Piezoelectric vibration energy collector capable of rapidly and accurately matching excitation frequency and having self-locking function

Abstract

The invention relates to a piezoelectric vibration energy collector capable of rapidly and accurately matching excitation frequency and having a self-locking function, and belongs to the technical field of energy collection. The moving unit is connected with a spring fixing hole in the fixing unit through a main beam spring, a main cantilever beam of the moving unit is installed in a rectangular sliding groove of the fixing unit in a sliding mode, guiding and limiting are achieved through a clamping piece, and the energy collecting unit is located at the tail end of the main cantilever beam. The self-locking units are located on the two sides of the base of the fixing unit and are in sliding connection with the moving unit through self-locking heads, locking of the collector moving unit is achieved through clamping fit between the self-locking heads and the self-locking clamping grooves, and the displacement sensor is fixedly installed on the upper side of the base through a fixing frame. The frequency self-adaptive energy collector has the advantages that the resonant frequency is quickly and accurately locked, the energy dissipation is reduced, the bandwidth is widened, the collection efficiency is improved, the energy dissipation of the collector is greatly reduced, and compared with a traditional frequency self-adaptive energy collector, the similar effective working bandwidth is maintained, but the output voltage is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy harvesting, and in particular relates to a piezoelectric vibration energy harvester with a self-locking function that can quickly and accurately match an excitation frequency. Background Art

[0002] With the rapid development of microelectronic devices, miniaturized and low-power electronic devices are becoming increasingly popular. Currently, these devices rely primarily on electrochemical batteries for power. While these batteries can meet operational needs, their limited battery life necessitates frequent replacement or recharging, limiting the long-term stability of the devices. To address this issue, researchers have proposed methods for harvesting clean, sustainable energy from the environment to power low-power devices. Among these, piezoelectric vibration energy harvesters have attracted considerable attention due to their simple structure and high conversion efficiency.

[0003] Traditional piezoelectric vibration energy harvesters are generally composed of a cantilever beam, a piezoelectric sheet attached to the root of the cantilever beam, and a mass block fixed to the end of the cantilever beam. When the excitation frequency is close to the natural frequency of the cantilever beam, the system exhibits good output performance. However, when the ambient excitation frequency changes continuously, this harvester cannot adapt to the changes in the ambient excitation frequency, the output performance drops significantly, and the effective working bandwidth is narrow.

[0004] To address this issue, patent CN216625608U discloses a novel self-matching piezoelectric vibration energy harvester. This device adjusts the cantilever beam's extended length by controlling a stepper motor, allowing the harvester's natural frequency to approach or reach a frequency that resonates with an external excitation source. Patent CN210839391U discloses a cantilever-type nonlinear piezoelectric vibration energy harvester. Manual adjustment of the cantilever beam's length changes the cantilever beam's resonant frequency, effectively matching the external excitation frequency. However, these frequency-adaptive energy harvesters rely on external motors or manual intervention, resulting in complex system structures, increased power consumption, and limitations in miniaturization and adaptive frequency regulation. Our research group previously proposed a frequency-adaptive piezoelectric vibration energy harvester that effectively adapts to the ambient excitation frequency and broadens the harvester's bandwidth. However, during the frequency adaptation process, the piezoelectric beam's axial stepless adjustment and the coupled oscillation of the longitudinal vibration result in significant energy dissipation and instability. Therefore, a low-energy-dissipation piezoelectric vibration energy harvester that requires no external energy consumption and can quickly and accurately achieve frequency adaptation is needed to improve energy harvesting efficiency and broaden its application scenarios. Summary of the Invention

[0005] The present invention provides a piezoelectric vibration energy harvester with a self-locking function that can quickly and accurately match the excitation frequency, so as to solve the problems that the current piezoelectric vibration energy harvester cannot accurately adapt to the changes in environmental vibration excitation and the frequency adjustment hysteresis. The resonant frequency is adaptively adjusted by releasing the axial displacement of the main cantilever beam. The resonant frequency of the harvester is quickly and accurately locked by setting a self-locking unit, thereby reducing energy dissipation, broadening the effective working bandwidth of the harvester, and improving the harvesting efficiency.

[0006] The technical solution adopted by the present invention is to include a fixed unit, a mobile unit, an energy collection unit, a self-locking unit and a displacement sensor, wherein the mobile unit is connected to the spring fixing hole in the fixed unit through a main beam spring, the main cantilever beam of the mobile unit is slidably installed in the rectangular slide groove of the fixed unit, and is guided and limited by a clip, the energy collection unit is located at the end of the main cantilever beam, the self-locking unit is located on both sides of the base of the fixed unit and is slidably connected to the mobile unit through a self-locking head, and the snap-fit ​​between the self-locking head and the self-locking slot realizes the locking of the collector mobile unit, and the displacement sensor is fixedly installed on the upper side of the base through a fixing frame.

[0007] The fixing unit includes a base, a spring preload adjustment slot, a spring preload adjustment piece, a spring fixing hole, a clip, a rectangular slide, a fixing bracket, a zero point calibration adjustment slot, a fastening bolt, a nut, a bolt hole, a pin hole, a tenon groove and a base fixing hole, wherein a pair of spring preload adjustment slots are opened on the left side of the base, the spring preload adjustment piece is fixed above the spring preload adjustment slot by a fastening bolt and a nut, a spring fixing hole is provided at the right end of the spring preload adjustment piece, the clip is fixed to the base by a fastening bolt and a nut, a rectangular slide is provided on the base, a zero point calibration adjustment slot is provided on the surface of the base for realizing the reference position adjustment of the displacement sensor, the fixing bracket is used to fix and install the displacement sensor, the base has a bolt hole, which is matched with the fastening bolt and the nut to realize overall fixation, the base surface is processed with a pin hole and a tenon groove, the pin hole and the tenon groove are respectively matched with the limit pin and the tenon with tolerance to realize detachable connection, and a base fixing hole is provided at the bottom of the base for connecting the base with an external excitation device.

[0008] The base is made of a photosensitive resin-based composite material.

[0009] The mobile unit includes a main cantilever beam, a secondary beam, a main beam spring, a spring connection hole and a displacement sensor fixing hole, wherein two secondary beams are vertically fixed at the left end of the main cantilever beam, a piezoelectric piece is pasted on the effective cantilever root of the main cantilever beam, the right side of the main cantilever beam is fixedly connected to the mass block, the right side of the main beam spring is connected to the spring connection hole on the left side of the main cantilever beam, and a displacement sensor fixing hole is opened on the surface of the main cantilever beam, which is connected to the sliding rod of the displacement sensor for real-time monitoring and recording of the moving distance of the main cantilever beam.

[0010] The main cantilever beam is made of brass.

[0011] The energy collection unit includes a piezoelectric sheet and a mass block arranged at the end of the main cantilever beam.

[0012] The piezoelectric piece is made of PZT-5H piezoelectric ceramic.

[0013] The self-locking unit includes a limit pin, a compression spring, a self-locking head, a self-locking block, a sliding groove, a self-locking slot and a tenon, wherein the limit pin is used to limit the movement range of the main cantilever beam to ensure that the main beam spring is in the elastic working range. The tenon is below the self-locking block. The self-locking block is symmetrically installed on both sides of the base, and a plurality of equidistant self-locking slots are processed on the surface. The surface of the self-locking block is provided with a sliding groove. When the self-locking head is disengaged from the self-locking slot, it slides directionally along the sliding slot to play a guiding role. The compression spring is sleeved on the auxiliary beam, and the self-locking head is slidably connected to the auxiliary beam and slides along the direction of the auxiliary beam under the elastic force of the compression spring. The self-locking unit is self-locked or released through the plug-in cooperation between the self-locking head and the self-locking slot.

[0014] The self-locking head is made of wear-resistant photosensitive resin material, and its head is designed as a frustum structure. The self-locking slot is a cylindrical groove structure, which forms a plug-in fit with the self-locking head. In order to optimize the sliding performance of the self-locking head, a 45° guide chamfer is provided at the opening of the self-locking slot.

[0015] The self-locking frequency range corresponding to the self-locking slot 406 is expressed as:

[0016] Frequency increase and extension self-locking range:

[0017]

[0018] High-frequency fallback self-locking range:

[0019]

[0020] In the formula Represents the number of self-locking card slots, is the elastic coefficient of the main beam spring, is the locking force of the self-locking unit, is the equivalent mass of the energy harvesting unit and the limited overhang length of the main cantilever beam, is the excitation amplitude, is the moving step length of the self-locking head, and its expression is:

[0021]

[0022] In the formula is the maximum extension distance of the main cantilever beam, is the minimum extension distance of the main cantilever beam, is the diameter of the self-locking slot.

[0023] The beneficial effects of the present invention are:

[0024] 1. This invention utilizes the synergistic effect of the main beam spring and main cantilever beam, combined with the staged locking mechanism of the self-locking unit, to achieve automatic resonant frequency matching without the need for external motors or manual intervention. The main cantilever beam dynamically adjusts its effective length through axial expansion and contraction under environmental excitation, significantly broadening the operating bandwidth and adapting to complex vibration environments.

[0025] 2. The plug-in design of the self-locking head and the equidistant self-locking slot, combined with the elastic drive of the compression spring, can quickly lock or release the axial displacement of the main cantilever beam when the inertial force changes, and the frequency adjustment hysteresis is reduced by more than 60%.

[0026] 3. Traditional frequency-adaptive energy harvesters suffer from significant energy dissipation due to the long duration of their nonlinear dynamic regulation process. This invention introduces a self-locking unit that enables the harvester to quickly and accurately match the ambient excitation frequency, significantly reducing the harvester's energy dissipation. While maintaining a similar effective operating bandwidth compared to traditional frequency-adaptive energy harvesters, the output voltage is significantly improved.

[0027] 4. This invention utilizes a single-degree-of-freedom cantilever beam structure, which offers novel design, low cost, and strong environmental adaptability, effectively improving the energy harvester's output performance. The self-locking mechanism proposed in this invention can be further extended to other energy harvesting structures, reducing system energy dissipation and further enhancing harvester performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are merely illustrative, and those skilled in the art can, without inventive effort, derive other implementation drawings from the provided drawings.

[0029] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein for understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, provided they do not affect the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0030] Figure 1 This is a schematic diagram of the overall appearance of an embodiment of the present invention;

[0031] Figure 2 It is an exploded view of the collector fixing unit in the embodiment of the present invention;

[0032] Figure 3 It is a schematic diagram of the configuration of each structural unit in the embodiment of the present invention;

[0033] Figure 4 Schematic diagram of the self-locking unit in an embodiment of the present invention;

[0034] Figure 5 It is a partial exploded view of the self-locking unit in an embodiment of the present invention;

[0035] Figure 6 It is a force diagram of the main cantilever beam in the extended state in the embodiment of the present invention.

[0036] Figure 7 It is a force diagram of the main cantilever beam in the contracted state in the embodiment of the present invention.

[0037] Figure 8 This is a comparison diagram of the time domain response of the cantilever beam displacement of the present invention, the traditional frequency adaptive energy harvester, and the fixed energy harvester at an excitation frequency of 10 Hz.

[0038] Figure 9 This is a comparison diagram of the time domain response of the cantilever beam displacement of the present invention, the traditional frequency adaptive energy harvester, and the fixed energy harvester at an excitation frequency of 25 Hz.

[0039] Figure 10 This is a comparison diagram of the time domain response of the cantilever beam displacement of the present invention, the traditional frequency adaptive energy harvester, and the fixed energy harvester at an excitation frequency of 30 Hz.

[0040] Figure 11 This is a comparison chart of the output voltage frequency domain response of the present invention, traditional frequency adaptive energy harvester, and fixed energy harvester. DETAILED DESCRIPTION

[0041] It is readily understood that, based on the technical solutions of the present invention, without altering the essential spirit of the present invention, those skilled in the art can envision various implementations of the piezoelectric vibration energy harvester with a self-locking function that can quickly and accurately match the excitation frequency. Therefore, the following specific embodiments and accompanying drawings are merely illustrative of the technical solutions of the present invention and should not be construed as the entire disclosure or as limiting or restricting the technical solutions of the present invention.

[0042] See Figure 1, including a fixed unit 1, a mobile unit 2, an energy collection unit 3, a self-locking unit 4 and a displacement sensor 5, wherein the mobile unit 2 is connected to the spring fixing hole 104 in the fixed unit 1 through the main beam spring 203, the main cantilever beam 201 of the mobile unit 2 is slidably installed in the rectangular slide groove 106 of the fixed unit 1, and is guided and limited by the clip 105, the energy collection unit 3 is located at the end of the main cantilever beam 201, the self-locking unit 4 is located on both sides of the base 101 of the fixed unit 1 and is slidably connected to the mobile unit 2 through the self-locking head 403, and the snap-fit ​​between the self-locking head 403 and the self-locking slot 406 realizes the locking of the collector mobile unit 2, and the displacement sensor 5 is fixedly installed on the upper side of the base 101 through the fixing bracket 107.

[0043] like Figure 2 As shown, the fixing unit 1 includes a base 101, a spring preload adjustment slot 102, a spring preload adjustment piece 103, a spring fixing hole 104, a clip 105, a rectangular slide 106, a fixing frame 107, a zero point calibration adjustment slot 108, a fastening bolt 109, a nut 110, a bolt hole 111, a pin hole 112, a tenon 113 and a base fixing hole 114, wherein a pair of spring preload adjustment slots 102 are opened on the left side of the base 101, the spring preload adjustment piece 103 is fixed above the spring preload adjustment slot 102 by fastening bolts 109 and nuts 110, a spring fixing hole 104 is provided on the right end of the spring preload adjustment piece 103, and the clip 105 is fastened by Bolts and nuts are fixed on the base 101. There is a rectangular slide groove 106 on the base 101. A zero point calibration adjustment groove 108 is provided on the surface of the base 101 for realizing the reference position adjustment of the displacement sensor 5. The fixing frame 107 is used to fix the displacement sensor 5. The base 101 has a bolt hole 111, which is used to fasten the bolts and nuts to achieve overall fixation. The surface of the base 101 is processed with a pin hole 112 and a tenon 113. The pin hole 112 and the tenon 113 are respectively matched with the limit pin 401 and the tenon 407 with H7 and g6 tolerances to achieve detachable connection. A base fixing hole 114 is provided at the bottom of the base 101 for connecting the base 101 with an external excitation device.

[0044] The base 101 is made of a photosensitive resin-based composite material and has a size of 140mm×40mm×15mm. The spring preload adjustment piece 103 is used to adjust the preload force of the main beam spring 203 with different stiffness, so that its initial value is 0;

[0045] The depth of the rectangular chute 106 is 0.5 mm. The main cantilever beam 201 is slidably installed in the rectangular chute 106 and guided and limited by the clip 105 .

[0046] like Figure 3As shown, the mobile unit 2 includes a main cantilever beam 201, a sub-beam 202, a main beam spring 203, a spring connecting hole 204 and a displacement sensor fixing hole 205, wherein two sub-beams 202 are vertically fixed at the left end of the main cantilever beam 201, a piezoelectric piece 301 is pasted on the effective cantilever root of the main cantilever beam 201, the right side of the main cantilever beam 201 is fixedly connected to the mass block 302, the right side of the main beam spring 203 is connected to the spring connecting hole 204 on the left side of the main cantilever beam 201, and a displacement sensor fixing hole 205 is opened on the surface of the main cantilever beam 201, which is connected to the sliding rod of the displacement sensor 5 for real-time monitoring and recording of the moving distance of the main cantilever beam 201.

[0047] The main cantilever beam 201 is made of brass, with dimensions of 80 mm×10 mm×0.5 mm. The initial effective cantilever length of the main cantilever beam 201 is 70 mm.

[0048] The energy harvesting unit 3 includes a piezoelectric sheet 301 and a mass block 302 disposed at the end of the main cantilever beam 201 .

[0049] The piezoelectric piece 301 is made of PZT-5H piezoelectric ceramic with a size of 10mm×10mm×0.2mm.

[0050] like Figure 3 、 4 5, the self-locking unit 4 includes a limit pin 401, a compression spring 402, a self-locking head 403, a self-locking block 404, a sliding groove 405, a self-locking slot 406 and a tenon 407, wherein the limit pin 401 is used to limit the movement range of the main cantilever beam 201 to ensure that the main beam spring 203 is in the elastic working range, the tenon 407 is below the self-locking block 404, the self-locking block 404 is symmetrically installed on both sides of the base 101, and a plurality of equidistant self-locking slots 406 are machined on the surface. 06. A sliding groove 405 is provided on the surface of the self-locking block 404. When the self-locking head 403 is disengaged from the self-locking slot 406, it slides along the sliding groove 405 in a directional manner to play a guiding role. The compression spring 402 is sleeved on the sub-beam 202, and the self-locking head 403 is slidably connected to the sub-beam 202. Under the elastic force of the compression spring 402, it slides along the direction of the sub-beam 202. Through the plug-in cooperation between the self-locking head 403 and the self-locking slot 406, the self-locking unit 4 is self-locked or released.

[0051] like Figure 5 As shown, the self-locking head 403 is made of wear-resistant photosensitive resin material, and its head is designed as a frustum structure. The self-locking slot 406 is a cylindrical groove structure, which forms a plug-in fit with the self-locking head 403. In order to optimize the sliding performance of the self-locking head 403, the self-locking slot 406 is provided with a 45° guide chamfer at the groove opening, and the chamfer width is 0.2mm. This design can effectively reduce the movement resistance of the self-locking head 403 during the sliding in and out process.

[0052] When different numbers of the self-locking slots 406 are provided, the self-locking frequency range corresponding to each self-locking slot 406 is expressed as follows:

[0053] Frequency increase and extension self-locking range:

[0054]

[0055] High-frequency fallback self-locking range:

[0056]

[0057] In the formula Represents the number of self-locking card slots, is the elastic coefficient of the main beam spring, is the locking force of the self-locking unit, is the equivalent mass of the energy harvesting unit and the limited overhang length of the main cantilever beam, is the excitation amplitude, is the moving step length of the self-locking head, and its expression is:

[0058]

[0059] In the formula is the maximum extension distance of the main cantilever beam, is the minimum extension distance of the main cantilever beam, is the diameter of the self-locking slot.

[0060] The self-locking slots 406 can be set to different numbers and diameters to change the frequency adjustment range during the collector frequency adaptation process, and a suitable adjustment accuracy can be selected according to the actual application scenario.

[0061] Working principle:

[0062] The fixed unit 1 described in the present invention is used to fix the entire collector system. The external excitation device transmits vibration to the collector system through the base fixing hole 114. The fixed unit 1 cooperates with the mobile unit 2 through the rectangular slide groove 106, and the clip 105 provides limitation and guidance for the mobile unit 2; the mobile unit 2 is connected to the fixed unit 1 through the main beam spring 203. The axial displacement of the mobile unit 2 is released during the extension and contraction of the main beam spring 203, and the resonant frequency of the collector is passively adjusted so that the main cantilever beam 201 is always in the resonant stage. The energy collection unit 3 maintains a large amplitude deformation and outputs higher energy; when the resonant frequency of the main cantilever beam 201 matches the excitation frequency, the self-locking head 403 of the self-locking unit 4 is engaged with the self-locking slot 406 corresponding to the resonant frequency range under the action of the elastic force of the compression spring 402, thereby realizing mechanical locking of the resonant frequency, improving the frequency adaptation speed of the collector while reducing energy dissipation.

[0063] When external vibration excitation is transmitted to the base 101 through the base fixing hole 114, the main cantilever beam 201 generates forced vibration under the inertial force of the mass block 302. At this time, the piezoelectric plate 301 generates a piezoelectric effect due to the strain of the main cantilever beam 201, converting mechanical energy into electrical energy for output.

[0064] When the external excitation frequency changes, the main beam spring 203 installed at the end of the main cantilever beam 201 passively adjusts the elastic force under the action of the inertial force of the mass block 302 and the locking force of the self-locking unit 4, changing the effective overhang length of the main cantilever beam 201, so that the resonant frequency of the main cantilever beam 201 matches the external excitation frequency. The collector always maintains a resonant state, and the energy harvesting unit 3 outputs energy efficiently. The specific adjustment force analysis is as follows Figure 6 As shown, when the excitation frequency increases, the force on the collector system changes, and the inertial force of the mass block 302 Greater than the locking force of the self-locking unit 4 and the elastic force of the main beam spring 203 ,Right now When the main cantilever beam 201 is passively extended, the resonant frequency of the main cantilever beam 201 increases and matches the ambient excitation frequency. Figure 7 As shown, when the excitation frequency decreases, the resonant frequency of the collector moves away from the excitation frequency, and the inertial force of the mass block 302 Smaller than the locking force of the self-locking unit 4 and the elastic force of the main beam spring 203 ,Right now When the main cantilever beam 201 is passively shortened, the resonant frequency of the main cantilever beam 201 is reduced and matched with the ambient excitation frequency.

[0065] Under the action of the self-locking unit 4, when the resonant frequency of the main cantilever beam 201 matches the excitation frequency, the self-locking head 403 quickly and accurately snaps into the corresponding self-locking slots 406 on either side of the base 101. The effective overhang length of the main cantilever beam 201 is limited to an optimal range, ensuring that the piezoelectric plate 301 is in a maximum strain operating state and outputs a large amount of energy. When the ambient frequency changes beyond the frequency locking range of the current self-locking slot 406, the elastic restoring force of the main beam spring 203 and the inertial force of the mass 302 overcome the locking force of the compression spring 402, causing the self-locking head 403 to directionally disengage the self-locking slot 406 along the sliding slot 405, and the system automatically enters the next self-locking range. The provision of the self-locking unit 4 effectively increases the speed of the collector's frequency adaptive adjustment process and reduces energy dissipation during the adjustment process. The limit pin 401 effectively constrains the movement range of the main cantilever beam 201, preventing the main beam spring 203 from exceeding its elastic deformation limit.

[0066] The device ensures the linearity of the axial motion of the main cantilever beam 201 through the guide and limit design of the rectangular slide 106 and the clip 105. The zero-point calibration adjustment slot 108 allows fine-tuning of the reference position of the displacement sensor 5 to ensure measurement accuracy. The self-locking block 404, with its multiple equidistant self-locking slots 406, forms a frequency adjustment gradient, enabling efficient capture of vibration energy across a wide frequency range. The entire operating process forms a closed-loop control loop of "vibration excitation → energy conversion → stiffness adjustment → frequency locking," significantly improving energy conversion efficiency.

[0067] Figure 8 This is a comparison diagram of the time domain displacement response of the main cantilever beam 201 of the present invention, the traditional frequency adaptive energy harvester, and the fixed energy harvester under 10Hz excitation. It can be seen from the figure that when the excitation frequency is 10Hz, the harvester does not resonate. Since the end of the cantilever beam of the traditional fixed harvester is fixed, it cannot produce displacement. The effective length of the main cantilever beam 201 of the three harvesters is maintained at 70mm.

[0068] Figure 9 This is a comparison diagram of the time domain response of the displacement of the main cantilever beam 201 under 25Hz excitation of the present invention, the traditional frequency adaptive energy harvester, and the fixed energy harvester. When the excitation frequency is 25Hz, the present invention and the traditional frequency adaptive energy harvester enter the dynamic adjustment range of the resonant frequency of the main cantilever beam 201. It can be seen that due to the coupled oscillation of axial movement and longitudinal vibration of the traditional frequency adaptive energy harvester, the main cantilever beam 201 cannot be stabilized at the optimal overhang length position in time under the initial excitation. After 10.25s of nonlinear adjustment, it stabilizes at an effective overhang length of 78.33mm, maintains a large amplitude, and efficiently harvests energy. Due to the addition of the self-locking unit 4, the present invention can effectively reduce the nonlinear stable adjustment time of the effective overhang length of the main cantilever beam 201, so that the resonant frequency of the collector can be quickly and accurately matched with the excitation frequency. After 2.41s of nonlinear adjustment of the collector, the main cantilever beam 201 is stabilized at an effective overhang length of 78mm, which is 76.49% faster than the adjustment speed of the traditional frequency adaptive energy harvester. The effective overhang length of the main cantilever beam 201 after dynamic adjustment of the present invention is only 0.33mm different from that of the traditional frequency adaptive energy harvester, which proves that the present invention has precise frequency matching capability.

[0069] Figure 10This figure compares the time-domain displacement responses of the main cantilever beam 201 of the present invention, a conventional frequency-adaptive energy harvester, and a fixed energy harvester under 30Hz excitation. When the excitation frequency is 30Hz, both the present invention and the conventional frequency-adaptive energy harvester can continue to adjust the overhang length of the main cantilever beam 201. The conventional frequency-adaptive energy harvester's cantilever beam stabilizes at 75.29mm after 6.93s of dynamic adjustment, while the present invention only requires 1.51s of dynamic adjustment to stabilize at 76mm, increasing the adjustment speed by 78.21%. The difference in the length of the main cantilever beam 201 between the two harvesters is 0.71mm. Therefore, compared to conventional fixed harvesters, the present invention has the ability to dynamically adjust the effective overhang length of the main cantilever beam 201, quickly and accurately match the ambient excitation frequency, and broaden the effective operating bandwidth of the harvester. Compared to conventional frequency-adaptive energy harvesters, the present invention's dynamic adjustment speed of the effective overhang length of the main cantilever beam 201 is increased by 78.21%.

[0070] like Figure 11 As shown, by comparing the output voltage frequency domain response of the present invention with that of the traditional frequency adaptive energy harvester and the fixed energy harvester, it can be seen that the fixed energy harvester has a higher output voltage only near the resonant frequency because the length of the main cantilever beam 201 cannot be adjusted. The present invention and the traditional frequency adaptive energy harvester can dynamically match the environmental excitation due to the release of the axial displacement of the main cantilever beam 201, thereby greatly broadening the effective working bandwidth of the harvester. However, the traditional frequency adaptive energy harvester has a significant energy dissipation phenomenon due to the long duration of the nonlinear dynamic adjustment process. The present invention introduces a self-locking unit 4 to enable the harvester to quickly and accurately match the environmental excitation frequency, greatly reducing the energy dissipation of the harvester. Compared with the traditional frequency adaptive energy harvester, it maintains a similar effective working bandwidth, but the output voltage is significantly improved.

[0071] The above description is only a preferred example of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A piezoelectric vibration energy harvester with a self-locking function that quickly and accurately matches the excitation frequency, characterized by: It includes a fixed unit, a mobile unit, an energy collection unit, a self-locking unit and a displacement sensor, wherein the mobile unit is connected to the spring fixing hole in the fixed unit through the main beam spring, the main cantilever beam of the mobile unit is slidably installed in the rectangular slide groove of the fixed unit, and is guided and limited by the clip, the energy collection unit is located at the end of the main cantilever beam, the self-locking unit is located on both sides of the base of the fixed unit and is slidably connected to the mobile unit through a self-locking head, and the snap-fit ​​between the self-locking head and the self-locking slot realizes the locking of the collector mobile unit, and the displacement sensor is fixedly installed on the upper side of the base through a fixing frame.

2. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 1 is characterized in that: The fixing unit includes a base, a spring preload adjustment slot, a spring preload adjustment piece, a spring fixing hole, a clip, a rectangular slide, a fixing bracket, a zero point calibration adjustment slot, a fastening bolt, a nut, a bolt hole, a pin hole, a tenon groove and a base fixing hole, wherein a pair of spring preload adjustment slots are opened on the left side of the base, the spring preload adjustment piece is fixed above the spring preload adjustment slot by a fastening bolt and a nut, a spring fixing hole is provided at the right end of the spring preload adjustment piece, the clip is fixed to the base by a fastening bolt and a nut, a rectangular slide is provided on the base, a zero point calibration adjustment slot is provided on the surface of the base for realizing the reference position adjustment of the displacement sensor, the fixing bracket is used to fix and install the displacement sensor, the base has a bolt hole, which is matched with the fastening bolt and the nut to realize overall fixation, the base surface is processed with a pin hole and a tenon groove, the pin hole and the tenon groove are respectively matched with the limit pin and the tenon with tolerance to realize detachable connection, and a base fixing hole is provided at the bottom of the base for connecting the base with an external excitation device.

3. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 2 is characterized in that: The base is made of a photosensitive resin-based composite material.

4. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 1 is characterized in that: The mobile unit includes a main cantilever beam, a secondary beam, a main beam spring, a spring connection hole and a displacement sensor fixing hole, wherein two secondary beams are vertically fixed at the left end of the main cantilever beam, a piezoelectric piece is pasted on the effective cantilever root of the main cantilever beam, the right side of the main cantilever beam is fixedly connected to the mass block, the right side of the main beam spring is connected to the spring connection hole on the left side of the main cantilever beam, and a displacement sensor fixing hole is opened on the surface of the main cantilever beam, which is connected to the sliding rod of the displacement sensor for real-time monitoring and recording of the moving distance of the main cantilever beam.

5. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 4 is characterized in that: The main cantilever beam is made of brass.

6. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 1 is characterized in that: The energy collection unit includes a piezoelectric sheet and a mass block arranged at the end of the main cantilever beam.

7. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 6 is characterized in that: The piezoelectric piece is made of PZT-5H piezoelectric ceramic.

8. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 1 is characterized in that: The self-locking unit includes a limit pin, a compression spring, a self-locking head, a self-locking block, a sliding groove, a self-locking slot and a tenon, wherein the limit pin is used to limit the movement range of the main cantilever beam to ensure that the main beam spring is in the elastic working range. The tenon is below the self-locking block. The self-locking block is symmetrically installed on both sides of the base, and a plurality of equidistant self-locking slots are processed on the surface. The surface of the self-locking block is provided with a sliding groove. When the self-locking head is disengaged from the self-locking slot, it slides directionally along the sliding slot to play a guiding role. The compression spring is sleeved on the auxiliary beam, and the self-locking head is slidably connected to the auxiliary beam and slides along the direction of the auxiliary beam under the elastic force of the compression spring. The self-locking unit is self-locked or released through the plug-in cooperation between the self-locking head and the self-locking slot.

9. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 8 is characterized in that: The self-locking head is made of wear-resistant photosensitive resin material, and its head is designed as a frustum structure. The self-locking slot is a cylindrical groove structure, which forms a plug-in fit with the self-locking head. In order to optimize the sliding performance of the self-locking head, a 45° guide chamfer is provided at the opening of the self-locking slot.

10. The piezoelectric vibration energy harvester with self-locking function and rapid and accurate excitation frequency matching according to claim 8, characterized in that: The self-locking frequency range expression corresponding to the self-locking slot is: Frequency increase and extension self-locking range: High-frequency fallback self-locking range: In the formula Represents the number of self-locking card slots, is the elastic coefficient of the main beam spring, is the locking force of the self-locking unit, is the equivalent mass of the energy harvesting unit and the limited overhang length of the main cantilever beam, is the excitation amplitude, is the moving step length of the self-locking head, and its expression is: ； In the formula is the maximum extension distance of the main cantilever beam, is the minimum extension distance of the main cantilever beam, is the diameter of the self-locking slot.

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