CN117220536A - Multi-ball impact broadband piezoelectric vibration energy collection device and method under low-frequency vibration - Google Patents

Abstract

The invention belongs to the technical field of energy acquisition devices, and particularly relates to a multi-ball impact broadband piezoelectric vibration energy acquisition device and method under low-frequency vibration; wherein, an L-shaped fixing plate is fixed in the U-shaped base plate, and the pipeline is sleeved in the two L-shaped fixing plates; the first cantilever beam is fixed in the U-shaped substrate, a piezoelectric layer is fixed on the first cantilever beam, namely the free end stretches into the pipeline, and a permanent magnet is fixed on the first cantilever beam; the piezoelectric layers are fixed on the third cantilever beam and the second cantilever beam and extend into the pipeline at the same time, and the inner side of the piezoelectric layers is fixed with a permanent magnet; the rear end of the pipeline is provided with a fourth cantilever beam, and a permanent magnet is fixed on the fourth cantilever beam; balls are respectively arranged at two sides of the pipeline; the piezoelectric layer is connected with the corresponding energy accumulator through a lead; the invention can efficiently collect vibration energy under the condition of ultralow frequency to low frequency vibration, is suitable for energy collection under various low frequency vibration environments, and has the advantages of simple structure, wide working frequency band, easy adjustment, convenient maintenance and the like.

Description

Multi-ball impact broadband piezoelectric vibration energy collection device and method under low-frequency vibration

Technical Field

The invention belongs to the technical field of energy acquisition devices, and particularly relates to a multi-ball impact broadband piezoelectric vibration energy acquisition device and method under low-frequency vibration.

Background

With the development of the internet of things and wireless sensors, low-power consumption electronic devices require a durable energy supply. The traditional chemical battery needs to be replaced frequently, and is large in size and short in service life, needs to be replaced or charged irregularly, and is especially not suitable for remote working occasions which cannot be reached by human beings and are high in service life requirement. Therefore, the development of a sustainable power supply green energy supply device has important practical significance.

In natural environment, various kinds of energy which can be collected and utilized exist, and scientific researchers put forward an environmental energy collection concept, namely, the environmental energy (such as light energy, wind energy, heat energy, vibration energy and the like) of the natural environment is collected through a miniature energy collector and is converted into electric energy to be stored in an energy storage device such as a battery, a capacitor and the like so as to meet the use requirements of micro devices and micro systems. In a plurality of environmental energies, solar energy and wind energy are easily influenced by the environment, so that the energy output efficiency is low, heat energy is required to be converted into electric energy through the temperature difference of a large-scale environment, a large heat dissipation groove is required, the total size of the system is increased, and the structure is not easy to miniaturize; vibration energy is a more common form of energy such as heart beating, arm and leg swing, natural plant swing, bird flapping wing, fish tail swing when a person walks. Thus, harvesting techniques by which vibrational energy is harvested and converted to electrical energy have a wider range of energy sources and applications.

Among the existing vibration energy collection modes, piezoelectric mode is a more common mode and is characterized by simple structure and compatibility with micro-machining technology. However, most piezoelectric vibration energy harvesting devices are based on linear conversion models and single cantilever structures only, and cannot adapt to a broadband random vibration environment in reality. In addition, most of vibration in natural environment is low-frequency vibration, and the vibration is far away from the resonance frequency of the cantilever beam, so that the output voltage of the linear conversion model and the single cantilever structure is very low, and the energy of the low-frequency vibration cannot be effectively collected.

Disclosure of Invention

In order to overcome the problems, the invention provides a multi-ball impact broadband piezoelectric vibration energy collecting device and a method under low-frequency vibration, which can collect the vibration energy in a broadband frequency range under the low-frequency vibration.

The broadband piezoelectric vibration energy collecting device comprises a U-shaped substrate 1, a first cantilever beam 2, a first piezoelectric layer 3, a second cantilever beam 4, a second piezoelectric layer 5, a first L-shaped fixing plate 6, a second L-shaped fixing plate 7, a third cantilever beam 8, a pipeline 9, a fourth cantilever beam 10, a third piezoelectric layer 11, a first small ball 12, a second small ball 13, a first permanent magnet 15, a second permanent magnet 16, a third permanent magnet 17, a fourth permanent magnet 18, a first energy accumulator 19, a second energy accumulator 20 and a third energy accumulator 21; the left and right sides of the pipeline 9 are respectively sleeved in the second L-shaped fixing plate 7 and the first L-shaped fixing plate 6; the front end of the first cantilever beam 2 is fixed on the inner side of the front end of the U-shaped substrate 1, the right side of the front end of the first cantilever beam 2 is fixed with a first piezoelectric layer 3, the rear end, namely the free end, of the first cantilever beam 2 extends into the center of the pipeline 9, and the left side of the first cantilever beam 2 positioned in the center of the pipeline 9 is fixed with a first permanent magnet 15; the rear ends of the third cantilever beam 8 and the second cantilever beam 4 are respectively fixed on the left side and the right side of the inner side of the rear end of the U-shaped substrate 1, a third piezoelectric layer 11 and a second piezoelectric layer 5 are respectively fixed outside the rear ends of the third cantilever beam 8 and the second cantilever beam 4, meanwhile, the front ends, namely the free ends, of the third cantilever beam 8 and the second cantilever beam 4 respectively extend into the pipeline 9, and a second permanent magnet 16 and a third permanent magnet 17 are respectively fixed inside the third cantilever beam 8 and the second cantilever beam 4 positioned inside the pipeline 9; the rear end of the pipeline 9 is provided with a fourth cantilever beam 10, wherein the right side of the fourth cantilever beam 10 is fixed on the inner side of the first L-shaped fixing plate 6, and a fourth permanent magnet 18 is fixed on the left side of the fourth cantilever beam 10, namely in front of the free end; a first ball 12 capable of freely moving is arranged in the pipeline 9 between the first cantilever beam 2 and the third cantilever beam 8, and a second ball 13 capable of freely moving is arranged in the pipeline 9 between the first cantilever beam 2 and the second cantilever beam 4;

the first energy accumulator 19 is fixed on the inner side of the front end of the U-shaped base plate 1, and the third energy accumulator 21 and the second energy accumulator 20 are respectively fixed on the left side and the right side outside the rear end of the U-shaped base plate 1; the first piezoelectric layer 3 is connected to the first energy store 19 by means of wires, the second piezoelectric layer 5 is connected to the second energy store 20 by means of wires, and the third piezoelectric layer 11 is connected to the third energy store 21 by means of wires.

The middle part of the pipeline 9 is provided with a square hole for placing the first permanent magnet 15, the pipeline 9 outside the first L-shaped fixing plate 6 is provided with a square hole for placing the third permanent magnet 17, and the pipeline 9 outside the second L-shaped fixing plate 7 is provided with a square hole for placing the second permanent magnet 16.

The shape of the pipe 9 is round or square.

The first pellets 12 and the second pellets 13 are round or cylindrical in shape.

The first small balls 12 are positioned in the pipeline 9 between the first cantilever beam 2 and the third cantilever beam 8, and the number is N ₁ ,N ₁ Greater than or equal to 0.

The second pellets 13 are positioned in the pipeline 9 between the first cantilever beam 2 and the second cantilever beam 4, and the number is N ₂ ，N ₂ Greater than or equal to 1.

The fourth cantilever beam 10 is placed vertically with respect to the first cantilever beam 2.

The fourth permanent magnet 18 and the first permanent magnet 15 are opposite in polarity, and repulsive force is generated between them.

The free ends of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 enter the pipeline 9 through square holes of the pipeline 9, the first small ball 12 collides with the first cantilever beam 2 and the third cantilever beam 8 when moving in the pipeline 9, and the second small ball 13 collides with the first cantilever beam 2 and the second cantilever beam 4 when moving in the pipeline 9.

A broadband piezoelectric vibration energy collection method for multi-ball impact under low-frequency vibration comprises the following steps:

step one, applying low-frequency excitation perpendicular to the direction of the first cantilever beam 2 to the U-shaped substrate 1, specifically: the broadband piezoelectric vibration energy collecting device is fixed on a horizontal sliding rail through bolts 14, when the broadband piezoelectric vibration energy collecting device is fixed, the radial direction of a pipeline 9 is consistent with the horizontal direction of the horizontal sliding rail, the horizontal sliding rail is driven by a servo motor, the servo motor is electrified, a driving signal of the servo motor is set to be a low-frequency harmonic signal, the servo motor generates low-frequency harmonic excitation, the horizontal sliding rail is driven to do periodic motion in the horizontal direction, and the whole device is driven to do periodic motion in the horizontal direction; the first small ball 12 and the second small ball 13 start to move in the pipeline 9 under the action of inertia force, and a differential equation of the movement of the first small ball 12 and the second small ball 13 is established, wherein the equation is as follows:

wherein m is _a And m _b The masses of the first small ball 12 and the second small ball 13 are respectively; f (f) _a And f _b Friction forces respectively applied to the first ball 12 and the second ball 13; x is X _a And X _b The displacement of the first small ball 12 and the second small ball 13 respectively; x is X _base Is the displacement of the U-shaped base plate 1; i _a And I _b The moment of inertia of the first ball 12 and the second ball 13 respectively; omega _a And omega _b Angular velocities of the first and second pellets 12, 13, respectively; r is (r) _a And r _b The radii of the first small ball 12 and the second small ball 13 are respectively;

step two, applying low-frequency excitation perpendicular to the direction of the first cantilever beam 2 to the U-shaped substrate 1, starting vibration of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10, and enabling the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered on the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 to generate bending deformation, and generating electric energy through positive piezoelectric effect; the equations of the motion differential equations of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 and the piezoelectric loop equations of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are established, and the formulas are as follows:

wherein M is ₁ 、M ₂ 、M ₃ 、M ₄ The mass of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 are respectively; c (C) ₁ 、C ₂ 、C ₃ 、C ₄ Equivalent damping of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 respectively; k (K) ₁ 、K ₂ 、K ₃ 、K ₄ Equivalent rigidities of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 are respectively; x is X ₁ 、X ₂ 、X ₃ 、Y ₁ The displacements of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 are respectively; θ ₁ 、θ ₂ 、θ ₃ The electromechanical coupling coefficients of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are respectively; v (V) ₁ 、V ₂ 、V ₃ Output voltages of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are respectively; c (C) _p1 、C _p2 、C _p3 Equivalent capacitances of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 respectively; r is R ₁ 、R ₂ 、R ₃ Equivalent resistances of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 respectively; f (F) _mx1 For the magnetic force applied to the first cantilever beam 2 in the horizontal direction, F _my1 Is the magnetic force applied to the first cantilever beam 2 in the vertical direction;

step three, when the first small ball 12 moves in the pipeline 9, the small ball collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8, when the second small ball 13 moves in the pipeline, the small ball collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, so that the free ends of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 can generate larger displacement under low-frequency excitation, and the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered to the root parts of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 generate larger bending deformation and generate more electric energy through positive piezoelectric effect, thereby realizing vibration energy acquisition under low-frequency excitation; after the first ball 12 collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8 and the second ball 13 collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, the speeds of the first ball 12, the second ball 13, the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 are obtained by the law of conservation of momentum, and the formula is as follows:

when the first ball 12 collides with the first cantilever beam 2:

when the first ball 12 collides with the third cantilever beam 8:

when the second pellet 13 collides with the first cantilever beam 2:

when the second ball 13 collides with the second cantilever beam 4:

angular velocity after impact of the first beads 12:

angular velocity after collision of the first beads 13:

wherein e is the collision loss coefficient; mu (mu) ₁ The friction coefficient of the first small ball 12 and the free end magnets of the first cantilever beam 2 and the third cantilever beam 8; mu (mu) ₂ The friction coefficient of the second small ball 13 and the free end magnets of the first cantilever beam 2 and the second cantilever beam 4;for the speed before collision of the first pellet 12, < >>Is the velocity of the first ball 12 after impact; />For the speed before collision of the second pellet 13, < >>Is the speed of the second pellets 13 after collision; />For the angular velocity before collision of the first pellet 12, is->Is the angular velocity after the collision of the first beads 12; />For the angular velocity before collision of the second pellet 13, is->Is the angular velocity after collision of the second pellets 13; />For the speed before collision of the first cantilever beam 2, is->Is the speed of the first cantilever beam 2 after collision; />For the speed before collision of the second cantilever beam 4, is->Is the speed of the second cantilever beam 4 after collision; />For the speed before collision of the third cantilever beam 8, is->Is the speed of the third cantilever beam 8 after collision;

under low-frequency excitation, the first small ball 12 frequently collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8, and the second small ball 13 frequently collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, so that the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered to the root parts of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 frequently generate larger bending deformation, the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 generate electric energy through positive piezoelectric effect, and the generated electric energy is transmitted to the first energy accumulator 19, the second energy accumulator 20 and the third energy accumulator 21 through wires carried on the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 for storage respectively, so that vibration energy collection under low-frequency excitation is realized.

The invention has the beneficial effects that:

1. according to the invention, as the plurality of pellets are placed in the pipeline, the pellets move in the pipeline under low-frequency excitation and impact the first cantilever beam, the second cantilever beam and the third cantilever beam, the free ends of the first cantilever beam, the second cantilever beam and the third cantilever beam are enabled to displace greatly, the piezoelectric layer is deformed greatly, larger electric energy output is obtained, and efficient vibration energy collection under low-frequency vibration is realized.

2. According to the invention, as the fourth cantilever beam is vertically arranged relative to the first cantilever beam, the polarities of the magnet on the fourth cantilever beam and the magnet on the first cantilever beam are opposite, repulsive force is generated between the magnets, and nonlinearity is introduced, so that the first cantilever beam can resonate under vibration excitation in a wider frequency range, and vibration energy collection in a wider range is realized.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following description will briefly explain the drawings to be used in the description of the embodiments of the present invention, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the contents of the embodiments of the present invention and these drawings without inventive effort for those skilled in the art.

FIG. 1 is a schematic diagram of the overall structure of the present invention;

FIG. 2 is a schematic view of the structure of the L-shaped fixing plate of the present invention;

FIG. 3 is a schematic view of the structure of the pipeline according to the present invention;

FIG. 4 is a 3/4 cross-sectional view of the piping structure of the present invention.

Detailed Description

The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.

Example 1

The broadband piezoelectric vibration energy collecting device comprises a U-shaped substrate 1, a first cantilever beam 2, a first piezoelectric layer 3 with leads, a second cantilever beam 4, a second piezoelectric layer 5 with leads, a first L-shaped fixing plate 6, a second L-shaped fixing plate 7, a third cantilever beam 8, a pipeline 9, a fourth cantilever beam 10, a third piezoelectric layer 11 with leads, a first small ball 12, a second small ball 13, a first permanent magnet 15, a second permanent magnet 16, a third permanent magnet 17, a fourth permanent magnet 18, a first energy accumulator 19, a second energy accumulator 20 and a third energy accumulator 21; the left and right sides of the pipeline 9 are respectively sleeved in the second L-shaped fixing plate 7 and the first L-shaped fixing plate 6; the front end of the first cantilever beam 2 is fixed on the inner side of the front end of the U-shaped substrate 1, the right side of the front end of the first cantilever beam 2 is fixed with a first piezoelectric layer 3, the rear end, namely the free end, of the first cantilever beam 2 extends into the center of the pipeline 9, and the left side of the first cantilever beam 2 positioned in the center of the pipeline 9 is fixed with a first permanent magnet 15; the rear ends of the third cantilever beam 8 and the second cantilever beam 4 are respectively fixed on the left side and the right side of the inner side of the rear end of the U-shaped substrate 1, a third piezoelectric layer 11 and a second piezoelectric layer 5 are respectively fixed outside the rear ends of the third cantilever beam 8 and the second cantilever beam 4, meanwhile, the front ends, namely the free ends, of the third cantilever beam 8 and the second cantilever beam 4 respectively extend into the pipeline 9, and the inner sides of the third cantilever beam 8 and the second cantilever beam 4 positioned inside the left side and the right side of the pipeline 9 are respectively fixed with a second permanent magnet 16 and a third permanent magnet 17; the rear end of the pipeline 9 is provided with a fourth cantilever beam 10, wherein the right side of the fourth cantilever beam 10 is fixed on the inner side of the first L-shaped fixing plate 6, and a fourth permanent magnet 18 is fixed on the left side of the fourth cantilever beam 10, namely in front of the free end; a first ball 12 capable of freely moving is arranged in the pipeline 9 between the first cantilever beam 2 and the third cantilever beam 8, and a second ball 13 capable of freely moving is arranged in the pipeline 9 between the first cantilever beam 2 and the second cantilever beam 4;

the first energy accumulator 19 is fixed on the inner side of the front end of the U-shaped base plate 1, and the third energy accumulator 21 and the second energy accumulator 20 are respectively fixed on the left side and the right side outside the rear end of the U-shaped base plate 1; the first piezoelectric layer 3 is connected to the first energy store 19 by means of wires, the second piezoelectric layer 5 is connected to the second energy store 20 by means of wires, and the third piezoelectric layer 11 is connected to the third energy store 21 by means of wires.

The middle part of the pipeline 9 is provided with a square hole for placing the first permanent magnet 15, the pipeline 9 outside the first L-shaped fixing plate 6 is provided with a square hole for placing the third permanent magnet 17, and the pipeline 9 outside the second L-shaped fixing plate 7 is provided with a square hole for placing the second permanent magnet 16.

The shape of the pipe 9 is round or square.

The first pellets 12 and the second pellets 13 are round or cylindrical in shape.

The first small balls 12 are positioned in the pipeline 9 between the first cantilever beam 2 and the third cantilever beam 8, and the number is N ₁ ,N ₁ Greater than or equal to 0.

The second pellets 13 are positioned in the pipeline 9 between the first cantilever beam 2 and the second cantilever beam 4, and the number is N ₂ ，N ₂ Greater than or equal to 1.

The fourth cantilever beam 10 is placed vertically with respect to the first cantilever beam 2.

The fourth permanent magnet 18 and the first permanent magnet 15 are opposite in polarity, and repulsive force is generated between them. I.e. the N-pole of the fourth permanent magnet 18 is opposite to the N-pole of the first permanent magnet 15 or the S-pole of the fourth permanent magnet 18 is opposite to the S-pole of the first permanent magnet 15.

The free ends of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 enter the pipeline 9 through square holes of the pipeline 9, the first small ball 12 collides with the first cantilever beam 2 and the third cantilever beam 8 when moving in the pipeline 9, and the second small ball 13 collides with the first cantilever beam 2 and the second cantilever beam 4 when moving in the pipeline 9.

A broadband piezoelectric vibration energy collection method for multi-ball impact under low-frequency vibration comprises the following steps:

step one, a first small ball 12 is placed between the first cantilever beam 2 and the third cantilever beam 8, and a second small ball 13 is placed between the first cantilever beam 2 and the second cantilever beam 4; the U-shaped substrate 1 is subjected to low frequency excitation perpendicular to the direction of the first cantilever beam 2, specifically: the broadband piezoelectric vibration energy collecting device is fixed on a horizontal sliding rail through bolts 14, when the broadband piezoelectric vibration energy collecting device is fixed, the radial direction of a pipeline 9 is consistent with the horizontal direction of the horizontal sliding rail, the horizontal sliding rail is driven by a servo motor, the servo motor is electrified, a driving signal of the servo motor is set to be a low-frequency harmonic signal, the servo motor generates low-frequency harmonic excitation, the horizontal sliding rail is driven to do periodic motion in the horizontal direction, and the whole device is driven to do periodic motion in the horizontal direction; the first small ball 12 and the second small ball 13 start to move in the pipeline 9 under the action of inertia force, and a differential equation of the movement of the first small ball 12 and the second small ball 13 is established, wherein the equation is as follows:

wherein m is _a And m _b The masses of the first small ball 12 and the second small ball 13 are respectively; f (f) _a And f _b Friction forces respectively applied to the first ball 12 and the second ball 13; x is X _a And X _b The displacement of the first small ball 12 and the second small ball 13 respectively; x is X _base Is the displacement of the U-shaped base plate 1; i _a And I _b The moment of inertia of the first ball 12 and the second ball 13 respectively; omega _a And omega _b Angular velocities of the first and second pellets 12, 13, respectively; r is (r) _a And r _b The radii of the first small ball 12 and the second small ball 13 are respectively;

step two, applying low-frequency excitation perpendicular to the direction of the first cantilever beam 2 to the U-shaped substrate 1, starting vibration of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10, and enabling the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered on the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 to generate bending deformation, and generating electric energy through positive piezoelectric effect; the equations of the motion differential equations of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 and the piezoelectric loop equations of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are established, and the formulas are as follows:

wherein M is ₁ 、M ₂ 、M ₃ 、M ₄ The mass of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 are respectively; c (C) ₁ 、C ₂ 、C ₃ 、C ₄ Equivalent damping of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 respectively; k (K) ₁ 、K ₂ 、K ₃ 、K ₄ Equivalent rigidities of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 are respectively; x is X ₁ 、X ₂ 、X ₃ 、Y ₁ Respectively isDisplacement of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10; θ ₁ 、θ ₂ 、θ ₃ The electromechanical coupling coefficients of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are respectively; v (V) ₁ 、V ₂ 、V ₃ Output voltages of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are respectively; c (C) _p1 、C _p2 、C _p3 Equivalent capacitances of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 respectively; r is R ₁ 、R ₂ 、R ₃ Equivalent resistances of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 respectively; f (F) _mx1 For the magnetic force applied to the first cantilever beam 2 in the horizontal direction, F _my1 Is the magnetic force applied to the first cantilever beam 2 in the vertical direction;

step three, when the first small ball 12 moves in the pipeline 9, the small ball collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8, when the second small ball 13 moves in the pipeline, the small ball collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, so that the free ends of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 can generate larger displacement under low-frequency excitation, and the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered to the root parts of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 generate larger bending deformation and generate more electric energy through positive piezoelectric effect, thereby realizing vibration energy acquisition under low-frequency excitation; after the first ball 12 collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8 and the second ball 13 collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, the speeds of the first ball 12, the second ball 13, the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 are obtained by the law of conservation of momentum, and the formula is as follows:

when the first ball 12 collides with the first cantilever beam 2:

when the first ball 12 collides with the third cantilever beam 8:

when the second pellet 13 collides with the first cantilever beam 2:

when the second ball 13 collides with the second cantilever beam 4:

angular velocity after impact of the first beads 12:

angular velocity after collision of the first beads 13:

wherein e is the collision loss coefficient; mu (mu) ₁ The friction coefficient of the first small ball 12 and the free end magnets of the first cantilever beam 2 and the third cantilever beam 8; mu (mu) ₂ The friction coefficient of the second small ball 13 and the free end magnets of the first cantilever beam 2 and the second cantilever beam 4;for the speed before collision of the first pellet 12, < >>Is the velocity of the first ball 12 after impact; />For the speed before collision of the second pellet 13, < >>Is the speed of the second pellets 13 after collision; />For the angular velocity before collision of the first pellet 12, is->Is the angular velocity after the collision of the first beads 12; />For the angular velocity before collision of the second pellet 13, is->Is the angular velocity after collision of the second pellets 13; />For the speed before collision of the first cantilever beam 2, is->Is the speed of the first cantilever beam 2 after collision; />For the speed before collision of the second cantilever beam 4, is->Is the speed of the second cantilever beam 4 after collision; />For the speed before collision of the third cantilever beam 8, is->Is the speed of the third cantilever beam 8 after collision;

under low-frequency excitation, the first small ball 12 frequently collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8, and the second small ball 13 frequently collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, so that the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered to the root parts of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 frequently generate larger bending deformation, the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 generate electric energy through positive piezoelectric effect, and the generated electric energy is transmitted to the first energy accumulator 19, the second energy accumulator 20 and the third energy accumulator 21 through wires carried on the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 for storage respectively, so that vibration energy collection under low-frequency excitation is realized.

Example 2

Referring to fig. 1, a broadband piezoelectric vibration energy collecting device for multi-ball impact under low-frequency vibration comprises a first L-shaped fixing plate 6, a second L-shaped fixing plate 7, a U-shaped substrate 1, a pipeline 9, a first cantilever beam 2, a second cantilever beam 4, a third cantilever beam 8, a fourth cantilever beam 10, a first permanent magnet 15, a second permanent magnet 16, a third permanent magnet 17, a fourth permanent magnet 18, a first piezoelectric layer 3 with a lead wire, a second piezoelectric layer 5 with a lead wire, a third piezoelectric layer 11 with a lead wire, a first small ball 12, a second small ball 13, a first energy accumulator 19, a second energy accumulator 20 and a third energy accumulator 21.

The first L-shaped fixing plate 6 and the second L-shaped fixing plate 7 are symmetrically arranged at the left end and the right end of the U-shaped base plate 1 and are fixed on the base plate 1 through screws, and in order to ensure that the first L-shaped fixing plate 6 and the second L-shaped fixing plate 7 do not deform in the vibration process, the first L-shaped fixing plate 6 and the second L-shaped fixing plate 7 are made of rigid materials, and in the example, the first L-shaped fixing plate 6 and the second L-shaped fixing plate 7 are made of metal aluminum plates.

Referring to fig. 3, in order to ensure that the axis of the pipe 9 passes through the centers of the holes on the first L-shaped fixing plate 6 and the second L-shaped fixing plate 7, the holes on the first L-shaped fixing plate 6 and the second L-shaped fixing plate 7 need to be finished, so that the pipe 9 is ensured to be horizontal, the lengths of the parts of the two ends of the pipe 9 extending out of the holes on the first L-shaped fixing plate 6 and the second L-shaped fixing plate 7 are the same, in order to ensure that the pipe 9 cannot move in the holes of the first L-shaped fixing plate 6 and the second L-shaped fixing plate 7 in the vibration process, the pipe 9 needs to be fixed, the pipe 9 is formed by processing transparent acrylic plates, and the inside of the pipe 9 needs to be kept at the same roughness, so that relatively precise processing needs to be performed on the inside of the pipe 9.

Referring to fig. 4, after the pipe 9 is installed, a number N is put in the left-end inlet of the pipe 9 ₁ Is placed in an amount N at the right inlet of the pipe 9 ₂ In this example, one copper ball is placed in the left inlet and the same copper ball is placed in the right inlet.

Referring to fig. 4, a square through hole is formed in the middle of a pipe 9, a first cantilever beam 2 is connected with the inner surface of the front end of a U-shaped substrate 1, a first piezoelectric layer 3 is attached to the right side surface of the first cantilever beam 2, a first permanent magnet 15 is fixed to the left side surface of the free end of the first cantilever beam 2, the center of the first permanent magnet 15 fixed to the free end of the first cantilever beam 2 is located on the axis of the pipe 9, the free end of the first cantilever beam 2 stretches into the pipe 9 to divide the pipe 9 into two sections, brass is adopted as the material of the first cantilever beam 2 in the example, a first small ball 12, namely a copper ball, is located in the left section, and a second small ball 13, namely a copper ball, is located in the right section. In order to prevent the first cantilever beam 2 from contacting the square through hole of the pipe 9 during vibration, the square through hole needs to be large enough.

Referring to fig. 4, the two ends of the pipe 9The second cantilever 4 is connected with the left inner surface of the rear end of the U-shaped substrate 1, a second piezoelectric layer 5 is stuck on the right side surface of the second cantilever 4, a third permanent magnet 17 is fixed on the left side surface of the free end of the second cantilever 4, the center of the third permanent magnet 17 at the free end of the second cantilever 4 is positioned on the axis of the pipeline 9, the free end of the second cantilever 4 stretches into the pipeline 9, the upper surface and the lower surface of the second cantilever 4 are not contacted with the square hole in the vibration process, in the example, the second cantilever 4 is made of brass, and the distance from the center of the fixed magnet on the free end of the second cantilever 4 to the center of the fixed magnet at the free end of the first cantilever 2 is L ₁ 。

Referring to fig. 4, a third cantilever beam 8 is connected to the inner surface of the right side of the rear end of the U-shaped substrate 1, a third piezoelectric layer 11 is attached to the left side surface of the third cantilever beam 8, a second permanent magnet 16 is fixed to the right side surface of the free end of the third cantilever beam 8, the center of the second permanent magnet 16 at the free end of the third cantilever beam 8 is located on the axis of the pipe 9, the free end of the third cantilever beam 8 extends into the pipe 9, the upper surface and the lower surface of the third cantilever beam 8 are not in contact with square holes during vibration, in this example, the third cantilever beam 8 is made of brass, and the distance from the center of the fixed magnet at the free end of the third cantilever beam 8 to the center of the fixed magnet at the free end of the first cantilever beam 2 is L ₂ . And has L ₂ Greater than L ₁ 。

Referring to fig. 4, the fourth cantilever 10 is connected with an L-shaped fixing plate 6 fixed at the right end of the U-shaped substrate 1, a fourth permanent magnet 18 is fixed at the right side surface of the free end of the fourth cantilever 10, the fourth permanent magnet 18 at the free end of the fourth cantilever 10 faces the first permanent magnet 15, the polarities are opposite, and the polarities are mutually repulsive, the upper surface and the lower surface of the fourth cantilever 10 are not in contact with square holes in the vibration process, in this example, the fourth cantilever 10 is made of brass, the center distance from the center of the fourth permanent magnet 18 to the center of the first permanent magnet 15 is D, and the center distance D is adjusted, so that the fourth cantilever 10 and the first cantilever 2 form good magnetic coupling.

When the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 are installed, more parts of the free ends of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 are ensured to enter the pipeline 9, and meanwhile, the free ends of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 are ensured not to contact with the inner wall of the pipeline 9 during vibration.

The first energy accumulator 19 is arranged on the inner side of the U-shaped substrate 1, the right side of the first cantilever beam 2, the second energy accumulator 20 is arranged on the outer side of the U-shaped substrate 1, the left side of the second cantilever beam 4, the third energy accumulator 21 is fixed on the outer side of the U-shaped substrate 1, and the right side of the third cantilever beam 8; the first piezoelectric layer 3 has wires connected to the first energy store 19, the second piezoelectric layer 5 has wires connected to the second energy store 20, and the third piezoelectric layer 11 has wires connected to the third energy store 21.

The working principle of the invention is as follows:

when the U-shaped substrate 1 is subjected to external low-frequency excitation, and the external low-frequency excitation direction is the same as the axis direction of the pipeline 9, copper balls in the left section of the pipeline 9 are affected by inertia force, the copper balls in the pipeline 9 are subjected to reciprocating motion to impact the first cantilever beam 2 and the third cantilever beam 8, in the impact process, part of kinetic energy of the copper balls is transferred to the first cantilever beam 2 and the third cantilever beam 8, so that the free ends of the first cantilever beam 2 and the third cantilever beam 8 generate larger bending deformation, the roots of the first cantilever beam 2 and the third cantilever beam 8 generate larger deformation, the first piezoelectric layer 3 and the third piezoelectric layer 11 generate larger deformation, more electric energy is generated through positive pressure piezoelectric effect, the generated electric energy is transferred to the first energy accumulator and the third energy accumulator respectively through wires carried by the first piezoelectric layer 3 and the third piezoelectric layer 11, the copper balls in the right section of the pipeline 9 are subjected to be subjected to reciprocating motion in the pipeline 9, the first cantilever beam 2 and the second cantilever beam 4 are impacted back and forth, in the impact process, in the root part of the copper balls is transferred to the first cantilever beam 2 and the second cantilever beam 4, the root part of the copper balls is transferred to the first cantilever beam 2 and the second cantilever beam 4 to the second cantilever beam 4, the larger bending deformation is generated, the first piezoelectric layer 2 and the second cantilever beam 4 generates larger deformation is generated, and the larger electric energy is transferred to the first piezoelectric layer 4 and the larger piezoelectric layer is transferred to the second cantilever layer 4, and larger deformation is generated, and larger electric energy is generated, and larger energy is transferred to the larger piezoelectric layer 4 is respectively through the first piezoelectric layer and larger energy is respectively.

When the low-frequency excitation is matched with the resonance frequency of the first cantilever beam 2, the fourth cantilever beam 10 and the first cantilever beam 2 are magnetically coupled, so that nonlinearity is introduced, the working bandwidth of the first cantilever beam 2 under the low-frequency excitation can be effectively widened, and vibration energy collection is realized in a wider low-frequency excitation range.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the scope of the present invention is not limited to the specific details of the above embodiments, and within the scope of the technical concept of the present invention, any person skilled in the art may apply equivalent substitutions or alterations to the technical solution according to the present invention and the inventive concept thereof within the scope of the technical concept of the present invention, and these simple modifications are all within the scope of the present invention.

In addition, the specific features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various possible combinations are not described further.

Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.

Claims (9)

1. The broadband piezoelectric vibration energy collecting device for multi-ball impact under low-frequency vibration is characterized by comprising a U-shaped substrate 1, a first cantilever beam 2, a first piezoelectric layer 3 with leads, a second cantilever beam 4, a second piezoelectric layer 5 with leads, a first L-shaped fixing plate 6, a second L-shaped fixing plate 7, a third cantilever beam 8, a pipeline 9, a fourth cantilever beam 10, a third piezoelectric layer 11 with leads, a first ball 12, a second ball 13, a first permanent magnet 15, a second permanent magnet 16, a third permanent magnet 17, a fourth permanent magnet 18, a first energy accumulator 19, a second energy accumulator 20 and a third energy accumulator 21; the left and right sides of the pipeline 9 are respectively sleeved in the second L-shaped fixing plate 7 and the first L-shaped fixing plate 6; the front end of the first cantilever beam 2 is fixed on the inner side of the front end of the U-shaped substrate 1, the right side of the front end of the first cantilever beam 2 is fixed with a first piezoelectric layer 3, the rear end, namely the free end, of the first cantilever beam 2 extends into the center of the pipeline 9, and the left side of the first cantilever beam 2 positioned in the center of the pipeline 9 is fixed with a first permanent magnet 15; the rear ends of the third cantilever beam 8 and the second cantilever beam 4 are respectively fixed on the left side and the right side of the inner side of the rear end of the U-shaped substrate 1, a third piezoelectric layer 11 and a second piezoelectric layer 5 are respectively fixed outside the rear ends of the third cantilever beam 8 and the second cantilever beam 4, meanwhile, the front ends, namely the free ends, of the third cantilever beam 8 and the second cantilever beam 4 respectively extend into the pipeline 9, and a second permanent magnet 16 and a third permanent magnet 17 are respectively fixed inside the third cantilever beam 8 and the second cantilever beam 4 positioned inside the pipeline 9; the rear end of the pipeline 9 is provided with a fourth cantilever beam 10, wherein the right side of the fourth cantilever beam 10 is fixed on the inner side of the first L-shaped fixing plate 6, and a fourth permanent magnet 18 is fixed on the left side of the fourth cantilever beam 10, namely in front of the free end; a first ball 12 capable of freely moving is arranged in the pipeline 9 between the first cantilever beam 2 and the third cantilever beam 8, and a second ball 13 capable of freely moving is arranged in the pipeline 9 between the first cantilever beam 2 and the second cantilever beam 4;

the first energy accumulator 19 is fixed on the inner side of the front end of the U-shaped base plate 1, and the third energy accumulator 21 and the second energy accumulator 20 are respectively fixed on the left side and the right side outside the rear end of the U-shaped base plate 1; the first piezoelectric layer 3 is connected to the first energy store 19 by means of wires, the second piezoelectric layer 5 is connected to the second energy store 20 by means of wires, and the third piezoelectric layer 11 is connected to the third energy store 21 by means of wires.

2. The broadband piezoelectric vibration energy collecting device for multi-ball impact under low-frequency vibration according to claim 1, wherein a square hole for placing the first permanent magnet 15 is formed in the middle of the pipeline 9, a square hole for placing the third permanent magnet 17 is formed in the pipeline 9 outside the first L-shaped fixing plate 6, and a square hole for placing the second permanent magnet 16 is formed in the pipeline 9 outside the second L-shaped fixing plate 7.

3. A broadband piezoelectric vibration energy harvesting apparatus for multi-ball impact under low frequency vibration according to claim 1, wherein the shape of the conduit 9 is circular or square.

4. The broadband piezoelectric vibration energy collecting apparatus for multi-ball impact under low frequency vibration according to claim 1, wherein the first and second balls 12 and 13 are in the shape of a sphere or a cylinder.

5. A broadband piezoelectric vibration energy collecting apparatus for multi-ball impact under low frequency vibration according to claim 1, wherein said first balls 12 are located in the pipe 9 between the first cantilever beam 2 and the third cantilever beam 8 in an amount of N ₁ ,N ₁ Greater than or equal to 0;

the second pellets 13 are positioned in the pipeline 9 between the first cantilever beam 2 and the second cantilever beam 4, and the number is N ₂ ，N ₂ Greater than or equal to 1.

6. The broadband piezoelectric vibration energy harvesting apparatus of claim 1, wherein said fourth cantilever beam 10 is disposed vertically with respect to the first cantilever beam 2.

7. The broadband piezoelectric vibration energy collecting apparatus for multi-ball impact under low frequency vibration according to claim 1, wherein the fourth permanent magnet 18 and the first permanent magnet 15 are opposite in polarity, and generate repulsive force therebetween.

8. The broadband piezoelectric vibration energy collecting device for multi-ball impact under low-frequency vibration according to claim 1, wherein the free ends of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 enter the pipeline 9 through square holes of the pipeline 9, the first ball 12 collides with the first cantilever beam 2 and the third cantilever beam 8 when moving in the pipeline 9, and the second ball 13 collides with the first cantilever beam 2 and the second cantilever beam 4 when moving in the pipeline 9.

9. A broadband piezoelectric vibration energy collection method for multi-ball impact under low-frequency vibration is characterized by comprising the following steps:

step one, applying low-frequency excitation perpendicular to the direction of the first cantilever beam 2 to the U-shaped substrate 1, specifically: the broadband piezoelectric vibration energy collecting device is fixed on a horizontal sliding rail through bolts 14, when the broadband piezoelectric vibration energy collecting device is fixed, the radial direction of a pipeline 9 is consistent with the horizontal direction of the horizontal sliding rail, the horizontal sliding rail is driven by a servo motor, the servo motor is electrified, a driving signal of the servo motor is set to be a low-frequency harmonic signal, the servo motor generates low-frequency harmonic excitation, the horizontal sliding rail is driven to do periodic motion in the horizontal direction, and the whole device is driven to do periodic motion in the horizontal direction; the first small ball 12 and the second small ball 13 start to move in the pipeline 9 under the action of inertia force, and a differential equation of the movement of the first small ball 12 and the second small ball 13 is established, wherein the equation is as follows:

wherein m is _a And m _b The masses of the first small ball 12 and the second small ball 13 are respectively; f (f) _a And f _b Friction forces respectively applied to the first ball 12 and the second ball 13; x is X _a And X _b The displacement of the first small ball 12 and the second small ball 13 respectively; x is X _base Is the displacement of the U-shaped base plate 1; i _a And I _b Moment of inertia of the first and second beads 12, 13, respectively；ω _a And omega _b Angular velocities of the first and second pellets 12, 13, respectively; r is (r) _a And r _b The radii of the first small ball 12 and the second small ball 13 are respectively;

step two, applying low-frequency excitation perpendicular to the direction of the first cantilever beam 2 to the U-shaped substrate 1, starting vibration of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10, and enabling the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered on the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 to generate bending deformation, and generating electric energy through positive piezoelectric effect; the equations of the motion differential equations of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 and the piezoelectric loop equations of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are established, and the formulas are as follows:

wherein M is ₁ 、M ₂ 、M ₃ 、M ₄ The mass of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 are respectively; c (C) ₁ 、C ₂ 、C ₃ 、C ₄ Equivalent damping of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 respectively; k (K) ₁ 、K ₂ 、K ₃ 、K ₄ Equivalent rigidities of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 are respectively; x is X ₁ 、X ₂ 、X ₃ 、Y ₁ The displacements of the first cantilever beam 2, the second cantilever beam 4, the third cantilever beam 8 and the fourth cantilever beam 10 are respectively; θ ₁ 、θ ₂ 、θ ₃ The electromechanical coupling coefficients of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are respectively; v (V) ₁ 、V ₂ 、V ₃ Output voltages of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 are respectively; c (C) _p1 、C _p2 、C _p3 Equivalent capacitances of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 respectively; r is R ₁ 、R ₂ 、R ₃ Equivalent resistances of the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 respectively; f (F) _mx1 For the magnetic force applied to the first cantilever beam 2 in the horizontal direction, F _my1 Is the magnetic force applied to the first cantilever beam 2 in the vertical direction;

step three, when the first small ball 12 moves in the pipeline 9, the small ball collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8, when the second small ball 13 moves in the pipeline, the small ball collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, so that the free ends of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 can generate larger displacement under low-frequency excitation, and the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered to the root parts of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 generate larger bending deformation and generate more electric energy through positive piezoelectric effect, thereby realizing vibration energy acquisition under low-frequency excitation; after the first ball 12 collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8 and the second ball 13 collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, the speeds of the first ball 12, the second ball 13, the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 are obtained by the law of conservation of momentum, and the formula is as follows:

when the first ball 12 collides with the first cantilever beam 2:

when the first ball 12 collides with the third cantilever beam 8:

when the second pellet 13 collides with the first cantilever beam 2:

when the second ball 13 collides with the second cantilever beam 4:

angular velocity after impact of the first beads 12:

angular velocity after collision of the first beads 13:

wherein e is the collision loss coefficient; mu (mu) ₁ The friction coefficient of the first small ball 12 and the free end magnets of the first cantilever beam 2 and the third cantilever beam 8; mu (mu) ₂ The friction coefficient of the second small ball 13 and the free end magnets of the first cantilever beam 2 and the second cantilever beam 4;for the speed before collision of the first pellet 12, < >>Is the velocity of the first ball 12 after impact; />For the speed before collision of the second pellet 13, < >>Is the speed of the second pellets 13 after collision; />For the angular velocity before collision of the first pellet 12, is->Is the angular velocity after the collision of the first beads 12; />For the angular velocity before collision of the second pellet 13, is->Is the angular velocity after collision of the second pellets 13; />For the speed before collision of the first cantilever beam 2, is->Is the speed of the first cantilever beam 2 after collision; />For the speed before collision of the second cantilever beam 4, is->Is the speed of the second cantilever beam 4 after collision; />For the speed before collision of the third cantilever beam 8, is->Is the speed of the third cantilever beam 8 after collision;

under low-frequency excitation, the first small ball 12 frequently collides with the free ends of the first cantilever beam 2 and the third cantilever beam 8, and the second small ball 13 frequently collides with the free ends of the first cantilever beam 2 and the second cantilever beam 4, so that the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 adhered to the root parts of the first cantilever beam 2, the second cantilever beam 4 and the third cantilever beam 8 frequently generate larger bending deformation, the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 generate electric energy through positive piezoelectric effect, and the generated electric energy is transmitted to the first energy accumulator 19, the second energy accumulator 20 and the third energy accumulator 21 through wires carried on the first piezoelectric layer 3, the second piezoelectric layer 5 and the third piezoelectric layer 11 for storage respectively, so that vibration energy collection under low-frequency excitation is realized.