High-power-density human body motion energy collector based on internal eccentric magnetic rotor

Abstract

The invention discloses a high-power-density human body motion energy collector based on an internal eccentric magnetic rotor, and belongs to the technical field of human body energy collection and microminiature power generation. The collector comprises a top coil layer, an eccentric magnetic rotor and a bottom coil layer; the top coil layer is connected with the top circuit board and installed on the lower surface of the top circuit board, and the bottom coil layer is connected with the bottom circuit board and installed on the upper surface of the bottom circuit board. The eccentric magnetic rotor is located between the top coil layer and the bottom coil layer, an eccentric structure is formed by the non-magnetic clamping piece and the soft magnetic clamping piece, when the eccentric magnetic rotor swings or rotates, the magnetic flux in the top coil layer and the bottom coil layer can be changed, and therefore the top coil layer and the bottom coil layer can generate current. And the current is transmitted to an external load by the top circuit board and the bottom circuit board. By increasing the space ratio of the transduction parts and increasing the magnetic flux through the soft magnetic clamping pieces, electromagnetic coupling between the transduction parts is enhanced, and therefore the output power density is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of human energy harvesting and micro-scale power generation, and particularly relates to a high power density human motion energy harvester based on an internally structured eccentric magnetic rotor. Background Art

[0002] As an important branch of the Internet of Things, the human body sensor network enhances the connection between people and information by connecting various wearable nodes, including miniaturized sensors, actuators, and micro intelligent terminals. Currently, these nodes mainly rely on traditional batteries for power supply. However, due to the limited battery life, they need to be repeatedly charged and replaced, which cannot guarantee long-term and continuous services, thus affecting people's quality of life. Especially for engineers, rescuers, and scientific researchers in off-grid environments, the interruption of body-borne information services caused by insufficient power will result in the suspension of operations, the loss of environmental perception ability, and even endanger life and health. Therefore, the research and development of energy harvesters that can effectively capture sustainable energy to replace traditional batteries has become an important research field. The moving human body, especially the arms or legs with relatively significant swinging amplitudes, has abundant exploitable mechanical energy, providing a readily available energy source for solving the above sustainable power supply problem. However, the movements of the human limbs have characteristics of ultra-low frequency (less than 5 Hz), multi-directional, and randomly variable, which requires that the human motion energy harvester not only meet the portability requirements but also adapt to these limb dynamic characteristics to achieve efficient mechanical energy capture and electromechanical energy conversion to ensure sufficient power supply.

[0003] The electromagnetic human motion energy harvester based on the Faraday electromagnetic induction principle uses a movable vibration pickup component to capture the mechanical energy of the human body and convert it into kinetic energy inside the device; then, the relative motion between the electromechanical energy conversion components, usually the motion between a permanent magnet and an induction coil, is used to further convert the kinetic energy into electrical energy output. Among various reported vibration pickup structures, the eccentric rotor structure shows excellent adaptability to the above human motion dynamic characteristics due to its multi-directional effectiveness and easier realization of ultra-low effective working frequency.

[0004] A typical human motion energy harvester based on an eccentric rotor is described in the article "Ultra-low frequency eccentric pendulum-based electromagnetic vibrational energy harvester" by Mingxue Li, Huichao Deng, Yufeng Zhang, Kexin Li, Shijie Huang, and Xiaowei Liu in *Micromachines* 11(2020):1009. The eccentric magnetic rotor designed in this article consists of six energy-converting permanent magnets that occupy half of the circumferential motion trajectory of the rotor. An induction coil that covers the entire circumference of the rotor's motion trajectory generates electrical energy output when it moves relative to the magnetic rotor. The main drawback of this energy harvester is that since the energy-converting permanent magnets only cover half of the induction coils, the magnetic flux change occurs only in half of the induction coils, resulting in low utilization rate of the internal space of the device and weak electrical energy output.

[0005] A typical human motion energy harvester based on an eccentric rotor is described in the article "Ultralow-frequency biomechanical energy scavenging and human activity recognition at different positions using a multifunctional wearable energy harvester" by Shuyu Fan, Mengyao Fu, Yushan Zhou, Dibo Hou, Guangxin Zhang, and Yunqi Cao in *IEEE Transactions on Instrumentation and Measurement* 73(2024):9510914. The eccentric magnetic rotor designed in this article consists of six energy-converting permanent magnets that occupy the entire circumferential motion trajectory of the rotor and an eccentric mass block adsorbed on the outside of one of the permanent magnets. When excited to rotate, the magnetic flux change occurs in all the induction coils that cover the entire circumference of its motion trajectory, and electrical energy output can be generated simultaneously. The main drawback of this energy harvester is that due to the presence of the eccentric mass block, the deployment space of the energy-converting permanent magnets in the radial direction of the magnetic rotor is limited, resulting in a limited effective magnetic flux change region and a low output power density of the device.

[0006] In the above-mentioned human motion energy harvester based on an eccentric rotor, the non-uniform distribution of the transducer permanent magnets used to form the eccentric structure, the external eccentric mass block on the rotor, etc. bring problems of low space occupancy of different forms of transducer components, limit the size of the area with effective magnetic flux change, result in weak electromagnetic coupling between transducer components, thus reducing the transducer efficiency and output power density of the human motion energy harvester, and being unfavorable for efficiently harvesting mechanical energy from the motion of the human arm or leg. Summary of the Invention

[0007] In view of the above problems, the present invention provides a high-power-density human motion energy harvester based on an internally structured eccentric magnetic rotor. By constructing an eccentric structure inside the magnetic rotor, the deployable space of the transducer permanent magnets in the radial direction of the magnetic rotor is increased under the condition of a given device volume, thereby increasing the space occupancy of the transducer components inside the device. Moreover, the soft magnetic clamping pieces used to construct the eccentric structure further exacerbate the change in the effective magnetic flux in the induction coil and enhance the electromagnetic coupling of the transducer components, thus improving the transducer efficiency and output power density of the human motion energy harvester.

[0008] The present invention is implemented by adopting the following technical solutions:

[0009] In a first aspect, the present invention discloses a high-power-density human motion energy harvester based on an internally structured eccentric magnetic rotor, including a top circuit board, a top coil layer, an eccentric magnetic rotor, a bottom coil layer, and a bottom circuit board; the top coil layer is electrically connected to the top circuit board and installed on the lower surface of the top circuit board, the bottom coil layer is electrically connected to the bottom circuit board and installed on the upper surface of the bottom circuit board; the eccentric magnetic rotor is disposed between the top coil layer and the bottom coil layer, and the eccentric magnetic rotor has an eccentric structure. When the eccentric magnetic rotor swings or rotates, it will cause a change in the magnetic flux between the top coil layer and the bottom coil layer, so that currents will be generated in the top coil layer and the bottom coil layer, and the currents will be transmitted to an external load through the top circuit board and the bottom circuit board respectively.

[0010] Further, the eccentric magnetic rotor includes a first semi-circular structure formed by sequentially connecting three first magnetic structures through magnetic attraction and a second semi-circular structure formed by sequentially connecting three second magnetic structures through magnetic attraction. The first semi-circular structure and the second semi-circular structure are spliced through magnetic attraction to form an eccentric magnetic rotor in a ring structure. The first magnetic structure is formed by clamping a soft magnetic clip between two cylindrical permanent magnets. The second magnetic structure is formed by clamping a non-magnetic clip between two cylindrical permanent magnets. The magnetization direction of the cylindrical permanent magnet is along its thickness direction. The magnetization directions of the two cylindrical permanent magnets in the first magnetic structure are the same. The magnetization directions of the two cylindrical permanent magnets in the second magnetic structure are the same. The magnetization directions of the cylindrical permanent magnets of adjacent two first magnetic structures or second magnetic structures are opposite, and the magnetization directions of the cylindrical permanent magnets of the adjacent first magnetic structure and second magnetic structure are also opposite. The soft magnetic clip is made of soft magnetic material, and the non-magnetic clip is made of light non-magnetic material, forming a mass difference with the soft magnetic clip to constitute the structural eccentricity effect of the eccentric magnetic rotor.

[0011] Further, the distance between the top coil layer and the eccentric magnetic rotor is equal to the distance between the top coil layer and the eccentric magnetic rotor. The top coil layer includes six top induction coils, which are evenly arranged around the center of the top circuit board, and adjacent two top induction coils are wound in opposite directions. In the static state, each top induction coil is in the same axial direction as a first magnetic structure or a second magnetic structure. The bottom coil layer includes six bottom induction coils, which are evenly arranged around the center of the bottom circuit board, and adjacent two bottom induction coils are wound in opposite directions. In the static state, each bottom induction coil is in the same axial direction as a first magnetic structure or a second magnetic structure. The top induction coils and the bottom induction coils are both cylindrical, and have the same thickness and hollow inner diameter. The top induction coils and the bottom induction coils have the same outer diameter as the cylindrical permanent magnets.

[0012] Further, the energy harvester further includes a ball bearing and a central shaft rod. The ball bearing is fixedly installed on the central shaft rod and is embedded in the center of the eccentric magnetic rotor, and is mutually fixed with the first magnetic structure and the second magnetic structure through magnetic attraction. The ball bearing can swing or rotate around the central shaft rod, so that the eccentric magnetic rotor can swing or rotate around the central shaft rod. The central shaft rod is located at the central position of the energy harvester and is connected to the top circuit board and the bottom circuit board to serve as a fixed bracket of the energy harvester to form a fixed frame. The material for preparing the central shaft rod is non-magnetic material.

[0013] In a second aspect, the present invention discloses a method for harvesting human motion energy using the energy harvester, comprising: wearing the energy harvester on the limbs of a human body by attaching the top circuit board or the bottom circuit board to the limbs of the human body; when the limbs of the human body move, driving the energy harvester to perform a reciprocating motion, causing the eccentric magnetic rotor in the energy harvester to swing or rotate under the action of inertia, and the swing or rotation of the eccentric magnetic rotor causes a change in the magnetic field distribution, resulting in a change in the magnetic flux in the top coil layer and the bottom coil layer, thereby generating a current in the top coil layer and the bottom coil layer, and the generated current is transmitted to an external load through the top circuit board and the bottom circuit board respectively.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] 1) By simply combining heterogeneous materials, an eccentric structure is formed inside the magnetic rotor to form an eccentric magnetic rotor in the present invention, without adding an additional eccentric mass block outside the magnetic rotor, increasing the deployable space of the energy conversion permanent magnet in the radial direction of the eccentric magnetic rotor under the condition of a given device volume, enhancing the electromagnetic coupling between the energy conversion components, and thus improving the output power density of the present invention;

[0016] 2) The soft magnetic clamping pieces adopted in the present invention enhance the magnetic flux and the effective magnetic flux change in the induction coils on both sides of the eccentric magnetic rotor, further enhancing the electromagnetic coupling, and thus improving the energy conversion efficiency of the present invention;

[0017] 3) The eccentric magnetic rotor provided by the present invention essentially changes the implementation manner of the eccentric vibration pickup structure of the human motion energy harvester, has broad guiding significance for improving the power density of the human motion energy harvester based on the eccentric magnetic rotor, and can also be combined with different improvement methods for the energy harvester based on the eccentric rotor (such as the frequency up-conversion mechanism, the unidirectional rotation modulation mechanism, etc.) to further enhance the adaptability of the energy harvester to different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic exploded view of the structure of the energy harvester of the present invention;

[0019] Figure 2 is a schematic structural view of the eccentric magnetic rotor;

[0020] Figure 3 is a schematic structural view of the top surface and the bottom surface of the top circuit board;

[0021] Figure 4 is a schematic structural view of the top surface and the bottom surface of the bottom circuit board;

[0022] Figure 5 is an effect diagram of the cross-sectional magnetic flux density distribution obtained by finite element simulation of two cylindrical permanent magnets clamped with soft magnetic clamping pieces;

[0023] Figure 6 It is the profile flux density distribution effect diagram of two cylindrical permanent magnets sandwiching a non-magnetic clip obtained by finite element simulation;

[0024] Figure 7 It is the result diagram of the spatial change rate of the effective magnetic flux at different axial distances of the eccentric magnetic rotor calculated from the finite element simulation results;

[0025] Figure 8 It is the test result diagram of the energy harvester of the present invention.

[0026] In the figure: 1. Top circuit board; 2. Top coil layer; 3. Eccentric magnetic rotor; 4. Ball bearing; 5. Central shaft rod; 6. Bottom coil layer; 7. Bottom circuit board; 8. First support column; 9. Second support column; 10. Interlayer lead; 11. First external lead; 12. Second external lead. Detailed implementation manners

[0027] The following further elaborates in detail on the specific implementation manners, structural features and their effects of the present invention in combination with the drawings and embodiments:

[0028] For the sake of convenience of description, spatial relative terms such as "bottom", "top", "top surface", "bottom surface", etc. can be used here to describe the spatial position relationship between a device or feature and other devices or features as shown in the figure. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the figure. For example, if the device in the drawing is inverted, the device or feature described as "bottom" or "top" will be positioned as "top" or "bottom" afterwards. Thus, the exemplary term "top" can include both "top" and "bottom" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding explanations are made for the spatial relative descriptions used here.

[0029] In the drawings, for the sake of convenience of illustration, the dimensions of some components have been slightly exaggerated. Therefore, the drawings are only examples and are not drawn strictly to scale.

[0030] As Figures 1 to 4 shown, the high-power density human motion energy harvester based on an internally structured eccentric magnetic rotor of the present invention at least includes a top circuit board 1, a top coil layer 2, an eccentric magnetic rotor 3, a ball bearing 4, a central shaft rod 5, a bottom coil layer 6, a bottom circuit board 7, a first support column 8, a second support column 9, an interlayer lead 10, a first external lead 11 and a second external lead 12.

[0031] The top circuit board 1 is circular. There is a circular first through hole 1-1 coaxial with the central shaft rod 5 at the center of the top circuit board 1. The outer edge of the top circuit board 1 includes a top first semi-circular groove 1-2 and a top second semi-circular groove 1-3. The top first semi-circular groove 1-2 and the top second semi-circular groove 1-3 are symmetrically distributed about the center of the top circuit board 1. The top coil layer 2 is fixedly bonded to the lower surface of the top circuit board 1. The top coil layer 2 includes six sets of cylindrical top induction coils connected in series in sequence. The six sets of cylindrical top induction coils are evenly arranged around the center of the top circuit board 1.

[0032] The bottom circuit board 7 is circular. There is a circular second through hole 7-1 coaxial with the central shaft rod 5 at the center of the bottom circuit board 7. The outer edge of the bottom circuit board 7 includes a bottom first semi-circular groove 7-2 and a bottom second semi-circular groove 7-3. The bottom first semi-circular groove 7-2 and the bottom second semi-circular groove 7-3 are symmetrically distributed about the center of the bottom circuit board 7 and are respectively aligned with the top first semi-circular groove 1-2 and the top second semi-circular groove 1-3 one by one. The bottom coil layer 6 is fixedly bonded to the upper surface of the bottom circuit board 7. It includes six sets of cylindrical bottom induction coils connected in series in sequence. The six sets of cylindrical bottom induction coils are evenly arranged around the center of the bottom circuit board 7 and are aligned with the cylindrical top induction coils of the top coil layer 2 one by one.

[0033] The central shaft rod 5 is cylindrical and is fixedly connected to the first through hole 1-1, the inner ring of the ball bearing 4, and the second through hole 7-1 in sequence to form a fixed frame of the high-power density human motion energy collector. The central shaft rod 5 remains relatively stationary with respect to the top coil layer 2, the ball bearing 4, and the bottom coil layer 6.

[0034] The first support column 8 is cylindrical and is fixedly connected to the top first semi-circular groove 1-2 and the bottom first semi-circular groove 7-2 in sequence. The second support column 9 is cylindrical and is fixedly connected to the top second semi-circular groove 1-3 and the bottom second semi-circular groove 7-3 in sequence.

[0035] The eccentric magnetic rotor 3 includes twelve cylindrical permanent magnets 3-1, three soft magnetic clips 3-2, and three non-magnetic clips 3-3. The soft magnetic clips 3-2 and the non-magnetic clips 3-3 are respectively clamped between every two cylindrical permanent magnets 3-1. The two types of clips with the same size but different materials form an asymmetric mass distribution inside the magnetic rotor, thus forming an internal eccentric structure. The eccentric magnetic rotor 3 is fixed to the outer ring of the ball bearing 4 by magnetic attraction and can swing or rotate around the central shaft rod 5. The eccentric magnetic rotor 3 is coaxially arranged with the top coil layer 2 and the bottom coil layer 6.

[0036] The interlayer lead 10 is electrically connected to the top coil layer 2 and the bottom coil layer 6 through the top circuit board 1 and the bottom circuit board 7 respectively, and the cylindrical top induction coil and the cylindrical bottom induction coil on both sides of the series eccentric magnetic rotor 3 are connected in series.

[0037] The first external lead 11 is electrically connected to the top coil layer 2 through the top circuit board 1, and the second external lead 12 is electrically connected to the bottom coil layer 6 through the bottom circuit board 7. The first external lead 11 and the second external lead 12 are respectively used as two voltage output electrodes of the present invention. When the human limb movement excitation is applied to the energy harvester of the present invention, the eccentric magnetic rotor 3 swings or rotates around the central shaft rod 5 by inertia, and significant magnetic flux changes are simultaneously generated in the top induction coil and the bottom induction coil on both sides of the eccentric magnetic rotor 3, and then an induced voltage is generated based on the electromagnetic induction principle, and electrical energy is output from the first external lead 11 and the second external lead 12.

[0038] As Figure 2 shown, the cylindrical permanent magnet 3-1 is a neodymium iron boron permanent magnet. Preferably, the grade of the neodymium iron boron permanent magnet is N52 neodymium iron boron permanent magnet, the diameter is 11 mm, and the thickness is 1.6 mm; the magnetization direction of the cylindrical permanent magnet 3-1 is along its thickness direction, and the magnetization directions of the cylindrical permanent magnets 3-1 on both sides of the same soft magnetic clip 3-2 (or non-magnetic clip 3-3) are the same, and the magnetization directions of adjacent two cylindrical permanent magnets 3-1 are opposite, so as to generate a magnetic flux distribution with alternating polarities on both sides of the eccentric magnetic rotor 3; at the same time, the magnetic attraction is used to prevent the separation between the components of the eccentric magnetic rotor 3 itself and between the eccentric magnetic rotor 3 and the outer ring of the ball bearing 4, ensuring the reliability of the structure of the present invention.

[0039] The soft magnetic clip 3-2 has the same diameter as the cylindrical permanent magnet 3-1 and a thickness twice that of the cylindrical permanent magnet 3-1. The soft magnetic clip 3-2 can be integrally formed by numerical control machining, wire cutting, powder metallurgy or 3D printing methods, with a diameter of 11 mm and a thickness of 3.2 mm; the preparation material of the soft magnetic clip 3-2 is a soft magnetic material, preferably pure iron for electrical engineering (DT4C) with a relatively high relative magnetic permeability (about 12000), so as to extrapolate the magnetic field generated by the cylindrical permanent magnets 3-1 on both sides and further increase the magnetic flux on both sides of the eccentric magnetic rotor 3.

[0040] The non-magnetic clip 3-3 has the same diameter as the cylindrical permanent magnet 3-1 and a thickness twice that of the cylindrical permanent magnet 3-1. The non-magnetic clip 3-3 can be integrally formed by numerical control machining or 3D printing methods, with a diameter of 11 mm and a thickness of 3.2 mm; the preparation material of the non-magnetic clip 3-3 is a light non-magnetic material, preferably polymethyl methacrylate (acrylic) material, which forms a significant mass difference with the soft magnetic clips 3-2-1, 3-2-2, 3-2-3 to enhance the structural eccentricity effect of the eccentric magnetic rotor 3.

[0041] As shown Figure 1 in FIG., the outer ring of the ball bearing 4 has the same diameter as the cylindrical permanent magnet 3-1, and is tightly fitted into the center of the twelve cylindrical permanent magnets 3-1 with clips, that is, tightly fitted into the center of the eccentric magnetic rotor 3. In a specific embodiment of the present invention, the outer diameter of the outer ring of the ball bearing 4 is 11 mm, the inner diameter is 5 mm, and the thickness is 5 mm, so as to be tightly fitted into the center of the twelve cylindrical permanent magnets 3-1 with clips. The material of the ball bearing 4 is bearing steel, and the outer ring of the ball bearing 4 is fixed to the eccentric magnetic rotor 3 by magnetic attraction force, ensuring the reliability of the structure of the present invention during the movement process.

[0042] As shown Figure 1 in FIG., the thickness of the induction coils of the top coil layer 2 and the bottom coil layer 6 is 5 mm each, and they have the same outer diameter as the cylindrical permanent magnet 3-1, which is 11 mm. The hollow inner diameter of the induction coils of the top coil layer 2 and the bottom coil layer 6 is 3 mm, and they are tightly wound with self-adhesive enameled wire with a wire diameter of 0.2 mm. Six groups of top induction coils and six groups of bottom induction coils are respectively arranged at the position 0.5 mm on both sides of the eccentric magnetic rotor 3. In the static state without external excitation, they are coaxially aligned with every two cylindrical permanent magnets 3-1 with clips one by one, and the adjacent induction coils in the same layer are wound in the opposite direction to make full use of the changing magnetic flux generated when the eccentric magnetic rotor 3 rotates, and superimpose the induced voltages generated by each group of induction coils.

[0043] As shown Figure 3 in FIG., the top surface (i.e., the upper surface) of the top circuit board 1 is provided with a first pad 1-4 and a second pad 1-5; the bottom surface (i.e., the lower surface) of the top circuit board 1 is provided with twelve pads, and every two pads are connected to form a pad group. One end of a top induction coil is connected to one pad in a pad group, and the other end of this top induction coil is connected to one pad in the adjacent pad group. Finally, the six top induction coils are connected through six pad groups to superimpose the induced voltages generated by each top induction coil.

[0044] As shown Figure 4 in FIG., the bottom surface of the bottom circuit board 7 includes a third pad 7-4 and a fourth pad 7-5; the top surface of the bottom circuit board 7 includes twelve pads, and every two pads are connected to form a pad group. One end of a bottom induction coil is connected to one pad in a pad group, and the other end of this bottom induction coil is connected to one pad in the adjacent pad group. Finally, the six bottom induction coils are connected through six pad groups to superimpose the induced voltages generated by each bottom induction coil.

[0045] As shown Figure 1 , Figure 3 and Figure 4As shown, the interlayer leads 10 are respectively welded to the first pad 1-4 and the third pad 7-4. The interlayer leads 10 are electrically connected to the top coil layer 2 and the bottom coil layer 6 through the top circuit board 1 and the bottom circuit board 7 respectively. The interlayer leads 10 are used to connect the induction coils on both sides of the eccentric magnetic rotor 3 in series and superimpose the induced voltages generated by the induction coils on both sides.

[0046] As Figure 1 , Figure 3 and Figure 4 shown, the first external lead 11 is welded to the second pad 1-5. The first external lead 11 is electrically connected to the top coil layer 2 through the top circuit board 1. The second external lead 12 is welded to the fourth pad 7-5. The second external lead 12 is electrically connected to the bottom coil layer 6 through the bottom circuit board 7.

[0047] As Figure 1 and Figure 3 shown, preferably, considering that the top circuit board 1 serving as the fixed frame of the present invention needs to have good portability and strength, FR-4 board is selected, with a diameter of 40 mm and a thickness of 1.2 mm. The diameter of the first through hole 1-1 at the center of the top circuit board 1 is 5 mm.

[0048] As Figure 1 and Figure 4 shown, preferably, considering that the bottom circuit board 7 serving as the fixed frame of the present invention needs to have good portability and strength, FR-4 board is selected, with a diameter of 40 mm and a thickness of 1.2 mm. The diameter of the second through hole 7-1 at the center of the bottom circuit board 7 is 5 mm.

[0049] As Figure 1 and Figure 3 shown, the positions of the top first semi-circular groove 1-2 and the top second semi-circular groove 1-3 do not overlap with the movement track of the eccentric magnetic rotor 3, and the radius of both is 1 mm. Similarly, as Figure 1 and Figure 4 shown, the positions of the bottom first semi-circular groove 7-2 and the bottom second semi-circular groove 7-3 respectively aligned with the top first semi-circular groove 1-2 and the top second semi-circular groove (1-3) do not overlap with the movement track of the eccentric magnetic rotor 3, and the radius of both is 1 mm, so as to avoid the magnetic rotor colliding with the first support column 8 and the second support column 9 during the movement process.

[0050] As Figure 1As shown, the materials forming the central shaft rod 5, the first support column 8, and the second support column 9 are all non-magnetic materials, preferably lightweight acrylic materials, to avoid magnetic field interference with the eccentric magnetic rotor 3 and to take into account the portability of the present invention. The central shaft rod 5 has a diameter of 5 mm and a length of 19.8 mm, and is fixedly connected to the inner ring of the ball bearing 4 by an interference fit, and is fixedly connected to the first through hole 1-1 and the second through hole 7-1 by an adhesive; the first support column 8 and the second support column 9 both have a diameter of 2 mm and a length of 19.8 mm, and are respectively fixedly connected to the top first semi-circular groove 1-2 and the bottom first semi-circular groove 7-2, the top second semi-circular groove 1-3 and the bottom second semi-circular groove 7-3 by an adhesive, playing an auxiliary supporting role for the fixed frame of the present invention.

[0051] As Figure 1 and Figure 4 shown, the bottom circuit board 7 includes a first ear-shaped outer edge 7-6, a second ear-shaped outer edge 7-7, a first small through hole 7-8, and a second small through hole 7-9. Preferably, the first ear-shaped outer edge 7-6 and the second ear-shaped outer edge 7-7 are arc-shaped, located on the outer edge of the bottom circuit board 7, spaced 30° from the bottom first semi-circular groove 7-2 and the bottom second semi-circular groove 7-3 respectively and symmetrically, with a diameter of 5 mm. The first small through hole 7-8 and the second small through hole 7-9 are both circular, and are coaxial with the first ear-shaped outer edge 7-6 and the second ear-shaped outer edge 7-7 respectively, with a diameter of 2 mm, facilitating the present invention to be worn on the limbs of the human body with a thin wristband.

[0052] The soft magnetic clip 3-2 and the non-magnetic clip 3-3 of the present invention are respectively clamped between the cylindrical permanent magnets 3-1. Since the two clips have the same size but different materials, an asymmetric mass distribution is formed inside the eccentric magnetic rotor 3, thus forming an internal eccentric structure, replacing the traditional way of forming an eccentric rotor by adding an additional mass block outside the magnetic rotor, and further increasing the deployable space of the cylindrical permanent magnet 3-1 for energy conversion in the radial direction of the eccentric magnetic rotor 3 under the condition of a given device volume, increasing the space occupation ratio of the energy conversion components inside the device, enhancing the electromagnetic coupling between the energy conversion components, and improving the output power density. The soft magnetic clip 3-2 enhances the magnetic flux generated by the cylindrical permanent magnet 3-1 in the induction coils on both sides of the eccentric magnetic rotor 3, further enhancing the electromagnetic coupling and improving the energy conversion efficiency. When a human limb movement excitation is applied, the eccentric magnetic rotor 3 swings or rotates around the central shaft rod 5 by inertia, and significant magnetic flux changes are simultaneously generated in the induction coils on both sides of it, and then an induced voltage is generated based on the electromagnetic induction principle, and the electric energy is output from the first external lead 11 and the second external lead 12, completing the efficient collection of human motion energy.

[0053] In a specific embodiment of the present invention, the present invention further provides an efficient human motion energy harvesting method using the energy harvester, including: wearing the energy harvester on the human limbs in such a way that the bottom circuit board 7 is attached to the human limbs. When the human limbs move, it drives the energy harvester to perform reciprocating motion, causing the eccentric magnetic rotor 3 in the energy harvester to swing or rotate under the action of inertia. The swing or rotation of the eccentric magnetic rotor 3 causes the magnetic field distribution to change, resulting in a change in magnetic flux in the top coil layer 2 and the bottom coil layer 6, so that the top coil layer 2 and the bottom coil layer 6 generate current, and the generated current is transmitted to an external load through the top circuit board 1 and the bottom circuit board 7 respectively.

[0054] The commercial finite element simulation software COMSOL Multiphysics 5.4 was used to simulate and calculate the cross-sectional magnetic flux density distribution when there were different clamping pieces between two cylindrical permanent magnets 3-1 in the embodiment of the present invention. The results are as Figure 5 and Figure 6 shown. It can be seen that the magnetic field on the outside of the two cylindrical permanent magnets 3-1 of the first magnetic structure with the soft magnetic clamping piece 3-2 (i.e., the permanent magnets in Figure 5 ) is enhanced, and it has a higher magnetic flux density than the two cylindrical permanent magnets 3-1 of the second magnetic structure with the non-magnetic clamping piece 3-3 (i.e., the permanent magnets in Figure 6 ). This helps to enhance the electromagnetic coupling between the transducer components. Therefore, the soft magnetic clamping piece 3-2 provided by the present invention helps to improve the energy conversion efficiency.

[0055] According to Faraday's law of electromagnetic induction, the instantaneous output induced voltage E of the human motion energy harvester based on the eccentric rotor is

[0056]

[0057] where Φ e is the effective magnetic flux, and θ is the relative angular displacement between the eccentric magnetic rotor 3 and the top induction coil (or the bottom induction coil). It can be seen that at the same rotor speed , the greater the spatial change rate of the effective magnetic flux, the stronger the electromagnetic coupling of the transducer components, and the greater the amplitude of the output induced voltage of the energy harvester. Figure 7 is the result diagram of the spatial change rate of the effective magnetic flux at different axial distances of the eccentric magnetic rotor obtained by calculating the finite element simulation results of the present invention. Under the condition of keeping the spatial volume swept by the motion trajectory of the eccentric rotor unchanged, compared with the traditional eccentric magnetic rotor that requires an external eccentric mass block, the eccentric magnetic rotor 3 of the present invention has a higher root mean square value of the spatial change rate of the effective magnetic flux at any axial distance. Therefore, the internally structured eccentric magnetic rotor provided by the present invention can provide a stronger electromagnetic coupling level of the transducer components and can improve the output power density of the present invention.

[0058] Figure 8 It is a test result diagram of the prototype of the present invention under different simple harmonic vibration excitation conditions. The excitation frequency is limited within the frequency range of the swing of the arm or leg during human movement, which is 1 - 5 Hz, and the excitation acceleration is limited within the acceleration range of the swing of the arm or leg during human movement, not exceeding 1.5g (g is the magnitude of the gravitational acceleration, 1g = 9.8 m / s 2 ). Under the condition of keeping the overall volume of the energy harvester the same, compared with the traditional eccentric rotor-based human motion energy harvester with an external eccentric mass block, the present invention has a significant improvement in the output power density.

[0059] The parts not described in detail in this embodiment belong to the well-known common means in this industry and will not be described one by one here. The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions, and it does not constitute a limitation on the protection scope of the present invention. Any changes, modifications, substitutions, combinations, and simplifications made by those skilled in the art based on the above content of the present invention without departing from the spirit and principle of the present invention shall be equivalent replacement methods and should be regarded as belonging to the protection scope of the present invention.

Claims

1. A high-power density human motion energy harvester based on an internally structured eccentric magnetic rotor, characterized in that It includes a top circuit board (1), a top coil layer (2), an eccentric magnetic rotor (3), a bottom coil layer (6) and a bottom circuit board (7); The top coil layer (2) is electrically connected to the top circuit board (1) and is installed on the lower surface of the top circuit board (1). The bottom coil layer (6) is electrically connected to the bottom circuit board (7) and is installed on the upper surface of the bottom circuit board (7). The eccentric magnetic rotor (3) is arranged between the top coil layer (2) and the bottom coil layer (6), and the eccentric magnetic rotor (3) is an eccentric structure. When the eccentric magnetic rotor (3) swings or rotates, it will cause a change in magnetic flux between the top coil layer (2) and the bottom coil layer (6). As a result, currents will be generated in the top coil layer (2) and the bottom coil layer (6), and the currents will be transmitted to an external load through the top circuit board (1) and the bottom circuit board (7) respectively.

2. The high-power density human motion energy harvester based on an internally structured eccentric magnetic rotor according to claim 1, wherein The top circuit board (1) is electrically connected to the bottom circuit board (7), so that the induction coils of the top coil layer (2) and the induction coils of the bottom coil layer (6) are connected in series, and the induced voltages generated by the two parts of the induction coils are superimposed.

3. The high-power density human motion energy harvester based on an internally structured eccentric magnetic rotor according to claim 1, wherein, The eccentric magnetic rotor (3) includes a first semi-circular structure formed by sequentially connecting three first magnetic structures through magnetic attraction and a second semi-circular structure formed by sequentially connecting three second magnetic structures through magnetic attraction. The first semi-circular structure and the second semi-circular structure are spliced through magnetic attraction to form an eccentric magnetic rotor (3) with an annular structure. The first magnetic structure is formed by clamping a soft magnetic clip (3-2) between two cylindrical permanent magnets (3-1). The second magnetic structure is formed by clamping a non-magnetic clip (3-3) between two cylindrical permanent magnets (3-1). The magnetization direction of the cylindrical permanent magnet (3-1) is along its thickness direction. The magnetization directions of the two cylindrical permanent magnets (3-1) in the first magnetic structure are the same. The magnetization directions of the two cylindrical permanent magnets (3-1) in the second magnetic structure are the same. The magnetization directions of the cylindrical permanent magnets (3-1) of adjacent two first magnetic structures or second magnetic structures are opposite, and the magnetization directions of the cylindrical permanent magnets (3-1) of adjacent first magnetic structure and second magnetic structure are also opposite; The soft magnetic clip (3-2) is made of soft magnetic material, and the non-magnetic clip (3-3) is made of light non-magnetic material, forming a mass difference with the soft magnetic clip (3-2) to constitute the structural eccentricity effect of the eccentric magnetic rotor (3).

4. The high-power density human motion energy harvester based on an internally-constructed eccentric magnetic rotor according to claim 3, wherein The soft magnetic clip (3-2), the non-magnetic clip (3-3) and the cylindrical permanent magnet (3-1) have equal diameters, and the thicknesses of both the soft magnetic clip (3-2) and the non-magnetic clip (3-3) are 2 times the thickness of the cylindrical permanent magnet (3-1).

5. The high-power density human motion energy harvester based on an internally structured eccentric magnetic rotor according to claim 3, characterized in that, The distance between the top coil layer (2) and the eccentric magnetic rotor (3) is equal to the distance between the bottom coil layer (6) and the eccentric magnetic rotor (3). The top coil layer (2) includes six top induction coils, and the six top induction coils are evenly arranged around the center of the top circuit board (1), and adjacent two top induction coils are wound in opposite directions. In the static state, each top induction coil is located in the same axial direction as a first magnetic structure or a second magnetic structure; The bottom coil layer (6) includes six bottom induction coils, which are evenly arranged around the center of the bottom circuit board (7), and two adjacent bottom induction coils are wound in opposite directions. In the static state, each bottom induction coil is in the same axial direction as a first magnetic structure or a second magnetic structure; Both the top induction coil and the bottom induction coil are cylindrical, and have the same thickness and hollow inner diameter. The top induction coil and the bottom induction coil have the same outer diameter as the cylindrical permanent magnet (3-1).

6. The high-power density human motion energy harvester based on an internally structured eccentric magnetic rotor according to claim 3, wherein The energy harvester further includes a ball bearing (4) and a central shaft rod (5). The ball bearing (4) is fixedly installed on the central shaft rod (5) and is embedded in the center of the eccentric magnetic rotor (3), and is mutually fixed to the first magnetic structure and the second magnetic structure through magnetic attraction; the ball bearing (4) can swing or rotate around the central shaft rod (5), so that the eccentric magnetic rotor (3) can swing or rotate around the central shaft rod (5); The central shaft rod (5) is located at the central position of the energy harvester and is connected to the top circuit board (1) and the bottom circuit board (7) to serve as a fixing bracket of the energy harvester to form a fixed frame; the material for preparing the central shaft rod (5) is non-magnetic material.

7. The high-power density human motion energy harvester based on an internally constructed eccentric magnetic rotor according to claim 6, characterized in that, The energy harvester further includes a plurality of support columns, and each support column is respectively connected to the top circuit board (1) and the bottom circuit board (7) to assist in supporting the fixed frame of the energy harvester; wherein, the installation position of the support column does not overlap with the movement track of the eccentric magnetic rotor (3) to avoid collision between the eccentric magnetic rotor (3) and the support column during movement, and the material for making the support column is non-magnetic material.

8. The high-power density human motion energy harvester based on an internally constructed eccentric magnetic rotor according to claim 1, wherein Two hole structures for matching with the wristband are provided on the bottom circuit board (7), and the two hole structures are symmetric with each other around the center of the bottom circuit board (7).

9. A high-power density human motion energy harvesting method using the energy harvester described in claim 1, characterized in that, Including: The energy harvester is worn on the human limbs in such a way that the top circuit board (1) or the bottom circuit board (7) is attached to the human limbs. When the human limbs move, it drives the energy harvester to generate a reciprocating motion, so that the eccentric magnetic rotor (3) in the energy harvester swings or rotates under the action of inertia. The swing or rotation of the eccentric magnetic rotor (3) causes a change in the magnetic field distribution, resulting in a change in the magnetic flux of the top coil layer (2) and the bottom coil layer (6), so that the top coil layer (2) and the bottom coil layer (6) generate current, and the generated current is respectively transmitted to an external load through the top circuit board (1) and the bottom circuit board (7).

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