Vibration-magnetic field energy harvesting circuit, wireless node and system based on anti-vibration hammer

Abstract

The present invention discloses a vibration-magnetic field energy collection circuit, a wireless node and a system based on a shockproof hammer, comprising a shockproof hammer type composite energy collector, the shockproof hammer type composite energy collector is used to collect the vibration energy and magnetic field energy of the transmission line and convert them into electrical energy, and the shockproof hammer type composite energy collector is connected to a power management circuit; the power management circuit comprises a rectifier charging circuit, a charge and discharge control circuit and a voltage stabilizing output circuit, the rectifier charging circuit is connected to the shockproof hammer type composite energy collector to convert its electrical energy into direct current, and the charge and discharge control circuit is connected to the rectifier charging circuit to store the electrical energy in the energy storage capacitor C S1 The voltage stabilization output circuit is connected to the charge and discharge control circuit to output a stable DC voltage. The present invention can collect the vibration energy and magnetic field energy of the transmission line and convert them into electrical energy, and output a DC voltage after voltage stabilization by the power management circuit to provide it to the wireless sensor node for use.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment monitoring, and in particular to a vibration-magnetic field energy collection circuit, a wireless node and a system based on an anti-vibration hammer. Background Art

[0002] The rapid development of science and technology and economy in my country has brought about the increasing scale of smart grids. Since the founding of New China, the total power generation in the country has increased by 25 times, and this figure is still increasing. The improvement of the power system and the expansion of the coverage of the power grid have an increasing impact on people's lives, industrial needs, and agricultural production. The safe operation of transmission lines can bring a very stable guarantee for regional development. The safety and reliability of the smart grid are directly reflected by the operating status of the transmission line. If a fault occurs, it will inevitably cause huge losses. When the power grid covers a large area, many lines will be in various inaccessible and complex environments, which are easily affected by high temperature, icing, wind vibration, lightning strikes, corrosion and other problems, and many faults will occur. Among them, the most common fault is the broken strands and broken wires of the transmission line. When the wire vibrates under the action of wind, sometimes even dancing, the force points of the wires are often pulled, bent and squeezed, causing the wire material to weaken and damage, and finally leading to broken strands and broken wires, and finally causing the performance of the transmission line, such as line current carrying capacity and mechanical properties, to decline. Therefore, it is necessary to monitor the operation status of the transmission line online in real time to prevent faults.

[0003] Online monitoring of the status of transmission lines plays a vital role in the economical, efficient, safe and reliable operation of smart grids. The online monitoring system of transmission lines has become an indispensable part of my country's smart grid. However, with the popularization of monitoring systems, the power supply problem has become an urgent problem to be solved. Due to the long-term location of transmission lines in harsh outdoor environments and the limitations of their own insulation conditions, the power supply of monitoring equipment cannot be directly obtained through the wires. Therefore, a complete self-powered system is urgently needed to power the monitoring equipment. This has a key role in promoting the maturity and technological advancement of my country's smart grids. In addition, self-powered power is currently an emerging research direction, which will have great research significance in environmental monitoring, smart industry, military fields, and energy and environmental protection.

[0004] At present, in order to meet the requirements of environmental friendliness and foresight, the best solution for self-power supply is to use the unused energy in the working environment of the sensor node for power supply. Compared with the traditional lithium battery, it is a great improvement. The traditional power supply method has the disadvantages of polluting the environment, high maintenance cost and short power supply cycle. By adopting a new way of self-collection and self-use, a new green decision is made for self-power supply, replacing the traditional power supply method upgrade to meet the long-term deployment needs of sensor nodes.

[0005] There are many unused energies around the transmission lines, such as wind energy, electric field energy, magnetic field energy, solar energy and vibration energy. Among them, solar energy and wind energy are subject to great environmental constraints and have strong limitations; the size of electric field energy is subject to the current and voltage of the transmission line; the magnetic field energy distribution is more sufficient; and vibration energy has many advantages such as not being easily disturbed by the electric field, a wide range of sources, a large electromechanical coupling coefficient and high energy density. Among the many energy collection technologies, the combination of magnetic field and vibration energy is used to generate electricity, and composite energy collection has the advantage of combining multiple advantages, which can effectively collect wider frequency band energy and increase output power. This is a current research hotspot and has great scientific research significance.

[0006] Therefore, the defect of the prior art is that there is a lack of a vibration-magnetic field energy collection circuit based on a shock-absorbing hammer, which can collect the vibration energy of the transmission line and convert the magnetic field energy into electrical energy, and output a DC voltage after being stabilized by a power management circuit to provide to the wireless sensor nodes for use. Summary of the invention

[0007] In view of at least one defect of the prior art, an object of the present invention is to provide a vibration-magnetic field energy harvesting circuit based on a shock-absorbing hammer, which can collect the vibration energy of the transmission line and convert the magnetic field energy into electrical energy, and output a DC voltage after being stabilized by a power management circuit to provide to wireless sensor nodes for use.

[0008] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a vibration-magnetic field energy collection circuit based on a shockproof hammer, comprising a shockproof hammer type composite energy collector, the shockproof hammer type composite energy collector is used to collect the vibration energy and magnetic field energy of the transmission line and convert them into electrical energy, and the shockproof hammer type composite energy collector is connected to a power management circuit; the power management circuit comprises a rectifier charging circuit, a charge and discharge control circuit and a voltage stabilizing output circuit, the rectifier charging circuit is connected to the shockproof hammer type composite energy collector to convert its electrical energy into direct current, and the charge and discharge control circuit is connected to the rectifier charging circuit to store the electrical energy in the energy storage capacitor C S1 In the invention, the voltage stabilizing output circuit is connected to the charge and discharge control circuit to output a stable DC voltage.

[0009] The shock-proof hammer type composite energy collector includes a shock-proof hammer, which is provided with a clamp, and also includes two main cantilever beams, two cross beams and four auxiliary cantilever beams. The two main cantilever beams are parallel to the cable, one end of the two main cantilever beams is connected to the clamp, the other ends of the two main cantilever beams are respectively connected to the cross beams, the middle of the cross beams is connected to the other end of the main cantilever beams, the cross beams are perpendicular to the main cantilever beams and are located in the same horizontal plane, and each of the two ends of the cross beams is respectively connected to an auxiliary cantilever beam, the auxiliary cantilever beams are parallel to the main cantilever beams, one end of the auxiliary cantilever beams is connected to one end of the cross beam, and the other end is extended toward the direction of the clamp and connected to a magnet block; a first piezoelectric layer is provided on the upper surface of the main cantilever beam, and a second piezoelectric layer is provided on the outer side of the auxiliary cantilever beam; the main cantilever beam is subjected to horizontal vibration transmitted by the transmission line to collect energy and transmit it to the first piezoelectric layer for power generation, and the auxiliary cantilever beam collects vertical vibration caused by the magnetic field energy of the transmission line through the magnet block to generate electricity for the second piezoelectric layer.

[0010] The rectifying and charging circuit includes a bridge rectifier circuit, the number of which is equal to the sum of the number of the first piezoelectric layer and the second piezoelectric layer, each of the first piezoelectric layer and the second piezoelectric layer is connected to a corresponding bridge rectifier circuit, the two input ends of the bridge rectifier circuit are connected to the two output ends of the first piezoelectric layer or the second piezoelectric layer, the positive output ends of all the bridge rectifier circuits are connected in parallel and then connected to the negative pole of the Zener diode D8, and the negative output ends of all the bridge rectifier circuits are connected in parallel and then connected to the positive pole of the Zener diode D8.

[0011] The charge and discharge control circuit includes an LTC3588 chip and an energy storage capacitor C S1 ; The PZ1 end of the LTC3588 chip is connected to the negative electrode of the voltage regulator D8, the PZ2 end of the LTC3588 chip is connected to the positive electrode of the voltage regulator D8, and the Vin end of the LTC3588 chip is connected to the energy storage capacitor C S1 One end of the energy storage capacitor C S1 The other end is grounded, and the Vin end of the LTC3588 chip is also connected to the CAP end of the LTC3588 chip via capacitor C3; the SW end of the LTC3588 chip is connected to the Vout end of the LTC3588 chip via inductor L1; the Vout end of the LTC3588 chip is grounded via capacitor C4, the Vin2 end of the LTC3588 chip is grounded via capacitor C6, the D0 end of the LTC3588 chip is connected to the Vin2 end in parallel with the D1 end; capacitor C4 is connected in parallel with capacitor C5.

[0012] The voltage-stabilized output circuit is provided with an AP7354 chip, the Vin end of the AP7354 chip is connected to the Vout end of the LTC3588 chip, the EN end of the AP7354 chip is connected to 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 via a capacitor C7, and the Vout end of the AP7354 chip outputs a 3.3 DC voltage.

[0013] A wireless sensor node comprising the vibration-magnetic field energy collection circuit is powered by the vibration-magnetic field energy collection circuit.

[0014] The wireless sensor node is provided with a temperature sensor, and the temperature sensor is connected to a radio frequency transmitting unit; the temperature sensor adopts a Si7050 temperature sensor, and the Si7050 temperature sensor is provided with a signal output terminal SCL and a signal output terminal SDA, and the radio frequency transmitting unit is provided with an NRF24LE1 module, and the P0.3 terminal and the P0.5 terminal of the NRF24LE1 module are respectively connected to the signal output terminal SCL and the signal output terminal SDA, and the NRF24LE1 chip is also connected to an antenna; the VDD terminal and the ground terminal of the Si7050 temperature sensor and the NRF24LE1 chip are respectively connected to the power output terminal and the ground terminal of the voltage stabilization output circuit.

[0015] A wireless sensor system including the wireless sensor node also includes a data receiving end and a data display end, the data receiving end adopts an NRF24L01 radio frequency module, the NRF24L01 radio frequency module is wirelessly connected to an NRF24LE1 module, the NRF24L01 radio frequency module is connected to an STM32F103RBT6 single-chip microcomputer, the data display end is a host computer, and the STM32F103RBT6 single-chip microcomputer is connected to the host computer.

[0016] Significant effect: The present invention provides a vibration-magnetic field energy collection circuit, wireless node and system based on a shock-absorbing hammer, which can collect the vibration energy of the transmission line and convert the magnetic field energy into electrical energy, and output a DC voltage after being stabilized by a power management circuit to provide to the wireless sensor node for use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of the shock-proof hammer type composite energy harvester;

[0018] Figure 2 This is the modal analysis diagram of the first four vibration modes of the shock-proof hammer type composite energy harvester;

[0019] Figure 3 This is the simulated open-circuit voltage analysis diagram of the shock-proof hammer type composite energy harvester;

[0020] Figure 4 This is the impedance matching and power generation analysis diagram of the shock-proof hammer type composite energy harvester;

[0021] Figure 5 The power generation performance analysis diagram of the shock-proof hammer type composite energy harvester under different excitation accelerations;

[0022] Figure 6 This is a design diagram of the power management circuit;

[0023] Figure 7 is a circuit diagram of a power management circuit;

[0024] Figure 8 This is the overall system structure diagram of the wireless temperature measurement system;

[0025] Fig. 9 This is the circuit schematic diagram of the temperature sensor;

[0026] Fig.10 This is the minimum system schematic diagram of NRF24LE1;

[0027] Fig.11 This is a cross-sectional schematic diagram of the piezoelectric cantilever beam affected by the magnetic field of the transmission line. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1-Figure 10 As shown, a vibration-magnetic field energy harvesting circuit, wireless node and system based on a shockproof hammer include a shockproof hammer, which is provided with a fixture 1, two main cantilever beams 2, two cross beams 3 and four auxiliary cantilever beams 4, the two main cantilever beams 2 are parallel to the cable, one end of the two main cantilever beams 2 is connected to the fixture 1, the other ends of the two main cantilever beams 2 are respectively connected to the cross beams 3, the middle part of the cross beam 3 is connected to the other end of the main cantilever beam 2, the cross beam 3 is perpendicular to the main cantilever beam 2 and is located in the same horizontal plane, and the two ends of each cross beam 3 are respectively connected to A secondary cantilever beam 4 is connected, and the secondary cantilever beam 4 is parallel to the main cantilever beam 2. One end of the secondary cantilever beam 4 is connected to one end of the cross beam 3, and the other end is extended toward the direction of the fixture 1 and connected to 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 secondary cantilever beam 4. The main cantilever beam 2 is subjected to horizontal vibration transmitted by the transmission line 9 to collect energy and transmit it to the first piezoelectric layer 6 for power generation, and the secondary cantilever beam 4 collects the vertical vibration caused by the magnetic field energy of the transmission line 9 through the magnet block 5 to generate electricity for the second piezoelectric layer 7.

[0030] 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 inertial mass block 8 .

[0031] The material of the inertial mass block 8 is resin.

[0032] The main cantilever beam 2, the cross beam 3 and the auxiliary cantilever beam 4 are all in plate shape, wherein the main cantilever beam 2 and the cross beam 3 are placed horizontally, and the auxiliary cantilever beam 4 is placed vertically.

[0033] The main cantilever beam 2, the cross beam 3, and the auxiliary cantilever beam 4 are made of beryllium bronze. The main cantilever beam 2 serves as the substrate of the first piezoelectric layer 6; the auxiliary cantilever beam 4 serves as the substrate of the second piezoelectric layer 7; the first piezoelectric layer 6 and the second piezoelectric layer 7 are respectively bonded to the main cantilever beam 2 and the auxiliary cantilever beam 4 by conductive silver glue; the first piezoelectric layer 6 and the second piezoelectric layer 7 are made of PZT-5H piezoelectric ceramics to convert vibration energy into electrical energy; the magnet block 5 is made of neodymium iron boron magnetic material.

[0034] The shock-proof hammer type composite energy collector is connected to a power management circuit. The power management circuit includes a rectifier charging circuit, a charge and discharge control circuit, and a voltage stabilization output circuit. The rectifier charging circuit is connected to the shock-proof hammer type composite energy collector to convert its electrical energy into direct current, and the charge and discharge control circuit is connected to the rectifier charging circuit to store the electrical energy in the energy storage capacitor C. S1 In the embodiment, the voltage stabilizing output circuit is connected to the charge and discharge control circuit to output a stable DC voltage. The voltage stabilizing output circuit supplies power to the wireless sensor node.

[0035] The rectifying and charging circuit is provided with a bridge rectifier circuit, the number of which is equal to the sum of the number of the first piezoelectric layer 6 and the second piezoelectric layer 7, each of the first piezoelectric layer 6 and the second piezoelectric layer 7 is connected with a corresponding bridge rectifier circuit, the two input ends of the bridge rectifier circuit are connected to the two output ends of the first piezoelectric layer 6 or the second piezoelectric layer 7, the positive output ends of all the bridge rectifier circuits are connected in parallel to the negative electrode of the voltage regulator tube D8, the negative output ends of all the bridge rectifier circuits are connected in parallel to the positive electrode of the voltage regulator tube D8, and the charging and discharging control circuit includes an LTC3588 chip and an energy storage capacitor C S1 .

[0036] The PZ1 terminal of the LTC3588 chip is connected to the negative electrode of the voltage regulator D8, the PZ2 terminal of the LTC3588 chip is connected to the positive electrode of the voltage regulator D8, and the Vin terminal of the LTC3588 chip is connected to the energy storage capacitor C S1 One end of the energy storage capacitor C S1 The other end is grounded, and the Vin end of the LTC3588 chip is also connected to the CAP end of the LTC3588 chip via capacitor C3; the SW end of the LTC3588 chip is connected to the Vout end of the LTC3588 chip via inductor L1; the Vout end of the LTC3588 chip is grounded via capacitor C4, the Vin2 end of the LTC3588 chip is grounded via capacitor C6, the D0 end of the LTC3588 chip is connected to the Vin2 end in parallel with the D1 end; capacitor C4 is connected in parallel with capacitor C5.

[0037] The voltage regulated output circuit is provided with an AP7354 chip, the Vout end of the LTC3588 chip is connected to the Vin end of the AP7354 chip, the EN end of the AP7354 chip is connected to 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 via capacitor C7, and the Vout end of the AP7354 chip outputs a 3.3 DC voltage to power the wireless sensor node.

[0038] A wireless sensor node is powered by the power management circuit.

[0039] The wireless sensor node is provided with a temperature sensor, and the temperature sensor is connected to a radio frequency transmission unit. The temperature sensor adopts a Si7050 temperature sensor, and the Si7050 temperature sensor is provided with a signal output terminal SCL and a signal output terminal SDA. The radio frequency transmission unit is provided with an NRF24LE1 module, and the P0.3 terminal and the P0.5 terminal of the NRF24LE1 module are respectively connected to the signal output terminal SCL and the signal output terminal SDA, and the NRF24LE1 module is connected to an antenna. The VDD terminal and the ground terminal of the Si7050 temperature sensor and the NRF24LE1 module are respectively connected to the Vout terminal and the ground terminal of the P7354 chip. The wireless sensor node can also be a wireless sensor node for images, wind speed, etc.

[0040] A wireless sensor system including the wireless sensor node also includes a data receiving end and a data display end, the data receiving end adopts an NRF24L01 radio frequency module, the NRF24L01 radio frequency module is wirelessly connected to an NRF24LE1 module, the NRF24L01 radio frequency module is connected to an STM32F103RBT6 single-chip microcomputer, the data display end is a host computer, and the STM32F103RBT6 single-chip microcomputer is connected to the host computer.

[0041] The structure of the shock-proof hammer type composite energy collector is as follows: Figure 1, mainly composed of a fixture 1, a main cantilever beam 2 arranged horizontally, a cross beam 3, a secondary cantilever beam 4 arranged vertically, a magnet block 5, a first piezoelectric layer 6, a second piezoelectric layer 7, etc. Among them, the fixture 1 can be made of materials such as nylon, which belongs to the existing mature technology, and its structure is not repeated, and plays the role of fixing on the transmission line 9; the main cantilever beam 2 connected to the fixture 1 in the middle will be subjected to the horizontal vibration transmitted by the transmission line 9 to collect energy and transmit it to the first piezoelectric layer 6 for power generation, and the secondary cantilever beam 4 connected to the magnet block 5 mainly collects the magnetic field energy of the transmission line 9 to cause vertical vibration to give energy to the second piezoelectric layer 7; the inertial mass block 8 is made of 8000 resin through 3D, which is used to connect devices and transmit inertia; the magnet block 5 is made of NdFeB strong magnetic material, which 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, which can convert vibration energy into electrical energy.

[0042] The composite energy harvester proposed in this embodiment provides a solution for online monitoring of transmission lines, which can effectively collect and output energy.

[0043] According to the previous Figure 1 The structure is designed using components in COMSOL, and the specific parameters are shown in Table 1.

[0044] Table 1 Structural parameters

[0045]

[0046] After building the model, it is necessary to define the material properties. The Young's modulus, Poisson's ratio and other parameters of each part are shown in Table 2.

[0047] Table 2 Material property parameters

[0048]

[0049] In the field of piezoelectric energy harvesting, modal analysis can show the inherent characteristics of the structure and is a good analysis method for structural mechanics and vibration. Piezoelectric crystals generate electricity mainly through deformation. The greater the deformation within the tolerable range, the stronger the power generation capacity, which is also a response to the mode. For the shock-proof hammer type composite energy harvester in this paper, the main thing is to first find the resonance frequency of each order and the vibration model of the resonance frequency, such as Figure 2 The first four vibration modes of the shock-proof hammer collector are given.

[0050] It can be seen that in the first four vibration modes, the frequency of the first vibration mode does not make the main cantilever beam 2 vibrate, and only the auxiliary cantilever beam 4 vibrates slightly, and its first-order frequency is 4.6Hz. The second and third vibration modes are similar. The main cantilever beam 2 and the auxiliary cantilever beam 4 are both vibrating with moderate vibration amplitudes. The second-order and third-order vibration frequencies are 11.3Hz and 16.2Hz respectively. In the fourth-order vibration mode, the main cantilever beam 2 and the auxiliary cantilever beam 4 move violently with the mass block, and the vibration frequency is 29.5Hz. This high-order vibration will cause the piezoelectric layer to deform in the width direction. This degree of torsional force will cause the piezoelectric crystal to break, and the best energy capture effect cannot be achieved. Therefore, it is better to make the environmental vibration frequency of the shock-proof hammer composite energy collector as close to the second-order and third-order vibration frequencies as possible to obtain better output.

[0051] In order to improve the output voltage of the shock-proof hammer type composite energy harvester and improve the system's efficiency in collecting environmental vibration energy, the simulated voltage response output characteristics are analyzed. At different frequencies, corresponding to different cantilever beam displacement changes, the obtained voltage and output power and other performance can be calculated. When the excitation source is set to 1g, the simulated open circuit voltage of the piezoelectric cantilever beam can be obtained as follows: Figure 3 shown.

[0052] It can be seen that when the frequency of the shock-absorbing hammer composite energy harvester is 11 Hz, the open circuit voltage peak value reaches 25.2 V, and when the frequency is 14.5 Hz, the open circuit voltage peak value is 11.5 V. This is also consistent with the previous modal response, and a relatively large output voltage is obtained when approaching the second and third order modes.

[0053] Impedance matching and power generation analysis: Piezoelectric crystals have internal resistance, so when an external load resistor is added, its power generation will change with the change of resistance. In order to find the best power generation, it is necessary to find the best impedance matching. The output power and load change curve at the peak frequency of 11Hz is as follows: Figure 4 shown.

[0054] Can be obtained from Figure 4 It can be seen that the load power increases linearly with the load resistance from the beginning. After reaching the best matching impedance of 10kΩ, the output power reaches a maximum value of 5.5mW, and then decreases with the increase of resistance. Under this trend of increasing load, the voltage will continue to increase and reach saturation.

[0055] Analysis of power generation performance under different excitation accelerations: The external excitation acceleration of the environment plays a key role in the power generation performance of the shock-proof hammer type composite energy harvester. By changing different excitation accelerations in the simulation, the following results can be obtained: Figure 5 Power generation performance diagram. Figure 5It can be seen that when other conditions remain unchanged, the greater the excitation acceleration, the greater the captured energy. Therefore, when designing the physical object, try to ensure that the excitation acceleration is large enough to obtain better output effects.

[0056] The energy harvester is greatly affected by the environmental excitation source, and the output AC power cannot directly drive the sensor node. Therefore, a bridge needs to be built for energy conversion matching. This bridge should have the functions of rectification and filtering, power conversion and stable output. Therefore, a power management circuit matching the collector is designed.

[0057] Overall design of power management circuit: The shock-proof hammer type composite energy harvester is composed of a rectifier circuit, an energy storage circuit and an output circuit, so the overall strategy of charging first, then rectifying, filtering, storing and finally releasing is adopted to design the power management solution. The internal equivalent impedance of the collector is very large, reaching several thousand Ω or even several MΩ, so the energy collected by the collector must pass through the rectifier circuit to enter the energy storage device. After charging is completed, the energy storage device will release all the energy and turn it into a stable 3.3V output power supply, which meets the power supply requirements of the load node and stably drives the load node to work. The overall design of the power management circuit is as follows: Figure 6 .

[0058] Since the output of the energy collector is AC voltage and current, it is impossible to directly charge the energy storage device. Therefore, a rectifier circuit is required to convert the AC voltage and current into DC in order to store energy. At the same time, considering that there are six power generation units in the designed shock-proof hammer type composite energy collector, there are different output phases. If they are connected in parallel and then connected to a rectifier circuit, the six power generation units will cancel each other's energy. Therefore, in order to make full use of energy and avoid energy loss, each power generation unit is first connected to a rectifier circuit separately, and then rectified into DC by the rectifier circuit and then output in parallel to the LTC3588 chip. The six power generation units require a total of six bridge rectifier circuits for rectification, and then connected in parallel to output DC after rectification. The figure is omitted.

[0059] Therefore, a full-bridge rectifier circuit is adopted as the energy harvesting rectifier circuit solution.

[0060] Since the output power of the designed collector is μW level, the loss is reduced as much as possible to ensure that there is enough energy to meet the load work, and a relatively ideal design scheme is selected to meet the required functions. ADI (ANALOGDEVICES) has launched an LTC3588 chip, which can realize the purpose of this patent with a small number of devices and low power consumption, complete the composition of the charge and discharge control circuit, and realize the energy storage capacitor C S1 Charge and discharge.

[0061] The output energy after the full-bridge rectifier is stored in the V IN The energy storage capacitor C on the pinS1 In addition, a small amount of electrical energy is stored in V IN The capacitor connected to the CAP pin is used as the energy source to drive the BUCK converter. The SLEEP comparator inside the chip can monitor the BUCK converter voltage in real time and control the charging and discharging of the energy storage capacitor at its front end.

[0062] The LTC3588-1 has a complete energy management solution inside and can directly output a 3.3V voltage. However, the LTC3588-1 output regulation function cannot perfectly regulate the over-high output voltage residual, and there is still a certain output variation ripple. In order to ensure that the circuit supplies power to the load node more stably, the output voltage of the LTC3588-1 charge and discharge control circuit can be designed to be 3.6V, and then a low dropout linear regulator (LDO) can be connected to the VOUT output to reduce the voltage difference and achieve a stable output voltage of 3.3V.

[0063] This embodiment uses the charge and discharge control circuit designed by LTC3588 chip and the power management circuit composed of AP7354 voltage regulator module. Figure 7 As shown. Before the energy collector is connected to the LTC3588 chip, a full-bridge rectifier circuit and a voltage regulator diode D8 are also connected. This is mainly because the output voltage of the friction power generation is as high as 80V, while the maximum input voltage allowed by the chip is only 20V. In order to avoid the chip being damaged due to excessive input voltage, a voltage regulator diode is introduced. That is, after the electric energy output by the energy collector is rectified, the input voltage is reduced to the acceptable input voltage range of the chip, which plays a role in chip protection at the input end. The D1 pin is directly connected to V IN2 The pin is in a high level state, and the resistors R1 and R2 connected to the D0 pin play the role of adjusting the D0 pin level. Setting resistor R2 to 0Ω and leaving resistor R1 blank means that D0 is connected to a logic high level, and the circuit output voltage is 3.6V. Leaving resistor R2 blank and setting resistor R1 to 0Ω means that D0 is connected to a logic low level, and the circuit output is 3.3V. According to the previous analysis, in order to ensure that the back-end LDO voltage regulator module can work normally, the voltage output scheme of LTC3588 selects the former resistor setting method, that is, 3.6V output voltage. At this time, the energy storage capacitor C S1 The rising threshold voltage is 5.05V, and the falling threshold voltage is as low as 3.75V.

[0064] Design of wireless temperature measurement system: Low or high temperature around the transmission line will cause transmission line failure, so temperature monitoring is of utmost importance in the online monitoring of the transmission line. Therefore, according to this demand, a low-power wireless temperature measurement system is designed. The overall system structure diagram is as follows: Figure 8shown.

[0065] The temperature sensor in the wireless temperature measurement system uses the high-precision temperature sensor Si7050 produced by Silicon Labs. The operating voltage is 1.9V-3.6V, which meets the output voltage standard of the management circuit mentioned above. Its sampling working current is 195nA, which has the advantage of low power consumption. The main control chip of the RF unit in the data transmitter uses the NRF24LE1 chip produced by NORDICSEMICONDUCTOR. This main control chip uses an 8051 MCU and a high-performance, low-power 2.4GHz RF transceiver. This design reduces the use of discrete devices and controls the overall power consumption. The data transmitter is powered by a shock-proof hammer-type composite energy collector, so the lower the power consumption of the transmitter, the better. Because the data receiver is far away from the transmission line, it uses a stable traditional power supply method. Therefore, the data receiver uses a combination of the main control chip STM32F103 and the NRF24L01 RF transceiver. Its advantage is that the received data can be directly uploaded to the host computer for clear display.

[0066] The temperature sensor Si7050 uses a six-pin DFN package, which is well integrated, small in size, and has an accuracy of ±1°C. Two pull-up resistors of 10KΩ are used to connect the clock pin SCL and the data pin SDA to the power input, and a 0.1uF filter capacitor C4 is provided. The circuit schematic is shown below: Fig. 9 shown.

[0067] The data transmitter has two functions: reading the temperature sensor and wirelessly sending data. The single-chip minimum system is designed. The main control chip and RF unit of the data acquisition transmitter are controlled by the NRF24LE1 chip, which can maintain the basic functions, thus reducing the energy consumption of the data reading segment. Fig.10 This is the minimum system schematic diagram of NRF24LE1.

[0068] The data receiving end uses the minimum system of STM32F103RBT6 and NRF24L01 RF module according to the data receiving function and data processing function. Its power supply system can be powered by a power adapter or a removable lithium battery, and is also equipped with a serial communication circuit to facilitate data transmission with a computer. The data of the STM32F103RBT6 microcontroller is transmitted to the computer com interface through a TTL to USB connector, and finally displayed by the host computer.

[0069] Principle of magnetic field energy collection: There is a rich and dense magnetic field around the transmission line. By replacing the mass block with a magnet at the end of the piezoelectric cantilever beam, the magnetic field energy is absorbed to drive the cantilever beam to vibrate. Based on the concept of magnetic charge, the magnetic field distribution generated by the magnetic circuit on the power line is analyzed. Since the three-dimensional field is generally complicated, the concept of magnetic charge is used here to obtain a relatively clear and simple solution. Fig.11 This is the schematic diagram of the cross section of the piezoelectric cantilever beam subjected to the magnetic field of the transmission line.

[0070] The center of the transmission line is taken as the origin of the coordinate axis, where the size, charge density and residual flux density of magnet i are

[0071] l mi ×b mi ×h mi and B ri (σ mi =B ri ), the source point P(x m1 ,y m1 ,z m1 ) to the spatial induction point Q(x,y,z) can be calculated by the following formula:

[0072]

[0073] where dM S =σ1dx1dy1 is the surface charge of point P(x1,y1,z1), σ1=±σm1, σm1 is the surface charge density of the magnet, and the cube of the distance between the two points is |r Q1 | 3 =[(x-x1) 2 +(y-y1) 2 +(z-z1) 2 ] 2 / 3 According to Ampere's law, only the y-component magnetic flux density acts on the transmission line. The differential expression of magnetic flux density can be expressed as:

[0074]

[0075] The y component of the magnetic flux density on the magnet surface for Q(x,y,z) can be calculated as:

[0076]

[0077] The magnetic flux density component of the magnet at point Q(x,y,z) is:

[0078]

[0079] Assuming that the current density of the conductive cross section of the transmission line is uniformly distributed, the vertical force acting on the transmission line can be derived. Select a transmission line with a length of l to calculate F y , expressed as:

[0080]

[0081] Where I0 and θ are the amplitude and phase angle of the alternating current, V cis the conductive volume of the transmission line, A m is the conductive volume V c The integral of the magnetic flux density. 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:

[0082] F(t)=-F y (2.50)

[0083] The output voltage V(t) of the second piezoelectric layer (7) is calculated by the following formula:

[0084]

[0085]

[0086] Among them, e 31 represents the piezoelectric constant, z pc represents the amplitude, b represents the width of the second piezoelectric layer 7, represents the load on the free end of the auxiliary cantilever beam 4, R L represents the load resistance, ω represents the angular frequency of the AC power supply, γ represents the aspect ratio of the second piezoelectric layer 7, and r c represents the radius of the electric line, v1 represents the deflection of one of the second piezoelectric layers 7, v2 represents the deflection of the other second piezoelectric layer 7, v3 represents the deflection of one of the magnet blocks 5, v4 represents the deflection of the other magnet block 5, θ1 represents the phase of the fundamental frequency of the vibration of the sub-cantilever beam 4, θ2 represents the phase of the second harmonic of the vibration of the sub-cantilever beam 4, θ3 represents the phase of the third harmonic of the vibration of the sub-cantilever beam 4, θ4 represents the phase of the fourth harmonic of the vibration of the sub-cantilever beam 4, I0 represents the current of the electric line, Δx represents the difference in the x direction, a1 and a3 represent the correction coefficient of one of the second piezoelectric layers 7, a2 and a4 represent the correction coefficient of the other second piezoelectric layer 7, k a represents the elastic coefficient of the auxiliary cantilever beam 4, and m represents the equivalent mass of the auxiliary cantilever beam 4.

[0087] Finally, it should be noted that the above examples are only specific implementation examples of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalent technologies, they should be considered to be within the scope of protection of the present invention.

Claims

1. A vibration-magnetic field energy harvesting circuit based on a shock-proof hammer, characterized in that: The invention comprises a shockproof hammer type composite energy collector, which is used to collect vibration energy and magnetic field energy of a transmission line (9) and convert them into electric energy. The shockproof hammer type composite energy collector is connected to a power management circuit; the power management circuit comprises a rectifier charging circuit, a charge and discharge control circuit and a voltage stabilizing output circuit. The rectifier charging circuit is connected to the shockproof hammer type composite energy collector to convert its electric energy into direct current. The charge and discharge control circuit is connected to the rectifier charging circuit to store the electric energy in an energy storage capacitor C. S1 In the embodiment, the voltage-stabilizing output circuit is connected to the charge-discharge control circuit to output a stable DC voltage; The shock-proof hammer type composite energy collector comprises a shock-proof hammer, which is provided with a fixture (1), and also comprises 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 the cable, one end of the two main cantilever beams (2) is connected to the fixture (1), the other ends of the two main cantilever beams (2) are respectively connected to the cross beams (3), the middle part of the cross beam (3) is connected to the other end of the main cantilever beam (2), the cross beam (3) is perpendicular to the main cantilever beam (2) and is located in the same horizontal plane, and the two ends of each cross beam (3) are respectively connected to an auxiliary cantilever beam (4), and the auxiliary cantilever beams (4) are respectively connected to the two ends of each cross beam (3). The cantilever beam (4) is parallel to the main cantilever beam (2); one end of the auxiliary cantilever beam (4) is connected to one end of the cross beam (3); the other end is extended in the direction of the fixture (1) and is connected to 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 main cantilever beam (2) receives horizontal vibration transmitted by the transmission line (9) to collect energy and transmit it to the first piezoelectric layer (6) for power generation, and the auxiliary cantilever beam (4) collects vertical vibration caused by magnetic field energy of the transmission line (9) through the magnet block (5) to generate power for the second piezoelectric layer (7); The main cantilever beam (2) and the cross beam (3), and the cross beam (3) and the auxiliary cantilever beam (4) are connected together via an inertial mass block (8); The material of the inertial mass block (8) is resin; The main cantilever beam (2), the cross beam (3) and the auxiliary cantilever beam (4) are all in the shape of plates, wherein the main cantilever beam (2) and the cross beam (3) are placed horizontally, and the auxiliary cantilever beam (4) is placed vertically; The main cantilever beam (2), the cross beam (3) and the auxiliary cantilever beam (4) are made of beryllium bronze; The output voltage V(t) of the second piezoelectric layer (7) is calculated by the following formula: Among them, e 31 represents the piezoelectric constant, z pc represents the amplitude, b represents the width of the second piezoelectric layer (7), represents the load at the free end of the auxiliary cantilever beam 4, R L represents the load resistance, ω represents the angular frequency of the AC power supply, γ represents the aspect ratio of the second piezoelectric layer 7, and r c represents the radius of the electric line, v1 represents the deflection of one of the second piezoelectric layers 7, v2 represents the deflection of the other second piezoelectric layer 7, v3 represents the deflection of one of the magnet blocks 5, v4 represents the deflection of the other magnet block 5, θ1 represents the phase of the fundamental frequency of the vibration of the sub-cantilever beam 4, θ2 represents the phase of the second harmonic of the vibration of the sub-cantilever beam 4, θ3 represents the phase of the third harmonic of the vibration of the sub-cantilever beam 4, θ4 represents the phase of the fourth harmonic of the vibration of the sub-cantilever beam 4, I0 represents the current of the electric line, Δx represents the difference in the x direction, a1 and a3 represent the correction coefficient of one of the second piezoelectric layers 7, a2 and a4 represent the correction coefficient of the other second piezoelectric layer 7, k a represents the elastic coefficient of the auxiliary cantilever beam 4, and m represents the equivalent mass of the auxiliary cantilever beam 4.

2. The vibration-magnetic field energy harvesting circuit based on the anti-vibration hammer according to claim 1, characterized in that: The rectifying and charging circuit comprises a bridge rectifier circuit, the number of which is equal to the sum of the number of the first piezoelectric layers (6) and the second piezoelectric layers (7), each of the first piezoelectric layer (6) and the second piezoelectric layer (7) is connected to a corresponding bridge rectifier circuit, the two input ends of the bridge rectifier circuit are connected to the two output ends of the first piezoelectric layer (6) or the second piezoelectric layer (7), the positive output ends of all the bridge rectifier circuits are connected in parallel and then connected to the negative pole of the voltage regulator tube D8, and the negative output ends of all the bridge rectifier circuits are connected in parallel and then connected to the positive pole of the voltage regulator tube D8.

3. The vibration-magnetic field energy harvesting circuit based on the anti-vibration hammer according to claim 2, characterized in that: The charge and discharge control circuit includes an LTC3588 chip and an energy storage capacitor C S1 ; The PZ1 end of the LTC3588 chip is connected to the negative electrode of the voltage regulator D8, and the PZ2 end of the LTC3588 chip is connected to the positive electrode of the voltage regulator D8. The Vin terminal of the LTC3588 chip is connected to the energy storage capacitor C S1 One end of the energy storage capacitor C S1 The other end is grounded, and the Vin end of the LTC3588 chip is also connected to the CAP end of the LTC3588 chip via capacitor C3; the SW end of the LTC3588 chip is connected to the Vout end of the LTC3588 chip via inductor L1; the Vout end of the LTC3588 chip is grounded via capacitor C4, the Vin2 end of the LTC3588 chip is grounded via capacitor C6, the D0 end of the LTC3588 chip is connected to the Vin2 end in parallel with the D1 end; capacitor C4 is connected in parallel with capacitor C5.

4. The vibration-magnetic field energy harvesting circuit based on the anti-vibration hammer according to claim 3 is characterized in that: The voltage-stabilized output circuit is provided with an AP7354 chip, the Vin end of the AP7354 chip is connected to the Vout end of the LTC3588 chip, the EN end of the AP7354 chip is connected to 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 via a capacitor C7, and the Vout end of the AP7354 chip outputs a 3.3 DC voltage.

5. A wireless sensor node comprising the vibration-magnetic field energy harvesting circuit as claimed in claim 1, characterized in that: The vibration-magnetic field energy collection circuit is used for power supply.

6. The wireless sensor node according to claim 5, characterized in that: The wireless sensor node is provided with a temperature sensor, and the temperature sensor is connected to a radio frequency transmitting unit; the temperature sensor adopts a Si7050 temperature sensor, and the Si7050 temperature sensor is provided with a signal output terminal SCL and a signal output terminal SDA, and the radio frequency transmitting unit is provided with an NRF24LE1 module, and the P0.3 terminal and the P0.5 terminal of the NRF24LE1 module are respectively connected to the signal output terminal SCL and the signal output terminal SDA, and the NRF24LE1 chip is also connected to an antenna; the VDD terminal and the ground terminal of the Si7050 temperature sensor and the NRF24LE1 chip are respectively connected to the power output terminal and the ground terminal of the voltage stabilization output circuit.

7. A wireless sensor system comprising the wireless sensor node according to claim 6, characterized in that: It also includes a data receiving end and a data display end. The data receiving end adopts an NRF24L01 radio frequency module. The NRF24L01 radio frequency module is wirelessly connected to an NRF24LE1 module. The NRF24L01 radio frequency module is connected to an STM32F103RBT6 single-chip microcomputer. The data display end is a host computer, and the STM32F103RBT6 single-chip microcomputer is connected to the host computer.

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