A wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester

Abstract

A wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester relates to the technical field of Internet of Things power system design. An elastic beam is horizontally fixed between the supports on both sides of the base, a mass unit is fixed at the center of the elastic beam, and piezoelectric composite units are symmetrically installed on the elastic beam at both sides of the mass unit. The piezoelectric composite unit includes two layers of cymbal structure and a piezoelectric ceramic sheet sandwiched and bonded therebetween. The piezoelectric composite unit is fixed between the fractures at the corresponding positions of the elastic beam in the tensile direction. The micro-energy management module rectifies and stores the AC power generated by the piezoelectric composite unit to provide power for the Internet of Things module, and the Internet of Things module performs wireless broadcasting. The piezoelectric composite unit is used as the main body to generate electrical energy during vibration and is integrated with wireless sensor technology to replace traditional batteries as power supply, which is conducive to improving space utilization and energy density.

Description

Technical Field

[0001] The present invention relates to the technical field of Internet of Things power system design, and in particular to a wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester. Background Art

[0002] With the vigorous development of the Internet of Things, virtual connections between objects and people, and between objects and objects have been built in the real world, realizing the intelligent perception and monitoring of objects and data. The construction of the Internet of Things is inseparable from a large number of sensors, which means that a large amount of power supply is also required. The traditional power supply is mainly in the form of batteries. Although battery technology is constantly developing, the use of batteries always faces the challenges of leakage and charging. In addition, excessive use of batteries will undoubtedly lead to abuse problems, increase the burden of battery recycling and waste disposal, and ultimately cause environmental pollution. In order to meet the growing demand for sensors in the Internet of Things, the development of a new form of power that is more environmentally friendly and clean to reduce dependence on batteries is a goal that academia and industry have been pursuing.

[0003] By using advanced energy capture technologies (such as solar and wind energy), IoT terminal devices can autonomously extract energy from the environment to maintain normal operation without the need for additional batteries. Such IoT systems are called passive IoT systems. However, current energy capture technologies are heavily dependent on favorable weather conditions. Solar and wind energy systems usually include a battery as the actual power source and an energy conversion module to charge the battery. In contrast, the recovery technology of dissipated energy such as heat, radio frequency and vibration shows obvious superiority because these types of energy are widely, stably and abundantly distributed in daily urban life. For example, vehicles continuously generate heat, vibration and radio frequency during operation, and only require electricity when running. This provides a good opportunity to develop a battery-free "symbiotic power source" that can utilize the energy dissipated during operation and immediately convert it into electricity for secondary use, thereby reducing the IoT's dependence on batteries and wiring requirements. However, to achieve this goal, current technologies still have the disadvantage of generally inefficient power generation capacity, especially in limited available space.

[0004] Piezoelectric vibration energy harvesters are considered to be a promising solution due to their green materials (such as lead-free piezoelectric ceramics), high energy conversion efficiency, lightness, simplicity, and scalability from microscopic to human scales, and their matching with vibration energy in daily life. However, existing high-performance piezoelectric vibration energy harvesters are generally bulky, and directly reducing their size and weight will lead to a significant decrease in performance, which seriously hinders the practical application of piezoelectric vibration energy harvesters in the field of the Internet of Things. Summary of the invention

[0005] In order to address the shortcomings of the background technology, the present invention provides a wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester. It uses a piezoelectric composite unit as the main body to generate electrical energy during vibration and is integrated with wireless sensor technology to replace traditional batteries as power supply, which is beneficial to improving space utilization and energy density.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester, comprising a base, an elastic beam, a piezoelectric composite unit, a mass unit and a sensor unit, supports are arranged on both sides of the base and the elastic beam is horizontally fixed between the two supports, the mass unit is fixed at the center of the elastic beam, and the piezoelectric composite units are symmetrically installed on the elastic beam at both sides of the mass unit, the piezoelectric composite unit comprises a piezoelectric ceramic sheet and a two-layer cymbal structure, the cymbal structure is an integrally formed structure and comprises two relatively arranged An arched beam and two connecting beams connecting the ends of the two beams, the piezoelectric composite unit is tensioned along the axis of the arched beam and fixed between the fractures at corresponding positions of the elastic beam, the piezoelectric ceramic sheet is clamped and bonded between the connecting beams of the two layers of cymbal structure, the sensor unit is arranged on the base and connected to the piezoelectric composite unit through wires, the sensor unit includes a micro energy management module and an Internet of Things module, the micro energy management module rectifies and stores the AC power generated by the piezoelectric composite unit to provide power for the Internet of Things module, and the Internet of Things module can perform wireless broadcasting.

[0007] Furthermore, the piezoelectric composite units are arranged in series in an array, and more than two piezoelectric composite units are arranged on the elastic beam on one side of the mass unit along the length direction, and the two layers of cymbal structures of two adjacent piezoelectric composite units are bonded and connected in the middle of the arched beam.

[0008] Furthermore, the piezoelectric composite unit is arranged at the 1 / 4 and 3 / 4 positions on the elastic beam.

[0009] Furthermore, the micro energy management module is controlled based on the LTC3588-1 chip, performs full-bridge rectification on the AC power generated by the piezoelectric composite unit, and stores the rectified DC power in the capacitor C STO middle.

[0010] Furthermore, the LTC3588-1 chip has a capacitor C STO The voltage across the two ends is V STO Hysteresis control is performed. When the voltage V STO When it reaches 5.05V, the capacitor C STO The stored electrical energy is converted to 3.3V voltage to drive the IoT module. STO When it drops to 3.67V, the capacitor C STOThe IoT module is disconnected, while the piezoelectric composite unit continues to charge the capacitor C STO to charge.

[0011] Furthermore, the Internet of Things module includes an HJ-131IMH chip and a sensor communicating with the chip. After the HJ-131IMH chip reads the data from the sensor, it performs periodic wireless broadcasting to the user's wireless terminal via Bluetooth Beacon.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: based on the planar design concept, force amplification mechanism and structural nonlinear characteristics, the present invention designs a quasi-2D tension-compression mode piezoelectric energy harvester with a piezoelectric composite unit as the main body, adopts the boundary condition of fixed supports at both ends, has strong nonlinearity in the vibration process, is conducive to broadening the vibration bandwidth, and integrates it with wireless sensing technology, replacing traditional batteries as power supply, reducing the Internet of Things' dependence on batteries and wiring requirements, and can achieve long-term battery-free wireless communication, avoiding battery leakage and charging problems, and is small in size and lightweight, and can be installed in a small and enclosed space. The cymbal structure of the piezoelectric composite unit has an amplifying effect on the piezoelectric effect, which helps to increase the power of energy capture. Through arrayed design, it can further meet the needs of higher power density, solve the bottleneck problem of low power caused by small size, and is conducive to improving space utilization and energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is an axonometric diagram of the overall structure of the wireless sensing system of the present invention;

[0014] Figure 2 is an exploded view of the piezoelectric composite unit of the present invention;

[0015] Figure 3 is a force diagram of the cymbal structure of the present invention;

[0016] Figure 4 is a circuit diagram of a sensor unit of the present invention;

[0017] Figure 5 It is a schematic diagram of the arrayed quasi-2D tension-compression mode piezoelectric energy harvester of the present invention.

[0018] In the figure: 1-base, 2-elastic beam, 3-piezoelectric composite unit, 4-mass unit, 5-sensor unit, 6-cymbal structure, 7-adhesive, 8-piezoelectric ceramic sheet, 9-arched beam, 10-micro energy management module, 11-Internet of Things module. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] like Figure 1 to Figure 5 As shown, a wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester includes a base 1, an elastic beam 2, a piezoelectric composite unit 3, a mass unit 4 and a sensor unit 5.

[0021] Combination Figure 1 As shown, supports are arranged on both sides of the base 1 and an elastic beam 2 is fixed horizontally between the two supports, which is used to carry a piezoelectric composite unit 3 and a mass unit 4. The mass unit 4 is fixed at the center of the elastic beam 2 by an adhesive 7 and can only produce displacement in the vertical direction. The mass unit 4 is an element with a predefined size and mass, which can tune the natural frequency of the system and capture more energy by changing the mass. The piezoelectric composite unit 3 is symmetrically installed on the elastic beam 2 at both sides of the mass unit 4. The piezoelectric composite unit 3 is fixed between the fractures at the corresponding positions of the elastic beam 2 by an adhesive 7 in the tensile direction, wherein the piezoelectric composite unit 3 is preferably arranged at the 1 / 4 and 3 / 4 positions on the elastic beam 2 to reduce the adverse bending moment transmitted from the elastic beam 2 to the piezoelectric composite unit 3. The elastic beam 2, the piezoelectric composite unit 3 and the mass unit 4 together form a quasi-2D tension-compression mode piezoelectric energy harvester. Quasi-2D means that the planarity of the structure is maintained to the maximum extent while retaining a certain thickness. In this scheme, planarization is specifically manifested as ensuring that the ratio of the width dimension to the thickness dimension of the piezoelectric energy harvester is greater than 10.

[0022] Combination Figure 2 As shown, the upper and lower layers of the piezoelectric composite unit 3 are both cymbal structures 6, and the middle layer is a piezoelectric ceramic sheet 8. The piezoelectric ceramic sheet 8 and the cymbal structure 6 are bonded and connected by an adhesive 7 to form a "cymbal structure-piezoelectric ceramic sheet-cymbal structure". The cymbal structure 6 is a mechanically integrated processing structure, which helps to improve the reliability and service life of the quasi-2D tension-compression mode piezoelectric energy harvester, and includes two relatively arranged arched beams 9 and two connecting beams connecting the ends of the two.

[0023] Combination Figure 3As shown, the piezoelectric composite unit 3 is tensile in the axial direction of the arched beam 9, and the piezoelectric ceramic sheet 8 is sandwiched and bonded between the connecting beams of the two layers of cymbal structure 6. When the mass unit 4 generates vibration excitation in the vertical direction, it will drive the elastic beam 2 to stretch, thereby generating a tensile force F1 at the arched beam 9 of the piezoelectric composite unit 3, and converting it into a pressure F2 of the two connecting beams on the piezoelectric ceramic sheet 8, so that the piezoelectric ceramic sheet 8 generates a piezoelectric effect. The tension-compression mode means that when the mass unit 4 vibrates in the vertical direction, the cymbal structure 6 in the piezoelectric composite unit 3 is stretched and exerts pressure on the piezoelectric ceramic sheet 8, thereby improving the energy capture effect.

[0024] Combination Figure 1 As shown, the sensor unit 5 is fixed to the base 1 by adhesive 7 and connected to the piezoelectric composite unit 3 by wires to provide power to it. The sensor unit 5 can use the power generated by the quasi-2D tension-compression mode piezoelectric energy harvester for long-term wireless broadcasting in a battery-free environment.

[0025] Combination Figure 4 As shown, the sensor unit 5 includes a micro energy management module 10 and an Internet of Things module 11. The micro energy management module 10 rectifies and stores the AC power generated by the piezoelectric composite unit 3 to provide power for the Internet of Things module 11 to ensure the subsequent stable startup and operation of the Internet of Things module 11, and the Internet of Things module 11 can perform wireless broadcasting.

[0026] The micro energy management module 10 is controlled based on the LTC3588-1 chip design, which can perform full-bridge rectification on the AC power generated by the quasi-2D tension-compression mode piezoelectric energy harvester and store the rectified DC power in the capacitor C. STO In addition, the LTC3588-1 chip can STO The voltage across the two ends is V STO Hysteresis control is performed. When the voltage V STO When the voltage reaches 5.05V, the micro energy management module 10 switches the capacitor C STO The stored electrical energy is converted into a stable 3.3V voltage to drive the IoT module 11, and then the voltage V STO Starts to decrease when the voltage V STO When the voltage drops to 3.67V, the micro energy management module 10 switches the capacitor C STO The Internet of Things module 11 is disconnected, and the micro energy management module 10 starts to continue to charge the capacitor C STO Charging, voltage V STO Starts to rise until the voltage V STO When the voltage reaches 5.05V again, the micro energy management module 10 starts supplying power to the Internet of Things module 11 again, and the reciprocating cycle completes the effective management of the electric energy generated by the quasi-2D tension-compression mode piezoelectric energy harvester.

[0027] The IoT module 11 is a Bluetooth low-power Beacon node, which is used to collect data from various sensors and broadcast wireless data. It includes a highly integrated Bluetooth low-power chip HJ-131IMH and sensors that communicate with it. The sensor selects a low-power sensor according to application requirements. The Bluetooth low-power chip HJ-131IMH and the sensor communicate sensor data through a suitable peripheral interface, such as I2C, SPI or UART. After the HJ-131IMH chip reads the sensor data, it broadcasts it wirelessly periodically through the Bluetooth Beacon method, and the user receives the broadcast sensor data through the wireless terminal.

[0028] Combination Figure 5 As shown, in order to further improve the performance of the quasi-2D tension-compression mode piezoelectric energy harvester, the piezoelectric composite unit 3 can be designed to be arranged in series in an array, that is, the piezoelectric composite unit 3 is taken as the basic unit, and it is connected in series in the manner of "a bow beam connecting the next bow beam" to form an array, and N (N≥2) piezoelectric composite units 3 are arranged on the elastic beam 2 on one side of the mass unit 4 along the length direction. Due to the symmetrical form, there are a total of 2N piezoelectric composite units 3 on the elastic beam 2, and the two-layer cymbal structure 6 of two adjacent piezoelectric composite units 3 is bonded and connected by an adhesive 7 in the middle position of the bow beam 9, which helps to improve the output power and space utilization.

[0029] In the material selection of the present invention, spring steel is selected as the material of the elastic beam 2 and the cymbal structure 6 because spring steel has excellent comprehensive properties (such as anti-elasticity reduction performance, etc.). PZT-5H is selected as the piezoelectric ceramic sheet 8 because of its high electromechanical coupling coefficient and strong piezoelectric performance. Nickel material has a high density, so the mass unit 4 is made of nickel material. In addition to the material selection given above, the materials of each component can also be replaced by other materials under the premise of achieving the same effect.

[0030] In summary, the present invention has the following innovative features:

[0031] 1. In order to seek a solution to replace battery dependence, a new concept of battery-free "symbiotic power source" is proposed, which has the characteristics of high power generation and low space requirements, providing a potential idea for achieving sustainable and efficient power solutions;

[0032] 2. Combining vibration energy harvesting technology with wireless sensing technology to achieve long-term data transmission in a battery-free environment. The designed quasi-2D tension-compression mode piezoelectric energy harvester can be installed in a small and confined space to power the sensor, solving the bottleneck problem of low power caused by small size;

[0033] 3. Based on the quasi-2D concept, the structural nonlinearity of the fixed-end beams and the amplification characteristics of the cymbal structure on the piezoelectric effect are combined, which not only broadens the working frequency band, but also improves the energy capture density.

[0034] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other forms of assembly without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0035] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester, characterized in that: The invention comprises a base (1), an elastic beam (2), a piezoelectric composite unit (3), a mass unit (4) and a sensor unit (5), wherein supports are arranged on both sides of the base (1) and the elastic beam (2) is horizontally fixed between the two supports, the mass unit (4) is fixed at the center of the elastic beam (2), and the piezoelectric composite unit (3) is symmetrically mounted on the elastic beam (2) at positions on both sides of the mass unit (4), the piezoelectric composite unit (3) comprises a piezoelectric ceramic sheet (8) and a two-layer cymbal structure (6), the cymbal structure (6) is an integrally formed structure and comprises two arched beams (9) arranged opposite to each other and two connecting beams connecting the ends of the two, the piezoelectric composite unit (3) takes the axial direction of the arched beam (9) as the tensile direction and The piezoelectric ceramic sheet (8) is fixed between the fractures at the corresponding positions of the elastic beam (2), and is clamped and bonded between the connecting beams of the two layers of the cymbal structure (6). The sensor unit (5) is arranged on the base (1) and is connected to the piezoelectric composite unit (3) through a wire. The sensor unit (5) includes a micro energy management module (10) and an Internet of Things module (11). The micro energy management module (10) rectifies and stores the alternating current power generated by the piezoelectric composite unit (3) to provide power for the Internet of Things module (11). The micro energy management module (10) is controlled based on the LTC3588-1 chip, performs full-bridge rectification on the alternating current power generated by the piezoelectric composite unit (3), and stores the rectified direct current power in a capacitor C STO The LTC3588-1 chip has a capacitor C STO The voltage across the two ends is V STO Hysteresis control is performed. When the voltage V STO When it reaches 5.05V, the capacitor C STO The electric energy stored in the 3.3V voltage is converted to drive the IoT module (11). When the voltage V STO When it drops to 3.67V, the capacitor C STO The piezoelectric composite unit (3) is disconnected from the Internet of Things module (11), while the piezoelectric composite unit (3) continues to connect the capacitor C STO The Internet of Things module (11) is capable of wireless broadcasting, and comprises an HJ-131IMH chip and a sensor communicating with the chip. After the HJ-131IMH chip reads the data from the sensor, it performs periodic wireless broadcasting to the user's wireless terminal in the form of a Bluetooth Beacon.

2. A wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester according to claim 1, characterized in that: The piezoelectric composite units (3) are arranged in series in an array, and more than two piezoelectric composite units (3) are arranged on the elastic beam (2) on one side of the mass unit (4) along the length direction, and the two layers of cymbal structures (6) of two adjacent piezoelectric composite units (3) are bonded and connected at the middle position of the arched beam (9).

3. A wireless sensing system powered by a quasi-2D tension-compression mode piezoelectric energy harvester according to claim 1 or 2, characterized in that: The piezoelectric composite unit (3) is arranged at the 1 / 4 and 3 / 4 positions on the elastic beam (2).

Images