CN115149626A - Vibration-magnetic field broadband composite energy collector based on vibration damper - Google Patents
Vibration-magnetic field broadband composite energy collector based on vibration damper Download PDFInfo
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H—ELECTRICITY
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- H02N2/186—Vibration harvesters
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Abstract
The invention discloses a vibration-magnetic field broadband composite energy collector based on a vibration damper, which comprises the vibration damper, wherein the vibration damper is provided with a clamp, and further comprises two main cantilever beams, two cross beams and four auxiliary cantilever beams, the two main cantilever beams are parallel to a cable, one ends of the two main cantilever beams are connected with the clamp, the other ends of the two main cantilever beams are respectively connected with the cross beams, the middle parts of the cross beams are connected with the other ends of the main cantilever beams, the cross beams are perpendicular to the main cantilever beams and are positioned in the same horizontal plane, two ends of each cross beam are respectively connected with one auxiliary cantilever beam, the auxiliary cantilever beams are parallel to the main cantilever beams, one ends of the auxiliary cantilever beams are connected with one ends of the main cantilever beams, and the other ends of the auxiliary cantilever beams extend towards the direction of the clamp and are connected with magnet blocks; the upper surface of the main cantilever beam is provided with a first piezoelectric layer, and the outer side surface of the auxiliary cantilever beam is provided with a second piezoelectric layer. The invention can collect horizontal vibration energy and magnetic field energy of the power transmission line and convert the horizontal vibration energy and the magnetic field energy into electric energy, and can provide the electric energy for the wireless sensor node.
Description
Technical Field
The invention relates to the technical field of power equipment monitoring, in particular to a vibration-magnetic field broadband composite energy collector based on a vibration damper.
Background
The influence of the improvement of the power system and the expansion of the coverage area of the power grid on the life of people, the industrial demand and the agricultural production is larger and larger, and the safe operation of the power transmission line can bring very stable guarantee to the regional development. The safety and the reliability of the intelligent power grid are directly reflected by the running state of the power transmission line, and huge loss is inevitably generated if a fault problem occurs. When the power grid covers a large area, a plurality of lines can be in various rare and complex environments, are easily affected by the problems of high temperature, icing, wind vibration, lightning stroke, corrosion and the like, and have a plurality of faults. The most common faults are strand breakage and wire breakage of the transmission line, vibration and sometimes even waving occur when the wire is subjected to wind, and stress points of the wire are often subjected to pulling, bending, extruding and other forces, so that fatigue and damage of the wire material are caused, the strand breakage and the wire breakage are finally caused, and the performance of the transmission line such as the current-carrying capacity of the line and the mechanical performance are finally reduced. Therefore, the operation condition of the transmission line needs to be monitored online in real time to prevent faults.
The online monitoring of the state of the power transmission line plays an important role in the economic, efficient, safe and reliable operation of the smart power grid, and the online monitoring system of the power transmission line is an indispensable part of the smart power grid in China. However, with the popularization of monitoring systems, the problem of power supply becomes an urgent problem. Because the power transmission line is located in a severe environment in the field for a long time and is limited by self insulation conditions, the power supply of the monitoring equipment can not directly obtain electric energy through the electric wire, a complete self-powered system is urgently needed to supply power to the monitoring equipment, the self-powered intelligent power grid has a key propulsion effect on the maturation and the science and technology of the intelligent power grid in China, self-powered is a new research direction at present, and the self-powered intelligent power grid has great research significance on the aspects of environmental monitoring, intelligent industry, military field and energy environmental protection.
At present, in order to meet the requirements of environmental friendliness and foresight, the optimal solution of self-power supply is to supply power by using energy which is not utilized in the working environment of the sensor node. Have fine promotion for traditional lithium cell, traditional power supply mode exists polluted environment, maintenance cost height and the short not enough of power supply cycle, accomplishes a green novel decision-making to the self-power formation through adopting the new mode of self-acquisition self-service, replaces traditional power supply mode to upgrade, satisfies the long-term demand of deploying of sensor node.
The power transmission line is filled with unused energy, such as wind energy, electric field energy, magnetic field energy, solar energy, vibration energy and other various energies. Wherein, solar energy and wind energy are greatly restricted by the environment and have strong limitation; the electric field energy is limited by the current and voltage of the transmission line; the magnetic field energy distribution is more sufficient; the vibration energy has the advantages of being not easily interfered by an electric field, wide in source, large in electromechanical coupling coefficient, high in energy density and the like. In a plurality of energy collection technologies, a mode of combining magnetic field and vibration energy for power generation is adopted, and the composite energy collection has the advantages of multiple advantages, can effectively collect wider frequency band energy and increase output power, is a research hotspot at present, and has great scientific research significance.
Therefore, the prior art is deficient in a vibration-magnetic field broadband composite energy collector based on a vibration damper, which can collect vibration energy of a power transmission line and convert magnetic field energy into electric energy, and provide the electric energy for a wireless sensor node.
Disclosure of Invention
In view of at least one of the defects of the prior art, the present invention provides a vibration-magnetic field broadband composite energy collector based on a vibration damper, which can collect vibration energy of a transmission line and convert magnetic field energy into electric energy, and can be provided for a wireless sensor node.
In order to achieve the purpose, the invention adopts the following technical scheme: a vibration-magnetic field broadband composite energy collector based on a vibration damper comprises the vibration damper, wherein the vibration damper is provided with a clamp, and further comprises two main cantilever beams, two cross beams and four auxiliary cantilever beams, the two main cantilever beams are parallel to a cable, one ends of the two main cantilever beams are connected with the clamp, the other ends of the two main cantilever beams are respectively connected with the cross beams, the middle parts of the cross beams are connected with the other ends of the main cantilever beams, the cross beams are perpendicular to the main cantilever beams and are positioned in the same horizontal plane, two ends of each cross beam are respectively connected with one auxiliary cantilever beam, the auxiliary cantilever beams are parallel to the main cantilever beams, one end of each auxiliary cantilever beam is connected with one end of each cross beam, and the other end of each auxiliary cantilever beam extends towards the direction of the clamp and is connected with a magnet block; the upper surface of the main cantilever beam is provided with a first piezoelectric layer, and the outer side surface of the auxiliary cantilever beam is provided with a second piezoelectric layer; the main cantilever beam is subjected to horizontal vibration collection energy transmitted by the power transmission line and transmitted to the first piezoelectric layer for power generation, and the auxiliary cantilever beam collects vertical vibration caused by the magnetic field energy of the power transmission line through the magnet block and transmits the vertical vibration to the second piezoelectric layer for power generation.
The main cantilever beam and the cross beam, and the cross beam and the auxiliary cantilever beam are connected together through inertia mass blocks.
The inertial mass is made of resin.
The main cantilever beam, the cross beam and the auxiliary cantilever beam are all in a plate shape, wherein the main cantilever beam and the cross beam are horizontally arranged, and the auxiliary cantilever beam is vertically arranged.
The main cantilever beam, the cross beam and the auxiliary cantilever beam are made of beryllium bronze, and the main cantilever beam is used as a substrate of the first piezoelectric layer; the secondary cantilever serves as a substrate of the second piezoelectric layer; the first piezoelectric layer and the second piezoelectric layer are respectively adhered to the main cantilever beam and the auxiliary cantilever beam through conductive silver adhesive; the first piezoelectric layer and the second piezoelectric layer are made of PZT-5H piezoelectric ceramics, and vibration energy is converted into electric energy; the magnet block is made of neodymium iron boron magnetic materials.
The vibration-magnetic field broadband composite energy collector based on the vibration-proof hammer has the remarkable effects that the vibration-magnetic field broadband composite energy collector based on the vibration-proof hammer can collect vibration energy of a power transmission line and magnetic field energy and convert the vibration energy and the magnetic field energy into electric energy, and the electric energy can be provided for wireless sensor nodes for use.
Drawings
FIG. 1 is a block diagram of the present invention;
FIG. 2 is a modal analysis diagram of the front four-order mode shape of the anti-seismic hammer type composite energy harvester;
FIG. 3 is a simulated open circuit voltage analysis plot of a damper-type composite energy collector;
FIG. 4 is a graph of impedance matching and generated power analysis for a crash proof hammer type composite energy harvester;
FIG. 5 is a graph of power generation performance analysis of various excitation accelerations for a crash proof hammer type composite energy collector;
FIG. 6 is a diagram of a power management circuit design;
FIG. 7 is a circuit diagram of a power management circuit;
FIG. 8 is a diagram of the overall system architecture of the wireless temperature measurement system;
FIG. 9 is a schematic circuit diagram of a temperature sensor;
FIG. 10 is a schematic diagram of a NRF24LE1 minimum system;
FIG. 11 is a schematic diagram of the operation of a piezoelectric crystal;
FIG. 12 is a schematic view of a cantilever beam motion model;
FIG. 13 is a schematic view of a piezoelectric cantilever beam unit under excitation;
FIG. 14 is an equivalent circuit schematic of a cross-sectional piezoelectric cantilever;
figure 15 is a cross-sectional schematic of a piezoelectric cantilever under the influence of a magnetic field of a power line.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
As shown in fig. 1-15, a vibration-magnetic field broadband composite energy collector based on a vibration damper comprises a vibration damper, wherein the vibration damper is provided with a clamp 1, and further comprises two main cantilever beams 2, two cross beams 3 and four auxiliary cantilever beams 4, the two main cantilever beams 2 are parallel to a cable, one ends of the two main cantilever beams 2 are connected with the clamp 1, the other ends of the two main cantilever beams 2 are respectively connected with the cross beams 3, the middle parts of the cross beams 3 are connected with the other ends of the main cantilever beams 2, the cross beams 3 are perpendicular to the main cantilever beams 2 and are positioned in the same horizontal plane, two ends of each cross beam 3 are respectively connected with one auxiliary cantilever beam 4, the auxiliary cantilever beams 4 are parallel to the main cantilever beams 2, one end of each auxiliary cantilever beam 4 is connected with one end of the cross beam 3, and the other end extends towards the clamp 1 and is connected with a magnet block 5; the upper surface of the main cantilever beam 2 is provided with a first piezoelectric layer 6, and the outer side surface of the auxiliary cantilever beam 4 is provided with a second piezoelectric layer 7; the horizontal vibration collected energy of the main cantilever beam 2 transmitted by the power transmission line 9 is transmitted to the first piezoelectric layer 6 to generate electricity, and the vertical vibration caused by the energy of the power transmission line 9 collected by the auxiliary cantilever beam 4 through the magnet 5 is transmitted to the second piezoelectric layer 7 to generate electricity.
The main cantilever beam 2 and the cross beam 3, and the cross beam 3 and the auxiliary cantilever beam 4 are connected together through an inertia mass block 8.
The inertial mass 8 is made of resin.
The main cantilever beam 2, the cross beam 3 and the auxiliary cantilever beam 4 are all in a plate shape, wherein the main cantilever beam 2 and the cross beam 3 are horizontally arranged, and the auxiliary cantilever beam 4 is vertically arranged.
The main cantilever beam 2, the beam 3 and the auxiliary cantilever beam 4 are made of beryllium bronze, and the main cantilever beam 2 is used as a substrate of the first piezoelectric layer 6; the secondary cantilever 4 acts as a substrate for the second piezoelectric layer 7; the first piezoelectric layer 6 and the second piezoelectric layer 7 are respectively adhered to the main cantilever beam 2 and the auxiliary cantilever beam 4 through conductive silver adhesive; the first piezoelectric layer 6 and the second piezoelectric layer 7 are made of PZT-5H piezoelectric ceramics, and vibration energy is converted into electric energy; the magnet block 5 is made of neodymium iron boron magnetic materials.
The shockproof hammer type composite energy collector is connected with a power management circuit. The power management circuit comprises a rectifying charging circuit, a charging and discharging control circuit and a voltage stabilizing output circuit, the rectifying charging circuit is connected with the shockproof hammer type energy collector to convert the electric energy of the shockproof hammer type energy collector into direct current, and the charging and discharging control circuit is connected with the rectifying charging circuit to store the electric energy in an energy storage capacitor C S1 And the voltage stabilizing output circuit is connected with the charge and discharge control circuit to output stable direct current voltage. And the voltage-stabilizing output circuit supplies power to the wireless sensing node.
The rectification charging circuit is provided with bridge rectifier circuits, the number of the bridge rectifier circuits is equal to the sum of the number of the first piezoelectric layers 6 and the number of the second piezoelectric layers 7, each of the first piezoelectric layers 6 and the second piezoelectric layers 7 is connected with the corresponding bridge rectifier circuit, two input ends of each bridge rectifier circuit are connected with two output ends of the first piezoelectric layers 6 or the second piezoelectric layers 7, positive output ends of all the bridge rectifier circuits are connected with the negative electrode of a voltage stabilizing tube D8 in parallel, and all the bridge rectifier circuits are connected with the negative electrode of the voltage stabilizing tube D8 in parallelThe negative output end of the rectification circuit is connected in parallel and then connected with the positive electrode of a voltage regulator tube D8, and the charge and discharge control circuit comprises an LTC3588 chip and an energy storage capacitor C S1 。
The PZ1 end of the LTC3588 chip is connected with the cathode of a voltage regulator tube D8, the PZ2 end of the LTC3588 chip is connected with the anode of the voltage regulator tube D8, and the Vin end of the LTC3588 chip is connected with an energy storage capacitor C S1 One terminal of (C), an energy storage capacitor S1 The other end of the LTC3588 chip is grounded, and the Vin end of the LTC3588 chip is also connected with the CAP end of the LTC3588 chip through a capacitor C3; the SW terminal of the LTC3588 chip is connected with the Vout terminal of the LTC3588 chip through an inductor L1; the Vout end of the LTC3588 chip is grounded through a capacitor C4, the Vin2 end of the LTC3588 chip is grounded through a capacitor C6, and the D0 end of the LTC3588 chip is connected with the D1 end in parallel and then connected with the Vin2 end; the capacitor C5 is connected in parallel with the capacitor C4.
The voltage stabilizing output circuit is provided with an AP7354 chip, the Vout end of the LTC3588 chip is connected with the Vin end of the AP7354 chip, the EN end of the AP7354 chip is connected with the PGOOD end of the LTC3588 chip, the GND end of the AP7354 chip is grounded, the Vout end of the AP7354 chip is grounded through a capacitor C7, and the Vout end of the AP7354 chip outputs 3.3 direct-current voltage to supply power for the wireless sensing node.
A wireless sensing node is powered by the power management circuit.
The wireless sensing node is provided with a temperature sensor, and the temperature sensor is connected with a radio frequency transmitting unit. The temperature sensor adopts Si7050 temperature sensor, and Si7050 temperature sensor is provided with signal output terminal SCL and signal output terminal SDA, the radio frequency sending unit is provided with NRF24LE1 module, and the P0.3 end and the P0.5 end of NRF24LE1 module are connected signal output terminal SCL and signal output terminal SDA respectively, and NRF24LE1 module is connected with the antenna. The VDD end and the ground end of the Si7050 temperature sensor and the NRF24LE1 module are respectively connected with the Vout end and the ground end of the P7354 chip. The wireless sensing node can also be a wireless sensing contact point of images, wind speeds and the like.
The utility model provides a contain wireless sensing system of wireless sensing node, still includes data receiving terminal and data show end, and the data receiving terminal adopts NRF24L01 radio frequency module, and NRF24L01 radio frequency module wireless connection NRF24LE1 module, NRF24L01 radio frequency module are connected with STM32F103RBT6 singlechip, the data show end is upper computer, and STM32F103RBT6 singlechip is connected upper computer.
The structure of the anti-vibration hammer type composite energy collector is shown in figure 1, and the anti-vibration hammer type composite energy collector mainly comprises a clamp 1, a horizontally arranged main cantilever beam 2, a cross beam 3, a vertically arranged auxiliary cantilever beam 4, a magnet block 5, a first piezoelectric layer 6, a second piezoelectric layer 7 and the like. The clamp 1 can be made of materials such as nylon and the like, belongs to the existing mature technology, is not described in detail, and plays a role of being fixed on the power transmission line 9; the middle part of the clamp 1 is connected with the main cantilever beam 2, can acquire energy by horizontal vibration transmitted by the power transmission line 9 and transmit the energy to the first piezoelectric layer 6 for power generation, the middle part of the clamp 5 is connected with the auxiliary cantilever beam 4, and vertical vibration is caused to transmit energy to the second piezoelectric layer 7 mainly by acquiring magnetic field energy of the power transmission line 9; the inertia mass block 8 is made of 8000 resin through 3D, and has the functions of connecting devices and transferring inertia; the magnet block 5 is made of a neodymium iron boron strong magnetic material, and can couple magnetic field energy and become a mass block to drive the cantilever beam to vibrate; the first piezoelectric layer 6 and the second piezoelectric layer 7 are made of PZT-5H piezoelectric ceramics, and can convert vibration energy into electric energy.
The composite energy collector provided by the embodiment provides a scheme for online monitoring of the power transmission line, and can effectively collect and output energy.
The components are designed in COMSOL according to the structure of FIG. 1 above, with the specific parameters as in Table 1.
TABLE 3.1 structural parameters
After the model is constructed, material properties need to be defined, wherein the parameters of young's modulus, poisson ratio and the like of each part are shown in table 2.
Table 2 material Property parameters
In the field of piezoelectric energy collection, the inherent characteristics of the structure can be displayed through modal analysis, and the method is a good analysis method for structural mechanics and vibration. The piezoelectric crystal mainly generates electricity through deformation, and the larger the deformation is in an endurable range, the stronger the electricity generation capacity is, and the reaction to the mode is also realized. For the shockproof hammer type composite energy collector, the resonance frequency of each order and a vibration model of the resonance frequency are mainly solved, and the front four-order vibration mode of the shockproof hammer type collector is shown in figure 2.
It can be seen that in the first four-order mode, the frequency of the first-order mode does not make the main cantilever beam 2 vibrate, only the auxiliary cantilever beam 4 slightly vibrates, and the first-order frequency is 4.6Hz. The second-order vibration mode is similar to the third-order vibration mode, the main cantilever beam 2 and the auxiliary cantilever beam 4 vibrate, the vibration amplitude is moderate, and the second-order vibration frequency and the third-order vibration frequency are 11.3Hz and 16.2Hz respectively. The fourth order vibration type main cantilever beam 2 and the auxiliary cantilever beam 4 move violently along with the mass block, the piezoelectric layer is deformed in the width direction due to the high-order vibration with the vibration frequency of 29.5Hz, the piezoelectric crystal is broken due to the torsional force of the degree, and the optimal energy harvesting effect cannot be achieved. Better output can be obtained by making the environmental vibration frequency of the anti-vibration hammer composite energy collector close to the second-order and third-order vibration frequencies as much as possible.
In order to improve the output voltage of the shockproof hammer type composite energy collector, the system improves the environmental vibration energy collection efficiency, and the simulated voltage response output characteristic is analyzed. Under different frequencies, corresponding to different cantilever beam displacement changes, the obtained voltage, output power and other properties can be calculated. With the excitation source with the excitation acceleration of 1g, the simulated open-circuit voltage of the piezoelectric cantilever can be obtained as shown in fig. 3.
It can be seen that the peak open circuit voltage of 25.2V is reached at a composite damper energy collector frequency of 11Hz, and the peak open circuit voltage of 11.5V is reached at a frequency of 14.5 Hz. This is also in good agreement with the previous modal response, with a relatively large output voltage being obtained near the second and third order modes.
Impedance matching and analyzing the generated power: the piezoelectric crystal has internal resistance, so when a load resistor is applied, the generated power of the piezoelectric crystal changes along with the change of the resistance, and in order to find the optimal generated power, the optimal impedance matching needs to be found. The output power versus load change curve at the frequency peak point set at 11Hz is shown in fig. 4.
As can be seen from fig. 4, the load power increases from the beginning as the load resistance increases linearly, and after reaching the best matching impedance of 10k Ω, the output power reaches a maximum of 5.5mW, and then decreases as the resistance increases. With this increasing load trend, the voltage will increase all the time, reaching saturation.
Analysis of power generation performance for different excitation accelerations: the environment external excitation acceleration plays a key role in the power generation performance of the anti-vibration hammer type composite energy collector, and the power generation performance graph shown in fig. 5 can be obtained by changing different excitation accelerations in simulation. As can be seen from fig. 5, when other conditions are not changed, the larger the excitation acceleration is, the larger the captured energy is, therefore, when the physical design is carried out, the excitation acceleration is ensured to be large enough as much as possible, and a better output effect can be obtained.
The energy collector is greatly influenced by an environmental excitation source, and the output alternating current cannot meet the requirement of directly driving the sensor node to work, so that a bridge needs to be built for energy conversion matching, and the bridge has the functions of rectification filtering, electric energy conversion and stable output. So the power management circuit matched with the collector is designed.
The overall scheme design of the power management circuit is as follows: aiming at the technical scheme that the shockproof hammer type composite energy collector consists of a rectifying circuit, an energy storage circuit and an output circuit, the overall strategy of charging, rectifying, filtering, storing and releasing is adopted to design a power management scheme. The equivalent impedance in the collector is very large, and reaches thousands of omega, even several M omega, so the collector must get the energy and enter the energy storage device through the rectifier circuit, the energy storage device can release all the energy and become the output power supply of stable 3.3V after charging, satisfy the requirement of load node power supply and drive load node work steadily. The overall design scheme of the power management circuit is shown in figure 6.
Because the output of the energy collector is alternating voltage and current which cannot directly charge the energy storage device, a rectifying circuit is needed to convert the alternating voltage and current into direct current to store energy. Meanwhile, considering that six power generation units exist in the designed shockproof hammer type composite energy collector, the output phases are different, and if the six power generation units are connected in parallel and then connected into a rectification circuit, the energy can be mutually offset by the six power generation units. Therefore, in order to fully utilize energy and avoid energy loss, each power generation unit is independently connected into a rectifying circuit, and is rectified by the rectifying circuit to become direct current and then is output to the LTC3588 chip in parallel. Six power generation units need six bridge rectifier circuits for rectification, and the six bridge rectifier circuits are connected in parallel to output direct current after rectification, which is not shown in the figure.
Therefore, a full-bridge rectification circuit is taken as an energy collection rectification circuit.
Because the output power of the designed collector is in the mu W level, the loss is reduced as much as possible, enough energy is ensured to meet the load operation, and an ideal design scheme is selected to meet the required functions. ADI (ANALOG DEVICES) company has provided a LTC3588 chip, which can realize a small number of DEVICES in the patent and achieve the purpose of low power consumption, complete the formation of a charge-discharge control circuit and realize an energy storage capacitor C S1 And (4) charging and discharging.
The output energy after passing through the full bridge rectifier is stored in the energy storage device and V IN Energy storage capacitor C on pin S1 And storing energy for the DC-DC converter at any time. In addition, a very small part of electric energy is stored in V IN The pin and the CAP pin are connected on a capacitor and used as an energy source for driving the BUCK converter. A SLEEP comparator in the chip can monitor the voltage of the BUCK converter in real time and control the charging and discharging of an energy storage capacitor at the front end of the BUCK converter.
The LTC3588-1 has a complete energy management scheme inside and can directly output 3.3V voltage. However, the output regulation function of the LTC3588-1 cannot perfectly regulate the output of the excessive voltage residual wave, and certain output variation ripple still exists. In order to ensure that the circuit supplies power to a load node more stably, the output voltage of the charge-discharge control circuit of the LTC3588-1 is designed to be 3.6V, and then a Low Dropout Regulator (LDO) is connected to the output end of VOUT to reduce the Dropout and output stable 3.3V voltage.
In this embodiment, a power management circuit formed by a charging and discharging control circuit designed by an LTC3588 chip and an AP7354 voltage regulator module is shown in fig. 7. A full-bridge rectifier circuit and a voltage stabilizing diode D are additionally connected before the energy collector is connected with the LTC3588 chip 8 Mainly, considering that the output voltage of the friction power generation is as high as 80V, the maximum voltage allowed to be input by a chip is only 20V, and in order to avoid the damage of the chip caused by overhigh input voltage, a voltage stabilizing diode is introduced. After the electric energy output by the energy collector is rectified, the input voltage is reduced to be within the acceptable input voltage range of the chip, and the chip protection function is achieved at the input end. D1 pin directly connected to V IN2 A resistor R connected to the pin D0 in high level state 1 And R 2 And functions to adjust the level of the D0 pin. Will resistance R 2 Set to 0 omega, resistance R 1 And leaving a blank position, representing that D0 is switched into a logic high level, and the output voltage of the circuit is 3.6V at the moment. Will resistance R 2 Position left blank, resistance R 1 Set to 0 Ω, representing D0 switched in to a logic low level, at which time the circuit output is 3.3V. According to the previous analysis, in order to ensure the normal operation of the back-end LDO regulator module, the voltage output scheme of the LTC3588 selects the former resistor setting mode, i.e., 3.6V output voltage. At this time, the energy storage capacitor C S1 The rising threshold voltage of (2) is 5.05V, and the falling threshold voltage is 3.75V at the lowest.
Designing a wireless temperature measurement system: the transmission line faults can be caused by low temperature or high temperature around the transmission line, so that the temperature monitoring is important in the online monitoring of the transmission line, and a low-power-consumption wireless temperature measuring system is designed according to the requirement, and the structural diagram of the whole system is shown in fig. 8.
The temperature sensor in the wireless temperature measuring system is a high-precision temperature sensor Si7050 produced by Silicon Labs, the working voltage is 1.9V-3.6V, the output voltage standard of the management circuit is met, the sampling working current is 195nA, the wireless temperature measuring system has the advantage of low power consumption, and a main control chip of a radio frequency unit in a data sending end is an NRF24LE1 chip produced by NORDIC SEMICONDUCTOR. An 8051MCU and a high-performance low-power consumption 2.4GHz radio frequency transceiver are used in the main control chip, and the design mode reduces the use of discrete devices and controls the whole power consumption. The data transmitting end is powered by a shockproof hammer type composite energy collector, so that the lower the power consumption of the transmitting end, the better the power consumption of the transmitting end. The data receiving end is far away from the power transmission line, and a stable traditional power supply mode is adopted, so that the data receiving end selects a combination of a main control chip STM32F103 and an NRF24L01 radio frequency transceiver, and the data receiving end has the advantages that received data can be directly uploaded to an upper computer for clear display.
The temperature sensor Si7050 adopts six-pin DFN packaging, and has perfect integration, small volume and precision of +/-1 ℃. Two pull-up resistors 10K Ω are used on the clock pin SCL and the data pin SDA to connect the power supply input, and a filter capacitor C4 of 0.1uF is provided. The schematic circuit diagram is shown in fig. 9.
The data sending end has two functions as follows: reading the temperature sensor and wirelessly transmitting data, and designing a minimum system of the singlechip. The functions of the main control chip and the RF unit of the data acquisition sending end are maintained by the NRF24LE1 chip, so that the requirement on energy consumption of a data reading section can be reduced. FIG. 10 is a schematic diagram of the NRF24LE1 minimum system.
And the data receiving end selects a minimum system of STM32F103RBT6 and an NRF24L01 radio frequency module according to the data receiving function and the data processing function. The power supply system can be powered by a power adapter or a detachable lithium battery, and is also matched with a serial communication circuit, so that data transmission with a computer is facilitated. And a data through TTL-to-USB connector of the STM32F103RBT6 singlechip is transmitted to a com interface of the computer, and finally, the data is displayed by the upper computer.
The following is an analysis of the working modes of the piezoelectric crystal, and when the piezoelectric crystal is subjected to an external force, different working modes are generated due to the polarization direction and different force-bearing directions. The main workings of piezoelectric crystals are divided into two categories: d 31 Mode and d 33 The method. As shown in fig. 11a and 11b, fig. 11 is a schematic diagram of the operation mode of the piezoelectric crystal; d 31 The working mode is that when the stress direction of the piezoelectric crystal is vertical to the polarization direction (transverse direction, stress direction is vertical to the direction of an electric field),the piezoelectric crystal is strained in the corresponding direction, and voltage is generated in the process; d 33 The working mode is that when the stress direction of the piezoelectric crystal is parallel to polarization (longitudinal direction, stress direction is parallel to electric field direction), the piezoelectric crystal generates corresponding voltage. The output formula under the two modes is as follows:
wherein sigma xx Is a stress; g is a piezoelectric voltage constant; d is the piezoelectric strain constant, and g and d have a relationship of g = d/epsilon, where epsilon is the dielectric constant and A is the electrode area. Generally speaking, the piezoelectric strain coefficient d 31 Is less than d 33 Piezoelectric pressure coefficient g 31 Specific gravity of 33 Is small. So d 33 Working mode power generation efficiency ratio d 31 Large working mode, but d 33 The piezoelectric crystal can not generate large mechanical deformation and is not easy to generate electricity under the vibration condition. d 31 The working mode can produce larger strain reaction under the condition of small stress, and the application is wide, so d is selected here 31 Piezoelectric crystals of the type.
Piezoelectric equation and performance parameters: the piezoelectric equation reflects the mutual coupling effect of the mechanical property and the electrical property of the piezoelectric crystal under the mechanical action, including stress and strain, electric field and electric displacement, and the relationship between force and electricity is analyzed through the standard of throughput. Regarding the piezoelectric crystal as a perfect mechanical system, the linear constitutive relation among the stress sigma, the electric displacement vector D, the strain xi and the electric field intensity E is as follows:
where d is the piezoelectric strain constant of the piezoelectric material,
in order to obtain an elastic compliance coefficient,
is the dielectric constant of the material, i, j =1,2.. 6,m, n =1,2,3 is the direction of the force and electric field.
In addition to the parameters of the piezoelectric strain constant, dielectric constant, and elastic compliance coefficient in the above piezoelectric equation, the dielectric loss, frequency constant, quality factor, and electromechanical coupling coefficient may also reflect the performance of the piezoelectric crystal, and these parameters are described below.
1. Dielectric loss: the dielectric body generates energy loss due to heating which cannot be avoided under the action of an electric field. The loss dielectric tangent loss is also the ratio of the out-of-phase component to the in-phase component. The two components are caused by the conduction process of the active current IR under the action of the alternating electric field; the reactive current IC is caused by the medium relaxation process. The loss dielectric tangent loss is expressed as:
in the formula, C is a dielectric capacitor, R is a loss resistor, and omega is an alternating electric field angular frequency. It can be seen that the larger the tan δ value is, the worse the piezoelectric crystal properties are, and can be used as a reference index in selecting a power generation material.
2. Frequency constant: resonant frequency f of the piezoelectric crystal r The product of the length L in the vibrator vibration direction can be expressed by a frequency constant N. The kind and characteristics of the material will affect the resonant frequency of the transistor; physical factors such as shape and size can affect the resonant frequency of the piezoelectric crystal. But it is specific that the frequency constant N is not influenced by other factors and is only dependent on the material properties and the way of the two vibrations.
3. Quality factor: in the process of piezoelectric material power generation, the piezoelectric crystal can overcome the internal mechanical loss, the self power-on can cause energy loss, the external load also has load loss, all losses are expressed by the quality factor of the piezoelectric crystal, and the expression is as follows:
in the formula Q m Quality factor, W 1 For mechanical energy stored internally in the piezoelectric crystal, W 2 For each piezoelectric crystal mechanical energy of periodic losses. The quality factor can be used for measuring the energy conversion efficiency, the larger the value is, the smaller the loss is, the higher the conversion efficiency is, and most PZT piezoelectric crystal materials are larger than 500.
4. Electromechanical coupling coefficient: the electromechanical coupling coefficient is a parameter for measuring the electromechanical coupling characteristic of the piezoelectric material, represents the coupling degree of mechanical energy and electric energy and the energy conversion capacity, and is defined as
Coefficient of electromechanical coupling k p Representing the performance of the piezoelectric crystal, the larger the electromechanical coupling coefficient is, the better the piezoelectric performance is, and the stronger the coupling capacity of the mechanical energy and the electric energy is when corresponding to the piezoelectric effect.
2.3 cantilever beam electromechanical coupling mathematical model: the most applied piezoelectric vibration energy collection is a cantilever beam structure, and the cantilever beam is subjected to mathematical modeling, so that a sufficient theoretical basis can be made for the structural design of the collector. Firstly, a vibration mechanics model of the cantilever beam is analyzed, the natural frequency of the cantilever beam can be obtained, and an electromechanical coupling equation of the piezoelectric cantilever beam can be deduced in a Gaussian theorem integral mode.
Euler-Bernoulli beam vibration theory analysis: in piezoelectric cantilever beam vibration energy harvesting, the vibration beam can be equivalent to an Euler-Bernoulli beam model. When the cantilever beam moves at a low frequency, the shear deformation and the moment of inertia can be ignored, the motion model is shown in fig. 12, and fig. 12 is a schematic diagram of the cantilever beam motion model; the motion equation is as follows:
where YI represents the flexural rigidity, I is the moment of inertia of the cross-section to the neutral axis, and Y is the Young's modulus of the material, so c s I internal strain damping, c a Denoted as viscous damping, ρ is the density of the beam, a (x) is set as the cross-sectional area at the origin x, and w (x, t) is the lateral displacement vibration of the beam at time x at t. f (x, t) is set as the magnitude of the external force at the x origin.
In order to analyze the vibration characteristics (under vibration conditions) of the beam, f (x, t) =0 in equation (2.7), and since we are studying beams of uniform cross section, the value of a (x) is a fixed constant, equation (2.7) can be simplified after ignoring the internal and external damping:
wherein m represents the mass per unit length of the beam, and the boundary condition is shown as the following formula:
to simplify the solution process, w (x, t) of (2.8) in the equation is expressed as the product of two functions with a single variable:
w(x,t)＝φ(x)η(t) (2.11)
in the formula, phi (x) is a mass normalization eigenfunction, and eta (t) is a vibration mode response function. Substituting formula (2.11) into formula (2.8) can yield:
where γ is a constant of significance, let γ = ω 2 . Equation (2.12) can be expanded into the following system of equations:
by solving the system of equations (2.13), one can obtain:
wherein A, B, C, D, E and F are unknown constants, and the relationship between lambda and omega is as follows:
by substituting equation (2.11) into boundary condition equation (2.9) and equation (2.10), respectively, it is possible to obtain:
substituting equation (2.14) into equation (2.16) yields the following system of equations:
then φ (x) in equation (2.14) can be simplified as:
substituting formula (2.19) into formula (2.15) yields:
since the equation represented by equation (2.20) is a homogeneous equation and a, C have non-zero solutions, the value of the determinant of the coefficient matrix is 0, i.e.:
equation (2.21) is the frequency equation for the beam vibration, since M t M, L and I t Are all known quantities, so the equation solution λ can be derived, which is the eigenvalue of the system. Let the characteristic value of the system at the nth order vibration be lambda n Then the characteristic equation (mass normalized eigenfunction) phi of the nth order vibration n (x) Comprises the following steps:
wherein ζ r This can be derived from formula (2.20), i.e.:
the natural frequency of the n-th order undamped vibration of the system can be obtained from equation (2.15):
a mechanical coupling equation; FIG. 13 is a schematic diagram of a piezoelectric cantilever model under excitation, where the absolute displacement of the cantilever at time t from the origin x is z b (x, t) displacement of the mass centroid relative to the base is z m (t) the absolute displacement of the mass center of mass is z m (t)+y(t)。
The cross section to the cantilever beam carries out the atress analysis, and the inertial force and the damping force of quality piece can let the cantilever beam produce additional moment of flexure, and the inverse piezoelectric effect also will produce additional moment of flexure in the piezoelectric layer, ignores the interior total moment of flexure of piezoelectric cantilever beam under the circumstances of internal damping and is:
wherein c is the linear viscous damping coefficient of mass center of mass, H (x) is the Heaviside function, m eq And theta is an inverse piezoelectric coupling coefficient which is equivalent mass of the whole structure.
Wherein the perturbation equation for the cantilever beam can be expressed as:
where YI (x) represents the bending stiffness of the cross-sectional cantilever. Thus, cantilever beam is at x = l b A displacement of z b (l b T) and angle of rotation theta (l) b And t) are respectively:
therefore, z m (t) is equal to z b (l b T) and θ (l) b T) the sum of the displacements, i.e.:
the flexural stiffness YI (x) and inverse piezoelectric coupling coefficient θ of the cross-sectional cantilever beam are given below. If z is N Is a neutral plane and has a neutral plane coordinate z according to FIG. 13 N Satisfies the equation:
the coordinates of the neutral plane are:
therefore, the bending rigidity YI (x) of the cross-section cantilever beam satisfies the equation:
when only the axial strain caused by bending of the piezoelectric material is considered, the stress in the x direction in the piezoelectric layer can be obtained according to the piezoelectric constitutive equation:
wherein,
the modulus of elasticity under an electric field. Wherein d is 31 ＝e 31 /Y p 。 E 3 Is the electric field in the piezoelectric layer in the z-axis direction, namely: e 3 ＝-V(t)/t p ，t p The thickness of the piezoelectric layer.
Is the axial strain of the piezoelectric layer.
Thus, the inverse piezoelectric effect causes the piezoelectric layer stress to change
So that the equivalent bending moment M generated by the inverse piezoelectric effect in the sectional piezoelectric layer p (x, t) is:
the inverse piezoelectric coupling coefficient is obtained as:
the mass center displacement can be obtained by bringing the vibration beam model into:
obtaining the equivalent mass m of the whole structure according to the Rayleigh method eq Comprises the following steps:
the simultaneous solution of the vibration differential equation can obtain a mass center displacement equation as follows:
comparing the vibration differential equation of the piezoelectric cantilever:
wherein, ω is n The vibration frequency is the undamped vibration frequency of the piezoelectric cantilever beam unit with the equal section; k is the equivalent stiffness; χ is an electromechanical coupling coefficient; zeta n Is the damping ratio of the system. Respectively expressed as:
2.3.2 Circuit coupling equation; if this section is a combination of mechanical and electrical, figure 14 is an equivalent circuit diagram of a cross-sectional piezoelectric cantilever beam. Calculating the output current of the section piezoelectric cantilever beam by using integral through Gaussian theorem, wherein the current equation is as follows:
in the formula,
is the electrical displacement vector of the piezoelectric layer;
is the unit vector of the outer normal, A area of a single electrode, R l External load and (4) resistance. Since the electrodes are perpendicular to the z-axis, the electrical displacement vector can be derived from piezoelectric equation (2.3) considering only the axial strain in the piezoelectric material caused by bending:
in the formula,
the dielectric constant under normal strain is related to the dielectric constant as follows:
S 1 for axial strain, the proportional relationship with curvature is
Therefore, the method comprises the following steps:
the coupled circuit equation is as follows:
wherein the internal capacitance of the piezoelectric layer is C p Let the electromechanical coupling coefficient in the circuit equation be κ.
Therefore, the single-degree-of-freedom bidirectional coupling set parameter model of the non-uniform section piezoelectric cantilever beam unit is
The underlying excitation is solved below as Y (t) = Y 0 e iωx The steady state response solution at. Because the mass center displacement response of the steady-state mass block of the piezoelectric cantilever beam with the equal section is the same as the voltage response component on the steady-state load resistor, the equation of omega =2 pi f is substituted into the formula to obtain the following formula:
thus, the displacement z of the mass center of mass of the piezoelectric cantilever beam unit m (t), the load output voltage V (t), the output power P (t) are:
2.4 magnetic field energy collection principle: the power transmission line is provided with abundant and dense magnetic fields around, and the mass block is replaced by the magnet at the upper end of the piezoelectric cantilever beam to absorb the energy of the magnetic field and drive the cantilever beam to vibrate. The magnetic field distribution generated by the magnetic circuit on the power line is analyzed based on the concept of magnetic charge, and the magnetic circuit is generally complex based on a three-dimensional field, wherein the concept of magnetic charge is used for obtaining a relatively clear and simple solution. Fig. 15 is a schematic cross-sectional view of a piezoelectric cantilever beam subjected to a magnetic field of a power line.
Taking the center of the power transmission line as the origin of the coordinate axis, wherein the size, the magnetic charge density and the residual magnetic flux density of the magnet i are l mi ×b mi ×h mi And B ri (σ mi ＝B ri ) Magnet surface Source Point P (x) m1 ,y m1 ,z m1 ) The magnetic flux density to the space induction point Q (x, y, z) can be calculated by the following equation:
wherein dM S ＝σ 1 dx 1 dy 1 Is point P (x) 1 ,y1,z 1 ) Watch (A)Surface magnetic charge, σ 1 ＝±σm 1 ，σm 1 Is the surface magnetic charge density of the magnet, the distance between two points is the third power of r Q1 | 3 ＝[(x-x 1 ) 2 +(y-y 1 ) 2 +(z-z 1 ) 2 ] 2/3 . According to ampere's law, only the flux density of the y component acts on the transmission line, y-direction
The magnetic flux density differential expression of (a) can be expressed as:
the y-component of the magnetic flux density of the magnet surface pair Q (x, y, z) can be calculated as:
the magnetic flux density component of the magnet at point Q (x, y, z) is:
assuming that the current density of the conductive cross-section on the transmission line is uniformly distributed, the vertical force acting on the transmission line can be deduced, and the length l of the transmission line is selected to calculate F y Expressed as:
in which I 0 And θ is the amplitude and phase angle of the alternating current, V c Is the conductive volume of the transmission line, A m Is a conductive volume V c The integral of the magnetic flux density of (a). According to newton's law, the force F (t) acting on the cantilever beam is equal to the ampere force on the transmission line, but in the opposite direction, expressed as:
F(t)＝-F y (2.50)
substituting the electromechanical coupling equation of the piezoelectric cantilever beam to obtain the voltage V (t):
wherein e is 31 Represents a piezoelectric constant, z pc Representing the amplitude, b the width of the second piezoelectric layer 7,
representing the load at the free end of the secondary cantilever 4, R L Representing the load resistance, ω the angular frequency of the alternating current source, γ the aspect ratio of the second piezoelectric layer 7, r c Representing radius of the power line, v 1 Showing the deflection, v, of one of the second piezoelectric layers 7 2 Represents the deflection, v, of another second piezoelectric layer 7 3 Shows the deflection of one of the magnet blocks 5, v 4 Shows the deflection of the other magnet block 5, [ theta ] 1 Representing the phase, theta, of the fundamental frequency of vibration of the secondary cantilever 4 2 Representing the phase, θ, of the second harmonic of vibration of the secondary cantilever 4 3 Representing the phase, theta, of the third harmonic of vibration of the secondary cantilever 4 4 Indicating the phase of the fourth harmonic of vibration of the secondary cantilever 4, I 0 Representing the current of the power line, Δ x representing the difference in the x-direction, a 1 And a 3 Represents the correction factor of one of the second piezoelectric layers 7, a 2 And a 4 Denotes a correction coefficient, k, of another second piezoelectric layer 7 a The spring constant of the secondary cantilever 4 is shown and m represents the equivalent mass of the secondary cantilever 4.
Finally, it is noted that: the above-mentioned embodiments are only examples of the present invention, and it is a matter of course that those skilled in the art can make modifications and variations to the present invention, and it is considered that the present invention is protected by the modifications and variations if they are within the scope of the claims of the present invention and their equivalents.
Claims (6)
1. A vibration-magnetic field broadband composite energy collector based on a vibration damper comprises the vibration damper, wherein the vibration damper is provided with a clamp (1), and the vibration damper is characterized by further comprising two main cantilever beams (2), two cross beams (3) and four auxiliary cantilever beams (4), wherein the two main cantilever beams (2) are parallel to a cable, one ends of the two main cantilever beams (2) are connected with the clamp (1), the other ends of the two main cantilever beams (2) are respectively connected with the cross beams (3), the middle part of each cross beam (3) is connected with the other end of each main cantilever beam (2), the cross beams (3) are perpendicular to the main cantilever beams (2) and are positioned in the same horizontal plane, two ends of each cross beam (3) are respectively connected with one auxiliary cantilever beam (4), the auxiliary cantilever beams (4) are parallel to the main cantilever beams (2), one end of each auxiliary cantilever beam (4) is connected with one end of each cross beam (3), and the other end of each auxiliary cantilever beam extends towards the direction of the clamp (1) and is connected with a magnet block (5); a first piezoelectric layer (6) is arranged on the upper surface of the main cantilever beam (2), and a second piezoelectric layer (7) is arranged on the outer side surface of the auxiliary cantilever beam (4); the horizontal vibration collected energy transmitted by the power transmission line (9) is transmitted to the first piezoelectric layer (6) by the main cantilever beam (2) for power generation, and the vertical vibration caused by the magnetic field energy collected by the power transmission line (9) by the auxiliary cantilever beam (4) through the magnet block (5) is transmitted to the second piezoelectric layer (7) for power generation.
2. The vibro-magnetic broadband composite energy collector based on a shakeproof hammer according to claim 1, characterized in that: the main cantilever beams (2) and the cross beams (3) and the auxiliary cantilever beams (4) are connected together through inertia mass blocks (8).
3. The vibro-magnetic broadband composite energy collector based on a shakeproof hammer according to claim 2, characterized in that: the material of the inertia mass block (8) is resin.
4. The vibro-magnetic broadband composite energy collector based on a shakeproof hammer according to claim 1, characterized in that: the main cantilever beam (2), the cross beam (3) and the auxiliary cantilever beam (4) are all in a plate shape, wherein the main cantilever beam (2) and the cross beam (3) are horizontally arranged, and the auxiliary cantilever beam (4) is vertically arranged.
5. The vibro-magnetic broadband composite energy collector based on a shakeproof hammer according to claim 1, characterized in that: the main cantilever beam (2), the cross beam (3) and the auxiliary cantilever beam (4) are made of beryllium bronze, and the main cantilever beam (2) is used as a substrate of the first piezoelectric layer (6); the secondary cantilever (4) is used as a substrate of the second piezoelectric layer (7); the first piezoelectric layer (6) and the second piezoelectric layer (7) are respectively adhered to the main cantilever beam (2) and the auxiliary cantilever beam (4) through conductive silver adhesive; the first piezoelectric layer (6) and the second piezoelectric layer (7) are made of PZT-5H piezoelectric ceramics, and vibration energy is converted into electric energy; the magnet block (5) is made of neodymium iron boron magnetic materials.
6. The vibro-magnetic broadband composite energy collector based on a shakeproof hammer according to claim 1, characterized in that: the second piezoelectric layer (7) has its output voltage V (t) calculated by the following formula:
wherein e is 31 Represents a piezoelectric constant, z pc Representing the amplitude, b the width of the second piezoelectric layer (7),
represents the load of the free end of the secondary cantilever beam (4), R L Represents the load resistance, omega represents the angular frequency of the alternating current source, gamma represents the aspect ratio of the second piezoelectric layer (7), r c Representing the radius of the power line, v 1 Represents the deflection, v, of one of the second piezoelectric layers (7) 2 Represents the deflection, v, of a further second piezoelectric layer (7) 3 Shows the deflection, v, of one of the magnet blocks (5) 4 Represents the deflection of the other magnet block (5) (. Theta.) 1 Representing the phase, theta, of the fundamental frequency of vibration of the secondary cantilever (4) 2 Represents the phase of the secondary harmonic of vibration of the secondary cantilever (4), theta 3 Represents the phase, theta, of the third harmonic of the vibration of the secondary cantilever (4) 4 Representing the phase of the fourth harmonic of the vibration of the secondary cantilever (4), I 0 Representing the current of the power line, Δ x representing the difference in the x-direction, a 1 And a 3 Represents a correction factor of one of the second piezoelectric layers (7), a 2 And a 4 Is shown in anotherCorrection factor, k, of a second piezoelectric layer (7) a The elastic coefficient of the auxiliary cantilever beam (4) is shown, and m represents the equivalent mass of the auxiliary cantilever beam (4).
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| CN118659611A (en) * | 2024-08-20 | 2024-09-17 | 广州蓝色能源研究院 | Elastic bistable overhead transmission line power generation device and line self-power supply method |
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