A variable stiffness energy harvesting backpack system based on electrostatic damping action

Abstract

The present disclosure provides a variable stiffness energy harvesting backpack system based on electrostatic damping effect, comprising a backpack body, a shoulder strap with a hollow layer, an elastic belt, and a self-powered variable stiffness device arranged between the backpack body and the shoulder strap; both ends of the elastic belt are fixed between the hollow layer of the shoulder strap and the backpack body; the self-powered variable stiffness device comprises a friction power supply unit, an electrostatic adsorption unit and a circuit management unit, the stator of the friction power supply unit and the electrostatic adsorption unit and the shoulder strap together constitute a stator part, and the mover of the friction power supply unit and the electrostatic adsorption unit and the backpack body together constitute a mover part; the friction power supply unit converts the kinetic energy stored in the elastic belt into electrical energy to drive the electrostatic adsorption unit based on the principle of frictional electrification, and provides electrical energy to the electrostatic adsorption unit after adjustment by the circuit management unit, the electrostatic adsorption unit changes the elastic stiffness of the backpack system based on the electrostatic adsorption effect, and realizes the electrostatic damping effect by increasing the sliding damping force between the backpack body and the shoulder strap.

Description

Technical Field

[0001] This disclosure relates to the field of bag application technology, specifically to a variable stiffness energy harvesting backpack system based on static damping. Background Technology

[0002] Backpacks, as portable storage devices, bring numerous conveniences to people's daily lives. However, traditional backpacks share a common problem: they float and move along with the body during activities such as walking or running, resulting in unnecessary effort, energy consumption, and fatigue. Furthermore, providing continuous power to portable wearable devices during outdoor activities such as scientific expeditions, hiking trips, military training, and fire rescue presents a technological challenge. Traditional power sources, such as batteries, have inherent limitations, including limited capacity and lifespan, the need for frequent charging and recharging, and difficulties in recycling. Therefore, exploring a suspension mechanism, such as an elastic band system, that decouples the backpack's movement from the body's, allowing relative sliding between them to reduce load vibration amplitude and achieve vibration reduction and effort savings, while simultaneously utilizing the relative motion between the backpack and the body to drive an energy harvesting module for energy collection during human movement, has significant practical application and scientific research value.

[0003] Human movement energy is a sustainable and green energy source, such as walking, running, and knee bending. Using this energy source, mechanical energy can be converted into electrical energy using an energy harvesting module to power electronic devices, constructing a self-powered power supply system, which is of great significance for the continuous supply of power in the wild. Currently, research on a nano-triboelectric nanogenerator (TENG) technology is emerging. It utilizes triboelectric generation and electrostatic induction coupling effects to harvest mechanical energy, and is particularly suitable for harvesting low-frequency energy such as human movement energy, with higher energy harvesting efficiency than electromagnetic and piezoelectric technologies. On the other hand, electrostatic adsorption is a common physical phenomenon that utilizes the attraction between positive and negative charges in a high-voltage electrostatic field to achieve the attraction and motion inhibition of objects. TENG can naturally output a high-voltage electrostatic field, which can be used to achieve electrostatic adsorption and generate static damping. Therefore, if TENG technology can be used to harvest human movement energy to generate continuous electrical energy, and its high-voltage electrostatic field can also be used to generate static damping to adjust the relative movement between the backpack and the human body, thereby achieving maximum vibration reduction and energy saving under different step frequencies, speeds, and strides.

[0004] A typical backpack system incorporating TENG technology is illustrated in the 2013 international journal *ACS Nano*, Volume 7, Issue 12, pp. 11317-11324. [1]A backpack system with a diamond-shaped grid-like power generation unit placed on the shoulder is reported. It utilizes TENG technology to harvest the mechanical energy of human movement and a multi-layered diamond-shaped grid structure to increase the power generation area and thus improve the output power. (Published in the international journal *Journal of Materials Chemistry C*, Vol. 5, No. 6, pp. 1488-1493, 2017). [2] The report describes a backpack system placed at the waist to harvest mechanical energy from walking, running, and lumbar flexion. It utilizes surface treatment technology to create friction materials with irregular surface structures to increase the contact area of ​​the TENG (Temperature Energy Generator) and thus increase the output electrical energy. Additionally, the applicant's research group published their findings in the international journal *ACS Nano*, Volume 15, Issue 2, pp. 2611-2623, in 2021. [3] This paper reports a suspended energy harvesting backpack system based on TENG technology. It utilizes a suspension system to achieve shock absorption and effort reduction, and TENG technology to harvest energy from human movement. A national invention patent for a backpack system based on TENG technology has also been applied for (ZL201910573414.6). [4] However, these backpack systems based on TENG technology have several shortcomings: First, the first two backpack technologies lack vibration reduction and fatigue-saving functions. Second, the first two backpack structures are not true backpack systems; they merely construct a TENG-based power generation module and attach it to an actual backpack, resulting in insufficient integration and limited practicality. Third, while the applicant's previous backpack system achieved vibration reduction, fatigue saving, and energy harvesting from human movement, its suspension system's elastic stiffness adjustment mechanism was difficult to operate, and the linear guide rail mechanism was complex and impractical. Excessive use of materials such as acrylic sheets resulted in a bulky overall structure, increasing the burden on the wearer. Furthermore, the initial backpack system did not integrate an electrostatic adsorption structure, thus lacking static damping and the ability to finely adjust the relative movement between the backpack and the human body.

[0005] Existing technology:

[0006] [1] Weiqing Yang, Jun Chen, Guang Zhu, Jin Yang, Peng Bai, Yuanjie Su, Qingsheng Jing, Xia Cao, Zhong Lin Wang. Harvesting Energy from the Natural Vibration of Human Walking[J]. ACS Nano, 2013, 7(12): 11317-11324. https: / / doi.org / 10.1021 / nn405175z [2]Arunkumar Chandrasekhar, Nagamalleswara Rao Alluri, VenkateswaranVivekananthan, Yuvasree Purusothaman, Sang-Jae Kim. A sustainable freestanding biomechanical energy harvesting smart backpack as a portable-wearable powersource[J]. Journal of Materials Chemistry C,2017,5(6):1488-1493.https: / / doi.org / 10.1039 / c6tc05282g

[0007] [3] Ze Yang, Yiyong Yang, Fan Liu, Zhaozheng Wang, Yinbo Li, Jiahao Qiu, Xuan Xiao, Zhiwei Li, Yijia Lu, Linhong Ji, Zhong Lin Wang, Jia Cheng. Powerbackpack for energy harvesting and reduced load impact[J]. ACS Nano, 2021, 15(2):2611-2623. https: / / doi.org / 10.1021 / acsnano.0c07498

[0008] [4] Cheng Jia, Yang Ze, Ji Linhong, Lu Yijia, Li Yinbo. An energy harvesting and weight reduction backpack based on triboelectricity [P]. Beijing: CN110269379B, 2021-06-04. https: / / kns.cnki.net / kcms2 / article / abstract?v=kxaUMs6x7-4I2jr5WTdXti3zQ9F92xu0jPYZ-6FemR80TpIUx9Y4vqcnVsRAJxFmz1ks88kUfuL7errdukqwr6aLd9xBRYrm&uniplatform=NZKPT Summary of the Invention

[0009] This disclosure aims to address at least one of the technical problems existing in the prior art.

[0010] Therefore, this disclosure provides a variable stiffness energy harvesting backpack system based on static damping. This backpack system, based on static damping technology, can achieve lighter vibration reduction and less effort, and can also adjust the stiffness of the backpack vibration reduction system.

[0011] To achieve the above objectives, the present disclosure adopts the following technical solution:

[0012] This disclosure provides a variable stiffness energy harvesting backpack system based on static damping, including a backpack body, a shoulder strap with a hollow layer, an elastic band fixed to the hollow layer of the shoulder strap, and a self-powered variable stiffness device disposed between the backpack body and the shoulder strap.

[0013] The elastic band has one end fixed to the hollow layer of the shoulder strap and the other end fixed to the backpack body.

[0014] The self-powered variable stiffness device includes a triboelectric power supply unit, an electrostatic adsorption unit, and a circuit management unit. Both the triboelectric power supply unit and the electrostatic adsorption unit have a stator and a mover. The stators of the triboelectric power supply unit and the electrostatic adsorption unit are connected via a first connector and together with the shoulder straps constitute the stator portion of the variable stiffness energy harvesting backpack system. The movers of the triboelectric power supply unit and the electrostatic adsorption unit are connected via a second connector and together with the backpack body constitute the mover portion of the variable stiffness energy harvesting backpack system. The triboelectric power supply unit converts the kinetic energy stored in the elastic band into electrical energy based on the principle of triboelectric generation to drive the electrostatic adsorption unit. After adjustment by the circuit management unit, electrical energy is provided to the electrostatic adsorption unit. The electrostatic adsorption unit changes the elastic stiffness of the variable stiffness energy harvesting backpack system based on electrostatic adsorption, achieving static damping by increasing the sliding damping force between the backpack body and the shoulder straps.

[0015] In some embodiments, the shoulder strap is made of a non-elastic material, with most of the elastic band located within the hollow layer of the shoulder strap and a small portion of the elastic band located outside the shoulder strap.

[0016] In some embodiments, the initial elastic stiffness of the variable stiffness energy harvesting backpack system is positively correlated with the length of the elastic band.

[0017] In some embodiments, the triboelectric power supply unit is positioned closer to the shoulder strap than the electrostatic adsorption unit. The triboelectric power supply unit adopts a symmetrical independent triboelectric layer nano-triboelectric generator structure, including a mover and a stator symmetrically arranged on both sides of the mover. The mover of the triboelectric power supply unit includes a drive plate, and a second triboelectric layer is fixedly provided on both sides of the drive plate facing the stator. The stator of the triboelectric power supply unit includes a first electrode substrate, a first electrode, and a first triboelectric layer stacked sequentially, and the first triboelectric layer is positioned closer to the mover of the triboelectric power supply unit than the first electrode substrate. The size of the first electrode substrate should cover the range of motion of the drive plate.

[0018] In some embodiments, the first electrode disposed on the first electrode substrate is arranged in a grid pattern, and the drive plate has the same grid-patterned protrusion structure on both sides facing the stator, the protrusion structure being consistent with the grid pattern arrangement of the first electrode.

[0019] In some embodiments, the first electrode substrate, the first electrode, and the first friction layer located on both sides of the drive plate are integrally fixed to the side of the shoulder strap facing the backpack body via the first connector; the drive plate and the second friction layer are connected to the backpack body together with the mover in the electrostatic adsorption unit via the second connector.

[0020] In some embodiments, the first connector and the second connector are both strip plates with a hollow structure. The first connector is connected between the upper and lower sides of the mover of the triboelectric power supply unit and the mover of the electrostatic adsorption unit, and the second connector is connected between the left and right sides of the mover of the triboelectric power supply unit and the mover of the electrostatic adsorption unit.

[0021] In some embodiments, the electrostatic adsorption unit is disposed closer to the backpack body than the triboelectric power supply unit. The electrostatic adsorption unit includes a buffer layer, a second electrode substrate, a second electrode, a first dielectric layer, a second dielectric layer, a third electrode, and a third electrode substrate arranged sequentially along the direction from the shoulder strap to the backpack body. The buffer layer, the second electrode substrate, the second electrode, and the first dielectric layer constitute the stator of the electrostatic adsorption unit, and the second dielectric layer, the third electrode, and the third electrode substrate constitute the mover of the electrostatic adsorption unit. The size of the first dielectric layer should completely cover the second electrode, the size of the second dielectric layer should completely cover the third electrode, and the size of the second electrode should completely cover the range of motion of the third electrode.

[0022] In some embodiments, there are two circuit management units. The triboelectric power supply unit has two AC output terminals. The first circuit management unit is connected between the first AC output terminal of the triboelectric power supply unit and one of the electrodes of the second and third electrodes of the electrostatic adsorption unit. The second circuit management unit is connected between the second AC output terminal of the triboelectric power supply unit and the other electrode of the second and third electrodes of the electrostatic adsorption unit. The circuit management unit includes a boost rectifier circuit and a switch connected to each other.

[0023] In some embodiments, the boost rectifier circuit includes a main circuit consisting of at least two diodes and the same number of capacitors connected together, and a Zener diode connected in parallel between the input and output terminals of the main circuit; the diodes are connected in series from end to end in sequence, and the capacitors are connected in series alternately between the corresponding two diodes.

[0024] This disclosure has the following beneficial effects:

[0025] This invention innovatively proposes a variable stiffness energy harvesting backpack system based on electrostatic damping. It employs electrostatic damping technology to achieve energy harvesting and overall stiffness adjustment. The backpack features a detachable assembly design, allowing the backpack body and carrying structure to be carried separately. The main functional modules include a triboelectric power generation unit and an electrostatic adsorption unit, which reduce the impact of carrying heavy loads on the human body, achieving a shock absorption effect. Simultaneously, the relative sliding between the human body and the backpack drives the triboelectric power generation unit to harvest energy from human movement. The electrical energy generated by the triboelectric power generation unit is transferred to the electrostatic adsorption unit through a circuit management unit. Upon receiving the electrical energy, the electrostatic adsorption unit generates electrostatic adsorption force, reducing the vibration amplitude generated by the backpack body and achieving the overall stiffness adjustment function of the backpack system. Attached Figure Description

[0026] Figure 1 A schematic diagram of the overall structure of a variable stiffness energy harvesting backpack system based on static damping provided in an embodiment of this disclosure;

[0027] Figure 2 for Figure 1 An exploded view of some structures in the backpack system shown.

[0028] Figure 3 for Figure 1 The diagram shows an exploded view of the overall structure of the backpack system.

[0029] Figure 4 for Figure 1 An exploded view of the triboelectric power supply unit in the backpack system shown.

[0030] Figure 5 for Figure 1An exploded view of the electrostatic adsorption unit in the backpack system shown.

[0031] Figure 6 for Figure 1 A schematic diagram of the moving part of the backpack system shown.

[0032] Figure 7 for Figure 1 The diagram shows the specific circuit connection structure of the triboelectric power supply unit driving the electrostatic adsorption unit in the backpack system shown.

[0033] Figure 8 A schematic diagram of the specific circuit structure of the backpack system provided in the embodiments of this disclosure.

[0034] In the diagram:

[0035] 10. Backpack body; 11. Card slot; 12. First connector; 13. Second connector; 14. Elastic band; 15. Shoulder strap; 20. Self-powered variable stiffness device; 100. Triboelectric power supply unit; 101. First electrode substrate; 102. First electrode; 103. Friction layer one; 104. Friction layer two; 105. Drive board; 200. Electrostatic adsorption unit; 201. Buffer layer; 202. Second electrode substrate; 203. Second electrode; 204. First dielectric layer; 205. Second dielectric layer; 206. Third electrode; 207. Third electrode substrate; 300. Circuit management unit; 311. Capacitor; 312. Diode; 313. Zener diode; 314. Switch S. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0037] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0038] Please see Figures 1 to 8This disclosure provides a variable stiffness energy harvesting backpack system based on electrostatic damping, comprising a backpack body 10, shoulder straps 15 (with a hollow interior), elastic bands 14 fixed inside the shoulder straps 15, and a self-powered variable stiffness device 20 disposed between the backpack body 10 and the shoulder straps 15. The backpack body 10 is used to hold items, and the shoulder straps 15 are preferably double shoulder straps. Typically, the backpack body 10, shoulder straps 15, elastic bands 14, and self-powered variable stiffness device 20 are used as a single integrated unit.

[0039] The shoulder strap 15 features a hollow structure and is made of non-elastic material. It serves solely as a connection between the backpack body 10 and the wearer's shoulders and is not extendable. The elastic band 14 is made of highly elastic material, with one end fixed to the inside of the shoulder strap 15 and the other end fixed to the inside of the slot 11. The slot 11 is fixedly located on the side of the backpack body 10 facing the shoulder strap 15. Most of the original length of the elastic band 14 is located inside the shoulder strap 15, with only a small portion extending beyond the shoulder strap 15 and exposed to the external environment. The elastic band 14 connects the shoulder strap 15 to the backpack body 10. Simultaneously, the elastic band 14 also constrains the freedom of movement of the backpack body 10, allowing for relative sliding perpendicular to the ground between the backpack body 10 and the shoulder strap 15. Furthermore, the high elasticity of the elastic band 14 reduces the inertial impact force generated by the backpack body 10, providing a shock absorption effect and achieving decoupling of movement between the backpack body 10 and the shoulder strap 15 to reduce the burden on the wearer.

[0040] The self-powered variable stiffness device 20 includes a friction power supply unit 100, an electrostatic adsorption unit 200, and a circuit management unit 300. Both the friction power supply unit 100 and the electrostatic adsorption unit 200 have a stator and a mover. The stator of the friction power supply unit 100 and the stator of the electrostatic adsorption unit 200 are connected by a first connector 12 and together with the shoulder strap 15, they constitute the stator part of the backpack system. The mover of the friction power supply unit 100 and the mover of the electrostatic adsorption unit 200 are connected by a second connector 13 and together with the backpack body 10, they constitute the mover part of the backpack system. The friction power supply unit 100 converts the kinetic energy stored in the elastic band 14 into electrical energy to drive the electrostatic adsorption unit 200 based on the principle of triboelectricity. After adjustment by the circuit management unit 300, electrical energy is provided to the electrostatic adsorption unit 200. The electrostatic adsorption unit 200 changes the elastic stiffness of the backpack system based on electrostatic adsorption, and achieves static damping by increasing the sliding damping force between the backpack body 10 and the shoulder strap 15.

[0041] In some embodiments, see Figure 3The shoulder strap 15 features a hollow design with sufficient internal space to ensure the elastic band 14 can be smoothly installed within its cavity. The elastic band 14 is made of a highly elastic material, such as rubber, polyurethane, or styrene. One end is fixed to the internal cavity of the shoulder strap 15, and the other end is fitted into a slot 11 located at the upper left and right ends of the backpack body 10. This ensures the elastic band 14 can evenly support the backpack body 10. Most of the original length of the elastic band 14 is located inside the shoulder strap 15, with only a small portion extending beyond the shoulder strap 15 and exposed to the external environment. The length of the elastic band 14 determines the initial elastic stiffness of the backpack system. If the original length of the elastic band 14 is relatively long, and the stretchable distance of the elastic band 14 is large, then the initial elastic stiffness of this backpack system is small, and the static damping effect generated by the electrostatic adsorption unit 200 has a greater impact on the change in the stiffness of this backpack system. Conversely, if the original length of the elastic band 14 is short, and the stretchable distance of the elastic band 14 is small, then the initial elastic stiffness of this backpack system is large, and the static damping effect generated by the electrostatic adsorption unit 200 has a smaller impact on the change in the stiffness of this backpack system. Therefore, under the premise of ensuring good support for the backpack body 10, the original length of the elastic band 14 should be increased as much as possible to ensure the effect of static damping on the adjustment of the stiffness of the backpack system.

[0042] In some embodiments, see Figure 4The triboelectric power supply unit 100 is positioned closer to the shoulder strap 15 than the electrostatic adsorption unit 200. The triboelectric power supply unit 100 is a symmetrical independent triboelectric layer nano-triboelectric generator structure, including a mover and a stator symmetrically arranged on both sides of the mover. The mover of the triboelectric power supply unit 100 includes a drive plate 105, and a second triboelectric layer 104 is fixedly provided on both sides of the drive plate 105 facing the stator. The stator of the triboelectric power supply unit 100 includes a first electrode substrate 101, a first electrode 102 and a first triboelectric layer 103 stacked in sequence. The first triboelectric layer 103 is positioned closer to the mover of the triboelectric power supply unit 100 than the first electrode substrate 101. The first triboelectric layer 103 should completely cover the electrode 102 to prevent short circuit. In order to meet the power generation principle of the nano-triboelectric generator, the first triboelectric layer 103 and the second triboelectric layer 104 are two thin film materials with different electronegativity. Specifically, a layer of non-connected metal conductive electrode is vapor-deposited on the side of the first electrode substrate 101 facing the mover as the first electrode 102, and the first electrode 102 is distributed in a grid pattern to improve the charge output efficiency of the triboelectric power supply unit 100. The first electrode substrate 101, the first electrode 102 and the first friction layer 103 located on both sides of the drive plate 105 are formed into a whole and fixed to the side of the shoulder strap 15 facing the backpack body 10 as a fixed component in the triboelectric power supply unit 100 through the first connector 12. The drive plate 105 has the same grid-type protrusion structure on both sides facing the stator. Preferably, the grid-type protrusion structure is consistent with the grid-type arrangement of the first electrode 102. A second friction layer 104 is provided on the surface of the protrusion structure on both sides. The drive plate 105 and the second friction layer 104 form the motion component of the triboelectric power supply unit 100 and are connected to the backpack body 10 through the second connector 13 and the mover in the electrostatic adsorption unit 200. The size of the first electrode substrate 101 should cover the motion range of the drive plate 105. Optionally, the first connector 12 is a strip plate connected to the upper and lower edges of the first electrode substrate 101 on both sides of the drive plate 105, and the second connector 13 is a strip plate connected to the left and right sides of the mover of the drive plate 105 and the electrostatic adsorption unit 200. Both the first connector 12 and the second connector 13 adopt a hollow design to reduce their weight. As the drive plate 105 slides under the driving action of the backpack body 10, the second friction layer 104 and the first friction layer 103 come into contact and rub against each other. Due to the different electronegativity of the materials, the contact interface carries an equal amount of opposite charges, forming an electrostatic field in the interface between the two friction layers. Based on the principle of electrostatic induction, the charge on the surface of the first electrode 102 is redistributed and continuously carried out as the drive plate 105 moves. The two output terminals of the first electrode 102 on one first electrode substrate 101 that are not connected serve as the first AC output terminals of the friction power supply unit 100, thereby outputting an equal amount of opposite charges to the outside. Similarly, the two output terminals of the first electrode 102 on the other first electrode substrate 101 that are not connected serve as the second AC output terminals of the friction power supply unit 100, thereby outputting an equal amount of opposite charges to the outside.

[0043] In some embodiments, see Figure 5The electrostatic adsorption unit 200 is positioned closer to the backpack body 10 than the triboelectric power supply unit 100. The electrostatic adsorption unit 200 primarily absorbs and reduces some of the kinetic energy generated by the backpack body 10 through electrostatic adsorption, achieving a function similar to a damper in a car suspension system. This increases the overall stiffness of the backpack system, thereby reducing the amplitude of the backpack body 10's vibration. Electrostatic adsorption mainly occurs by applying a high voltage of hundreds or thousands of volts to the metal electrodes, generating an adsorption phenomenon under electrostatic induction or polarization. Through electrostatic induction and polarization, equal amounts of opposite charges accumulate on the surfaces of the electrodes and the adsorbed object. Based on the principle that like charges repel each other and unlike charges attract each other, an electrostatic adsorption force is generated between the conductive electrode and the adsorbed object, thus achieving the adsorption effect. The electrostatic adsorption unit 200 of this embodiment is composed of a buffer layer 201, a second electrode substrate 202, a second electrode 203, a first dielectric layer 204, a second dielectric layer 205, a third electrode 206, and a third electrode substrate 207 arranged sequentially along the direction from the shoulder strap 15 to the backpack body 10. The buffer layer 201, the second electrode substrate 202, the second electrode 203, and the first dielectric layer 204 constitute the stator of the electrostatic adsorption unit 200, and the second dielectric layer 205, the third electrode 206, and the third electrode substrate 207 constitute the mover of the electrostatic adsorption unit 200. Specifically, the buffer layer 201 is made of sponge or other material with built-in vibration damping; the second electrode 203 and the third electrode 206 are sheet electrodes made of copper foil, differing only in geometric shape (specifically, the widths of the second electrode 203 and the third electrode 206 are equal, and the length of the second electrode 203 should cover the range of motion of the third electrode 206, thus ensuring that electrostatic adsorption always occurs between them when energized); the first dielectric layer 204 and the second dielectric layer 205 are made of polyimide or other dielectric materials (the first dielectric layer 204 and the second dielectric layer 205...). The dielectric layers 204 and 205 serve to isolate each other, creating an insulating state between them. They can be made of the same or different dielectric materials, as long as they are insulated from each other and have low surface roughness to facilitate relative sliding. The first dielectric layer 204 and the second dielectric layer 205 differ only in geometric shape. The dielectric layers completely cover the conductive electrodes to prevent short circuits (specifically, the first dielectric layer 204 needs to completely cover the second electrode 203, and the second dielectric layer 205 needs to completely cover the third electrode 206 to ensure that the second electrode 203 and the third electrode 206 do not come into contact, thus achieving charge storage).When the electrical energy generated by the triboelectric power supply unit 100 is output from the first electrode 102 and transferred to the electrostatic adsorption unit 200, specifically, after the two AC output terminals of the triboelectric power supply unit 100 are rectified and switched on and off by a corresponding circuit management unit 300, positive and negative currents (or charges) are formed respectively. All the positive charges (or currents) are injected into one of the electrodes of the second electrode 203 and the third electrode 206, while all the negative charges (or currents) are injected into the other electrode of the second electrode 203 and the third electrode 206, thereby forming an electrostatic field and generating electrostatic adsorption between the second electrode 203 and the third electrode 206. Under the action of static resistance damping, the overall stiffness of this backpack system will increase. Specifically, the backpack body 10 will reduce the amplitude of reciprocating vibration under the action of electrostatic adsorption force, thereby increasing the stiffness of the backpack system. At the same time, the circuit management unit 300 also plays the role of controlling the current on and off to adjust the presence or absence of electrostatic adsorption.

[0044] In some embodiments, see Figure 6 The third electrode substrate 207, the third electrode 206, and the second dielectric layer 205 form a whole as the mover of the electrostatic adsorption unit 200. The drive plate 105 and the second friction layer 104 in the triboelectric power supply unit 100 form a whole as the mover of the triboelectric power supply unit 100. The mover of the electrostatic adsorption unit 200 and the mover of the triboelectric power supply unit 100 are connected through the second connector 13 and form the mover unit of the backpack system with the backpack body 10. Except for the mover of the backpack system, all others are fixedly connected to the shoulder straps 15 to form a whole as the stator of the backpack system. When a person walks using this backpack system, the backpack body 10 slides vertically back and forth due to inertia and the elasticity of the elastic band 14, which drives the mover unit of the backpack system to slide back and forth.

[0045] In some embodiments, see Figure 7 , Figure 8The backpack system in this embodiment includes two circuit management units 300, which are respectively connected between one AC output terminal of the triboelectric power supply unit 100 and one of the electrodes of the second electrode 203 and the third electrode 206 of the electrostatic adsorption unit 200, and between the other AC output terminal of the triboelectric power supply unit 100 and the other electrode of the second electrode 203 and the third electrode 206 of the electrostatic adsorption unit 200. The two circuit management units 300 have the same structure, each including a boost rectifier circuit and a switch S 314 connected to each other. The boost rectifier circuit consists of at least two diodes 312 and the same number of capacitors 311. The diodes are connected in series in the same direction, and the capacitors 311 are connected in series alternately between the two diodes 312. Therefore, the boost rectifier circuit can add or remove a certain number of diodes and capacitors according to the output circuit requirements. However, it must be ensured that the number of diodes and capacitors is equal before actual use. Due to the unidirectional conduction characteristic of diodes, the capacitor plates on the same side as the positive terminals of the series diodes are also positive terminals. To stabilize the output voltage, a Zener diode 313 is connected in parallel at both output terminals of the circuit. Simultaneously, due to the series and parallel characteristics of multiple capacitors in the circuit management unit 300, the boost rectifier circuit achieves both boost and rectification functions. A switch S 314 is connected between the boost rectifier circuit and the electrostatic adsorption unit 200. By controlling the opening and closing of switch S, the presence or absence of the electrostatic adsorption effect can be adjusted.

[0046] The working principle of this disclosure embodiment is described below:

[0047] When using this backpack system, heavy objects are placed inside the backpack body 10. The appropriate elastic band 14 with suitable stiffness and length is selected based on the weight of the load inside the backpack body 10 to accommodate the corresponding carrying weight and achieve shock absorption. Specifically, if the carrying weight is too heavy and causes the backpack body 10 to sag excessively, it indicates that the elastic band 14's contraction force is insufficient to support the carried weight. In this case, the elastic band 14 needs to be replaced to increase its stiffness, ensuring that the contraction force of the elastic band 14 is sufficient to support the current carrying weight, allowing the backpack body 10 to remain suspended in a balanced, intermediate position.

[0048] Subsequently, the person inserts their arms into the backpack straps 15 to use the backpack normally. When the person walks or runs while carrying the backpack, due to the human body's movement mechanism, the body's center of gravity will fluctuate up and down in the direction perpendicular to the ground. At this time, the backpack body 10 is decoupled from the human body's movement under the action of the elastic band 14, thereby realizing the relative sliding of the backpack body 10 with respect to the straps 15. The absolute displacement of the backpack body 10 with respect to the ground is small or almost non-existent. Specifically, when the person walks forward, the double upright support state changes to a double cross support state, and the person's center of gravity will drop at the moment of taking a step. The person's center of gravity will drop relative to the ground before the backpack. Since the backpack body 10 is fixed on the third electrode substrate 207 and is fixedly connected to the mover of the triboelectric power supply unit 100 and the mover of the electrostatic adsorption unit 200 to form a whole, the backpack body 10 can slide relative to the stator part of this backpack system through the second connector 13. When a person walks forward and takes a step, their center of gravity drops, causing the shoulder straps 15 to drop as well. The elastic band 14 is stretched accordingly, and the backpack body 10 and the shoulder straps 15 undergo relative displacement. Due to the elasticity of the elastic band 14, the absolute displacement of the backpack body 10 relative to the ground is small or almost zero. The process of the person's center of gravity rising is similar to the process of falling. Therefore, when a person walks or runs, their center of gravity shifts vertically, and the backpack body 10 and the shoulder straps 15 slide relative to each other. At the same time, the backpack body 10 is in a "suspended" state relative to the ground, which reduces the impact of the backpack's weight on the person, achieving the effects of shock absorption, energy saving, and relieving pressure on the shoulders.

[0049] Furthermore, the backpack body 10 undergoes vertical reciprocating sliding due to inertia and the elasticity of the elastic band 14. Part of the inertial force generated by the backpack body 10 is absorbed by the elastic band 14, and the other part is transmitted to the mover of the friction power supply unit 100 through the second connector 13. This drives the mover of the friction power supply unit 100 to perform sliding friction and generate corresponding charges. The electrical energy output by the friction power supply unit 100 is input into the circuit management unit 300. After being boosted, rectified, and controlled by the circuit management unit 300, it enters the electrostatic adsorption unit 200, providing voltage to the second electrode 203 and the third electrode 206 respectively, generating corresponding electrostatic adsorption forces to improve the overall stiffness of the backpack system. At this time, the backpack body 10 will reduce the amplitude of reciprocating vibration under the action of the electrostatic adsorption force, realizing the function of adjusting the stiffness of the backpack system. In addition, in this embodiment, by controlling the on / off state of the switch S inside the circuit management unit 300, it is possible to select whether to transfer the electrical energy generated by the friction power supply unit 100 to the electrostatic adsorption unit 200, thereby realizing the active controllable function of the stiffness of the backpack system.

[0050] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

[0051] In the description of the embodiments disclosed herein, it should be understood that the terms "top", "bottom", "up and down", "left and right", "coplanar", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0052] In the embodiments of this application, unless otherwise explicitly specified and limited, the terms "fixed connection", "fixed connection", "adhesion", "gluing", "bonding", "coating", "locking", etc., should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium, etc. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0053] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A variable stiffness energy harvesting backpack system based on static damping, characterized in that, It includes a backpack body, a shoulder strap with a hollow layer, an elastic band fixed to the hollow layer of the shoulder strap, and a self-powered variable stiffness device disposed between the backpack body and the shoulder strap. The elastic band has one end fixed to the hollow layer of the shoulder strap and the other end fixed to the backpack body. The self-powered variable stiffness device includes a triboelectric power supply unit, an electrostatic adsorption unit, and a circuit management unit. Both the triboelectric power supply unit and the electrostatic adsorption unit have a stator and a mover. The stators of the triboelectric power supply unit and the electrostatic adsorption unit are connected via a first connector and together with the shoulder strap, form the stator part of the variable stiffness energy harvesting backpack system. The movers of the triboelectric power supply unit and the electrostatic adsorption unit are connected via a second connector and together with the backpack body, form the mover part of the variable stiffness energy harvesting backpack system. The triboelectric power supply unit converts the kinetic energy stored in the elastic band into electrical energy based on the principle of triboelectric generation to drive the electrostatic adsorption unit. After adjustment by the circuit management unit, electrical energy is provided to the electrostatic adsorption unit. The electrostatic adsorption unit changes the elastic stiffness of the variable stiffness energy harvesting backpack system based on electrostatic adsorption, achieving static damping by increasing the sliding damping force between the backpack body and the shoulder strap. The triboelectric power supply unit is positioned closer to the shoulder strap than the electrostatic adsorption unit. The triboelectric power supply unit adopts a symmetrical independent triboelectric layer nano-triboelectric generator structure, including a mover and a stator symmetrically arranged on both sides of the mover. The mover of the triboelectric power supply unit includes a drive plate, and a second triboelectric layer is fixedly provided on both sides of the drive plate facing the stator. The stator of the triboelectric power supply unit includes a first electrode substrate, a first electrode, and a first triboelectric layer stacked in sequence. The first triboelectric layer is positioned closer to the mover of the triboelectric power supply unit than the first electrode substrate. The size of the first electrode substrate should cover the range of motion of the drive plate.

2. The variable stiffness energy harvesting backpack system according to claim 1, characterized in that, The shoulder strap is made of a non-elastic material, with most of the elastic band located inside the hollow layer of the shoulder strap and a small portion of the elastic band located outside the shoulder strap.

3. The variable stiffness energy harvesting backpack system according to claim 2, characterized in that, The initial elastic stiffness of the variable stiffness energy harvesting backpack system is positively correlated with the length of the elastic band.

4. The variable stiffness energy harvesting backpack system according to claim 1, characterized in that, The first electrode, which is disposed on the first electrode substrate, is arranged in a grid pattern. The drive plate has the same grid-patterned protrusion structure on both sides facing the stator. The protrusion structure is consistent with the grid pattern arrangement of the first electrode.

5. The variable stiffness energy harvesting backpack system according to claim 1, characterized in that, The first electrode substrate, the first electrode, and the first friction layer located on both sides of the drive plate are fixed as a whole to the side of the shoulder strap facing the backpack body through the first connector; the drive plate and the second friction layer are connected to the backpack body together with the mover in the electrostatic adsorption unit through the second connector.

6. The variable stiffness energy harvesting backpack system according to claim 1, characterized in that, Both the first connector and the second connector are strip plates with a hollow structure. The first connector is connected between the upper and lower sides of the mover of the triboelectric power supply unit and the mover of the electrostatic adsorption unit, and the second connector is connected between the left and right sides of the mover of the triboelectric power supply unit and the mover of the electrostatic adsorption unit.

7. The variable stiffness energy harvesting backpack system according to claim 1, characterized in that, The electrostatic adsorption unit is positioned closer to the backpack body than the triboelectric power supply unit. The electrostatic adsorption unit includes a buffer layer, a second electrode substrate, a second electrode, a first dielectric layer, a second dielectric layer, a third electrode, and a third electrode substrate arranged sequentially along the direction from the shoulder strap to the backpack body. The buffer layer, the second electrode substrate, the second electrode, and the first dielectric layer constitute the stator of the electrostatic adsorption unit, and the second dielectric layer, the third electrode, and the third electrode substrate constitute the mover of the electrostatic adsorption unit. The size of the first dielectric layer should completely cover the second electrode, the size of the second dielectric layer should completely cover the third electrode, and the size of the second electrode should completely cover the range of motion of the third electrode.

8. The variable stiffness energy harvesting backpack system according to claim 7, characterized in that, The circuit management unit is provided in two parts. The triboelectric power supply unit has two AC output terminals. The first circuit management unit is connected between the first AC output terminal of the triboelectric power supply unit and one of the electrodes of the second and third electrodes of the electrostatic adsorption unit. The second circuit management unit is connected between the second AC output terminal of the triboelectric power supply unit and the other electrode of the second and third electrodes of the electrostatic adsorption unit. The circuit management unit includes a boost rectifier circuit and a switch connected to each other.

9. The variable stiffness energy harvesting backpack system according to claim 8, characterized in that, The boost rectifier circuit includes a main circuit consisting of at least two diodes and the same number of capacitors connected together, and a Zener diode connected in parallel between the input and output terminals of the main circuit; the diodes are connected in series from end to end in sequence, and the capacitors are connected in series alternately between the corresponding two diodes.

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