resonant circuit 212 including the power receiving coil CLB.

[0049] In the resonant circuit 212 of the power receiving device 200, an AC current is induced in the power receiving coil CLB due to the oscillation of the magnetic field of the relay coil CLC. The induced AC current is rectified by the rectifier circuit 211 and converted to a predetermined voltage in the power supply circuit 220, and a charging current flows, thereby charging the secondary battery 223.

[0050] Next, a configuration example of the power receiving side processor 230 will be described with reference to Fig. 4. Fig. 4 is a block diagram showing a functional configuration example of the power receiving side processor 230. The power receiving side processor 230 includes a memory 231, a power comparison unit 232, AD conversion units 233 and 234, a control current value determination unit 235, a current control unit 236, and a current flag determination unit 237.

[0051] The memory 231 stores data or programs referenced during processing executed by the power receiving side processor 230, and temporarily stores data generated during processing executed by the power receiving side processor 230. The memory 231 stores, for example, a power value converted by the AD conversion unit 233.

[0052] The power comparison unit 232 compares the power value of the previous sample stored in the memory 231 (for example, the power value detected during the previous periodic interrupt process) with the current (latest) power value converted by the AD conversion unit 233. The power comparison unit 232 sends the comparison result and the current flag from the current flag determination unit 237 (i.e., the current flag determined during the previous periodic interrupt process, see below) to the control current value determination unit 235.

[0053] The AD conversion unit 233 converts the current power value detected by the power sensor 240 into a digital value at each periodic interrupt process, stores the digital power value in the memory 231 , and sends it to the power comparison unit 232 .

[0054] The AD conversion unit 234 converts the current value detected by the current sensor 250 into a digital value at each periodic interrupt process, and sends the digital current value to the control current value determination unit 235 .

[0055] Based on the output from the power comparison section 232 and the current current value converted by the AD conversion section 234, the control current value determination section 235 determines a constant charging current to be supplied from the constant current circuit 222 to the secondary battery 223 as a control current value, and sends the control current value to each of the current control section 236 and the current flag determination section 237. Details of the determination of the control current value will be described later with reference to FIG.

[0056] Based on the output from the control current value determination unit 235 (i.e., the control current value), the current control unit 236 generates a control signal for supplying a constant charging current from the constant current circuit 222 to the secondary battery 223, and sends the control signal to the constant current circuit 222 of the power supply circuit 220.

[0057] The current flag determination unit 237 determines a current flag (positive current flag) indicating that the control current value is to be increased compared to the current value of one sample before (i.e., the control current value determined at the time of the previous periodic interrupt process) based on the output (i.e., the control current value) from the control current value determination unit 235, or a current flag (negative current flag) indicating that the control current value is to be decreased compared to the current value of one sample before (i.e., the control current value determined at the time of the previous periodic interrupt process). The current flag determination unit 237 sends the current flag determination result to the power comparison unit 232.

[0058] Next, an example of an operation procedure of periodic power control in the power receiving device 200 according to the first embodiment will be described with reference to Figs. 5 to 8. Fig. 5 is a graph showing an example of characteristics indicating a transition of impedance with respect to a load current in the power receiving device. Fig. 6 is a graph showing an example of characteristics indicating a transition of a coil current with respect to an impedance in the power receiving device. Fig. 7 is a graph showing an example of characteristics indicating a transition of a load power with respect to a load current in the power receiving device. Fig. 8 is a flowchart showing an example of an operation procedure of power control in the power receiving device 200 according to the first embodiment. The process in Fig. 8 is executed mainly by the power receiving side processor 230 at a predetermined cycle (X milliseconds). X is, for example, 10.

[0059] When a configuration is adopted in which the outer periphery of the casing is covered with a magnetic body (see Figs. 2A to 2C) as in the underwater vehicle 70 according to the first embodiment, a characteristic PTY1 is obtained between the load current I of the power receiving device 200 and the impedance Z of the power receiving device 200 as shown in Fig. 5. In other words, when the load current I increases, the impedance Z decreases. The load current I is a current corresponding to the power supply voltage supplied from the DC / DC power supply circuit 221 to the constant current circuit 222. The impedance Z is the impedance of the power receiving circuit 210.

[0060] Furthermore, in the case of a configuration in which the outer periphery of the housing is covered with a magnetic body (see Figs. 2A to 2C) as in the underwater vehicle 70 according to the first embodiment, a characteristic PTY2 is obtained between the impedance Z (see above) of the power receiving device 200 and the coil current Ic of the power receiving device 200 as shown in Fig. 6. That is, when the load current I is increased and the impedance Z decreases, the coil current Ic (i.e., the current flowing through the power receiving coil CLB of the power receiving circuit 210) increases, and when the impedance Z becomes lower than a certain impedance Za, magnetic saturation occurs and the coil current Ic begins to decrease.

[0061] Therefore, in the case of a configuration in which the outer periphery of the housing is covered with a magnetic body (see Figs. 2A to 2C) as in the underwater vehicle 70 according to the first embodiment, a specific PTY3 is obtained in which the load power (in other words, the power supplied to the constant current circuit 222) is maximized immediately before or immediately after magnetic saturation (see above) occurs, as shown in Fig. 7. The power receiving device 200 according to the first embodiment uses this characteristic to monitor and control the load current I in the power receiving processor 230 so that the load power is maximized.

[0062] Specifically, when the load current I is less than Im (in other words, in region A where the load power increases as the load current I increases), the power receiving processor 230 controls the load current to gradually increase. Also, when the load current I is greater than or equal to Im (in other words, in region B where the load power decreases as the load current I increases), the power receiving processor 230 controls the load current to gradually decrease.

[0063] 8, the power receiving processor 230 acquires a current power value from the power sensor 240 (St1) and acquires a current current value from the current sensor 250 (St2). The power receiving processor 230 determines whether the current flag determined during the previous periodic interrupt process is positive or not based on the output from the current flag determination unit 237 (St3).

[0064] If the power receiving side processor 230 determines that the current flag is positive (St3, YES), this means that the control current value was increased during the previous periodic interrupt processing, so it considers the current state to be in area A and performs the processing of step St4.

[0065] That is, the power receiving processor 230 judges whether the current power value acquired in step St1 is greater than the power value of one sample before (St4). When the power receiving processor 230 judges that the current power value acquired in step St1 is greater than the power value of one sample before (St4, YES), it determines the current current value acquired in step St2 plus a predetermined value δ (for example, a very small value of about 10 mA) as the control current value (St5) and determines the current flag corresponding to the current periodic interrupt processing as a positive current flag (St6). This is because it is possible to judge from the judgment result of step St4 that the polarity of the current load power has not been inverted in the region A (in other words, the load power has not passed the maximum value) since the current flag was determined to be positive in the previous periodic interrupt processing.

[0066] On the other hand, when the power receiving processor 230 judges that the current power value acquired in step St1 is smaller than the power value of the previous sample (St4, NO), it determines the current current value acquired in step St2 minus a predetermined value δ (for example, a very small value of about 10 mA) as the control current value (St7), and determines the current flag corresponding to the current periodic interrupt processing as a negative current flag (St8). This is because it is possible to judge from the judgment result of step St4 that the polarity of the current load power has reversed in region A (in other words, the load power has passed the maximum value and started to decrease) since the current flag was determined to be positive in the previous periodic interrupt processing.

[0067] If the power receiving side processor 230 determines that the current flag is negative (St3, NO), this means that the control current value was reduced during the previous periodic interrupt processing, so it considers the current state to be in area B and performs the processing of step St9.

[0068] The power receiving processor 230 judges whether the current power value acquired in step St1 is greater than the power value of one sample before (St9). When the power receiving processor 230 judges that the current power value acquired in step St1 is greater than the power value of one sample before (St10, YES), it determines the current value acquired in step St2 minus a predetermined value δ (for example, a very small value of about 10 mA) as the control current value (St10) and determines the current flag corresponding to the current periodic interruption process as a negative current flag (St11). This is because it is possible to judge from the judgment result of step St9 that the polarity of the current load power has not been inverted in the region B (in other words, the load power has not passed the maximum value) since the current flag was determined to be negative in the previous periodic interruption process.

[0069] On the other hand, when the power receiving processor 230 judges that the current power value acquired in step St1 is smaller than the power value of the previous sample (St9, NO), it determines the current current value acquired in step St2 plus a predetermined value δ as the control current value (St12) and determines the current flag corresponding to the current periodic interruption process as a positive current flag (St13). This is because it is possible to judge from the judgment result of step St9 that the polarity of the current load power has reversed in region B (in other words, the load power has passed the maximum value and started to decrease) since the current flag was determined to be negative in the previous periodic interruption process.

[0070] As described above, in the underwater power supply system 1000 according to the first embodiment, the power receiving device 200 has a housing that is movable underwater and has an outer periphery surrounded by a magnetic body (for example, a core 850). The power receiving device 200 includes a power receiving unit (for example, a power receiving circuit 210) that receives power wirelessly transmitted from the power transmitting device 100, a power supply unit (for example, a power supply circuit) that has a storage battery (for example, a secondary battery 223) and charges the storage battery based on the power received by the power receiving unit, a power detection unit (for example, a power sensor 240) that repeatedly detects the power value during operation of the power supply unit, and a power receiving side processor 230 that determines a control current value for operating the power supply unit based on a comparison result between the power value detected by the power detection unit and the power value detected by the power detection unit last time, and controls the operation of the power supply unit based on the determined control current value.

[0071] As a result, even if the outer periphery of the housing of the underwater vehicle 70 on which the power receiving device 200 is mounted is surrounded by a magnetic material (e.g., ferrite 852), the power receiving device 200 can suppress the occurrence of magnetic saturation in the power receiving device 200 underwater, thereby improving the transmission efficiency of power from the power transmitting device 100.

[0072] In addition, the power detection unit periodically detects the power value of the power supply unit during operation. The power value previously detected by the power detection unit is the power value detected one cycle before the predetermined cycle (e.g., 10 milliseconds before). This allows the power receiving device 200 to periodically determine whether a constant charging current that should be supplied during charging by the power supply unit (e.g., the power supply circuit 220) is maximized.

[0073] The power receiving device 200 further includes a current detection unit (e.g., a current sensor 250) that repeatedly detects a current value during operation of the power supply unit. The power receiving side processor 230 increases or decreases the control current value based on the current value detected by the current detection unit. This allows the power receiving device 200 to adjust the value of the load current to a value around the load current when magnetic saturation occurs, and adaptively improves the efficiency of power transmission from the power transmitting device 100.

[0074] Furthermore, when the power receiving processor 230 increases the previous control current value and the power value detected by the power detection unit is greater than the previous detected power value, it increases the current value detected by the current detection unit by a predetermined amount δ. In this way, the power receiving device 200 can efficiently maximize the load power based on the magnitude relationship between the detected current power value and the power value detected during the previous periodic interrupt process, in consideration of the characteristics of the current load current and load power that the load power increases as the load current increases.

[0075] Furthermore, when the power receiving processor 230 increases the previous control current value and the power value detected by the power detection unit is smaller than the previous detected power value, it decreases the current value detected by the current detection unit by a predetermined amount δ. In this way, the power receiving device 200 can efficiently maximize the load power based on the magnitude relationship between the detected current power value and the power value detected during the previous periodic interrupt process, in consideration of the characteristics of the current load current and load power that the load power decreases as the load current increases.

[0076] Furthermore, when the power receiving processor 230 reduces the previous control current value and the power value detected by the power detection unit is greater than the previous detected power value, it reduces the current value detected by the current detection unit by a predetermined amount δ. In this way, the power receiving device 200 can efficiently maximize the load power based on the magnitude relationship between the detected current power value and the power value detected during the previous periodic interrupt process, in consideration of the characteristics of the current load current and load power that the load power decreases as the load current increases.

[0077] Furthermore, when the power receiving processor 230 reduces the previous control current value and the power value detected by the power detection unit is smaller than the previous detected power value, it increases the current value detected by the current detection unit by a predetermined amount δ. In this way, the power receiving device 200 can efficiently maximize the load power based on the magnitude relationship between the detected current power value and the power value detected during the previous periodic interrupt process, in consideration of the characteristics of the current load current and load power that the load power decreases as the load current increases.

[0078] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, corrections, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure. In addition, the components in the various embodiments described above may be arbitrarily combined within the scope of the invention.

[0079] In the above-described embodiment, the power receiving device 200 may be a generator or the like installed on the seabed. In this case, the power receiving device 200 is fixedly installed underwater. In this way, even if the structure is fixedly installed on the seabed and it is difficult to move the structure for charging, the power transmitting device 100 can approach the power receiving device 200 to improve the efficiency of power transmission underwater and charge the device.

[0080] In the above-described embodiment, the power transmitting coil CLA and the multiple relay coils CLC are arranged transversely (horizontally) in seawater, but they may be arranged vertically (vertically). In the vertical orientation, the planes of the power transmitting coil CLA and the relay coil CLC are substantially parallel to the water surface. In the vertical orientation, the power receiving coil CLB mounted on the AUV 800 may also be mounted vertically so as to be aligned with the magnetic field direction. In other words, the plane of the power receiving coil CLB may be substantially parallel to the water surface. In the case of a power transmitting coil structure in which the power transmitting coil CLA and the relay coil CLC are connected via a connector, even if the power transmitting coil structure is arranged vertically, the underwater vehicle 70 may be able to enter and exit the power transmitting coil horizontally. On the other hand, in the case of a transmission coil in which the transmission coil CLA and the relay coil CLC are wound around a bobbin bn, if the transmission coil is arranged vertically, the underwater vehicle 70 may enter the inside of the transmission coil through openings of the bobbin bn located at the upper and lower ends of the bobbin bn. [Industrial Applicability]

[0081] The present disclosure is useful as a power receiving device and a power control method that suppresses the occurrence of magnetic saturation in a power receiving device underwater and improves the efficiency of power transmission from a power transmitting device, even when the outer periphery of the housing is surrounded by a magnetic material. [Explanation of symbols]

[0082] 50 ships 70 Underwater vehicle 100 Power transmission equipment 110 AC power supply 120 ADC 130 Power transmission processor 150 Power transmission circuit 151 Drivers 152, 212 resonant circuit 153, 213 matching circuit 200 Powered Device 210 Receiving circuit 211 Rectifier circuit 220 Power supply circuit 221 DC / DC power supply circuit 222 Constant current circuit 223 Secondary battery 230 Receiving Processor 231 Memory 232 Power comparison section 233, 234 AD conversion section 235 Control current value determination unit 236 Current control section 237 Current flag determination unit 240 Power Sensor 250 Current Sensor 850 cores 1000 Underwater Power Supply System CLA Transmitting Coil CLB Receiving coil

Claims

1. A power receiving device that is movable underwater and has a housing whose outer periphery is surrounded by a magnetic material, a power receiving unit that receives power wirelessly transmitted from a power transmitting device; a power supply unit including a storage battery and configured to charge the storage battery based on the power received by the power receiving unit; a power detection unit that repeatedly detects a power value during operation of the power supply unit; a current detection unit that repeatedly detects a current value during operation of the power supply unit; a power receiving side processor that determines a control current value for operating the power supply unit based on a comparison result between a power value detected by the power detection unit and a power value previously detected by the power detection unit, and controls the operation of the power supply unit based on the determined control current value; the power receiving processor determines the control current value based on the current value detected by the current detection unit in accordance with either a case where the power value increases when the control current value is increased or a case where the power value decreases when the control current value is increased. Powered device.

2. the power detection unit periodically detects a power value of the power supply unit during operation, The power value previously detected by the power detection unit is a power value detected one cycle prior to the predetermined cycle. The power receiving device according to claim 1 .

3. when the power value increases when the control current value is increased and the power value detected by the power detection unit is greater than a previously detected power value, the power receiving processor increases the current value detected by the current detection unit by a predetermined amount. The power receiving device according to claim 1 .

4. when the power value increases when the control current value is increased, and when the power value detected by the power detection unit is smaller than the previously detected power value, the power receiving processor reduces the current value detected by the current detection unit by a predetermined amount. The power receiving device according to claim 1 .

5. when the power value decreases when the control current value is increased, and when the power value detected by the power detection unit is greater than a previously detected power value, the power receiving processor reduces the current value detected by the current detection unit by a predetermined amount. The power receiving device according to claim 1 .

6. when the power value decreases when the control current value is increased, and when the power value detected by the power detection unit is smaller than the previously detected power value, the power receiving processor increases the current value detected by the current detection unit by a predetermined amount. The power receiving device according to claim 1 .

7. A power control method performed by a power receiving device having a housing capable of moving underwater and having an outer periphery surrounded by a magnetic material, comprising: Receives power wirelessly transmitted from a power transmitting device; charging the storage battery based on the power received by a power supply unit having the storage battery; Repeatedly detecting a power value during operation of the power supply unit; Repeatedly detecting a current value during operation of the power supply unit; determining a control current value for operating the power supply unit based on a comparison result between the detected power value and a previously detected power value; Controlling the operation of the power supply unit based on the determined control current value; the control current value is determined based on the detected current value in response to either a case where an increase in the control current value results in an increase in the power value or a case where an increase in the control current value results in a decrease in the power value. Power control methods.

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