AU2021101797A4

AU2021101797A4 - Multi-degree-of-freedom up-conversion piezoelectric energy harvester

Info

Publication number: AU2021101797A4
Application number: AU2021101797A
Authority: AU
Inventors: Shiqiao GAO; Haipeng Liu; Junru Wu; Li Yan; Guangyi Zhang
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2021-04-08
Filing date: 2021-04-08
Publication date: 2021-05-27
Anticipated expiration: 2029-04-08

Abstract

A multi-degree-of-freedom up-conversion piezoelectric energy harvester is disclosed. The frequency conversion piezoelectric energy harvester includes a housing, 5 a multi-degree-of-freedom swinging device, piezoelectric materials, and base beams that all arranged in the housing. The swinging device includes a spring and a metal ball. One end of the spring is fixedly connected to the top of the housing, and the other end of the spring is connected to the metal ball and is used for pulling the metal ball to swing freely at a low frequency in multiple directions. The base beams include multiple vertical base 10 beams and a horizontal base beam. The vertical base beams are arranged on the periphery of the swinging device. The horizontal base beam is arranged at the bottom of the swinging device and is perpendicular to the vertical base beams. The metal ball can knock the multiple base beams arranged on the periphery and the bottom of the swinging device while swinging. A piezoelectric material is attached to the outer surface of each 15 base beam. In use, the piezoelectric beams can vibrate freely at a high frequency under the impact of the metal ball, so as to provide up-conversion energy conversion in a low frequency environment. 20 [FIG. 1 for publication] 1/2 5 FIG. 1

Description

1/2

5

FIG. 1

MULTI-DEGREE-OF-FREEDOM UP-CONVERSION PIEZOELECTRIC ENERGY HARVESTER

FIELD The present disclosure relates to the technical field of piezoelectric energy harvesters, and in particular, to a multi-degree-of-freedom up-conversion piezoelectric energy harvester.

DEFINITION In the present description and claims, the term "comprising" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term "comprising" such as "comprise" and "comprises".

BACKGROUND Microelectronic devices are mainly powered either by external power supplies and chemical batteries. External power supply circuits of external power supplies are complex, need regular maintenance, have high installation and maintenance cost, and are not applicable for use with passive wireless, or other environments such as harsh environments. Chemical batteries need to be replaced regularly and their energy density is low. Used chemical batteries are also a source of environmental pollution. Therefore, it is desirable to find an environment-friendly energy resource which is energy-saving and is not constrained by the environment. Vibration sources are ubiquitous in daily life. Vibration energy is an environment friendly and pollution-free energy resource. Vibration energy can be collected and stored to provide an alternate energy source for the microelectronic devices. Known methods for harvesting vibration energy include piezoelectric energy harvesting, electromagnetic energy harvesting, and the like. Most traditional piezoelectric energy harvesters are of single cantilever structures. The single structures have a narrow working frequency band and low energy utilization rate. The resonant frequency of traditional piezoelectric energy harvesters is also high, and the vibration frequency in the environment is mostly low frequency (below 100 Hz). This means that it is difficult to realize high-efficiency energy conversion by using piezoelectric materials. The reference to prior art in the background above is not and should not be taken as an acknowledgment or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia or in any other country.

SUMMARY The present disclosure relates to a multi-degree-of-freedom up-conversion piezoelectric energy harvester which can in some aspects be used in an ultra-low frequency environment, may improve the utilization rate of the vibration energy, expand the working frequency band. Piezoelectric beams vibrate freely at a high frequency under the impact of a metal ball which allows for realize high-efficiency conversion of up conversion energy in a low-frequency environment. The present disclosure therefore provides the following: A multi-degree-of-freedom up-conversion piezoelectric energy harvester comprising a housing, a multi-degree-of-freedom swinging device, piezoelectric materials, and base beams. The swinging device, the piezoelectric materials, and the base beams are all arranged in the housing. The swinging device includes a spring and a metal ball. One end of the spring is fixedly connected to the top of the housing, and the other end of the spring is connected to the metal ball and is used for pulling the metal ball to swing freely in multiple directions. The base beams include multiple vertical base beams and one horizontal base beam. The vertical base beams are arranged on the periphery of the swinging device and are vertically and fixedly connected to the top of the housing. The horizontal base beam is arranged at the bottom of the swinging device, is horizontally and fixedly connected to a wall surface of one side of the housing and is perpendicular to the vertical base beams. The metal ball can knock the multiple base beams arranged on the periphery and the bottom of the swinging device while swinging. A piezoelectric material is attached to the outer surface of each base beam. The piezoelectric material includes a piezoelectric piece, an upper electrode, and a lower electrode. The lower electrode is arranged on one side tightly close to the base beams. The main material of the piezoelectric piece is PZT. The piezoelectric piece is arranged between the upper electrode and the lower electrode. An upper electrode conductor and a lower electrode conductor are respectively arranged on the upper electrode and the lower electrode of the piezoelectric material. The electric charges produced by the upper electrode and the lower electrode of the piezoelectric material are respectively output through the upper electrode conductor and the lower electrode conductor. Optionally, the base beams and the piezoelectric materials are rectangular, and the piezoelectric materials are shorter than the base beams in length direction. The present disclosure provides a multi-degree-of-freedom up-conversion piezoelectric energy harvester, as compared to traditional energy harvesters having a single structure. The disclosed energy harvester in some aspects may substantially fully utilize the multi-direction vibration energy in the environment. In order to improve the electric energy production, the base beams are arranged in multiple degrees of freedom, which improves the utilization rate of the vibration energy. Up-conversion is obtained by means of the combination of the low-frequency swinging of the metal ball and the high-frequency vibration of the base beams as the metal ball knocks the base beams while swinging. The piezoelectric beams vibrate freely at a high frequency under the impact of the metal ball, so as to realize high-efficiency conversion of up-conversion energy in the low-frequency vibration environment.

BRIEF DESCRIPTION OF THE DRAWINGS To describe the technical solutions in the embodiments of the present disclosure or in the prior art more clearly, the following briefly describes the accompanying drawings required for describing the embodiments. Apparently, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and those of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts. FIG. 1 is an overall structural diagram of a multi-degree-of-freedom up-conversion piezoelectric energy harvester of an embodiment of the present disclosure; FIG. 2 is a front view of an overall structure of the multi-degree-of-freedom up conversion piezoelectric energy harvester of the embodiment of FIG. 1; FIG. 3 is a bottom view of the multi-degree-of-freedom up-conversion piezoelectric energy harvester of the embodiment of FIG. 1. Numerals in the drawings are: 1-housing; 2-spring; 3-piezoelectric material, 4-base beam; 5-metal ball; 6-piezoelectric piece; 7-upper electrode; 8-lower electrode; 9-upper electrode conductor; 10-lower electrode conductor.

DETAILED DESCRIPTION The technical solutions in the embodiments of the present disclosure will be clearly and completely described herein below with reference to the accompanying drawings in the embodiments of the present disclosure. It is apparent that the described embodiments are merely part of the embodiments of the present disclosure, but not all of the embodiments. On the basis of the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present disclosure. The present disclosure is directed towards providing a multi-degree-of-freedom up conversion piezoelectric energy harvester which may improve the utilization rate of vibration energy. Piezoelectric beams vibrate freely at a high frequency under the impact of a metal ball, so as to obtain high-efficiency conversion of up-conversion energy in a low-frequency environment. The multi-degree-of-freedom up-conversion piezoelectric energy harvester as disclosed herein may address disadvantages of low energy utilization rate and insufficient output power of a conventional energy harvester and improve the output power under the condition of a constant volume parameter. Piezoelectric materials are arranged in multiple degrees of freedom, which makes use of the low-frequency vibration energy in the environment. An up-conversion manner is adopted, and the piezoelectric beams are impacted by the multi-degree-of-freedom low-frequency swinging of the small ball, so that the piezoelectric beams vibrate freely at a high frequency under the impact of the metal ball, thereby realizing high-efficiency conversion of up-conversion energy in the low-frequency environment, and improving the output energy. Compared with the traditional external power supplies and chemical batteries, the multi-degree-of-freedom up-conversion piezoelectric energy harvester disclosed herein has the advantages of simple structure and convenience in installation without a complex circuit or regular maintenance or replacement. The low-frequency vibration in the environment is utilized. The multi-degree-of-freedom up-conversion piezoelectric energy harvester is pollution free, sustainable, applicable to passive, wireless, and other special or harsh environments, and has strong environmental applicability.

With the development of wireless sensor systems, intelligent control systems, individual wearable systems for single soldiers, and the like, the disclosed multi-degree of-freedom up-conversion piezoelectric energy harvester in some aspects may allow an energy supply of micro and small electronic equipment to be used in limited space, harsh environment, and vibration conditions. The present disclosure focuses on collecting and utilizing the low-energy vibration energy, so as to supply power to micro and small devices, such as sensors, on mechanical equipment. In order to make the above features, and advantages of the present disclosure more apparent and more comprehensible, the present disclosure is further described in detail below with reference to the accompanying drawings and specific implementation manners. FIG. 1 is an overall structural diagram of a multi-degree-of-freedom up-conversion piezoelectric energy harvester of the embodiment of the present disclosure; FIG. 2 is a front view of an overall structure of the multi-degree-of-freedom up-conversion piezoelectric energy harvester of the embodiment of the present disclosure; FIG. 3 is a bottom view of the multi-degree-of-freedom up-conversion piezoelectric energy harvester of the embodiment of the present disclosure. As shown in FIGS. 1 to 3, a multi-degree-of-freedom up-conversion piezoelectric energy harvester includes a housing 1, a swinging device, piezoelectric materials 3, and base beams 4; the swinging device, the piezoelectric materials 3, and the base beams 4 are all arranged in the housing 1; the swinging device includes a spring 2 and a metal ball 5; one end of the spring 2 is fixedly connected to the top of the housing 1, and the other end of the spring is connected to the metal ball 5 and is used for pulling the metal ball 5 to swing freely in multiple directions; the base beams 4 include multiple vertical base beams and a horizontal base beam; the vertical base beams are arranged on the periphery of the swinging device, and are vertically and fixedly connected to the top of the housing 1; the horizontal base beam is arranged at the bottom of the swinging device, is horizontally and fixedly connected to a wall surface of one side of the housing 1, and is perpendicular to the vertical base beams; the metal ball 5 can knock the multiple base beams 4 arranged on the periphery and the bottom of the swinging device while swinging; a piezoelectric material 3 is attached to the outer surface of each base beam 4; the piezoelectric material 3 includes a piezoelectric piece 6, an upper electrode 7, and a lower electrode 8; the lower electrode 8 is arranged on one side tightly close to the base beams 4; the main material of the piezoelectric piece 6 is PZT; the piezoelectric piece 6 is arranged between the upper electrode 7 and the lower electrode 8; an upper electrode conductor 9 and a lower electrode conductor 10 are respectively arranged on the upper electrode and the lower electrode of the piezoelectric material 3; the electric charges produced by the upper electrode 7 and the lower electrode 8 of the piezoelectric material 3 are respectively output through the upper electrode conductor 9 and the lower electrode conductor 10. Both the base beams 4 and the piezoelectric materials 3 are rectangular, and the piezoelectric materials 3 are shorter than the base beams 4 in length direction. Specific implementation manner 1, as shown in FIG. 1, the base beams 4 include four vertical base beams and one horizontal base beam. The four vertical base beams are arranged on the periphery of the swinging device, and are vertically and fixedly connected to the top of the housing 1. The horizontal base beam is arranged at the bottom of the swinging device, is horizontally and fixedly connected to a wall surface of one side of the housing 1, and is perpendicular to the vertical base beams. The metal ball 5 can knock the five base beams arranged on the periphery and the bottom of the swinging device while swinging. A specific working process is as follows: the housing 1 of the multi-degree-of freedom up-conversion piezoelectric energy harvester generates vibration in a low frequency vibration environment. The vibration of the housing 1 drives the base beams 4 at various degrees of freedom and the piezoelectric materials 3 thereon to vibrate, and the upper electrodes and the lower electrodes of the piezoelectric materials 3 produce corresponding positive and negative charges because of the existence of a positive piezoelectric effect. Meanwhile, the spring 2 drives the metal ball 5 to swing. The metal ball 5 knocks the base beams 4 at all degrees of freedom while swinging, which improves the vibration frequency of the base beams 4. Meanwhile, the electric charges produced by the upper electrodes 7 and the lower electrodes 8 of the piezoelectric materials 3 are respectively output through the upper electrode conductor 9 and the lower electrode conductor 10. Specific implementation manner 2, the difference between the present implementation manner and the specific implementation manner 1 is that there are multiple vertical base beams arranged on the periphery of the swinging device, as long as the vertical base beams are uniformly arranged on the periphery of the swinging device. The others are the same as the specific implementation manner 1. The disclosure multi-degree-of-freedom up-conversion piezoelectric energy harvester makes innovations in structure, changes the single structure of the traditional energy harvester, and makes use of the low-frequency vibration energy in the environment. In order to improve the electric energy production, the base beams are arranged in multiple degrees of freedom, which improves the utilization rate of the vibration energy. Meanwhile, an up-conversion manner is adopted, the swinging of the metal ball and the vibration of the base beams are combined, so that the metal ball knocks the base beams while swinging, thereby improving the vibration frequency of the piezoelectric materials. The piezoelectric beams vibrate freely at a high frequency under the impact of the metal ball, so high-efficiency conversion of up-conversion energy in the low-frequency environment is realized, and the energy harvesting effect is the best. The multi-degree-of-freedom up-conversion piezoelectric energy harvester has the advantages of environment friendliness, pollution free, high energy density, no electromagnetic interference, high reliability, strong environmental adaptability, low maintenance cost, easiness in processing, easiness in realization of miniaturization, and the like. Herein, specific examples are used to describe the principle and implementation manners of the present disclosure. The description of the embodiments above is merely intended to help understand the method and its core idea of the present disclosure. In addition, those of ordinary skill in the art may make modifications based on the idea of the present disclosure with respect to the specific implementation manners and the application scope. In conclusion, the contents of the present specification shall not be construed as a limitation to the present disclosure.

Claims

CLAIMS:

1. A multi-degree-of-freedom up-conversion piezoelectric energy harvester, comprising a housing, a multi-degree-of-freedom swinging device, piezoelectric materials, and base beams, wherein the swinging device, the piezoelectric materials, and the base beams are all arranged in the housing; the swinging device comprises a spring and a metal ball; one end of the spring is fixedly connected to the top of the housing, and the other end of the spring is connected to the metal ball and is used for pulling the metal ball to swing freely in multiple directions; the base beams include multiple vertical base beams and a horizontal base beam; the vertical base beams are arranged on the periphery of the swinging device, and are vertically and fixedly connected to the top of the housing; the horizontal base beam is arranged at the bottom of the swinging device, is horizontally and fixedly connected to a wall surface of one side of the housing, and is perpendicular to the vertical base beams; the metal ball can knock the multiple base beams arranged on the periphery and the bottom of the swinging device while swinging; a piezoelectric material is attached to the outer surface of each base beam; the piezoelectric material comprises a piezoelectric piece, an upper electrode, and a lower electrode; the lower electrode is arranged on one side tightly close to the base beams; the main material of the piezoelectric piece is PZT; the piezoelectric piece is arranged between the upper electrode and the lower electrode; an upper electrode conductor and a lower electrode conductor are respectively arranged on the upper electrode and the lower electrode of the piezoelectric material; the electric charges produced by the upper electrode and the lower electrode of the piezoelectric material are respectively output through the upper electrode conductor and the lower electrode conductor.

2. The multi-degree-of-freedom up-conversion piezoelectric energy harvester according to claim 1, wherein both the base beams and the piezoelectric materials are rectangular, and the piezoelectric materials are shorter than the base beams in length direction.