Compact energy collection device with time-varying potential energy

Abstract

The invention relates to the technical field of nonlinear dynamics, in particular to a compact energy collection device with time-varying potential energy. The area can adjust the potential energy form of the system and the effective frequency band of energy collection; meanwhile, the energy collecting device has a certain space compactness; the energy collecting device comprises a base used for supporting, a movable trolley and at least two elastic beams. When the energy collecting device is subjected to external mechanical excitation, the two elastic beams generate two-degree-of-freedom displacement; and the two groups of magnets at the left end and the right end interact with each other at respective degrees of freedom and generate vertical nonlinear elastic restoring force, so that the two elastic beams generate nonlinear displacement in the vertical direction. According to the design of the compact energy collecting device with the time-varying potential energy, the space occupied by the energy collecting device can be greatly saved. By changing the initial position of the trolley on the sliding track, the potential energy function of the system can be switched among a monostable mode, a bistable mode and a tristable mode.

Description

Technical Field

[0001] The present invention relates to the technical field of nonlinear dynamics, and in particular to a compact energy harvesting device with time-varying potential energy. Background Art

[0002] Vibration energy harvesters (VEHs) are relatively common and widely used in our daily lives. The earliest linear VEHs were designed to harvest available vibration energy from the environment, and theoretical modeling and optimization strategies for linear VEHs have been studied to accurately predict their operational performance. Linear VEHs have a narrow operating frequency band, with their effective energy harvesting region confined to near the resonant frequency. When the frequency of the external excitation is outside the resonant frequency, the energy harvesting efficiency of linear VEHs significantly decreases. To optimize energy harvesting devices, various energy harvesting devices with nonlinear mechanisms have been introduced to broaden their effective operating frequency band and thus improve their energy harvesting efficiency. Energy harvesting devices with nonlinear mechanisms offer high energy harvesting efficiency and therefore hold promising application prospects in engineering. Incorporating magnetic coupling or geometrically nonlinear elastic bodies into the mechanical vibration portion of an energy harvester is a relatively common approach. Based on the number of minima (equilibrium positions) of the system's potential energy function, nonlinear energy harvesting devices can be categorized as monostable, bistable, tristable, quadristable, and other multistable energy harvesting devices. A tristable energy harvesting (TEH) device has five equilibrium points (three stable and two unstable). Therefore, the nonlinear characteristics of TEH are much more complex than those of monostable and bistable systems. The nonlinear stiffness of TEH also exhibits more complex softening and hardening trends (including mixed occurrences), which may affect the system's energy harvesting performance. Existing piezoelectric energy harvesting devices have higher space requirements, which limits the feasibility of their designs. Therefore, the design of a compact energy harvesting device has become a pressing technical challenge. Summary of the Invention

[0003] The present invention addresses the problems encountered in the prior art by proposing a compact energy harvesting device with time-varying potential energy. This device is intended to improve its applicability in practical engineering applications, increasing its energy output and effective operating bandwidth, and thus be used to power miniaturized wireless sensor devices.

[0004] The technical solution of the present invention is a compact energy harvesting device with time-varying potential energy. The energy harvesting device includes at least one region capable of adjusting the potential energy form of the system and the effective energy harvesting frequency band. At the same time, the energy harvesting device has a certain degree of spatial compactness.

[0005] The energy harvesting device comprises a base for support, a movable trolley and at least two elastic beams;

[0006] The base is used to provide basic support for the entire energy collection device. An upwardly protruding platform is provided on one side of the base; a first elastic beam is provided on the platform; a guide rail is provided at the other end of the base; and the trolley slides along the guide rail.

[0007] The second elastic beam is arranged on the first elastic beam, and the first magnet and the second magnet are respectively arranged at both ends of the second elastic beam, and two sets of third magnets are arranged on the corresponding trolley; the third magnets generate magnetic interaction with the second magnets;

[0008] The first magnet generates magnetic interaction with a fourth magnet disposed on the first elastic beam;

[0009] When the energy harvesting device is subjected to external mechanical excitation, the two elastic beams produce displacements in two degrees of freedom; the two groups of magnets at the left and right ends interact in their respective degrees of freedom and generate vertical nonlinear elastic restoring forces, causing the two elastic beams to produce nonlinear displacements in the vertical direction.

[0010] Preferably, the piezoelectric elements are arranged in two symmetrical groups, and are respectively located on the first elastic beam and the second elastic beam.

[0011] Preferably, different magnetic interactions occur when the trolley is in different positions, thereby generating different forms of potential energy.

[0012] Preferably, the potential energy function of the system is switched between the monostable, bistable and tristable modes by tracking and changing the initial position of the vehicle.

[0013] Preferably, when the displacement of the trolley is small, the deformation of the elastic beam generates a linear vertical stiffness; and under the influence of the vertical displacement, the piezoelectric element generates an induced voltage.

[0014] Preferably, a plurality of bolts for fixing with external devices are reserved on the base.

[0015] Preferably, the fourth magnet mounted on the first elastic beam and the first magnet mounted on the second elastic beam are located at the same horizontal height.

[0016] Preferably, the second magnet is fixed to the second elastic beam by a fastener, and the second elastic beam is fastened together with the first elastic beam.

[0017] Preferably, the second elastic beam is not fixed to the first elastic beam at the installation position facing the first magnet, and the first elastic beam and the second elastic beam maintain relative movement at this position.

[0018] Preferably, the piezoelectric element fixed on the first elastic beam is arranged close to the fourth magnet and is located on a side of the fourth magnet away from the first magnet;

[0019] The piezoelectric element fixed on the second elastic beam is arranged close to the second magnet and is located on a side away from the third magnet.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] 1. The design of the energy harvesting device is based on the structural characteristics of spatially stacked cantilever beams. Compared with existing dual-degree-of-freedom magnet-spring oscillator energy harvesting devices, this structure is compact and can save space.

[0022] 2. The interaction between the magnets makes the stiffness of the system nonlinear and has low dynamic stiffness, which is conducive to low-frequency energy harvesting;

[0023] 3. By changing the initial position of the car, the potential energy form of the system is changed, which is suitable for excitation in various environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 3D schematic diagram of an energy harvesting system with time-varying electric potential.

[0025] Figure 2 When the parameter α=1, the parameter Characteristics of the system's potential energy function as it changes.

[0026] Figure 3(a) shows the distribution images of the three initial positions of the car.

[0027] FIG3( b ) is a time series of a function of potential change under the change of the control parameter Y value.

[0028] Figure 3(c) shows the control parameter ω a Time series of a function of potential change under changing value.

[0029] Figure 4 When the parameter α=1, the parameter Characteristics of the system's potential energy function as it changes.

[0030] Figure 5 is the nonlinear characteristic of the cart at its static potential energy when the cart is at position 1.

[0031] Figure 6 Based on Figure 6 The distribution of the basins of attraction is shown, giving the phase trajectory curve of the system in each color region.

[0032] Figure 7 is the nonlinear characteristic of the cart under its static potential energy when the cart is at position 3.

[0033] Figure 8 Based on Figure 8The distribution of the basins of attraction is shown, giving the phase trajectory curve of the system in each color region.

[0034] Figure 9 is the nonlinear characteristic of the cart under its static potential energy when the cart is at position 2.

[0035] Figure 10 Based on Figure 10 The distribution of the attraction basins shown gives the phase trajectory curve of the system in each color region.

[0036] Figure 11 When the parameter Y is 0.25, the parameter ω is the horizontal coordinate, and the parameter ω a As the vertical axis, the distribution diagram of the RMS value of the system induced voltage when the car is at different initial positions is plotted.

[0037] Figure 12 When the parameter Y is 0.5, the parameter ω is the horizontal coordinate, and the parameter ω a As the vertical axis, the distribution diagram of the RMS value of the system induced voltage when the car is at different initial positions is plotted.

[0038] Figure 13 When the parameter Y is 0.75, the parameter ω is the horizontal coordinate, and the parameter ω a As the vertical axis, the distribution diagram of the RMS value of the system induced voltage when the car is at different initial positions is plotted.

[0039] Figure 14 When the parameter Y is 0.75, the parameter ω is the horizontal coordinate, and the parameter As the vertical axis, the distribution diagram of the RMS value of the system induced voltage when the car is at different initial positions is plotted.

[0040] Figure numerals: 1. piezoelectric element; 2. first elastic beam; 3. second elastic beam; 41. first magnet; 42. second magnet; 43. third magnet; 44. fourth magnet; 5. bolt; 6. base; 7. guide rail; 8. trolley. DETAILED DESCRIPTION

[0041] Example 1

[0042] like Figure 1 As shown, the present invention proposes a compact energy harvesting device with time-varying potential energy, the energy harvesting device includes at least one region that can adjust the potential energy form of the system and the energy harvesting effective frequency band; at the same time, the energy harvesting device has a certain spatial compactness;

[0043] The energy collection device includes a base 6 for support, a movable trolley 8 and at least two elastic beams;

[0044] The base 6 is used to provide basic support for the entire energy collection device. Several bolts 5 are reserved on the base 6 for fixing to external devices. An upwardly protruding platform is provided on one side of the base 6. The fourth magnet 44 mounted on the first elastic beam 2 and the first magnet 41 mounted on the second elastic beam 3 are located at the same level. The first elastic beam 2 is mounted on this platform. A guide rail 7 is provided at the other end of the base 6. The trolley 8 slides along the guide rail 7.

[0045] The second elastic beam 3 is arranged on the first elastic beam 2, and a first magnet 41 and a second magnet 42 are respectively arranged at both ends of the second elastic beam 3, and two sets of third magnets 43 are arranged on the corresponding trolley 8; the third magnets 43 and the second magnets 42 generate magnetic interaction;

[0046] The first magnet 41 generates magnetic interaction with the fourth magnet 44 provided on the first elastic beam 2;

[0047] When the energy harvesting device is subjected to external mechanical excitation, the two elastic beams produce displacements in two degrees of freedom; the two groups of magnets at the left and right ends interact in their respective degrees of freedom and generate vertical nonlinear elastic restoring forces, causing the two elastic beams to produce nonlinear displacements in the vertical direction.

[0048] Two symmetrical groups of piezoelectric elements 1 are arranged, one on the first elastic beam 2 and the other on the second elastic beam 3. The second magnet 42 is fixed to the second elastic beam 3 by fasteners, which also secure the second elastic beam 3 to the first elastic beam 2. The second elastic beam 3 is not fixed to the first elastic beam 2 at the installation position facing the first magnet 41, and the first and second elastic beams 2 and 3 maintain relative motion at this position. The piezoelectric element 1 fixed to the first elastic beam 2 is placed in close proximity to the fourth magnet 44 and is located on the side of the fourth magnet 44 away from the first magnet 41. The piezoelectric element 1 fixed to the second elastic beam 3 is placed in close proximity to the second magnet 42 and is located on the side away from the third magnet 43.

[0049] In this embodiment, different magnetic interactions occur when the cart 8 is in different positions, generating different forms of potential energy. By tracking and changing the initial position of the cart 8, the system's potential energy function switches between three modes: monostable, bistable, and tristable. When the displacement of the cart 8 is small (within 10% of the geometric dimensions (length) of the elastic beam), the deformation of the elastic beam produces a linear vertical stiffness; affected by the vertical displacement, the piezoelectric element 1 generates an induced voltage.

[0050] In this embodiment, the model of the energy harvesting device is as follows:

[0051] The Euler-Lagrange equations are composed of the mechanical coordinates (q1, q2) and the voltage coordinates (U P1 ,U P2) is represented. Therefore, assuming that the matrix Q

[0052] Q=[q1(t),q2(t),U P1 (t),U P2 (t)] (1)

[0053] Afterwards, you can get

[0054]

[0055] Where Γ = T - E + W, where T is the kinetic energy, E is the potential energy (primarily determined by the interaction between the magnets and the vertical stiffness of the elastic beam), W is the total piezoelectrically induced energy, and t is time. Furthermore, the vertical displacement of the elastic beam also produces a certain damping effect, and the energy dissipated by this damping effect is represented by C.

[0056] Fitting the interaction force of the magnetic blocks to obtain the polynomial of the elastic restoring force of the system in two independent cases

[0057] f1(q1)=a1q1+b1q1 3 +e1q1 5 (3)

[0058] f2(q2)=a2q2+b2q2 3 (4)

[0059] At this time, the potential energy of the system is shown in formula (5), and the kinetic energy of the system is shown in formula (6)

[0060]

[0061] Where a1, b1, a2, b2 and e1 are the Duffing coefficients of the magnetic interaction effect, k1 and k2 are the vertical stiffness of the piezoelectric beam, and m i is the mass parameter of the mass element.

[0062] The effect produced by the piezoelectric sensing device can be expressed in terms of electrical energy, and the dissipated energy of the system can be described by the sum of the Rayleigh dissipation function and the electrical dissipation function:

[0063]

[0064] Among them C Pi is the capacitance of the piezoelectric element, θ1 and θ2 are the electromechanical coupling constants, R i is the equivalent resistance of the load and piezoelectric element circuit, c i is the viscous damping coefficient.

[0065] When constructing the dynamic model of the system, it is assumed that the system is subjected to external mechanical disturbances and its motion is in the form of harmonics.

[0066] By dimensionlessly processing formulas (9)-(12), we can obtain

[0067]

[0068] in

[0069] ζ1=c1 / (2ω1m1), ζ2=c2 / (2ω1m1), δ1=a1 / (ω1 2 m1),η1=b1 / (ω1 2 m1),μ1=e1 / (ω1 2 m1),α=m2 / m1, δ2=a2 / (ω1 2 m1),η2=b2 / (ω1 2 m1), φ1=θ1U0 / (k1l), φ2=θ2U0 / (k1l), x1=q1 / l, x2=q2 / l, ρ1=1 / (C P1 R1ω1),ρ2=1 / (C P2 R2ω1),σ1=θ1l / (C P1 V),σ2=θ2l / (C P2 V),A=A0ω 2 / l,ω=ω0 / ω1,τ=ω1t.

[0070] In this embodiment, the design of this compact energy harvesting device with time-varying potential energy can greatly save the space occupied by the energy harvesting device. By changing the initial position of the trolley on the sliding track, the system's potential energy function can be switched between three modes: monostable, bistable, and tristable. The combination of two-degree-of-freedom systems enables the system to adapt to various excitation environments. The control function effectively drives the trolley, which can significantly increase the peak value of the system's induced voltage and the width of its effective working range.

[0071] Example 2

[0072] The trend toward miniaturization of electronic components has led to reduced energy consumption, ultimately making wireless sensing devices increasingly popular in a growing number of technological applications. Wireless sensors require self-powering, while primary batteries are expensive to manage. Therefore, an autonomous energy source is needed to power wireless sensor nodes and electronic devices. The human environment contains numerous vibration sources, such as those caused by electromechanical devices, human motion, water flow, and wind. This vibration energy can be converted into electricity through piezoelectric or electromagnetic effects, making it a promising candidate for addressing the energy supply challenges faced by wireless sensors.

[0073] The following will be combined with the accompanying drawings in this patent to describe the technical solution in more detail. This embodiment is only used to explain the present invention and does not constitute a limitation on the scope of protection of the present invention.

[0074] like Figure 1 As shown, the design of the energy harvester is based on the structural properties of spatially stacked cantilever beams and the theory of nonlinear restoring forces generated by the interaction of multiple sets of magnets. The device consists of two elastic beams: the green elastic beam I (connected to elastic beam I at its right end) and the peripheral white elastic beam II (connected to a support on the base at its left end). When the energy harvester is subjected to external mechanical excitation, the two elastic beams produce displacements in two degrees of freedom, with four displacement modes. The two sets of magnets at the left and right ends interact in their respective degrees of freedom, generating vertical nonlinear elastic restoring forces that cause the two elastic beams to undergo nonlinear vertical displacements. A cart equipped with magnets can be adjusted on a guide rail, tracking changes in its initial position. Different magnetic interactions occur at different cart positions, generating different forms of potential energy. When the displacement is small, the deformation of the piezoelectric beams produces a linear vertical stiffness (ignoring the effects of higher-order modes). The piezoelectric element generates an induced voltage due to the vertical displacement.

[0075] The stability analysis can be illustrated by evaluating the dimensionless form of the potential energy function (Eq. (17)). Figure 2 When the parameter α=1, the parameter Characteristics of the system's potential energy function under varying conditions. The distribution of the colored regions reflects the potential energy distribution of the system under two displacement combinations. Yellow dots represent stable equilibrium positions, red triangles represent unstable saddle equilibrium positions, and blue polygons represent unstable source equilibrium positions.

[0076] Figure 2 Parameters are displayed The stability distribution of the value of the multi-color diagram represents the potential energy value, darker colors represent lower potential energy, and lighter colors represent higher potential energy. In the smaller case, there are 15 equilibrium positions in the system, of which 6 are stable, 7 are unstable saddle type, and 2 are unstable source type. As the parameter α increases, the symmetry of the color region changes, and the spacing between unstable and stable saddle points also changes (as the distance between a stable point and one of the saddle points decreases, the spacing between the stable point and the other direction increases). When the system is reduced to 11 equilibrium points, 4 of which are stable, 5 are unstable saddle points, and 2 are source-type points. As the parameter continues to increase, the width of the colored region of the potential energy function narrows. The source-type unstable points disappear, and the number of equilibrium points decreases from 11 to 3. The system also leaves the tristable state.

[0077] The parameter Y defines the percentage range of the cart's displacement relative to its maximum motion, which is limited by Position 1 and Position 2. On the other hand, ω a is the frequency at which the car reaches the limit position defined by Y. Figure 3(a) shows the distribution of the three initial positions of the car (position 1, position 3, and position 2). (b) shows the time series of the potential change function under the change of the control parameter Y. (c) shows the time series of the potential change function under the change of the control parameter ω. a .

[0078] Figure 4 Shows three different initial positions of the car and the parameter ω a And the influence of parameter Y on the control function.

[0079] When the value of Υ is 0, we are dealing with a static potential energy function that does not change with time. At this time, the change of the potential energy function of the system at different initial positions can be referred to Figure 4 . Figure 4 When the parameter α=1, the parameter Characteristics of the system's potential energy function under varying conditions. The distribution of the colored regions reflects the potential energy distribution of the system under two displacement combinations. Yellow points represent stable equilibrium positions, red triangles represent unstable saddle equilibrium positions, and blue polygons represent unstable source equilibrium positions. The control function affects the nonlinear terms of the system, and the potential energy graph shows how the system's steady-state form and the number of equilibrium points are affected. By adjusting the initial position of the cart, the system's steady-state form, the depth of the potential well, and the height of the potential barrier can be changed.

[0080] There is an inseparable correlation between the nonlinear motion behavior of a system and the properties of the coexistence solution. The choice of initial displacement and initial velocity (initial values) on the phase trajectory plane will directly determine the properties of the system's coexistence solution. Multiple attractors may appear simultaneously on the phase trajectory plane, each corresponding to a stable trajectory. By giving a series of different initial value choices in the phase trajectory plane, the distribution of different stable trajectories of the system within this range (the distribution of attraction basins) can be obtained. From the perspective of theoretical analysis and practical application, people are interested in ultimately determining the stable phase trajectory from a certain initial state.

[0081] Table 1 Expressions and mathematical meanings of system parameters

[0082]

[0083]

[0084] The performance analysis of energy harvesting devices is usually defined by electrical output variables. To test the effectiveness of the system's energy harvesting, many qualitative indicators are available, the most commonly used of which is based on the root mean square value of the voltage induced on the piezoelectric electrodes. To evaluate the energy harvesting efficiency of the system, the root mean square (RMS) value of the piezoelectric device voltage is used as a metric. Using this visualization of computer simulation results, we can evaluate the control parameter ω( Figure 5 (a) Figure 7 (a) and Figure 9 (a) Energy harvesting effectiveness under a wide range of variations.

[0085] Figure 5 The nonlinear characteristics of the cart are studied under its static potential energy when it is at position 1. (a) shows the distribution of the RMS value of the induced voltage in the system as the frequency of the external excitation varies. (b), (d), and (f) show the distribution of the attraction basin of the system's first degree of freedom at different excitation frequencies. (c), (e), and (g) show the distribution of the attraction basin of the system's second degree of freedom at different excitation frequencies. (Note: The initial value of the attraction basin is selected based on the phase trajectory plane of the first degree of freedom.) Figure 5 (b)-(g) show the distribution of the system's basin of attraction at different excitation frequencies when the cart is in position 1. The percentage of the area of each basin of attraction within its given region (A is the area scale factor) is given in the form of a pie chart. On the other hand, Figure 6 Based on Figure 5 The distribution of the basins of attraction is shown, and the phase trajectory curve of the system in each color region is given. Unlike the plane chosen for the initial value, the phase trajectory coordinates here are expressed in terms of the respective degrees of freedom. Figure 6 Given Figure 5 Phase trajectory curves within the attraction basin in (b)-(g). To achieve correct correspondence, the color of the phase trajectory curve corresponds to the color of the attraction basin. In the RMS value image of the induced voltage, there are smooth and sudden segments. We define the location of the sudden change in the RMS value as a "fault." Near the "fault," the structure of the attraction basin is very likely to form an irregular band characterized by strong mixing. The occurrence of in-well vibrations often occurs in smooth segments with lower energy distribution. Due to different initial values, the system produces single-cycle in-well vibrations and multi-cycle in-well oscillations in different stable regions (potential wells), which is determined by the combination of the steady-state forms of each degree of freedom. The nonlinear characteristics of the system are more obvious near the "fault." At this time, the system's sensitivity to the initial value increases. With different choices of initial values, the initial high-energy inter-well vibration will be transformed into low-energy in-well vibration.

[0086] Different from position 1, when the cart is in position 3, the system has a flatter potential well, which contributes to the smooth operation and energy harvesting of the system. Figure 7The nonlinear characteristics of the cart are studied under its static potential energy when it is at position 3. (a) shows the distribution of the RMS value of the induced voltage in the system as the frequency of the external excitation varies. (b), (d), and (f) show the distribution of the attraction basin of the system's first degree of freedom at different excitation frequencies. (c), (e), and (g) show the distribution of the attraction basin of the system's second degree of freedom at different excitation frequencies. (Note: The initial value of the attraction basin is selected based on the phase trajectory plane of the first degree of freedom.) Figure 7 (b)-(g) show the distribution of the system’s basin of attraction in each frequency band when the cart is at position 3. Figure 8 Based on Figure 7 The distribution of the basins of attraction is shown, and the phase trajectory curve of the system in each color region is given. Unlike the plane chosen for the initial value, the phase trajectory coordinates here are expressed in terms of the respective degrees of freedom. Figure 8 Shows Figure 7 By observing the given information of the basin of attraction. Figure 7 (d) Figure 7 (f) Figure 8 (c) and Figure 8 In Figure (e), it's easy to see that the high-energy trajectory of the first degree of freedom occupies the vast majority of the area. This is the advantage of a flat potential well. In this case, the system can more easily break through the potential barrier, achieving high-energy single-cycle or multi-cycle inter-well oscillations.

[0087] When the car is in position 2, the nonlinear characteristics of the first degree of freedom of the system disappear and are replaced by a linear form. Therefore, we lose interest in studying the first degree of freedom. Figure 9 The nonlinear characteristics of the cart are investigated under its static potential when it is at position 2. (a)-(g) show the distribution of the second degree of freedom basin of attraction for different excitation frequencies. (Note: The initial value of the basin of attraction is selected based on the phase trajectory plane of the second degree of freedom.) Figure 9 The drawing plane of the attraction basin is built on the phase trajectory plane of the second degree of freedom. Since the second degree of freedom is not affected by the position of the car, it is always in a bistable state. Figure 9 As shown in (a), since the first degree of freedom is presented in a linear form, the high-energy distribution area of the RMS value of the induced voltage of the first degree of freedom becomes narrower. Figure 9 (b)-(f) show the distribution of the second degree of freedom attraction basin of the system in each frequency band. When the excitation frequency is close to 1.5, the induced voltage on the first and second degrees of freedom will reach the maximum. The area of the high energy attraction basin near this frequency increases. Figure 9 The yellow area in (d) accounts for 48.2% of the area. In contrast, the area farther from the peak frequency ( Figure 9 (g)) accounts for only 2.6%.

[0088] Based on the given position of the car, the energy harvesting effect of the system in the form of time-varying potential energy is evaluated. The target parameters of the test are Υ and ω a From a dynamics point of view, it is reasonable to change one parameter while keeping another constant.

[0089] Figures 11 to 13 The numerical results given in show that the parameters The effect of changes in the parameter Y on the system's energy harvesting effectiveness is shown. This includes the RMS value of the induced voltage in the first degree of freedom and the RMS value of the induced voltage in the second degree of freedom. The induced voltage in the first degree of freedom is limited by the mechanical displacement of the first degree of freedom, while the displacement difference between the two degrees of freedom determines the induced voltage in the second degree of freedom.

[0090] The increase of parameter Y can improve the peak value of the RMS value of the induced voltage in all aspects and widen the width of the effective working frequency band of energy harvesting. Figure 11 (a) and Figure 13 (a), we can see this more clearly. When the parameter Υ = 0.25, the energy harvesting performance of the system has a clear advantage when the car is at position 3. This is the advantage provided by the flat tristable potential energy function. However, considering the time-varying nature of the system's potential energy function, as the parameter Υ increases, the flatness of the potential energy function is destroyed. By observing Figure 11 and Figure 13 , it can be seen that the original advantages of high energy and wider working frequency band of position 3 no longer exist. At this time, when the initial position of the car is position 1, the performance of the energy harvesting system will reach the highest.

[0091] Parameter ω a The effect of the change on the energy harvesting efficiency of the system is not always favorable. a The value of is large (ω a >4), the energy collection efficiency of the system is likely to decrease, which is manifested in a decrease in the peak value of the RMS value of the system induced voltage or a narrowing of the effective operating frequency band of the system. a ∈[1,4], the energy harvesting efficiency of the system may be optimal (analysis of the induced voltage generated in the first degree of freedom). a Larger values of may also produce beneficial effects (for the second degree of freedom). Figure 13 As shown in (b), when ω a When the value is larger, the peak value of the induced voltage generated by the piezoelectric piece located at the second degree of freedom position increases, while the effective operating frequency does not become narrower.

[0092] With parameter ω as the horizontal coordinate, parameter The RMS value of the induced voltage in the system is plotted on the vertical axis, as Figure 14 Parameters The change of mainly affects the energy harvesting performance of the second degree of freedom of the system. Before the value reaches 1.8, the peak value of the RMS value of the induced voltage of the system and the width of the effective working area increase with Subsequently, the RMS values of the induced voltages of the two degrees of freedom of the system begin to decrease, among which the change of the induced voltage of the first degree of freedom is not significant. The situation of the second degree of freedom is different. When the value of is greater than 4, the RMS value of the induced voltage shows a clear downward trend. After comprehensive evaluation, when the parameters When the value of is in the range of 1.5 to 2, the overall energy harvesting efficiency of the system will be maximized.

[0093] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A compact energy harvesting device with time-varying potential energy, characterized in that: The energy harvesting device includes at least one region capable of adjusting the potential energy form of the system and the effective energy harvesting frequency band; and the energy harvesting device has a certain spatial compactness; The energy collection device comprises a base (6) for support, a movable trolley (8) and at least two elastic beams; The base (6) is used to provide basic support for the entire energy collection device. An upwardly protruding platform is provided on one side of the base (6); a first elastic beam (2) is provided on the platform; a guide rail (7) is provided at the other end of the base (6); and a trolley (8) slides along the guide rail (7); The second elastic beam (3) is arranged on the first elastic beam (2), and a first magnet (41) and a second magnet (42) are respectively arranged at both ends of the second elastic beam (3), and two groups of third magnets (43) are arranged on the corresponding trolley (8); the third magnets (43) and the second magnets (42) generate magnetic interaction; The first magnet (41) generates magnetic interaction with a fourth magnet (44) arranged on the first elastic beam (2); When the energy harvesting device is subjected to external mechanical excitation, the two elastic beams produce displacements in two degrees of freedom. The two sets of magnets at the left and right ends interact with each other in their respective degrees of freedom and generate vertical nonlinear elastic restoring forces, causing the two elastic beams to produce nonlinear displacements in the vertical direction.

2. A compact energy harvesting device with time-varying potential energy according to claim 1, characterized in that: The piezoelectric elements (1) are arranged in two symmetrical groups and are respectively located on the first elastic beam (2) and the second elastic beam (3).

3. The compact energy harvesting device with time-varying potential energy according to claim 1, characterized in that: Different magnetic interactions occur when the trolley (8) is in different positions, thereby generating different forms of potential energy.

4. The compact energy harvesting device with time-varying potential energy according to claim 1, characterized in that: By tracking and changing the initial position of the trolley (8), the potential energy function of the system is switched between the three modes of monostable, bistable and tristable; the combination of the two-degree-of-freedom systems enables the system to adapt to various different excitation environments; the control function effectively drives the trolley to increase the peak value of the induced voltage of the system and the width of the effective working range.

5. The compact energy harvesting device with time-varying potential energy according to claim 2, characterized in that: When the displacement of the trolley (8) is small, the deformation of the elastic beam generates a linear vertical stiffness; under the influence of the vertical displacement, the piezoelectric element (1) generates an induced voltage.

6. The compact energy harvesting device with time-varying potential energy according to claim 1, characterized in that: A plurality of bolts (5) for fixing with external devices are reserved on the base (6).

7. The compact energy harvesting device with time-varying potential energy according to claim 2, characterized in that: The fourth magnet (44) mounted on the first elastic beam (2) and the first magnet (41) mounted on the second elastic beam (3) are located at the same level.

8. The compact energy harvesting device with time-varying potential energy according to claim 2, characterized in that: The second magnet (42) is fixed to the second elastic beam (3) via a fastener, and the second elastic beam (3) and the first elastic beam (2) are fastened together.

9. The compact energy harvesting device with time-varying potential energy according to claim 8, characterized in that: The second elastic beam (3) is not fixed to the first elastic beam (2) at the installation position facing the first magnet (41), and the first elastic beam (2) and the second elastic beam (3) maintain relative movement at this position.

10. The compact energy harvesting device with time-varying potential energy according to claim 2, characterized in that: The piezoelectric element (1) fixed on the first elastic beam (2) is arranged close to the fourth magnet (44) and is located on a side of the fourth magnet (44) away from the first magnet (41); The piezoelectric element (1) fixed on the second elastic beam (3) is arranged close to the second magnet (42) and is located on a side away from the third magnet (43).

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